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Hydrodynamic Performance of Vertical Porous Structures Under Regular Waves

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China Ocean eng.neering 2013年第4期27卷 451-468页

作者： A.S.Koraim O.S.Rageh Water and Water Structure eng. dept. Faculty of Eng. Zagazig University Irrigation and Hydraulics dept. Faculty of Eng. El-Mansoura University

The hydrodynamic efficiency of the vertical porous structures is investigated under regular waves by use of physical models. The hydrodynamic efficiency of the breakwater is presented in terms of the wave transmission （kt）, reflection （kr） and energy dissipation （ka） coefficients. Different wave and structural parameters affecting the breakwater efficiency are tested. It is found that, the transmission coefficient （kt） decreases with the increase of the relative water dept. （h/L）, the wave steepness （Hi^L）, the relative breakwater widths （B/L, B/h）, the relative breakwater height （D/h）, and the breakwater porosity （n）. The reflection coefficient （kr） takes the opposite trend of kt when D/h=l.25 and it decreases with the increasing h/L, HJL and B/L when D/h〈1.0. The dissipation coefficient （kd） increases with the increasing h/L, HilL and B/L when D/h〈_l.O and it decreases when D/h=l.25. In which, it is possible to achieve values ofkt smaller than 0.3, k~ larger than 0.5, and kd larger than 0.6 when D/h=1.25, B/h=0.6, h/L〉0.22, B/L〉O. 13, and H/L 〉0.04. Empirical equations are developed for the estimation of the transmission and reflection coefficients. The results of these equations are compared with other experimental and theoretical results and a reasonable agreement is obtained.

关键词： water waves porous breakwaters wave attenuation wave transmission wave reflection wave dissipation

EFFECT OF THE OPEN CRACK ON THE PULL-IN INSTABILITY OF AN ELECTROSTATICALLY ACTUATED MICRO-BEAM

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Acta Mechanica Solida Sinica 2012年第6期25卷 627-637页

作者： Asadollah Motallebi Mohammad Fathalilou Ghader Rezazadeh Mech. eng. dept. Islamic Azad University Mech. eng. dept. Urmia University

In this paper, the effects of the open crack on the static and dynamic pull-in volt- ages of an electrostatically actuated fixed-fixed and cantilever micro-beam are investigated. By presenting a mathematical modeling, the governing static and dynamic equations are solved by SSLM and Galerkin-based Reduced Order Model, respectively. Then, each single-side open crack in the micro-beam is modeled by a massless rotational spring and the cracked mode shapes and corresponding natural frequencies are calculated by considering the boundary and patching con- ditions and using transfer matrix methods. Finally, the effects of the crack dept. ratio, crack position and crack number on the pull-in voltage of the micro-beams are studied. It is shown that beside the residual stresses created in the machining process, the crack（s） can be initiated, growth and consequently change the pull-in voltage of the system by decreasing the natural frequencies. The results show that the crack position is effective beside the crack dept. ratio in decreasing the pull-in voltage. Also it is shown that in the fixed-fixed micro-beam there are several points for the crack location in which, the pull-in voltage is extremum.

关键词： MEMS open crack electrostatic pull-in instability

Computational Fluid Dynamic Simulation of Liquid-Liquid Mixing in a Static Double-T-shaped Micromixer

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过程工程学报 2008年第6期8卷 1080-1084页

作者： Elmabruk A. MANSUR 王运东戴猷元 The State Key Lab. Chem. eng. Dept. Chem. Eng.Tsinghua University

The laminar flow structure and mixing performance of T-shaped and double-T-shaped micromixers with rectangular cross-section have been investigated using computational fluid dynamic (CFD) simulation. FLUENT software is used to evaluate the mixing efficiency. The numerical simulation results show that the presented double-T-micromixer is highly efficient over T-shaped micromixer. The performance of double-T-micromixer with and without static mixing elements (SME) is also investigated. The enhancement in mixing performance is thought to be caused by the generation of eddies and lateral velocity component when the mixture flows through these elements. Mixing efficiency as higher as 97% is reached within a mixing leng.h of 320 μm downstream from the first T-junction with the enhancement of three SMEs.

关键词：计算方法流体动力学模拟方法液液混合双T形微混合器物理过程

Numerical Simulation and Physical Simulation of Sea Wave Groups

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China Ocean eng.neering 1996年第3期11卷 295-305页

作者： Yu Yuxiu and Gui ManhaiProfessor, dept. of Civil eng. Dalian University of Technology (DUT), Dalian 116024 . Master, dept. of Civil eng. DUT, Dalian, 116024 dept. of Civil eng. Dalian University of Technology Dalian 116024 dept. of Civil eng. DUT Dalian 116024

Based on field wave data, an empirical formula of wave envelope spectrum is given in this paper. Then the methods of both numerical and physical simulation of sea wave groups with the given spectrum and groupiness par... 详细信息

关键词： wave group wave envelope spectrum numerical simulation physical simulation

Fluvial Processes in the Meandering Reach of the Lower Wei River During the Course of Degradation

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四川大学学报（工程科学版） 2005年第S1期37卷 46-51页

作者： Xia, Junqiang Wang, Guangqian Wu, Baosheng dept. of Hydraulic eng. Tsinghua Univ. Beijing 100084 China

This paper presents an analysis of the changes of the longitudinal and lateral profiles in the meander- ing reach of the Lower Wei River over the period from October 1973 to October 1976 during the course of *** results indicated that retrogressive erosion and subsequent downstream erosion occurred in the reach due to the lowering in the Tongguan elevation and the inflowing water carrying low sediment con- *** the end of the degradation,the main channel widths of the majority ...

