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arXiv 2024年

作者： Liu, Yuanwei Ouyang, Chongjun Wang, Zhaolin Xu, Jiaqi Mu, Xidong Swindlehurst, A. Lee The Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong The School of Electrical and Electronic Engineering College of Engineering and Architecture University College Dublin DublinD04 V1W8 Ireland The School of Electronic Engineering and Computer Science Queen Mary University of London LondonE1 4NS United Kingdom The Department of Electrical Engineering and Computer Science University of California IrvineCA92697 United States Queen’s University Belfast BelfastBT3 9DT United Kingdom

Multiple-antenna technologies are evolving towards larger aperture sizes, extremely high frequencies, and innovative antenna types. This evolution is fostering the emergence of near-field communications (NFC) in future wireless systems. Considerable attention has been directed towards this cutting-edge technology due to its potential to enhance the capacity of wireless networks by introducing increased spatial degrees of freedom (DoFs) in the range domain. Within this context, a comprehensive review of the state of the art on NFC is presented, with a specific focus on its i) fundamental operating principles, ii) channel modeling, iii) performance analysis, iv) signal processing techniques, and v) integration with other emerging applications. Specifically, i) the basic principles of NFC are characterized from both physics and communications perspectives, unveiling its unique properties in contrast to far-field communications. ii) Building on these principles, deterministic and stochastic near-field channel models are explored for spatially-discrete (SPD) and continuous-aperture (CAP) arrays. iii) Based on these models, existing contributions to near-field performance analysis are reviewed in terms of DoFs/effective DoFs (EDoFs), the power scaling law, and transmission rate. iv) Existing signal processing techniques for NFC are systematically surveyed, which include channel estimation, beamforming design, and low-complexity beam training. v) Major issues and research opportunities in incorporating near-field models into other promising technologies are identified to advance NFC’s deployment in next-generation networks. Throughout this paper, promising directions are highlighted to inspire future research endeavors in the realm of NFC, underscoring its significance in the advancement of wireless communication technologies. © 2024, CC BY.

关键词： Near field communication

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Performance of Linear Receive Beamforming for Continuous Aperture Arrays (CAPAs)

arXiv

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arXiv 2024年

作者： Ouyang, Chongjun Wang, Zhaolin Zhang, Xingqi Liu, Yuanwei The School of Electrical and Electronic Engineering UCD College of Engineering and Architecture University College DublinD04 V1W8 Ireland The School of Electronic Engineering and Computer Science Queen Mary University of London LondonE1 4NS United Kingdom The Department of Electrical and Computer Engineering University of Alberta EdmontonABT6G 2R3 Canada The Department of Electrical and Electronic Engineering The University of Hong Kong Hong Kong

The performance of linear receive beamforming in continuous aperture array (CAPA)-based uplink communications is analyzed. Continuous linear beamforming techniques are proposed for CAPA receivers under the criteria of maximum-ratio combining (MRC), zero-forcing (ZF), and minimum mean-square error (MMSE). i) For MRC beamforming, a closed-form expression for the beamformer is derived to maximize per-user signal power, and the achieved uplink rate and mean-square error (MSE) in detecting received data symbols are analyzed. ii) For ZF beamforming, a closed-form beamformer is derived using channel correlation to eliminate interference, with a function space interpretation demonstrating its optimality in maximizing signal power while ensuring zero inter-user interference. iii) For MMSE beamforming, it is proven to be the optimal linear receive approach for CAPAs in terms of maximizing per-user rate and minimizing MSE. A closed-form expression for the MMSE beamformer is then derived, along with the achievable sum-rate and sum-MSE. The proposed linear beamforming techniques are then compared with those for conventional spatially discrete arrays (SPDAs). Analytical and numerical results indicate that: i) for both CAPAs and SPDAs, the considered linear beamformers can be represented as weighted sums of each user’s spatial response, with weights determined by channel correlation;ii) CAPAs achieve higher sum-rates and lower sum-MSEs than SPDAs under ZF and MMSE beamforming;and iii) SPDAs may outperform CAPAs with MRC beamforming in interference-dominated scenarios. Copyright © 2024, The Authors. All rights reserved.

