Thèse--Sc. phys.--Paris VI, 1983. / Bibliogr. p. 247-256.

Digital musical instruments pose a number of unique challenges for designers and performers. These issues stem primarily from the lack of innate physical connection between the performance interface and means of sound generation, for the latter is usually dematerialised. Thus, this relationship must instead be explicitly determined by the designer, and can be essentially any desired. However, many design issues and constraints remain poorly understood, from the nature of control to the provision of performer-instrument feedback. This practice-based research contends that while the digital and acoustic domains are so different as to be fundamentally incompatible, useful antecedents for digital musical instruments can be found in the histories of electronic music. Specifically, it argues that the live electronics of David Tudor are of particular prescience. His home-made circuits offer an electronic music paradigm quite antithetical to both the familiar keyboard interface and the electronic music studios that grew up in the years after World War II, and are seen to embody a number of aspirational qualities. These include performer-instrument interaction more akin to steering rather than fine control, the potential for musical outcomes that are unknown and unknowable in advance, and distinct instrumental character. This leads to the central contribution of this research; the development of a Tudor-inspired conceptual framework that can inform how digital musical instruments are designed, played, and evaluated. To enable more detailed and nuanced discussion, the framework is broken down into a series of sub-themes. These include both design issues such as nuance, plasticity and emergence, and human issues such as experience, expressiveness, skill, learning, and mastery. The notion of sketching in hardware and software is also developed in relation to the rapid iteration of multiple designs. Informed by this framework, seven new digital musical instruments are presented. These instruments are tested from two different perspectives, with the personal experiences of the author supplemented with data from a series of smallscale user studies. Particular emphasis is placed on how the instruments are played, the music they can produce, and their capacity to convey the musical intentions of the performer (i.e. their expressiveness). After the evaluation of the instruments, the Tudorian framework is revisited to form the basis of the conclusions. A number of modifications to the original framework are proposed, from the addition of a dialogical model of performerinstrument interaction, to the situation of digital musical instruments within a wider musical ecology. The thesis then closes with a suggestion of possibilities for future research.

The purpose of this study was to explore whether Indian counsellors and psychotherapists in the UK practice in an indigenous way with their Indian clients. The aim was to find out more information about the different types of Indian indigenous interventions that may currently be used by these professionals. The study also bridges the gap in the literature about the lack of research on the practical uses and applications of Indian indigenous counselling skills in the UK.The study reports data from six face-to-face open-ended semi-structured interviews with Indian counsellors who have been trained in Western psychotherapeutic approaches and have knowledge of Indian psychotherapeutic approaches. The research was analysed using Interpretative Phenomenological Analysis (IPA). Firstly, the analysis concluded the use of several Indian indigenous interventions used by the participants, such as Prekshadhyan which can be used for psychosomatic pain relief, Jain virtue of forgiveness which can be useful for working with sexual abuse, use of spirituality and cultural beliefs for bereavement, and so on. Secondly, the analysis identified some of the most common barriers to therapy (e.g. stigmas and taboos) experienced by Indian clients in the UK, and it provided suggestions on how to overcome these. Finally, the analysis suggested factors that therapists should pay attention to (e.g. client context and use of Indian languages) in order to maximise Indian clients’ engagement in therapy and to minimise their exclusion from it.

No description available.

Thèse de doctorat : Sciences physiques pour l'ingénieur. Mécanique et ingénierie : Bordeaux 1 : 2008. / Titre provenant de l'écran-titre.

No description available.

Philosophiae Doctor - PhD / Metal matrix composites harness the superior attributes of their individual constituents to form high performance materials that would rather be impossible from monolithic substances. Owing to many possible combinations, a myriad of metal matrix composite systems can be fabricated with a metal (or a metal alloy) as a matrix (continuous) phase and a ceramic as a reinforcement (discontinuous) phase. The current study focuses on two matrices, namely Nickel Aluminide and Austenitic Steel as well as two reinforcements namely, Titanium Carbide and Oxynitrides. NiAl alloys are candidates for high temperature structural materials due to their high melting temperature, low density, good thermal conductivity, and excellent oxidation resistance.

Pour l'intégration 3D, le procédé d'interconnexion par flip chip est très utilisé. Le principal inconvénient de ce procédé est l'utilisation de traitement complémentaire des puces avant leur assemblage. Pour résoudre ce problème, a été développé, un nouveau procédé d'interconnexion par micro-insertion de micro-cylindres de nickel appelés micro-inserts directement dans les zones de connexion des puces en aluminium. Cependant, il existe trop d'interrogations sur la fiabilité des interconnexions réalisées. Afin de répondre à certaines de ces interrogations ce travail de thèse présente une étude localisée de l'insertion d'un micro-insert de nickel isolé dans un film d'aluminium. L'étude de l'insertion a été effectuée grâce à la modification de la technique de nanoindentation. Ceci a permis de mettre en évidence les modes de déformation des matériaux en contact pour différents diamètres et différentes forces maximales et de mesurer en parallèle la résistance de contact électrique.

