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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.
31

Bivariate B-splines and its Applications in Spatial Data Analysis

Pan, Huijun 1987- 16 December 2013 (has links)
In the field of spatial statistics, it is often desirable to generate a smooth surface for a region over which only noisy observations of the surface are available at some locations, or even across time. Kriging and kernel estimations are two of the most popular methods. However, these two methods become problematic when the domain is not regular, such as when it is rectangular or convex. Bivariate B-splines developed by mathematicians provide a useful nonparametric tool in bivariate surface modeling. They inherit several appealing properties of univariate B-splines and are applicable in various modeling problems. More importantly, bivariate B-splines have advantages over kriging and kernel estimation when dealing with complicated domains. The purpose of this dissertation is to develop a nonparametric surface fitting method by using bivariate B-splines that can handle complex spatial domains. The dissertation consists of four parts. The first part of this dissertation explains the challenges of smoothing over complicated domains and reviews existing methods. The second part introduces bivariate B-splines and explains its properties and implementation techniques. The third and fourth parts discuss application of the bivariate B-splines in two nonparametric spatial surface fitting problems. In particular, the third part develops a penalized B-splines method to reconstruct a smooth surface from noisy observations. A numerical algorithm is derived, implemented, and applied to simulated and real data. The fourth part develops a reduced rank mixed-effects model for functional principal components analysis of sparsely observed spatial data. A numerical algorithm is used to implement the method and tested on simulated and real data.
32

Variation analysis of involute spline tooth contact /

DeCaires, Brian J., January 2006 (has links) (PDF)
Thesis (M.S.)--Brigham Young University. Dept. of Mechanical Engineering, 2006. / Includes bibliographical references (p. 131-134).
33

A dynamic programming approach to smoothing and differentiating data with splines /

Dohrmann, Clark, January 1986 (has links)
Thesis (M.S.)--Ohio State University, 1986. / Includes bibliographical references (leaves 89-90). Available online via OhioLINK's ETD Center
34

Estimation non paramétrique de la régression : régressogramme et méthodes spline.

Rahmania, Nadji, January 1900 (has links)
Th. 3e cycle--Math. appl.--Lille 1, 1980. N°: 859. / Rés.
35

