检索结果-内蒙古大学图书馆

SSRN 2024年

作者： Zhang, Mingkuan Gao, Qi Zhao, Zhiyuan Guo, Luna Li, Xuan Zhang, Chao Zhang, Xudong Rao, Wei Tianjin Key Laboratory for Advanced Mechatronic System Design and Intelligent Control School of Mechanical Engineering Tianjin University of Technology Tianjin300384 China National Demonstration Center for Experimental Mechanical and Electrical Engineering Education Tianjin University of Technology China School of mechanical engineering Tianjin University of Commerce Tianjin300134 China Institute of Refrigeration and Cryogenics Shanghai Jiao Tong University Shanghai200240 China Key Laboratory for Thermal Science and Power Engineering of Ministry of Education Department of Engineering Mechanics Tsinghua University Beijing Beijing100084 China CAS Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences China Beijing Key Lab of CryoBiomedical Engineering and Key Lab of Cryogenics Beijing100190 China

The reduction in transistor dimensions and advancements in chip integration have led to a dramatic increase in the heat flux of chip. Advanced heat dissipation technology has become the pivotal in ensuring the normal operation of chips and fully utilizing chip performance. Room temperature liquid metal convection cooling technology has demonstrated its efficacy as a viable approach for addressing high heat flux heat dissipation. However, the smaller specific heat capacity of liquid metal leads to a large temperature rise, imposing a constraint on the progression of liquid metal cooling technology. To overcome this drawback, this paper proposed a liquid metal manifold channel structure designed to convert the continuous long-range flow into a segmented short-range flow. The good matching between liquid metal and manifold structures is adequately demonstrated through a comparison with alternative coolant and channel structure. The simulation results demonstrate the effectiveness of liquid metal manifold channel cooling in dealing with a heat flux of 1000 W/cm², ensuring that the maximum temperature of the chip remains below 351.7 K. Moreover, the convective heat transfer coefficient even reaches 106 W/(m2·K), which is ten times larger than that of water conventional microchannel heat sink. The orthogonal experiments were conducted to analyze how the structural parameters affect the dissipation performance, including the height of the microchannel, ratio of manifold length to fin length, length of fin in manifold, width of channel, and ratio of fin with to channel width. It concluded that the height of the microchannel has been identified as the most critical factor. This manifold structure mitigates the inherent limitation of the lower specific heat capacity of liquid metal, paving the way for effective thermal management of electronic devices subjected to ultra-high heat flux. © 2024, The Authors. All rights reserved.

关键词： Heat flux

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Aerial Active STAR-RIS-assisted Satellite-Terrestrial Covert Communications

arXiv

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arXiv 2025年

作者： Zhang, Chuang Sun, Geng Li, Jiahui Wang, Jiacheng Zhang, Ruichen Niyato, Dusit Mao, Shiwen Quek, Tony Q.S. Computer Science and Technology Jilin University Changchun130012 China Singapore University of Technology and Design Singapore487372 Singapore College of Computer Science and Technology Jilin University Changchun130012 China College of Computing and Data Science Nanyang Technological University Singapore639798 Singapore Key Laboratory of Symbolic Computation and Knowledge Engineering of Ministry of Education Jilin University Changchun130012 China Department of Electrical and Computer Engineering Auburn University AuburnAL36849 United States Information System Technology and Design Pillar Singapore University of Technology and Design Singapore487372 Singapore

