Dissertations / Theses: 'Solution adaptive'

1

Kühnlein, Christian. "Solution-adaptive moving mesh solver for geophysical flows." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-135874.

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2

Ghoneim, Youssef Ahmed. "Indirect adaptive control using the linear quadratic solution." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=72028.

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This thesis studies the indirect adaptive control for discrete linear time invariant systems. The adaptive control strategy is based on the linear quadratic regulator that places the closed loop poles such that an infinite stage quadratic cost function is minimized. The plant parameters are identified recursively using a projection algorithm.
First, we study the effect of the model over-parametrization. For this purpose, we introduce an algorithm to generate the controller parameters recursively. This asymptotic reformulation is shown to overcome situations in which the pole-zero cancellation is a limit point of the identification algorithm. We also show that the algorithm will generate a unique control sequence that converges asymptotically to the solution of the Diophantine (pole assignment) equation.
Next, we study the stability of the proposed adaptive scheme in both deterministic and stochastic cases. We show that the global stability of the resulting adaptive scheme is obtained with no implicit assumptions about parameter convergence or the nature of the external input. Then the global convergence of the adaptive algorithm is obtained if the external input is "persistently exciting". By convergence we mean that the adaptive control will converge to the optimal control of the system.
The performance of the adaptive algorithm in the presence of deterministic disturbances is also considered, where we show that the adaptive controller performs relatively well if the model order is high enough to include a description of the disturbances.

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3

Jackson, Nicolas Alain. "Adaptive finite element solution of option pricing problems." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393612.

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4

Robertson, Mairi Laidlaw. "The adaptive numerical solution of phase change problems." Thesis, University of Strathclyde, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366834.

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5

Várnai, Csilla. "Adaptive QM/MM simulations for reactions in solution." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609933.

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6

Kasmai, Naser Talon Shamsi. "Solution adaptive meshing strategies for flows with vortices." Master's thesis, Mississippi State : Mississippi State University, 2008. http://library.msstate.edu/etd/show.asp?etd=etd-07082008-134106.

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7

Juarez-Romero, David. "The adaptive solution of evolutive and equilibrium distributed systems." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/7461.

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8

Walsh, Paul Charles. "Adaptive solution of viscous aerodynamic flows using unstructured grids." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0014/NQ35361.pdf.

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9

Senguttuvan, Vinoad. "Solution adaptive isotropic and anisotropic mesh refinement using general elements." Master's thesis, Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/etd/show.asp?etd=etd-04062005-104308.

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10

Saeed, Usman. "Adaptive numerical techniques for the solution of electromagnetic integral equations." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41173.

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Various error estimation and adaptive refinement techniques for the solution of electromagnetic integral equations were developed. Residual based error estimators and h-refinement implementations were done for the Method of Moments (MoM) solution of electromagnetic integral equations for a number of different problems. Due to high computational cost associated with the MoM, a cheaper solution technique known as the Locally-Corrected Nyström (LCN) method was explored. Several explicit and implicit techniques for error estimation in the LCN solution of electromagnetic integral equations were proposed and implemented for different geometries to successfully identify high-error regions. A simple p-refinement algorithm was developed and implemented for a number of prototype problems using the proposed estimators. Numerical error was found to significantly reduce in the high-error regions after the refinement. A simple computational cost analysis was also presented for the proposed error estimation schemes. Various cost-accuracy trade-offs and problem-specific limitations of different techniques for error estimation were discussed. Finally, a very important problem of slope-mismatch in the global error rates of the solution and the residual was identified. A few methods to compensate for that mismatch using scale factors based on matrix norms were developed.

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11

Lee, Yeaw Chu. "Adaptive multilevel solution of elliptic equations with strongly discontinuous coefficients." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426838.

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12

Nicola, Aurelian. "Numerical solution of Hamilton-Jacobi equations using adaptive moving meshes." Thesis, University of Strathclyde, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424354.

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13

Shapiro, Richard Abraham. "An adaptive finite element solution algorithm for the Euler equations." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/35946.

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14

Bhagat, Nitin. "A block structured adaptive solution to the shallow water equations." Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-06252004-135938.

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15

Sykes, L. A. "On the numerical solution of compressible flows containing shock discontinuities." Thesis, University of Hertfordshire, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234329.

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16

Schlegel, Martin. "Adaptive discretization methods for the efficient solution of dynamic optimization problems /." Düsseldorf : VDI-Verl, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=013053068&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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17

Watson, Aaron Michael. "The WN adaptive method for numerical solution of particle transport problems." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3133.

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The source and nature, as well as the history of ray-effects, is described. A benchmark code, using piecewise constant functions in angle and diamond differencing in space, is derived in order to analyze four sample problems. The results of this analysis are presented showing the ray effects and how increasing the resolution (number of angles) eliminates them. The theory of wavelets is introduced and the use of wavelets in multiresolution analysis is discussed. This multiresolution analysis is applied to the transport equation, and equations that can be solved to calculate the coefficients in the wavelet expansion for the angular flux are derived. The use of thresholding to eliminate wavelet coefficients that are not required to adequately solve a problem is then discussed. An iterative sweeping algorithm, called the SN-WN method, is derived to solve the wavelet-based equations. The convergence of the SN-WN method is discussed. An algorithm for solving the equations is derived, by solving a matrix within each cell directly for the expansion coefficients. This algorithm is called the CWWN method. The results of applying the CW-WN method to the benchmark problems are presented. These results show that more research is needed to improve the convergence of the SN-WN method, and that the CW-WN method is computationally too costly to be seriously considered.

