PLC互锁与转移指令的应用研究

分别针对PLC在互锁和转移程序段中有上升沿微分和下降沿微分指令时会出现动作不稳定现象进行研究,设计出相应的优化程序,消除了动作不稳定现象。分析转移程序段在PLC中的执行特征,提出在两段不同时执行的转移程序中可用双线圈,并应用到有两种或以上控制方式的PLC控制系统中,实现系统状态由一种控制方式平滑地过渡到另一种控制方式。     

一类Lotka-Volterra模型的全局结构分析

利用微分方程定性理论,对具有竞争关系的Lotka-Volterra系统:dx/dt=x(a1 b1x c1y),dy/dt=y(a2 b2x c2y)进行全局结构分析,并得到了相应的结论.     

关于“二阶非线性泛函微分方程解的振动性质”一文的一点注记

文中就文1所讨论的二阶非线性泛函微分方程x″(t) p(t)x′(t-τ(t)) q(t)f(x(τ(t))=0的解的振动性质,利用文2的已知结果改进了文1的相应结果。     

某类双参数非线性微分方程组边值问题的奇摄动

本文研究一类含有双参数非线性微分方程组y'=f(x,y,z,ε，μ），y(l,ε，μ）＝a(ε，μ) εy”=F(x,y,z,z',ε，μ),z'(O,ε，μ)=b(ε，μ),z(1,ε，μ)=c(ε，μ)的奇摄动，在适当的假设条件下，利用微分不等式理论，证明了摄动解的存在，并给出了解的直到O（^N＋1∑k=0ε^N 1-Kμ^k）阶的一致有效渐近展开式。     

差热分析影响因素及实验技术

差热分析方法是一种动态温度分析技术，操作方便，应用普及，但影响其实验结果DTA曲线的因素甚多，通过反复实验，总结出了影响DTA曲线的主要因素和实验技术。     

R&D subsidies & external collaborative breadth: Differential gains and the role of collaboration experience

External collaboration breadth is important for firms to acquire the knowledge needed to innovate. In this paper, we combine cross-sectional and longitudinal data from the Spanish Panel of Technological Innovation Survey (PITEC) to examine the indirect impact of R&D subsidies on firm external collaboration breadth. We contribute to understanding of the indirect impacts of R&D subsidies by first providing strong evidence of an economically significant average positive impact of R&D subsidies on firm external collaboration breadth. Second, our results advance understanding of the differential impacts of R&D subsidies by revealing the vast heterogeneity of the impact at the firm level, where approximately only half of treated firms experience a positive collaboration impact from R&D subsidies, while the remainder experience no impact or a negative effect. Finally, we advance understanding of the characteristics explaining the differential impact of R&D subsidies on external collaboration breadth by utilising the organisational learning literature to demonstrate the important role of firm collaboration experience.     

The gender gap in early career transitions in the life sciences

We examined the extent to which and why early career transitions have led to women being underrepresented among faculty in the life sciences. We followed the careers of 6,336 scientists from the post-doctoral fellowship stage to becoming a principal investigator (PI) – a critical transition in the academic life sciences. Using a unique dataset that connects individuals’ National Institutes of Health funding histories to their publication records, we found that a large portion of the overall gender gap in the life sciences emerges at this transition. Women become PIs at a 20% lower rate than men. Differences in “productivity” (publication records) can explain about 60% of this differential. The remaining portion appears to stem from gender differences in the returns to similar publication records, with women receiving less credit for their citations.     

An analysis of Differential Item Functioning on INVALSI tests,designed to explore gender gap in mathematical tasks

This study presents a quantitative approach based on Differential Item Functioning analysis within the Item Response Theory framework, to quantify gender differences in tackling specific mathematical items. We use this approach to explore two crucial topics in mathematics education (misconceptions in decimal numbers, and estimation) by analysing answers given by Italian students to specific mathematical items taken from a sample of 1400 items administered in INVALSI tests since 2008. For each item, we have a sample of 30,000 students per year, statistically representative of the entire Italian student population. The results section presents a didactic interpretation of the statistical evidence and shows how interdisciplinarity between statistics and mathematics education, with a mixed-method approach (Johnson & Onwuegbuzie, 2004), represents a good approach to exploring the gender gap in relation to specific constructs of math education. This approach, common in many disciplines, can also make an interesting contribution to mathematics education research.