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2018 |
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| 1. | Rao, Suman; Thankachan, Prashanth; Amrutur, Bharadwaj; Washington, Maryann; Mony, Prem Continuous, real-time monitoring of neonatal position and temperature during Kangaroo Mother Care using a wearable sensor: A techno-feasibility pilot study Journal Article Pilot and Feasibility Studies, 99 (4), pp. 1-7, 2018. Abstract | BibTeX | Tags: Health, Remote Neonatal Monitoring and Intervention | Links: @article{Rao2018, title = {Continuous, real-time monitoring of neonatal position and temperature during Kangaroo Mother Care using a wearable sensor: A techno-feasibility pilot study}, author = {Suman Rao and Prashanth Thankachan and Bharadwaj Amrutur and Maryann Washington and Prem Mony}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/Rao_et_al-2018-Pilot_and_Feasibility_Studies.pdf}, doi = {10.1186/s40814-018-0293-5}, year = {2018}, date = {2018-05-21}, journal = {Pilot and Feasibility Studies}, volume = {99}, number = {4}, pages = {1-7}, abstract = {Background: Remote biomonitoring of vital parameters in hospitals and homes has the potential to improve coverage and quality of maternal and neonatal health. Wearable sensors coupled with modern information and communication technology now offer an opportunity to monitor temperatures and kangaroo mother care (KMC) adherence in a continuous and real-time manner remotely for several days’ duration in hospital and home settings. Using an innovative remote biomonitoring device to measure both temperature and baby position, we undertook a techno-feasibility study in preparation for a clinical trial. Methods: We designed and developed a wearable sensor for tracking KMC adherence and neonatal temperature, using social innovation design principles. After screening mother-infant dyads using clinical and logistic eligibility criteria, we piloted this wearable sensor along with a gateway device and the commercial cellular network. The dyads were recruited during hospitalization and followed up in the hospital and home phases for several days. Simple descriptive statistical analysis was undertaken. Results: Recruitment rate was 50% (6/12), and consenting rate was 83% (5/6) during a 2-month period. These five neonates contributed a total of 39 study days (15 hospital days and 24 home days). Their mean [± standard deviation (S.D.)] birth weight was 1490 (± 244) g. The mean (± S.D.) of the vital signs for the five babies was temperature [36.5 °C (± 0.3)], heart rate [146.5/min (± 14)], and oxygen saturation [94% (± 4)]. No severe or moderate side-effects were noted; one baby developed mild dermatitis under the device that was transient and self-limiting, yielding an incidence proportion of 20% and incidence rate of 2.6/100 person-days. None of the mothers reported any discomfort with the use of the device. Temperatures detected from 81 paired readings revealed that those from the wearable sensor were 0.2 °C lower than those detected by clinical thermometers [36.4 (± 0.7) vs 36.6 (± 0.3); < 0.001]. There was also iterative feedback that was useful for hardware and software design specifications of the wearable sensor, the gateway device, and the analytics platform. Lastly, lessons were learnt with regard to the logistics of research team interactions with healthcare professionals and study participants during the hospitalization and post-discharge home phases of the study. Conclusions: The pilot study has shown that it is feasible and acceptable to track KMC adherence as well as maternal and newborn temperatures in a potentially safe manner on a real-time mode for several days’ duration during hospitalization and home phases. The pilot has also helped inform modifications in clinical monitoring, technological modifications, and logistics planning in preparation for the definitive clinical trial.}, keywords = {Health, Remote Neonatal Monitoring and Intervention}, pubstate = {published}, tppubtype = {article} } Background: Remote biomonitoring of vital parameters in hospitals and homes has the potential to improve coverage and quality of maternal and neonatal health. Wearable sensors coupled with modern information and communication technology now offer an opportunity to monitor temperatures and kangaroo mother care (KMC) adherence in a continuous and real-time manner remotely for several days’ duration in hospital and home settings. Using an innovative remote biomonitoring device to measure both temperature and baby position, we undertook a techno-feasibility study in preparation for a clinical trial. Methods: We designed and developed a wearable sensor for tracking KMC adherence and neonatal temperature, using social innovation design principles. After screening mother-infant dyads using clinical and logistic eligibility criteria, we piloted this wearable sensor along with a gateway device and the commercial cellular network. The dyads were recruited during hospitalization and followed up in the hospital and home phases for several days. Simple descriptive statistical analysis was undertaken. Results: Recruitment rate was 50% (6/12), and consenting rate was 83% (5/6) during a 2-month period. These five neonates contributed a total of 39 study days (15 hospital days and 24 home days). Their mean [± standard deviation (S.D.)] birth weight was 1490 (± 244) g. The mean (± S.D.) of the vital signs for the five babies was temperature [36.5 °C (± 0.3)], heart rate [146.5/min (± 14)], and oxygen saturation [94% (± 4)]. No severe or moderate side-effects were noted; one baby developed mild dermatitis under the device that was transient and self-limiting, yielding an incidence proportion of 20% and incidence rate of 2.6/100 person-days. None of the mothers reported any discomfort with the use of the device. Temperatures detected from 81 paired readings revealed that those from the wearable sensor were 0.2 °C lower than those detected by clinical thermometers [36.4 (± 0.7) vs 36.6 (± 0.3); < 0.001]. There was also iterative feedback that was useful for hardware and software design specifications of the wearable sensor, the gateway device, and the analytics platform. Lastly, lessons were learnt with regard to the logistics of research team interactions with healthcare professionals and study participants during the hospitalization and post-discharge home phases of the study. Conclusions: The pilot study has shown that it is feasible and acceptable to track KMC adherence as well as maternal and newborn temperatures in a potentially safe manner on a real-time mode for several days’ duration during hospitalization and home phases. The pilot has also helped inform modifications in clinical monitoring, technological modifications, and logistics planning in preparation for the definitive clinical trial. |
| 2. | Sawant, Omkar; Bhowmick, Anirban; Sreenivas, Thippur V Enhanced directional sensitivity using acoustic dish reflector Conference Forthcoming International Conference on Signal Processing and Communications (SPCOM 2018), 16.-19.07.18, Bangalore (India), Forthcoming. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Sawant2018, title = {Enhanced directional sensitivity using acoustic dish reflector}, author = {Omkar Sawant and Anirban Bhowmick and Thippur V. Sreenivas}, url = {http://www.rbccps.org/wp-content/uploads/2018/05/PID5361497.pdf}, year = {2018}, date = {2018-07-19}, booktitle = {International Conference on Signal Processing and Communications (SPCOM 2018), 16.-19.07.18, Bangalore (India)}, abstract = {An acoustic reflector is a passive device which is used with microphones to reflect and focus sound waves from a longer distance. They are effective for long-range sound recording without intrusion, such as to record wildlife sounds. In this paper, our objective is to investigate the feasibility of using a dish reflector microphone for indoor activity monitoring of large premises. Acoustic gain and frequency response of the microphone with different parabolic, near parabolic and non- parabolic reflectors are compared with that of the same micro- phone without the reflector. It is observed that the use of dish reflector does significantly enhance the directivity and sensitivity of sound recording. Keeping to a moderate size reflector, among various shapes and materials, the best reflector has given a 14 dB gain improvement over microphone without reflector at 0 degree azimuth. We also found that among steel and plastic dish reflector of approximately same size and shape, steel dish reflector does give a higher performance as expected. The increased directivity of the dish reflector is giving a significant improvement in indoor monitoring and also for sound source tracking.}, keywords = {Sensing and Actuation Systems}, pubstate = {forthcoming}, tppubtype = {conference} } An acoustic reflector is a passive device which is used with microphones to reflect and focus sound waves from a longer distance. They are effective for long-range sound recording without intrusion, such as to record wildlife sounds. In this paper, our objective is to investigate the feasibility of using a dish reflector microphone for indoor activity monitoring of large premises. Acoustic gain and frequency response of the microphone with different parabolic, near parabolic and non- parabolic reflectors are compared with that of the same micro- phone without the reflector. It is observed that the use of dish reflector does significantly enhance the directivity and sensitivity of sound recording. Keeping to a moderate size reflector, among various shapes and materials, the best reflector has given a 14 dB gain improvement over microphone without reflector at 0 degree azimuth. We also found that among steel and plastic dish reflector of approximately same size and shape, steel dish reflector does give a higher performance as expected. The increased directivity of the dish reflector is giving a significant improvement in indoor monitoring and also for sound source tracking. |
| 3. | Kumar, Saurabh; Amrutur, Bharadwaj; Asokan, Sundarrajan Evaluation of Fiber Bragg Grating sensor interrogation using InGaAs linear detector arrays and Gaussian approximation on embedded hardware Journal Article Review of Scientific Instruments, 89 (2), 2018. Abstract | BibTeX | Tags: Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing | Links: @article{Kumar2018b, title = {Evaluation of Fiber Bragg Grating sensor interrogation using InGaAs linear detector arrays and Gaussian approximation on embedded hardware}, author = {Saurabh Kumar and Bharadwaj Amrutur and Sundarrajan Asokan}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/1.5022548.pdf}, doi = {10.1063/1.5022548}, year = {2018}, date = {2018-02-28}, journal = {Review of Scientific Instruments}, volume = {89}, number = {2}, abstract = {Fiber Bragg Grating (FBG) sensors have become popular for applications related to structural health monitoring, biomedical engineering, and robotics. However, for successful large scale adoption, FBG interrogation systems are as important as sensor characteristics. Apart from accuracy, the required number of FBG sensors per fiber and the distance between the device in which the sensors are used and the interrogation system also influence the selection of the interrogation technique. For several measurement devices developed for applications in biomedical engineering and robotics, only a few sensors per fiber are required and the device is close to the interrogation system. For these applications, interrogation systems based on InGaAs linear detector arrays provide a good choice. However, their resolution is dependent on the algorithms used for curve fitting. In this work, a detailed analysis of the choice of algorithm using the Gaussian approximation for the FBG spectrum and the number of pixels used for curve fitting on the errors is provided. The points where the maximum errors occur have been identified. All comparisons for wavelength shift detection have been made against another interrogation system based on the tunable swept laser. It has been shown that maximum errors occur when the wavelength shift is such that one new pixel is included for curve fitting. It has also been shown that an algorithm with lower computation cost compared to the more popular methods using iterative non-linear least squares estimation can be used without leading to the loss of accuracy. The algorithm has been implemented on embedded hardware, and a speed-up of approximately six times has been observed.}, keywords = {Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing}, pubstate = {published}, tppubtype = {article} } Fiber Bragg Grating (FBG) sensors have become popular for applications related to structural health monitoring, biomedical engineering, and robotics. However, for successful large scale adoption, FBG interrogation systems are as important as sensor characteristics. Apart from accuracy, the required number of FBG sensors per fiber and the distance between the device in which the sensors are used and the interrogation system also influence the selection of the interrogation technique. For several measurement devices developed for applications in biomedical engineering and robotics, only a few sensors per fiber are required and the device is close to the interrogation system. For these applications, interrogation systems based on InGaAs linear detector arrays provide a good choice. However, their resolution is dependent on the algorithms used for curve fitting. In this work, a detailed analysis of the choice of algorithm using the Gaussian approximation for the FBG spectrum and the number of pixels used for curve fitting on the errors is provided. The points where the maximum errors occur have been identified. All comparisons for wavelength shift detection have been made against another interrogation system based on the tunable swept laser. It has been shown that maximum errors occur when the wavelength shift is such that one new pixel is included for curve fitting. It has also been shown that an algorithm with lower computation cost compared to the more popular methods using iterative non-linear least squares estimation can be used without leading to the loss of accuracy. The algorithm has been implemented on embedded hardware, and a speed-up of approximately six times has been observed. |
| 4. | George, Jude Baby; Abraham, Grace; Rashid, Zubin; Amrutur, Bharadwaj; Sikdar, Sujit Random neuronal ensembles can inherently do context dependent coarse conjunctive encoding of input stimulus without any specific training Journal Article Scientific Reports, 8 , pp. 1-10, 2018. Abstract | BibTeX | Tags: Systems Engineering | Links: @article{George2018b, title = {Random neuronal ensembles can inherently do context dependent coarse conjunctive encoding of input stimulus without any specific training}, author = {Jude Baby George and Grace Abraham and Zubin Rashid and Bharadwaj Amrutur and Sujit Sikdar}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/41598_2018_Article_19462.pdf}, doi = {10.1038/s41598-018-19462-3}, year = {2018}, date = {2018-01-23}, journal = {Scientific Reports}, volume = {8}, pages = {1-10}, abstract = {Conjunctive encoding of inputs has been hypothesized to be a key feature in the computational capabilities of the brain. This has been inferred based on behavioral studies and electrophysiological recording from animals. In this report, we show that random neuronal ensembles grown on multi-electrode array perform a coarse-conjunctive encoding for a sequence of inputs with the first input setting the context. Such an encoding scheme creates similar yet unique population codes at the output of the ensemble, for related input sequences, which can then be decoded via a simple perceptron and hence a single STDP neuron layer. The random neuronal ensembles allow for pattern generalization and novel sequence classification without needing any specific learning or training of the ensemble. Such a representation of the inputs as population codes of neuronal ensemble outputs, has inherent redundancy and is suitable for further decoding via even probabilistic/random connections to subsequent neuronal layers. We reproduce this behavior in a mathematical model to show that a random neuronal network with a mix of excitatory and inhibitory neurons and sufficient connectivity creates similar coarse-conjunctive encoding of input sequences.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {article} } Conjunctive encoding of inputs has been hypothesized to be a key feature in the computational capabilities of the brain. This has been inferred based on behavioral studies and electrophysiological recording from animals. In this report, we show that random neuronal ensembles grown on multi-electrode array perform a coarse-conjunctive encoding for a sequence of inputs with the first input setting the context. Such an encoding scheme creates similar yet unique population codes at the output of the ensemble, for related input sequences, which can then be decoded via a simple perceptron and hence a single STDP neuron layer. The random neuronal ensembles allow for pattern generalization and novel sequence classification without needing any specific learning or training of the ensemble. Such a representation of the inputs as population codes of neuronal ensemble outputs, has inherent redundancy and is suitable for further decoding via even probabilistic/random connections to subsequent neuronal layers. We reproduce this behavior in a mathematical model to show that a random neuronal network with a mix of excitatory and inhibitory neurons and sufficient connectivity creates similar coarse-conjunctive encoding of input sequences. |
