一类有环的双色有向图的本原指数

一个双色有向图的D是本原的,当且仅当存在非负整数h和k,且h+k>0,使得D中的每一对顶点(i,j)都存在从i到j的(h,k)途径,此时称h+k的最小值为D的本原指数.利用代数与图论的方法,研究一类带有环的双色有向圈的本原指数,给出了本原指数和本原指数上界。     

技能竞赛与“可编程序控制器应用”课程教学改革

"可编程序控制器(PLC)应用"是机电一体化专业的核心专业课程,根据社会对人才的需求和课程自身的特点,将职业技能竞赛融入该课程的理论与改革实践,可进一步提高该课程的教学质量和效果。     

基于发动机外特性实验的三元催化转换器净化性能研究

文章通过发动机外特性实验,分别对没有安装催化器、安装原催化器和安装改进型催化器三种状态下发动机功率、油耗和尾气进行测量分析,对优化三元催化转化器结构设计及改善三元催化转化器净化效率等方面具有重要意义。     

关于提高发光二极管出光效率途径的探讨

提高发光二极管(LED)的出光效率是当前的一个研究热点。本文首先讲述了LED的发光原理以及影响LED出光效率的内量子效率、外量子效率概念,分析了几种常见的提高LED外量子效率的途径,生长分布布拉格反射层结构、表面粗化技术、倒装芯片技术,重点探讨利用光子晶体提高LED出光效率的原理及其优势。     

基于PIC单片机的自动门驱动器硬件设计

针对自动门开启快速与平稳、关闭无撞击及低噪声的特点,进行无刷直流电机驱动器硬件设计．该控制器以PICl6F77单片机为主控芯片,分析电源、霍尔位置传感器电路、驱动电路芯片IR2103等设计思路和原理．实验结果表明,无刷直流电机运行平稳、可靠,满足自动门的使用要求．     

Motivation and Burnout in Professional Rugby Players

Abstract

A survey of the literature on the development of physical education tests reveals little of value to the researcher confronted with the problem of assessing the gross motor ability of manpower pools and predicting success in related tasks. Flexible instructions, subjective scoring, limited concepts of validity, and other factors involving a disregard or misinterpretation of principles of test construction have greatly reduced the usefulness of research in this field (1, p. 1).     

网络多元化视阈下高校数字图书馆对外服务模式分析

【目的/意义】随着网络多元化的发展,传统高校数字图书馆的服务模式已无法为用户提供更有效的服务, 亦无法满足用户对服务的多元化需求,因此急需推进高校数字图书馆对外服务与网络技术的深度融合。【方法/过 程】首先对网络多元化视阈下高校数字图书馆对外基本服务模式进行分析,探讨当下存在的资源建设、资源使用, 以及安全隐私等方面的问题,结合网络多元化时代高校数字图书馆对外服务的发展趋向,在此基础上提出解决方 案。【结果/结论】网络多元化背景下通过完善对外服务基础设施层、提升对外服务资源利用率、实现对外个性化信 息服务和保障信息隐私安全,来优化和完善高校数字图书馆对外服务模式,力求为用户带来更高效、高质的服务体 验。【创新/局限】本文通过深入研究,旨在推动图书馆事业的完善和发展,实现数字图书馆的个性化、智能化、多元 化的对外服务创新模式。后续以待相关量化研究进一步充实。     

Assessing Methods for Generalizing Experimental Impact Estimates to Target Populations

ABSTRACT

Randomized experiments are considered the gold standard for causal inference because they can provide unbiased estimates of treatment effects for the experimental participants. However, researchers and policymakers are often interested in using a specific experiment to inform decisions about other target populations. In education research, increasing attention is being paid to the potential lack of generalizability of randomized experiments because the experimental participants may be unrepresentative of the target population of interest. This article examines whether generalization may be assisted by statistical methods that adjust for observed differences between the experimental participants and members of a target population. The methods examined include approaches that reweight the experimental data so that participants more closely resemble the target population and methods that utilize models of the outcome. Two simulation studies and one empirical analysis investigate and compare the methods’ performance. One simulation uses purely simulated data while the other utilizes data from an evaluation of a school-based dropout prevention program. Our simulations suggest that machine learning methods outperform regression-based methods when the required structural (ignorability) assumptions are satisfied. When these assumptions are violated, all of the methods examined perform poorly. Our empirical analysis uses data from a multisite experiment to assess how well results from a given site predict impacts in other sites. Using a variety of extrapolation methods, predicted effects for each site are compared to actual benchmarks. Flexible modeling approaches perform best, although linear regression is not far behind. Taken together, these results suggest that flexible modeling techniques can aid generalization while underscoring the fact that even state-of-the-art statistical techniques still rely on strong assumptions.     

心理尺度对大学生学习积极性的影响

大学生学习积极性受内在因素和外在因素的综合影响。外在因素中包括不同心理尺度的因素。通过设计问卷,调查不同心理尺度对大学生学习积极性的影响。结果表明:小环境对大学生学习积极性影响较大(F=10.481,df=3,P<0.05),尤其是寝室的学习风气。学校学生管理和教学管理部门以小尺度单位为管理重点,有助于提高大学生学习积极性。     

符号经济时代中原文化的价值开发与对外传播

在符号经济时代,符号价值超越商品价值。以“源”文化、“根”文化、“中”文化及“农”文化为核心的中原文化要发挥其在促进文化品牌发展及中原经济区建设中的作用,就要紧扣符号经济时代的特征,深化中原文化内涵,提升文化品味与价值,关照消费者的个性体验,突出过程消费与意义消费,在“求同”、“兼容”前提下建构立体化对外传播体系。