Time filter

Source Type


Asano T.,Japan Advanced Institute of Science and Technology | Buchin K.,TU Eindhoven | Buchin M.,TU Eindhoven | Korman M.,Polytechnic University of Catalonia | And 3 more authors.
Computational Geometry: Theory and Applications

A constant-work-space algorithm has read-only access to an input array and may use only O(1) additional words of O(logn) bits, where n is the input size. We show how to triangulate a plane straight-line graph with n vertices in O(n2) time and constant work-space. We also consider the problem of preprocessing a simple polygon P for shortest path queries, where P is given by the ordered sequence of its n vertices. For this, we relax the space constraint to allow s words of work-space. After quadratic preprocessing, the shortest path between any two points inside P can be found in O(n2/s) time. © 2013 Elsevier B.V. All rights reserved. Source

Ryu S.-J.,Korea Advanced Institute of Science and Technology | Kirchner M.,WWU Munster | Lee M.-J.,Information Technology Randnter | Lee H.-K.,Korea Advanced Institute of Science and Technology
IEEE Transactions on Information Forensics and Security

This paper proposes a forensic technique to localize duplicated image regions based on Zernike moments of small image blocks. We exploit rotation invariance properties to reliably unveil duplicated regions after arbitrary rotations. We devise a novel block matching procedure based on locality sensitive hashing and reduce false positives by examining the moments' phase. A massive experimental test setup benchmarks our algorithm against state-of-the-art methods under various perspectives, examining both pixel-level localization and image-level detection performance. By taking signal characteristics into account and distinguishing between 'textured' and 'smooth' duplicated regions, we find that the proposed method outperforms prior art in particular when duplicated regions are smooth. Experiments indicate high robustness against JPEG compression, blurring, additive white Gaussian noise, and moderate scaling. © 2005-2012 IEEE. Source

Gunther T.,Cooperative State University Baden Wuertemberg | Preuss M.,WWU Munster
2015 IEEE Conference on Computational Intelligence and Games, CIG 2015 - Proceedings

Procedural Content Generation (PCG) is nowadays widely applied to many different aspects of computer games. However, it can do more than to assist level designers during game creation. It can generate personalized levels according to the tastes and abilities of players online. This has already been demonstrated for (largely 1D) scrolling games and we show in this work how personalized, difficulty-Adjusted levels can be generated for the more complex 2D platformer Spelunky. As direct and indirect player feedback is taken into account, the method may be filed under the Experience-Driven PCG approach. Our approach is based on a rather generic rule set that may also be transferred to similar games. We also present a user study showing that most users appreciate the online adaptation but are especially critical about making the game easier to play at any time. © 2015 IEEE. Source

Abbas H.A.,Clausthal University of Technology | Abbas H.A.,National Research Center of Egypt | Argirusis C.,Clausthal University of Technology | Kilo M.,Clausthal University of Technology | And 4 more authors.
Solid State Ionics

Cubic scandia-stabilised zirconia (ScSZ) has a very high oxygen ion conductivity, significantly higher than the more common yttria-stabilised zirconia (YSZ). However, its practical use is hindered by an ordered rhomboedric phase being present at low temperature which is unique for zirconias. The occurrence of this phase can be suppressed by co-doping scandia-stabilised with ternary metal oxides. It is the aim of this study to investigate the influence of co-doping with various cations on the ionic conductivity, and on the phase transition towards lower temperatures. To do that, we prepared scandia-stabilised zirconia containing 10 mol% Sc2O3 and up to 1.0 mol% Gd2O3, CaO, or CeO2, respectively, using a sol-gel method starting with nitrates of the metals. Powders were sintered at 1500 °C to obtain dense material with grain sizes in the range of 0.5 to 1.0 μm. An addition of more than 0.5 mol% Gd 2O3 significantly decreased the transition temperature of the phase transition between cubic and rhombohedral. The low temperature AC conductivity, measured in the range of 400 to 950 °C, was highest for ScSZ containing 1 mol% CeO2. The Arrhenius plot was strongly curved, indicating association or ordering of oxygen vacancies, which were explained with literature models. © 2010 Elsevier B.V. All rights reserved. Source

Janots E.,WWU Munster | Janots E.,University of Bern | Berger A.,University of Bern | Berger A.,Copenhagen University | Engi M.,University of Bern

This study assesses the effects of fluid, whole-rock composition and oxygen fugacity, on the texture and composition of monazite, allanite, and xenotime. For this purpose, these were investigated in 13 mono-metamorphic metasediments from a single locality of the Central Alps (Switzerland), which record greenschist facies conditions (T~400-450 °C). Two of the samples contain hydrothermal veins dominated by quartz and calcite+quartz, respectively. In metasediments devoid of veins, the light rare earth elements (LREE) are concentrated in allanite in all samples except for one metamarl (Ga06). Allanite formation is texturally coeval with apatite, chloritoid and xenotime, during the main tectono-metamorphic stage. Allanite formation implies significant mass transfer of Ca and P via a fluid phase, which is not clearly related to advective transport. In Ga06, elongate monazite grains have a detrital core rimmed by newly formed monazite. Significant arsenic contents are found in newly formed monazite, xenotime and apatite. Monazite texture and composition suggest (re)crystallization by pressure solution, at an oxygen fugacity sufficient to partly oxidize As, S, U, and Fe. Whether or not monazite is preserved appears to be but weakly dependent on the Ca/Al ratio and thus whole-rock composition at greenschist facies conditions. Samples with veins show peculiar features. Along carbonate-bearing veins allanite occurs as porphyroblasts overgrowing the main foliation of the host rock. As similar allanite porphyroblasts occur in calcite-bearing metamarl, their formation is attributed to environments rich in CO2-bearing fluid. A new generation of monazite is found in and along retrograde quartz veins. This study demonstrates that, at least in metasediments up to chloritoid-grade, REE minerals record fluid/rock interaction that occurred at different deformation stages. Arsenic concentrations in REE phosphates appear to reflect conditions of elevated oxygen fugacity. In cases where such conditions are not inherited from the sedimentary protolith, the oxidation reflects a hydrothermal event, the age of which may be directly datable by U/Th-Pb of As-rich monazite. © 2010 Elsevier B.V. Source

Discover hidden collaborations