| 5. | Mony, Prem; Thankachan, Prashanth; Bhat, Swarnarekha; Rao, Suman; Washington, Maryann; Antony, Sumi; Thomas, Annamma; Nagarajarao, Sheela C; Rao, Hiteshwar; Amrutur, Bharadwaj Remote biomonitoring of temperatures in mothers and newborns: Design, development and testing of a wearable sensor device in a tertiary-care hospital in southern India Journal Article BMJ Innovations, pp. 1-8, 2018. Abstract | BibTeX | Tags: Health, Remote Neonatal Monitoring and Intervention | Links: @article{Mony2018b, title = {Remote biomonitoring of temperatures in mothers and newborns: Design, development and testing of a wearable sensor device in a tertiary-care hospital in southern India}, author = {Prem Mony and Prashanth Thankachan and Swarnarekha Bhat and Suman Rao and Maryann Washington and Sumi Antony and Annamma Thomas and Sheela C Nagarajarao and Hiteshwar Rao and Bharadwaj Amrutur}, url = {http://www.rbccps.org/wp-content/uploads/2018/06/bmjinnov-2016-000153.full_.pdf}, doi = {10.1136/bmjinnov-2016-000153}, year = {2018}, date = {2018-02-14}, journal = {BMJ Innovations}, pages = {1-8}, abstract = {Objective: Newer technologies such as wearables, sensors, mobile telephony and computing offer opportunities to monitor vital physiological parameters and tackle healthcare problems, thereby improving access and quality of care. We describe the design, development and testing of a wearable sensor device for remote biomonitoring of body temperatures in mothers and newborns in southern India. Methods: Based on client needs and technological requirements, a wearable sensor device was designed and developed using principles of ‘social innovation’ design. The device underwent multiple iterations in product design and engineering based on user feedback, and then following preclinical testing, a techno- feasibility study and clinical trial were undertaken in a tertiary-care teaching hospital in Bangalore, India. Clinical trial phases I and IIa for evaluation of safety and efficacy were undertaken in the following sequence: 7 healthy adult volunteers; 18 healthy mothers; 3 healthy babies; 10 stable babies in the neonatal care intensive unit and 1 baby with morbidities. Time stamped skin temperature readings obtained at 5 min intervals over a 1-hour period from the device secured on upper arms of mothers and abdomen of neonates were compared against readings from thermometers used routinely in clinical practice. Results: Devices were comfortably secured on to adults and neonates, and data were efficiently transmitted via the gateway device for secure storage and retrieval for analysis. The mean skin temperatures in mothers were lower than the axillary temperatures by 2°C; and in newborns, there was a precision of –0.5°C relative to axillary measurements. While occasional minimal adverse events were noted in healthy volunteers, no adverse events were noted in mothers or neonates. Conclusions: This proof-of-concept study shows that this device is promising in terms of feasibility, safety and accuracy (with appropriate calibration) with potential for further refinements in device accuracy and pursuit of further phases of clinical research for improved maternal and neonatal health.}, keywords = {Health, Remote Neonatal Monitoring and Intervention}, pubstate = {published}, tppubtype = {article} } Objective: Newer technologies such as wearables, sensors, mobile telephony and computing offer opportunities to monitor vital physiological parameters and tackle healthcare problems, thereby improving access and quality of care. We describe the design, development and testing of a wearable sensor device for remote biomonitoring of body temperatures in mothers and newborns in southern India. Methods: Based on client needs and technological requirements, a wearable sensor device was designed and developed using principles of ‘social innovation’ design. The device underwent multiple iterations in product design and engineering based on user feedback, and then following preclinical testing, a techno- feasibility study and clinical trial were undertaken in a tertiary-care teaching hospital in Bangalore, India. Clinical trial phases I and IIa for evaluation of safety and efficacy were undertaken in the following sequence: 7 healthy adult volunteers; 18 healthy mothers; 3 healthy babies; 10 stable babies in the neonatal care intensive unit and 1 baby with morbidities. Time stamped skin temperature readings obtained at 5 min intervals over a 1-hour period from the device secured on upper arms of mothers and abdomen of neonates were compared against readings from thermometers used routinely in clinical practice. Results: Devices were comfortably secured on to adults and neonates, and data were efficiently transmitted via the gateway device for secure storage and retrieval for analysis. The mean skin temperatures in mothers were lower than the axillary temperatures by 2°C; and in newborns, there was a precision of –0.5°C relative to axillary measurements. While occasional minimal adverse events were noted in healthy volunteers, no adverse events were noted in mothers or neonates. Conclusions: This proof-of-concept study shows that this device is promising in terms of feasibility, safety and accuracy (with appropriate calibration) with potential for further refinements in device accuracy and pursuit of further phases of clinical research for improved maternal and neonatal health. |
2017 |
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| 6. | Sekuboyina, Anjany Kumar; Devarakonda, Surya Teja; Seelamantula, Chandra Sekhar A convolutional neural network approach for abnormality detection in wireless capsule endoscopy Conference Proceedings of the 2017 IEEE International Symposium on Biomedical Imaging, 18.-21.04.2017, Melbourne (Australia), 2017. Abstract | BibTeX | Tags: Cyber Surgery and Remote Patient Care, Health | Links: @conference{Sekuboyina2017, title = {A convolutional neural network approach for abnormality detection in wireless capsule endoscopy}, author = {Anjany Kumar Sekuboyina and Surya Teja Devarakonda and Chandra Sekhar Seelamantula}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/07950698.pdf}, doi = {10.1109/ISBI.2017.7950698}, year = {2017}, date = {2017-06-19}, booktitle = {Proceedings of the 2017 IEEE International Symposium on Biomedical Imaging, 18.-21.04.2017, Melbourne (Australia)}, pages = {1057-1060}, abstract = {In wireless capsule endoscopy (WCE), a swallowable miniature optical endoscope is used to transmit color images of the gastrointestinal tract. However, the number of images transmitted is large, taking a significant amount of the medical expert’s time to review the scan. In this paper, we propose a technique to automate the abnormality detection in WCE images. We split the image into several patches and extract features pertaining to each block using a convolutional neural network (CNN) to increase their generality while overcoming the drawbacks of manually crafted features. We intend to exploit the importance of color information for the task. Experiments are performed to determine the optimal color space components for feature extraction and classifier design. We ob- tained an area under receiver-operating-characteristic (ROC) curve of approximately 0.8 on a dataset containing multiple abnormalities, namely, aphthae, bleeding, chylous cysts, lymphangiectasias, polypoids, stenoses, ulcers, and villous oedema.}, keywords = {Cyber Surgery and Remote Patient Care, Health}, pubstate = {published}, tppubtype = {conference} } In wireless capsule endoscopy (WCE), a swallowable miniature optical endoscope is used to transmit color images of the gastrointestinal tract. However, the number of images transmitted is large, taking a significant amount of the medical expert’s time to review the scan. In this paper, we propose a technique to automate the abnormality detection in WCE images. We split the image into several patches and extract features pertaining to each block using a convolutional neural network (CNN) to increase their generality while overcoming the drawbacks of manually crafted features. We intend to exploit the importance of color information for the task. Experiments are performed to determine the optimal color space components for feature extraction and classifier design. We ob- tained an area under receiver-operating-characteristic (ROC) curve of approximately 0.8 on a dataset containing multiple abnormalities, namely, aphthae, bleeding, chylous cysts, lymphangiectasias, polypoids, stenoses, ulcers, and villous oedema. |
| 7. | Bhargava, Srivatsa; Gorur, Pushkar; Amrutur, Bharadwaj A distributed object detector-tracker aided video encoder for smart camera networks Conference Proceedings of the 11th International Conference on Distributed Smart Cameras (ICDSC), 05.-07.09.17, Stanford (USA), 2017. Abstract | BibTeX | Tags: Efficient architectures and algorithms for distributed video analytics for Smart Cities, Modeling and Simulation and Analytics | Links: @conference{Srivatsa2017, title = {A distributed object detector-tracker aided video encoder for smart camera networks}, author = {Srivatsa Bhargava and Pushkar Gorur and Bharadwaj Amrutur}, doi = {10.1145/3131885.3131920}, year = {2017}, date = {2017-09-07}, booktitle = {Proceedings of the 11th International Conference on Distributed Smart Cameras (ICDSC), 05.-07.09.17, Stanford (USA)}, pages = {69-75}, abstract = {In this paper, we propose a Region of Interest (ROI) modulated H.264 video encoder system, based on a distributed object detector-tracker framework, for smart camera networks. Locations of objects of interest, as determined by detector-tracker are used to semantically partition each frame into regions assigned with multiple levels of importance. A distributed architecture is proposed to implement the object detector-tracker framework to mitigate the computational cost. Further, a rate control algorithm with modified Rate-Distortion(RD) cost is proposed to determine Quantization Parameter(QP) and skip decision of Macro Blocks based on their relative levels of importance. Our experiments show that, the proposed system achieves upto 3x reduction in bitrate without significant reduction in PSNR of ROI(head-shoulder region of pedestrians). We also demonstrate the trade-off between total computational cost and compression possible with the proposed distributed detector-tracker framework. }, keywords = {Efficient architectures and algorithms for distributed video analytics for Smart Cities, Modeling and Simulation and Analytics}, pubstate = {published}, tppubtype = {conference} } In this paper, we propose a Region of Interest (ROI) modulated H.264 video encoder system, based on a distributed object detector-tracker framework, for smart camera networks. Locations of objects of interest, as determined by detector-tracker are used to semantically partition each frame into regions assigned with multiple levels of importance. A distributed architecture is proposed to implement the object detector-tracker framework to mitigate the computational cost. Further, a rate control algorithm with modified Rate-Distortion(RD) cost is proposed to determine Quantization Parameter(QP) and skip decision of Macro Blocks based on their relative levels of importance. Our experiments show that, the proposed system achieves upto 3x reduction in bitrate without significant reduction in PSNR of ROI(head-shoulder region of pedestrians). We also demonstrate the trade-off between total computational cost and compression possible with the proposed distributed detector-tracker framework. |
| 8. | Ramaswamy, Arunselvan; Bhatnagar, Shalabh A generalization of the Borkar-Meyn theorem for stochastic recursive inclusions Journal Article Mathematics of Operations Research, 42 (3), pp. 648-661, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Ramaswamy2017, title = {A generalization of the Borkar-Meyn theorem for stochastic recursive inclusions}, author = {Arunselvan Ramaswamy and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/moor.2016.0821.pdf}, doi = {10.1287/moor.2016.0821}, year = {2017}, date = {2017-08-31}, journal = {Mathematics of Operations Research}, volume = {42}, number = {3}, pages = {648-661}, abstract = {In this paper, the stability theorem of Borkar and Meyn is extended to include the case when the mean field is a set-valued map. Two different sets of sufficient conditions are presented that guarantee the “stability and convergence” of stochastic recursive inclusions. Our work builds on the works of Benaïm, Hofbauer and Sorin as well as Borkar and Meyn. As a corollary to one of the main theorems, a natural generalization of the Borkar and Meyn theorem follows. In addition, the original theorem of Borkar and Meyn is shown to hold under slightly relaxed assumptions. As an application to one of the main theorems, we discuss a solution to the “approximate drift problem.” Finally, we analyze the stochastic gradient algorithm with “constant-error gradient estimators” as yet another application of our main result.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } In this paper, the stability theorem of Borkar and Meyn is extended to include the case when the mean field is a set-valued map. Two different sets of sufficient conditions are presented that guarantee the “stability and convergence” of stochastic recursive inclusions. Our work builds on the works of Benaïm, Hofbauer and Sorin as well as Borkar and Meyn. As a corollary to one of the main theorems, a natural generalization of the Borkar and Meyn theorem follows. In addition, the original theorem of Borkar and Meyn is shown to hold under slightly relaxed assumptions. As an application to one of the main theorems, we discuss a solution to the “approximate drift problem.” Finally, we analyze the stochastic gradient algorithm with “constant-error gradient estimators” as yet another application of our main result. |
| 9. | Rathod, Nihesh; Subramanian, Renu; Sundaresan, Rajesh A GIS- and measurement-aided framework for placement of relays in a heterogeneous propagation environment Conference Forthcoming Proceedings of the 9th International Conference on Communication Systems and Networks (COMSNETS), 04.-08.01.17, Bangalore, Forthcoming. BibTeX | Tags: Design of large-scale IoT networks, Smart Campus Water Management: Closing the IoT Loop from Network to Knowledge @conference{Rathod2017, title = {A GIS- and measurement-aided framework for placement of relays in a heterogeneous propagation environment}, author = {Nihesh Rathod and Renu Subramanian and Rajesh Sundaresan}, year = {2017}, date = {2017-01-08}, booktitle = {Proceedings of the 9th International Conference on Communication Systems and Networks (COMSNETS), 04.-08.01.17, Bangalore}, keywords = {Design of large-scale IoT networks, Smart Campus Water Management: Closing the IoT Loop from Network to Knowledge}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 10. | Joseph, Ajin George; Bhatnagar, Shalabh A model based search method for prediction in model-free Markov decision process Conference Proceedings of the 2017 International Joint Conference on Neural Networks (IJCNN), 14.-19.05.17, Anchorage (USA), 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @conference{Joseph2017, title = {A model based search method for prediction in model-free Markov decision process}, author = {Ajin George Joseph and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/07965851.pdf}, doi = {10.1109/IJCNN.2017.7965851}, year = {2017}, date = {2017-07-03}, booktitle = {Proceedings of the 2017 International Joint Conference on Neural Networks (IJCNN), 14.-19.05.17, Anchorage (USA)}, pages = {170-177}, abstract = {In this paper, we provide a new algorithm for the problem of prediction in the model-free MDP setting, i.e., estimating the value function of a given policy using the linear function approximation architecture, with memory and computation costs scaling quadratically in the size of the feature set. The algorithm is a multi-timescale variant of the very popular cross entropy (CE) method which is a model based search method to find the global optimum of a real-valued function. This is the first time a model based search method is used for the prediction problem. A proof of convergence using the ODE method is provided. The theoretical results are supplemented with experimental comparisons. The algorithm achieves good performance fairly consistently on many benchmark problems.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {conference} } In this paper, we provide a new algorithm for the problem of prediction in the model-free MDP setting, i.e., estimating the value function of a given policy using the linear function approximation architecture, with memory and computation costs scaling quadratically in the size of the feature set. The algorithm is a multi-timescale variant of the very popular cross entropy (CE) method which is a model based search method to find the global optimum of a real-valued function. This is the first time a model based search method is used for the prediction problem. A proof of convergence using the ODE method is provided. The theoretical results are supplemented with experimental comparisons. The algorithm achieves good performance fairly consistently on many benchmark problems. |
