• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1412
  • 616
  • 202
  • 169
  • 106
  • 96
  • 84
  • 75
  • 62
  • 55
  • 32
  • 27
  • 20
  • 17
  • 10
  • Tagged with
  • 3392
  • 1665
  • 530
  • 350
  • 343
  • 324
  • 298
  • 297
  • 269
  • 243
  • 204
  • 192
  • 166
  • 162
  • 155
  • 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.
481

Deconvolution of three-dimensional medical ultrasound

Gomersall, William Henry January 2011 (has links)
No description available.
482

Three Dimensional Printing Surgical Instruments: Are We There Yet?

Rankin, Timothy M. January 2014 (has links)
Background: The applications for rapid prototyping have expanded dramatically over the last 20 years. In recent years, additive manufacturing has been intensely investigated for surgical implants, tissue scaffolds, and organs. There is, however, scant literature to date that has investigated the viability of 3D printing of surgical instruments. Materials and Methods: Using a fused deposition manufacturing (FDM) printer, an army/ navy surgical retractor was replicated from polylactic acid (PLA) filament. The retractor was sterilized using standard FDA approved glutaraldehyde protocols, tested for bacteria by PCR, and stressed until fracture in order to determine if the printed instrument could tolerate force beyond the demands of an operating room. Results: Printing required roughly 90 minutes. The instrument tolerated 13.6 kg of tangential force before failure, both before and after exposure to the sterilant. Freshly extruded PLA from the printer was sterile and produced no PCR product. Each instrument weighed 16g and required only $0.46 of PLA. Conclusions: Our estimates place the cost per unit of a 3D printed retractor to be roughly 1/10th the cost of a stainless steel instrument. The PLA Army/ Navy is strong enough for the demands of the operating room. Freshly extruded PLA in a clean environment, such as an OR, would produce a sterile, ready to use instrument. Due to the unprecedented accessibility of 3D printing technology world wide, and the cost efficiency of these instruments, there are far reaching implications for surgery in some underserved and less developed parts of the world.
483

Slovak Influences in 20th Century Music as Represented in Selected Works of Bartók, Janáček and Novák

Majkut, Martin January 2008 (has links)
The goal of this document is to demonstrate how Slovak folk music inspired creation of some early 20th century chamber, orchestral, and vocal-instrumental compositions. In examples drawn from works of Vítězslav Novák, Leoš Janáček and Béla Bartók the author analyzes the different ways of translating folk music idioms into the compositional language of these composers. The first of the introductory chapters presents an outline of distinctive features of Slovak folk music. It talks about the role of folk song in the life of Slovaks and its connection to social events in the villages. It also analyzes the relationship between language and music. The coexistence of modal and tonal music is emphasized and songs are divided into historical periods. In the second part of the introduction an historic overview of the influence of Slovak folk music in classical music is given. The chapter covers the first known occurrences of this influence in the collections of songs and dances from the Baroque era and the occasional references in the Classical and Romantic music. The impulses behind the wave of interest in Slovak folk music in the 20th century are also examined. The first chapter documents the influence of Slovak folk music on Vítězslav Novák. It describes his early career and his first encounters with Slovakia. The central part of this chapter consists of analysis of the symphonic poem In the Tatras, a work inspired by Slovakia and containing Slovak music references. The second chapter of this document is devoted to Leoš Janáček. His multifaceted approach to folk music included an intimate knowledge of people’s lifestyle, traditions, local dialects and speech patterns. The fruit of his research is documented in the song collection 26 Folk Ballads. The majority of these arrangements for voice and piano are of Slovak origin. The final chapter examines the personal and artistic ties of Béla Bartók to Slovakia. Bartók employed folk music elements in his compositions with a genius which made him a master of such compositional approach. The variety of ways by which Bartók used Slovak folk music is scrutinized in the analysis of Three Village Scenes.
484

