No description available.

This study was divided into four sections: the literature review; the mechanism by which a package defect becomes a leak; and the imposed pressures generated within a package during distribution; comparison of the threshold leak size to the critical leak size and their effect on loss of package sterility; and the relationships between microorganism characterisitics and the threshold leak size, and their effect on the critical leak size. Section II. The mechanism by which a package defect converts to a leaker in an effort to develop a relationship between the threshold leak size and loss of package sterility was studied. The threshold leak size is the hole size at which the onset of leakage occurs. The threshold pressure is that which is required to initiate a leak. Leak initiation was studied in terms of the interaction between three components: liquid attributes of liquid food products, defect size, and pressures required to initiate liquid flow. Liquid surface tension, viscosity, and density were obtained for sixteen liquids. The imposed pressures (Po) required to initiate flow through microtubes of IDs 0, 2, 5, 7, 10, 20 or 50 m, were measured using 63 test cells filled with safranin red dye, tryptic soy broth, and distilled water with surface tensions of 18.69 mN/m, 44.09 mN/m, and 64.67 mN/m, respectively. Significant differences were found between observed threshold pressures for safranin red dye, tryptic soy broth, and distilled water (p < 0.05). Liquids with small surface tensions such as safranin red dye required significantly lower threshold imposed pressures than liquids with large surface tensions such as distilled water (p < 0.05). An equation was developed to quantify the relationship between liquid surface tension, threshold imposed pressure, and defect size. Observed threshold pressures were not significantly different (p > 0.05) than those predicted by the equation. Imposed pressures and vacuums generated within packages during random vibration and sweep resonance tests were measured for brick-style aseptic packages (250 ml), metal cans size 76.2-mm x 114.3-mm (425 ml), quart gable top packages (946 ml), one-half gallon gable top packages (1.89 L) and one-gallon milk jugs (4.25 L). Significant differences were found between packages for observed generated pressures during vibration testing (p < 0.05). An equation to calculate the threshold like size based on liquid surface tension and imposed pressure was established. Section III. The onset of liquid flow through a defect as a result of imposed positive pressures or vacuum were linked to the sterility loss of a package. Five-hundred sixty-three test cells, each with microtubes of 0, 2, 5, 7, 10, 20 or 50 m, manufactured to simulate packages with defects, were biochallenged via an aerosol concentration of 106 cells/cm3 of Pseudomonas fragi Lacy-1052, under conditions of imposed positive pressure or vacuum of 20.7, 13.8, 6.9, 0, -6.9, -13.8, -20.7 kPa, respectively and temperatures of 4 , 25 and 37 C. A statistically significant relationship between loss of sterility due to microbial ingress in test cells and the initiation of liquid flow were found (p < 0.05). Microbial ingress was not found in test cells with microtube IDs of 2 m. Leak sizes critical to the sterility maintenance were found to be different based on the liquid surface tension, and imposed package pressures. The threshold leak size where the onset of liquid flow was initiated, and the critical leak size at which loss of sterility occured were not significantly different (p > 0.05). Section IV. The effects of microorganism size and motility, and the imposed pressure required to initiate liquid flow, on the leak size critical to the sterility of a package were measured. Pseudomonas fragi Lacy-1052, Bacillus atrophaeus ATCC 49337, and Enterobacter aerogenes ATCC 29007 were employed to indicate loss of package sterility. One hundred twenty-six microtubes with interior diameters (I.D.s) of 5, 10, and 20 m and 7 mm in length were used as the manufactured defects. Forty-two solid microtubes were used as a control. An equation was used to calculate imposed pressures sufficient to initiate the flow of tryptic soy broth through all defects. No significant differences were found for loss of sterility as a result of microbial ingress into test cells with microtube ID sizes of 5, 10, and 20 m between the test organisms (p > 0.05). Interactions between the initiation of liquid flow as a result of imposed pressures, and the sterility loss of test cells were significant (p < 0.05). / Ph. D.

