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Chinese Physics Letters 2019年第1期36卷 10-13页

作者： mei-zhe lv Bin Xu Li-Chao Cai Feng Jia Xing-Dong Yuan School of Materials Science and Engineering Shandong University School of Materials Science and Engineering Shandong Jianzhu University

The possibilities of hexagonal boron nitride(hBN) and lithium boron nitride(Li_3BN_2) transition into cubic boron nitride(cBN) under synthetic pressure 5.0 GPa and synthetic temperature 1700 K are analyzed with the use of the empirical electron theory of solids and molecules. The relative differences in electron density are calculated for dozens of bi-phase interfaces hBN/cBN, Li_3BN_2/cBN. These relative differences of hBN/cBN are in good agreement with the first order of approximation(<10%), while those of Li_3BN_2/cBN are much greater than 10%.This analysis suggests that Li_3BN_2 is impossible to be intermediate phase but is a catalyst and cBN should be directly transformed by hBN.

关键词： Transition Mechanism Cubic Boron Valence Electron Structure Calculation

New Li-ion Battery Evaluation Research Based on Thermal Property and Heat Generation Behavior of Battery

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Chinese Journal of Chemical Physics 2012年第6期25卷 725-732,I0004页

作者： zhe lv Xun Guo Xin-ping Qiu Key Laboratory of Organic Optoelectronics and Molecular Engineering Department of ChemistryTsinghua University Be~iing 100084 China

We do a new Li-ion battery evaluation research on the effects of cell resistance and polariza- tion on the energy loss in batteries based on thermal property and heat generation behavior of battery. Series of 18650 cells with different capacities and electrode materials are evalu- ated by measuring input and output energy which change with charge-discharge time and current. Based on the results of these tests, we build a model of energy loss in cells＇ charge- discharge process, which include Joule heat and polarization heat impact factors. It was reported that Joule heat was caused by cell resistance, which included De-resistance and reaction resistance, and reaction resistance could not be easily obtained through routine test method. Using this new method, we can get the total resistance R and the polarization parameter U. The relationship between R, η, and temperature is also investigated in order to build a general model for series of different Li-ion batteries, and the research can be used in the performance evaluation, state of charge prediction and the measuring of consistency of the batteries.

关键词： Li-ion battery Energy loss Heat Cell resistance Polarization State of chargeprediction

Comparative study on flow and heat transfer characteristics of sinusoidal and zigzag channel printed circuit heat exchangers

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Science China(Technological Sciences) 2020年第4期63卷 655-667页

作者： WEN zhe-Xi lv Yi-Gao LI Qing School of Energy Science and EngineeringCentral South UniversityChangsha 410083China

Printed circuit heat exchangers(PCHEs)are promising candidates for recuperators in supercritical CO2 Brayton cycles.A comparative study is given in this paper on the flow and heat transfer characteristics of PCHEs with sinusoidal and zigzag *** mass flow rates of 0.6–1.8 kg/h and the bend angles of 15°–30°,the thermal-hydraulic performance of the PCHEs is *** show that the sinusoidal channel is superior to the zigzag channel in its comprehensive *** bend angles result in greater reductions in pressure drop if sinusoidal channels are used instead of zigzag channels and a maximum of 48.4%reduction can be obtained in the considered working ***,the inlet sections should be carefully optimized since these sections account for up to 31%and 17%of the total pressure drop in the sinusoidal and zigzag channels,*** corner shape of the zigzag channel can be specially designed to further reduce the pressure *** nonuniform density and heat flux distributions in both channels are found to be related to the periodic changes of flow directions and the centrifugal forces should not be ignored when optimizing the sinusoidal and zigzag channels.

关键词： printed circuit heat exchanger supercritical CO2 thermal-hydraulic performance sinusoidal channel numerical simulation

Index-free triangle-based graph local clustering

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Frontiers of Computer Science 2024年第3期18卷 143-153页

作者： zhe YUAN zhewei WEI Fangrui lv Ji-Rong WEN The Country and Area Studies Academy Beijing Foreign Studies UniversityBeijing 100089China Gaoling School of Artificial Intelligence Renmin University of ChinaBeijing 100872China

Motif-based graph local clustering(MGLC)is a popular method for graph mining tasks due to its various ***,the traditional two-phase approach of precomputing motif weights before performing local clustering loses locality and is impractical for large *** some attempts have been made to address the efficiency bottleneck,there is still no applicable algorithm for large scale graphs with billions of *** this paper,we propose a purely local and index-free method called Index-free Triangle-based Graph Local Clustering(TGLC^(*))to solve the MGLC problem w.r.t.a ***^(*)directly estimates the Personalized PageRank(PPR)vector using random walks with the desired triangleweighted distribution and proposes the clustering result using a standard sweep *** demonstrate TGLC^(*)’s scalability through theoretical analysis and its practical benefits through a novel visualization ***^(*)is the first algorithm to solve the MGLC problem without precomputing the motif *** experiments on seven real-world large-scale datasets show that TGLC^(*)is applicable and scalable for large graphs.

