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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
311

Automating Telemetry Tracking Systems Operational Tests

Pedroza, Moises 10 1900 (has links)
International Telemetering Conference Proceedings / October 22-25, 2001 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Automating Telemetry Tracking Systems Operational Readiness Tests is a concept that was introduced at White Sands Missile Range in the early 1980’s. The idea was to determine the condition of a Telemetry Tracking System in a reliable manner in a short time as possible. A series of RF and Servo Tests designed to determine the condition of a Telemetry Tracking System was implemented using HP BASIC. The latest personal computers are faster and have more storage capacity plus the capability to be programmed in higher level languages such as C/C++ and LabView. This technology makes it easier to automate system tests. Many of these tests need to be conducted just prior to supporting a mission. Some tests are required to be performed on mobile systems after moving the system from one location to another, especially if the move was over long distances and rugged terrain. Tests such as G/T are conducted before each mission because it yields accurate information on the Figure of Merit, or, System Sensitivity. Noise Figure Measurements are more difficult to perform to determine the System Sensitivity since modern RF Subsystems have pre-amplifiers with Noise Figures of less than 1.0 dB. The “down-sizing” of personnel increases the possibility of failure in mission support scenarios due to the many critical readiness tests needed to assess the Telemetry Tracking Systems. Also, conventional test methods can be time consuming and are subject to human error. This paper describes four critical tests that have been automated to improve reliability of the test data and decrease the amount of time required to conduct the tests. The “C/C++” language was used to write the automation programs. More tests will be automated later.
312

Time-dependent analysis and amplitude analysis of B0 ! K0s K0s K0s decays with the BABAR experiment

Sitt, Simon 29 September 2010 (has links) (PDF)
Deux analyses indépendantes du canal de désintegration B0 ! K0s K0s K0s ont été effectuées, utilisant un échantillon de 468 millions de paires B¯B enregistrées par le détecteur BABAR auprès de l'usine à B PEP-II à SLAC National Laboratory. La première analyse est dépendant du temps et integrée sur l'espace de phase. Son but est d'extraire simultanément des deux sous-canaux B0 ! 3K0s (¼+¼−) et B0 ! 2K0s (¼+¼−)K0s (¼0¼0), les paramètres S et C de violation de CP. Il est intéressant de comparer les valeurs mesurées avec les mesures des modes charmonium. Le résultat obtenu est • S = −0.94+0.24 −0.21 ± 0.06 • C = −0.17+0.18 −0.18 ± 0.04 , où la première incertitude est statistique et la deuxième est systématique. Ce résultat est compatible avec la prédiction du modèle standard et les mesures des modes charmonium. La deuxième analyse est une analyse en amplitude (ou dans le plan de Dalitz). Elle est intégrée sur le temps. Son but est d'extraire le rapport de branchement total, ainsi que les rapports de branchement des modes résonnants partiels. C'est la première fois que cette analyse est effectuée pour le canal étudié. Le résultat est • B(B0 ! K0s K0s K0s ) = (6.18 ± 0.47 ± 0.14 ± 0.06) × 10−6 • B(B0 ! f0(980)K0s ; f0(980) ! K0s K0s ) = (2.69+1.25 −1.18 ± 0.35 ± 1.87) × 10−6 • B(B0 ! f0(1710)K0s ; f0(1710) ! K0s K0s ) = (0.50+0.46 −0.23 ± 0.04 ± 0.12) × 10−6 • B(B0 ! f2(2010)K0s ; f2(2010) ! K0s K0s ) = (0.54+0.21 −0.20 ± 0.03 ± 0.44) × 10−6 • B(B0 ! Nonresonant; K0s K0s K0s) = (13.31+2.23 −2.30 ± 0.55 ± 2.77) × 10−6 • B(B0 ! Âc0K0s ; Âc0 ! K0s K0s) = (0.46+0.25 −0.16 ± 0.01 ± 0.19) × 10−6 , où la première incertitude est statistique, la deuxième est systématique et la troisième est liée au modèle de l'amplitude. Aucun signal statistiquement significatif de la résonance controversée fX(1500) n'a été observé. dumm
313