An integration of satellites and terrestrial networks is crucial for enhancing performance of next generation communication systems. However, the networks are hindered by the long-distance path loss and security risks in dense urban environments. In this work, we propose a satellite-terrestrial covert communication system assisted by the aerial active simultaneous transmitting and reflecting reconfigurable intelligent surface (AASTAR-RIS) to improve the channel capacity while ensuring the transmission covertness. Specifically, we first derive the minimal detection error probability (DEP) under the worst condition that the Warden has perfect channel state information (CSI). Then, we formulate an AASTAR-RIS-assisted satellite-terrestrial covert communication optimization problem (ASCCOP) to maximize the sum of the fair channel capacity for all ground users while meeting the strict covert constraint, by jointly optimizing the trajectory and active beamforming of the AASTAR-RIS. Due to the challenges posed by the complex and high-dimensional state-action spaces as well as the need for efficient exploration in dynamic environments, we propose a generative deterministic policy gradient (GDPG) algorithm, which is a generative deep reinforcement learning (DRL) method to solve the ASCCOP. Concretely, the generative diffusion model (GDM) is utilized as the policy representation of the algorithm to enhance the exploration process by generating diverse and high-quality samples through a series of denoising steps. Moreover, we incorporate an action gradient mechanism to accomplish the policy improvement of the algorithm, which refines the better state-action pairs through the gradient ascent. Simulation results demonstrate that the proposed approach significantly outperforms important benchmarks, and also validate the performance and practicality under different algorithm parameters and environment settings. Copyright © 2025, The Authors. All rights reserved.

关键词： Deep reinforcement learning

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Noncontact Doppler Radar-based Heart Rate Detection on the SVD and ANC

Noncontact Doppler Radar-based Heart Rate Detection on the S...

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IEEE International Conference on Bioinformatics and Biomedicine (BIBM)

作者： Qiuxia Shi Bin Hu Fuze Tian Qinglin Zhao Gansu Provincial Key Laboratory of Wearable Computing School of Information Science and Engineering Lanzhou University School of Computer and Communication Lanzhou University of Technology Ministry of Education Key Laboratory of Special Functional Materials and Structural Design (Lanzhou University) Lanzhou China CAS Center for Excellence in Brain Science and Intelligence Technology Shanghai Institutes for Biological Sciences Chinese Academy of Sciences Joint Research Center for Cognitive Neurosensor Technology of Lanzhou University & Institute of Semiconductors Chinese Academy of Sciences Engineering Research Center of Open Source Software and Real-Time System(Lanzhou University) Ministry of Education Key Laboratory of Special Functional Materials and Structural Design Ministry of Education Lanzhou University Lanzhou China

ISBN: (数字)9781665468190

ISBN: (纸本)9781665468206

In the Doppler biological radar-based applications of noncontact measurement of vital signs, effectively extracting heartbeat information from weak thoracic mechanical motion is an important problem to be solved. This study is aimed at extracting heartbeat signal via the technology combined with Short Time Fourier Transform (STFT), Singular Value Decomposition (SVD) and Adaptive Noise Canceller (ANC) from radar recording. The simulated data and the data collected by Doppler radar biosensor realized in laboratory are employed to validate the proposed method. The results show that the proposed method has the ability of detection for the heart rate and heart rate variability indexes in rest state, it has certain advantages in time-consuming and detection accuracy. Therefore, the current method provides another way to process vital sign signals recorded by Doppler radar.

关键词： Biomedical measurement Noise cancellation Time measurement Doppler radar Recording Doppler effect Biosensors

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Uncovering the Iceberg in the Sea: Fundamentals of Pulse Shaping and Modulation design for Random ISAC Signals

arXiv

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arXiv 2025年

作者： Liu, Fan Xiong, Yifeng Lu, Shihang Li, Shuangyang Yuan, Weijie Masouros, Christos Jin, Shi Caire, Giuseppe The National Mobile Communications Research Laboratory Southeast University Nanjing210096 China The School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen518055 China The School of Information and Electronic Engineering Beijing University of Posts and Telecommunications Beijing100876 China The Chair of Communications and Information Theory Technical University of Berlin Berlin10623 Germany The Department of Electrical and Electronic Engineering University College London LondonWC1E 7JE United Kingdom

