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Polyvinyl alco.ol fiber cement-stabilized macadam:A review and performance evaluation

Journal of Traffic and Transportation engineering(English Edition) 2024年第3期11卷 406-423页

作者： Chaohui Wang Jikang Liu Shaochang Chen Feng Chen Zhiwei Gao School of Highway Chang'an UniversityXi'an 710064China Shaanxi Transportation Technology consulting co. Ltd.Xi'an 710068China School of Information engineering Xizang Minzu UniversityXianyang 712082China

This review evaluated research results on polyvinyl alco.ol fiber cement-stabilized macadam(PVA-FCSM)to further improve the long-term durability of road structures and promote its in-depth study and high-quality *** suitable PVA fiber technical indexes for ordinary cement-stabilized macadam(CSM)were *** difference in the mechanical properties between CSM and PVA-FCSM was *** extent to which PVA fibers enhance the durability of CSM were ***,the mechanism of enhancement of CSM by PVA fibers was ***,the performance of each type of fiber cement-stabilized macadam(FCSM)was co.pared and *** results indicated that the suggested PVA fiber length and co.tent for CSM were 12-30 mm and 0.6-1.2 kg/m^(3),*** different ages,the mean degree of improvement in the unco.fined co.pressive strength was 14%,20%,and 14%,that in the co.pressive resilience modulus was 8%,11%,and 6%,and that in the splitting strength was 29%,15%,and 22%,*** different ages,the mean degree of decreased in the dry shrinkage co.fficient was 21%,16%,and 15%and that in the temperature shrinkage co.fficient(20℃-30℃)was 23%,23%,and 18%,*** co.fficients increased with extended curing ***,at the same stress level,PVA-FCSM has a higher fatigue life co.pared to *** bridging effect,high strength,and high modulus of PVA fiber enhance the strength and anti-cracking of *** reco.mended fiber type for CSM is PVA fiber.

关键词： Highway and railway engineering PVA fiber cement-stabilized macadam Mechanical performance Durability Enhancement mechanism Performance valuation

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Observation and analysis of positive leader re-illumination in a 10 m ultra-high voltage transmission line gap under switching impulse voltages

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Plasma Science and Technology 2024年第10期26卷 93-100页

作者： Biao HUANG Xuan ZHOU She WANG Chijie ZHUANG Rong ZENG Le DENG Eliet engineering School Changsha University of Science&TechnologyChangsha 410114People’s Republic of China State Key Laboratory of Disaster Prevention&Reduction for power Grid Changsha University of Science&TechnologyChangsha 410114People’s Republic of China China International engineering consulting co. Ltd.Beijing 100048People’s Republic of China Department of Electrical engineering Tsinghua UniversityBeijing 100084People’s Republic of China

The leader propagation is one of the most important stages in long air gap *** mechanism behind leader re-illumination remains *** high humidity co.ditions(20.0–30.1 g/m^(3)),we have co.ducted experiments of long sparks in a 10 m ultra-high voltage(UHV)transmission line gap under switching impulse *** positive leaders predominantly propagate disco.tinuously,with almost no significantly co.tinuous propagation *** leader channels are intensely luminous and each elongation segment is straight,with streamers resembling the“branch type”which differs from the“diffuse type”streamers at the front of co.tinuous propagation *** distribution of the propagation velocities is highly random(3.7–18.4 cm/μs),and the average velocity(9.2 cm/μs)significantly exceeds that of co.tinuous propagation(1.5–2.0 cm/μs).Analysis suggests that the current-velocity models suitable for co.tinuous leader propagation do not align well with the experimental data in re-illumination *** on the discharge current waveforms and optical images,it is speculated that the newly elongated leader in re-illumination mode does not evolve gradually from the stem(about 1 cm)but rather evolves overall from a thermal channel much longer than stem.

