线状需求下两阶段设施选址问题     

王紫萌  周建勤 《上海海事大学学报》2020,41(3):60-65

鉴于大型交通线路建设项目的物资需求随时间变化(在初期阶段需求较低;在后续阶段项目全面展开,需求显著上升),本文采用线积分对沿线连续分布的线状物资需求进行刻画,构建两阶段设施选址模型,第一阶段进行部分设施的选址,第二阶段对剩余设施选址,以实现系统总成本最低的目标。针对模型特点,设计基于Voronoi图的两阶段交替定位-分配(alternative location-allocation,ALA)算法进行求解,并进行实例分析,比较两阶段模型与传统模型的异同。研究表明,将两阶段设施选址模型应用于交通线路建设项目多物流节点选址,能节约运营成本,并缓解初期资金压力。  相似文献   

The context dependence of physics identity: Examining the role of performance/competence,recognition, interest,and sense of belonging for lower and upper female physics undergraduates     

Zahra Hazari  Deepa Chari  Geoff Potvin  Eric Brewe 《科学教学研究杂志》2020,57(10):1583-1607

While there is a growing body of work that examines disciplinary identity development, unlike qualitative work in this area, quantitative research has not fully incorporated the importance of different contexts, nor has it uniquely focused on underrepresented groups (in this case, women in physics). This study examines how the constructs posited by prior work as important for physics identity, as well as an additional theorized construct, may interrelate and affect female students' physics identity differently depending on the context. Context in this study refers to two different experiential levels in college. The constructs examined include performance/competence, recognition, and interest, as well as sense of belonging. In particular, we used structural equation modeling to examine the effect that these constructs have on the physics identity of two groups of female physics undergraduates: first year students and senior year students. The results reveal that the relationship of the theorized constructs with physics identity vary between the two groups as well as compared to prior research with broad college student populations (not just physics majors). Unlike broad college student populations, for our sample of female physics undergraduates, interest did not have a direct effect on physics identity while sense of belonging was significant only for senior year students. These results exemplify the importance of examining context or different types of student experiences when studying disciplinary identity development rather than generalizing previous frameworks to all contexts.  相似文献   

Digital Module 16: Longitudinal Data Analysis     

Jeffrey R. Harring  Tessa L. Johnson 《Educational Measurement》2020,39(3):137-138

In this digital ITEMS module, Dr. Jeffrey Harring and Ms. Tessa Johnson introduce the linear mixed effects (LME) model as a flexible general framework for simultaneously modeling continuous repeated measures data with a scientifically defensible function that adequately summarizes both individual change as well as the average response. The module begins with a nontechnical overview of longitudinal data analyses drawing distinctions with cross-sectional analyses in terms of research questions to be addressed. Nuances of longitudinal designs, timing of measurements, and the real possibility of missing data are then discussed. The three interconnected components of the LME model—(1) a model for individual and mean response profiles, (2) a model to characterize the covariation among the time-specific residuals, and (3) a set of models that summarize the extent that individual coefficients vary—are discussed in the context of the set of activities comprising an analysis. Finally, they demonstrate how to estimate the linear mixed effects model within an open-source environment (R). The digital module contains sample R code, diagnostic quiz questions, hands-on activities in R, curated resources, and a glossary.  相似文献   

Searching for the impact of teacher behavior on promoting students’ cognitive and metacognitive skills     

《Studies in Educational Evaluation》2020

This study investigates the impact of teaching factors on students’ cognitive and metacognitive achievement in mathematics. Written tests and the “Metacognitive Skills and Knowledge Assessment” tool were administered to grade 4 and 5 students (n = 924) at the beginning and end of the school year 2013-2014. A student questionnaire was used for measuring teaching factors. Multilevel SEM analyses revealed a reciprocal relationship between students’ cognitive and metacognitive skills. All teaching factors of the dynamic model of educational effectiveness were found to be associated with mathematics achievement but only four factors (modeling, assessment, questioning, and dealing with misbehavior) were associated with two aspects of metacognition (i.e. prediction and evaluation). Implications of findings are drawn.  相似文献   