关键词： graph local clustering triangle motif index-free sampling method visualization

Estimation of solid concentration in solid-liquid two-phase flow in horizontal pipeline using inverse-problem approach

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Particuology 2022年第3期20卷 1-13页

作者： Ji Zhang Han Yuan Ning mei zhe Yan Marine Engineering College of EngineeringOcean University of ChinaQingdao 266100China Offshore Engineering Department of CivilEnvironmental and MiningUniversity of Western Australia35 Stirling HwyCrawleyWA 6009Australia Power Engineering and Engineering Thermophysics School of Mechanical EngineeringShanghai Jiao Tong UniversityShanghai 200240China

In this study,an inverse-problem method was applied to estimate the solid concentration in a solid-liquid two-phase *** algebraic slip mixture model was introduced to solve the forward problem of solid-liquid convective heat *** time-average conservation equations of mass,momentum,energy,as well as the volume fraction equation were computed in a computational fluid dynamics(CFD)*** solid concentration in the CFD model was controlled using an external program that included the inversion iteration,and an optimal estimation was performed via experimental *** using a fly-ash-water mixture and sand-water mixture with different solid concentrations in a horizontal pipeline were conducted to verify the accuracy of the inverse-problem *** estimated results were rectified using a method based on the relationship between the estimated results and estimation error;consequently,the accuracy of the corrected inversion results improved *** a verification through experiments,the inverse-problem method was concluded to be feasible for predicting the solid concentration,as the estimation error of the corrected results was within 7%for all experimental samples for a solid concentration of less than 50%.The inverse-problem method is expected to provide accurate predictions of the solid concentration in solid-liquid two-phase flow systems.

关键词： Solid-liquid two-phase flow Solid concentration estimation Coupling calculation Inverse heat transfer problem Algebraic slip mixture model

Characterization of aircraft emissions and air quality impacts of an international airport

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Journal of Environmental Sciences 2018年第10期30卷 198-207页

作者： Xiaowen Yang Shuiyuan Cheng Jianlei Lang Ran Xu zhe lv Key Laboratory of Beijing on Regional Air Pollution Control Beijing University of TechnologyBeijing 100124 China Collaborative Innovation Center of Electric Vehicles in Beijing Beijing 100081 China National Meteorological Center of CMA Beijing 100081 China

Beijing Capital International Airport（ZBAA） is the world＇s second busiest airport. In this study, the emissions of air pollutants from aircraft and other sources at ZBAA in 2015 were estimated using an improved method, which considered the mixing layer height calculated based on aircraft meteorological data relay（AMDAR）, instead of using the height（915 m）recommended by ICAO. The yearly emissions of NOx, CO, VOCs, SO2, and PM2.5 at the airport were 8.76 × 10^3, 4.43 × 10^3, 5.43 × 10^2, 4.80 × 10^2, and 1.49 × 10^2 ton/year, respectively. The spatial–temporal distribution of aircraft emissions was systematically analyzed to understand the emission characteristics of aircraft. The results indicated that NOxwas mainly emitted during the take-off and climb phases, accounting for 20.5% and 55.5% of the total emissions. CO and HC were mainly emitted during the taxi phase, accounting for 91.6%and 92.2% of the total emissions. Because the mixing layer height was high in summer, the emissions of aircraft were at the highest level throughout the year. Based on the detailed emissions inventory, four seasons simulation using WRF-CMAQ model was performed over the domain surrounding the airport. The results indicated that the contribution to PM2.5 was relatively high in winter; the average impact was about 1.15 μg/m3 within a radius of1 km around the airport. Meanwhile, the near surroundings and southwest areas of the airport are the most sensitive to PM2.5.

关键词： Beijing Capital International Airport Aircraft Emission inventory Air quality

Thermoelastic stress analysis of multilayered films in a micro-thermoelectric cooling device

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Acta Mechanica Sinica 2012年第6期28卷 1644-1650页

作者： Yu-mei Yang Xing-zhe Wang Wen-Jie Zhang Key Laboratory of Mechanics on Environment and Disaster in Western China The Ministry of Education of China College of Civil Engineering and Mechanics Lanzhou University

This paper presents an analytical solution for the thermoelastic stress in a typical in-plane＇s thin-film micro- thermoelectric cooling device under different operating con- ditions. The distributions of the permissible temperature fields in multilayered thin-films are analytically obtained, and the characteristics, including maximum temperature dif- ference and maximum refrigerating output of the thermo- electric device, are discussed for two operating conditions. Analytical expressions of the thermoelastic stresses in the layered thermoelectric thin-films induced by the tempera- ture difference are formulated based on the theory of mul- tilayer system. The results demonstrate that, the geometric dimension is a significant factor which remarkably affects the thermoelastic stresses. The stress distributions in layers of semiconductor thermoelements, insulating and support- ing membrane show distinctly different features. The present work may profitably guide the optimization design of high- efficiency micro-thermoelectric cooling devices.

