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Flow Accelerated Corrosion Experience at Comanche Peak Steam Electric StationNakka, Ravi Kumar 05 1900 (has links)
Flow accelerated corrosion (FAC) is a major concern in the power industry as it causes thinning of the pipes by the dissolution of the passive oxide layer formed on the pipe surface. Present research deals with comparing the protection offered by the magnetite (Fe3O4) versus maghemite (γ-Fe2O3) phases thickness loss measurements. Fourier transform infrared spectroscopy (FTIR) is used in distinguishing these two elusive phases of iron oxides. Representative pipes are collected from high pressure steam extraction line of the secondary cycle of unit 2 of Comanche Peak Steam Electric Station (CPSES). Environmental scanning electron microscopy (ESEM) is used for morphological analysis. FTIR and X-ray diffraction (XRD) are used for phase analysis. Morphological analysis showed the presence of porous oxide surfaces with octahedral crystals, scallops and "chimney" like vents. FTIR revealed the predominance of maghemite at the most of the pipe sections. Results of thickness measurements indicate severe thickness loss at the bend areas (extrados) of the pipes.
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Caractérisation et modélisation de l'évolution de la microstructure et du gonflement d'aciers austénitiques représentatifs des internes inférieurs de Réacteur à Eau Pressurisée sous irradiations aux ions / Microstructural characterizations of austenitic stainless steels representative of PWR internals irradiated with ions and comparison to cluster dynamic simulationsMichaut, Bertrand 16 March 2017 (has links)
Le contexte industriel actuel, animé d'un désir de prolonger la durée de fonctionnement des Réacteurs à Eau Pressurisée (REP) jusqu'à des durées de 60 ans, nécessite la compréhension de l'évolution de la microstructure et notamment d'un éventuel gonflement en conditions REP. Deux nuances de 304 (haut et bas carbone), représentatives des internes inférieurs de REP, ont été irradiées aux ions depuis les faibles doses jusqu'à des doses supérieures à la centaine de dpa, à 450°C (proche des conditions REP par la prise en compte d’un décalage flux/température), ainsi qu'à une dose intermédiaire à plus haute température 550°C. Sur la base des résultats expérimentaux des modélisations par dynamique d’amas avec le code CRESCENDO ont été réalisées afin d’étudier l’évolution de la microstructure.Les microstructures de boucles de Frank, du réseau de dislocations, des cavités et de la précipitation ont été caractérisées par Microscopie Électronique en Transmission (MET) à chacune des doses et par Sonde Atomique Tomographique (SAT) à 100 dpa. À 450°C, les conditions d’irradiations conduisent à une saturation du réseau de dislocations et des boucles de Frank, les cavités sont en faible densité induisant une fraction volumique faible (<0,1%) même dans la nuance bas carbone plus sensible au gonflement. La précipitation observée est principalement composée de carbures. En plus de l’évolution avec la dose, cette étude a permis d’analyser les effets de températures, de composition chimique et d’irradiation aux ions.Un jeu de paramètres d’entrée permettant de modéliser l’évolution de la microstructure avec la dose et le long du profil de dommage a été établi. Par modélisation il a été étudié les effets des interstitiels injectés, de la surface d’irradiation ou de la modification de l’efficacité des cascades avec la profondeur d’irradiation. / The French nuclear industry is looking into the extension of the operation time of pressurized water reactors (PWR) up to 60 years. This implies a good comprehension of the microstructural evolution under irradiation in Pressurized Water Reactors’ conditions.Two representatives stainless steels from PWR’s internals, 304 type steels, which differ in carbon content, has been irradiated form low to high doses (more than 100 dpa) at 450°C, irradiation at a second temperature (550°C) has also been performed at an intermediate dose. The choice of the temperature (450°C) was motivated by considering a temperature shift between neutron and ion irradiations due to their large difference in term of dose rate.The microstructural evolution has been characterized by transmitted electron microscopy on each conditions and by atom probe on highest irradiated samples. And modelling of the microstructure was performed using cluster dynamics code CRESCENDO.For both steels, at 450°C the dislocation network and Frank loops reach a saturation regime. As the cavity size and density are low the volume fraction is also low, even in the low carbon content steels, which is more favorable to swelling. The precipitation is mainly carbides. The effects of temperature, chemical composition and of ion irradiation were also investigated.Based on experimental results, a set of parameters which reproduces the evolution of the microstructure in respect to the dose and the depth of observation has been established. It has allowed to understand the effects of the irradiated surface, the injected interstitials and a possible evolution of the cascade efficiency along the damage profile.
