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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Triple-layer Tissue Prediction for Cutaneous Skin Burn Injury: Analytical Solution and Parametric Analysis

Oguntala, George A., Indramohan, V., Jeffery, S., Abd-Alhameed, Raed 08 May 2021 (has links)
Yes / This paper demonstrates a non-Fourier prediction methodology of triple-layer human skin tissue for determining skin burn injury with non-ideal properties of tissue, metabolism and blood perfusion. The dual-phase lag (DPL) bioheat model is employed and solved using joint integral transform (JIT) through Laplace and Fourier transforms methods. Parametric studies on the effects of skin tissue properties, initial temperature, blood perfusion rate and heat transfer parameters for the thermal response and exposure time of the layers of the skin tissue are carried out. The study demonstrates that the initial tissue temperature, the thermal conductivity of the epidermis and dermis, relaxation time, thermalisation time and convective heat transfer coefficient are critical parameters to examine skin burn injury threshold. The study also shows that thermal conductivity and the blood perfusion rate exhibits negligible effects on the burn injury threshold. The objective of the present study is to support the accurate quantification and assessment of skin burn injury for reliable experimentation, design and optimisation of thermal therapy delivery.
22

Crystal plasticity finite element simulations using discrete Fourier transforms

Al-Harbi, Hamad F. 22 May 2014 (has links)
Crystallographic texture and its evolution are known to be major sources of anisotropy in polycrystalline metals. Highly simplified phenomenological models cannot usually provide reliable predictions of the materials anisotropy under complex deformation paths, and lack the fidelity needed to optimize the microstructure and mechanical properties during the production process. On the other hand, physics-based models such as crystal plasticity theories have demonstrated remarkable success in predicting the anisotropic mechanical response in polycrystalline metals and the evolution of underlying texture in finite plastic deformation. However, the integration of crystal plasticity models with finite element (FE) simulations tools (called CPFEM) is extremely computationally expensive, and has not been adopted broadly by the advanced materials development community. The current dissertation has mainly focused on addressing the challenges associated with integrating the recently developed spectral database approach with a commercial FE tool to permit computationally efficient simulations of heterogeneous deformations using crystal plasticity theories. More specifically, the spectral database approach to crystal plasticity solutions was successfully integrated with the implicit version of the FE package ABAQUS through a user materials subroutine, UMAT, to conduct more efficient CPFEM simulations on both fcc and bcc polycrystalline materials. It is observed that implementing the crystal plasticity spectral database in a FE code produced excellent predictions similar to the classical CPFEM, but at a significantly faster computational speed. Furthermore, an important application of the CPFEM for the extraction of crystal level plasticity parameters in multiphase materials has been demonstrated in this dissertation. More specifically, CPFEM along with a recently developed data analysis approach for spherical nanoindentation and Orientation Imaging Microscopy (OIM) have been used to extract the critical resolved shear stress of the ferrite phase in dual phase steels. This new methodology offers a novel efficient tool for the extraction of crystal level hardening parameters in any single or multiphase materials.
23

A New Subgroup Chain for the Finite Affine Group

Lingenbrink, David Alan, Jr. 01 January 2014 (has links)
The finite affine group is a matrix group whose entries come from a finite field. A natural subgroup consists of those matrices whose entries all come from a subfield instead. In this paper, I will introduce intermediate sub- groups with entries from both the field and a subfield. I will also examine the representations of these intermediate subgroups as well as the branch- ing diagram for the resulting subgroup chain. This will allow us to create a fast Fourier transform for the group that uses asymptotically fewer opera- tions than the brute force algorithm.
24

[pt] ANÁLISE DE PROBLEMAS TRIDIMENSIONAIS SOLO-ESTRUTURA PELO MÉTODO DOS ELEMENTOS FINITOS NO DOMÍNIO DE FOURIER / [es] ANÁLISIS DE PROBLEMAS TRIDIMENSIONALES SUELO-EXTRUCTURA POR EL MÉTODO DE LOS ELEMENTOS FINITOS EN EL DOMINIO DE FOURIER / [en] THREE-DIMENSIONAL ANALYSIS OF SOIL-STRUCTURE PROBLEMS USING THE FINITE ELEMENT METHOD IN THE FOURIER DOMAIN

