Saturn's magnetosphere is unique in the solar system. The rotation-driven convection consists of alternating channels of cool plasma from an interior source moving outward and hot plasma from outside moving inward, making Saturn’s inner magnetosphere a dynamical region. This thesis describes work on developing numerical models to simulate the plasma convection pattern in Saturn's inner magnetosphere. Chapter 2 introduces the numerical Rice Convection Model (RCM), a multi-fluid model that was originally developed for Earth’s magnetosphere. We adapt it for Saturn’s conditions in this thesis. In Chapter 3, we show results of initial RCM simulation runs, in which only cool plasma from the interior source is considered. We also include the Coriolis force and the pickup effect. Because the cool plasma is much denser than the hot plasma and always dominant in determining the convection pattern, it is important and necessary to investigate it first. Chapter 4 compares several cool plasma source models and determines the one that produces the best simulation results when compared to Cassini spacecraft observations. In Chapter 5, we add the finite temperature and associated plasma pressure of the cool plasma. The effect of ionospheric Pedersen conductance is also investigated. Finally in Chapter 6, we add hot plasma at the outer boundary, and simulate the V-shape signatures of the injection-dispersion events, which are considered the most definitive evidence of rotation-driven convection in Saturn's inner magnetosphere. Our simulations conform to the observed fact that wider, slower outflow channels of cooler, denser plasma alternate with narrower, faster inflow channels of hotter, more tenuous plasma. Comparisons between simulated and observed results show great consistency.

Corrosion of reinforcing steel in concrete due to chloride ingress is one of the main causes of the deterioration of reinforced concrete structures, particularly in marine environments. It is therefore important to develop a reliable prediction model of chloride ingress into concrete, which can be used to predict the chloride concentration profiles accurately to help to assess the service life for reinforced concrete structures. Cementitious materials are porous media with a highly complex and active chemical composition. Ionic transport in cementitious materials is a complicated process involving mechanisms such as diffusion, migration, ionic binding, adsorption and electrochemical interactions taking place in the pore solution of the materials. The process is dependent on not only the microstructural properties of the materials such as porosity, pore size distribution and connectivity but also the electrochemical properties of the pore solution including ionic adsorption and ion-ion interactions. This thesis presents a numerical study on the multi-component ionic transport in concrete with the main focus on the microscopic scale. This study first investigated the impact of the Electric Double Layer (EDL) on the ionic transport in cement-based materials. The EDL is a well-known phenomenon found in porous materials, which caused by the surface charges at the interface between solid surfaces and pore solutions. The numerical investigation is performed by solving the multi-component ionic transport model with considering the surface charges for a cement paste subjected to an externally applied electric field. The surface charge in the present model is taken into account by modifying the Nernst-Planck equation in which the electrostatic potential is dependent not only on the externally applied electric field but also on the dissimilar diffusivity of different ionic species including the surface charges. Some important features about the impact of surface charge on the concentration distribution, migration speed and flux of individual ionic species are discussed. Then a new one-dimensional numerical model for the multi-component ionic transport in concrete to simulate the rapid chloride migration test is proposed. Advantages and disadvantages of the traditional methods used to determine the local electrostatic potential, i.e. electro-neutrality condition and Poisson’s equation, are illustrated. Based on the discussion a new electro-neutrality condition is presented, which can avoid the numerical difficulties caused by the Poisson’s equation, and remain the non-linearity of the electric field distribution. This model with the new electro-neutrality condition is employed to simulate the RCM test to prove its applicability. The new model is promising in solving the multi-component ionic transport problems especially in microscopic scale. Lastly, a one-dimensional numerical investigation on the chloride ingress in a surface-treated mortar with considering the penetration of sealer induced porosity gradient was performed. The numerical model was carefully treated to apply governing equations of ionic transport to this situation of two pore structures, with every parameter clearly defined on the microscopic scale.

