Tesis sobre el tema "Reduced method"
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Garlapati, Revanth Reddy. "Reduced basis method for Boltzmann equation". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39218.
Texto completoIncludes bibliographical references (p. 103-106).
The main aim of the project is to solve the BGK model of the Knudsen parameterized Boltzmann equation which is 1-d with respect to both space and velocity. In order to solve the Boltzmann equation, we first transform the original differential equation by replacing the dependent variable with another variable, weighted with function t(y); next we obtain a Petrov Galerkin weak form of this new transformed equation. To obtain a stable and accurate solution of this weak form, we perform a transformation of the velocity variable y, such that the semi-infinite domain is mapped into a finite domain; we choose the weighting function t(y), to balance contributions at infinity. Once we obtain an accurate and well defined finite element solution of the problem. The next step is to perform the reduced basis analysis of the equation using these accurate finite element solutions. We conclude the project by verifying that the orthonormal reduced Basis method based on the greedy algorithm converges rapidly over the chosen test space.
by Revanth Reddy Garlapati.
S.M.
Badrous, Therese y Ebba Lund. "Reduced stress method for steel in class 4 cross-sections : Evaluation of the reduced stress method for a railway bridge". Thesis, KTH, Byggteknik och design, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302525.
Texto completoIdag behandlas ståltvärsnitt i tvärsnittklass 4 generellt med hjälp av metoden effektivt tvärsnitt för att beakta lokal buckling. Metoden är en aning komplicerad och tidskrävande, vilket leder till att konstruktörer överlag inte använder profiler i tvärsnittsklass 4. Reducerad spänning är en alternativ metod för hantering av slanka ståltvärsnitt. Dessa två metoder beskrivs i Eurokoden varav den sist nämnda mer kortfattat. I den nationella bilagan står det att metoden reducerad spänning ej bör användas dock utan motivering till det allmänna rådet. Studien är en jämförelse av de två olika metoderna och är ämnad till att ge en bättre förståelse av metoden reducerad spänning. Således kan beräkningsgången samt projektering för stålprofiler i tvärsnittsklass 4 effektiviseras. Detta genom att avgöra när det är mest lönsamt att använda reducerad spänning framför effektivt tvärsnitt. Följaktligen kan användning av profiler i tvärsnittsklass 4 bli ett mer självklart val i branschen. Denna studie omfattade en fritt upplagd I-balk i en öppen järnvägsbro utsatt för böjande moment där samma förutsättningar har undersökts för respektive metod. Effektivt tvärsnitt går ut på att reducera en tvärsnittsarea och har utförts via handberäkningar. I metoden reducerad spänning är det sträckgränsen som reduceras. I denna studie undersöktes reducerad spänningsmetoden via FEM samt handberäkningar. Resultatet påvisade att metoden reducerad spänning utförd via FEM gav ett liknande resultat som metoden effektivt tvärsnitt, vilket gör det till en attraktiv metod. Reducerad spänning via handberäkning gav dock ett mer konservativt resultat. Metoderna är relativt olika och rekommendationer för tillämpning av respektive metod presenteras i denna rapport.
Wahl, Jean-Baptiste. "The Reduced basis method applied to aerothermal simulations". Thesis, Strasbourg, 2018. http://www.theses.fr/2018STRAD024/document.
Texto completoWe present in this thesis our work on model order reduction for aerothermal simulations. We consider the coupling between the incompressible Navier-Stokes equations and an advection-diffusion equation for the temperature. Since the physical parameters induce high Reynolds and Peclet numbers, we have to introduce stabilization operators in the formulation to deal with the well known numerical stability issue. The chosen stabilization, applied to both fluid and heat equations, is the usual Streamline-Upwind/Petrov-Galerkin (SUPG) which add artificial diffusivity in the direction of the convection field. We also introduce our order reduction strategy for this model, based on the Reduced Basis Method (RBM). To recover an affine decomposition for this complex model, we implemented a discrete variation of the Empirical Interpolation Method (EIM) which is a discrete version of the original EIM. This variant allows building an approximated affine decomposition for complex operators such as in the case of SUPG. We also use this method for the non-linear operators induced by the shock capturing method. The construction of an EIM basis for non-linear operators involves a potentially huge number of non-linear FEM resolutions - depending on the size of the sampling. Even if this basis is built during an offline phase, we usually can not afford such expensive computational cost. We took advantage of the recent development of the Simultaneous EIM Reduced basis algorithm (SER) to tackle this issue
Pomplun, Jan [Verfasser]. "Reduced basis method for electromagnetic scattering problems / Jan Pomplun". Berlin : Freie Universität Berlin, 2010. http://d-nb.info/1024541436/34.
Texto completoPau, George Shu Heng. "Reduced basis method for quantum models of crystalline solids". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/40376.
Texto completoIncludes bibliographical references (p. 203-213).
