首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 109 毫秒
1.
本文建立了隐式QL算法中变量间的一个重要关系:“在整个隐式QL过程中,变量ζ_i与s_i的比值是与i 无关的常量,且恒为(-σ)”。利用该结论,首先在§3中设计了一个新的“隐-显”格式,它避免了显式与隐式算法的缺陷,且比[6]节省了大量计算。接着,在§4中指出[3]中关于有理算法的一处疏忽,同时得到了基于§3的有理化的隐-显格式。有理由指出,它比普通的有理隐式方法更为稳定和有效。  相似文献   

2.
系统研究了具有急性和慢性两个阶段的MSIS流行病模型.由两节构成,第1节建立和研究了具有急慢性阶段的MSIS流行病模型;第2节在第1节的基础上建立和研究了具有慢性病病程的MSIS流行病模型.第1节的模型是四个常微分方程构成的方程组.第2节的模型既含有常微分方程,又含有偏微分方程.运用微分方程和积分方程中的理论和方法,得到了这两个模型再生数R0的表达式.证明了当R0<1时,无病平衡态是全局渐近稳定性,给出了各模型地方病平衡态的存在性和稳定性条件.  相似文献   

3.
本文根据全国工学、经济学硕士研究生招生考试陕西省高校考生的数学成绩及评卷情况对2 0 0 2年数学一、二、三、四各卷的试题质量、特点进行总体分析。  一、2 0 0 0 2年陕西省考研数学的基本情况及成绩分布2 0 0 2年陕西省工学、经济学硕士研究生招生考试 ,考生人数及成绩分布见表 1。表 1 考生成绩分布表二零零二年科  目 考生人数 及格率 考 生 成 绩 分 布10 0 - 9989- 80 79- 70 6 9- 6 0 5 9- 5 5 5 4- 5 0 4 9- 40 39- 30 2 9- 2 0≤ 19数学一 10 4 174 7.4 419110 2 91773194 986 2 85 5 130 890 2 6 78870数学二 187936 …  相似文献   

4.
在许多数学问题中,虽然数量、图形在不断运动变化,但常常存在一些或显或隐的不变量,如定点、定直线、恒等式、定角、距离、面积、体积等.在解题中,若能善于在变量的变化过程中挖掘并利用这些不变量,往往能打开解题突破口,化繁为简、化难为易,提高解题的简洁性、准确性、有效性. 1 利用不变量打开解题突破口  相似文献   

5.
曹重光 《数学季刊》1991,6(3):73-76
设R记实数域,Q记R上四元数代数,若x∈EQ,x=a+bi+cj+dk,其中a、b、c、d在R中,则x的共轭元=a—bi—cj—dk,x的范数N(x)=a~2+b~2+c~2+d~2。设Q~(×n)(或R~(×))记Q(或R)上n×n矩阵构成的R代数,我们以Hom(Q~×,R~(4×4))记Q~(×)的全部R代数表示的集合。还以E_(ij)表示(i,j)位置是1,其余位置是0的n阶方阵,I_r记r阶单位阵;GLr(Q)及GLr(R)分别记Q上及R上一般线性群。  相似文献   

6.
多维抛物型方程的分支绝对稳定的显式格式   总被引:24,自引:0,他引:24  
其中及R={0≤x_i≤1,j=1,2,…,p),(?)R只为区域只的边界。 对多维抛物型方程(1)的差分解法,古典显式格式的稳定性条件为r=Δt/(Δx)~2≤1/2p,十分苛刻;古典隐式格式虽是无条件稳定,却需解线性方程组。因此两者的计算量都很大,且它们的精度较低,其局部截断误差仅为O(Δt+(Δx)~2)。因此,对多维抛物型方程而言,构造显式计算、稳定性能良好且精度较高的差分格式便具有十分明显的理论意义和实用价值。本文针对上述古典显式与隐式格式所存在的问题,构造一类对任何p维空间变量的抛物型方程(1)都适用的。分支绝对稳定的显式差分格式,其局部截断误差阶为O((Δt)~2+(Δx)~2),从而避免了解线性代数方程组,大大地减少了计算工作量,且精度较高。 令Δx_k=h_k=Δx=h=1/M(k=1,2,…p)表示空间方向步长,Δt=τ=[T/N]表示时间方向步长,M、N均为正整数。 为简便计,引入下列记号  相似文献   

