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作者： Hu, Bin Leitner, Markus Raidl, Günther R. Institute of Computer Graphics and Algorithms Vienna University of Technology Austria Department of Telematics and Network Engineering Carinthia University of Applied Sciences Austria

We consider the generalized minimum edge-biconnected network problem where the nodes of a graph are partitioned into clusters and exactly one node from each cluster is required to be connected in an edge-biconnected way. Instances of this problem appear, for example, in the design of survivable backbone networks. We present different variants of a variable neighborhood search approach that utilize different types of neighborhood structures, each of them addressing particular properties as spanned nodes and/or the edges between them. For themorecomplex neighborhood structures,weapply efficient techniques-such as a graph reduction-to essentially speedupthe search process. For comparison purposes, we use a mixed integer linear programming formulation based on multi-commodity flows to solve smaller instances of this problem to proven optimality. Experiments on such instances indicate that the variable neighborhood search is also able to identify optimal solutions in the majority of test runs, but within substantially less time. Tests on larger Euclidean and random instances with up to 1,280 nodes, which could not be solved to optimality by mixed integer programming, further document the efficiency of the variable neighborhood search. In particular, all proposed neighborhood structures are shown to contribute significantly to the search process. © 2009 Wiley Periodicals, Inc.

关键词： Integer programming

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2010 4th International Conference on Research Challenges in Information Science, RCIS 2010

作者： Obweger, Hannes Suntinger, Martin Schiefer, Josef Raidl, Gunther UC4 Senactive Software GmbH Vienna Austria Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria

ISBN: (纸本)9781424448401

In this paper we present a generic similarity model for time-stamped sequences of complex business events. It builds upon the idea of deriving similarity from deviations between the pattern sequence and its best-possible representation in the candidate sequence. Which representation is considered optimal solely depends on the analyst's current focus and interest;the model thus foresees highest configurability to adequately balance aspects such as single-event similarities, order, timing, and missing events. The model is furthermore applicable for both sub-sequence searching and full-sequence matching. As an extension to the base model, we discuss enhanced patternmodeling facilities, e.g., to ensure a maximal time interval between two or more candidate events. The proposed tree-search algorithm allows for a seamless integration of such extensions. © 2010 IEEE.

关键词： Data mining

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On the two-architecture connected facility location problem

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Electronic Notes in Discrete Mathematics 2013年 41卷 359-366页

作者： Leitner, Markus Ljubić, Ivana Sinnl, Markus Werner, Axel Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria Department of Statistics and Operations Research University of Vienna Vienna Austria Zuse Institute Berlin Berlin Germany

We introduce a new variant of the connected facility location problem that allows for modeling mixed deployment strategies (FTTC/FTTB/FTTH) in the design of local access telecommunication networks. Several mixed integer programming models and valid inequalities are presented. Computational studies on realistic instances from three towns in Germany are provided. © 2013 Elsevier B.V.

关键词： Branch-and-cut Connected facility location FTTx deployment

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Feature peeling 07

Feature peeling

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graphics Interface 2007

作者： Malik, Muhammad Muddassir Möller, Torsten Gröller, M. Eduard Institute of Computer Graphics and Algorithms Vienna University of Technology Austria Lab. Computing Science Department Simon Fraser University Canada

ISBN: (纸本)1568813376

We present a novel rendering algorithm that analyses the ray profiles along the line of sight. The profiles are subdivided according to encountered peaks and valleys at so called transition points. The sensitivity of these transition points is calibrated via two thresholds. The slope threshold is based on the magnitude of a peak following a valley, while the peeling threshold measures the depth of the transition point relative to the neighboring rays. This technique separates the dataset into a number of feature layers. The user can scroll through the layers inspecting various features from the current view position. While our technique has been inspired by opacity peeling approach, we demonstrate that we can reveal detectable features even in the third and forth layers for both CT and MRI datasets.

关键词： Feature extraction

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Obscurance-based volume rendering framework

Obscurance-based volume rendering framework

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Joint IEEE/EG 7th International Symposium on Volume graphics, VG 2008 and 5th Symposium on Point-Based graphics, PBG 2008

作者： Ruiz, M. Boada, I. Viola, I. Bruckner, S. Feixas, M. Sbert, M. Graphics and Imaging Laboratory University of Girona Spain Department of Informatics University of Bergen Norway Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

ISBN: (纸本)9783905674125

Obscurances, from which ambient occlusion is a particular case, is a technology that produces natural-looking lighting effects in a faster way than global illumination. Its application in volume visualization is of special interest since it permits us to generate a high quality rendering at a low cost. In this paper, we propose an obscurance-based framework that allows us to obtain realistic and illustrative volume visualizations in an interactive manner. Obscurances can include color bleeding effects without additional cost. Moreover, we obtain a saliency map from the gradient of obscurances and we show its application to enhance volume visualization and to select the most salient views. © The Eurographics Association 2008.

