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1
Carsbring, Amanda. "Heat Treatment and Secondary Phase Formation in FeCrNi Medium Entropy Alloys". Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291251.
Abstract (sommario):
The topics of high entropy alloys (HEA) and medium entropy alloys (MEA) have been heavily researched in recent years. A HEA usually consists of five or more base elements, and a MEA would have three or four base elements. These types of alloys are multi-principal element alloys (MPEA) that have been thought to have interesting properties due to their high configurational entropy, which was thought to be the reason for stabilized simple solid solution phase in the HEA. The high entropy effect contributing to stable single phase in these alloys has been discussed and has not been found to be a predicament to which MPEA that will present as single phase at lowered temperatures. Still, some of the HEA and MEA investigated have interesting properties such as high ductility and good thermal properties, as is the case for the commonly researched CoCrFeMnNi HEA and the CoCrNi MEA which are both solid solution FCC phase at lower temperatures. This master thesis aims to investigate one of the less commonly researched MEA: equimolar FeCrNi. This alloy has been studied previously, and it was found there might be a possibility of precipitation hardening the alloy. To further study this alloy system, three FeCrNi alloys in the close-to equimolar range were produced and underwent a series of aging heat treatments to study the amount of precipitated secondary phase with composition changes and different aging temperatures. The objective is to evaluate and interpret the data found in the different CALPHAD databases used in Thermo-Calc and FactSage software and make comparisons to the experimental results. This to discuss the possibilities of hardening this alloy through aging treatment. The alloys selected and produced are 33Fe33Cr33Ni, 40Fe30Cr30Ni and 45Fe30Cr25Ni, all in mol%. Through experimental investigation using x-ray diffraction (XRD) analysis, it is found that Cr-rich BCC phase is formed in all alloys after most of the aging treatments performed. The volume fraction of BCC was quantified through the reference intensity ratio (RIR) method. From quantification, the largest volume fraction BCC is found in the equimolar 33Fe33Cr33Ni alloy, and the lowest fraction BCC is shown in the 40Fe30Cr30Ni alloy. The increased volume fraction of BCC coincides with an elevated hardness in all three alloys. It is also found that out of the three equilibrium phase calculations used in this project, the ThermoCalc steel database TCHEA4 seems to give results that are in closest agreement with the experimental results. For future studies in this subject, the recommendation is to further study the mechanical properties of the FeCrNi MEA and assess possibilities for application.Högentropilegeringar och mediumentropilegeringar har studerats närmre de senaste åren på grund av deras intressanta mekaniska egenskaper. En högentropilegering består vanligtvis av fem eller flera baselement, och en mediumentropilegering har tre eller fyra baselement. Detta skiljer dem från konventionella legeringar som i regel har ett, maximalt två, baselement. Dessa typer av multi-baslegeringar har ansetts ha intressanta egenskaper på grund av deras höga konfigurationsentropi, vilken tros vara orsaken till stabilisering av fast lösningsfas i legeringarna. Högentropieffekten som bidrar till stabil enfas i dessa legeringar har diskuterats och har emellertid inte visat sig vara tillförlitligt för att förutsäga vilka multi-baslegeringar som blir fast lösningsfas vid ett lägre temperaturintervall. Ändå har några av de undersökta legeringarna intressanta egenskaper som hög duktilitet och goda termiska egenskaper, vilket är fallet för högentropilegeringen CoCrFeMnNi och mediumentropilegeringen CoCrNi som båda är enkel FCC-fas vid lägre temperaturer. Detta examensarbete syftar till att undersöka en av de mindre omnämnda mediumentropilegeringarna: ekvimolär FeCrNi. Denna legering har studerats tidigare, och det visade sig att det kan finnas en möjlighet att utskiljningshärda legeringen. För att ytterligare studera detta legeringssystem producerades tre FeCrNi-legeringar i ett sammansättningsintervall nära ekvimolär sammansättning, som sedan genomgick en serie åldringsbehandlingar för att studera mängden utskild sekundär fas beroende på sammansättning och åldringstemperatur. Målet är att utvärdera och tolka data som finns i de olika CALPHAD-databaserna som används i beräkningsverktygen Thermo-Calc och FactSage, och därefter göra jämförelser med experimentresultaten. Detta för att diskutera möjligheterna att härda dessa legeringar med partikelutskiljning. De legeringar som valts och tillverkats är 33Fe33Cr33Ni, 40Fe30Cr30Ni och 45Fe30Cr25Ni, alla angivna i molprocent. Genom experimentella undersökningar med röntgendiffraktionsanalys hittades att BCC-fas med höga halter Cr bildats i alla legeringar efter majoriteten av åldringsbehandlingarna som utförts. Volymfraktionen av BCC kvantifierades genom beräkningar från referensintensitetsförhållande (RIR). Från kvantifiering fås den största volymfraktionen BCC i den ekvimolära 33Fe33Cr33Ni-legeringen, och den lägsta fraktionen BCC i 40Fe30Cr30Ni-legeringen. Högre volymfraktion BCC sammanfaller med en förhöjd hårdhet i alla tre legeringarna. Det visar sig också att utav de tre jämviktsfasberäkningarna som används i detta projekt så är det ThermoCalc-ståldatabasen TCFE10 som gett resultat som överensstämmer med experimentresultaten. För framtida undersökningar inom detta område rekommenderas att studera de mekaniska egenskaperna hos FeCrNi och bedöma möjligheterna för tillämpning av materialet.
2
Howe, Christopher J. "Medium-energy ions scattering studies of ultrathin metallic films on the face-centred cubic (111) surface". Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/35637.
Abstract (sommario):
An experimental investigation of ultrathin metallic films on face centred cubic(111) surfaces using medium energy ion scattering as a primary experimental technique is reported. A suite of custom software written for data-processing, calibration and analysis has also been described. The specific experimental systems investigated are 0.25 ML to 3.89 ML of palladium on copper(111) and 0.23 ML to 3.74 ML of silver on aluminium(111). The Pd CU(111) system was shown to exhibit 42% twinning at 0.25 ML through 4.74 ML. At 0.25 ML coverage it has been shown that the Pd migrates into the top three layers of the substrate. The Pd was shown to be distributed 27% ± 3%, 67% ± 3% and 6% ± 3% in the 1st, 2nd and 3rd layers. The first and second interlayer spacings we also found to contract by 4% and expand by 4% respectively for the 0.25 ML coverage.
3
Vernon, Kristy C. "Strongly localised plasmons in metallic nanostructures". Thesis, Queensland University of Technology, 2008. https://eprints.qut.edu.au/19318/2/Kristy_Vernon_Citation.pdf.
