检索结果-内蒙古大学图书馆

SSRN 2022年

作者： Xu, Xiao Ma, Xinjian Zhang, Jun Shen, Yan Zhang, Junyan School of Mechatronics and Power Engineering Jiangsu University of Science and Technology Zhangjiagang215600 China Shanghai Space Propulsion Technology Research Institute Shanghai201109 China Key Laboratory of Unsteady Aerodynamics and Flow Control Ministry of Industry and Information Technology Nanjing University of Aeronautics and Astronautics Nanjing210016 China China Academy of Aerospace Aerodynamics Beijing100074 China

An information preservation (IP) optimization approach for supersonic flow simulation is proposed in this paper. According to the conversion of the variables integrated in half-space and the analogical analysis, a similarity relationship between the integrated variables in the governing equations of the preserved information and macroscopic variables in Navier-Stokes equations is obtained. The computational approach of the flux for the correlation terms is reconstructed using the Advection Upstream Splitting Method (AUSM) scheme, giving the IP method windward characteristics. Additionally, the pressure boundary treatment is modified to improve the stability and accuracy of the IP method in the simulation of rarefied supersonic flow driven by high pressure. The particle number threshold method is proposed to solve the "carbuncle point" problem caused by insufficient local collisions. The IP optimization method combines the advantages of the AUSM scheme and the low statistical scatter method;thus, it can accurately and effectively investigate real-time variation characteristics of rarefied supersonic flow. This method simulates the supersonic microscale jet flow and hypersonic macroscale nozzle flow. The results indicate that the real-time statistical accuracy of the IP optimization method is much better than the direct simulation Monte Carlo method, whereas the correctness and accuracy of this method are satisfactory. Therefore, the proposed method provides an efficient algorithm for the variation mechanism and unsteady flow-characteristic research on rarefied supersonic flow on different scales. © 2022, The Authors. All rights reserved.

关键词： Supersonic flow

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Nonreciprocal thermal radiation in ultrathin magnetized epsilon-near-zero semiconductors

arXiv

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arXiv 2022年

作者： Liu, Mengqi Xia, Shuang Wan, Wenjian Qin, Jun Li, Hua Zhao, Changying Bi, Lei Qiu, Cheng-Wei Institute of Engineering Thermophysics MOE Key Laboratory for Power Machinery and Engineering School of Mechanical Engineering Shanghai Jiao Tong University Shanghai200240 China Department of Electrical and Computer Engineering National University of Singapore Singapore117583 Singapore National Engineering Research Center of Electromagnetic Radiation Control Materials University of Electronic Science and Technology of China Chengdu610054 China State Key Laboratory of Electronic Thin-Films and Integrated Devices University of Electronic Science and Technology of China Chengdu610054 China Key Laboratory of Terahertz Solid State Technology Shanghai Institute of Microsystem and Information Technology Chinese Academy of Sciences Shanghai2000509 China Center of Materials Science and Optoelectronics Engineering University of Chinese Academy of Science Beijing1000049 China

Spectral/angular emissivity e and absorptivity α of an object are widely believed to be identical by Kirchhoff's law of thermal radiation in reciprocal systems, but this introduces an intrinsic and inevitable energy loss for energy conversion and harvesting devices. So far, experimental evidences of breaking this well-known balance are still absent, and previous theoretical proposals are restricted to narrow single-band nonreciprocal radiation. Here we observe for the first time, to our knowledge, the violation of Kirchhoff's law using ultrathin (0.6 has been experimentally demonstrated under a moderate external magnetic field. Moreover, based on magnetized ENZ building blocks supporting asymmetrically radiative Berreman and surface ENZ modes, we show versatile shaping of nonreciprocal thermal radiation: single-band, dual-band, and broadband nonreciprocal emission spectra at different wavebands. Our findings of breaking Kirchhoff's law will advance the conventional understanding of emission and absorption processes of natural objects, and lay a solid foundation for more comprehensive studies in designing various nonreciprocal thermal emitters. The reported recipe of diversely shaping nonreciprocal emission will also breed new possibilities in renovating next-generation nonreciprocal energy devices in the areas of solar cells, thermophotovoltaic, radiative cooling, etc. Copyright © 2022, The Authors. All rights reserved.