7.
探讨隐变量交互作用分析的建模方法及其在SA S软件上的实现;首先阐述隐变量交互作用分析建模的原理,通过拟合一个隐变量交互作用分析示例,对加入交互作用项的统计分析结果与无交互作用项的统计分析结果进行对比;示例中交互作用项引起的变异在结果变量的总变异中占到79.20%.在应用结构方程模型分析隐变量产生的效应时,有时候不进行隐变量交互作用的分析可能会产生偏倚.  相似文献   

8.
如何培养中学生的数学应用意识和能力 ,是中学数学教师十分关心的一个重要课题 ,也是数学教学改革中面临的一个重要问题 .作为一名中学数学教师 ,要做好两方面的探索 :一方面注意编拟适合中学生的数学应用问题 (这一方面在数学通讯 2 0 0 0年第 1期“如何编拟适合中学生的数学应用问题”一文中已谈及 ) ;另一方面在数学教学中 ,采取“案例教学法”进行数学应用问题教学 ,并在问题解决中渗透数学建模思想 .案例 1  (洗衣服的数学问题 )在洗衣服时 ,衣服已打好了肥皂 ,揉搓得很充分了 ,再拧一拧 ,当然不可能把水拧干 ,设衣服上还残留含有污物…  相似文献   

9.
中学生都知道牛顿定律 ,知道牛顿是世界有名的物理学家 .其实牛顿还是有名的数学家 .他的“牛吃草问题”也是人们感兴趣的长期研究的数学问题 :一牧场每天都长草 (每天长草一样多 ) ,放养 1 4头牛 5天吃完草 ;放养 8头牛 2 0天吃完草 .(1 )如果要在 40天吃完草 ,应放养几头牛 ?(2 )要使牧草永远吃不完最多能放养几头牛 ?这个问题 ,难倒许多中学生 ,因为每天草量都在变 ,不好解答 .但是有三个量是不变的 :1 .每头牛每天吃草量不变 ;2 .每天长草量不变 ;3 .牧场原有的草量不变 .抓住这三个不变量即可解答这个问题 .设每头牛每天吃草量为 1份 ,…  相似文献   

10.
著名的数学大师陈省身先生为青少年提词 :“数学好玩” .本文拟与同学们共同“走进美妙的数学花园”,玩赏图 1一束美丽的数字“等和之花”.在《中学生数学》 2 0 0 3年 1月下期的“智慧窗”里 ,有一道这样的趣题 :将 1~ 7这 7个数字填入图 1中 ,使每个圆圈中的数之和都相等 .填答结果如图 2所示 .观察图 2 ,容易发现 :所填数字除中心 1外 ,其余图 2数字按位置可分为内、外两层 .其中 ,外层为偶数 ,从小到大 2、4、6按顺时针向排列 ;内层为奇数 ,由小到大3、5、7也按顺时针向排列 ,而且 2和 3处于相对的位置 .不难明白 ,图 2可与图3( 1)所示…  相似文献   

11.
In spite of sustained efforts tertiary institutions implement to try and improve student academic performance, the number of students succeeding in first-year mathematics courses remains disturbingly low. For most students, the gap between their mathematical capability and the competencies they are expected and need to develop to function effectively in these courses persists even after course instruction. In this study, an instrument for identifying and examining factors affecting student performance and success in a first-year Mathematics university course was developed and administered to 86 students. The overall Cronbach's Alpha coefficient for the questionnaire was found to be 0.916. Having identified variables from prior research known to affect student performance, factor analysis was used to identify variables exhibiting the greatest impact on student performance. The variables included prior academic knowledge, workload, student approaches to learning, assessment, student support teaching quality, methods and resources. From the analysis, students' perceptions of their workload emerged as the factor having the greatest impact on student's performance, followed by the matriculation examination score. The findings are discussed and strategies that can be used to improve teaching and contribute to student success in a first-year mathematics course in a South African context are presented.  相似文献   

