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See detailA Simplified Approach to Computing Efficiency Bounds in Semiparametric Models
Severini, Thomas A.; Tripathi, Gautam UL

in Journal of Econometrics (2001), 102

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See detailSimplified density indexes of walls and tie-columns for confined masonry buildings in seismic zones
Cai, Gaochuang UL; Su, Q.W; Tsavdaridis, K.D. et al

in Journal of Earthquake Engineering (2017)

This paper discusses and quantifies the minimum requirements of walls and tie-columns in confined masonry (CM) buildings located in earthquake-prone regions. A research database including 238 damaged CM ... [more ▼]

This paper discusses and quantifies the minimum requirements of walls and tie-columns in confined masonry (CM) buildings located in earthquake-prone regions. A research database including 238 damaged CM buildings obtained from the 2008 Wenchuan earthquake survey is established and comprehensively examined. The requirements of masonry walls in CM buildings are discussed, and a simplified tie-column density index is proposed for evaluating the potential damage of the structures. Besides, the minimum requirements of reinforced concrete tie-columns and their maximum allowable spacing in CM buildings at different seismic intensity zones are discussed. [less ▲]

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See detailSimplified formation process for Cu2ZnSnS4-based solar cells
Berg, Dominik UL; Crossay, Alexandre UL; Guillot, Jérôme et al

in Thin Solid Films (2014), 573

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See detailSimplified Reducibility Proofs of Church-Rosser for beta- and beta-eta-reduction
Kamareddine, Fairouz; Rahli, Vincent UL

in Electronic Notes in Theoretical Computer Science (2009), 247

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See detailSimulación Numérica de la Combustión en Lecho Estacionario
Peters, Bernhard UL

in Ingenieria Quimica -Madrid- (2000), 366

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See detailSimulated and experimental results on heat recovery from hot steel beams in a cooling bed applying modified solar absorbers
Tarrés Font, Joana UL; Maas, Stefan UL; Scholzen, Frank UL et al

in Journal of Cleaner Production (2014), (68), 261-271

In recent years, the steel industry has undertaken efforts to increase energy efficiency by reducing energy consumption and recover otherwise lost heat. About 60% of the energy consumed in a steel plant ... [more ▼]

In recent years, the steel industry has undertaken efforts to increase energy efficiency by reducing energy consumption and recover otherwise lost heat. About 60% of the energy consumed in a steel plant is lost in cooling beds where the hot steel beams are cooled down by natural convection and radiation. In this paper, the potential of heat recovery by radiation in a cooling bed was determined. Firstly, numerical simulations of the heat flux were done and validated with experimental measures. Secondly, a pilot test to recover the heat with modified solar absorbers was installed at the side of the cooling bed. The standard solar panels were painted with high absorption paint in the wavelength range of the hot beams. The results showed that up to 1 kW/m2 could be recovered with a temperature of 70°C at the side of the cooling bed, with a thermal efficiency of approximately 40%. As the experimental results were promising, further research is suggested to find an adequate selective coating and glazing. This would maximize the absorption at the wavelength range of the hot beams and minimize the emissivity at operational temperature of the absorber (100°C). Additionally, it would be of interest to find the optimum position for the absorbers in the cooling bed, which maximizes the heat recovery and does not interfere in the production process. [less ▲]

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See detailSimulating Communication Processes in Energy-Efficient Cloud Computing Systems
Kliazovich, Dzmitry UL; Bouvry, Pascal UL; Khan, Samee Ullah

in CLOUDNET (2012)

Cloud computing data centers are becoming increasingly popular for the provisioning of computing resources. The cost and operating expenses of data centers have skyrocketed with the increase in computing ... [more ▼]

Cloud computing data centers are becoming increasingly popular for the provisioning of computing resources. The cost and operating expenses of data centers have skyrocketed with the increase in computing capacity. In this chapter, we survey the main techniques behind enabling energy efficiency in data centers and present simulation environment for energy-aware cloud computing. Along with the workload distribution, the focus is devoted to simulating packet-level communications in realistic setups. Finally, the effectiveness of common power management solutions is assessed and a scheduling methodology that combines energy efficiency and network awareness is presented. [less ▲]

