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ON THE SUPERSINGULAR LOCUS OF SHIMURA VARIETIES FOR QUATERNIONIC UNITARY GROUPS

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arXiv 2023年

作者： Terakado, Yasuhiro Xue, Jiangwei Yu, Chia-Fu School of System Design and Technology Tokyo Denki University 5 Senju Asahi-cho Adachi-ku Tokyo120-8551 Japan Collaborative Innovation Center of Mathematics School of Mathematics and Statistics Wuhan University Luojiashan Hubei Wuhan430072 China Hubei Key Laboratory of Computational Science Wuhan University Hubei Wuhan430072 China Institute of Mathematics Academia Sinica Astronomy Mathematics Building No. 1 Sec. 4 Roosevelt Rd. Taipei106319 Taiwan

We study a Shimura variety attached to a unitary similitude group of a skew-Hermitian form over a totally indefinite quaternion algebra over a totally real number field. We give a necessary and sufficient condition for the existence of skew-Hermitian self-dual lattices. Under this condition we show that the superspecial locus in the fiber at p of the associated Shimura variety is non-empty. We also give an explicit formula for the number of irreducible components of the supersingular locus when p is odd and unramified in the quaternion algebra. Copyright © 2023, The Authors. All rights reserved.

关键词： Algebra

Tri-Polarized Holographic MIMO Surface in Near-Field: Channel Modeling and Precoding design

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arXiv 2022年

作者： Wei, Li Huang, Chongwen Alexandropoulos, George C. Yang, Zhaohui Yang, Jun Sha, Wei E.I. Zhang, Zhaoyang Debbah, Mérouane Yuen, Chau Pillar Singapore University of Technology and Design 487372 Singapore College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China International Joint Innovation Center Zhejiang University Haining314400 China Hangzhou310027 China The Department of Informatics and Telecommunications National and Kapodistrian University of Athens Panepistimiopolis Ilissia Athens15784 Greece The Technology Innovation Institute Abu Dhabi United Arab Emirates The State Key Laboratory of Mobile Network and Mobile Multimedia Technology Shenzhen518055 China Wireless Product R&D Institute ZTE Corporation Shenzhen518057 China The College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China The Technology Innovation Institute Masdar City Abu Dhabi9639 United Arab Emirates CentraleSupelec University Paris-Saclay Gif-sur-Yvette91192 France

This paper investigates the utilization of triple polarization (TP) for multi-user (MU) holographic multiple-input multi-output surface (HMIMOS) wireless communication systems, targeting at capacity boosting and diversity exploitation without enlarging the antenna array sizes. We specifically consider that both the transmitter and receiver are both equipped with an HMIMOS consisting of compact sub-wavelength TP patch antennas within near-field (NF) regime. To characterize TP MU-HMIMOS systems, a TP NF channel model is constructed using the dyadic Green’s function, whose characteristics are leveraged to design two precoding schemes for mitigating the cross-polarization and inter-user interference contributions. Specifically, a user-cluster-based precoding scheme assigns different users to one of three polarizations at the expense of system’s diversity, and a two-layer precoding scheme removes interference using Gaussian elimination method at high computational cost. The theoretical correlation analysis for HMIMOS in NF region is also investigated, revealing that both the spacing of transmit patch antennas and user distance impact transmit correlation factors. Our numerical results show that the users far from transmit HMIMOS experience higher correlation than those closer within NF regime, resulting in a lower channel capacity. Meanwhile, in terms of channel capacity, TP HMIMOS can almost achieve 1.25 times gain compared with dual-polarized HMIMOS, and 3 times compared with conventional HMIMOS. In addition, the proposed two-layer precoding scheme combined with two-layer power allocation realizes a higher spectral efficiency than other schemes without sacrificing diversity. Copyright © 2022, The Authors. All rights reserved.

