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The effect of pressure on the log reduction of six strains of E. coli O157:H7 and five serovars of Salmonella enterica were investigated in tryptic soy broth, sterile distilled water and commercially sterile orange and apple juice. Samples were subjected to high hydrostatic pressure (HHP) at 300 and 550 MPa for 2 minutes at 6°C, and then held for 24 hours at 4°C following treatment. E. coli O157:H7 strain E009 was the most pressure resistant, having a decrease of only 0.77 log10 CFU/ml directly after pressurization in TSB. S. Agona was the most pressure resistant Salmonella serovar tested with a decrease of 3.79 log¬10 CFU/ml in TSB at 550 MPa. The two most pressure resistant cultures were then used in a subsequent study using HHP in conjunction with antimicrobials (dimethyl dicarbonate [DMDC] at 62.5 and 125 ppm, hydrogen peroxide at 150 and 300 ppm, cinnamic acid, potassium salt at 125 and 250 ppm, potassium sorbate [KS] at 500 and 1000 ppm and sodium benzoate [NaB] at 500 and 1000). For both E. coli O157:H7 and Salmonella, the most effective antimicrobial was DMDC having a 5.79 and 5.96 log10 CFU/ml decrease directly following pressurization, respectively. Other treatments that were significantly different from the samples treated with no antimicrobial were hydrogen peroxide, and NaB at 500 ppm for E. coli O157:H7 and a treatment of NaB at 1000 ppm for S. Agona. After 24 hours at 4°C, S. Agona samples with added antimicrobials had a close to or above 5-log10 CFU/ml reduction. DMDC should be further investigated as an antimicrobial agent that can work in conjunction with HHP. / Master of Science

This thesis deals with the issue of hydrostatic bearings. The aim was to design a test rig for an axial hydrostatic bearing. The axial hydrostatic bearing was calculated and designed with respect to the function of the tester. The construction of the test equipment was further supported by calculations of the main parts together with FEM analyses. The design was also accompanied by an introduction to the hydraulic parts of the hydrostatic bearing, which took place in consultation with Bosch Rexroth. The aim of the work, the design of a test device in a scale of 1:10, was completed. The following results from hydrostatic bearing tests will allow the introduction of new procedures in the production of turntables mounted on a hydrostatic bearing. Examination of operating conditions and permissible assembly inaccuracies will make it possible to reduce the production requirements for bearing mounting.

Typescript (photocopy). / Digitized by Kansas Correctional Industries

Several research groups have applied elevated hydrostatic pressure to ONH astrocytes cultured on a rigid substrate as an in vitro model for glaucoma. These studies have shown significant biological effects and this hydrostatic pressure model is now becoming generally accepted in the ophthalmic community. However, since the applied pressures were modest the finding of significant biological effects due to pressure alone is surprising. We hypothesized that the application of hydrostatic pressure as described in these studies also altered gas tensions in the culture media. Our goal was to design equipment and carry out experiments to separate the biologic effects of pressure from those of hypoxia on cultured astrocytes. We designed equipment and carried out experiments to subject cultures of DITNC1 astrocytes to the four combinations of two levels of each parameter. We explored the morphology and migration rates of astrocytes, but observed no significant change in any of these properties.

Neste trabalho avaliou-se experimentalmente a influência da onfiguração de bobinagem no comportamento mecânico de cilindros de compósito polimérico com bobinagem simétrica e assimétrica. Para tanto, foram fabricados pelo processo de bobinamento filamentar (filament winding) dois grupos de cilindros com extremidades abertas, que apresentaram alteração no posicionamento das camadas em relação ao plano médio, caracterizando laminados simétrico e assimétrico. No compósito deste estudo, utilizou-se uma matriz com sistema tricomponente com resina epoxídica e reforço de fibra de carbono. Para avaliação da resistência mecânica, os cilindros foram submetidos a ensaio hidrostático que consistiu da pressurização interna em dispositivo apropriado mediante a utilização de um fluido até que ocorresse o colapso. Adicionalmente, as deformações e os modos de falha dos dois grupos de cilindros foram analisados e comparados. A utilização de um programa de cálculo de elementos finitos permitiu concluir que esta ferramenta, muito usada em projeto, não consegue identificar tensões na orientação da fibra em cada uma das camadas do compósito, bem como tensões de cisalhamento interlaminares que surgem nos cilindros com configuração assimétrica. Os resultados dos ensaios mostraram que as configurações de bobinagem exercem influência no comportamento mecânico dos cilindros de material compósito, favorecendo a construção do tipo simétrica. / This work evaluated experimentally the influence of the stacking sequence of layers symmetrical and asymmetrical on the mechanical behavior of polymeric composite cylinders. For so much, two open-ended cylinders groups were manufactured by filament winding process, which had different stacking sequence related to the laminate midplane, characterizing symmetrical and asymmetrical laminates. The composite cylinders were made with epoxy matrix and carbon fiber as reinforcement. For evaluation of the mechanical strength, the cylinders were tested hydrostatically, which consisted of internal pressurization in a hydrostatic device through the utilization of a fluid until the cylinders burst. Additionally, were compared the strains and failure modes between the cylinders groups. The utilization of a finite element program allowed to conclude that this tool, very used in design, does not get to identify tensions in the fiber direction in each composite layer, as well as interlaminar shear stress, that appears in the cylinders with asymmetrical stacking sequence. The tests results showed that the stacking sequence had influence in the mechanical behavior of the composite cylinders, favoring the symmetrical construction.

