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1
Jiang, Wei Ping. "Determination of crustal velocity structures from teleseismic p waves." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/25773.
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Ma, Xiaofei. "USArray Imaging of North American Continental Crust." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6904.
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The layered structure and bulk composition of continental crust contains important clues about its history of mountain-building, about its magmatic evolution, and about dynamical processes that continue to happen now. Geophysical and geological features such as gravity anomalies, surface topography, lithospheric strength and the deformation that drives the earthquake cycle are all directly related to deep crustal chemistry and the movement of materials through the crust that alter that chemistry.
The North American continental crust records billions of years of history of tectonic and dynamical changes. The western U.S. is currently experiencing a diverse array of dynamical processes including modification by the Yellowstone hotspot, shortening and extension related to Pacific coast subduction and transform boundary shear, and plate interior seismicity driven by flow of the lower crust and upper mantle. The midcontinent and eastern U.S. is mostly stable but records a history of ancient continental collision and rifting.
EarthScope’s USArray seismic deployment has collected massive amounts of data across the entire United States that illuminates the deep continental crust, lithosphere and deeper mantle. This study uses EarthScope data to investigate the thickness and composition of the continental crust, including properties of its upper and lower layers. One-layer and two-layer models of crustal properties exhibit interesting relationships to the history of North American continental formation and recent tectonic activities that promise to significantly improve our understanding of the deep processes that shape the Earth’s surface. Model results show that seismic velocity ratios are unusually low in the lower crust under the western U.S. Cordillera. Further modeling of how chemistry affects the seismic velocity ratio at temperatures and pressures found in the lower crust suggests that low seismic velocity ratios occur when water is mixed into the mineral matrix, and the combination of high temperature and water may point to small amounts of melt in the lower crust of Cordillera.
3
Olivares, Espinosa Hugo. "Steady-state model of neutron star crust." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21975.
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The advent of X-ray astronomy has turned the study of compact objects into one of the most active research fields in modern-day physics. Diverse luminosity phenomena have been remarked upon in neutron stars and it is believed that in many of them the neutron star crust plays a critical role. This work presents a steady-state model for the neutron star crust that describes, in particular, the profiles of temperature and flux along this region. It is divided as follows: First, a review of observational phenomena in neutron stars, where crust characteristics are thought to be crucial, are presented, alongside general aspects of the theoretical models applied. Second, the different elements that are needed to construct this model are considered. Third, the set of structure equations to be resolved and the calculations of the components of these equations are provided. Finally, the results are shown and discussed and the conclusion is presented.L'avènement de l'astronomie des rayons X a transformé l'étude des objets compacts en un des champs de recherche des plus actifs en physique moderne. Divers phénomènes de luminosité ont été observés dans les étoiles neutron et on estime que la croûte de l'étoile neutron joue un rôle important dans beaucoup de ces phénomènes. Cet ouvrage présente un modèle d'équilibre stable pour la croûte de l'étoile neutron qui décrit, en particulier, les profiles de température et flux dans cette région. L'ouvrage est divisé comme suit: Premièrement, une révision des phénomènes observés dans les étoiles neutron, où les caractéristiques de la croûte sont supposées être cruciaux, est présentée, avec les aspects généraux des modèles théoriques utilisés. Deuxièmement, les différents éléments nécessaires pour construire ce modèle sont examinés. Troisièmement, l'ensemble des équations de structure à résoudre et les calculs des composantes de ces équations sont présentés. Finalement, les résultats sont montrés et discutés et la conclusion est présentée.
4
Tay, Pui Leng. "Upper crustal velocity and structures from surface seismics : applications to the Mediterranean Ridge and West Orkney Basins." Thesis, Imperial College London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314230.
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McCarthy, Emily Suzanne. "Investigating the velocity structure beneath the Southern and Central Atlantic : implications for evolution of oceanic crust and lithosphere." Thesis, University of Leicester, 2015. http://hdl.handle.net/2381/32528.
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Presented here is the shear velocity structure of the crust and upper mantle beneath the central and southern Atlantic Ocean from inversion of high resolution group velocity tomography. The path average group velocities from Rayleigh waves were picked using multi filter technique and phase match filtering for 14,000 paths. They were then combined within a tomographic inversion, to obtain the regional variations of velocity structure at a range of short to intermediate periods (14 s - 100 s). These group velocities have depth sensitivities from the surface to approximately 90 km depth, constraining the focus to velocity variations within the crust and mantle lithosphere. Tomographic results highlight short wavelength variations at periods sensitive to shallow depths, implying the possibility for a more complex velocity structure than currently expected for the oceanic region. The results show a clear relationship between increasing group velocities and increasing sea floor age. Group models are then inverted to obtain the shear velocity structure with respect to depth. The shear velocity model highlights slow velocities beneath the ridge, interpreted as the upwelling of asthenosphere between depths between 30 km and 50 km. Models of crustal and lithospheric thickness are extrapolated from the data. These models suggest the evolution of the Atlantic Ocean is more complex than the simple mathematical cooling models. It is suggested that the main control on crustal thickness is tectonic processes associated with the slow spreading rate and not controlled by to the mantle potential temperature. Additionally, results are presented which incorporate 2 azimuthal anisotropy in the tomographic inversions. At the longest periods test show that the recovered anisotropy is an artefact of the inversion process, and cannot be interpreted in terms of mantle flow. At the shortest periods there is a possible relationship between the fast direction and the stress field.
6
Christodoulou, Apostolos A. "Etude sismotectonique et inversion tridimensionnelle en Grèce du Nord." Grenoble 1, 1986. http://www.theses.fr/1986GRE10086.
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Première Partie: Etude sismotectonique d'un graben complexe, exemple: le graben Mygdonien (Grèce du Nord). Durant les printemps de 1984 et 1985 nous avons installé un réseau sismologique de 29 stations portables dans la région du graben Mydgonien près de Thessaloniki. La sismicité et les mécanismes au foyer ont montré une structure complexe. Des phénomènes compressifs ont été observés au centre du graben. Nous proposons un modèle pour la formation et l'évolution du graben. Au départ la déformation a lieu le long des failles pré-existantes de direction NW-SE ou NNE-SSW avec des mouvements normaux ou décrochants. Dans une deuxième étape il y a formation d'une nouvelle famille de failles normales, dirigées E-W. Cette famille a une direction perpendiculaire à l'axe T moyen, trouvé par les mécanismes au foyer et vient se superposer aux failles initiales. Elle devient rapidement la famille principale et les failles initiales jouent un rôle d'ajusteur de déformation dans cet ensemble. En outre les anciennes failles fonctionnent comme des barrières à l'évo lution des failles dirigées E-W. Deuxième partie: Etudes tridimensionnelle de la croûte et du manteau supérieur à partir de l'inversion des ondes P des téléséismes. A partir des résidus relatifs de temps de parcours des ondes P des téléséismes, enregistrés par le réseau permanent du laboratoire de Géophysique de Thessaloniki, nous avons tenté une inversion tridimensionnelle selon la méthode de Aki, Christofferson et Husebye. Nous avons obtenu des modèles de vitesse en 3D pour les ondes P sous la Grèce du nord, jusqu'à une profondeur de 250 km. Nous avons essayé d'expliquer les variations latérales des vitesses observées, à l'aide de l'isostasie, du flux de chaleur et de la sismicité
7
Salstrand, Daniel Koewing. "A mathematical model for magma-hydrothermal systems in the oceanic crust." Thesis, Georgia Institute of Technology, 1989. http://hdl.handle.net/1853/25700.
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Håkman, Olof. "Boltzmann Equation and Discrete Velocity Models : A discrete velocity model for polyatomic molecules." Thesis, Karlstads universitet, Institutionen för matematik och datavetenskap (from 2013), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-76143.
