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Reho, Riccardo. "A higher derivative fermion model." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/19852/.
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Nel presente elaborato studiamo un modello fermionico libero ed invariante di scala con
derivate di ordine elevato. In particolare, controlliamo che la simmetria di scala sia estendibile
all'intero gruppo conforme. Essendoci derivate di ordine più alto il modello non è unitario,
ma costituisce un nuovo esempio di teoria conforme libera. Nelle prime sezioni riguardiamo la
teoria generale del bosone libero, partendo dapprima con modelli semplici con derivate di ordine
basso, per poi estenderci a dimensioni arbitrarie e derivate più alte. In questo modo illustriamo
la tecnica che ci permette di ottenere un modello conforme da un modello invariante di scala,
attraverso l'accoppiamento con la gravità e richiedendo l'ulteriore invarianza di Weyl. Se questo è
possibile, il modello originale ammette certamente l'intera simmetria conforme, che emerge come
generata dai vettori di Killing conformi. Nel modello scalare l'accoppiamento con la gravità
necessita di nuovi termini nell'azione, indispensabili anche la teoria sia appunto invariante
di Weyl. La costruzione di questi nuovi termini viene ripetuta per un particolare modello
fermionico, con azione contenente l'operatore di Dirac al cubo, per il quale dimostriamo
l'invarianza conforme. Tale modello descrive equazioni del moto con derivate al terzo ordine.
Dal momento che l'invarianza di Weyl garantisce anche l'invarianza conforme, ci si aspetta
che il tensore energia-impulso corrispondente sia a traccia nulla. Per ogni modello introdotto
controlliamo sistematicamente che tale condizione sia verifiata, ed in particolar modo per il
caso della teoria fermionica con operator di Dirac cubico, che rappresenta il contributo originale di questa tesi.
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Garolera, Huguet Blai. "Probing gauge theories: Exact results and holographic computations." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/289346.
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The holographic duality between gauge theories and string theories has opened a new door to access the strongly coupled regime of quantum field theories and offers, at the same time, a completely new way to understand the elusive nature of quantum gravity and the non-perturbative regime of string theory. After almost two decades of research, the current status of the correspondence is that of a solid conjecture that has passed a great number of nontrivial tests, to the point that it is generally believed to be true.
The present thesis includes a collection of four papers published in peer-reviewed scientific journals, all of them in the context of the AdS/CFT correspondence and with a particular focus on studying gauge theories by inserting heavy external probes, following prescribed trajectories and transforming under various representations of the gauge group.
Each of these works reports a little step forward in the development of new strategies for capturing correc- tions beyond the leading order as well as in using exact results available in quantum field theory in order to derive exact expressions for other relevant observables and new non-trivial string theory predictions.
In chapters 2 and 3 we use the AdS/CFT correspondence in order to compute several observables of N = 4 SU (N ) super Yang-Mills theory related with the presence of an infinitely heavy particle transforming in the k-symmetric or the k-antisymmetric representations of the gauge group and following particular trajectories. This is achieved by means of adding certain D-brane probes with electric fluxes turned on and reaching the boundary of AdS on the very trajectories followed by the dual particles. For the antisymmetric case we consider D5-branes reaching the boundary at arbitrary time-like trajectories, while for the symmetric case, we consider a D3-brane fully embedded in AdS5 that reaches the boundary at either a straight line or a hyperbola. This generalizes previous computations that used fundamental strings, which are claimed to be dual to infinitely heavy point particles transforming in the fundamental. Besides the intrinsic interest of these generalizations, our main motivation in studying them is that, as it happens in the computation of certain Wilson loops, the results obtained with D3-branes give an all- orders series of corrections in 1/N to the leading order result for the fundamental representation obtained by means of fundamental strings.
It is important to remark, one more time, that we can not really extrapolate up to k = 1, since this is beyond the regime of validity of the supergravity approximation. Therefore, it is not justified a priori to set k = 1 in our results. Nevertheless, when compared with the exact results available, we find that the D3-brane computation reproduces the correct result in the large N , λ limit and with k = 1.
This better than expected performance suggests the exciting possibility that certain D3-branes with electric fluxes might capture correctly all the 1/N corrections, but it is fair to say that we still lack of a precise string-theoretic argument to prove this.Durant les darreres dues dècades ha aparegut un nou paradigma que permet reformular completament certes teories quàntiques de camps i ens aporta una nova eina que ens permet realitzar càlculs analítics en règims fins ara inaccessibles. Aquest nou paradigma sorgeix del descobriment d’una correspondència o dualitat exacta entre dues teories aparentment molt diferents. Per una banda de la dualitat tenim certes teories quàntiques de camps, com per exemple les denominades teories de Yang-Mills, similars a les teories del Model Estàndard. Aquestes descriuen partícules interactuant en un espai pla d-dimensional sense gravetat. A l’altra banda de la dualitat trobem teories que inclouen la gravetat, com ara la Teoria de la Relativitat General d’Einstein o les seves generalitzacions en el marc de la Teoria de Cordes. Aquestes teories de gravetat estan definides sobre espais de dimensió més alta que d, i és per això que aquesta correspondència rep sovint l’adjectiu de “hologràfica”. Depenent del context, aquesta rep el nom de dualitat gauge/gravetat, dualitat gauge/corda o AdS/CFT (acrònim anglès per la correspondència particular entre teoria de cordes a espais d’Anti-de Sitter i teories de camps conformes). Fins ara, una de les correspondències més ben estudiades i que comprenem millor (i sobre la qual es centra la present tesi) és la dualitat entre la teoria quatre-dimensional N = 4 super Yang-Mills amb grup de gauge SU (N ) i teoria de cordes tipus IIB en un espai deu-dimensional AdS5 × S5 . Aquesta tesi presenta una recopilació de quatre articles publicats en revistes científiques d’alt impacte, tots ells en el camp de la correspondència AdS/CFT i centrats en l’estudi de teories gauge supersimètriques mitjançant la inserció de partícules de prova infinitament massives, seguint trajectòries determinades i transformant sota diverses representacions del grup de gauge. Cadascun d’aquests treballs aporta un pas endavant en el desenvolupament de noves estratègies per calcular correccions més enllà del primer ordre així com en l’ús de resultats exactes accessibles a la Teoria Quàntica de Camps per tal de derivar expressions exactes d’altres observables rellevants de la teoria i realitzar prediccions de Teoria de Cordes.
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Riedel, Gårding Elias. "Quantum structure of holographic black holes." Thesis, KTH, Fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-284694.
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We study a free quantum scalar field in the BTZ spacetime as a model of the AdS/CFT correspondence for black holes, and show the essential steps in computing Bogolyubov coefficients between modes on either side of the wormhole. As background, we review the BTZ geometry in standard, Kruskal and Poincaré coordinates, holographic renormalisation of the dual field theory and canonical quantisation in curved spacetime.Vi studerar ett fritt skalärt kvantfält i BTZ-rumtiden som en modell av AdS/CFT-dualiteten för svarta hål och visar huvudstegen i beräkningen av Bogolyubov-koefficienter mellan moder på olika sidor av maskhålet. Som bakgrund redogör vi för BTZ-geometrin i standard-, Kruskal- och Poincarékoordinater, holografisk renormering av den duala fältteorin och kanonisk kvantisering i krökt rumtid.
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Dector, Oliver Aldo. "Ads/CFT Correspondence and Superconductivity: Various Approaches and Magnetic Phenomena." Doctoral thesis, Universitat de Barcelona, 2015. http://hdl.handle.net/10803/348872.
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The AdS/CFT correspondence is one of the most important developments in the history of theoretical physics. Using as a binding bridge superstring theory, or, more concretely, some theoretical aspects in the interaction between superstrings and D-branes, the Maldacena conjecture establishes that the physics of a strongly-coupled, perturbatively-inaccessible quantum field theory in d-dimensions can be described equivalently in terms of the dynamics of a dual classical gravitational theory in (d + 1)-dimensional AdS space. Two particular aspects of the duality are of great importance. First, the duality ascertains that the quantum field theory lives in the boundary of the AdS space in which the dual gravitational system exists, and that the two-point functions of the dual field theory are computed in terms boundary-to-bulk propagators. This difference between the dimensions of the theories makes the duality holographic, so giving evidence to the idea that a quantum theory of gravity should be indeed a holographic in nature.
The second important aspect we must mention is that the AdS/CFT co-rrespondence is a strong/weak-coupling duality: it allows one to formulate a strongly-coupled quantum problem in terms of the classical Einstein equations of the dual higher-dimensional gravitational system. Because of this particular nature of the duality, it provides a promising new way of studying quantum gauge theories in the strongly-coupled regime, where the usual perturbative methods fail to apply. The gauge/gravity duality has thus been used to gain insight in a wide variety of physical systems where a satisfactory description in terms of standard methods is lacking, such as the quark-gluon plasma or in condensed matter theory.En aquesta tesi s'ha demostrat que la correspondència AdS/CFT ofereix una nova manera d'estudiar la fase superconductora de les teories large-N al règim fortament acoblat. En discutir els cuprats al final del Capítol 1, veiem algunes de les deficiències que els acostaments usuals basats en teories de camps tenen quan es tracta d'abordar sistemes de molts cossos fortament acoblats. Potser que la més greu d'aquestes deficiències és el col.lapse del concepte de quasi-partícula a causa de les fortes interaccions involucrades. La dualitat gauge/gravity ens permet plantejar problemes gairebé intractables en sistemes quàntics de molts cossos en termes de la dinàmica clàssica d'un sistema dual de gravetat en l'espai AdS. Usant aquest nou punt de vista hologràfic, la condensació de parells de Cooper al costat de la teoria del camps es tradueix en la creació espontània de solucions amb pèl carregat al costat gravitatori de la dualitat. Això dóna lloc a una fase en la teoria del camps dual, on es recuperen els aspectes fenomenològics fonamentals de la superconductivitat. Crida l'atenció que amb només observar al problema des d'un punt de vista hologràfic, es pot demostrar que aquests sistemes completament intractables en el règim d'acoblament fort presenten una fase superconductora. a causa de l'èxit del mètode hologràfic i les dificultats ja esmentades sobre els enfocaments estàndard basats en teories de camps, pot ser que no sigui massa agosarat imaginar que, efectivament, la definició teòrica natural de la superconductivitat en el règim fort acoblament està donada pel sistema dual de gravetat. Amb aquestes consideracions generals en ment, en aquesta tesi ens hem esforçat a presentar una imatge el més completa possible dels diferents enfocaments seguits en la superconductivitat hologràfica.
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Papoulias, Ilias. "Compassionfokuserad terapi i grupp som tillägg till dagvårdsbehandling för patienter med ätstörningar : En pilotstudie." Thesis, Stockholms universitet, Psykologiska institutionen, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-182231.
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Ätstörningar är allvarliga sjukdomar som medför stort lidande för patienter och deras närstående. De rekommenderadebehandlingsmetoderna kan hjälpa vissa patienter men det behövs effektivare behandlingsmetoder. Det finns teoretiskt stöd och ännu begränsat empiriskt stöd för att compassionfokuserad terapi (CFT) kan vara hjälpsam för patienter med ätstörningar. I föreliggande studie var syftet att utvärdera CFT i grupp vad gäller metodens genomförbarhet, acceptabilitet och preliminära effektivitet för patienter med ätstörningar som behandlas i dagvård. En åttasessioners manualbaserad CFT-grupp som tillägg till ätstörningsdagvård utvärderades enligt en single-group studiedesign (n=8). CFT-gruppen visade god genomförbarhet och acceptabilitet. Patienter förbättrades med måttliga till stora effektstorlekar vad gäller ätstörningssymptom, vikt, självkritik och självuppmuntran. Dock uppnådde inget effektmått statistisk signifikans. Studiens resultat tyder på att CFT i grupp som tillägg till ätstörningsdagvård kan vara en genomförbar och acceptabel behandling som möjligen kan bidra till tillfriskande av patienter med ätstörningar.Eating disorders are serious illnesses that cause great suffering for patients and their caregivers. The recommended treatment methods help some patients, but more effective treatment methods are needed. There is theoretical support and still limited empirical support that compassion-focused therapy (CFT) may be helpful for patients with eating disorders. The aim of the present study was to evaluate the feasibility, acceptability and preliminary effectiveness of group CFT for patients with eating disorders who receive day care treatment. An eight-session manual-based CFT group was evaluated as an adjunct to day patient program for eating disorders according to a single-group design (n=8). The CFT group demonstrated good feasibility and acceptability. Patients improved with moderate to large effect sizes on eating disorder symptoms, weight, self-criticising and self-reassuring. However, no effect was statistically significant. Results suggest that group CFT as an adjunct to day patient program for eating disorders may be a feasible and acceptable treatment that may contribute to the recovery of patients with eating disorders.
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Santos-Oliván, Daniel. "Numerical Relativity studies in Anti-de Sitter spacetimes: Gravitational Collapse and the AdS/CFT correspondence." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/460681.
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In this thesis we study several open problems using Numerical Relativity on asymptotically Anti-de Sitter (AdS) spacetimes. The understanding of the dynamics of AdS is interesting not only because of pure theoretical reasons but also because of its importance in the correspondence gauge/gravity. In the thesis we present three different topics. The first is our research on the gravitational collapse of massless scalar fields in AAdS spacetimes. We have developed a new method that combines two different formulations of the Einstein Field Equations to get closer and with more accuracy to the collapse. The simulation starts with a Cauchy evolution with pseudo-spectral methods and when the collapse is taking place, it performs a change of coordinates to a characteristic one to track the formation of the apparent horizon. The collapse of the scalar field happens after a number of bounces with the critical points being the separation between the different branches. We have numerical evidence that in the separation of the branches there is a power law for subcritical configurations in addition to the one for supercritical ones. This new power law confirms that there is a gap in the mass of the apparent horizon. In the second part, we introduce a shock waves model in AdS to study the far-from-equilibrium regime in the heavy ion collisions through the holographic correspondence in a non-conformal theory. Holographic collisions have attracted a lot of attention in the last few years because of the possibility of simulating strongly coupled systems but, as a drawback, we do not know yet the exact dual of the QCD that should explain the phenomena. In the models used until now, the shock waves correspond to conformal gauge theories while QCD is not conformal. In order to get closer to a description of the actual physical collisions we present the first shock wave collisions in a non-conformal theory. With this, we show how the non-conformality increases the hydrodynamisation time and also that this can happen before the equation of state is fulfilled. In the last part, we propose the use of spectral methods as a very strong option for high precision computations. Arbitrary precision arithmetic has two main problems. The first is the necessity of increasing a lot the discretisation units to reach the precision we want. The other one is the slowing down in the computational performance due to the fact that we need to emulate the fundamental operations with software because current processors are not adapted to carry out computations with precision different from the standard one. The exponential convergence of spectral methods can approximate functions to a very high accuracy with a few hundred terms in our spectral expansion while in other numerical methods it would be a few orders of magnitude larger. This makes these methods very attractive because they facilitate the accessibility to very small error simulations, removes the bottleneck of the memory demand and also help in the computational speed because fewer points are needed for the computation. We have tested this idea with the ANETO library for simulations in AdS spacetimes and the gravitational collapse in an asymptotically flat spacetime with very promising results. This library has been developed as a direct result of this thesis and that can be downloaded as Free Software.
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Farstad, Øyvind. "CFD av strømningskarakteristikker i hydrauliske motorer." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10525.
