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Limit theorems for the position of a tagged particle in the stirring-exclusion process

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Frontiers of Mathematics in China 2013年第3期8卷 479-496页

作者： peng chen Fuxi zhang School of Mathematical Sciences Peking University Beijing 100871 China

Stirring-exclusion processes are exclusion processes with particles being stirred. We investigate a tagged particle among a Bernoulli product environment measure on the lattice Zd. We show the strong law of large numbers and the central limit theorem for the tagged particle. The proof of the central limit theorem is based on the method of martingale decomposition with a sector condition.

关键词： Tagged particle stirring-exclusion central limit theorem sectorcondition

Photodegradation of perfluorooctanoic acid by 185 nm vacuum ultraviolet light

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Journal of Environmental Sciences 2007年第4期19卷 387-390页

作者： chen Jing zhang peng-yi LIU Jian Department of Environmental Science and Engineering Tsinghua University Beijing 100084 China.

The photodegradation of persistent and bioaccumulative perftuorooctanoic acid （PFOA） in water by 185 nm vacuum ultraviolet （VUV） light was examined to develop an effective technology to deal with PFOA pollution. PFOA degraded very slowly under irradiation of 254 nm UV light. However, 61.7% of initial PFOA was degraded by 185 nm VUV light within 2 h, and defluorination ratio reached 17.1%. Pseudo first-order-kinetics well simulated its degradation and defluorination. Besides, fluoride ion formed in water, 4 shorter-chain perfluorinated carboxylic acids （PFCAs）, that is, perfluoroheptanoic acid, perfluorohexanoic acid, perfluoropentanoic acid, and perfluorobutanoic acid. These were identified as intermediates by LC-MS measurement. These PFCAs consecutively formed and further degraded with irradiation time. According to the mass balance calculation, no other byproducts were formed. It was proposed that PFCAs initially are decarboxylated by 185 nm light, and the radical thus formed reacts with water to form shorter-chain PFCA with one less CF2 unit.

关键词： photodegradafion perfluorooctanoic acid perfluorinated carboxylic acid vacuum ultraviolet

BPF-based reconstruction algorithm for multiple rotation-translation scan mode

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Progress in Natural Science:Materials International 2008年第2期18卷 209-216页

作者： Ming chen,Huitao zhang,peng zhang Computer Tomography Laboratory,Capital Normal University,Beijing 100037,China Computer Tomography Laboratory Capital Normal University Beijing 100037 China

In industrial CT,it is often required to inspect large objects using short line-detectors. To acquire the complete CT data for the scan-ning slice of large objects using short line-detectors,some multi-scan modes have been developed. But the existing methods reconstruct-ing an image from the data scanned by multi-scan modes have to rebin the data into fan-beam or parallel-beam form via data interpolation. The data rebinning process not only increases great computational cost,but also degrades image resolution. In this paper,we propose a backprojection-filtration (BPF)-based reconstruction algorithm for rotation-translation (RT) multi-scan mode. An impor-tant feature of the proposed algorithm is that data rebinning process is not introduced. The simulation results have verified the validity of the proposed algorithm.

关键词： Backprojection-filtration Reconstruction algorithm Multiple rotation-translation scan mode Fan-beam

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盾构管片开口解析分析方法及其应用

中国公路学报 2024年第7期37卷 189-203页

作者：陈张鹏臧延伟杨仲轩徐荣桥龚晓南王金昌刘长宝严佳佳浙江大学建筑工程学院浙江杭州310058 浙江大学平衡建筑研究中心浙江杭州310058 中国电建集团华东勘测设计研究院有限公司浙江杭州311120 公路数智养护浙江省工程研究中心浙江杭州310051

为方便隧道中人员和车辆在灾害中能就近逃生和避险,需要设置大量的地下结构联络通道,这就带来了盾构隧道管片开口问题。采用Timoshenko曲梁理论描述管片的力学行为,通过土弹簧和荷载模拟周围土体对隧道的约束和加载作用,三向弹簧模拟环... 详细信息

为方便隧道中人员和车辆在灾害中能就近逃生和避险,需要设置大量的地下结构联络通道,这就带来了盾构隧道管片开口问题。采用Timoshenko曲梁理论描述管片的力学行为,通过土弹簧和荷载模拟周围土体对隧道的约束和加载作用,三向弹簧模拟环内纵缝接头,均布剪切弹簧模拟环间接头,建立了分析模型。首先采用状态空间法,推导了不考虑开口时多环衬砌传递方程。其次引入自由边界条件,调整荷载和系统矩阵,导出了考虑开口工况和错缝拼装的多环衬砌传递方程,得到了开口工况下盾构隧道的响应。最后结合之江路联络通道工程,通过数值算例,验证所提方法的同时分析了大直径盾构隧道开口工况下开口环和邻近环的变形和内力分布规律,研究了地质条件和环间连接情况对衬砌开口的影响。结果表明:开口环位移增加而内力减小,邻近环则位移和内力都增加;周围地质条件越好,隧道受开口工况的影响越小。在实际工程中,可以通过增强环间连接的方法来减小开口工况对于衬砌受力的影响。

