Дисертації з теми "Bearing formations"

Le contrôle des formations basées sur les bearings (direction relative à l’observateur) permettent aux flottes de quadrirotors de se déplacer vers une géométrie désirée, en utilisant des mesures extraites de caméras embarquées. Des travaux antérieurs ont traité les quadrirotors comme des intégrateurs, et donc la formation doit ralentir de manière à compenser les non-linéarités non modélisées. Cette thèse a pour objectif d’atteindre des formations rapides en tenant compte des dynamiques non-linéaires du quadrirotor et des mesures visuelles. Deux contrôleurs sont développés, à savoir un contrôleur basé sur un asservissement visuel dynamique et une commande prédictive, montrant des performances améliorées avec des contraintes réelles. Toutes les formations basées sur des bearings dépendent d’un degré suffisant de rigidité. Bien que celui-ci puisse être évalué numériquement, la rigidité est une fonction de la position de tous les robots dans la flotte. Ceci étant, les travaux précédents ne pouvaient pas garantir la rigidité pour des formations plus larges que quelques robots. La deuxième contribution de cette thèse est l’évaluation des géométries singulières où une certaine formation rigide devient flexible. Ceci mène à un système de classification basé sur des contractions d’ensembles de contraintes, qui permet d’identifier les géométries singulières pour des grandes formations afin de garantir la rigidité
Bearing formation control allows groups of quadrotors to manoeuver in a desired geometry, using only visual measurements extractable from embedded monocular cameras. Prior works have treated quadrotors as single or double integrators, and as a result must operate slowly to compensate for unmodelled non-linearities. This thesis allows for faster bearing formations by developping higher-order controllers, considering the non-linear quadrotor and visual feature dynamics. A dynamic feedback controller based on second-order visual servoing and a model predictive controller are developped and tested in simulation and experiments, showing improved dynamic manoeuvering performance. The later is augmented with constraints such as field of view limitations and obstacle avoidance. All bearing formation algorithms depend on a sufficient degree of bearing rigidity to guarantee performance. This may be evaluated numerically, but as the rigidity is a function of the formation embedding, previous work could not guarantee rigidity in formations larger than a few robots. The second main contribution of this thesis is the evaluation of bearing rigidity singularities (i.e. embeddings where an otherwise rigid formation becomes flexible) by applying existing geometric analysis methods on an kinematic mechanism which is analoguous to the kinematic constraints imposed by the formation controller and robot models. This is extended to a novel classification system based on a contraction of constraint sets that can determine singular geometries for large formations, allowing for a formulation of a set of guaranteed rigid configurations without an ad-hoc kinematic analysis of individual formations

Thesis (M.S.)--West Virginia University, 2006.
Title from document title page. Document formatted into pages; contains x, 72 p. : ill. (some col.), maps. Includes abstract. Includes bibliographical references (p. 69-72).

Tato disertační práce se zaměřuje na studium závislosti mezi reakčním momentem ložiska mazaného plastickým mazivem s lithným mýdlem a vlastnostmi maziva, jako například tloušťka vytvářeného mazacího filmu, jeho reologie, struktura zpevňovadla, trakční vlastnosti či vliv topografie povrchu. Typ maziva poskytujícího nižší odpor závisí na podmínkách provozu ložiska, zejména rychlosti. Chování mazacího filmu za nízkých rychlostí má vliv na reakční moment ložiska v nízkých rychlostech. Mez toku a trakční chování koreluje s momentem ložiska za vysokých rychlostí. Schopnost zpevňovadla vstupovat do kontaktu má vliv na tloušťku filmu, vzhled kavitační oblasti na výstupu kontaktu a chování hladovění. Důvod vstupu zpevňovadla do kontaktu je jeho chemická struktura. Vysoká polárnost hydroxylových sloučenin zpevňovadla podporuje jeho vtažení kontaktními povrchy. Mazivo s nejvyšší polaritou prokázalo na površích obsahujících denty nejčastější vstup do prostoru dentů. Na základě předchozích pozorování je navržen popis principu mechanismu mazání.

It is an established fact that segregation during casting affects the physical properties of carbon-based ferro alloys; this motivates the study of the segregation behaviour of carbon and carbide-forming solute elements. In this context, this thesis investigates two different situations: the effects of cooling rate and turbulence on the precipitation behaviour of the graphite nodules in nodular cast iron; the nature of carbide precipitation in a bearing steel grade and the effects of subsequent soaking on these carbides. The structures of boiling water reactor inserts cast by the uphill and downhill casting of nodular cast iron were examined. The samples were taken from representative locations in the top, middle and bottom cross sections of the castings. It was observed that in uphill-cast inserts the nodules were larger but fewer in number the bottom section, whereas in downhill-cast inserts the nodules in the bottom section were smaller, but greater in number. Variation in volume fraction of the graphite nodules across the inserts was also observed. The probable cause of this variation was the difference in cooling rate in different sections of the insert. Between the steel tubes located at the central part of the casting, the fraction of graphite was lower, which could be the result of carburization of the steel tubes. To study the effects of melt stirring during the solidification of nodular cast iron, several experiments were conducted at variable cooling rates and for different stirring times. Examination of the microstructure was conducted using Light Optical Microscope (LOM) and Scanning Electron Microscope (SEM). It was observed that during stirring the melt oxidized and oxide nuclei were formed. The number of nucleation sites for the precipitation of graphite nodules increased, which raised the nodule count and the fraction of the graphite precipitated. The matrix transformed from pearlite to ferrite, which could be due to the fact that more carbon had diffused out of the matrix. The segregation behaviour in hypereutectoid bearing steel produced by ingot casting was also studied. The effects of soaking on micro and macro segregation was investigated in samples taken from as cast and soaked ingots; emphasis was laid on the bulk matrix and A-segregation channels. Samples were also taken from ingots which were soaked and then hot worked. The micro and macro examination of the microstructure was conducted using LOM and SEM. Quantitative and qualitative composition analysis was performed using Energy-dispersive X-ray spectroscopy (EDX) and an electron micro probe analyzer (EMPA). It was observed that M3C, M2C and M6C had precipitated. The carbide morphology in the bulk matrix was different to that in the A-segregation channels. All the primary carbides in the bulk matrix were found to have dissolved after 4 hours of soaking at 1200oC.
Det är ett faktum att segringar som uppstår under gjutning påverkar materialegenskaperna hos kolbaserade järnlegeringar; detta utgör motivationen till studien av segringsuppträdandet hos kol och karbidbildande ämnen. Denna avhandling behandlar två olika aspekter inom ramen för detta ämne: påverkan av kylningshastighet och turbulens på kärnbildningen av grafitnoduler i nodulärt gjutjärn samt karbidbildning i kullagerstål och dess påverkan på den efterföljande värmebehandlingen av dessa karbider. Strukturen hos rör till vattenkokare som tillverkats av nodulärt gjutjärn som gjutits med fyllning från botten eller från toppen undersöktes. Prover togs från representativa tvärsnittspositioner från toppen, mitten och botten av de gjutna ämnena. Resultaten visade att användandet av bottenfyllda kokiller gav upphov till större men färre karbider i nedre delen av ämnet, medans användandet av toppfyllda kokiller gav upphov till mindre men fler karbider i nedre delen av ämnet. Variationer av volymfraktionen av grafitnoduler längs tvärsnitten observerades också. Den mest sannolika orsaken till denna variation var skillnaden i kylhastighet i de olika områdena av tvärsnitten. Hos rör tillverkade av det centrala delen av ämnet så var fraktionen grafit lägre, vilket kan bero på en uppkolning av rören. Ett flertal experiment utfördes med varierande kylningshastigheter och olika omrörningstider för att studera inverkan av omrörning av smältan på stelningen av nodulärt gjutjärn. Studier av mikrostrukturen genomfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Resultaten visade att smältan oxiderades under omrörningen, vilket resulterade i bildandet av oxider. Detta ledde till en ökning av kärnbildningsområden för grafitnoduler, vilket ledde till en ökning av antalet noduler samt fraktionen av grafit som fälldes ut. Strukturen omvandlades från perlit till ferrit, vilket troligen orsakades av att kol hade diffunderat ut från strukturen. Segringsbeteendet hos hypereutektoida kullagerstål tillverkade genom götgjutning undersöktes också. Effekten av värmebehandling på mikro- och makrosegringar undersöktes i prover tagna från gjutna och värmebehandlade ämnen. Fokus var på att studera strukturen i ämnena samt A-segringar. Dessutom togs prover från ämnen som först värmebehandlats och därefter varmbearbetats. Både mikro- och makroundersökningar av mikrostrukturen utfördes med ljusoptisk mikroskopi och svepelektronmikroskopi. Dessutom så genomfördes kvantitativa sammansättningsbestämningar med energidispersiv röntgenspektroskopi och elektronmikroprobsanalys. Resultaten visade att M3C, M2C och M6C karbider hade fällts ut. Karbidmorfologin i huvuddelen av strukturen skiljde sig från den som återfanns i A-segringar. Samtliga primära karbider i huvuddelen av strukturen hade lösts upp efter 4 timmars värmebehandling vid 1200oC.

QC 20180523

Thesis (Ph.D.)--Civil and Environmental Engineering, Georgia Institute of Technology, 2008.
Committee Chair: J. Carlos Santamarina; Committee Member: Carolyn D. Ruppel; Committee Member: Costas Tsouris; Committee Member: Glenn J. Rix; Committee Member: J. David Frost

The formation of iron-bearing intermetallics in the 413 type of aluminum alloys was investigated comprehensively. Both synthetic and commercial 413 alloys were studied with iron concentrations in the range of 0.4-1.2 wt. % and manganese up to 0.5 wt.%. The effects of cooling rate during solidification and of melt chemistry on the morphology of iron intermetallic phases were determined. Image analysis was used to quantify the intermetallic size, volume fraction, and number, as a function of both melt chemistry and cooling rate. The total volume fraction of intermetallic compounds in these alloys was related to cooling rate by an exponential equation.
The kinetics of both dissolution of intermetallics on melting, and of re-formation on cooling of the liquid were investigated by means of quenching experiments. Quantitative evaluation of intermetallic size and number revealed that the change in volume fraction of intermetallics in the liquid state is controlled by nucleation.
The effect of settling time and the rate of gravity segregation of intermetallic compounds in a stagnant liquid metal were investigated. It was found that, in the absence of convection, settling obeys Stokes' law with the terminal velocity reached at very short times and very close to the melt surface.
Strontium was used to modify or eliminate the iron-intermetallics. (Abstract shortened by UMI.)

