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1
Smith, Paul James. "Palladium catalysed Suzuki cross-coupling reactions in ambient temperature ionic liquids." Thesis, Imperial College London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.405785.
Повний текст джерела
2
Ponton, Lisa M. "Coupling Temperature Control with Electrochemically Modulated Liquid Chromatography Fundamental Aspects and Applications." Washington, D.C. : Oak Ridge, Tenn. : United States. Dept. of Energy. Office of Science ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/835378-qpyPNX/webviewable/.
Повний текст джерелаАнотація:
19 Dec 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "IS-T 1944" Lisa M. Ponton. 12/19/2004. Report is also available in paper and microfiche from NTIS.
3
Henrichs, Leonard Frederic. "Magnetoelectric coupling in single-phase multiferroics at room temperature via scanning probe microscopy." Thesis, University of Leeds, 2015. http://etheses.whiterose.ac.uk/11905/.
Повний текст джерелаАнотація:
In ceramic samples of the material, (BiFe1-xCoxO3)0.4-(Bi1/2K1/2TiO3)0.6 (BFCBKT), a new kind of nano-sized region, so called multiferroic clusters (MFC) were found at room-temperature. These exhibit the largest reported magnetoelectric (ME) coupling coefficient, α ≈ 1.0 x 10-5 s/m (corresponding to a Voltage coefficient dE/dH ≈ 1300 V/(cm Oe)) for a single phase multiferroic so far, to the best of the author’s knowledge. Furthermore, they are ferroelectric and ferrimagnetic at the same time, which has not yet been observed directly in one material. Using a broad range of experimental techniques, formation of the MFC has been understood in terms of the nonergodic relaxor properties and ferrimagnetism in inherent Bi(Fe,Co)O3 rich regions. Furthermore, the presence of magnetic nanoregions (MNR) was confirmed and their formation and role in ME coupling are discussed. Solid solutions of the system (PbZr0.52Ti0.48O3)1-x-(PbFe2/3W1/3O3)x (PZTPFW) were prepared which, however, did not show ME effects. Nevertheless, analogies to BFC-BKT concerning occurrence of characteristic magnetic phases were established. Since piezoresponse force microscopy (PFM) played an important role in this study, the method was subject to detailed investigations concerning e.g. the signal stability. Among others, it was found that it is highly beneficial to use diamond coated tips in PFM. In addition, a useful and easily applicable technique for distinguishable marking of micro-sized areas has been developed. It is expected that especially the findings on BFC-BKT will have wider implications, as they enable an entirely new perspective for such relaxortype ferrimagnetic multiferroics, which were barely considered in research so far. The relaxor properties are expected to play an important role in the strong ME coupling. Since the MFC are well-separated and offer large ME coupling, they are suitable to serve as bits in an electrically controlled magnetic nanodot storage device (MERAM). Various possibilities, the for realization of such a device are discussed.
4
Walker, Nan Delene. "Sea surface temperature-rainfall relationships and associated ocean-atmosphere coupling mechanisms in the southern African region." Doctoral thesis, University of Cape Town, 1989. http://catalog.hathitrust.org/api/volumes/oclc/32830668.html.
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Newhouse-Illige, T., Y. H. Xu, Y. H. Liu, S. Huang, H. Kato, C. Bi, M. Xu, B. J. LeRoy, and W. G. Wang. "Temperature dependence of interlayer coupling in perpendicular magnetic tunnel junctions with GdO X barriers." AMER INST PHYSICS, 2018. http://hdl.handle.net/10150/627087.
Повний текст джерелаАнотація:
Perpendicular magnetic tunnel junctions with GdOX tunneling barriers have shown a unique voltage controllable interlayer magnetic coupling effect. Here, we investigate the quality of the GdOX barrier and the coupling mechanism in these junctions by examining the temperature dependence of the tunneling magnetoresistance and the interlayer coupling from room temperature down to 11 K. The barrier is shown to be of good quality with the spin independent conductance only contributing a small portion, 14%, to the total room temperature conductance, similar to AlOX and MgO barriers. The interlayer coupling, however, shows an anomalously strong temperature dependence including sign changes below 80 K. This non-trivial temperature dependence is not described by previous models of interlayer coupling and may be due to the large induced magnetic moment of the Gd ions in the barrier. Published by AIP Publishing.
6
Fang, Zhou. "Current-induced torques in ferromagnets at room temperature." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/268099.
Повний текст джерелаАнотація:
This thesis uses ferromagnetic resonance to explore the current-induced torques (CITs) in two different systems, namely YIG/heavy metal bilayers and bulk NiMnSb, at room temperature. We apply a microwave current to the sample while sweeping the external magnetic field, and measure the longitudinal DC voltage. From a symmetry analysis of the ferromagnetic resonance lineshape, the amplitudes and directions of the CITs parameterised by an effective magnetic field are accurately estimated. In Chapter 4, YIG samples of different thickness, capped by either Pt or Ta, are studied. The resonance is driven by both spin-transfer torque and Oersted field, and the DC voltage is attributed to both spin rectification and spin pumping. The CITs can be well analysed from the lineshape of the voltage and its dependence on YIG thickness, from which we deduce that the Oersted field dominates over the spin-transfer torque in driving magnetization dynamics. In Chapter 5, we characterise the CITs in bulk NiMnSb induced by the relativistic spin-orbit coupling effect. Both field-like and antidamping-like spin-orbit torques are observed and analysed in detail. At the end of this chapter, we study the spin-wave resonance driven by the CITs, from which the exchange stiffness of NiMnSb is determined. In Chapter 6, we extrapolate a new form of magnetoresistance in NiMnSb: unidirectional spin-orbit magnetoresistance (USOMR). USOMR scales linearly with the current and has opposite sign when the magnetization is reversed. Similar to the giant magnetoresistance in magnetic multilayers, USOMR can be used to distinguish between two opposite magnetization directions directly in the bulk of the ferromagnet.
7
Anderson, Nolan Alan. "Coupling RELAP5-3D and Fluent to analyze a Very High Temperature Reactor (VHTR) outlet plenum." Texas A&M University, 2006. http://hdl.handle.net/1969.1/4160.
Повний текст джерелаАнотація:
The Very High Temperature Reactor (VHTR) system behavior should be
predicted during normal operating conditions and during transient conditions. To predict
the VHTR system behavior there is an urgent need for development, testing and
validation of design tools to demonstrate the feasibility of the design concepts and guide
the improvement of the plant components. One of the identified design issues for the
gas-cooled reactor is the thermal mixing of the coolant exiting the core into the outlet
plenum. Incomplete thermal mixing may give rise to thermal stresses in the downstream
components. This analysis was performed by coupling a RELAP5-3Dé VHTR model to
a Fluent outlet plenum model. The RELAP5 VHTR model outlet conditions provide the
inlet boundary conditions to the Fluent outlet plenum model. By coupling the two codes
in this manner, the important three-dimensional flow effects in the outlet plenum are
well modeled without having to model the entire reactor with a computationally
expensive code such as Fluent. The two codes were successfully coupled. The values of
pressure, mass flow rate and temperature across the coupled boundary showed only
slight differences. The coupling tool used in this analysis can be applied to many different cases requiring detailed three-dimensional modeling in a small portion of the
domain.
8
Jason, Johan. "Fibre-Optic Displacement and Temperature Sensing Using Coupling Based Intensity Modulation and Polarisation Modulation Techniques." Doctoral thesis, Mittuniversitetet, Avdelningen för elektronikkonstruktion, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-18964.
Повний текст джерелаАнотація:
Optical fibre sensors are employed in the measurements of a number of different physical properties or for event detection in safety and security systems. In those environments which suffer from electromagnetic disturbance, in harsh environments where electronics cannot survive and in applications in favour of distributed detection, fibre-optic sensors have found natural areas of use. In some cases they have replaced conventional electronic sensors due to better performance and long-term reliability, but in others they have had less success mainly due to the higher costs which are often involved in fibre-optic sensor systems. Intensity modulated fibre-optic sensors normally require only low-cost monitoring systems principally based on light emitting diodes and photodiodes. The sensor principle itself is very elemental when based on coupling between fibres, and coupling based intensity modulated sensors have been utilised over a long period of time, mainly within displacement and vibration sensing. For distributed sensing based on intensity modulation, optical time domain reflectometer (OTDR) systems with customised sensor cables have been used in the detection of heat, water leakage and hydrocarbon fluid spills. In this thesis, new concepts for intensity modulated fibre-optic sensors based on coupling between fibres are presented, analysed, simulated and experimentally verified. From a low-cost and standard component perspective, alternative designs are proposed and analysed using modulation function simulations and measurements, in order to find an improved performance. Further, the development and installation of a temperature sensor system for industrial process monitoring is presented, involving aspects with regards to design, calibration, multiplexing and fibre network installation. The OTDR is applied as an efficient technique for multiplexing several coupling based sensors, and sensor network installation with blown fibre in microducts is proposed as a flexible and cost-efficient alternative to traditional cabling. As a solution to alignment issues in coupling based sensors, a new displacement sensor configuration based on a fibre to a multicore fibre coupling and an image sensor readout system is proposed. With this concept a high-performance sensor setup with relaxed alignment demands and a large measurement range is realised. The sensor system performance is analysed theoretically with complete system simulations, and an experimental setup is made based on standard fibre and image acquisition components. Simulations of possible error contributions show that the experimental performance limitation is mainly related to differences between the modelled and the real coupled power distribution. An improved power model is suggested and evaluated experimentally, showing that the experimental performance can be improved down towards the theoretical limit of 1 μm. The potential of using filled side-hole fibres and polarisation analysis for point and distributed detection of temperature limits is investigated as a complement to existing fibre-optic heat detection systems. The behaviour and change in birefringence at the liquid/solid phase transition temperature for the filler substance is shown and experimentally determined for side-hole fibres filled with water solutions and a metal alloy, and the results are supported by simulations. A point sensor for on/off temperature detection based on this principle is suggested. Further the principles of distributed detection by measurements of the change in beat length are demonstrated using polarisation OTDR (POTDR) techniques. It is shown that high-resolution techniques are required for the fibres studied, and side-hole fibres designed with lower birefringence are suggested for future studies in relation to the distributed application.Fiberoptiska sensorer används för mätning av ett antal olika fysikaliska parametrar eller för händelsedetektering i larm- och säkerhetssystem. I miljöer med elektromagnetiska störningar, i andra besvärliga miljöer där elektronik inte fungerar samt i tillämpningar där distribuerade sensorer är att föredra, har fiberoptiska lösningar funnit naturliga applikationer. I vissa fall har de ersatt konventionella elektroniska sensorer på grund av bättre prestanda och tillförlitlighet, medan de i andra sammanhang har haft mindre framgång huvudsakligen på grund av den i många fall högre kostnaden för fiberoptiska sensorsystem. Intensitetsmodulerade fiberoptiska sensorer kräver normalt endast billiga utläsningssystem huvudsakligen baserade på lysdioder och fotodioder. Principen för sådana sensorer baserade på koppling mellan fibrer är mycket enkel, och denna typ av sensorer har haft tillämpningar under en lång tid, främst inom mätning av positionsförändring och vibrationer. För distribuerade intensitetsmodulerade sensorer har system baserade på optisk tidsdomän-reflektometer (OTDR) och skräddarsydda sensorkablar funnit tillämpningar i detektion av värme/brand, vattenläckage och kolvätebaserade vätskor. I denna avhandling presenteras, simuleras, testas och utvärderas praktiskt några nya koncept för kopplingsbaserade intensitetsmodulerade fiberoptiska sensorer. Från ett lågkostnads- och standardkomponentperspektiv föreslås och analyseras alternativa lösningar för förbättrad prestanda. Utveckling och installation av en temperatursensor för en industriell tillämpning, innehållande aspekter på sensormultiplexering och nätverksbyggande, behandlas. OTDR-teknik används som en effektiv metod för multiplexering av flera kopplingsbaserade sensorer, och installation av sensornätverk genom användning av blåsfiberteknik och mikrodukter föreslås som ett flexibelt och kostnadseffektivt alternativ till traditionell kabelinstallation. Som en lösning på förekommande upplinjeringsproblem för kopplingsbaserade sensorer, föreslås en ny sensorkonfiguration baserad på koppling mellan en fiber och en multikärnefiber/fiberarray och med ett bildsensorsystem för detektering. Med detta koncept kan ett högpresterande, upplinjeringsfritt sensorsystem med ett stort mätområde åstadkommas. Sensorsystemets prestanda har analyserats teoretiskt med kompletta systemsimuleringar, och en experimentell uppställning baserad på standardfiber och en kamera av standardtyp har gjorts. Simuleringar av möjliga felbidrag visar att systemets experimentella prestanda främst begränsas av skillnader mellan den modellerade och den verkliga optiska effektfördelningen. En förbättrad modell för effektfördelningen föreslås och utvärderas experimentellt. Det visas att prestanda är möjlig att förbättra ner mot den teoretiska gräns på 1 μm som erhållits vid systemsimuleringar. Möjligheterna att använda fyllda hålfibrer och polarisationskänslig mätning för detektering av temperaturgränser studeras i syfte att komplettera befintliga fiberoptiska värmedetektorsystem. Förändringen i fiberns dubbelbrytning vid övergångstemperaturen mellan vätske- och fast fas för ämnet i hålen visas och bestäms experimentellt för hålfibrer fyllda med vattenlösningar respektive en metallegering, och resultaten understöds också av simuleringar. En punktsensor för temperaturdetektering baserad på denna princip föreslås. Vidare visas principerna för distribuerad detektering genom registrering av förändringen i dubbelbrytning med polarisations-OTDR (POTDR). Det visas att OTDR-teknik med hög spatial upplösning behövs för övervakning av de studerade fibrerna, och hålfibrer utformade med lägre dubbelbrytning föreslås för framtida studier av tillämpningen.