关键词： III-V semiconductors

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A Review of Metal Powder-CO2 Propulsion technology

A Review of Metal Powder-CO2 Propulsion Technology

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International Conference on Vision, Image and Signal Processing (ICVISP)

作者： Hanxiao Wu Kun Cai Haiwang Li Tiantong Xu Weidong Fang Wenbin Wang Pengpeng Nie National Key Laboratory of Science and Technology on Aero-Engine Aero-Thermodynamics Beihang University Beijing People’s Republic of China School of Energy and Power Engineering Beihang University Beijing People’s Republic of China ShenYuan Honors College of Beihang University Beihang University Beijing People’s Republic of China Beijing Institute of Control Engineering Space Propulsion Product Development Center Beijing People’s Republic of China Research Institute of Aero-Engine Beihang University Beijing People’s Republic of China

ISBN: (纸本)9781665408356

With the advancement of Mars exploration and deep space exploration technology, the metal powder-CO! rocket engine suitable for the Martian atmosphere has received more and more attention from scholars. In this paper, we summarized some researches about power-CO 2 propulsion technology, including the combustion mechanism studies and pivotal technologies. Then, we pointed out some potential research directions in the future.

关键词： Temperature distribution Mars Powders Metals Ignition Combustion Temperature control

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Effect of lactic acid on internal stress and mechanical properties of electrodeposited Ni-P alloys for ultraprecision manufacturing

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Colloids and Surfaces A: Physicochemical and engineering Aspects 2025年 722卷

作者： Pengfei Xu Bo Wang Lei Wang Zhihao Liu Zhengkuo Wang Zekun Liu Yuxin Gong Fei Ding Langping Wang Yanji Yang Dianlong Wang State Key Laboratory of Space Power-Sources School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin 150001 China MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage School of Chemistry and Chemical Engineering Harbin Institute of Technology Harbin 150001 China Center for Precision Engineering Harbin Institute of Technology Harbin 150001 China State Key Laboratory of Advanced Welding and Joining Harbin Institute of Technology Harbin 150001 China Key Laboratory for Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing 100049 China

Achieving Ni-P alloy coatings with ultra-low internal stress, excellent mechanical properties, and high current efficiency is critical for meeting the stringent demands of ultra-precision manufacturing. This study aims to explore the effects of lactic acid concentration and current density on the internal stress, mechanical properties, and current efficiency of Ni-P coatings electrodeposited on copper substrates under direct current (DC) conditions. The lactic acid concentration was varied from 39.6 to 48.4 g L −1 . Theoretical calculations and electrochemical tests were employed to investigate the solvation behavior of Ni 2+ in the plating bath and the subsequent influence on the electrodeposition process. Results indicated that lactic acid forms a stable solvation structure with Ni 2+ , enhancing the polarization during deposition, modifying the nucleation mechanism from instantaneous to progressive nucleation, and ultimately affecting the coating properties. Under the optimized conditions of 44 g L −1 lactic acid concentration and 1.6 A dm −2 current density, the Ni-P coating achieved an ultra-low internal stress of + 0.029 MPa, a high Vickers hardness of 707 HV, a ultimate tensile strength of 1537 MPa, a current efficiency of 95.28 %, and a phosphorus content of 1.92 at%. This study provides valuable insights for the development of high-performance Ni-P coatings tailored for ultra-precision applications.

关键词： Tensile strength

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Condition evaluation method of wind turbine based on real-time reliability

Condition evaluation method of wind turbine based on real-ti...

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2019 International Conference on Sensing, Diagnostics, Prognostics, and control, SDPC 2019

作者： He, Chengbing Ma, Li Wang, Runze Li, Xiaobo Jiao, Xiaofeng Song, Lei North China Electric Power University School of Energy Power and Mechanical Engineering Beijing China Inner Mongolia Electric Power Science Research Institute Inner Mongolia Hohhot China Chinese Academy of Sciences Technology and Engineering Center for Space Utilization Line Beijing China

ISBN: (纸本)9781728101996

With the rapid development of wind power generation worldwide, the condition evaluation of wind turbine has received more and more attention. In this paper, wind turbine is divided into three levels: component level, device level, and subsystem level, and the system of condition evaluation is constructed. The real-time reliability analysis model of wind turbine is proposed. The real-time reliability reduction is calculated from component level, equipment level and subsystem level in turn by using variable weight synthesis method. Finally, the condition evaluation of wind turbine is realized. The validity of this method is verified by a case analysis. The research results in this paper can provide decision-making assistance for the management of daily operation and maintenance of wind turbines and improve the operational efficiency of wind farms. © 2019 IEEE.

