Dissertations / Theses on the topic 'Internal diffusion'
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1
Otto, Oliver, Sebastian Sturm, Nadanai Laohakunakorn, Ulrich Keyser, and Klaus Kroy. "Rapid internal contraction boosts DNA friction." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183656.
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Chung, Samwon. "The effect of internal stress on diffusion." Case Western Reserve University School of Graduate Studies / OhioLINK, 1995. http://rave.ohiolink.edu/etdc/view?acc_num=case1058210791.
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Brutzer, Hergen, Alexander Huhle, Daniel Klaue, and Ralf Seidel. "Internal friction of a migrating Holliday junction." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183596.
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Otto, Oliver, Sebastian Sturm, Nadanai Laohakunakorn, Ulrich Keyser, and Klaus Kroy. "Rapid internal contraction boosts DNA friction." Diffusion fundamentals 20 (2013) 77, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13665.
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Brutzer, Hergen, Alexander Huhle, Daniel Klaue, and Ralf Seidel. "Internal friction of a migrating Holliday junction." Diffusion fundamentals 20 (2013) 72, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13659.
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Li, Lilong, and Songhua Chen. "Incorporating internal gradient and restricted diffusion effects in Nuclear Magnetic Resonance log interpretation." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186342.
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It is shown that internal gradient combined with the restricted diffusion effect can significantly influence the D-T2 cross plots, which are
widely used for fluid typing in Nuclear Magnetic Resonance (NMR) well-logging applications. By using models that capture the most important features of the internal gradient in the sedimentary rocks, such effects can be accounted for in the D-T2 inversion process, making fluid typing more accurate.
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Perkins, Edward William. "The spatial dynamics of internal migration : implications for the diffusion of HIV." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621237.
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Lorenzo, Oswaldo J. "Development of a model of internal diffusion and infusion of enterprise systems." Thesis, University of Warwick, 2004. http://wrap.warwick.ac.uk/73548/.
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After most large industrial companies have installed enterprise systems (ES), the managerial concern moves to the effective diffusion and infusion of ES throughout a company. Diffusion means the degree in which a system has been shared throughout the company and infusion is the degree in which a system has penetrated a company in terms of importance, impact, and significance. Little of the ES literature has considered these new larger issues. This thesis develops a model of internal diffusion and infusion of ES. The ES diffusion model presents the ES implementation as an iterative, cumulative, and virtuous process over time. The model recounts and validates the authentic characteristics of ES projects, places "use" as both product and fomenter of the implementation activity, and putting emphasis upon the importance of experiential learning. The ES infusion model develops a framework of ES capabilities to analyse the extent and quality of the use of ES in organizational contexts (i.e. infusion). To investigate these issues this research has borrowed the perspective of organizational introduction of a technological innovation from the innovation discipline. The scope of the investigation is limited to three selected organizations overseas, which had each already installed at least a single functional component of the system and had decided (or was working on) the diffusion of the system in further departments or locations. The data collection was a combination of retrospective and real-time analysis. Hence, a multiple-case studies for constructing theory from the observed field data was developed.
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Li, Lilong, and Songhua Chen. "Incorporating internal gradient and restricted diffusion effects in Nuclear Magnetic Resonance log interpretation." Diffusion fundamentals 14 (2010) 4, S. 1-5, 2010. https://ul.qucosa.de/id/qucosa%3A13850.
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It is shown that internal gradient combined with the restricted diffusion effect can significantly influence the D-T2 cross plots, which are
widely used for fluid typing in Nuclear Magnetic Resonance (NMR) well-logging applications. By using models that capture the most important features of the internal gradient in the sedimentary rocks, such effects can be accounted for in the D-T2 inversion process, making fluid typing more accurate.
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Sigmund, Eric, Ravinder Regatte, Mark Schweitzer, Hyungjoon Cho, and Yi-Qiao Song. "In vivo imaging of signal decay due to diffusion in the internal field in human knee trabecular bone." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-192231.
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This study presents the first demonstration of the MR signal decay due to diffusion in the internal field (DDIF) for in vivo knee trabecular bone imaging. DDIF contrast was compared with high resolution FLASH, T1, and T2* mapping in healthy volunteers. DDIF
maps showed spatial variation, superimposed on a T1 background, reflecting trabecular structure. DDIF and T2* maps showed correlated contrast near dense trabeculae, but their spatial textures differed, suggesting distinct structural sensitivities.
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Liu, Huabing, Marcel Nogueira D’Eurydice, Sergei Obruchkov, and Petrik Galvosas. "Pore length scales and pore surface relaxivity of sandstone determined by internal magnetic fields modulation at 2 MHz NMR." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-178759.
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Pore length scales and pore surface relaxivities of sandstone were studied on a 2 MHz Rock Core Analyzer in this work. To determine the pore length scales of rock cores, high eigenmodes of diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields B in. The results were confirmed by a 64 MHz NMR system. Furthermore, this methodology was combined with relaxometry measurements , which provides the two-dimensional correlation of pore length with relaxation time and yield information on the surface relaxivity of rock cores. The estimated surface relaxivities were compared with the results from an independent NMR method.
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Seland, John Georg. "Dynamic correlations between inhomogeneous magnetic fields, internal gradients, diffusion and transverse relaxation, as a probe for pore geometry and heterogeneity." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-178804.
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In this study we have applied 2D NMR experiments where the spatial inhomogeneous magnetic field (Bi) inside a porous sample is correlated to respectively internal gradient (G0), diffusion coefficient (D), and transverse relaxation time (T2) of a confined liquid. Experiments were performed on samples having different pore system geometry and heterogeneity, leading to different types of confinement of the liquid.
The results show that the correlation between G0 and Bi is more sensitive to the type of confinement, and thus also of the pore geometry and heterogeneity, compared to the corresponding correlations involving D and T2.
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Knaub, Karl R. "On the asymptotic behavior of internal layer solutions of advection-diffusion-reaction equations /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/6772.
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Larsson, Henrik. "Internal oxidation processing : New alloys and new simulation techniques." Doctoral thesis, KTH, Materialvetenskap, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3715.
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Nitriding and oxidising treatments of alloys for toolingpurposes have been investigated both experimentally andtheoretically. Specimens prepared by a combination of differentprocessing steps are investigated by light-optical, scanningand transmission electron microscopy and hardness measurments.The bounds of carbon and nitrogen concentration profiles duringnitriding are obtained from simulations using the DICTRA code.As a result, a new processing route to produce oxide-dispersediron-base alloys with large volume fraction of carbides issuggested. On the theoretical side the methods based on the random walktechnique have been investigated and developed further. The newmethods have been applied to study a vide range of phenomenae.g. internal oxidation, diffusion in inhomogeneous media,phase transformations and formation of porosity due to theKirkendall effect in welded joints. Probability distributionsare introduced to replace random number generators in order toincrease computational efficiency. A general method to simulatediffusional phase transformations in multicomponent systems isdeveloped and applied to ternary alloys.QC 20100506
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Omar, Nur Farhayu. "Diffusion weighted imaging and relaxometry in abdominal organs." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/35939/.
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This thesis presents the application of diffusion weighted imaging (DWI) and relaxometry MRI studies in three organs in the abdomen, the kidney, colon and liver. These methods are first applied at 1.5 Tesla in healthy volunteers and patients with Cardiorenal Syndrome (CRS), a clinical condition in which cardiac and renal dysfunctions (RD) coexist. Diffusion parameters are determined using the mono-exponential ADC, bi-exponential IVIM, stretched-exponential and Kurtosis models, as well as diffusion tensor imaging (DTI) in order to assess pathophysiology and structural changes in the kidney. Complementary longitudinal relaxation time (T1) mapping and PC-MRI flow measures are collected for comparison with diffusion parameters. The assessment of the colonic content using T1 measures as a biomarker of water absorption and health is presented in the second study. The main objective of the study was to determine the robustness of bi-exponential model in the fitting of T1 in the colonic contents of ascending colon. T1 measurements of colonic content are made at different positions in the ascending colon, before and after a liquid challenge. The reliability of T1 measurements of colonic content were compared across observers. The heterogeneity in the measurements was evaluated by considering different ROI sizes and locations. The final study is the assessment of liver function associated with Chronic Liver Disease (CLD) using DWI and T1 measurement at 1.5 T and a comparison with histological measures. the Measurements of T1 and diffusion parameters (ADC and IVIM) to stratify fibrosis stage in liver disease are combined with T2* measurement of iron accumulation. The repeatability and reproducibility of this protocol is then tested in the healthy liver using MRI at 3T for the assessment of structural and haemodynamic changes for future studies, with an evaluation of the choice of b-values to inform fitting of the bi-exponential (IVIM) model provided.
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Godinho, Manuel Fernando Cilia Mira. "Innovation diffusion in the Portuguese and Italian clothing industry." Thesis, University of Sussex, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239480.
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In this thesis a model to describe the diffusion of a cluster of inter-related innovations is put forward. Unlike conventional diffusion approaches, which deal with each innovation independently, this model is based on a system of "aggregated measures of diffusion" (AMDs). Such AMDs assume a common technological base and a learning sequence in adoption, and they are derived from a system of double weighting, with scores attached for a) the complexity of each innovation and b) the time-span since adoption. In addition to diffusion measurement, AMDs can be used to assess technological capability of individual firms, industries, regions or countries. In this role they can replace conventional technology measures, particularly when the object of analysis are "traditional industries" or "catching up regions". In the present application, the diffusion of nine innovations available for use in the clothing industry was tracked. Alternative weighting schemes generated different AMDs, successively taken as the dependent variable in a multiple regression exercise. The variables entered into the model matched broadly the conceptual framework, with proxies of technological competence ("qualified technicians" or "intangible investment") and firm size ("sales" or "employment") displaying greater association with the AMDs. Interestingly, the dummy "country" was not selected as significant. This is in line with previous findings in the thesis, which showed an average initial lag between Portuguese and Italian firms of 4 years, narrowing to 2.5 years as diffusion proceeds. These results suggest that the productivity gap (2.6: I) derives mostly from factors other than differences in the adoption of recent hardware. Future policies to narrow this gap could better consider how to improve the handling of existing hardware (training, skills) and other intangible factors (design, quality, marketing and distribution), than concentrating exclusively on fixed capital formation. If these intangible factors are addressed by public policy, it is possible to believe that the Portuguese clothing industry will have an opportunity to survive and prosper. With regard to Italy, there are signs that some of the traditional factors of competitiveness have suffered recently a process of erosion. With the expected phasing out of the MultiFibre Arrangement, Italian tirms must concentrate further in up-market niches and relocate part of their assembling operations to lower cost regions abroad. The possibility of radical technological change reversing dramatically this industry'S pattern of comparative advantage is not a realistic prospect in the short/medium-term. However. the likelihood of full automation in a longer-term remains, and it is possible to expect that those firms which have gone further in adopting certain LT.-related innovations will have a decisive advantage early next century.