| 11. | Gayarthi, H; Aparna, P M; Verma, Ashish A review of studies on understanding crowd dynamics in the context of crowd safety in mass religious gatherings Journal Article International Journal of Disaster Risk Reduction, 2017. Abstract | BibTeX | Tags: The Kumbh Mela Experiment | Links: @article{Gayarthi2017, title = {A review of studies on understanding crowd dynamics in the context of crowd safety in mass religious gatherings}, author = {H. Gayarthi and P. M. Aparna and Ashish Verma}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/1-s2.0-S2212420917302212-main.pdf}, doi = {10.1016/j.ijdrr.2017.07.017}, year = {2017}, date = {2017-08-03}, journal = {International Journal of Disaster Risk Reduction}, abstract = {Understanding the principles and applications of crowd dynamics in mass gatherings is very important, specifically with respect to crowd risk analysis and crowd safety. Historical trends from India and other countries suggest that the stampedes in mass gatherings, especially in religious events occur frequently highlighting the importance of studying the crowd behaviour more scientifically. This is required to support appropriate and timely crowd management principles, in the planning of crowd control measures and provision of early warning systems at mass gatherings. Common pedestrian behaviours in crowd like group formation, self-organization, leader follower effect, queue formation and bottleneck conditions have substantial influence on crowd dynamics. It is important not to let a single aspect go overlooked with respect to mass gatherings since it can lead to major stampedes. Kumbh Mela, one of the largest mass religious gatherings in the world, features these different crowd scenarios observed often in the same event area and thus provides a unique opportunity to study the crowd behaviour in a holistic way. Understanding these pedestrian behaviours and having a clear understanding of the normal behaviour may provide opportunities to change crowd dynamics and overcome the adverse effects resulting in safer mass religious gatherings in future. This paper provides an exhaustive review of the current understanding of crowd dynamics and explores the modelling techniques that are available to enhance crowd safety. The purpose of this literature review is to improve the understanding of crowd dynamics,and highlight the research gaps in the context of crowd safety in mass religious gatherings like Kumbh Mela.}, keywords = {The Kumbh Mela Experiment}, pubstate = {published}, tppubtype = {article} } Understanding the principles and applications of crowd dynamics in mass gatherings is very important, specifically with respect to crowd risk analysis and crowd safety. Historical trends from India and other countries suggest that the stampedes in mass gatherings, especially in religious events occur frequently highlighting the importance of studying the crowd behaviour more scientifically. This is required to support appropriate and timely crowd management principles, in the planning of crowd control measures and provision of early warning systems at mass gatherings. Common pedestrian behaviours in crowd like group formation, self-organization, leader follower effect, queue formation and bottleneck conditions have substantial influence on crowd dynamics. It is important not to let a single aspect go overlooked with respect to mass gatherings since it can lead to major stampedes. Kumbh Mela, one of the largest mass religious gatherings in the world, features these different crowd scenarios observed often in the same event area and thus provides a unique opportunity to study the crowd behaviour in a holistic way. Understanding these pedestrian behaviours and having a clear understanding of the normal behaviour may provide opportunities to change crowd dynamics and overcome the adverse effects resulting in safer mass religious gatherings in future. This paper provides an exhaustive review of the current understanding of crowd dynamics and explores the modelling techniques that are available to enhance crowd safety. The purpose of this literature review is to improve the understanding of crowd dynamics,and highlight the research gaps in the context of crowd safety in mass religious gatherings like Kumbh Mela. |
| 12. | Lakshminarayanan, Chandrashekar; Bhatnagar, Shalabh A stability criterion for two-timescale stochastic approximation schemes Journal Article Automatica, 79 , pp. 108-114, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Lakshminarayanan2017, title = {A stability criterion for two-timescale stochastic approximation schemes}, author = {Chandrashekar Lakshminarayanan and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/1-s2.0-S0005109816305222-main.pdf}, doi = {10.1016/j.automatica.2016.12.014}, year = {2017}, date = {2017-05-31}, journal = {Automatica}, volume = {79}, pages = {108-114}, abstract = {We present the first sufficient conditions that guarantee stability of two-timescale stochastic approxima- tion schemes. Our analysis is based on the ordinary differential equation (ODE) method and is an extension of the results in Borkar and Meyn (2000) for single-timescale schemes. As an application of our result, we show the stability of iterates in a two-timescale stochastic approximation scheme arising in reinforce- ment learning.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } We present the first sufficient conditions that guarantee stability of two-timescale stochastic approxima- tion schemes. Our analysis is based on the ordinary differential equation (ODE) method and is an extension of the results in Borkar and Meyn (2000) for single-timescale schemes. As an application of our result, we show the stability of iterates in a two-timescale stochastic approximation scheme arising in reinforce- ment learning. |
| 13. | A., Prashanth L; Bhatnagar, Shalabh; Fu, Michael; Marcus, Steve Adaptive system optimization using random directions stochastic approximation Journal Article IEEE Transactions on Automatic Control, 62 (5), pp. 2223-2238, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Prashanth2017, title = {Adaptive system optimization using random directions stochastic approximation}, author = {Prashanth L. A. and Shalabh Bhatnagar and Michael Fu and Steve Marcus}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/07544612.pdf}, doi = {10.1109/TAC.2016.2600643}, year = {2017}, date = {2017-05-31}, journal = {IEEE Transactions on Automatic Control}, volume = {62}, number = {5}, pages = {2223-2238}, abstract = {We present new algorithms for simulation op- timization using random directions stochastic approxima- tion (RDSA). These include first-order (gradient) as well as second-order (Newton) schemes. We incorporate both continuous-valued as well as discrete-valued perturbations into both types of algorithms. The former are chosen to be independent and identically distributed (i.i.d.) symmet- ric uniformly distributed random variables (r.v.), while the latter are i.i.d. asymmetric Bernoulli r.v.s. Our Newton al- gorithm, with a novel Hessian estimation scheme, requires N -dimensional perturbations and three loss measurements per iteration, whereas the simultaneous perturbation New- ton search algorithm of [1] requires 2N-dimensional per- turbations and four loss measurements per iteration. We prove the asymptotic unbiasedness of both gradient and Hessian estimates and asymptotic (strong) convergence for both first-order and second-order schemes. We also pro- vide asymptotic normality results, which in particular estab- lish that the asymmetric Bernoulli variant of Newton RDSA method is better than 2SPSA of [1]. Numerical experiments are used to validate the theoretical results.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } We present new algorithms for simulation op- timization using random directions stochastic approxima- tion (RDSA). These include first-order (gradient) as well as second-order (Newton) schemes. We incorporate both continuous-valued as well as discrete-valued perturbations into both types of algorithms. The former are chosen to be independent and identically distributed (i.i.d.) symmet- ric uniformly distributed random variables (r.v.), while the latter are i.i.d. asymmetric Bernoulli r.v.s. Our Newton al- gorithm, with a novel Hessian estimation scheme, requires N -dimensional perturbations and three loss measurements per iteration, whereas the simultaneous perturbation New- ton search algorithm of [1] requires 2N-dimensional per- turbations and four loss measurements per iteration. We prove the asymptotic unbiasedness of both gradient and Hessian estimates and asymptotic (strong) convergence for both first-order and second-order schemes. We also pro- vide asymptotic normality results, which in particular estab- lish that the asymmetric Bernoulli variant of Newton RDSA method is better than 2SPSA of [1]. Numerical experiments are used to validate the theoretical results. |
| 14. | Joseph, Ajin George; Bhatnagar, Shalabh An incremental fast policy search using a single sample path Conference Proceedings of the 7th International Conference on Pattern Recognition and Machine Intelligence (PReMI), 05.-08.12.17, Kolkata (India), Lecture Notes in Computer Science 2017. Abstract | BibTeX | Tags: Machine Learning | Links: @conference{Joseph2017c, title = {An incremental fast policy search using a single sample path}, author = {Ajin George Joseph and Shalabh Bhatnagar}, doi = {10.1007/978-3-319-69900-4_1}, year = {2017}, date = {2017-11-01}, booktitle = {Proceedings of the 7th International Conference on Pattern Recognition and Machine Intelligence (PReMI), 05.-08.12.17, Kolkata (India)}, pages = {3-10}, series = {Lecture Notes in Computer Science}, abstract = {In this paper, we consider the control problem in a reinforcement learning setting with large state and action spaces. The control problem most commonly addressed in the contemporary literature is to find an optimal policy which optimizes the long run γ-discounted transition costs, where γ∈[0,1). They also assume access to a generative model/simulator of the underlying MDP with the hidden premise that realization of the system dynamics of the MDP for arbitrary policies in the form of sample paths can be obtained with ease from the model. In this paper, we consider a cost function which is the expectation of a approximate value function w.r.t. the steady state distribution of the Markov chain induced by the policy, without having access to the generative model. We assume that a single sample path generated using a priori chosen behaviour policy is made available. In this information restricted setting, we solve the generalized control problem using the incremental cross entropy method. The proposed algorithm is shown to converge to the solution which is globally optimal relative to the behaviour policy.}, keywords = {Machine Learning}, pubstate = {published}, tppubtype = {conference} } In this paper, we consider the control problem in a reinforcement learning setting with large state and action spaces. The control problem most commonly addressed in the contemporary literature is to find an optimal policy which optimizes the long run γ-discounted transition costs, where γ∈[0,1). They also assume access to a generative model/simulator of the underlying MDP with the hidden premise that realization of the system dynamics of the MDP for arbitrary policies in the form of sample paths can be obtained with ease from the model. In this paper, we consider a cost function which is the expectation of a approximate value function w.r.t. the steady state distribution of the Markov chain induced by the policy, without having access to the generative model. We assume that a single sample path generated using a priori chosen behaviour policy is made available. In this information restricted setting, we solve the generalized control problem using the incremental cross entropy method. The proposed algorithm is shown to converge to the solution which is globally optimal relative to the behaviour policy. |
| 15. | Amrutur, Bharadwaj; Rajaraman, Vasanth; Acharya, Srikrishna; Ramesh, Rakshit; Joglekar, Ashish; Sharma, Abhay; Simmhan, Yogesh; Lele, Abhijit; Mahesh, Ashwin; Sankaran, Sathya An open Smart City IoT test bed: Street light poles as Smart City spines Conference Proceedings of the 2nd International Conference on Internet-of-Things Design and Implementation (IoTDI), 18.-21.04.17, Pittsburgh (USA), 2017. Abstract | BibTeX | Tags: Smart City test bed, Systems Engineering | Links: @conference{Amrutur2017, title = {An open Smart City IoT test bed: Street light poles as Smart City spines}, author = {Bharadwaj Amrutur and Vasanth Rajaraman and Srikrishna Acharya and Rakshit Ramesh and Ashish Joglekar and Abhay Sharma and Yogesh Simmhan and Abhijit Lele and Ashwin Mahesh and Sathya Sankaran}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/p323-Amrutur.pdf}, doi = {10.1145/3054977.3057303}, year = {2017}, date = {2017-06-15}, booktitle = {Proceedings of the 2nd International Conference on Internet-of-Things Design and Implementation (IoTDI), 18.-21.04.17, Pittsburgh (USA)}, pages = {323-324}, abstract = {Street light poles will be a key enabler for a smart city's hardware infrastructure, thanks to their ubiquity throughout the city as well as access to power. We propose an IoT test bed around light poles for the city, with a modular hardware and software architecture to enable experimentation with various technologies.}, keywords = {Smart City test bed, Systems Engineering}, pubstate = {published}, tppubtype = {conference} } Street light poles will be a key enabler for a smart city's hardware infrastructure, thanks to their ubiquity throughout the city as well as access to power. We propose an IoT test bed around light poles for the city, with a modular hardware and software architecture to enable experimentation with various technologies. |
| 16. | Ramaswamy, A; Bhatnagar, Shalabh Analysis of gradient descent methods with non-diminishing bounded errors Journal Article IEEE Transactions on Automatic Control, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Ramaswamy2017b, title = {Analysis of gradient descent methods with non-diminishing bounded errors }, author = {A. Ramaswamy and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/08016343.pdf}, doi = {10.1109/TAC.2017.2744598}, year = {2017}, date = {2017-08-24}, journal = {IEEE Transactions on Automatic Control}, abstract = {The main aim of this paper is to provide an analysis of gradient descent (GD) algorithms with gradient errors that do not necessarily vanish, asymptotically. In particular, sufficient conditions are presented for both stability (almost sure boundedness of the iterates) and convergence of GD with bounded, (possibly) non-diminishing gradient errors. In addition to ensuring stability, such an algorithm is shown to converge to a small neighborhood of the minimum set, which depends on the gradient errors. It is worth noting that the main result of this paper can be used to show that GD with asymptotically vanishing errors indeed converges to the minimum set. The results presented herein are not only more general when compared to previous results, but our analysis of GD with errors is new to the literature to the best of our knowledge. Our work extends the contributions of Mangasarian and Solodov, Bertsekas and Tsitsiklis and Tadic and Doucet. Using our framework, a simple yet effective implementation of GD using simultaneous perturbation stochastic approximations (SP SA), with constant sensitivity parameters, is presented. Another important improvement over many previous results is that there are no “additional” restrictions imposed on the step-sizes. In machine learning applications where step-sizes are related to learning rates, our assumptions, unlike those of other papers, do not affect these learning rates. Finally, we present experimental results to validate our theory.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } The main aim of this paper is to provide an analysis of gradient descent (GD) algorithms with gradient errors that do not necessarily vanish, asymptotically. In particular, sufficient conditions are presented for both stability (almost sure boundedness of the iterates) and convergence of GD with bounded, (possibly) non-diminishing gradient errors. In addition to ensuring stability, such an algorithm is shown to converge to a small neighborhood of the minimum set, which depends on the gradient errors. It is worth noting that the main result of this paper can be used to show that GD with asymptotically vanishing errors indeed converges to the minimum set. The results presented herein are not only more general when compared to previous results, but our analysis of GD with errors is new to the literature to the best of our knowledge. Our work extends the contributions of Mangasarian and Solodov, Bertsekas and Tsitsiklis and Tadic and Doucet. Using our framework, a simple yet effective implementation of GD using simultaneous perturbation stochastic approximations (SP SA), with constant sensitivity parameters, is presented. Another important improvement over many previous results is that there are no “additional” restrictions imposed on the step-sizes. In machine learning applications where step-sizes are related to learning rates, our assumptions, unlike those of other papers, do not affect these learning rates. Finally, we present experimental results to validate our theory. |
| 17. | Shyam, Pranav; Gupta, Shubham; Dukkipati, Ambedkar Attentive recurrent comparators Conference Proceedings of the 34th International Conference on Machine Learning (ICML 2017), 06.-11.08.17, Sydney (Australia), 70 , 2017. Abstract | BibTeX | Tags: CyberGut: A Bio-CPS approach to understand gut biology | Links: @conference{Shyam2017, title = {Attentive recurrent comparators}, author = {Pranav Shyam and Shubham Gupta and Ambedkar Dukkipati}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/shyam17a.pdf}, year = {2017}, date = {2017-08-11}, booktitle = {Proceedings of the 34th International Conference on Machine Learning (ICML 2017), 06.-11.08.17, Sydney (Australia)}, volume = {70}, pages = {3173-3181}, abstract = {Rapid learning requires flexible representations to quickly adopt to new evidence. We develop a novel class of models called Attentive Recurrent Comparators (ARCs) that form representations of objects by cycling through them and making observations. Using the representations extracted by ARCs, we develop a way of approximating a dynamic representation space and use it for one- shot learning. In the task of one-shot classifi- cation on the Omniglot dataset, we achieve the state of the art performance with an error rate of 1.5%. This represents the first super-human re- sult achieved for this task with a generic model that uses only pixel information.}, keywords = {CyberGut: A Bio-CPS approach to understand gut biology}, pubstate = {published}, tppubtype = {conference} } Rapid learning requires flexible representations to quickly adopt to new evidence. We develop a novel class of models called Attentive Recurrent Comparators (ARCs) that form representations of objects by cycling through them and making observations. Using the representations extracted by ARCs, we develop a way of approximating a dynamic representation space and use it for one- shot learning. In the task of one-shot classifi- cation on the Omniglot dataset, we achieve the state of the art performance with an error rate of 1.5%. This represents the first super-human re- sult achieved for this task with a generic model that uses only pixel information. |