关键词： Polarization

The Age of Generative AI and AI-Generated Everything

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arXiv 2023年

作者： Du, Hongyang Niyato, Dusit Kang, Jiawen Xiong, Zehui Zhang, Ping Cui, Shuguang Shen, Xuemin Mao, Shiwen Han, Zhu Jamalipour, Abbas Vincent Poor, H. Kim, Dong In School of Computer Science and Engineering Nanyang Technological University Singapore639798 Singapore School of Automation Guangdong University of Technology Key Laboratory of Intelligent Information Processing and System Integration of IoT Ministry of Education Guangzhou510006 China Guangdong-HongKong-Macao Joint Laboratory for Smart Discrete Manufacturing Guangzhou510006 China Pillar of Information Systems Technology and Design Singapore University of Technology and Design Singapore487372 Singapore State Key Laboratory of Networking and Switching Technology Beijing University of Posts and Telecommunications China Chinese University of Hong Kong Shenzhen China Department of Electrical and Computer Engineering University of Waterloo WaterlooONN2L 3G1 Canada Department of Electrical and Computer Engineering Auburn University AuburnAL36849-5201 United States Department of Electrical and Computer Engineering University of Houston HoustonTX77004 United States Department of Computer Science and Engineering Kyung Hee University Seoul446-701 Korea Republic of School of Electrical and Information Engineering University of Sydney SydneyNSW2006 Australia Department of Electrical and Computer Engineering Princeton University PrincetonNJ08544 United States Department of Electrical and Computer Engineering Sungkyunkwan University Suwon16419 Korea Republic of

Generative AI (GAI) has emerged as a significant advancement in artificial intelligence, renowned for its language and image generation capabilities. This paper presents "AIGenerated Everything" (AIGX), a concept that extends GAI beyond mere content creation to real-time adaptation and control across diverse technological domains. In networking, AIGX collaborates closely with physical, data link, network, and application layers to enhance real-time network management that responds to various system and service settings as well as application and user requirements. Networks, in return, serve as crucial components in further AIGX capability optimization through the AIGX lifecycle, i.e., data collection, distributed pre-training, and rapid decision-making, thereby establishing a mutually enhancing interplay. Moreover, we offer an in-depth case study focused on power allocation to illustrate the interdependence between AIGX and networking systems. Through this exploration, the article analyzes the significant role of GAI for networking, clarifies the ways networks augment AIGX functionalities, and underscores the virtuous interactive cycle they form. This article paves the way for subsequent future research aimed at fully unlocking the potential of GAI and networks. © 2023, CC BY.

关键词： Decision making

Comparison on Thermodynamic Performances between Basic and Regenerative Sub-Critical Organic Rankine Cycles Coupled with Low Grade Heat Source

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IOP Conference Series: Materials science and Engineering 2019年第1期473卷

作者： Pengfei Yuan Chao Zhang Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control 300384 Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin 300384 China

The coupling effects of low grade heat source on thermodynamic performances of both the basic and regenerative sub-critical Organic Rankine cycle (ORC) systems are investigated and compared. Turbine inlet pressure and turbine inlet temperature are treated as independent variables. The system exergy efficiency is selected as the thermodynamic performance criterion. The waste hot water with temperature range of 373.15K to 423.15K is selected as the low grade heat source. Optimization studies are carried out by using eight common organic working fluids to recover heat energy, and relevant operating conditions are obtained respectively. The results indicate that both hot fluid inlet temperature and the allowable minimum hot fluid outlet temperature influence the optimal working fluid, relevant turbine inlet condition and system exergy efficiency. Optimal system exergy efficiency increases monotonously with increasing of hot fluid temperature for both ORC systems above. In comparison to the basic cycle configuration, optimal system exergy efficiency for the regenerative system using the same working fluid is not changed if relevant turbine inlet vapor is saturated, but is significantly improved if relevant turbine inlet vapor is overheating. Besides, the optimal working fluid is dependent on the heat source temperature and specific cycle configuration.

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Flow Mechanism of Cooling Effectiveness Improvement for the Cylindrical Film Cooling Hole with Contoured Craters

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IOP Conference Series: Materials science and Engineering 2019年第1期473卷

作者： Linchao Bai Chao Zhang Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control 300384 Tianjin China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education (Tianjin University of Technology) Tianjin 300384 China

In this paper, a typical cylindrical hole with contoured craters is investigated in terms of the downstream flow field by numerical method at blowing ratios of 0.5, 1 and 1.5. The flow field and the cooling effectiveness are analyzed using three-dimensional Reynolds-averaged Navier-Stokes equations with the shear stress transport turbulence model. In comparison to the cylindrical hole, the cratered hole shows a wider coolant coverage in lateral direction and a lower penetration into the mainstream flow due to the larger hole exit area. Moreover, the interaction between the coolant and the curved protrusion induces a new anti-kidney-shaped vortex pair, which can obviously improve the cooling coverage and thus the cooling effectiveness. The area-averaged cooling effectiveness for the cratered hole is always higher than that for the cylindrical hole at all three blowing ratios.

