The repair welding of main steam pipelines, which involves the welding of new material onto service-exposed material, are investigated. This paper investigates the literature and experimental work surrounding this subject. The introduction provides a background to the applicable welding technology. In section two the heat-affected zone is discussed with emphasis on the residual stresses that develop in this zone. The mechanical properties of the heat-affected zone are also investigated. This includes the tensile, toughness and hardness properties as well as inspecting the relevant microstructures. The effect of post weld heat treatment on these properties is also investigated. Section three investigates the phenomenon of creep. Not only is this important due to the high temperatures at which these pipelines operate, but creep is also associated with some failures of these weld during post weld heat treatment. The creep properties of the heat-affected zone are investigated in detail with the use of weld simulation. Sections four and five detail reasons for weld failure after welding due to hydrogen and reheat cracking. Hydrogen cracking is investigated with the use of slow strain rate tensile tests during cathodical charging the specimen with hydrogen. The phenomenon of reheat cracking is investigated with the use of high temperature tensile tests as well as a novel approach in which the stress relief of a welded joint is simulated while measuring crack growth and stress relieved. / Dissertation (MEng)--University of Pretoria, 2014. / gm2014 / Materials Science and Metallurgical Engineering / Unrestricted

The effectiveness of an optimization algorithm can be reduced to its ability to navigate an objective function’s topology. Hybrid optimization algorithms combine various optimization algorithms using a single meta-heuristic so that the hybrid algorithm is more robust, computationally efficient, and/or accurate than the individual algorithms it is made of. This thesis proposes a novel meta-heuristic that uses search vectors to select the constituent algorithm that is appropriate for a given objective function. The hybrid is shown to perform competitively against several existing hybrid and non-hybrid optimization algorithms over a set of three hundred test cases. This thesis also proposes a general framework for evaluating the effectiveness of hybrid optimization algorithms. Finally, this thesis presents an improved Method of Characteristics Code with novel boundary conditions, which better characterizes pipelines than previous codes. This code is coupled with the hybrid optimization algorithm in order to optimize the operation of real-world piston pumps.

As of 1999, high school teachers without majors in their subject areas number 37% of biology teachers, 59% of physical science teachers, and 60% of mathematics teachers. These discouraging statistics grow more extreme in middle schools and high poverty public high schools, especially regarding mathematics and physical sciences instruction. The statistics are especially worrisome given the strong correlation between thorough teacher subject matter preparation and higher student performance. Unfortunately, the literature is limited in terms of a direct comparison between mathematics and science majors and individuals who become mathematics and science teachers. This study was undertaken to add to the body of literature in hopes of informing universities and school districts of the characteristics of individuals who enter the mathematics and science teacher pipeline. The purpose of this study was to determine whether predictive relationships exist among the independent variables and the dependent variable, and whether certain attributes account for significant differences between mathematics and science degree earners who choose to enter the mathematics and science teacher pipeline and those who show no interest in mathematics and science teaching. This study provided a snapshot of the characteristics of both groups of individuals. The sample for this investigation came from the Baccalaureate and Beyond Longitudinal Study (B&B: 08/09) cohort of approximately 19,000. B&B:08/09 examined information on students’ educational and work experiences after they completed a bachelor’s degree, with a special emphasis on the experiences of new elementary and secondary teachers. In the present study, the sample consisted of 2,400 individuals majoring in mathematics and science fields including mathematics and science education. The research design that was used is the analytical cross sectional design. The analytical cross sectional design investigates associations and measures differences between groups. In this study, deep descriptions were used to describe the sample. A logistic regression analysis was used to assess the degree to which the dependent (outcome) variable, teacher pipeline status, is related to the independent (predictor) variables (persistence, academic performance, selected demographics).

We consider the problem of extracting a specific feature from a noisy signal generated by a multi-channels Remote Field Eddy Current Sensor. The sensor is installed on a mobile robot whose mission is the detection of anomalous regions in metal pipelines. Given the presence of noise that characterizes the data series, anomaly signals could be masked by noise and therefore difficult to identify in some instances. In order to enhance signal peaks that potentially identify anomalies we consider an entropy filter built on a-posteriori probability density functions associated with data series. Thresholds based on the Neyman-Pearson criterion for hypothesis testing are derived. The algorithmic tool is applied to the analysis of data from a portion of pipeline with a set of anomalies introduced at predetermined locations. Critical areas identifying anomalies capture the set of damaged locations, demonstrating the effectiveness of the filter in detection with Remote Field Eddy Current Sensor.

