Department of Electrical Engineering

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IIT Jodhpur

A unified approach of directional solvent vapor annealing for crystal alignment in solution-processed organic semiconductors is proposed. Highly crystalline molecular self-assembly of the drop-cast technique is further enhanced by postprocessing scheme of the solvent vapor annealing with additional benefit of alignment of the crystalline domains. In this technique, a mixture of carrier gas and solvent vapors are made to flow in a certain direction and in the close proximity of the surface of the substrates carrying the solution. Flow of the carrier gas imparts directionality to the semiconducting crystalline ribbons, whereas the influx of the solvent vapors improves the crystalline order in the semiconducting film. The flow rate of the carrier gas and the position of the substrate in the interaction chamber are the primary regulating factors, which have the ability to provide a semiconducting layer with a well-aligned and interconnected assembly of long ribbons. These favorable film properties further materialize in the form of electrical performance of the corresponding field-effect transistors. The versatility of this technique makes it a viable alternative for the solution processing of organic semiconductors. © 2017 American Chemical Society.

World University root node

ACS Applied Materials and Interfaces

Directional Solvent Vapor Annealing for Crystal Alignment in Solution-Processed Organic Semiconductors

Segmentation of the phonocardiography (PCG) signal into cardiac cycles is a primary task for the diagnosis of cardiovascular diseases. However, PCG is highly susceptible to noise, and extra sound called murmur may also be present in the PCG signal due to pathology. These components cause difficulties in the segmentation and therefore, segmentation is often preceded by the denoising of the PCG signal to emphasize the fundamental heart sounds S1 and S2, by removing these unwanted components. For the denoising of the PCG signal, discrete wavelet transform (DWT) based algorithms have shown good performance because such algorithms suppress in-band noise besides the out-of-band noise. Selection of threshold value and threshold function significantly affects the performance of these algorithms. In this paper, for threshold value estimation, an adaptive method based on statistical parameters of the given PCG signal is proposed. The statistical parameters are found to be highly effective for this purpose. We also propose a new threshold function, non-linear mid function, to address the issues of SNR and transients in the existing threshold functions, soft and hard. The proposed method is applied on a large number of PCG signals with additive white Gaussian noise, red noise, and pink noise. The Performance of the proposed method is also evaluated on the PCG signals recorded in real-life noisy scenarios and signals with murmur sound. The obtained results show that the proposed method is significantly superior to the competitive algorithms. © 2017 Elsevier Ltd

Biomedical Signal Processing and Control

An adaptive thresholding method for the wavelet based denoising of phonocardiogram signal

A sliding mode control algorithm for discrete-time uncertain systems at higher sampling rates is proposed in this paper. The traditional shift operator based discrete-time systems at higher sampling rates fail to capture the dynamics of its continuous counter part, as the system matrix approaches to the identity matrix. To overcome this problem, the Delta operator has been used to represent the discrete system where the discrete system dynamics converges to the continuous system at higher sampling rates. Here, a periodic output feedback (POF) based sliding mode controller which makes use of infrequent output measurements is proposed to guarantee a stable sliding mode motion along a designed sliding surface for the Delta operator system. The design philosophy of this controller is to obtain the POF gain which will bring a sliding mode for the Delta operator system. It is shown here that there exists a POF gain for sliding mode to occur for any controllable and observable Delta operator system. Further, the sliding surface for this gain is derived. The design method is illustrated for an uncertain system with bounded matched uncertainty. © 2016 European Control Association

European Journal of Control

Discrete time sliding mode control for uncertain Delta operator systems with infrequent output measurements

In this paper, we consider the event triggered control of the singularly perturbed linear system, where the communication between sensor and the controller/actuator is through a digital communication network and the transmission is based on some state dependent criterion. The models of slow and fast subsystems of the plant are added at the controller and are used for the estimation of states between the transmission times. Whenever the difference between estimated and actual states exceeds a certain threshold, controller is updated with the actual states of the plant provided by the sensor. This effectively reduces the communication frequency. The stability properties of overall closed loop system is studied and it is found that for sufficiently small value of singular perturbation parameter, system attains practical stability and by adequately selecting trigger function parameters, asymptotic stability is also achieved. A numerical example is shown to illustrate the results of the paper. © 2017 IEEE.

Department of Chemistry

Proceedings of the IEEE International Conference on Industrial Technology

Event triggered control of singularly perturbec linear system based on its slow and fast model

With the aim to establish the possibility of synthesis of GaN inclusions by co-implantation of Ga and N ions in silicon and SiO2 films on a silicon substrate, the chemical composition and photoluminescence of implanted layers have been investigated. It is observed that the heavy loss of implanted atoms occurs owing to the out-diffusion (Ga from Si, and Ga and N from SiO2) in the process of post-implantation annealing. Preliminary implantation of nitrogen to form silicon nitride or oxynitride layers is shown to reduce the degree of impurity losses. In the photoluminescence spectrum of both Si and SiO2 subjected to Ga and N co-implantation, the band at 530-550 nm is present, which can be related to 'defect' luminescence of GaN. Copyright © 2017 Inderscience Enterprises Ltd.