关键词： Mean square error

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On regular simplex division in copositivity detection

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AIP Conference Proceedings 2019年第1期2070卷

作者： J. M. G. Salmerón L. G. Casado * E. M. T. Hendrix 1Department of Computer Science Universidad de Almería (ceiA3) Almería Spain 2Department of Computer Architecture Universidad de Málaga Málaga spain

Over the last decades checking copositivity of matrices by simplicial subdivision of the unit simplex has made a big progress. Recently it has been shown that surprisingly the use of regular simplicial subdivisions may have some advantage over traditional iterative bisection of simplices. In this contribution, we pose the question whether regular subdivisions may provide opportunities in copositivity testing.

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High photocurrent in gated graphene-silicon hybrid photodiodes

arXiv

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arXiv 2017年

作者： Riazimehr, Sarah Kataria, Satender Bornemann, Rainer Bolivar, Peter Haring Ruiz, Francisco Javier Garcia Engström, Olof Godoy, Andres Lemme, Max C. University of Siegen School of Science and Technology Department of Electrical Engineering and Computer Science Hölderlinstr. 3 Siegen57076 Germany Dpto. de Electrónica y Tecnología de Computadores Facultad de Ciencias Universidad de Granada Av. Fuentenueva S/N Granada18071 Spain RWTH Aachen University Faculty of Electrical Engineering and Information Technology Chair for Electronic Devices Otto-Blumenthal-Str. 25 Aachen52074 Germany

Graphene/silicon (G/Si) heterojunction based devices have been demonstrated as high responsivity photodetectors that are potentially compatible with semiconductor technology. Such G/Si Schottky junction diodes are typically in parallel with gated G/silicon dioxide (SiO2)/Si areas, where the graphene is contacted. Here, we utilize scanning photocurrent measurements to investigate the spatial distribution and explain the physical origin of photocurrent generation in these devices. We observe distinctly higher photocurrents underneath the isolating region of graphene on SiO2 adjacent to the Schottky junction of G/Si. A certain threshold voltage (VT) is required before this can be observed, and its origins are similar to that of the threshold voltage in metal oxide semiconductor field effect transistors. A physical model serves to explain the large photocurrents underneath SiO2 by the formation of an inversion layer in Si. Our findings contribute to a basic understanding of graphene / semiconductor hybrid devices which, in turn, can help in designing efficient optoelectronic devices and systems based on such 2D/3D heterojunctions. Copyright © 2017, The Authors. All rights reserved.

关键词： Schottky barrier diodes

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A Primer on Near-Field Communications for Next-Generation Multiple Access

arXiv

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arXiv 2024年

作者： Ouyang, Chongjun Wang, Zhaolin Chen, Yan Mu, Xidong Zhu, Peiying The School of Electrical and Electronic Engineering College of Engineering and Architecture University College DublinD04 V1W8 Ireland The School of Electronic Engineering and Computer Science Queen Mary University of London LondonE1 4NS United Kingdom The School of Electronic Engineering and Computer Science Queen Mary University of London LondonE1 4NS United Kingdom Queen’s University Belfast BelfastBT3 9DT United Kingdom The Wireless Technology Lab HUAWEI Technologies Canada Company Ltd. OttawaONK2K 3J1 Canada

Multiple-antenna technologies are advancing toward the development of extremely large aperture arrays and the utilization of extremely high frequencies, driving the progress of next-generation multiple access (NGMA). This evolution is accompanied by the emergence of near-field communications (NFC), characterized by spherical-wave propagation, which introduces additional range dimensions to the channel and enhances system throughput. In this context, a tutorial-based primer on NFC is presented, emphasizing its applications in multiuser communications and multiple access (MA). The following areas are investigated: i) the commonly used near-field channel models are reviewed along with their simplifications under various near-field conditions. ii) Building upon these models, the information-theoretic capacity limits of NFC-MA are analyzed, including the derivation of sum-rate capacity and capacity region, and their upper limits for both downlink and uplink scenarios. iii) A detailed investigation of near-field multiuser beamforming design is presented, offering low-complexity and effective NFC-MA design methodologies in both the spatial and wavenumber (angular) domains. Throughout these investigations, near-field MA is compared with its far-field counterpart to highlight its superiority and flexibility in terms of interference management, thereby laying the groundwork for achieving NGMA. Copyright © 2024, The Authors. All rights reserved.