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Corrosion fatigue in nickel base alloys for nuclear steam generator applicationsBallinger, Ronald George, 1945- January 1982 (has links)
Thesis (Sc.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Ronald George Ballinger. / Sc.D.
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Desarrollo e implementación de algoritmos para la optimización energética en tiempo real de redes hidráulicas a presiónAlonso Campos, Joan Carles 20 January 2022 (has links)
[ES] El objetivo general de la presente Tesis es investigar metodologías que permitan obtener en tiempo real los parámetros de operación de redes hidráulicas a presión que minimicen el consumo y/o el coste energético, garantizando el cumplimiento de las condiciones de funcionamiento necesarias para una adecuada calidad del servicio.
Al tratarse del ámbito de la operación diaria de la red, una de las condiciones indispensables que deben reunir los métodos de optimización es una respuesta lo suficientemente rápida como para que no solo se pueda disponer de las soluciones más convenientes en el momento de ejecutar las consignas de operación, sino que además se habilite un procedimiento flexible que permita dar respuesta a posibles cambios en las predicciones o eventos que puedan producirse.
Se ha abordado de manera aislada la optimización energética de los subsistemas de transporte de agua y la de los subsistemas de distribución debido a las distintas características que se pueden observar en ellos.
En la parte relativa a los subsistemas de distribución, particularizada al caso de un sistema de riego con bombeo directo a red, se han explorado los métodos metaheurísticos de optimización, realizando varias aportaciones originales orientadas a la mejora en la eficiencia computacional de los mismos, debido a la necesidad de obtener una respuesta rápida compatible con la toma de decisiones en tiempo real.
En cuanto a los subsistemas de transporte, se ha explorado la aplicabilidad del método determinista de optimización por programación lineal, a la vista de las importantes ventajas que presenta respecto al resto de métodos generales de optimización.
Asimismo, en el contexto de los subsistemas de transporte, se ha trabajado en la definición de una heurística basada en el cálculo del coste energético y/o económico del agua entregada en los puntos de consumo y almacenada en los depósitos intermedios, que ha permitido formular un algoritmo voraz para la optimización energética en cada instante de tiempo. Este método ha conseguido igualar el desempeño alcanzado mediante la programación lineal y se espera que ofrezca unas mejores capacidades en sistemas con un comportamiento marcadamente no lineal, así como también una mejor adaptación a problemas de optimización con la participación de energías renovables. / [CA] L'objectiu general de la present Tesi és la investigació de metodologies que permeten obtindre en temps real els paràmetres d'operació de xarxes hidràuliques a pressió que minimitzen el consum i/o el cost energètic, garantint el compliment de les condicions de funcionament necessàries per a una adequada qualitat del servei.
En tractar-se de l'àmbit de l'operació diària de la xarxa, una de les condicions indispensables que han de reunir els mètodes d'optimització és una resposta prou ràpida com perquè no sols es puga disposar de les solucions més convenients en el moment d'executar les consignes d'operació, sinó que a més s'habilite un procediment flexible que permeta donar resposta a possibles canvis en les prediccions o esdeveniments que puguen produir-se.
S'ha abordat de manera aïllada l'optimització energètica dels subsistemes de transport d'aigua i la dels subsistemes de distribució (reg per injecció directa) a causa de les diferents característiques que es poden observar en ells.
En el treball amb els subsistemes de distribució s'han explorat les possibilitats que ofereixen els mètodes meta-heurístics d'optimització, realitzant diverses aportacions originals orientades a la millora en l'eficiència computacional dels mateixos a causa de la necessitat d'obtindre una resposta més ràpida que siga compatible amb la presa de decisions en temps real.
Quant als subsistemes de transport, s'ha explorat l'aplicabilitat del mètode determinista d'optimització per programació lineal a la vista dels importants avantatges que presenta respecte a la resta de mètodes generals d'optimització.
Així mateix, en el context dels subsistemes de transport, s'ha treballat en la definició d'una bona heurística basada en el càlcul del cost energètic i/o econòmic de l'aigua entregada en els punts de consum i en els dipòsits intermedis, que ha permés formular un mètode voraç per a l'optimització energètica en cada instant de temps. Aquest mètode ha aconseguit igualar l'acompliment aconseguit mitjançant la programació lineal i s'espera que oferisca unes millors capacitats en sistemes amb un comportament més marcadament no lineal, així com també una millor adaptació a problemes d'optimització amb participació d'energies renovables. / [EN] The general objective of this Thesis is the research of methodologies to obtain in real time the operating parameters of pressurized hydraulic networks that minimize energy consumption and/or cost, ensuring compliance with the operating conditions necessary for an appropriate quality of service.
