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Sun, 12 Oct 2014 14:11:41 +0100Sun, 12 Oct 2014 14:11:41 +0100Transit Dependent Evacuation Planning for Kathmandu Valley: A Case Study
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3944
Due to the increasing number of natural or man-made disasters, the application of operations research methods in evacuation planning has seen a rising interest in the research community. From the beginning, evacuation planning has been highly focused on car-based evacuation. Recently, also the evacuation of transit depended evacuees with the help of buses has been considered.
In this case study, we apply two such models and solution algorithms to evacuate a core part of the metropolitan capital city Kathmandu of Nepal as a hypothetical endangered region, where a large part of population is transit dependent. We discuss the computational results for evacuation time under a broad range of possible scenarios, and derive planning suggestions for practitioners.Urmila Pyakurel; Marc Goerigk; Tanka Dhamala; Horst W. Hamacherreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3944Wed, 10 Dec 2014 14:11:41 +0100Investigate the hardware description language Chisel - A case study implementing the Heston model
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3639
This paper presents a case study comparing the hardware description language „Constructing Hardware in a Scala Embedded Language“(Chisel) to VHDL. For a thorough comparison the Heston Model was implemented, a stochastic model used in financial mathematics to calculate option prices. Metrics like hardware utilization and maximum clock rate were extracted from both resulting designs and compared to each other. The results showed a 30% reduction in code size compared to VHDL, while the resulting circuits had about the same hardware utilization. Using Chisel however proofed to be difficult because of a few features that were not available for this case study.Christopher Stumm; Christian Brugger; Norbert Wehnreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3639Mon, 28 Oct 2013 15:31:15 +0100Investigate the high-level HDL Chisel
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3638
Chisel (Constructing Hardware in a Scala embedded language) is a new programming language, which embedded in Scala, used for hardware synthesis. It aims to increase productivity when creating hardware by enabling designers to use features present in higher level programming languages to build complex hardware blocks. In this paper, the most advertised features of Chisel are investigated and compared to their VHDL counterparts, if present. Afterwards, the authors’ opinion if a switch to Chisel is worth considering is presented. Additionally, results from a related case study on Chisel are briefly summarized. The author concludes that, while Chisel has promising features, it is not yet ready for use in the industry.Florian Heilmann; Christian Brugger; Norbert Wehnreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3638Mon, 28 Oct 2013 15:22:26 +0100Gesunde Kommune - Sport und Bewegung als Faktor der Stadt- und Raumentwicklung - Projektbericht 2011
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3594
Sport und Bewegung sind seit jeher wesentliche Bestandteile des öffentlichen Lebens. Der in den letzten Jahren erkennbare und sich weiter verstärkende demographische und gesellschaftliche Wandel führt allerdings zu einer Veränderung des Sport- und Bewegungsverhaltens und damit auch der Nachfrage nach Sportstätten und Bewegungsräumen. Die sich zunehmend verändernde Situation von Sport und Bewegung findet bislang weder auf der politischen Ebene noch auf der Ebene der kommunalen Planung ausreichend Berücksichtigung. Vor dem Hintergrund stetig steigender Bedarfe zur Sicherung der kommunalen Daseinsvorsorge müssen jedoch zeitnah Lösungen gefunden werden, die den veränderten Rahmenbedingungen auch zukünftig gerecht werden. Ausgehend hiervon befasst sich das in den Jahren 2011 und 2012 durchgeführte Forschungs- und Entwicklungsprojekt „Gesunde Kommune – Sport und Bewegung als Faktor der Stadt- und Raumentwicklung“ mit der Bedeutung von Sport und Bewegung für die rheinland-pfälzischen Kommunen und verfolgt das Ziel, Verknüpfungen zwischen räumlichen und sportlichen Entwicklungsfeldern zu erschließen sowie