| 18. | Krishnaswamy, S; P.T., Akhil; Arapostathis, A; Shakkottai, S; Sundaresan, Rajesh Augmenting max-weight with explicit learning for wireless scheduling with switching costs Conference Proceedings of the 2017 IEEE International Conference on Computer Communications (INFOCOM), 01.-04.05.17, Atlanta (USA), 2017. Abstract | BibTeX | Tags: Design of large-scale IoT networks | Links: @conference{Krishnaswamy2017, title = {Augmenting max-weight with explicit learning for wireless scheduling with switching costs}, author = {S. Krishnaswamy and Akhil P.T. and A. Arapostathis and S. Shakkottai and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/08056983.pdf}, doi = {10.1109/INFOCOM.2017.8056983}, year = {2017}, date = {2017-10-05}, booktitle = {Proceedings of the 2017 IEEE International Conference on Computer Communications (INFOCOM), 01.-04.05.17, Atlanta (USA)}, abstract = {In small-cell wireless networks where users are connected to multiple base stations (BSs), it is often advantageous to opportunistically switch off a subset of BSs to minimize energy costs. We consider two types of energy cost: (i) the cost of maintaining a BS in the active state, and (ii) the cost of switching a BS from the active state to inactive state. The problem is to operate the network at the lowest possible energy cost (sum of activation and switching costs) subject to queue stability. In this setting, the traditional approach – a Max-Weight algorithm along with a Lyapunov-based stability argument – does not suffice to show queue stability, essentially due to the temporal co-evolution between channel scheduling and the BS activation decisions induced by the switching cost. Instead, we develop a learning and BS activation algorithm with slow temporal dynamics, and a Max-Weight based channel scheduler that has fast temporal dynamics. We show using convergence of time-inhomogeneous Markov chains, that the co-evolving dynamics of learning, BS activation and queue lengths lead to near optimal average energy costs along with queue stability.}, keywords = {Design of large-scale IoT networks}, pubstate = {published}, tppubtype = {conference} } In small-cell wireless networks where users are connected to multiple base stations (BSs), it is often advantageous to opportunistically switch off a subset of BSs to minimize energy costs. We consider two types of energy cost: (i) the cost of maintaining a BS in the active state, and (ii) the cost of switching a BS from the active state to inactive state. The problem is to operate the network at the lowest possible energy cost (sum of activation and switching costs) subject to queue stability. In this setting, the traditional approach – a Max-Weight algorithm along with a Lyapunov-based stability argument – does not suffice to show queue stability, essentially due to the temporal co-evolution between channel scheduling and the BS activation decisions induced by the switching cost. Instead, we develop a learning and BS activation algorithm with slow temporal dynamics, and a Max-Weight based channel scheduler that has fast temporal dynamics. We show using convergence of time-inhomogeneous Markov chains, that the co-evolving dynamics of learning, BS activation and queue lengths lead to near optimal average energy costs along with queue stability. |
| 19. | Kadavankandy, Arun; Avrachenkov, Konstantin; Cottatellucci, Laura; Sundaresan, Rajesh Belief propagation for subgraph detection with imperfect side-information Conference Proceedings of the 2017 IEEE International Symposium on Information Theory (ISIT), 25.-30.06.17, Aachen (Germany), 2017. Abstract | BibTeX | Tags: Modeling and Simulation and Analytics | Links: @conference{Kadavankandy2017, title = {Belief propagation for subgraph detection with imperfect side-information}, author = {Arun Kadavankandy and Konstantin Avrachenkov and Laura Cottatellucci and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/08006800.pdf}, doi = {10.1109/ISIT.2017.8006800}, year = {2017}, date = {2017-08-15}, booktitle = {Proceedings of the 2017 IEEE International Symposium on Information Theory (ISIT), 25.-30.06.17, Aachen (Germany)}, pages = {1603-1607}, abstract = {We propose a local message passing algorithm based on Belief Propagation (BP) to detect a small hidden Erdos-Rényi (ER) subgraph embedded in a larger sparse ER random graph in the presence of side-information. We consider side-information in the form of revealed subgraph nodes called cues, some of which may be erroneous. Namely, the revealed nodes may not all belong to the subgraph, and it is not known to the algorithm a priori which cues are correct and which are incorrect. We show that asymptotically as the graph size tends to infinity, the expected fraction of misclassified nodes approaches zero for any positive value of a parameter λ, which represents the effective Signal-to-Noise Ratio of the detection problem. Previous works on subgraph detection using BP without side-information showed that BP fails to recover the subgraph when λ <; 1/e. Our results thus demonstrate the substantial gains in having even a small amount of side-information.}, keywords = {Modeling and Simulation and Analytics}, pubstate = {published}, tppubtype = {conference} } We propose a local message passing algorithm based on Belief Propagation (BP) to detect a small hidden Erdos-Rényi (ER) subgraph embedded in a larger sparse ER random graph in the presence of side-information. We consider side-information in the form of revealed subgraph nodes called cues, some of which may be erroneous. Namely, the revealed nodes may not all belong to the subgraph, and it is not known to the algorithm a priori which cues are correct and which are incorrect. We show that asymptotically as the graph size tends to infinity, the expected fraction of misclassified nodes approaches zero for any positive value of a parameter λ, which represents the effective Signal-to-Noise Ratio of the detection problem. Previous works on subgraph detection using BP without side-information showed that BP fails to recover the subgraph when λ <; 1/e. Our results thus demonstrate the substantial gains in having even a small amount of side-information. |
| 20. | Joseph, Ajin George; Bhatnagar, Shalabh Bounds for off-policy prediction in reinforcement learning Conference Proceedings of the 2017 International Joint Conference on Neural Networks (IJCNN), 14.-19.05.17, Anchorage (USA), 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy, Machine Learning | Links: @conference{Joseph2017b, title = {Bounds for off-policy prediction in reinforcement learning}, author = {Ajin George Joseph and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/07966359.pdf}, doi = {10.1109/IJCNN.2017.7966359}, year = {2017}, date = {2017-07-03}, booktitle = {Proceedings of the 2017 International Joint Conference on Neural Networks (IJCNN), 14.-19.05.17, Anchorage (USA)}, pages = {3991-3997}, abstract = {In this paper, we provide for the first time, error bounds for the off-policy prediction in reinforcement learning. The primary objective in off-policy prediction is to estimate the value function of a given target policy of interest using the linear function approximation architecture by utilizing a sample trajectory generated by a behaviour policy which is possibly different from the target policy. The stability of the off-policy prediction has been an open question for a long time. Only recently, could Yu provide a generalized proof, which makes our results more appealing to the reinforcement learning community. The off-policy prediction is useful in complex reinforcement learning settings, where the sample trajectory is hard to obtain and one has to rely on the sample behaviour of the system with respect to an arbitrary policy. We provide here error bound on the solution of the off-policy prediction with respect to a closeness measure between the target and the behaviour policy.}, keywords = {Control and Optimisation and Policy, Machine Learning}, pubstate = {published}, tppubtype = {conference} } In this paper, we provide for the first time, error bounds for the off-policy prediction in reinforcement learning. The primary objective in off-policy prediction is to estimate the value function of a given target policy of interest using the linear function approximation architecture by utilizing a sample trajectory generated by a behaviour policy which is possibly different from the target policy. The stability of the off-policy prediction has been an open question for a long time. Only recently, could Yu provide a generalized proof, which makes our results more appealing to the reinforcement learning community. The off-policy prediction is useful in complex reinforcement learning settings, where the sample trajectory is hard to obtain and one has to rely on the sample behaviour of the system with respect to an arbitrary policy. We provide here error bound on the solution of the off-policy prediction with respect to a closeness measure between the target and the behaviour policy. |
| 21. | Anjana, G R; Kumar, Mohan M S; Amrutur, Bharadwaj Comparison of different controllers for equitable water supply in water networks Conference Proceedings of the 15th International Computing & Control for the Water Industry Conference (CCWI), 05.-07.09.17, Sheffield (UK), 2017. Abstract | BibTeX | Tags: Water | Links: @conference{Anjana2017, title = {Comparison of different controllers for equitable water supply in water networks}, author = {G. R. Anjana and M. S. Mohan Kumar and Bharadwaj Amrutur}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/F108.pdf}, doi = {10.15131/shef.data.c.3867985.v1}, year = {2017}, date = {2017-09-07}, booktitle = {Proceedings of the 15th International Computing & Control for the Water Industry Conference (CCWI), 05.-07.09.17, Sheffield (UK)}, abstract = {Equitable distribution of water among consumers is one of the most important agenda for many water authorities around the world. Many methods have been listed in literature for equitable distribution of water. In recent years, different automatic controller based approaches were also introduced for flow control in water systems. In this work, a comparative study is carried out among dynamic inversion based PID (DI-PID), model predictive control (MPC) and EnKF based PID controllers for flow control applications in real time for a water distribution network – Bangalore inflow water distribution system. It was observed that the DI-PID and EnKF based PID controllers are better than other controllers for equitable distribution of water in a mega city like Bangalore.}, keywords = {Water}, pubstate = {published}, tppubtype = {conference} } Equitable distribution of water among consumers is one of the most important agenda for many water authorities around the world. Many methods have been listed in literature for equitable distribution of water. In recent years, different automatic controller based approaches were also introduced for flow control in water systems. In this work, a comparative study is carried out among dynamic inversion based PID (DI-PID), model predictive control (MPC) and EnKF based PID controllers for flow control applications in real time for a water distribution network – Bangalore inflow water distribution system. It was observed that the DI-PID and EnKF based PID controllers are better than other controllers for equitable distribution of water in a mega city like Bangalore. |
| 22. | Sharma, Abhay; Murthy, Chandra R Computationally tractable algorithms for finding a subset of non-defective items from a large population Journal Article IEEE Transactions on Information Theory, 63 (11), pp. 7149-7165, 2017. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Sharma2017b, title = {Computationally tractable algorithms for finding a subset of non-defective items from a large population}, author = {Abhay Sharma and Chandra R. Murthy }, url = {http://www.rbccps.org/wp-content/uploads/2018/01/08024008.pdf}, doi = {10.1109/TIT.2017.2748143}, year = {2017}, date = {2017-09-01}, journal = {IEEE Transactions on Information Theory}, volume = {63}, number = {11}, pages = {7149-7165}, abstract = {In the classical non-adaptive group testing setup, pools of items are tested together, and the main goal of a recovery algorithm is to identify the complete defective set given the outcomes of different group tests. In contrast, the main goal of a non-defective subset recovery algorithm is to identify a subset of non-defective items given the test outcomes. In this paper, we present a suite of computationally efficient and analytically tractable non-defective subset recovery algorithms. By analyzing the probability of error of the algorithms, we obtain bounds on the number of tests required for non-defective subset recovery with arbitrarily small probability of error. Our analysis accounts for the impact of both the additive noise (false positives) and dilution noise (false negatives). By comparing with information theoretic lower bounds, we show that the upper bounds on the number of tests are orderwise tight up to a log^2 K factor, where K is the number of defective items. We also provide simulation results that compare the relative performance of the different algorithms and reveal insights into their practical utility. The proposed algorithms significantly outperform the straightforward approaches of testing items one-by-one, and of first identifying the defective set and then choosing the non-defective items from the complement set, in terms of the number of measurements required to ensure a given success rate.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } In the classical non-adaptive group testing setup, pools of items are tested together, and the main goal of a recovery algorithm is to identify the complete defective set given the outcomes of different group tests. In contrast, the main goal of a non-defective subset recovery algorithm is to identify a subset of non-defective items given the test outcomes. In this paper, we present a suite of computationally efficient and analytically tractable non-defective subset recovery algorithms. By analyzing the probability of error of the algorithms, we obtain bounds on the number of tests required for non-defective subset recovery with arbitrarily small probability of error. Our analysis accounts for the impact of both the additive noise (false positives) and dilution noise (false negatives). By comparing with information theoretic lower bounds, we show that the upper bounds on the number of tests are orderwise tight up to a log^2 K factor, where K is the number of defective items. We also provide simulation results that compare the relative performance of the different algorithms and reveal insights into their practical utility. The proposed algorithms significantly outperform the straightforward approaches of testing items one-by-one, and of first identifying the defective set and then choosing the non-defective items from the complement set, in terms of the number of measurements required to ensure a given success rate. |
| 23. | Sundaresan, Rajesh Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector Technical Report 2017. BibTeX | Tags: Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector, Energy | Links: @techreport{Sundaresan2017, title = {Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector}, author = {Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2017/06/KeralaEnergyEfficiencyAluva.pdf}, year = {2017}, date = {2017-03-31}, keywords = {Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector, Energy}, pubstate = {published}, tppubtype = {techreport} } |
| 24. | Bora, Ashish; Borkar, Vivek S; Garg, Dinesh; Sundaresan, Rajesh Edge conductance estimation using MCMC Conference Proceedings of the 54th Annual Allerton Conference on Communication, Control, and Computing, 27.-30.09.16, Monticello (USA), 2017. Abstract | BibTeX | Tags: Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector | Links: @conference{Bora2016, title = {Edge conductance estimation using MCMC}, author = {Ashish Bora and Vivek S. Borkar and Dinesh Garg and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/07852230.pdf}, doi = {10.1109/ALLERTON.2016.7852230}, year = {2017}, date = {2017-02-13}, booktitle = {Proceedings of the 54th Annual Allerton Conference on Communication, Control, and Computing, 27.-30.09.16, Monticello (USA)}, pages = {202-208}, abstract = {We propose an iterative and distributed Markov Chain Monte Carlo scheme for estimation of effective edge conductances in a graph. A sample complexity analysis is provided. The theoretical guarantees on the performance of the proposed algorithm are weak compared to those of existing algorithms. But numerical experiments suggest that the algorithm might still be effective while offering the advantages of low per iterate computation and memory requirements.}, keywords = {Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector}, pubstate = {published}, tppubtype = {conference} } We propose an iterative and distributed Markov Chain Monte Carlo scheme for estimation of effective edge conductances in a graph. A sample complexity analysis is provided. The theoretical guarantees on the performance of the proposed algorithm are weak compared to those of existing algorithms. But numerical experiments suggest that the algorithm might still be effective while offering the advantages of low per iterate computation and memory requirements. |
