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Gas-kinetic numerical method for solving mesoscopic velocity distribution function equation

Acta Mechanica Sinica 2007年第2期23卷 121-132页

作者： zhihui li Hanxin Zhang National Laboratory for Computational Fluid Dynamics Beijing 100083 China Hypervelocity Aerodynamics Institute.Mianyang 621000 China

A gas-kinetic numerical method for directly solving the mesoscopic velocity distribution function equation is presented and applied to the study of three-dimensional complex flows and micro-channel flows covering various flow regimes. The unified velocity distribution function equation describing gas transport phenomena from rarefied transition to continuum flow regimes can be presented on the basis of the kinetic Boltzmann-Shakhov model equation. The gas-kinetic finite-difference schemes for the velocity distribution function are constructed by developing a discrete velocity ordinate method of gas kinetic theory and an unsteady time-splitting technique from computational fluid dynamics. Gas-kinetic boundary conditions and numerical modeling can be established by directly manipulating on the mesoscopic velocity distribution function. A new Gauss-type discrete velocity numerical integra- tion method can be developed and adopted to attack complex flows with different Mach numbers. HPF paral- lel strategy suitable for the gas-kinetic numerical method is investigated and adopted to solve three-dimensional complex problems. High Mach number flows around three-dimensional bodies are computed preliminarilywith massive scale parallel. It is noteworthy and of practical importance that the HPF parallel algorithm for solving three-dimensional complex problems can be effectively developed to cover various flow regimes. On the other hand, the gas-kinetic numerical method is extended and used to study micro-channel gas flows including the classical Couette flow, the Poiseuillechannel flow and pressure-driven gas flows in twodimensional short micro-channels. The numerical experience shows that the gas-kinetic algorithm may be a powerful tool in the numerical simulation of microscale gas flows occuring in the Micro-Electro-Mechanical System （MEMS）.

关键词： Gas kinetic theory . Velocity distributionfunction . Boltzmann model equation .Spacecraft flows . Micro-scale gas flows

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Microstructure and properties of an Al-Zn-Mg-Cu alloy pre-stretched plate under various ageing conditions

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Rare Metals 2008年第6期27卷 652-656页

作者： DONG Xiaorui li zhihui College of Mechatromc Engineering North University of China Taiyuan 030051 China State Key Laboratory for Fabrication and Processing of Nonferrous Metals General Research Institute for Nonferrous Metals Beijing 100088 China

The microstructures after various ageing treatments and their relation to the strength, fracture toughness, and corrosion behavior of an Al-Zn-Mg-Cu alloy pre-stretched plate were investigated. The results show that retrogression and reaging （RRA） treatment led to a combination of high strength and stress corrosion cracking （SCC） resistance of the alloy. The TEM microstructure of the RRA-treated alloy is a distribution of very fine precipitates in the aluminum matrix grains, similar to that obtained under T6 condition, and the distribution of coarse η MgZn2 precipitates on the grain boundaries similar to that obtained by T7 temper. SEM observations revealed that most of the intergranular fracture characteristics were present on the fracture surface of both the T6 and RRA-treated specimens. On the contrary, the fractographs of the T7 treated specimens mainly consisted of dimple-type ductile transgranular fracture with minor intergranular cracking.

关键词： Al-Zn-Mg-Cu alloy microstructure tensile strength stress corrosion cracking fracture characteristics

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The optimal information rate for graph access structures of nine participants

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Frontiers of Computer Science 2015年第5期9卷 778-787页

作者： Yun SONG zhihui li Yongming li Ren XIN College of Mathematics and Information Science Shaanxi Normal University Xi'an 710062 China College of Computer Science Shaanxi Normal University Xi'an 710062 China School of Civil Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The information rate is an important metric of the performance of a secret-sharing scheme. In this paper we consider 272 non-isomorphic connected graph access structures with nine vertices and eight or nine edges, and either determine or bound the optimal information rate in each case. We obtain exact values for the optimal information rate for 231 cases and present a method that is able to derive information-theoretical upper bounds on the optimal information rate. Moreover, we apply some of the constructions to determine lower bounds on the information rate. Regarding information rate, we conclude with a full listing of the known optimal information rate （or bounds on the optimal information rate） for all 272 graphs access structures of nine participants.