Damage characterisation and lifetime prediction of bonded joints under variable amplitude fatigue loading

Shenoy, Vikram January 2009 (has links)
Adhesive bonding is one of the most attractive joining techniques for any structural application, including high profile examples in the aerospace, automotive, marine construction and electrical industries. Advantages of adhesive bonding include; superior fatigue performance, better stress distribution and higher stiffness than conventional joining techniques. When the design of bonded joints is considered, fatigue is of critical importance in most structural applications. There are two main issues that are of importance; a) in-service damage characterisation during fatigue loading and, b) lifetime prediction under both constant and variable amplitude fatigue loading. If fatigue damage characterisation is considered, there has been some work to characterise damage in-situ using the backface strain (BFS) measurement technique, however, there has been little investigation of the effects of different types of fatigue behaviour under different types of geometry and loading. Regarding fatigue lifetime prediction of bonded joints, most of the work in the literature is concentrated with constant amplitude fatigue, rather than variable amplitude fatigue. Fatigue design of a bonded structure based on constant amplitude fatigue, when the actual loading on the structure is of the variable amplitude fatigue, can result in erroneous lifetime prediction. This is because of load interaction effects caused by changes in load ratio, mean load etc., which can decrease the fatigue life considerably. Therefore, the project aims to a) provide a comprehensive study of the use of BFS measurements to characterise fatigue damage, b) develop novel techniques for predicting lifetime under constant amplitude fatigue and c) provide an insight into various types of load interaction effects. In this project, single lap joints (SLJ) and compound double cantilever beam geometries were used. Compound double cantilever beams were used mainly to determine the critical strain energy release rate and to obtain the relationship between strain energy release rate and fatigue crack growth rate. The fatigue life of SLJs was found to be dominated by crack initiation at lower fatigue loads. At higher fatigue loads, fatigue life was found to consist of three phases; initiation, stable crack propagation and fast crack growth. Using these results, a novel damage progression model was developed, which can be used to predict the remaining life of a bonded structure. A non-linear strength wearout model (NLSWM) was also proposed, based on strength wearout experiments, where a normalised strength wearout curve was found to be independent of the fatigue load applied. In this model, an empirical parameter determined from a small number of experiments, can be used to determine the residual strength and remaining life of a bonded structure. A fracture mechanics approach based on the Paris law was also used to predict the fatigue lifetime under constant amplitude fatigue. This latter method was found to under-predict the fatigue life, especially at lower fatigue loads, which was attributed to the absence of a crack initiation phase in the fracture mechanics based approach. A damage mechanics based approach, in which a damage evolution law was proposed based on plastic strain, was found to predict the fatigue life well at both lower and higher fatigue loads. This model was able to predict both initiation and propagation phases. Based on the same model, a unified fatigue methodology (UFM) was proposed, which can be used to not only predict the fatigue lifetime, but also various other fatigue parameters such as BFS, strength wearout and stiffness wearout. The final part of the project investigated variable amplitude fatigue. In this case, fatigue lifetime was found to decrease, owing to damage and crack growth acceleration in various types of variable amplitude fatigue loading spectra. A number of different strength wearout approaches were proposed to predict fatigue lifetime under variable amplitude fatigue loading. The NLSWM, where no interaction effects were considered was found to over-predict the fatigue life, especially at lower fatigue loads. However, approaches such as the modified cycle mix and normalised cycle mix approaches were found to predict the fatigue life well at all loads and for all types of variable amplitude fatigue spectra. Progressive damage models were also applied to predict fatigue lifetime under variable amplitude fatigue loading. In this case a fracture mechanics based approach was found to under-predict the fatigue life for all types of spectra at lower loads, which was established to the absence of a crack initiation phase in this method. Whereas, a damage mechanics based approach was found to over-predict the fatigue lifetime for all the types of variable amplitude fatigue spectra, however the over- prediction remained mostly within the scatter of the experimental fatigue life data. It was concluded that, the damage mechanics based approach has potential for further modification and should be tested on different types of geometry and spectra.
314

