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 two single-layer miniaturized bandpass frequency selective surfaces (FSSs) with single and dual-band resonances. Transmission zeros (TZs) are introduced near to the sidebands which in effect improve the filter selectivity at the resonance. The basic FSS prototype consists of a capacitive grid (CG) loaded cross-dipole aperture (CDA) which shows a passband center at 6.22 GHz with a 3 dB bandwidth (BW) of 20.3 %. Later the CG structure is modified by adding parallel slot lines (PSL) which are extended towards the center to realize the second FSS unit cell. The proposed FSS-2 exhibits closely spaced dual passbands center at 5.5 and 7.48 GHz with a frequency ratio of 1.36. Passband insertion losses at two frequencies are 0.19 and 0.46 dB with BWs of 31.7 and 13.5 %. The proposed single and dual-band FSSs show polarization insensitive filter response with oblique angle stability of 40° and 55° respectively. © 2021 IEEE.

Department of Electrical Engineering

World University root node

2021 IEEE International Symposium on Antennas and Propagation and USNC-URSI {\ldots}

Miniaturized Angularly Stable Single and Dual Bands Bandpass Frequency Selective Surfaces with Transmission Zeros Near the Sidebands

This paper presents a composite right-left hand (CRLH) transmission line (TL) inspired 5-bit digital phase shifter. The proposed phase shifter comprises three cascaded CRLH unit cells with overall eight PIN diodes are mounted on the horizontal and vertical outer fingers of the element. A systematic design approach is adopted to obtain phase shifts of 5.656,11.317,22.248,44.491, and 89.687 degrees with respect to a reference line at frequency 10 GHz. The proposed design possesses the advantages of low insertion loss (\lt 2.16\mathrm{~dB}) and return loss \gt 12\mathrm{~dB} with high power handling capability over the frequency range of 9.9-10.1 GHz. © 2021 IEEE.

2021 IEEE MTT-S International Microwave and RF Conference (IMARC)

Novel 5-bit Phase Shifter using CRLH Transmission Line with Interdigital Capacitor and Shorted Stubs

In this work, a broadband transmissive type linear-circular polarizer with wide angular stability is demonstrated. It shows a 3 dB Axial Ratio (AR) bandwidth of 21.05 GHz (from 20.17 - 41.22 GHz) with 68.58 % fractional bandwidth (FBW) covering K and Ka-bands. The angular stability of the converter is examined, and it possesses a stable AR response up to 50° (for φ = 0°) and 40° (for φ = 90°). The design is compact with the periodicity of 0.107L x 0.141L, where L is the free-space wavelength corresponding to the lowest frequency over the broadband. Authors' strongly believed that the proposed design has broadband 3 dB AR, better angular stability, and compactness made it suitable for countervailing the effect of Faraday rotation in satellite communication applications. © 2021 IEEE.

Broadband and Wide Angular Stable Inductive Grid-Based Linear to Circular Transmission Type Polarizer for Satellite Communication Applications

This paper presents a new compact uniplanar electromagnetic bandgap (EBG) structure for K band applications. The proposed unit cell consists of corner square patches which are connected at the center by meander lines and interdigital capacitors (IDC) along the edges. The dispersion characteristic of the EBG is analyzed using an Eigenmode solver and later the bandgap property is verified using an open-ended symmetric transmission line method. Numerical simulation of the proposed EBG shows a bandgap of 21.5 % over 17.33-21.5 GHz. The unit cell has the periodicity of 0.16 λ0, where λ0 is the wavelength at the center frequency of the bandgap. © 2021 IEEE.

2021 IEEE 19th International Symposium on Antenna Technology and Applied Electromagnetics, ANTEM 2021

A Compact Uniplanar Electromagnetic Bandgap Structure with Wide Bandgap

Automatic learning algorithms for improving the image quality of diagnostic B-mode ultrasound (US) images have been gaining popularity in the recent past. In this work, a novel convolutional neural network (CNN) is trained using time of flight corrected in-vivo receiver data of plane wave transmit to produce corresponding high-quality minimum variance distortion less response (MVDR) beamformed image. A comprehensive performance comparison in terms of qualitative and quantitative measures for fully connected neural network (FCNN), the proposed CNN architecture, MVDR and Delay and Sum (DAS) using the dataset from Plane wave Imaging Challenge in Ultrasound (PICMUS) is also reported in this work. The CNN architecture can leverage the spatial information and will be more region adaptive during the beamforming process. This is evident from the improvement seen over the baseline FCNN approach and conventional MVDR beamformer, both in resolution and contrast with an improvement of 6 dB in CNR using only zero-angle transmission over the baseline. The observed reduction in the requirement of number of angles to produce similar image metrics can provide a possibility for higher frame rates.