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See detailSimulating Multi-graph Transformations Using Simple Graphs
Hermann, Frank UL; Kastenberg, Harmen; Boneva, Iovka et al

in Workshop on Graph Transformation and Visual Modelling Techniques (GT-VMT'07) (2007)

Application of graph transformations for software verification and model transformation is an emergent field of research. In particular graph transformation approaches provide a natural way of modelling ... [more ▼]

Application of graph transformations for software verification and model transformation is an emergent field of research. In particular graph transformation approaches provide a natural way of modelling object oriented systems and semantics of object-oriented languages. There exist a number of tools for graph transformations that are often specialised in a particular kind of graphs and/or graph transformation approaches, depending on the desired application domain. The main drawback of this diversity is the lack of interoperability. In this paper we show how (typed) multigraph production systems can be translated into (typed) simple-graph production systems. The presented construction enables the use of multigraphs with DPO transformation approach in tools that only support simple graphs with SPO transformation approach e.g. the GROOVE tool. [less ▲]

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See detailSimulating Realistic Mobility Models for Large Heterogeneous MANETs
Hogie, Luc UL; Bouvry, Pascal UL; Guinand, Frédéric et al

in 9th ACM/IEEE International Symposium on Modeling, Analysis and Simulation of Wireless and Mobile Systems (MSWIM'06) (2006)

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See detailSimulating topological changes in real time for surgical assistance
Bordas, Stéphane UL; Kerfriden, Pierre; Courtecuisse, Hadrien et al

Speeches/Talks (2016)

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See detailSimulation and computer-assisted analysis of actin cytoskeleton dynamics in living cells using fluorescence microscopy methods
Halavatyi, Aliaksandr UL

Doctoral thesis (2012)

Controlled in time and space by a variety of actin-binding proteins, assembly and disassembly of the actin cytoskeleton is involved in many biological and biophysical phenomena. In order to understand the ... [more ▼]

Controlled in time and space by a variety of actin-binding proteins, assembly and disassembly of the actin cytoskeleton is involved in many biological and biophysical phenomena. In order to understand the dynamics of such a complex intracellular system quantitative time-lapse imaging approaches are required. This thesis presents the results of the interdisciplinary project aimed at the quantitative evaluation of the effects of actin-binding proteins on actin turnover under physiological conditions. It combines fluorescence microscopy experiments, development of mathematical models and data processing tools to understand how regulatory proteins control actin dynamics. Confocal-microscopy-based Fluorescence Recovery After Photobleaching (FRAP) technique is a major experimental tool to measure the exchange of actin and actin-binding proteins between polymerised and monomeric pools. The developed models and computational algorithms allow to predict actin dynamics depending on regulatory proteins and to connect the experimental data to parameters characterising polymerisation dynamics, length and structures of actin filaments and activities of tested regulatory proteins. To test the models and to evaluate the activities of actin binding proteins without cellular constrains I combined quantitative FRAP analysis with a biomimetic assay which allows to reproduce major features of actin motility. This combination of techniques was utilised to measure the influence of previously characterised actin-binding proteins working together on actin dynamics in a concentration-dependent manner. In particular we investigated how capping and severing of actin filaments influences actin exchange in a bulk meshwork generated from spatially restricted nucleation. The experimental and analysis methods I developed were also used to investigate the dynamics of the actin cytoskeleton at focal adhesions of living cells. Taking as an example the focal adhesion protein zyxin and its binding partner Tes we addressed how the interactions of these proteins with actin regulate cytoskeleton dynamics. Taken together, the developed approaches and collected data help to better understand how regulatory proteins control actin dynamics in living cells. [less ▲]

