On the Complexity of Constructing Evolutionary Trees

In this paper we study a few important tree optimization problems with applications to computational biology. These problems ask for trees that are consistent with an as large part of the given data as possible. We show that the maximum homeomorphic agreement subtree problem cannot be approximated within a factor of , where N is the input size, for any 0 in polynomial time unless P = NP, even if all the given trees are of height 2. On the other hand, we present an O(N log N)-time heuristic for the restriction of this problem to instances with O(1) trees of height O(1) yielding solutions within a constant factor of the optimum. We prove that the maximum inferred consensus tree problem is NP-complete, and provide a simple, fast heuristic for it yielding solutions within one third of the optimum. We also present a more specialized polynomial-time heuristic for the maximum inferred local consensus tree problem.     

理想和现实的冲突——解读毛姆《月亮和六便士》的主题

毛姆的长篇小说《月亮和六便士》揭示了人性自由的追求与社会现实之间的矛盾.主人公无法割舍身边的"六便士",又执着追求虚幻的"月亮",凸现了现实与理想的矛盾冲突,显示毛姆对人性的矛盾以及人生内涵的复杂性的深刻探索.     

Center and Distinguisher for Strings with Unbounded Alphabet

Consider two sets and of strings of length L with characters from an unbounded alphabet , i.e., the size of is not bounded by a constant and has to be taken into consideration as a parameter for input size. A closest string s* of is a string that minimizes the maximum of Hamming¹ distance(s, s*) over all string s : s . In contrast, a farthest string t* from maximizes the minimum of Hamming distance(t*,t) over all elements t: t . A distinguisher of from is a string that is close to every string in and far away from any string in . We obtain polynomial time approximation schemes to settle the above problems.     

提高计算方法教学质量的方法探讨

文章阐述了提高计算方法教学质量的意义以及指导式教学法的内涵,在教学实践中应用指导式教学法取得了良好的效果。     

实现网络结点编号和添加虚工序的一种计算机处理方法

本文介绍一种算法,可对工程管理网络图的各个结点进行编号,并实现虚工序的自动添加。文末给出了算法的时间复杂度分析。     

复杂性理论:透视学科建设问题的独特视角

把复杂性理论引入到教育学中,可以为许多教育问题提供独特的视角。高等学校的学科建设是一个学校核心竞争力的集中体现。学科建设不是一蹴而就的,它与一个学校办学特点和学校历史积淀息息相关。本文以复杂性理论为基础,来探讨学科建设过程中存在的问题,展示复杂性理论解决问题的独特方式。     

原语语篇类型对汉英口译任务复杂度的影响

译者在口译训练及实践中要处理不同语篇类型的语料。而不同语篇类型的口译任务复杂度也有差异，从而影响着译者口译输出的准确度和流利度。     

Measuring the complexity of generalized linear hierarchical models

Measuring a statistical model's complexity is important for model criticism and comparison. However, it is unclear how to do this for hierarchical models due to uncertainty about how to count the random effects. The authors develop a complexity measure for generalized linear hierarchical models based on linear model theory. They demonstrate the new measure for binomial and Poisson observables modeled using various hierarchical structures, including a longitudinal model and an areal‐data model having both spatial clustering and pure heterogeneity random effects. They compare their new measure to a Bayesian index of model complexity, the effective number p_D of parameters (Spiegelhalter, Best, Carlin & van der Linde 2002); the comparisons are made in the binomial and Poisson cases via simulation and two real data examples. The two measures are usually close, but differ markedly in some instances where p_D is arguably inappropriate. Finally, the authors show how the new measure can be used to approach the difficult task of specifying prior distributions for variance components, and in the process cast further doubt on the commonly‐used vague inverse gamma prior.     

On Integer Programming Approaches for Morphological Template Decomposition Problems in Computer Vision

In morphological image processing and analysis, a template or structuringelement is applied to an image. Often savings in computation time and abetter fit to the given computer architecture can be achieved by using thetechnique of template decomposition. Researchers have written a multitude ofpapers on finding such decompositions for special classes of templates.Justifying recent integer programming approaches to the morphologicaltemplate decomposition problem in its general form, this paper proves theNP-completeness of this problem.     

Is subsidiarity a conditio sine qua non for sustainability?

This paper argues that subsidiarity is a condicio sine qua non for sustainability. Through the complexity paradigm, the paper provides a historical reconstruction of both concepts to the end of elucidating their interdependence. The main thesis is that subsidiarity to sustainability is what self-organisation is to emergence. The paper ends with a sketch of future global governance structures based on a subsidiarity where cities take the lead on sustainability.