Möglichkeiten zur gezielten Nutzung von Sport und Bewegung für die nachhaltige Raumentwicklung aufzuzeigen. Die raumwirksamen Leistungen von Sport und Bewegung werden hierbei unter den Aspekten Gesundheit, Ökonomie, Ökologie und Soziales betrachtet. Ein wesentliches Projektziel bildete darüber hinausgehend die Bewusstseinsbildung und Sensibilisierung aller relevanten Akteure auf Landes- und Kommunalebene. Das Projekt wurde Erarbeitet durch den Lehrstuhl Stadtplanung der TU Kaiserslautern in Kooperation mit dem Fachgebiet Sportwissenschaft der TU Kaiserslautern im Auftrag der Entwicklungsagentur Rheinland-Pfalz e.V..Gerhard Steinebach; Arne Güllich; Henning Stepper; Lukas Esper; Dirk Jung; Andreas Kühn; Cordula Uhligreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3594Mon, 19 Aug 2013 10:35:52 +0200Gesunde Kommune - Sport und Bewegung als Faktor der Stadt- und Raumentwicklung - Abschlussbericht 2012
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3426
Sport und Bewegung sind seit jeher wesentliche Bestandteile des öffentlichen Lebens. Der in den letzten Jahren erkennbare und sich weiter verstärkende demographische und gesellschaftliche Wandel führt allerdings zu einer Veränderung des Sport- und Bewegungsverhaltens und damit auch der Nachfrage nach Sportstätten und Bewegungsräumen. Die sich zunehmend verändernde Situation von Sport und Bewegung findet bislang weder auf der politischen Ebene noch auf der Ebene der kommunalen Planung ausreichend Berücksichtigung. Vor dem Hintergrund stetig steigender Bedarfe zur Sicherung der kommunalen Daseinsvorsorge müssen jedoch zeitnah Lösungen gefunden werden, die den veränderten Rahmenbedingungen auch zukünftig gerecht werden. Ausgehend hiervon befasst sich das in den Jahren 2011 und 2012 durchgeführte Forschungs- und Entwicklungsprojekt „Gesunde Kommune – Sport und Bewegung als Faktor der Stadt- und Raumentwicklung“ mit der Bedeutung von Sport und Bewegung für die rheinland-pfälzischen Kommunen und verfolgt das Ziel, Verknüpfungen zwischen räumlichen und sportlichen Entwicklungsfeldern zu erschließen sowie Möglichkeiten zur gezielten Nutzung von Sport und Bewegung für die nachhaltige Raumentwicklung aufzuzeigen. Die raumwirksamen Leistungen von Sport und Bewegung werden hierbei unter den Aspekten Gesundheit, Ökonomie, Ökologie und Soziales betrachtet. Ein wesentliches Projektziel bildete darüber hinausgehend die Bewusstseinsbildung und Sensibilisierung aller relevanten Akteure auf Landes- und Kommunalebene. Das Projekt wurde Erarbeitet durch den Lehrstuhl Stadtplanung der TU Kaiserslautern in Kooperation mit dem Fachgebiet Sportwissenschaft der TU Kaiserslautern im Auftrag der Entwicklungsagentur Rheinland-Pfalz e.V.. Die Dokumentation und Veröffentlichung erfolgte sowohl im Rahmen eines Projektberichts 2011 sowie eines Abschlussberichts 2012.Gerhard Steinebach; Arne Güllich; Henning Stepper; Lukas Esper; Dirk Jung; Andreas Kühn; Cordula Uhligreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3426Fri, 15 Feb 2013 10:13:23 +0100Construction of discrete shell models by geometric finite differences
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3322
In the presented work, we make use of the strong reciprocity between kinematics and geometry to build a geometrically nonlinear, shearable low order discrete shell model of Cosserat type defined on triangular meshes, from which we deduce a rotation–free Kirchhoff type model with the triangle vertex positions as degrees of freedom. Both models behave physically plausible already on very coarse meshes, and show good
convergence properties on regular meshes. Moreover, from the theoretical side, this deduction provides a
common geometric framework for several existing models.C. Weischedel; A. Tuganov; T. Hermansson; J. Linn; M. Wardetzkyreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3322Thu, 11 Oct 2012 16:59:06 +0200Integration of nonlinear models of flexible body deformation in Multibody System Dynamics
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3321