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CFD-vertøy er i dagens industri et mye brukt redskap for analyse av komplekse strømningsdynamiske problemstillinger. Dette gjelder også hos Rolls-Royce Marine Deckmachinery i Brattvåg. Her blir CFD brukt på hydrauliske komponenter som ventiler og motorer. Målet med denne oppgaven er å studere muligheten for å modellere og analysere motorene til nettopp Rolls-Royce med CFD. Motoren som blir brukt i denne oppgaven er av typen MX6300, som er en hydraulisk vingemotor. Dette arbeidet bestod i å bearbeide en CAD-modell av motoren slik at den ble hensiktsmessig for CFD-analyse i programmet Fluent 6.3.26. Denne bearbeidingen gikk i å forenkle modellen på en slik måte at de viktigste strømningsegenskapene til motoren ikke gikk tapt. En ny metode for spaltesimulering ble testet ut. Denne gikk ut på å erstatte tynne spalter med en porøs sone, som har en definert strømningsmotstand som gir samme trykktap som over den tynne spalten. Dette vil gi en forenklet geometri, og dermed redusere antall celler i meshet. For å kunne verifisere resultatene fra CFD-analysen, har det blitt utført eksperimentelle virkningsgradsmålinger på den virkelige motoren. Målingene ble utført ved en teststand hos Rolls-Royce i Brattvåg. Resultatene fra CFD-analysen var lovende. En fikk gode indikasjoner på at implementering av en porøs sone i stedet for spalter i en avansert modell, fungerer på en god måte. Det totale strømningsbildet viste imidlertid avvik fra et realistisk bilde. Det er forventet at en stor forbedring vil skje dersom et finere mesh benyttes. Dette vil også kreve mer dataressurser.
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Kiryo, Josef. ""Annan finansiell verksamhet" - En tolkning i ljuset av CFC-lagstiftningen : En tolkning i ljuset av CFC-lagstiftningen." Thesis, Jönköping University, JIBS, Commercial Law, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-12851.
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The initial provisions concerning CFC-legislation were introduced 1990 and has since been subject to several revisions and adaptations. The fundamental purpose of the CFC-legislation is to prohibit and prevent tax evasion undertaken by such companies that own other foreign companies where generated income is subject to low rates of taxation. The CFC-legislation aims to provide the Swedish government with an op-portunity to tax this income. This is important in order to prevent tax avoidance and preserve the integrity of the system of taxation within Sweden. In order for the CFC-legislation to be as effective as possible there must exist a clear way of defining which activity that is to be regulated within its scope. There are several types of income re-gulated within the scope of CFC-legislation. An extensive part of the market consists of such activity that can be labeled as financial activity. Financial income is an impor-tant part of corporate finance and as such demands a clear definition. The CFC-legislation contains several provisions pertaining to income that may not be ex-empted from CFC-taxation. Such income is mainly derived from financial activity. This financial activity may be defined as pertaining to a bank or financial entity which operates in a professional and independent way. There is however a third category of financial activity merely designated as “other financial activity”, according to the wording of the legislation. This gives rise to the question of what the definition of “other finan-cial activity” is and how it should be interpreted. This thesis aims to define what this abstract prerequisite for CFC-taxation of financial activity means. This will be done with an emphasis on what constitutes an ordinary financial activity according to Swe-dish Law and how this is to be seen in contrast to “other financial activity” The basic concepts of the definition of financial activity many times mirrors the definition of “other financial activity”. A comparison and deeper analysis of different types of finan-cial activity is therefore required in order to provide a correct and clear answer.
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Svedjeland, Magnus. "CFD-simulering av luft- och temperaturflöde i ett apparatskåp." Thesis, University West, Department of Technology, Mathematics and Computer Science, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:hv:diva-756.
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Törnblom, Nicklas. "Uppskattning av Ytkurvatur och CFD-simuleringar i Mänskliga Bukaortor." Thesis, Linköping University, Department of Mechanical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2906.
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By applying a segmentation procedure to two different sets of computed tomography scans, two geometrical models of the abdominal aorta, containing one inlet and two outlets have been constructed. One of these depicts a healthy blood vessel while the other displays one afflicted with a Abdominal Aortic Aneurysm.
After inputting these geometries into the computational dynamics software FLUENT, six simulations of laminar, stationary flow of a fluid that was assumed to be Newtonian were performed. The mass flow rate across the model outlet boundaries was varied for the different simulations to produce a basis for a parameter analysis study.
The segmentation data was also used as input data to a surface description procedure which produced not only the surface itself, but also the first and second directional derivatives in every one of its defining spatial data points. These sets of derivatives were followingly applied in an additional procedure that calculated values of Gaussian curvature.
A parameter variance analysis was carried out to evaluate the performance of the surface generation procedure. An array of resultant surfaces and surface directional derivatives were obtained. Values of Gaussian curvature were calculated in the defining spatial data points of a few selected surfaces.
The curvature values of a selected data set were visualized through a contour plot as well as through a surface map. Comparisons between the curvature surface map and one wall shear stress surface map were made.
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Nordberg, Johan, and John Persson. "CFO-rollen i Sverige idag : Finansiell rapportör eller driven affärsman?" Thesis, Uppsala University, Department of Business Studies, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-110593.
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Bakgrund och problemformulering: Revisions- och konsultbyrån Grant Thornton genomförde i september 2008 en undersökning med 400 VD:ar i svenska företag. Resultatet visade att svenska företag är tämligen duktiga på att kunna förutspå omvärldsförändringar men att det alltför sällan leder till någon form av strategisk planering och handling. Företagets Chief Financial Officer (CFO), som ansvarig för ekonomifunktionen och som den med bäst insyn i företagets finansiella ställning, har en nyckelroll i företagets förmåga att hantera omvärldsförändringar. Det är därför vitalt att CFO arbetar strategiskt och kan vidta snabba åtgärder vid behov och därmed inte bedriver en reaktiv styrning där åtgärder vidtas först när problem redan har hunnit uppstå. Syfte: Syftet med undersökningen är att utreda huruvida CFO i svenska företag arbetar strategiskt i sin roll samt vilka faktorer som påverkar CFO:s möjligheter till att bedriva strategiskt arbete. Metod: Författarna har valt en kvalitativ ansats för undersökningen. För att få en tydligare helhetsbild har en informantintervju genomförts med en forskare inom verksamhetsstyrning. Därutöver har respondentintervjuer genomförts med CFO:s på Kemwell, Previa, SF Bio och TNT Sverige i syfte att få en djupare förståelse för problemområdet. Undersökningens resultat och slutsatser: Undersökningen som genomförts poängterar betydelsen av att som CFO besitta en god kommunikativ förmåga och att detta är en viktig faktor för att CFO ska kunna vidareutvecklas till att fungera som en affärspartner i företaget. Vidare konstateras att samtliga intervjuade CFO:s har ambitionen att arbeta mer strategiskt men att möjligheterna till strategiskt arbete skiljer sig åt beroende på omständigheter som organisationens storlek, organisationsstrukturen, samt individens egna ambitioner att utvecklas i CFO-rollen. Om ekonomichefen historiskt sett varit redovisningsspecialist, anser författarna att CFO-rollen idag fordrar en generalist med bred kompetens inom flertalet olika områden, som aktivt kan hjälpa VD att driva och utveckla företaget.
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Breivik, Simen Røst. "CFD-analyse av løpehjul og sugerør i en Francis turbin." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for energi- og prosessteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13653.
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Denne masteroppgaven evaluerer svingningene is sugerørsstrømingen til en Francis turbinved dellast. Bakgrunnen for dette studiet er delvis på grunn av verdens økende energibehov. Med varierende energipriser og vannivåer i magasinene opererer vannturbiner på varierende last. Operasjon ved fullast og dellast skaper trykkpulsasjoner i turbinen, hvor en av årsakene er ustabil strømning i sugerøret. Hovedmålet med denne oppgaven er å gjennomføre en CFD-analyse av løpehjulet og sugerøret i en Francis turbin ved dellast.Resultatene fra CFD-analysen stemmer godt overens med modelltesten gjennomført i Vannkraftlaboratoriet. Ved bestpunktet er sugerørsstrømingen symmetrisk og stabil både i CFD-analysen og i laboratoriet.Ved fullast er søgerørsstrømningne også symmetrisk og stabil, men det er et stort lavtrykksområde under løpehjulets boss. I laboratoriet kaviterte vannetpå grunn av det lave trykket. Ved dellast blir sugerørsstrømingen ustabil, og trykkpulsasjoner ble målt. En sugerørsvirvel formet som en korketrekker oppstod i sugerørskonusen i laboratoriet. CFD analysen er en-fase, uten mulighet for å kavitere, men en trykkoverflate viser en tilsvarende virvelform i sugerørskonusen.Frekvensen på trykkpulsasjonene målt ved dellast stemmer godt med den teoretiskefrekvensen ved det samme operasjonspunktet.
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Casals, Senent Teresa. "Patologia molecular del gen CFTR: Fibrosi quística i fenotips relacionats." Doctoral thesis, Universitat de Barcelona, 2004. http://hdl.handle.net/10803/865.
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La tesi presenta l'anàlisi molecular del gen CFTR a la població espanyola. L'estudi inclou afectats i famílies de fibrosi quística (FQ) així com pacients de les malalties relacionades (agenèsia bilateral de conductes deferents, pancreatitis crònica i bronquiectàsies). La FQ és una malaltia genètica recessiva caracteritzada per malaltia pulmonar crònica, insuficiència pancreàtica i infertilitat en l'home. Per l'anàlisi del gen (250kb) s'han utilitzat dues tècniques de cribatge: l'electroforesi en gels de gradient desnaturalitzant (DGGE) i l'anàlisi de la conformació de la cadena senzilla (SSPC/HD) amb la posterior seqüenciació dels patrons anòmals per tal d'identificar les mutacions. A més s'ha evaluat l'eficiència de l'equip comercial que permet l'anàlisi directa de 31 mutacions freqüents del gen. L'estudi evidencia l'heterogeneïtat molecular de la població espanyola amb únicament dotze mutacions que presenten una freqüència superior a l'1%. La mutació majoritària al món, F508del, representa el 51% d'al·lels. La mutació G542X és la segona més freqüent amb un 8% d'al·lels. L'equip comercial permet identificar el 76% dels al·lels, el que suposa la total caracterització del genotip en el 59% dels pacients FQ. Amb l'estratègia emprada s'han caracteritzat 108 mutacions que representen el 97% dels al·lels FQ.
A l'ABCD el 85% dels pacients presenten al menys una mutació i/o variant, sent la variant 5T la més prevalent (39%) en aquest grup. Pel que fa als fenotips PC i BQ, un 35% dels pacients presenten al menys una mutació i/o variant CFTR. En general, aquests fenotips (ABCD, PC, BQ) presenten heterogeneïtat molecular encara que amb un espectre de mutacions diferent, predominant les mutacions amb error de sentit. Aquestes mutacions que determinen un canvi d'aminoàcid poden afectar de forma molt diversa la funció i estabilitat de la proteïna. Tanmateix, l'alta freqüència d'individus heterocigots suggereix que aquests tenen una major predisposició a desenvolupar les diferents malalties, probablement, en un context multifactorial.
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Nuthall, Hugh. "Analysis of DNase I hypersensitive sites in the CFTR gene." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298724.
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Stråhle, Helena. "Autoimmuna aspekter i Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome : En litteraturstudie rörande indikationer på autoimmunitet i ME/CFS." Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-96736.
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Bakgrund: Myalgic Encephalomyelitis eller Chronic Fatigue Syndrome (ME/CFS) omfattar ett spektrum av olika symptom som bland annat påverkar de autonoma och neurologiska systemen, kognitiv funktion och ger immunologiska störningar med mera. De karakteristiska symptomen är oförklarlig kronisk trötthet, ansträngningsutlöst fysisk och mental uttröttbarhet Post Exertional Malaise (PEM). Trots forskning inom ett flertal områden är den underliggande molekylära orsaken bakom ME/CFS inte fastställd. Flertalet hypoteser om sjukdomsorsaken finns, varav en är att ME/CFS är en autoimmun sjukdom. Syfte: Syftet med litteraturstudien är att undersöka huruvida det finns autoimmuna aspekter i ME/CFS. Metod: Systematisk litteraturstudie utifrån vetenskapliga artiklar, publicerade 2010—2020 i databasen PubMed. Resultat: Studieresultaten är inte helt entydiga när det kommer till att påvisa autoimmuna aspekter i ME/CFS. Antikroppsstudier riktade mot neuronalt protein hos ME/CFS-patienter och behandlingar riktade mot antikroppar, immunoadsorption och rituximab, gav negativa resultat. Däremot observeras HSP60 (heat shock protein 60) antikroppar för specifika korsreaktiva epitoper i en undergrupp av ME/CFS-patienter, vilket stämmer överens med infektionsutlöst autoimmunitet. Även i de två genstudierna, HLA-association (human leucocyte antigen) och SNP (single nucleotide polymorphism) genotypning i immungener, observeras karakteristiska riskgener för autoimmun sjukdom, tydligast resultat observerades hos de patienter som har en infektionsutlöst ME/CFS. Slutsats: Trots delvis negativa resultat ges visst stöd för hypotesen då dessa indikerar autoimmuna aspekter i en undergrupp av infektionsutlöst ME/CFS.Background: Myalgic Encephalomyelitis or Chronic Fatigue Syndrome (ME/CFS) is a debilitating disease which is characterized by unexplained and persistent post exertional fatigue (PEM) and a myriad of symptoms related to neurological disturbance, immunological, cognitive and autonomous dysfunction. Despite biomedical research from a disparate field of expertise the pathogenesis and etiology of ME/CFS is not well-understood. Several hypotheses regarding the pathogenesis have been proposed one of which is that ME/CFS is an autoimmune disease. Aim: The purpose of the literature study is to investigate whether there are autoimmune aspects in ME/CFS. Method: A systematic literature study based on scientific articles, published 2010-2020 in the PubMed database. Results: The study results are not entirely consistent when it comes to detecting autoimmune aspects in ME/CFS. Antibody studies targeting neuronal proteins in ME/CFS-patients and antibody treatments, immunoadsorption, and rituximab yielded negative results. In contrast, HSP60 (heat shock protein 60) antibodies for specific cross-reactive epitopes are observed in a subset of ME/CFS patients, which corresponds to infection-triggered autoimmunity. The two gene studies, HLA (human leucocyte antigen) association and genotyping of SNP (single nucleotide polymorphism) in immune genes, observed characteristic risk genes for autoimmune disease. Significant results were observed in ME/CFS- patients with an infection-triggered onset. Conclusion: Despite partially negative results, some support exists for the hypothesis as results indicate autoimmune aspects in ME/CFS with an infection-triggered onset.
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Bergquist, Maja, and Malin Tafvelin. "Hållbarhet och lönsamhet : Förhållandena mellan CSP och CFP i en svensk kontext." Thesis, Umeå universitet, Företagsekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-124644.
