To see the other types of publications on this topic, follow the link: FEx.
Dissertations / Theses on the topic 'FEx'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'FEx.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
SARDINHA, F. C. "O Efeito Magnetocalórico nas Ligas Heusler Ni54[Mn(1-x)Fex]19Ga27." Universidade Federal do Espírito Santo, 2008. http://repositorio.ufes.br/handle/10/4759.
Full textAbstract:
Made available in DSpace on 2016-08-29T15:35:47Z (GMT). No. of bitstreams: 1
tese_2944_.pdf: 4789530 bytes, checksum: 523ebc25e4140437c1560cdf118c63dc (MD5)
Previous issue date: 2008-03-28Neste trabalho, verificou-se experimentalmente a variação da entropia magnética nas ligas Heusler não-estequiométricas Ni54[Mn(1-x)Fex]19Ga27, substituindo-se parcialmente (até 50%) os átomos de Mn por átomos de Fe. Tal estudo focalizou-se principalmente na região de transformação magneto-estrutural a baixas temperaturas. A análise dos difratogramas de raios-X indica que a substituição parcial de Mn por Fe nessa faixa de concentração, ocasiona uma predominância da fase- L21, porém acompanhada de outras fases espúrias. As medidas de magnetização em função da temperatura realizadas a campos baixos revelam que, em toda a faixa de concentração estudada (0 x 0,5), o sistema apresenta uma transição magnética (Ferromagnético Paramagnético) ao atingir a temperatura de Curie, TC, um pouco acima da temperatura ambiente, quando o material se encontra na fase austenítica. E, assim como muitas outras ligas Heusler, o material sofre uma transição estrutural ao ser resfriado a temperaturas inferiores à temperatura de transição martensítica, TM. À medida que se aumenta a concentração de Fe, a temperatura de Curie, TC, sofre uma pequena variação, aumentando em torno de 5%, enquanto que TM diminui lenta e monotonicamente. A variação da entropia, para um campo de 5T, apresenta um máximo SM = - 9,3 J/kg.K para x = 0,1, a uma temperatura T = 250K e, então, diminui para x 0,3, variando linearmente com o campo aplicado.
2
Sardinha, Farley Correia. "O efeito magnetocalórico nas ligas Heusler Ni54[Mn(1-x)Fex]19Ga27." Universidade Federal do Espírito Santo, 2008. http://repositorio.ufes.br/handle/10/6285.
Full textAbstract:
Made available in DSpace on 2016-12-23T14:20:01Z (GMT). No. of bitstreams: 1
EMC_Heusler- parte 1.pdf: 1976712 bytes, checksum: 54cbe3c62f71ef7121b79c6f4e1efaa0 (MD5)
Previous issue date: 2008-03-28Conselho Nacional de Desenvolvimento Científico e Tecnológico
In this work, magnetic entropy change of nonstoichiometric Ni54[Mn(1-x)Fex]19Ga27 Heusler alloys was experimentally verified by partial substitution (up to 50%) of the Mn atoms by magnetic Fe atoms. Such study was mainly concentrated in the magneto-structural transformation region, at low temperatures. The analysis of X-ray diffraction patterns indicate that the partial substitution of Mn atoms by Fe atoms causes predominance of the L21 -phase, however accompanied by spurious phases. The magnetization measurements as a function of the temperature in the low magnetic field reveals that, in all concentration range (0 x 0.5), the system presents a magnetic transition (Ferromagnetic Paramagnetic) at a temperature, TC, near the room temperature, when the material lay in the austenitic phase. Moreover, as many others Heusler alloys, the material undergoes a martensitic structural transition at low temperatures, TM. As the Fe concentration increases, the Curie temperature, TC, undergoes a little variation, increasing around 5%, while TM decreases slowly and monotonically. The magnetic entropy change, for a field of 5T, presents a maximum SM = - 9,3 J/kg.K, for x = 0.1, at a temperature of 250K, and than decreases for x 0.3, changing linearly with the maximum applied field.
Neste trabalho, verificou-se experimentalmente a variação da entropia magnética nas ligas Heusler não-estequiométricas Ni54[Mn(1-x)Fex]19Ga27, substituindo-se parcialmente (até 50%) os átomos de Mn por átomos de Fe. Tal estudo focalizou-se principalmente na região de transformação magneto-estrutural a baixas temperaturas. A análise dos difratogramas de raios-X indica que a substituição parcial de Mn por Fe nessa faixa de concentração, ocasiona uma predominância da fase- L21, porém acompanhada de outras fases espúrias. As medidas de magnetização em função da temperatura realizadas a campos baixos revelam que, em toda a faixa de concentração estudada (0 x 0,5), o sistema apresenta uma transição magnética (Ferromagnético Paramagnético) ao atingir a temperatura de Curie, TC, um pouco acima da temperatura ambiente, quando o material se encontra na fase austenítica. E, assim como muitas outras ligas Heusler, o material sofre uma transição estrutural ao ser resfriado a temperaturas inferiores à temperatura de transição martensítica, TM. À medida que se aumenta a concentração de Fe, a temperatura de Curie, TC, sofre uma pequena variação, aumentando em torno de 5%, enquanto que TM diminui lenta e monotonicamente. A variação da entropia, para um campo de 5T, apresenta um máximo SM = - 9,3 J/kg.K para x = 0,1, a uma temperatura T = 250K e, então, diminui para x 0,3, variando linearmente com o campo aplicado.
3
Kelekar, Rajesh. "Study of potentially half-metallic Co²Cr₁₋x[subscript]Fex[subscript]Al heusler alloys /." May be available electronically:, 2006. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Full text
4
Anas, Muhammad. "Étude de la magnétorésistance dans les alliages Fex SiO1-x et des multicouches discontinues FE/SiO." Nancy 1, 2001. http://www.theses.fr/2001NAN10212.
Full textAbstract:
Des films minces d'alliages Fex(SiO)1-x et des multicouches discontinues Fe/SiO ont été préparés par coévaporation de fer et d'oxyde de silicium. La structure des films a été caractérisée par microscopie électronique, diffraction de rayons X et spectrométrie d'absorption infrarouge. Les propriétés magnétiques ont été décrites à partir des cycles d'hystérésis de l'aimantation en fonction du champ magnétique appliqué et des courbes FC-ZFC. Les propriétés de transport électronique ont été déterminées à partir de mesures de magnétorésistance. Les alliages Fex(SiO)1-x avec 0,40°≤°x°≤°0,50 sont superparamagnétiques et on observe un effet de magnétorésistance tunnel de l'ordre de 2°% vers 100°K. Les multicouches avec une épaisseur de fer comprise entre 5 et 8°Å présentent également un comportement superparamagnétique. La magnétorésistance, mesurée dans les directions parallèle et perpendiculaire aux couches, reste inférieure à 2°%Thin films of Fex(SiO)1-x alloys and Fe/SiO discontinuous multilayers were prepared by coevaporation of iron and silicon oxyde. The structure of the films was characterized with electron microscopy, X?ray diffraction and infrared absorption spectrometry. The magnetic properties were described from the hysteresis loops of the magnetization versus the applied magnetic field and from FC-ZFC curves. The properties of electronic transport were determined from magnetoresistance measurements. The alloys with 0,30°≤°x°≤°0,50 are superparamagnetic and a tunnel magnetoresistance is observed. Its value is equal to about 2°% near 100°K. For an iron thickness between 5 and 8°Å, the multilayers present a superparamagnetic behavior. The magnetoresistance, measured in the directions parallel and perpendicular to the films, remains less than 2°%
5
Bensamka, Faouzi. "Etude par mesures de susceptibilité magnétique et par spectrométrie Mössbauer du comportement verre de spin dans les composés isolants dilués Fex Mg1-x Cl2." Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37595941b.
Full text
6
Karlsson, Maija. "Finn fem fel : Ett verktyg för återmatning och hantering av fel i SDE's montering." Thesis, Mälardalen University, Department of Innovation, Design and Product Development, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-908.
Full textAbstract:
Examensarbetets syfte är att utforma rutiner och verktyg för att säkerställa att relevant information om allvarliga och frekventa problem når föregående processer. Den information som föregående processer tar emot ska vara av sådan karaktär att de vet vad de ska fokusera på i sitt förbättringsarbete. Strävan har varit att ta fram ett felrapporteringsverktyg där alla fel som påträffas i produktionen ska kunna gå att rapporteras in. Utifrån den datainsamling som har gjorts via sekundär- och primärdata har den information som ska rapporters in tagits fram. Felrapporteringen ska ske i en Lotus Notes databas, detta för att programmet redan finns inom SDE`s väggar. De fel som hittas och rapporters in i felrapporteringsverktyget riktas var och en mot ett ansvarigt område. Tillexempel om det fattas ett hål på en artikel och det hålet finns med på ritningen riktas felet mot inköp. Varje ansvarigt område ska månadsvis skriva ut och åtgärda sina tre ”fem i botten” scorecard i kategorierna konsekvens, kostnad och frekvens. Fem i botten scorecarden bygger på paretoprincipen, det betyder att scorecarden visar de fem största felen varje månad i de tre olika kategorierna. Den information som loggas in i felrapporteringsverktyget kommer även att vara ett reklamationsunderlag då inköp står som ansvarigt område. Dataanalysen kommer att göras i ett Business Intelligence verktyg som heter QlikView. Detta för att QlikView på ett smidigt sätt tar data från en eller flera databaser och gör det möjligt för användaren att snabbt och enkelt analysera informationen.
7
Garçon, Guillaume. "Role potentiel du fer (fe2+, fe3+) dans la toxicite pulmonaire d'une exposition concomitante aux oxydes de fer (wustite, hematite) et au benzo(a)pyrene chez le rat sprague dawley (doctorat : toxicologie)." Lille 2, 2000. http://www.theses.fr/2000LIL2P257.
Full text
8
Wilder, Marie. "Fet, ful, helt fel...? : Om beröringspunkter mellan skam och kropp." Thesis, Umeå universitet, Psykoterapi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-42113.
Full textAbstract:
Denna studie har ägnats åt att studera och fördjupa kunskapen kring skamaffekten i relation till negativa kroppsupplevelser. Det har skett genom en litterarstudie vars utgångspunkt har varit tre frågeställningar. Den första frågeställningen har berört hur skamaffekten kan beskrivas. Som svar på denna frågeställning visar studien att skammen har många markörer, att skammen har sina tidliga kroppsliga uttryck, att skamupplevelsen är en mycket obehaligt upplevelser och att människor på en mängd sätt försöker skydda sig från skamupplevelsen. Till följd av alla skyddsmekanismer kan skamaffekten uppträda i en högst förklädd form och vara svår att identifiera som just skam. Studien visar även att skam som en social emotion påverkar den relationella förmågan på ett högst negativt sätt. Skam bidrar till att individen isolerar sig och till uppkomst av olika former av patologiska tillstånd. Samtidigt belyses att skam på många sätt fyller viktiga funktioner för individen och för individen i samhället. Frågeställning nummer två har gällt vilka källor skam har. Studen visar flera olika skamkällor och olika tankar kring hur skam uppstår. Intrapsykiska källor har belysts liksom relationella och även källor till skam sprungna ur den sociala kontexten. Genus och traumaperspektiv har lyfts fram och även perspektivrörande personlighetsstruktur. Den tredje frågeställningen har handlat om skammens koppling till människans kroppslighet. Här visar studien att utvecklingsperspektiv kan visa på kopplingar mellan skam och kroppslighet. Det faktum att skammen tenderar att verka i det fördolda knyter affekten till icke- verbaliserat upplevande. Sexualiteten och männskans behov av beröring är kroppsnära och även skamnära områden visar studien. Normer i det postmodernistiska samhållet, genus och samhälleliga hierarkier, med koppling tilltill kroppen och skamaffekten, är ytterligare perspektiv som belyses. Diskussionen understryker det kliniska värdet av att ha fördjupande kunskaper om skamaffekten liksom värdet av att det kliniska arbetet med negativa kroppsupplevelser göra det utifrån kunskaper om skammens olika markörer och källor. Behov av ytterligare studier inom områdets påtalas.
9
Drissi, Sidi El Hassane. "Oxydation des espèces du fer en milieu aqueux carbonate : préparation et propriétés thermodynamiques de l'hydroxyde carbonate Fe2+-Fe3+ en milieu aqueux (rouille verte 1 carbonatée) et sa formation directe à partir du fer métallique." Nancy 1, 1995. http://www.theses.fr/1995NAN10349.
Full textAbstract:
Les ions carbonate constituent l'espèce la plus abondante en solution dans les eaux naturelles continentales. Ce travail consiste à déterminer les conditions de préparation de l'hydroxyde Fe2+-Fe3+ carbonate de structure rouille verte I à partir de l'oxydation d'hydroxyde ferreux précipite en mélangeant du sulfate ferreux (mélantérite) et de la soude et en ajoutant immédiatement du carbonate de sodium Na2Co3. Les deux paliers d'oxydation observés correspondent, pour le premier à la formation de la rouille verte I, et pour le second à celle du produit final qui peut être un oxyhydroxyde ferrique ou de la magnétite. Le rapport des concentrations initiales R=
10
Marcelli, Thierry. "Propagation de feux de forêt : Modélisation et étude expérimentale de la transition d'un feu de surface vers un feu de cime." Corte, 2002. http://www.theses.fr/2002CORT0005.
Full textAbstract:
Ce travail porte sur la modélisation de la transition feu de surface-feu de cime. Pour cela, nous avons développé un modèle semi-physique de transition. Ce modèle est basé sur le modèle de propagation d'un feu de litière développé à l'Université de Corse ; ce modèle ne prenant en compte les échanges vers une strate supérieure de combustible nous avons décidé d'utiliser une méthode d'amélioration basée sur la réduction de modèle complet, en particulier celui de l'IUSTI de Marseille. Cette réduction a fait apparaître un terme d'échange entre la colonne chaude convective et le combustible de la strate supérieure, et a permis l'amélioration de notre modèle par l'ajout d'un terme supplémentaire représentant ces échanges. Afin d'évaluer ce terme, nous avons mis en place une campagne de mesure à l'échelle du laboratoire. Etant les premiers à effectuer ce genre d'expériences à l'Université de Corse, nous avons dû tout d'abord mettre au point un protocole afin d'accéder aux données caractéristiques du feu : température, vitesse de propagation. Les mesures de température ont été réalisées à l'aide de thermocouples, dans la zone de combustion et de panache. Nous avons développé une méthode originale de compensation numérique de température dans la zone de flamme, car les thermocouples utilisés ne donnent pas une bonne représentation des fluctuations de température. Cette compensation a permis de restituer la dynamique des phénomènes, et ainsi, à l'aide du calcul du temps de transit entre deux capteurs, de calculer la vitesse ascensionnelle des gaz de combustion. Une autre série d'expériences réalisée sur la transition a permis de calculer le terme d'échange afin d'effectuer des simulations de notre modèle. Les résultats obtenus sont encourageants, ils représentent bien les étapes et les tendances de la transition d'un feu de surface vers un feu de cime.