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In the study of kinetic theory and especially in the study of rarefied gas dynamics one often turns to the Boltzmann equation. The mathematical theory developed by Ludwig Boltzmann was at first sight applicable in aerospace engineering and fluid mechanics. As of today, the methods in kinetic theory are extended to other fields, for instance, molecular biology and socioeconomics, which makes the need of finding efficient solution methods still important. In this thesis, we study the underlying theory of the continuous and discrete Boltzmann equation for monatomic gases. We extend the theory where needed, such that, we cover the case of colliding molecules that possess different levels of internal energy. Mainly, we discuss discrete velocity models and present explicit calculations for a model of a gas consisting of polyatomic molecules modelled with two levels of internal energy.I studiet av kinetisk teori och speciellt i studiet av dynamik för tunna gaser vänder man sig ofta till Boltzmannekvationen. Den matematiska teorien utvecklad av Ludwig Boltzmann var vid första anblicken tillämpbar i flyg- och rymdteknik och strömningsmekanik. Idag generaliseras metoder i kinetisk teori till andra områden, till exempel inom molekylärbiologi och socioekonomi, vilket gör att vi har ett fortsatt behov av att finna effektiva lösningsmetoder. Vi studerar i denna uppsats den underliggande teorin av den kontinuerliga och diskreta Boltzmannekvationen för monatomiska gaser. Vi utvidgar teorin där det behövs för att täcka fallet då kolliderande molekyler innehar olika nivåer av intern energi. Vi diskuterar huvudsakligen diskreta hastighetsmodeller och presenterar explicita beräkningar för en modell av en gas bestående av polyatomiska molekyler modellerad med två lägen av intern energi.
9
Berg, Peter. "Optimal-velocity models of motorway traffic." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367664.
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Makin, Alexis David James. "Velocity memory." Thesis, University of Manchester, 2011. https://www.research.manchester.ac.uk/portal/en/theses/velocity-memory(c5c1c28d-0a23-44a5-93bc-21f993d2e7ad).html.
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It is known that primates are sensitive to the velocity of moving objects. We can also remember velocity information after moving objects disappear. This cognitive faculty has been investigated before, however, the literature on velocity memory to date has been fragmented. For example, velocity memory has been disparately described as a system that controls eye movements and delayed discrimination. Furthermore, velocity memory may have a role in motion extrapolation, i.e. the ability to judge the position of a moving target after it becomes occluded. This thesis provides a unifying account of velocity memory, and uses electroencephalography (EEG) to explore its neural basis. In Chapter 2, the relationship between oculomotor control and motion extrapolation was investigated. Two forms of motion extrapolation task were presented. In the first, participants observed a moving target disappear then reappear further along its path. Reappearance could be at the correct time, too early or too late. Participants discriminated reappearance error with a two-alternative forced choice button press. In the second task, participants saw identical targets travel behind a visible occluder, and they attempted to press a button at the exact time that it reached the other side. Tasks were completed under fixation and free viewing conditions. The accuracy of participant's judgments was reduced by fixation in both tasks. In addition, eye movements were systematically related to behavioural responses, and small eye movements during fixation were affected by occluded motion. These three results imply that common velocity memory and pre-motor systems mediate eye movements and motion extrapolation. In Chapter 3, different types of velocity representation were explored. Another motion extrapolation task was presented, and targets of a particular colour were associated with fast or slow motion. On identical-velocity probe trials, colour still influenced response times. This indicates that long-term colour-velocity associations influence motion extrapolation. In Chapter 4, interference between subsequently encoded velocities was explored. There was robust interference between motion extrapolation and delayed discrimination tasks, suggesting that common processes are involved in both. In Chapter 5, EEG was used to investigate when memory-guided tracking begins during motion extrapolation. This study compared conditions where participants covertly tracked visible and occluded targets. It was found that a specific event related potential (ERP) appeared around 200 ms post occlusion, irrespective of target location or velocity. This component could delineate the onset of memory guided tracking during occlusion. Finally, Chapter 6 presents evidence that a change in alpha band activity is associated with information processing during motion extrapolation tasks. In light of these results, it is concluded that a common velocity memory system is involved a variety of tasks. In the general discussion (Chapter 7), a new account of velocity memory is proposed. It is suggested that a velocity memory reflects persistent synchronization across several velocity sensitive neural populations after stimulus offset. This distributed network is involved in sensory-motor integration, and can remain active without visual input. Theoretical work on eye movements, delayed discrimination and motion extrapolation could benefit from this account of velocity memory.
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Silvennoinen, H. (Hanna). "3D structure of the crust and upper mantle beneath Northern Fennoscandian shield." Doctoral thesis, University of Oulu, 2015. http://urn.fi/urn:isbn:9789526210681.
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Abstract
The crustal and upper mantle structures of the Shield on the regional scale were
investigated using the data of the POLENET/LAPNET passive seismic array and
the previously published models of active and passive seismic experiments in the
study area. This area is centred in northern Finland and it extends to surrounding
areas in Sweden, Norway and northwestern Russia. The bedrock there is mostly of
the Archaean origin and the lithosphere of the region was reworked by two orogenies
during Palaeoproterozoic.
One of the results of the thesis was a new map of the Moho depth of the study area,
for which new estimates of the crustal thickness were obtained using receiver function
method and complemented by published results of receiver function studies and controlled
source seismic profiles. The map differs from the previously published maps in
two locations, where we found significant deepening of the Moho. The 3D structure of
the upper mantle was studied using teleseismic traveltime tomography method. The
resulting model shows high seismic velocities below three cratonic units of the study
area, which may correspond to non-reworked fragments of cratonic lithosphere and a
low velocity anomaly separating these cratonic units from each other.
The regional scale studies were complemented by two smaller scale studies in upper
crust level using combined interpretation of seismic profiling and gravity data. These
studies were centred on Archaean Kuhmo Greenstone Belt in eastern Finland and
central Lapland in northern Finland located in the crust reworked during Palaeoproterozoic.
Both areas are considered as prospective ones for mineral exploration. Both
studies demonstrate the advantage of gravity data inversion in studying 3D density
structure of geologically interesting formations, when the Bouguer anomaly data is
combined with a priori information from petrophysical and seismic datasets.
12
Kelley, Daniel F. "Toward an Integrated Model of the Crust in the Icelandic Rift Zones." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1244046067.
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Bianchi, Irene <1981>. "Velocity structure and seismic anisotropy in the crust and upper mantle from Receiver Function analysis: three case studies in Italy." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2614/.
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The research for this PhD project consisted in the application of the RFs analysis technique to different data-sets of teleseismic events recorded at temporary and permanent stations located in three distinct study regions: Colli Albani area, Northern Apennines and Southern Apennines. We found some velocity models to interpret the structures in these regions, which possess very different geologic and tectonics characteristics and therefore offer interesting case study to face.
In the Colli Albani some of the features evidenced in the RFs are shared by all the analyzed stations: the Moho is almost flat and is located at about 23 km depth, and the presence of a relatively shallow limestone layer is a stable feature; contrariwise there are features which vary from station to station, indicating local complexities. Three seismic stations, close to the central part of the former volcanic edifice, display relevant anisotropic signatures with symmetry axes consistent with the emplacement of the magmatic chamber. Two further anisotropic layers are present at greater depth, in the lower crust and the upper mantle, respectively, with symmetry axes directions related to the evolution of the volcano complex.
In Northern Apennines we defined the isotropic structure of the area, finding the depth of the Tyrrhenian (almost 25 km and flat) and Adriatic (40 km and dipping underneath the Apennines crests) Mohos. We determined a zone in which the two Mohos overlap, and identified an anisotropic body in between, involved in the subduction and going down with the Adiratic Moho. We interpreted the downgoing anisotropic layer as generated by post-subduction delamination of the top-slab layer, probably made of metamorphosed crustal rocks caught in the subduction channel and buoyantly rising toward the surface.
