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Research on mechanical performance of longitudinal joints in segmental tunnel linings strengthened by fiber-reinforced plastic grid with polymer−cement−mortar method

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Frontiers of Structural and Civil Engineering 2024年第10期18卷 1610-1625页

作者： Xianda FENG dejun liu Yihao GUO Fei ZHONG Jianping ZUO Wei liu School of Civil Engineering and Architecture University of JinanJinan 250022China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China State Key Laboratory of Coal Resources and Safe Mining China University of Mining and TechnologyBeijing 100083China

In this study,we propose the use of a fiber-reinforced plastic grid with polymer−cement−mortar(FRP Grid-PCM)to reinforce segment joints in tunnel shield *** joints play a crucial role in determining bearing capacity but are vulnerable to deterioration during *** investigate how to enhance the flexural performance of longitudinal shield lining joints,we built eccentric short column specimens by bolting two half-corbel columns together and tested them in the *** test program comprised two control specimens and three strengthened specimens with FRP grid applied on one side,away from the axial *** tests varied two main parameters:loading eccentricity and the number of FRP grid *** conducted a detailed analysis of the failure process,bearing capacity,and bending stiffness of longitudinal joints under different ***,we developed an analytical model to predict the flexural bearing capacity of longitudinal joints upgraded with the FRP Grid-PCM method and validated it through experimental *** research demonstrates that the FRP grid effectively reduces joint opening and rotation angles while enhancing the bearing capacity of the short column,particularly with concurrent increases in loading eccentricity and the number of FRP grid ***,our findings offer a novel alternative for improving the flexural performance of longitudinal joints in shield tunnels.

关键词： longitudinal joints flexural performance eccentric short column fiber-reinforced grid experiment theoretical model

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Experimental and numerical study of coal-rock bimaterial composite bodies under triaxial compression

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International Journal of Coal Science & Technology 2021年第5期8卷 908-924页

作者： Yulong Chen Jianping Zuo dejun liu Yingjie Li Zhenbo Wang State Key Laboratory of Coal Resources and Safe Mining China University of Mining and TechnologyBeijing 100083China School of Energy and Mining Engineering China University of Mining and TechnologyBeijing 100083China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing 100083China

To accurately predict coal burst hazards and estimate the failure of coal pillars in underground coal mining systems,it is of great significance to understand the mechanical behavior of coal-rock bimaterial composite *** paper presents experimental and numerical investigations on the response of rock-coal,coal-rock,and rock-coal-rock bimaterial composite structures under triaxial *** triaxial compression experiments are conducted under confining pressures in the range of 0-20 *** resulting inside fracture networks are detected using X-ray-based computed tomography(CT).The experimentally observed data indicate that the mechanical parameters of the rock-coalrock composites are superior to those of the rock-coal and coal-rock *** compression failure,the coal-rock combination specimens are analyzed via X-ray *** results display that the failure of the coal-rock composite bodies primarily takes place within the ***,the bursting proneness is reduced by increasing confining ***,the corresponding numerical simulations of the experiments are carried out by using the particle flow *** numerical results reveal that coal is vulnerable with regard to energy storage and accumulation.

关键词： Coal-rock bimaterial composite body Triaxial compression Strength and deformation X-ray CT Numerical simulation Energy

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Low-velocity impact response and infrared radiation characteristics of thermoplastic/thermoset composites

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Chinese Journal of Aeronautics 2022年第10期35卷 365-380页

作者： Zhibin ZHAO Zhengwei YANG Wei ZHANG dejun liu Yin LI Jinshu CHEN School of Missile Engineering Rocket Force University of EngineeringXi'an 710038China School of Mechanical Engineering Xi'an Jiaotong UniversityXi'an 710049China China Aerodynamics Research and Development Center Mianyang 621000China

The low-velocity impact response and infrared radiation characteristics of composites have rarely been focused on *** study aims to investigate the low-velocity impact response and infrared radiation characteristics of the glass fiber reinforced thermoplastic polypropylene and carbon fiber reinforced thermosetting epoxy resin laminates wildly used in the aircraft *** impact tests were conducted at five energy *** parameters such as impact load,displacement,and absorbed energy were *** damage evolution and damage modes of the laminates were analyzed through active and passive thermography,ultrasonic C-scan,and optical *** results indicate that Thermosets(TS)laminates exhibit better impact resistance,while Thermoplastics(TP)laminates show higher delamination ductility,and the maximum contact force of TP laminates is much smaller than that of the TS laminates under lowvelocity impacts,but the low bending stiffness and low ductility of the TP matrix cause the difference in energy absorption level between the two not *** temperature characteristic changes of passive infrared thermography heat maps could characterize the damage mode of the *** correlation between the heat maps and the impact characteristic curves is explained;the fluctuation of the impact characteristic curves is directly related to the hot spot characteristics changes of the heat *** frequent curve fluctuations correspond to a larger and brighter hot spot on the heat map,which peaks at the maximum impact load after the impact force versus time curve fluctuation cutoff point,the maximum center displacement of the impact force versus displacement curve,and the maximum absorbed energy of the absorbed energy versus time curve.

