2017 |
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| 1. | Sekuboyina, Anjany Kumar; Devarakonda, Surya Teja; Seelamantula, Chandra Sekhar A convolutional neural network approach for abnormality detection in wireless capsule endoscopy Conference Forthcoming Proceedings of the 2017 IEEE International Symposium on Biomedical Imaging, 18-21 April 2017, Melbourne (Australia), Forthcoming. Abstract | BibTeX | Tags: Cyber Surgery and Remote Patient Care, Health @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}, year = {2017}, date = {2017-04-28}, booktitle = {Proceedings of the 2017 IEEE International Symposium on Biomedical Imaging, 18-21 April 2017, Melbourne (Australia)}, 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 = {forthcoming}, 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. |
| 2. | Bhargava, Srivatsa; Gorur, Pushkar; Amrutur, Bharadwaj A distributed object detector-tracker aided video encoder for smart camera networks Conference Forthcoming 11th International Conference on Distributed Smart Cameras (ICDSC), 05.-07.09.17, Stanford (USA), Forthcoming. BibTeX | Tags: Efficient architectures and algorithms for distributed video analytics for Smart Cities, Modeling and Simulation and Analytics @conference{Srivatsa2017, title = {A distributed object detector-tracker aided video encoder for smart camera networks}, author = {Srivatsa Bhargava and Pushkar Gorur and Bharadwaj Amrutur}, year = {2017}, date = {2017-09-07}, booktitle = {11th International Conference on Distributed Smart Cameras (ICDSC), 05.-07.09.17, Stanford (USA)}, keywords = {Efficient architectures and algorithms for distributed video analytics for Smart Cities, Modeling and Simulation and Analytics}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 3. | 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: 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 = {Smart Campus Water Management: Closing the IoT Loop from Network to Knowledge}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 4. | 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}, 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. |
| 5. | 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}, 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. |
| 6. | 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: Systems Engineering @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}, year = {2017}, date = {2017-05-04}, 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 = {Systems Engineering}, 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. |
| 7. | Anjana, G R; Kumar, Mohan M S; Amrutur, Bharadwaj Comparison of different controllers for equitable water supply in water networks Conference Forthcoming Proceedings of the 15th International Computing & Control for the Water Industry Conference (CCWI), 05.-07.09.17, Sheffield (UK), Forthcoming. Abstract | BibTeX | Tags: Water @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}, 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 = {forthcoming}, 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. |
| 8. | 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} } |
| 9. | 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}, 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)}, 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. |
| 10. | Khandelwal, T; Rajwanshi, K; Bharadwaj, P; Garani, S S; Sundaresan, Rajesh Exploiting appliance state constraints to improve appliance state detection Conference Forthcoming Proceedings of the 8th ACM International Conference on Future Energy Systems (ACM eEnergy), 16.-19.05.17, Hong Kong (China), Forthcoming. BibTeX | Tags: Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector @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}, 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)}, keywords = {Developing a framework for using electricity consumption data to drive energy efficiency in the residential sector}, pubstate = {forthcoming}, tppubtype = {conference} } |
| 11. | 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} } |
| 12. | 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} } |
| 13. | 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} } |
| 14. | Kundu, Atreyee; Daafouz, Jamal; Heemels, Maurice Stabilization of discrete-time switched linear systems: Lyapunov-Metzler inequalities versus S-procedure characterizations Conference Forthcoming Proceedings of the 20th World Congress of the International Federation of Automatic Control (IFAC 2017), 09.-14.07.17, Toulouse (France), Forthcoming. Abstract | BibTeX | Tags: Control and Optimisation and Policy @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}, 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)}, 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 = {forthcoming}, 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. |
| 15. | 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}, 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. |
2016 |
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| 16. | 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}, 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. |
| 17. | 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}, 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. |
| 18. | 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). |
| 19. | Varma, Manoj Article does not explain the origin of free-solution protein interaction signals Journal Article Proceedings of the National Academy of Sciences of the United States of America, 113 (34), pp. 4930, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Varma2016, title = {Article does not explain the origin of free-solution protein interaction signals}, author = {Manoj Varma}, doi = {10.1073/pnas.1608094113}, year = {2016}, date = {2016-08-23}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {113}, number = {34}, pages = {4930}, abstract = {Bornhop et al. had shown that interactions between protein molecules in solution can be detected by measuring the solution refractive index shifts using a technique referred to as backscattering interferometry (BSI). The origin of the BSI signal was unclear. In a recent article in PNAS, Bornhop et al. claim to provide an explanation of its origin. Based on a large body of published literature, they argue that solvation and conformational changes during protein interactions could have a large effect on BSI signal. However, other than pointing out this possibly important fact, this article does not really provide an explanation of the BSI signal origin.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Bornhop et al. had shown that interactions between protein molecules in solution can be detected by measuring the solution refractive index shifts using a technique referred to as backscattering interferometry (BSI). The origin of the BSI signal was unclear. In a recent article in PNAS, Bornhop et al. claim to provide an explanation of its origin. Based on a large body of published literature, they argue that solvation and conformational changes during protein interactions could have a large effect on BSI signal. However, other than pointing out this possibly important fact, this article does not really provide an explanation of the BSI signal origin. |
| 20. | Suran, Swathi; Bharadwaj, Krishna; Raghavan, Srinivasan; Varma, Manoj Bright-field nanoscopy: Visualizing nano-structures with localized optical contrast using a conventional microscope Journal Article Scientific Reports, 6 , pp. 7, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Suran2016, title = {Bright-field nanoscopy: Visualizing nano-structures with localized optical contrast using a conventional microscope}, author = {Swathi Suran and Krishna Bharadwaj and Srinivasan Raghavan and Manoj Varma}, doi = {doi:10.1038/srep25011}, year = {2016}, date = {2016-04-26}, journal = {Scientific Reports}, volume = {6}, pages = {7}, abstract = {Most methods for optical visualization beyond the diffraction limit rely on fluorescence emission by molecular tags. Here, we report a method for visualization of nanostructures down to a few nanometers using a conventional bright-field microscope without requiring additional molecular tags such as fluorophores. The technique, Bright-field Nanoscopy, is based on the strong thickness dependent color of ultra-thin germanium on an optically thick gold film. We demonstrate the visualization of grain boundaries in chemical vapour deposited single layer graphene and the detection of single 40 nm Ag nanoparticles. We estimate a size detection limit of about 2 nm using this technique. In addition to visualizing nano-structures, this technique can be used to probe fluid phenomena at the nanoscale, such as transport through 2D membranes. We estimated the water transport rate through a 1 nm thick polymer film using this technique, as an illustration. Further, the technique can also be extended to study the transport of specific ions in the solution. It is anticipated that this technique will find use in applications ranging from single-nanoparticles resolved sensing to studying nanoscale fluid-solid interface phenomena.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } Most methods for optical visualization beyond the diffraction limit rely on fluorescence emission by molecular tags. Here, we report a method for visualization of nanostructures down to a few nanometers using a conventional bright-field microscope without requiring additional molecular tags such as fluorophores. The technique, Bright-field Nanoscopy, is based on the strong thickness dependent color of ultra-thin germanium on an optically thick gold film. We demonstrate the visualization of grain boundaries in chemical vapour deposited single layer graphene and the detection of single 40 nm Ag nanoparticles. We estimate a size detection limit of about 2 nm using this technique. In addition to visualizing nano-structures, this technique can be used to probe fluid phenomena at the nanoscale, such as transport through 2D membranes. We estimated the water transport rate through a 1 nm thick polymer film using this technique, as an illustration. Further, the technique can also be extended to study the transport of specific ions in the solution. It is anticipated that this technique will find use in applications ranging from single-nanoparticles resolved sensing to studying nanoscale fluid-solid interface phenomena. |