Since this is the field of daily network operation, one of the indispensable conditions that optimization methods must meet is a response fast enough so that not only the most convenient solutions are available at the time of executing the operating instructions, but also a flexible procedure is provided to allow a response to possible changes in the predictions or events that may occur.
The energy optimization of the water transport subsystems and that of the distribution subsystems (direct injection irrigation) have been approached separately due to the different characteristics that can be observed in them.
In the work with distribution subsystems, the possibilities offered by metaheuristic optimization methods have been explored, making several original contributions aimed at improving their computational efficiency due to the need to obtain a faster response that is compatible with real-time decision making.
Regarding transport subsystems, the applicability of the deterministic method of optimization by linear programming has been explored in view of the important advantages it presents with respect to the rest of the general optimization methods.
Also, in the context of transport subsystems, there has been a work on the definition of a good heuristic based on the calculation of the energy and/or economic cost of the water delivered at the consumption points and intermediate reservoirs, which has allowed to formulate a greedy method for energy optimization at each time instant. This method has been able to match the performance achieved by linear programming and is expected to offer better capabilities in systems with a more marked non-linear behaviour, as well as a better adaptation to optimization problems involving renewable energies. / Alonso Campos, JC. (2021). Desarrollo e implementación de algoritmos para la optimización energética en tiempo real de redes hidráulicas a presión [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/180389 / TESIS
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Hardware-in-the-loop simulation of pressurized water reactor steam-generator water-level control, designed for use within physically distributed testing environmentsBrink, Michael Joseph 21 May 2013 (has links)
No description available.
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Predicting Maize Yield, Nutrient Concentration and Uptake in P and K Fertilized Soils: Pressurized Hot Water and Other Alternatives to Mehlich I Extraction in Guatemala SoilsHunsaker, Heather Mae 26 July 2006 (has links) (PDF)
The inaccessibility and cost of soil testing reduce effectiveness of fertilizer use on small-scale subsistence farms, and inadequate funding promotes adoption of soil tests in developing countries with minimal validation. For example, Mehlich-I extraction of phosphorus (P) currently used extensively in Guatemala may not be suitable for its broad range of soils. At least four alternatives are available but are relatively untested [Bray 1, Mehlich III, Olsen and pressurized hot water (PHW)]. Pressurized hot water is relatively simple and inexpensive, but is not yet tested against other extraction methods under variable P or potassium (K) fertilization levels. To determine whether PHW-extracted nutrients could be used to predict maize yield, as nutrient content and uptake, soil, plant tissue and grain samples were obtained from a multiple-site field study and calibration studies were conducted using five rates of P and three rates of K on soils incubated without plants or cropped with maize in greenhouse and field conditions. In the multiple-site field study, maize yield related significantly to PHW-extractable P (r2=0.36) and to leaf P concentration (r2=0.23), but Mehlich I did not. In the two soils used in the greenhouse study, maize yield, vegetative P concentration and total P uptake by maize were predicted by PHW extractable P (R2=0.72, 0.75 and 0.90, respectively). In the field experiment, grain yield was not improved by P or K application, but P content of maize leaf tissue did relate significantly with PHW-extracted P (R2=0.40), but Mehlich I did not. There were no yield responses to K application in any experiment, but relationships defined between extractable K for all five K-extraction procedures and soil applied K were similarly significant. In comparing P extraction methods, PHW was as good as or better than Olsen, Bray 1 and Mehlich III for relating soil P extraction to the parameters measured in these experiments, and these four alternative extraction methods were consistently better than Mehlich I. Mehlich I extraction should be replaced by one of the four alternatives tested, and PHW is the least expensive and, thus, most viable for use in Guatemala soils.
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Pressurized intraperitoneal aerosol chemotherapy (PIPAC) in patients with peritoneal surface malignancies (PSM): a prospective single-center registry studyEberth, Jonas Alexander 27 June 2024 (has links)
Malignome des Peritoneums (peritoneal surface malignancies, PSMs) treten als Mesotheliome oder Metastasen auf. Ihre Diagnose bedeutet häufig eine schlechtere Prognose als bei anderen Fernmetastasen. Die Standardtherapie in palliativer Intention ist in der Regel eine systemische Chemotherapie (sCHT).
