Department of Electrical Engineering

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In this paper we study the last round of the discrete Voronoi game in R-2, a problem which is also of independent interest in competitive facility location. The game consists of two players P1 and P2, and a finite set U of users in the plane. The players have already placed two disjoint sets of facilities F and S, respectively, in the plane. The game begins with P1 placing a new facility followed by P2 placing another facility, and the objective of both the players is to maximize their own total payoffs. In this paper we propose polynomial time algorithms for determining the optimal strategies of both the players for arbitrarily located existing facilities F and S. We show that in the L-1 and the L-infinity metrics, the optimal strategy of P2, given any placement of P1, can be found in O (n log n) time, and the optimal strategy of P1 can be found in O (n(5) log n) time. In the L-2 metric, the optimal strategies of P2 and P1 can be obtained in O (n(2)) and O (n(8)) times, respectively. (C) 2017 Elsevier B.V. All rights reserved.

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COMPUTATIONAL GEOMETRY-THEORY AND APPLICATIONS

The discrete Voronoi game in R-2

Analysis of electromechanical (E-M) window provides an early marker of several cardiovascular diseases. The E-M window is defined as the duration between the electrical systole (QT) and the mechanical systole (QS2). Traditional methods for the estimation of the electrical systole and the mechanical systole are electrocardiography (ECG) and phonocardiography (PCG). PCG is a widely used method due its features such as portability and cost effectiveness. However, it needs to be improvise in terms of its size and weight, to make it convenient to wear for long-Term. Further, the PCG signal is susceptible to various noises, which limits its use in clinical environment. Henceforth, in this paper, we presented a novel system to estimate the E-M window using seismocardiogaphy (SCG) in replacement of the PCG. The SCG uses a sensor called accelerometer, which is small in size and low weight and hence it is convenient to wear. Furthermore, it does not require a microphone, as required in case of the PCG, and hence it is robust to environmental noises. We analysed the performance of the proposed system compared to the PCG, for the estimation of the E-M window. For this purpose ECG, PCG, and SCG signals are acquired simultaneously, for 10 subjects and then validated the obtained results using Bland-Altman plots. Results show that the proposed method is a suitable alternative to estimate the E-M window. © 2016 IEEE.

2016 International Conference on Systems in Medicine and Biology, ICSMB 2016

Seismocardiography: An alternate method to estimate electro-mechanical window

This paper presents the performance of a highly selective ethanol sensor based on MoS2-functionalized porous silicon (PSi). The uniqueness of the sensor includes its method of fabrication, wafer scalability, affinity for ethanol, and high sensitivity. MoS2 nanoflakes (NFs) were synthesized by sulfurization of oxidized radio-frequency (RF)-sputtered Mo thin films. The MoS2 NFs synthesis technique is superior in comparison to other methods, because it is chip-scalable and low in cost. Interdigitated electrodes (IDEs) were used to record resistive measurements from MoS2/PSi sensors in the presence of volatile organic compound (VOC) and moisture at room temperature. With the effect of MoS2 on PSi, an enhancement in sensitivity and a selective response for ethanol were observed, with a minimum detection limit of 1 ppm. The ethanol sensitivity was found to increase by a factor of 5, in comparison to the single-layer counterpart levels. This impressive response is explained on the basis of an analytical resistive model, the band gap of MoS2/PSi/Si, the interface formed between MoS2 and PSi, and the chemical interaction of the vapor molecules and the surface. This two-dimensional (2D) composite material with PSi paves the way for efficient, highly responsive, and stable sensors. © 2017 American Chemical Society.

ACS Applied Materials and Interfaces

Wafer-Scale Synthesized MoS2/Porous Silicon Nanostructures for Efficient and Selective Ethanol Sensing at Room Temperature

A high speed efficient broadband photodetector based on a vertical n-MoS2/p-porous silicon heterostructure has been demonstrated. Large area MoS2 on electrochemical etched porous silicon was grown by sulphurization of a sputtered MoO3 thin film. A maximum responsivity of 9 A/W (550-850 nm) with a very high detectivity of ∼1014 Jones is observed. Transient measurements show a fast response time of ∼9 μs and is competent to work at high frequencies (∼50 kHz). The enhanced photodetection performance of the heterojunction made on porous silicon over that made on planar silicon is explained in terms of higher interfacial barrier height, superior light trapping property, and larger junction area in the MoS2/porous silicon junction. © 2017 Author(s).

Fulltext

Applied Physics Letters

High performance broadband photodetector based on MoS2/porous silicon heterojunction

Bacteria entrapment in water is one of the major concerns around the globe. With increase in pollution levels, automation, altering weather, global warming etc., the quality of natural resources of water is in a big doubt. This paper presents the fabrication, characterization and testing of a bioactive surface which comprises of a hetero-structure. The surface contains porous silicon with a capping of titania nanostructures. The bio-studies were done in presence of E. coli bacteria and its ensnarement was confirmed from SEM and Photoluminescence (PL) studies. The surface was found to be extremely sensitive to 102 CFU/mL of bacteria. © 2017 IEEE.