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Under de senaste årtiondena har ansvarfullt företagande (CSR) varit ett ämne som erhållit allt mer fokus inom forskning och således även för företag och samhället i stort. CSR är ett ämne som är högst aktuellt då globalisering är ett faktum och medför att de företag som är verksamma idag bär ett globalt ansvar, då dessa är stora aktörer i en värld som kantas av ekonomiska kriser, miljöproblem och humanitär försummelse. Det ökade intresset från samhället för CSR har medfört att företagen idag ser detta som en strategisk investering och företags satsning i hållbarhetsaktiviteter har kommit att erhålla en allt större del av företags verksamhet. Frågan kvarstår om detta endast är en investering som ökar företagets etik och moral eller om det faktiskt är lönsamt, och även om lönsamma företag ökar sin investering i hållbarhetsarbete. En stor mängd forskning har utförts för att undersöka förhållandena mellan hållbarhet och lönsamhet, dock utan att konsensus i forskningsgrenen har uppkommit. Grundat på den nuvarande forskningssituationen syftade denna studie till att undersöka vilken effekt ansvarsfullt företagande har på olika lönsamhetsmått, samt vilken effekt de olika lönsamhetsmåtten har på ansvarsfullt företagande, i företag registrerade på large cap och mid cap på Nasdaq OMX Stockholm. För att besvara studiens problemformulering och uppfylla studiens syfte har en kvantitativ forskningsansats brukats och ett urval av företag listade på large och mid cap Nasdaq OMX Stockholm har undersökts. För att sätta ett mått på ansvarsfullt företagande (CSP) har en innehållsanalys av företags årsrapporter och hållbarhetsrapporter genomförts, lönsamhetsmåtten (CFP) har utgått från redovisningsbaserade mått (ROE och ROA) samt ett marknadsbaserat mått (total avkastning). Vidare undersöks även relationen mellan variablerna, CSP och CFP, med en tidsaspekt och kontrollvariablerna storlek, risk, FoU och industritillhörighet har brukats. De teorier som har använts för att förklara CFP:s effekt på CSP är slappa resurser och direktörsopportunism, och effekten CSP har på CFP har teorierna intressentteorin, resursbaserad synvinkel och kompromissteorin använts. Det resultat som framkommit genom de multipla regressionerna som testat studiens hypoteser visar att ROE:s effekt på CSP är positiv, medan både ROA:s och avkastningens effekt på CSP är neutral. Slutsatsen blir således delad då lönsamhetsmåttet ROE visar att företag som har en högre lönsamhet kommer investera mer i hållbarhet, denna effekt knyts samman med teorin om slappa resurser. Å andra sidan visar både ROA och avkastning på en neutral effekt på CSP vilket ej kan knytas till varken slappa resurser eller direktöropportunism. Vidare när istället CSP:s effekt på ROE, ROA och avkastning undersökts visar samtliga på en neutral påverkan. Den slutsats som kan dras från detta resultat är att hållbarhetsarbete ej empiriskt kan säkerställa en högre eller lägre lönsamhet, och varken intressentteorin, resursbaserad synvinkel eller kompromissteorin kan förklara resultatet. Med icke-konklusiva resultat föreslår författarna för vidare forskning inom området där mer forskning i den svenska kontexten är nödvändig.
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Hasaas, Åsmund. "Verifisering av inntakshydraulikk i grunt inntaksmagasin for småkraftverk med bruk av CFD-verktøy." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for vann- og miljøteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18993.
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I denne masteroppgaven har inntaksmagasinet til Juvfossen kraftverk, ved Stranda på Sunnmøre blitt modellert med CFD programmet STAR-CCM+. Modelleringen er gjort for å se om strømningsmønsteret i inntaksmagasinet kan gjenskapes, og om det er mulig å forutse driftsproblemer. Strømningsfeltet fra CFD modellen av inntaksmagasinet er sammenliknet mot feltmålinger for både 2,2 m3/s og 7,9 m3/sGeometrien til selve inntaksmagasinet har blitt skannet med en laserskanner. Geometrien til elven som renner inn i inntaksmagasinet er oppmålt til cirka 55 meter oppstrøms inntaksmagasinet med GPS punktmålinger. Demning og inntakskonstruksjon er tegnet i AutoCAD i 3D fra byggetegningene. Geometrien har blitt inndelt i flere forskjellige regioner for å kunne sette forskjellige grensebetingelser. Modellen har blitt kjørt med vann og luft med VOF til å beregne vannflaten, og kun med vann. Hvor robust modellen er, har blitt undersøkt ved at det har blitt kjørt med forskjellige innstillinger for ruhet, cellestørrelse, tidsskritt, 1. og 2. ordens diskretiserings skjema for tid, 1. og 2. ordens oppstrøms skjema og vannet har kommet inn i hele eller deler av modellen.Modellen som er kjørt med VOF klarte ikke å gjenskape strømningsforholdene, mens modellkjøringene som ble utført med kun vann klarte gjenskape hovedstrømningene i inntaksmagasinet relativ bra. Modellen er sensitiv for geometrien i elven oppstrøms, men er ikke spesielt sensitiv for parametere som ruhet, cellestørrelse osv. Modellen viser tydelig konsentrasjonen av hastigheten i inntaksmagasinet. Andre parametere som skjærspenning mot bunnen, TKE og virvlingstall, vil kunne gi nyttig informasjon om strømningsforholdene og gi en god pekepinn på om inntaket vil fungere som planlagt.
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Gadré, Nathalie. "Etableringsfrihet- Rättfärdigade inskränkningar på skatterättens och bolagsrättens område : I förhållande till svensk CFC-lagstiftning." Thesis, Högskolan i Jönköping, Internationella Handelshögskolan, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-18117.
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Syftet med denna uppsats är att utreda konsekvensen av att det finns distinktioner i de rättfärdigade inskränkningarna inom etableringsfriheten mellan bolagsrätt och skatterätt samt att undersöka hur de svenska CFC-reglerna kan anses utgöra en rättfärdigad inskränkning i den grundläggande principen om rätten till fri etablering. Etableringsfriheten stadgar medborgare och bolags rätt att fritt etablera sig och bilda bolag inom Europeiska unionen. För att en medlemsstats nationella regler ska kunna inskränka den grundläggande etableringsfriheten krävs att inskränkningen kan rättfärdigas. De rättfärdigade inskränkningarna ser olika ut beroende på inom vilket rättsområde de tilllämpas. Etableringsfriheten är mer långtgående på bolagsrättens område som enbart innefattar en rättfärdigad inskränkning. Inskränkningen kan motiveras av bristen på en unionsrättslig reglering på området. På skatteområdet ser rättsläget dock annorlunda ut. Inom etableringsfriheten finns det ett flertal rättfärdigade inskränkningar på skatteområdet. Att skatterättsområdet är mer reglerat är bolagsrättsområdet har motiverats av att en medlemsstats skatteintäkter är en väsentlig del för en medlemsstats existens. Dessutom skiljer sig de olika medlemsstaternas skattelagstiftningar åt på grund av politiska, historiska och ekonomiska skäl. Konsekvensen av att CFC-beskattas innebär att en delägare löpande blir beskattad för vins-terna i hans utländska dotterbolag som är etablerat i ett lågbeskattat land. CFC-lagstiftningen syftar till att förhindra och försvåra skatteflykt. Efter Cadbury Schweppes-domen har de svenska CFC-reglerna omarbetats. Den nya svenska regleringen harmoniserar mer förenligt med EU och etableringsfriheten. Utfallet från Cadbury Schweppes-domen har även minskat distinktionerna i de rättfärdigade inskränkningarna mellan skatterättens och bolagsrättens område. Effekten av domslutet är ett stort steg framåt i strävan för en enhetlig inre marknad och en mer harmoniserad etableringsfrihet.The purpose of this paper is to investigate the consequence of that there are distinctions in the justified restrictions in freedom of Establishment between company law and tax law and to investigate how the Swedish CFC-legislation could be considered a justified restriction on the fundamental principle of freedom of Establishment. Freedom of Establishment statutes citizens and companies rights to establish and to set up companies within the European Union. In order for a Member State's national legislation to restrict the fundamental freedom of Establishment a justification is required. The justified restrictions various depending on which area of law they apply to. Freedom of Establishment is more comprising on company law, which only includes one justified restrictive. The restriction can be justified by the lack of a common Unity regulation in the company law. The fiscal situation looks quite different. Within the establishment there are several justifications restrictions on tax matters. The tax law is more regulated then the company law. The tax law has been motivated by the fact that a Member State tax revenue is an essential part of a Member of existence. In addition, differences between the various Member States tax regulations are based on account of political, historical and economic reasons. The consequence of being CFC-taxed is that a shareholder continuously will be taxed for his subsidiary established in a low-tax country. CFC-legislation seeks to bar and hinder tax evasion. After the Cadbury Schweppes-case, the Swedish CFC-legislation was revised. This new Swedish legislation is better harmonized with the EU and the freedom of Establishment. The outcome of the Cadbury Schweppes-judgement has also reduced the distinctions in the justification restrictions between tax law and company law. The effect of the judgement is a major step forward in the ambition for a unified internal market and a more harmonized freedom of Establishment.
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Emil, Svensson. "CFD-simulering av kallras från fönster : Konvektorers och nischdjupets inverkan på lufthastigheter i rummet." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-228150.
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During cold winter days it is likely that people in buildings with older windows or high glass facades experience thermal discomfort due to cold air down draughts. Earlier work has been aimed at finding analytical methods to predict the speed of the airflow in a room and in practice heating appliances are often placed beneath the windows to reduce the draught along the floor. In a study from 2012 Mohammad Parchami developed a method for estimating the required heating power to counteract the downdraught with such heating appliances. In this study, Computational Fluid Dynamics (CFD) was used to evaluate the usefulness of Parchami’s method and also to examine the potential of adapting the depth of the inward window sill as a means of decreasing the down draught. The result suggested that Parchami’s method is in need of certain modifications and further CFD-simulations can be a useful tool to make the method more acceptable to the building profession. Further, it was also shown that an adapted sill depth could considerably reduce the airflow speed in the room and the result indicated that there is an “effective sill depth” at which the airflow speed from the downdraught reaches a minimum. It is likely that this effective sill depth in large part depends on the boundary layer thickness at the window, in which case the constructors are given the alternative to determine the window sill depth by an easy estimation of the boundary layer thickness.
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Finstad, Pål Henrik Enger. "Undersøkelse av ustasjonære og turbulente forhold i minirigg ved hjelp av LDV, trykkmålinger og CFD." Thesis, Norwegian University of Science and Technology, Department of Energy and Process Engineering, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10509.
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Diplomoppgava fortsetter arbeidet som blei starta i prosjektoppgava høsten 2008. Det er utført laboratorieforsøk på en minirigg der spinn settes opp i et vertikalt rør. Nedstrøms kan vann injiseres tangentielt gjennom ei dyse i motsatt retning av spinnet. Strømningsbildet og trykksvingninger er tidligere undersøkt ved hjelp av pitot og trykkmålinger. Arbeidet i denne oppgava omfatter utbedring av miniriggen for måling med LDV, samt supplerende målinger av hastighet med LDV og trykkmålinger. En rekke målinger av hastighet og trykk er gjort for å undersøke strømningsbildet uten og med vanninjeksjon. De eksperimentelle resultata er sammenligna med numeriske beregninger gjort i ANSYS CFX. Det er funnet at vanninjeksjon dreper spinnet i strømninga, og gir lavere tangentiell hastighet. I flere tilfeller minsker trykkpulsasjonene, men det er også funnet at vanninjiseringa kan ha motsatt effekt. Dette avhenger av swirlnummer og trykk i strømninga. Det er ikke funnet sammenfallende frekvenser for trykkpulsasjona og det turbulente hastighetsleddet. De numeriske simuleringene beskriver strømningsbildet på en tilfredsstillende måte uten vanninjeksjon. Spinnet underpredikerers, i tillegg til at profilformen avviker noe. Ved vanninjeksjon dempes spinnet betraktelig mer i de numeriske simuleringene enn hva som virkelig er målt i lab. Særlig den tangentielle hastigheta og det tangentielle momentet avviker mye i verdi.
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Holderness, Kathryn. "Identification of immunodominant T cell epitopes from enterotoxigenic E. coli colonization factor antigen I (CFA/I) responsible for T helper cell cytokines." Thesis, Montana State University, 2012. http://etd.lib.montana.edu/etd/2012/holderness/HoldernessK0512.pdf.
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Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal disease contracted by consuming contaminated food or water. ETEC is able to adhere to the small intestine by utilizing pili or fimbriae, one of which is the fimbriae Colonization Factor Antigen/I (CFA/I). The extracellular portion of CFA/I fimbriae is comprised of two fimbrial subunits, cfaB and cfaE. Expression of CFA/I fimbriae on the surface of an attenuated Salmonella vaccine vector, Salmonella-CFA/I, results in a biphasic T cell response in immunized mice. This response is characterized by the initial production of Th2-type cytokines, including IL-4 and IL-5, followed by a shift after 4 weeks toward an IFN-gamma-associated, Th1 response. Restimulation of CD4 + T cells from Salmonella-CFA/Iimmunized mice with CFA/I fimbriae also generates the anti-inflammatory cytokine, IL-10. Salmonella-CFA/I is able to generate antigen-independent Foxp3 + regulatory T cells, which are able to reduce symptoms of Experimental Autoimmune Encephalomyelitis in immunized SJL mice and Collagen Induced Arthritis in DBA/I and C57BL/6 mice, via production of IL-10 and TGF-beta by phenotypically distinct regulatory T cell subsets. The following research describes the contribution of cfaB and cfaE to the observed therapeutic and immunological responses. This was measured by independently expressing recombinant cfaB and cfaE proteins and evaluating the associated cytokine responses from the co-culture of these proteins with CD4 + T cells from immunized mice. Major Histocompatibility Complex II-restricted immunodominant regions were also mapped for both cfab and cfae proteins using cytokine ELISAs, ELISPOTs, Proliferation Assays, and flow cytometry. We mapped an IFN-gamma-producing peptide from cfaB and an IL-4-producing peptide from cfaE. We further determined that co-culture with peptides from both fimbrial proteins is able to generate regulatory T cell-associated cytokines including IL-10 and TGF-beta as well as the newly described suppressive cytokine, IL-35. These results show that the immune responses to cfaB and cfaE are mediated by multiple immunodominant regions within each protein.
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Haines, Sara. "Identification of environmental and genetic factors influencing virulence gene expression in Enterotoxigenic Escherichia coli." Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10017.
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Furlan, Karolina. "CFC-reglerna : -en studie av den svenska CFC-lagstiftningen och dess förenlighet med internationella åtaganden i form av skatteavtal baserade på OECD:s modellavtal beträffande inkomst och förmögenhet." Thesis, Jönköping University, JIBS, Commercial Law, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-822.
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Den svenska CFC-lagstiftningens förenlighet med internationella åtaganden i form av skatteavtal baserade på OECD:s modellavtal har varit ett omdiskuterat ämne inom svensk lagstiftning under mer än ett decennium. Tvistigheten kring CFC-lagstiftningens förenlighet med skatteavtal förekommer också i andra medlemsstater av OECD.
Den svenska CFC-lagstiftningen tillämpas sedan 1 januari 2004. Rättsföljden av lagstiftningen framgår av 39 a kap. 13 § IL. Syftet med CFC-lagstiftningen är att förhindra en erosion av den svenska skattebasen. Utan CFC-lagstiftning skulle en skattebetalare kunna etablera företag i lågbeskattde jurisdiktioner enbart i syfte att minska den totala skattebördan. Genom att tillämpa CFC-lagstiftningen beskattas en delägare löpande för sitt innehav i den utländska juridiska personen.
Enligt förarbeten är CFC-lagstiftningen förenlig med de svenska skatteavtalen. Lagstiftaren lägger stor vikt vid ordalydelsen i kommentarerna till OECD:s modellavtal. OECD rekommenderar medlemsstaterna att tillämpa lagstiftningen.
Uppsatsen visar att CFC-lagstiftningen är förenlig med skatteavtal baserade på OECD:s modellavtal. Syftet med skatteavtal är att förhindra juridisk dubbelbeskattning. CFC-lagstiftningen ger upphov till ekonomisk dubbelbeskattning. Diskussionen gällande CFC-lagstiftningens förenlighet med skatteavtal beror på kommentarernas rättsliga verkan samt därtill framställda anmärkningar.
