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1.
Nowadays airborne laser scanning is used in many territorial studies, providing point data which may contain strong discontinuities. Motivated by the need to interpolate such data and preserve their edges, this paper considers robust nonparametric smoothers. These estimators, when implemented with bounded loss functions, have suitable jump‐preserving properties. Iterative algorithms are developed here, and are equivalent to nonlinear M‐smoothers, but have the advantage of resembling the linear Kernel regression. The selection of their coefficients is carried out by combining cross‐validation and robust‐tuning techniques. Two real case studies and a simulation experiment confirm the validity of the method; in particular, the performance in building recognition is excellent. 相似文献
2.
For testing the hypothesis that several (s?2) linear regression surfaces Xki=αk+βkcki+Zki (k=1,…,s) are parallel to one another, i.e., β1=?=βs, a class of rank-order tests are considered. The tests are shown to be asymptotically distribution-free, and their asymptotic efficiency relative to the general likelihood ratio test is derived. Asymptotic optimality in the sense of Wald is also discussed. 相似文献
3.
Examination and visualisation of the simplifying assumption for vine copulas in three dimensions 下载免费PDF全文
Matthias Killiches Daniel Kraus Claudia Czado 《Australian & New Zealand Journal of Statistics》2017,59(1):95-117
Vine copulas are a highly flexible class of dependence models, which are based on the decomposition of the density into bivariate building blocks. For applications one usually makes the simplifying assumption that copulas of conditional distributions are independent of the variables on which they are conditioned. However this assumption has been criticised for being too restrictive. We examine both simplified and non‐simplified vine copulas in three dimensions and investigate conceptual differences. We show and compare contour surfaces of three‐dimensional vine copula models, which prove to be much more informative than the contour lines of the bivariate marginals. Our investigation shows that non‐simplified vine copulas can exhibit arbitrarily irregular shapes, whereas simplified vine copulas appear to be smooth extrapolations of their bivariate margins to three dimensions. In addition to a variety of constructed examples, we also investigate a three‐dimensional subset of the well‐known uranium data set and visually detect the fact that a non‐simplified vine copula is necessary to capture its complex dependence structure. 相似文献
4.
Methods for Uncertainty Analysis: A Comparative Survey 总被引:1,自引:0,他引:1
This paper presents a survey and comparative evaluation of methods which have been developed for the determination of uncertainties in accident consequences and probabilities, for use in probabilistic risk assessment. The methods considered are: analytic techniques, Monte Carlo simulation, response surface approaches, differential sensitivity techniques, and evaluation of classical statistical confidence bounds. It is concluded that only the response surface and differential sensitivity approaches are sufficiently general and flexible for use as overall methods of uncertainty analysis in probabilistic risk assessment. The other methods considered, however, are very useful in particular problems. 相似文献
5.
基于场所理论的春熙路商业步行街设计分析 总被引:5,自引:0,他引:5
郑晓山 《西南交通大学学报(社会科学版)》2004,5(6):139-142
罗格·特兰西克的场所理论认为,构成场所实体形态的三个主要要素是空间形态、建筑立面以及 街道铺装和家具,这些要素如果都能在建筑中得到正确体现,将会营造出良好的场所精神。改造后的春熙路商业 步行街虽然取得了一定经济效益,但在营造独特的场所精神方面却是失败的。 相似文献
6.
Valley Creek watershed, located in southeastern Pennsylvania, is a small, fourth-order stream that empties into the Schuylkill
River at Valley Forge National Historic Park, thirty-five kilometers northwest of Philadelphia. The 64 km2 watershed has been under extreme urbanization pressure over the past 30 years, resulting in rapidly increasing impervious
surface cover and decreasing open space. The purpose of this study was to document some of the effects of urbanization on
fish assemblages by quantifying the fish communities at fifteen sites throughout the watershed. Long-term effects of continued
urbanization were identified, as data from the present study were compared to similar work completed nearly ten years earlier.
There has been a shift in species composition from intolerant, coldwater species to more tolerant, eurythermal species. Currently,
Valley Creek is supporting a naturally reproducing population of brown trout, but there has been a marked decline in relative
abundance and range since 1993. Increased stream temperature from urban run-off is one of the primary issues in Valley Creek.
Species composition was unique at each of the 15 stations owing to the effect of local land use in each station’;s drainage
area. Fish assemblages revealed a patchy, non-continuous pattern of fish distribution. 相似文献
7.
8.
3D object recognition: Representation and matching 总被引:1,自引:0,他引:1
Three-dimensional object recognition entails a number of fundamental problems in computer vision: representation of a 3D object, identification of the object from its image, estimation of its position and orientation, and registration of multiple views of the object for automatic model construction. This paper surveys three of those topics, namely representation, matching, and pose estimation. It also presents an overview of the free-form surface matching problem, and describes COSMOS, our framework for representing and recognizing free-form objects. The COSMOS system recognizes arbitrarily curved 3D rigid objects from a single view using dense surface data. We present both the theoretical aspects and the experimental results of a prototype recognition system based on COSMOS. 相似文献
9.
《Journal of Statistical Computation and Simulation》2012,82(2):177-182
Two different approaches to obtaining finite-sample corrections to score tests are the analytical and the computational approaches. The former is based either on a Bartletttype correction to the test statistic or on the inversion of an Edgeworth expansion to its null distribution. The latter, on the other hand, is usually based on a bootstrapping resampling scheme. This paper provides a numerical comparison of the size and power properties of these two approaches both under correct model specification and under model misspecification. 相似文献
10.
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