Electronic structure problems in solids usually involve repetitive determination of quantities of interest, evaluation of which requires the solution of an underlying partial differential equation. We present in this thesis the application of the reduced basis method in accurate and rapid evaluations of outputs associated with some nonlinear eigenvalue problems related to electronic structure calculations. The reduced basis method provides a systematic procedure by which efficient basis sets and computational strategies can be constructed. The essential ingredients are (i) rapidly convergent global reduced basis approximation spaces; (ii) an offline-online computational procedure to decouple the generation and projection stages of the approximation process; and (iii) inexpensive a posteriori error estimation procedure for outputs of interest. We first propose two strategies by which we can construct efficient reduced basis approximations for vectorial eigensolutions - solutions consisting of several eigenvectors. The first strategy exploits the optimality of the Galerkin procedure to find a solution in the span of all eigenvectors at N judiciously chosen samples in the parameter space.
(cont.) The second strategy determines a solution in the span of N vectorial basis functions that are pre-processed to better represent the smoothness of the solution manifold induced by the parametric dependence of the solutions. We deduce from numerical results conditions in which these approximations are rapidly convergent. For linear eigenvalue problems, we construct a posteriori asymptotic error estimators for our reduced basis approximations - extensions on existing work in algebraic eigenvalue problems. We further construct efficient error estimation procedures that allow efficient construction of reduced basis spaces based on the "greedy" sampling procedure. We extend our methods to nonlinear eigenvalue problems, utilizing the empirical interpolation method. We also provide a more efficient construction procedure for the empirical interpolation method. Finally, we apply our methods to two problems in electronic structure calculations - band structure calculations and electronic ground state calculations. Band structure calculations involve approximations of linear eigenvalue problems; we demonstrate the applicability of our methods in the many query limit with several examples related to determination of spectral properties of crystalline solids.
(cont.) Electronic ground state energy calculations based on Density Functional Theory involve approximations of nonlinear eigenvalue problems; we demonstrate the potential of our methods within the context of geometry optimization.
by George Shu Heng Pau.
Ph.D.
Purdie, Stuart. "Magnetic ordering in systems of reduced dimensionality". Thesis, University of St Andrews, 2005. http://hdl.handle.net/10023/12927.
Texto completoKumar, Ashutosh. "Towards a Reduced-Scaling Method for Calculating Coupled Cluster Response Properties". Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/83846.
Texto completoPh. D.
Skoglund, Oskar y Daniel Samvin. "Design of slender steel members : A comparison between the reduced stress method and the effective width method". Thesis, KTH, Bro- och stålbyggnad, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189029.
Texto completoI Sverige behandlas problemet med lokal buckling av stålkonstruktioner vanligtvis med hjälpav den effektiva bredd metoden, vilket är en dimensionergsmetod som återfinns i Eurocode.En ytterligare dimensionerings metod för lokal buckling som presenteras i Eurocode är denreducerade spänningsmetoden. Den senare nämnda metoden är fördelaktig då den kombinerasmed linjära finita element analyser, vilket resulterar i en mindre tidskrävandedimensioneringsprocess. Dock är metoden känd för att ofta resultera i överdimensioneradekonstruktioner, vilket bidragit till att mindre antal konstruktörer använder sig av denna metod.Syftet med denna rapport blir därmed att jämföra och utvärdera den reduceradespänningsmetoden gentemot den effektiva bredd metoden och olinjär finita element metoden.De olinjära finita element analyserna genomfördes med syfte att simulera det verkligabeteendet och för att sedan jämföra dessa resultat med de två andra metoderna. Analyser harutförts på flera stålbalkar med olika lastkombinationer och slankhet för att inkludera devanligaste fallen inom byggindustrin. Dessutom har det tagits fram några rekommendationerför användningen av metoderna och dessa är presenterade med avseende på de erhållnaresultaten. Rekommendationer för den reducerade spänningsmetoden har presenterats ochytterligare studier gällande dessa metoder och andra konstruktionselement har föreslagits. Deslutsatser som kunde dras är att den reducerade spänningsmetoden kan användas förkonstruktioner som inte påverkas i allt för stor grad av intryckning. För att ge tillförliterligaresultat så rekommenderas att kritiska spänningar erhålles från linjära finita element analyser.
Ozgur, Soner. "Reduced Complexity Sequential Monte Carlo Algorithms for Blind Receivers". Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10518.
Texto completoSchiela, Anton. "The control reduced interior point method : a function space oriented algorithmic approach /". München : Hut, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015438070&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
Texto completoVidal, Codina Ferran. "A reduced-basis method for input-output uncertainty propagation in stochastic PDEs". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/82417.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (p. 123-132).
