共查询到20条相似文献，搜索用时 212 毫秒
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合理标注零件尺寸方法的分析 总被引：1，自引：0，他引：1
合理标注零件尺寸，是每个设计师不可回避的问题。本从零件功能分析入手，提出零件的重要尺寸要首先直接标注；零件的重要表面要做主要尺寸基准；标注零件尺寸要兼顾其工艺要求和零件尺寸的标注步骤等，在上述几个方面进行了比较系统的阐述，对设计人员和图学教育工作将有所补益。 相似文献
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由于尺寸标注的重要性、尺寸标注与图形表达的关联性、尺寸标注本身的综合性和复杂性,我认为进一步介绍尺寸标注是必要的。此外,对尺寸标注的教学研究,无疑促进了尺寸标注的研究课题,即标注的智能化研究。 相似文献
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用AutoCAD进行机械设计时，标注尺寸公差是设计人员经常遇到的一个问题。使用传统的方法标注时较为不便。笔者尝试用Autolisp语言编写一个自动标注尺寸公差的程序，可大大提高公差标注的速度。 相似文献
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在绘制和阅读工程图样时,尺寸标注是一个非常重要且不易掌握的环节.详细论述了标注尺寸的基本规则及标注时的具体要求,并通过具体实例详细论述了标注尺寸的方法和步骤,以及标注尺寸时应注意的事项. 相似文献
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李华明 《中国科教创新导刊》2011,(26):196-198
AutoCAD尺寸标注方面也有强大的功能,利用AutoCAD的尺寸标注命令,可以方便快速地标注图纸中各种方向、形式的尺寸,将它应用到《机械制图》教学中,非常有利于学生对尺寸标注的分析理解,在正确理解尺寸注法的基本规则;正确、完整、清晰地标注组合体尺寸等教学难点问题中得到较好的教学效果。 相似文献
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尺寸标注是机械图样的一项重要内容，它贯穿机械制图教学的整个过程，但学生往往掌握不好，在标注过程中普遍存在大量问题。本文从教学的角度出发，通过多年的教学实践，对平面图形、组合体、零件图形的尺寸标注中学生普遍存在的疑问，提出自己的见解，循序渐进地进行了分析和讨论。 相似文献
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李振斌 《长江工程职业技术学院学报》2003,20(2):45-48
通过AutoCAD 2000尺寸标注中比较典型的带前缀后缀的标注及引线标注的各种常见形式的标注方法分析,用实例说明了标注的设置、修改和处理技巧,对高效、准确、美观地完成各种尺寸标注,恰当地使用标注方式和标注设置,提高标注效率具有指导意义. 相似文献
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殷永敬 《唐山师范学院学报》2005,27(5):105-106
班级规模对教育效果的影响很大。国内外有关研究表明：规模越大，教育效果越差，规模适中，教育效果最好。因此，教育工作者应适当安排班级规模，以提高教育效果。 相似文献
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Daniel H. Robinson Tiffany A. Whittaker Natasha J. Williams S. Natasha Beretvas 《Journal of Experimental Education》2013,81(1):51-64
The authors investigated the influence of effect size and comment inclusion on readers' perceptions of research results. In three experiments, undergraduates, graduates, and faculty read a journal article that either included or did not include an effect size and commentary about the effect size. Contrary to a previous study by Robinson, Fouladi, Williams, and Bera (2002), which concluded that including effect sizes causes readers to overestimate result importance, the authors found that including a comment about the magnitude of the effect size was more important than simply including the effect size in influencing undergraduates' perceptions of research results' importance. Graduate students and faculty members were less influenced by inclusion of either effect sizes or comments. Recommendations concerning effect size and comment inclusion polices are discussed. 相似文献
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Using student evaluations of their instructor as an outcome measure, we estimate and compare class size and teacher effects for higher education, with an emphasis on determining whether a comprehensive class size reduction policy that draws on the hiring of new teachers is likely to improve educational outcomes. We find that first time teachers perform significantly worse than their peers, and we find substantial class size effects. Hence higher education institutions face a tradeoff if they wish to increase admission. This tradeoff implies that as class size increases, at first the negative class size effect is smaller than that of introducing a first time teacher. However, beyond a certain level, the class size effect dominates and it is better to create a new class with a first time teacher.1 相似文献
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Jessica Middlemis Maher Jonathan C. Markey Diane Ebert-May 《CBE life sciences education》2013,12(3):345-351
