Indian Institute of Technology Palakkad&nbsp;(IIT Palakkad or IIT PKD) is a public autonomous&nbsp;engineering&nbsp;and&nbsp;research&nbsp;institute located in&nbsp;Palakkad,&nbsp;Kerala. It was&nbsp;one of the five new&nbsp;IITs&nbsp;proposed in the&nbsp;2014 Union budget of India. The campus was inaugurated on 3 August 2015. The institute has 94 faculty, 978 students, and 63 non-teaching staffs.

IT Palakkad currently offers four-year Bachelor of Technology (B.Tech) and two years MS programmes in 8 different engineering disciplines including&nbsp;Computer Science, Electrical, Mechanical, Civil among others.

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IIT Palakkad

This paper presents a K-band 4-bit phase shifter using micro-electromechanical system-based dc contact single-pole-sixteen-throw (SP16T) switching networks. The circuit is fabricated on 63-μm alumina substrate using surface micromachining process. Compact circular type SP16T switch is the primary functional building block of the 4-bit phase shifter. SP16T switch demonstrates an average insertion loss of ∼1.9 dB, isolation of better than 14 dB and average return loss of better than 14 dB in the 18-26-GHz band. Total area of the fabricated SP16T switch is only ∼2.5 mm2. Finally, two SP16T switches are cascaded with different delay lines to develop the complete 4-bit phase shifter. The 4-bit phase shifter demonstrates an average insertion loss of 3.47 dB in the 19.75-20.25-GHz band with a return loss of better than 14 dB and average phase error is less than ∼1.77 °at 20 GHz. Total area of the fabricated 4-bit phase shifter is ∼13.5 mm2. The reliability of the SPST and SP16T switches show more than 1 billion (B) cycles with an RF power of 0.1-1 W. Finally, device demonstrates &gt;1 B cycles with cold switched and &gt; ∼600 million cycles with hot switched conditions. To the best of our knowledge, this is the first reported high reliable and more compact MEMS 4-bit phase shifter in the literature that has undergone extensive measurement stages with minimum number of switching elements per phase state. © 2018 IEEE.

World University root node

Department of Electrical Engineering

Journal of Microelectromechanical Systems

K -Band 4-Bit Phase Shifter Using Two Back to Back MEMS SP16T Switching Networks

In this paper, we introduce an analytical surface potential based model for sheet carrier density and current in N-polar GaN/AlN/AlGaN metal insulator semiconductor high electron mobility transistors (MIS-HEMTs). The proposed sheet carrier density model is derived in terms of Fermi-level (E-{f}), gate potential (V-{g}) and channel potential (V-{c}). The surface potential current model using charge control equations and high field saturation Canali mobility model are in close agreement with simulation and experimental data over a wide range of applied gate biases. © 2018 IEEE.

2018 4th IEEE International Conference on Emerging Electronics, ICEE 2018

A Surface-Potential Model for N-Polar GaN/AlN/AlGaN MIS-HEMTs

This paper presents a new capacitance-to-frequency converter (CFC) with high linearity and accuracy. In the CFC, the capacitance-to-frequency conversion is achieved using a negative feedback mechanism. In the feedback, the output frequency controls the charge injected by a switched-capacitor (SC) network such that the difference error is automatically minimized. The feedback mechanism ensures that the final output is insensitive to the nonlinearity errors of the units employed to realize the forward path, namely, a capacitance-to-voltage converter and a voltage-to-frequency converter. A simple error correction mechanism employed ensures that the digital output obtained is insensitive to the number of nonideal circuit parameters. The proposed converter uses a dc reference voltage for the excitation and helps to achieve high accuracy. A prototype of the improved CFC has been developed and tested for sensor capacitance Cx in the range of 5-25 pF. A prototype of the conventional open-loop CFC was also developed, and the linearity has been evaluated. The proposed closed-loop approach has lower (0.1%) nonlinearity error compared to the conventional CFC (0.8%). This improvement is achieved without the use of any error-compensating schemes, and hence the complexity level of the system remains the same as that of any typical CFC. The response time of the CFC designed is about 400 μs for a 5-25 pF step change in Cx. The results obtained from the prototype CFC confirmed its usefulness. © 2018 IEEE.

IEEE Transactions on Instrumentation and Measurement

An Improved Closed-Loop Switched Capacitor Capacitance-to-Frequency Converter and Its Evaluation

Inverter dead-time is known to make open-loop induction motor drives oscillatory, while operating at light-loads in particular. While dead-time compensation schemes exist, precise compensation of the same is often challenging as it involves factors such as device and driver delays and switching transition times, which are difficult to be quantified accurately. Hence, the effect of dead-time could be under or overcompensated. This paper presents a comprehensive analysis of the impact of such undercompensation and overcompensation on the stability of a 100-kW induction motor drive, along with experimental investigations of the same. The effects of undercompensation and overcompensation on the inverter output voltage are analyzed on a switching-cycle average basis. Further, small-signal models are proposed for an open-loop drive, when it is undercompensated and overcompensated. Stability analysis of the above motor drive is reported, which predicts oscillatory behavior with both under and overcompensation, over certain fundamental frequency ranges, respectively. Further, two different types of oscillatory behavior, characterized by different oscillating frequencies, are observed for the cases of under and overcompensation. The analyses are supported by simulations. Experimental investigations carried out also support the analyses and simulation results. © 1972-2012 IEEE.

