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arXiv 2020年

作者： Zhang, Kangkang Wang, Cong Zhang, Minhao Bai, Zhanbin Xie, Fangfang Tan, Yuanzhi Guo, Yilv Hu, Kuo-Juei Cao, Lu Zhang, Shuai Tu, Xuecou Kang, Lin Chen, Jian Wu, Peiheng Wang, Xuefeng Wang, Jinlan Liu, Junming Wang, Baigeng Wang, Guanghou Xie, Suyuan Ji, Wei Shi, Su-Fei Reed, M.A. Song, Fengqi National Laboratory of Solid State Microstructures Collaborative Innovation Center of Advanced Microstructures School of Physics Nanjing University Nanjing210093 China Beijing Key Laboratory of Optoelectronic Functional Materials & Micro-Nano Devices Department of Physics Renmin University of China Beijing100872 China State Key Laboratory of Physical Chemistry of Solid Surfaces Department of Chemistry College of Chemistry and Chemical Engineering Xiamen University Xiamen361005 China School of Physics Southeast University Nanjing211189 China School of Electronic Science and Engineering and Collaborative Innovation Center of Advanced Microstructures Nanjing University Nanjing210023 China Department of Chemical and Biological Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Departments of Applied Physics and Electrical Engineering Yale University New HavenCT06520 United States Nanjing211805 China

Single molecular electrets exhibiting single‐molecule electric polarization switching have been long desired as a platform for extremely small non-volatile storage devices, although it is controversial because of the poor stability of single molecular electric dipoles. Here we study the single molecular device of Gd@C82, where the encapsulated Gd atom forms a charge center, and we have observed a gate-controlled switching behavior between two sets of single-electron-transport stability diagrams. The switching is operated in a hysteresis loop with a coercive gate field of around 0.5 V/nm. Theoretical calculations have assigned the two conductance diagrams to corresponding energy levels of two states that the Gd atom is trapped at two different sites of the C82 cage, which possess two different permanent electrical dipole orientations. The two dipole states are stabilized by the anisotropic energy and separated by a transition energy barrier of 70 meV. Such switching is then accessed to the electric field driven reorientation of individual dipole while overcoming the barriers by the coercive gate field, and demonstrates the creation of a single molecular electret. Copyright © 2020, The Authors. All rights reserved.

关键词： Switching

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Exploration of Additive Manufacturing for HTS Cable Components for Electric Aircrafts

Exploration of Additive Manufacturing for HTS Cable Componen...

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2018 AIAA/IEEE Electric Aircraft Technologies Symposium, EATS 2018

作者： Cheetham, Peter Nowell, Robert Al-Taie, Aws McAulev, James Han Kim, Chul Graber, Lukas Pamidi, Sastry Center for Advanced Power Systems Florida State University TallahasseeFL32310 United States Innovation Hub Florida State University TallahasseeFL32304 United States FAMU-FSU College of Engineering Department of Electrical and Computer Engineering TallahasseeFL32310 United States Georgia Institute of Technology College of Engineering Department of Electrical and Computer Engineering AtlantaGA30332 United States

ISBN: (数字)9781624105722

ISBN: (纸本)9781624105722

High temperature Superconducting (HTS) technology has the potential to deliver the required power densities necessary for electric aircrafts. A promising HTS cable design for electric aircraft applications that we have been investigating is the Superconducting Gas-Insulated Transmission Line (S-GIL). The S-GIL requires insulator spacers that are compatible with cryogenic temperatures as well as the high electrical and mechanical stresses. One of the major mechanical stresses currently limiting the design options is the compatibility of insulation materials and designs for cryogenic temperatures and associated thermal shocks. This paper discusses the investigation of using various 3D printed materials to fabricate prototype insulator spacer designs for the S-GIL and evaluate their compatibility with the required cryogenic operating conditions. The studies demonstrated that several materials and designs selected show suitability to operate at cryogenic temperature and we plan to proceed with further mechanical and electrical characterization of the 3D printed components. © 2018 AIAA.

