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Khosrovaneh, Abolhassan K. "Fatigue analysis and reconstruction of helicopter load spectra." Diss., Virginia Polytechnic Institute and State University, 1989. http://hdl.handle.net/10919/54213.
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Helicopter load histories applied to notched metal samples are taken as examples, and their fatigue lives are predicted by using a simplified version of the local strain approach. This simplified method requires an input load history in the form of the rain-flow matrix and places bounds on the fatigue life. A peak-valley reconstructed history is generated based on the standard spectrum Helix. A second history studied is a more irregular one based on actual flight data. lt is used to generate three reconstructed histories based on three principles: peak-valley, to-from, and rain-flow. Emphasis is given to the rain-flow reconstruction method, and different reconstruction methods based on rain-flow cycle counting are presented. Life predictions are presented for all of the above cases, and the comparison with test data and other considerations suggest that the most promising reconstruction approach is one based on rain-flow cycle counting. Finally, a method is presented which reconstructs a history with the same rain-flow cycles and also the same distribution of relative time increments between adjacent peaks and valleys. This reconstructed history gives the same fatigue life as the original history.<br>Ph. D.
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Zitounis, Vasilios. "Fatigue crack growth rates under variable amplitude load spectra containing tensile underloads." Thesis, Cranfield University, 2003. http://dspace.lib.cranfield.ac.uk/handle/1826/105.
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An extensive research program was performed to investigate the load interaction effect of the combined action of small amplitude high R ratio cycles and large amplitude low R ratio underloads on the crack growth of large cracks. The study was driven by the needs of the damage tolerance approach in the helicopter structures, which requires robust knowledge on the crack growth behaviour of the advance high strength alloys under the characteristic helicopter spectra loading. The study was conducted on three metallic alloys, Ti-10V-2Fe-3Al, Al8090 T852 and Al7010 T76351 using compact tension specimens (w=70mm, t=17mm). The potential drop technique was used for the measurements of the crack length. The crack opening loads were determined from the applied load versus crack opening mouth displacement curve using a curve fitting technique and crack opening displacement gauge. The experimental results show that cracks can grow faster than the life predictions with no load interaction effects under spectra containing tensile underloads. The acceleration effects are different depending on the number of the small cycles, the Kmax, the R ratio of the small cycles, the underload cycle and the material. Significant closure observations on the underloads and on the small cycles of variable amplitude loading spectra were made. Based on the test finding and on the studies of other researchers, it is suggested that the acceleration effects are mainly due to the reduction of crack opening point of the tensile underloads comparing with the Constant Amplitude Loading (CAL) data. An extensive evaluation of the ability of FASTRAN model to predict the fatigue lives under the tested loading spectra was carried out. The evaluation focuses on the influence of the constraint factor a and the ∆Keff curve inputs on the predictions. The model produces very good and consistent predictions for the three alloys, when the inputs represent adequately the actual fatigue mechanism. The model predicts the measured acceleration effects by reducing the closure level of the underloads.
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Lee, Hongchul. "Advanced aircraft service life monitoring method via flight-by-flight load spectra." Diss., Online access via UMI:, 2009.
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Thesis (Ph. D.)--State University of New York at Binghamton, Thomas J. Watson School of Engineering and Applied Science, Department of Mechanical Engineering, 2009.<br>Includes bibliographical references.
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Walter, Richard W. "Study of statistical variations of load spectra and material properties on aircraft fatigue life." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24056.
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Shan, Martin [Verfasser]. "Load Reducing Control for Wind Turbines: Load Estimation and Higher Level Controller Tuning based on Disturbance Spectra and Linear Models / Martin Shan." Kassel : Universitätsbibliothek Kassel, 2017. http://d-nb.info/1154972496/34.
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Entesar, Abdullah Ali. "Statistical analysis of truck loading on Swedish highways." Thesis, KTH, Transportvetenskap, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-45980.
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Vehicle over loading, or single axle over loading, is one of the major causes of pavement deterioration. Trafik Verket (TV), the Swedish Transport Administration, recognized that the current process for estimating traffic volume should be reevaluated, and if possible improved. This degree project uses data from the Bridge Weigh in Motion (BWIM) system to study the actual loads applied to Swedish highways. The axle load spectrum is plotted with the conventional frequency distribution plots, and with a new cumulative distribution approach. The paper introduces the maximum allowable potential vehicle weight MAPVW concept, and uses this visual technique to identify overloads for different vehicle geometries. The paper concludes that for 5 and 6 axle trucks the triple axle is frequently overloaded, while for longer trucks one of the dual axles is often over loaded. The highest over loads tend to be on the driving axle, suggesting incorrect loading procedures.
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Fontenele, Heliana Barbosa. "Representação do tráfego de veículos rodoviários de carga através de espectros de carga por eixo e seu efeito no desempenho dos pavimentos." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/18/18143/tde-12032012-111950/.
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A caracterização das cargas do tráfego é de grande importância para o dimensionamento de pavimentos, bem como para a quantificação do desempenho para fins de gerência de pavimentos. A utilização de abordagens empíricas para determinar os efeitos das cargas do tráfego nas estruturas de pavimentos, datadas dos anos 1960, apresentam sérias limitações, pois seus resultados são válidos somente para os mesmos, ou muito similares, fatores intervenientes que prevaleciam quando do seu desenvolvimento. Os fatores relativos às solicitações do tráfego e às características dos veículos (tipo de eixo, tipo de rodagem, pressão de enchimento dos pneus e tipo de suspensão) são bem diferentes, atualmente, daquelas existentes há 50 anos. Tendo em vista que os modelos de desempenho são importantes ferramentas dos sistemas de gerência de pavimentos (SGP) para prever a evolução da condição ao longo do tempo e/ou tráfego acumulado e, portanto, dependentes de uma consistente caracterização do tráfego, o objetivo desta pesquisa foi analisar os efeitos da caracterização do tráfego sobre o desempenho dos pavimentos, a partir da geração de modelos estatísticos baseados no conceito proposto pelo método da AASHTO 2002, de espectros de carga por eixo dos veículos comerciais de carga, comparando-os com o conceito de equivalência de carga, desenvolvido a partir do AASHO Road Test na década de 1950. Dados de pesagens realizadas no ano de 2008 no Posto de Pesagem de Veículos da SP-160 Rodovia dos Imigrantes, km 28, pista Sul, foram utilizados para o desenvolvimento dos espectros de carga e posterior modelagem. Testes estatísticos e práticos foram realizados para determinar a variabilidade mensal dos Fatores de Veículos (FV) em relação ao valor médio do ano de 2008. Apesar da análise estatística com a aplicação do teste Kolmogorov-Smirnov (K-S) ter apresentado diferenças significativas entre os espectros mensais e anuais, a variação observada nos fatores de tráfego não resultou em diferenças práticas na espessura final do pavimento. Os modelos estatísticos foram desenvolvidos separadamente para cada classe de veículo e de eixos que o compunha, tendo sido usadas distribuições de probabilidade Log-normal e Weibull para modelar os espectros de carga. Os parâmetros dos modelos foram obtidos através do método dos mínimos quadrados, complementado com a realização de testes K-S e Qui-quadrado, destacando-se a obtenção de coeficientes de determinação (R2) superiores a 0,90. A comparação entre os resultados previstos pelos modelos e os dados originais, feita tanto pela abordagem empírica como empírico-mecanística, com uso dos programas computacionais ELSYM5 e MEPDG, evidencia o modelo Weibull como o mais indicado para aplicação em rodovias brasileiras com características de tráfego semelhantes às da Rodovia dos Imigrantes.<br>The characterization of traffic loads is of great importance for pavement design, as well as for the measurement of performance in a pavement management system. The use of empirical approaches to determine the effects of traffic load on pavement structures, dating from the 1960\'s, presents serious limitations, since its results are just valid for the same or very similar intervening factors that prevailed at the time of its development. The traffic load factors and vehicle characteristics (axle type, tire type, tire inflation pressure, and suspension type) are quite different today from those existing 50 years ago. Given that the performance models are important tools of pavement management systems (PMS) to predict the evolution of pavement condition over time and/or accumulated traffic and therefore dependent on a consistent characterization of the traffic, the objective of this research was to analyze the effects of traffic characteristics on pavement performance through the generation of statistical models based on the concept proposed by the AASHTO 2002 method, axle load spectra of commercial vehicles, comparing them with the concept of load equivalence factor, developed through the AASHO Road Test in the 1950s. Data collected in 2008 in a weighing station located on Immigrant Highway - SP-160, km 28, southern runway, were used for the development of load spectra and subsequent modeling. Practical and statistical tests were performed to determine the variability of monthly vehicle-factors (FV) to the mean value for the year 2008. Despite the statistical analysis, performed by applying the Kolmogorov-Smirnov (KS) test, have shown significant differences between the monthly and annual spectra variation, there were not practical differences in the final thickness of the pavement associated to changes in vehicle-factors. Statistical models were developed for each vehicle class and for its axles, having been used Log-normal and Weibull probability distributions to model the load spectra. The model parameters were obtained from the method of least squares, complemented by the KS and chi-square tests, being important to mention that the coefficients of determination (R2) were greater than 0.90. The comparison between the results predicted by the models and the original data, made either by empirical and empiricalmechanistic approaches, with use of computer programs ELSYM5 and MEPDG, shows that the Weibull model is the most suitable for application in Brazilian highways with similar traffic characteristics to the Immigrants Highway.
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Frankhouser, Andrew. "Characterization of Ohio Traffic Data for Integration into the Mechanistic-Empirical Pavement Design." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1365980149.
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Elsässer, Robert. "Spectral methods for efficient load balancing strategies." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965647145.
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Reytier, Thomas. "Modelling fatigue spectra of aircraft structure under gust loads." Toulouse 3, 2012. http://thesesups.ups-tlse.fr/1614/.
