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arXiv 2023年

作者： Du, Zhen Liu, Fan Xiong, Yifeng Han, Tony Xiao Eldar, Yonina C. Jin, Shi The School of Electronic and Information Engineering Nanjing University of Information Science and Technology Nanjing China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen China The School of Information and Electronic Engineering Beijing University of Posts and Telecommunications Beijing China Huawei Technologies Co. Ltd Shenzhen China The Faculty of Mathematics and Computer Science Weizmann Institute of Science Rehovot Israel National Mobile Communications Research Laboratory Southeast University Nanjing210096 China

Integrated sensing and communications is regarded as a key enabling technology in the sixth generation networks, where a unified waveform, such as orthogonal frequency division multiplexing (OFDM) signal, is adopted to facilitate both sensing and communications (S&C). However, the random communication data embedded in the OFDM signal results in severe variability in the sidelobes of its ambiguity function (AF), which leads to missed detection of weak targets and false detection of ghost targets, thereby impairing the sensing performance. Therefore, balancing between preserving communication capability (i.e., the randomness) while improving sensing performance remains a challenging task. To cope with this issue, we characterize the random AF of OFDM communication signals, and demonstrate that the AF variance is determined by the fourth-moment of the constellation amplitudes. Subsequently, we propose an optimal probabilistic constellation shaping (PCS) approach by maximizing the achievable information rate (AIR) under the fourth-moment, power and probability constraints, where the optimal input distribution may be numerically specified through a modified Blahut-Arimoto algorithm. To reduce the computational overheads, we further propose a heuristic PCS approach by actively controlling the value of the fourth-moment, without involving the communication metric in the optimization model, despite that the AIR is passively scaled with the variation of the input distribution. Numerical results show that both approaches strike a scalable performance tradeoff between S&C, where the superiority of the PCS-enabled constellations over conventional uniform constellations is also verified. Notably, the heuristic approach achieves very close performance to the optimal counterpart, at a much lower computational complexity. Copyright © 2023, The Authors. All rights reserved.

关键词： Orthogonal frequency division multiplexing

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Emergent grain boundary phases in stressed polycrystalline thin films

arXiv

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arXiv 2022年

作者： Wang, Mengyuan Yan, Ruilin Han, Xiao Wang, Hailong Upmanyu, Moneesh 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 Anhui Hefei230027 China Department of Mechanical and Industrial Engineering Northeastern University BostonMA02115 United States

The grain boundary (GB) microstructure influences and is influenced by the development of residual stresses during synthesis of polycrystalline thin films. Recent studies have shown that the frustration between the preferred growth direction and rotations of abutting crystals to local cusps in GB energies leads to internal stresses localized within nanoscopic surface layers around the valleys and ridges that form at emergent boundaries (eGBs). Using a combination of continuum frameworks, numerical analyses and all-atom simulations of bicrystal h111i copper films, we show that eGBs tune their surface morphology and rotation extent in response to external strains. Compression favors rotation to and growth of low energy GB phases (complexions) at eGB valleys while tension favors the transitions at eGB ridges, a reflection of the stress-induced mass efflux/influx that changes the energetic balance between interfacial and deformation energies. Molecular dynamics simulations of strained and growing bicrystal films reveal that the eGB phase transition is coupled to island formation at the surface triple junctions, providing a direct link between eGB phases and surface step flow. The interplay between eGB structure, morphology and mechanics emerges as a crucial ingredient for predictive understanding of stress and morphological evolution during film growth, with broad implications for multifunctional response of polycrystalline surfaces in a diverse range of surface phenomena such as surface mediated deformation, interfacial embrittlement, thermal grooving, stress corrosion, surface catalysis and topological conduction. © 2022, CC BY.

关键词： Residual stresses

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CAD and Robotics in Architecture and Construction 1

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1000年

作者： A. Bijl R. Krishnamurti O. Akin C.-C. Chen B. Dave S. Pithavadian G. Schmitt J.-C. Robert J. Weeks U. Flemming R. Coyne T. Glavin Y. E. Kalay A. C. Harfmann L. M. Swerdloff M. Rychener L. Koskela R. Hynynen M. Kallavuo K. Kahkönen J. Salokivi A. H. Bridges A. Polistina W. L. Whittaker E. Bandari B. Motazed Y. Hasegawa C. Abel A. H. Slocum R. Kangari M.-C. Wanner M. Skibniewski P. Derrington C. Hendrickson R. F. Woodbury W. T. Keirouz I. J. Oppenheim D. R. Rehak C. F. Earl N. Kano J. L. Crowley P. J. Drazan H.-R. Oeser N. Tanaka M. Saito K. Arai K. Banno T. Ochi S. Kikuchi T. Ueno J. Maeda T. Yoshida S. Suzuki