International Journal of Nanotechnology

Composition and luminescence of Si and SiO2 layers co-implanted with Ga and N ions

The increased usage of hydrogen as a next generation clean fuel strongly demands the parallel development of room temperature and low power hydrogen sensors for their safety operation. In this work, we report strong evidence for preferential hydrogen adsorption at edge-sites in an edge oriented vertically aligned 3-D network of MoS2 flakes at room temperature. The vertically aligned edge-oriented MoS2 flakes were synthesised by a modified CVD process on a SiO2/Si substrate and confirmed by Scanning Electron Microscopy. Raman spectroscopy and PL spectroscopy reveal the signature of few-layer MoS2 flakes in the sample. The sensor's performance was tested from room temperature to 150 degrees C for 1\% hydrogen concentration. The device shows a fast response of 14.3 s even at room temperature. The sensitivity of the device strongly depends on temperature and increases from similar to 1\% to similar to 11\% as temperature increases. A detail hydrogen sensing mechanism was proposed based on the preferential hydrogen adsorption at MoS2 edge sites. The proposed gas sensing mechanism was verified by depositing similar to 2-3 nm of ZnO on top of the MoS2 flakes that partially passivated the edge sites. We found a decrease in the relative response of MoS2-ZnO hybrid structures. This study provides a strong experimental evidence for the role of MoS2 edge-sites in the fast hydrogen sensing and a step closer towards room temperature, low power (0.3 mW), hydrogen sensor development. Published by AIP Publishing.

Fulltext

APPLIED PHYSICS LETTERS

Fast detection and low power hydrogen sensor using edge-oriented vertically aligned 3-D network of MoS2 flakes at room temperature

This paper presents a novel method for detecting bearing faults using multi-resolution analysis of stator current signals based on Stockwell Transform. The sampled stator current signals are analyzed with the help of Stockwell Transform to extract features namely maximum magnitude and maximum phase angle. The statistics of these features are further utilized to detect and classify the bearing faults in outer race, inner race, cage and balls. The experimental results show that the proposed approach is capable of detecting various bearing faults in induction motor. © 2016 IEEE.

2016 IEEE 7th Power India International Conference, PIICON 2016

Application of stockwell transform in bearing fault diagnosis of induction motor

The performance of a free space optical (FSO) communication system is significantly affected by various atmospheric turbulence conditions and pointing errors (PEs) apart from the additive noise, which is assumed to be Gaussian. Optical pre-amplifiers are an essential component of FSO systems for improving the receiver sensitivity. However, optical pre-amplification results in amplified spontaneous emission (ASE), which dominates the receiver thermal and shot noises. The square law photodetection process at the receiver in a FSO system necessitates the consideration of chi-square statistics for the decision variable contrary to the Gaussian approximation that is widely used in the literature. In this paper, we evaluate the bit error rate (BER) performance of a FSO system assuming non-return-to-zero on-off keying modulation in the presence of ASE noise under weak, moderate to strong, and very strong atmospheric turbulence regimes and PEs. We also derive asymptotic BER expressions for the considered FSO system for large values of the signal-to-noise ratio in terms of simple elementary functions. Further insight into the system is provided by performing a diversity analysis. © 2017 Optical Society of America.

Journal of Optical Communications and Networking

BER performance of an optically pre-amplified FSO system under turbulence and pointing errors with ASE noise

Detecting the reflection symmetry axis present in an object has been an active research problem in computer vision and computer graphics due to its various applications such as object recognition, object detection, modelling, and symmetrization of 3D objects. However, the problem of computing the reflection symmetry map for a given image containing objects exhibiting reflection symmetry has received a very little attention. The symmetry map enables us to represent the pixels in the image using a score depending on the probability of each of them having a symmetric counterpart. In this work, we attempt to compute the 2-D reflection symmetry map. We pose the problem of generating the symmetry map as an intra-image dense symmetric pixels correspondence problem, which we solve efficiently using a randomized algorithm by observing the reflection symmetry coherency present in the image. We introduce an application of symmetry map called symmetry preserving image stylization. © 2017 IEEE.

Proceedings - 2017 IEEE International Conference on Computer Vision Workshops, ICCVW 2017

SymmMap: Estimation of the 2-D Reflection Symmetry Map and Its Applications

Smart video surveillance of indoor and outdoor scenes is a challenging task for modern surveillance systems. Different imaging conditions like bad illumination, adverse weather, etc., makes the surveillance process difficult. Recently, researchers have proposed smart surveillance systems with additional features for more accurate monitoring of events, but not much attention is paid to improve the system such that the monitoring process consumes as minimum resources as possible. In this paper, we propose a novel surveillance system that enhances visibility in adverse weather conditions and summarizes the captured videos automatically to reduce storage space. As the summarization process is based on the events in a scene, video interpretation becomes fast and easy. We propose perceptual features that can be used for more meaningful and robust summarization of the video than the existing summarization algorithms. We test the system for both indoor and outdoor scenes and show that the system works well even with multiple moving objects and complex motions. © 2017 IEEE.