11
Schatt, Nathan A. "Finite Element Modeling of Ultrasonic Wire Bonding on Polyvinyl Acetate-Nanocomposite Substrates." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396634471.
Full text
12
Giroud, Frédérique. "Contribution à la modélisation de la propagation des feux : approche multiphasique des feux de forêt. Développement d'un feu de propergol en milieu semi-confiné." Aix-Marseille 1, 1997. http://www.theses.fr/1997AIX11023.
Full textAbstract:
Partie 1 ce travail presente une nouvelle approche de la modelisation de la propagation d'un feu, basee sur l'interaction entre le combustible et la dynamique des gaz environnants. Le combustible est considere comme un milieu multiphasique, constitue d'une phase gazeuse et de plusieurs phases solides. Une formulation, basee sur des moyennes spatiales ponderees est developpee et conduit a l'etablissement de systemes d'equations multiphasiques, reactifs et radiatifs. On effectue des simulations numeriques monodimensionnelles d'un feu a co et contre-courant, dans un milieu heterogene compose de particules combustibles fixes. On presente ensuite un modele quasi-bidimensionnel deduit directement des equations generales et resolu pour simuler la propagation d'un feu dans des litieres de pin maritime et de pin d'alep, en fonction de la pente et de la charge du lit de combustible. Les resultats obtenus sont compares a des resultats experimentaux. Partie 2 une etude numerique d'un ecoulement de propergol induit par un feu de propergol solide en cavite est presente. La cavite possede une ouverte en plafond, obturee par un opercule qui se rompt des que la pression depasse un seuil limite. Les conditions limites particulieres qui sont la zone de combustion et la section de sortie au niveau de l'opercule sont traitees respectivement par un demi probleme et par un probleme de riemann. L'evolution dans le temps de la temperature et de la pression moyenne du gaz ainsi que de la disparition d'oxygene est examinee pour deux cas d'ouverture de l'opercule.
13
Toussaint, Marie. "L'épreuve du feu : politiques de la nature, savoirs, feux de brousse et décolonisation en Nouvelle-Calédonie." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEH024/document.
Full textAbstract:
Depuis une vingtaine d’années, les feux de brousse constituent un phénomène récurrent et préoccupant en Nouvelle-Calédonie, car ils menacent des formations végétales endémiques et particulièrement originales, et mettent en péril les équilibres environnementaux du territoire insulaire de la Nouvelle-Calédonie. Répondant à une commande de la Province nord de la Nouvelle-Calédonie, ce travail entendait mettre au jour les usages contemporains du feu, en particulier en milieu kanak. De l’ethnographie de pratiques interdites à l’analyse socio-historique du secteur forestier, cette thèse explore la manière dont le phénomène des feux de brousse a été pensé et encadré sur la longue durée coloniale. Loin de constituer un phénomène nouveau, les feux de brousse sont un élément constitutif de la conquête coloniale et de la ségrégation raciale qui ont marqué l’histoire de la Nouvelle-Calédonie. Devenu un « problème public environnemental » dans les années 1970, le phénomène a progressivement acquis le caractère de menace pour la biodiversité, de telle sorte que les politiques environnementales contemporaines se concentrent sur l’éradication du phénomène, via le renforcement de politiques de sensibilisation et de lutte contre les feux. Dans le même temps, les usages et représentations kanak passés et contemporains du feu, et plus largement de l’environnement naturel, ont été très fortement réprimés et de facto rendus invisibles.Au-delà de ces aspects environnementaux, l’analyse de la question des feux de brousse permet d’explorer des questions politiques : de la construction et de la formation de l’État colonial en Nouvelle-Calédonie, à sa transformation depuis les Accords politiques de Matignon-Oudinot (1988) et de Nouméa (1998). L’ensemble de cette thèse explore ainsi la trajectoire coloniale et postcoloniale calédonienne à l’épreuve du phénomène des feux en étudiant l’évolution des structures règlementaires et des institutions forestières, mais également la circulation des savoirs liés aux feux et aux forêts, et le rôle essentiel des acteurs dans ces processus. Ce travail met en évidence les liens multiples entre des formes de savoirs et des structures de pouvoir, et en particulier la sédimentation progressive de certaines formes d’ignorance, et le rôle des acteurs dans leur maintien. Il permet également de documenter l’histoire environnementale de l’ile depuis son annexion par la France et de renouveler les questions relatives à la gestion de cet environnement naturel. L’analyse de l’évolution de la problématique des feux de brousse, et sa prise en charge par les institutions calédoniennes ouvrent des questions intéressantes et importantes sur la formulation de politiques environnementales dans un contexte de décolonisation négociéeFor almost twenty years, bush fires have been a recurrent phenomenon and serious concern in New Caledonia, because they threat endemic and particularly original vegetal formations, and endanger the environmental equilibrium of the insular territory of New Caledonia. Meeting a demand formulated by the Northern Province of New Caledonia, this work intended to describe the contemporary uses of fire, particularly in the Kanak world. From the ethnography of forbidden practices to the socio-historical analysis of the forest sector, this doctoral research explores the way the bush fires phenomenon has been thought out and framed on the colonial long-span. Far from constituting a new phenomenon, bush fires were a constitutive element of the colonial conquest and racial segregation which marked New Caledonia’s recent history. Having become an “environmental public problem” in the 1970’s, the phenomenon was progressively characterized as a threat to biodiversity in such a way that contemporary environmental policies concentrate on its eradication through the reinforcement of awareness campaigns and firefighting policies. Nevertheless both past and contemporary Kanak uses and social representations of fire and more generally of natural environment have been severely repressed and actually made invisible. Beyond those environmental aspects, analyzing the question of bush fires enables the exploration of political questions: from the colonial state construction and formation in New Caledonia to its transformation since the political agreements of Matignon-Oudinot (1988) and Nouméa (1998). The thesis as a whole thus explores the New Caledonia colonial and post-colonial trajectory through the lens of the fire phenomenon. For this, it studies the evolution of regulatory frameworks and forestry institutions, but also the circulation of fire and forests knowledge, and the critical role of social actors in those processes. This work highlights the multiple links between forms of knowledges and structures of power, in particular the gradual sedimentation of some forms of ignorance and the role of social actors in reproducing them. It also allows documenting the environmental history of the island since its annexation by France and offering fresh insights into questions regarding the management of natural environment. Analyzing how the bush fires issue evolved over time and how it was dealt with by Caledonian institutions opens up meaningful and relevant questions for the formulation of environmental policies in the current context of negotiated decolonization
14
Vareskic, Srdjan. "Utmattningsanalys av tryckkärl i enlighet med SS-EN 13445-3." Thesis, Högskolan i Halmstad, Akademin för ekonomi, teknik och naturvetenskap, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-28737.
Full textAbstract:
Detta examensarbete har utförts i samarbete med Fagerström Industrikonsult AB i Helsingborg. Fagerström Industrikonsult AB är ett ingenjörsföretag som har specialiserat sig på mekaniska och mekatroniska produkter inom flera branchområden. Ett av företagets tidigare projekt, som bland annat bygger på tryckbärande kärl och som kommer återanvändas för ett nytt projekt, är i behov av en uppdaterad analys mot utmattningsbrott.För att en tryckbärande utrustning skall kunna säljas och användas inom Europa, måste tillverkarna följa det Europeiska direktivet 97/23/EG, även kallat PED-direktiv. Detta direktiv sätter regler för konstruktion, tillverkning, märkning och kontroll. I Sverige finns denna beskrivning i Arbetsmiljöverkets författnings-samling (AFS 1999:4 2011). För att uppfylla alla de konstruktionsmässiga och tillverkningsmässiga krav på tryckkärlet som ställs i PED direktivet, så måste harmoniserade standarder användas. I detta arbete används tryckkärlsstandarden (SS-EN 13445-3: 2014) som sätter regler för design och verifiering av tryckbärande anordningar.Ett av projekten som finansierats av den Europeiska kommissionen, visade att 25% av alla tryckbärande anordningars haverier beror på utmattning. Tryckkärl är den typ av tryckbärande anordning, som är mest utsatt för skador orsakade av utmattning. Utmattningsbrott har varit känt sedan början på 1800-talet och man har länge studerat detta fenomen. Man har efter lång tids arbete hittat metodik för att ta fram analytiska modeller och prediktionstekniker samt säkra och noggranna livslängdsberäkningar för stålkonstruktioner. Fagerström Industrikonsult AB söker idag en metod för att utföra utmattningsanalys på tryckkärl i enlighet med tryckkärlsstandarden där linjärstatisk analys utförs med finita elementmetoden. Företaget eftersträvar också mer kunskap inom ämnet för att ge konstruktörerna bättre kännedom om utmattningsproblematiken samt ge möjlighet att redan i konstruktionsstadiet kunna sätta rimliga krav på tillverkning ur mekaniskt utmattningsperspektiv.This master thesis has been carried out in collaboration with Fagerström Industrikonsult AB in Helsingborg. Fagerström Industrikonsult AB is an engineering company, specialized in mechanical and mechatronic products across a wide range of industry segments. One of the company's previous project, which is among other sub-products based on pressurized vessels, and that will be reused for a new project, needs an updated analysis against fatigue failure.In order to sell or use a pressurized equipment in Europe, the manufacturers must comply with the European Directive 97/23/EC, also called PED-directive. This directive sets the rules for design, production, marking and inspections. In Sweden, this directive is described in “Arbetsmiljöverkets Författningssamling” (AFS 1999:4 2011). In order to meet all the design and manufacturing requirements for pressure vessels that are required by the PED Directive, it is required to use harmonized standards. In this thesis, pressure vessel standard (SS-EN 13445-3: 2014) is used, which sets the rules for design and verification of pressure vessel.One of the projects funded by the European Commission, showed that 25 % of all pressure equipment failure are caused by fatigue. Pressure vessel is one type of these pressure equipment, which is most vulnerable to damage caused by fatigue. Fatigue failure has been known since the beginning of 19th century and this phenomenon has been studied for a long time. Under this extensive period of time, methods have been succefully developed for analytical models and prediction techniques as well as safe and accurate life calculations for steel structures. Fagerström Industrikonsult AB is today seeking a method to perform fatigue analysis of pressure vessels in accordance with European pressure vessel standard, where the linear static analysis is performed using the finite element method. The company is also pursuing more knowledge of the subject so its designers have more understanding of fatigue phenomena in order to be able to set reasonable requirements during design stage for production and in order to prevent this phenomena.
15
Elgström, Eskil. "Practical implementation of hyperelastic material methods in FEA models." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-5654.
Full textAbstract:
This thesis will be focusing on studies about the hyperelastic material method and how to best implement it in a FEA model. It will look more specific at the Mooney-Rivlin method, but also have a shorter explanation about the different methods. This is due to problems Roxtec has today about simulating rubber takes long time, are instable and unfortunately not completely trustworthy, therefore a deep study about the hyperelastic material method were chosen to try and address these issuers. The Mooney-Rivlin method (which is a part of the hyperelastic material method) is reliant on a few constant to represent the material, how to obtain these constants numerical and later implement these is suggested in this thesis as well. The results is the methodology needed to obtain constants for Mooney-Rivlin and later how to implement these in FEA software. In this thesis the material Roxylon has been studied and given suggestion on these constants as well as an implementation of the given material.För en bra simulering utav hyperelastiska material, exempelvis för gummi, har detta examensarbete fokuserat på att undersöka hyperelastiska material metoder och hur man kan implementera det i FEA program.
16
Lefrère, Yannick. "Propriétés d'absorption optique du Fe2+ et du Fe3+ dans des verres d'intérêt industriel : mesure, modélisation et implications structurales." Paris 7, 2002. http://www.theses.fr/2002PA077108.
Full text
17
Valcanover, João Alberto. "Propriedades magneticas de ligas desordenadas Fe1-X Mnx na fase HCP e do sistema pseudobinario Fe2 (Nb1-xMnx)." reponame:Repositório Institucional da UFSC, 1996. http://repositorio.ufsc.br/xmlui/handle/123456789/76480.
Full textAbstract:
Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciencias Fisicas e MatematicasMade available in DSpace on 2012-10-16T10:44:21Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T20:23:46Z : No. of bitstreams: 1 104295.pdf: 2313482 bytes, checksum: 9b4a3edf687c2da953afab81db0fa9c2 (MD5)
Neste trabalho é apresentado um estudo das propriedades magnéticas das ligas desordenadas Fe1-xMnx na fase hexagonal de agrupamento compacto (hcp), e do sistema pseudobinário Fe2(Nb1-xMnx). Foram utilizadas as técnicas experimentais de difração de raios-X (DRX), espcetroscopia Mössbauer (EM), calorimetria diferencial de varredura (DSC) e magnetização. As amostras das ligas foram preparadas por fusão num forno a arco voltaico, sob atmosfera inerte de argônio, a partir dos componentes de pureza eletrolítica (99,9%). Quatro amostras foram analisadas para as ligas desordenadas Fe1-xMnx, com x=0,17, 0,21, 0,23 e 0,26. Para a amostra com x = 0,17 foi verificada a presença de três fases bcc, fcc e hcp. Para o sistema Fe2(Nb1-xMnx), foram analisadas ligas com x = 0,1 até x=0,09. Os resultados indicam que a adição de manganês na matriz do Fe2Nb mantém uma fase única (hcp) até cerca de x =0,3. A partir daí surgem duas novas fases, coexistindo com a fase hcp primária; uma delas foi identificada como uma estrutura cúbica de fase centrada (fcc), e a outra, como uma estrutura hcp, conhecidas como fase g e e , respectivamente.
18
Goller, Daniel, Christian Glenk, and Frank Rieg. "Entwicklung und Implementierung einer Finite-Elemente-Software für mobile Endgeräte." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-172479.
Full text
19
Dupaigne, Bernard. "Les Maîtres du fer et du feu : étude de la métallurgie du fer chez les Koouy du nord du Cambodge, dans le contexte historique et ethnographique de l'ensemble kmer." Paris, EHESS, 1987. http://www.theses.fr/1987EHES0065.
