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Unveiling strain-enhanced moiréexciton localization in twisted van der Waals homostructures

Nano Research 2024年第4期17卷 3245-3252页

作者： Henry Rui He Haihong Zheng Biao Wu Shaofei Li Junnan Ding Zongwen Liu Jian-Tao Wang Anlian Pan Yanping Liu Institute of Quantum Physics School of PhysicsCentral South UniversityChangsha 410083China State Key Laboratory of Precision Manufacturing for Extreme Service Performance Central South UniversityChangsha 410083China School of Chemical and Biomolecular Engineering The University of SydneyNSW 2006Australia beijing National Laboratory for Condensed Matter Physics Institute of PhysicsChinese Academy of SciencesBeijing 100190China College of Materials Science and Engineering Hunan UniversityChangsha 410082China State Key Laboratory of High-Performance Complex Manufacturing Central South UniversityChangsha 410083China Shenzhen Research Institute of Central South University Shenzhen 51800China

Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission ***,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light ***,the intricate interplay between strain and moirépotential remains partially ***,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiré*** low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission ***,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.

关键词： moirésuperlattices strain engineering moiréexcitons moirépotential

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Heat Leakage Numerical Investigation of a Compound Parabolic ConcentratorPulsating Heat Pipe Solar Collector

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Journal of Thermal Science 2022年第5期31卷 1318-1326页

作者： XU Rongji CHEN Jingyan ZHANG Xiaohui WANG Ruixiang XU Shuhui beijing Engineering Research Center of Sustainable Energy and Buildings Beijing University of Civil Engineering and ArchitectureBeijing100044China

As a new type of equipment for solar medium temperature utilization, the compound parabolic concentrator-pulsating heat pipe solar collector(CPC-PHPSC) uses pulsating heat pipe(PHP) as an endotherm, which can realize efficient energy conversion. The design of proper concentration ratio of compound parabolic concentrator(CPC) ensures that the incident sunlight can be concentrated on the evaporator section surface of PHP without solar tracking system. The objective of the present work is to study the influence of solar radiation intensity, air speed, material thickness(glass and insulation board) and tilt angle on the thermal performance of the new collector, which is difficult to control in the experiment. The heat leakage process and characteristics of the CPC-PHPSC were numerically studied by establishing a 3D numerical model of the collector unit. The results show that the theoretical collector efficiency of CPC-PHPSC reaches 74.5%, which is consistent with the experimental results. During operation, the heat collection performance is the best when the tilt angle is 45° and the solar radiation intensity is 1000 W/m^(2), while the excessive air speed will increase the convective heat loss. Increasing the thickness of insulation board and glass has little effect on the collector efficiency.

关键词： solar collector CPC(Compound Parabolic Concentrator) pulsating heat pipe solar irradiation intensity glass thickness

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Deformation mechanism analysis of roll forming for Q&P980 steel based on finite element simulation

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Journal of Iron and Steel Research International 2019年第11期26卷 1178-1187页

作者： Fei Han Yun Wang Li-li Niu School of Mechanical and Materials Engineering North China University of Technology.Beijing 100144China

Roll forming is a sheet metal forming process,which can form the profiles gradually to improve the formability of Q&P980 *** plastic deformation mechanism of roll forming was expounded by analysing the stress and strain distribution at the comer of a hat-type profile when the Q&P980 steel sheet passed through a series of continuous *** the plastic deformation mainly accumulated when the sheet metal was not in contact with the rolls.A simple mathematical model was derived by considering the longitudinal bending strain and the geometrical relationships of forming parameters,to analyse the longitudinal strain development in the deformation *** addition,the roll forming experiments on hat-type profile parts of Q&P980 steel were carried out,and the theoretical analysis and simulation results are consistent with the experimental results.

关键词： Roll forming Numerical simulation Q&P980 steel-Deformation area

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Effect of the particle temperature on lift force of nanoparticle in a shear rarefied flow

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Chinese Physics B 2021年第7期30卷 324-331页

作者： Jun-Jie Su Jun Wang Guo-Dong Xia MOE Key Laboratory of Enhanced Heat Transfer and Energy Conservation Beijing Key Laboratory of Heat Transfer and Energy ConversionBeijing University of TechnologyBeijing 100124China

The nanoparticles suspended in a shear flow are subjected to a shear lift force,which is of great importance for the nanoparticle *** previous theoretical analysis on the shear lift,it is usually assumed that the particle temperature is equal to the temperature of the surrounding gas ***,in some particular applications,the particle temperature can significantly differ from the gas *** the present study,the effect of particle temperature on the shear lift of nanoparticles is investigated and the corresponding formulas of shear lift force are derived based on the gas kinetic *** extremely small nanoparticles(with radius R20 nm),the influence of the particle temperature can be *** the intermediate particle size,the relative error induced by the equal gas–particle temperature can be *** findings can bring an insight into accurate evaluation of the nanoparticle transport properties.