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18

Mekwi, Wankere Rinwi. "Adaptive solution of partial differential equations using mesh movement and refinement." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431776.

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19

Jorti, Zakariae. "Fast solution of sparse linear systems with adaptive choice of preconditioners." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS149.

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L'objectif de cette thèse est d'étudier l'utilisation de méthodes de Krylov préconditionnées de façon adaptative dans des applications qui peuvent être modélisées par des équations aux dérivées partielles. Pour ces méthodes, le préconditionnement est souvent indispensable pour résoudre efficacement des systèmes d'équations creux et de grande taille. Toutefois, un préconditionneur donné ne peut être optimal pour tous les usages, compte tenu des caractéristiques changeantes de l'opérateur linéarisé. Cette thèse aborde les types de préconditionneurs et méthodes de résolution qui peuvent s'adapter à la complexité des systèmes linéaires en se basant sur des estimateurs d'erreur a posteriori. Dans un premier temps, nous proposons des stratégies adaptatives globales et locales fondées sur l'estimation a posteriori d'erreur et un préconditionneur hybride block-jacobi et ILU(0). Dans un second temps, l’estimation d’erreur a posteriori est utilisée pour partitionner le préconditionneur, et une approche type complément de Schur est utilisée pour le préconditionnement du bloc avec une forte erreur. Puis, nous introduisons une variante de cette dernière approche qui utilise des approximations de bas rang pour remplacer les factorisations exactes, qui sont parfois très coûteuses à calculer. Par la suite, nous définissons un préconditionneur adaptatif fondé sur l'estimation d'erreur a posteriori permettant de contrôler la norme de l'erreur algébrique locale. Enfin, nous prouvons l'efficacité de ces stratégies adaptatives sur des exemples de simulation de réservoir en 2D pour milieux poreux hétérogènes
This thesis analyzes the use of adaptive preconditioned Krylov methods in applications which can be modeled by partial differential equations. Preconditioning is generally essential for efficiently solving large sparse nonlinear systems of equations. However, the optimality of the available preconditioners is not guaranteed for all uses due to the changing nature of the linearized operator. This thesis explores some types of preconditioners and solve procedures that can adapt to the complexity of linear systems using information from a posteriori error estimates. First, we propose global and local adaptive strategies based on a posteriori error estimation and a hybrid block-jacobi and ILU(0) preconditioner. Second, the a posteriori error estimation is used to partition the matrix, and a Schur complement-based approach is used for the preconditioning of the block with a high error. Then, we introduce a variant of this latter approach which replaces the costly exact factorizations by low-rank approximations. We also define an adaptive preconditioner based on a posteriori error estimation that allows to control a local algebraic error norm. Finally, we prove the efficiency of our adaptive strategies on two-dimensional reservoir simulation examples for heterogeneous porous media

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20

Harbrecht, Helmut, and Reinhold Schneider. "Wavelet based fast solution of boundary integral equations." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600649.

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This paper presents a wavelet Galerkin scheme for the fast solution of boundary integral equations. Wavelet Galerkin schemes employ appropriate wavelet bases for the discretization of boundary integral operators which yields quasi-sparse system matrices. These matrices can be compressed such that the complexity for solving a boundary integral equation scales linearly with the number of unknowns without compromising the accuracy of the underlying Galerkin scheme. Based on the wavelet Galerkin scheme we present also an adaptive algorithm. By numerical experiments we provide results which demonstrate the performance of our algorithm.

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21

Taylor, Simon. "Design environment and anisotropic adaptive meshing in computational magnetics." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301211.

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22

Gomony, Manil Dev. "An adaptive solution for power efficiency and QoS optimization in WLAN 802.11n." Thesis, Linköping University, Communication Systems, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54764.

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The wide spread use of IEEE Wireless LAN 802.11 in battery operated mobile devices introduced the need of power consumption optimization while meeting Quality-of-Service (QoS) requirements of applications connected through the wireless network. The IEEE 802.11 standard specifies a baseline power saving mechanism, hereafter referred to as standard Power Save Mode (PSM), and the IEEE 802.11e standard specifies the Automatic Power Save Delivery (APSD) enhancement which provides support for real-time applications with QoS requirements. The latest amendment to the WLAN 802.11 standard is the IEEE 802.11n standard which enables the use of much higher data rates by including enhancements in the Physical and MAC Layer. In this thesis, different 802.11n MAC power saving and QoS optimization possibilities are analyzed comparing against existing power saving mechanisms.

Initially, the performance of the existing power saving mechanisms PSM and Unscheduled-APSD (UAPSD) are evaluated using the 802.11n process model in the OPNET simulator and the impact of frame aggregation feature introduced in the MAC layer of 802.11n was analyzed on these power saving mechanisms. From the performance analysis it can be concluded that the frame aggregation will be efficient under congested network conditions. When the network congestion level increases, the signaling load in UAPSD saturates the channel capacity and hence results in poor performance compared to PSM. Since PSM cannot guarantee the minimum QoS requirements for delay sensitive applications, a better mechanism for performance enhancement of UAPSD under dynamic network conditions is proposed.