It is believed that home ownership has a positive connection with family formation and child bearing as there is a speed up process of attaining home-ownership when the couples are in anticipation of starting family and having children. However, home ownership in relation with family formation and child bearing are not always in positive connection as other factors are necessary to be taken into consideration when associating relationship between them, such as (i) postponement of marriage and child bearing, (ii) family background, (iii) housing markets and financial systems, and (iv) government policies which will be investigated internationally in this research and tested the hypothesis in Hong Kong. With the family budget constraints, cost competition between housing and marriage or child bearing is one of the significant factors affecting the couples’ decision in home purchasing. Our empirical results from the questionnaire survey demonstrated that home ownership is perceived as a precondition to marriage and child bearing and indicated that the cost competition between becoming home owners and becoming parents was strong. Postponement of marriage and child bearing are found over the past decade and decrease in number of children that the respondents wanted to have are the current trend. Our empirical results also show that family background is an important factor affects decision of the couples in home purchasing when getting married and in anticipation of having children. Facing a budget constraint, most of the young couples depend on their parents who are in owner-occupied housing tenure for financial assistance to succeed their home purchasing dreams. Nowadays, Hong Kong residential property value has also increased sharply in recent years and costs of housing with increasing mortgage rate would affect decision of the young couples in home purchase, a series of measures are therefore launched by the government to solve the problems of housing since its inauguration aiming at increasing private and subsidized housing flats as well as land for affordable housing development to cool down the overheating property market. People’s home purchase is greatly affected by the prevailing housing policy found in the survey and their recommendations to the government are to provide more HOS flats, stabilize the house price, increase in amenities and facilities provision in the suburb housing developments and resume Home Assistance Loan Scheme in order to satisfy their housing needs in forming families and planning to child bearing.
published_or_final_version
Housing Management
Master
Master of Housing Management

Le but de cette thèse est d'étendre l'état de l'art par des contributions sur le comportement collectif d'un groupe de robots volants, à savoir des quadrirotors UAV. Afin de pouvoir sûrement naviguer dans un environnement, ces derniers peuvent se reposer uniquement sur leurs capacités à bord et non sur des systèmes centralisés (e.g., Vicon ou GPS). Nous réalisons cet objectif en offrant une possible solution aux problèmes de contrôle en formation et de localisation à partir de mesures à bord et via une communication locale. Nous abordons ces problèmes exploitant différents concepts provenant de la théorie des graphes algébriques et de la théorie de la rigidité. Cela nous permet de résoudre ces problèmes de façon décentralisée et de proposer des algorithmes décentralisés capables de prendre en compte également des limites sensorielles classiques. Les capacités embarquées que nous avons mentionnées plus tôt sont représentées par une caméra monoculaire et une centrale inertielle (IMU) auxquelles s'ajoute la capacité de chaque robot à communiquer (par RF) avec certains de ses voisins. Cela est dû au fait que l'IMU et la caméra représentent une possible configuration économique et légère pour la navigation et la localisation autonome d'un quadrirotor UAV
The aim of this Thesis is to give contributions to the state of the art on the collective behavior of a group of flying robots, specifically quadrotor UAVs, which can only rely on their onboard capabilities and not on a centralized system (e.g., Vicon or GPS) in order to safely navigate in the environment. We achieve this goal by giving a possible solution to the problems of formation control and localization from onboard sensing and local communication. We tackle these problems exploiting mainly concepts from algebraic graph theory and the so-called theory of rigidity. This allows us to solve these problems in a decentralized fashion, and propose decentralized algorithms able to also take into account some typical sensory limitations. The onboard capabilities we referred to above are represented by an onboard monocular camera and an inertial measurement unit (IMU) in addition to the capability of each robot to communicate (through RF) with some of its neighbors. This is due to the fact that an IMU and a camera represent a possible minimal, lightweight and inexpensive configuration for the autonomous localization and navigation of a quadrotor UAV

Disposal of acid generating sulphidic tailings is a major environmental problem facing the Canadian as well as the international mining and mineral industries. If the deposited tailings are not treated the sulphide minerals oxidise and create an acidic environment. The leachate from such a site is rich in soluble heavy metals and has the potential to contaminate the groundwater as well as the local surface watercourses. This thesis explores an alternative treatment method via ettringite formation, which stabilises and solidifies these highly reactive tailings.
Ettringite has the capacity of uptaking other metals into its structure by isomorphous substitution. Ettringite has also a negative surface charge, which makes it a good adsorbent for positively charged cations. Furthermore, the high pH solution required for ettringite formation will cause the precipitation of heavy metals from the solution. Therefore, ettringite in a lime-remediated sulphate rich acid mine drainage system could serve as a physical and chemical stabilization agent, which could also reduce the remediation costs over other commercially available stabilization technology.
In order to assess the feasibility of forming ettringite in sulphide rich tailings, a thermodynamic model was used to investigate the optimal geochemical parameters. The model predicts that ettringite is stable over a wide range of compositions and pH. Results presented in this thesis show that the sulphate content of the tailings samples could limit the precipitation of ettringite, and monosulphate could be the end-precipitate.
Long-term leachability and durability analysis showed that ettringite can be formed as a stable mineral in lime, fly ash, and aluminum rich sulphidic tailings samples. Ettringite formation reduced the leachability of the heavy metals and improved the geotechnical characteristics of the treated samples. Freeze and thaw analyses showed that formation of ettringite produce a low permeability and high strength tailings sample capable of withstanding harsh environmental fluctuations.

Iron meteorites are Fe-Ni alloys that are thought to represent samples of the cores of differentiated asteroids. A minority of the iron meteorites contain silicate inclusions, the so-called silicate-bearing or non-magmatic iron meteorites. The presence of chemically evolved silicate inclusions in a high-density Fe-Ni metal raises questions about their origin. The IIE group belongs to the non-magmatic iron meteorites and contains primitive as well as evolved silicate inclusions. The object of this thesis is to investigate the formation processes of the silicate-bearing iron meteorites by examination of the primitive IIE irons. The first chapter provides an overview of the state of the art of silicate-bearing iron meteorites and highlights the existing open questions. The second chapter discusses the most important analytical techniques that have been used during this thesis. The third chapter contains all the research conducted on the Mont Dieu meteorite, a new primitive member of the IIE group. This meteorite represents a unique member of the IIE group as it contains chondrules in its silicate inclusions. Together with the Netschaëvo meteorite, they are the only two IIE irons that show such a primitive texture. Based on the mineralogy, the major element composition and the oxygen isotope composition, we conclude that Mont Dieu originated as an H chondrite. The observation of a series of features, including silicate darkening, thick metal veins containing angular clasts, and the need for a heterogeneous heat source, led to an impact-based origin for Mont Dieu. The fourth chapter is dedicated to the investigation of two samples of the primitive Netschaëvo IIE meteorite, that show lithologies that are very different to those described in the literature. The investigated pieces of Netschaëvo can be classified as impact melt rocks (IMR) and we show that the precursor material of these IMR and the primitive clasts both originated from the same parent body. The occurrence of both lithologies in the same meteorite suggests that Netschaëvo itself is a breccia containing metamorphosed and IMR clasts and that the meteorite formed as the result of an impact event. The fifth chapter focuses on the fine-grained matrix material found in the silicate inclusions of Netschaëvo IIE. This study provides insights into core-mantle boundary environments and confirms the impact-origin of Netschaëvo by the presence of minerals and textures pointing to a very rapid cooling. The investigations show that the re-partitioning of phosphorus from the metal into the silicate material during cooling might be a general process during planetary differentiation. In the sixth chapter, the veins present in the silicate inclusions of Mont Dieu are described in detail, and compared to the veining structures found in Techado IIE silicate. The characteristics of the processes causing the formation of these veins are discussed. The seventh chapter summarizes the conclusions of this thesis. The detailed petrographic and geochemical examinations conducted on the investigated samples show that collisions played a major role in the formation of the IIE iron meteorites. The work performed in the framework of this thesis provides a significant contribution towards a more complete and in-depth understanding of the formation mechanisms of silicate-bearing iron meteorites.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

Lifetime maximization is a key challenge in the design of sensor-network-based tracking applications. In this dissertation, formation of optimal coalitions of nodes is investigated for data acquisition in bearings-only target localization such that the average sleep times allocated to the nodes are maximized. Targets are assumed to be localized with a pre-defined accuracy where the determinant of the Bayesian Fisher information matrix (B-FIM) is used as the metric for estimation accuracy. Cooperative game theory is utilized as a tool to devise a distributed dynamic coalition formation algorithm in which nodes autonomously decide which coalition to join, while maximizing their feasible sleep times. Nodes in the sleep mode do not record any measurements; hence, save power in both sensing and transmitting the sensed data. The proposed scheme reduces the number of sensor measurements by capturing the spatio-temporal correlation of the information provided by the sensors from one side and bounding the localization accuracy to the pre-defined value from the other side. It is proved that if each node operates according to this algorithm, the average sleep time for the entire network converges to its maximum feasible value. In numerical examples, we illustrate the inherent trade-off between the localization accuracy and the average sleep time allocated to the nodes and demonstrate the superior performance of the proposed algorithm via Monte Carlo simulations.

A spacecraft formation possesses several benefits over a single-satellite mission. However, launching a fleet of satellites is a high-cost, high-risk venture. One way to mitigate much of this risk is to demonstrate hardware and algorithm performance in groundbased testbeds. It is typically difficult to experimentally replicate satellite dynamics in an Earth-bound laboratory because of the influences of gravity and friction. An air bearing provides a very low-torque environment for experimentation, thereby recapturing the freedom of the space environment as effectively as possible. Depending upon con- figuration, air-bearing systems provide some combination of translational and rotational freedom; the three degrees of rotational freedom provided by a spherical air bearing are ideal for investigation of spacecraft attitude dynamics and control problems. An interest in experimental demonstration of formation flying led directly to the development of the Distributed Spacecraft Attitude Control System Simulator (DSACSS). The DSACSS is a unique facility, as it uses two air-bearing platforms working in concert. Thus DSACSS provides a pair of "spacecraft" three degrees of attitude freedom each. Through use of the DSACSS we are able to replicate the relative attitude dynamics between nodes of a formation such as might be required for co-observation of a terrestrial target. Many dissertations present a new mathematical technique or prove a new theory. This dissertation presents the design and development of a new experimental system. Although the DSACSS is not yet fully operational, a great deal of work has gone into its development thus far. This work has ranged from configuration design to nonlinear analysis to structural and electrical manufacturing. In this dissertation we focus on the development of the attitude determination subsystem. This work includes development of the equations of motion and analysis of the sensor suite dynamics. We develop nonlinear filtering techniques for data fusion and attitude estimation, and extend this problem to include estimation of the mass properties of the system. We include recommendations for system modifications and improvements.
Ph. D.