ISBN: (数字)9781468474046

ISBN: (纸本)9781850912538

After two decades, data processing has finally, and probably forever, found its niche among civil engineering and construction (CEC) professionnals, through word processors, digitizing tables, management software, and increasingly via drawing software and computer-aided design (CAD), recently, robots have even started invading work sites. What are the main trends of CAD and robotics in the field of architecture and civil enginee ring? What type of R&D effort do university and industrial laboratories undertake to devise the professional software that will be on the market in the next three to five years? These are the issues which will be addressed during this symposium. To this effect, we have planned concurrently an equipment and software show, as well as a twofold conference. Robotic is just starting in the field of civil engineering and construction. A pioneer, the Civil Engineering Departement of Carnegie-Mellon University, in the United States, organized the first two international symposia, in 1984 and 1985 in Pittsburgh. This is the third meeting on the subject (this year, however, we have also included CAD). It constitutes the first large international symposium where CAD experts, specialists in architecture and CEC robotics will meet. From this standpoint, it should be an ideal forum for exchanging views and expe riences on a wide range of topics, and we hope it will give rise to novel applications and new syntheses. This symposium is intented for scientists, teachers, students and also for manufacturers and all CEC professionals.

关键词： Robotics and Automation science, Humanities and Social sciences, multidisciplinary

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On Corrosion of Zirconium Alloy in Dissolved Oxygen Water：The Role of Cu Addition

SSRN

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SSRN 2023年

作者： Huang, Zongwen Liu, Qingdong Zheng, Fengxin Peng, Jianchao Yu, Yixiao Zeng, Qifeng Li, Qiang Zhao, Yi Institute of Materials Shanghai University Shanghai200072 China School of Material Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Laboratory for Microstructures Shanghai University Shanghai200444 China Shanghai Nuclear Engineering Research & Design Institute Co. Ltd Shanghai200233 China Science and Technology on Reactor Fuel and Materials Laboratory Nuclear Power Institute of China Sichuan Chengdu610213 China

It is of significantly important to improve the corrosion resistance of Zr-Sn-Nb alloys in dissolved oxygen (DO) high temperature water by compositional modification. Here, the effect of Cu addition on the corrosion behaviors of Zr-0.5Sn-0.2Nb-0.4Fe-0.2Cr alloy was studied by using an autoclave circulating water loop at 360℃/20MPa up to 250 days. The oxide microstructures were characterized by a combination of SEM, TEM, STEM-EELS and PED. The results showed that compared with 0Cu alloy and 0.07Cu alloy, 0.13Cu alloy shows better corrosion resistance and its final weight gain after 250 days exposure is even lower than that of commercial Zr-4 alloy. The oxides for 0.07Cu and 0.13Cu alloys are more orderly arranged and thinner with less lateral cracks, and the columnar grains show a stronger {10-3} texture, than the Cu-free counterpart. The t-Zr2Cu SPPs have oxidized in the oxygen-rich layer below the O/M interface. The Cu ions tend to diffuse towards the grain boundary of dense columnar grains and maybe strengthen the grain boundaries, avoiding the defect generation under intrinsic stress in the oxide. © 2023, The Authors. All rights reserved.

关键词： Copper corrosion

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A Reduced-order Extrapolation Model Based on Proper Orthogonal Decomposition Technique for Rayleigh-Bénard convection

引用

Journal of Physics: Conference Series 2019年第2期1176卷

作者： Jinghua Yang Dengfeng Lu Zhiguang Deng Xiang Guan Qing Shi Sichuan Electric Power Design & Consulting Co. Ltd Chengdu Sichuan 610041 China National Key Labortory of Science and Technology on Reactor System Design Technology Sichuan 610213 China

In order to quickly calculate the flow characteristics in the simulated two-dimensional Rayleigh-Bénard convection model, a reduced-order extrapolation difference model for solving two-dimensional Rayleigh-Bénard is established based on the Proper Orthogonal Decomposition (POD) method. Firstly, the classical difference format is used to calculate the flow field on the initial time span, the sample data is to construct the POD basis, and the truncation error generated in the process of constructing the POD base is analysed. Then, the two-dimensional reduced-order extrapolation Rayleigh-Bénard model is constructed by combining the SVD and POD methods. By numerical examples, the classical difference model and the reduced-order extrapolation model are numerically simulated under the given initial boundary value. The reliability and effective of the reduced-order method are verified by comparing the flow field temperature cloud maps in the two calculation stages.

