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Real space characterization of nonlinear hall effect in confined directions

npj Computational Materials 2024年第1期10卷 2829-2835页

作者： Sheng Luo Chuang-Han Hsu Guoqing Chang Arun Bansil Hsin Lin Gengchiau Liang Department of Electrical and Computer Engineering National University of SingaporeSingapore 117576Singapore Institute of Physics Academia SinicaTaipei 11529Taipei Division of Physics and Applied Physics School of Physical and Mathematical SciencesNanyang Technological UniversitySingaporeSingapore Department of Physics Northeastern UniversityBostonMA 02115USA Industry Academia Innovation School National Yang-Ming Chiao Tung UniversityHsinchu City 300093Taipei

The nonlinear Hall effect(NLHE)is a phenomenon which could produce a transverse Hall voltage in a time-reversal-invariant ***,we report the real space characterizations of NLHE evaluated through quantum transport in TaIrTe4 nanoribbon without the explicit Berry curvature dipole(BCD)*** first characterize the NLHE in both transverse confined directions in global-level *** impact of quantum confinement in NLHE is evaluated by adjusting the width of ***,the probing area is trimmed to the atomic scale to evaluate the local texture,where we discover its patterns differ among the probed neighboring atomic *** analysis of charge distribution reveals the connections between NLHE’s local patterns and its non-centrosymmetric nature,rendering nearly an order of Hall voltage enhancement through probe *** work paves the way to expand the range of NLHE study and unveil its physics in more versatile material systems.

关键词： directions nonlinear confined

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Element-specific high-bandwidth ferromagnetic resonance spectroscopy with a coherent extreme-ultraviolet source

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Physical Review applied 2024年第6期21卷 064047-064047页

作者： Michael Tanksalvala Anthony Kos Jacob Wisser Scott Diddams Hans T. Nembach Justin M. Shaw Applied Physics Division Time & Frequency Division Electrical Computer & Energy Engineering Department of Physics Physical Measurement Laboratory

In this paper, we apply a tabletop, ultrafast, high-harmonic generation (HHG) source to measure the element-specific ferromagnetic resonance (FMR) in ultrathin magnetic alloys and multilayers on an opaque Si substrate. We demonstrate a continuous-wave bandwidth up to 62 GHz, with a promise to extend it to 100 GHz or higher. This laboratory-scale instrument detects the FMR using ultrafast, extreme-ultraviolet (EUV) light, with photon energies spanning the M-edges of the most relevant magnetic elements. A radiofrequency frequency comb generator is used to produce a microwave excitation that is intrinsically synchronized to the EUV pulses with a timing jitter of 1.1 ps or better. We apply this system to measure the dynamics in a multilayer system as well as Ni-Fe and Co-Fe alloys. Since this instrument operates in reflection mode, it is a milestone toward measuring and imaging the dynamics of the magnetic state and spin transport of active devices on arbitrary substrates on a tabletop. The higher bandwidth also enables measurements of materials with high magnetic anisotropy, as well as ferrimagnets, antiferromagnets, and short-wavelength (high-wavevector) spin waves in nanostructures or nanodevices. Furthermore, the coherence and short wavelength of the EUV will enable extending these studies using dynamic nanoscale lensless imaging techniques such as coherent diffractive imaging, ptychography, and holography.

关键词： High-order harmonic generation Magnetization dynamics Magneto-optical Kerr effect Ultrafast phenomena Ferromagnetic resonance Optical nanoscopy Spectroscopy X-ray techniques

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Effects of dynamical dielectric screening on the excitonic spectrum of monolayer semiconductors

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Physical Review B 2024年第12期110卷 125301页

作者： Dinh Van Tuan Hanan Dery Department of Electrical and Computer Engineering Department of Physics and Astronomy

