基于区分度的智能组卷难度正态分布算法

给出了一种依据试卷区分度确定算法参数的智能组卷难度正态分布算法.实例表明,相对于目前的通过设定组卷难度区间的概率和为1来确定算法参数,生成的试卷更好地体现了组卷难度分布设计所要求的试卷对不同考生的知识能力的区分和鉴别的考核要求.     

基于动态试题难度参数的智能组卷策略*

针对网络考试系统的即时性和高效性,提出了基于动态试题难度参数的智能组卷算法的设计策略,利用二项分布函数做难度曲线分布模型,结合目标函数对试题多种参数进行优化。根据试卷的整体难度,以试题难度参数为优先,运用试题选题参数调节知识点之间的平衡,试题曝光参数选取出卷频率比较低的试题,从而确定各种题型不同试题难度数量,实现快速自动组卷的目标。     

基于层次分析方法与人工鱼群算法的智能组卷*

针对已有智能组卷方法难以满足考核要求,设计了一种基于层次分析方法与人工鱼群算法的新方法。首先根据试卷总分、考试时间、章节分数、知识点分数、题型分数、能力层次分数、试卷难度与试卷区分度八个考核要求建立多目标、多约束组卷模型;然后利用层次分析方法确定各组卷目标的权重,进而通过线性加权求和将多目标规划模型转换为单目标规划模型;最后利用改进的人工鱼群算法求解模型得到最优组卷方案。该方法适用于单套组卷与多套组卷。同时,讨论了该方法的优缺点以及发展趋势。     

基于分割策略的快速抽题组卷算法

本文介绍了两个基于分割策略的算法，用在考试组卷系统中，一是用来完成如何根据试卷的难度系数确定不同难度系数试题抽取的数量；二是用来完成如何从试题库中抽取满足试卷要求的一定数量的试题。     

蚁群算法在自动组卷建模中的应用研究

在自动组卷优化控制的研究中,自动组卷是一个多约束条件下的多目标参数优化问题,各个目标之间互相牵制,采用传统算法求解相当的困难,导致组卷效率和成功率都比较低.结合自动组卷的多目标组合优化特点,提出一种蚁群算法的自动组卷模型.模型首先根据试卷要求建立试卷质量评价体系,然后根据题型、总分、考试时间等要求建立多约束条件、多目标的数学模型,然后用蚁群算法对数学模型进行求解,输出最优组卷方案.仿真结果表明,蚁群算法充分利用了蚁群算法群体智能特点,提高了组卷效率和成功率,很好满足自动组卷的效能要求.     

试题库随机组卷系统的研究与探讨

组卷和试卷测评是网络考试系统的核心内容,为此,在深入研究的基础上,提出了基于难度级别的多约束组题算法,实现了快速组卷过程。基于该组卷方式,介绍了试卷的3个主要评测指标。该算法已经成功应用于实际网络考试系统中。     

基于改进的遗传算法的智能组卷算法研究

随着人工智能技术在高校信息化过程的不断推广,智能在线考试模式已成为高校教学改革的一种新手段。目前现有的在线考试系统由于一些现实约束,还存在很多不足。文中针对现有的考试系统存在智能组卷后的试卷难度不均衡、题库试题难度系数确定不合理的现象,提出一种基于改进的遗传算法自动组卷策略。利用伯努利大数定律和机器自适应学习方式,确定题库中试题合理的难度系数。在试题的难度系数确定后,试卷的难度系数就是参入组卷的试题的平均难度系数,组卷中,只需指定试卷的平均难度系数和各类题型的数量即可。     

基于基因表达式编程的计算机组卷算法研究

随着计算机技术的发展,传统的手动组卷方法难以满足新时代下的各种领域的需求,为解决传统手动组卷在性能、速度、题型分配等方面的缺陷,基于计算机技术的智能组卷问题日渐变为人们关注的问题。然而目前的组卷算法存在成功率低、计算时间久、知识点覆盖不完整、难度系数难以把握、生成的试卷难以满足要求等问题,导致了生成的试卷无法达到理想的效果。为改善上述问题,引入了基因表达式编程算法,通过使用适当的遗传算子,采用线性定长的编码方式,构造了新的智能组卷方法,避免了传统组卷算法成功率低以及适应性差等问题,解决了多约束条件下试卷的分数分配、章节分配、难度等一系列问题。实验证明,该算法有着较高的效率,能够快速地生成满足要求的试卷。     