<p>In Chapter 2 an experiment has been conducted to measure the quenching distance of a premixed fuel-air mixture. Quenching distance refers to the physical limit below which combustion of a fuel and an oxidizer, even if present in sufficient proportions, cannot maintain combustion and propagate a flame. It is dependent on the physical area that is present for the flame to travel through, the temperature and pressure conditions, the thermal conductivity of the walls, and the specific fuel and oxidizer present. Applicable in a wide variety of industries from the automotive industry to the aerospace industry, the ability to control a combustion reaction and where it occurs can lead to increased safety and efficiency in devices such as injectors, mixing chambers, engine pistons, combustors, propellant turbopumps, and fuel-air heat exchangers. Currently, little to no quenching distance data exists for heavier-than-air hydrocarbons. Using a parallel ceramic plate setup with spark rods inside a pressure vessel to contain the initial combustion reaction, the quenching distances of the hydrocarbons is measured and a relationship with equivalence ratio is found. This relationship is used to construct a model to apply to heavier-than-air hydrocarbons.</p> <p>Chapter 3 focuses on an experiment designed to measure the flow rates of leaks in fuel-air heat exchangers. The ability to accurately quantify and understand these flow rates is crucial for assessing the performance and safety of such systems. Furthermore, the obtained flow rate data will be compared with a Computational Fluid Dynamics (CFD) model developed for micro-scale flows resulting from fuel leakage into a cross-flow of heated air within the heat exchanger. These flow rates provide a model of the volume and rate of fuel being injected into the air channels, aiding in the assessment of potential risks and hazards associated with the leakage. To validate the accuracy and reliability of the model developed for micro-scale flow, the measured flow rates obtained from the experimental setup are compared against the corresponding predictions of the model. By establishing a correlation between the experimental data and the model results, the validity of the model can be confirmed, ensuring its efficacy for future simulations and analyses.</p> <p>Chapter 4 details the creation and analysis of a program developed in Python and MATLAB for assessing combustion risk in microscale fuel-air heat exchanger channels. The Safety Net for Unquenched Flame Fronts (SNUFF) is designed as a design assistance tool for microscale flows of fuel and oxidizer, specifically for heat exchangers. This application helps analyze combustion risks in these microscale flow channels due to leaks or unintended flows caused by damage or manufacturing defects. SNUFF integrates REFPROP and flame simulation data with the models for quenching distance and microscale flow from previous chapters to generate sensitivity plots for various design parameters. This tool enables engineers to assess combustion risks in fuel-air channels, allowing them to design processes that accommodate manufacturing limitations in numerous microscale channel applications.</p>

No description available.

Recently, attention has been drawn to the viability of using S-CO(2) as a working fluid in modern reactor designs. Near the critical point, CO2 has a rapid rise in density allowing a significant reduction in the compressor work of a closed Brayton Cycle. Therefore, 45% efficiency can be achieved at much more moderate temperatures than is optimal for the helium Brayton cycles. An additional benefit of the S-CO2 system is its universal applicability as an indirect secondary Power Conversion System (PCS) coupled to most GEN-IV concept reactors, as well as fusion reactors. The United States DOE's GNEP is now focusing on the liquid Na cooled primary as an alternative to conventional Rankine steam cycles. This primary would also benefit from being coupled to an S-CO2 PCS. Despite current progress on designing the S-CO2 PCS, little work has focused on the principal supporting systems required. Many of the required auxiliary systems are similar to those used in other nuclear or fossil-fired units; others have specialized requirements when CO2 is used as the working fluid, and are therefore given attention in this thesis. Auxiliary systems analyzed within this thesis are restricted to those specific to using CO2 as the working fluid. Particular systems discussed include Coolant Make-up and Storage, Coolant Purification, and Coolant Leak Detection. / Contract number: N62271-97-G-0026. / US Navy (USN) author

Introduction Advanced Kadish stage esthesioneuroblastoma requires more extensive resections and aggressive adjuvant therapy to obtain adequate disease-free control, which can lead to higher complication rates. We describe the case of a patient with Kadish D esthesioneuroblastoma who underwent multiple surgeries for infectious, neurologic, and wound complications, highlighting potential preventative and salvage techniques. Case Presentation A 61-year-old man who presented with a large left-sided esthesioneuroblastoma, extending into the orbit, frontal lobe, and parapharyngeal nodes. He underwent margin-free endoscopic-assisted craniofacial resection with adjuvant craniofacial and cervical radiotherapy and concomitant chemotherapy. He then returned with breakdown of his skull base reconstruction and subsequent frontal infections and ultimately received 10 surgical procedures with surgeries for infection-related issues including craniectomy and abscess evacuation. He also had surgeries for skull base reconstruction and CSF leak, repaired with vascularized and free autologous grafts and flaps, synthetic tissues, and CSF diversion. Discussion Extensive, high Kadish stage tumors necessitate radical surgical resection, radiation, and chemotherapy, which can lead to complications. Ultimately, there are several options available to surgeons, and although precautions should be taken whenever possible, risk of wound breakdown, leak, or infection should not preclude radical surgical resection and aggressive adjuvant therapies in the treatment of esthesioneuroblastoma.