Role of teacher-related factors and educational resources in science literacy: An international perspective     

《Studies in Educational Evaluation》2020

The study evaluated the relationship among teaching, leadership, teacher certification, student and teacher number related factors, and index of economic, social and cultural status (ESCS), and science literacy from an international comparative perspective. 2015 dataset of the Programme for International Student Assessment for Turkey, Singapore, the United States, Korea, Italy, and Brazil was used. Two-level hierarchical linear models were established for analysis. Results revealed that school ESCS was the best predictor of science literacy across six countries and additionally teacher-related factors came to the forefront of science literacy performance. The study underlined policymakers should focus primarily on policies that increase equity in education. Furthermore, the effectiveness of investments made in factors related to leadership, teacher certification, the number of students and teachers, which contribute very little to science literacy performance, need to be more questioned. Inferences about the findings were discussed in detail, and recommendations for further research were made.  相似文献   

The impact of workplace information literacy on organizational innovation: An empirical study     

《International Journal of Information Management》2020

The present study investigates the relationship between CEO’s information literacy and innovation in small and medium-sized enterprises (SMEs). Even if information literacy’s business value has been recognized in recent literature, its impact on organizational innovation, a critical and strongly information intensive process, has never been studied before. Structural equation modeling based analysis of data collected from 184 company CEOs in Finland revealed that CEOs’ information literacy has a positive impact on the development of exploratory and exploitative innovations in SMEs. Additionally, opportunity recognition mediates the relationship between information literacy and innovation. Overall, the influence of information literacy is slightly stronger on exploitation than exploration. Nevertheless, the mutual positive effect suggests that information literacy enhances innovation ambidexterity in organizations. Based on these findings, we discuss theoretical and practical implications as well as future research opportunities in workplace information literacy research.  相似文献   

产学研科技创新的竞争力形成机理研究     

陈勇军  张飞涟  陈艳 《科技管理研究》2016,(7):24-29

采用半结构访谈与书面案例研究及实践现象观察的定性研究方法,提炼出产学研科技创新竞争力的主要影响因素,向固定的对象发放大量的调查问卷,基于结构方程模型的方法,运用SPSS18.0和AMOS7.0等统计软件进行数据分析和假设检验,研究产学研科技创新的竞争力形成机理,得到相关研究结论,并从产学研科技创新竞争力的4个主要影响因素等方面提出相关对策建议.  相似文献   

基于预测有效度的组合预测模型研究   总被引：44，自引：2，他引：44  

陈华友 《预测》2001,20(3):72-73,68

本文基于预测方法有效度的概念，建立了改进组合预测模型，并给出其线性规划的解法。该模型具有计算简便的特点，而且具有可比性，能反映不同时间序列预测方法有效性。  相似文献   

Two direct Tustin discretization methods for fractional-order differentiator/integrator   总被引：1，自引：0，他引：1  

Blas M. Vinagre  Ivo Petráš 《Journal of The Franklin Institute》2003,340(5):349-362

This paper deals with fractional calculus and its approximate discretization. Two direct discretization methods useful in control and digital filtering are presented for discretizing the fractional-order differentiator or integrator. Detailed mathematical formulae and tables are given. An illustrative example is presented to show the practically usefulness of the two proposed discretization schemes. Comparative remarks between the two methods are also given.  相似文献   

Bond graph models of structured parameter uncertainties     

Casimir Sié Kam 《Journal of The Franklin Institute》2005,342(4):379-399

Taking into account uncertainties in model parameter values is a crucial point for studying robustness in modeling and in control. This paper proposes to construct in a systematic and graphical procedure two forms of the linear state equation usually found in the literature for dealing with the robustness problem in the case of structured uncertainties on parameters. It is shown how to model uncertainties in a bond graph approach, in the case of additive or multiplicative parametric variations.  相似文献