一个简单的演示虚物点成像的实验

本介绍了一些关于虚物点成像的演示实验方法,加深了学生对虚物的概念及其虚物点成像情况的理解。     

Image contrast in X‐ray reflection interface microscopy: comparison of data with model calculations and simulations

The contrast mechanism for imaging molecular‐scale features on solid surfaces is described for X‐ray reflection interface microscopy (XRIM) through comparison of experimental images with model calculations and simulated measurements. Images of elementary steps show that image contrast is controlled by changes in the incident angle of the X‐ray beam with respect to the sample surface. Systematic changes in the magnitude and sign of image contrast are asymmetric for angular deviations of the sample from the specular reflection condition. No changes in image contrast are observed when defocusing the condenser or objective lenses. These data are explained with model structure‐factor calculations that reproduce all of the qualitative features observed in the experimental data. These results provide new insights into the image contrast mechanism, including contrast reversal as a function of incident angle, the sensitivity of image contrast to step direction (i.e. up versus down), and the ability to maximize image contrast at almost any scattering condition defined by the vertical momentum transfer, Q_z. The full surface topography can then, in principle, be recovered by a series of images as a function of incident angle at fixed momentum transfer. Inclusion of relevant experimental details shows that the image contrast magnitude is controlled by the intersection of the reciprocal‐space resolution function (i.e. controlled by numerical aperture of the condenser and objective lenses) and the spatially resolved interfacial structure factor of the object being imaged. Together these factors reduce the nominal contrast for a step near the specular reflection condition to a value similar to that observed experimentally. This formalism demonstrates that the XRIM images derive from limited aperture contrast, and explains how non‐zero image contrast can be obtained when imaging a pure phase object corresponding to the interfacial topography.     

Hereditary noetherian categories with a tilting complex

We are characterizing the categories of coherent sheaves on a weighted projective line as the small hereditary noetherian categories without projectives and admitting a tilting complex. The paper is related to recent work with de la Peña (Math. Z., to appear) characterizing finite dimensional algebras with a sincere separating tubular family, and further gives a partial answer to a question of Happel, Reiten, Smalø (Mem. Amer. Math. Soc. 120 (1996), no. 575) regarding the characterization of hereditary categories with a tilting object.

     

复杂环境下运动目标偏振成像检测方法研究

针对低对比度、低信噪比等复杂环境下运动目标检测失检率较高的问题,提出了基于稳定性主成分寻踪的运动目标偏振成像检测方法。首先将预处理后的连续帧偏振图像组合成一个矩阵,依据帧间图像信息相关性,建立了稳定性主成分寻踪数学模型,将该矩阵分解成低秩、稀疏,噪声三部分,其中稀疏矩阵包含了帧间目标信息;再以低秩矩阵核范数与稀疏矩阵1范数的和为目标函数,利用增广拉格朗日乘子法求得目标函数值最小时的稀疏矩阵;最后采用马尔科夫随机场滤除稀疏矩阵中的噪声。实验结果表明,该方法对复杂环境有很好的适应能力,且检测准确率优于其他算法。     

Recursion in Partial Type-1 Objects With Well-Behaved Oracles

We refine the definition of II-computability of [12] so that oracles have a “consistent”, but natural, behaviour. We prove a Kleene Normal Form Theorem and closure of semi-recursive relations under ?¹. We also show that in this more inclusive computation theory Post's theorem in the arithmetical hierarchy still holds. Mathematics Subject Classification: 03D65, 03D75.     

河面上漂浮物体的运动

稳定流动的河面上的漂浮物体所能达到的最大速度，并不象一般想象的物体漂浮速度比河水流速慢，物体越轻漂流速度越快，而是比河水速度快，且物体越重速度越快，原因在于河水面是个倾斜面，本对这一问题进行定量分析，给出物理漂浮速度与时间的关系式。     

Object‐oriented parallel algorithms for computing three‐dimensional isopycnal flow

In this paper, we derive an object‐oriented parallel algorithm for three‐dimensional isopycnal flow simulations. The matrix formulation is central to the algorithm. It enables us to apply an efficient preconditioned conjugate gradient linear solver for the global system of equations, and leads naturally to an object‐oriented data structure design and parallel implementation. We discuss as well, in less detail, a similar algorithm based on the reduced system, suitable also for parallel computation. Favorable performances are observed on test problems. Copyright © 2002 John Wiley & Sons, Ltd.     

Visualization of 3D variable in time object based on data gathered by active measurement system

The recent needs of analysis and visualization of variable in time real 3D objects in many applications require development of new approach towards combining rapid 3D shape acquisition and the methodology of data processing in order to perform visualization and analysis of real 3D dynamic objects. In this paper, the general concept of visualization system of data gathered by means of optical 4D (x,y,z,t) shape measurement system is presented. The concept of a virtual camera, as the mean for interactive object visualization is introduced. The experimental results for processing of simulated and real variable in time 3D object are presented and discussed. The directions of future works focused on full implementation of the concept are introduced.     

A Monatomic Optical Near-Field Microscope with Subnanometer Spatial Resolution

We propose the principle of operation of an optical near-field microscope on the basis of linear steady-state optical dimensional resonances in the system atom-probe–atoms of the sample. It is shown that such a microscope has high sensitivity and a spatial resolution of less than 1 nm and does not set limits on the choice of samples. The distribution of the optical fields in the wave and near zones in the near-field microscope at frequencies close to the optical dimensional resonances arising as a result of dipole-dipole interactions of atoms at small distances has been investigated. The optical scheme of the monatomic near-field microscope is presented.     

Optimality in Social Choice

Marengo and Settepanella (2010) have developed a geometric model of social choice when it takes place among bundles of interdependent elements, showing that by bundling and unbundling the same set of constituent elements an authority has the power of determining the social outcome. In this article, we will tie the model above to tournament theory, solving some of the mathematical problems arising in their work and opening new questions which are interesting from both a mathematical and social choice point of view. In particular, we will introduce the notion of u-local optima and study it from both a theoretical and a numerically probabilistic point of view; we will also describe an algorithm that computes the universal basin of attraction of a social outcome in O(M ³log M) time (where M is the number of social outcomes).