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Large eddy simulation of flow over a three-dimensional hill with different slope angles

Frontiers of Earth Science 2024年第1期18卷 98-111页

作者： liang LI Deqian ZHENG Guixiang chen Pingzhi fang Wenyong MA Shengming TANG School of Civil Engineering Henan University of TechnologyZhengzhou 450001China Henan International Joint Laboratory of Modern Green Ecological Storage System Zhengzhou 450001China Henan Key Laboratory of Grain Storage Facility and Safety Zhengzhou 450001China Shanghai Typhoon Institute of China Meteorological Administration Shanghai 200030China Wind Engineering Research Center Shijiazhuang Tiedao UniversityShijiazhuang 050043China

Slope variation will significantly affect the characteristics of the wind field around a *** paper conducts a large-eddy simulation(LES)on an ideal 3D hill to study the impact of slope on wind field *** slopes ranging from 10°to 45°at 5°intervals are considered,which covers most conventional hill *** inflow turbulence for the LES is generated by adopting a modified generation method that combines the equilibrium boundary conditions with the Fluent inherent vortex method to improve the simulation *** time-averaged flow field and the instantaneous vortex structure under the eight slopes are comparatively *** accuracy of the present method is verified by comparison with experimental *** slope can affect both the mean and fluctuating wind flow fields around the 3D hill,especially on the hilltop and the leeward side,where a critical slope of 25°can be *** fluctuating wind speeds at the tops of steep hills(with slope angles beyond 25°)decrease with increasing slope,while the opposite phenomenon occurs on gentle *** increasing slope,the energy of the high-speed descending airflow is enhanced and pushes the separated flow closer to the hill surface,resulting in increased wind speed near the wall boundary on the leeward side and inhibiting the development of *** vortex shedding trajectory in the wake region becomes wider and longer,suppressing the growth of the mean wind near the wall boundary and enhancing the turbulence intensity.

关键词： large eddy simulation inflow turbulence topographic wind field critical slope flow mechanism

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Quasi-two dimensional Ruddlesden−Popper halide perovskites for laser applications

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Frontiers of physics 2024年第2期19卷 53-71页

作者： Kun chen Qianpeng Zhang Yin liang Jiepeng Song Chun Li Shi chen fang Li Qing Zhang School of Mechanical and Electrical Engineering Wuhan Institute of TechnologyWuhan 430205China School of Materials Science and Engineering Peking UniversityBeijing 100871China Institute of Applied Physics and Materials Engineering Macao UniversityMacao 999078China

Quasi-two-dimensional(2D)Ruddlesden‒Popper(RP)halide perovskites,as a kind of emerged two-dimensional layered materials,have recently achieved great attentions in lasing materials field owing to their large exciton binding energy,high emission yield,large optical gain,and wide-range tuning of optical *** review will introduce research progresses of RP halide perovskites for lasing applications in aspects of materials,photophysics,and devices with emphasis on emission and lasing properties tailored by the molecular composition and *** materials,structures and fabrications are introduced in the first ***,the optical transitions and amplified spontaneous emission properties are discussed from the aspects of electronic structure,exciton,gain dynamics,and interface ***,the research progresses on lasing devices are summarized and several types of lasers including VCSEL,DFB lasers,microlasers,random lasers,plasmonic lasers,and polariton lasers are *** last,the challenges and perspectives would be provided.

关键词： two-dimensional materials metal halide perovskite Ruddlesden−Popper halide perovskites lasing emission

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Non-interactive SM2 threshold signature scheme with identifiable abort

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Frontiers of Computer Science 2024年第1期18卷 171-185页

作者： Huiqiang liang Jianhua chen School of Mathematics and Statistics Wuhan UniversityWuhan 430072China

A threshold signature is a special digital signature in which the N-signer share the private key x and can construct a valid signature for any subset of the included t-signer,but less than t-signer cannot obtain any *** the breakthrough achievements of threshold ECDSA signature and threshold Schnorr signature,the existing threshold SM2 signature is still limited to two parties or based on the honest majority setting,there is no more effective solution for the multiparty *** make the SM2 signature have more flexible application scenarios,promote the application of the SM2 signature scheme in the blockchain system and secure cryptocurrency *** paper designs a non-interactive threshold SM2signature schemebasedon partially homomorphic encryption and zero-knowledge *** the last round requires the message input,so make our scheme non-interactive,and the pre-signing process takes 2 rounds of communication to complete after the key *** allow arbitrary threshold t

关键词： SM2 signature secure multi-party computation threshold signature UC-secure dishonest majority

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chen Nianzu,pioneer of medical popularization

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Journal of Traditional Chinese Medical Sciences 2024年第1期11卷 1-2页

作者： Yongxuan liang Yinghua Huang Beijing University of Chinese Medicine Beijing 100029China

chen Nianzu,also known as chen Xiuyuan and chen Shengxiu(1573—1823)was from the Mei Village,Changle Xi,Fujian *** was a distinguished traditional Chinese medicine(TCM)theorist,clinician and educator of the Qing Dynasty and the author of the Three-Character Primer of Medicine(Yi Xue San Zi Jing),Versified Currrent Formulas(Shi fang Ge Kuo),Briefly Annotated Treatise on Cold-induced Diseases(Shang Han Lun Qian Zhu),and Briefly Annotated Essentials fromthe Golden Cabinet(Jin Kui Yao Lue Qian Zhu),etc.

