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Danús, del Pedregal Sebastián Ignacio. "Comportamiento del modelo Weap en la cuenca alta del río Cachapoal, Chile, usando forzantes meteorológicas distribuidas." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/167866.
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Ingeniero CivilHoy en día la mayor incertidumbre en la estimación de caudales en cuencas de montaña en Chile corresponde a la escasez de información de las variables meteorológicas en altura. El procedimiento tradicional para estimar las forzantes meteorológicas se basa en la determinación de gradientes definidos a base de estaciones que se ubican a cotas que en general no superan los 1500 m.s.n.m. Actualmente, se dispone de antecedentes satelitales y modelos de reanálisis atmosférico que han permitido extrapolar los datos observados de precipitación diaria y temperatura máxima y mínima diaria para todo Chile, como datos grillados en celdas de 0.05° por 0.05°. De esta manera, se estima que es posible cuantificar con menor incertidumbre la serie temporal diaria de las variables señaladas. Este trabajo de título busca la actualización de un modelo hidrológico (WEAP) en la cuenca alta del río Cachapoal, utilizando un set de datos de forzantes meteorológicas distribuidas. La metodología consideró el análisis de las URH ya definidas y la modificación de las series de tiempo utilizadas para la calibración del modelo WEAP previamente implementado en la parte alta de la cuenca. De esta forma se comparan los valores simulados de las variables de salida del modelo, tanto con las observaciones disponibles como con las previamente simuladas. También se estudia la representatividad de los valores de la grilla usando el inverso de la distancia como método de escalamiento. La implementación del modelo supuso re-calibrar los parámetros según las diferencias de las series de precipitación y temperatura con las previamente estimadas, dándose los contrastes más marcados en los meses de invierno. Al evaluar la eficiencia de la calibración a nivel diario se obtuvieron índices de Nash-Sutcliffe y Nash-Sutcliffe logarítmico mayores a 0.71 y 0.73, respectivamente, para todos los sistemas modelados (Las Leñas, Cortaderal, Cachapoal en 5 km bajo Cortaderal). Al comparar la simulación con la calibración antigua se constata de una mejor representación de los caudales altos y bajos de la cuenca, al menos en Las Leñas y el sistema completo. La calibración del modelo en Cortaderal supuso mayores dificultades al presentar en promedio las temperaturas más bajas y precipitaciones más altas. Analizando los valores distribuidos se percató de un aumento de la incertidumbre al representar escalas espaciales muy pequeñas, lo cual sugiere una redefinición de las bandas de elevación acorde a la resolución del producto. Se concluye que el modelo WEAP, a pesar de ser un modelo poderoso y eficaz, presenta limitaciones al modelar cuencas altas en donde predomina la influencia nival al no tener incorporado en su balance salidas por sublimación, variable que según lo investigado puede alcanzar a nivel anual alrededor de un 30 % de la precipitación caída en la cuenca.
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Mena, Pardo Diego Ignacio. "Análisis de Impactos del Cambio Climático en la Cuenca Andina del Río Teno, Usando el Modelo Weap." Tesis, Universidad de Chile, 2009. http://repositorio.uchile.cl/handle/2250/103570.
Full textAbstract:
La cantidad de recursos hídricos disponibles en una región es una variable de importancia que
puede limitar el desarrollo de la vida y también incidir en el desarrollo de actividades productivas
tales como agricultura, minería e hidroelectricidad. Por ello, resulta fundamental el análisis de
cual será la disponibilidad futura de este vital elemento. En este estudio se intentó proveer la
información necesaria para comprender los alcances del cambio climático, en términos de
vulnerabilidad del sector de los recursos hídricos en la cuenca andina del Río Teno,
caracterizada por la estación fluviométrica Río Teno después de Junta con Río Claro, con el fin
de contribuir al proceso de toma de decisiones sobre medidas de adaptación frente al Cambio
Climático.
Para lograr este objetivo se usó un modelo de simulación hidrológica generado por el Instituto
del Medio Ambiente SEI (Stockholm Environment Institute), conocido como Water Evaluation
And Planning System o simplemente WEAP. El modelo fue calibrado y validado a partir de
datos históricos mensuales representativos de la cuenca disponibles entre Abril de 1975 y
Marzo de 2005. Los parámetros calibrados y validados fueron utilizados para simular la
disponibilidad futura del recurso a base de escenarios futuros de las variables meteorológicas
de entrada (precipitación y Temperatura) necesarias para la operación del modelo, derivados de
datos obtenidos en el modelo PRECIS por el Departamento de Geofísica de la Universidad de
Chile para el escenario A2 en los períodos 2036-2065 y 2071-2100.
Los resultados mostraron una baja de los caudales medios mensuales futuros del Río Teno de
un 30% y 40% para los periodos 2036-2065 y 2071-2100 respectivamente y un aumento en el
número y prolongación de periodos secos en la cuenca, causados principalmente por la
disminución de la precipitación anual y del aumento de la temperatura anual. A pesar de los
cambios en las magnitudes del caudal, el régimen mixto nivo-pluvial del Río Teno no varió
sustancialmente, salvo un desplazamiento del peak de primavera del mes de Diciembre a
Noviembre.
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Mardones, Morales Gabriel Antonio. "Implementación y Uso del Modelo Weap en Cuencas Nivales de la IV Región para el Análisis del Cambio Climático." Tesis, Universidad de Chile, 2009. http://www.repositorio.uchile.cl/handle/2250/103399.
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Los recursos hídricos forman una parte importante en el desarrollo económico del país, más aun en regiones en las cuales se tiene un amplio desarrollo del área agrícola como el caso de la IV región.
El objetivo principal de este trabajo es simular mediante el modelo WEAP los caudales futuros en los períodos 2036 – 2065 y 2071 - 2100 en las cuencas nivales de la IV Región Elqui en Algarrobal y Hurtado en San Agustín. Se construyeron los modelos de ambas cuencas, los cuales fueron calibrados y validados obteniendo coeficientes de Nash - Sutcliffe del orden de 0,7, a los cuales posteriormente se les aplicaron condiciones futuras de temperatura y precipitación.
Para simular las condiciones meteorológicas futuras se han desarrollado posibles escenarios de emisión de gases de efecto invernadero y aerosoles, basándose en distintas directrices de desarrollo de la población mundial. En el presente estudio se utilizaron los resultados del modelo PRECIS para el escenario A2 generados por el departamento de geofísica de la Universidad de Chile.
Las variables generadas por el modelo PRECIS en la zona de estudio, sobrestiman las precipitaciones y entregan datos de temperatura más bajos que los registrados en las estaciones para el período de observación, por lo que fue necesario realizar correcciones de estos datos mediante métodos estadísticos.
Las correcciones a los datos meteorológicos del modelo PRECIS muestran una disminución en las precipitaciones medias anuales. En la cuenca Elqui en Algarrobal de 140 mm/año entre los años 1979-2005 a 130 mm/año entre los años 2071-2100, y en la cuenca Hurtado en San Agustín de 175 mm/año entre los años 1977-2005 a 125 mm/año entre los años 2071-2100 y un aumento de 6ºC en la temperatura media anual para el periodo 2071-2100, lo que se traduce en una disminución de los caudales futuros en ambos periodos analizados (aproximadamente 30% menos en el periodo 2071-2100), y lo que es aun más grave, es el aumento del estrés hídrico y periodos más prolongados de sequías, debido principalmente a un cambio de régimen hidrológico en ambas cuencas, originado por un adelantamiento en el derretimiento de nieve.
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Cepeda, Abad Javier Alonso. "Análisis de los caudales nivo-glaciares históricos y proyectados en la cuenca del Río Olivares: comparación entre el modelo DHSVM y WEAP." Tesis, Universidad de Chile, 2017. http://repositorio.uchile.cl/handle/2250/144605.
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Magíster en Ciencias de la Ingeniería, Mención Recursos y Medio Ambiente Hídrico.
Ingeniero CivilLos glaciares ubicados en los Andes de Chile central constituyen parte fundamental del medioambiente y la economía, ya que contribuyen en gran medida al escurrimiento de verano. En la actualidad se han realizado numerosos estudios para comprender tanto la magnitud actual de estos aportes como la respuesta que tendrán los glaciares ante perturbaciones climáticas como es el cambio climático. En el presente trabajo se analiza el comportamiento histórico y futuro del caudal de la cuenca del río Olivares antes de su junta con el río Colorado, con énfasis en las variaciones que presentará el aporte glaciar. Para esto se utilizan dos modelos hidrológicos con distinta esquematización, lo que permite tener una mayor consistencia en los resultados y, a la vez, analizar las diferencias dada la conceptualización de los distintos procesos y su escala espacial. El primero de ellos corresponde a un modelo distribuido de base física, DHSVM, mientras que el segundo posee una topología de carácter semi-distribuido con características conceptuales y de base física, WEAP. Ambos modelos se calibran a escala diaria en el período 2001/02-2011/12 comparando tanto el comportamiento del caudal como la cobertura nival. Las proyecciones de cambio climático utilizadas en el estudio se realizan considerando cinco modelos de circulación global (GCM por sus siglas en inglés) del escenario RCP 8.5, escogidos en base al comportamiento de la precipitación y temperatura simuladas contrastadas con las observaciones en la estación base Pirque. Analizando las variaciones en las forzantes meteorológicas entre la línea base (1985/86-2004/05) y el futuro cercano (2015/16-2044/45) y lejano (2045/46-2074/75) se obtiene que en promedio los modelos proyectan un incremento de la temperatura media anual de la estación de 1.3°C para el futuro cercano y 2.9 °C para el futuro lejano, lo que representa un 9 y 20% respectivamente, mientras que para la precipitación anual se proyecta una disminución de 33.6 mm para el futuro cercano y 93.2 mm para el futuro lejano., representando un 7 y 19% respectivamente. Se estima que la mayoría de los glaciares en la cuenca del río Olivares habrán desaparecido para fines del período analizado, quedando en promedio 1.2 km^2 según la modelación realizada por DHSVM y 6.8 km^2 según WEAP. Además, el caudal total presenta disminuciones de entre un 15 y un 46% para el futuro lejano, mientras que el caudal glaciar presenta disminuciones de entre un 53 y un 85% para el futuro lejano, dependiendo del GCM y modelo hidrológico utilizado.
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Camarena, Campos Oscar Miguel, and Calderón Samuel Pablo Meza. "Evaluación de estrategias de gestión de recursos hídricos para enfrentar futuras situaciones de escasez, utilizando el modelo weap en la sub cuenca blanco." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2020. http://hdl.handle.net/10757/653344.
