The main aim of this work was to develop a method of screening HgCdTe materials for carrier concentration and mobility using Faraday rotation θ and absorption α. Faraday rotation provides N/m*2, where N is the carrier concentration and m* is the effective mass. Since m* was not known in HgCdTe, a Faraday rotation spectrometer was developed to systematically measure it as a function of temperature and Cd mole fraction. Effective masses in n-InSb, and n-GaAs were measured and compared with known values in the literature to validate the method. Mobility is proportional to θ/α. The proportionalities were determined in HgCdTe, n-InSb, and n-GaAs at infrared wavelengths. The dissertation consists of the preface, introduction, three chapters, summary and main conclusions, references, list of publications and abstract (in Lithuanian).

The main aim of this work was to develop a method of screening HgCdTe materials for carrier concentration and mobility using Faraday rotation θ and absorption α. Faraday rotation provides N/m*2, where N is the carrier concentration and m* is the effective mass. Since m* was not known in HgCdTe, a Faraday rotation spectrometer was developed to systematically measure it as a function of temperature and Cd mole fraction. Effective masses in n-InSb, and n-GaAs were measured and compared with known values in the literature to validate the method. Mobility is proportional to θ/α. The proportionalities were determined in HgCdTe, n-InSb, and n-GaAs at infrared wavelengths.

Automated narrow-gap girth-butt welds are replacing conventional welding methods to join sections of austenitic stainless steel pipe in the primary circuit of Pressurised Water Reactors, to reduce manufacturing costs and improve quality. To ensure the safe operation of these systems, reliable structural integrity assessments have to be undertaken, requiring the mechanical properties of welded joints to be characterised alongside the weld residual stress magnitude and distribution.This research project characterised, for the first time, the weld residual stress field and the tensile and ductile fracture toughness properties of a 33 mm thick narrow-gap 304L stainless steel pipe weld. The residual stress was characterised using two complementary approaches: deep hole drilling and neutron diffraction. A novel neutron diffraction scanning technique was developed to characterise the residual stress field, without cutting an access window into the component, leaving the original weld residual stress field undisturbed. A modified deep hole drilling technique was developed to characterise the residual stress retained in fracture mechanics specimens extracted from the pipe weld in two orientations. The modified technique was shown to measure the original weld residual stress field more accurately than through conventional deep hole drilling. Residual stresses, exceeding 50% of the weld material proof strength, were retained in axially-orientated fracture mechanics specimens.Tensile tests showed that the weld was approximately 60% overmatched. It was demonstrated that neither retained residual stress, nor specimen orientation, had a discernible effect on the measured fracture toughness of the weld material. In less ductile materials, however, the level of retained residual stress may unduly influence the measurement of fracture toughness. At initiation, the fracture toughness properties of both the parent and weld materials were far in excess of the measuring capacity of the largest fracture mechanics specimens that could be machined from the weld.The influence of residual stress and fracture toughness on the performance of narrow-gap welded pipework was investigated. Full elastic-plastic finite element analyses were used to model the pipe weld, containing a postulated defect under combined primary and secondary loading. The results, applied within the framework of an R6 structural integrity assessment, compared different plasticity interaction parameters on the prediction of failure load; the conventional ρ-parameter approach was compared with the recently developed, more advanced, g-parameter. It was shown that the g-parameter significantly reduced the conservatism of the ρ-parameter approach. However, for this pipe weld, plastic collapse was predicted to precede failure by ductile initiation, suggesting that a plastic collapse solution may be an appropriate failure criterion to use in structural integrity assessments of similar component and defect combinations.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第19522号 / 理博第4182号 / 新制||理||1600(附属図書館) / 32558 / 京都大学大学院理学研究科化学専攻 / (主査)教授 吉村 一良, 教授 有賀 哲也, 教授 北川 宏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

As the switching rates in electronic and optoelectronic devices are pushed to even higher frequencies, it is crucial to probe carrier dynamics in semiconductors on femtosecond timescales. Time resolved spectroscopy is an excellent tool to probe the relaxation dynamics of photoexcited carriers; where after the initial photoexcitation, the nonequilibrium population of electrons and holes relax by a series of scattering processes including carrier-carrier and carrier-phonon scattering. Probing carrier and spin relaxation dynamics in InAs and InSb based narrow-gap semiconductors is crucial to understand the different scattering mechanisms related to the systems. Similar studies in InSb quantum wells are also intriguing, especially for their scientifically unique features (such as small effective mass, large g-factor etc). Our time resolved techniques demonstrated tunability of carrier and spin dynamics which might be important for charge and spin based devices. The samples studied in this work were provided by the groups of Prof. Wessels (Northwestern University) and Prof. Santos (University of Oklahoma). Theoretical calculations were performed by the group of Prof. Stanton (University of Florida). The THz measurements were performed at Wright State University in collaboration with Prof. Jason Deibel. This work has been supported by the National Science Foundation through grants Career Award DMR-0846834, AFOSR Young Investigator Program 06NE231. A portion of this work was performed at the National High Magnetic Field Laboratory (in collaboration with Dr. Stephen McGill), which is supported by National Science Foundation Cooperative Agreement No. DMR-0654118, the State of Florida, and the U.S. Department of Energy. / Ph. D.