关键词： Volume rendering

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Structural alignment of two RNA sequences with lagrangian relaxation

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) 2004年 3341卷 113-123页

作者： Bauer, Markus Klau, Gunnar W. Institute of Computer Graphics and Algorithms Vienna University of Technology Austria

RNA is generally a single-stranded molecule where the bases form hydrogen bonds within the same molecule leading to structure formation. In comparing different homologous RNA molecules it is usually not sufficient to consider only the primary sequence, but it is important to consider both the sequence and the structure of the molecules. Traditional alignment algorithms can only account for the sequence of bases, but not for the base pairings. Considering the structure leads to significant computational problems because of the dependencies introduced by the base pairings and the presence of pseudoknots. In this paper we address the problem of optimally aligning two given RNA sequences either with or without known structure (allowing for pseudoknots). We phrase the problem as an integer linear program and then solve it using Lagrangian relaxation. In our computational experiments we could align large problem instances-18S and 23S ribosomal RNA with up to 1500 bases within minutes while preserving pseudoknots. © Springer-Verlag 2004.

关键词： RNA

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A Sky Dome Visualisation for Identification of Astronomical Orientations

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Information Visualization 2006年第2期5卷 152 - 166页

作者： Georg Zotti Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria

It has long been known that ancient temples were frequently oriented along the cardinal directions or to certain points along the horizon where the Sun or the Moon rises or sets on special days of the year. In the last decades, archaeologists have found evidence of even older building structures buried in the soil, with doorways that also appear to have distinct *** paper presents a novel diagram combining archaeological maps with a folded-apart, flattened view of the whole sky, showing the local horizon and the daily paths of the Sun, Moon and brighter stars. By use of this diagram, interesting groupings of astronomical orientation directions, for example, to certain sunrise and sunset points could be identified, which were evidently used to mark certain days of the year. Orientations towards rising and setting points of a few significant stars very likely indicated the beginning of the agricultural year in the middle neolithic period.

关键词： Archaeology astronomy data mining

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Interactive local tone mapping operator with the support of graphics hardware 07

Interactive local tone mapping operator with the support of ...

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23rd Spring Conference on computer graphics, SCCG 2007

作者： Roch, B. Artusi, A. Michael, D. Chrysanthou, Y. Chalmers, A. Institute of Computer Graphics and Algorithms Vienna University of Technology Vienna Austria Cyprus Warwick Digital Laboratory University of Warwick Warwick United Kingdom

ISBN: (纸本)9781605589565

The flexibility of current graphics hardware is still not enough to ensure the full implementation of an original complex algorithm such as a local tone mapping operator, which maintains the same quality performances as its original CPU implementation. Significant changes are often needed to the original CPU implementation in order to overcome many of the limitations of the current graphics hardware. As a result of this we often have reduced quality reproduction, and the frame rate of the GPU implementation is not always acceptable for real-time applications. In this paper, we show how to change the CPU implementation of a state of the art local tone mapping operator for accelerating the computation process to real time frame rates. We also present a modification of the luminance local adaptation computation, showing a simple but not yet exploited property of the Gaussian filter, allowing us to maintain the same quality appearance of the original tone mapping operator. Finally we test the hardware implementation on NVIDIA graphics cards on several images and as well as a video. We compare our hardware implementation with the corresponding CPU implementation and previous work. Copyright © 2007 by the Association for Computing Machinery, Inc.

关键词： Mapping

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Sonar Explorer: A New Tool for Visualization of Fish Schools from 3D Sonar Data

Sonar Explorer: A New Tool for Visualization of Fish Schools...

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9th Joint Eurographics/IEEE VGTC Symposium on Visualization, EuroVis 2007

作者： Balabanian, Jean-Paul Viola, Ivan Ona, Egil Patel, Ruben Gröller, Eduard Department of Informatics University of Bergen Norway Institute of Computer Graphics and Algorithms Vienna University of Technology Austria Institute of Marine Research Norway

ISBN: (纸本)9783905673456

We present a novel framework for analysis and visualization of fish schools in 3D sonar surveys. The 3D sonar technology is new and there have not been applications to visualize the data in 3D. We have created an application called Sonar Explorer that satisfies the requirements of domain scientists. Sonar Explorer provides easy and intuitive semi-automatic fish school tracking and survey map generation. The overall pipeline is described and all pipeline stages relevant for visualization are highlighted. We present techniques to deal with 3D sonar data specifics: highly anisotropic volume data aligned on a curvilinear grid. Domain scientists provide initial impressions on interaction and outlook. © The Eurographics Association 2007.

关键词： Sonar

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The fractional prize-collecting steiner tree problem on trees

The fractional prize-collecting steiner tree problem on tree...

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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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