Department of Electrical Engineering

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

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.

World University root node

Proceedings - International Symposium on Biomedical Imaging

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

The accurate emotional assessment of humans can prove beneficial in health care, security investigations and human interaction. In contrast to emotion recognition from facial expressions which can prove to be inaccurate, analysis of electroencephalogram (EEG) activity is a more accurate representation of one’s state of mind. With advancements in deep learning, various methods are being employed for this task. In this research, importance of attention mechanism in EEG signals is introduced through two vision transformer based methods for the classification of EEG signals on the basis of emotions. The first method utilizes 2-D images generated through continuous wavelet transform (CWT) of the raw EEG signals and the second method directly operates on the raw signal. The publicly available and widely accepted DEAP dataset has been utilized in this research for validating the proposed approaches. The proposed approaches report very high accuracies of 97% and 95.75% using CWT and 99.4% and 99.1% using raw signal for valence and arousal classifications respectively, which clearly highlights the significance of attention mechanism for EEG signals. The proposed methodology also ensures faster training and testing time which suits the clinical purposes.Clinical Relevance— This work establishes a highly accurate algorithm for emotion recognition using EEG signals which has potential applications in music-based therapy.

2021 43rd Annual International Conference of the IEEE Engineering in {\ldots}

Introducing Attention Mechanism for EEG Signals : Emotion Recognition with Vision Transformers

Ultrasound (US) imaging is becoming the routine modality for the diagnosis and prognosis of lung pathologies. Lung US imaging relies on artifacts from acoustic impedance (Z) mismatches to distinguish and interpret the normal and pathological lung conditions. The air-pleura interface of the normal lung displays specularity due to the huge Z mismatches. However, in the presence of pathologies, the interface alters exhibiting a diffuse behavior due to increased density and reduced spatial distribution of air in the sub-pleural space. The specular or the diffuse behavior influences the reflected acoustic intensity distribution. This study aims to understand the reflection pattern in a normal and pathological lung through a novel approach of determining pixel-level acoustic intensity vector field (IVF) at high frame rates. Detailed lung modeling procedures using k-Wave US toolbox under normal, edematous, and consolidated conditions are illustrated. The analysis of the IVF maps on the three lung models clearly shows the drifting of the air-pleura interface from specular to diffuse with the severity of the pathology.Clinical Relevance— The presented acoustic simulation lung models are an aid to teaching and research by providing a quick visual and intuitive understanding of lung ultrasound physics. The proposed intensity vector field maps are supplementary information to aid diagnostics and characterization of any tissue composed of specular and diffuse components.

Pixel Intensity Vector Field : An Inside Out Approach of Looking at Ultrasound Reflections from the Lung at High Frame Rates

In ultrasound (US) imaging, the reflections from the tissue interfaces are either diffuse or specular based on their sizes relative to the US signal wavelength and acoustic impedance mismatches at the interfaces. Diffuse reflections have low intensity and directivity, unlike specular reflections which have high intensity and directivity that depend on the incidence angle of the transmit signal and the interface orientation. This reduces the detection probability if the apodization in beamforming (as in conventional delay and sum) is inappropriate or the reflections are directed to the outside of the transducer aperture resulting in misdiagnosis (e.g., anisotropy). This puts forth the necessity to consider both the magnitude and direction of the reflected intensity before arriving at a definitive decision. In this work, a novel approach is proposed to represent the spatial distribution of acoustic intensity of each pixel as a vector field. The reflected intensity from each pixel to each transducer element is considered as a vector that has a magnitude and direction and varies depending on the nature of the pixel (diffuse/specular). This approach can supplement visualization, aid in transducer probe adjustment, selection of the right set of transmit angles/focus and characterization of reflections in musculoskeletal studies and needle tracking.

2021 IEEE International Ultrasonics Symposium (IUS)

Intensity Vector Field: A Tool for Visualization and Characterisation of Tissue Reflections in High Frame Rate Ultrasound Imaging

This paper has carried out a detailed investigation on oscillatory mode information-based system inertia estimation techniques. In the first step, the critical modes of oscillation are extracted from the post-disturbance frequency deviation signal which is obtained from the phasor measurement units (PMUs). In this process, two popular methods for parameter estimation such as Estimation of Signal Parameter via Rotational Invariance Techniques (ESPRIT) and Matrix Pencil technique are deployed to extract the mode information. The investigation reveals the superiority of the Matrix Pencil method over the ESPRIT method for inertia estimation application. Once the mode information is available, an equivalent swing equation is used to estimate the inertia at any desired bus of the power system. The analysis is carried out on both Kundur's two-Area system and the IEEE-39 bus system. The results obtained demonstrate the superiority of Matrix Pencil based method over ESPRIT method for inertia estimation application. © 2021 IEEE.

