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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

Simultaneous Fixed Bed Removal of Nitrogen Oxides and Mercury Using Manganese and Cerium Mixed Metal Oxide Catalysts at Low Temperature SCR

Patil, Aniket January 2018 (has links)
No description available.
132

Control-oriented modelling and diagnostics of diesel after-treatment catalysts

Mora Pérez, Javier 21 January 2019 (has links)
[ES] Esta tesis doctoral abarca el desarrollo de algoritmos orientados a mejorar el sistema de control de emisiones en motores Diesel. Para este propósito, la inclusión en el vehículo de sensores embarcados como los de temperatura, los de NOx o el de NH3 permite realizar diagnóstico a bordo de los sistemas de post-tratamiento foco de este trabajo, los cuales son el DOC y el SCR. Así pues, el objetivo es el de satisfacer las normativas de diagnóstico a bordo para mantener las emisiones por debajo del umbral permitido por la normativa a lo largo del tiempo. Los tests experimentales, incluyendo las medidas con analizador de gases, permiten tener una visión más amplia de las especies en la línea de escape. Complementariamente, se utilizan unidades nuevas y envejecidas para tener el efecto experimental del envejecimiento en los catalizadores. De esta manera, se analiza el efecto de la temperatura, el gasto de escape, las concentraciones de las especies y el envejecimiento en el DOC y en el SCR, así como la evaluación de algunas de las medidas relevantes realizadas por los sensores. Las temperaturas tienen una influencia destacada en el funcionamiento de los catalizadores, por lo que se requiere la evaluación de las medidas de los sensores de temperatura, junto con el desarrollo de modelos de transmisión de calor, para alimentar las funciones a continuación desarrolladas. En este sentido, la medida lenta del sensor aguas arriba del DOC se mejora en condiciones transitorias mediante una técnica de fusión de la información basada en un filtro de Kalman. Luego, se presenta un modelo de transmisión de calor 1D y un modelo agrupado 0D, en los cuales se evalúan las entradas aguas arriba según el uso del modelo. Por otra parte, se presenta una técnica para estimar el incremento de temperatura debido a la oxidación de los pulsos de post-inyección en el DOC. Se proponen modelos para ambos DOC y SCR para estimar el efecto del envejecimiento en las emisiones, en los cuales el factor de envejecimiento es modelado como un parámetro sintonizable que permite variar desde estados nuevos a envejecidos. Por una parte, un modelo agrupado 0D es desarrollado para el DOC con el propósito de estimar el desliz de HC y CO, el cual es validado en un WLTC para después ser usado en simulación. Por otra parte, un modelo 1D y un modelo 0D se desarrollan para el SCR, los cuales se usan a continuación para alimentar la estrategia de diagnóstico y para simulación. Finalmente, las estrategias de diagnóstico se presentan para fallo total o retirada de DOC, así como para la estimación de la eficiencia en DOC y SCR. Por una parte, la primera estrategia se divide en pasiva y activa, en la que se usan post-inyecciones en la activa para excitar el sistema y confirmar el fallo total si es el caso. A continuación, la eficiencia del DOC se estima a través de una técnica indirecta en la que la temperatura de activación se detecta y se relaciona con el incremento de emisiones a través del modelo. Por otra parte, se desarrolla un observador para estimar el estado de envejecimiento del SCR, el cual está basado en un filtro de Kalman extendido. Sin embargo, para evitar asociar baja eficiencia del catalizador debido a pobre calidad de la urea inyectada, a envejecimiento del SCR, un indicador de la calidad de la urea se ejecuta en paralelo. / [CA] Esta tesi doctoral abasta el desenvolupament d'algoritmes orientats a millor el sistema de control d'emissions en motors Diesel. Per a este propòsit, la inclusió en el vehicle de sensor embarcats com els de temperatura, els de NOx o el d'NH3 permet realitzar el diagnòstic a bord dels sistemes de post-tractament focus d'este treball, els quals són el DOC i el SCR. Així doncs, l'objectiu és el de satisfer les normatives de diagnòstic a bord per a mantindre les emissions per baix de l'umbral permés per la normativa al llarg del temps. Els tests experimentals, incloent les mesures amb analitzador de gasos, permeten obtindre una visió més àmplia de les espècies en la línia d'escapament. Complementàriament, s'utilitzen unitats noves i envellides per tal de tindre l'efecte experimental de l'envelliment en els catalitzadors. D'aquesta manera, s'analitza l'efecte de la temperatura, la despesa d'escapament, les concentracions de les espècies i l'envelliment en el DOC i en el SCR, així com l'avaluació d'algunes mesures rellevants realitzades pels sensors. Les temperatures tenen una influència destacada en el funcionament dels catalitzadors, pel que es requerix l'avaluació de les mesures dels sensors de temperatura, junt amb el desenvolupament de models de transmissió de calor, per a alimentar