A simple transformation of the Equation of Motion (EoM) allows us to directly integrate nonlinear structural models into the recursive Multibody System (MBS) formalism of SIMPACK. This contribution describes how the integration is performed for a discrete Cosserat rod model which has been developed at the ITWM. As a practical example, the run-up of a simplified three-bladed wind turbine is studied where the dynamic deformations of the three blades are calculated by the Cosserat rod model.Martin Schulze; Stefan Dietz; Andrey Tuganov; Joachim Linn; Holger Langreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3321Thu, 11 Oct 2012 16:58:40 +0200Geometrically exact Cosserat rods with Kelvin-Voigt type viscous damping
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3320
We present the derivation of a simple viscous damping model of Kelvin–Voigt type for geometrically exact
Cosserat rods from three–dimensional continuum theory. Assuming a homogeneous and isotropic material,
we obtain explicit formulas for the damping parameters of the model in terms of the well known stiffness
parameters of the rod and the retardation time constants defined as the ratios of bulk and shear viscosities to
the respective elastic moduli. We briefly discuss the range of validity of our damping model and illustrate
its behaviour with a numerical example.J. Linn; H. Lang; A. Tuganovreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3320Thu, 11 Oct 2012 16:58:20 +0200Multi-level Monte Carlo methods using ensemble level mixed MsFEM for two-phase flow and transport simulations
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3319
In this paper, we propose multi-level Monte Carlo(MLMC) methods that use ensemble level mixed multiscale methods in the simulations of multi-phase flow and transport. The main idea of ensemble level multiscale methods is to construct local multiscale basis functions that can be used for any member of the ensemble. We consider two types of ensemble level mixed multiscale finite element methods, (1) the no-local-solve-online ensemble level method (NLSO) and (2) the local-solve-online ensemble level method (LSO). Both mixed multiscale methods use a number of snapshots of the permeability media to generate a multiscale basis.
As a result, in the offline stage, we construct multiple basis functions for
each coarse region where basis functions correspond to different realizations.
In the no-local-solve-online ensemble level method one uses the whole set of pre-computed basis functions to approximate the solution for an arbitrary realization. In the local-solve-online ensemble level method one uses the pre-computed functions to construct a multiscale basis for a particular realization. With this basis the solution corresponding to this
particular realization is approximated in LSO mixed MsFEM. In both approaches
the accuracy of the method is related to the number of snapshots computed based on different realizations that one uses to pre-compute a
multiscale basis. We note that LSO approaches share similarities with reduced basis methods [11, 21, 22].
In multi-level Monte Carlo methods ([14, 13]), more accurate (and expensive) forward simulations are run with fewer samples while less accurate(and inexpensive) forward simulations are run with a larger number of samples. Selecting the number of expensive and inexpensive simulations carefully, one can show that MLMC methods can provide better accuracy
at the same cost as MC methods. In our simulations, our goal is twofold. First, we would like to compare NLSO and LSO mixed MsFEMs. In particular, we show that NLSO
mixed MsFEM is more accurate compared to LSO mixed MsFEM. Further, we use both approaches in the context of MLMC to speed-up MC
calculations. We present basic aspects of the algorithm and numerical
results for coupled flow and transport in heterogeneous porous media.Y. Efendiev; O. Iliev; C. Kronsbeinreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3319Thu, 11 Oct 2012 14:20:02 +0200A direction splitting approach for incompressible Brinkmann flow
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3318
The direction splitting approach proposed earlier in [6], aiming at the efficient solution of Navier-Stokes equations, is extended and adopted here to solve the Navier-Stokes-Brinkman equations describing incompressible flows in plain and in porous media. The resulting pressure equation is a perturbation of the