Full textAbstract:
L'etude de la metallurgie du fer au cambodge est essentielle pour la comprehension de la civilisation du cambodge ancien et moderne. Les prestigieux et puissants empires cambodgiens n'ont pu se constituer sans la presence de fer : pour les armees, pour l'edification des temples, et pour la constitution d'un systeme hydraulique elabore qui a permis le developpement de la production agricole. Ce fer etait produit anciennement au cambodge, par des metallurgistes dont on ne sait rien ; simplement qu'ils etaient installes aupres des gisements de minerai de fer, dans une region qui n'est pas tres eloignee d'angkor, et qui etait reliee aux capitales khmeres par une chaussee presque en ligne droite. Si l'on ne sait rien des metallurgistes anciens, l'etude presentee ici permet de connaitre tres precisement les metallurgistes de la region de kompong-thom qui reduisaient le fer, avec les techniques actuelles, depuis plus de cinq cents ans. La reduction du minerai de fer etait accompagnee, dans toutes ses etapes, par des rites minutieux et extremement compliques. C'est le bon accomplissement de ces rites qui permettait aux divinites protectrices de permettre le melange des elements primordiaux de la nature, la terre, l'eau, le vent, le feu, pour donner naissance au ferOld and modern cambodia cannot be understand without the study of iron metallurgy. The powerful cambodian empires could not have been edified without iron. Iron was needed for the army, for the building of the temples, and for the constitution of the elaborated irrigation channels. In ancient cambodia, iron was produced by metallurgists settled near the iron ore mines, not far from angkor. The mines were relied to angkor by roads. The study presented here put in the light the metallurgists of the kompong - thom province, with their techniques, probably the same tham five hundred years ago. Reduction of iron ore was accompagnied by numerous rituals. Those religious rituals were extremly precise and complex. They were to permit the deities to let the ore to be changed in iron, with action of the main elements : earth, wind, water, fire the technic of the work of reduction of the ore is detailed in this work. As well as the economy of the production of iron in the society
20
Dupaigne, Bernard. "Les Maîtres du fer et du feu étude de la métallurgie du fer chez les Kouy du nord du Cambodge, dans le contexte historique et ethnographie de l'ensemble Khmer /." Lille 3 : ANRT, 1989. http://catalogue.bnf.fr/ark:/12148/cb37604759x.
Full text
21
DECAP, GUILLAUME. "ETUDE STRUCTURALE ET MAGNETIQUE DE PHASES FLUOREES DANS LES SYSTEMES PbF2-MF-2M'F3 (M=MN²+, FE2+; M'=FE3+, Al3+)." Rennes 1, 1994. http://www.theses.fr/1994REN10069.
Full textAbstract:
Pb#2mnfe#2f#1#2, 3h#2o est le premier fluorure a triples chaines isolees d'octaedres contenant du fer. Partant de ce compose, deux phases isotypes, pb#2fe#3f#1#2, 3h#2o et pb#1#. #5fe#3f#1#2, 3h#2o, ont ete obtenues par synthese hydrothermale basse temperature. Les structures cristallines de ces composes ont ete etablies par diffraction de rayons x sur monocristal ou sur poudre. L'etude thermique de ces trois hydrates a ete realisee par thermodiffractometrie, diffraction neutronique et spectrometrie mossbauer. La deshydratation de pb#1#. #5fe#3f#1#2, 3h#2o a permis de stabiliser la phase anhydre. Les temperatures d'ordre magnetique sont comprises entre 17 et 33 k. En accord avec la topologie cationique, le caractere magnetiquement frustre de ces composes a ete mise en evidence par diffraction neutronique et spectrometrie mossbauer sous champ. Dans les binaires pbf#2mf#3, deux nouveaux composes ont ete synthetises: pb#3fe#2f#1#2 et pb#3al#2f#1#2. Ils presentent une configuration en tetrameres (m#4f#2#0)#8# isoles inseres dans un sous-reseau de fluors independants. Les deux composes se differencient par la disposition des tetrameres dans le sous-reseau. Le comportement magnetique du groupement (fe#4f#2#0) est etudie par spectrometrie mossbauer a tres basse temperature (21 mk) et est discute en terme de clusters magnetiques isoles. La structure de la phase de composition voisine, pb#5al#3f#1#9, a ete reexaminee. L'hydrate kpbfef#6, h#2o a ete egalement synthetise. Sa structure, formee d'octaedres (fef#6) isoles, est apparentee a la famille des elpasolites. Une etude de deshydratation a ete menee par thermodiffractometrie. Les mesures mossbauer a tres basses temperatures permettent d'observer un ordre magnetique tridimensionnel a tn 3. 7 k
22
Przybyla-Toscano, Jonathan. "Étude des protéines NFU, ISCA et FDX, impliquées dans la maturation des centres fer-soufre dans les mitochondries d’Arabidopsis thaliana." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0127.
Full textAbstract:
Chez les plantes, les protéines à centre fer-soufre (Fe-S) sont impliquées dans de nombreux processus cellulaires (e.g. photosynthèse, respiration). La maturation de ces protéines nécessite la synthèse de novo des centres Fe-S à l’aide de machineries d’assemblage spécifiques. Les plantes possèdent trois machineries d’assemblage nommées SUF, ISC et CIA, dédiées à la maturation des protéines plastidiales, mitochondriales et nucléaires ou cytosoliques, respectivement. Lors de la maturation des protéines mitochondriales, un centre [2Fe-2S] est initialement assemblé sur la protéine d’échafaudage ISU puis transféré vers les apoprotéines cibles à l’aide de chaperons et de diverses protéines de transfert. Si ces étapes semblent suffisantes pour la maturation de protéines incorporant des centres [2Fe-2S], un couplage réductif de deux centres [2Fe-2S] est nécessaire pour la maturation des protéines de type [4Fe-4S]. Cette conversion nécessite des protéines de transfert et un donneur d’électrons, potentiellement la même ferrédoxine que celle qui agit déjà lors des étapes précoces pour la réduction du soufre. En combinant des approches moléculaires, biochimiques et génétiques, l’implication des protéines de transfert NFU et ISCA et des ferrédoxines mitochondriales (mFDX) dans les étapes tardives de transfert et de conversion a été explorée au cours de cette thèse chez la plante modèle Arabidopsis thaliana. Des expériences de complémentation en levure ont démontré que les protéines NFU et ISCA de plantes peuvent assurer les mêmes fonctions que leurs orthologues respectifs, suggérant que ces étapes tardives ont été conservées. Cependant, contrairement à la levure, l’analyse de lignées n’exprimant pas les deux protéines NFU indiquent qu’elles sont essentielles pour le développement de l’embryon. Au niveau moléculaire, les analyses effectuées à l’aide d’approches in vivo et/ou in vitro ont permis d’identifier une interaction entre ISCA1a ou ISCA1b et ISCA2, NFU4 et NFU5 mais aucune interaction avec les deux mFDX dont le rôle dans les dernières étapes d’assemblage des centres Fe-S reste donc incertain. La formation d’holo-hétérocomplexes entre ISCA1 et ISCA2 a été confirmée par co-expression chez E. coli et purification des protéines recombinantes. Globalement, en associant la littérature à propos de la machinerie ISC et les résultats obtenus, le modèle qui ressort est que des hétérocomplexes ISCA1/2 agiraient immédiatement en amont des protéines NFU qui permettraient a minima la maturation des centres [4Fe-4S] de la lipoate synthase. Ce seul partenaire pourrait expliquer en grande partie la létalité d’un mutant nfu4 x nfu5 car l’activité de plusieurs protéines centrales pour le métabolisme mitochondrial dépend de l’acide lipoïqueIn plants, iron-sulfur (Fe-S) proteins are involved in crucial processes such as photosynthesis and respiration. The maturation of these proteins requires the de novo synthesis of their Fe-S clusters through dedicated assembly machineries. Plants have three Fe-S cluster assembly machineries, namely SUF, ISC and CIA, devoted to the maturation of plastidial, mitochondrial and nuclear or cytosolic proteins, respectively. During the mitochondrial Fe-S protein maturation, a [2Fe-2S] cluster is first assembled on the ISU scaffold protein then transferred to target proteins with the help of chaperones and various transfer proteins. If these steps are sufficient for the maturation of [2Fe-2S] proteins, a reductive coupling process of two [2Fe-2S] clusters is required for the maturation of [4Fe-4S] proteins. This conversion needs transfer proteins and an electrons donor, potentially the same ferredoxin which acts during the first step of the Fe-S cluster biogenesis for sulfur reduction. By combining molecular, biochemical and genetic approaches, the involvement of NFU and ISCA transfer protein and mitochondrial ferredoxin (mFDX) in the late transfer and conversion steps has been explored during this PhD project by using the Arabidopsis thaliana plant model. Yeast complementation experiments have demonstrated that plant NFU and ISCA proteins have functions similar to their respective orthologs, suggesting that these late steps are conserved. However, unlike yeast, the characterization of nfu mutant lines indicates that both proteins are essential for early embryonic development. At the molecular level, in vivo and in vitro approaches have shown an interaction between ISCA1a or ISCA1b and ISCA2, NFU4 and NFU5 but no interaction with the two mFDX whose participation in the late steps remains uncertain. The formation of ISCA1-ISCA2 holo-heterocomplexes has been confirmed by co-expression in E. coli and purification of recombinant proteins. Overall, the literature and results obtained here highlight a model where ISCA1/2 heterocomplexes would act immediately downstream of NFU proteins which would a minima allow [4Fe-4S] cluster maturation of the lipoate synthase. This sole partner could primarily explain the lethality of a nfu4 x nfu5 double mutant because the activity of several proteins central for the mitochondrial metabolism depends on lipoic acid
23
Zucchi, Maria do Rosário. "Existência de diferentes estados de spin dos íons Fe2+ e Fe3+ do citocromo c resultante da interação com lipossomos modelos." Universidade de São Paulo, 2001. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-07042010-154320/.
Full textAbstract:
A associação lipídio/citocromo c é importante e deve ser estudada, pois repercute na atividade peroxidática da proteína abordada e pode contribuir para o processo apoptótico, ou morte programada da célula, e também desempenha um papel significativo na cadeia respiratória. A natureza e a especificidade da interação do citocromo c com bicamadas lipídicas têm sido bastante investigadas ultimamente, mas informações detalhadas e precisas sobre tais assuntos ainda não existem. É aceito que ocorre primeiramente uma interação eletrostática entre a proteína citocromo c e as membranas fosfolipídicas. Em seguida, há uma interação hidrofóbica. Entretanto, ainda não é bem compreendido o papel da cadeia fosfolipídica. A associação do citocromo c com membranas lipídicas induz mudanças no estado de spin do átomo de ferro. A interação entre as vesículas carregadas e o citocromo c induz mudanças estruturais na proteína, as quais são refletidas no seu centro ativo, ou grupo heme. As mudanças do campo cristalino no sítio do ferro hemínico de forte para fraco são acompanhadas por mudanças do estado de spin de baixo para alto, respectivamente. Neste trabalho, estuda-se sistematicamente a natureza da interação entre o citocromo c e a cadeia fosfolipídica. As mudanças estruturais no grupo heme foram correlacionadas com a natureza do lipídio, ou seja, com a carga da cabeça e com o tamanho e o tipo da cadeia fosfolipídica. Foram utilizados treze lipídios diferentes, naturais e sintetizados, com cabeças polares negativas e neutras e com cadeias carbônicas saturadas e insaturadas de diferentes comprimentos. Para tal investigação, utilizamos as técnicas: Ressonância Paramagnética Eletrônica (RPE) Onda Contínua (CW) e Pulsada (PW) e Dicroísmo Circular Magnético (MCD). As técnicas enunciadas avaliam as mudanças de estado de spin e a simetria do citocromo c nos seus estados férrico e ferroso. A interação lipoprotéica lipídio/citocromo c foi avaliada com lipídios diferentes, inclusive com o lipossomo PCPECL, que mimetiza a membrana interna da mitocôndria nos eucariontes. A partir dos resultados experimentais, sugerimos um modelo para esse tipo de associação.This association lipid/cytochrome c is interesting to study in order to understand the peroxidase activity of this protein, that plays an important role in the respiratory chain and in the apoptosis process or the programmed cell death. The nature and specificity of the interaction of cytochrome c with lipid bilayers have been major goals in recent studies, but detailed information on that issue is not yet widely available. In this regard, it is generally accepted that the electrostatic interaction is an important factor in the association of cytochrome c with phospholipid membranes, followed by a hydrophobic interaction. However, the role played by the phospholipid chain is not well understood. The association of cytochrome c with negative membranes induces a change in the heme iron spin state. The interaction between the charged vesicles and cytochrome c leads to structural changes in the active central or heme group. The changing of the crystalline field of the heme iron from strong to weak is accompanied by spin states changes from low to high spin, respectively. These facts concerned us to investigate more systematically the nature of the interaction between cytochrome c and the phospholipid chains. The lipid-induced effects in the heme iron crystalline field are correlated to the nature of the charged head group and to the size and type of the phospholipid chain. Thirteen different lipids, nature and synthetic, were used, with negative and neutra1 polar head group and saturated and unsaturated acyl chains with different length. This work investigates the change of heme iron spin state and symmetry of ferric cytochrome c using Continuous Wave (CW) and pulsed (PW) Electron Paramagnetic Resonance (EPR) and Magnetic Circular Dichroism (MCD) techniques. These techniques analyze the spin state change and the symmetry of the iron cytochrome c in its ferric and ferrous states. The effect of the different lipids were analyzed, including PCPECL membrane that mimetics the inner mitocondrial membrane in eukaryotes.
24
Voisset, Edwige. "Etude de l'implication des protéines fes et fer dans la signalisation des recepteurs à activité tyrosine kinase kit et FLT3." Aix-Marseille 2, 2008. http://theses.univ-amu.fr.lama.univ-amu.fr/2008AIX22027.pdf.
Full textAbstract:
La recherche de nouveaux acteurs de la signalisation du récepteur tyrosine kinase KIT, nous a conduit à étudier les protéines tyrosine kinase cytoplasmiques FES et FER. Trois projets ont émané de cette identification. Une première étude a porté sur le récepteur oncogénique KITD816V (mutant retrouvé chez la majorité des patients atteints de mastocytose). Dans ce contexte, FES est phosphorylée sur tyrosines, reflétant son activation constitutive. De plus, en aval de ce récepteur, FES est un régulateur positif de la prolifération cellulaire et plus précisément, cette kinase est impliquée dans la transition des phases G1/S du cycle cellulaire. Au plan moléculaire, FES n’est pas nécessaire à l’activation de la MAP Kinase p38, mais pour celles des protéines STAT et p70S6K. Alors que l’action de FES sur la phosphorylation des STAT semble dépendante du modèle d’étude, son action sur la p70S6K s’avère toujours être une régulation positive. De plus, en aval de KITD816V, FER n’est pas impliquée dans la prolifération cellulaire. Un deuxième sujet tente de déterminer la ou les fonction(s) de FES dans le contexte du récepteur KITWT. Ainsi, nous avons déjà pu montrer que FES interagissait avec KIT stimulé par son ligand et que selon la même cinétique, FES était activée. Ces deux événements sont d’une part, relativement tardifs et d’autre part, transitoires. D’un point de vue fonctionnel, FES et FER interviennent dans le chimiotactisme en réponse au SCF mais pas dans la prolifération cellulaire. Un troisième travail a été mené sur les rôles des protéines FES et FER en aval du récepteur oncogénique FLT3ITD (mutation majoritaire chez les patients atteints de LAM). Pour ces deux kinases, leurs activations sont dépendantes du contexte oncogénique induit par FLT3ITD. L’absence de FES ou de FER dans le système FLT3ITD provoque une diminution de la prolifération cellulaire. Dans le cas de FER, cet effet est consécutif à des défauts de transition entre les phases G1/S et G2/M du cycle cellulaire. Dans le cas de FES, sa présence semble nécessaire à la survie cellulaire. Au niveau moléculaire, ces deux protéines sont des régulateurs positifs de l’activation de STAT5 et des protéines en aval de la PI3Kinase. Ces études ont donc conduit à révéler les protéines FES et FER comme des effecteurs indispensables en aval des récepteurs KIT et FLT3.