Submarine mass movement processes on the North Sea Fan as interpreted from the 3D seismic data

Gafeira Gonçalves, Joana January 2010 (has links)
This research has been focused on the characterisation and analysis of the deposits of large-scale mass movement events that shaped the North Sea Fan since the Mid-Pleistocene. Located at the mouth of the cross-shelf trough Norwegian Channel, the North Sea Fan is one of the largest through-mouth fans in the glaciated european margin with an area of approximately 142,000 km2. Submarine mass movement processed have occurred intermittenrly throughout the Quarternary history of the North Sea Fan, related to recurrent climate-related episodes of growth and retreat of the ice sheets. These processes can transport large amounts of sediment from the upper shelf up to the abyssal basins, playing an important role on the evolution of continental margins and can also reporesnet major geological hazards. This thesis uses mainly 3D seismic data to investigate the external geometry and internal structure of large-scale mass movement deposits. The high spatial resolution provided by the 3D seismic data has allowed a detailed geomorpholocial analysis of these deposits, This study involved the interpretation of the seismic data and the detailed pickling of key reflectors followed by tge extraction of both horizon and window-based seismic attributes. Digital elevation models of the key reflectors and their seismic attribute maps were then transferred to a geographical information system (GIS) where they were interactively interpreted using spatial analysis tools and the full visualisation potential of the software. The outcomes of this study highlight the importance of detailed horizon pickling and interactice interpretation followed by spatial analysis and visualisation in GIS environment. The identification of acoustic patterns within deposits that are normally described from 2D seismic as chaotic or acoustically transparent emphasizes the potential of detailed analysis of 3D seismic data. It gives an example of how this type of data can provide new insights into the mechanisms and processes associated with mass movements. In particular, amplitude and RMS amplitude maps provide remarkable detailed information of internal deformation structures whereas slope, shaded-relief and thickness maps allowed detailed characterisation of the external geometry. Various types of kinematic indicators can be recognized within the mass movement deposits through combined seismic analysis and detaield morphological mapping.
315

Theory and methods of frequency-dependent AVO Inversion

Wilson, Adam January 2010 (has links)
Amplitude-versus-offset, AVO, approximations allow the estimation of various properties from pre-stack seismic gathers. Recently it has been suggested that fluid mobility is a controlling factor in pore pressure equalisation and can result in anomalous velocity dispersion in the seismic bandwidth. However, current approximations all assume an elastic subsurface and are unable to account for velocity dispersion. I have applied existing methodologies to a real dataset to qualitatively detect and interpret spectral amplitude anomalies. Three areas had AVO and spectral signature consistent with frequency-dependent AVO theory. The results suggest that it is feasible to measure such effects on real data in the presence of random noise. It would imply that the relaxation parameter, tau, is larger in the field than has been measured in water-saturated real and synthetic sandstones in the laboratory. I extended a two-term AVO approximation by accounting for velocity dispersion and showed how the resultant reflection coefficient becomes frequency-dependent. I then used this to measure P- and S-wave reflectivity dispersion using spectrally-balanced amplitudes. The inversion was able to quantify the affect of the P-wave velocity dispersion as an instantaneous effect on the reflection. NMO stretch was an issue at the far offsets and I limited myself to the near offsets and effectively measured only the P-wave reflectivity dispersion. I showed how the P-wave reflectivity dispersion signs depend on the AVO classification of the reflection whilst the magnitude depends on the crack density of my model. I showed how the effect of noise and thin-bed tuning can enter uncertainties into the interpretation of spectral anomalies. Whilst it is possible to detect frequency-dependent AVO signatures on pre-stack gathers, the interpretation remains non-unique. I have quantitatively measured a new physical property, reflectivity dispersion, from pre-stack seismic data. I have presented a method of detecting and measuring velocity dispersion in pre-stack gathers but there remain ambiguities in the interpretation of such results. The approach incorporates spectrally decomposed data in an extended AVO inversion scheme. Future work should investigate the application of the methodology to a real seismic dataset.
316

