化学激光器燃烧室两步反应法的实验研究

 在环柱型增益发生器实验系统燃烧室的设计中,将主稀释剂He从两个不同的区域注入燃烧室,其中一部分与D2预混以后通过D2喷注孔注入,另一部分通过主喷管叶片后端的后向喷注孔注入。讨论了不同区域的主稀释剂流量的变化对激光器特性的影响。实验结果表明：后He流量改变时,激光器的功率变化及点火稳定性等明显优于前He流量改变的情况。若要增加主稀释剂比例,应优先考虑调整后He。     

Hydrogen and syngas production from two-step steam reforming of methane using CeO2 as oxygen carrier

CeO2 oxygen carrier was prepared by precipitation method and tested by two-step steam reforming of methane (SRM). Two-step SRM for hydrogen and syngas generation is investigated in a fixed-bed reactor. Methane is directly converted to syngas at a H2/CO ratio close to 2 : 1 at a high temperature (above 750 °C) by the lattice oxygen of CeO2; methane cracking is found when the reduction degree of CeO2 was above 5.0% at 850 °C in methane isothermal reaction. CeO2?δ obtained from methane isothermal reaction can split water to generate CO-free hydrogen and renew its lattice oxygen at 700 °C; simultaneously, deposited carbon is selectively oxidized to CO2 by steam following the reaction (C+2H2O→CO2+2H2). Slight deactivation in terms of amounts of desired products (syngas and hydrogen) is observed in ten repetitive two-step SRM process due to the carbon deposition on CeO2 surface as well as sintering of CeO2.     

Preparation,Morphology, and Structure of Thermotropic Liquid Crystalline Polyester-imide/Phenol-formaldehyde Resin Blends

As a novel toughening agent, thermotropic liquid crystalline polymers (TLCPs) possess excellent properties of high strength, high modulus, low expanding coefficient, and high thermal stability. In this study, a thermotropic liquid crystalline poly(ester-imide) derived from N,N’-hexane-1,6-diylbis(tri-millitimide) (IA6), p-hydroxylbenzoic acid (PHB), and 4,4’-dihydroxybenzophenone (DHBP) was synthesized by the Higashi's direct polycondensation method. The structure and properties of the TLCP were studied using Fourier transformed infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), thermogravimetic analyses (TGA), polarized light microscopy (POM), and wide angle X-ray diffraction (WAXD). The results revealed that the synthesized polyester-imide is a nematic TLCP with good thermal stability and its starting decomposition temperature is up to 439°C. Additionally, polymer blends of phenol-formaldehyde (PF) resin with different contents of polyester-imide were prepared and characterized by POM and WAXD. POM results demonstrated that two-step blending is an ideal method for blending TLCP and PF resin. By this method, continuous filamentous stripes can be clearly observed at 230°C for TLCP/PF blend of 10 wt% poly(ester-imide).     

Preparation of ZnO/GO composite material with highly photocatalytic performance via an improved two-step method

ZnO/graphene oxide(ZnO/GO) composite material,in which ZnO nanoparticles were densely coated on the GO nanosheets,was successfully prepared by an improved two-step method and characterized by IR, XRD,TEM,and UV-vis techniques.The improved photocatalytic property of the ZnO/GO composite material,evaluated by the photocatalytic degradation of methyl orange(MO) under UV irradiation,is ascribed to the intimate contact between ZnO and GO,the enhanced adsorption of MO,the quick electron transfer from excited ZnO particles to GO sheets and the activation of MO molecules viaπ-πinteraction between MO and GO.     

Asymptotically optimal estimation in the linear regression problem in the case of violation of some classical assumptions

We consider the problem of estimating the unknown parameters of linear regression in the case when the variances of observations depend on the unknown parameters of the model. A two-step method is suggested for constructing asymptotically linear estimators. Some general sufficient conditions for the asymptotic normality of the estimators are found, and an explicit form is established of the best asymptotically linear estimators. The behavior of the estimators is studied in detail in the case when the parameter of the regression model is one-dimensional.     

Sm原子的偶宇称高激发态的光谱研究

采用双色三步激发和光电离过程,对Sm原子的偶宇称高激发态的光谱进行了研究.先采用两条激发路线分别将Sm原子两步共振激发至待测的高激发态,然后利用光电离技术对其进行探测.分别将第一束激光的波长固定在627.50nm和624.41nm上,以便将Sm原子从亚稳态共振激发到由4f⁶6s6p电子组态所构成的两个原子状态上.第二束激光在440-700nm的波段范围内扫描,不仅使Sm原子在30040-38065cm^-1能域内的偶宇称高激发态上布居,将其进一步光电离,测量了其光谱.通过光谱定标和选择定则等分析手段,本工作不仅精确获得了136个态的能级位置,而且也唯一确定了其总角动量,并且给出了相关跃迁的相对谱线强度.     

基于两阶段思想处理拒绝推断的信用评分模型

本文首先从数据缺失机制的角度分析了信用评分模型的开发和应用中所存在的样本偏差问题,提出了可以用拒绝推断来处理此类问题;然后在曾经被应用于拒绝推断问题处理的Heckman两阶段模型的基础上,提出了用拟似然两阶段模型和广义偏线性模型这两种新的两阶段方法来处理信用评分模型中的拒绝推断问题。经过实证分析发现,应用这两种方法可以得到很理想的结果。另外根据本文的研究,人行征信这类外部数据是拒绝推断最有效的方法,如果此类数据缺乏,则用拟似然两阶段模型和广义偏线性模型是比较有效的拒绝推断方法。     

全息照相实验的新思路

在全息照相实验中,增加两种拍摄全息光栅的光路,在一张全息底片上,经过三次曝光,拍摄一幅全息图和两种光栅常量值的全息光栅,可使学生深刻地理解一张全息底片能够记录多个不同信息的原理。     

双通道自聚焦计算全息匹配滤波器

介绍了一种双通道自聚集的匹配滤波器。它是在计算全息的基础上,通过对两个物的傅里叶谱或共轭谱分别加正的或负的二次相位因子,求和后进行编码,制图,缩微而得,该滤波器可以分别对两个物实现匹配。文中还给出了与理论相符的实验结果。     

解不适定算子方程的一个定常二步隐式迭代法

On the basis of an implicit iterative method for ill-posed operator equations,we introduce a relaxation factor and a weighted factor , and obtain a stationarytwo-step implicit iterative method. The range of the factors which guarantee theconvergence of iteration is explored.We also study the convergence properties and ratesfor both non-perturbed andperturbed equations.An implementable algorithm is presented by using Morozov discrepancy principle.The theoretical results show that the convergence rates of the new methods always lead to optimal convergentrates which are superior to those of the original one after choosing suitable relaxation and weightedfactors. Numerical examplesare also given, which coincide well with the theoretical results.