Les différents types de vibrations des garnitures de forage jouent un rôle important dans le dysfonctionnement des opérations de forage car celles-ci conduisent à la rupture prématurée des trains de tiges, par conséquent, à la perte de l'outil au fond du trou et aussi à l'endommagement de la machine. En s'intéressant au forage de type rotary, cette thèse étudie le phénomène des vibrations de torsion de point de vu, modélisation par une EDP (modèle distribué) dont on établi les conditions aux limites adéquats. Une large partie de notre analyse dans ce mémoire concerne la commande du phénomène de vibration de torsion conduisant à une vitesse de rotation contrôlée sur le bord. La modélisation du phénomène de torsion affectant le train de tiges lors d'un forage pétrolier a été représentée par une équation aux dérivées partielles (1D) d'ordre deux: type linéaire intégrant le phénomène de frottement. Deux entrées apparaissent dans les conditions aux limites en termes de vitesse de rotation du train et de la réaction avec le sol. Il s'agit donc de designer la commande en vitesse qui assure la rotation adéquate pour le forage et qui n'excite pas le phénomène du torsion en tenant en compte l'interaction de la formation avec le sol. La stabilité de la garniture de forage dépend d'un système de boue du fluide qui doit injecté. Nous traitons une connexion entre le système de forage rotary et le système du fluide. Nous obtenons un système couplé sous la forme EDP-EDO. Egalement, nous avons transformé le système couplé à un système neutre avec retard. Nos achevons ce mémoire par la construction d'une loi de contrôle pour l'observateur du système de forage rotary avec une seule mesure aux limites dans le haut de la colonne pour estimer les paramètres de l'outil de forage qui sont accessibles à mesurer. / The different types of drilling vibrations play an important role in the malfunctioning of the drilling operations because the lead to the premature rupture of the trains, consequently, to the Loss of the tool at the bottom hole and also damage to the machine. Much of our analysis in this specification relates to the control of the phenomenon of vibration of twisting leading to a controlled rotational speed on the edge. The mathematical aspects and simulation results will be detailed. The modeling of the torsion phenomenon affecting the drill string during was represented by a second order partial differential equation : linear type integrating the phenomenon of friction. Two entries appear in the boundary conditions in terms of the speed of the train and the reaction with the soil. It is therefore a matter of designating the speed which ensures adequate rotation for drilling and which avoid the torsional phenomenon of twist taking into account the interaction of formation with the soil. The dynamic of the drill string stability depends on a system of fluid which should be injected to bring cuttings out of the well bore and amplify the torsional vibrations phenomena. To suppress fracturing collapse or influx of fluids surrounding the well, it is important to integrate the dynamic of the pressure in this study : PDE-ODE control problem. Finally, we are concerned with the problem of boundary observer stabilization for a system of hyperbolic PDEs which describes the drilling systems. The design relies on the top boundary measurements only.

The stabilisation of archaeological iron is considered as one of the major problems facing the archaeological conservator today. Free chlorides, held as counter ions at the metallic anode, act as electrolytes and promote corrosion of metallic iron This study examines and compares the efficiency of a range of aqueous wash methods currently used to remove chloride ions from archaeological iron and determines how these various treatments work. It also investigates the effect of selected aqueous wash treatments on the chloride rich metastable corrosion product 0-FeOOH. The amount of Cl'removed from 0-FeOOH and any transformations to new compounds are recorded. Iron objects were treated using aqueous Soxhlet extraction with nitrogen, aqueous sodium hydroxide and aqueous alkaline sulphite solutions. Synthetic O-FeOOH and PFeOOH1Fe3Om4 ixtures were washed in aqueouss odium hydroxide, aqueousa lkaline sulphite solution, aqueous sodium sulphite, hot and cold deionised water. The outcome of the work showed that: (1) For archaeological iron objects: O. SM nitrogen de-aerated aqueous NaOH solutions are very efficient chloride extractors, often approaching a 100% efficiency. Almost as efficient were 0.5M aqueous... NaOH/Na2SO3 treatment solutions. Nitrogen de-aeration of treatment solutions improves their cr extraction efficiency, by freeing Cl' from its counter ion role. Hydroxide ions improve extraction efficiency of Cl- from iron objects in nitrogen and Na2S03 de-aerated environments. The de-aerated aqueous Soxhlet extraction method, as suggested by Scott and Seeley (1986), is a less efficient chloride extractor than either nitrogen de-aerated 0.5M NaOH or 0.5M NaOH/Na2SO3. De-aerated NaOH treatment solutions are to be preferred to NaOH/Na2SO3 solutions, as they do not introduce residual electrolyte ions (SO 42). (2) For O-FeOOH samples: Pure O-FeOOH and P-FeOOH/Fe3O4 mixtures reacted differently during washing. Pure 0-FeOOH completely transformed to cc-FeOOH in the alkaline environments provided by NaOH and NaOH/Na2SO3. This released all the chloride from the PFeOOH. In NaOH solutions within the range pH8.5 to 10.5 0-FeOOH/Fe3O4 transformed mostly to Fe304. Above pH1 1 there was limited conversion. Improved release of Cl' from P-FeOOII/Fe3O4 mixture correlated with the transformation of PFeOOH to Fe304.

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Microwave holography is a well established method of using the Fourier relationship between an antenna’s current distribution and its complex beam-pattern to produce surface maps of large parabolic antennas. As the final part of a surface upgrade, a holographic map of the HartRAO 26 m telescope was produced. This showed that the surface has an RMS error of 0.45 mm. The measurement used a small reference dish to correlate against and retrieve amplitude and phase values. Due to system phase instabilities, this dish had to be attached to the measured antenna in order to enable sharing a high frequency local oscillator (LO). The movement was modelled and corrected for. However, a slight distortion remained. It is recommended that, either the LO distribution system is stabilised by using multiple PLLs or amplifiers and low loss cables are used to enable moving the reference antenna to a stationary position.

© Cranfield University / This thesis focuses on what stability is, and what interventions have supported stability in four communities in Afghanistan and Nepal. It is the author’s view that this is the first in-depth village level assessment of how populations conceive of stability and stabilisation and thus presents a challenge to existing analysis and research about how to foster stability in contexts in extreme tension and often violent conflict. The thesis argues that international, particularly Western, notions of stability and stabilisation processes have failed to grasp the importance of local political legitimacy formation, which is a vital aspect of contemporary statebuilding of a ‘non-Westphalian’ nature. The interventions, across defence, diplomatic and defence lines, have also at times undermined one another and in some cases contributed to instability. This is particularly acute when the interventions have been motivated by the conflicting demands of statebuilding, counter-insurgency (COIN) and development theories. The thesis argues that the nature of the interventions, their conception of stability and exogenously-driven goals limit the ability to promote stability. Research findings indicate that that local processes of stabilisation have, at times, proven to be more enduring but only in circumstances where a combination of local and national political processes have allowed political legitimacy to be formed and maintained. Research findings also suggest that the more successful stability interventions have been critically supported by humanitarian and security activities which have provided for the immediate needs of the population. Longer term stability has only been embedded in contexts which have also been able to exploit economic opportunities.