折光率法测定对苯二酚在若干溶剂中不同温度下的浓度及饱和溶解度

用折光率法测定了45℃、52℃、60℃三种温度下,对苯二酚在乙醇、正丁醇、正戊醇、异丙醚中浓度与折光率的关系以及饱和溶解度。首先进行了实验方法可靠性的验证,试验表明回收率在94.5%-102.4%之间,因而方法的可信度较高。最大溶解度平衡时间的测量表明:对于不饱和体系,振荡2小时,静置0.5小时,误差已小于0.1%;对于饱和溶解度,则必须振荡6-9小时,才能达到最大溶解度,这时误差小于0.02%。工作曲线表明,在这些溶剂中,对苯二酚的溶解度可大到接近23%,其折光率与浓度关系是一条较好的直线。与同一溶剂的苯酚工作曲线相比,相同浓度时对苯二酚的折射率较大,但相差不是很大,因而用平均工作曲线可以测量混合酚类的浓度,误差不大于2%。对于在线估计混合酚类的浓度,这是一个快速而有意义的方法。如果利用气相色谱估计得到对苯二酚与苯酚的比例,则利用内插工作曲线,用本方法测定的混合酚类的浓度误差可小到0.1%。对苯二酚在几种溶剂中的饱和溶解度是有用的热力学数据,尚未见过何处公开发表。     

一条磨光的拟合曲线

通过对类似直角梯形的曲线进行磨光构造了一条光滑拟合曲线。     

空间曲线的切线方程的一种求法

分析高等数学教材中空间曲线的切线方程和曲面的切平面方程的推导过程，给出求空间曲线的切线方程的另一种方法．     

考虑减排学习效应和次品率的供应链优化研究

考虑减排学习效应和次品率,构建基于生产速度、订购频率和订购批量3决策变量的供应链优化模型,并证明模型在特定条件下存在唯一最优解。通过数值分析,得到生产速度、碳排放价格、次品率和碳排放学习能力分别怎样影响供应链成本项目和零售商订购策略的结论。当政府趋向采用更严厉的碳减排政策带来市场上碳排放价格上升时,次品率对供应链成本的负面影响以及供应链在碳减排上提高学习能力的正面影响均被放大。     

Changes in self-esteem across the first year in college: the role of achievement goals

This longitudinal study examined the effects of achievement goals on the growth trajectories of self-esteem during the first-year at a comprehensive public university. College freshmen (N?=?311) were followed for one academic year with three time points. Between-individual differences and within-individual change in achievement goals were distinguished and used as predictors for the growth trajectories of self-esteem. A growth curve analysis revealed that initially high mastery goals and subsequent increases in mastery goals were related to high self-esteem while initially high performance-avoidance goals were related to low self-esteem. The initial levels of performance-approach goals were not related to self-esteem but subsequent increases in performance-approach goals were associated with low self-esteem. Theoretical and practical implications are discussed.     

Using Design-Based Latent Growth Curve Modeling With Cluster-Level Predictor to Address Dependency

The authors compared the effects of using the true Multilevel Latent Growth Curve Model (MLGCM) with single-level regular and design-based Latent Growth Curve Models (LGCM) with or without the higher-level predictor on various criterion variables for multilevel longitudinal data. They found that random effect estimates were biased when the higher-level predictor was not included and that standard errors of the regression coefficients from the higher-level were underestimated when a regular LGCM was used. Nevertheless, random effect estimates, regression coefficients, and standard error estimates were consistent with those from the true MLGCM when the design-based LGCM included the higher-level predictor. They discussed implication for the study with empirical data illustration.     

运用BP算法神经网络拟合传感器的输出特性

首先介绍了BP算法神经网络的基本原理，然后将BP算法神经网络应用于拟合传感器的输出特性，并在MATLAB下通过训练和仿真验证了应用BP算法神经网络拟合传感器的输出特性的优越性。     

对Bezier曲线不均匀性的改进

计算机辅助几何设计是一门迅速发展的新兴学科,Bézier曲线是辅助设计当中的一种样条曲线,在工程领域中应用较广泛,但也有一些不足之处.本文利用参数均匀化给出了一些改进的意见.     

供应商管理库存对供应商的成本分析

本文定量论述了供应商管理库存对于供求双方企业带来的总成本节约，是企业实施VMI的主要激励因素。同时还揭示出实施VMI并非总是如人们通常认为的供应商库存成本必然会增加。相反，在一定条件下实施VMI后还可能使供应商的存货成本较以前减少。     

七叶一枝花株高生长曲线方程及其拟合性研究

研究了七叶一枝花的生长曲线方程及其拟合性,该过程应用了统计软件SPSS中非线性回归子程序,对其进行生长曲线拟合.同时对株高生长与外部形状的变化进行了跟踪记录并进行数据比较分析,进行数据时采用了logistic生长模型,对七叶一枝花株高生长进行了曲线方程拟合.其结果表明:曲线方程拟合度为0.992,很好地反应了七叶一枝花株高生长的趋势,且同时记录了七叶一枝花生长过程的外部形状的变化,从而为七叶一枝花高产栽培和良种选育提供第一手素材和有效的参考数据.