关键词： Thermoelectric cooling device Multilayeredthin-film Thermoelastic stress - Analytical solution

On the Seidel Integral Complete Multipartite Graphs

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Acta Mathematicae Applicatae Sinica 2012年第4期28卷 705-710页

作者： Sheng-mei lv Liang WEI Hai-xing ZHAO Department of Mathematics Qinghai Nationality University Department of Mathematics Qinghai Normal University

For a simple undirected graph G, denote by λ（G） the （0, 1）-adjacency matrix of G. Let the matrix S（G） = J-I-2A（G） be its Seidel matrix, and let SG（A） = det（AI-S（G）） be its Seidel characteristic polynomial, where I is an identity matrix and J is a square matrix all of whose entries are equal to 1. If all eigenvalues of SG（λ） are integral, then the graph G is called S-integral, In this paper, our main goal is to investigate the eigenvalues of SG（A） for the complete multipartite graphs G = Kn1,n2,...,n,. A necessary and sufficient condition for the complete tripartite graphs Km,n,t and the complete multipartite graphs Km,.... m,n,...,n to be S-integral is given, respectively.

关键词： S-polynomial S-integral complete multipartite graphs

Damage behavior of tungsten fiber-reinforced copper matrix composite after high-speed impact

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Rare Metals 2014年第3期33卷 330-336页

作者： zhe Wu Chun-mei Yang Qian-Jun Liu Yan Ma College of Mechanical and Electrical Engineering Northeast Forestry University

Wf/Cu82Al10Fe4Ni4composite was fabricated by means of infiltration casting. By the microstructure observation of the composite with the aid of scanning electron microscopy（SEM） and transmission electron microscopy（TEM）, it can be found that there are（Fe, Ni）,AlFe, Al3 Ni, and Cu3 Al precipitated phases existing in the matrix alloy. By two-stage light gas gun, Wf/Cu82Al10-Fe4Ni4composite hypervelocity projectile into concrete target test with the speed of 2.2 kmás-1is finished. By microstructure observation, it can be found that the failure mode of Wf/Cu82Al10Fe4Ni4composite projectile during penetration is the rapid peeling of tungsten fibers from the projectile, which makes the projectile display good selfsharpening property. Meanwhile, it can be found that microstructure morphology change of Wf/Cu82Al10Fe4Ni4composite occurs after hypervelocity impact. The density of dislocations around the large-dimensional（Fe, Ni）,AlFe, Al3 Ni, and Cu3 Al precipitated phases in the matrix alloy rises sharply. At the same time, there are largedimensional deformed twins existing in local regions and stacking faults existing inside the twins.

关键词： Composites Microstructure Damagebehavior High-speed impact

Active flow control of S-duct by plasma synthetic jet

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Journal of zhejiang University-Science A(Applied Physics & Engineering) 2022年第8期23卷 652-668页

作者： Ru-bing LIU Xiao-yin mei Sheng-hui XUE Yu-wen LU zhe-zhe SU Qi LIN School of Aerospace Engineering Xiamen UniversityXiamen 361102China Fujian Key Laboratoryof Plasmaand Magnetic ResonanceResearch Xiamen 361102China

Flow separation and secondary flow in the S-duct of an aircraft engine cause severe pressure loss and airflow distortion at the outlet,lowering engine ***,a serial two-electrode plasma synthetic jet(PSJ)actuator array is used to actively control the flow field in the duct and improve its *** results show that the PSJ significantly increases the wall pressure recovery coefficient,suppresses flow separation,and improves the outlet pressure *** primary and secondary orders of the influencing factors are as follows:control position>jet momentum coefficient>excitation frequency>jet *** best jet control position is near the separation location,and the best jet configuration is the‘Λ’*** higher the jet momentum coefficient and excitation frequency,the better the flow *** wall pressure coefficient increases by up to 127.8%,and the outlet steady pressure distortion index decreases by 9.15%.The control mechanism is the direct energy injection into the flow boundary layer through a high-speed jet and the indirect control effect of the induced streamwise *** the one hand,the PSJ suppresses flow separation by improving the ability of the boundary layer to resist the inverse pressure *** the other hand,it reduces pressure distortion by decreasing the intensity of the secondary flow and weakening the *** study thus provides a new technology for the active control of the flow-field characteristics in an S-duct and has significance for guiding the application of synthetic jet technology in S-ducts.

关键词： S-duct Flow control Plasma synthetic jet(PSJ) Flow separation Pressure distortion