Thin silver films are widely used in low-emissivity coatings for building glazing due to their high reflectance in the infrared and high transmittance in the visible spectrum. The determining parameter for the infrared reflectance is the electrical conductance of the layer stack - the better the conductance the higher the reflectance. Electrically conductive films of thicknesses smaller than the electron mean free path exhibit a strong increase in the residual resistivity proportional to the inverse of the film thickness. Despite intensive discussions, which have extended over tens of years, it is not understood yet if this conductive behavior originates from electron scattering at interfaces (Fuchs-Sondheimer model) or grain boundaries (Mayadas-Shatzkes model). To achieve a fundamental understanding of the prevailing electron scattering mechanisms, aluminum-doped zinc oxide (ZnO:Al) / Ag / ZnO:Al layer stacks produced by magnetron sputtering were investigated concerning their electronic structure and electrical transport properties. The electronic structure of the layer stacks was probed and analyzed by electron energy-loss spectroscopy. By this technique, plasmonic excitations are observed, which can be categorized into excitations of the electrons in the bulk silver and excitations at the ZnO:Al / Ag interface. The plasmons were analyzed with respect to their dispersion and the peak width, and brought into relation with electrical conductivity measurements by calculating the plasmon lifetime and the electron scattering rate. The difficulty in determining the relative contributions of the interface and grain boundary scattering in experimental conditions is due to the fact that the way in which these scattering mechanisms depend on the film thickness, is very similar. Understanding the electron transport in thin films is of paramount importance, because the differentiation between the scattering mechanisms is a key issue for the improvement of the coatings. In the present work, the solution came from the expected difference in the temperature-dependent behavior of the resistivity between electron scattering at interfaces and electron scattering at grain boundaries. Hence, the resistivity was measured as a function of the temperature on layer stacks with different silver film thickness varying in the range of 4 to 200 nm. The data were analyzed using the extended Mayadas-Shatzkes model involving both electron scattering at interfaces (Fuchs-Sondheimer model), and electron scattering at grain boundaries. The results demonstrate that electron scattering at grain boundaries dominates for all film thicknesses. The basic layer stack was compared to more sophisticated systems, obtained either by adding a thin titanium layer in between silver and ZnO:Al, or by exposing the growing silver film to an oxygen partial pressure (oxidizing the film). Furthermore, the effect of annealing at 250°C was studied for all these systems. / Dünne Silberfilme werden aufgrund ihres hohen Reflexionsvermögens im infraroten Spektrum und ihres hohen Transmissionsvermögens im Spektrum des Sonnenlichtes als Wärmeschutzbeschichtungen für Fensterglas verwendet. Der entscheidende Parameter für das Reflexionsvermögen der Schicht ist die elektrische Leitfähigkeit - je höher die Leitfähigkeit, desto stärker wird Infrarotlicht reflektiert. Elektrisch leitende Schichten mit Schichtdicken dünner als die mittlere freie Weglänge der Elektronen weisen einen starken Anstieg des spezifischen Widerstandes auf, der sich proportional zur inversen Schichtdicke verhält. Trotz ausführlicher Diskussionen während der letzten Jahrzehnte, ist noch nicht geklärt ob dieses Verhalten auf Streuung von Elektronen an Grenzflächen (Fuchs-Sondheimer-Modell) oder an Korngrenzen (Mayadas-Shatzkes-Modell) zurückzuführen ist. Um ein grundlegendes Verständnis der vorherrschenden Streumechanismen zu erlangen, wurden Schichtstapel der Struktur Aluminium-dotiertes Zinkoxid (ZnO:Al) / Ag / ZnO:Al, welche mittels Magnetron-Sputtern hergestellt wurden, hinsichtlich ihrer Transporteigenschaften und elektronischen Struktur untersucht. Die elektronische Struktur der Schichtsysteme ist mittels Elektronen-Energieverlust-Spektroskopie untersucht und bezüglich ihrer plasmonischen Anregungen analysiert wurden. Diese können in Anregungen der Volumenelektronen des Silbers und Anregungen der Elektronen aus der ZnO:Al / Ag Grenzfläche unterteilt werden. Die Plasmonen wurden hinsichtlich ihrer Impulsabhängigkeit und Anregungsbreite analysiert und durch Berechnung der Plasmonenstreurate mit den Messungen der elektrischen Leitfähigkeit verglichen. Aufgund der Tatsache, dass Genzflächen- und Korngrenzstreuung eine ähnliche Schichtdickenabhängigkeit aufweisen, gestaltet sich die Bestimmung der relativen Beiträge beider Streumechanismen als schwierig. Diese Problem kann durch die Untersuchung der Temperaturabhängigkeit der Streumechanismen, die sich für Grenzflächen- und Korngrenzstreuung unterscheidet, gelöst werden. Der spezifische Widerstand wurde in Abhängigkeit von der Temperatur an mehreren Proben unterschiedlicher Silberschichtdicke (im Bereich von 4 bis 200 nm) gemessen. Die Daten wurden anhand des erweiterten Mayadas-Shatzkes-Modells, welches sowohl Streuung an Grenzflächen (Fuchs-Sondheimer-Modell) als auch an Korngrenzen berücksichtigt, evaluiert. Die Ergebnisse zeigen eindeutig, dass für alle Schichtdicken die Elektronenstreuung an Korngenzen der dominierende Streumechanismus ist. Die Ergebnisse der Analyse des fundmentalen Schichtsystems wurden mit denen komplexerer Systeme verglichen, bei denen zum einen durch Hinzufügen einer dünnen Titanschicht die Grenzfläche zwischen Silber und ZnO:Al modifiziert wurde und zum anderen der Silberfilm durch einen erhöhten Sauerstoff-Partialdruck während der Beschichtung oxidiert wurde. Des Weiteren wurde der Effekt einer Temperung bei 250°C an allen Systemen untersucht. / Les vitrages bas-émissifs sont fréquemment élaborés par dépôts de revêtements dont la couche active est un film mince d'argent. Le paramètre qui détermine la réflexion dans l'infra-rouge est la conductance électrique de l'empilement. La résistivité électrique résiduelle de films dont l'épaisseur est inférieure au libre parcours moyen des électrons croît fortement en fonction de l'inverse de l'épaisseur. En dépit d'intenses recherches menées pendant des dizaines d'années, l'origine de cet accroissement de résistivité - réflexion des électrons par les interfaces (modèle de Fuchs-Sondheimer) ou par les joints de grains (modèle de Mayadas-Shatzkes). Pour comprendre les mécanismes à l'œuvre dans le transport des électrons, des couches ZnO dopé aluminium (ZnO:Al) / Ag / (ZnO:Al) produites par pulvérisation plasma ont été étudiée concernant leur structure électronique et propriétés de transport électrique. Les empilements ont été examinés par spectroscopie de pertes d'énergie d'électrons. Les spectres font apparaître les excitations des électrons de volume de l'argent et les excitations à l'interface ZnO:Al / Ag. Les excitations ont été analysés concernant leur dispersion. En outre, la durée de vie moyenne des plasmons déterminée d'après la largeur du pic de plasmon d'interface se compare bien à la l'inverse de la fréquence de diffusion des électrons qui se déduit de l'application du modèle de Drude aux données relatives à la résistivité. La difficulté dans la détermination des contributions relatives des modèles de Fuchs-Sondheimer et Mayadas-Shatzkes dans les conditions expérimentales est due au fait que ces deux modèles présentent des variations très similaires en fonction de l'épaisseur des films. D'importance primordiale pour la compréhension du transport dans les films minces, la question est une clé pour l'amélioration des revêtements bas-émissifs. La solution a été apportée ici par la différence de comportement en fonction de la température des diffusions des électrons aux interfaces et aux joints de grains. D'après cela, la résistance d'empilements comportant des films d'argent d'épaisseurs comprises entre 4 et 200 nm a été mesurée en fonction de la température. Les données ont été analysées au moyen de la version du modèle de Mayadas-Shatzkes qui inclut à la fois la diffusion des électrons aux interfaces (modèle de Fuchs-Sondheimer) et la diffusion des électrons aux joints de grains. Il a té démontré que, pour toutes les épaisseurs, la diffusion des électrons aux joints de grains constitue l'effet dominant. Les résultats de l'analyse du système fondamental ont été comparées avec les résultats de systèmes plus sophistiqués, obtenus soit en intercalant une couche additionnelle de titane entre l'argent et le ZnO (méthode communément utilisée pour améliorer le mouillage du ZnO par l'argent), soit par exposition à une pression partielle du film d'argent encours de croissance (pour oxyder le film). En outre, l'effet du recuit à 250°C a été étudié pour tous ces systèmes.

