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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.
191

Wintering population estimates and microplastics prevalence for tidal marsh birds of Mississippi

Weitzel, Spencer 25 November 2020 (has links)
Due to the global loss of tidal marsh area, potential anthropogenic and natural disturbances to these systems, and coastal marshes’ affinity for trapping environmental pollutants, understanding how marsh birds inhabiting these ecosystems will adapt to these changes is paramount. To quantify future changes, I first needed to have something to compare against – baseline estimates. To this end, I performed distance sampling line transect surveys during the nonbreeding season to estimate species-specific population abundance, density, and habitat associations and captured two species of marsh bird, Clapper Rail (Rallus crepitans) and Seaside Sparrow (Ammospiza maritima), to estimate baseline ingestion of one such environmental pollutant – microplastics. By providing the first baseline population and density estimates for numerous nonbreeding marsh birds, my findings suggest that the tidal marshes of Mississippi provide critical habitat for many of these species. Additionally, I was able to document the first evidence of microplastic ingestion by resident tidal marsh birds.
192

Parameter estimation in tidally influenced numerical models:determination of an appropriate objective function

Tate, Jennifer N 09 August 2008 (has links)
The research detailed in this study focuses on the determination of an appropriate objective function to aid parameter estimation when simulating areas influenced by tidally varying flows. Three objective functions that are measures of how well the model results match field data at several locations and times were tested. A set of test cases is developed to represent tidally influenced systems and allow for the testing of the objective functions. These objective functions were tested by computing their values and comparing them for the various estimated parameters. Based on results of the first method of testing a further analysis was performed using PEST, an automatic parameter estimation tool. A weighted least squares of the velocity and water surface values with a weight function on the velocity term based on the shallow water equations is found to be a reasonable objective function at this point in the research.
193

Stellar Death in the Nearby Universe

Holoien, Thomas Warren-Son 27 October 2017 (has links)
No description available.
194

Augmented Tidal Resonant System: Design for Uninterrupted Power Generation

Moreira, Tulio Marcondes 23 May 2016 (has links)
No description available.
195

Design and Evaluation of a Novel Method to Noninvasively Estimate Tidal Volumes During Administration of Nasal Cannula Therapy

Mollica, Hunter Thomas 02 January 2024 (has links)
Administration of nasal cannula therapy tasks providers with periodically monitoring their patients and adjusting settings according to patient needs. Conventionally, providers monitor a patient's oxygen demand using pulse oximetry and a qualitative assessment of the patient's work of breathing. The motivation for this research is to augment the traditional qualitative assessment of work of breathing with a quantitative measurement of a patient's tidal volume, the volume of air inhaled with each breath. This thesis presents a novel approach to measure tidal volume using a nasal cannula with built-in pressure sensors. Pressure waveforms obtained from continuous measurement of the pressure at the tip of the cannula are used to estimate nasal flowrates, and these nasal flowrates are time-integrated to estimate tidal volumes. Computational fluid dynamics (CFD) models were used to simulate fluid flow in a simplified nasal passage undergoing nasal cannula therapy. These simulations used a range of flow conditions characteristic of both low-flow and high-flow nasal cannula treatments. The simulations produced a transformation from cannula tip pressure to instantaneous nasal flowrate, and this transformation was evaluated using a matching empirical experiment. This empirical experiment used a matching physical geometry with a similar range of flow conditions, and the transformation obtained from CFD was able to estimate the actual tidal volumes with 85% accuracy. This study showed that continuous pressure measurement at the tip of a nasal cannula produces enough information to estimate nasal flowrates and tidal volumes. No similar studies were found during the literature review, so an accuracy of 85% is promising for this stage. If this technique could be made more accurate and deployed in an unobtrusive way, the resulting nasal cannula device could be used to continuously, comfortably monitor patients' tidal volumes. / Master of Science / Oxygen therapy is the most common prescription in hospitals across the United States, and the most common form of oxygen therapy is nasal cannula therapy. Administration of nasal cannula therapy requires providers to periodically assess their patients' oxygen saturations and work of breathing. Oxygen saturation can be quantitatively monitored using pulse oximetry but work of breathing must be qualitatively monitored using visual exams or walking tests. The motivation of this research is to augment this qualitative assessment with a quantitative metric. In our research, we chose the volume of inhaled air (the "tidal volume") as a proxy metric for a patient's work of breathing. This thesis presents our attempt to use a nasal cannula augmented with pressure sensors to estimate the tidal volume of a mannequin undergoing nasal cannula therapy. Our concept is that more intense inhalations/exhalations produce larger pressure swings at the tip of the nasal cannula. For this proof-of-concept study, a simplified nasal passage geometry was used. Pressure waveforms obtained from continuous measurement of the pressure at the tip of the cannula are used to estimate nasal flowrates, and these nasal flowrates are time-integrated to estimate tidal volumes. Computational fluid dynamics (CFD) simulations were used to predict how the cannula tip pressure changes as a function of nasal flowrates and cannula flowrates, then this relationship was tested using a matching empirical experiment. This matching empirical experiment showed that our technique of estimating tidal volumes was 85% accurate. This study showed that continuous pressure measurement at the tip of a nasal cannula produces enough information to estimate nasal flowrates and tidal volumes. No similar studies were found during the literature review, so an accuracy of 85% is promising for this stage. If this technique could be made more accurate and deployed in an unobtrusive way, the resulting nasal cannula device could be used to continuously, comfortably monitor patients' tidal volumes.
196

