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Schwamberger V.,Max Planck Institute for Biological Cybernetics | Franz M.O.,Konstanz University of Applied Sciences
MM and Sec'10 - Proceedings of the 2010 ACM SIGMM Multimedia and Security Workshop | Year: 2010

Most current algorithms for blind steganalysis of images are based on a two-stages approach: First, features are extracted in order to reduce dimensionality and to highlight potential manipulations; second, a classifier trained on pairs of clean and stego images finds a decision rule for these features to detect stego images. Thereby, vector components might vary significantly in their values, hence normalization of the feature vectors is crucial. Furthermore, most classifiers contain free parameters, and an automatic model selection step has to be carried out for adapting these parameters. However, the commonly used cross-validation destroys some information needed by the classifier because of the arbitrary splitting of image pairs (stego and clean version) in the training set. In this paper, we propose simple modifications of normalization and for standard cross-validation. In our experiments, we show that these methods lead to a significant improvement of the standard blind steganalyzer of Lyu and Farid. © 2010 ACM.

Thimm T.,Konstanz University of Applied Sciences
Sustainable Development | Year: 2016

Sustainable tourism in Kerala is on the rise. Therefore, this South Indian state is assessed according to the sustainable tourism criteria of the Strasdas et al. (2007) framework. Kerala as a state does not qualify as a sustainable tourism destination, although individual success stories at the NGO and government level exist. This conceptual paper delivers a detailed analysis of the three dimensions of sustainability, i.e. ecology, economy and socio-cultural aspects, of the 'Kerala tourism model' and discusses the question of whether this model can be transferred to other developing countries. © 2016 John Wiley & Sons, Ltd and ERP Environment.

On February 22, 2011 the city of Christchurch in New Zealand was struck by an unexpectedly strong earthquake, causing 181 casualties and yet unknown socio-economic losses. More than 50 % of the buildings in the CBD were severely damaged, 25 to 30 % beyond repair. From March 25 to April 2 the author had the opportunity to join a reconnaissance team of the American Precast Concrete Institute (PCI) in order to inspect the damage that buildings and bridges suffered. Because the standard of earthquake resistant design is very high in New Zealand, and because the corresponding New Zealand design codes have been the basis for seismic design codes world wide since the early 1980's, it was particularly interesting to study the performance of modern buildings designed using capacity design principles. The paper describes the situation during the stay in Christchurch with respect to safety issues, the civil defence operations and the procedure followed by local authorities to evaluate the safety of damaged buildings. Also, the peculiarities of the February 22, 2011 earthquake and some of the significant examples of damage suffered by multi-storey buildings despite of modern design principles are discussed. Looking at two modern buildings that escaped the February 22 earthquake with almost no damage, a brief outlook is finally given on new earthquake resistant design concepts that will significantly reduce the expected economic losses. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Burkhart D.,University of Kaiserslautern | Hamann B.,University of California at Davis | Umlauf G.,Konstanz University of Applied Sciences
Computer Graphics Forum | Year: 2010

We present a volumetric iso-geometric finite element analysis based on Catmull-Clark solids. This concept allows one to use the same representation for the modeling, the physical simulation, and the visualization, which optimizes the design process and narrows the gap between CAD and CAE. In our method the boundary of the solid model is a Catmull-Clark surface with optional corners and creases to support the modeling phase. The crucial point in the simulation phase is the need to perform efficient integration for the elements. We propose a method similar to the standard subdivision surface evaluation technique, such that numerical quadrature can be used. Experiments show that our approach converges faster than methods based on tri-linear and tri-quadratic elements. However, the topological structure of Catmull-Clark elements is as simple as the structure of linear elements. Furthermore, the Catmull-Clark elements we use are C2-continuous on the boundary and in the interior except for irregular vertices and edges. Journal compilation © 2010 The Eurographics Association and Blackwell Publishing Ltd.

Karl Bernhard is one of the significant German civil engineers of the beginning of the 20th century. His two bridges along the Heerstrasse in Berlin, the Stössensee Bridge and the Frey Bridge which are crossing the Havel River, have been since 1909 of paramount importance for the East-West traffic connection of the city. The Frey Bridge was demolished in March 2015 in order to make room for a new substitution bridge. How was it possible at all that from a historical and traffic-technical point of view such an important construction has been neglected so long that it became ripe for demolition? And although it was under preservation since 1971? This article is a homage to Bernhard's Havel Bridge and follows up its rich history. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

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