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Cette thèse est consacrée à l'analyse de fatigue et de tolérance aux dommages des structures d'avions soumis aux rafales de vent. L'analyse de fatigue et de tolérance aux dommages est un enjeu essentiel dans la conception des structures d'avions. Elle permet de définir un programme d'inspection de la structure afin d'assurer sa sécurité tout au long de la vie de l'avion. La première partie passe en revue l'état de l'art dans les différents domaines impliqués dans le processus global d'analyse de fatigue des structures d'avions soumis aux rafales de vent: la modélisation de la turbulence atmosphérique, le calcul des charges et des contraintes à l'aide d'analyses par éléments finis, la construction du spectre de fatigue et enfin, l'analyse de fatigue et de tolérance aux dommages. La deuxième partie présente le processus complet actuellement implémenté au sein d'Airbus. Les points forts et les points faibles de ce processus sont d'identifiés et permettent de dégager des axes d'amélioration. A partir du modèle de turbulence continue basé sur la densité spectrale de puissance (DSP) de Von Karman, les contraintes calculées sont insérées selon des statistiques établies par des mesures envol dans le spectre de fatigue pour former une séquence de cycles de contraintes. Les données d'entrée pour l'analyse de fatigue et tolérance aux dommages sont obtenues à partir de la définition des différents profils de mission, des valeurs de contraintes unitaires, de la réponse dynamique de la structure et des statistiques de turbulence. Dans la troisième partie, une nouvelle méthodologie est présentée afin d'obtenir des séquences temporelles des contraintes dues à la turbulence de manière précise et efficace. Cette méthode s'appuie sur de nouveaux résultats permettant de générer des signaux temporels corrélés à partir des DSP. Tout d'abord, les DSP des différentes composantes des contraintes sont directement obtenues à l'aide d'une analyse par éléments finis à partir de la DSP de Von Karman. Puis, les séquences temporelles corrélées de ces contraintes sont générées et sont ensuite distribuées dans le spectre de fatigue selon la loi statistique de l'intensité de la turbulence atmosphérique. Ce nouveau processus permet d'améliorer le calcul des contraintes et la génération du spectre de fatigue. Il remplace les statistiques de turbulence par des statistiques de franchissement de niveaux de contraintes raisonnablement conservatives définies par une formule analytique. De plus, le temps de livraison des données d'entrée pour l'analyse de fatigue et tolérance aux dommages est significativement réduit. Les résultats présentés, issus de l'analyse de fatigue et de tolérance aux dommages, permettent de souligner la qualité des améliorations apportées à la fois en termes de précision et de durée du processus<br>This thesis is dedicated to the fatigue and damage tolerance analysis of the aircraft structures under gust loads. The fatigue and damage tolerance analysis is a significant issue in the aircraft structure design. It aims at defining the inspection program of the aircraft structure in order to ensure its safety through its entire life. The first part reviews the state-of-the-art in the various involved topics for the global process for fatigue analysis of aircraft structure under gust loads: the atmospheric turbulence modelling, the load and stress computation by a finite element analysis, the generation of the fatigue spectrum and at the end, the fatigue and damage tolerance analysis. The second part presents the whole process currently implemented at Airbus. The main strengths and weaknesses are pointed out and this en-ables the identification of several improvement axes. From the continuous turbulence model based on the Von Karman Power Spectral Density(PSD), the computed stresses are included according to statistics established from in-flight measurements in the fatigue spectrum in order to build a stress cycle sequence. The input data for the fatigue and damage tolerance analysis are obtained from the definition of the various fatigue mission profiles, the unitary stress values, the dynamic response of the structure and the turbulence statistics. In the third part,a new methodology is presented in order to obtaine efficiently and accurately the temporal stress sequences due to the atmospheric turbulence. This method relies on new results enabling the generation of correlated time signals from the PSD functions. First, the PSD of the various stress components are directly obtained from the Von Karman PSD via a finite element analysis. Then, the correlated temporal stress sequences are generated and distributed in the fatigue spectrum according to the turbulence intensity statistical law. This new process enables the improvement of the stress computation and the fatigue spectrum generation. It replaces the turbulence statistics by stress exceedance statistics which are defined by an analytical formula in a reasonably conservative way. In addition, the lead time to build the input data for the fatigue and damage tolerance analysis is significantly reduced. Results from the fatigue and damage tolerance analysis are presented in order to highlight the quality of the improved processes both in terms of accuracy and lead time
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Zhong, Shiyin. "Electricity Load Modeling in Frequency Domain." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/75109.
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In today's highly competitive and deregulated electricity market, companies in the generation, transmission and distribution sectors can all benefit from collecting, analyzing and deep-understanding their customers' load profiles. This strategic information is vital in load forecasting, demand-side management planning and long-term resource and capital planning.
With the proliferation of Advanced Metering Infrastructure (AMI) in recent years, the amount of load profile data collected by utilities has grown exponentially. Such high-resolution datasets are difficult to model and analyze due to the large size, diverse usage patterns, and the embedded noisy or erroneous data points. In order to overcome these challenges and to make the load data useful in system analysis, this dissertation introduces a frequency domain load profile modeling framework. This framework can be used a complementary technology alongside of the conventional time domain load profile modeling techniques.
There are three main components in this framework: 1) the frequency domain load profile descriptor, which is a compact, modular and extendable representation of the original load profile. A methodology was introduced to demonstrate the construction of the frequency domain load profile descriptor. 2) The load profile Characteristic Attributes in the Frequency Domain (CAFD). Which is developed for load profile characterization and classification. 3) The frequency domain load profile statistics and forecasting models. Two different models were introduced in this dissertation: the first one is the wavelet load forecast model and the other one is a stochastic model that incorporates local weather condition and frequency domain load profile statistics to perform medium term load profile forecast.
7 different utilities load profile data were used in this research to demonstrate the viability of modeling load in the frequency domain. The data comes from various customer classes and geographical regions. The results have shown that the proposed framework is capable to model the load efficiently and accurately.<br>Ph. D.
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Remington, A. M. "Selective attention and perceptual load in autism spectrum disorder." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19503/.
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This thesis examines selective attention in young adults with Autism Spectrum Disorder (ASD). Existing literature regarding this issue is mixed; some research suggesting an overly-focused attentional style (Rincover & Ducharme, 1987) while others highlight an abnormally broad attentional lens (Burack, 1994). The research presented here has, for the first time, examined selective attention in individuals with ASD using a theoretically-led approach based on Lavie’s Load Theory of attention and cognitive control (Lavie et al., 2004). Load theory states that the perceptual load (amount of potentially task relevant information) of a task affects selective attention. This theory may explain the equivocal findings in the current data on selective attention and ASD. Using behavioural measures, the pattern of selective attention under various levels of load was explored in individuals with ASD and matched controls. The results provide evidence of increased perceptual capacity in ASD. This means that, at any one time, individuals with ASD may be able to process more information from the visual environment. This increase in capacity was evident on tasks of both unconscious and conscious perception. In light of the social deficits observed in the condition, the work in this thesis also explored selective attention in the presence of social distractor stimuli. Results indicated that faces are less salient for individuals with ASD and, unlike for typical adults, are not processed in an automatic and mandatory fashion. These results bring together findings on selective attention with work on social processing in an attempt to find basic abnormalities which might be fundamental in explaining the disorder.
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ONO, YUICHIRO, SHIN'YA YAMADA, MASASHI FURUTA, et al. "The Scale Method as a Spectral Analysis for Accommodative Fluctuation." Nagoya University School of Medicine, 1987. http://hdl.handle.net/2237/17496.
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Donati, Dario. "Analysis of aircraft load spectrum by means of flight simulator." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9346/.
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Damage tolerance analysis is a quite new methodology based on prescribed inspections. The load spectra used to derive results of these analysis strongly influence the final defined inspections programs that for this reason must be as much as possible representative of load acting on the considered structural component and at the same time, obtained reducing both cost and time.
The principal purpose of our work is in improving the actual condition developing a complete numerical Damage Tolerance analysis, able to prescribe inspection programs on typical aircraft critical components, respecting DT regulations, starting from much more specific load spectrum then those actually used today. In particular, these more specific load spectrum to design against fatigue have been obtained through an appositively derived flight simulator developed in a Matlab/Simulink environment. This dynamic model has been designed so that it can be used to simulate typical missions performing manually (joystick inputs) or completely automatic (reference trajectory need to be provided) flights. Once these flights have been simulated, model’s outputs are used to generate load spectrum that are then processed to get information (peaks, valleys) to perform statistical and/or comparison consideration with other load spectrum. However, also much more useful information (loads amplitude) have been extracted from these generated load spectrum to perform the previously mentioned predictions (Rainflow counting method is applied for this purpose). The entire developed methodology works in a complete automatic way, so that, once some specified input parameters have been introduced and different typical flights have been simulated both, manually or automatically, it is able to relate the effects of these simulated flights with the reduction of residual strength of the considered component.
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Babish, John. "A modal/spectral analysis of mass distribution effects in a fluid-load plate." Thesis, Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19472.
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Li, Ran. "Load profiling on time and spectral domain : from big data to smart data." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.665434.
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With the promotion of demand side responses (DSRs) and low carbon technologies (LCTs), there is a growing interest in visualising the demand information at individual consumer and low voltage (LV) network level, where demands are less aggregated and highly volatile. Yet, traditional load profiling techniques, which are carried out on small data, are struggling to meet the requirements on accuracy and granularity. This thesis contributes to this area by extending traditional load profiling to a big-data context, where refined load profiles (smart data) can be extracted by two novel load profiling techniques for LV networks and individual consumers. The refined load profiles aim to: i) economically visualise LV networks with limited smart-grid monitoring data; ii) transform the smart metering data into a high-detail granular representation of the customers’ daily demand. For the LV networks, this thesis develops a novel concept, LV network templates, which aim to visualise the LV networks in a cost-effective manner. A novel three-stage load profiling method is proposed as: clustering, classification and scaling. By using statistical time-series analysis, three steps are undertaken: i) cluster a vast amount of load data according to their load shapes; ii) classify un-monitored substations to the most similar cluster without sample metering; iii) and also scale them to the right magnitude without sample metering. Through this method, limited representative monitoring data can be used to develop a library of typical load profiles for un-monitored networks, thus saving the cost of extensive monitoring for every single substation. In addition, it is the first load profiling method that can accurately express both load shapes and magnitudes for LV networks. Regarding the customer’s demand representation, the developed time-series analysis needs to be updated due to the volatile and uncertain nature of smart metering data, including inter-related factors such as overall load shapes, sudden spikes and magnitudes. Therefore, an innovative spectral load profiling is proposed to decompose these factors into different spectral levels, characterised by spectral features. By analysing the extracted features on each spectral level separately through multi-resolution analysis, the interference among different factors can effectively be prevented. The proposed method, for the first time, is able to fully capture the energy characteristics at the household level. The developed LV network load templates provide an economical but straightforward way to quantify the available headroom of unmonitored substations over time, providing quantitative information for distribution network operators to integrate LTCs at the minimal costs. The spectral load profiling gives an insight into customer’s energy behaviours with high granularity and accuracy. It can support the customer-specified DSR, tariff design, smart metering validation and load forecasting.
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Yoo, Byungseok. "Practical Aspects of Assessing Nonlinear Ultrasonic Response of Cyclically Load 7075-T6 Aluminum." Thesis, Virginia Tech, 2006. http://hdl.handle.net/10919/36335.