Este trabalho apresenta um estudo prático da aplicação do conceito Leak Before Break (LBB), usualmente aplicado em usinas nucleares, em uma tubulação fabricada a partir de aço AISI 316LN soldada com a utilização de eletrodo revestido AISI 316L. O LBB é um critério fundamentado em análises de mecânica da fratura, que considera que um vazamento proveniente de uma trinca, presente em uma tubulação, possa ser detectado por sistemas de detecção de vazamento, antes que esta trinca alcance um tamanho crítico que implique na falha da tubulação. Na tubulação estudada, foram realizados ensaios mecânicos de tração e análises de Ramberg-Osgood, bem como ensaios de tenacidade à fratura para a obtenção da curva de resistência J-R do material. Os ensaios foram realizados considerando o metal base, a solda e a zona termicamente afetada (ZTA), nas temperaturas de operação de uma planta nuclear. Para as propriedades mecânicas encontradas nos ensaios foram realizadas análises de carga limite para se determinar o tamanho da trinca que cause um vazamento detectável e, também, o seu tamanho crítico que cause a falha por colapso plástico. Para o tamanho crítico de trinca encontrado na solda, região que apresentou a menor tenacidade, foram realizadas análises de Integral J e de módulo de rasgamento T, considerando falha por rasgamento dúctil. Os resultados demonstram um comportamento bem definido entre o metal base, a ZTA e a solda, onde o metal base apresenta um comportamento altamente tenaz, a solda um comportamento pouco tenaz e a ZTA apresentou propriedades mecânicas intermediárias entre o metal base e a solda. Utilizando o software PICEP, foram determinadas as curvas de taxa de vazamento versus tamanho de trinca e também o tamanho crítico da trinca, considerando análise por carga limite. Observou-se que, após certo tamanho de trinca, a taxa de vazamento do metal base é muito maior do que para a ZTA e solda, para um mesmo comprimento de trinca. Isso ocorre porque é esperado que a trinca cresça de forma mais arredondada no metal base, devido à sua maior tenacidade. O menor tamanho crítico de trinca foi encontrado para o metal base para trincas circunferenciais. Para as análises de Integral J realizadas na solda, foi demonstrado que a falha por rasgamento dúctil não ocorrerá nas condições consideradas e essa hipótese foi sedimentada pela análise de mecânica da fratura elasto-plástica (MFEL) com o uso do diagrama J/T. Dessa forma, pode-se concluir que a tubulação estudada estaria apta a ser empregada em um circuito primário de um reator que utilizasse o critério de LBB, nas condições de carregamento e geometria consideradas. Adicionalmente, concluiu-se que nessas condições apenas o modo de falha por colapso plástico é esperado. / This work presents a study of application of the Leak Before Break (LBB) concept, usually applied in nuclear power plants, in a pipe made from steel AISI type 316LN welded a coated electrode AISI type 316L. LBB concept is a criterion based on fracture mechanics analysis to show that a crack leak, present in a pipe, can be detected by leak detection systems, before this crack reaches a critical size that results in pipe fail. In the studied pipe, tensile tests and Ramberg-Osgood analyses were performed, as well as fracture toughness tests for obtaining the material resistance curve J-R. The tests were performed considering the base metal, weld and heat affected zone (HAZ), at the same operating temperatures of a nuclear power plant. For the mechanical properties found in these tests, load limit analyses were performed in order to determine the size of a crack which could cause a detectable leakage and the critical crack size, considering failure by plastic collapse. For the critical crack size found in the weld, which is the region that presented the lowest toughness, Integral J and tearing modulus T analyses were performed, considering failure by tearing instability. Results show a well-defined behavior between the base metal, HAZ and weld zones, where the base metal has a high toughness behavior, the weld has a low toughness behavior and the HAZ showed intermediate mechanical properties between the base metal and the weld. Using the PICEP software, the leak rate curves versus crack size and also the critical crack size were determined by considering load limit analysis. It was observed that after a certain crack size, the leak rate in base metal is much higher than for the HAZ and the weld, considering the same crack length. This occurs because in the base metal crack, it is expected that the crack grows in a more rounded form due to its higher toughness. The lowest critical crack size was found for the base metal presenting circumferential cracks. For the Integral J analyses performed in the weld, it was demonstrated that the failure by tearing instability will not occur under the considered conditions and this hypothesis was confirmed by elastic-plastic fracture mechanic (EPFM) analysis using the J/T diagram. Thereby, it can be concluded that it would be possible to apply the investigated pipe in a primary circuit of a reactor that utilizes the criterion LBB under the considered geometry and load conditions. Additionally, it was found that under these conditions, only the failure mode by plastic collapse is expected.

