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A shift algorithm for exact computation in sequential tests with binary outcome

BIOMETRICAL JOURNAL 2000年第2期42卷 189-196页

作者： Högel, J Univ Ulm Dept Biometry & Med Documentat D-89069 Ulm Germany

A simple shift algorithm is described enabling the exact determination of power functions and sample size distributions for a large variety of closed sequential two-sample designs with a binary outcome variable. The test statistics are assumed to be based on relative frequencies of successes or failures, but the number of interim analyses, the monitoring times, and the continuation regions may be specified as desired. To give examples, exact properties of designs proposed by the program package EaSt (CYTEL. 1992) are determined, and plans with interim analyses are considered where decisions are based on the conditional power given the observations obtained so far.

关键词： binary outcome variable exact computation group sequential plans sequential tests shift algorithm two-sample comparison

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The permutation distribution of the Friedman test

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COMPUTATIONAL STATISTICS & DATA ANALYSIS 1997年第1期26卷 83-99页

作者： Rohmel, J FED INST DRUG & MED PROD D-13353 BERLINGERMANY

In this article an algorithm is presented to compute the exact permutation distribution of the nonparametric Friedman test for the two-way layout with possible stochastic dependencies within rows. Apart from regular convolution methods this algorithm uses the rich algebraic structure of the full permutation group. This leads to a substantial reduction of the computational workload. The algorithm makes use of some mathematical operators on k-dimentional arrays which all are available in the computer language APL (take, transpose and ravel). However, these operators are explained in detail in this article to facilitate understanding without knowledge of APL. APL programs are provided. (C) 1997 Elsevier Science B.V.

关键词： Friedman test two-way layout permutation group symmetric group APL shift algorithm

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On the exact distribution of maximally selected rank statistics

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COMPUTATIONAL STATISTICS & DATA ANALYSIS 2003年第2期43卷 121-137页

作者： Hothorn, T Lausen, B Univ Erlangen Nurnberg Ins Medizininformat Biometr & Epidemiol D-91054 Erlangen Germany

The construction of simple classification rules is a frequent problem in medical research. Maximally selected rank statistics allow the evaluation of cutpoints, which provide the classification of observations into two groups by a continuous or ordinal predictor variable. The computation of the exact distribution of a maximally selected rank statistic is discussed and a new lower bound of the distribution is derived based on an extension of an algorithm for the exact distribution of a linear rank statistic. Therefore, the test based on the upper bound of the P-value is of level alpha. For small to moderate sample sizes the lower bound of the exact distribution is a substantial improvement compared to approximations based on an improved Bonferroni inequality or based on the asymptotic Gaussian process. The lower bound of the distribution is compared to the exact distribution by means of a simulation study and the proposal is illustrated by three clinical studies. (C) 2003 Elsevier Science B.V. All rights reserved.

关键词： cutpoint selection small sample exact distribution of rank statistics censoring classification shift algorithm

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An exact paired rank test

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BIOMETRICAL JOURNAL 2002年第5期44卷 584-593页

作者： Munzel, U Brunner, E Merz & Co GMBH & Co Dept Med Biometr & Data Management D-60318 Frankfurt Germany Univ Gottingen Dept Med Stat D-3400 Gottingen Germany

An exact rank test for two dependent samples based on overall mid-ranks is discussed which can be applied to metric as well as to ordinal data. The exact conditional distribution of the test statistic given the observed vector of rank differences is determined. A recursion formula is given as well as a fast shift algorithm in SAS/IML code. Moreover, it is demonstrated that the paired rank test can be more powerful than other tests for paired samples by means of a simulation study. Finally, the test is applied to a psychiatric trial with longitudinal ordinal data.

关键词： ordinal data ordered categorical data ties sign test Wilcoxon signed rank test shift algorithm

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AN ADAPTIVE INTEGRATION MODEL OF VECTOR POLYLINE TO DEM DATA BASED ON SPHERICAL DEGENERATE QUADTREE GRIDS

AN ADAPTIVE INTEGRATION MODEL OF VECTOR POLYLINE TO DEM DATA...

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International-Society-for-Photogrammetry-and-Remote-Sensing 3rd International Workshop on Web Mapping and Geoprocessing Services and Applications (WebMGS) / 8th International Workshop on Dynamic Multidimensional GIS (DMGIS)

作者： Zhao, Xuesheng Wang, Jiaojiao Yuan, Zhengyi Gao, Yuan China Univ Min & Technol Beijing Geosci & Surveying Engn Coll Beijing Peoples R China

