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11th Annual European Symposium on algorithms, ESA 2003

作者： Klau, Gunnar W. Ljubić, Ivana Mutzel, Petra Pferschy, Ulrich Weiskircher, René Institute of Computer Graphics and Algorithms Vienna University of Technology Austria Department of Statistics and Operations Research University of Graz Austria

ISBN: (纸本)3540200649

We consider the fractional prize-collecting Steiner tree problem on trees. This problem asks for a subtree T containing the root of a given tree G = (V,E) maximizing the ratio of the vertex profits (Formula Presented) and the edge costs (Formula Presented) plus a fixed cost c0 and arises in energy supply management. We experimentally compare three algorithms based on parametric search: The binary search method, Newton’s method, and a new algorithm based on Megiddo’s parametric searchmethod. We show improved bounds on the running time for the latter two algorithms. The best theoretical worst case running time, namely O(|V | log |V |), is achieved by our new algorithm. A surprising result of our experiments is the fact that the simple Newton method is the clear winner of the tested algorithms. © Springer-Verlag Berlin Heidelberg 2003.

关键词： Newton-Raphson method

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Hierarchical difference scatterplots interactive visual analysis of data cubes

Hierarchical difference scatterplots interactive visual anal...

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ACM SIGKDD Workshop on Visual Analytics and Knowledge Discovery, VAKD '09

作者： Piringer, Harald Buchetics, Matthias Hauser, Helwig Gröller, Eduard VRVis Research Center Vienna Austria Department of Informatics University of Bergen Norway Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

ISBN: (纸本)9781605586700

Data cubes as employed by On-Line Analytical Processing (OLAP) play a key role in many application domains. The analysis typically involves to compare categories of different hierarchy levels with respect to size and pivoted values. Most existing visualization methods for pivoted values, however, are limited to single hierarchy levels The main contribution of this paper is an approach called Hierarchical Difference Scatterplot (HDS). A HDS allows for relating multiple hierarchy levels and explicitly visualizes differences between them in the context of the absolute position of pivoted values. We discuss concepts of tightly coupling HDS to other types of tree visualizations and propose the integration in a setup of multiple views, which are linked by interactive queries on the data. We evaluate our approaches by analyzing social survey data in collaboration with a domain expert. © 2009 ACM.

关键词： Visualization

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Architectural style classification of building facade windows

Architectural style classification of building facade window...

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7th International Symposium on Visual Computing, ISVC 2011

作者： Shalunts, Gayane Haxhimusa, Yll Sablatnig, Robert Institute of Computer Aided Automation Computer Vision Lab. Vienna University of Technology Austria Institute of Computer Graphics and Algorithms Pattern Recongition and Image Processing Lab. Vienna University of Technology Austria

Building facade classification by architectural styles allows categorization of large databases of building images into semantic categories belonging to certain historic periods, regions and cultural influences. Image databases sorted by architectural styles permit effective and fast image search for the purposes of content-based image retrieval, 3D reconstruction, 3D city-modeling, virtual tourism and indexing of cultural heritage buildings. Building facade classification is viewed as a task of classifying separate architectural structural elements, like windows, domes, towers, columns, etc, as every architectural style applies certain rules and characteristic forms for the design and construction of the structural parts mentioned. In the context of building facade architectural style classification the current paper objective is to classify the architectural style of facade windows. Typical windows belonging to Romanesque, Gothic and Renaissance/Baroque European main architectural periods are classified. The approach is based on clustering and learning of local features, applying intelligence that architects use to classify windows of the mentioned architectural styles in the training stage. © 2011 Springer-Verlag.

关键词： Semantics

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Classification of gothic and baroque architectural elements

Classification of gothic and baroque architectural elements

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2012 19th International Conference on Systems, Signals and Image Processing, IWSSIP 2012

作者： Shalunts, Gayane Haxhimusa, Yll Sablatnig, Robert Institute of Computer Aided Automation Computer Vision Lab. Vienna University of Technology Austria Institute of Computer Graphics and Algorithms Pattern Recognition and Image Processing Lab. Vienna University of Technology Austria

ISBN: (纸本)9783200023284

Architectural elements are the components and details of buildings. Their unique set, combination, design, construction technique form the architectural style of buildings. Building facade classification by architectural styles is viewed as a task of classifying separate architectural structural elements. In the scope of building facade architectural style classification the current paper targets the problem of classification of Gothic and Baroque architectural elements called tracery, pediment and balustrade. Since certain gradient directions dominate on the shape of each architectural element, discrimination between dominating gradients means classification of architectural elements and thus architectural styles. We use local features to describe gradient directions. Our approach is based on clustering and learning of local features and yields a high classification rate. © 2012 institute of Telecommunica.

关键词： Classification (of information)

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High-quality volume rendering with resampling in the frequency domain

High-quality volume rendering with resampling in the frequen...

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7th Joint Eurographics - IEEE VGTC Symposium on Visualization, VisSym 2005

作者： Artner, Martin Möller, Torsten Viola, Ivan Gröller, Meister E. Institute of Computer Graphics and Algorithms Vienna University of Technology Austria School of Computing Science Simon Fraser University Vancouver Canada

ISBN: (纸本)3905673193

This work introduces a volume rendering technique that is conceptually based on the shear-warp factorization. We propose to perform the shear transformation in the frequency domain. Unlike the standard shear-warp algorithm, we allow for arbitrary sampling distances along the viewing rays, independent from the view direction. The accurate scaling of the volume slices is achieved by using the zero padding interpolation property. Finally, a high quality gradient estimation scheme is presented which uses the derivative theorem of the Fourier transform. Experimental results show that the presented method outperforms established algorithms in the quality of the produced images. If the data is sampled above the Nyquist rate the presented method is capable of a perfect reconstruction of the original function. © The Eurographics Association 2005.

