Superlarge deviation probabilities for sums of independent lattice random variables with exponential decreasing tails

In the note we study large and superlarge deviation probabilities of sum of i.i.d. lattice random variables, whose distribution function has an exponentially decreasing tail at infinity.     

Comparative study on the process behavior and reaction kinetics in sonocatalytic degradation of organic dyes by powder and nanotubes TiO2

Sonocatalytic degradation of various organic dyes (Congo Red, Reactive Blue 4, Methyl Orange, Rhodamine B and Methylene Blue) catalyzed by powder and nanotubes TiO₂ was studied. Both catalysts were characterized using transmission electron microscope (TEM), surface analyzer, Raman spectroscope and thermal gravimetric analyzer (TGA). Sonocatalytic activity of powder and nanotubes TiO₂ was elucidated based on the degradation of various organic dyes. The former catalyst was favorable for treatment of anionic dyes, while the latter was more beneficial for cationic dyes. Sonocatalytic activity of TiO₂ nanotubes could be up to four times as compared to TiO₂ powder under an ultrasonic power of 100 W and a frequency of 42 kHz. This was associated with the higher surface area and the electrostatic attraction between dye molecules and TiO₂ nanotubes. Fourier transform-infrared spectrometer (FT-IR) was used to identify changes that occurred on the functional group in Rhodamine B molecules and TiO₂ nanotubes after the reaction. Sonocatalytic degradation of Rhodamine B by TiO₂ nanotubes apparently followed the Langmuir-Hinshelwood adsorption kinetic model with surface reaction rate of 1.75 mg/L min. TiO₂ nanotubes were proven for their high potential to be applied in sonocatalytic degradation of organic dyes.     

小学生穿暴走鞋的步行行为研究

通过小学生群体穿运动鞋与暴走鞋的步态,研究运动鞋、无轮暴走鞋、有轮暴走鞋在步行过程中的步行行为特点.用高速摄像机从侧面拍摄小学生穿运动鞋与暴走鞋时的步态过程,分析正常步行时的步长、步频、步速与落地角的步行行为指标特征,检验鞋跟高度差异对步行的影响.结果表明:小学生步行时的最长步长是运动鞋,有轮暴走鞋最短;运动鞋、无轮暴走鞋、有轮暴走鞋的步频、步速与落地角呈现递减趋势;运动鞋与有轮暴走鞋、无轮暴走鞋与有轮暴走鞋的步长、步速与落地角的平均值差异非常显著(P0.01),运动鞋与有轮暴走鞋、无轮暴走鞋与有轮暴走鞋的步频平均值差异显著(P0.05).     

Simulation of supersonic turbulent flow in the vicinity of an inclined backward-facing step

Large eddy simulation (LES) is a viable and powerful tool to analyse unsteady three-dimensional turbulent flows. In this article, the method of LES is used to compute a plane turbulent supersonic boundary layer subjected to different pressure gradients. The pressure gradients are generated by allowing the flow to pass in the vicinity of an expansion–compression ramp (inclined backward-facing step with leeward-face angle of 25°) for an upstream Mach number of 2.9. The inflow boundary condition is the main problem for all turbulent wall-bounded flows. An approach to solve this problem is to extract instantaneous velocities, temperature and density data from an auxiliary simulation (inflow generator). To generate an appropriate realistic inflow condition to the inflow generator itself the rescaling technique for compressible flows is used. In this method, Morkovin's hypothesis, in which the total temperature fluctuations are neglected compared with the static temperature fluctuations, is applied to rescale and generate the temperature profile at inlet. This technique was successfully developed and applied by the present author for an LES of subsonic three-dimensional boundary layer of a smooth curved ramp. The present LES results are compared with the available experimental data as well as numerical data. The positive impact of the rescaling formulation of the temperature is proven by the convincing agreement of the obtained results with the experimental data compared with published numerical work and sheds light on the quality of the developed compressible inflow generator.     

高温高应变率下材料拉伸性能测试的一种新方法

为了实现高温环境下材料高应变率动态拉伸实验技术,将分离式Hopkinson杆直接拉伸装置中试样与拉杆的螺纹连接形式变成楔形连接形式,并加装了气动同步装置系统。这样,在对试样加高温时,能使靠近试样的入射和透射杆端处于较低温度。当撞击管向传递法兰运动时,气动同步装置瞬间拖动透射杆和试样,使两者之间的间隙为零,此时沿入射杆传递的入射波同时对试样拉伸加载。经实验验证,此方法可以有效实现材料高温高应变率拉伸加载。     

Impulse and mass transport in a cartilage bioreactor using the lattice Boltzmann method

Mass and Impulse transport of oxygen enriched water in cartilage cell breeding reactor are simulated using the lattice Boltzmann method (LBM). The solver is attached with a shear stress and pressure calculator to quantify the load distribution on the cells. The solver was validated using the backward-facing step flow, which is a classical benchmark of similar discrete geometry for the bioreactor. This is achieved by comparing the qualitative and quantitative results obtained by LBM with the traditional solution and experimental approach for such a problem. The D2Q9 lattice model is used to carry out the calculations for the flow field, with a first order bounce-back boundary condition. Oxygen consumption efficiency levels in the bioreactor were reported.     

Flexure of Clamped Rectangular Plates Resting on Winkler Foundations

ABSTRACT

The flexure under uniform load of clamped rectangular plates resting on elastic foundations is treated via eigenfunction expansions. The expansion coefficients are determined by expanding each of the nonorthogonal eigen-functions in terms of an orthogonal set of real functions. The numerical convergence of the associated eigenfunction expansions for some aspect ratios of the plate and some values of the foundation modulus are presented.     

双向拟静力加载规则对钢筋混凝土高墩滞回性能的影响

通过四种不同双向加载规则的钢筋混凝土高墩拟静力试验,初步研究了双向拟静力加载规则对其滞回特性的影响规律。本文主要介绍钢筋混凝土高墩的试验构件设计,加载装置、测试方法和加载规则,着重比较了对角线加载、正方形加载、菱形加载和圆形加载等四种加载规则的钢筋混凝土高墩的滞回性能,包括荷载-位移滞回曲线、荷载-位移骨架曲线、荷载退化、刚度退化以及累积滞回耗能的特点,并分析这些特点与双向加载规则之间的关系。结论认为:对角线加载模式加载效率高且能较好反映高墩双向抗震滞回性能,适合于高墩的双向拟静力试验研究。     

Precision Sulfonic Acid Ester Copolymers

Linear ethylene copolymers containing sulfonic acid ethyl esters precisely spaced on every 21st carbon have been synthesized using metathesis polycondensation chemistry. These precision structures with one directly attached and one aromatic spaced sulfonic acid ester are synthesized with the goal of tailoring layered higher order morphologies in contrast to conventional clustered ionic polyolefins. Primary structural characterization confirms the precision polymer structures. Additional secondary microstructural analysis by DSC shows a recoverable endothermic melt transition of polyethylene‐like lamellae crystallites of the directly attached ester while completely amorphous behavior is observed when the ester is spaced away from the backbone with an aromatic group.

     

Engineering the Maxwell-Wagner polarization effect

Layered structures, when supporting the Maxwell-Wagner polarization mechanism, exhibit very large effective electric permittivity and thus can be used for miniaturizing purposes. However, the large interfacial dimensions evolved, limit the Maxwell-Wagner polarization at relatively low frequencies. Any element or mechanism that causes a spatial variation of charge density, contributes to the dielectric susceptibility of a medium. Thus, intentionally planted polarization states can be used for further exploiting the Maxwell-Wagner polarization mechanism.