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ADAPTIVITY IN SPACE AND TIME FOR MAGNETOQUASISTATICS

Journal of Computational Mathematics 2009年第5期27卷 642-656页

作者： Markus Clemens Jens Lang Delia Teleaga georg wimmer Helmut-Schmidt-Universitat Hamburg Holstenhofweg 8522043 HamburgGermany Technische Universitat Darmstadt Schlossgartenstraβe 764289 DarmstadtGermany

This paper addresses fully space-time adaptive magnetic field computations. We describe an adaptive Whitney finite element method for solving the magnetoquasistatic formulation of Maxwell＇s equations on unstructured 3D tetrahedral grids. Spatial mesh re- finement and coarsening are based on hierarchical error estimators especially designed for combining tetrahedral H（curl）-conforming edge elements in space with linearly implicit Rosenbrock methods in time. An embedding technique is applied to get efficiency in time through variable time steps. Finally, we present numerical results for the magnetic recording write head benchmark problem proposed by the Storage Research Consortium in Japan.

关键词： Magnetoquasistatics Space-time adaptivity Edge elements Rosenbrock meth-ods Hierarchical error estimator SRC benchmark problem.

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Quest for the best endoscopic imaging modality for computer-assisted colonic polyp staging

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World Journal of Gastroenterology 2019年第10期25卷 1197-1209页

作者： georg wimmer Michael Gadermayr Gernot Wolkersdorfer Roland Kwitt Toru Tamaki Jens Tischendorf Michael Hafner Shigeto Yoshida Shinji Tanaka Dorit Merhof Andreas Uhl Department of Computer Sciences University of Salzburg Interdisciplinary Imaging and Vision Institute Aachen RWTH Aachen Department of Internal Medicine I Paracelsus Medical University/Salzburger Landeskliniken(SALK) Department of Information Engineering Graduate School of EngineeringHiroshima University Internal Medicine and Gastroenterology University Hospital Aachen Department of Gastroenterologie and Hepatologie Krankenhaus St.Elisabeth Department of Endoscopy and Medicine Graduate School of Biomedical and Health ScienceHiroshima University Department of Endoscopy Hiroshima University Hospital

BACKGROUND It was shown in previous studies that high definition endoscopy, high magnification endoscopy and image enhancement technologies, such as chromoendoscopy and digital chromoendoscopy [narrow-band imaging(NBI), iScan] facilitate the detection and classification of colonic polyps during endoscopic sessions. However, there are no comprehensive studies so far that analyze which endoscopic imaging modalities facilitate the automated classification of colonic polyps. In this work, we investigate the impact of endoscopic imaging modalities on the results of computer-assisted diagnosis systems for colonic polyp *** To assess which endoscopic imaging modalities are best suited for the computerassisted staging of colonic *** In our experiments, we apply twelve state-of-the-art feature extraction methods for the classification of colonic polyps to five endoscopic image databases of colonic lesions. For this purpose, we employ a specifically designed experimental setup to avoid biases in the outcomes caused by differing numbers of images per image database. The image databases were obtained using different imaging modalities. Two databases were obtained by high-definition endoscopy in combination with i-Scan technology(one with chromoendoscopy and one without chromoendoscopy). Three databases were obtained by highmagnification endoscopy(two databases using narrow band imaging and one using chromoendoscopy). The lesions are categorized into non-neoplastic and neoplastic according to the histological *** Generally, it is feature-dependent which imaging modalities achieve high results and which do not. For the high-definition image databases, we achieved overall classification rates of up to 79.2% with chromoendoscopy and 88.9% without chromoendoscopy. In the case of the database obtained by high-magnification chromoendoscopy, the classification rates were up to 81.4%. For the combination of high-magnification endoscopy with NBI, results

关键词： Endoscopy Colonic polyps Automated diagnosis system Narrow-band imaging Chromoendoscopy Imaging modalities Image enhancement technologies

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