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Ramotar, Mario. "The internal diffusion of new digital innovations : a case of enterprise social networking adoption." Thesis, University of Warwick, 2016. http://wrap.warwick.ac.uk/83157/.
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Despite a growing interest in processes of diffusion within organisations and some understanding of the social processes of creating and enacting external and internal IT innovations, little empirical research has studied potentially relevant intra-organisational diffusion dynamics underlying the movement of innovations adopted at an organisational level, into the front-line practices of organisational subunits. Furthermore, we know even less about the diffusion processes of non-transactional digital innovations, such as enterprise social networking (ESN). ESNs embedded “ideology of openness” and its nontransactional nature particularly create social tensions that largely run against the grain of organisational rationality and efficiency, pervade key organisational processes and lead to wide variations in how organisational actors interpret and appropriate ESN features within organisations. The goal of this research is to theorize about the institutional mechanisms and processes by which these highly flexible digital innovations become misaligned, aligned and diffused at the micro-level of everyday work, as well as the enabling and precipitating dynamics that condition and trigger these mechanisms. This theorization involved a longitudinal exploration of how different communities of actors in a globally distributed technology services firm appropriated an ESN platform over a four year period, and how managerial intervention shaped appropriation outcomes. These dynamics can be understood through a rhetorical legitimation lens as a process where organisational actors with competing interests use strategic communications, to legitimate and enable the generation of collective meanings around distinctly different IT features and practices. Findings indicate that the core internal diffusion process was intra-organisational theorizing around ESN. Intra-organisational theorizing was an on-going process of elaborating and refining the organisational level theorization for ESN to suit front- line employees in their immediate contexts. In this way, it gradually helped to standardize and scale the ESNs features and functions as it was appropriated by different communities of actors (infusion). In each infusion, intra-organisational theorizing unfolded in three cumulative and relatively sequential phases of legitimation: (1) rationale framing (2) value advertising, and (3) motivating engagement, which were instrumental for respectively managing political, technical and cultural institutional misalignments, and promoting intra-group meaning making. On the other hand, negotiation and inter-group meaning-making was enabled by strategically grafting on other intra-organisational theorizations, and co-opting people, ESN functions, and practices from other infusions. Further, these legitimation processes unfolded as a sequence of primarily pragmatic pathos and logos appeals. In particular, early and on-going logos appeals helped to de-legitimate established, competing technologies, and directly enabled legitimation and collective meaning-making around ESN.
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Sigmund, Eric, Ravinder Regatte, Mark Schweitzer, Hyungjoon Cho, and Yi-Qiao Song. "In vivo imaging of signal decay due to diffusion in the internal field in human knee trabecular bone." Diffusion fundamentals 10 (2009) 18, S. 1-3, 2009. https://ul.qucosa.de/id/qucosa%3A14109.
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This study presents the first demonstration of the MR signal decay due to diffusion in the internal field (DDIF) for in vivo knee trabecular bone imaging. DDIF contrast was compared with high resolution FLASH, T1, and T2* mapping in healthy volunteers. DDIF
maps showed spatial variation, superimposed on a T1 background, reflecting trabecular structure. DDIF and T2* maps showed correlated contrast near dense trabeculae, but their spatial textures differed, suggesting distinct structural sensitivities.
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Liu, Huabing, Marcel Nogueira D’Eurydice, Sergei Obruchkov, and Petrik Galvosas. "Pore length scales and pore surface relaxivity of sandstone determined by internal magnetic fields modulation at 2 MHz NMR." Diffusion fundamentals 22 (2014) 7, S. 1-5, 2014. https://ul.qucosa.de/id/qucosa%3A13487.
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Pore length scales and pore surface relaxivities of sandstone were studied on a 2 MHz Rock Core Analyzer in this work. To determine the pore length scales of rock cores, high eigenmodes of diffusion equation were detected with optimized encoding periods in the presence of internal magnetic fields B in. The results were confirmed by a 64 MHz NMR system. Furthermore, this methodology was combined with relaxometry measurements , which provides the two-dimensional correlation of pore length with relaxation time and yield information on the surface relaxivity of rock cores. The estimated surface relaxivities were compared with the results from an independent NMR method.
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Hughes, Malcolm. "The Role of Internal Convection in Respiratory Gas Transfer in Larval Zebrafish." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37904.
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Purely diffusive O2 transport typically is insufficient to sustain aerobic metabolism in most multicellular organisms. In small animals, however, a high surface-to-volume ratio may allow passive diffusion alone to supply sufficient O2 transfer. The purpose of this thesis was to explore the impacts of internal convection on the exchange of respiratory gases in a small complex organism, the larval zebrafish (Danio rerio). Thus, I tested the hypothesis that internal convection is required for the normal transfer of the respiratory gases O2 and CO2 and maintenance of resting aerobic metabolic rate. Use of morpholino knockdown of the VEGF-A and TNNT2 proteins allowed examination of two independent models lacking internal convection. Using micro-respirometry, I demonstrated that loss of internal convection reduces resting rates of O2 consumption and CO2 excretion in larvae at 4 days post fertilization. I also used the scanning micro-optrode technique to demonstrate that acute loss of internal convection resulted in reduced rates of cutaneous O2 flux, a trait that was reversed upon the restoration of internal convection. Finally, I demonstrated that in larval zebrafish, loss of internal convection resulted in decreased hypoxic performance and loss or severe reduction of the hypoxic cardiorespiratory responses. The results from these experiments showed that internal convection is i) required to maintain resting rates of respiratory gas transfer in the larval zebrafish, ii) important in facilitating the hypoxic cardiorespiratory responses in larval zebrafish and iii) augments O2 extraction capacity in the face of progressive hypoxia.
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Taljan, Kyle Andrew Ignatius. "Investigations of Anatomical Connectivity in the Internal Capsule of Macaques with Diffusion Magnetic Resonance Imaging." Cleveland State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=csu1311093061.
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Seland, John Georg. "Dynamic correlations between inhomogeneous magnetic fields, internal gradients, diffusion and transverse relaxation, as a probe for pore geometry and heterogeneity." Diffusion fundamentals 22 (2014) 10, S. 1-5, 2014. https://ul.qucosa.de/id/qucosa%3A13490.
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In this study we have applied 2D NMR experiments where the spatial inhomogeneous magnetic field (Bi) inside a porous sample is correlated to respectively internal gradient (G0), diffusion coefficient (D), and transverse relaxation time (T2) of a confined liquid. Experiments were performed on samples having different pore system geometry and heterogeneity, leading to different types of confinement of the liquid.
The results show that the correlation between G0 and Bi is more sensitive to the type of confinement, and thus also of the pore geometry and heterogeneity, compared to the corresponding correlations involving D and T2.
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Myrén, Niklas. "Components based on optical fibers with internal electrodes." Licentiate thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1685.
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The topic of this thesis is development ofdevices fortelecom applications based on poled optical fibers. The focusis on two different specific functions, wavelength conversionand optical switching.
Optical switching is demonstrated in a poled optical fiberat telecom wavelengths (~1.55 mm). The fiber has two holesrunning along the core in which electrodes are inserted. Thefiber device is made electro-optically active with a polingprocess in which a strong electric field is recorded in thefiber at a temperature of 270 o C. The fiber is then put in onearm of a Mach-Zehnder interferometer and by applying a voltageacross the two electrodes in the fiber the refractive index ismodulated and the optical signal switched from one output portto the other. So far the lowest switching voltage achieved is~1600 V which is too high for a commercial device, but byoptimizing the design of the fiber and the poling process aswitching voltage as low as 50 V is aimed for.
A method to deposit a thin silver electrode inside the holesof an optical fiber is also demonstrated. A new way of creatingperiodic electrodes by periodically ablating the silver filmelectrode inside the holes of an optical fiber is also shown.The periodic electrodes can be used to create a quasi-phasematched (QPM) nonlinearity in the fiber which is useful forincreasing the efficiency of a nonlinear process such aswavelength conversion. Poling of a fiber with silver electrodesshowed a huge increase in the nonlinearity. This could be dueto a resonant enhancement caused by silver nanoclusters.
Keywords:Poling, twinhole fiber, fiber electrodes,silver film electrodes, silver diffusion, quasi-phase matching,optical switching, frequency conversion, optical modulation
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Alford, Matthew. "Observations of overturning and double diffusive processes in the thermocline : the context of ocean mixing /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9907820.
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Hardy, Steven M. "Study of hyperpolarised 3He MRI diffusion on asthma and cystic fibrosis, and development of hyperpolarised 129Xe MRI lung imaging." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/37921/.