The key idea of this thesis is to apply advanced formation control methods to swarms of drones, considering the leaders driven by maneuver regulation techniques. The approaches presented in this work propose an efficient solution to several cooperative multi-agent problems, e.g., in surveillance applications. In this thesis, the general dynamic model of the quadrotor is presented, paying particular attention to its differential flatness property. This property is exploited in the control technique of the quadrotor, where the centroid position vector and the yaw angle are taken as flat output vectors. Subsequently, the concept of maneuver is introduced, focusing on a circular path and proposing a maneuver regulation technique. This technique is widely applied in collision avoidance problems, given that the robot has to follow geometrical references. The adopted spatial trajectory is defined in terms of the circumference radius and tangential velocity. At this point, quadrotors are treated as general agents, belonging to a distributed cooperative network of agents, divided into leaders and followers. Indeed, a novel bearing-based approach is exploited to steer the followers to pursue a target formation, leaving the leaders unconstrained. For that reason, circular maneuver regulation techniques have been applied to them. The main contribution of this thesis is the validation of both the maneuver regulator and the bearing-based formation control technique. The simulation is based on the ROS 2 Toolbox ChoiRbot, where a cooperative multi-agent network can be easily managed. The code was implemented in Python, and thanks to its scalability with respect to the number of agents, formation algorithms with geometrical constraints of the maneuver can be performed.

Les hydrates de méthane (MHs), composés de gaz de méthane et d’eau, se forment naturellement à haute pression et faible température dans les sédiments marins ou pergélisols. Ils sont actuellement considérés comme une ressource énergétique (principalement MHs dans les sédiments sableux) mais aussi une source de géo-hasards et du changement climatique (MHs dans les sédiments grossiers et fins). La connaissance de leurs propriétés mécaniques/physiques, qui changent considérablement avec la morphologie et distribution des hydrates dans les pores, est très importante pour minimiser les impacts environnementaux liés aux futures exploitations du gaz de méthane à partir des sédiments sableux contenant des MHs (MHBS). La plupart des études expérimentales concernent MHBS synthétiques à cause des difficultés pour récupérer des échantillons intacts. Différentes méthodes ont été proposées pour former MHs dans les sédiments au laboratoire pour reconstituer des sédiments naturels, mais sans grand succès. Cette thèse a pour objectif d’évaluer la morphologie, la distribution des MHs dans les MHBS synthétiques à différentes échelles et d’étudier les effets des MHs (leur morphologie et teneur en hydrate) sur les propriétés mécaniques des MHBS. Deux méthodes de formation d’hydrates dans les sédiments sableux ont été proposées. Au niveau macroscopique, la distribution des hydrates au niveau des pores est évaluée en se basant sur la vitesse de propagation d’onde de compression (mesurée et calculée à partir des modèles existants). Des essais triaxiaux ont été utilisés pour étudier l’influence des MHs à différentes teneurs en hydrate sur les propriétés mécaniques des MHBS. Par ailleurs, l’Imagerie par Résonance Magnétique a été utilisée pour étudier la cinétique de formation/dissociation d’hydrates et aussi la distribution des hydrates sur l’ensemble de l’échantillon. Les résultats montrent qu’un cycle de température en conditions non drainées complète la redistribution des hydrates dans les pores après la saturation en eau de l’échantillon à haute teneur en hydrate. La distribution des hydrates sur l’ensemble de l’échantillon devient plus homogène avec la saturation en eau suivie par un cycle de température. En outre, les propriétés mécaniques des sédiments augmentent avec l’augmentation de la teneur en hydrate.A l’échelle du grain, la tomographie aux rayons X (XRCT) et celle au Synchrotron XRCT (SXRCT, Synchrotron SOLEIL) ont été utilisées pour observer la morphologie et la distribution des MHs au niveau des pores des sédiments sableux. Ce travail n’a pas été facile car il nécessitait des dispositifs expérimentaux compliqués (pour maintenir la haute pression et faible température) mais aussi en raison du faible contraste entre MHs et l’eau sur les images de XRCT, SXRCT. Des dispositifs spécifiques ont été développés pour étudier la formation d’hydrates, la morphologie et la distribution à l’échelle du grain des MHs en utilisant XRCT, SXRCT. De plus, une nouvelle méthode a été développée pour déterminer plus précisément les fractions volumiques d’un milieu triphasé à partir des images XRCT. Des observations au Microscope Optique (en coopération avec l’Université de Pau) ont également été faites pour confirmer diverses morphologies de MHs dans les sédiments sableux. Les morphologies et distributions d’hydrates observées sont comparées avec les modèles existants. Les observations montrent que la formation des MHs dans les sédiments sableux est un processus instable et compliqué. Différentes morphologies et distributions au niveau des pores des MHs peuvent coexister. Il parait indispensable de tenir compte des vraies morphologies et distributions au niveau des pores des MHs pour les études numériques utilisant des modèles simplifiés.Mots-clés: hydrate de méthane, sédiments sableux, formation, dissociation, morphologies, distribution, propriétés mécaniques, XRCT, SXRCT, microscope optique, essais triaxiaux, modèle de mécanique des roches
Methane hydrates (MHs), being solid ice-like compounds of methane gas and water, form naturally at high pressure and low temperature in marine or permafrost settings. They are being considered as an alternative energy resource (mainly methane hydrate-bearing sand, MHBS) but also a source of geo-hazards and climate change (MHs in both coarse and fine sediments). Knowledge of physical/mechanical properties of sediments containing MHs, depending considerably on hydrate morphologies and pore-habits, is of the importance to minimize the environmental impacts of future exploitations of methane gas from MHBS. Existing experimental works mainly focus on synthetic samples due to challenges to get cored intact methane hydrate-bearing sediment samples. Various methods have been proposed for MH formation in sandy sediments to mimic natural MHBS, but without much success. The main interests of this thesis are to investigate morphologies and pore-habits of MHs formed in synthetic MHBS at various scales and to study the effects of MHs (MH morphology and MH saturation) on the mechanical properties of MHBS.Two MH formation methods (modified from two methods existing in the literature) have been first proposed to create MHs in sandy sediments at different pore-habits. At the macroscopic scale, MH pore-habits have been predicted via comparisons between sonic wave velocities, measured and that calculated based on rock physic models. The effects of MHs formed following the two proposed methods (at different hydrate saturations) on the mechanical properties of MHBS were investigated by triaxial tests. Furthermore, Magnetic Resonance Imaging (MRI) has been used to investigate the kinetics of MH formation, MH distribution along with sample height and also MH dissociation following the depressurization method which has been considered as the most economical method for MH production from MHBS. A temperature cycle in undrained conditions was supposed to not only complete MH redistribution in pore space after the water saturation of the sample at high hydrate saturation but also make MHs distributed more homogeneously in the sample even at low hydrate saturation. Furthermore, the mechanical properties of sediments (e.g. stiffness, strength) were found higher at higher MH saturation.At the grain scale, the MH morphologies and pore habits in sandy sediments were observed by X-Ray Computed Tomography (XRCT, at Navier laboratory, Ecole des Ponts ParisTech) and Synchrotron XRCT (SXRCT, at Psiche beamline of Synchrotron SOLEIL). It has been really challenging due to not only the need of special experimental setups (needing both high pressure and low temperature controls) but also poor XRCT, SXRCT image contrast between methane hydrate and water. Specific experimental setups and scan conditions were then developed for pore-scale investigations of MH growth and MH morphologies in sandy sediments by using XRCT, SXRCT. Besides, a new method has been developed for accurate determination of volumetric fractions of a three-phase media from XRCT images. Observations (at better spatial and temporal resolution) via Optical Microscopy (in cooperation with the University of Pau) were finally used to confirm diverse MH morphologies in sandy sediments. Comparisons between observed MH morphologies, pore habits, and existing idealized models have been discussed. Methane hydrate formation in sandy sediments was supposed to be an unstable and complex process. Different types of MH morphologies and pore habits could exist in the sample. It seems vital that numerical studies on the mechanical behavior of gas hydrates in sediments, based on four idealized hydrate pore-habits, should take into account realistic hydrate morphologies and pore habits.Keywords:Methane hydrates, sandy sediments, formation, dissociation, morphologies, pore-habits, mechanical properties, XRCT, SXRCT, optical microscopy, triaxial tests, rock physic model

Pyrite oxidation in coal-bearing strata is recognised as the main precursor to Acidic Mine Drainage (AMD) generation. Predicting AMD quality and quantity for remediation, or proposed extraction, requires assessment of interactions between oxidising fluids and pyrite, and between oxidation products and groundwater. Current predictive methods and models rarely account for individual mineral weathering rates, or their distribution within rock. Better constraints on the importance of such variables in controlling rock leachate are required to provide more reliable predictions of AMD quality. In this study assumptions made during modelling of AMD generation were tested including; homogeneity of rock chemical and physical characteristics, controls on the rate of embedded pyrite oxidation and oxidation front ingress. The main conclusions of this work are:• The ingress of a pyrite oxidation front into coal-bearing strata depends on dominant oxidant transport mechanism, pyrite morphology and rock pore-size distribution.• Although pyrite oxidation rates predicted from rate laws and derived from experimental weathering of coal-bearing strata agree, uncertainty in surface area of framboids produces at least an order of magnitude error in predicted rates.• Pyrite oxidation products in partly unsaturated rock are removed to solution via a cycle of dissolution and precipitation at the water-rock interface. Dissolution mainly occurs along rock cleavage planes, as does diffusion of dissolved oxidant.• Significant variance of whole seam S and pyrite wt % existed over a 30 m exposure of an analysed coal seam. Assuming a seam mean pyrite wt % to predict net acid producing potential for coal and shale seams may be unsuitable, at this scale at least.• Seasonal variation in AMD discharge chemistry indicates that base-flow is not necessarily representative of extreme poor quality leachate. Summer and winter storms, following relatively dry periods, tended to release the greatest volume of pyrite oxidation products.

