基于copula 函数对相依部件系统可靠度的度量和改进

将copula函数引入可靠性理论中的一些典型不可修串并联系统，用以度量部件相依时系统的可靠度，给出了相依时系统度量的改进，并在理论上分析了独立与相依时系统可靠度的优劣。     

基于时间序列数据Hull-White模型半参数估计方法

基于时间序列数据,对Hull-White短期利率模型进行半参数估计。通过两阶段估计方法,原半参数估计模型转化为非参数估计模型和全参数估计模型。前者使用核函数估计方法,后者使用极大似然估计,从而简化整个参数估计过程。实证的结果表明,在给定合适窗宽条件下,基于Hull-White模型的似然值将得到改善。     

一种Archimedean copula函数模型选择的新方法

首先证明样本Kendall秩相关系数■是总体Kendall秩相关系数τ的一致估计量,且样本Spearman秩相关系数■是总体Spearman秩相关系数ρ_s的一致估计量.其次,在■、■这两个一致估计量的基础上,构建了一种新的一致估计量.实证分析表明,基于新的一致估计量的函数选择模型较原来方法有较大的改进.     

广义加权函数平均组合预测模型参数估计方法

提出一种新的组合预测模型--广义加权函数平均组合预测模型, 并利用二次规划算法给出其加权系数的2种不同的参数估计方法. 最后, 以预测实例说明了模型的有效性并对2种参数估计方法进行了比较, 得到一个对参数估计方法进行正确应用的有用结论.     

两类半拟齐次函数的正规型

利用半拟齐次函数的性质,得到了证明两类半拟齐次函数正规型的一种比较初等的方法,更简明的给出了两类半拟齐次函数的分类。     

解函数题的两种边缘化方法

系统地研究高中数学教材的边缘化解题方法,是深化教学研究的途径,有利于教师吃透高考命题,有利于学生备战高考的高效复习.解函数题就有两种边缘化方法:在解题过程中运用极限工具;同一题中二次或多次求导.     

多维正态分布参数估计的损失函数和风险函数的Bayes估计

给出了多维正态分布在NP(θ,∑)和方差∑已知情况下多维参数均值θ=(θ1,θ2,…,θP)估计的损失函数和风险函数的Bayes估计.     

多维正态分布参数估计的损失函数和风险函数的Bayes估计

在N P(θ,Σ)和方差Σ已知情况下,给出了多维正态分布多维参数均值θ=(θ1,θ2,…,θΡ)估计的损失函数和风险函数的Bayes估计。     

关于多元函数的半连续性的研究

给出了半连续函数的定义，研究了函数具有半连续性的条件，推出了半连续函数的一些性质。     

两种分布函数定义的比较

对两种分布函数的定义作了比较.其结论是:在不同方式的定义下,同一随机变量的分布函数几乎处处相等.     

河水化学需氧量测定方法的对比

同时采用高锰酸钾法和重铬酸钾法测定河水水样的化学需氧量(COD),结果表明,用重铬酸钾法所测得的COD值较高,因此,不能把两种方法所测定的结果互相混用。     

A Comparison of Two Methods for Structuring Performance Domains

This research evaluated two methods for structuring a performance domain for a certification test in emergency nursing. The first method utilized task frequency ratings obtained from a national sample of 659 emergency nurses who completed a job analysis survey consisting of 125 tasks. The second method was based on judgments of task similarity among the same 125 tasks; the similarity judgments were provided by a panel of 21 subject-matter experts. The two types of data, task frequency ratings and task similarity judgments, were subjected to cluster analysis and multidimensional scaling in order to derive a framework for organizing the 125 tasks into some limited number of performance categories. The similarity judgments produced fewer clusters and fewer dimensions and were more adequately modeled by both multivariate procedures. The results based on the similarity judgments were also easier to interpret within a conceptually meaningful framework. The results question the traditional approach of applying multivariate procedures to task frequency ratings for purposes of clustering tasks and structuring performance domains.     

凸函数的Hadamard不等式的两种证明方法

利用连续函数的稠密性定理给出了Schur等凸函数的一些性质和“xy”控制不等式的理论和方法,并应用这些理论和方法证明了著名的Hadamard不等式.     

Comparison of Two Methods of Studying History

This study examined the effects of team teaching on selected attitudes and achievement of ninth grade students in English and World History after 1 year. Seventy-four ninth grade students from a local school were randomly assigned to a team teaching treatment group while the remaining seventy-one members of the freshman class received traditional instruction in three separate classrooms. A teacher constructed test was employed to measure achievement in subject matter, and a personality inventory was used to measure changes in selected attitudes. The findings indicated that the team teaching approach did not appear to complement academic growth over traditional teaching methods but it did have a significant impact on student attitudes toward teachers, interest in subject matter, sense of personal freedom, and self-reliance.     

多种内插算法的信道估计比较

分析了梳状导频插入方式下的信道估计算法的原理和性能,在频域上先对导频子载波进行最小平方估计(LS),并运用多种内插方法获取信道频率响应。运用MATLAB软件进行了仿真,比较分析了OFDM系统中各种信道估计算法的性能优劣。仿真结论对OFDM通信系统以及其它通信系统的信道估计有一定的研究价值。     

A Comparison of Two Methods of Learning

ABSTRACT

This is an impact evaluation of the Technical Support to Failing Schools Program, a Chilean compensatory program that provided 4-year in-school technical assistance to low-performing schools to improve students’ academic achievement. The author implemented a quasi-experimental design by using difference-in-differences estimation combined with propensity scores matching procedures to estimate treatment effects. The main findings were the following: (a) the program had positive effects on fourth-grade students’ achievement in both language and mathematics; (b) program effect size was 0.23 standard deviations, and not sensitive to control for covariates; (c) there were larger effects for students in the middle part of the students’ test-score distribution; (d) after the intervention had ceased, the program impact declined rapidly; and (e) the program reduced grade retention by 1.5 percentage points.     

基于VPN的两种教学方法比较

本文以计算机网络安全课程中VPN教学为实例,从教学思路、教学手段、教学方法等多个方面,对两种不同的教学方法加以比较,新的教学方法在继承传统教学方法的基础上强化了实践教学,以学生为主体,教师为主导,有利于学生个性、特长的发展,有利于学生创新能力的培养。     

Semiparametric Item Response Functions in the Context of Guessing

We present a logistic function of a monotonic polynomial with a lower asymptote, allowing additional flexibility beyond the three‐parameter logistic model. We develop a maximum marginal likelihood‐based approach to estimate the item parameters. The new item response model is demonstrated on math assessment data from a state, and a computationally efficient strategy for choosing the order of the polynomial is demonstrated. Finally, our approach is tested through simulations and compared to response function estimation using smoothed isotonic regression. Results indicate that our approach can result in small gains in item response function recovery and latent trait estimation.     

两种黄芪多糖提取方法比较

为了优选黄芪多糖提取的工艺,分别用水提醇沉法、微波提取法提取黄芪多糖,比较两种工艺提取黄芪多糖的提取率和提取时间,并采用紫外分光光度法测定黄芪多糖含量。结果:水提醇沉法的黄芪多糖提取率4.468%,含量29.40%;微波提取法的黄芪多糖提取率4.502%,含量31.25%。试验结果表明:微波提取法具有省时、高效、节能等优点,在提高黄芪多糖产率和有效缩短提取时间等方面优于传统的水提醇沉法,是获得较高黄芪多糖提取率及含量的方法。