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Hyperpolarised gas Magnetic Resonance Imaging (MRI) is a non-invasive method developed to provide images of the void spaces of the lungs, and evaluate the distal airways via diffusion weighted techniques. The work in this thesis covers the use of both hyperpolarised 3He and hyperpolarised 129Xe gas MRI, for both diffusion measurement studies and ventilation imaging, on healthy, asthmatic and cystic fibrosis volunteers. The first study covered in this thesis aimed to determine the nature of the acinar airway involvement in asthma sufferers via the use of Computed Tomography densitometry and hyperpolarised 3He diffusion MRI at multiple timescales alongside standard lung function tests such as spirometry and multiple breath washout (MBW). It was hypothesised that Asthma patients with an elevated MBW parameter 'Sacin' would manifest altered long-range diffusion, as suggestive of intra-acinar airway disease. It was found that there appeared to be an association between the MBW 'Sacin' parameter and subtle alterations in diffusion within the acinar airways for participants with asthma, suggesting a structural abnormality in the pulmonary acinus. However, further longitudinal studies are required before the long-term prognostic significance of acinar airway disease in asthma can be determined. The second study aimed to determine if a relationship exists between measurements from standard lung function test, spirometry and body plethysmography, and the measurements of hyperpolarised 3He diffusion MRI. 18 Cystic Fibrosis patients were recruited, alongside 27 age-matched healthy subjects. It was found that the short timescale diffusion values were lower in patients with Cystic Fibrosis, although not substantial enough to use an indicator to distinguish between a healthy volunteer and a Cystic Fibrosis patient. No strong correlations were found between the lung function measurements and the hyperpolarised 3He diffusion MRI measurements. The final section of this thesis looks at the preliminary results of a pilot study to develop scan sequences, protocols and gas delivery of hyperpolarised 129Xe MRI, in preparation for future clinical studies at the University of Nottingham. The main focus was on the development of in vivo ventilation images of the human lungs, to a high standard of quality and repeatability. Good progress was demonstrated, with lung images achieved down to 2.5 cm thick slices, with initial images of both dynamic ventilation and dissolved-phase 129Xe lung images. However the pilot study was not yet complete, and more development on the techniques discussed was still required.
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Gamero, Rafael. "Mass transfer during isothermal drying of a porous solid containing multicomponent liquid mixtures." Licentiate thesis, KTH, Chemical Engineering and Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1748.
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Mass transfer in a porous solid, partially saturated with asingle solvent and multicomponent liquid mixtures, has beenexperimentally and theoretically studied. A porous materialcontaining single liquids and mixtures of organic solvents wasisothermally dried. Experiments were performed using a jacketedwind tunnel, through which a humidity andtemperature-controlled air stream flowed. The wetted porousmaterial was placed in a cylindrical vessel, whose top isexposed to the air stream until the material became dried to acertain extent. Drying experiments with the single solventswater, methanol, ethanol and 2-propanol, were performed atdifferent temperatures and transient liquid content profileswere determined. In isothermal drying experiments with liquidmixtures,the transient concentration profiles of thecomponents along the cylindrical sample as well as the totalliquid content were determined. The liquid mixtures examinedwere water-methanolethanol and isopropanol-methanol-ethanol.Two different temperatures and initial compositions were usedin the experiments. Mathematical models that describe nonsteadystate isothermal drying of a solid containing single liquidsand multicomponent liquid mixtures were developed. In the solidwetted with a single liquid, capillary movement of the liquidwas the main mechanism responsible for mass transfer. In thesolid containing liquid mixtures, interactive diffusion inliquid phase was superimposed to the capillary movement of theliquid mixture. In addition, interactive diffusion of thevapours in empty pores was considered. The parameters todescribe the retention properties of the solid and thecapillary movement of the liquid were determined by comparingtheoretical and experimental liquid content profiles obtainedduring drying of the solid wetted with single liquids. Tosimulate the transport of the liquid mixtures these parameterswhere weighed according to liquid composition. A fairly goodagreement between theoretical and experimental liquidcomposition profiles was obtained if axial dispersion isincluded in the model when the moisture consists of amixture.
Keywords:Internal mass transfer, capillary flow,multicomponent, diffusion, solvent mixtures
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Bogdanoff, Alec Setnor. "Physics of diurnal warm layers : turbulence, internal waves, and lateral mixing." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108895.
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Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 167-179).
The daily heating of the ocean by the sun can create a stably stratified near-surface layer when the winds are slight and solar insolation is strong. This type of shallow stable layer is called a Diurnal Warm Layer (DWL). This thesis examines the physics and dynamics of DWLs from observations of the subtropical North Atlantic Ocean associated with the Salinity Processes in the Upper ocean Regional Study (SPURS-I). Momentum transferred from the atmosphere to the ocean through wind stress becomes trapped within the DWL, generating shear across the layer. During SPURS-I, strong diurnal shear across the DWL was coincident with enhanced turbulent kinetic energy (TKE) dissipation ([epsilon], [epsilon] > 10⁻⁵ W/kg) observed from glider microstructure profiles of the near-surface. However, a scale analysis demonstrated that surface forcing, including diurnal shear, could not be the sole mechanism for the enhanced TKE dissipation. High-frequency internal waves ([omega] >> f) were observed in the upper ocean during the daytime within the DWL. Internal waves are able to transfer energy from the deep ocean into the DWL through the unstratified remnant mixed layer, which is the intervening layer between the DWL and seasonal thermocline. As the strength of the stratification of the DWL increases, so does the shear caused by the tunneling internal waves. The analysis demonstrates that internal waves can generate strong enough shear to cause a shear-induced instability, and are a plausible source of the observed enhanced TKE dissipation. Vertically-varying horizontal transport across the upper ocean occurs because a diurnal current exists within the DWL, but not in the unstratified remnant mixed layer below. Therefore, when a DWL is present, the water within DWL is horizontally transported a different distance than the water below. Coupled with nocturnal convection that mixes the DWL with the unstratified layer at night, this cycle is a mechanism for submesoscale (1-10 km) lateral diffusion across the upper ocean. Estimates of a horizontal diffusion coefficient are similar in magnitude to current estimates of submesoscale diffusion based on observations, and are likely an important source of horizontal diffusion in the upper ocean.
by Alec Setnor Bogdanoff.
Ph. D.
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Lucas, Cyrille. "Étude du modèle de l'agrégation limitée par diffusion interne." Thesis, Paris 10, 2011. http://www.theses.fr/2011PA100173/document.
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Cette thèse contient quatre travaux sur le modèle d'Agrégation Limitée par Diffusion Interne (iDLA), qui est un modèle de croissance pour la construction récursive d'ensembles aléatoires. Le premier travail concerne la dimension 1 et étudie le cas où les marches aléatoires formant l'agrégat évoluent dans un milieu aléatoire. L'agrégat normalisé converge alors non pas vers une forme limite déterministe comme dans le cas de marches aléatoires simples mais converge en loi vers un segment contenant l'origine dont les extrémités suivent la loi de l'Arcsinus. Dans le deuxième travail, on considère le cas où l'agrégat est formé par des marches aléatoires simples en dimension d > 1. On donne alors des résultats de convergence et de fluctuations sur la fonction odomètre introduite par Levine et Peres, qui compte en chaque point le nombre de passages des marches ayant formé l'agrégat. Dans le troisième travail, on s'intéresse au cas où l'agrégat est formé par des marches aléatoires multidimensionnelles qui ne sont pas centrées. On montre que sous une normalisation appropriée, l'agrégat converge vers une forme limite qui s'identifie à une vraie boule de chaleur. Nous répondons ainsi à une question ouverte en analyse concernant l'existence d'une telle boule bornée. Le quatrième travail concerne le cas particulier où une borne intérieure est connue pour l'agrégat. On donne alors des conditions suffisantes sur le graphe ainsi que sur la nature de cette borne pour qu'elle implique une borne extérieure. Ce résultat est appliqué au cas de marches évoluant sur un amas de percolation par arêtes surcritique, complétant ainsi un résultat de ShellefThis thesis contains four works on the Internal Diffusion Limited Aggregation model (iDLA), which is a growth model that recursively builds random sets. The first work is set in dimension 1 and studies the case where the random walks that build the aggregate evolve in a random environment. The normalised aggregate then does not converges towards a deterministic limiting shape as it is the case for simple random walks, but converges in law towards a segment that contains the origin and which extremal points follow the Arcsine law. In the second work, we consider the case where the aggregate is built by simple random walks in dimension d > 1. We give convergence and fluctuation results on the odometer function introduced by Levine and Peres, which counts at each point the number of visits of walkers throughout the construction of the aggregate. In the third work, we examine the case where the aggregate is built using multidimensional drifted random walks. We show that under a suitable normalisation, the aggregate converges towards a limiting shape which is identified as a true heat ball. We thus give an answer to an open question in analysis concerning the existence of such a bounded shape. The last work deals with the special case where an interior bound is known for the aggregate. We give a set of conditions on the graph and on the nature of this interior bound that are sufficient to imply an outer bound. This result is applied to the case of random walks on the supercritical bond percolation cluster, thus completing a result by Shellef
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Xiao, Kewei. "A diffusion-viscous analysis and experimental verification of the drying behavior in nanosilver-enabled low-temperature joining technique." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25137.
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The low-temperature joining technique (LTJT) by silver sintering is being implemented by major manufacturers of power electronics devices and modules for bonding power semiconductor chips. A common die-attach material used with LTJT is a silver paste consisting of silver powder (micron- or nano-size particles) mixed in organic solvent and binder formulation. It is believed that the drying of the paste during the bonding process plays a critical role in determining the quality of the sintered bond-line. In this study, a model based on the diffusion of solvent molecules and viscous mechanics of the paste was introduced to determine the stress and strain states of the silver bond-line. A numerical simulation algorithm of the model was developed and coded in the C++ programming language. The numerical simulation allows determination of the time-dependent physical properties of the silver bond-line as the paste is being dried with a heating profile. The properties studied were solvent concentration, weight loss, shrinkage, stress, and strain. The stress is the cause of cracks in the bond-line and bond-line delamination. The simulated results were verified by complementary experiments in which the formation of cracks in bond-line and interface delamination was observed during the pressure-free drying of a die-attach nanosilver paste. Furthermore, the important drying parameters, such as drying pressure, low temperature drying time and temperature ramp rate of nanosilver LTJT process, are experimentally studied and analyzed with the numerical simulation. The simulated results were consistent with the experimental findings that the quality of sintered silver bond-line increases with increasing external drying pressure, with increasing low temperature drying time, and with decreasing temperature ramp rate. The insight offered by this modeling study can be used to optimize the process profile that enable pressure-free, low-temperature sintering of the die-attach material to significantly lower the cost of implementing the LTJT in manufacturing.Ph. D.
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Herschberg, Basualdo Rafael. "Modeling the Diffusion of Interstitial Impurities and their Impact on the Ageing of Ferritic Steels." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS443/document.
