共查询到20条相似文献,搜索用时 15 毫秒
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Although post-equating (PE) has proven to be an acceptable method in the scaling and equating of items and forms, there are times when the turn-around period for equating and converting raw scores to scale scores is so small that PE cannot be undertaken within the prescribed time frame. In such cases, pre-equating (PrE) could be considered as an acceptable alternative. Assessing the feasibility of using item calibrations from the item bank (as in PrE) is conditioned on the equivalency of the calibrations and the errors associated with it vis a vis the results obtained via PE. This paper creates item banks over three periods of item introduction into the banks and uses the Rasch model in examining data with respect to the recovery of item parameters, the measurement error, and the effect cut-points have on examinee placement in both the PrE and PE situations. Results indicate that PrE is a viable solution to PE provided the stability of the item calibrations are enhanced by using large sample sizes (perhaps as large as full-population) in populating the item bank. 相似文献
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Annika Radermacher Stefanie Reese 《International journal for numerical methods in engineering》2016,107(6):477-495
The constantly rising demands on finite element simulations yield numerical models with increasing number of degrees‐of‐freedom. Due to nonlinearity, be it in the material model or of geometrical nature, the computational effort increases even further. For these reasons, it is today still not possible to run such complex simulations in real time parallel to, for example, an experiment or an application. Model reduction techniques such as the proper orthogonal decomposition method have been developed to reduce the computational effort while maintaining high accuracy. Nonetheless, this approach shows a limited reduction in computational time for nonlinear problems. Therefore, the aim of this paper is to overcome this limitation by using an additional empirical interpolation. The concept of the so‐called discrete empirical interpolation method is translated to problems of solid mechanics with soft nonlinear elasticity and large deformations. The key point of the presented method is a further reduction of the nonlinear term by an empirical interpolation based on a small number of interpolation indices. The method is implemented into the finite element method in two different ways, and it is extended by using different solution strategies including a numerical as well as a quasi‐Newton tangent. The new method is successfully applied to two numerical examples concerning hyperelastic as well as viscoelastic material behavior. Using the extended discrete empirical interpolation method combined with a quasi‐Newton tangent enables reductions in computational time of factor 10 with respect to the proper orthogonal decomposition method without empirical interpolation. Negligibly, orders of error can be reached. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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《International Journal of Engineering Science》1986,24(1):55-68
In this article a new mesh optimization technique for finite element methods is presented. The mesh modification strategy is based on a minimization of an interpolation error estimate and can be viewed as a generalization of existing conformai map-type mesh generators. The new mesh results in an essential improvement of finite element approximation which is illustrated in numerical examples. 相似文献
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Dual-reciprocity BEM based on global interpolation functions 总被引:2,自引:0,他引:2
Several global shape functions are introduced to interpolate the body-force term in the dual-reciprocity boundary-element method. These global-interpolation functions, which include polynomial, trigonometric, and hyperbolic series, can be used in place of the locally based radial shape function. For the several examples presented, the global functions have demonstrated superior convergence properties. 相似文献
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Scientometrics - Scholarly community detection has important applications in various fields. Current studies rely heavily on structured scholar networks, which have high computational complexity... 相似文献
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James C. Cavendish William J. Gordon Charles A. Hall 《International journal for numerical methods in engineering》1977,11(9):1405-1421
In this paper we describe a new class of locally refined macro finite elements which are especially amenable to the use of substructuring techniques for the efficient solution of the resulting idealization. The tools and guidelines illustrated by the examples of modelling crack tips, point load singularities and singularities at re-entrant corners should enable an analyst to construct other such blended macro elements specifically tailored to his particular class of problems. The use of such substructured macro elements in finite element calculations permits substantial reduction in the manual effort of data preparation and the computational cost of numerical solution. 相似文献
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局部均值分解(Local Mean Decomposition,LMD)方法是一种较新的自适应信号分析方法。LMD算法的核心思想是将原始信号分解为多个乘积函数(Production Function,PF),其中每个PF都是一个包络函数和一个纯调频函数的乘积。在LMD算法中需要提取信号的局部均值函数和包络估计,然而常规的提取方法会带来局部误差且分解速度慢。为了解决此问题,提出了利用三次B样条对信号上、下极值点进行插值得到上、下包络线,进而获取信号局部均值和包络估计的新方法。对仿真信号和机械振动信号的对比实验验证了该方法的优越性。 相似文献
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In two recent papers del Barrio et al. (1999) and del Barrio et al. (2000) consider a new class of goodness-of-fit statistics
based on theL
2-Wasserstein distance. They derive the limiting distribution of these statistics and show that the normal distribution is
the only location-scale family for which this limiting distribution has the “loss of degrees of freedom” property, due to
the estimation of the unknown parameters. In this paper a weightedL
2-Wasserstein distance is considered and it is proven that these statistics retain the loss of degrees of freedom property
for general classes of distributions if applied separately to the location family and to the scale family and if the “right”
weight function is used. These weight functions are such that the corresponding minimum distance estimators for the location
parameter and the scale parameter are asymptotically efficient. Examples are discussed for both location and scale families. 相似文献
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