Data mining of market information to assess at-home pork demand

Asatryan, Armen A. 30 September 2004 (has links)
This study analyzes the economic and demographic patterns of at-home pork consumption for representative individuals over 18 years of age in the United States. Three data sets purchased by the National Pork Board (NPB) are mined for this purpose: (1) National Eating Trends (NET) data from National Panel Diary (NPD) on individuals' intake and their demographic characteristics; (2) weekly retail prices for fresh meats and fresh pork cuts from FreshLook; and (3) weekly retail prices for processed pork products from A.C. Nielsen. Heckman sample selection models are used to find demographic, health, and attitudinal/lifestyle patterns of consumption of twelve fresh and processed pork products as well as beef, chicken, and seafood. In the fall, individuals have a higher probability of eating beef, chicken, pork tenderloin, and bacon, but a lower probability of eating fresh seafood, canned ham, and smoked ham relative to the spring. The New England region has the highest likelihood of eating fresh pork, beef, chicken, seafood, pork roasts, pork tenderloin, and pork hotdogs. Blacks, on average, eat more fresh and processed pork, chicken, pork sausage, bacon, and canned ham, but less beef relative to whites. Concern about serving food with fat is negatively related with the likelihood of eating processed pork, lunchmeat, ham, and bacon, but it is positively related with the likelihood of eating pork hotdogs. A three-stage selectivity-adjusted censored LA/AIDS model is developed and estimated to find demand-price relationships for: (1) fresh meats (pork, beef, chicken, and seafood) and (2) nine fresh and processed pork cuts. However, aggregate fresh meats are substitutes for each other in at-home market, but there are substantial complementarities between pork cuts. Pork sausage is the major competitor for the processed products, pork roasts and pork tenderloin, but a major complement for pork ribs. There is relatively week substitutability between pork and beef, and relatively strong substitutability between pork and chicken and between beef and chicken. This could suggest opportunities for some joint marketing efforts between pork and beef commodity interests. This information can be used as a guide for marketing strategists for targeting and promotion as well as for category management of the disaggregated pork products.
485

Extended three-dimensional ADCIRC hydrodynamic model to include baroclinic flow and sediment transport

Pandoe, Wahyu Widodo 30 September 2004 (has links)
The objective of this research is to identify the circulation patterns of the water and sediment fluxes in coastal and estuarine zones, where the shoaling processes correlate with tide generating flow patterns. The research provides a better understanding of the characteristics of spatial and temporal variability of currents. An important deviation from previous research is the inclusion of the baroclinic term, which becomes very important in density driven flows. The understanding of this process provides a basis for determining how the water circulation three-dimensionally controls the hydrodynamics of the system and ultimately transports the suspended and soluble materials due to combined currents and waves. A three-dimensional circulation model is used to calculate the water circulation. The model is based on the three-dimensional (3D) version of Advanced Circulation (AD-CIRC) Hydrodynamic Model with extending the Sediment Transport module. The model is based on the finite element method on unstructured grids. The output of the hydrody-namic model is used to estimate spatial and temporal advections, dispersions and bottom shear stress for the erosion, suspension, deposition and transport of sediment. The model development includes extending the existing three-dimensional (3D) ADCIRC Model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for both cohesive and non-cohesive type sediments. The inclusion of the baroclinic demonstrates the potential of over or underpredicting the total net transport of suspended cohesive sediment under influence of currents. The model provides less than 6% error of theoretical mass conservation for eroded, suspended and deposited sediment material. The inclusion of the baroclinic term in stratified water demonstrates the prevailing longshore sediment transport. It is shown that the model has an application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast. The model is also applicable to determine the design erosion thickness of a cap for isolating contaminated dredged material and to evaluate the appro-priate grain size of cap sediments to minimize the erosion.
486

Optimized profile extraction and three dimensional reconstruction techniques applied to bubble shapes

Vasudevamurthy, Gokul 30 September 2004 (has links)
In order to predict the behavior of bubbly flows, it is necessary to know the three dimensional profiles of the bubbles present in the flow. With advancements in the field of flow visualization, accurate reconstruction of the bubble shape has become necessary. The PIV and the SIV techniques, used to acquire images of particles and bubbles, have been found to be extremely useful in this regard. The study, development, implementation, applications and limitations of a unique reconstruction technique applied to various regular and irregular bubble shapes, using the two orthogonal projections of the three-dimensional bubble profiles as captured by the SIV cameras are presented here. The technique is a blend of neural networks, combinatorial optimization and advanced computer aided design methods. The technique involves the robustness and ruggedness of the neural network approach and the flexibility and reliability of advanced computer aided design methods. The technique uses a well-known problem in neural networks and combinatorial optimization known as the Traveling Salesman Problem approach to identify the bubble boundaries on the images. An optimization solution technique known as the Simulated Annealing technique is employed to solve the Traveling Salesman Problem and obtain the bubble profiles. These results are employed to reconstruct bubble shapes using NURBS computer aided design software. Two main applications of this technique are demonstrated and the results are found to be promising. The first application included the calculation of the void fraction at a particular depth of the channel/ pipe and at a particular radius of the channel. The second application was Lagrangian tracking of bubbles, wherein the centroids of the bubbles were tracked between image frames to determine the linear and transverse velocities of the bubbles. This technique has shown scope for development including the development as integrated bubble surface reconstruction software and advanced modifications at various levels for efficient and accurate reconstruction.
487

