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Search Results: 1 - 10 of 927 matches for " Hartmut Prautzsch "
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Analyzing Midpoint Subdivision
Hartmut Prautzsch,Qi Chen
Computer Science , 2009,
Abstract: Midpoint subdivision generalizes the Lane-Riesenfeld algorithm for uniform tensor product splines and can also be applied to non regular meshes. For example, midpoint subdivision of degree 2 is a specific Doo-Sabin algorithm and midpoint subdivision of degree 3 is a specific Catmull-Clark algorithm. In 2001, Zorin and Schroeder were able to prove C1-continuity for midpoint subdivision surfaces analytically up to degree 9. Here, we develop general analysis tools to show that the limiting surfaces under midpoint subdivision of any degree >= 2 are C1-continuous at their extraordinary points.
General Midpoint Subdivision
Qi Chen,Hartmut Prautzsch
Computer Science , 2012,
Abstract: In this paper, we introduce two generalizations of midpoint subdivision and analyze the smoothness of the resulting subdivision surfaces at regular and extraordinary points. The smoothing operators used in midpoint and mid-edge subdivision connect the midpoints of adjacent faces or of adjacent edges, respectively. An arbitrary combination of these two operators and the refinement operator that splits each face with m vertices into m quadrilateral subfaces forms a general midpoint subdivision operator. We analyze the smoothness of the resulting subdivision surfaces by estimating the norm of a special second order difference scheme and by using established methods for analyzing midpoint subdivision. The surfaces are smooth at their regular points and they are also smooth at extraordinary points for a certain subclass of general midpoint subdivision schemes. Generalizing the smoothing rules of non general midpoint subdivision schemes around extraordinary and regular vertices or faces results in a class of subdivision schemes, which includes the Catmull-Clark algorithm with restricted parameters. We call these subdivision schemes generalized Catmull-Clark schemes and we analyze their smoothness properties.
Self-repairing material systems―a dream or a reality?  [PDF]
Hartmut Fischer
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.28110
Abstract: Currently, most industrial materials rely entirely on passive protection mechanisms; such me chanisms are readily applicable and universal for many different materials systems. However, they will always stay passive, and therefore their lifetime and functionality is limited and related to the amount of protective additives and the intensity of their consumption. Therefore, better, and preferentially active process for the protection/repair of damaged materials―selfrepairing processes―were developed and need to be developed further. Although it sounds futuristic or like a fiction in the modern, trendy times, which in many ways affects also directions of research; self healing of material systems exists already for a long time in all sorts of systems of materials or functionalities. The aim of this work is to go beyond the scope of a classical review the ones published recently in this field which almost entirely focused only onto polymeric systems. In this work, an analysis of the underlying functional and constructional principles of existing natural and synthetically selfhealing systems spanning over a range of classes of materials is given leading to general rules and principles for the design of new and application tailored selfhealing material systems.
Designing and Verifying Communication Protocols Using Model Driven Architecture and Spin Model Checker  [PDF]
Prabhu Kaliappan, Hartmut Koenig
Journal of Software Engineering and Applications (JSEA) , 2008, DOI: 10.4236/jsea.2008.11003
Abstract: The need of communication protocols in today’s environment increases as much as the network explores. Many new kinds of protocols, e.g. for information sharing, security, etc., are being developed day-to-day which often leads to rapid, premature developments. Many protocols have not scaled to satisfy important properties like deadlock and livelock freedom, since MDA focuses on the rapid development rather than on the quality of the developed models. In order to fix the above, we introduce a 2-Phase strategy based on the UML state machine and sequence diagram. The state machine is converted into PROMELA code as a protocol model and its properties are derived from the sequence diagram as Linear Temporal Logic (LTL) through automation. The PROMELA code is interpreted through the SPIN model checker, which helps to simulate the behavior of protocol. Later the automated LTL properties are supplemented to the SPIN for the verification of protocol properties. The results are compared with the developed UML model and SPIN simulated model. Our test results impress the designer to verify the expected results with the system design and to identify the errors which are unnoticed during the design phase.
