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Instability of forced flow in a rotating cylindrical pool with a differentially rotating disk on the free surface

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science china(Technological sciences) 2010年第9期53卷 2477-2488页

作者： WU ChunMei & LI YouRong college of Power engineering,chongqing university,chongqing 400044,china college of Power engineering Chongqing University

The instability of forced flow in a rotating cylindrical pool with a differentially rotating disk on the free surface is investigated through a series of unsteady three-dimensional numerical *** results show that the basic flow state of this system is axisymmetric and steady,but has rich structures at the meridian ***,when the rotation Reynolds number exceeds a critical value,the flow will undergo a transition to three-dimensional oscillatory flow,characterized by the velocity fluctuation waves traveling in the azimuthal *** main characteristics of the flow patterns are presented,including the propagating direction,velocity,amplitude and wave number,which depend on the rotation rates and directions of the disk and the cylindrical pool,and the critical conditions for the onset of oscillatory flow are also *** the case of disk-only rotation,the centrifugal instability is responsible for the flow transition,and when the disk isoand counter-rotates with the cylindrical pool,the mechanisms for the transition are elliptic and of circular shear instabilities,respectively.

关键词： rotation flow transition flow instability

Scenario simulation and forecast of land use/cover in northern china

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Chinese science Bulletin 2008年第9期53卷 1401-1412页

作者： LI YueChen 1,2,3 & HE ChunYang 3 1 college of Geographical science, chongqing Normal university, chongqing 400047, china 2.college of Resources and Environmental science, chongqing university, chongqing 400044, china 3 college of Resources science & Technology, Beijing Normal university, Beijing 100875, china college of Geographical science Chongqing Normal University Chongqing 400047 China college of Resources and Environmental science Chongqing University Chongqing 400044 China college of Resources science & Technology Beijing Normal University Beijing 100875 China

Modeling land use/cover scenario changes and its potential impacts on structure and functions of ecosystem in typical regions are helpful to understanding the interactive mechanism between land use/cover system and ecosystem. Based on the analysis of the existing land use/cover simulation and forecast models, a land use/cover scenario dynamics model by the integration of System Dynamics (SD) model, Back Propagation Neural Network (BPNN) and Cellular Automata (CA) model is developed with land use/cover scenario changes in northern china in the next 30 years and simulated in this paper. The model is to simulate the land use/cover scenario demands by using a SD model at first, and then allocating the land use scenario patterns at the local scale with the considerations of land use/cover suitability, inheritance ability and neighborhood effect by using BPNN-CA model to satisfy the balance between land use/cover scenario demands and supplies. It integrates the advantages of SD, BPNN and CA. Macro-driving factors and the micro-spatial pattern are also fully taken into account. The BPNN simplifies the identification of the factors’ weights used in CA model and improves the reliability of the simulation results. The simulation accuracy of the model developed in this paper was found to be about 74%. It suggests that the model has the ability to reflect the complexity of land use/cover system at different scales to some extent and it is a useful tool for assessing the potential impacts of land use system on ecosystem. The simulated results also indicate that the urban land, water area and forest will increase significantly, and farmland and unable land will decrease gradually. Obvious land use/cover changes will take place in the farming-pastoral zone and the southeast area of northern china.

关键词：土地利用中国北方细胞自动机系统动力学

Air flow exploration of abrasive feed tube

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Acta Mechanica Sinica 2009年第6期25卷 761-768页

作者： Shijin Zhang Xiaohong Li Yilei Gu college of Resources and Environmental science,chongqing university, 400044 chongqing, china college of Resources and Environmental science Chongqing University Chongqing China

An abrasive water-jet cutting process is one in which water pressure is raised to a very high pressure and forced through a very small orifice to form a very thin high speed jet beam. This thin jet beam is then directed through a chamber and then fed into a secondary nozzle, or mixing tube. During this process, a vacuum is generated in the cham- ber, and garnet abrasives and air are pulled into the chamber, through an abrasive feed tube, and mixes with this high speed stream of water. Because of the restrictions introduced by the abrasive feed tube geometry, a vacuum gradient is generated along the tube. Although this phenomenon has been recog- nized and utilized as a way to monitor nozzle condition and abrasive flowing conditions, yet, until now, conditions inside the abrasive feed line have not been completely understood. A possible reason is that conditions inside the abrasive feed line are complicated. Not only compressible flow but also multi- phase, multi-component flow has been involved in inside of abrasive feed tube. This paper explored various aspects of the vacuum creation process in both the mixing chamber and the abrasive feed tube. Based on an experimental exploration, an analytical framework is presented to allow theoretical calculations of vacuum conditions in the abrasive feed tube.

