Modelling of modern automotive petrol engine performance using Support Vector Machines

Modern automotive petrol engine performance is significantly affected by effective tune-up. Current practice of engine tune-up relies on the experience of the automotive engineer, and tune-up is usually done by trial-and-error method and then the vehicle engine is run on the dynamometer to show the actual engine performance. Obviously the current practice involves a large amount of time and money, and then may even fail to tune up the engine optimally because a formal performance model of …     

On the structural features of fiber suspensions in converging channel flow

The structural features of fiber suspensions are dependent on the fiber alignment in the flows. In this work the orientation distribution function and orientation tensors for semi-concentrated fiber suspensions in converging channel flow were calculated, and the evolutions of the fiber alignment and the bulk effective viscosity were analyzed. The results showed that the bulk stress and the effective viscosity were functions of the rate-of-strain tensor and the fiber orientation state; and that the fiber suspensions evolved to steady alignment and tended to concentrate to some preferred directions close to but not same as the directions of local streamlines. The bulk effective viscosity depended on the product of Reynolds number and time. The decrease of effective viscosity near the boundary benefited the increase of the rate of flow. Finally when the fiber alignment went into steady state, the structural features of fiber suspensions were not dependent on the Reynolds number but on the converging channel angle. Projects (No. 19925210) supported by the National Natural Science Foundation of China     

On the structural features of fiber suspensions in converging channel flow

INTRODUCTIONModelingfiber fiberinteractionsinnon di lutefibersuspensionsanddescribinghowtheseinteractionsaffecttherheologicalpropertiesofthesuspensionsintheflowsarefundamentalandimportantinmulti phaseflowsresearch .Ulti matelywewouldliketobeabletodesignan…     

Primary instabilities and bicriticality in fiber suspensions between rotating cylinders

The linear stability of fiber suspensions between two concentric cylinders rotating independently is studied. The modified stability equation is obtained based on the fiber orientation model and Hinch-Leal closure approximation. The primary instabilities and bicritical curves have been calculated numerically. The critical Reynolds number,wavenumber and wave speeds of fiber suspensions as functions of the aspect ratio,volume concentration of the fibers and the gap width of cylinders are obtained.     

Science Letters： Research on 3D fiber orientation distribution in arbitrary planar flows

A non-stretchable fiber rotation in planar flows has been solved. The fiber will rotate periodically or run to the asymptotical direction decided by a discriminant defined in the paper involving the fiber aspect ratio and the flow characteristics. Subsequently the fiber orientation distribution is derived directly without the bother of solving the Fokker-Planck equation. The research clearly indicates the overall configuration of a fiber rotation movement in planar flows.     

Research on the behavior of fiber orientation probability distribution function in the planar flows

INTRODUCTION The orientation of fibers plays an important rolein determining the rheological properties of fibersuspensions and the behaviors of composite materialsproduced by various forming operations. A fiber canbe treated as a rigid cylinder with length l and di-ameter d. It is convenient to define three regimes ofconcentration: dilute, semi-concentrated and concen-trated. Dilute regime is defined when c<(d/l)2, wherec is the volume fraction of fibers. In this regime fibersare …     

Research on the orientation distribution of fibers immersed in a pipe flow

The computed orientation distribution of fibers immersed in laminar pipe flows showed that the longitudinal distributions are wide for small Reynolds numbers and become narrower with increasingRe. For lowRe number, the axial orientation distributions are broad with almost no preferred orientations. For highRe number, the axial distribution becomes narrow, with sharp maxima. The mean values of the longitudinal orientation depend strongly on theRe number. The computed results are in qualitative agreement with relevant experimental results. Project (No. 19925210) supported by the National Natural Science Foundation for Outstanding Youth of China     

On the hydrodynamic stability of a particle-laden flow in growing flat plate boundary layer

INTRODUCTION Turbulent particulate flows occur in many in-dustrial applications, such as in pneumatic transportof particulates, cyclone separators and chemical re-actors. The particles suspended in fluid play a role inthe turbulence modulation, which has been known forseveral years. The observation that adding dust to airflowing in turbulent motion through a pipe can ap-preciably reduce the resistance coefficient was re-ported by Sproull (1961). The observation can beexpressed as saying …     

Effect of particle loading on heat transfer enhancement in a gas-solid suspension cross flow

Heat transfer between gas-solid multiphase flow and tubes occurs in many industry processes, such as circulating fluidized bed process, pneumatic conveying process, chemical process, drying process, etc. This paper focuses on the influence of the presence of particles on the heat transfer between a tube and gas-solid suspension. The presence of particles causes positive enhancement of heat transfer in the case of high solid loading ratio, but heat transfer reduction has been found for in the case of very low solid loading ratio (M _s of less than 0.05 kg/kg). A useful correlation incorporating solid loading ratio, particle size and flow Reynolds number was derived from experimental data. In addition, thek-∈ two-equation model and the Fluctuation-Spectrum-Random-Trajectory Model (FSRT Model) are used to simulate the flow field and heat transfer of the gasphase and the solid-phase, respectively. Through coupling of the two phases the model can predict the local and total heat transfer characteristics of tube in gas-solid cross flow. For the total heat transfer enhancement due to particles loading the model predictions agreed well with experimental data. Project supported by National Natural Science Foundation for Distinguished Young Scholars (No. 50025618)     

