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Rahul Mishra

Publications and source records attributed to Rahul Mishra.

53 records · Page 3Linked to original sources

Generating Fact Checking Summaries for Web Claims

We present SUMO, a neural attention-based approach that learns to establish the correctness of textual claims based on evidence in the form of text documents (e.g., news articles or Web documents). SUMO further generates an extractive summary by presenting a diversified set of sentences from the documents that explain its decision on the correctness of the textual claim. Prior approaches to address the problem of fact checking and evidence extraction have relied on simple concatenation of claim and document word embeddings as an input to claim driven attention weight computation. This is done so as to extract salient words and sentences from the documents that help establish the correctness of the claim. However, this design of claim-driven attention does not capture the contextual information in documents properly. We improve on the prior art by using improved claim and title guided hierarchical attention to model effective contextual cues. We show the efficacy of our approach on datasets concerning political, healthcare, and environmental issues.

cs.CL↗

MuSeM: Detecting Incongruent News Headlines using Mutual Attentive Semantic Matching

Measuring the congruence between two texts has several useful applications, such as detecting the prevalent deceptive and misleading news headlines on the web. Many works have proposed machine learning based solutions such as text similarity between the headline and body text to detect the incongruence. Text similarity based methods fail to perform well due to different inherent challenges such as relative length mismatch between the news headline and its body content and non-overlapping vocabulary. On the other hand, more recent works that use headline guided attention to learn a headline derived contextual representation of the news body also result in convoluting overall representation due to the news body's lengthiness. This paper proposes a method that uses inter-mutual attention-based semantic matching between the original and synthetically generated headlines, which utilizes the difference between all pairs of word embeddings of words involved. The paper also investigates two more variations of our method, which use concatenation and dot-products of word embeddings of the words of original and synthetic headlines. We observe that the proposed method outperforms prior arts significantly for two publicly available datasets.

cs.CL↗

A Survey on Deep Neural Network Compression: Challenges, Overview, and Solutions

Deep Neural Network (DNN) has gained unprecedented performance due to its automated feature extraction capability. This high order performance leads to significant incorporation of DNN models in different Internet of Things (IoT) applications in the past decade. However, the colossal requirement of computation, energy, and storage of DNN models make their deployment prohibitive on resource constraint IoT devices. Therefore, several compression techniques were proposed in recent years for reducing the storage and computation requirements of the DNN model. These techniques on DNN compression have utilized a different perspective for compressing DNN with minimal accuracy compromise. It encourages us to make a comprehensive overview of the DNN compression techniques. In this paper, we present a comprehensive review of existing literature on compressing DNN model that reduces both storage and computation requirements. We divide the existing approaches into five broad categories, i.e., network pruning, sparse representation, bits precision, knowledge distillation, and miscellaneous, based upon the mechanism incorporated for compressing the DNN model. The paper also discussed the challenges associated with each category of DNN compression techniques. Finally, we provide a quick summary of existing work under each category with the future direction in DNN compression.

cs.LG↗

Emerging spintronics phenomena and applications

Development of future sensor, memory, and computing nanodevices based on novel physical concepts is one of the significant research endeavors in solid-state research. The field of spintronics is one such promising area of nanoelectronics which utilizes both the charge and spin of an electron for device operations. The advantage offered by spin systems is in their non-volatility and low-power functionality. This paper reviews emerging spintronic phenomena and the research advancements in diverse spin based applications. Spin devices and systems for logic, memories, emerging computing schemes, flexible electronics and terahertz emitters are discussed in this report.

