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131.
A. Brezger L. Fahrmeir A. Hennerfeind 《Journal of the Royal Statistical Society. Series C, Applied statistics》2007,56(3):327-345
Summary. Functional magnetic resonance imaging has become a standard technology in human brain mapping. Analyses of the massive spatiotemporal functional magnetic resonance imaging data sets often focus on parametric or non-parametric modelling of the temporal component, whereas spatial smoothing is based on Gaussian kernels or random fields. A weakness of Gaussian spatial smoothing is underestimation of activation peaks or blurring of high curvature transitions between activated and non-activated regions of the brain. To improve spatial adaptivity, we introduce a class of inhomogeneous Markov random fields with stochastic interaction weights in a space-varying coefficient model. For given weights, the random field is conditionally Gaussian, but marginally it is non-Gaussian. Fully Bayesian inference, including estimation of weights and variance parameters, can be carried out through efficient Markov chain Monte Carlo simulation. Although motivated by the analysis of functional magnetic resonance imaging data, the methodological development is general and can also be used for spatial smoothing and regression analysis of areal data on irregular lattices. An application to stylized artificial data and to real functional magnetic resonance imaging data from a visual stimulation experiment demonstrates the performance of our approach in comparison with Gaussian and robustified non-Gaussian Markov random-field models. 相似文献
132.
张学元 《湖南文理学院学报(社会科学版)》1995,(6)
本文沿用文[1]的思想方法,以M矩阵为工具,研究变系数线性大系统零解的稳定性,得到一系列稳定性的显式代数判据,我们统称为M-判别法。 相似文献
133.
Kinship and Population Subdivision 总被引:1,自引:1,他引:0
The coefficient of kinship between two diploid organisms describes their overall genetic similarity to each other relative to some base population. For example, kinship between parent and offspring of 1/4 describes gene sharing in excess of random sharing in a random mating population. In a subdivided population the statistic F
st describes gene sharing within subdivisions in the same way. Since F
st among human populations on a world scale is reliably 10 to 15%, kinship between two individuals of the same human population is equivalent to kinship between grandparent and grandchild or between half siblings. The widespread assertion that this is small and insignificant should be reexamined. 相似文献
134.
A. Boyarsky 《Revue canadienne de statistique》1976,4(1):143-149
Let Wt be a one-dimensional Brownian motion on the probability space (Ω,F,P), and let dxt = a(xt)dt + b(xt)dwt, b2(x) > 0, be a one-dimensional Ito stochastic differential equation. For a(x) = a0 + a1x + … + anxn on a bounded interval we obtain a lower bound for p(t,x,y), the transition density function of the homogeneous Markov process xt, depending directly on the coefficients a0,a1, …, an, and b(x). 相似文献
135.
穿层钻孔周围煤体次生应力变形及瓦斯流动规律的研究 总被引:1,自引:0,他引:1
从煤层钻孔周围煤体发生的次生应力和变形出发,建立了受煤体次生应力、瓦斯压力等因素影响的煤体变透气性系数的新数学模型,并以此改进了钻孔周围瓦斯流动的本构方程。通过对白皎煤矿20102试验区穿层钻孔周围瓦斯流场的解算,证明该模型和本构方程与实际相符,同时对常、变透气性也做了对比。 相似文献
136.
George J. Borjas 《Journal of statistical planning and inference》1982,7(2):131-137
This paper considers a regression model in which coefficients obtained from a previous regression are themselves the object of analysis. It is shown that the parameters of interest can be obtained in two ways: pooling across observations and subsamples, or a two-stage process of first estimating the coefficients within each subsample, and then using these coefficients as dependent variables in a second stage regression. The relative properties of these estimators are analyzed, and the conditions under which the two estimators are equivalent are derived. 相似文献
137.
A.Haug 《上海理工大学学报(社会科学版)》1988,(3)
Partial condensation of refrigerant R-11 was experimentally and theoretically studied. The test apparatus consisted of two concentric tubes, with the vapor flowing downward in the inner tube and the cooling water in the annular space in countercurrent direction. By using the available dimensionless correlation, the mean heat transfer coefficient of the cooling water was determined, and then the mean condensationheat transfer coefficient was calculated from the overall heat transfer coefficient.The model of a homogeneous two-phase mixture of liquid and vapor, and Prandtl's principle of analogy between the momentum and heat transfer were used to establish the type of the correlation. Adopting the methods of the gradually linear regression and F-level evidence testing, the present paper proposed the dimensionless correlation to predict the relationship among the mean Nusselt number, Prandtl number, Kutateladze number and the dimensionless tube length. 相似文献
138.
武星亮 《山西农业大学学报(社会科学版)》2014,(1):5-11
日本山梨县城乡一体化的现状,从经济结构上看,表现在就业者的产业结构、国民收入及恩格尔系数和社会商品零售额等方面;从基础设施上看,体现在人均铺装道路面积、医疗机构以及上下水状况等公共设施的发展水平上;从人的现代化上看,反映在教育、文化、体育、休闲等方面。它给我们的启示是:城乡一体化是一个长期过程,是一项系统工程,是一种现代文明。 相似文献
139.
对信息资源测度"信息资源丰裕系数"的解析与优化探讨 总被引:2,自引:0,他引:2
徐世伟 《重庆工商大学学报(社会科学版)》2004,21(3):51-53
要衡量一个国家或地区信息资源的丰富程度,就要对信息资源进行量化,目前,学者们普遍采用信息资源丰裕系数模型进行测度.该模型从信息产品的生产能力与发展潜力角度分析信息资源的测试模型,具有一定的可操作性,但该模型存在较大的缺陷,需要对该模型进行优化,应考虑丰裕系数各分指标量纲不同的可比性问题,同时应考虑各分指标的权重. 相似文献
140.
Miroslav Šiman 《统计学通讯:理论与方法》2013,42(10):1733-1738
This brief article extends the theory of sample Kendall's autocorrelations by providing their exact variances at lags higher than one under the null hypothesis of randomness, by introducing and investigating their weighted modifications, and by numerical demonstration of these results and their usefulness. 相似文献