A Methodology to Assess the Safety of Aircraft Operations When Aerodrome Obstacle Standards Cannot Be Met  [PDF]
Hartmut Fricke, Christoph Thiel
Open Journal of Applied Sciences (OJAppS) , 2015, DOI: 10.4236/ojapps.2015.52007
Abstract: When Aerodrome Obstacle Standards cannot be met as a result of urban or technical development, an aeronautical study can be carried out with the permission of EASA, in conjunction with ICAO, to prove how aircrafts can achieve an equivalent level of safety. However currently, no detailed guidance for this procedure exists. This paper proposes such a safety assessment methodology in order to value obstacle clearance violations around airports. This method has already been applied to a safety case at Frankfurt Airport where a tower elevating 4 km out of threshold 25R severely violates obstacle limitation surfaces. The model data refers to a take-off and landing performance model (TLPM) computing precisely aircraft trajectories for both standard and engine out conditions at ground proximity. The generated tracks are used to estimate collision risk incrementally considering EASA/FAA, EU-OPS & ICAO clearance criteria. Normal operations are assessed with a probabilistic analysis of empirical take-off/landing track data generating the local actual navigation performance (ANP) on site. The ANP shows integration to collision risk for an aircraft with any obstacle. The obstacle is tested for clearance within a “5-step-plan” against all performance requirements for landing climb and take-off climb. The methodology thereby delivers a comprehensive risk picture: The presented safety case for Frankfurt Airport showed an equivalent safety level despite the violation of standards. The collision risk during both normal and degraded performance operations was still found to be within ICAO Collision Risk Model (CRM) limits, requiring only limited risk mitigation measures. The presented work should complement ICAO Doc 9774 Appendix 3.
Measuring and Modeling of P- and S-Wave Velocities on Crustal Rocks: A Key for the Interpretation of Seismic Reflection and Refraction Data
Hartmut Kern
International Journal of Geophysics , 2011, DOI: 10.1155/2011/530728
Abstract: Lithologic interpretations of the earth crust from seismic wave velocities are non-unique so that inferences about composition can not be drawn. In order to evaluate how elastic properties of rock materials are controlled by lithology at in situ pressures and temperatures, compressional (Vp), shear wave velocities (Vs) and velocity anisotropy of crustal rocks were measured at conditions of greater depth. The first part deals with the interdependence of elastic wave propagation and the physical and lithological parameters. In the second part data from laboratory seismic measurements and theoretical calculations are used to interpret (1) a shallow seismic reflection line (SE Finland) and (2) a refraction profile of a deep crust (Central China). The comparison of the calculated velocities with the experimentally-derived in situ velocities of the Finnish crustal rocks give hints that microcracks have an important bearing on the in situ seismic velocities, velocity anisotropy and the reflectivity observed at relative shallow depth. The coupling of the experimentally-derived in situ velocities of P- and S-wave and corresponding Poisson's ratios of relevant exhumed high-grade metamorphic crustal rocks from Central China with respective data from seismic refraction profiling provided a key for the lithologic interpretation of a deep seismic crustal structure.