The functionality and performance of the proposed algorithm is evaluated under different network conditions and using different contention settings. From the performance results it can be concluded that, by using the proposed algorithm the congestion level in the network is reduced dynamically thereby providing a better power saving and QoS by utilizing the frame aggregation feature efficiently.

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23

Akargun, Yigit Hayri. "Least-squares Finite Element Solution Of Euler Equations With Adaptive Mesh Refinement." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614138/index.pdf.

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Least-squares finite element method (LSFEM) is employed to simulate 2-D and axisymmetric flows governed by the compressible Euler equations. Least-squares formulation brings many advantages over classical Galerkin finite element methods. For non-self-adjoint systems, LSFEM result in symmetric positive-definite matrices which can be solved efficiently by iterative methods. Additionally, with a unified formulation it can work in all flight regimes from subsonic to supersonic. Another advantage is that, the method does not require artificial viscosity since it is naturally diffusive which also appears as a difficulty for sharply resolving high gradients in the flow field such as shock waves. This problem is dealt by employing adaptive mesh refinement (AMR) on triangular meshes. LSFEM with AMR technique is numerically tested with various flow problems and good agreement with the available data in literature is seen.

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24

Alharbi, Abdulghani Ragaa. "Numerical solution of thin-film flow equations using adaptive moving mesh methods." Thesis, Keele University, 2016. http://eprints.keele.ac.uk/2356/.

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Thin liquid films are found everywhere in nature. Their flows play a fundamental role in a wide range of applications and processes. They are central to a number of biological, industrial, chemical, geophysical and environmental applications. Thin films driven by external forces are susceptible to instabilities leading to the break-up of the film into fingering-type patterns. These fingering-type patterns are usually undesirable as they lead to imperfections and dry spots. This behaviour has motivated theoreticians to try to understand the behaviour of the flow and the mechanisms by which these instabilities occur. In the physically relevant case when surface tension is large, the film’s free surface exhibits internal layers where there is rapid spatial variation in the film’s curvature over very short lengthscales and away from these internal layers the film’s curvature is almost negligible. This provides the main motivation for this thesis which is to develop adaptive numerical solution techniques for thin film flow equations that fully resolve such internal layers in order to obtain accurate numerical solutions. We consider two thin film flow problems in one and two-dimensions to test the adaptive numerical solution techniques developed in this thesis. The first problem we consider is related to a liquid sheet or drop spreading down an inclined pre-wetted plane due to influence of gravity. The second problem we consider is also related to the spreading of a liquid sheet or drop down an inclined pre-wetted plane including surfactant-related effects in addition to gravity. We follow the r-adaptive moving mesh technique which uses moving mesh partial differential equations (MMPDEs) to adapt and move the mesh coupled to the underlying PDE(s). We show how this technique can accurately resolve the various one and two-dimensional structures observed in the above test problems as well as reduce the computational effort in comparison to numerical solutions using a uniform mesh.

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25

Wishart, Stuart Jackson. "A Parallel Solution Adaptive Implementation of the Direct Simulation Monte Carlo Method." University of Sydney. School of Aerospace, Mechanical and Mechatronic Engineering, 2005. http://hdl.handle.net/2123/619.

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This thesis deals with the direct simulation Monte Carlo (DSMC) method of analysing gas flows. The DSMC method was initially proposed as a method for predicting rarefied flows where the Navier-Stokes equations are inaccurate. It has now been extended to near continuum flows. The method models gas flows using simulation molecules which represent a large number of real molecules in a probabilistic simulation to solve the Boltzmann equation. Molecules are moved through a simulation of physical space in a realistic manner that is directly coupled to physical time such that unsteady flow characteristics are modelled. Intermolecular collisions and moleculesurface collisions are calculated using probabilistic, phenomenological models. The fundamental assumption of the DSMC method is that the molecular movement and collision phases can be decoupled over time periods that are smaller than the mean collision time. Two obstacles to the wide spread use of the DSMC method as an engineering tool are in the areas of simulation configuration, which is the configuration of the simulation parameters to provide a valid solution, and the time required to obtain a solution. For complex problems, the simulation will need to be run multiple times, with the simulation configuration being modified between runs to provide an accurate solution for the previous run�s results, until the solution converges. This task is time consuming and requires the user to have a good understanding of the DSMC method. Furthermore, the computational resources required by a DSMC simulation increase rapidly as the simulation approaches the continuum regime. Similarly, the computational requirements of three-dimensional problems are generally two orders of magnitude more than two-dimensional problems. These large computational requirements significantly limit the range of problems that can be practically solved on an engineering workstation or desktop computer. The first major contribution of this thesis is in the development of a DSMC implementation that automatically adapts the simulation. Rather than modifying the simulation configuration between solution runs, this thesis presents the formulation of algorithms that allow the simulation configuration to be automatically adapted during a single run. These adaption algorithms adjust the three main parameters that effect the accuracy of a DSMC simulation, namely the solution grid, the time step and the simulation molecule number density. The second major contribution extends the parallelisation of the DSMC method. The implementation developed in this thesis combines the capability to use a cluster of computers to increase the maximum size of problem that can be solved while simultaneously allowing excess computational resources to decrease the total solution time. Results are presented to verify the accuracy of the underlying DSMC implementation, the utility of the solution adaption algorithms and the efficiency of the parallelisation implementation.