25
Touma, Johannes, and Simon Kasselia. "Konstruktion av upphängningsanordning till T22 provrigg." Thesis, KTH, Hållbar produktionsutveckling (ML), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-276725.
Full textAbstract:
Detta examensarbete går ut på att konstruera en upphängningsanordning för en provrigg på Scania. Scania har i dagsläget ett flertal olika provriggar, en provrigg de har är T22. Syftet med detta arbete är att utveckla en fixtur som har egenskapen att stödja en tung växellåda så den utgående axeln på växellådan kan provas i provriggen T22. Metoden som används för denna utveckling består av flera moment där den första delen är att mäta nuvarande mått på växellådan och modellera en fixtur med hjälp av de mått som tagits i CAD-programmet CATIA. Därefter kan fixturen som konstruerats i CATIA sammanställas ihop med växellådan för att se om dimensionerna stämmer. När sammanställningen har genomförts kan mekaniska analyser utföras och sedan avslutas med tester. Resultatet av projektet blev en upphängningsanordning som monteras på Scanias växellådor som i sin tur kopplas ihop med provrigg T22. Scanias befintliga komponenter som lyftbalk och cirkulär konsol användes och kompletterades med armar som möjliggör att montera växellådan bakifrån i provrigg T22. Av det här resultatet kan vi dra slutsatsen att Scania kan montera fixturen på de allra flesta GW växellådorna och utföra mätningar via provriggen T22.This thesis is about designing a suspension device for a test rig at Scania. Scania currently has several different test rigs, one test rig they have is T22. The purpose of this work is to develop a fixture that has the property of supporting a large gearbox so that the output shaft of the gearbox can be tested in the test rig T22. The method used for this development consists of several parts where the first part is to measure the current dimensions of the gearbox and then create a fixture in the CAD program CATIA V5 adapted to the dimensions taken before on the gearbox. Then the fixture constructed in CATIA V5 can be assembled with the gearbox to check if the dimensions are correct and fits together. Once the compilation has been completed, mechanical analyzes can be performed and then conclude with tests.The result of the project was a suspension device that is mounted on Scania's gearboxes which in turn are connected to test rig T22. Scania's existing components such as lifting beam and circular adapter were used and supplemented with arms that allow the gearbox to be mounted from behind in test rig T22.From this result we can conclude that Scania can mount the fixture on most GW gearboxes and perform measurements using the test rig T22.
26
Prathan, Kanthee. "Optimization of sprue design for advanced investment casting through FEA analysis." Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-50027.
Full textAbstract:
Investment casting is a complex manufacturing method with many challenges that must be solved before components of the right quality can be produced. TPC is a company that utilizes investment casting to produce a variety of products, lately the company has higher ambition in wanting to cast higher technical demanding component like heat resistant gas turbine blades. This requires a sprue that can control the filling process, by allowing the fallen stream of molten metal to enter the moulds cavity in a laminar manner. This study has implemented the product development process by (Ulrich, 2012) to develop the requested sprue. The primary support for this study is study material given by the company also known as "PMG running spreadsheet TPC" base on theory and equations from (Jolly, 2002), which is believed to have origin in sand casting manufacturing process. The project began with recreating the textbook model after establishing a number of control parameter such as critical velocity. Then simulation software Nova flow was used to evaluate the velocity and FEM in Solidworks to study if the dimension of the model can be directly use for investment casting process. The results show that it was not possible, therefore in the concept generating phase only theory of casting was used to create new concept. Then 3 existing sprues were chosen for benchmarking to gain deeper understanding about their design intension. One of the concepts was inspired by the CEO Mark Irwin “concentric pipe design” and in total 10 concepts were created of which 6 were tested for both flow and FEM analysis. 2 concepts were chosen for further development which also became 2 final concepts, after 3 iterations of improvement. These concepts show that many improve in terms of laminar filling and higher yield than the existing benchmark sprues. Although further development is required. The analysis shows that every step in the project has its own flaws, but that is the nature of being an engineer, as long as the problem encountered can be viewed with critical and analytical eyes. A well-considered and balanced solution can be provided, although nothing of this can be certain before a trail of test can provided to confirm any assumptions which is not included in this work. The discussion section processes the thoughts, experience, and doubts about the project in general and the decision making leading to this report and what could have been done differently. The most significant lesson learn from this is that section is when solving a complex issue there must be very clear delimitations and well-defined goals to every specific solution. Otherwise the workload will be extensive and cause more harm than necessary. The conclusion of this project shows that two concepts generated with the help from the product development process work better than the case study, which can be found in section 4.3, that was based on “PMG running spreadsheet TPC” calculation model, from the velocity perspective. To achieve this, the sprue uses its own geometry constrain and constricts the flow by collecting the molten metal in a “well” before the calmer stream could be distributed throughout the whole cavity. Indirectly this means that the studied material given from TPC AB could not be directly implemented into the investment production process. The given material should be seen as a complement and guidance when creating new sprues. Concerning the FEM analysis tool, it was helpful in this project in evaluating the sprues geometry expose to the assumed force in the production process to avoid unnecessary failure and therefore waste. Although if the company do not intend further work with the development of other sprues then this method is not necessary and would not have significant value to their current manufacturing process.
27
Silva, Roney Carlos da. "Mecanismos de condução e relaxação elétrica em cerâmicas multiferróicas de Pb(Fe2/3W1/3)O3 e Pb(Fe1/2Nb1/2)O3." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/4976.
Full textAbstract:
Made available in DSpace on 2016-06-02T20:15:32Z (GMT). No. of bitstreams: 1
5887.pdf: 17427536 bytes, checksum: 86a72410b26eb5474b5d0a693e193449 (MD5)
Previous issue date: 2013-12-19Financiadora de Estudos e Projetos
Multiferroic are materials which have at least two of the three ferroics orders: ferromagnetism, ferroelectricity and/or ferroelasticity. The coupling between these properties, make multiferroic materials of great technological and scientific interest, mainly in the design of new devices such as sensors and spintronic devices. The lead iron tungstate Pb(Fe2=3W1=3)O3 (PFW) is a relaxor multiferroic with ferroelectric transition TC ~ 180K and antiferromagnetic TN ~ 340K, it is a member of the relaxor ferroelectrics family with perovskite structure, in which the two types of cations (Fe3+ e W6+) are randomly distributed in the B site, causing the formation of polar nanoregions (or clusters) of order/disorder at microscopic scale, which would be the origin of the relaxor behavior. Lead iron niobate Pb(Fe1=2Nb1=2)O3 (PFN) is a ferroelectric with diffuse phase transition (DPT) around TC ~ 380K and antiferromagnetic, with the G-type ordering below the Néel temperature, reported in TN ~ 143K. This material has a high dielectric constant, and excellent ferroelectric properties. The Pb2+, at site A, and Nb5+, at site B are responsible for the ferroelectric order, as the Fe3+ at site B is responsible to provide the necessary magnetic moment for the magnetic ordering. In this work, the electrical conduction and relaxation mechanism of multiferroics PFW and PFN ceramics were investigated. The PFW and PFN samples were prepared by solid state reaction method through two stages. This method was effective to obtain samples with majoritary perovskite phase (95,6% and 95,7%), respectively. After the densification process through sintering methods used in this work (conventional sintering, hot pressing and spark plasma), the perovskite phase was increased, being almost 100 %. The samples of PFW and PFN obtained by the different densification techniques, were dense and practically free of pores. For the analysis of the dielectric response of the samples, it was proposed in this work, an analysis protocol, which was effective to find the responsible mechanisms for the dielectric response of the studied materials. Two relaxation processes were identified for each studied sample, which were labeled as: PR-1, PR-2 or PR *. These processes can be attributed to the interfacial polarization and polarization by hopping, occurring due to the presence of defects in the lattice, such as the oxygen vacancies and lead vacancies. From the dependence of the DC electrical conductivity versus temperature, it was possible to identify regions with different mechanisms of electrical conduction for the samples of PFW and PFN. These mechanisms are, thermally activated at high temperatures, hopping of small polarons at intermediate temperatures and variable range hopping at low temperatures.
Multiferróicos são materiais que têm pelo menos duas das três ordens ferróicas: ferromagnetismo, ferroeletricidade e/ou ferroelasticidade. O acoplamento entre essas propriedades, faz com que os materiais multiferróicos despertem um grande interesse científico e tecnológico, principalmente na concepção de novos dispositivos, como sensores e dispositivos de spintrônica. O tungstanato de ferro e chumbo Pb(Fe2=3W1=3)O3 (PFW) é um multiferróico relaxor com transição ferroelétrica TC ~ 180K e antiferromagnética TN ~ 340K, ele é membro da família dos ferroelétricos relaxores com uma estrutura perovskita, em que os dois tipos de cátions (Fe3+ e W6+) são aleatoriamente distribuídos no sítio B, fazendo com que em escala microscópica existam nanoregiões polares (ou clusters) de ordem/desordem neste sítio, que seriam a origem do comportamento relaxor. O niobato de ferro e chumbo Pb(Fe1=2Nb1=2)O3 (PFN) é um ferroelétrico com transição de fase difusa (TFD) ao redor de TC ~ 380K, e antiferromagnético, com ordenamento do tipo-G abaixo da temperatura de Néel reportada em TN ~ 143K. Ele ainda apresenta uma alta constante dielétrica, além de excelentes propriedades ferroelétricas. Neste material o Pb2+, no sítio A, e Nb5+, no sítio B são responsáveis pelo ordenamento ferroelétrico, enquanto o Fe3+ no sítio B é responsável em fornecer o momento magnético necessário para o ordenamento magnético. Neste trabalho, os mecanismos de condução e relaxação elétrica das cerâmicas multiferróicas de PFW e PFN foram investigados. As amostras de PFW e PFN foram preparadas por reação de estado sólido através do método de dois estágios, que se mostrou eficaz na obtenção de amostras com fase perovskita majoritaria (95,6% e 95,7%), respectivamente. De modo geral, essas amostras ao passar pelo processo de densificação através dos métodos de sinterização utilizados nesse trabalho (sinterização convencional, sinterização por prensagem uniaxial a quente e sinterização por spark plasma), tiveram suas fases perovskitas majoritarias aumentadas, chegando à praticamente 100%. As amostras de PFW e PFN, obtidas pelas diferentes técnicas de densificação, mostraram-se densas e praticamente livres de poros. Para análise da resposta dielétrica apresentada por essas amostras, foi proposto neste trabalho um protocolo de análise, que se mostrou eficaz em descrever o comportamento da resposta dielétrica apresentado pelas mesmas. Foram identificados dois processos de relaxação para cada amostra em estudo, os quais foram identificados por: PR-1, PR-2 ou PR*. Esses processos podem ser atribuídos à polarização interfacial e à polarização por salto, os quais ocorrem pela presença de defeitos na rede, tais como, as vacâncias de oxigênio e as vacâncias de chumbo. Através da dependência da condutividade elétrica DC em função da temperatura, foi possível identificar regiões com diferentes mecanismos de condução para as amostras de PFW e PFN. Dentre eles estão, ativação térmica em altas temperaturas, hopping de pequenos polarons em temperaturas intermediárias e hopping de alcance variável em baixas temperaturas.
28
Bendaoud, Rachid. "Propriétés magnétiques de particules finement divisées d'oxyde de fer Fe0 étude de la dynamique du verre de spin Fe,Mg,Cl /." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37611791w.
Full text
29
Bicha-Benkirat, Dalila. "Pouvoir thermoélectrique du fer et des alliages fer-azote et fer-carbone." Lyon, INSA, 1985. http://www.theses.fr/1985ISAL0062.
Full textAbstract:
Le but de l’étude était de déterminer les relations entre les variations du pouvoir thermoélectrique (PTE), mesuré à 20°C ou en fonction de la température, et l’état microstructure du fer et des alliages fer-azote et fer-carbone. La première partie concerne f’effet de l’écroussiage du der pur, de la restauration et de la recristallisation, ainsi que l’influence du carbone et de l’azote en solution solide : les dislocations et les atomes interstitiels réduisent essentiellement la composante de réseau du PTE. La deuxième partie porte sur les cinétiques de précipitation des nitrures et carbures de fer. Pour interpréter les variations du PTE on considère que cette propriété est sensible essentiellement à la teneur résiduelle en azote ou en carbone en solution solide ; Différentes techniques complémentaires sont utilisées : frottement intérieur, résistivité, microscopie électronique. Les différents stades de précipitation sont mis en évidence : - formation de Fe₁₆N₂ puis Fe₄N dans le fer-azote, - formation de la phase ε puis de Fe₃C dans le fer-carbone, un stade inital précédent la formation de la phase ε semble confirmé par nos résultats.
30
Benkirat, Dalila. "Pouvoir thermoélectrique du fer et des alliages fer-azote et fer-carbone." Grenoble : ANRT, 1985. http://catalogue.bnf.fr/ark:/12148/cb37594492m.
Full text
31
Yaméogo, Urbain Gnourègma. "Le feu, un outil d'ingénierie écologique au Ranch de Gibier de Nazinga au Burkina Faso." Orléans, 2005. http://www.theses.fr/2005ORLE2087.
