检索结果-内蒙古大学图书馆

Breakdown of the static dielectric screening approximation of Coulomb interactions in atomically thin semiconductors

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Mhenni, Amine Ben Van Tuan, Dinh Geilen, Leonard Petrić, Marko M. Erdi, Melike Watanabe, Kenji Taniguchi, Takashi Tongay, Sefaattin Müller, Kai Wilson, Nathan P. Finley, Jonathan J. Dery, Hanan Barbone, Matteo Walter Schottky Institute TUM School of Natural Sciences MCQST Technical University of Munich Munich Germany Department of Electrical and Computer Engineering University of Rochester RochesterNY United States Walter Schottky Institute TUM School of Computation Information and Technology MCQST Technical University of Munich Munich Germany School for Engineering of Matter Transport and Energy Arizona State University TempeAZ United States Research Center for Electronic and Optical Materials National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Research Center for Materials Nanoarchitectonics National Institute for Materials Science 1-1 Namiki Tsukuba305-0044 Japan Department of Physics and Astronomy University of Rochester RochesterNY United States

Coulomb interactions in atomically thin materials are uniquely sensitive to variations in the dielectric screening of the environment, which can be used to control exotic quantum many-body phases and engineer exciton potential landscapes. A static approximation of the dielectric response, where increased dielectric screening is predicted to cause an energy redshift of the exciton resonance, has been until now sufficient. Here, we use charge-tunable exciton resonances to study screening effects in transition metal dichalcogenide monolayers embedded in materials with dielectric constants ranging from 4 to more than 1000, a range two orders of magnitude larger than previous studies. In contrast to the redshift predicted by static models employed until now, we observe a blueshift of the exciton resonance exceeding 30 meV for larger dielectric constant environments. By introducing a dynamical screening model based on a new solution to the Bethe-Salpeter equation, we find that while the exciton binding energy remains mostly controlled by the static dielectric response, the exciton self-energy is dominated by the high-frequency one. Our results supplant the understanding of screening in layered materials and their heterostructures, introduce a knob to tune selected many-body effects, and open new routes to detect and control correlated quantum many-body states and to design optoelectronic and quantum devices. © 2024, CC BY-NC-ND.

关键词： Nanocrystals

Quantum nutcracker for near-room-temperature H_2 dissociation

学校读者我要写书评

暂无评论

Science Bulletin 2019年第1期64卷 4-7页

作者： Lei Tao Wei Guo Yu-Yang Zhang Yan-Fang Zhang Jiatao Sun Shixuan Du Sokrates T.Pantelides Institute of Physics & University of Chinese Academy of Sciences Chinese Academy of Sciences School of Physics Beijing Institute of Technology CAS Center for Excellence in Topological Quantum Computation Department of Physics and Astronomy and Department of Electrical Engineering and Computer Science Vanderbilt University

Solid surfaces are well known to mediate the dissociation of molecules via electronic interactions (heterogeneous catalysis).In particular,H2 dissociation on metal surfaces has been widely studied for several decades because it is an important step in hydrogenation *** efficiency of the process depends on both the electronic properties of the metal surface and the surface microstructures [1].Enhanced efficiency and reduced cost are usually achieved by using nanoparticles,which have increased the surface-to-volume ratio and low-coordination atoms [2].Another approach is to optimize the local electronic states of the metal surface by doping [3],alloying with other elements [4],or by taking advantage of strong interactions between metal nanoparticles and the supporting substrate [5].These methods often work together to tailor the adsorption properties on surfaces and show major efficiency enhancement.

关键词： Quantum nutcracker Electron interaction The electronic properties

A new approach for automatic segmentation and evaluation of pigmentation lesion by using Active Contour Model and Speeded Up Robust Features

学校读者我要写书评

暂无评论

arXiv 2021年

作者： Mardanisamani, Sara Karimi, Zahra Jamshidzadeh, Akram Yazdi, Mehran Farshad, Melika Farshad, Amirmehdi Department of Electrical Engineering Zarghan Branch Islamic Azad University Zarghan Iran Pharmaceutical Sciences Research Center Shiraz University of Medical Sciences Shiraz Iran Department of Dentistry Shiraz University of Medical Sciences Shiraz Iran Department of Pharmacology and Toxicology Faculty of Pharmacy Shiraz University of Medical Sciences Shiraz Iran Department of Communications and Electronics Faculty of Electrical and Computer Engineering Shiraz University Shiraz Iran Department of Power and Control Engineering School of Electrical and Computer Engineering Shiraz University Shiraz Iran

