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Bienner, Aurélien. "Real-gas effects on freestream induced transition and losses in ORC turbine flows." Electronic Thesis or Diss., Paris, HESAM, 2024. http://www.theses.fr/2024HESAE016.
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Les cycles de Rankine organique (ORC) apparaissent comme l'une des solutions pour répondre aux défis énergétiques et environnementaux actuels, en raison de leur important potentiel énergétique. L'un des composants clés des ORC est le détendeur, généralement une turbine. Pour les petits systèmes, cette dernière fonctionne dans les régimes transsoniques à supersoniques et peut être influencée par les propriétés de la vapeur organique utilisée, présentant ainsi des effets non idéaux. Dans cette étude, nous examinons les transitions de couche limite (CL) et le mécanisme des pertes au sein des turbines dans des conditions représentatives des ORC pour le fluide Novec649. Nous débutons par la présentation des premières simulations numériques directes (DNS) et des simulations à grandes échelles (LES) de CL transitionnant et turbulentes de Novec dans des conditions subsoniques élevées. Dans l'état turbulent, les profils des propriétés dynamiques de l'écoulement sont peu affectés par les propriétés du gaz et demeurent très proches de la DNS incompressible, malgré la vitesse élevée de l'écoulement subsonique, même si de véritables mais très faibles effets de compressibilité sont présents. Notre stratégie LES est validée par rapport à la DNS et est utilisée pour étudier l'influence de la fréquence et de l'amplitude du forçage sur l'état turbulent établi. Ensuite, pour la première fois, nous étudions, par LES, la transition induite par la turbulence extérieure (FST) de CL de gaz dense sur des plaques planes et autour du bord d'attaque d'une turbine. En raison du nombre de Reynolds élevé, les fines CL interagissent avec de larges structures turbulentes qui peuvent, pour des intensités relativement élevées, favoriser un mécanisme de transition non linéaire au lieu du mécanisme classique de transition par stries laminaires. Comparées au Novec, les CL d'air se révèlent légèrement plus instables mais conservent globalement des caractéristiques similaires, notamment en ce qui concerne les mécanismes de transition observés. Enfin, l'écoulement autour d'une configuration idéalisée d'aube est abordé au moyen de simulations DDES (Delayed Detached-Eddy Simulations), permettant une analyse fine des phénomènes instationnaires. À mesure que la non-idéalité de l'écoulement augmente, le rapport de pression diminue et les pertes augmentent. Comparativement à l'air, la capacité thermique élevée du Novec réduit les fluctuations de température, éliminant ainsi le phénomène dit de séparation d'énergie, tout en accentuant les fluctuations de pression dans le sillage. En comparaison avec les DDES, les simulations RANS conduisent à une sous-estimation des pertes d'environ 20%Organic Rankine Cycle (ORC) systems appear as one of the solutions to answer the current energy and environmental challenges, owing to their significant potential for generating power. A key component for ORC is the expander, most often a turbine. For small systems, the latter works in the transonic to supersonic regimes and can be affected by the properties of the organic vapor used and exhibit strong non-ideal effects. In the present study, we investigate boundary layer (BL) transitions and losses mechanism in turbines under conditions representative of ORC for the organic vapor Novec649. We begin by reporting the first direct numerical simulation (DNS) and large-eddy simulations (LES) of transitional and turbulent BL of Novec at high-subsonic conditions. In the turbulent state, the profiles of dynamic flow properties are little affected by the gas properties and remain very close to incompressible DNS, despite the high-subsonic flow speed and even if genuine but very small compressibility effects are present. Our LES strategy is validated against the reference DNS and is used to investigate the influence of forcing frequency and amplitude on the established turbulent state. Then, for the first time, we investigate freestream turbulence (FST)-induced transition of dense-gas BL on flat plates and around the leading-edge of a turbine by means of LES. Due to the high Reynolds number conditions, the thin BL experience large-scale incoming turbulent structures which can, for relatively high intensities, promote a non-linear transition mechanism instead of the classical laminar streak transition mechanism. Compared to Novec flows, air BL are found to be slightly more unstable but retains overall similar characteristics, in particular concerning the transition mechanisms observed. Finally, the flow around an idealized blade vane configuration is tackle by means of Delayed Detached-Eddy Simulations (DDES), allowing fine-detail analysis of unsteady flow phenomena. As the non-ideality of the flow increases, a lower pressure ratio is achieved and the losses increases. With regards to air, Novec's high heat capacity reduces temperature fluctuations, suppressing the so-called energy separation phenomena, while accentuating pressure fluctuations in the wake. Compared to DDES, RANS simulations leads to an underestimation of the losses by about 20%
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Westwell, Jeremy R. "Fast infrared spectroscopy of excited states." Thesis, University of Nottingham, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262165.
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Yates, Kelley Anne. "Graduate Preparedness for the Transition to Teaching: An Examination of Predictors of Transitional Difficulties during the First Year of Employment." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/367115.
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This thesis focused on the transition from university education to the first year of teaching. This may be a difficult transition, with several researchers reporting that 20% to 25% of newly qualified teachers do not teach beyond the first five years (Fimian & Blanton, 1987; Goddard & O'Brien, 2003a; Keeffe, Patton, & Spooner-Lane, 2005; Mackel, 2002; Stevens, Parker, & Burroughs, 2007), and that some teachers may experience symptoms of burnout after just eight months of employment (Fimian & Blanton, 1987; Goddard & O'Brien, 2003a, 2003b, 2006; O'Brien, O'Keeffe, & Goddard, 2008). The aim of this thesis was to examine graduate preparedness for teaching, and identify a set of skills and personal resources that may ameliorate burnout and turnover intentions during the first year of employment. Theories of Person-Environment Fit, along with the adaptation approach to stress, were adopted as conceptual frameworks for the thesis, and possible determinants of Demands-Abilities and Supplies-Values Fit were examined as resources that may enhance graduate preparedness and prevent burnout and turnover intentions. More specifically, graduates‟ perceptions of their own competency (perceived competency), their teaching self-efficacy and the training pathways they had followed to obtain their qualifications were considered as factors that may enhance Demands-Abilities Fit; while the graduates‟ sense of commitment to their careers (career commitment), their expectations regarding the rewards associated with teaching (reward expectations) and their expectations of the difficulties they would face in the workplace (challenge expectations) were considered as factors that may impact on Supplies-Values Fit.Thesis (PhD Doctorate)
Doctor of Philosophy in Organisational Psychology (PhD OrgPsych)
School of Psychology
Griffith Health
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Richards, Martyn W. "Chemical reactions of caesium, tellurium and oxygen with transition metal alloys." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.276201.
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Whyte, Alex. "Thin film studies of planar transition metal complexes." Thesis, University of Edinburgh, 2013. http://hdl.handle.net/1842/7966.
