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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.
11

Vibration absorption in the tennis grip and the effects on racquet dynamics

Savage, Nicholas James, nicolasshu709@hotmail.com January 2007 (has links)
The modern game of tennis has changed in recent years as a result of lightweight, stiffer racquets. The evolution of the tennis racquet, with respect to both design and materials, has increased the speed of the game but also the levels of stress placed on the player's bodies. Many believe that injuries such as lateral epicondylitis (tennis elbow) are caused and aggravated by the absorption of racquet energy by the player, in the form of shock and vibration. This thesis presents an experimental investigation into the absorption of racquet vibration to the player's hand and forearm. Quantification of the tennis grip has been achieved in this research using different experimental techniques to analyse different aspects of the tennis grip. Grip pressure distribution profiles during impact have been established using both pressure sensitive film and real-time data acquisition methods. Quantification of grip tightness during impact, together with gripping times, has also been quantified using a strain gauge cantilever system manufactured specifically for this research. The experimental data acquired in this research has provided the base for grip pressure distribution profiles to be established for three stroke types (e.g. Forehand, service and the problematic backhand). The profiles depict the distribution of pressure in the tennis grip in relation to the ball impact, in the time domain. Based on these grip profiles, the research hypothesises hand movements in an attempt to establish muscle contractions (and moreover locations of vibration absorption) specific to stroke types. The research investigates the absorption of racquet vibrations by the player's hand in the time domain. Filtering of accelerometer data allows for the isolation of specific frequencies of interest (i.e. below 200Hz). Logarithmic decrement of racquet vibration has been calculated and related to the grip pressure distributions in the time domain, and the relationship between grip pressure and vibration damping has been modelled. The correlation between grip pressure and the logarithmic decrement has been show to be significant (p less than 0.005) and non-linear. The relationship between the tennis grip and the damping of racquet vibrations has been found to be dependant on both grip pressure and the proximity of grip pressure application in proximity to the handle node. Grip pressure applied to the racquet close to the handle node has a greater damping effect than a similar pressure further away. In addition to these key research findings, the effectiveness of a piezoelectric racquet damping system is also investigated. A comprehensive modal analysis of two tennis racquets is given with further ball impact tests. The ball impact tests showed that the damping system has a 28% difference in racquet vibrations during freely suspended grip conditions. However, under hand-held grip conditions the inclusion of grip damping into the system provides a much greater damping entity (880% greater). Therefore, the effect of the piezoelectric system was deemed to be negligible.
12

Optimalizace energetického hospodářství galvanovny / Improvement of energy supply in industrial process

Pavlíček, Lukáš January 2009 (has links)
The main subjekt of that diploma thesis is an optimalization energetic ekonomy of a bathroom. The ojective is propose suitable resolution for decrease decrement heating and employ outlet heat of burnt gas which are going from steam generator. In the first part of thesis is evaluation inceptive state, inlet and outlet flows of energies. In the next part, there are confront indivudual resolving from technically angle and economically angle.
13

Automatic modal variation tracking via a filter-free random decrement technique application to ambient vibration recordings on high-rise buildings / Suivi automatique de variations modales à l’aide du technique de décrément aléatoire sans filtrage application à des enregistrements de vibrations ambiantes des bâtiments