Neste trabalho são apresentados diversos métodos de localização de vazamentos, desde as técnicas e equipamentos mais elementares, como a inspeção visual e o geofone mecânico, até o uso dos sofisticados armazenadores de ruídos e de modelação computacional. Algumas dessas técnicas são amplamente difundidas e largamente utilizadas pelas empresas de saneamento, outras porém, constituem-se em ótimas promessas para o aperfeiçoamento do controle das perdas físicas nos sistemas de abastecimento. É dada ênfase na utilização do diagrama de resposta em freqüência para localizar e quantificar vazamentos, com especial aplicação às adutoras de água tratada. A técnica de utilização da resposta em freqüência desenvolvida por Lee et al. (2005) é esmiuçada, inclusive acerca do impacto que um vazamento impõe ao diagrama de resposta em freqüência. São abordadas as formas de obtenção do referido diagrama, tanto do ponto de vista do modelo matemático e computacional, quanto dos ensaios de campo necessários. / This work presents some methods for leak location, from de most elementary techniques and equipments, as visual inspection and mechanical geophone, until using sophisticated noise data-logger and computational modeling. Some of these techniques are very well issued and largely used by water companies, but others play excellent promises for the improvement of leak control in systems of water supply. The pattern of the frequency response diagram is used for leak location and quantification, with special application in drinking water pipelines. The frequency response technique developed by Lee et al. (2005) is studied in details, including the impact produced by the leak on the frequency response diagram. The ways to obtain the frequency response diagram, by using mathematical and computational models or necessary field data survey, are also discussed.

Este trabalho apresenta um estudo prático da aplicação do conceito Leak Before Break (LBB), usualmente aplicado em usinas nucleares, em uma tubulação fabricada a partir de aço AISI 316LN soldada com a utilização de eletrodo revestido AISI 316L. O LBB é um critério fundamentado em análises de mecânica da fratura, que considera que um vazamento proveniente de uma trinca, presente em uma tubulação, possa ser detectado por sistemas de detecção de vazamento, antes que esta trinca alcance um tamanho crítico que implique na falha da tubulação. Na tubulação estudada, foram realizados ensaios mecânicos de tração e análises de Ramberg-Osgood, bem como ensaios de tenacidade à fratura para a obtenção da curva de resistência J-R do material. Os ensaios foram realizados considerando o metal base, a solda e a zona termicamente afetada (ZTA), nas temperaturas de operação de uma planta nuclear. Para as propriedades mecânicas encontradas nos ensaios foram realizadas análises de carga limite para se determinar o tamanho da trinca que cause um vazamento detectável e, também, o seu tamanho crítico que cause a falha por colapso plástico. Para o tamanho crítico de trinca encontrado na solda, região que apresentou a menor tenacidade, foram realizadas análises de Integral J e de módulo de rasgamento T, considerando falha por rasgamento dúctil. Os resultados demonstram um comportamento bem definido entre o metal base, a ZTA e a solda, onde o metal base apresenta um comportamento altamente tenaz, a solda um comportamento pouco tenaz e a ZTA apresentou propriedades mecânicas intermediárias entre o metal base e a solda. Utilizando o software PICEP, foram determinadas as curvas de taxa de vazamento versus tamanho de trinca e também o tamanho crítico da trinca, considerando análise por carga limite. Observou-se que, após certo tamanho de trinca, a taxa de vazamento do metal base é muito maior do que para a ZTA e solda, para um mesmo comprimento de trinca. Isso ocorre porque é esperado que a trinca cresça de forma mais arredondada no metal base, devido à sua maior tenacidade. O menor tamanho crítico de trinca foi encontrado para o metal base para trincas circunferenciais. Para as análises de Integral J realizadas na solda, foi demonstrado que a falha por rasgamento dúctil não ocorrerá nas condições consideradas e essa hipótese foi sedimentada pela análise de mecânica da fratura elasto-plástica (MFEL) com o uso do diagrama J/T. Dessa forma, pode-se concluir que a tubulação estudada estaria apta a ser empregada em um circuito primário de um reator que utilizasse o critério de LBB, nas condições de carregamento e geometria consideradas. Adicionalmente, concluiu-se que nessas condições apenas o modo de falha por colapso plástico é esperado. / This work presents a study of application of the Leak Before Break (LBB) concept, usually applied in nuclear power plants, in a pipe made from steel AISI type 316LN welded a coated electrode AISI type 316L. LBB concept is a criterion based on fracture mechanics analysis to show that a crack leak, present in a pipe, can be detected by leak detection systems, before this crack reaches a critical size that results in pipe fail. In the studied pipe, tensile tests and Ramberg-Osgood analyses were performed, as well as fracture toughness tests for obtaining the material resistance curve J-R. The tests were performed considering the base metal, weld and heat affected zone (HAZ), at the same operating temperatures of a nuclear power plant. For the mechanical properties found in these tests, load limit analyses were performed in order to determine the size of a crack which could cause a detectable leakage and the critical crack size, considering failure by plastic collapse. For the critical crack size found in the weld, which is the region that presented the lowest toughness, Integral J and tearing modulus T analyses were performed, considering failure by tearing instability. Results show a well-defined behavior between the base metal, HAZ and weld zones, where the base metal has a high toughness behavior, the weld has a low toughness behavior and the HAZ showed intermediate mechanical properties between the base metal and the weld. Using the PICEP software, the leak rate curves versus crack size and also the critical crack size were determined by considering load limit analysis. It was observed that after a certain crack size, the leak rate in base metal is much higher than for the HAZ and the weld, considering the same crack length. This occurs because in the base metal crack, it is expected that the crack grows in a more rounded form due to its higher toughness. The lowest critical crack size was found for the base metal presenting circumferential cracks. For the Integral J analyses performed in the weld, it was demonstrated that the failure by tearing instability will not occur under the considered conditions and this hypothesis was confirmed by elastic-plastic fracture mechanic (EPFM) analysis using the J/T diagram. Thereby, it can be concluded that it would be possible to apply the investigated pipe in a primary circuit of a reactor that utilizes the criterion LBB under the considered geometry and load conditions. Additionally, it was found that under these conditions, only the failure mode by plastic collapse is expected.