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Load-bearing behaviors of sandwich plates with non-uniformly distributed grid cores: Dynamic impact and blast

Research Square

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Research Square 2024年

作者： Wang, Youlong Yang, Haixia Chen, Jie Ma, Quanjin Song, Yiheng Key Laboratory of Concrete and Prestressed Concrete Structures Ministry of Education School of Civil Engineering Southeast University Nanjing211189 China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen518055 China School of Engineering The University of Tokyo Tokyo113-8656 Japan

Sandwich plates with grid-core structures possess extensive applications, and non-uniform grid plates (NUGPs) show enhanced potential under varied loading modes. The current study embarks on an investigation into NUGPs by adjusting the dimensions of transverse and longitudinal grid walls. This comprehensive analysis explores the dynamic responses of these plates when subjected to impact and blast loads, focusing on deformation patterns, damage, and the underlying processes. The findings are illustrated as follows. 1) NUGPs, specifically those with an optimized configuration of grid walls termed the d2 structure, display improved resistance to blast and impact loads compared to their uniformly distributed grid plate counterparts. Notably, designs featuring a less dense grid in the central area yield a more evenly distributed damage pattern under impact loads and a lesser severity of damage from blast loads. 2) The study also reveals that under impact loads, the sandwich structure showcases distinct behaviors through three stages evident in the load-displacement curves: initial localized indentation, followed by overall deformation, and ending with deformation recovery. 3) Moreover, when facing blast loads, the initial response involves rapid plastic deformation of the upper skin, succeeded by compression and buckling of the core. This sequence effectively dissipates energy, acting as a protective shield for the lower skin. 4) The optimized NUGPs design achieves a perfect balance between stiffness and ductility, reducing displacement through adequate stiffness while ensuring the effective absorption of dynamic forces through significant ductility, thus preventing catastrophic failure. This research significantly advances topology optimization for sandwich plates, providing essential insights for designing lightweight structures resilient under various modes. © 2024, CC BY.

关键词： Stiffness

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Study on Processing Process of SiC Single Crystal Cut with Wire Saw Excited by Ultrasonic

Study on Processing Process of SiC Single Crystal Cut with W...

引用

International Conference on Mechanical, Control and Computer Engineering (ICMCCE)

作者： Lun Li Shaodong Yang Bofeng Du Shiyu Xu Jishun Li Henan Key Laboratory for Machinery Design and Transmission System Henan University of Science and Technology Luoyang China Zhongqi Changxing (Luoyang) Mechanical and Electrical Equipment Engineering Co. Ltd. Luoyang China Shenzhen Zhaowei Machinery & Electronics Co. Ltd. Shenzhen China

ISBN: (数字)9781728146898

ISBN: (纸本)9781728146904

Owing to high hardness and brittleness, SiC single crystal is the typical difficult-to-machine material. The SiC single crystal workpiece was cut by wire saw excited by transverse ultrasonic, and the cutting process was analyzed in current research. The kinematics equation of ultrasonic excitation wire saw and ordinary wire saw were established, and two different kinematics characteristics were analyzed respectively. The trajectory of abrasive particles in two cutting mode changed fundamentally. The finite element simulation model of single diamond abrasive cutting SiC single crystal was established. The influence of processing parameters on sawing force, surface morphology of SiC single crystal cut with abrasive excited by ultrasonic and ordinary diamond abrasive cutting was analyzed. The results show that sawing force of diamond abrasive excited by ultrasonic is much less than that of ordinary diamond abrasive cutting and the surface morphology is fairly flat. The cutting depth of abrasive has a significant influence on the sawing force and wafer surface.

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Boosting weather forecast via generative superensemble

arXiv

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arXiv 2024年

作者： Nai, Congyi Chen, Xi Yang, Shangshang Liang, Yuan Xiao, Ziniu Pan, Baoxiang Key Laboratory of Earth System Numerical Modeling and Application Institute of Atmospheric Physics Chinese Academy of Science Beijing China Institute of Atmospheric Physics Chinese Academy of Science Beijing China School of Engineering and Design Technical University of Munich Munich Germany Potsdam Institute for Climate Impact Research Potsdam Germany TianJi Weather Science and Technology Company Beijing China

