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Now showing 1 - 10 of 609
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    Crystal structure of (2S,4S,7S)-7,7-dichloro-4-(1-chloro-1-methylethyl)-1- (2,2,2-trichloroethyl)bicyclo[4.1.0]heptane, C12H16Cl 6
    (Berlin : de Gruyter, 2009) Boualy, B.; el Firdoussi, L.; Ali, M.A.; Karim, A.; Spannenberg, A.
    C12H16Cl6, orthorhombic, P2 12121 (no. 19), a = 6.0742(3) Å, b = 9.7189(6) Å, c = 26.700(1) Å, V = 1576.2 Å3, Z = 4, Rgt(F) = 0.019, wRref(F2) = 0.045, T= 200 K. © by Oldenbourg Wissenschaftsverlag.
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    Mechanisms of bonding effected by nanoparticles in zirconia coatings applied by spraying of suspensions
    (Saarbrücke : Leibniz-Institut für Neue Materialien, 2008) Adam, Jens; Aslan, Mesut; Drumm, Robert; Veith, Michael
    Zirconia coatings consisting of a mixture of coarse and fine grained zirconia powders prepared by spraying of suspensions and subsequent thermal treatment at limited temperatures (up to 500°C) are poor in adherence and in intrinsic mechanical strength. We have shown elsewhere that mechanical properties of these coatings can be improved clearly by adding a small amount of nanoscaled zirconia. Here, the structural and the chemical development of this coating material and of the nanoparticles is examined to gain information about the underlying bonding mechanisms. The applied temperature is relatively low in comparison to the usual onset temperature of accelerated sintering. Nevertheless, the results show that diffusion controlled material transport mechanisms play their role in bonding. The condensation of surface OH groups may participate in bonding, too. These first results confirm the potential of nanoparticles to act as inorganic binder. Additional research effort to clarify the underlying mechanisms in detail is of interest. For the practical side, it can be concluded that the resulting effect of mechanical consolidation of ceramic structures at relatively low temperatures enables new ceramic applications, for example a new type of ceramic coatings on metallic substrates.
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    Stratifying modular representations of finite groups
    (Oberwolfach : Mathematisches Forschungsinstitut Oberwolfach, 2008) Benson, Dave; Iyengar, Srikanth B.; Krause, Henning
    We classify localising subcategories of the stable module category of a finite group that are closed under tensor product with simple (or, equivalently all) modules. One application is a proof of the telescope conjecture in this context. Others include new proofs of the tensor product theorem and of the classification of thick subcategories of the finitely generated modules which avoid the use of cyclic shifted subgroups. Along the way we establish similar classifications for differential graded modules over graded polynomial rings, and over graded exterior algebras.
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    Simulations of 3D/4D precipitation processes in a turbulent flow field
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2009) John, Volker; Roland, Michael
    Precipitation processes are modeled by population balance systems. A very expensive part of the simulation of population balance systems is the solution of the equation for the particle size distribution (PSD) since this equation is defined in a higher dimensional domain than the other equations in the system. This paper studies different approaches for the solution of this equation: two finite difference upwind schemes and a linear finite element flux--corrected transport method. It is shown that the different schemes lead to qualitatively different solutions for an output of interest.
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    Plasma induced pulse breaking in filamentary self-compression
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2009) Brée, Carsten; Demircan, Ayhan; Skupin, Stefan; Berg´e, Luc; Steinmeyer, Günter
    A plasma induced temporal break-up in filamentary propagation has recently been identified as one of the key events in the temporal self-compression of femtosecond laser pulses. An analysis of the Nonlinear Schrödinger Equation coupled to a noninstantaneous plasma response yields a set of stationary states. This analysis clearly indicates that the emergence of double-hump, characteristically asymmetric temporal on-axis intensity profiles in regimes where plasma defocusing saturates the optical collapse caused by Kerr self-focusing is an inherent property of the underlying dynamical model.
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    Fast, stable and accurate method for the Black-Scholes equation of American options
    (Berlin : Weierstraß-Institut für Angewandte Analysis und Stochastik, 2008) Ehrhardt, Matthias; Mickens, Ronald E.
    We propose a simple model for the behaviour of long-time investors on stock markets, consisting of three particles, which represent the current price of the stock, and the opinion of the buyers, or sellers resp., about the right trading price. As time evolves both groups of traders update their opinions with respect to the current price. The update speed is controled by a parameter $\gamma$, the price process is described by a geometric Brownian motion. The stability of the market is governed by the difference of the buyers' opinion and the sellers' opinion. We prove that the distance
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    Increased biocompatibility and bioactivity after energetic PVD surface treatments
    (Basel : MDPI, 2009) Mändl, S.
    Ion implantation, a common technology in semiconductor processing, has been applied to biomaterials since the 1960s. Using energetic ion bombardment, a general term which includes conventional ion implantation plasma immersion ion implantation (PIII) and ion beam assisted thin film deposition, functionalization of surfaces is possible. By varying and adjusting the process parameters, several surface properties can be attuned simultaneously. Extensive research details improvements in the biocompatibility, mainly by reducing corrosion rates and increasing wear resistance after surface modification. Recently, enhanced bioactivity strongly correlated with the surface topography and less with the surface chemistry has been reported, with an increased roughness on the nanometer scale induced by self-organisation processes during ion bombardment leading to faster cellular adhesion processes. © 2009 by the authors;.
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    Zeitaufgelöste PIV-Untersuchungen zur Strömungskontrolle mittels elektromagnetischer Kräfte in schwach leitfähigen Fluiden
    (Dresden : Forschungszentrum Dresden-Rossendorf, 2009) Cierpka, Christian
    [no abstract available]
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    Polyhedral surface approximation of non-convex voxel sets and improvements to the convex hull computing method
    (Dresden : Forschungszentrum Dresden-Rossendorf, 2009) Schulz, Henrik
    In this paper we introduce an algorithm for the creation of polyhedral approximations for objects represented as strongly connected sets of voxels in three-dimensional binary images. The algorithm generates the convex hull of a given object and modifies the hull afterwards by recursive repetitions of generating convex hulls of subsets of the given voxel set or subsets of the background voxels. The result of this method is a polyhedron which separates object voxels from background voxels. The objects processed by this algorithm and also the background voxel components inside the convex hull of the objects are restricted to have genus 0. The second aim of this paper is to present some improvements to our convex hull algorithm to reduce computation time.