Tesi sul tema "Hybrid method"
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1
Kang, David Sung-Soo. "Hybrid stress finite element method". Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14973.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERO
Bibliography: leaves 257-264.
by David Sung-Soo Kang.
Ph.D.
2
Slemp, Wesley Campbell Hop. "Integrated Sinc Method for Composite and Hybrid Structures". Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/77111.
Testo completoAbstract (sommario):
Composite materials and hybrid materials such as fiber-metal laminates, and functionally graded materials are increasingly common in application in aerospace structures. However, adhesive bonding of dissimilar materials makes these materials susceptible to delamination. The use of integrated Sinc methods for predicting interlaminar failure in laminated composites and hybrid material systems was examined. Because the Sinc methods first approximate the highest-order derivative in the governing equation, the in-plane derivatives of in-plane strain needed to obtain interlaminar stresses by integration of the equilibrium equations of 3D elasticity are known without post-processing. Interlaminar stresses obtained with the Sinc method based on Interpolation of Highest derivative were compared for the first-order and third-order shear deformable theories, the refined zigzag beam theory and the higher-order shear and normal deformable beam theory. The results indicate that the interlaminar stresses by the zigzag theory compare well with those obtained by a 3D finite element analysis, while the traditional equivalent single layer theories perform well for some laminates.
The philosophy of the Sinc method based on Interpolation of Highest Derivative was extended to create a novel weak form based approach called the Integrated Local Petrov-Galerkin Sinc Method. The Integrated Local Petrov-Galerkin Sinc Method is easily utilized for boundary-value problem on non-rectangular domains as demonstrated for analysis of elastic and elastic-plastic plane-stress panels with elliptical notches. The numerical results showed excellent accuracy compared to similar results obtained with the finite element method.
The Integrated Local Petrov-Galerkin Sinc Method was used to analyze interlaminar debonding of composite and fiber-metal laminated beams. A double-cantilever beam and a fixed-ratio mixed mode beam were analyzed using the Integrated Local Petrov-Galerkin Sinc Method and the results were shown to correlate well with those by the finite element method. An adaptive Sinc point distribution technique was implemented for the delamination analysis which significantly improved the methods accuracy for the present problem. Delamination of a GLARE, plane-strain specimen was also analyzed using the Integrated Local Petrov-Galerkin Sinc Method. The results correlate well with 2D, plane-strain analysis by the finite element method, including interlaminar stresses obtained by through-the-thickness integration of the equilibrium equations of 3D elasticity.Ph. D.
3
Kooreman, Gabriel. "Consistent hybrid diffusion-transport spatial homogenization method". Thesis, Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52950.
Testo completoAbstract (sommario):
Recent work by Yasseri and Rahnema has introduced a consistent spatial homogenization (CSH) method completely in transport theory. The CSH method can very accurately reproduce the heterogeneous flux shape and eigenvalue of a reactor, but at high computational cost. Other recent works for homogenization in diffusion or quasi-diffusion theory are accurate for problems with low heterogeneity, such as PWRs, but are not proven for more heterogeneous reactors such as BWRs or GCRs.
To address these issues, a consistent hybrid diffusion-transport spatial homogenization (CHSH) method is developed as an extension of the CSH method that uses conventional flux weighted homogenized cross sections to calculate the heterogeneous solution. The whole-core homogenized transport calculation step of the CSH method has been replaced with a whole- core homogenized diffusion calculation. A whole-core diffusion calculation is a reasonable replacement for transport because the homogenization procedure tends to smear out transport effects at the core level. The CHSH solution procedure is to solve a core-level homogenized diffusion equation with the auxiliary source term and then to apply an on-the-fly transport-based re-homogenization at the assembly level to correct the homogenized and auxiliary cross sections. The method has been derived in general geometry with continuous energy, and it is implemented and tested in fine group, 1-D slab geometry on controlled and uncontrolled BWR and HTTR benchmark problems. The method converges to within 2% mean relative error for all four configurations tested and has computational efficiency 2 to 4 times faster than the reference calculation.
4
Liu, Yunshan. "P-adaptive hybrid/mixed finite element method /". The Ohio State University, 1998. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487950153602937.
Testo completo
5
Msiza, Andrew Khutso. "Hybrid synthesis method for mass exchange networks". Master's thesis, University of Cape Town, 2001. http://hdl.handle.net/11427/5434.
Testo completoAbstract (sommario):
Bibliography: leaves 121-[123].Process synthesis can be approached from three techniques: heuristics, physical and thermodynamic insight, and mathematical programming. Hybrid methods where two or all of the synthesis methods are combined are now becoming used, taking advantage of the combined strength of the individual techniques. In this thesis the option of combining pinch analysis (a physical and thermodynamic insight-based approach) and superstructure-based programming is explored.
6
Baboulet, Olivier. "Path Exchange Method for Hybrid Life-Cycle Assessment". Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9930.
Testo completoAbstract (sommario):
To keep process-specificity while extending system boundaries hybrid techniques were developed allowing the micro structure of the important parts of a system to be revealed at the same time the entire economic system in which the system is embedded to be covered. Despite the substantial improvements bestowed by hybrid techniques some downsides still hold. Tiered hybrid LCA first does not model feedbacks whereas the relationship between the process-based system and the input-output based system is interactive and second it may suffer from double counting incidents as a process may be instigated in both the IO and LCI data. Integrated hybrid LCA overcomes those aforementioned pitfalls but only at a price of high labor and data intensity. This work aims to elaborate a new hybridisation method that avoids previously mentioned drawbacks. This technique is designed to not operate anymore at the matrix level as is the case for current hybridisation techniques but at the structural path level, per se the finest level of detail possible for the disaggregation of the Leontief inverse, and as such an ad hoc basis to carry out an hybrid analysis. It is argued that the method presented here constitutes a culmination amongst hybridization techniques. Its operability and capabilities are demonstrated before an interpretation from an input-output vantage point is carried out on a case-study not to be found in the literature, a comparison across the faculties of a university.
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Robertson, Bradford E. "A hybrid probabilistic method to estimate design margin". Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50375.
Testo completoAbstract (sommario):
Weight growth has been a significant factor in nearly every space and launch vehicle development program. In order to account for weight growth, program managers allocate a design margin. However, methods of estimating design margin are not well suited for the task of assigning a design margin for a novel concept. In order to address this problem, a hybrid method of estimating margin is developed. This hybrid method utilizes range estimating, a well-developed method for conducting a bottom-up weight analysis, and a new forecasting technique known as executable morphological analysis. Executable morphological analysis extends morphological analysis in order to extract quantitative information from the morphological field. Specifically, the morphological field is extended by adding attributes (probability and mass impact) to each condition. This extended morphological field is populated with alternate baseline options with corresponding probabilities of occurrence and impact. The overall impact of alternate baseline options can then be estimated by running a Monte Carlo analysis over the extended morphological field. This methodology was applied to two sample problems. First, the historical design changes of the Space Shuttle Orbiter were evaluated utilizing original mass estimates. Additionally, the FAST reference flight system F served as the basis for a complete sample problem; both range estimating and executable morphological analysis were performed utilizing the work breakdown structure created during the conceptual design of this vehicle.
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Eckbo, Ryan. "Simulating vortex ring collisions: extending the hybrid method". Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18476.
