Abstract Methods are proposed to take account of the effect of emergent vegetation (which covers only part of the channel bed) on conveyance and depth-averaged velocity in open channels. For emergent vegetation strips parallel to the flow direction, discharge can be predicted separately for each vegetated or non-vegetated zone. The equations of Kaiser (1985) and Nuding (1991, 1994) can predict the influence of the vegetation on conveyance within the non-vegetated zone via the composite roughness formula of Pavlovski (1931). In order to predict the lateral distribution of depth-averaged velocity within the non-vegetated zone, the equations of Nuding (1991, 1994) have been modified to take account of the relation between non-vegetated zone width, apparent shear stress on the vegetation interface and the maximum velocity which will occur. For more complex geometries, two-dimensional numerical hydraulic models using existing software and existing relations for the prediction of eddy viscosity are recommended.

Desde 2004, o grupo de estudos do Laboratório de Hidráulica Computacional (LHC) estuda as taxas de recargas hidráulicas do Aquifero Guarani, na Bacia do Ribeirão da Onça. Entretanto, não havia se estudado a quantificação do escoamento superficial. Para sanar esta deficiência, este trabalho visou analisar as metodologias de estimativa de vazão com qualidade para a Bacia do Ribeirão da Onça. Para a realização do trabalho, foi adquirido o equipamento Flo-Tote3, capaz de medir velocidade e nível d\'água. A princípio, o equipamento foi verificado e comparado em laboratório, medindo velocidades 3% inferiores que o molinete e estimando vazões de 0,5 a 7,2% de diferença que o vertedor triangular. No Ribeirão da Onça, foi escolhida e construída uma seção de controle de vazão e instalado o Flo-Tote. O equipamento mediu velocidades 5% inferiores que o molinete, com variações de 0,3 a 8,7%. Além disso, um vertedor circular foi instalado em 6 ocasiões, resultando em vazões de 3 a 15% inferiores as vazões estimadas pelo molinete, em virtude do vazamento que ocorreu entre o vertedor e a parede de concreto. A partir de dezembro de 2007, foram iniciadas medições de níveis d\'água com a construção do linígrafo e estimadas as vazões de modo contínuo com o auxílio de equações teóricas. Como a jusante da seção de controle de vazão existe um sistema de bombeamento, as equações para determinar a vazão sofrem interferencias. Entretanto, foi aplicado o método das isotáquias, que utiliza valores de velocidades e níveis d\'água para o cálculo da vazão e que não sofre interferências com o represamento e instalações de vertedores. Apesar de ocorrer problemas de falta de energia e de manutenção, o escoamento superficial foi quantificado com qualidade para futuros estudos da área afim. / Since 2004, the group of studies of the Computational Hydraulic Laboratory (LHC) studied the rates of water recharge in the Guarani Aquifer recharges water in the Ribeirão da Onça basin. However, it had not studied the quantification of runoff. To remedy this deficiency, this study aimed to analyze the methodologies for estimation of flow quality for the Ribeirão da Onça basin. To carry out the work, it was acquired a Flo-Tote3, capable of measuring velocities and water levels. First, this equipment was checked and compared in the laboratory, measuring velocities 3% below, those obtained using flowmeters and 0.5 to 7.2% differences when compared with results using triangular weir. In Ribeirão da Onça, was chosen and built a section of control flow and installed the Flo-Tote. The equipment measured velocities 5% below the current meters, with variations from 0.3 to 8.7%. In addition, a circular weir was installed on 6 occasions, resulting in flow rates from 3 to 15% lower than those estimated by current meters because of the flow that occurred between the bridge and weir. Since December 2007, started the measurements of water levels and the estimated flow on a continuous basis with the aid of theoretical equations. As the downstream section of the control flow is a pumping system, the equations to determine the flow are interfered. However, it was applied the method of the lines of the same velocities, which uses values of velocities and water levels to calculate the flow without interference with the impoundment and installation of weirs. Despite the problems of lack of energy and maintenance, the runoff was quantified with quality for future studies of the area.