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The ultrasonic NDE technique to characterize the ultrasonic nonlinear response of the cyclically load 7075-T6 aluminum is described in this thesis. In order to estimate the nonlinear relation of the ultrasonic waves due to material fatigue damage or degradation, the spectral analysis techniques such as the power spectrum, bispectrum, and bicoherence spectrum are applied. The ultrasonic nonlinearity parameters by Cantrell and Jhang are introduced and presented as a function of the material fatigue growth, the number of fatigue cycles. This thesis presents the effectiveness of the bispectral analysis for evaluating the nonlinear aspects of the ultrasonic wave propagation. The results show that the nonlinearity parameters by Cantrell and Jhang are responsive to the output amplitude of the received signal and vary for the various materials, and independent of the input frequency and the ultrasonic wave propagation distance. By using the bispectral analysis tools, particularly the bicoherence spectrum, the increase of the coupling levels between the fundamental, its harmonic, and subharmonic frequency components is presented as the number of fatigue cycles is increased. This thesis suggests that the application of the bicoherence spectrum based on the nonlinear wave coupling relations be more effective for estimating the level of the material fatigue life.<br>Master of Science
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Tillmann, J. E. "Cross-modal selective attention and perceptual load in autism spectrum disorder." Thesis, University College London (University of London), 2016. http://discovery.ucl.ac.uk/1474696/.
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This thesis investigated cross-modal selective attention in children and adolescents with Autism Spectrum Disorder (ASD) and typically developing (TD) individuals using the Load Theory of Selective Attention and Cognitive Control (Lavie, 1995). Perceptual load theory states that perception of irrelevant stimuli depends on the perceptual load of the task (the amount of task relevant information). At low levels of perceptual load, when finite perceptual capacity is not reached, remaining resources ‘spill over’ and irrelevant stimuli are automatically processed; when perceptual load exhausts capacity, irrelevant stimuli are no longer processed. In ASD, there is some evidence that on visual attention tasks, individuals with ASD continue to process visual information at higher levels of perceptual load than controls, indicative of an increased perceptual capacity (Remington, Swettenham, & Lavie, 2012; Remington, Swettenham, Campbell, & Coleman, 2009; Swettenham, Remington, Murphy, Feuerstein, Grim, & Lavie, 2014). This thesis tested novel predictions derived from these findings for contexts of cross-modal selective attention. Using behavioural measures, the extent to which participants were able to attend to auditory information was examined as a function of the perceptual demands of a visual task. It was shown that individuals with ASD continued to report awareness of auditory information at higher levels of visual perceptual load than matched typically developing individuals. This was evident on tasks that measured both awareness for an unexpected, as well as expected auditory stimulus. Together, these findings suggest that individuals with ASD are characterised by an increased perceptual capacity that operates across sensory modalities.
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Gros-Borot, Maeva. "Modelling a foil load spectrum using recorded data on a racing foiling yacht." Thesis, KTH, Marina system, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226532.
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The intent of this Master Thesis is to investigate foil loadings on racing foiling yacht based on recorded data. This work was done by means of recorded microstrains along the foil and other recorded data such as boat speed and fly height. Composite foils are developed by the company GSea Design using an in-house software called Sofia which uses Fluid Structure Interaction (FSI) to design deformable appendages. In this Master Thesis, a tool that enables to get a numerical model of the foil adjusted to the recorded strains at a given time was designed. For that, recorded strains along the foil were first evaluated and post-processed to calculate the corresponding bending moments along the foil. Then an optimization loop based on the Sofia software was implemented. This loop automatically adjusts the numerical model of the foil to the recorded bending moments and computes the global Up and Side forces (vertical and anti- leeway forces, respectively) applied on the foil that contribute to the boat’s equilibrium. This approach was set up and tested during this Master Thesis. It enabled to show that building a representative load case in terms of global Up and Side forces with the corresponding numerical model using recorded data at a given time was possible. This work also highlighted some remaining constraints such as long calculation times to get an adjusted model automatically on recorded data. It implies that future work on data processing or optimisation improvements will constitute the next steps developed by GSea Design to be able to set up a foil design in terms of lifetime.<br>Avsikten med detta examensarbete är att undersöka bärplansbelastningar på en foilande racingsegelbåt baserat data uppmätta under segling, såsom töjningar i bärplanen, båthastighet, och flyghöjd. Kompositbärplan utvecklas av företaget GSea Design med hjälp av en egen mjukvara som heter Sofia, som bygger på modellering av fluid-struktur interaktion (FSI). I detta examensarbete har ett verktyg utvecklats som gör det möjligt att justera en numerisk modell av ett bärplan till uppmätta töjningar vid en given tidpunkt. Med utgångspunkt från uppmätta töjningar i bärplanet beräknas först motsvarande böjningsmoment längs bärplanet. Därefter implementerades en optimeringsprocedur baserat på Sofia som automatiskt anpassar bärplansmodellen till de uppmätta böjningsmomenten och beräknar de globala upp- och sidokrafterna (tillhörande vertikala och avdrift krafterna) på bärplanet som bidrar till båtens jämvikt. Utvärdering visar att den utvecklade metodiken fungerar bra för att formulera representativa lastkonditioner. Återstående begränsningar diskuteras, som till exempel att långa beräkningstider krävs, och rekommendationer ges för fortsatt utveckling av databehandling och optimeringsförbättringar för att möjliggöra bärplansdesign baserat på livstidsanalys.
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Parveen, Tania. "Composite load model decomposition : induction motor contribution." Thesis, Queensland University of Technology, 2009. https://eprints.qut.edu.au/31301/1/Tania_Parveen_Thesis.pdf.
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In this thesis, a new technique has been developed for determining the composition of a collection of loads including induction motors. The application would be to provide a representation of the dynamic electrical load of Brisbane so that the ability of the power system to survive a given fault can be predicted. Most of the work on load modelling to date has been on post disturbance analysis, not on continuous on-line models for loads. The post disturbance methods are unsuitable for load modelling where the aim is to determine the control action or a safety margin for a specific disturbance. This thesis is based on on-line load models. Dr. Tania Parveen considers 10 induction motors with different power ratings, inertia and torque damping constants to validate the approach, and their composite models are developed with different percentage contributions for each motor. This thesis also shows how measurements of a composite load respond to normal power system variations and this information can be used to continuously decompose the load continuously and to characterize regarding the load into different sizes and amounts of motor loads.
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Bellec, Enora. "Spectres de chargement pour le dimensionnement à la fatigue d’un véhicule automobile : identification, analyse et modélisation." Electronic Thesis or Diss., Brest, École nationale supérieure de techniques avancées Bretagne, 2023. http://www.theses.fr/2023ENTA0003.
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Les constructeurs automobiles se doivent d’assurer la fiabilité de l’ensemble des pièces de la liaison au sol sur toute la durée de vie du véhicule. Cependant, aucun cadre normatif global n’existe pour le dimensionnement de ces pièces. Ils doivent donc se baser sur leur expérience. Il est nécessaire pour tout protocole de dimensionnement de maîtriser précisément les chargements vus par les pièces. La sollicitation perçue par la liaison au sol est d’autant plus complexe à considérer qu’elle est à amplitude variable (suivant les situations de vie rencontrées) et multi-entrées (chargements perçus à chaque roue simultanément). Pour le dimensionnement à la fatigue, les sollicitations perçues aux roues sont modélisées comme la somme des chargements issus des manoeuvres, dits Driven Road, et de ceux induits par les aléas de la route, dits Random Road. Un processus de validation de cette partition est illustré à partir de mesures réelles. Il tire parti des particularités de chaque type de chargement, corrélation temporelle et caractéristiques fréquentielles, pour prendre en compte le caractère multi-entrées de la sollicitation. Ce modèle apporte au constructeur des éléments supplémentaires pour caractériser les chargements<br>Car manufacturers are responsible for ensuring the reliability of all chassis components throughout the life of the vehicle. Nevertheless, no global standard framework exists. Therefore, they must rely on their own experience. For any design protocol, it is imperative to precisely define the loads seen by the parts. The load measures by the chassis system is even more complex to assess as it faces variable amplitude (depending on the life situations encountered) and multi-input load case (loads perceived at each wheel simultaneously). For fatigue design, the loads measured at the wheels are modelled as the sum of the ones induced by the manoeuvers, called Driven Road, and the ones induced by the road conditions, called Random Road. A validation process of the partition is illustrated using real time series. It benefits from the particularities of each loading type, time correlation and frequency characteristics, to consider the multi-input character of the load case. This model provides the manufacturer with additional elements to characterise the loadings
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Sanz, de la Garza María. "Characterization of the spectrum of cardiac adaptation to endurance exercise: Impact of gender and training load." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/585889.
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The beneficial impact of regular physical activity on cardiovascular health is well established. However, the ideal amount of exercise required to provide these benefits is not well defined, with some recent reports showing no further cardiovascular benefits and even detrimental effects when performing exercise with high training loads, particularly for endurance sports disciplines. Indeed, during the last two decades, an increasing amount of data has related high endurance training loads with an increased susceptibility for atrial arrhythmias as well as with a detrimental right ventricle remodelling. In our study, we analysed structural and functional acute changes after an endurance race at three different distances and demonstrated a dose-response relationship between endurance exercise “doses” and acute impairment in right ventricular (RV) and atrial performance without left ventricle involvement. However, high interindividual variability was observed between participants performing the same amount of exercise. We identified different patterns of RV and atrial adaptation to exercise and highlighted RV diastolic dysfunction at rest as a potential early sign of RV maladaptation to exercise. Although we could not determine if these acute RV and atrial changes induced by a bout of endurance exercise would persist or are reversible, our experimental model of long-term endurance exercise showing impairment in RV performance promoted by very high endurance training loads suggested that, independently of individual factors, there is a threshold for safe exercise, determined by both intensity and duration, beyond which cardiac adaptation might be no longer benign but become deleterious. Additionally, we observed that the RV segments showed different adaptations to exercise, with the basal segment playing the major role in increasing stroke volume during
exercise but also, due to its thinner wall and bigger cavity, being more vulnerable to the exercise-induced high wall stress, compared to the RV apex.
Finally, we showed that long-term endurance training promoted a similar cardiac remodelling in both men and women. However, male athletes had larger right heart cavities and lower atrial and ventricular deformation values, compared to female athletes. These results imply that the right heart cavities of male athletes work under different conditions in maintaining RV and atrial stroke volume, with larger volumes and lower myocardial deformation. Thus, they are provided with an enhanced functional reserve during exercise but also work with increased atrial and RV wall stress. The mechanism underlying these gender-related differences in atrial and RV remodelling in response to exercise and the clinical significance of the findings warrant further investigation<br>Los efectos beneficiosos de la actividad física regular sobre la salud cardiovascular son incuestionables. Sin embargo, la cantidad óptima de ejercicio para proporcionar estos beneficios no está aún bien establecida, sugiriéndose que altas cargas de entrenamiento podrían llegar incluso a tener efectos deletéreos. De hecho, varias publicaciones han relacionado el entrenamiento de resistencia con una mayor susceptibilidad a arritmias auriculares y con un remodelado patológico del ventrículo derecho (VD). En el presente estudio, analizamos los cambios agudos experimentados por el corazón tras la realización de una carrera de resistencia con tres distancias distintas y demostramos una relación dosis- respuesta entre el empeoramiento en el funcionamiento del VD y las aurículas y la carga de ejercicio realizada. Sin embargo, objetivamos una gran variabilidad inter-individual entre participantes que ejecutaron la misma carga de ejercicio. Identificamos distintos patrones de adaptación del VD y las aurículas al ejercicio de resistencia y señalamos como la disfunción diastólica del VD en reposo podría ser un signo incipiente de mala adaptación al ejercicio. Aunque no pudimos determinar la persistencia o temporalidad de estos cambios, nuestro modelo experimental demostró un empeoramiento de la funcionalidad del VD inducida por el entrenamiento de resistencia, sugiriendo que, independientemente de factores individuales, hay un verdadero límite para la práctica deportiva segura, determinado por la intensidad y la duración, a partir del cual la adaptación cardíaca al ejercicio podría pasar de fisiológica a patológica.
