<p>In the finite element simulation of problems with contact there arises</p><p>the need to change the mesh and continue the simulation on a new mesh.</p><p>This is encountered when the mesh has to be changed because the original mesh experiences severe distortion or the mesh is adapted to minimize errors in the solution. In such instances a crucial component is the transfer of data from the old mesh to the new one. </p><p>This work proposes a strategy by which such remeshing can be accomplished in the presence of mortar-discretized contact, </p><p>focusing in particular on the remapping of contact variables which must occur to make the method robust and efficient. </p><p>By splitting the contact stress into normal and tangential components and transferring the normal component as a scalar and the tangential component by parallel transporting on the contact surface an accurate and consistent transfer scheme is obtained. Penalty and augmented Lagrangian formulations are considered. The approach is demonstrated by a number of two and three dimensional numerical examples.</p> / Dissertation

Modern computational science permits the accurate solution of nonlinear partial differential equations (PDEs) on overlapping computational domains, known as an overset approach. The complex grid interconnectivity inherent in the overset method can introduce errors in the solution through “orphan” points, i.e., grid points for which reliable solution donor points cannot be located. For this reason, a variety of data transfer strategies based on scattered data interpolation techniques have been assessed with application to both overset and hybrid methodologies. Scattered data approaches are attractive because they are decoupled from solver type and topology, and may be readily applied within existing methodologies. In addition to standard radial basis function (RBF) interpolation, a novel steered radial basis function (SRBF) interpolation technique has been developed to introduce data adaptivity into the data transfer algorithm. All techniques were assessed by interpolating both continuous and discontinuous analytical test functions. For discontinuous functions, SRBF interpolation was able to maintain solution gradients with the steering technique being the scattered-data analog of a slope limiter. In comparison with linear mappings, the higher-order approaches were able to more accurately preserve flow physics for arbitrary grid configurations. Overset validation test cases included an inviscid convecting vortex, a shock tube, and a turbulent ship airwake. These were studied within unsteady Reynolds-Averaged Navier-Stokes (URANS) simulations to determine quantitative and qualitative improvements when applying RBF interpolation over current methods. The convecting vortex was also analyzed on a grid configuration which contained orphan points under the state-of-the-art overset paradigm. This was successfully solved by the RBF-based algorithm, which effectively eliminated orphans by enabling high-order extrapolation. Order-of-magnitude reductions in error compared to the exact vortex solution were observed. In addition, transient conservation errors that persisted in the original overset methodology were eliminated by the RBF approach. To assess the effect of advanced mapping techniques on the fidelity of a moving grid simulation, RBF interpolation was applied to a hybrid simulation of an isolated wind turbine rotor. The resulting blade pressure distributions were comparable to a rotor simulation with refined near-body grids.

<p>This dissertation addresses interface problems simulated with the finite element method (FEM) with mesh adaptivity. More specifically, we concentrate on the strategies that adaptively modify the mesh and the associated data transfer issues. </p><p>In finite element simulations there often arises the need to change the mesh and continue the simulation on a new mesh. Analysts encounter such an issue when they adaptively refine the mesh to reduce the computational cost, smooth distorted elements to improve system conditioning, or introduce new surfaces and change the domain in simulations of fracture problems. In such circumstances, the transfer of data from the old mesh to the new one is of crucial importance, especially for nonlinear problems. We are concerned in this work with contact problems with adaptive re-meshing and fracture problems modeled with the eXtended finite element method (X-FEM). For the former ones, the transfer of surface data is built upon the technique of parallel transport, and the error of such a transfer strategy is investigated through classic benchmark tests. A transfer scheme based on a least squares problem is also proposed to transfer the bulk data when nearly incompressible hyperelastic materials are employed. For the latter type of problems, we facilitate the transfer of internal variables by making partial elements utilize the same quadrature points from the uncut parent elements and meanwhile adjusting the quadrature weights via the solution of moment fitting equations. The proposed scheme helps avoid the complicated remapping procedure of internal variables between two different sets of quadrature points. A number of numerical examples are presented to demonstrate the robustness and accuracy of our proposed approaches.</p><p>Another renowned technique to simulate fracture problems is based upon the phase-field formulation, where a set of coupled mechanics and phase-field equations are solved via FEM without modeling crack geometries. However, losing the ability to model distinct surfaces in the phase-field formulation has drawbacks, such as difficulties simulating contact on crack surfaces and poorly-conditioned stiffness matrices. On the other hand, using the pure X-FEM in fracture simulations mandates the calculation of the direction and increment of crack surfaces at each step, introducing intricacies of tracing crack evolution. Thus, we propose combining phase-field and X-FEM approaches to utilize their individual benefits based on a novel medial-axis algorithm. Consequently, we can still capture complex crack geometries while having crack surfaces explicitly modeled by modifying the mesh with the X-FEM.</p> / Dissertation

In the field of communications, a high data rate and low multi-path fading is required for efficient information exchange. Orthogonal Frequency Division Multiplexing (OFDM) is a widely accepted IEEE 802.11n (and many others) standard for usage in communication systems operating in fading dispersive channels. In this thesis, we modeled the OFDM algorithm at the behavioral level in VHDL/Verilog that was successfully synthesized/verified on an FPGA. Due to rapid technology scaling, FPGAs have become popular and are low-cost and high performance alternatives to (semi-) custom ASICs. Further, due to reprogramming flexibility, FPGAs are useful in rapid prototyping. As per the IEEE standard, we implemented both transmitter and receiver with four modulation schemes (BPSK, QPSK, QAM16, and QAM64). We extensively verified the design in simulation as well as on Altera Stratix IV EP4SGX230KF40C2 FPGA (Terasic DE4 Development Board). The synthesized design ran at 100 MHz clock frequency incurring 54 µ sec. end-to-end latency and 8% logic utilization.

