基于学分绩点与综合素质测评的换算模型建立

学生综合素质测评体系的完善对有效实施大学生综合素质测评工作以及指导大学生健康发展有重要意义,其中,学生综合素质测评体系的关键在于学分绩点与综合素质测评的换算模型的转化。通过分析高校现行学分绩点测评公式,发现其存在的主要缺陷是转化公式不满足统计学原理,并指出学分绩点测评的换算公式应建立在对特定学生群体特征参数群数值分析的基础上。以西南石油大学某专业学生某学年的成绩分布数据进行验证,采取统计原理、常数变异法和不动点原理进行建模,利用求导方法对学分绩点测评中的特征参数群进行层次划分,然后对每段划分积分,通过归一化来确定变异项,得出新的换算模型。结果表明新模型能更好地反映学生的学习成绩在综合素质测评中的地位。     

Production and changeover control policies of a class of failure prone buffered flow-shops

This article deals with a stochastic optimal control problem for a class of buffered multi-parts flow-shops manufacturing system. The involved machines are subject to random breakdowns and repairs. The flow-shop under consideration is not completely flexible and hence requires setup time and cost in order to switch the production from a part type to another, this changeover is carried on the whole line. Our objective is to find the production plan and the sequence of setups that minimise the cost function, which penalises inventories/backlogs and setups. A continuous dynamic programming formulation of the problem is presented. Then, a numerical scheme is adopted to solve the obtained optimality conditions equations for a two buffered serial machines two parts case. A complete heuristic policy, based on the numerical observations which describe the optimal policies in system states, is developed. It will be shown that the obtained policy is a combination of a KANBAN/CONWIP and a modified hedging corridor policy. Moreover, based on our observations and existent research studies extension to cover more complex flow-shops is henceforth possible. The robustness of such a policy is illustrated through sensitivity analysis.     

Goodness-of-fit tests of generalized linear mixed models for repeated ordinal responses

Categorical longitudinal data are frequently applied in a variety of fields, and are commonly fitted by generalized linear mixed models (GLMMs) and generalized estimating equations models. The cumulative logit is one of the useful link functions to deal with the problem involving repeated ordinal responses. To check the adequacy of the GLMMs with cumulative logit link function, two goodness-of-fit tests constructed by the unweighted sum of squared model residuals using numerical integration and bootstrap resampling technique are proposed. The empirical type I error rates and powers of the proposed tests are examined by simulation studies. The ordinal longitudinal studies are utilized to illustrate the application of the two proposed tests.     

船舶反弯扭螺旋桨水力特性的数值模拟与分析

运用计算流体力学方法(CFD)对船舶反弯扭螺旋桨的水力特性进行数值模拟计算,获得了螺旋桨的推力系数、扭矩系数及敞水效率等水力特性参数,与试验结果进行了比较,两者吻合良好.模拟计算提供了详细的三维流场分布,可对反弯扭桨叶的工作特性和叶梢涡、尾涡及气蚀的分布状态进行深入的分析.在叶面邻近区域采用层叠式的半结构网格以适应边界层的计算要求,在边界层外的流动区域采用非结构网格,取得了较高的计算精度.     

数控技术课程教学浅探

通过对当前机械制造业发展状况的分析,说明机械类专业开设数控技术课程教学的必要性。同时针对我院数控技术课程教学过程中存在的问题,提出新形势下提高数控技术课程教学质量的途径和方法。     

Reconsidering the philanthropic foundation minimum payout policy under a “new normal”

With the increasing salience of foundations in many policy fields, and recent changes in market conditions, policies towards foundations designed decades ago seem outdated. In this article we suggest reassessing foundation payout minimums. To examine the impact of payout rates on grantmaking foundations lifespan and performance under “new normal” economics, we simulate multiple foundations lifecycles using Monte Carlo methods in diverse capital market conditions, with varied investment and payout strategies.We find that while under past market regime perpetuity seems to be a given, under more probable future scenarios, foundations might face increasingly early mortality and endowment depletion, limiting their potential impact. Furthermore, lower payout rates allow for higher lifetime grantmaking, higher mean annual grantmaking, and lower giving volatility. Accordingly, we suggest a tiered payout policy, in line with foundations’ missions and proper financial planning.     

强吹除雪气固两相流流场数值模拟分析

为研究和分析机场强吹除雪气固两相流流场的压力、速度和雪粒运移规律,依据离散粒子模型建立了强吹除雪气固两相流方程,并采用计算流体力学数值分析方法,对机场强吹除雪的气固两相流流场进行数值模拟分析,得到了气固两相流流场的压力、速度分布曲线和不同时刻下的雪粒分布规律．数值分析结果表明,气固两相流场发展过程迅速,速度分布符合射流理论,湍流强度变化剧烈．数值模拟得到强风强吹除雪的吹雪时间为2．5s．     

海水淡化装置水流特性的三维数值模拟

运用计算流体力学方法，对多级闪发式海水淡化装置第一级的流动进行了三维数值模拟，分析了闪发室内的水流特性，并将有阻流板的与无阻流板的计算结果进行了比较，数值模拟结果表明，闪发室内存在着大尺度的环流和旋涡，且主导着闪发室内的流态，对闪发效率产生重要影响；阻流板确能很大地改变整个闪发室的水流特性，但目前的阻流板设置方式对提高闪发效率是不利的．     

油水旋流分离器数值模拟优化研究

采用计算流体动力学（CFD）软件中的雷诺应力模型（RSM）对油水分离旋流器内部流场进行了数值模拟,研究发现采出液在进口处的相互流动干扰对油水分离效果有重要影响,据此提出了一种新型结构——带有空间阿基米德螺旋线进口流道和导流螺旋的油水旋流分离器。进一步的优化设计和性能试验表明：空间阿基米德螺旋线进口流道和导流螺旋实现了平滑过渡,从而得到较稳定的流场和较高的分离效率。     

大气边界层中天线风载特性的数值分析

基于Reynolds时均N-S方程和RSM湍流模型,以大气边界层中具体地貌的风速剖面为入口边界条件,对某一车载雷达天线的风载进行数值模拟,得到天线的阻力系数;并与目前天线设计采用的均一风速为边界条件的计算结果进行比较,研究了工作高度、风速、地貌等因素对大气边界层中天线风载特性的影响。计算结果表明,大气边界层中天线的阻力系数随工作高度及风速的增加而增大;而地面粗糙度对天线阻力系数的影响则由天线相对于标准参考高度的位置决定。