Thermography is a non-destructive technique which uses infrared radiation to obtain the temperature distribution of an object. The technique is increasingly used in the pulp and paper industry. To convert the detected infrared radiation to a temperature, the emittance of the material must be known. For several influencing parameters the emittance of paper and board has not previously been studied in detail. This is partly due to the lack of emittance measurement methods that allow for studying the influence of these parameters. An angle-resolved goniometric method for measuring the infrared emittance of a material was developed in this thesis. The method is based on the reference emitter methodology, and uses commercial infrared cameras to determine the emittance. The method was applied to study the dependence on wavelength range, temperature, observation angle, moisture ratio, sample composition, and sample structure of the emittance of paper and board samples. It was found that the emittance varied significantly with wavelength range, observation angle and moisture ratio. The emittance was significantly higher in the LWIR (Long-Wavelength Infrared) range than in the MWIR (Mid-Wavelength Infrared) range. The emittance was approximately constant up to an observation angle of 60° in the MWIR range and 70° in the LWIR range, respectively. After that it started to decrease. The emittance of moist samples was significantly higher than that of dry samples. The influence of moisture ratio on the emittance could be estimated based on the moisture ratio of the sample, and the emittance of pure water and dry material, respectively. The applicability of measured emittance values was demonstrated in an investigation of the mechanical properties of sack paper samples. An infrared camera was applied to monitor the generation of heat during a tensile test of a paper sample. It was found that the observed increase in thermal energy at the time of rupture corresponded well to the value of the elastic energy stored in the sample just prior to rupture. The measured emittance value provided an increased accuracy in the thermal energy calculation based on the infrared images. / <p>QC 20121121</p>