IEEE Transactions on Industry Applications

Impact of Undercompensation and Overcompensation of Dead-Time Effect on Small-Signal Stability of Induction Motor Drive

The Poincaré representation of equations of motion provides a global characterization of the dynamics of a rigid body subjected to external torques. We use this representation to obtain the global dynamics of a spherical robot with three independent internal rotors rolling on a plane. The robot is subjected to nonholonomic constraints arising out of pure rolling motion. The dynamics of the system is obtained by projecting the kinematic vector fields on the constrained distribution using the nonholonomic affine connection. The rotor torques are incorporated into the dynamics by way of the total angular momentum of the robot about the point of contact. © 2018 IEEE.

2018 Indian Control Conference, ICC 2018 - Proceedings

Poincaré representation of the equations of motion of a spherical robot actuated by internal rotors

Accurate and reliable identification of the first (S1) and second (S2) sounds of the phonocardiogram (PCG) is still a challenging task due to the presence of the S3 and S4, murmurs, high-pitched sounds, physiological interference, and other environmental noises. This paper presents an automated method for identification of the S1 and S2 sounds by simultaneously recording, processing, and fusing the extracted fiducial points of the PCG and photoplethysmogram (PPG) signals. The method consists of four main stages: the PCG and PPG signal sensing with Arduino interfacing, the heart sound delineation (HSD) and pulse waveform delineation (PWD) using variational mode decomposition (VMD), and the S1/S2 identification based on the estimated timings of the pulse onset, peak, upward slope zerocrossing, and downward slope zerocrossing of the pulsatile waveform. The accuracy and robustness of the HSD and PWD algorithms are evaluated using both the benchmark databases and simultaneous PCG and PPG recordings. Then, the proposed S1/S2 identification method is evaluated using the simultaneous PCG and PPG recordings. The VMD-based HSD algorithm achieves an average sensitivity (SE) = 99.80%, positive predictivity (PP) = 99.0%, and accuracy (ACC) = 98.81% whereas the Gaussian derivative filter (GDF)-based HSD and bandpass filter (BPF)-based HSD algorithms achieve the average SE = 99.75%, PP = 93.59%, and ACC = 93.37% and the average SE = 99.67%, PP = 84.97%, and ACC = 84.73%, respectively, for the recorded PCG signals with SNR value of 5 dB. The proposed S1/S2 identification method achieves a correct identification rate of 99.75% which outperforms the GDF+systole interval(SI)/diastole interval(DI) and the BPF+SI/DI feature-based methods having 66% and 59.25%, respectively, in the case of noisy recordings with a SNR value of 5 dB. The proposed method has great potential in improving the identification accuracy and robustness in the presence of other sounds and murmurs, and different kinds of environmental noises. © 2018 IEEE.

IEEE Sensors Journal

Automatic identification of S1 and S2 heart sounds using simultaneous PCG and PPG recordings

Solid-state transformers (SSTs) have attracted recent interests due to its potential in providing ancillary services in addition to step-up/step-down of voltages. In SSTs, a common topology used in the first AC-DC stage is the cascaded H-bridge (CHB) multilevel active rectifier. This paper proposes a novel dual-model predictive control method for the CHB multilevel active rectifier that achieves sinusoidal source current, maintains DC voltages at set-points, and balances the DC voltages in each of the H-bridge cells. The primary model of the CHB multilevel active rectifier aims to enable control over source current and output voltage. The secondary model uses conservation of energy to calculate the reference source current, which eliminates the need for a PI-control-based outer loop. A Luenberger-based observer is also implemented to estimate the DC load currents. The effectiveness of the proposed method under steady-state and transient conditions is validated through a laboratory prototype of a single-phase 7-level CHB active rectifier. © 2018 IEEE.

2018 IEEE Energy Conversion Congress and Exposition, ECCE 2018

Dual-Model Predictive Control for Cascaded H-Bridge Multilevel Active Rectifier with DC Voltage Balancing in a Solid-State Transformer

We propose a new neutron-capture site in early metal-poor and metal-free stars of ∼20-30 M o that results from proton ingestion in the He shell during late stages of the stars' lives. Most of the neutron capture occurs in the first ≲106 s following proton ingestion when 13C(α, n)16O produces neutron densities typical of the intermediate neutron-capture process. This phase may be followed by another lasting 107 s with 17O(α, n)20Ne producing much lower neutron densities typical of the slow neutron-capture process. We explore the dependence of the proposed neutron-capture nucleosynthesis on the amount and time of proton ingestion, the initial metallicity, and the ensuing supernova shock. We obtain a range of heavy-element abundance patterns, including those attributed to the slow neutron-capture process or a combination of the slow and rapid neutron-capture processes. Our results can account for the observed ubiquity of heavy elements such as Sr and Ba in the early Galaxy and explain puzzling abundance patterns of these elements in at least some very metal-poor (VMP) stars, including those of the carbon-enhanced varieties. In the latter case, the explanation by the single site proposed here differs from the existing paradigm that attributes various classes of VMP stars to enrichment by multiple different sites. © 2018. The American Astronomical Society. All rights reserved.