Testo completoAbstract (sommario):
Vortex filaments are isolated tubes of vorticity, the behaviour of which is important to the understanding of the fluid flows they are found in. Vortex reconnection, the change in filament topology when filaments collide, is a particular phenomenon that cannot be modelled by the traditional vortex method, which leads (Ghuneim, 2002) to integrate it with the level set method. However, the computational complexity of this method's traditional implementation severly limits the types of simulations possible. Motivated by this, we propose a new level set implementation that stores voxels in a tree data structure such that neighborhood relationships are recursively encoded. We then modify the hybrid method to use this data structure, allowing for longer, more expansive, accurate and versatile filament evolutions. A simpler mechanism for handling reconnections is also proposed. We demonstrate the advantages of the extended hybrid method and the new level set implementation with simulations of a variety of laboratory filament evolutions with reconnection events.Les filaments de vortex sont des tubes de vorticité isolés, et il est important de comprendre leur comportement pour caractériser les fluides dans lesquels ils apparaissent. La reconnection de vortex, i.e. le changement de topologie qui survient lorsque des filaments entrent en collision, est un phénomène particulier qui ne peut être modelisé par la méthode traditionnelle des vortex, ce qui mène (Ghuneim, 2002, Ghuneim et al., 2002) à l'intégrer avec la méthode des ensembles de niveau. Cependant, la complexité de l'implémentation traditionnelle de la méthode des ensembles de niveau limite grandement le type de simulations qui sont possibles. Motivés par ceci, nous proposons une nouvelle implémentation qui organise les voxels dans une structure de données en arbre, ce qui permet des évolutions de filaments plus longues, plus étendues, plus précises et plus versatiles. Un méchanisme simplifié pour gérer les reconnections est aussi proposé. Nous démontrons les avantages de la méthode hybride étendue et de la nouvelle implémentation par ensembles de niveau par des simulations d'une variété d'évolutions de filaments avec des événements de reconnection.
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Atalianis, Christos Andreas. "Hydrodynamic analysis of structures by a hybrid method". Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283649.
Testo completo
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COSSIO, MARCO ULISES DE LA QUINTANA. "SENSIVITY ANALYSIS WITH THE HYBRID BOUNDARY ELEMENT METHOD". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1998. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=1405@1.
Testo completoAbstract (sommario):
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOREste trabalho apresenta um estudo do cálculo de sensibilidades necessário para a análise de problemas inversos e de otimização, usando o método híbrido dos elementos de contorno. Com esta finalidade, é desenvolvida uma formulação que permite obter as sensibilidades à mudança de forma, por diferenciação implícita das integrais de contorno, de uma estrutura já discretizada. Demonstra-se que as sensibilidades das matrizes obtidas desta formulação apresentam propriedades espectrais definidas, que são derivadas da formulação básica do método híbrido dos elementos de contorno. Todo o desenvolvimento é feito para um problema da elastostática tridimensional, embora sejam apresentadas apenas aplicações de problemas bidimensionais e de potencial, como casos particulares. As singularidades que surgem na integração no cálculo das sensibilidades são facilmente solucionáveis a partir das integrais da formulação básica do método híbrido dos elementos de contorno. As implementações numéricas são feitas utilizando a linguagem de programação Maple V release 3. Para ambos os casos, de potencial e elasticidade bidimensional, são usados elementos lineares para a representação do contorno. São apresentadas comparações entre os resultados analíticos obtidos através desta formulação com os resultados obtidos usando a técnica de diferenças finitas (centradas), com o objetivo de demonstrar a eficiência e precisão da metodologia aqui desenvolvida.
The present work describes a formulation for computing design sensitivities required in inverse problems and shape optimization of solid objects, in the frame of the hybrid boundary element method. The so-called direct differentiation method is applied in order to calculate the gradients, i.e. the implicit diferentiation of the discretized boundary is performed, resulting in a general and efficient analysis technique for shape design sensitivity analysis of all structural quantities. It is demonstrated that the resulting sensitivities matrices present some useful spectral properties, which are related to the matrix spectral properties of the basic hybrid formulation. This formulation is valid for tridimensional solids, although only potential and bidimensional applications are considered as particular cases. The singularities that appear in the resulting boundary integrals are exactly the same which have already been dealt with in the basic formulation. The analytical and numerical procedures were performed by using the mathematical package Maple V release 3. Linear boundary elements were used for both potential and elasticity problems. Numerical results obtained by the present procedure are compared to finite differences results to demonstrate the effectiveness of the present formulation.
Este trabajo presenta un estudio del cálculo de sensibilidades, que tiene gran importancia en el análisis de problemas inversos y de optimización, usando el método híbrido de los elementos de contorno. Con esta finalidad, se desarrolla una formulación que permite obtener las sensibilidades al cambio de forma de una extructura ya discretizada, por diferenciación implícita de las integrales de contorno. Se demuestra que las sensibilidades de las matrices obtenidas por esta formulación presentan propriedades espectrales definidas, que son derivadas de la formulación básica del método híbrido de los elementos de contorno. El desarrollo de la formulación se realiza para un problema de elastostática tridimensional, aunque se presentan apenas las aplicaciones de problemas bidimensionales y de potencial, como casos particulares. Las singularidades que surgen en la integración en el cálculo de las sensibilidades pueden ser fácilmente resueltas a partir de las integrales de la formulación básica del método híbrido de los elementos de contorno. La implementación numérica utiliza el lenguaje de programación Maple V release 3. Para los casos de potencial y elasticidad bidimensional, se utilizan elementos lineales para la representación del contorno. Se comparan los resultados analíticos obtenidos a través de esta formulación con los resultados obtenidos usando la técnica de diferencias finitas (centradas), con el objetivo de demostrar la eficiencia y precisión de la metodología aqui desarrollada.
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Takahashi, Hitoshi. "Study of Double-Hypernuclei with Hybrid-Emulsion Method". 京都大学 (Kyoto University), 2003. http://hdl.handle.net/2433/149060.
Testo completo
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Dao, Tuan Anh. "A stable and accurate hybrid FE-FD method". Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-396844.
Testo completoAbstract (sommario):
We develop a hybrid method to couple finite difference methods and finite element methods in a nonconforming multiblock fashion. The aim is to optimize computational efficiency when complex geometries present. The proposed coupling technique requires minimal changes in the existing schemes while maintaining strict stability, accuracy, and conservation. Analysis and computational results are shown for a linear problem (to the advection-diffusion equation) and a nonlinear problem (to the viscous Burger's equation) in two spatial dimensions
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Radiy, Mamon. "A hybrid method for capacitated vehicle routing problem". Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/69.
Testo completoAbstract (sommario):
The vehicle routing problem (VRP) is to service a number of customers with a fleet of vehicles. The VRP is an important problem in the fields of transportation, distribution and logistics. Typically the VRP deals with the delivery of some commodities from a depot to a number of customer locations with given demands. The problem frequently arises in many diverse physical distribution situations. For example bus routing, preventive maintenance inspection tours, salesmen routing and the delivery of any commodity such as mail, food or newspapers.We focus on the Symmetric Capacitated Vehicle Routing Problem (CVRP) with a single commodity and one depot. The restrictions are capacity and cost or distance. For large instances, exact computational algorithms for solving the CVRP require considerable CPU time. Indeed, there are no guarantees that the optimal tours will be found within a reasonable CPU time. Hence, using heuristics and meta-heuristics algorithms may be the only approach. For a large CVRP one may have to balance computational time to solve the problem and the accuracy of the obtained solution when choosing the solving technique.This thesis proposes an effective hybrid approach that combines domain reduction with: a greedy search algorithm; the Clarke and Wright algorithm; a simulating annealing algorithm; and a branch and cut method to solve the capacitated vehicle routing problem. The hybrid approach is applied to solve 14 benchmark CVRP instances. The results show that domain reduction can improve the classical Clarke and Wright algorithm by 8% and cut the computational time taken by approximately 50% when combined with branch and cut.Our work in this thesis is organized into 6 chapters. Chapter 1 provides an introduction and general concepts, notation and terminology and a summary of our work. In Chapter 2 we detail a literature review on the CVRP. Some heuristics and exact methods used to solve the problem are discussed. Also, this Chapter describes the constraint programming (CP) technique, some examples of domain reduction, advantages and disadvantage of using CP alone, and the importance of combining CP with MILP exact methods. Chapter 3 provides a simple greedy search algorithm and the results obtained by applying the algorithm to solve ten VRP instances. In Chapter 4 we incorporate domain reduction with the developed heuristic. The greedy algorithm with a restriction on each route combined with domain reduction is applied to solve the ten VRP instances. The obtained results show that the domain reduction improves the solution by an average of 24%. Also, the Chapter shows that the classical Clarke and Wright algorithm could be improve by 8% when combined with domain reduction. Chapter 4 combines domain reduction with a simulating annealing algorithm. In Chapter 4 we use the combination of domain reduction with the greedy algorithm, Clarke and Wright algorithm, and simulating annealing algorithm to solve 4 large CVRP instances.Chapter 5 incorporates the Branch and Cut method with domain reduction. The hybrid approach is applied to solve the 10 CVRP instances that we used in Chapter 4. This Chapter shows that the hybrid approach reduces the CPU time taken to solve the 10 benchmark instances by approximately 50%. Chapter 6 concludes the thesis and provides some ideas for future work. An appendix of the 10 literature problems and generated instances will be provided followed by bibliography.