Recently there has been a growing interest in quantifying the effects of random inputs in the solution of partial differential equations that arise in a number of areas, including fluid mechanics, elasticity, and wave theory to describe phenomena such as turbulence, random vibrations, flow through porous media, and wave propagation through random media. Monte-Carlo based sampling methods, generalized polynomial chaos and stochastic collocation methods are some of the popular approaches that have been used in the analysis of such problems. This work proposes a non-intrusive reduced-basis method for the rapid and reliable evaluation of the statistics of linear functionals of stochastic PDEs. Our approach is based on constructing a reduced-basis model for the quantity of interest that enables to solve the full problem very efficiently. In particular, we apply a reduced-basis technique to the Hybridizable Discontinuous Galerkin (HDG) approximation of the underlying PDE, which allows for a rapid and accurate evaluation of the input-output relationship represented by a functional of the solution of the PDE. The method has been devised for problems where an affine parametrization of the PDE in terms of the uncertain input parameters may be obtained. This particular structure enables us to seek an offline-online computational strategy to economize the output evaluation. Indeed, the offline stage (performed once) is computationally intensive since its computational complexity depends on the dimension of the underlying high-order discontinuous finite element space. The online stage (performed many times) provides rapid output evaluation with a computational cost which is several orders of magnitude smaller than the computational cost of the HDG approximation. In addition, we incorporate two ingredients to the reduced-basis method. First, we employ the greedy algorithm to drive the sampling in the parameter space, by computing inexpensive bounds of the error in the output on the online stage. These error bounds allow us to detect which samples contribute most to the error, thereby enriching the reduced basis with high-quality basis functions. Furthermore, we develop the reduced basis for not only the primal problem, but also the adjoint problem. This allows us to compute an improved reduced basis output that is crucial in reducing the number of basis functions needed to achieve a prescribed error tolerance. Once the reduced bases have been constructed, we employ Monte-Carlo based sampling methods to perform the uncertainty propagation. The main achievement is that the forward evaluations needed for each Monte-Carlo sample are inexpensive, and therefore statistics of the output can be computed very efficiently. This combined technique renders an uncertainty propagation method that requires a small number of full forward model evaluations and thus greatly reduces the computational burden. We apply our approach to study the heat conduction of the thermal fin under uncertainty from the diffusivity coefficient and the wave propagation generated by a Gaussian source under uncertainty from the propagation medium. We shall also compare our approach to stochastic collocation methods and Monte-Carlo methods to assess the reliability of the computations.
by Ferran Vidal-Codina.
S.M.
Glenn, Russell David. "A reduced order controller design method based on the Youla parameterization of all stabilizing controllers". Ohio : Ohio University, 1995. http://www.ohiolink.edu/etd/view.cgi?ohiou1174396903.
Texto completoYamazato, Takaya, Iwao Sasase y Shinsaku Mori. "A New Viterbi Algorithm with Adaptive Path Reduction Method". IEICE, 1993. http://hdl.handle.net/2237/7839.
Texto completoBrand, Jason M. "Biaxial Material Design Method for the ReducedAperture Waveguide Model". Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1421064567.
Texto completoLison-Pick, Mandy. "Accepting a reduced self after acute trauma". Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/201.
Texto completoNames, Benjamin Joseph. "An Efficient Reduced Order Modeling Method for Analyzing Composite Beams Under Aeroelastic Loading". Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/71676.
Texto completoMaster of Science
Gavros, Athanasios. "Use of the Reduced Precision Redundancy (RPR) method in a radix4 FFT implementation". Thesis, Monterey, California. Naval Postgraduate School, 2010. http://hdl.handle.net/10945/5162.
Texto completoReduced precision redundancy (RPR), as a new method for improving fault tolerance in FPGAs, appears promising in replacing triple modular redundancy (TMR) to prevent the single event effects due to radiation in arithmetic processes. As a test of this approach, the RPR technique was used to implement a Radix-4 fast Fourier transform (FFT). This design was implemented in a Xilinx Virtex 2 FPGA in order to find the possible gain in speed and power as compared to the TMR method. This thesis deals with a 64-point Radix-4 in-place FFT, based on an improved FFT algorithm. The whole FFT structure was implemented based on self-designed modules and by manipulating the embedded Virtex II FPGA's modules. The point was to create a fast and small FFT module that could be altered according to specific application requirements. The implementation of the FFT was successful, managing to handle data in real time at a speed of 134MHz. Based on this FFT design, the next challenge was the implementation of TMR and RPR modules. The first attempt was the TMR structure, implemented by creating three identical replicas of the FFT and installing a voter per FFT stage. This implementation was unsuccessful due to space limitations. The next step was the alteration of the existing FFT and the creation of a smaller 8 x 8 bit butterfly module for the RPR structure. After the successful completion of this step, implementation of a RPR module with an 8/32 degree was commenced. Ambiguities and inefficient radiation protection were identified in this implementation. Finally, adopting a new RPR approach and a higher degree of 14/32, a smooth and correct RPR module was created that could work in real time, and handle data at a speed of 163MHz. Both TMR and RPR with a degree of 14/32 methods were compared, confirming the RPR's advantage in power consumption and in occupied FPGA's resources.
Syrén, Ludvig. "A method for introducing flexibility in rigid multibodies from reduced order elastic models". Thesis, Umeå universitet, Institutionen för fysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-160417.
Texto completoHammerschmidt, Martin [Verfasser]. "Optical simulation of complex nanostructured solar cells with a reduced basis method / Martin Hammerschmidt". Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1106250745/34.
Texto completoTan, Yong Kwang Alex. "Reduced basis method for 2nd order wave equation : application to one-dimensional seismic problem". Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/39209.
Texto completoMIT Institute Archives copy: pages 93 and 94 bound in reverse order.
Includes bibliographical references (p. 93-95).