Nasser-Barakat, Fatima 28 May 2015 (has links)
Cette thèse propose une nouvelle approche pour surveiller automatiquementles variations des fréquences et des taux d’amortissement des batiments de grande hauteursoumis à des vibrations ambiantes. L’approche vise à relever simultanément avec les défissuivants: signaux multi-composants enregistrées sur les bâtiments mentionnés ci-dessusavec des réponses impulsionnelles ayant des modes de fréquences rapprochées, des amplitudesfaibles, exponentielles et amorties noyées dans des bruits additifs élevés. La méthoderepose sur l’application de la technique de décrément aléatoire directement sur le signal multicomposantece qui conduit à l’estimation d’une signature de décrément aléatoire multi-modeéquivalente à la réponse impulsionnelle de système. Pour caractériser une telle signature,nous proposons un modèle de signal basé sur la structure physique du bâtiment à partir delaquelle les paramètres modaux peuvent être estimés. Dans le but d’avoir une estimationnon biaisée, nous proposons d’utiliser une méthode itérative sur la base d’une estimation dumaximum de vraisemblance optimisé par une technique de recuit simulé. Afin d’initialiserles paramètres de ce dernier, une première étape est conçu qui peut être considéré commeun estimateur indépendant des paramètres modaux. L’originalité de cette étape réside danssa capacité à définir automatiquement le nombre de modes de la signature estimé grâce àl’utilisation des propriétés statistiques d’un spectre estimé par une transformée de Fourier.Les paramètres modaux estimés par l’étape d’initialisation sont finalement affinés par l’étaped’estimation du maximum de vraisemblance. Celui-ci réduit le biais de l’estimation et donnedes résultats plus fiables et plus robustes. Toutes ces étapes sont définies de manière à être enmesure de surveiller automatiquement l’état de santé d’un bâtiment par l’intermédiaire d’unsuivi long terme en temps réel des variations modales dans le temps sans que l’interventionde l’utilisateur soit nécessaire. En outre, l’approche proposée a accordé une attention touteparticulière à l’estimation automatique du paramètre modal les plus problématique, c’està-dire, le taux d’amortissement. Ces deux caractéristiques sont des atouts originaux parrapport aux techniques existantes. L’adaptabilité et la fonctionnalité de l’AMBA a été validésur six bâtiments réels excités par des vibrations ambiantes. D’après les résultats obtenus,AMBA a prouvé une grande efficacité dans l’estimation automatique des fréquences et destaux d’amortissement dans le cas de modes de fréquences rapprochées et avec un très faiblerapport signal-sur-bruit. AMBA a ainsi démontré une bonne performance pour suivre lesvariations modales au fil du temps. / This thesis proposes a novel approach to automatically monitor the variationsof the frequencies and the damping ratios of actual high-rise buildings subjected to realworldambient vibrations. The approach aims at dealing simultaneously with the followingchallenges: multi-component signals recorded over the aforementioned buildings and havingclosely-spaced frequency modes with low, exponential and damped amplitudes of theirimpulse responses and contaminated with high additive noises. The approach relies on theapplication of the Random Decrement Technique directly over the multi-component signalunder study which leads to the extraction of a Multi-mode Random Decrement Signatureequivalent to the system impulse response. To characterize such a signature, we propose asignal model based on the physical structure of the building from where the modal parameterscan be estimated. For the purpose of non-biased modal estimate, we propose to usean iterative method based on a Maximum-Likelihood Estimation optimized by a simulatedannealing technique. In order to initialize the parameters of the latter, a first step is designedwhich can be considered as an independent estimator of the modal parameters. Theoriginality of this step lies in its ability to automatically define the number of modes of theestimated signature through the use of the statistical properties of a Welch spectrum. Themodal parameters estimated by the spectral-based initialization step are finally refined bythe Maximum-Likelihood Estimation step. The latter reduces the bias in the estimation andyields more reliable and robust results. All these steps are defined in order to be able to automaticallymonitor the health of a building via a long-term real-time tracking of the modalvariations over time without the need to any user intervention . In addition, the proposedapproach has paid very special attention to the automatic estimation of the most problematicmodal parameter, i.e., the damping ratio. Such features making two of the original featuresas compared to existing techniques. The adaptability and functionality of AMBA is validatedover six actual buildings excited by real-world ambient vibrations. From the obtained results,AMBA proved high efficiency in automatically estimating the frequencies and moreover thedamping ratios in case of closely-spaced frequency modes and very low signal-to-noise ratiolevel. AMBA as well demonstrated a good performance for tracking the modal variationsover time.
14

Reestruturação do ensino superior privado no Brasil e precarização do trabalho docente: o caso da Fit/Uniesp (2006/2014)

