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A CONSERVATIVE UNSTRUCTURED STAGGERED GRID SCHEME FOR INCOMPRESSIBLE NAVIER-STOKES EQUATIONS

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Journal of Hydrodynamics 2010年第2期22卷 173-184页

作者： LV Biao JIN Sheng AI Cong-fang State key laboratory of Coastal and Offshore engineering Dalian University of Technology Dalian 116024China key laboratory of engineering Sediment of Ministry of Communications Tianjin Research Institute for WaterTransport Engineering Tianjin 300456 China

A finite-volume formulation is proposed to solve the three-dimensional,non-hydrostatic Navier-Stokes equations on an unstructured,staggered,z-lever grid,with the goal of simulating non-hydrostatic processes in the free-surface *** advection and diffusion terms in the momentum equation are discretized explicitly with the Eulerian scheme,which has the attractive property of being *** integral method of the top-layer pressure is applied to account for the full effects of non-hydrostatic pressure at the free-surface *** is shown that the results obtained with a small number of vertical layers（e.g.,2-3 layers） are in good agreements with experimental data or analytical solutions,demonstrating the efficiency and accuracy of the model in simulating a range of free-surface flow problems including wave motion and tide-induced motion.

关键词： unstructured staggered grid finite-volume formulation non-hydrostatic free surface flows

Selective Oxidation of Isobutane to Methacrylic Acid over Supported V-Mo-P Based Composite Oxide Catalysts

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Journal of Energy Chemistry 2002年第Z2期 120-126页

作者： Feifei Sun, Yunfeng Geng, Shunhe ZhongCollege of Chemical engineering and Technology, State key laboratory of Cl Chemistry and Technology,tianjin University, tianjin 300072, china

Heteropolyacid, the most popular catalyst for the direct oxidation of isobutane, exhibits high catalytic activity, poor thermal stability and a short lifetime. Therefore, the catalyst requires further research to improve its performance. Catalysts composed of mixed oxides (V2O5, P2O5, or MoO3) supported on silica were prepared by the sol-gel method to catalyze the reaction. Results of XRD, IR, and BET corroborated that the mixed oxides were dispersed homogeneously on the surface of support. The activity of lattice oxygen in the catalysts was studied by TPR, and the chemisorption property of isobutane on the surface of the catalysts was investigated by the TPD method. H2-TPR of the catalysts revealed that the lattice oxygen of the vanadium-based catalysts is more active than that of the molybdenum-based catalysts. The redox property of V or Mo species is slightly affected by other compositions of the series catalysts. The TPD curves illustrate that there are two kinds of adsorptive species of isobutane on

关键词： 

Control of Pinhole Defects Formation in Semi-flexible Coaxial Cable by Vertical Tin-Plating Process

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Transactions of tianjin University 2011年第5期17卷 320-323页

作者：程方杰肖鑫孙贵铮杨立军张凤玉 School of Materials Science and engineering Tianjin University tianjin key laboratory of Advanced Joining Technology tianjin Anxunda Ltd

Holistic tin-plating on the outer conductor is one of the key processes in the manufacture of semi-flexible coaxial cable, which is widely applied to the third generation (3G) mobile communication system. However, in the traditional horizontal tin-plating process, disadvantages such as the pinhole defects and low productivity effect cannot be avoided. In this paper, a vertical tin-plating process was proposed to reduce the pinhole defects and improve the tincoating quality. Compared with the traditional horizontal tin-plating process, the immersion length was reduced from 300-400 mm to 10-100 mm and the tin-plating time was reduced from 7 s to 3 s in the proposed method. The experimental results indicate that immersion length and time are key parameters for the tin-plating quality. With this new tin-plating process, the experimental results show that the pinhole defects can be eliminated effectively by controlling the immersion depth below 100 mm and tin-plating time at 3 s. The thickness of tin-coating increased from not more than 5 μm to 12.3 μm with the proposed vertical tin-plating process. Meanwhile, the thickness of the intermetallic compounds (IMCs) layer between the tin-coating and copper wires was reduced from 3.26 μm to 0.62 μm if the immersion time decreased from 30 s to 1 s. Besides, a self-developed flux, which possesses a boiling point or decomposed temperature of active components over 300℃, exhibits a better efficiency in reducing the pinhole formation.

关键词： 3G communication network semi-flexible coaxial cable vertical tin-plating pinhole defect

Iris Localization Algorithm Based on Improved Generalized Symmetry Transform

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Transactions of tianjin University 2004年第4期10卷 259-264页

作者：左坤隆刘文耀朱昊王晓东 School of Precision Instruments and Opto-Electronics engineering Tianjin University Tianjin 300072 China key laboratory of Opto-Electronics Information and Technical Science (tianjin University) Ministry of Education Tianjin 300072 China

Accuracy and fastness of iris localization are very important in automatic iris recognition. A new fast iris localization algorithm based on improved generalized symmetry transform (GST) was proposed by utilizing (iris) symmetry. GST was improved in three aspects:1) A new distance weight function is defined. The new weight function, which is effective in iris localization, utilized the characteristic of irises that the iris is a circular object and it has one inner boundary and one outer boundary. 2) Each calculation of the symmetry measurement of a pair of symmetry points was performed by taking one point of a pair as the starting point of the transformation. This is the most important reason for fast iris localization,due to which, repetitious computation was largely excluded. 3) A new phase weight function was proposed to adjust GST to locate circle target much better because the inner part of iris is darker than the outer part. The edge map of iris image was acquired and GST was only implemented on the edge point, which decreased computation without loss of accuracy. The modification of distance weight function and phase weight function leads to the accuracy of localization, and other ideas speed up the localization. Experiments show that the average speed of new algorithm is about 7.0—8.5 times as high as traditional ones including integro-differential operator and Hough transform method.