Two organic synthetic methods for the generation of methyl bearing chiral centers have been developed using: 1) dimerization of methylketene and 2) a free radical-based addition/elimination reaction involving allyl bromides. The first method, the asymmetric dimerization of methyl ketene, followed by an asymmetric aldol reaction and the appropriate functional group manipulations enabled us to construct the (2S, 4S, 6S) trimethylnonyl subunit found in the siphonariene class of natural products. The latter method explored the stereoselective potential of a free radical-based condensation reaction by examining compounds which are known to be able to support chiral auxiliaries and chiral Lewis acids. Additionally, substituent effect on the rates of this reaction were examined closely and found to be comparable to similar, previously examined systems. The synthetic utility, magnitude and scope of this reaction are discussed.
Ph. D.

Well-preserved echinoderm faunas are rare in the fossil record, and when uncovered, understanding their occurrence can be useful in interpreting other faunas. In this study, two such faunas of the same age from separate localities in the shallow-marine Ramey Creek Member of the Slade Formation in the Upper Mississippian (Chesterian) rocks of eastern Kentucky are examined. Of the more than 5,000 fossil specimens from both localities, only 9–34 percent were echinoderms from 3–5 classes. Nine non-echinoderm (8 invertebrate and one vertebrate) classes occurred at both localities, but of these, bryozoans, brachiopods and sponges dominated. To understand the attributes of both localities (Valley Stone and 213 quarries), the geologic and structural settings, lithofacies and depositional environments, as well as faunal makeup and abundances (diversity, evenness, density), were compared and contrasted. Faunas from the Valley Stone Quarry were located on an uplifted fault block in more shallow, open-marine waters with higher energies. As indicated by four distinct lithofacies, the depositional setting was more extensive and varied with interspersed shoals and basins that could accommodate a greater richness (65 species), even though organism densities and abundance were less. In contrast, fauna from the 213 Quarry were located on a downdropped fault block in a more localized, deeper, storm-shelf setting, characterized by a single lithofacies. Although organism density and abundance were nearly twice as high as that at the Valley Stone Quarry, species richness was lower (45 species), and only one species, a bryozoan, predominated. Overall, echinoderm classes, species and individuals were more abundant at the Valley Stone Quarry, and I suggest that this is related to the shallower and more varied depositional environments that developed in response to presence on the shallow, uplifted fault block. This suggests the importance of regional features like faults in controlling environments and organism distribution through time. Although the faunas were originally collected for their echinoderm-dominated “crinoid gardens,” in fact, echinoderms were in the minority, and bryozoans and brachiopods predominated in the communities. Hence, the communities might better be described as bryozoan “thickets” and brachiopod “pavements.”

SEM and CT X-ray imaging were used to quantify the surface geometries of sandstone pore and throat networks of the oil-bearing Stanley Sandstone of the Eutaw Formation of Jasper County, Mississippi, both in dry samples and in samples that had undergone laboratory simulations of Microbial Permeability Profile Modification (MPPM) oil-recovery technology. The goal of the study was to acquire some quantified understanding of the way induced bacterial activity affected the surface geometries and impacted the porosity and permeability of the oil-bearing Stanley Sandstone. Visible porosity remained high, but significant permeability modification occurred ubiquitously with pore and throat spaces of 10 ìm 20 μm diameter. Based upon quantitative analysis of photomicrographs, biofilm did not completely fill porosity but did clog pore throats, thus significantly impacting permeability.

Coal beds are one of the most promising reservoirs for geologic carbon dioxide (CO₂) sequestration, as CO₂ can strongly adsorb onto organic matter and displace methane; however, little is known about the long-term fate of CO₂ sequestered in coal beds. The "2800' sand" of the Olla oil field is a coal-bearing, oil and gas-producing reservoir of the Paleocene–Eocene Wilcox Group in north-central Louisiana. In the 1980s, this field, specifically the 2800' sand, was flooded with CO₂ in an enhanced oil recovery (EOR) project, with 9.0×10⁷m³ of CO₂ remaining in the 2800' sand after injection ceased. This study utilized isotopic and geochemical tracers from co-produced natural gas, oil and brine from reservoirs located stratigraphically above, below and within the 2800' sand to determine the fate of the remaining EOR-CO₂, examining the possibilities of CO₂ migration, dissolution, mineral trapping, gas-phase trapping, and sorption to coal beds, while also testing a previous hypothesis that EOR-CO₂ may have been converted by microbes (CO₂-reducing methanogens) into methane, creating a microbial "hotspot". Reservoirs stratigraphically-comparable to the 2800' sand, but located in adjacent oil fields across a 90-km transect were sampled to investigate regional trends in gas composition, brine chemistry and microbial activity. The source field for the EOR-CO₂, the Black Lake Field, was also sampled to establish the δ¹³C-CO₂ value of the injected gas (0.9‰ +/- 0.9‰). Four samples collected from the Olla 2800' sand produced CO₂-rich gas with δ¹³C-CO₂ values (average 9.9‰) much lower than average (pre-injection) conditions (+15.9‰, average of sands located stratigraphically below the 2800' sand in the Olla Field) and at much higher CO₂ concentrations (24.9 mole %) than average (7.6 mole %, average of sands located stratigraphically below the 2800' sand in the Olla Field), suggesting the presence of EOR-CO₂ and gas-phase trapping as a major storage mechanism. Using δ¹³C values of CO₂ and dissolved organic carbon (DIC), CO₂ dissolution was also shown to be a major storage mechanism for 3 of the 4 samples from the Olla 2800' sand. Minor storage mechanisms were shown to be migration, which only affected 2 samples (from 1 well), and some EOR-CO₂ conversion to microbial methane for 3 of the 4 Olla 2800' sand samples. Since methanogenesis was not shown to be a major storage mechanism for the EOR-CO₂ in the Olla Field (CO₂ injection did not stimulate methanogenesis), samples were examined from adjacent oil fields to determine the cause of the Olla microbial "hot-spot". Microbial methane was found in all oil fields sampled, but indicators of methanogenesis (e.g. alkalinity, high δ¹³C-DIC values) were the greatest in the Olla Field, and the environmental conditions (salinity, pH, temperature) were most ideal for microbial CO₂ reduction in the Olla field, compared to adjacent fields.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2004.
Includes bibliographical references.
In Part I the development of a new method for the construction of oxindoles and benzofuranones bearing quaternary stereocenters is discussed. A planar-chiral PPY derivative catalyzes the O-to-C acyl group migration (Black rearrangement) in a highly efficient and enantioselective manner. The utility of this method is further demonstrated by the formal total synthesis of the natural product aplysin. In Part II reactivity of bisphosphine palladium-complexes is discussed. It is shown that the oxidative addition of bisphosphine palladium-complexes bearing P(t-Bu₂)Me occurs through an SN2-type mechanism. This discovery allows us rationalize the difference in catalytic activity between Pd(P(t-Bu₂)Me)₂ and Pd(P(t-Bu₂)Et)₂ for the cross-coupling of alkyl electrophiles. The reductive elimination of H-X from bisphosphine palladium-hydride complexes is also discussed. The discovery that (P(t-Bu)₃)₂PdHCl undergoes facile reductive elimination in the presence of Cy₂NMe, while (PCy₃)₂PdHCl does not, is explained using X-ray crystal structures. These reactivity patterns may help to explain why Pd(P(t-Bu)₃)₂ is a much better catalyst than Pd(PCy₃)₂ for the Heck coupling of aryl chlorides. Finally, Part III describes preliminary work on a palladium-hydride catalyzed isomerization of allylic alcohols as well as initial attempts to study the mechanism of nickel-catalyzed cross-couplings of secondary alkyl-electrophiles.
by Ivory Derrick Hills.
Ph.D.

Проведено аналіз і кількісну оцінку локальних структур Бориславсько-Покутської зони з використанням структурно-тектонічних, лінійно-геометричних, кутових показників та показників порушеності. Виділено морфологічні різновиди локальних структур в залежності від механізму їх утворення. На основі геолого-математичного моделювання розроблена класифікація локальних структур, в основу якої покладена ступінь порушеності структури тектонічними рухами в процесі складкоутворення (морфологічні ознаки) і характер зміни кількісних показників, які їх описують. Змодельовано механізм формування локальних структур у межах Борис-лавсько-Покутської зони, що визначається місцем руйнування суцільності гірських порід в ядрі антиклінальної або в ядрі синклінальної складки. Встановлено, що при формуванні структур вирішальну роль, окрім горизонтальних рухів, відігравало також і бічне тертя. Визначено структурні умови, при яких поперечні тектонічні порушення є екранами покладів нафти і газу для умов Бориславсько-Покутської зони. Встановлено, що ділянки максимальної концентрації напруг в нафтогазоносному відношенні є слабоперспективними і проведення на них пошукових та розвідувальних робіт з використанням сучасних методик і технологій є недоцільним.
Диссертационная работа посвящена изучению морфологических особенностей строения, условий формирования и нефтегазоносности локальных структур Бориславско-Покутской зоны Предкарпатского прогиба. В результате изучения геодинамических условий залегания структурных форм Бориславско-Покутской зоны, используя структурно-тектонические, линейногеометрические, угловые показатели и показатели тектонической нарушености, установлено, что структуры с определенными морфологическими особенностями своего строения описываются присущими только им количественными показателями. При этом наблюдается четкая дифференциация структур по комплексу таких показателей, как коэффициент интенсивности структурообразования (м/км2), плотность тектонических нарушений (км/км2), напряженность горных пород (МПа), угол наклона осевой поверхности (град.). Тогда как такие показатели, как амплитуда, площадь, объем и линейные размеры структуры могут быть одинаковыми для сопредельных групп структур. Разработана классификация локальных структур Бориславско-Покутской зоны, в основу которой положена степень разрушения структуры тектоническими движениями в процессе складкообразования (морфологические признаки) и характер изменения количественных показателей, которыми они описываются. Используя количественные показатели, которые можно определить со структурной карты и характер соотношения между ними, можно моделировать морфологические особенности нового объекта при подготовке к поисковому и разведочному бурению. Морфологические разновидности структурных форм Бориславско-Покутской зоны сформировались в процессе складкообразования и могут быть определены местом разрушения целостности горных пород: в ядре первично антиклинальной или в ядре первично синклинальной складки. Образование структур I и II групп разработанной классификации происходило при разрушении пород в ядре синклинальной складки. Определяющим фактором при формировании складок I группы были горизонтальные движения, II группы - горизонтальные движения и боковое трение. Формирование складок III и IV групп происходило при разрушении целостности горных пород в ядре антиклинальной складки и определяющим фактором при их формировании, кроме тангенциальных усилий, является боковое (одностороннее или двустороннее) трение. Установлено, что изолированные ловушки (залежи) нефти и газа в опущенных тектонических блоках могут существовать при следующих условиях: вертикальная амплитуда смещения блоков по плоскости тектонического нарушения превышает толщину продуктивной части разреза; горизонтальная амплитуда смещения блоков по плоскости тектонического нарушения равняется или превышает половину ширины складки в поднятом блоке; горные породы в обоих блоках имеют одинаковые углы падения (одинаковый наклон крыльев) и через тектоническое нарушение породы-коллекторы контактируют с непроницаемыми породами. Возможны также разные комбинации вышеупомянутых условий, которые могут привести или к существованию тектонически изолированной ловушки в опущенном блоке, или к ее отсутствию. Проведенные исследования по определению количественных показателей локальных структур и характера их взаимосвязи с нефтегазоносностью позволили установить, что участки, для которых характерна максимальная концентрация напряжений и деформаций, в нефтегазоносном отношении слабоперспективны, поэтому проведение на них Поисковых и разведочных работ является нецелесообразным.
The quantitative description of folded structures of the Boryslav-Pokytska zones is conducted, using structurai-tectonic, linearly-geometrical, angular parameters and parameters of a tectonic disturbance, that has permitted to secure morphological types of folded structures depending on the gear of their formation. For representation of the conducted quantitative and qualitative descriptions the designed classification, in the basis by which one was the trusted to measure disturbance of frame tectonic by motions in process of structures formations (morphological characters) and nature of change of quantitive indicators, which describe them. The gear of formation of local tucks in borders of Boryslav-Pokytska zone is simulated, which one is determined by a demolition site of rocks: in a core of anticline or in a core of a synclinal tuck. It is established, that during the frames formation a main role was played not only by platforming moves but also lateral frictions as well. The structural conditions are determined, at which one the cross-sectional tectonic disturbances are screens of reservoirs of oil and gas for Boryslav-Pokytska zone conditions. It is established, that segments of maximum stress concentration and deformations are low perspective according for oil and gas bearing and discovering of a new considerable reservoires of oil and gas and the realization of search and reconnaissance works using of modern techniques and technologies are not expedient.