| 21. | 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}, 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. |
| 22. | 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}, 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. |
| 23. | Singh, Chandramani; Kumar, Anurag; Sundaresan, Rajesh Combined base station association and power control in multi-channel cellular networks Journal Article IEEE/ACM Transactions on Networking, 24 (2), pp. 1065-1080, 2016. Abstract | BibTeX | Tags: Systems Engineering | Links: @article{Singh2016b, title = {Combined base station association and power control in multi-channel cellular networks}, author = {Chandramani Singh and Anurag Kumar and Rajesh Sundaresan}, doi = {10.1109/TNET.2015.2417217}, year = {2016}, date = {2016-04-01}, journal = {IEEE/ACM Transactions on Networking}, volume = {24}, number = {2}, pages = {1065-1080}, abstract = {A combined base station association and power control problem is studied for the uplink of multichannel multicell cellular networks, in which each channel is used by exactly one cell (i.e., base station). A distributed association and power update algorithm is proposed and shown to converge to a Nash equilibrium of a noncooperative game. We consider network models with discrete mobiles (yielding an atomic congestion game), as well as a continuum of mobiles (yielding a population game). We find that the equilibria need not be Pareto efficient, nor need they be system optimal. To address the lack of system optimality, we propose pricing mechanisms. It is shown that these mechanisms can be implemented in a distributed fashion.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {article} } A combined base station association and power control problem is studied for the uplink of multichannel multicell cellular networks, in which each channel is used by exactly one cell (i.e., base station). A distributed association and power update algorithm is proposed and shown to converge to a Nash equilibrium of a noncooperative game. We consider network models with discrete mobiles (yielding an atomic congestion game), as well as a continuum of mobiles (yielding a population game). We find that the equilibria need not be Pareto efficient, nor need they be system optimal. To address the lack of system optimality, we propose pricing mechanisms. It is shown that these mechanisms can be implemented in a distributed fashion. |
| 24. | 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. |
| 25. | 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}, 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. |
| 26. | 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. |
| 27. | 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. |
| 28. | 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}, 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. |
| 29. | Singh, Puneet; Jana, Sumitash; Ghosal, Ashitava; Murthy, Aditya Exploration of joint redundancy but not task space variability facilitates supervised motor learning Journal Article Proceedings of the National Academy of Sciences of the United States of America, 113 (50), pp. 14414-14419, 2016. Abstract | BibTeX | Tags: Cyber Surgery and Remote Patient Care, Health | Links: @article{Singh2016, title = {Exploration of joint redundancy but not task space variability facilitates supervised motor learning}, author = {Puneet Singh and Sumitash Jana and Ashitava Ghosal and Aditya Murthy}, doi = {10.1073/pnas.1613383113}, year = {2016}, date = {2016-10-27}, journal = {Proceedings of the National Academy of Sciences of the United States of America}, volume = {113}, number = {50}, pages = {14414-14419}, abstract = {Theories of reinforcement learning claim that motor variability helps in motor learning and are supported by recent experimental work. In contrast, theories of motor control propose that variability is noise that needs to be suppressed. We attempt to reconcile these apparent contradictory positions. Using the formulation of the unconstrained manifold hypothesis, we show that motor variability has two components – a part arising out of the redundancy that does not affect task-space and another component related to task-space variability. We show that the motor variability component resulting from the redundancy determines both dynamic and kinematic learning ability across subjects without affecting task-space variability.}, keywords = {Cyber Surgery and Remote Patient Care, Health}, pubstate = {published}, tppubtype = {article} } Theories of reinforcement learning claim that motor variability helps in motor learning and are supported by recent experimental work. In contrast, theories of motor control propose that variability is noise that needs to be suppressed. We attempt to reconcile these apparent contradictory positions. Using the formulation of the unconstrained manifold hypothesis, we show that motor variability has two components – a part arising out of the redundancy that does not affect task-space and another component related to task-space variability. We show that the motor variability component resulting from the redundancy determines both dynamic and kinematic learning ability across subjects without affecting task-space variability. |
| 30. | Prasad, Prashanth R; Selvaraja, Shankar K; Varma, Manoj Full-range detection in cascaded microring sensors using thermooptical tuning Journal Article Journal of Lightwave Technology, 34 (22), pp. 5157-5163, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Prasad2016, title = {Full-range detection in cascaded microring sensors using thermooptical tuning}, author = {Prashanth R. Prasad and Shankar K. Selvaraja and Manoj Varma}, doi = {10.1109/JLT.2016.2608979}, year = {2016}, date = {2016-11-15}, journal = {Journal of Lightwave Technology}, volume = {34}, number = {22}, pages = {5157-5163}, abstract = {We present detailed analysis and experimental demonstration of full-range detection in cascaded microring sensors by using thermooptical tuning. A cascaded microring sensor translates spectrum shifts into intensity changes eliminating the need for expensive spectral analysis equipment for sensing applications. Without tuning capability, this configuration provides high sensitivity, but a small detection range since the intensity output decays toward zero for low overlap between spectra of individual microrings. We overcome this limitation by using thermooptic tuning in one of the microrings for extending the detection range to span an entire free spectral range of the probing microring. Additionally, we analyze the impact of resonance linewidths and differences in free spectral ranges (FSRs) of microrings on the widths of output intensity peaks. With full FSR thermooptical tuning, we demonstrate a total detection range of 0.0241 refractive index units (RIU) and a limit of detection of 4.6 × 10-5 RIU for microrings with 100-μm radii. Photodetector-based signal readout combined with CMOS compatible manufacturability makes this device design attractive as a silicon-based optical sensing platform.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } We present detailed analysis and experimental demonstration of full-range detection in cascaded microring sensors by using thermooptical tuning. A cascaded microring sensor translates spectrum shifts into intensity changes eliminating the need for expensive spectral analysis equipment for sensing applications. Without tuning capability, this configuration provides high sensitivity, but a small detection range since the intensity output decays toward zero for low overlap between spectra of individual microrings. We overcome this limitation by using thermooptic tuning in one of the microrings for extending the detection range to span an entire free spectral range of the probing microring. Additionally, we analyze the impact of resonance linewidths and differences in free spectral ranges (FSRs) of microrings on the widths of output intensity peaks. With full FSR thermooptical tuning, we demonstrate a total detection range of 0.0241 refractive index units (RIU) and a limit of detection of 4.6 × 10-5 RIU for microrings with 100-μm radii. Photodetector-based signal readout combined with CMOS compatible manufacturability makes this device design attractive as a silicon-based optical sensing platform. |