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En zonas alto andinas, el suministro de agua depende de la capacidad de almacenamiento y formas de distribución. Por ende, se utilizó un modelo de planificación y evaluación de recursos hídricos (WEAP) en la sub cuenca Blanco, ubicada en la intercuenca Huallaga; para evaluar estrategias de gestión en escenarios futuros y lograr hacer frente a una probable escasez de agua entre 2034 y 2049. Este estudio consideró los recursos hídricos de cada distrito de la subcuenca y comparó cuatro escenarios futuros distintos alternando medidas estructurales y no estructurales para periodos secos y normales.
Los resultados muestran que el consumo agua aumentará considerablemente en los distritos de estudio, y que habrá una situación de estrés hídrico de agua sin nuevos sistemas de captación de agua. La prevención de la escasez de agua en el futuro requiere la implementación de medidas de ahorro de agua y el uso de nuevas infraestructuras hidráulicas.
La implementación de medidas estructurales (reservorios, presas, bocatomas, canales de regadío) y las medidas no estructurales (capacitaciones, tecnificación del uso del agua, planes de contingencia, etc) pueden dar como resultado un potencial de ahorro de agua de 89% y 35% respectivamente, mientras que la implementación de ambas medidas da un 100% de cobertura para las demandas en el año 2034. Por otra parte, para 2049 el potencial de ahorro usando medidas estructurales sería de 50%, mientras que si sólo se usan medidas no estructurales el ahorro sería de 35%. Sin embargo, adoptando ambas estrategias se puede ahorrar el 100%.In high Andean areas, water supply depends on storage capacity and forms of distribution. Therefore, a water resources planning and evaluation model (WEAP) was used in the Blanco sub-basin, located in the Huallaga inter-basin; to evaluate management strategies in future scenarios and manage to face a probable water shortage between 2034 and 2049. This study considered the water resources of each district of the sub-basin and compared four different future scenarios alternating structural and non-structural measures for dry periods and normal. The results show that water consumption will increase considerably in the study districts, and that there will be a situation of water stress without new water collection systems. Preventing water shortages in the future requires the implementation of water saving measures and the use of new hydraulic infrastructures. The implementation of structural measures (reservoirs, dams, intakes, irrigation canals) and non-structural measures (training, modernization of water use, contingency plans, etc.) can result in a potential water saving of 89% and 35% respectively, while the implementation of both measures gives 100% coverage for the demands in the year 2034. On the other hand, by 2049 the savings potential using structural measures would be 50%, while if only measures are used non-structural savings would be 35%. However, adopting both strategies can save 100%.
Tesis
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TRIGUEIRO, Halana Oliveira. "Estimativa da disponibilidade hídrica para usos múltiplos em reservatórios sob periódicas crises hídricas: estudo de caso." Universidade Federal de Campina Grande, 2016. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/1344.
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Capes
Nesse estudo foi realizado o desenvolvimento de cenários de adaptação, com base no gerenciamento de demandas e tendências políticas e socioeconômicas, a fim de verificar a possibilidade no atendimento de usos múltiplos do reservatório Epitácio Pessoa, localizado na região semiárida do estado da Paraíba, Brasil, por meio do Modelo Água, Avaliação e Planejamento (WEAP). A geração de cenários resultou em onze diferentes opções de operação do reservatório para a série 2005-2015, que foram divididos em Atual/Referência, Otimistas e Pessimistas. Os c enários simulados no WEAP demonstram a aplicabilidade do modelo para montar um sistema de recursos hídricos em SIG e analisar esse tipo de problema através de diversas formas de apresentação. Estas características o definem como um bom auxiliador na tomada de decisões para o planejamento e gestão dos recursos hídricos. Sua aplicação mostrou ainda que, é possível a prática de irrigação suprida pelo açude Epitácio Pessoa, desde que seja realizada uma gestão eficiente das águas do reservatório, por meio de ações que objetivem a redução das perdas no sistema de abastecimento pelo menos a 20%, o uso de tecnologias para reaproveitamento de águas de chuva e o atendimento das demandas ser reduzido aos limites disponíveis ou, no máximo e por exigência legal, ao limite da outorga.
In this study was the development of adaptation scenarios, based on management demands and political and socio-economic trends in order to verify the possibility to service multiple uses of Epitacio Pessoa reservoir, located in the semiarid region of the state of Paraiba, Brazil, by Water Model, Evaluation and Planning (WEAP). The generation scenarios resulted in eleven different operating options from the reservoir to the 2005-2015 series, which were divided into Current / Reference, Optimists and Pessimists. The scenarios simulated in WEAP demonstrate the applicability of the model to build a system of water resources in GIS and analyze this problem through various forms of presentation. These characteristics define it as a good assist in decision making for planning and management of water resources. Its application also showed that it is possible to practice irrigation supplied by Pessoa dam, since efficient management of the reservoir water is carried out through actions that aim to reduce losses in the supply system at least 20% the use of technologies for rainwater reuse and meet the demands be reduced to the limits available, or at most and legal requirement, the grant limit.
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Farias, Vera Lúcia da Silva [UNESP]. "Modelagem da perda de fósforo por erosão hídrica." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/148007.
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Com a crescente preocupação com as perdas de fósforo na água de enxurrada e sedimentos erodidos enriquecidos com P, que podem aumentar o risco de eutrofização dos corpos d´água superficiais, o interesse no uso de modelos que avaliam os impactos do uso do solo, tornou-se importante. O modelo WEPP, tem uma ampla gama de aplicabilidade, uma vez que pode ser usado para simular processos de erosão, escoamento e transporte de elementos orgânicos e químicos. Entretanto, no Brasil, não há casos em que um algoritmo tenha sido associado ao WEPP para modelar o transporte de P. Assim, o objetivo deste trabalho foi avaliar o desempenho de modelos para estimar as perdas de fósforo disponível, no sedimento erodido predito pelo WEPP, em uma pequena bacia hidrográfica. O presente trabalho foi realizado em área localizada no município de Tabapuã, noroeste do Estado de São Paulo. Os dados para alimentar o banco de dados do WEPP basearam-se nos componentes: climático, hidrológico e desenvolvimento vegetal. Os sedimentos erodidos foram classificados em: frações primárias, areia, silte, agregados pequenos e grandes. Com tais frações foi calculada a taxa de enriquecimento por fósforo com o WEPP (WER). Outros dois algoritmos foram utilizados para estimar o fósforo transportado com o sedimento erodido: ln(ER) = 2,682 – 0,278 ln(Sed) e) ln(ER) = 2 - 0,2 ln(Sed). Para a validação das estimativas de P nos sedimentos, utilizaram-se os critérios: o coeficiente de Nash-Sutcliffe (NS), o erro quadrático médio (RMSE), o coeficiente de massa residual (CRM) e o índice de concordância (d). Os modelos testados para estimar as taxas de enriquecimento do sedimento erodido e enxurrada por P são eficientes, quando em uso com as predições do Water Erosion Prediction Project (WEPP). As taxas de enriquecimento obtidas com o WEPP (WER), equação ln(ER) = 2,682 – 0,278 ln(Sed) e ln(ER) = 2 - 0,2 ln(Sed), respectivamente, apresentaram coeficiente de Nash-Sutcliffe (NS) próximo de 1. As perdas de P com o sedimento e enxurrada apresentaram moderado grau de dependência especial (GDE), enquanto que a erosão estimada pelo WEPP apresentou alto GDE. Perdas de fósforo solúvel com a enxurrada acima de 0,02 mg L-1, valor crítico para eutrofização, podem ser obtidas em 81% da área da bacia com uma probabilidade superior a 75%.
With the growing concern over phosphorus losses with the runoff water and eroded sediment enriched with P that can increase the risk of eutrophication of surface water bodies, interest in the use of models that assess the impacts of land use, has if important. The WEPP model has a wide range of applicability, since it can be used to simulate erosion, drainage and transport and organic chemicals. However, in Brazil, there aren’t cases in which an algorithm has been associated with the WEPP to model the transport P. Thus, the objective with this study was to evaluate the performance of mode loss of phosphorus with eroded sediment in agricultural environment to estimate phosphorus losses available in the sediment eroded predicted the WEPP in a small catchment. This work was carried out in an area located in the municipality of Tabapuã, northwest of São Paulo. The sediment losses were estimated with the WEPP model. Two approaches (P-empirical) estimated ER according to an empirical relationship, and the other approach used WER calculated by WEPP (P-WEPP). Models to estimate enrichment rates of the sediment (Sed) and runoff with the Water Erosion Prediction Project (WEPP), WER - WEPP, an equation ln(ER) = 2.682 - 0.278 ln(Sed) and ln(ER) = 2 - 0.2 ln (Sed) present coefficient of Nash-Sutcliffe (NS) next 1.
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Franklin, Francis James. "Modelling mild wear." Thesis, University of Sheffield, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312780.
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Ding, Huali. "Dynamic wear models for gear systems." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1194025602.
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Sevcik, Jaroslav. "Program transformations in weak memory models." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3132.
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We analyse the validity of common optimisations on multi-threaded programs in two memory models—the DRF guarantee and the Java Memory Model. Unlike in the single-threaded world, even simple program transformations, such as common subexpression elimination, can introduce new behaviours in shared-memory multi-threading with an interleaved semantics. To validate such optimisations, most current programming languages define weaker semantics, called memory models, that aim to allow such transformations while providing reasonable guarantees. In this thesis, we consider common program transformations and analyse their safety in the two most widely used language memory models: (i) the DRF guarantee, which promises sequentially consistent behaviours for data race free programs, and (ii) the Java Memory Model, which is the semantics of multithreaded Java. The DRF guarantee is the semantics of Ada and it has been proposed as the semantics of the upcoming revision of C++. Our key results are: (i) we prove that a large class of elimination and reordering transformations satisfies the DRF guarantee; (ii) we find that the Java language is more restrictive—despite the claims in the specification, the Java Memory Model does not allow some important program transformations, such as common subexpression elimination. To establish the safety results, we develop a trace semantic framework and describe important program optimisations as relations on sets of traces. We prove that all our elimination and reordering transformations satisfy the DRF guarantee, i.e., the semantic transformations cannot introduce new behaviours for data race free programs. Moreover, we prove that all the transformations preserve data race freedom. This ensures safety of transformations composed from eliminations and reorderings. In addition to the DRF guarantee, we prove that for arbitrary programs, our transformations prevent values appearing “outof- thin-air”—if a program does not contain constant c and does not perform any operation that could create c, then no transformation of the program can output c. We give an application of the semantic framework to a concrete language and prove safety of several simple syntactic transformations. We employ similar semantic techniques to prove validity of several classes of transformations, such as the elimination of an overwritten write or reordering of independent memory accesses, in the Java Memory Model. To establish the iii negative results for the Java Memory Model, we provide counterexamples showing that several common optimisations can introduce new behaviours and thus are not safe.