关键词： long air gap discharge positive leader re-illumination disco.tinuous leader propagation

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Arc Grounding Fault Identification Using Integrated Characteristics in the power Grid

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Energy engineering 2024年第7期121卷 1883-1901页

作者： Penghui Liu Yaning Zhang Yuxing Dai Yanzhou Sun School of Electrical engineering and Automation Henan Polytechnic UniversityJiaozuo454003China Research and Development Center Guangdong Zhicheng Champion Group Co.Ltd.Dongguan523000China henan Key Laboratory of Intelligent Detection and co.trol of co.l Mine Equipment Henan Polytechnic UniversityJiaozuo454003China

Arc grounding faults occur frequently in the power grid with small resistance grounding neutral *** existing arc fault identification technology only uses the fault line signal characteristics to set the identification index,which leads to detection failure when the arc zero-off characteristic is *** solve this problem,this paper presents an arc fault identification method by utilizing integrated signal characteristics of both the fault line and sound ***,the waveform characteristics of the fault line and sound lines under an arc grounding fault are *** that,the co.vex hull,gradient product,and co.relation co.fficient index are used as the basic characteristic parameters to establish fault identification ***,the logistic regression algorithm is employed to deal with the reference samples,establish the machine discrimination model,and realize the discrimination of fault ***,simulation test results and experimental results verify the accuracy of the proposed *** co.parison analysis shows that the proposed method has higher reco.nition accuracy,especially when the arc dissipation power is smaller than 2×10^(3) W,the zero-off period is not *** co.clusion,the proposed method expands the arc fault identification theory.

关键词： Arc fault co.vex hull algorithm co.relation co.fficient fault identification gradient logistic regression

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Review on heat-to-power co.version technologies for hypersonic vehicles

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Chinese Journal of Aeronautics 2024年第5期37卷 148-179页

作者： Yinke QI Xiaofeng MA Peixue JIANG Yinhai ZHU Key Laboratory for Thermal Science and power engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Beijing Key Laboratory of co.(2)Utilization and Reduction Technology Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

Hypersonic vehicles have enormous military and eco.omic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and *** the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the *** paper provides a co.prehensive review of heat-to-power co.version technologies on hypersonic vehicles,including the indirect co.version of Brayton and Rankine cycles,direct co.version of thermoelectric materials,and co.bined *** the open Brayton cycle with hydrocarbon fuel as the working fluid,the power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few co.ponents of the ***,its work capacity is limited by the flow rate of the supplied *** closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and co.version *** Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about *** thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power *** review provides a basis for selecting and developing heat-to-power co.version technologies on hypersonic vehicles.

关键词： Hypersonic vehicles Heat-to-power co.version Brayton cycle Rankine cycle Thermoelectric materials

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Partition-based Network Equivalent Method for power System Subsynchronous Oscillation Analysis

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Journal of Modern power Systems and Clean Energy 2024年第1期12卷 313-320页

作者： Chenxuan Wang Weimin Zheng Zhen Wang Yangqing Dan Ping Ju the Department of Electrical engineering Zhejiang UniversityHangzhou 310027China the Eco.omic Research Institute of State Grid Zhejiang Electric power co. Ltd.Hangzhou 310016China the co.lege of Energy and Electrical engineering Hohai UniverstiyNanjing 211100China

Given large-scale modern power systems with pow er electronic co.verters,the numerical simulation with subsyn chronous oscillation(SSO)faces great challenges in engineering practice due to sharply enlarged modeling scale and high co. putational *** reduce the modeling scale,network parti tion and equivalent beco.es a vital technique in numerical sim *** several methods have been developed for net work equivalent,a generally accepted rule for network parti tion is still *** paper proposes that the system can be partitioned into three parts,i.e.,the internal,the middle,and the external subsystems,in which the internal subsystem co.sists of all power electronic co.ponents,the middle subsys tem includes those selected AC dynamic co.ponents with de tailed models,and the remaining co.ponents and buses co.sti tute the external *** external subsystem is further represented by an equivalent RLC network determined by the frequency dependent network equivalent(FDNE)*** the proposed method,the observability index and the electrical distance index are used to identify the interface between the middle and the external *** studies based on a modified Hydro-Quebec system are used to verify the effective ness of the proposed method.

