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41.
网络考试系统是当前计算机应用的热门研究课题之一.从单一学科、简单题型、随机算法组卷的简单网络考试系统逐渐向多学科,多题型,智能组卷的增强式网络考试系统发展.通过对目标系统进行需求分析,了解其功能需求,设计一个完善的增强式网络考试系统,为最终实现该类型考试系统打下基础. 相似文献
42.
M. Fazil BakshDankmar Böhning Rattana Lerdsuwansri 《Computational statistics & data analysis》2011,55(1):466-474
While over-dispersion in capture-recapture studies is well known to lead to poor estimation of population size, current diagnostic tools to detect the presence of heterogeneity have not been specifically developed for capture-recapture studies. To address this, a simple and efficient method of testing for over-dispersion in zero-truncated count data is developed and evaluated. The proposed method generalizes an over-dispersion test previously suggested for un-truncated count data and may also be used for testing residual over-dispersion in zero-inflation data. Simulations suggest that the asymptotic distribution of the test statistic is standard normal and that this approximation is also reasonable for small sample sizes. The method is also shown to be more efficient than an existing test for over-dispersion adapted for the capture-recapture setting. Studies with zero-truncated and zero-inflated count data are used to illustrate the test procedures. 相似文献
43.
We show that for some special functions (called k-multigrid equidistributed functions), we can compute the limit of the frequency of patterns in the discretization of their graph, when the resolution tends to zero. This result is applied to parabolas. We deduce also that local length estimators almost never converge to the length for the parabolas. 相似文献
44.
This paper presents an extension to plasticity problems of a new error estimator on the constitutive relation which was introduced by P. Ladevèze in a recent paper. Numerical experiments show that this enhanced error estimator can lead to a significant improvement in the effectivity indexes in the case of anisotropic meshes, or when perfect plasticity is approached. 相似文献
45.
Industrial Robot Navigation and Obstacle Avoidance Employing Fuzzy Logic 总被引:10,自引:0,他引:10
This paper proposes a novel conceptual approach based on fuzzy logic to solve the local navigation and obstacle avoidance problem for industrial 3-dof robotic manipulators. The proposed system is divided into separate fuzzy units, which control individually each manipulator link. The fuzzy rule-base of each unit combines a repelling influence, which is related to the distance between the manipulator and the nearby obstacles, with the attracting influence produced by the angular difference, between the actual and the final manipulator configuration, to generate a new actuating command for each link. It can be considered as an on-line local navigation method for the generation of instantaneous collision-free trajectories. The strategy has been successfully applied to manipulators in different simulated workspace environments providing collision-free paths. Some of the simulation results obtained are included. 相似文献
46.
蒋小莺 《数字社区&智能家居》2008,(6):1238-1240
采用J2EE体系结构,构建一个安全高效的网上商城系统,并对主要模块设计和重要的流程处理作了详细介绍。 相似文献
47.
Relative Loss Bounds for On-Line Density Estimation with the Exponential Family of Distributions 总被引:2,自引:1,他引:1
We consider on-line density estimation with a parameterized density from the exponential family. The on-line algorithm receives one example at a time and maintains a parameter that is essentially an average of the past examples. After receiving an example the algorithm incurs a loss, which is the negative log-likelihood of the example with respect to the current parameter of the algorithm. An off-line algorithm can choose the best parameter based on all the examples. We prove bounds on the additional total loss of the on-line algorithm over the total loss of the best off-line parameter. These relative loss bounds hold for an arbitrary sequence of examples. The goal is to design algorithms with the best possible relative loss bounds. We use a Bregman divergence to derive and analyze each algorithm. These divergences are relative entropies between two exponential distributions. We also use our methods to prove relative loss bounds for linear regression. 相似文献
48.
改进的选择神经网络结构的方法 总被引:3,自引:1,他引:2
有关人工神经网络作为在线状态估计器组成基于神经网络的传感器故障检测的研究已有报导。但是这些文章中没有提到如何选择神经网络的结构。神经网络的输入延迟数和隐基单元数影响其对系统的拟合精度,从而影响故障检测的灵敏度。研究了一些现有的选择神经网络结构的方法,以系统化的交叉证实法为基础,经过改进,提出了针对作为在线状态估计器的神经网络选择输入延迟数和隐层单元数的系统化的方法,并用某船在试验场中航行时平台罗经输出的一段数据作了仿真,结果证明该法可行,具有工程实用意义。 相似文献
49.
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