Por otra parte, observamos que los segmentos del VD muestran diferentes adaptaciones al ejercicio, siendo el basal el que juega un mayor papel en el aumento del volumen latido durante el ejercicio, pero también el más vulnerable al estrés de pared inducido por el ejercicio.
Finalmente, objetivamos que el entrenamiento de resistencia indujo un remodelado cardiaco similar en ambos géneros. Sin embargo, los varones mostraron cavidades derechos mayores y menores valores de deformación miocárdica tanto a nivel ventricular como auricular que las mujeres. Estos hallazgos sugieren que las cavidades cardiacas derechas de los hombres deportistas, trabajan en condiciones diferentes para mantener el volumen latido, con volúmenes mayores y menor deformación; lo cual implica una reserva funcional aumentada durante la práctica de ejercicio pero también un mayor estrés de pared auricular y ventricular.
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Mason, Patrick H. "Identification of random loads impinging on the RAH-66 Comanche Helicopter empennage using spectral analysis." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1998. http://handle.dtic.mil/100.2/ADA349809.
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Thesis (M.S. in Aeronautical Engineering) Naval Postgraduate School, June 1998.<br>Thesis advisor(s): E. Roberts Wood, Donald A. Danielson, Joshua H. Gordis. "June 1998." Includes bibliographical references (p. 143-144). Also available online.
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Berton, Marco. "Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424397.
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The aim of this thesis is to unveil the nature of the so-called parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (F-NLS1s). These sources are a subclass of active galactic nuclei which was recently identified as the third class of $\gamma$-ray emitting AGN. They likely harbor a relativistic jet directed toward the observer. The aim was to understand how do they appear when observed under a different inclination. To study their parent population I built four samples of parent candidates, that is steep-spectrum narrow-line Seyfert 1 galaxies (S-NLS1s), radio-quiet narrow-line Seyfert 1 (RQNLS1s), disk-hosted radio-galaxies (disk RGs) and finally compact steep-spectrum sources with high excitation spectrum (CSS/HERGs). For each sample I calculated the black hole mass and Eddington ratio, to compare them with those of F-NLS1s. I studied the differences in the narrow-line region of RQNLS1s and radio-loud NLS1s, to find traces of interactions with a relativistic jet. Finally, I built the first luminosity function of F-NLS1s, to compare it with that of CSS/HERGs. I concluded that a F-NLS1, when observed at large angles, appears as a S-NLS1s and later as a disk RGs. Both of them can be included in the larger group of CSS/HERGs. In general then F-NLS1s are CSS/HERGs observed inside their relativistic jet.<br>Questa tesi si propone di svelare la natura della cosiddetta popolazione madre delle galassie narrow-line Seyfert 1 radio brillanti a spettro piatto (F-NLS1). Queste sorgenti sono una sottoclasse di nuclei galattici attivi che di recente è stata identificata come la terza classe degli AGN con emissione di raggi $\gamma$. Esse ospitano un getto relativistico diretto verso l'osservatore. Lo scopo era di comprendere come questi oggetti appaiono quando osservati da una diversa inclinazione. Per studiare ciò ho costruito quattro campioni di candidati, ossia narrow-line Seyfert 1 radio brillanti a spettro ripido (S-NLS1), narrow-line Seyfert 1 radio quiete (RQNLS1), radio-galassie ospitate in una galassia a disco (disk RG) e oggetti compatti a spettro ripido con spettro ad alta eccitazione (CSS/HERG). Per ciascun campione ho calcolato la massa del buco nero e il rapporto di Eddington, per confrontarlo con i valori già noti delle F-NLS1. Ho studiato le differenze fra le narrow-line region delle RQNLS1 e delle NLS1 radio brillanti, per trovare segni di interazione con il getto relativistico. Infine, ho costruito la prima funzione di luminosità delle F-NLS1, per confrontarla con quella dei CSS/HERG. Ho concluso che una F-NLS1, quando osservata ad angoli via via crescenti, appare prima come una S-NLS1 e dopodiché come una disk RG. Entrambe queste sorgenti possono essere incluse nella più vasta classe dei CSS/HERG. In generale quindi le F-NLS1 sono dei CSS/HERG osservate all'interno del loro getto relativistico.
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Alp, Dennis. "X-ray spectral analysis of the radio-loud narrow-line Seyfert 1 galaxy RX J1633+4718." Thesis, KTH, Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-189051.
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Mekonnen, Muluneh Admass. "Modeling flow and sediment transport in water bodies and watersheds." Doctoral thesis, KTH, Vattendragsteknik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4703.
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The research focus is on the various modeling aspects of flow and sediment transport in water bodies and watersheds. The interaction of flow with a mobile bed involves a complex process in which various turbulent scales characterized by coherent structures cause a chaotic sediment motion. In many rivers and natural waterways secondary flows that are dominating flow struc-tures bring about more complications. In estuaries and open waterbodies thermal stratification and internal mixing control the flow structure besides the flow interaction with the mobile bed. To adequately model these processes 3D coupled flow and transport models are needed. The research is based on use and adaptation of open source codes for 3D hydrodynamic and sediment transport model known as Estuarine Coastal Ocean Model (ECOMSED) and the Soil and Water Assessment Tool (SWAT) model. A bed load transport model was developed and coupled to ECOMSED. The flow and sediment transport characteristics in a curved channel and a river reach were successfully captured by the model. Improvements in ECOMSED were made to study the effect of wind and basin bathymetry on mixing and flow exchange between two estuaries. Using spectral analysis the hydrological component of SWAT model was investigated for its applicability under limited data conditions in three Ethiopian catchments.<br>QC 20100827
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Zhang, Han. "Global Analysis and Structural Performance of the Tubed Mega Frame." Thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147382.
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The Tubed Mega Frame is a new structure concept for high-rise buildings which is developed by Tyréns. In order to study the structural performance as well as the efficiency of this new concept, a global analysis of the Tubed Mega Frame structure is performed using finite element analysis software ETABS. Besides, the lateral loads that should be applied on the structure according to different codes are also studied. From the design code study for wind loads and seismic design response spectrums, it can be seen that the calculation philosophies are different from code to code. The wind loads are approximately the same while the design response spectrums vary a lot from different codes. In the ETABS program, a 3D finite element model is built and analyzed for linear static, geometric non-linearity (P-Delta) and linear dynamic cases. The results from the analysis in the given scope show that the Tubed Mega Frame structural system is potentially feasible and has relatively high lateral stiffness and global stability. For the service limit state, the maximum story drift ratio is within the limitation of 1/400 and the maximum story acceleration is 0.011m/sec 2 which fulfill the comfort criteria.
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Harwood, Jeremy James. "The dynamics and energetics of radio-loud active galaxies." Thesis, University of Hertfordshire, 2014. http://hdl.handle.net/2299/14409.
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In this thesis, I use the new generation of radio interferometer along with X-ray observations to investigate the dynamics and energetics of radio-loud active galaxies which are key to understanding AGN feedback and the evolution of galaxies as a whole. I present new JVLA observations of powerful radio source and use innovative techniques to undertake a detailed analysis of JVLA observations of powerful radio galaxies. I compare two of the most widely used models of spectral ageing, the Kardashev-Pacholczyk and Jaffe-Perola models and also results of the more complex, but potentially more realistic, Tribble model. I find that the Tribble model provides both a good fit to observations as well as providing a physically realistic description of the source. I present the first high-resolution spectral maps of the sources and find that the best-fitting injection indices across all models take higher values than has previously been assumed. I present characteristic hot spot advance speeds and compare them to those derived from dynamical ages, confirming that the previously known discrepancy in speed remains present in older radio sources even when ages are determined at high spectral and spatial resolutions. I show that some previously common assumptions made in determining spectral ages with narrow-band radio telescopes may not always hold. I present results from a study of the powerful radio galaxy 3C223 at low frequencies with LOFAR to determine its spectrum on spatially small scales and tightly constrain the injection index, which I find to be consistent with the high values found at GHz frequencies. Applying this new knowledge of the low energy electron population, I perform synchrotron / inverse-Compton model fitting and find that the total energy content of the radio galaxy lobes increases by a factor greater than 2 compared to previous studies. Using this result to provide revised estimates of the internal pressure, I find the northern lobe to be in pressure balance with the external medium and the southern lobe to be overpressured. I go on to present the first large sample investigation of the properties of jets in Fanaroff and Riley type I radio galaxies (FR-I) at X-ray energies based on data from the Chandra archive. I explore relations between the properties of the jets and the properties of host galaxies in which they reside. I find previously unknown correlations to exist, relating photon index, volume emissivity, jet volume and luminosity, and find that the previously held assumption of a relationship between luminosities at radio and X-ray wavelengths is linear in nature when bona fide FR-I radio galaxies are considered. In addition, I attempt to constrain properties which may play a key role in determination of the diffuse emission process. I test a simple model in which large-scale magnetic field variations are primarily responsible for determining jet properties; however, we find that this model is inconsistent with our best estimates of the relative magnetic field strengths in my sample.
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Palma, Cruz Norman I. "Multiwavelength Analysis of the Gamma-Ray Blazar PKS 0528+134 in Quiescence." Ohio University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1289321486.
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Wu, Long. "Separating Load Torque Oscillation and Rotor Faults in Stator Current Based-Induction Motor Condition Monitoring." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14545.
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Stator current spectral analysis techniques are usually used to detect rotor faults in induction machines. Magnetic field anomalies in the airgap due to the rotor faults result in characteristic side-band harmonic components in the stator current spectrum, which can be measured as rotor fault signatures. A position-varying load torque oscillation at multiples of the rotational speed, however, has exactly the same effect. Stator current harmonics due to a load torque oscillation often obscure and even overwhelm rotor eccentricity fault detection since the magnitude of load oscillation induced harmonics is usually much larger.
Although previous research has suggested some methods to differentiate between these two effects, most of them rely heavily on the accurate estimation of motor parameters. The objective of this research is to develop a far more practical and computationally efficient method to detect rotor faults effectively in the presence of a load torque oscillation. A significant advantage of the proposed scheme is that it does not need any knowledge of motor parameters. The normalized negative sequence information induced by a mixed rotor eccentricity in the stator current or terminal voltage space vector spectra, serves as a reliable rotor fault indicator to eliminate load oscillation effects.