incompressibility constrained using a direction-wise factorized operator as proposed in [6]. We prove that this approach is unconditionally stable for the unsteady Navier-Stokes-Brinkman problem. We also provide numerical illustrations of the method's accuracy and efficiency.T. Gornak; J. L. Guermond; O. Iliev; P. D. Minevreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3318Thu, 11 Oct 2012 14:16:40 +0200Deklarative Spezifikation von Datentransformationen
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3175
Deklarative Spezifikation von Datentransformationen.Mathias Weberreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3175Fri, 15 Jun 2012 13:19:56 +0200Statistical RNA Secondary Structure Sampling Based on a Length-Dependent SCFG Model
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3152
One of the fundamental problems in computational structural biology is the prediction of RNA secondary structures from a single sequence. To solve this problem, mainly two different approaches have been used over the past decades: the free energy minimization (MFE) approach which is still considered the most popular and successful method and the competing stochastic context-free grammar (SCFG) approach. While the accuracy of the MFE based algorithms is limited by the quality of underlying thermodynamic models, the SCFG method abstracts from free energies and instead tries to learn about the structural behavior of the molecules by training the grammars on known real RNA structures, making it highly dependent on the availability of a rich high quality training set. However, due to the respective problems associated with both methods, new statistics based approaches towards RNA structure prediction have become increasingly appreciated. For instance, over the last years, several statistical sampling methods and clustering techniques have been invented that are based on the computation of partition functions (PFs) and base pair probabilities according to thermodynamic models. A corresponding SCFG based statistical sampling algorithm for RNA secondary structures has been studied just recently. Notably, this probabilistic method is capable of producing accurate (prediction) results, where its worst-case time and space requirements are equal to those of common RNA folding algorithms for single sequences.
The aim of this work is to present a comprehensive study on how enriching the underlying SCFG by additional information on the lengths of generated substructures (i.e. by incorporating length-dependencies into the SCFG based sampling algorithm, which is actually possible without significant losses in performance) affects the reliability of the induced RNA model and the accuracy of sampled secondary structures. As we will see, significant differences with respect to the overall quality of generated sample sets and the resulting predictive accuracy are typically implied. In principle, when considering the more specialized length-dependent SCFG model as basis for statistical sampling, a higher accuracy of predicted foldings can be reached at the price of a lower diversity of generated candidate structures (compared to the more general traditional SCFG variant or sampling based on PFs that rely on free energies).Markus E. Nebel; Anika Scheidreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/3152Mon, 21 May 2012 19:19:25 +0200Constitutive models for static granular systems and focus to the Jiang-Liu hyperelastic law
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2991
Granular systems in solid-like state exhibit properties like stiffness
dependence on stress, dilatancy, yield or incremental non-linearity
that can be described within the continuum mechanical framework.
Different constitutive models have been proposed in the literature either based on relations between some components of the stress tensor or on a quasi-elastic description. After a brief description of these
models, the hyperelastic law recently proposed by Jiang and Liu [1]
will be investigated. In this framework, the stress-strain relation is
derived from an elastic strain energy density where the stable proper-
ties are linked to a Drucker-Prager yield criteria. Further, a numerical method based on the finite element discretization and Newton-
Raphson iterations is presented to solve the force balance equation.
The 2D numerical examples presented in this work show that the stress
distributions can be computed not only for triangular domains, as previoulsy done in the literature, but also for more complex geometries.