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Khlifi, Rachid. "Hybrid space discretizing method -method of moments for numerical modeling of transient interference". kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/620327/document.pdf.
Testo completo
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Hagdahl, Stefan. "Hybrid methods for computational electromagnetics in the frequency domain". Licentiate thesis, KTH, Numerical Analysis and Computer Science, NADA, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1655.
Testo completoAbstract (sommario):
In this thesis we study hybrid numerical methods to be usedin computational electromagnetics. We restrict the methods tospectral domain and scattering problems. The hybrids consist ofcombinations of Boundary Element Methods and Geometrical Theoryof Diffraction.
In the thesis three hybrid methods will be presented. Onemethod has been developped from a theoretical idea to anindustrial code. The two other methods will be presented mainlyfrom a theoretical perspective. We will also give shortintroductions to the Boundary Element Method and theGeometrical Theory of Diffraction from a theoretical andimplementational point of view.
Keywords:Maxwells equations, Geometrical Theoryof Diffraction, Boundary Element Method, Hybrid methods,Electromagnetic Scattering
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Eiderbrant, Tobias. "Automating a test method for a hybrid test environment". Thesis, Linköping University, Department of Computer and Information Science, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-57646.
Testo completoAbstract (sommario):
Ericsson has a very big and expensive test environment with a lot of GSM AXE equipment. In order to decrease the cost of testing Ericsson has developed a combination of simulated and real hardware, the Hybrid Test Environment (HTE). There is no formal supervision and testing of the HTE system today and this has left the HTE system unstable and the testers have been avoiding using HTE. It is important for Ericsson that the confidence for HTE will increase. The goal of this thesis is to produce a method for testing the HTE system. An automated test tool has been implemented in order to monitor and test the HTE system. During the two weeks that the test tool has been operational it has discovered 4 servers in 3 different HTE rigs that malfunctioned. These servers were fixed and were operational before the end-users could discover any problem.
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MOSQUEIRA, DANIEL HUAMAN. "THE HYBRID BOUNDARY ELEMENT METHOD FOR GRADIENT ELASTICITY PROBLEMS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2013. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=23938@1.
Testo completoAbstract (sommario):
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Atualmente está bem difundido o uso de novas modelagens matemáticas para o estudo do comportamento de micro e nano sistemas mecânicos e eléctricos. O problema de escala é notável quando o tamanho das moléculas, partículas, grãos ou cristais de um sólido é relativamente considerável em relação ao comprimento do microdispositivo. Nesses casos a teoria clássica dos meios contínuos não descreve apropriadamente a solicitação estrutural e é necessária uma abordagem mais geral através de teorias generalizadas não-clássicas que contém a elasticidade clássica como um caso particular delas, onde os parâmetros constitutivos que representam às partículas são desprezíveis. Quando os efeitos microestruturais são importantes, o comportamento não responde como um material homogêneo se não como um material homogêneo. Cem anos atrás os irmãos Cosserat desenvolveram uma teoria de grãos rígidos imersos dentro de um macromeio elástico; posteriormente Toupin, Mindlin e outros pesquisadores na década de 60 formularam a chamada teoria gradiente de deformações, que recentemente é um objeto de muitas investigações analíticas e experimentais. Na década de oitenta, Aifantis e colaboradores conseguiram desenvolver uma teoria de gradiente de deformações simplificada, baseada em só uma constante elástica adicional não-clássica representativa da energia de deformação volumétrica para caracterizar satisfatoriamente os padrões dos fenômenos não-clássicos. Beskos e colaboradores estenderam o campo de aplicações da proposta inicial de Aifantis e fizeram as primeira implementações de elementos de contorno 2D e 3D para análises de elasticidade gradiente estática, no domínio da frequência e a mecânica da fratura. Desde o tempo de Toupin e Mindlin, procura-se estabelecer uma base variacional da teoria e uma formulação consistente das condições de contorno cinemáticas e de equilíbrio, o que parece ter tido êxito com os recentes trabalhos de Amanatidou e Aravas. Esta tese apresenta a formulação do método híbrido de elementos de contorno e finitos na elasticidade gradiente desenvolvida por Dumont e Huamán decompondo o potencial de Hellinger-Reissner em dois princípios de trabalhos virtuais: o primeiro em deslocamentos virtuais e o segundo em forças virtuais. Com esta finalidade é considerado além dos parâmetros clássicos, o trabalho realizado pelas tensões, deformações, forças e deslocamentos não-clássicos. É apresentado o desenvoltimento das soluções fundamentais singulares e polinomiais atráves das equações diferenciais de sexta ordem obtidas da equação de equilíbrio em termos de deslocamento na elasticidade gradiente. É apresentada também a aplicaçõ do método híbrido de contorno para problemas de tensão axial unidimensional e flexão bidimensional de vigas. Finalmente mostra-se a aplicação numérica do método em elementos finitos, é verificado o patch test de elementos finitos de diferentes ordem e mostra-se também análises de convergência.
The use of new mathematical modeling in the study of micro and Nano electro mechanical systems is currently becoming widespread. The scaling problem is apparent when the length of molecules, particles or grains immersed in the material is relatively important compared with the whole micro device dimension. Under this approach the classical theories of mechanics cannot describe suitably the structural requirement and it is necessary a more general outlook through non classical generalized theories which enclose the classical elasticity as a particular case where the non-classical constitutive parameters are negligible. When the microstructural effects are important, the material does not respond as a homogeneous but as a non-homogeneous one. A hundred years ago Cosserat brothers formulated a new theory of rigid grains which were embedded in an elastic macro medium; later Toupin, Mindlin along others researchers in 1960s developed a gradient strain theory which has been recently the source of many analystics and experimental investigations. In 1980s Ainfantis et al could develop a simplified strain gradient theory with just one additional non classical elastic constant which represents the volumetric elastic strain energy and characterized successfully the whole non classical pattern phenomenon. Beskos et al extended the treatment proposed initially by Aifantis and developed the first numerical applications for 2D and 3D boundary element methods and solved static as dynamic and crack problems. Since the times of Toupin and Mindlin it is looking for to establish a variational theory with a consistent cinematic and equilibrium boundary conditions, which seemed to have had success in the recent works of Amanatiodou and Aravas. This work presents the formulation of the hybrid boundary and finite element methods under the strain gradient scope which were developed by Dumont and Huamán through the versatile decomposition of the Hellinger-Reissner potential in two work principles: the displacements virtual work and the forces virtual work; both principles contain the virtual work performed by the non-classical magnitudes. Following, it is presented the complete development of singular and polynominal fundamental solutions abtained through the sixth order strain gradient differential equilibrium equations in terms of displacements. Next it is shown an application of the method to unidimensional truss element and bidimensional beam. Finally, it is presented a numerical application to strain gradient finite element, it is checked the patch tests to different elements orders and it is also shown a series of convergence analysis.
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Quinelato, Thiago de Oliveira. "Mixed hybrid finite element method in elasticity and poroelasticity". Laboratório Nacional de Computação Científica, 2017. https://tede.lncc.br/handle/tede/273.