关键词： Wind turbines

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research on fault diagnosis method based on FMEA/FTA and bayesian network

Research on fault diagnosis method based on FMEA/FTA and bay...

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2019 International Conference on Sensing, Diagnostics, Prognostics, and control, SDPC 2019

作者： He, Chengbing Wang, Runze Ma, Li Li, Xiaobo Jiao, Xiaofeng Song, Lei North China Electric Power University School of Energy Power and Mechanical Engineering Beijing China Inner Mongolia Electric Power Science Research Institute Inner Mongolia Hohhot China Chinese Academy of Sciences Technology and Engineering Center for Space Utilization Line Beijing China

ISBN: (纸本)9781728101996

The construction of Bayesian network (BN) model is a bottleneck problem that needs to be solved urgently in the field of fault diagnosis. Combining failure mode and effect analysis(FMEA) and fault tree analysis(FTA) can solve this problem well. In this paper, a BN model based on FMEA/FTA is proposed. The transformation methods of FMEA to BN and FTA to BN are analyzed. The structural matrix is used to realize the information transformation. The noisy-max model is used to determine the BN parameters. Taking the rub-impact fault between the high pressure rotor and the front shaft seal of a 600 MW turbogenerator unit as an example, the application of the BN model based on FMEA/FTA in fault diagnosis is realized from three aspects which are BN model construction, prior probability and conditional probability assignment, and diagnosis reasoning, respectively. © 2019 IEEE.

关键词： Bayesian networks

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research on damping addition and vibration reduction technology of frame aerospace electronic chassis

引用

Journal of Physics: Conference Series 2021年第1期1754卷

作者： Zhang yu Zhang bolin Beijing Satellite Manufacturing Co. LTD Beijing Space Power Supply Transformation and Control Engineering Research Center Beijing 100080 China

This paper poses a box instrumentation in aerospace electronic chassis TO-5 encapsulation relay under the action of impact environmental load state of reverse fault mode, by reasonable single frames of viscoelastic damping materials added, increasing box style structure between the PCB mechanical installation interface damping ratio and frequency ratio, finally realizes the transfer rate is reduced, achieve instrumentation relay PCB, lower impact acceleration response. By adding damping cushion to the frame machine installation interface, the load transfer path of impact mechanics is optimized to reduce the installation stiffness and change the fundamental frequency characteristics of the whole machine.

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Coordinated control strategy of a DC grid with energy storage system

Coordinated control strategy of a DC grid with energy storag...

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作者： Yang, Bo Sang, Bingyu Yang, Zhihan Li, Menbo Xiang, Wang Lu, Xiaojun Yao, Liangzhong Tao, Yibin School of Electrical Engineering Southeast University Nanjing China State Key Laboratory of Operation and Control of Renewable Energy ＆ Storage Systems China Electric Power Research Institute Beijing China China Electric Power Research Institute Nanjing China Jiangsu Engineering Technology Research Center for Energy Storage Conversion and Application China Electric Power Research Institute Nanjing China State Key Laboratory of Advanced Electromagnetic Engineering and Technology Huazhong University of Science and Technology Wuhan China

DC grid has a prospect of application in collecting and transmitting large-scale renewable energy over long distance. However, the randomness and fluctuation of the renewable power may hamper the stable operation of DC grid. Energy storage device is able to actively absorb or supplement active power, which can be used to smooth the power fluctuation. The paper investigates a DC grid topology with energy storage and proposes a coordinated control strategy. The proposed strategy enables coordinated control of the renewable energy output power, pumped storage power and the grid consuming power. During the steady state, the control strategy enables the system DC voltage stable and power flow of the grid under zero-error control. During the faulted time, the coordinate control strategy enables the converter fast response and maintains the system DC voltage within safety margin. The effectiveness of the coordinated control strategy is verified by simulation in PSCAD/ EMTDC. © 2019 Institution of engineering and *** right reserved.

关键词： Energy storage

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Construction of an example system for AC/DC hybrid power grid with high-proportion renewable energy

Construction of an example system for AC/DC hybrid power gri...