碩士
國立中央大學
土木工程研究所
87
Under the natural condition, the ground usually sedimented in layered formation. In layered formations, when the depth of the upper layer is relatively large than the width of the foundation, the bearing capacity can be evaluated by the strength characteristic of the upper layer. However, when the upper layer is not deep enough, which is relative to the width of the foundation, or the effect ranges to two different kinds of soil layers, we''ll have to make some corrections to evaluate the bearing capacity of the layered formations. This thesis continues the topic of thin layer sand underlying weak clay layer. Besides a strip footing on layered formation, instances clay overlying sandstone and sandstone overlying clay, this thesis deals with the bearing capacity of clay and sandstone. The topic of bearing capacity has been studied through experiments and numerical analyses (finite difference methods, FLAC program). A series of the model tests was performed with the usage of a rigid footing to approximate natural condition. In another aspect, we can also observe the failure modes of foundation. The test results will be compared with numerical analyses. The test results of clay and clay overlying sandstone are close to the FLAC analyses. Although the model test results of sandstone are different from the most of the theoretical methods, they are quiet close to upper bounds method (Chen and Drucker (1969)), plasticity equilibrium methods (Ladanyi (1968), Sowers (1979), Pells (1980), Wyllie (1992)) may be appropriate. The empirical method of Satyanarayana and Garg (1980) has a more accurate prediction of the results of sandstone overlying clay. This thesis has been studied through parametric study and the results have been charted. For practice purpose, the bearing capacity of rock overlying clay can be easily evaluated by the strength characteristic of the upper layer and use design chart to get the bearing capacity factor .

As hydrocarbon exploration and development moves into deeper water and onshore arctic environments, it becomes increasingly important to quantify the drilling hazards posed by gas hydrates. To address these concerns, a 1D semi-analytical model for heat and fluid transport in the reservoir was coupled with a numerical model for temperature distribution along the wellbore. This combination allowed the estimation of the dimensions of the hydratebearing layer where the initial pressure and temperature can dynamically change while drilling. These dimensions were then used to build a numerical reservoir model for the simulation of the dissociation of gas hydrate in the layer. The bottomhole pressure (BHP) and formation properties used in this workflow were based on a real field case. The results provide an understanding of the effects of drilling through hydratebearing sediments and of the impact of drilling fluid temperature and BHP on changes in temperature and pore pressure within the surrounding sediments. It was found that the amount of gas hydrate that can dissociate will depend significantly on both initial formation characteristics and bottomhole conditions, namely mud temperature and pressure. The procedure outlined suggested in this work can provide quantitative results of the impact of hydrate dissociation on wellbore stability, which can help better design drilling muds for ultra deep water operations.

It is essential to understand natural fracture systems embedded in shale-gas reservoirs and the stress fields that influence how induced fractures form in targeted shale units. Multicomponent seismic technology and elastic seismic stratigraphy allow geologic formations to be better images through analysis of different S-wave modes as well as the P-wave mode. Significant amounts of energy produced by P-wave sources radiate through the Earth as downgoing SV-wave energy. A vertical-force source is an effective source for direct SV radiation and provides a pure shear-wave mode (SV-SV) that should reveal crucial information about geologic surfaces located in anisotropic media. SV-SV shear wave modes should carry important information about petrophysical characteristics of hydrocarbon systems that cannot be obtained using other elastic-wave modes. Regardless of the difficulties of extracting good-quality SV-SV signal, direct shear waves as well as direct P and converted S energy should be accounted for in 3C seismic studies. Acquisition of full-azimuth seismic data and sampling data at small intervals over long offsets are required for detailed anisotropy analysis. If 3C3D data can be acquired with improved signal-to-noise ratio, more uniform illumination of targets, increased lateral resolution, more accurate amplitude attributes, and better multiple attenuation, such data will have strong interest by the industry. The objectives of this research are: (1) determine the feasibility of extracting direct SV-SV common-mid-point sections from 3-C seismic surveys, (2) improve the exploration for stratigraphic traps by developing systematic relationship between petrophysical properties and combinations of P and S wave modes, (3) create compelling examples illustrating how hydrocarbon-bearing reservoirs in low-permeable rocks (particularly anisotropic shale formations) can be better characterized using different S-wave modes (P-SV, SV-SV) in addition to the conventional P-P modes, and (4) analyze P and S radiation patterns produced by a variety of seismic sources. The research done in this study has contributed to understanding the physics involved in direct-S radiation from vertical-force source stations. A U.S. Patent issued to the Board of Regents of the University of Texas System now protects the intellectual property the Exploration Geophysics Laboratory has developed related to S-wave generation by vertical-force sources. The University’s Office of Technology Commercialization is actively engaged in commercializing this new S-wave reflection seismic technology on behalf of the Board of Regents.
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Les mines de fer de Cauê et de Conceiçao sont situées dans le District d'Itabira, dans la partie sud du Craton Sao Francisco, au Brésil. Trois unités géologiques, métamorphosées au faciès amphibolite, sont présentes aux deux mines: (1) une séquence volcano-sédimentaire Archéenne; (2) une formation de fer Protérozoïque et; (3) une unité de quartzite Protérozoïque. La formation de fer est recoupée par des dykes d'amphibolite et est tectoniquement imbriquée avec des schistes à talc et des amphibolites de la séquence volcano-sédimentaire. Les roches des trois unités ont été affectées par trois phases de déformation, subissant les chevauchements et boudinages associés. Dans la formation de fer, les structures associées à D1 et à D2 ont été générées par un cisaillement simple progressif dont la direction de transport est de l'Est vers l'Ouest. La structure D3 est caractérisée par des plis ouverts auxquels sont associés des clivages de crénulation. La jacutinga est la roche hôte des minéralisations d'or palladifère exploitées dans les formations de fer des mines de Cauê et de Conceiçao. La jacutinga est un faciès fortement cisaillé, métamorphisé et hydrothermalement altéré de la formation de fer de type Lac Supérieur, et est composée d'hématite, de quartz, de talc, de phlogopite, et de quantités mineures de tourmaline, d'apatite et de monazite. Le gisement aurifère de Cauê est composé de cinq corps minéralisés: Corpo Y, Corpo X, Central, Aba Leste et Aba Norte. Dans le corps minéralisé Corpo Y, les plus fortes concentrations d'or sont rencontrées dans les veines de quartz, alors que dans les quatre autres corps minéralisés les plus fortes concentrations d'or sont dans les veines d'hématite localement enrichies en quartz. Les veines riches en or sont parallèles à la foliation S1 dans tous les corps minéralisés, sauf pour Aba Norte où les veines d'hématite boudinées enrichies en or sont parallèles à S2. L'or et le palladium du minerai se trouvent dans les minéraux suivants: l'or, l'or palladifère, le palladium, l'oxyde de palladium, la palladséite et l'arsénopalladinite. La teneur en palladium dans les grains d'or varie de 1 à 20 %. Les plus hautes teneurs de palladium sont rencontrées dans les corps minéralisés Corpo X et Corpo Y, là où les grains d'or contiennent des inclusions d'oxyde cuivre-palladium se présentant sous forme d'îlots et sous forme de reliques en texture de remplacement. Dans le corps minéralisé Aba Leste, le palladium forme un alliage homogène avec l'or. Dans le corps Aba Norte, les grains d'or ne contiennent pas de palladium mais sont plutôt porteurs de rhodium à des teneurs jusqu'à 1,5 %. L'unique corps minéralisé en or et palladium de la mine de Conceiçao est parallèle à la foliation mylonitique. Cette minéralisation se retrouve dans le flanc des plis macroscopiques associés à D1 et à D2 et a été démembrée par la déformation de cisaillement progressif. L'or se trouve sous forme de grains aplatis, parallèles à la foliation mylonitique, et sous forme d'inclusions dans les grains d'hématite commune dans les horizons de goethite résultant de l'altération des carbonates. Une teneur en palladium jusqu'à 0,8 % est rencontrée dans les grains d'or en plaquettes recourbées. Le principal événement minéralisateur est contemporain au maximum du métamorphisme thermique (T=600°C), durant les cisaillements et chevauchements associés à D1. L'âge de l'événement minéralisateur a été estimé à 1,9 +/- 0,2 Ga par datation isotopique Pb/Pb. Cet âge est en accord avec l'âge métamorphique du Supergroupe du Minas, et correspond à l'âge de l'Orogène Transamazonien dans la partie sud du Craton Sao Francisco. L'altération hydrothermale associée à cet événement tectonique, caractérisée par la formation de talc, de phlogopite et de tourmaline, et par la formation de veines d'hématite et de quartz, a engendré la roche de type jacutinga. L'altération superficielle de la jacutinga a résulté en l'altération des silicates en kaolins et des oxydes en goethite. Aux hautes températures et hautes fugacités d'oxygène, le palladium et l'or ont pu être transportés sous forme de complexes chlorures; leur déposition serait reliée à une augmentation du pH. Il est proposé que cette augmentation du pH ait été causée par la réaction entre le fluide minéralisateur et la roche précurseur de la jacutinga, une itabirite dolomitique. La source la plus probable des métaux précieux est la séquence volcano-sédimentaire Archéenne. Les caractéristiques des minéralisations de Cauê et de Conceiçao amènent la définition d'un nouveau type de gisement aurifère, que nous nommons "Gisement d'or palladifère associé aux formations de fer de type Lac Supérieur fortement cisaillées et métamorphisées". D'autres occurences d'or palladifère sont aussi rencontrées dans la jacutinga, le long de la frontière est de la partie sud du Craton Sao Francisco, suggérant que cet environnement géologique est exceptionnellement favorable pour le type de minéralisation décrit.