Systemic risks of genetically modified crops: the need for new approaches to risk assessment
Hartmut Meyer
Environmental Sciences Europe , 2011, DOI: 10.1186/2190-4715-23-7
Abstract: The article reviews the development of biosafety regulations in the USA and the EU, focussing on diverging concepts applied for assessing the risks of genetically modified organisms (GMOs).The dominant environmental risk assessment methodology has been developed to answer basic questions to enable expedient decision making. As a first step, methodologies that take into account complex environmental and landscape aspects should be applied. Expanding the scope of risk assessment, more holistic concepts have been developed, for example the Organisation for Econonomic Co-operation and Development (OECD) concept of systemic risks which includes socio-economic aspects. International bodies as the OECD, the Convention on Biological Diversity (CBD) and the European Union (EU) have developed the Strategic Environmental Assessment (SEA) as an instrument that includes the additional aspects of risk assessment as demanded by many stakeholders. Interestingly, there had been no attempts yet to link the existing frameworks of GMO risk assessment and SEA.It is recommended to adapt current models of SEA to assess the systemic risks of GMOs. It is also suggested to revise the EU GMO legislation to promote the inclusion of SEA elements.The first genetically modified organisms (GMO) deregulated and commercialised was the Flavr Savr tomato in 1994 in the USA, which did not prove to be commercially viable. US genetically modified (GM) agriculture actually started with Bt cotton planting in 1995, but it only was the introduction of Roundup Ready soybeans in 1996, being exported worldwide as basic ingredient for the feed and food industry that initiated the worldwide public debate on the use of GM crops. Meanwhile, James reports that 15 countries grow more than 50,000 ha of GM crops each with a sum of 133.9 million hectares [1]. According to FoEI--pointing to the fact that the data presented by James are mostly based on personal communic1ations by representatives of the biotechnology indus
Information Retrieval and Search Engines in Full-text Databases
Hartmut Zillmann
Liber Quarterly : The Journal of European Research Libraries , 2000,
Abstract: OSIRIS and ELIB are two cooperative projects at the Osnabrück University supported by the German Research Society (DFG) and the Ministry of Science and Culture (MWK) Niedersachsen (Germany). They deal with natural language retrieval systems and with indexing techniques for full-text databases using natural language processing. Very complex processes in the context of syntactical and semantical analysis of textual phrases including sophisticated valuation criteria could be implemented in large relational databases with online realtime indexing requirements.
Supportive therapy in medical therapy of head and neck tumors []
Link, Hartmut
GMS Current Topics in Otorhinolaryngology, Head and Neck Surgery , 2012, DOI: 10.3205/cto000083
Abstract: [english] Fever during neutropenia may be a symptom of severe life threatening infection, which must be treated immediately with antibiotics. If signs of infection persist, therapy must be modified. Diagnostic measures should not delay treatment. If the risk of febrile neutropenia after chemotherapy is ≥20%, then prophylactic therapy with G-CSF is standard of care. After protocols with a risk of febrile neutropenia of 10–20%, G-CSF is necessary, in patients older than 65 years or with severe comorbidity, open wounds, reduced general condition. Anemia in cancer patients must be diagnosed carefully, even preoperatively. Transfusions of red blood cells are indicated in Hb levels below 7–8 g/dl. Erythropoies stimulating agents (ESA) are recommended after chemotherapy only when hemoglobin levels are below 11 g/dl. The Hb-level must not be increased above 12 g/dl. Anemia with functional iron deficiency (transferrin saturation <20%) should be treated with intravenous iron, as oral iron is ineffective being not absorbed. Nausea or emesis following chemotherapy can be classified as minimal, low, moderate and high. The antiemetic prophylaxis should be escalated accordingly. In chemotherapy with low emetogenic potential steroids are sufficient, in the moderate level 5-HT3 receptor antagonists (setrons) are added, and in the highest level Aprepitant as third drug.
Rente und subnationale Gewalt. Der Beitrag der politischen konomie
Hartmut Elsenhans
Behemoth : a Journal on Civilisation , 2009,
Abstract: Rents are a basic element of the political economy of underdeveloped economies. They hinder and often block the mechanism of social integration through gainful employment and veto the power of labour, which characterizes capitalist societies and the constitution of citizenship. The impact of rent on political structures is, however, ambiguous. Anomie is only one possible result. Hence the link between raw material exports and non-state violence is also ambiguous. Many societies, which are characterized by rents, have developed quite powerful mechanisms of keeping internal peace, possibly with limited participation. The conditions of differential impacts of rent on social structures and political behaviour call for an analysis of internal interest mediation.
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