掺钛空心玻璃微球制备技术

为实现惯性约束聚变靶用空心玻璃微球的均匀掺杂,采用溶胶-凝胶技术结合炉内成球法,以钛酸四丁酯为掺杂剂,对钛掺杂玻璃溶胶-钛掺杂玻璃凝胶-钛掺杂干凝胶粒子-钛掺杂空心玻璃微球（Ti-HGM）这一掺钛空心玻璃微球的制备方法进行了探索。实验结果表明：掺钛效应使空心玻璃微球壁厚均匀性、同心度有所降低,但对壁厚、直径控制基本无影响;Ti与Si原子分数比为2.23%的Ti-HGM掺杂基本均匀,近70%微球的保气半寿命在一个月以上。     

Four-component superlattice empirical pseudopotential method for InAs/GaSb superlattices

For the design of InAs/GaSb superlattice (SL) heterojunction infrared photodetectors with very low dark current we have extended the standard two-component superlattice empirical pseudopotential method (SEPM) and implemented a four-component model including interface layers. For both models, the calculated bandgap values for a set of SL samples are compared to bandgaps determined by photoluminescence measurements. While the bandgap resulting from the two-component model agrees well with experimental data for SL structures with individual layer thicknesses of 7 monolayers and more, we show that for SLs with thinner GaSb layers the four-component SEPM model is accurate, when the As-content in the interface and barrier layers is included in the model.     

Early transient responses of multi-span stepped single-walled carbon nanotubes using the method of reverberation ray matrix

The early transient responses of multi-span stepped single walled carbon nanotubes (SWCNTs) under impact loadings are studied by the method of reverberation ray matrix (MRRM). The dynamics model of the carbon nanotubes is established in the Fourier phase space on the basis of the nonlocal Timoshenko beam model. The wave solutions of SWCNTs with arbitrary boundary conditions are obtained by the wave method. The reverberation ray matrix of the multi-span stepped SWCNTs is the product of scattering, phase and permutation matrices, which can be determined by the impact loadings, continuous conditions and boundary conditions. The early transient responses can be calculated by the inverse Fourier transform of the sum of initial ray groups. It can be found that the early transient displacement response in the very short time subjected to the impact loading is very small, while the transient transverse shear strain becomes large in the very short time. The influences of nanotubes span number, nanotubes type and boundary conditions on the early transient responses of multi-span stepped SWCNTs are investigated.     

Numerical study of the heat transfer and electro-thermo-convective flow patterns in dielectric liquid layer subjected to unipolar injection

In this article we study the electro-thermal convection in a dielectric liquid layer placed between two electrodes and subjected to the simultaneous action of an electric field and a thermal gradient. The full set of equations describing the electro-thermo-convective phenomena is directly solved using a finite volume method. We first heat the liquid from below at time t = 0, wait for the thermal steady state and then inject the electric charges by applying the electric potential. The development of the electro-convective motion is analysed in detail in two cases: 1) strong injection from the lower electrode, 2) strong injection from the upper one. We also study the heat transfer enhancement due to electro-convection. The evolution in time of the Nusselt number Nu for different combinations of the two usual non-dimensional parameters associated to the electro-thermo-convection phenomena (Rayleigh number Ra and the electrical parameter T) is also given and analysed.     

Determination of trapping–detrapping events,recombination processes and gap-state parameters by modulated photocurrent measurements on amorphous silicon

Analysis of the out-of-phase modulated photocurrent (MPC) signal, the so-called Y signal, is proposed for determining the trapping–detrapping events, recombination processes and gap-state parameters in amorphous silicon. This is demonstrated by analysing experimental Y spectra obtained on this material from different laboratories including our own. Model simulations are also employed in which the amphoteric nature of the dangling bonds and their distribution according to the defect-pool model are taken into account. From the reconstruction of the Y signal, phase shift and MPC amplitude spectra, several contributions resolved from the frequency dependence of the experimental Y spectra are identified. Two electron trapping–detrapping processes are resolved. These are attributed to hydrogen-related positive defects and to transitions involving the D^+/0 level of the normal dangling bonds from the defect-pool distribution. At lower frequencies a residual contribution is resolved that is attributed to a term related to recombination through the D^+/0 and D^0/? levels. Between 300 and 150?K the above recombination contribution is essentially from the D^0/? and dominates the Y signal at lower frequencies. In this region a characteristic phase lead appears, which is attributed to the existence of safe hole traps in the valence band tail. Around 150?K, trapping–detrapping events in the conduction band tail dominate.     