| 31. | Dana, Saswati; Varma, Manoj Gas-selective signal amplification in fluctuation based graphene FET sensors Journal Article IEEE Sensors Journal, 16 (17), pp. 6533-6536, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Dana2016, title = {Gas-selective signal amplification in fluctuation based graphene FET sensors}, author = {Saswati Dana and Manoj Varma}, doi = {10.1109/JSEN.2016.2585739}, year = {2016}, date = {2016-09-01}, journal = {IEEE Sensors Journal}, volume = {16}, number = {17}, pages = {6533-6536}, abstract = {The power spectrum of conductance fluctuations arising from the adsorption of gas molecules to a graphene field-effect transistor was shown to contain the signature of the adsorbing species recently. A detailed mechanism of the phenomena was not provided although it was remarked that these conductance fluctuations arise due to the number fluctuations of the adsorbed molecules, which may donate (or accept) electrons to (or from) graphene. In this paper, we report on a phenomenological model based on conductance fluctuations and analyze a novel sensing configuration consisting of a sinusoidally varying gate voltage sweeping across the Dirac point, which changes the sign of conductance response to adsorption. We show that this configuration leads to gas-selective amplification of peaks of the conductance fluctuation spectra.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } The power spectrum of conductance fluctuations arising from the adsorption of gas molecules to a graphene field-effect transistor was shown to contain the signature of the adsorbing species recently. A detailed mechanism of the phenomena was not provided although it was remarked that these conductance fluctuations arise due to the number fluctuations of the adsorbed molecules, which may donate (or accept) electrons to (or from) graphene. In this paper, we report on a phenomenological model based on conductance fluctuations and analyze a novel sensing configuration consisting of a sinusoidally varying gate voltage sweeping across the Dirac point, which changes the sign of conductance response to adsorption. We show that this configuration leads to gas-selective amplification of peaks of the conductance fluctuation spectra. |
| 32. | Altman, Eitan; Hanawal, Manjesh Kumar; Sundaresan, Rajesh Generalising diagonal strict concavity property for uniqueness of Nash equilibrium Journal Article Indian Journal of Pure and Applied Mathematics, 47 (2), pp. 213-228, 2016. Abstract | BibTeX | Tags: Systems Engineering | Links: @article{Altman2016, title = {Generalising diagonal strict concavity property for uniqueness of Nash equilibrium}, author = {Eitan Altman and Manjesh Kumar Hanawal and Rajesh Sundaresan}, doi = {10.1007/s13226-016-0185-4}, year = {2016}, date = {2016-06-01}, journal = {Indian Journal of Pure and Applied Mathematics}, volume = {47}, number = {2}, pages = {213-228}, abstract = {In this paper, we extend the notion of diagonally strictly concave functions and use it to provide a sufficient condition for uniqueness of Nash equilibrium in some concave games. We then provide an alternative proof of the existence and uniqueness of Nash equilibrium for a network resource allocation game arising from the so-called Kelly mechanism by verifying the new sufficient condition. We then establish that the equilibrium resulting from the differential pricing in the Kelly mechanism is related to a normalised Nash equilibrium of a game with coupled strategy space.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {article} } In this paper, we extend the notion of diagonally strictly concave functions and use it to provide a sufficient condition for uniqueness of Nash equilibrium in some concave games. We then provide an alternative proof of the existence and uniqueness of Nash equilibrium for a network resource allocation game arising from the so-called Kelly mechanism by verifying the new sufficient condition. We then establish that the equilibrium resulting from the differential pricing in the Kelly mechanism is related to a normalised Nash equilibrium of a game with coupled strategy space. |
| 33. | Prasad, Prashanth R; Selvaraja, Shankar K; Varma, Manoj High precision measurement of intensity peak shift in tunable cascaded microring intensity sensors Journal Article Optics Letters, 41 (14), pp. 3153-3156, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Prasad2016b, title = {High precision measurement of intensity peak shift in tunable cascaded microring intensity sensors}, author = {Prashanth R. Prasad and Shankar K. Selvaraja and Manoj Varma}, doi = {10.1364/OL.41.003153}, year = {2016}, date = {2016-07-05}, journal = {Optics Letters}, volume = {41}, number = {14}, pages = {3153-3156}, abstract = {We demonstrate a method to precisely track intensity peak shifts in tunable cascaded double-microring based refractive index sensors. Without modifications, width of the intensity peak of a tunable cascaded microring device limits the precision of peak-shift measurements and thereby the limit of detection of the sensor. We overcome this limitation by using dual harmonic lock-in detection for precisely determining the position of the intensity maximum. Using this modification, we have demonstrated a reduction in the full width at half-maximum (FWHM) of the intensity peak by a factor of over 1300. We show that such a reduction in FWHM of the peak curve can significantly improve the detection limit of a tunable cascaded microring-based sensor.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } We demonstrate a method to precisely track intensity peak shifts in tunable cascaded double-microring based refractive index sensors. Without modifications, width of the intensity peak of a tunable cascaded microring device limits the precision of peak-shift measurements and thereby the limit of detection of the sensor. We overcome this limitation by using dual harmonic lock-in detection for precisely determining the position of the intensity maximum. Using this modification, we have demonstrated a reduction in the full width at half-maximum (FWHM) of the intensity peak by a factor of over 1300. We show that such a reduction in FWHM of the peak curve can significantly improve the detection limit of a tunable cascaded microring-based sensor. |
| 34. | Reddy, Sai Koti D; A., Prasanth L; Bhatnagar, Shalabh Improved Hessian estimation for adaptive random directions stochastic approximation Conference Proceedings of 2016 IEEE Conference on Decision and Control (CDC), Las Vegas (USA), 2016. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @conference{Reddy2016, title = {Improved Hessian estimation for adaptive random directions stochastic approximation}, author = {D. Sai Koti Reddy and Prasanth L. A. and Shalabh Bhatnagar}, doi = {10.1109/CDC.2016.7798823}, year = {2016}, date = {2016-12-14}, booktitle = {Proceedings of 2016 IEEE Conference on Decision and Control (CDC), Las Vegas (USA)}, pages = {3682-3687}, abstract = {We propose an improved Hessian estimation scheme for the second-order random directions stochastic approximation (2RDSA) algorithm. The proposed scheme reduces the error in the Hessian estimate by (i) incorporating a zero-mean feedback term; and (ii) optimizing the step-sizes used in the Hessian recursion of 2RDSA. We prove that 2RDSA with our Hessian improvement scheme (2RDSA-IH) converges asymptotically to the true Hessian. The advantage with 2RDSA-IH is that it requires only 75% of the simulation cost per-iteration for 2SPSA with improved Hessian estimation (2SPSA-IH). Numerical experiments show that 2RDSA-IH outperforms both 2SPSA-IH and 2RDSA without the improved Hessian estimation scheme.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {conference} } We propose an improved Hessian estimation scheme for the second-order random directions stochastic approximation (2RDSA) algorithm. The proposed scheme reduces the error in the Hessian estimate by (i) incorporating a zero-mean feedback term; and (ii) optimizing the step-sizes used in the Hessian recursion of 2RDSA. We prove that 2RDSA with our Hessian improvement scheme (2RDSA-IH) converges asymptotically to the true Hessian. The advantage with 2RDSA-IH is that it requires only 75% of the simulation cost per-iteration for 2SPSA with improved Hessian estimation (2SPSA-IH). Numerical experiments show that 2RDSA-IH outperforms both 2SPSA-IH and 2RDSA without the improved Hessian estimation scheme. |
| 35. | Pal, Parama; Sasikumar, Harish; Varma, Manoj Label-free biosensing using diffractive optical analysis Conference Proceedings of the 13th International Conference on Fiber Optics and Photonics, 04.-06.12.16, Kanpur (India), 2016. Abstract | BibTeX | Tags: Health, Smart phone interferometer | Links: @conference{Pal2016, title = {Label-free biosensing using diffractive optical analysis}, author = {Parama Pal and Harish Sasikumar and Manoj Varma}, doi = {10.1364/PHOTONICS.2016.Th2F.1}, year = {2016}, date = {2016-12-08}, booktitle = {Proceedings of the 13th International Conference on Fiber Optics and Photonics, 04.-06.12.16, Kanpur (India)}, abstract = {We demonstrate a biosensing technique based on high-resolution (~10-6 refractive index units) refractometric measurements for detecting time-resolved concentration variations in surface (due to the binding of adsorbates) as well as in bulk samples.}, keywords = {Health, Smart phone interferometer}, pubstate = {published}, tppubtype = {conference} } We demonstrate a biosensing technique based on high-resolution (~10-6 refractive index units) refractometric measurements for detecting time-resolved concentration variations in surface (due to the binding of adsorbates) as well as in bulk samples. |