les funcions a continuació desenvolupades. En este sentit, la mesura lenta del sensor a l'entrada del DOC es millora en condicions transitòries mitjançant una tècnica de fusió de la informació basada en un filtre de Kalman. Després, es presenta un model de transmissió de calor 1D i un model agrupat 0D, en els quals s'avaluen les entrades a l'entrada segons l'ús del model. Per altra banda, es presenta una tècnica per a estimar l'increment de temperatura degut a l'oxidació dels polsos de post-injecció en el DOC. Es proposen models per a DOC i SCR per a estimar l'efecte de l'envelliment en les emissions, en els quals es modela el factor d'envelliment com un paràmetre sintonitzable, que permet variar des d'estats nous a envellits. Per altra banda, un model agrupat 0D _es desenvolupat per al DOC amb el propòsit d'estimar la relliscada de HC i CO, el qual és validat en un WLTC per a després ser usat en simulació. Per altra banda, un model 1D i un model 0D es desenvolupen per al SCR, els quals s'usen a continuació per a alimentar l'estratègia de diagnòstic i per a simulació. Finalment, les estratègies de diagnòstic es presenten per a la fallada total o retirada del DOC, així com per a l'estimació de l'eficiència en DOC i SCR. Per altra banda, la primera estratègia es divideix en passiva i activa, en la que s'utilitzen post-injeccions en la activa per a excitar el sistema i confirmar la fallada total si es dona el cas. A continuació, l'eficiència del DOC s'estima a través d'una tècnica indirecta en la que la temperatura d'activació es detecta i es relaciona amb l'increment d'emissions a través del model. Per altra banda, es desenvolupa un observador per a estimar l'estat d'envelliment del SCR, el qual està basat en un filtre de Kalman extés. No obstant això, per a evitar associar baixa eficiència degut a pobre qualitat de l'urea injectada a l'envelliment del SCR, un indicador de la qualitat de l'urea s'executa en paral·lel. / [EN] This dissertation covers the development of algorithms oriented to improve the emission control system of Diesel engines. For this purpose, the inclusion of on-board sensors like temperature, NOx and NH3 sensors allows performing on-board diagnostics to the after-treatment systems focus of this work, which are the DOC and the SCR system. Then, the target is to meet on-board diagnostics regulations in order to keep emissions below a regulation threshold over time. Experimental tests, including gas analyzer measurements, allow having a wider view of the species in the exhaust line. Complementary, new and aged units are used in order to have the experimental effect of ageing on the catalysts. Then, the effect of temperature, exhaust mass flow, species concentrations and ageing is analyzed for DOC and SCR, in combination with the assessment of some relevant sensors measurements. As a result, the characteristics, opportunities and limitations extracted from experimental data are used as the basis for the development of models and diagnostics techniques. The assessment of temperature sensors measurements, along with the development of heat transfer models is required to feed temperature dependent functions. In this sense, the slow measurement of the DOC upstream temperature sensor is improved in transient conditions by means of a data fusion technique, based on a fast model and a Kalman filter. Then, a 1D and a 0D lumped heat transfer models are presented, in which the upstream inputs are assessed in relation to its use. On the other hand, a technique to estimate the temperature increase due to post-injection pulses oxidation is also presented. Both DOC and SCR models are proposed in order to estimate the effect of ageing on emissions, in which an ageing factor is modelled as a tunable parameter that allows varying from new to aged states. On the one hand, a 0D lumped model is developed for DOC in order to estimate the HC and CO species slip, which is validated in a WLTC and is then used for simulation. On the other hand, a 1D and a 0D models are developed for SCR, which are then used to feed the diagnostics strategy and for simulation. Finally, diagnostics strategies are presented for total failure or removal of DOC, as well as for efficiency estimation of DOC and SCR. On the one hand, the former strategy is separated into passive and active diagnostics, in which post-injections are used in active diagnostics in order to excite the system and confirm a total failure, in case. Then, the DOC efficiency estimation is done by means of an indirect technique in which the light-off temperature is detected and an emissions increase is related by means of the DOC ageing model. On the other hand, an observer to estimate the SCR ageing state is developed, which is based on an extended Kalman filter. However, in order to avoid associating low SCR efficiency to ageing, an indicator of the injected urea quality is developed to run in parallel. / Mora Pérez, J. (2018). Control-oriented modelling and diagnostics of diesel after-treatment catalysts [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/115937
133

