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Loewy Decomposition of Linear Differential Equations 1

丛书名： Texts & Monographs in Symbolic Computation

2012年

作者： Fritz Schwarz

ISBN: (数字)9783709112861

ISBN: (纸本)3709112850

The central subject of the book is the generalization of Loewy's decomposition - originally introduced by him for linear ordinary differential equations - to linear partial differential equations. Equations for a single function in two independent variables of order two or three are comprehensively discussed. A complete list of possible solution types is given. Various ad hoc results available in the literature are obtained algorithmically. The border of decidability for generating a Loewy decomposition are explicitly stated. The methods applied may be generalized in an obvious way to equations of higher order, in more variables or systems of such equations.

关键词： Symbolic and Algebraic Manipulation Differential Equations Mathematical and Computational Engineering Applications

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Sparse Grids and Applications

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2012年

作者： Jochen Garcke Michael Griebel

ISBN: (纸本)9783642317026

In the recent decade, there has been a growing interest in the numerical treatment of high-dimensional problems. It is well known that classical numerical discretization schemes fail in more than three or four dimensions due to the curse of dimensionality. The technique of sparse grids helps overcome this problem to some extent under suitable regularity assumptions. This discretization approach is obtained from a multi-scale basis by a tensor product construction and subsequent truncation of the resulting multiresolution series expansion. This volume of LNCSE is a collection of the papers from the proceedings of the workshop on sparse grids and its applications held in Bonn in May 2011. The selected articles present recent advances in the mathematical understanding and analysis of sparse grid discretization. Aspects arising from applications are given particular attention.

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Efficient gradient and Hessian calculations for numerical optimization algorithms applied to atomistic molecular simulations

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Journal of Physics: Conference Series 2013年第1期410卷

作者： Marco Hülsmann Sonja Kopp Markus Huber Dirk Reith Fraunhofer-Institute for Algorithms and Scientific Computing (SCAI) Schloß Birlinghoven 53754 Sankt Augustin Germany

Computer simulations of chemical systems can be used to reliably predict physical properties. Accurate molecular models, which are indispensable, are mathematically described by force fields, which have to be parameterized. Recently, an automated gradient-based parametrization procedure was published by the authors based on the minimization of a loss function between simulated and experimental physical properties. The applicability of the utilized algorithms is not trivial at all because of two reasons: First, simulation data is affected by statistical noise and second, the molecular simulations required for the loss function evaluations (involving finite differences approximations of gradients and Hessians) are extremely time-consuming. In this work, a more efficient approach to compute gradients and Hessians is presented. The method developed here is based on directional instead of partial derivatives. It is shown that up to 75% of the simulations can be avoided using this method.

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Uncertainty quantification using nonparametric quantile estimation and metamodeling

Uncertainty quantification using nonparametric quantile esti...

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6th European Congress on Computational Methods in Applied Sciences and Engineering, ECCOMAS 2012

作者： Rhein, Beate Clees, Tanja Ruschitzka, Margot University of Applied Sciences Cologne Betzdorfer Str. 2 50679 Koeln Germany Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven 53754 Sankt Augustin Germany

ISBN: (纸本)9783950353709

In many applications, particularly in the engineering field, the need to consider uncertainties is recognized. To reduce the number of necessary simulations, metamodels can be used. We present a novel method on the basis of metamodels, that allows us to model not only the deterministic responses, but also the propagation of uncertainty in the entire design space. Our procedure makes it possible to determine the robust optimum quickly with common multi-criteria optimization algorithms. The novel approach offers the possibility to include the tolerance of the metamodel in the calculation. We introduce a new class of robustness measures that characterizes the propagation of uncertainty more accurately than usual: the median as measure of central tendency and the difference between median and a high quantile q as measure of dispersion. This allows the user to adjust the degree of robustness to his wishes via q. It can handle even extremely skewed distributions in an appropriate way. For the determination of the quantiles we use a novel combination of sampling scheme and nonparametric quantile estimation. This enables a fast computation on a local level. The suitability of the proposed proceeding is proved on several examples. The applicability is demonstrated on a real life example from automotive industry.