Full textAbstract:
L’étude a porté sur les effets de divers types de feux sur les principaux milieux végétaux du Ranch de Gibier de Nazinga au Burkina Faso ainsi que les perceptions du milieu et les pratiques de feux des populations riveraines. L’objectif a été de suivre l’évolution de la végétation ligneuse et herbacée après le feu et en déduire l’usage qu’on peut faire du feu comme outil de gestion du milieu ; et de mettre en évidence les connaissances locales et les pratiques de feu des populations locales en vue de concilier les objectifs de production et de conservation du Ranch. Les effets des feux sur la végétation ont été étudiés à partir de parcelles installées dans trois milieux végétaux différents et soumises à trois types de feu. Les perceptions du milieu par les populations riveraines et les pratiques de feux dans la zone ont été faites à l’aide d’enquêtes et d’observations participantes. Le comportement alimentaire des herbivores sauvages induit par les feux contrôlés a été fait à partir d’observations directes dans les milieux brûlés et d’enquêtes auprès des acteurs. L’étude a permis de montrer que les effets du feu sur la végétation du Ranch de Gibier de Nazinga diffèrent selon le type de feu, le type de végétation, les espèces végétales et les conditions climatiques. Elle a mis en évidence des modifications due à l’influence du feu sur la composition floristique, la richesse floristique, la production de repousses et l’évolution de la végétation. L’étude a montré que les populations riveraines du Ranch ont des pratiques socioculturelles liées au feu. L’utilisation raisonnée du feu en savane permet d’en faire un outil de gestion sans une dégradation du milieu.
32
Roussel, Bertrand. "Contribution à l'étude d'une technique préhistorique : la production du feu par percussion de la pierre." Montpellier 3, 2005. http://www.theses.fr/2005MON30002.
Full textAbstract:
Ce travail a pour ambition de faire le point sur la production du feu par percussion de la pierre et sur l'utilisation de cette technique durant la Préhistoire, à partir d'une double approche : expérimentale et ethnographique. La première partie propose une présentation de la production du feu par percussion ainsi que les résultats de nos expérimentations. La deuxième section a pour but de mettre en lumière l'emploi de cette technique par les peuples actuels et subactuels afin de d'évaluer son utilisation durant la Préhistoire. Les deux derniers chapitres sont consacrés aux vestiges archéologiques liés à ce mode d'allumage du feu : la troisième partie traite des objets lithiques, alors que la quatrième propose une approche des nombreux matériaux organiques aptes à s'embraser au contact des étincelles produites par la percussion et développe une réflexion sur l'interprétation de certains vestiges organiques, mis au jour en milieu humide, dans différents sites préhistoriquesThe aim of this work is to take stock of the production of fire by stone striking and the use of this technique during prehistory. It is based on a dual approach: both experimental and ethnographic. The first part presents the production of fire by stone striking, as well as the results of our own experimentations in that field. The objective of the second section is to highlight the use of this technique by present peoples all over the world, in order to better estimate its use during prehistoric times. The last two chapters are dedicated to the archaeological remains which can be linked with this method of fire lighting. The third part deals with lithic artifacts, whereas the fourth one proposes an approach to the numerous organic materials able to catch fire when in contact with the sparks produced by the striking of two stones. It also develops a reflection on the interpretation of some organic remains that have been unearthed in a humid environment in different prehistoric sites
33
Nordström, Veronica. "Fem blivande officerare & fem blivande stridspiloter." Thesis, Malmö högskola, Lärarutbildningen (LUT), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:mau:diva-32423.
Full textAbstract:
SAMMANFATTNINGDet sägs att vi lever i ett individualistiskt och flexibelt samhälle. För den starka individen innebär detta att karriär, utveckling och privata intressen värderas högre än lojalitet gentemot arbetsgivaren. Att byta arbetsgivare under sitt yrkesverksamma liv betraktas idag mer som regel än undantag. Hur resonerar då blivande officerare och stridspiloter som har valt att utbilda sig till ett yrke som endast går att utöva i en enda organisation? Kan studenter, som i princip bara har en arbetsgivare att välja på, verkligen ha behov av karriärvägledning? Syftet med studien är att få en förståelse för hur blivande officerare och stridspiloter ser på sig själva i organisationen, samt vilka upplevda behov de har av karriärvägledning. För att undersöka detta område närmare har jag genomfört gruppintervjuer med fem blivande officerare och fem blivande stridspiloter. Resultatet visar att en majoritet av deltagarna i studien har en marknadsmässig inställning. Karriär, utveckling och privata intressen är i hög grad styrande för deras val, men de visar också tecken på institutionalisering då de har tagit till sig organisationens värderingar som sina egna. Studenterna upplever ett behov av både taktisk och strategisk karriärvägledning.
34
Awad, Carmen. "Études numériques et expérimentales des feux marginaux." Thesis, Corte, 2021. http://www.theses.fr/2021CORT0001.
Full textAbstract:
La lutte contre les incendies de forêt commence très en amont des départs de feux par une politique volontariste de prévention du risque. Une des méthodes la plus utilisée est la réduction de la charge du combustible en utilisant la technique des feux contrôlés appelés aussi feux dirigés. Ces feux sont souvent menés en forêt et doivent être à faible intensité pour ne pas causer des dégâts importants sur les arbres et sur le sol. Ainsi, ils sont toujours conduits avec des conditions de propagation marginales. Ainsi une légère modification de ces conditions peut provoquer leur extinction. En effet, la probabilité de succès de ce type de feux dépend de plusieurs facteurs naturels (température ambiante, humidité relative, vitesse de vent…) et également des propriétés du couvert végétal (teneur en eau, forme, taille, densité, …). Le but de cette étude est d’identifier les principales propriétés du combustible permettant une propagation du feu dans ces conditions particulières, ainsi que l’influence de certaines propriétés du combustible et des conditions météorologiques (vitesse de vent, température ambiante, …) sur le comportement des feux marginaux. La valeur seuil de la teneur en eau provoquant une extinction sera plus particulièrement investiguée.Dans un premier travail portant sur la détermination de la teneur en eau d’extinction sous conditions de vent et pente nuls, trois modèles ont été utilisés : un modèle physique complet, basé sur une approche multiphasique (« FireStar2D »), un modèle analytique publié en 2014 par Balbi et al., et deux modèles expérimentaux, dont le premier est basé sur des séries de tests de brûlages réalisés au sein du laboratoire UMR CNRS SPE 6134 de l’université de Corse et dont le deuxième, purement empirique, a été proposé par Wilson en 1985. Ainsi, des simulations ont été réalisées avec FireStar2D à l’échelle du terrain, pour l’herbe et le maquis sous des conditions de vent faible et de pente nulle. En outre, des tests de brûlages sont menés à partir de la frisure de bois à l’échelle du laboratoire. Les différents résultats des simulations et des tests expérimentaux sont en adéquation avec ceux obtenus avec le modèle semi-physique. De plus, cette étude a permis de mettre en évidence l’effet de la charge surfacique et du LAI, « Leaf Area Index », sur le seuil d’extinction relié à la teneur en eau de la végétation.La deuxième partie de recherche a porté sur la détermination de la teneur en eau d’extinction sous condition d’un vent modéré ou fort. Des simulations numériques sont menées à l’échelle du terrain avec de l’herbe sous condition de vent afin de relier la teneur en eau d’extinction à la vitesse du vent et à la charge surfacique du combustible. Cette étude a permis également d’évaluer l’influence du vent et de la teneur en eau sur le comportement d’un feu marginal et plus particulièrement sur les caractéristiques de la flamme.Les résultats de ce travail de recherche sont encourageants et très intéressants pour les opérationnels qui travaillent dans les domaines de la gestion de terrain et de la lutte contre les incendies, vu l’importance des applications des feux marginaux dans ces deux domainesWildfire suppression begins before the start of a fire incidence with the application of many proactive prevention policies. One of the most common method is the reduction of the fuel load accumulation by using controlled fires techniques also called prescribed fires. These fires are often conducted in forests and their intensity must be low to prevent any major damage on trees and on the soil. Thus, they must propagate under marginal conditions. So, a slight modification of the propagation conditions can cause their extinction. Indeed, the probability of sustainability of this type of fire depends on several natural factors (ambient temperature, relative humidity, wind speed, etc.) and also on the fuel properties (water content, shape, size, density, specific heat of combustion…). The aim of this study is to identify the fuel properties allowing fire propagation under these particular conditions. Also, the influence of some fuel properties, and of meteorological conditions (wind speed, ambient temperature, etc.) on the behavior of marginal fires and especially on the fuel moisture content of extinction are investigated.During a first work about the determination of the threshold value of the fuel moisture content involving fire extinction under no wind and no slope conditions, three models were used: a complete physical model, based on a multiphase formulation (“FireStar2D”), an analytical model published in 2014 by Balbi et al., and two experimental models. The first one is based on experimental tests carried out in the UMR SPE 6134 laboratory at the University of Corsica and the second one is an empirical model proposed by Wilson in 1985. Thus, field scale simulations were carried out using FireStar2D, with grassland and shrubs as fuel under conditions of light wind and no slope. Moreover, laboratory scale experimental burnings were conducted with excelsior fuel beds. The different results of the simulations and the burning tests are in agreement with those obtained with the semi-physical model. In addition, the effect of fuel load and the LAI, « Leaf Area Index », on the fuel moisture extinction threshold are studied.In a second study, several field scale numerical simulations are conducted with grassland under non-zero wind conditions in order to relate the fuel moisture content threshold to wind speed and to fuel load. This study also allows us to evaluate the influence of wind speed and fuel moisture content on marginal fire behavior and especially on flame characteristics.The results are encouraging and interesting to operational people working in fire management and firefighting fields, given the importance of marginal fire applications in these two domains
35
Ulfberg, Adrian. "Probabilistic non-linear finite element analysis of concrete buttress dams." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-72701.
Full textAbstract:
Assessment of concrete buttress dams today consists of using analytical methods to investigate the stability in different failure modes. However, they simplify the problem at hand and neglect certain important features linked to geometry and thus not truthfully appraise the structures real stability. This could be economically costly in assessments of both existing dam structures as this would eventually lead to unwarranted rehabilitation. The same can be said for dams under design. Kalhovd dam is a concrete buttress dam that has recently undergone assessment where certain sections proved unstable in either failure mode. This study focused specifically on a buttress, numbered 49, of said dam which was deemed in the assessment to be unstable in the overturning and sliding failure mode. The methodology used was to assess and compare stability for different methods of calculation, meaning analytical versus numerical analysis. The numerical analysis was performed with two-dimensional finite element analyses in a commercial FEM-software called ATENA which focuses on reinforced concrete structures. The numerical models made, were then probabilistically analysed by randomizing various material parameters to see their effect on stability. Some FEA models discarded the conventional way of modelling loads, as required by standards, to more realistically portray load actions on dams based on historical measurement. Results from this study showed dissimilarity of stability for buttress 49 depending on which method of analysis was performed. Analytical methods proved to yield the most conservative results and concluded the structure unsafe, while including an accurate representation of the geometry in FEA models improved the stability such that it can be considered stable against load actions stated in guidelines. Furthermore, material parameters randomized in the probabilistic analysis substantiated that various concrete variables had relatively little effect on structural overall strength in the most common failure modes.
36
PADUR, DIVYACHAPAN SRIDHARAN. "DEVELOPMENT AND TESTING OF AN ENHANCED PREPROCESSOR FOR CREATING 3D FINITE ELEMENT MODELS OF HIGHWAY BRIDGES AND A POST PROCESSOR FOR EFFICIENT RESULT GENERATION." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1078472870.
Full text
37
Gradin, Ebba. "Fel är inte fel : när fel är en del av att göra rätt." Thesis, Konstfack, IBIS - Institutionen för bild- och slöjdpedagogik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-7350.
Full textAbstract:
I studien behandlas frågeställningen ”Hur kan fel användas som ett verktyg av elever i bildämnets skapande processer?”. Med antagandet om att rätt och fel är en norm i skolan och dess undervisning har jag spenderat en vecka med en klass i årskurs åtta. Där utfördes en deltagande observation och några intervjuer. Syftet med studien var att identifiera normen om rätt och fel i skolundervisningen för att se hur elever kan arbeta med sina fel i bildämnets skapande processer. Studien vägleds av ett sociokulturellt perspektiv – där interaktion och kollektivt lärande var av intresse. Det är med denna teoretiska utgångspunkt jag analyserat resultatet från studien och finner att många av eleverna interagerar med varandra för att ta sig framåt i sina processer. De interagerar med läraren om klasskompisarna inte har svaret de söker. Resultatet från studien visar att fel i bildämnets skapande processer kan tas tillvara genom bland annat språkliga verktyg samt att det krävs trygghet för att eleven ska våga prata om sina fel. Andra exempel på verktyg är kunskaper om olika tekniker och material för att självständigt navigera genom dessa i sina projekt. Ges dessa förutsättningar kan fel användas som ett meningsfullt verktyg i bildundervisningen. Som gestaltning till studien har en Skolplansch framställts. Denna skolplansch följer en skoltradition där rätt redovisas i tydligt manér, men denna plansch berättar om någonting annat. Den uppmuntrar, bekräftar och påminner om att fel kan uppstå. Skolplanschen välkomnas in i ett 2020 talets bildklassrum där fel är en del av att göra rätt.
38
Nascimento, William Junior do. "Sinterização de cerâmicas multiferróicas nanoestruturadas de Pb(Fe1/2Nb1/2)O3 e Pb(Fe2/3W1/3)O3 via Spark Plasma Sintering SPS." Universidade Federal de São Carlos, 2013. https://repositorio.ufscar.br/handle/ufscar/4960.
Full textAbstract:
Made available in DSpace on 2016-06-02T20:15:28Z (GMT). No. of bitstreams: 1
5160.pdf: 6005480 bytes, checksum: 6aae866e51fab054ffc455e4b0479f2f (MD5)
Previous issue date: 2013-02-25Financiadora de Estudos e Projetos
Considering the search for miniaturization of electronic devices, the development of new methods and techniques for the production and characterization of nanostructured materials is fundamental, beyond understanding of the effect of grain size on the properties of materials in nanoscale. Therefore, it was proposed in this work the obtaining of nanostructured multiferroic materials, in bulk, with high density and microstructural control, with grains ranging from micrometer to nanometer scale. To achieve this goal, was developed a methodology for obtaining the powder of lead iron niobate, Pb(Fe1/2Nb1/2)O3 (PFN) and lead iron tungstate, Pb(Fe2/3W1/3)O3 (PFW), with average particle size around 150 nm, contamination-free, minimal agglomeration and with highly reproductive results using the micro-milling technique. Regarding consolidation materials, conventional sintering requires higher temperatures and long holding times for a satisfactory densification, resulting in a grain growth higher than the desired. Through the fast sintering technique, only high heating rates are not sufficient to ensure a satisfactory densification and also inhibit the growth of grains. The obtain nanostructured dense samples with average grain size of approximately 200 nm was only possible using spark plasma sintering technique (SPS), which allows sintering at temperatures corresponding to the intermediate sintering stage, inhibiting the grain growth. PFN and PFW samples obtained through the SPS technique showed high conductivity at room temperature due the extreme reduction suffers in the system plus the use of high current densities during sintering, being necessary the samples oxidation. Through the dielectric characterization, the decrease in grain size of micrometer to nanometer scale results in lower permittivity values in phase transition temperature, besides a peak broadening. Moreover, the SPS technique added to the oxidation process makes it possible to obtain PFW samples with high dielectric values (in order of 104) at room temperature, a motivation results with regard to the application.
