No description available.

During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.

El Tomógrafo es un equipo que se utiliza para obtener imágenes axiales del paciente, viene de dos vocablos griegos, Tomos que significa “corte” y grafo (graficar, mostrar). Este equipo es utilizado en medicina, arqueología, biología, geofísica, oceanografía y en otras ciencias, en el presente trabajo me voy a referir a los equipos destinados al uso medico. El primer equipo de Tomografía sale a la venta en 1970 y a partir de este momento el desarrollo tecnológico de la Tomografía a sido imparable, llegando a ser en la actualidad un equipo de ayuda al diagnostico inprecindible en cualquier Clínica u Hospital, lamentablemente en el Perú todavía existe un déficit muy alto de equipamiento Tomografico existiendo inclusive capitales de departamento que no cuentan con estos equipos. Desde la instalación del Tomógrafo hasta la puesta de funcionamiento de este se requiere una serie de trabajos que en el Perú son realizados por los Ingenieros Electrónicos a cargo del Servicio Técnico, podemos mencionar el room planning, protección radiológica, calculo de la capacidad de los equipos de aire acondicionado, anclaje del equipo, calibración, puesta en funcionamiento y entrenamiento en la operación del equipo, este entrenamiento se le da al personal (Tecnólogo Medico) encargado de operar el equipo, en otros países estos trabajos son multidisciplinarios. Mi experiencia en Tomografía empieza en 1990 cuando realice mi primera instalación en el Hospital Edgardo Rebagliati M. – EsSalud equipo que en la actualidad sigue trabajando realizando mas de 50 pacientes diarios.

O objetivo deste trabalho é descrever a estrutura das linhas axiais principais e médias de imersões de superfícies em R4 na vizinhança de pontos axiumbílicos. Pontos axiumbílicos são aqueles nos quais a elipse de curvatura se degenera em um círculo. Estudamos a perturbação dos ciclos axiais principais, e obtemos resultados sobre a genericidade dos ciclos axiais principais hiperbólicos e semi-hiperbólicos. / The aim of this work is to describe the structure of principal and mean axial lines of immersions of surfaces into R4, close to axiumbilic points. Axiumbilic points are those which the ellipse of curvature denegerate in a circle. We study the perturbation of principal axial cycles, and we obtain results about genericity of hyperbolic and semi-hyperbolic principal axial cycles.

This thesis lays the foundations for the development of a small autonomous coaxial helicopter. This is an helicopter with two propellers mounted on the same axis and revolving in opposite directions. To steer the helicopter, this thesis proposes a mechanism that moves the helicopter’s centre of mass. Although such a mechanism has already been investigated experimentally in the literature, it has never been rigorously modeled, and a theoretical analysis has never been performed. This thesis, for the first time, presents an accurate mathematical model of the coaxial helicopter which takes into account the gyroscopic effects of the rotors, the reaction forces and torques exerted by the moving mass actuator on the helicopter body, and the fact that the inertia of the helicopter is time-varying. A nonlinear controller is rigorously derived which makes the helicopter hover at desired positions in three-space. A number of physical prototypes are discussed. None of them is capable of autonomous flight yet, but the experimental and simulation results provide reassurances that the proposed methodology is viable.

This thesis lays the foundations for the development of a small autonomous coaxial helicopter. This is an helicopter with two propellers mounted on the same axis and revolving in opposite directions. To steer the helicopter, this thesis proposes a mechanism that moves the helicopter’s centre of mass. Although such a mechanism has already been investigated experimentally in the literature, it has never been rigorously modeled, and a theoretical analysis has never been performed. This thesis, for the first time, presents an accurate mathematical model of the coaxial helicopter which takes into account the gyroscopic effects of the rotors, the reaction forces and torques exerted by the moving mass actuator on the helicopter body, and the fact that the inertia of the helicopter is time-varying. A nonlinear controller is rigorously derived which makes the helicopter hover at desired positions in three-space. A number of physical prototypes are discussed. None of them is capable of autonomous flight yet, but the experimental and simulation results provide reassurances that the proposed methodology is viable.

Background: Disc herniations are common and have been demonstrated as one potential source of low back pain. To date epidemiological studies have found associations between lifting, lifting and twisting and twisting with increased risk in the development of disc herniations (Greenough and Fraser, 1994, Kelsey et al., 1984, Mundt et al., 1993). Subsequent, in vitro investigations were able to produce disc herniations through repeatitive flexion extension motions on cervical porcine functional spinal units (Callaghan and McGill, 2001). However, in vitro investigations on axial torque have drawn mixed conclusions and controversy remains on the role it plays with respect to disc herniations (Farfan et al., 1970, Adams et al., 1981). Therefore, the work in this thesis was to investigate the role of dynamic axial torque on the disc herniation mechanism. Methods: Porcine cervical spines were used as they are a good approximation to the human lumbar spine (Yingling et al., 1999). The study design involved repetitive flexion extension motions of the spinal units either preceded or followed by dynamic axial torque. During axial torque the spinal units were loaded to 17.5 Nm (standard deviation = 0.5 Nm) of dynamic axial torque for either 2000 or 4000 testing cycles. These spinal units were compared to spinal units that were loaded in repetitive flexion extension motions only and axial torque only. The spinal units were tested in a servohydraulic dynamic testing machine, combined with a custom jigs which allowed loading in flexion/extension, axial torque and compression. Plane film radiographs with contrast in the nucleus were obtained at regular intervals during and following the mechanical testing. Final dissection determined the disc injury patterns. Results and Discussion: Examination of the sectioned intervertebral discs indicated axial torque in combination with repetitive flexion extension motions, regardless of order, encouraged radial delamination. While, repetitive flexion extension motion alone encouraged posterior or posterolateral herniation patterns. Axial torque alone was unable to initiate a disc herniation. There was an increase in both rotation and stiffness of the intervertebral disc in response to repeated axial torque. There were no differences in rotation and stiffness between the groups. Both x-ray images and computed tomography scans were equally as good at identifying posterior or posterolateral herniations but were not good at detecting radial delamination.