关键词： Electrical distance network equivalent subsyn chronous oscillation observability index

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Solid Desiccant Heat Pump Fresh Air Unit using co.posite Silica Gel

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Journal of Thermal Science 2024年第4期33卷 1286-1300页

作者： YANG Tianyu GUO Defang GE Tianshu Institute of Refrigeration and Cryogenics Shanghai Jiao Tong UniversityKey Laboratory of Power Mechanical EngineeringMOE ChinaShanghai200240China Qingdao Haier A/C Electronic co. LtdQingdao266101China

The introduction of fresh air into the indoor space leads to a significant increase in co.ling or heating *** desiccant heat pump fresh air unit which can handle the latent and sensible load of fresh air efficiently have been proposed *** improve the performance of the solid desiccant heat pump fresh air unit in the fresh air handling process,in this paper,the application of co.posite silica gel in a heat pump fresh air unit was *** co.parison between silica gel co.ting(SGC)and co.posite silica gel co.ting(CSGC)shows that the adsorption rate and water uptake capacity of CSGC are more than two times higher than those of *** experimental setup for the solid desiccant heat pump fresh air unit was *** performance of SGC and CSGC was tested in the setup *** show that under summer co.ditions,co.pared with the solid desiccant heat pump fresh air unit using silica gel(SGFU),the average moisture removal and co. of the one using co.posite silica gel(CSGFU)increased by 15%and 30%,*** winter co.ditions,co.pared with SGFU,the average humidification and co. of CSGFU increased by 42%and 17%.With optimal operation co.ditions of 3 min switchover time and 40 r/s co.pressor frequency,the co. of CSGFU under summer co.ditions can reach *** also show that the CSGFU and SGFU have higher co. and dehumidification rate under higher outdoor temperature and humidity ratio.

关键词： fresh air system desiccant co.ted heat exchanger humidification dehumidification experimental co.parison

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A Numerical Study on the Effect of the Backflow Hole Position on the Performances of a Self-Priming Pump

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Fluid Dynamics & Materials Processing 2024年第5期20卷 1103-1122页

作者： Dongwei Wang Lijian Cao Weidong Wang Jiajun Hu School of Energy and power engineering Lanzhou University of TechnologyLanzhou730050China Sanlian Pump Industry co. Ltd.Ma’anshan243000China

A self-priming pump is a centrifugal pump that has the ability to prime itself. Typically, its performance dependson the co.figuration of its reflux hole. In this study, the ANSYS FLUENT software is used to investigate the effectsof three different radial positions of the reflux hole on gas-liquid two-phase distribution, pressure pulsation, andimp during self-priming. The research results indicate that: (1) The effective channel size for the reflux liquid toenter the volute varies depending on the location of the reflux hole. The effect of the impeller rotation on thereflux liquid beco.es more obvious as the setting distance of the reflux aperture decreases. (2) The position ofthe reflux hole significantly affects the gas phase mass fraction inside the impeller, resulting in a significant reductionin the time it takes for the mass fraction to exceed 80%. (3) The position of the reflux hole significantly affectsthe average pressure on each monitoring surface. (4) Placing the reflux hole at a excessively distant radial distancecan result in an excessive vertical co.ponent. (5) The self-priming performance of the pump can be improved tosome extent by placing the return hole at a small radial distance.

关键词： Self-priming pump self-priming time numerical calculation gas-liquid two-phase flow

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Analysis of the Influence of Geometrical Parameters on the Performance of a Proton Exchange Membrane Fuel Cell

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Fluid Dynamics & Materials Processing 2024年第1期20卷 219-237页

作者： Guodong Zhang Huifang Tao Da Li Kewei Chen Guoxiang Li Shuzhan Bai Ke Sun School of Energy and power engineering Shandong UniversityJinan250061China Sinotruk Jinan Special Purpose Vehicle co. Ltd.Jinan250117China

A suitable channel structure can lead to efficient gas distribution and significantly improve the power density of fuel *** this study,the influence of two channel design parameters is investigated,namely,the ratio of the channel width to the bipolar plate ridge width(i.e.,the channel ridge ratio)and the channel *** impact of these parameters is evaluated with respect to the flow pattern,the gas co.position distribution,the temperature field and the fuel cell output *** results show that a decrease in the channel ridge ratio and an increase in the channel depth can effectively make the distributions of velocity,temperature and co.centration more uniform in each channel and improve the output capability of the fuel *** increase in the channel ridge ratio and depth obviously reduces the flow resistance and improves the flow characteristics.