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See detailSimulation and Performance Analysis of Data Intensive and Workload Intensive Cloud Computing Data Centers
Kliazovich, Dzmitry UL; Bouvry, Pascal UL; Khan, Sameeullah

in Kachris, Christoforos; Bergman, Keren; Tomkos, Ioannis (Eds.) Optical Interconnects for Future Data Center Networks (2013)

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See detailSimulation der aktiven Schwingungskontrolle von Fluid-Struktur Wechselwirkung durch piezoelektrische Materialien
Sun, Peng; Dinkler, Dieter; Zilian, Andreas UL

in PAMM (2008), 8(1), 10529--10530

Ein numerisches Modell zur aktiven Kontrolle des dynamischen Verhaltens von Tragwerken unter transienter Windeinwirkung wird vorgestellt. Auf der Oberschicht passiver Tragstrukturen werden ... [more ▼]

Ein numerisches Modell zur aktiven Kontrolle des dynamischen Verhaltens von Tragwerken unter transienter Windeinwirkung wird vorgestellt. Auf der Oberschicht passiver Tragstrukturen werden piezoelektrische Sensoren und Aktoren appliziert. Die resultierenden adaptierbaren Strukturen sind mit einem Regler gekoppelt. Die Modellierung der elektroelastischen Struktur erfolgt mit der geometrisch nichtlinearen Elastizitätstheorie und der Maxwell–Faraday–Theorie der Elektrostatik. Die Windumströmung der Struktur ist als inkompressibles, Newton'sches Fluid mit den Navier–Stokes–Gleichungen beschrieben. Die Diskretisierung der gekoppelten Modellgleichungen beider Kontinua erfolgt mit finiten Raum–Zeit–Elementen. Zeitliche Änderungen der Zustandsgrößen werden mit dem diskontinuierlichen Galerkin–Verfahren approximiert. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [less ▲]

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See detailSimulation des Traktionsverhaltens von Reifen auf granularem Untergrund durch eine Kopplung zwischen der Finiten (FEM) und der Diskreten Element Methode (DEM)
Michael, Mark UL; Peters, Bernhard UL; Vogel, Frank

in VDI-Berichte "Reifen-Fahrwerk-Fahrbahn" (2013, October)

Kurzfassung Innerhalb dieses Beitrags wird die numerische Simulationsmethode der Extended Discrete Element Methode (XDEM) vorgestellt, mit der die Wechselwirkung zwischen Reifen und steinigem Untergrund ... [more ▼]