Digital image processing techniques have wide applications in different scientific fields including the medicine. By use of image processing algorithms, physicians have been more successful in diagnosis of different diseases and have achieved much better treatment results. In this paper, we propose an automatic method for segmenting the skin lesions and extracting features that are associated to them. At this aim, a combination of Speeded-Up Robust Features (SURF) and Active Contour Model (ACM), is used. In the suggested method, at first region of skin lesion is segmented from the whole skin image, and then some features like the mean, variance, RGB and HSV parameters are extracted from the segmented region. Comparing the segmentation results, by use of Otsu thresholding, our proposed method, shows the superiority of our procedure over the Otsu theresholding method. Segmentation of the skin lesion by the proposed method and Otsu thresholding compared the results with physician’s manual method. The proposed method for skin lesion segmentation, which is a combination of SURF and ACM, gives the best result. For empirical evaluation of our method, we have applied it on twenty different skin lesion images. Obtained results confirm the high performance, speed and accuracy of our method. © 2021, CC0.

关键词： Image segmentation

Parameter estimation and control of an unmanned aircraft-based transportation system for variable-mass payloads

学校读者我要写书评

暂无评论

Parameter estimation and control of an unmanned aircraft-bas...

作者： Alatorre, Armando Espinoza, Eduardo S. Sánchez, Bonifacio Ordaz, Patricio Muñoz, Filiberto García Carrillo, Luis Rodolfo French-Mexican Laboratory of Informatics and Automatics Center of Research and Advanced Studies of the National Polytechnic Institute México City Mexico Automatic Control Department Center of Research and Advanced Studies of the National Polytechnic Institute México City Mexico Research Center of Information Technologies and Systems Autonomous University of the State of Hidalgo Hidalgo Mexico Klipsch School of Electrical and Computer Engineering New Mexico State University Las CrucesNM United States

This paper deals with the development of an adaptive robust controller for an Unmanned Aircraft System with variable mass. The goal is to improve trajectory tracking and energy performance while the aircraft mass is gradually reducing due to payload release. To improve the trajectory tracking performance, we propose an algorithm that merges the concepts of least squares method and sliding mode observer for the estimation of the vehicle mass. The nonlinear observer estimates the linear velocities and accelerations, which are further used to obtain the vehicle mass. A robust adaptive pole placement controller based on the Attractive Ellipsoid Method uses this estimation to update the controllers gains due to the mass variation. To validate the effectiveness of the proposed algorithm for performing aerial transportation and deployment of payloads, we present a numerical example comparing the performance of the proposed method with respect to using Proportional Derivative controllers as well as Robust controllers. © 2021 Chinese Automatic control Society and John Wiley & Sons Australia, Ltd

关键词： controllers

Coverage Probability Analysis of RIS-Assisted High-Speed Train Communications

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Liu, Changzhu He, Ruisi Niu, Yong Ai, Bo Han, Zhu Ma, Zhangfeng Gao, Meilin Zhong, Zhangdui Wang, Ning State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing China Research Center of Networks and Communications Peng Cheng Laboratory Shenzhen China Department of Electrical and Computer Engineering University of Houston HoustonTX77004 United States Beijing National Research Center for Information Science and Technology Tsinghua University China School of Information Engineering Zhengzhou University Zhengzhou450001 China

Reconfigurable intelligent surface (RIS) has received increasing attention due to its capability of extending cell coverage by reflecting signals toward receivers. This paper considers a RIS-assisted high-speed train (HST) communication system to improve the coverage probability. We derive the closed-form expression of coverage probability. Moreover, we analyze impacts of some key system parameters, including transmission power, signal-to-noise ratio threshold, and horizontal distance between base station and RIS. Simulation results verify the efficiency of RIS-assisted HST communications in terms of coverage probability. Copyright © 2022, The Authors. All rights reserved.