A New Method to Predict Vessel Capsizing in a Realistic Seaway

Vishnubhotla, Srinivas 08 August 2007 (has links)
A recently developed approach, in the area of nonlinear oscillations, is used to analyze the single degree of freedom equation of motion of a oating unit (such as a ship) about a critical axis (such as roll). This method makes use of a closed form analytic solution, exact upto the rst order, and takes into account the the complete unperturbed (no damping or forcing) dynamics. Using this method very-large-amplitude nonlinear vessel motion in a random seaway can be analysed with techniques similar to those used to analyse nonlinear vessel motions in a regular (periodic) or random seaway. The practical result being that dynamic capsizing studies can be undertaken considering the shortterm irregularity of the design seaway. The capsize risk associated with operation in a given sea state can be evaluated during the design stage or when an operating area change is being considered. Moreover, this technique can also be used to guide physical model tests or computer simulation studies to focus on critical vessel and environmental conditions which may result in dangerously large motion amplitudes. Extensive comparitive results are included to demonstrate the practical usefulness of this approach. The results are in the form of solution orbits which lie in the stable or unstable manifolds and are then projected onto the phase plane.
317

Influência da amplitude de movimento do quadril no resultado do teste Timed Up and Go em pacientes com osteoartrite / Influence of hip range of motion on the Timed Up and Go test result in patients with osteoarthritis

Silva, Patrícia Costa da 04 February 2019 (has links)
A osteoartrite do quadril é uma grande causa de incapacidade da população idosa. A doença é caracterizada pela deterioração da cartilagem articular, perda do espaço cartilaginoso, esclerose do osso subcondral e presença de osteofitos. O teste Timed Up And Go (TUG) tem sido considerado como uma das ferramentas para avaliar a função do membro inferior, mobilidade e risco de quedas. O presente estudo visa determinar a influência da amplitude de movimento (ADM) do quadril no resultado do teste TUG em pacientes com osteoartrite de quadril, visto que há poucos estudos sobre o tema. Fizeram parte do estudo um total de 40 indivíduos divididos em dois grupos, 20 indivíduos no grupo controle e 20 no grupo de osteoartrite de quadril (grupo OA) com idade entre 40 e 75 anos. Para a inclusão dos indivíduos no grupo OA, utilizamos os critérios clínicos do American College of Rheumatology e para graduar a intensidade do comprometimento articular utilizamos a classificação de Tönnis. Os critérios de exclusão foram a presença de cirurgia prévia no membro inferior, fratura prévia no membro inferior, osteoartrite bilateral, dor lombar, obesidade mórbida, pacientes com estado geral comprometido por doenças sistêmicas graves, comprometimento cognitivo ou comprometimento neurológico. Através de um goniômetro examinadores independentes realizaram a medida de ADM ativa do quadril e com um cronômetro digital o tempo do teste TUG. Foi aplicado o Questionário de Western Ontario Universities (WOMAC) e a escala visual analógica de dor (EVA). Realizou-se a somatória da ADM de todos os movimentos do quadril e através do coeficiente de correlação de Pearson observamos a associação linear entre as variáveis ADM total ativa do quadril e tempo do teste TUG, nos grupos controle e OA. Nos resultados a ADM total ativa do quadril e o tempo do TUG do grupo OA apresentaram uma correlação negativa e moderada (r = - 0,69; p < 0,0001) porém no grupo controle observou-se fraca correlação (r = -0,08; p = 0,46). Os dados do estudo demonstram uma moderada correlação entre o tempo do TUG e a ADM total ativa do quadril em indivíduos com OA. Porém, mais estudos são necessários para determinar todas as variáveis que influenciam o resultado do teste. / Hip osteoarthritis is a major cause of disability in the elderly population. The disease is characterized by deterioration of articular cartilage, loss of cartilaginous space, sclerosis of subchondral bone and presence of osteophytes. The Timed Up And Go (TUG) test has been considered as one of the tools for assessing lower limb function, mobility, and risk of falls. The present study aims to determine the influence of the range of motion (ROM) on the TUG test result in patients with hip osteoarthritis, since there are few studies on the subject. A total of 40 individuals were divided into two groups, 20 in the control group and 20 in the group of hip osteoarthritis (OA group) aged between 40 and 75 years. For the inclusion of the individuals in the OA group we used the clinical criteria of the American College of Rheumatology and to grade the severity of the joint degeneration we used the Tönnis classification. Exclusion criteria were the presence of previous surgery on the lower limb, previous lower limb fracture, bilateral osteoarthritis, low back pain, morbid obesity, patients with poor general condition due to severe systemic diseases, cognitive impairment or neurological impairment. With a goniometer independent examiners performed the measurement of active ROM of the hip and with a digital timer the TUG test time. Western Ontario Universities Questionnaire (WOMAC) and visual analogue pain scale (VAS) were applied. We performed the summation of the ROM of all hip movements and through the Pearson correlation coefficient we observed the linear association between the active total ROM of the hip and the time of the TUG test in the control and OA groups. In the results, the total active ROM of the hip and the TUG time of the OA group presented a negative and moderate correlation (r = -0.64; p <0.0001), but in the control group there was a weak correlation (r = -0.08; p =0.46) . Data from the study demonstrate a moderate correlation between TUG time and total active ROM in subjects with OA. However, more studies are needed to determine all the variables that influence the test result.
318