| 25. | Khandelwal, T; Rajwanshi, K; Bharadwaj, P; Garani, S S; Sundaresan, Rajesh Exploiting appliance state constraints to improve appliance state detection Conference Proceedings of the 8th ACM International Conference on Future Energy Systems (ACM eEnergy), 16.-19.05.17, Hong Kong (China), (111-120), 2017. Abstract | BibTeX | Tags: Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector | Links: @conference{Khandelwal2017, title = {Exploiting appliance state constraints to improve appliance state detection}, author = {T. Khandelwal and K. Rajwanshi and P. Bharadwaj and S. S. Garani and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/p111-Khandelwal.pdf}, doi = {10.1145/3077839.3077859}, year = {2017}, date = {2017-05-19}, booktitle = {Proceedings of the 8th ACM International Conference on Future Energy Systems (ACM eEnergy), 16.-19.05.17, Hong Kong (China)}, number = {111-120}, abstract = {This work deals with non-intrusive load monitoring using a single inexpensive device at the mains. We argue that very low sampling rates (of 1 Hz) may suffice. This enables significant compression and cheaper end-devices. There are challenges when operating at such low sampling rates, of course. To achieve good appliance inference performance we propose improved event detection, feature extraction, and inference algorithms. The inference algorithm exploits state transition constraints and proposes the use of a maximum likelihood sequence detection for improved performance.}, keywords = {Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector}, pubstate = {published}, tppubtype = {conference} } This work deals with non-intrusive load monitoring using a single inexpensive device at the mains. We argue that very low sampling rates (of 1 Hz) may suffice. This enables significant compression and cheaper end-devices. There are challenges when operating at such low sampling rates, of course. To achieve good appliance inference performance we propose improved event detection, feature extraction, and inference algorithms. The inference algorithm exploits state transition constraints and proposes the use of a maximum likelihood sequence detection for improved performance. |
| 26. | Vinerbi, Lorenzo; Babu, Arun Framework for automation of hazard log management on large critical projects Book Chapter Bondavalli, Andrea; Branca, Francesco (Ed.): Certifications of Critical Systems – The CECRIS Experience, Chapter 5, pp. 103-115, River Publishers, 2017, ISBN: 9788793519565. Abstract | BibTeX | Tags: Systems Engineering | Links: @inbook{Vinerbi2017, title = {Framework for automation of hazard log management on large critical projects}, author = {Lorenzo Vinerbi and Arun Babu}, editor = {Andrea Bondavalli and Francesco Branca}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/05_Chapter_05.pdf}, doi = {10.13052/rp-9788793519558}, isbn = {9788793519565}, year = {2017}, date = {2017-09-08}, booktitle = {Certifications of Critical Systems – The CECRIS Experience}, pages = {103-115}, publisher = {River Publishers}, chapter = {5}, abstract = {A hazard (HZ) is any situation that could cause harm to the system or lives. HZ depends on the system and its environment, and the probability of the HZ to cause harm is known as risk. HZs are analyzed by identifying their causes and the possible negative consequences that might ensue. For example, the dangerous failure of a traffic signal could be caused by a logic error in the traffic signaling controller’s software program. The consequence could be conflicting traffic flows simultaneously receiving green signals. A hazard log (HL) is a database of all risk management activities in a project. Maintaining its correctness and consistency on large safety/mission critical projects involving multiple vendors, suppliers, and partners is critical and challenging. IBM DOORS is one of the popular tool used for HZ management in mission critical applications. However, not all stake-holders are familiar with it. Also, it may not always feasible for all stake-holders to provide correct, well structured, and consistent HZ data. IBM DOORS have been reported to be useful in managing DO-178 compliance for avionics. Also, HL in DOORS allows capabilities for tracing requirements and test results. However, DOORS has steeper learning curve and is difficult to use by common people and beginners. Also, they lack validation capabilities. Custom checks may require difficult to use plug-ins which are not generic. This complexity makes it difficult to maintain the rules; preventing reuse in other projects. This chapter demonstrates a modular and extensible way to specify rules for checks locally at the stake-holder side, as well as while combining data from various parties to form the HL. The HZ-LOG automatization tool simplifies the process of HZ data collection on large projects to form the HL, while ensuring data consistency and correctness. The data provided by all parties are collected using a template containing scripts. The scripts check for mistakes/errors based on internal standards of company in charge of the HZ management. The collected data is then subjected to merging in DOORS, which also contain scripts to check and import data to form the HL. The requirements of HL tool are: (i) Perform checks of incoming data from vendors and partners; (ii) It shall allow to collect and keep log for all information related to iden- tified HZs (and related identified mitigations), structuring information accordingly; (iii) It shall be possible to manage the status of the HZs and related mitiga- tions, allowing for the control of risk. Only allowed HZ status transitions shall be possible and logging of the related status transition activity shall be kept in the tool for traceability purposes; (iv) Only RAMS specialist are allowed to manage HZs being necessary no different user profiles for the management of HZs in the tool; (v) A function of the tool shall allow to extract the “current” status of the project system HL by allowing the creation of documentary reports containing the set of necessary information about the predicted HZs, mitigations identified, and the status of all related risk control activities.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {inbook} } A hazard (HZ) is any situation that could cause harm to the system or lives. HZ depends on the system and its environment, and the probability of the HZ to cause harm is known as risk. HZs are analyzed by identifying their causes and the possible negative consequences that might ensue. For example, the dangerous failure of a traffic signal could be caused by a logic error in the traffic signaling controller’s software program. The consequence could be conflicting traffic flows simultaneously receiving green signals. A hazard log (HL) is a database of all risk management activities in a project. Maintaining its correctness and consistency on large safety/mission critical projects involving multiple vendors, suppliers, and partners is critical and challenging. IBM DOORS is one of the popular tool used for HZ management in mission critical applications. However, not all stake-holders are familiar with it. Also, it may not always feasible for all stake-holders to provide correct, well structured, and consistent HZ data. IBM DOORS have been reported to be useful in managing DO-178 compliance for avionics. Also, HL in DOORS allows capabilities for tracing requirements and test results. However, DOORS has steeper learning curve and is difficult to use by common people and beginners. Also, they lack validation capabilities. Custom checks may require difficult to use plug-ins which are not generic. This complexity makes it difficult to maintain the rules; preventing reuse in other projects. This chapter demonstrates a modular and extensible way to specify rules for checks locally at the stake-holder side, as well as while combining data from various parties to form the HL. The HZ-LOG automatization tool simplifies the process of HZ data collection on large projects to form the HL, while ensuring data consistency and correctness. The data provided by all parties are collected using a template containing scripts. The scripts check for mistakes/errors based on internal standards of company in charge of the HZ management. The collected data is then subjected to merging in DOORS, which also contain scripts to check and import data to form the HL. The requirements of HL tool are: (i) Perform checks of incoming data from vendors and partners; (ii) It shall allow to collect and keep log for all information related to iden- tified HZs (and related identified mitigations), structuring information accordingly; (iii) It shall be possible to manage the status of the HZs and related mitiga- tions, allowing for the control of risk. Only allowed HZ status transitions shall be possible and logging of the related status transition activity shall be kept in the tool for traceability purposes; (iv) Only RAMS specialist are allowed to manage HZs being necessary no different user profiles for the management of HZs in the tool; (v) A function of the tool shall allow to extract the “current” status of the project system HL by allowing the creation of documentary reports containing the set of necessary information about the predicted HZs, mitigations identified, and the status of all related risk control activities. |
| 27. | Sankaran, Raman; Bach, Francis R; Bhattacharyya, Chiranjib Identifying groups of strongly correlated variables through smoothed ordered weighted L1-norms Journal Article Proceedings of the 20th International Conference on Artificial Intelligence and Statistics (AISTATS), 20.-22.04.17, Fort Lauderdale (USA), pp. 1123-1131, 2017. Abstract | BibTeX | Tags: Machine Learning | Links: @article{Sankaran2017, title = {Identifying groups of strongly correlated variables through smoothed ordered weighted L1-norms}, author = {Raman Sankaran and Francis R. Bach and Chiranjib Bhattacharyya}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/sankaran17a.pdf}, year = {2017}, date = {2017-08-16}, journal = {Proceedings of the 20th International Conference on Artificial Intelligence and Statistics (AISTATS), 20.-22.04.17, Fort Lauderdale (USA)}, pages = {1123-1131}, abstract = {The failure of LASSO to identify groups of correlated predictors in linear regression has sparked significant research interest. Recently, various norms were proposed, which can be best described as instances of ordered weighted ℓ1 norms (OWL), as an alternative to ℓ1 regularization used in LASSO. OWL can identify groups of correlated variables but it forces the model to be constant within a group. This artifact induces unnecessary bias in the model estimation. In this paper we take a submodular perspective and show that OWL can be posed as the Lovász extension of a suitably defined submodular function. The submodular perspective not only explains the group-wise constant behavior of OWL, but also suggests alternatives. The main contribution of this paper is smoothed OWL (SOWL), a new family of norms, which not only identifies the groups but also allows the model to be flexible inside a group. We establish several algorithmic and theoretical properties of SOWL including group identification and model consistency. We also provide algorithmic tools to compute the SOWL norm and its proximal operator, whose computational complexity O(dlogd) is significantly better than that of general purpose solvers in O(d2logd). In our experiments, SOWL compares favorably with respect to OWL in the regimes of interest.}, keywords = {Machine Learning}, pubstate = {published}, tppubtype = {article} } The failure of LASSO to identify groups of correlated predictors in linear regression has sparked significant research interest. Recently, various norms were proposed, which can be best described as instances of ordered weighted ℓ1 norms (OWL), as an alternative to ℓ1 regularization used in LASSO. OWL can identify groups of correlated variables but it forces the model to be constant within a group. This artifact induces unnecessary bias in the model estimation. In this paper we take a submodular perspective and show that OWL can be posed as the Lovász extension of a suitably defined submodular function. The submodular perspective not only explains the group-wise constant behavior of OWL, but also suggests alternatives. The main contribution of this paper is smoothed OWL (SOWL), a new family of norms, which not only identifies the groups but also allows the model to be flexible inside a group. We establish several algorithmic and theoretical properties of SOWL including group identification and model consistency. We also provide algorithmic tools to compute the SOWL norm and its proximal operator, whose computational complexity O(dlogd) is significantly better than that of general purpose solvers in O(d2logd). In our experiments, SOWL compares favorably with respect to OWL in the regimes of interest. |
| 28. | Chakrabortty, Tuhin; Varma, Manoj Inferring existence of physical feedback mechanisms from short-lived synchronization events in complex systems Conference Forthcoming Proceedings of the 2017 Conference on Complex Systems, 17.-22.09.17, Cancun (Mexico), Forthcoming. BibTeX | Tags: Sensing and Actuation Systems @conference{Chakrabortty2017, title = {Inferring existence of physical feedback mechanisms from short-lived synchronization events in complex systems}, author = {Tuhin Chakrabortty and Manoj Varma}, year = {2017}, date = {2017-09-22}, booktitle = {Proceedings of the 2017 Conference on Complex Systems, 17.-22.09.17, Cancun (Mexico)}, keywords = {Sensing and Actuation Systems}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 29. | Prasad, Oppili; Jha, Prateek; Pillai, Sreelal; Prasad, Mandya; Amrutur, Bharadwaj; Sambandan, Sanjiv Interconnects on elastomers: Optimizing for stretchability, speed and layout area Journal Article Flexible and Printed Electronics, 2 (4), 2017. Abstract | BibTeX | Tags: Systems Engineering | Links: @article{Prasad2017, title = {Interconnects on elastomers: Optimizing for stretchability, speed and layout area}, author = {Oppili Prasad and Prateek Jha and Sreelal Pillai and Mandya Prasad and Bharadwaj Amrutur and Sanjiv Sambandan}, url = {http://www.rbccps.org/wp-content/uploads/2017/11/Prasad_2017_Flex._Print._Electron._2_045007.pdf}, doi = {10.1088/2058-8585/aa91ba}, year = {2017}, date = {2017-11-03}, journal = {Flexible and Printed Electronics}, volume = {2}, number = {4}, abstract = {The design of interconnects on elastomers is of interest in flexible electronics. The geometric design of interconnects must take into account the electrical and mechanical aspects, along with layout area. This work discusses the impact of the geometry of stretchable interconnects on various user specifications, namely layout area, stretchability given by mechanical stiffness coefficient and speed given by electrical impedance. Analytical models have been derived and an optimization methodology is developed to help pick the best design for the given application. The analytical models are corroborated with simulations and experiments. Interconnect designs have been fabricated on a copper-viscoelastic adhesive-elastomer stack architecture, using laser toner-transfer process where the viscoelastic adhesive prevents delamination and in which the process flow is in line with conventional printed circuit board fabrication techniques.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {article} } The design of interconnects on elastomers is of interest in flexible electronics. The geometric design of interconnects must take into account the electrical and mechanical aspects, along with layout area. This work discusses the impact of the geometry of stretchable interconnects on various user specifications, namely layout area, stretchability given by mechanical stiffness coefficient and speed given by electrical impedance. Analytical models have been derived and an optimization methodology is developed to help pick the best design for the given application. The analytical models are corroborated with simulations and experiments. Interconnect designs have been fabricated on a copper-viscoelastic adhesive-elastomer stack architecture, using laser toner-transfer process where the viscoelastic adhesive prevents delamination and in which the process flow is in line with conventional printed circuit board fabrication techniques. |
| 30. | Vaidhiyan, Nidhin K; Arun, S P; Sundaresan, Rajesh Neural dissimilarity indices that predict oddball detection in behaviour Journal Article IEEE Transactions on Information Theory, 63 (8), pp. 4778-4796, 2017. Abstract | BibTeX | Tags: Modeling and Simulation and Analytics | Links: @article{Vaidhiyan2017, title = {Neural dissimilarity indices that predict oddball detection in behaviour}, author = {Nidhin K. Vaidhiyan and S. P. Arun and Rajesh Sundaresan}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/07937887.pdf}, doi = {10.1109/TIT.2017.2707485}, year = {2017}, date = {2017-06-01}, journal = {IEEE Transactions on Information Theory}, volume = {63}, number = {8}, pages = {4778-4796}, abstract = {Neuroscientists have recently shown that images that are difficult to find in visual search elicit similar patterns of firing across a population of recorded neurons. The L1 distance between firing rate vectors associated with two images was strongly correlated with the inverse of decision time in behavior. But why should decision times be correlated with L1 distance? What is the decision-theoretic basis? In our decision theoretic formulation, we model visual search as an active sequential hypothesis testing problem with switching costs. Our analysis suggests an appropriate neuronal dissimilarity index, which correlates equally strongly with the inverse of decision time as the L1 distance. We also consider a number of other possibilities, such as the relative entropy (Kullback-Leibler divergence) and the Chernoff entropy of the firing rate distributions. A more stringent test of equality of means, which would have provided a strong backing for our modeling, fails for our proposed as well as the other already discussed dissimilarity indices. However, test statistics from the equality of means test, when used to rank the indices in terms of their ability to explain the observed results, places our proposed dissimilarity index at the top followed by relative entropy, Chernoff entropy, and the L1 indices. Computations of the different indices require an estimate of the relative entropy between two Poisson point processes. An estimator is developed and is shown to have near unbiased performance for almost all operating regions.}, keywords = {Modeling and Simulation and Analytics}, pubstate = {published}, tppubtype = {article} } Neuroscientists have recently shown that images that are difficult to find in visual search elicit similar patterns of firing across a population of recorded neurons. The L1 distance between firing rate vectors associated with two images was strongly correlated with the inverse of decision time in behavior. But why should decision times be correlated with L1 distance? What is the decision-theoretic basis? In our decision theoretic formulation, we model visual search as an active sequential hypothesis testing problem with switching costs. Our analysis suggests an appropriate neuronal dissimilarity index, which correlates equally strongly with the inverse of decision time as the L1 distance. We also consider a number of other possibilities, such as the relative entropy (Kullback-Leibler divergence) and the Chernoff entropy of the firing rate distributions. A more stringent test of equality of means, which would have provided a strong backing for our modeling, fails for our proposed as well as the other already discussed dissimilarity indices. However, test statistics from the equality of means test, when used to rank the indices in terms of their ability to explain the observed results, places our proposed dissimilarity index at the top followed by relative entropy, Chernoff entropy, and the L1 indices. Computations of the different indices require an estimate of the relative entropy between two Poisson point processes. An estimator is developed and is shown to have near unbiased performance for almost all operating regions. |
