湍流大气成像系统长曝光传递函数的研究

采用傅里叶变换法对在Kolmogorov谱大气湍流下望远镜的长曝光成像进行了模拟,给出了湍流大气成像系统长曝光传递函数的数值模拟方法,求出了在此情况下的长曝光传递函数。给出了大气湍流在Kolmogorov谱假设下成像系统长曝光传递函数的理论值。基于空间目标为点目标的假设,提出了一种湍流大气成像系统长曝光传递函数的测量方法。对由三种方法获取的大气湍流长曝光传递函数进行了比对分析。结果表明,由三种方法获取的大气湍流长曝光传递函数基本上是一致的,由傅里叶变换法模拟和实际测量得到的传递函数是合理的。     

高功率微波辐射场功率密度测量系统

 根据功率密度大、脉冲短、形状不规则的特点，研制出一种能适应各种条件下使用的高功率微波功率密度测量装置。从已有的测量手段出发，比较其不同原理和适用性，选定了峰值检波法。根据实际工作需要，着重从结构及测量的可靠性、降低系统误差等方面，进行优化设计。该装置采用矩形波导和可靠性高的耦合衰减，利用示波器进行测量。最后详细地给出了测量系统的标定方法。     

Hot-carrier transient transport

In this article a review is presented of the present knowledge on the problem of transient transport of charge carriers in semiconductors with high applied electric fields. After a summary of the fundamentals of charge transport the Monte Carlo method is presented as applied to such problems. Transient transport is then presented with special emphasis on the most modern results related to autocorrelation function of velocity fluctuations.     

Finite-element modeling of an acoustic cloak for three-dimensional flexible shells with structural excitation

A finite-element model for three-dimensional acoustic cloaks in both cylindrical and spherical coordinates is presented. The model is developed through time-harmonic analysis to study pressure and velocity field distributions as well as the cloak’s performance. The model developed accounts for the fluid-structure interaction of thin fluid-loaded shells. A plane strain model is used for the thin shell. Mechanical harmonic excitation is applied to the fluid-loaded shell to investigate the effect of mechanical oscillation of the shell on the performance of the acoustic cloak. In developing this model, a deeper insight into the acoustic cloak phenomena presented by Cummer and Shurig in 2007 is presented. Different nonlinear coordinate transformations are presented to study their effect on the acoustic cloak performance.     

Determination of structural parameters from EXAFS: Application to solutions and catalysts

Summary A review is presented of applications of extended X-ray absorption fine-structure (EXAFS) spectroscopy to the determination of structural detail in inorganic solutions and supported metal catalyst particles. Similarities in these applications are noted and the possible role of disorder on the reliability of the EXAFS results is discussed. A brief summary of data analysis procedures is presented with examples. Paper presented at the Workshop on ?EXAFS Data Analysis in Disordered Systems?, held in Parma, October 5–7, 1981.     

Feynman’s Relativistic Electrodynamics Paradox and the Aharonov-Bohm Effect

An analysis is done of a relativistic paradox posed in the Feynman Lectures of Physics involving two interacting charges. The physical system presented is compared with similar systems that also lead to relativistic paradoxes. The momentum conservation problem for these systems is presented. The relation between the presented analysis and the ongoing debates on momentum conservation in the Aharonov-Bohm problem is discussed.     

Perspectives for neutrino physics at CERN

The experimental status of neutrino oscillation searches at accelerators is presented, and the future medium and long baseline projects at CERN are discussed, including the knowledge on the neutrino beam production. Perspectives on future neutrino factories based on muon storage rings are also presented.     

Automatic 3D tracking of cardiac material markers using slice-following and harmonic-phase MRI

A method to track a grid of cardiac material points in three dimensions using slice-following (SF) tagged magnetic resonance imaging (MRI) and harmonic-phase MRI is presented. A three-dimensional grid of material points on the lines of intersections of short-axis (SA) and long-axis (LA) planes is automatically tracked by combining two-dimensional pathlines that are computed on both SA and LA image planes. This process yields the true three-dimensional motion of points originating on the image plane intersections. Experimental data from normal volunteers, each obtained in four short breath-holds using the SF harmonic phase MRI pulse sequence, is presented. A validation of two-dimensional in-plane tracks using this pulse sequence on a moving phantom is also presented.     

Cylindricity of ablation-controlled arcs

A rigorous calculation of ablation-controlled arcs in cylindrical tubes that can reproduce a noncylindrical arc boundary correctly is presented. Earlier workers on the subject implicitly assumed nearly cylindrical arcs. The more rigorous results presented a posteriori justify those simplifications. A complete scan of sonic solutions is presented     

Metal–insulator transition in Si–MOS structures

A survey is presented on recent investigations of the metal-to-insulator transition in two-dimensional systems with special emphasis on n-Si–MOS structures. Experimental facts are presented and the currently open questions on the nature of this transition are addressed.     