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At present the field of molecular electronics - also known as molecular semiconductors, organic semiconductors, plastic electronics or organic electronics - is dominated by organic materials, both polymeric and molecular, with much less attention being focused on transition metal based complexes despite the advantages they can offer. Such advantages include tuneable frontier orbitals through the ligand/metal interaction and the ability to generate stable paramagnetic species. Devices containing radical materials are particularly interesting in order to examine the interplay between conduction and spin - an effect which is not yet properly understood but can give rise to exotic behaviour. A series of homoleptic, bis-ligand Ni(II) and Cu(II) complexes were prepared using three structurally related phenolic oxime ligands, 2-hydroxy-5-t-octylacetophenone oxime (t-OctsaoH), 2-hydroxy-5-n-propylacetophenone oxime (n-PrsaoH) and 2- hydroxyacetophenone oxime (HsaoH). The complexes were characterised by single-crystal X-ray diffraction, cyclic voltammetry, UV/Vis spectroscopy, field-effect-transistor measurements, DFT/TD-DFT calculations and in the case of the paramagnetic species, EPR and magnetic susceptibility. Variation of the substituent on the ligand from t-octyl to n-propyl to H enabled electronic isolation of the complexes in the crystal structures of M(t-OctsaoH)2, which contrasted with π-stacking interactions observed in the crystal packing of M(n-PrsaoH)2 and of M(HsaoH) (M = Ni, Cu). This was further evidenced by comparing the antiferromagnetic interactions observed in samples of Cu(n-PrsaoH)2 and Cu(HsaoH)2 with the ideal paramagnetic behaviour for Cu(t-OctsaoH)2 down to 1.8 K. Despite isostructural single crystal structures for M(n-PrsaoH)2, thin-film X-ray diffraction and SEM revealed different morphologies depending on the metal and the deposition method employed. However, the complexes of M(n-PrsaoH)2 and M(HsaoH) failed to demonstrate significant charge transport in an FET device despite displaying the ability to form π- stacking structures. A series of planar Ni(II), Cu(II) and Co(II) dibenzotetraaza[14]annulenes (dbtaa) and dinapthotetraaza[14]annulenes (dntaa) were synthesised and studied crystallographically, optically, electrochemically and magnetically. Thin films of each of these complexes have been prepared by vacuum deposition to evaluate the field-effect transistor (FET) performance as well as the morphology and crystallinity of the film formed. Single crystal data revealed that Ni(dbtaa) and Cu(dbtaa) are isomorphous to each other, with Co(dbtaa) displaying a different crystallographic packing. The electrochemistry and UV/Vis absorption studies indicate the materials are redox active and highly coloured, with molar extinction coefficients as large as 80,000 M-1cm-1 in the visible region. The paramagnetic Cu(II) and Co(II) complexes display weak 1-dimensional antiferromagnetic interactions and were fit to the Bonner-Fisher chain model. The data revealed that the Co(II) species possesses much stronger magnetic exchange interactions compared with the Cu(II) complex. Each of the materials formed polycrystalline films when vacuum deposited and all showed ptype field-effect transistor behaviour, with modest charge carrier mobilities in the range of 10-5 to 10-9 cm2 V-1 s-1 . SEM imaging of the substrates indicates that the central metal ion, and its sublimation temperature, has a crucial role in defining the morphology of the resulting film. Structurally related Cu(II) and Ni(II) dithiadiazoletetraaza[14]annulene (dttaa) macrocycles were synthesised and studied in the context of their thin film electrochemical, conducting and morphological properties. Both the Ni(II) and Cu(II) complexes were found to be volatile under reduced pressure, which allowed crystals of both materials to be grown and the single crystal structures solved. Interestingly, the crystal packing of these heterocyclic macrocycles varies depending on whether the central metal ion is Cu(II) or Ni(II), which is in contrast to the analogous dibenzotetrazaannulenes complexes. Soluble Ni(II) analogues containing benzoyl groups on the meso- positions of the macrocycle (dttaaBzOR) were also prepared and contrasted with the insoluble Ni(dttaa) complexes in terms of their solution optical and electrochemical properties. Thin film electrochemical studies of Cu(dttaa) and Ni(dttaa) showed chemically reversible oxidative processes but on scanning to reductive potentials the films disintegrated almost immediately as the bulky counter tetrabutylammonium cation entered the thin film. FET studies undertaken on polycrystalline films of both complexes, using various device configurations and surface treatments, failed to realise any gate effect. Thin film XRD measurements indicate that films of both complexes formed by vacuum deposition are crystalline and contain a mixture of molecular alignments, with molecules aligning “edge on” and “face down” to the substrate. SEM imaging failed to effectively resolve the morphology of the films implying the sizes of the crystallites are small, which may help to explain the lack of FET effect. A series of bis-ligand diimine Ni, Cu and Pd complexes have been synthesised from the ligand 4,5-bis(dodecyloxy)benzene-1,2-diamine (dbdaH2). The same ligand was also used to prepare a series of soluble Cu(II) and Ni(II) tetraaza[14]annulene macrocycles. All the bis-ligand diimine complexes were found to suffer from instability in air due to the ease at which the complexes are oxidised. The Ni complex, Ni(dbda)2, was found to display a NIR transition in the region of 971 to 1024 nm depending on the polarity of the solvent that the molecule is dissolved in. Solution electrochemistry studies of Ni(dbda)2 reaffirmed the facile nature of the first oxidative process, with the HOMO energy calculated at -4 eV by hybrid-DFT. This compound failed to yield semiconducting behaviour in an FET device despite the use of surface treatments aimed at promoting suitable molecular alignment across the conducting channel.
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Hughes, Kevin Michael. "A mission in transition: Legitimacy, philosophical fit and student affairs cultures." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1550154095.
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Mitchell, Julie B. "Exploring Midcareer Women's Graduate School Transition: Department Socialization Tactics and Perceived Fit." [Kent, Ohio] : Kent State University, 2010. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1270745471.
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Thesis (M.A.)--Kent State University, 2010.Title from PDF t.p. (viewed May 26, 2010). Advisor: Robyn Parker. Keywords: organizational socialization; proactive newcomers; nontraditional graduate students; socialization tactics. Includes bibliographical references (p. 114-122).
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Conteh, Emmanuel. "Youth livelihoods in transition : poverty, 'fast money' and diamonds in Kono District, Sierra Leone." Thesis, University of Reading, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.553030.
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Sierra Leone, one of the world's poorest countries, is still recovering from a protracted civil war in which diamonds were implicated as the main source of financing for rebel activity. The view that diamonds still present a significant threat in the post-conflict period are based on fears that the high numbers of youth gangs (principally comprised of ex-combatants and school dropouts) in mining camps could threaten the delicate peace that was so difficult to establish. But despite growing concerns over the sector's growth, minimal research has been carried out to identify what drives youths to participate in the sector. Moreover, the country's Poverty Reduction Strategy Paper (PRSP) and allied policies fail to articulate what ultimately motivates youths to move to the mines or the extent to which these individuals depend on the sector for their livelihoods. A broadened understanding of these drivers is an important first step towards designing effective policies for poverty reduction, as well as minimising the probability of future civil violence. It is against this background that this thesis examines prevailing livelihood diversification patterns among youths m diamondiferous regions of Sierra Leone, and critically analyses the policy implications of their movements. The thesis draws upon research carried out in Kono District, which has the highest concentration of artisanal miners in Sierra Leone. Relevant primary documents, as well as feedback from interviews with key informants, focus group discussions with youth, and life histories of selected miners informed the analysis. The thesis concludes that there is no single factor driving youth movement into Sierra Leone's diamond mining camps: that migration is largely determined by individual circumstances. The country's youth diggers, therefore, should no longer be viewed as a iii homogenous entity similar in the way in which they are categorised in the literature and by policy makers. A distinct pattern, however, emerged from the analysis, which can be used to categorise particular individuals in the camps visited: 1) those looking to 'get rich quick', most of whom are ex-combatants; and 2) those driven by hardship, the majority of whom are farmers originating from the North of the country ('Northerners'), who, unlike most ex- combatants interviewed, have migrated to diamond-rich communities such as Kono to escape poverty. Despite carrying out the bulk of the laborious mining activity in Kono, most of the youth diggers (both ex-combatants and Northerners) consulted remain poverty-stricken. The lack of required skills for gainful employment, high illiteracy rates, solid networks and a sense of 'shame' have trapped many youth diggers in these camps. This is problematic from a policy standpoint because no single aspect of the country's PRSP attempts to address the very different issues and circumstances facing ex-combatants and Northerners. Further, the major initiatives implemented by Government and donors to improve the welfare of the country's diamond diggers and dependent communities have done little to address the specific problems facing youth diggers. The findings suggest there is a need for increased collaboration between key stakeholders, including the Government of Sierra Leone, large-scale mining companies, non- governmental organisations and local leaders. Specifically, there is need to broaden understanding of the dynamics on the ground and to enhance the capacity of these diggers to pursue alternative livelihoods. To achieve this, a broad policy mix is needed - specifically, a blueprint that emphasises the implementation of more sustainable alternative livelihoods, farm and non-farm, that would appeal to a range of youths (Northerners and ex-combatants).
