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Theoretical investigations on heat transfer to H2O/CO2 mixtures in supercritical region

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Science China(Technological Sciences) 2020年第6期63卷 1018-1024页

作者： chen LongFei LIU Dong ZHANG HanLin LI qiang MIIT Key Laboratory of Thermal Control of Electronic Equipment School of Energy and Power EngineeringNanjing University of Science and TechnologyNanjing 210094China

The supercritical H2O/CO2 mixture is the working fluid to drive a turbine in a novel power generation system with coal gasified in supercritical *** system is promising because of zero pollution emission in contrast to the conventional coal-fired power *** transfer coefficients of the supercritical H2O/CO2 mixtures are important to design heat transfer devices in this system,which is similar to the role of heat transfer to supercritical water in conventional ***,heat transfer to supercritical mixtures has received less ***,we show that the supercritical mixtures with H2O being one of the components,have similar convection heat transfer behavior to supercritical pure fluids for temperatures and pressures above the critical point of *** phenomenon was demonstrated from two ***,the forced convection heat transfer coefficients of supercritical mixtures were numerically calculated using the simulation model for supercritical pure fluids and using the thermophysical properties(density,heat capacity,thermal conductivity and viscosity)of supercritical mixtures as *** calculated results agree well with experimental data in the supercritical ***,the calculated results also agree well with the correlations for supercritical pure *** mechanisms were investigated by molecular dynamics simulations on the diffusion of supercritical *** results lay the foundation for predicting convection heat transfer coefficients of supercritical mixtures and for designing heat transfer devices with supercritical mixtures as heat transfer fluids.

关键词： supercritical fluid H2O/CO2 mixture forced convection molecular dynamics

Basic research on machinery fault diagnostics： Past, present, and future trends

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Frontiers of Mechanical Engineering 2018年第2期13卷 264-291页

作者： Xuefeng chen Shibin WANG Baijie QIAO qiang chen State Key Laboratory for Manufacturing Systems Engineering Xi'an Jiaotong University Xi'an 710049 China School of Mechanical Engineering Xi'an Jiaotong University Xi'an 710049 China

Machinery fault diagnosis has progressed over the past decades with the evolution of machineries in terms of complexity and scale. High-value machineries require condition monitoring and fault diagnosis to guarantee their designed functions and performance throughout their lifetime. Research on machinery Fault diagnostics has grown rapidly in recent years. This paper attempts to summarize and review the recent R＆D trends in the basic research field of machinery fault diagnosis in terms of four main aspects： Fault mechanism, sensor technique and signal acquisition, signal processing, and intelligent diagnostics. The review discusses the special contributions of Chinese scholars to machinery fault diagnostics. On the basis of the review of basic theory of machinery fault diagnosis and its practical applications in engineering, the paper concludes with a brief discussion on the future trends and challenges in machinery fault diagnosis.

关键词： fault diagnosis fault mechanism feature extraction signal processing intelligent diagnostics

A study on boundary integral equations for dynamic elastoplastic analysis for the plane problem by TD-BEM

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Acta Mechanica Sinica 2021年第4期37卷 662-678,I0003页

作者： Hongjun Li Weidong Lei Rui chen qiang Hu Urban and Rural Construction Institute Hebei Agricultural UniversityBaoding 071001China School of Civil and Environmental Engineering Harbin Institute of Technology(Shenzhen)Shenzhen 518055China China Academy of Railway Sciences Corporation Limited Beijing 100081.China

The equivalent stress fundamental solution for the elastoplastic dynamic plane strain problem is proposed to transform the virtual work in the third direction to the ***,based on Betti reciprocal theorem,by adopting the time dependent fundamental solutions in terms of displacement,traction and equivalent stress,the boundary integral equations for dynamic elastoplastic analysis for the plane strain problem are *** establishment procedures for the displacement and the stress boundary integral equations,together with the stress equation at boundary points,are presented in details,while the standard discretization both in time and space under the frame of time domain boundary element method(TD-BEM)and the solution of the algebraic equations are also briefly *** verification examples are presented from different viewpoints,for elastic and elastoplastic analysis,for 1-D and 2-D geometries,and for finite and infinite *** TD-BEM formulation for dynamic elastoplastic analysis is presented for the plane strain problem as an example,where the formulation is also applicable for the plane stress problem by properly transforming the elastic constants and adopting the corresponding fundamental solutions.