Made available in DSpace on 2014-06-12T17:35:33Z (GMT). No. of bitstreams: 2 arquivo608_1.pdf: 1327860 bytes, checksum: a749ea707d97030f835fdb3e19f45a5f (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2010 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O avanço tecnológico verificado nos últimos tempos proporciona à sociedade mundial melhorias em diversos campos de atuação. No entanto, este processo dinâmico é também complexo, com decisões conflitantes que acarretam conseqüências não apenas para as organizações, mas para toda a sociedade. Neste contexto, este trabalho apresenta dois modelos distintos de decisão multicritério baseados na teoria utilidade multiatributo (MAUT) que serão aplicados em áreas diferentes. O primeiro modelo proposto integra um método multicritério com a abordagem de manutenção centrada em confiabilidade conhecida como RCM. Através deste modelo uma análise quantitativa das consequências das falhas é apresentada, disponibilizando para o gerente de manutenção dados importantes para a tomada de decisões gerenciais, obtidos com base nas preferências do decisor. O segundo modelo proposto está relacionado com o transporte de hidrogênio em gasodutos. É utilizado para a avaliação dos riscos em dutos de transporte de hidrogênio, onde ações são definidas em classes de prioridade com o intuito de mitigar os riscos, levando em consideração a avaliação das dimensões financeira, humana e ambiental. Desta forma, os dois modelos apresentados buscam contribuir com a sociedade, a partir do momento que proporcionam uma tomada de decisão mais estruturada, a partir da utilização de uma abordagem quantitativa e multidimensional que leva em consideração as incertezas associadas ao problema

Submitted by Pedro Barros (pedro.silvabarros@ufpe.br) on 2018-06-29T20:01:42Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Mariana Losada Agudelo.pdf: 1620466 bytes, checksum: 2b5b3eb5e07c5705d529062cbc717484 (MD5) / Made available in DSpace on 2018-06-29T20:01:42Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO Mariana Losada Agudelo.pdf: 1620466 bytes, checksum: 2b5b3eb5e07c5705d529062cbc717484 (MD5) Previous issue date: 2017-02-23 / CAPES / Devido ao rápido incremento dos avanços tecnológicos que tem melhorado diferentes aspectos da sociedade, tem-se uma maior exigência para as indústrias, pois cada dia os consumidores pedem maior qualidade e melhores tempos de atendimento. Nestes sentido as organizações em procura de melhorar seus processos devem tomar decisões muitas vezes conflitantes que acarretam consequências para a organização e para a sociedade em geral. Este trabalho apresenta a aplicação de um modelo de decisão multicritério baseado na teoria utilidade multiatributo MAUT integrado com a abordagem de manutenção centrada em confiabilidade conhecido como RCM (Reliability-Centered Maintencance), este modelo será aplicado na priorização de modos de falha em plantas industriais. O modelo permite uma avaliação quantitativa das consequências dos modos de falha incorporando as preferencias do decisor (gerente de manutenção). Desta forma, é proporcionada informação para a tomada de decisão para o planejamento da manutenção. Com a aplicação do modelo, procura-se evidenciar sua funcionalidade na priorização e planejamento da manutenção em diferentes plantas industriais, considerando as consequências dos modos de falha em cinco dimensões (humana, ambiental, financeira, operacional com interrupção dos processos, operacional sem interrupção dos processos), contribuindo na melhora da estruturação das decisões relacionadas à manutenção, que podem contribuir na melhora da qualidade e atendimento final para a sociedade. / With the rapid increase in technological breakthroughs that have improved different aspects of society, the industries have a greater challenge, as each day consumers demand higher quality and better service times. In this sense, the organizations seeking to improve their processes must take decisions are often conflicting and with consequences for the organization and for the society. According to the above, this paper presents the application of a multicriteria decision model based on the MAUT (Multi-Attribute Utility Theory) integrated with the Reliability-Centered Maintenance (RCM) approach, this model will be applied in the prioritization of failure modes in industrial plants. The model allows a quantitative evaluation of the consequences of failure modes incorporating the preferences of the decision maker (maintenance manager). In this way, information is provided for decision making in maintenance planning. With the application of the model, we tried to evidence its functionality in the prioritization and planning of maintenance in differents industrial plants, considering the consequences of failure modes in five dimensions (human, environmental, financial, operational with interruption of processes, operational without interruption of processes), contributing to the improvement of structuring decisions related to maintenance, which can contribute to the improvement of quality and final service to society.