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Atawa, Bienvenu. "Mobilité moléculaire et vieillissement physique des composés amorphes chiraux." Thesis, Normandie, 2018. http://www.theses.fr/2018NORMR125/document.
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Dans le cadre de cette thèse, nous avons réalisé l’étude de systèmes amorphes moléculaires chiraux en évaluant leur vieillissement, leur mobilité ainsi que leur capacité à recristalliser en fonction de la composition énantiomérique du matériau. Pour limiter les facteurs additionnels à la chiralité, ce travail s’est concentré sur des systèmes modèles formant des conglomérats stables : N-acetyl-α-methylbenzylamine (Nac-MBA) et 5-ethyl-5-methylhydantoin (12H). De ces travaux il ressort que l’impact le plus spectaculaire de la chiralité est exprimé dans la propension à la cristallisation ou l’habilité à former un verre (qui augmente de façon inversement proportionnelle de l’excès enantiomérique (ee)). Les cinétiques de vieillissement sont implicitement impactées par l’ee : Celles-ci sont plus lentes pour les ee importants. Enfin, il semble que les processus de relaxation ainsi que les temps associés soient identiques quelle que soit l’ee, bien que le comportement à la cristallisation soit lui significativement impacté. A noter que la signature la plus manifeste de la chiralité dans l’état amorphe du Nac-MBA s’exprime dans l’intensité diélectrique des processus D et αIn the framework of this thesis, we carried out the study of amorphous chiral molecular systems by evaluating their molecular mobility, the evolution of physical properties during aging and the recrystallization behavior as function of the initial enantiomeric excess (ee). In order to avoid factors additional to chirality itself, we focused on enantiomeric systems forming stable conglomerates (full chiral discrimination in the solid state) by choosing two model compounds: 5-ethy-5-methylhydantoin (12H) and N-acetyl-α-methylbenzylamine (Nac-MBA). From this thesis it was shown that the most spectacular effects of chirality in the amorphous state is expressed in the GFA or the crystallization propensity. The GFA increases as the ee decreases. The kinetics of physical aging is implicitly impacted by chirality. Glassy pure enantiomer requires more time to reach equilibrium than that of an intermediate composition. This situation is hypothetically due to constraints effects mostly resulting from a strong nucleation behavior in the glass state at high ee. Furthermore, the time scale of all the processes (D, α, βJG, γ) and the evolution of their temperature dependency are approximatively identical even though the crystallization behavior is highly impacted by ee. it seems that molecular mobility would not be a key parameter in the crystallization behavior of Nac-MBA. The main expression of chirality in amorphous Nac-MBA is evidenced in the signature of the dielectric strength of both D and α processes
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Bowers, Carla J. "The freshman transition process /." view abstract or download file of text, 2007. http://proquest.umi.com/pqdweb?did=1421620451&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Abela, Paul, Omar Roquet, and Ali Armand Zeaiter. "Determining Organisational Readiness for the Future-Fit for Business Benchmark." Thesis, Blekinge Tekniska Högskola, Institutionen för strategisk hållbar utveckling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12718.
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Holmen, Rune. "Heat and Mass Transfer during Solid-Liquid Phase Transition of n-Alkanes in the C16 to C19 Range." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Engineering Science and Technology, 2002. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-50.
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The main goal of this project has been to study heat and mass transfer during solid-liquid phase transition of n-alkanes in the C16 to C19 range. Phase transitions of both mixtures and pure components have been investigated.
All experiments and simulations have been performed without any convection.
Thermal conductivities have been determined at the melting point for solid and liquid unbranched alkanes ranging from C16 to C19. An assessment of the error of the method has been performed.
The measurements of solid conductivities are in accordance with measurements reported previously and confirm the applicability of the method. Liquid conductivities are higher than extrapolated values from the literature. The enhanced conductivity is believed to be caused by structural changes close to the melting point which is not taken into account when extrapolating values from the literature.
Experiments have been performed for the purpose of investigating the freezing of mixtures of n-alkanes in the C16 to C19 range. The positions of the solid-liquid interfaces have been measures as freezing occured.
Calculations of the ratio of liquid and solid conductivities show that the solid structure of mixtures of the investigated n-alkanes is predominantly in a rotator structure at the temperatures investigated. There are indications of a transformation into an orthorhombic structure at lower temperatures.
The temperature on the solid-liquid interface have been measured, and compared with calculated values from chapter 4. The temperature of the interface is represented better by the measured interfacial temperatures than by the calculated interfacial temperatures.
The experimental results indicate that the diffusion of heat is the limiting mechanism of phase transition. This result in a homogeneous liquid composition.
A numerical model has been developed in order to simulate the experimental freezing of mixtures. The model represents the results of the experiments within the limit of the uncertainties of the physical properties and the interfacial temperatures.
Also the numerical model suggests that the solid structure is predominantly in a rotator structure at the temperatures investigated. The properties of the rotator phase are represented better by physical properties of solid C17 than by molar averages.
The results from the simulations support the hypothesis that the limiting mechanism of deposition is the diffusion of heat to the interface. This implies that further work should focus on the determination of the thermophysical properties of solid fax instead of further development of models for the solid liquid equilibrium.
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Hernandez, Nicole M. "Archaeological Starch Preservation and Methodological Parameters: Where Does Qaraqara Fit?" The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429231987.
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Stalides, Dimitrios Jason. "College veteran transition stories : the use of weblogs to explore military-to-college transition narratives /." Available to subscribers only, 2008. http://proquest.umi.com/pqdweb?did=1594484821&sid=4&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Alharbi, Thamer. "Electromagnetic transition rates in 34P, 138Ce and 140Nd using the fast timing γ-ray coincidence technique." Thesis, University of Surrey, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.583354.
