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Journal of Mountain Science 2024年第8期21卷 2844-2854页

作者： chen Wenhua XIANG tian School of Civil Engineering Beijing Jiaotong UniversityBeijing 202303China

Water freezing in rock fractures causes volumetric expansion and fracture development through frost *** study introduces a novel analytical model to investigate how uneven freezing force and surrounding rock pressure influence fracture initiation,based on mass conservation,elasticity,and water-ice phase transition principles.A model for rock fracture initiation considering freezing temperature,uneven freezing expansion,in-situ stress,and lateral pressure was proposed based on fracture *** for stress intensity factors were developed and validated using the phase field *** effects of rock elastic modulus anisotropy and critical fracture energy density on fracture initiation were also *** results show that the values of KI and KII exhibit an upward trend as the freezing temperature,uneven expansion,in-situ stress,and lateral pressure *** uneven freezing expansion has the most significant influence on KI and KII values among these *** the uneven freezing expansion coefficient increases to 0.5,the fracture initiation mode shifts from tensile fracture to shear *** the lateral pressure coefficient increases to 1,the fracture initiation mode shifts from tensile fracture to shear *** elastic modulus anisotropy causes fractures to propagate in a clockwise direction,forming a'butterfly'*** fracture energy density an isotropy causes counterclockwise deviation in propagation direction,resulting in branching paths and an'H'-shaped pattern.

关键词： Rock fractures Fracture water Uneven freezing expansion Phase field method Initiation angle Anisotropy

A modern survey method for determining live loads based on multi-source and open-access data on the Internet

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Frontiers of Structural and Civil Engineering 2024年第8期18卷 1135-1147页

作者： chi XU Jun chen Jie LI School of Civil Engineering Tongji UniversityShanghai 200092China The State Key Laboratory on Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China

Sufficient survey data are required to describe the stochastic behaviors of live ***,due to manual and on-site operation required by traditional survey methods,traditional surveys face challenges like occupant resistance,high costs,and long implementation *** study proposes a new survey method to access live load data online and *** samples are acquired from multi-source,open-access and dynamically updated data on the *** change intervals,geometrical dimensions and object quantities are obtained from transaction information,building attributes and virtual reality models on real estate websites,*** object weights are collected from commodity information on e-commerce *** integration of the aforementioned data allows for the extraction of necessary statistics to describe a live load *** proposed method is applied to a live load survey in china,covering 20040 m^(2),with around 90000 samples acquired for object weights and load *** survey results reveal that about 70%−80%of the amplitude statistics are attributable to 1/6 of the total object types.

关键词： live load online survey method data acquisition data integration

A Systematic Analysis of Early Life Exposure to the chinese Famine(1959-1961)and the Health of Older Adults-china,2008-2023

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china CDC weekly 2024年第11期6卷 203-207,I0001-I0003页

作者： chi Shen Xi chen School of Public Policy and Administration Xi’an Jiaotong UniversityXi’an CityShaanxi ProvinceChina Department of Health Policy and Management Yale School of Public HealthNew HavenCTU.S Department of Economics Yale UniversityNew HavenCTU.S

What is already known about this topic?There is mounting evidence indicating that the aging process initiates during early life stages,with in utero the individual’s environment playing a significant ***,it is crucial to comprehend the enduring effects of early life circumstances on health in old *** is added by this report?In this study,we conducted a meta-analysis to examine the effects of the chinese Famine(1959–1961)on the health of older *** also explored potential mechanisms underlying these *** are the implications for public health practice?The complex interplay between early life circumstances,multiple health-related sectors,and healthy aging necessitates a comprehensive life-course approach and strategic interventions to enhance public health in an aging society.

关键词： life aging mount

Review of the Configuration and Transient Stability of Large-scale Renewable Energy Generation through Hybrid DC Transmission

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CES Transactions on Electrical Machines and Systems 2024年第2期8卷 115-126页

作者： Xinshou tian Yongning chi Longxue Li Hongzhi Liu Institute of Energy Power Innovation North China Electric Power UniversityBeijing 102206China china Electric Power Research Institute No.15Xiaoying East RoadQingheHaidian DistrictBeijing 100192China.