关键词： optimal information rate perfect secret-sharingscheme entropy method graph access structure splittingconstruction L-decomposition weighted decomposition

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Residual stress with asymmetric spray quenching for thick aluminum alloy plates

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International Journal of Minerals,Metallurgy and Materials 2023年第11期30卷 2200-2211页

作者： Ning Fan zhihui li Yanan li Xiwu li Yongan Zhang Baiqing Xiong State Key Laboratory of Nonferrous Metals and Processes GRINM Group Co.Ltd.Beijing 100088China GRIMAT Engineering Institute Co. Ltd.Beijing 101407China General Research Institute for Nonferrous Metals Beijing 100088China

Solution and quenching heat treatments are generally carried out in a roller hearth furnace for large-scale thick aluminum alloy ***,the asymmetric or uneven spray water flow rate is inevitable under industrial production conditions,which leads to an asymmetric residual stress *** spray quenching treatment was conducted on self-designed spray equipment,and the residual stress along the thickness direction was measured by a layer removal method based on *** the asymmetric spray quenching condition,the subsurface stress of the high-flow rate surface was lower than that of the low-flow rate surface,and the difference between the two subsurface stresses increased with the increase in the difference in water flow *** subsurface stress underneath the surface with a water flow rate of 0.60 m^(3)/h was 15.38 MPa less than that of 0.15 m^(3)/*** simulated residual stress by finite element(FE)method of the high heat transfer coefficient(HTC)surface was less than that of the low HTC surface,which is consistent with the experimental *** FE model can be used to analyze the strain and stress evolution and predict the quenched stress magnitude and distribution.

关键词： aluminum alloy spray quenching residual stress layer removal method finite element method

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Elevated temperature endurance and creep properties of extruded 2D70 Al alloy rods

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Rare Metals 2011年第3期30卷 310-315页

作者： WANG Guojun XIONG Baiqing ZHANG Yong＇an li zhihui State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous Metals Beijing 100088 China Northeast light Alloy Co. Ltd. Harbin 150060 China

The elevated temperature performances of 2D70 Al alloy hot extrusion rods after two-stage homogenization and intensive deformation were studied by measuring the elevated temperature enduring strength and the creep ultimate strength. The fracture morphology of some selected samples after testing at different elevated temperatures was observed by scanning electron microscopy （SEM）. The results indicate that, as the test temperature increases, the elevated temperature enduring strength of 2D70 Al alloy decreases gradually. In a comparison between 150 C and 240 C, the notch enduring strength drops from 375 to 185 MPa and the smooth enduring strength drops from 337 to 130 MPa. Enduring strength is not sensitive to the notch. The notch sensitivity ratio （NSR） coefficient is in the range of 1.119 to 1.423 from 150 C to 240 C. The creep test results show that, as the test temperature increases from 150 C to 240 C, the creep ultimate strength of 2D70 Al alloy rods drops gradually from 312 to 117 MPa.

关键词： aluminum alloys high temperature properties strength of materials creep notched bar tensile testing

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Sound Source Localisation for a High-Speed Train and Its Transfer Path to Interior Noise

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Chinese Journal of Mechanical Engineering 2019年第4期32卷 168-183页

作者： Jie Zhang Xinbiao Xiao Xiaozhen Sheng zhihui li State Key Laboratory of Traction Power Southwest Jiaotong University