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26

Wishart, Stuart Jackson. "A Parallel Solution Adaptive Implementation of the Direct Simulation Monte Carlo Method." Thesis, The University of Sydney, 2004. http://hdl.handle.net/2123/619.

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This thesis deals with the direct simulation Monte Carlo (DSMC) method of analysing gas flows. The DSMC method was initially proposed as a method for predicting rarefied flows where the Navier-Stokes equations are inaccurate. It has now been extended to near continuum flows. The method models gas flows using simulation molecules which represent a large number of real molecules in a probabilistic simulation to solve the Boltzmann equation. Molecules are moved through a simulation of physical space in a realistic manner that is directly coupled to physical time such that unsteady flow characteristics are modelled. Intermolecular collisions and moleculesurface collisions are calculated using probabilistic, phenomenological models. The fundamental assumption of the DSMC method is that the molecular movement and collision phases can be decoupled over time periods that are smaller than the mean collision time. Two obstacles to the wide spread use of the DSMC method as an engineering tool are in the areas of simulation configuration, which is the configuration of the simulation parameters to provide a valid solution, and the time required to obtain a solution. For complex problems, the simulation will need to be run multiple times, with the simulation configuration being modified between runs to provide an accurate solution for the previous run's results, until the solution converges. This task is time consuming and requires the user to have a good understanding of the DSMC method. Furthermore, the computational resources required by a DSMC simulation increase rapidly as the simulation approaches the continuum regime. Similarly, the computational requirements of three-dimensional problems are generally two orders of magnitude more than two-dimensional problems. These large computational requirements significantly limit the range of problems that can be practically solved on an engineering workstation or desktop computer. The first major contribution of this thesis is in the development of a DSMC implementation that automatically adapts the simulation. Rather than modifying the simulation configuration between solution runs, this thesis presents the formulation of algorithms that allow the simulation configuration to be automatically adapted during a single run. These adaption algorithms adjust the three main parameters that effect the accuracy of a DSMC simulation, namely the solution grid, the time step and the simulation molecule number density. The second major contribution extends the parallelisation of the DSMC method. The implementation developed in this thesis combines the capability to use a cluster of computers to increase the maximum size of problem that can be solved while simultaneously allowing excess computational resources to decrease the total solution time. Results are presented to verify the accuracy of the underlying DSMC implementation, the utility of the solution adaption algorithms and the efficiency of the parallelisation implementation.

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27

Na, Xiaodong. "NONLINEAR IDENTIFICATION AND CONTROL: A PRACTICAL SOLUTION AND ITS APPLICATION." Lexington, Ky. : [University of Kentucky Libraries], 2008. http://hdl.handle.net/10225/765.

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Thesis (Ph. D.)--University of Kentucky, 2008.
Title from document title page (viewed on March 18, 2008). Document formatted into pages; contains: xiv, 178 p. : ill. (some col.). Includes abstract and vita. Includes bibliographical references (p. 168-176).

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28

Thorne, Jr Daniel Thomas. "Multigrid with Cache Optimizations on Adaptive Mesh Refinement Hierarchies." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_diss/325.

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This dissertation presents a multilevel algorithm to solve constant and variable coeffcient elliptic boundary value problems on adaptively refined structured meshes in 2D and 3D. Cacheaware algorithms for optimizing the operations to exploit the cache memory subsystem areshown. Keywords: Multigrid, Cache Aware, Adaptive Mesh Refinement, Partial Differential Equations, Numerical Solution.

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29

Kühnlein, Christian [Verfasser], and Ulrich [Akademischer Betreuer] Schumann. "Solution-adaptive moving mesh solver for geophysical flows / Christian Kühnlein. Betreuer: Ulrich Schumann." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2011. http://d-nb.info/1016615345/34.

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30

Renzo, Arina. "Orthogonal adaptive grids and their application to the solution of the Euler equations." Doctoral thesis, Universite Libre de Bruxelles, 1987. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/213438.

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31

Al-Riyami, Ahmed. "Towards an adaptive solution to data privacy protection in hierarchical wireless sensor networks." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/towards-an-adaptive-solution-to-data-privacy-protection-in-hierarchical-wireless-sensor-networks(a096db2a-251c-4e9e-a4ff-8bfe4c6f1bf4).html.