Considerando a busca pela miniaturização dos dispositivos eletrônicos é fundamental o desenvolvimento de novos métodos e técnicas para a produção e caracterização de materiais nanoestruturados, além do entendimento do efeito do tamanho de grão sobre as propriedades dos materiais em escala nanométrica. Dessa forma, propôs-se neste trabalho a obtenção de materiais multiferróicos nanoestruturados, na forma de bulk com alta densidade e controle microestrutural, com grãos variando de escala micrométrica a nanométrica. Para alcançar este objetivo, foi desenvolvida uma metodologia para a obtenção de pós de niobato de ferro e chumbo, Pb(Fe1/2Nb1/2)O3 (PFN) e tungstanato de ferro e chumbo, Pb(Fe2/3W1/3)O3 (PFW), com tamanhos médios de partículas em torno de 150 nm, livre de contaminação, mínima aglomeração e com resultados altamente reprodutivos por meio da técnica de micromoagem. Em relação à consolidação dos materiais, o procedimento convencional requer altas temperaturas e longos tempos de patamar para uma densificação satisfatória, resultando em um crescimento de grão superior ao desejado. Por meio da técnica de sinterização rápida fast sintering , somente altas taxas de aquecimento não são suficientes para garantir uma densificação satisfatória bem como inibir o crescimento de grãos. A obtenção de amostras densas nanoestruturadas com tamanhos médio de grão de aproximadamente 200 nm só foi possível utilizando a técnica spark plasma sintering (SPS), que permite a sinterização a temperaturas correspondentes ao estágio intermediário de sinterização, inibindo o crescimento de grãos. As amostras de PFN e PFW obtidas por meio da técnica de SPS apresentaram alta condutividade à temperatura ambiente devido às condições extremas de redução que a amostra sofre somada ao uso de altas densidades de corrente durante a sinterização, sendo necessária a oxidação das mesmas. Através da caracterização dielétrica, verifica-se que a diminuição nos tamanhos de grãos de escala micrométrica para nanométrica resulta em menores valores de permissividade na temperatura de transição de fase, além de um alargamento dos picos. Contudo, a técnica de sinterização SPS somada ao processo de oxidação torna possível a obtenção de amostras de PFW com altos valores de constate dielétrica (na ordem de 104), a temperatura ambiente, resultado extremamente motivador no que diz respeito à aplicação.
39
Rocha, HÃlio Henrique Barbosa. "Estudo das propriedades estruturais e de transporte dos compÃsitos magneto-dielÃtricos [(Fe5/8Cr3/8)2O3]x-[(Fe1/4Cu3/8Ti3/8)2O3]100âx." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=7065.
Full textAbstract:
O processamento em escala laboratorial de soluÃÃes sÃlidas, procedentes dos sistemas Fe2O3/CuO/TiO2 e Fe2O3/Cr2O3, dos seus compÃsitos, e o estudo das propriedades estruturais e de transporte estabelecem o tema principal do trabalho. As granadas ferrimagnÃticas despertam manifesto interesse quanto ao seu emprego em dispositivos aplicÃveis a sistemas de telecomunicaÃÃo operantes nas microondas, sobretudo, em funÃÃo das propriedades dielÃtricas e magnÃticas adequadas. Devido à semelhanÃa estequiomÃtrica, e com a finalidade de se obter materiais com propriedades similares, foram elaborados dois meios magneto-dielÃtricos: (Fe1/4Cu3/8Ti3/8)2O3, um titanato de cobre e ferro, e (Fe5/8Cr3/8)2O3, um Ãxido especÃfico de ferro e cromo. Estas soluÃÃes sÃlidas substitucionais foram sintetizadas por reaÃÃo de estado sÃlido. O processamento avanÃou envolvendo tratamentos mecÃnico e tÃrmico. Foram preparados espÃcimes pulverulentos e com configuraÃÃo definida. A estrutura cristalina dos espÃcimes foi identificada por difraÃÃo de raios-X. Os dados de difraÃÃo de raios-X por policristais foram refinados pelo emprego do mÃtodo de Rietveld. Fez-se uso da espectroscopia MÃssbauer para realizar a sondagem do ferro presente na estrutura cristalina. A morfologia dos espÃcimes, dispostos como peÃas cilÃndricas rÃgidas, foi explorada por Microscopia EletrÃnica de Varredura, assistida por microssonda EDX, para anÃlise quÃmica elementar. Por espectroscopia dielÃtrica foram investigadas as propriedades dielÃtricas permissividade dielÃtrica relativa e fator de perda dielÃtrico e a propriedade de transporte condutividade elÃtrica. As propriedades dielÃtricas e de transporte foram analisadas em funÃÃo da freqÃÃncia, a temperatura ambiente, numa faixa compreendida entre 100 Hz e 40 MHz. Dos dados por difraÃÃo de raios-X, alÃm da identificaÃÃo dos materiais avaliados, foram extraÃdas, apÃs refinamento estrutural, informaÃÃes cristalogrÃficas, no caso das soluÃÃes sÃlidas individuais, e sua quantificaÃÃo, no caso dos compÃsitos por elas constituÃdos. Pela espectroscopia MÃssbauer foram confirmados o estado de oxidaÃÃo do ferro presente nos materiais analisados, a geometria do sÃtio cristalino no qual està presente, a natureza magnÃtica das amostras, e seu provÃvel ordenamento, alÃm da quantificaÃÃo realizada em funÃÃo da quantidade de ferro presente nos compÃsitos. A morfologia dos materiais Ã, em geral, caracterizada pela diversidade de formas e tamanhos dos grÃos, bem como sua disposiÃÃo no artefato explorado. A anÃlise quÃmica elementar forneceu resultados quantitativos acerca dos elementos presentes nos meios investigados. Pela resposta observada na faixa de freqÃÃncia percorrida, ficou evidenciada uma regiÃo de dispersÃo, caracterÃstica do processo de polarizaÃÃo dipolar. Os resultados das propriedades dielÃtricas para as fases sintetizadas mostraram-se parcialmente antagÃnicos: a fase IB100 apresentou a maior permissividade dielÃtrica relativa, porÃm, maior fator de perda dielÃtrica em relaÃÃo à fase IC100, que por sua vez apresentou a menor permissividade dielÃtrica relativa entre todos os materiais investigados. Para os compÃsitos, formados pela mistura aleatÃria de quantidades especÃficas das duas fases sintetizadas, foi evidenciado um comportamento nÃo linear, de forma que estes nÃo representam apenas o reflexo das respostas observadas para as fases individualmente. A fase IB100, em virtude da constante dielÃtrica observada, à o material com maior potencial para aplicaÃÃes em altas freqÃÃncias.
40
Audonnet, Jean-Christophe Francis. "Protéines de la membrane externe régulées par le fer chez Escherichia coli : clonage, expression et propriétés de Iut A et Fep A." Lyon 1, 1989. http://www.theses.fr/1989LYO10036.
Full textAbstract:
Pour acquerir le fer, rendu indisponible chez l'hote par suite de sa complexation aux transferrines, les bacteries pathogenes disposent de systemes de transport hautement specialises. L'expression de ces systemes est regulee par la concentration en fer, et se traduit par l'excretion d'un siderophore (compose chelateur du fer) et la synthese d'un recepteur proteique, specifique du siderophore ferrique, situe dans la membrane externe de la bacterie. Les deux principaux recepteurs de siderophores mis en evidence chez les escherichia coli septicemiques sont les proteines ivt a et fep a, qui correspondent respectivement aux siderophores aerobactine et enterobactine. Apres avoir montre que la presence, au niveau de la membrane externe, des proteines regulees par le fer accroit la protection induite par vaccination avec des corps bacteriens entiers, le but de ce travail a ete de produire les proteines ivt a et fep a, par recombinaison genetique, en absence de toute regulation par le fer. La comparaison des sequences nucleotidiques de trois genes ivta, isoles de souches e. Coli d'origines differentes, montre que la conservation antigenique de la proteine ivt a provient d'une stricte conservation du gene ivt a au sein de l'operon aerobactine. Les genes ivt a et fep a ont ete clones dans un vecteur d'expression. L'expression des genes se fait en l'absence de regulation par le fer et conduit a la synthese massive des proteines ivt a et fep a et de leurs precurseurs sous forme d'inclusions intracytoplasmiques, en meme temps que les recepteurs synthetises s'integrent de facon normale dans la membrane externe. Ces derniers sont fonctionnellement et antigeniquement identiques a leurs homologues naturels
41
Audonnet, Jean-Christophe. "Protéines de la membrane externe régulées par le fer chez Escherichia coli clonage, expression et propriétés de Iut A et Fep A /." Grenoble 2 : ANRT, 1989. http://catalogue.bnf.fr/ark:/12148/cb37611354k.
Full text
42
Liu, Fei. "Réactions de fluoration de dérivés azotés insaturés en milieu superacide." Poitiers, 2010. http://theses.edel.univ-poitiers.fr/theses/2010/Liu-Fei/2010-Liu-Fei-These.pdf.
Full textAbstract:
L'utilisation des milieux superacides modifiant la réactivité des substrats organiques permet d'effectuer de nouvelles réactions et d'accéder rapidement à des produits originaux difficilement accessibles par les méthodes classiques. Il est alors possible de réaliser de nombreuses transformations directes, notamment des réactions de fluoration originales. Ce travail est consacré à l'étude de la réactivité de dérivés azotés insaturés en milieu superacide HF/SbF5 et en particulier au développement de nouvelles méthodes de fluoration de ce type de composés. Basée sur la formation d'intermédiaires dicationiques superélectrophiles, une nouvelle réaction d'hydrofluoration a été développée. L'utilisation de l'activation superélectrophile en milieu superacide a également permis la synthèse originale de sulfonamides cycliques et/ou fluorés. Après identification d'intermédiaires réactionnels polycationiques par analyse RMN in situ, une nouvelle méthode de synthèse de dérivés azotés gem-chlorofluorés et gem-difluorés a finalement été élaboréeIn superacid the reactivity of organic substrates is strongly modified and new reactions can be performed, which allows a rapid access to original products. In these conditions, multiple direct transformations occur and especially original fluorination reactions. This work was devoted to the study of the reactivity of unsaturated nitrogen derivatives in superacid (HF/SbF5) and to the development of new methods of fluorination of these compounds. Based on the formation of superelectrophilic dicationic intermediates, a new reaction of hydrofluorination has been developed. The use of superelectrophilic activation in superacid also allowed the original synthesis of benzofused sultams and/or fluorinated sulfonamides. After identification of reaction polycationic intermediates by NMR in situ analysis, a new synthetic route to gem-chlorofluoro nitrogen derivatives or gem-difluoro nitrogen derivatives has finally been set up
43
Freire, Francisco Nivaldo Aguiar. "SÃntese e estudo das propriedades estruturais e dielÃtricas de matrizes cerÃmicas compÃsitas (CMC) baseadas em: (Fe1/4Cu1/8Ti3/8)2O3 / (Fe5/8Cr3/8)2O3 / Pb(Fe1/2Nb1/2)O3 / CaTiO3 para uso em dispositivos eletrÃnicos." Universidade Federal do CearÃ, 2008. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1401.