Borges, Jonathan Xavier 24 June 2015 (has links)
Made available in DSpace on 2016-04-27T16:33:02Z (GMT). No. of bitstreams: 1 Jonathan Xavier Borges.pdf: 877097 bytes, checksum: 240e2eb8d5f58e047ea469c36387ceea (MD5) Previous issue date: 2015-06-24 / This study aims to investigate the changes occurred at Faculdade de Itapecerica da Serra (FIT), private higher education and non-philanthropic institution based in Itapecerica da Serra, at Grande São Paulo. The period analyzed is between the years 2006 and 2014, i.e., from its establishment in the year after it was acquired by União das Instituições Educacionais do Estado de São Paulo (UNIESP), one of the major corporations active in this sector in Brazil. We verified that large conglomerates are absorbing small educational institutions of higher education, increasing its range nationally and on a number of alumni. We start from the assumption that acquisitions like occurred to UNIESP / FIT are configured as a case of corporate expansion, generating institutional changes covering the entire teaching and administrative structure and consequently a conflict between organizational culture (CAVEDON, 2000; DIAS, 2013) of the former and current maintainer. We found that this process ended up generating a continuous loss of teaching quality and decrement of the teaching profession. The sources used were, in addition to the bibliography on the subject (Guimarães, 2008; OLIVEIRA, 2013), documents illustrating the history of the institutions in question and interviews with teachers, collected using the methodology of Oral History (Alberti, 2004; POLLACK 1992) / O presente estudo tem por objetivo investigar as mudanças ocorridas na Faculdade de Itapecerica da Serra (FIT), instituição de ensino superior de caráter particular e não filantrópica localizada na cidade de Itapecerica da Serra, região da grande São Paulo. O recorte temporal compreende o período de 2006 a 2014, desde sua fundação até o ano posterior ao que foi adquirida pela União das Instituições Educacionais do Estado de São Paulo (UNIESP), uma das grandes corporações atuantes nesse setor no Brasil. Verifica-se que grandes conglomerados educacionais estão absorvendo pequenas instituições de ensino superior, aumentando sua abrangência em nível nacional e número de alunos. Partimos da hipótese que aquisições como da UNIESP/FIT se configuram como um caso de expansão corporativa, gerando mudanças institucionais que contemplam toda estrutura pedagógica e administrativa e, consequentemente, um conflito entre a cultura organizacional (CAVEDON, 2000; DIAS, 2013) da antiga e da atual mantenedora. Foi constatado que esse processo acabou por gerar uma contínua perda da qualidade de ensino e precarização do trabalho docente. As fontes utilizadas foram, além da bibliografia de referência sobre o tema (GUIMARÃES, 2008; OLIVEIRA, 2013), documentos que ilustram a trajetória das instituições em questão e entrevistas com professores, coletadas utilizando a metodologia da História Oral (ALBERTI, 2004 ; POLLACK 1992)
15

Attention soutenue et vieillissement normal : étude des mécanismes cognitifs et neuronaux associés au contrôle attentionnel / Sustained attention and normal aging : study of cognitive and neuronal mechanisms associated with attentional control

Staub, Bérengère 17 September 2014 (has links)
L’objectif de ces travaux de thèse était d’avancer dans la connaissance des effets du vieillissement normal sur les capacités d’attention soutenue et les mécanismes de contrôle attentionnel qui les sous-tendent. A cette fin, nous avons combiné l’utilisation de mesures comportementales, subjectives, et électrophysiologiques (potentiels évoqués). Les résultats comportementaux mettent en évidence des effets différenciés de l’âge sur les capacités d’attention soutenue en fonction de l’approche utilisée : détérioration dans les tâches de détection, et préservation dans les tâches d’inhibition. Les données électrophysiologiques mettent en évidence plusieurs spécificités des seniors dans l’engagement des mécanismes de contrôle attentionnel en situation d’attention soutenue : une activation globalement plus importante de ces mécanismes, une activation maintenue ou augmentée de ces mécanismes au fil de la tâche, et une topographie plus frontale des régions qui les sous-tendent. / The purpose of this project was to gain more knowledge about the effects of normal aging on sustained attention ability and attentional control mechanisms underlying this ability. To that end, we combined the use of behavioral, subjective and electrophysiological (event-related potentials) measures. Behavioral results evidenced differential effects of age on sustained attention ability according to the approach used: deterioration in detection tasks, and preservation in inhibition tasks. Electrophysiological data evidenced several special features of seniors regarding the recruitment of attentional control mechanisms in a situation of sustained attention: overall greater activation of these mechanisms, stable or increased activation of these mechanisms over the course of the task, and a more frontal topography of the regions underlying these mechanisms.
16

