Department of Electrical Engineering

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IIT Jodhpur

Crucial sensor parameters like sensitivity, response time and recovery time at low ppm were studied and analysed by photoluminescence (PL) quenching technique. A comparison was drawn from various porous silicon samples prepared under different electrochemical anodization conditions. Porosity dependent sensing results were analysed and it was observed that samples turned more sensitive with an increase in porosity. Samples were tested in the presence of linear aliphatic alcohols (methanol to n-octanol) and water in the range of 10100 ppm. Trifling response was shown for water, while a discernible change in sensitivity was observed when samples were tested with alcohols. The morphological changes in porous structure and the chemical nature of organic adsorbates were ascertained to be the primary reasons for sensing by porous silicon. © 2011 World Scientific Publishing Company.

World University root node

International Journal of Nanoscience

Photoluminescence quenching technique: A sensitive probe for detecting organic vapors at low PPM

In this paper, a novel dynamic stochastic resonance (DSR)-based non-blind watermark extraction technique has been proposed for robust extraction of a grayscale watermark. The watermark embedding has been carried out using singular value decomposition (SVD). Dynamic stochastic resonance has been strategically used to improve the robustness of the extraction algorithm by utilizing the noise added during attacks itself. Resilience of this technique to attacks has been tested in the presence of various noise, geometrical, enhancement, compression and filtering attacks. Using the DSR-based proposed extraction algorithm, a very robust extraction of watermark can be done without trading-off with visual quality of the watermarked image. Performance of the proposed technique has also been compared with the plain SVD-based and hybrid DCT-SVD based technique and is found to give better performance. © 2011 IEEE.

Robust watermark extraction using SVD-based dynamic stochastic resonance

This paper considers the nonlinear surface design for uncertain discrete time system with state delay. Using Lyapunov-Krasovskii method delay-independent conditions are derived for the stable sliding motion along the nonlinear sliding surface. The sliding surface is typically designed to obtain the high speed response without exhibiting the overshoot. This can be achieved by keeping the damping ratio initially small and as the trajectory approaches to the origin, damping ratio is made high to avoid the overshoot in response. © 2011 ICROS.

International Conference on Control, Automation and Systems

Discrete-time sliding mode control for state delay systems using nonlinear sliding surface

This paper introduces a formulation for design of Fast Output Sampling (FOS) controllers for three-time-scale systems. It is shown that the FOS control gain for a three-time-scale system can be obtained by combining the solutions of the three subsystem problems, obtained separately. Since three smaller order subsystem problems are to be solved in lieu of one high order problem, numerical ill-conditioning is completely avoided. Techniques for block-diagonalization and composite control of a three-time-scale system are also discussed. The proposed method is applied to the problem of spatial control of advanced heavy water reactor (AHWR). The model of AHWR is decomposed into three subsystems respectively named slow, fast 1, and fast 2, and separate subsystem control problems are cast from which an FOS controller for the original system is derived. Efficacy of the controller thus obtained is demonstrated through dynamic simulations. The controller thus designed employs only the output information to achieve arbitrary pole placement. © 2011 IEEE.

IEEE Transactions on Nuclear Science

Design of fast output sampling controller for three-time-scale systems: Application to spatial control of advanced heavy water reactor

This article aims in bringing out the benefits of multiSensor data fusion in controlling vibrating modes of a piezoactuated beam, using multirate output feedback control namely, periodic output feedback control and fast output sampling control. The vibrating modes are measured by two homogeneous piezoelectric sensors. The states estimated from sensor outputs using information filters are fused using information fusion. The system output is computed from the fused states and it is used to generate the controller output. The performance of the controllers for the suppression of first two modes of vibration is evaluated through simulation and in real time. Improved closed-loop performance is obtained with data fusion. © 2011 Taylor & Francis.