White-light emission from porous-silicon-aluminum Schottky junctions

Summary Porous-silicon-based white-light-emitting devices are presented. The fabrication process on different substrates is described. The peculiarities of technological steps for device fabrication (porous-silicon formation and aluminum treatment) are underlined. Doping profile of the porous layer, current-voltage characteristics, time response, lifetime tests and electroluminescence emission spectrum of the device are presented. A model for electrical behaviour of Al/porous silicon Schottky junction is presented. Electroluminescence spectrum of the presented devices showed strong similarities with white emission from crystalline silicon junctions in the breakdown region. Paper presented at the III INSEL (Incontro Nazionale sul Silicio Emettitore di Luce), Torino, 12–13 October 1995.     

A method of developing regional road traffic noise management strategies

Road traffic noise management strategies or noise action plans are a necessary tool for pro-active road traffic noise management. A method is proposed for regional scale noise action plans, in part using noise mapping, which is flexible towards various data qualities. A six step method is proposed which links GIS data to road traffic noise calculation methods with the final strategies being presented in GIS format. A ‘Parcel Priority Index’ and a ‘Link Priority Index’ are presented as key variables in the production of regional strategies and planning visions on a road link basis. The noise management strategy method presented is used on a large regional area in South East Queensland, Australia which covers seven local government areas. The results presented indicate the method is successful in prioritising road links equitably for detailed road traffic noise management actions.     

Investigation of the convergence of the mixed displacement-pressure formulation for three-dimensional poroelastic materials using hierarchical elements

Recently, a mixed pressure displacement [u, P] formulation based on Biot's poroelasticity equations has been presented for porous materials. This model leads to a reduction of the number of degrees of freedom required for the modeling of three-dimensional porous media in comparison to classical displacement-displacement [u, U] formulations. In this paper, an extension of the [u, P] formulation based on hierarchical elements is presented. First, a variant of the weak integral form of the [u, P] formulation is presented and its numerical implementation using hierarchical elements is detailed, together with the application of boundary and loading conditions. Numerical results are presented to show the accuracy and performance of the present approach. In particular, the importance of correctly capturing the coupling effects between the two phases is highlighted.     

A quantitative analysis of the simulated annealing algorithm: A case study for the traveling salesman problem

A quantitative study is presented of the typical behavior of the simulated annealing algorithm based on a cooling schedule presented previously by the authors. The study is based on the analysis of numerical results obtained by systematically applying the algorithm to a 100-city traveling salesman problem. The expectation and the variance of the cost are analyzed as a function of the control parameter of the cooling schedule. A semiempirical average-case performance analysis is presented from which estimates are obtained on the expectation of the average final result obtained by the simulated annealing algorithm as a function of the distance parameter, which determines the decrement of the control parameter.     

明胶全息图环境稳定性的研究

参照Ｎａｉｋ对明胶全息图环境性的考察工作，对双敏感中心红敏明胶材料中所记录的全息图的环境稳定性进行了实验考察，结果表明，用ＤＣ－ＭＢＤＣＧ记录的全息图比各酸明胶全息图有高的多的环境稳定性。本文还对实验结果的机理进行了讨论，并给出了一种明胶全息图抗水涂层制备新工艺。     

Neutron diffraction studies of simple molecular liquids

Summary A brief review is presented of the structural characteristics of diatomic and tetrahedral molecular liquids. Paper presented at the workshop ?Highlights on Simple Liquids?, held in Turin at ISI on 1–3 May, 1989.     

基于子曲面分割和迭代的自由曲面光线追迹方法

根据光学自由曲面数学描述复杂,但面形较为平滑的特点,提出一种新的基于子曲面分割和迭代的自由曲面光线追迹方法。通过离散点分割形成子曲面阵列,根据三角形内角和定理确定目标子曲面,对目标子曲面进行切平面迭代完成光线追迹。通过数值仿真,采用所提方法分别对偶次非球面、双圆锥曲面、扩展多项式面和单透镜无像散系统进行光线追迹,并与ZEMAX追迹结果进行比对。结果表明:该方法在离散点采样密度很低的情况下（降低了计算机的内存消耗和运算时间）仍然可以保证光线追迹的精确性,与ZEMAX中光线和自由曲面交点的偏差达到10-3（nm）量级,出射光线角度的偏差达到10-3（）量级。     

光学材料光学均匀性的波长调谐两步绝对测量法

光学均匀性是光学材料的重要指标,目前高精度的测量方法一般采用绝对测量法,而该方法步骤繁琐,容易受环境影响。根据波长移相干涉仪的移相特点,提出了测量光学材料光学均匀性的波长调谐两步绝对测量法。该方法在波长移相干涉仪中通过平行平板放入测量和空腔测量两个步骤得到平行平板的光学均匀性。在模拟仿真验证方法的正确性后,进行了实验研究,并与传统的绝对测量法的测量结果进行比较。结果表明,波长调谐两步绝对测量法可用于测量平行平板的光学均匀性,且测量步骤简单,精度较高。     

住宅隔声的预测:计及侧向传声的简易方法

本文提出了一种预测房间隔声的方法，它考虑了侧向传声，而以容易得到有关于房屋布局，隔墙及其支撑的资料作为基础，分离了三种传声路长并作出解释，最后给出一些测量与计算之间相比较的例子。