Vishet i arbetslivet : En utveckling av ett arbetslivsanpassat vishetsformulär

Lagerholm, Anna January 2014 (has links)
Vishet som fenomen har en lång historia, dock har begreppet under de senaste åren uppmärksammats allt mer av empirisk forskning. Det råder oenigheter kring fenomenets innebörd. Många studier visar dock att vishet kännetecknas av kognitiva och reflekterande dimensioner - precis som i Ardelts teori där vishet förklaras genom kognitiva, affektiva och reflekterande egenskaper. Denna studie utgår från Ardelts teori. En enkätundersökning med 110 deltagare genomfördes med syftet att utforma ett för arbetslivet modifierat vishetsformulär. Dessutom ämnade studien jämföra kön, ålder och privat respektive kommunal sektor. Resultatet visade hög korrelation mellan det modifierade vishetsformuläret (ViA) och Ardelts tredimensionella visdomsskala (3D-WS). Dessutom visade resultatet att privat sektor erhöll signifikant högre poäng än kommunal sektor i 3D-WS, samt att kvinnor i snitt fick högre poäng än män. Åldersskillnader påvisades inte. Studiens brister i form av bland annat representativitet, antalet deltagare och utformningen av enkäten diskuterades.
488

Three dimensional evaluation of the TMJ condyle position in different types of skeletal patterns

Guedes, Ines H. 06 March 2014 (has links)
Objective: To evaluate three-dimensional position of the TMJ condyle within the glenoid fossa in different types of skeletal patterns. Materials and methods: Ninety CBCT images were consecutively selected and divided into skeletal class I, class II and class III. The images were analyzed locating landmarks in the different areas of the condyle and glenoid fossa. All landmarks presented acceptable reliability. The mean results were compared using ANOVA and Bonferroni post-hoc test (p < 0.05). Results: There was a tendency for the anterior joint space to be smaller than the posterior joint space. Statistical analysis, however, evidenced no significant differences between the anterior, superior and posterior joint spaces and the different skeletal patterns or between sides. Conclusion: There was non-concentricity of the condyle for all the groups studied, and no particular direction was statistically significantly favored. It is unclear whether the differences found would be clinically significant, considering anatomical individual variations.
489

Three phase boundary length and effective diffusivity in modeled sintered composite solid oxide fuel cell electrodes

Metcalfe, Thomas Craig 05 1900 (has links)
Solid oxide fuel cells with graded electrodes consisting of multiple composite layers yield generally lower polarization resistances than single layer composite electrodes. Optimization of the performance of solid oxide fuel cells with graded electrode composition and/or microstructure requires an evaluation of both the three phase boundary length per unit volume and the effective diffusion coefficient in order to provide insight into how these properties vary over the design space. A numerical methodology for studying the three phase boundary length and effective diffusivity in composite electrode layers with controlled properties is developed. A three dimensional solid model of a sintered composite electrode is generated for which the mean particle diameter, composition, and total porosity may be specified as independent variables. The total three phase boundary length for the modeled electrode is calculated and tomographic methods are used to estimate the fraction of this length over which the electrochemical reactions can theoretically occur. Furthermore, the open porosity of the modeled electrode is identified and the effective diffusion coefficient is extracted from the solution of the concentration of the diffusing species within the open porosity. Selected example electrode models are used to illustrate the application of the methods developed, and the resulting connected three phase boundary length and diffusion coefficients are compared. A significant result is the need for thickness-specific effective diffusivity to be determined, rather than the general volume averaged property, for electrodes with porosity between the upper and lower percolation thresholds. As the demand for current increases, more of the connected three phase boundaries become active, and therefore a greater fraction of the electrode layer is utilized for a given geometry, resulting in a higher apparent effective diffusivity compared to the same electrode geometry operating at a lower current. The methods developed in this work may be used within a macroscopic electrode performance model to investigate optimal designs for solid oxide fuel cell electrodes with stepwise graded composition and/or microstructure.
490

Trimačių galerijų šablonų generavimas / Generation of three-dimensional gallery patterns

Zigmantaitė, Danguolė 27 August 2009 (has links)
Šiame darbe apžvelgtos įvairios trimatės galerijos ir jų kūrimo principai. Atlikta programų ir įrankių, skirtų galerijoms kurti, analizė. Atlikta VRML programavimo kalbos galimybių ir jos taikymų trimatės grafikos sistemose analizė. Supažindinama su šablonų generavimo būdais. Atlikta įskiepų, skirtų trimačių galerijų naršyklėse peržiūrai, analizė. Panaudojant ArchiCad projektavimo įrankį ir VRML kalbą, sukurtas trimatis galerijos šablonas. / This paper reviews various three – dimensional galleries and their development principles. There was made an analysis of programmes and tools, which were designed for the creation of galleries. The analysis was also made of VRLM programming language – its options and applications in three–dimensional graphics systems. This work acquaints with methods of template generation. There was made an analysis of plugins, which are intended for the viewing in the browsers of three–dimensional galleries. There was created the three–dimensional template of the gallery, by using ArchiCad and VRML design tool.

Page generated in 0.0228 seconds