If the slope of the heap is greater than a critical value, numerical instabilities appear and no elastic solution can be found, as predicted by
the theory. As main result, the dependence of the material parameter
Xi on the maximum angle of repose is established.Clement Zemerli; Arnulf Latz; Heiko Andräreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2991Thu, 19 Apr 2012 07:49:55 +0200An overview on the usage of some model reduction approaches for simulations of Li-ion transport in batteries
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2990
In this work, some model reduction approaches for performing simulations
with a pseudo-2D model of Li-ion battery are presented. A full pseudo-2D model of processes in Li-ion batteries is presented following
[3], and three methods to reduce the order of the full model are considered. These are: i) directly reduce the model order using proper
orthogonal decomposition, ii) using fractional time step discretization in order to solve the equations in decoupled way, and iii) reformulation
approaches for the diffusion in the solid phase. Combinations of above
methods are also considered. Results from numerical simulations are presented, and the efficiency and the accuracy of the model reduction approaches are discussed.O. Iliev; A. Latz; J. Zausch; S. Zhangreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2990Thu, 19 Apr 2012 07:47:12 +0200Residual Demand Modeling and Application to Electricity Pricing
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2989
Worldwide the installed capacity of renewable technologies for electricity production is
rising tremendously. The German market is particularly progressive and its regulatory
rules imply that production from renewables is decoupled from market prices and electricity
demand. Conventional generation technologies are to cover the residual demand
(defined as total demand minus production from renewables) but set the price at the
exchange. Existing electricity price models do not account for the new risks introduced
by the volatile production of renewables and their effects on the conventional demand
curve. A model for residual demand is proposed, which is used as an extension of
supply/demand electricity price models to account for renewable infeed in the market.
Infeed from wind and solar (photovoltaics) is modeled explicitly and withdrawn from
total demand. The methodology separates the impact of weather and capacity. Efficiency
is transformed on the real line using the logit-transformation and modeled as a stochastic process. Installed capacity is assumed a deterministic function of time. In a case study the residual demand model is applied to the German day-ahead market
using a supply/demand model with a deterministic supply-side representation. Price trajectories are simulated and the results are compared to market future and option
prices. The trajectories show typical features seen in market prices in recent years and the model is able to closely reproduce the structure and magnitude of market prices.
Using the simulated prices it is found that renewable infeed increases the volatility of forward prices in times of low demand, but can reduce volatility in peak hours. Prices
for different scenarios of installed wind and solar capacity are compared and the meritorder effect of increased wind and solar capacity is calculated. It is found that wind
has a stronger overall effect than solar, but both are even in peak hours.Andreas Wagnerreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2989Thu, 19 Apr 2012 07:44:01 +0200Multiscale Finite Element Coarse Spaces for the Analysis of Linear Elastic Composites
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2988
In this work we extend the multiscale finite element method (MsFEM)
as formulated by Hou and Wu in [14] to the PDE system of linear elasticity.
The application, motivated from the multiscale analysis of highly heterogeneous
composite materials, is twofold. Resolving the heterogeneities on
the finest scale, we utilize the linear MsFEM basis for the construction of
robust coarse spaces in the context of two-level overlapping Domain Decomposition
preconditioners. We motivate and explain the construction
and present numerical results validating the approach. Under the assumption
that the material jumps are isolated, that is they occur only in the
interior of the coarse grid elements, our experiments show uniform convergence
rates independent of the contrast in the Young's modulus within the
heterogeneous material. Elsewise, if no restrictions on the position of the
high coefficient inclusions are imposed, robustness can not be guaranteed
any more. These results justify expectations to obtain coefficient-explicit
condition number bounds for the PDE system of linear elasticity similar to
existing ones for scalar elliptic PDEs as given in the work of Graham, Lechner
and Scheichl [12]. Furthermore, we numerically observe the properties
of the MsFEM coarse space for linear elasticity in an upscaling framework.
Therefore, we present experimental results showing the approximation errors
of the multiscale coarse space w.r.t. the fine-scale solution.M. Buck; O. Iliev; H. Andräreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2988Thu, 19 Apr 2012 07:42:13 +0200A Two-Dimensional Model of the Pressing Section of a Paper Machine Including Dynamic Capillary Effects
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2987
The paper production is a problem with significant importance for the society
and it is a challenging topic for scientific investigations. This study is concerned
with the simulations of the pressing section of a paper machine. A two-dimensional
model is developed to account for the water flow within the pressing zone. Richards’
type equation is used to describe the flow in the unsaturated zone. The dynamic capillary
pressure–saturation relation proposed by Hassanizadeh and co-workers (Hassanizadeh
et al., 2002; Hassanizadeh, Gray, 1990, 1993a) is adopted for the paper
production process.