This thesis introduces a rock typing method for application in shale gas reservoirs using conventional well logs and core data. Shale gas reservoirs are known to be highly heterogeneous and often require new or modified petrophysical techniques for accurate reservoir evaluation. In the past, petrophysical description of shale gas reservoirs with well logs has been focused to quantifying rock composition and organic-matter concentration. These solutions often require many assumptions and ad-hoc correlations where the interpretation becomes a core matching exercise. Scale effects on measurements are typically neglected in core matching. Rock typing in shale gas provides an alternative description by segmenting the reservoir into petrophysically-similar groups with k-means cluster analysis which can then be used for ranking and detailed analysis of depth zones favorable for production. A synthetic example illustrates the rock typing method for an idealized sequence of beds penetrated by a vertical well. Results and analysis from the synthetic example show that rock types from inverted log properties correctly identify the most organic-rich model types better than rock types detected from well logs in thin beds. Also, estimated kerogen concentration is shown to be most reliable in an under-determined problem. Field cases in the Barnett and Haynesville shale gas plays show the importance of core data for supplementing well logs and identifying correlations for desirable reservoir properties (kerogen/TOC concentration, gas saturation, and porosity). Qualitative rock classes are formed and verified using inverted estimates of kerogen concentration as a rock-quality metric. Inverted log properties identify 40% more of a high-kerogen rock type over well-log based rock types in the Barnett formation. A case in the Haynesville formation suggests the possibility of identifying depositional environments as a result of rock attributes that produce distinct groupings from k-means cluster analysis with well logs. Core data and inversion results indicate homogeneity in the Haynesville formation case. However, the distributions of rock types show a 50% occurrence between two rock types over 90 ft vertical-extent of reservoir. Rock types suggest vertical distributions that exhibit similar rock attributes with characteristic properties (porosity, organic concentration and maturity, and gas saturation). This method does not directly quantify reservoir parameters and would not serve the purpose of quantifying gas-in-place. Rock typing in shale gas with conventional well logs forms qualitative rock classes which can be used to calculate net-to-gross, validate conventional interpretation methods, perform well-to-well correlations, and establish facies distributions for integrated reservoir modeling in hydrocarbon-bearing shale.
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Formations containing gas hydrates are encountered both during ocean drilling for oil or gas, as well as gas hydrate exploration and exploitation. Because the formations are usually permeable porous media, inevitably there are energy and mass exchanges between the water-based drilling fluids and gas hydrates-bearing formation during drilling, which will affect the borehole’s stability and safety. The energy exchange is mainly heat transfer and gas hydrate dissociation as result of it. The gas hydrates around the borehole will be heated to decomposition when the drilling fluids’ temperature is higher than the gas hydrates-bearing formation in situ. while mass exchange is mainly displacement invasion. In conditions of close-balanced or over-balanced drilling, the interaction between drilling fluids and hydrate-bearing formation mainly embodies the invasion of drilling fluids induced by pressure difference and hydrate dissociation induced by heat conduction resulting from differential temperatures. Actually the invasion process is a coupling process of hydrate dissociation, heat conduction and fluid displacement. They interact with each other and influence the parameters of formation surrounding the borehole such as intrinsic mechanics, pore pressure, capillary pressure, water and gas saturation, wave velocity and resistivity. Therefore, the characteristics of the drilling fluids invading into the hydrate-bearing formation and its influence rule should be thoroughly understood when analyzing on wellbore stability, well logging response and formation damage evaluation of hydrate-bearing formation. It can be realized by establishing numerical model of invasion coupled with hydrate dissociation. On the assumption that hydrate is a portion of pore fluids and its dissociation is a continuous water and gas source with no uniform strength, a basic mathematical model is built and can be used to describe the dynamic process of drilling fluids invasion by coupling Kamath’s kinetic equation of heated hydrate dissociation into mass conservation equations.

碩士
國立成功大學
地球科學系碩博士班
93
Abstract The deep oil-bearing Talu sandstone of the Miocene age was investigated for microbiological analyses in this study. A total of 18 bacterial strains were isolated from the surface soil and the downcore of 3380 m-deep Talu sandstone and 3200 m-deep drilling muds in an oil well of the Miaol area. When examined by transmission electron microscopey (TEM) and Gram’s stain, most of the bacterial isolates appeared to be rod-shaped or short rod-shaped. They also varied in the colonial morphology. The isolated strains were identified based on the bacterial phylogeny and the 16S rDNA gene sequence alignment with the reference strains in association with the biochemical assay using the API microbiology Kit. In the different depths (3200m and 3386m) of the downcore, all Gram-negative bacteria are not the same in morphology. The effects of the temperature, pH, and salinity on the growth of bacterial isolates were investigated. As for temperature, the FM21, FM30, TG12, TG31 and SN10 isolates could survive up to 90℃, in which TG31 could also be well reproducible at 90℃. As for pH, the FM21, FM22, FM31, TG20, TG31, and TG32 isolates could survive at pH11. As for salinity, the SR10, SR21, SR22, and SR30 isolates could survive up to 50‰.

碩士
國立成功大學
環境工程學系碩博士班
98
Cement is an important building materials in Asian countries. Due to the limitation of raw material for cement in Taiwan and huge energy consumption during the process of cement production, this study focus on using four types of inorganic wastes including oyster husk ash, rice husk ash, water treatment plant sludge and basic oxygen furnace slag as substitution of raw material in cement production. Belite rich cement is sintered by stabilizing β phase in dicalcium silicate (Ca2SiO4，C2S) using heavy metals from electroplating sludge and leather sludge under reduction environment. Through the control of sintering environment, Cr is presented as Cr(III) which has low mobility in material. In addition, leaching behavior of heavy metal after clinkered in different environments is preformed by leaching tests to evaluate the effect of sintering environment towards formation of C2S and transformation of Cr valancy. The results from chemically mixed cement clinkers revealed reduction environment could engage the growth of β-C2S crystalline phase and reduced 10 wt.% of γ-C2S formation. Further investigation by replacing cement raw materials with electroplating sludge and leather sludge successfully produced belite rich cement. With 14 wt.% of electroplating sludge addition, sintered cement contained 77-79 wt.% of β-C2S with γ-C2S lower than 0.8 wt.%. While addition of leather sludge sintered cement had 77 wt.% of β-C2S and formation of γ-C2S was lower than 1 wt.%. According to the transformation of Cr valancy in clinkers, sintered under oxidation environment could increased the formation of Cr(VI) and with reduction environment, Cr was controlled in the form of Cr(III) with over 90% composition in total Cr. From the leaching tests, the leaching of Cr from chemical clinkers sintered under oxidation environment was higher than those sintered under reduction environment. After substitution of electroplating sludge and leather sludge into cement clinkers, a leaching of 68% of total Cr was observed in acetic acid. As Cr in clinkers sintered under reduction environment was in the form of Cr(III), the leaching of total Cr was only 0.29%. Concluded from above observations, although cement sintered with chrome sludge substitution may result in vaporization of heavy metals under reduction environment, the leaching of Cr from cement was much lower than those sintered under oxidation environment. Therefore, materialization of chrome sludge in cement production under reduction environment could stabilize Cr in the form of Cr(III) which not only decrease the risk to the environmental but also achieve the principle of environmental friendly characteristics.

Mannoproteins form the outermost layer of the cell wall in Saccharomyces cerevisiae. These glycoproteins are first synthesized in the endoplasmic reticulum and undergo posttranslational modification before they are transported through the secretory pathway. Some of the glycosylphosphatidyl inositol (GPI) anchored proteins are incorporated into the cell wall where their GPI-anchor is first trimmed off before they are anchored into the β-glucan network in the cell wall. The yeast cells are constantly faced with different environmental conditions and the cell surface mannoproteins are responsible for different morphological transitions that allow the cell to survive harsh conditions. The Flo proteins or adhesins encoded for by the family of FLO genes are known to confer adhesion to biotic and abiotic surfaces, hydrophobicity, biofilm and pseudohyphal filamentation. These phenotypes are suggested to be passive mechanisms employed by the cells to escape from stress or to prevent being washed away. The adhesion properties conferred by the adhesins are important in biotechnological processes. Identification of genes that have the potential to release more adhesins into the culture media will facilitate studies on the fine structural details and functional domains in these glycoproteins. The knowledge will also help in the formulation of fungal drugs since the adhesion of fungal pathogens to host such as humans is known to be the first step of infection. In this study, yeast strains with a deletion in KNR4 or GPI7, which are genes related to the biogenesis of the cell wall were employed to over-express FLO genes. Flocculation intensity and hydrophobicity of cells in the stationary phase were used as a measure of phenotypic changes of the cell surface. The effects of these deletions on the cell surface phenotypes in transgenic strains over-expressing FLO genes were assessed. We found that the KNR4 deletion resulted in a 50% decrease in cell-cell adhesion compared to the wild type. The deletion in GPI7 was found to have no effect in flocculation or the cell initiated a response that resulted in the expression of other genes to compensate for the loss of GPI7. The ability of the yeast cells to invade agar surfaces was not affected by the deletion of GPI7 or KNR4. The observed flocculation intensity was found to correlate with cell surface hydrophobicity. A decrease in the level of flocculation was also accompanied by a decrease in cell surface hydrophobicity. The results of this study indicate that deletion of the KNR4 gene affects the adhesins more than the deletion of the GPI7 gene. A screen of other genes related to cell wall biosynthesis will allow for a selection of genes with the potential to release adhesins to the cell culture medium.
Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2013.