In this thesis, we solve the 2nd order wave equation, which is hyperbolic and linear in nature, to determine the pressure distribution for a one-dimensional seismic problem with smooth initial pressure and rate of pressure change with time. With Dirichlet and Neumann boundary conditions, the pressure distribution is solved for a total of 500 time steps, which is slighter more than a periodic cycle. Our focus is on the dependence of the output, the average surface pressure as it varies with time, on the system parameters ,u, which consist of the earthquake source x8 and the occurring time T. The reduced basis method, the offline-online computational procedures and the associated a posteriori error estimation are developed. We have shown that the reduced basis pressure distribution is an accurate approximation to the finite element pressure distribution. The greedy algorithm, the procedure of selecting the basis vectors which span the reduced basis space, works reasonably well although a period of slow convergence is experienced: this is because the finite element pressure distribution along the edges of the earthquake source-time space are fairly "unique" and cannot be accurately represented as a linear combination of the existing basis vectors;
(cont.) hence, the greedy algorithm has to bring these "unique" finite element pressure distribution into the reduced basis space individually, accounting for the slow convergence rate. Lastly, applying the online stage instead of the finite element method does not result in a reduction of computational cost: the dimension of the finite element space Af = 200 is comparable with the dimension of the reduced basis space N = 175; however, when the two-dimensional model problem is run, the dimension of the finite element space is A = 3.98 x .04 while the dimension of the reduced basis space is N = 267 and the online stage is around 62.2 times faster then the finite element method. The proposition for the a posteriori error estimation developed shows that the maximum effectivity. the maximum ratio of the error bound over the norm of the reduced basis error, is of magnitude O(103) and increases rapidly when the tolerance is lower. However, this high value is due to the norm of the reduced basis error having a low value and hence not a cause for concern. Furthermore, the ratio of the maximum error bound over the maximum norm of the reduced basis error has a constant magnitude of only 0(102).
(cont.) Lastly, the maximum output effectivity is significantly larger than the maximum effectivity of the pressure distribution due to a conservative bound for the dual contribution. The offline-online computational procedures work well in determining the reduced basis pressure distribution. However, during the a posteriori error estimation, heavy canceling of the various offline stage matrices results in small values for the square of the dual norm of the residuals which decreases as the tolerance is lowered. When the tolerance is of magnitude 0(10-6), the square of the dual norm of the residuals is of magnitude 0(10-14) which is very close to machine precision. Hence, precision error sets in and the offline-online computational procedures break down. Finally, the inverse problem works reasonably well, giving a "possibility region" of the set of system parameters where the actual system parameters may reside. We note that at least 9 time steps should be selected for observation to ensure that the rising and dropping region of the output is detected. Lastly, the greater the measured field error, the larger the "possibility region" we obtain.
by Tan Yong Kwang, Alex.
S.M.
Ruchi, Sangeetika. "Computational Modeling of Laser Therapy of Port-Wine Stains- Based on Reduced Scattering Method". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1428070493.
Texto completoDcunha, Ruhee Lancelot. "Towards an Improved Method for the Prediction of Linear Response Properties of Small Organic Molecules". Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/104677.
Texto completoDoctor of Philosophy
Theoretical chemistry attempts to provide connections between the structure of molecules and their observable properties. One such family of observables are chiroptical properties, or the effect of the medium on the light which passes through it. These properties include the scattering, absorption and change in polarization of light. Light being classically an electromagnetic field, chiroptical properties can be derived by treating molecules quantum mechanically and the light classically. The prediction of chiroptical properties on computers using the principles of quantum mechanics is still a growing field, being very sensitive to the method used, and requiring considerations of factors such as conformations and anharmonic corrections. Matching experimental properties is an important step in the creation of a reliable method of predicting properties of systems in order to provide more information than can be obtained through experimental observation. This work begins by addressing the problem of matching experimentally obtained quantities. Our results show that current time-intensive methods still fall short in the matching of experimental data. Thus, we then move on to approximating a more robust but computationally expensive method in order to be able to use a more accurate method on a larger scale than is currently possible. On obtaining positive results for small test systems, we test the new method on larger systems, and explore possible improvements to its accuracy and efficiency.
Liu, Biheng. "Reduced order models for the analysis of offshore lattice structures". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2022.
Buscar texto completoArkalgud, Ravi. "Vortex shedding analysis and control using reduced order modelling and viscous cell boundary element method". Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274099.
Texto completoUdoff, Geoffrey. "An Alternate Trawling Method: Reduced Bycatch and Benthic Disturbance Achieved with the Wing Trawling System". ScholarWorks@UNO, 2016. http://scholarworks.uno.edu/td/2217.
Texto completoKarlsson, Fredrik y Jan van Doorn. "Applying the Vowel Formant Dispersion (VFD) method to the study of reduced or alterered vowel productions". Umeå universitet, Institutionen för språkstudier, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-74416.
Texto completoZhang, Zhenying Verfasser], Karen [Akademischer Betreuer] [Veroy y Michael [Akademischer Betreuer] Herty. "Certified reduced basis method for variational inequalities / Zhenying Zhang ; Karen Paula Veroy-Grepl, Michael Matthias Herty". Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156922216/34.
Texto completoZhang, Zhenying [Verfasser], Karen [Akademischer Betreuer] Veroy y Michael [Akademischer Betreuer] Herty. "Certified reduced basis method for variational inequalities / Zhenying Zhang ; Karen Paula Veroy-Grepl, Michael Matthias Herty". Aachen : Universitätsbibliothek der RWTH Aachen, 2016. http://d-nb.info/1156922216/34.