JANAINA VEIGA CARVALHO 03 August 2001 (has links)
[pt] Este trabalho estuda problemas geotécnicos e de interação solo-estrutura utilizando o método dos elementos finitos acoplado com a transformada de Fourier. Pela aplicação da transformada de Fourier, as equações diferenciais que governam o problema elástico linear, com as correspondentes condições de contorno, são reescritas no plano de Fourier, permitindo que um problema de natureza tridimensional possa ser numericamente analisado por uma discretização bidimensional. Esta técnica foi empregada neste trabalho para certos problemas de engenharia, como dutovias, túneis e fundações tipo radier, onde a geometria e os parâmetros dos materiais mantêm-se constantes ao longo do eixo longitudinal do corpo, porém admitindo-se variações espaciais no carregamento imposto ao sistema, gerando , assim, um estado tridimensional de tensões. Alguns elementos de interface, com formulação publicada na literatura, foram também considerados na implementação computacional, visto que em problemas de interação solo- estrutura o comportamento do sistema é bastante influenciado pelas propriedades e características mecânicas do solo imediatamente vizinho à estrutura. Os exemplos numéricos apresentados são comparados, sempre que possível, com os resultados obtidos por outra solução analítica ou numérica, procurando discutir as vantagens e limitações do acoplamento da transformada de Fourier com o método dos elementos finitos para a análise de determinada classe de problemas geotécnicos tridimensionais. / [en] In this work some geotechnical and soil-structure interaction problems are studied using the finite element method coupled with a Fourier transform technique. For linear elastic problems, Fourier transforms are applied to the governing field equations, thus enabling that some specific tridimensional problems can be analyzed using a 2D finite element mesh. In conventional finite element applications, a 3D discretization is usually required, but difficulties associated with the preparation of the finite element mesh and the involved computational efforts prevent, in general, the use of a true 3D model. The integral transform method is used in this research for the analysis of some very common problems in geotechnical engineering, such as piping systems, raft foundations and tunnels, where the geometry and the soil profile may be considered constant along a coordinate direction. The applied loading, however, can assume any possible surface distribution, which does not allow to treat the problem under the plane strain assumptions. Some special finite elements presented in the literature, called joint or interface elements, are also incorporated into the finite element computational program written in this research, given that for soil-structure interaction problems the material behavior at the common interface may greatly affect the entire system results. Some numerical examples are presented, and their numerical results are compared, whenever possible, with other solutions obtained using analytical or other numerical technique. Advantages and limitations of the integral transform method to solve tridimensional geomechanics problems are also discussed in this work. / [es] Este trabajo estudia problemas geotécnicos y de interacción suelo-extructura utilizando el método de los elementos finitos acoplado con la transformada de Fourier. Por la aplicación de la transformada de Fourier, las ecuaciones diferenciales que goviernan el problema elástico lineal, con las correspondentes condiciones de contorno, son reescritas en el plano de Fourier, permitiendo que un problema de naturaleza tridimensional pueda ser numericamente analizado por una discretización bidimensional. Esta técnica fue utilizada en este trabajo para ciertos problemas de Ingeniería, como canales, túneles y fundaciones tipo radier, donde la geometría y los parámetros de los materiales se mantienen constantes a lo largo del eje longitudinal del cuerpo, aunque se admiten variaciones espaciales en la carga impuesta al sistema, generando , así, un estado tridimensional de tensiones. En la implementación computacional fueron considerados algunos elementos de la interfaz, con formulación publicada en la literatura, ya que en problemas de interacción suelo-extructura, el comportamiento del sistema está bastante influenciado por las propiedades y características mecánicas del suelo imediatamente vecino a la extructura. Los ejemplos numéricos presentados se compararon, siempre que fue posible, con los resultados obtenidos por otra solución analítica o numérica, discutiendo las ventajas y limitaciones del acoplamiento de la transformada de Fourier con el método de los elementos finitos para el análisis de determinada clase de problemas geotécnicos tridimensionales.
25