关键词： Near field communication

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Energy Mapping of Existing Building Stock in Cambridge using Energy Performance Certificates and Thermal Infrared Imagery

arXiv

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arXiv 2024年

作者： He, Yinglong Pan, Jiayu Debnath, Ramit Bardhan, Ronita Cullen, Luke Jenkins, Marco Gomez Mackie, Erik Hawker, George Parry, Ian Institute of Astronomy University of Cambridge CambridgeCB3 0HA United Kingdom Department of Architecture University of Cambridge CambridgeCB2 1PX United Kingdom EPRG Cambridge Judge Business School University of Cambridge CambridgeCB2 1AG United Kingdom Cambridge Zero Department of Computer Science and Technology Department of Architecture CambridgeCB3 OFD United Kingdom Division of Humanities and Social Science California Institute of Technology Pasadena91125 United States School of Mechanical Engineering Sciences University of Surrey SurreyGU2 7XH United Kingdom

Energy performance certificate (EPC) and thermal infrared (TIR) images both play a key role in the energy performance mapping of the urban building stock. In this paper, we developed parametric building archetypes using an EPC database and conducted temperature clustering on TIR images acquired through drones and satellite datasets. We evaluated 1725 EPCs of existing building stock in Cambridge, UK to generate energy consumption profiles. Drone-based TIR images of individual buildings in two Cambridge University colleges were processed using a machine learning pipeline for thermal anomaly detection and investigated the influence of two specific factors that affect the reliability of TIR for energy management applications: ground sample distance (GSD) and angle of view (AOV). The EPC-level results suggest that the construction year of the buildings influences their energy consumption. For example, modern buildings were over 30% more energy-efficient than older ones. Parallelly, older buildings were found to show almost double the energy savings potential through retrofitting than newly constructed buildings. TIR imaging results showed that thermal anomalies can only be properly identified in images with a GSD of 1m/pixel or less. A GSD of 1-6m/pixel can detect hot areas of building surfaces. We found that a GSD > 6m/pixel cannot characterise individual buildings but does help identify urban heat island effects. Additional sensitivity analysis showed that building thermal anomaly detection is more sensitive to AOV than to GSD. Our study informs newer approaches to building energy diagnostics using thermography and supports decision-making for retrofitting at a large scale. Copyright © 2024, The Authors. All rights reserved.

关键词： Drones

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MTLSegFormer: Multi-task Learning with Transformers for Semantic Segmentation in Precision Agriculture

MTLSegFormer: Multi-task Learning with Transformers for Sema...

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2023 IEEE/CVF Conference on computer Vision and Pattern Recognition Workshops, CVPRW 2023

作者： Goncalves, Diogo Nunes Marcato, Jose Zamboni, Pedro Pistori, Hemerson Li, Jonathan Nogueira, Keiller Goncalves, Wesley Nunes Federal University of Mato Grosso Do Sul Faculty of Computer Science Av. Costa e Silva Campo Grande79070-900 MS Brazil Federal University of Mato Grosso Do Sul Faculty of Engineering Architecture and Urbanism and Geography Av. Costa e Silva Campo Grande79070-900 MS Brazil Dom Bosco Catholic University INOVISAO Avenida Tamandaré 6000 Campo Grande79117-900 MS Brazil University of Waterloo Department of Geography and Environmental Management WaterlooONN2L 3G1 Canada University of Stirling Scotland StirlingFK9 4LA United Kingdom