The goal of this project was to study some unexplored optical and magneto-optical properties of the newest member of III-V ferromagnetic structures, InMnSb, as well as InSb films and InSb/AlInSb quantum wells. The emphasis was on dynamical aspects such as charge and spin dynamics in order to address several important issues of the spin-related phenomena. The objectives in this project were to: 1) understand charge/spin dynamics in NGS with different confinement potentials, 2) study phenomena such as interband photo-galvanic effects, in order to generate spin polarized current, 3) probe the effect of magnetic impurities on the spin/charge dynamics. This thesis describes three experiments: detection and measurement of spin polarized photocurrents in InSb films and quantum wells arising from the circular photogalvanic effect, and measurements of the carrier and spin relaxation in InSb and InMnSb structures by magneto-optical Kerr effect and differential transmission. The samples for our studies have been provided by Prof. Heremans at Virginia Tech, Prof. Santos at the University of Oklahoma, and Prof. Furdyna at the University of Notre Dame. / Ph. D.

La présente étude vise à comprendre les écoulements ainsi que les transferts de chaleur par convection dans une configuration représentative d’un moteur de traction automobile. La zone d’étude est constituée d’un stator extérieur lisse et fixe et d’un rotor intérieur tournant. Deux géométries de rotor ont été étudiées : un rotor cylindrique et un rotor encoché. Un écoulement axial est superposé à l’écoulement produit par la rotation. Pour le rotor lisse, des mesures ont été réalisées pour des valeurs du nombre de Reynolds axial de 2500 à 13900 et de rotation de 1250 à 4000. Pour le rotor encoché, le nombre de Reynolds axial varie également de 2500 à 13900 et le nombre de Reynolds de rotation de 5000 à 26000. Les mesures de vitesse réalisées par PIV au sein des encoches montrent un écoulement tourbillonnaire contrarotatif complexe. Dans la zone d’entrée, on peut noter une forte interaction entre l’écoulement des encoches et celui provenant des zones polaires. Les résultats thermiques obtenues par thermographie infrarouge sur le rotor encoché montrent que les transferts thermiques augmentent avec l’augmentation du nombre de Reynolds axial mais l’influence de la vitesse de rotation est plus complexe. Enfin, la comparaison des résultats thermiques entre rotors lisse et encoché, a permis de mieux comprendre l’effet des encoches sur le refroidissement global. / The present work aimed to experimentally study the flow and heat transfer in a configuration corresponding to the gap of an automotive electrical motor (a thin airlayer between the rotating (rotor) and stationary (stator) parts.) Two rotor geometries are studied: one cylindrical and the other one with four slots which reproduce a synchronous motor used in automotive traction. An axial flow is superimposed to the rotation flow thanks to a ventilation system. The two most important parameters are axial Reynolds number and rotational Reynolds number. Velocity measurements are performed by PIV and heat transfer by infrared thermography coupled with heated thin foils. A complex counter rotational vortex flow has been recorded in the slots. Moreover, this slot flow seems to interact with the pole flow in the inlet region. This interaction seems to disappear rapidly after entrance area. Heat transfer rate is 3D, with great differences between the two slots faces and the pole. Classically, heat transfer rate grows with increasing axial Reynolds number. The relation between heat transfer rate and rotation Reynolds number is more complex

LUKOSZ Ondřej: Welding of heat - resistent steels by method SMAW into the narrow gap. The project elaborated in frame of engineering studies branch 2307. The project is submitting design of technology production of the weld procedure creep metal. It uses in manufactory power equipment. The power equipment, the type of steam turbine, uses steel 30CrMoNiV 5-11. The welding into the narrow gap has its specifics. The most important parameter is the choice of flux and filler metal. We must decide appropriate flux for convenient disposing of slag. Based on the literature study these problems were proposed the specified welding procedure, appropriate flux and appropriate additional material. For the experiment was selected appropriate temperature of preheating.

In recent years, spin relaxation, injection, and manipulation in semiconductors have attracted considerable interest because of several potential applications in "spintronic" devices and the necessity to understand and control spin-based phenomena. In light of the growing interest in spin-related phenomena and devices, there is now renewed interest in the science and engineering of narrow gap semiconductors (NGS). NGS based heterostructures are particularly interesting for spintronic applications due to their large spin-orbit coupling, which leads to considerable zero-field spin splitting. NGS are also candidates for electronic applications, such as high-speed and low-power microprocessors; as reported recently by Intel. Furthermore, as switching rates in electronic devices are pushed to even higher frequencies, it is important to understand dynamics in semiconductors such as NGS on femtosecond time-scales. In this thesis, time-resolved studies of magnetic and non-magnetic NGS using ultrafast-laser spectroscopy techniques such as pump-probe spectroscopy and magneto-optical Kerr/Faraday effect, are reported. Our samples include: InSb-based quantum wells with different confinement potentials; InMnSb films, the newest III-V ferromagnetic semiconductors; and InAs films. The samples for these studies have been provided by the groups of Prof. Santos at the University of Oklahoma, Prof. Furdyna at the University of Notre Dame, and Prof. Guido at Virginia Tech. The objectives in this thesis have been to: a) understand charge/spin dynamics in NGS with novel confinement potentials, b) probe the effect of magnetic impurities on the spin/charge dynamics, and c) develop concepts for spin based device applications. Several specific questions and concepts have been addressed including: the effect of large spin-orbit interaction in NGS on the dynamics, how large Rashba spin splitting in these materials affect the spin coherence life time, and carrier/spin dynamics in ferromagnetic semiconductor structures. / Ph. D.