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This thesis reports on the utilisation of γ-ray coincidences between germanium and cerium doped lanthanum tri-bromide LaBr3(Ce) scintillation detectors for the determination of electromagnetic transition rates in the pico-to-nanosecond regime. The technique uses the high quality full energy peak resolution of the LaBr3(Ce) detectors coupled with their excellent timing responses in order to study discrete energy γ-ray cascades from nuclei populated using the lS0CSO,pn)34p, 130TeC2C,4n)13SCe and 12STeC60,4n)140Nd fusion-evaporation reactions. These studies were carried out at the Tandem van de Graaff accelerator laboratory in Bucharest, Romania. Coincidence measurements were performed using a mixed array of eight HPGe and eight LaBr3(Ce) detectors. The HPGe detectors were used to define the decay path of nucleus of interest, while the LaBr3(Ce) detectors were used to measure the decay times spectra of selected levels. In the first experiment, excited states in 34p were populated using the 18O(18O,pn) fusion-evaporation reaction at beam energy of 36 Me V. In this experiment, a fast timing method was used to mea- sure the half-life of the Iπ = 4- intruder state to be 2.0(1) ns. This structure and decay rate of this level are compared to predictions of restricted basis nuclear shell model cal- culations using on spdf basis which incorporates excitations into the f7/2 negative parity orbital. In the second experiment, N=80 isotones 13SCe and 140Nd were populated using the 130Te(12C,4n) and 12STeC60,4n) fusion-evaporation reactions at incident beam energy of 56 Me V and 66 Me V, respectively. The half-life of the Iπ =6+ yrast state at 2294 ke V in 13SCe was measured to be T1/2=880(19) ps. The B(E2; 6+ -+ 4+) is compared with the predictions of the restricted basis shell model and the systematics of the region and shows an anomalous behaviour compared to the neighbouring isotonic and isotopic chains. Half- lives of the yrast Iπ = 5-, 11+ and 14+ states in 138Ce have also been determined for the first time. Reduced transition probabilities have been calculated for the electromagnetic decays from these states. For 140Nd, the half-life of the Iπ = 8- yrast state at 3240 keY was measured to be Tl/2=100(12) ps. The centroid shift method was used to determine the half-life of this state because the half-life of the nuclear state was significantly shorter than the time resolution (full width at half-maximum) for the LaBr3(Ce) setup. Reduced transition probabilities B(E2) and B(M1) associated with the 178- and 1017 keY transi- tions decaying from the Iπ = 8- state in 140Nd have been calculated for the values of the E2/M1 mixing ratios.
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Maceratesi, Vittorio. "Studio di acceleranti e indurenti per migliorare le proprietà di materiali compositi a matrice epossidica." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13864/.
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In questo lavoro di tesi sono state preparate diverse formulazioni di resine epossidiche da utilizzare in preimpregnati (pre-pregs) per la produzione di compositi rinforzati in fibra di carbonio. Le modifiche della formulazione prese in esame durante il presente lavoro si sono incentrate sulla variazione del sistema indurente utilizzato, modificando l’indurente e/o aggiungendo accelerante al formulato. L’obiettivo di tali modifiche è stato quello di ottenere resine epossidiche che curassero più velocemente e/o che potessero raggiungere temperature di transizione vetrosa maggiori rispetto alla formulazione industriale attualmente utilizzata.
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Caruel, Matthieu. "Mechanics of Fast Force Recovery in striated muscles." Phd thesis, Palaiseau, Ecole polytechnique, 2011. https://pastel.hal.science/docs/00/66/83/01/PDF/Caruel_PhD_Thesis.pdf.
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Cette thèse est consacrée à la modélisation de la réponse transitoire d'une fibre musculaire squelettique soumise à des sollicitations mécaniques rapides. A l'échelle du nanomètre, la fibre musculaire contient des filaments d'actine et de myosine regroupés en unités contractiles appelées "sarcomères". Le filament de myosine est un assemblage de moteurs mol ́eculaires qui, en présence d'ATP, s'attachent et se d ́etachent p ́eriodiquement au filament d'actine. Au cours de ce processus d'attachement-détachement, la myosine génère une force lors d'un changement de conformation appelé "power-stroke". Ses caractéristiques peuvent être étudiées lors de la réponse transitoire de la fibre soumise à des sollicitations mécaniques rapides. Nous proposons un modèle mécanique innovant du demi-sarcomere permettant de relier les caractéristiques de la myosine à la réponse de la fibre complète. A la différence des modèles existants, privilégiant une approche discrète, ce modèle s'appuie sur la définition d'un potentiel d'énergie continu qui prend en compte une interaction de champ moyen entre les moteurs moléculaires. Ce système présente des réponses radicallement différentes à longueur imposée et à force imposée. Nous proposons en particulier une explication à la différence de cinétique observée expérimentalement. Nous montrons également que le demi-sarcomere est m ́ecaniquement instable ce qui explique les inhomogénéités de longueurs observées dans une myofibrilleThis thesis is devoted to the modelling of transient response of muscle fibers submitted to fast mechanical loadings. At the nanometer scale, the muscle fiber contains actin and myosin filaments grouped to form contracile units called 'sarcomeres'. Myosin filament is an assembly of molecular motors that periodically attach and detach to the actin filament in presence of ATP. During this attachement-detachement process, myosin undergoes a force generating conformational change called the 'power-stroke' whose characteristics can be revealed by the transient responses following fast mechanical loadings. We propose an innovative mechanical model of a half sarcomere that links the characteristics of myosin to the response of the whole fiber. Unlike existing models, using a discrete approach, this model is based on the definition of a continuous energy landscape that takes into account a mean field interaction between the molecular motors. This system presents radically different responses under imposed length and imposed force conditions. We particularly emphasize a difference in the kinetics, also observed experimentally. We show that the half-sarcomere is inherently unstable which explains the sarcomere length inhomogeneities observed recently on myofibril
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Caruel, Matthieu. "Mechanics of Fast Force Recovery in striated muscles." Phd thesis, Ecole Polytechnique X, 2011. http://pastel.archives-ouvertes.fr/pastel-00668301.
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Cette thèse est consacrée à la modélisation de la réponse transitoire d'une fibre musculaire squelettique soumise à des sollicitations mécaniques rapides. A l'échelle du nanomètre, la fibre musculaire contient des filaments d'actine et de myosine regroupés en unités contractiles appelées "sarcomères". Le filament de myosine est un assemblage de moteurs mol ́eculaires qui, en présence d'ATP, s'attachent et se d ́etachent p ́eriodiquement au filament d'actine. Au cours de ce processus d'attachement-détachement, la myosine génère une force lors d'un changement de conformation appelé "power-stroke". Ses caractéristiques peuvent être étudiées lors de la réponse transitoire de la fibre soumise à des sollicitations mécaniques rapides. Nous proposons un modèle mécanique innovant du demi-sarcomere permettant de relier les caractéristiques de la myosine à la réponse de la fibre complète. A la différence des modèles existants, privilégiant une approche discrète, ce modèle s'appuie sur la définition d'un potentiel d'énergie continu qui prend en compte une interaction de champ moyen entre les moteurs moléculaires. Ce système présente des réponses radicallement différentes à longueur imposée et à force imposée. Nous proposons en particulier une explication à la différence de cinétique observée expérimentalement. Nous montrons également que le demi-sarcomere est m ́ecaniquement instable ce qui explique les inhomogénéités de longueurs observées dans une myofibrille.
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Sun, Deqiang. "Landau-Zener transitions in noisy environment and many-body systems." [College Station, Tex. : Texas A&M University, 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-05-773.
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Acquaah-Harrison, Thelma E. "Vowel formant transitions in children and adults who stutter." Tallahassee, Fla. : Florida State University, 2008. http://purl.fcla.edu/fsu/lib/digcoll/undergraduate/honors-theses/341798.
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Thesis (Honors paper)--Florida State University, 2008.Advisor: Dr. Lisa Scott, Florida State University, College of Communication, Dept. of Communication Sciences & Disorders. Includes bibliographical references.
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Liao, Pei-Ju. "Essays on demographic transition and economic growth." Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1872151741&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Stillman, Kevin L. "Electronic structure studies of transition metal phosphides." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1445042561&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Abdulnour, Joseph. "The Effect of Menopausal Transition on Body Composition, Cardiometabolic Risk Factors, Physical Activity and Cardiorespiratory Fitness." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34174.