International Journal of Image and Data Fusion

Multirate feedback control of piezoactuated structures with multisensor data fusion

Control of Rotary Inverted Pendulum (RIP) is a classic control problem. It represents a broader class of underactuated systems. The dynamical equations of RIP are nonlinear coupled and complex. The nonlinear feature and the complex internal dynamics makes the design of the control challenging. This paper presents swing up and stabilization both via sliding modes. Tracking control of rotary actuator using sliding modes is developed for swing up of RIP till the pendulum reaches in the linear region around the vertical upright position. Once it reaches in the linear region, a stabilization control using sliding mode is switched on. A linear model of the RIP is used for developing the SMC law for stabilization. Effectiveness of the method is validated in simulation as well as by experiment. © 2011 IFAC.

IFAC Proceedings Volumes (IFAC-PapersOnline)

Swing-up and stabilization of Rotary Inverted Pendulum using sliding modes

Top-gate bottom-contact field-effect transistors based on solution-processed films of molecules in which two naphthalene-1,8:4,5- bis(dicarboxdiimide)s are bridged by thieno[3,2-b]thiophene, dithieno[3,2-b:2′,3′-d]thiophene and dithieno[3,2-b:2′, 3′-d]pyrrole exhibit electron mobility values of up to 1.5 cm2 V-1 s-1. © 2011 American Chemical Society.

Chemistry of Materials

Solution-processed molecular bis(naphthalene diimide) derivatives with high electron mobility

We report on vertically stacked complementary inverters implemented with a solution-processed [6,6]-phenyl c61 butyric acid methyl ester (PCBM) n-channel thin-film transistor (TFT) fabricated on top of a 6,13- bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) and poly(triarylamine) (PTAA) blend p-channel TFT. With a shared common gate electrode positioned between two dielectric layers, bottom-contact p- and top-contact n-channel TFTs showed saturation mobility values of 0.25 and 0.004 cm2/V s and threshold voltages of -3.9, and 0.3 V, respectively. The inverter yielded a gain value of -24 V/V with a switching threshold voltage value of 3.3 V at a supply voltage of 7 V. This demonstration of the use of solution-processed semiconductors in a vertically stacked complementary inverter geometry is a step forward towards the development of low-cost complementary electronics. © 2011 Elsevier B.V. All rights reserved.

Organic Electronics

Vertically stacked complementary inverters with solution-processed organic semiconductors

This paper presents an algorithm for classification of fetal health status using fetal heart rate variability (fHRV) analysis through phonocardiography. First, the fetal heart sound signals are acquired from the maternal abdominal surface using a specially developed Bluetooth-based wireless data recording system. Then, fetal heart rate (FHR) traces are derived from these signals. Ten numbers of linear and nonlinear features are extracted from each FHR trace. Finally, the multilayer perceptron (MLP) neural network is used to classify the health status of the fetus. Results show very promising performance toward the prediction of fetal wellbeing on the set of collected fetal heart sound signals. Finally, this work is likely to lead to an automatic screening device with additional potential of predicting fetal wellbeing. © 2011 World Scientific Publishing Company.

Journal of Mechanics in Medicine and Biology

Fetal heart rate variability analysis from phonocardiographic recordings

This paper presents a novel and generic algorithm for reduction in computational complexity associated with the estimation of LS based predictor. Many lossless compression algorithms used predictor based on Least Squares and its variance for decorrelation of images. However, computational complexity associated with estimation of such predictor is huge. So, in order to reduce the computational complexity, we proposed to estimate a LS based predictor of order p-1 and estimates the coefficients of predictor of order p. We have reduced the predictor order form p to (p - 1) that results into a saving of computational power. We have also reduced the predefined error threshold in EDP and RALP algorithm in order to negotiate the slight loss in prediction accuracy due to synthetically generated prediction coefficient. The proposed algorithm is generic that can be used with most of the LS based lossless compression algorithms reported in literature. Our proposed algorithm gives same prediction quality as compared to when we use the actual prediction coefficient and there is around 25% to 40% reduction in computational complexity. © 2011 IEEE.