Texto completoMalik, Muhammad Haris. "Reduced order modeling for smart grids' simulation and optimization". Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/405730.
Texto completoCette these présente l'étude de la réduction de modeles pour les réseaux électriques et les réseaux de transmission. Un point de vue mathématique a été adopté pour la réduction de modeles. Les réseaux électriques sont des réseaux immenses et complexes, dont l'analyse et la conception nécessite la simulation et la résolution de grands modeles non-linéaires. Dans le cadre du développement de réseaux électriques intelligents (smart grids) avec une génération distribuée de puissance, l'analyse en temps réel de systemes complexes tels que ceux-ci nécessite des modeles rapides, fiables et précis. Dans la présente étude, nous proposons des méthodes de réduction de de modeles a la fois a priori et a posteriori, adaptées aux modeles dynamiques des réseaux électriques. Un accent particulier a été mis sur la dynamique transitoire des réseaux électriques, décrite par un modele oscillant nonlinéaire et complexe. La non-linéarité de ce modele nécessite une attention particuliere pour bénéficier du maximum d'avantages des techniques de réduction de modeles. lnitialement, des méthodes comme POD et LATIN ont été adoptées avec des degrés de succes divers. La méthode de TPWL, qui combine la POD avec des approximations linéaires multiples, a été prouvée comme étant la méthode de réduction de modeles la mieux adaptée pour le modele dynamique oscillant. Pour les lignes de transmission, un modele de parametres distribués en domaine fréquentiel est utilisé. Des modeles réduits de type PGD sont proposés pour le modele DP des lignes de transmission. Un probleme multidimensionnel entierement paramétrique a été formulé, avec les parametres électriques des lignes de transmission inclus comme coordonnées additionnelles de la représentation séparée. La méthode a été étendue pour étudier la solution du modele des lignes de transmission pour laquelle les parametres dépendent de la fréquence.
Esta tesis presenta un estudio de la reducción de modelos (MOR) para redes de transmisión y distribución de electricidad. El enfoque principal utilizado ha sido la dinámica transitoria y para la reducción de modelos se ha adoptado un punto de vista matemático. Las redes eléctricas son complejas y tienen un tamaño importante. Por lo tanto, el análisis y diseño de este tipo de redes mediante la simulación numérica, requiere la resolución de modelos no-lineales complejos. En el contexto del desarrollo de redes inteligentes, el objetivo es un análisis en tiempo real de sistemas complejos, por lo que son necesarios modelos rápidos, fiables y precisos. En el presente estudio se proponen diferentes métodos de reducción de modelos, tanto a priori como a posteriori, adecuados para modelos dinámicos de redes eléctricas. La dinámica transitoria de redes eléctricas, se describe mediante modelos dinámicos oscilatorios no-lineales. Esta no-linearidad del modelo necesita ser bien tratada para obtener el máximo beneficio de las técnicas de reducción de modelos. Métodos como la POD y la LATIN han sido inicialmente utilizados en esta problemática con diferentes grados de éxito. El método de TPWL, que combina la POD con múltiples aproximaciones lineales, ha resultado ser el mas adecuado para sistemas dinámicos oscilatorios. En el caso de las redes de transmisión eléctrica, se utiliza un modelo de parámetros distribuidos en el dominio de la frecuencia. Se propone reducir este modelo basándose en la PGD, donde los parámetros eléctricos de la red de transmisión son incluidos como coordenadas de la representación separada del modelo paramétrico. Este método es ampliado para representar la solución de modelos con parámetros dependientes de la frecuencia para las redes de transmisión eléctrica
Nyangiwe, Nangamso Nathaniel. "Graphene based nano-coatings: synthesis and physical-chemical investigations". Thesis, UWC, 2012. http://hdl.handle.net/11394/3237.
Texto completoIt is well known that a lead pencil is made of graphite, a naturally form of carbon, this is important but not very exciting. The exciting part is that graphite contains stacked layers of graphene and each and every layer is one atom thick. Scientists believed that these graphene layers could not be isolated from graphite because they were thought to be thermodynamically unstable on their own and taking them out from the parent graphite crystal will lead them to collapse and not forming a layer. The question arose, how thin one could make graphite. Two scientists from University of Manchester answered this question by peeling layers from a graphite crystal by using sticky tape and then rubbing them onto a silicon dioxide surface. They managed to isolate just one atom thick layer from graphite for the first time using a method called micromechanical cleavage or scotch tape. In this thesis chemical method also known as Hummers method has been used to fabricate graphene oxide (GO) and reduced graphene oxide. GO was synthesized through the oxidation of graphite to graphene oxide in the presence of concentrated sulphuric acid, hydrochloric acid and potassium permanganate. A strong reducing agent known as hydrazine hydrate has also been used to reduce GO to rGO by removing oxygen functional groups, but unfortunately not all oxygen functional groups have been removed, that is why the final product is named rGO. GO and rGO solutions were then deposited on silicon substrates separately. Several characterization techniques in this work have been used to investigate the optical properties, the morphology, crystallography and vibrational properties of GO and rGO.
Song, Huimin. "Rigorous joining of advanced reduced-dimensional beam models to 3D finite element models". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33901.
