(in English): This paper focuses mainly on the problem of the Mesolithic-Neolithic contact in the Iron Gates gorge at the turn of the 7th and 6th millenniums BC. A special emphasis is put on the eponymous site of Lepenski Vir. From a geographic point of view, this area represents a natural border between countries Serbia and Romania. There, in different layers and at different locations, were excavated and explored settlements documenting activities and social contact between the Mesolithic and Neolithic populations, as well as the transition from the Mesolithic way of life to the sedentary Neolithic one. The first part of the paper is devoted to an overview of scientific research, a development of views on the process of Neolitization and all the important aspects of culture. The second part deals with the examination of the first form of contact between Mesolithic and Neolithic populations based on the results of natural and archaeological research with theoretical application of the migration model, from the American anthropologist David W. Anthony.

The goals of this project are study Cu free back contact alternatives for CdS/CdTe thin film solar cells, and to research dry etching for CdTe surface preparation before contact application. In addition, an attempt has been made to evaluate the stability of some of the contacts researched. The contacts studied in this work include ZnTe/Cu2Te, Sb2Te3, and Ni-P alloys. The ZnTe/Cu2Te contact system is studied as basically an extension of the earlier work done on Cu2Te at USF. RF sputtering from a compound target of ZnTe and Cu2Te respectively deposits these layers on etched CdTe surface. The effect of Cu2Te thickness and deposition temperature on contact and cell performance will be studied with the ZnTe depositions conditions kept constant. C-V measurements to study the effect of contact deposition conditions on CdTe doping will also be performed. These contacts will then be stressed to high temperatures (70-100 degrees C) and their stability with stress time is analyzed. Sb2Te3 will be deposited on glass using RF sputtering, to study film properties with deposition temperature. The Sb2Te3 contact performance will also be studied as a function of the Sb2Te3 deposition temperature and thickness. The suitability of Ni-P alloys for back contacts to CdTe solar cells was studied by forming a colloidal mixture of Ni2P in graphite paste. The Ni-P contacts, painted on Br-methanol etched CdTe surface, will be studied as a function of Ni-P concentration (in the graphite paste), annealing temperature and time. Some of these cells will undergo temperature stress testing to determine contact behavior with time. Dry etching of CdTe will be studied as an alternative for wet etching processes currently used for CdTe solar cells. The CdTe surface is isotropically etched in a barrel reactor in N2, Ar or Ar:O2 ambient. The effect of etching ambient, pressure, plasma power and etch time on contact performance will be studied.

Electrical contacts to devices which pose low resistance continue to be of interest as the dimensions of devices decrease and nanotechnology demands better means of creating electrical access. Continued improvement in the performance of ohmic contacts requires techniques to better characterise and quantify the performance of such contacts. In order to study and estimate the resistance of such contacts or the resistance posed by the interface(s) in such contacts, accurate test structures and evaluation techniques need to be used. The resistance posed by an interface is quantified using its specific contact resistivity (SCR), which is denoted using ƒâc (units: £[cm2). Cross Kelvin resistor (CKR) test structures have been used for the measurement of low values of SCR. A simplified approach to this problem of SCR evaluation (developed previously at RMIT University) using the CKR test structures with varying contact sizes was used and during this work was shown to be accurate for the estimation of low values (less than10-8 £[cm2) of SCR. The silicides of interest in this study were titanium silicide (TiSi2) and nickel silicide (NiSi). These thin films are known for their low resistivity and low barrier heights to both n-type and p-type silicon. The research involved thin film formation and substantial materials characterisation of these thin films. The silicide thin films were formed by vacuum annealing metal thin films on silicon substrates. Silicide thin films formed from metal films deposited by DC magnetron sputtering and electron beam evaporation were compared. The composition, crystallographic orientation, and morphology of these thin films were studied using spectroscopy (AES, SIMS, RBS, in situ Raman spectroscopy), diffraction (Bragg-Brentano and glancing angle XRD, RHEED), and microscopy techniques (TEM, SEM, and AFM). TiSi2 and NiSi thin films were also found to be suitable for microsystems fabrication due to their ability to withstand wet etching of silicon using potassium hydroxide. The SCR of aluminium-titanium silicide ohmic contacts was evaluated to be as low as 6 x 10-10 ƒÇcm2, which is the lowest reported for any two- layer single-interface contact. Characterisation of ohmic contacts comprising of aluminium, nickel silicide, and doped silicon (with shallow implants) were also carried out using the same technique. SCR values as low as 5.0 x 10-9 ƒÇcm2 for contacts to antimony-doped silicon and 3.5 x 10-9 £[cm2 to boron-doped silicon were evaluated.

