Design and analysis of a novel tunable optical power splitter

A novel tunable optical power splitter,with a Y-branch waveguide based on the total internal reflection and a microprism with tunable index refraction,is presented.Numerical simulation of its optical performance shows that a high dynamic range,low optical loss,and relatively low wavelength-dependence can be achieved.This component offers numerous advantages such as ease for fabrication,low cost,and compact size,which are very useful for potential application in integrated optical devices.     

碳纳米管内金纳米线的结构与热稳定性

采用分子动力学模拟方法, 研究了填充在(8,8)单壁碳纳米管内的Au纳米线的结构和热稳定性. 研究表明, 经高温退火至室温, Au在碳纳米管内能生成多样而稳定的结构上明显区别于自由状态Au纳米线的壳层螺旋结构Au纳米线, 其螺旋结构会随着温度的变化而转变. 束缚在碳纳米管内的壳层螺旋结构Au纳米线有非常好的热稳定性, 稳定温度高于块体Au晶体的熔化温度. 关键词： 纳米线 碳纳米管 热稳定性 分子动力学模拟     

1+1/2对转涡轮高压动叶气膜冷却数值研究

对1 1/2对转涡轮高压动叶设计了冷却方案,在高压动叶前缘滞止线,压力面和吸力面分别开设了冷却孔,并对冷却方案进行了三维数值模拟.为了研究变工况下,高压动叶气膜冷却性能,对三种典型的工况进行了详细的数值模拟.研究了不同转速对高压动叶前缘冷却效果的影响,以及吹风比对高压动叶前缘气膜冷却效果的影响;给出了前缘、压力面、吸力面冷气射流的流动特征;分析了冷气喷射对高压动叶型面马赫数,型面压力的影响.最后探讨了高压动叶吸力面后部70%轴向弦长处冷气喷射对高压动叶通道内波系结构的影响.     

太阳能热气流系统内传热与流动的实验模拟

构建了小尺寸太阳能热气流发电的实验模型,测定了系统的温度随时间和空间的分布,测定了烟囱内的速度随时间的变化关系.实验结果表明:集热棚内温度分布和季节对系统传热与流动特性的影响符合理论分析结果,而由于烟囱较薄,散热较高,在烟囱内的温度降低显著.     

Simulation of plasma doping process by using the localized molecular dynamics method

Plasma doping is the candidate for semiconductor doping. Accurate simulation of the doping technology is needed for the advanced integrated circuit manufacturing. In this paper, the plasma doping process simulation is performed by using the localized molecular dynamics method. Models that involve the statistics of the implanted compositions, angles and energies are developed. The effect of the model on simulation results is studied. The simulation results about the doping concentration profile are supported by experimental data.     

Particle-in-Cell/Monte Carlo Collision simulation of planar DC magnetron sputtering

In this paper a numerical simulation of a planar DC magnetron discharge is performed with the Particle-in Cell/Monte Carlo Collision （PIC/MCC） method. The magnetic field used in the simulation is calculated with finite element method according to experimental configuration. The simulation is carried out under the condition of gas pressure of 0.665 Pa and voltage magnitude of 400V. Typical results such as the potential distribution, charged particle densities, the discharge current density and ion flux onto the target are calculated. The erosion profile from the simulation is compared with the experimental data. The maximum erosion position corresponds to the place where the magnetic field lines are parallel to the target surface.     

Design and end chamfer simulation of PEFP beam line curved dipole magnets

The design, fabrication and field measurement of 11 DC curved dipole magnets for the PEFP Beam Line have been completed. In this paper, a design method for a complex end chamfer using OPERA-3D is proposed. The conventional method for estimating chamfer shape is extended and applied to a curved dipole magnet by a coordinate transformation. Using the interface with CAD software, the complex end chamfer is modeled and fully determined by 3D simulation to meet the field uniformity requirement. The magnetic field measurement results are in good agreement with the simulation. The design considerations, field simulation results, end chamfer development process and measurement results are presented in detail.     

有旋和无旋气固两相湍流的不同结构

了解有旋和无旋突扩气粒两相详细湍流结构对控制燃料-空气混合、火焰稳定以及燃烧污染物生成很重要.周力行等曾经对其中的两相时平均流场和湍流特性进行过雷诺平均的RANS模拟和测量的研究,但是BANS模拟不能给出详细的两相湍流的瞬态结构.本文建立了二阶矩两相亚网格尺度应力模型,对有旋和无旋同轴突扩气粒两相流动进行了双流体大涡模...     

基于DES方法的平板孤立冷却孔数值模拟研究

本文运用DES(Detached-Eddy Simulation)分离涡方法,对吹风比为0.51和1.04的平板孤立直圆孔和弯圆孔下游的换热特性和漩涡结构进行了数值研究,并简要分析了下游涡量场的结构。模拟结果显示,预测的壁面温度场的趋势与实验值吻合较好;与RANS方法相比,DES方法得到了更加丰富的流场细节和旋涡结构,同时再现了冷却孔下游具有流场的间歇性,对进一步理解和研究冷却孔下游流场内的旋涡结构提供了参考。     

非定常Navier-Stokes方程基于完全重叠型区域分解的有限元并行算法

基于完全重叠型区域分解技巧,提出三种求解非定常Navier-Stokes方程的有限元并行算法.其基本思想是首先对空间施行完全重叠区域分解,然后各个处理器使用向后Euler格式独立并行求解关于时间t的常微分方程;对于非线性的对流项,分别采用半隐格式和全隐格式进行处理.算法中每个处理器所负责的子问题是一个全局问题,它定义在整个求解区域上,但绝大部分自由度来自其所负责的子区域,从而使得算法实现简单,通信需求少.数值算例验证了算法的有效性及其良好的并行性能.