| 36. | Chakraborty, Krishnendu; Varma, Manoj; Venkatapathi, Murugesan Measuring pair-wise molecular interactions in a complex mixture Conference Proceedings of SPIE 2016 Colloidal Nanoparticles for Biomedical Applications XI, 13.02.16, San Francisco (USA), 9722 , 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Chakraborty2016b, title = {Measuring pair-wise molecular interactions in a complex mixture}, author = {Krishnendu Chakraborty and Manoj Varma and Murugesan Venkatapathi}, doi = {10.1117/12.2211669}, year = {2016}, date = {2016-03-07}, booktitle = {Proceedings of SPIE 2016 Colloidal Nanoparticles for Biomedical Applications XI, 13.02.16, San Francisco (USA)}, volume = {9722}, pages = {5}, abstract = {Complex biological samples such as serum contain thousands of proteins and other molecules spanning up to 13 orders of magnitude in concentration. Present measurement techniques do not permit the analysis of all pair-wise interactions between the components of such a complex mixture to a given target molecule. In this work we explore the use of nanoparticle tags which encode the identity of the molecule to obtain the statistical distribution of pair-wise interactions using their Localized Surface Plasmon Resonance (LSPR) signals. The nanoparticle tags are chosen such that the binding between two molecules conjugated to the respective nanoparticle tags can be recognized by the coupling of their LSPR signals. This numerical simulation is done by DDA to investigate this approach using a reduced system consisting of three nanoparticles (a gold ellipsoid with aspect ratio 2.5 and short axis 16 nm, and two silver ellipsoids with aspect ratios 3 and 2 and short axes 8 nm and 10 nm respectively) and the set of all possible dimers formed between them. Incident light was circularly polarized and all possible particle and dimer orientations were considered. We observed that minimum peak separation between two spectra is 5 nm while maximum is 184nm.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } Complex biological samples such as serum contain thousands of proteins and other molecules spanning up to 13 orders of magnitude in concentration. Present measurement techniques do not permit the analysis of all pair-wise interactions between the components of such a complex mixture to a given target molecule. In this work we explore the use of nanoparticle tags which encode the identity of the molecule to obtain the statistical distribution of pair-wise interactions using their Localized Surface Plasmon Resonance (LSPR) signals. The nanoparticle tags are chosen such that the binding between two molecules conjugated to the respective nanoparticle tags can be recognized by the coupling of their LSPR signals. This numerical simulation is done by DDA to investigate this approach using a reduced system consisting of three nanoparticles (a gold ellipsoid with aspect ratio 2.5 and short axis 16 nm, and two silver ellipsoids with aspect ratios 3 and 2 and short axes 8 nm and 10 nm respectively) and the set of all possible dimers formed between them. Incident light was circularly polarized and all possible particle and dimer orientations were considered. We observed that minimum peak separation between two spectra is 5 nm while maximum is 184nm. |
| 37. | Varma, Manoj Modelling refractive index changes due to molecular interactions Conference Proceedings of SPIE 2016 Biophysics, Biology, and Biophotonics: The Crossroads, 13.-14.02.16, San Francisco (USA), 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Varma2016b, title = {Modelling refractive index changes due to molecular interactions}, author = {Manoj Varma}, doi = {10.1117/12.2211662}, year = {2016}, date = {2016-03-09}, booktitle = {Proceedings of SPIE 2016 Biophysics, Biology, and Biophotonics: The Crossroads, 13.-14.02.16, San Francisco (USA)}, pages = {6}, abstract = {There are a large number of sensing techniques which use optical changes to monitor interactions between molecules. In the absence of fluorophores or other labels, the basic signal transduction mechanism relies on refractive index changes arising from the interactions of the molecules involved. A quantitative model incorporating molecular transport, reaction kinetics and optical mixing is presented which reveals important insights concerning the optimal detection of molecular interactions optically. Although conceptually simple, a comprehensive model such as this has not been reported anywhere. Specifically, we investigate the pros and cons of detecting molecular interactions in free solution relative to detecting molecular interactions on surfaces using surface bound receptor molecules such as antibodies. The model reveals that the refractive index change produced in surface based sensors is 2-3 orders of magnitude higher than that from interactions in free solution. On the other hand, the model also reveals that it is indeed possible to distinguish specific molecular interactions from non-specific ones based on free-solution bulk refractometry without any washing step necessary in surface based sensors. However, the refractive index change for free solution interactions predicted by the model is smaller than 10-7 RIU, even for large proteins such as IgG in sufficiently high concentrations. This value is smaller than the typical 10-6 RIU detection limit of most state of the art optical sensing techniques therefore requiring techniques with substantially higher index sensitivity such as Back Scattering Interferometry.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } There are a large number of sensing techniques which use optical changes to monitor interactions between molecules. In the absence of fluorophores or other labels, the basic signal transduction mechanism relies on refractive index changes arising from the interactions of the molecules involved. A quantitative model incorporating molecular transport, reaction kinetics and optical mixing is presented which reveals important insights concerning the optimal detection of molecular interactions optically. Although conceptually simple, a comprehensive model such as this has not been reported anywhere. Specifically, we investigate the pros and cons of detecting molecular interactions in free solution relative to detecting molecular interactions on surfaces using surface bound receptor molecules such as antibodies. The model reveals that the refractive index change produced in surface based sensors is 2-3 orders of magnitude higher than that from interactions in free solution. On the other hand, the model also reveals that it is indeed possible to distinguish specific molecular interactions from non-specific ones based on free-solution bulk refractometry without any washing step necessary in surface based sensors. However, the refractive index change for free solution interactions predicted by the model is smaller than 10-7 RIU, even for large proteins such as IgG in sufficiently high concentrations. This value is smaller than the typical 10-6 RIU detection limit of most state of the art optical sensing techniques therefore requiring techniques with substantially higher index sensitivity such as Back Scattering Interferometry. |
| 38. | Bhatnagar, Shalabh; Lakshmanan, K Multiscale Q-learning with linear function approximation Journal Article Discrete Event Dynamic Systems, 26 (3), pp. 477-509, 2016. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @article{Bhatnagar2016, title = {Multiscale Q-learning with linear function approximation}, author = {Shalabh Bhatnagar and K. Lakshmanan}, doi = {10.1007/s10626-015-0216-z}, year = {2016}, date = {2016-09-30}, journal = {Discrete Event Dynamic Systems}, volume = {26}, number = {3}, pages = {477-509}, abstract = {We present in this article a two-timescale variant of Q-learning with linear function approximation. Both Q-values and policies are assumed to be parameterized with the policy parameter updated on a faster timescale as compared to the Q-value parameter. This timescale separation is seen to result in significantly improved numerical performance of the proposed algorithm over Q-learning. We show that the proposed algorithm converges almost surely to a closed connected internally chain transitive invariant set of an associated differential inclusion.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {article} } We present in this article a two-timescale variant of Q-learning with linear function approximation. Both Q-values and policies are assumed to be parameterized with the policy parameter updated on a faster timescale as compared to the Q-value parameter. This timescale separation is seen to result in significantly improved numerical performance of the proposed algorithm over Q-learning. We show that the proposed algorithm converges almost surely to a closed connected internally chain transitive invariant set of an associated differential inclusion. |
