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排序方式: 共有262条查询结果,搜索用时 15 毫秒
21.
Niederer SA Kerfoot E Benson AP Bernabeu MO Bernus O Bradley C Cherry EM Clayton R Fenton FH Garny A Heidenreich E Land S Maleckar M Pathmanathan P Plank G Rodríguez JF Roy I Sachse FB Seemann G Skavhaug O Smith NP 《Philosophical transactions. Series A, Mathematical, physical, and engineering sciences》2011,369(1954):4331-4351
Ongoing developments in cardiac modelling have resulted, in particular, in the development of advanced and increasingly complex computational frameworks for simulating cardiac tissue electrophysiology. The goal of these simulations is often to represent the detailed physiology and pathologies of the heart using codes that exploit the computational potential of high-performance computing architectures. These developments have rapidly progressed the simulation capacity of cardiac virtual physiological human style models; however, they have also made it increasingly challenging to verify that a given code provides a faithful representation of the purported governing equations and corresponding solution techniques. This study provides the first cardiac tissue electrophysiology simulation benchmark to allow these codes to be verified. The benchmark was successfully evaluated on 11 simulation platforms to generate a consensus gold-standard converged solution. The benchmark definition in combination with the gold-standard solution can now be used to verify new simulation codes and numerical methods in the future. 相似文献
22.
Matthias Engleder Dr. Tea Pavkov‐Keller Dr. Anita Emmerstorfer Altijana Hromic Sabine Schrempf Dr. Georg Steinkellner Dr. Tamara Wriessnegger Prof. Erich Leitner Dr. Gernot A. Strohmeier Dr. Iwona Kaluzna Dr. Daniel Mink Dr. Martin Schürmann Dr. Silvia Wallner Prof. Peter Macheroux Prof. Karl Gruber Dr. Harald Pichler 《Chembiochem : a European journal of chemical biology》2015,16(12):1730-1734
Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration. 相似文献
23.
We describe algorithms to implement fully dynamic and kinetic three-dimensional unconstrained Delaunay triangulations, where the time evolution of the triangulation is not only governed by moving vertices but also by a changing number of vertices. We use three-dimensional simplex flip algorithms, a stochastic visibility walk algorithm for point location and in addition, we propose a new simple method of deleting vertices from an existing three-dimensional Delaunay triangulation while maintaining the Delaunay property. As an example, we analyse the performance in various cases of practical relevance. The dual Dirichlet tessellation can be used to solve differential equations on an irregular grid, to define partitions in cell tissue simulations, for collision detection etc. 相似文献
24.
Thomas Plötz Gernot A. Fink 《International Journal on Document Analysis and Recognition》2009,12(4):269-298
Since their first inception more than half a century ago, automatic reading systems have evolved substantially, thereby showing
impressive performance on machine-printed text. The recognition of handwriting can, however, still be considered an open research
problem due to its substantial variation in appearance. With the introduction of Markovian models to the field, a promising
modeling and recognition paradigm was established for automatic offline handwriting recognition. However, so far, no standard
procedures for building Markov-model-based recognizers could be established though trends toward unified approaches can be
identified. It is therefore the goal of this survey to provide a comprehensive overview of the application of Markov models
in the research field of offline handwriting recognition, covering both the widely used hidden Markov models and the less
complex Markov-chain or n-gram models. First, we will introduce the typical architecture of a Markov-model-based offline handwriting recognition system
and make the reader familiar with the essential theoretical concepts behind Markovian models. Then, we will give a thorough
review of the solutions proposed in the literature for the open problems how to apply Markov-model-based approaches to automatic
offline handwriting recognition. 相似文献
25.
B. Wilthan H. Reschab R. Tanzer W. Schützenhöfer Gernot Pottlacher 《International Journal of Thermophysics》2008,29(1):434-444
Numerical simulation of vacuum arc re-melting, pressurized or protective electro-slag re-melting, and ingot casting have become
quite important in the metal industry. However, a major drawback of these simulation techniques is the lack of accurate thermophysical
properties for temperatures above 1,500 K. Heat capacity, heat of fusion, density, and thermal conductivity are important
input parameters for the heat transfer equation. Since, direct measurements of thermal conductivity of alloys in the liquid
state are almost impossible, its estimation from electrical conductivity using the Wiedemann–Franz law is very useful. The
afore-mentioned thermophysical properties of several steels are investigated within the context of an ongoing project. Here,
we present a full set of thermophysical data for the chromium–nickel–molybdenum steel meeting the standard DIN 1.4435 (X2CrNiMo18-14-3);
these values will be used by our partner to simulate various re-melting and solidification processes. Wire-shaped samples
of the steel are resistively volume-heated, as part of a fast capacitor discharge circuit. Time-resolved measurements with
sub-μs resolution of current through the specimen are performed with a Pearson probe. The voltage drop across the specimen
is measured with knife-edge contacts and ohmic voltage dividers, the temperature of the sample with a pyrometer, and the volumetric
expansion of the wire with a fast acting CCD camera. These measurements enable the heat of fusion, the heat capacity, and
the electrical resistivity to be determined as a function of temperature in the solid and liquid phases. The thermal conductivity
and thermal diffusivity are estimated via the Wiedemann–Franz law. 相似文献
26.