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Speirs, Neil Alexander. "Composite models of weak gauge bosons." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/6817/.
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Composite models of quarks, leptons and weak bosons are reviewed. It is shown that they can reproduce the low energy results of the Standard Weinberg-Salam Model of electroweak interactions. The consequences of assuming composite W and Z bosons are examined and many new particles are predicted, including excited W and Z states and their pseudoscalar partners. Estimates of the masses and decay widths of these particles are given. It is also shown that coloured weak bosons may exist in the energy range 100-200 GeV. The decays of a composite Z boson are studied in detail using both a potential model and an effective Lagrangian approach. It is found that the width is likely to be significantly different from that of the elementary Z of the Standard Model, In particular there are additional contributions to the decays Z → qqg and Z → ggg which are likely to affect the total Z width by an appreciable amount. The decay of the Z into hypercoloured particles is also examined and it is found that the width is likely to exceed greatly the current experimental bound. It is concluded that the W and Z bosons are likely to be elementary particles because if they were composite their decay widths would be much greater than is found experimentally, unless of course their internal dynamics are quite unlike the model which has been employed.
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Zhang, Sizhuo. "Constructing and evaluating weak memory models." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122690.
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This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2019
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 211-224).
A memory model for an instruction set architecture (ISA) specifies all the legal multithreaded-program behaviors, and consequently constrains processor implementations. Weak memory models are a consequence of the desire of architects to preserve the flexibility of implementing optimizations that are used in uniprocessors, while building a shared-memory multiprocessor. Commercial weak memory models like ARM and POWER are extremely complicated: it has taken over a decade to formalize their definitions. These formalization efforts are mostly empirical--they try to capture empirically observed behaviors in commercial processors--and do not provide any insights into the reasons for the complications in weak-memory-model definitions. This thesis takes a constructive approach to study weak memory models. We first construct a base model for weak memory models by considering how a multiprocessor is formed by connecting uniprocessors to a shared memory system.
We try to minimize the constraints in the base model as long as the model enforces single-threaded correctness and matches the common assumptions made in multithreaded programs. With the base model, we can show not only the differences among different weak memory models, but also the implications of these differences, e.g., more definitional complexity or more implementation flexibility or failures to match programming assumptions. The construction of the base model also reveals that allowing load-store reordering (i.e., a younger store is executed before an older load) is the source of definitional complexity of weak memory models. We construct a new weak memory model WMM that disallows load-store reordering, and consequently, has a much simpler definition. We show that WMM has almost the same performance as existing weak memory models.
To evaluate the performance/power/area (PPA) of weak memory models versus that of strong memory models like TSO, we build an out-of-order superscalar cachecoherent multiprocessor. Our evaluation considers out-of-order multiprocessors of small sizes and benchmark programs written using portable multithreaded libraries and compiler built-ins. We find that the PPA of an optimized TSO implementation can match the PPA of implementations of weak memory models. These results provide a key insight that load execution in TSO processors can be as aggressive as, or even more aggressive than, that in weak-memory-model processors. Based on this insight, we further conjecture that weak memory models cannot provide better performance than TSO in case of high-performance out-of-order processors. However, whether weak memory models have advantages over TSO in case of energy-efficient in-order processors or embedded microcontrollers remains an open question.
by Sizhuo Zhang.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
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SOUZA, Waldemir Pereira de. "Abordagem física do WEPP na erosão em solos em ambiente semiárido." Universidade Federal Rural de Pernambuco, 2015. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5333.
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Soil erosion is an irreversible phenomenon that causes soil degradation and deterioration of water quality, therefore, models such as water erosion prediction project (WEPP) physical base can be increasingly used to assess erosion rill in semiarid environment. The objective was to quantify the rill erosion with relationships the WEPP and evaluate the hydraulic conditions of runoff under conditions of rill preformed. The experiment was conducted in the exu watershed in Serra Talhada, semiarid region of Pernambuco where was prepared 16 rill preformed who underwent different flow levels: 5.87 L min-1, 12.10 L min-1, 20.33 L min-1 and 27.57 L min-1 in Entisol fluvent. With the performance of the concentration of runoff in rill experimental produced flow regimes slow turbulent in the largest flows applied characterizing the characterizing the occurrence of erosion in rill. The erodibility values in rill (Kr)was 0.0011 kgN-1s-1 and critical shear corresponds to 1.91 Pa. The values of soil losses to erosion rill were considered high for Entisol fluvent behaving smaller particle size composition with a higher percentage of sand.
A erosão do solo é um fenômeno irreversível que causa a degradação do solo e a deterioração da qualidade da água, dessa forma, modelos como o Projeto de Predição de Erosão Hídrica (WEPP) de base física podem ser cada vez mais utilizados na avaliação da erosão do solo em sulcos em ambiente semiárido. Objetivou-se quantificar a erosão em sulcos com as relações de erosão do WEPP e avaliar as condições hidráulicas do escoamento superficial sob condições de sulcos pré-formados. O experimento foi realizado na Bacia do Riacho Exu, no município de Serra Talhada, região semiárida de Pernambuco onde foram preparadas parcelas experimentais que consistiram em 16 sulcos pré-formados que foram submetidos a aplicação de diferentes níveis de vazão: 5,87 Lmin-1, 12,10 Lmin-1, 20,33 Lmin-1 e 27,57 Lmin-1 em Neossolo Flúvico. Com a atuação da concentração do escoamento superficial nos sulcos experimentais produziram regimes de escoamento na faixa de turbulento lento nos maiores fluxos aplicados caracterizando a ocorrência da erosão em sulcos. Os valores de erodibilidade em sulcos (Kr) foi de 0,0011 KgN-1s-1 e a tensão crítica de cisalhamento corresponde a 1,91 Pa. Os valores das perdas de solo para a erosão em sulcos foram consideradas altas para um Neossolo Flúvico comportando menor composição granulométrica com maior percentagem de areia.
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Zhang, Sizhuo. "WMM : a resilient Weak Memory Model." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103667.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 61-65).
A good memory model should have a precise definition that can be understood by any computer architect readily. It should also be resilient in the sense that it should not break when new microarchitecture optimizations are introduced to improve single-threaded performance. We introduce WMM, a new weak memory model, which meets these criteria. WMM permits all load-store reorderings except a store is not allowed to overtake a load. WMM also permits both memory dependency speculation and load-value prediction. We define the operational semantics of WMM using a novel conceptual device called invalidation buffer, which achieves the effect of out-of-order instruction execution even when instructions are executed in-order and one-at-a-time. We show via examples where memory fences need to be inserted for different programming paradigms. We highlight the differences between WMM and other weak memory models including Release Consistency and Power. Our preliminary performance evaluation using the SPLASH benchmarks shows that WMM implementation performs significantly better than the aggressive implementations of SC. WMM holds the promise to be a vendor-independent stable memory model which will not stifle microarchitectural innovations.
by Sizhuo Zhang.
S.M.
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Phan, Quang. "Weak factor model in large dimension." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/69442/.
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This thesis presents some extensions to the current literature in high-dimensional static factor models. When the cross-section dimension (represented by N hence-forth) is very large, the standard assumption for each common factor is to have the number of non-zero loadings grow linearly with N . On the other hand, an idiosyncratic error for each component can only be correlated with a finite number of other components in the cross-section. These two assumptions are crucial in standard high-dimensional factor analysis, as they allow us to obtain consistent estimators for the factors, the loadings and the number of factors. However, together they rule out the possibility that we may have some factors that have strictly less than N but still non-negligible number of non-zero loadings, e.g. N for some 0 < < 1 . The existence of these weak factors will decrease the signal-to-noise ratio as now the gap between the systematic and idiosyncratic eigenvalues is more narrow. As the consequence, in such model it is harder to establish the consistency of the factors estimated by sample principle components. Furthermore, the number of factors is even more challenging to identify because most existing methods rely on the large signal-to-noise ratio. In this thesis, I consider a factor model that allows general strength for each factor, i.e. both strong and weak factors can exist. Chapter 1 gives more discussions about the current literature on this and the motivation for my contribution. In Chapter 2, I show that the sample principle components are still the consistent estimators for the factors (up to the spanning space), provided that the factors are not too weak. In addition, I derive the lower bound that the strength of the weakest factor needs to achieve for being consistently estimated. More precisely, what I mean by strength is the order of the number of non-zero loadings of the factor. Chapter 3 presents a novel method to determine the number of factors, which is asymptotically consistent even when the factors are weak. I run extensive Monte Carlo simulations to compare the performance of this method to the two well-known ones, i.e. the class of criteria proposed in Bai and Ng (2002) and the eigenvalue ratio method in Ahn and Horenstein (2013). In Chapter 4 and 5, I show some applications that are based on the work of this thesis. I mainly focus on two issues: selecting the factor models in practice and using factor analysis to compute the large static covariance matrix.
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Done, Vamshidhar. "Numerical modeling of dry wear : Experimental study of fretting wear, fretting wear simulations with debris entrapped and industrial applications of fretting wear models." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI137.
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De nombreux modèles numériques sont proposés dans la littérature en utilisant des méthodes d'éléments finis et d'éléments finis discrets pour étudier l'usure par frottement, ils incluent à peine l'effet des débris d'usure. Ces modèles étant coûteux en termes de calcul, simuler un grand nombre de cycles d'usure par frottement n'est pas réalisable dans la pratique. Une nouvelle méthodologie est proposée qui ne nécessite que des propriétés de matériau en vrac comme les coefficients de frottement / usure et utilise des méthodes semi-analytiques pour simuler l'usure par frottement avec des débris piégés. Dans cette approche, les débris sont supposés être attachés à l'une des surfaces pendant le processus de fretting. Les résultats obtenus à partir de cette approche ont été comparés avec des expériences de fretting. La méthode proposée permet de saisir la profondeur d'usure et la largeur des cicatrices, et les résultats sont très proches de ceux observés dans les expériences. L'assemblage des soupapes des moteurs à combustion subit une usure par frottement en raison d'un phénomène complexe impliquant une rigidité structurelle et une tribologie de contact. L'usure des soupapes a de nombreux effets néfastes sur les performances du moteur. Il provoque une récession de la soupape entraînant des changements dans les connexions du mécanisme d'entraînement de la soupape, ce qui perturbe l'ouverture et la fermeture des soupapes. Avec des normes d'émission strictes, l'utilisation de lubrifiant pour réduire la friction au contact est limitée. Si l'usure à travers la circonférence n'est pas uniforme, il y aura une fuite de gaz et le moteur donne moins de puissance. Il est nécessaire de bien comprendre la raison de l'usure des soupapes et de développer un modèle numérique capable de prédire l'usure par frottement de la soupape pour le nombre d'heures de fonctionnement donné. Des expériences ont été réalisées pour comprendre le mécanisme d'usure et calculer les coefficients d'usure qui peuvent être utilisés dans le modèle numérique. Un modèle d'usure numérique est construit qui capture la rigidité structurelle de l'ensemble de soupape et le mécanisme d'usure au contact du siègeMany numerical models are proposed in the literature using finite element and finite discrete element methods to study fretting wear, they barely include the effect of wear debris. These models being computationally expensive, simulating large number of fretting wear cycles is not practically feasible. A new methodology is proposed which needs only bulk material properties like friction/wear coefficients and uses semi-analytical methods to simulate fretting wear with entrapped debris. In this approach, debris are assumed to be attached to one of the surfaces during the fretting process. The results obtained from this approach were compared with fretting experiments. The proposed method permits to capture the wear depth and scar width, and results are very close to that observed in the experiments. Valve assembly of combustion engines undergo fretting wear due to a complex phenomenon involving structural stiffness and contact tribology. Valve wear has many detrimental effects on the engine performance. It causes valve recession leading to changes in connections of valve drive train in turn disturbing the opening and closing of valves. With stringent emission norms, usage of lubricant to reduce friction at the contact is restricted. If the wear across the circumference is not uniform, there will be leakage of gas and the engine gives lesser power output. There is a need to thoroughly understand the reason for valve wear and develop a numerical model that can predict valve fretting wear for the given number of operating hours. Experiments were performed to understand the wear mechanism and derive wear coefficients that can be used in the numerical model. A numerical wear model is built that captures structural stiffness of the valve assembly and wear mechanism at seat contact
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Perez-Bidegain, Mario. "Modeling phosphorus transport using the WEPP model." [Ames, Iowa : Iowa State University], 2007.