Study and characterization of electrical overstress aggressors on integrated circuits and robustness optimization of electrostatic discharge protection devices / Etude et caractérisation des agresseurs électriques de sur-résistance sur les circuits intégrés et optimisation de la robustesse des dispositifs de protection contre les décharges électrostatiques

Loayza Ramirez, Jorge Miguel 08 June 2017 (has links)
Cette thèse de doctorat s’inscrit dans la thématique de la fiabilité des circuits intégrés dans l’industrie de la microélectronique. Un circuit intégré peut être exposé à des agresseurs électriques potentiellement dangereux pendant toute sa durée de vie. Idéalement, les circuits devraient pouvoir encaisser ces excès d’énergie sans perdre leur fonctionnalité. En réalité, des défaillances peuvent être observées lors de tests de qualification ou en application finale. Il est donc dans l’intérêt des fabricants de réduire ces défaillances. Actuellement, il existe des circuits de protection sur puce conçus pour dévier l’énergie de ces agresseurs à l’écart des composants fragiles. Le terme anglophone Electrical Overstress (EOS) englobe tous les agresseurs électriques qui dépassent une limite au-delà de laquelle les composants peuvent être détruits. La définition de ce terme est traitée en détail dans la thèse. L’objectif de cette thèse est de comprendre le statut du sujet des EOS dans l’industrie. On propose ensuite une nouvelle méthodologie de caractérisation de circuits pour quantifier leur robustesse face à des formes d’onde représentatives présélectionnées. On propose également des solutions de circuits de protection sur puce que ce soit au niveau de nouveaux composants actifs ou au niveau de la conception des circuits électroniques de protection. Par exemple on propose un nouveau composant basé sur le thyristor qui a la capacité de s’éteindre même si la tension d’alimentation est présente sur l’anode. Une autre proposition est de désactiver les circuits de protection face aux décharges électrostatiques lorsque les puces sont dans un environnement où l’on est sur ou ces agresseurs ne présentent plus de danger. Finalement, des perspectives du travail de thèse sont citées. / This Ph.D. thesis concerns reliability issues in the microelectronics industry for the most advanced technology nodes. In particular, the Electrical OverStress (EOS) issue is studied. Reducing EOS failures in Integrated Circuits (ICs) is becoming more and more important. However, the EOS topic is very complex and involves many different causes, viewpoints, definitions and approaches. In this context, a complete analysis of the current status of the EOS issue is carried out. Then, the Ph.D. objectives can be defined in a clear way. In particular, robustness increase of on-chip protection structures and IC characterization against EOS-like aggressors are two of the main goals. In order to understand and quantify the behavior of ICs against these aggressors, a dedicated EOS test bench is put in place along with the definition of a characterization methodology. A full characterization and comparison is performed on two different Electro- Static Discharge (ESD) power supply clamps. After identifying the potential weaknesses of the promising Silicon-Controlled Rectifier (SCR) device, a new SCR-based device with a turn-off capability is proposed and studied thanks to 3-D Technology Computer-Aided Design (TCAD)simulation. Triggering and turn-off behaviors are studied, as well as its optimization. Finally, three different approaches are proposed for improving the robustness of the IC onchip protection circuits. They are characterized thanks to the EOS test bench which allows identifying their assets as well as their points of improvement.
134