DYNAMIC HARMONIC DOMAIN MODELING OF FLEXIBLE ALTERNATING CURRENT TRANSMISSION SYSTEM CONTROLLERS

Vyakaranam, Bharat GNVSR January 2011 (has links)
No description available.
26

Genomic sequence processing: gene finding in eukaryotes

Akhtar, Mahmood, Electrical Engineering & Telecommunications, Faculty of Engineering, UNSW January 2008 (has links)
Of the many existing eukaryotic gene finding software programs, none are able to guarantee accurate identification of genomic protein coding regions and other biological signals central to pathway from DNA to the protein. Eukaryotic gene finding is difficult mainly due to noncontiguous and non-continuous nature of genes. Existing approaches are heavily dependent on the compositional statistics of the sequences they learn from and are not equally suitable for all types of sequences. This thesis firstly develops efficient digital signal processing-based methods for the identification of genomic protein coding regions, and then combines the optimum signal processing-based non-data-driven technique with an existing data-driven statistical method in a novel system demonstrating improved identification of acceptor splice sites. Most existing well-known DNA symbolic-to-numeric representations map the DNA information into three or four numerical sequences, potentially increasing the computational requirement of the sequence analyzer. Proposed mapping schemes, to be used for signal processing-based gene and exon prediction, incorporate DNA structural properties in the representation, in addition to reducing complexity in subsequent processing. A detailed comparison of all DNA representations, in terms of computational complexity and relative accuracy for the gene and exon prediction problem, reveals the newly proposed ?paired numeric? to be the best DNA representation. Existing signal processing-based techniques rely mostly on the period-3 behaviour of exons to obtain one dimensional gene and exon prediction features, and are not well equipped to capture the complementary properties of exonic / intronic regions and deal with the background noise in detection of exons at their nucleotide levels. These issues have been addressed in this thesis, by proposing six one-dimensional and three multi-dimensional signal processing-based gene and exon prediction features. All one-dimensional and multi-dimensional features have been evaluated using standard datasets such as Burset/Guigo1996, HMR195, and the GENSCAN test set. This is the first time that different gene and exon prediction features have been compared using substantial databases and using nucleotide-level metrics. Furthermore, the first investigation of the suitability of different window sizes for period-3 exon detection is performed. Finally, the optimum signal processing-based gene and exon prediction scheme from our evaluations is combined with a data-driven statistical technique for the recognition of acceptor splice sites. The proposed DSP-statistical hybrid is shown to achieve 43% reduction in false positives over WWAM, as used in GENSCAN.
27

Genomic sequence processing: gene finding in eukaryotes

Akhtar, Mahmood, Electrical Engineering & Telecommunications, Faculty of Engineering, UNSW January 2008 (has links)
Of the many existing eukaryotic gene finding software programs, none are able to guarantee accurate identification of genomic protein coding regions and other biological signals central to pathway from DNA to the protein. Eukaryotic gene finding is difficult mainly due to noncontiguous and non-continuous nature of genes. Existing approaches are heavily dependent on the compositional statistics of the sequences they learn from and are not equally suitable for all types of sequences. This thesis firstly develops efficient digital signal processing-based methods for the identification of genomic protein coding regions, and then combines the optimum signal processing-based non-data-driven technique with an existing data-driven statistical method in a novel system demonstrating improved identification of acceptor splice sites. Most existing well-known DNA symbolic-to-numeric representations map the DNA information into three or four numerical sequences, potentially increasing the computational requirement of the sequence analyzer. Proposed mapping schemes, to be used for signal processing-based gene and exon prediction, incorporate DNA structural properties in the representation, in addition to reducing complexity in subsequent processing. A detailed comparison of all DNA representations, in terms of computational complexity and relative accuracy for the gene and exon prediction problem, reveals the newly proposed ?paired numeric? to be the best DNA representation. Existing signal processing-based techniques rely mostly on the period-3 behaviour of exons to obtain one dimensional gene and exon prediction features, and are not well equipped to capture the complementary properties of exonic / intronic regions and deal with the background noise in detection of exons at their nucleotide levels. These issues have been addressed in this thesis, by proposing six one-dimensional and three multi-dimensional signal processing-based gene and exon prediction features. All one-dimensional and multi-dimensional features have been evaluated using standard datasets such as Burset/Guigo1996, HMR195, and the GENSCAN test set. This is the first time that different gene and exon prediction features have been compared using substantial databases and using nucleotide-level metrics. Furthermore, the first investigation of the suitability of different window sizes for period-3 exon detection is performed. Finally, the optimum signal processing-based gene and exon prediction scheme from our evaluations is combined with a data-driven statistical technique for the recognition of acceptor splice sites. The proposed DSP-statistical hybrid is shown to achieve 43% reduction in false positives over WWAM, as used in GENSCAN.
28