The Swedish CFC legislation and its compatibility with international commitments in form of tax treaties based on OECD Model have been disputed in the Swedish legislation for more than a decade. Whether CFC legislation is compatible with tax treaties is also disputed in many other Member States of the OECD.
The Swedish controlled foreign company legislation entered into force on 1 January 2004. The legal effect of the legislation is covered in chapter 39 a, section 10 of the Swedish Income Tax Act. The basic purpose of CFC legislation is to prevent an erosion of the Swedish tax basis. Without CFC regulations a taxpayer would be free to establish companies in low-tax jurisdictions for the sole purpose of reducing the overall tax burden. By applying the legislation a Swedish resident shareholder will be taxed on all the income that is attributed from a foreign subsidiary, regardless of when the income is distributed.
In the preparatory works the government argues that the CFC legislation is compatible with Sweden’s tax treaties, based on OECD Model. The government’s opinion is mostly based on the statement in the Commentary to the OECD Model. The legislation is recommended by the OECD.
This thesis concludes that the CFC legislation is compatible with tax treaties based on the OECD Model. The purpose with tax treaties is to avoid juridical double taxation. The CFC-legislation gives rise to economic double taxation. Therefore the legislation can be justified. The discussion of the CFC legislation compatible with tax treaties depends of the relevance of the Commentary but also on observations given to the Commentaries.
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Pons, Cots Ramon Maria. "Computational analysis of fluid dynamics at the asceding thoracic aorta in Marfan syndrome patients." Doctoral thesis, Universitat Ramon Llull, 2020. http://hdl.handle.net/10803/669234.
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Els aneurismes aòrtics són una dilatació progressiva i irreversible de la paret aòrtica, que pot causar la ruptura o dissecció dels vasos, el que resulta en una pèrdua catastròfica de sang que condueix a la mort. El tractament farmacològic inicial se centra en aturar el creixement per prevenir la ruptura, però requereix una reparació invasiva oberta o una reparació endovascular en pacients en risc. El maneig del pacient i l'estratificació de risc després del diagnòstic són crítics, especialment en l'aorta ascendent, ja que actualment no hi ha tractaments endovasculars disponibles. Segons les directrius actuals, el diàmetre aòrtic màxim és l'únic criteri geomètric o fluidodinàmic específic del pacient acceptat com a predictor clínic del risc de ruptura. No obstant això, l'anormal fluidodinàmica en l'aorta ascendent s'ha reportat àmpliament com una possible font d'aneurismes aòrtics i la seva comprensió podria millorar l'avaluació del risc del pacient.
En aquest estudi, es va avaluar la fluidodinàmica en aortes de controls sans i pacients amb síndrome de Marfan. Per fer això, hem comparat el rendiment de les simulacions de dinàmica de fluids computacional i d'interacció fluid-estructura utilitzant imatges clíniques com a condicions específiques del pacient. També hem dissenyat un sistema in vitro que podria exposar les cèl·lules endotelials aòrtiques humanes a un entorn fluidodinàmic que imita el de les simulacions aòrtiques.
L'estudi ha revelat, en pacients Marfan, que considerà l'elasticitat de la paret en les simulacions és essencial per obtenir amb precisió els valors fluidodinàmics que tenen el potencial d'estratificar aquests pacients. En aquest sentit, les simulacions d'interacció fluid-estructura han superat la fluidodinàmica computacional clàssica a un cost computacional moderat. Com a resultat d'aquest estudi, un paràmetre adimensional, la relació d'esforç tallant, ha determinat el seu potencial com a marcador de progressió d'aneurisma en pacients amb Marfan.Los aneurismas aórticos son una dilatación progresiva e irreversible de la pared aórtica, que puede causar la ruptura o disección de los vasos, lo que resulta en una pérdida catastrófica de sangre que conduce a la muerte. El tratamiento farmacológico inicial se centra en detener el crecimiento para prevenir la ruptura, pero se requiere una reparación invasiva abierta o una reparación endovascular en pacientes en riesgo. El manejo del paciente y la estratificación del riesgo después del diagnóstico son críticos, especialmente en la aorta ascendente, ya que actualmente no hay tratamientos endovasculares disponibles. Según las directrices actuales, el diámetro aórtico máximo es el único criterio geométrico o fluidodinámico específico del paciente aceptado como predictor clínico del riesgo de ruptura. Sin embargo, la anormal fluidodinámica en la aorta ascendente se ha reportado ampliamente como una posible fuente de aneurismas aórticos y su comprensión podría mejorar la evaluación del riesgo del paciente. En este estudio, se evaluó la fluidodinámica en aortas de controles sanos y pacientes con síndrome de Marfan. Para hacer esto, hemos comparado el rendimiento de las simulaciones de dinámica de fluidos computacional y de interacción fluido-estructura utilizando imágenes clínicas como condiciones específicas del paciente. También hemos diseñado un sistema in vitro que podría exponer las células endoteliales aórticas humanas a un entorno fluidodinámico que imita el de las simulaciones aórticas. El estudio ha revelado, en pacientes Marfan, que considerar la elasticidad de la pared en las simulaciones es esencial para obtener con precisión los valores dinámicos de los fluidos que tienen el potencial de estratificar a estos pacientes. En este sentido, las simulaciones de interacción fluido-estructura han superado la fluidodinámica computacional clásica a un costo computacional moderado. Como resultado de este estudio, un parámetro adimensional, la relación de esfuerzo cortante, ha demostrado su potencial como marcador de progresión de aneurisma en pacientes con Marfan.
Aortic aneurysms are a progressive and irreversible dilation of the aortic wall, which can lead to vessel rupture or dissection, resulting in catastrophic blood loss leading to death. Initial pharmacological treatment is focused on growth arrest to prevent rupture, but invasive open repair or endovascular repair are required in patients at risk. Patient management and risk stratification after diagnosis are critical, especially in the ascending aorta since no endovascular treatments are currently available. According to current guidelines, maximum aortic diameter is the only patient-specific geometrical or fluidodynamic criterion accepted as clinical rupture risk predictor. However, abnormal fluid dynamics at the ascending aorta have been widely reported as potential origin of aortic aneurysms and their understanding could improve the risk assessment of patients. In this study, the fluid dynamics of aortae from healthy controls and patients with Marfan syndrome have been evaluated. To do so, we have compared the performance of computational fluid dynamics and fluid-structure interaction simulations using clinical imaging as patient-specific inputs. We have also designed an in vitro system that could expose human aortic endothelial cells to a fluidodynamic environment that mimics that of aortic simulations. The study has revealed, in Marfan patients, that considering the wall elasticity in simulations is critical to derive precisely fluid dynamic values that hold the potential to stratify such patients. In this sense, fluid-structure interaction simulations have outperformed classic computational fluid dynamics at a moderate computational cost. As a result of this study, a dimensionless parameter, the shear stress ratio, has shown its potential as marker of aneurysm progression in Marfan patients.
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Nylund, Annika. "De måste åtminstone tro oss : En enkätstudie om hur personer med ME/CFS blir bemötta i primärvården." Thesis, Röda Korsets Högskola, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:rkh:diva-2528.
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Background: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome is a complex disease with unknown cause. It affects about 0.4 percent of the population. It is a chronic disease that manifests itself in an impairment fatigue that is impaired by physical exertion. Purpose: The purpose of the study was to illustrate how people diagnosed with ME/CFS experience the primary care treatment. Method: An empirical questionnaire with mixed method was used. Most questionnaires were quantitative, and one question was qualitative. Result: ME patients may wait several years and meet several doctors before they get their diagnosis. The result showed that most respondents felt that they did not receive good treatment in primary care. Conclusion: People with ME/CFS want to be treated with respect and want primary care to listen and take them seriously. In a partnership between the primary care and healthcare personnel, they could meet more equally, and the ME sufferers would not have to wait several years to meet several doctors before receiving the assistance and support they need in their illness. Clinical significance: New research on how healthcare professionals can help people with ME/CFS is needed. Research would also be needed on how the role of nurse could be extended to be a key part of primary care for people with ME/CFS.
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Mateu, Morante Eva. "Anàlisi de la variació genètica de les regions CFTR i GBA en poblacions humanes de tot el món." Doctoral thesis, Universitat Pompeu Fabra, 2001. http://hdl.handle.net/10803/7063.
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Aquest treball és una contribució als estudis de diversitat del genoma humà i pretén estudiar la variació genètica existent a nivell mundial en dos gens, causants de malaltia, el gen CFTR i el gen GBA, en cromosomes d'individus sans. Mutacions en aquests gens produeixen la fibrosi quística i la malaltia de Gaucher respectivament. La fibrosi quística és la malaltia autosòmica recessiva més comuna en poblacions europees. La malaltia de Gaucher és la malaltia lisosòmica d'acumulació lipídica més freqüent. L'estudi analitza la variació genètica en diferents polimorfismes d'ambdós gens; reconstrueix els haplotips i analitza la seva distribució geogràfica; i analitza l'extensió i distribució geogràfica del desequilibri de lligament entre loci. Pel gen GBA, hem ampliat la regió, abastant fins al gen PKLR (que codifica per a la piruvat quinasa). A més a més, pel cas de CFTR, pot ajudar a entendre l'origen de les mutacions més freqüents causants de fibrosi quística.This work is a contribution to human genome diversity studies and it aims to study the world-wide genetic variation that exists in two disease genes, CFTR and GBA gene, in healthy chromosomes. Mutations in these genes are known to cause cystic fibrosis and Gaucher disease respectively. Cystic fibrosis is the most common severe autosomal recessive disease in patients of European descent. Gaucher disease is the most frequent lysosomal storage disorder. The study analyzes the genetic variation in CFTR and GBA polymorphisms; estimates haplotype frequencies and describes their geographic distribution; and measures linkage disequilibrium between loci. For GBA gene, we have extended the analysis covering PKLR gene (that encodes for a pyruvate kinase). Moreover, for CFTR gene, we have tried to understand the origin of the most common cystic fibrosis causing mutations.
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Shirdel, Mariam. "Probing protein - Pili interactions by optical tweezers and 3D molecular modelling." Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-68747.
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Pilonieta, Maria Carolina. "Transcriptional Regulation of Virulence Genes in Enterotoxigenic Escherichia coli and Shigella flexneri by Members of the AraC/XylS Family." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_dissertations/111.
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Pathogenesis of enterotoxigenic Escherichia coli (ETEC) and Shigella flexneri relies predominantly on members of the AraC/XylS family of transcriptional regulators, Rns (or its homolog, CfaD) and MxiE, respectively. Rns/CfaD regulate the expression of pili, which allow the bacteria to attach to the intestinal epithelium. Better understanding of the role Rns plays in virulence was attained by expanding our knowledge of the Rns regulon, revealing that it functions as an activator of cexE, a previously uncharacterized gene. By in vitro DNase I footprinting two Rns-binding sites were identified upstream of cexEp, both of which are required for full activation of cexE. The amino terminus of CexE also contains a secretory signal peptide that is removed during translocation to the periplasm. Though the function of CexE remains unknown, these studies suggest that CexE is a novel ETEC virulence factor since it is regulated by Rns/CfaD. In Shigella flexneri, the expression of a subset of virulence genes (including, ipaH9.8 and ospE2) is dependent upon the activator MxiE and a cytoplasmic chaperone IpgC. To define the molecular mechanism of transcriptional activation by this chaperone-activator pair, an in vitro pull down assay was performed revealing that MxiE specifically interacts with IpgC in a complex. Additionally, IpgC recognizes three polypeptide regions in MxiE: within MxiE(1-46), MxiE(46-110) and MxiE(196-216). Furthermore, it seems that MxiE and IpgC regulate transcription of ipaH9.8 and ospE2 promoters differently. In the bacterium, the formation of the MxiE-IpgC complex is initially prevented because IpgC is sequestered in individual complexes with effector proteins, IpaB and IpaC. Upon contact with an eukaryotic host cell the effector proteins are secreted, thereby freeing IpgC to form a complex with MxiE and activate the expression of virulence genes. This new characterization of the role of Rns and MxiE in virulence gene regulation in ETEC and S. flexneri, respectively will give new insights into the pathogenesis of the regulators.
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Climent, Agustina Javier. "Development of a modelling tool to perform hydrodynamics coupled with biological processes in the secondary stage of wastewater treatment plants." Doctoral thesis, Universitat Jaume I, 2019. http://hdl.handle.net/10803/668408.
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Simulation models based on tools associated with computational fluid dynamics (CFD) and applied to wastewater treatment have been developed. The hydrodynamic effect of the internal elements that govern the flow behavior in the biological reactors combined with the biochemical models that reproduce the purification process has been investigated. An experimental work of validation of CFD models has been carried out in real scale.Se han desarrolado modelos de simulación basados en herramientas asociadas a la dinámica computacional de fluidos (CFD) y aplicados al tratamiento de aguas residuales. Se ha investigado el efecto hidrodinámico de los elementos internos que gobiernan el comportamiento del flujo en los reactores biológicos combinado con los modelos bioquímicos que reproducen el proceso de depuración. Se ha realizado un trabajo experimental de validación de modelos CFD a escala real.
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Katea, Billy. "CFD Analysis of Air Flow Through a New Design For an Outlet Louver of a Cooling System : CFD Analys av luftflödet genom en ny design för utloppet i ett kylsystem." Thesis, Karlstads universitet, Institutionen för ingenjörsvetenskap och fysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-62647.
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In order to improve the performance of the outlet louver for the cooling system used in the Combat Vehicle CV90, the manufacturing company BAE System Hägglunds AB recently came out with a new design. This project deals with the possible modifications of the new design to achieve a higher performance in terms of air flow resistance without losing any protection capabilities. 18 versions of BAE Systems Hägglunds AB new design were modeled using Creo Parametric 3.0 3D CAD-software. These versions were modeled with respect to the requirement of protection, when several possible threat scenarios were carefully reviewed and studied. The air flow through each one of these designs was CFD-simulated using ABAQUS/CAE 6.14 CFD-code, the pressure drop received in each CFD-model was compared to the pressure drop over the currently used design of the outlet louver. The concept called concept Arrows RD shows the lowest pressure drop, which is nearly 50 % lower than the pressure drop over the original design, showing that the new design could be a reasonable replacement to the currently used design.
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Chen, Lujia. "Investigation on the feasibility of trifluoroiodomethane (CF₃I) for application in gas-insulated lines." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/80744/.