The mathematical model accounts for the co-existence of saturated and unsaturated
zones in a multilayer computational domain. The discretization is performed
by the MPFA-O method. The numerical experiments are carried out for parameters
which are typical for the production process. The static and dynamic capillary
pressure–saturation relations are tested to evaluate the influence of the dynamic
capillary effect.O. Iliev; G. Printsypar; S. Riefreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2987Thu, 19 Apr 2012 07:39:47 +0200Multibody dynamics simulation of geometrically exact Cosserat rods
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2985
In this paper, we present a viscoelastic rod model that is suitable for fast and accurate dynamic simulations. It is based on Cosserat’s geometrically exact theory of rods and is able to represent extension, shearing (‘stiff’ dof), bending and torsion (‘soft’ dof). For inner dissipation, a consistent damping potential proposed by Antman is chosen. We parametrise the rotational dof by unit quaternions and directly use the quaternionic evolution differential equation for the discretisation of the Cosserat rod curvature. The discrete version of our rod model is obtained via a finite difference discretisation on a staggered grid. After an index reduction from three to zero, the right-hand side function f and the Jacobian \(\partial f/\partial(q, v, t)\) of the dynamical system \(\dot{q} = v, \dot{v} = f(q, v, t)\) is free of higher algebraic (e. g. root) or transcendental (e. g. trigonometric or exponential) functions and therefore cheap to evaluate. A comparison with Abaqus finite element results demonstrates the correct mechanical behavior of our discrete rod model. For the time integration of the system, we use well established stiff solvers like RADAU5 or DASPK. As our model yields computational times within milliseconds, it is suitable for interactive applications in ‘virtual reality’ as well as for multibody dynamics simulation.Holger Lang; Joachim Linn; Martin Arnoldreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2985Thu, 19 Apr 2012 07:33:08 +0200On convergence of a discrete problem describing transport processes in the pressing section of a paper machine including dynamic capillary effects: one-dimensional case
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2986
This work presents a proof of convergence of a discrete solution to a continuous one. At first, the continuous problem is stated as a system
of equations which describe filtration process in the pressing section of a
paper machine. Two flow regimes appear in the modeling of this problem.
The model for the saturated flow is presented by the Darcy’s law and the mass conservation. The second regime is described by the Richards approach together with a dynamic capillary pressure model. The finite
volume method is used to approximate the system of PDEs. Then the existence of a discrete solution to proposed finite difference scheme is proven.
Compactness of the set of all discrete solutions for different mesh sizes is
proven. The main Theorem shows that the discrete solution converges
to the solution of continuous problem. At the end we present numerical
studies for the rate of convergence.G. Printsypar; R. Ciegisreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2986Wed, 18 Apr 2012 18:00:37 +0200Structure and pressure drop of real and virtual metal wire meshes
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2978
An efficient mathematical model to virtually generate woven metal wire meshes is
presented. The accuracy of this model is verified by the comparison of virtual structures with three-dimensional
images of real meshes, which are produced via computer tomography. Virtual structures
are generated for three types of metal wire meshes using only easy to measure parameters. For these
geometries the velocity-dependent pressure drop is simulated and compared with measurements
performed by the GKD - Gebr. Kufferath AG. The simulation results lie within the tolerances of
the measurements. The generation of the structures and the numerical simulations were done at
GKD using the Fraunhofer GeoDict software.M. Knefel; E. Wegenke; A. Wiegmann; S. Rief; E. Glattreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2978Wed, 18 Apr 2012 17:52:59 +0200Geometric characterization of particles in 3d with an application to technical cleanliness
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2983
Continuously improving imaging technologies allow to capture the complex spatial
geometry of particles. Consequently, methods to characterize their three
dimensional shapes must become more sophisticated, too. Our contribution to
the geometric analysis of particles based on 3d image data is to unambiguously
generalize size and shape descriptors used in 2d particle analysis to the spatial
setting.