Abstract (sommario):
Strongly localised plasmons in metallic nano-structures offer exciting characteristics for guiding and focusing light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved resolution of optical microscopy. The work presented in this thesis focuses on two major areas of plasmonics research - nano-focusing structures and nano-sized waveguides. Nano-focusing structures focus light to an area smaller than the wavelength and will find applications in sensing, efficiently coupling light to nano-scale devices, as well as improving the resolution of near field microscopy. In the past the majority of nano-focusing structures have been nano-scale cones or tips, which are capable of focusing light to a spot of nano-scale area whilst enhancing the light field. The alternatives are triangular nano-focusing structures which have received far less attention, and only one type of triangular nano-focusing structure is known – a sharp V-groove in a metal substrate. This structure focuses light to a strip of nano-scale width, which may lead to new applications in microscopy and sensing. The difficulty with implementing the V-groove is that the structure is not robust and is quite difficult to fabricate. This thesis aims to develop new triangular nano-focusing devices which will overcome these difficulties, whilst still producing an intense light source on the nano-scale. The two proposed structures presented in this thesis are a metallic wedge submerged in uniform dielectric and a tapered metal film lying on a dielectric substrate, the latter being the easier to fabricate and the more structurally sound and robust. The investigation is performed using the approximation of continuous electrodynamics, the geometrical optics approximation and the zero-plane method. The second aim of this thesis is to investigate plasmonic waveguides and couplers for the development of nano-optical circuitry, more compact photonic devices and sensors. The research will attempt to fill the gaps in the current knowledge of the V-groove waveguide, which consists of a sharp triangular groove in a metal substrate, and the gap plasmon waveguide, which consists of a rectangular slot in a thin metal film. The majority of this work will be performed using the author’s in house finite-difference time-domain algorithm and FEMLAB as well as the effective medium method and geometric optics approximation. The V-groove may be used as either a nano-focusing or waveguiding device. As a waveguide the V-groove is one of the most promising plasmonic waveguides in the optical regime. However, there exist quite a number of gaps in the current knowledge of V-groove waveguides which this thesis will attempt to fill. In particular, the effect of rounded groove tip on plasmon propagation has been assessed for the V-groove. The investigation of rounded groove tip is important, as due to modern fabrication processes it’s not possibly to produce an infinitely sharp groove, and the existing literature has not considered the impact of this problem. The thesis will also investigate the impacts of the inclusion of dielectric filling in the groove on plasmon propagation parameters. This research will be important for optimising the propagation characteristics of the mode for certain applications, but it may also lead to easier methods of fabricating the V-groove device and prevent oxidation of the metal film. The gap plasmon waveguide is easier to fabricate than the V-groove, and is a new type of sub-wavelength waveguide which displays many advantages over other types of plasmon waveguides, including ease of fabrication, almost 100% transmission around sharp bends, sub-wavelength localisation and long propagation distances of the guided mode, etc. This waveguide may prove invaluable in the development of compact photonic devices. In the past the modes supported by this structure were not thoroughly analysed and the possibility of using this structure to develop sub-wavelength couplers for sensing and nano-optical circuits was not considered in detail. This thesis aims to resolve these issues. In conclusion, the results of this thesis will lead to a better understanding of Vgroove and gap plasmon waveguide devices for the development of nano-optical circuits, compact photonic devices and sensors. This thesis also proposes two new nano-focusing structures which are easier to fabricate than the V-groove structure and will lead to applications in sensing, coupling light efficiently into nano-scale devices and improving the resolution of near-field microscopy.
4
Vernon, Kristy C. "Strongly localised plasmons in metallic nanostructures". Queensland University of Technology, 2008. http://eprints.qut.edu.au/19318/.
Abstract (sommario):
Strongly localised plasmons in metallic nano-structures offer exciting characteristics for guiding and focusing light on the nano-scale, opening the way for the development of new types of sensors, circuitry and improved resolution of optical microscopy. The work presented in this thesis focuses on two major areas of plasmonics research - nano-focusing structures and nano-sized waveguides. Nano-focusing structures focus light to an area smaller than the wavelength and will find applications in sensing, efficiently coupling light to nano-scale devices, as well as improving the resolution of near field microscopy. In the past the majority of nano-focusing structures have been nano-scale cones or tips, which are capable of focusing light to a spot of nano-scale area whilst enhancing the light field. The alternatives are triangular nano-focusing structures which have received far less attention, and only one type of triangular nano-focusing structure is known – a sharp V-groove in a metal substrate. This structure focuses light to a strip of nano-scale width, which may lead to new applications in microscopy and sensing. The difficulty with implementing the V-groove is that the structure is not robust and is quite difficult to fabricate. This thesis aims to develop new triangular nano-focusing devices which will overcome these difficulties, whilst still producing an intense light source on the nano-scale. The two proposed structures presented in this thesis are a metallic wedge submerged in uniform dielectric and a tapered metal film lying on a dielectric substrate, the latter being the easier to fabricate and the more structurally sound and robust. The investigation is performed using the approximation of continuous electrodynamics, the geometrical optics approximation and the zero-plane method. The second aim of this thesis is to investigate plasmonic waveguides and couplers for the development of nano-optical circuitry, more compact photonic devices and sensors. The research will attempt to fill the gaps in the current knowledge of the V-groove waveguide, which consists of a sharp triangular groove in a metal substrate, and the gap plasmon waveguide, which consists of a rectangular slot in a thin metal film. The majority of this work will be performed using the author’s in house finite-difference time-domain algorithm and FEMLAB as well as the effective medium method and geometric optics approximation. The V-groove may be used as either a nano-focusing or waveguiding device. As a waveguide the V-groove is one of the most promising plasmonic waveguides in the optical regime. However, there exist quite a number of gaps in the current knowledge of V-groove waveguides which this thesis will attempt to fill. In particular, the effect of rounded groove tip on plasmon propagation has been assessed for the V-groove. The investigation of rounded groove tip is important, as due to modern fabrication processes it’s not possibly to produce an infinitely sharp groove, and the existing literature has not considered the impact of this problem. The thesis will also investigate the impacts of the inclusion of dielectric filling in the groove on plasmon propagation parameters. This research will be important for optimising the propagation characteristics of the mode for certain applications, but it may also lead to easier methods of fabricating the V-groove device and prevent oxidation of the metal film. The gap plasmon waveguide is easier to fabricate than the V-groove, and is a new type of sub-wavelength waveguide which displays many advantages over other types of plasmon waveguides, including ease of fabrication, almost 100% transmission around sharp bends, sub-wavelength localisation and long propagation distances of the guided mode, etc. This waveguide may prove invaluable in the development of compact photonic devices. In the past the modes supported by this structure were not thoroughly analysed and the possibility of using this structure to develop sub-wavelength couplers for sensing and nano-optical circuits was not considered in detail. This thesis aims to resolve these issues. In conclusion, the results of this thesis will lead to a better understanding of Vgroove and gap plasmon waveguide devices for the development of nano-optical circuits, compact photonic devices and sensors. This thesis also proposes two new nano-focusing structures which are easier to fabricate than the V-groove structure and will lead to applications in sensing, coupling light efficiently into nano-scale devices and improving the resolution of near-field microscopy.