We present a method to solve the dynamical Bethe-Salpeter equation numerically. The method allows one to investigate the effects of dynamical dielectric screening on the spectral position of excitons in transition-metal dichalcogenide monolayers. The dynamics accounts for the response of optical phonons in the materials below and on top of the monolayer to the electric field lines between the electron and hole of the exciton. The inclusion of this effect unravels the origin of a counterintuitive energy blueshift of the exciton resonance, observed recently in monolayer semiconductors that are supported on ionic crystals with large dielectric constants. A surprising result is that while energy renormalization of a free electron in the conduction band or a free hole in the valence band is controlled by the low-frequency dielectric constant, the band-gap energy introduces a phase between the photoexcited electron and hole, rendering contributions from the high-frequency dielectric constant also important when evaluating self-energies of the exciton components. As a result, band-gap renormalization of the exciton is not the sum of independent contributions from energy shifts of the conduction and valence bands. The theory correctly predicts the energy shifts of exciton resonances in various dielectric environments that embed two-dimensional semiconductors.

关键词： Bethe-Salpeter equation Excitons Permittivity 2-dimensional systems Transition metal dichalcogenides Green's function methods

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Network Embedding Methods: Study and Comparison

EEA - Electrotehnica, Electronica, Automatica

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EEA - Electrotehnica, Electronica, Automatica 2024年第4期72卷 72-78页

作者： Benbatata, Sabrina Saoud, Bilal LIMPAF laboratory Department of Computer Sciences University of Bouira Bouira10000 Algeria Electrical Engineering Department Sciences and Applied Sciences Faculty LISEA laboratory University of Bouira Bouira10000 Algeria

Graph is a powerful language that can model many systems in different fields such as information sciences, social sciences, Biology, mathematics, physics, etc. Graphs can capture very well the relationships between nodes and their structure. Representing data through graphs has some limitations and is challenging to use them like input in machine learning and deep learning models. This challenge can be overcome by using network embedding. Embedding represents a network into low-dimensional vector space. Several methods have been proposed to embed networks. Methods like DeepWalk, Node2Vec and GraphSAGE have gained traction. DeepWalk employs random walks to capture local neighborhood information, generating embeddings using skip-gram models. Node2Vec extends this by incorporating biased random walks, balancing exploration and exploitation of the network. GraphSAGE adopts a neighborhood aggregation strategy, aggregating features from a node's local graph structure through different convolutional layers. These methods facilitate downstream tasks like node classification, link prediction and clustering. Challenges include scalability to large networks, handling heterogeneous information and preserving structural characteristics. Recent advancements integrate techniques like attention mechanisms and reinforcement learning for improved embeddings. Network embedding methods continue to evolve, catering to diverse applications in social networks, biology and recommendation systems, offering insights into complex network structures. In this paper we provide networks embedding concepts and some methods. A comparison between embedding methods is presented. Embedding network methods on node classification tasks on different benchmark datasets have been conducted in order to evaluate them. Through rigorous evaluation, we assess their effectiveness in capturing latent features and improving classification accuracy across various domains. © Editura ELECTRA 2024. All rights reserved

关键词： Graph embeddings

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Quantitative phase imaging endoscopy with a metalens

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Light(Science & Applications) 2024年第12期13卷 3196-3209页

作者： Aamod Shanker Johannes E.Fröch Saswata Mukherjee Maksym Zhelyeznyakov Steven L.Brunton Eric J.Seibel Arka Majumdar Department of Electrical and Computer Engineering University of WashingtonSeattleWA 98195USA Center for Vision Science University of RochesterNew YorkNY 14623USA Department of Mechanical Engineering University of WashingtonSeattleWA 98105USA Department of Physics University of WashingtonSeattle 98195USA

Quantitative phase imaging(QPI)recovers the exact wavefront of light from intensity *** and optical density maps of translucent microscopic bodies can be extracted from these quantified phase *** demonstrate quantitative phase imaging at the tip of a coherent fiber bundle using chromatic aberrations inherent in a silicon nitride hyperboloid *** method leverages spectral multiplexing to recover phase from multiple defocus planes in a single capture using a color *** 0.5mm aperture metalens shows robust quantitative phase imaging capability with a 28°field of view and 0.2πphase resolution(~0.1λin air)for experiments with an endoscopic fiber *** the spectral functionality is encoded directly in the imaging lens,the metalens acts both as a focusing element and a spectral *** use of a simple computational backend will enable real-time *** limitations in the adoption of phase imaging methods for endoscopy such as multiple acquisition,interferometric alignment or mechanical scanning are completely mitigated in the reported metalens based QPI.