Objectives: The purpose of this study was to examine the relationship of velocities in the back squat between one repetition maximum (1RM) and submaximally loaded repetition maximum (RM) conditions, specifically in regard to what has been described as the minimal velocity threshold (MVT). The MVT describes a minimum concentric velocity that an individual must reach or surpass in order to successfully complete a repetition. Design: To test the presence of a MVT, participants were tested for 1RM and RM back squat ability. The mean concentric veloci ties (MCV) of the last successful repetition of each condition were then compared. Methods: Fourteen male participants familiar with the back squat volunteered to participate in the current study (age = 25.0 y ± 2.6, height = 178.9 cm ± 8.1, body mass = 88.2 kg ± 15.8). The mean concentric velocity (MCV) during the last successful repetition from each testing condition was considered for the comparison. Results: Results indicated a non-significant negative relationship of MCV between the 1RM and RM conditions (r = -0.135), no statistical difference between testing conditions (p = 0.266), with a small-to-moderate effect size (d = 0.468). Conclusions: The results of this study suggest that MVT should be further investigated to enhance its use in the practical setting. Additionally, coaches considering using a velocity-based approach for testing athletes should use data from either 1RM or RM conditions, but not both interchangeably. Coaches should be cautious when considering group averages or comparing velocity data between athletes, which may not be appropriate based on our results.

Esta tesis doctoral llevó a cabo el estudio, desarrollo e implementación de algoritmos para la navegación con sistemas globales de navegación por satélite (GNSS), enfocándose en la determinación precisa de la posición, velocidad y aceleración usando GPS, en modo post-procesado y lejos de estaciones de referencia. Uno de los objetivos era desarrollar herramientas en esta área y hacerlas disponibles a la comunidad GNSS. Por ello el desarrollo se hizo dentro del marco del proyecto preexistente de software libre llamado GPS Toolkit (GPSTk). Una de las primeras tareas realizadas fue la validación de las capacidades de la GPSTk para el procesado del pseudorango, realizando comparaciones con una herramienta de procesamiento de datos probada (BRUS). La gestión de datos GNSS demostró ser un asunto importante cuando se intentó extender las capacidades de la GPSTk al procesamiento de datos obtenidos de las fases de la señal GPS. Por ello se desarrollaron las Estructuras de Datos GNSS (GDS), que combinadas con su paradigma de procesamiento aceleran el proceso de desarrollo de software y reducen errores. La extensión de la GPSTk a los algoritmos de procesado en fase se hizo mediante la ayuda de las GDS, proporcionándose importantes clases accesorias que facilitan el trabajo. Se implementó el procesado de datos Precise Point Positioning (PPP) con ejemplos relativamente simples basados en las GDS, y al comparar sus resultados con otras aplicaciones de reputación ya establecida, se encontró que destacan entre los mejores. También se estudió cómo obtener la posición precisa, en post-proceso, de un receptor GPS a cientos de kilómetros de la estación de referencia más cercana y usando tasas de datos arbitrarias (una limitación del método PPP). Las ventajas aportadas por las GDS permitieron la implementación de un procesado semejante a un PPP cinemático basado en una red de estaciones de referencia, estrategia bautizada como Precise Orbits Positioning (POP) porque sólo necesita órbitas precisas para trabajar y es independiente de la información de los relojes de los satélites GPS. Los resultados de este enfoque fueron muy similares a los del método PPP cinemático estándar, pero proporcionando soluciones de posición con una tasa mayor y de manera más robusta. La última parte se enfocó en la implementación y mejora de algoritmos para determinar con precisión la velocidad y aceleración de un receptor GPS. Se hizo énfasis en el método de las fases de Kennedy debido a su buen rendimiento, desarrollando una implementación de referencia y demostrando la existencia de una falla en el procedimiento propuesto originalmente para el cálculo de las velocidades de los satélites. Se propuso entonces una modificación relativamente sencilla que redujo en un factor mayor que 35 el RMS de los errores 3D en velocidad. Tomando ideas de los métodos Kennedy y POP se desarrolló e implementó un nuevo procedimiento de determinación de velocidad y aceleración que extiende el alcance. Este método fue llamado Extended Velocity and Acceleration determination (EVA). Un experimento usando una aeronave ligera volando sobre los Pirineos mostró que tanto el método de Kennedy (modificado) como el método EVA son capaces de responder ante la dinámica de este tipo de vuelos. Finalmente, tanto el método de Kennedy modificado como el método EVA fueron aplicados a una red en la zona ecuatorial de Sur América con líneas de base mayores a 1770 km. En este escenario el método EVA mostró una clara ventaja tanto en los promedios como en las desviaciones estándar para todas las componentes de la velocidad y la aceleración. / This Ph.D. Thesis focuses on the development of algorithms and tools for precise GPS-based position, velocity and acceleration determination very far from reference stations in post-process mode. One of the goals of this thesis was to develop a set of state-of-the-art GNSS data processing tools, and make them available for the research community. Therefore, the software development effort was done within the frame of a preexistent open source project called the GPSTk. Therefore, validation of the GPSTk pseudorange-based processing capabilities with a trusted GPS data processing tool was one of the initial task carried out in this work. GNSS data management proved to be an important issue when trying to extend GPSTk capabilities to carrier phasebased data processing algorithms. In order to tackle this problem the GNSS Data Structures (GDS) and their associated processing paradigm were developed. With this approach the GNSS data processing becomes like an assembly line, providing an easy and straightforward way to write clean, simple to read and use software that speeds up development and reduces errors. The extension of GPSTk capabilities to carrier phase-based data processing algorithms was carried out with the help of the GDS, adding important accessory classes necessary for this kind of data processing and providing reference implementations. The performance comparison of these relatively simple GDS-based source code examples with other state-of-the art Precise Point Positioning (PPP) suites demonstrated that their results are among the best. Furthermore, given that the GDS design is based on data abstraction, it allows a very flexible handling of concepts beyond mere data encapsulation, including programmable general solvers, among others. The problem of post-process precise positioning of GPS receivers hundreds of kilometers away from nearest reference station at arbitrary data rates was dealt with, overcoming an important limitation of classical post-processing strategies like PPP. The advantages of GDS data abstraction regarding solvers were used to implement a kinematic PPP-like processing based on a network of stations. This procedure was named Precise Orbits Positioning (POP) because it is independent of precise clock information and it only needs precise orbits to work. The results from this approach were very similar (as expected) to the standard kinematic PPP processing strategy, but yielding a higher positioning rate. Also, the network-based processing of POP seems to provide additional robustness to the results, even for receivers outside the network area. The last part of this thesis focused on implementing, improving and testing algorithms for the precise determination of velocity and acceleration hundreds of kilometers away from nearest reference station. Special emphasis was done on the Kennedy method because of its good performance. A reference implementation of Kennedy method was developed, and several experiments were carried out. Experiments done with very short baselines showed a flaw in the way satellite velocities were computed, introducing biases in the velocity solution. A relatively simple modification was proposed, and it reduced the RMS of 5-min average velocity 3D errors by a factor of over 35. Then, borrowing ideas from Kennedy method and the POP method, a new velocity and acceleration determination procedure named EVA was developed and implemented that greatly extends the effective range. An experiment using a light aircraft flying over the Pyrenees showed that both the modified-Kennedy and EVA methods were able to cope with the dynamics of this type of flight. Finally, both modified-Kennedy and EVA method were applied to a challenging scenario in equatorial South America, with baselines over 1770 km, where EVA method showed a clear advantage in both averages and standard deviations for all components of velocity and acceleration. Lloc i