ISBN: (纸本)9798350302493

Multi-task learning has proven to be effective in improving the performance of correlated tasks. Most of the existing methods use a backbone to extract initial features with independent branches for each task, and the exchange of information between the branches usually occurs through the concatenation or sum of the feature maps of the branches. However, this type of information exchange does not directly consider the local characteristics of the image nor the level of importance or correlation between the tasks. In this paper, we propose a semantic segmentation method, MTLSegFormer, which combines multi-task learning and attention mechanisms. After the backbone feature extraction, two feature maps are learned for each task. The first map is proposed to learn features related to its task, while the second map is obtained by applying learned visual attention to locally re-weigh the feature maps of the other tasks. In this way, weights are assigned to local regions of the image of other tasks that have greater importance for the specific task. Finally, the two maps are combined and used to solve a task. We tested the performance in two challenging problems with correlated tasks and observed a significant improvement in accuracy, mainly in tasks with high dependence on the others. © 2023 IEEE.

关键词： Semantics

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High-precision fe-analysis for seismic collapse simulation of steel building frames

High-precision fe-analysis for seismic collapse simulation o...

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3rd International Conference on Computational Methods in Structural Dynamics and Earthquake Engineering, COMPDYN 2011

作者： Yamashita, T. Miyamura, T. Ohsaki, M. Kohiyama, M. Isobe, D. Onda, K. Hori, M. Zhang, J.Y. Akiba, H. Kajiwara, K. Hyogo Earthquake Eng. Research Center National Research Inst. for Earth Science and Disaster Prevention 1501-21 Nishikameya Mitsuda Shijimi Miki 673-0515 Japan Dept. of Computer Science College of Eng. Nihon University 1 Nakagawara Tokusada Tamura Koriyama 963-8642 Japan Dept. of Architecture Graduate School of Eng. Hiroshima University 1-4-1 Kagamiyama Higashi-Hiroshima 739-8527 Japan Dept. of System Design Eng. Keio University 3-14-1 Hiyoshi Kohoku Yokohama 223-8522 Japan Dept. of Engineering Mechanics and Energy University of Tsukuba 1-1-1 Tennodai Tsukuba 305-8573 Japan Allied Engineering Corporation Toyosu Front 9F 3-2-20 Toyosu Koto Tokyo 135-0061 Japan Earthquake Research Institute University of Tokyo 1-1-1 Yayoi Bunkyo Tokyo 113-0032 Japan Dept. of Architecture and Urban Design Ritsumeikan University 1-1-1 Noji-higashi Kusatsu 525-8577 Japan

The project of E-Simulator is under way at Hyogo Earthquake Engineering Research Center (E-Defense), which belongs to National Research Institute for Earth science and Disaster Prevention (NIED), Japan. E-Defense facilitates the world's largest shaking table. The E-Simulator uses the parallel EF-analysis software package called ADVENTURECluster (ADVC) as a platform, and we carried out elastoplastic seismic response analysis of high-rise building frame with over 70-million DOFs. In this study, we report the results of high-precision FE-analysis for simulation of dynamic collapse behavior of the 4-story steel building frame. The whole frame is discretized into hexahedral elements with linear interpolation functions. In order to improve the accuracy of collapse simulation, a new piecewise linear combined isotropic and kinematic hardening rule is implemented for steel material, and its parameters are identified from the uniaxial material test result. The stud bolts are precisely modeled using multipoint constraints and nonlinear springs. The wire-meshes in the concrete slab are modeled using hexahedral elements. The damping due to plastic energy dissipation of exterior walls is modeled by shear springs between the floors. The accuracy of the model is verified in comparison to the physical test of steel-concrete composite beam subjected to static deformation. It will be shown that elastoplastic dynamic responses of the 4-story frame can be estimated with good accuracy using a high-precision FE-analysis without resort to macro-models such as plastic hinge and composite beam effect.