A ocorrência de elevados índices de perdas por vazamentos em sistemas de abastecimento de água é frequentemente ligada às inúmeras quebras de tubulações originadas em decorrência de elevados níveis de pressão atuantes. O controle efetivo de tais perdas requer a detecção e localização dos vazamentos para uma rápida reparação do sistema. Neste sentido, a consideração de análises hidráulicas no escoamento transitório tem se revelado especialmente útil aos propósitos de calibração e detecção de vazamentos. Tal análise pode revelar substancial quantidade de informações sobre as propriedades físicas e o nível de integridade do sistema, pois as ondas de pressão resultantes são afetadas pelos diversos dispositivos e fenômenos, incluindo os vazamentos. Assim, o presente trabalho visa o estudo dos transitórios hidráulicos para a calibração e detecção de vazamentos em modelos de sistemas de distribuição de água. Para tanto, são utilizados dados de redes hipotéticas e de laboratório, e modelos inversos resolvidos por métodos de busca global e local. Devido o emprego de tubos plásticos no circuito de laboratório, o clássico modelo da coluna elástica demonstrou-se ineficiente na reprodução do comportamento hidráulico de tal sistema. Resultados satisfatórios foram obtidos somente com um modelo hidráulico que considere o comportamento viscoelástico dos materiais dos tubos do circuito experimental. / The occurrence of large leakage losses in water supply systems has been frequently linked with pipe breaks resulting from high pressures levels in pipes. Efficient location of leakages is required in order to effectively control water losses and quickly repair the system. Analysis of hydraulic transients has been particularly useful for calibration and leak detection purposes. System observation for such analysis can reveal a substantial amount of information concerning physical properties and the integrity of the system, since water hammer waves are affected by different features and phenomena, including leaks. Thus, this research focuses on hydraulic transients for leak detection and calibration of water distribution system models. These objectives are achieved using data obtained from experiments performed on an experimental facility and numerical experiments on hypothetical networks. Inverse methods were based on both global and local search methods. Classic water hammer theory proved to be imprecise in describing the observed behavior of the hydraulic system composed of plastic pipes. Satisfactorily results were obtained with a hydraulic transient solver considering viscoelastic behavior of the pipe material.