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The evolution of fast electronics

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Chinese Science Bulletin 2010年第23期55卷 2479-2488页

作者： AN qi wang YanFang Fast Electronics Laboratory University of Science & Technology of China Hefei 230026 China

This paper analyzes the process from gestation to maturity of fast electronics,describes the three-level relations formed in the development of fast electronics,*** of application,technique and theory,and summarizes in brief the progresses in simulation of electromagnetic fields,high-speed parallel sampling,and research of time *** results of fast electronics in national economy and national major science projects are also introduced.

关键词：电子技术应用快速电子快电子学应用程序大肠杆菌高速并行时间抖动科技项目

Patch-based topic model for group detection

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Science China(Information Sciences) 2017年第11期60卷 235-241页

作者： Mulin CHEN qi wang Xuelong LI School of Computer Science and Center for Optical Imagery Analysis and Learning Northwestern Polytechnical University Unmanned System Research Institute Northwestern Polytechnical University Center for Optical Imagery Analysis and Learning Xi'an Institute of Optics and Precision MechanicsChinese Academy of Sciences

Pedestrians in crowd scenes tend to connect with each other and form coherent groups. In order to investigate the collective behaviors in crowds, plenty of studies have been conducted on group ***, most of the existing methods are limited to discover the underlying semantic priors of individuals. By segmenting the crowd image into patches, this paper proposes the Patch-based Topic Model(PTM) for group detection. The main contributions of this study are threefold:(1) the crowd dynamics are represented by patchlevel descriptor, which provides a macroscopic-level representation;(2) the semantic topic label of each patch are inferred by integrating the Latent Dirichlet Allocation(LDA) model and the Markov Random Fields(MRF);(3) the optimal group number is determined automatically with an intro-class distance evaluation *** results on real-world crowd videos demonstrate the superior performance of the proposed method over the state-of-the-arts.

关键词： group detection collective behavior crowd analysis latent topic

Comparison and analysis of two Coulomb friction models on the dynamic behavior of slider-crank mechanism with a revolute clearance joint

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Applied Mathematics and Mechanics(English Edition) 2018年第9期39卷 1239-1258页

作者： Xudong ZHENG Runsen ZHANG qi wang School of Aeronautic Science and Engineering Beihang University

The objective of this study is to investigate the effects of the Coulomb dry friction model versus the modified Coulomb friction model on the dynamic behavior of the slider-crank mechanism with a revolute clearance joint. The normal and tangential forces acting on the contact points between the journal and the bearing are described by using a Hertzian-based contact force model and the Coulomb friction models, *** dynamic equations of the mechanism are derived based on the Lagrange equations of the first kind and the Baumgarte stabilization method. The frictional force is solved via the linear complementarity problem(LCP) algorithm and the trial-and-error ***, three numerical examples are given to show the influence of the two Coulomb friction models on the dynamic behavior of the mechanism. Numerical results show that due to the stick friction, the slider-crank mechanism may exhibit stick-slip motion and can balance at some special positions, while the mechanism with ideal joints cannot.

关键词： revolute clearance joint slider-crank mechanism stick friction stick-slip linear complementarity problem(LCP)

MoM-based topology optimization method for planar metallic antenna design

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Acta Mechanica Sinica 2016年第6期32卷 1058-1064页

作者： Shutian Liu qi wang Renjing Gao State Key Laboratory of Structural Analysis for Industrial Equipment Dalian University of Technology

The metallic antenna design problem can be treated as a problem to find the optimal distribution of conductive material in a certain domain. Although this problem is well suited for topology optimization method, the volumetric distribution of conductive material based on 3D finite element method (FEM) has been known to cause numerical bottlenecks such as the skin depth issue, meshed 'air regions' and other numerical problems. In this paper a topology optimization method based on the method of moments (MoM) for configuration design of planar metallic antenna was proposed. The candidate structure of the planar metallic antenna was approximately considered as a resistance sheet with position-dependent impedance. In this way, the electromagnetic property of the antenna can be analyzed easily by using the MoM to solve the radiation problem of the resistance sheet in a finite domain. The topology of the antenna was depicted with the distribution of the impedance related to the design parameters or relative densities. The conductive material (metal) was assumed to have zero impedance, whereas the non-conductive material was simulated as a material with a finite but large enough impedance. The interpolation function of the impedance between conductive material and non-conductive material was taken as a tangential function. The design of planar metallic antenna was optimized for maximizing the efficiency at the target frequency. The results illustrated the effectiveness of the method.

