Skeleton computation of orthogonal polyhedra

Skeletons are powerful geometric abstractions that provide useful representations for a number of geometric operations. The straight skeleton has a lower combinatorial complexity compared with the medial axis. Moreover, while the medial axis of a polyhedron is composed of quadric surfaces the straight skeleton just consist of planar faces. Although there exist several methods to compute the straight skeleton of a polygon, the straight skeleton of polyhedra has been paid much less attention. We require to compute the skeleton of very large datasets storing orthogonal polyhedra. Furthermore, we need to treat geometric degeneracies that usually arise when dealing with orthogonal polyhedra. We present a new approach so as to robustly compute the straight skeleton of orthogonal polyhedra. We follow a geometric technique that works directly with the boundary of an orthogonal polyhedron. Our approach is output sensitive with respect to the number of vertices of the skeleton and solves geometric degeneracies. Unlike the existing straight skeleton algorithms that shrink the object boundary to obtain the skeleton, our algorithm relies on the plane sweep paradigm. The resulting skeleton is only composed of axis‐aligned and 45° rotated planar faces and edges.     

Hardness of preorder checking for basic formalisms

We investigate the complexity of preorder checking when the specification is a flat finite-state system whereas the implementation is either a non-flat finite-state system or a standard timed automaton. In both cases, we show that simulation checking is Exptime-hard, and for the case of a non-flat implementation, the result holds even if there is no synchronization between the parallel components and their alphabets of actions are pairwise disjoint. Moreover, we show that the considered problems become Pspace-complete when the specification is assumed to be deterministic. Additionally, we establish that comparing a synchronous non-flat system with no hiding and a flat system is Pspace-hard for any relation between trace containment and bisimulation equivalence, even if the flat system is assumed to be fixed.     

平面内一组线段的可见性

给定平面内一组互不相交的线段,本文讨论其相对于某点的可见性,给出了时间复杂性为O(mlogm)的算法,并证明了这一算法在时间上是最优的.     

Some Empirical Criteria for Attributing Creativity to a Computer Program

Over recent decades there has been a growing interest in the question of whether computer programs are capable of genuinely creative activity. Although this notion can be explored as a purely philosophical debate, an alternative perspective is to consider what aspects of the behaviour of a program might be noted or measured in order to arrive at an empirically supported judgement that creativity has occurred. We sketch out, in general abstract terms, what goes on when a potentially creative program is constructed and run, and list some of the relationships (for example, between input and output) which might contribute to a decision about creativity. Specifically, we list a number of criteria which might indicate interesting properties of a program’s behaviour, from the perspective of possible creativity. We go on to review some ways in which these criteria have been applied to actual implementations, and some possible improvements to this way of assessing creativity.

Prime Number Generation Based On Pocklington's Theorem

Public-key cryptosystems base their security on well-known number-theoretic problems, such as factorisation of a given number n . Hence, prime number generation is an absolute requirement. Many prime number generation techniques have been proposed up-to-date, which differ mainly in terms of complexity, certainty and speed. Pocklington's theorem, if implemented, can guarantee the generation of a true prime. The proposed implementation exhibits low complexity at the expense of long execution time.     

广东省电网建设与经济发展关系实证研究

以广东省1993--2011年相关时间序列数据为基础,建立了反映电网建设水平与社会经济发展关系的向量自回归（VAR）模型,在VAR模型的基础上,分析了广东省电网建设指标与社会经济发展指标的格兰杰因果关系,运用脉冲响应函数和方差分解方法分析了电网建设与社会经济发展之间的动态影响。研究结果表明,电网建设是经济增长的基础条件之一,在电网建设与经济增长的相互作用中,电网建设对经济增长的促进作用更为显著。     

西藏自治区藏中电网光纤通信网的建设及发展

西藏自治区由于受地理环境等多方面因素的制约，长期以来各地区级的电网均独立运行，造成通信网发展相对滞后。但近几年随着电业大发展，地区电网相互连接共同进行，促进了通信网的快速发展。文章详细介绍了藏中电网光纤通信网的发展现状，包括网络拓扑结构、SDH和PCM设备、光纤线路的建设情况以及现存的问题，并阐述了今后的发展规划。     

信息网格中具有动态变更适应性的元数据发布策略

信息源元数据的动态变更可能造成应用对信息源引用关系不一致，在不改应用程序的条件下，用户不能正确访问信息源。基于网格地址空间模型，使得应用程序通过虚拟层元数据，即应用领域元数据，来间接使用信息源元数据；当信息源元数据变更时，不是改应用程序而是通过调整信息源元数据和应用领域元数据之间的映射来保证应用对信息源引用关系的一致性，从元数据发布的角度出发，提出了一个具有动态适应性的元数据发布算法(Vega adaptive mapping)，通过此算法自动调整信息源元数据和应用领域元数据之间的映射；并将此算法相应的方法和现有的元数据发布方法进行了比较，比较结果表明此方法在适应元数据变更性方面具有一定的优越性。     

基于复杂地形上三角网数字地面模型的建立

本文提出了一种生成三角网数字地面模型的新方法，它首先利用凸多边形的性质与凸锥的特性来将离散点连成一三角网，计算工作特别快速有效；其次在三角网形成过程中，能将特征信息线作为三角形的边参加构网并采用了优化手段来优化三角网的现状。该方法能有效地限制狭长三角形的出现，并使生成的三角网能密贴地面，真实反映出地表形状。与其它算法相比，该方法具有思路简单明了、成网速度快、编程容易及成网质量高的特点。实际应用表明     

2005年中国风电产业回顾和未来5年的展望

在对2005年风电装机容量进行准确统计的基础上,分析了风电场建设快速增长但国产设备制造能力仍然薄弱的态势。回顾2005年内发生的对风电具有里程碑意义的事件及对发展趋势的影响。指出“十五规划”期间风电的进展和教训,强调未来5a应以国产化能力和风电上网电量衡量业绩。