| 39. | Singh, Chandramani; Ramachandran, Santosh; Anand, S V R; Hedge, Malati; Kumar, Anurag; Sundaresan, Rajesh Neighbor oblivious and finite-state algorithms for circumventing local minima in geographic forwarding Journal Article Ad Hoc Networks, 50 , pp. 1-12, 2016. Abstract | BibTeX | Tags: Systems Engineering | Links: @article{Singh2016b, title = {Neighbor oblivious and finite-state algorithms for circumventing local minima in geographic forwarding}, author = {Chandramani Singh and Santosh Ramachandran and S. V. R. Anand and Malati Hedge and Anurag Kumar and Rajesh Sundaresan}, doi = {10.1016/j.adhoc.2016.05.010}, year = {2016}, date = {2016-11-01}, journal = {Ad Hoc Networks}, volume = {50}, pages = {1-12}, abstract = {We propose distributed link reversal algorithms to circumvent communication voids in geographic routing. We also solve the attendant problem of integer overflow in these algorithms. These are achieved in two steps. First, we derive partial and full link reversal algorithms that do not require one-hop neighbor information, and convert a destination-disoriented directed acyclic graph (DAG) to a destination-oriented DAG. We embed these algorithms in the framework of Gafni and Bertsekas [1] in order to establish their termination properties. We also analyze certain key properties exhibited by our neighbor oblivious link reversal algorithms, e.g., for any two neighbors, their t-states are always consecutive integers, and for any node, its t-state size is upper bounded by log(N). In the second step, we resolve the integer overflow problem by analytically deriving one-bit full link reversal and two-bit partial link reversal versions of our neighbor oblivious link reversal algorithms. We also discuss the work and time complexities of the proposed algorithms.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {article} } We propose distributed link reversal algorithms to circumvent communication voids in geographic routing. We also solve the attendant problem of integer overflow in these algorithms. These are achieved in two steps. First, we derive partial and full link reversal algorithms that do not require one-hop neighbor information, and convert a destination-disoriented directed acyclic graph (DAG) to a destination-oriented DAG. We embed these algorithms in the framework of Gafni and Bertsekas [1] in order to establish their termination properties. We also analyze certain key properties exhibited by our neighbor oblivious link reversal algorithms, e.g., for any two neighbors, their t-states are always consecutive integers, and for any node, its t-state size is upper bounded by log(N). In the second step, we resolve the integer overflow problem by analytically deriving one-bit full link reversal and two-bit partial link reversal versions of our neighbor oblivious link reversal algorithms. We also discuss the work and time complexities of the proposed algorithms. |
| 40. | Thirumulanathan, D; Sundaresan, Rajesh; Narahari, Y Optimal mechanism for selling two items to a single buyer having uniformly distributed valuations Conference Proceedings of the 12th International Conference on Web and Internet Economics (WINE), 11.-14.12.16, Montreal (Canada), 2016. Abstract | BibTeX | Tags: Systems Engineering | Links: @conference{Thirumulanathan2016, title = {Optimal mechanism for selling two items to a single buyer having uniformly distributed valuations}, author = {D. Thirumulanathan and Rajesh Sundaresan and Y. Narahari}, doi = {10.1007/978-3-662-54110-4_13}, year = {2016}, date = {2016-12-11}, booktitle = {Proceedings of the 12th International Conference on Web and Internet Economics (WINE), 11.-14.12.16, Montreal (Canada)}, pages = {174-187}, abstract = {We consider the design of an optimal mechanism for a seller selling two items to a single buyer so that the expected revenue to the seller is maximized. The buyer's valuation of the two items is assumed to be the uniform distribution over an arbitrary rectangle [c1,c1+b1]×[c2,c2+b2] in the positive quadrant. The solution to the case when (c1,c2)=(0,0) was already known. We provide an explicit solution for arbitrary nonnegative values of (c1,c2,b1,b2). We prove that the optimal mechanism is to sell the two items according to one of eight simple menus. We also prove that the solution is deterministic when either c1 or c2 is beyond a threshold. Finally, we conjecture that our methodology can be extended to a wider class of distributions. We also provide some preliminary results to support the conjecture.}, keywords = {Systems Engineering}, pubstate = {published}, tppubtype = {conference} } We consider the design of an optimal mechanism for a seller selling two items to a single buyer so that the expected revenue to the seller is maximized. The buyer's valuation of the two items is assumed to be the uniform distribution over an arbitrary rectangle [c1,c1+b1]×[c2,c2+b2] in the positive quadrant. The solution to the case when (c1,c2)=(0,0) was already known. We provide an explicit solution for arbitrary nonnegative values of (c1,c2,b1,b2). We prove that the optimal mechanism is to sell the two items according to one of eight simple menus. We also prove that the solution is deterministic when either c1 or c2 is beyond a threshold. Finally, we conjecture that our methodology can be extended to a wider class of distributions. We also provide some preliminary results to support the conjecture. |
| 41. | Khanum, Khadija K; Rao, Abhishek; Balaji, N C; Mani, Monto; Ramamurthy, Praveen Performance evaluation for PV systems to synergistic influences of dust, wind and panel temperatures: Spectral insight Conference Proceedings of the 43rd IEEE Photovoltaic Specialists Conference (PVSC 2016), Portland (USA), 2016. Abstract | BibTeX | Tags: Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions | Links: @conference{Khanum2016b, title = {Performance evaluation for PV systems to synergistic influences of dust, wind and panel temperatures: Spectral insight}, author = {Khadija K. Khanum and Abhishek Rao and N. C. Balaji and Monto Mani and Praveen Ramamurthy}, doi = {10.1109/PVSC.2016.7749917}, year = {2016}, date = {2016-11-21}, booktitle = {Proceedings of the 43rd IEEE Photovoltaic Specialists Conference (PVSC 2016), Portland (USA)}, abstract = {Dust is a ubiquitous occurrence influencing PV performance, primarily by cutting the solar radiation reaching the PV cell. Since the PV cell is always encapsulated, the dynamics of light reaching the cell involves a complex interplay of scattering, absorption and reflection of light starting from surface of glass till it reaches the cell. Dust settling on the glass adds to this complex interplay and alters the way both direct and diffused radiation reaches the PV cell. The impact of dust thus far has always been understood to be detrimental, which may not be valid under all conditions. Dust on PV (panel) glass could be studied as optical filters determining which wavelength of light reaches the PV cell. While few studies on dust have dealt with the spectral-band of light necessary for PV output, they have overlooked the fact that the remainder of the spectra is absorbed by the PV system, and could influence its output. It is possible that dust actually absorbs the unwanted IR that would otherwise increase cell temperature, degrading its output. Preliminary study concurs that certain kind of dust deposition at specific settlement densities could be beneficial for PV performance by absorbing unwanted IR. The current study deals with Si based PV which is known to predominantly operate on the visible part of the solar spectrum, and is easily affected by temperature (IR absorption) and dust.}, keywords = {Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions}, pubstate = {published}, tppubtype = {conference} } Dust is a ubiquitous occurrence influencing PV performance, primarily by cutting the solar radiation reaching the PV cell. Since the PV cell is always encapsulated, the dynamics of light reaching the cell involves a complex interplay of scattering, absorption and reflection of light starting from surface of glass till it reaches the cell. Dust settling on the glass adds to this complex interplay and alters the way both direct and diffused radiation reaches the PV cell. The impact of dust thus far has always been understood to be detrimental, which may not be valid under all conditions. Dust on PV (panel) glass could be studied as optical filters determining which wavelength of light reaches the PV cell. While few studies on dust have dealt with the spectral-band of light necessary for PV output, they have overlooked the fact that the remainder of the spectra is absorbed by the PV system, and could influence its output. It is possible that dust actually absorbs the unwanted IR that would otherwise increase cell temperature, degrading its output. Preliminary study concurs that certain kind of dust deposition at specific settlement densities could be beneficial for PV performance by absorbing unwanted IR. The current study deals with Si based PV which is known to predominantly operate on the visible part of the solar spectrum, and is easily affected by temperature (IR absorption) and dust. |
| 42. | Varma, Manoj Performance limitations of label-free sensors in molecular diagnosis using complex samples Conference Proceedings of SPIE 2016 Frontiers in Biological Detection: From Nanosensors to Systems VIII, 13.02.16, San Francisco (USA), 9725 , 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Varma2016b, title = {Performance limitations of label-free sensors in molecular diagnosis using complex samples}, author = {Manoj Varma}, doi = {10.1117/12.2211655}, year = {2016}, date = {2016-04-22}, booktitle = {Proceedings of SPIE 2016 Frontiers in Biological Detection: From Nanosensors to Systems VIII, 13.02.16, San Francisco (USA)}, volume = {9725}, pages = {4}, abstract = {Label-free biosensors promised a paradigm involving direct detection of biomarkers from complex samples such as serum without requiring multistep sample processing typical of labelled methods such as ELISA or immunofluorescence assays. Label-free sensors have witnessed decades of development with a veritable zoo of techniques available today exploiting a multitude of physical effects. It is appropriate now to critically assess whether label-free technologies have succeeded in delivering their promise with respect to diagnostic applications, particularly, ambitious goals such as early cancer detection using serum biomarkers, which require low limits of detection (LoD). Comparison of nearly 120 limits of detection (LoD) values reported by labelled and label-free sensing approaches over a wide range of detection techniques and target molecules in serum revealed that labeled techniques achieve 2-3 orders of magnitude better LoDs. Data from experiments where labelled and label-free assays were performed simultaneously using the same assay parameters also confirm that the LoD achieved by labelled techniques is 2 to 3 orders of magnitude better than that by label-free techniques. Furthermore, label-free techniques required significant signal amplification, for e.g. using nanoparticle conjugated secondary antibodies, to achieve LoDs comparable to labelled methods substantially deviating from the original “direct detection” paradigm. This finding has important implications on the practical limits of applying label-free detection methods for molecular diagnosis.