12.
A variety of factors contributes to student achievement in mathematics, including but not limited to student behaviors and student, teacher, and school characteristics. The purpose of this study was to explore which of these factors have an impact on student mathematics achievement. The target population for this study was North Carolina Algebra II students. Analyses of variance models were examined for group differences and a Three‐level Hierarchical Linear Modeling method was employed to examine individual predictors of student achievement in mathematics. Statistically, significant differences were found between students of different ethnicities, socioeconomic statuses (SES), and parental education levels. No gender effects were statistically significant. All teacher‐level variables investigated were found to be statistically significant, impacting student achievement in mathematics. School size and SES were not found to significantly contribute to student achievement. More research on the relationships between these factors shown to make statistically significant differences on mathematics achievement is needed to further explain several phenomena that this research reveals.  相似文献   

13.
The purpose of this paper is to describe the model of a mathematics and science staff development cooperative and focus on the evaluation of the mathematics component. The Mathematics and Science Education Cooperative (MSEC) was a comprehensive, long‐range staff development program to improve the teaching and learning of mathematics and science at the elementary school level. The special features of MSEC were (a) it provided year‐round, multiyear involvement, and (b) each year an affective strand was included. Statistically significant student mathematics results from the years 1998–2000 are presented.  相似文献   

14.
This study investigated K‐12 teachers' beliefs and reported teaching practices regarding calculator use in their mathematics instruction. A survey was administered to more than 800 elementary, middle and high school teachers in a large metropolitan area to address the following questions: (a) what are the beliefs and practices of mathematics teachers regarding calculator use? and (b) how do these beliefs and practices differ among teachers in three grade bands? Factor analysis of 20 Likert scale items revealed four factors that accounted for 54% of the variance in the ratings. These factors were named Catalyst Beliefs, Teacher Knowledge, Crutch Beliefs, and Teacher Practices. Compared to elementary teachers, high school teachers were significantly higher in their perception of calculator use as a catalyst in mathematics instruction. However, the higher the grade level of the teacher, the higher the mean score on the perception that calculator use may be a way of getting answers without understanding mathematical processes. The mean scores for teachers in all three grade bands indicated agreement that students can learn mathematics through calculator use and using calculators in instruction will lead to better student understanding and make mathematics more interesting. The survey results shed light on teachers' self reported beliefs, knowledge, and practices in regard to consistency with elements of the National Council of Teachers of Mathematics Principles and Standards for School Mathematics (2000) technology principle and the NCTM use of technology position paper (2003). This study extended previous research on teachers' beliefs regarding calculator use in classrooms by examining and comparing the results of teacher surveys across three grade bands.  相似文献   

15.
Cross-national research studies such as the Program for International Student Assessment and the Third International Mathematics and Science Study (TIMSS) have contributed much to our understandings regarding country differences in student achievement in mathematics, especially at the primary (elementary) and lower secondary (middle school) levels. TIMSS, especially, has demonstrated the central role that the concept of opportunity to learn plays in understanding cross-national differences in achievement Schmidt et al., (Why schools matter: A cross-national comparison of curriculum and learning  2001). The curricular expectations of a nation and the actual content exposure that is delivered to students by teachers were found to be among the most salient features of schooling related to academic performance. The other feature that emerges in these studies is the importance of the teacher. The professional competence of the teacher which includes substantive knowledge regarding formal mathematics, mathematics pedagogy and general pedagogy is suggested as being significant—not just in understanding cross-national differences but also in other studies as well (Hill et al. in Am Educ Res J 42(2):371–406, 2005). Mathematics Teaching in the 21st Century (MT21) is a small, six-country study that collected data on future lower secondary teachers in their last year of preparation. One of the findings noted in the first report of that study was that the opportunities future teachers experienced as part of their formal education varied across the six countries (Schmidt et al. in The preparation gap: Teacher education for middle school mathematics in six countries, 2007). This variation in opportunity to learn (OTL) existed in course work related to formal mathematics, mathematics pedagogy and general pedagogy. It appears from these initial results that OTL not only is important in understanding K-12 student learning but it is also likely important in understanding the knowledge base of the teachers who teach them which then has the potential to influence student learning as well. This study using the same MT21 data examines in greater detail the configuration of the educational opportunities future teachers had during their teacher education in some 34 institutions across the six countries.  相似文献   