Orientador: Alice Maria B. H. Tokarnia / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-07T23:40:08Z (GMT). No. of bitstreams: 1 Silva_RogerioSigrist_M.pdf: 816659 bytes, checksum: 206ce45bc9176489805fd6c7f8f0e260 (MD5) Previous issue date: 2006 / Resumo: Este trabalho descreve três algoritmos para a síntese de sistemas embutidos atendendo à restrição de desempenho representada pela taxa de chegada dos dados, através de uma estrutura de pipeline de processadores para execução das tarefas, ao mesmo tempo em que minimizam diferentes parâmetros de qualidade dos sistemas: número de processadores; custo e latência total. Os algoritmos realizam o particionamento hardware-software das tarefas, a alocação dos processadores, o mapeamento e escalonamento das tarefas. A alocação de processadores e o mapeamento e escalonamento de tarefas são problemas classificados como NP-Completo e, portanto, foram aplicados métodos heurísticos para suas resoluções. Como exemplos de aplicação são apresentados os pipelines sintetizados pelos algoritmos para grafos sintéticos e para um compressor de áudio digital (AC3). Os pipelines sintetizados atingem métricas de qualidade superiores a outros algoritmos publicados / Abstract: This work presents three heuristics for sinthesizing pipelined embedded systems that satisfy a throughput constraint derived from the maximum input data are adopting a pipeline structure of processors while minimizing system quality parameters: cost, number of processors, or number of stages. The algorithms perform tasks hardware-software partitioning, processors allocation and task mapping and scheduling. Since processors allocation and task mapping and scheduling are NP-Complete problems, heuristics methods were applied. The examples present the pipelines synthesized by the algorithms for large synthetic systems comparing the quality parameters minimization results and for a real audio compressor (AC3) application. The pipelines reached quality metrics higher than other published algorithms / Mestrado / Engenharia de Computação / Mestre em Engenharia Elétrica

The primary purpose of this research was to improve the accuracy and robustness of pipeline transient modeling. An algorithm was developed to model the transient flow in closed tubes for thin walled pipelines. Emphasis was given to the application of this type of flow to pipelines with small radius 90° elbows. An additional loss term was developed to account for the presence of 90° elbows in a pipeline. The algorithm was integrated into an optimization routine to fit results from the improved model to experimental data. A web based interface was developed to facilitate the pre- and post- processing operations. Results showed that including a loss term that represents the effects of 90° elbows in the Method of Characteristics (MOC) [1] improves the accuracy of the predicted transients by an order of magnitude. Secondary objectives of pump optimization, blockage detection and removal were investigated with promising results.

Frontotemporal dementia is a neurodegenerative disorder with high heterogeneity on the genetic, pathological and clinical level. The familial form of the disease is mainly caused by pathogenic variants of three genes: C9orf72, MAPT and GRN. As there is no clear correlation between the mutation and the clinical phenotype, symptom severity or age of onset, the demand for predictive biomarkers is high. While there is no fluid biomarker for frontotemporal dementia in use yet, there is strong hope that changes of protein concentrations in the blood or cerebrospinal fluid can aid prognostics many years before symptoms develop. Increasing amounts of data are becoming available because of long-term studies of families affected by familial frontotemporal dementia, but its analysis is time-consuming and work intensive. In the scope of this project a pipeline was built for the automated analysis of proteomics data. Specifically, it aims to identify proteins useful for differentiation between two groups by using random forest, a supervised machine learning method. The analysis results of the pipeline for a data set containing blood plasma protein concentration of healthy controls and participants affected by frontotemporal dementia were promising and the generalized functioning of the pipeline was proven with an independent breast cancer proteomics data set.

