Department of Electrical Engineering

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IIT Jodhpur

In this paper a different view on the classical Terminal Sliding Mode (TSM) control is presented. The backstepping procedure is used to synthesize a new TSM-like control law for the second and third order integrator chain. A strict Lyapunov function (LF) for the entire closed loop dynamics is given naturally by design. Further, it is shown, under a certain choice of parameters, that the LF is valid for the classical TSM control law, as well. Finite-time convergence of all states to the origin is proven for both control algorithms using this LF. Finally, the new TSM-like control law is validated in simulations for the third order case. © 2020 IEEE.

World University root node

CCTA 2020 - 4th IEEE Conference on Control Technology and Applications

Backstepping-induced terminal sliding mode control with strict lyapunov function

Objectively assessing the perceptual quality of an ocular fundus image is essential for the reliable diagnosis of various ocular diseases. A fair amount of work has been done in this field to date. However, the generalizability of the current work is limited, as the existing quality models were developed and evaluated with data-sets built with limited subjective inputs. This paper aims at addressing this limitation with the following two contributions. First, a new fundus image quality assessment (FIQuA) data-set is presented, containing 1500 fundus images with three classes of quality: Good, Fair, and Poor. Also, for each image, subjective scores (in the range [0-10]) were collected for six quality parameters, including structural and generic properties of the fundus images. Second, a new multivariate regression based convolutional neural network (CNN) model is proposed to predict the fundus image quality. The proposed model consists of two individually trained blocks. The first block consists of four pre-trained models, trained against the subjective scores for the six quality parameters, and aims at deriving the optimized features for classification. Next, the optimized features from each of the four models are ensembled together and transferred to the second block for final classification. The proposed model achieves a strong correlation with the subjective scores, with the values 0.941, 0.954, 0.853, and 0.401 obtained for SROCC, LCC, KCC, and RMSE respectively. Its classification accuracy is 95.66% over the FIQuA data-set, and 98.96% and 88.43% respectively over the two publicly available data-sets DRIMDB and EyeQ. © 2013 IEEE.

Fulltext

IEEE Access

Multivariate Regression-Based Convolutional Neural Network Model for Fundus Image Quality Assessment

Melanoma is a life-threatening form of skin cancer when left undiagnosed at the early stages. Although there are more cases of non-melanoma cancer than melanoma cancer, melanoma cancer is more deadly. Early detection of melanoma is crucial for the timely diagnosis of melanoma cancer and prohibit its spread to distant body parts. Segmentation of skin lesion is a crucial step in the classification of melanoma cancer from the cancerous lesions in dermoscopic images. Manual segmentation of dermoscopic skin images is very time consuming and error-prone resulting in an urgent need for an intelligent and accurate algorithm. In this study, we propose a simple yet novel network-in-network convolution neural network (CNN) based approach for segmentation of the skin lesion. A Faster Region-based CNN (Faster RCNN) is used for preprocessing to predict bounding boxes of the lesions in the whole image which are subsequently cropped and fed into the segmentation network to obtain the lesion mask. The segmentation network is a combination of the UNet and Hourglass networks. We trained and evaluated our models on ISIC 2018 dataset and also cross-validated on PH2 and ISBI 2017 datasets. Our proposed method surpassed the state-of-the-art with Dice Similarity Coefficient of 0.915 and Accuracy 0.959 on ISIC 2018 dataset and Dice Similarity Coefficient of 0.947 and Accuracy 0.971 on ISBI 2017 dataset. © 2020, Springer Nature Singapore Pte Ltd.

Communications in Computer and Information Science

Detector-SegMentor Network for Skin Lesion Localization and Segmentation

This paper provides a comprehensive review of the control approaches and the power-decoupling topologies to mitigate 2ω-ripple problem in the single-phase inverters, its solutions, and discusses open challenges yet to be addressed. The cause and effects of 2ω-ripple problem and its solution based on the passive and active power-decoupling techniques are discussed. A subcategory of the active power-decoupling technique nominated as the control-oriented compensation technique is reviewed in detail, this technique can achieve the ripple-mitigation at the source through the control but not necessarily adds extra circuit or active filter to the system. The control-oriented compensation techniques can be applied in the two-stage DC-DC-AC converters and the single-stage inverters having a front-end control capability with the H-bridge such as in the quasi-switched-boost inverters. The merits and associated challenges of these techniques are listed and summarized in a tabular form. Finally, a conclusive discussion with open challenges is presented. © 2013 IEEE.

Control Strategies and Power Decoupling Topologies to Mitigate 2ω-Ripple in Single-Phase Inverters: A Review and Open Challenges

In this work, a microhollow cathode variant consisting of cylindrical cathode structure and a coaxial anode, with a layer of dielectric barrier on the inner wall of the cathode cavity, has been investigated. This arrangement allows the device to be operated at atmospheric pressure reaching electron densities up to 1018 m-3 in the microhollow cathode cavity. The discharge initiates from the narrow gap region between the cathode and the anode, followed by hollow cathode discharge. The presence of the anode in the discharge cavity causes the discharge electrons to be absorbed by the anode. A theoretical approach has been followed and it establishes a criterion for sustenance of this discharge in the microhollow cathode cavity. This criterion resulted from the fact that for discharge to be sustained in the hollow cathode cavity, the generation of electrons should be balanced by the absorption of electrons. Both these phenomena have been quantitatively explained by electron multiplication quotient and a multipass parameter for hollow cathode discharge has been evaluated. © 1973-2012 IEEE.