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } Label-free biosensors promised a paradigm involving direct detection of biomarkers from complex samples such as serum without requiring multistep sample processing typical of labelled methods such as ELISA or immunofluorescence assays. Label-free sensors have witnessed decades of development with a veritable zoo of techniques available today exploiting a multitude of physical effects. It is appropriate now to critically assess whether label-free technologies have succeeded in delivering their promise with respect to diagnostic applications, particularly, ambitious goals such as early cancer detection using serum biomarkers, which require low limits of detection (LoD). Comparison of nearly 120 limits of detection (LoD) values reported by labelled and label-free sensing approaches over a wide range of detection techniques and target molecules in serum revealed that labeled techniques achieve 2-3 orders of magnitude better LoDs. Data from experiments where labelled and label-free assays were performed simultaneously using the same assay parameters also confirm that the LoD achieved by labelled techniques is 2 to 3 orders of magnitude better than that by label-free techniques. Furthermore, label-free techniques required significant signal amplification, for e.g. using nanoparticle conjugated secondary antibodies, to achieve LoDs comparable to labelled methods substantially deviating from the original “direct detection” paradigm. This finding has important implications on the practical limits of applying label-free detection methods for molecular diagnosis. |
| 43. | Joseph, Ajin George; Bhatnagar, Shalabh Revisiting the cross entropy method with applications in stochastic global optimization and reinforcement learning Conference Proceedings of the 22nd European Conference on Artificial Intelligence (ECAI 2016): Frontiers in Artificial Intelligence and Applications, The Netherlands, 285 , 2016. Abstract | BibTeX | Tags: Control and Optimisation and Policy | Links: @conference{Joseph2016, title = {Revisiting the cross entropy method with applications in stochastic global optimization and reinforcement learning}, author = {Ajin George Joseph and Shalabh Bhatnagar}, doi = {10.3233/978-1-61499-672-9-1026}, year = {2016}, date = {2016-09-02}, booktitle = {Proceedings of the 22nd European Conference on Artificial Intelligence (ECAI 2016): Frontiers in Artificial Intelligence and Applications, The Netherlands}, journal = {Proceedings of the 22nd European Conference on Artificial Intelligence (ECAI 2016): Frontiers in Artificial Intelligence and Applications, The Netherlands}, volume = {285}, pages = {1026-1034}, abstract = {In this paper, we provide a new algorithm for the problem of stochastic global optimization where only noisy versions of the objective function are available. The algorithm is inspired by the well known cross entropy (CE) method. The algorithm takes the shape of a multi-timescale stochastic approximation algorithm, where we reuse the previous samples based on discounted averaging, and hence it saves the overall computational and storage cost. We provide proof of the stability and the global optimization property of our algorithm. The algorithm shows good performance on the noisy versions of global optimization benchmarks and outperforms a state-of-the-art algorithm for non-linear function approximation in reinforcement learning.}, keywords = {Control and Optimisation and Policy}, pubstate = {published}, tppubtype = {conference} } In this paper, we provide a new algorithm for the problem of stochastic global optimization where only noisy versions of the objective function are available. The algorithm is inspired by the well known cross entropy (CE) method. The algorithm takes the shape of a multi-timescale stochastic approximation algorithm, where we reuse the previous samples based on discounted averaging, and hence it saves the overall computational and storage cost. We provide proof of the stability and the global optimization property of our algorithm. The algorithm shows good performance on the noisy versions of global optimization benchmarks and outperforms a state-of-the-art algorithm for non-linear function approximation in reinforcement learning. |
| 44. | Suran, Swathi; Bharadwaj, Krishna; Raghavan, Srinivasan; Varma, Manoj Seeing the unseen with localized optical contrast Conference Proceedings of SPIE 2016 Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications XIII, 13.02.16, San Francisco (USA), 9721 , 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Suran2016b, title = {Seeing the unseen with localized optical contrast}, author = {Swathi Suran and Krishna Bharadwaj and Srinivasan Raghavan and Manoj Varma}, doi = {10.1117/12.2212028}, year = {2016}, date = {2016-04-22}, booktitle = {Proceedings of SPIE 2016 Nanoscale Imaging, Sensing, and Actuation for Biomedical Applications XIII, 13.02.16, San Francisco (USA)}, volume = {9721}, pages = {6}, abstract = {Optical wide-field imaging of sub-diffraction limit nanostructures is of interest in a wide array of applications. In applications where the nanostructures to be visualized are well isolated, a high enough optical contrast is sufficient to detect these. Here we demonstrate a technique to visualize nanoscale features, such as grain boundaries in Chemical Vapor Deposited (CVD) single layer graphene, which are just a few atom length defects, using regular bright field optical microscopy. This remarkably low lateral length scale was imaged using of a special thin film structure consisting of a water-soluble thin film layer deposited on a metal substrate, which produces a strong color change as a function of the film thickness. Small local water transport differences in the graphene layer result in thickness variation of the underlying thin film due to its solubility in water and produces color contrast readily observable under a normal brightfield optical microscope with the naked eye. We demonstrate the use of this technique for direct optical visualization of grain boundaries in graphene as wide as 2-5 nm and sub-100 nm photoresist lines. By using super-resolution image processing algorithms, we may be able to detect structure even smaller in size than currently achieved. We believe that this technique can be extended to single molecule detection.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } Optical wide-field imaging of sub-diffraction limit nanostructures is of interest in a wide array of applications. In applications where the nanostructures to be visualized are well isolated, a high enough optical contrast is sufficient to detect these. Here we demonstrate a technique to visualize nanoscale features, such as grain boundaries in Chemical Vapor Deposited (CVD) single layer graphene, which are just a few atom length defects, using regular bright field optical microscopy. This remarkably low lateral length scale was imaged using of a special thin film structure consisting of a water-soluble thin film layer deposited on a metal substrate, which produces a strong color change as a function of the film thickness. Small local water transport differences in the graphene layer result in thickness variation of the underlying thin film due to its solubility in water and produces color contrast readily observable under a normal brightfield optical microscope with the naked eye. We demonstrate the use of this technique for direct optical visualization of grain boundaries in graphene as wide as 2-5 nm and sub-100 nm photoresist lines. By using super-resolution image processing algorithms, we may be able to detect structure even smaller in size than currently achieved. We believe that this technique can be extended to single molecule detection. |
| 45. | Khanum, Khadija K; Mani, Monto; Ramamurthy, Praveen Spectral studies investigating the influence of dust on solar transmittance 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{Khanum2016, title = {Spectral studies investigating the influence of dust on solar transmittance}, author = {Khadija K. Khanum and Monto Mani and Praveen Ramamurthy}, doi = {10.4229/EUPVSEC20162016-5BV.2.64}, year = {2016}, date = {2016-06-24}, booktitle = {Proceedings of the 32nd European Photovoltaic Solar Energy Conference and Exhibition (EU PVSEC 2016), Munich (Germany)}, pages = {2049-2051}, abstract = {Photovoltaic (PV) performance is significantly impacted due to dust settlement on the glass covering the panel, fundamentally understood as transmittance loss. Maintaining a dust free PV panel requires a minimum of 0.5 L/m2 of water daily in most tropical conditions where dust settlement is common. Most commercially available cells are Si based which harnesses as electricity most of the visible part of the solar spectrum, while the rest of the spectrum is absorbed as heat. However given the fact that the cross-section of a typical solar panel is multi-layered, with the top being a hi-transmittance glass, it is crucial to understand influence of dust on this primary layer. Dust though universally present is not universally uniform and varies depending on the atmospheric pollution, terrain (natural and anthropogenic) aggravations and vegetation. The composition is thus extremely varied. Little is understood on the geometry of settled dust, its composition and spectral absorptivity in response to incident direct and diffused radiation and its angle of incidence. The current study experimentally investigates the spectral response (Spectroradiometer) of dust characteristic to Bangalore for varying densities from mild soiling (~1g/m2) to heavy soiling (>5g/m2) and its elemental composition. The spectral absorptivity has also been compared for near direct solar incidence vs diffused. Elemental composition (EDAX) of the dust samples partially explained their spectral absorptivity. The results of the study provides critical insight into possible benefit of dust, at specific densities and compositions, in reducing the heat gain of solar cell by absorbing IR at the surface of the glass.