Point defects control many properties of technological importance in intermetallic compounds such as atomic diffusion, creep, hardness, mechanical properties and sintering. Farther, since intermetallic compounds are characterized by long range atomic order, the point defects in these compounds can be qualitatively different from those in pure metals and disordered alloys. In the present study, we have chosen β-NiAl for our point defect studies since it is a potential candidate for high temperature applications and a model system for the study of basic phenomena in ordered alloys. We have used a mean field formulation for studying point defect concentrations. The outline of the formulation is as follows: We divide the rigid, body centred cubic lattice into two interpenetrating cubic sublattices called α and j3 which are made up of the cube corners and body centres respectively. We write a generic free energy function (G) that involves the temperature T and the six sublattice occupancies viz., the A (Ni), B (Al) and vacancies (V) on the two sublattices α andβ. We use the constraints on the number of α and β sublattice sites viz., the number of α sublattice sites is equal to the number of β sublattice sites, to write G as a function of four of the six sublattice occupancies and T. We define three auxiliary parameters η1, η2 and η3 which correspond to the vacancy concentration, the differential B species population on the two sublatices (the chemical or atomic order), and the differential vacancy population on the two sublattices, respectively. We then rewrite G as a function of T, xB and ηi. The G can now be minimized with respect to the three auxiliary variables so that we recover the free energy (G) as a function of XB and T only. The formulation requires as inputs the Ni-Ni, Al-Al, Ni-Al, Ni-V and Al-V interaction energies in the nn and nnn shells. We have obtained the Ni-Ni, Al-Al and Ni-Al interaction energies from the effective pair potentials reported in the literature. For the Ni-V and Al-V interaction energies we have used a bond breaking model in which we have assumed that the Ni-V and Al-V interaction energies in the nnn shell to be zero. Using the above interaction parameters in our mean field formulation we have determined the concentrations of various types of point defects in β-NiAL We have specifically chosen the temperature range of 800 - 2000 K and the composition range of 45 - 55 atomic% Al. Our results can be summarised as follows: 1.The predominant defect in the stoichiometric alloy is a combination of an Ni-antisite defect and two vacancies on the Ni sublattice. 2.The Al-rich alloys of composition (50 + ∆) atomic% contain 2∆% vacancies;since the alloys are almost perfectly ordered, these vacancies predominantly occupy the Ni sublattice. Similarly, the Ni-rich alloys of composition (50 — ∆)atomic% contain ∆% Ni antisites. 3.Both the vacancies on the Ni sublattice (in Al-rich alloys) and Ni-antisites (in Ni-rich alloys) show negligible temperature dependence, and hence owe their origin to the off-stoichiometry. 4.In all the alloys, the Al-antisites have the lowest concentration (of the order 10-6 even at 2000 K) and the concentration of the vacancies on the β sublattice is the next lowest. Thus, our results support the view that β-NiAl is a triple defect B2 and, if we consider constitutional vacancies as those which have a little or no temperature dependence, there exist constitutional vacancies in Al-rich β-NiAl. This conclusion is in agreement with some of the experimental results. However, it must be pointed out that there is considerable disagreement among experimental results from different groups.