关键词： Hydrogen fuel cell bipolar plate flow channel multiphysics co.pling

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Cu nanowire array with designed interphases enabling high performance Si anode toward flexible lithium-ion battery

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Nano Research 2024年第3期17卷 1516-1524页

作者： Pengfei Su Ziqi Zhang Linshan Luo Zhiyong Zhang Chaofei Lan Yahui Li Shaowen Xu Shanpeng Pei Guangyang Lin Cheng Li Xiang Han Wei Huang Songyan Chen Fujian Provincial Key Laboratory of Semico.ductors and Applications Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient DevicesDepartment of PhysicsXiamen UniversityXiamen 361005China co.lege of Materials Science and engineering Nanjing Forestry UniversityNanjing 210037China Science and Technology on Analog Integrated Circuit Laboratory Chongqing 400060China Shandong Electric power engineering consulting Institute co. Ltd.Jinan 250013China

To meet the growing demand for wearable smart electronic devices,the development of flexible lithium-ion batteries(LIBs)is *** is an ideal candidate for the anode material of flexible lithium-ion batteries due to its high specific capacity,low working potential,and earth *** largest challenge in developing a flexible silico. anode is how to maintain structural integrity and ensure stable electrochemical reactions during external *** this work,we propose a novel design for fabricating co.e–shell electrodes based on a co.per nanowire(CuNW)array co.e and magnetron sputtered Si/C *** nanowire array structure has characteristics of bending under longitudinal stress and twisting under transverse stress,which helps to maintain the mechanical stability of the structure during electrode bending and *** low-temperature annealing generates a small amount of Cu3Si alloy,which enhances the co.nection strength between Si and the co.ductive network and solves the poor co.ductivity problem of Si,which is known as a semico.ductor *** unique co.figuration design of CuNW@Si@C-400℃ leads to stable long cycle performance of 1109 mAh∙g^(-1) after 1000 cycles and excellent rate performance of 500 mAh∙g^(-1) at a current density of 10 A∙g^(-1).Furthermore,the CuNW@Si@C-400℃||LiFePO_(4)(LFP)full battery demonstrates excellent flexibility,with a capacity retention of more than 96%after 100 *** study provides a promising strategy for the development of flexible lithium-ion batteries.

关键词： flexible lithium-ion battery silico. anode magnetron sputtering co.e–shell electrode Cu nanowire array

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Fault DiagnosisMethod of Energy Storage Unit of Circuit Breakers Based on EWT-ISSA-BP

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Energy engineering 2024年第7期121卷 1991-2007页

作者： Tengfei Li Wenhui Zhang Ke Mi Qingming Lin Shuangwei Zhao Jiayi Song Puneng Electric power Technology engineering Branch Shanghai Hengnengtai Enterprise Management Co.Ltd.Shanghai200437China School of Electrical engineering Sichuan UniversityChengdu610065China

Aiming at the problem of energy storage unit failure in the spring operating mechanism of low voltage circuit breakers(LVCBs).A fault diagnosis algorithm based on an improved Sparrow Search Algorithm(ISSA)optimized Backpropagation Neural Network(BPNN)is proposed to improve the operational safety of *** the 1.5kV/4000A/75kA LVCB as an *** to the current operating characteristics of the energy storage motor,fault characteristics are extracted based on Empirical Wavelet Transform(EWT).Traditional BPNN has problems such as difficulty adjusting network weights and thresholds,being sensitive to initial weights,and quickly falling into local optimal *** Sparrow Search Algorithm(SSA)with self-adjusting weight factors co.bined with bidirectional mutations is added to optimize the selection of BPNN *** results show that the ISSA-BPNN can accurately and quickly distinguish six co.ditions of motor voltage reduction:motor voltage increase,motor voltage decrease,energy storage spring stuck,transmission gear stuck,regular state and energy storage spring not *** is suitable for fault diagnosis and detection of the energy storage part of LVCB.

关键词： Low voltage circuit breakers energy storage motor current sparrow search algorithm empirical wavelet transform fault diagnosis

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