考虑孔压梯度和应变梯度影响的饱和土剪切稳定性分析

Nomenclatureσey　effectivestressin ydirectionτ　shearstressγ　shearstrain γ　 shearStrainratiop　porepressureζ = 2 p x2 　porepressuregradientη = 2 γ x2 　straingradientρ　 densityofsaturatedsoilμ　 viscosityofwaterk　 physicalpermeabilityC1　materialparameterEr　reboundmodulusofgrainsα　frequencyofperturbationβ　 wavenumberofperturbationR0 　strainhardeningcoefficientQ0 　porepressuresofteningcoefficientH0 　strainratiohardeningcoefficientS0 　straingradientofcoefficientP0 　pore…     

Dynamic instability of tunnel in blocky rock mass

The displacements and geometry of the rock blocks and the properties of the rock struc-ture play an important role in the stability of tunnels.Based on the key block model,the dynamic instability analysis of underground tunnel subjected to intensive short-time compressional wave was conducted.The instability of the tunnel caused by the spallation and the inertial effect was distin-guished.And the influence of the roof contour curvature of tunnel was also determined.     

不安定刺激性开放空间设计

在现代社会,人们对于空间的精神要求越来越趋向于多元化,在享受安宁恬淡的同时,人们又追求不安与刺激的空间所带来的愉悦。目的:设计具有一定愉悦性的不安定刺激性开放空间。方法:首先研究不安定刺激空间的相关概念、与不安定刺激有关的一些性质、典型的不安定空间类型、刺激缓和手法、不安定空间叠加方式等相关方面,再以一个虚拟的刺激性公园不安定刺激区域为例,进行范例设计。     

基因工程菌发酵过程中的不稳定性研究

从基因工程菌(细胞)的生长动力学模型入手,阐述了导致基因工程菌不稳定的原因及不稳定性的表现;探讨了防止或降低基因工程菌不稳定性的对策,包括组建合适载体、选择适当宿主、施加选择压力、控制基因过量表达及控制培养条件等。     

圆柱射流截面形状的周向变化对界面不稳定性的影响

This paper concentrated on the effect of azimuthal variation of section shape on the instability of a cylindrical jet.A single fluid model under certain assumptions was constructed.The characteristic relation between frequency and wave number is obtained using the normal-mode method.The effect of some parameters on the stability was examined and some phenomena in experiments were explained.     

Some Problems in Nonlinear Dynamic Instability and Bifurcation Theory for Engineering Structures

In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories. The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on.     

Properties of frictional bridging in fiber pull-out for fiber-reinforced composites

Stress equilibrium equations, boundary- and continuity-conditions were used to establish a theoretical model of progressive debonding with friction at the debonded interface. On a basis of the minimum complementary energy principle, an expression for the energy release rate G was derived to explore the interfacial fracture properties. An interfacial debonding criterion G≥Гi was introduced to determine the critical debond length and the bridging law. Numerical calculation results for fiber-reinforced composite SCS-6/Ti-6Al-4V were compared with those obtained by using the shear-lag models.     

自聚焦克尔类电介质中非傍轴光束调制非稳的研究

Propagation stability of non-paraxial beam in nonlinear Kerr media is investigated with a linear stability method.Both theoretical analysis and numerical simulation show that modulation instability(MI) gain spectrum has three different distribution features determined by the times of incident power P0 and the non-paraxial parameter a. Furthermore,the corresponding criterion is put forward to distinguish the three different distributions.     

In vitro inhibition of pigmentation and fiber development in colored cotton

Colored cotton has naturally pigmented fibers. The mechanism of pigmentation in cotton fiber is not well documented. This experiment was conducted to study the effects of respiratory chain inhibitors, i.e., rotenone and thiourea, on pigmentation and fiber development in colored cotton. After 1 d post-anthesis, ovaries were harvested and developing ovules were cultured on the liquid medium containing different concentrations of rotenone and thiourea for 30 d. The results demonstrate that both respiratory inhibitors reduced fiber length and ovule development under ovule culture conditions, and the inhibition efficiency of rotenone was much higher than that of thiourea. Rotenone and thiourea also showed significant effects on fiber pigment (color) development in colored cotton. In green cotton fiber, rotenone advanced fiber pigment development by 7 d at 200 μmol/L, while thiourea inhibited fiber pigmentation at all treatment levels (400, 600, 800, 1 000, and 2 000 μmol/L). Both respiratory inhibitors, however, had no significant effects on pigmentation of brown cotton fibers. The activities of cytochrome c oxidase (COX) and polyphenol oxidase (PPO) decreased significantly with increasing levels of both respiratory inhibitors. It is suggested that both respiratory inhibitors have important roles in deciphering the mechanism of pigmentation and fiber development in colored cotton.     

Comparative features of colorectal and gastric cancers with microsatellite instability in Chinese patients

Objective  

The purpose of this study was to determine the unique and universal features of microsatellite instability-high (MSI-H) colorectal cancer (CRC) and MSI-H gastric cancer (GC) in the Chinese population.     

风暴潮极值状态下珠江河网白坭水道内的不稳定流动

利用1999年洪季和9316号台风风暴潮的实测资料,通过ECOMSED数学模型对珠江河网广州区域进行数值模拟计算.计算结果显示,在99年洪季时,河网内白坭水道流动为通常的往复流动;但在风暴潮极值状态下,由于受极值流速及地形的影响,流动在白坭水道中弯曲扭摆,呈现出流动不稳定现象.