Texto completoDaversin, Catty Cécile. "Reduced basis method applied to large non-linear multi-physics problems : application to high field magnets design". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD019/document.
Texto completoThe magnetic field constitutes a powerfull tool for researchers, especially to determine the properties of the matter. This kind of applications requires magnetic fields of high intensity. The "Laboratoire National des Champs Magnetiques Intenses" (LNCMI) develops resistive magnets providing such magnetic field to scientists. The design of these magnets represents a challenge interms of design. We have developed a range of non-linear coupled models taking into account the whole involved physics, implemented through the Feel++ library. Designed for many query context, the reduced basis method applied to the multi-physics model aims to circumvent the complexity of the problem. lts efficiency allows to move towards parametric studies and sensitivity analysis in various concrete applications. Especially, the method SER we introduce in this thesis is a significant breakthrough for non-linear and non-affine problems in an industrial context
Tonn, Timo [Verfasser]. "Reduced-Basis Method (RBM) for Non-Affine Elliptic Parametrized PDEs : (Motivated by Optimization in Hydromechanics) / Timo Tonn". Ulm : Universität Ulm. Fakultät für Mathematik und Wirtschaftswissenschaften, 2012. http://d-nb.info/1026992222/34.
Texto completoLülf, Fritz Adrian. "An integrated method for the transient solution of reduced order models of geometrically nonlinear structural dynamic systems". Phd thesis, Conservatoire national des arts et metiers - CNAM, 2013. http://tel.archives-ouvertes.fr/tel-00957455.
Texto completoRowland, David J. Reid. "Reduced exposure time as a method of minimising the impact of vibration on electronic speckle pattern interferometry". Master's thesis, University of Cape Town, 2002. http://hdl.handle.net/11427/5475.
Texto completoMay, David. "The TLC Method for Modeling Creep Deformation and Rupture". Honors in the Major Thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1620.
Texto completoB.S.M.E.
Bachelors
Mechanical and Aerospace Engineering
Engineering and Computer Science
Mechanical Engineering
Di, Donfrancesco Fabrizio. "Reduced Order Models for the Navier-Stokes equations for aeroelasticity". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS603.
Texto completoThe numerical prediction of aeroelastic systems responses becomes unaffordable when parametric analyses with high-fidelity CFD are required. Reduced order modeling (ROM) methods have therefore been developed in view of reducing the costs of the numerical simulations while preserving a high level of accuracy. The present thesis focuses on the family of projection based methods for the compressible Navier-Stokes equations involving deforming meshes in the case of aeroelastic applications. A vector basis obtained by Proper Orthogonal Decomposition (POD) combined to a Galerkin projection of the system equations is used in order to build a ROM for fluid mechanics. Masked projection approaches are therefore implemented and assessed for different test cases with fixed boundaries in order to provide a fully nonlinear formulation for the projection-based ROMs. Then, the ROM is adapted in the case of deforming boundaries and aeroelastic applications in a parametric context. Finally, a Reduced Order Time Spectral Method (ROTSM) is formulated in order to address the stability issues which involve the projection-based ROMs for fluid mechanics applications
Pratt, Robert L. "AFFORDABLE, ALTERNATIVE TEST METHOD FOR MEETING CIVIL AVIATION REDUCED VERTICAL SEPARATION MINIMUM (RVSM) REQUIRMENTS ON MILITARY/COMMERCIAL AIRCRAFT". International Foundation for Telemetering, 2000. http://hdl.handle.net/10150/608286.
Texto completoA recent Air Traffic Management (ATM) initiative has reduced certain oceanic routes from a 2,000-foot vertical separation minimum to a 1,000-foot (300 m) separation minimum between flight levels of 29,000 feet and 41,000 feet. As a result of this initiative, an aircraft transitioning from the Continental United States (CONUS) to Europe or Asia will be required to have a validated, certified altimeter reporting system within the specified tolerances. The aging military airframes are not currently Reduced Vertical Separation Minimum (RVSM) certified. The impact on military deployment time to foreign theatres as well as high- fuel cost makes this a high-priority DoD issue. This paper describes the test and evaluation (T&E) challenge, viable solutions and test method for meeting the RVSM requirements in an approved, affordable, and least down-time (minimal aircraft modification) manner. The test method described herein utilizes a PACER aircraft in formation with the RVSM candidate aircraft. The RVSM is just one of the many Global Air Traffic Management (GATM) requirements which must be met for military aircraft to fly within premium airspace during overseas deployment. The commercial equivalent of GATM is Communications Navigation and Surveillance/Air Traffic Management (CNS/ATM). Our focus will be on meeting the RVSM certification requirements as related to the test environment.
Clark, M. Sean. "Generalist predators in reduced-tillage corn : predation on armyworm, habitat preferences, and a method to estimate absolute densities /". Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-11102009-020213/.
Texto completoBenner, P., R. Byers y E. Barth. "HAMEV and SQRED: Fortran 77 Subroutines for Computing the Eigenvalues of Hamiltonian Matrices Using Van Loanss Square Reduced Method". Universitätsbibliothek Chemnitz, 1998. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-199800926.