关键词： phase bundle exact

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Strong frequency correlation and anticorrelation between a Raman laser and its pump laser for positive and negative dispersions

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Physical Review A 2024年第6期109卷 063513-063513页

作者： Zifan Zhou Ruoxi Zhu Selim M. Shahriar Department of Electrical and Computer Engineering Department of Physics and Astronomy

We show that the frequency of a Raman laser is highly correlated or anticorrelated with the frequency of the Raman pump laser, depending on whether the dispersion experienced by the Raman laser is positive or negative. For a subluminal laser, corresponding to a positive dispersion with a group index that is much larger than unity, the shift in its frequency is approximately the same as that in the Raman pump laser. In contrast, for a superluminal laser, corresponding to a negative dispersion with a group index that is close to zero, its frequency shifts in the direction opposite to that of the Raman pump lasers and has an amplitude that is larger by a factor approximately equaling the inverse of the group index. These findings would play a critical role in determining the maximum achievable sensitivity of sensors employing such lasers, especially under conditions where the pump laser linewidth is broadened significantly beyond the Schawlow-Townes linewidth due to classical fluctuations.

关键词： Atom lasers Optics & lasers Stark effect

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A Single-Phase Reactive Power Compensator with Reduced-Size Film Capacitors and Active Power Decoupling Control 8

A Single-Phase Reactive Power Compensator with Reduced-Size ...

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8th IEEE Workshop on the Electronic Grid, eGRID 2023

作者： Serban, Ioan Musona, Ronald Transilvania University of Brasov Department of Electrical Engineering and Applied Physics Brasov Romania

ISBN: (纸本)9798350327007

Enhancing the reliability of power electronic systems poses a significant challenge, prompting intensive investigation into both control and hardware solutions. To address this, the paper proposes a single-phase reactive power compensator that integrates an H-bridge inverter with reduced-size film capacitors and an active power decoupling control. The proposed compensator offers a notable advantage by eliminating the necessity of electrolytic capacitors on the inverter DC-link, achieved through the adoption of a minimalist power decoupling solution. This technique relies exclusively on durable film-type capacitors of reduced size and requires no additional power semiconductors. The proposed system's performance was assessed through simulation results. © 2023 IEEE.

关键词： Electrolytic capacitors

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Study and Design of a Teaching electrical engineering System Based on Motion Sensors Using Arduino

Study and Design of a Teaching Electrical Engineering System...

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2023 International Conference on Electromechanical and Energy Systems, SIELMEN 2023

作者： Lelutiu, Laura-Mihaela Aciu, Lia Elena Transylvania University of Brasov Department of Electrical Engineering and Applied Physics Brasov Romania

ISBN: (纸本)9798350315240

The aim of the paper is a didactic one considering this work useful for the students of Transylvania University of Brasov-Faculty of electrical engineering and computer Sciences, the department of electrical engineering and applied physics, at the courses electrical Measurement and Data Acquisition. The disciplines are compulsory for our second-year students from the electrical engineering program from both, the Romanian and English language study programs of BA level. We start by covering a theoretical part including the principles of using measuring motion sensors, how they work and their role, as well as basic principles regarding the use of a servomotor and of the Arduino development board. After understanding the theory and practice of using the Arduino Board we present the actual experiment where 34 students were asked to answer a questionnaire highlighting how their learning and evaluation process was affected by the used method. The students were also asked to justify and explain their answers. We believe that by designing and implementing this method and application students will be able to put into practice the acquired theoretical knowledge, therefore the study could contribute to the improvement of the educational didactic process. © 2023 IEEE.