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Nous modélisons la diffusion des atomes interstitiels (C et O) dans des solutions solides (Fe-Cr et Nb-V) et comparons nos résultats aux données expérimentales disponibles dans la littérature. Un ensemble d’énergies de liaisons entre interstitiels et solutés substitutionnels, et de barrières de migration des interstitiels, ont d’abord été calculés en utilisant la théorie de la fonctionnelle de la densité. Des modèles d’interactions de paires ont ensuite été ajustés sur ces données pour calculer les barrières de migration dans n’importe quel environnement chimique local. Ces modèles de paires sont enfin intégrés dans des simulations Monte Carlo cinétiques, afin de modéliser des expériences de diffusion de traceur et de frottement interne. Dans les alliages Fe-Cr-C, les simulations prévoient la formation d’un pic de Snoek unique, dans tout le domaine de composition entre le fer pur et le chrome pur. La barrière de migration moyenne du carbone, donnée par la température de ce pic, augmente progressivement avec la teneur en chrome, l’augmentation étant très faible en dessous de 6% de Cr. Dans les alliages riches en Cr, la barrière de migration moyenne obtenue lors d’une simulation de diffusion de traceur est plus grande que celle obtenue lors d’une simulation de frottement interne. Nous en concluons que la barrière mesurée lors d’une expérience de diffusion de traceur est fortement affectée par le piégeage du carbone dans des environnements riches en fer, qui limite la diffusion à grande distance ; alors que la barrière mesurée par friction interne, qui ne nécessite qu’une diffusion à courte distance, est principalement contrôlée par les barrières de migration des configurations les plus probables. Dans les alliages Nb-V-O dilués, les simulations font apparaitre un pic de Snoek à haute température lorsque la concentration en oxygène est plus faible que celle en vanadium. Quand la concentration en oxygène devient plus importante, un deuxième pic apparait à plus basse température, tandis que le premier pic se déplace vers des températures plus petites. Nous en concluons que le pic à haute température correspond à des paires V-O, et que celui à basse température correspond à la diffusion de l’oxygène dans le niobium pur. Les simulations sont utilisées pour tester le modèle de Koiwa, dans la limite de l’alliage ternaire infiniment dilué. Les deux approches sont en bon accord et nous montrons que la position du pic à haute température n’est pas reliée à une fréquence de saut unique, mais à une fonction complexe de plusieurs fréquences de sauts. Nous présentons enfin les résultats d’une étude préliminaire sur l’effet du carbone sur les cinétiques de séparation de phases dans les alliages fer-chrome irradiés. Nous montrons que la forte attraction entre atomes de carbone et défauts d’irradiation (auto-interstitiels et surtout lacunes) peut dans certaines conditions limiter l’accélération de la précipitation du chrome habituellement provoquée par l’irradiationThe diffusion of interstitial atoms (C and O) in bcc solid solutions (Fe-Cr and Nb-V) is modelled and compared to experimental data. A set of binding energies and migration barriers for the direct interstitial diffusion mechanism in different local chemical environments are first calculated using Density Functional Theory. Two different pair interaction models are developed in order to reproduce these data and predict the migration barriers in all possible environments. The diffusion models are then implemented in a kinetic Monte Carlo method to simulate tracer diffusion experiments, using a standard procedure, and internal friction experiments, using a novel method. In the Fe-Cr-C systems our internal friction simulations show a unique Snoek peak in the whole concentration range, between pure iron and pure chromium. The average migration enthalpy for C diffusion in Fe-Cr alloys is found to increase progressively with the Cr concentration, with a small rate below 6 %Cr. In Cr-rich alloys, the effective migration barrier for C diffusion is found to be larger in tracer diffusion than in the internal friction simulations. We conclude that the effective migration barrier extracted from tracer diffusion is closely related to trapping effects of C atoms in Fe-rich local environments, whereas the migration barrier associated with internal friction is mainly controlled by the spectrum of migration barriers of the most frequent configurations, as it is clearly shown in the Cr-rich domain. In the dilute Nb-V-O alloys, we find a high temperature Snoek peak when the concentration of oxygen is lower than the vanadium content. But when the oxygen concentration is higher, we see the appearance of a second peak but at a lower temperature and a shift of the first peak to lower temperatures. We conclude that the high temperature peaks correspond to the oxygen-vanadium pairs, and the low temperature peak corresponds to the oxygen Snoek peak in pure Nb. We also use our model in order to validate the Koiwa model in infinitely dilute ternary alloys. Both approaches are in good agreement and we observe that the high temperature peak cannot be directly related to a single jump frequency but to a complex function of them. We also show preliminary results on the effect of C in the precipitation of the Fe-Cr phase separation under irradiation. We observee that a strong attraction between carbon atoms and point defects (vacancies and self-interstitials) might be able to slow down the acceleration of the α’ precipitation
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Kolitcheff, Svetan. "Approche multitechnique des phénomènes de diffusion en hydrotraitement de distillats." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSE1033/document.
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Dans l'industrie du raffinage, les procédés de craquage catalytique permettent la production de carburants à partir de coupes pétrolières lourdes, telles que les distillats sous vides (DSV). Pour optimiser ces procédés, un hydrotraitement préalable est nécessaire. Ces dernières années, les travaux conséquents de R&D ont considérablement amélioré l'activité des catalyseurs d'hydrotraitement. Par conséquent, le transfert de matière interne peut devenir limitant, il doit donc être quantifié.Une méthodologie utilisant la chromatographie inverse liquide a été développée afin de caractériser le transfert de matière dans des supports aluminiques de catalyseur. Le système a ensuite été déployé pour caractériser l'influence de l'adsorption, de la température et des précurseurs de la phase active. Dans des alumines mésoporeuses, le régime de diffusion est moléculaire pour des composés saturés allant des coupes essences au DSV. Ainsi, pour différentes alumines, des valeurs de tortuosité ont été estimées et corrélées aux propriétés texturales (porosité, surface spécifique et distribution en taille des pores). Ces relations montrent que les valeurs de tortuosité obtenues ne sont pas en accord avec un solide homogène vis-à-vis des propriétés de transfert de matière. Il y aurait donc une organisation dans la porosité des alumines.Un test catalytique en réacteur agité a aussi été développé pour étudier le transfert de matière en conditions réactives. L'impact de la taille des grains sur l'hydrodésulfuration d'une molécule synthétisée a été caractérisé et modélisé. Ces résultats ont été comparés aux expériences de chromatographie inverse avec un bon accordThe catalytic cracking has an important role in fuels production from heavy oil cuts like vacuum gas oil (VGO). To optimize these processes, a pre-hydrotreatment is required. The amount of work dealt by the research community in the last years has highly contributed to the enhancement of the catalyst’s activity. Therefore, the internal mass transfer can become the limiting step and it must be quantified.A methodology based on inverse liquid chromatography has been developed to characterize the mass transfer within alumina catalyst supports. The experimental setup was also used to study the influence of several parameters into mass transfer properties such as, adsorption, temperature, and active phase precursors. In mesoporous aluminas, the diffusion regime undertaken by saturated compounds, going from gasoline to VGO is the molecular regime. For different alumina supports, tortuosity values were estimated and correlated to the textural properties (porosity, specific surface area and pore size distribution). These results showed that the aluminas can not be considered as homogeneous supports given the estimated mass transfer properties. Thus, we assume that a hierarchical porous structure might be in cause. A catalytic test promoted in a stirred reactor was also developed to study the mass transfer properties under reactive conditions. The impact of the particle grains size into the hydrodesulphurization of a synthetized molecule was characterized and modeled. A good agreement was found between the data obtained using the inverse chromatography experiments and the catalytic tests
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Kruse, Clemens. "An Analysis of the External Environmental and Internal Organizational Factors Associated With Adoption of the Electronic Health Record." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3006.
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Despite a Presidential Order in 2004 that launched national incentives for the use of health information technology, specifically the Electronic Health Record (EHR), adoption of the EHR has been slow. This study attempts to quantify factors associated with adoption of the EHR and Computerized Provider Order Entry (CPOE) by combining multiple organizational theories and empirical studies. The study is conducted in two phases. The primary phase of this study identifies and evaluates the effects of external environmental and internal organizational factors on healthcare organizations to adopt the EHR. From secondary data, twelve IVs (df=19) are chosen based on existing models and literature. Logistic regression is used to determine the association between the environmental factors and EHR adoption. The secondary phase of this study examines the adoption of five variations of CPOE using the same IVs from phase one. This EHR component of CPOE is chosen due to its promotion as a solution to help cross the quality chasm (IOM, 2001). Secondary data are analyzed and logistic regression is used to quantify the association between the factors of EHR adoption and CPOE adoption. Eleven of the twelve IVs are significant between the two phases (p<.1). This study uses data from 2009 because the HITECH Act was passed that year and significant government incentives were offered for those health care organizations (HCOs) that meet the qualifications of meaningful use. This study serves as a baseline for future studies, extends the work of other empirical studies, and fills a gap in the literature concerning factors associated with the adoption of the EHR and specific dimensions of CPOE. The Kruse Theory developed is strongly based in literature and reflects complexity commensurate with the health care industry.
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Rawiso, Michel. "Etude structurale de macromolecules lineaires par diffusion de neutrons." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13209.
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Wang, Huan, and Huan Wang. "Flow Field Penetration in Thin Nanoporous Polymer Films under Laminar Flow by Förster Resonance Energy Transfer Coupled with Total Internal Reflectance Fluorescence Microscopy." Diss., The University of Arizona, 2015. http://hdl.handle.net/10150/565916.