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Sampling step importance in hierarchical semantic segmentation of microscopic images

Sampling step importance in hierarchical semantic segmentati...

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15th International Conference on System Theory, Control and Computing, ICSTCC 2011

作者： Smochina, Cristian Manta, Vasile Kropatsch, Walter Department of Computer Science and Engineering Gheorghe Asachi Technical University of Iasi Romania Pattern Recognition and Image Processing Group Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

ISBN: (纸本)9781457711732

The objective of semantic segmentation in microscopic images is to extract the cellular, nuclear or tissue components. This problem is challenging due to the large variations of these components features (size, shape, orientation or texture). In this paper we improve the technique presented in [17] used to identify the epithelial nuclei (crypt) against interstitial nuclei in microscopic images taken from colon tissues. In the proposed enhanced approach, the crypt inner boundary is detected using the closing morphological pyramid instead of morphological hierarchy. The outer crypt border is determined by the epithelial nuclei, overlapped by the maximal isoline of the inner boundary. The use of sampling in building the pyramid offers computational efficiency, reduces the amount of used memory, increase the robustness and preserve the quality results. An analysis of the two approaches is performed considering the number of pixels processed to create each level. Also the relation between the levels of the hierarchical structures is established. © 2011 Faculty of Auto Control.

关键词： Computational efficiency

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Efficient real-time shadows 13

Efficient real-time shadows

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ACM Special Interest Group on computer graphics and Interactive Techniques Conference, SIGGRAPH 2013

作者： Eisemann, Elmar Assarsson, Ulf Schwarz, Michael Valient, Michal Wimmer, Michael Delft University of Technology Netherlands Department of Computer Science and Engineering Chalmers University Sweden Guerrilla Games / Sony Computer Entertainment Netherlands Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

ISBN: (纸本)9781450323390

This course provides an overview of efficient, real-time shadow algorithms. It presents the theoretical background but also discusses implementation details for facilitating efficient realizations (hard and soft shadows, volumetric shadows, reconstruction techniques). These elements are of relevance to both experts and practitioners. The course also reviews budget considerations and analyzes performance trade-offs, using examples from various AAA game titles and film previsualization tools. While physical accuracy can sometimes be replaced by plausible shadows, especially for games, film production requires more pecision, such as scalable solutions that can deal with highly detailed *** course builds upon earlier SIGGRAPH courses as well as the recent book Real-Time Shadows (A K Peters, 2011) by four of the instructors (due to its success, a second edition is planned for 2014). And with two instructors who have worked on AAA game and movie titles, the course presents interesting behindthe-scenes information that illuminates key topics.

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A memetic algorithm for multi layer hierarchical ring network design

Lecture Notes in Computer Science (including subseries Lectu...

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Lecture Notes in computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) 2014年 8672卷 832-841页

作者： Schauer, Christian Raidl, GüNther R. Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria

We address the Multi Layer Hierarchical Ring Network Design Problem. This problem arises in the design of large telecommunication backbones, when high reliability is emphasized. The aim is to connect nodes that are assigned to different layers using a hierarchy of rings of bounded length. We present a memetic algorithm that focuses on clustering the nodes of each layer into disjoint subsets. A decoding procedure is then applied to each genotype for determining a ring connecting all nodes of each cluster. For local improvement we incorporate a previous variable neighborhood search. We experimentally evaluate our memetic algorithm on various graphs and show that it outperforms the sole variable neighborhood search approach in 13 out of 30 instances, while in eight instances they perform on par. © Springer International Publishing Switzerland 2014.

关键词： Network layers

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Variable Neighborhood Search for a prize collecting capacity constrained connected facility location problem

Variable Neighborhood Search for a prize collecting capacity...

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2008 International Symposium on Applications and the Internet, SAINT 2008

作者： Leitnef, Markus Raidl, Günther R. Carinthia University of Applied Sciences School of Telematics Network Engineering Klagenfurt Austria Vienna University of Technology Institute of Computer Graphics and Algorithms Vienna Austria

ISBN: (纸本)9780769532974

We present a Variable Neighborhood Search approach for a network design problem occurring in real world when the bandwidth of an existing network shall be enhanced. Using two different neighborhood structures we show that a carefully designed combination of a metaheuristic and an exact method based on integer linear programming is able to improve solution quality compared to using heuristic methods only. © 2008 IEEE.

关键词： Heuristic methods

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Exact crossing minimization

Exact crossing minimization

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13th International Symposium on Graph Drawing, GD 2005

作者： Buchheim, Christoph Ebner, Dietmar Jünger, Michael Klau, Gunnar W. Mutzel, Petra Weiskircher, René Department of Computer Science University of Cologne Institute of Computer Graphics and Algorithms Vienna University of Technology Department of Mathematics and Computer Science FU Berlin Department of Computer Science University of Dortmund CSIRO Mathematical and Information Sciences

ISBN: (纸本)3540314253

The crossing number of a graph is the minimum number of edge crossings in any drawing of the graph into the plane. This very basic property has been studied extensively in the literature from a theoretic point of view and many bounds exist for a variety of graph classes. In this paper, we present the first algorithm able to compute the crossing number of general sparse graphs of moderate size and present computational results on a popular benchmark set of graphs. The approach uses a new integer linear programming formulation of the problem combined with strong heuristics and problem reduction techniques. This enables us to compute the crossing number for 91 percent of all graphs on up to 40 nodes in the benchmark set within a time limit of five minutes per graph. © Springer-Verlag Berlin Heidelberg 2005.

关键词： Graph theory

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