关键词： Metallic antenna design Topology optimization Method of moments Resistance sheet Impedance boundary condition

Control of friction oscillator by Lyapunov redesign based on delayed state feedback

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Acta Mechanica Sinica 2009年第2期25卷 257-264页

作者： Zhicong Li qi wang Haiping Gao School of Science Beihang UniversityBeijing 100083 China School of Science Hebei University of Science and TechnologyShijiazhuang 050018 China

The stability and boundedness of mechanical system have been one of important research topics. In this paper ultimate boundedness of a dry friction oscillator, belonging to nonsmooth mechanical system, is investigated by proposing a controller design method. Firstly a sufficient condition of the stability for the nominal system with delayed state feedback is derived by constructing a Lyapunov-Krasovskii function. The delayed feedback gain matrix is calculated by applying linear matrix inequality method. Secondly on the basis of the delayed state feedback, a continuous function is designed by Lyapunov redesign to ensure that the solutions of the friction oscillator system are ultimately bounded under the overall control. Moreover, the ultimate bound can be adjusted in practice by choosing appropriate parameter. Accordingly friction-induced vibration or instability can be controlled effectively. Numerical results show that the pro- posed method is valid.

关键词： Time-delay Nonsmooth system Linear matrix inequality (LMI) Dry friction oscillator Ultimate boundedness

Challenges in characterization of nanoplastics in the environment

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Frontiers of Environmental Science & Engineering 2022年第1期16卷 141-143页

作者： Wen Zhang qi wang Hao Chen John A.Reif Jr.Department of Civil and Environmental EngineeringNew Jersey Institute of TechnologyNewarkNJ 07102USA Department of Chemistry and Environmental Science New Jersey Institute of TechnologyNewarkNJ 07102USA

Plastic pollution has been a legacy environment problems and more recently,the plastic particles,especially those ultrafine or small plastics particles,are widely recognized with increasing environmental and ecological *** small plastics,microplastics are intensively studied,whereas the physicochemical properties,environmental abundance,chemical states,bioavailability and toxicity toward organisms of nanoplastics are inadequately *** are substantial difficulties in separation,visualization and chemical identification of nanoplastics due to their small sizes,relatively low concentrations and interferences from coexisting substances(e.g.,dyes or natural organic matters).Moreover,detection of polymers at nanoscale is largely hampered by the detection limit or sensitivity for existing spectral techniques such as Transformed Infrared Spectroscopy(FTIR)or Raman *** article critically examined the current state of art techniques that are exclusively reported for nanoplastic characterization in environmental *** on their operation principles,potential applications and limitations of these analytical techniques are carefully analyzed.

关键词： Nanoplastics Microplastics Plastic characterization Particle separation

The risks of sulfur addition on cadmium accumulation in paddy rice under different water-management conditions

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Journal of Environmental Sciences 2022年第8期34卷 101-111页

作者： Zhe Liu qi-qi wang Si-yu Huang Ling-xuan Kong Zhong Zhuang qi wang Hua-fen Li Ya-nan Wan Beijing Key Laboratory of Farmland Soil Pollution Prevention and Remediation Key Laboratory of Plant-Soil Interactions of the Ministry of EducationCollege of Resources and Environmental SciencesChina Agricultural UniversityBeijing 100193China