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Esta tese é focada no desenvolvimento e na análise de aproximações em dimensão finita das equações que descrevem problemas de elasticidade linear e poroelasticidade. A estratégia de aproximação é baseada em formulações de elementos finitos mistas hibridas desses problemas e a construção dos espaços de dimensão finita é guiada por várias propriedades desejadas: continuidade das trações (conservação do momento linear), simetria do tensor de tensão (conservação do momento angular), número reduzido de graus de liberdade globais e robustez sob distorção de malha. A principal dificuldade está relacionada com o atendimento simultâneo da condição inf-sup e da simetria do tensor de tensão. O ultimo requisito é relaxado, sendo satisfeito de maneira fraca pela introdução de um multiplicador de Lagrange. A maior contribuição é o desenvolvimento e a análise de espaços de dimensão finita estáveis para aproximação mista dos problemas de elasticidade linear e poroelasticidade em malhas quadrilaterais arbitrárias. Esses espaços são capazes de fornecer convergência com taxa ótima do campo de tensão na norma H(div) em malhas de quadriláteros arbitrários, o que é provado pela análise numérica e confirmado por experimentação.
This thesis is focused on the development and analysis of finite dimensional approximations of the equations describing linear elasticity and poroelasticity problems. The approximation strategy is based on mixed hybrid finite element formulations of those problems and the construction of the finite dimensional spaces is guided by several desired properties: continuity of the tractions (conservation of linear momentum), symmetry of the stress tensor (conservation of angular momentum), reduced number of global degrees of freedom, and robustness under mesh distortion. The main difficulty is related with the simultaneous fulfillment of the inf-sup condition and the symmetry of the stress tensor. The last requirement is relaxed, being enforced in the weak sense through the introduction of a Lagrange multiplier. The main contribution is the development and analysis of stable finite dimensional spaces for mixed approximation of linear elasticity and poroelasticity problems on arbitrary quadrilateral meshes. These spaces are capable of providing optimal order convergence of the stress field in the H(div)-norm on meshes of arbitrary quadrilaterals, which is proved by numerical analysis and confirmed by experimentation.
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Whitacre, Jonathan H. "A Hybrid Method For Solving A Single Nonlinear Equation". Youngstown State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1296145853.
Testo completo
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Biglarifadafan, Ali. "A general hybrid force-based method for structural analysis". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5266/.
Testo completoAbstract (sommario):
The form of the energy function (i.e. Total, Hellinger-Reissner, Hu-Washizu or Complementary energy functions) has a significant influence on FEM performance. Motivated by the ability of the force-based method to satisfy the equilibrium equation and ability of the displacement-based method to satisfy compatibility equation, this thesis proposes a mathematical framework, namely the ‘Hybrid Force-Based Method’ which employs two physical concepts; the Total and Complementary Potential Energy functions. Satisfaction of both the Total and Complementary Potential Energy function is critical to the success of the Hybrid Force-Based Method. The Hybrid Force-Based Method is constructed using these two independent energy functions in order to perform inelastic structural analyses. The method has been proposed, implemented and evaluated across the entire structure, element, section and material domains first considering each domain separately and then in combination. The equilibrium and compatibility equations are satisfied simultaneously by discretisation of these two equations, and accuracy is controlled by specifying the upper and lower bounds of the results. Outcomes following evaluation of the proposed method can be classified into the following three categories: (i) structure-level performance (see Chapter 2), (ii) material-level performance (see Chapter 3), and (iii) element level performance (see Chapter 4). The proposed Hybrid Force-Based Method is constructed by deriving the governing equations directly from the Total and Complementary Potential Energy functions, leading to two distinct variants of the hybrid approach (i) the so-called ‘augmented Hybrid Force-Based Method’, and (ii) the so-called ‘unaugmented Hybrid Force-Based Method’. A number of numerical posterior process tests were devised and used to demonstrate the performance of these two variations of the hybrid method (see Sections 2.9.4.1 and 2.9.5.1) to demonstrate those methods ability in convergence in contrast to the Large Increment Method. Due to the occurrence of numerical instabilities experienced when using various established solution algorithms in solving the fundamental equations at the material level, within implicit approach (such as the Standard Implicit Method, the Cutting Plane Method, and the Closest Point Projection Method). A new form of the constitutive equation solver is proposed in Sections 3.9, referred to as the General Implicit Method (GIM). It is shown that the GIM can be implemented both in the strain and stress domains, and is therefore appropriate for use in both the displacement- and the force-based solution family of methods. The GIM is then evaluated by comparing its predictions to those of other common solution algorithms for inelastic analysis. Performance evaluation involves the use of a new error indicator that guarantees the uniqueness and accuracy of a solution in both the stress and the strain domains. Three iso-error maps serve to emphasis the accuracy, reliability, and computational performance of the General Implicit Method as a solution method compared to those are evaluated for the defined Stress Increment Ratio. The fundamental equations at the element level are followed, based on structured fibre discretisation. The decomposition of the various degrees of freedom into deformational and rigid-body motion serve as a mechanism by which independent equilibrium equations can be determined for each element. The subsequent equation is able to involve axial force, torsion, and both in and out of plane moments while a general form of shear strain distribution is also involved. The original form of the solution at the cross section of the elements leads to novel governing equations that are based on the characteristics of the hybrid force-based approach. The numerical evaluation in Section 4.11.7.1 demonstrates the performance of the proposed method. The newly defined error indicators demonstrate the accuracy and computational performance of the method and the uniqueness of the solution in satisfying both the equilibrium and compatibility equations for Euler-Bernoulli, Timoshenko, and Reddy strain distributions across the element section. Further to the structured fibre, distributed, semi-distributed and concentrated inelastic approach elements, as a simplified form of the element are implemented and evaluated. Although performance of those original formulations is evaluated independently in in comparison with the conventional approaches, compatibility of those as an important issue is followed as well. The numerical evaluation demonstrates higher accuracy and reliability by following the proposed method, further to the higher computational performance respect to the conjugate approaches.
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Chatzilias, Dimitris. "A Hybrid Difficulty Balancing Method on “Casual” Mobile Game". Thesis, KTH, Skolan för datavetenskap och kommunikation (CSC), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-173953.
Testo completoAbstract (sommario):
A new hybrid Video Game Difficulty Balancing method which stands in between the two traditional methods (Static and Dynamic) has been suggested in this project aiming to discreetly estimate the player’s difficulty preference and make the respective in-game adjustment. This method has been based on the hypothesis that the user’s difficulty preferences can be to some extent predicted by some of their in-game actions. A casual mobile game containing a User Testing part has been developed for this purpose and played by 56 participants. The extracted results offer some insights on various gamers’ demographic groups behaviors and some indications that the intended prediction is feasible.
22
Olander, Jonathan. "Comparison of the hybrid and thermal lattice-Boltzmann methods". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/31826.
Testo completoAbstract (sommario):
Thesis (M. S.)--Paper Science Engineering, Georgia Institute of Technology, 2010.Committee Chair: Aidun, Cyrus; Committee Member: Graham, Samuel; Committee Member: Joshi, Yogendra. Part of the SMARTech Electronic Thesis and Dissertation Collection.
23
Tsoi, Sai Hong. "On a hybrid finite element with weak Kirchhoff assumption". HKBU Institutional Repository, 2000. http://repository.hkbu.edu.hk/etd_ra/218.
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Liu, Wenjie. "A multiscale hybrid method for materials containing defects and inhomogeneities /". Search for this dissertation online, 2006. http://www.lib.umi.com/cr/ksu/main.
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Arbault, Damien. "Globalized impacts International trade accounting in a hybrid LCI method". Thesis, KTH, Urban and Regional Studies, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-24863.
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26
Wiedermann-Ondrej, Nadine. "Hybrid Instruments and the Indirect Credit Method - Does it work?" SFB International Tax Coordination, WU Vienna University of Economics and Business, 2007. http://epub.wu.ac.at/1018/1/document.pdf.
