The measurements of correlation times of molecules adsorbed on silica gel,alumina and charcoal using NOESY and MAS NMR

The correlation times (τ_c) and cross relaxation rates of toluene, dimethylformamide, tetrahydrofuran, water-acetone and water-dioxane adsorbed on silica gel, alumina and charcoal were obtained by measurements of the integrated intensities of cross and diagonal peaks in their NOESY spectra. The (τ_c) of the above mentioned systems is in the range of 10^?6?10^?9 s, much longer than that in the liquid (10^?12?10^?14 s). It was found that intramolecular rotation of toluene adsorbed on charcoal is slower than that on SiO₂, Al₂O₃ and the inversion of α and β protons in tetrahydrofuran is very fast (τ_c = 1.76×10^?9 s). The cross relaxation plays an important role in the relaxation of molecules adsorbed on solid surfaces with low electron densities.     

A linear system solver based on a modified Krylov subspace method for breakdown recovery

Despite its usefulness in solving eigenvalue problems and linear systems of equations, the nonsymmetric Lanczos method is known to suffer from a potential breakdown problem. Previous and recent approaches for handling the Lanczos exact and near-breakdowns include, for example, the look-ahead schemes by Parlett-Taylor-Liu [23], Freund-Gutknecht-Nachtigal [9], and Brezinski-Redivo Zaglia-Sadok [4]; the combined look-ahead and restart scheme by Joubert [18]; and the low-rank modified Lanczos scheme by Huckle [17]. In this paper, we present yet another scheme based on a modified Krylov subspace approach for the solution of nonsymmetric linear systems. When a breakdown occurs, our approach seeks a modified dual Krylov subspace, which is the sum of the original subspace and a new Krylov subspaceK _m (w _j ,A ^T ) wherew _j is a newstart vector (this approach has been studied by Ye [26] for eigenvalue computations). Based on this strategy, we have developed a practical algorithm for linear systems called the MLAN/QM algorithm, which also incorporates the residual quasi-minimization as proposed in [12]. We present a few convergence bounds for the method as well as numerical results to show its effectiveness.Research supported by Natural Sciences and Engineering Research Council of Canada.     

用界面单元法分析复合材料界面力学性能

本文利用界面单元的固有特性，将其用来模拟复合材料中纤维与基体之间的界面特征，计算了一个沿Ｘ轴方向纤维周期排列的单尾板，在横向载荷作用下的应力分布问题．给出了三相（纤维、基体和界面）特性各种配比时应力分布等高线图以及通过界面时径向应力σｒ的变化情况，反映了界面特性对应力分布的影响．     

Interior-point methods for nonlinear complementarity problems

We present a potential reduction interior-point algorithm for monotone nonlinear complementarity problems. At each iteration, one has to compute an approximate solution of a nonlinear system such that a certain accuracy requirement is satisfied. For problems satisfying a scaled Lipschitz condition, this requirement is satisfied by the approximate solution obtained by applying one Newton step to that nonlinear system. We discuss the global and local convergence rates of the algorithm, convergence toward a maximal complementarity solution, a criterion for switching from the interior-point algorithm to a pure Newton method, and the complexity of the resulting hybrid algorithm.This research was supported in part by NSF Grant DDM-89-22636.The authors would like to thank Rongqin Sheng and three anonymous referees for their comments leading to a better presentation of the results.     

Optimization‐free superoscillatory lens using phase and amplitude masks

A superoscillatory focusing lens has been experimentally demonstrated by optimizing Fresnel zone plates (FZP), with limited physical insight as to how the lens feature contributes to the focal formation. It is therefore imperative to establish a generalized viable account for both FZP (amplitude mask) and binary optics (phase mask). Arbitrary superoscillatory spots can now be customized and realized by a realistic optical device, without using optimization. It is counterintuitively found that high spatial frequency with small amplitude and destructive interference are favorable in superfocusing of a superoscillation pattern. The inevitably high sidelobe is pushed 15λ away from the central subwavelength spot, resulting in significantly enlarged field of view for viable imaging applications. This work therefore not only reveals the explicit physical role of any given metallic/dielectric rings but also provides an alternative design roadmap of superresolution imaging. The robust method is readily applicable in superthin longitudinally polarized needle light, quantum physics and information theory.     

二维各向同性谐振子的双波描述

二维各同性谐振子体系除哈密顿量外还有三个独立的守恒量。本文给出了对这些不同描术宾比较。     

多孔硅表面Ag层对吸附其上的若丹明B染料分子表面增强Raman散射的影响

采用溶液电镀方法在多孔硅表面制备纳米尺寸的银颗粒,测量了不同镀银多孔硅表面吸附的ＲｈＢ染料分子以及固态的ＲｈＢ染料的Ｒａｍａｎ散射谱。在相同的激发强度下,固态ＲｈＢ染料的Ｒａｍａｎ散射最弱,而镀银的多孔硅表面具有明显的增强效果（～１０＾４）。     

快中子引起的背向溅射

描述了用实验方法测量快中子引起的背向溅射,测量了Mg、Al、Sc、V、Fe、CO、Cu、Zr、Au和316型不锈钢等10种材料的背向溅射产额,并与正向产额进行了比较,发现背向和正向溅射产额的比值与核反应的类型有关.本实验的结果同其它小组的结果进行了比较,并用溅射理论对实验结果进行了解释.