In the Southern Apennines, we found the Moho depth for 16 seismic stations, and highlighted the presence of an anisotropic layer underneath each station, at about 15-20 km below the whole study area. The moho displays a dome-like geometry, as it is shallow (29 km) in the central part of the study area, whereas it deepens peripherally (down to 45 km); the symmetry axes of anisotropic layer, interpreted as a layer separating the upper and the lower crust, show a moho-related pattern, indicated by the foliation of the layer which is parallel to the Moho trend.
Moreover, due to the exceptional seismic event occurred on April 6th next to L’Aquila town, we determined the Vs model for two station located next to the epicenter. An extremely high velocity body is found underneath AQU station at 4-10 km depth, reaching Vs of about 4 km/s, while this body is lacking underneath FAGN station. We compared the presence of this body with other recent works and found an anti-correlation between the high Vs body, the max slip patches and earthquakes distribution. The nature of this body is speculative since such high velocities are consistent with deep crust or upper mantle, but can be interpreted as a as high strength barrier of which the high Vs is a typical connotation.
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Rao, Ying. "Seismic tomography for velocity and attenuation model reconstruction." Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/11882.
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Saracusa, Emily L. "A Mathematical Model for Acid Mine Drainage Removal and Iron Hydroxide Crust Formation." University of Akron / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=akron1302448347.
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Sung, Hsing-Wen. "In vitro velocity measurements in a pulmonary artery model." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/13388.
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Polorigni, Christian Leprince. "Primary sedimentation tank model with characterized settling velocity groups." Master's thesis, University of Cape Town, 2020. http://hdl.handle.net/11427/32526.
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Primary sedimentation involves the separation of solids and liquid in primary settling tanks (PSTs) of wastewater treatment systems. These physical processes are described by various settling conditions such as discrete and flocculent settling, along with other phenomena such as flocculation, coagulation, ammonification or hydrolysis. The modelling of primary sedimentation has often been overlooked because (i) it involves various intricacies that are difficult to replicate and (ii) primary sedimentation has been assumed to be an input to most of the main unit process models, including the activated sludge (AS) system and the anaerobic digestion (AD) models. Though there has been a wide range of proposed mathematical models to describe how PSTs function, the need to correctly disaggregate the total suspended solids (TSS) into realistic fractions of unbiodegradable particulate organics (UPO), biodegradable particulate organics (BPO) and inorganic settleable solids (ISS), remains. This is because PST models that are unable to correctly split the TSS into its characteristic components make incorrect assumptions. These assumptions lead to inconsistencies in predicting the compositions of the primary sludge (PS) that is fed to the AD unit and the settled wastewater (settled WW) that is treated in the AS system. Hence, it becomes difficult to correctly simulate the entire system (plant-wide) towards a holistic evaluation of system strategies. In this study, a realistic PST model was developed, with characterized settling velocity groups, within a plant-wide setting, for municipal wastewater. This involved the improvement of a current TSS-based model into a more accurate and realistic model that could account for the settling of raw wastewater particles. The model was therefore expected to predict the composition of the PS that is treated in the AD system and the composition of the settled WW that is going to the AS unit processes. This could be achieved by splitting the TSS into UPO, BPO and ISS fractions. In developing preparation of such a realistic PST model, the following objectives were established: 1. Disaggregate the TSS into realistic UPO, BPO and ISS fractions, by means of discrete particle settling modelling (Kowlesser, 2014) and the particle settling velocity distribution (PSVD) approach of Bachis et al. (2015). 2. Verify that the model is internally consistent with wastewater treatment plant (WWTP) data, by means of mathematical material mass balances and other specific scenarios. 3. Demonstrate the application and impact of such a model by performing steady state plant-wide simulations. Using the discrete particle settling approach of Kowlesser (2014), a discrete particle settling model was developed in Microsoft Excel and implemented into a dynamic PST framework in WEST® (Vanhooren et al., 2003). The discrete particle settling model was described using steady state and dynamic calculations and the insights obtained from these calculations were implemented in the current TSS-based PST model of Bachis et al. (2015). This was performed towards developing the University of Cape Town Primary Sedimentation Unit (UCTPSU). The influent raw wastewater TSS was fractionated into UPO, BPO and ISS fractions and settling proportions of these fractions were assigned to five settling velocity groups. In addition, a distinct settling velocity was assigned to each settling velocity group. Previous studies data from WRC (1984) and Ekama (2017), were used in the discrete particle settling model, which was able to reproduce PS and settled WW outputs, through steady state and dynamic calculations and under strict material mass balances. As a result, UPO, BPO and ISS settling proportions as well as settling velocities, were extracted from these calculations and used as input parameters into the UCTPSU model. This dynamic model was rigorously verified to be internally consistent with regards to strict material mass balances. The verification scenarios also included variations of high and low settling velocities as well as a combination of both high and low velocities and checking that the model was behaving as expected. The application and impact of the UCTPSU model were demonstrated using plant-wide scenarios in proposing a preliminary integration, under steady state conditions. It showed how incorrect disaggregation of the TSS into UPO, BPO and ISS fractions can lead to incorrect predictions in terms of the settled WW composition, the AS system capacity, the effluent quality, as well as the energy consumption and generation in the AS system and AD unit respectively. The investigation also revealed the need to measure key wastewater parameters such as particle settling velocities and the unbiodegradable particulate COD fraction, when it comes to realistically modelling of primary sedimentation of municipal wastewater, with the view of optimizing plant operations and tactical decision making. The study thereafter recommended the need to conduct an extensive experimental campaign to measure in-situ diurnal data, mainly in terms of settling velocities and settling proportions of UPO, BPO and ISS. It was also suggested to use the settleometer as a tool to extract these settling velocities and settling proportions, after performing biodegradability tests. As such, the data collected from the experimental campaign and the biodegradability tests could be used in calibrating the UCTPSU model and validation could be undertaken by means of full plant scale data.
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Chao, Tzu-Kai Kevin. "Temporal changes of shear wave velocity and anisotropy in the shallow crust induced by the 10/22/1999 m6.4 Chia-yi, Taiwan earthquake." Thesis, Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28088.
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Temporal changes of seismic velocity and anisotropy in the shallow crust are quantified using local earthquakes recorded at a 200-m-deep borehole station CHY in Taiwan. This station is located directly above the hypocenter of the 10/22/1999, M6.4 Chia-Yi earthquake. Three-component seismograms recorded at this station show clear direct (up-going) and surface-reflected (down-going) P- and S-waves, and S-wave splitting signals. The two-way travel times in the top 200 m is obtained by measuring the time delays between the up-going and down-going waves in the auto-correlation function. The S-wave travel times measured in two horizontal components increase by ~1-2% at the time of Chia-Yi main shock, and followed by a logarithmic recovery, while the temporal changes of S-wave splitting and P-wave are less than 1% and are not statistically significant. We obtain similar results by grouping earthquakes into clusters according to their locations and waveform similarities. This suggests that the observed temporal changes are not very sensitive to the seismic ray path below CHY, but are mostly controlled by the variation of material property in the top 200 m of the crust. We propose that strong ground motions of the Chia-Yi main shock cause transient openings of fluid-filled microcracks and increases the porosity in the near-surface layers, followed by a relatively long healing process. Because we observe no clear changes in the shear wave anisotropy, we infer that the co-seismic damages do not have a preferred orientation. Our results also show a gradual increase of time delays for both the fast and slow S-waves in the previous 7 years before the Chia-Yi main shock. Such changes might be caused by variations of water table, sediment packing or other surficial processes.
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SOARES, GEORGE ALVES. "INDUCTION MOTOR VELOCITY BY SUBSYNCHRONOUS CASCADE AND 6TH ORDER MODEL." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 1988. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=9841@1.