Detailed airgap magnetic field analysis for an eccentric motor is performed and all machine inductance matrices as well as their derivatives are reformulated accordingly. Careful observation of these inductance matrices provides a fundamental understanding of motor operation characteristics under a fault condition. Simulation results based on both induction motor dynamic model and Maxwell 2D Finite Element Model demonstrate clearly the existence of the predicted rotor fault indicator. Extensive experimental results also validate the effectiveness and feasibility of the proposed detection scheme.
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Aswegan, Kevin Paul. "Rational Procedure for Damage Based Serviceability Design of Steel Buildings Under Wind Loads and a Simple Linear Response History Procedure for Building Codes." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/51549.
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This thesis is divided into two topics: the development of a procedure for wind serviceability design of steel buildings and the development of a simple linear response history analysis for building codes.
In the United States the building codes are generally silent on the issue of serviceability. This has led to a wide variation in design practices related to service level wind loads. Chapter 2 of this thesis contains a literature review which discusses pertinent aspects of wind drift serviceability, including selecting the mean recurrence interval (MRI), mathematical modeling of the structure, and establishment of rational deformation limits. Chapter 3 contains a journal article submitted to Engineering Journal which describes the recommended procedure for damage based wind serviceability design of steel structures. The procedure uses a broad range of MRIs, bases damage measurement on shear strains, includes all sources of deformation in the model, and bases deformation limits on fragility curves.
Chapter 4 of this thesis contains a literature review which examines issues related to performing linear response history analysis. Chapter 5 contains a conference paper submitted to the Tenth U.S. National Conference on Earthquake Engineering which serves as a position paper promoting the inclusion of a linear response history analysis procedure in future editions of the NEHRP Recommended Seismic Provisions and ASCE 7. The procedure address the following issues: selection and scaling of ground motions, the use of spectral matched ground motions, design for dependent actions, and the scaling of responses with the response modification coefficient (R) and the deflection amplification factor (Cd).<br>Master of Science
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Kaabia, Bassem. "Méthodes avancées d'évaluation des charges de vent sur les structures de concentrateurs solaires." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11315.
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L’énergie solaire photovoltaïque concentré (CPV) est une solution de remplacement prometteuse aux structures solaires conventionnelles. Ce type de structure modulable doit être optimisé afin d’être compétitif par rapport aux autres types de production d’énergie. Les forces de vent demeurent la première préoccupation dans la conception de la structure porteuse en acier d’un tel système. L’objectif principal de cette recherche est d’assembler des outils numériques et analytiques afin de prédire les caractéristiques de sa réponse dynamique sous charges de vent turbulent. La maîtrise de cette étape est essentielle afin d’étudier d’une façon plus générique des solutions d’optimisation de la structure support par rapport à sa réponse dynamique sous charges de vent. Pour ce faire, la méthodologie principale de cette étude est composée en trois parties : (i) étude expérimentale à grandeur nature de la réponse globale sous les conditions réelles du vent ; (ii) développement des modèles d’analyse numérique dans lesquels les caractéristiques de structures réelles et des
modèles de forces aérodynamiques adéquates sont prises en compte ; (iii) application des outils développés dans une étude paramétrique pour évaluer plusieurs solutions à partir de cas d’étude dans le contexte d’une conception préliminaire.
Cette thèse est présentée sous forme de deux articles qui ont été soumis dans des revues évaluées par des comités de lecture ainsi que d’un article soumis et présenté dans un congrès international qui démontrent les contributions de cette recherche pour améliorer les pratiques de calcul des charges de vent sur des structures de concentration solaire non conventionnelles. Ces articles sont présentés comme suit (a) Étude expérimentale à échelle réelle de la réponse d’un prototype de concentrateur solaire sous charges de vent. Ce premier article a permis la validation de calcul des coefficients de forces aérodynamiques statiques et la révision des hypothèses de l’application du code ASCE 7-10 pour prédire les forces maximales agissant sur la structure dans la direction du vent ; (b) l’analyse temporelle
de la réponse dynamique d’une structure de concentrateur solaire sous charges de
vent. Cette étude a montré que le modèle et la méthode d’analyse développés selon des hypothèses simplifiées permettaient de prédire correctement les caractéristiques statistiques de la réponse dynamique mesurée en cohérence avec la méthode spectrale stochastique ; (c) Étude des effets des configurations structurales et des paramètres de vent sur l’optimisation de structure solaires sous charges de vent. Cette étude paramétrique a mis en évidence l’importance de l’effet des paramètres structuraux et ceux définissant le vent sur l’optimisation de la conception structural pour ce type de structure. Des recommandations pour optimiser l’action dynamique dans une phase de conception préliminaire ont été proposées. Ce projet de recherche a démontré finalement l’importance d’étudier d’une façon juste et pratique la réponse dynamique sous charges de vent qui mène à résoudre des préoccupations d’optimisation liées à différents types de structures d’énergie solaire en adoptant des hypothèses pratiques pour les ingénieurs.<br>Abstract : Concentrated Solar Photovoltaic (CPV) is a promising alternative to conventional solar
structures. These solar traking structures need to be optimized to be competitive against
other types of energy production. Wind action is the main concern in the design of the
steel support structure of such movable system. The main purpose of this research is to
assemble advanced numerical and analytical tools that allows realistic dynamic study of
structures under wind loading. This help to study accurately optimized alternative in
term of selecting structural and wind site conditions parameters. The methodology of the
present study involves three main steps : (i) experimental full-scale study of the global
response under real life wind conditions ; (ii) numerical modeling that captures the characteristics
of the real structures and include the aerodynamic force models to conduct
time-domain dynamic analyses ; (iii) preliminary design application that include the study
of the effect of stuctural and wind parameters in optimizing the dynamic wind action and
consequently the steel support structure.
The thesis is presented as an ensemble of three articles written for refereed journals and a
conference that showcase the contributions of the present study to thoroughly understand
the wind load effect on these nonconventionnel structures. The articles presented are as
follow (a) full-scale measurement of the response of a CPV tracker structure prototype
under wind load. The results presented in this first article help design engineers to evaluate
the use of the aerodynamic force coefficients for calculating wind load on similar structures
and to apply properly the ASCE7-10 in evaluating the maximum design wind force using
the equivalent static approach ; (b) time-domain analysis of solar concentrator structure
under gust wind. This study showed that the developed time-domain model using simplified
hypothesis could successfully predict the statistical parameters of the measured
dynamic response in coherence with the stochastic spectral approach ; (c) effect of structure
configurations and wind characteristics on the design of solar concentrator support
structure under dynamic wind action. This parametric study highlighted the importance
of selecting structural and wind parameters in order to minimize the dynamic action and
the steel support structure. Recommendations for optimizing dynamic wind action in a
preliminary design phase were proposed. The present research project has shown the need
to study accurately wind response to solve optimization concerns related to different type
of solar system structures. In addition, this study proposes simplified methods that are
useful for practical engineers when there is the need to solve similar problems.
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Roche, Laëtitia. "Percevoir l'interaction sociale dans le mouvement humain : études psychophysiologiques du développement typique et dans les troubles du spectre autistique." Thesis, Tours, 2013. http://www.theses.fr/2013TOUR3323/document.
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L'interaction sociale représente l’une des difficultés majeures des patients atteints de troubles envahissants du développement (TED). Or, la perception des mouvements humains contribue à la mise en place des comportements sociaux et représenterait un « marqueur » du développement de la cognition sociale. Cette étude de suivi du regard et de pupillométrie visait à caractériser l’attention visuo-spatiale et la charge cognitive au cours de la perception de mouvements biologiques humains porteurs d'intention sociale (MHS) chez 139 participants typiques (PaTYP) et 62 patients atteints d’un TED (PaTED). Chez les PaTYP, l’exploration augmente pour les MHS. Chez les PaTED, un déficit d’exploration des MHS est corrélé à la sévérité de la symptomatologie autistique globale. Ces anomalies de l’attention visuo-spatiale des PaTED réduiraient leur accès à l’information sociale et pourraient participer au trouble de l’interaction sociale et de la communication<br>Social interaction is one of the main difficulties for patients with pervasive developmental disorders (PDD). However, the perception of human movement contributes to the development of social behavior and represents a "marker" for the development of social cognition. This eye tracking and pupillometric study aims to characterize the visuospatial attention and cognitive load during perception of social human biological motion (SHM) in 139 typical participants (PaTYP) and 62 patients with ASD (PaTED). In PaTYP, exploration increases for SHM. In PaTED, deficit of the exploration of MHS is correlated with the severity of the global autistic symptomatology. These abnormalities of visuospatial attention in PaTED could reduce their access to social information and participate in social interaction and communication disorders
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Ge, Zhongfu. "Analysis of surface pressure and velocity fluctuations in the flow over surface-mounted prisms." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/25965.
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The full-scale value of the Reynolds number associated with wind loads on structures is of the order of 10^7. This is further complicated by the high levels of turbulence fluctuations associated with strong winds. On the other hand, numerical and wind tunnel simulations are usually carried out at smaller values of Re. Consequently, the validation of these simulations
should only be based on physical phenomena derived with tools capable of their identification. In this work, two physical aspects related to extreme wind loads on low-rise structures are examined. The first includes the statistical properties and prediction of pressure peaks. The second involves the identification of linear and nonlinear relations between pressure peaks and associated velocity fluctuations.
The first part of this thesis is concerned with the statistical properties of surface pressure time series and their variations under different incident flow conditions. Various statistical tools, including space-time correlation, conditional sampling, the probability plot and the probability plot correlation coefficient, are used to characterize pressure peaks measured on the top surface of a surface-mounted prism. The results show that the Gamma distribution provides generally the best statistical description for the pressure time series, and that the method of moments is sufficient for determining its parameters. Additionally, the shape parameter of the Gamma distribution can be directly related to the incident flow conditions. As for prediction of pressure peaks, the results show that the probability of non-exceedence can best be derived from the Gumbel distribution. Two approaches for peak prediction, based on analysis of the parent pressure time series and of observed peaks, are presented. The prediction based on the parent time series yields more conservative estimates of the probability of non-exceedence.
The second part of this thesis is concerned with determining the linear and nonlinear relations between pressure peaks and the velocity field. Validated by analytical test signals, the wavelet-based analysis is proven to be effective and accurate in detecting intermittent linear and nonlinear relations between the pressure and velocity fluctuations. In particular, intermittent linear and nonlinear velocity pressure relations are observed over the nondimensional frequency range fH/U<0.32. These results provide the basis for flow parameters and characteristics required in the simulation of the wind loads on structures.<br>Ph. D.
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Desaunay, Pierre. "Etudes comportementale et électrophysiologique de la mémoire dans les troubles du spectre de l'autisme Memory in autism spectrum disorders : a meta-analysis of experimental studies Prospective memory in adolescents with autism : a preliminary study of the impact memory load Impact of semantic relatedness on associative memory : an ERP study Exploring the ERP time-cours of associative recognition in autism Autisme et connectivité cérébrale : contribution des études de neuroimagerie à la compréhension des signes cliniques." Thesis, Normandie, 2019. http://www.theses.fr/2019NORMC051.