5
Zhao, Sicheng. "Interactive dynamics of fluid flow and metallic alloys solidification". Thesis, Aix-Marseille 3, 2011. http://www.theses.fr/2011AIX30010.
Abstract (sommario):
Nous avons étudié les phénomènes convectifs et leur interaction dynamique avec la formation des microstructures pendant la solidification dirigée d’alliages étalliquesbinaires.La méthode post-mortem a été utilisée d’abord pour étudier la Transition olonnaire-Equiaxe pendant la solidification dirigée d’échantillons cylindriques d’Al-3,5wt%Ni non affiné sous la Technique de Rotation Accélérée de Creuset. La simulation numérique a été éffectuée et acquérie les résultats en concordance avec les manipulations.La technique in-situ a été appliquée pour comprendre l’évolution en fonction de temps des grains pendant solidification d’Al-4wt%Cu. La caractéstiques tatistiques des grains ont été discutées.La convection d’instabilité déclenchée par la poussée ou la tension superfaciale sous les gradients thermiques verticale et horizontale dans un système de double couches liquide-zone poreuse ont réspectivement étudié par analysis d’instabilité linéaire.L’inhomogénéité de la perméabilité de zone pateuse dendritique a été tenue en compte afin de comprendre son influence sur le début de convection pendant la solidification dirigée d’Al-3,5wt%LiWe studied the convective phenomena and their dynamical interaction with the formation of the microstructurs during directional solidification of binary metallic alloys.The post-mortem method was used first to study the Columnar-Equiaxed-Transition during the directional solidification of unrefined Al-3.5wt%Ni in cylindric samples under the Accelerated Crucible Rotation Technique. The numerical imulation was carried out and achieved the results in agreement with experiments.The in-situ technique was applied to understand the evolution of equiaxed grains during solidification of Al-4wt%Cu in function of time. The statistical characteristics of equiaxed grains were discussed.The buoyancy-driven and surface-tension-driven instability convection under vertical and horizontal thermal gradients in a liquid-porous double-layered system were respectively investigated through linear instability analysis.The inhomogeneity of the dendritic mush permeability was taken into account in order to understand its influence on the triggering of convection during the directional solidification of Al-3.5wt%Li
6
Espinoza-Camino, P., I. Macassi-Jaurequi, C. Raymundo-Ibañez e F. Dominguez. "Warehouse management model using FEFO, 5s, and chaotic storage to improve product loading times in small- and medium-sized non-metallic mining companies". Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/656393.
Abstract (sommario):
This article addresses one of the main problems faced by small- and medium-sized business in the non-metallic mining sector in Peru. These companies own warehouses and face the major problem of failing to deliver orders correctly and in a timely manner. This problem usually occurs when the business grows from a small- to medium-sized company in a short span of time; this situation leads to new processes within warehouses that are mostly not standardized. Besides, facilities are no longer optimal in space and the workers are not properly trained. The case study shows that the orders were not delivered on time due to factors such as lack of product identification, although the products have an expiration date and a warehouse without signaling and surrounded by traffic. To tackle this situation, a labeling process has been designed for the products, an adequate distribution technique is used in the warehouse through a newly designed warehouse layout, and a First Expired, First Out system has been implemented. Similarly, the design is accompanied by the 5s tool to provide a basis for order and continuous improvement. The results show that deliveries with delays were reduced from 38% to 10%. These results show that companies can grow rapidly and maintain quality of service through orderly management.
7
Lecoq, Marie. "Étude du colmatage de filtres métalliques par un aérosol liquide". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0006.
Abstract (sommario):
Le confinement des installations industrielles susceptibles de contenir des matières dangereuses est assuré en grande partie par des filtres à très haute efficacité (THE) intégrés dans les réseaux de ventilation. Dans les procédés, mis en œuvre dans l'industrie nucléaire, certains scénarios accidentels peuvent conduire au dégagement de liquide sous forme de gouttelettes en suspension (aérosol liquide). Dans ce cas de figure, leur présence peut affecter les performances des filtres THE en engendrant une élévation rapide et importante de leur perte de charge pouvant conduire à une diminution notable du débit de ventilation, voire atteindre la limite de leur résistance mécanique et leur capacité à retenir les contaminants aéroportés. Pour pallier ce problème, une des solutions envisagées est l'utilisation d'un préfiltre à fibres métalliques (plus résistant mécaniquement mais moins efficace) pour protéger le filtre THE constituant le dernier niveau de filtration ou pour à minima augmenter sa durée de vie en cas de scénarios accidentels. Afin de valider cette solution, il est nécessaire d'étudier, face à un aérosol liquide, le comportement de ces préfiltres composés par un empilement de plusieurs monocouches de médias de caractéristiques différentes. Les différents médias métalliques testés ont été caractérisés, dans un premier temps, en termes d'épaisseur, de compacité et de distribution granulométrique de fibres. L'évolution de l'efficacité de collecte et de la perte de charge au cours du colmatage par un aérosol liquide DEHS a ensuite été étudiée à différentes vitesses de filtration (0,9 à 18 cm/s). On retrouve l'évolution classique décrite dans la littérature : augmentation quasi-linéaire de la perte de charge avant une croissance exponentielle et une stabilisation. Les médias multicouches présentent, cependant, une phase de stabilisation de la perte de charge plus progressive comparativement aux monocouches. Un scénario de colmatage a été proposé et un modèle simpliste d'évolution de la perte charge en fonction de la masse de liquide accumulé au sein du filtre est présenté pour les médias monocouches. Afin de figer le liquide accumulé au sein du média et permettre une visualisation par micro-tomographie X des médias partiellement ou totalement colmatés, des résines thermodurcissables ont été testées. Les premiers résultats ont mis en évidence une perte de volume des résines trop importante après séchage ce qui rend difficile l'interprétation des clichés obtenusIndustrial installations often contain hazardous materials in aerosol form. High efficiency filters (HEPA) are usually the last barrier that ensure the containment of these airborne particles. In the nuclear industry, a large amount of radioactivity is handled in liquid form, that may release, in few scenarios, liquid aerosols. These particles may affect the performance of HEPA filters with a huge increase of the pressure drop, which lead in return to a significant reduction of the ventilation flowrate. In such scenarios the pressure drop increase may exceed the filter mechanical strength and induce degradations of the media and leading to a deterioration of its capacity to retain aerosol pollutants. To overcome this problem, and to protect HEPA filter, one of the solutions is to use pre-filter (more mechanically resistant but less efficient) made up with metallic fibers. To validate this approach, it is necessary to study the behavior of these prefilters, composed of a stack of different monolayers of media. In my work, I first focused on the clogging of industrial prefilters with liquid aerosol particles. Then, for a more analytical study, I study the clogging each layer separately, in order, to model, on the future, the behavior of the assembly. The microphysical of each media (thickness, packing density, and fiber size distribution) are determined. The evolution of both filter collection efficiency and pressure drop are studied along the clogging by a submicron liquid aerosol DEHS, for different filtration velocity (0,9 à 18 cm/s). For monolayer filters, I measure pressure drops in line with the previous results found in the literature. These experiments first highlight a quasi-linear increase of the pressure drop, associate with a collection of the droplets by the fibers. Then an exponential growth is measures, that corresponds to the clogging of the pores. And finally, an abrupt stabilization is observed corresponding a liquid film formation and its continuous drainage by the airflow. However, I show a more gradual stabilization for multilayer filters. A clogging scenario is proposed, and a simplistic model is established to forecast the pressure drop as a function of the mass of liquid accumulated. To this aim, I develop a new method to freeze the liquid accumulation using resin, that where further analyze using X-ray tomography
8
Deng, Xiaodong. "Nondestructive evaluation of thermal sprayed coating by acoustic microscopy and Eddy current testing". Thesis, Lyon, INSA, 2014. http://www.theses.fr/2014ISAL0030/document.
