排序方式: 共有15条查询结果,搜索用时 296 毫秒
1.
In the present article, we discuss the regression of a point on the surface of a unit sphere in d dimensions given a point on the surface of a unit sphere in p dimensions, where p may not be equal to d. Point projection is added to the rotation and linear transformation for regression link function. The identifiability of the model is proved. Then, parameter estimation in this set up is discussed. Simulation studies and data analyses are done to illustrate the model. 相似文献
2.
Matthias Neumann Christian Hirsch Jakub Stank Viktor Bene Volker Schmidt 《Scandinavian Journal of Statistics》2019,46(3):848-884
We investigate the problem of estimating geodesic tortuosity and constrictivity as two structural characteristics of stationary random closed sets. They are of central importance for the analysis of effective transport properties in porous or composite materials. Loosely speaking, geodesic tortuosity measures the windedness of paths, whereas the notion of constrictivity captures the appearance of bottlenecks resulting from narrow passages within a given materials phase. We first provide mathematically precise definitions of these quantities and introduce appropriate estimators. Then, we show strong consistency of these estimators for unboundedly growing sampling windows. In order to apply our estimators to real data sets, the extent of edge effects needs to be controlled. This is illustrated using a model for a multiphase material that is incorporated in solid oxide fuel cells. 相似文献
3.
宣满友 《绍兴文理学院学报》2003,(9)
得到deSitter空间s_1~(n+1)(c)中标准数量曲率为常数c的类空超曲面的一个定理:设M~n是de Sitter空间s_1~(n+1)(c)中标准数量曲率r与s_1~(n+1)(c)的截面曲率c相等的n维(n>2)紧致的类空超曲面,则M~n是全测地超曲面. 相似文献
4.
Markov chain Monte Carlo methods explicitly defined on the manifold of probability distributions have recently been established. These methods are constructed from diffusions across the manifold and the solution of the equations describing geodesic flows in the Hamilton–Jacobi representation. This paper takes the differential geometric basis of Markov chain Monte Carlo further by considering methods to simulate from probability distributions that themselves are defined on a manifold, with common examples being classes of distributions describing directional statistics. Proposal mechanisms are developed based on the geodesic flows over the manifolds of support for the distributions, and illustrative examples are provided for the hypersphere and Stiefel manifold of orthonormal matrices. 相似文献
5.
宣满友 《绍兴文理学院学报》2001,21(7):19-23
研究局部对称空间中具有平行平均曲率向量的紧致等距浸入子流形,推广了局部对称空间中极小子流形的一个分类结果. 相似文献
6.
宣满友 《绍兴文理学院学报》2006,26(1):1-5
文章讨论了Sasakian空间形式中标准平均曲率向量平行的C-全实伪脐子流形,得到了紧致的C-全实伪脐子流形的一个刚性结果. 相似文献
7.
设M是S~(n+1)的闭定向极小超曲面,众所周知,如果M的高斯映射的象取决于S~(n+1)的开半球,则M为全测地。当n=2时此定理已由文[2]准确地给出,本文讨论n≥2时的情形。 相似文献
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9.
Alfredo Alegría Emilio Porcu Reinhard Furrer 《Journal of Statistical Computation and Simulation》2018,88(10):1850-1862
ABSTRACTMatrix-valued covariance functions are crucial to geostatistical modelling of multivariate spatial data. The classical assumption of symmetry of a multivariate covariance function is overly restrictive and has been considered as unrealistic for most of the real data applications. Despite of that, the literature on asymmetric covariance functions has been very sparse. In particular, there is some work related to asymmetric covariances on Euclidean spaces, depending on the Euclidean distance. However, for data collected over large portions of planet Earth, the most natural spatial domain is a sphere, with the corresponding geodesic distance being the natural metric. In this work, we propose a strategy based on spatial rotations to generate asymmetric covariances for multivariate random fields on the d-dimensional unit sphere. We illustrate through simulations as well as real data analysis that our proposal allows to achieve improvements in the predictive performance in comparison to the symmetric counterpart. 相似文献
10.
Ludovic Seifert Romain Hérault Léo Wattebled Keith Davids 《Journal of applied statistics》2013,40(11):2317-2331
This study examined the temporal dynamics of the inter-limb angles of skilled and less skilled ice climbers to determine how they explored ice fall properties to adapt their coordination patterns during performance. We observed two circular time series corresponding to the upper- and lower-limbs of seven expert and eight inexperienced ice climbers. We analyzed these data through a multiple change-point analysis of the geodesic (or Fréchet) mean on the circle. Guided by the nature of the geodesic mean obtained by an optimization procedure, we extended the filtered derivative method, known to be computationally very cheap and fast, to circular data. Local estimation of the variability was assessed through the number of change-points computed via the filtered derivatives with p-value method for the time series and integrated squared error (ISE). Results of this change-point analysis did not reveal significant differences of the number of change-points between groups but indicated higher ISE that supported the existence of plateaux for beginners. These results emphasized higher local variability of limb angles for experts than for beginners suggesting greater dependence on the properties of the performance environment and adaptive behaviors in the former. Conversely, the lower local variance of limb angles assessed in beginners may reflect their independence of the environmental constraints, as they focused mainly on controlling body equilibrium. 相似文献