Find full text
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Tiscareno-Lopez, Mario 1957. "Sensitivity analysis of the WEPP Watershed model." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/292034.
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Uncertainty in the hydrologic and soil erosion predictions of the WEPP Watershed model due to errors in model parameter estimation was identified through a sensitivity analysis based on the Monte-Carlo method. Identification of parameter sensitivities provides guidance in the collection of parameter data in places where the model is intended to simulate soil erosion. Changes in model predictions caused by changes in model parameters were quantified for model applications in semi-arid rangeland watersheds. The magnitude of the changes in model parameters was defined by the spatial variability of parameters in a watershed. Model sensitivities in predicting overland flow and soil erosion on hillslopes and channels are presented considering rainfall characteristics. The results show that WEPP predictions are very sensitive to attributes that define a storm event (amount, duration, and ip). Model sensitivity to soil erosion parameters also depends of the type of storm event.
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Danner, Constance L. "Documentation and testing of the WEAP model for the Rio Grande/Bravo Basin." Thesis, (4 MB), 2006. http://handle.dtic.mil/100.2/ADA471843.
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Thesis (M.S. in Engineering)--University of Texas at Austin, 2006."August 2006." Description based on title screen as viewed on June 1, 2010. DTIC Descriptor(s): Computer Programs, Ground Water, Basins (Geographic), Computerized Simulation, Volume, Water Flow, Reservoirs, Mexico, North America, Streams, Banks (Waterways), Models, Physical Properties, Theses. DTIC Identifier(s): Rio Grande/Bravo Basin, Water Evaluation and Planning System, WEAP (Water Evaluation and Planning System), Weap Model, IBWC (International Boundary and Water Commission). Includes bibliographical references (p. 39-41). Also available in print.
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Ibiapina, Thiago Vinicius Barros [UNESP]. "Processo de erosão de um argissolo utilizando o modelo Wepp." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/142961.
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000865683.pdf: 1045931 bytes, checksum: 1a14f8cae49f107bcc52e6948da88cc6 (MD5)A erosão do solo tem sido assunto de grande preocupação mundial devido às grandes mudanças no planeta. Dentre elas, estão as mudanças climáticas e as perdas na biodiversidade do planeta, mas outras mudanças pouco comentadas, mas não menos importantes são as mudanças nos ciclos de nitrogênio e fósforo. Parte deste estudo comprova que o carreamento de sedimentos gerados por erosão pode ser o grande vilão das eutrofizações de corpos de água. O presente trabalho foi realizado em área localizada no município de Tabapuã, noroeste do Estado de São Paulo, cujas coordenadas geográficas são: Latitude 21º 05' 57, S e Longitude 49º 01' 02 W. O objetivo principal deste trabalho foi estimar a erosão com o modelo WEPP em área cultivada de Tabapuã - SP, e com os seguintes objetivos específicos: 1) adaptar o modelo para uso em climas tropicais, como o clima brasileiro; 2) aplicar o modelo para a mensuração de cenários dos possíveis impactos causados pela erosão hídrica para cultivos de cana-de-açúcar, milho e soja na área de estudo. Tem-se como resultado a composição granulométrica do sedimento dividida em cinco frações que correspondem às frações argila, silte, areia muito fina, areia fina e areia grossa, respectivamente. Nas condições do estudo, a cultura da cana-de-açúcar mostrou-se a menos protecionista quando comparada com as culturas de milho e soja. Com a geração da componente clima para a cidade do experimento, têm-se dados mais confiáveis para a mensuração dos impactos causados pelo manejo na perda de solos da área do estudo. O modelo WEPP foi eficiente na geração dos valores de erosão líquida para a área em estudo onde, na bacia, há a deposição de sedimentos
Soil erosion has been the subject of great concern worldwide due to major changes in the planet. These include climate change, and biodiversity loss on the planet, but little commented other changes, but no less important are the changes in nitrogen and phosphorus cycles. Part of this study shows that the carrying of sediments generated by erosion can be the villain of eutrofizações bodies of water. This work was carried out in an area located in the municipality of Tabapuã, northwest of São Paulo, whose geographical coordinates are: Latitude 21 05 '57 S and Longitude 49 01' 02 W. The main objective of this study was to estimate the erosion with the WEPP model in acreage of Tabapuã (SP), and with the following specific objectives: 1) to adjust the model for use in tropical climates like Brazil's climate; 2) apply the model to measure scenarios of possible impacts caused by water erosion for cane sugar crops, corn and soybeans in the study area. There has resulted in the particle size composition of the sediment divided into five fractions corresponding fractions clay, silt, very fine sand, fine sand and sand respectively. Under the conditions of the study the culture of cane sugar was shown to be less protectionist when compared to corn and soybeans. With the generation of climate component to the city of the experiment have been more reliable data to measure the impacts of management in the loss of the study area soils. The WEPP model was efficient in the generation of net erosion values for the studied area in the basin where there is a deposition of sediments
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Ibiapina, Thiago Vinicius Barros. "Processo de erosão de um argissolo utilizando o modelo Wepp /." Jaboticabal, 2015. http://hdl.handle.net/11449/142961.
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Orientador: Marcílio Vieira Martins FilhoBanca: José Renato Zanini
Banca: Diego Silva Siqueira
Banca: Zigomar Menezes de Souza
Banca: Rafael Montanari
Resumo: A erosão do solo tem sido assunto de grande preocupação mundial devido às grandes mudanças no planeta. Dentre elas, estão as mudanças climáticas e as perdas na biodiversidade do planeta, mas outras mudanças pouco comentadas, mas não menos importantes são as mudanças nos ciclos de nitrogênio e fósforo. Parte deste estudo comprova que o carreamento de sedimentos gerados por erosão pode ser o grande vilão das eutrofizações de corpos de água. O presente trabalho foi realizado em área localizada no município de Tabapuã, noroeste do Estado de São Paulo, cujas coordenadas geográficas são: Latitude 21º 05' 57, S e Longitude 49º 01' 02 W. O objetivo principal deste trabalho foi estimar a erosão com o modelo WEPP em área cultivada de Tabapuã - SP, e com os seguintes objetivos específicos: 1) adaptar o modelo para uso em climas tropicais, como o clima brasileiro; 2) aplicar o modelo para a mensuração de cenários dos possíveis impactos causados pela erosão hídrica para cultivos de cana-de-açúcar, milho e soja na área de estudo. Tem-se como resultado a composição granulométrica do sedimento dividida em cinco frações que correspondem às frações argila, silte, areia muito fina, areia fina e areia grossa, respectivamente. Nas condições do estudo, a cultura da cana-de-açúcar mostrou-se a menos protecionista quando comparada com as culturas de milho e soja. Com a geração da componente clima para a cidade do experimento, têm-se dados mais confiáveis para a mensuração dos impactos causados pelo manejo na perda de solos da área do estudo. O modelo WEPP foi eficiente na geração dos valores de erosão líquida para a área em estudo onde, na bacia, há a deposição de sedimentos
Abstract: Soil erosion has been the subject of great concern worldwide due to major changes in the planet. These include climate change, and biodiversity loss on the planet, but little commented other changes, but no less important are the changes in nitrogen and phosphorus cycles. Part of this study shows that the carrying of sediments generated by erosion can be the villain of eutrofizações bodies of water. This work was carried out in an area located in the municipality of Tabapuã, northwest of São Paulo, whose geographical coordinates are: Latitude 21 05 '57 S and Longitude 49 01' 02 W. The main objective of this study was to estimate the erosion with the WEPP model in acreage of Tabapuã (SP), and with the following specific objectives: 1) to adjust the model for use in tropical climates like Brazil's climate; 2) apply the model to measure scenarios of possible impacts caused by water erosion for cane sugar crops, corn and soybeans in the study area. There has resulted in the particle size composition of the sediment divided into five fractions corresponding fractions clay, silt, very fine sand, fine sand and sand respectively. Under the conditions of the study the culture of cane sugar was shown to be less protectionist when compared to corn and soybeans. With the generation of climate component to the city of the experiment have been more reliable data to measure the impacts of management in the loss of the study area soils. The WEPP model was efficient in the generation of net erosion values for the studied area in the basin where there is a deposition of sediments
Doutor
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Söderberg, Anders. "Interface modeling - friction and wear." Doctoral thesis, KTH, Maskinkonstruktion (Avd.), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9861.