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O controle de velocidade do motor de indução do rotor
bobinado, através de uma cascata de conversores
estáticos
no rotor, conhecido como Sistema Kramer Estático, é
considerado um dos melhores acionamentos para motores
acima de 500 Hp, devido às suas características de baixo
custo inicial, menor complexidade do sistema de
conversores e regeneração de energia.
Nestas últimas décadas, as pesquisas nesta área se
concentraram basicamente na melhoria da estrutura dos
conversores estáticos, o projeto de controle recebeu
pouca
atenção e sua estrutura de controle continuava inspirada
no controle do motor de corrente contínua. Em um recente
trabalho (1987) foi proposto um controlador PI com
realimantação proporcional de corrente no elo c.c. .
Contudo, este projeto, como os outros, foram baseados em
uma modelagem simples.
Nesta dissertação de mestrado, revê-se e critica-se
modelagens e projetos de controle existentes, desenvolve-
se um modelo de 6ª ordem e propõe-se um projeto de
controle que atente às especificações usuais de
controle.
A estrutura proposta é composta de um regulador de
estado
mais um observador parcial de estado. Esta estrutura é
fisicamente realizável e o seu algoritmo de projeto é
simples, claro e direto. Comprova-se que o uso de
modelos
mais completos e estruturas de controle mais eficazes
não
implicam em controladores complexos e irrealizáveis.The speed control of wound rotor induction motor by a static converter cascade (Kramer Static System) is considered one of the best large motor drive (above 500 Hp.) due to its characteristics of low initial cost, less complexity of the converters and energy regeneration. In the last decades, the researches emphasize basicilly the improvement of the converter structure. The control design was almost forgotten and its structure was Kept based on the direct current motor control. In 1987, it was proposed a PI controller with proportional feedback of direct current. But, this last design, like the others, was based on a simple model. In this dissertation, the modellings and control designs are reviewed and criticized. Besides this, a sixth order model is developed and a new control design is proposed in order to solve the usual control requirements. This proposed structure is composed of a state regulator plus a partial state observer. It´s also of easy achievement and its design algolirhm is simple, easy and direct. It´s confirmed that the use of morepowerful control structure doesn´t implacate in complex and unfeasible controller.
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Al, Jailawi Samer Saadi Hussein. "Damage detection using angular velocity." Diss., University of Iowa, 2018. https://ir.uiowa.edu/etd/6539.
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The present work introduces novel methodologies for damage detection and health monitoring of structural and mechanical systems. The new approach uses the angular velocity inside different mathematical forms, via a gyroscope, to detect, locate, and relatively quantify damage. This new approach has been shown to outperform the current state-of-the-art acceleration-based approach in detecting damage on structures. Additionally, the current approach has been shown to be less sensitive to environmental acoustic noises, which present major challenges to the acceleration-based approaches. Furthermore, the current approach has been demonstrated to work effectively on arch structures, which acceleration-based approaches have struggled to deal with. The efficacy of the new approach has been investigated through multiple forms of structural damage indices.
The first methodology proposed a damage index that is based on the changes in the second spatial derivative (curvature) of the power spectral density (PSD) of the angular velocity during vibration. The proposed method is based on the output motion only and does not require information about the input forces/motions. The PSD of the angular velocity signal at different locations on structural beams was used to identify the frequencies where the beams show large magnitude of angular velocity. The curvature of the PSD of the angular velocity at these peak frequencies was then calculated. A damage index is presented that measures the differences between the PSD curvature of the angular velocity of a damaged structure and an artificial healthy baseline structure.
The second methodology proposed a damage index that is used to detect and locate damage on straight and curved beams. The approach introduces the transmissibility and coherence functions of the output angular velocity between two points on a structure where damage may occur to calculate a damage index as a metric of the changes in the dynamic integrity of the structure. The damage index considers limited-frequency bands of the transmissibility function at frequencies where the coherence is high. The efficacy of the proposed angular-velocity damage-detection approach as compared to the traditional linear-acceleration damage-detection approach was tested on straight and curved beams with different chord heights. Numerical results showed the effectiveness of the angular-velocity approach in detecting damage of multiple levels. It was observed that the magnitude of the damage index increased with the magnitude of damage, indicating the sensitivity of the proposed method to damage intensity. The results on straight and curved beams showed that the proposed approach is superior to the linear-acceleration-based approach, especially when dealing with curved beams with increasing chord heights. The experimental results showed that the damage index of the angular-velocity approach outweighed that of the acceleration approach by multiple levels in terms of detecting damage.
A third methodology for health-monitoring and updating of structure supports, which resemble bridges’ bearings, is introduced in this work. The proposed method models the resistance of the supports as rotational springs and uses the transmissibility and coherence functions of the output response of the angular velocity in the neighborhood of the bearings to detect changes in the support conditions. The proposed methodology generates a health-monitoring index that evaluates the level of deterioration in the support and a support-updating scheme to update the stiffness resistance of the supports. Numerical and experimental examples using beams with different support conditions are introduced to demonstrate the effectiveness of the proposed method. The results show that the proposed method detected changes in the state of the bearings and successfully updated the changes in the stiffness of the supports.
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Yu, Changpeng [Verfasser]. "Microseismic inversion for anisotropic velocity model in unconventional reservoirs / Changpeng Yu." Berlin : Freie Universität Berlin, 2016. http://d-nb.info/1108270921/34.
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Sexton, Paul. "3D velocity-depth model building using surface seismic and well data." Thesis, Durham University, 1998. http://etheses.dur.ac.uk/4824/.
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The objective of this work was to develop techniques that could be used to rapidly build a three-dimensional velocity-depth model of the subsurface, using the widest possible variety of data available from conventional seismic processing and allowing for moderate structural complexity. The result is a fully implemented inversion methodology that has been applied successfully to a large number of diverse case studies. A model-based inversion technique is presented and shown to be significantly more accurate than the analytical methods of velocity determination that dominate industrial practice. The inversion itself is based around two stages of ray-tracing. The first takes picked interpretations in migrated-time and maps them into depth using a hypothetical interval velocity field; the second checks the validity of this field by simulating fully the kinematics of seismic acquisition and processing as accurately as possible. Inconsistencies between the actual and the modelled data can then be used to update the interval velocity field using a conventional linear scheme. In order to produce a velocity-depth model that ties the wells, the inversion must include anisotropy. Moreover, a strong correlation between anisotropy and lithology is found. Unfortunately, surface seismic and well-tie data are not usually sufficient to uniquely resolve all the anisotropy parameters; however, the degree of non-uniqueness can be measured quantitatively by a resolution matrix which demonstrates that the model parameter trade-offs are highly dependent on the model and the seismic acquisition. The model parameters are further constrained by introducing well seismic traveltimes into the inversion. These introduce a greater range of propagation angles and reduce the non- uniqueness.
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Sirivolu, Dushyanth. "An Analytical Model for High-Velocity Impact of Composite Sandwich Panels." University of Akron / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=akron1227548412.
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Gang, Liu. "VERIFICATION OF SHEAR WAVE VELOCITY BASED LIQUEFACTION CRITERIA USING CENTRIFUGE MODEL." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1228274570.
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Lalander, Emilia, Paul Thomassen, and Mats Leijon. "Evaluation of a model for predicting the tidal velocity in fjord entrances." Uppsala universitet, Elektricitetslära, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-197317.
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Sufficiently accurate and low-cost estimation of tidal velocities is of importance when evaluating a potential site for a tidal energy farm. Here we suggest and evaluate a model to calculate the tidal velocity in fjord entrances. The model is compared with tidal velocities from Acoustic Doppler Current Profiler (ADCP) measurements in the tidal channel Skarpsundet in Norway. The calculated velocity value from the model corresponded well with the measured cross-sectional average velocity, but was shown to underestimate the velocity in the centre of the channel. The effect of this was quantified by calculating the kinetic energy of the flow for a 14-day period. A numerical simulation using TELEMAC-2D was performed and validated with ADCP measurements. Velocity data from the simulation was used as input for calculating the kinetic energy at various locations in the channel. It was concluded that the model presented here is not accurate enough for assessing the tidal energy resource. However, the simplicity of the model was considered promising in the use of finding sites where further analyses can be made.