Kurzfassung Innerhalb dieses Beitrags wird die numerische Simulationsmethode der Extended Discrete Element Methode (XDEM) vorgestellt, mit der die Wechselwirkung zwischen Reifen und steinigem Untergrund detailliert beschrieben werden kann. Dabei wird der Reifen als ein Kontinuum betrachtet, das mit der Finiten Element Methode (FEM) abgebildet wird. Der grobkörnige Untergrund, wie beispielsweise Sand oder Kies, wird als granulares Medium betrachtet. Dieses kann sehr vorteilhaft mit der Diskreten Element Methode (DEM) behandelt werden, die eine Betrachtung der individuellen Partikel zulässt. Basierend auf den Gesetzen von Newton werden Position und Orientierung aller Partikel berechnet, wobei Kräfte zwischen den Partikeln und dem Reifen berücksichtigt werden. Kräfte zwischen Partikeln und Reifen treten als Randbedingungen in der FEM Struktur des Reifens auf, und führen damit zur Deformation und somit zu Spannungverteilung in der Reifenstrucktur. Eine Integration in der Zeit bestimmt sowohl den Zustand des Untergrunds als auch die Reaktion des Reifens. Dies wird durch eine innovative Kopplung zwischen der Discrete Particle Method (DPM) zur Beschreibung des granularen Mediums und dem Finite Element Löser DiffPACK erreicht und deshalb als Extended Discrete Element Methode bezeichnet wird. Beides sind objekt- orientierte Software-Werkzeuge, die über eine Schnittstelle die notwendigen Daten austauschen, so dass der Anwender sein Augenmerk auf die Problemlösung richten kann als sich mit Datenaustausch und Algorithmen zu befassen. Damit wurde ein vielseitiges und flexibles Werkzeug zur Lösung vielfältiger Probleme wie auch die Bewegung eines Reifens im Schnee geschaffen. Das neuartige Konzept ist sowohl auf Windows als auch auf UNIX basierenden Betriebssystemen verfügbar. Abstract The objective of this contribution is to resolve different length scales in structure analysis by an interface coupling the Discrete Element Method (DEM) with the Finite Element Method (FEM) and therefore, is labelled Extended Discrete Element Methode (XDEM). This approach distinguishes itself from other methods in so far that no overlapping domains between Finite and Discrete Elements exist. Both domains are separated in physical space and numerical simulation domain. The proposed approach is relevant to almost all engineering applications that deal with granular matter such as storage in hoppers, transport on conveyor belts or displacement of granular material as in mixers or excavation of soil. For these applications an engineering device such as mixer blades or cutting tools are in contact with granular matter. Contacts with individual particles generate contact forces that act on both the engineering device and the granular material. The latter experiences a displacement of individual particles whereby the engineering structure responds with deformation and stresses. In order to predict and optimize both the behaviour and motion of granular material and the structures in contact, numerical simulation tools are increasingly employed [1]. Simulations are popular especially because experiments which are often expensive, time- consuming and sometimes even dangerous [2]. The continuous increase in computing power is now enabling researchers to implement numerical methods that do not focus on the granular assembly as an entity, but rather deduce its global characteristics from observing the individual behaviour of each grain. An interaction between granular media and a structure relies on a transfer of forces between them. Granular media consists of an ensemble of particles of which a number of particles may be in contact with a surface e.g. walls as surfaces of solid structures. The contact is resolved similar to inter-particle contacts by a representative overlap. It defines the position of impact as well as the force acting on the particle at this position. The same force, however, into the opposite direction defines a mechanical load for the structure. In order to determine the effect of forces on the solid structure, it is discretised by finite elements. The impact of the force is transferred to the nodes of the respective surface element and appears as a load for the finite element system. Hence, integrating particle dynamics and the response of the solid structure due to particle impacts advances both new position of particles and corresponding deformation and stress of the solid structure in time. Developing flexible software which is capable of performing simulation in different applications will enable the engineers to focus entirely on their specific problem and hence save them valuable time. This concept is supported by the software tools of the Discrete Particle Method (DPM) and Diffpack. Hence, the solid structure is analysed by the Finite Element Method under load due to the impact of individual particles that changes both in time and space. For this purpose traditional formulations of the Finite Element Method are employed that are available by the commercial multi-physics software package Diffpack. It represents object-oriented hierarchy of classes that provide an excellent interface to introduce external loads from particle impact onto the finite element structure. Diffpack is an object-oriented development environment, which comes as a rich set of C++ classes, for the numerical modelling and solution of arbitrary differential equations. User applications cover a wider range of engineering areas and span from simple educational applications to major product development projects. The behaviour of granular material is represented by the advanced software package of the Discrete Particle Method (DPM), which is based on the Discrete Element Method. It is designed to relieve users from underlying mathematics and software design and allows them to focus on physics and their applications. The software uses object oriented techniques that support objects representing three-dimensional particles of various shapes such as cylinders, discs or tetrahedrons for example, size and material properties. This makes it a highly versatile tool dealing with a large variety of different applications of granular matter arising in the automotive industry, such as road tire interaction. Various force models for the inter- particle and particle-wall contacts are also available. A minimal user interface easily allows extending the software further by adding user-defined impact models or material properties to an already available selection of materials and properties. Thus, the user is relieved of the underlying mathematics or software design, and therefore, is able to direct his focus entirely onto the application. The Discrete Particle Method is written in C++ programming language and works both in Linux and Windows environments. [less ▲]

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See detailSimulation of Shear Deformable Plates using Meshless Maximum Entropy Basis Functions
Hale, Jack UL; Baiz, P. M.