CFD Simulation of Urea Evaporation in STAR-CCM+

Ottosson, Oscar January 2019 (has links)
Diesel engines produce large amounts of nitrogen oxides (NOX) while running. Nitrogen oxides are highly toxic and also contribute towards the formation of tropospheric ozone. Increasingly stringent legislation regarding the amount of nitrogen oxides that are allowed to be emitted from diesel-powered vehicles has forced manufacturers of diesel-engines to develop after-treatment systems that reduce the amount of nitrogen oxides in the exhaust. One of the main components in such a system is selective catalytic reduction (SCR), where nitrogen oxides are reduced to diatomic nitrogen and water with the help of ammonia. A vital part of this process is the spraying of a urea-water-solution (UWS), which is needed in order to produce the reducing agent ammonia. UWS spraying introduces the risk of solid deposits (such as biuret, ammelide and ammeline) forming in the after-treatment system, should the flow conditions be unfavourable. Risk factors include high temperatures, but also low dynamics and high thickness of the resulting liquid film that forms as the UWS spray hits the surfaces of the after-treatment system. It is thus essential that manufacturers of SCR after-treatment systems have correct data on how much UWS that should be sprayed into the exhaust for any given flow condition. Experimental tests are thoroughly used to assess this but are very expensive and are thus limited to prototype testing during product development. When assessing a wider range of concepts and geometries early on in the product development stage, simulation tools such as computational fluid dynamics (CFD) are used instead. One of the most computationally heavy processes to simulate within a SCR after-treatment system is the UWS spray and its interaction with surfaces inside the after-treatment system, where correct prediction of the formation of solid deposits are of great importance. Most CFD models used for this purpose hold a relatively good level of accuracy and are utilized throughout the whole industry where SCR aftertreatment is applied. Despite this, these models are limited in the fact that they are only able to cover timescales in the scope of seconds to minutes while using a tolerable amount of computational power. However, the time spectrum for solid deposit formation is minutes to hours. Scania is one of Sweden’s biggest developers of SCR after-treatment, with the technology being incorporated directly into its silencers. AVL Fire is the main UWS spray simulation tool for engineers at Scania at the moment. One major drawback of using AVL Fire for UWS spray simulations is that it is deemed too time-consuming to set up new cases and too unstable during simulation, which makes it too costly in terms of expensive engineering hours. This project has investigated the potential of using STAR-CCM+ for UWS spray simulations at Scania instead. A standard method has been evaluated, as well as parameters that will prove useful in further investigations of a potential speedup method. The studied method in STAR-CCM+ is easy to setup and the simulation process is robust and stable. Various other perks come from using STAR-CCM+ as well, such as: a user-friendly interface, easy and powerful mesh-generation and great post-process capabilities. Several different parameters have been investigated for their impact on the studied method, such as mesh refinement of the spray injector area and the number of parcels injected every time-step through the spray injector (simply put the resolution of the spray). A possible speedup by freezing the momentum equations when allowed and lowering the amount of inner iterations has also been investigated. A handful of operating conditions have been studied for two different geometries. The attained simulation results display correlations with physical measurements, but further assessment for identifying the risk of solid deposit needs to be performed on the studied cases to assess the full accuracy of solid deposit prediction of the studied method. Recommendations for future work includes fully implementing and evaluating the speedup method available for spray simulations in STAR-CCM+ as well as directly comparing how the accuracy and performance of the method relates to that of the method used in AVL Fire for spray simulations. / Dieselmotorer producerar under körning stora mängder kväveoxider (NOx). Kväve-oxider är starkt giftiga föreningar som även bidrar till att öka mängden marknära ozon. Allt strängare lagstiftning gällande mängden kväveoxider som får släppas ut från fordon med dieselmotorer har lett till att tillverkare av dieselmotorer blivit tvingade att utveckla efterbehandlingssystem som renar avgasen från motorn. En av huvudkomponenterna i ett sådant system idag är selective catalytic reduction (SCR; på svenska selektiv katalytisk reduktion), där kväveoxider omvandlas till kvävgas och vatten med hjälp av ammoniak. För att producera ammoniak används en lösning av urea och vatten (t.ex. AdBlue®), som introduceras till efterbehandlingssystemet via spray. Denna process har dock en stor nackdel, då det under omvandlingsprocessen kan finnas risk för klumpbildning av ämnen som biuret, ammelid och ammelin ifall flödesförhållandena är ogynnsamma. Riskfaktorer för klumpbildning inkluderar höga temperaturer samt låg dynamik och hög tjocklek för den vätskefilm som bildas när sprayen med urea-lösning kommer i kontakt med ytor i efterbehandlingssystemet. Det är därför av stor vikt för tillverkare av efterbehandlingssystem som använder SCR att känna till hur mycket urealösning som kan sprayas in för varje givet flöde. Experimentella tester används till stor del för att utvärdera detta, men är väldigt dyra och kan endast göras för ett fåtal prototyper under en produkts utveckling. För att kunna utvärdera ett större antal koncept och geometrier tidigare i utvecklingsstadiet av en ny produkt används därför ofta datorkraft med simuleringsverktyg som CFD (Computational Fluid Dynamics). En av de mest beräkningstunga processerna att simulera i ett efterbehandlingssystem med SCR är sprayandet av urea-lösning och dess interaktion med ytor, där korrekta förutbestämmelser av huruvida det finns risk för klumpbildning eller inte är av stor betydelse. De flesta CFD modeller som används i detta syfte har förhållandevis god noggrannhet och används i stor utsträckning i den bransch där efterbehandling med SCR tillämpas. Däremot är dessa modeller begränsade i att de endast kan åstadkomma simuleringar (med en acceptabel mängd datorkraft) som sträcker sig i tidsintervallet sekunder till minuter. Bildningen av klump är dock en process som kan ta upp till flera timmar. Scania är en av Sveriges största tillämpare av SCR, då tekniken används i de efterbehandlingssystem som finns inbyggda i tillverkarens ljuddämpare. Scania använder främst AVL Fire för simulering av spray med urea. AVL Fire anses dock vara för tidskrävande vid skapelsen av nya simuleringsfall och för instabilt under simulering. Detta projekt har därför undersökt möjligheten att använda STAR-CCM+ för simulering av spray med urea hos Scania. Den metod i STAR-CCM+ som utvärderats är enkel att använda då nya simuleringsfall ska skapas, samtidigt som den är robust och stabil under simulering. Relevanta parametrar för en potentiell uppsnabbningsmetod har också undersökts. STAR-CCM+ i sin helhet är användarvänligt, där verktyget för att skapa och generera mesh är enkelt att använda såväl som kraftfullt när mer avancerade operationer krävs. Möjligheterna för postprocessing är väldigt smidiga för transienta förlopp, vilket är ett stort plus för simuleringar med urea-spray, vars injektion och resulterande processer är väldigt transienta skeenden i sig. Flera olika parametrar har undersökts, för att granska hur stor påverkan de har på prestandan och noggrannheten hos den studerade metoden. Två av dessa är tätheten av beräkningsnoder i den region där spray-munstycket är placerat samt antalet paket med urea-vatten lösning som injiceras varje tidssteg via spray-munstycket. En möjlig uppsnabbning av metoden, som går ut på att frysa ekvationerna för bevarelse av rörelsemängd (eng - momentum equations) när det är tillåtet och samtidigt minska antalet inre iterationer för varje tidssteg, har också undersökts. Ett flertal olika flödesförhållanden har också undersökts för två olika geometrier. De erhållna resultaten tyder på korrelation med data från fysiska experiment. Dock bör ytterligare hydrodynamiska utvärderingar tillämpas för att ordentligt kunna redogöra för hur väl STAR-CCM+ kan användas för att förutse risken för klump- bildning i en spray-process med urea-vatten lösning. Framtida arbete borde fokusera på att utvärdera den uppsnabbningsmetod som finns för spray-simuleringar i STAR-CCM+, samt direkt jämföra hur väl metodens noggrannhet och prestanda står sig gentemot den metod som används i AVL Fire för spray-simuleringar.
135