关键词： Time domain boundary element method Dynamic elastoplastic analysis Equivalent stress fundamental solution Boundary integral equation

A method characterizing urban expansion based on land cover map at 30 m resolution

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Science China Earth Sciences 2016年第9期59卷 1738-1744页

作者： YU Xi ZHANG BingQi LI qiang chen Jin College of Resources Science and Technology Beijing Normal University State Key Laboratory of Earth Surface Process and Resources Ecology Beijing Normal University

Based on the global land cover data at 30 m resolution(Globe Land30) in the year 2000 and 2010, the urban expansion process of 320 cities in China was analyzed using lognormal regression, and the expansion model were established. Three metrics were presented for the models, including the peak position, the full width at half maximum, and the skewness. It was found that the three metrics could reveal different patterns of the urban expansion process of cities with different sizes. Specifically, cities with larger size tend to expand outward strongly, and their expansion intensity and influence are likely to be higher. Moreover, most cities' expansion occurs around the urban core with spatially limited influence. In addition, it was also found that the city's expansion intensity is related to the city size. These results showed that the lognormal regression model could describe the distribution of urban expansion with effectiveness and robustness.

关键词： Urbanization Urban expansion Remote sensing Lognormal distribution Characteristic metrics Global land cover map

Quality measure of color images based on properties ofvision psychology and color distortion in MPEG-21

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The Journal of China Universities of Posts and Telecommunications 2007年第2期14卷 112-119页

作者： chen qiang chen He-xin SANG Ai-jun Key Laboratory of New Communication and Technology School of Communication Engineering Jilin University Changchun 130025 China

In this article, a new way to evaluate the quality of color images is proposed, in which the properties of human vision psychology, objective fidelity, edge information, and color distortion will be combined through utilizing 3-D matrix transform. There exists color redundancy and structural similarity between three different frames of a color image, the definition of vision properties will be measured by 3-D submatrix integration transform （SIT）, in which three color components are integrated into one model and color redundancy can be exploited fully. The simulation results show that the measure index is very effective and objective in accord with vision properties.

关键词： color image quality measure vision property 3-D submatrix integration transform PSNR MPEG-21

From ultra-low friction to superlubricity state of black phosphorus:Enabled by the critical oxidation and load

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Friction 2023年第10期11卷 1829-1844页

作者： qiang LI Fenghua SU Yanjun chen Jianfang SUN School of Mechanical&Automotive Engineering South China University of TechnologyGuangzhou 510641China Guangdong Provincial Key Laboratory of Technique and Equipment for Macromolecular Advanced Manufacturing South China University of TechnologyGuangzhou 510640China

Based on the density functional theory(DFT),we investigate the friction properties of inevitable oxidized black phosphorus(o-BP).o-BP with the weaker interlayer adhesion exhibits their great potential as a solid *** the zero load,the friction property of o-BP is adjusted by its oxidation ***,ultra-low friction of P4O2(50%oxidation,O:P=2:4=50%)is obtained,which is attributed to the upper O atoms with lower sliding resistance in the O channel formed by lower layer O *** attractive,we observe superlubricity behavior of o-BP at the critical load/distance due to the flattening potential energy surface(PES).The flattening PES is controlled by the electrostatic role for the high-load(P4O3,O:P=3:4=75%),and by the electrostatic and dispersion roles for the low-load(P4O2).Distinctly,the transform from ultra-low friction to superlubricity state of black phosphorus(BP)can be achieved by critical oxidation and load,which shows an important significance in engineering *** addition,negative friction behavior of o-BP is a general phenomenon(Z>Z_(min),Z_(min)is the interlayer distances between the outermost P atoms of minimum load.),while its surface-surface model is different from the fold mechanism of the tip-surface model(Z_(0)Z_(min)).In summary,o-BP improves the friction performance and reduces the application limitation,comparing to graphene(Gr),MoS2,and their oxides.