关键词： Electric lines

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Approximate dynamic programming with probabilistic temporal logic constraints

arXiv

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arXiv 2018年

作者： Li, Lening Fu, Jie Robotics Engineering Program Department of Electrical and Computer Engineering Worcester Polytechnic Institute WorcesterMA01609 United States

In this paper, we develop approximate dynamic programming methods for stochastic systems modeled as Markov Decision Processes, given both soft performance criteria and hard constraints in a class of probabilistic temporal logic called Probabilistic Computation Tree Logic (PCTL). Our approach consists of two steps: First, we show how to transform a class of PCTL formulas into chance constraints that can be enforced during planning in stochastic systems. Second, by integrating randomized optimization and entropy-regulated dynamic programming, we devise a novel trajectory sampling-based approximate value iteration method to iteratively solve for an upper bound on the value function while ensuring the constraints that PCTL specifications are satisfied. Particularly, we show that by the on-policy sampling of the trajectories, a tight bound can be achieved between the upper bound given by the approximation and the true value function. The correctness and efficiency of the method are demonstrated using robotic motion planning examples. Copyright © 2018, The Authors. All rights reserved.

关键词： Stochastic systems

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Fast online reinforcement learning control using state-space dimensionality reduction

arXiv

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arXiv 2019年

作者： Sadamoto, Tomonori Chakrabortty, Aranya Imura, Jun-Ichi Department of Mechanical and Intelligent Systems Engineering Graduate School of Informatics and Engineering University of Electro Communications 1-5-1 Chofugaoka Chofu Tokyo182-8585 Japan Electrical and Computer Engineering North Carolina State University RaleighNC27695 United States Department of Systems and Control Engineering Graduate School of Engineering Tokyo Institute of Technology Oh-Okayama Meguro Tokyo2-12-1 Japan

Reinforcement Learning (RL) is an effective way of designing model-free linear quadratic regulator (LQR) controller for linear time-invariant (LTI) networks with unknown state-space models. However, when the network size is large, conventional RL can result in unacceptably long learning time. In this paper we resolve this problem by developing an alternative approach for RL-based LQR that combines dimensionality reduction with RL theory. The approach is to construct a compressed state vector by projecting the measured state through a projective matrix. This matrix is constructed from the state measurements, and can be viewed as an empirical controllability gramian that captures the level of redundancy in the controllability of the open-loop network model. Next, a RL-controller is learned using the reduced-dimensional state instead of the original state such that the resultant cost is close to the optimal LQR cost. Numerical benefits as well as the cyber-physical implementation benefits of the proposed approach are verified using illustrative examples including an example of wide-area control of the IEEE benchmark power system. Copyright © 2019, The Authors. All rights reserved.

关键词： Controllers

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THz near-field imaging of extreme subwavelength metal structures

arXiv

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arXiv 2021年

作者： Chen, Xinzhong Liu, Xiao Guo, Xiangdong Chen, Shu Hu, Hai Nikulina, Elizaveta Yao, Ziheng Betchel, Hans Martin, Michael C. Carr, G. Lawrence Dai, Qing Zhuang, Songlin Hu, Qing Zhu, Yiming Hillenbrand, Rainer Liu, Mengkun You, Guanjun Department of Physics and Astronomy Stony Brook University Stony BrookNY11794 United States Shanghai Key Lab of Modern Optical Systems Terahertz Technology Innovation Research Institute Engineering Research Center of Optical Instrument and System Ministry of Education University of Shanghai for Science and Technology Shanghai200093 China Division of Nanophotonics CAS Center for Excellence in Nanoscience National Center for Nanoscience and Technology Beijing100190 China CIC nanoGUNE Donostia-San Sebastián20018 Spain CIC nanoGUNE UPV/EHU Donostia-San Sebastián20018 Spain IKERBARSQUE Basque Foundation of Science Bilbao48013 Spain Advanced Light Source Division Lawrence Berkeley National Laboratory BerkeleyCA94720 United States National Synchrotron Light Source II Brookhaven National Laboratory UptonNY11973 United States Department of Electrical Engineering and Computer Science Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA02139 United States

Modern scattering-type scanning near-field optical microscopy (s-SNOM) has become an indispensable tool in material research. However, as the s-SNOM technique marches into the far-infrared (IR) and terahertz (THz) regimes, emerging experiments sometimes produce puzzling results. For example, "anomalies" in the near-field optical contrast have been widely reported. In this letter, we systematically investigate a series of extreme subwavelength metallic nanostructures via s-SNOM near-field imaging in the GHz to THz frequency range. We find that the near-field material contrast is greatly impacted by the lateral size of the nanostructure, while the spatial resolution is practically independent of it. The contrast is also strongly affected by the connectivity of the metallic structures to a larger metallic "ground plane". The observed effect can be largely explained by a quasi-electrostatic analysis. We also compare the THz s-SNOM results to those of the mid-IR regime, where the size-dependence becomes significant only for smaller structures. Our results reveal that the quantitative analysis of the near-field optical material contrasts in the long-wavelength regime requires a careful assessment of the size and configuration of metallic (optically conductive) structures. Copyright © 2021, The Authors. All rights reserved.