Based on the complementary advantages of Line Commutated Converter(LCC)and Modular Multilevel Converter(MMC)in power grid applications,there are two types of hybrid DC system topologies:one is the parallel connection of LCC converter stations and MMC converter stations,and the other is the series connection of LCC and MMC converter stations within a single *** hybrid DC transmission system faces broad application prospects and development potential in large-scale clean energy integration across regions and the construction of a new power system dominated by new energy sources in *** paper first analyzes the system forms and topological characteristics of hybrid DC transmission,introducing the forms and topological characteristics of converter-level hybrid DC transmission systems and system-level hybrid DC transmission ***,it analyzes the operating characteristics of LCC and MMC inverter-level hybrid DC transmission systems,provides insights into the transient stability of hybrid DC transmission systems,and typical fault ride-through control ***,it summarizes the networking characteristics of the LCC-MMC series within the converter station hybrid DC transmission system,studies the transient characteristics and fault ridethrough control strategies under different fault types for the LCC-MMC series in the receiving-end converter station,and investigates the transient characteristics and fault ride-through control strategies under different fault types for the LCC-MMC series in the sending-end converter station.

关键词： Hybrid DC transmission Transient stability Configuration Control system

Transient long-range distance measurement by a Vernier spectral interferometry

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Photonics Research 2024年第6期12卷 1107-1114页

作者： LIANG XU KUN WANG chen LIU WENYING chen chi ZHANG XINLIANG ZHANG Wuhan National Laboratory for Optoelectronics Huazhong University of Science and TechnologyWuhan 430074China Optics Valley Laboratory Wuhan 430074China

Rapid and long-range distance measurements are essential in various industrial and scientific applications,and among them,the dual-comb ranging system attracts great attention due to its high ***,the tem-poral asynchronous sampling results in the tradeoff between frame rate and ranging precision,and the non-ambiguity range(NAR)is also limited by the comb cycle,which hinders the further advancement of the dual-comb ranging *** this constraint,we introduce a Vernier spectral interferometry to improve the frame rate and NAR of the ranging ***,leveraging the dispersive time-stretch technology,the dual-comb interferometry becomes spectral ***,the asynchronous time step is unlimited,and the frame rate is improved to 100 ***,dual-wavelength bands are introduced to implement a Vernier spectral interferometry,whose NAR is enlarged from 1.5 m to 1.5 ***,this fast and long-range system also demonstrated high precision,with a 22.91-nm Allan deviation over 10-ms averaging *** a result,the proposed Vernier spectral interferometry ranging system is promising for diverse applications that necessitate rapid and extensive distance measurement.

关键词： interferometry spectral system

Giant piezotronic effect in ferroelectric field effect transistor

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Nano Research 2024年第9期17卷 8465-8471页

作者： Haiming Zhang Mengshuang chi Shidai tian tian Liang Jitao Liu Xiang Zhang Lingyu Wan Zhong Lin Wang Junyi Zhai Center on Nanoenergy Research School of Physical Science&TechnologyGuangxi UniversityNanning 530004China Beijing Key Laboratory of Micro-Nano Energy and Sensor Center for High-Entropy Energy and SystemsBeijing Institute of Nanoenergy and NanosystemsChinese Academy of SciencesBeijing 101400China School of Nanoscience and Engineering University of Chinese Academy of ScienceBeijing 100049China School of Electronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Georgia Institute of Technology AtlantaGA 30332USA

The piezotronics effect utilizes a piezopotential to modulate and control current in *** materials,as a type of piezoelectric materials,possess piezoelectric coefficients that are significantly larger than those found in conventional piezoelectric ***,we propose a strain modulated ferroelectric field-effect transistor(St-FeFET)utilizing external strain instead of gate voltage to achieve ferroelectric modulation,which eliminates the need for gate *** applying a very small strain(0.01%),the St-FeFET can achieve a maximum on-off current ratio of 1250%and realizes a gauge factor(GF)of 1.19×10^(6),which is much higher than that of conventional strain *** work proposes a new method for realizing highly sensitive strain sensors and presents innovative approaches to the operation methods of ferroelectric field-effect transistors as well as potential applications for coupling of strain sensors and various devices across different fields.

