Department of Electrical Engineering

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IIT Jodhpur

Various ocular diseases, such as cataract, diabetic retinopathy, and glaucoma have affected a large proportion of the population worldwide. In ophthalmology, fundus photography is used for the diagnosis of such retinal disorders. Nowadays, the set-up of fundus image acquisition has changed from a fixed position to portable devices, making acquisition more vulnerable to distortions. However, a trustworthy diagnosis solely relies upon the quality of the fundus image. In recent years, fundus image quality assessment (IQA) has drawn much attention from researchers. This study presents a detailed survey of the fundus IQA research. The survey covers a comprehensive discussion on the factors affecting the fundus image quality and the real-time distortions. The fundus IQA algorithms have been analysed on the basis of the methodologies used and divided into three classes, namely: (i) similarity-based, (ii) segmentation-based, and (iii) machine learning based. In addition, limitations of state of the art in this research field are also presented with the possible solutions. The objective of this study is to provide a detailed information about the fundus IQA research with its significance, present status, limitations, and future scope. To the best of the authors' knowledge, this is the first survey paper on the fundus IQA research. © 2019 The Institution of Engineering and Technology.

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IET Image Processing

Fundus image quality assessment: Survey, challenges, and future scope

Two-dimensional \alpha-MoO3 semiconductor material having wide band gap can be potentially used in a wide range of UV-light detection application. Here, we grown the large-scale film composed of \alpha-MoO3 microplates by using chemical vapor deposition process and fabricated a UV detector. The X-ray diffraction and Raman spectroscopy confirmed the continuity and crystallinity of the deposited MoO3 film on SiO2/Si substrate. The device exhibited a high responsivity of 500 mA/W and a photo/dark current ratio of over 6 and a significant fast response time under UV-light (360 nm) irradiation. An efficient UV-light detection of the MoO3 microplates can be attributed to the depletion-layer modulation process. © 2019 IEEE.

IEMECON 2019 - 9th Annual Information Technology, Electromechanical Engineering and Microelectronics Conference

Ultraviolet photodetector based on chemical vapor deposition grown MoO3 microplates

We report sensitive and selective AlGaN/GaN High Electron Mobility Transistor (HEMT)-based sensor for Lead ion (Pb2+) detection. The gate region of the HEMT was functionalized by 2,5-dimercapto-1,3,4-thiadiazole (DMTD). The response of the sensor is observed by monitoring drain to source current (\text{I} {\textsf {DS}}) for different concentrations of Pb2+ ions at a fixed drain to source voltage (\text{V} {\textsf {DS}} ). Our sensor reaches the lower detection limit of 0.018 ppb, which is much lower than the standard detection limit recommended by the World Health Organization (WHO) for drinking water. Furthermore, the sensor exhibited a rapid response time of 4 seconds and high sensitivity of 0.607μ \text{A} /ppb. Moreover, the selectivity analysis was performed and found that the sensor was highly selective towards Pb2+ ions. The change in electron concentration at 2-dimensional electron gas (2DEG) upon the capture of Pb2+ ions at gate region by DMTD, causes a change in the \text{I} {\textsf {DS}} , which showed excellent sensing response towards Pb2+ ions. The highly sensitive, selective, and rapid detection of Pb2+ ions paves the way for stable sensing performance based on DMTD functionalized AlGaN/GaN HEMT sensor. © 1980-2012 IEEE.

IEEE Electron Device Letters

Sensitive and Selective Detection of Pb2+ Ions Using 2,5-Dimercapto-1,3,4-Thiadiazole Functionalized AlGaN/GaN High Electron Mobility Transistor

Increase penetration of intermittent renewable sources causes reduction and time variation in system inertia, forcing dynamic changes in system coherency status. Besides increased penetration levels, other factors like intermittent generation and change in distribution of renewables also influence the system coherency that needs to be addressed. This paper examines the impact of variability of renewables on system coherency and proposes a coherency identification method based on spectrum similarity approach. The proposed method uses discrete cosine Stockwell transform to derive multiple time-frequency (TF) features that captures pair-wise similarity between synchrophasor frequency signals. Thereafter, mean shift spectral clustering is used to cluster the buses with most homogeneous TF spectrum. The proposed method is validated with renewable generation in the IEEE-39 bus system and a real transmission system of India grid. © 1969-2012 IEEE.

IEEE Transactions on Power Systems

A Spectrum Similarity Approach for Identifying Coherency Change Patterns in Power System Due to Variability in Renewable Generation

Real-time classification of events facilitates corrective control strategies, supervisory protection schemes, and on-line transient stability assessment of a power system. The synchrophasor-based event classification techniques face challenges like similar responses for different classes of events, i.e., inter-class similarity (ICS), applicability to limited classes of events, and moderate real-time performance for a large power system. In addition, the enhanced ICS effect of increased renewable penetration on events classification needs to be addressed. This paper proposes a kernel density estimation approach for accurate real-time classification of events in a power system with renewables using synchrophasor data. The proposed method uses a diffusion type kernel density estimator (DKDE) to characterize the shape of 3-D voltage and frequency distribution along time in terms of probability density functions (PDFs). That have distinct scale, shape, and orientation for different classes of events. Thereafter, a set of statistical features is derived from PDFs to train a multi-layered deep neural network for event classification. The proposed method is validated for renewables in IEEE-39 bus system and real transmission system of India grid using DIgSILENT/PowerFactory and also on a real phasor measurement unit data for India grid, where it showed better performance for ICS and renewable integration cases. © 2010-2012 IEEE.