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Tethered polymer layers at solid-fluid interfaces are used widely in a variety of surface science applications. Although many of these applications require exposure to dynamic flow conditions, flow field penetration into densely grafted polymer brushes, is still a question open to debate despite the fact that it is a fundamental process crucial to mass transport through these polymer films. Although most theoretical work has indicated flow field penetration into polymer films, with varying predicted penetration depths predicted, the limited experimental attempts to investigate this phenomenon have resulted in inconsistent conclusions due to lack of a proper analytical method. To help resolve this controversy, in this Dissertation, a new spectroscopic method, FRET-TIRFM, based on a combination of Förster resonance energy transfer (FRET) and total internal reflectance fluorescence microscopy (TIRFM), is developed to provide the first direct, quantitative measurements on flow field penetration by measuring linear diffusion coefficients of small molecules through densely grafted, thin poly(N-isopropylacryl-amide) (pNIPAM) films. Decay curves from FRET of the acceptor with a donor covalently attached at the substrate surface were fit to a combined Taylor-Aris-Fickian diffusion model to obtain apparent linear diffusion coefficients of the acceptor molecules for different flow rates. These values can then be used to obtain quantitative estimates of flow field penetration depths. For a pNIPAM surface of 110 nm dry thickness, with a 0.6 chain/nm² grafting density, apparent diffusion coefficients ranging from 1.9-9.1 × 10-12 cm²/s were observed for flow rates ranging from 100 to 3000 μL/min. This increase in apparent diffusion coefficient with applied fluid flow rate is indicative of flow field penetration of the polymer film. The depth of penetration of the flow field is estimated to range from ~6% of the polymer film thickness to ~57% of the film thickness in going from 100 to 3000 μL/min flow rate of a good solvent. Factors other than flow rate that may impact flow field penetration were also investigated using this new FRET-TIRFM method. Solvent quality and polymer brush grafting density are the two most important parameters due to the fact that they influence changes in tethered polymer chain conformation. This work demonstrates that polymer films are most penetrable in a good solvent and least penetrable in a poor solvent under identical flow conditions. These findings are consistent with polymer chain conformational changes going from extended brushes to compact globules. For flow rates ranging from 100 to 3000 μL/min, flow field penetration depth ranges from ~6% of the film thickness to ~57% of film thickness for a good solvent compared to ~4% to ~19% for a poor solvent. Thus, by simply changing solvent quality from good to poor, flow field penetration decreases by about 38%. Grafting density has a less pronounced effect than solvent quality on penetration depth, probably due to the small range of grafting densities chosen for study. However, a roughly 10-20% difference in penetration depth was observed between high density (0.60 chain/nm²) and low density (0.27 chain/nm²) pNIPAM surfaces in the same solvent. Changes in grafting density have a less significant impact in a good solvent compared to a poor solvent. This is most likely caused by the fact that grafting density impacts polymer chain conformation mainly through polymer-polymer repulsion, which becomes less significant in a solvent that better solvates the polymer. For the two extreme cases studied here at flow rates ranging from 100 to 3000 μL/min, the penetration depth is estimated to range from ~4-19% of the original solvent-swollen film thickness for high density pNIPAM films in a poor solvent and from ~7-67% for low density films in a good solvent. One important assumption that underlies all of this work is that the dominant mass transport mechanism for small molecules in dense polymer brushes is diffusion. This assumption was further validated through the use of two different small molecule quenchers, RhB and 2-nitrobenzylalcohol. These molecules are significantly different in size, charge, and structure, and operate by different quenching mechanisms. Despite these differences, the results for flow field penetration are statistically the same for both. These observations validate the assumption of diffusive mass transport in these films.
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Lindsay, John Christopher. "Stress corrosion cracking and internal oxidation of alloy 600 in high temperature hydrogenated steam and water." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/stress-corrosion-cracking-and-internal-oxidation-of-alloy-600-in-high-temperature-hydrogenated-steam-and-water(1d6b037c-baf1-4397-a6c9-43835e7bb39a).html.
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In this study, the possibility of using low pressure hydrogenated steam to simulate primary water reactor conditions is examined. The oxides formed on Alloy 600 (WF675) between 350 Celsius and 500 Celsius in low pressure hydrogenated steam (with a ratio of oxygen at the Ni/NiO to oxygen in the system of 20) have been characterised using analytical electron microscopy (AEM) and compared to oxide that formed in a high pressure water in a autoclave at 350 Celsius with 30 cc/kg of hydrogen. Preferential oxidation of grain boundaries and bulk internal oxidation were observed on samples prepared by oxide polishing suspension (OPS). Conversely, samples mechanically ground to 600 grit produced a continuous, protective oxide film which suppressed the preferential and internal oxidation. The surface preparation changed the form of the oxides in both steam and autoclave tests. The preferential oxidation rate has been determined to be K_{oxide} = Aexp{-Q/RT}with A = 2.27×10^(−3) m^(2)s^(−1) and Q = 221 kJ.mol^(−1) (activation energy) for WF675 and A = 5.04 × 10^(−7) m^(2)s^(−1) and Q = 171 kJ.mol^(−1) for 15% cold worked WF675. These values are consistent with the activation energy of primary water stress corrosion cracking (PWSCC) initiation. Bulk oxygen diffusivities were calculated from the internal oxidation after 500 h exposures. At 500 Celsius the oxygen diffusivity was determined to be 1.79×10^(−20) m^(2)s^(−1) for WF675 and 1.21×10^(−20) m^(2)s^(−1) for 15% cold worked WF675, the oxygen diffusivity at 400 Celsius in 15% cold worked WF675 was calculated to be 1.49×10^(−22) m^(2)s^(−1).The Cr-depletion associated with preferential oxidation has been assessed by AEM. The Cr-depletion was asymmetric and it could not be accounted for by local variations in the diffusion rate. Chemically induced grain boundary migration is suggested as a possible explanation. Constant load SCC tests conducted in hydrogenated steam at 400 Celsius have shown a similar trend to the classical dependency of PWSCC as a function of potential. The SCC samples were also prepared with two surface finishes, OPS and 600 grit. In all SCC tests, significantly more cracking was observed on the OPS surface and all failures initiated from this surface.
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Chmyrov, Andriy. "Photo-induced dark states influorescence spectroscopy – investigations & applications." Doctoral thesis, KTH, Experimentell biomolekylär fysik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12372.
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This thesis focuses on investigations of transient dark states of fluorescentmolecules using spectroscopic techniques. The main purpose is to show andconvince the reader that transient dark states are not always a nuisance, butalso represent an additional source of information. Several studies with fluorescencecorrelation spectroscopy were performed, all related to non-fluorescentstates such as triplet state or isomerized states.Photobleaching is one of the main problems in virtually all of the fluorescencetechniques. In this thesis, mechanisms that retard photobleaching arecharacterized. Several compounds, antioxidants and triplet state quenchers,which decrease photobleaching, are studied, and guidelines for achieving optimalfluorescence brightness using these compounds are presented.Triplet state quenching by several compounds was studied. Detailed investigationsof the fluorescence quencher potassium iodide demonstratedthat for some of fluorophores, except of quenching, there is fluorescence enhancementmechanism present. In agreement with the first publication inthis thesis, antioxidative properties were found to play an important role inthe fluorescence enhancement. Quenching of the triplet state is proposedas a tool for monitoring diffusion mediated reactions over a wide range offrequencies.Specially designed fluorophores combining high triplet yields with reasonablefluorescence brightness and photostability were characterized forpossible applications in novel super-resolution imaging techniques based onfluorescence photoswitching. Except of benefits for imaging techniques, photoinducedswitching to non-fluorescent states could be used for monitoringmolecular diffusion, which was also demonstrated in this thesis.Studies of the triplet state kinetics of fluorophores close to dielectric interfaceswere performed using fluorescence spectroscopy. The analysis of thetriplet state kinetic can provide information about the local microenvironmentand electrostatic interactions near dielectric interfaces.QC 20100414
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Grandini, Carlos Roberto. "Difusão e relaxação anelástica devido ao hidrogênio em solução sólida em ligas de Nb-Ti e Nb-Zr." Universidade de São Paulo, 1993. http://www.teses.usp.br/teses/disponiveis/54/54131/tde-26032009-103212/.
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Foi estudado o efeito do hidrogênio dissolvido intersticialmente em ligas de nióbio-titânio e nióbio-zircônio. Nas ligas de nióbio-titânio, foram efetuadas medidas de decremento logarítmico por intermédio de medidas de atrito interno em um pêndulo de torção oscilando com freqüência em torno de 4.0 Hz, para amostras puras e dopadas com hidrogênio. Os resultados mostraram a interação do hidrogênio com a matriz metálica através do Efeito Gorsky. Nas ligas de nióbio-zircônio, foram efetuadas medidas de atenuação ultra-sônica para freqüências de 10 e 30 MHz, em amostras puras, contendo hidrogênio e contendo oxigênio e hidrogênio. Os resultados mostraram a interação do hidrogênio com a matriz metálica através de um processo de reorientação induzida por tensão de átomos de hidrogênio localizados em sítios intersticiais tetraedrais em torno de átomos de oxigênio congelados em sítios intersticiais octaedrais, próximos de átomos de nióbio da matriz metálica.We study the effect of hydrogen dissolved interstitially in niobium-titanium and niobium-zirconium alloys. In the niobimn-titanium alloys, the logarithmic decrement was studied by internal friction measurements in a torsion pendulum with frequency about 4.0 Hz, on pure and hydrogen doped samples. Our results showed the interaction of hydrogen with the metallic matrix by the Gorsky effect. In the niobium-zirconium alloys, the ultrasonic attenuation was measured by the echo-pulse method with frequencies of 10 and 30 MHz, for pure, doped with hydrogen and doped with oxygen and hydrogen. The results have shown the interaction of hydrogen with the metallic matrix by a stress induced ordering of hydrogen atoms localized at tetrahedral sites around frozen oxygen atoms localized in the octahedral sites near the niobium atoms in the metallic matrix.
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Mokhtari, Zakia. "Étude de la dynamique interne du noyau d'une cellule vivante, par des expériences de diffusion dynamique de la lumière." Thesis, Lyon, École normale supérieure, 2015. http://www.theses.fr/2015ENSL0990/document.