Statnamic Lateral Load Testing and Analysis of a Drilled Shaft in Liquefied Sand

Bowles, Seth I. 02 December 2005 (has links) (PDF)
Three progressively larger statnamic lateral load tests were performed on a 2.59 m diameter drilled shaft foundation after the surrounding soil was liquefied using down-hole explosive charges. An attempt to develop p-y curves from strain data along the pile was made. Due to low quality and lack of strain data, p-y curves along the test shaft could not be reliably determined. Therefore, the statnamic load tests were analyzed using a ten degree-of-freedom model of the pile-soil system to determine the equivalent static load-deflection curve for each test. The equivalent static load-deflection curves had shapes very similar to that obtained from static load tests performed previously at the site. The computed damping ratio was 30%, which is within the range of values derived from the log decrement method. The computer program LPILE was then used to compute the load-deflection curves in comparison with the response from the field load tests. Analyses were performed using a variety of p-y curve shapes proposed for liquefied sand. The best agreement was obtained using the concave upward curve shapes proposed by Rollins et al. (2005) with a p-multiplier of approximately 8 to account for the increased pile diameter. P-y curves based on the undrained strength approach and the p-multiplier approach with values of 0.1 to 0.3 did not match the measured load-deflection curve over the full range of deflections. These approaches typically overestimated resistance at small deflections and underestimated the resistance at large deflections indicating that the p-y curve shapes were inappropriate. When the liquefied sand was assumed to have no resistance, the computed deflection significantly overestimated the deflections from the field tests.
17

Proměny struktury obyvatelstva ve věku 15-59 let podle rodinného stavu v České republice po roce 1930 / Changes in the marital status in the age group from 15 to 59 years in the Czech Republic after 1930

Boušová, Marie January 2012 (has links)
Changes in the marital status in the age group from 15 to 59 years in the Czech Republic after 1930 Abstract The aim of this thesis is to analyze the changes in population structure according to the individual marital statuses. For this analysis sex-specific and age-specific nuptuality rates and multistate life tables were use, in order to be able to describe transitions between the individual marital statuses. In the first part of this thesis the data sources and the methods of creating the transversal increment- decrement life tables were described. Following chapters deal with the historical development of the Czech Republic population since the year 1930 and the trends of nuptuality, divorce and mortality. Second part is dedicated to the analysis of the transitions between the individual marital statuses. The findings of this thesis conclude that people in the individual marital states tend to react similarly to the historical events in Czech Republic, unless some events are purposefully aiming to influence only a part of the population. Key words: nuptuality rate, divorce rate, mortality rate, marital status, multistate demography, transversal increment-decrement life tables, Czech Republic
18

運用Cox模型於短期現金支出之研究-以公務人員退撫基金為例 / Applying Cox Model in Short-term Cash Ouflow-A Case Study of Public Employees Retirement System