Flow structures in wake of a pile-supported horizontal axis tidal stream turbine

Zhang, J., Lin, X., Wang, R., Guo, Yakun, Zhang, C., Zhang, Y. 12 May 2020 (has links)
Yes / This study presents results from laboratory experiments to investigate the wake structure in the lee side of a scaled three-bladed horizontal axis tidal stream turbine with a mono-pile support structure. Experiments are conducted for a range of approaching flow velocity and installation height of rotor. Analysis of the results shows that bed shear stress increases with the increase of approaching velocity and decrease of installation height within 2D (D is the diameter of the rotor) downstream of the rotor. The flow field within 2D downstream of the rotor is greatly influenced by the presence of nacelle and mono-pile. Low stream-wise flow velocity and large turbulence intensity level is detected along the flume center right behind the nacelle and mono-pile from 1D to 2D downstream of the rotor. Stream-wise velocity at the blade tip height lower than the nacelle increases sharply from 1D to 2D and gradually grows afterwards. Correspondingly, the turbulence intensity decreases quickly from 1D to 2D and slowly afterwards. Large bed shear stress is measured from 1D to 2D, which is closely related to turbulence induced by the mono-pile. It is also found that the presence of the mono-pile might make the flow field more ‘disc-shaped’. / National Key Research and Development Program of China (No.2017YFC1404200), the Marine Renewable Energy Research Project of State Oceanic Administration (No.GHME2015GC01), the Fundamental Research Funds for the Central Universities of China (No.2017B696X14) and the Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (No.KYCX17_0448)
197

Applications for Assessing Sediment Sources in Back-Barrier Systems

Ladlow, Caroline 29 October 2019 (has links) (PDF)
In order to improve our understanding of present and future coastal environmental change, we look into the past using sediment that accumulates in coastal environments. We have done this for two disparate systems: a back-barrier lagoon in southwestern Japan, and freshwater tidal marshes along the Hudson River, New York, USA. In Japan, we used a 2,500-year sediment record to investigate coastal flood risk from tsunamis and typhoons. This is a critical area of study to better understand the spatial and temporal variability of these hazards in Japan. In the Hudson River we looked at modern (since 1800) deposition of sediment in anthropogenically constructed embayments that have formed tidal wetlands in the last few centuries. A better understanding of the factors that have attributed to these successful tidal marsh systems in the past can help inform future management decisions in the face of future sea level rise. Studying the history of coastal systems using the sediment record is a valuable tool for assessing hazard risk and habitat loss in the present and future.
198