Emerging economies and the behaviour of firms domiciled in these markets is beginning to develop as a research area; yet little empirical work exists (Bruton, Ahlstrom, & Obloj, 2008; Hoskisson, Eden, Lau, & Wright, 2000; Meyer & Peng, 2005; Peng, Wang, & Jiang, 2008; Wright, Filatotchev, Hoskisson, & Peng, 2005). An extensive and critical review of the literature revealed that there was limited research that focused on the internationalisation of emerging economy firms to other emerging and developed economies. In order to address this clear gap in our understanding, the broad research problem that this thesis sets out to investigate is ‘how do institutions, organisational governance and managerial intentionality effect the internationalisation of smaller Indian firms’? It is argued that in order for research in strategy to make a lasting contribution, there is a need to contemplate whether the theories and methodologies developed in primarily mature and developed economies are applicable to the emerging economy context (Wright et al., 2005). In addressing this concern, this study draws on institutional theory, transaction cost theory, the resource-based view and aspects of the organisational capabilities perspective in order to understand the internationalisation of smaller Indian firms. In particular, the aim of this research was to understand the effect of institutions (Research Question One), organisational governance (Research Question Two) and the moderating effect of managerial intentionality (Research Question Three) on the internationalisation of smaller Indian firms. India was chosen as the context for the study due to its rapid growth in recent years which places it among the four big emerging economies of the world (Wilson & Purushothaman, 2003). The relatively recent liberalisation of the Indian economy in 1991 provides an interesting context within which to study the internationalisation behaviour of firms. Prior to its liberalisation India adopted what was known as an inward-focused, socialist-style, economic framework (Wilson & Keim, 2006). The liberalisation of the Indian economy has increased the country’s trade linkages with other emerging and developed countries, yet little research has been conducted on the internationalisation of Indian firms (Peng et al., 2008; Wright et al., 2005). Further, India’s linguistic distance but geographic closeness to emerging markets, yet western Commonwealth past and geographic distance to developed markets makes it a unique context. The research methodology adopted in this study entailed a qualitative design conducted through multiple case studies. The case study firms comprised four smaller manufacturing and four smaller service firms. Cases for the study were selected theoretically (Eisenhardt, 1989) using intensity sampling, snowball sampling, criterion sampling and opportunistic sampling techniques (Patton, 1990). To determine the size of the firms, the definition proposed by the Government of India was used. One key growth region in India was chosen due to the institutional diversity in India. Bangalore was chosen as it is considered a high growth region of the country that is well reputed for its service sector, as well as a competitive manufacturing sector (Ahya, Xie, Roach, Sheth, & Yam, 2006). The adoption of a multiple case study design facilitated an aggregated cross-case analysis. The data was collected through in-depth, semi-structured interviews with senior management in the selected case study firms. In addition, documentary evidence was collected through newspaper articles, information from trade journals and information from the company websites. The interviews were guided by an interview protocol and a case study database was created for each firm in order to increase the reliability and validity of the data. The data was coded using NVivo (version 7) and analysed using the ‘template approach’ (Crabtree & Miller, 1999). To date, literature originating out of mature markets has regarded institutions as background information due to the stability and maturity of institutions in these markets (Ingram & Silverman, 2002). However, when studied in an emerging market context, the role of institutions is argued to be pushed to the forefront of strategy research due to its relative underdevelopment (Meyer & Peng, 2005). This study used Scott’s (1995) three institutional pillars (regulative, normative and cognitive) to gain an institution-based view of the business strategies pursued by the smaller Indian firms (Peng et al., 2008). The findings highlighted regulatory institutional influences at the home country, host country and trade policy levels. The findings from this study shed light on the notion of institutional entrepreneurship, thereby extending institutional theory to take into