陳靜宜, Jin-i Chen Unknown Date (has links)
本研究主要以Cox 迴歸模型為主軸,以1995年7月1日至1999年5月7日公務人員退撫基金成員:公務人員及教育人員為研究對象,分析影響基金成員各項脫退的個別變數,並量化所擇取之變數的影響,以估計各個基金成員的脫退率。同時針對現有基金成員,評估退撫基金短期現金支出並分析之。實證結果發現:藉由Cox迴歸模型之分析可知,相異的脫退因素,被不同的迴歸變數所影響著,且各個變數對各項脫退的影響程度亦存在著差異。短期現金支出的評估結果顯示,各項給付支出,以退休給付的支出佔最大的比例,次為資遣、死亡及離職給付。而人數比例較少的教育人員,其脫退給付支出金額,高於公務人員之給付支出。 略 / Cox regression model is proposed in this study to investigate the demographic factors (i.e., gender, age, seniority, salary scale and the entry date) that influence the turnover pattern of the plan members. This research has focused on the government employees and public school teachers in Taiwan Public Employees Retirement System (Tai-PERS). Quantitative analyses on turnover are performed through monitoring and selecting the significant factors in Cox regression model. Finally based on the current members in Tai-PERS, the short-term cash outflow is projected. Based on the empirical results, different causes of turnover (i.e., death, withdrawal, layoff and retirernent) are influenced by the selected factors. Significant differences have been found within the various causes of decrements. Result from the short-term cash outflow shows that the payment due to retirement has the largest proportion. Then follows the payment amount due to payoff, death and withdrawal if we rank them in order. In additions, the total payments of the public school teachers are larger than those of the government employees, while the plan members of the public school teachers are comparatively less.
19

Nivåbedömning i oktavband: Är det rimligt vid hörapparatanpassning? / Level evaluation in octave bands: Is it reasonable when fitting hearing aids?

Stolt, Petter, Wahlsten, Markus January 2023 (has links)
Bakgrund: Finjusteringar av hörapparatens förstärkning görs för att validera förstärkningen. Patientens förmåga att kategorisera ljudbilden ligger till grund för de justeringar som görs. Syfte: Att utvärdera en praktiknära metod för finjustering av hörapparater. Metod: Deltagarna (N = 18) fick lyssna på och bedöma ljudbilden för ett talmaterial med slumpade nivåmodifieringar i oktavbandet 4 kHz. Försöksledaren korrigerade ljudbilden utifrån deltagarnas nivåbedömning, till dess att deltagarna upplevde att ljudbilden var naturlig. Deltagarna fick efter halva undersökningen, som intervention, lyssna på en genomgång som förklarade och jämförde de olika ljudbilderna. Resultat: Deltagarnas nivåbedömningar ledde till korrigeringar i oktavbandet som var statistiskt signifikanta, men en normalisering av oktavbandet uppnåddes inte. Efter genomgången kunde fler nivåmodifikationer korrigeras med en statistiskt signifikant skillnad. Nivåmodifikationer som kan kategoriseras som metalliska/skarpa ledde oftare till en statistiskt signifikant korrigering, än nivåmodifikationer som kan kategoriseras som otydliga/dova. Slutsatser: Om finjusteringar av hörapparaterna görs, bör audionomen ha klart för sig att det kan behövas större nivåförändringar i större frekvensband, för att patienten ska ha möjlighet att uppleva en skillnad i ljudbilden i en klinisk miljö. / Background: Fine-tuning of the hearing aid amplification is done to validate the amplification. The patient's ability to describe the sound quality lays as a foundation for the fine-tuning. Aim: To evaluate a practice-oriented method for fine-tuning hearing aids. Methods: The participants (N = 18) listened to and evaluated the sound quality for a speech-material with randomized level modifications in the octave band 4 kHz. The sound quality was adjusted according to the participants' evaluation, until a normalized sound quality was perceived by the participants. Halfway through the examination the participants, as an intervention, listened to a briefing which explained and compared differences in the different sound qualities. Results: The participants level evaluation led to adjustment in the octave band that was statistically significant, but a normalization of the octave band could not be achieved. After the briefing a larger number of level modifications were adjusted with a statistical significance. Level modifications which were categorized as metallic/sharp more often led to a statistically significant adjustment compared to level modifications categorized as unclear/dull. Conclusions: If fine-tuning of hearing aids is done, the audiologist should be aware that bigger level adjustment in broad bands might be needed, for the patient to be able to notice a difference in sound quality in a clinical setting.

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