Proceedings of IEEE Sensors

Capturing bacteria through a bio-sensitive heterostructure surface: Photoluminescence studies

Image quality assessment (IQA) plays a crucial role in monitoring quality control in image communication systems, and in benchmarking and optimizing parameters in enhancement algorithms. The full-reference IQA metrics require a good-quality reference image, obtaining which may not be practical in real-life applications. This paper, therefore, proposes a no-reference IQA metric based on the hypothesis that every image has latent additive white Gaussian noise (AWGN). A mathematical model was developed on a dataset of fifty test images by computing gradient-based structural similarity of corrupted images w.r.t. the original. Statistical modeling of the observations were found to fit an exponential parametric model. The standard deviation of the latent (or apparent) AWGN present in any image was estimated using an SVD-based approach. The proposed metric, referred to as the no-reference gradient-based structural integrity (NRGSI), is then computed by a simple backprojection of the estimated noise deviation on the exponential model. The accuracy of the proposed objective metric is characterized by its comparison with subjective quality scores given by ten subjects, and with a classical perceptual quality measure. © 2017 IEEE.

No-Reference image quality assessment using gradient-based structural integrity and latent noise estimation

Room temperature hydrogen sensors were fabricated from Au embedded ZnO nano-networks using a 30 mW GaN ultraviolet LED. The Au-decorated ZnO nano-networks were deposited on a SiO2/Si substrate by a chemical vapour deposition process. X-ray diffraction (XRD) spectrum analysis revealed a hexagonal wurtzite structure of ZnO and presence of Au. The ZnO nanoparticles were interconnected, forming nano-network structures. Au nanoparticles were uniformly distributed on ZnO surfaces, as confirmed by FESEM imaging. Interdigitated electrodes (IDEs) were fabricated on the ZnO nano-networks using optical lithography. Sensor performances were measured with and without UV illumination, at room temperate, with concentrations of hydrogen varying from 5 ppm to 1%. The sensor response was found to be ∼21.5% under UV illumination and 0% without UV at room temperature for low hydrogen concentration of 5 ppm. The UV-photoactivated mode enhanced the adsorption of photo-induced O- and O2- ions, and the d-band electron transition from the Au nanoparticles to ZnO - which increased the chemisorbed reaction between hydrogen and oxygen. The sensor response was also measured at 150 °C (without UV illumination) and found to be ∼18% at 5 ppm. Energy efficient low cost hydrogen sensors can be designed and fabricated with the combination of GaN UV LEDs and ZnO nanostructures. © 2017 IOP Publishing Ltd.

Nanotechnology

Efficient room temperature hydrogen sensor based on UV-activated ZnO nano-network

Anatase phase dominated TiO2 nanoplates were deposited on p-Si by Radio-Frequency magnetron sputtering technique. Metal-TiO2 nanoplates-Metal (M-TN-M) planer electrodes were fabricated using various metal electrodes such as Al, Ag, Ni, and Au. Temperature dependent current-voltage (I-V) characteristics of M-TN-M devices were measured in air and 1% hydrogen atmosphere. Barrier height between metal and TiO2 nanoplates is decreased in presence of hydrogen as compared to air and increases with temperature. The sensing response of the device is strongly dependent on the alteration of barrier height and operating temperature. The relative response was observed ∼46% for Ohmic Al electrodes. The effective barrier heights were measured to be ∼0.15 eV for Ag, ∼0.17 eV for Ni and ∼0.19 eV for Au electrodes at 175 °C and corresponding change in relative response were measured ∼49%, ∼58%, and ∼77%, respectively. Response and recovery times for highest sensitivity device (Au-TN-Au) were found to be ∼7 and 114 s respectively at 175 °C operating temperature. © 2017 Hydrogen Energy Publications LLC

International Journal of Hydrogen Energy

Effect of Schottky barrier height on hydrogen gas sensitivity of metal/TiO2 nanoplates

The present work reports impedance based electrochemical sensing and remediation of 4-nitro phenol (4-NP) using biosynthesized (CuO) copper oxide nanoparticles. The synthesis of CuO nanoparticles is achieved using fruit extract of plant Fortunella japonica as reducing and stabilizing agent. The CuO nanoparticles were characterized using various analytical techniques like UV–Visible spectroscopy, Atomic force microscopy (AFM), High resolution transmission electron microscopy (HR-TEM), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and X-ray diffraction (XRD). For electrochemical sensing of 4-NP, the CuO nanoparticles were drop casted on screen printed electrode (SPE) and electrode is referred at SPE/CuONPssensor. The mechanism of 4-NP redox reactions was examined using cyclic voltammetry (CV). The electrochemical sensing of 4-NP has been done using square wave voltammetry (SWV) and impedance spectroscopy. In SWV, the oxidation peak current increased with increase in the concentration of 4-NP from 10 nM to 10 mM having regression coefficient of 0.996. In impedometric sensing, change in charge transfer resistance (Rct) with change in 4-NP concentration was used as a signal. The Rctdecreased with increase in 4-NP concentration which is in accordance with SWV results. The effect of solution pH on impedometric response of SPE/CuONPssensor was also evaluated. The SPE/CuONPssensor exhibited good reproducibility and selectivity towards the analyte and is able to perform real sample analysis. The CuO nanoparticles act as a catalyst and showed good degradation percentage of 4-NP pollutant. © 2016 Elsevier B.V.

Chemical Engineering Journal

Electrochemical sensing and remediation of 4-nitrophenol using bio-synthesized copper oxide nanoparticles

In this paper, we have mathematically modeled and analyzed the composite cavity Semiconductor Fiber Ring Laser for its use as an inertial rotation sensor or gyroscope. The rate equations of Semiconductor Optical Amplifier and the transfer function of other components in the configuration, viz. optical filter, output coupler and Y-junction coupler have been considered separately for modelling. The final output expression shows the effect of these components on the intensity of the beat signal. The frequency of the beat signal intensity is shown to be independent of the parameters of the components, which underlines the advantage of frequency-domain sensing. © 2016, The Optical Society of India.