Noise is one of the key issues in the operation of high-speed railways, with sound source localisation and its transfer path as the two major aspects. This study investigates both the exterior and interior sound source distribution of a high-speed train and presents a method for performing the contribution analysis of airborne sound with regard to the interior noise. First, both exterior and interior sound source locations of the high-speed train are identified through in-situ measurements. Second, the sound source contribution for di erent regions of the train and the relationships between the exterior and interior noises are analysed. Third, a method for conducting the contribution analysis of airborne sound with regard to the interior noise of the high-speed train is described. Lastly, a case study on the sidewall area is carried out, and the contribution of airborne sound to the interior noise of this area is obtained. The results show that, when the high-speed train runs at 310 km/h, dominant exterior sound sources are located in the bogie and pantograph regions, while main interior sound sources are located at the sidewall and roof. The interior noise, the bogie area noise and the sound source at the middle of the coach exhibit very similar rates of increase with increasing train speed. For the selected sidewall area, structure-borne sound dominates in most of the 1/3 octave bands.

关键词： High-speed train Interior noise Sound transfer path Noise source identification Exterior noise Airborne sound

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Entropy Generation Analysis in a Mixed-Flow Compressor with Casing Treatment

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Journal of Thermal Science 2019年第5期28卷 915-928页

作者： ZHANG Qianfeng DU Juan li zhihui li Jichao ZHANG Hongwu Advanced Gas Turbine Laboratory Institute of Engineering Thermophysics Chinese Academy of Sciences Beijing 100190 China University of Chinese Academy of Sciences Beijing 100049 China

Casing treatments(CT) can effectively extend compressors flow ranges with the expense of efficiency penalty. Compressor efficiency is closely linked to loss. Only revealing the mechanisms of loss generation can design a CT with high aerodynamic performance. In the paper, a highly-loaded mixed-flow compressor with tip clearance of 0.4 mm was numerically studied at a rotational speed of 30,000 r/min to reveal the effects of axial slot casing treatment(ASCT) on the loss mechanisms in the compressor. The results showed that both isentropic efficiency and stall margin were improved significantly by the ASCT. The local entropy generation method was used to analyze the loss mechanisms and to quantify the loss distributions in the blade passage. Based on the axial distributions of entropy generation rate, for both the cases with and without ASCT, the peak entropy generation rate increased in the rotor domain and decreased in the stator domain during throttling the compressor. The peak entropy generation in rotor was mainly caused by the tip leakage flow and flow separations near the rotor leading edge for the mixed-flow compressor no matter which casing was applied. The radial distributions of entropy generation rate showed that the reduction of loss in the rotor domain from 0.4 span to the rotor casing was the major reason for the efficiency improved by ASCT. The addition of ASCT exerted two opposite effects on the losses generated in the compressor. On the one hand, the intensity of tip leakage flow was weakened by the suction effect of slots, which alleviated the mixing effect between the tip leakage flow and main flow, and thus reduced the flow losses;On the other hand, the extra losses upstream the rotor leading edge were produced due to the shear effect and to the heat transfer. The aforementioned shear effect was caused by the different velocity magnitudes and directions, and the heat transfer was caused by temperature gradient between the injected flow and the incom

关键词： numerical simulation mixed-flow compressor loss mechanism casing treatment

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Investigation on the deactivation cause of lead-zinc double oxide for the synthesis of diphenyl carbonate by transesterification

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Journal of Natural Gas Chemistry 2009年第1期18卷 104-109页

作者： zhihui li Yanji Wang Xiaoshu Ding Xinqiang Zhao School of Chemical Engineering and Technology Hebei University of Technology Tianjin 300130 China School of Energy and Environmental Engineering Hebei University of Technology Tianjin 300401 China

The deactivation cause of lead-zinc double oxide for synthesis of diphenyl carbonate （DPC） by transesterification of dimethyl carbonate （DMC） with phenol has been investigated. X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, infrared spectroscopy （IR）, thermogravimetry analysis （TG）, atomic absorption spectroscopy and elementary analysis are employed for the catalyst characterization. The results show that, the formation of Pb4O（OC6H5）6 through the reaction of phenol and lead species in the catalyst leads to the crystal phase change of active component and serious leaching of lead, which is the cause of the catalyst deactivation. In addition, the composition of the leached lead is ascertained to be a mixture of Pb4O（OC6H5）6 and PbO with the weight percentage of 62.7% and 37.3%, respectively.