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Menopause transition is a natural process in a woman’s life associated with altered body fat distribution, increased cardiometabolic risk, and the presentation of vasomotor symptoms including hot flashes and night sweats. A 5-year observational, longitudinal study (MONET: Montreal Ottawa New Emerging Team), was performed to document the effect of menopause transition on body composition and cardiometabolic risk factors. Initially, the study included 102 healthy non-obese premenopausal women between the age of 47 and 55 years. By the end of year 5, 91 women completed the study, 4% were still premenopausal, 29% were perimenopausal and 67% became postmenopausal. The major finding of the first study was that the increases in body fat mass and visceral fat in our cohort of non-obese women followed through the menopause transition were independent of the increase in body weight. Furthermore, these changes in body composition and body fat distribution were not associated with cardiometabolic deteriorations. We further examined whether specific factors such as reporting vasomotor symptoms (hot flashes and/or night sweats), exaggerated exercise systolic blood pressure, physical activity levels and cardiorespiratory fitness, may be associated with adiposity, body fat distribution and cardiometabolic profile. Overall, women that experienced vasomotor symptoms (paper 2) or presented an exaggerated exercise systolic blood pressure (paper 3), did not present any alterations in their body composition, body fat distribution and cardiometabolic profile compared to asymptomatic women and participants with normal blood pressure response to exercise, respectively. Furthermore, exaggerated exercise systolic blood pressure was not predictive of future hypertension after a 5-year follow-up throughout menopause transition. On the other hand, total volume of physical activity was not linked with measures of a cardiometabolic profile, cardiorespiratory fitness appeared to have the greatest cardioprotective effect (paper 4). Therefore, in generally healthy physically active non-obese premenopausal women, the menopause transition does not generally alter cardiometabolic risk factors, and suggests that cardiorespiratory fitness may have greater cardiometabolic protective effects in this cohort.
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Ehrhorn, Anna M. "The Transition from a Novel Word to a Known Word in Preschool-Age Typically Developing Children." Bowling Green State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1395652335.
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Diop, Ngom Balla. "Structural and physical properties of ReN i03 (Re=Sm, N d) nanostructured films prepared by Pulsed Laser Deposition." University of the Western Cape, 2010. http://hdl.handle.net/11394/8229.
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Philosophiae Doctor - PhDVery few systems allow the study of the relationship between structural changes and physical properties in such a clear way as rare earth nickelate ReNi03 perovskites (Re (rare earth) = Pr, Nd, Sm and Gd). Synthesized for the first time by Demazeau et al [1] in 1971 and completely forgotten for almost twenty years, these compounds have regained interest since the discovery of high-temperature superconductivity and giant magnetoresistive effects in other perovskite-related systems. Due to its Metal-Insulator Transition (MIT) and thermochromic properties, the rare earth nickelate perovskite ReNi03 has received a great deal of attention for the past ten years in their thin films form [12]. Such unusual electronic and optical features are all the more interesting since the metal-insulator transition temperature (TMn) can be tuned by changing the Re cation: LaNi03 is metallic. No minimum of the metallic conductivity of Sm0 . ssNd 0.45Ni03, as observed by Gire et al [12] (entropic effect), was reported by Ambrosini and Hamet [11]. It has been suggested by Obradors et al. [13] that changing the rare earth cation in the ReNi03 system, acts as internal chemical pressure (increasing internal pressure by substituting the rare earth cation with another one of larger ionic radius) which can lead, as for the isostatic pressure experiment, to a tunability of the metal-insulator transition temperature [14, 15]. Obradors et al [13] reported on a decrease of T MIT upon increasing isostatic pressure but with remaining metallic properties of PrNi03 and NdNi03 (same magnitude and thermal dependence of the electrical resistivity)
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Zaffran, Jérémie. "Linear energy relations for biomass transformation under heterogeneous catalysis : a fast prediction of polyalcohol dehydrogenation on transition metals." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2014. http://tel.archives-ouvertes.fr/tel-00992665.
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Biomass valorization is an interesting alternative to fossil resources, which is frequently performed via heterogeneous catalysis. Designing new catalysts is a challenging task that can be significantly accelerated in silico. However, biomass molecules are often complex and highly oxygenated, hence rendering calculations more difficult and time consuming. Among these compounds, polyols are particularly important. We developed linear relations of the Brønsted-Evans-Polanyi (BEP) type from the DFT study of C-H or O-H bond dissociation elementary steps for a family of monoalcohol molecules on metallic catalysts (Co, Ni, Ru, Rh, Pd, Ir, Pt). Such relations aim at predicting activation energies from reaction energies. The accuracy of the obtained linear energy models is better than 0.10 eV on the sampling set. Then, the relations were applied for the prediction of the dehydrogenation elementary steps of glycerol, chosen as a prototype of polyalcohols, with an accuracy better than 0.10 eV and with a systematic error around ±0.10 eV for Rh. Keeping in mind that the main difference between glycerol and monoalcohols comes from intramolecular H-bonds present in the former, we designed linear relations for water-assisted dehydrogenation of monoalcohols. These new relations allowed us to improve the prediction on glycerol and to eliminate the systematic deviation in the case of OH bond breaking. Even if in this study we focused on glycerol dehydrogenation, similar methods may be applied to other polyols with other chemical reactions, and considerably speed up the computational design of solid catalysts. This work paves the way for the development of novel numerical techniques to address the issue of biomass conversion.
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Hahn, Lauren. "The Pinochet case and post-transitional Chile." Tallahassee, Fla. : Florida State University, 2010. http://purl.fcla.edu/fsu/lib/digcoll/undergraduate/honors-theses/2181951.
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Thesis (Honors paper)--Florida State University, 2010.Advisor: Dr. Sumner Twiss, Florida State University, College of Social Sciences, Dept. of International Affairs. Includes bibliographical references.
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Wang, John S. "Pseudocapacitive effects in nanostructured transition metal oxide materials." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1680034181&sid=11&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Cook, Charles A. "Encumbered consolidation historical continuity in Mexico's democratic transition /." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1663116661&sid=2&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Sirota, Benjamin. "Investigation into the Semiconducting and Device Properties of MoTe2 and MoS2 Ultra-Thin 2D Materials." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1157626/.
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The push for electronic devices on smaller and smaller scales has driven research in the direction of transition metal dichalcogenides (TMD) as new ultra-thin semiconducting materials. These ‘two-dimensional' (2D) materials are typically on the order of a few nanometers in thickness with a minimum all the way down to monolayer. These materials have several layer-dependent properties such as a transition to direct band gap at single-layer. In addition, their lack of dangling bonding and remarkable response to electric fields makes them promising candidates for future electronic devices. For the purposes of this work, two 2D TMDs were studied, MoS2 and MoTe2. This dissertation comprises of three sections, which report on exploration of charge lifetimes, investigation environmental stability at elevated temperatures in air, and establishing feasibility of UV laser annealing for large area processing of 2D TMDs, providing a necessary knowledge needed for practical use of these 2D TMDs in optoelectronic and electronic devices.
(1) A study investigating the layer-dependence on the lifetime of photo-generated electrons in exfoliated 2D MoTe2 was performed. The photo-generated lifetimes of excited electrons were found to be strongly surface dependent, implying recombination events are dominated by Shockley-Read-Hall effects (SRH). Given this, the measured lifetime was shown to increase with the thickness of exfoliated MoTe¬2; in agreement with SRH recombination. Lifetimes were also measured with an applied potential bias and demonstrated to exhibit a unique voltage dependence. Shockley-Read-Hall recombination effects, driven by surface states were attributed to this result. The applied electric field was also shown to control the surface recombination velocity, which lead to an unexpected rise and fall of measured lifetimes as the potential bias was increased from 0 to 0.5 volts.