Gernot Standfest Alexander Petutschnigg Manfred Dunky Bernhard Zimmer 《Holz als Roh- und Werkstoff》2009,67(1):83-87
In this work the vertical density profiles of three different commercial wood based panels (particleboard, MDF, OSB) were investigated using a conventional X-ray method as well as an industrial computer tomography (CT) method. The reconstructed gray level images of the obtained CT data were used to calculate a standardized density profile of each panel. The results showed that the measured (X-ray) and the calculated (CT) density profiles of the panels fit well in the core layer of the boards; in the most outer surface layers some anomalies in the results can occur in both methods. The advantage in the implementation and evaluation of the more complicated CT measurement compared to the conventional X-ray procedure is the three-dimensional data structure and the opportunity to do appropriate structural analysis of the investigated wood based panels. 相似文献
27.
Katharina Resch Gernot M. Wallner Christian Teichert Günther Maier Markus Gahleitner 《Polymer Engineering and Science》2006,46(4):520-531
Polypropylene homopolymers and ethylene/propylene‐random‐copolymers formulated with and without anti‐blocking additives were extruded to cast films with an industrial scale extruder equipped with a soft box, a specific air knife that expels a higher volume of air at lower velocity. The films were analyzed as to their optical properties haze and clarity. A comprehensive topographical characterization was performed using atomic force microscopy (AFM) and confocal microscopy. To obtain morphological information on a nanometer scale AFM phase imaging, micro‐thermal analysis and small angle X‐ray scattering (SAXS) were done. A significant effect of additives and processing conditions on the film topography and the optical properties was revealed. The films without anti‐blocking and antacid aids showed the best optical properties and lowest vertical roughness fluctuations. In contrast, the addition of anti‐blocking and antacid aids reduced the optical properties associated with an increase in surface roughness. While for films without anti‐blocking aids an enhanced soft box condition resulted in lower vertical fluctuations of roughness and better optical properties, the behavior was in reverse for films with anti‐blocking aid. By means of SAXS crystalline lamellae with a thickness of about 2.5 nm were detected. High‐resolution phase imaging AFM yielded thicker crystal lamellae on the film surface. POLYM. ENG. SCI., 46:520–531, 2006. © 2006 Society of Plastics Engineers. 相似文献
28.
Nico Vieweg Mehmet Ali Celik Sabine Zakel Vineet Gupta Gernot Frenking Martin Koch 《Journal of Infrared, Millimeter and Terahertz Waves》2014,35(5):478-485
We present the first systematic study of cyanobiphenyls (CBs) and the phenylcyclohexanes in the range between 50 cm-1 (1.5 THz) and 500 cm-1 (15 THz). The impact of the alkyl chain length and of variations in the core structure on the spectrum is investigated using liquid crystals from the cyanobiphenyl and phenylcyclohexane families. Our measurements are supported by calculations based on density functional theory. This enables us to shine light on the vibrational dynamics of liquid crystal molecules in the terahertz frequency range. 相似文献
29.
Jonathan P. Caulkins Dieter Grass Gustav Feichtinger Gernot Tragler 《Computers & Operations Research》2008
This paper deals dynamically with the question of how recruitment to terror organizations is influenced by counter-terror operations. This is done within an optimal control model, where the key state is the (relative) number of terrorists and the key controls are two types of counter-terror tactics, one (“water”) that does not and one (“fire”) that does provoke recruitment of new terrorists. The model is nonlinear and does not admit analytical solutions, but an efficient numerical implementation of Pontryagin's minimum principle allows for solution with base case parameters and considerable sensitivity analysis. Generally, this model yields two different steady states, one where the terror organization is nearly eradicated and one with a high number of terrorists. Whereas water strategies are used at almost any time, it can be optimal not to use fire strategies if the number of terrorists is below a certain threshold. 相似文献
30.
Eight experiments examined the conditions under which a color singleton that is presented for the 1st time without prior announcement captures attention. The main hypothesis is that an unannounced singleton captures attention to the extent that it deviates from expectations. This hypothesis was tested within a visual-search paradigm in which set-size effects were used to infer attentional capture. The results showed that attentional capture by an unannounced color singleton was due to a mismatch with expectations concerning the color of the object and not due to its being a singleton. Thus, the results imply that theories of attention have to consider expectation discrepancy as a determinant of attention shifts. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献