Distance field computation for geological slab surface data sets

The three-dimensional shapes of tectonic plates that sink into the Earth’s mantle (slabs) are the starting point for a range of geoscience studies, from determining the forces driving the motion of tectonic plates, to potential seismic and tsunami hazards, to the sources of magmas beneath active volcanos. For many of these applications finite element methods are used to model the deformation or fluid flow, and therefore the input model parameters, such as feature geometries, temperature or viscosity, must be defined with respect to a smooth, continuous distance field around the slab. In this paper we present a framework for processing sparse and noisy seismic data (earthquake locations), defining the shape of the slab and computing a continuous distance function on a mesh with variable node spacing. Due to the inhomogeneous volumetric distribution of earthquakes within the slab and significant inaccuracies in the locations of earthquakes occurring hundreds of kilometers below the Earth’s surface, the seismicity data set is extremely noisy and incomplete. Therefore, the preprocessing is the major part of the framework consisting of several steps including a point based smoothing procedure, a powerful method to use other observational constraints on slab location (e.g., seismic tomography or geologic history) to extend of the slab shape beyond earthquake data set and continuous resampling using moving least squares method. For the preprocessed point data we introduce approaches for finding the three-dimensional boundary of the slab and a subdivision of the slab into quadric implicit polynomials. The resulting distance field is then compiled from distances to the piecewise continuous approximation of the slab and distances to slab boundary.     

Sicherung der Netzneutralität

Die Geschichte des Internets ist eine Erfolgsgeschichte. Dieser Erfolg beruht u.a. auf einer neutralen Datenübermittlung, die dadurch gekennzeichnet ist, dass Netzbetreiber Datenpakete von und an ihre Kunden unver?ndert und gleichberechtigt übertragen, unabh?ngig davon, woher diese stammen und welche Anwendungen die Pakete generiert haben. In jüngster Zeit werden Forderungen nach Verkehrsregelungen im Internet lauter. Begründet wird diese Initiative mit einer drohenden Netzüberlastung, die durch die wachsende Popularit?t von Videoangeboten wie YouTube oder Streaming-Angeboten wie Hulu entsteht. Kritiker befürchten, dass durch den Einsatz neuer Netzwerkmanagementtechniken die Innovationsoffenheit und die freie Kommunikation im Internet gef?hrdet werden. Der Beitrag analysiert die M?glichkeiten und Grenzen der Gew?hrleistung von Netzneutralit?t durch das deutsche Telekommunikations- und Medienrecht.     

Simulation based analysis of secondary effects on solder fatigue

Secondary effects on thermal fatigue of solder joints, which frequently have been neglected, were studied by means of the finite element method (FEM). Based on a semi-empirical approach to predict fatigue life by evaluating the cyclic accumulated equivalent creep strain or energy density, effects of organic boards intrinsic properties on solder joint fatigue were investigated. Aspects of more realistic FR-4 board modelling were studied, in particular concerning its in-plane anisotropy and intrinsic warpage behaviour. Intrinsic board warpage was measured on test board level as well as for boards from series production. High intrinsic warpage was in particular found for several test boards. The effects for the worst case scenario observed so far were analysed for both first level and second level interconnects. The change in predicted fatigue life varied between 30% and 500%, the latter most critical effects were found at large QFN components. Another secondary effect studied was to include the frequently neglected interfacial intermetallics into FEM. It turned out that for components with relatively large standoff like LFBGAs the effects were actually negligible, but for the highly miniaturized components like chip resistors CR0201 they are the decisive factor.     

Optimization models for operative planning in drinking water networks

The topic of this paper is minimum cost operative planning of pressurized water supply networks over a finite horizon and under reliable demand forecast. Since this is a very hard problem, it is desirable to employ sophisticated mathematical algorithms, which in turn calls for carefully designed models with suitable properties. The paper develops a nonlinear mixed integer model and a nonlinear programming model with favorable properties for gradient-based optimization methods, based on smooth component models for the network elements. In combination with further nonlinear programming techniques (Burgschweiger et al. in ZIB Report ZR-05-31, Zuse Institute Berlin, 2005), practically satisfactory near-optimum solutions even for large networks can be generated in acceptable time using standard optimization software on a PC workstation. Such an optimization system is in operation at Berliner Wasserbetriebe.     

Environmental chemistry of aminopolycarboxylate chelating agents

Aminopolycarboxylate chelating agents are under scrutiny due to their influence on metal availability and mobility and in particular due to their persistence in the environment. In this review chelate adsorption, metal-mobilization, metal-exchange, mineral dissolution, reactive transport, photodegradation, and chemical degradation are all shown to be substantially affected by the chelated metal ion. The different reactivities of the metal-complexes have to be considered when assessing the reactions of chelating agents in the environment because they occur in natural waters predominantly in the form of metal complexes. Knowing the speciation of chelating agents in natural waters is therefore crucial for predicting their environmental fate. Despite this importance, only a few speciation measurements have been reported for natural waters, and model calculations have been frequently used instead. These calculations are, however, complicated by slow metal-exchange reactions that result in a nonequilibrium speciation and by the presence of naturally occurring ligands that compete with the chelating agents for available metals. The basis for a refined risk assessment of aminocarboxylate chelates should be the actual speciation in the natural water directly determined by analytical methods. The discussion of the influence of chelates on metal availability and fate also has to include the potential presence of other aminopolycarboxylate chelating agents besides the well-known EDTA and NTA.     

Determination of beam parameters and coherence properties of laser radiation by use of an extended Hartmann-Shack wave-front sensor

A combination of a Hartmann-Shack sensor and a standard far-field measurement on one single detector is proposed. The technique is fast and operates without movable parts, thus permitting a compact design. It is not only suited for characterization of the wave-front distribution but may also be considered for determination of the important parameters of beam width, beam divergence, and beam propagation ratio M2 of partially coherent laser beams. First results indicate that a fairly thorough beam characterization, including spatial coherence, propagation characteristics, and beam quality, can be achieved with this method.     

(Ba,Ca)TiO3 PTCR Ceramics with LaNiO3 Thin-Film Electrodes: Preparation and Characterization of the Interface

Conductive LaNiO₃ thin film electrodes were deposited by chemical solution deposition (CSD) from nitrate solutions onto polycrystalline Al₂O₃ and (Ba,Ca)TiO₃ PTCR ceramic substrates. The electrical properties of the LaNiO₃ thin film on Al₂O₃ and of the interface consisting of LaNiO₃ and the semiconductive oxide ceramic were investigated. The deposited LaNiO₃ films were about 250 nm thick and consisted of nanosized particles. The resistivity of the LaNiO₃ film was about 3 × 10^-3cm at 20°C. The PTCR ceramic consisted of m sized particles and exhibited an electronic resistivity of about 10 cm at 20°C and a steep increase of the resistivity of a few orders of magnitude above the Curie point at about 120°C. The electrical properties of the LaNiO₃/PTCR interface were dominated by the properties of a barrier layer between the PTCR ceramic and the LaNiO₃ electrode. The potential dependence of the impedance indicated that the barrier layer consisted of a depletion layer within the PTCR ceramic, when the flat band potential of LaNiO₃ on the PTCR ceramic at about –250 mV was exceeded. Additionally the formation of an insulating layer at the LaNiO₃ electrode has to be taken into account.