基于H.264的视频编码标准的关键技术分析

H.261是ITU-T于1990年制定的一个视频编码标准,设计目的是能够在带宽为64kbps的倍数的综合业务数字网上传输质量可接受的视频信号,是最早的运动图像压缩标准,本文对H.261的视频编码标准关键技术研究。     

Frequency domain regularization of d-dimensional structure tensor-based directional fields

The present work is intended to address two of the major difficulties that can be found when tackling the estimation of the local orientation of the data in a scene, a task which is usually accomplished by means of the computation of the structure tensor-based directional field. On one hand, the orientation information only exists in the non-homogeneous regions of the dataset, while it is zero in the areas where the gradient (i.e. the first-order intensity variation) remains constant. Due to this lack of information, there are many cases in which the overall shape of the represented objects cannot be precisely inferred from the directional field. On the other hand, the orientation estimation is highly dependent on the particular choice of the averaging window used for its computation (since a collection of neighboring gradient vectors is needed to obtain a dominant orientation), typically resulting in vector fields which vary from very irregular (thus yielding a noisy estimation) to very uniform (but at the expense of a loss of angular resolution). The proposed solution to both drawbacks is the regularization of the directional field; this process extends smoothly the previously computed vectors to the whole dataset while preserving the angular information of relevant structures. With this purpose, the paper introduces a suitable mathematical framework and deals with the d-dimensional variational formulation which is derived from it. The proposed formulation is finally translated into the frequency domain in order to obtain an increase of insight on the regularization problem, which can be understood as a low-pass filtering of the directional field. The frequency domain point of view also allows for an efficient implementation of the resulting iterative algorithm. Simulation experiments involving datasets of different dimensionality prove the validity of the theoretical approach.     

多元分析法在沉淀滴定中的应用

将多元分析法应用于沉淀滴定之中 ,提出固定电位的方法 ,建立了沉淀滴定中各组分浓度与体积之间关系的数学模型 ,对卤素和硫氰酸盐混合体系进行了测定。     

The use of genetic algorithms for assessment of high voltage fields

There are several numerical methods for calculation of electric fields but they need some sort of experience and trial and error to get the correct solution. A genetic algorithm (GA) based approach is used to eliminate the need for the experience and to save time and effort spent in the trial and error. Two enhancement techniques, namely, Refreshment Method and No-Twins Method, are used with the GA operators to improve the performance of the GA in assessment of high voltage fields. The performance of these two enhancement techniques has been studied for computing the electrostatic field in high voltage applications.     

Comparison of image reconstruction by using near‐field and far‐field data for an imperfect conductor

Image reconstruction by using near‐field and far‐field data for an imperfectly conducting cylinder is investigated. A conducting cylinder of unknown shape and conductivity scatters the incident wave in free space and the scattered near and far fields are measured. By using measured fields, the imaging problem is reformulated into an optimization problem and solved by the genetic algorithm. Numerical results show that the convergence speed and final reconstructed results by using near‐field data are better than those obtained by using far‐field data. This work provides both comparative and quantitative information. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 69–73, 2001.     

The Philosophy of Critical Realism—An Opportunity for Information Systems Research

It is argued that recent research in the information systems field has tended to either emphasise the structural/collective dimension or the agency/individual dimension, not both. Structuration theory is a more recent attempt to address both agency and structure, however there are a number of issues with the use of structuration theory in information systems research, not the least of which is its lack of recognition of the temporal and longitudinal nature of information systems development. A relatively new philosophy, critical realism, provides the potential for a new approach to social investigations in its provision of an ontology for the analytical separation of structure and agency. The philosophy is introduced and its implications for sociological investigation are discussed.     

基于Visual Foxpro的北京奥运会倒计时显示牌的设计

详细分析与探讨了用Visual Foxpro设计距2008北京奥运会开幕倒计时显示牌的方法和步骤。首先在设计北京奥运会倒计时显示牌表单界面及相关属性的基础上,阐明了北京奥运会倒计时显示牌的功能目标,进一步分析相应对象相关事件的基本过程,并提供相应的Visual Foxpro程序代码。     

浅析信息化教育环境下，高校教师如何提高教学质量

随着信息技术教育在高校的深入发展,教学质量受到进一步的关注,该文探讨了在高校信息技术教育背号下,作为教师,应该如何提高教学质量。     

基于编译原理的四则混合运算器的实现

计算机只能执行机器代码,只有专业程序人员才能较好地使用此类语言。因此编译程序已成为计算机系统的最重要的系统程序之一。本文主要通过对四则混合计算器的软件的设计分析讲述了编译程序的工作过程及具体实现。     

Robust tracking control design for uncertain robotic systems with persistent bounded disturbances

In this study, a robust nonlinear L_∞‐gain tracking control design for uncertain robotic systems is proposed under persistent bounded disturbances. The design objective is that the peak of the tracking error in time domain must be as small as possible under persistent bounded disturbances. Since the nonlinear L_∞ ‐gain optimal tracking control cannot be solved directly, the nonlinear L_∞ ‐gain optimal tracking problem is transformed into a nonlinear L_∞ ‐gain tracking problem by given a prescribed disturbance attenuation level for the L_∞ ‐gain tracking performance. To guarantee that the L_∞ ‐gain tracking performance can be achieved for the uncertain robotic systems, a sliding‐mode scheme is introduced to eliminate the effect of the parameter uncertainties. By virtue of the skew‐symmetric property of the robotic systems, sufficient conditions are developed for solving the robust L_∞ ‐gain tracking control problems in terms of an algebraic equation instead of a differential equation. The proposed method is simple and the algebraic equation can be solved analytically. Therefore, the proposed robust L_∞ ‐gain tracking control scheme is suitable for practical control design of uncertain robotic systems. Copyright © 2008 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society