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La mémoire est une fonction cognitive majeure, support de nos souvenirs personnels, et permettant les apprentissages et les résultats académiques. Son étude dans les troubles du spectre de l’autisme (TSA) est principalement comportementales et peu imagerique, avec une hétérogénéité de résultats et certain domaines peu explorés. Dans cette perspective, nous présentons dans cette thèse les résultats d’une méta-analyse de la mémoire dans les TSA, des résultats comportementaux en mémoire prospective event-based, et des données préliminaires en électroencéphalographie (EEG). Les résultats de la méta-analyse suggèrent des difficultés globales en mémoire dans les TSA, mais des performances d’autant meilleures que les tâches mnésiques ont un chevauchement important avec le système de mémoire sémantique : mémoire épisodique, matériel verbal, récupération avec support (rappel indicé, reconnaissance). Nous identifions des difficultés en mémoire prospective event-based, et des stratégies de compensation de nature verbale. L’étude des potentiels évoqués de la tâche en EEG suggère des difficultés en mémoire associative visuel pouvant résulter d’une diminution de l’intégration précoce des informations perceptuelles visuelles et sémantiques. Ces résultats suggèrent des difficultés mnésiques dans certains domaines, pouvant s’intégrer au modèle de la sous-connectivité dans les TSA. La mise en évidence de compétences mnésiques préservées est un élément important, pouvant s’associer, sur le plan cognitif, à un chevauchement plus important avec le système de mémoire sémantique, et sur le plan physiologique, à des réseaux de connectivité préservée<br>Memory is a main cognitive function, supporting our personal memories and enabling learning and academic results. Its study in autism spectrum disorder (ASD) is mainly behavioral, with heterogeneous results or underexplored domains. In this perspective, we present in this thesis the results of a meta-analysis of memory in ASD, behavioral results on event-based prospective memory, and preliminary results in electroencephalography (EEG). Results of the meta-analysis suggest overall difficulties in memory in ASD, but higher performance when greater overlap between the memory tasks and the semantic memory system, i.e. episodic memory, verbal material, supported retrieval (cued recall, recognition). We identify difficulties in event-based prospective memory, and verbal compensatory strategies. Study of Event Related Potentials in the EEG task suggests difficulties in visual associative memory that may result from a diminution in the early integration of perceptual visual and semantic information. Together, these results suggest some memory difficulties that may result from under-connectivity in ASD. By contrast, preserved memory domains are important, and may be associated on the cognitive level, with a greater overlap of the memory tasks with the semantic memory system, and on the physiological level, with networks of preserved connectivity
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Goodin, Jacob, Caleb D. Bazyler, J. R. Bernards, Satoshi Mizuguchi, J. Walters, and Michael H. Stone. "Comparison of Power and Velocity in the High Bar and Low Bar Back Squat across a Spectrum of Loads." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/3833.
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PURPOSE: To examine differences in mean power output between high bar (HBS) and low bar back squats (LBS). METHODS: Six trained males (25.0 ± 3.1 years, 1.78 ± 0.04 m, 87.6 ± 7.5 kg) with previous squatting experience (experience: 7.5 ± 4.1 years, HBS 1RM: 157.0 ± 15.3 kg, squat/bodyweight: 1.8 ± 0.18) completed the study using a crossover design. Subjects completed a 4-week familiarization phase with both conditions. Mean power data was collected over 2 sessions using dual uniplanar force plates and 4 linear position transducers sampling at 1,000 Hz. Subjects were randomly assigned to the HBS or LBS for 1 set of 3 repetitions at 20, 30, 40, 50, 60, 70, 80, and 90% of their most recent HBS training 1RM with 3 to 5 minutes’ rest between sets and 2-7 days between testing conditions. A 2x8 repeated measures analysis of variance was used to determine interactions and main effects for condition and load with post-hoc tests conducted for statistical main effects. RESULTS: Analysis revealed significant main effects for load (p < 0.01) but not for condition. CONCLUSIONS: According to this pilot data, athletes seeking to increase power production ability should choose a squatting style in which they feel most proficient and comfortable. Furthermore, either the HBS or LBS can be used as the primary squatting movement, or as a secondary movement to provide variation. However, based on previous research it is likely that sport specific biomechanical parameters will influence the squatting style selection for the majority of athletes who participate in sports that involve jumping, sprinting, and change of direction.
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Goodin, Jacob R., Caleb D. Bazyler, Jake R. Bernards, Joseph Walters, Satoshi Miziguchi, and Michael H. Stone. "Comparison of Power and Velocity in the High Bar and Low Bar Back Squat across a Spectrum of Loads." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etsu-works/3820.
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Wagstaff, Robert H. "The spectre of Lord Atkin in the aftermath of 9/11 : the rule of law and terror detentions in the United States & the United Kingdom." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543601.
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Janošková, Lenka. "Dynamická analýza konstrukce zatížené seismickým zatížením." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2013. http://www.nusl.cz/ntk/nusl-226464.
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In this diploma thesis the seismic load on two different models is solved – the first model is a beam hall and the second model is a multistory building. The calculation of seismic load was performed according to standard ČSN EN 1998-1 (Eurocode 8) using the response spectrum analysis and the method of equivalent static forces (substi-tute load). For the combination of seismic responses in different directions are used SRSS and CQC rules. Models and calculations were solved in a student’s version of program RFEM 4.10 (Ing. Software Dlubal, s.r.o.). The comparison of mentioned methods in each models, also the comparison of combinative rules in calculation and the final evaluation of seismic responses on both of models are the subject of this thesis.
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Trajin, Baptiste. "Analyse et traitement de grandeurs électriques pour la détection et le diagnostic de défauts mécaniques dans les entraînements asynchrones. Application à la surveillance des roulements à billes." Phd thesis, Institut National Polytechnique de Toulouse - INPT, 2009. http://tel.archives-ouvertes.fr/tel-00554240.
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Les entraînements électriques à base de machine asynchrone sont largement utilisés dans les applications industrielles en raison de leur faible coût, de leurs performances et de leur robustesse. Cependant, des modes de fonctionnement dégradés peuvent apparaître durant la vie de la machine. L'une des raisons principales de ces défaillances reste les défauts de roulements à billes. Afin d'améliorer la sûreté de fonctionnement des entraînements, des schémas de surveillance peuvent être mis en place afin d'assurer une maintenance préventive. Ce travail de thèse traite de la détection et du diagnostic des défauts mécaniques et plus particulièrement des défauts de roulements dans une machine asynchrone. Généralement, une surveillance vibratoire peut être mise en place. Cette méthode de surveillance est cependant souvent chère du fait de la chaîne de mesure. Une approche, basée sur l'analyse et le traitement des courants statoriques, est alors proposée, afin de suppléer à l'analyse vibratoire. L'étude est basée sur l'existence et la caractérisation des effets des oscillations du couple de charge sur les courants d'alimentation. Un schéma de détection est alors introduit pour détecter différents types de défauts de roulements. De plus, des variables mécaniques, telles que la vitesse ou le couple, sont également reconstruites afin de fournir une indication sur la présence de défauts de roulements. Par ailleurs, un diagnostic des modulations des courants statoriques est proposé, en régime permanent et en régime transitoire, quel que soit le rapport entre les fréquences porteuse et modulante. Les méthodes étudiées sont la transformée de Hilbert, la transformée de Concordia, l'amplitude et la fréquence instantanées ainsi que la distribution de Wigner-Ville.
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VELOSO, MARCELO N. "Avaliação in vitro dos efeitos da radiação ionizante em tecido ósseo bovino por espectroscopia ATR-FTIR e análise dinâmico-mecânica." reponame:Repositório Institucional do IPEN, 2013. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10573.
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Made available in DSpace on 2014-10-09T12:42:07Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:04:44Z (GMT). No. of bitstreams: 0<br>Dissertação (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
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Atila, Zelić. "Uticaj sila zakošenja na zamor noseće konstrukcije mosne dizalice pri njenom kretanju." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2018. https://www.cris.uns.ac.rs/record.jsf?recordId=107221&source=NDLTD&language=en.
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Disertacija obrađuje problematiku praktičnog uvođenja opterećenja izazvanihzakošavanjem dizalice u normiranu proceduru dokaza zamorne čvrstoće njene nosećekonstrukcije. U prvom delu rada koncizno je izložena teorijska podloga zakošavanjamosne dizalice, neophodna za potpunije razumevanje relevantnih obeležja predmetaistraživanja. Predložene su metode za eksperimentalnu determinaciju bočnih sila uinterakciji točak – šina, odn. vodeća rolna – šina. Testiranje predloženih metodaspovedeno je kroz eksperimente na realnom objektu – jednogredoj električnoj mosnojdizalici nosivosti 3,2 t i raspona 8,91 m. Komentarisani su reprezentativni rezultati idate su smernice za sprovođenje dokaza zamorne čvrstoće detalja noseće konstrukcijedizalice, uzimajući u obzir pri tom i spektre sila zakošenja. Takođe je ukazano i naneke nejasnoće i nedorečenosti u važećim standardima, a u vezi proračunskogodređivanja sila zakošenja.<br>The dissertation deals with the problem of practical application of loadings caused bycrane skewing, in normative procedures of fatigue strength proof calculations of cranesupporting structure. In the first part, the theoretical framework of bridge craneskewing, necessary for better understanding of relevant characteristics of the researchtopic, has been concisely elaborated. Methods are proposed for experimentaldetermination of lateral forces in wheel/rail and guiding roller/rail contacts. Thesemethods were tested through a series of experiments on a real object – an electricallydriven single girder bridge crane with a capacity of 3.2 t, and span 8.91 m. Somerepresentative measurement results are discussed and guidelines are given forperforming the fatigue strength proof calculation of crane supporting structure details,taking into account skewing forces spectra, too. Also, attention has been drawn tocertain unclear points and inconsistencies in norms in force, concerning calculativedetermination of skewing forces.
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Šulerová, Zdeňka. "Dynamická analýza konstrukce zatížená seismickým zatížením." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226647.
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This thesis deals with the calculation of response of reinforced concrete construction on the effect of seismic tension. Time and spectral analysis were made. They are mentioned as possible ways of calculation in EN 1998 - 1:2004 norm. Final figures of global deformations and stress on selected beam from the time and spectral analysis were firstly compared for the horizontal components of seismic stress affecting only in one direction. Subsequently comparison of time progress to combination of these effects mentioned in relevant norm was made. In the conclusion the results of used analysis are appraised.
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Piquet, Arthur. "Analyse physique et simulation numérique des phénomènes de décollement de jet dans les tuyères supersoniques." Thesis, Normandie, 2017. http://www.theses.fr/2017NORMIR09/document.