Intraperitoneale Druck-Aerosol-Chemotherapie (Pressurized intraperitoneal aerosol chemotherapy, PIPAC) ist eine neue, palliative Behandlungsmöglichkeit für ausgewählte Personen mit PSMs. Das Prinzip der laparoskopischen Vernebelung von Chemotherapeutika soll die Bioverfügbarkeit im Vergleich zu und anderen intraabdominellen Applikationen erhöhen. Sie wird meist in Kombination mit sCHT eingesetzt und zielt darauf ab, die Symptom- und Asziteslast der Behandelten zu reduzieren.
Diese monozentrische, prospektive Registerstudie untersucht die Sicherheit, Durchführbarkeit und Wirksamkeit der PIPAC. Einschlusskriterien waren ein histologisch gesichertes PSM und eine positive Tumorboard-Entscheidung. Ausschlusskriterien waren extraperitoneale Fernmetastasen und ein Eastern Cooperative Oncology Group (ECOG) Performance Status größer als 2.
Vor jeder PIPAC wurde eine strukturierte Anamnese, eine körperliche Untersuchung, sowie eine ausführliche chirurgische und onkologische Aufklärung durchgeführt.
Die PIPAC-Prozeduren wurden laparoskopisch in Allgemeinanästhesie gemäß interner Standard Operating Procedure durchgeführt. Zunächst wurde Aszites aspiriert und quantifiziert. Anschließend wurde eine diagnostische Laparoskopie durchgeführt, der Zugang zum Abdomen als „access“ oder „non access“ beschrieben, sowie der peritoneale Adhäsionsindex (peritoneal adhesion index, PAI) nach Coccolini und der peritoneale Krebsindex (peritoneal cancer index, PCI) nach Sugarbaker erhoben. Sechs Peritonealbiopsien wurden standardisiert entnommen. Nach Präparation und Färbung mit Hämatoxylin und Eosin wurde die relative Tumormenge bestimmt.
Nacheinander wurden Cisplatin und Doxorubicin in einer an die Körperoberfläche angepassten Dosierung appliziert. Die Chemotherapeutika wurden mit einer Injektionspumpe bei 200 psi und mit einer Flussrate von 0,5 ml/min über einen Hochdruckschlauch zum Vernebler gefördert. Dieser wurde auf dem 12 mm Trokar befestigt und verteilte die Medikamente im Abdomen. Währenddessen befand sich das gesamte Operationspersonal im separaten Einleitungsraum. Die Applikation wurde über einen Fußschalter gesteuert und durch ein Sichtfenster überwacht. Über den Druck im Kapnoperitoneum konnte freiwerdendes Aerosol detektiert werden. Nach 30 min wurde das Aerosol analog zu Narkosegasen in die Krankenhausentlüftung abgeleitet. Anschließend wurden die Behandelten für einige Stunden im Aufwachraum überwacht und dann auf die Normalstation gebracht. Postoperative Komplikationen wurden nach der Clavien Dindo Klassifikation (CDC) dokumentiert.
Insgesamt wurden 108 Patient:innen (n = 55 Frauen, n = 53 Männer) mit einem medianen Alter von 60 Jahren (Interquartilsabstand [IQA] 53–69 Jahre) eingeschlossen. Sie wiesen Primärtumore verschiedener Entitätsgruppen auf: n = 41 (38 %) gastral, n = 26 (24 %) kolorektal, n = 9 (8 %) gynäkologisch und n = 15 (14 %) weitere (n = 7 Mesotheliome, n = 3 Pseudomyxoma peritonei, n = 5 Krebserkrankungen mit unbekanntem Primärtumor). Im Median wurden zwei PIPAC-Prozeduren pro Patient:in durchgeführt (IQA 1–3). Bei 12 Patient:innen wurde zuvor eine zytoreduktive Chirurgie (CRS) mit hyperthermer intraperitonealer Chemoperfusion (HIPEC) durchgeführt.
Von 230 geplanten PIPAC-Prozeduren konnten 189 durchgeführt werden. 41 Prozeduren mussten abgebrochen oder storniert werden: 9 Patient:innen zeigten bei der Aufnahmeuntersuchung einen verschlechterten Allgemeinzustand (z. B. neue Fernmetastasen im Computertomogramm). 3 Patient:innen aspirierten während der Narkoseeinleitung. Bei 7 Laparoskopien war makroskopisch kein PSM mehr nachweisbar. In 22 Fällen war das Abdomen nicht zugänglich (non-access) und/oder es kam zu Darmläsionen.