[pt] Um dos principais mecanismos de falha em risers flexíveis é o rompimento de arames da armadura de tração. A experiência tem mostrado que esta classe de dano tende a surgir primariamente na parte emersa do riser, próximo à sua terminação. A ruptura dos arames ocorre de forma progressiva, podendo ser causada por diferentes processos, tais como corrosão pelo ingresso de fluido no espaço anular entre capa e armadura, desgaste excessivo associado com o contato e atrito entre arames adjacentes ou entre as diferentes camadas metálicas da armadura, ou mesmo a presença de níveis elevados de tensões produzidas pelos carregamentos mecânicos aos quais o riser é submetido durante a operação. O deterioramento progressivo pode dar origem a defeitos localizados que agem como concentradores de tensão e levam o arame à ruptura através de um processo de fadiga. O duto flexível é capaz de manter-se em operação mesmo com alguns dos arames de suas armaduras rompidos, porém uma sequencia de rupturas pode levar à ocorrência de vazamentos ou mesmo a falhas catastróficas. O monitoramento contínuo em tempo real é uma das principais alternativas para evitar que o dano progressivo nas armaduras do riser resulte em acidentes com severas consequências econômicas e ambientais. As técnicas de monitoramento da integridade de risers flexíveis podem ser classificadas como diretas, onde é possível identificar diretamente a existência de um dano/falha, ou indiretas, em que o sistema de sensoriamento registra indicações secundárias, possivelmente consequência da falha. Esta dissertação relata o desenvolvimento de um sistema de monitoramento baseado em vibrações. Trata-se de uma técnica indireta baseada em eventos, onde no momento da ruptura do arame um sinal de vibração, distinto tanto na frequência quanto na amplitude, é detectado por acelerômetros instalados na capa polimérica externa do riser. No trabalho, são apresentados resultados de quatro ensaios em escala real que demonstraram a viabilidade do sistema para um primeiro teste de campo. Estratégias de instrumentação dos dutos e as variações dos sinais detectados são apresentadas e discutidas. Os resultados mostraram que a resposta vibratória do sinal de ruptura apresenta características específicas, garantindo uma boa confiabilidade na detecção. Porém, em se tratando de uma técnica indireta, verifica-se que quando dois sistemas de monitoramento de naturezas complementares são empregados em conjunto, as probabilidades de detecção dos eventos de rupturas aumentam significativamente. / [en] The main failure in flexible risers is the disruption of the wires from the tensile armor layer. Experience has shown that this class of damage occurs primarily near to the top riser connector. The breaking of the wires occurs gradually and may be caused by different processes as corrosion by inflow of fluid in the annular space, excessive wear associated with the contact and friction between adjacent wires or between different riser layers. The progressive deterioration can lead to localized defects that act as stress concentrators and may break the wire from the tensile armor layer through a fatigue process. The flexible pipe is able to remain in operation even with some broken wires, but a sequence of ruptures can conduce to a catastrophic failure. Real time continuous monitoring is one of the main alternatives to prevent progressive wire damage results in an accident with severe economic and environmental consequences. This thesis describes the development of a monitoring system based on vibrations. This is an indirect technique based on events, where in the moment of the wire break, one vibration signal is registered. This signal can be distinguished both in frequency and amplitude and detected by accelerometers installed on the polymeric outer layer of the riser. We present results of four tests in real scale that demonstrated the viability of the system for an initial field test. Instrumentation strategies in riser and the variations of the signals detected are presented and discussed. The results showed that the vibrational signal has specific characteristics ensuring good detection reliability.