关键词： Infrared thermography Low-velocity impact Thermoplastic composites Thermoset composites Damage characterization Failure mechanism

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Numerical Simulation of a Multi-Frequency Resistivity Logging-While-Drilling Tool Using a Highly Accurate and Adaptive Higher-Order Finite Element Method

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Advances in Applied Mathematics and Mechanics 2012年第4期4卷 439-453页

作者： Zhonghua Ma dejun liu Hui Li Xinsheng Gao College of Geophysics and Information Engineering China University of Petroleum18 Fuxue RoadChangping DistrictBeijing 102249China LandOcean Energy Services Co. LtdBeijing 100084China

A novel,highly efficient and accurate adaptive higher-order finite element method(hp-FEM)is used to simulate a multi-frequency resistivity loggingwhile-drilling(LWD)tool response in a borehole *** in this study are the vector expression of Maxwell’s equations,three kinds of boundary conditions,stability weak formulation of Maxwell’s equations,and automatic hpadaptivity *** new hp-FEM can select optimal refinement and calculation strategies based on the practical formation model and error *** experiments show that the new hp-FEM has an exponential convergence rate in terms of relative error in a user-prescribed quantity of interest against the degrees of freedom,which provides more accurate results than those obtained using the adaptive *** numerical results illustrate the high efficiency and accuracy of the method at a given LWD tool structure and parameters in different physical models,which further confirm the accuracy of the results using the Hermes library(http://***/hermes)with a multi-frequency resistivity LWD tool response in a borehole environment.

关键词： Resistivity logging-while-drilling higher-order finite element method adaptive exponential convergence numerical simulation

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Optimized design and experiment on ring mold pelletizer for producing biomass fuel pellets

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International Journal of Agricultural and Biological Engineering 2016年第3期9卷 57-66页

作者： Gao Wei Lope G Tabil Zhao Rongfei liu dejun College of Engineering Shenyang Agricultural UniversityShenyang 110866China Department of Chemical and Biological Engineering University of SaskatchewanSaskatoon S7N 5A9Canada College of Water Conservancy Shenyang Agricultural UniversityShenyang 110866China

The forming process of biomass fuel pellets using a ring mold pelletizer was analyzed,optimized,tested and evaluated in this *** effects of stress amplitude and the stress ratio on the fatigue failure of the ring mold under 4-,3-,and 2-roller designs were *** on the calculation of stress amplitude acting on the ring mold,the 4-roller design was chosen for having the smallest value of stress amplitude in this *** determining the main design parameters,a three-dimensional model of the ring mold pelletizer was established based on the Pro/Engineer software,and the model was transferred into ADAMS software through Mechanism/Pro which is a dedicated interface *** ADAMS software was used to run *** order to obtain the highest efficiency and the lowest power consumption,the optimal result was the 4-roller ***,a prototype of the ring mold pelletizer with four rollers was designed and manufactured for biomass fuel pellet *** stover biomass was used as material for experimental manufacturing of fuel *** and evaluation showed that the optimized pellet durability was 99.79%with ground corn stover particles passing a screen size of 1.97 mm,moisture content of 21.2%*** a material moisture conditioning time of 3.82 *** formed in the prototype ring mold pelletizer using corn stover had acceptable durability according to European standards.

关键词： biomass pellet ring mold pelletizer optimized design biofuel corn stover Pro/Engineer Adams pellet durability

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Presence and Antimicrobial Susceptibility of RE-cmeABC-Positive Campylobacter Isolated from Food-Producing Animals, 2014–2016

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Engineering 2020年第1期6卷 34-39页

作者： dejun liu Weiwen liu Xing Li Hong Yao Zhangqi Shen Yang Wang Jianzhong Shen Beijing Advanced Innovation Center for Food Nutrition and Human Health College of Veterinary MedicineChina Agricultural UniversityBeijing 100193China

