Constructing the Maximum Consensus Tree from Rooted Triples

We investigated the problem of constructing the maximum consensus tree from rooted triples. We showed the NP-hardness of the problem and developed exact and heuristic algorithms. The exact algorithm is based on the dynamic programming strategy and runs in O((m + n ²)3 ⁿ ) time and O(2 ⁿ ) space. The heuristic algorithms run in polynomial time and their performances are tested and shown by comparing with the optimal solutions. In the tests, the worst and average relative error ratios are 1.200 and 1.072 respectively. We also implemented the two heuristic algorithms proposed by Gasieniec et al. The experimental result shows that our heuristic algorithm is better than theirs in most of the tests.     

Approximation and Exact Algorithms for RNA Secondary Structure Prediction and Recognition of Stochastic Context-free Languages

For a basic version (i.e., maximizing the number of base-pairs) of the RNA secondary structure prediction problem and the construction of a parse tree for a stochastic context-free language, O(n³) time algorithms were known. For both problems, this paper shows slightly improved O(n³(log log n)^1/2/(log n)^1/2) time exact algorithms, which are obtained by combining Valiant's algorithm for context-free recognition with fast funny matrix multiplication. Moreover, this paper shows an O(n^2.776 + (1/)^O(1)) time approximation algorithm for the former problem and an O(n^2.976 log n + (1/)^O(1)) time approximation algorithm for the latter problem, each of which has a guaranteed approximation ratio 1 – for any positive constant , where the absolute value of the logarithm of the probability is considered as an objective value in the latter problem. The former algorithm is obtained from a non-trivial modification of the well-known O(n³) time dynamic programming algorithm, and the latter algorithm is obtained by combining Valiant's algorithm with approximate funny matrix multiplication. Several related results are shown too.     

论生物学教学中学生创新能力的培养

引进生物学热点问题和新进展、加强生物学理论和生活及经济的联系、运用新教学手段、充分利用教学媒体、培养创新意识,从而对传统的生物学课堂教学进行创新。     

从中学生物课外活动看师范生能力的培养

课外活动对培养人才、提高素质具有重要的意义, 教师在其中起着关键作用; 在生物课中显得尤为重要。通过调查分析, 我们认为只有对师范生进行实验技能、创造性思维及学科知识相互渗透的培养, 才能使其成为一个能驾驭生物课外活动的合格教师     

地方院校生物类专业实践教学体系的构建与实践

实践教学是高等学校教学活动的重要组成部分,有着理论教学不可替代的作用。文章在分析地方高校生物类专业实践教学的基础上,提出了构建实践教学体系的总体思路和整体性、针对性、系统性、全程性等基本原则,构建了以课程实验教学为基础、以各种设计为核心、以科学研究和教学实习为依托、以第二课堂活动为补充的与理论教学既相互联系、又相对独立的完整的生物类专业实践教学体系,进行了实践并取得了一定的成效。     

哲学嫉妒

关于“人的科学”的观念长期以来诱惑着西方的思想家们。自然科学的每一次突破都被用来佐证哲学已经被自然科学所取代。自然科学家们常常对哲学家和文学家们不能达成一致不厌其烦。他们把这种不一致与作为自然科学的经验性的信条的标志的共识和稳步前进进行不公平的比较。最近在对大脑功能的研究方面和进化论生物学领域都取得的一些研究成果,在这种意义上也被认作为对哲学的部分的取代。然而斯蒂夫·平克用这些自然科学信条解决政治和社会问题的企图并没有什么意义。对于政治和社会问题,平克和他的盟友们提供不了任何具体的、实用的建议。他们错误地认为我们需要关于人性的理论作为解决政治和社会问题的原理。但事实并非如此,政治和社会指针只能从对人类历史的研究而不是生物学的研究中产生。西方哲学史的精神在于关于人性的理论应被关于历史的研究所取代,关于非历史的人类本质的理论,不论是哲学的还是生物学的,都不值得我们认真对待。     

新课程实验课教学存在的问题及对策

通过问卷、访谈和实地考察,并结合文献资料分析发现,目前影响琼南地区初中生物新课程实验课教学的因素主要有社会、学校和教师三个层面,针对各个层面提出了相应的对策和建议。     

Teaching about science

Science is one of the most exciting frontiers of human endeavor and yet is often poorly understood. In this article I argue that improved education of both our children and our adults is key for the future. It is incumbent on all scientists to help educate our citizenry. In addition to the traditional methods we should make better use of television for this purpose. I strongly advocate permeating regular news programs with science news and education.     

A Sieve model for extreme values

From the class of extreme value distributions, we focus on the set of heavy-tailed distributions which produce low-frequency, high-cost events. The regular Pareto distribution is the basic model of choice, being the simplest heavy-tailed distribution. Real data suggest that modifications of the Pareto distribution may be a better fit; an alternative model is the truncated Pareto distribution (TPD). For further study, this paper proposed a TPD Sieve class of distributions. The properties and estimation on the Sieve class are also discussed. We fit the models to the largest Black Sea bass caught in Buzzard's Bay, MA, USA and the costliest Atlantic hurricanes from 1900 to 2005. Using measures of model adequacy, the TPD Sieve model is generally found to be the best-fitting model.     

构建我国农业信息保障体系的思考

从农业系统学的角度论述了以农业图书馆为主体 ,构建由农业生物、农业环境、农业技术、农业经济四大信息系统所组成的我国农业信息保障体系的多级网络结构模式