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Hierarchical Wireless Sensor networks (WSNs) are becoming attractive to many applications due to their energy efficiency and scalability. However, if such networks are deployed in a privacy sensitive application context such as home utility consumption, protecting data privacy becomes an essential requirement. Our threat analysis in such networks has revealed that PPDA (Privacy Preserving Data Aggregation), NIDA (Node ID Anonymity) and ENCD (Early Node Compromise Detection) are three essential properties for protecting data privacy. The scope of this thesis is on protecting data privacy in hierarchical WSNs byaddressing issues in relation to two of the three properties identified, i.e., NIDA and ENCD, effectively and efficiently. The effectiveness property is achieved by considering NIDA and ENCD in an integrated manner, and the efficiency property is achieved by using an adaptive approach to security provisioning. To this end, the thesis has made the following four novel contributions. Firstly, this thesis presents a comprehensive analysis of the threats to data privacy and literature review of the countermeasures proposed to address these threats. The analysis and literature review have led to the identification of two main areas for improvements: (1) to reduce the resources consumed as the result of protecting data privacy, and (2) to address the compatibility issue between NIDA and ENCD.Secondly, a novel Adaptive Pseudonym Length Estimation (AdaptPLE) method has been proposed. The method allows the determination of a minimum acceptable length of the pseudonyms used in NIDA based on a given set of security and application related requirements and constraints. In this way, we can balance the trade-off between an ID anonymity protection level and the costs (i.e., transmission and energy) incurred in achieving the protection level. To demonstrate its effectiveness, we have evaluated the method by applying it to two existing NIDA schemes, the Efficient Anonymous Communication (EAC) scheme and theCryptographic Anonymous Scheme (CAS).Thirdly, a novel Adaptive Early Node Compromise Detection (AdaptENCD) scheme for cluster-based WSNs has been proposed. This scheme allows early detections of compromised nodes more effectively and efficiently than existing proposals. This is achieved by adjusting, at run-time, the transmission rate of heartbeat messages, used to detect nodes' aliveness, in response to the average message loss ratio in a cluster. This adaptive approach allows us to significantly reduce detection errors while keeping the number of transmitted heartbeat messages as low as possible, thus reducing transmission costs. Fourthly, a novel Node ID Anonymity Preserving Scheme (ID-APS) for clusterbased WSNs has been proposed. ID-APS protects nodes ID anonymity while, at the same time, also allowing the global identification of nodes. This later property supports the identification and removal of compromised nodes in the network, which is a significant improvement over the state-of-the-art solution, the CAS scheme. ID-APS supports both NIDA and ENCD by making a hybrid use of dynamic and global identification pseudonyms. More importantly, ID-APS achieves these properties with less overhead costs than CAS. All proposed solutions have been analysed and evaluated comprehensively to prove their effectiveness and efficiency.

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32

Alexe, Mihai. "Adjoint-based space-time adaptive solution algorithms for sensitivity analysis and inverse problems." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/37515.

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Adaptivity in both space and time has become the norm for solving problems modeled by partial differential equations. The size of the discretized problem makes uniformly refined grids computationally prohibitive. Adaptive refinement of meshes and time steps allows to capture the phenomena of interest while keeping the cost of a simulation tractable on the current hardware. Many fields in science and engineering require the solution of inverse problems where parameters for a given model are estimated based on available measurement information. In contrast to forward (regular) simulations, inverse problems have not extensively benefited from the adaptive solver technology. Previous research in inverse problems has focused mainly on the continuous approach to calculate sensitivities, and has typically employed fixed time and space meshes in the solution process. Inverse problem solvers that make exclusive use of uniform or static meshes avoid complications such as the differentiation of mesh motion equations, or inconsistencies in the sensitivity equations between subdomains with different refinement levels. However, this comes at the cost of low computational efficiency. More efficient computations are possible through judicious use of adaptive mesh refinement, adaptive time steps, and the discrete adjoint method. This dissertation develops a complete framework for fully discrete adjoint sensitivity analysis and inverse problem solutions, in the context of time dependent, adaptive mesh, and adaptive step models. The discrete framework addresses all the necessary ingredients of a stateâ ofâ theâ art adaptive inverse solution algorithm: adaptive mesh and time step refinement, solution grid transfer operators, a priori and a posteriori error analysis and estimation, and discrete adjoints for sensitivity analysis of fluxâ limited numerical algorithms.
Ph. D.

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33

Tu, Shuangzhang. "Development of a solution adaptive cartesian-grid solver for 2-D thermochemical nonequilibrium flows." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/12477.

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34

Montagut, Climent Mario Alberto. "DESIGN, DEVELOPMENT AND EVALUATION OF AN ADAPTIVE AND STANDARDIZED RTP/RTCP-BASED IDMS SOLUTION." Doctoral thesis, Universitat Politècnica de València, 2015. http://hdl.handle.net/10251/48549.