关键词： Automotive industry

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Large scale chemical patent mining with UIMA and UNICORE

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Journal of Cheminformatics 2012年第1期4卷 1-2页

作者： Alexander Klenner Marc Zimmermann Sandra Bergmann Mathilde Romberg Fraunhofer-Institute for Algorithms and Scientific Computing (SCAI) Sankt Augustin 53754 Germany Forschungszentrum Juelich GmbH Juelich 52425 Germany

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A new optimization phase for scientific workflow management systems

A new optimization phase for scientific workflow management ...

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IEEE International Conference on e-Science and Grid computing

作者： Sonja Holl Olav Zimmermann Martin Hofmann-Apitius Juelich Supercomputing Centre (JSC) Juelich Germany Fraunhofer Institute for Algorithms and Scientific Computing (SCAI) Sankt Augustin Germany

scientific workflows have emerged as an important tool for combining computational power with data analysis for all scientific domains in e-science. They help scientists to design and execute complex in silico experiments. However, with increasing complexity it becomes more and more infeasible to optimize scientific workflows by trial and error. To address this issue, this paper describes the design of a new optimization phase integrated in the established scientific workflow life cycle. We have also developed a flexible optimization application programming interface (API) and have integrated it into a scientific workflow management system. A sample plugin for parameter optimization based on genetic algorithms illustrates, how the API enables rapid implementation of concrete workflow optimization methods. Finally, a use case taken from the area of structural bioinformatics validates how the optimization approach facilitates setup, execution and monitoring of workflow parameter optimization in high performance computing e-science environments.

关键词： Optimization methods Planning Abstracts Engines Data analysis Genetic algorithms

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Improving Distantly Supervised Extraction of Drug-Drug and Protein-Protein Interactions 12

Improving Distantly Supervised Extraction of Drug-Drug and P...

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Conference of The European Chapter of The Association for Computational Linguistics

作者： Tamara Bobic Roman Klinger Philippe Thomas Martin Hofmann-Apitius Fraunhofer Institute for Algorithms and Scientific Computing (SCAI) Schloss Birlinghoven 53754 Sankt Augustin Germany Bonn-Aachen Center for Information Technology Dahlmannstrasse 2 53113 Bonn Germany Fraunhofer Institute for Algorithms and Scientific Computing (SCAI) Schloss Birlinghoven 53754 Sankt Augustin Germany Computer Science Institut Humboldt-Universitaet Unter den Linden 6 10099 Berlin Germany

ISBN: (纸本)9781622764907

Relation extraction is frequently and successfully addressed by machine learning methods. The downside of this approach is the need for annotated training data, typically generated in tedious manual, cost intensive work. Distantly supervised approaches make use of weakly annotated data, like automatically annotated corpora. Recent work in the biomedical domain has applied distant supervision for protein-protein interaction (PPI) with reasonable results making use of the IntAct database. Such data is typically noisy and heuristics to filter the data are commonly applied. We propose a constraint to increase the quality of data used for training based on the assumption that no self-interaction of real-world objects are described in sentences. In addition, we make use of the University of Kansas Proteomics Service (KUPS) database. These two steps show an increase of 7 percentage points (pp) for the PPI corpus AIMed. We demonstrate the broad applicability of our approach by using the same workflow for the analysis of drug-drug interactions, utilizing relationships available from the drug database DrugBank. We achieve 37.31 % in F_1 measure without manually annotated training data on an independent test set.

关键词： Protein-Protein Interaction Training data pulse position indicator Drug Interactions Heuristics Manual handling Database

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Scalable parallel AMG on ccNUMA machines with OpenMP

Scalable parallel AMG on ccNUMA machines with OpenMP

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作者： Förster, Malte Kraus, Jiri Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven 53754 Sankt Augustin Germany