基于背包问题的在线组卷算法

针对当前计算机在线自动组卷效率低和效果不理想的问题,提出一种基于背包问题求解的组卷算法,并改进了传统的背包问题求解思想:即按照题型和难度将试卷大包划分成试卷小包,进而分别求解,利用背包问题求解其过程。实验表明,算法可根据专家设计的组卷策略自动生成试卷,效率和成功率都是比较理想的。     

试题库中自动组卷的算法及试卷测评策略

组卷和试卷测评是网络考试系统的核心内容,为此,在深入研究的基础上,提出了基于难度级别的分割递归算法和状态链表的随机抽题算法,实现了快速组卷过程.基于该组卷方式,介绍了试卷的4个主要评测指标.最后给出了具体实例加以论证.该算法已经成功应用于实际网络考试系统中.     

基于蒙特卡罗方法的试卷难度分布研究

本文根据教育测量学理论对试题难度和试卷难度分布问题进行了概率学研究，提出了基于蒙特卡罗方法的试卷难度分布求解思路并进行了实现。文中针对常模参照性考试详细讨论了正态分布的适用范围，并讨论了蒙特卡罗方法的收敛性，同时给出了该方法的计算结果。研究表明，蒙特卡罗方法在解决试卷难度分布问题方面具有较好的优势。     

Size and power properties of some tests in the Birnbaum-Saunders regression model

The Birnbaum-Saunders distribution has been used quite effectively to model times to failure for materials subject to fatigue and for modeling lifetime data. In this paper we obtain asymptotic expansions, up to order n^−1/2 and under a sequence of Pitman alternatives, for the non-null distribution functions of the likelihood ratio, Wald, score and gradient test statistics in the Birnbaum-Saunders regression model. The asymptotic distributions of all four statistics are obtained for testing a subset of regression parameters and for testing the shape parameter. Monte Carlo simulation is presented in order to compare the finite-sample performance of these tests. We also present two empirical applications.     

基于Simulink配电变压器模型的建立及仿真

在电力系统Simulink仿真环境下,本文提出了一种新的变压器模块参数设置方法。在一定假设条件下,采用等效电路法,求取10kV配变参数,搭建配变模型,并设计出变压器空载和短路试验仿真系统,对配变模型进行仿真。通过对仿真结果的分析,证明了本方法的正确性和有效性。     

一种多扫描链混合测试数据压缩方法

针对集成电路测试数据量大、测试应用时间长和测试结构复杂等问题,提出一种多扫描链的混合测试数据压缩方法。对于含无关位较多的测试向量,使用伪随机向量产生器生成。对于含无关位较少的向量,则直接使用自动测试设备存储。将该方法与另一种基于扫描阻塞的测试方法进行比较,理论分析和实验结果表明,该方法对数据的压缩效果优于单纯用伪随机方式的扫描阻塞测试方法。     

飞行器供配电系统地面通用测试接口设计

供配电地面测试负责为飞行器提供模拟供电、控制状态切换、采集并传输系统状态信息,配合完成全飞行器全周期的综合测试任务;飞行器与地面测试系统之间接口复杂,各项目接口方式也不统一,导致测试系统中专用设备比例仍然很高,设备继承性和互换性不强,研制费用高;首先简要介绍了供配电地面测试系统的基本功能和设备组成,明确各组成部分之间的能源流和信息流,然后对供电、控制、测量的典型接口电路进行分析,从实现方式上进行简化和归类,最后提出基于先进背板总线架构的模块化板卡方案实现测试设备的接口通用化设计;经实际产品研制和系统测试,能够满足飞行器从综合试验到靶场测试发射的全生命周期测试需求,已在两个项目中实现产品共用,经济效益明显,为电气系统地面测试设备通用化研究提供了支撑。     