关键词： Finite element method

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Hybrid Genetic Algorithms and Heuristics for Nonlinear Short-Term Hydropower Optimization: A Comparative Analysis

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Procedia computer science 2024年 246卷 282-291页

作者： M. Jafari Aminabadi S. Séguin I. Fofana Department of applied sciences Université du Québec à Chicoutimi Saguenay (Qc) Canada G7H 2B1 GERAD Montréal (Qc) Canada H3T 1J4 Department of computer science and mathematics Université du Québec à Chicoutimi Saguenay (Qc) Canada G7H 2B1 Canada Research Chair tier 1 in Aging of Oil-Filled Equipment on High Voltage Lines (ViAHT)

In this paper, a Mixed Integer Nonlinear Programming (MINLP) for the short-term hydropower optimization problem considering operational constraints such as demand and startup costs, is presented. Since solving the MINLP is complicated and, in many cases, impossible, three methods are proposed based on reducing the complexity, which is hybridized with the exact solver. Method A, a binary genetic algorithm; method B, an iterative heuristic method; and method C, using the iterative heuristic method in the genetic algorithm. Based on computational results in a case study, method B converges to a solution very quickly and with few iterations, whereas methods A and C perform more efficiently. A comparison between methods A and C indicates that method C not only reduces the computational burden for convergence but also yields better results. The proposed methods are evaluated by comparing them with optimal solutions. The results indicate that the proposed methods are highly effective in achieving favorable results.

关键词： Nonlinear Short-term Hydropower Optimization Mixed Integer Nonlinear Programming Genetic algorithm Heuristic algorithm Meta-heuristic algorithm

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Self-Awareness for Autonomous Systems

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PROCEEDINGS OF THE IEEE 2020年第7期108卷 971-975页

作者： Dutt, Nikil Regazzoni, Carlo S. Rinner, Bernhard Yao, Xin Nikil Dutt (Fellow IEEE) received the Ph.D. degree from the University of Illinois at Urbana–Champaign Champaign IL USA in 1989.""He is currently a Distinguished Professor of computer science (CS) cognitive sciences and electrical engineering and computer sciences (EECS) with the University of California at Irvine Irvine CA USA. He is a coauthor of seven books. His research interests include embedded systems electronic design automation (EDA) computer architecture distributed systems healthcare Internet of Things (IoT) and brain-inspired architectures and computing.""Dr. Dutt is a Fellow of ACM. He was a recipient of the IFIP Silver Core Award. He has received numerous best paper awards. He serves as the Steering Committee Chair of the IEEE/ACM Embedded Systems Week (ESWEEK). He is also on the steering organizing and program committees of several premier EDA and embedded system design conferences and workshops. He has served on the Editorial Boards for the IEEE Transactions on Very Large Scale Integration (VLSI) Systems and the ACM Transactions on Embedded Computing Systems and also previously served as the Editor-in-Chief (EiC) for the ACM Transactions on Design Automation of Electronic Systems. He served on the Advisory Boards of the IEEE Embedded Systems Letters the ACM Special Interest Group on Embedded Systems the ACM Special Interest Group on Design Automationt and the ACM Transactions on Embedded Computing Systems. Carlo S. Regazzoni (Senior Member IEEE) received the M.S. and Ph.D. degrees in electronic and telecommunications engineering from the University of Genoa Genoa Italy in 1987 and 1992 respectively.""He is currently a Full Professor of cognitive telecommunications systems with the Department of Electrical Electronics and Telecommunication Engineering and Naval Architecture (DITEN) University of Genoa and a Co-Ordinator of the Joint Doctorate on Interactive and Cognitive Environments (JDICE) international Ph.D. course started initially as EU Erasmus Mundus Project and

Autonomous systems are able to make decisions and potentially take actions without direct human intervention, which requires some knowledge about the system and its environment as well as goal-oriented reasoning. In computer systems, one can derive such behavior from the concept of a rational agent with autonomy (“control over its own actions”), reactivity (“react to events from the environment”), proactivity (“act on its own initiative”), and sociality (“interact with other agents”) as fundamental properties \n[1]\n. Autonomous systems will undoubtedly pervade into our everyday lives, and we will find them in a variety of domains and applications including robotics, transportation, health care, communications, and entertainment to name a few. \nThe articles in this month’s special issue cover concepts and fundamentals, architectures and techniques, and applications and case studies in the exciting area of self-awareness in autonomous systems.

关键词： Special issues and sections Autonomous systems Self-aware Robot sensing systems Computational modeling

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