Differential genetic etiology of reading disability as a function of mathematics performance

In order to assess the etiology of reading disability as a function of mathematics performance, data from 168 monozygotic (MZ) and 127 same-sex dizygotic (DZ) twin pairs in which at least one member of each pair was reading-disabled were subjected to quantitative genetic analyses. MZ and DZ concordance rates for reading disability were computed for different levels of mathematics performance, and reading performance data were fitted to an extension of the basic multiple regression model for the analysis of selected twin data. Results of these analyses suggest that genetic factors may be especially salient as a cause of reading disability in children with borderline deficits in mathematics performance: thus, mathematics performance may be a valid dimension for diagnosing subtypes of reading disability.     

积分因子的存在性定理及其应用

给出了一阶微分方程M(x,y)dx N(x,y)dy=0具有形如μ(x,y)=φ(f(x)g(y))的一类积分因子的充分必要条件以及积分因子的计算公式.作为主要结果的应用,讨论了一类特殊微分方程的解法.     

磁粉离合器在小汽车差速系统中的应用

现有的差速器在汽车中存在差速不差力,结构复杂,加工成本高,维修难等问题.经过研究,运用磁粉离合器恒力矩运行的特性以及结构简单,制造成本低,运行可靠,控制方便,差速也差力的优点,对小汽车差速器进行了设计.     

充分利用《技术性贸易壁垒协议》,积极扩大中国农产品出口

技术性贸易壁垒是世贸组织管辖范围内主要商品贸易协议之一，主要涉及国际贸易中的一些新问题，而被越来越多的国家所采用。章在分析《技术贸易壁垒协议》和中国农产品贸易现状的基础上，就中国农产品如何充分利用《技术性贸易壁垒协议》扩大农产品出口，提出了自己的认识和看法。     

年内不均匀系数探讨

本文从物理概念、年内不均匀系数等值线图、计算机程序应用提出用年内分配不均匀变差系数Ca研究年内不均匀系数；并用长江上游地区干支流250个水文站多年平均Ca、C1、完全年调节系数C2翔实资料进行全面论证，对完善年内不均系数有一定的理论和实用价值。     

Dog Treat Ball: An Activity to Introduce Systems of Differential Equations

Abstract

This paper describes an activity using a dog treat ball to introduce systems of first-order differential equations. Beads are placed in the first of two hemispherical chambers of a food-dispensing dog toy. As the ball is turned, students track the number of beads in the first chamber, the second chamber, and the exterior of the ball. Students develop a working assumption, write a system of differential equations to model the number of beads in each region, and use a spreadsheet to compare their experimental and model results.     

Capitalizing on advances in mathematics and k-12 mathematics education in undergraduate mathematics: An inquiry-oriented approach to differential equations

This paper provides an overview of the Inquiry-Oriented Differential Equations (IO-DE) project and reports on the main results of a study that compared students’ beliefs, skills, and understandings in IO-DE classes to more conventional approaches. The IO-DE project capitalizes on advances within mathematics and mathematics education, including the instructional design theory of Realistic Mathematics Education and the social negotiation of meaning. The main results of the comparison study found no significant difference between project students and comparison students on an assessment of routine skills and a significant difference in favor of project students on an assessment of conceptual understanding. Given these encouraging results, the theoretical underpinnings of the innovative approach may be useful more broadly for undergraduate mathematics education reform.     

微分变换方法求解时间和空间同时带分数阶导数的耦合Burgers方程组

首先介绍了Caputo分数阶导数的定义及广义的二维微分变换方法,然后应用微分变换方法求解时间和空间带分数阶导数的耦合Burgers方程组,最后通过一些实例说明应用微分变换方法求解分数阶耦合Burgers方程组是可靠的和有效的.     

一类高阶线性微分方程解的复振荡

本文研究了高阶线性微分方程f(k)+(Ak-1(z)epk-1(z)+Dk-1(z))f(k-1)+…+(A0(z)ep0(z)D0(z))f=0和f(k)+(Ak-1(z)epk-1(z)+Dk-1(z))f(k-1)+…+(A0(z)ep0(z)+D0(z))f=F(z)解的增长性问题,其中,pj(z)=a jzn+bj,1zn-1+…+bj,n,Aj(z)、Dj(z)和F(z)都是有限级整函数。针对pj(z)中aj(j=0,1,k-1)的幅角主值不全相等的情形,得到了方程解的增长级的精确估计。     

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。