Três ensaios em finanças públicas

Nojosa, Glauber Marques January 2014 (has links)
NOJOSA, Glauber Marques. Três ensaios em finanças públicas / Glauber Marques Nojosa. - 2014. 85f. Tese (Doutorado) - Universidade Federal do Ceará, Programa de Pós Graduação em Economia, CAEN, Fortaleza, 2014. / Submitted by Mônica Correia Aquino (monicacorreiaaquino@gmail.com) on 2017-06-05T20:02:40Z No. of bitstreams: 1 2014_tese_gmnojosa.pdf: 1133605 bytes, checksum: d61b26224277dd836369aace6b4edc75 (MD5) / Approved for entry into archive by Mônica Correia Aquino (monicacorreiaaquino@gmail.com) on 2017-06-05T20:03:13Z (GMT) No. of bitstreams: 1 2014_tese_gmnojosa.pdf: 1133605 bytes, checksum: d61b26224277dd836369aace6b4edc75 (MD5) / Made available in DSpace on 2017-06-05T20:03:13Z (GMT). No. of bitstreams: 1 2014_tese_gmnojosa.pdf: 1133605 bytes, checksum: d61b26224277dd836369aace6b4edc75 (MD5) Previous issue date: 2014 / This essay is composed of three articles. The first article analyzes the presence of the flypaper effect and its variability by using data from Brazilian municipalities. I implemented threshold model proposed by Hansen (2000) in which political strength variable assumes the role of threshold to infer about the variability of the flypaper effect on public finance of Brazilian municipalities. Results indicate the presence of the flypaper effect on those municipalities. Moreover, it proves empirically the relationship between political and budget decisions, in which the flypaper effect is stronger in those municipalities with larger political allies base in the City Council. Municipalities whose mayor is politically strong and various parties divide the City Council there are clientelistic practices and intensification of the flypaper effect. Second article analyzes the sustainability of the Brazilian public debt trajectory, from 1991 to 2009, by considering a reaction function to the debt with parameters varying over time. Estimation was conducted by using a penalized spline regression adapted to tax rule developed by Bohn (1998). Main results indicate that Brazil did not follow a sustainable debt policy during the period analyzed. Third article evaluates the contribution of public capital on the product of Brazilian economy, considering the possibility of changes in the coefficients of the aggregate production function. Data for GPD and public and private capital was obtained from 1950 to 2008. Cointegration with structural breaks approach developed by Kejriwal and Perron (2006) was used. Cointegrated vectors were estimated by Dynamic Ordinary Least Squares (DOLS) method. Engle-Granger cointegration test (1987) was used to confirm long-run relationship and the Hansen test (1992) verified model stability. According to the results, aggregate production function was stable with two structural breaks in its deterministic structure, 1958 and 1966. Public capital effects on the product are inconstant, from 0.25 to 0.48, among the selected regime. / O presente ensaio é composto de três artigos. O primeiro artigo busca analisar a presença do efeito flypaper e sua variabilidade utilizando dados para os municípios brasileiros. Para isso, utiliza-se um modelo com efeito limiar (threshold), proposto por Hansen (2000) cuja variável força política, assume o papel de threshold ao se inferir acerca da variabilidade do efeito flypaper nas finanças públicas dos municípios brasileiros. Dentre os principais resultados encontrados, ratifica-se a presença do efeito flypaper nas finanças dos municípios brasileiros. Além disso, comprova-se empiricamente a relação entre as decisões políticas e orçamentárias, ocorrendo efeito flypaper mais intenso em municípios com maior base aliada nas Câmaras de Vereadores. Verifica-se, ainda, que municípios cujo prefeito é politicamente forte e uma grande quantidade de partidos dividem o legislativo local, há o favorecimento de práticas clientelistas e a intensificação do efeito flypaper. Já no segundo artigo, busca-se estudar a sustentabilidade da trajetória da dívida pública federal brasileira, de 1991 a 2009, considerando uma função de reação ao endividamento com parâmetros variáveis no tempo. Para estimação, utiliza-se uma regressão por splines penalizados (penalized spline regression) adaptada à regra fiscal desenvolvida por Bohn (1998). Dentre os principais resultados, verifica-se que o Brasil não seguiu uma política de endividamento sustentável no período analisado. No terceiro artigo, busca-se avaliar a contribuição do capital público no produto da economia brasileira, considerando a possibilidade de mudanças nos coeficientes da função de produção agregada para a economia brasileira. Para isso, utilizam-se dados anuais de 1950 a 2008 para o Produto Interno bruto (PIB), capital privado e público. Empiricamente, adota-se a abordagem de cointegração com quebras estruturais, desenvolvida por Kejriwal e Perron (2006). Para estimação dos vetores cointegrantes aplica-se o método dos Mínimos Quadrados Ordinários Dinâmicos (DOLS). Utiliza-se ainda o teste de cointegração de Engle-Granger (1987) para confirmar as relações de equilíbrio de longo prazo e o teste de Hansen (1992) para verificar a estabilidade do modelo. De acordo com os resultados, a função de produção agregada apresenta-se estável com duas quebras estruturais em sua estrutura determinística, em 1958 e 1966. Já os efeitos do capital público sobre o produto se mostraram variáveis, de 0,25 a 0,48, entre os regimes selecionados.
36

O uso de Thin-Plate Splines na transformação de coordenadas com modelagem de distorções entre realizações de referenciais geodésicos

Magna Júnior, João Paulo [UNESP] 27 January 2012 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:33:31Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-01-27Bitstream added on 2014-06-13T19:44:22Z : No. of bitstreams: 1 magnajunior_jp_dr_prud.pdf: 3558640 bytes, checksum: fe0b1f329eb24d9ac82adc5a8e9815c8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O avanço das técnicas de posicionamento, sobretudo do posicionamento por satélites artificiais, impulsionou os processos de atualização da estrutura geodésica fundamental em diversos países. No Brasil, a mais recente mudança foi a adoção do SIRGAS2000 em fevereiro de 2005, se tornando o terceiro referencial adotado oficialmente pelo Sistema Geodésico Brasileiro. A mudança de referencial faz com que produtos cartográficos possam ter suas coordenadas associadas a diferentes referenciais e/ou realizações. Portanto, tornam-se necessários processos de transformação de coordenadas entre sistemas e/ou realizações, que possam modelar as distorções existentes nas materializações e garantir a integridade dos dados. A evolução das técnicas de posicionamento e a atualização dos sistemas de referência são processos dinâmicos, portanto, os métodos para mudança de coordenadas são uma necessidade atual e constante. Nesta pesquisa é apresentado um método para transformação de coordenadas tridimensionais entre realizações de referenciais geodésicos com modelagem de distorções baseado em Thin-Plate Splines (TPS). Pretende-se explorar a capacidade da técnica TPS em modelar dados provenientes de uma transformação linear, juntamente com distorções de natureza... / The advances in the positioning techniques, especially in the satellite positioning, drove the updating process in the fundamental geodesic network in several countries. In Brazil, the most recent change was the adoption of the SIRGAS2000 in February, 2005, as the third official referential adopted by the Brazilian Geodetic System. The change of reference system let cartographic products with his coordinates associated to different reference systems and/or frames. So, processes of coordinates change between reference systems and/or frames are necessary, which are able to model the distortion in the reference frames and guarantee the data integrity. The evolution of the positioning techniques and the updating of reference frames are dynamic processes, so, the methods of coordinates change are an actual and continuous necessity. In this research a method is presented for transformation of threedimensional coordinates between reference frames with modeling of distortions based on Thin-Plate Splines (TPS). It is explored the capacity of the TPS in modeling data originated from a linear transformation, together... (Complete abstract click electronic access below)
37