Tidal gravity anomalies in southeastern North America

Holland, Dwight Allen January 1986 (has links)
Tidal variations of gravity were measured at fourteen sites in southeastern North America for periods of between 40 and 199 days. These measurements were used to obtain tidal gravity anomalies that indicate the geologic effect of the earth on tidal gravity. The tidal gravity anomaly is a vector quantity representing the difference between measured tidal gravity and the theoretical tidal gravity on a spherically symmetrical earth model subject to ocean tidal loading. The real part of the anomaly vectors include 8 values in the range of ±0.5 microgals, 4 values in the range of 0.5 to 1.5 microgals, 1 value of 1.5 to 2.5 microgals, and 1 other value in the range of -0.5 to -1.5 microgals, This grouping is consistent with a worldwide distribution of values from regions where the asthenosphere is at intermediate depth, the stress conditions are not excessive, and geothermal heat flow is approximately 60 mW/m². / Master of Science
199

Impact des hétérogénéités sédimentaires sur le stockage géologique du CO2

Issautier, Benoit 20 December 2011 (has links)
La démarche d’intégration des hétérogénéités dans les modèles réservoirs en est à ses prémices dans le domaine du stockage géologique de CO2. C’est dans ce contexte que s’inscrivent ces travaux de thèse. Un protocole d’analyse depuis l’étude de terrain jusqu’aux simulations réservoirs a été établi. La caractérisation du Minjur Sandstone (formation Triasique d’Arabie Centrale) met en avant le caractère crucial de la connectivité des corps dans l’architecture du réservoir, notamment en liant génétiquement leur nature, leur connectivité et leur position dans la séquence de dépôt. S’appuyant sur la connaissance de cette formation, un modèle conceptuel est construit, puis reproduit stochastiquement par un algorithme permettant l’élaboration de modèles conditionnés par une histoire sédimentaire. Le protocole prévoit la création de 50 scénarios illustrant divers degrés de connectivité ; chaque scénario étant composé de deux modèles de même architecture mais à remplissage sédimentaire différent. Cette approche permet d’appréhender (a) l’impact de la connectivité et (b) des hétérogénéités sédimentaires sur les performances réservoirs. L’estimation de capacité par l’approche statique des volumes disponibles estime une capacité moyenne d’environ 13Mt (aquifère semi-infini de 25 km par 25 km et 60m d’épaisseur à 1000 m de profondeur). Les hétérogénéités internes (sédiments argileux appelés oxbow lakes) entraînent une différence de capacité de 30%. Les simulations dynamiques confirment ces résultats et révèle une variabilité de capacité de 23% liée la connectivité des corps. De plus les hétérogénéités réduisent la migration verticale du gaz ce qui peut augmenter l’intégrité du stockage. / In the CO2 storage context, heterogeneity has only been rarely considered in reservoir models to date. To address this key issue, the project aims at developing a workflow that manages the heterogeneity from the field observations up to the reservoir simulation. The characterisation of the Minjur Sandstone (a Triassic formation from Central Saudi Arabia) shows the crucial role of connectivity in the reservoir architecture, and the genetic link between the nature, location and connectivity of the sedimentary bodies in the sequence. Stemming from this study, a conceptual model was established and stochastically reproduced through an algorithm simulating models conditioned to a sedimentary history. Fifty scenarios were simulated, representing various connectivity degrees. Each of these scenarios is composed of two models, identical by their architecture but different in their internal sedimentary fill. This approach allows the study of the impact of the (a) reservoir bodies’ connectivity and (b) their internal sedimentary heterogeneity on the reservoir’s performances. The capacity estimates using a static calculation based on the available pore volumes reveals a mean capacity of 13 Mt (for a 25 x 25 km x 60 m semi finite aquifer at 1000m deep). The sedimentary heterogeneity (shaly deposits called oxbow lakes) is responsible for a 30% difference of capacity. The flow simulations confirm these results and show that the connectivity of the reservoir bodies creates a 23% capacity variation. Moreover, the heterogeneities tend to reduce the amount of CO2 able to reach the uppermost reservoir which may enhance the storage integrity.
200