Testo completoAbstract (sommario):
This paper analyses the possibility of double non-taxation of hybrid instruments in cross border transactions where the country of the investor has implemented the indirect credit method for mitigation or elimination of double taxation. From an isolated perspective a double non-taxation cannot be obtained because typically no taxes are paid in the foreign country due to the classification as debt and therefore even in the case of a classification as a dividend in the country of the investor no indirect credit can be given to the taxpayer. Using this as a starting point this paper investigates the impact of asymmetric tax treatment of hybrid instruments on the indirect credit method and the potentials for minimizing the tax burden or even the possibility of obtaining a double non-taxation. On this basis the paper develops a formula that identifies the optimal investment strategy based on given tax rates. Special interest is given to the limitations and possible barriers to hybrid transactions. This paper intents to initiate a scientific discussion concerning the tax impact of hybrid instruments in countries where the indirect credit method is employed. (author's abstract)Series: Discussion Papers SFB International Tax Coordination
27
Schlottke-Lakemper, Michael [Verfasser]. "A Direct-Hybrid Method for Aeroacoustic Analysis / Michael Schlottke-Lakemper". München : Verlag Dr. Hut, 2017. http://d-nb.info/1135596190/34.
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CAVACO, MARCO ANTONIO MARTINS. "AN HYBRID METHOD FOR PHOTOELASTIC ANALYSIS OF ORTHOTROPIC COMPOSITE MATERIALS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1990. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=20636@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOEste trabalho apresenta uma nova técnica para análise de tensões em modelos fotoelásticos planos. Essa técnica baseia-se na determinação de coeficientes para funções de tensão aproximadas, através da coleta dos dados extraídos de ordens de franjas isocromáticas e de condições de contorno de modelos fotoelásticos planos. O modelo tem como vantagens a determinação de fatores de concentração de tensões com boa precisão, além de permitir a separação de tensões em pequenas ou grandes regiões de modelos fotoelásticos planos, sem requerer a leitura de franjas isoclínicas. Uma outra grande vantagem está na possibilidade imediata de acoplamento desse método com um analisador de imagens para determinação automática de Kt. Foram encontrados excelentes resultados em problemas onde haviam concentradores de tensão e no estudo de regiões próximas a cargas concentradas. A determinação dos coeficientes das funções foi feita através de um programa escrito em BASIC, que utiliza o método de Newton-Raphson em conjunto com o ajuste dos dados por mínimos quadrados. Vários exemplos foram estudados com o objetivo de avaliar sua performance. Entre eles estão: carga concentrada sobre uma superfície semi-infinita; placa infinita e finita com futo circular sujeita à tração; disco circular submetidos à cargas diametrais compressivas; viga reta carregada à tração constante e a momento constante; e barra com duplo entalhe em U submetida a momento constante.
This work presents a new technique for improving stress analysis in photoelastic plane models. This technique is based on the determination of coefficients of approximated stress functions through the collection of isochromatic fringe data, and by the applications of boundary conditions to photoelastic plane models. The technique has as advantages the accurate determination of stress concentration factors and the stress without the need for collecting isoclinic fringe data. Another great advantage, is the immediate use of this method coupled with an image analyzer device for automatic extraction of Kt. Excellent results were found in problems where stress concentration or concentrated loading were present. The coefficients of the stress functions were determined by a BASIC program, using a Newton-Raphson technique coupled to a least square algorithm. Many example were tested to evaluate its performance. Among them are: concentrated force at a point of a straight boundary; infinite and finite plate with circular holes subjected to uniaxial tensile loads; circular disk under compressive diametral forces; bar subjected to pure tensile and pure bending loads; and a double U-notched bar under pure bending.
29
CASTRO, LUIZ OTAVIO GUERREIRO DE. "AN HYBRID METHOD FOR PHOTOELASTIC ANALYSIS OF ORTHOTROPIC COMPOSITE MATERIALS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1992. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24947@1.
Testo completoAbstract (sommario):
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOFUNDAÇÃO DE APOIO À PESQUISA DO ESTADO DO RIO DE JANEIRO
Este trabalho tem como finalidade a apresentação de um método novo e eficiente para a análise e separação de tensões em materiais compostos (conjugados). O método híbrido consiste no acoplamento da lei ótica para materiais ortotrópicos com as equações de compatibilidade e equilíbrio para corpos anisotrópicos. As soluções destas equações são representadas por funções analíticas de variáveis complexas. O método propõe que se aproximem as funções analíticas por funções polinomiais. Estas funções aproximadas são determinadas através do acoplamento das equações de equilíbrio e compatibilidade com dados experimentais, obtidos da resposta fotoelástica, e com métodos numéricos (Newton-Raphson e mínimos quadrados), possibilitando a determinação dos coeficientes integrantes das funções polinomiais. O método apresenta como principal vantagem a capacidade de separar as tensões, com precisão, em pequenas ou mesmo em grandes regiões de modelos fotoelásticos planos, sem requerer a leitura de franjas isoclínicas. São apresentados excelentes resultados obtidos com a aplicação do método desenvolvido em alguns casos específicos, envolvendo um material composto por uma matriz de resina reforçada por fibras de vidro com arranjo unidirecional. Três casos são objetos de estudo: A) Barra retangular submetida à tração, com a direção do reforço paralela a direção da carga aplicada. B) Barra retangular submetida à tração. com direção do reforço fazendo um ângulo qualquer com a direção da carga aplicada. C) Plano semi-infinito submetido à carga concentrada atuando perpendicularmente à direção do reforço.
The objective of this paper is to present a new and efficient method to analyse and separate stresses in composite materials. The hybrid method associates the stress-optic law for orthotropic materials with the compatibility and equlibrium equations for anisotropic bodies. The solutions of these equatios are represented by analytical functions of complex variables. The method proposes that these analytical functions be approximate by polynomial functions. These aapproximate functions are determined by the association of the compatibility equilibrium equatios with experimental data (obtained from the photoelastic response) and numerical methods (Newton-Raphson and least squares method). The method presents as a major advantage the capacity to separate stresses precisely in small or even in large regions of photoelastic plane models, without needign to collect isoclinic fringe data. The thesis presents excellent results obtained by the application of the developed method in some specific cases, where a fiber glass reinforced epoxy resin is used as a model material, will be shown. Three cases are studied: A) Rectangular bar in tension with the fiber reinforcement axis parallel to the applied load direction B) Rectangular bar in tension with the fiber reinforcement axis making a known angle with the applied load direction C) Semi-infinite plane subjected to a concentrated edge load which is perpendicular to the fiber reinforcement axis.
30
Docherty, Stephanie Y. "Rarefied gas flows in microscale geometries : a hybrid simulation method". Thesis, University of Strathclyde, 2015. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=25916.