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Abo, Abdulla. "A three-dimensional flow model for different cross-section high-velocity channels." Thesis, University of Plymouth, 2013. http://hdl.handle.net/10026.1/2852.
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High velocity channels are typically designed to discharge surplus water during severe flood events, and these types of flow are distinguished by high velocity, usually supercritical. A major challenge in high velocity channel design is to predict the free surface flow. Being able to predict the free surface flow profile beforehand can assist in selecting the best design for the channel as a whole. When the flow encounters a bridge pier, the streamline of the flow is separated and pressure may drop to a minimum; in contrast, velocity rises to its maximum value. As a result, cavitation damage may occur. The present study has used the computational fluid dynamics code ANSYS-CFX to investigate a full scale, three-dimensional engineering flow simulation of high velocity channels with different cross sections. The simulations were carried out on a high performance computing HPC cluster with 32 nodes. The code is based on the finite volume method and the Volume of Fluid (VOF) method was used to predict the position of the free surface profile. The impact of variation of the following parameters was investigated in terms of the free surface flow profile, both along the centreline and the wall of the channel: the minimum cavity index, and maximum shear stress on both bed and wall of the channel and on bridge pier; aspect ratio (channel bed width/flow depth), bed and side slopes of the channel, different discharges, which are represented by Froude numbers; the length and thickness of the bridge pier. First, the code sensitivity tools for convergence were examined. For this purpose, cases with different mesh sizes were examined and the best size chosen, depending on computation expense and convergence. Then, different turbulence models, such as the standard k-ε, RNG k-ε, and SST turbulence models were tested. The results show that the standard k-ε gives satisfactory results. Next, efforts were made to establish whether the flow achieved steady state conditions. This involved simulating two cases, one with steady state and the other with a transient state. Comparison of the two results shows that the flow properties do not change after three seconds and stay stable thereafter, so the flow can be considered as attaining a steady state. Finally, symmetry within the model geometry was tested, as this would allow a reduction in computation time, with only one side of the symmetrical model needing to be simulated. Two cases were investigated: firstly a simulation of only half of the channel geometry, and secondly a full geometry simulation. A comparison of the results of each case showed that the flow can be considered symmetrical along the centreline of the channel. Next, the code was validated against both numerical and experimental published results. For the free surface flow profile and velocity distribution the published experimental and numerical work of Stockstill (1996) was used; the ANSYS-CFX code results agree more closely with Stockstill’s experimental data than Stockstill’s numerical data. To test for shear stress distribution on the wall, uniform flow within a trapezoidal cross section channel was investigated and the results compared with those presented in the literature. The comparison shows good agreement between the ANSYS-CFX and published experimental works, for the predicted shear stress distributions on the walls and the bed of the channel. In total, sixty cases were simulated in order to investigate the impact of variations in the aforementioned parameters on maximum flow depth (both along the centreline and the wall of the channel) minimum cavity index, and maximum shear stress on both bed and wall of the channel and on bridge pier. Finally, non-dimensional curves are provided in addition to formulae derived from the data regression, which are intended to provide useful guidelines for designers.
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Sillanpää, Jussi. "Phenomenological model for electronic stopping of low-velocity ions in chrystalline solids." Helsinki : University of Helsinki, 2000. http://ethesis.helsinki.fi/julkaisut/mat/fysii/vk/sillanpaa/.
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Klüver, Tilman. "Velocity model building using analytic and model-based diffraction traveltime functions Geschwindigkeitsmodellbildung unter Benutzung analytischer und modellbasierter Diffraktionslaufzeitfunktionen /." [S.l. : s.n.], 2007. http://digbib.ubka.uni-karlsruhe.de/volltexte/1000006764.
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Buckingham, David 1962. "The developmental course of distance, time, and velocity concepts : a generative connectionist model." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=68076.
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Two sets of connectionist simulations of children's acquisition of distance (d), time (t), and velocity (v) concepts using a generative algorithm, cascade-correlation (Fahlman & Lebiere, 1990), are reported. Pure condition simulations represent a situation in which memory demands across the concepts are equal. The limited memory condition explores the effects of differing memory demands.It was found that the rules that correlated most highly with network responses during training were consistent with the developmental course of children's concepts (Wilkening, 1981; 1982). Networks integrated the defining dimensions of the concepts first by identity rules (e.g., v = d), then additive rules (e.g., v = d-t), and finally multiplicative rules (e.g., v = d $ div$ t).
The results are discussed in terms of similarity to children's development, the effects of memory demands, the contribution of connectionism to cognitive development, and directions for future research. It is argued that cascade-correlation provides an explicit mechanism of developmental change--weight adjustment and hidden unit recruitment.
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Cousins, David Bruce. "A model-based algorithm for environmentally adaptive bathymetry and sound velocity profile estimation /." View online ; access limited to URI, 2005. http://0-wwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186901.
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Styles, Julie M. "A wind tunnel study of the velocity field above a model plant canopy." [Canberra] : CSIRO Land and Water, 1997. http://nla.gov.au/nla.arc-13482.
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Thesis (B.Sc. (Honours)) - Australian National University, 1997.Title from title screen (viewed on May 20, 2002). "A thesis submitted in partial fulfilment of the requirements for the Degree of Bachelor of Science (Honours)"--Title screen. Bibliography: p. 64-66. Available full text via the internet.
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Savage, Jonathan A. "Assessment of Hybrid Coordinate Model velocity fields during Agulhas Return Current 2012 cruise." Monterey, California: Naval Postgraduate School, 2013. http://hdl.handle.net/10945/34738.
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Approved for public release; distribution is unlimitedPerformance of the Navys latest operational ocean forecast model (the Hybrid Coordinate Model, HYCOM, which became operational in March 2013) is systematically evaluated by comparing its velocity fields with actual ADCP velocities collected during a two-week cruise in the Agulhas Return Current region in 2012 (ARC 12). This chaotic region is complex and highly variable, with velocities sometimes exceeding 200 cm/s. Assessment using in-situ velocity measurements is very rare. This analysis characterizes the uncertainty in the model output and its predictions that Undersea Warfare operators, as well as other warfighters, obtain from the HYCOM output, and use in real world operations. Qualitative comparisons show good placement by HYCOM of persistent and energetic ocean current and eddy features, but difficulty (as expected, because HYCOM cannot resolve features finer than eddy scale) resolving the finer-scale variability present in the chaotic ARC region. Quantitative comparisons showed that the overall Root Mean Squared Error (RSME) is 35 cm/s and 47 near-surface, and 17 cm/s and 32 at 500 m depth, showing a general decrease of RMSE with depth.
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Vincent, Carolynn E. (Carolynn Elizabeth) 1976. "Earthquake location using a 3D velocity model : an example in Sichuan Province, China." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/59092.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 2000.Includes bibliographical references (leaves 50-52).
We investigate the benefits of applying three-dimensional velocity models to seismic event location. We develop a technique for three-dimensional seismic event location, utilizing a finite difference method for travel time calculation and a grid search method for location. We apply this technique to the location of three events in Sichuan Province, China, an area of complex deformation and scattered seismicity. The lateral differences between published event locations and those obtained using this three dimensional technique are between 6.2 and 12.8 km, suggesting that the relocation of a larger number of events may refine our understanding of deformation in this region. The locations using the three-dimensional velocity model compare favorably with locations using a one-dimensional model, returning location depths consistent with the geology of the area and showing smaller location variability when using a jackknifing technique.
by Carolynn E. Vincent.
S.M.
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Augusto, Fabio Lekecinskas. "An improvement on the gas transfer velocity model with application to scatterometer data." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/21/21135/tde-07102015-143819/.