In February 2007, the U.S. Department of Energy, BP Exploration (Alaska), Inc., and the U.S. Geological Survey conducted an extensive data collection effort at the "Mount Elbert #1" gas hydrates stratigraphic test well on the Alaska North Slope (ANS). The 22-day field program acquired significant gas hydrate-bearing reservoir data, including a full suite of open-hole well logs, over 500 feet of continuous core, and open-hole formation pressure response tests. Hole conditions, and therefore log data quality, were excellent due largely to the use of chilled oilbased drilling fluids. The logging program confirmed the existence of approximately 30 m of gashydrate saturated, fine-grained sand reservoir. Gas hydrate saturations were observed to range from 60% to 75% largely as a function of reservoir quality. Continuous wire-line coring operations (the first conducted on the ANS) achieved 85% recovery through 153 meters of section, providing more than 250 subsamples for analysis. The "Mount Elbert" data collection program culminated with open-hole tests of reservoir flow and pressure responses, as well as gas and water sample collection, using Schlumberger's Modular Formation Dynamics Tester (MDT) wireline tool. Four such tests, ranging from six to twelve hours duration, were conducted. This field program demonstrated the ability to safely and efficiently conduct a research-level openhole data acquisition program in shallow, sub-permafrost sediments. The program also demonstrated the soundness of the program's pre-drill gas hydrate characterization methods and increased confidence in gas hydrate resource assessment methodologies for the ANS.

Hot extrusion of aluminum is widely practiced in industries for economic production of structural components. The surface finish and tolerance of the extruded components, both from design and aesthetic requirement, are important parameters. Hot extrusion involves forcing of aluminum in the form of a billet at a predetermined temperature through a shaped opening called die. Attempts, over time, are made to evolve the die profile to produce quality components. The main geometric feature of the die enables it in imparting plastic deformation and subsequent surface generation of the extrudate. The surface of extrudate is generated on the portion of the die called bearing channel or die land. Aluminum metal which moves relative to bearing channel experiences a different state-of-stress as it passes through the bearing channel. At the entry side of the bearing channel, the stress is compressive which is large in magnitude and this magnitude of compressive stress gets diminished as metal moves towards exit side and eventually becomes zero at the exit. Temperature gradients and its distribution along the bearing channel, similar to stress gradient, are reported. Literature reports formation of the transfer layer on the bearing channel. The transfer layer is of two distinctive types, the one near entry side which virtually leads to contact between aluminum and die steel and the other nearer to exit side which isolates aluminum from die steel. The understanding of the mechanism of formation of transfer layer is most important since it is instrumental in determining the surface finish of the extruded component. All of the previous studies were conducted either in an actual extrusion press or using an instrumented extrusion press in the laboratory. The variables during these experiments could be the temperature of billet, extrusion ratio and speed of ram. Conducting these experiments using extrusion press is expensive and time consuming. To do experiments where the condition in a bearing channel can be simulated would be useful in conducting a more comprehensive study. To simulate the condition in the bearing channel a high temperature vacuum based pin-on-disc machine is designed and built. The fact that in a bearing channel there is virtually metal to metal contact with minimal or no chance of any intervening oxide layer, necessitated studies to be conducted under vacuum. A pin-on-disc test conducted under vacuum and high temperature would almost simulate condition on a bearing channel. Using this specially designed and built experimental setup the parameters influencing the transfer layer formation, temperature, sliding speed, load on the specimen, vacuum level and surface characteristics of the die are studied. Another feature of the test rig is that the configuration of pin and disc setup is vertical, which is different from regular pin on disc tribo-system, where pin and disc are held in horizontal configuration. The advantage of holding in vertical configuration is to eliminate the possibility of trapping the debris which alters the existing friction force and conditions. The test rig is constructed using a cylindrical shell and a matching dome shell. The test rig, to facilitate the isolation of the instrumentations used to measure the forces and wear from the heat source is partitioned into two portions. The cylindrical bottom compartment called test chamber and dome shaped top compartment called sensor chambers are separated by a plate. On the plate in the sensor chamber, a load-cell to pickup friction force, a linear variable differential transformer (LVDT) to measure linear wear and loading lever mechanisms for imparting normal load and measuring friction force are fitted. The lever mechanism, in particular the one which magnifies the normal load is designed to conserve the space in the vacuum chamber. Housing the instrumentation inside the vacuum chamber thereby reducing the number of ports required to sense mechanical signals, increases the efficiency of the pumping system. The cylindrical shell of the testing chamber is a double walled structure and water cooled in order to prevent the exposer of sensors to higher testing temperature. Rubber ‘O’ rings are used, wherever it is required to seal the vacuum. The necessary temperature required at the contact interface in the testing chamber is obtained by an electric resistance furnace, which is configured in such a way in the chamber that the heat generated is completely directed to the area where pin and disc are positioned. The interface temperature is monitored using a chromal-alumal thermocouple which is fixed very close to sliding interface on the pin holder. The power input to the furnace is controlled using PID (proportional integral derivative). The required sliding speed is achieved with the help of direct current (DC) servomotor. The shaft on which the disc or ring is fixed is connected to a timer-pulley. The timer-pulley in turn is connected to servomotor through a timer-belt. The diameter ratio of the driving pulley and driven -timer-pulley is selected in such a way that the rpm of driven-pulley is reduced by four times and the torque increased by four times resulting in a more stable mechanical input to the sliding pair. The necessary high vacuum level in the test chamber is created by using rotary pump and diffusion pump combination. Following tests are carried out. 1. Compression test: The strain rate response of aluminum (6060) under compressive state of loading is studied at strain rates 10-3s-1, 10-2s-1, 10-1s-1, 1s-1, 10s-1 and 102sand temperature ranging from 573 to 823K. The compression specimen is machined out of homogenized aluminum alloy (6060) cast ingots. True stress and true strain are estimated from load-displacement data of compression test. The true stress and true strain data are made use of in predicting the friction coefficient and sliding mode during sliding of aluminum relative to die steel at various temperature and other independent variables in vacuum. 2. The tensile test: A series of tensile tests at different temperatures and 10-1s-1 strain rate are conducted. The temperatures employed are from 423K to 723K. True stress, true strain, ultimate tensile strength and total percentage of elongation are estimated using load displacement data. The estimated ultimate tensile strength and total percentage of elongation are used for qualitatively explaining the morphology of transfer layer formed in the sliding experiments under different independent variables like temperature, speed, normal load, and surface texture of steel surface. 3. Adhesion test: The interaction at different temperature between the die steel (H11) and aluminum (6060) pair under static load is studied by conducting test in vacuum. The pin is made of homogenized aluminum and disc is made of die steel whose surface is generated by polishing on diamond paste until the average surface roughness (Sa) is of the order of 0.1 microns. The test temperatures are varied from 423 to 723K. The result is used in qualitatively explaining the morphology of transfer layer formed during sliding of aluminum and die steel pair in vacuum at various temperature, speeds and, normal load. 4. Sliding experiment: Steel pin and aluminum disc Pin on disc experiments are conducted at different temperatures in vacuum of the order of 4X10-4Pa. The experiments are conducted employing factorial design. The temperature, speed and load are the experimental parameters. The pin and disc are respectively made out of die steel and aluminum. Experiments are carried out with normal loads 20N, 40N, 63N, 80N, and 100N and speeds 0.1ms-1, 0.3ms-1, 0.5ms-1, 1.0ms-1, and 1.5ms-1 and with temperature over a range from 423 to 773K. The sliding distance covered is 500 meters. The friction force during sliding is monitored and used for estimating friction coefficient. Scanning electron microscopic study is carried out on surface, subsurface, wear track. The results, specifically, the friction coefficient and morphology of transfer layer are used to evaluate the influence of independent parameters on transfer mechanisms. The data generated from subsurface study and compression tests are used for estimating friction coefficient using Rigney’s plastic deformation model at 0.1ms-1. 5. Sliding experiment: aluminum pin and Steel disc The experiments reported in the previous paragraph where aluminum disc is slid against die steel pin had developed only the stresses of the order 16MPa. The estimated magnitude of stress level on bearing surface of extrusion die by various methods including numerical analysis is found to be more than 16MPa. In order to achieve a higher magnitude of stress and preserve the transfer layer mechanism, sliding an aluminum pin over the part of the textured surface of die steel ring is carried out. The changed boundary condition resulted in a nominal stress of 28 MPa which is comparatively more at 723K. The experiments are conducted employing factorial design. The other advantage of doing these experiments is that the effect of texture on the die surface can be studied by sliding aluminum pin over various surfaces. Thus temperature and surface texture are the experimental parameters for the present test. Different textured die steel surface is generated by machining process like, milling, electro discharge machining (EDM), wire electro discharge machining, silicon carbide slurry polishing, silicon carbide wheel grinding, CNC-milling and diamond paste polishing. Thus surfaces are basically of two types 1) with a lay on the surface and 2) a random surface. The tests are conducted at ambient temperature, 423, 573, 673, and 723K with a normal load of 56N and speed of 0.129ms-1. The morphology of transfer layer on the die steel ring is studied in scanning electron microscope. The friction coefficient is estimated from monitored friction force. The average surface roughness (Sa), results of compression test, and transfer layer are made use of to identify the sliding mode. The sliding of aluminum pin on diamond polished surface showed interesting results. Hence, another series of experiments using only diamond polished surface are conducted. The surface roughness of the steel surface achieved is 0.05 micro-meters. The load is 47N and speed is 0.043ms-1. The morphology of transfer layer and pin surface is studied using a Scanning Electron Microscope. Results of compression and tensile test: The flow stress is found to decrease with increase in compression test temperature. The SEM micrograph indicates large amount of fragmentation of harder phase with increase in strain rate at all temperature except for 423K. The fractured surface under tensile loading shows both intergranular and transgranular failure. Results of adhesion test: The area covered by the material transfer is found to increase with increase in temperature. The test can be used, to study the adhesive tendency between two pair of contacting surfaces. The area covered by the material transfer is found to be maximum at 723K. Results of sliding of die-steel pin on aluminum disc in vacuum: 1. The ANOVA (analysis of variance) results indicate the existence of transition speed of about 0.5ms-1, more than which the friction coefficient was found constant. The extrusion speeds employed in industries are in the range of 0.1ms-1 to 1.7ms-1 and the transition speed found in the present study is within this range. 2. The magnitude of friction, with a few exceptions, is found to be independent of temperature and sliding speed when the sliding speed is 0.5ms-1and above. The invariance of friction coefficient with temperature and sliding speed beyond 0.5ms-1 is beneficial in that it will not lead to any instability like stick-slip or squeal. 3. Though both ambient temperature and speed influence the morphology of transfer layer and friction coefficient, speed is found to be dominant according to statistical analysis. 4. The observed dependency of friction coefficient and morphology of transfer layer on test temperature and normal load is attributed to decrease in flow stress and increase in friction factor ‘m’, a ratio of interfacial shear stress to shear yield stress of the softer material. Though ANOVA shows the significance of speed and not that of temperature, the observed dependence of friction coefficient on temperature is attributed to the enhanced effect of adhesion at elevated temperature observed in the adhesion test. 5. The state of stress at the contacting surface is found to control the morphology of transfer layer. When the normal load exceeded 40N, it gave rise to higher magnitude of stress state at the contacting surface, resulting in formation of continuous transfer layer and hence the higher magnitude of friction coefficient. 6. Plastic deformation model based on Rigney’s approach for estimating friction coefficient can be used. The estimated friction coefficient is on the higher side. Hence, any design of equipments based on the Rigney’s plastic deformation model is a conservative design. 7. There appears to be a close relation between the morphology of wear track and quantity of wear-loss. The formation of debris and rough track, primarily for low temperature sliding indicate larger magnitude of wear-loss. The parameters, which bring about increased ductility of aluminum as observed in the case of higher temperature of sliding, results in reduced wear-loss due to large scale smearing and back transfer of material. The results of sliding of aluminum pin on die-steel ring in vacuum: 1. The mode of sliding changes from adhesive to abrasive mode depending on depth of penetration, tan(θ) where θ is the base angle of the conical asperity and average roughness parameter Sa ,all of them in turn depend on morphology of die steel surface and test temperature. 2. The friction coefficient and morphology of transfer layer are found to depend on the mode of sliding. The sub-surface plastic deformation, which characterizes the friction coefficient and morphology of transfer layer, is dependent on temperature of sliding. 3. The sliding experiment is capable of simulating the stress state on the bearing channel of the die; elucidating evolution of transfer layer, with change in operating parameters. 4. The ANOVA has clearly indicated the significance in friction coefficient at different temperatures and surface textures. In addition, the complex comparison below and above homogenization temperature (573K) has indicated significance in friction coefficient and thereby recognizing the importance of extrusion of aluminum at a temperature where it is in a single phase. Also, ANOVA indicates the dependency of both friction coefficient and transfer layer on the texture, i.e. either a lay or random. The results of sliding aluminum pin on diamond polished die steel ring: 1. Shearing of the cold welded junction is a probable mechanism involved in the formation of transfer layer up to 423K. 2. The transgranular and intergranular mode of fracture are identified to be the two possible modes of fracture of the asperity at temperatures greater than 573K. The large ductility of the aluminum alloy facilitated smearing resulting in a continuous transfer layer at temperatures greater than 573K. 3. The formation of a continuous transfer layer at temperatures greater than 573K is responsible for the observed high friction coefficient at these temperatures. Scanning electron microscopy observations of the fracture surfaces of the tensile test specimen revealed fracture to be a combination of both transgranular and intergranular modes.