Testo completoAbstract (sommario):
Accurate predictions of the flow behaviour in microscale geometries are needed, for example, to design and optimise micro devices, and to ensure their safety/reliability. Rarefied gas flows in such geometries tend, however, to be far from local thermodynamic equilibrium, meaning that the flow behaviour cannot be described by conventional fluid mechanics. Alternative approaches for modelling 'non-equilibrium' gas flows have been proposed in recent years; because analytical solution methods are subject to significant limitations, the direct simulation Monte Carlo (DSMC) method is, at present, the most practical numerical simulation tool for dilute gases. Unfortunately, the computational expense of tracking and computing collisions between thousands (or perhaps millions) of DSMC particles means that simulating the scales of realistic flow problems can require months (or even years) of computing time. This has resulted in the development of continuum-DSMC 'hybrid' methods, which aim to combine the efficiency of a conventional continuum-fluid description with the detail and accuracy of the DSMC method. This thesis focuses on the development of a continuum-DSMC method that offers a more general approach than existing methods. Using a heterogeneous framework with a field-wise coupling strategy, this new method is not subject to the limitations of the well-known domain decomposition framework, or the restrictions of the heterogeneous point-wise coupling approach. The continuum-fluid description is applied across the entire flow field, while the DSMC method is performed in dispersed micro elements that can be any size and at any location; these elements then provide the continuum description with updated constitutive and boundary information. Unlike most methods in the literature, the coupling strategy presented here is able to cope with heat transfer, and so non-isothermal flows can be simulated. Testing and validation of this new continuum-DSMC method is performed by simulating a number of benchmark cases and comparing the results with full DSMC solutions of the same cases. Two 1D flow problems are considered: a micro Fourier flow problem tests the energy coupling procedure of the method, and a high-speed micro Couette flow problem demonstrates the full coupling algorithm. In general, the method's accuracy is found to depend on the arrangement of the micro elements - with sufficient micro resolution, good agreement with the equivalent full DSMC simulations can be obtained. Although the hybrid method offers no computational speed-up over the full DSMC simulations for several of these 1D test cases and only modest speed-ups for the others, both of these 1D ow problems are simulated only to validate the coupling strategy of the method. Considerable speed-ups are offered by the method when simulating a larger and more realistic flow problem: a microchannel with a high-aspect-ratio cross-section acts as a representative geometry for modelling a gas flow through a narrow microscale crack. While the limitations of existing hybrid methods preclude their use for this type of high-aspect-ratio geometry, the new hybrid method is able to model this problem under isothermal and non-isothermal conditions. The implementation of the method is simplified to 2D by assuming that the flow variation in the streamwise direction is negligible, i.e. the method is applied to the microchannel cross-section only. Accurate predictions of the mass flow rate and the streamwise velocity field are obtained for a number of test cases; accurate predictions of the temperature field are also obtained when there is a temperature difference between the bounding walls.
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Ichikawa, Atsuko. "Study of S=-2 Nuclear Systems with Hybrid Emulsion Method". 京都大学 (Kyoto University), 2001. http://hdl.handle.net/2433/150816.
Testo completoAbstract (sommario):
本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第8712号
理博第2284号
新制||理||1199(附属図書館)
UT51-2001-F42
京都大学大学院理学研究科物理学・宇宙物理学専攻
(主査)教授 今井 憲一, 教授 西川 公一郎, 教授 笹尾 登
学位規則第4条第1項該当
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Piellard, Mélanie. "A hybrid method for computational aeroacoustics applied to confined geometries". Ecully, Ecole centrale de Lyon, 2008. http://bibli.ec-lyon.fr/exl-doc/TH_T2175_mpiellard.pdf.
Testo completoAbstract (sommario):
Ce travail de thèse concerne le développement d une méthode de calcul du bruit aéroacoustique pour des applications industrielles. Les contraintes liées à ce contexte imposent de choisir une méthode hybride basée sur l’utilisation de codes de calcul commerciaux, adaptée aux écoulements turbulents basse vitesse. Cette approche repose sur l’analogie de Lighthill, et son application fait intervenir deux étapes. Dans la première, l’écoulement turbulent instationnaire est calculé et permet de déterminer les termes sources acoustiques, lesquels sont ensuite propagés dans une seconde étape afin d’obtenir le champ acoustique rayonné. L’implémentation choisie, à savoir le couplage entre les codes Fluent (CFD) et Actran/LA (acoustique) dans une formulation variationnelle, est particulièrement bien adaptée pour l’industrie puisque la complexité des géométries est facilement prise en compte dans les méthodes aux volumes finis (Fluent) et éléments finis (Actran/LA). On considère plusieurs configurations académiques. Le rayonnement acoustique de deux tourbillons corotatifs avec et sans écoulement moyen est d’abord étudié pour valider la méthode; en particulier, on souhaite démontrer la nécessité de prendre en compte l’écoulement moyen local dans le calcul du terme source. Pour ce faire, une simulation numérique directe (DNS) est effectuée avec Fluent pour obtenir une solution de référence, ce qui met en évidence la nature de quadrupôle tournant de la source acoustique. La méthode hybride est ensuite mise en oeuvre avec succès: les termes sources sont calculés à partir des champs de vitesse obtenus dans le calcul DNS, puis ils sont propagés en champ lointain dans le domaine spectral avec Actran/LA. Une deuxième vérification, complémentaire à la comparaison au calcul direct, consiste à résoudre de manière analytique l’équation de Lighthill en utilisant le tenseur de Lighthill calculé par DNS. On retrouve par ailleurs que la présence d’un écoulement moyen à la fois dans les zones de propagation acoustique et de sources a seulement une influence sur la réfraction des ondes acoustiques; en revanche, il n’est pas nécessaire d’en tenir compte dans la détermination du terme source. La deuxième étude académique porte sur la gestion de la sortie de structures turbulentes du domaine de calcul. Ceci produit un rayonnement dipolaire parasite, d’origine purement numérique, et dont les niveaux sont suffisamment élevés pour perturber la solution. On choisit ici de modéliser le problème par la convection d’un tourbillon parfait à travers une frontière fictive. Divers filtres spatiaux sont testés pour ramener les termes sources à zéro à la traversée de la frontière; le réglage optimal de ces filtres dépend de la taille de la structure à dissiper ainsi que de sa vitesse de convection. Enfin, une application réelle est considérée, le diaphragme en conduit à faible nombre de Mach. Une première simulation des grandes échelles (LES) est effectuée sur un modèle réduit de la géométrie puisque l’envergure est tronquée à 10% de sa valeur totale. Malgré les limitations de cette approche, en particulier du fait que la trop petite extension du domaine selon l’envergure empêche un développement tridimensionnel correct de la turbulence, le calcul acoustique bidimensionnel associé produit des résultats consistants. Le modèle 3D complet est ensuite étudié, avec, de la même manière, une LES qui met en évidence des caractéristiques aérodynamiques cette fois tout à fait conformes à la DNS de référence. Une décimation des termes sources par interpolation spatiale est nécessaire pour réduire la taille du modèle acoustique 3D; les résultats après propagation souffrent donc de cette approximation qui nécessite une plus ample validationThis PhD work deals with the development of a Computational Aeroacoustics (CAA) method for industrial applications. The constraints linked to this context impose the choice of a hybrid method based on the use of commercial computing codes adapted to turbulent low velocity flows. This approach is based on Lighthill’s Acoustic Analogy, and its application involves two steps. In the first step, the unsteady turbulent flow is computed to determine acoustic source terms, the latter being then propagated in a second step to produce the radiated acoustic field. The implementation is a variational formulation of Lighthill’s Acoustic Analogy with the coupling of Fluent CFD code and Actran/LA acoustic code. It is well adapted to the industry since complex geometries are easily handled in both finite volumes (Fluent) and finite elements (Actran/LA) methods. Two academic configurations are considered. The acoustic radiation produced by two corotating vortices with and without mean flow is first studied for validation. In particular, the goal is to show the necessity to take the local mean flow field into account when computing the source term. A Direct Numerical Simulation (DNS) is therefore performed within Fluent to yield a reference solution; this also reveals the rotating quadrupole nature of the acoustic source. The hybrid method is then applied with success: the source terms are computed from the velocity fields of the DNS, and then propagated to the far field in the spectral domain within Actran/LA. A second verification, in addition to the comparison with DNS results, consists in the analytical resolution of Lighthill’s equation using the Lighthill’s tensor obtained from the DNS. Another important conclusion of this study is that the presence of a mean flow field in both the propagation and source regions only acts on the acoustic waves refraction; however, it is not required to account for it in the source term determination. The second academic study concerns the handling of outgoing turbulent structures from the computing domain. These indeed produce a spurious dipolar acoustic radiation, of numeric nature purely, and with levels high enough to perturb the whole solution. This issue is modeled here with the convection of a perfect vortex through a virtual boundary. Several spatial filters are tested to smooth source terms down to zero at the boundary; the optimal filter tuning depends on the size and convection velocity of the structures to be dissipated. Finally, a real application is considered, the ducted diaphragm at low Mach number. A first Large Eddy Simulation (LES) is performed on a reduced geometry consisting of 10% of the total span. In spite of the model limitations, mainly due to the span reduction preventing a correct three-dimensional development of turbulence, the associated twodimensional acoustic computation yields consistent results. The full scale 3D flow field is then studied, with similarly a LES in which aerodynamic features conform well with the reference DNS. In order to reduce the acoustic model size, source terms are decimated through spatial interpolation. After propagation, the acoustic results suffer from this approximation that would require a more thorough validation
33
Al-Deghaither, Saleh E. "A hybrid FE-BE method for dynamic soil-structure interaction /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858417983533.
