"克字号"小麦品种产量因素遗传改良的研究

通过对“克字号”小麦不同育种阶段代表品种产量与产量因素遗传改良的分析,研究“克字号”小麦的遗传改良进程,及其优质高产的原因。结果表明:在现代栽培技术条件下,目前推广的品种比地方品种增产近50%(47.1%),收获指数和千粒重分别增加了62.9%和32.5%。90年代以前产量的提高主要来源于穗粒重的增加,90年代后产量的提高则主要来源于千粒重和收获指数的提高。     

基于改进小生境遗传算法的自适应组卷系统

针对传统基于简单遗传算法的组卷系统收敛速度慢,组卷质量较差等缺陷,设计一种基于改进小生境遗传算法的自适应组卷系统。首先依照组卷约束权重比,生成适应度值较高的初始种群．其次对选择策略进行优化。引入小生境预选机制以维持种群多样性,防止过早收敛。再次根据组卷特点改进交叉算子和变异算子,根据种群进化情况,自动调整交叉概率和变异概率。最后经过若干迭代后达到终止条件,以自适应方式生成目标试卷。实验结果证明,与简单遗传算法相比,改进的遗传算法在收敛速度和组卷质量上均有显著的提高。     

Math Fluency: Accuracy Versus Speed in Preoperational and Concrete Operational First and Second Grade Children

Cognitive abilities as well as math fluency play an important role in mathematical skills. Understanding the relationship between cognitive abilities and mathematical skills is imperative to teaching effective arithmetic skills. The present study aimed to investigate the relationship between cognitive ability and math fluency with 38 first and second grade elementary aged children. Results demonstrate that preoperational children lacked the speed of concrete operational children but achieved comparable levels of accuracy when completing arithmetic problems.     

一种基于遗传算法的连续属性离散化方法

连续属性离散化是基于粗糙集的数据挖掘中的关键问题。针对该问题提出了一种遗传算法,在保持不可分辨关系的前提下,以最小断点集为目标,对交叉算子、变异算子进行了改进。最后,使用UCI机器学习数据对算法进行了验证,并与其它的离散化算法进行了比较,结果表明算法是有效的。     

亚式股票期权的定价及其在期股激励中的应用

亚式股票期权是当今金融衍生品市场最为活跃的新型期权之一。文章介绍了亚式股票期权的概念,讨论了亚式股票期权的定价公式及应用,并举例说明了亚式股票期权在期股激励中的应用。     

Optimal design of pressure vessel using an improved genetic algorithm

As the idea of simulated annealing （SA） is introduced into the fitness function, an improved genetic algorithm （GA） is proposed to perform the optimal design of a pressure vessel which aims to attain the minimum weight under burst pressure constraint. The actual burst pressure is calculated using the arc-length and restart analysis in finite element analysis （FEA）. A penalty function in the fitness function is proposed to deal with the constrained problem. The effects of the population size and the number of generations in the GA on the weight and burst pressure of the vessel are explored. The optimization results using the proposed GA are also compared with those using the simple GA and the conventional Monte Carlo method.     

Are first graders' arithmetic skills related to the quality of mathematics textbooks? A study on students’ use of arithmetic principles

A major goal of the first years of schooling is students' development from using counting strategies to using calculation strategies – or even recall – to solve addition or subtraction problems. It requires the perception and usage of arithmetic principles. Although the continued use of counting strategies is problematic for further learning progress, they are frequently used by many students beyond Grade 1. While learning resources possibly play a role in students' development in this field, our knowledge about their impact is limited. In this study we investigated the presented learning opportunities of four different textbooks regarding arithmetic principles in Grade 1, and subsequently the relation to first graders' strategy use by analyzing a one-year dataset of 1614 students from 86 classes. The analyses show differences in the textbooks' quality concerning arithmetic principles as well as a considerable connection to students' strategy use at the end of Grade 1.     

重庆市主城区降雨侵蚀力特征分析

文章根据重庆市自建气象站以来的降雨过程资料(1954～2001)，对重庆市主城区降雨侵蚀力(R)及其特征进行了研究和分析。研究结果表明，研究区降雨侵蚀力主要集中在5月～9月，48年里研究区年降雨侵蚀力值变幅均较大，但从整体上来看，趋势保持平稳，其离差系数Cv和变化趋势系数r值分别为0.65和0.061； 研究区次降雨量与次降雨侵蚀力，月降雨量与月降雨侵蚀力均呈乘幂关系，而年降雨量与年降雨侵蚀力呈现指数关系； 为了解决在降雨资料不足的情况下对降雨侵蚀力的计算，文章利用不同的降雨资料与侵蚀力之间进行相关分析，最终确定了适合研究区的两种降雨侵蚀力简易算法。     

关于高阶等差数列的一个不变量

设｛xn｝n≥0是任意的m阶等差数列，本文证明：对任意的n≥0，（m＋1）阶行列式的值与n无关，因而是这类数列的一个不变量，并且这一结论是一般常系数齐次线性追归数列的一个普遍性质的特例．     

Statistical Tools and Statistical Literacy: The Case of The Average

This article is intended to serve as a starting point for a dialogue regarding the goals of teaching students about averages and how to assess their emerging knowledge.