2021 43rd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC)

Towards Fast Region Adaptive Ultrasound Beamformer for Plane Wave Imaging Using Convolutional Neural Networks

In the case of typical beamforming in ultrasound imaging, apodization schemes assume a geometric delay driven diffuse reflection model and are not robust for specular reflections. Conversely, the beamforming schemes exclusive to emphasizing specularity suppress the diffuse reflections and speckles. This results in separate beamforming modes for normal tissue scanning and specular reflectors like needles. However, most tissue reflections compose of both diffuse and specular components and a synergistic approach is important. Towards this, a novel approach called reflection tuned apodization (RTA) using coherent plane-wave compounding is proposed, where the apodization window is aligned appropriately by analyzing the reflections from the transmitted plane wave angles for each pixel. A reflection similarity measure is estimated from the plane wave angles to differentiate and characterize the tissue reflections. The beamforming results with the proposed RTA on experimental data show a remarkable improvement in the visibility of specular regions without the suppression of diffuse reflections and speckles compared to the conventional apodization approach. © 2021 IEEE.

Proceedings - International Symposium on Biomedical Imaging

Towards diffuse beamforming for specular reflectors: A pixel-level reflection tuned apodization scheme for ultrasound imaging

We develop a method to compute thermally mediated transition rates between the ground state and long-lived isomers in nuclei. We also establish criteria delimiting a thermalization temperature above which a nucleus may be considered a single species and below which it must be treated as two separate species: a ground-state species and an astrophysical isomer ("astromer") species. Below the thermalization temperature, the destruction rates dominate the internal transition rates between the ground state and the isomer. If the destruction rates also differ greatly from one another, the nuclear levels fall out of or fail to reach thermal equilibrium. Without thermal equilibrium, there may not be a safe assumption about the distribution of occupation probability among the nuclear levels when computing nuclear reaction rates. In these conditions, the isomer has astrophysical consequences and should be treated as a separate astromer species which evolves separately from the ground state in a nucleosynthesis network. We apply our transition-rate methods and perform sensitivity studies on a few well-known astromers. We also study transitions in several other isomers of likely astrophysical interest. © 2020. The American Astronomical Society. All rights reserved.

Department of Physics

Astrophysical Journal, Supplement Series

Astromers: Nuclear Isomers in Astrophysics

VizieR Online Data Catalog, J/ApJ/891/

VizieR Online Data Catalog: LAMOST DR3 very metal-poor stars of the Galactic halo (Yuan+, 2020)

Study Region: The contiguous United States (CONUS). Study Focus: This study assesses the effects of the large-scale oceanic-atmospheric oscillations such as El Niño southern oscillation (ENSO), Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), and Pacific Decadal Oscillation (PDO) on streamflow levels. Two robust and powerful non-parametric procedures, namely, the Joint Rank Fit (JRFit) and the rank-based partial least squares regression are used to identify and quantify the strength and direction of teleconnections (individual analysis). Further, JRFit is used to model the interactive effects (coupled analysis) of ENSO with AMO/PDO/NAO cycles on streamflows. New Hydrological Insights for the Region: Individual analysis results identified new significant ENSO, PDO, AMO and NAO tele-connections with streamflows across CONUS. PLS analysis showed a stronger AMO teleconnection with streamflows compared to other oscillations. The coupled analyses results were categorized into three groups based on the types of interactions of the ENSO phases. Type 1 interactions where a phase of ENSO is modulated by phases of decadal/multidecadal cycles, are seen across all (majority of) regions in CONUS. Interesting results were obtained for type 2 (type 3) interactions as the effects of ENSO phases were opposite (similar but enhanced), compared to individual analysis of ENSO, when associated with the phases of PDO/AMO/NAO. The results provide several new findings and useful information for forecasting of water resources in the CONUS region. © 2021

Department of Civil Engineering

Fulltext

Journal of Hydrology: Regional Studies

Effect of ENSO modulation by decadal and multi-decadal climatic oscillations on contiguous United States streamflows

The effective width method (EWM) for calculating the ultimate strength of cold-formed steel (CFS) members assumes simply supported boundary conditions along the plate edges. Unstiffened plates, simply supported along three edges and unsupported along one longitudinal edge buckle in a single half-wave equal to plate length when subjected to uniform compression. It has been observed from the finite element analysis results that the simply supported unstiffened plates with large length to width ratios (L/ b≥ 10) the deformation pattern changes from a single half-wave to a combination of three half-waves corresponding to the ultimate load. One of the possible reasons for this is the nearly same elastic buckling stresses in the first few modes leading to the interaction of higher buckling modes. At larger L/b ratios the interaction of the third buckling mode with fundamental mode was observed causing the reduction in the ultimate strength. A similar reduction in the ultimate strength due to buckling mode interactions are also found in CFS plain equal angle sections, as such sections composed of only unstiffened plates which buckle simultaneously. In sections like plain channels, where additional rotational restraint along the supported longitudinal edge is present, such mode interactions are found to not influence the strength of unstiffened elements in sections. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.