While being defined and meaningful for arbitrary particles, the characteristics
were actually selected motivated by the application to technical cleanliness. Residual
dirt particles can seriously harm mechanical components in vehicles, machines,
or medical instruments. 3d geometric characterization based on micro-computed
tomography allows to detect dangerous particles reliably and with
high throughput. It thus enables intervention within the production line. Analogously
to the commonly agreed standards for the two dimensional case, we
show how to classify 3d particles as granules, chips and fibers on the basis of
the chosen characteristics. The application to 3d image data of dirt particles is
demonstrated.Irene Vecchio; Katja Schladitz; Michael Godehardt; Markus J. Henekareporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2983Wed, 18 Apr 2012 17:45:02 +0200Invariant input loads for full vehicle multibody system simulation
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2984
Input loads are essential for the numerical simulation of vehicle multibody system
(MBS)- models. Such load data is called invariant, if it is independent of the specific system under consideration. A digital road profile, e.g., can be used to excite MBS models of different
vehicle variants. However, quantities efficiently obtained by measurement such as wheel forces
are typically not invariant in this sense. This leads to the general task to derive invariant loads
on the basis of measurable, but system-dependent quantities. We present an approach to derive
input data for full-vehicle simulation that can be used to simulate different variants of a vehicle
MBS model. An important ingredient of this input data is a virtual road profile computed by optimal control methods.Michael Burger; Klaus Dreßler; Michael Speckertreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2984Wed, 18 Apr 2012 17:43:03 +0200Translating SHIM to Guarded Actions
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2881
SHIM is a concurrent deterministic programming language for embedded systems built on rendezvous communication. It abstracts away many details to give the developer a high-level view that includes virtual shared variables, threads as orthogonal statements, and deterministic concurrent exceptions.
In this paper, we present a new way to compile a SHIM-like language into a set of asynchronous guarded actions, a well-established intermediate representation for concurrent systems. By doing so, we build a bridge to many other tools, including hardware synthesis and formal verification. We present our translation in detail, illustrate it through examples, and show how the result can be used by various other tools.Jens Brandt; Klaus Schneiderreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2881Tue, 14 Feb 2012 02:51:56 +0000AmICA - Design and implementation of a flexible, compact, and low-power node platform
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2807
Wireless sensor networks are the driving force behind many popular and interdisciplinary research areas, such as environmental monitoring, building automation, healthcare and assisted living applications. Requirements like compactness, high integration of sensors, flexibility, and power efficiency are often very different and cannot be fulfilled by state-of-the-art node platforms at once. In this paper, we present and analyze AmICA: a flexible, compact, easy-to-program, and low-power node platform. Developed from scratch and including a node, a basic communication protocol, and a debugging toolkit, it assists in an user-friendly rapid application development. The general purpose nature of AmICA was evaluated in two practical applications with diametric requirements. Our analysis shows that AmICA nodes are 67% smaller than BTnodes, have five times more sensors than Mica2Dot and consume 72% less energy than the state-of-the-art TelosB mote in sleep mode.Sebastian Wille; Norbert Wehn; Ivan Martinovic; Simon Kunz; Peter Göhnerreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2807Thu, 24 Nov 2011 07:23:55 +0000An online approach to detecting changes in nonlinear autoregressive models
https://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2772
In this paper we develop monitoring schemes for detecting structural changes
in nonlinear autoregressive models. We approximate the regression function by a
single layer feedforward neural network. We show that CUSUM-type tests based
on cumulative sums of estimated residuals, that have been intensively studied
for linear regression in both an offline as well as online setting, can be extended
to this model. The proposed monitoring schemes reject (asymptotically) the null
hypothesis only with a given probability but will detect a large class of alternatives
with probability one. In order to construct these sequential size tests the limit
distribution under the null hypothesis is obtained.Claudia Kirch; Joseph Tadjuidje Kamgaingreporthttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/2772Mon, 24 Oct 2011 10:46:14 +0000