Syftet med detta examensarbete är att systematisk utveckla en underhållsplan för att öka tillgängligheten för en pressfilteranläggning genom förebyggande underhåll. För att uppnå syftet har tydliga mål tagits fram för att ett systematisk arbetssätt ska kunna användas. Pressfilteranläggningen som det handlar om är belägen hos företaget LKAB i ett utav deras kulsinterverk. Anläggningen huvudsakliga uppgift är att filtrera bort vatten från en blandning mellan järnmalm och vatten med hjälp av tryckluft. Det systematiska arbetssättet består utav åtta steg där varje steg ämnar till att uppfylla ett utav de uppsatta målen. Steg ett innebär att identifiera befintliga underhållsplaner och tillståndskontroller för att få en förståelse hur underhållet utförs idag. Steg två innebär att studera hur ett annat företag arbetar med förebyggande underhåll av en pressfilteranläggning. Detta utförs så jämförelser kan utföras för att därefter kunna förbättra detta examensarbete. Steg tre handlar om att upprätta en systemnedbrytning över pressfilteranläggningen för att få en uppfattning vilka enheter och komponenter anläggningen består utav. Steg fyra innebär att hämta och analysera avbrottsstatistik för att få en uppfattning om vad som orsakar driftsstopp. Steg fem handlar om att beräkna tillgängligheten för anläggningen för att få en uppfattning om nuläget. Steg sex innebär att med hjälp utav ett paretodiagram kartlägga vilka enheter eller komponenter som bidrar till flest driftsstopp. Steg sju handlar om att upprätta en FMECA för de enheter och komponenter som bidrar till flest driftsstopp. Detta utförs för att kartlägga hur enheter kan gå sönder men även identifiera de mest kritiska enheterna och komponenterna. Steg åtta som är det sista steget innebär att upprätta en underhållsplan för de enheter och komponenter som bidrar till flest driftsstopp. Detta utförs genom att använda TDBUA-metodiken för att på ett systematiskt sätt upprätta en underhållsplan. Slutresultatet av detta arbete är en underhållsplan som täcker de enheter och komponenter som bidrar till flest driftsstopp. Underhållsplanen anger både vilka tillståndskontroller samt underhållsåtgärder som ska utföras för varje enhet och komponent. Den framtagna underhållsplanen ämnar till att öka tillgängligheten för pressfilteranläggningen vilket också är syftet med detta examensarbete.

Changes in the temporal variability of precipitation at all timescales are expected due to global warming. Such changes affect urban water infrastructure by potentially influencing their performance and risk of failure. Unfortunately, there is considerable uncertainty about how hydrological variables will change in the future. While uncertainty is present at all timescales, the climate signal in the daily time series simulated by climate models, for instance, can be estimated with much greater certainty than in the simulated hourly time series. That is problematic as sub-daily precipitation time series are essential to solving specific water resource engineering problems, especially in urban hydrology, where times of concentrations are typically less than a day. For instance, hourly or sub-hourly precipitation time series are routinely used to design stormwater and road drainage systems. Rainfall variability at sub-daily time steps is often represented as Intensity-Duration-Frequency (IDF) curves, relating precipitation duration (of basin time of concentration) to return period and average precipitation intensity. Naturally, several researchers investigated the integration of climate change in IDF curves, leading to methods of variable complexity and variable performance. This thesis aims to a) make a critical analysis of the most commonly used methods for IDF curves under climate change in Canada and b) identify the methods with optimal performance for a set of stations located in the South Nation watershed in Ottawa, Ontario, and c) perform a case study highlighting the effect of the choice of the temporal disaggregation method on the estimated risk of failure/performance of an urban water system. The first part of the thesis examines Equidistant Quantile Mapping (EQM) used in the IDF_CC tool developed for the Canadian Water Network project. Two conceptual flaws in the