关键词： Abrasive feed tube- Water jet cutting. Vacuum gradient

Influential Factors on Deicing Performance of Electrically Conductive Concrete Pavement

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Journal of Wuhan university of Technology(materials science) 2006年第2期21卷 123-127页

作者：唐祖全 college of materials science & engineering Chongqing UniversityChongqing 400045China

The deicing experiment of carbon fiber reinforced electrically conductive concrete （CFRC） slab was conducted in laboratory at first, then the deicing process of CFRC parement was analyzed by means of finite element method （FEM）. At last, based on the energy conservation law and the computing restdts of finite element method, the influential factors including the setting of electric heating layer, environmental temperature, the thickness of ice, material parameters, and deicing power on deicing performance and energy consumption were discussed.

关键词： electrically conductive concrete deicing performance electrothermal effect energy consumption influence factors

Grain refinement of Mg-Li-Al cast alloys by adding typical master alloys

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Progress in Natural science:materials International 2011年第3期21卷 236-239页

作者： Bin JIANG~(1,2),Qing-shan YANG~2,Ming-xing ZHANG~3,Dong QIU~3,Rui-hong LI~2,Fu-sheng PAN~(1,2) 1.National engineering Research Center for Magnesium Alloys,chongqing university,chongqing 400044,china 2.college of materials science and engineering,chongqing university,chongqing 400044,china 3.Division of materials,School of Mechanical and Mining engineering, The university of Queensland,St Lucia,QLD 4072,Australia National engineering Research Center for Magnesium Alloys Chongqing University college of materials science and engineering Chongqing University Division of materials School of Mechanical and Mining Engineering The University of Queensland

Commercial Al-3Ti-1C and Al-5Ti-1B master alloys were added in order to refine the grains of Mg-Li-Al *** effects of their addition levels on grain refinement of Mg-Li-Al cast alloy were investigated and the mechanism of the grain refinement was *** results showed that the addition of Al-3Ti-1C master alloy reduced the grain size of LA141 cast alloy from 900μm to 400μm,while the addition of Al-5Ti-1B master alloy reduced the grain size of LA51 cast alloy from 500μm to 240μ*** grain refining mechanism was the heterogeneity nucleation of TiC and TiB2,because of less than 10%mismatches of TiC/β-Li and TiB2/α-Mg.

关键词： magnesium lithium alloy master alloy grain refinement

A Numerical Stress-strain Response Model of All Grades of Concretes under Uniaxial Compression

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Journal of Wuhan university of Technology(materials science) 2006年第3期21卷 149-152页

作者：王勇威 college of Water Resource & Hydropower Sichuan UniversityChengdu 610065China

An important problem facing stress-strain response modeling of concrete is the complexity of the compressive strength grades. 21 groups of speeimens with different cubic compressive strength （56.3- 164.9 MPa ） hate beets numerically analyzed. Using only the compressive strength, a stress-strain response model of different concrete grade was established. The numerical simulation model not only qualitatively reproduces the relationship of uniaxial compressive strength, peak value stress and cubic compressive strength, but realizes the consistence of the ascending branch of stress-strain cunts with different strength grades by introducing the correction coefficient k. The results indicate k increases gradually from 0 to approximate 1 with the increase of the compressive strength, corresponding to the transition from the paracurve to straight line branch in stress-strain curves. When k is 0, the madel is identical to the Hognestad equation. A good agreement with the experiment data was obtained.