2021 9th IEEE International Conference on Power Systems (ICPS)

Detailed Investigation of Mode Information based System Inertia Estimation using Synchrophasor Measurements

High-efficiency solar cells based on organometal-halide perovskites have been extensively reported. While there are many reports in literature regarding improved performance in these devices, only few reports provide detailed performance and theoretical efficiency limits in perovskite-based solar cells (PSCs). An analytical model accounting for both optical and electrical losses in a PSC has been largely unexplored. Our calculations provide a simple semi-analytical framework for the analysis of different loss mechanisms in a PSC, which enables the determination of theoretical performance and loss limits more accurately. We believe that this will aid in the design of high-performance PSCs.

2021 IEEE 16th Nanotechnology Materials and Devices Conference (NMDC)

Analysis of electrical and optical loss in perovskite solar cells using a semi-analytical model

This letter addresses an event-based state estimation for a linear discrete-time system with a remote estimator, when measurements are affected by multiplicative noise. An innovation-based scheduling scheme is used to communicate measurements from the sensor to the remote estimator. A maximum a posteriori estimator is employed to deal with multiplicative noise, enabling the recursive equations for the updated state and its covariance. The sensor to estimator communication rate is derived in terms of a predefined threshold that is used to trigger the sensor measurement. The results proposed are validated using a numerical example and Monte Carlo simulations. © 2017 IEEE.

IEEE Control Systems Letters

An Efficient Event-Based State Estimator for Linear Discrete-Time System with Multiplicative Measurement Noise

Electrochemical metallization-based two-dimension- al (2D) material memristors with vertical transport and small inter-electrode distances have been reported recently. Their device characteristics exhibit multiple conductance states with relatively low switching voltages, which make them well-suited for low power neuromorphic applications. Our work models the transport in these 2D material-based memristors, with a focus on explaining and capturing their current-voltage characteristics. The model also captures the dynamics of switching (with an emphasis on the estimation of switching energies and delays), and quantitatively captures the experimentally observed spike-time-dependent plasticity behaviour in these devices. The simulation results obtained using our model (and implemented in Verilog-A) have been validated with experimental data from multiple sources. Our work demonstrates the flexibility of including different transport mechanisms (such as, tunneling, space charge limited conduction) in a unified simulation framework. © 2002-2012 IEEE.

IEEE Transactions on Nanotechnology

Modeling of Electrochemical Metallization-Based Two-Dimensional Material Memristors for Neuromorphic Applications

A wideband angular stable linear-cross and linear-circular reflective type polarization converter has been illustrated in this work. The unitcell comprises a 45° rotated circular-arc based I-shaped resonator printed on top of a thin FR-4 grounded dielectric substrate. The proposed metasurface converts y/x- polarized incidence wave to its cross-polarization in three different frequency ranges: C, X, and Ku-bands. This design can also convert linearly polarized wave into circular polarization in C and Ku-bands along with linear-orthogonal conversion. The response is stable up to 45° (for linear-cross) and 30° (linear-circular) for both oblique incidences (TE and TM). The uniqueness of the design lies in dual-polarization conversion in the same bands and cell compactness with periodicity 0.1539 λL, and 0.0535 λL (λL refers to the longest free-space wavelength of the operational band). Authors strongly believe this design has the potential to be used in real-time application where the dual-polarization conversion (linear as well circular) has the primary need. © 2021 IEEE.

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

A Simple I-Shaped Wideband Linear-Linear and Linear-Circular Reflective Type Polarizer

This work presents a miniaturized angularly stable frequency selective surface (FSS) on a single layer substrate. Unit cell comprises of convoluted circular rings connected cross dipole and linear arrow headed dipole printed on both sides of the substrate. A closely spaced dual stop band resonances are obtained at 10 and 14.3 GHz with frequency ratio of 1.43. FSS shows a − 10 dB stopband bandwidth (BW) from 7.32 to 11.05 GHz (40.61%) and 12.68 to 15.97 GHz (22.97%) with >30 dB stop band rejection at center frequencies. FSS poses the features of stable performance under change in polarization and angularly stable response up to 60° incident angle. Later the proposed FSS is printed on grounded thick dielectric substrate and it shows broadband reflection type co to cross polarization conversion from 7.2 to 17.32 GHz (82.54%) with polarization conversion ratio >80% and oblique angle stability up to 35°. To the best of authors' knowledge, this is the first time in literature a single unit cell geometry with two different properties, spatial filtering on transmission and polarization conversion on reflection have been designed and analyzed in details. A finite array with size 25 × 25 of the proposed FSS is fabricated and the measured filter response shows a good agreement with simulated performance at normal and oblique incidences. The proposed FSS is used as a reflector of a dual band monopole antenna and the simulation results shows gain improvement of 5.51 and 3.8 dB at the two stopband frequencies. © 2021 Wiley Periodicals LLC.