The main purpose of this project is to analyse used protocols in vehicles available under the OBD II specifications. In the project we will also focus on processing diagnostic data. We will design device for vehicle diagnostic. This device will be able to send processed data on external web server via Internet network. Obtained data will be saved on data server. Building of functional receiver will be the major part of master´s thesis.

This diploma thesis deals with analysis of existing solutions for collecting maintenance data and technical condition of the aircraft. Based on this analysis, it proposes a trend monitoring system based on the existing structure and data from the flight data recorder.

Tato práce je zaměřena na zpracování a analýzu USB komunikačního protokolu a implementace jeho jednotlivých částí do FPGA obvodu s využitím programovacího jazyka VHDL. Ve finální podobě by měla práce představovat souhrnný a ucelený dokument popisující principy USB rozhraní a jeho komunikace doplněných praktickým návrhem v jazyce VHDL, který by byl schopen převést data do USB.

This master thesis presents a topic of testing network address translation. It describes basic principles of network address translation and general methods for testing network devices. These methods are then applied on NAT devices. Thesis then introduces a design of a  framework for performing functional tests. The designed framework is then implemented as a part of the thesis and used to test a newly developed high-speed NAT application.

Enterprise JavaBeans (EJB) ermöglichen die Erstellung von leistungsfähigen, mehrschichtigen Client/Server-Anwendungen auf Basis der Programmiersprache Java. Eine grundlegende und wichtige Entscheidung, die häufig unterschätzt wird, ist die Art und Weise, wie Daten zwischen komplexen Java-Clients (Fat-Clients) und Servern transportiert werden sollen. Während der Implementierung kann ein fehlendes Konzept zur Übertragung von Daten dazu führen, daß Entwickler unterschiedliche Verfahren wählen, die verschiedenen Anforderungen an die Anwendung, wie z.B. ein möglichst gutes Leistungsverhalten, widersprechen und evtl. unter hohem Aufwand rückgängig zu machen sind. Verschiedene Übertragungsverfahren erschweren außerdem die Erweiterung und Wartung des Systems, da zu analysieren ist, wie in verschiedenen Fällen die Datenübertragung gelöst wird. In diesem Beitrag werden deshalb neue Vorgehensweisen vorgestellt, um Daten zwischen einer objektorientierten Applikationsschicht, die sich auf dem Server befindet, und den Clients zu übertragen. Aktive Daten-Container (ADCs) stellen einen einheitlichen Transportmechanismus bereit, der zusätzliche Funktionalität besitzt, um die Datenübertragung zu optimieren. Dazu gehört z.B. der automatische Datenaustausch mit Geschäftsobjekten, um das manuelle Beschreiben und Auslesen des Daten-Containers durch den Anwendungsentwickler einzusparen. Zusätzlich wird die Optimierung des Datenübertragungsvorgangs im Sinne des Leistungsverhaltens angestrebt. ADCs sind sehr flexibel und können in der Anwendungsentwicklung als universelles und zentral zur Verfügung gestelltes Datenübertragungskonzept dienen. Eine Untersuchung des Leistungsverhaltens zeigt, daß mit den vorliegenden Konzepten der Transaktionsdurchsatz hinsichtlich der Kommunikation bis zum Faktor 8 gesteigert werden kann. Im Rahmen eines Industrieprojekts konnte mit Hilfe der Konzepte Entwicklungsaufwand im Umfang von ca. 18% der erforderlichen Codezeilen einer komplexen Anwendung eingespart werden.

The focus of this thesis is on transferring data between mobile devices. It analyzes the resource consumption of using the Wireless LAN interface in some situations, and proposes and evaluates some new applications involving the transfer of voice and data files. Measurements show the high consumption of battery power due to the operation of a wireless network interface, even if it is not “actively” used to transfer data, while the memory consumption of the running applications is very limited. This thesis includes also an application to transfer files between two or more Pocket PCs: it is proposed as an addition to the VoIP application Minisip. Finally I have developed an application in order to explore the possibility to make a voice call by transferring real-time encoded text using UDP and/or RTP streams. This could be used together with speech-to-text and text-to-speech conversion applications at the end points to allow a “voice conversation” even on wireless links with very limited capacity, whereas a standard VoIP conversation would not be affordable. / Fokus i detta examensarbete ligger på överföring av data mellan mobila enheter. Det analyserar resursutnyttjandet vid användande av Wireless LAN-anslutning i några situationer, samt brukar analysen för att föreslå och utvärdera ett antal nya applikationer för överföring av röstsamtal och filer. Mätningar visar den höga konsumtion av batterikraft som anslutning till ett trådlöst nätverk gränsnitt, även då det inte används "aktivt" för dataöverföring, medan de applikationer som använts här behöver bara mycket begränsad minneskapacitet. I detta examensarbete ingår även ett program för överföring av filer mellan två eller flera mobila apparater, föreslaget att ingå i Minisip, en VoIP applikation. Dessutom föreslås och utvärderas en applikation som undersöker möjligheterna att vid röstsamtal överföra realtidskodad text via RTP och/eller UDP stream. Använd tillsammans med en röst-till-text- och text-till-röstomvandling i ändpunkterna möjliggör denna genomförande av röstsamtal även då mycket begränsade trådlösa anslutningar nyttjas. / <p>Exchange student from Pisa.</p>