Bei der Aufnahmeuntersuchung vor jeder PIPAC-Prozedur wiesen die Patient:innen in den meisten Fällen keine der spezifisch erhobenen Symptome auf. 55 (24 %) klagten über Bauchschmerzen, 47 (21 %) über Übelkeit oder Erbrechen, 16 (7 %) über Obstipation und 4 (2 %) über Dysphagie (mehrere Symptome gleichzeitig möglich). Die folgenden prä- und perioperativ erhobenen Werte änderten sich nicht signifikant mit aufeinanderfolgenden PIPAC-Prozeduren pro Patient:in (Varianzanalyse [analysis of variance, ANOVA], p > 0,1): ECOG Performance Status (Median 1, IQA 0–1), American Society of Anesthesiologists Klassifikation (Median 3, IQA 2–3), nutritional risk screening (NRS) (Median 2, IQA 2–3), global health status der European Organization for Research and Treatment of Cancer (EORTC) (Median 50, IQA 33–67), Operationsdauer (Mittelwert 104 min, Standardfehler des Mittelwertes 1,5 min), PCI (Median 15, IQA 6–24), PAI (Median 4, IQA 0–12) und maximaler histologischer Tumoranteil (Median 24 %, IQA 5–60 %). Die ersten drei konsekutiven PIPAC-Prozeduren zeigten eine signifikante Reduktion des Aszitesvolumens (ANOVA, p = 0,016). Die mediane postoperative Liegedauer betrug 4 Tage (IQA 3 4 Tage). Bei 31 von 213 PIPAC-Prozeduren (14,6 %), bei denen die Patient:innen in den Operationstrakt gebracht worden waren, traten postoperative Komplikationen auf (10,8 % Grad II, 2,4 % Grad IV, 1,4 % Grad V nach CDC).
Insgesamt wurden 21 non access-Fälle (9,9 % der 213 PIPAC-Prozeduren, bei denen die Patient:innen in den Operationstrakt gebracht worden waren) und 14 intraoperative Komplikationen (6,6 %) dokumentiert. In den 21 non access-Situationen traten 8 Darmläsionen auf (n = 4 Serosaläsionen, n = 4 transmurale Perforationen). Postoperativ kam es bei den non access Fällen zu 4 Komplikationen Grad II nach CDC und keinen höhergradigen Komplikationen. Bei 3 weiteren Prozeduren traten Darmläsionen ohne non access auf (n = 1 Serosa, n = 2 transmural). Ein:e Patient:in verstarb nach Darmläsion mit nachfolgender Nahtinsuffizienz, Peritonitis und Sepsis. Bei 3 Narkoseeinleitungen aspirierten die Patient:innen und entwickelten daraufhin eine Pneumonie. Auf der Intensivstation wurde sofort eine kalkulierte Antibiotikatherapie eingeleitet. Dennoch verstarben 2 von 3 Patient:innen nach 3 bzw. 4 Tagen. Ein:e Patient:in konnte erfolgreich behandelt und nach 15 Tagen entlassen werden.
Aufgrund der hohen Inzidenz von non access und Darmläsionen wurde nach prädiktiven Markern gesucht. Patient:innen mit einer CRS mit HIPEC in der Vorgeschichte hatten ein signifikant erhöhtes Risiko für non access (Odds Ratio [OR] 5,9, χ², p < 0,01) und Darmläsionen (OR 6,4, χ², p < 0,01). Patient:innen mit mehr als zwei Voroperationen im Bauchraum wiesen ebenso ein signifikant erhöhtes Risiko für non-access (OR 4,9, χ², p < 0,01) und Darmläsionen (OR 4,9, χ², p = 0,01) auf.
Am Ende des Studienzeitraums befanden sich noch 6 Patient:innen in Therapie. Bei den Übrigen (bei denen mindestens eine PIPAC-Prozedur durchgeführt wurde) gab es unterschiedliche Gründe für die Beendigung der Therapie: n = 26 (34 %) verstorben, n = 20 (26 %) Progression der Grunderkrankung, n = 12 (16 %) Regression der Grunderkrankung (n = 7 ohne weitere Therapie, n = 5 anschließend CRS mit HIPEC), n = 6 (8 %) non-access, n = 5 (6 %) Patient:innenwunsch, n = 8 (10 %) kein Grund dokumentiert. Das mediane Gesamtüberleben ab der ersten geplanten PIPAC-Prozedur betrug 264 Tage (IQA 108–586).