IEEE Transactions on Plasma Science

Investigations of Discharge Sustenance in a Dielectric Barrier-Based Microhollow Cathode

We have developed a highly tunable film bulk acoustic wave resonator (TFBAR) using magnetostrictive (MS) Fe65Co35 thin films in acoustic layer stack. The resonator acoustic layer stack consists of Pt/ZnO/Fe65Co35 layers to tune the devices. Due toΔ E effect, TFBAR resonance frequency was up-shifted 106.9 MHz (4.91%) in the presence of 2-kOe magnetic field. From experimental measurement, Δ E enhancement was estimated to be 35 GPa. Further, it is observed that return loss (S11), phase response, and quality factor were improved in the presence of magnetic field. This improvement is due to the field-induced stiffness in the magnetic layer. Equivalent-modified Butterworth-Van Dyke (mBVD) circuit model was developed and fit with the experimental data, and circuit parameters were extracted. The proposed resonator is compact, low loss, power efficient, and highly tunable. This method also facilitates a new method of tuning FBAR devices using MS thin films. © 1986-2012 IEEE.

IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control

Highly Tunable Film Bulk Acoustic Wave Resonator Based on Pt/ZnO/Fe65Co35Thin Films

Here, we present a highly sensitive and fast hydrogen (H2) sensor for 1% H2, well below the critical limit of explosion ignite in air, in a temperature range of 28–150 °C by using monolayer MoS2 pyramid structures with enhanced adsorption sites. The monolayer MoS2 pyramid structures is synthesized by modified chemical vapor deposition technique and characterized by field emission scanning electron microscopy, Raman, photoluminescence and atomic force microscopy. The highest sensitivity of 69.1% was achieved at a moderate temperature with a response time of 32.9 s for the monolayer MoS2 pyramid structures. At room temperature (RT), the sensor showed a sensitivity of 6% with a faster response of 11.3 s and recovery time of 125.3 s. The availability of favourable adsorption sites on in-plane MoS2 and edges of MoS2 in monolayer MoS2 structures provide enhanced adsorption sites for gas sensing and resulted in the high sensitivity and low response time compared to that of bare MoS2 and other nanostructures-based H2 sensor. The detailed gas sensing mechanism is proposed in the light of detail surface morphology and density function theory (DFT). This study reveals that tailoring the favourable adsorption sites in 2D materials is helpful to develop the highly sensitive and fast H2 sensor for next generation safety devices for H2 fueled vehicle and clean energy applications. © 2020 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Enhanced adsorption sites in monolayer MoS2 pyramid structures for highly sensitive and fast hydrogen sensor

Metal oxide semiconductors-based gas sensors have been extensively explored due to their high sensing response, cost-effectivity, long-term stability, and simple fabrication. However, their utilization at low operating temperature is still challenging. Thus, reduction in power consumption is highly essential for long-term usage of gas sensors. ZnO nanostructures-based gas sensors are one of the most eligible candidates where a real-time detection of explosive and toxic gases is needed. On this subject, numerous efforts have been made to improve the sensing response at reduced working temperature with the assistance of various methods. In this report, several techniques related to the synthesis of ZnO nanostructures and their efficient performance in sensing are reviewed. The report primarily focuses on different means of improving the sensing properties, such as functionalization of noble metal nanoparticles, doping of metals, inclusion of carbonaceous nanomaterials, using nanocomposites of different MOx, UV activation, and post-treatment method of high-energy irradiation on ZnO nanostructures, with their possible sensing mechanisms. This study will therefore shed light on future proposals of ZnO-based gas sensors showing high sensitivity even at low operating temperature. © 2019 The Authors

Energy Reports

Enhanced sensing performance of ZnO nanostructures-based gas sensors: A review

The aim of this study was to investigate whether parameters from an instrumented one-leg stance (OLS) on a force plate could provide relevant information related to fall risk in older people. Forty-two community dwelling older people including 17 fallers and 25 nonfallers, and 25 young subjects performed a OLS while standing on a force plate, with parameters related to transferring weight onto one leg and postural sway in singe-leg stance evaluated. No differences were observed between older fallers and nonfallers and the younger participants for any of the weight transfer parameters. The younger participants were able to reduce their postural sway during the OLS test after the first 0-2 s period, unlike older participants who swayed the same amount throughout the test. The older fallers swayed significantly more than both nonfallers and younger participants throughout the 10-s of OLS evaluated. When the tests were used to classify older participants as fallers, the instrumented OLS achieved 100% accuracy, compared to 69.0% classification accuracy for the five times sit-to-stand test, 61.9% for the standard OLS, and 47.6% for the timed-up-and-go test. These findings suggest that the standard OLS test might not be suitable to detect fall risk. In contrast, an instrumented version of the OLS could provide valuable additional information that could identify older fallers. Future work will include a prospective study of the instrumented OLS in a larger population of older people. © 2020 BMJ Publishing Group. All rights reserved.

Department of Mathematics

Journal of Biomechanical Engineering

A Pilot Study to Detect Balance Impairment in Older Adults Using an Instrumented One-Leg Stance Test

The Sit-to-Stand (STS) is a widely used test of physical function to screen older people at risk of falls and frailty and is also one of the most important components of standard screening for sarcopenia. There have been many recent studies in which instrumented versions of the STS (iSTS) have been developed to provide additional parameters that could improve the accuracy of the STS test. This systematic review aimed to identify whether an iSTS is a viable alternative to a standard STS to identify older people at risk of falling, frailty, and sarcopenia. A total of 856 articles were found using the search strategy developed, with 12 articles retained in the review after screening based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Six studies evaluated the iSTS in fallers, five studies in frailty and only one study in both fallers and frailty. The results showed that power and velocity parameters extracted from an iSTS have the potential to improve the accuracy of screening when compared to a standard STS. Future work should focus on standardizing the segmentation of the STS into phases to enable comparison between studies and to develop devices integrated into the chair used for the test to improve usability. © 2020 by the authors. Licensee MDPI, Basel, Switzerland.