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Cette thèse, initiée par un programme de coopération franco-britannique entre la DGA et la DSTL, est consacrée à l’étude des phénomènes de décollement de jet au sein des tuyères propulsives sur-détendu. L’aérothermodynamique des systèmes propulsifs (missile, avion supersonique ou lanceur) est un des domaines de la mécanique des fluides où des progrès décisifs restent à réaliser pour améliorer les performances des ensembles moteurs, en terme de bilan de poussée, de stabilité, de fiabilité et de réduction de nuisances (bruit, émission de polluants, etc.). Les conditions de vols et la complexité des phénomènes caractéristiques n’étant pas reproductibles sur bancs d’essais à l’aide des outils expérimentaux actuelles, l’utilisation de simulation numérique permettrait une étude approfondie et précise des phénomènes mis en jeu. Le besoin d’informations concernant l’instationnarité de l’écoulement s’affirmant de plus en plus, notamment sur les phénomènes basse fréquence dû aux décollements de jets, l’utilisation des simulations numériques aux grandes échelles (LES) permettrait de faire face au coût prohibitif des simulations directes (DNS). Les tuyères sur-détendu souffrent de charges latérales, caractérisées par des forces instationnaires orthogonales à la direction de l’écoulement. Ils sont causés par le décollement de la couche limite se développant le long de la paroi, provoquant des excursions de chocs importants, parfois asymétrique. Ces phénomènes instationnaires ont déjà été observés expérimentalement et numériquement. Ces instationnarités émergent d’une combinaison de phénomène complexe, tels que les interactions choc/couche limite sur la paroi de la tuyère, les couches de mélange décollées ou les zones de recirculation en aval du décollement, toutes produisant des modes énergétiques à différente fréquence caractéristique et tout particulièrement dans la plage de basse fréquence. Capturer le phénomène de décollement est un véritable défi dû à la nécessité de résoudre plusieurs échelles spatiales et temporelles. L’utilisation des simulations directes (DNS) ou résolu proche paroi (WR-LES) devient difficile compte tenu des ressources en calcul numérique actuelles. Pour parer ce problème, l’utilisation d’une stratégie de modélisation proche paroi est nécessaire. Le modèle de paroi développé par Kawai & Larsson (2013) est intégré à la simulation LES, combiné au modèle de viscosité de Duprat et al. (2011) afin de tenir compte des gradients de pression rencontré tout au long de la tuyère. Le développement d’un code curviligne a également permis de réduire le coût de calcul des simulations cylindriques en utilisant un maillage raffiné proche paroi. Les résultats obtenus à partir des simulations modélisés (WM-LES) permettent de bien mettre en évidence les phénomènes d’instationnarité menant au problème de charge latérale. Le coût de calcul étant réduit de 40 fois comparé à une simulation résolu proche paroi WR-LES, la production d’une base de donnée basse fréquence devient possible. La comparaison des calculs modélisés aux calculs résolus et aux données expérimentales confirme la bonne implémentation du modèle pour des simulations LES de tuyère propulsive. La caractérisation des différents phénomènes est faite à l’aide d’analyses spectrales effectuées sur la base de donnée permettant de mettre en avant le phénomène basse fréquence rencontré dans les tuyères sur-détendu<br>The present thesis, sponsored by a Franco-British cooperation program between the DGA and the DSTL, is devoted to the study of separation phenomenon in over-expanded nozzle. The aerothermodynamic of propulsion systems (missile, supersonic aircraft or launcher) is one the fields of fluid mechanics where important progress remains to be made in order to improve the performance of the engine, in terms of thrust, stability, reliability and pollutant (noise reduction, pollutant emissions, etc.). Since the flight conditions and the complexity of the characteristic phenomena are not reproducible on experimental benches, the use of numerical simulation would allow a thorough and precise study of the phenomena involved. The instationnarity observed in the separation of the boundary layer is becoming a main concern nowadays, especially the low-frequency phenomenon observed in some experiments, the use of large scale simulations (LES) would fit perfectly the computational power allocated on supercomputer compared to the prohibitive cost of direct simulations (DNS). Over-expanded nozzles are known to suffer from side loads, characterized by undesired unsteady forces orthogonal to the flow direction. They are caused by boundary-layer separation that causes significant and asymmetrical shock excursions within the nozzle. These phenomena have been studied experimentally and numerically. They emerge from a combination of complex unsteady flow phenomena, not yet fully understood, such as shock/boundary-layer interactions at the nozzle walls, detached mixing layers, and large regions of recirculating flow, all producing energetic motions at frequencies one or two orders of magnitudes lower than the characteristic frequency of the incoming turbulence. Capturing the phenomenon is a real challenge due to the need to resolve at least four decades of time scales, from the energetic scales of the incoming turbulence. This makes both direct (DNS) and wall-resolved large-eddy simulations (WR-LES) rather impractical. Instead, a wall-modelled LES (WM-LES) strategy is employed here, following the approach of Kawai & Larsson (2013) together with the eddy-viscosity modification of Duprat et al. (2011) so as to account for pressure gradients. The WM-LES is found to accurately reproduce the flow topology, as well as the spectral content obtained by a reference WR-LES. The development of a curvilinear code has allowed us to decrease the cost of computation of the simulations by using a stretched mesh close to the wall. The results obtained from the wall-modeled simulations (WM-LES) allowed us to capture and study the phenomena of instationnarity leading to the problem of side-loads. The WM-LES being about 40 times cheaper, the low-frequency motions may be statistically converged, enabling the study of the very low frequencies. The comparison of the modeled simulations with the resolved simulations and the experimental data confirms the good implementation of the model for LES computations of over-expanded nozzle flow. The characterization of the different phenomena is done through spectral analyses, carried out on the LES database allowing the highlight of the low-frequency phenomenon encountered in the over-expanded nozzle flow
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Alfonso, Medina Hugo Leonardo. "Caractérisation et modélisation des assemblages multi-matériaux sous sollicitations mixtes quasi-statiques pour la conception des structures automobiles." Thesis, Brest, 2016. http://www.theses.fr/2016BRES0118/document.
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Durant ces dernières années, les émissions de CO2 liées à l’utilisation des voitures ont atteint des niveaux critiques contribuant au réchauffement climatique et causant des problèmes de santé. Afin de réduire ces émissions, l’industrie automobile française a décidé de réduire la masse des véhicules via l’utilisation de matériaux plus légers tels que les matériaux composites. Cependant, les techniques d'assemblage classiquement utilisées ne sont pas compatibles pour assembler ces nouveaux matériaux à la structure du véhicule (acier et aluminium). Le principal objectif de cette étude a donc été la caractérisation et la modélisation de nouvelles techniques d'assemblages multimatériaux permettant une bonne résistance mécanique.Quatre techniques d’assemblages multi-matériaux (métal/composite) ont été étudiées : (i) le collage par goujon, (ii) la soudure laser, (iii) le rivetage auto-perçant et (iv) le collage. Des essais traditionnels de simple recouvrement et de traction transverse ont été utilisés pour caractériser les deux premières techniques. Ensuite, un nouveau test de caractérisation basé sur un dispositif Arcan modifié a été proposé pour analyser le comportement des assemblages rivetés et le collage. Parmi les quatre techniques testées, le collage a été retenu comme la technique la plus adaptée aux exigences de l'industrie. Par conséquent, des essais Arcan ont été réalisés afin de déterminer le comportement quasi-statique des adhésifs de l’étude (Betamate1822 et Sikapower498). Ces essais ont ensuite été utilisés pour proposer et identifier une nouvelle loi de comportement 3D viscoélastique spectrale non-linéaire. La procédure d'identification des paramètres des adhésifs n'est basée que sur trois essais de fluage multiniveaux, permettant un dimensionnement rapide des structures collées. Enfin, la loi de comportement proposée a été validée grâce à la bonne corrélation entre les prédictions numériques et les courbes expérimentales des essais monotones à différents vitesses de sollicitation et des essais de traction incrémentale.La présente étude a été développée dans le cadre d’un projet automobile. Néanmoins, les conclusions et les perspectives de l'étude peuvent être extrapolées à d'autres domaines tout aussi intéressants<br>Nowadays, the emissions of CO2 due to the use of automobiles have reached critical levels causing global warming and health problems. In order to reduce these emissions, the French automotive industry has decided to reduce the car weight by means of the use of lighter materials such as composite materials. However, the classical joining techniques are not adapted to assembly these new materials to the structure of the car (aluminum and steel alloys). Therefore, the characterization and modeling of new joining techniques of dissimilar materials is a problem that has been treated in the current study.Four different joining techniques of dissimilar materials (metal/composite) have been studied: (i) stud bonding, (ii) laser welding, (iii) self-pierce riveting and (iv) adhesive bonding systems. Traditional lap-shear and cross-tension tests were used to characterize the first two joining techniques. Then, a new characterization test based on a modified Arcan device has been proposed to analyze the behavior of self-piercing rivet and adhesive bonding systems. Among all the four tested techniques, adhesive joints have been selected as the most adapted technique according to the requirements of the industry. Therefore, modified Arcan tests have been performed in order to determine the behavior of the adhesives of the study (Betamate1822 and Sikapower498). These tests were then used to propose and identify a new 3D non-linear viscoelastic spectral model. The identification procedure of the material parameters is only based on three multilevel creep tests, which permits the rapid dimensioning of adhesively bonded structures. Finally, the proposed behavior law was validated by the good concordance between the numerical predictions and the experimental curves of monotonic tests at different loading rates and increasing cyclic tests.The current study was developed in the framework of an automotive project. Nevertheless, the conclusions and prospects of the study can be extrapolated to other interesting fields
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Nedbal, David. "Návrh manuální pravoúhlé frézovací hlavy určené pro technologické operace na středně těžkých obrobcích." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2018. http://www.nusl.cz/ntk/nusl-382413.
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This thesis deals with mechanical design of right-angle manual milling head for headstock of horizontal boring machine of Fermat production. The thesis includes research of milling head types, Fermat production heads, but also heads of competition companies with similar parameters like designed head. Design part of thesis is about describing used components of chosen solution. The thesis includes also technical report describing calculation of load spectrum from machining, design of gears, calculation of reactions in spindle bearings, spindle deformation and control of spindle bearings. The end of the thesis describes financial evaluation including also comparation with competitive milling heads with similar parameters.
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Tabatabaei, Araghi Pedram. "Seismic analysis of concrete structures within nuclear industry." Thesis, KTH, Betongbyggnad, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147215.