(2) An investigation into the environmental stability of exfoliated 2D MoTe2 was conducted using a passivation layer of amorphous boron nitride as a capping layer for back-gated MoTe2 field effect transistor (FET) devices. A systematic approach was taken to understand the effects of heat treatment in air on the performance of FET devices. Atmospheric oxygen was shown to negatively affect uncoated MoTe2 devices while BN-covered FETs showed remarkable chemical and electronic characteristic stability. Uncapped MoTe2 FET devices, which were heated in air for one minute, showed a polarity switch from n- to p-type at 150 °C, while BN-MoTe2 devices switched only after 200 °C of heat treatment. Time-dependent experiments at 100 °C showed that uncapped MoTe2 samples exhibited the polarity switch after 15 min of heat treatment while the BN-capped device maintained its n-type conductivity. X-ray photoelectron spectroscopy (XPS) analysis suggests that oxygen incorporation into MoTe2 was the primary doping mechanism for the polarity switch.
(3) The feasibility of UV laser annealing as a post-process technique to sinter 2D crystal structures from sputtered amorphous MoS2 was explored. Highly crystalline materials are sought after for their use in electron and opto-electronic devices. Sputtered MoS2 has the advantage of potential for large area deposition and high scalability, however, it requires high temperatures (>350 °C) for their crystalline growth. Which creates difficulty for devices grown on polymer substrates. Low-temperature and room temperature deposition results in amorphous films which is detrimental for electric devices. A one-step lase annealing procedure was developed to provide amorphous to crystalline conversion of nanometer thin MoS2 films. Samples were annealed using an unfocused laser beam from a KrF (248 nm) excimer source. The power density was found to be 1.04 mJ/mm2. Raman analysis of laser annealed MoS2 was shown to exhibit a significant improvement of the 2D MoS2 crystallinity compared to as-deposited films on both SiO2/Si, as well as polydimethylsiloxane (PDMS) substrates. Annealed samples showed improvement of their conductivity on an order of magnitude. A top-gated FET device was fabricated on flexible PDMS substrates using Al2O3 as a gate oxide. Measured field effect mobility of annealed samples showed significant improvement over as-deposited devices.
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Ding, Yifu. "Influence of Molecular Weight and Architecture on Polymer Dynamics." University of Akron / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=akron1115933800.
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George, Sijo. "Simulation numérique directe de la transition laminaire turbulent sur un hydrofoil flexible." Thesis, Ecole centrale de Nantes, 2021. http://www.theses.fr/2021ECDN0010.
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Dans cette thèse, les vibrations induites par la transition laminaire turbulent sur un hydrofoil NACA66 à un nombre de Reynolds Re=450 000 sont étudiées. Des simulations numériques directes (DNS) sont mises en place afin de prédire un écoulement de couche limite incompressible, qui sont couplées avec un hydrofoil en mouvement de rotation libre. Ainsi, un couplage fluide structure de type implicite est développé dans le code Nek5000. Du fait du caractère très amont de cette méthode, de nombreux cas de validations sont effectués, menant au cas des vibrations induites par la transition. Ensuite, les recherches se basent sur une étude paramétrique, consistant à mener des cas d’oscillation forcées (rotations imposées) et d’oscillations libres (mouvements du au chargement induit par l’écoulement). Cela permet d’analyser finement les interactions entre les vibrations de l’hydrofoil et son écoulement de couche limite transitionnel. A ce titre, de nouveaux paramètres adimensionnels sont mis en place, permettant de caractériser les interactions fluides structures sur ce type d’écoulement. Du point de vue de l’écoulement de couche limite, il a été observé que la localisation du point de transition est proportionnelle à l’amplitude des mouvements de rotation de l’hydrofoil, de sa vitesse de rotation ainsi que du ratio fréquentiel entre la fréquence Naturelle du système et la fréquence de lâchers tourbillonnaire liée à la transition. La génération d’ondes TS (premier pas vers la transition de couche limite) est aussi sensible aux vibrations. Ensuite, les résultats ont montré que les structures cohérentes formées en aval de ces ondes TS, subissent une évolution spatiale dont la longueur d’onde transversale est proportionnelle à l’épaisseur de déplacement de la couche limite. Le déplacement de la région transitionnelle vers le bord d’attaque tend à réduire les fluctuations de pressions périodiques liées à cette transition, tandis que de celle-ci devient plus étendue dans la direction de l’écoulement. Finalement, lorsque la fréquence naturelle de l'hydrofoil se rapproche de la fréquence de lâcher du bulbe (ratio fréquentiel proche de 1), il a été observé une réponse multi-fréquentielle, liée à une forte interaction entre la transition et les vibrations de l’hydrofoil. L’étude suggère que dans ce cas précis, les interactions fluides structures tendent à perturber le comportement spatio-temporel de la transition laminaire turbulent. Cette analyse doit être confirmée expérimentalement. Cependant ce phénomène a déjà été identifié lors d'une campagne de mesure menée en tunnel hydrodynamique à l’Institut de Recherche de l’École Navale (IRENav), à un nombre de Reynolds cependant plus élevéThe laminar to turbulent transition induced vibration over a NACA66 hydrofoil at Re = 450000 is investigated in this thesis. DNS is used to simulate the 3D incompressible boundary layer flow, and it is coupled with a freely pitching hydrofoil. An implicit coupling is developed within the fluid solver Nek5000. A number of cases are performed to validate this method, which lead to study the transition induced vibration. Then, a parametric study consisting of two forced and three free oscillations allowed analyzing the interactions between the vibration and the boundary layer transitional flow. A set of specific non-dimensional parameters are set, which aim at characterize the fluid structure interactions in such flow regime. From the boundary layer flow analysis, it was observed that the spatial location of the transition point is proportional to the amplitude of pitch, velocity, and frequency ratio. The generation of TS waves (the first stage of laminar to turbulent transition) is also influenced by the vibrations. It was also observed that the span wise wavelength of coherent structures (so called “hair-pin” structures” that form downstream of the TS waves) is proportional to the displacement thickness. The spatial advancement of the transition point reduces the amplitude of periodic pressure fluctuations in the transition regime. In addition, the length of the transition region is increased. Finally, a multi-scaled frequency response is observed due to the enhanced interaction between transition and pitch oscillation when the transition and natural frequencies are close to each other. The study suggests that in this case, the fluid structure interaction tends to disturb the spatio-temporal behavior of laminar to turbulent transition. Although it has to be confirmed, this phenomenon has already identified experimentally through measurements performed at the Naval Academy Research Institute (IRENav) in hydrodynamic tunnel for a higher Reynolds number case
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Chen, Leiming. "Tilt phase transitions in disordered systems /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251884301&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 126-128). Also available for download via the World Wide Web; free to University of Oregon users.
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Wong, Hok Wui. "Endogenous capital mobility and regime transitions." Diss., Restricted to subscribing institutions, 2008. http://proquest.umi.com/pqdweb?did=1665712501&sid=16&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Crowley, Kyle McKinley. "Electrical Characterization, Transport, and Doping Effects in Two-Dimensional Transition Metal Oxides." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1597327584506971.
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Ismael, Alexander. "Comparison of fast frequency reserve strategies for Nordic grid frequency stability." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-411503.