ISBN: (纸本)9781629935201

Traditional geometry-based approach can maintain the characteristics of vector data. However, complex interpolation calculations limit its applications in high resolution and multi-source spatial data integration at spherical scale in digital earth systems. To overcome this deficiency, an adaptive integration model of vector polyline and spherical DEM is presented. Firstly, Degenerate Quadtree Grid (DQG) which is one of the partition models for global discrete grids, is selected as a basic framework for the adaptive integration model. Secondly, a novel shift algorithm is put forward based on DQG proximity search. The main idea of shift algorithm is that the vector node in a DQG cell moves to the cell corner-point when the displayed area of the cell is smaller or equal to a pixel of screen in order to find a new vector polyline approximate to the original one, which avoids lots of interpolation calculations and achieves seamless integration. Detailed operation steps are elaborated and the complexity of algorithm is analyzed. Thirdly, a prototype system has been developed by using VC++ language and OpenGL 3D API. ASTER GDEM data and DCW roads data sets of Jiangxi province in China are selected to evaluate the performance. The result shows that time consumption of shift algorithm decreased about 76% than that of geometry-based approach. Analysis on the mean shift error from different dimensions has been implemented. In the end, the conclusions and future works in the integration of vector data and DEM based on discrete global grids are also given.

关键词： Adaptive integration DQG DEM Vector polyline shift algorithm

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Capturing and Stitching Images with a Large Viewing Angle and Low Distortion Properties for Upper Gastrointestinal Endoscopy

Capturing and Stitching Images with a Large Viewing Angle an...

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2nd Conference of the Optics-and-Photonics-Society-of-Singapore / International Conference on Optics in Precision Engineering and Nanotechnology (icOPEN)

作者： Liu, Ya-Cheng Chung, Chien-Kai Lai, Jyun-Yi Chang, Han-Chao Hsu, Feng-Yi Natl Appl Res Labs Instrument Technol Res Ctr 20 R&D Rd 6 Hsiuchu 30076 Taiwan Taiwan Surg Corp Hsinchu Taiwan

ISBN: (纸本)9780819495679

Upper gastrointestinal endoscopies are primarily performed to observe the pathologies of the esophagus, stomach, and duodenum. However, when an endoscope is pushed into the esophagus or stomach by the physician, the organs behave similar to a balloon being gradually inflated. Consequently, their shapes and depth-of-field of images change continually, preventing thorough examination of the inflammation or anabrosis position, which delays the curing period. In this study, a 2.9-mm image-capturing module and a convoluted mechanism was incorporated into the tube like a standard 10-mm upper gastrointestinal endoscope. The scale-invariant feature transform (SIFT) algorithm was adopted to implement disease feature extraction on a koala doll. Following feature extraction, the smoothly varying affine stitching (SVAS) method was employed to resolve stitching distortion problems. Subsequently, the real-time splice software developed in this study was embedded in an upper gastrointestinal endoscope to obtain a panoramic view of stomach inflammation in the captured images. The results showed that the 2.9-mm image-capturing module can provide approximately 50 verified images in one spin cycle, a viewing angle of 120 degrees can be attained, and less than 10% distortion can be achieved in each image. Therefore, these methods can solve the problems encountered when using a standard 10-mm upper gastrointestinal endoscope with a single camera, such as image distortion, and partial inflammation displays. The results also showed that the SIFT algorithm provides the highest correct matching rate, and the SVAS method can be employed to resolve the parallax problems caused by stitching together images of different flat surfaces.

关键词： Upper gastrointestinal endoscopy convoluted image-capturing module shift algorithm SVAS method

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Parallel QR algorithm for the C-method: application to the diffraction by gratings and rough surfaces 15

Parallel QR algorithm for the C-method: application to the d...

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Simulation Multiconference

作者： Cihui Pan Nahid Emad Richard Dusseaux Laboratoire PRiSM Universite de Versailles Saint-Quentin en Yvelines laboratoire PRiSM Universite de Versailles Saint-Quentin en Yvelines laboratoire LATMOS

ISBN: (纸本)9781510801011

The curvilinear coordinate method (C-method) is an exact method for analysing of electromagnetic waves scattering from rough surfaces. It is based on Maxwell's equations under covariant form written in a non-orthogonal coordinate system. This method leads to an eigenvalue system. All the eigenvalues and eigenvectors of the scattering matrix are required. The QR algorithm seems to be a suitable solution for this high dimension, dense, non-symmetric and complex scattering matrix. In this paper, we present the parallel QR algorithm that is specifically designed for the C-method. We define the "early shift" for the scattering matrix according to the property that we have observed. We mixed the "early shift", Wilkinson's shift and exceptional shift together to accelerate the convergence. Especially, we use the "early shift" first in order to have quick deflation of the real eigenvalues of the scattering matrix. The multi-window bulge chain chasing and parallel aggressive early deflation are used. The multi-window bulge chain chasing approach ensures that most computations are performed in 3 BLAS operations. The aggressive early deflation approach can detect deflation much quicker and thus accelerate convergence. Mixed MPI-OpenMP techniques are utilized for performing the codes to distributed memory platforms. Numerical experiments are performed and applications of this parallel QR algorithm are applied to a real physical problem of diffraction.

关键词： Electromagnetism Parallel QR shift algorithm Multishift Aggressive early deflation S-matrix theory QR algorithms Electromagnetic fields Electromagnetism Rough surfaces quick release deflation deflation diffraction Gratings Parallel Lines

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