关键词： ferroelectric field-effect transistors piezotronics [Pb(Mg1/3Nb2/3)O3](1-x)-[PbTiO3]x(PMN-PT) strain sensors

Protective effects of baffles with different positions,row spacings,heights on debris flow impact

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Journal of Mountain Science 2024年第7期21卷 2352-2367页

作者： SUN Xinpo chen Min BI Yuzhang ZHENG Lu CHE chi XU Ao tian Zijian JIANG Zheyuan College of Civil Engineering Sichuan University of Science and EngineeringZigong 643000China College of Resources and Environment Fujian Agriculture and Forestry UniversityFuzhou 350002China School of Civil Engineering Fuzhou UniversityFuzhou 350108China Jiangsu Key Laboratory of Urban Underground Engineering&Environmental Safety Institute of Geotechnical EngineeringSoutheast UniversityNanjing 210096China Beijing Urban Construction Science Technology Promoting Association Beijing 100055China SUSE-BZ Geoenvironmental Engineering Joint Laboratory Sichuan University of Science and EngineeringZigong 643000China

The baffle effectively slowed down debris flow velocity,reduced its kinetic energy,and significantly shortened the distance of debris flow ***,they are widely used for protection against natural hazards such as landslides and *** study,based on the threedimensional DEM(Discrete Element Method),investigated the impact of different baffle positions on debris flow *** flow velocity and kinetic energy variations were studied through single-factor *** baffle positions were preliminarily selected by analyzing the influence of the first-row baffle position on the impact force and accumulation mass of debris ***,based on the selected baffle positions and four factors influencing the effectiveness of baffle protection(baffle position(P),baffle height(h),row spacing(S_(r)),and angle of transit area(α)),an orthogonal design was employed to further explore the optimal arrangement of *** research results indicate that the use of a baffle structure could effectively slow down the motion velocity of debris flows and dissipate their *** the baffle is placed in the transit area,the impact force on the first-row baffle is greater than that when the baffle is placed in the deposition ***,when the baffle is placed in the transit area,the obstruction effect on debris flow mass is also greater than that when the baffle is placed in the deposition *** orthogonal experimental range analysis,when the impact on the first row of baffles is used as the evaluation criterion,the importance of each influencing factor is ranked asα>P>S_(r)>*** the mass of debris flow behind the baffle is regarded as the evaluation criterion,the rank is changed to P>α>S_(r)>*** experimental simulation results show that the optimal baffle arrangement is:P_(5),S_(r)=16,α=35°,h=9.

关键词： Debris flow Baffle Protective effect Discrete element

Vibration-assisted vat photopolymerization for pixelated-aliasing-free surface fabrication

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International Journal of Extreme Manufacturing 2024年第3期6卷 440-456页

作者： Han Xu Renzhi Hu Shuai chen Junhong Zhu chi Zhou Yong chen Center for Advanced Manufacturing University of Southern CaliforniaLos AngelesCA 90007United States of America Daniel J.Epstein Department of Industrial and Systems Engineering University of Southern CaliforniaLos AngelesCA 90089United States of America Department of Aerospace and Mechanical Engineering University of Southern CaliforniaLos AngelesCA 90089United States of America Department of Industrial and Systems Engineering University of BuffaloBuffaloNY 14260United States of America