关键词： Metals

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Radiality constraints for resilient reconfiguration of distribution systems: Formulation and application to microgrid formation

arXiv

引用

arXiv 2019年

作者： Lei, Shunbo Chen, Chen Song, Yue Hou, Yunhe Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109 United States Energy Systems Division Argonne National Laboratory ArgonneIL60439 United States Department of Electrical and Electronic Engineering University of Hong Kong Hong Kong University of Hong Kong Shenzhen Institute of Research and Innovation Shenzhen518027 China

Network reconfiguration is an effective strategy for different purposes of distribution systems (DSs), e.g., resilience enhancement. In particular, DS automation, distributed generation integration and microgrid (MG) technology development, etc., are empowering much more flexible reconfiguration and operation of the system, e.g., DSs or MGs with flexible boundaries. However, the formulation of DS reconfiguration-related optimization problems to include those new flexibilities is non-trivial, especially for the issue of topology, which has to be radial. That is, the existing methods of formulating the radiality constraints can cause under-utilization of DS flexibilities. Thus, in this work, we propose a new method for radiality constraints formulation that fully enables the topological and some other related flexibilities of DSs, so that the reconfiguration-related optimization problems can have extended feasibility and enhanced optimality. Graph-theoretic supports are provided to certify its theoretical validity. As integer variables are involved, we also analyze the issues of tightness and compactness. The proposed radiality constraints are specifically applied to post-disaster MG formation, which is involved in many DS resilience-oriented service restoration and/or infrastructure recovery problems. The resulting new MG formation model, which allows more flexible merge and/or separation of the sub-grids, etc., establishes superiority over the models in the literature. Demonstrative case studies are conducted on two test systems. Copyright © 2019, The Authors. All rights reserved.

关键词： Optimization

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Robust lane marking detection algorithm using drivable area segmentation and extended SLT

arXiv

引用

arXiv 2019年

作者： Ozgunalp, Umar Fan, Rui Cheng, Shanshan Sun, Yuxiang Zuo, Weixun Zhu, Yilong Xue, Bohuan Zheng, Linwei Liang, Qing Liu, Ming Electrical and Electronics Engineering Cyprus International University North Cyprus Turkey Department of Electronic and Computer Engineering Hong Kong University of Science and Technology Hong Kong Hong Kong Hangzhou ATG Intelligent Technology Co. Ltd. Hangzhou China Guolu Gaoke Engineering Technology Institute Co. Ltd. Beijing China Robotics and Multiperception Laboratory Robotics Institute Hong Kong University of Science and Technology Hong Kong Hong Kong

In this paper, a robust lane detection algorithm is proposed, where the vertical road profile of the road is estimated using dynamic programming from the v-disparity map and, based on the estimated profile, the road area is segmented. Since the lane markings are on the road area and any feature point above the ground will be a noise source for the lane detection, a mask is created for the road area to remove some of the noise for lane detection. The estimated mask is multiplied by the lane feature map in a bird's eye view (BEV). The lane feature points are extracted by using an extended version of symmetrical local threshold (SLT), which not only considers dark light dark transition (DLD) of the lane markings, like (SLT), but also considers parallelism on the lane marking borders. The segmentation then uses only the feature points that are on the road area. A maximum of two linear lane markings are detected using an efficient 1D Hough transform. Then, the detected linear lane markings are used to create a region of interest (ROI) for parabolic lane detection. Finally, based on the estimated region of interest, parabolic lane models are fitted using robust fitting. Due to the robust lane feature extraction and road area segmentation, the proposed algorithm robustly detects lane markings and achieves lane marking detection with an accuracy of 91% when tested on a sequence from the KITTI dataset. Copyright © 2019, The Authors. All rights reserved.