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It is widely acknowledged that the world needs to reduce the level of greenhouse gas emissions. It is proposed to use potentially cleaner renewable energy sources to replace fossil fuels, and thus reduce greenhouse gas emissions. A significant challenge facing renewable energy sources, however, is that the power generation facilities are often located far from the load centres, meaning that new high capacity long-distance transmission systems would need to be built. This is a particular issue since there are increasing difficulties in obtaining approval to construct new overhead lines (OHL). An alternative is gas-insulated lines (GIL), a system for the transmission of electricity over long distance and is considered as a viable technical solution in places where OHL cannot be constructed. The currently adopted gas medium in GIL, however, is sulphur hexafluoride (SF₆), which is a potent greenhouse gas. Trifluoroiodomethane (CF₃I) has been proposed as an alternative insulation medium to SF6 in GIL, and this thesis investigates the potential of using a CF₃I gas mixture in GIL applications. It is hoped that the research can lead to a new form of environmentally friendly power transmission system that could cope with the increasing power demand in large metropolitan areas, and contribute to the reduction of SF6 usage in the high-voltage industry. The literature survey reviewed the research work on CF₃I gas and its mixtures to date. Several research gaps were identified, and these informed the investigations carried out in this research. Reduced-scale coaxial test systems with the electric field properties of a full-scale 400 kV GIL were designed, developed and fabricated. The designs were simulated using COMSOL to ensure that the highest field would be along the centre of the conductor. The effective ionisation coefficients of various CF3I gas mixtures were calculated using BOLSIG+, which provided estimated values for the critical reduced field strength of each gas mixture. Extensive laboratory tests using a standard lightning impulse (1.2/50) were conducted on the fabricated prototypes using various CF₃I/CO₂ and CF₃I/N₂ gas mixtures to determine the 50% breakdown voltage. The breakdown characteristics of CF3I gas mixtures were examined for pressure, geometric ratio, impulse polarity, buffer gas and mixture content. Based on the measured breakdown voltage and calculated critical reduced field strength of various CF3I gas mixtures, a two-stage streamer/leader mathematical model was developed to evaluate the reduction in field strength at higher pressures. A comparative study was carried out on CF3I gas mixtures in a rod-plane electrode configuration under standard lightning impulse and steep-front square impulse waveforms. This investigation focused on the V-t characteristics of CF3I gas mixtures in this particular configuration. A phase equilibrium experiment was also carried out to determine the boiling point of various CF3I gas mixtures.
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Al, Taweel Maher. "CFD simulering av kallras : Undersökning av temperatur- och luftbeteende intill höga glasfasader och i vistelsezon med golvvärme som en värmekälla." Thesis, KTH, Tillämpad termodynamik och kylteknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-133483.
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Glass has sophisticated front properties and are used as facades in high buildings. During cold periods, these glass facades could cause thermal discomfort, due to cold downdraught. Cold downdraught can be countered by placing heaters under glass surfaces. Nowadays technology offers highly insulating windows, which is why there is an interest to investigate the indoor climate with only underfloor heating. The research in this area is limited, and few empirical methods are available. Theoretical analysis has begun but it still brand new. The aim of this investigation was to present the thermal indoor climate influenced by various parameters, such as outdoor temperature, U-value and the glass height. The results were also meant to be used as reference tools in future projects. A reference building was modeled in simulation software called CFD Star-CCM+. The assignment was initiated by Incoord, a leading consulting company in energy, indoor climate and installation planning. The results showed that the air velocity increases with decreasing outdoor temperature and decreases with increasing thermal insulation (lower U-value). At the edges of the glass the air velocity becomes twice as large compared to the velocity of the air in the middle of the atrium. The air velocity (maximum and average) at 0.1 m above the floor is always higher than at 2.0 m. The lowest air velocities start from about 0.25 m/s at 0 ℃ and reaches to 0.60 m/s at -20 ℃. That means these air velocities are too high for what is accepted as a good indoor climate, where the maximum allowable air velocity is 0.15 m/s. The outdoor temperatures and the glass facade’s U-value also have an effect on the surface temperature of the glass facade. This decreases the surface temperature with decreased outdoor temperature, and the surface temperature increases at lower U-value. The height of the glass facades proved to affect both the air velocity in the occupied zone and in the glass surface temperature. The air velocity increases with the glass’ height. The increase is higher at 0.1 m than at 2.0 m above the floor. The result shows also that the average air velocity is lower than 0,15 m/s at window height lower than 5 m. But, at the same height the maximum air velocity is higher than 0.3 m/s. The surface temperature of the glass facades increases with the glass’ height. This is because the indoor heat transfer coefficient increases with height. The outdoor heat transfer coefficient is a function of the wind speed and was assumed to be constant. The underfloor heating, which is represented in the simulations with a floor surface temperature of 27 ℃, is not enough to maintain a good indoor climate in any of simulations. The results of this thesis showed a strong relation between indoor climate, outdoor temperature, U-value and the glass height. This study also showed that the floor heating is not enough to counteract the cold draft during extreme cold periods, in high glass buildings. The presented results can be used as a reference tool for the assessment of air velocities and surface temperatures, in similar high buildings.
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Smrček, Jaromír. "Pokročilé nástroje pro měření výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2008. http://www.nusl.cz/ntk/nusl-235878.
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This thesis presents the I/O layer of Linux kernel and shows various tools for tuning and optimization of its performance. Many tools are presented and their usage and outputs are studied. The thesis then focuses on the means of combining such tools to create more applicable methodology of system analysis and monitoring. The practical part consists of applying SystemTap scripts for blktrace subsystem and creating a fragmentation monitoring tool with graphical output.
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Johansson, Eric. "Utvärdering av dataprogram för vindresursberäkningar : En jämförelse av vindresursberäkningar i kuperad skogsterräng med programmet WAsP (linjär modellering) och CFD-programmet WindSim." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-194296.
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Vindkraft för generering av el har under de senaste åren vuxit kraftigt i Sverige och utbyggnaden väntas fortsätta. Ett viktigt steg när nya vindkraftsparker skall byggas är att göra en vindanalys för det aktuella området. Vindanalysen är ett viktigt underlag för att avgöra om en investering i vindkraftverk kommer vara ekonomiskt lönsamt på den aktuella platsen. Som underlag till vindanalysen sätts vanligen mätutrustning upp i området och vindförhållandena på platsen mäts upp. Att installera och underhålla mätmaster är kostsamt och därför mäts vindarna på ett begränsat antal platser i det intressanta området. Sedan används olika beräkningsprogram för att extrapolera de uppmätta vindresurserna till positioner där mätningar saknas. För närvarande används programmet WAsP som standard av många vindkraftsprojektörer. WAsP:s beräkningsmodell är relativt enkel och tar till exempel inte hänsyn till turbulens som uppkommer då terrängen är kuperad. Som ett alternativ till WAsP har olika CFD-program introducerats på marknaden under senare år. Dessa programs modeller är mer avancerade och de kräver därför längre beräkningstid jämfört med WAsP, men förhoppningen är att de skall ge mer tillförlitliga modelleringsresultat. I denna studie har vindmodelleringar i det linjära modelleringsprogrammet WAsP jämförts med modelleringar i CFD-programmet WindSim. Syftet har varit att undersöka om WAsP ger tillförlitliga modelleringsresultat i svenskt kuperat skogslandskap och om WindSims CFD-beräkningar kan ge en ökad noggrannhet i jämförelse. Prestandan hos respektive program har utvärderats genom att jämföra extrapolerade medelvindar med faktiska mätningar. Vindmätningar har funnits att tillgå från en period av 12 månader från två mätmaster med givare på 60, 80 och 100 meters höjd. Avståndet mellan masterna är cirka 10 kilometer. Resultaten från studien tyder på att WindSim kan ge en något ökad noggrannhet jämfört med WAsP, men resultaten visar samtidigt att en CFD-modellering inte med automatik ger mer tillförlitliga modelleringsresultat. Studien har visat att resultatet från WindSim är starkt beroende av hur modellen sätts upp och det kan därför vara enklare att göra fel i WindSim jämfört med WAsP. Det blev också tydligt att en modell där den simulerad vindskjuvning (variation av vindhastigheten i höjdled) stämde bra överens med den uppmätta inte behöver betyda att WindSim-modellen gör bra extrapolationer av vindförhållandena från den ena masten till den andra. Vidare visade sig WAsP missbedöma effekter från topografin något och om vindmätningar görs på utmärkande höjder är det sannolikt att WAsP överskattar vindförhållandena i de lågt belägna delarna av terrängen. I WindSim undersöktes två olika modelluppsättningar, en med WindSims skogsmodul där skogen simuleras som 3D objekt och en modell där skogen hanteras med på samma sätt som i WAsP med råhetslängd och nollplansförskjutning. När skogsmodulen användes var det inte möjligt att erhålla en modellerad vindskjuvning som stämde överens med den uppmätta i en neutral atmosfär, vilket är WindSims standardinställning för atmosfärsstabiliteten. I en neutral atmosfär med skogsmodulen överskattades vindhastigheten på låga höjder. Om atmosfären simulerades som stabil i medeltal var det möjligt att få den simulerad vindskjuvning att stämma överens med den uppmätta, men extrapolationerna i horisontalled blev inte bra med denna modell. Om atmosfären skall simuleras som stabil i WindSim tyder resultaten från studien på att vindmätningarna måste delas in efter rådande atmosfärstabilitet för den aktuella tidpunkten för mätningen. Det fungerade inte tillfredställande att använda alla vindmätningar i samma modell och försöka hitta ett passande medelvärde för stabiliteten. Om vindmätningarna skall delas upp efter rådande stabilitet kommer varje stabilitet kräva en egen modellering vilket betyder att beräkningstiden kommer öka markant. Att simulera skogen i WindSim med en råhetslängd och en nollplansförskjutning visade sig fungera bra. En modellerad vindskjuvning som stämde bra överens med den uppmätta kunde erhållas i en neutral atmosfär och denna modell presterade sammantaget bäst av alla undersökta modeller i den här studien. Det studerade området består övervägande av skog och vindmätningarna som använts är utförda inom skogsområdet. WindSim skogsmodul kan tänkas vara mer användbar och viktig om skog förekommer i begränsade partier och då tänkta vindturbiner inte placeras direkt inom skogsområdet. En förhoppning på CFD-program är att vindmätningar utförda på låg höjd skall kunna användas för att förutse vinden på högre höjder med större noggrannhet jämfört med WAsP. Resultat från den här studien visar dock att det kan vara svårt att uppnå en bra modellerad vindskjuvning i WindSim. Även i WindSim är således viktigt att ha vindmätningar från flera olika höjder för att kunna verifiera modellen mot innan programmet kan förväntas förutse vinden på högre höjder korrekt. Sammanfattningsvis förefaller en bra inställd WindSim-modell kunna ge en något ökad noggrannhet av extrapolerade vindförhållanden jämfört med WAsP, men om extrapolationer skall göras mellan liknade områden i terrängen, till exempel från en kulle till en annan kulle, är det tveksamt om den lilla ökade noggrannheten ger skäl för den ökade beräkningstiden i WindSim.An evaluation of wind energy software: a comparison of wind resource calculations made with the software WAsP (linear model) and the CFD software WindSim over a hilly forested area. Results produced from the wind modeling linear program WAsP were compared with modeling results produced by the CFD program WindSim. The aim was to investigate whether WAsP achieves accurate calculation results over a hilly forested area in Sweden, and if the CFD modeling in WindSim provides more accurate results than WAsP. The performance of each program was evaluated by comparing extrapolated average wind speed data to actual measurements. The study shows that WindSim may achieve an increased accuracy of extrapolated wind conditions compared to WAsP, as well as indicates that a CFD calculation does not automatically provide more reliable extrapolations than linear modeling in WAsP. The accuracy of the WindSim extrapolations was highly dependent on how the model was set up, and hence it may be easier to make errors with WindSim compared to WAsP. A model in WindSim with accurate simulated wind shear did not necessarily mean that the model made good extrapolations of wind conditions horizontally. Furthermore, WAsP was shown to slightly misjudge orographic effects, and when wind measurements are made over hilltops, WAsP most likely overestimates the average wind speed in the lower parts of the terrain. When a good model was established, WindSim provided slightly more accurate results than WAsP, but if extrapolations are to be made between similar areas in the terrain, for example from one hill to another hill, it is doubtful that the small increase in accuracy gives enough reason for the increased time in calculation required by WindSim.
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Brogren, Felix, and Peter Gustafsson. "VIBRATION ANALYSIS OF THE FLUE GAS FAN IN MÄLARENERGI’S UNIT 6 : Troubleshooting using CFD simulations in ANSYS to locate the origin of the vibration spikes and suggest solutions for a more optimized performance." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-40030.
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The purpose of this study is to investigate the flue gas fan in Mälarenergi’s Unit 6 and try to find what is causing the vibrations increase. The Fast Fourier transform (FFT) method was used for this degree project. A comparison was made with previous studies using FFT in order to pinpoint the source of the problem with vibrations. After a possible source had been identified, a computational fluid dynamics (CFD) simulation was performed using ANSYS to visualize the problem. Two cases were simulated using two different turbulence models: the K-epsilon model and the Large-eddy simulation (LES) model. The result from the CFD simulations was compared with previous studies that used similar turbulence models. The flue gas fan’s high vibrations are most likely flow-induced. The simulation result indicates that LES model performed better than the Kepsilon model. The lack of validation in this degree work means that it is hard to know the accuracy of the model. Based on the simulation results the most promising solution seems to be inlet straighteners.Syftet med studien är att undersöka rökgasfläkten i Mälarenergis Unit 6 och att försöka hitta vad som orsakar vibrationsökningarna. Fast Fourier transform metoden har används i detta examensarbete. En jämförelse har gjorts med tidigare studier som använt FFT metoden för att kunna urskilja källan till vibrationsproblemet. Efter en rimlig källa hittades så utfördes en CFD-simulering i ANSYS för att visualisera problemet. Två fall simulerades med två olika turbulensmodeller: K-epsilon modellen och Largeeddy simulation modellen. Resultatet från CFD-simuleringarna jämfördes med tidigare studier som använt liknande metoder. Rökgasfläktens höga vibrationer är med störst sannolikhet flödesinducerad. Simuleringsresultatet indikerar att LES modellen utfördes bättre än Kepsilon modellen. Då det saknas en validering i form av flödesmätningar så är det svårt att säga hur lik modellen är med verkligheten. Baserat på resultatet från simuleringarna så verkar inloppsgaller vara den mest lovande lösningen.
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Zhao, Yuer. "A Numerical Study of Melt Pool Heat Transfer in the IVR of a PWR." Thesis, KTH, Fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297867.