Integrated Sensing and Communications (ISAC) is expected to play a pivotal role in future 6G networks. To maximize time-frequency resource utilization, 6G ISAC systems must exploit data payload signals, that are inherently random, for both communication and sensing tasks. This paper provides a comprehensive analysis of the sensing performance of such communication-centric ISAC signals, with a focus on modulation and pulse shaping design to reshape the statistical properties of their auto-correlation functions (ACFs), thereby improving the target ranging performance. We derive a closed-form expression for the expectation of the squared ACF of random ISAC signals, considering arbitrary modulation bases and constellation mappings within the Nyquist pulse shaping framework. The structure is metaphorically described as an "iceberg hidden in the sea", where the "iceberg" represents the squared mean of the ACF of random ISAC signals, that is determined by the pulse shaping filter, and the "sea level" characterizes the corresponding variance, caused by the randomness of the data payload. Our analysis shows that, for QAM/PSK constellations with Nyquist pulse shaping, Orthogonal Frequency Division Multiplexing (OFDM) achieves the lowest ranging sidelobe level across all lags. Building on these insights, we propose a novel Nyquist pulse shaping design to enhance the sensing performance of random ISAC signals. Numerical results validate our theoretical findings, showing that the proposed pulse shaping significantly reduces ranging sidelobes compared to conventional root-raised cosine (RRC) pulse shaping, thereby improving the ranging performance. Copyright © 2025, The Authors. All rights reserved.

关键词： Orthogonal frequency division multiplexing

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Influence of manufacturing errors of bearing components on rotational accuracy of cylindrical roller bearings

Research Square

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Research Square 2021年

作者： Yu, Yongjian Li, Jishun Xue, Yujun School of Mechatronics Engineering Henan University of Science and Technology Luoyang471003 China Henan Key Laboratory for Machinery Design and Transmission System Henan University of Science and Technology Luoyang471003 China Luoyang LYC Bearings Co. Ltd State Key Laboratory of Aviation Precision Bearings Luoyang471039 China

Understanding the influence of bearing component manufacturing errors and roller number on the rotational accuracy of rolling bearings is crucial in the design of high precision bearings. The rotational accuracy of an assembled bearing is dependent upon roller number and manufacturing error of the bearing components. We propose a model for calculating the rotational accuracy of a cylindrical roller bearing;we experimentally verified the effectiveness of the model in predicting the radial run-out of the inner ring proposed in the previous paper in this series. We sought to define the key contributing factors to the rotational accuracy by studying both the influence of the coupling effect of the roller number and the influence of the manufacturing errors in the inner raceway, outer raceway, and rollers on the motion error. The model and results will help engineers choose reasonable manufacturing tolerances for bearing components to achieve the required rotational accuracy. © 2021, CC BY.

关键词： Rollers (machine components)

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Phase distribution characteristics of cap bubbly flow in 5×5 rod bundles with mixing vane spacer grids 27

Phase distribution characteristics of cap bubbly flow in 5×...

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27th International Conference on Nuclear Engineering: Nuclear Power Saves the World!, ICONE 2019

作者： Ren, Quan-Yao Pu, Zeng-Ping Pan, Liang-Ming Zheng, Mei-Yin Wang, Hao-Yu Zhou, Wen-Xiong Wei, Lie Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of China Chengdu610041 China Key Laboratory of Low-grade Energy Utilization Technologies and Systems Chongqing University Ministry of Education Chongqing400044 China