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How long would modern society cope with a power outage, what would happen to vital systems that we today take for granted in modern society. The Nordic electricity grid is facing a major shift where electricity production from non-renewable sources are to be replaced increasingly by renewable sources. By increasing the penetration of wind and solar power the electric power system might be exposed to disturbances due to decreasing inertia as a result of the electricity transition. Currently the electric power system has different reserves to use to maintain frequency stability but there are other reserves that could help further in the fight for the balance between electricity production and consumption. This project examines whether the new reserve service, fast frequency reserve (FFR), can help the existing frequency containment reserve for disturbed (FCR-D) operation. Therefore, two experiments were conducted using the simulation tool ARISTO, addressing relevant issues involving frequency stability. Motivation for the hypothesis was to investigate if FFR could reduce the frequency transients and improve frequency variations by developing various setups and cases when inertia was retained and when the system inertia was reduced at different stages. The results of the experiments showed that the global minimum frequency, nadir, had increased for all test cases compared to the reference case when using FFR, this proved that the FFR in fact help reducing frequency transients. The results showed furthermore that when the FFR had a duration time of 30 seconds compared to only 5 seconds, the frequency variations could be improved for certain setups for experiment 2.
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Viljoen, Christiaan Gerhardus. "Machine learning for particle identification & deep generative models towards fast simulations for the Alice Transition Radiation Detector at CERN." Master's thesis, Faculty of Science, 2019. https://hdl.handle.net/11427/31781.
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This Masters thesis outlines the application of machine learning techniques, predominantly deep learning techniques, towards certain aspects of particle physics. Its two main aims: particle identification and high energy physics detector simulations are pertinent to research avenues pursued by physicists working with the ALICE (A Large Ion Collider Experiment) Transition Radiation Detector (TRD), within the Large Hadron Collider (LHC) at CERN (The European Organization for Nuclear Research).
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Almendarez, Bertha Longoria. "Mexican American elders and nursing home transition : a dissertation /." San Antonio : UTHSC, 2007. http://proquest.umi.com/pqdweb?did=1390289481&sid=1&Fmt=2&clientId=70986&RQT=309&VName=PQD.
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Spears, Julia Marie. "Experiences of low-income students' transition to graduate school /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1456290061&sid=9&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Thesis (Ph. D.)--Southern Illinois University Carbondale, 2007."Department of Educational Administration and Higher Education." Includes bibliographical references (leaves 193-203). Also available online.
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Farrington, Amber L. "Personality trait change in the transition to college life." Click here for download, 2009. http://proquest.umi.com/pqdweb?did=1827393541&sid=1&Fmt=2&clientId=3260&RQT=309&VName=PQD.
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Richter, Marilize. "Dietary fat intake and blood lipid profiles of South African communities in transition in the North–West Province : the PURE study / M. Richter." Thesis, North-West University, 2010. http://hdl.handle.net/10394/4654.
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Aim and objectives: This study set out to investigate the diet and blood lipid profiles of subjects in
transition in the North West Province in South Africa. It looked specifically at how the diet differed
between rural and urban areas, how the blood lipid profiles differed between rural and urban subjects,
establishing an association between dietary fat, fatty acid and cholesterol intakes respectively and blood
lipid profiles, as well as investigating the differences in blood lipid profiles at different ages, body mass
index (BMI) and genders respectively in rural and urban areas.
Design: The present study was a cross–sectional data analysis nested within the Prospective Urban and
Rural Epidemiology (PURE) study that is currently undertaken in the North West Province of South
Africa amongst other countries.
Methods: Baseline data was obtained in 2005. A randomised paper selection was done of people
between 35 - 70 years of age with no reported chronic diseases of lifestyle, TB or HIV of those enrolled
into the PURE study if they had provided written consent. Eventually a paper selection was made of 2000
subjects, 500 people in each of the four communities (rural, urban–rural, urban, established urban). For
the interpretation purposes of this study, data was stratified for rural (1000 subjects) and urban (1000
subjects) only, with no further sub–division into communities. Physical activity levels and habitual diets
were obtained from these subjects. Demographic and dietary intake data in the PURE study was collected
using validated, culture sensitive questionnaires. Anthropometric measures and lipid analysis were
determined using standardised methodology. Descriptive statistics (means, standard deviations and
proportions) were calculated. One–way analysis of variance (ANOVA) was used to determine
differences between the different levels of urbanisation on blood lipid profiles and dietary intake. When a
dietary intake variable proved to be significant for different levels of a factor (urbanisation, blood lipid
profile), post–hoc tests were calculated to determine which levels for specific variables differed
significantly. Bonferroni–type adjustments were made for the multiple comparisons. Spearman
correlations were calculated to determine associations.
Results: Mean fat intake was significantly higher in urban areas than in rural areas (67.16 ± 33.78 g vs.
32.56 ± 17.66 g, p<0.001); and the same was true for the individual fatty acid intakes. Fat and fatty acid
intakes were still within recommendations even for urban areas, and low for rural areas. N–3 intake was
very low in both rural and urban areas. Serum lipids did not differ significantly between rural and urban
areas. Almost half of rural (43%) and urban (47%) subjects presented with elevated total cholesterol
(5.0 mmol/L). In rural areas 52% and in urban areas 55% of subjects had elevated LDL–C (3.0
mmol/L). Amongst 23% of males in rural areas and 18% of males in urban areas HDL–C levels were
decreased. Of the females living in rural areas 34.3% had decreased HDL–C levels and 39% of those who lived in urban areas presented with lowered HDL–C levels. In rural areas 16.3% of subjects and in urban
areas 23% of subjects presented with high triglyceride levels. TC, LDL–C and triglyceride levels were
higher in higher body mass index (BMI) classes, however, obese subjects did not differ significantly from
overweight subjects in terms of blood lipids, suggesting that values stabilise after reaching overweight
status. These blood lipids were also higher in higher age groups and higher in women than men, probably
due to the high incidence of obesity in women.
Conclusions: Associations between the diet and blood lipid profiles were weak, and diet is not likely to
be the only factor responsible for high TC and LDL–C levels. Blood lipid profiles did not differ
significantly between rural and urban areas due to the fact that the diet was prudent in terms of fat intake
in both rural and urban areas. Higher prevalence of underweight was noted in males (32% in rural areas
and 28% in urban areas), while overwieght was a bigger problem amongst women (48% in rural areas and
54% in urban areas). TC, LDL–C and TAG were higher with higher BMI’s, while HDL–C levels were
lower. TC, LDL–C, and TAG were higher in higher age goups while HDL–C levels were lower. Female
subjects presented with higher mean triglycerides than males, probably due to higher prevalence of
overweight and obesity.Thesis (M.Sc. (Dietetics))--North-West University, Potchefstroom Campus, 2011.
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Gu, Mingxia. "Effects of Dielectric Relaxation on Director Dynamics in Uniaxial Nematic Liquid Crystals." Kent State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=kent1236368118.
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Harris, John Dylan. "The cage effect : understanding the recombination of transition metal-centered radicals /." view abstract or download file of text, 2007. http://proquest.umi.com/pqdweb?did=1400962361&sid=5&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2007.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 144-153). Also available for download via the World Wide Web; free to University of Oregon users.
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Hightower, Sean E. "Preparative and computational studies of metal complexes containing molecular cages." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1400962461&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Petersen, Dan D. "An examination of school-to-work action plans in southwest Idaho schools /." ProQuest subscription required:, 2000. http://proquest.umi.com/pqdweb?did=990270541&sid=3&Fmt=2&clientId=8813&RQT=309&VName=PQD.