Load Commutated SCR Current Source Inverter Fed Induction Motor Drive With Sinusoidal Motor Voltage And Current

Banerjee, Debmalya 01 July 2008 (has links)
This thesis deals with modeling, simulation and implementation of Load Commutated SCR based current source Inverter (LCI) fed squirrel cage induction motor drive with sinusoidal voltage and sinusoidal current. In the proposed system, the induction motor is fed by an LCI. A three level diode clamped voltage source inverter (VSI) is connected at the motor terminal with ac chokes connected in series with it. The VSI currents are controlled in such a manner that it injects the reactive current demanded by the induction motor and the LCI for successful commutation of the SCRs in the LCI. Additionally, it absorbs the harmonic frequency currents to ensure that the induction motor draws sinusoidal current. As a result, the nature of the motor terminal voltage is also sinusoidal. The concept of load commutation of the SCRs in the LCI feeding an induction motor load is explained with necessary waveforms and phasor diagrams. The necessity of reactive compensation by the active filter connected at the motor terminal for the load commutation of the thyristors, is elaborated with the help of analytical equations and phasor diagrams. The requirement of harmonic compensation by the same active filter to achieve sinusoidal motor current and motor voltage, is also described. Finally, to achieve the aforementioned induction motor drive, the VA ratings of the active filter (VSI) and the CSI with respect to VA rating of the motor, are determined theoretically. The proposed drive scheme is simulated under idealized condition. Simulation results show good steady state and dynamic response of the drive system. Load commutation of the SCRs in the LCI and the sinusoidal profile of motor current and voltage, have been demonstrated. As in LCI fed synchronous motor drives, a special mode of operation is required to run up the induction motor from standstill. As the SCRs of the LCI are load commutated, they need motor terminal voltages for commutation. At standstill these voltages are zero. So, a starting strategy has been proposed and adopted to start the motor with the aid of the current controlled VSI to accelerate until the motor terminal voltages are high enough for the commutation of the SCRs in the LCI. The proposed drive is implemented on an experimental setup in the laboratory. The IGBT based three level diode clamped VSI has been fabricated following the design of the standard module in the laboratory. A generalized digital control platform is also developed using a TMS320F2407A DSP. Two, three phase thyristor bridges with necessary firing pulse circuits have been used as the phase controlled rectifier and the LCI respectively. Appropriate protection scheme for such a drive is developed and adopted to operate the drive. Relevant experimental results are presented. They are observed to be in good agreement with the simulation results. The effect of capacitors connected at the output of the LCI in the commutation process of the SCRs in the LCI is studied and analyzed. From the analysis, it is understood that the capacitors form a parallel resonating pair with filter inductor and the motor leakage inductance, which results in an undesired oscillation in the terminal voltage during each of the commutation intervals leading to commutation failure. So, in the final system, the capacitors are removed to eliminate any chance of commutation failure of the SCRs in the LCI. It is shown by experiment that the commutation of the SCRs takes place reliably in the absence of the capacitors also. The commutation process is studied and analyzed without the capacitors to understand the motor terminal voltage waveform of the experimental results.
136

Μελέτη καταλυτικών συστημάτων απομάκρυνσης οξειδίων του αζώτου και διοξειδίου του θείου με in situ φασματοσκοπία Raman