16.
数学实验活动是提高学生数学素养,提高学生应用能力和创造能力的有效途径.高师院校学生肩负着未来培养中小学生的数学探究能力和创造能力的重大使命.因此,高师院校数学实验的教学改革研究具有双重的意义.本文通过对高师院校数学实验课程体系改革的理论研究与教学实践,探讨了高师院校数学实验教学的一条新路,提供了适合高师院校学生数学实验能力培养的新教学模式和新途径.  相似文献   

17.
依据1998~2006年间河南高等教育、科技与经济所考查指标的统计数据,运用相关与回归分析方法分别建立以人均GDP为因变量的数学模型,并对模型进行了分析.这11个指标的因子分析结果,得出与人均GDP联系密切的指标主要有5个,以这5个指标为自变量对人均GDP进行逐步回归分析,所得回归方程达极显著水平,同时得出,对人均GDP影响的重要程度从高到低依次为:人均RD经费支出,以每万人口在校大学生数,每万名科技人员发表论文数,每万人口中科技活动人员数.并就各指标对人均GDP的影响给出了合理的解释.  相似文献   

18.
This article presents our work in translating the Mathematics Teaching Efficacy Beliefs Instrument (MTEBI) from English to Thai and our resulting investigation of validity with Thai preservice teachers. The translation process occurred over several meetings between two U.S. mathematics educators and one Thai mathematics educator. To check for reliability the instrument was translated into Thai, back‐translated into English, and then cognitive interviews were conducted with native Thai speakers to check for accuracy, meaning, and readability. We used the newly translated Thai‐Mathematics Teaching Efficacy Beliefs Instrument (T‐MTEBI) to measure teacher efficacy beliefs as they related to Thai preservice mathematics teachers. Eight of the questions measure Mathematics Teaching Outcome Expectancy (MTOE). The mean of the scores on these questions was computed to form a MTOE score for each student. The remaining 13 questions measure Personal Mathematics Teaching Efficacy (PMTE). The mean of these scores was computed to obtain the PMTE score for each student. The mean of all 21 questions was computed to find an overall efficacy score for each student. The results of this study showed that the newly constructed T‐MTEBI produced reliability and validity measures comparable to the original MTEBI (Enochs, Smith, & Huinker, 2000).  相似文献   

19.
Parental influence has been identified as an important factor affecting student achievement, but the variables addressed by various parent-school partnership programs vary, and lack literature support. This deficiency was ameliorated in this study through an analysis of a national data base from the Longitudinal Study of American Youth (LSAY). AH parental variables investigated in LSAY were considered in this study, and significant variables of students' achievement in seventh grade mathematics were selected through the Backward Elimination Procedure in the Statistical Analysis System (SAS). The results show that those variables significant at α= .05 have accounted for around 22% variability of the student achievement. A further analysis of the empirical results seems to indicate that parent education and encouragement are strongly related to improved student achievement. However, parents should attempt to understand students' feeling, and expect students to take the full responsibility for their successes in the school.  相似文献   

20.
The 2007 Trends in International Mathematics and Science Survey highlighted how attitudes to mathematics had declined sharply for students in many of the high attaining countries in the survey, England being no exception. There is a notable drop in positive attitudes to mathematics between 9 and 14, as well as a remarkable decline for 14 year olds over time. This paper explores survey data collected from over 3000 11-year-olds in 16 schools during 2008 with the goal of exploring possible factors that might be contributing to this attitudinal decline. The association between student-centred teaching and enjoyment of learning mathematics is reported as part of a multi-scale analysis that shows the extent to which student experiences differ between schools and between classes within schools.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号