关键词： shear lift force nanoparticle temperature effect gas kinetic theory

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Omnidirectional Antenna Diversity System for High-Speed Onboard Communication

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Engineering 2022年第4期8卷 72-79页

作者： Yongjian Zhang Yue Li Weiquan Zhang Zhijun Zhang Zhenghe Feng Department of Electronic Engineering Tsinghua UniversityBeijing 100084China beijing National Research Center for Information Science and Technology Tsinghua UniversityBeijing 100084China

In this article,an omnidirectional dual-polarized antenna with synergetic electromagnetic and aerodynamic properties is propounded for high-speed diversity *** propounded antenna comprises a probe-fed cavity for horizontally polarized radiation and a microstrip-fed slot for vertical ***-layer metasurfaces are properly designed as artificial magnetic conductor boundaries with direct metal-mountable onboard installation and compact *** attached wedge-shaped block is utilized for windage reduction in *** propounded antenna is fabricated for design verification,and the experimental results agree well with the simulated *** vertical polarization,the operating bandwidth is in the range of 2.37–2.55 GHz,and the realized gain variation in the azimuthal radiation pattern is 3.67 decibels(dB).While an impedance bandwidth in the range of 2.45–2.47 GHz and a gain variation of 3.71 dB are also achieved for horizontal polarization.A port isolation more than 33 dB is obtained in a compact volume of 0.247λ_(0)×0.345λ_(0)×0.074λ_(0),whereλ_(0)represents the wavelength in vacuum at the center frequency,wherein the wedge-shaped block is *** propounded diversity antenna has electromagnetic and aerodynamic merits,and exhibits an excellent potential for high-speed onboard communication.

关键词： Antenna diversity system Aerodynamics Electromagnetics Omnidirectional radiation High-speed onboard communication

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Vascular dysfunction of postural tachycardia syndrome in children

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World Journal of Pediatrics 2018年第1期14卷 13-17页

作者： Wei Bai Si-Yao Chen Hong-Fang Jin Jun-Bao Du Department of Pediatrics Peking University First HospitalBeijing100034China Department of Cardiac Surgery Guangdong CardiovascularInstituteGuangdong General Hospital and GuangdongAcademy of Medical SciencesGuangzhouChina

Background Postural orthostatic tachycardia syndrome (POTS) is a form of orthostatic intolerance, and its incidence in children is approximately 6.8% (1)The pathogenesis of POTS is complex with multiple, overlapping, interacting pathophysi-ological mechanisms. Although the specific pathogenic mechanism has remained perplexing, with the discovery of various gasotransmitters and biological peptides, the vascular dysfunction has aroused overwhelming attention. Data sources On the basis of searching in a wide range of recent original literatures, we reviewed the pathogenesis of vas-cular dysfunction in children with POTS. Results The flow-mediated vasodilation of POTS patients was greater than that of healthy controls, and the vasodilator factors were increased in patients with POTS under basal condition or under a standing position, while the vasoconstriction factors were reduced. Conclusions Vascular dysfunction, as one of pathogenesis in pediatric POTS patients, affects the occurrence and develop-ment of diseases through a variety of factors.

关键词： Children Postural orthostatic tachycardia syndrome Vasodilation

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A Novel Networked Predictive Control Method for Systems with Random Communication Constraints

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Journal of Systems Science & Complexity 2021年第4期34卷 1364-1378页

作者： PANG Zhonghua BAI Chuandong LIU Guoping HAN Qinglong ZHANG Xianming Key Laboratory of Fieldbus Technology and Automation of beijing North China University of TechnologyBeijing 100144China Department of Artificial Intelligence and Automation Wuhan UniversityWuhan 430072China School of Software and Electrical Engineering Swinburne University of TechnologyMelbourneVIC 3122Australia

This paper presents a novel observer-based predictive control method for networked systems where random network-induced delays,packet disorders and packet dropouts in both feedback and forward channels are *** proposed method has three significant features:i)A concept of destination-based lumped(DBL)delay is introduced to represent the combined effects of random communication constraints in each channel;ii)in view of different natures of the random DBL delays in the feedback and forward channels,different compensation schemes are designed;and iii)it is actual control inputs rather than predicted ones that are employed to generate future control signals based on the latest system state estimate available in the *** the resulting closed-loop system,a necessary and sufficient stability condition is derived,which is less conservative and also independent of random communication constraints in both *** results are provided to demonstrate the effectiveness of the proposed method.