关键词： lead-zinc double oxide deactivation dimethyl carbonate transesterification diphenyl carbonate organic lead

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Research on microstructure in as-cast 7A55 aluminum alloy and its evolution during homogenization

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Rare Metals 2011年第6期30卷 664-668页

作者： LV Xinyu GUO Erjun li zhihui WANG Guojun The School of Materials Science and Engineering Harbin University of Science and Technology Harbin 150080 China Northeast light alloy Co. Ltd. Harbin 150060 China State Key Laboratory of Nonferrous Metals and Processes General Research Institute for Nonferrous Metals Beijing 100088 China

The microstructure of the as-cast 7A55 aluminum alloy and its evolution during homogenization were investigated by means of optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, X-ray diffraction （XRD）, and differential scanning calorimetry （DSC） analysis. The results indicate that the microstructure of the as-cast 7A55 aluminum alloy mainly consists of the dendritic network of aluminum solid solution, Al/AIZnMgCu eutectic phases, and intermetaUic compounds MgZn2, Al2CuMg, Al7Cu2Fe, and Al23CuFe4. After homogenization at 470℃ for 48 h, Al/AlZnMgCu eutectic phases are dissolved into the matrix, and a small amount of high melting-point secondary phases were formed, which results in an increasing of the starting melting temperature of 7A55 aluminum alloy The high melting-point secondary phases were eliminated mostly when the homogenization time achieved to 72 h. Therefore, the reasonable homogenization heat treatment process for 7A55 aluminum alloy ingots was chosen as 470℃/72 h.

关键词： 7A55 aluminum alloy as-cast constituents homogenization

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Study on the challenge and influence of the built thermal environment on elderly health in rural areas:Evidence from Shandong,China

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Building Simulation 2023年第8期16卷 1345-1360页

作者： Yanxue li Yue Gu zhihui li Xiaoyi Zhang Weijun Gao Fu Xiao Innovation Institute for Sustainable Maritime Architecture Research and Technology Qingdao University of TechnologyFushun Road 11Qingdao 266033China Department of Building Environment and Energy Engineering The Hong Kong Polytechnic UniversityHong KongChina Qingdao Women and Children’s Hospital Tongfu Road 6Qingdao 266000China Faculty of Environmental Engineering The University of KitakyushuKitakyushu808-0135Japan

Elderly health is increasingly recognized as a worldwide challenge with the continuous social aging *** study aimed to investigate the thermal conditions of the elderly in rural areas of Shandong,*** thermal sensation and physiological response performances of elderly participants were examined in their own *** show a clear seasonal pattern in cardiovascular disease mortality,cold stress increases the cardiovascular disease *** coal-based stoves serve as the main source of home heating and their limited coverage of the room area gave rise to poor quality of thermal *** analysis of skin temperature for those under 65 and above did not reveal any significant difference in response to different indoor *** regression results confirm that a colder home leads to a rising value of the elderly’s systolic blood pressure,rising by more than 1 mmHg for every 1℃decrease in indoor temperature and thus posing a greater risk of cardiovascular *** systolic blood pressure value of older subjects rise more when they are exposed to decreasing indoor temperatures,possibly due to an age-related decline in their ability to maintain stability of blood *** is noteworthy that the average blood velocity of older subjects reduces less in response to decreasing indoor temperatures,indicating a weakened capacity to resist cold stress and its associated high risk of *** investigation provides evidence in favor of improving the thermal environment of the elderly and reducing their risk of cardiovascular diseases.

关键词： rural house thermal environment cardiovascular diseases physiological parameters elderly

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