cond-mat.mtrl-sci↗

Analysis, Modeling, and Representation of COVID-19 Spread: A Case Study on India

Coronavirus outbreak is one of the most challenging pandemics for the entire human population of the planet Earth. Techniques such as the isolation of infected persons and maintaining social distancing are the only preventive measures against the epidemic COVID-19. The actual estimation of the number of infected persons with limited data is an indeterminate problem faced by data scientists. There are a large number of techniques in the existing literature, including reproduction number, the case fatality rate, etc., for predicting the duration of an epidemic and infectious population. This paper presents a case study of different techniques for analysing, modeling, and representation of data associated with an epidemic such as COVID-19. We further propose an algorithm for estimating infection transmission states in a particular area. This work also presents an algorithm for estimating end-time of an epidemic from Susceptible Infectious and Recovered model. Finally, this paper presents empirical and data analysis to study the impact of transmission probability, rate of contact, infectious, and susceptible on the epidemic spread.

cs.SI↗

Microscopic Origin of Spin-Orbit Torque in Ferromagnetic Heterostructures: A First Principles Approach

We present an {\it ab initio}-based theoretical framework which elucidates the origin of the spin-orbit torque (SOT) in Normal-Metal(NM)/Ferromagnet(FM) heterostructures. The SOT is decomposed into two contributions, namely, {\it spin-Hall} and the {\it spin-orbital} components. We find that {\it (i)} the Field-Like (FL) SOT is dominated by the spin-orbital component and {\it (ii)} both components contribute to the damping-like torque with comparable magnitude in the limit of thick Pt film. The contribution of the spin-orbital component to the DL-SOT is present only for NMs with strong SOC coupling strength. We demonstrate that the FL-SOT can be expressed in terms of the non-equilibrium spin-resolved orbital moment accumulation. The calculations reveal that the experimentally reported oxygen-induced sign-reversal of the FL-SOT in Pt/Co bilayers is due to the significant reduction of the majority-spin orbital moment accumulation on the interfacial NM atoms.

cond-mat.mes-hall↗

Long spin coherence length and bulk-like spin-orbit torque in ferrimagnetic multilayers

Ferromagnetic spintronics has been a main focus as it offers non-volatile memory and logic applications through current-induced spin-transfer torques. Enabling wider applications of such magnetic devices requires a lower switching current for a smaller cell while keeping the thermal stability of magnetic cells for non-volatility. As the cell size reduces, however, it becomes extremely difficult to meet this requirement with ferromagnets because spin-transfer torque for ferromagnets is a surface torque due to rapid spin dephasing, leading to the 1/ferromagnet-thickness dependence of the spin-torque efficiency. Requirement of a larger switching current for a thicker and thus more thermally stable ferromagnetic cell is the fundamental obstacle for high-density non-volatile applications with ferromagnets. Theories predicted that antiferromagnets have a long spin coherence length due to the staggered spin order on an atomic scale, thereby resolving the above fundamental limitation. Despite several spin-torque experiments on antiferromagnets and ferrimagnetic alloys, this prediction has remained unexplored. Here we report a long spin coherence length and associated bulk-like-torque characteristic in an antiferromagnetically coupled ferrimagnetic multilayer. We find that a transverse spin current can pass through > 10 nm-thick ferrimagnetic Co/Tb multilayers whereas it is entirely absorbed by 1 nm-thick ferromagnetic Co/Ni multilayer. We also find that the switching efficiency of Co/Tb multilayers partially reflects a bulk-like-torque characteristic as it increases with the ferrimagnet-thickness up to 8 nm and then decreases, in clear contrast to 1/thickness-dependence of Co/Ni multilayers. Our results on antiferromagnetically coupled systems will invigorate researches towards energy-efficient spintronic technologies.