[en] AMPLITUDE ANALYSIS OF THE DECAY D+ K (PI)-(PI)+(PI)+ IN FOCUS EXPERIMENT / [pt] ANÁLISE DE AMPLITUDES DO DECAIMENTO D+ KS(PI)-(PI)+(PI)+ NO EXPERIMENTO FOCUS

JUAN MARTIN OTALORA GOICOCHEA 26 February 2008 (has links)
[pt] O presente trabalho de tese é destinado ao estudo do decaimento do méson D+ KS(pi)&#8722;(pi)+(pi)+ com dados coletados pelo experimento FOCUS do Fermilab. O estado final, composto por 4 mésons pseudo- escalares, pode ser alcançado através de uma considerável variedade de sub- estruturas ressonantes. O proposito da análise é encontrar quais são estes possíveis canais intermediários através de suas contribuições e fases relativas. Para tanto, é utilizado o formalismo de Análise de Amplitudes usando o chamado Modelo Isobárico. A dinâmica do decaimento é definida através de uma função que contém as características (formas funcionais das ressonâncias, distribuição angular, etc) dos canais que intervêm no decaimento e cujo domínio é um espaço o de fase determinado por 5 invariantes (devido às restrições de decaimento em quatro corpos sem spin). A função é então ajustada ao conjunto de dados coletados. Nos resultados, verificamos uma grande contribuição do méson vetor-axial a1(1260) (52%) seguido do vetor-axial K1(1400) (34%). Além disso, o modelo apresenta contribuição da ressonância (sigma) (cerca de 8%, vinda de a1(sigmapi)KS e sigmaKSpi) e uma razoável contribuição da ressonância escalar K&#8722; (14%). O estado K já foi visto em seu modo neutro em outros decaimentos de charme, porém ainda não em seu modo carregado. Não encontramos contribui ção significativa do decaimento direto em 4 corpos (não- ressonante). Esta tese vem se somar ao esforço no entendimento da dinâmica das intera ções fortes a baixas energias, que nos últimos anos tem ganhado da física de mésons charmosos uma importante contribuição. / [en] This thesis is devoted to the study of the decay D+ KS(pi)&#8722; (pi)+(pi)+ with data collected from the FOCUS experiment, at Fermilab. The final state composed of 4 pseudo-scalars can be produced through a number of resonant sub-structures. The purpose of this analysis is to find the contributing intermediate states by measuring their relative strenghts and phases. For that, the Amplitude Analysis formalism is used, with the so-called Isobar Model. The decay dynamics is described through a function which has the features of the contributing channels (functional forms of the resonances, angular distribution, etc) and which domain is a phase space determined by 5 invariants (due to the kinematical constraints of a 4- body spinless decay). The data sample is thus fitted to this function. Our results show a dominant contribution of the axial- vector meson a1(1260) (52%), followed by the K1(1400) axial-vector (34%). Moreover, the model presents a contribution from the sigma meson (about 8% as a1(sigmapi)KS and sigmaKSpi) and a significant contribution from the scalar k&#8722;. The k state has been reported in its neutral mode in other charm decays but not is its charged mode. We find no significant contribution from the direct 4-body decay (non-resonant). This work adds to the effort in the understanding of the strong-interaction dynamics at low energies, which in recent years have been receiving an important contribution from charm meson physics.
319