Neste trabalho avaliou-se experimentalmente a influência da onfiguração de bobinagem no comportamento mecânico de cilindros de compósito polimérico com bobinagem simétrica e assimétrica. Para tanto, foram fabricados pelo processo de bobinamento filamentar (filament winding) dois grupos de cilindros com extremidades abertas, que apresentaram alteração no posicionamento das camadas em relação ao plano médio, caracterizando laminados simétrico e assimétrico. No compósito deste estudo, utilizou-se uma matriz com sistema tricomponente com resina epoxídica e reforço de fibra de carbono. Para avaliação da resistência mecânica, os cilindros foram submetidos a ensaio hidrostático que consistiu da pressurização interna em dispositivo apropriado mediante a utilização de um fluido até que ocorresse o colapso. Adicionalmente, as deformações e os modos de falha dos dois grupos de cilindros foram analisados e comparados. A utilização de um programa de cálculo de elementos finitos permitiu concluir que esta ferramenta, muito usada em projeto, não consegue identificar tensões na orientação da fibra em cada uma das camadas do compósito, bem como tensões de cisalhamento interlaminares que surgem nos cilindros com configuração assimétrica. Os resultados dos ensaios mostraram que as configurações de bobinagem exercem influência no comportamento mecânico dos cilindros de material compósito, favorecendo a construção do tipo simétrica. / This work evaluated experimentally the influence of the stacking sequence of layers symmetrical and asymmetrical on the mechanical behavior of polymeric composite cylinders. For so much, two open-ended cylinders groups were manufactured by filament winding process, which had different stacking sequence related to the laminate midplane, characterizing symmetrical and asymmetrical laminates. The composite cylinders were made with epoxy matrix and carbon fiber as reinforcement. For evaluation of the mechanical strength, the cylinders were tested hydrostatically, which consisted of internal pressurization in a hydrostatic device through the utilization of a fluid until the cylinders burst. Additionally, were compared the strains and failure modes between the cylinders groups. The utilization of a finite element program allowed to conclude that this tool, very used in design, does not get to identify tensions in the fiber direction in each composite layer, as well as interlaminar shear stress, that appears in the cylinders with asymmetrical stacking sequence. The tests results showed that the stacking sequence had influence in the mechanical behavior of the composite cylinders, favoring the symmetrical construction.

<p>The purpose of the thesis has been to design and simulate different concepts of a secondary controlled swing drive for a wheel excavator. Secondary control is a known technology in the field of hydraulics that offers precise positioning as well as the possibility of energy recuperation. Secondary control is today used in certain industrial applications and is rather unemployed in mobile machinery. An excavator moves high loads in cyclic motions which are ideal conditions for energy recuperating systems. A study of the potential of a secondary controlled swing drive is therefore interesting. The focus has been on testing different circuit architectures and emergency brake concepts.</p><p>The results of the design process have been three types of circuit architectures and two types of hydraulic safety concepts. The results of the simulation have shown that the open and closed circuit architecture have similar energy efficiency. The closed circuit with low pressure accumulator however offers the best controllability. At least 20% energy savings can be achieved by storing thekinetic energy when braking.</p><p>A hydraulic emergency brake must function, independent on the direction of rotation of the excavator during a failure. The first principle recognises the rotation direction and changes the swivel angle of the secondary unit so that a braking torque is created. In the second principle a pressure difference is built up over the secondary unit that always results in a braking torque. Simulationshave shown that the principle with recognition of the speed direction is the most effective safety concept.</p>

<p>Hydrostatic transmission is used in many applications where high torque at low speed is demanded. For this project a forest vehicle is at focus. Komatsu Forest would like to have a model for the pressure in the hose between the hydraulic pump and the hydraulic motor. Pressure peaks can arise when the vehicle changes speed or hit a bump in the road, but if a good model is achieved some control action can be developed to reduce the pressure peaks.</p><p>For simulation purposes a model has been developed in Matlab-Simulink. The aim has been to get the simulated values to agree as well as possible with the measured values of the pressure and also for the rotations of the pump and the motor.</p><p>The greatest challenge has been due to the fact that the pressure is a sum of two flows, if one of these simulated flows is too big the pressure will tend to plus or minus infinity. Therefore it is necessary to develop models for the rotations of the pump and the motor that stabilize the simulated pressure.</p><p>Different kinds of models and methods have been tested to achieve the present model. Physical modeling together with a black box model are used. The black box model is used to estimate the torque from the diesel engine. The probable torque from the ground has been calculated. With this setup the simulated and measured values for the pressure agrees well, but the fit for the rotations are not as good.</p>