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The Investigation of Removal and Mechanism by Different Permeable Paving systems on Runoff Pollutants

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SSRN

SSRN 2024年

作者： Zhang, Ziyang Yang, Ying Li, Zhifei Chen, Hongrui Zhang, Xiaoran Gong, Yongwei Tan, Chaohong Li, Haiyan Key Laboratory of Urban Stormwater System and Water Environment Ministry of Education Beijing University of Civil Engineering and Architecture Beijing102616 China Beijing Energy Conservation & Sustainable Urban and Rural Development Provincial Ministry Co-construction Collaboration Innovation Center Beijing100044 China Beijing General Municipal Engineering Design ＆ Research Institute Co. Ltd Beijing100082 China CRRC Environmental Science & Technology Cooperation Beijing100067 China Beijing Engineering Research Center of Sustainable Urban Sewage System Construction and Risk Control Beijing University of Civil Engineering and Architecture Beijing100044 China

In order to investigate the runoff pollutant control effects by different types of permeable paving systems (PPS), Porous asphalt (PA), Porous concrete (PC), Cement brick (CTB), Ceramic brick (CCB), Sand base brick (SBB) and Shale brick (SB) were selected. The removal effects and mechanisms of six PPS and individual filler layer on chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), nitrate nitrogen (NO3-N), total nitrogen (TN) and total phosphorus (TP)were investigated. Studies have shown that the removal of runoff pollutants varies widely among different PPS. PA had the best removal effect for nearly all runoff pollutants, which the maximum removal rate was 100% for both COD and NH4+-N. Permeable bricks could effectively control on NO3-N and TN pollutants, which the best removal efficiency were more than 94% for SB. Compared with other runoff pollutants, PC was more effective in removing TP with a removal rate of 95.8%. Furthermore, compared with surface material, base layer, subbase layer and soil layer were the most effective in controlling pollution in runoff, which the removal rate were more than 80%. Due to the deeper length, pollutants in runoff could contact with filler longer time and increased the removal efficiency. At the same time, graded gravel and medium sand have a stronger adsorption capacity for pollutants in runoff, resulting in a better purification. This study provides theoretical and practical significance not only for runoff pollution control, but also for the design and use of PPS in runoff. © 2024, The Authors. All rights reserved.

关键词： Fillers

Hard Carbon Aerogels: Superelastic Hard Carbon Nanofiber Aerogels (Adv. Mater. 23/2019)

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Advanced Materials 2019年第23期31卷

作者： Zhi‐Long Yu Bing Qin Zhi‐Yuan Ma Jin Huang Si‐Cheng Li Hao‐Yu Zhao Han Li Yin‐Bo Zhu Heng‐An Wu Shu‐Hong Yu Division of Nanomaterials & Chemistry Hefei National Laboratory for Physical Sciences at the Microscale CAS Center for Excellence in Nanoscience Hefei Science Center of CAS Department of Chemistry University of Science and Technology of China Hefei 230026 China CAS Key Laboratory of Mechanical Behavior and Design of Materials Department of Modern Mechanics CAS Center for Excellence in Complex System Mechanics University of Science and Technology of China Hefei 230027 China

Pervasive Machine Learning for Smart Radio Environments Enabled by Reconfigurable Intelligent Surfaces