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作者： Zhao, Dawei Ma, Jin Qian, Minhui Zhu, Lingzhi Yao, Liangzhong Ding, Kun Han, Hualing State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources North China Electric Power University Changping District Beijing China State Key Laboratory of Operation and Control of Renewable Energy and Storage Systems Jiangsu Engineering Technology Research Center for Energy Storage Conversion and Application China Electric Power Research Institute Gulou District Nanjing China Wind Power Technology Center of Gansu Electric Power Company Qilihe District Lanzhou China

Large-scale wind and solar power generations have got rapid development in recent years in China and abroad. They always connect to load centres through high-voltage direct current (HVDC) transmission or ultra HVDC (UHVDC) transmission lines. Such systems are so large and it is necessary to make appropriate equivalence according to the purpose of different research. At present, the analysis model of this kind of real system is few, and simplified single-machine infinite-bus system or IEEE example system is adopted most of the time, which may affect the accuracy of analysis results. Here, the UHVDC project from a practical renewable energy base to load centres in China is chosen as an example, the actual structure and parameters are used to establish a typical example system for AC/DC hybrid power grid with high-proportion renewable energy. The new-generation synchronous condenser with large capacity and the supporting synchronous generators are all considered. First, the installed power generation, power grid structure, and load configuration of example system are introduced. Then the load flow distribution and transient stability characteristics are analysed by using DIgSILENT powerFactory software. Finally, the feasibility of the proposed example system is shown by simulation results. © 2019 Institution of engineering and *** right reserved.

关键词： Electric load flow

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Einstein Probe discovery of EP240408a: a peculiar X-ray transient with an intermediate timescale

