基于CFD的射流抛光喷射距离的分析和优化

分析了喷射距离对射流抛光效果的影响,基于计算流体动力学进行了喷射距离的分析和优化.通过构建射流抛光不同喷射距离的物理模型,采用能更好地处理流线弯曲程度较大的流动的RNG k-ε紊流模型应用于射流抛光的数学建模,使用SIMPLEC算法对射流模型进行数值计算,得到了不同模型的射流抛光冲击射流流场及工件壁面上的冲击压力、紊动强度、壁流速度分布.根据射流抛光对冲击射流特性的要求,比较和分析不同喷距模型的数值仿真结果,结果显示,射流抛光最优化喷距范围为喷嘴口径的10倍至12倍之间.     

特殊环境下织物的导热系数试验研究

舱外航天服织物的研究是舱外航天服设计工作中的一项重要环节,尤其是其热特性,对航天员舱外作业安全和工效有着重要的影响.为此,本文通过对织物的传热机理、服装的热舒适性及平板导热仪的原理等进行分析,研制了一种新型的双平板式导热仪对特殊环境(超低温、真空)下的织物导热系数进行了试验研究,得到了不同特殊环境下织物的导热系数,并对结果进行了分析和讨论.     

不同等离子体积力模型诱导流动对比研究

基于不同等离子简化模型,对比研究了5 kV电压下等离子诱导流场.结果表明,由于假定电荷分布依赖于电势分布,模型一导致体积力过大,诱导流场速度最大达6 m/s;模型二中内外电场叠加并根据实验拟合壁面电荷分布,最大诱导速度仅为1 m/s,与实验结果接近;而模型三由于不易选取合理的电场强度分布线性化参数,最大诱导速度达7 m/s,也与实验结果相差较大.     

不同燃烧当量比对二甲醚燃烧的影响研究

利用分子束质谱结合真空紫外同步辐射光电离技术研究了低压层流预混二甲醚/氧气/氩气火焰.通过测量火焰物种的离子信号强度随燃烧炉位置的关系曲线,计算了主要火焰物种的摩尔分数曲线.分析了燃料当量比(φ)为0.8,1.0和1.5时主要火焰物种的摩尔分数曲线,阐述了燃烧当量比对低压层流预混二甲醚/氧气/氩气火焰化学结构的影响.研究为进一步认识二甲醚燃烧提供了实验数据.     

Multiparty-Controlled Remote Preparation of Two-Particle State

We propose a scheme for multiparty-controlled remote preparation of the two-particle state by using two non-maximally Greenberger-Horne-Zeilinger states as quantum channel. Our scheme consists of one sender and n remote receivers. It will be shown that the sender can help either one of the n receivers to remotely preparation the original state with the appropriate probability, and the sender Alice＇s two-particle projective measurement and the controllers＇ single-particle product meazurements are needed. We also obtained the probability of the successful remote state preparation.     

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利用通用有限元程序ANSYS对中国氦冷固态氚增殖剂实验包层模块(CH HCSB TBM)第一壁进行了稳态热分析。结果表明,第一壁铍保护板和RAFM钢的最高温度符合热工安全设计要求。对第一壁表面热流密度随时间变化的瞬态情况进行了分析,给出了随时间变化的结果。对第一壁两种典型的事故情形开展了初步分析,并对分析结果和事故影响进行了相应讨论。     

Three-Dimensional Waves in Tilt Thermal Boundary Layers

We numerically and theoretically study the stabilities of tilt thermal boundary layers immersed in stratified air. An interesting phenomenon is revealed： the stationary longitudinal-roll mode becomes unstable to some oscillating state even when the Grashof number is smaller than its corresponding critical value. By stability analysis, this phenomenon is explained in terms of a new three-dimensional wave mode. The effect of the tilt angle on the stability of the boundary flows is investigated. Since the new three-dimensional wave is found to be the most unstable mode when the title angle is between 30° and 64°, it is expected to play an important role in the transition to turbulence.     

Investigation on Guided-Mode Characteristics of Hollow-Core Photonic Crystal Fibre at Near-Infrared Wavelengths

Guided-mode characteristics of hollow-core photonic crystal fibre （HC-PCF） are experimentally and theoretically investigated. The transmission spectrum in the range from 755 to 845nm is observed and the loss is measured to be 0.12dB/m at 800nm by cut-back method. Based on the full-vector beam propagation method and the full-vector plane-wave method, the characteristics of mode field over propagation distance 1 m are simulated, and the results show that the propagation efficiency can be above 80%. Compared with the fundamental guided mode well confined in air core within shorter propagation distance, the second-order guided mode leaks into the cladding region and gradually attenuates due to larger refractive index difference. The primary loss factors in HC-PCF and the corresponding solutions are elementarily discussed.     

Derivative of Electron Density in Non-Equilibrium Green's Function Technique and Its Application to Boost Performance of Convergence

The non-equilibrium Green＇s function （NEGF） technique provides a solid foundation for the development of quantum mechanical simulators. However, the convergence is always of great concern. We present a general analytical formalism to acquire the accurate derivative of electron density with respect to electrical potential in the framework of NEGF. This formalism not only provides physical insight on non-local quantum phenomena in device simulation, but also can be used to set up a new scheme in solving the Poisson equation to boost the performance of convergence when the NEGF and Poisson equations are solved self-consistently. This method is illustrated by a simple one-dimensional example of an N＋＋ N＋ N＋＋ resistor. The total simulation time and iteration number are largely reduced.     

Re-entrant-Groove-Assisted VLS Growth of Boron Carbide Five-Fold Twinned Nanowires

We report a preferential growth of boron carbide nanowires with a five-fold twinned internal structure. The nanowires are found to grow catalytically via iron boron nanoparticles, but unusually the catalytic particle is in contact with the low-energy surfaces of boron carbide with V-shaped contact lines. We propose that this catalytical growth may be caused by preferential nucleation at the re-entrant grooves due to the twinning planes, followed by rapid spreading of atomic steps. This is consistent with the observed temperature dependence of the five-fold twinned nanowire growth.