Texto completoWang, Zegao, Pingjian Li, Yuanfu Chen, Jiarui He, Wanli Zhang, Oliver G. Schmidt y Yanrong Li. "Pure thiophene–sulfur doped reduced graphene oxide: synthesis, structure, and electrical properties". Royal Society of Chemistry, 2014. https://tud.qucosa.de/id/qucosa%3A36294.
Texto completoKasnakoglu, Cosku. "Reduced order modeling, nonlinear analysis and control methods for flow control problems". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1195629380.
Texto completoZhao, Xiaopeng. "Modeling and Simulation of MEMS Devices". Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11227.
Texto completoPh. D.
Mummidivarapu, Satya Sri. "A Method for Determining Body Weight Replacement Load during Squat Exercise in Weightlessness". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690685.
Texto completoGao, Haotian. "POD-Galerkin based ROM for fluid flow with moving boundaries and the model adaptation in parametric space". Diss., Kansas State University, 2018. http://hdl.handle.net/2097/38776.
Texto completoDepartment of Mechanical and Nuclear Engineering
Mingjun Wei
In this study, a global Proper Orthogonal Decomposition (POD)-Galerkin based Reduced Order model (ROM) is proposed. It is extended from usual fixed-domain problems to more general fluid-solid systems with moving boundaries/interfaces. The idea of the extension is similar to the immersed boundary method in numerical simulations which uses embedded forcing terms to represent boundary motions and domain changes. This immersed boundary method allows a globally defined fixed domain including both fluid and solid, where POD-Galerkin projection can be directly applied. However, such a modified approach cannot get away with the unsteadiness of boundary terms which appear as time-dependent coefficients in the new Galerkin model. These coefficients need to be pre-computed for prescribed periodic motion, or worse, to be computed at each time step for non-prescribed (e.g. with fluid-structure interaction) or non-periodic situations. Though computational time for each unsteady coefficient is smaller than the coefficients in a typical Galerkin model, because the associated integration is only in the close neighborhood of moving boundaries. The time cost is still much higher than a typical Galerkin model with constant coefficients. This extra expense for moving-boundary treatment eventually undermines the value of using ROMs. An aggressive approach is to decompose the moving boundary/domain to orthogonal modes and derive another low-order model with fixed coefficients for boundary motion. With this domain decomposition, an approach including two coupled low-order models both with fixed coefficients is proposed. Therefore, the new global ROM with decomposed approach is more efficient. Though the model with the domain decomposition is less accurate at the boundary, it is a fair trade-off for the benefit on saving computational cost. The study further shows, however, that the most time-consuming integration in both approaches, which come from the unsteady motion, has almost negligible impact on the overall dynamics. Dropping these time-consuming terms reduces the computation cost by at least one order while having no obvious effect on model accuracy. Based on this global POD-Galerkin based ROM with forcing term, an improved ROM which can handle the parametric variation of body motions in a certain range is also presented. This study shows that these forcing terms not only represent the moving of the boundary, but also decouple the moving parameters from the computation of model coefficients. The decoupling of control parameters provides the convenience to adapt the model for the prediction on states under variation of control parameters. An improved ROM including a shit mode seems promising in model adaptation for typical problems in a fixed domain. However, the benefit from adding a shit mode to model diminishes when the method is applied to moving-boundary problems. Instead, a combined model, which integrates data from a different set of parameters to generate the POD modes, provides a stable and accurate ROM in a certain range of parametric space for moving-boundary problems. By introducing more data from a different set of parameters, the error of the new model can be further reduced. This shows that the combined model can be trained by introducing more and more information. With the idea of the combined model, the improved global ROM with forcing terms shows impressive capability to predict problems with different unknown moving parameters, and can be used in future parametric control and optimization problems.
Meng, Liang. "Reduced shape-space : approach to material characterization instrumented indentation test case". Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2377/document.
Texto completoThe thesis lies at the intersection of three disciplines : numerical methods, experimental techniques, and machine learning. The primary aim of this work is to develop a group of algorithms for characterization by inverse analysis of a material’s constitutive law. In the field of material characterization, indentation test is especially attractive since it is considered non-destructive, and may be performed even on a structure in service. The test, similar to a hardness test, consists in penetrating an indenter into the surface of the material. The force exerted on the indenter is recorded against the penetration depth over a series of time instants, leading to a force-displacement (P-h) curve, which is the most frequently used source of information for the identification of material properties. However, the inverse problem based solely on this curve tends to be ill-posed, leading to nonunique identification solution, i.e., the "mystical material pair", for whom the corresponding force-displacement curves are almost identical despite the very different material properties. The basic idea is then to complete the identification process with innovative experimental measurements, such as laser microscope, which allows measuring the 3D residual imprint after the withdrawal of the indenter. To address the advantage of this measurement over P-h curve, we propose to construct, within a reduced affine space, a manifold of shapes admissible to the postulated constitutive law, experimental and simulation setups, based on synthetic data. The intrinsic dimensionality of the manifold limits the number of identifiable parameters allowing to validate numerically experimental procedures. Considering both the model and measurement errors, we develop a series of local manifold learning algorithms to solve the inverse problem iteratively for experimental results obtained in cooperation with INSA de Rennes. This approach allows us to characterize diverse metallic materials of increasing complexity, based on actual experimental measurements. For example, for the Hollomon’s law, the mystical pair is alleviated in using a single imprint, while for the Voce law, a multi-depth experimental protocol is proposed to differentiate mystical siblings
HERATH, MUTHUKUMARA MUDIYANSELAGE Samantha Chandani. "Using EEG measures to quantify reduced daytime vigilance in patients diagnosed with obstructive sleep apnoea using a novel electroencephalogram analysis method". Thesis, The University of Sydney, 2013. http://hdl.handle.net/2123/9726.