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This thesis aims to provide the thermal condition of melt pool convection by CFD simulation, which is important to the assessment of the invessel melt retention (IVR) strategy widely adopted in Generation III pressurized water reactors (PWRs). As a severe accident mitigation measure, the IVR strategy is realized through external cooling of the lower head of a reactor pressure vessel (RPV). To achieve the coolability and retention of the corium pool in the RPV lower head, the heat flux at the outer surface of the vessel should be less than the critical heat flux (CHF) of boiling around the lower head. Under such condition, the integrity of the RPV is guaranteed by the adequate thickness of the unmelted vessel wall. The thesis work starts from the selection and validation of a turbulence model in the CFD computational tool chosen (Fluent). Afterwards a numerical model is set up for estimation of melt pool heat transfer of a reference PWR with the power capacity of 1000 MWe, including a mesh sensitivity study. Based on the numerical model of a twolayer melt pool, four tasks are carried out to investigate the effects of Zr oxidation ratio, Fe content, and radiation emissivity on heat flux profiles, as well as the focus effect under extreme conditions. Selection and validation of the turbulence model are conducted by comparing the simulation results of different turbulence models with the DNS data on the convection of volumetrically heated fluid layer bounded by rigid isothermal horizontal walls at equal temperature. The internal Rayleigh numbers of the flow reach up to 10e6. The comparison shows a good agreement of the SST k-ω turbulence model results with the DNS data. The simulations with the Zr oxidation ratio of 0, 0.2 and 0.5, correspondingly, the oxide layer of 1.389m, 1.467m and 1.580m, and the metal layer of 0.705m, 0.646m and 0.561m in height, show that, the temperature of the oxide layer will increase with Zr oxidation ratio, while the temperature of the metal layer will decrease resulting in more heat transfer through the oxide layer sidewall and less top radiation. Nevertheless, the effect of the Zr oxidation ratio is not pronounced in the range of 00.5. The simulations with the Fe mass of 22t, 33t and 45t, and respective height of the metal layer of 0.462m, 0.568m and 0.646m, show that, the inner metal layer will significantly increase the temperatures of both the metal layer and the oxide layer. The percentage of heat transfer at the oxide layer sidewall will increase to supplement the reduction of that at the metal layer. The simulations with the radiation emissivity of 0.2, 0.35, 0.45 and 0.7 show that, the emissivity below 0.45 has an impact on heat transfer, and the temperatures and sidewall heat flux of both the oxide layer and the metal layer will increase with decreasing emissivity. The impact is negligible when the emissivity is above 0.45. The simulations under the hypothetically extreme conditions with either an adiabatic top boundary or a very thin metal layer show the focusing effect may occur, i.e., the heat flux through the metal sidewall is larger than that in the oxide layer. But the local high heat flux is flattened by the vessel wall with good heat conductivity. In summary, the simulations demonstrate that, except for the cases under extreme conditions, the heat fluxes of the melt pools in all other cases are significantly lower than the CHF of external cooling of the lower head. Therefore, the safety margin of the IVR strategy of the PWR chosen is seems sufficient. However, due to some limitations (e.g., simplification and assumptions) in the simulation cases and coupling of different influential factors, as indicated by the present study, the precise predictions of heat flux under all scenarios are still difficult. Therefore, the conclusions could not be generalized to the other conditions or other configurations of the molten pools. By discussing the model and simplifications/assumptions adopted in this work, the improvement directions of the numerical model and other perspectives are proposed at the end of the thesis.Denna avhandling syftar till att tillhandahålla det termiska tillståndet för smältbassängskonvektion genom CFD-simulering, vilket är viktigt för bedömningen av IVR-strategin som allmänt antagits i tryckvattenreaktorer (PWR) i Generation III. Som en åtgärd för att mildra allvarliga olyckor realiseras IVR-strategin genom extern kylning av det nedre huvudet av ett reaktortryckkärl (RPV). För att uppnå kylbarhet och kvarhållning av koriumbassängen i det nedre RPV-huvudet bör värmeflöde vid den yttre ytan av kärlet vara mindre än det kritiska värmeflödet (CHF) som kokar runt det nedre huvudet. Under sådant tillstånd garanteras RPV: s integritet av den osmälta kärlväggens tillräckliga tjocklek. Examensarbetet startar från valet och valideringen av en turbulensmodell i det valda CFD-beräkningsverktyget (Fluent). Därefter sätts en numerisk modell upp för uppskattning av smältbassängens värmeöverföring av en referens PWR med en effektkapacitet på 1000 MWe, inklusive en nätkänslighetsstudie. Baserat på den numeriska modellen för en tvålagers smältbassäng utförs fyra uppgifter för att undersöka effekterna av Zr-oxidationsförhållande, Fe-innehåll och strålningsemissivitet på värmeflödesprofiler, liksom fokuseffekten under extrema förhållanden. Val och validering av turbulensmodellen utförs genom att jämföra simuleringsresultaten för olika turbulensmodeller med DNS-data för konvektionen av volymetriskt uppvärmt fluidskikt avgränsat av styva isoterma horisontella väggar vid lika temperatur. De interna Rayleigh-siffrorna i flödet når upp till 10e6. Jämförelsen visar att SST k-ω turbulensmodellresultaten överensstämmer med DNS-data. Simuleringarna med Zr-oxidationsförhållandet 0, 0,2 och 0,5, motsvarande oxidskiktet på 1,389 m, 1,467 m och 1,580 m, och metallskiktet på 0,705 m, 0,664 m och 0,561 m i höjd, visar att temperaturen av oxidskiktet kommer att öka med Zr-oxidationsförhållandet, medan metallskiktets temperatur kommer att minska vilket resulterar i mer värmeöverföring genom oxidskiktets sidovägg och mindre toppstrålning. Ändå är effekten av Zr-oxidationsförhållandet inte uttalad i intervallet 00,5. Simuleringarna med Fe-massan på 22t, 33t och 45t och respektive höjd av metallskiktet på 0,462m, 0,568m och 0,664m visar att det inre metallskiktet avsevärt kommer att öka temperaturerna för både metallskiktet och oxiden lager. Andelen värmeöverföring vid oxidskiktets sidovägg ökar för att komplettera minskningen av den vid metallskiktet. Simuleringarna med strålningsemissiviteten 0,2, 0,35, 0,45 och 0,7 visar att emissiviteten under 0,45 påverkar värmeöverföringen, och temperaturerna och sidoväggens värmeflöde för både oxidskiktet och metallskiktet kommer att öka med minskande emissivitet. Effekten är försumbar när strålningen är över 0,45. Simuleringarna under de hypotetiskt extrema förhållandena med antingen en adiabatisk övre gräns eller ett mycket tunt metallskikt visar att fokuseringseffekten kan uppstå, dvs. värmeflödet genom metallsidan är större än det i oxidskiktet. Men det lokala höga värmeflödet plattas ut av kärlväggen med god värmeledningsförmåga. Sammanfattningsvis visar simuleringarna att, förutom fall under extrema förhållanden, är värmeflödet från smältpoolerna i alla andra fall betydligt lägre än CHF för extern kylning av nedre huvudet. Därför verkar säkerhetsmarginalen för IVR-strategin för den valda PWR tillräcklig. På grund av vissa begränsningar (t.ex. förenkling och antaganden) i simuleringsfall och koppling av olika inflytelserika faktorer, vilket indikeras av den aktuella studien, är de exakta förutsägelserna av värmeflöde under alla scenarier fortfarande svåra. Därför kunde slutsatserna inte generaliseras till de andra förhållandena eller andra konfigurationer av de smälta poolerna. Genom att diskutera modellen och förenklingar / antaganden som antagits i detta arbete föreslås förbättringsriktningarna för den numeriska modellen och andra perspektiv i slutet av avhandlingen.
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Monden, Andreas [Verfasser], and Markus [Akademischer Betreuer] Sause. "Adhäsion zwischen epoxidharzbasiertem CFK und oberflächenmodifiziertem Stahl: Grenzschichtversagen von Hybridlaminaten unter Mode I, Mode II und Mixed-Mode Belastung / Andreas Monden ; Betreuer: Markus Sause." Augsburg : Universität Augsburg, 2016. http://d-nb.info/1119707129/34.
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Rego, Christopher Ashok. "Microwave spectroscopy of CHâ†3HgX (X = Cl, CN) and SiFâ†3X (X = Cl, I) and the internal rotors CFâ†3SH, CHâ†3B(OH)â†2." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.232898.
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Habla, Florian [Verfasser], Kai-Olaf [Akademischer Betreuer] Hinrichsen, Ville R. I. [Akademischer Betreuer] Kaila, and Harald [Akademischer Betreuer] Klein. "Modeling and CFD simulation of viscoelastic single and multiphase flows / Florian Habla. Gutachter: Ville R. I. Kaila ; Kai-Olaf Hinrichsen ; Harald Klein. Betreuer: Kai-Olaf Hinrichsen." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1072758083/34.
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Williams-Wilson, Melinda. ""I had to give up so, so much" : a narrative study to investigate the impact of Chronic Fatigue Syndrome (CFS) on the lives of young people." Thesis, Bournemouth University, 2009. http://eprints.bournemouth.ac.uk/20331/.
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The aim of this research was to explore the experiences of Chronic Fatigue Syndrome among a small group of adolescents, through three research questions: What are the personal experiences of young people with CFS – how does the condition affect their daily lives – including educational, social and psychological perspectives. Secondly, how does CFS impact family life – how does the condition influence not only the lives of sufferers but also those closest to them? Finally, can the knowledge base be deepened to help guide practice for those caring for the needs of adolescent CFS sufferers and their families? The study used a narrative approach in an attempt to capture young people‘s stories, and to provide a window of insight into the personal impacts of CFS on the lives of individuals. Open-ended interviews with eight young CFS sufferers (11 to 18 year olds) were employed that explored personal experiences of CFS. In addition four email interviews were conducted with primary caregivers to explore the impacts of CFS from a carers perspective. Five themes arose from a generic qualitative analysis of data - adolescent CFS is experienced as: (1) having to adapt to debilitating physical symptoms; (2) living with changes in family relationships and loved one‟s life experiences; (3) living with isolation and a disruption to a full and satisfying teenage life; and (4) feeling misunderstood and judged. Also a fifth and universal overarching theme, that CFS in adolescents is experienced as having to put life on hold. This is a major life adjustment, not only for the individual sufferers but for their family members also, who have to adapt to a new way of life accommodating for the limitations of one member. The implications for clinical practice and further research are discussed.
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Youssefová, Kristina. "Autentizace RF vysílačů na základě nedokonalostí rádiového řetězce." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2021. http://www.nusl.cz/ntk/nusl-442423.
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Tato práce se zaměřuje na klasifikaci vysokofrekvenčních vysílačů v závislosti na nedokonalostech jejich komponent pomocí algoritmu strojového učení. Práce je rozdělena na dvě části - teoretickou a praktickou.V teoretické části je nejprve popsána základní struktura vysílače s přímou konverzí a jsou uvedeny nedokonalosti rádiového front-endu, které mohou být využity ke klasifikaci. Dále jsou vysvětleny vybrané metody strojového učení s učitelem, zejména metoda support vector machines a neuronové sítě. Praktická část se zabývá implementací a dosaženými výsledky těchto dvou metod v prostředí MATLAB na problému klasifikace rádiových front-endů.
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Masvidal, Sanz Laia. "Estudi dels mecanismes moleculars subjacents en mutacions CFTR que afecten l’eficiència de l’splicing. Desenvolupament de tècniques complementàries per a la caracterització a nivell de DNA, RNA i proteïna en cèl·lules epitelials." Doctoral thesis, Universitat Autònoma de Barcelona, 2011. http://hdl.handle.net/10803/82073.
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La Fibrosis quística (FQ) és la malaltia genètica recessiva letal més freqüent a la població caucàsica. Més de 1600 mutacions al gen CFTR han estat descrites com a responsables de FQ i/o han estat associades a altres malalties com l¿absència bilateral de conductes deferents, la pancreatitis crònica i les bronquiectàsies.
El procés d’splicing està estrictament regulat per diferents seqüències genòmiques i factors de transcripció. Aquest fi engranatge és susceptible de veure’s afectat de forma absoluta o parcial per la presència de mutacions, donant lloc a un número variable de transcrits i, en conseqüència, a un ampli espectre fenotípic. Per determinar la rellevància clínica dels nivells d'expressió de CFTR, l’objectiu principal d’aquest treball ha estat l’estudi dels mecanismes moleculars subjacents en mutacions CFTR que afecten l’splicing, mitjançant el desenvolupament de tècniques complementàries per la seva caracterització a nivell de DNA, RNA i proteïna.
Per dur a terme aquest objectiu s’ha emprat l’epiteli nasal, una mostra accessible, que ens ha permès, l’anàlisi d’expressió del gen i la localització de la proteïna CFTR. La seva caracterització genòmica ha estat fonamental per la identificació de mutacions i SNPs, i ha permès la formació acurada de grups d’estudi (individus controls, portadors i pacients). L’RT-qPCR ha estat una tècnica essencial i la normalització de dades n'és un pas imprescindible per determinar l'expressió. En aquest treball s'ha aplicat un procés acurat de selecció de gens de referència (geNorm, NormFinder, Kruskal-Wallis) i s’han validat els gens GUSB i PMCA4 com la millor combinació per l’estudi de l’expressió de CFTR.
L’anàlisi in silico i qualitatiu de més de 30 mutacions missense, nonsense i d’splicing al gen CFTR ha permès la identificació de transcrits aberrants en les mutacions c.580-1G>T, c.2657+5G>A i c.3718-1G>A. La quantificació de transcrits per la mutació c.2657+5G>A ha portat a la identificació d’un nou al·lel complex amb el cSNP c.2562T>G (p.=). A nivell proteic, la manca de proteïna observada en les tres mutacions correlaciona amb els nivells de transcrits quantificats en cada una de elles, i ambdós ho fan amb el fenotip dels individus portadors de mutacions d’splicing.
En conclusió, l’anàlisi quantitativa de transcrits ha mostrat una correlació amb el fenotip d’individus portadors de mutacions d’splicing, i en conseqüència pot ser útil com a paràmetre complementari per a l’avaluació de teràpies moleculars dirigides a la correcció d’splicings aberrants.Cystic fibrosis (CF) is the most common recessive genetic disease in Caucasian population. Over 1,600 cystic fibrosis transmembrane conductance regulator (CFTR) gene sequence variations have been identified in patients with cystic fibrosis (CF) and/or related disorders such as congenital bilateral absence of the vas deferens, chronic pancreatitis and bronchiectasis. The splicing process has been shown to be regulated in multiple ways. An interplay of cis-acting sequences and trans-acting factors modulates splicing by the interaction of many complexes, proteins, DNA domains, etc. This fine machinery is susceptible to be disrupted by mutations and single nucleotide polymorphism leading to a variable number of transcripts and therefore to a broad phenotypic spectrum. The purpose of this work has been to study the subjacent molecular mechanism of CFTR mutations that affect the efficiency of splicing as well as to develop complementary techniques for its characterization at DNA, RNA and protein level in epithelial cells; by doing so we aim to determine the clinical relevance of CFTR expression levels. In order to reach our goals we used nasal epithelium, an accessible sample that allowed us to study CFTR gene expression and CFTR protein localization. Mutations and single nucleotide polymorphism analysis was done in all individuals to accurately group them into controls, carriers and patients. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) was essential to determine the expression level of CFTR. As Normalization of qPCR data is a necessary step reference genes must be selected for each gene/tissue. Therefore, we applied an accurate approach to select reference genes for CFTR expression analysis (geNorm, NormFinder, Kruskal-Wallis). GUSB and ATP2B4 have been validated as the most reliable gene combination. An in silico analysis along with a qualitative assessment of more than 30 CFTR mutations (missense, nonsense and splicing) identified an aberrant transcript for three of the mutations analyzed, c.580-1G>T, c.2657+5G>A and c.3718-1G>A. Its quantification led to the identification of a novel complex allele c.2562T>G (p.=)-c.2675+5G>A. At the protein level, the lack of CFTR on the membrane for the three mutations analyzed correlated with both the transcript level observed and patient phenotypes. In conclusion, CFTR quantitative transcript analysis showed a clear correlation with the phenotype of individuals carrying a splicing mutation. Therefore, it could be a useful parameter for the evaluation of aberrant splicing-targeted therapies.
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Sánchez, Morales Valentin. "Experimental and CFD analysis of the flow in the wake of a vertical axis wind turbine." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/454742.
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Aquesta tesi es divideix en dos blocs on s'analitza el flux d'una VAWT.
El primer bloc se centra en l'estudi experimental i numèric d'una VAWT amb vuit pales basada en el fenomen de resistència. A la primera part, la velocitat del vent es fixa en 10 m/s per mesurar la corba de potència de la turbina i els resultats es comparen amb els d'altres turbines Savonius en diferents túnels de vent. També s'ha analitzat la reducció del nombre de pales i s'ha comprovat que el rendiment augmenta. A la segona part, la velocitat del vent s'estableix en 4,5 m/s per a realitzar experiments de visualització de fum. La tècnica de visualització del fum ha permès validar qualitativament les simulacions 2D perquè els patrons de flux visualitzats són similars als simulats numèricament. Les simulacions numèriques han demostrat que el rendiment és més gran amb quatre pales.