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The increase of carbon dioxide in the atmosphere observed in recent decades is causing the acidification of the oceans besides the global warming. The amount of carbon dioxide that crosses the air-sea interface is not well known because this amount depends upon the partial pressure of carbon dioxide and the gas transfer velocity. The gas transfer velocity is a variable based on Fick\'s Law of Diffusion and is normally parametrized as a function of wind velocity at the height of 10 meters. However, the result of this parametrization have errors greater than 100%. Newer parametrization include the effects of temperature, friction velocity and the presence of surface waves. Based on the simplest model of air-sea gas transfer model, the stagnant film theory, this study developed a methodology to improve the knowledge of the relation between the gas transfer velocity and the mean square slope. This variable accounts for the mean curvature of the waves in the surface. The data used was gathered within the scope of the DOGEE project in 2007. In that, a drifting buoy measured several parameters relative to the waves and the gas transfer velocity. The results show that the mean square slope calculated with waves whose wavenumber is between 40 and 50 radians per meter has the lowest root mean square errors of the regression between the mean square slope and the gas transfer velocity. This result showed to be very consistent when applied to the QuikSCAT scatterometer data and compared to a recent published study.O aumento da concentração de dióxido de carbono na atmosfera observado nas últimas décadas é responsável por alterações climáticas e ambientais em escala global. Uma das consequências desse aumento da concentração de gás carbônico é o aquecimento global. Outra consequência é a acidificação dos oceanos. Isto ocorre devido ao dióxido de carbono atravessar a interface ar-mar e se dissolver no oceano. A quantidade de dióxido de carbono que atravessa a interface ar-mar é um dado não conhecido com precisão devido a esta quantidade depender de uma constante conhecida por velocidade de transferência do gás carbônico. Esta velocidade de transferência é normalmente uma parametrização do transporte turbulento do gás na interface oceano-atmosfera. Como o dado mais comum para essa parametrização é o vento à altura de 10 metros, muitos estudos foram desenvolvidos utilizando esta variável. No entanto, os resultados destas parametrizações possuem erros da ordem de 100%. Este estudo desenvolveu uma metodologia para obter uma melhor estimativa da velocidade de transferência. Para isto, optou-se por relacionar esta variável à inclinação quadrática média (MSS) das ondas. Segundo a literatura científica recente, o MSS é uma variável mais relacionada à transferência gasosa do que o vento a 10 metros de altura. Os resultados mostram que a inclinação quadrática média calculado com números de onda entre 40 e 50 radianos por metro possuem o menor erro no ajuste linear com os dados de velocidade de transferência. Este resultado indica uma mudança da dinâmica da interface nesse intervalo de número de onda. Com isso, um novo ajuste linear entre o MSS e a velocidade de transferência é sugerido como parametrização. A aplicação desta nova parametrização a dados de satélite do tipo escaterômetro mostrou-se consistente quando comparado a um estudo recente relacionando a velocidade de transferência do gás carbônico diretamente a dados do satélite oceanográfico QuikSCAT.
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Beale, Jacob N. "Local Earthquake Tomography at Mt. Pinatubo, Philippines." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/34635.
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A new high-resolution 3-dimensional P-wave velocity model for Mt. Pinatubo volcano was developed by tomographic inversion of P-wave arrivals from 3,007 earthquakes recorded during a four month period from May to August, 1991. The arrivals were recorded by a network of seismic stations, consisting of seven pre-eruption stations and seven post-eruption stations. Two stations survived the June eruptions. First-arrival travel times were calculated using a finite-difference solution to the eikonal equation. An iterative, linearized approximation of the nonlinear tomography problem was used to solve separately for both velocity structure and hypocenter locations. Several inversions performed with different initial parameters and convergence schemes, and synthetic checkerboard reconstructions indicate a horizontal spatial resolution of velocity perturbations near 4 km. However, the network sparseness allows for a substantial trade-off between focal depth, origin time, and the vertical velocity profile. Many hypocenter clusters collapse from diffuse clouds into tighter features after 3-D relocation. These bands of earthquakes appear to represent fault-related structures. Three low-velocity (relative to the horizontal average) anomalies exist within the well-resolved portion of the velocity model. These anomalies are spatially associated with pre- and post-eruption earthquakes oriented along mapped surface fault zones. Similar anomalies observed at different volcanoes have been previously interpreted as magma related. The low-velocity anomalies at Pinatubo are interpreted as highly fractured, hot volumes of mostly competent rock, which may contain partial melt.Master of Science
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Pandey, Shantanu [Verfasser]. "High resolution 3D Rayleigh wave velocity model of China and surrounding area / Shantanu Pandey." Berlin : Freie Universität Berlin, 2013. http://d-nb.info/1031100822/34.
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Pasquale, Daniel L. (Daniel Louis). "Characterizing drag and velocity within model mangrove forests of ordered and random tree arrangement." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111525.
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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 50).
Changes in velocity and drag force on model mangrove trees within 13 different simulated mangrove forest segments in a flume were investigated. The simulated forests were composed of 1/12 scale model Rhizophora mangrove trees placed at three densities: low (3.42 trees/m²), medium (6.34 trees/m²), and high (9.27 trees/m²). For the low tree density cases, one forest with ordered tree placement and six forests with random tree placement were studied. For the medium and high tree density cases, one ordered tree arrangement and two random tree arrangements were studied. Spatial arrangements of the forests were described using the mean distance to nearest neighbor (NN) for all trees in a particular forest. The forest arrangements were also described using the spatial aggregation index developed by Clark and Evans. [9] For forests of ordered tree arrangement, depth-averaged velocity was found to decrease from the leading edge to the trailing edge of the forest segment at each density, and the reduction in velocity moving through the forest was greater for denser forests. Vertical profiles of velocity show that a region of high velocity developed above the root zone when moving from the leading edge to the trailing edge of the forest. This effect was more pronounced in the forests with random tree arrangement and low mean NN distance. For all spatial arrangements, the drag force acting on an individual tree decreased from the leading edge to the trailing edge of the forest. Larger decreases in drag force occurred within denser forests. Mangrove tree drag coefficient values were found to be similar or slightly higher for trees within forests of random arrangement compared to trees within forests of ordered arrangement, but further study examining a greater amount of random tree arrangements is needed. This study describes changes in the vulnerability of a mangrove forest that could occur if mangrove trees were removed from the forest by natural or human causes.
by Daniel L. Pasquale.
M. Eng.
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McWilliams, Steven P. "Tests of a New Model of Paclitaxel-Induced Neuropathy and the Effects of Paclitaxel on the Dorsal Root Ganglia." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc84251/.
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This study examined a new model of paclitaxel-induced neuropathic pain and the effects of systemic paclitaxel on the gap junction protein subunit Cx43 and potassium inwardly-rectifying channel Kir4.1 within the dorsal root ganglia. In the new neuropathic pain model, subplantar injections of paclitaxel resulted in decreased conduction velocities of A-beta fiber compound action potentials in the sciatic (5.9%) and tibial nerves (6.8%) as well as in M (10.6%) and H (10.2%) waves. By using repeated recordings it was found that following paclitaxel injection, conduction velocities in the contralateral plantar nerve increased (9.2%). Systemic injections of paclitaxel resulted in reduced Kir4.1 immunolabeling in the dorsal root ganglia compared to vehicle injections. This reduction was observed in total labeling (32.4%) as well as in areas of intense labeling (28.7%). Reductions in overall Cx43 immunolabeling (25%) and area (25%) following systemic paclitaxel injections were not statistically significant. The results of these studies suggest that subplantar injections of paclitaxel can result in reduced peripheral nerve conduction velocities. The results also show that a unilateral neuropathy can result in contralateral changes in conduction velocities. The effects of paclitaxel on reducing Kir4.1 levels suggest that neuropathic pain caused by paclitaxel may share mechanisms in common with other types of neuropathies which show similar changes in Kir4.1 levels.