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Earthquake has always been a hazard for civil structures and keeping the structures integrity during and after an earthquake is of vital importance. This phenomenon’s impact is sudden and there is little or no warning to make the preparations for this natural disaster. Much damage has been done on structures which have led to major collapses and loss of many lives. Civil structures such as nuclear power plants are designed to withstand earthquakes and in the event of a major seismic event, to shut down safely. The aim of this thesis is to present the seismic design procedures for concrete structures, in basic and detailed design, according to Eurocode 8. Also to describe and understand the difference between Eurocode 8 and the DNB in seismic analysis of nuclear power plants. To evaluate the use of DNB instead of Eurocode 8 with Swedish seismic conditions is also another aim in this thesis. Loads and actions which apply on a structure in a seismic design and corresponding load combinations are presented for Eurocode 8 and the DNB. An example is also given to clarify the design of primary seismic beams and columns with high ductility class (DCH). A case study of a nuclear structure from a test project named SMART2013 has been made by analyzing and comparing the results from Eurocode 8 and the DNB with a finite element model in FEM-Design software. Natural frequencies of the model are compared with the tested model in SMART2013-project to evaluate the finite element modeling. The model is seismically analyzed with load combinations from Eurocode 8 and the DNB with Swedish elastic ground response spectrum with the probability of 10-5. Results obtained from the primary seismic beams and columns are compared and analyzed. Being on the safe and conservative side of the design values is always preferred in seismic analysis of a vital and sensitive structure such as nuclear power plants. The results from this thesis shows that, purely structural, combination of Swedish elastic ground response spectrum with the Eurocode 8 load combination will give more conservative values than the DNB.<br>I stora delar av världen har jordbävningar alltid varit ett hot för byggnaders integritet. Karaktären av en jordbävning är plötslig och föranleds av små eller inga varningar. Om jordbävningen medför att byggnader kollapsar sker ofta stora förluster av människoliv direkt eller indirekt. Kärnkraftsverk är anläggningar som dimensioneras för att klara jordbävningar och ska kunna gå till säker avställning vid en sådan händelse. Syftet med föreliggande rapport är att presentera hur betongkonstruktioner dimensioneras för jordbävning enligt Eurokod 8. Rapporten redogör även för skillnader mellan att dimensionera enligt Eurokod 8 och DNB (Dimensionering av nukleära byggnadskonstruktioner) samt hur det slår att använda Eurokod med svenska seismiska förhållanden. Laster och lastkombinationer som används vid jordbävningsdimensionering av betongbyggnader är presenterad enligt både Eurokod och DNB. Ett exempel presenteras för att visa hur primära balkar och pelare med hög duktilitetsklass (DCH) dimensioneras för seismisk påverkan. En fallstudie av en nukleär byggnad från ett internationellt projekt, SMART2013, har använts för att analysera och utvärdera resultaten från Eurokod och DNB. Byggnaden har analyserats med finita element med programvaran FEM Design. Modellens riktighet har verifierats genom att jämföra bland annat egenfrekvenser med de från officiella rapporter från SMART2013. Byggnaden är analyserad för seismisk last enligt svenska förhållanden med markresponsspektra 10-5, och primära balkar och pelare har analyserats och utvärderats enligt både Eurokod och DNB.
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Ruchert, Cassius Olivio Figueiredo Terra. "Correlação de estrias de fadiga com espectro de cargas em liga de Al aeronáutica SAE-AMS 7475 T 7351." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-10092008-095023/.
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Este trabalho discutiu a relação entre o espaçamento inter-estrias , isto é, a taxa de propagação da trinca microscópica SL (local) e SP (projetada) e a taxa de propagação macroscópica , da/dN, obtido após o ensaio de propagação de trinca por fadiga. Corpos de prova compacto C(T) foram extraídos na orientação LT do centro de uma placa laminada de liga de alumínio SAE-AMS 7475 T7351 onde posteriormente foram realizados ensaios de fadiga sob carga ou ΔK constantes, à temperatura ambiente de acordo com a Norma ASTM-E647 (1993). Para o ensaio sob carga constante foram obtidos os dados do estágio II e III da curva da/dN vs. ΔK. Para o ensaio de fadiga sob ΔK constante, quatro níveis de ΔK foram utilizados com taxas de crescimento de trinca variando entre 0,15 à 2,4 μm/ciclo. Adicionalmente foram realizados ensaios de tenacidade à fratura, KIC nas direções LT e TL conforme a Norma ASTM-E1820 (1999). A análise fratográfica por microscopia eletrônica de varredura foi conduzida no ensaio de fadiga a ΔK constante para determinar os espaçamentos inter-estrias. As taxas de propagação macroscópica e microscópica foram comparadas e boas correlações foram obtidas para um intervalo entre 0,1 a 1,0 μm/ciclo. Através da técnica proposta por Berkovitz (1995), o espectro de carregamento foi estimado através da técnica de parametrização do fator K e os resultados foram comparados ao espectro de carregamento real imposto pela máquina de ensaio. Utilizando o espaçamento inter-estrias local, SL, e para valores de ΔK menores que 23 MPam 1/2 (região de Paris), a estimativa de carregamento exibiu um erro menor que 15%. As vidas estimadas em propagação fornecidas pelas taxas microscópicas de propagação de trinca foram comparadas à vida real de propagação obtida a partir da taxa de propagação de trinca macroscópica e o erro absoluto entre ambos os valores foi menor que 15,7 %. Estes resultados sugerem que a vida em fadiga e o espectro de carga podem ser adequadamente estimados utilizando o espaçamento inter-estrias local, SL.<br>This work discusses the relationship between striation spacing, i.e. the microscopic crack propagation rate, SL (local) e SP (projected), as measured in post-mortem fractographic inspection of fatigue fractured surfaces, and the macroscopic crack propagation rate, da/dN, as monitored during fatigue crack growth tests. Compact tensile specimens C(T) were extracted in LT orientation from the core of a laminated plate of a SAE-AMS 7475-T7351 Al alloy and subsequently fatigue tested either at constant load or at constant ΔK, at room temperature, according to ASTM-E647. For constant amplitude loading fatigue tests, da/dN- ΔK data points were obtained for Regions II and III of crack growth curve. For constant ΔK fatigue tests, four ΔK levels were selected to give crack growth rates typically ranging from 0.15 to 2.4 μm/cycle. Additionally, KIC fracture toughness tests were performed in both LT and TL directions, according to ASTM E1820. SEM fractographic analysis was conducted on constant ΔK fatigue specimens, in order to determine striation spacing created during the fatigue test. Macro- and microscopic crack growth rates were compared and good correlation have been obtained for data within the range from 0,1 to 1,0 μm/ciclo. Using the technique proposed by Berkovitz, loading history was estimated by the K-factor parametrization and the results were compared to the true loading spectrum imposed by the testing machine. Using the local striation spacing SL and for ΔK values lower than 23 MPam 1/2 (Paris region), the estimated loading exhibits an error less than 15%. Propagation life estimated by local striation spacing (microscopic crack growth rate) was compared to the true propagation life obtained from macroscopic crack growth rate values and the absolute difference between them was less than 15,7%. These results suggest that both life and loading history can be adequately estimated using the local SL striation spacing values.
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Zebiri, Boubakr. "Étude numérique des interactions onde de choc / couche limite dans les tuyères propulsives Shock-induced flow separation in an overexpanded supersonic planar nozzle A parallel high-order compressible flows solver with domain decomposition method in the generalized curvilinear coordinates system Analysis of shock-wave unsteadiness in conical supersonic nozzles." Thesis, Normandie, 2020. http://www.theses.fr/2020NORMIR06.
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La nécessité d’une meilleure compréhension du mécanisme d’entrainement pour l’instabilité à basse fréquence observée dans un écoulement dans une tuyère sur-détendue a été discutée. Le caractère instable de l’onde de choc/couche limite reste un défi pratique important pour les problèmes des écoulements dans les tuyères. De plus, pour une couche limite turbulente incidente donnée, ce type d’écoulement présente généralement des mouvements de choc à basse fréquence plus élevées qui sont moins couplés aux échelles de temps de la turbulence en amont. Cela peut être bon du point de vue d’un expérimentateur, en raison de difficultés à mesurer des fréquences plus élevées, mais c’est plus difficile d’un point de vue calcul numérique en raison de la nécessité d’obtenir des séries temporelles plus longues pour résoudre les mouvements à basse fréquence. En excellent accord avec les résultats expérimentaux, une série de calcul LES de très longue durée a été réalisée, il a été clairement démontré l’existence de mouvements énergétiques à basse fréquence et à large bande près du point de séparation. Des efforts particuliers ont été faits pour éviter tout forçage à basse fréquence en amont, et il a été explicitement démontré que les oscillations de choc à basse fréquence observées n’étaient pas liées à la génération de turbulence d’entrée, excluant la possibilité d’un artefact numérique. Différentes méthodes d’analyse spectrales, et en décomposition en mode dynamique ont été utilisées pour montrer que les échelles de temps impliquées dans un tel mécanisme sont environ deux ordres de grandeur plus grandes que les échelles de temps impliquées dans la turbulence de la couche limite, ce qui est cohérent avec les mouvements de basse fréquence observés. En outre, ces échelles de temps se sont avérées être fortement modulées par la quantité de flux inversé à l’intérieur de la bulle de séparation. Ce scénario peut, en principe, expliquer à la fois l’instabilité des basses fréquences et sa nature à large bande<br>The need for a better understanding of the driving mechanism for the observed low-frequency unsteadiness in an over-expanded nozzle flows was discussed. The unsteady character of the shock wave/boundary layer remains an important practical challenge for the nozzle flow problems. Additionally, for a given incoming turbulent boundary layer, this kind of flow usually exhibits higher low-frequency shock motions which are less coupled from the timescales of the incoming turbulence. This may be good from an experimenter’s point of view, because of the difficulties in measuring higher frequencies, but it is more challenging from a computational point of view due to the need to obtain long time series to resolve low-frequency movements. In excellent agreement with the experimental findings, a very-long LES simulation run was carried out to demonstrate the existence of energetic broadband low-frequency motions near the separation point. Particular efforts were done in order to avoid any upstream low-frequency forcing, and it was explicitly demonstrated that the observed low-frequency shock oscillations were not connected with the inflow turbulence generation, ruling out the possibility of a numerical artefact. Different methods of spectral analysis and dynamic mode decomposition have been used to show that the timescales involved in such a mechanism are about two orders of magnitude larger than the time scales involved in the turbulence of the boundary layer, which is consistent with the observed low-frequency motions. Furthermore, those timescales were shown to be strongly modulated by the amount of reversed flow inside the separation bubble. This scenario can, in principle, explain both the low-frequency unsteadiness and its broadband nature
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Skalka, Miroslav. "Analýza vlivu mechanického momentu asynchronního stroje na sycení magnetického obvodu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-233534.
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e main goal of this thesis is mechanical torque analysis of induction machine based on magnetic circuit saturation, oversaturated areas classification and the possibility of oversaturated areas reduction of their influence on machine properties. Whole problem is solved by finite element method in ANSYS program. Work is divided into the description and creating of electromagnetic model, a method of the induction machine equivalent circuit parameters determination, the electromagnetic field calculation by finite element method, experimental measurement using LabVIEW program with measurement accessories (PCIe card National Instruments), data processing program in DIAdem, results analysis of calculations in terms of magnetic circuit saturation, the influence of magnetic circuit material based on electromagnetic field distribution and the magnetic flux density along the air gap including spectral analysis using MATLAB and the electromagnetic torque and its parasitic torque components calculation.