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Richard, Joshua (Joshua Glenn). "A strategy for transition from a uranium fueled, open cycle SFR to a transuranic fueled, closed cycle sodium cooled fast reactor." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/76972.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 110-111).
Reactors utilizing a highly energetic neutron spectrum, often termed fast reactors, offer large fuel utilization improvements over the thermal reactors currently used for nuclear energy generation. Conventional fast reactor deployment has been hindered by the perceived need to use plutonium as fuel, coupling the commercial introduction of fast reactors to the deployment of large-scale thermal reactor used fuel reprocessing. However, the future of used fuel treatment in the United States is highly uncertain, creating a bottleneck for the introduction of fast reactor technology. A strategy centered around using uranium-fueled fast reactor cores in a once-through mode-a uranium startup fast reactor (USFR)-decouples fast reactor commercialization from fuel reprocessing and enables transition to a recycle mode once the technology becomes available and economic. The present work investigates the optimal strategy for recycling spent fuel from once-through sodium cooled fast reactors (SFRs), by analyzing the performance of various designs. A range of acceptable transitions are described and their economic, breeding, nonproliferation, and safety performance are characterized. A key finding is that the burnups of all cores were limited by the allowable fluence to the cladding rather than by the core reactivity. The carbide cores achieve fluence-limited burnups 15-25% greater than the comparable metal cores, though the metal cores can be optimized via decrementing the fuel volume fraction to reach fluence-limited burnups within 10% of the carbide cores. The removal of minor actinides from the recycled fuel has a minimal impact on the achievable burnups of both types of fuels, decreasing the fluence-limited burnup by less than half a percent in all cases. Similarly, long-term storage of the USFR fuel had minimal impact on the achievable burnups of all cores, decreasing the fluencelimited burnup by no more than 2% in all cases. Levelized fuel costs were in the range of 5.98 mills/kWh to 7.27 mills/kWh for the carbide cores, and 6.81 mills/kWh to 7.57 mills/kWh for the optimized metal cores, which is competitive with fuel costs of current LWRs and once-through SFRs. The metal and carbide multicore cores, made using slightly more than one once-through SFR core, functioned as slight fissile burners with fissile inventory ratios (FIRs) near 0.9. The uranium+ cores, made using one oncethrough SFR core plus natural uranium makeup, functioned in a fissile self-sustaining mode with FIRs near unity. All cores discharged fuel that was less attractive for weapon use than that of an LWR. The carbide cores had maximum sodium void worths in the range of $2.81-$2.86, approximately half the worth of the metal cores, which were in the range of $4.97-$5.14. Carbide and metal multicore cores possessed initial reactivities in the range of 15,000 pcm, requiring either multi-batch staggered reloading or control system modifications to achieve acceptable shutdown margins. The uranium+ carbide and metal cores achieved acceptable shutdown margin with the nominal control configuration and the single-batch reloading scheme. The overall conclusion is that USFR spent fuel is readily usable for recycle.
by Joshua Richard.
S.M.
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Chung, Hsiu-Ying. "Synthesis and characterization of ultra-incompressible, hard transition metal diborides." Diss., Restricted to subscribing institutions, 2007. http://proquest.umi.com/pqdweb?did=1481672591&sid=1&Fmt=2&clientId=1564&RQT=309&VName=PQD.
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Blackett, Alex. "Understanding the 'fast-track' transition between elite athlete and high-performance coach in men's Association Football and Rugby Union : a grounded theory." Thesis, University of Lincoln, 2017. http://eprints.lincoln.ac.uk/28658/.
Full textAbstract:
It is commonplace for many high-performance coaches to be former elite athletes in the same sports they coach (Christensen, 2013; Mielke, 2007; Werthner & Trudel, 2009). In many cases, such individuals are ‘fast-tracked’ through formal coach accreditation structures into these high-performance coaching roles (Rynne, 2014). The reasons why former elite athletes dominate coaching roles in professional sports clubs and why a ‘fast-track’ pathway from elite athlete to high-performance coach is supported remain unclear. The project builds upon existing research on coach development to understand the social processes for how high-performance athletes negotiate the career transition into post-athletic high-performance coaching roles in men’s association football and rugby union. The project employed a Straussian grounded theory methodology which consisted of three iterations of empirical data collection and analysis. The first and second iterations respectively sampled eight senior club directors and 11 academy directors of men’s professional association football and rugby union clubs on why they appointed ‘fast-tracked’ coaches and how they valued particular sources of coaching knowledge. Data were abductively analysed (Blaikie, 2009) and signified Bourdieu’s concepts of habitus, capital and hexis in addition to Foucault’s concepts of docile bodies, surveillance and technologies of power. The data suggested that elite athletes were drawn through within their clubs into high-performance coaching roles based on three main themes: a) to ensure the perpetuation of specific playing and coaching philosophies; b) clubs’ former athletes were regarded to act as docile bodies when embodying the clubs’ values in their coaching, and; c) ‘fast-tracked’ appointments were often based upon enhanced levels of symbolic capital and the perceived ability to gain player ‘respect’. Such appointment processes imposed symbolic violence onto other populations for whom competing in male elite sport is inaccessible, most distinctly women. The final iteration investigated how current or former elite athletes negotiated a ‘fast-tracked’ career trajectory when developing their coaching identities. Current or former elite athletes (n=15) were interviewed on two occasions over a 10-12 month period whilst registered onto their respective national governing body’s level three coach qualification. Both courses were designed only for senior professional athletes to attend. The resulting grounded theory provides an original contribution to the field of coach development by signifying a number of distinct social process for how the athletes negotiated the ‘fast-track’ coaching pathway for developing their coaching identities. The difficulties the coaches encountered in balancing the values imposed on them by their clubs during the process of consolidating their own coaching identities are critically discussed in alignment with Bourdieu and Foucault’s conceptual frameworks. Recommendations for the provision of formal coach education programmes are made concerning how coaches mediate developing their own coaching philosophies against imposed structural regimes of truth, along with conceptualising the value the coaches attributed to informal mentors over formal mentors. Recommendations are also provided to inform the policies surrounding coach recruitment at the high-performance level in the hope that directors’ recorded subconscious discriminatory practices are addressed.
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Radue, Elizabeth Lee. "Study of Variations of the Dynamics of the Metal-Insulator Transition of Thin Films of Vanadium Dioxide with An Ultra-Fast Laser." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1477068473.
Full textAbstract:
Vanadium dioxide is an intensely studied material, since it goes through an insulator-metal transition at a critical temperature just above room temperature at 340~K. The dramatic change in conductivity and the easily accessible transition temperature makes it an attractive material for novel technologies. Thin films of VO2 have a reversible transition without any significant degradation in contrast, and depending on the microstructure of the films, the properties of the transition are tunable. In this work, I study the dynamics of the insulator-transition in thin films grown on different substrates using a pump-probe configuration. The energy needed to trigger the transition, as well as the time constants of the change in reflectivity are affected by the strain in the VO2 films. I also characterized the samples using Raman spectroscopy and XRD measurements in order to identify what underlies the differences in behavior. Finally, in collaboration with Dr. Yamaguchi's group at RPI, I show that it is possible to trigger the transition using a THz pulse that directly pumps energy into the lattice, and at lower energies than needed to pump films by photoinducing the electrons across the band gap.
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Kosine, Natalie R. "Self-advocacy, metacognition, and transition in college freshmen with learning disabilities." Laramie, Wyo. : University of Wyoming, 2006. http://proquest.umi.com/pqdweb?did=1216741321&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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