9
Tanabe, Mikio. "Longitudinal and transverse coupling of the beam temperature caused by the laser cooling of 24Mg[+]." 京都大学 (Kyoto University), 2008. http://hdl.handle.net/2433/136874.
Повний текст джерела
10
Hellgren, Mikael. "Pressure oscillations over Scandinavia during the last century and coupling with regional temperature and precipitation." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 1998. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-392448.
Повний текст джерелаАнотація:
Conclusions In this work we have used a multiple linear regression model, to see how different predictors are correlated to each other, and how they are correlated to temperature and precipitation in the southern part of Sweden. The correlation between the large and small indices vary over the year, but both cases show an increase in correlation during the winter. The MoVa index and the ViGö index are much better correlated than what the NAO and the KaUp indices are. One possible explanation for this can be the much shorter distace between the lines MoVa and ViGö in the latitudinal direction, compared to the distance in the longitudinal direction between NAO and KaUp. The correlation between the predictors and the predictands, temperature and precipitation, vary between different stations. The south-north predictors, NAO and KaUp, show different signs concerning the temperature in the summer. This is remarkable, but one should have in mind, that the correlation coefficient between the two is very low during the summer months. To recieve a good approximation concerning the precipitation amount by using this multiple regression model, it’s almost enough to use the mean pressure predictor, because the other predictors are very low or not even significant, except for some stations. The NAO predictor is only significant for a few months concerning precipitation. It should also be mentioned, that the model shows a lower amount of precipitation than what is observed when we are talking about great amounts of precipitation. Finally, this regression model is based on pressure differences or just the mean pressure. This means, that the model doesn’t take into account such phenomena as convective clouds, local rain or thunder storms, subsidence inversions, sea breeze effects, etc.
11
Zhang, Huaibao. "HIGH TEMPERATURE FLOW SOLVER FOR AEROTHERMODYNAMICS PROBLEMS." UKnowledge, 2015. https://uknowledge.uky.edu/me_etds/64.
Повний текст джерелаАнотація:
A weakly ionized hypersonic flow solver for the simulation of reentry flow is firstly developed at the University of Kentucky. This code is the fluid dynamics module of known as Kentucky Aerothermodynamics and Thermal Response System (KATS). The solver uses a second-order finite volume approach to solve the laminar Navier– Stokes equations, species mass conservation and energy balance equations for flow in chemical and thermal non-equilibrium state, and a fully implicit first-order backward Euler method for the time integration. The hypersonic flow solver is then extended to account for very low Mach number flow using the preconditioning and switch of the convective flux scheme to AUSM family. Additionally, a multi-species preconditioner is developed.
The following part of this work involves the coupling of a free flow and a porous medium flow. A new set of equation system for both free flows and porous media flows is constructed, which includes a Darcy–Brinkmann equation for momentum, mass conservation, and energy balance equation. The volume-average technique is used to evaluate the physical properties in the governing equations. Instead of imposing interface boundary conditions, this work aims to couple the free/porous problem through flux balance, therefore, flow behaviors at the interface are satisfied implicitly.
12
Jordaan, Haimi. "Thermal analysis of a feedwater heater tubesheet through coupling of a 1D network solver and CFD." Diss., University of Pretoria, 2019. http://hdl.handle.net/2263/79248.
Повний текст джерелаАнотація:
A feedwater heater is a typical component in power plants which increases the cycle efficiency. Over the last decade, renewable energies have significantly developed and been employed in the power grid. However, weather conditions are inconsistent and therefore produce variable power. Fossil fuel power stations are often required to supplement the variable renewable energies, which increased the rate of power cycling to an unforeseeable extent over the past decade. Power cycling results in changes in the flow rate, pressure, and temperature of a feedwater heater’s inlet flows. In a tubesheet-type feedwater heater, these transients induce cycling stress in the tubesheet and failures due to thermal fatigue occur. The header-type feedwater is currently employed in high pressure applications as it is more resistant to thermal fatigue compared to the tubesheet-type. However, the tubesheet-type is more cost effective to construct and maintain. It would be advantageous if the cyclic thermal stresses in the tubesheet can be better analysed and alleviated to support the use of the tubesheet-type.
A detailed transient temperature distribution of the tubesheet is required to understand the thermal fatigue. Normally, engineers opt towards a full CFD to obtain such results. However, the size and complexity of a feedwater heater is immense and cannot be simulated practically solely using CFD spatial elements. This study developed a multiscale approach that thermally couples 1D network elements, CFD spatial elements, and macroscopic heat transfer correlations to reduce the computational expense substantially. The combination of the various selected techniques and the specific application of this methodology is unique. This approach is capable of obtaining the detailed transient temperature distribution of the tubesheet in a reasonable time, as well as include the effects of the upstream and downstream components within the network model. The methodology was implemented using Flownex and Ansys Fluent for the 1D network and CFD solvers, respectively. The internal tube flow was modelled using 1D network elements, while the steam was modelled with CFD. Thermal discretisation, mapping, and convergence were considered to create a robust methodology not limited to feedwater heaters only. Additionally, a method was developed to analyse flow maldistribution in tube-bundles using the coupled 1D-3D approach. The implementation of the methodology consists of two parts, of which one is for development purposes, and the other serves as a demonstration. The development was done on a simple TEMA-FU heat exchanger which is representative of a feedwater heater. The methodology was tested by varying the primary fluid’s flow rates, changing the fluid media, and conducting transient simulations. The temperature distributions obtained were compared against a full CFD model and corresponded very well with errors less than 4%. A reduction in computational time of more than 40% was achieved but is highly dependent on the specific problem. Improvements to be made in future studies include the accuracy of the laminar case method and the stability of the flow maldistribution algorithm.
The methodology was demonstrated by applying it to an existing industrial feedwater heater. No plant data was available to use for input conditions and therefore were assumed. The steam in the DSH was modelled using 3D CFD elements and the tube flow with 1D network elements. The condensing zone’s heat transfer was approximated using an empirical correlation. A steady state case was simulated and the outlet temperatures corresponded well with the manufacturer’s data. The temperature distribution of the tubesheet and surrounding solids were obtained. Finally, assumed sinusoidal transient perturbations to the inlet conditions were imposed. It was evident that the thermal gradients of both sides of the tubesheet were misaligned which highlights the thermal lag and inertia that cause differential temperatures.
The 1D-CFD methodology was developed successfully with results that proved to correspond well, for a wide range of conditions, to full CFD. The methodology was applied and can be, in future work, validated with experimental results or extended by modelling upstream and downstream components in the network solver.Dissertation (MEng)--University of Pretoria, 2019.
Mechanical Engineering
MEng
Unrestricted
13
Evans, Donald M. "Properties of a new room temperature multiferroic - PZTFT - with emphasis on the coupling between the order parameters." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.673847.
Повний текст джерелаАнотація:
This work focuses on characterising the recently discovered room temperature multiferroic PZTFT, which has demonstrated some unusual properties. This investigation is done on both large scales (mm) the bulk ceramic - and small length scales (nm)within each grain that makes up the ceramic. The aim is to gain a detailed understanding of what properties the material has, Chapter 3: how the are connected, Chapter 4; how the respond to different stimuli - like electric and magnetic fields, Chapter 5. These properties are rationalised in terms of the Landau free energy expansion, which shown in Chapter 6, indicates the presence of a quadratic coupling term in this material.
14
Qin, Yueyue. "Climate Change Assessment in Columbia River Basin (CRB) Using Copula Based on Coupling of Temperature and Precipitation." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2312.
Повний текст джерелаАнотація:
The multi downscaled-scenario products allow us to better assess the uncertainty of the variations of precipitation and temperature in the current and future periods. Joint Probability distribution functions (PDFs), of both the climatic variables, might help better understand the interdependence of the two, and thus in-turn help in accessing the future with confidence. In the present study, we have used multi-modelled statistically downscaled ensemble of precipitation and temperature variables. The dataset used is multi-model ensemble of 10 Global Climate Models (GCMs) downscaled product from CMIP5 daily dataset, using the Bias Correction and Spatial Downscaling (BCSD) technique, generated at Portland State University. The multi-model ensemble PDFs of both precipitation and temperature is evaluated for summer (dry) and winter (wet) periods for 10 sub-basins across Columbia River Basin (CRB). Eventually, Copula is applied to establish the joint distribution of two variables on multi-model ensemble data. Results have indicated that the probabilistic distribution helps remove the limitations on marginal distributions of variables in question and helps in better prediction. The joint distribution is then used to estimate the change in trends of said variables in future, along with estimation of the probabilities of the given change. The joint distribution trends are varied, but certainly positive, for summer and winter time scales based on sub-basins. Dry season, generally, is indicating towards higher positive changes in precipitation than temperature (as compared to historical) across sub-basins with wet season inferring otherwise. Probabilities of changes in future, as estimated by the joint precipitation and temperature, also indicates varied degree and forms during dry season whereas the wet season is rather constant across all the sub-basins.
15
Fogliano, Francesco. "Ultrasensitive nanowire force sensors in extreme conditions : from dilution temperature to ultra-strong coupling in cavity nano-optomechanics." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAY070.