关键词： Dynamic programming

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Leveraging large-deviation statistics to decipher the stochastic properties of measured trajectories

arXiv

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arXiv 2020年

作者： Thapa, Samudrajit Wylomańska, Agnieszka Sikora, Grzegorz Wagner, Caroline E. Krapf, Diego Kantz, Holger Chechkin, Aleksei V. Metzler, Ralf Institute for Physics & Astronomy University of Potsdam Potsdam-Golm14476 Germany Faculty of Pure and Applied Mathematics Hugo Steinhaus Center Wroclaw University of Science and Technology Wroclaw Poland Princeton Environmental Institute Princeton University PrincetonNJ08544 United States Department of Ecology and Evolutionary Biology Princeton University PrincetonNJ08544 United States Department of Electrical and Computer Engineering Colorado State University Fort CollinsCO80523 United States School of Biomedical Engineering Colorado State University Fort CollinsCO80523 United States Max Planck Institute for the Physics of Complex Systems Dresden Germany Akhiezer Institute for Theoretical Physics National Science Center "Kharkov Institute of Physics and Technology" Akademicheskaya st.1 Kharkov61108 Ukraine

Extensive time-series encoding the position of particles such as viruses, vesicles, or individual proteins are routinely garnered in single-particle tracking experiments or supercomputing studies. They contain vital clues on how viruses spread or drugs may be delivered in biological cells. Similar time-series are being recorded of stock values in financial markets and of climate data. Such time-series are most typically evaluated in terms of time-average mean-squared displacements, which remain random variables for finite measurement times. Their statistical properties are different for different physical stochastic processes, thus allowing us to extract valuable information on the stochastic process itself. To exploit the full potential of the statistical information encoded in measured time-series we here propose an easy-to-implement and computationally inexpensive new methodology, based on deviations of the time-averaged mean-squared displacement from its ensemble average counterpart. Specifically, we use the upper bound of these deviations for Brownian motion to check the applicability of this approach to simulated and real data sets. By comparing the probability of deviations for different data sets, we demonstrate how the theoretical bound for Brownian motion reveals additional information about observed stochastic processes. We apply the large-deviation method to data sets of tracer beads tracked in aqueous solution, tracer beads measured in mucin hydrogels, and of geographic surface temperature anomalies. Our analysis shows how the large-deviation properties can be efficiently used as a simple yet effective routine test to reject the Brownian motion hypothesis and unveil crucial information on statistical properties such as ergodicity breaking and short-time correlations. Copyright © 2020, The Authors. All rights reserved.

关键词： Time series

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Impact of cell geometry on zero-energy turn-off of SiC power MOSFETs

Impact of cell geometry on zero-energy turn-off of SiC power...

引用

International Conference on Silicon Carbide and Related Materials, ICSCRM 2017

作者： Liu, X.Q. Chowdhury, S. Hitchcock, C.W. Chow, T.P. Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute TroyNY12180 United States Monolith Semiconductor Inc 408 Fannin Avenue Round RockTX78664 United States

ISBN: (纸本)9783035711455

1200V SiC power MOSFETs of various cell geometries are modeled in Synopsis Inc. Sentaurus TCAD. The impact of cell geometry on switching loss is studied by comparing the turnon and turn-off losses using refined calculation methods. Under optimum circuit conditions, two different novel unit cell designs each achieve lower switching losses than conventional designs. For all the designs, lossless turn-on is impossible but lossless turn-off is achievable under circuit and biasing conditions that produce sufficiently rapid gate slew. © 2018 Trans Tech Publications, Switzerland.

关键词： Silicon carbide

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The science case and challenges of space-borne sub-millimeter interferometry