O presente trabalho tem como objetivo avaliar a influência do efeito da corrosão no comportamento geotécnico de condutos enterrados através da utilização de ensaios em modelos reduzidos. Foram empregados diferentes padrões de corrosão, em que se variou o grau e a localização da corrosão. Os resultados do trabalho mostram as localizações mais danosas à estrutura, correlacionando resultados dos tubos corroídos com os de tubos intactos. O duto danificado desencadeou um carregamento assimétrico que deve ser considerado para a prevenção de possíveis deslocamentos. Finalmente, o trabalho avalia a influência conjunta da corrosão e da flexibilidade do conduto no comportamento mecânico das tubulações enterradas. De modo a permitir comparações para averiguar a validade do modelo laboratorial adotado, utilizaram-se simulações numéricas, que possibilitam o estudo do problema de forma mais abrangente. / This work evaluates the influence of corrosion effect on the geotechnical behavior of underground conduits. Small-scale tests were carried out on two different types of pipes, in which the degree and location of the corrosion were changed. The results show the most harmful corrosion locations relative to the intact conduits. The damaged conduits built in and located under asymmetric condition behave as if they were subjected to an asymmetric loading condition and this must be considered to the prevention of possible displacements. Finally, the work evaluates the joined influence of the corrosion and conduit\'s flexibility on the mechanical behavior of underground pipelines. To allow comparisons to inquire the validation of the adopted laboratorial model, numeric simulations were used, which enable the study of the problem considering other corrosion layouts.