关键词： Railroads

Energy Efficient Train-Ground mmWave Mobile Relay System for High Speed Railways

学校读者我要写书评

暂无评论

arXiv 2022年

作者： Wang, Lei Ai, Bo Niu, Yong Zhong, Zhangdui Mao, Shiwen Wang, Ning Han, Zhu The State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong University Beijing100044 China Beijing Engineering Research Center of High-speed Railway Broadband Mobile Communications Beijing Jiaotong University Beijing100044 China Peng Cheng Laboratory Henan Joint International Research Laboratory of Intelligent Networking and Data Analysis Zhengzhou University Zhengzhou450001 China The National Mobile Communications Research Laboratory Southeast University Nanjing211189 China The Department of Electrical and Computer Engineering Auburn University AuburnAL36949-5201 United States The School of Information Engineering Zhengzhou University Zhengzhou450001 China The Department of Electrical and Computer Engineering The University of Houston HoustonTX77004 United States The Department of Computer Science and Engineering Kyung Hee University Seoul446-701 Korea Republic of

The rapid development of high-speed railways (HSRs) puts forward high requirements on the corresponding communication system. Millimeter wave (mmWave) can be a promising solution due to its wide bandwidth, narrow beams, and rich spectrum resources. However, with the large number of antenna elements employed, energy-efficient solutions at mmWave frequencies are in great demand. Based on a mmWave HSR communication system with multiple mobile relays (MRs) on top of the train, a dynamic power-control scheme for train-ground communications is proposed. The scheme follows the regular movement characteristics of high-speed trains and considers three phases of train movement: the train enters the cell, all MRs are covered in the cell, and the train leaves the cell. The transmit power is further refined according to the number of MRs in the cell and the distance between the train and the remote radio head. By minimizing energy consumption under the constraints of the transmitted data and transmit power budget, the transmit power is allocated to multiple MRs through the multiplier punitive function-based algorithm. Comprehensive simulation results, where the velocity estimation error is taken into account, are provided to demonstrate the effectiveness of the proposed scheme over several baseline schemes. Copyright © 2022, The Authors. All rights reserved.

关键词： Energy efficiency

Probing rotational decoherence with a trapped-ion planar rotor

学校读者我要写书评

暂无评论

arXiv 2023年

作者： Glikin, Neil Stickler, Benjamin A. Tollefsen, Ryan Mouradian, Sara Yadav, Neha Urban, Erik Hornberger, Klaus Häffner, Hartmut Department of Physics University of California Berkeley BerkeleyCA94720 United States Challenge Institute for Quantum Computation University of California Berkeley BerkeleyCA94720 United States Institute for Complex Quantum Systems Center for Integrated Quantum Science and Technology Ulm University Albert-Einstein-Allee 11 Ulm89069 Germany Department of Electrical and Computer Engineering University of Washington SeattleWA98195 United States University of Duisburg-Essen Faculty of Physics Lotharstraße 1 Duisburg47057 Germany

The quantum rotor is one of the simplest model systems in quantum mechanics, but only in recent years has theoretical work revealed general fundamental scaling laws for its decoherence. For example, a superposition of orientations decoheres at a rate proportional to the sine squared of the angle between them. Here we observe scaling laws for rotational decoherence dynamics for the first time, using a 4 µm-diameter planar rotor composed of two Paul-trapped ions. We prepare the rotational motion of the ion crystal into superpositions of angular momentum with well-defined differences ranging from 1 − 3 ℏ, and measure the rate of decoherence. We also tune the system-environment interaction strength by introducing resonant electric field noise. The observed scaling relationships for decoherence are in excellent agreement with recent theoretical work, and are directly relevant to the growing development of rotor-based quantum applications. © 2023, CC BY.