Abstract (sommario):
La thèse a mis en œuvre deux méthodes inverses pour l’évaluation non destructive d’un milieu multicouche anisotrope : la microscopie acoustique et les courants de Foucault. Pour la microscopie acoustique, nous avons adapté un modèle de propagation de l'onde acoustique dans un milieu multicouche, en calculant les coefficients de réflexion et de transmission d’un revêtement multicouche sur un substrat et en modélisant la réponse acoustique V(z) propre à la microscopie acoustique. Une méthode inverse utilisant l’algorithme de Levenberg-Marquardt donne accès à l’épaisseur, au module de Young et à la densité du revêtement. Pour les courants de Foucault, une méthode inverse similaire basée sur le formalisme de Tree a été mise au point, qui donne accès à l’épaisseur, à la conductivité électrique et à la perméabilité magnétique du revêtement. Après des vérifications de l’algorithme sur des matériaux massifs de référence, nous avons appliqué ces méthodes à un métal revêtu pour tuyauteries de centrale thermique : de l’acier inoxydable austénitique type 304 revêtu par pulvérisation thermique de superalliage Hastelloy C22 à base de nickel. La corrosion sèche sous l’effet des gaz chauds (air contenant du gaz SO2) amincit graduellement la paroi des tubes, ce qui peut les rendre dangereux. Il a fallu tenir compte de l’effet du grenaillage préalable à la pulvérisation, qui crée une mince couche de martensite à laquelle les courants de Foucault sont très sensibles : un modèle à trois couches substrat / martensite / revêtement a été utilisé. Nous avons caractérisé des échantillons de métal avant et après exposition à l’air avec ou sans SO2 à 650°C. Les deux méthodes d’évaluation non destructive permettent une détermination très satisfaisante de l’épaisseur de revêtement et se complètent bien. L’évaluation des caractéristiques physiques (acoustiques et électromagnétiques) met en évidence des hétérogénités du revêtement liées à son mode d’élaboration et des évolutions au cours du temps. Des pistes d’amélioration des méthodes sont proposéesIn the current work, we investigate the nondestructive evaluation of a thermal sprayed coating (Hastelloy C22 Ni-based alloy) on substrate (type 304 austenitic stainless steel) using acoustic microscopy and ECT method. Two models were built for the evaluation of this kind of material: one is for acoustic V(z) measurement and the other is for swept eddy current measurement. The implementation of these two models is used for the evaluation and properties measurement of the thermal sprayed coatings, such as elastic properties, electromagnetic properties. In particular, the main achievements and results are as follows: 1. Acoustic wave propagation in an anisotropic multilayered medium was investigated. The formula for calculating the reflection and transmission coefficients of the multilayered medium on or without a substrate were derived, which is necessary for the modeling of acoustic V(z) measurement of the thermal sprayed coating on substrate. 2. A model was built for the acoustic V(z) measurement of the thermal sprayed coatings on substrate, which can deal with anisotropic multilayered media. Specifically, we used a model of multilayered coatings with graded properties on substrate to calculate the acoustic reflection coefficient of our sample. Treating the thermal sprayed coating, deposited on a 304 steel substrate, as FGMs, we evaluated the coating thickness and the Young’s modulus evolution along the depth of the coating. 3. A model was built for the swept eddy current measurement of the thermal sprayed coatings. Since before the spraying process, the surface of the substrate is usually shot-peened (SP), the coated material is considered as a three-layer medium. The coating thickness and electromagnetic properties of each of the 3 layers were determined by an effective reverse process. 4. The thermal sprayed coated material after exposure in different conditions, i.e., as-received, heat-treated in air and heat-treated in SO2 environment, and after different exposure time was evaluated by the integrity of acoustic microscopy and ECT method. The coating thickness and the electromagnetic properties of the coated material under different conditions were measured
9
Al, Husseny Adel Ahmed Niameh Mehdy. "Heat transfer enhancement using rotating metallic porous media". Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/heat-transfer-enhancement-using-rotating-metallic-porous-media(1a50759b-fd87-4836-b7ab-5fa0ab6d6c5d).html.
Abstract (sommario):
The present research is dedicated to numerically optimise the heat transfer enhancement achieved by means of utilising rotating metallic porous media. Three systems that play a crucial role in power generation systems are examined. The first is the cooling passages used to dissipate the heat generated within the rotor conductors in electrical generators, the second is the double pipe-heat exchanger, and the last is the rotary thermal regenerator. In all of the systems under consideration, the main objective is to improve the overall performance achieved and to determine the optimum values of the parameters affecting it. Concerning the first system examined, an enhancement way is proposed through filling such rotating cooling passages either fully or partially with open-cell metal foams. A compound heat transfer enhancement is utilised in the second system through applying an axial rotation to a double-pipe heat exchanger occupied with open-cell metal foams structures. The enhancement process carried out using the third system is examined through proposing an effective and less-costly way to simulate and design rotary regenerators based on a porous medium approach. The developing three-dimensional convective fluid flow across the porous media utilised in all the systems investigated is considered laminar and incompressible. Both thermal dispersion and rotational effects, including centrifugal buoyancy and Coriolis force, are taken into account in the first and second systems, while they are neglected in the latter. The momentum equations are mathematically formulated using the generalised model with considering that fluid and solid phases are in a local thermal non-equilibrium. The governing equations are discretised based on the finite volumes method and then solved iteratively using the SIMPLE algorithm, where an in-house FORTRAN code has been developed to investigate the first system, while the other two systems have been simulated using the STAR-CCM+ CFD commercial code. Inspecting the worth of using metal foams to enhance the heat dissipated by the rotating channels reveals the potential of this proposal to outperform the turbulent flow in rotating clear channels, which confirms that this enhancement way is practically justified and efficient. Moreover, the overall system performance achieved using the compound enhancement employed in the second system is incomparable, i.e. OSP=O(102). The porous medium approach, on the other hand, has been found to be sufficient to accurately simulate the convective flow across the third system. Hence, it can be utilised as an effective and more economical alternative to design such sort of heat exchangers rather than the traditional experimental or numerical ways. The resulted data reveal that heat transfer can be improved considerably by manipulating the design factors including the operating conditions as well as the geometrical and thermal characteristics of the porous medium used. However, care must be taken to avoid unnecessary expenses resulting from potential augmentation in pressure drop.