account the strategic behaviour of firms. The findings further emphasised the need to gain legitimacy in international markets as a means to gain access to resources and overcome the liabilities of foreignness and newness. In doing so, the findings from this study extended Mathews’ (2006) ‘linkage, leverage and learning’ strategy to a ‘linkage, leverage, learning and legitimising’ strategy. Next, the findings from Research Question One extended the U-Model of internationalisation to highlight the importance of domestic market experience when gained in an institutionally complex market such as India. Finally, the findings highlighted the interaction between the path-dependent experience of the founders and the various dimensions of their managerial intentionality in managing the institutional influences on the firm. In studying organisational governance decisions (Research Question Two), transaction cost theory was used as the key conceptual perspective. This study used Williamson’s (1975) governance continuum to understand the organisational governance decisions of smaller Indian firms. Interestingly, the findings emphasised a move away from the narrow comparative-efficiency framework developed by Williamson (1975), towards a more eclectic understanding of the effect of transaction costs. The findings highlighted the choice of governance modes not as discrete designs, but as those that overlap as a result of being influenced by institutions, the experience of the firm with a particular mode, the propensity to trust, the constraints on firm behaviour, the managerial intentionality of the founders and the need to gain local knowledge from network partners. In adopting this broader perspective, the findings addressed the call by Madhok (1997) to understand the choice of governance modes from more than a cost minimisation perspective. Hutzschenreuter, Pedersen and Volberda (2007) suggested that the role of managerial discretion to date is downplayed in existing IB literature and hence called for research to focus on the role of managerial intent in the strategies of established multinationals rather than on the process of ‘becoming a multinational’. Research Question Three highlighted the moderating effect of managerial intentionality in managing the institutional influences and governance decisions of the firm. This study extended Hutzschenreuter et al.’s (2007) conceptualisation of managerial intentionality by emphasising the resilience as well as the reluctance of the founders (due to past experiences) as important in the emerging economy context. This study has practical implications for the case study firms as well as for potential entrants into India. Firstly, for the case study firms it is important to develop clear internationalisation strategies (as opposed to a reactive approach) due to the increasing competition both locally and internationally. Second, for the manufacturing firms, it is important to move beyond their pure low cost advantage. Partnering with other companies to leverage their resources and capabilities in international markets is one possibility. Third, for these firms to remain globally competitive, the sourcing of international talent is likely to increase their legitimacy and reduce their liability of foreignness. Finally, the continued liberalisation of the Indian economy has made it an attractive destination for foreign firms. While the case study companies have recognised the opportunities overseas, they should not ignore their domestic market where they enjoy a ‘home court advantage’. For potential entrants into India, it is important to recognise the potential competitive advantage that local incumbents have with regard to the environment. Second, foreign firms entering India and competing with smaller players need to understand the subtleties of the market and tailor their strategies to meet local needs. Finally, while this study has made contributions to the field, the findings must be interpreted in light of the limitations of the study. First, this study focused on one key big emerging market; India. Further, within India only one key region was examined. The findings reflect the business strategies by firms domiciled in Bangalore. Hence future studies could extend this research to other emerging markets and other regions of India to gain a more detailed perspective. Second, given the qualitative nature of the study, only analytical generalisations can be made. However, these insights can provide a basis for future researchers to develop quantitative measures to test the inferences drawn. Finally, this study was cross sectional in nature. In order to gain a more detailed analysis on the effect of institutions, future researchers may consider a longitudinal design to capture the institutional transitions over time.