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Fan, Taian. "Zero-Group-Velocity Propagation Of Electromagnetic Wave Through Nanomaterial." ScholarWorks @ UVM, 2016. https://scholarworks.uvm.edu/graddis/549.
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This research will investigate the problem on the propagation of electromagnetic wave through a specific nanomaterial. The nanomaterial analyzed is a material consisting of a field of Pt nanorods. This field of Pt nanorods are deposited on a substrate which consists of a RuO2 nano structure. When the nanorod is exposed to an electron beam emitted by a TEM (Transmission electron microscopy). A wave disturbance has been observed. A video taken within the chamber shows a wave with a speed in the scale of um/s (Á?10Á?^(-6) m/s), which is 14 orders of magnitude lower than speed of light in free space (approximate 3ÁÁ?10Á?^8 m/s ). A physical and mathematical model is developed to explain this phenomenon. Due to the process of fabrication, the geometry of the decorated Pt nanorod field is assumed to be approximately periodic. The nanomaterials possess properties similar to a photonic crystal. Pt, as a noble metal, shows dispersive behaviours that is different from those ones of a perfect or good conductors. A FDTD algorithm is implemented to calculate the band diagram of the nanomaterials. To explore the dispersive properties of the Pt nanorod field, the FDTD algorithm is corrected with a Drude Model. The analysis of the corrected band diagram illustrates that the group velocity of the wave packet propagating through the nanomaterial can be positive, negative or zero. The possible zero-group velocity is therefore used to explain the extremely low velocity of wave (wave envelope) detected in the TEM.
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Disotell, Kevin James. "A semi-empirical model of the wall-normal velocity induced by flow-shaping plasma actuators." Connect to resource, 2010. http://hdl.handle.net/1811/45413.
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Dougherty, Sara L. "Development of a 3-D upper crustal velocity model for the Goldstream Valley, central Alaska." Thesis, Boston College, 2008. http://hdl.handle.net/2345/352.
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The uppermost crustal velocity structure of the Goldstream Valley, central Alaska is investigated using a series of five explosions that were detonated in schist bedrock and recorded at >120 local stations to develop 1-D and 3-D models of the upper crust. Simple refraction analyses reveal that both P- and S-wave arrival times are azimuth dependent, with the fastest velocities in the southeast and northeast directions. The Swave velocity structure of the upper crust is also determined through multiple filter analysis and a damped, least squares inversion of 0.2-2 sec period Rg waves. The shear wave velocity model from the surface-wave analysis is combined with the refraction analysis results to develop 1-D P- and S-wave models to a depth of 2 km. In order to better constrain P- and S-wave velocity variations both laterally and with depth throughout the Goldstream Valley, 3-D velocity models are produced using a numerical simulation modelThesis (MS) — Boston College, 2008
Submitted to: Boston College. Graduate School of Arts and Sciences
Discipline: Geology and Geophysics
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Staley, Alan Joseph. "A Finite Difference Approach to Modeling High Velocity/Variable Loads using the Timoshenko Beam Model." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/76954.
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Electromagnetic launchers (railguns) are set to replace traditional large caliber ship mounted cannons in the near future. The success of the railgun depends heavily upon a comprehensive understanding of beam behavior during periods of heavy dynamic loading. It is hypothesized that the combination of velocity transition effects, electromagnetic loading, and other non-linear or design specific effects contribute to areas of high stresses/strains over the length of the rail/beam during launch.
This paper outlines the use of the Timoshenko beam model, a model which builds upon the traditional Bernoulli-Euler beam theory with the addition of shear deformation and rotary inertia effects, a necessity for high wave velocities. Real-world experimental setups are simplified and approximated by a series of linear springs and dampers for model prediction and validation.
The Timoshenko beam model is solved using finite difference (FD) methods for the approximation of spatial derivatives and MATLAB ordinary differential equation (ODE) solvers. The model shows good convergence and precision over a large range of system parameters including load velocities, foundation stiffness values, and beam dimensions. Comparison to experimental strain data has validated model accuracy to an acceptable level. Accuracy is further enhanced with the inclusion of damping and non-linear or piecewise effects used to mimic experimental observations. The MATLAB software package presents a valid preliminary analysis tool for railgun beam and foundation design while offering advantages in ease of use, computation time, and system requirements when compared to traditional FEA tools.Master of Science
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Loth, Francis. "Velocity and wall shear measurements inside a vascular graft model under steady and pulsatile flow conditions." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/15907.
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Tamrakar, Swaraj. "Analytical Model Study of Flow Through Trapezoidal, Half-Trapezoidal and Rectangular Channels with Submerged and Un-submerged Rigid Cylinders." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1380.
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For this study, two analytical models were developed for predicting the depth-averaged velocity distribution (U) in trapezoidal, half-trapezoidal and rectangular channels with submerged and unsubmerged rigid cylinders. The first model uses linear superposition of momentum defects (MDS) and mass conservation, and is referred to as the MDS model. The second model uses linear superposition of velocity defects (VDS) and mass conservation, and is referred to as the VDS model. For implementing either the VDS or MDS model, a criterion is required for considering the wake created by an individual cylinder to be fully dissipated (i.e., a cutoff criterion). Also, implementing the MDS model requires numerical integration. Analyses were conducted to identify suitable cutoff criterion and an appropriate subinterval size for the numerical integration. Data from a physical model study conducted in a flume with a half-trapezoidal channel section was used to calibrate and validate the models. Data from a physical model study conducted in a rectangular channel section was also used to validate the model. Predicted values of U from the VDS and MDS models were within the range of ± 20 % of the trapezoidal channel section validation data. The models failed to accurately predict U for the rectangular channel section data. It is concluded that the models developed herein should be used only for half-trapezoidal channel sections. With respect to the trapezoidal channel section validation data, the MDS model yields a sum of squared errors that is 36% less than that yielded by the VDS model. Therefore, the MDS model is regarded as the best model overall for computing U in half-trapezoidal channel sections.
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Carney, Brooke J. "Building Velocity Models for Steep-Dip Prestack Depth Migration through First Arrival Traveltime Tomography." Thesis, Virginia Tech, 2000. http://hdl.handle.net/10919/35941.
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Although the petroleum industry has imaged reflections from the sides of salt domes,
steeply dipping structures have not been imaged as reflectors outside of sedimentary
basins; to do so requires appropriate data acquisition, prestack depth migration, and an
excellent seismic velocity model. Poststack time migrated seismic images, normal
moveout velocity analysis, well logs, and other geologic information are used to build the
velocity model. In regions of interest outside of sedimentary basins, such as major strike-slip
faults, seismic reflectivity is often sparse and little is known of detailed subsurface
geology. Alternate methods of velocity model construction must be used. First arrival
(refraction and turning ray) traveltime tomography is proposed to construct the
preliminary velocity model for steep-dip prestack depth migration in settings with little a
priori subsurface information. A densely spaced synthetic seismic data set with long-offset
recording, modeled after a real survey across the San Andreas Fault, was
constructed using a finite-difference algorithm. First arrival traveltimes were picked
from the data and a velocity model was constructed using tomography. The velocity
model was used to perform a Kirchhoff prestack depth migration of the synthetic shot
gathers. The subsurface structure was sufficiently reconstructed that the velocity model
could be refined through migration velocity analysis. A series of tomography tests was
used to determine the spatial resolution limits of the velocity model. Isolated erroneous
anomalies with sizes near the resolution limits were added to the velocity model derived
from tomography and used as input for migration. This pessimistic test provided an
adequate image and identifiable arrivals in migrated common image gathers, allowing the
velocity model to be improved through migration moveout analysis. Data acquisition requirements for tomography include long recording offsets and times, larger sources, and dense spacings, very similar to the requirements for steep-dip reflection imaging.Master of Science
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Arlemark, Erik. "CFD model of fluid flow in reactor : A simulation of velocity and heat distribution in a channel." Thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-162581.