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Nowadays, we are witnessing a transition from physical togetherness towards networked togetherness around media content. Novel forms of shared media experiences are gaining momentum, allowing geographically distributed users to concurrently consume the same media content while socially interacting (e.g., via text, audio or video chat). Relevant use cases are, for example, Social TV, networked games and multi-party conferencing. However, realizing enjoyable shared media services faces many challenges. In particular, a key technological enabler is the concurrent synchronization of the media playout across multiple locations, which is known as Inter-Destination Multimedia Synchronization (IDMS). This PhD thesis presents an inter-operable, adaptive and accurate IDMS solution, based on extending the capabilities of RTP/RTCP standard protocols (RFC 3550). Concretely, two new RTCP messages for IDMS have been defined to carry out the necessary information to achieve IDMS. Such RTCP extensions have been standardized within the IETF, in RFC 7272. In addition, novel standard-compliant Early Event-Driven (EED) RTCP feedback reporting mechanisms have been also designed to enhance the performance in terms of interactivity, flexibility, dynamism and accuracy when performing IDMS. The designed IDMS solution makes use of globally synchronized clocks (e.g., using NTP) and can adopt different (centralized and distributed) architectural schemes to exchange the RTCP messages for IDMS. This allows efficiently providing IDMS in a variety of networked scenarios and applications, with different requirements (e.g., interactivity, scalability, robustness…) and available resources (e.g., bandwidth, latency, multicast support…). Likewise, various monitoring and control algorithms, such as dynamic strategies for selecting the reference timing to synchronize with, and fault tolerance mechanisms, have been added. Moreover, the proposed IDMS solution includes a novel Adaptive Media Playout (AMP) technique, which aims to smoothly adjust the media playout rate, within perceptually tolerable ranges, every time an asynchrony threshold is exceeded. Prototypes of the IDMS solution have been implemented in both a simulation and in real media framework. The evaluation tests prove the consistent behavior and the satisfactory performance of each one of the designed components (e.g.,protocols, architectural schemes, master selection policies, adjustment techniques…). Likewise, comparison results between the different developed alternatives for such components are also provided. In general, the obtained results demonstrate the ability of this RTP/RTCP-based IDMS solution to concurrently and independently maintain an overall synchronization status (within allowable limits) in different logical groups of users, while avoiding annoying playout discontinuities and hardly increasing the computation and traffic load.
Montagut Climent, MA. (2015). DESIGN, DEVELOPMENT AND EVALUATION OF AN ADAPTIVE AND STANDARDIZED RTP/RTCP-BASED IDMS SOLUTION [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48549
TESIS
Premiado

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35

Just, Elke [Verfasser]. "Adaptive use of extended systems for the efficient verified solution of nonlinear systems / Elke Just." Wuppertal : Universitätsbibliothek Wuppertal, 2014. http://d-nb.info/1053770847/34.

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36

Tam, Anna. "An anisotropic adaptive method for the solution of 3-D inviscid and viscous compressible flows." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0003/NQ40309.pdf.

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37

Tabler, John A. "An integrated adaptive bias solution for zero passive component count high-performance mixed-signal ICs." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/13339.

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38

Gan, Eng Kiat Russell. "Adaptive Branch and Bound for Efficient Solution of Mixed-Integer Programs Formulated with Big-M." Thesis, Monterey, California. Naval Postgraduate School, 2012. http://hdl.handle.net/10945/17370.

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Approved for public release; distribution is unlimited
This thesis describes three specialized branch-and-bound (B and B) algorithms for solving a mixed-integer program (MIP) that incorporates standard big-M constructs. The goal is to identify valid values for M that also lead to short solution times. One algorithm initializes large instances of M (giving a weak relaxation of the MIP), and decreases these as required to increase efficiency of the standard B and B. Two algorithms initialize small and possibly invalid instances of M, and subsequently increase those values in an attempt to ensure solution validity. Each algorithm requires a model-specific test condition to detect weak or invalid Ms. We test all algorithms on an uncapacitated k-median problem (a variant of the uncapacitated facility location problem), and one algorithm on a shortest-path interdiction problem (SPIP). We observe substantial reduction in run times in almost all cases tested. When solving for exact solutions, computational results show that the proposed algorithms may reduce solution times by up to 75 per cent for the uncapacitated k-median problem and 99 per cent for the SPIP. When the algorithms yield marginally suboptimal solutions, substantial solution-time improvements are also recorded. While testing is limited, this thesis serves as a proof-of-concept that the proposed adaptive algorithms can be effective in reducing solution times and producing optimal or nearly optimal solutions.

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39

Weissinger, Judith. "Development of a discrete adaptive gridless method for the solution of elliptic partial differential equations." Thesis, Cranfield University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.273483.

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40

Xie, Yi-Min. "Finite element solution and adaptive analysis for static and dynamic problems of saturated-unsaturated porous media." Thesis, Swansea University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524666.

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Yang, Keo S. "An adaptive communication solution applying commercial off-the-shelf (COTS) cellular technology to tactical communication requirements." Thesis, Monterey, California. Naval Postgraduate School, 2011. http://hdl.handle.net/10945/5524.

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Approved for public release; distribution is unlimited.
This thesis will research the availability and applicability of using commercial off-the-shelf (COTS) cellular software, running on a smartphone hardware platform to address communication requirements as identified in a 1st Marine Division, Universal Needs Statement (UNS). Having only conducted introductory research in to this topic, preliminary results have shown that the majority of the research conducted in the past have centered on either COTS cellular software specific to an application, or on the utility of tactical communication devices as they are currently being employed. The intent of this research is to discover if a bridge is possible and available for cellular COTS software running on a COTS smartphone device to be leveraged, thus satisfying communication requirements of small-unit leaders in a tactical environment. Our hypothesis is that COTS technology can provide a number of viable options to address tactical communication shortfalls based on the fact that the communication shortfalls identified, are capabilities that the commercial industry currently exercise on a daily basis, (e.g., text, chat, voice, position location information, imagery and map viewing, streaming video, web browsing and e-mail). All of these identified communication capabilities are available in military command and control systems however, they reside primarily at the higher headquarter levels, requiring large communication assets to establish those services. Furthermore, due to technology shortfalls and asset limitations, only a few of these capabilities are currently being extended down to the small unit level. Many small-unit leaders are experiencing that these limitations in communication capabilities are needlessly placing risks on their mission and their personnel. With COTS smartphone technology and the advancements made in the commercial cellular industry, this research intends to advance the study towards discovery of a viable COTS solution that can satisfy tactical communication requirements for the small-unit leader.