关键词： Networked control systems(NCSs) network-induced delay networked predictive control packet disorder packet dropout

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Two-Timescale Online Learning of Joint User Association and Resource Scheduling in Dynamic Mobile Edge Computing

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China Communications 2021年第8期18卷 316-331页

作者： Jian Zhang Qimei Cui Xuefei Zhang Xueqing Huang Xiaofeng Tao National Engineering Laboratory for Mobile Network Technologies Beijing University of Posts and TelecommunicationsBeijing 100876China Department of Computer Science New York Institute of TechnologyOld WestburyNY11568USA

For the mobile edge computing network consisting of multiple base stations and resourceconstrained user devices,network cost in terms of energy and delay will incur during task offloading from the user to the edge *** the limitations imposed on transmission capacity,computing resource,and connection capacity,the per-slot online learning algorithm is first proposed to minimize the time-averaged network *** particular,by leveraging the theories of stochastic gradient descent and minimum cost maximum flow,the user association is jointly optimized with resource scheduling in each time *** theoretical analysis proves that the proposed approach can achieve asymptotic optimality without any prior knowledge of the network ***,to alleviate the high network overhead incurred during user handover and task migration,a two-timescale optimization approach is proposed to avoid frequent changes in user *** user association executed on a large timescale and the resource scheduling decided on the single time slot,the asymptotic optimality is *** results verify the effectiveness of the proposed online learning algorithms.

关键词： user association resource scheduling stochastic gradient descent two-timescale optimization mobile edge computing

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Shaking table experimental study of recycled concrete frame-shear wall structures

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Earthquake Engineering and Engineering Vibration 2014年第2期13卷 257-267页

作者： Zhang Jianwei Cao Wanlin Meng Shaobin Yu Cheng Dong Hongying College of Architecture and Civil Engineering Beijing University of Technology Department of Engineering Technology University of North Texas

In this study, four 1/5 scaled shaking table tests were conducted to investigate the seismic performance of recycled concrete frame-shear wall structures with different recycled aggregates replacement rates and concealed bracing detail. The four tested structures included one normal concrete model, one recycled coarse aggregate concrete model, and two recycled coarse and fi ne aggregate concrete models with or without concealed bracings inside the shear walls. The dynamic characteristics, dynamic response and failure mode of each model were compared and analyzed. Finite element models were also developed and nonlinear time-history response analysis was conducted. The test and analysis results show that the seismic performance of the recycled coarse aggregate concrete frame-shear wall structure is slightly worse than the normal concrete structure. The seismic resistance capacity of the recycled concrete frame-shear wall structure can be greatly improved by setting up concealed bracings inside the walls. With appropriate design, the recycled coarse aggregate concrete frame-shear wall structure and recycled concrete structure with concealed bracings inside the walls can be applied in buildings.

关键词： recycled concrete frame-shear wall concealed bracings shaking table test nonlinear time-history response analysis

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Stochastic geometry based analysis for heterogeneous networks: a perspective on meta distribution

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Science China(Information Sciences) 2020年第12期63卷 230-250页

作者： Xinlei YU Qimei CUI Yuanjie WANG Na LI Xiaofeng TAO Mikko VALKAMA National Engineering Laboratory for Mobile Network Technologies Beijing University of Posts and Telecommunications National Computer Network Emergency Response Technical Team/Coordination Center of China (CNCERT/CC) Department of Electrical Engineering Tampere University

The meta distribution as a new performance metric can provide much more fine-grained information about the individual link reliability, and is of great value for the analysis and design of the future cellular networks. In this paper, we investigate the stochastic geometry based analysis for heterogeneous networks from the perspective on the meta distribution. The comprehensive overview for the fundamental framework of the meta distribution is provided, which involves the concepts of the meta distribution and its related performance metric(e.g., mean local delay and spatial outage capacity) and the efficient calculation methods of the meta distribution. The insights of the meta distribution are also stated by the comparison with standard success probability. The various applications of the meta distribution to heterogeneous networks are summarized and categorized by different types of technologies. Furthermore, some open issues and future work are discussed to promote the development and application of the meta distribution.

关键词： meta distribution stochastic geometry heterogeneous network success probability per-link reliability

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