cond-mat.mtrl-sci↗

Terahertz Emission from Compensated Magnetic Heterostructures

Terahertz emission spectroscopy (TES) has recently played an important role in unveiling the spin dynamics at a terahertz (THz) frequency range. So far, ferromagnetic (FM)/nonmagnetic (NM) heterostructures have been intensively studied as THz sources. Compensated magnets such as a ferrimagnet (FIM) and antiferromagnet (AFM) are other types of magnetic materials with interesting spin dynamics. In this work, we study TES from compensated magnetic heterostructures including CoGd FIM alloy or IrMn AFM layers. Systematic measurements on composition and temperature dependences of THz emission from CoGd/Pt bilayer structures are conducted. It is found that the emitted THz field is determined by the net spin polarization of the laser induced spin current rather than the net magnetization. The temperature robustness of the FIM based THz emitter is also demonstrated. On the other hand, an AFM plays a different role in THz emission. The IrMn/Pt bilayer shows negligible THz signals, whereas Co/IrMn induces sizable THz outputs, indicating that IrMn is not a good spin current generator, but a good detector. Our results not only suggest that a compensated magnet can be utilized for robust THz emission, but also provide a new approach to study the magnetization dynamics especially near the magnetization compensation point.

cond-mat.mes-hall↗

Oscillatory spin-orbit torque switching induced by field-like torques

Deterministic magnetization switching using spin-orbit torque (SOT) has recently emerged as an efficient means to electrically control the magnetic state of ultrathin magnets. The SOT switching still lacks in oscillatory switching characteristics over time, therefore, it is limited to bipolar operation where a change in polarity of the applied current or field is required for bistable switching. The coherent rotation based oscillatory switching schemes cannot be applied to SOT because the SOT switching occurs through expansion of magnetic domains. Here, we experimentally achieve oscillatory switching in incoherent SOT process by controlling domain wall dynamics. We find that a large field-like component can dynamically influence the domain wall chirality which determines the direction of SOT switching. Consequently, under nanosecond current pulses, the magnetization switches alternatively between the two stable states. By utilizing this oscillatory switching behavior we demonstrate a unipolar deterministic SOT switching scheme by controlling the current pulse duration.

cond-mat.mtrl-sci↗

Room temperature magnetization switching in topological insulator-ferromagnet heterostructures by spin-orbit torques

Topological insulators (TIs) with spin momentum locked topological surface states (TSS) are expected to exhibit a giant spin-orbit torque (SOT) in the TI/ferromagnet systems. To date, the TI SOT driven magnetization switching is solely reported in a Cr doped TI at 1.9 K. Here, we directly show giant SOT driven magnetization switching in a Bi2Se3/NiFe heterostructure at room temperature captured using a magneto-optic Kerr effect microscope. We identify a large charge to spin conversion efficiency of ~1-1.75 in the thin TI films, where the TSS is dominant. In addition, we find the current density required for the magnetization switching is extremely low, ~6x10^5 A cm-2, which is one to two orders of magnitude smaller than that with heavy metals. Our demonstration of room temperature magnetization switching of a conventional 3d ferromagnet using Bi2Se3 may lead to potential innovations in TI based spintronic applications.

cond-mat.mtrl-sci↗

Anomalous current-induced spin torques in ferrimagnets near compensation

While current-induced spin-orbit torques (SOTs) have been extensively studied in ferromagnets and antiferromagnets, ferrimagnets have been less studied. Here we report the presence of enhanced spin-orbit torques resulting from negative exchange interaction in ferrimagnets. The effective field and switching efficiency increase substantially as CoGd approaches its compensation point, giving rise to 9 times larger spin-orbit torques compared to that of non-compensated one. The macrospin modelling results also support efficient spin-orbit torques in a ferrimagnet. Our results suggest that ferrimagnets near compensation can be a new route for spin-orbit torque applications due to their high thermal stability and easy current-induced switching assisted by negative exchange interaction.

cond-mat.mtrl-sci↗

Incentive Schemes for Mobile Peer-to-Peer Systems and Free Riding Problem: A Survey

