Multiple piecewise constant with geodesic active contours (MPC-GAC) framework for interactive image segmentation using graph cut optimization

This paper proposes an improved variational model, multiple piecewise constant with geodesic active contour (MPC-GAC) model, which generalizes the region-based active contour model by Chan and Vese, 2001 [11] and merges the edge-based active contour by Caselles et al., 1997 [7] to inherit the advantages of region-based and edge-based image segmentation models. We show that the new MPC-GAC energy functional can be iteratively minimized by graph cut algorithms with high computational efficiency compared with the level set framework. This iterative algorithm alternates between the piecewise constant functional learning and the foreground and background updating so that the energy value gradually decreases to the minimum of the energy functional. The k-means method is used to compute the piecewise constant values of the foreground and background of image. We use a graph cut method to detect and update the foreground and background. Numerical experiments show that the proposed interactive segmentation method based on the MPC-GAC model by graph cut optimization can effectively segment images with inhomogeneous objects and background.     

一种在开发时实现分布式仿真系统通信协议的异构方案

分布式仿真系统通信协议的异构是解决不同协议下仿真资源重用的关键,也是近几年仿真领域研究的热点之一.设计了一种在仿真系统开发阶段实现通信协议异构的方案,该方案的重点是实现一个与通信协议无关的开发包,从实例连接、对象管理、事件管理和公共接口四个方面讨论了该开发包的基本原型.对比运行时的异构方案,分析了该方案的特点,指出开发...     

用户级实时线程的设计与实现

连续媒质的应用程序要求有实时线程高效灵活的支持,包括对线程属性的动态管理和多线程模式的支持。本文介绍在RT－Mach微内核上用户实时线程的设计和实现。     

安全DBMS的数据字典设计与实现

本文介绍了我们在设计一个安全实时DBMS原型系统时所采用的一些基本安全策略,包括了基于角色的自主访问控制、强制访问控制和审计;并设计实现了相应的数据字典,对传统的数据字典进行了圈套的扩展。     

HLA联邦开发执行过程及发展趋势

对高层体系结构（HLA）的组成、最新发展的联邦开发执行过程（FEDEP）和支撑软件进行了详细的介绍,给出了联邦开发执行过程的发展趋势,并对我国开展这方面的研究提出了方向和目标。     

计算机基础教育研究与实践

本文依据“三个层次”的构思,阐述了新形势下对计算机基础教育的基本要求,总结了在层次教育、实践性教育和素质教育等方面的做法。     

非重复初始化水平集方法的图像轮廓检测

水平集方法(LevelSet Method)是一种用于计算曲线演化位置的有效方法。该文针对传统LevelSet Method进行图像检测中需要重复初始化水平集函数的缺点,研究了不需要重复设置水平集函数的图像检测方法.实验表明,该方法能更好的检测多目标图像轮廓。     

数字校园PKI/CA认证体系的规划和建设

文章首先简单分析了PKI/CA认证技术;接着分析了PKI/CA目前主流的三种建设模式,并结合校园的实际情况,提出了校园PKI/CA采用完全自建的模式,并采用层次信用体系结构,给出了具体的结构模型。最后对校园PKI/CA认证体系建设中会遇到的主要问题进行了简要分析。     

Design of distributed compliant micromechanisms with an implicit free boundary representation

In this paper, a parameterization approach is presented for structural shape and topology optimization of compliant mechanisms using a moving boundary representation. A level set model is developed to implicitly describe the structural boundary by embedding into a scalar function of higher dimension as zero level set. The compactly supported radial basis function of favorable smoothness and accuracy is used to interpolate the level set function. Thus, the temporal and spatial initial value problem is now converted into a time-separable parameterization problem. Accordingly, the more difficult shape and topology optimization of the Hamilton–Jacobi equation is then transferred into a relatively easy size optimization with the expansion coefficients as design variables. The design boundary is therefore advanced by applying the optimality criteria method to iteratively evaluate the size optimization so as to update the level set function in accordance with expansion coefficients of the interpolation. The optimization problem of the compliant mechanism is established by including both the mechanical efficiency as the objective function and the prescribed material usage as the constraint. The design sensitivity analysis is performed by utilizing the shape derivative. It is noted that the present method is not only capable of simultaneously addressing shape fidelity and topology changes with a smooth structural boundary but also able to avoid some of the unfavorable numerical issues such as the Courant–Friedrich–Levy condition, the velocity extension algorithm, and the reinitialization procedure in the conventional level set method. In particular, the present method can generate new holes inside the material domain, which makes the final design less insensitive to the initial guess. The compliant inverter is applied to demonstrate the availability of the present method in the framework of the implicit free boundary representation.     

国内外信息安全管理体系研究

该文对国内外主流的信息安全管理体系进行了梳理和研究,对不同体系的框架和内容进行探讨,为企业选择和建立适合的、完善的信息安全管理体系提供有意义的借鉴。