一类特殊矩阵特征值的绝对扰动上界     

孔祥强 《巢湖学院学报》2011,13(3):5-7

利用矩阵的奇异值分解和矩阵的计算技巧研究了Hermite矩阵特征值的扰动界,得到了Hermite矩阵特征值的绝对扰动上界,对以往的结果进行了改进,并推广了Wielandt-Hoffman定理。  相似文献   

The predictive role of early childhood dysregulation profile on the parallel growth trajectories of reading and math performance across elementary and middle school     

《Contemporary educational psychology》2023

This study examined the heterogeneity in the co-developmental trajectories of reading and math performance (i.e., parallel changes in the initial scores and growth patterns) and identified the number, size and shape of the co-developmental trajectory across elementary and middle schools. In addition, this investigation focused on how an early childhood dysregulation profile (DP; indexed by a high co-occurrence of emotional, behavior, and attention problems) was associated with distinct co-developmental trajectories of reading and math performance. Specifically, we examined whether early childhood DP level can predict (a) membership assignment into each distinct co-development group and (b) variability in initial scores and changes in growth with each distinct co-development group. Participants were 784 academically at-risk students (47 % girls) predominantly from low socioeconomic status families who were recruited in first grade (Mean age = 6.57 years) and followed annually through the final year of middle school (ninth grade). Results revealed two distinct co-developmental trajectories of reading and math performance, including (a) a lower initial reading (higher increasing) and higher initial math (lower increasing) class (85.3 %) and (b) a lower initial math (higher increasing) and higher initial reading (lower increasing) class (14.7 %). Our results provided evidence for the compensatory pattern of co-developmental trajectories, indicating initial lower skills grow at a faster rate than the initial high. Further, early childhood DP was not associated with the membership assignment for these two distinct classes, which means that regardless of children’s early DP level, they have equal chances to be assigned to each of the classes. However, children with higher parent and teacher-reported DP in first grade demonstrated lower initial scores and a slower improvement rate in both classes after controlling for kindergarten literacy skills, gender, ethnicity, intelligence, socioeconomic status, and grade retention. Our study findings demonstrated (a) substantial heterogeneity in the co-developmental trajectories of reading and math performance across elementary and middle school ages; and (b) the importance of promoting self-regulation beginning in early childhood, especially for academically at-risk children in families facing economic challenges.  相似文献   

The relation between teacher-set performance goals and students’ mathematical achievement     

《Studies in Educational Evaluation》2016

The relation between teacher-set performance goals for 361 individual students and these students’ mathematics achievement was investigated. High performance goals were found to strongly relate to student performance, with an effect size of d = 0.80. The performance goals were set by the teachers at the end of a step-by-step procedure, consisting of initial teacher expectations, the use of data, and team input. This procedure was expected to decrease negative expectancy bias. Higher teacher performance goals than teachers’ initial expectations, so-called positive changes, were positively associated with the performance of initially low achievers. Initially high achievers, for whom the teachers made a positive change, performed worse than comparable students for whom initial expectation and final goal were the same.  相似文献   

石墨炉原子吸收直接法测定海水镍和钒     

黄卓尔  杨秀环  郭越生  张展霞 《中山大学学报论丛》1990,(1)

本文研究了海水基体和共存离子对镍和钒的影响,选用酒石酸、乙酸铵分别作为镍和钒的基体改进剂。未加基体改进剂前,海水镍回收率只有77％,钒的测量精度为11％;加人改进剂后均有改善。采用塞曼效应背景校正技术,热解涂层石墨管,建立了石墨炉原子吸收直接测定海水镍和钒的分析方法。镍和钒的特征质量值(mo)分别为8.4pg和17pg;实际检测限:镍为0.25μgL~(-1)和钒为0.41μgL~(-1)。回收率镍为86～110％,钒为88～106％范围。最大相对标准偏差为谋5.5％,钒4.2％。  相似文献   

复正交矩阵的实正交相抵标准形     

张锦川 《泉州师范学院学报》2001,19(4):1-4

利用矩阵的奇异值分解及基本理论 ,文中给出复正交矩阵的实正交相抵标准形及其全系不变量 .即 :(1)设M =A Bi∈En(C) (复正交阵 ) ,其中A ,B∈Rn×n.则存在Q ,R∈En(R) (实正交阵 ) ,使得QMR =diagσ1σ21- 1i-σ21- 1iσ1(1),… ,σ1σ21- 1i-σ21- 1iσ1(r1);… ;σk σ2 k- 1i-σ2 k- 1iσk (1),… ,σk σ2 k- 1i-σ2 k- 1iσk (rk);In- 2r ,其中σ1>σ2 >… >σk>1,r =r1 r2 … rk.(2 )二复正交矩阵实正交相抵之充要条件是它们的实部有完全相同的奇异值 .  相似文献   

线性方程组相容性定理的新证法     

刘锋 《天津职业院校联合学报》2002,4(1):87-91

线性方程组解的判定在线性代数教学中具有十分重要的作用，但线性方程组相容性定理的传统证明方法需要较多的理论准备，现研究以克莱姆法则和行列式为工具，仅借用矩阵的秩这一概念，给出线性方程组相容性定理一种新的证明方法。  相似文献   

滚动矩阵及其性质     

马海成 《青海师专学报》1997,17(4):32-34

对矩阵引进了滚动运算，然后研究了它的一些有趣性质。  相似文献   

软代数[0,1]上非零矩阵的广义逆     

明平华 《黄冈师范学院学报》2004,24(3):14-16,44

本文在软代数[0，1]上矩阵的schein秩等于其秩的基础上，构造性地证明了[0，1]上任一非零矩阵都存在唯一的广义逆矩阵．  相似文献   

Dimensionality and reliability of a screening instrument for students at-risk of dropping out from Higher Education     

《Studies in Educational Evaluation》2021

Dropout stems from a complex, gradual process of decision-making in which the demands and benefits of university attendance are weighed. Early identification of at-risk students benefits from quick and large-scale screening instruments. This study presents the dimensionality of a screening instrument for students at risk of dropping out of Higher Education, integrating three scales: Academic Exhaustion, Satisfaction with Education and Dropout Intention. A sample of 611 first-year university students was considered in the statistical analysis. The results demonstrate evidence of internal and external validity as well as the reliability of the screening instrument scores. The differences in correlation coefficients between these three scales and the students’ intentions of completing the course and completing their education at their university, evaluated at two different points during the first semester, suggest that dropout analysis requires collecting information throughout the process of adjustment to higher education.  相似文献   

The role of academic competences and learning processes in predicting Bachelor’s and Master’s thesis grades     

《Studies in Educational Evaluation》2021

Writing an academic thesis is an important and complex task and the thesis grade should reflect students’ academic competences. The present study aims, firstly, at exploring how Bachelor’s and Master’s students self-evaluate their academic competences and approaches to learning and whether their evaluations differ from each other. In addition, the study aims at investigating how academic competences and approaches to learning are related to the thesis grades of Bachelor’s and Master’s students. The data consisted of 1 019 Bachelor's and Master’s students, all of whom completed an electronic questionnaire at the time of their graduation. The results imply that Bachelor’s students already possess a considerable number of academic competences. It seems that students’ organising skills should be supported, especially in the Bachelor phase. Finally, the present study raises the question of what the thesis grade actually measures if its relations to both learning processes and academic competences are questionable.  相似文献