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Janzon, Alexandra. "Applications and Limitations of the Hybrid L1/L2Multicarrier Analysis Method". Thesis, Luleå tekniska universitet, Rymdteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-86347.
Testo completoAbstract (sommario):
The multipactor phenomenon is a major concern in modern satellites that operate with highpower transmission in many frequency bands. It occurs when electrons inside RF componentsare accelerated by the RF fields. These electrons then hit walls inside the device, produc-ing secondary electrons. As the number of electrons increases, it may create noise inside thecomponent, thus deteriorating the original signal-to-noise ratio. When designing radio fre-quency equipment for space applications, it is therefore important to know at which powerlevels this occurs. Multicarrier simulations are time consuming and demand high amounts ofcomputer resources. In this thesis the hybrid L1/L2 method has been tested, which is a methodthat separates the geometric and multicarrier simulations into two parts resulting in a shortercomputation time. The conclusion is that the method is more reliable than single carrier sim-ulations, and that it can be used as a first step in the designing process of RF components.It is also a way of estimating a preliminary threshold before starting a full-scale multicarriersimulation.
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Sasi, Kumar Sarath K. "A multi-exchange heuristic for formation of balanced disjoint rings". Texas A&M University, 2005. http://hdl.handle.net/1969.1/4428.
Testo completoAbstract (sommario):
Telecommunication networks form an integral part of life. Avoiding failures on
these networks is always not possible. Designing network structures that survive these
failures have become important in ensuring the reliability of these network structures.
With the introduction of SONET (Synchronous Optical Network) technology, rings
have become the preferred survivable network structure. This network configuration
has a set of disjoint rings (each node being a part of single ring), and these disjoint
rings are connected via another main ring. In this research, we present a mathematical
model for the design of such disjoint rings with node number balance criterion
among the rings. When, given a set of nodes and distances between them, the Balanced
Disjoint Rings (BDR) problem is the minimum total link length clustering of
nodes into a given number of disjoint rings in such a way that there is almost the
same number of nodes in each ring. The BDR problem is a class of the standard
Traveling Salesman Problem (TSP). It is clear from this observation that the BDR
problem becomes a TSP when the number of rings required is set to one. Hence
BDR is NP-Hard, and we do not expect to obtain a polynomial time algorithm for
its solution. To overcome this problem, we developed a set of construction heuristics
(Break-MST, Distance Method, Hybrid Method, GRASP-Based Distance Method)
and improvement heuristics (Multi-Exchange, Single Move). Different combinations of construction and improvement heuristics were implemented and the quality of solution
thus obtained was compared to the standard Branch and Cut Technique. It was
found that the algorithm with GRASP-Based Distance Method as the construction
heuristic and multi-exchange - single-move combination as the improvement heuristic
performed better than other combinations. All combinations performed better in
general than the standard Branch and Cut technique in terms of solution time.
36
吳牧哲. "A Hybrid Method of Text Mining". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/67978399864138435975.
Testo completoAbstract (sommario):
碩士國立彰化師範大學
資訊工程學系
97
「There are estimates that 85% of business information lives in the form of text 」. It is obvious that the structure of most data in real world is not rigorous. In the age of information explosion, it is very convenient to get information through the network, but it will make people difficult to figure out the hidden knowledge in a large amount of information. Therefore, lots of searching or indexing applications have been developed to help people to solve above problem. For example Yahoo and Google are two of these kinds of applications. Text mining is an important branch of data mining; it is a process to extract knowledge and information from unstructured text data sets by applying the techniques of data mining. The mined results can be applied to the development or improvement of a search engine system. In this thesis a two steps clustering method has been proposed to group documents based on the characteristics of terms. It takes the advantages of k-means and fuzzy c-means clustering algorithms. At the beginning, the proposed method constructs groups of terms from collected text data, and finds out the relationships between terms and formed groups based one the ideas of co-occurrence. When constructing the vector spaces of documents, a switch mechanism is introduced to decide whether TF-IDF method will be adopted or not. Finally, the vector spaces of documents will be input into k-means algorithm for clustering. The experiments show that the proposed method can yield robust results than clustering text data by applying k-means algorithm alone.
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YIE, ZONG-CHENG, e 謝宗城. "A hybrid method for root-locus plotting". Thesis, 1988. http://ndltd.ncl.edu.tw/handle/42986335762330826354.
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Liao, Yu-Sheng, e 廖祐笙. "A Study of Hybrid GA/CSP Method". Thesis, 1999. http://ndltd.ncl.edu.tw/handle/42775500618179706576.
Testo completoAbstract (sommario):
碩士東海大學
工業工程學系
87
Genetic Algorithm (GA) is an effective and sound searching method which has been widely used in artificial intelligence research and some industries applications. However, it is more difficult in finding out the right representation than the good answers. Constraint Satisfaction is a very power way in representing the problems. Thus, many real life industrial problems could be represented as a kind of Constraint Satisfaction Problem (CSP). Although GA is good in using multiple searchs to find out the "good" solution. However, it effectiveness and the efficiency is based on the randomness and greedy method. The merit of CSP is due to its constraint propagation. That is the solution space is truncated by the posted constraints. However, it is suffering by the poor search strategy. In this research, we proposed a CSP based representation combined with the dual graph and uniform crossover method. In the preliminary study, it is very promising in limiting the search of GA in the partial-feasible solution space than the whole state space. The quality of the solutions could be enhanced and the time in finding them could be decreased effectively as well.
39
Bi-NaWu e 伍碧那. "A hybrid discretization method for classification algorithms". Thesis, 2014. http://ndltd.ncl.edu.tw/handle/89127564223669943961.
Testo completoAbstract (sommario):
碩士國立成功大學
資訊管理研究所
102
Discretization is one of the major approaches for processing continuous attributes for classifiers. Hybrid discretization sets the method for discretizing each continuous attribute individually. A previous study found that hybrid discretization method is a better approach to improve the performance of naïve Bayesian classifier than unified discretization. That approach determines the discretization method for each attribute based on whether accuracy can be improved or not. The objectives of this study is to develop a hybrid discretization method applicable for classifiers such that it can determine the discretization method for each attribute in data preprocessing step instead of using accuracy. This study will first build a network optimization models based on the association among attributes and the class. Dynamic programming is then employed to find the optimal solution for the network, and this solution indicates the discretization method for each continuous attribute. The classification tools for testing our methods are decision trees, naïve Bayesian classifiers, and rule-based classifiers. The experimental results on 20 data sets show that the computational cost of our method is low, and that in general, the hybrid discretization method have a better performance in naïve Bayesian classifiers and rule-based classifiers, but not in decision trees.
40
Kuo, Wei-Te, e 郭偉德. "A Hybrid Method for Image Enlargement Improvement". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/69205073374847457950.
Testo completoAbstract (sommario):
碩士淡江大學
資訊工程學系
92
Cubic spline interpolation is a standard method for image enlargement but it also causes edges to be blurred. In this paper we use an Incorporated Gradient Method for computing gradient and the idea that pixels have different processing priority in watershed to improve blurry edges from an enlarged image. In our propose method, similar to the watershed segmentation method, each pixel has a priority according to its gradient and is processed in order by an estimate function K(G) to correct its intensity value. Finally, contrast enhancement on intensity and Gaussian denoising on chromaticity are applied to the image for post processing. Experiments to verify the efficiency of the proposed method and comparison to some existing techniques are also presented.