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42

Nadeem, Sarfraz Ahmad. "Parallel domain decomposition preconditioning for the adaptive finite element solution of elliptic problems in three dimensions." Thesis, University of Leeds, 2001. http://etheses.whiterose.ac.uk/1296/.

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A novel weakly overlapping two level additive Schwarz domain decomposition preconditioning algorithm is presented which is appropriate for the parallel finite element solution of elliptic partial differential equations in three dimensions. This algorithm allows each processor to be assigned one or more subdomains and, as with most parallel domain decomposition solvers, each processor is able to solve its own subproblem(s) concurrently. The novel feature of the technique proposed here is that it requires just a single layer of overlap in the elements which make up each subdomain at each level of refinement, and it is shown that this amount of overlap is sufficient to yield an optimal preconditioner. The number of elements in this overlap region between subdomains is O(h-2 ) as the mesh size h -> 0. This is an improvement over the O(h-3) overlapping elements required to obtain optimality for a conventional two level additive Schwarz algorithm. The quality and effectiveness of this new algorithm is examined using both global uniform and local non-uniform refinement with two representative partitions of the domain . This preconditioning algorithm is then generalized such that the resulting preconditioner is not only suitable for symmetric problems but also for nonsymmetric and convection-dominated elliptic problems. This generalization, in the absence of theoretical or mathematical background, is based on empirical observations. Moreover, it turns out to be more effective and robust than the original symmetric preconditioning algorithm when applied to symmetric positive definite problems. This generalized algorithm is tested on symmetric, nonsymmetric and convection-dominated partial differential equations, where the number of iterations observed suggests that the preconditioner may in fact be optimal, i.e. the condition number of the preconditioned systems is bounded as the mesh is refined or the number of subdomains is increased. Due to non-physical oscillations in the solution of convection-dominated problems when discretized by the Galerkin finite element method, unless the size of elements is sufficiently small, we have extended our implementation of the generalized preconditioning algorithm to be applicable to systems arising from a more stable finite element discretization technique based upon streamline diffusion. Numerical experiments for a wide variety of problems are included to demonstrate the optimal or near-optimal behaviour and quality of this generalized algorithm. Parallel performance of the generalized preconditioning algorithm is also evaluated and analyzed. All the timings quoted are for a SG Origin 2000 computer and all software implementations described in this thesis have been coded and tested using ANSI C and the MPI communication library.

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43

Bernales, Odino Maria Carolina. "From primitive social housing to modern accommodation solution: guidelines for the adaptive reuse ofChilean Cités in Santiago." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2006. http://hub.hku.hk/bib/B42181574.

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Siyahhan, Bercan. "A Two Dimensional Euler Flow Solver On Adaptive Cartesian Grids." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609482/index.pdf.

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In the thesis work, a code to solve the two dimensional compressible Euler equations for external flows around arbitrary geometries have been developed. A Cartesianmesh generator is incorporated to the solver. Hence the pre-processing can be performed together with the solution within a single code. The code is written in the C++ programming language and its object oriented capabilities have been exploited to save memory in the data structure developed. The Cartesian mesh is formed by dividing squares successively into its four quadrants. The main advantage of using this type of a mesh is the ability to generate meshes around geometries of arbitrary complexity quickly and to adapt the mesh easily based on the solution. The main disadvantage of this method is that the treatment of the cells that are cut by the geometry. For the solution procedure Roe&rsquo
s method as well as flux vector splitting methods are used for the flux evaluation. The flux vector splitting schemes used are van Leer, AUSM, AUSMD and AUSMV methods. Time discretization is performed using a multi-stage method. To increase the accuracy least squares reconstruction is employed. The code is validated by performing calculations around a NACA0012 airfoil profile. The effect of reconstruction is demonstrated by plotting the pressure coefficient on the airfoil. The distribution obtained using reconstruction is very close to the experimental one while there is a considerable deviation for the case without reconstruction. Also the shock capturing capabilities of different methods have been investigated. In addition the performance of each method is analyzed for flow around an NLR 7301 airfoil with a flap.

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45

Kaennakham, S. "A solution adaptive grid (SAG) for incompressible flows simulations : an attempt towards enhancing SAG algorithm for large eddy simulation (LES)." Thesis, Coventry University, 2010. http://curve.coventry.ac.uk/open/items/c3a447e1-979d-841e-4dec-9b6c2f9c4515/1.