This dissertation revisits, develops, and documents methods that can be used to calibrate spaceborne microwave radiometers once in orbit. The on-orbit calibration methods discussed within this dissertation can provide accurate and early results by utilizing Calibration Attitude Maneuvers (CAM), which encompasses Deep Space Calibration (DSC) and a new use of the Second Stokes (SS) analysis that can provide early and much needed insight on the performance of the instrument. This dissertation describes pre-existing and new methods of using DSC maneuvers as well as a simplified use of the SS procedure. Over TRMM's 17 years of operation it has provided invaluable data and has performed multiple CAMs over its lifetime. These maneuvers are analyzed to implement on-orbit calibration procedures that will be applied for future missions. In addition, this research focuses on the radiometric calibration of TMI that will be incorporated in the final processing (Archive/Legacy of the NASA TMI 1B11 brightness temperature data product). This is of importance since TMI's 17-year sensor data record must be vetted of all known calibration errors so to provide the final stable data for science users, specifically, climatological data records.

A novel technique for measuring gas temperature and spectral particle emissivity in high-temperature gas-particle streams is presented. The main application of this optical sensor is to improve the process control of batch unit operations, such as steelmaking furnaces. The spectral emission profile of CO and CO2 and the continuous particle emission in the 3.5 to 5 μm wavelength region was recorded and analyzed in real time with a low-resolution passive sensor. The sensor consisted of light collecting optics, a dispersion element (grating spectrometer) and a 64-pixel pyroelectric array. Wavelength and radiance calibrations were performed. The temperature of the gas-particle medium (Tg+p) followed from the least-squares minimization of the difference between the measured radiance in the 4.56-4.7 μm region –which saturates due to the large CO2 concentrations and path lengths in industrial furnaces– and the corresponding blackbody radiance. Particle emissivity (εp) was calculated at 3.95 μm from an asymptotic approximation of the Radiative Transfer Equation that yields the emerging radiance from a semi-infinite particle cloud. The major source of error in the magnitude of Tg+p and εp could come from particle scattering. Through the method of embedded invariance an expression was developed to estimate the lowering effect of particle size and volume fraction on the saturation of the 4.56-4.7 μm CO2 emission region. An iterative procedure for correcting the values of the gas-particle temperature and particle emissivity was applied to the datasets from the two industrial tests. Results from the measurement campaigns with the infrared sensor prototype at two full-scale furnaces are presented. A proof-of-concept test at a coal-fired boiler for electricity production was followed by more extensive measurements at a Basic Oxygen Furnace (BOF) for steelmaking. The second test provided temperature and particle emissivity profiles for eight heats, which highlighted the simplicity of the technique in obtaining in-situ measurements for modeling studies. Through the analysis of the particle emissivity profile in the BOF and the definition of a new variable –the minimum carbon time– a novel end-point strategy to stop the injection of high-purity oxygen during low-carbon heats in BOF converters was proposed.

A novel technique for measuring gas temperature and spectral particle emissivity in high-temperature gas-particle streams is presented. The main application of this optical sensor is to improve the process control of batch unit operations, such as steelmaking furnaces. The spectral emission profile of CO and CO2 and the continuous particle emission in the 3.5 to 5 μm wavelength region was recorded and analyzed in real time with a low-resolution passive sensor. The sensor consisted of light collecting optics, a dispersion element (grating spectrometer) and a 64-pixel pyroelectric array. Wavelength and radiance calibrations were performed. The temperature of the gas-particle medium (Tg+p) followed from the least-squares minimization of the difference between the measured radiance in the 4.56-4.7 μm region –which saturates due to the large CO2 concentrations and path lengths in industrial furnaces– and the corresponding blackbody radiance. Particle emissivity (εp) was calculated at 3.95 μm from an asymptotic approximation of the Radiative Transfer Equation that yields the emerging radiance from a semi-infinite particle cloud. The major source of error in the magnitude of Tg+p and εp could come from particle scattering. Through the method of embedded invariance an expression was developed to estimate the lowering effect of particle size and volume fraction on the saturation of the 4.56-4.7 μm CO2 emission region. An iterative procedure for correcting the values of the gas-particle temperature and particle emissivity was applied to the datasets from the two industrial tests. Results from the measurement campaigns with the infrared sensor prototype at two full-scale furnaces are presented. A proof-of-concept test at a coal-fired boiler for electricity production was followed by more extensive measurements at a Basic Oxygen Furnace (BOF) for steelmaking. The second test provided temperature and particle emissivity profiles for eight heats, which highlighted the simplicity of the technique in obtaining in-situ measurements for modeling studies. Through the analysis of the particle emissivity profile in the BOF and the definition of a new variable –the minimum carbon time– a novel end-point strategy to stop the injection of high-purity oxygen during low-carbon heats in BOF converters was proposed.