Campylobacter spp. are the leading cause of human gastroenteritis worldwide. RE-CmeABC is a newly identified resistance-enhancing multidrug efflux pump of Campylobacter spp. (C. spp.) that confers high-level resistance to fluoroquinolones, phenicols, macrolides, and tetracyclines (TETs), all of which are critical drugs in both human and veterinary medicine. In this study, we analyzed the presence and antimicrobial susceptibility of RE-cmeABC-positive Campylobacter isolates of food-animal origin from three representative regions (Shandong, Shanghai, and Guangdong) in China over three successive years, from 2014 to 2016. A total of 1088 Campylobacter isolates (931 C. coli and 157 C. jejuni) were recovered from the RE-cmeABC screening. We detected 122 (11.2%) RE-cmeABC-positive isolates of chicken origin, including 111 (70.7%) C. jejuni and 11 (1.2%) C. coli. This multidrug efflux pump is more prevalent among C. jejuni than C. coli. The level of resistance was significantly different in 111 RE-cmeABC-positive C. jejuni versus 46 RE-cmeABC-negative C. jejuni for florfenicol, clindamycin, and erythromycin (P < 0.05), but not for ciprofloxacin (CIP), TET, and gentamicin (GEN). However, the isolates harboring RE-cmeABC could shift the minimum inhibitory concentration distribution to the higher range for CIP and TET. Pulsed-field gel electrophoresis (PFGE) analysis suggested that horizontal transmission might be involved in the dissemination of RE-cmeABC in Shanghai and Guangdong, while clonal expansion was predominant in Shandong. Three isolates shared the indiscriminate PFGE types of RE-cmeABC-positive C. jejuni isolates in Shanghai and Guangdong, and four isolates in Shanghai and Shandong. Our study suggests the possibility of a wide dissemination of RE-cmeABC in Campylobacter of food-animal origin, which would pose a significant threat to public health.

关键词： RE-cmeABC Campylobacter Ciprofloxacin Florfenicol

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Aerodynamic characteristics of a high-speed train crossing the wake of a bridge tower from moving model experiments

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Railway Engineering Science 2022年第2期30卷 221-241页

作者： Jinfeng Wu Xiaozhen Li C.S.Cai dejun liu Department of Bridge Engineering School of Civil EngineeringSouthwest Jiaotong UniversityChengduChina 610031 Department of Bridge Engineering School of TransportationSoutheast UniversityNanjingJiangsuChina Department of Civil and Environmental Engineering Louisiana State UniversityBaton RougeLA 70803USA College of Civil Engineering and Architecture Jiaxing UniversityJiaxing 314001ZhejiangChina

In a strong crosswind,the wake of a bridge tower will lead to an abrupt change of the aerodynamic forces acting on a vehicle passing through it,which may result in problems related to the transportation *** study investigates the transient aerodynamic characteristics of a high-speed train moving in a truss girder bridge and passing by a bridge tower in a wind *** scaled ratio of the train,bridge,and tower are 1:*** of various parameters such as the incoming wind speed,train speed,and yaw angle on the aerodynamic performance of the train were *** the sudden change mechanism of aerodynamic loads on the train when it crosses over the tower was further *** results show that the bridge tower has an apparent shielding effect on the train passing through it,with the influencing width being larger than the width of the *** train speed is the main factor affecting the influencing width of aerodynamic coefficients,and the mutation amplitude is mainly related to the yaw angle obtained by changing the incoming wind speed or train *** vehicle movement introduces an asymmetry of loading on the train in the process of approaching and leaving the wake of the bridge tower,which should not be neglected.

关键词： Vehicle aerodynamics Wind tunnel test Moving train Bridge tower Shielding effect Sudden change mechanism Truss bridge

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Stress corrosion behavior of 2195-T8 Al-Li alloy with an artificial pit exposed to a 30vol%HNO3 solution

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Chinese Journal of Aeronautics 2023年第2期36卷 304-315页

作者： dejun liu Gan TIAN Zhengwei YANG Guofeng JIN Wei ZHANG Yin WANG Huali WEI School of Missile Engineering Rocket Force University of EngineeringXi'an 710038China Xi'an Institute of Aerospace Composites Xi'an 710025China

This paper experimentally studied the stress corrosion behavior of 2195-T8 Al-Li alloys with prefabricated pits in 30vol%*** microstructure was observed and determined by the scanning electron microscopy and the transmission electron *** typical corrosion features,i.e.,regular or irregular corrosion pits and sub/intergranular corrosion,were investigated,and the role of stress were *** statistical results of the number and area of corrosion pits in various sizes were studied using an improved image processing *** results demonstrate that stress affects the intergranular corrosion or sub-intergranular corrosion of the alloy most,and promotes them to evolve into cracks under stress *** also plays a role in accelerating corrosion severity of certain corrosion *** number of corrosion pits with an area of 0–50μm~2 can be seen as an index to reflect the degree of ***,a corrosion phenomenon,i.e.,the pit bottom in the site with the maximum stress locally suffering from no severe corrosion,was observed and discussed.