ISBN: (纸本)9784888983051

To improve the understanding on the mechanisms of phase distribution and bubble interaction for cap bubbly flow in rod bundles, the adiabatic upward cap bubbly flow has been investigated experimentally in 5×5 rod bundles with prototypical mixing vane spacer grids (MVSGs). Miniaturized four-sensor conductivity probe (MFSCP) has been developed to measure the local two phase flow parameters, such as void fraction, interfacial area concentration (IAC), bubble velocity, and bubble chord length. The detailed local parameters in cap bubbly flow has been measured and analyzed, based on which the phase distribution characteristics have been analyzed for Group I and II bubbles in detail. Moreover, the axial development and the effect of MVSG have also been analyzed. Some interesting phenomenon have been observed: Group I void fraction profile is almost flat at the measuring line while Group II void fraction profile has the skewed peaks near the sub-channel center resulted for the limitation of rod walls and the strong secondary flow;Group I IAC is the main contribution to the total IAC, whose profile has the peaks near the rod gap due to the smaller bubble size near the rod walls. For current cap bubbly flow condition, the bubble velocity and size are the two determined factors for Group I IAC for the similar void fraction, while the void fraction is the key factor for Group II IAC for the larger bubble size. Furthermore, because of the shear force of MVSG and induced stronger turbulence, the large Group II bubbles break up into Group I bubbles and smaller Group II bubbles, which results in the smaller bubble size and larger Group I void fraction and IAC. According to the analysis on the axial development of local parameter profiles, the MVSG dissipation length might be larger than 19.4 L/Dh, but smaller than 32.1 L/Dh for current cap bubbly flow condition. Copyright © 2018-2019 by JSME

关键词： Void fraction

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A systematic Review of Multi-Sensor Information Fusion for Equipment Fault Diagnosis

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IEEE Transactions on Instrumentation and Measurement 2025年

作者： Lin, Tantao Ren, Zhijun Zhu, Linbo Zhu, Yongsheng Feng, Ke Ding, Weiping Yan, Ke Beer, Michael Xi'an Jiaotong University Key Laboratory of Education Ministry for Modern Design & Rotor-Bearing System Xi'an710049 China Xi'an Jiaotong University Frontier Institute of Science and Technology Xi'an710049 China Xi'an Jiaotong University School of School of Chemical Engineering and Technology Xi'an710049 China Xi'an Jiaotong University School of Mechanical Engineering Xi'an710049 China Nantong University School of Artificial Intelligence and Computer Science Nantong226019 China City University of Macau Faculty of Data Science Macau999078 China Leibniz University Institute for Risk and Reliability Hannover30167 Germany University of Liverpool Department of Civil and Environmental Engineering LiverpoolL69 3BX United Kingdom Tongji University International Joint Research Center for Resilient Infrastructure International Joint Research Center for Engineering Reliability and Stochastic Mechanics Shanghai200092 China

In contrast to fault diagnosis relying solely on a single sensor, the method of multi-sensor information fusion for fault diagnosis (MSIFFD) broadens the spectrum of available information sources. It is renowned for its high accuracy and reliability, traits that have attracted growing attention within the research community and led to the generation of a substantial body of publications. However, there is currently a lack of a comprehensive and systematic review in this domain. Thereby, this review aims to thoroughly explore all research achievements in the field of MSIFFD. At the outset, an analysis is undertaken to delineate the fusion level of multi-sensor information, with a specific focus on its location and types of inputs and outputs within the information flow. Subsequently, an examination of the six primary fundamental operations for amalgamating multi-sensor information is undertaken to clarify the motivations and processes involved in information fusion across various operations. Following this, factors influencing fusion diagnostics and strategies aimed at improving their performance are examined to explore approaches for enhancing fusion accuracy. The subsequent sections delve into the analysis of sensor types and application scenarios, providing a reference guide for practical applications. Finally, this review outlines potential future challenges in the field of MSIFFD and provides a range of recommendations and possible solutions for consideration. © 1963-2012 IEEE.

关键词： Information fusion

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Initiating a High-Rate and Stable Aqueous Air Battery by Using Organic N-Heterocycle Anode

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Angewandte Chemie 2024年第11期136卷

作者： Dr. Senlin Li Dr. Sanlue Hu Prof. Hongfei Li Prof. Cuiping Han Faculty of Materials Science and Energy Engineering/Institute of Technology for Carbon Neutrality Shenzhen Institute of Advanced Technology Chinese Academy of Sciences Shenzhen 518055 China School of System Design and Intelligent Manufacturing Southern University of Science and Technology Shenzhen 518055 China Songshan Lake Materials Laboratory Dongguan Guangdong 523808 China