En el segon bloc, es proposa i analitza un nou model per predir l'estela de les VAWTs. El model es basa en el disc actuador i en els mètodes de Doble tub de flux múltiple. El model, anomenat MAB (Multiple Actuator Block), es basa en la definició, dins el domini computacional, de múltiples blocs paral·lelepipèdics distribuïts al llarg de la trajectòria de les pales. Els embornals volumètrics de moment s'imposen en aquests blocs per modelar l'efecte de les pales sobre el flux. Les simulacions amb el model MAB s'han comparat amb una simulació de volum finit complet usant la tècnica de malla lliscant. Aquesta simulació requereix aproximadament deu vegades més temps de CPU que les simulacions usant el model MAB. S'ha trobat que les característiques a gran escala del deixant llunyana poden ser reproduïdes utilitzant el model MAB.Esta tesis se divide en dos bloques donde se analiza el flujo de una VAWT. El primer bloque se centra en el estudio experimental y numérico de una VAWT con ocho palas basada en el fenómeno de resistencia. En la primera parte, la velocidad del viento se fija en 10 m/s para medir la curva de potencia de la turbina y los resultados se comparan con los de otras turbinas Savonius en diferentes túneles de viento. También se ha analizado la reducción del número de palas y se ha comprobado que el rendimiento aumenta. En la segunda parte, la velocidad del viento se establece en 4,5 m/s para realizar experimentos de visualización de humo. La técnica de visualización del humo ha permitido validar cualitativamente las simulaciones 2D porque los patrones de flujo visualizados son similares a los simulados numéricamente. Las simulaciones numéricas han demostrado que el rendimiento es mayor con cuatro palas. En el segundo bloque, se propone y analiza un nuevo modelo para predecir la estela de las VAWTs. El modelo se basa en el disco actuador y en los métodos de Doble tubo de flujo múltiple. El modelo, denominado MAB (Multiple Actuator Block), se basa en la definición, dentro del dominio computacional, de múltiples bloques paralelepipédicos distribuidos a lo largo de la trayectoria de las palas. Los sumideros volumétricos de momento se imponen en estos bloques para modelar el efecto de las palas sobre el flujo. Las simulaciones con el modelo MAB se han comparado con una simulación de volumen finito completo usando la técnica de malla deslizante. Esta simulación requiere aproximadamente diez veces más tiempo de CPU que las simulaciones usando el modelo MAB. Se ha encontrado que las características a gran escala de la estela lejana pueden ser reproducidas utilizando el modelo MAB.
This thesis is divided in two blocks where the flow around a VAWT is analysed. The first block is focused on the experimental and numerical study of a VAWT with eight blades based in drag phenomenon. The experiments are carried out in two parts. In the first part, the wind velocity is set to 10 m/s to measure the power curve of the turbine and the results are compared with those of Savonius turbines in different wind tunnels. The reduction of the number of blades of the turbine has been also analysed and it has been found that the performance increases. In the second part, the wind velocity is set to 4.5 m/s to perform smoke visualization experiments. The smoke visualization technique has allowed the qualitative validation of the 2D simulations because the flow patterns visualized are similar to those numerically simulated. The numerical simulations have demonstrated that the four blades turbine generates higher torque than the turbine with eight blades. In the second block, a new model to predict the wake of VAWTs is proposed and analysed. The model is based on the actuator disk and the Double Multiple Stream Tube methods. The model, denoted as Multiple Actuator Block (MAB), is based on the definition, inside the computational domain, of multiple parallelepipedic blocks distributed along the path of the blades. Volumetric momentum sinks are imposed in these blocks to model the effect of the blades on the flow. The simulations with the MAB model have been compared with a complete finite volume simulation using the sliding mesh technique. This simulation requires about ten times more CPU time than the simulations using the MAB model. It has been found that the large scale features of the far wake can be reproduced using the MAB model.
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Wolke, Silvana Ines. "Quimica organometalica de superficie de metais dos grupos 5 e 6 : reatividade dos complexos [V(=NtBu)(Np3)], Np= neopentila, e [Mo(=CHCMe2Ph)(=NAr)(OR)2], Ar = 2,6-i-Pr2-C6H3, R = tBu e CMe(CF3)2, em relação a superficie de oxidos inorganicos." [s.n.], 2000. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249148.
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Orientador : Regina BuffonTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Guerrero, Catells Ángel. "Contribution to the advanced analysis and prevention of the mechanisms of natural fire induced structural collapse in highrise buldings." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/30710.
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El progresivo incremento de la altura de los Edificios de Gran Altura (EGA) ha aumentado las consecuencias reales y potenciales cuando irrumpen en ellos incendios naturales. A la vista de dichas pérdidas, el objeto principal de esta Tesis es la contribución al análisis avanzado y prevención de los mecanismos de colapso estructural en EGAs inducidos por incendios naturales, mejorando el conocimiento actual de los fenómenos involucrados en los mecanismos de fallo estructural introducidos por la acción de dichos incendios naturales y de las consecuencias de ciertas estrategias de extinción de incendios.
Durante el calentamiento del Hormigón de Alta Resistencia (HSC), tienen lugar diversos fenómenos complejos, con interacciones físicas, químicas y mecánicas que resultan en cambios significativos de sus propiedades, comportando una pérdida de la capacidad portante y de otras características de servicio de las estructuras de HSC. Un fenómeno significativo conducente a un mecanismo de fallo estructural específico de los HSCs es el Spalling Térmico. Esta Tesis fija el citado objeto, en primer lugar, en los dominios del análisis computacional del Spalling Térmico por medio del software de análisis higro-termo-quimo-mecánico (HTCM) más avanzado y basado en el denominado Modelo de Padua, el software High Temperature Concrete and Spalling o HITECOSP con los objetivos de:
Desarrollar un abanico de nomogramas de Spalling con el objeto de evaluar la sensibilidad de los procesos HTCM involucrados en el comportamiento de los HSC, bajo condiciones de incendio natural, a determinados parámetros relevantes; Analizar si el Spalling es energéticamente viable en un abanico de casos reales; Discernir cuál es la contribución energética al Spalling Térmico por parte del gas comprimido y cuál es la correspondiente a la energía elástica constreñida (los dos factores clave conducentes, conjuntamente, al Spalling Térmico).
Se han desarrollado más de 91 análisis HTCM, resultantes de la combinación de los valores de los parámetros considerados, a saber: el contenido inicial de humedad del HSC, su permeabilidad intrínseca, la intensidad del fuego, la resistencia a compresión, el conjunto de propiedades del HSC y el espesor del elemento estructural.
Otra materia escasamente estudiada en relación con el objeto de la Tesis, es el análisis del efecto de las estrategias de extinción en el estado estructural de los EGAs durante incendios naturales. El choque térmico inducido por la aplicación de un chorro de agua sobre la superficie de un elemento estructural, produce una reducción significativa de la resistencia a flexión y a compresión, mientras que fenómenos de Spalling (Post-Spalling) pueden tener lugar durante y después de la extinción.
Esta Tesis fija por tanto su objeto, en segundo lugar, en el dominio del análisis del efecto de un espectro de procesos de enfriamiento en el estado HTCM de un elemento estructural de nuevo con HITECOSP con los siguientes objetivos: Analizar el efecto de un espectro de procesos de enfriamiento en el estado HTCM de un elemento estructural, fabricado con
HSC, durante el desarrollo de un incendio natural en un EGA; Desarrollar un análisis comparativo del estado HTCM final de un elemento estructural después de diferentes tipos y subtipos de procesos de enfriamiento, incluyendo la comparación de enfriamientos ambientales y de superficie, diferentes instantes de inicio y velocidades de los procesos de enfriamiento; Proporcionar suficiente información para analizar la influencia en el comportamiento HTCM de un elemento estructural, durante los procesos de enfriamiento, de diversos parámetros no relacionados con los propios procesos de enfriamiento.
Dos casos de referencia han sido seleccionados y analizados en profundidad incluyendo numerosas variaciones de: tipo de enfriamiento bien enfriando los gases del escenario bien la superficie del elemento estructural, instante de inicio del proceso de enfriamiento y su velocidad.
Este segundo encuadre de objetivos incluye el desarrollo de más de 20 Simulaciones de Dinámica de Fluidos Computacional por medio del software Fire Dynamics Simulator (FDS) para extraer la evolución de la temperatura en las superficies de los elementos estructurales durante diversas acciones de extinción.
Finalmente se incluye un análisis heurístico del efecto de los procesos de enfriamiento en el estado HTCM de una columna cuadrada, fabricada con HSC, durante el desarrollo de un incendio natural en un EGA, entendiéndose como una extensión introductoria de los anteriores análisis a casos con flujos 2D como las columnas cuadradas, en las cuales el Spalling de esquina es el más peligroso.The progressive gain of height of High-Rise Buildings (HRB) has increased the actual and potential consequences when natural fires irrupt. In sight of these losses, the major aim of this Thesis is to contribute to the advanced analysis and prevention of the mechanisms of natural fire-induced structural collapse in HRB, by improving the current knowledge of both the phenomena involved in the structural failure mechanisms introduced by natural fires action and of the consequences of certain fire fighting strategies developed during these fires. During heating of High Strength Concrete (HSC), there take place several complex, interacting physical, chemical and mechanical phenomena resulting in significant changes of the material inner structure and properties, leading to a loss of the load bearing capacity and of other important service features of concrete structures. A significant phenomenon leading to a structural failure mechanism very specific for the HSC used in HRBs and of a great practical importance is the Thermal Spalling. This Thesis settles, first, the abovementioned major aim in the domain of the computational Thermal Spalling analysis by means of the most advanced hygrothermo chemo-mechanical (HTCM) analysis software based on the so-called Model of Padova, High Temperature Concrete and Spalling software (HITECOSP) – with the objectives of: Develop a spectrum of spalling nomograms addressed to evaluate the sensitivity of the HTCM processes involved on the HSCs behaviour under a natural fire to some relevant parameters; Analyze if spalling is energetically possible in a variety of actual cases; Discern what is the energetic contribution of compressed gas to Thermal Spalling and what is that corresponding to the constrained elastic energy (namely, the two key factors leading, together, to Thermal Spalling). There are developed more than 91 HTCM analyses resulting from combinations of the parameters’ values initially considered: the initial moisture content of concrete, its intrinsic permeability, the rate of temperature increase, the porosity, compressive strength and, in general, the whole set of properties of concrete and the thickness of the structural element. Another scarcely studied matter related to the major aim of this Thesis is the analysis of the effect of fire fighting strategies on the structural state of the HRB during natural fires. Thermal shock, induced by the application of water jets on the surface of structural elements, produces a significant reduction in both the flexural strength the compressive strength, whereas Post-cooling spalling may occur after the fire is over, after cooling down or maybe even during extinguishing (especially those containing calcareous aggregates). This Thesis settles, second, the major aim in the domain of the analysis of the effect of a spectrum of cooling processes on the HTCM state of a structural element, manufactured with HSC, during the development of a natural fire in a HRB again with HITECOSP with the objectives of: Analyze the effect of a spectrum of cooling processes on the HTCM state of a structural element, manufactured with HSC, during the development of a natural fire in a HRB; Develop a comparative analysis to compare the final HTCM state of a structural element after the development of different types and subtypes of cooling processes, including comparisons about the Environment vs. Structural element’s Surface cooling attacks, among different start instants and for several velocities of the cooling processes; Provide enough information to analyze the influence on the HTCM behaviour of the structural element during the cooling processes of several parameters non-related to the own cooling processes. Two reference cases are selected where the extinguishing actions conditions are varied in order to cover the widest possible range of situations found by Fire-Fighting Services during a natural fire extinguishment: the type of cooling, the cooling start instant and its rate. This second settling of objectives also includes the development of more than 20 Computational Fluid Dynamics simulations by means of Fire Dynamics Simulator software (FDS) in order to work out the evolution of temperature at surfaces during several extinguishing actions. To conclude, the development of a heuristic analysis of the effect of cooling processes on the HTCM state of a square column, manufactured with HSC, during the development of a natural fire in a HRB, is also included, being understood as an introductory extension of the abovementioned analyses to cases with 2D fluxes such as square columns, where Corner Thermal Spalling is the most dangerous type.
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Sadrizadeh, Sasan. "Design of Hospital Operating Room Ventilation using Computational Fluid Dynamics." Doctoral thesis, KTH, Strömnings- och klimatteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-181053.
Full textAbstract:
The history of surgery is nearly as old as the human race. Control of wound infection has always been an essential part of any surgical procedure, and is still an important challenge in hospital operating rooms today. For patients undergoing surgery there is always a risk that they will develop some kind of postoperative complication. It is widely accepted that airborne bacteria reaching a surgical site are mainly staphylococci released from the skin flora of the surgical staff in the operating room and that even a small fraction of those particles can initiate a severe infection at the surgical site. Wound infections not only impose a tremendous burden on healthcare resources but also pose a major threat to the patient. Hospital-acquired infection ranks amongst the leading causes of death within the surgical patient population. A broad knowledge and understanding of sources and transport mechanisms of infectious particles may provide valuable possibilities to control and minimize postoperative infections. This thesis contributes to finding solutions, through analysis of such mechanisms for a range of ventilation designs together with investigation of other factors that can influence spread of infection in hospitals, particularly in operating rooms. The aim of this work is to apply the techniques of computational fluid dynamics in order to provide better understanding of air distribution strategies that may contribute to infection control in operating room and ward environments of hospitals, so that levels of bacteria-carrying particles in the air can be reduced while thermal comfort and air quality are improved. A range of airflow ventilation principles including fully mixed, laminar and hybrid strategies were studied. Airflow, particle and tracer gas simulations were performed to examine contaminant removal and air change effectiveness. A number of further influential parameters on the performance of airflow ventilation systems in operating rooms were examined and relevant measures for improvement were identified. It was found that airflow patterns within operating room environments ranged from laminar to transitional to turbulent flows. Regardless of ventilation system used, a combination of all airflow regimes under transient conditions could exist within the operating room area. This showed that applying a general model to map airflow field and contaminant distribution may result in substantial error and should be avoided. It was also shown that the amount of bacteria generated in an operating room could be minimized by reducing the number of personnel present. Infection-prone surgeries should be performed with as few personnel as possible. The initial source strength (amount of colony forming units that a person emits per unit time) of staff members can also be substantially reduced, by using clothing systems with high protective capacity. Results indicated that horizontal laminar airflow could be a good alternative to the frequently used vertical system. The horizontal airflow system is less sensitive to thermal plumes, easy to install and maintain, relatively cost-efficient and does not require modification of existing lighting systems. Above all, horizontal laminar airflow ventilation does not hinder surgeons who need to bend over the surgical site to get a good view of the operative field. The addition of a mobile ultra-clean exponential laminar airflow screen was also investigated as a complement to the main ventilation system in the operating room. It was concluded that this system could reduce the count of airborne particles carrying microorganisms if proper work practices were maintained by the surgical staff. A close collaboration and mutual understanding between ventilation experts and surgical staff would be a key factor in reducing infection rates. In addition, effective and frequent evaluation of bacteria levels for both new and existing ventilation systems would also be important.Tidigt i mänsklighetens utveckling har kirurgin funnits med i bilden. Hantering av infektioner har genom tiderna varit en oundviklig del av alla kirurgiska ingrepp, och finns kvar ännu idag som en viktig utmaning i operationssalar på sjukhus. För patienter som genomgår kirurgi finns alltid en risk att de efter ingreppet utvecklar någon behandlingsrelaterad komplikation. Allmänt accepterat är att de luftburna bakterier som når operationsområdet huvudsakligen består av stafylokocker frigjorda från hudfloran av operationspersonalen i operationssalen, och att endast en liten del av dessa partiklar behövs för att initiera en allvarlig infektion i det behandlade området. Sårinfektioner innebär inte bara en enorm börda för hälso- och sjukvårdsresurser, utan utgör också en betydande risk för patienten. På sjukhus förvärvad infektion finns bland de främsta dödsorsakerna i kirurgiska patientgrupper.. En bred kunskap och förståelse av spridningsmekanismer och källor till infektionsspridande partiklar kan ge värdefulla möjligheter att kontrollera och minimera postoperativa infektioner. Denna avhandling bidrar till lösningar genom analys av en rad olika ventilationssystem tillsammans med undersökning av andra faktörer som kan påverka infektionsspridningen på sjukhus, främst i operationssalar. Syftet med arbetet är att med hjälp av CFD-teknik (Computational Fluid Dynamics) få bättre förståelse för olika luftspridningsmekanismers betydelse vid ventilation av operationssalar och vårdinrättningar på sjukhus, så att halten av bacteriebärande partiklar i luften kan minskas samtidigt som termisk komfort och luftkvalité förbättras. Flera luftflödesprinciper för ventilation inklusive omblandade strömning, riktad (laminär) strömning och hybridstrategier har studerats. Simuleringar av luft-, partikel- och spårgasflöden gjordes för alla fallstudier för att undersöka partikelevakuering och luftomsättning i rummet. Flera viktiga parametrar som påverkar detta undersöktes och relevanta förbättringar föreslås i samarbete med industrin. Av resultaten framgår att mängden genererade bakterier i en operationssal kan begränsas genom att minska antalet personer i operationsteamet. Infektionsbenägna operationer skall utföras med så lite personal som möjligt. Den initiala källstyrkan (mängden kolonibildande enheter som en person avger per tidsenhet) från operationsteamet kan avsevärt minskas om högskyddande kläder används. Av resultaten framgår också att ett horisontellt (laminärt) luftflöde kan vara ett bra alternativ till det ofta använda vertikala luftflödet. Ett horisontellt luftflöde är mindre känsligt för termisk påverkan från omgivningen, enkelt att installera och underhålla, relativt kostnadseffektivt och kräver vanligen ingen förändring av befintlig belysningsarmatur. Framför allt begränsar inte denna ventilationsprincip kirurgernas rörelsemönster. De kan luta kroppen över operationsområdet utan att hindra luftflödet. En flyttbar flexibel skärm för horisontell spridning av ultraren ventilationsluft i tillägg till ordinarie ventilation undersöktes också. Man fann att denna typ av tilläggsventilation kan minska antalet luftburna partiklar som bär mikroorganismer om operationspersonalen följer en strikt arbetsordning. Bra samarbete och förståelse mellan ventilationsexperter och operationsteamet på sjukhuset är nyckeln till att få ner infektionsfrekvensen. Det är också viktigt med effektiva och frekventa utvarderingar av bakteriehalten i luften, för såväl nya som befintliga ventilationssystem.