Повний текст джерелаАнотація:
Les progrès récents réalisés dans le domaine des systèmes nano-optomécaniques ont démontré leur potentiel pour détecter des forces extrêmement faibles et ouvrir de nouveaux champs d’étude en physique. Ce travail de thèse vise à étendre le champ d’application des mesures de force ultrasensibles basées sur la lecture optique des vibrations de nanofils suspendus à de nouveaux domaines : d’abord à très basse température, en démontrant la possibilité de les exploiter dans un cryostat à dilution, ensuite dans le domaine de la nano-optomécanique en cavité où leur extrême sensibilité permet d’atteindre le régime de couplage ultra-fort.Leur mise en œuvre dans un cryostat à dilution permet en effet de réduire leur bruit thermique tout en bénéficiant d’une augmentation de leur cohérence mécanique mais nécessite de réduire drastiquement les sources de bruits externes, d’origine électrique ou mécanique, tout en opérant à des puissances optiques extrêmement faibles afin de limiter le chauffage par absorption. Nous présentons les développements réalisés, qui nous ont permis d’observer un nanofil présentant une température de bruit de 32 mK grâce à des techniques de mesures fonctionnant en régime de comptage de photon, lorsque moins d’un photon est détecté par période mécanique. Nous étudions les propriétés mécaniques et thermique de ces sondes de force à très basses températures, qui ont permis d’atteindre une sensibilité record pour une sonde locale, de l’ordre de quelques dizaines de zN/Hz^1/2, ce qui est en principe suffisante pour détecteur l’interaction électron-électron à une distance de plus de 100 µm.Dans la seconde partie du manuscrit, on décrit une nouvelle expérience de nano-optomécanique en cavité fonctionnant à température ambiante. Elle consiste à insérer l’extrémité vibrante d’un nanofil suspendu dans une micro-cavité fibrée de grande finesse. La combinaison de son volume de mode très réduit, de la très grande sensibilité en force des nanofils et de l’interaction optomécanique gigantesque obtenue rend cette approche extrêmement intéressante pour la nano-optomécanique en cavité. En effet, on démontre qu’il est possible d’atteindre le régime de couplage ultrafort, dans lequel un seul photon intra-cavité est capable de déplacer le nano-résonateur de plus que ses fluctuations de point zéro. Ceci nécessite d’avoir une constante de couplage par photon g0 dépassant la fréquence mécanique du nanofil Wm. Après avoir décrit l’expérience, on étudie comment le nanofil permet d’imager le champ lumineux intra-cavité en cartographiant ses propriétés optiques en fonction de la position du nanofil de diamètre sub-longueur d’onde dans l’onde stationnaire. Cela permet de quantifier et de cartographier l’intensité et l’orientation de l’interaction optomécanique qui acquiert alors un caractère vectoriel. De plus nous avons étudié l’interaction en sens inverse, en cartographiant le champ de force intra-cavité ressenti par le nanofil en fonction de sa position dans le mode de cavité et comparé nos résultats à des simulations numériques.La mise en œuvre de cette approche optomécanique dite du «nanofil au milieu» à très basse température devrait permettre de réduire suffisamment le bruit thermique des nanofils pour explorer l’optomécanique en cavité au photon unique. Dans ce régime, un seul photon intra-cavité est capable de rendre le système bistable statiquement, ce qui ouvre la voie à des développements nouveaux en optique quantique, ne serait que parce que les théories de champ moyen ne sont alors plus pertinentesIn recent years nano-optomechanical systems have proven to be a powerful resource to detect ultra-weak forces, thus providing new insights on fundamental interactions. In this work we extend the experimental range of ultrasensitive force measurements based on optically readout vibrations of suspended silicon carbide nanowires to novel experimental regimes: first through operations at dilution temperatures, second in the ultrastrong coupling regime of cavity nano-optomechanics.Operating those force sensors at dilution temperatures permits to reduce their thermal noise and further benefit from an increased mechanical coherence. However this requires eliminating the sources of unwanted vibrations, such as electrical or mechanical noises, and operating at ultralow optical powers to avoid unwanted laser heating. We expose the experimental developments that lead us to observe a nanowire featuring a noise temperature measured at the 32mK level, while exploiting novel optical readout schemes operating in the photon counting regime, where less than a photon is detected per mechanical period. We discuss their mechanical and thermal properties at low temperatures and report on enhanced force sensitivities of a few tens of zN/Hz^1/2, which are sufficient in principle to detect the electron-electron Coulomb interaction over distances larger than 100 µm.In the second part of the manuscript, we describe a novel cavity nano-optomechanical experiment at room temperature that consists in inserting the vibrating extremity of a suspended nanowire with sub-wavelength sized diameter, in a high finesse fiber micro-cavity. The combination of its small mode volume, of the extreme force sensitivity of the nanowires and of the large optomechanical interaction strength demonstrated makes the system very interesting for further explorations of the field of cavity nano-optomechanics. In particular we demonstrate that one can reach the so-called ultrastrong coupling regime, where one single intracavity photon can displace the oscillator by more than its zero point fluctuations. This is achieved when the single photon coupling strength g0 exceeds the mechanical frequency Wm. After having described the experimental platform, we investigate how the nanowire perturbs the intracavity field by mapping the cavity properties as a function of the nanowire position within the standing wave. This permits to quantify and spatially map the optomechanical interaction strength, which acquires a vectorial character. Furthermore we explored the interaction in the reversed direction by mapping the intracavity optical force field experienced by the nanowire and compared our results with dedicated numerical simulations.Implementing this nanowire in the middle optomechanical scheme at low temperatures will permit, by significantly reducing the nanowire thermal noise, to explore the regime of single photon cavity nano-optomechanics. In this regime, particularly interesting for fundamental quantum optics, one single intracavity photon should render the cavity statically bistable and mean field descriptions should not be relevant anymore
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Musser, Daniel L. "On Propagation of Heat in Atomistic Simulations." University of Akron / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=akron1280258705.
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Meier, Roland. "Curie temperature and magnetic phase transition of nanostructured ultrathin Fe/GaAs(001) size dependence and relevance of dipolar coupling." Berlin mbv, 2009. http://d-nb.info/100028090X/04.
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Turon, Violette. "Coupling dark fermentation with microalgal heterotrophy : influence of fermentation metabolites mixtures, light, temperature and fermentation bacteria on microalgae growth." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS201/document.
Повний текст джерелаАнотація:
La production de microalgues en hétérotrophie présente plusieurs avantages pour la production de biocarburants par rapport à la production autotrophe, comme une productivité plus importante en termes de biomasse et de lipides. Cependant, le développement industriel de ce procédé est limité par les coûts de productions associés au substrat organique (i.e. glucose) et à ceux liés à la stérilisation des fermenteurs. Les effluents de fermentation sombre, composés principalement d’acétate et de butyrate, pourraient être utilisés comme milieux de culture peu onéreux pour la culture hétérotrophe ou mixotrophe de microalgues. Les objectifs de cette thèse étaient i) de mieux appréhender la croissance algale sur des mélanges variés d’acétate et de butyrate en fonction de la présence ou l’absence de lumière et de la température de croissance et ii) d’évaluer la faisabilité d’utiliser des effluents de fermentation non stérilisés pour soutenir la croissance de microalgues oléagineuses. Tout d’abord, un modèle basé sur des bilans de masse a été construit afin de caractériser la croissance hétérotrophe de Chlorella sorokiniana et Auxenochlorella protothecoides (taux de croissance et rendements) sur des mélanges d’acétate et de butyrate. Les résultats ont montré que le rapport acétate:butyrate et la concentration en butyrate étaient deux paramètres clés pour soutenir la croissance hétérotrophe. Puis, il a été démontré que la présence de lumière et l’utilisation d’une température suboptimale (30 °C) pour la croissance algale permettaient de réduire l’inhibition du butyrate en permettant une production de biomasse autotrophe ou en améliorant la croissance sur acétate. Enfin, il a été montré que les microalgues peuvent être compétitives sur l’acétate lors de la croissance sur des effluents bruts de fermentation sombre en présence de bactéries fermentaires, grâce à la croissance rapide des microalgues sur acétate (1.75 j-1) et à un changement drastique des conditions de culture peu favorables à la croissance des bactéries d’origine fermentaireGrowing microalgae in heterotrophic mode present several advantages over autotrophic mode such as a higher productivity in terms of biomass and lipids for biofuels production. Nevertheless, this process is limited by the production cost associated with the organic substrate (i.e. glucose) and fermenters sterilization costs. Dark fermentation effluents, mainly composed of acetate and butyrate, could be used as a low-cost medium to grow microalgae heterotrophically or mixotrophically. The aims of this PhD were i) to optimize microalgae growth on various mixtures of fermentations metabolites using the presence or absence light and different cultivation temperatures and ii) to assess the feasibility of using unsterilized fermentation effluents. First, a model based on mass balance was built to characterize heterotrophic growth rates and yields when Chlorella sorokiniana and Auxenochlorella protothecoides were supplemented with different mixtures of acetate and butyrate. Results showed that the acetate:butyrate ratio and the butyrate concentration per se were two key parameters for promoting heterotrophic growth. Then, further studies showed that the presence of light and the use of suboptimal temperature (30 °C) could reduce the butyrate inhibition on growth by either triggering autotrophic production of biomass or enhancing growth on acetate. Finally, it was shown that microalgae could outcompete fermentation bacteria for acetate when growing on raw dark fermentation effluents, thanks to a fast algal growth on acetate (1.75 d-1) and a drastic change of culture conditions to the detrimental of bacterial growth
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SEDEQI, FAISAL. "High Temperature Co-Electrolysis Model for Sector Coupling : Thermodynamic and Detailed Models of Solid Oxide Electrolysis Cells and Systems." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-286048.
Повний текст джерелаАнотація:
The increased development of intermittent renewable energy supplies not only demands robust storage technology, but also alternative means to produce materials in ways to avoid fossil fuel consumption and make use of the increasing electricity supply. Power to gas (PtG) through solid oxide cell (SOC) co-electrolysis reactors provide an attractive manner to overcome both challenges. The performance of co-electrolysis reactors for sector coupling purposes was investigated through mathematical models at the stack and system level.The system level model involved the development of an ideal power to methane (PtM) system with no losses in the auxiliary units and ideal SOC operation. This model was used to determine the maximum achievable efficiencies independent of technology, for a co-electrolysis and steam electrolysis based PtM in two different schemes: atmospheric SOC with pressurised methanation reactor and equal pressure between the SOC and methanation reactor. The performance of the system was analysed through the exergy method for different operating temperatures and pressures. The system was designed to be completely coupled, where the heat generated by one process was usable for another. Functional exergy efficiency was one of the main performance criteria used for comparison. It was found that for an ideal system, co-electrolysis operation was marginally beneficial over steam electrolysis at the system level based on exergetic efficiency. This is further compounded when considering the product yield, where the co-electrolysis systems outperform the steam electrolysis systems significantly.The stack level model involved introducing a new modelling framework based on fundamental charge transfer interactions to modify a transient steam/𝐻𝐻2 based SOC reactor modelled with Modelica at the DLR. This also involved modifying the reversible potential model to account for co-electrolysis as well as novel implementation of the DGM for co-electrolysis. The model was validated against experimental results of steady state operation for 1.4bar, 4bar and 8bar and feed gas compositions of 60% steam, 30% 𝐶𝐶𝑂𝑂2 and 10% 𝐻𝐻2; and 45% steam, 45% 𝐶𝐶𝑂𝑂2 and 10% 𝐻𝐻2 by volume. The model results agree with the experimental results. Further analysis of the reactor under co-electrolysis operation was performed. The 𝐶𝐶𝑂𝑂2 consumption mechanism was investigated as well as various electrochemical and thermal phenomena, to understand the operating behaviour of co-electrolysis stacks and to obtain general trends in operation with different operating conditions. The SOC reactor model was also used to predict the reactor behaviour under elevated pressure operation outside of the validation scope. Elevated pressure operation reduced polarisation overpotentials and ohmic resistance due to higher methanation rate, this led to lower cell voltages at high operating current densities thereby reducing the power demand compared to the lower pressure operation. However, the higher methanation rate led to higher methane content in the reactor outlet.The trends with pressure and temperature in the stack model were used to determine the theoretical limits of the PtM system with a state-of-the-art reactor. Invariable efficiencies were applied to the auxiliary units as average efficiencies to consider a wide range of equipment efficiencies. The system performance was analysed for different operating temperatures, pressures, current densities, and stack active areas. System and stack performance increased with temperature, while pressure had marginal impact on system performance but reasonable impact on the stack performance especially for lower auxiliary unit efficiency. The system and stack performance decreased with current density while increasing the SOC area resulted in higher efficiencies to nearly ideal, for constant flow rates.The results of the models suggest that SOC based co-electrolysis reactors provide an attractive method for sector coupling purposes. The exergy method provided a broad method to analyse and compare different systems. More research is required, especially on the thermal aspects of SOC reactor and 𝐶𝐶𝑂𝑂2 consumption mechanisms in co-electrolysis reactors.Den ökade utvecklingen av förnybara energikällor kräver inte bara pålitlig lagringsteknik utan också alternativa sätt att producera material på sätt att undvika fossila bränsleförbrukningar och använda sig av den ökande elförsörjningen. Kraft till gas (PtG) genom fasta oxidceller (SOC) samelektrolysreaktorer ger ett attraktivt sätt att övervinna båda utmaningarna. Prestanda hos samelektrolysreaktorer för sektorkopplingsändamål undersöktes genom matematiska modeller på komponent- och systemnivå.Systemnivåmodellen involverade utvecklingen av ett idealiskt kraft-till-metan-system (PtM) utan förluster i hjälpenheterna och idealisk SOC-drift. Denna modell användes för att bestämma de maximalt uppnåbara effektiviteterna oberoende av teknik, för en samelektrolys och ångelektrolysbaserad PtM i två olika scheman: atmosfärisk SOC med trycksatt metaneringsreaktor och lika tryck mellan SOC och metaneringsreaktorn. Systemets prestanda analyserades genom exergimetoden för olika driftstemperaturer och tryck. Systemet var utformat för att vara helt kopplat, där värmen som genereras av en process kunde används vidare. Funktionell energieffektivitet var ett av de viktigaste prestationskriterierna som användes för jämförelse. Det visade sig att för ett idealiskt system var samelektrolysoperation marginellt fördelaktig jämfört med ångelektrolys på systemnivå baserat på exergetisk effektivitet. Detta blandas ytterligare när man överväger produktutbytet, där samelektrolyssystemen överträffar ångelektrolyssystemen avsevärt.Stacknivåmodellen involverade införandet av ett nytt modelleringsramverk baserat på grundläggande laddningsöverföringsinteraktioner för att modifiera en övergående ånga/𝐻𝐻2-baserad SOC-reaktor modellerad med Modelica vid DLR. Detta involverade också modifiering av den reversibla potentiella modellen för att ta hänsyn till samelektrolys samt ny implementering av DGM för samelektrolys. Modellen validerades mot experimentella resultat vid stationärt förhållande för 1,4bar, 4bar och 8bar och matargaskompositioner av 60% ånga, 30% 𝐶𝐶𝑂𝑂2 och 10% 𝐻𝐻2; och 45% ånga, 45% 𝐶𝐶𝑂𝑂2 och 10% 𝐻𝐻2 i volym. Modellresultaten överensstämmer med de experimentella resultaten. Ytterligare analys av reaktorn under samelektrolysoperation utfördes. 𝐶𝐶𝑂𝑂2-förbrukningsmekanismen undersöktes liksom olika elektrokemiska och termiska fenomen, för att förstå driftsbeteendet hos samelektrolysstaplar och för att få generella trender i drift med olika driftsförhållanden. SOC-reaktormodellen användes också för att förutsäga reaktorns beteende under förhöjd tryck utanför valideringsområdet. Förhöjt tryckdrift minskade polariseringsöverpotentialen och ohmskt motstånd på grund av högre metaneringshastighet, vilket ledde till lägre cellspänningar vid höga driftsströmtätheter, vilket minskade effektbehovet jämfört med lägre tryckoperation. Den högre metaneringshastigheten ledde emellertid till högre metanhalt i reaktorutloppet.Trenderna med tryck och temperatur i stackmodellen användes för att bestämma de teoretiska gränserna för PtM-systemet med en toppmodern reaktor. Konstanta verkningsgrader applicerades på hjälpenheterna som genomsnittliga verkningsgrad för att överväga ett brett spektrum av utrustningsverkningsgrad. Systemets prestanda analyserades med avseende på olika driftstemperaturer, tryck, strömtäthet och stack-aktiva områden. Systemets och stackens prestanda ökade med temperaturen, medan trycket hade marginell inverkan på systemets prestanda men rimlig inverkan på stackens prestanda, särskilt för de lägre hjälpaggregatens verkningsgrad. Systemets och stackens prestanda minskade med strömtätheten medan en ökning i SOC yta-resulterade i högre effektivitet till nästan idealisk för konstanta flödeshastigheter.Resultaten av modellerna antyder att SOC-baserade samelektrolysreaktorer ger en attraktiv metod för sektorkoppling. Exergimetoden gav en bred metod för att analysera och jämföra olika system. Mer forskning krävs, särskilt om de termiska aspekterna av SOC-reaktorn och 𝐶𝐶𝑂𝑂2-förbrukningsmekanismerna i samelektrolysreaktorer.
