冲击高度对自由冲击射流影响的实验研究

采用热线风速仪测量了雷诺数为 ２３ ０００时四种冲击高度下率流自由冲击射流流场，并给出详细的结果．表明壁面的“阻尼”影响主要集中在近壁面０．５Ｄ以内．小冲击高度时径向速度下降得比大冲击高度时明显要快，量值也较小；在ｒ／Ｄ≤１．５处，小冲击高度时紊动能的数值大小和分布趋势与大冲击高度时不同，特别是在喷管出口距冲击板高度Ｚ与喷管直径Ｄ之比Ｚ／Ｄ为８时分布特殊，在其它测点处，紊动能的分布趋势基本一致，只是大冲击高度下的值较大；流动结构在Ｚ／Ｄ为６～８时发生了较大的变化，这种变化与势流核心区有关，在势流核心区的顶端以及下游的一段距离内紊流度都很高．     

A note on the growth of velocities in a collisionless plasma

We consider the initial value problem for the classical Vlasov–Poisson system with smooth compactly supported initial data. In the electrostatic case, we show that the size of the velocity support of the distribution function grows at most like t^2/7+bfε for any ε> 0 . Copyright © 2010 John Wiley & Sons, Ltd.     

Artificial neural network prediction to the hot compressive deformation behavior of Al–Cu–Mg–Ag heat-resistant aluminum alloy

The behavior of the flow stress of Al-Cu-Mg-Ag heat-resistant aluminum alloys during hot compression deformation was studied by thermal simulation test. The temperature and the strain rate during hot compression were 340-500 °C, 0.001 s⁻¹ to 10 s⁻¹, respectively. Constitutive equations and an artificial neural network (ANN) model were developed for the analysis and simulation of the flow behavior of the Al-Cu-Mg-Ag alloys. The inputs of the model are temperature, strain rate and strain. The output of the model is the flow stress. Comparison between constitutive equations and ANN results shows that ANN model has a better prediction power than the constitutive equations.     

High-pressure and high-temperature generation using diamond/sic composite anvils prepared with hot isostatic pressing

Using a hot isostatic pressing (HIP) technique, we synthesized diamond/SiC composites from diamond and Si powders. At an HIP condition of 1450 °C and 100 MPa, a pressure much lower than that of the diamond stability field, diamond powders react with molten Si to form well-sintered diamond/SiC composites. Cubes of the composites with 15 mm edge length were thereby fabricated, and an application to the second stage anvils in a Kawai-type high-pressure apparatus was attempted. A hybrid anvils system using four cubes of the composites and four of the conventional WC was introduced and heating experiments up to 1600 °C became possible. Because the diamond/SiC composites are transparent to X-rays, the present system is applicable not only to diffraction studies but also to radiographic studies that need a larger window for an X-ray image.     

二氧化铬阴离子光电子能谱的理论研究

凭借密度泛函理论,采用不同基组对中性分子CrO2的基态（ 3B1）以及阴离子CrO2‾的基态（ 4B 1）进行几何优化和振动频率分析;应用量化计算得到的力常数及结构和光谱参数,基于推得的两维四模Franck-Condon重叠积分的代数表示,对CrO2 ( 3B1)－CrO2‾ ( 4B1) 的光脱附过程进行Franck-Condon分析和光谱模拟,理论上得到光电子能谱的谱线相对强度及振动结构分布,理论谱与实验测得的二氧化铬阴离子光电子能谱达到一致,并对光电子能谱的振动结构进行归属及热带分析;另外,在光谱模拟过程中通过迭代Franck-Condon分析过程,推得CrO2‾（ 4B1）与CrO2（ 3B1）平衡几何结构之差：ΔR(Cr-O)= 0.05Å,Δ(O-Cr-O)=12o.     

磁层-电离层耦合过程中等离子体粒子运动的周期轨

运用重合度理论探讨了一类非线性问题的周期解,然后将其应用于磁层-电离层耦合过程中等离子体粒子运动模型的周期解问题的研究,得到了一定条件下该模型存在周期轨的结果. 关键词： 非线性 等离子体 周期解     

Analysis of volatiles associated with industrial scale processing of expanded polystyrene Part II: Identification and quantitation

Expanded polystyrene was pyrolyzed on a laboratory scale hot wire cutter. The resulting volatiles were characterized using GC/MS as the primary analytical tool. Use was also made of retention data from a complex petrochemical standard. In situ bromination of the pyrolysate further helped in structure elucidation. Air samples were collected in the field and compared to the model experiments from a laboratory scale hot wire cutter. The results indicate that alkylbenzene type compounds were the primary compounds in this environment. A few oxygenated substances were also formed. Traces of brominated compounds were detected in the model experiments but not in the samples collected in the field, with one exception. Quantitative data are presented from a typical industrial operation.     

1.54 μm Light emission from Er/O and Er/F doped Si p–i–n diodes grown by molecular beam epitaxy

Various light emitting devices (LED) have been processed using Er/O- and Er/F-doped Si layered structures grown by molecular beam epitaxy (MBE) at low temperature. A comparative study has been carried out in order to provide more understanding of the electroluminescence (EL) excitation and de-excitation mechanisms in particular at a high injection current regime. Comparing the experimental results with model calculations the values of excitation cross section, σ_ex, and effective Auger coefficient, C_A, have been determined for various devices operated at different biases. Time-resolved EL measurements of these Er/O- and Er/F-doped MBE Si structures, using an experimental set-up with a time response of 200 ns, have been performed with different excitation conditions. Besides the spontaneous Er emission (700 μs), some fast EL decay processes associated with the Auger energy transfer via free carriers (4 μs), and the hot carrier effects (200 ns) have been identified.     

Development and characterisation of an XeCl excimer laser-generated soft-X-ray plasma source and its applications

Summary A large-aperture, long-pulse XeCl excimer laser has been used to generate a soft-X-ray plasma source. Several laser optical configurations have been employed to optimise X-ray emission, including positive-branch unstable resonators and injection by seeding the gain region of the laser with a small commercial excimer laser, resulting in power densities in the range 10¹²–10¹⁴ W cm⁻². The characteristics of the plasma source for each different laser configuration and for different target materials are investigated. The most suitable source conditions (spectral energy distribution, time duration, etc.) for specific applications are discussed. Supported by the Royal Society, UK. Supported by INFM, Italy.     

磁镜装置中ECR等离子体硬X射线强度观测

本文描述用硬X射线针孔成象法测量简单磁镜装置中ECR等离子体辐射特性的方法及其结果。这种非破坏性的成象法,直接显示了热电子等离子体的空间分布,一次放电可成一帧清晰的象,且由此可得出二维的等发射强度线。大量结果表明电子环是非轴对称的,并非为一个整环,而是在微波注入口的对面有一个缺口。当微波功率改变时,环也在改变。