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The general trend toward increased use of computer models and simulations during product development calls for accurate and reliable product models. The function of many products relies on contact interfaces between interacting components. Simulating the behavior of such products requires accurate models of both components and interfaces. Depending on the purpose of the simulation, interface models of different degrees of detail are needed. In simulating very large systems with many interfaces, it might be computationally expensive to integrate detailed models of each individual interface. Condensed models, or abstractions, that describe the interface properties with the fewest degrees of freedom are therefore required. This thesis deals with the modeling and simulation of mechanical interfaces in a systems context. The five appended papers discuss the issue from both the simulation and tribological points of view. The aim is to study how friction and wear can be modeled in the behavioral simulation of technical systems and to discuss the convenience and applicability of using different types of models as building blocks of a system model in simulations. Paper A reviews existing friction models of sliding contacts under different running conditions. Paper B uses a simplified contact model, the elastic foundation model, to model friction in a boundary-lubricated rolling and sliding contact. The model is integrated into a dynamic rigid body model of a mechanical system, and the system behavior is simulated. Paper C discusses the application of the elastic foundation model to rough surface contact problems and investigates how the error in its results depends on surface roughness. Papers D and E address how the wear of the contact surfaces at the pad-to-rotor interface in a passenger car disc brake can be simulated using finite element analysis (FEA).QC 20100811
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Garcia, Alessandra Reis. "Uso do modelo WEPP ( Water Erosion Prediction Project ) modificado para estimar taxas de erosão em estradas florestais." reponame:Repositório Institucional da UFS, 2001. https://ri.ufs.br/handle/riufs/793.
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Este trabalho teve como objetivo geral determinar o volume total de água escoada e a produção de sedimentos provenientes de segmentos de estradas florestais submetidas às condições de chuva natural e, com esses resultados, validar o modelo WEPP por meio de comparações entre dados observados e dados preditos pelo modelo. A pesquisa foi realizada no projeto de reflorestamento, povoamento de Pinus caribaea Morelet e Pinus oocarpa Schiede, pertencente à Fazenda Monte Alegre, em Agudos – São Paulo. O universo abrangido pela pesquisa foi constituído de 16 segmentos de estrada. Foram estudadas duas declividades (1 e 7%) e dois comprimentos (20 e 40 m), caracterizando quatro tratamentos: comprimento do segmento de 20 m e 1% de declividade, comprimento de 40 m e 1% de declividade, comprimento de 20 m e 7% de declividade e comprimento de 40 m e 7% de declividade. De cada tratamento foram feitas quatro repetições. Para determinação da quantidade de material erodido foram instalados tambores coletores, localizados na parte inferior das estradas. Posteriormente, os arquivos de clima, precipitação, solo, inclinação e comprimento do segmento foram introduzidos e adaptados ao modelo de predição de erosão WEPP com o propósito de dar validação a este, visando a confecção de um modelo apropriado às condições florestais brasileiras. Os resultados das análises permitiram concluir o seguinte: a) nos valores observados de volume de enxurrada, o efeito de comprimento do segmento de estrada foi significativo, ao passo que o efeito de declividade não apresentou diferença significativa; b) nos valores observados de peso do solo, o efeito de declividade do segmento foi mais significativo que o efeito de comprimento; c) nos valores de volume de enxurrada e peso do solo preditos pelo modelo WEPP, o efeito de declividade do segmento foi mais significativo que o efeito de comprimento; d) à medida que se aumentou a precipitação, ocorreu aumento quadrático do volume de enxurrada observado em todos os tratamentos; e) à medida que a precipitação aumentou, ocorreu aumento linear do peso do solo observado no comprimento do segmento de 20 m e 1% de declividade; entretanto, nos outros tratamentos, o aumento no peso do solo observado foi quadrático; f) em todos os tratamentos, o peso do solo observado cresceu exponencialmente em função do incremento no volume de enxurrada; g) na validação do modelo WEPP, os valores preditos de volume de enxurrada foram em média 166,58% superiores aos dados observados; h) os valores observados de peso do solo na declividade de 1% apresentaram variação superior de 1125,09% no segmento de estrada com 20 m de comprimento e de 724,41% no segmento com 40 m de comprimento, em relação aos valores preditos pelo modelo WEPP, indicando que, nas menores declividades, o modelo se comportou de forma não-satisfatória, subestimando as perdas; i) os valores de peso do solo preditos pelo modelo WEPP na declividade de 7% apresentaram variação superior de 6,73% no segmento de estrada com 20 m de comprimento e de 120,25% no segmento com 40 m de comprimento, em relação aos valores observados; e j) o modelo brasileiro de predição de erosão pela água (WEPP – Brasil) não se encontra totalmente calibrado para nossas condições. _________________________________________________________________________________________ ABSTRACT: The general objective of this work was to determine the total volume of the water runoff and the production of sediments from segments of forest roads under normal rainfall conditions, and, with the results, to test the WEPP model through comparisons between data observed and data predicted by the model. The research was carried out in a reforestation project with Pinus caribaea Morelet and Pinus oocarpa Schiede plantations, of the Fazenda Monte Alegre, in Agudos – São Paulo State, Brazil. The area covered by the research was of 16 road segments. Two slopes (1 and 7%) and two lengths (20 and 40 m) were studied, totalling four treatments: length of the segment of 20 m and slope of 1%; length of 40 m and slope of 1%; length of 20 m and slope of 7%; and length of 40 m and slope of 7%. Of each treatment, four repetitions were made. For the determination of amount of eroded matter, collector drums were placed in the lowest part of the roads. Later, files of climate, precipitation, soil, slope and segment length were included and adapted to the erosion prediction WEPP model, with the purpose of validating the model, viewing the elaboration of a model suited to the Brazilian forest conditions. The analyses results allowed the following conclusions: a) in the observed volumes of runoff, the effect of road segment length was significant, while the slope effect did not present a significant difference; b) in the observed values of soil weights, the slope effect of the segment was more significant than the length effect; c) in the values of runoff volume and soil weight predicted by the WEPP model, the slope effect of the segment was more significant than the length effect; d) as the precipitation increased, the runoff volume increased in a quadratic way, which was observed in all the treatments; e) as the precipitation increased, a linear increase of soil weight occurred in the segment length of 20 m and slope of 1%. However, in the other treatments, the increase observed in soil weight was quadratic; f) in all the treatments, the observed soil weight increased exponentially in function of the increase in the runoff volume; g) in the validation of the WEPP model, the runoff volumes predicted were, in average, 166.58% greater than the observed data; h) the observed soil weight values in the 1% slope presented a higher variation of 1125.09% in the road segment with length of 20 m, and 724.41% in the segment with 40 m in relation to the values predicted by the WEPP model. This indicates that, in lower slope values, the behaviour of the model was not satisfactory, subestimating losses; i) the soil weight values predicted by the WEPP model in the 7% of slope presented a higher variation of 6.73% in the road segment of 20 m, and 120.25% in the segment of 40m, in relation to the observed values; and j) the Brazilian model for prediction of erosion by water (WEPP-Brasil), is not totally adjusted to these conditions.
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Salminen, Henry. "Parametrizing tyre wear using a brush tyre model." Thesis, KTH, Aerodynamik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-163716.
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Studying rubber wear is important because it can save money, minimize health and environmental issues related to the particles generated from tyre wear and reduce fuel consumption. The wear of rubber is considered to be the result of energy dissipation due to friction. There are many models that describe the dynamical behaviour of vehicles and tyre, but less e ort has been dedicated to consider the tyre wear in these models. The purpose of the thesis was to create an easy to understand and trend-accurate tyre wear model for implementation in a complete car model. The tyre wear in the thesis is determined to be the amount of rubber volume loss due to sliding per unit length that the tyre travels. A literature study was performed with the objective of gaining knowledge of tyre models and the a ecting parameters of tyre wear. The most important parameters in determining tyre wear were identied as the forward velocity, side-slip angle, longitudinal slip, vertical load, and tyre ination pressure. The wear was chosen to be calculated with Archards wear law for these parameters both separately and combined in pairs in order to obtain a deeper understanding of the wear. The results show that wear is increasing exponentially for the forward velocity. Tyre wear decreases linearly as tyre ination pressure (vertical bristle sti ness) increases. The vertical load, longitudinal slip and side-slip angle yielded exponentially increasing wear. The most inuential parameters a ecting the tyre wear were the longitudinal slip and side-slip angle, these yielded wear rates up to 107 higher compared with the reference case. The developed tyre wear model is a good base for future work. More measurement data are needed in order to validate the model. For future work it is also recommended to implement camber angle and temperature dependency in order to study these two important parameters inuence on tyre wear.
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Gauttreau, Jeffrey Tyler, and Jeffrey Tyler Gauttreau. "Wear Rate Prediction Model for Large Mining Trucks." Thesis, The University of Arizona, 2017. http://hdl.handle.net/10150/624991.
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A mining trucks purpose is to move materials from one place to another. Due to the materials loaded and the conditions for which the trucks are operated, the useful life of truck bed surfaces can vary greatly. For a mining company, waiting for repairs on a truck will substantially cut into profits. This model aims to predict the rate at which the truck will wear and therefore give the customer foresight for when repairs will be necessary.
We will show how the systems was designed and verified along the project lifecycle. This document verifies how system requirements have been met and the customer is satisfied with the project.
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Riquelme, Serey Jaime Patricio. "Incertidumbre de las Variable Meteorológicas en la Estimación de los Recursos Hídricos Futuros en la Cuenca del Río Pangal." Tesis, Universidad de Chile, 2010. http://repositorio.uchile.cl/handle/2250/103762.
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Existe en la comunidad científica un amplio consenso que el cambio climático modificará, entre otros efectos, la disponibilidad de los recursos hídricos alrededor del planeta. Esto se basa en los resultados de modelos meteorológicos de gran escala que sirven de entrada a modelos hidrológicos aplicados a situaciones locales.
El objetivo principal de este trabajo es cuantificar la variación que sufren las series de caudales medios mensuales, producto de los datos meteorológicos y configuraciones adoptadas en la modelación del río Pangal, el cual se encuentra ubicado en la Región del Libertador General Bernardo O’Higgins, Chile, utilizando el modelo de gestión WEAP desarrollado por el Stockholm Environment Institute.
Para el análisis de la variabilidad e incertidumbre de los resultados, se consideraron un conjunto de parámetros, siendo éstos: i) división espacial de la cuenca, ii) gradientes meteorológicos, iii) series alternativas futuras y iv) parámetros modelo WEAP.
Generados los gradientes en base a registros de estaciones existentes en el área de interés, y utilizando el modelo de humedad del suelo, se implementó la cuenca en WEAP considerando tres escenarios consistentes en una, dos y seis bandas de altura, los cuales fueron calibrados y validados en el escenario actual utilizando el coeficiente de Nash – Sutcliffe. Se observó que a medida que la cuenca se modela de manera más concentrada, el valor del coeficiente disminuye desde 0,82 a 0,62, lo que se ve reflejado en una subestimación importante de los caudales de deshielo.
Para la generación de los caudales futuros en el periodo 2005 a 2035, se utilizaron series mensuales de temperatura y precipitación para los escenarios A2 como B2 definidos por el IPCC. Las series meteorológicas futuras fueron derivadas del modelo de circulación global HadCM3, escaladas con el software SDSM, generando un modelo con coeficiente R2 de 0,53 y 0,42 para la temperatura y precipitación, respectivamente.