Full textAbstract:
The basic problem of operating a boiling water nuclear reactor (BWR) is that of maximizing the power output while avoiding fuel rod over-heating (dry-out). For the safe operation of BWRs this entails a detailed understanding of the flow of water and steam through the reactor core. In a BWR the water functions not only as a coolant, but also as a moderator for the neutrons emitted in the fission process. To describe the thermohydraulic properties of the reactor a number of parameters are of common interest. Examples of such parameters are void, pressure, temperature, water and steam velocities, pressure, sheer forces and turbulent kinetic energy. There are a few ways of revealing these values such as experiments built up to behave like a reactors and computer simulations using models based on the laws of fluid dynamics and thermodynamics. This research concerns a computer based model which uses a continuous fluid dynamic, (CFD), calculation program called OpenFOAM (Open Field Operation and Manipulation). OpenFOAM uses Navier Stokes equations for continuity, momentum- and energy conservation to simulate flows. The method used in this research has been to first build a model which describes the adiabatic flow correctly by using an already existing solver which uses the continuity and momentum conservation laws. In order to achieve a model that can solve temperature distributions in the flow the energy equation is added to the program coding in OpenFOAM. There are totally 12 turbulence models. Some of the models have not produced results on account of that they either diverged or needed input that was not attainable. The models which were tested and used were four k -ε models, one RSTM model and two low-Re models. A question that is addressed in this report is which of the many turbulence models that describes the experimental flow most correctly. The low-Re model LienLeschzinerLowRe produces the results with best congruence to the experimental data. The k -ε models model RNGkEpsilon and the RSTM model LRR were also fairly close. It is found that there are a few turbulence models that describe the experimental flows sufficiently well. LaunderSharmaKe was the turbulence model which simulated the temperature distribution best and was almost within the error bar limit of 5 K in all of the plots. It is interesting that the two low-Re models show the best results if only one characteristic at the time is studied. One of the turbulence models describes only the velocity profile well and the other one oppositely describes the temperature distribution the best. It can thereby be stated that if the user wants a turbulence model that describes both velocity profiles and temperature distribution the RSTM model LRR is the best one. If on the other hand computer capacity is a limiting factor it might be profitable to use the simpler k -ε model RNGkEpsilon. An other conclusions of this thesis is that the LRR and RNGkepsilon models are suited for the simulations of the geometries described in this work provided that the channel is wide enough for the model to simulate a correct temperature profile. With the use of gmsh a case geometry with wider channel area could easily be created. It would of course be necessary to use experimental data to validate the assumption that more realistic results can be obtained on wider channels.
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Thompson, Thomas L. "Velocity measurements near the blade tip and in the tip vortex core of a hovering model rotor." Diss., Georgia Institute of Technology, 1986. http://hdl.handle.net/1853/13003.
Full text
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Cotton, John Rowland. "A viscoelastic model for the response of a step change in velocity of the human otolith organs." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/44113.
Full textAbstract:
The otolith organs are housed in the inner ear and are responsible for sensing accelerations
and gravity. These inertial sensing systems are modeled in this thesis as a three
material system consisting of a rigid otoconial plate attached to the skull by a gel layer, surrounded
by a viscous endolymph fluid. The gel layer is considered to be a viscoelastic solid,
and modeled as a simple Kelvin element. The governing differential equations are derived
and nondimensionalized, yielding three nondimensional parameters: nondimensional density,
R, nondimensional viscosity, M, and nondimensional elasticity, 6. The equations are
solved using uÌ nite difference techniques on a digital computer. By comparing the modelâ s
response with previous biological research, values for the nondimensional parameters are
found. The value of R is 0.75 and the value of 6 is between 0.3 and 0.075. While the value
of M is placed between 5. and 10., results indicate that to properly model the long time
response of the otolith, a single and constant value for viscosity is not feasible.Master of Science
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Rapp, Travis J. (Travis Joseph). "Resilient acquisition : unlocking high-velocity learning with model-based engineering to deliver capability to the fleet faster." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122610.
Full textAbstract:
Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Thesis: S.M. in Engineering and Management, Massachusetts Institute of Technology, System Design and Management Program, 2019
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 161-165).
As the nation's security needs call for a growing naval fleet, the public-private industrial base for construction and weapon system acquisition will be stressed to perform at a high level of operational excellence. While reaching the required fleet size is a major challenge, ships are the delivery vehicles for complex weapons systems whose design and production is equally critical to deliver capability that the Fleet needs. Underperformance in defense acquisitions is found to be caused by complexity, uncertainty, and risk manifested through poor requirements that are unadaptable to the changing reality of the global security landscape. This thesis hypothesizes that use of model-based engineering (MBE) will enable the needed efficiency and responsiveness.
MBE consists of digital tools motivated by the principles of traceability and high-velocity design iteration that collectively connect requirements to technical specifications in a model-centric format in contrast to the document-based form prevalent today. Given the problem of disengagement between the request for proposal and the finished product, prior case examples of using MBE elsewhere in the defense and industrial establishment show a bridge for the divide between capability requirements and technical realization. An original process-based shipbuilding production model further demonstrates how understanding effects of component changes affects overall system production. Changes in a ship's required operational capabilities, translated to technical design parameters, are mapped to production steps. The simulated performance is compared across three successive stages of construction when the change is ordered.
Results of model simulations demonstrate that similar MBE applications contribute to increased early requirement fidelity, decreases in rework through missed changes, and more rapid design iteration when the models used are properly verified and validated. Verification and validation (V&V) must be performed in a very specific environment to engender confidence in model usage through a systemic framework. One method of V&V, System Theoretic Process Analysis for Security, is illustrated using an original concept illustration of a Fictional Submarine Strategic Missile. The domain of MBE is expanded to include definition of cybersecurity requirements for a new weapon system to illustrate an iteration of model-based system design. The modeling of these requirements contributes to validated resilience upon delivery, decreasing the likelihood that cyber-physical systems will be forced to rely on time-consuming updates that delay the capability delivery.
by Travis J. Rapp.
Nav. E.
S.M. in Engineering and Management
Nav.E. Massachusetts Institute of Technology, Department of Mechanical Engineering
S.M.inEngineeringandManagement Massachusetts Institute of Technology, System Design and Management Program
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Kelly, Annabel. "The crustal velocity and density structure of Northwest Europe : a 3D model and its implications for isostasy." Thesis, University of Leicester, 2005. http://hdl.handle.net/2381/30458.
Full textAbstract:
A new seismic P-wave velocity model has been constructed for a region of northwest Europe encompassing Britain, Ireland and the surrounding marine sedimentary basins. This model has considerably higher resolution than previously published velocity models for the region and is unique in being quantitatively constrained. The velocity model provides a tool for future work in seismology, allowing crustal correction for teleseismic arrivals recorded in Britain and Ireland, refined local earthquake location and provides a starting model for local and regional seismic tomography. The velocity model has been developed in conjunction with a crustal density model. The new models indicate that: the mean crustal velocity and density are related to the near-surface geology; the near-surface velocity is well correlated with the near-surface geology; there may be a regional trend from high velocity crust near the northwest continental margin to lower velocity crust under continental Europe; there may be a weak trend of increasing density with increasing crustal thickness; and that the crustal structure beneath the sedimentary basin varies from basin to basin. In addition to the geological interpretation, the density model has been used to investigate isostasy in the region using a newly developed method for estimating the elastic thickness of the lithosphere. This approach uses the relationship between the predicted height of topography for local isostatic equilibrium and the true topography to estimate the degree of compensation, which is in turn related to the elastic thickness. However, the results of this investigation are inconsistent across the different wavelengths tested and so the elastic thickness is resolved with less constraint than the range in published values for the region.