Mask image projection-based vat photopolymerization(MIP-VPP)offers advantages like low cost,high resolution,and a wide material range,making it popular in industry and ***,MIP-VPP employing liquid crystal displays(LCDs)has gained traction,increasingly replacing digital micromirror devices,particularly among hobbyists and in educational settings,and is now beginning to be used in industrial ***,LCD-based MIP-VPPsuffers from pronounced pixelated aliasing arising from LCD’s discrete image pixels and itsdirect-contact configuration in MIP-VPP machines,leading to rough surfaces on the 3D-printed ***,we propose a vibration-assisted MIP-VPP method that utilizes a microscalevibration to uniformize the light intensity distribution of the LCD-based mask image on VPP’s building *** maintaining the same fabrication speed,our technique generates asmoother,non-pixelated mask image,reducing the roughness on flat surfaces and boundary segments of 3D-printed *** light intensity modeling and simulation,we derived an optimal vibration pattern for LCD mask images,subsequently validated by *** assessed the surface texture,boundary integrity,and dimensional accuracy of componentsproduced using the vibration-assisted *** notably smoother surfaces and improved boundary roughness enhance the printing quality of MIP-VPP,enabling its promisingapplications in sectors like the production of 3D-printed optical devices and others.

关键词： additive manufacturing vat photopolymerization piezo vibration sub-pixel resolution aliasing

Short-time maritime target detection based on polarization scattering characteristics

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Journal of Systems Engineering and Electronics 2024年第1期35卷 55-64页

作者： chen Shichao LUO Feng tian Min LYU Wanghan College of Computer and Information Engineering(College of Artificial Intelligence) Nanjing Tech UniversityNanjing 211816China Hangzhou Institute of Technology Xidian UniversityHangzhou 311200China

In this paper,a detection method combining Cameron decomposition based on polarization scattering characteristics in sea clutter background is ***,the Cameron decomposition is exploited to fuse the radar echoes of full polarization channels at the data *** to the artificial material structure on the surface of the target,it can be shown that the non-reciprocity of the target cell is stronger than that of the clutter ***,based on the analysis of the decomposition results,a new feature with scattering geometry characteristics in polarization domain,denoted as Cameron polarization decomposition scattering weight(CPD-SW),is extracted as the test statistic,which can achieve more detailed descriptions of the clutter scattering characteristics utilizing the difference between their scattering ***,the superiority of the proposed CPD-SW detector over traditional detectors in improving detection performance is verified by the IPIX measured dataset,which has strong stability under short-time observation in threshold detection and can also improve the separability of feature space zin anomaly detection.

关键词： sea clutter small target radar detection Cameron decomposition characteristics analysis

Design of acceleration control schedule for adaptive cycle engine based on direct simulation model

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chinese Journal of Aeronautics 2024年第6期37卷 307-318页

作者： Keran SONG Linyuan JIA Yuchun chen tian TAN School of Power and Energy Northwestern Polytechnical UniversityXi’an 710072China

To design the optimum acceleration control schedule for the Adaptive Cycle Engine(ACE)in the full flight envelope,this paper establishes a direct simulation model of the ACE transient *** this model,geometric parameters are used to replace the component state *** corresponding relationship between geometric parameters and component state parameters is determined by sensitivity *** geometric variables are controlled when the geometric adjustment speed exceeds the limit,and at the same time the corresponding component state parameters are *** gradient optimization algorism is used to optimize the ground acceleration process of ACE,and the control schedule in terms of operating point of compression components and corrected acceleration rate is used as the full-envelope acceleration control schedule based on the similarity *** acceleration control schedules of the triple-bypass mode and the double-bypass mode are designed in this *** acceleration processes under various flight conditions are simulated using the acceleration control *** with the acceleration process with the linear geometric adjustment schedule,the acceleration performance of ACE is improved by the acceleration control schedule,with the impulse of the acceleration process of the triple-bypass mode being increased by 8.7%-12.3% and the impulse of the double-bypass mode acceleration process being increased by 11.8%-14.1%.

关键词： Adaptive Cycle Engine(ACE) Direct simulation method Acceleration Control schedule Full flight envelope