Los resultados de la modelación indican que al seleccionar de las 20 series generadas con cada gradiente, aquella con mayor disminución de precipitación y mayor aumento de la temperatura, se produce en el escenario A2 un descenso promedio de los caudales medios anuales de un 16%, aunque los caudales medios mensuales pueden tener importantes variaciones (37% en Noviembre). Por otra parte, si se selecciona aquella serie con menor disminución de precipitación y menor aumento de temperaturas, se tiene un aumento promedio de los caudales medios anuales de un 12%. Finalmente, en el escenario B2 se observa la misma tendencia, sin embargo las variaciones son de una menor magnitud (disminución de un 4% en el caso más desfavorable, y aumento de 5% en el más favorable). Lo anterior refleja la necesidad de mayor investigación para disminuir la incertidumbre inherente a estas modelaciones.Existe en la comunidad científica un amplio consenso que el cambio climático modificará, entre otros efectos, la disponibilidad de los recursos hídricos alrededor del planeta. Esto se basa en los resultados de modelos meteorológicos de gran escala que sirven de entrada a modelos hidrológicos aplicados a situaciones locales. El objetivo principal de este trabajo es cuantificar la variación que sufren las series de caudales medios mensuales, producto de los datos meteorológicos y configuraciones adoptadas en la modelación del río Pangal, el cual se encuentra ubicado en la Región del Libertador General Bernardo O’Higgins, Chile, utilizando el modelo de gestión WEAP desarrollado por el Stockholm Environment Institute. Para el análisis de la variabilidad e incertidumbre de los resultados, se consideraron un conjunto de parámetros, siendo éstos: i) división espacial de la cuenca, ii) gradientes meteorológicos, iii) series alternativas futuras y iv) parámetros modelo WEAP. Generados los gradientes en base a registros de estaciones existentes en el área de interés, y utilizando el modelo de humedad del suelo, se implementó la cuenca en WEAP considerando tres escenarios consistentes en una, dos y seis bandas de altura, los cuales fueron calibrados y validados en el escenario actual utilizando el coeficiente de Nash – Sutcliffe. Se observó que a medida que la cuenca se modela de manera más concentrada, el valor del coeficiente disminuye desde 0,82 a 0,62, lo que se ve reflejado en una subestimación importante de los caudales de deshielo. Para la generación de los caudales futuros en el periodo 2005 a 2035, se utilizaron series mensuales de temperatura y precipitación para los escenarios A2 como B2 definidos por el IPCC. Las series meteorológicas futuras fueron derivadas del modelo de circulación global HadCM3, escaladas con el software SDSM, generando un modelo con coeficiente R2 de 0,53 y 0,42 para la temperatura y precipitación, respectivamente. Los resultados de la modelación indican que al seleccionar de las 20 series generadas con cada gradiente, aquella con mayor disminución de precipitación y mayor aumento de la temperatura, se produce en el escenario A2 un descenso promedio de los caudales medios anuales de un 16%, aunque los caudales medios mensuales pueden tener importantes variaciones (37% en Noviembre). Por otra parte, si se selecciona aquella serie con menor disminución de precipitación y menor aumento de temperaturas, se tiene un aumento promedio de los caudales medios anuales de un 12%. Finalmente, en el escenario B2 se observa la misma tendencia, sin embargo las variaciones son de una menor magnitud (disminución de un 4% en el caso más desfavorable, y aumento de 5% en el más favorable). Lo anterior refleja la necesidad de mayor investigación para disminuir la incertidumbre inherente a estas modelaciones.
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Theodoridis, John Apostolis 1972. "Borehole electromagnetic prospecting for weak conductors." Monash University, School of Geosciences, 2004. http://arrow.monash.edu.au/hdl/1959.1/5225.
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Andersson, Evelina. "Water demand and supply in Dar es Salaam : A WEAP-model to estimate future scenarios." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-257209.
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The water and sewage company in Dar es Salaam, Tanzania has expressed a lack of integrated development plan for their service area. The current planning does not combine the social, economic and environmental stakeholders. This project investigated how rapid urbanisation and Tanzania’s vision of going from a low to middle-income country before 2025 will affect the water demand together with an investigation of the sustainability of the water supply in the city, Dar es Salaam. Furthermore, the study also investigated the collected historical data from the city’s biggest water supplier, Ruvu river, to examine if there are any changes in waterflow. The study used previous research, collaboration with students and interviews with the stakeholder and experts to collect information and estimate historical patterns. With the software, Water And Evaluation Planning (WEAP), the study processed the historical data to simulate future scenarios with aim on sustainability and development mentioned above. The study shows an increased demand in the future as a result of both urbanisation and economic growth and unmet demand in all scenarios. From the historical data the study shows a small decrease in total quantity and an upgoing trend of the peaks that occur during the biggest annual rainy season. Lastly, the study finds a need of looking at the current sources of supply to achieve sustainable utilization of the resource.Det här projektet undersöker hur en snabb urbanisering och Tanzanias vision att gå från låg- till mellaninkomstland kan komma att påverka efterfrågan på färskvattnet i Dar es Salaam fram till 2030. Från historisk flödesdata från stadens största vattengivare, Ruvu floden undersöks om det går att utläsa några ändringar i flödena sedan 1980 fram till 2010. Fortsättningsvis diskuteras även hur ett hållbart nyttjande går att åstadkomma. Information och historisk data samlades från litteratursök, intervjuer och med samarbete med studenter och vatten- och sanitetsföretaget i staden. För att undersöka framtiden för stadens vattentillgång och efterfråga användes simulationsprogrammet Water And Evaluation Planning (WEAP) som genom att processerna historisk data, kan simulera liknande variationer i framtiden. Programmet gör det också möjligt för användaren att undersöka parallella scenarios med ändrade flöden och efterfråga. Studien visar att efterfrågan på vatten kommer att öka i alla scenarios och omött efterfrågan i alla scenarios. Studien finner att för hållbart nyttjande av denna resurs kräves mer undersökningar eller alternativ för att säkra tillgången på färskvattnet. De historiska data samlade från floden visar en liten nedåtgående trend i flödesmängd och en uppåtgående trend på mängd vatten som kommer under årets största regnperiod.
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Thapen, Neil. "The weak pigeonhole principle in models of bounded arithmetic." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249222.
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Travkin, Oleg [Verfasser]. "Verifying concurrent programs under weak memory models / Oleg Travkin." Paderborn : Universitätsbibliothek, 2017. http://d-nb.info/1148506217/34.
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Alvarez, Benjamin. "Scattering Theory for Mathematical Models of the Weak Interaction." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0227.
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Dans ce travail nous considérons d'abord un modèle mathématique de la désintégration des bosons W en leptons. L'hamiltonien d'énergie libre est perturbé par un terme d'interaction issu du modèle standard de la physique des particules. Après avoir introduit des coupures en hautes énergies ainsi qu'en espace, nous démontrons que l'Hamiltonien est un opérateur auto-adjoint sur un produit tensoriel d'espaces de Fock. Nous en étudions la théorie de la diffusion. D'abord, nous supposons que les neutrinos ont une masse non nulle et la complétude asymptotique est vérifiée pour une valeur quelconque de la constante de couplage. Dans un deuxième temps, nous considérons des neutrinos non massifs dans un modèle simplifié. Nous démontrons alors la complétude asymptotique en supposant que la constante de couplage est suffisamment petite, en utilisant une théorie de Mourre singulière, des estimations de propagation adaptées ainsi que la conservation d'une certaine combinaison linéaire d'opérateurs de nombre de particules. Nous étudions par ailleurs des modèles de théorie des champs pour un nombre fini mais quelconque de fermions de spin 1/2. Le terme d'interaction est obtenu en considérant toutes les combinaisons possibles pour les opérateurs de création et d'annihilation. Les différents champs peuvent être massifs comme non massifs et le noyau d'interaction doit vérifier des hypothèses de régularité en espace comme en moment. L'hamiltonien est alors un opérateur auto-adjoint, quelque soit l'intensité de l'interaction, sur un produit tensoriel d'espaces de Fock. Nous démontrons par ailleurs l'existence d'un état fondamental. Nos résultats s'appuient sur une interpolation d'estimation en Nτ et peuvent intervenir dans la modélisation de processus d'interaction faible dans la théorie de Fermi. Nous présenterons enfin une façon de retirer la troncature en espace sur des modèles jouets anfin de définir un modèle invariant par translationIn this work, we consider, first, mathematical models of the weak decay of the vector bosons W into leptons. The free quantum field Hamiltonian is perturbed by an interaction term from the standard model of particle physics. After the introduction of high energy and spatial cut-offs, the total quantum Hamiltonian defines a self-adjoint operator on a tensor product of Fock spaces. We study the scattering theory for such models. First, the masses of the neutrinos are supposed to be positive: for all values of the coupling constant, we prove asymptotic completeness of the wave operators. In a second model, neutrinos are treated as massless particles and we consider a simpler interaction Hamiltonian: for small enough values of the coupling constant, we prove again asymptotic completeness, using singular Mourre's theory, suitable propagation estimates and the conservation of the difference of some number operators. We moreover study Hamiltonian models representing an arbitrary number of spin 1/2 fermion quantum fields interacting through arbitrary processes of creation or annihilation of particles. The fields may be massive or massless. The interaction form factors are supposed to satisfy some regularity conditions in both position and momentum space. Without any restriction on the strength of the interaction, we prove that the Hamiltonian identifies to a self-adjoint operator on a tensor product of anti-symmetric Fock spaces and we establish the existence of a ground state. Our results rely on novel interpolated Nτ estimates. They apply to models arising from the Fermi theory of weak interactions, with ultraviolet and spatial cut-offs. Finally, the removal of spatial cut-off to define translation invariant toy models will be quickly discussed in the last chapter
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Hendricks, Jeffrey James. "Spectral Stability of Weak Detonations in the Majda Model." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3626.
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Using analytical and numerical Evans-function techniques, we examine the spectral stability of weak-detonation-wave solutions of Majda's scalar model for a reacting gas mixture. We provide a proof of monotonicity of solutions. Using monotonicity we obtain a bound on possible unstable eigenvalues for weak-detonation-wave solutions that improves on the more general bound given by Humpherys, Lyng, and Zumbrun. We use a numerical approximation of the Evans function to search for possible unstable eigenvalues in the bounded region obtained by the energy estimate. For the parameter values tested, our results combined with the result of Lyng, Raoofi, Texier, and Zumbrun demonstrate that these waves are nonlinearly phase-asymptotically orbitally stable throughout the parameter space for which solutions were obtainable.
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Hulcher, Zachary R. "Resolution effects in the hybrid strong/weak coupling model." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/111887.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 33-34).
Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower within it to arbitrary resolution. We introduce a screening length parameter, LRes, proportional to the inverse of the local temperature in the plasma, estimating the value of the proportionality constant from both weakly coupled QCD calculations and holographic calculations appropriate in strongly coupled plasma. We then modify the hybrid model so that when a parton in a jet shower splits, its two offspring are initially treated as unresolved, and are only treated as two separate partons losing energy independently after they are separated by a distance LRes. This modification delays the quenching of partons with intermediate energy, resulting in the survival of more hadrons in the final state with PT in the several GeV range. We demonstrate that this effect modifies the jet shapes and jet fragmentations functions, as it makes it more probable for particles carrying a small fraction of the jet energy at larger angles from the jet axis to survive their passage through the quark-gluon plasma. We analyze the consequences of different choices for the value of the resolution length LRes on both partonic and hadronic jet shapes and fragmentation functions, as well as on missing-PT observables. More generally, we discuss the qualitative consequences, and importance, of including the effects of finite resolution.
by Zachary R. Hulcher.
S.B.
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Oztekin, Tekin. "Modification and evaluation of WEPP water table management model /." The Ohio State University, 2000. http://rave.ohiolink.edu/etdc/view?acc_num=osu1488196234908385.
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Hulcher, Zachary R. "Resolution effects in the hybrid strong/weak coupling model." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111887.
Full textAbstract:
Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 33-34).
Within the context of a hybrid strong/weak coupling model of jet quenching, we study the consequences of the fact that the plasma produced in a heavy ion collision cannot resolve the substructure of a collimated parton shower within it to arbitrary resolution. We introduce a screening length parameter, LRes, proportional to the inverse of the local temperature in the plasma, estimating the value of the proportionality constant from both weakly coupled QCD calculations and holographic calculations appropriate in strongly coupled plasma. We then modify the hybrid model so that when a parton in a jet shower splits, its two offspring are initially treated as unresolved, and are only treated as two separate partons losing energy independently after they are separated by a distance LRes. This modification delays the quenching of partons with intermediate energy, resulting in the survival of more hadrons in the final state with PT in the several GeV range. We demonstrate that this effect modifies the jet shapes and jet fragmentations functions, as it makes it more probable for particles carrying a small fraction of the jet energy at larger angles from the jet axis to survive their passage through the quark-gluon plasma. We analyze the consequences of different choices for the value of the resolution length LRes on both partonic and hadronic jet shapes and fragmentation functions, as well as on missing-PT observables. More generally, we discuss the qualitative consequences, and importance, of including the effects of finite resolution.
by Zachary R. Hulcher.
S.B.
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Hadley, John Willam. "The influence of chemical composition on the tribological performance of middle distillate fuels in steel on steel contacts." Thesis, Liverpool John Moores University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244443.
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Matamoros, Efrain Pantaleón. "Modelo de desgaste oxidativo baseado em parâmetros termodinâmicos." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/3/3132/tde-30042004-180341/.
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Durante o desgaste por deslizamento há a ocorrência de calor gerado por atrito, que favorece a oxidação nas superfícies de contato dos metais. O resultado deste fenômeno pode provocar uma diminuição da taxa de desgaste, a qual usualmente é associada com transições no tipo de contato: metal-metal, metal-óxido ou óxido-óxido. Este trabalho tem como objetivo desenvolver um modelo teórico do desgaste oxidativo. O modelo tenta correlacionar parâmetros termodinâmicos e tribológicos dos materiais, como energia de Gibbs, carga, área real de contato, velocidade e temperatura do contato. Para testar o modelo, realizaram-se ensaios do tipo pino-sobre-disco convencional, para análise da influência dos parâmetros tribológicos, de forma a obter diversas relações entre temperatura de contato, carga, velocidade e as propriedades físico-químicas dos materiais. Os ensaios foram realizados com variação contínua de carga, em intervalos de 20 a 120 N, 20 a 80 N e de 20 a 40 N. Os materiais escolhidos para serem ensaiados foram pino de aço ferramenta M2 temperado e revenido, enquanto que o disco foi de aço 1045 austemperado com microestrutura do tipo bainítica. A caracterização superficial antes e depois dos ensaios foi feita usando-se diferentes técnicas auxiliares, tais como microscopia óptica e eletrônica de varredura. Analisando as curvas obtidas a partir do modelo, assim como as obtidas pelas análise das experiências feitas para sua avaliação, pôde-se concluir que força motriz que causa a taxa de desgaste é a energia de contato, a qual depende das condições físico-químicas, do meio e das solicitações impostas às condições de contato, sendo também as propriedades do material essenciais para a influência na taxa de desgaste, propriedades que estão intrínsecas no modelo, assumindo a energia de Gibbs do material.During sliding wear, heat generated friction occurs, which favors oxidation occurrence on the contacting surfaces of metallic materials. The oxidation phenomenon can result in wear rate attenuation due to transitions in the contact feature from metal-metal to either metal-oxide or oxide-oxide. This work aimed to develop a theoretical modeling on oxidational wear. In the obtained model, both thermodynamic and tribological parameters were used, such as Gibbs energy, load, actual area of contact, velocity and contact temperature. In order to obtain experimental data for the model assessment, usual pin-on-disk tests were conducted under some load and velocity conditions. Relations among the variables, such as contact temperature, load, velocity and physical-chemical properties of the materials, were attained. The tests were performed under continuous rising on load. Intervals from 20 to 120 N, 20 to 80 N and 20 to 40 N were tested. The pin material was made of quenched and tempered M2 tool steel and the disks were of austempered AISI 1045 steel with bainitic microstructure. Surface characterization was carried out before and after the tests, through optical and scanning electronic microscopes. Analyzing the results obtained from the model and from the experimental tests, it was possible to conclude that the wear phenomenon is related to the contact energy, which depends on the physical-chemical conditions of the surfaces, the environment and the mechanical loading the surfaces undergo. The material properties, which do also influence the wear rate, were taken into consideration in the model as the Gibbs energy of the materials.
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Van, den Berg Gideon. "Hidden Markov models for tool wear monitoring in turning operations." Diss., Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-05302005-114238/.
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Al-Salim, Taha Hussein. "A comparative application of flood routing models on the rivers Wear and Tees with special reference to the state variable model." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5126/.
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An analysis of a number of flood routing methods has been carried out in this study. These methods are namely, the Muskingum-Cunge Method, the Variable Parameter Diffusion Method, the State Variable Kinematic Wave Model, and the state variable modelling of nonlinear Muskingum Model. The Muskingum-Cunge and Variable Parameter Diffusion Methods are recommended for use on British Rivers by the Natural Environment Research Council flood studies report, 1975.In using numerical flood routing model, it is very important to calculate the model parameters. For instance storage routing models require a suitable form of storage-discharge relationship. Past flow records were used for the above calculation. The state Variable Kinematic Wave Model has been applied for routing the flood hydrograph through river reaches. The stage and discharge are computed by a kinematic wave routing technique using the state variable approach in which the one-dimensional differential equations of unsteady flow are solved by state and output equations of the state variable model. The nonlinear Muskingum equation has been solved using the state variable modelling technique. Two parameter estimation techniques namely, Hooke-Jeeves and linear regression, are employed for the calibration of the nonlinear Muskingum model parameters (a, x, and m).The applicability of the flood routing model computer programs to different flood events of different seasons for reaches of both the Rivers Wear and Tees is demonstrated. Discriptions of the geology and hydrological data for reaches of both the Rivers Wear and Tees are given in this study. The computed and observed hydrographs of flood routing models used in this study are compared.
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Mess, Francis McCarthy. "Wear model for chemo-mechanical polishing of single crystal silicon." Thesis, Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/15984.
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Elalem, Khaled Taher. "Development of a micro-scale dynamic model for wear simulation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0007/MQ59800.pdf.
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Leonard, Catherine Danielle Bartlett. "Beyond the standard cosmological paradigm with weak gravitational lensing." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:15c2979e-f085-4836-97be-6890740ed4ba.
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Next-generation cosmological surveys will demand an unprecedented understanding of the interplay between theoretical and observational aspects of weak gravitational lensing. This thesis presents a study of the parameter degeneracies and theoretical uncertainties which will affect weak lensing tests of cosmology beyond the standard paradigm. In particular, tests of alternative theories of gravity and of spatial curvature are considered. First, by considering linear-order departures from the standard gravitational theory of general relativity, a novel expression is derived for the weak lensing convergence power spectrum under alternative theories of gravity. Using this expression, degeneracies between gravitational parameters in weak lensing observations are explored, first with a focus on scale-independent parameterisations of gravity, then considering new physical scales introduced by alternative theories. The degeneracy-breaking offered by the combination of weak lensing and redshift-space distortions is shown to be robust to the time-dependence of the functions parameterising modified gravity. Next, the gravity-testing statistic EG is investigated, and a new theoretical expression for its observationally-motivated definition is presented. The theoretical uncertainty of EG is compared to forecast statistical errors, and found to be significant in the case of a more futuristic measurement. Predictions are then computed for EG under deviations from general relativity, and the ongoing utility of EG as a probe of gravity is discussed. Finally, an investigation is made of the potential for measuring or constraining the spatial curvature using weak lensing and complementary observables. The predicted constraint on the spatial curvature is forecast for a suite of upcoming surveys, and the effect of including parameters which may be degenerate with the spatial curvature is explored. It is found that upcoming observations are likely to constrain spatial curvature at a 10⁻³ level, but not to reach the best-case constraint of ~10⁻⁴.
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Fish, Randall K. "Dynamic models of machining vibrations, designed for classification of tool wear /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/6033.
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Blomberg, Niclas. "Higher Criticism Testing for Signal Detection in Rare And Weak Models." Thesis, KTH, Matematisk statistik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103284.
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examples - we need models for selecting a small subset of useful features from high-dimensional data, where the useful features are both rare and weak, this being crucial for e.g. supervised classfication of sparse high- dimensional data. A preceding step is to detect the presence of useful features, signal detection. This problem is related to testing a very large number of hypotheses, where the proportion of false null hypotheses is assumed to be very small. However, reliable signal detection will only be possible in certain areas of the two-dimensional sparsity-strength parameter space, the phase space. In this report, we focus on two families of distributions, N and χ2. In the former case, features are supposed to be independent and normally distributed. In the latter, in search for a more sophisticated model, we suppose that features depend in blocks, whose empirical separation strength asymptotically follows the non-central χ2ν-distribution. Our search for informative features explores Tukey's higher criticism (HC), which is a second-level significance testing procedure, for comparing the fraction of observed signi cances to the expected fraction under the global null. Throughout the phase space we investgate the estimated error rate, Err = (#Falsely rejected H0+ #Falsely rejected H1)/#Simulations, where H0: absence of informative signals, and H1: presence of informative signals, in both the N-case and the χ2ν-case, for ν= 2; 10; 30. In particular, we find, using a feature vector of the approximately same size as in genomic applications, that the analytically derived detection boundary is too optimistic in the sense that close to it, signal detection is still failing, and we need to move far from the boundary into the success region to ensure reliable detection. We demonstrate that Err grows fast and irregularly as we approach the detection boundary from the success region. In the χ2ν-case, ν > 2, no analytical detection boundary has been derived, but we show that the empirical success region there is smaller than in the N-case, especially as ν increases.