Multi-environment probability density function method for modelling turbulent combustion using realistic chemical kinetics

A computational fluid dynamics (CFD) tool for performing turbulent combustion simulations that require finite-rate chemistry is developed and tested by modelling a series of bluff-body stabilized flames that exhibit different levels of finite-rate chemistry effects ranging from near equilibrium to near global extinction. The new modelling tool is based on the multi-environment probability density function (MEPDF) methodology and combines the following: the direct quadrature method of moments (DQMOM); the interaction-by-exchange-with-the-mean (IEM) mixing model; and realistic combustion chemistry. Using DQMOM, the MEPDF model can be derived from the transport PDF equation by depicting the joint composition PDF as a weighted summation of a finite number of multi-dimensional Dirac delta functions in the composition space. The MEPDF method with multiple reactive scalars retains the unique property of the joint PDF method of treating chemical reactions exactly. However, unlike the joint PDF methods that typically must resort to particle-based Monte-Carlo solution schemes, the MEPDF equations (i.e. the transport equations of the weighted delta-peaks) can be solved by traditional Eulerian grid-based techniques. In the current study, a pseudo time-splitting scheme is adopted to solve the MEPDF equations; the reaction source terms are computed with a highly efficient and accurate in-situ adaptive tabulation (ISAT) algorithm. A 19-species reduced mechanism based on quasi-steady state assumptions is used in the simulations of the bluff-body flames. The modelling results are compared with the experimental data, including mixing, temperature, major species and important minor species such as CO and NO. Compared with simulations using a Monte-Carlo joint PDF method, the new approach shows comparable accuracy.     

同轴线方法测量束流耦合阻抗的有效性分析

 根据同轴线方法测量阻抗的原理，用模拟方法讨论了该测量方法的有效性问题。从均匀圆波导和同轴线结构中的电磁场解析分析，说明了该方法有效性问题的起源和基本物理图像，简单回顾其他方法讨论该问题的结论，最后数值模拟分析了同轴线方法测量束流耦合阻抗的有效性，所得主要结论能够对阻抗测量平台的设计提供可靠的依据。     

玻色-爱因斯坦凝聚体中的超流现象

在玻色－爱因斯坦凝聚（BEC）的超流现象的研究中，人们通常采用平均场近似下求解Gross-Pitaveskii方程的方法，我们采用更严格的准确对角化的方法对弱排斥相互作用下两维旋转N－Boson体系的凝聚状态进行了研究，研究表明，弱相互作用下的基态并不是人们通常认为的单一凝聚态，而是一个碎裂凝聚态，通过碎裂态能谱与平均场方法给出的能谱之间的比较以及条件几率分布函数的计算，我们指出这种碎裂凝聚态有着内在的不稳定性，很容易破缺到一个单一凝聚状态；计算给出的条件几率分布可以用来揭示破缺石的状态，其分布图案与平均场近似下得到的涡旋图形相类似，我们进一步注意到过去研究工作主要集中在弱相互作用极限下和强相互作用Thomas-Fermi近似极限下这两种极端情况，为考察两种极限间的中间过渡区域，我们研究了中等相互作用强度下体系的基态性质。     

等离子体二维密度重建的影响因素

利用超强超短激光脉冲产生的高能质子束的库仑能量损失可以重建稠密等离子体的二维密度分布,使用同时迭代重建算法（SIRT算法）研究等离子体二维密度重建的影响因素.研究等离子体密度梯度、密度量级和质子束入射能量对重建误差的影响,分析质子束成像探测等离子体密度之前获得等离子体大概方位的重要性,通过数据拟合确定了能量噪声和重建误差之间的解析关系式.     

考虑Soret和Dufour效应的方腔内双扩散自然对流格子Boltzmann模拟

采用格子Boltzmann方法,考虑Soret和Dufour效应,对内置高浓度发热圆的方腔内部双扩散自然对流现象进行数值模拟.高浓度发热圆位于方腔中心,四周壁面均为低温低浓度.在该模型中,用三个独立的LBGK方程分别模拟速度场、温度场和浓度场,并通过Boussinesq近似将它们耦合起来.分析Soret数和Dufour数对方腔内部双扩散自然对流的影响,得到流线图、等温线图、等浓度线图、发热圆表面平均Nusselt数和平均Sherwood数.结果表明：Soret和Dufour效应对方腔内双扩散自然对流影响明显,不能忽略.