10
Mansour, Yehia. "Études théorique et expérimentale de la formation des nanoparticules métalliques par ablation laser en milieu liquide. Modélisations des propriétés optiques et thermiques de l'interaction Laser-Nanoparticules". Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0283.
Abstract (sommario):
Les nanoparticules (NPs) de métaux nobles sont le siège d’un phénomène de résonance plasmon de surface résultant de l’oscillation collective de leurs électrons de conduction sous l’effet d’une onde électromagnétique. Dans le cas de NPs d’or et l’argent, la fréquence de résonance est située dans visible ce qui confère à ces NPs plasmoniques des propriétés optiques uniques. En particulier, la position et l’intensité de la bande de résonance plasmon peuvent varier en fonction de leur taille, leur forme (rapport d'aspect) et de l'indice du milieu hôte. Les possibilités d’applications nécessitent des échantillons purs et de distribution mono disperse. La synthèse des NPs par voie chimique permet de contrôler dans une certaine mesure la forme et la taille des NPs. Elle nécessite cependant l’utilisation d’agents stabilisants qui mènent à une contamination de surface par les résidus de synthèse. Pour limiter cet inconvénient, la technique physique d’ablation laser en milieu liquide est une alternative prometteuse qui souffre cependant d’un manque de contrôle de la forme et de la taille des NPs produites. La forme et la taille des NPs élaborées par ablation laser en milieu liquide (ALML) sont étroitement liées aux trois étapes essentielles du processus : Interaction cible/laser ; Transport de masse ; Interaction laser/NPs en suspension dans le liquide. Afin d’appréhender les mécanismes régissant chacune de ces étapes, il est nécessaire de les étudier séparément. Dans ce travail, nous nous sommes focalisés sur les mécanismes d’interaction entre le faisceau laser et les NPs en suspension dans le liquide. Suivant la densité d’énergie absorbée par les NPs en suspension, celles-ci subissent la fragmentation ou le remodelage. Par la suite nous avons étudié les mécanismes à l’origine du phénomène de la fragmentation. L’évolution de la distribution de forme des NPs lors de la fragmentation des NPs a été étudiée en développant une technique originale et quantitative de spectroscopie optique in-situ. De même, l’évolution de la fraction volumique des NPs au cours de leur élaboration par ALML par spectroscopie optique in-situ est obtenue et analysée. En parallèle aux travaux expérimentaux, nous avons développé des modèles théoriques pour la compréhension des mécanismes de formation des nanoparticules métalliques par ablation laser en un milieu liquide. Une autre étude approfondie sur la modélisation des propriétés optiques et thermiques de l'interaction Laser-Nanoparticules est discutée dans cette thèse. Un modèle thermique de Takami modifié nommé MTM (Modified Takami Model) a été également introduit. Son utilité importante a été démontrée pour l’interprétation des mécanismes de l’interaction laser-NPsNoble metal nanoparticles (NPs) are the site of a surface plasmon resonance phenomenon resulting from the collective oscillation of their conduction electrons under the effect of an electromagnetic wave. In the case of gold and silver NPs, the resonant frequency is in the visible range, which gives these plasmonic NPs unique optical properties. In particular, the position and intensity of the plasmon resonance depend on their size, shape (aspect ratio) and the index of the host medium. The possible applications require pure samples and mono-dispersed distribution. The chemical synthesis of NPs allows the shape and size of NPs to be controlled. However, it requires the use of stabilizing agents, which lead to surface contamination by synthetic residues. To limit this disadvantage, the physical technique of laser ablation in a liquid medium is a promising alternative, which, however, suffers from a lack of control over the shape and size of the NPs produced. The shape and size of NPs produced by liquid laser ablation (ALML) are closely related to the three essential steps of the process: Target / laser interaction; Mass transport; Laser / NPs interaction suspended in the liquid. In order to understand the mechanisms governing each of these stages, it is necessary to study them separately. In this work, we focused on the mechanisms of interaction between the laser beam and the NPs suspended in the liquid. Depending on the energy density absorbed by the suspended NPs, they undergo fragmentation or remodeling. We then studied the mechanisms behind the phenomenon of fragmentation. The evolution of the shape distribution of NPs during NP fragmentation was studied by developing an original and quantitative technique of in-situ optical spectroscopy. And, the evolution of the volume fraction of NPs during their preparation by ALML by in-situ optical spectroscopy is obtained and analyzed. In parallel with the experimental work, we have developed theoretical models for understanding the mechanisms of formation of metallic nanoparticles by laser ablation in a liquid medium. A modest study on the modeling of optical and thermal properties of the Laser-Nanoparticle interaction is discussed in this thesis. A modified Takami thermal model named MTM was also presented. Its important utility has been demonstrated for mechanisms for the interpretation of the mechanisms of laser-NPs interaction
11
Lappas, Ingo. "Heterogene Katalyse in überkritischen Medien Charakterisierung von Metall- und Legierungskatalysatoren /". [S.l. : s.n.], 2001. http://elib.tu-darmstadt.de/diss/000179.
12
Behra, Philippe. "Etude du comportement d'un micropolluant metallique (le mercure) au cours de sa migration a travers un milieu poreux sature : identification experimentale des mecanismes d'echanges et modelisation des phenomenes". Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13120.
13
AL-Ghezi, Hammid. "Optical Propagation in Anisotropic Metamaterials: Application to Analysis and Design of Metallo-Dielectric Filters". University of Dayton / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1628263495632462.
14
Hübschen, Bettina. "Grundlagenuntersuchungen zur Tiefenfiltration von Metallen /". Aachen : Shaker, 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=013109603&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
15
Klement, Kai. "Nichtgleichgewichtsdefekte in extrem verformten Metallen /". Göttingen : Sierke, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016072212&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
16
SANNA, ALESSANDRO. "Studio di un modello di correlazione tra la fluttuazione del tenore di metalli pesanti e di altri fattori ambientali e la salute umana in Sardegna". Doctoral thesis, Università degli Studi di Cagliari, 2016. http://hdl.handle.net/11584/266896.