关键词： Students

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A Comparative Performance Analysis between the Buck and Boost Differential Single-Phase Inverters with Active Power Decoupling

A Comparative Performance Analysis between the Buck and Boos...

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2023 International Aegean Conference on electrical Machines and Power Electronics and 2023 International Conference on Optimization of electrical and Electronic Equipment, ACEMP-OPTIM 2023

作者： Musona, Ronald Serban, Ioan Transilvania University of Brasov Department of Electrical Engineering and Applied Physics Brasov Romania

ISBN: (纸本)9798350311495

Differential single-phase inverters offer the advantage of achieving active power decoupling without adding additional semiconductor devices. This paper presents a comparative performance analysis of two types of differential single-phase inverters with active power decoupling: a single stage differential boost topology and a two-stage differential buck topology. The targeted applications are small photovoltaic power plants, which typically require boosting the input voltage. The aim of this research is to evaluate the two topologies in terms of voltage and current stresses and losses, under various operating conditions, and taking as reference a conventional H-bridge inverter. The analysis includes the mathematical description of each topology, which is later used to implement the control and to establish the voltage and current limits. Between the two topologies, differential boost inverters can simultaneously achieve both DC input voltage boosting as well as generate output AC voltage waveforms using a single-stage topology. This offers the advantages of a low component count and high-power density. However, it experiences higher voltage and current stresses when compared to the differential buck inverter with an additional DC-DC input boost stage. These stresses ultimately impact efficiency, and as a result, the differential buck inverter exhibits a higher efficiency compared to the differential boost inverter. © 2023 IEEE.

关键词： Topology

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Enhancing biometric authentication security through the novel integration of graph theory encryption and chaotic logistic mapping

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Multimedia Tools and Applications 2025年第16期84卷 16909-16943页

作者： El-Shafai, Walid El-Mesady, A. Kamal, F.M. Security Engineering Lab Computer Science Department Prince Sultan University Riyadh11586 Saudi Arabia Department of Electronics and Electrical Communications Engineering Faculty of Electronic Engineering Menoufia University Menouf32952 Egypt Department of Physics and Engineering Mathematics Faculty of Electronic Engineering Menoufia University Menouf32952 Egypt Mathematics and Engineering Physics Department Faculty of Engineering Mansoura University PO 35516 Mansoura Egypt

The escalating reliance on biometric systems for identity verification underscores the imperative for robust data protection mechanisms. Biometric authentication, leveraging unique biological and behavioral characteristics, offers unparalleled precision in individual identification. However, the integrity and confidentiality of biometric data remain paramount concerns, given its susceptibility to compromise. This research delineates the development and implementation of an innovative framework for cancellable biometrics, focusing on facial and fingerprint recognition. This study introduces a novel cancellable biometrics framework that integrates graph theory encryption with three-dimensional chaotic logistic mapping. The methodology encompasses a multifaceted approach: initially employing graph theory for the secure and efficient encryption of biometric data, subsequently enhanced by the complexity and unpredictability of three-dimensional chaotic logistic mapping. This dual-layered strategy ensures the robustness of the encryption, thereby significantly elevating the security of biometric data against unauthorized access and potential compromise. Thus, the resulting cancellable biometrics, characterized by the ability to transform biometric data into an adjustable representation, addresses critical challenges in biometric security. It allows for the revocation and reissuance of biometric credentials, thereby safeguarding the original biometric characteristics of individuals. This feature not only enhances user privacy and data security but also introduces a dynamic aspect to biometric authentication, facilitating adaptability across diverse systems and applications. Preliminary evaluations of the proposed framework demonstrate a marked improvement in the security of face and fingerprint recognition systems. Through the application of graph theory encryption, coupled with three-dimensional chaotic logistic mapping, our framework mitigates the risks associated with t

关键词： Cryptography

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