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Wang, Ruxi. "High Power Density and High Temperature Converter Design for Transportation Applications." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28264.
Повний текст джерелаАнотація:
The continual development of high-power-density power electronic converters is driven particularly by modern transportation applications like electrical vehicles and more electric aircraft where the space and carrier capability is limited. However, there are several challenges related to transportation applications such as fault tolerance for safety concern, high temperature operation in extreme environments and more strict electromagnetic compatibility requirement. These challenges will increase difficulties for more electrical system adoption in the transportation applications.
In this dissertation, comprehensive methodologies including more efficient energy storage solution, better power electronics devices capability, better packaging performance and more compact EMI filter design are analyzed and proposed for the goal of high power density converter design in transportation applications.Ph. D.
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Collado, Morata Elena. "Impact of the unsteady aerothermal environment on the turbine blades temperature." Thesis, Toulouse, INPT, 2012. http://www.theses.fr/2012INPT0094/document.
Повний текст джерелаАнотація:
Ce travail de thèse, menée dans le cadre d'une convention CIFRE entre TURBOMECA et le CERFACS, s'inscrit dans un contexte d'amélioration des performances des turbines de type axial équipant les turboréacteurs d'hélicoptère. L'une des principales difficultés rencontrée dans cette démarche concerne la maîtrise de la température que voient les pales de ce composant, notamment la roue haute pression. Les travaux de cette thèse s'articulent autour de deux axes principaux: - Le premier traite l'analyse de la Simulations aux Grandes Echelles (SGE) autour de pales. Une approche numérique SGE sur des maillages non-structurés est comparée aux résultats Reynolds Averaged Navier-Stokes (RANS) sur des maillages structurés, usuels dans ce type de configuration, ainsi qu'à une approche SGE sur maillages structurés. La SGE sur maillage non-structuré démontre sa capacité à prendre en compte les phénomènes qui ont un impact sur les flux de chaleur pariétaux. - Le second axe de recherche a pour objectif de développer un outil numérique de couplage pour assurer le transfert d'information entre un code SGE réactif sur maillage non-structuré, employé dans les chambres de combustion, et un code non-réactif en RANS, utilisé par les industriels pour modéliser l'étage turbine. Cet outil a été validé sur plusieurs cas tests qui montrent le potentiel de cette méthodologie pour le couplage multi-composantThis PhD dissertation, conducted as part of a CIFRE research project between TURBOMECA and CERFACS, deals with improving performance of axial turbines from helicopter engines. One of the main difficulties with such an objective is the control of the temperature prediction around the blades, especially the temperature of the high pressure rotor. The work of this thesis focusses on two axes: - First concerns the analysis of Large Eddy Simulation (LES) predictions around blades: a numerical LES approach on unstructured meshes is compared to Reynolds Averaged Navier-Stokes (RANS) results on structured meshes as well as to LES on structured meshes. LES on unstructured meshes demonstrates its capacity of taking into account the phenomena which have an impact on wall heat flux around blades. - The second axis deals with the development of a numerical tool for coupling and transferring information between a reactive LES code, used in combustion chambers, and a non-reactive RANS solver, employed by industrial actors for modeling the turbine stage. This tool is validated on a number of test cases which show the potential of this methodology for multi-component predictions
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Feng, Chih-Wei. "Prediction of long-term creep behavior of epoxy adhesives for structural applications." Thesis, Texas A&M University, 2004. http://hdl.handle.net/1969.1/2560.
Повний текст джерелаАнотація:
The mechanical property of polymeric materials changes over time, especially when they are subjected to long-term loading scenarios. To predict the time-dependent viscoelastic behaviors of epoxy-based adhesive materials, it is imperative that reliable accelerated tests be developed to determine their long-term performances under different exposed environments. A neat epoxy resin system and a commercial structural adhesive system for bonding aluminum substrates are investigated. A series of moisture diffusion tests have been performed for more than three months in order to understand the influence of the absorbed moisture on creep behavior. The material properties, such as elastic modulus and glass transition temperature, are also studied under different environmental conditions. The time-temperature superposition method produces a master curve allowing the long-term creep compliance to be estimated. The physics-based Coupling model is found to fit well the long-term creep master curve. The equivalence of the temperature and moisture effect on the creep compliance of the epoxy adhesives is also addressed. Finally, a methodology for predicting the long-term creep behavior of epoxy adhesives is proposed.
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Meyer, Katja Elizabeth. "Perovskite-type Oxides as Electrocatalysts in High Temperature Solid Electrolyte Reactor Applications." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1493821638601215.
Повний текст джерела
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Eroglu, Sinan. "Coupling of CFD analysis of the coolant flow with the FE thermal analysis of a diesel engine." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/12655.
Повний текст джерелаАнотація:
In the process of engine design, it is important for the engine designer to predict the accurate component temperatures. Controlling the temperature of engine components requires a better understanding of the coolant behaviour in the coolant jacket of an engine which is critical to internal combustion engine design, The studies reported in the literature emphasize the influence of the cooling system on other engine operation such as exhaust emission, fuel consumption and engine wear. In this context, much work has been done with the purpose of improving the coolant jacket design and components of the cooling system to achieve higher performance. (Some of these studies) Previous researches have shown the possibility of achieving higher engine efficiency and performance with higher coolant temperature. This project aims at understanding the coolant flow behaviour in the coolant jackets of a diesel engine and investigating the possibility of running the engine at higher coolant temperatures by predicting the temperature distribution of the structure which is required for the assessment of the durability ofthe engine components. In this thesis, CFD (Computational Fluid Dynamics) and FE (Finite Element) techniques are used to study coolant flow in the coolant jackets and to predict the temperature distribution within the engine structure respectively. The objectives are to develop an FE model of the engine structure for thermal analyses and a CFD model of the fluid domain for the coolant flow CFD analyses. A number of case studies are carried out with the purpose of determining the most suitable technique for accurate temperature prediction. The methodology of manual coupling approach between CFD and FE analyses, which is more widely used in industry, and conjugate approach are demonstrated. Using these approaches, thermal analysis of the engine is conducted with the purpose of identifying the thermally critical locations throughout the engine. Furthermore, the influences of higher coolant temperature on these thermally critical regions of the engine are highlighted by carrying out four case studies with coolant inlet temperatures of 110°C, !ISOC, 117.5"C and !20°C. The temperature rise at the particular points around thermally critical regions is found to be in the range of 3-9 degrees at the higher coolant temperatures. This slight increase in temperature of critical locations may affect the durability of the structure. However, without carrying out the structural analyses it is not possible to comment on the durability of the engine structure. The effects of surface roughness and viscosity on heat transfer rate are also investigated and shown to be insignificant.
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Hagke, Christoph von [Verfasser]. "Coupling between climate and tectonics? : low temperature thermochronology and structural geology applied to the pro-wedge of the European Alps / Christoph von Hagke." Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1028495854/34.
Повний текст джерела
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Iwalewa, Tajudeen. "Coupling source term, mineral reactivity and flow in radionuclide transport." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/265633.
Повний текст джерелаАнотація:
The focus of this work is to investigate the dissolution of MW25, a non-radioactive simulant of UK high-level nuclear waste borosilicate glass, and to predict its performance in the near field of a geological repository. A single-pass flow-through (SPFT) experimental system was used to measure the forward dissolution rates of MW25. Experiments were conducted in two parts. Experiment Part 1 considers the dissolution of the waste glass in deionised water at 40 and 90 oC and circum-neutral pH. Experiment Part 2 considers the dissolution of the waste glass in simulant groundwaters, with similar compositions to groundwaters of Callovo-Oxfordian clay (lower-strength sedimentary rock (LSSR)) and Borrowdale Volcanic Group rocks (higher-strength rock (HSR)), at 40 oC and pH 7. The forward dissolution rate measured in deionised water was found to be approximately one order of magnitude higher at 90 oC than at 40 oC. A similar release was observed for Si, Mg and Al at 40 oC and 90 oC, whereas the B, Cs, Na, Li and Mo showed an order of magnitude increase when the temperature was increased from 40 to 90 oC for low q/S values. The activation energy (Ea) of the reactions shows that the dissolution process is a surface phenomenon. At 90 oC the net effect of the processes governing MW25 dissolution led to the preferential release of boron and alkali metals relative to the release of Si during the transient dissolution stage, accompanied by an increase in the concentration of silicic acid. This suggests that the solution activity of silicic acid at a higher temperature has a weak influence on the release of the mobile elements. The forward dissolution rate measured in LSSR simulant groundwater was found to be slightly higher than that measured in HSR simulant groundwater. The dissolution behaviour of MW25 in both groundwaters is consistent with its behaviour in deionised water at 40 oC, with the dissolution rates of elements increasing as flow rates were increased. However, forward dissolution rates measured in the simulant groundwaters were lower than the forward dissolution rates measured in deionised water under these experimental conditions. This is attributable to the interaction of the components of the simulant groundwaters with the glass, as revealed by post-reaction surface analyses, and a consequential lower alkalinity of the leachates collected in the experiments with simulant groundwater than in deionised water. Reactive chemical transport simulations of waste glass dissolution and radionuclide release in a hypothetical near field were conducted over a time span of a million years with GoldSim. The results showed that enclosing the waste glass in a steel canister covered by a copper canister and emplacing the waste package in a granite host rock is optimal for the long-term isolation of the radionuclides. The waste glass was found to play a significant role in the overall performance of the near field. This study features a new method for estimating the surface area of reacted glass powder more accurately than the geometric surface area estimate, which is the preferred standard method among researchers.