| 31. | Heemels, Maurice; Kundu, Atreyee; Daafouz, Jamal On Lyapunov-Metzler inequalities and S-Procedure characterizations for the stabilization of switched linear systems Journal Article IEEE Transactions on Automatic Control, 62 (9), pp. 4593-4597, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Heemels2017, title = {On Lyapunov-Metzler inequalities and S-Procedure characterizations for the stabilization of switched linear systems}, author = {Maurice Heemels and Atreyee Kundu and Jamal Daafouz}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/07733093.pdf}, doi = {10.1109/TAC.2016.2624987}, year = {2017}, date = {2017-08-28}, journal = {IEEE Transactions on Automatic Control}, volume = {62}, number = {9}, pages = {4593-4597}, abstract = {In this note we present connections between two celebrated tools for the design of stabilising switching laws for continuous-time and discrete-time switched linear systems, namely Lyapunov-Metzler inequalities and S-procedure.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } In this note we present connections between two celebrated tools for the design of stabilising switching laws for continuous-time and discrete-time switched linear systems, namely Lyapunov-Metzler inequalities and S-procedure. |
| 32. | Prasanth, V; Parekhji, Rubin; Amrutur, Bharadwaj Safety analysis for integrated circuits in the context of hybrid systems Conference Forthcoming International Test Conference (ITC 2017), 31.10.-02.11.17, Fort Worth (USA), Forthcoming. BibTeX | Tags: Systems Engineering @conference{Prasanth2017, title = {Safety analysis for integrated circuits in the context of hybrid systems}, author = {V. Prasanth and Rubin Parekhji and Bharadwaj Amrutur}, year = {2017}, date = {2017-11-02}, booktitle = {International Test Conference (ITC 2017), 31.10.-02.11.17, Fort Worth (USA)}, keywords = {Systems Engineering}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 33. | Sharma, Abhay; Acharya, Srikrishna; Rajaraman, Vasanth; Ramesh, Rakshit; Babu, Arun; Amrutur, Bharadwaj Schemas for IoT interoperability for Smart Cities Conference Forthcoming Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems, 05.-09.11.17, Delft (The Netherlands), Forthcoming. Abstract | BibTeX | Tags: Smart City test bed, Systems Engineering @conference{Sharma2017, title = {Schemas for IoT interoperability for Smart Cities}, author = {Abhay Sharma and Srikrishna Acharya and Vasanth Rajaraman and Rakshit Ramesh and Arun Babu and Bharadwaj Amrutur}, year = {2017}, date = {2017-11-09}, booktitle = {Proceedings of the 15th ACM Conference on Embedded Networked Sensor Systems, 05.-09.11.17, Delft (The Netherlands)}, abstract = {One of the key aspects of smart city ecosystem is enabling easy collection and exchange of data to develop new applications. Providing good, open APIs for smart city middleware along with standardising the data schemas will be vital for application and devise ecosystem to evolve. In this paper we present the resource catalogue component of the middleware along with a framework to develop data schemas for IoT devices. Using data schemas one can provide meta-data which enables effective use of the device data.}, keywords = {Smart City test bed, Systems Engineering}, pubstate = {forthcoming}, tppubtype = {conference} } One of the key aspects of smart city ecosystem is enabling easy collection and exchange of data to develop new applications. Providing good, open APIs for smart city middleware along with standardising the data schemas will be vital for application and devise ecosystem to evolve. In this paper we present the resource catalogue component of the middleware along with a framework to develop data schemas for IoT devices. Using data schemas one can provide meta-data which enables effective use of the device data. |
| 34. | Harshitha, S K; Harkar, Shalini; Mishra, Ayushi; Joge, Shubham; Singh, Varsha; Varma, Manoj Social intelligence in Pseudomonas Aeruginosa Conference Forthcoming Proceedings of the 2017 Conference on Complex Systems, 17.-22.09.17, Cancun (Mexico), Forthcoming. BibTeX | Tags: Development of chemotactic robots, Sensing and Actuation Systems, Understanding swarming and collective motion in bacterial populations @conference{Harshitha2017, title = {Social intelligence in Pseudomonas Aeruginosa}, author = { S. K. Harshitha and Shalini Harkar and Ayushi Mishra and Shubham Joge and Varsha Singh and Manoj Varma}, year = {2017}, date = {2017-09-22}, booktitle = {Proceedings of the 2017 Conference on Complex Systems, 17.-22.09.17, Cancun (Mexico)}, keywords = {Development of chemotactic robots, Sensing and Actuation Systems, Understanding swarming and collective motion in bacterial populations}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 35. | Kundu, Atreyee; Daafouz, Jamal; Heemels, Maurice Stabilization of discrete-time switched linear systems: Lyapunov-Metzler inequalities versus S-procedure characterizations Conference Proceedings of the 20th World Congress of the International Federation of Automatic Control (IFAC 2017), 09.-14.07.17, Toulouse (France), 50 (1), 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @conference{Kundu2017, title = {Stabilization of discrete-time switched linear systems: Lyapunov-Metzler inequalities versus S-procedure characterizations}, author = {Atreyee Kundu and Jamal Daafouz and Maurice Heemels}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/1-s2.0-S2405896317309679-main.pdf}, doi = {10.1016/j.ifacol.2017.08.594}, year = {2017}, date = {2017-07-14}, booktitle = {Proceedings of the 20th World Congress of the International Federation of Automatic Control (IFAC 2017), 09.-14.07.17, Toulouse (France)}, volume = {50}, number = {1}, pages = {3412-3417}, abstract = {In this paper we study connections between Lyapunov-Metzler inequalities and S-procedure characterizations in the context of stabilizing discrete-time switched linear systems using min-switching strategies. We propose two generalized versions of S-procedure characterization along the lines of the generalized versions of Lyapunov-Metzler inequalities recently proposed in the literature. It is shown that the existence of a solution to the generalized version(s) of Lyapunov-Metzler inequalities is equivalent to the existence of a solution to the generalized version(s) of S-procedure characterization with a restricted choice of the scalar quantities involved in the latter. This recovers some of our earlier works on the classical Lyapunov-Metzler inequalities as a special case. We also highlight and discuss an open question of whether the generalized versions of S-procedure characterization are strictly less conservative than the generalized versions of Lyapunov-Metzler inequalities, which in turn are equivalent to periodic stabilizability as was recently shown.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {conference} } In this paper we study connections between Lyapunov-Metzler inequalities and S-procedure characterizations in the context of stabilizing discrete-time switched linear systems using min-switching strategies. We propose two generalized versions of S-procedure characterization along the lines of the generalized versions of Lyapunov-Metzler inequalities recently proposed in the literature. It is shown that the existence of a solution to the generalized version(s) of Lyapunov-Metzler inequalities is equivalent to the existence of a solution to the generalized version(s) of S-procedure characterization with a restricted choice of the scalar quantities involved in the latter. This recovers some of our earlier works on the classical Lyapunov-Metzler inequalities as a special case. We also highlight and discuss an open question of whether the generalized versions of S-procedure characterization are strictly less conservative than the generalized versions of Lyapunov-Metzler inequalities, which in turn are equivalent to periodic stabilizability as was recently shown. |
| 36. | Kundu, Atreyee; Chatterjee, Debasish Stabilizing switching signals: A transition from point-wise to asymptotic conditions Journal Article Systems & Control Letters, 106 , pp. 16-23, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Kundu2017b, title = {Stabilizing switching signals: A transition from point-wise to asymptotic conditions}, author = {Atreyee Kundu and Debasish Chatterjee}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/1-s2.0-S0167691117301044-main.pdf}, doi = {10.1016/j.sysconle.2017.06.001}, year = {2017}, date = {2017-06-29}, journal = {Systems & Control Letters}, volume = {106}, pages = {16-23}, abstract = {Characterization of classes of switching signals that ensure stability of switched systems occupies a significant portion of the switched systems literature. This article collects a multitude of stabilizing switching signals under an umbrella framework. We achieve this in two steps: Firstly, given a family of systems, possibly containing unstable dynamics, we propose a new and general class of stabilizing switching signals. Secondly, we demonstrate that prior results based on both point-wise and asymptotic characterizations follow our result. This is the first attempt in the switched systems literature where these switching signals are unified under one banner.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } Characterization of classes of switching signals that ensure stability of switched systems occupies a significant portion of the switched systems literature. This article collects a multitude of stabilizing switching signals under an umbrella framework. We achieve this in two steps: Firstly, given a family of systems, possibly containing unstable dynamics, we propose a new and general class of stabilizing switching signals. Secondly, we demonstrate that prior results based on both point-wise and asymptotic characterizations follow our result. This is the first attempt in the switched systems literature where these switching signals are unified under one banner. |
| 37. | Harshitha, S K; Harkar, Shalini; Mishra, Ayushi; Joge, Shubham; Singh, Varsha; Varma, Manoj Swarming in Pseudomonas Aeruginosa : Global optimisation from local interaction Conference Forthcoming Proceedings of the 12th Physics of Living Matter Symposium (PLM), 14.-15.09.17, Cambridge (UK), Forthcoming. BibTeX | Tags: Development of chemotactic robots, Understanding swarming and collective motion in bacterial populations @conference{Harshitha2017b, title = {Swarming in Pseudomonas Aeruginosa : Global optimisation from local interaction}, author = {S. K. Harshitha and Shalini Harkar and Ayushi Mishra and Shubham Joge and Varsha Singh and Manoj Varma}, year = {2017}, date = {2017-09-15}, booktitle = {Proceedings of the 12th Physics of Living Matter Symposium (PLM), 14.-15.09.17, Cambridge (UK)}, keywords = {Development of chemotactic robots, Understanding swarming and collective motion in bacterial populations}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 38. | Babu, Arun; Branca, Francesco; Bondavalli, Andrea; Ceccare, Andrea SYSML-UML like modeling environment based on Google Blockly customization Book Chapter Bondavalli, Andrea; Branca, Francesco (Ed.): Certifications of Critical Systems – The CECRIS Experience, Chapter 3, pp. 65-79, River Publishers, 2017, ISBN: 9788793519565. Abstract | BibTeX | Tags: Systems Engineering | Links: @inbook{Babu2017, title = {SYSML-UML like modeling environment based on Google Blockly customization}, author = {Arun Babu and Francesco Branca and Andrea Bondavalli and Andrea Ceccare}, editor = {Andrea Bondavalli and Francesco Branca}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/03_Chapter_03.pdf}, doi = {10.13052/rp-9788793519558}, isbn = {9788793519565}, year = {2017}, date = {2017-09-08}, booktitle = {Certifications of Critical Systems – The CECRIS Experience}, pages = {65-79}, publisher = {River Publishers}, chapter = {3}, abstract = {In industries, it is often observed that system designers may not be CS/OO/SysML experts and often required lot of training and support to use the modeling tools. Ideally, designers should spend all their effort on modeling and nothing else. However, existing modeling tools have lot of issues related to installation and plug-ins. The use of Google Blockly was envisaged for use of modeling and simulation of systems. Blockly is a visual programming library, used to model/program using interlocked blocks. Each of the blocks also support traditional input widgets such as labels, images, textbox, checkbox, combo box, etc. It can be configured in such a way that only compatible blocks can be connected together (i.e. can be made “valid by design”). Blockly supports code and XML generation, and requires only a modern web browser which can be run on any device or operating system. However, Blockly was not readily useable for modeling SysML/UML like models. A lot of changes and customizations were made in Blockly to make it more suitable for such type of modeling.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {inbook} } In industries, it is often observed that system designers may not be CS/OO/SysML experts and often required lot of training and support to use the modeling tools. Ideally, designers should spend all their effort on modeling and nothing else. However, existing modeling tools have lot of issues related to installation and plug-ins. The use of Google Blockly was envisaged for use of modeling and simulation of systems. Blockly is a visual programming library, used to model/program using interlocked blocks. Each of the blocks also support traditional input widgets such as labels, images, textbox, checkbox, combo box, etc. It can be configured in such a way that only compatible blocks can be connected together (i.e. can be made “valid by design”). Blockly supports code and XML generation, and requires only a modern web browser which can be run on any device or operating system. However, Blockly was not readily useable for modeling SysML/UML like models. A lot of changes and customizations were made in Blockly to make it more suitable for such type of modeling. |
| 39. | Prakash, Praneeth; Varma, Manoj Trapping/Pinning of colloidal microspheres over glass substrate using surface features Journal Article Nature: Scientific Reports, 7 , 2017. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Prakash2017, title = {Trapping/Pinning of colloidal microspheres over glass substrate using surface features}, author = {Praneeth Prakash and Manoj Varma}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/s41598-017-15984-4.pdf}, doi = {10.1038/s41598-017-15984-4}, year = {2017}, date = {2017-11-16}, journal = {Nature: Scientific Reports}, volume = {7}, abstract = {Suspensions of micro/nano particles made of Polystyrene, Poly(methyl methacrylate), Silicon dioxide etc. have been a standard model system to understand colloidal physics. These systems have proved useful insights into phenomena such as self-assembly. Colloidal model systems are also extensively used to simulate many condensed matter phenomena such as dynamics in a quenched disordered system and glass transition. A precise control of particles using optical or holographic tweezers is essential for such studies. However, studies of collective phenomena such as jamming and flocking behaviour in a disordered space are limited due to the low throughput of the optical trapping techniques. In this article, we present a technique where we trap and pin polystyrene microspheres ~10 μm over ‘triangular crest’ shaped microstructures in a microfluidic environment. Trapping/Pinning occurs due to the combined effect of hydrodynamic interaction and non-specific adhesion forces. This method allows trapping and pinning of microspheres in any arbitrary pattern with a high degree of spatial accuracy which can be useful in studying fundamentals of various collective phenomena as well as in applications such as bead detachment assay based biosensors.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Suspensions of micro/nano particles made of Polystyrene, Poly(methyl methacrylate), Silicon dioxide etc. have been a standard model system to understand colloidal physics. These systems have proved useful insights into phenomena such as self-assembly. Colloidal model systems are also extensively used to simulate many condensed matter phenomena such as dynamics in a quenched disordered system and glass transition. A precise control of particles using optical or holographic tweezers is essential for such studies. However, studies of collective phenomena such as jamming and flocking behaviour in a disordered space are limited due to the low throughput of the optical trapping techniques. In this article, we present a technique where we trap and pin polystyrene microspheres ~10 μm over ‘triangular crest’ shaped microstructures in a microfluidic environment. Trapping/Pinning occurs due to the combined effect of hydrodynamic interaction and non-specific adhesion forces. This method allows trapping and pinning of microspheres in any arbitrary pattern with a high degree of spatial accuracy which can be useful in studying fundamentals of various collective phenomena as well as in applications such as bead detachment assay based biosensors. |