Abstract (sommario):
Since the first half of the 20th century, the incidence of Multiple Sclerosis (MS), Type 1 Diabetes (T1D) and
Autism Spectrum Disorders (ASDs) has increased in Sardinia. T1D results from autoimmune destruction of
insulin, producing beta cells of the pancreas; MS is a chronic disease of the central nervous system, causing
neurological affliction; Autism is defined as a complex developmental disability that generally appears
during the first three years of life. Concerning MS and T1D, Sardinia island has one of the highest incidence
rate in the world. In this island, there is the presence of phenotypes of these diseases, due to the
homogeneous genetic background of the local population. Indeed, Sardinia population is a genetic isolate.
The genetic background by itself does not explain such increasing incidence. T1D and MS increase with
latitude, but Sardinia is an exception. Furthermore, mining exploitation was one of the most important
economic activities in Sardinia during the past centuries and a lot of data are today available for the
researchers. For this reasons Sardinia is an ideal setting to study a possible correlation between
environmental factors and the diseases above, because of sardinian people genetic background and
environmental peculiarities of the island.
A set of environmental data and the frequency data of MS, T1D and ASD were investigated to evaluate the
correlation between environmental factors and the frequency of these diseases. In particular, among the
environmental factors, geochemical data are included in the Geochemical Database of the Department of
Civil, Environmental Engineering and Architecture (DICAAR) of the Cagliari University. This Database is
populated by thousands of data concerning soils, rocks and stream sediments. A stream-sediment-type
sampling, which is widely used for mineral prospecting, has the advantage of effectively representing the
overall geochemical print of a wide portion of territory such as a stream basin. Environmental and diseases
data were analyzed through the statistical methods which were used by mining prospections activities.
Environmental factors considered in this study are: geochemical values of each lithology, lithology and
geology, sun exposure and climate. Also spatial analysis distribution of MS, T1D and ASDs was done.
Therefore, a correlation between the environmental factors in reference to the total population and the
frequency of the diseases was evaluated. Moreover, the correlation between the environmental factors in
both male and female population and the frequency of the diseases was investigated. In a first time these
relationships were investigate for each municipalities. Afterwards, 109 Homogeneous Areas (HA) from
lithological point of view were identified. Each Homogeneous Area includes one or more municipalities,
which have the same lithological features. Then, the relationship between the environmental factors and the
frequency of diseases was evaluated for each HA.
About T1D analyses, they revealed negative associations between the incidence of the disease and some
elements, such as Cu (r = -0.349, Pvalue = 2*10-4) and Zn (r = -0.332, Pvalue = 4.20*10-4), while, concerning
MS, a mild correlation was present between Cu (r = -0.460, Pvalue = 1*10-3) and the distribution of the
disease in the male gender. A significant correlations was calculated among Pb (r = 0.478, Pvalue = 3.43*10-
6), Cd (r = 0.412, Pvalue = 8.10*10-5), Zn (r = -0.378, Pvalue = 3.3*10-4) and the presence of ASDs.
In this research was used for the first time a geo-epidemiological approach to identify environmental factors
involved to the geographical distribution of above diseases. Moreover, the elements significantly correlated
with MS, T1D and ASDs could be markers (pathfinders) of other elements not analyzed in this study
(confounding), but they could be potentially involved on the onset of the diseases. Also, our results should be
considered as hypothesis-generating rather than hypothesis testing study. This kind of study is unusual and it
has a deep interdisciplinary approach so the present results must be better confirmed in future studies.
17
Metreveli, George [Verfasser], e F. [Akademischer Betreuer] Himmel. "Kolloidale Wechselwirkungen und kolloidgetragener Transport von Metall(oid)en in porösen Medien / George Metreveli. Betreuer: F. Himmel". Karlsruhe : KIT-Bibliothek, 2008. http://d-nb.info/101369628X/34.
18
Ievsieieva, Ievgeniia. "Simulação com o código GEANT4 de medida de espessura de revestimento metálico em metal por XRF". Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=4154.
Abstract (sommario):
Conselho Nacional de Desenvolvimento Científico e TecnológicoNesta dissertação são apresentados resultados de simulações Monte Carlo de fluorescência de raios X (XRF), utilizando o programa GEANT4, para medidas de espessura de revestimento metálico (Ni e Zn) em base metálica (Fe). As simulações foram feitas para dois tamanhos de espessura para cada metal de revestimento, (5μm e 10μm), com passos de 0,1 μm e 0,001 μm e com 106 histórias. No cálculo da espessura do revestimento foram feitas as aproximações de feixe de raios X monoenegético, com a análise da transmissão apenas da energia do K-alfa e para uma geometria compatível com um sistema real de medição (ARTAX-200). Os resultados mostraram a eficiência da metodologia de simulação e do cálculo da espessura do revestimento, o que permitirá futuros cálculos, inclusive para multirevestimentos metálicos em base metálica.
This dissertation is presented results of x-ray fluorescence (XRF) Monte Carlo simulations) using GEANT4 for metallic coating (Ni and Zn) thickness determination on metallic base (Fe). The simulations were made for two values of coating thickness for each covering (5 μm and 10 μm), with steps of 0.1 μm and 0.001 μm, and with 106 stories. The monoenergetic x-ray approach was used assuming the transmission of only K-alpha line. The experiment and geometry was similar to the real system of measurement (ARTAX-200 ). The results showed the efficiency of the simulation methodology, as well as the ability to measure the thickness of coating by XRF. Thus, a continuation of this study for multilayer metal coating could be promising.
