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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

Biomechanical analysis of the sit-to-stand transition

Campos Padilla, Ivette Yadira January 2016 (has links)
The Sit-to-Stand (STS) transition is a voluntary daily activity that consists of rising from a sitting position to a standing position, an activity that is typically performed by a person several times a day. To undertake the activity successfully requires the coordination of the body limbs in order to transfer the body weight between the sitting and standing positions, maintaining the balance, in order to avoid a fall. A biomechanical analysis of the STS transition provides useful information about the motor ability and control strategy of a person and as such, it is commonly employed to assess functional performance, and as an indicator of lower limb strength in the elderly and in people with disabling diseases. The aim of the work described in this thesis was to investigate and analyse the STS transition in two groups of healthy subjects, a cohort (n=10) of younger adult participants (age range 28±2 years) and a cohort (n=10) of older adult participants (age range 56±8 years), in order to identify the differences in the performances within and between the two groups when the STS transition was undertaken at different speeds. The two groups of participants performed STS transition trials at three, different, self-selected speeds (normal, slow and fast) during which data was recorded from a caption systems, consisting of a set of six infrared-cameras and two force plates. The in-vivo data obtained was applied to a link segment biomechanical model enabling the kinematic contribution of the major body segments to the STS activity to be determined for each participant. A principal component analysis (PCA) was undertaken to identify any aggregate and segmental differences in the STS transition performance between speeds. In addition, a kinetic analysis was performed to determine the torque and power contributions of the lower limb joints during the STS transition. The results from the analysis showed that younger and older participants performed the STS transition with a similar pattern, but they used different strategies to ascend according to the speed at which the activity was being performed. The younger participants used the same strategy at slow speed than the older participants used at slow and normal speeds. Likewise, the younger participants used the same strategy at normal and fast speeds as the older participants used at fast speed. From the segmental analysis it was found that the upper-body and pelvis segments presented the larger variability than the other segments. From the joint analysis, the knee and hip joints were identified as the joints that provide the greatest contribution to the STS transition as they generated most of the power and torque required for the activity. The results obtained and the methodology developed could help clinicians with the diagnosis, planning and selection of treatment for patients with a lack of mobility. This type of analysis may also find application in fields such as robotics, ergonomics and sports training.
22

Nondormant alfalfa varieties for Arizona 2016

Ottman, Michael J 10 1900 (has links)
2 pp. / Alfalfa varieties differ in fall dormancy, defined as growth during the fall. Nondormant alfalfa varieties are usually planted in mild winter areas for their ability to grow in the late fall, winter, and early spring. Select alfalfa varieties that have resistance to potential pest problems. Alfalfa varieties are available that have salt tolerance or are Roundup Ready. Ratings are provided in this publication. Many of the varieties listed in this publication have been tested for yield and final stand by the University of Arizona in small plot trials. Revised 10/2016. Most recent version 09/2015
23

The Influence of Muscular Fatigue on Human Multi-Joint Movement: Determinants of Sit-to-Stand Capacity with Aging

Bryanton, Megan January 2016 (has links)
The sit-to-stand (STS) is a multi-articular movement of daily living that requires significantly higher knee extensor (KE) efforts compared to ankle and hip musculature, which approach near maximal levels in older adults populations. As well, fatigue may develop more readily with repetitive actions. Consequently, it is understandable how KE strength reserves have been previously correlated with both functional independence and STS strategy characteristics in older persons, and why STS capacity is a significant predictor of disability. However, it is still unclear why compensatory movement strategies manifest when rising from a seated position, and how this may be influenced by aging. The purpose of this thesis compilation was to evaluate alterations in muscular contributions at the ankle, knee, and hip, in relation to STS performance strategies in young and older adults either: a) with repetitive multi-joint STS exercise or b) before and after isolated fatigue of KE musculature. Results showed that aging caused a redistribution of joint torques when ascending from a seated position, and was associated with significantly higher quadriceps muscular efforts in older persons in comparison to their younger counterparts. In contrast, young and older adults exhibited similar compensatory movement and loading strategies during repetitive STS exercise, which appeared to be limited by the ability to sustain KE force output. In turn, lower KE strength reserves of older persons were responsible for their disproportionately higher quadriceps efforts and reduced STS capacities. Young and older persons also appeared to employ motor strategies to compensate for reduced KE force output via increased contribution of the biarticular rectus femoris within the quadriceps KE synergy, as well as through increases in the initially less active ankle plantar flexor and hip extensor musculature. Older adults may benefit from strengthening of thigh extensor musculature to maintain or improve their strength reserves to promote independent living.
24

Evaluation Of A Test Stand To Assess The Performance Of A Range Of Ceramic Media Filter Elements