关键词： high-strength concrete stress-strain response mechanical property

Surface Nanocrystallization of Magnesium Alloy AZ91D by High-Energy Shot Peening

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Journal of Wuhan university of Technology(materials science) 2009年第4期24卷 515-519页

作者：张津 School of materials science & engineering University of Science and Technology Beijing college of materials science & engineering Chongqing University of Technology

High-energy shot peening （HESP）, a method to produce severe plastic deformation by high velocity flying balls, was applied on die cast magnesium alloy AZ91D. Effects of surface nanocrystallization by HESP and heat treatment at different temperatures were investigated. The mi- crostructure evolution was conducted using X-ray diffraction （XRD） and field emission scanning electronic microscopy （FESEM）. The hardness was measured by microhardness tester. The experimental results show that surface nanocrystrallization of AZ91D obtained by HESP would lead to the increase of microhardness. Low temperature heated at 100℃ for 1 h do not change the property obviously. However, both the microstructure and microhardness vary greatly after heat treatment at 400℃ for 1 h.

关键词： AZ91 D surface nanocrystallization HESP microhardnss corrosion resistance

Influence of stacking fault energy on formation of long period stacking ordered structures in Mg-Zn-Y-Zr alloys

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Progress in Natural science:materials International 2011年第6期21卷 485-490页

作者： Fu-sheng PAN~(1,2),Su-qin LUO~1,Ai-tao TANG~(1,2),Jian PENG~(1,2),Yun LU~3 1.college of materials science and engineering,chongqing university,chongqing 400044,china 2.National engineering Research Center for Magnesium Alloys,chongqing university,chongqing 400044,china 3.Faculty of engineering,Chiba university,Chiba 263-8522,Japan college of materials science and engineering Chongqing University Chongqing 400044 China National engineering Research Center for Magnesium Alloys Chongqing University Chongqing 400044 China Faculty of engineering Chiba University Chiba 263-8522 Japan

The influence of alloying elements on the stacking fault energy（SFE） of Mg-Y-Zn-Zr alloys was calculated by using first-principles,and the microstructure of as-cast Mg-1.05Y-0.79Zn-0.07Zr（mole fraction,%） alloy prepared by conventional casting was investigated by SEM,TEM and *** block-like long period stacking ordered（LPSO） phase,the lamellar LPSO phase and stacking faults were observed simultaneously and the lamellar LPSO structure and stacking faults were both formed on （0001）α-Mghabit plane and grown or extended along[01 1 0]α-*** calculation results by the first-principles showed that the addition of Y can sharply decrease the stacking fault energy of the Mg-Zn-Y-Zr alloy,while Zn slightly increases the stacking fault energy of the *** influence of stacking fault energy on the formation of LPSO was *** shows that LPSO may nucleate directly through stacking faults and the lower stacking fault energy was in favor of formation of LPSO.

关键词： magnesium alloy Mg-Zn-Y-Zr long period stacking ordered(LPSO) structures stacking fault energy(SFE) firstprinciples calculation

Effect of Sr on microstructure and aging behavior of Mg-14Li alloys

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Progress in Natural science:materials International 2012年第2期22卷 160-168页

作者： Bin Jiang a,b,c,Ying Zeng b,Hengmei Yin a,b,Ruihong Li a,b,Fusheng Pan a,b a National engineering Research Center for Magnesium Alloys,chongqing university,chongqing 400030,china b college of materials science and engineering,chongqing university,chongqing 400030,china c New materials Center,chongqing Academy of science and Technology,chongqing 401123,china National engineering Research Center for Magnesium Alloys Chongqing University college of materials science College of Engineering Chongqing University New materials Center Chongqing Academy of Science and Technology

The as-cast and as-extruded Mg-14 wt%Li-xSr(x=0.14,0.19,0.39 wt%)alloys were,respectively,prepared through a simple alloying process and hot *** effects of Sr addition on microstructure and aging behavior of the Mg-14 wt%Li-xSr alloys were *** results indicated that b(Li)and Mg2Sr were the two primary phases in the microstructures of both as-cast and as-extruded Mg-14 wt%Li-xSr ***,with the increase of Sr content from 0.14 wt%to 0.39 wt%,the grain sizes of the as-cast and as-extruded Mg-14 wt%Li-xSr alloys markedly decreased from 5000 mm and 38 mm to 330 mm and 22 mm respectively,while no obvious changes of the micro-hardness and microstructure of the as-extruded alloys were observed during the aging treatment.

关键词： Magnesium-lithium alloys Microstructure Grain refinement Aging behavior