Recently, the application of sulfur(S) has been recommended to control the accumulation of cadmium(Cd) in rice in contaminated paddy soil. However, the effects of exogenous S on Cd transfer in paddy rice systems under different water-management practices have not been systematically investigated. Pot experiments were performed to monitor the composition of soil pore water and the Cd accumulation in iron plaque and rice tissue were compared under different S(0 and 200 mg/kg Na_(2)SO_(4)) and water(continuous and discontinuous flooding) treatments. Sulfur application significantly increased Cd concentrations in soil pore water under discontinuous flooding conditions, but slightly reduced them under continuous flooding. Moreover, the oxidation/reduction potential(Eh) was the most critical factor that affected the Cd levels. When the Eh exceeded-42.5 mV, S became the second critical factor, and excessive S application promoted Cd dissolution. In addition, S addition elevated the Cd levels in iron plaque and reduced the Cd transfer from the iron plaque to rice roots. In rice, S addition inhibited Cd transfer from the rice roots to the straw;thus, more Cd was stored in the rice roots. Nevertheless, additional S application increased the Cd content in the rice grains by 72% under discontinuous flooding, although this effect was mitigated by continued flooding. Under simulated practical water management conditions, S addition increased the risk of Cd contamination in rice, suggesting that S application should be reconsidered as a paddy fertilization strategy.

关键词： Rice Cadmium Sulfur Water management Iron plaque Accumulation

Influence of shaped charge structure parameters on the formation of linear explosively formed projectiles

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Defence Technology（防务技术） 2022年第10期18卷 1863-1874页

作者： Tian-bao Ma Jing Liu qi wang State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China

The research of LEFP(linear explosive forming projectile)is of great value to the development of new warhead due to its excellent *** further improve the damage ability of the shaped charge warhead,a special shell overhanging structure was designed to increase the charge based on the traditional spherical charge,in which case the crushing energy of LEFP could be ***-DYNA was used to simulate different charge structures obtained by changing the number of detonation points,the length of shell platform,the radius of curvature and the thickness of *** RSM(response surface model)between the molding parameters of LEFP and the structural parameters of charge was *** on RSM model,the structure of shaped charge was optimized by using multi-objective genetic ***,the formation process of jet was analyzed by pulsed X-ray *** results show that the velocity,length-diameter ratio and specific kinetic energy of the LEFP were closely related to the structural parameters of the shaped *** the optimization of charge structure,the forming effect and penetration ability of LEPP had been significantly *** experimental data of jet velocity and length were consistent with the numerical results,which verifies the reliability of the numerical results.

关键词： LEFP Numerical simulation Shaped charge Structure optimization

Assessing the dynamics of O_(2) desorption from cobalt phthalocyanine by in situ electrochemical scanning tunneling microscopy

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Journal of Energy Chemistry 2024年第11期98卷 144-148页

作者： Yu-qi wang Yue Feng Xiang wang Dong wang CAS Key Laboratory of Molecular Nanostructure and Nanotechnology CAS Research/Education Center for Excellence in Molecular SciencesBeijing National Laboratory for Molecular Science(BNLMS)Institute of ChemistryChinese Academy of SciencesBeijing 100190China University of Chinese Academy of Sciences Beijing 100049China

We report here the in situ electrochemical scanning tunneling microscopy(ECSTM) study of cobalt phthalocyanine(CoPc)-catalyzed O_(2) evolution reaction(OER) and the dynamics of CoPc-O_(2) *** self-assembled CoPc monolayer is fabricated on Au(111) substrate and resolved by ECSTM in 0.1 M KOH *** OH^(-)adsorption on CoPc prior to OER is observed in ECSTM *** OER,the generated O_(2) adsorbed on Co Pc is observed in the CoPc *** step experiment is employed to monitor the desorption of OER-generated O_(2) from CoPc,which results in the decreasing surface coverage of CoPc-O_(2) with *** rate constant of O_(2) desorption is evaluated through data *** insights into the dynamics of Co-O_(2) dissociation at the molecular level via in situ imaging help understand the role of Co-O_(2) in oxygen reduction reaction(ORR) and OER.

关键词： Electrochemical scanning tunneling microscopy Oxygen evolution reaction Cobalt phthalocyanine