关键词： oxidized black phosphorus(o-BP) ultra-low friction superlubricity critical load/distance first-principles

Adaptive command filter constraint control of rolling mill torsional vibration under current harmonic

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Journal of Iron and Steel Research International 2023年第9期30卷 1782-1791页

作者： Shu-zong chen cheng Jia Chang-chun Hua Jia-qiang chen Institute of Electrical Engineering Yanshan UniversityQinhuangdao 066004HebeiChina

An adaptive command filter control strategy was proposed to realize the asymptotic tracking of the roll speed,which successfully suppressed torsional vibration for the main drive system of the rolling mill with nonlinear friction,nonlinear damping,current harmonic,time-varying stiffness and unknown disturbance.A finite time predetermined performance method was proposed,so that the speed tracking error of the main transmission system was always constrained in the performance function and converged to its minimum boundary within the specified *** on the adaptive estimation of harmonic amplitude,the torque control law of the motor was obtained by using the filter backstepping method,which prevented the torsional vibration of the system caused by the input fluctuation and avoided the complexity explosion of the controller design,and the stability of the closed-loop system was strictly proved by the Lyapunov *** actual numerical simulation verified the effectiveness of the proposed control strategy.

关键词： Main drive system Torsional vibration Command filter Finite time predetermined performance

Study on Quality Improvement Effect and Separate Character of Soybean Male Sterile (MS1) Recurrent Selection Population

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Agricultural Sciences in China 2007年第5期6卷 545-551页

作者： ZHAO shuang-jin ZHANG Meng-chen JIANG Chun-zhi YANG Chun-yan LIU Bing-qiang CUI Jue Institute of Food and Oil Crops Hebei Academy of Agricultural and Forestry Sciences~National Soybean Improvement Center ShijiazhuangSub-Center Shijiazhuang 050031 P.R.China

To solve the problem that soybean has narrow genetic base, we constructed a series of male sterile recurrent selection populations, and studied the effects of quality improvement and practical value. An LD-base population, which fits to our ecology type was constructed by 6 years＇ gene enrichment through the introduction of new genes from 23 local varieties and recurrent selection. The LD-base populations were then improved by making crosses with high protein and high oil genotypes. As a result we obtained a high protein sub-population （db） and a high oil sub-population （gy）, For the db sub-population, the protein content is 1.18% higher than the base population, 22.38% of the individuals contain 45% or more of protein, which is 10.99% higher than the base population. For the gy sub-population, oil content is 0.24% higher than the base population. Individuals with oil content of 20% or more are 11.05% higher than the base population. The quantitative characters such as flowering date, mature date, pod habit, and hilum color, etc., all showed wide range of separation, and the segregation ratio approached balance. The c.v. of branch number of ms1 recurrent population （72.8%） is higher than general cross-population （57.3%）, and the c.v. of 100 seed weight of ms1 （18.1%） is higher than general cross population （16.5%）, the coefficient of variation of plant height, pods per plant, and seeds per pod were not significantly different. It was demonstrated in this paper that the quality character of ms 1 male sterile recurrent selection population was improved by adding new genes. And the segregation of other characters widened, making the populations suitable for the objective of soybean breeding. In this paper, we also discussed the breeding method, key technology, and selection effect of soybean ms 1 population.

关键词： soybean recurrent selection population ms 1 gene quality improvement segregating characteristics

Functionally Graded Stainless Steel Fabricated by Direct Laser Deposition: Anisotropy of Mechanical Properties and Hardness

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Acta Metallurgica Sinica(English Letters) 2018年第1期31卷 19-26页

作者： qiang Wang Song Zhang Chun-Hua Zhang chen-Liang Wu Ling Ren Jian-qiang Wang Jiang chen School of Stomatology China Medical University School of Materials Science and Engineering Shenyang University of Technology Shenyang Dalu Laser Group Co. Ltd. Institute of Metal Research Chinese Academy of Sciences

Direct laser metal deposition is a kind of advanced rapid manufacturing technology, which can produce near net shape parts by depositing metal powders layer by layer. This study demonstrates fabrication, the anisotropy of mechanical properties and hardness of a graded steel. The characteristics of constituent phases, microstructure, mechanical anisotropy, and microhardness were investigated using electron backscatter diffraction, optical microscopy, tensile test machine, and microhardness tester. It was found that the graded steel is dense and free of cracks. The crystal structures of the as-built samples evolved in three grades from fcc structures to fcc ＋ bcc structures and then to bcc ＋ fcc structures. Samples in x and z directions showed obvious mechanical anisotropy. The samples machined in x direction showed higher strength and lower elongation than those machined in z direction due to the presence of lack-of-fusion pores and the higher metallurgical bonding between layers in the x direction. The microhardness of the as-built samples increased along the cross section from the substrate （159.7 HV） to the top surface （545.4 HV）.

关键词： Graded steel Direct laser metal deposition Electron backscatter diffraction (EBSD) Anisotropy of mechanical orooerties