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Park, Daehyun. "Development of Surface Wear and Lapping Simulation Models for Hypoid Gears." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1251739728.
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Cox, Gregory Fletcher. "Advances in Weak Identification and Robust Inference for Generically Identified Models." Thesis, Yale University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10633240.
Full textAbstract:
This dissertation establishes tools for valid inference in models that are only generically identified with a special focus on factor models.
Chapter one considers inference for models under a general form of identification failure, by studying microeconometric applications of factor models. Factor models postulate unobserved variables (factors) that explain the covariation between observed variables. For example, school quality can be modeled as a common factor to a variety of school characteristics. Observed variables depend on factors linearly with coefficients that are called factor loadings. Identification in factor models is determined by a rank condition on the factor loadings. The rank condition guarantees that the observed variables are sufficiently related to the factors that the parameters in the distribution of the factors can be identified. When the rank condition fails, for example when the observed school characteristics are weakly related to school quality, the asymptotic distribution of test statistics is nonstandard so that chi-squared critical values no longer control size.
Calculating new critical values that do control size requires characterizing the asymptotic distribution of the test statistic along sequences of parameters that converge to points of rank condition failure. This paper presents new theorems for this characterization which overcome two technical difficulties: (1) non-differentiability of the boundary of the identified set and (2) degeneracy in the limit stochastic process for the objective function. These difficulties arise in factor models, as well as a wider class of generically identified models, which these theorems cover. Non-differentiability of the boundary of the identified set is solved by squeezing the distribution of the estimator between a nonsmooth, fixed boundary and a smooth, drifting boundary. Degeneracy in the limit stochastic process is solved by restandardizing the objective function to a higher-order so that the resulting limit satisfies a unique minimum condition. Robust critical values, calculated by taking the supremum over quintiles of the asymptotic distributions of the test statistic, result in a valid robust inference procedure.
Chapter one demonstrates the robust inference procedure in two examples. In the first example, there is only one factor, for which the factor loadings may be zero or close to zero. This simple example highlights the aforementioned important theoretical difficulties. For the second example, Cunha, Heckman, and Schennach (2010), as well as other papers in the literature, use a factor model to estimate the production of skills in children as a function of parental investments. Their empirical specification includes two types of skills, cognitive and noncognitive, but only one type of parental investment out of a concern for identification failure. We formulate and estimate a factor model with two types of parental investment, which may not be identified because of rank condition failure. We find that for one of the four age categories, 6-9 year olds, the factors are close to being unidentified, and therefore standard inference results are misleading. For all other age categories, the distribution of the factors is identified.
Chapter two provides a higher-order stochastic expansion of M- and Z- estimators. Stochastic expansions are useful for a wide variety of stochastic problems, including bootstrap refinements, Edgeworth expansions, and identification failure. Without identification, the higher-order terms in the expansion may become relevant for the limit theory. Stochastic expansions above fourth order are rarely used because the expressions in the expansion become intractable. For M- and Z- estimators, a wide class of estimators that maximize an objective function or set an objective function to zero, this paper provides smoothness conditions and a closed-form expression for a stochastic expansion up to an arbitrary order.
Chapter three provides sufficient conditions for a random function to have a global unique minimum almost surely. Many important statistical objects can be defined as the global minimizing set of a function, including identified sets, extremum estimators, and the limit of a sequence of random variables (due to the argmax theorem). Whether this minimum is achieved at a unique point or a larger set is often practically and/or theoretically relevant. This paper considers a class of functions indexed by a vector of parameters and provides simple transversality-type conditions which are sufficient for the minimizing set to be a unique point for almost every function.
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Wedgwood, Kyle C. A., Kevin K. Lin, Ruediger Thul, and Stephen Coombes. "Phase-Amplitude Descriptions of Neural Oscillator Models." BioMed Central, 2013. http://hdl.handle.net/10150/610255.
Full textAbstract:
Phase oscillators are a common starting point for the reduced description of many single neuron models that exhibit a strongly attracting limit cycle. The framework for analysing such models in response to weak perturbations is now particularly well advanced, and has allowed for the development of a theory of weakly connected neural networks. However, the strong-attraction assumption may well not be the natural one for many neural oscillator models. For example, the popular conductance based Morris-Lecar model is known to respond to periodic pulsatile stimulation in a chaotic fashion that cannot be adequately described with a phase reduction. In this paper, we generalise the phase description that allows one to track the evolution of distance from the cycle as well as phase on cycle. We use a classical technique from the theory of ordinary differential equations that makes use of a moving coordinate system to analyse periodic orbits. The subsequent phase-amplitude description is shown to be very well suited to understanding the response of the oscillator to external stimuli (which are not necessarily weak). We consider a number of examples of neural oscillator models, ranging from planar through to high dimensional models, to illustrate the effectiveness of this approach in providing an improvement over the standard phase-reduction technique. As an explicit application of this phase-amplitude framework, we consider in some detail the response of a generic planar model where the strong-attraction assumption does not hold, and examine the response of the system to periodic pulsatile forcing. In addition, we explore how the presence of dynamical shear can lead to a chaotic response.
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Enblom, Roger. "On Simulation of Uniform Wear and Profile Evolution in the Wheel - Rail Contact." Doctoral thesis, Stockholm : Dept. of aeronautics and vehicle engineering, Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4184.
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Abachi, Siamak. "Wear Analysis Of Hot Forging Dies." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605706/index.pdf.
Full textAbstract:
WEAR ANALYSIS OF HOT FORGING DIES
ABACHI, Siamak
M. S., Department of Mechanical Engineering
Supervisor: Prof. Dr. Metin AKKÖK Co-Supervisor: Prof. Dr. Mustafa lhan GÖ
KLER December 2004, 94 pages The service lives of dies in forging processes are to a large extent limited by wear, fatigue fracture and plastic deformation, etc. In hot forging processes, wear is the predominant factor in the operating lives of dies. In this study, the wear analysis of a closed die at the final stage of a hot forging process has been realized. The preform geometry of the part to be forged was measured by Coordinate Measuring Machine (CMM), and the CAD model of the die and the worn die were provided by the particular forging company. The hot forging operation was carried out at a workpiece temperature of 1100°
C and die temperature of 300°
C for a batch of 678 on a 1600-ton mechanical press. The die and the workpiece materials were AISI L6 tool steel and DIN 1.4021, respectively. The simulation of forging process for the die and the workpiece was carried out by Finite Volume Method using MSC.SuperForge. The flow of the material in the die, die filling, contact pressure distribution, sliding velocities and temperature distribution of the die have been investigated. In a single stroke, the depth of wear was evaluated using Archard&rsquo
s wear equation with a constant wear coefficient of 1¥
10-12 Pa-1 as an initial value. The depth of wear on the die surface in every step has been evaluated using the Finite Volume simulation results and then the total depth of wear was determined. To be able to compare the wear analysis results with the experimental worn die, the surface measurement of the worn die has been done on CMM. By comparing the numerical results of the die wear analysis with the worn die measurement, the dimensional wear coefficient has been evaluated for different points of the die surface and finally a value of dimensional wear coefficient is suggested. As a result, the wear coefficient was evaluated as 6.5¥
10-13 Pa-1 and considered as a good approximation to obtain the wear depth and the die life in hot forging processes under similar conditions.
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Albers, Tony. "Weak nonergodicity in anomalous diffusion processes." Doctoral thesis, Universitätsbibliothek Chemnitz, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-214327.
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Anomale Diffusion ist ein weitverbreiteter Transportmechanismus, welcher für gewöhnlich mit ensemble-basierten Methoden experimentell untersucht wird. Motiviert durch den Fortschritt in der Einzelteilchenverfolgung, wo typischerweise Zeitmittelwerte bestimmt werden, entsteht die Frage nach der Ergodizität. Stimmen ensemble-gemittelte Größen und zeitgemittelte Größen überein, und wenn nicht, wie unterscheiden sie sich? In dieser Arbeit studieren wir verschiedene stochastische Modelle für anomale Diffusion bezüglich ihres ergodischen oder nicht-ergodischen Verhaltens hinsichtlich der mittleren quadratischen Verschiebung. Wir beginnen unsere Untersuchung mit integrierter Brownscher Bewegung, welche von großer Bedeutung für alle Systeme mit Impulsdiffusion ist. Für diesen Prozess stellen wir die ensemble-gemittelte quadratische Verschiebung und die zeitgemittelte quadratische Verschiebung gegenüber und charakterisieren insbesondere die Zufälligkeit letzterer. Im zweiten Teil bilden wir integrierte Brownsche Bewegung auf andere Modelle ab, um einen tieferen Einblick in den Ursprung des nicht-ergodischen Verhaltens zu bekommen. Dabei werden wir auf einen verallgemeinerten Lévy-Lauf geführt. Dieser offenbart interessante Phänomene, welche in der Literatur noch nicht beobachtet worden sind. Schließlich führen wir eine neue Größe für die Analyse anomaler Diffusionsprozesse ein, die Verteilung der verallgemeinerten Diffusivitäten, welche über die mittlere quadratische Verschiebung hinausgeht, und analysieren mit dieser ein oft verwendetes Modell der anomalen Diffusion, den subdiffusiven zeitkontinuierlichen ZufallslaufAnomalous diffusion is a widespread transport mechanism, which is usually experimentally investigated by ensemble-based methods. Motivated by the progress in single-particle tracking, where time averages are typically determined, the question of ergodicity arises. Do ensemble-averaged quantities and time-averaged quantities coincide, and if not, in what way do they differ? In this thesis, we study different stochastic models for anomalous diffusion with respect to their ergodic or nonergodic behavior concerning the mean-squared displacement. We start our study with integrated Brownian motion, which is of high importance for all systems showing momentum diffusion. For this process, we contrast the ensemble-averaged squared displacement with the time-averaged squared displacement and, in particular, characterize the randomness of the latter. In the second part, we map integrated Brownian motion to other models in order to get a deeper insight into the origin of the nonergodic behavior. In doing so, we are led to a generalized Lévy walk. The latter reveals interesting phenomena, which have never been observed in the literature before. Finally, we introduce a new tool for analyzing anomalous diffusion processes, the distribution of generalized diffusivities, which goes beyond the mean-squared displacement, and we analyze with this tool an often used model of anomalous diffusion, the subdiffusive continuous time random walk