Influência do uso de fita nasal na capacidade e função respiratória de equinos da raça Árabe durante e após o exercício / Influence of the nasal strips on respiratory capacity and function of Arabian horses during and after exercise

Oliveira, Tiago Marcelo 13 November 2015 (has links)
A fita nasal é amplamente utilizada em equinos durante o exercício, porém seus resultados são controversos e pouco conhecidos em animais que disputam provas de resistência. Os objetivos desse trabalho foram verificar se o uso da fita nasal influencia parâmetros durante o exercício predominantemente aeróbico, como frequência respiratória, volume tidal, volume minuto, tempos de inspiração e expiração, população de células por meio de lavado broncoalveolar, frequência cardíaca e lactato sanguíneo. Foram utilizados seis equinos da raça Árabe que realizaram dois testes de longa duração em esteira, sendo um teste com fita e outro sem a fita nasal. Durante os testes eram realizadas coletas de sangue, espirometria com obtenção de curvas de fluxo e volume respiratório, e registro da frequência cardíaca por meio de frequencímetro. Duas horas após o término do exercício foi realizado lavado broncoalveolar para realização de citologia da secreção pulmonar. Não houveram diferenças entre os parâmetros ventilatórios analisados entre os animais quando correram com ou sem a fita nasal. Entretanto, a frequência cardíaca foi em média menor durante o exercício nos animais que se exercitaram com a fita nasal (p<0,05), podendo indicar uma melhor oferta de oxigênio durante o exercício de longa duração com o uso da fita nasal, apesar de não encontrarmos alterações nos parâmetros de fluxo e volume respiratório. Na avaliação citológica do conteúdo do lavado broncoalveolar, foi verificada maior porcentagem de neutrófilos após o exercício nos animais que se exercitaram com a fita nasal (p<0,05), indicando que o turbilhonamento na passagem do ar através da cavidade nasal pode ter diminuído permitindo que partículas maiores se depositassem em porções mais distais do sistema respiratório, induzindo uma resposta neutrofílica mais intensa. O uso da fita nasal parece influenciar alguns parâmetros durante e após o exercício em animais que realizam provas de longa duração. Outros estudos devem ser realizados para verificar se essa influência pode melhorar o desempenho desses animais em exercícios predominantemente aeróbicos / The nasal strip is widely used in horses during exercise, but the results are controversial and little known in animals that compete for endurance events. The aim of this study was to determine whether the use of nasal strips influence parameters during predominantly aerobic exercise, such as respiratory frequency, tidal volume, minute ventilation, inspiratory and expiratory times, population of cells by bronchoalveolar lavage, heart rate and blood lactate. Six Arabian horses were submitted to two low intensity tests on a treadmill, one of them with nasal strip and one without nasal strip. During the tests were carried out blood samples, airflow and volume curves with spirometry mask, and heart rate was recorded through heart rate monitor. Two hours after the exercise was performed bronchoalveolar lavage to perform cytology of pulmonary secretions. There were no differences among ventilatory parameters analyzed when the horses performed the exercise with or without the nasal strip. However, heart rate was lower on average during the exercise when the horses were exercised with nasal strip (p <0.05), which may indicate a better supply of oxygen during the low intensity exercise with the use of nasal strip, despite we did not find changes in the airflow and respiratory volume parameters. In cytological evaluation of the content of bronchoalveolar lavage, increased percentage of neutrophils was observed after exercise in animals with nasal strip (p <0.05), indicating that turbulence in the airflow through the nasal cavity may have diminished allowing larger particles to be deposited in distal portions of the respiratory system, inducing a more intense neutrophilic response. The use of nasal strips appears to influence some parameters during and after exercise in horses that perform low intensity and endurance tests. Further studies should be conducted to verify that this influence can improve the performance of these horses in predominantly aerobic exercises

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