Γιακουμέλου, Ιωάννα 09 March 2009 (has links)
Στην παρούσα διατριβή μελετήθηκε η μοριακή δομή και καταλυτική ενεργότητα καταλυτών V2O5/TiO2 και CrOx/TiO2 για την αντίδραση καταλυτικής αναγωγής των NO με χρήση NH3 (αντίδραση SCR) καθώς και καταλυτών V2O5-Cs2SO4/SiO2 (καταλύτες υγρής υποστηριγμένης φάσης) για την αντίδραση οξείδωσης του διοξειδίου του θείου. Η μελέτη της μοριακής δομής έγινε με χρήση in-situ φασματοσκοπία Raman υπό διάφορες αέριες συνθήκες (O2, NH3/N2, NH3/NO/N2, NH3/NO/O2/N2, 8% H2O/O2/N2, SO2/N2, SO2/O2/N2) και θερμοκρασίες. Γενικά σε χαμηλές φορτίσεις, σχηματίζονται αρχικά απομονωμένα τετραεδρικά βαναδικά (ή χρωμικά) είδη και αυξανόμενης της φόρτισης οδηγούμαστε στο σχηματισμό διμερών/ ολιμερών αλυσίδων. Η in-situ φασματοσκοπία ESR έδωσε συμπληρωματικές πληροφορίες για την μοριακή δομή των V4+, Cr5+ & Cr3+ ειδών, σε οξειδωτικές και αναγωγικές συνθήκες. Τέλος, η μελέτη της συμπεριφοράς της συχνότητας αναστροφής (TOF) στους καταλύτες βαναδίου έδειξε ότι η αντίδραση επιταχύνεται κατά την παρουσία γειτονικών κέντρων βαναδίου. Οι καταλύτες βαναδίου / καισίου είναι οι μοναδικοί στο είδος τους καταλύτες υποστηριγμένης υγρής φάσης, όπου σε συνθήκες αντίδρασης, η ενεργός φάση βρίσκεται υγρή ή διαλυμένη σε ένα μη πτητικό διάλυμα που “φιλοξενείται” στους πόρους του υποστρώματος. Η in-situ μελέτη Raman έδειξε ότι το ενεργό είδος για την καταλυτική οξείδωση του SO2 είναι τα βαναδικά οξοθειϊκά σύμπλοκα (VO)2O(SO4)44-. / In this ph.d. thesis, the molecular structure and catalytic reactivity of V2O5/TiO2 and CrOx/TiO2 catalysts was studied for the SCR reaction. Furthermore, the molecular structure of the unique SLP catalysts V2O5-Cs2SO4/SiO2 was studied for the reaction of the oxidation of SO2. This study was performed by the use of in-situ Raman spectroscopy in various “real” gas conditions (O2, NH3/N2, NH3/NO/N2, NH3/NO/O2/N2, 8% H2O/O2/N2, SO2/N2, SO2/O2/N2) and temperatures. In general, at low loadings isolated species are formed, and as the loading is increased, the formation of dimeric / oligomeric species is favoured. In situ ESR spectroscopy gave supplementary information about the structure of V4+, Cr5+ & Cr3+ species in oxidative / reductive environment. The behaviour of TOF numbers showed that the reaction is accelerated in the presence of neighbour vanadium centers (in case of vanadium catalysts). Finally, the vanadium / caesium catalysts are the unique in their kind molten salt catalysts, were in reaction conditions, the active phase is in liquid form or dissolved in a non-volatile solution which is “hosted” inside the pores of the support. Activation of these catalysts, following exposure to a SO2/O2/N2 mixture, results in uptake of SO3 and formation of a pyrosulfate molten salt which – as shown by in-situ Raman spectroscopy – vanadium occurs predominantly in the form if binuclear (VO)2O(SO4)44- which are considered to be the active species for the reaction.
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台灣壽險公司資本適足率分析-以Solvency II QIS5原則計算 / A study on the solvency capital requirements of the life insurance companies in Taiwan-estimated in Solcency II QIS5 principles

林正國, Lin, Cheng Kuo Unknown Date (has links)
歐盟保險業新監理架構Solvency II 於第5 次量化衝擊研究完成後計畫將在近年正式施行,我國保險業監理制度是否朝採用Solvency II 架構的方向前進仍未為定論,但必頇先行瞭解採行此制度可能對業界造成的影響。 本研究以2010 年8 月時CEIOPS 對Solvency II 所進行的第5 次量化衝擊研究QIS5 設立的標準與原則,對公司的資產與負債做假設後,以公帄價值法衡量壽險公司各部位資產位與負債,包括準備金的公帄價值衡量,並利用QIS5 所提供之計算工具標準法計算四家台灣壽險公司在2009 年底時的清償資本要求SCR。而QIS5 是在金融風暴後不久,當時環境使得利率極低,為了估算在利率環境較正常的情況下,本研究以2007 年底之利率做敏感度分析,重新計算各公司之資產與負債狀況與清償資本要求SCR。 研究結果發現在本研究假設下,負債面的準備金提存不足,保險公司以經濟 資本角度來衡量已經屬於破產狀態。投資型分離帳戶以外的準備金計算與目前準備金計提的方式除了頇以公帄價值衡量保險責任的最佳估計外,另外需要計提風險邊際,此數額約為最佳估計總額的12.4%至30.2%,保險公司自有資本不足有很大的因素是由於此部分準備金的計提。 也發現所計算出的SCR 中所最大的比率為利率風險或匯率風險,在假設以較 高利率環境做敏感度分析後發現壽險公司淨值仍然為負數,且所需要的SCR 與之前所得結果相差不大,顯示壽險公司負債部位對利率敏感度相當高,即使曝險部位變少,對於未來的利率變動仍需要準備相當大的資本以防範虧損。 / After the completion of the Fifth Quantitative Impact Study (QIS5) for the new insurance industrial regulation framework- Solvency II, European Union planned to implement the project in few years. No matter that the regulatory system of insurance industry in Taiwan will follow the trend or will not, it is a must that we should estimate the impacts on the whole industry before making the decisions. This study have an aim to estimate the Solvency Capital Requirements of 4 life insurance companies in Taiwan in the same principles with QIS5, which were took place in August 2010 by CEIOPS. In order to calculate the SCR, we made a lot of hypotheses and then estimated the fair value of the company assets and liabilities, including the fair value of technical provision. By means of the calculating helpers provided by CEIOPS used in QIS5, we found out the SCRs of these companies when they were on 31 December 2009. Then we performed the sensitivity analysis by the different interest rate which is based on the data on 31 December 2007, and recalculated the SCRs of the companies. This study had conclusions that the technical provisions were not sufficient to fulfill the obligations in aspect of the economic value. The surplus of companies were exhausted, because the technical provisions increased by fair valuation. Also, the heavy loadings of risk margins as 12.4% to 30.2% of the best estimates were the important reason of the negative own fund. We found that the capital requirements of interest risk and currency risk took great percentages of total SCRs. And the SCRs will not reduce in great amount caused by technical provisions reduced in the situation that interest rate come back to the level in 2007. It showed that the SCRs had great sensitivity to the interest risk and insurance companies should prepare sufficient own fund to prevent financial crisis caused by interest rate shock.
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Proposition d'une approche intégrée basée sur les réseaux de Petri de haut niveau pour simuler et évaluer les systèmes contrôlés en réseau