In many numerical simulation codes the backbone of the application covers the solution of linear systems of equations. Often, being created via a discretization of differential equations, the corresponding matrices are very sparse. One popular way to solve these sparse linear systems are multigrid methods-in particular AMG- because of their numerical scalability. But looking at modern multi-core architectures, also the parallel scalability has to be taken into account. With the memory bandwidth usually being the bottleneck of sparse matrix operations these linear solvers can't always benefit from increasing numbers of cores. To exploit the available aggregated memory bandwidth on larger scale NUMA machines evenly distributed data is often more an issue than load balancing. Additionally, using a threading model like OpenMP, one has to ensure the data locality manually by explicit placement of memory pages. On non uniform data it is always a tradeoff between these three principles, while the ideal strategy is strongly machine- and application dependent. In this paper we want to present some benchmarks of an AMG implementation based on a new performance library. Main focus is on the comparability to state-of-the-art solver packages regarding sequential performance as well as parallel scalability on common NUMA machines. To maximize throughput on standard model problems, several thread and memory configurations have been evaluated. We will show that even on large scale multi-core architectures easy parallel programming models, like OpenMP, can achieve a competitive performance compared to more complex programming models. © Springer-Verlag 2011.

关键词： Matrix algebra

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Compensation of pressure peaks in PWK-type hydraulic pumps

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Key Engineering Materials 2011年 490卷 33-44页

作者： Osiecki, Leszek Patrosz, Piotr Zawistowski, Tomasz Landvogt, Bettina Piechna, Janusz Zyliñski, Bartek Gdansk University of Technology ul. Narutowicza 11/12 80-233 Gdansk Poland Space Research Center Polish Academy of Sciences ul. Bartycka 18A 00-716 Warszawa Poland Fraunhofer Institute for Algorithms and Scientific Computing SCAI Schloss Birlinghoven 53754 Sankt Augustin Germany Warsaw University of Technology Pl. Politechniki 1 00-661 Warszawa Poland Bandak Engineering Postboks 1505 Ålesund Norway

Hydraulic axial pumps equipped with cam-driven commutation unit (PWK pumps) proved their high efficiency up to 55 MPa and ability to work self-sucking, even at high speed. Displacement of PWK pump may easily be changed by moving its control cam. Full discharge from hydrostatic forces makes such control possible by direct action of a low-energy actuator like proportional electromagnet or stepping motor. That eliminates heavy and costly hydraulic servomechanism, necessary in other variable displacement machines. Such a control mechanism was positively evaluated in prototype tests in Department of Hydraulics and Pneumatics of Gdañsk University of Technology. The new commutation unit generates however harmful pressure peaks. The paper presents the compensation method for pressure peaks by use of the elastic compensation chamber. It shows also results of multidisciplinary FEA and CFD analysis necessary to properly design the compensation chamber. © 2012 Trans Tech Publications, Switzerland.

关键词： Stepping motors

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Achieving an improved understanding of the factors affecting an aircraft environmental control system by coupling a 1D cabin air distribution system model with a 3D passenger cabin model using Co-simulation middleware

Achieving an improved understanding of the factors affecting...

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SAE 2009 AeroTech Congress and Exhibition

作者： Kelsall, David Ludhi, Abdul Bayrasy, Pascal Wolf, Klaus Flowmaster Ltd Fraunhofer Institute for Algorithms and Scientific Computing SCAI

Aircraft Environmental Control Systems (ECS) are designed to optimize passenger comfort by providing satisfactory cabin pressurization, and temperature and humidity control whilst minimising the risks to passenger health from airborne toxins and diseases. The paper presents a case study that investigates how the cooling load discharge from an ECS system affects the flow behaviour inside a typical mid-size, wide-body aircraft passenger cabin. The investigation uses commercial off-the-shelf one dimensional (1D) Computational Fluid Dynamics (CFD) software to model the cooling pack, cabin air distribution system, and three quarters of the passenger cabin. The centre section of the cabin is modelled using a commercial off-the-shelf three dimensional (3D) CFD package, with the co-simulation middleware providing coupling adapters to ensure that two-way, bilateral exchange of boundary parameters between the 1D and the 3D CFD models gives continuity of mass and momentum transfer. The 1D and 3D CFD applications and Co-simulation middleware are supplied by 3 independent commercial organisations. The results of the case study are discussed including the co-simulated 'velocity field of the air discharge' and the 'temperature gradient inside the cabin' within the 3D CFD model as well as the flow and temperature fields within the one-dimensional ECS cooling pack model. The paper concludes by discussing how the proper implementation of the co-simulation methods developed in this case study could bring significant benefits to engineering companies using CFD tools, including improved quality of simulation results and reduced simulation run times. Copyright © 2009 SAE International.

关键词： Computational fluid dynamics

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