关键词： the Lower Wei River fluvial processes batse level of erosion channel widening channel undercut

DRYING OF GRANULAR MATERIALS IN AGITATED FLUIDIZED BED

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Journal of Hydrodynamics 2001年第2期13卷 29-31页

作者： Ma, J.H. Liu, H. Feng. D.Z. dept. of Air-Condition eng. Shandong Inst. of Civil Eng. Jinan 250014 China

An experimental study of the drying characteristics of an agitated fluidized bed dryer is presented and discussed. In the study, the citric acid particles were used as bed material with the diameters ranging from 0.2 mm to 1.3 mm. The variables affecting apparently the drying rate were found to be the mass flow rate, the inlet air temperature, the rotary speed of agitating mechanism and the particles feed rate. Comparing with other variables considered, mass flow rate was found to have the least important influence on the drying rate. The agitated fluidized bed dryer is suitable to drying agglomerating or sticky materials.

关键词： Dryers (equipment) Drying Experiments Mass transfer

Ce^(4+)-Induced Apoptosis of Taxus cuspidata Cells in Suspension Culture

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Journal of Rare Earths 2002年第2期20卷 139-144页

作者：葛志强元英进王艳东马振毅胡宗定 dept. of Biochem. eng. Sch. of Chem. Eng. and Technol. Tianjin Univ. Tianjin 300072 China

The standard detection hallmarks of apoptosis of Taxus cuspidata cells in suspension culture with Ce 4+ were studied. The condensation and margination of chromatin were observed under the electron microscopy. DNA fragmentation ranged 'DNA ladder' on agarose gel electrophoresis. TdT mediated dUTP nick end labeling (TUNEL) analysis of the cells reveals that the nuclear DNA strand breaks can be identified by labeling free 3′ OH termini. These results suggest that Ce 4+ can induce apoptosis of Taxus cuspidata cells and also indicate that there is a certain relationship between apoptosis and secondary metabolite product Taxol.

关键词： rare earths cerium apoptosis Taxus cuspidata cell suspension culture

Two Bandwidth Packing Algorithms for the Centralized Wireless Network and Their Average-case Analysis

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Journal of Shanghai Jiaotong university(Science) 2007年第3期12卷 397-404页

作者：陈建新龚玲杨宇航曾鹏 dept. of Electronic eng. Shanghai Jiaotong Univ. dept. of Computer eng. of Nanjing Univ. of Posts & Telecommunications

This paper presents a detail analysis of two bandwidth packing algorithms, used for processing connection requests in the centralized wireless network. Each call comes with a specific bandwidth request. A request can be satisfied only if there is sufficient bandwidth available during resource scheduling and allocation. Unsatisfied requests were held in a queue. The metric of bandwidth utilization ratio was used to quantify the performance of our algorithms. By theoretical analysis, our algorithms can improve the average bandwidth usage ratio significantly, about 8%~10% without adding much computation complexity. Moreover, our algorithms outperform next fit with fragmentation (NFF) algorithm when the bandwidth resource is scarce. In this paper, the contributions follows: Introducing bandwidth packing problem into wireless network; Proposing two new bandwidth packing algorithms for wireless network where the complicate scheduling algorithms are prohibited; Studying the average performance of our algorithms mathematically, which agree well with the simulation results.

关键词： wireless network average performance bandwidth packing problem (BWP)

Bedload resistance in supercritical flow

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International Journal of Sediment Research 2009年第4期24卷 400-409页

作者： Alireza HABIBZADEH Mohammad Hossein OMID dept.of Irrigation and Reclamation eng. University of Tehran dept. of Irrigation and Reclamation eng. University of Tehran

The movement of bedload in subcritical flow produces additional roughness as compared to flow in a rigid bed. The magnitude of this bed load roughness is proportional to the thickness of the sediment layer moving along the bed, the particle size and the sediment concentration. In a supercritical flow, however, further resistance is expected due to the momentum absorption by the high flow velocity. In this study the effect of sediment movement on the flow resistance in supercritical flow was experimentally investigated. The experiments included flows over smooth and rough beds carrying sediment of mean diameters D 50 =2.80, 5.42 and 7.06 mm in a rigid rectangular channel. The results show that the sediment transport may increase the friction factor by up to 90% and 60% in smooth and rough beds, respectively. Bedload extracts its momentum from the flow, which causes a reduction of near bed flow velocity and steeper velocity gradient near the bed resulting in an increase in shear velocity as well as in roughness height. The increase in friction factor is directly related to bedload concentration and particle size.

关键词： Hydraulic resistance Friction factor Bedload transport Supercritical flow