Full textAbstract:
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgicoNeste trabalho utilizou-se reaÃÃes do estado sÃlido com sucesso na produÃÃo de matrizes cerÃmicos compositas a base de Cr0,75Fe1,25O3(CRFO100), Fe0,5Cu0,75Ti0,75O3(FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO), para o estudo de suas propriedades estruturais e elÃtricas visando o seu possivel uso em circuitaria eletrÃnica, de rÃdio-frequencia e microondas. Os procedimentos envolvidos para obtenÃÃo das amostras seguiram a rota de produÃÃo de cerÃmicas, sendo que numa primeira etapa realizou-se a homogeneizaÃÃo dos pÃs com o objetivo de tornar a reaÃÃo mais eficaz, pois a promoÃÃo do contato por igual dos reagentes facilita a formaÃÃo da substÃncia desejada. ApÃs o procedimento de homogeneizaÃÃo, a obtenÃÃo de cada sÃrie de amostras seguiram suas caracterÃsticas operacionais, como por exemplo: tempo e temperatura de reaÃÃo. As duas primeiras sÃries Cr0,75Fe1,25O3(CRFO100)-- Fe0,5Cu0,75Ti0,75O3 (FCTO100), e Pb(Fe0,5Nb0,5O3) (PFN100)--Cr0,75Fe1,25O3 (CRFO100), foram estudadas por raios-X, MEV, EDSX, espectroscopia MÃssbauer, propriedades elÃtricas em funÃÃo da temperatura, caracterizaÃÃes na faixa de micoondas com a tÃcnica Hakki-Coleman e por Ãltimo a caracterizaÃÃo das amostras como antenas ressoadoras dielÃtricas. A Ãltima sÃrie Cr0,75Fe1,25O3 (CRFO100)-- CaTiO3 (CTO) foi estudada por todas as tÃcnicas mencionadas, com exceÃÃo das tÃcnicas MEV, EDSX, espectroscopia MÃssbauer. Este trabalho tem como objetivo sintetizar, caracterizar novas materiais ceramicos compositos para uso em dispositivos eletrÃnicos, microondas e radio-freqÃÃncia. Foram sintetizadas e caracterizadas amostras com as seguintes estequiometrias: Cr0,75Fe1,25O3 (CRFO100), Fe0,5Cu0,75Ti0,75O3 (FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO). Mediante a sÃntese das amostras anteriomente relatadas procedeu-se a formaÃÃo dos compÃsitos em diferentes concentraÃÃes e consequente formaÃÃo das sÃries na seguinte ordem: (CRFO)x-(FCTO)100-x, com x= 0, 17, 34, 50, 66, 83 e 100% em massa; (PFN)x -(CRFO)100-x, com x = 0, 10, 50, 90 e 100% em massa e xCRFO- (1- x)CTO com x= 0, 10, 50, 90 e 100% em mol. A identificaÃÃo e o subsequente refinamento dos dados para a primeira sÃrie revelaram uma estrura trigonal para o CRFO100 e uma estutra cÃbica para o FCTO100. no caso da segunda sÃrie o PFN100 apresentou uma estrutura tetragonal e na terceirasÃrie o CTO uma estrutura ortorrÃmbica. Pela espectrosocopia MÃssbauer foram confirmados no caso das duas primeiras sÃries, o estado de oxidaÃÃo do ferro (Fe3+) presente nas amostras analisadas e sua coordenaÃÃo no sÃtio cristalino em funÃÃo da quantidade de ferro presente nos compÃsitos. Com exceÃÃo do PFN100, a morfologia das amostras em geral foi caracterizada pela diversidade de formas e tamanho para todas as amostras das duas primeira sÃries. A anÃlise quÃmica elementar forneceu resultados quantitativos acerca dos elementos presentes nas amostras investigadas. Pelas respostas observadas na faixa de radio-freqÃÃncia, ficou evidenciada uma regiÃo de dispersÃo, caracteristica de processo de polarizaÃÃo dipolar. Experimentos foram realizados com variaÃÃo de temperatura e as propriedades dielÃtricas foram medidas (permissividade e perda dielÃtrica). Foi obtido o TCC (Coeficiente de Temperatura da CapacitÃncia), numa faixa de temperatura de 250C a 1000C, observando que as duas primeiras sÃries apresentaram relaxaÃÃo ativada pela temperatura. Medidas na regiÃo de microondas (300 MHz < f < 30 GHz) foram realizadas, no caso da primeira sÃrie para as amostras CRFO100, CRFO50 e FCTO100. Os resultados apresentados sÃo promissores para aplicaÃÃes como dispositivos em microondas. No caso da segunda sÃrie apenas em duas amostras (CRFO100 e PFN10) foi possÃvel determinar a freqÃÃncia ressonante, permissividade dielÃtrica e a perda dielÃtrica pelo o mÃtodo utilizado neste estudo (mÃtodo Hakki-Coleman), provalvelmente devido a elevada perda dielÃtrica apresentada pelas amostras. Para a terceira sÃrie, em todas as amostras foi possÃvel a localizaÃÃo da frequencia ressonante, permissividade dielÃtrica e a perda dielÃtrica. Para a serie CRFO-CTO foi observada a possibilidade de obtenÃÃo de um composito com TCC=0. Amostras nas tres series estudadas apresentam permissividades dieletricas altas (10) e algumas com baixas perdas podendo ser usadas na miniaturizaÃÃo em dispositivos de microndas e aplicaÃÃes em telecomunicaÃÃes
In this work the solid state procedure was used, with success, in the production of ceramic matrix composites based in Cr0,75Fe1,25O3(CRFO100), Fe0,5Cu0,75Ti0,75O3 (FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO), for the study of the structural and electrical properties of these composites for the possible use in electronic, radio-frequency and microwave circuitry. The first two series Cr0,75Fe1,25O3(CRFO100)--Fe0,5Cu0,75Ti0,75O3 (FCTO100), and Pb(Fe0,5Nb0,5O3) (PFN100)--Cr0,75Fe1,25O3 (CRFO100), were studied by the X-ray, MEV, EDSX, MÃssbauer spectroscopy and electrical properties as a function of temperature . The study of the electrical properties at the microwave region was done using the Hakki-Coleman technique and operating the samples as a dielectric resonator antenna. The series Cr0,75Fe1,25O3 (CRFO100)--CaTiO3 (CTO) was studied by all the mentioned techniques, except for the techniques MEV, EDSX and MÃssbauer spectroscopy. This work has the objective to synthesize and to characterize new composite materials for use in electronic, microwave and radio-frequency devices. After the synthesis of the samples the formation of the composites in the following series: (CRFO)x-(FCTO)100-x, with x = 0, 17, 34, 50, 66, 83 and 100% in mass; (PFN)x - (CRFO)100-x, with x = 0, 10, 50, 90 and 100 in mass % and xCRFO - (1-x)CTO with x = 0, 10, 50, 90 and 100 in mol %. The identification and the subsequent refinement of the data for the first series revealed a trigonal structure for the CRFO100 and a cubic structure for the FCTO100. In the case of the second series, the PFN100 present a tetragonal structure and in the third series, the CTO present an ortorhombic structure. The MÃssbauer spectroscopy confirmed in the case of the first two series, the state of oxidation of the iron (Fe3+) and itÂs coordination in all composites. Except for the PFN100, the morphology of the grains in the samples was characterized by the diversity in the form and size for all the samples of the first two series. The elementary chemical analysis supplied quantitative results concerning of the present elements in the investigated samples. It was observed by the RF measurements a dispersion which is characteristic of the process of dipolar polarization. The dielectric properties with temperature was also studied. The TCC (Temperature Coefficient of Capacitance) and activation energy associated to the modulus formalism was obtained in a temperature interval of 25oC to 100oC. Measurements in the microwave region (300 MHz
44
Freire, Francisco. "Síntese e estudo das propriedades estruturais e dielétricas de matrizes cerâmicas compósitas (CMC) baseadas em: (Fe1/4Cu1/8Ti3/8)2O3 / (Fe5/8Cr3/8)2O3 / Pb(Fe1/2Nb1/2)O3 / CaTiO3 para uso em dispositivos eletrônicos." reponame:Repositório Institucional da UFC, 2008. http://www.repositorio.ufc.br/handle/riufc/1248.
Full textAbstract:
FREIRE,F.N.A. Síntese e estudo das propriedades estruturais e dielétricas de matrizes cerâmicas compósitas (CMC) baseadas em: (Fe1/4Cu1/8Ti3/8)2O3 / (Fe5/8Cr3/8)2O3 / Pb(Fe1/2Nb1/2)O3 / CaTiO3 para uso em dispositivos eletrônicos . 2008. 168 f. Tese (Doutorado em Química Inorgânica) – Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2008Submitted by irlana araujo (irlanaaraujo@gmail.com) on 2011-11-25T19:16:19Z No. of bitstreams: 1 2008_tes_Fran Freire.pdf: 21853243 bytes, checksum: 806a52bbbcd5d3ef54ef64697b3d49e5 (MD5)
Approved for entry into archive by Aline Nascimento(vieiraaline@yahoo.com.br) on 2011-11-26T11:53:46Z (GMT) No. of bitstreams: 1 2008_tes_Fran Freire.pdf: 21853243 bytes, checksum: 806a52bbbcd5d3ef54ef64697b3d49e5 (MD5)
Made available in DSpace on 2011-11-26T11:53:46Z (GMT). No. of bitstreams: 1 2008_tes_Fran Freire.pdf: 21853243 bytes, checksum: 806a52bbbcd5d3ef54ef64697b3d49e5 (MD5) Previous issue date: 2008-01-24
In this work the solid state procedure was used, with success, in the production of ceramic matrix composites based in Cr0,75Fe1,25O3(CRFO100), Fe0,5Cu0,75Ti0,75O3 (FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO), for the study of the structural and electrical properties of these composites for the possible use in electronic, radio-frequency and microwave circuitry. The first two series Cr0,75Fe1,25O3(CRFO100)--Fe0,5Cu0,75Ti0,75O3 (FCTO100), and Pb(Fe0,5Nb0,5O3) (PFN100)--Cr0,75Fe1,25O3 (CRFO100), were studied by the X-ray, MEV, EDSX, Mössbauer spectroscopy and electrical properties as a function of temperature . The study of the electrical properties at the microwave region was done using the Hakki-Coleman technique and operating the samples as a dielectric resonator antenna. The series Cr0,75Fe1,25O3 (CRFO100)--CaTiO3 (CTO) was studied by all the mentioned techniques, except for the techniques MEV, EDSX and Mössbauer spectroscopy. This work has the objective to synthesize and to characterize new composite materials for use in electronic, microwave and radio-frequency devices. After the synthesis of the samples the formation of the composites in the following series: (CRFO)x-(FCTO)100-x, with x = 0, 17, 34, 50, 66, 83 and 100% in mass; (PFN)x - (CRFO)100-x, with x = 0, 10, 50, 90 and 100 in mass % and xCRFO - (1-x)CTO with x = 0, 10, 50, 90 and 100 in mol %. The identification and the subsequent refinement of the data for the first series revealed a trigonal structure for the CRFO100 and a cubic structure for the FCTO100. In the case of the second series, the PFN100 present a tetragonal structure and in the third series, the CTO present an ortorhombic structure. The Mössbauer spectroscopy confirmed in the case of the first two series, the state of oxidation of the iron (Fe3+) and it´s coordination in all composites. Except for the PFN100, the morphology of the grains in the samples was characterized by the diversity in the form and size for all the samples of the first two series. The elementary chemical analysis supplied quantitative results concerning of the present elements in the investigated samples. It was observed by the RF measurements a dispersion which is characteristic of the process of dipolar polarization. The dielectric properties with temperature was also studied. The TCC (Temperature Coefficient of Capacitance) and activation energy associated to the modulus formalism was obtained in a temperature interval of 25oC to 100oC. Measurements in the microwave region (300 MHz
Neste trabalho utilizou-se reações do estado sólido com sucesso na produção de matrizes cerâmicos compositas a base de Cr0,75Fe1,25O3(CRFO100), Fe0,5Cu0,75Ti0,75O3(FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO), para o estudo de suas propriedades estruturais e elétricas visando o seu possivel uso em circuitaria eletrônica, de rádio-frequencia e microondas. Os procedimentos envolvidos para obtenção das amostras seguiram a rota de produção de cerâmicas, sendo que numa primeira etapa realizou-se a homogeneização dos pós com o objetivo de tornar a reação mais eficaz, pois a promoção do contato por igual dos reagentes facilita a formação da substância desejada. Após o procedimento de homogeneização, a obtenção de cada série de amostras seguiram suas características operacionais, como por exemplo: tempo e temperatura de reação. As duas primeiras séries Cr0,75Fe1,25O3(CRFO100)-- Fe0,5Cu0,75Ti0,75O3 (FCTO100), e Pb(Fe0,5Nb0,5O3) (PFN100)--Cr0,75Fe1,25O3 (CRFO100), foram estudadas por raios-X, MEV, EDSX, espectroscopia Mössbauer, propriedades elétricas em função da temperatura, caracterizações na faixa de micoondas com a técnica Hakki-Coleman e por último a caracterização das amostras como antenas ressoadoras dielétricas. A última série Cr0,75Fe1,25O3 (CRFO100)-- CaTiO3 (CTO) foi estudada por todas as técnicas mencionadas, com exceção das técnicas MEV, EDSX, espectroscopia Mössbauer. Este trabalho tem como objetivo sintetizar, caracterizar novas materiais ceramicos compositos para uso em dispositivos eletrônicos, microondas e radio-freqüência. Foram sintetizadas e caracterizadas amostras com as seguintes estequiometrias: Cr0,75Fe1,25O3 (CRFO100), Fe0,5Cu0,75Ti0,75O3 (FCTO100), Pb(Fe0,5Nb0,5O3) (PFN100) e CaTiO3 (CTO). Mediante a síntese das amostras anteriomente relatadas procedeu-se a formação dos compósitos em diferentes concentrações e consequente formação das séries na seguinte ordem: (CRFO)x-(FCTO)100-x, com x= 0, 17, 34, 50, 66, 83 e 100% em massa; (PFN)x -(CRFO)100-x, com x = 0, 10, 50, 90 e 100% em massa e xCRFO- (1- x)CTO com x= 0, 10, 50, 90 e 100% em mol. A identificação e o subsequente refinamento dos dados para a primeira série revelaram uma estrura trigonal para o CRFO100 e uma estutra cúbica para o FCTO100. no caso da segunda série o PFN100 apresentou uma estrutura tetragonal e na terceirasérie o CTO uma estrutura ortorrômbica. Pela espectrosocopia Mössbauer foram confirmados no caso das duas primeiras séries, o estado de oxidação do ferro (Fe3+) presente nas amostras analisadas e sua coordenação no sítio cristalino em função da quantidade de ferro presente nos compósitos. Com exceção do PFN100, a morfologia das amostras em geral foi caracterizada pela diversidade de formas e tamanho para todas as amostras das duas primeira séries. A análise química elementar forneceu resultados quantitativos acerca dos elementos presentes nas amostras investigadas. Pelas respostas observadas na faixa de radio-freqüência, ficou evidenciada uma região de dispersão, caracteristica de processo de polarização dipolar. Experimentos foram realizados com variação de temperatura e as propriedades dielétricas foram medidas (permissividade e perda dielétrica). Foi obtido o TCC (Coeficiente de Temperatura da Capacitância), numa faixa de temperatura de 250C a 1000C, observando que as duas primeiras séries apresentaram relaxação ativada pela temperatura. Medidas na região de microondas (300 MHz < f < 30 GHz) foram realizadas, no caso da primeira série para as amostras CRFO100, CRFO50 e FCTO100. Os resultados apresentados são promissores para aplicações como dispositivos em microondas. No caso da segunda série apenas em duas amostras (CRFO100 e PFN10) foi possível determinar a freqüência ressonante, permissividade dielétrica e a perda dielétrica pelo o método utilizado neste estudo (método Hakki-Coleman), provalvelmente devido a elevada perda dielétrica apresentada pelas amostras. Para a terceira série, em todas as amostras foi possível a localização da frequencia ressonante, permissividade dielétrica e a perda dielétrica. Para a serie CRFO-CTO foi observada a possibilidade de obtenção de um composito com TCC=0. Amostras nas tres series estudadas apresentam permissividades dieletricas altas (10) e algumas com baixas perdas podendo ser usadas na miniaturização em dispositivos de microndas e aplicações em telecomunicações
45
Pöttker, Walmir Eno. "Estudo do comportamento magnético de Ligas Heusler X2YZ (L21) Fe2+xT1-x-Al, T= Cr, V e Mn e do Sistema Fe1-xRUx." reponame:Repositório Institucional da UFSC, 2012. http://repositorio.ufsc.br/xmlui/handle/123456789/92740.
Full textAbstract:
Tese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas, Programa de Pós-Graduação em Física, Florianópolis, 2009.Made available in DSpace on 2012-10-24T11:45:49Z (GMT). No. of bitstreams: 0
Neste trabalho foram investigadas as propriedades estruturais e magnéticas de ligas Heusler X2YZ com estrutura (L21) para o sistema Fe2+xT1-xAl, com T = Cr, V e Mn e x = -0,1; 0,0 e 0,1. Os compostos foram obtidos através da fusão em arco voltaico em atmosfera de ar e caracterizados pelas técnicas experimentais de: difração de raios X, magnetização, termogravimetria e espectroscopia Mössbauer. Nas regiões analisadas, todas as ligas apresentaram a estrutura L21 e uma segunda fase minoritária identificada como tetragonal de face centrada (fct). A fase majoritária (L21) apresentou comportamento ferromagnético à temperatura ambiente nas ligas dos sistemas Fe2+xCr1-xAl e Fe2,5-xV1+ xAl0,5, e a baixa temperatura na liga Fe2+xMn1-xAl. Em 4.2 K foi observado comportamento magnético de vidro de spin na maioria das ligas. Incluímos aqui também um estudo referente à substituição parcial de Fe por átomos de Ru, no sistema Fe1-xRux em x = 0,02; 0,04; 0,06; 0,10; 0,30; 0,50 e 0,70. Utilizamos como técnica de analises a espectroscotpia Mössbauer, difração de raios X, termogrametria, calorimetria exploratória diferencial. Nossos resultados mostraram que as ligas com x = 0,30, apresentam estrutura de rede cúbica de corpo centrado (bcc) e comportamento ferromagnético à temperatura ambiente (RT). Por outro lado, para x = 0,30 as ligas são hexagonais (hcp) e paramagnéticas a RT. Além disso, o volume médio por átomo na fase hcp é aproximadamente 3 vezes maior quando comparado com a fase bcc. Este aumento no volume da célula unitária, provoca mudanças na fase cristalográfica e um colapso no campo magnético hiperfino e na distribuição quadrupolar dos sítios de ferro.