[en] SEISMIC ABSORPTION AND CORRECTION METHODS / [pt] ABSORÇÃO SÍSMICA E MÉTODOS DE CORREÇÃO

KARINE RIBEIRO PEREIRA 22 January 2016 (has links)
[pt] Este trabalho tem como objetivo analisar o problema das perdas por absorção dos dados de reflexão sísmica, bem como testar três métodos disponíveis na literatura para sua correção. Utilizamos a modelagem da absorção apresentada por Romanelli Rosa, com a noção de frequência instantânea, e analisamos os seguintes métodos de correção: a Compensação Q, o método de Varela et al. e o método de Duarte, que é um filtro recursivo. Observamos que o método de Duarte é computacionalmente mais rápido que os demais. Ainda assim, podemos utilizar a Transformada de Fourier para torná-lo mais rápido nos casos em que a recursão é interrompida em uma etapa M, menor que o número de amostras N do dado sísmico e maior que lnN. Por fim, testamos o desempenho dos métodos em uma linha de reflexão sísmica marítima da Bacia de Sergipe-Alagoas, fornecida pela Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP). A linha foi reprocessada, com a correção das perdas por absorção aplicada antes do empilhamento, para cada método estudado. Para comparar os resultados, o dado também foi processado sem correção da absorção. Verificamos que houve um aumento da resolução das camadas geológicas de subsuperfície em todos os métodos testados em comparação com o dado sem correção, porém o método de Duarte mostrou-se mais rápido que os demais. / [en] This work aims at analyzing the problem of losses by absorption in seismic reflection data and test three correction methods available in the literature. We use the modeling of the absorption presented by Romanelli Rosa, with the concept of instantaneous frequency, and analyzed the following correction methods: Q compensation, Varela s method and Duarte s method, which is a recursive filter. We note that Duarte s method is computationally faster than the others. However, we can use the Fourier Transform to make it faster in cases where the recursion is interrupted at a step M, smaller than the number of samples N in the seismic data and greater than ln N. Finally, we test the performance of the methods in a marine seismic line in Sergipe-Alagoas Basin, provided by the Agência Nacional do Petróleo, Gás Natural e Biocombustíveis (ANP). The line was reprocessed, with the correction of the losses by absorption applied before stacking, for each method studied. In order to compare the results, the data was also processed without correction of absorption. We observe an increase in the resolution of the geological subsurface in all methods tested in comparison with the data without correction. We also observe the computational advantage of Duarte s method.
29

High Spurious-Free Dynamic Range Digital Wideband Receiver for Multiple Signal Detection and Tracking

Sarathy, Vivek 18 December 2007 (has links)
No description available.
30

Inhomogeneous self-similar sets and measures

Snigireva, Nina January 2008 (has links)
The thesis consists of four main chapters. The first chapter includes an introduction to inhomogeneous self-similar sets and measures. In particular, we show that these sets and measures are natural generalizations of the well known self-similar sets and measures. We then investigate the structure of these sets and measures. In the second chapter we study various fractal dimensions (Hausdorff, packing and box dimensions) of inhomogeneous self-similar sets and compare our results with the well-known results for (ordinary) self-similar sets. In the third chapter we investigate the L {q} spectra and the Renyi dimensions of inhomogeneous self-similar measures and prove that new multifractal phenomena, not exhibited by (ordinary) self-similar measures, appear in the inhomogeneous case. Namely, we show that inhomogeneous self-similar measures may have phase transitions which is in sharp contrast to the behaviour of the L {q} spectra of (ordinary) self-similar measures satisfying the Open Set Condition. Then we study the significantly more difficult problem of computing the multifractal spectra of inhomogeneous self-similar measures. We show that the multifractal spectra of inhomogeneous self-similar measures may be non-concave which is again in sharp contrast to the behaviour of the multifractal spectra of (ordinary) self-similar measures satisfying the Open Set Condition. Then we present a number of applications of our results. Many of them are related to the notoriously difficult problem of computing (or simply obtaining non-trivial bounds) for the multifractal spectra of self-similar measures not satisfying the Open Set Condition. More precisely, we will show that our results provide a systematic approach to obtain non-trivial bounds (and in some cases even exact values) for the multifractal spectra of several large and interesting classes of self-similar measures not satisfying the Open Set Condition. In the fourth chapter we investigate the asymptotic behaviour of the Fourier transforms of inhomogeneous self-similar measures and again we present a number of applications of our results, in particular to non-linear self-similar measures.

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