Schemmel, Andrew L 06 May 2017 (has links)
High Efficiency Particulate Air (HEPA) filters are defined as extended-medium, dry-type filters with: (1) a minimum particle removal efficiency of no less than 99.97 percent for 0.3 micrometer particles, (2) a maximum, clean resistance of 1.0 inch water column (in. WC) when operated at 1,000 cubic feet per minute (CFM), and (3) a rigid casing that extends the full depth of the medium. Specifically, ceramic media HEPA filters provide better performance at elevated temperatures, are moisture resistant and nonflammable, can perform their function if wetted and exposed to greater pressures, and can be cleaned and reused. This paper describes the modification and design of a large scale test stand which properly evaluates the filtration characteristics of a range of ceramic media filters challenged with a nuclear aerosol agent in order to develop Section FO of ASME AG-1.
25

[pt] ANÁLISE E LOCALIZAÇÃO ÓTIMA DOS SUPORTES ESTRUTURAIS EM LINHAS DE TUBULAÇÃO EM USINAS NUCLEARES / [es] ANÁLISIS Y LOCALIZACIÓN ÓPTIMA DE LOS SOPORTES EXTRUCTURALES EN LÍNEAS DE TUBERÍAS EN CENTRALES NUCLEARES / [en] OPTIMAL STRUCTURES SUPPORT LOCATION BY PIPELINES AT NUCLEAR POWER

NELLY PIEDAD RUBIO RUBIO 26 July 2001 (has links)
[pt] Este trabalho apresenta uma metodologia para a determinação da localização ótima de suportes em linhas de tubulação de centrais nucleares, visando minimizar o número de suportes empregados. Incorporam-se a esta metodologia os critérios e restrições de projeto descritos em normas e relatórios técnicos específicos para sistemas de tubulações de centrais nucleares. Por exemplo, a localização dos suportes estruturais deve ser efetuada de tal forma que as tensões atuantes nos elementos da linha de tubulação, devido aos vários carregamentos impostos, estejam dentro dos limites especificados no código da ASME- American Society of Mechanical Engineers e da ANSI- American National Standards Institute e que os deslocamentos da linha de tubulação não excedam o valor do deslocamento máximo admissível. A etapa de análise para obtenção dos esforços e deformações é realizada utilizando-se um programa de elementos finitos, KWUROHR, desenvolvido pela Siemens especificamente para análise de tubulações. Empregam-se na modelagem dos tubos elementos de viga. A partir de uma análise preliminar formula-se o problema de otimização topológica com restrições de geometria, tensões e deslocamentos. A solução deste problema se dá empregando-se técnicas de programação matemática, mais especificamente, programação quadrática recursiva. Os esforços e deformações finais são obtidos por meio de nova análise para o sistema otimizado. / [en] This work presents a methodology for the determination of the optimal support locations for nuclear power plant pipelines. The objective here is to minimize the number of supports taking into account the specific design criteria present in the codes and regulatory guides for these special structures. The stress analysis is performed with a finite element program, KWUROHR, developed by Siemens specifically for the analysis of pipelines. On the tube modeling beam elements are employed. From a preliminary stress analysis performed on a trial structure, the topology optimization problem is formulated. Stresses and displacements, as well as the sensitivity analysis, obtained for this structure are the inputs for the optimization procedure. The solution of the optimization problem is obtained with mathematical programming techniques, more specifically with recursive quadratic programming. Final stresses and deformations are obtained through reanalysis of the optimal structure. / [es] Este trabajo presenta una metodología para la determinación de la localización óptima de los soportes, en líneas de tuberías de las centrales nucleares, minimizando el número de soportes empleados. Se Incorporan a esta metodología los criterios y restricciones del proyecto, que están descritos en las normas e informes técnicos específicos para sistemas de tuberías de centrales nucleares. Por ejemplo, la localización de los soportes extructurales debe ser efectuada de tal forma que las tensiones que actúan en los elementos de la línea de tubería, debido a las cargas impuestas, estén dentro de los límites especificados en el código de la ASME-American
26

Investigation of Graphite Bipolar Plates for PEM Fuel Cell Performance

Kruszewski, Eric 04 December 2001 (has links)
The largest cost in manufacturing PEM fuel cells for automotive applications is due to the bipolar plate. The current graphite material used for the bipolar plate is very brittle and difficult to machine to the rigorous specifications needed for fuel cell stacks. This paper introduces the development of a fuel cell test stand for simultaneous testing of six individual fuel cells. To establish a long-term performance evaluation, the fuel cells incorporate a baseline graphite material that undergoes testing in the fuel cell environment. The graphite is an industry standard material that should not corrode when subjected to continual testing. The baseline model will be used in development of novel composite materials that will be tested under the same conditions for comparison to the graphite. Furthermore, the new materials and applied manufacturing methods could reduce the overall cost of fuel cell stacks in the future. Funding for this project was generously donated by the Virginia Center for Innovative Technology and the National Science Foundation. / Master of Science
27