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Zhang, Rongwei. "Novel conductive adhesives for electronic packaging applications: a way towards economical, highly conductive, low temperature and flexible interconnects." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39548.
Повний текст джерелаАнотація:
Isotropically conductive adhesives (ICAs) are promising as a lead-free interconnect material; However, ICAs have a higher resistivity compared to tin/lead solder. The higher resistivity of ICAs results from the large contact resistance between conductive fillers. Several novel approaches to engineer the interface between electrically conductive fillers were studied to develop highly conductive ICAs. Shown in this dissertation are three methodologies to reduce contact resistance: low temperature sintering, fast sintering and in-situ reduction. Furthermore, two approaches, surface modification and in-situ protection, were developed to prevent oxidation and corrosion of silver-coated copper flakes to produce low cost ICAs. The findings and insights in this dissertation significantly contribute to (1) understanding of filler-filler, filler-polymer and structure-property relationships of ICAs; (2) the structural design and formulation of high performance ICAs; and (3) the wider use of ICAs in emerging applications such as printed electronics and solar cells.
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Hagke, Christoph von [Verfasser]. "Coupling between climate and tectonics? : low temperature thermochronology and structural geology applied to the pro-wedge of the European Alps / Christoph von Hagke. Deutsches GeoForschungsZentrum GFZ." Potsdam : Deutsches GeoForschungsZentrum GFZ, 2012. http://nbn-resolving.de/urn:nbn:de:kobv:b103-12148.
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Cavill, Stuart Alan. "A phonon study of semiconductor tunnelling devices." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325724.
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Francois, Bruno. "Capteurs passifs à ondes élastiques de surface sans fil pour mesure paramétrique sur une gamme de température étendue (25 / 650ºC)." Thesis, Besançon, 2013. http://www.theses.fr/2013BESA2027.
Повний текст джерелаАнотація:
Les travaux visant au développement de capteurs passifs interrogeables sans fil pour sonder des températures supérieures à 600 °C s’inscrivent dans le projet européens SAWHOT. Des capteurs à ondes élastiques de surface sont modélisés, réalisés et caractérisés par une liaison radiofréquence. Le paramètre physique mesuré par ce capteur est la température, avec une mesure au-delà de 900°Cpour les applications de maintenance préventive des turbines à combustion ou pour le contrôle de procédés dans les fours de synthèse de nano-tubes de carbone. Les substrats piezoélectriques standards tels que le quartz ou le niobate de lithium ne sont pas envisageables : l’ensemble de ces travaux s’articule autour de la langasite, substrat piezoélectrique opérant jusqu’à 1470°C et ne présentant aucune température de transition (température de Curie) jusqu’à sa température de fusion située à 1470°C. Compte tenu de la vitesse des ondes élastiques de surface des coupes considérés et également des limitations imposées par les moyens de réalisations technologiques, ces résonateurs sont mesurés sans fil à une fréquence proche de la bande ISM centré en 434 MHz. Les dispositifs ainsi réalisés ont été encapsulés via une procédure innovante de mise en boîtier qui permet alors la mesure de capteurs à ondes élastiques de surface dans des environnements où la température dépasse 700°C. De nombreuses études expérimentales ont alors été menés dans le but d’évaluer les performances des capteurs à ondes élastiques de surface en terme de bilan de liaison radiofréquence, reproductible de la mesure, vieillissement au cours des cycles en températuresDevelopment of wireless passive sensor for temperature measurement above 600°C has been performed in the frame of the European SAWHOT project. In this context, surface acoustic wave sensors have been designed, fabricated and characterized by radiofrequency measurement. Physical parameter measured by these sensors is the temperature, reaching values up to 900°C for monitoring in combustion engines andIn ovens used for carbon nano-tubes growth. In order to measure temperature in harsh environments, classical piezoelectric substrates are not usuable: langasite substrate has been considered as a favorable option since it exhibits no transition temperature and is able to operate until its exhibits no transition temperature and is able to operate until its melting temperature, at 1470 °C. regarding the parameters of the surface acoustic waves and the limitation of the fabrication process and devices, the resonators are measured wirelessly in the ISM band centered at 434 MHz (3μm of interdigital transducer period and a transducers with of 1μm). Two main manufacturing technologies are considered, stepper and nano-imprint technologies. The fabricated devices have been packaged by using an innovative process protecting the devices and allowing fir wireless measurements until 700°C. Multiple experiments have been performed in order to characterize the radiofrequency link between the reader and the sensor, the reproducibility of the measurement, the aging effect on the response of the device after high temperature cycles
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Raut, Prasad S. "Towards Development Of Polymeric Compounds For Energy Storage Devices And For Low Energy Loss Tires." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1493947416353888.
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Steinbeck-Behrens, Cord. "Elektrisch-thermisch-mechanisch gekoppelte Simulation an den Beispielen eines Aktuators und eines Steckers." Universitätsbibliothek Chemnitz, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-171808.
Повний текст джерелаАнотація:
In einer Einleitung werden verschiedene Möglichkeiten der Kopplung unterschiedlicher physikalischer Domänen diskutiert. Begriffe wie Kopplung auf Systemebene über Terminals und auf Feldebene über Lastvektor oder Matrixkopplung werden zugeordnet. Wie diese Kopplungsmöglichkeiten sich in der ANSYS Simulationsumgebung wiederfinden, wird aufgezeigt. Am Beispiel eines Akuators wird erläutert, welche physikalischen Domänen gekoppelt betrachtet werden müssen, um die hier vorhandenen temperaturabhängigen Materialeigenschaften zu berücksichtigen. In einem Beispiel zu einer Steckverbindung wird aufgezeigt, wie eine vom Kontaktdruck abhängige Leitfähigkeit berücksichtigt wird und Ergebnisse aus dieser Simulation werden diskutiert.
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Arapan, Lilia. "Thin Film Plate Acoustic Resonators for Frequency Control and Sensing Applications." Doctoral thesis, Uppsala universitet, Fasta tillståndets elektronik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-178592.
Повний текст джерелаАнотація:
The recent development of the commercially viable thin film electro-acoustic technology has triggered a growing interest in the research of plate guided wave or Lamb wave components owing to their unique characteristics. In the present thesis i) an experimental study of the thin film plate resonators (FPAR) performance operating on the lowest symmetrical Lamb wave (S0) propagating in highly textured AlN membranes versus a variety of design parameters has been performed. The S0 mode is excited through an Interdigital Transducer and confined within the structure by means of reflection from metal strip gratings. Devices operating in the vicinity of the stop-band center exhibiting a Q-value of up to 3000 at a frequency around 900MHz have been demonstrated. Temperature compensation of this type of devices has been studied theoretically and successfully realized experimentally for the first time. Further, integrated circuit-compatible S0 Lamb based two-port FPAR stabilized oscillators exhibiting phase noise of -92 dBc/Hz at 1 kHz frequency offset with feasible thermal noise floor below -180 dBc/Hz have been tested under high power for a couple of weeks. More specifically, the FPARs under test have been running without any performance degradation at up to 27 dBm loop power. Further, the S0 mode was experimentally demonstrated to be highly mass and pressure sensitive as well as suitable for in-liquid operation, which together with low phase noise and high Q makes it very suitable for sensor applications; ii) research in view of FPARs operating on other types of Lamb waves as well as novel operation principles has been initiated. In this work, first results on the design, fabrication and characterization of two novel type resonators: The Zero Group Velocity Resonators (ZGVR) and The Intermode-Coupled Thin Film Plate Acoustic Resonators (IC-FPAR), exploiting new principles of operation have been successfully demonstrated. The former exploits the intrinsic zero group velocity feature of the S1 Lamb mode for certain combination of design parameters while the latter takes advantage of the intermode interaction (involving scattering) between S0 and A1 Lamb modes through specially designed metal strip gratings (couplers). Thus both type of resonators operate on principles of confining energy under IDT other than reflection.
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García, Arellano Guadalupe. "Influence of the concentration and temperature on the spin relaxation time of donor-bound electrons immersed in a CdTe quantum well." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS109.
Повний текст джерелаАнотація:
Ce travail présente une étude de l'influence de la concentration de dopage, de la température et du champ magnétique longitudinal sur le temps de relaxation de spin des électrons liés aux donneurs immergés au milieu d'un puits quantique (PQ) de CdTe. En insérant les donneurs dans un PQ, les règles de sélection optique de la lumière polarisée circulairement sont purifiées, ce qui permet un meilleur degré d'orientation optique des spins des électrons que dans les cristaux 3D. En utilisant une technique de rotation Faraday photo-induite, nous mesurons d’abord le temps de relaxation de spin des électrons liés aux donneurs pour différentes concentrations de dopage à basse température dans le régime isolant. Ensuite, pour évaluer les mécanismes de relaxation de spin dans notre système, nous calculons l'énergie d'échange d'une paire d'électrons liés aux donneurs immergés au milieu d'un PQ infini, pour toute distance inter-donneur et différentes épaisseurs. En utilisant ce calcul, nous expliquons le comportement expérimental comme une interaction de deux mécanismes : l’interaction hyperfine et l’anisotrope d’échange. De plus, nous déterminons la constante spin-orbite dans CdTe αso = 0.079. Ensuite, nous présentons le développement d’une expérience pompe-sonde étendue permettant de mesurer les temps de relaxation de spin à l’échelle microseconde. Nous discutons brièvement des premiers résultats expérimentaux pour le temps de relaxation de spin longitudinal d'électrons liés aux donneurs immergés dans un PQ de CdTe avec différentes concentrations de dopage. Enfin, nous étudions l'évolution en température de la relaxation de spin de 10 à 80 K. On explique le comportement expérimental en invoquant l'échange de spin entre les électrons localisés et le spin d'électrons promus en états de conduction. Le spin des électrons localisés subit l’effet des interactions hyperfine et anisotrope, le mécanisme de D’yakonov-Perel’ régit la relaxation de spin des électrons de conductionThis work presents a study of the influence of doping concentration, temperature and longitudinal magnetic field on the spin relaxation time of donor-bound electrons immersed in the middle of a CdTe quantum well (QW). By inserting the donors in a QW, the optical selection rules for circularly polarized light are purified, allowing a higher degree of optical orientation of the electron spins than in 3D crystals. By using a photo-induced Faraday rotation technique, we first measure the spin relaxation time of donor-bound electrons for different doping concentrations at low temperature in the insulating regime. Then, in order to evaluate the spin relaxation mechanisms in our system, we calculate the exchange energy of a pair of donor-bound electrons immersed in the middle of an infinite QW, for any inter-donor distance and for different thicknesses. By using this calculation, we explain the experimental behavior as an interplay of two mechanisms: hyperfine and anisotropic exchange interactions. Moreover we determine the CdTe spin-orbit constant: αso = 0.079. Afterwards we present the development of an extended pump-probe experiment allowing to measure spin relaxation times at the microsecond scale. We briefly discuss the first experimental results for the longitudinal spin relaxation time of donor-bound electrons immersed in a CdTe QW with different doping concentrations. Finally, we investigate the temperature evolution of the spin relaxation in the range 10-80 K. The experimental behavior is explained by invoking spin exchange between electron spins localized on donors and the spin of electrons promoted to conduction states. The spin of localized electrons undergoes the effect of hyperfine and anisotropic exchange interactions, the D’yakonov-Perel’ mechanism governs the spin relaxation of the conduction electrons
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Renisch, Dennis [Verfasser]. "Installation and operation of a high-temperature surface ion source for the online coupling of TRIGA-SPEC to the TRIGA Mainz research reactor and high-precision mass measurements of transuranium nuclides at TRIGA-TRAP / Dennis Renisch." Mainz : Universitätsbibliothek Mainz, 2016. http://d-nb.info/1105495981/34.