arXiv

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arXiv 2024年

作者： Zhang, Wenda Yuan, Weimin Ling, Zhixing Chen, Yong Rea, Nanda Rau, Arne Cai, Zhiming Cheng, Huaqing Zelati, Francesco Coti Dai, Lixin Hu, Jingwei Jia, Shumei Jin, Chichuan Li, Dongyue O'Brien, Paul Shen, Rongfeng Shu, Xinwen Sun, Shengli Sun, Xiaojin Wang, Xiaofeng Yang, Lei Zhang, Bing Zhang, Chen Zhang, Shuang-Nan Zhang, Yonghe An, Jie Buckley, David Coleiro, Alexis Cordier, Bertrand Dou, Liming Eyles-Ferris, Rob Fan, Zhou Feng, Hua Fu, Shaoyu Fynbo, Johan P.U. Galbany, Lluis Jha, Saurabh W. Jiang, Shuaiqing Kong, Albert Kuulkers, Erik Lei, Weihua Li, Wenxiong Liu, Bifang Liu, Mingjun Liu, Xing Liu, Yuan Liu, Zhu Maitra, Chandreyee Marino, Alessio Monageng, Itumeleng Nandra, Kirpal Sanders, Jeremy Soria, Roberto Tao, Lian Wang, Junfeng Wang, Song Wang, Tinggui Wang, Zhongxiang Wu, Qingwen Wu, Xuefeng Xu, Dong Xu, Yanjun Xue, Suijian Xue, Yongquan Zhang, Zijian Zhu, Zipei Zou, Hu Bao, Congying Chen, Fansheng Chen, Houlei Chen, Tianxiang Chen, Wei Chen, Yehai Chen, Yifan Cui, Chenzhou Cui, Weiwei Dai, Yanfeng Fan, Dongwei Guan, Ju Han, Dawei Hou, Dongjie Hu, Haibo Huang, Maohai Huo, Jia Jia, Zhenqing Jiang, Bowen Jin, Ge Li, Chengkui Li, Junfei Li, Longhui Li, Maoshun Li, Wei Li, Zhengda Lian, Tianying Liu, Congzhan Liu, Heyang Liu, Huaqiu Lu, Fangjun Luo, Laidan Ma, Jia Mao, Xuan Pan, Haiwu Pan, Xin Song, Liming Sun, Hui Tan, Yunyin Tang, Qingjun Tao, Yihan Wang, Hao Wang, Juan Wang, Lei Wang, Wenxin Wang, Yilong Wang, Yusa Wu, Qinyu Xu, Haitao Xu, Jingjing Xu, Xinpeng Xu, Yunfei Xu, Zhao Xue, Changbin Xue, Yulong Yan, Ailiang Yang, Haonan Yang, Xiongtao Yang, Yanji Zhang, Juan Zhang, Mo Zhang, Wenjie Zhang, Zhen Zhang, Zhen Zhang, Ziliang Zhao, Donghua Zhao, Haisheng Zhao, Xiaofan Zhao, Zijian Zhou, Hongyan Zhou, Yilin Zhu, Yuxuan Zhu, Zhencai National Astronomical Observatories Chinese Academy of Sciences Beijing100101 China School of Astronomy and Space Sciences University of Chinese Academy of Sciences Beijing100049 China Key Laboratory of Particle Astrophysics Institute of High Energy Physics Chinese Academy of Sciences Beijing100049 China CSIC BarcelonaE-08193 Spain BarcelonaE-08034 Spain Max Planck Institute for Extraterrestrial Physics Garching85748 Germany Innovation Academy for Microsatellites Chinese Academy of Sciences Shanghai201210 China Department of Physics University of Hong Kong Hong Kong School of Physics and Astronomy University of Leicester LeicesterLE1 7RH United Kingdom School of Physics and Astronomy Sun Yat-Sen University Zhuhai519082 China Department of Physics Anhui Normal University Wuhu241002 China Shanghai Institute of Technical Physics Chinese Academy of Sciences Shanghai200083 China Physics Department Tsinghua University Beijing100084 China Nevada Center for Astrophysics University of Nevada Las Vegas Las VegasNV89154 United States Department of Physics and Astronomy University of Nevada Las Vegas Las VegasNV89154 United States South African Astronomical Observatory Cape Town7935 South Africa Department of Astronomy University of Cape Town Rondebosch7701 South Africa Department of Physics University of the Free State Bloemfontein9300 South Africa Université Paris Cité CNRS Astroparticule et Cosmologie ParisF-75013 France Université Paris Cité CEA Paris-Saclay IRFU DAp-AIM Gif-sur-Yvette91191 France Department of Astronomy Guangzhou University Guangzhou510006 China Copenhagen2200 Denmark Niels Bohr Institute University of Copenhagen Copenhagen2200 Denmark Department of Physics and Astronomy Rutgers the State University of New Jersey PiscatawayNJ08854-8019 United States Institute for Cosmic Ray Research The University of Tokyo Kashiwa277-8582 Japan ESA ESTEC Noordwijk2201 AZ Netherlands Department of Astronomy Schoo

We report the discovery of a peculiar X-ray transient, EP240408a, by Einstein Probe (EP) and follow-up studies made with EP, Swift, NICER, GROND, ATCA and other ground-based multiwavelength telescopes. The new transient was first detected with Wide-field X-ray Telescope (WXT) on board EP on April 8th, 2024, manifested in an intense yet brief X-ray flare lasting for 12 seconds. The flare reached a peak flux of 3.9 × 10−9 erg cm−2 s−1 in 0.5-4 keV, ∼300 times brighter than the underlying X-ray emission detected throughout the observation. Rapid and more precise follow-up observations by EP/FXT, Swift and NICER confirmed the finding of this new transient. Its X-ray spectrum is non-thermal in 0.5-10 keV, with a power-law photon index varying within 1.8-2.5. The X-ray light curve shows a plateau lasting for ∼4 days, followed by a steep decay till becoming undetectable ∼10 days after the initial detection. Based on its temporal property and constraints from previous EP observations, an unusual timescale in the range of 7-23 days is found for EP240408a, which is intermediate between the commonly found fast and long-term transients. No counterparts have been found in optical and near-infrared, with the earliest observation at 17 hours after the initial X-ray detection, suggestive of intrinsically weak emission in these bands. We demonstrate that the remarkable properties of EP240408a are inconsistent with any of the transient types known so far, by comparison with, in particular, jetted tidal disruption events, gamma-ray bursts, X-ray binaries and fast blue optical transients. The nature of EP240408a thus remains an enigma. We suggest that EP240408a may represent a new type of transients with intermediate timescales of the order of ∼10 days. The detection and follow-ups of more of such objects are essential for revealing their origin. © 2024, CC BY-NC-ND.

关键词： Infrared devices

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