19
Klages, Kilian. "Laserstrahl-Mikroschweissen ungleicher Metalle durch Nahtschweissen mit gepulsten Nd:YAG-Lasern /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016030450&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
20
Thielecke, Frank. "Parameteridentifizierung von Simulationsmodellen für das viskoplastische Verhalten von Metallen : Theorie, Numerik, Anwendung /". Braunschweig : Mechanik-Zentrum, 1998. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=015613208&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
21
Ma, Anxin. "Modeling the constitutive behavior of polycrystalline metals based on dislocation mechanisms /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014901396&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
22
Näslund, Jan. "Solvated trivalent metal ions in solution : a coordination chemistry study /". Uppsala : Swedish University of Agricultural Sciences, 2000. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=009419319&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
23
Mandt, Dietmar. "Eigenschaften und Einsatzverhalten von leichten und dämpfenden Werkstoffverbund-Zahnrädern /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014919182&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
24
Hiess, Arno. "Untersuchungen zur Konkurrenz der magnetischen Wechselwirkungen in elektronisch hochkorrelierten Metallen : Neutronenstreuung - magnetische Röntgendiffraktion Mössbauer-Spektroskopie - Magnetisierungsexperimente /". Aachen : Shaker, 1997. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=007536200&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
25
Fuhrmann, Tino Hahn Ortwin. "Zur Berechnung von Klebverbindungen in Fahrzeugstrukturen aus Faser-Kunststoff-Verbunden und Metallen mit Hilfe der Finiten Elemente Methode /". Aachen : Shaker, 2007. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016685468&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
26
Richter, Karsten. "Untersuchungen zum Einsatz von frei modulierbaren gepulsten Nd:YAG-Laserstrahlquellen für das Schweissen von Refraktärmetallen /". Aachen : Shaker, 2006. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016151308&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
27
Willach, Jens. "Herstellung von konturierten Bohrungen in Mehrschichtsystemen mit Nd:YAG-Laserstrahlung /". Aachen : Shaker, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014833932&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
28
Geldern, Maike van. "Herstellung von hochschmelzenden Metallmatrix-Verbundwerkstoffen durch Schleudergiessen /". Aachen : Shaker, 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014709815&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
29
Terçariol, Walter Luis 1975. "Contribuição ao projeto de circuitos integrados de reguladores de tensão com charge pump em tecnologia CMOS : aceleração do tempo de partida, redução do ripple, redução do efeito kick-back e técnica indireta de medida da tensão de saída". [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/260876.
Abstract (sommario):
Orientador: José Antonio Siqueira DiasTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
Made available in DSpace on 2018-08-26T13:53:46Z (GMT). No. of bitstreams: 1 Tercariol_WalterLuis_D.pdf: 1322557 bytes, checksum: 4f45518a1a62907cd9a61afa627408c3 (MD5) Previous issue date: 2014
Resumo: Este trabalho visa compilar três contribuições na melhoria dos projetos de reguladores de tensão com unidades de bombeamento de carga embutidos (células elevadoras de tensão Dickson - BC). A primeira aborda uma técnica inovadora de arranque na partida deste módulo elevador quando habilitado. Este projeto se refere à aceleração da inicialização do modulo BC, tendo como objetivo a diminuição do intervalo de tempo da rampa ascendente da tensão de saída Vo até atingir o nível alvo de regulação. A técnica consiste em gerenciar o aumento da freqüência do relógio de bombeamento entregue as unidades de bombeamento durante a fase de subida, quando a regulação estiver estabelecida o sistema se regenera voltando ao estado original de freqüência de bombeamento natural. Uma segunda proposta inovadora de projeto é referente à homogeneização e redução da aleatoriedade da ondulação da tensão de saída Vo, referente ao regulador com o modulo BC embutido, baseado em comparadores com trava, com proposta de redução do erro de comparação devido ao efeito aleatório durante o estagio de comparação comumente encontrado neste tipo de abordagem, a técnica consiste em suprimir o acoplamento capacitivo nocivo durante a fase de isolamento elétrico no processo de comparação mantendo o espelho de corrente do comparador na região de saturação. Esta técnica visa proporcionar uma redução significativa da capacitância de desacoplamento utilizada para filtragem da tensão Vo. Uma terceira e última contribuição é referente a uma inovadora técnica de medição indireta da tensão de saída Vo do regulador com módulo BC baseada em uma medida simples e precisa dos pares tensão da porta e fonte (VPS) e corrente elétrica do dreno (Idreno) de um dispositivo NMOS de alta tensão adicionado de modo que duas tensões conhecidas (preestabelecidas) são aplicadas na porta do dispositivo e as respectivas correntes de dreno são mensuradas e uma terceira desconhecida (oriunda do regulador elevador BC) desconhecida pode ser extrapolada de forma simples. Esta técnica visa ser útil para medição de reguladores de baixa potencia pois o carregamento do regulador (Vo) é quase nulo.Todas as inovações e melhorias propostas foram analisadas em veículos de teste (silício) e com as provas de conceito, feitas em simulações elétricas
Abstract: This work aims to compile contributions in improving designs based on voltage regulators with voltage elevator with built-in charge pump CP. The first deals with an innovative technique rump-up this module when enabled. This project refers to the acceleration of startup the CP module, aiming at the reduction of the period of stabilization of the ramp output voltage Vo to the level of regulation target. The technique is to manage increasing the frequency of pumping clock during the phase of rump up and when the setting established the system regenerates back to the original state pumping frequency. A second innovative project proposal was made on the homogenization and reduction of the ripple of the output voltage Vo, referring to the regulator with the |CP module, based on latch comparators , alignment error reduction proposal because of the random effect during the stage comparison commonly found in this type of approach, the technique is to remove the harmful capacitive coupling during electrical isolation phase on the comparison keeping the comparator current mirror in saturation region. This technique aims to provide a significant reduction in the decoupling capacitance used for filtering the voltage Vo. A third and final contribution is related to an innovative technique of indirect measurement of the output voltage Vo of the regulator module CP, based on a simple and accurate measure of the gate voltage and couples the drain electric current of a high voltage NMOS device
Doutorado
Eletrônica, Microeletrônica e Optoeletrônica
Doutor em Engenharia Elétrica
30
Yeh, Chih-Ting, e 葉致廷. "Experimental Study of Free Convection Heat Transfer in the Metallic Porous Medium Heat Sink for LED Lamp". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/78460533427921265582.
Abstract (sommario):
碩士建國科技大學
機械工程系暨製造科技研究所
100
This study experimentally investigated the free convective heat transfer characteristics of annular and fin shaped metal foam heat sinks applied to the cooling of LEDs. The basic body of the heat sink made of aluminum alloy was an annular cup with/without radially fins, and had 76 mm in diameter, 14.6mm in height and 3mm in thickness. The annular metal foam heat sink was to cover the annular 0.97-porosity copper foam layer onto the external surface of the annular cup; while the fin shaped metal foam heat sink was to attach the 0.97-porosity cooper foam plates at both sides of each fin of the finned annular cup. The variable parameters were the difference of the temperatures between the heated surface and the environment (ΔT=30~60℃), the pore density of the copper foam material (PPI=20, 30 and 40), the thickness of the annular foam layer (tc=5, 11 and 14.5mm), the fin number (n=7, 8 and 9), the fin length (t=5 and 11mm), and the thickness of the copper foam plates attached onto the fins (s=5, 8 and 11mm). The experimental results indicate that, for annular metal foam heat sinks with tc=5mm, the heat transfer coefficient (h) would drop with increase of PPI. However, the heat transfer coefficient (h) would rise with increase of PPI as tc=11 and 14.5mm. The PPI effect showed reverse about at tc=6.5~7.5mm. For the fin shaped metal foam heat sinks with s=5mm, the effect of PPI on the heat transfer was insignificant. In addition, as the rise of the s, the heat transfer coefficient (h) wound be elevated with increase of the PPI. Among the current test cases, the fin shaped metal foam heat sink with 40PPI, n=9, t=11mm and s=11mm has the maximum free convective heat transfer capacity.