Statistical significance testing is the cornerstone of quantitative research, but studies that fail to report measures of effect size are potentially missing a robust part of the analysis. We provide a rationale for why effect size measures should be included in quantitative discipline-based education research. Examples from both biological and educational research demonstrate the utility of effect size for evaluating practical significance. We also provide details about some effect size indices that are paired with common statistical significance tests used in educational research and offer general suggestions for interpreting effect size measures. Finally, we discuss some inherent limitations of effect size measures and provide further recommendations about reporting confidence intervals. 相似文献
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Borland Melvin V. Howsen Roy M. 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》2003,49(5):463-474
Prior studies that have investigated the relationship between school size and student academic achievement have produced conflicting results. For example, some studies found a positive relationship between school size and student achievement; other studies found that the relationship is negative. Typically, however, these past studies have not accounted for the influence of student ability in their analysis of the impact of school size on student achievement. The purpose of this paper is to examine the effect of school size on student achievement while accounting for student ability, among other variables. The results reported in this paper suggest that school size has a nonlinear relationship with respect to student achievement. Thus, there is an optimal school size with respect to the maximization of student achievement. 相似文献
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在对数机率格纸上分别对表示泥沙颗粒粒径的对数坐标和表示小于某粒径沙重百分数的机率格坐标与普通坐标进行转换 ,导出数学模型 ,从而解决了通过数学计算得出颗粒级配曲线以及已知颗粒粒径查算出小于该粒径沙重百分数和已知小于某粒径沙重百分数查算出对应的颗粒粒径、中数粒径的查算等。计算结果表明 ,线型和数据成果与手工查算成果基本吻合 相似文献
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用在设计阶段可以收集到的3个规模度量分析类规模对面向对象度量与易维护性之间关联关系的混和效果.为得到尽可能通用的结论,在127个C＋＋系统和113个Java系统上分析类规模的混和效果.首先,对每个面向对象度量,在单个系统上计算代表由类规模造成的关联扭曲的间接效果和它的方差.然后,利用统计的元分析方法计算这些系统上的平均间接效果并判断它是否显著地区别于零.实验结果表明,不论使用哪个类规模度量进行分析,类规模对面向对象度量与易维护性之间关联关系的混和效果通常是存在的.因此,验证面向对象度量与易维护性之间关系的实验研究应将类规模视为一个混和变量. 相似文献
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用于线性优化的基于核函数的动态步长原-对偶内点算法 总被引：1，自引：2，他引：1
In this paper, primal-dual interior-point algorithm with dynamic step size is implemented for linear programming （LP） problems. The algorithms are based on a few kernel functions, including both serf-regular functions and non-serf-regular ones. The dynamic step size is compared with fixed step size for the algorithms in inner iteration of Newton step. Numerical tests show that the algorithms with dynaraic step size are more efficient than those with fixed step size. 相似文献
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《International Journal of Educational Research》2006,45(3):202-215
In this paper we analyze class size effects in the case of primary schools in Poland. We use two empirical strategies to avoid endogeneity bias. First, we use average class size in a grade as an instrumental variable for actual class size. This allows us to control for within school selection of pupils with different abilities to classes of different sizes. Additionally, we estimate fixed effects for schools to control for differences between them. Second, we exploit the fact that there is an informal maximum class size rule. We estimate class size effect only for those enrollment levels where some schools decide to add a new class and thus dramatically lower class sizes. For such enrollment levels variance of class size is mainly exogenous and we argue that this allows estimation of quasi-experimental class size effects. In this case we again use average class size as an instrument with enrollment as a key control variable. Using both strategies we obtain similar findings. We found that the positive effects observed with OLS regression disappear when we use instrumental variables. If we avoid endogeneity bias, then class size negatively affects student achievement. However, this effect is rather small. We discuss methodology, possible bias of results and the importance of our findings to current policy issues in Poland. 相似文献