关键词： iris recognition edge detection morphology generalized symmetry transform (GST)

Finite Element Analysis of Internal Gear in High-Speed Planetary Gear Units

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Transactions of tianjin University 2008年第1期14卷 11-15页

作者：葛楠张俊 School of Mechanical engineering Tianjin University

The stress and the elastic deflection of internal ring gear in high-speed spur planetary gear units are investigated. A rim thickness parameter is defined as the flexibility of internal ring gear. Six evenly spaced linear springs are used to describe the fitting status between internal ring gear and the gearcase. The finite element model of the whole internal ring gear is established by means of Pro/E and ANSYS. The loads on meshing teeth of internal ring gear are applied according to the contact ratio and the load-sharing coefficient. With the finite element analysis (FEA), the influences of flexibility and fitting status on the stress and elastic deflection of internal ring gear are predicted. The simulation reveals that the principal stress and deflection increase with the decrease of rim thickness of internal ring gear. Moreover, larger spring stiffness helps to reduce the stress and deflection of internal ring gear. Therefore, the flexibility of internal ring gear must be considered during the design of high-speed planetary gear transmissions.

关键词： planetary gear transmissions internal ring gear finite element method

Numerical Simulation on Nugget Formation and Evolution in Spot Welding of Aluminum Alloy

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Transactions of tianjin University 2011年第1期17卷 28-32页

作者：程方杰张建优胡绳荪单平 School of Material Science and engineering Tianjin University tianjin key Lab of Advanced Welding and Joining

With the squeeze of electrode tips, the oxide film on aluminum (Al) alloy surface is broken and numbers of micro-gaps are formed randomly. The micro-gaps act as conducting spots at the beginning of welding, so the contact resistance is extremely high and unstable in spot welding of Al alloy. In this paper, a new contact resistance model is adopted to simulate the nugget forming process. This model describes the random distribution characteristic of conducting spots. The simulation results indicate that, within the first 5 ms of welding current (AC, 50 Hz), the temperature distribution at the workpieces interface is seriously irregular. In addition, the nugget does not nucleate from the weld center and grow continuously, however, it nucleates randomly from several points almost instantaneously and then merges into an entity quickly. Experimental results agreed with the numerical simulation.

关键词： aluminum alloy spot welding nugget oxide film contact resistance

Anode Simulation and Cathode Design for Electrolytic Dressing of Diamond Profile Wheel

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Transactions of tianjin University 2005年第3期11卷 172-175页

作者：邹峰于爱兵谭业发 key laboratory for Advanced Ceramics and Machining Technology of Education Ministry School of Mechanical Engineering Tianjin University Tianjin 300072 China Nanjing engineering Institute Nanjing 210007 China

The design methods of anode and cathode are proposed for precision profile grinding. Based on the electrolytic machining theory, electrolytic equilibrium condition and Faraday′s law of electrolysis are applied to establishing the mathematical model of profile diamond dressing process- es. A finite element method (FEM) program is developed to solve the inverse boundary problem of Laplace′s equation. Desired anode contour or cathode shape is determined by computing the distribution of electric potential layer by layer. Electrolytic machining experiment is carried out to verify the simulated anode shape. The research result shows that shape deviation between designed cathode and profile wheel increases with the value of angle between feed rate and the normal to anode surface. The shape of simulated anode is consistent with the contour of metal-bonded diamond profile wheel for a given cathode. Based on the anode contour, cathode shape can also be designed accurately.

关键词： profile wheel dressing electrolysis FEM diamond

Comparison Study of Two Mehods for Realizing Real-time High-efficiency JTC

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Chinese Journal of Lasers 1995年第5期B4卷 455-462页

作者： GE Baozhen QIN Yuwen ZHANG Yimo HUANG Zhanhua ZHANG Hong (Institute of Contemporary Optical Instruments engineering,tianjin University, tianjin 300072, china) tianjin Univ Tianjin China

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关键词： optical pattern recognition optical self-adaptation hybrid optical correlator

NUMERICAL ANALYSIS OF THE PERFORMANCE OF HORIZONTAL AND WAVY SUBSURFACE FLOW CONSTRUCTED WETLANDS

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Journal of Hydrodynamics 2011年第3期23卷 339-347页

作者： WANG Jun HUANG Sui-liang HE Cheng-da NG Chiu-On College of Environmental Science and engineering Nankai University Tianjin 300071 China Numerical Simulation Group for Water Environment Key Laboratory of Pollution Processes and EnvironmentalCriteria of Ministry of Education Tianjin Key Laboratory of Environmental Remediation and Pollution ControlCollege of Environmental Science and Engineering Nankai University Tianjin 300071 China College of Environmental Science and engineering Yangzhou University Yangzhou 225009 China Department of Mechanical engineering The University of Hong Kong Hong Kong China

A three-dimensional numerical model is proposed for modeling the TP transport in the Horizontal Subsurface Flow （HSSF） and Wavy subsurface Flow （WSSF） constructed wetland in this article. Both numerical simulations and physical experiments indicate that the removal efficiency of WSSF is higher than that of HSSF. The difference ofperforrnance in removing pollutants, e.g., Total Phosphorus （TP）, between HSSF and WSSF is numerically analyzed from three interactive aspects, that is, the hydraulic behavior, the substrate and the plant roots. It is shown that the dead zone volume in WSSF is smaller than in HSSF with less short circuiting. The soil in the top layer is more used in WSSF than in HSSF. The TP uptake by the plant roots in WSSF is higher than that in HSSF.

关键词： numerical model constructed wetland hydraulic behavior Retention Time Distribution (RTD) removal efficiency