对大模数齿轮精铣齿形的数控加工

数控立式工加工中心机床对于形状复杂但却有一定规律的零件,如:大模数渐开线齿轮,可通过利用数控原理中数学计算,根据工艺过程,按照指定数控系统的功能指令代码及程序段格式,逐段编写加工程序,可实现准确的自动加工。提高了产品的精度,加工效率,满足了产品的使用性能的要求。     

New method of improving parts accuracy by adding heat balance support in selective laser sintering

In order to improve parts accuracy, a method of adding heat balance support （HBS） was proposed, and the detailed algorithm for generating HBS was developed. A number of experiments and a comparison between similar softwares, showed that the algorithm is efficient and feasible. Moreover, different features of riBS were studied for different kinds of materials, such as PS and nylon. The research findings indicate that automatically adding HBS can significantly improve the accuracy of the parts, and that the algorithm for generating HBS is efficient and precise.     

教育认知诊断测验的信度和效度研究评述

信度和效度是衡量一个测量工具质量的关键指标,教育认知诊断测验中的信度和效度研究近年来受到研究者的关注。诊断测验的信度系数基本上源自基于α系数的属性信度系数、经验属性信度系数、四分相关系数、模拟重测一致性和分类一致性指标;效度系数主要包括模拟判准率、分类准确性和理论构想效度等。教育认知诊断测验的信度和效度研究较新,仍存在着一定的不足且缺乏全面的比较研究,更缺少系统的评价体系。     

元认知与有效学习:原理与条件

研究者通常将元认知分为监测与调控两个子系统进行研究,并对元认知监测与元认知调控的关系及二者对个体学习的影响作用做深入探讨。基于元认知监测的学习调控是有条件的,首先是个体要有利用监测指导调控的机会,更重要的是个体的元认知监测要足够精确。通常情况下,个体的监测并不精确,但它是可以提高的。     

Elite golfers' kinematic sequence in full-swing and partial-swing shots

The aim of this study was to investigate whether kinematic proximal-to-distal sequencing (PDS) and speed-summation are common characteristics of both partial and full-swing shots in golf players of different skill levels and genders. A total of 45 golfers participated, 11 male tournament professionals, 21 male and 13 female elite amateurs. They performed partial shots with a wedge to targets at three submaximal distances, 40, 55 and 70 m, and full-swing shots with a 5 iron and a driver for maximal distance. Pelvis, upper torso and hand movements were recorded in 3D with an electromagnetic tracking system (Polhemus Liberty) at 240 Hz and the magnitude of the resultant angular velocity vector of each segment was computed. The results showed a significant proximal-to-distal temporal relationship and a concomitant successive increase in maximum (peak) segment angular speed in every shot condition for both genders and levels of expertise. A proximal-to-distal utilization of interaction torques is indicated. Using a common PDS movement strategy in partial and full-swing golf shots appears beneficial from mechanical and control points of view and could serve the purpose of providing both high speed and accuracy.     

Validity of an upper-body-mounted accelerometer to measure peak vertical and resultant force during running and change-of-direction tasks

This study assessed the validity of a tri-axial accelerometer worn on the upper body to estimate peak forces during running and change-of-direction tasks. Seventeen participants completed four different running and change-of-direction tasks (0°, 45°, 90°, and 180°; five trials per condition). Peak crania-caudal and resultant acceleration was converted to force and compared against peak force plate ground reaction force (GRF) in two formats (raw and smoothed). The resultant smoothed (10 Hz) and crania-caudal raw (except 180°) accelerometer values were not significantly different to resultant and vertical GRF for all running and change-of-direction tasks, respectively. Resultant accelerometer measures showed no to strong significant correlations (r = 0.00–0.76) and moderate to large measurement errors (coefficient of variation [CV] = 11.7–23.9%). Crania-caudal accelerometer measures showed small to moderate correlations (r = ? 0.26 to 0.39) and moderate to large measurement errors (CV = 15.0–20.6%). Accelerometers, within integrated micro-technology tracking devices and worn on the upper body, can provide a relative measure of peak impact force experienced during running and two change-of-direction tasks (45° and 90°) provided that resultant smoothed values are used.     

三性与修辞学——重读李晋荃《“准确性、鲜明性、生动性”是修辞的要求吗？——兼谈修辞学的研究对象》

毛泽东在《工作方法六十条（草案）》（1958年1月）中提出＂三性＂（准确性、鲜明性、生动性）之后,很快成为修辞学的纲领。李晋荃的《＂准确性、鲜明性、生动性＂是修辞的要求吗？——兼谈修辞学的研究对象》（1980年）是一篇拨乱反正的论文。三十年之后,李文中的观点需要重新认识,这其实是对修辞学的性质与对象的再思考。     

高中学业水平考试研究(二):考试质量评价

学业水平考试试题和试卷的质量直接影响学业评价和诊断结果的有效性和可靠性。本文以上海市高中思想政治学科学业水平考试为例,从试题和题组功能偏差、试题得分与总分的相关系数、识别指数分析及分类一致性和准确性四个方面对考试的质量进行了定量评价,以介绍学业水平考试质量评价的方法。     

陀螺逆转点法定向的数据处理

对陀螺逆转点法定向的数据处理进行了综述和比较。     

话语情景中简要表述的意义和结构分析

语言作为一种交流工具，用以表达思想、传递信息。简要的语言表述在特定的语言环境下，可以更好地抒情达意，渲染气氛，产生更强的艺术感染力。美国9．11事件发生后美国各报刊争相报道，人们在紧急时刻的用语及记们精辟的措辞使英语的简要表述发挥得淋漓尽致。确实英语简要表述的语用效果值得我们研究和探讨。