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La connaissance de la dynamique interne du noyau d’une cellule vivante semble essentielle pour la compréhension du fonctionnement des cellules eucaryotes. Ainsi, depuis plus d'une quinzaine d’année, de nombreuses études ont été menées pour sonder cette dynamique. Le projet de recherche de cette thèse s’est inscrit dans cette problématique. Nous avons monté une expérience originale de diffusion dynamique de la lumière pour sonder la dynamique interne du noyau d’une cellule. Le principe est simple, nous faisons passer un faisceau laser à travers le noyau d’une cellule et nous détectons les variations temporelles de l’intensité lumineuse diffusée. Les signaux obtenus sont complexes, non stationnaires, avec plusieurs échelles de temps. Une partie importante du travail de thèse a consisté à trouver une manière fiable de les analyser pour en extraire la dynamique interne du noyau ; nous arrivons à sonder cette dynamique sur quasiment 7 ordres de grandeurs (10-5 – 40 s). En utilisant ce montage et les techniques de traitement du signal qu’on a développé, nous avons étudié la dynamique interne du noyau de cellules issues de deux lignées humaines (SHEP et HeLa) au cours de leur cycle cellulaire. Nous observons des différences notables entre les phases G1, S et G2 et nous pouvons voir les gammes de temps affectées par le changement de phase du cycle cellulaire. Ensuite, nous avons étudié la dynamique du noyau de cellules (SHEP et HeLa), en phase G1, en présence d’une drogue cytobloquante dans le milieu de culture. Nous avons aussi étudié l’effet de la température. Pour des cellules en phase G1, nous avons baissé la température de 37°C à 25° C. Nous avons pu suivre l’évolution de la dynamique lors du refroidissement et à 25°C. Enfin, nous avons étudié la dynamique du noyau des cellules SHEP et HELA fixéesThe knowledge of the internal dynamics of a living cell nucleus appears essential for the comprehension of the activity of eukaryotic cells. Therefore, for the last fifteen years, many studies have been conducted to probe this dynamics. The research project of this thesis is a part of this issue. We set up an original experience of dynamic light scattering to probe the internal dynamics of a cell nucleus. The principle is simple, we pass a laser beam through the nucleus of a cell and we detect the temporal variations of the scattered light intensity. The signals obtained are complex, non-stationary, with different time scales. An important part of the thesis was to find a reliable way to analyze them to extract the internal dynamic of the nucleus; we can probe this dynamic on almost 7 orders of magnitude (10-5 – 40 s). By using this experience and the signal procession techniques that we developed, we studied the internal dynamics of the nucleus of two human cell lines (HELA and SHEP) in their cell cycle. We observe significant differences between the G1 phase, S and G2 and we can see the time ranges affected by phase change of the cell cycle. Next, we have studied nucleus dynamics of cells (SHEP and HELA), in the G phase, in the presence of cytobloquante drug in the culture environment. We also studied the effect of temperature. For cell in G1 phase, we lowered the temperature of 37°C to 25° C. We were able to follow the changing dynamics during the cooling and at 25°C. Finally, we have studied nucleus dynamics of fixed SHEP and HELA cells
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Demange, Jérémie. "Schémas numériques d'advection et de propagation d'ondes de gravité dans les modèles de circulation océanique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENM096/document.
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Les modèles numériques d'océans régionaux tridimensionnels sont basés sur la résolution des équations primitives et utilisent pour la plupart des méthodes de résolution eulérienne de type différences finies sur des grilles décalées. Ces modèles doivent représenter fidèlement les transports et transferts d'énergie. L'amélioration de ces modèles numériques exige donc (i) l'identification des processus prépondérants, notamment en terme de dissipation, dans ces transferts et (ii) la construction de méthodes numériques respectant un certain nombre d'équilibres. La première partie du travail se concentre sur la propagation des ondes externes et internes de gravité. Nous nous intéresserons en premier lieu à la stabilité de la séparation en mode rapide (barotrope) et lents (baroclines) et montrons qu'elle peut être ameliorée en levant certaines hypothèses traditionnellement effectuées. Dans un second temps, nous étudions l'impact de la discrétisation (ordre des schémas, grilles décalées ou non) sur la propagation des ondes internes de gravité provenant du couplage vitesse pression. Une décomposition en modes verticaux nous permet également de proposer un schéma espace temps très efficace. La seconde partie étudie en détail les schémas d'advection de quantité de mouvement et de traceurs, tout particulièrement dans l'objectif d'une réduction de la diffusion diapycnale (diffusion dans les directions orthogonales aux couches de densité constante). Ce travail nous amène tout d'abord à porter notre attention sur les schémas d'advection verticaux souvent négligés au regard de la dimension horizontale. Les bonnes propriétés d'un schéma compact (et de ses variantes espace temps et monotones) sont mises en avant. Enfin nous analysons le comportement multidimensionnel de ces schémas d'advectionThree-dimensional regional ocean numerical models are based on solving the primitive equations and mostly use Eulerian finite differences methods of resolution on staggered grids. These models must accurately represent transports and energy transfers. Improving these numerical models therefore requires (i) the identification of predominant process, particularly in terms of dissipation in these transfers and (ii) the construction of numerical methods respecting a number of balances. The first part of the work focuses on the propagation of external and internal gravity waves. We focus primarily on the stability of the separation in fast mode (barotropic) and slow (baroclinic) and show that it can be improved by removing certain assumptions traditionally made. In a second step, we study the impact of the discretization (order of schemes, staggered grids or not) on the propagation of internal gravity waves coming from the coupling velocity pressure. A decomposition into vertical modes also allows us to offer a highly effective space-time scheme. The second part examines in detail the numerical advection schemes of momentum and tracers, especially with the aim of reducing the diapycnal diffusion (diffusion in the orthogonal direction of constant density layers). This work leads us first to focus our attention on the vertical advection schemes often overlooked in front of the horizontal dimension. The good properties of a compact schema (and its space-time and monotonous variants ) are highlighted. Finally we analyze the multidimensional behavior of these advection schemes
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Prillieux, Aurélien. "Hydrogen and water vapour effects on oxygen solubility and diffusivity in high temperature Fe-Ni alloys." Phd thesis, Toulouse, INPT, 2017. http://oatao.univ-toulouse.fr/18676/1/PRILLIEUX_Aurelien.pdf.
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It is a worldwide priority to reduce emissions of greenhouse gases such as CO2. One solution for reducing these emissions is to improve the efficiency of energy production units by increasing their operating temperature. However, in order to increase operating temperature, new austenitic materials based on the Fe-Ni-Cr system have to be designed. In addition, these materials need to exhibit good protection against high temperature oxidation, which is achieved by the formation of a slow growing chromium oxide or alumina scale on the metal. However, to predict the formation of a protective scale, knowledge of the oxygen permeability, the product of oxygen solubility and diffusivity, in the base alloy is required. The objective of this study is to measure the permeability, solubility and diffusivity of oxygen in Fe- Ni alloys at temperatures above 1,000°C. In order to obtain the best results, the formation of an external oxide layer during the experiment has to be avoided. To achieve this, the oxygen partial pressure was fixed at the Fe/FeO equilibrium pressure in all experiments. In addition, two types of atmospheres were used: one dry and one wet, in order to investigate the effect of water vapour on oxygen permeability, solubility and diffusivity. The dry atmosphere was achieved using the Rhines Pack technique. The samples were oxidised in vacuum-sealed quartz capsules, which contained a mixture of powdered iron and wüstite. The humid atmosphere was obtained by using H2/H2O gas mixtures with the appropriate water vapour to hydrogen ratio to fix oxygen partial pressure at the Fe/FeO equilibrium. The maximum oxygen solubility was found in pure iron, and decreased continuously with nickel additions to the alloy. The dependence of solubility on alloy composition is non-ideal, and cannot be predicted from simple models. Moreover, the presence of water vapour in the atmosphere seems to increase the solubility by a factor of 2 in alloys with nickel content lower than 80 at.% at temperatures near 1,000°C. However, at 1,150°C the solubility of the oxygen is independent of the environment. The oxygen permeability was determined by measuring the internal oxidation kinetics of Fe-Ni-Cr alloy. These kinetics were evaluated by measuring the internal oxidation zone depth by optical microscopy, or by continuous and discontinuous thermogravimetry. Results showed that the oxygen permeability exhibits the same variation with alloy composition as the oxygen solubility, independent of the atmosphere. In particular, no significant effect of water vapour on oxygen permeability values was observed. In the present study, the oxygen diffusion coefficient was also determined using permeability, in addition to the independent measurement of the oxygen solubility carried out in the present study. For temperature above 1,000°C, the variation of oxygen diffusion coefficient with the alloy composition is similar in all environments tested, and a maximum is observed for alloys with a nickel content of 40 at.%. However, for a given nickel content up to 60 at.%, the presence of water vapour in the atmosphere decreases the value of the oxygen diffusion coefficient by a factor of 2-3 at 1,000°C. In addition, this difference between diffusion coefficients measured in a dry and wet atmosphere increases as the temperature decreases. Overall, it was found that the water vapour has no effect on the way in which oxygen permeability, solubility and diffusivity vary with the alloy composition. However, the presence of water vapour in the environment appears to increase the oxygen solubility and decrease the oxygen diffusivity in iron-rich alloys, the effect being more significant at low temperatures. These results suggest further research into interactions between O, H and metal vacancies, particularly for temperature around 1,000°C and below, as the latter defect is thought to change the diffusion and solubility properties of interstitial species.
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Vidon, Antoine. "Probing the proton structure through deep virtual Compton scattering at COMPASS, CERN." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS340/document.