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arXiv 2022年

作者： Alexandropoulos, George C. Stylianopoulos, Kyriakos Huang, Chongwen Yuen, Chau Bennis, Mehdi Debbah, Mérouane The Department of Informatics and Telecommunications National and Kapodistrian University of Athens Panepistimiopolis Ilissia Athens15784 Greece The Technology Innovation Institute 9639 Masdar City Abu Dhabi United Arab Emirates The College of Information Science and Electronic Engineering Zhejiang University Hangzhou310027 China The International Joint Innovation Center Zhejiang University Haining314400 China The Zhejiang Provincial Key Laboratory of IPCAN Hangzhou310027 China Pillar Singapore University of Technology and Design 487372 Singapore Centre for Wireless Communications University of Oulu Oulu90014 Finland The Technology Innovation Institute The Mohamed Bin Zayed University of Artificial Intelligence Masdar City Abu Dhabi9639 United Arab Emirates

The emerging technology of Reconfigurable Intelligent Surfaces (RISs) is provisioned as an enabler of smart wireless environments, offering a highly scalable, low-cost, hardware-efficient, and almost energy-neutral solution for dynamic control of the propagation of electromagnetic signals over the wireless medium, ultimately providing increased environmental intelligence for diverse operation objectives. One of the major challenges with the envisioned dense deployment of RISs in such reconfigurable radio environments is the efficient configuration of multiple metasurfaces with limited, or even the absence of, computing hardware. In this paper, we consider multi-user and multi-RIS-empowered wireless systems, and present a thorough survey of the online machine learning approaches for the orchestration of their various tunable components. Focusing on the sum-rate maximization as a representative design objective, we present a comprehensive problem formulation based on Deep Reinforcement Learning (DRL). We detail the correspondences among the parameters of the wireless system and the DRL terminology, and devise generic algorithmic steps for the artificial neural network training and deployment, while discussing their implementation details. Further practical considerations for multi-RIS-empowered wireless communications in the sixth Generation (6G) era are presented along with some key open research challenges. Differently from the DRL-based status quo, we leverage the independence between the configuration of the system design parameters and the future states of the wireless environment, and present efficient multi-armed bandits approaches, whose resulting sum-rate performances are numerically shown to outperform random configurations, while being sufficiently close to the conventional Deep Q-Network (DQN) algorithm, but with lower implementation complexity. © 2022, CC BY-NC-ND.

关键词： Backpropagation

A comprehensive comparison of micro heterojunction thermoelectric generators based on a carrier transport model

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International Journal of Heat and Mass Transfer 2023年 217卷

作者： Lin, Lin Jing, Zhen-Hua Zheng, Shao-Fei Chen, Wei-Hsin Lee, Duu-Jong Wang, Xiao-Dong School of Energy and Environmental Engineering University of Science and Technology Beijing Beijing100083 China State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Beijing102206 China Researcher Center of Engineering Thermophysics North China Electric Power University Beijing102202 China Department of Aeronautics and Astronautics National Cheng Kung University Tainan701 Taiwan Department of Mechanical Engineering City University of Hong Kong Kowloon Tong999077 Hong Kong Department of Chemical Engineering & Materials Science Yuan Ze University Chung-Li32003 Taiwan

To be a crucial aspect in the performance of thermoelectric generators, carrier transport in thermoelectric materials cannot be captured by existing multiphysics models. In this work, a carrier transport model for heterojunction thermoelectric generators (TEG) is developed with the drift-diffusion equation comprehensively considering the effect of carrier mobility on the current density. Subsequently, based on the concept of inverse- and homo-heterojunction, three micro TEG are designed considering Si and Si0.7Ge0.3 bases with the doped boron and arsenic and compared with the original design for revealing the effects of load resistance and temperature difference on the thermoelectric performance. It has been demonstrated that for homo-heterojunction, the thermoelectric power and conversion efficiency are significantly improved at hot temperatures from 600 to 1000 K, with a maximum improvement of 18.09% compared to the conventional TEG. For inverse-heterojunction, the optimal temperature of the thermoelectric performance is 1100–1300 K, and its efficiency is 23.50% higher than that of the conventional TEG. Both the doping impurity ionization and intrinsic carrier excitation contribute to a high density of majority carriers and are responsible for the better performance of homo-heterojunction at low working temperatures. For inverse-heterojunction, a high working temperature can significantly promote the excitation of minority carriers because of the built-in electric field and leads to better performance. Finally, we propose a novel heterojunction by combining both homo- and inverse-heterojunction which can improve thermoelectric efficiency by up to 27.72%. © 2023 Elsevier Ltd

关键词： Thermoelectric equipment