This thesis describes the use of multiply-substituted stable isotopologues of carbonate minerals and methane gas to better understand how these environmentally significant minerals and gases form and are modified throughout their geological histories. Stable isotopes have a long tradition in earth science as a tool for providing quantitative constraints on how molecules, in or on the earth, formed in both the present and past. Nearly all studies, until recently, have only measured the bulk concentrations of stable isotopes in a phase or species. However, the abundance of various isotopologues within a phase, for example the concentration of isotopologues with multiple rare isotopes (multiply substituted or 'clumped' isotopologues) also carries potentially useful information. Specifically, the abundances of clumped isotopologues in an equilibrated system are a function of temperature and thus knowledge of their abundances can be used to calculate a sample’s formation temperature. In this thesis, measurements of clumped isotopologues are made on both carbonate-bearing minerals and methane gas in order to better constrain the environmental and geological histories of various samples.

Clumped-isotope-based measurements of ancient carbonate-bearing minerals, including apatites, have opened up paleotemperature reconstructions to a variety of systems and time periods. However, a critical issue when using clumped-isotope based measurements to reconstruct ancient mineral formation temperatures is whether the samples being measured have faithfully recorded their original internal isotopic distributions. These original distributions can be altered, for example, by diffusion of atoms in the mineral lattice or through diagenetic reactions. Understanding these processes quantitatively is critical for the use of clumped isotopes to reconstruct past temperatures, quantify diagenesis, and calculate time-temperature burial histories of carbonate minerals. In order to help orient this part of the thesis, Chapter 2 provides a broad overview and history of clumped-isotope based measurements in carbonate minerals.

In Chapter 3, the effects of elevated temperatures on a sample’s clumped-isotope composition are probed in both natural and experimental apatites (which contain structural carbonate groups) and calcites. A quantitative model is created that is calibrated by the experiments and consistent with the natural samples. The model allows for calculations of the change in a sample’s clumped isotope abundances as a function of any time-temperature history.

In Chapter 4, the effects of diagenesis on the stable isotopic compositions of apatites are explored on samples from a variety of sedimentary phosphorite deposits. Clumped isotope temperatures and bulk isotopic measurements from carbonate and phosphate groups are compared for all samples. These results demonstrate that samples have experienced isotopic exchange of oxygen atoms in both the carbonate and phosphate groups. A kinetic model is developed that allows for the calculation of the amount of diagenesis each sample has experienced and yields insight into the physical and chemical processes of diagenesis.

The thesis then switches gear and turns its attention to clumped isotope measurements of methane. Methane is critical greenhouse gas, energy resource, and microbial metabolic product and substrate. Despite its importance both environmentally and economically, much about methane’s formational mechanisms and the relative sources of methane to various environments remains poorly constrained. In order to add new constraints to our understanding of the formation of methane in nature, I describe the development and application of methane clumped isotope measurements to environmental deposits of methane. To help orient the reader, a brief overview of the formation of methane in both high and low temperature settings is given in Chapter 5.

In Chapter 6, a method for the measurement of methane clumped isotopologues via mass spectrometry is described. This chapter demonstrates that the measurement is precise and accurate. Additionally, the measurement is calibrated experimentally such that measurements of methane clumped isotope abundances can be converted into equivalent formational temperatures. This study represents the first time that methane clumped isotope abundances have been measured at useful precisions.

In Chapter 7, the methane clumped isotope method is applied to natural samples from a variety of settings. These settings include thermogenic gases formed and reservoired in shales, migrated thermogenic gases, biogenic gases, mixed biogenic and thermogenic gas deposits, and experimentally generated gases. In all cases, calculated clumped isotope temperatures make geological sense as formation temperatures or mixtures of high and low temperature gases. Based on these observations, we propose that the clumped isotope temperature of an unmixed gas represents its formation temperature — this was neither an obvious nor expected result and has important implications for how methane forms in nature. Additionally, these results demonstrate that methane-clumped isotope compositions provided valuable additional constraints to studying natural methane deposits.

碩士
國立東華大學
化學系
104
(1) In this thesis, we investigate the reaction of Si(3P) – SiH4(X1A1) in single collision condition. Density functional theory with functional, B3LYP and coupled cluster theory, and CCSD with cc-pVTZ basis set are used to optimize the geometries of the collision complexes, intermediates, products and transition states. The CCSD/CBS energies are then obtained. In this reaction, the intermediate 3i1 can convert to 1i1 via intersystem crossing. The minimum-energy crossing structures are predicted by CPMCSCF method with TZVPP basis set. The products observed experimentally are presumably singlet surface. The RRKM rate constants are computed to estimate product yields on singlet surface. The major product is found to be disilavinylidene (SiSiH2), an isovalent analogue of vinylidene (CCH2). (2) The molecular orbitals for the platinum complexes of mesoionic-triazol-5-ylidene and pyridine-bis-imidazol-2-ylidene with acetonitrile. We use B3LYP functional with SDD basis set optimize the ground state geometries, and carry out time-dependent DFT calculations for the vertical transitions. The results have compared with experiments.

博士
國立臺灣大學
化學研究所
95
In this thesis, carbon-carbon bond formations are studied through three kinds of reactions: styrene polymerization, cross-couplings and nucleophilic additions. A new series of Ni(II) complexes [(N,N'')NiBr2] bearing bidentate amino-oxazoline ligands have been synthesized and applied for polymerization of styrene. With cocatalyst, MAO, these Ni(II) complexes 4 are highly efficient catalysts for styrene polymerization with activities up to ~107 g / mol [Ni] × h under optimized conditions, which possess the best performance among the catalytic Ni systems now. Effects of the structures of catalysts and the reaction parameters on the activities and characteristic properties for the polymers have been discussed here. From the 13C NMR data, the degree of stereoregularity of the synthesized polystyrene could be moderately controlled by the chiral center in the oxazoline ring although atactic polymers were generally obtained by these Ni(II) catalysts. The neutral Pd(II) complexes [(N,N'')PdCH3Cl] 5 and the cationic complexes [(N,N'')PdCH3L]+ 7 were prepared for studying the mechanism for polymerization. For the neutral Pd complexes, their coordination chemistry, dynamic behavior, geometric isomerization, and reactivity toward alkynes have been studied herein. Furthermore, reactions of cationic Pd complexes with styrene, which led to the η3-π-benzyl Pd(II) complexes, made the possible mechanism of the polymerization of styrene for the Ni(II) system. Neutral Pd(II) complexes were synthesized and involved nitrogen-containing ligands, such as mono-oxazolines, amino-oxazolines and pyridyl-pyrazoles. Among them, the chloromethylpalladium(II) complex with bidentate pyridyl-pyrazole ligands exhibited excellent activities toward Heck coupling reactions with high TONs up to 95,000,000, comparable to the palladacycle systems. In addition, the pyridyl-azolate ligands are good candidates for catalytic Suzuki-Miyaura cross-coupling reactions. In the presence of Pd(OAc)2, KF as base, and such ligands in EtOH, the couplings of aryl bromides with phenylboronic acids could proceed with high conversions at room temperature in the air. Under the same conditions, it could slowly couple aryl chloride with phenylboronic acids, which is rare for Pd catalysts with bidentate nitrogen donor ligands. Finally, we synthesized a series of cationic allylpalladium(II) complexes bearing asymmetric amino-oxazoline ligands. The isomer interconversion is demonstrated by NOESY spectra to show a syn-syn, anti-anti exchange. Nucleophilic attacks to the Pd complexes would result in the linear and branched products. The regioselectivity is strongly dependent on the steric/electronic properties of the nucleophiles and the polarity of the used solvents.