[ES] El análisis de los fenómenos transitorios durante las operaciones de llenado en conducciones de agua ha sido estudiado de manera detallada comparado con las maniobras de vaciado. En este último se encontró que no existen modelos matemáticos capaces de predecir el fenómeno. Esta investigación inicia estudiando el fenómeno transitorio generado durante el vaciado en una tubería simple, como paso previo para entender el comportamiento de las variables hidráulicas y termodinámicas durante el vaciado de agua en conducciones presurizadas de perfil irregular. Los análisis son realizados considerando dos situaciones: (i) la situación No. 1 corresponde al caso donde no hay válvulas de aire instaladas o cuando éstas han fallado por problemas operacionales o de mantenimiento, que representa la condición más desfavorable con respecto a la depresión máxima alcanzada; y (ii) la situación No. 2 corresponde al caso en donde se han instalado válvulas de aire en los puntos más elevados de la conducción para dar fiabilidad mediante el aire introducido al sistema previniendo de esta manera la depresión máxima. En esta tesis doctoral se ha desarrollado un modelo matemático para predecir el comportamiento de las operaciones de vaciado. El modelo matemático es propuesto para las dos situaciones mencionadas anteriormente. La fase líquida (agua) es simulada con un modelo de columna rígida, en el cual se desprecia la elasticidad del agua y de la tubería debido a que la elasticidad del aire es mucho mayor que estas; y la interfaz aire-agua es modelada con un modelo de flujo pistón, el cual asume que la columna de agua es perpendicular a la dirección principal del flujo. La fase de aire es modelada usando tres ecuaciones: (a) un modelo politrópico basado en el comportamiento energético, que considera la expansión de las bolsas de aire; (b) la formulación de las válvulas de aire para cuantificar la magnitud del caudal de aire admitido; y (c) la ecuación de continuidad de la bolsa de aire. Un sistema ordinario de ecuaciones diferenciales es solucionado utilizando la herramienta de Simulink de Matlab. El modelo matemático es validado empleando bancos experimentales localizados en los laboratorios de hidráulica de la Universitat Politècnica de València (Valencia, España) y en el Instituto Superior Técnico de la Universidad de Lisboa (Lisboa, Portugal). Los resultados muestran que el modelo matemático predice adecuadamente los datos experimentales de las presiones de las bolsas de aire, las velocidades del agua y las longitudes de las columnas de agua. Finalmente, el modelo matemático es aplicado a un caso de estudio para mostrar su aplicabilidad a situaciones prácticas, con el fin de poder ser empleado por ingenieros para estudiar el fenómeno en conducciones reales y así tomar decisiones acerca de la planificación de esta operación. / [CAT] L'anàlisi dels fenòmens transitoris durant les operacions d'ompliment en conduccions d'aigua ha sigut estudiat de manera detallada comparat amb les maniobres de buidatge. En este últim es va trobar que no hi ha models matemàtics capaços de predir el fenomen. Esta investigació inicia estudiant el fenomen transitori generat durant el buidatge en una canonada simple, com a pas previ per a entendre el comportament de les variables hidràuliques i termodinàmiques durant el buidatge d'aigua en conduccions pressuritzades de perfil irregular. Les anàlisis són realitzats considerant dos situacions: (i) la situació No. 1 correspon al cas on no hi ha vàlvules d'aire instal·lades o quan estes han fallat per problemes operacionals o de manteniment, que representa la condició més desfavorable respecte a la depressió màxima aconseguida; i (ii) la situació No. 2 correspon al cas on s'han instal·lat vàlvules d'aire en els punts més elevats de la conducció per a donar fiabilitat per mitjà de l'aire introduït al sistema prevenint d'esta manera la depressió màxima. En esta tesi doctoral s'ha desenrotllat un model matemàtic per a predir el comportament de les operacions de buidatge. El model matemàtic és proposat per a les dos situacions mencionades anteriorment. La fase líquida (aigua) és simulada amb un model de columna rígida, en el qual es desprecia l'elasticitat de l'aigua i de la canonada pel fet que l'elasticitat de l'aire és molt major que estes; i la interfície aire-aigua és modelada amb un model de flux pistó, el qual assumix que la columna d'aigua és perpendicular a la direcció principal del flux. La fase d'aire és modelada usant tres equacions: (a) un model politròpic basat en el comportament energètic, que considera l'expansió de les bosses d'aire; (b) la formulació de les vàlvules d'aire per a quantificar la magnitud del cabal d'aire admés; i (c) l'equació de continuïtat de la bossa d'aire. Un sistema ordinari d'equacions diferencials és solucionat utilitzant la ferramenta de Simulink de Matlab. El model matemàtic és validat emprant bancs experimentals localitzats en els laboratoris d'hidràulica de la Universitat Politècnica de València (València, Espanya) i en l'Institut Superior Tècnic de la Universitat de Lisboa (Lisboa, Portugal). Els resultats mostren que el model matemàtic prediu adequadament les dades experimentals de les pressions de les bosses d'aire, les velocitats de l'aigua i les longituds de les columnes d'aigua. Finalment, el model matemàtic és aplicat a un cas d'estudi per a mostrar la seua aplicabilitat a situacions pràctiques, a fi de poder ser empleat per enginyers per a estudiar el fenomen en conduccions reals i així prendre decisions sobre la planificació d'esta operació. / [EN] The analysis of transient phenomena during water filling operations in pipelines of irregular profiles has been studied much more compared to emptying maneuvers. In the literature, there is a lack of knowledge about mathematical models of emptying operations. This research starts with the analysis of a transient phenomenon during emptying maneuvers in single pipelines, which is a previous stage to understand the emptying operation in pipelines of irregular profiles. Analysis are conducted under two typical situations: (i) one corresponding to either the situation where there are no air valves installed or when they have failed due to operational and maintenance problems which represents the worse condition due to causing the lowest troughs of subatmospheric pressure, and (ii) the other one corresponding to the situation where air valves have been installed at the highest point of hydraulic installations to give reliability by admitting air into the pipelines for preventing troughs of subatmospheric pressure. Particularly, this research developed a mathematical model to predict the behavior of the emptying operations. The mathematical model is proposed for the two aforementioned situations. The liquid phase (water) is simulated using a rigid water column model (RWCM), which neglects the pipe and water elasticity given that the elasticity of the entrapped air pockets is much higher than the one from the pipe and the water. The air-water interface is simulated with a piston flow model assuming that the water column is perpendicular with the main direction of the flow. Gas phase is modeled using three formulations: (a) a polytropic model based on its energetic behavior, which considers an expansion of air pockets; (b) an air valve characterization to quantify the magnitude of admitted air flow; and (c) a continuity equation of the air. An ordinary differential equations system is solved using the Simulink tool of Matlab. The proposed model has been validated using experimental facilities at the hydraulic laboratories of the Universitat Politècnica de València, Valencia, Spain, and the Instituto Superior Técnico, University of Lisbon, Lisbon, Portugal. The results show how the mathematical model adequately predicts the experimental data, including the pressure oscillation patterns, the water velocities, and the lengths of the water columns. Finally, the mathematical model is applied to a case study to show a practical application, which can be used for engineers to study the phenomenon in real pipelines to make decisions about performing of the emptying operation. / Coronado Hernández, ÓE. (2019). Transient phenomena during the emptying process of water in pressurized pipelines [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/120024 / TESIS