Separation of nanocolloids driven by dielectrophoresis: A molecular dynamics simulation

The nonequilibrium molecular dynamics (MD) method was used to model the nanocolloids and the solvent particles. By introducing a non-uniform electric field, colloids were polarized to have opposite polarities. Separation of colloids driven by dielectrophoresis (DEP) could be seen clearly under a strong electric field at low temperatures. Analyzing the ratio of DEP velocities of colloids to thermal velocities of neutral solvent particles showed that when the ratio was correspondingly big, collision between colloids and solvent particles would be intense, making the DEP velocity of colloids fluctuate frequently. By changing the electric field strength, it was found that the enhancement of electric field strength would quicken the separation of colloids. But when the electric field strength increased to a certain degree, the separation motion would be slow because of the strong friction resistance of the solvent particles to the colloids. Moreover, studying the separation reason of colloids based on the potential energy showed that after colloids were polarized, the attractive potential energy among the colloids would be weaker than before, while the increase of temperature would reduce the attractive potential energy and increase the repulsive potential energy, which accorded with the DLVO theory. Supported by the National Hi-Tech Research and Derelopment Program of China (“863” Project) (Grant No. 2006AA04Z351) and the National Natural Science Foundation of China (Grant Nos. 50675033, 30770553)     

Rapid prediction method for nonlinear expansion process of medical vascular stent

A neural network model with high nonlinear recognition capability was constructed to describe the relationship between the deformation impact factors and the deformation results of vascular stent.Then,using the weighted correction method with the attached momentum term,the network training algorithm was optimized by introducing learning factor η and momentum factor ψ,so the speed of the network training and the system robustness were enhanced.The network was trained by some practi-cal cases,and the statisti...     

Fractional partial differential equation denoising models for texture image

In this paper,a set of fractional partial differential equations based on fractional total variation and fractional steepest descent approach are proposed to address the problem of traditional drawbacks of PM and ROF multi-scale denoising for texture image.By extending Green,Gauss,Stokes and Euler-Lagrange formulas to fractional field,we can find that the integer formulas are just their special case of fractional ones.In order to improve the denoising capability,we proposed 4 fractional partial differential equation based multiscale denoising models,and then discussed their stabilities and convergence rate.Theoretic deduction and experimental evaluation demonstrate the stability and astringency of fractional steepest descent approach,and fractional nonlinearly multi-scale denoising capability and best value of parameters are discussed also.The experiments results prove that the ability for preserving high-frequency edge and complex texture information of the proposed denoising models are obviously superior to traditional integral based algorithms,especially for texture detail rich images.     

VB与Matlab混合编程在梯度胶片制作中的应用

在梯度胶片制作系统的设计中,为了完成制胶系统上位机数据计算、图形显示、系统管理软件的设计,采用Matlab函数根据采样数据合出步进电机进给控制曲线,结合VB将曲线和数据显示在人机交互界面上,将所计算的参数提供给下位控制系统,系统通过曲线插补计算对步进电机进行控制来完成胶片制作.经实践检验,这种方法所设计的监控程序功能完善、界面良好、操作方便.     

油气井钻进钻铤进动特性仿真研究

油气井钻进破岩过程发生于地下几千米,难以获取井底钻具组合的运动状态.井底钻具组合与岩石的相互作用产生多种形式的振动及振动的耦合.为进一步研究破岩引发钻进中振动的产生机理,建立了井底钻具组合钻铤段非线性动力学模型,通过数值仿真,分析了破岩过程中转速、钻井液、井底钻具组合偏心距、摩擦等对钻铤段旋转进动的影响.数值研究表明,系统参数的变化导致井底钻具组合进动轨迹的多样性和不可预测性;井底钻具组合受到外力作用,导致钻铤进动出现混沌;钻进过程中钻铤与井壁间会发生周期性碰摩现象,为研究钻进引发钻柱黏滑振动提供新的研究思路.     