Alkaline metal-air batteries are advantageous in high voltage, low cost, and high safety. However, metal anodes are heavily eroded in strong alkaline electrolytes, causing serious side reactions including dendrite growth, passivation, and hydrogen evolution. To address this limitation, we successfully synthesized an organic N-heterocycle compound (NHCC) to serve as an alternative anode. This compound not only exhibits remarkable stability but also possesses a low redox potential (−1.04 V vs. Hg/HgO) in alkaline environments. To effectively complement the low redox potential of the NHCC anode, we designed a dual-salt highly concentrated electrolyte (4.0 M KOH+10.0 M KCF 3 SO 3 ). This electrolyte expands the electrochemical stability window to 2.3 V through the robust interaction between the O atom in H 2 O molecule with the K + of KCF 3 SO 3 (H−O⋅⋅⋅KCF 3 SO 3 ). We further demonstrated the K + uptaken/extraction storage mechanism of NHCC anodes. Consequently, the alkaline aqueous NHCC anode-air batteries delivers a high battery voltage of 1.6 V, high-rate performance (101.9 mAh g −1 at 100 A g −1 ) and long cycle ability (30,000 cycles). Our work offers a molecular engineering strategy for superior organic anode materials and develops a novel double superconcentrated conductive salt electrolyte for the construction of high-rate, long-cycle alkaline aqueous organic anode-air batteries.

关键词： Alkaline Aqueous Electrolyte Superconcentrated Electrolyte N-Heterocycle Compounds Organic Anode Air Battery

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Application of feedforward predictive control in DC furnace coordination system

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Journal of Physics: Conference Series 2021年第1期1780卷

作者： Zhiguang DENG HE Zhengxi ZHU Biwei ZHU Jialiang LV Xin WU Qian National Key Labortory of Science and Technology on Reactor System Design Technology Chengdu610213China

In order to solve the control difficulties such as large dynamic delay, serious coupling between machine and furnace and strong nonlinear, the feedforward and feedback predictive control is proposed to control the coordinated system on the basis of multi-model predictive control, and the static feedforward part designs the feed line feedforward of coal quantity against coal quality disturbance on the basis of the accurate balance of energy. Thus, the reference total fuel quantity under the target load instruction is determined, and the dynamic part fully considers the dynamic compensation of the unit energy storage, gives a certain overshoot fuel quantity to the boiler regulation, speeds up its response, and ensures the rapidity of the unit. The real-time simulation results of virtual DPU (Distributed Processing Unit) show that the designed feedforward-feedback predictive control can quickly respond to load change, improve the resistance to fuel disturbance, reduce the fluctuation of main steam pressure, and better ensure the safe, economic and stable operation of the coordination system.

关键词：

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Copula method of the kinematic accuracy of cylindrical roller bearing

Research Square

引用

Research Square 2021年

作者： Li, Lihong Xue, Yujun Li, Jishun Vehicles & Transportation Engineering Institute Henan University of Science and Technology Luoyang471003 China Henan Key Laboratory for Machinery Design and Transmission System Henan University of Science and Technology Luoyang471003 China State Key Laboratory of Aviation Precision Bearings Luoyang LYC Bearings Co. Ltd. Luoyang471039 China

The kinematic accuracy of cylindrical rollers bearing isn’t only influenced by the dimensional and form precision of its parts, but also more influenced by the cooperation among them. For cylindrical rollers bearing, the main indices of the kinematic accuracy are the ending beat and the radial run out of bearings. There must be dependent relationship between the cooperative action among the parts of bearings and the ending beat or the radial run out of bearings. This relationship is hardly expressed by mathematical formula. However, because the parts dimension deviation and the run out of bearings follow statistic law and have their distribution characteristics, while the copula joint distribution function can connect the run out of bearings with multiple parts dimension accuracy, the copula function is introduced to analyze the dependent relationship between bearing parts cooperative action and its kinematic accuracy. Based on the copula function of statistic theory, the kinematic accuracy of bearings can be forecast by parts geometric accuracy. © 2021, CC BY.

关键词： Kinematics

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