IEEE Transactions on Smart Grid

Real-Time Event Classification in Power System with Renewables Using Kernel Density Estimation and Deep Neural Network

In this work, a Novel Adaptive Filter (NAF) is proposed for optimal control of grid-integrated solar PV (Photovoltaic) generating system. The proposed NAF is the improved form of classical adaptive vectorial filter (AVF), where inherent problems of AVF technique, like unable to handle the phase imbalance and phase shift issues, are successfully mitigated. For performance evaluation of NAF based control technique, a single-stage topology of three-phase grid integrated solar PV system is taken, where the loads are connected at the PCC (Point of Common Coupling). The prime objective of proposed NAF based control technique is to meet the active power requirement of loads from generated solar PV power, and after fulfill the load demand, the excess power is supplied to the grid. However, when generated PV power is not sufficient for the load then the NAF based control fulfills the load demand by taking extra required power from the grid. During this process, the power quality of the grid power is improved. The controller action provides, power factor correction, harmonics filtering and mitigation of other power quality issues. Moreover, when the solar irradiation is zero, then the voltage source converter acts as a distribution static compensator (DSTATCOM), which enhances the utilization factor of the system. The proposed techniques are modeled and their performances are verified experimentally on a developed prototype, in solar insolation variation conditions, unbalanced loading, as well as in different grid disturbances such as overvoltage, under-voltage, phase imbalance, harmonics distortion in the grid voltage etc. © 2018 IEEE.

4th IEEE International Conference on Universal Village 2018, UV 2018

Integration of Solar PV Generation with Distribution Grid: Using Novel Adaptive Filter Based Control Technique

Several different ambient energy sources available like ocean waves, thermoelectricity, piezoelectricity and physical motions. The energy harvesting from these sources are applicable to WSNs and portable electronic equipment. This paper review about energy harvesting technologies their significance and limitations. © 2017 IEEE.

International Conference on Innovations in Control, Communication and Information Systems, ICICCI 2017

A Survey of Energy Harvesting Technologies

Prolonged exposure of ammonia results in many potential health hazards for humans as it interacts immediately upon contact with available moisture in the eyes, skin, oral cavity, respiratory tract and particularly mucous surfaces, thereby, causes cellular destruction and tissue necrosis. In this paper, we report a detailed comparison between ammonia gas sensing, spectral, structural, and morphological properties of the dodecyl benzene sulphonic acid doped polyaniline (PANI-DBSA) nanostructures synthesized using a template free direct route using surfactant dopants as structure directing agents and using indirect route. Two different samples of PANI-DBSA nanostructures have been prepared via template free direct route (Nanostructured DBSA doped PANI has been prepared by emulsion polymerization of aniline in the presence of DBSA) and indirect doping route (Nanostructured DBSA doped PANI has been prepared via chemical oxidative polymerization of aniline monomer). Different characterizations revealed that the spectral, structural, morphological, and ammonia gas sensing properties of the synthesized PANI-DBSA nanostructures are highly dependent on the synthesis route. Thin film of nanostructured PANI-DBSA prepared using template free direct route exhibited better ammonia gas sensing response (7.97) as compared to thin film of nanostructured PANI-DBSA prepared using indirect doping (3.24) due to availability of large number of grain boundaries and higher doping levels. © 2019 IEEE.

2019 IEEE 16th India Council International Conference, INDICON 2019 - Symposium Proceedings

Performance analysis of ammonia sensors based on nanostructured PANI-DBSA synthesised by template free direct doping route using surfactant and indirect doping route

In this paper, technology for a gas sensor platform with borofloat as the substrate material is presented. Comprehensive characterization of the platform, its comparison with silicon and alumina, fabrication yield improvement and a study of reliability of the micro-heater platform have been carried out. Usually, the chips are suspended in air to reduce power consumption. However, the presented technology is a non-MEMS technique and doesn’t require any complex packaging. Borofloat has much lower thermal conductivity in comparison to silicon and alumina, thereby reducing the thermal losses, making it possible to operate the device with low power consumption. The process adapted for the fabrication of the gas sensor platform has lesser complexities and the process cost is reduced compared to conventional gas sensor fabrication, as it does not require thermal oxidation and bulk micromachining. Different substrates (silicon, alumina and glass) have been simulated using COMSOL to depict the benefit of lower thermal conductivity. Micro-heater has also been fabricted on all the three above mentioned substrates and the power consumption is compared. Various reliability analysis have been carried out on the glass based platform such as maximum temperature test, long term ON test and ON–OFF pulse test. © 2019, Springer-Verlag GmbH Germany, part of Springer Nature.

Microsystem Technologies

Development and reliability analysis of micro gas sensor platform on glass substrate

With use of surface-enhanced Raman scattering (SERS) substrate, we are able to identify alkaloids of tobacco leaves. First, porous Si arrays were developed using metal-assisted chemical etching and followed by gold (Au) thin layer (50 nm) coating. Au decorated porous Si arrays provide a strong localized electric field and responsible for the enhancement of weak Raman signals of target molecules. Detection of model molecule rhodamine B at low concentration (10−9 M) confirmed the SERS activity of the developed substrates. The enhancement factor was calculated to be approximate 106. Further, developed substrates were utilized to identify alkaloid in solution of dry tobacco leaves (1 g and 0.25 g) and water (100 Ml). Raman peak 1030 cm−1 corresponding to standard nicotine was observed. Understanding of tobacco composition and their Raman vibration mode could be beneficial to decide the biomarker of various diseases related to tobacco chewing and smoking. This work highlights the level free detection of tobacco alkaloids and confirms that Raman spectroscopy technique can utilize for quality control, forensic and bioanalytical analyses of tobacco alkaloids at trace level. © 2019, Springer Nature Switzerland AG.