QC 20160129
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Alós, Moya José. "Análisis de la respuesta frente al fuego de puentes mixtos multijácena." Doctoral thesis, Universitat Politècnica de València, 2019. http://hdl.handle.net/10251/116625.
Full textAbstract:
[ES] El diseño de puentes, a diferencia de lo que ocurre con el diseño de edificios o con el diseño de túneles ha dejado de lado la consideración de la acción del fuego hasta la fecha. Este vacío normativo, combinado con la gran repercusión económica y social de colapsos de puentes en el pasado como consecuencia de incendios, ha motivado un rápido incremento del número de estudios relativos a la ingeniería frente al fuego en el ámbito de los puentes. Aunque la acción del fuego no resulta del todo desconocida en el ámbito de las estructuras, sí que existen una serie de singularidades que impiden la trasposición directa de recomendaciones o de modelos de fuego simplificados ya desarrollados en otros campos que ya incorporan la acción del fuego en el diseño.
En este contexto, el trabajo que a continuación se expone parte de un incendio ocurrido en el estado de Alabama en 2002, cuyas consecuencias fueron la demolición de un puente mixto de 37 metros de vano central, para plantear y validar una metodología que aborda el problema de forma numérica mediante tres modelos acoplados secuencialmente: modelo de incendios, modelo térmico y modelo mecánico
Realizada una validación a nivel general se descubre que, aunque la configuración geométrica final obtenida se ajustan bastante a la realidad, la definición del incendio ha supuesto un gran número de hipótesis. Es por ello que se decide, en una segunda parte, realizar una campaña experimental que permita registrar la potencia del fuego, las temperaturas del gas y del acero y las flechas en un puente construido ad-hoc en el campus de la Universitat Politècnica de València. Este puente experimental tenía un vano único de 6 m de luz y fue sometido a cargas de fuego de hasta 1.3 MW.
Mediante el empleo de los registros realizados en la campaña experimental se ha validado el modelo de incendio, el modelo térmico y el modelo mecánico. Con todo ello se ha puesto en evidencia la importancia del viento en la acción del fuego, la magnitud de los gradientes térmicos espaciales y la urgencia de desarrollar procedimientos simplificados que permitan la incorporación del fuego como acción en el ámbito de los puentes Las validaciones específicas de cada modelo han permitido además llegar a una serie de conclusiones de gran interés para la realización de futuras campañas experimentales en puentes a mayor escala.[CAT] El disseny de ponts, a diferència del que passa amb el disseny d'edificis o amb el disseny de túnels ha deixat de banda la consideració de l'acció del foc. Aquest buit normatiu, combinat amb la gran repercussió econòmica i social de col·lapses de ponts com a conseqüència d'incendis, ha motivat un ràpid increment del nombre d'estudis relatius a l'enginyeria del foc del foc en l'àmbit dels ponts. Encara que l'acció del foc no resulta del tot desconeguda en l'àmbit de les estructures, sí que hi ha una sèrie de singularitats que impedeixen la transposició directa de recomanacions o de models de foc simplificats ja desenvolupats en altres camps que ja incorporen l'acció del foc al disseny. En aquest context, el treball que a continuació s'exposa part d'un incendi ocorregut a l'estat d'Alabama en 2002 i que va provocar la demolició d'un pont mixt de 37 metres de va, per plantejar i validar una metodologia que aborda el problema de forma numèrica mitjançant tres models acoplats seqüencialment: model d'incendis, model tèrmic i model mecànic Realitzada una validació a nivell general es descobreix que, encara que la configuració geomètrica final obtinguda s'ajusta en gran mesura a la realitat, la definició de l'incendi ha suposat un gran nombre d'hipòtesis. És per això que es decideix, en una segona part, realitzar una campanya experimental que permeta registrar la potència del foc, les temperatures del gas i de l'acer i les fletxes en un pont construït ad hoc al campus de la Universitat Politècnica de València. Aquest pont experimental presenta un va únic de 6 m de llum i va ser sotmès a càrregues de foc de fins a 1.3 MW. Mitjançant l'ús dels registres realitzats a la campanya experimental s'ha validat el model d'incendi, el model tèrmic i el model mecànic. Amb tot això s'ha posat en evidència la importància del vent en l'acció del foc, la magnitud dels gradients tèrmics espacials i la urgència de desenvolupar procediments simplificats que permetin la incorporació del foc com a acció en l'àmbit dels ponts Les validacions específiques de cada model han permès a més arribar a una sèrie de conclusions de gran interès per a la realització de futures campanyes experimentals en ponts a major escala.
[EN] To date, the fire action has been left aside in the bridge design despite this action has been widely considered in other structures such as building and tunnels. This regulatory vacuum, combined with the great economic and social impact of bridge collapses in recent times as a result of fires, has led to a rapid increase in the number of studies related to fire engineering in the field of bridges. Although the action of fire is not entirely unknown in the field of structures, there are a number of singularities that prevent the direct transposition of recommendations or simplified fire models from such fields. In this context, the study started by using a real fire which occurred in the state of Alabama in 2002 and led to the demolition of the 37-meter main span of a composite concrete and steel bridge to introduce and validate a methodology that numerically addresses the problem by uncoupling the problem in three different models: fire model, thermal model and mechanical model. Once the validation was accomplished at a general level, it was discovered that, although the geometrical data were quite adjusted to reality, the definition of the fire had involved a large number of hypotheses. That is why carrying out an experimental campaign to record the power of the fire, the gas and steel temperatures and the vertical deflections of a bridge built ad-hoc on the campus of the Universitat Politècnica de València became a priority. This 6-meter single span experimental bridge was subjected to fire loads of up to 1.3 MW. Through the use of the information recorded during the experimental campaign, the fire model, the thermal model and the mechanical model were validated. Moreover, the importance of wind in the action of fire, the magnitude of spatial thermal gradients and the urgency of developing simplified procedures which allow the consideration of fire as an action in the field of bridges were also highlighted. Last but not least, the validation of the different models allowed the author to include useful guidelines in order to define future experimental campaigns with more powerful fires and longer span bridges.
Alós Moya, J. (2018). Análisis de la respuesta frente al fuego de puentes mixtos multijácena [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/116625
TESIS
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Skosana, Banele Irene. "Validation of the Fluorescence Polarization Assay (FPA) for the diagnosis of Bovine Brucellosis." Diss., 2021. http://hdl.handle.net/10500/27541.
Full textAbstract:
Abstracts in English and ZuluFluorescence polarization assay (FPA), a serological assay, was validated as an alternative test for the rapid and cost-effective diagnosis of bovine brucellosis, with the aim of improving the control of brucellosis in South Africa. The FPA is anticipated to distinguish between vaccinated and infected cattle, circumventing the challenge associated with the tests that are currently used. Positive cattle serum samples (n =420) confirmed by Complement Fixation Test were tested in conjunction with serum samples (n = 446) from non-infected cattle initially tested on Rose Bengal Test, CFT and compared with FPA. The optimum cut-off value that offers the highest diagnostic sensitivity (Dsn) and diagnostic specificity (Dsp) was determined as 87 mP with the use of ROC analysis. The Dsn and Dsp of FPA using this cut-off value was calculated at 99.09% - 100% and 68.09%- 76.61% respectively with a 95% confidence interval (cl). The area under curve (AUC) was calculated at 0.9842 with a 95% standard error (S.E) of 0.005532 with positive and negative likelihood ratio (+LR) (-LR) at 3.643 and 1.002, respectively. The FPA was found to be as effective as CFT and should be considered because of its accuracy and other advantages such as speed, high throughput and the objectivity of the interpretation of results that can be obtained electronically by the (PHERAstar) machine. The test should be included in routine serological diagnosis for brucellosis.
I- Fluorescence polarization assay (i-FPA) ukuhlolwa kwe-serological okuqinisekiswe njengenye indlela yokuhlola ukuxilongwa okusheshayo nengabizi kwe-bovine brucellosis, okuzokwenza ngcono ukulawulwa kwe-brucellosis eNingizimu Afrika. Ngaphezu kwalokho, i-FPA kulindeleke ukuthi yehlukanise phakathi kwezinkomo ezigonyiwe nezithelelekile futhi lokhu kuzonciphisa inselelo ehambisana nokuhlolwa esetshenziswa njengamanje. Amasampula amahle avumayo we-serum ezinkomo (n = 420) aqinisekiswa yi-CFT ahlolwe ngokuhlangana namasampula e-serum (n = 446) avela ezinkomeni ezingathelelekile ezahlolwa kuqala ku-RBT, CFT futhi kuqhathaniswa ne-FPA. Inani elinqunyiwe elikhulu elinikezela ukuzwela okuphezulu kokuxilonga (i-Dsn) kanye nokucaciswa kokuxilongwa (i-Dsp) kunqunywe njenge-87 mP kusetshenziswa ukuhlaziywa kwe-ROC. I-Dsn ne-Dsp ye-FPA esebenzisa leli nani elisikiwe libalwe ngama-99.09% - 100% no-68.09% - 76.61% ngokulandelana kwesikhathi sokuzethemba esingu-95% (cl). Indawo engaphansi kwe-Curve noma ijika thizeni (i-AUC) ibalwe ku-0.9842 enephutha elingu-95% elijwayelekile (SE) lika- 0.005532 elinezilinganiso ezinhle nezimbi ze-likehood (+ LR) (-LR) ngo-3.643 no- 1.002, ngokulandelana. I-FPA isebenza njenge-CFT futhi kufanele ibhekwe ngenxa yokunemba eneqiniso kwayo nezinye izinzuzo ezifana nejubane lokuthola imiphumela kanye nenhloso yokuchazwa kwemiphumela engatholakala ngomshini wekhomphuyitha (PHERAstar), i-FPA kufanele ifakwe ekuhlolweni okuvamile ngokujwayelekile kwe-serological ye-brucellosis.
Agriculture and Animal Health
M. Sc. (Agriculture)
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Cheng, Po-Wen, and 鄭博文. "Joint I/Q Imbalance and CFO Estimation with Interference Cancellation in OFDMA Uplink." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/83020721608121338495.
Full textAbstract:
碩士國立臺灣科技大學
電子工程系
101
The orthogonal frequency division multiple access (OFDMA) sys- tems are very sensitive to carrier frequency offsets (CFOs) that de- stroy the orthogonality among the subcarriers . Also, the in-phase/q uadrature-phase (I/Q) imbalance may produce amplitude and phase mismatch producing the unwanted image interference to affect the desired signal and degrading the accuracy of CFO estimation. In this thesis, we present a maximumlikelihood(ML)-based scheme for joint estimation of CFO and I/Q imbalance in the uplink of in- terleaved OFDMA systems. In light of the fact that the received signal is contaminated by multiple access interference (MUI) and inter-carrier interference (ICI), the successive interference cancella- tion (SIC) are employed before proceeding the parameter estimation. For every transmitted symbol, SIC is first invoked to alleviate the MUI and ICI, the CFO and I/Q imbalance are then estimated based on the successively refined signals. Thereafter, to mitigate the inter- ference caused by the undetected symbol, a minimum mean-square error (MMSE) multiuser detector is employed to determine the out- put. As such, the CFO and I/Q imbalance estimates are refined sequentially. While the overall computational complexity is slightly higher, the developed scheme, as shown by simulations, provides su- perior performance compared with pervious works.
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Ahmad, Nawaz. "Numerical Modeling and Analysis of Small Gas Turbine Engine : Part I: Analytical Model and Compressor CFD." Thesis, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184855.
Full textAbstract:
The thesis work aims at devising analytical thermodynamic model and numerical modeling of the compressor of a small gas turbine to be operated on producer gas with lower heating contents. The turbine will serve as a component of “EXPLORE-Biomass Based Polygeneration” project to meet the internal electrical power requirements of 2-5 KW. The gas turbine engine is of radial type (one stage radial compressor, one stage radial turbine). Small gas turbines give less electrical efficiencies especially when operated with lower heating contents fuels like producer gas. This necessitates for optimum designing of components of the entire machine. Detailed analytical thermodynamic modeling of the engine has been analyzed for both internally and externally fired gas turbine cycles. Efforts are put on optimum utilization of energy available in the cycle and to enhance the efficiency thereby including various components. Numerical modeling of compressor using CFX has been performed for both steady and unsteady states. First different mesh sizes have been investigated followed by study of RMS residual targets on the results. Compressor performance has been studied for various speed lines. Thereafter, detailed steady state and unsteady simulations are performed for various cases including compressor single blade passage, 360 degree complete compressor, compressor connected with straight inlet pipe and for the compressor connected with 90 degree bended pipe. The operating point of the entire engine is analyzed. The numerical results are compared with each other and then to the ones from the 1D modeling. A good agreement has been found between the numerical results. Compared to 1D modeling, CFD presents higher performance at higher mass flow rates. However, for lower mass flow rates both 1D model and CFD present a similar performance.This study was funded by Higher Education Commission (HEC) of Pakistan.