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Drouet, Emeline. "Impact de la température sur la carbonatation des matériaux cimentaires : prise en compte des transferts hydriques." Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2010. http://tel.archives-ouvertes.fr/tel-00618092.
Повний текст джерелаАнотація:
La carbonatation est une pathologie du béton armé qui peut engendrer la corrosion des armatures et à terme de la fissuration. Dans le cadre de la gestion des déchets radioactifs, les structures et les conteneurs seraient soumis simultanément à un échauffement (exothermie des déchets), au CO2 atmosphérique, ainsi qu'à un séchage important. Afin de rendre compte de leur évolution à l'échelle séculaire, les données actuelles relatives à la carbonatation à température ambiante doivent être complétées, d'une part par une description de la phénoménologie en température, et d'autre part, par la prise en compte de l'impact des transferts hydriques en température (séchage) sur la carbonatation en insaturé. Le travail présenté se focalise sur l'étude de la durabilité de quatre pâtes de ciment différentes dont deux sont directement dérivées des formulations de référence sélectionnées par l'Andra (CEM I et CEM V) et un mélange baspH. Le premier volet est dédié à l'étude des transferts hydriques reposant sur la conduite d'essais de désorption. Il a notamment permis la caractérisation des isothermes de désorption en température (20, 50et 80°C). L'impact thermique modifie les isothermes : la teneur en eau à l'équilibre chute avec la température et le point d'amorçage de la condensation capillaire est déplacé. Une phase de modélisation a conjointement été conduite en support aux expérimentations. L'utilisation de l'équation de Clausius-Clapeyron a permis de décrire l'effet de la température sur les isothermes (par la détermination de la chaleur isostérique d'adsorption de chacun des matériaux). Bien que l'impact de la température sur la microstructure des pâtes de ciment soit avéré, la prise en compte du déplacement des équilibres thermodynamiques suffit à restituer cet effet thermique sur les isothermes. La détermination des perméabilités intrinsèques par exploitation des cinétiques de désorption (par analyse inverse) a montré la thermoactivation du transport d'eau. La contribution de l'évolution de la microstructure en température ne peut-être négligée sur la perméabilité des matériaux.Le deuxième volet exploratoire, est consacré à l'étude de la carbonatation en température. Il repose sur la mise en place d'un dispositif de carbonatation spécifique (fonctionnement en température) et la conduite d'essais de carbonatation à HR et température contrôlées. La campagne de caractérisation (DRX et ATG)a conduit à l'obtention de profils de carbonatation caractéristiques de chaque couple (HR, Température).Les évolutions minéralogiques (décomposition des hydrates, distribution polymorphique du carbonate de calcium précipité) mises en évidence en température se rapprochent de celles identifiées à température ambiante. En revanche, il ressort que les conditions environnementales influencent significativement les proportions polymorphiques : plus l'HR est faible, plus les teneurs en phases métastables (vatérite,aragonite) sont élevées. Les réactions de dissolution-précipitation mises en jeu dans la transformation polymorphique (des états métastables vers la calcite) sont inhibées à faible HR, par manque de milieu réactionnel. La cinétique de carbonatation, également impactée par les conditions environnementales, est régie par la concurrence de l'effet thermique sur les transferts hydriques et sur la solubilité rétrograde des réactifs. Les profondeurs carbonatées sont maximales aux points d'amorçage de la condensation capillaire propres aux différents matériaux et à chaque température. Les profondeurs carbonatées augmentent avec la température jusqu'à une température limite, caractéristique de la formulation, au-delà de laquelle la solubilité rétrograde des réactifs deviendrait le facteur limitant.Cette phase de compréhension des mécanismes mis en jeu dans la carbonatation en température et de leur niveau de couplage effectuée, les modèles prédictifs de carbonatation en insaturé pourront être étendus à l'application en température. Les résultats de ce travail fournissent les données d'entrées et de validation nécessaires à la validation des simulations numériques.
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Thomas, Anthony. "Transfert d'eau et de chaleur dans une pile à combustible à membrane : mise en évidence expérimentale du couplage et analyse des mécanismes." Thesis, Université de Lorraine, 2012. http://www.theses.fr/2012LORR0143/document.
Повний текст джерелаАнотація:
Les piles à combustible à membrane échangeuse de protons (PEMFC) permettent de convertir efficacement de l'énergie chimique en électricité. Pour cela l'hydrogène s'oxyde sur une des électrodes de la pile, les protons ainsi créés traversent l'électrolyte (membrane) tandis que les électrons parcourant le circuit extérieur fournissent l'énergie électrique. Tous ces éléments se recombinent à la seconde électrode qui, à l'aide de la réduction de l'oxygène, va former de l'eau. Le rendement n'étant pas parfait, une partie de l'énergie des réactifs est aussi dégradée sous forme de chaleur. Malgré de récents progrès, la commercialisation à grande échelle des piles à combustible est toujours entravée par des problèmes de durabilité, liés notamment à la gestion de l'eau et de la température au sein de ce système. Afin de quantifier le comportement thermique et son effet sur le transport de l'eau, une pile à combustible a été instrumentée, permettant la mesure de la température aux électrodes, des flux de chaleur et d'eau. Les résultats montrent que de forts gradients de température (jusqu'à environ 30 K/mm) peuvent exister pour une pile fonctionnant dans des conditions standard. Il a été observé une nette influence du champ de température dans le coeur de pile sur le transport de l'eau qui se fait vers la partie la plus froide de la pile (généralement les canaux d'alimentation), l'eau traversant les couches de diffusion poreuses sous forme vapeur dans nos conditions expérimentalesProton exchange membrane fuel cells (PEMFC) make it possible to convert efficiently chemical energy into electricity. For this, hydrogen is oxidized at one of the electrodes of the cell, created protons pass through the electrolyte (membrane) while electrons flow across the external circuit provide the electrical energy. All these elements recombine at the second electrode, with oxygen, to produce water. Performance is not perfect within a cell and a part of the reactants energy is also degraded as heat. Despite recent advances, the large scale commercialization of PEMFC is still hampered by durability issues, some of them being related to water and thermal management. In order to quantify the thermal behavior and its effect on the water transport, a fuel cell has been instrumented for the electrodes temperature, water and heat fluxes measurement. The results show that high temperature gradients (up to about 30 K/mm) can exist in a cell operating under standard conditions. It was observed a clear influence of the temperature field in the cell on the water transport. Water flows towards the coldest part of the cell (usually the channels), passing through the porous layers in vapor phase in our experimental conditions
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Stanciu, Victor. "Magnetism of Semiconductors and Metallic Multilayers." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5844.
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Bhadra, Sharmistha. "Electrode-based wireless passive pH sensors with applications to bioprocess and food spoilage monitoring." IEEE, 2011. http://hdl.handle.net/1993/30366.
Повний текст джерелаАнотація:
This thesis purposes and develops inductively coupled LC (inductive-capacitive) pH sensors based on pH-sensitive electrode pair. The LC resonator circuit is based on a varactor and measures the low frequency potential difference. For wireless pH monitoring, the resonator circuit is integrated with a pH-sensitive electrode pair. This sensor demonstrates a linear response over 2 to 12 pH dynamic range, 0.1 pH accuracy and long-term stability. Accurate measurement of pH using electrode-based sensors is affected by temperature variation. A technique of simultaneously measuring two parameters, pH and temperature, with a single RLC resonator based sensor is presented. An algorithm is developed, which applies both pH and temperature measurement to incorporate temperature compensation in pH measurement. For in-fluid applications, an encapsulation method is applied to the LC resonator based sensor to reduce the influence of medium permittivity and conductivity on the sensor measurement. Non-invasive way to obtain reliable pH information from bacterial culture bioprocesses is demonstrated with the fluid embeddable sensor. The pH sensor is remodeled to an acidic and basic volatile sensor by embedding the electrodes in a hydrogel host electrolyte. Tests demonstrate that the volatile sensor has a detection limit of 1.5 ppm and 2 ppm for ammonia and acetic acid vapor, respectively. Application of the volatile sensor to fish spoilage monitoring shows that the sensor is capable of detecting the product rejection level with good sensitivity in real-time. It is important to develop low cost wireless passive pH sensor technologies for embedded applications such as bioprocess and food spoilage monitoring. The electrode-based passive LC sensor approach employed in this thesis overcomes drawbacks of some of the early developed passive pH sensors and can lead to an inexpensive implementation using printed electronics technology.
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Peci, Erind. "Implementazione e Dimostrazione di un Client Mobile Completo per l'Arrowhead Framework." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2020.
Знайти повний текст джерелаАнотація:
Come spiega l’autore Kevin Ashton di “How to fly a horse: The secret history of creation, invention, and discovery“, negli anni "90 la creazione di sensori collegati a Internet non era una pratica diffusa e "l’idea di creare una vasta rete di sensori per raccogliere dati sulle cose nel mondo reale sembrava molto strana".
\newline Oggi, dopo anni di sviluppo tecnologico , è cambiato non solo l'idea per i sensori ma anche la necessità di dare un identità informatica ad ogni oggetto fisico nel contesto della rete dell'Internet of Things.L'idea di dotare queste entità con la capacità di scambiare informazioni e di utilizzare le informazioni che sono state scambiate orienta l'infrastruttura informatica verso i servizi.\newline Avendo presente l'impatto che presentano oggi i sistemi automatizzati negli ambienti IT , minimizzando le inefficienze dovute all’intervento umano, Arrowhead Framework fornisce un’architettura per la creazione di sistemi di automazione basati su Internet of Things secondo i principi della sicurezza IT, la scalabilità del sistema e la semplicità di progettazione.
\newline In questa tesi si trattano argomenti legati all'architettura orientata ai servizi,l'interoperabilità e si da una dimostrazione reale dell'esecuzione di questi principi nel contesto di un sistema che funziona secondo il framework Arrowhead.
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Alloui, Lotfi. "Modélisation tridimensionnelle des matériaux supraconducteurs." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112215.
Повний текст джерелаАнотація:
Nous présentons une contribution à la modélisation tridimensionnelle des phénomènes électromagnétiques et thermiques couplés dans les matériaux supraconducteurs à haute température critique. La méthode des volumes finis est adoptée comme méthode de résolution des équations aux dérivées partielles caractéristiques aux phénomènes physiques traités. Le couplage électromagnétique thermique est assuré par un algorithme alterné. L’ensemble des modèles mathématico-numériques ainsi développés et implémentés sous Matlab, sont appliqués pour étudié le comportement des supraconducteurs dans le cadre des paliers magnétiques et pour étudier le comportement des supraconducteurs durant le processus d’aimantation. Les résultats à caractère magnétique et ceux à caractère thermique sont largement présentés. La validité du travail proposé est atteinte par comparaison des résultats ainsi obtenus à ceux donnés par l’expérimentationWe present a contribution for three-dimensional modeling of coupled electromagnetic and thermal phenomena in high temperature superconductor. The control volume method is used for the resolution of the partial derivative equations characterising of the treated physical phenomena. The electromagnetic and thermal coupling is ensured by an alternate algorithm. All mathematical and numerical models thus developed and implemented in Matlab software, are used for the simulation. The results in magnetic term and those in thermal term are largely presented. The validity of the suggested work is reached by the comparison of the results so obtained to those given by the experiment
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Shin, Minju. "Caractérisation électrique et modélisation des transistors FDSOI sub-22nm." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAT098/document.