关键词： Al-Li alloy Artificial pit Corrosion features Image processing Stress corrosion

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Encrypted optical fiber tag based on encoded fiber Bragg grating array

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International Journal of Extreme Manufacturing 2023年第3期5卷 658-665页

作者： Zhihao Cai Bozhe Li Zhiyong Bai dejun liu Kaiming Yang Bonan liu Cong Zhao Mengqiang Zou Jie Zhou Shangben Jiang Jingyi Huang Li liu Xuming Zhang Junle Qu Yiping Wang Changrui Liao Shenzhen Key Laboratory of Photonic Devices and Sensing Systems for Internet of Things Guangdong and Hong Kong Joint Research Centre for Optical Fibre SensorsState Key Laboratory of Radio Frequency Heterogeneous IntegrationShenzhen UniversityShenzhen 518060People’s Republic of China Shenzhen Key Laboratory of Ultrafast Laser Micro/Nano Manufacturing Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education/Guangdong ProvinceCollege of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060People’s Republic of China Guangdong Laboratory of Artificial Intelligence and Digital Economy(SZ) Shenzhen 518107People’s Republic of China Department of Electronic Engineering Chinese University of Hong KongHong KongPeople’s Republic of China Department of Applied Physics The Hong Kong Polytechnic UniversityHongKongPeople’sRepublic of China

Optical fibers are typically used in telecommunications services for data transmission,where the use of fiber tags is essential to distinguish between the different transmission fibers or channels and thus ensure the working functionality of the communication *** physical entity marking methods for fiber labeling are bulky,easily confused,and,most importantly,the label information can be accessed easily by all potential *** work proposes an encrypted optical fiber tag based on an encoded fiber Bragg grating(FBG)array that is fabricated using a point-by-point femtosecond laser pulse chain inscription *** with different resonant wavelengths and reflectivities are realized by adjusting the grating period and the refractive index *** is demonstrated that a binary data sequence carried by a fiber tag can be inscribed into the fiber core in the form of an FBG array,and the tag data can be encrypted through appropriate design of the spatial distributions of the FBGs with various reflection wavelengths and *** proposed fiber tag technology can be used for applications in port identification,encrypted data storage,and transmission in fiber networks.

关键词： fiber Bragg grating femtosecond laser micromachining encrypted information optical fiber tag

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Microstructured Cantilever Probe on Optical Fiber Tip for Microforce Sensor

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Photonic Sensors 2024年第2期14卷 89-99页

作者： Famei WANG Changrui LIAO Mengqiang ZOU dejun liu Haoqiang HUANG Chao liu Yiping WANG Shenzhen Key Laboratory of Ultrafast Laser Micro/Nano Manufacturing Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education/Guangdong ProvinceCollege of Physics and Optoelectronic EngineeringShenzhen UniversityShenzhen 518060China Shenzhen Key Laboratory of Photonic Devices and Sensing Systems for Internet of Things Guangdong and Hong Kong Joint Research Centre for Optical Fibre SensorsState Key Laboratory of Radio Frequency Heterogeneous IntegrationShenzhen UniversityShenzhen 518060China School of Electronics Science Northeast Petroleum UniversityDaqing 163318China

Benefiting from the great advances of the femtosecond laser two-photon polymerization(TPP)technology,customized microcantilever probes can be accurately 3-dimensional(3D)manufactured at the nanoscale size and thus have exhibited considerable potentials in the fields of microforce,micro-vibration,and microforce *** this work,a controllable microstructured cantilever probe on an optical fiber tip for microforce detection is demonstrated both theoretically and *** static performances of the probe are firstly investigated based on the finite element method(FEM),which provides the basis for the structural *** proposed cantilever probe is then 3D printed by means of the TPP *** experimental results show that the elastic constant k of the proposed cantilever probe can be actively tuned from 2.46N/m to 62.35N/*** force sensitivity is 2.5nm/μN,the Q-factor is 368.93,and the detection limit is ***,the mechanical properties of the cantilever probe can be flexibly adjusted by the geometric configuration of the ***,it has an enormous potential for matching the mechanical properties of biological samples in the direct contact mode.

关键词： Optical fiber sensor microforce sensing microstructured cantilever two-photon polymerization

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