On the uniqueness of minimizing harmonic maps to a closed hemisphere

We study the uniqueness of minimizing harmonic maps to a closed hemisphere. We are able to describe the boundary data for which there are more than one minimizer, and to describe in these cases the corresponding set of minimizers. This is a limiting case for a former result of W.Jäger and H.Kaul.This article was processed by the author using the Springer-Verlag T_EX PJourlg macro package 1991.     

Facial reduction in partially finite convex programming

We consider the problem of minimizing an extended-valued convex function on a locally convex space subject to a finite number of linear (in)equalities. When the standard constraint qualification fails a reduction technique is needed to derive necessary optimality conditions. Facial reduction is usually applied in the range of the constraints. In this paper it is applied in the domain space, thus maintaining any structure (and in particular lattice properties) of the underlying domain. Applications include constrained approximation and best entropy estimation.Research partially supported by the Natural Sciences and Engineering Research Council of Canada.     

Optimal impulse control problems for degenerate diffusions with jumps

Optimal stopping and impulse control problems for degenerate diffusion with jumps are studied in this paper. Lipschitzian coefficients for the diffusion process, data with polynomial growth, and evolution in the whole space are the main assumptions on the models. Several characterizations of the optimal cost functions are given. Existence of optimal policies is obtained.This research has been supported in part by Army Research Office Contract DAAG29-83-K-0014 and by National Science Foundation Grant DMS-8601998.     

Ce-MCM-48介孔分子筛的合成、表征和催化性能

尝试以混合模板剂pH调节水热合成掺入铈的介孔分子筛CeMCM48,并采用X射线衍射、高分辨透射电镜、紫外可见漫反射、X射线荧光光谱、氮气吸附脱附测试手段对样品进行表征.结果表明,新合成的掺铈介孔材料仍保持立方介孔的有序结构,有序性及吸附性能得到改善.所合成的掺铈的立方介孔分子筛对环己烷的液相氧化反应的催化活性和选择性较高.CeMCM48催化环己烷氧化反应的转化率较MCM48催化的转化率提高了8.3%～14.2%,对主要产物的选择性提高了63.4%～68.8%.     

Approximation of a laminated microstructure for a rotationally invariant,double well energy density

Summary. We give error estimates for the approximation of a laminated microstructure which minimizes the energy for a rotationally invariant, double well energy density . We present error estimates for the convergence of the deformation in the convergence of directional derivatives of the deformation in the “twin planes,” the weak convergence of the deformation gradient, the convergence of the microstructure (or Young measure) of the deformation gradients, and the convergence of nonlinear integrals of the deformation gradient. Received July 25, 1995 / Revised version received November 20, 1995     

Fabrication of Cu2ZnSn(SxSe1−x)4 thin film solar cell by single step sulfo-selenization of stacked metallic precursors

We have synthesized an efficient Cu₂ZnSn(S_xSe_1−x)₄ (CZTSSe) absorbers by using single-step rapid thermal sulfo-selenization process of sputtered stack metallic precursor (Zn/Sn/Cu) films. The structural and morphological studies confirm that the suitability of the rapid thermal sulfo-selenization process for the synthesis of a CZTSSe absorber without any secondary phases with large grains. The annealing atmosphere with a mixed-chalcogen source enhances the grain growth of the CZTSSe absorber as compared with pure Cu₂ZnSnS₄ (CZTS) and Cu₂ZnSnSe₄ (CZTSe) absorbers. The CZTSSe thin film solar cell shows the best conversion efficiency of ∼7%.     

聚丙烯腈基碳纤维原丝在纺丝过程中纳米孔变化规律与机理研究

应用小角X射线散射等方法, 系统、定量地测试表征了聚丙烯腈基碳纤维原丝中纳米孔的尺寸、形状、体积分数、单位体积中纳米孔绝对数量以及纤维总孔洞率等形态结构参量, 并对这些参量在水洗、水洗牵伸、热致密化、高压蒸汽牵伸及热稳定化等工艺过程中的变化规律及原因进行了研究. 结果表明, 纺丝过程中牵伸及高温热处理均可使纤维总孔洞率逐步下降. 纳米孔尺寸体积分数V_i测试表明, 对于小于10 nm³的小纳米孔和大于10³ nm³的较大纳米孔, 两者的V_i在纺丝初期水洗牵伸工艺中分别为0.217和0.369, 而在纺丝后期热稳定化处理后发生大幅度改变, 分别为0.948 与0.015. 其原因并不是在高压蒸汽牵伸及热稳定处理中较小纳米孔含量的增加, 而是较大纳米孔含量的大幅度减少. 纳米孔形状研究表明, 纺丝工艺中的多次牵伸处理均使纳米孔的长短轴比加大, 而大于玻璃化温度的热处理均使纳米孔长短轴比收缩, 并且对于较小纳米孔来说这种收缩更为显著.     

用固体核磁方法研究MCM-22分子筛中的Al状态

用固体NMR技术研究了新型分子筛MCM-22在不同水合状态下的²⁷Al谱和¹H谱.并用新的¹H/²⁷Al双共振方法TRAPDOR对MCM-22分子筛的各种铝状态进行了研究,得到了样品脱水后B酸位(Bronsted)、L酸位(Lewis)以及非骨架Al(OH)的四极耦合常数.     

二级轻气炮发射过程中前冲气体的初步研究

 在二级轻气炮发射过程中,靶室内的残存气体和绕行到弹丸前方的推进气体都有可能对实验结果造成影响。利用石英传感器测量并得到了二级轻气炮高速弹丸发射时前冲气体的压力信号,并计算得到了相应的压力。实验结果表明：二级轻气炮发射时确实存在前冲气体现象,但其压力幅值较小,约为10^-2 GPa量级,不会对高压物理实验的结果造成明显的影响。