关键词：隧道工程盾构隧道状态空间法解析方法管片开口

Stable hydrogen isoscape in precipitation generated using data fusion for East China

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Science China Earth Sciences 2024年第9期67卷 2972-2988页

作者： Jiacheng chen Jie chen Xunchang John zhang Peiyi peng State Key Laboratory of Water Resources Engineering and Management Wuhan UniversityWuhan 430072China Hubei Key Laboratory of Water System Science for Sponge City Construction Wuhan UniversityWuhan 430072China USDA-ARS Oklahoma and Central Plains Agricultural Research Center El Reno OK 73036USA Southwest Research Institute for Hydraulic and Water Transport Engineering Chongqing Jiaotong UniversityChongqing 400016China

The stable hydrogen isotope in precipitation is an effective environmental tracer for climatic and hydrologic ***,accurate and high-precision precipitation hydrogen isoscapes are currently unavailable in *** this study,a data fusion method based on Convolutional Neural Networks(CNN)is used to fuse the hydrogen isotopic composition(δ^(2)H_(p))of observations and isotope-equipped general circulation model(iGCM)simulations.A precipitation hydrogen isoscape with a temporal resolution of monthly and a spatial resolution of 50-60 km is established for East China for the 1969-2017 *** to building the isoscape,the performance of three data fusion methods(DFMs)and two bias correction methods(BCMs)is *** results indicate that the CNN fusion method performs the best with a correlation coefficient larger than 0.90 and root mean square error smaller than 10.5‰ when using observation as a *** fusion methods based on back propagation and long short-term memory neural network perform similarly,while slightly outperforming the bias correction ***,the CNN method is used to generate the hydrogen isoscape,and the temporal and spatial distribution characteristics of the hydrogen isotope in precipitation are analyzed based on this *** generated isoscape shows similar spatial and temporal distribution characteristics to *** general,the distribution pattern of δ^(2)H_(p) is consistent with the temperature effect in northern China,and consistent with the precipitation amount effect in southern *** trend of the δ^(2)H_(p) time series is consistent with that of observed precipitation and ***,the generated isoscape effectively reproduces the observations,and has the characteristics of time continuity and relative spatial regularity,which can provide valuable data support for tracking atmospheric and hydrological processes.

关键词： Precipitation Precipitation isotope General circulation model Data fusion Dataset

Acoustic carrier signal transmission technology and its potential for in-site monitoring of sliding electrical contact used in gas-insulated switchgear/gas-insulated transmission line

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High Voltage 2024年第2期9卷 287-295页

作者： chen chen Yutong zhang Huijun Zhao Zongren peng Qingyu Wang Xi'an Jiaotong University Xi'anChina

A wireless signal transmission technology based on acoustic carrier is proposed,which overcomes the limitation of electromagnetic signal shielding and shows great potential for in-site monitoring of sliding electrical contact used in gas-insulated switchgear(GIS)/gasinsulated transmission line(GIL).Here,the state parameter of the sliding electrical contact is modulated onto the frequency domain of an ultrasound *** a mechanical wave,the ultrasonic wave is immune to electromagnetic shielding,so that it could carry the sensing signal to penetrate the metal shielding layer and transmit to the external terminals of GIS/*** principle and signal modulation process of the acoustic carrier based transmission system have been demonstrated in *** simulation and experiment have been conducted to analyse the system characteristics as well as optimise the system *** a proof-of-concept application,the in situ and on-line monitoring of the thermal rise of a slide electrical contact both in a current loading equivalent model and a prototype of GIS is *** results fit well with the physical process,and show a good measurement accuracy of 0.6%and tem-perature sensitivity of 400 Hz/℃.

关键词： electrical potential Acoustic

Study of poly-disperse aerosols deposition in turbulent flow with different Reynolds numbers

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Particuology 2024年第6期89卷 32-43页

作者： Zhichao Gao Yongzheng chen Dandi zhang peng chen Lili Tong Xuewu Cao School of Mechanical Engineering Shanghai Jiao Tong UniversityShanghai200240China China Nuclear Power Technology Research Institute Co. Ltd.Shenzhen518000China

The turbulent deposition mechanism is one of the main mechanisms of aerosol deposition in nuclear power plant *** experimental study of poly-disperse aerosol deposition in a horizontal tube is conducted,where the nominal Reynolds number(Re)is in a range of 3600–200,*** aerosol deposition velocity first increases and then decreases with the increase of Res,and at high Re,particle rebound occurs during aerosol deposition in the *** the Re is low,the aerosol deposition velocity increases with the increase of aerosol *** the Re is greater than 60,000,the deposition velocity first increases and then decreases with the increase of aerosol diameter due to particle surface rebound.A new aerosol deposition model has been developed by establishing the energy conservation equation of the rebounded particles in the viscous *** calculated results of the new model are in good agreement with these experimental results,and the error between the aerosol deposition velocity calculated by the model and experimental results is between−60%and 150%.