Brahimi, Belynda 05 December 2007 (has links) (PDF)
L'étude des systèmes en réseau supports d'applications collaboratives, distribuées et interconnectées par un réseau repose sur l'identification des exigences de fonctionnement de l'application appelées Qualité de Contrôle (QdC), et sur l'évaluation des performances du réseau pour obtenir son niveau de Qualité de Service (QdS). « Cette thématique comporte d'importants verrous de nature fondamentale relevant du domaine de l'automatique, de la robotique, des capteurs, de la théorie de l'information, des réseaux. Par souci de simplification, les travaux sur les systèmes en réseau se repartissent selon deux approches: la première compense les perturbations générées par les communications au niveau de l'application (« control over network »). La seconde adapte les performances du réseau en fonction des besoins applicatifs (« control of network »). L'objectif de nos travaux de thèse est donc de proposer un environnement de modélisation intégré permettant de représenter le comportement des SCRs. Nous avons choisi les Réseaux de Petri de haut niveau qui possède un fort pouvoir d'expression, de formalisation et dont la modularité permet d'ajouter et/ou de faire évoluer les modèles qui sont développés dans ce travail. Dans un premier temps, nous avons proposé un modèle Ethernet Commuté gérant des mécanismes d'ordonnancement. Le choix de ce réseau a été guidé par le fait qu'il est de plus en plus utilisé dans les SCRs. Ensuite, le modèle d'un SCR a été proposé, et modélisé par des Réseaux de Petri de haut de niveau, en intégrant au modèle Ethernet Commuté, l'environnement applicatif : Contrôleur, Process,.. Enfin, des stratégies pour commander le réseau de façon à adapter sa Qualité de Service en regard de la Qualité de Contrôle requise par l'application, ont été mises en oeuvre. Pour cela, des ordonnanceurs à priorité stricte et de type WRR sont utilisés. Les résultats de simulation montrent clairement que des dispositifs de compensation du réseau pour améliorer les performances du système de communication, permettent aussi d'améliorer les performances du système à commander.
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Industry and traffic related particles and their role in human health