Dans le cadre de la mission spatiale SMOS (Soil Moisture and Ocean Salinity), nous présentons dans cette thèse une nouvelle approche numérique de modélisation du calcul de l’émissivité et du coefficient bi-statique de systèmes forestiers sol-litière en Bande L. Le système sol-litière est représenté par deux couches diélectriques 3D comportant des interfaces rugueuses, une démarche qui n’apparait pas actuellement dans la littérature. Nous validons notre approche pour une seule couche en comparant les simulations de l'émissivité avec celles produites par la méthode des moments et des données expérimentales. A partir de ce nouveau modèle, nous évaluons la sensibilité de l’émissivité du système sol-litière en fonction de l’humidité et de la rugosité de la litière. Ce nouveau modèle permettra de créer une base de données synthétiques d’émissivités calculées en fonction de nombreux paramètres qui contribuera à améliorer la prise en compte de la litière dans l'algorithme d’inversion des données de la mission spatiale SMOS. / In the context of the SMOS (Soil Moisture and Ocean Salinity) mission, we present a new numerical modelling approach for calculating the emissivity and bistatic scattering coefficient of the soil-litter system found in forests, at L-band. The soil-litter system is modelled as two 3-dimensional dielectric layers, each with a randomly rough surface, which to our knowledge has not previously been achieved. We investigate the validity of the approach for a single layer by comparing emissivity simulations with results of Method of Moments simulations, and experimental data. We then use the approach to evaluate the sensitivity of the soil-litter system as a function of moisture content and the roughness of the litter layer. The numerical modelling approach which has been developed will allow us in the future to create a synthetic database of the emissivity of the soil-litter system as a function of numerous parameters, which will contribute to validating and improving the inversion algorithm used by the SMOS mission to retrieve soil moisture over forests.

The thesis is composed of three parts - theoretical, computational and a project part. The theoretical part deals with heat sharing through conduction, flow and radiation. The computational part is focused on the overall calculation of the heating system to operate smoothly and reliably. Three gas condensing boilers are designed as a source of heat. The heating of the water is solved as a reservoir. It's source of heat is one gas condensation boiler. The project part contains a technical report and the project documentation on the stage of the implementation dossier.

The diploma thesis is partly dedicated to energetic efficiency of buildings and describes possibilities how to evaluate energetic efficiency of buildings in the Czech Republic. We also get to know with distribution of thermal insulators by material base and use in construction. There are also mentioned methods how to determine thermal insulations characteristics of heat insulations, so called heat conductivity coefficient. The last and the crucial chapter of theoretic part is dedicated to thermal-reflective insulations. There are mentioned some of the basic characteristics of insulations, material composition and heat transfer mechanism in their structure as well. Practical part describes measurement of thermal resistance of chosen samples of thermal-reflective insulations per measuring device on the principal of Hot Box method. In the next step was determined emissivity of aluminium foils which forms the surface of chosen samples of thermal-reflective insulations. In the end of thesis are defined possibilities of use thermal-reflective insulations in building structures especially in passive and low-energy buildings in climatic conditions of the Czech Republic.

This diploma thesis is about thermomechanics of passenger car tires. The research part dealing with existing tire models is followed by the practical part. The practical part is based on the designs of thermomechanical models. The first model determines a dependence of temperature on the air pressure inside a tire when a temperature changes. The second thermomechanical model captures all the heat fluxes which affect a tire while a vehicle is in motion. The third thermomechanical model calculates temperatures of parts of the tire during driving tests. All models are programmed in MATLAB.

This work thoroughly analyzes a previously created computational model for predicting characteristic properties of the combustion process in an experimental combustion chamber. Any found shortcomings of the original model are removed and the model is further improved prior to its application on 11 real cases of combustion tests performed at various conditions and with various fuels. Data provided by the model are confronted with the data obtained during the combustion tests and the model accuracy is evaluated, based on local heat flux along the length of the combustion chamber. Finally, the overall usefulness of the model is determined by the means of evaluating the acquired accuracy values, and further possibilities of model improvement and use are presented.