method that led to a systematic underestimation of extreme events were discovered. Two corrections are proposed to the EQM, leading to the development of two new methods for IDF generation. The output of EQM and its improved version is a time series of annual maximum precipitation intensity for different durations that can be used to derive IDF curves. These time series generated using the above approach are not appropriate for rainfall-runoff models for which continuous time series of precipitation (not only maximums) are required. The second part of the thesis tackles the issue, which examines a different approach to evaluating the risk of failure/performance of urban water systems under a changing climate. This second approach yields continuous time series of precipitation that can be fed in rainfall-runoff models used for IDF curve generation. The proposed method is applied in three steps: i) projections of future daily precipitation are generated by downscaling the output of climate models; ii) the downscaled daily precipitation time series are temporally disaggregated to an hourly time step using various techniques; iii) finally, the disaggregated future precipitation time series are used as inputs to rainfall-runoff models or used to generate IDF curves. This approach relaxes several strong assumptions made to develop the EQM approach, such as the implicit (and strong) assumption that the annual maximum precipitation at two different time steps occurs during the same event. That assumption is not necessarily valid and can affect the realism of the generated IDF curves. The method's performance is obviously dependent on the temporal disaggregation technique used in step 3. In this thesis, a simple steady-state stochastic disaggregation model that generates wet/dry day occurrence using a binomial distribution and precipitation intensity using an exponential distribution is proposed and compared to widely used temporal disaggregation methods: the multiplicative random cascade model (MRC), the Hurst-Kolmogorov process (HKP), and three versions of the K-nearest neighbor model (KNN) using the nonparametric Kolmogorov- Smirnov (KS) test. The six disaggregation techniques were assessed at four stations located in South Nation River Watershed located in Eastern Ontario, Canada. The third part of the thesis is a case study of the impact of climate change on stormwater management. First, a stormwater management model (SWMM) of St. Catharines, Ontario, developed in a previous study, was selected to simulate its stormwater and sanitary system. The model was forced with downscaled and temporally disaggregated precipitation outputs of the Canadian Regional Climate Model at the Port Dalhousie station, simulated under emission scenario RCP8.5. The temporal disaggregation was done using the Fahad-Ousmane and the KNN (30) methods developed in the previous chapter. The impact of climate change on the frequency, volume, and quality of combined sewer overflows and other hydraulic parameters is examined. Results suggest an increase in the total volume, flow frequency percentage, maximum flow, and average flow in the stormwater system due to climate change. Therefore, adaptation measures should be implemented for the distribution network and wastewater treatment plant to convey and treat the wastewater resulting from wet and dry events.

La siguiente propuesta de implementación está formada por tres capítulos en el primero se está considerando el marco teórico investigado de fuentes con revistas indexadas y respaldado por autores especialistas en los temas de confiabilidad, mantenibilidad definición, evolución, técnica, aplicación y tipos de mantenimiento. En el segundo capítulo la situación y diagnostico actual de la empresa, identificación del activo más relevante y el impacto económico que genera. En el tercer capítulo se muestra la propuesta de la implementación con respecto al diagnóstico que se realizó en los capítulos anteriores. En el cuarto capítulo se muestra la simulación del proceso actual del activo, así como la aplicación de la metodología del RCM, en el cual podemos evaluar la viabilidad de dicha implementación. Finalmente, las conclusiones y recomendaciones. / The following implementation