Improved Peňa-Rodriguez portmanteau test

Several problems with the diagnostic check suggested by Peňa and Rodriguez [2002. A powerful portmanteau test of lack of fit for time series. J. Amer. Statist. Assoc. 97, 601-610.] are noted and an improved Monte-Carlo version of this test is suggested. It is shown that quite often the test statistic recommended by Peňa and Rodriguez [2002. A powerful portmanteau test of lack of fit for time series. J. Amer. Statist. Assoc. 97, 601-610.] may not exist and their asymptotic distribution of the test does not agree with the suggested gamma approximation very well if the number of lags used by the test is small. It is shown that the convergence of this test statistic to its asymptotic distribution may be quite slow when the series length is less than 1000 and so a Monte-Carlo test is recommended. Simulation experiments suggest the Monte-Carlo test is usually more powerful than the test given by Peňa and Rodriguez [2002. A powerful portmanteau test of lack of fit for time series. J. Amer. Statist. Assoc. 97, 601-610.] and often much more powerful than the Ljung-Box portmanteau test. Two illustrative examples of enhanced diagnostic checking with the Monte-Carlo test are given.     

机载线缆的分布式并行测试系统设计与研究

面向机载信号线缆的测试需求,提出以主控器构成管理中心,以分布式测试单元形成测试前端,以CAN总线为信息交换方式,实现线缆的分布式并行测试系统;采用比例法的模数转换技术,实现了线缆导通阻抗的高准确度和稳定性;采用虚拟现实3D显示技术,实现故障线缆的定位,为排故提供方便;同时也对多芯线缆的断线检测方法进行了实验研究,其结果表明,该测试系统能满足线缆多种故障的检测需求.     

On the versatility of the combination of the weighted log-rank statistics

In many applied situations, it is difficult to specify in advance the types of survival differences that may exist between two groups. Therefore, it is tempting to use some tests that emphasize these differences, but are sensitive to a wide range of the survival differences. In this paper such versatile tests are considered, whose procedures are based on the simultaneous use of the weighted log-rank statistics that are asymptotically normal under the null hypothesis of no difference between two groups. Simulations are performed to examine power of the tests in small and moderate sample sizes when the data are uncensored to heavily censored. Implementation of the procedures are discussed in a real data example for illustration.     

Fourier methods for testing multivariate independence

Recently a power study of some popular tests for bivariate independence based on ranks has been conducted. An alternative class of tests appropriate for testing not only bivariate, but also multivariate independence is developed, and their small-sample performance is studied. The test statistics employ the familiar equation between the joint characteristic function and the product of component characteristic functions, and may be written in a closed form convenient for computer implementation. Simulations on a distribution-free version of the new test statistic show that the proposed method compares well to standard methods of testing independence via the empirical distribution function. The methods are applied to multivariate observations incorporating data from several major stock-market indices. Issues pertaining to the theoretical properties of the new test are also addressed.     

Testing hypotheses in the Birnbaum-Saunders distribution under type-II censored samples

The two-parameter Birnbaum-Saunders distribution has been used successfully to model fatigue failure times. Although censoring is typical in reliability and survival studies, little work has been published on the analysis of censored data for this distribution. In this paper, we address the issue of performing testing inference on the two parameters of the Birnbaum-Saunders distribution under type-II right censored samples. The likelihood ratio statistic and a recently proposed statistic, the gradient statistic, provide a convenient framework for statistical inference in such a case, since they do not require to obtain, estimate or invert an information matrix, which is an advantage in problems involving censored data. An extensive Monte Carlo simulation study is carried out in order to investigate and compare the finite sample performance of the likelihood ratio and the gradient tests. Our numerical results show evidence that the gradient test should be preferred. Further, we also consider the generalized Birnbaum-Saunders distribution under type-II right censored samples and present some Monte Carlo simulations for testing the parameters in this class of models using the likelihood ratio and gradient tests. Three empirical applications are presented.