Oravisjärvi, K. (Kati) 08 October 2013 (has links)
Abstract Combustion generated ultrafine particles have been found to be responsible for adverse effects on human health. New emission reduction technologies and fuels will change the composition of particle emissions. It is important to confirm that the new reduction technologies are designed to minimise the adverse health effects. In this doctoral thesis the potential health effects caused by traffic and industrially generated particles were studied using epidemiological, experimental and in silico studies. The effects of short-term changes in PM2.5 on the respiratory health of symptomatic children living near a steel works were studied to investigate whether specific sources of PM2.5 have the possible health effects. The PM2.5 emission sources were identified: long-range transport, a steel works, soil and street dust and a mechanical engineering works. Significant associations were not found between respiratory symptoms and PM2.5 or the sources markers. The deposition of traffic-related particles into the human respiratory system was computed using the lung deposition model. Particle size distribution was measured from diesel- and compressed natural gas (CNG)-fuelled busses and an off-road diesel engine under different combustion situations. The majority of the measured traffic-related particle numbers reach the alveolar region of the lungs. There were differences in the deposition of particles when different catalysts, engines or fuels were used. CNG or a diesel particulate filter (DPF) significantly reduced lung exposure to particles. Also physical activity, age and gender affected the deposition of particles. The diesel particles comprised compounds (carcinogenic PAHs, transition metals), which may have the ability to generate reactive oxygen. This study provides new knowledge how of the emission abatement technologies and fuels affects particle number and their composition, as well health hazards. Cleaner technology (CNG, DPF), emits significantly fewer particles in numbers, especially large particles, but they emit high amounts of small-size particles, which penetrate most easily to the deepest parts of the lungs. In addition, particles from engines with DPF include the largest variety of transition metals and other hazardous compounds compared to combustion systems having different emission after-treatment units. / Tiivistelmä Palamisprosesseista peräisin olevien ultrapienten hiukkasten on todettu olevan haitallisia ihmisen terveydelle. Uudet pako- ja savukaasujen puhdistusteknologiat ja polttoaineet vaikuttavat hiukkaspäästöihin ja niiden koostumukseen. Uusien menetelmien käytön tulee vähentää hiukkasten mahdollisia terveyshaittoja. Tässä väitöskirjassa tutkittiin liikenteestä ja teollisuudesta peräisin olevien hiukkasten mahdollisia terveyshaittoja käyttäen epidemiologista, kokeellista ja in silico- menetelmiä. Työssä tutkittiin PM2.5-hiukkasten lyhytaikaisvaihtelun yhteyttä terästehtaan läheisyydessä asuvien hengitystieoireisten lasten terveyteen ja päästölähteiden yhteyttä mahdollisiin terveysvaikutuksiin. Merkittäviä PM2.5-päästölähteitä olivat kaukokulkeuma, terästehdas, maaperä ja tiepöly sekä konepaja. Tutkimuksessa ei havaittu lasten hengitystieoireiden ja PM2.5:n tai päästölähteiden merkkiaineiden välillä merkittävää yhteyttä. Liikenneperäisten hiukkasten kulkeutumista ihmisen hengitysteihin tutkittiin keuhkodepositiomallilla. Diesel- ja maakaasukäyttöisten (CNG) bussien ja dieselkäyttöisen työkoneen hiukkaskokojakaumat mitattiin eri palamisolosuhteissa. Suurin osa mitatuista hiukkaslukumääristä kulkeutui keuhkojen alveolaaritasolle. Erilaisten katalysaattorien, moottoreiden tai polttoaineiden käytön seurauksena hiukkasten lukumääräpitoisuudet vaihtelivat ja siten hiukkasten kulkeutumisessa hengitysteihin oli eroja. CNG:n tai hiukkassuodattimen (DPF) käyttö vähensi merkittävästi hiukkaslukumääriä ja keuhkojen altistumista hiukkasille. Myös liikunta, ikä ja sukupuoli vaikuttivat hengitysteihin kulkeutuvien hiukkasten määriin. Dieselhiukkaset sisälsivät yhdisteitä (karsinogeeniset PAH:t, siirtymämetallit), jotka tuottavat hengitysteissä reaktiivisia happiradikaaleja. Tämä tutkimus antaa uutta tietoa päästövähennysmenetelmien ja polttoaineiden vaikutuksista hiukkasten lukumäärään ja koostumukseen sekä hiukkasten terveyshaitoihin. Puhtaamman teknologian käyttö (CNG, DPF) vähentää huomattavasti pakokaasun hiukkasten lukumäärää, etenkin suurten hiukkasten, mutta tuottaa silti suuria määriä pieniä hiukkasia, jotka kulkeutuvat helpommin keuhkojen syvimpiin osiin. Lisäksi moottoreiden hiukkaspäästöt käytettäessä hiukkassuodatinta, sisälsivät enemmän erilaisia siirtymämetalleja ja muita haitallisia aineita verrattuna polttoon, jossa käytettiin muita päästöjen jälkikäsittelymenetelmiä.
140

Možnosti eliminace čpavkového skluzu v technologických vodách elektráren / Possibilities of elimination of residual ammonia content from technological water in power plants

Hajzler, Jan January 2016 (has links)
This master thesis aims to study the possibilities of eliminating, or separation of ammonium shares from technological water of plants, where is introduced a secondary method of flue gas denitrification (SCR, SNCR). The need for elimination of ammonium shares arose after introduction of emission cap, which have been tightened since January 2015. The denitrification technologies were installed on devices that did not comply with the new limits. The theoretical part of the thesis deals with the description of combustion processes, as a fluid, and high temperature combustion of solid fuels, mechanisms of emissions and their reduction options. At the conclusion of the theoretical part is discussed the contents of the ammoniacal nitrogen in waters used in electricity and heating facilities to transport, or from which are separated by solid products of some processes such as desulphurization. There are also discussed some options for removal of ammonium salts from technological waters. Experimental part deals with finding appropriate method of determination of ammoniacal nitrogen, and the possibilities of its elimination by conversion to insoluble compound. Last but not least, the work deals with the evaluation of the sustainability of the proposed solutions. And as well as the real possibilities of their application in practice.

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