41
WU, ZHI-GIANG, e 吳志強. "Partial hybrid stress method of laminated plates". Thesis, 1990. http://ndltd.ncl.edu.tw/handle/10392151814052575821.
Testo completoAbstract (sommario):
碩士淡江大學
土木工程研究所
78
P.H.S.M.的優點是能解決橫向剪應力於積層板層間介面橫向剪應力不連續的問題，并 能正確地求得剪應力沿厚度方向的分布，尤其當板的厚度逐漸增加時，P.H.S.M.比有 限元素位移法更能模擬板的行為，因此本文將P.H.S.M.與一階層板及兩種高階層板理 論的板元素結合，利用材料性質為直交祑向性的特性，將六個應力分量分割成伸張撓 曲部份及橫向剪力部份，以位移及橫向剪應力為獨立變數，代入Hellinger-Reissner functional中，經變分處理后，得到滿足彈力三大要素及邊界條件，元素自身亦能滿 足應力平衡的要求，故應力場的假設能得到很大的便利。 本文發展的方法，主要是解決橫向剪應力不連續的問題，所得的位移與應力分析結果 亦屬良好，為了驗證此元素的全理性，因此分別探討不同幾何形狀及寬厚比(spanto- thickness ratio)，不同加強織維角度與不同層數的復合材料板之行為，以討論本文 新發展之P.H.S.M.其位移分析的收斂性與應力分析之結果，并與三維彈性解和有限元 素位移法所得結果做比較。
42
Po-AnLin e 林柏安. "A Hybrid Classification Method for Conference Information". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/11565827412416413748.
Testo completoAbstract (sommario):
碩士國立成功大學
資訊管理研究所
100
There are many researchers who want to realize the latest research topic and exchange information with others. They will surf the Internet for scholar conference information, and choose some of them to attend. Some websites have provided part of conference information, but most of them cannot help users find the information users really want to explore; besides, it is a hard work to filter the searched conference information by human. Hence, it is an important issue to help reseachers find out the suited conference information from the huge dataset to attend. To find out the suited conference information efficiently for researcher, this study will classify the conference by text mining. The previous references of traditional classification algorithm like Decision Tree, Naïve Bayes Classifier and Support Vector Machine are not designed to classify documents of conference information, so when we classify these academic documents, we may get some incorrect answers. Therefore, the goal of this study is designing a classification algorithm for conference information. Because there are many terminology nouns or phrases which consist of two words in the conference, when we analyze the importance of the terms, we should take this situation into consideration. Moreover, there are pros and cons in different existing classification algorithms, so the hybrid classification is adopted to integrate the traditional algorithm. We expect the new method designing for conference information can help researchers find the suited conferences efficiently and exactly.
43
"Sensivity analysis with the hybrid boundary element method". Tese, MAXWELL, 1998. http://www.maxwell.lambda.ele.puc-rio.br/cgi-bin/db2www/PRG_0991.D2W/SHOW?Cont=1405:pt&Mat=&Sys=&Nr=&Fun=&CdLinPrg=pt.
Testo completo
44
Picado, de Carvalho Serranho Pedro Miguel. "A Hybrid Method for Inverse Obstacle Scattering Problems". Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-B38F-0.
Testo completo
45
"Kirchho migration using hybrid WENO fast sweeping method". 2015. http://repository.lib.cuhk.edu.hk/en/item/cuhk-1291349.
Testo completoAbstract (sommario):
Zuo, Cheng.Thesis M.Phil. Chinese University of Hong Kong 2015.
Includes bibliographical references (leaves 49-51).
Abstracts also in Chinese.
Title from PDF title page (viewed on 21, September, 2016).
46
Reuß, Silvia. "A Grid-Adaptive Algebraic Hybrid RANS/LES Method". Doctoral thesis, 2015. http://hdl.handle.net/11858/00-1735-0000-0028-8717-2.
Testo completo
47
JIANG, CHENG-SHUN, e 江承舜. "The conceptual design method of hybrid power system". Thesis, 2008. http://ndltd.ncl.edu.tw/handle/21539674221222640812.
Testo completoAbstract (sommario):
碩士國立臺灣大學
機械工程學研究所
96
The purpose of this study is to identify the function and the structure of a hybrid power system clearly, and to search possible conceptual design of hybrid power system efficiently. According to the rules, developed based on graph theory and the characteristics of the system several types of graphs, i.e., structural graph, power flow graph, combined functional graph, can be generated for complete and detailed analysis of the hybrid power system. Then, the possible conceptual design of the hybrid system can be synthesised using this representation through enumeration and selection. The method can be applied to three design topics: 1.Increasing the functions of the system. 2.Muti-structure system synthesis. 3.The synthesis of muti power source system. At last, some case of studies, three design examples, are presented to show the usefulness and effectiveness of the design method.
48
Chiu, Chih-Cheng, e 邱志成. "Research of Production ForecastWith Hybrid Artificial Intelligence Method". Thesis, 2006. http://ndltd.ncl.edu.tw/handle/16101114047160405542.
Testo completoAbstract (sommario):
碩士國立高雄第一科技大學
資訊管理所
94
Abstract Enterprises must make proper decisions to face diversified environments. And prediction will play an important role for enterprises. No matter make decisions or plans, there are more or less uncertainties and risks for implementing in the future. So the main purpose of prediction lies in estimating some events or situations in the future in advance and offer administrator the best information that can find out about the uncertain conditions and reduce the risks in the decision-making process. Artificial intelligence methods are gradually paid attention to in recent years. Among them, neural network is extensive and effective one that applies to prediction questions. Because of most prediction questions mainly belong to non-linear model, and neural networks possess to construct non-linear model. So, this research is mainly probed back-propagation neural network assesses the performance of production forecast. Simultaneously, in order to get best prediction result, combine the advantages of Genetic algorithms and Taguchi Methods. The experimental result shows the hybrid artificial intelligence method obviously superior to two kinds of traditional methods that are gray prediction and regression analysis. Therefore we can know the research represents hybrid artificial intelligence method is more accurate than single model or other traditional methods from all assessment indexes. Also, it III can really offer references to the relevant industry that will proceed with production prediction.
49
Cheng, Yutang, e 鄭玉堂. "A Hybrid Method for Frequent Closed Itemsets Mining". Thesis, 2005. http://ndltd.ncl.edu.tw/handle/02249668949985078124.
Testo completoAbstract (sommario):
碩士國立清華大學
資訊工程學系
93
Frequent itemset mining is a typical question in the data mining domain. There are many researches about this problem already. We can use frequent closed itemset to find all frequent itemset, and the number of frequent closed itemset is much smaller than frequent itemset. Because of these strong points, frequent closed itemset mining becomes an important topic recently. In former researches, we can separate the approaches by data format into two ways: horizontal format and vertical format. And they can be transformed to each other easily. However, no matter what kind of format we use, we have to check if the answer is "closed". And that is overhead. Our new approach uses both horizontal format and vertical format data at the same time. One characteristics of this approach is that we do not need to check “closed” again. Moreover, in certain special dataset our approach has extremely good performance.
50
Lee, ChunHao, e 李俊豪. "Color Filter Array Interpolation Using a Hybrid Method". Thesis, 2004. http://ndltd.ncl.edu.tw/handle/39585069636785838637.
Testo completoAbstract (sommario):
碩士元智大學
資訊工程學系
92
Most digital still cameras capture the natural image using sensors of charge coupled device(CCD) or complementary metal oxide semiconductor (CMOS). The surface of the sensor is usually covered with a color filter array(CFA). In this arrangement, only one color sample is taken for each pixel, and the values of the other colors must be estimated from the neighboring pixels. This process is called the demosaicing process, or the CFA interpolation. In this paper, we propose a new demosaicing method that consists of two steps: an interpolation step that reconstructs to full color by a hybrid method, and a post-processing step that suppresses noticeable demosaicing artifacts by adaptive median filtering. Experimental results will show the proposed method has better perceptual quality as compared to the other published methods.