The thesis introduces a novel alloy system based on submicron distributions of intermetallic phases realised through eutectic solidification in the ternary system Ni-Al-Zr. Various compositions in this system comprising of intermetallic phases distributed in different eutectic structures show ultra-high strength at temperatures upto 700°C combined with reasonable tensile plasticity, exceptional oxidation resistance and high temperature structural stability. Intermetallics have long been used in high temperature alloys systems such as in the classical Ni-base superalloys that derive their strength from nanoscale dispersions of the aluminide, Ni3Al(γ’) in a matrix of disordered fcc Ni (γ), alloyed with expensive, high density refractory elements such as Re and Ru. The high temperature applications of intermetallics derive from their strength retention to high temperatures, creep resistance enabled by low diffusion rates, and attractive oxidation resistance based on high concentration of elements such as Al that forms stable oxides. Several decades of effort on the development of new generation of intermetallic alloys through the 80’s and 90’s have gone unrewarded, with the exception of TiAl based alloys that are now used in recent generation aircraft engines. The promise of intermetallics as high temperature candidate materials is limited by their poor ductility or toughness arising from several intrinsic properties such as low grain boundary cohesive strength (in the case of Ni3Al) or an insufficient number of slip systems (as in NiAl) or extrinsic effects such as embrittlement by hydrogen (Fe3Al) that derive fundamentally from the existence of directionality in bonding. However, low ductility or toughness can often be alleviated by limiting the length scale for slip. We have therefore examined the possibility of combining intermetallics in the form of eutectic structures, potentially limiting slip lengths within each intermetallic constituent. Eutectic structures in binary systems limit the choice of intermetallic combinations so that finding such combinations with engineering potential is difficult. On the other hand combinations of three elements or more would enable a significantly larger set of permutations of eutectic intermetallics, provided the constituent binary phase diagrams contain either eutectic or peritectic reactions involving intermetallic phases, as well as intermediate intermetallic phases. The ternary Ni-Al-Zr system met our criterion in several ways. The Ni-Al binary phase diagram shows a peritectic reaction from liquid and NiAl (Pm 3m, B2 with a lattice parameter of 0.288nm) to form Ni3Al (Pm 3m, L12 with a lattice parameter of 0.356 nm), intermetallics that have been extensively investigated in earlier literature. The Ni-Zr system shows a peritectic reaction between liquid and the Ni7Zr2 (C12/m1 with a lattice parameters a=0.469nm, b=0.823nm, c=1.219nm) phase to form the intermetallic Ni5Zr (F 43m with a lattice parameter of 0.670nm). Further the NiAl and Ni7Zr2 are both intermediate phases and should therefore form a mono-variant eutectic on the composition line joining these two phases in the ternary system. We note that Zr participates in many glass forming systems. In the Ni-Zr system, for example, glass forming ability has been associated with the structure of the liquid phase and associated low diffusivity. As a consequence, a fine scale eutectic structure may be expected. Zr has also been reported to strengthen and ductilise Ni3Al and NiAl. Finally, both Al and Zr form stable oxides and might promote oxidation resistance. After introducing the thesis in Chapter 1, the experimental details are outlined in the Chapter 2. The experimental results and subsequent discussions are presented in three subsequent chapters. Chapter 3 reports the microstructural aspects of as cast alloys in this ternary system Previous literature and our analysis of phase equilibria in the Ni-Al-Zr system based on Thermo-Calc, suggested that solidification from the liquid to form the Ni3Al + Ni5Zr, Ni3Al + Ni7Zr2 and NiAl+ Ni7Zr2 eutectics is possible. We obtained eutectic structures involving combinations of these intermetallic phases along a constant zirconium section at 11 at. %. The alloy A (Ni-77 at.%, Zr-11at.% and rest Al) contains eutectic structures containing the Ni3Al and Ni5Zr phases in two morphologies, a planar, lamellar structure and a more irregular form. The alloys B (Ni-74 at.%, Zr-11at.% and rest Al) and C (Ni-71 at.%, Zr-11at.% and rest Al) contain two different eutectic structures that combine the Ni3Al and Ni7Zr2 phases, and the NiAl and Ni7Zr2 phases. These phases were identified by a combination of X-ray diffraction, transmission electron microscopy coupled with energy dispersive spectroscopy and electron probe microanalysis. The volume fraction of each eutectic constituent is different in the two compositions in that alloy B(Ni-74 at.%, Zr-11at.% and rest Al) contains significantly higher volume fractions of the eutectic containing the Ni3Al and Ni7Zr2 phases than the alloy C (Ni-71 at.%, Zr¬11at.% and rest Al). In order to understand effect of individual phases we have melted several other alloys (alloy D to I) bounding these eutectic alloys (7-25 at.% Al, 5-15 at.% Zr and rest Ni) that form primary solidification phases of the intermetallic structures that constitute the eutectics. Chapter 4 discusses the mechanical behaviour of the fully eutectic alloys alloys as well as alloys with a combination of primary phases along with a eutectic. Mechanical behaviour was assessed in vacuum arc melted and suction cast material. The compressive strength of eutectic and off-eutectic compositions has been evaluated as a function of temperature. Very high strength levels of around 2 GPa could be achieved accompanied by reasonable room temperature tensile plasticity in the range 3-4%. The introduction of the respective primary phases of NiAl, Ni3Al, Ni5Zr and Ni7Zr2 results in decrease of strength. We have explored the origins of strength and tensile plasticity in alloys through micro and pico indentation (hardness) measurements and an examination of slip lines and crack initiation on pre-polished surface of the tensile tested samples as well as by transmission electron microscopy. Chapter 5 explores the oxidation resistance of these alloys in isothermal tests. The oxidation resistance of alloys compares well with recently developed cast single crystal alloys. Clearly, the oxide scale is extremely adherent and no spalling occurs. Electron microprobe analysis shows the presence of a fine scale, layered oxide structures and reaction zones within the substrate. The oxidation behaviour has been characterized using TGA, XRD and EPMA. We have attempted to understand the mechanism of oxidation through analysis of rate constants and activation energy coupled with microstructural observations. Chapter 6 presents a summary of the current work and present the scope for further work.