| 40. | Karmakar, Prasenjit; Bhatnagar, Shalabh Two time-scale stochastic approximation with controlled Markov noise and off-policy temporal difference learning Journal Article Mathematics of Operations Research: Articles in Advance, pp. 1-22, 2017. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Karmakar2017, title = {Two time-scale stochastic approximation with controlled Markov noise and off-policy temporal difference learning}, author = {Prasenjit Karmakar and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2018/01/moor.2017.0855.pdf}, doi = {10.1287/moor.2017.0855}, year = {2017}, date = {2017-07-13}, journal = {Mathematics of Operations Research: Articles in Advance}, pages = {1-22}, abstract = {We present for the first time an asymptotic convergence analysis of two time- scale stochastic approximation driven by “controlled” Markov noise. In particular, the faster and slower recursions have nonadditive controlled Markov noise components in addition to martingale difference noise. We analyze the asymptotic behavior of our framework by relating it to limiting differential inclusions in both time scales that are defined in terms of the ergodic occupation measures associated with the controlled Markov processes. Finally, we present a solution to the off-policy convergence problem for temporal-difference learning with linear function approximation, using our results.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } We present for the first time an asymptotic convergence analysis of two time- scale stochastic approximation driven by “controlled” Markov noise. In particular, the faster and slower recursions have nonadditive controlled Markov noise components in addition to martingale difference noise. We analyze the asymptotic behavior of our framework by relating it to limiting differential inclusions in both time scales that are defined in terms of the ergodic occupation measures associated with the controlled Markov processes. Finally, we present a solution to the off-policy convergence problem for temporal-difference learning with linear function approximation, using our results. |
2016 |
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| 41. | Ramaswamy, Arunselvan; Bhatnagar, Shalabh A generalization of the Borkar-Meyn theorem for stochastic recursive inclusions Journal Article Mathematics of Operations Research, 2016. Abstract | BibTeX | Tags: Modeling and Simulation and Analytics | Links: @article{Ramaswamy2016, title = {A generalization of the Borkar-Meyn theorem for stochastic recursive inclusions}, author = {Arunselvan Ramaswamy and Shalabh Bhatnagar}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/moor.2016.0821.pdf}, doi = {10.1287/moor.2016.0821}, year = {2016}, date = {2016-12-16}, journal = {Mathematics of Operations Research}, abstract = {In this paper, the stability theorem of Borkar and Meyn is extended to include the case when the mean field is a set-valued map. Two different sets of sufficient conditions are presented that guarantee the “stability and convergence” of stochastic recursive inclusions. Our work builds on the works of Benaïm, Hofbauer and Sorin as well as Borkar and Meyn. As a corollary to one of the main theorems, a natural generalization of the Borkar and Meyn theorem follows. In addition, the original theorem of Borkar and Meyn is shown to hold under slightly relaxed assumptions. As an application to one of the main theorems, we discuss a solution to the “approximate drift problem.” Finally, we analyze the stochastic gradient algorithm with “constant-error gradient estimators” as yet another application of our main result.}, keywords = {Modeling and Simulation and Analytics}, pubstate = {published}, tppubtype = {article} } In this paper, the stability theorem of Borkar and Meyn is extended to include the case when the mean field is a set-valued map. Two different sets of sufficient conditions are presented that guarantee the “stability and convergence” of stochastic recursive inclusions. Our work builds on the works of Benaïm, Hofbauer and Sorin as well as Borkar and Meyn. As a corollary to one of the main theorems, a natural generalization of the Borkar and Meyn theorem follows. In addition, the original theorem of Borkar and Meyn is shown to hold under slightly relaxed assumptions. As an application to one of the main theorems, we discuss a solution to the “approximate drift problem.” Finally, we analyze the stochastic gradient algorithm with “constant-error gradient estimators” as yet another application of our main result. |
| 42. | Prabuchandran, K J; Bhatnagar, Shalabh; Borkar, Vivek S Actor-critic algorithms with online feature adaptation Journal Article ACM Transactions on Modeling and Computer Simulation (TOMACS), 26 (4), pp. 24:1-24:26, 2016. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Prabuchandran2016, title = {Actor-critic algorithms with online feature adaptation}, author = {K. J. Prabuchandran and Shalabh Bhatnagar and Vivek S. Borkar}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/a24-prabuchandran.pdf}, doi = {10.1145/2868723}, year = {2016}, date = {2016-05-31}, journal = {ACM Transactions on Modeling and Computer Simulation (TOMACS)}, volume = {26}, number = {4}, pages = {24:1-24:26}, abstract = {We develop two new online actor-critic control algorithms with adaptive feature tuning for Markov Decision Processes (MDPs). One of our algorithms is proposed for the long-run average cost objective, while the other works for discounted cost MDPs. Our actor-critic architecture incorporates parameterization both in the policy and the value function. A gradient search in the policy parameters is performed to improve the performance of the actor. The computation of the aforementioned gradient, however, requires an estimate of the value function of the policy corresponding to the current actor parameter. The value function, on the other hand, is approximated using linear function approximation and obtained from the critic. The error in approximation of the value function, however, results in suboptimal policies. In our article, we also update the features by performing a gradient descent on the Grassmannian of features to minimize a mean square Bellman error objective in order to find the best features. The aim is to obtain a good approximation of the value function and thereby ensure convergence of the actor to locally optimal policies. In order to estimate the gradient of the objective in the case of the average cost criterion, we utilize the policy gradient theorem, while in the case of the discounted cost objective, we utilize the simultaneous perturbation stochastic approximation (SPSA) scheme. We prove that our actor-critic algorithms converge to locally optimal policies. Experiments on two different settings show performance improvements resulting from our feature adaptation scheme.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } We develop two new online actor-critic control algorithms with adaptive feature tuning for Markov Decision Processes (MDPs). One of our algorithms is proposed for the long-run average cost objective, while the other works for discounted cost MDPs. Our actor-critic architecture incorporates parameterization both in the policy and the value function. A gradient search in the policy parameters is performed to improve the performance of the actor. The computation of the aforementioned gradient, however, requires an estimate of the value function of the policy corresponding to the current actor parameter. The value function, on the other hand, is approximated using linear function approximation and obtained from the critic. The error in approximation of the value function, however, results in suboptimal policies. In our article, we also update the features by performing a gradient descent on the Grassmannian of features to minimize a mean square Bellman error objective in order to find the best features. The aim is to obtain a good approximation of the value function and thereby ensure convergence of the actor to locally optimal policies. In order to estimate the gradient of the objective in the case of the average cost criterion, we utilize the policy gradient theorem, while in the case of the discounted cost objective, we utilize the simultaneous perturbation stochastic approximation (SPSA) scheme. We prove that our actor-critic algorithms converge to locally optimal policies. Experiments on two different settings show performance improvements resulting from our feature adaptation scheme. |
| 43. | Mani, Monto; Aaditya, Gayathri; Balaji, N C Appreciating performance of a BIPV lab in Bangalore (India) Conference Proceedings of the 32nd European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC 2016), Munich (Germany), 2016. Abstract | BibTeX | Tags: Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions | Links: @conference{Mani2016, title = {Appreciating performance of a BIPV lab in Bangalore (India)}, author = {Monto Mani and Gayathri Aaditya and N. C. Balaji}, doi = {10.4229/EUPVSEC20162016-6AV.5.24}, year = {2016}, date = {2016-06-24}, booktitle = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC 2016), Munich (Germany)}, pages = {2769-2774}, abstract = {A BIPV (Building Integrated Photovoltaic) is essentially PV integrated as a building envelope (roof, wall, façade, and fenestration) regulating indoor thermal comfort and generating on-site energy. Tropical regions are solar rich (>4 kWH/m2/day) and generally warmer (20~30°C) and impose a specific need for preventing indoor heat build-up and increased natural ventilation. Roofs have been found to be the single largest contributor of indoor heat gain, and with PV integration this gain is amplified due to low thermal mass and higher radiation. This results in a stratified temperature gradient between the (PV) roof and the floor below in conjunction with a higher natural buoyancy of warm air below the PV panel. In tropical conditions, PV performance is characterized by higher a higher operating temperature that is generally detrimental to its efficiency and aggravates indoor heat buildup when integrated as the roof. The interplay between indoor thermal comfort and PV performance needs to be carefully investigated particularly the influence of stratified indoor temperature on thermal comfort and the natural buoyancy induced ventilation on PV performance. The current study is an experimental investigation into a 5.25 kWp roof integrated BIPV lab located at the campus of the Indian Institute of Science, Bangalore (India).}, keywords = {Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions}, pubstate = {published}, tppubtype = {conference} } A BIPV (Building Integrated Photovoltaic) is essentially PV integrated as a building envelope (roof, wall, façade, and fenestration) regulating indoor thermal comfort and generating on-site energy. Tropical regions are solar rich (>4 kWH/m2/day) and generally warmer (20~30°C) and impose a specific need for preventing indoor heat build-up and increased natural ventilation. Roofs have been found to be the single largest contributor of indoor heat gain, and with PV integration this gain is amplified due to low thermal mass and higher radiation. This results in a stratified temperature gradient between the (PV) roof and the floor below in conjunction with a higher natural buoyancy of warm air below the PV panel. In tropical conditions, PV performance is characterized by higher a higher operating temperature that is generally detrimental to its efficiency and aggravates indoor heat buildup when integrated as the roof. The interplay between indoor thermal comfort and PV performance needs to be carefully investigated particularly the influence of stratified indoor temperature on thermal comfort and the natural buoyancy induced ventilation on PV performance. The current study is an experimental investigation into a 5.25 kWp roof integrated BIPV lab located at the campus of the Indian Institute of Science, Bangalore (India). |
| 44. | Pillai, Rohitkumar; Aaditya, Gayathri; Mani, Monto; Ramamurthy, Praveen Cell (module) temperature regulated performance of a building integrated photovoltaic system in tropical conditions Journal Article Renewable Energy, 72 , pp. 140-148, 2016. Abstract | BibTeX | Tags: Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions | Links: @article{Pillai2016, title = {Cell (module) temperature regulated performance of a building integrated photovoltaic system in tropical conditions}, author = {Rohitkumar Pillai and Gayathri Aaditya and Monto Mani and Praveen Ramamurthy}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/1-s2.0-S0960148114003632-main.pdf}, doi = {10.1016/j.renene.2014.06.023}, year = {2016}, date = {2016-12-30}, journal = {Renewable Energy}, volume = {72}, pages = {140-148}, abstract = {The performance of a building integrated photovoltaic system (BIPV) has to be commendable, not only on the electrical front but also on the thermal comfort front, thereby fulfilling the true responsibility of an energy providing shelter. Given the low thermal mass of BIPV systems, unintended and undesired outcomes of harnessing solar energy − such as heat gain into the building, especially in tropical regions − have to be adequately addressed. Cell (module) temperature is one critical factor that affects both the electrical and the thermal performance of such installations. The current paper discusses the impact of cell (module) temperature on both the electrical efficiency and thermal comfort by investigating the holistic performance of one such system (5.25 kWp) installed at the Centre for Sustainable Technologies in the Indian Institute of Science, Bangalore. Some recommendations (passive techniques) for improving the performance and making BIPV structures thermally comfortable have been listed out.}, keywords = {Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions}, pubstate = {published}, tppubtype = {article} } The performance of a building integrated photovoltaic system (BIPV) has to be commendable, not only on the electrical front but also on the thermal comfort front, thereby fulfilling the true responsibility of an energy providing shelter. Given the low thermal mass of BIPV systems, unintended and undesired outcomes of harnessing solar energy − such as heat gain into the building, especially in tropical regions − have to be adequately addressed. Cell (module) temperature is one critical factor that affects both the electrical and the thermal performance of such installations. The current paper discusses the impact of cell (module) temperature on both the electrical efficiency and thermal comfort by investigating the holistic performance of one such system (5.25 kWp) installed at the Centre for Sustainable Technologies in the Indian Institute of Science, Bangalore. Some recommendations (passive techniques) for improving the performance and making BIPV structures thermally comfortable have been listed out. |
| 45. | Sridhar, Sabarish; Misra, Prasant; Gill, Gurinder Singh; Warrior, Jay CheepSync: A time synchronization service for resource constrained bluetooth low energy advertisers Journal Article IEEE Communications Magazine, 54 (1), pp. 136-143, 2016. Abstract | BibTeX | Tags: Control and Prevention of Hospital Acquired Infections (HAI), Health | Links: @article{Sridhar2016, title = {CheepSync: A time synchronization service for resource constrained bluetooth low energy advertisers}, author = {Sabarish Sridhar and Prasant Misra and Gurinder Singh Gill and Jay Warrior}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/07378439.pdf}, doi = {10.1109/MCOM.2016.7378439}, year = {2016}, date = {2016-01-12}, journal = {IEEE Communications Magazine}, volume = {54}, number = {1}, pages = {136-143}, abstract = {Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans. It improves the efficiency, modularity, and scalability of the system, and optimizes use of event triggers. For IoTH, BLE - a subset of the recent Bluetooth v4.0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes. While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation. This article presents and describes CheepSync, a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms. Designed on top of the existing Bluetooth v4.0 standard, the CheepSync framework utilizes low-level timestamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift, and other system-specific constraints. CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners). We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups, and show that its average (single-hop) time synchronization accuracy is in the 10 μs range.}, keywords = {Control and Prevention of Hospital Acquired Infections (HAI), Health}, pubstate = {published}, tppubtype = {article} } Clock synchronization is highly desirable in distributed systems, including many applications in the Internet of Things and Humans. It improves the efficiency, modularity, and scalability of the system, and optimizes use of event triggers. For IoTH, BLE - a subset of the recent Bluetooth v4.0 stack - provides a low-power and loosely coupled mechanism for sensor data collection with ubiquitous units (e.g., smartphones and tablets) carried by humans. This fundamental design paradigm of BLE is enabled by a range of broadcast advertising modes. While its operational benefits are numerous, the lack of a common time reference in the broadcast mode of BLE has been a fundamental limitation. This article presents and describes CheepSync, a time synchronization service for BLE advertisers, especially tailored for applications requiring high time precision on resource constrained BLE platforms. Designed on top of the existing Bluetooth v4.0 standard, the CheepSync framework utilizes low-level timestamping and comprehensive error compensation mechanisms for overcoming uncertainties in message transmission, clock drift, and other system-specific constraints. CheepSync was implemented on custom designed nRF24Cheep beacon platforms (as broadcasters) and commercial off-the-shelf Android ported smartphones (as passive listeners). We demonstrate the efficacy of CheepSync by numerous empirical evaluations in a variety of experimental setups, and show that its average (single-hop) time synchronization accuracy is in the 10 μs range. |