In this thesis, least-squares based finite element models (LSFEM) for the Poisson equation and Navier-Stokes equation are presented. The least-squares method is simple, general and reliable. Least-squares formulations offer several computational and theoretical advantages. The resulting coefficient matrix is symmetric and positive-definite. Using these formulations, the choice of approximating space is not subject to any compatibility condition. The Poisson equation is cast as a set of first order equations involving gradient of the primary variable as auxiliary variables for the mixed least-square finite element model. Equal order C0 continuous approximation functions is used for primary and auxiliary variables. Least-squares principle was directly applied to develop another model which requires C1continous approximation functions for the primary variable. Each developed model is compared with the conventional model to verify its performance. Penalty based least-squares formulation was implemented to develop a finite element for the Navier Stokes equations. The continuity equation is treated as a constraint on the velocity field and the constraint is enforced using the penalty method. Velocity gradients are introduced as auxiliary variables to get the first order equivalent system. Both the primary and auxiliary variables are interpolated using equal order C0 continuous, p-version approximation functions. Numerical examples are presented to demonstrate the convergence characteristics and accuracy of the method.

This study aims to better understand the characteristics of the tidal- current profiles and the near-bed boundary layer structures off the southwestern coast of Taiwan. The velocity profile is measured by a bottom-mounted ADCP. Six experiments were conducted, each lasted 10~20 days and the water depth ranging 12~18 m. Twenty-minute averaged velocity profiles have been fitted to a logarithmic form with 4% accuracy. The friction velocity (u*) and roughness length (z0) are then derived from the slope and intercept of the best-fitted straight lines. Our results show that the profile shape and friction velocity vary tidally, the latter reaches O(0.06)ms-1 during peak current flow. The magnitude of z0 is large and scattered, but it shows a general trend of decrease with increasing flow speed. The observed log-layer height increases, and the bottom drag coefficient (CD) decrease, respectively with increasing flow speed. Measurements also show that water turbidity increases with rainfall, as a result the z0 and CD also increase. Finally, harmonic analysis of the tidal currents indicate significant changes between winter (homogeneous) and summer (stratified) conditions. In winter the vertical variation of orientation and phase is small, whereas in summer there was a 150 orientation and 250 phase difference (the bottom currents lead the surface currents) between the near surface and near bed regions.