Le tellurure de mercure et de cadmium (HgCdTe ou MCT) est un matériau reconnu pour la physique de la matière condensée, dont l'histoire, datant aujourd'hui de plus de cinquante ans, constitue un excellent exemple des progrès remarquables réalisés dans la recherche sur les semi-conducteurs et les semi-métaux. Notre travail est principalement motivé par l’intérêt fondamental que suscitent ces systèmes, mais notre recherche peut également avoir un impact pratique (indirect) sur la médecine, la surveillance ou la détection de l’environnement ainsi que sur les systèmes de sécurité. Cela peut aider à améliorer les performances des photodétecteurs dans la limite des grandes longueurs d'onde ou à faciliter la fabrication de dispositifs émettant de la lumière.La présente thèse de doctorat vise principalement à combler certaines des lacunes de notre compréhension de la structure de bande électronique des hétérostructures 2D et quasi-2D basées sur les matériaux HgTe/HgCdTe et InAs/InSb, qui peuvent être transformés en phase topologiquement isolante à l'aide des paramètres de croissance. Pour explorer leurs propriétés, la technique expérimentale de base, la magnéto-spectroscopie infrarouge et THz fonctionnant dans un large éventail de champs magnétiques, est combinée à des mesures complémentaires de magnéto-transport. Cette combinaison de méthodes expérimentales nous permet d’obtenir de précieuses informations sur les états électroniques non seulement à l’énergie de Fermi, mais également dans son voisinage relativement large. Diverses hétérostructures ont été étudiées avec des caractéristiques globales et/ou spécifiques déterminées principalement par les paramètres de croissance.La réponse magnéto-optique observée, due aux excitations intra-bande (résonance cyclotron) et interbandes (entre les niveaux de Landau) peut être interprétée dans le contexte d'études antérieures sur des échantillons 3D, des puits quantiques et des super-réseaux, mais également en rapport aux attentes théoriques. Ici, nous visons à obtenir une explication quantitative des données expérimentales recueillies, mais également à développer un modèle théorique fiable. Ce dernier comprend le réglage précis des paramètres de structure de bande présents dans le modèle établi de Kane, mais surtout, l'identification de termes supplémentaires pertinents (d'ordre élevé) nécessaires pour parvenir à un accord quantitatif avec nos expériences. On peut s’attendre à ce que les corrections dues à ces termes supplémentaires affectent davantage les sous-bandes de valence, généralement caractérisées par des masses effectives relativement importantes et, par conséquent, par une grande densité d’états ou, lorsque le champ magnétique est appliqué, par un espacement assez étroit (et mélange important) des niveaux de Landau. / Mercury cadmium telluride (HgCdTe or MCT) is a time-honored material for condensed matter physics, whose history  nowadays more than fifty years long  may serve as an excellent example of remarkable progress made in research on semiconductors and semimetals. The ternary compound HgCdTe implies two important aspects, which largely contributed to its undoubted success in solid-states physics.The present PhD thesis primarily aims at filling some of existing gaps in our understanding of the electronic band structure in 2D and quasi-2D heterostructures based on HgTe/HgCdTe and InAs/InSb materials, which both may be tuned into topologically insulating phase using particular structural parameter. To explore their properties, the primal experimental technique, infrared and THz magneto-spectroscopy operating in a broad of magnetic fields, is combined with complementary magneto-transport measurements. This combination of experimental methods allows us to get valuable insights into electronic states not only at the Fermi energy, but also in relatively broad vicinity.The observed magneto-optical response - due to intraband (cyclotron resonance) and interband inter-Landau level excitations - may be interpreted in the context of previous studies performed on bulk samples , quantum wells and superlattices, but also compared with theoretical expectations. Here we aim at achieving the quantitative explanation of the collected experimental data, but also further developing a reliable theoretical model. The latter includes the fine-tuning of the band structure parameters present in the established Kane model, but even more importantly, identifying additional relevant (high-order) terms and finding their particular strengths, needed to achieve quantitative agreement with our experiments. One may expect that corrections due to these additional terms will more affect the valence subbands, which are in general characterized by relatively large effective masses. Consequently, valence subbands have larger density of states compared to conduction band or, when the magnetic field is applied, rather narrow spacing (and possibly large mixing) of Landau levels.