资金和风险约束下的多产品报童模型最优解的研究

通过考虑近年来比较热门的多产品报童问题。以资金约束为第一约束,风险约束为第二约束,从而构成四种组合。在风险的刻画上,采用半方差来衡量;在资金约束的限制下,采用两种启发式算法来简化运算,通过实现费用函数的最小化来寻求满足约束条件的最优订购量。最后对文中叙述的结论加以数值分析。     

Does lengthening the school day increase students’ academic achievement? Results from a natural experiment in Chile

This study (an impact evaluation of the Chilean full school day program) uses difference-in-differences to estimate the effect of a large increase in instructional time on high school students’ academic achievement. The main findings are (i) the program had a positive effect on students’ achievement in both mathematics and language; (ii) the effect-size on language achievement was 0.05–0.07 standard deviations and not sensitive to control for covariates, different control groups, and historical trends; (iii) the effect on mathematics achievement was not sensitive to control for covariates, but was sensitive to use different control groups, and historical trends; the effect-size on mathematics achievement ranged from 0.00 to 0.12 standard deviations; and (iv) the program effect has been constant over time. Finally, there is evidence suggesting that the program had larger positive effects on rural students, students who attended public schools, and students situated in the upper part of the achievement distribution.     

Associations of Resource and Service Utilization, Risk Level, and College Outcomes

We tracked resource and service utilizations and first-year college outcomes for the entering first-year class (n = 1,534) at a traditional 4-year postsecondary institution. We grouped specific resources and services offered by the institution into four general categories (academic services, social resources, recreational resources, and advising sessions). We investigated the interrelation of risk, resource and service utilization, and first-year GPA and retention. We found that utilization of each resource/service category was positively associated with GPA and/or retention. Of particular interest, we tested whether the associations of resource and service utilization and outcomes were moderated by risk. We found that the associations of academic services and advising sessions with GPA were more pronounced for higher-risk students. We discuss the implications of the findings, including how the differential associations of resource and service utilizations and outcomes can affect intervention decisions with high-risk students. This research was a collaborative project between ACT and NAU. Steven Robbins, Jeff Allen, Alex Casillas, and Adaeze Akamigbo are members of ACT Research. Margot Saltonstall is Assessment Coordinator, Enrollment Management and Student Affairs, Rebecca Campbell is Associate Professor of Educational Psychology, and Eileen Mahoney is Director of the Gateway Student Success Center, all at Northern Arizona University. Paul Gore is Associate Professor of Educational Psychology at the University of Utah and former director of the Career Transitions Research Department at ACT.     

There—be存在句的优选论分析

在优选论的理论框架下,从语音、句法、语用三个层面同时对英语There—be存在句的产生过程进行分析,并且对英汉两种语言的存在句进行了比较。EPP原则、主语共现原则、信息焦点原则、末尾重心原则和完全解释原则都是促使和限制英汉存在句生成的制约条件,普遍存在于两种语言之中,但它们在英汉两种语言中的等级排列顺序不同,因而导致两种语言存在句结构的不同。     

Higher education expansion and low-income students in Taiwan

In this paper, we report on a study of 1510 undergraduates from five national universities in Taiwan, and we show that compared to “non-prestigious” universities, a larger proportion of students at prestigious universities come from middle and high socioeconomic classes and a smaller proportion experience financial insecurity These results are timely in the wake of Taiwan's expansion in the number of universities and of university students. At non-prestigious universities, a higher percentage of students experience economic constraints, spend several hours per week engaged in paid employment during their university studies, and have parents who did not go to college. These different characteristics of the student bodies at elite and non-elite institutions of higher education may create quite different university contexts, which may in turn affect students’ college experiences, professional choices, and opportunities in the future.     