关键词： Aerosol Turbulent deposition Rebound High Reynolds number

Microstructure Evolution and Mechanical Properties of Friction Stir Welded Al-Cu-Li Alloy

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Acta Metallurgica Sinica(English Letters) 2024年第5期37卷 855-871页

作者： peng chen Wenhao chen Jiaxin chen Zhiyu chen Yang Tang Ge Liu Bensheng Huang Zhiqing zhang School of New Energy and Materials Southwest Petroleum UniversityChengdu 610500China Sichuan Provincial Engineering Research Center of Advanced Materials Manufacturing Technology for Shale Gas High-Efficient Exploitation Southwest Petroleum UniversityChengdu 610500China College of Materials Science and Engineering Chongqing UniversityChongqing 400045China School of Mechatronic Engineering Southwest Petroleum UniversityChengdu 610500China School of Robot Engineering Yangtze Normal UniversityChongqing 408100China

The investigation concentrates on friction stir welded(FSW)Al-Cu-Li alloy concerning its local microstructural evolution and mechanical *** grain features were characterized by electron back scattered diffraction(EBSD)technology,while precipitate characterization was conducted by using transmission electron microscopy(TEM)aligned along[011]Al and[001]Al zone *** mechanical properties are evaluated through micro-hardness and tensile *** can be found that nugget zones exhibit finely equiaxed grains evolved through complete dynamic recrystallization(DRX),primarily occurring in continuous dynamic recrystallization(CDRX)and discontinuous dynamic recrystallization(DDRX).In the thermal-mechanically affected zone(TMAZ),numerous sub-structured grains,exhibiting an elongated morphology,were created due to partial DRX,signifying the dominance of CDRX,DDRX,and geometric dynamic recrystallization(GDRX)in this region.T_(1)completely dissolves in the nugget zone(NZ)leading to the formation of Guinier-Preston zones and increase ofδ′,β′and S′.Conversely,T_(1)partially solubilizes in TMAZ,the lowest hardness zone(LHZ)and heat affected zone(HAZ),and the residual T_(1)undergoes marked coarsening,revealing various T_(1)*** solubilization and coarsening of T_(1)are primary contributors to the degradation of hardness and strength.θ′primarily dissolves and coarsens in NZ and TMAZ,whilst this precipitate largely coarsens in HAZ and LHZ.σ,TB,grain boundary phases(GBPs)and precipitate-free zone(PFZ)are newly generated during FSW.σexists in the TMAZ,LHZ and HAZ,whereas TB nucleates in *** and PFZ mostly develop in LHZ and HAZ,which can cause strain localization during tensile deformation,potentially leading to LHZ joint fracture.

关键词： Al-Cu-Li alloy Friction stir welding Microstructure evolution Mechanical properties

Risk Assessment for Hybrid AC/DC Systems Based on Transient Energy Function

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CSEE Journal of Power and Energy Systems 2024年第4期10卷 1654-1663页

作者： peng Sun Yun Teng Mingli zhang Zhe chen Shenyang University of Technology Shenyang 110870China Liaoning Electric Power Co.Ltd.Economic Research Institute Shenyang 110000China Department of Energy Technology Aalborg UniversityAalborgDK DK 9220

In order to accurately assess the risk of the hybrid AC/DC network under fault,a risk assessment method for the hybrid AC/DC system based on the transient energy function is ***,based on the energy transfer relationship of the hybrid AC/DC power system,the transient energy function model of the hybrid AC/DC system is *** on the operating data of the power grid,the energy function is used as an efficiency variable,and the efficiency variable is integrated into the prior risk probability calculation of nodes in the network,and a Bayesian network-based risk assessment model of hybrid AC/DC system is *** the dynamic update model of network cascading failures,the clique tree propagation algorithm is used to dynamically calculate the posterior risk probability of the node to realize the dynamic assessment of the network ***,the improved IEEE-39 node hybrid AC/DC system is used as an example for *** results show that the proposed model can not only effectively evaluate the overall safety of the network,but also has feasibility in predicting faults,which can provide a theoretical basis for the stability control of the hybrid AC/DC system.

关键词： Cascading failure energy function hybrid AC-DC system risk assessment