Insgesamt stellt die PIPAC eine neuartige off-label-Therapie für Patient:innen mit PSMs dar, deren Wirksamkeit und Sicherheit untersucht werden muss. Sie sollte daher nur im Rahmen klinischer Studien durchgeführt werden. Die vorliegende Studie liefert eine genaue Dokumentation von Symptomen, Komplikationen und unerwünschten Ereignissen im Zusammenhang mit PIPAC.
In Zusammenschau der vorhandenen Studien scheint die PIPAC gut geeignet zu sein, PSMs und Lebensqualität zu stabilisieren. Zum Nachweis eines kausalen Effekts sind jedoch randomisierte, kontrollierte Studien nötig.:Einführung 1
Epidemiologie 1
Magenkarzinom 1
Kolorektales Karzinom 1
Ovarialkarzinom 1
Pankreaskarzinom 2
Mesotheliom 2
Pseudomyxoma peritonei 2
Pathophysiologie 2
Ablösung vitaler Krebszellen 2
Intraperitonealer Transport 3
Adhäsion und Invasion 3
Wachstum und Metastasierung 3
Symptome/Klinik 3
Diagnostik 3
Bildgebende Verfahren 3
Peritonealer Krebsindex 5
Peritonealer Adhäsionsindex 5
Therapie 5
Systemische Therapie 6
Zytoreduktive Chirurgie 6
Hypertherme intraperitoneale Chemoperfusion 6
Intraperitoneale Druck-Aerosol-Chemotherapie 7
Weitere Therapieoptionen 8
Zielsetzung 8
Publikation 9
Zusammenfassung 21
Literaturverzeichnis 24
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Characterization and Measurement of Hybrid Gas Journal BearingsLawrence, Tom Marquis 28 August 2012 (has links)
Indiana University-Purdue University Indianapolis (IUPUI) / This thesis concentrates on the study of hybrid gas journal bearings (bearings with externally pressurized mass addition). It differs from most work in that it goes back to “basics” to explore the hydrodynamic phenomena in the bearing gap. The thesis compares geometrically identical bearings with 2 configurations of external pressurization, porous liners where mass-addition compensation is varied by varying the liner’s permeability, and bushings with 2 rows of 6 feedholes where the mass-addition compensation is varied by the feedhole diameter. Experimentally, prototype bearings with mass-addition compensation that spans 2 orders of magnitude with differing clearances are built and their aerostatic properties and mass addition characteristics are thoroughly tested. The fundamental equations for compressible, laminar, Poiseuille flow are used to suggest how the mass flow “compensation” should be mathematically modeled. This is back-checked against the experimental mass flow measurements and is used to determine a mass-addition compensation parameter (called Kmeas) for each prototype bushing. In so doing, the methodology of modeling and measuring the mass addition in a hybrid gas bearing is re-examined and an innovative, practical, and simple method is found that makes it possible to make an “apples-to-apples” comparison between different configurations of external pressurization. This mass addition model is used in conjunction with the Reynolds equation to perform theory-based numerical analysis of virtual hybrid gas journal bearings (CFD experiments). The first CFD experiments performed
use virtual bearings modeled to be identical to the experimental prototypes and replicate the experimental work. The results are compared and the CFD model is validated. The ontological significance of appropriate dimensionless similitude parameters is re-examined and a, previously lacking, complete set of similitude factors is found for hybrid bearings. A new practical method is developed to study in unprecedented detail the aerostatic component of the hybrid bearings. It is used to definitively compare the feedhole bearings to the porous liner bearings. The hydrostatic bearing efficiency (HBE) is defined and it is determined that the maximum achievable hydrostatic bearing efficiency (MAHBE) is determined solely by the bearing’s mass addition configuration. The MAHBE of the porous liner bearings is determined to be over 5 times that of the feedhole bearings. The method also presents a means to tune the Kmeas to the clearance to achieve the MAHBE as well as giving a complete mapping of the hitherto misunderstood complex shapes of aerostatic load versus radial deflection curves. This method also rediscovers the obscure phenomenon of static instability which is called in this thesis the “near surface effect” and appears to be the first work to present a practical method to predict the range of static instability and quantify its resultant stiffness fall-off. It determines that porous liner type bearings are not subject to the phenomenon which appears for feedhole type bearings when the clearance exceeds a critical value relative to its mass-addition compensation. The standing pressure waves of hydrostatic and hybrid bearings with the 2 configurations of external pressurization as well as a geometrically identical hydrodynamic bearing are studied in detail under the methodology of the “CFD microscope”. This method is used to characterize and identify the development, growth, and movement of the pressure wave extrema with increased hydrodynamic action (either increasing speed or increasing eccentricity). This method is also used to determine the “cause” of the “near surface effect”. A gedanken experiment is performed based on these results which indicates that a bearing with a “stronger aerostatic strength” component should be more stable than one with a low aerostatic strength component. Numerical instability “speed limits” are found that are also related to the hydrostatic strength of the bearing. The local conditions in the standing waves are characterized in terms of their local Mach number, Knudsen number, Reynolds number, and Taylor Number. It is concluded that low eccentricity bearing whirl can be attributed to the off load-line orientation of the bearing load force caused by the overlay of the hydrodynamic bearing standing wave onto the hydrostatic bearing wave of the hybrid bearing, whereas it is hypothesized that aperiodic and random self-excited vibration which occurs at high eccentricity, as reported in the literature, is probably due to shock waves, turbulence, near surface effect, and slip at local areas of the standing wave.