Smooth Path Planning Using Splines For Unmanned Planetary Vehicles

January 2013 (has links)
abstract: One of the main challenges in planetary robotics is to traverse the shortest path through a set of waypoints. The shortest distance between any two waypoints is a direct linear traversal. Often times, there are physical restrictions that prevent a rover form traversing straight to a waypoint. Thus, knowledge of the terrain is needed prior to traversal. The Digital Terrain Model (DTM) provides information about the terrain along with waypoints for the rover to traverse. However, traversing a set of waypoints linearly is burdensome, as the rovers would constantly need to modify their orientation as they successively approach waypoints. Although there are various solutions to this problem, this research paper proposes the smooth traversability of the rover using splines as a quick and easy implementation to traverse a set of waypoints. In addition, a rover was used to compare the smoothness of the linear traversal along with the spline interpolations. The data collected illustrated that spline traversals had a less rate of change in the velocity over time, indicating that the rover performed smoother than with linear paths. / Dissertation/Thesis / M.S. Computer Science 2013
38

Algorithm for Optimal Triangulations in Scattered Data Representation and Implementation

Dyer, Bradley W., Hong, Don 01 January 2003 (has links)
Scattered data collected at sample points may be used to determine simple functions to best fit the data. An ideal choice for these simple functions is bivariate splines. Triangulation of the sample points creates partitions over which the bivariate splines may be defined. But the optimality of the approximation is dependent on the choice of triangulation. An algorithm, referred to as an Edge Swapping Algorithm, has been developed to transform an arbitrary triangulation of the sample points into an optimal triangulation for representation of the scattered data. A Matlab package has been completed that implements this algorithm for any triangulation on a given set of sample points.
39

Skinning engineering models with non-uniform, hierarchical B-spline surfaces

Coe, David H. 05 September 2009 (has links)
This thesis presents the algorithms and methods to represent the skin of an engineering model with non-uniform, hierarchical B-spline surfaces. Non-uniform, hierarchical B-splines offer the mechanical designer many advantages: parametrically defined components may be added to a surface while maintaining C² surface continuity; detailed features may be added to a surface without globally affecting the B-spline control net; and an appropriate geometric basis for finite element meshing and analysis in the conceptual design phase can be established. These algorithms are applied to ASCYNT, a conceptual aircraft design code, to verify and validate the algorithms. A single-surface definition of an aircraft skin, appropriate for computational fluid dynamic and radar and infrared cross-section analysis, is designed using non-uniform hierarchical B-spline surfaces. / Master of Science
40

Investigating the Utility of Age-Dependent Cranial Vault Thickness as an Aging Method for Juvenile Skeletal Remains on Dry Bone, Radiographic and Computed Tomography Scans

Kamnikar, Kelly R 07 May 2016 (has links)
Age estimation, a component of the biological profile, contributes significantly to the creation of a post-mortem profile of an unknown set of human remains. This goal of this study is to: (1) refine the juvenile age estimation method of cranial vault thickness (CVT) through MARS modeling, (2) test the method on known age samples, and (3) compare CVT and dental development age estimations. Data for this study comes from computed tomography (CT) scans, radiographic images, and dry bone. CVT was measured at seven cranial landmarks (nasion, glabella, bregma, vertex, vertex radius, lambda and opisthocranion). Results indicate that CVT models vary in their predictive ability; vertex and lambda produce the best results. Predicted fit values and prediction intervals for CVT are larger, and less accurate than dental development age estimates. Aging by CVT could benefit from a larger known age sample composed of individuals older than 6 years old.

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