Accurate weather forecasting is essential for socioeconomic activities. While data-driven forecasting demonstrates superior predictive capabilities over traditional Numerical Weather Prediction (NWP) with reduced computational demands, its deterministic nature and limited advantages over physics-based ensemble predictions restrict operational applications. We introduce the generative ensemble prediction system (GenEPS) framework to address these limitations by randomizing and mitigating both random errors and systematic biases. GenEPS provides a plug-and-play ensemble forecasting capability for deterministic models to eliminate random errors, while incorporating cross-model integration for cross-model ensembles to address systematic biases. The framework culminates in a superensemble approach utilizing all available data-driven models to further minimize systematic biases. GenEPS achieves an Anomaly Correlation Coefficient (ACC) of 0.679 for 500hPa geopotential (Z500), exceeding the ECMWF Ensemble Prediction system’s (ENS) ACC of 0.646. Integration of the ECMWF ensemble mean further improves the ACC to 0.683. The framework also enhances extreme event representation and produces energy spectra more consistent with ERA5 reanalysis. GenEPS establishes a new paradigm in ensemble forecasting by enabling the integration of multiple data-driven models into a high-performing super-ensemble system. © 2024, CC BY-NC-SA.

关键词： Prediction models

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Information Freshness in A Dual Monitoring system

Information Freshness in A Dual Monitoring System

引用

GLOBECOM 2022 - 2022 IEEE Global Communications Conference

作者： Dapeng Deng Zhengchuan Chen Howard H. Yang Nikolaos Pappas Limei Hu Min Wang Yunjian Jia Tony Q.S. Quek School of Microelectronics and Communication Engineering Chongqing University Chongqing China National Mobile Communications Research Laboratory Southeast University Nanjing China Zhejiang University/University of Illinois at Urbana-Champaign Institute Zhejiang University Haining China Department of Computer and Information Science Linkoping University Linkoping Sweden School of Optoelectronics Engineering Chongqing University of Posts and Telecommunications Chongqing China Information System Technology and Design Pillar Singapore University of Technology and Design Singapore

ISBN: (纸本)9781665435413

We study the average age of information (AoI) and peak AoI (PAoI) of a dual-queue status update system that monitors a common stochastic process. We capture the state transition characteristics of the considered system by establishing a Markov chain. Using the state flow graph analysis method, we derive closed-form expressions of the average peak age of information (PAoI) and the average age of information (AoI) for the dual-queue update system. The numerical results show that compared with the single-queue update system, the average PAoI of the dual-queue update system is reduced by 33.5% and the average AoI dropped by 37.5%.

关键词： Closed-form solutions Markov processes Reliability theory Information age Sensor systems Real-time systems Sensors

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Investigation of Heat Transfer and Flow Boiling Characteristics of a New Symmetric Cosine Mini-Channel Heat Exchanger with High Heat Flow Density

SSRN

引用

SSRN 2023年

作者： Xu, Zhanying Liu, Huan-Ling Xie, Gongnan Shaanxi Key Laboratory of Space Solar Power Station System School of Electromechanical Engineering Xidian University Xi’an710071 China Key Laboratory of Electronic Equipment Structure Design Ministry of Education School of Electromechanical Engineering Xidian University Xi’an710071 China School of Marine Science and Technology Northwestern Polytechnical University Xi’an710072 China

A novel symmetric cosωx mini-channel heat exchanger (SCMC) with a combined bionic leaf vein diverter with ethanol as coolant is designed to meet the heat dissipation requirements for high heat flux chips. The mini-channel is firstly passed through a bionic leaf vein diverter to ensure the uniformity of the liquid distribution in the different mini-channels. Firstly, the homogeneity of the liquid distribution in different mini-channels is ensured by a bionic leaf vein divertor. Then, in order to obtain the flow characteristics and bubble features in the channel under conjugate conditions, a systematic three-dimensional numerical study is carried out by coupling the phase transition model with the volume of fluid (VOF) model. It is found that the symmetric distribution structure of the SCMC flow channel not only provides nucleation points for bubble generation, but also provides rupture points for large bubbles that can block the flow channel due to bubble aggregation, which reduces the instability of phase transition heat. Compared with the smooth flow channel structure of ω=1 and ω=1.5, the steep structure of ω=2 not only helps the mixing of coolant, but also increases the probability of bubbles hitting the sharp structure, which is more helpful for the rupture of large bubbles. In addition, the effects of waviness (ω ~ 0-2) and inlet velocity (Re ~ 234.07-1170.37) on the heat transfer performance under non-constant flow boiling conditions are investigated. The results show that the heat transfer capacity of SCMC increases firstly and then decreases with the increase of ω and subsequently increases again with the constant Re. The performance factor shows a decrease and then increases, which gets the maximum value at ω=2 and still shows an increasing trend. In the case of constant ω, the heat transfer capacity of SCMC is enhanced with the increase of Re, but the enhancement trend gradually slows down, and the performance factor shows a trend of increasing at first an

关键词： Heat exchangers

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