}, keywords = {Energy, Studies into Impact of Dust and PV Temperature on PV System (Performance) Efficiency in Tropical Regions}, pubstate = {published}, tppubtype = {conference} } Photovoltaic (PV) performance is significantly impacted due to dust settlement on the glass covering the panel, fundamentally understood as transmittance loss. Maintaining a dust free PV panel requires a minimum of 0.5 L/m2 of water daily in most tropical conditions where dust settlement is common. Most commercially available cells are Si based which harnesses as electricity most of the visible part of the solar spectrum, while the rest of the spectrum is absorbed as heat. However given the fact that the cross-section of a typical solar panel is multi-layered, with the top being a hi-transmittance glass, it is crucial to understand influence of dust on this primary layer. Dust though universally present is not universally uniform and varies depending on the atmospheric pollution, terrain (natural and anthropogenic) aggravations and vegetation. The composition is thus extremely varied. Little is understood on the geometry of settled dust, its composition and spectral absorptivity in response to incident direct and diffused radiation and its angle of incidence. The current study experimentally investigates the spectral response (Spectroradiometer) of dust characteristic to Bangalore for varying densities from mild soiling (~1g/m2) to heavy soiling (>5g/m2) and its elemental composition. The spectral absorptivity has also been compared for near direct solar incidence vs diffused. Elemental composition (EDAX) of the dust samples partially explained their spectral absorptivity. The results of the study provides critical insight into possible benefit of dust, at specific densities and compositions, in reducing the heat gain of solar cell by absorbing IR at the surface of the glass. |
| 46. | Pahal, Suman; Raichur, Ashok M; Varma, Manoj Subdiffraction-resolution optical measurements of molecular transport in thin polymer films Journal Article Langmuir, 32 (22), pp. 5460-5467, 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @article{Pahal2016, title = {Subdiffraction-resolution optical measurements of molecular transport in thin polymer films}, author = {Suman Pahal and Ashok M. Raichur and Manoj Varma}, doi = {10.1021/acs.langmuir.6b00527}, year = {2016}, date = {2016-05-13}, journal = {Langmuir}, volume = {32}, number = {22}, pages = {5460-5467}, abstract = {The measurement of molecular transport within polymer films yields information about the internal structural organization of the films and is useful in applications such as the design of polymeric capsules for drug delivery. Layer-by-layer assembly of polyelectrolyte multilayer films has been widely used in such applications where the multilayer structure often exhibits anisotropic transport resulting in different diffusivities in the lateral (parallel to the film) and transverse (normal to the film) directions. Although lateral transport can be probed using techniques such as fluorescence recovery after photobleaching (FRAP), it cannot be applied to probing transverse diffusivity in polymer films smaller than the diffraction limit of light. Here we present a technique to probe the transport of molecules tagged with fluorphores in polymer films thinner than the optical diffraction limit using the modulation of fluorescence emission depending on the distance of the tagged molecules from a metal surface. We have used this technique to probe the diffusion of proteins biotin and bovine serum albumin (BSA) in polyelectrolyte multilayer films. We also studied the interdiffusion of chains in multilayer films using this technique. We observed a 3 order of magnitude increase in interdiffusion as a function of the ionic strength of the medium. This technique, along with FRAP, will be useful in studying anisotropic transport in polymer films, even those thinner than the diffraction limit, because the signal in this technique arises only from transverse and not lateral transport. Finally, this technique is also applicable to studying the diffusion of chromophore-labeled species within a polymer film. We demonstrate this aspect by measuring the transverse diffusion of methylene blue in the PAH–PAA multilayer system.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {article} } The measurement of molecular transport within polymer films yields information about the internal structural organization of the films and is useful in applications such as the design of polymeric capsules for drug delivery. Layer-by-layer assembly of polyelectrolyte multilayer films has been widely used in such applications where the multilayer structure often exhibits anisotropic transport resulting in different diffusivities in the lateral (parallel to the film) and transverse (normal to the film) directions. Although lateral transport can be probed using techniques such as fluorescence recovery after photobleaching (FRAP), it cannot be applied to probing transverse diffusivity in polymer films smaller than the diffraction limit of light. Here we present a technique to probe the transport of molecules tagged with fluorphores in polymer films thinner than the optical diffraction limit using the modulation of fluorescence emission depending on the distance of the tagged molecules from a metal surface. We have used this technique to probe the diffusion of proteins biotin and bovine serum albumin (BSA) in polyelectrolyte multilayer films. We also studied the interdiffusion of chains in multilayer films using this technique. We observed a 3 order of magnitude increase in interdiffusion as a function of the ionic strength of the medium. This technique, along with FRAP, will be useful in studying anisotropic transport in polymer films, even those thinner than the diffraction limit, because the signal in this technique arises only from transverse and not lateral transport. Finally, this technique is also applicable to studying the diffusion of chromophore-labeled species within a polymer film. We demonstrate this aspect by measuring the transverse diffusion of methylene blue in the PAH–PAA multilayer system. |
| 47. | Prasad, Prashanth R; Selvaraja, Shankar K; Varma, Manoj Thermo-optical tuning of cascaded double micro-ring resonators for dynamic range enhancement Conference Proceedings of SPIE 2016 Frontiers in Biological Detection: From Nanosensors to Systems VIII, 13.02.16, San Francisco (USA), 9725 , 2016. Abstract | BibTeX | Tags: Sensing and Actuation Systems | Links: @conference{Prasad2016b, title = {Thermo-optical tuning of cascaded double micro-ring resonators for dynamic range enhancement}, author = {Prashanth R. Prasad and Shankar K. Selvaraja and Manoj Varma}, doi = {10.1117/12.2211651}, year = {2016}, date = {2016-04-22}, booktitle = {Proceedings of SPIE 2016 Frontiers in Biological Detection: From Nanosensors to Systems VIII, 13.02.16, San Francisco (USA)}, volume = {9725}, pages = {5}, abstract = {We report on a silicon-photonic cascaded microring sensor with thermo-optic tuning for extension of detection range. Cascaded microring resonators have been used to realize refractive index sensors with high sensitivity in the intensity detection mode. In this configuration, one ring is used to probe analyte while the other ring (called filter) is used for spectrum overlap measurement. A significant drawback of this configuration is decreased range of detection. We overcome this problem by thermo-optically tuning the spectrum the filter ring to track the position of maximum overlap, as the spectrum of the probing ring undergoes shift. Using this peak tracking method, we have experimentally demonstrated range enhancement by a factor of 7.8, compared to the intensity detection scheme. This method can use a broadband source for operation, and has a potential for development of low cost, point of care biomedical applications.}, keywords = {Sensing and Actuation Systems}, pubstate = {published}, tppubtype = {conference} } We report on a silicon-photonic cascaded microring sensor with thermo-optic tuning for extension of detection range. Cascaded microring resonators have been used to realize refractive index sensors with high sensitivity in the intensity detection mode. In this configuration, one ring is used to probe analyte while the other ring (called filter) is used for spectrum overlap measurement. A significant drawback of this configuration is decreased range of detection. We overcome this problem by thermo-optically tuning the spectrum the filter ring to track the position of maximum overlap, as the spectrum of the probing ring undergoes shift. Using this peak tracking method, we have experimentally demonstrated range enhancement by a factor of 7.8, compared to the intensity detection scheme. This method can use a broadband source for operation, and has a potential for development of low cost, point of care biomedical applications. |