Texto completoCapaldo, Matteo. "A new approximation framework for PGD-based nonlinear solvers". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLN011/document.
Texto completoThe aim of this work is to introduce an approximation framework, called Reference Points Method (RPM), in order to decrease the computational complexity of algebraic operations when dealing with separated variable approximations in the Proper Generalized Decomposition (PGD) framework.The PGD has been introduced in [1] in the context of the LATIN method to solve efficiently time dependent and/or parametrized nonlinear partial differential equations in structural mechanics (see, e.g., the review [2] for recent applications). Roughly, the PGD technique consists in seeking the solution of a problem in a relevant Reduced-Order Basis (ROB) which is generated automatically and on-the-fly by the LATIN method. This latter is an iterative strategy which generates the approximations of the solution over the entire time- space-parameter domain by successive enrichments. At a particular iteration, the ROB, which has been already formed, is at first used to compute a projected Reduced-Order Model (ROM) and find a new approximation of the solution. If the quality of this approximation is not sufficient, the ROB is enriched by determining a new functional product using a greedy algorithm.However, model reduction techniques are particularly efficient when the ROM needs one construction only. This is not the case for the model reduction techniques when they are addressed to nonlinear problems. Indeed, in such a case, the operators which are involved in the construction of the ROM change all along the iterative process and no preliminary computations can be performed in advance to speed up the online process. Hence, the construction of the ROM is an expensive part of the calculation strategy in terms of CPU. It ensues from the need to evaluate the high-dimensional nonlinear function (and eventually its Jacobian) and then to project it to get the low-dimensional operators at each computational step of a solution algorithm. This amounts to being the bottleneck of nonlinear model reduction strategies.The present work is then focused on a further reduction of the computational cost, thanks to the introduction of a new approximation framework dedicated to PGD-based nonlinear solver. It is based on the concept of reference times, points and parameters and allows to define a compressed version of the data. Compared to other similar techniques [3,4] this is not an interpolation technique but an algebraic framework allowing to give an inexpensive first approximation of all quantities in a separated variable form by explicit formulas. The space of compressed data shows interesting properties dealing the elementary algebraic operations. The RPM is introduced in the PGD-based nonlinear solver to compute some repetitive operations. These operations are related to the resolution of the time/parameter problem that involves the update of the tangent operator (for nonlinear problems) and the projection of this latter on the Reduced Order Basis. For that the RPM allows to simplify and reduce the number of operations needed.[1] Ladevèze P., Sur une famille d’algorithmes en mécanique des structures, Comptes Rendus Académie des Sciences. Paris. Ser. II 300, pp.41-44, 1985.[2] Chinesta, F., Ladevèze, P., and Cueto, E. A short review on model order reduction based on proper generalized decomposition. Archives of Computational Methods in Engineering, 18, pp.395-404, 2011.[3] Barrault M., Maday Y., Nguyen N., Patera A., An ’empirical interpolation’ method: application to efficient reduced-basis discretization of partial differential equations, Comptes Rendus Académie des Sciences. Paris. Ser. I, 339, pp. 667-672, 2004.[4] Chaturentabut S., Sorensen D., Nonlinear model reduction via discrete empirical interpolation, Society for Industrial and Applied Mathematics 32(5), pp.2737-2764, 2010
Ori, Miklós. "Local Buckling of Doubly-Symmetric I-Sections Subjected to Warping Torsion : The limitations of the Reduced Cross-Section Method under unconventional loading". Thesis, KTH, Bro- och stålbyggnad, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-251031.
Texto completoAlvarez, Boto Roberto. "Development of the NCI method : high performance optimization and visualization". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066220/document.
Texto completoNon-covalent interactions are of paramount importance in chemistry. Interactions between a catalyst and its substrate, self-assembly of nanomaterials, enantiomer production and many other chemical reactions, are most of the time non-covalent in nature. They are also fundamental for crystallographic analysis, since they set up the scenario for molecular crystallization, whose guiding rules are still a fruitful filed of research. Non-covalent interactions are frequently visualized using distance dependent contacts, generally without consideration of hydrogen atoms. Most of these interactions are usually identified by the use of tabulated van der Waals radii, which are not flexible enough to reveal the interplay with the environment. New approaches, based on 3D functions that can be derived either form experiment or computation (e.g. the electro density) are now widely used to identify and visualize non-covalent interactions. In this thesis we analyse the NCI method, and namely, its main ingredient, the reduced density gradient. Its capabilities for visualizing chemical interactions are examined. This 3D function is then, connected with the kinetic energy density and a interpretation of the reduced density gradient in terms of the bosonic behaviour of the electronic system is presented. Then, the NCI method is applied to visualise and analyse chemical interactions: from covalent to non-covalent interactions. The chemical reactivity is also addressed. The NCI method is applied to rationalised the outcome of several reactions