proposal consists of three chapters. In the first one is considering the theoretical framework researched from sources with indexes journals and supported by specialist authors in terms of reliability, maintainability, definition, evolution, technique, application and types of maintenance. The second chapter is about the situation and current diagnosis of the company, identification of the most relevant asset and the economic impact it generates. The third chapter shows the proposal of the implementation with respect to the diagnosis that was made in the previous chapter. The fourth chapter shows the simulation of the current asset process, as well as the application of the RCM methodology, in which we can evaluate the feasibility of such implementation. Finally, the conclusions and recommendations. / Tesis

New environmental regulations as well as the increasing industrial competitiveness have set new more demanding rules on the manufacturing industry. In order to abide by those rules not only from the legal point of view but also to be able survive, manufacturing has to be more sustainable from many aspects, especially the economical one. One way to achieve the previous target is an unfortunately often oversighted aspect of the industry sector, the maintenance strategy. Condition based maintenance, CBM, can be used successfully in the industry and accurate estimation of spindle life time can lead to large savings in downtime and cost. CBM requires accurate sensors and equipment in order to get the right indicators whether equipment performance is deteriorating or not. One performance factor when planning a machining process is chatter vibration and one way to avoid this deteriorating phenomenon is to choose cutting parameters that allow stable machining. Various types of sensors are available for vibration and other CBM related measurements. Depending on the situation, the most applicable sensor is selected. The core of this thesis is to investigate the usefulness of measurements with the contactless excitations and response unit in terms of condition based maintenance. In the first part of the thesis, some of the theoretical aspects of maintenance are extensively elaborated upon and later on, the experimental part is presented along with the results’ discussion. The hardware required by the experiments has been provided by KTH and the experiments took place in two of an automotive industry’s production sites. There have been two visits at site A and one at site B, apart from the initial meetings. The measurements have been analyzed with the use of MATLAB. / Nya miljöregler samt ökande industriell konkurrens har satt nya mer krävande regler för tillverkningsindustrin. För att följa dessa regler, inte bara ur rättslig synpunkt utan också för att kunna överleva, behöver tillverkningen ske mer hållbar ur många aspekter, särskilt den ekonomiska. Ett sätt att uppnå målen är via, en tyvärr ofta underskattad metod, underhållsstrategin. Tillståndsbaserat underhåll, CBM, kan användas med framgång inom branschen och korrekt uppskattning av spindellivstid kan leda till stora besparingar genom minskade driftstopp och kostnader. CBM kräver noggranna sensorer och utrustning för att få rätt indikatorer för att avgöra om utrustningens prestanda försämras eller ej. En prestationsavgörande faktor vid planering av bearbetningsprocesser är vibrationer. Ett sätt att undvika dessa försämrade fenomen är att välja skärparametrar som tillåter stabil bearbetning. Olika typer av sensorer finns tillgängliga för vibrations- och andra CBM-relaterade mätningar. Beroende på situation, väljs den mest lämpliga sensorn. Kärnan i denna rapport är att undersöka nyttan av mätningar med en beröringsfri excitations- och mätenhet för tillståndsbaserat underhåll. I de första avsnitten av rapporten redogörs några av de teoretiska aspekterna av underhåll och i de senare är den experimentella delen presenterad, tillsammans med diskussion kring resultat. Hårdvaran som krävs för experimenten har tillhandahållits av KTH och experimenten ägde rum på två produktionsanläggningar hos en fordonstillverkare. Det har varit två besök på plats A och ett besök på plats B, bortsett från inledande möten. Mätningarna har analyserats med hjälp av MATLAB.