关键词： Province. Golden pioneer

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Multifunctional Integrated Organic-Inorganic-Metal Hybrid Aerogel for Excellent Thermal Insulation and Electromagnetic Shielding Performance

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Nano-Micro Letters 2024年第10期16卷 163-175页

作者： Zhaoqi Niu Fengjin Qu fang chen Xiaoyan Ma Beixi chen Luyao Wang Miao Xu Shumeng Wang liang Jin chengshuang Zhang Xiao Hou Ministry of Industry and Information Technology Key Laboratory of Special Function and Smart Polymer Materials Key Laboratory of Materials Physics and Chemistry of Ministry of Education for Extraordinary ConditionsNorthwestern Polytechnical UniversityXi'an 710072People's Republic of China Spallation Neutron Source Science Center Institution Dongguan 523803People's Republic of China Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049People's Republic of China China Aerospace Science and Industry Corporation Sixth Academy Hohhot 022185People's Republic of China Xi'an Aerospace Composites Research Institute Xi'an 710025People's Republic of China China Aerospace Science and Technology Corporation Beijing 100037People's Republic of China

Vehicles operating in space need to withstand extreme thermal and electromagnetic environments in light of the burgeoning of space science and *** is imperatively desired to high insulation materials with lightweight and extensive mechanical ***,a boron-silica-tantalum ternary hybrid phenolic aerogel(BSiTa-PA)with exceptional thermal stability,extensive mechanical strength,low thermal conductivity(49.6 mW m^(-1)K^(-1)),and heightened ablative resistance is prepared by an expeditious *** extremely thermal erosion,the obtained carbon aerogel demonstrates noteworthy electromagnetic interference(EMI)shielding performance with an efficiency of 31.6 dB,accompanied by notable loading property with specific modulus of 272.8 kN·m kg^(-1).This novel design concept has laid the foundation for the development of insulation materials in more complex extreme environments.

关键词： Multi-hybrid aerogel Metal-phenolic coordination Thermal insulation EMI shielding Convertibility and multifunctionality

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Enhanced hydrogen evolution performance by 3D ordered macroporous Ru-CoP@NC electrocatalysts

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Rare Metals 2024年第3期43卷 1095-1107页

作者： chen-chen Zhang Sheng Wei Li-Xian Sun Yi-fang Ouyang Fen Xu Hai-liang Chu Hong-GePan Li-Xin chen Xue-Zhang Xiao School of Material Science and Engineering Guilin University of Electronic TechnologyGuilin541004China School of Chemistry and Chemical Engineering Guangxi UniversityNanning530004China Shenzhen Institute of Advanced Technology Chinese Academy of SciencesShenzhen518055GuangdongChina Institute of Science and Technology for New Energy Xi'an Technological UniversityXi'an710021China School of Materials Science and Engineering Zhejiang UniversityHangzhou310058China

Electrocatalytic water splitting coupled with sustainable energies is identified as an environmentally friendly and renewable strategy to generate high-quality hydrogen for the fuel ***,the main challenge is to develop high performance,low cost and chemically stable electrocatalysts to decline the energy barriers and enhance the sluggish kinetics of hydrogen evolution reaction(HER).Herein,a three-dimensional hierarchically ordered macroporous Ru-CoP@NC electrocatalyst(3DOM Ru-CoP@NC)derived from ordered macro-microporous metal-organic frameworks has been prepared using the precursor@template and double-solvent *** prepared 3DOM Ru-CoP@NC catalyst exhibits an overpotential of 15 mV(j=10 mA·cm^(-2))and a reaction Tafel slope of 38 mV·dec^(-1)in alkaline electrolyte,which are superior to commercial Pt@C ***,the overpotential and reaction Tafel slope of this catalyst in acidic media are 45 mV and 50 mV·dec^(-1),*** outstanding HER activities of 3DOM Ru-CoP@NC catalysts are ascribed to the 3D highly interconnectedreticular nanospaces that can increase effective reaction active *** N dope d carbon framework improves the electronic properties and ***,the strong interaction of Ru and CoP nanoparticles also boosts the HER *** results indicate that 3DOM Ru-CoP@NC catalysts with high catalytic activities have a broad application prospect in the future.