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La diffusion Compton virtuelle (DVCS) est un processus idéal pour étudier la structure interne du proton. Cette réaction exclusive permet d’accéder aux distributions de partons généralisées (GPDs) qui encodent les corrélations entre impulsion longitudinale et position transverse des partons à l’intérieur du proton. Le DVCS consiste à sonder le proton au moyen d’un photon virtuel de grande virtualité pour produire dans l’état final un unique photon réel de grande énergie tout en laissant le proton intact.A COMPASS au CERN, où deux années de données ont été collectées en 2016 et 2017 afin de mesurer la section efficace du processus DVCS, le photon virtuel est issu de la diffusion d’un faisceau de μ⁺ ou de μ⁻ polarisé de 160 GeV sur une cible d’hydrogène liquide. Toutes les particules de la réaction sont détectées dans l’expérience : le muon incident est détecté dans le télescope du faisceau, le muon diffracté et le photon réel sont détectés à l’avant dans le spectromètre et les trois calorimètres tandis que le proton de recul est détecté dans un détecteur de temps de vol placé autour de la cible.Je présente dans cette thèse l’état de l’analyse du processus DVCS sur les données collectées à COMPASS en 2016. Après un rappel du contexte théorique et expérimental, je décris l’expérience COMPASS. Je détaille ensuite mon travail de calibration du détecteur de proton de recul et de détermination de la position exacte de la cible de 2 cm de diamètre et 2.5 m de longueur. J’étudie dans la partie suivante la sélection de différents canaux de physique permettant de contrôler de manière systématique la qualité des détecteurs : la diffusion profondément inélastique (DIS) qui implique le télescope du faisceau et le spectromètre, la production exclusive de ρ⁰ qui inclut aussi le détecteur de temps de vol ; puis je présente la première analyse de la production exclusive de photons uniques qui implique en plus les trois calorimètres. Dans une dernière partie j’évoque les étapes nécessaires à la détermination de la section efficace du DVCS à partir de cette sélection, et je présente les premiers résultats issus de la simulation associéeVirtual Compton Scattering (DVCS) is an ideal process to study the internal structure of proton. This exclusive reaction provides access to generalised parton distributions (GPDs), which encode the correlations between longitudinal momentum and transverse position of partons inside the proton. DVCS consists in probing a proton with a virtual photon of high virtuality, in order to produce a single high energy real photon while leaving the proton intact in the final state.At COMPASS at CERN, where two years of data were collected in 2016 and 2017 to measure the DVCS cross section, the virtual photon is produced by scattering of a 160 GeV polarised μ⁺ or μ⁻ beam on a liquid hydrogen target. All particles are detected in the experiment: the incident muon is detected in the beam telescope, the diffracted muon and the real photon are detected in the forward spectrometer and the three calorimeters, while the recoil proton is detected in a time-of-flight detector positioned around the target.In this thesis I present the state of the analysis of the DVCS process on the data collected at COMPASS in 2016. After a reminder of the theoretical and experimental context, I describe the COMPASS experiment. I then detail my work on calibrating the recoil proton detector and determining the the exact position of the 2 cm diameter and 2.5 m long target. In the next section, I study the selection of different physics channels used to systematically control detector quality: Deep Inelastic Scattering (DIS) which involves the beam-telescope and spectrometer, exclusive ρ⁰ production which requires the addition of the time-of-flight detector and I follow with the first analysis of the exclusive single photon production which depends as well on the calorimetres quality. In a last part, I discuss the necessary steps needed to extract the DVCS cross-section out of this event selection, and present the first results associated to the Monte-Carlo simulation
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Sammoud, Rihab. "La diffusion de la stratégie au sein de l’entreprise : le cas du secteur bancaire." Thesis, Bordeaux 4, 2013. http://www.theses.fr/2013BOR40037.
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Ce travail de recherche porte sur la diffusion de la stratégie au sein de la banque. En effet, nous avons cherché à déterminer les étapes clés de la mise en évidence d’un processus de diffusion au sein de la banque, de déterminer les freins que peuvent rencontrés les banquiers lors de ce processus et d’évaluer leur impact sur la mise en oeuvre de la stratégie. En effet, la diffusion est le processus par lequel la stratégie est déclinée à travers toute la banque. Or, la compréhension et le soutien qu’accordent les membres de la banque dépendent, entre autres, du processus grâce auquel iles en prennent connaissance. C’est pourquoi, l’étude de la diffusion apparait pertinente. Ainsi, comprendre en profondeur le processus de la diffusion en termes de modalités et de contenus, nous a permis de détecter les éléments qui peuvent freiner le développement d’une représentation stratégique partagée et comprise par l’ensemble de la banque, de la stratégie envisagée, et influencer la qualité de la mise en oeuvre. Notre analyse s’est essentiellement basée sur une démarche abductive qui consiste à procéder par allers retours entre théorie et terrain et qui nous a permis de renforcer la validité de notre cadre conceptuel et de le compléter par les éléments de notre analyse des cas. Au final, nous avons détecté un ensemble de freins à la diffusion de la stratégie au sein de la banque qui sont essentiellement : la sur information, les capacités cognitives, la résistance au changement, la nature de la stratégie et le nombre des niveaux hiérarchiques et dont l’impact le plus marquant est le dérapage de la mise en oeuvreThis study deals with the communication of strategy within the banking sector. Our aim was to highlight the key steps involved in the communication process of banks, identify the challenges faced by bankers regarding that process and assess their role in the promotion of the strategy. Indeed, communication is the channel through which the strategy will be spread throughout the bank. Yet, the understanding and defense of the strategy by the employees, greatly depends on the way it has been conveyed to them; hence the importance and relevance of communication studies. Thus, a deep understanding of communication processes in terms of form as well as content, allowed us to pinpoint the elements that might prevent the development of a common strategic representation, understood by all, and affect the quality of its implementation. Our study is essentially based on an abductive approach that consists in going back and forth between theory and confirmation on the field. This method allowed us to strengthen the validity of our conceptual framework and supplement it with examples derived from our study case. In the end, we came up with the conclusion that many elements prevent the good circulation of strategy information within a bank. The main ones being: over-information, cognitive capacities, the resistance to change, the nature of the strategy as well as the number of hierarchical levels whose most striking consequence is the failure of implementation
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Nicolas, André. "Etude de l'Evolution Physico-Chimique du Substrat lors de l'Oxydation à Haute Température des Alliages Modèle Ni-Cr à Faible Teneur en Chrome et de l'Alliage Modèle Ni-16Cr-9Fe." Phd thesis, Ecole Nationale Supérieure des Mines de Saint-Etienne, 2012. http://tel.archives-ouvertes.fr/tel-00848591.
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Le travail réalisé au cours de cette thèse concerne l'analyse des conséquences de l'oxydation à 950°C des alliages base Ni sur la composition de l'alliage à proximité de l'interface alliage/oxyde. Deux catégories d'alliages ont été analysées : alliages à faible teneur en chrome conduisant à l'oxydation interne et l'alliage chromino-formeur Ni-16Cr-9Fe.Une description complète des mécanismes de l'oxydation interne du chrome est obtenue à partir du développement du modèle analytique de Wagner d'oxydation interne et du développement du modèle numérique de Feulvarch. Ces modèles décrivent l'évolution de l'oxydation interne jusqu'à la transition oxydation interne / oxydation externe à 11 %poids de chrome environ.L'analyse par la spectroscopie d'électrons Auger de l'alliage modèle Ni-16Cr-9Fe à 950°C oxydé pendant 10 heures a permis d'explorer la zone à proximité immédiate de l'interface alliage/oxyde et de déterminer la concentration en chrome à l'interface à 0,5%poids (i.e. dans 20 premiers nanomètres), ce qui est en accord avec le modèle analytique de Wagner d'oxydation en couche compacte. La description des profils de déchromisation et des profils de cavités pour plusieurs temps d'exposition allant de 100h à 5000h a permis de mettre en évidence une corrélation forte entre ces deux phénomènes (même constante parabolique). Pour ces durées d'oxydation les profils de déchromisation présentent un point d'inflexion ce qui se traduit par l'augmentation de la teneur en chrome à l'interface. Les résultats sont interprétés dans le cadre d'un nouveau modèle analytique avec l'hypothèse d'injection des lacunes produites par l'effet Kirkendall au point d'inflexion.
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Chen, Yong. "New Calibration Approaches in Solid Phase Microextraction for On-Site Analysis." Thesis, University of Waterloo, 2004. http://hdl.handle.net/10012/1285.
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Calibration methods for quantitative on-site sampling using solid phase microextraction (SPME) were developed based on diffusion mass transfer theory. This was investigated using adsorptive polydimethylsiloxane/divinylbenzene (PDMS/DVB) and Carboxen/polydimethylsiloxane (CAR/PDMS) SPME fiber coatings with volatile aromatic hydrocarbons (BTEX: benzene, toluene, ethylbenzene, and o-xylene) as test analytes. Parameters that affected the extraction process (sampling time, analyte concentration, water velocity, and temperature) were investigated. Very short sampling times (10-300 s) and sorbents with a strong affinity and large capacity were used to ensure a 'zero sink' effect calibrate process. It was found that mass uptake of analyte changed linearly with concentration. Increase of water velocity increased mass uptake, though the increase is not linear. Temperature did not affect mass uptake significantly under typical field sampling conditions. To further describe rapid SPME analysis of aqueous samples, a new model translated from heat transfer to a circular cylinder in cross flow was used. An empirical correlation to this model was used to predict the mass transfer coefficient. Findings indicated that the predicted mass uptake compared well with experimental mass uptake. The new model also predicted rapid air sampling accurately. To further integrate the sampling and analysis processes, especially for on-site or in-vivo investigations where the composition of the sample matrix is very complicated and/or agitation of the sample matrix is variable or unknown, a new approach for calibration was developed. This involved the loading internal standards onto the extraction fiber prior to the extraction step. During sampling, the standard partially desorbs into the sample matrix and the rate at which this process occurs, was for calibration. The kinetics of the absorption/desorption was investigated, and the isotropy of the two processes was demonstrated, thus validating this approach for calibration. A modified SPME device was used as a passive sampler to determine the time-weighted average (TWA) concentration of volatile organic compounds (VOCs) in air. The sampler collects the VOCs by the mechanism of molecular diffusion and sorption on to a coated fiber as collection medium. This process was shown to be described by Fick's first law of diffusion, whereby the amount of analyte accumulated over time enable measurement of the TWA concentration to which the sampler was exposed. TWA passive sampling with a SPME device was shown to be almost independent of face velocity, and to be more tolerant of high and low analyte concentrations and long and short sampling times, because of the ease with which the diffusional path length could be changed. Environmental conditions (temperature, pressure, relative humidity, and ozone) had little or no effect on sampling rate. When the SPME device was tested in the field and the results compared with those from National Institute of Occupational Health and Safety (NIOSH) method 1501 good agreement was obtained. To facilitate the use of SPME for field sampling, a new field sampler was designed and tested. The sampler was versatile and user-friendly. The SPME fiber can be positioned precisely inside the needle for TWA sampling, or exposed completely outside the needle for rapid sampling. The needle is protected within a shield at all times hereby eliminating the risk of operator injury and fiber damage. A replaceable Teflon cap is used to seal the needle to preserve sample integrity. Factors that affect the preservation of sample integrity (sorbent efficiency, temperature, and sealing materials) were studied. The use of a highly efficient sorbent is recommended as the first choice for the preservation of sample integrity. Teflon was a good material for sealing the fiber needle, had little memory effect, and could be used repeatedly. To address adsorption of high boiling point compounds on fiber needles, several kinds of deactivated needles were evaluated. RSC-2 blue fiber needles were the more effective. A preliminary field sampling investigation demonstrated the validity of the new SPME device for field applications.