Повний текст джерелаАнотація:
Parmi les architectures candidates pour les générations sub-22nm figurent les transistors sur silicium sur isolant (SOI). A cette échelle, les composants doivent intégrer des films isolants enterrés (BOX) et des canaux de conduction (Body) ultra-minces. A ceci s'ajoute l'utilisation d'empilements de grille avancés (diélectriques à haute permittivité / métal de grille) et une ingénierie de la contrainte mécanique avec l'utilisation d'alliages SiGe pour le canal des transistors de type P. La mise au point d'une telle technologie demande qu'on soit capable d'extraire de façon non destructive et avec précision la qualité du transport électronique et des interfaces, ainsi que les valeurs des paramètres physiques (dimensions et dopages), qui sont obtenues effectivement en fin de fabrication. Des techniques d'extraction de paramètres ont été développées au cours du temps. L'objectif de cette thèse est de reconsidérer et de faire évoluer ces techniques pour les adapter aux épaisseurs extrêmement réduites des composants étudiés. Elle combine mesures approfondies et modélisation en support. Parmi les résultats originaux obtenus au cours de cette thèse, citons notamment l'adaptation de la méthode split CV complète qui permet désormais d'extraire les paramètres caractérisant l'ensemble de l'empilement SOI, depuis le substrat et son dopage jusqu'à la grille, ainsi qu'une analyse extrêmement détaillée du transport grâce à des mesures en régime de couplage grille arrière à température variable ou l'exploitation de la magnétorésistance de canal depuis le régime linéaire jusqu'en saturation. Le mémoire se termine par une analyse détaillée du bruit basse fréquenceSilicon on insulator (SOI) transistors are among the best candidates for sub-22nm technology nodes. At this scale, the devices integrate extremely thin buried oxide layers (BOX) and body. They also integrate advanced high-k dielectric / metal gate stacks and strain engineering is used to improve transport properties with, for instance, the use of SiGe alloys in the channel of p-type MOS transistors. The optimization of such a technology requires precise and non-destructive experimental techniques able to provide information about the quality of electron transport and interface quality, as well as about the real values of physical parameters (dimensions and doping level) at the end of the process. Techniques for parameter extraction from electrical characteristics have been developed over time. The aim of this thesis work is to reconsider these methods and to further develop them to account for the extremely small dimensions used for sub-22nm SOI generations. The work is based on extended characterization and modelling in support. Among the original results obtained during this thesis, special notice should be put on the adaptation of the complete split CV method which is now able to extract the characteristic parameters for the entire stack, from the substrate and its doping level to the gate stack, as well as an extremely detailed analysis of electron transport based on low temperature characterization in back-gate electrostatic coupling conditions or the exploitation of channel magnetoresistance from the linear regime of operation to saturation. Finally, a detailed analysis of low-frequency noise closes this study
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Davies, Richard G. H. "Analysis of the influence of temperature on the performance of adhesively bonded single lap joints." Thesis, London South Bank University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367906.
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Gonzalez, Minerva. "Impact of Li non-stoichiometry on the performance of acoustic devices on LiTaO3 and LiNbO3 single crystals." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2007/document.
Повний текст джерелаАнотація:
Les technologies de filtres, résonateurs, oscillateurs et capteurs sont des éléments essentiels dans lesindustries des télécommunications, automobile, militaire, médical, etc. Les monocristaux de LiTaO3 (LT) etLiNbO3 (LN) sont les matériaux les plus utilisés pour la fabrication de filtres de radiofréquence à ondesélastiques des téléphones portables, car ils possèdent un facteur de couplage électromécanique (K2) élevé.Cependant, ils présentent une problématique liée à la variation de la fréquence de fonctionnement avec latempérature (CTF), dont la valeur est environ de -40 à -95 ppm/°C. D’autre part, il a été démontré dans lalittérature que les propriétés de LT et LN changent avec la non-stoechiométrie du Li.L’objectif de cette thèse a été l’étude de l’effet de la concentration en Li2O sur la performance desdispositifs acoustiques à ondes élastiques de surface, utilisant comme substrat piézoélectrique desmonocristaux de LT coupe YXl/42 (42 RY-LT) et LN coupe YXl/128 (128 RY-LT). Cette étude vise àl’amélioration du CTF sans la dégradation d’autres propriétés (K2 et pertes d’insertion) dans le cas du 42 RYLTet la stabilité de dispositifs utilisés à haute densité de puissance dans le cas du 128 RY-LN. Tout d’abord,nous avons préparé des monocristaux de LT et LN avec différente concentration en Li2O :48.5-50 mol%, enutilisant la méthode d’équilibration par transport en phase vapeur (VTE). Ensuite, nous avons fabriqué etcaractérisé des dispositifs à ondes élastiques de volume et de surface à base de LT et LN, traités par VTE, afind’étudier l’effet de la non-stoechiométrie de Li et l’effet des domaines ferroélectriques sur leur performanceThe filter technologies, resonators, oscillators and sensors are essential elements fortelecommunications, automotive, military, medical industries. The most of radio frequency surface acousticwave (RF-SAW) filters, present in mobile phones, are based in LiNbO3 (LN) and LiTaO3 (LT) single crystalsbecause they have high electromechanical coupling factor (K2). However, these materials have a problemrelated to the variation of the operating frequency with temperature (TCF), whose value is about -40 to -95ppm / ° C. On the other hand, it has been previously shown in the literature that the physical and structuralproperties of LT and LN change with Li non-stoichiometry, including elastic properties.The aim of this work was the investigation of the impact of Li2O concentration on the performance ofSAW devices based on YXl/42 (42 RY-LT) and YXl/128 (128 RY-LN) single crystals. In the case of 42 RY-LT,we focused in the reduction of TCF without the degradation of other properties (K2 and insertion losses) andin the case of 128 RY-LN crystals we focused in the stability of devices at high power densities. First, singlecrystals of LT and LN with different Li2O concentration: 48.5-50 ml% were prepared, by using the VaporTransport Equilibration (VTE) method. Afterwards, SAW and bulk acoustic wave (BAW) devices based on LTand LN VTE treated crystals, were fabricated and characterized, in order to study the effect of Li nonstoichiometryand the effect of ferroelectric domains on the performance of devices
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Ruiz-Tijerina, David A. "Kondo Physics and Many-Body Effects in Quantum Dots and Molecular Junctions." Ohio University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1385982088.
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Bellec, Morgane. "Études du couplage entre turbulence et gradient de température pour l'intensification des transferts de chaleur dans les récepteurs solaires à haute température." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0005/document.
Повний текст джерелаАнотація:
Une voie prometteuse pour améliorer le rendement des centrales solaires à tour consiste à chauffer de l'air pressurisé à haute température afin d'alimenter un cycle thermodynamique de Brayton. Pour cela, il est indispensable de concevoir des récepteurs solaires performants,permettant de forts transferts de chaleur vers le fluide. Le développement de tels récepteurs passe par une compréhension fine de leurs écoulements internes. Il s'agit d'écoulements complexes, combinant de hauts niveaux de turbulence et un fort gradient de température entre la paroi irradiée par le flux solaire concentré et la paroi arrière isolée. On se propose dans ce travail de réaliser une étude amont numérique et expérimentale de ce type d'écoulements.D'une part, des mesures de vitesse par SPIV (vélocimétrie par images de particules stéréoscopique) sont effectuées dans une soufflerie de canal plan turbulent lisse dont la cellule de mesure est représentative d'un récepteur solaire surfacique. On observe en particulier l'influence d'un chauffage asymétrique sur les statistiques de la turbulence. Ces mesures sont d'autre part complétées par des simulations fines LES (simulation des grandes échelles)menées dans les conditions de la soufflerie. Pour finir, une simulation LES d'un canal plan texturé sur une paroi par une géométrie innovante est conduite. Cette architecture interne du récepteur combine des générateurs de tourbillon et des riblets afin d'intensifier les échanges de chaleur vers le fluideA promising line of research to increase the efficiency of solar tower power plants consists in heating pressurized air to high temperatures in order to fuel a Brayton thermodynamic cycle. This requires to design effective solar receivers that allow for intense heat transfers toward the fluid. To develop such receivers, an in-depth understanding of their internal flows is needed. These are complex flows, combining strong turbulence and strong temperature gradient between the concentrated sun irradiated wall and the back insulated wall.The aim of this work is to investigate numerically and experimentally such flows.On one hand, velocities are measured by SPIV (Stereoscopic Particle Image Velocimetry) in a turbulent channel flow wind tunnel whom measurement cell is similar to a surface solar receiver. The influence of an asymmetric heating on the turbulence statistics are especially investigated. These measurements are supplemented by Large Eddy Simulations run under the same conditions as the wind tunnel. Finally, a Large Eddy Simulation is run in a channel flow textured on one wall by an innovative geometry. This internal receiver design combines vortex generators and riblets in order to enhance the heat transfers
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Gazeau, Camille. "Développement d’outils numériques pour la sélection et l’optimisation de matériaux conducteurs mixtes pour l’oxycombustion." Thesis, Orléans, 2014. http://www.theses.fr/2014ORLE2031.
Повний текст джерелаАнотація:
Les conducteurs mixtes (MIECs) sont des matériaux prometteurs pour la réalisation de membranes séparatrices de l’oxygène de l’air à haute température. Cette séparation s’effectue par semi-Perméation de l’oxygène à travers la membrane. Ce phénomène induit un gradient de potentiel chimique à l’origine de la rupture de certaines membranes. La prévision des gradients en service et la connaissance des propriétés mécaniques sont essentielles pour la prévision de la fiabilité des futurs sites de production. La semi-Perméation suit la théorie de Wagner en volume, mais aucun consensus n'excite pour les échanges en surface. En outre, les modèles d’échanges en surface décrivent l'état stationnaire, et ne peuvent être étendus au régime transitoire. Dans cette thèse, un nouveau modèle d'échange de surface est proposé. Il prend en compte l'association / dissociation de l'oxygène et le coût énergétique élevé de réduction / oxydation de l’oxygène par l’introduction de la conservation d’une espèce chimique transitoire seulement présente à la surface. Ce modèle permet de reproduire les états stationnaires et transitoires. En parallèle, un dispositif expérimental de caractérisation des propriétés mécaniques des MIECs a été développé à 900°C. L’essai mis en place est un essai « pseudo brésilien » instrumenté par une mesure optique. Le post-Traitement s’effectue par une méthode « Integrated Digital Image Correlation ». Les propriétés élastiques de sept nuances de conducteurs mixtes ont pu ainsi être caractériséesMixed Conductors (MIECs) are promising membrane materials for oxygen separating from air at high temperature. The oxygen semi-Permeation is the most important property of the membrane. This property induces a chemical potential gradient, which is the origin of some membrane ruptures. Forecasting gradients in service and the knowledge of MIECs mechanical properties are necessary for predict the reliability of future power plants. While the diffusion is well described by the Wagner theory, no consensus has yet emerged regarding the surface exchange models proposed in the literature. Furthermore, these models describe the stationary state, and cannot be extended to the transient stage. In this thesis, a new surface exchange model is proposed. This model takes into account the association/dissociation of oxygen and the high energetic cost of oxygen reduction/oxidation thanks to the balance of a transient species only present at the surface. This model can reproduce stationary state and transient stage. In parallel, a test device for characterizing the mechanical properties of the MIECs has been developed at 900 ° C. The test is “pseudo-Brazilian test” instrumented by an optical measurement. Post-Processing is carried out by a "Integrated Digital Image Correlation" method. The elastic properties of seven mixed conductors have been characterized
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Willschütz, Hans-Georg. "Thermomechanische Modellierung eines Reaktordruckbehälters in der Spätphase eines Kernschmelzunfalls." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1138712734373-55289.