Företaget LKAB producerar järnmalmspellets i förädlingsverk i Svappavaara. Dessa förädlingsverk har haft en oväntat låg tillgänglighet under 2021. Denna låga tillgänglighet har lett till en oförmåga att producera enligt uppsatt budget. Syftet med detta arbete är att identifiera enheter som orsakar oplanerade produktionsstoppoch föreslå reviderade förebyggande underhållsåtgärder för att öka anläggningens tillgänglighet. Detta uppnås genom att utföra en RCM-analys, samt en sammanställning av underhållsplaner enligt TDBUA metodiken. Arbetet med RCM tar sin början i att välja ut de enheter som skall analyseras. Detta urval sker genom att kartlägga vilka produktionskritiska enheter som bidrar med mest oplanerad ståtid orsakad av haverier. De enheter som är både produktionskritiska, och bidrar med mest oplanerad ståtid väljs ut för fortsatt analys. De enheter som valts från analys av stilleståndsdata analyseras vidare enligt RCM-metodiken. Analysen fortsätter med systemkartläggning. Vid arbetet med systemkartläggning skapas en systemnedbrytning för att enkelt kunna visa på vilka enheter, eller komponenter som är kritiska. Denna systemnedbrytning följs av en FMEA där komponenternas möjliga fellägen och effekten av fel kartläggs. I FMEA:n sammanställs även vilka underhållsåtgärder som behöver utföras för att motverka feltillstånd, samt vilken övervakningsmetod som bör användas för att upptäcka degraderade tillstånd eller fel. De underhållsåtgärder som föreslås i FMEA:n sammanställs sedan till underhållsplaner enligt TDBUA metodiken. I underhållsplanerna tecknas inspektionsrutiner och övervakningsmetoder ned. Även reservdelar, samt vilken arbetskraft som krävs tecknas ned i underhållsplanerna. Resultatet av detta arbete är således sammanställda underhållsplaner för kritiska enheter iLKAB:s förädlingsverk i Svappavaara. Dessa underhållsplaner ämnar öka anläggningarnas tillgänglighet. / The corporation LKAB produces iron ore pellets in their enrichment plants in Svappavaara.These enrichment plants have suffered from a low availability in 2021. This low availability has caused LKAB to be unable to produce according to budget. The purpose of this work is to identify units that cause unplanned stops in the production line and to propose revised preventative maintenance plans to increase the availability of the enrichment plants. This purpose is reached by conducting an RCM-analysis and by putting together maintenance plans using the TDBUA methodology. The work with RCM starts with choosing which units to analyse. This is done by identifying the critical units that contributes the most unplanned downtime caused by breakdowns. The units that have been chosen from analysing downtime is further analysed using the RCM methodology. This analysis starts creating a system breakdown to get an understanding of the analysed units. The system breakdown is then followed by an FMEA, where failure modes, causes of failure, and effects of failure is identified. Maintenance actions are proposed to avoid failure, and surveillance methods are developed to detect when failure is about to occur. The maintenance actions that are proposed in the FMEA is combined into maintenance plans according to the TDBUA methodology. Inspection routines, spare parts, work hours, andlabour is also written into the maintenance plans. The results of this work is preventative maintenance plans for critical units in LKAB:s production plants in Svappavaara. These maintenance plans should help increase theavailability of the production plants.

En el presente artículo se muestra la aplicación de la metodología de RCM en las excavadoras de una empresa de alquiler de maquinaria pesada. La aplicación de la metodología RCM permitió el análisis de los tres sistemas más críticos de las excavadoras John Deere. Así también, se determinó el modo de falla y efecto de falla. Para determinar el plan de mantenimiento óptimo, se realizó el llenado de la hoja de análisis modal de efecto y fallas (AMEF) y con la ayuda del número de prioridad de riesgo (NPR) se seleccionaron los modos de fallas más críticos. Posteriormente, se analizaron los modos de fallas en la hoja de decisión para poder determinar las tareas de mantenimiento y las frecuencias. Además, se determinó el plan de mantenimiento de las excavadoras, con ello, se puede pronosticar el abastecimiento de los repuestos. Finalmente, a través de la simulación con el software ProModel se logró validar exitosamente los tres indicadores de mantenimiento; disponibilidad mecánica, tiempo promedio de reparación (MTTR) y tiempo promedio entre fallas (MTBF), con lo cual, la empresa generará mayores ingresos. / This article shows the application of the RCM methodology in the excavators of a heavy machinery rental company. The application of the RCM methodology allowed the analysis of the ee most critical systems of John Deere excavators. Also, the failure mode and effects analysis were determined. To determine the optimal maintenance plan, the filling of the failure mode effects analysis (FMEA) sheet was carried out and with the risk priority number (RPN), the most critical failure modes were selected. Subsequently, the failure modes were pointed out in the decision sheet in order to determine maintenance tasks and frequencies. In addition, the maintenance plan of the excavators was determined, with it, it is possible to forecast the supply of the spare parts. Finally, through the simulation with the Promodel software, it was possible to validate the three maintenance indicators; mechanical availability, the mean time to repair (MTTR) and the mean time between failures (MTBF), therefore the company will generate higher revenues. / Trabajo de Suficiencia Profesional