| 48. | Amrutur, Bharadwaj; Kumar, Mohan M S; Kumar, Sheetal K R; Patel, Lovelesh; Sundaresan, Rajesh; Vaidhiyan, Nidhin K WaterOpt: A method for checking near-feasibility of continuous water supply Conference Proceedings of the 2nd International Workshop on Cyber-Physical Systems for Smart Water Networks, CPS Week 2016, 11.-14.04.16, Vienna (Austria), 2016. Abstract | BibTeX | Tags: Smart Campus Water Management: Closing the IoT Loop from Network to Knowledge | Links: @conference{Amrutur2016, title = {WaterOpt: A method for checking near-feasibility of continuous water supply}, author = {Bharadwaj Amrutur and M. S. Mohan Kumar and K. R. Sheetal Kumar and Lovelesh Patel and Rajesh Sundaresan and Nidhin K. Vaidhiyan}, doi = {10.1109/CySWater.2016.7469057}, year = {2016}, date = {2016-05-16}, booktitle = {Proceedings of the 2nd International Workshop on Cyber-Physical Systems for Smart Water Networks, CPS Week 2016, 11.-14.04.16, Vienna (Austria)}, pages = {7-13}, abstract = {This paper proposes a systematic approach to explore the search space of control parameters on an existing water network in a locality within Mysore, India, to see if continuous water supply can be provided to meet a nominal diurnal demand pattern. The control parameters are the initial states of the reservoirs at some reference hour and hourly maximum flow rates across control valves. The system state should return to its initial state after twenty four hours to follow a diurnal rhythm without overflow or underflow of reservoirs. The number of configurational changes should also be small. The paper proposes an optimisation framework that relaxes the constraints via convex penalty functions, performs approximate gradient descent to minimise the net penalty, and thus identifies a suitable configuration. The proposed framework is ideal for integration into a cyber physical system that can actuate the controls based on real-time demand and flow information.}, keywords = {Smart Campus Water Management: Closing the IoT Loop from Network to Knowledge}, pubstate = {published}, tppubtype = {conference} } This paper proposes a systematic approach to explore the search space of control parameters on an existing water network in a locality within Mysore, India, to see if continuous water supply can be provided to meet a nominal diurnal demand pattern. The control parameters are the initial states of the reservoirs at some reference hour and hourly maximum flow rates across control valves. The system state should return to its initial state after twenty four hours to follow a diurnal rhythm without overflow or underflow of reservoirs. The number of configurational changes should also be small. The paper proposes an optimisation framework that relaxes the constraints via convex penalty functions, performs approximate gradient descent to minimise the net penalty, and thus identifies a suitable configuration. The proposed framework is ideal for integration into a cyber physical system that can actuate the controls based on real-time demand and flow information. |
2015 |
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| 49. | Venugopalakrishna, Y R; Murthy, Chandra R; Misra, Prasant; Warrior, Jay A column matching based algorithm for target self-localization using beacon nodes Conference Proceedings of the 14th International Conference on Information Processing in Sensor Networks (IPSN), USA, 2015. Abstract | BibTeX | Tags: Control and Prevention of Hospital Acquired Infections (HAI), Health | Links: @conference{Venugopalakrishna2015, title = {A column matching based algorithm for target self-localization using beacon nodes}, author = {Y. R. Venugopalakrishna and Chandra R. Murthy and Prasant Misra and Jay Warrior}, doi = {10.1145/2737095.2742935}, year = {2015}, date = {2015-04-16}, booktitle = {Proceedings of the 14th International Conference on Information Processing in Sensor Networks (IPSN), USA}, pages = {380-381}, abstract = {In this work, an algorithm is proposed for self-localization of a target node using power measurements from beacon nodes transmitting from known locations. The geographical area is overlaid with a virtual grid, and the problem is treated as one of testing overlapping subsets of grid cells for the presence of the target node. The proposed algorithm is validated both by Monte Carlo simulations as well as using experimental data collected from commercially-off-the-shelf bluetooth low energy (BLE) beacon nodes.}, keywords = {Control and Prevention of Hospital Acquired Infections (HAI), Health}, pubstate = {published}, tppubtype = {conference} } In this work, an algorithm is proposed for self-localization of a target node using power measurements from beacon nodes transmitting from known locations. The geographical area is overlaid with a virtual grid, and the problem is treated as one of testing overlapping subsets of grid cells for the presence of the target node. The proposed algorithm is validated both by Monte Carlo simulations as well as using experimental data collected from commercially-off-the-shelf bluetooth low energy (BLE) beacon nodes. |
| 50. | Zimik, Soling; Vandersickel, Nele; Nayak, Alok Ranjan; Panfilov, Alexander V; Pandit, Rahul A comparative study of early afterdepolarization-mediated fibrillation in two mathematical models for human ventricular cells Journal Article PLoS ONE, 10 (6), 2015. Abstract | BibTeX | Tags: Cardiac Arrhythmias: In Silico Studies in Realistic Mathematical Models for Cardiac Tissue, Health | Links: @article{Zimik2015, title = {A comparative study of early afterdepolarization-mediated fibrillation in two mathematical models for human ventricular cells}, author = {Soling Zimik and Nele Vandersickel and Alok Ranjan Nayak and Alexander V. Panfilov and Rahul Pandit}, doi = {10.1371/journal.pone.0130632}, year = {2015}, date = {2015-06-30}, journal = {PLoS ONE}, volume = {10}, number = {6}, abstract = {Early afterdepolarizations (EADs), which are abnormal oscillations of the membrane potential at the plateau phase of an action potential, are implicated in the development of cardiac arrhythmias like Torsade de Pointes. We carry out extensive numerical simulations of the TP06 and ORd mathematical models for human ventricular cells with EADs. We investigate the different regimes in both these models, namely, the parameter regimes where they exhibit (1) a normal action potential (AP) with no EADs, (2) an AP with EADs, and (3) an AP with EADs that does not go back to the resting potential. We also study the dependence of EADs on the rate of at which we pace a cell, with the specific goal of elucidating EADs that are induced by slow or fast rate pacing. In our simulations in two- and three-dimensional domains, in the presence of EADs, we find the following wave types: (A) waves driven by the fast sodium current and the L-type calcium current (Na-Ca-mediated waves); (B) waves driven only by the L-type calcium current (Ca-mediated waves); (C) phase waves, which are pseudo-travelling waves. Furthermore, we compare the wave patterns of the various wave-types (Na-Ca-mediated, Ca-mediated, and phase waves) in both these models. We find that the two models produce qualitatively similar results in terms of exhibiting Na-Ca-mediated wave patterns that are more chaotic than those for the Ca-mediated and phase waves. However, there are quantitative differences in the wave patterns of each wave type. The Na-Ca-mediated waves in the ORd model show short-lived spirals but the TP06 model does not. The TP06 model supports more Ca-mediated spirals than those in the ORd model, and the TP06 model exhibits more phase-wave patterns than does the ORd model.}, keywords = {Cardiac Arrhythmias: In Silico Studies in Realistic Mathematical Models for Cardiac Tissue, Health}, pubstate = {published}, tppubtype = {article} } Early afterdepolarizations (EADs), which are abnormal oscillations of the membrane potential at the plateau phase of an action potential, are implicated in the development of cardiac arrhythmias like Torsade de Pointes. We carry out extensive numerical simulations of the TP06 and ORd mathematical models for human ventricular cells with EADs. We investigate the different regimes in both these models, namely, the parameter regimes where they exhibit (1) a normal action potential (AP) with no EADs, (2) an AP with EADs, and (3) an AP with EADs that does not go back to the resting potential. We also study the dependence of EADs on the rate of at which we pace a cell, with the specific goal of elucidating EADs that are induced by slow or fast rate pacing. In our simulations in two- and three-dimensional domains, in the presence of EADs, we find the following wave types: (A) waves driven by the fast sodium current and the L-type calcium current (Na-Ca-mediated waves); (B) waves driven only by the L-type calcium current (Ca-mediated waves); (C) phase waves, which are pseudo-travelling waves. Furthermore, we compare the wave patterns of the various wave-types (Na-Ca-mediated, Ca-mediated, and phase waves) in both these models. We find that the two models produce qualitatively similar results in terms of exhibiting Na-Ca-mediated wave patterns that are more chaotic than those for the Ca-mediated and phase waves. However, there are quantitative differences in the wave patterns of each wave type. The Na-Ca-mediated waves in the ORd model show short-lived spirals but the TP06 model does not. The TP06 model supports more Ca-mediated spirals than those in the ORd model, and the TP06 model exhibits more phase-wave patterns than does the ORd model. |