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Oxydation et relâchement des alliages base nickel en milieu primaire : dispositif de suivi in situ de la cinétique et interprétations / Oxidation et cation release of nickel base alloys in primary water : in situ measurements of kinetics and interpretations.Proust, Antoine 26 October 2010 (has links)
Pour un réacteur à eau pressurisée, la contamination radioactive du circuit primaire constitue un problème majeur pour les opérations de maintenance. La principale source de cette contamination est le relâchement des produits de corrosion des tubes GV en alliages base nickel représentant environ les trois quarts de la surface totale du circuit primaire. L’oxydation des alliages base nickel en milieu primaire, à l’origine du relâchement, a fait l’objet de nombreuses études. Certaines pistes d’amélioration ont d’ailleurs d’ores et déjà été explorées comme la métallurgie des tubes et plus précisément leur état de surface, la pré-oxydation, l’addition de zinc au sein du milieu primaire. Cependant, la compréhension du phénomène demeure lacunaire. La nature et la structure de la couche d’oxyde formée sur les alliages base nickel est relativement bien connue, mais pas sa cinétique de formation et de relâchement ou de façon bien moins précise. L’objet principal de cette étude est donc le développement et la mise en œuvre d’un dispositif expérimental innovant permettant de suivre l’épaisseur d’oxyde formée par une mesure optique de réflectométrie in situ, ainsi que le relâchement en ligne par mesure de concentration par ICP – MS. Les échantillons utilisés lors des différents essais expérimentaux ont également été analysés par diverses techniques notamment l’XPS et le MET afin d’apporter de nouveaux éléments sur la nature ou la structure des couches d’oxyde. En outre, ces analyses, permettant également d’évaluer les épaisseurs d’oxyde ont contribué à valider les résultats d’oxydation obtenus par réflectométrie. L’utilisation de ce moyen expérimental a permis d’obtenir des résultats, certes peu nombreux mais aux perspectives prometteuses. / The radioactive contamination is a significant issue for the maintenance of the primary loop of a water pressurized reactor. The corrosion products released by steam generators tubes made of nickel base alloys, which represent seventy five percent of the whole primary loop surfaces, are highly responsible for this pollution. The oxidation of nickel base alloys in primary water is thus a widely studied subject. Besides, some mitigation means have already been performed like the control of tube manufacturing and of their surface state in particular, a pre-oxidation process, the injection of zinc into primary water. However, the phenomenon remains deficiently understood. The oxide layer nature and structure, formed on nickel base alloys is relatively well known, but this knowledge is far less precise about the layer formation and release kinetics. The main subject of this study is thus to develop an innovative experimental facility which permits to obtain the layer thickness by in situ optical reflectometry measurements, and the corrosion products release by concentration ICP – MS in line measurements. The implementation of these two techniques has needed lots of theoretical and technical adjustments, especially in situ way of using the reflectometry. Some analyses, XPS and MET in particular, have been performed on the different used samples to bring new facts about the nature and structure of oxide layers. Moreover, these analyses have contributed to validate the oxidation results, by measuring the oxide layer thickness and comparing it to the reflectometric results. The different tests realized with this new experimental device are quite promising and should be used and improved to perform others valuable tests.