Scientific Conference (2011, June)

First-order Shear Deformable Plate Theory (FSDT) is widely used throughout engineering practice to simulate structures with planar dimensions much larger than their thickness. Meshless methods have seen ... [more ▼]

First-order Shear Deformable Plate Theory (FSDT) is widely used throughout engineering practice to simulate structures with planar dimensions much larger than their thickness. Meshless methods have seen use in the literature as a method for discretising the FSDT equations and hold numerous advantages over traditional mesh based techniques. A recent advance in the area of meshless methods are Maximum Entropy approximants (MaxEnt). MaxEnt combines many properties of various prior meshless approximants such as a weak Kronecker-delta property, seamless blending with Delaunay triangulations, high continuity, and convexity. In this work MaxEnt along with other meshless approximants have been implemented in a hybrid object-oriented Python/C++/Fortran computer simulation for the simulation of static deflection, free vibration and linear buckling of FSDT plates. The relative performance and ease of implementation of each of the methods will be discussed. The causes of shear locking along with the merits of various alleviation techniques will be covered, including matching fields method, mixed-variational formulations and construction of higher order polynomial basis via both intrinsic and extrinsic (partition of unity) methods. Convergence results show that MaxEnt provides in most cases similar and in some cases superior behaviour to MLS and RPIM approximants when used to discretise the FSDT equations. [less ▲]

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See detailSimulation of the time-variable gravity field by means of coupled geophysical models
Gruber, Th; Bamber, J. L.; Bierkens, M. F. P. et al

in Earth System Science Data (2011), 3(1), 19-35

Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by ... [more ▼]

Time variable gravity fields, reflecting variations of mass distribution in the system Earth is one of the key parameters to understand the changing Earth. Mass variations are caused either by redistribution of mass in, on or above the Earth's surface or by geophysical processes in the Earth's interior. The first set of observations of monthly variations of the Earth gravity field was provided by the US/German GRACE satellite mission beginning in 2002. This mission is still providing valuable information to the science community. However, as GRACE has outlived its expected lifetime, the geoscience community is currently seeking successor missions in order to maintain the long time series of climate change that was begun by GRACE. Several studies on science requirements and technical feasibility have been conducted in the recent years. These studies required a realistic model of the time variable gravity field in order to perform simulation studies on sensitivity of satellites and their instrumentation. This was the primary reason for the European Space Agency (ESA) to initiate a study on ''Monitoring and Modelling individual Sources of Mass Distribution and Transport in the Earth System by Means of Satellites''. The goal of this interdisciplinary study was to create as realistic as possible simulated time variable gravity fields based on coupled geophysical models, which could be used in the simulation processes in a controlled environment. For this purpose global atmosphere, ocean, continental hydrology and ice models were used. The coupling was performed by using consistent forcing throughout the models and by including water flow between the different domains of the Earth system. In addition gravity field changes due to solid Earth processes like continuous glacial isostatic adjustment (GIA) and a sudden earthquake with co-seismic and post-seismic signals were modelled. All individual model results were combined and converted to gravity field spherical harmonic series, which is the quantity commonly used to describe the Earth's global gravity field. The result of this study is a twelve-year time-series of 6-hourly time variable gravity field spherical harmonics up to degree and order 180 corresponding to a global spatial resolution of 1 degree in latitude and longitude. In this paper, we outline the input data sets and the process of combining these data sets into a coherent model of temporal gravity field changes. The resulting time series was used in some follow-on studies and is available to anybody interested. [less ▲]

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See detailSimulation of the Tractive Performance of Tire Treads on Granular Terrain by Means of Finite and Discrete Element Coupling
Michael, Mark UL; Peters, Bernhard; Vogel, Frank

Presentation (2013, October 22)

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See detailSimulation of Thermal Conversion of Solid Fuel By The Discrete Particle Method
Peters, Bernhard UL; Dzuigys, Algis; Navakas, Robertas

in Lithuanian Journal of Physics (2011)

Detailed reference viewed: 129 (12 UL)