46
Rocha, Hélio Henrique Barbosa. "Estudo das propriedades estruturais e de transporte dos compósitos magneto-dielétricos : [(Fe5/8Cr3/8)2O3]X-[(Fe1/4Cu3/8Ti3/8)2O3]100-X." reponame:Repositório Institucional da UFC, 2006. http://www.repositorio.ufc.br/handle/riufc/2114.
Full textAbstract:
ROCHA, H. H. B. Estudo das propriedades estruturais e de transporte dos compósitos magneto-dielétricos: [(Fe5/8Cr3/8)2O3]X-[(Fe1/4Cu3/8Ti3/8)2O3]100-X. 2006. 92 f. Dissertação (Mestrado em Engenharia e Ciência de Materiais) - Centro de Tecnologia, Universidade Federal do Ceará, Fortaleza, 2006.Submitted by Marlene Sousa (mmarlene@ufc.br) on 2012-02-23T18:37:43Z No. of bitstreams: 1 2006_dis_hhbrocha.pdf: 9553687 bytes, checksum: 1e8d229a74aeec3080c9a6321653f3e3 (MD5)
Approved for entry into archive by Marlene Sousa(mmarlene@ufc.br) on 2012-02-23T18:40:01Z (GMT) No. of bitstreams: 1 2006_dis_hhbrocha.pdf: 9553687 bytes, checksum: 1e8d229a74aeec3080c9a6321653f3e3 (MD5)
Made available in DSpace on 2012-02-23T18:40:01Z (GMT). No. of bitstreams: 1 2006_dis_hhbrocha.pdf: 9553687 bytes, checksum: 1e8d229a74aeec3080c9a6321653f3e3 (MD5) Previous issue date: 2006
The processing in laboratorial scale of solid solutions, derived from Fe2O3/CuO/TiO2 and Fe2O3/Cr2O3 systems, of their composites, and the study of the structural and transport properties establish the main theme of the work. The ferrimagnetic garnets arouse great interest in view of their use in devices applicable to telecommunication systems, in the microwaves, above all, in function of appropriate dielectric and magnetic properties. Due to stoichiometric resemblance, and with the purpose of obtaining materials with similar properties, two magneto-dielectric media were elaborated: (Fe1=4Cu3=8Ti3=8)2O3, a copper-iron titanate, and (Fe5=8Cr3=8)2O3, a particular oxide of iron and chrome. These substitutional solid solutions were synthesized by solid state reaction technique. The processing advanced involving mechanic and thermal treatments. Were prepared specimens powdered and sintered. The crystalline structure of the specimens was identified by X-ray diffraction. The X-ray diffraction data were refined by the employment of the Rietveld’s method. Use of the Mössbauer spectroscopy was made to accomplish the inspection of the iron present in the crystalline structure. The morphology of the specimens, disposed as rigid cylindrical pieces, was explored by means of Scanning Electron Microscopy, assisted by EDX, for elementary chemical analysis. Through dielectric spectroscopy, the dielectric properties relative dielectric permittivity and dielectric loss factor and the transport property electric conductivity were investigated. The dielectric and transport properties were analyzed in function of the frequency, at room temperature, in the range between 100 Hz and 40 MHz. Of the X-ray diffraction data, in addition to the identification of the examined materials, were extracted, after structural refinement, crystallographic information, in the case of the individual solid solutions, and their quantification, for the composites. For the Mössbauer spectroscopy, were confirmed the state of oxidation of iron presents in the analyzed materials, the geometry of the crystalline sites in which it is present, the magnetic nature of the samples, and their probable ordering, in addition to the quantification consummated in function of the amount of iron present in the composites. The morphology of the materials was, in general, characterized by the diversity of forms and sizes of the grains, as well as its arrangement in the observed samples. The elementary chemical analysis supplied quantitative results concerning the elements present in the investigated samples. For the response observed in the range of frequency, a dispersion region, characteristic of the dipolar polarization mechanism, was evidenced. The results of the dielectric properties for the synthesized phases were shown partially antagonistic: the phase IB100 presented the largest relative dielectric permittivity, however, larger dielectric loss factor compared to the phase IC100, the one which presented the smallest relative dielectric permittivity among all the investigated materials. For the composites, formed by the random mixture of specific amounts of the two synthesized phases, a non linear behavior was evidenced, so that these do not represent the responses observed for the phases individually. The phase IB100, by virtue of its dielectric constant, is the material with the great potential for applications in high frequencies.
O processamento em escala laboratorial de soluções sólidas, procedentes dos sistemas Fe2O3/CuO/TiO2 e Fe2O3/Cr2O3, dos seus compósitos, e o estudo das propriedades estruturais e de transporte estabelecem o tema principal do trabalho. As granadas ferrimagnéticas despertam manifesto interesse quanto ao seu emprego em dispositivos aplicáveis a sistemas de telecomunicação operantes nas microondas, sobretudo, em função das propriedades dielétricas e magnéticas adequadas. Devido à semelhança estequiométrica, e com a finalidade de se obter materiais com propriedades similares, foram elaborados dois meios magneto-dielétricos: (Fe1=4Cu3=8Ti3=8)2O3, um titanato de cobre e ferro, e (Fe5=8Cr3=8)2O3, um óxido específico de ferro e cromo. Estas soluções sólidas substitucionais foram sintetizadas por reação de estado sólido. O processamento avançou envolvendo tratamentos mecânico e térmico. Foram preparados espécimes pulverulentos e com configuração definida. A estrutura cristalina dos espécimes foi identificada por difração de raios-X. Os dados de difração de raios-X por policristais foram refinados pelo emprego do método de Rietveld. Fez-se uso da espectroscopia Mössbauer para realizar a sondagem do ferro presente na estrutura cristalina. A morfologia dos espécimes, dispostos como peças cilíndricas rígidas, foi explorada por Microscopia Eletrônica de Varredura, assistida por microssonda EDX, para análise química elementar. Por espectroscopia dielétrica foram investigadas as propriedades dielétricas permissividade dielétrica relativa e fator de perda dielétrico e a propriedade de transporte condutividade elétrica. As propriedades dielétricas e de transporte foram analisadas em função da freqüência, a temperatura ambiente, numa faixa compreendida entre 100 Hz e 40 MHz. Dos dados por difração de raios-X, além da identificação dos materiais avaliados, foram extraídas, após refinamento estrutural, informações cristalográficas, no caso das soluções sólidas individuais, e sua quantificação, no caso dos compósitos por elas constituídos. Pela espectroscopia Mössbauer foram confirmados o estado de oxidação do ferro presente nos materiais analisados, a geometria do sítio cristalino no qual está presente, a natureza magnética das amostras, e seu provável ordenamento, além da quantificação realizada em função da quantidade de ferro presente nos compósitos. A morfologia dos materiais é, em geral, caracterizada pela diversidade de formas e tamanhos dos grãos, bem como sua disposição no artefato explorado. A análise química elementar forneceu resultados quantitativos acerca dos elementos presentes nos meios investigados. Pela resposta observada na faixa de freqüência percorrida, ficou evidenciada uma região de dispersão, característica do processo de polarização dipolar. Os resultados das propriedades dielétricas para as fases sintetizadas mostraram-se parcialmente antagônicos: a fase IB100 apresentou a maior permissividade dielétrica relativa, porém, maior fator de perda dielétrica em relação à fase IC100, que por sua vez apresentou a menor permissividade dielétrica relativa entre todos os materiais investigados. Para os compósitos, formados pela mistura aleatória de quantidades específicas das duas fases sintetizadas, foi evidenciado um comportamento não linear, de forma que estes não representam apenas o reflexo das respostas observadas para as fases individualmente. A fase IB100, em virtude da constante dielétrica observada, é o material com maior potencial para aplicações em altas freqüências.
47
Persson, Petter. "Finite element analysis of hot rolling in the blooming mill." Thesis, Högskolan Dalarna, Materialteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:du-22676.
Full textAbstract:
During this thesis work a coupled thermo-mechanical finite element model (FEM) was builtto simulate hot rolling in the blooming mill at Sandvik Materials Technology (SMT) inSandviken. The blooming mill is the first in a long line of processes that continuously or ingotcast ingots are subjected to before becoming finished products. The aim of this thesis work was twofold. The first was to create a parameterized finiteelement (FE) model of the blooming mill. The commercial FE software package MSCMarc/Mentat was used to create this model and the programing language Python was used toparameterize it. Second, two different pass schedules (A and B) were studied and comparedusing the model. The two pass series were evaluated with focus on their ability to healcentreline porosity, i.e. to close voids in the centre of the ingot. This evaluation was made by studying the hydrostatic stress (σm), the von Mises stress (σeq)and the plastic strain (εp) in the centre of the ingot. From these parameters the stress triaxiality(Tx) and the hydrostatic integration parameter (Gm) were calculated for each pass in bothseries using two different transportation times (30 and 150 s) from the furnace. The relationbetween Gm and an analytical parameter (Δ) was also studied. This parameter is the ratiobetween the mean height of the ingot and the contact length between the rolls and the ingot,which is useful as a rule of thumb to determine the homogeneity or penetration of strain for aspecific pass. The pass series designed with fewer passes (B), many with greater reduction, was shown toachieve better void closure theoretically. It was also shown that a temperature gradient, whichis the result of a longer holding time between the furnace and the blooming mill leads toimproved void closure.
48
Wells, Jonathan C. K. "Energy metabolism in breast-fed and formula-fed infants." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.294997.
Full text
49
Peixoto, André Luís de Castro. "Ozonização catalítica do chorume proveniente do antigo aterro controlado da cidade de Guaratinguetá-SP utilizando os íons Fe2+, Fe3+, Zn2+, Mn2+, Ni2+ e Cr3+." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-26092012-142104/.
Full textAbstract:
Durante anos, o lixo da cidade de Guaratinguetá foi aterrado e o seu produto recalcitrante não passou por nenhum tratamento físico ou mesmo químico, percolando diretamente sob o aterro. Mesmo tendo sido desativado e transformado em Parque Ecológico, o material depositado no local ao longo dos anos, continuará a ser decomposto por microrganismos e continuará a ser produzido o lixiviado como fonte de poluição ambiental. Inicialmente, fez-se a caracterização do chorume \"in natura\", demonstrando-se como fonte de matéria orgânica recalcitrante, com massa molar característica de macromoléculas (5,58 kDa e polidispersidade de 1,16), DBO não determinável pela recalcitrância molecular e/ou pela ação tóxica e DQO característica de lixiviado estabilizado (1.013 mg L-1). A fração inorgânica total, dada pela quantidade de sólidos fixos, foi de 3.670 mg L-1, valor esse 3,6 vezes maior que a fração orgânica. O estudo de tratamento do chorume, por ozonização catalítica homogênea foi desenvolvido, principalmente, pelo uso seqüencial de dois arranjos ortogonais de Taguchi, sendo o primeiro, matriz L16, para estudo exploratório dos fatores mais importantes na redução percentual da DQO. Os fatores estudados foram vazão de ozônio, concentração dos íons Fe2+, Fe3+, Zn2+, Mn2+, Ni2+ e Cr3+, pH do meio reacional e presença/ausência de fonte de radiação UV (254 nm). Dentre os metais de transição, os íons Fe2+ e Fe3+ demonstraram-se como mais viáveis como catalisadores na geração de radicais livres hidroxilas devido à sua significância estatística (p = 0,005), e por terem maior tolerância ao descarte no meio ambiente (menor toxicidade) frente aos demais íons. Com a utilização do arranjo ortogonal L8 de Taguchi, foi possível atingir degradação máxima de DQO da ordem de 50 %. A melhor configuração dos fatores, visando aumentar o percentual de redução da DQO foi: vazão de ozônio igual a 5 L h-1 (589,9 mg h-1 O3), concentração de íon de íon ferroso igual a 10 mg L-1, concentração de íon férrico igual a 5 mg L-1 e pH 5.During many years, the garbage of Guaratinguetá city was landfilled and its recalcitrant product was not submitted to any physical or chemical treatment, leaching directly through the area. After deactivating and transforming the landfill into an Ecological Park, the material deposited in the place by the past years, will continue being decomposed by microorganisms and will continue producing the leached one as a mean of environment pollution. Initially, the leachate \"in natura\" was characterized, demonstrating itself as a source of recalcitrant organic substance with a higher molecular size characteristic of 5,58 kDa and polidispersity of 1,16 and stabilized effluent (not determinable DBO due to molecular recalcitrance and/or toxicity and DQO of 1,013 mg L-1). The total inorganic fraction, given by the amount of total fixed solids was 3,670 mg L-1, which means 3,6 times bigger than the organic fraction. The study of leachate treatment by homogeneous catalytic ozonation was given, mainly, for the sequential use of two Taguchi\'s orthogonal arrangements, being the first, L16 design, for exploratory studies of the most important factors in the percentual reduction of DQO. The factors studied were the ozone outflow, the Fe2+, Fe3+, Zn2+, Mn2+, Ni2+ and Cr3+ ions concentration, the reaction medium pH and the presence/absence of UV radiation source UV (254 nm). Amongst the transition metals, Fe2+ and Fe3+ ions have demonstrated to be as more viable as free hydroxyl radicals catalyst due to its statistics significance (p = 0,005) and also because they have a greater tolerance to the environment discarding (less toxicity) compared to the other ions. The use of L8 Taguchi\'s orthogonal arrays gives the possibility to reach 50 % maximum COD depletion. The best factors configuration, using COD percentage reduction as experimental design response was: 5 L h-1 (589,9 mg h-1 O3) ozone outflow, 10 mg L-1 ferrous concentration, 5 mg L-1 ferric ion concentration and pH 5.
50
Omasta, Milan. "Pevnostní analýza protézy dolní končetiny." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228770.
Full textAbstract:
This masters´s thesis deals with computational modeling of transtibial lower-limb prosthesis. For assesment of loading character and geometrical configuration, the gait analysis of an amputee, including ground reaction force measurement, strain gauge analysis and motion analysis, was accomplished. Information on geometry was obtained using 3D optical scanning procedure. Material model was gathered using non-destructive mechanical testing and mimicked in a FEA software. For loading conditions the static structure analysys using FEM was accomplished. The critical poins in construction was found. Recognition of agreement about experimental and computational model was accomplished.