Silvicultural Methods for Improving Hardwood Management on Non-Industrial Private Forest land in Virginia

Matthews, Bonnie L. C. 21 July 2005 (has links)
Hardwood management has been discouraged because of long rotations, low stumpage values, expensive treatments, and an undependable market (Bechtold and Phillips 1983). Knowledge gaps on how various biological factors affect hardwood growth also exist. Stand improvement methods attempt to shift growth to desirable stems. Three different hardwood stand improvement treatments were evaluated. A pre-commercial chemical thin occurred in a twelve year old stand in 1990. In 1995, two of the treatments showed a significant increase in dbh over the control. However, the 2004 measurements of the stand did not find any significant differences between treatments. A case study examined paired plots throughout the state of Virginia where the crown touching crop tree release method was applied. In both the Piedmont and Ridge and Valley regions of the state an increase in dbh was observed. Finally, a timber stand improvement study examined different treatments in a 60-80 year old stand, but did not result in any significant increases in volume after three years. When oaks are harvested or a major disturbance occurs, the number of oaks that regenerates is less than there were previously (Smith 1992). Therefore, oak regeneration is a problem and methods are needed to facilitate oak regeneration (Smith 1992). One method of oak regeneration was examined. Burning five years after a deferment cut did not result in significantly more stems of oak regeneration. Various reductions in basal area also did not result in an increase in oak regeneration under our 60-80 year old timber stand improvement study. These studies attempt to close knowledge gaps in hardwood management and provide useful information for non-industrial private forest (NIPF) landowners. It is so important to target NIPF landowners because the 350 million acres of timberland they own will play a large part in the future of the United States timber supply (Haynes 2002). / Master of Science
28

Competency to Stand Trial: A Systematic Evaluation and Validation of the GCCT, MacCAT-CA, and ECST as Competency Measures

Grandjean, Nicole Rae 05 1900 (has links)
Competency to stand trial cases constitute the largest percentage of forensic referrals for clinical psychologists. Furthermore, research suggests that the use of forensic measures facilitates the decisions of competency made by forensic examiners. This study investigated the construct validity of three competency measures: (a) the GCCT-MSH, (b) the MacCAT-CA, and (c) the ECST with 100 adult males incarcerated at the Tarrant County Jail in Fort Worth, TX. Construct validity was investigated via the use of a multitrait-multimethod research design for the three-prong conceptualization of the Dusky standard. Results indicated that current competency measures do an adequate job of assessing for factual understanding, but lack construct validity for two prongs: rational understanding and the ability to consult with counsel. In addition, the atypical presentation scales of the both GCCT and the ECST performed well at screening individuals for feigning. Finally, prediction of competency from clinical variables was also investigated. Psychotic symptoms and overall impairment were the strongest predictors of incompetency.
29

The Arkansas approach to competency to stand trial : "nailing jelly to a tree" /

Looney, Jerry Wayne. January 2008 (has links)
Thesis (M.J.S.)--University of Nevada, Reno, 2008. / "December, 2008." Includes bibliographical references (leaves 53-57). Library also has microfilm. Ann Arbor, Mich. : ProQuest Information and Learning Company, [2009]. 1 microfilm reel ; 35 mm. Online version available on the World Wide Web.
30

Klinische und radiologische Ergebnisse nach ventraler Spondylodese mit stand - alone - Cages bei degenerativen Halswirbelsäulenveränderungen

Franke, Anne-Catherine 03 June 2014 (has links) (PDF)
Ziel dieser Arbeit ist die retrospektive Auswertung der operativ mit ventraler Dekompression und intersomatischer Fusion (ACDF) durch stand alone Cage versorgten Patienten und die Diskussion, ob eine postoperative Sinterung Einfluss auf das Outcome hat. Material und Methoden: Es wurden 33 Segmente operativ durch ACDF mit standalone-Cage bei 17 Patienten (11 Frauen und 6 Männer) Durchschnittsalter 56 Jahre (33 bis 82 Jahre) versorgt und nach durchschnittlich jeweils 8 und 26 Monaten klinisch, radiologisch und durch Scoreerhebung nachuntersucht. Ergebnisse: 70,6 % der Patienten (12/17) und 50,5% der Segmente (18/33) zeigten eine Sinterung. 36,3% der Sinterungen (12/33) bereits zur 1. NU nach 8 Monaten. Zur 2. NU nach 26 Monaten fand sich bei 100% eine Fusion ohne Pseudarthrose. Zusammenfassung: Die Sinterung des Cages hat keinen negativen Einfluss auf das Outcome. Wesentlich für das Outcome sind das Ausmaß und die Dauer der vorbestehenden Symptome. Es sollte besonders bei festgestellter Myelopathie frühzeitig eine operative Intervention erfolgen.

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