| 46. | Gubbi, Sagar Venkatesh; Rao, Hiteshwar; Amrutur, Bharadwaj Continuous ambulatory electrocardiography Technical Report Robert Bosch Centre for Cyber-Physical Systems 3rd Floor, SID Building, Entrepreneurship Centre, Indian Institute of Science, Bangalore - 560012, (RBCCPS/TR/0002), 2016. Abstract | BibTeX | Tags: RBCCPS | Links: @techreport{Gubbi2016, title = {Continuous ambulatory electrocardiography}, author = {Sagar Venkatesh Gubbi and Hiteshwar Rao and Bharadwaj Amrutur}, url = {https://github.com/s-gv/rnicu/blob/master/ecg/report/ecg_tech_report.pdf}, year = {2016}, date = {2016-02-29}, number = {RBCCPS/TR/0002}, address = {3rd Floor, SID Building, Entrepreneurship Centre, Indian Institute of Science, Bangalore - 560012}, institution = {Robert Bosch Centre for Cyber-Physical Systems}, abstract = {Continous ambulatory recording of the electrocardiogram could help in early detection of cardiovascular diseases, which could lower healthcare costs and improve prognosis. For such continuous recordings, sensors that are discreet and have few electrodes are needed. Two electrode ECG systems exhibit worse power line interference than three electrode systems, but are desirable because they have one less electrode. A circuit model that captures power line interference is reviewed, which is then used to analyse the performance characteristics of different interface circuits. For two electrode systems, an adaptive filter is found to be effective in digitally removing any remnant power line interference. Finally, our analysis shows that the low-impedance electrode in a three electrode system may be sized differently than the high impedance electrodes while keeping the power line interference sufficiently small. This observation leads to a pseudo two electrode electrocardiograph which is in fact a three electrode system with an inconspicuous third electrode.}, keywords = {RBCCPS}, pubstate = {published}, tppubtype = {techreport} } Continous ambulatory recording of the electrocardiogram could help in early detection of cardiovascular diseases, which could lower healthcare costs and improve prognosis. For such continuous recordings, sensors that are discreet and have few electrodes are needed. Two electrode ECG systems exhibit worse power line interference than three electrode systems, but are desirable because they have one less electrode. A circuit model that captures power line interference is reviewed, which is then used to analyse the performance characteristics of different interface circuits. For two electrode systems, an adaptive filter is found to be effective in digitally removing any remnant power line interference. Finally, our analysis shows that the low-impedance electrode in a three electrode system may be sized differently than the high impedance electrodes while keeping the power line interference sufficiently small. This observation leads to a pseudo two electrode electrocardiograph which is in fact a three electrode system with an inconspicuous third electrode. |
| 47. | Kumar, Saurabh; Shrikanth, Venkoba; Amrutur, Bharadwaj; Asokan, Sundarrajan; Bobji, Musuvathi S Detecting stages of needle penetration into tissues through force estimation at needle tip using Fiber Bragg grating sensors Journal Article Journal of Biomedical Optics, 21 (12), 2016. Abstract | BibTeX | Tags: Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing, Health | Links: @article{Kumar2016, title = {Detecting stages of needle penetration into tissues through force estimation at needle tip using Fiber Bragg grating sensors}, author = {Saurabh Kumar and Venkoba Shrikanth and Bharadwaj Amrutur and Sundarrajan Asokan and Musuvathi S. Bobji}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/127009.pdf}, doi = {doi:10.1117/1.JBO.21.12.127009}, year = {2016}, date = {2016-12-30}, journal = {Journal of Biomedical Optics}, volume = {21}, number = {12}, abstract = {Several medical procedures involve the use of needles. The advent of robotic and robot assisted procedures requires dynamic estimation of the needle tip location during insertion for use in both assistive systems as well as for automatic control. Most prior studies have focused on the maneuvering of solid flexible needles using external force measurements at the base of the needle holder. However, hollow needles are used in several procedures and measurements of forces in proximity of such needles can eliminate the need for estimating frictional forces that have high variations. These measurements are also significant for endoscopic procedures in which measurement of forces at the needle holder base is difficult. Fiber Bragg grating sensors, due to their small size, inert nature, and multiplexing capability, provide a good option for this purpose. Force measurements have been undertaken during needle insertion into tissue mimicking phantoms made of polydimethylsiloxane as well as chicken tissue using an 18-G needle instrumented with FBG sensors. The results obtained show that it is possible to estimate the different stages of needle penetration including partial rupture, which is significant for procedures in which precise estimation of needle tip position inside the organ or tissue is required.}, keywords = {Fiber Bragg Grating Sensors for Distributed Bio-Chemical Sensing, Health}, pubstate = {published}, tppubtype = {article} } Several medical procedures involve the use of needles. The advent of robotic and robot assisted procedures requires dynamic estimation of the needle tip location during insertion for use in both assistive systems as well as for automatic control. Most prior studies have focused on the maneuvering of solid flexible needles using external force measurements at the base of the needle holder. However, hollow needles are used in several procedures and measurements of forces in proximity of such needles can eliminate the need for estimating frictional forces that have high variations. These measurements are also significant for endoscopic procedures in which measurement of forces at the needle holder base is difficult. Fiber Bragg grating sensors, due to their small size, inert nature, and multiplexing capability, provide a good option for this purpose. Force measurements have been undertaken during needle insertion into tissue mimicking phantoms made of polydimethylsiloxane as well as chicken tissue using an 18-G needle instrumented with FBG sensors. The results obtained show that it is possible to estimate the different stages of needle penetration including partial rupture, which is significant for procedures in which precise estimation of needle tip position inside the organ or tissue is required. |
| 48. | Sasikumar, Harish; Prasad, Vishnu; Pal, Parama; Varma, Manoj Diffractive interference optical analyzer (DiOPTER) Conference Proceedings of the 2016 SPIE International Conference Optical Diagnostics and Sensing XVI: Toward Point-of-Care Diagnostics, 13.02.16, San Francisco (USA), 9715 , 2016. Abstract | BibTeX | Tags: Health, Smart phone interferometer | Links: @conference{Sasikumar2016, title = {Diffractive interference optical analyzer (DiOPTER)}, author = {Harish Sasikumar and Vishnu Prasad and Parama Pal and Manoj Varma}, doi = {10.1117/12.2211745}, year = {2016}, date = {2016-02-16}, booktitle = {Proceedings of the 2016 SPIE International Conference Optical Diagnostics and Sensing XVI: Toward Point-of-Care Diagnostics, 13.02.16, San Francisco (USA)}, volume = {9715}, abstract = {This report demonstrates a method for high-resolution refractometric measurements using, what we have termed as, a Diffractive Interference Optical Analyzer (DiOpter). The setup consists of a laser, polarizer, a transparent diffraction grating and Si-photodetectors. The sensor is based on the differential response of diffracted orders to bulk refractive index changes. In these setups, the differential read-out of the diffracted orders suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6x10(-7) RIU was achieved in glass. This work focuses on devices with integrated sample well, made on low-cost PDMS. As the detection methodology is experimentally straightforward, it can be used across a wide array of applications, ranging from detecting changes in surface adsorbates via binding reactions to estimating refractive index (and hence concentration) variations in bulk samples. An exciting prospect of this technique is the potential integration of this device to smartphones using a simple interface based on transmission mode configuration. In a transmission configuration, we were able to achieve an LoD of 4x10(-4) RIU which is sufficient to explore several applications in food quality testing and related fields. We are envisioning the future of this platform as a personal handheld optical analyzer for applications ranging from environmental sensing to healthcare and quality testing of food products.}, keywords = {Health, Smart phone interferometer}, pubstate = {published}, tppubtype = {conference} } This report demonstrates a method for high-resolution refractometric measurements using, what we have termed as, a Diffractive Interference Optical Analyzer (DiOpter). The setup consists of a laser, polarizer, a transparent diffraction grating and Si-photodetectors. The sensor is based on the differential response of diffracted orders to bulk refractive index changes. In these setups, the differential read-out of the diffracted orders suppresses signal drifts and enables time-resolved determination of refractive index changes in the sample cell. A remarkable feature of this device is that under appropriate conditions, the measurement sensitivity of the sensor can be enhanced by more than two orders of magnitude due to interference between multiply reflected diffracted orders. A noise-equivalent limit of detection (LoD) of 6x10(-7) RIU was achieved in glass. This work focuses on devices with integrated sample well, made on low-cost PDMS. As the detection methodology is experimentally straightforward, it can be used across a wide array of applications, ranging from detecting changes in surface adsorbates via binding reactions to estimating refractive index (and hence concentration) variations in bulk samples. An exciting prospect of this technique is the potential integration of this device to smartphones using a simple interface based on transmission mode configuration. In a transmission configuration, we were able to achieve an LoD of 4x10(-4) RIU which is sufficient to explore several applications in food quality testing and related fields. We are envisioning the future of this platform as a personal handheld optical analyzer for applications ranging from environmental sensing to healthcare and quality testing of food products. |
| 49. | Chakraborty, Krishnendu; Tiwari, Abhay; Varma, Manoj; Venkatapathi, Murugesan Enhancement of scattering from nanoparticles using substrate effect Conference Proceedings of SPIE 2016 Plasmonics in Biology and Medicine XIII, 13.02.16, San Francisco (USA), 9724 , 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Chakraborty2016b, title = {Enhancement of scattering from nanoparticles using substrate effect}, author = {Krishnendu Chakraborty and Abhay Tiwari and Manoj Varma and Murugesan Venkatapathi}, doi = {10.1117/12.2211637}, year = {2016}, date = {2016-04-22}, booktitle = {Proceedings of SPIE 2016 Plasmonics in Biology and Medicine XIII, 13.02.16, San Francisco (USA)}, volume = {9724}, pages = {6}, abstract = {Scattering cross-section of metal nanoparticles is enhanced due to Localized Surface Plasmons Resonance (LSPR) permitting the observation of single metal nanoparticles as small as 40 nm using dark-field microscopy. Single particle resolved measurements allow the study of reactions happening on the nanoparticle surface involving an ultra-low number of reactant molecules to understand stochastic effects in reactive systems. Here we report a method to enhance the intensity of resonantly scattered light by using appropriately designed substrates. Specifically, we show that by using a multi-layer dielectric substrate with its high reflectance window spanning the LSPR resonance position, one can increase the intensity of scattered light by nearly an order of magnitude. We took three substrates namely Silicon, glass and the multilayer dielectric mirror. Disk shaped gold nanostructures with sizes ranging from 80 nm – 300 nm were fabricated using electron beam lithography on all three substrates. Sizes of individual nanostructures were determined by atomic force microscopy (AFM) and the dark-field image of each nanostructure was taken with an optical microscope. It was observed that the intensity of light scattered by single nanparticles was roughly an order magnitude larger than that from Silicon and glass substrates. We used a numerical scheme based on Discrete Dipole Approximation to computationally validate our results. The numerical results matched the experiments quite well. The substrate enhanced scattering signal will useful to improve the signal to noise ratio in single particle resolved measurements.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } Scattering cross-section of metal nanoparticles is enhanced due to Localized Surface Plasmons Resonance (LSPR) permitting the observation of single metal nanoparticles as small as 40 nm using dark-field microscopy. Single particle resolved measurements allow the study of reactions happening on the nanoparticle surface involving an ultra-low number of reactant molecules to understand stochastic effects in reactive systems. Here we report a method to enhance the intensity of resonantly scattered light by using appropriately designed substrates. Specifically, we show that by using a multi-layer dielectric substrate with its high reflectance window spanning the LSPR resonance position, one can increase the intensity of scattered light by nearly an order of magnitude. We took three substrates namely Silicon, glass and the multilayer dielectric mirror. Disk shaped gold nanostructures with sizes ranging from 80 nm – 300 nm were fabricated using electron beam lithography on all three substrates. Sizes of individual nanostructures were determined by atomic force microscopy (AFM) and the dark-field image of each nanostructure was taken with an optical microscope. It was observed that the intensity of light scattered by single nanparticles was roughly an order magnitude larger than that from Silicon and glass substrates. We used a numerical scheme based on Discrete Dipole Approximation to computationally validate our results. The numerical results matched the experiments quite well. The substrate enhanced scattering signal will useful to improve the signal to noise ratio in single particle resolved measurements. |
| 50. | Chakraborty, Krishnendu; Kumawat, N; Sultana, Sabiha; Varma, Manoj Enhancing the quality factor of grating coupled plasmon resonance in optical recording media Journal Article Sensors and Actuators A: Physical, 244 , pp. 50-55, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Chakraborty2016, title = {Enhancing the quality factor of grating coupled plasmon resonance in optical recording media}, author = {Krishnendu Chakraborty and N. Kumawat and Sabiha Sultana and Manoj Varma}, url = {http://www.rbccps.org/wp-content/uploads/2017/10/1-s2.0-S0924424716301704-main.pdf}, doi = {10.1016/j.sna.2016.04.025}, year = {2016}, date = {2016-04-11}, journal = {Sensors and Actuators A: Physical}, volume = {244}, pages = {50-55}, abstract = {Optical recording media such as Digital Video Discs (DVDs) or Blu-ray discs provide a readily available source for high quality 1D diffractive structures at the sub-wavelength scale in the visible spectrum. These are useful for several optical sensing methodologies such as Surface Plasmon Resonance (SPR) where the grating couples incident light into plasmon modes supported by the structure. The gratings available in these off-the-shelf devices are not optimized for SPR based sensing. Here we describe a simple method to improve the quality factor, an important performance metric of SPR based sensors, of optical recording media based plasmonic sensors. We reduced the linewidth of SPR response from a DVD based SPR sensor by an order of magnitude using a 100 nm thick polyelectrolyte multilayer film deposited using sequential layer by layer assembly from solutions. Numerical modeling and Atomic Force Microscopy studies established the origin of quality factor improvement from the change in the topography of the grating due to a polymer assembly. We demonstrate a limit of detection (LoD) of 7 × 10−6 RIU using the modified DVD based grating coupled SPR sensor.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Optical recording media such as Digital Video Discs (DVDs) or Blu-ray discs provide a readily available source for high quality 1D diffractive structures at the sub-wavelength scale in the visible spectrum. These are useful for several optical sensing methodologies such as Surface Plasmon Resonance (SPR) where the grating couples incident light into plasmon modes supported by the structure. The gratings available in these off-the-shelf devices are not optimized for SPR based sensing. Here we describe a simple method to improve the quality factor, an important performance metric of SPR based sensors, of optical recording media based plasmonic sensors. We reduced the linewidth of SPR response from a DVD based SPR sensor by an order of magnitude using a 100 nm thick polyelectrolyte multilayer film deposited using sequential layer by layer assembly from solutions. Numerical modeling and Atomic Force Microscopy studies established the origin of quality factor improvement from the change in the topography of the grating due to a polymer assembly. We demonstrate a limit of detection (LoD) of 7 × 10−6 RIU using the modified DVD based grating coupled SPR sensor. |
