带自由表面水流与离散颗粒耦合模型研究

基于考察泥沙运动的细观行为特征,采用离散单元法(DEM)模拟泥沙颗粒运动,结合带自由表面的水动力学计算模型,建立了CFD-DEM耦合数值模型。计算程序开发基于Fortran语言来实现。耦合模型中实现了硬球模型和软球模型两种颗粒碰撞模型,应用范围较广。作为自由表面水流与泥沙颗粒流数值模型的初步研究,在模型建立的基础上,对模型做了基本的验证。分别通过单颗粒静水沉降和混合颗粒群分选两个计算工况,验证了模型的正确性及模拟精度。该耦合模型可进一步丰富带自由表面水流条件下泥沙运动的研究手段。     

Crystal Growth Kinetics of Nanocrystalline ZnS under Surface Adsorption

The crystal growth mechanism,kinetics,and microstructure development play a fundamental role in tailoring the materials with controllable size and morphology. In this study,by introducing the strong surface adsorption of the concentrated NaOH,two-stage crystal growth kinetics of ZnS nanoparticles was observed. In the first stage,the primary particles grow into a size over a hundred times of the original volume and the growth is controlled by the crystal-lographically specific oriented attachment. The first stage data were fitted by the "multistep OA kinetic model" built based on the molecular collision and reaction. In the second stage,following the dispersal of nanoparticles,an abrupt transition from asymptotic to parabola growth kinetics occurs,which can be fitted by a standard Ostwald ripening volume diffusion model. The presence of surface adsorption causes the two-stage growth kinetics and permits an almost exclusive OA-based growth to dominate in the first stage.     

空间机器人捕获卫星操作基于柔顺装置的无源模糊避撞柔顺控制

讨论了漂浮基空间机器人在轨捕获非合作卫星过程避免关节受冲击及过载破坏的避撞柔顺控制问题。在关节电机与机械臂之间配置了一种柔顺装置——旋转型串联弹性执行器(RSEA),其作用一是在捕获阶段,通过其内置弹簧的变形来缓冲捕获过程中被捕获卫星对空间机器人关节产生的冲击能量;二是在捕获完成后的镇定运动阶段,结合所设计的避撞柔顺策略来适时开关关节电机以保证关节冲击力矩受限在安全范围。首先,根据拉格朗日法及牛顿-欧拉法分别建立了含柔顺装置空间机器人与目标卫星系统的动力学方程;之后,结合整个系统动量守恒关系、系统运动几何及位置约束关系,建立了捕获操作后两者形成混合体系统的动力学方程。在此基础上,针对捕获操作后不稳定的混合体系统,提出了一种基于无源性理论的避撞柔顺模糊控制方案以实现其镇定控制。最后,通过仿真实验验证了所提避撞柔顺策略的有效性。     

单个Nafion@Ru和Au-Nafion@Ru纳米粒子的电化学和电化学发光碰撞行为研究

通过静电作用在Nafion和Au-Nafion纳米粒子(NPs)上负载钌联吡啶(Ru(bpy)32+)分别制得Nafion@Ru和Au-Nafion@Ru NPs.分析并比较了Au-Nafion@Ru和Nafion@Ru NPs在金超微电极(Au UME)上随机碰撞产生电流响应峰的平均峰大小、峰电量和单峰持续时间,建立...     

基于碰撞模型的斜坡滚石颗粒速度预测

滑坡滚石灾害是西部山区常见的地质灾害类型,具有突发性和随机性强的特点,是山区地质灾害预测和防治工作的重点和难点. 本文基于颗粒接触理论,考虑影响斜坡滚石碰撞过程中的随机因素,建立了用于预测斜坡滚石颗粒碰撞后速度的理论模型. 根据冲量及冲量矩定理建立滚石颗粒碰撞基本方程,得到斜坡滚石颗粒碰撞后反弹速度的解析解. 结果表明:斜坡滚石碰撞后反弹速度的解析解包含了坡角、坡体上被碰颗粒速度以及角度、入射速度和角度以及撞击角度等随机因素;当考虑入射滚石颗粒与坡体上被碰颗粒的撞击角度变化时,模型预测结果与试验结果吻合较好;本文进一步预测了滚石颗粒碰撞后颗粒反弹线速度和角度以及反弹旋转角速度的概率分布情况. 结果显示,反弹颗粒速度和角度以及反弹旋转角速度的概率分布均服从高斯分布;当坡体上被碰颗粒速度和坡角发生变化时,其对反弹颗粒速度和角度以及反弹旋转角速度概率分布定性上没有影响,但是对概率分布的中心参数有显著影响.      

Electron transfer in proton-hydrogen collisions in nonideal classical plasmas

Effects of nonideality of classical plasma on the reaction: p + H(1s) → H(nlm) + p has been investigated by carrying out fully quantum mechanical calculations within the framework of a first-order distorted wave method. Scattering amplitude is calculated conveniently by employing a simple, variationally determined wave function of hydrogen atom embedded in nonideal classical plasma. A detailed study is made on the changes in electron transfer cross sections due to the nonideality of plasma varying from 0 to 4 and the incident proton energy lying between 10 and 500 keV. It has been found that nonideality of plasma causes substantial change in capture cross section.     

小球与均质定轴杆的碰撞

从小球与均质定轴杆（质心轴）的碰撞问题出发,讨论了不同类型碰撞所遵循的物理规律,总结了完全非弹性碰撞过程的能量特征．     

Maximum number of collisions among identical hard spheres

It is proved that the maximum number of collisions among three identical hard spheres in more than one dimension is four. It is conjectured that the maximum number of collisions amongn hard spheres ind dimensions is independent ofd, provideddn-1.     

质子与Be原子的碰撞电离过程研究

本文采用初态程函近似一连续扭曲波方法研究了质子和Be原子的碰撞电离过程：计算了入射离子能量从50keV／u到10000keV／u时一阶和二阶微分散射截面随电离电子能量和角度的变化规律,并对各种碰撞电离机理进行了详细讨论;计算所得总截面随入射离子能量的变化规律也与已有数据一致;另外采用FAC代码研究了Be原子的内壳层电子（1s）被电离后的俄歇过程．