关键词： Trapped ions

Variational approach to the dynamics of dissipative quantum impurity models

学校读者我要写书评

暂无评论

arXiv 2024年

作者： Qu, Yi-Fan Stefanini, Martino Shi, Tao Esslinger, Tilman Gopalakrishnan, Sarang Marino, Jamir Demler, Eugene Institute for Theoretical Physics ETH Zurich Zurich8093 Switzerland Institut für Physik Johannes Gutenberg-Universität Mainz MainzD-55099 Germany CAS Key Laboratory of Theoretical Physics Institute of Theoretical Physics Chinese Academy of Sciences Beijing100190 China CAS Center for Excellence in Topological Quantum Computation School of Physical Sciences University of Chinese Academy of Sciences Beijing100049 China Institute for Quantum Electronics & Quantum Center ETH Zurich Zurich8093 Switzerland Department of Electrical and Computer Engineering Princeton University PrincetonNJ08540 United States

Recent experiments with quantum simulators using ultracold atoms and superconducting qubits have demonstrated the potential of controlled dissipation as a versatile tool for realizing correlated many-body states. However, determining the dynamics of dissipative quantum many-body systems remains a significant analytical and numerical challenge. In this work, we focus on a dissipative impurity problem as a testbed for new methodological developments. We introduce an efficient non-perturbative framework that combines the superposition of Gaussian states (SGS) variational ansatz with the quantum trajectory approach to simulate open systems featuring a dissipative impurity. Applying this method to a spinful impurity subject to two-body losses and embedded in a bath of noninteracting fermions, we explore the full crossover from weak to strong dissipation regimes. The non-perturbative nature of the SGS ansatz allows us to thoroughly examine this crossover, providing comprehensive insights into the system’s behavior. In the strong dissipation regime, our approach reproduces the finding that localized two-body losses can induce the Kondo effect [arXiv:2406.03527], characterized by a slowdown of spin relaxation and an enhancement of charge conductance. Furthermore, we reveal an exotic "reverse conductance" phenomenon at zero potential bias – a counter-intuitive single-body effect resulting from intermediate dissipation and finite bandwidth. Finally, we investigate the formation of ferromagnetic domains and propose an extension to realize a higher-spin Kondo model using localized dissipation. Copyright © 2024, The Authors. All rights reserved.

关键词： Variational techniques

Surface Charging Phenomena on HVDC Spacers for Compressed SF_(6) Insulation and Charge Tailoring Strategies

学校读者我要写书评

暂无评论

CSEE Journal of Power and Energy Systems 2020年第1期6卷 83-99页

作者： Chuanyang Li Yuan Xu Chuanjie Lin Geng Chen Youping Tu Yao Zhou Zhipeng Lei Tao Han Simone Vincenzo Suraci Jian Wang Weidong Liu M.Tariq Nazir Shun He Andrea Cavallini Giovanni Mazzanti Davide Fabiani Jinliang He Electrical Insulation Research Center Institute of Materials ScienceElectrical and Computer EngineeringUniversity of ConnecticutStorrsCT 06269USA. China Electric Power Research Institute Beijing 100192China Department of Electrical Electronicand Information Engineering“Guglielmo Marconi”University of BolognaViale Risorgimento 2Bologna40136Italy State Key Laboratory of Power Systems Department of Electrical EngineeringTsinghua UniversityBeijing 100084China Beijing Area Major Laboratory of High Voltage and Electromagnetic Compatibility North China Electric Power UniversityBeijing 102206China Shanxi Key Laboratory of Mining Electrical Equipment and Intelligent Control National and Provincial Joint EngineeringTaiyuan University of TechnologyTaiyuan 030024China Key Laboratory of Smart Grid of Education Ministry School of Electrical and Information EngineeringTianjin UniversityTianjin 300072China School of Mechanical and Manufacturing Engineering University of New South Wales SydneyNSW 2052Australia Electric Power Research Institute Yunnan Electric Power Grid Co.ltd.KunmingYunnan 650217China

Surface flashover of spacers is a key factor limiting the application of HVDC GIS/GIL,while the charge accumula-tion on the surface of the spacer could have a potential adverse effect on the surface flashover *** paper discusses the laws regarding distribution patterns of surface charges and the related *** field-dependent property is discussed in detail to comprehensively illustrate the charge transport mecha-nism and explain the research differences regarding different surface charge patterns obtained by previous *** addition,the main surface charge control methods for epoxy resin are summarized and *** potential research directions of charge control methods and key points in manufacturing of spacers used in HVDC GIS/GIL are also explored.

关键词： GIL HVDC insulator SF6 surface charge accumulation surface flashover