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Avaliação da atividade antioxidante e antimicrobiana de extratos de araçá (Psidium grandifolium Mart. ex DC.) obtidos por líquido pressurizado (PLE) e por fluido supercrítico (SFE) / Evaluation of the antioxidante and atimicrobial activity of araçá extracts (Psidium grandifolium Mart. ex DC.) obtained by pressurized liquid extraction (PLE) and supercritical fluid extraction (SFE)Bittencourt, Gabriela Marques 26 July 2018 (has links)
O araçá é um fruto, pertencente à espécie Psidium grandifolium Mart. ex DC, nativo da mata atlântica brasileira pouco caracterizado pela literatura ciêntífica. Esta pesquisa visou estudar o rendimento de extração e avaliar as atividades antioxidante e antimicrobiana do óleo essencial de araçá obtido por extração com dióxido de carbono supercrítico (SFE) e dos diferentes extratos obtidos por extração com etanol pressurizado (PLE) seguindo um delineamento composto central rotacional com temperatura e tempo estático como variáveis independentes estudadas. Avaliou-se também o perfil de voláteis do óleo essencial, o teor de compostos fenólicos totais dos extratos etanólicos e as alterações causadas na matriz vegetal por diferentes processos de extração. Com a SFE conseguiu-se extrair toda a fração lipídica do fruto (2,33% ± 0,04.10-2%), a análise dos compostos voláteis do óleo essencial obtido permitiu inferir que este possui diversos compostos com potencial bioativo tais como E-cariofileno (17.56%), α-humuleno (16,26%) e β-sesquifelandreno (14.27%); porém este óleo essencial não apresentou atividade antioxidante relevante. O extrato etanólico com maior rendimento (17, 49%) foi obtido a 74 °C por 6 min, mesma condição em que obteve-se a maior atividade antioxidante (EC50 = 6,37 mg/mL), porém o maior teor de compostos fenólicos totais (136,95 mg EGA/100 g de massa seca) foi obtido quando aplicou-se 60°C por 9 min. Em relação à atividade antimicrobiana, tanto os extratos obtidos por PLE quanto por SFE apresentaram atividade contra cepas de P. aeruginosa, S. aureus e B. cereus, somente extratos etanólicos apresentaram atividade contra cepas de L. monocytogenes e nenhum dos extratos apresentaram atividade contra cepas de B. subtilis, E. coli e Salmonella. Em ambos os extratos foi possível identificar compostos com potencial aplicação farmacológica. O estudo de processos de extração que envolvam inovação tecnológica na obtenção extratos com atividade biológica visa contribuir com o extrativismo consciente ou estimular o plantio em maior escala de mais um fruto tropical empregado na medicina popular brasileira. / The araçá is a fruit, belonging to the species Psidium grandifolium Mart. ex DC, native of the Brazilian Atlantic Forest, is not largely characterized by the scientific literature. This research work aimed to study the extraction yield and to evaluate the antioxidant and antimicrobial activities of the araçá essential oil obtained by supercritical carbon dioxide extraction (SFE) and the different extracts obtained by pressurized ethanol extraction (PLE) following a central composite design with temperature and static time as independent variables studied. It was also evaluated the volatile profile of the essential oil, the content of total phenolic compounds of the ethanolic extracts and the changes caused in the vegetal matrix by different extraction processes. SFE was able to extract the whole lipid fraction of the fruit (2.33% ± 0.04.10-2%), the analysis of the volatile compounds of the essential oil obtained allowed to infer that it has several compounds with bioactive potential such as E-caryophyllene (17.56%), α-humulene (16.26%) and β-sesquipelandene (14.27%); but this essential oil had no relevant antioxidant activity. The highest ethanolic extract (17, 49%) was obtained at 74 °C for 6 min, the same condition in which the highest antioxidant activity was obtained (EC50 = 6.37 mg/mL), but the higher content of total phenolics contente (136.95 mg EGA / 100 g dry mass) was obtained when 60 °C was applied for 9 min. In relation to the antimicrobial activity, both extracts obtained by PLE and SFE showed activity against P. aeruginosa, S. aureus and B. cereus strains, only ethanolic extracts showed activity against L. monocytogenes strains and none of the extracts presented activity against B. subtilis, E. coli and Salmonella strains. In both extracts it was possible to identify compounds with potential pharmacological application. The study of extraction processes that involve technological innovation in obtaining extracts with biological activity aims to contribute to the conscious extraction or stimulate the larger scale cultivation of another tropical fruit used in Brazilian popular medicine.
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