关键词： Hydrogen evolution reaction Template method 3D ordered macroporous Ru-CoP@NC

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A methodology for laser tool setters calibration and its precise mathematical model

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Chinese Journal of Aeronautics 2024年第7期37卷 564-581页

作者： Tao fang Zixi fang Ze Zhong chen Zhiyong CHANG School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Gina Cody School of Engineering and Computer Science Concordia UniversityMontrealQuebec H3G 1M8Canada Changsha Optimum CNC Corporation Changsha 410221China Institute for Aero-engine Smart Assembly of Shaanxi Province Xi’an 710072China

On-machine tool setting is a pivotal approach in achieving intelligent manufacturing,and laser tool setters have become a crucial component of smart machine *** tool setters play a crucial role in precisely measuring the dimensions of cutting tools during the part machining process,focusing on tool length and *** a measuring instrument,the positions of the laser axis of the laser tool setter need to be accurately calibrated before ***,in actual calibration scenarios,traditional calibration methods face challenges due to installation errors in the tool setter and geometric errors in the measuring *** address this issue,this study proposes a novel calibration ***,the calibration mechanism of the laser beam axis is *** on the accurate mathematical model of the laser beam and the measuring rod,and using the polygon clipping algorithm,the mathematical mechanism of the laser tool setter’s work is ***,a novel method is introduced to calculate the compensation distance between the laser beam reference point and the rod bottom center point at each moment during ***,by utilizing the kinematic chain of the tool setter calibration system,a new calibration method is developed to accurately calibrate the position of the laser beam axis in the machine tool coordinate ***,the accuracy of the calibration method is verified through simulation experiments and calibration *** method improves the calibration accuracy of the tool setter,and the mathematical model of the laser tool setter can be extended to the measurement of tools,thereby improving the precision of tool *** research significantly improves the efficient production performance of smart machine tools.

关键词： On-machine tool setting Smart machine tools Mathematical model Calibration method Laser tool sette

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AFM probe for measuring~10^(−5)ultra-low friction coefficient:Design and application

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Friction 2024年第1期12卷 64-73页

作者： Yushan chen liang JIANG Linmao QIAN Tribology Research Institute State Key Laboratory of Traction PowerSouthwest Jiaotong UniversityChengdu 610031China

Superlubricity provides a novel approach to addressing friction and wear issues in mechanical ***,little is known regarding improving the atomic force microscope(AFM)friction coefficient measurement ***,this study established the theoretical formula for the AFM friction coefficient measurement and deduced the measurement ***,the formula was applied to the AFM probe with a rectangular cross-section *** measurement resolution is associated with the dimensional properties of the AFM probe,the mechanical properties of the cantilever material,the properties of the position-sensitive detector(PSD),and probably the anti-vibration performance of the *** is feasible to make the cantilever as short as possible and the tip as high as possible to improve the measurement *** AFM probe for measuring an ultra-low friction coefficient was designed and *** cantilever’s length,width,and thickness are 50,35,and 0.6μm,*** tip height is 23μ*** measurement resolution can reach 7.1×10^(−6) under the maximum normal ***,the AFM probe was applied to measure the superlubricity between graphene *** friction coefficient is 0.00139 under 853.08 *** work provides a promising method for measuring a~10^(−5) friction coefficient of superlubricity.

关键词： atomic force microscope(AFM) superlubricity friction coefficientμ probe

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Big Theta Equals Small Theta Generically

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Acta Mathematica Sinica,English Series 2024年第3期40卷 717-730页

作者： Rui chen Jia liang ZOU Institute for Advanced Study in Mathmatics Zhejiang UniversityHangzhou 310058P.R.China Department of Mathematics University of Michigan530 Church StAnn ArborMI 48109USA

In this paper we consider the theta correspondence over a non-Archimedean local *** the homological method and the theory of derivatives,we show that under a mild condition the bigtheta lift is irreducible.

关键词： Theta correspondence derivatives

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Heat Transfer Characteristics of a Microchannel Heat Sink with Highly-Dense Micro-Jet Arrays

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Journal of Thermal Science 2024年第3期33卷 1148-1160页

作者： ZHANG Yu chen Xiaoyan MIAO Lin chen liang HOU Yu State Key Laboratory of Multiphase Flow in Power Engineering Xi’an Jiaotong UniversityXi’an710049China Beijing Aerospace Technology Institute Beijing100083China

This paper proposed a new structure of highly-dense micro-jet arrays for hybrid jet-impingement/microchannel heat sinks(~120 jet per cm^(2) with jet width of 0.35 mm).Parametric study is performed to investigate the influence of structure and flow parameters on the convective heat transfer of water jet cooling in confined *** simulation results show that the optimal jet width,jet spacing and impingement distance are around 0.2 mm,0.2 mm and 0.3 mm,respectively,which can achieve a low thermal resistance as well as a relatively low pressure *** analysis of the heat transfer pathways shows that the micro-fin jet structures can extend the impinging heat transfer area and conduct a considerable proportion of heat,which can reach up to 38.9%with the Reynolds number ranging from 797.1 to *** heat transfer characteristics in the heat sink will shift from impingement dominated heat transfer to the channel-convection dominated heat transfer as the jet impingement distance increases.A correlation is proposed to predict the average Nusselt number on the stagnation area for the heat sink with different structure parameters,and the deviations of predictions from the numerical results are less than 10%.

关键词： hybrid heat sink impingement microchannel thermal management high heat flux

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