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Lagorce-Tachon, Aurélie. "Propriétés mécaniques, structure interne et mécanismes de transfert de l'oxygène dans le liège." Thesis, Dijon, 2015. http://www.theses.fr/2015DIJOS073/document.
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Lors de la conservation des vins en bouteilles, des réactions d’oxydation prématurées peuvent se produire et les propriétés barrières à l’oxygène de l’obturateur en liège sont souvent mises en cause. À l’heure actuelle, aucune étude n’a permis de déterminer la structure interne du liège ou l’effet de l’hydratation sur ses propriétés mécaniques. Quant aux propriétés barrières à l’oxygène, l’étape limitante au transfert reste indéterminée ainsi que l’effet de la compression et le rôle de l’interface verre/liège. L’étude de la structure interne du liège par imagerie a permis de visualiser la macroporosité du matériau et de conclure que pour les qualités de liège étudiées, les lenticelles ne sont pas interconnectées. La caractérisation des propriétés mécaniques du liège a montré que le module de Young n’était pas affecté pour une humidité relative < 50 %. En milieu plus humide, ce dernier diminue à cause de la formation de clusters de molécules d’eau entre les chaines de polymères constituants les parois cellulaires. En comparant le comportement du liège brut avec celui d’autres obturateurs, un effet de la taille des particules de liège et du ratio liège/additifs utilisés dans ces obturateurs, a également été mis en évidence. Au regard du mécanisme de transfert de gaz, les mécanismes en jeu et en particulier l’étape limitante ont été clairement déterminés : il s’agit de la diffusion au travers des parois cellulaires selon la loi de Fick. L’effet de la compression du bouchon ne modifie pas significativement le transfert d’oxygène tandis que le rôle de l’interface verre/liège semble gouverner les transferts de gaz de l’extérieur vers l’intérieur de la bouteilleDuring the post bottling aging, premature oxidation reactions could occur and the oxygen barrier properties of the stopper are often pointed out. Nowadays, the internal structure of this material or the effect of hydration on its mechanical properties are still undetermined. Moreover, regarding the barrier properties, the limiting step of the oxygen transfer was not yet fully understood as well as the effect of compression or the role of the glass/cork interface in a bottleneck. The study of the internal structure of cork stopper allowed us to visualize the macroporosity of the material and conclude that there is no interconnectivity between lenticels, for the two qualities studied. The effect of hydration on the mechanical properties of cork was also investigated. The results shown that the rigidity of the material was not significantly affected for relative humidity < 50 %. Above this hydration level, the Young’s moduli decrease due to clusters formation of water molecules. Comparing the natural cork behavior to other stoppers, an effect of the particle size and the ratio cork/additives used in these stoppers was also highlighted. Regarding the transport mechanism of gas through cork, the limiting step was clearly determined: it’s the diffusion through the cell wall according to a Fickian mechanism. The compression of the stopper does not have a significant impact on the effective diffusion coefficient of oxygen. However, the role of the glass/cork interface is really important and seems to govern the gas transfer from the surrounding atmosphere into the bottle
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Dewalle, Pascale Hervé Philippe. "Caractérisation des aérosols émis par interaction laser-matière dans le cadre d'expériences de décapage de peintures par laser." S. l. : S. n, 2009. http://bdr.u-paris10.fr/theses/internet/2009PA100026.pdf.
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Desnault, Camille. "Mesure de la section efficace d'électroproduction de photons sur le neutron à Jefferson Lab en vue de la séparation du terme de diffusion Compton profondément virtuelle." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112163/document.
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La section efficace d'électroproduction de photons sur le nucléon est proportionnelle aux amplitudes au carré de diffusion Compton profondément virtuelle (DVCS) et du Bethe-Heitler ainsi qu'un terme d'interférence de ces deux processus. Sa mesure sur le neutron fut réalisée dans le cadre de l'expérience E08-025 qui s'est déroulée en 2010 dans le Hall A à Jefferson Lab (USA). Par une forte sensibilité au terme d'interférence, elle aura permis l'extraction de trois observables dépendantes des Distributions Généralisées de Partons (GPDs), ainsi que la perspective de séparer par une méthode Rosenbluth le terme |DVCS|².Les GPDs sont des fonctions de structure qui nous permettent de comprendre la structure interne des nucléons en terme de corrélation entre les distributions en position transverse et en impulsion longitudinale des quarks au sein du nucléon. Plus qu'un moyen d'accéder à une image tri-dimensionnelle de la composition élémentaire du nucléon, la détermination des GPDs du neutron permettrait par la règle de somme de Ji l'accès au moment angulaire des quarks dans le nucléon, la pièce manquante à la compréhension du mystère lié au spin du nucléon.Cette thèse aborde le contexte théorique de la mesure de la section efficace d'électroproduction de photons sur le neutron, puis une description de la configuration expérimentale utilisée pour sa réalisation. Elle expose la sélection des données d'intérêt pour cette mesure et présente les résultats obtenus par une méthode d'ajustement des données à une simulation Monte Carlo dont la démarche est expliquée en détails. Pour finir, une étude systématique des résultats achève ce manuscritThe photon electroproduction cross section off the nucleon is proportional to the deeply virtual Compton scattering (DVCS) and Bethe-Heitler amplitudes squared together with an interference term between these two processes. Its measurement on the neutron has been performed in the framework of the E08-025 experiment which took place in 2010 in Hall A at Jefferson Lab (USA). Thanks to a high sensibility to the interference term, it made possible the extraction of three Generalized Parton Distributions (GPDs) dependent observables, as well as the prospect to extract the |DVCS|² term through a Rosenbluth separation.The GPDs are structure functions which allow to understand the internal structure of nucleons in term of the correlation between transverse spatial and longitudinal momentum distributions of quarks inside the nucleon. More than a way to access a three-dimensional picture of the elementary arrangement of the nucleon, the measurement of GPDs on the neutron would give access by the Ji's sum rule to the angular momentum of quarks in the nucleon, the missing piece for the understanding of the nucleon spin puzzle.This thesis outlines the theoretical context of the measurement of the photon electroproduction cross section off the neutron, and the experimental setup used for its achievement. It describes the selection of the experimental data of interest for this measurement and presents the results obtained from a fitting method of data to a Monte Carlo simulation, which is explained in detail. Finally, a systematic study of the results completes this manuscript
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Rochdi, Mounir. "Utilisation des agents conversationnels pour la diffusion de l'information." Aix-Marseille 3, 2007. http://www.theses.fr/2007AIX30001.
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L’utilisation des multiples robots disponibles sur le Web constitue aujourd’hui une étape incontournable dans la recherche d’information sur Internet. Plusieurs de ces robots permettent d’identifier, plus ou moins rapidement, les pages susceptibles de répondre à un besoin précis. Mais les possibilités de recherche n’empêche pas d’être noyé sous le volume des réponses et d’être déçu par l’impossibilité dans certains cas, de surveiller l’évolution d’une recherche. Des outrils, plus ou moins sophistiques sont apparus pour aider les processus de veille. En complément de l’interrogation simultanée de divers robots et annuaires, ces outils permettent en effet d’éliminer les doublons de vérifier la validité des liens, de télécharger les résultats de surveiller l’apparition de nouveaux documents sur un sujet ou encore d’aspirer un site tout en surveillant ses mises à jour. Dans ce cadre, nous avons développé un assistant virtuel permettant de répondre aux questions posés par les internautes. Le travail présente l’utilisation et le développement de Chatterbot dans le cadre d’une société informatique, la Société CybionThe use of the multiple robots available on the Web constitutes today a stage impossible to circumvent in the search for information on Internet. Several of these robots make it possible to identify, more or less quickly, the pages likely to meet a definite need. But the possibilities of research does not prevent from being drowned under the volume of the answers and to be disappointed by impossibility in certain cases, to supervise the evolution of a research. These tools, more or less sophisticated appeared to help the processes technology watch. In complement of the simultaneous interrogation of various robots and directories, these tools indeed make it possible to eliminate the doubled blooms to check the validity of the bonds, to download the results monitoring the appearance of new documents on a subject or aspiring a site while monitoring its updates. Within this framework, we developed a virtual assistant allowing to answer the questions posed by the Net surfers. Work presents the use and the development of Chatterbot within the framework of a data-processing of the Cybion Company
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Ashley, Nancy Winniford. "Diffusion of network information retrieval in academia." Diss., The University of Arizona, 1995. http://hdl.handle.net/10150/187072.
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NIR, network information retrieval, is the act of finding and retrieving information on interconnected computer networks. The research investigated the extent to which NIR awareness and use has diffused through a broad research population, and why and how academics become aware of and use NIR. Everett Rogers' diffusion of innovation theory was adapted to guide the investigation. A survey of 888 faculty members at the University of Arizona with Internet-accessible computer accounts resulted in a 32% return of surveys. Respondents from the various colleges at the university use between 20% and 39% of available NIR technologies, suggesting that NIR is in an early stage of diffusion in all colleges. Twenty-one one hour open-ended interviews were conducted with faculty from a variety of disciplines. Analysis of coded interview comments was used to test the usefulness of Rogers' theory in describing the diffusion of NIR. Predictions that mass media communication channels which go outside the local community will be more likely to result in awareness and use of NIR were not supported. Predictions that use of NIR would be associated with the perception that NIR (1) is compatible with needs and social norms, and (2) has relative advantage over previous practice, were supported. The predictions that use would be associated with perceptions of (1) compatibility with previous conditions, (2) low NIR complexity, and (3) trialability of NIR, were not supported. The explanatory power of the diffusion of innovation theory is improved for diffusion of NIR if NIR technologies are not studied in a vacuum. Rather, NIR technologies need to be studied in association with particular types of information resources (i.e. general interest and research-related resources) and particular types of communities (i.e. research communities). The study suggests that before NIR will diffuse in research communities, academics will need to agree that NIR dissemination of information will be rewarded in the promotion and tenure process. Such redefinition of social norms will help to create within research areas a critical mass of NIR users, and thus contribute to the diffusion of NIR.
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Djama, Ismail Krief Francine Ahmed Toufik. "Adaptations inter-couches pour la diffusion des services vidéo sans fil." S. l. : Bordeaux 1, 2008. http://ori-oai.u-bordeaux1.fr/pdf/2008/DJAMA_ISMAIL_2008.pdf.
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