31
Zhen, Yurong. "Plasmonic properties and applications of metallic nanostructures". Thesis, 2013. http://hdl.handle.net/1911/72071.
Abstract (sommario):
Plasmonic properties and the related novel applications are studied on various
types of metallic nano-structures in one, two, or three dimensions. For 1D nanostructure,
the motion of free electrons in a metal-film with nanoscale thickness is confined in
its normal dimension and free in the other two. Describing the free-electron motion at
metal-dielectric surfaces, surface plasmon polariton (SPP) is an elementary excitation
of such motions and is well known. When further perforated with periodic array of
holes, periodicity will introduce degeneracy, incur energy-level splitting, and facilitate
the coupling between free-space photon and SPP. We applied this concept to achieve
a plasmonic perfect absorber. The experimentally observed reflection dip splitting
is qualitatively explained by a perturbation theory based on the above concept. If
confined in 2D, the nanostructures become nanowires that intrigue a broad range of
research interests. We performed various studies on the resonance and propagation
of metal nanowires with different materials, cross-sectional shapes and form factors,
in passive or active medium, in support of corresponding experimental works. Finite-
Difference Time-Domain (FDTD) simulations show that simulated results agrees well
with experiments and makes fundamental mode analysis possible. Confined in 3D,
the electron motions in a single metal nanoparticle (NP) leads to localized surface
plasmon resonance (LSPR) that enables another novel and important application:
plasmon-heating. By exciting the LSPR of a gold particle embedded in liquid, the
excited plasmon will decay into heat in the particle and will heat up the surrounding
liquid eventually. With sufficient exciting optical intensity, the heat transfer from NP
to liquid will undergo an explosive process and make a vapor envelop: nanobubble.
We characterized the size, pressure and temperature of the nanobubble by a simple
model relying on Mie calculations and continuous medium assumption. A novel
effective medium method is also developed to replace the role of Mie calculations.
The characterized temperature is in excellent agreement with that by Raman scattering.
If fabricated in an ordered cluster, NPs exhibit double-resonance features and
the double Fano-resonant structure is demonstrated to most enhance the four-wave
mixing efficiency.
32
Power, Sean Michael. "An appraisal of homoeopathic quinquagenimillesimal potencies of plumbum metallicum and stannum metallicum by means of nuclear magnetic resonance spectroscopy". Thesis, 1999. http://hdl.handle.net/10321/2697.
Abstract (sommario):
Dissertation submitted in partial compliance with the requirements for the Master's Degree in Technology: Homoeopathy, Technikon Natal, 1999.The purpose of this study was to investigate the Nuclear Magnetic Resonance spectra of samples of LM6; LM14 and LM22 homoeopathic quinquagenimillesimal (LM) potencies of tin (Stannum metallicum), lead (Plumbum metallicum) and two lactose based controls: one control which is prepared by the means of potentisation and one control prepared without the means of potentisation. It was hypothesised that in terms of the effect of different substances (Stannum metallicum and Plumbum metallicum, and the lactose controls) and of different dilutions (LM6, LM14, LM22) of these substances that significant differences exist between the chemical shift and relative integration values of the CH3, CH2, OH and H20 signals of these homoeopathic substances.
M
33
Lappas, Ingo [Verfasser]. "Heterogene Katalyse in überkritischen Medien : Charakterisierung von Metall- und Legierungskatalysatoren / vorgelegt von Ingo Lappas". 2001. http://d-nb.info/963635239/34.
34
Gioka, Christiana. "Characterization of substances released from polymeric and metallic orthodontic materials and assessment of their biological properties /". 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=013070147&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
35
Vaithilingam, Vimlen. "The effectiveness of a homoeopathic complex (Germanium metallicum 30CH, Nux vomica 12CH, Kalium phosphoricum 6CH, Picricum acidum 6CH) in the treatment of job burnout in the human services field". Thesis, 2008. http://hdl.handle.net/10321/464.
Abstract (sommario):
Dissertation submitted in partial compliance with the requirements of the Master’s Degree in Technology: Homoeopathy, in the Faculty of Health Sciences at the Durban University of Technology, 2008.The purpose of this double blind placebo-controlled study was to evaluate the efficacy of a homoeopathic complex (Germanium metallicum 30CH, Nux vomica 12CH, Kalium phosphoricum 6CH, Picricum acidum 6CH) in the treatment of job burnout in the human services field. In total 30 participants were chosen according to specific inclusion and exclusion criteria. The sample group was then randomly divided into a treatment group consisting of 15 participants, and a placebo group consisting of 15 participants. The study was conducted at the Durban University of Technology. The Maslach Burnout Inventory – Human Services Survey (Appendix A) was used as a measurement tool. There was an initial consultation with the researcher which consisted of a full consultation, physical examination and administration of the survey. Thereafter there were two follow-up consultations at 4 week intervals at which the survey was re-administered. Medication was dispensed to the participants at the initial and the first follow up consultations only. The data obtained from the Maslach Burnout Inventory – Human Services Survey was statistically analysed using the SPSS software package (Version 15). Due to the small sample size of the study non-parametric tests were conducted. The intra-group analysis was performed using Friedman‟s Test and Wilcoxon‟s Signed Rank Test. The inter-group analysis was performed using the Kruskal-Wallis Test. Friedman‟s Test indicated a significant improvement in the emotional exhaustion subscale for both the treatment and placebo groups. The subscales of depersonalisation and personal accomplishment did not however reflect a significant difference.The Wilcoxon‟s Signed Rank Test indicated that for both groups there was a significant improvement in the emotional exhaustion subscale between baseline and follow up 1 and between follow up 2 and baseline (i.e. P<0.05). The Kruskal-Wallis Test showed no significant difference between the treatment and placebo groups. This was the case for all three subscales of the Maslach Burnout Inventory – Human Services Survey. The results of the study led to the conclusion that statistically the homoeopathic complex (Germanium metallicum 30CH, Nux vomica 12CH, Kalium phosphoricum 6CH, Picricum acidum 6CH) was not effective in the treatment of job burnout.
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Damerau, Georg. "Werkstoffwissenschaftliche Untersuchung eines experimentellen Verfahrens zur Herstellung eines Verbundes zwischen Metall und Verblendkunststoff /". 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014710821&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Füngling, Georg. "Der Einfluss der Oberflächenkonditionierung auf den Metall-Keramik-Haftverbund von CAD-CAM-gefertigten Restaurationen /". 2005. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=014282972&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.