Background: Disc herniations are common and have been demonstrated as one potential source of low back pain. To date epidemiological studies have found associations between lifting, lifting and twisting and twisting with increased risk in the development of disc herniations (Greenough and Fraser, 1994, Kelsey et al., 1984, Mundt et al., 1993). Subsequent, in vitro investigations were able to produce disc herniations through repeatitive flexion extension motions on cervical porcine functional spinal units (Callaghan and McGill, 2001). However, in vitro investigations on axial torque have drawn mixed conclusions and controversy remains on the role it plays with respect to disc herniations (Farfan et al., 1970, Adams et al., 1981). Therefore, the work in this thesis was to investigate the role of dynamic axial torque on the disc herniation mechanism. Methods: Porcine cervical spines were used as they are a good approximation to the human lumbar spine (Yingling et al., 1999). The study design involved repetitive flexion extension motions of the spinal units either preceded or followed by dynamic axial torque. During axial torque the spinal units were loaded to 17.5 Nm (standard deviation = 0.5 Nm) of dynamic axial torque for either 2000 or 4000 testing cycles. These spinal units were compared to spinal units that were loaded in repetitive flexion extension motions only and axial torque only. The spinal units were tested in a servohydraulic dynamic testing machine, combined with a custom jigs which allowed loading in flexion/extension, axial torque and compression. Plane film radiographs with contrast in the nucleus were obtained at regular intervals during and following the mechanical testing. Final dissection determined the disc injury patterns. Results and Discussion: Examination of the sectioned intervertebral discs indicated axial torque in combination with repetitive flexion extension motions, regardless of order, encouraged radial delamination. While, repetitive flexion extension motion alone encouraged posterior or posterolateral herniation patterns. Axial torque alone was unable to initiate a disc herniation. There was an increase in both rotation and stiffness of the intervertebral disc in response to repeated axial torque. There were no differences in rotation and stiffness between the groups. Both x-ray images and computed tomography scans were equally as good at identifying posterior or posterolateral herniations but were not good at detecting radial delamination.

No description available.

Deep foundations are commonly recommended when large displacements are expected. Typically, though, their design involves only checking and providing for sufficient capacity to carry the applied loads. Load-displacement behavior of piles is considered secondary to the axial capacity; displacements are ordinarily overlooked or not calculated if and when the estimated pile capacity is two to three times the design or expected loading. However, in cases, such as long piles or piles in dense cohesionless soils, displacements can be the critical factor in design or it could be a structural requirement to limit the displacements. In this dissertation, the displacements of axially loaded single piles are investigated by conducting analyses with the aid of an approach based on elasticity. The original solution predicting displacements due to a vertical load within a semi-infinite soil mass has been modified for varying soil conditions and layering, and assumptions of stresses and displacements acting on the soil-pile interface. Aside from the available/known factors of the pile (length, diameter, cross-sectional area, etc.) and the layering of the surrounding soil, Young's modulus and Poisson's ratio of the soil encompassing a pile are the unknowns required as input to obtain predictions based on the elastic method. In this study, attention is directed towards determining Young's modulus because the range and variability of Poisson's ratio is not significant in displacement calculations. Axial pile load testing data were provided by the California Department of Transportation as part of a project to improve its general approach to pile design. All of the tested piles were driven into the ground. Measurements of displacements and loads were made only at the top of the pile. Supplementary in-situ testing involving cone penetration (CPT) and standard penetration (SPT), drilling, and sample collection, were conducted in addition to laboratory testing to enhance the available information. In this research, predicted displacements are compared with those deduced from pile load tests. Two sets of predictions based on elastic method are conducted for comparing displacements. First, various correlations for Young's modulus are employed to determine how accurately each predicts the actual measured displacement. The chosen correlations utilize laboratory triaxial undrained shear strength and standard penetration test blowcount for cohesive and cohesionless soils, respectively. Secondly, the same data are also utilized to obtain back-calculated values of Young's moduli for analyses involving the elastic method. The measured displacements at loads of a third, a half, twothirds, and equal to the failure load were matched iteratively. Results from this research are deemed to have an impact on engineering practice by improving the determination of Young's modulus for displacement analyses involving the elastic method. A unique approach that has potential is the reconciliation of load ratios (percentage of failure load) with displacement calculations to provide a better overview of the range of load ratios for which these newly formulated correlations may be employed. Through this research, it is anticipated that better determination of soil parameters for elastic analysis of axial pile displacements can be made by researchers and engineers alike.