arXiv

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arXiv 2022年

作者： Gurvits, Leonid I. Paragi, Zsolt Amils, Ricardo I. van Bemmel, Ilse Boven, Paul Casasola, Viviana Conway, John Davelaar, Jordy Carmen Díez-González, M. Falcke, Heino Fender, Rob Frey, Sándor Fromm, Christian M. Gallego-Puyol, Juan D. García-Miró, Cristina Garrett, Michael A. Giroletti, Marcello Goddi, Ciriaco Gómez, José L. van der Gucht, Jeffrey Guirado, José Carlos Haiman, Zoltán Helmich, Frank Hudson, Ben Humphreys, Elizabeth Impellizzeri, Violette Janssen, Michael Johnson, Michael D. Kovalev, Yuri Y. Kramer, Michael Lindqvist, Michael Linz, Hendrik Liuzzo, Elisabetta Lobanov, Andrei P. López-Fernández, Isaac Malo-Gómez, Inmaculada Masania, Kunal Mizuno, Yosuke Plavin, Alexander V. Rajan, Raj T. Rezzolla, Luciano Roelofs, Freek Ros, Eduardo Rygl, Kazi L.J. Savolainen, Tuomas Schuster, Karl Venturi, Tiziana Verkouter, Marjolein de Vicente, Pablo Visser, Pieter N.A.M. Wiedner, Martina C. Wielgus, Maciek Wiik, Kaj Anton Zensus, J. Joint Institute for VLBI ERIC Dwingeloo Netherlands Faculty of Aerospace Engineering Delft University of Technology Delft Netherlands Yebes Observatory IGN Spain INAF Institute of Radio Astronomy Bologna Italy Department of Space Earth and Environment Chalmers University of Technology Onsala Space Observatory Onsala 439 92 Sweden Department of Astronomy Columbia University New YorkNY10027 United States Center for Computational Astrophysics Flatiron Institute 162 Fifth Avenue New YorkNY10010 United States Radboud University P.O. Box 9010 Nijmegen 6500 GL Netherlands Oxford University United Kingdom Konkoly Observatory Res. Centre for Astronomy and Earth Sciences Budapest Hungary Institute of Physics ELTE Eötvös Loránd University Budapest Hungary Goethe-Universität Frankfurt Germany Jodrell Bank Centre for Astrophysics The University of Manchester United Kingdom Leiden Observatory Leiden University Netherlands Dipartimento di Fisica Università degli Studi di Cagliari Monserrato Italy INAF - Osservatorio Astronomico di Cagliari Selargius Italy Instituto de Astrofísica de Andalucía CSIC Granada Spain Observatorio Astronómico University of Valencia Spain Kapteyn Institute University of Groningen Netherlands KISPE Space Systems Limited United Kingdom ESO Garching Germany Max-Planck-Institut für Radioastronomie Auf dem Hügel 69 BonnD-53121 Germany Center for Astrophysics Harvard & Smithsonian CambridgeMA02138 United States Black Hole Initiative at Harvard University 20 Garden Street CambridgeMA02138 United States Astro Space Center Lebedev Physical Institute Moscow Russia Moscow Institute of Physics and Technology Dolgoprudnyi Russia Max Planck Institute for Astronomy Heidelberg Germany Shaping Matter Lab Faculty of Aerospace Engineering Delft University of Technology Netherlands Faculty of Electrical Engineering Mathematics and Computer Science Delft University of Technology Delft Netherlands Aalto University Department of Electroni

Ultra-high angular resolution in astronomy has always been an important vehicle for making fundamental discoveries. Recent results in direct imaging of the vicinity of the supermassive black hole in the nucleus of the radio galaxy M87 by the millimeter VLBI system Event Horizon Telescope and various pioneering results of the Space VLBI mission RadioAstron provided new momentum in high angular resolution astrophysics. In both mentioned cases, the angular resolution reached the values of about 10−20 microrcseconds (0.05−0.1 nanoradian). Further developments toward at least an order of magnitude "sharper" values, at the level of 1 microarcsecond are dictated by the needs of advanced astrophysical studies. The paper emphasis that these higher values can only be achieved by placing millimeter and submillimeter wavelength interferometric systems in space. A concept of such the system, called Terahertz Exploration and Zooming-in for Astrophysics, has been proposed in the framework of the ESA Call for White Papers for the Voayage 2050 long term plan in 2019. In the current paper we present new science objectives for such the concept based on recent results in studies of active galactic nuclei and supermassive black holes. We also discuss several approaches for addressing technological challenges of creating a millimeter/sub-millimeter wavelength interferometric system in space. In particular, we consider a novel configuration of a space-borne millimeter/sub-millimeter antenna which might resolve several bottlenecks in creating large precise mechanical structures. The paper also presents an overview of prospective space-qualified technologies of low-noise analogue front-end instrumentation for millimeter/sub-millimeter telescopes. Data handling and processing instrumentation is another key technological component of a sub-millimeter Space VLBI system. Requirements and possible implementation options for this instrumentation are described as an extrapolation of the current st

关键词： Data handling

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