Mobile peer-to-peer networks are quite prevalent and popular now days due to advent of business scenarios where all the services are going mobile like whether it's to find good restaurants, healthy diet books making friends, job-hunting, real state info or cab-sharing etc. As the mobile users are increasing day by day, peer-to-peer networks getting bigger and complex. In contrast to client server system in peer-to-peer network resource sharing is done on the basis of mutual consent and agreed policies with no central authority and controlling entity. Incentive schemes for P2P networks are devised to encourage the participation and to adhere the policies agreed. P2P services based only on altruistic behaviour of users are facing serious challenges like Free riding or The tragedy of commons. Free riders are the users who consume the bandwidth of the system (perform downloading) but don't show altruistic behaviour (deny uploading) and act as a parasite for the P2P network. To counter the free riding issue many Incentive schemes are suggested by the researchers. In this paper we will survey the different incentive schemes, their architectures keeping eye on how they handle the challenges of modern P2P network.

cs.DC↗

Coherent Sub-Nanosecond Switching of Perpendicular Magnetization by the Field-like Spin-Orbit Torque without an External Magnetic Field

We theoretically study the influence of a predominant field-like spin-orbit torque on the magnetization switching of small devices with a uniform magnetization. We show that for a certain range of ratios (0.23-0.55) of the Slonczewski to the field-like torques, it is possible to deterministically switch the magnetization without requiring any external assist field. A precise control of the pulse length is not necessary, but the pulse edge sharpness is critical. The proposed switching scheme is numerically verified to be effective in devices by micromagnetic simulations. Switching without any external assist field is of great interest for the application of spin-orbit torques to magnetic memories.

cond-mat.mtrl-sci↗

Path Based Mapping Technique for Robots

The purpose of this paper is to explore a new way of autonomous mapping. Current systems using perception techniques like LAZER or SONAR use probabilistic methods and have a drawback of allowing considerable uncertainty in the mapping process. Our approach is to break down the environment, specifically indoor, into reachable areas and objects, separated by boundaries, and identifying their shape, to render various navigable paths around them. This is a novel method to do away with uncertainties, as far as possible, at the cost of temporal efficiency. Also this system demands only minimum and cheap hardware, as it relies on only Infra-Red sensors to do the job.

cs.RO↗

Personalized real time weather forecasting

Temperature forecasting and rain forecasting in today's environment is playing a major role in many fields like transportation, tour planning and agriculture. The purpose of this paper is to provide a real time forecasting to the user according to their current position and requirement. The simplest method of forecasting the weather, persistence, relies upon today's conditions to forecast the conditions tomorrow i.e. analyzing historical data for predicting future weather conditions. The weather data used for the DM research include daily temperature, daily pressure and monthly rainfall.

cs.OH↗

Non Equilibrium Green's Function Analysis of Double Gate SiGe and GaAs Tunnel FETs

In recent past extensive device simulation work has already been done on TFETs. Various ways have been suggested to model TFETs. In our paper we look at one such particular way to model these devices. The Non equilibrium green's formalism has proved effective in modeling nano scale devices. We model complete SiGe and GaAs tunnel FET for the first time using the NEGF formalism, also taking acoustic phonon scattering into account. We analyze them on the grounds of I-V curve, Ion-Ioff ration and subthreshold slope. The poisson equation and the equilibrium statistical mechanical equation has been solved by providing the potential profile.

cond-mat.mes-hall↗

Device Improvement and Circuit Performance Evaluation of complete SiGe Double Gate Tunnel FETs

In recent part extensive simulation work has already been done on TFETs. However this is limited to device performance analysis. Evaluation of circuit performance is a topic that is very little touched. This is due to the non availability of compact models of Tunnel FETs in the commercial simulator. In our paper for the first time we perform the circuit analysis of tunnel FETs (extended channel TFETs), we test them over basic digital circuit. We generate the TFET models by using the model editor in Orcad. Extensive circuit simulation is then performed by using these models in the Pspice circuit design. Performance of extended channel double gate TFET is evaluated on the grounds of power and delay in inverter, nand gate, nor gate and ring oscillator. Before that we perform device analysis of double gate extended channel TFETs, extended channel has been tried before on SOI TFETs we try it for the first time on double gate Si1-xGex TFETs. We even look at the effect of introducing Si layer. The performance of this device is compared for different Ge mole fraction and also with MOSFETs

cond-mat.mes-hall↗