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A study of the use of solution adaptive grid (SAG) method for simulations of incompressible flows is carried out in this work. Both laminar and turbulent types of flows are chosen. Investigation on laminar flow simulation starts with mesh adaptation criteria that are based on strong changes of some selected flow parameters; pressure and velocity components. Three most common laminar types of flows are studied; flow in a circular pipe, flow in a channel with sudden expansion and flow in a cavity with a moving lid. It is found that with the use of SAG, a reduction in both computational grid nodes and CPU time can be obtained when compared to those of fixed grid while satisfactory solutions are also achievable. Nevertheless, the refinement criteria setup procedure reveals inconveniences and requirement for several judgments that have to be defined ‘ad hoc’. This hence, makes the refinement criteria dubious for real engineering applications. For the study of turbulent flows with large eddy simulation (LES) and implicit filtering, examination of literature reveals that the lack of connections between the filter width and a physical scale has made LES somewhat unclosed, i.e. in a physical sense. In addition, it is known that numerical and modelling errors are always combined and it is difficult to study each of them separately making the total error magnitude difficult to control. Since both error types are characterised by the grid size, LES users very often find cases where a finer mesh no longer provides better accuracy. An attempt to address this ‘physical’ enclosure property of LES and its complication to implement/setup in FLUENT begins with the construction of a new refinement variable as a function of the Taylor scale. Then a new SAG algorithm is formed. The requirement to satisfy a condition of the selected subgrid scale (SAG) model, the Smagorinsky model, is taken into consideration to minimize the modeling error. The construction of a new refinement algorithm is also aimed to be the key to studying the interaction between the two types of error and could lead to the means of controlling their total magnitude. The validation in terms of its effectiveness, efficiency and reliability of the algorithm are made based on several criteria corresponding to suitability for practical applications. This includes the simplicity to setup/employ, computational affordability, and the accuracy level. For this, two different turbulent flow types that represent different commonly found turbulent phenomena are chosen; plane free jet and the flow over a circular cylinder. The simulations of the two cases were carried out in two dimensions. It is found that there are two key factors that strongly determine the success of the algorithm. The first factor is the Taylor scale definition, with literature only available for the turbulent plane jet study, for which good level of accuracy is expected. Unfortunately, this is not true for the flow over a circular cylinder, indicating a need for further analytical work. The second encountered difficulty results from limited access to software codes, which makes it impossible to implement the proposed scheme. As a result, the algorithm formulation needs be modified with carful judgment. Nevertheless, overall results are in reasonably good agreement with their corresponding experimental data.

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46

Bernales, Odino Maria Carolina. "From primitive social housing to modern accommodation solution guidelines for the adaptive reuse of Chilean Cités in Santiago/." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B42181574.

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47

Pralx, Laurent. "Commande linéaire adaptative : solutions bornées et leurs propriétés." Paris 9, 1988. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=1988PA090035.

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On est amené à modifier des lois d'adaptation en remarquant que les effets non modélisés par un modèle linéaire peuvent sous des hypothèses réalistes être majorées par une norme des signaux d'entrées-sorties. D'autre part, on propose une méthode d'analyse des portraits de phase des systèmes linéaires adaptatifs

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48

Benedix, Olaf [Verfasser], Thomas [Akademischer Betreuer] Apel, and Boris [Akademischer Betreuer] Vexler. "Adaptive Numerical Solution of State Constrained Optimal Control Problems / Olaf Benedix. Gutachter: Thomas Apel ; Boris Vexler. Betreuer: Boris Vexler." München : Universitätsbibliothek der TU München, 2011. http://d-nb.info/1014861411/34.

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49

Morrelll, J. M. "A cell by cell anisotropic adaptive mesh Arbitrary Lagrangian Eulerian method for the numerical solution of the Euler equations." Thesis, University of Reading, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440088.

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50

D'Heedene, Stefan F. 1977. "An operator-customized wavelet-finite element approach for the adaptive solution of second-order partial differential equations on unstructured meshes." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/28939.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Civil and Environmental Engineering, 2005.
Includes bibliographical references (p. 139-142).Unlike first-generation wavelets, second-generation wavelets can be constructed on any multi-dimensional unstructured mesh. Instead of limiting ourselves to the choice of primitive wavelets, effectively HB detail functions, we can tailor the wavelets to gain additional qualities. In particular, we propose to customize our wavelets to the problem's operator. For any given linear elliptic second-order PDE, and within a Lagrangian FE space of any given order, we can construct a basis of compactly supported wavelets that are orthogonal to the coarser basis functions with respect to the weak form of the PDE. We expose the connection between the wavelet's vanishing moment properties and the requirements for operator-orthogonality in multiple dimensions. We give examples in which we successfully eliminate all scale-coupling in the problem's multi-resolution stiffness matrix. Consequently, details can be added locally to a coarser solution without having to re-compute the coarser solution.
The Finite Element Method (FEM) is a widely popular method for the numerical solution of Partial Differential Equations (PDE), on multi-dimensional unstructured meshes. Lagrangian finite elements, which preserve C⁰ continuity with interpolating piecewise-polynomial shape functions, are a common choice for second-order PDEs. Conventional single-scale methods often have difficulty in efficiently capturing fine-scale behavior (e.g. singularities or transients), without resorting to a prohibitively large number of variables. This can be done more effectively with a multi-scale method, such as the Hierarchical Basis (HB) method. However, the HB FEM generally yields a multi-resolution stiffness matrix that is coupled across scales. We propose a powerful generalization of the Hierarchical Basis: a second-generation wavelet basis, spanning a Lagrangian finite element space of any given polynomial order.
by Stefan F. D'Heedene.
Ph.D.

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Dissertations / Theses on the topic 'Solution adaptive'

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