集值决策信息系统属性约简的启发式算法

在集值决策信息系统中,通过引入信息量和条件信息量,对属性的重要性进行了定义.给出了分配约简（广义决策约简）的一种启发式算法：条件信息量约简算法,分析了该算法的时间复杂度,时间复杂度为O（｜A｜3｜U｜2）;最后通过例子说明,该算法能得到集值决策信息系统的一个约简.     

试论汉语的“数量范围”

基于汉语大量的语料事实,文章对汉语“数量范围”的内涵及表现形式进行了分析,认为,汉语“数量范围”除了有常见的表达式外,还具有多种标记词,这些标记词有的可以“对”用,有的可以“叠”用,标记词的“对”用使范围更加具体明确,而“叠”用则对范围起到了确认或强调作用。     

Analysis of postponement strategy by EPQ-based models with planned backorders

This paper develops economic production quantity (EPQ)-based models with planned backorders to evaluate the impact of the postponement strategy on a manufacturer in a supply chain. We derive the optimal total average costs per unit time for producing and keeping n end-products in a postponement system and a non-postponement system, respectively. By comparing the optimal total average costs of the two systems, we evaluate the impact of postponement on the manufacturer under four circumstances. Our results show that postponement strategy can give a lower total average cost under certain circumstances. We also find that the key factors in postponement decisions are the variance of the machine utilization rates and the variance of the backorder costs.     

Confidence intervals for a two-parameter exponential distribution: One- and two-sample problems

The problems of interval estimating the mean, quantiles, and survival probability in a two-parameter exponential distribution are addressed. Distribution function of a pivotal quantity whose percentiles can be used to construct confidence limits for the mean and quantiles is derived. A simple approximate method of finding confidence intervals for the difference between two means and for the difference between two location parameters is also proposed. Monte Carlo evaluation studies indicate that the approximate confidence intervals are accurate even for small samples. The methods are illustrated using two examples.     

桌面式PPCNC在《CAD/CAM》教学实践中的应用

随着数字化技术的迅速发展及其与制造业的紧密融合,CAD/CAM技术已成为机械工程师不可或缺的一项专业技能。很多工科院校已将《CAD/CAM》课程纳入本科教学的专业主干课群中。在课堂教学中引入桌面式PPCNC,实时展示数控加工过程,并建设开放式CAD/CAM技术平台和组建CAD/CAM技术实践小组,对凸显CAD/CAM技术的实践性、适应应用型人才的培养目标、提升课程教学质量、调动学生积极性、激发学生的自主能动性都是有益的探索和尝试。     

预防机械加工类专业职业性肌肉骨骼疾患的措施

通过对职业性肌肉骨骼疾患概念、机械加工类专业职业性肌肉骨骼疾患的国内外研究现状和常见职业性肌肉骨骼疾患的阐述,以及对其病因的分析,提出中等专业学校体育预防机械加工类专业职业性肌肉骨骼疾患的措施及建议。     

机械制图课程与学生能力的培养

面对目前我国教育和人才培养的现状,认真分析了导致教学质量滑坡、学生能力低下的根本原因.对于工科院校的学生来说,机械制图课程在培养学生工程能力和综合素质方面具有得天独厚的优势和条件,承担该课程教学任务的教师在培养学生能力和素质方面大有作为.     

保护与建构城市空间文化的对策与途径

中国在快速城市化的步履下,城市空间中的文化遗产破坏、文化畸形、文化贫血现象成为普遍的城市症候.在文化需求、文化活动和文化建设行动急剧增加的形势到来时,相应的规划理论、策略和方法都明显落后于城市建设实践的需要.文章通过城市空间文化的本体述要、城市空间文化的类型学分析和城市空间的文化盘点,深入探讨并提出了保护与建构城市空间文化或文化的城市空间的具体对策和途径.     

Saving for Children’s College Education: An Empirical Analysis of the Trade-off Between the Quality and Quantity of Children

This paper examines the effect of children’s college expenses on household savings. The theoretical model introduces life-cycle savings into the quality–quantity model of fertility and derives predictions for the impact of expected expenses on parents’ savings. Using the actual amount of parents’ financial support reported in the Survey of Consumer Finances, the empirical model estimates the expected expenditures on children’s college education and investigates the effect of expected expenditures on parents’ savings. The results show that parents’ support for each of their children’s college expenses decreases with the number of children. The results are consistent with the predictions of the life-cycle theory of saving and consumption that households save in advance for expected expenses to smooth their consumption.

The quality–quantity trade-off in fertility across parent earnings levels: a test for credit market failure

The dominant economic theory of the family explains the negative correlation between family size and child achievement, a ‘quality–quantity trade-off’, through borrowing constraints and credit market failure. This paper presents a model in which the opportunity cost of time spent with children is increasing, thus creating a trade-off even in economies with perfect credit markets. While both produce a family size effect, temporal and financial constraints predict different patterns for the trade-off across levels of parent income. Using data from the National Child Development Study, the trade-off is found even among high-earning families who presumably do not face credit constraints. Moreover, the trade-off does not grow as parent earnings diminish. Both of these findings suggest that temporal and not financial constraints explain the quality–quantity trade-off.