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Considering the late in-vessel phase of an unlikely core melt down scenario in a light water reactor (LWR) with the formation of a corium pool in the lower head of the reactor pressure vessel (RPV) the possible failure modes of the RPV and the time to failure have to be investigated to assess the possible loadings on the containment. In this work, an integral model was developed to describe the processes in the lower plenum of the RPV. Two principal model domains have to be distinguished: The tem-perature field within the melt and RPV is calculated with a thermodynamic model, while a mechanical model is used for the structural analysis of the vessel wall. In the introducing chapters a description is given of the considered accident scenario and the relevant analytical, experimental, and numerical investigations are discussed which were performed worldwide during the last three decades. Following, the occurring physical phenomena are analysed and the scaling differences are evaluated between the FOREVER-experiments and a prototypical scenario. The thermodynamic and the mechanical model can be coupled recursively to take into account the mutual influence. This approach not only allows to consider the temperature dependence of the material parameters and the thermally induced stress in the mechanical model, it also takes into account the response of the temperature field itself upon the changing vessel geometry. New approaches are applied in this work for the simulation of creep and damage. Using a creep data base, the application of single creep laws could be avoided which is especially advantageous if large temperature, stress, and strain ranges have to be covered. Based on experimental investigations, the creep data base has been developed for an RPV-steel and has been validated against creep tests with different scalings and geometries. It can be stated, that the coupled model is able to exactly describe and predict the vessel deformation in the scaled integral FOREVER-tests. There are uncertainties concerning the time to failure which are related to inexactly known material parameters and boundary conditions. The main results of this work can be summarised as follows: Due to the thermody-namic behaviour of the large melt pool with internal heat sources, the upper third of the lower RPV head is exposed to the highest thermo-mechanical loads. This region is called hot focus. Contrary to that, the pole part of the lower head has a higher strength and therefore relocates almost vertically downwards under the combined thermal, weight and internal pressure load of the RPV. On the one hand, it will be possible by external flooding to retain the corium within the RPV even at increased pressures and even in reactors with high power (as e.g. KONVOI). On the other hand, there is no chance for melt retention in the considered scenario if neither internal nor external flooding of the RPV can be achieved. Two patents have been derived from the gained insights. Both are related to passively working devices for accident mitigation: The first one is a support of the RPV lower head pole part. It reduces the maximum mechanical load in the highly stressed area of the hot focus. In this way, it can prevent failure or at least extend the time to failure of the vessel. The second device implements a passive accident mitigation measure by making use of the downward movement of the lower head. Through this, a valve or a flap can be opened to flood the reactor pit with water from a storage reservoir located at a higher position in the reactor building. With regard to future plant designs it can be stated - differing from former presumptions - that an In-Vessel-Retention (IVR) of a molten core is possible within the reactor pressure vessel even for reactors with higher powerFür das unwahrscheinliche Szenario eines Kernschmelzunfalls in einem Leichtwasserreaktor mit Bildung eines Schmelzesees in der Bodenkalotte des Reaktordruckbehälters (RDB) ist es notwendig, mögliche Versagensformen des RDB sowie Versagenszeiträume zu ermitteln, um die daraus resultierende mögliche Belastung des Sicherheitsbehälters bestimmen zu können. In dieser Arbeit wird ein integrales Modell entwickelt, das die Vorgänge im unteren Plenum beschreibt. Dabei sind zwei prinzipielle Modellbereiche zu unterscheiden: Das Temperaturfeld in der Schmelze und im RDB wird mit einem thermodynamischen Modell berechnet, während für die Strukturanalyse des RDB ein mechanisches Modell verwendet wird. Zunächst werden das betrachtete Unfallszenario dargestellt und die bisher in den letzten drei Dekaden weltweit durchgeführten wesentlichen analytischen, experimentellen und numerischen Untersuchungen diskutiert. Anschließend werden die auftretenden physikalischen Vorgänge analysiert. Gleichzeitig werden Skalierungsunterschiede zwischen den in dieser Arbeit betrachteten Experimenten der FOREVER-Reihe und einem prototypischen Szenario herausgearbeitet. Das thermodynamische und das mechanische Modell können rekursiv gekoppelt werden, wodurch die wechselseitige Beeinflussung berücksichtigt werden kann. Insbesondere werden damit neben der Temperaturabhängigkeit der Materialparameter und den thermisch induzierten Spannungen im mechanischen Modell auch die Rückwirkungen der Behälterverformung auf das Temperaturfeld selber erfasst. Für die Kriech- und Schädigungssimulation werden in dieser Arbeit neue Verfahren angewendet. Durch die Entwicklung und den Einsatz einer Kriechdatenbasis konnte die bei sehr unterschiedlichen Temperaturen, Spannungen und Dehnungen ungeeignete Verwendung einzelner Kriechgesetze umgangen werden. Aufbauend auf experimentellen Untersuchungen wurde eine Kriechdatenbasis für einen RDB-Stahl entwickelt und an Hand von Kriechversuchen verschiedener Geometrie und Dimension validiert. Als Ergebnis lässt sich festhalten, dass das gekoppelte Modell prinzipiell in der Lage ist, die Behälterdeformation im Falle der skalierten FOREVER-Experimente exakt zu beschreiben bzw. vorherzusagen. Unsicherheiten bezüglich der Versagenszeit resultieren aus nicht exakt bekannten Materialparametern und Randbedingungen. Die wesentlichen Ergebnisse dieser Arbeit lassen sich wie folgt zusammenfassen: Aufgrund des thermodynamischen Verhaltens eines großen Schmelzesees mit inneren Wärmequellen erfolgt die höchste thermomechanische Belastung des RDB im oberen Drittel der Bodenkalotte. Dieser Bereich wird als heißer Fokus bezeichnet. Der untere Bereich der Kalotte weist hingegen eine höhere Festigkeit auf und verlagert sich deswegen bei entsprechender Belastung des RDB im wesentlichen senkrecht nach unten. Bei einer externen Flutung besteht auch bei hohen Innendrücken für einen Reaktor großer Leistung (KONVOI) die Möglichkeit, die Schmelze im RDB zurückzuhalten. Ohne interne oder externe Flutung besteht für das betrachtete Szenario keine Aussicht für eine Schmelzerückhaltung im RDB. Aus den gewonnenen Erkenntnissen wurden zwei Patente abgeleitet. Dabei handelt es sich um passiv wirkende Einrichtungen zur Schadensbegrenzung: Die erste reduziert durch Abstützen des unteren Kalottenzentrums die Maximalspannungen im hochbeanspruchten Bereich des heißen Fokus und kann damit ein Versagen verhindern oder zumindest verzögern. Die zweite Einrichtung ermöglicht die passive Auslösung einer Flutung, indem die Abwärtsbewegung der Kalotte zur Steuerung genutzt wird. Hierdurch kann beispielsweise ein Ventil geöffnet werden, um Wasser aus im Gebäude höher angeordneten Reservoirs in die Reaktorgrube zu leiten. Abweichend von bisherigen Annahmen kann im Hinblick auf die Entwicklung zukünftiger Baulinien festgehalten werden, dass eine Kernschmelzerückhaltung im Reaktordruckbehälter auch für Reaktoren größerer Leistung möglich ist
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Low, Zi Kang. "Matériaux cellulaires isolants haute température : Relation microstructure-propriétés." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI122.
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Cette thèse CIFRE réalisée en collaboration avec Saint-Gobain Research Provence porte sur la modélisation des propriétés thermiques d’une mousse d’alumine NorFoam XPure®, conçue pour l’isolation thermique haute température (1200°C–1700°C). L’objectif est de développer et valider des modèles numériques multiéchelles pour calculer le transfert de chaleur par conduction et rayonnement dans cette mousse, à partir des microstructures 3D tomographiées et des propriétés intrinsèques des composants. La mousse étant composée des cellules ouvertes et d’un squelette solide lui-même poreux, la prise en compte de l’influence de cette double porosité est particulièrement novatrice. Dans un premier temps, le transfert thermique par conduction à travers la mousse est modélisé avec des techniques d’homogénéisation par éléments finis. Il est démontré que des conditions aux limites périodiques couramment utilisées ne sont pas adaptées aux mousses tomographiées, et qu’un jeu de conditions aux limites mixtes permet d’obtenir des résultats plus précis sur ces dernières. Quant au transfert radiatif à travers le squelette poreux, qui présente une forte diffusion volumique avec des phénomènes ondulatoires, le développement d’une nouvelle approche de modélisation basée sur l’approximation dipolaire discrète permet de prendre en compte l’influence desdits phénomènes. Les propriétés radiatives de la mousse sont ensuite calculées par méthode de lancer de rayons en tenant compte du comportement radiatif complexe du squelette poreux. L’influence des phénomènes de réflexion et réfraction non-spéculaires aux interfaces entre le squelette et les cellules a été étudiée. Enfin, une modélisation numérique basée sur les techniques d’homogénéisation permet de calculer le transfert thermique à travers la mousse, avec couplage de la conduction et du rayonnement. Le bon accord entre les résultats issus de chaque modèle et les mesures thermiques et optiques réalisées sur la mousse et le squelette poreux confirme le caractère prédictif des modèles développésThis CIFRE doctoral study, performed in collaboration with Saint-Gobain Research Provence, aims to model the thermal properties of NorFoam XPure®, an alumina foam designed for high temperature thermal insulation (1200°C–1700°C). The goal is to develop and validate multiscale numerical models to compute the conductive and radiative heat transfer through the foam from 3D tomography-reconstructed microstructures and the intrinsic properties of each constituent phase. Specific attention is given to the complex porosity in the studied foam: in addition to the open-cell network, smaller pores are also found within the foam skeleton. Novel approaches are proposed in the present work to take into account the influence of this dual-scale porosity. Firstly, effective heat conduction through the foam is modeled with finite element homogenization techniques. It is demonstrated that the commonly used periodic boundary conditions are unsuitable for tomography-reconstructed foams, and that a set of mixed boundary conditions gives more accurate and precise results for such foams. As radiative transfer through the porous foam skeleton is characterized by high volume scattering and significant wave effects, a novel physical optics approach based on the discrete dipole approximation is next developed to model the influence of these phenomena. The radiative properties of the foam are then determined through a ray tracing method that takes into account the complex radiative behavior of the porous foam skeleton. The influence of non-specular reflection and refraction at the interfaces between the foam cells and skeleton is studied. Finally, the homogenized properties are applied to simulate the coupled conductive and radiative heat transfer through the foam. The model predictions are systematically compared to thermal and spectroscopic measurements performed on samples of the foam and the foam skeleton material. The good agreement between numerical and experimental results confirms the predictive capabilities of the models developed in this study
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Lange, Makhles Reuter. "Efeitos acoplados da temperatura e evolução de dano em meios contínuos elasto-plásticos." Universidade do Estado de Santa Catarina, 2011. http://tede.udesc.br/handle/handle/1789.
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The development of new materials, in addition to the increasing industrial demand for more efficient numerical tools capable of predicting defects in metal forming processes, has stimulated research on new material models. In this context, the Continuum Damage Mechanics has proved to be able of successfully predicting ductile failure onset in metal forming operations. The main objective of this work is the study of a thermo-elastic-plastic formulation and thermo-mechanical coupling schemes aiming at prediction of mechanical degradation of ductile materials. The material internal degradation is described using a modified version of Lemaitre s (1985) damage model, in which the void opening and void closure effects associated to tensile and compressive stress states are accounted for. The mechanical and thermal problems are formulated using the Finite Element Method. Coupling of thermal effects is defined by a sensitivity factor included in the yield function and by a component describing the energy generated due to dissipation of plastic work. Two coupling procedures are addressed in this work: staggered scheme and iterative scheme. Accuracy of the iterative coupling scheme is assessed by the analysis of the load increment size. In this case, the results show that the iterative procedure is more accurate than the staggered scheme. The study of the coupled thermal and mechanical effects is discussed by the analysis of the influence of the temperature and the heat transfer coefficient based upon the simulation of tensile tests of U-notched specimens. The results show that the internal degradation of the material is strongly affected by its temperature and heat transfer coefficient, i.e., higher temperatures increase the material capacity to deform with smaller rates of material degradation.
O surgimento de novos materiais, aliado ao aumento da demanda industrial por ferramentas numéricas capazes de prever o aparecimento de defeitos em processos de conformação mecânica, tem estimulado o desenvolvimento de novos modelos materiais. A Mecânica do Dano Contínuo, em cujo contexto este trabalho está inserido, provou ser uma abordagem capaz de prever o início da fratura dúctil em operações de conformação mecânica. O principal objetivo deste trabalho é o estudo da formulação termo-elastoplástica de problemas com acoplamento termomecânico visando a sua aplicação na predição da degradação mecânica de materiais dúcteis. A descrição da degradação interna do material é feita através da modificação do modelo de dano de Lemaitre (1985) para incluir efeitos de abertura e fechamento de vazios relacionados a estados de tensão trativos e compressivos. Os problemas térmico e mecânico são formulados utilizando o método de Elementos Finitos. O acoplamento dos efeitos térmicos é definido através da inclusão de um fator de sensibilidade na função de escoamento e da geração de calor por dissipação plástica. Dois métodos de acoplamento foram abordados: método particionado e método iterativo. A avalição da precisão do método de solução iterativo do problema acoplado é feita através da análise de influência do incremento de carga. Neste caso, os resultados obtidos mostraram que o método iterativo é mais preciso que o método particionado. O estudo dos efeitos térmico e mecânico acloplados é feito através da análise da influência da temperatura e do coeficiente de troca de calor na simulação de um ensaio de tração usando um corpo de prova cilíndrico. Os resultados mostram que a degradação interna do material é fortemente influenciada pela temperatura do material e pelo coeficiente de troca de calor, ou seja, quanto maior a temperatura, maior é a capacidade do material de se deformar plasticamente com uma redução da taxa de degradação. interna do material.