珠三角区域科技协同创新的现状、问题及对策研究

珠江三角洲区域是我国改革开放的前沿阵地,也是广东省科技创新发展的先导区域,科技协同创新发展已成为珠三角地区重要的战略任务。基于珠三角地区政策背景及其现实条件,分析珠三角地区科技协同创新投入与产出现状,并指出珠三角地区科技协同创新所存在的问题和原因,提出要实现区域科技资源共享、重大项目联合攻关、产业集群协同创新、增强科技中介活力、科技金融协同行动等一系列提升珠三角区域科技协同创新绩效的政策建议。     

The verticality of policy mixes for sustainability transitions: A case study of solar water heating in China

Climate change and sustainable development are the defining challenges of the modern era. The field of sustainability transitions seeks systematic solutions for fundamental transformations of socio-technical systems towards sustainability, and exploring the role of policy mixes has been a central research agenda within the field. In the extant literature, there exists a lack of both conceptual and empirical research on the vertical dimension of policy mixes for sustainability transitions. This study provides a multilevel and evolutionary interpretation of the vertical interactions of policy mixes in the process of industrial path development towards sustainability transitions. An exemplary case of solar water heating (SWH) technology in Shandong Province in China is presented, capturing both the bottom-up and top-down processes of interactions. On the one hand, urban-level policy initiatives can inform higher-level policymaking; on the other hand, national-level priorities can greatly configure policy strategies for lower-level governments. Moreover, as the industry matures, the interactions of multilevel policy mixes evolve from simpler, unidirectional patterns to more complex, bidirectional ones through a vertical policy-learning feedback mechanism. This study generates two important policy implications that extend beyond the Chinese context: first, dynamic vertical interactions between multilevel governments indicate the need to develop more nuanced perspectives on the design of policy mixes; second, policy makers need to hold a more dynamic view of policy mixes by recognizing their temporal and coevolutionary nature through the policy learning process.     

Mind,Language and Artworks as Real Constraints on Students' Critical Reasoning about Meaning in Art

To engage in discussions of artwork meaning is to engage in critical reasoning, a factor that is central to the interpretation of artworks in the art classroom. While this may appear as a common‐sense claim that reflects the tacit assumptions most art educators have about students' critical dispositions in art, it is also evident that little is known about the deeper structures underlying students’ critical reasoning and how such structures shape students’ interpretations of artworks. Drawing on my research on students’ theories of critical meaning in art, this article explores the nature of practical and theoretical constraints on students’ critical reasoning about the meaning of artworks. I account for how intentional beliefs, language and representational artefacts function as a nexus of real constraints that condition students’ advance into interpretations of the social meaning of art. After briefly outlining the design and methodology of my study, I examine students’ critical reasoning performances during the formative period of development between middle to late childhood. The findings reveal that with increasing age students gradually learn to exercise their own critical intentions and represent inferences that acknowledge the significance of constitutive rules and force of a collective intentionality in the artworld on their interpretations of artworks as artefacts. I then make some conclusions about the relationship of domain‐specific shifts in art understanding, the role of intentionality, representational understanding, beliefs about art and reasoning skills to the linguistic, theoretical and artefactual constraints conditioning students’ intuitive advance into real understandings of art.     

创新驱动作用下上市公司股利政策影响融资约束的实证研究

上市公司过高的股利发放率会增加对外部融资的依赖,从而增大融资成本,但是由于创新重要性的突显,上市公司对RD投入的不断加大降低了股利政策对融资约束的影响。利用2012—2014年我国A股上市公司为样本,实证研究基于RD投入调节作用下公司股利政策对融资约束的影响,得到结论:(1)加入RD投入调节前,上市公司股利政策对融资约束有负向影响;(2)加入RD投入调节后,上市公司股利政策对融资约束有正向影响。最后提出上市公司创新驱动发展战略建议。     

利用关键链技术进行科研项目计划进度管理改进探索

基于某科研项目的实际实施情况,总结传统方法带来的问题,提出引入新的计划进度管理方法——关键链技术,通过考虑资源约束和设置缓冲管理,进行科研项目计划进度管理的改进探索。对比传统方法效果表明,关键链技术能够更科学的制定科研项目计划并实现进度控制目标。