Effects of CaO and Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> on the reduction of high silicon iron ores

The effects of CaO and Na₂CO₃ on the reduction of high silicon iron ores at 1 250 °C were studied. The experimental results showed that the metallization rate was significantly hindered by the addition of CaO and Na₂CO₃, particularly at the early stage of roasting, compared to the rate without additives. In the absence of additives, iron oxides were quickly reduced to metallic iron, and fayalite was difficult to form. When CaO and Na₂CO₃ were added, the low reducible iron-containing silicate compounds formed and melted, subsequently retarding the metallization process. The inhibition of Na₂CO₃ was more noticeable than that of CaO, and higher Na₂CO₃ doses resulted in stronger inhibition of the increased metallization rate. However, when Na₂CO₃ was added prior to CaO, the liquid phase formed, which facilitated the growth of the metallic phase. To reinforce the separation of the metallic phase and slag, an appropriate amount of liquid phase generated during the reduction is necessary. It was shown that when 10% CaO and 10% Na₂CO₃ were added, a high metallization rate and larger metallic iron particles were obtained, thus further decreasing the required Na₂CO₃ dosage.     

Improved visible transparency of SIO<Subscript>2</Subscript>/ZNO:AL /CEO<Subscript>2</Subscript>-TIO<Subscript>2</Subscript>/SIO<Subscript>2</Subscript> multilayer films with high UV absorption and infrared reflection rate

New visible transparent, UV absorption, and high infrared reflection properties have been realized by depositing multilayer SiO₂/ZnO: Al/CeO₂-TiO₂/SiO₂ films onto glass substrates at low temperature by radio frequency magnetron sputtering. Optimum thickness of SiO₂, ZnO: Al (ZAO) and CeO₂-TiO₂ (CTO) films were designed with the aid of thin film design software. The degree of antireflection can be controlled by adjusting the thickness and refractive index. The outer SiO₂ film can diminish the interference coloring and increase the transparency; the inner SiO₂ film improves the adhesion of the coating on the glass substrate and prevents Ca²⁺, Na⁺ in the glass substrate from entering the ZAO film. The average transmittance in the visible light range increases by nearly 18%-20%, as compared to double layer ZAO/CTO films. And the films display high infrared reflection rate of above 75% in the wavelength range of 10-25 μm and good UV absorption (> 98%) properties. These systems are easy to produce on a large scale at low cost and exhibit high mechanical and chemical durability. The triple functional films with high UV absorption, antireflective and high infrared reflection rate will adapt to application in flat panel display and architectural coating glass, automotive glass, with diminishing light pollution as well as decreasing eye fatigue and increasing comfort.     

重力异常处理中小子域滤波法的改进

在重力资料处理中,小子域滤波法会导致异常边界严重失真。为了弥补这一缺陷,提出一种改进的小子域滤波法,通过对子域剖分方式的改进以达到提升计算速度和控制异常边界失真的效果。通过模型试验对该方法的可行性进行验证,试验结果表明:重力异常数据利用改进的小子域滤波法多次迭代计算后,可以较好地反映地质体边界的分布情况,失真现象得到明显抑制;利用该方法描绘出虎林盆地断裂分布图,得到了25条断裂的分布情况,与已有的地质资料存在很好的对应关系。     

铝合金电阻点焊预压接触分析

为了探究铝合金电阻点焊的接触压力分布及初始导电区域,利用ABAQUS软件建立球面形电极条件下的预压接触二维轴对称有限元模型并对模型施加不同的电极压力.在可视化模块中得到了各个接触面上接触压力随载荷变化曲线、电极上的轴力分布云图及工件内的有效塑性应变云图.有限元分析结果表明,各接触面上的接触压力分布是不均匀的,电极-工件间的接触压力受电极球形端面轴向应力分布影响;工件间接触压力与材料所处状态有关;随着电极压力的增大,工件间接触半径呈线性增长.说明电阻点焊时可以通过选取不同截面的电极来改善接触压力的分布,进而改变初始导电区域的大小.     

高铬铸铁的正火组织与性能研究

研究正火温度对新型高铬铸铁组织、硬度(HRC)及冲击韧性的影响。实验结果表明高铬铸铁在800~950℃正火时,其组织由珠光体+少量铁素体+网状共晶碳化物组成;在1 000~1 050℃正火时,碳化物溶解析出,珠光体球化,得到铁素体基体上分布的粒状碳化物+共晶碳化物+少量珠光体,硬度略有降低;在1 100~1 150℃正火时,共晶碳化物溶解得更多,冷却过程中奥氏体中析出弥散碳化物,冷却后得到马氏体(过饱和铁素体)基体上弥散碳化物+共晶碳化物,硬度明显升高,并在1 150℃时硬度达到最大值,在800~1 150℃正火加热温度范围内,冲击韧性在4.2~4.7 Jcm2之间波动,总体变化不大。