Department of Physics

Astrophysical Journal

New Neutron-capture Site in Massive Pop III and Pop II Stars as a Source for Heavy Elements in the Early Galaxy

Observations suggest that the interstellar medium (ISM) might have been highly enriched in carbon at very early times. We explore nucleosynthesis in massive carbon-enhanced metal-poor (CEMP) stars of 12-$40, mathrm{M}_odot$ formed from such an ISM with [Fe] ≤ -2. We find substantial production of elements heavier than Fe, mostly up to Sr, by the weak s-process in stars with initial abundances of [CNO] > -1.5. Even heavier elements, up to Ba, can be produced for [CNO] > -0.5. The efficiency of this s-process is sensitive to the initial enhancement of C (or more generally, CNO) and mass of the star, with the yield increasing approximately linearly with the initial Fe abundance. The s-process in CEMP stars of ${gtrsim } 20 , mathrm{M}_odot$ with [CNO] > -1.5 can be an important source for heavy elements in the early Galaxy. © 2018 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.

Fulltext

Monthly Notices of the Royal Astronomical Society

S-Process in massive carbon-enhanced metal-poor stars

We study the existence of positive radial solutions to the problem 8 { -Δpu = λK1(jxj)f(v) in Ωe; -Δpv = λK2(jxj)g(u) in Ωe; u = v = 0 if jxj = r0; u(x) → 0; v(x) → 0 as jxj → 1; where Δpw := div(jrwjp-2rw), 1 0 and Ωe := {x 2 Rnj jxj > r0}. Here, Ki : [r0;∞) → (0;∞), i = 1; 2 are continuous functions such that limr→1 Ki(r) = 0, and f; g : [0;1) → R are continuous functions which are negative at the origin and have a superlinear growth at infinity. We establish the existence of a positive radial solution for small values of λ via degree theory and rescaling arguments. © 2018 Khayyam Publishing. All rights reserved.}, funding_details={Simons FoundationSimons Foundation, 317872}, funding_details={European Social FundEuropean Social Fund, ESF}, funding_text_1={Since ‖u‖∞ → ∞ as λ → 0, we have maxt∈[0,1]f(v(t)) → ∞ as λ → 0. This implies that ‖v‖∞ → ∞ as λ → 0. Similarly if ‖v‖∞ → ∞ as λ → 0, we can prove ‖u‖∞ → ∞ as λ → 0. Hence, both ‖u‖∞ and ‖v‖∞ → ∞ as λ → 0. Hence, Theorem 1.1 is proven. Acknowledgment. This work was partially supported by the project EXLIZ-CZ.1.07/2.3.00/30.0013, which is co-financed by the European Social Fund and the state budget of the Czech Republic and by the INSPIRE faculty award by the Department of Science and Technology, India for Lakshmi Sankar. This work was also partially supported by a grant from the Simons Foundation (#317872) for Ratnasingham Shivaji.}, references={Abebe, A., Chhetri, M., Sankar, L., Shivaji, R., Positive solutions for a class of superlinear semipositone systems on exterior domains Boundary Value Problems, 2014 (2014), p. 198; Allegretto, W., Nistri, P., Zecca, P., Positive solutions of elliptic non-positone problems (1992) Differential Integral Equations, 5, pp. 95-101; Ambrosetti, A., Arcoya, D., Buoni, B., Positive solutions for some semi-positone problems via bifurcation theory (1994) Differential Integral Equations, 7, pp. 655-663; Ambrosetti, A., Azorero, J.G., Peral, I., Multiplicity results for some nonlinar elliptic equations (1996) Journal of Functional Analysis, 137, pp. 219-242; Anuradha, V., Hai, D.D., Shivaji, R., Existence results for superlinear semipositone BVP's (1996) Proc. Amer. Math. 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Appl., 217, pp. 672-686; Hai, D.D., Shivaji, R., Maya, C., An existence result for a class of superlinear p- Laplacian semipositone systems (2001) Differential Integral Equations, 14, pp. 231-240; Jacobsen, J., Schmidtt, K., Radial solutions of quasilinear elliptic differential equations (2004) Handbook of Differential Equations, pp. 359-435. , Elsevier/North-Holland, Amsterdam; Ko, E., Lee, E.K., Shivaji, R., Multiplicity results for classes of singular problems on an exterior domain (2013) Discrete and Continuous Dynamical Systems, 33, pp. 5153-5166; Manasevich, R., Mawhin, J., Boundary value problems for nonlinear perturbations of vector p-Laplacian-like operators (2000) J. Korean Math. Soc., 378, pp. 665-685; Smoller, J., Wasserman, A., Existence of positive solutions for semilinear elliptic equations in general domains (1987) Arch. Rational Mech. Anal., 98, pp. 229-249}, publisher={Khayyam Publishing}, issn={08934983}, language={English}, abbrev_source_title={Differ. Integr. Equ.}, document_type={Article}, source={Scopus},