Síntese digital direta de sinais aplicada ao acionamento de máquinas elétricas

Maurício da Graça Botelho 01 November 1996 (has links)
Neste trabalho propomos a aplicação da síntese digital direta coerente ao acionamento de máquinas elétricas de corrente alternada (CA). Inicialmente são apresentadas as técnicas mais comumente utilizadas na implementação de moduladores de largura de pulso (PWMs) para o acionamento de máquinas CA. Mostramos, para as diferentes técnicas, os efeitos na composição harmônica do sinal PWM obtido e concluímos que a técnica PWM otimizada apresenta o melhor desempenho. Apresentamos então nossa proposta para implementação de moduladores PWM através da síntese digital direta coerente, discutindo preliminarmente as técnicas mais comuns de síntese digital de sinais. A viabilidade técnica de nossa proposta é demonstrada com a implementação de um modulador PWM otimizado, destinado ao acionamento de um motor CA trifásico. Os resultados experimentais de nossa implementação são então comparados com os de previsões teóricas e simulações, verificando-se um desempenho do sistema e uma comparação favorável com outros implementados com técnicas convencionais.
320

Influence of Electromyogram (EMG) Amplitude Processing in EMG-Torque Estimation

Bida, Oljeta 29 January 2005 (has links)
A number of studies have investigated the relationship between surface electromyogram (EMG) and torque exerted about a joint. The standard deviation of the recorded EMG signal is defined as the EMG amplitude. The EMG amplitude estimation technique varies with the study from conventional type of processing (i.e. rectification followed by low pass filtering) to further addition of different noise rejection and signal-to-noise ratio improvement stages. Advanced EMG amplitude processors developed recently that incorporate signal whitening and multiple-channel combination have been shown to significantly improve amplitude estimation. The main contribution of this research is a comparison of the performance of EMG-torque estimators with and without these advanced EMG amplitude processors. The experimental data are taken from fifteen subjects that produced constant-posture, non-fatiguing, force-varying contractions about the elbow while torque and biceps/triceps EMG were recorded. Utilizing system identification techniques, EMG amplitude was related to torque through a zeros-only (finite impulse response, FIR) model. The incorporation of whitening and multiple-channel combination separately reduced EMG-torque errors and their combination provided a cumulative improvement. A 15th-order linear FIR model provided an average estimation error of 6% of maximum voluntary contraction (or 90% of variance accounted for) when EMG amplitudes were obtained using a four-channel, whitened processor. The equivalent single-channel, unwhitened (conventional) processor produced an average error of 8% of maximum voluntary contraction (variance accounted for of 68%). This study also describes the occurrence of spurious peaks in estimated torque when the torque model is created from data with a sampling rate well above the bandwidth of the torque. This problem is anticipated when the torque data are sampled at the same rate as the EMG data. The problem is resolved by decimating the EMG amplitude prior to relating it to joint torque, in this case to an effective sampling rate of 40.96 Hz.

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