一类求解线性约束非线性规划问题的可行方向法

Wilson,Han和Powell提出的序列二次规划方法(简称SQP方法)是求解非线性规划问题的一个著名方法,这种方法每次迭代的搜索方向是通过求解一个二次规划子问题得到的,本文受[1]启发,得到二次规划子问题的一个近似解,进而给出了一类求解线性约束非线性规划问题的可行方向法,在约束集合满足正则性的条件下,证明了该算法对五种常用线性搜索方法具有全局收敛性。     

DME/LPG混合燃料HCCI燃烧模拟

根据碳氢燃料化学反应系统具有层次结构的特性,本文通过分析二甲醚(DME)与液化石油气(LPG)的详细化学反应机理,构建了反映DME／LPG混合燃料均质压燃(HCCI)燃烧的详细化学反应机理．采用该机理应用单区燃烧模型对DME／LPG混合燃料HCCI燃烧的化学反应动力学过程进行了数值计算．计算结果与试验结果对比表明,所构建的DME／LPG混合燃料氧化的详细化学反应机理能够准确预测DME／LPG混合燃料的两阶段放热特性,对低温和高温着火始点的预测很好;但高温反应过程预测欠佳,高温反应机理需要改进．     

一种改进的计算探测器校正因子的相关抽样方法

对于小尺寸探测器处于大块介质的情形, 在探测器的校正因子的Monte Carlo模拟中, 存在两个难题: 一是由于探测器尺寸很小粒子难以到达探测器并发生碰撞; 二是两个随机变量比值难以达到要求精度. 本文使用经过改进的粒子碰撞自动重要抽样方法, 再结合相关抽样方法, 解决了这两个难题, 并在MCNP-4C程序平台上加以实现. 除了粒子碰撞自动重要抽样以外, 还选用了其他3种方法: 直接模拟、区域分裂、强迫碰撞+Dxtran球分别与相关抽样方法结合, 对一个简化的探测器校正因子计算模型进行了计算. 实际计算结果表明, 相关抽样方法无论与哪种方法结合, 都起到了提高相关量计算效率的作用; 而它与粒子碰撞自动重要抽样结合, 比其他方法具有明显的优越性.     

Structural and magnetic properties of RF sputtered FePt/Fe multilayers

Series of [FePt(4min)/Fe(t_Fe)]₁₀ multilayers have been prepared by RF magnetron sputtering and post-annealing in order to optimize their magnetic properties by structural designs. The structure, surface morphology, composition and magnetic properties of the deposited films have been characterized by X-ray diffractometer (XRD), Rutherford backscattering (RBS), scanning electron microscope (SEM), energy dispersive X-ray spectroscope (EDX) and vibrating sample magnetometer (VSM). It is found that after annealing at temperatures above 500 °C, FePt phase undergoes a phase transition from disordered FCC to ordered FCT structure, and becomes a hard magnetic phase. X-ray diffraction studies on the series of [FePt/Fe]_n multilayer with varying Fe layer thickness annealed at 500 and 600 °C show that lattice constants change with Fe layer thickness and annealing temperature. Both lattice constants a and c are smaller than those of standard ones, and lattice constant a decreases as Fe layer deposition time increases. Only a slight increase in grain size was observed as Fe layer decreased in samples annealed at 500 °C. However, the increase in grain size is large in samples annealed at 600 °C. The coercivities of [FePt/Fe]_n multilayers decrease with Fe layer deposition time, and the energy product (BH)_max reaches a maximum in the samples with Fe layer deposition time of 3 min. Comparison of magnetic properties with structure showed an almost linear relationship between the lattice constant a and the coercivities of the FePt phase.     

Effect of the dispersibility of ZrO2 nanoparticles in Ni-ZrO2 electroplated nanocomposite coatings on the mechanical properties of nanocomposite coatings

ZrO₂ nanoparticles was uniformly co-deposited into a nickel matrix by electroplating of nickel from a Watts bath containing particles in suspension which were monodispersed with dispersant under DC electrodeposition condition. It was found that morphology, orientation and hardness of the nanocomposite coatings with monodispersed ZrO₂ nanoparticles had lots of difference from the nanocomposite coatings with agglomerated ZrO₂ nanoparticles and pure nickel coatings. Especially, the result of hardness showed that only a very low volume percent (less than 1 wt.%) of monodispered ZrO₂ nanoparticles in Ni-ZrO₂ nanocomposite coatings would result in higher hardness of the coatings. The hardness of Ni-ZrO₂ nanocomposite coatings with monodispersed and agglomerated ZrO₂ nanoparticles were 529 and 393 HV, respectively. The hardness value of the former composite coatings was over 1.3 times higher than that of the later. All these composite coatings were two-three times higher than that of pure nickel plating (207 HV) prepared under the same condition. The strengthening mechanisms of the Ni-ZrO₂ nanocomposite coatings based on a combination of grain refinement strengthening from nickel matrix grain refining and dispersion strengthening from dispersion state of ZrO₂ nanoparticles in the coatings.     

敏化光波长对(Fe,Ni):LiNbO3晶体全息记录性能的影响

分别采用514 nm绿光、488 nm蓝光和390 nm紫外光作为敏化光,633 nm红光作为记录光,详细研究了敏化光波长对氧化(Fe,Ni):LiNbO3晶体全息记录性能的影响.结果表明:随着敏化光波长的逐渐减小,氧化(Fe,Ni):LiNbO3晶体的非挥发全息记录性能逐渐优化,390 nm紫外光是这三种敏化光中最优的敏化光.考虑敏化光的吸收,为了在双中心全息记录中获得最优的性能,应当选择合适波长的敏化光:一方面短波长敏化光能有效地敏化深中心;另一方面短波长敏化光的吸收太强(如对光折变效应无用的基质吸收),不能沿厚度方向有效地敏化晶体,所以实际上需折衷考虑,并从理论上给予了解释.     

A complete global solution to the pressure gradient equation

We study the domain of existence of a solution to a Riemann problem for the pressure gradient equation in two space dimensions. The Riemann problem is the expansion of a quadrant of gas of constant state into the other three vacuum quadrants. The global existence of a smooth solution was established in Dai and Zhang [Z. Dai, T. Zhang, Existence of a global smooth solution for a degenerate Goursat problem of gas dynamics, Arch. Ration. Mech. Anal. 155 (2000) 277-298] up to the free boundary of vacuum. We prove that the vacuum boundary is the coordinate axes.     

The Level-split of the Two-level Entangled Atom in an Optical Field

The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field.