The petroleum industry faces problems in transportation of crude petroleum be- cause of the deposition of paraffins, hydrates and asphaltenes on the insides of the pipeline. These are conventionally removed using either chemical inhibitors or mechani- cal devices, called pigs, which travel through the pipeline and mechanically scrape away the deposits. These pigs are propelled by the pipeline product itself and hence travel at the same velocity as the product. Research has indicated that cleaning would be better if the pigs are traveling at a relatively constant velocity of around 70% of the product velocity. This research utilizes the concept of regulating the bypass flow velocity in order to maintain the pig velocity. The bypass flow is regulated by the control unit based on the feedback from the turbine flowmeter, which monitors the bypass flow. A motorized butterfly valve is used for actually controlling the bypass flow. In addition to cleaning, the proposed pig utilizes on-board electronics like accelerom- eter and pressure transducers to store the data gathered during the pig run. This data can then be analyzed and the condition of the pipeline predicted. Thus, this research addresses the problem of designing a pig to maintain a constant velocity in order to achieve better cleaning. It also helps gather elementary data that can be used to predict the internal conditions in the pipe.

<p>The role of nitric acid (HNO₃) on the atmospheric corrosion of metals has so far received little or no attention. However, the last decades of decreasing sulphur dioxide (SO₂) levels and unchanged HNO₃ levels in many industrialized countries have resulted in an increased interest in possible HNO₃-induced atmospheric corrosion effects. In this study a new method was developed for studying the corrosion effects of HNO₃ on metals at well-defined laboratory exposure conditions. The method has enabled studies to be performed on the influence of individual exposure parameters, namely HNO₃-concentration, air velocity, temperature and relative humidity, as well as comparisons with newly generated field exposure data.</p><p>The corrosion rate and deposition rate of HNO₃ on copper was shown to follow a linear increase with HNO3 concentration. The deposition velocity (Vd) of HNO₃ increased up to an air velocity of 11.8 cm s^-1. Only at a higher air velocity (35.4 cm s^-1) the Vd on copper was lower than the Vd on an ideal absorbent, implying the Vd of HNO3 at lower air velocities to be mass-transport limited.</p><p>Within the investigated temperature range of 15 to 35 ºC only a minor decrease in the HNO₃-induced copper corrosion rate could be observed. The effect of relative humidity (RH) was more evident. Already at 20 % RH a significant corrosion rate could be measured and at 65 % RH the Vd of HNO₃ on copper, zinc and carbon steel reached maximum and nearly ideal absorption conditions.</p><p>During identical exposure conditions in HNO_3-containing atmosphere, the corrosion rate of carbon steel was nearly three times higher than that of copper and zinc. The HNO₃-induced corrosion effect of copper, zinc and steel turned out to be significantly higher than that induced by SO2 alone or in combination with either NO₂ or O₃. This is mainly attributed to the much higher water solubility and reactivity of HNO3 compared to SO₂, NO₂ and O_3. Relative to SO₂, zinc exhibits the highest sensitivity to HNO₃, followed by copper, and carbon steel with the lowest sensitivity.</p><p>Extrapolation of laboratory data to an assumed average outdoor wind velocity of 3.6 m s-1 enabled a good comparison with field data. Despite the fact that ambient SO₂ levels are still much higher than HNO₃ levels, the results show that HNO₃ plays a significant role for the atmospheric corrosion of copper and zinc, but not for carbon steel. The results generated within this doctoral study emphasize the importance of further research on the influence of HNO₃ on degradation of other materials, e.g. stone and glass, as well as of other metals. </p>

No description available.

Hydrate-bearing sediments may contribute to the availability of energy resources, affect climate change, or cause seafloor instability. The comprehensive study of hydrate-bearing sediments documented in this manuscript includes physicochemical aspects of hydrate nucleation near mineral surfaces, the validity of THF as a substitute guest molecule for the study of hydrate-bearing sediments, and the effects of hydrate formation on the electromagnetic and the mechanical properties of various soils with a wide range of specific surface. Natural marine sediments are included as part of this investigation to explore the effects of inherent fabric, salts, organic matter, and stress history on the geophysical properties of hydrate-bearing sediments. Experiments are designed to reproduce the state of effective stress in the field at the time of hydrate formation. A comprehensive set of instruments is deployed in this study, and the unprecedented development of electrical resistivity tomography for the study of hydrate formation and dissociation is also documented in detail. Results from this research have important implications for geophysical field characterization and monitoring processes such as production.