This thesis deals with electron correlation effects within low-dimensional, mesoscopic systems. We study phenomena within two different types of system in which correlations play an important role. The first involves the spectra and spin structure of small symmetric quantum dots, or &quoteartificial atoms&quote. The second is the &quote0.7 structure&quote, a well-known but mysterious anomalous conductance plateau which occurs in the conductance profile of a quantum point contact. Artificial atoms are manufactured mesoscopic devices: quantum dots which resemble real atoms in that their symmetry gives them a &quoteshell structure&quote. We examine two-dimensional circular artificial atoms numerically, using restricted and unrestricted Hartree-Fock simulation. We go beyond the mean-field approximation by direct calculation of second-order correlation terms; a method which works well for real atoms but to our knowledge has not been used before for quantum dots. We examine the spectra and spin structure of such dots and find, contrary to previous theoretical mean-field studies, that Hund's rule is not followed. We also find, in agreement with previous numerical studies, that the shell structure is fragile with respect to a simple elliptical deformation. The 0.7 structure appears in the conductance of a quantum point contact. The conductance through a ballistic quantum point contact is quantised in units of 2e^2/h. On the lowest conductance step, an anomalous narrow conductance plateau at about G = 0.7 x 2e^2/h is known to exist, which cannot be explained in the non-interacting picture. Based on suggestive numerical results, we model conductance through the lowest channel of a quantum point contact analytically. The model is based on the screening of the electron-electron interaction outside the QPC, and our observation that the wavefunctions at the Fermi level are peaked within the QPC. We use a kinetic equation approach, with perturbative account of electron-electron backscattering, to demonstrate that these simple features lead to the existence of a 0.7-like structure in the conductance. The behaviour of this structure reproduces experimentally observed features of the 0.7 structure, including the temperature dependence and the behaviour under applied in-plane magnetic fields.

Past research on the acceleration phase in sprint running has concentrated on the kinematics of sprint blocks set-up and the initial steps after exiting the sprint blocks. In contrast, there has been limited research on the ground reaction forces (GRF) generated during the initial post-block foot contacts. These initial foot contacts in sprinting are important for optimising performance in the initial acceleration phase of sprinting. However, little is known about the GRF elite sprinters generate during the initial foot contacts and how these GRF characteristics relate to performance. It is the anterior-posterior (A-P) GRF that are of most importance as they indicate the sprinter’s motion from the start to the finish line. This thesis investigates the A-P GRF of the first two foot contacts of the sprint start after leaving the blocks. The participants included seventeen male and six female sprinters with a mean age of 22.6 (SD 4.4 years). Seventeen of the sprinters had competed at international/national level competitions and six at recreational/amateur level competitions. The athletes were classified as senior male elite (SME), senior female elite (SFE), junior male elite (JME) and senior male recreational (SMR). The sprinters were instructed to perform block starts at maximal effort to produce the fastest time over 5 metres on a 30 metre indoor laboratory track. Timing gates were used to record 5 metre times and two strain gauge force plates were placed in series to collect GRF data from the first two foot contacts after leaving the starting blocks. From the GRF data, braking time, maximum A-P braking force, A-P braking impulse, propulsive time, maximum A-P propulsive force, A-P propulsive impulse and A-P contact impulse were determined for each trial. The A-P propulsive phase constituted greater than 90% of the total contact time, had approximately twice the magnitude of the maximum force of the braking phase and accounted for more than 95% of the total contact impulse across the four groups of sprinters. The SME group produced a significantly larger A-P propulsive impulse on the first and second steps compared to the SFE (p less than 0.05 and p less than 0.05 respectively), JME (not significant and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The SME group’s maximum A-P propulsive force was significantly larger on the first and second steps than the SFE (p less than 0.05 and p less than 0.05 respectively), JME (p less than 0.05 and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The SME group’s propulsive time on the first and second steps was not significantly different compared to the SFE (both not significant) but was significantly shorter compared to the JME (p less than 0.05 and p less than 0.05 respectively) and SMR (p less than 0.05 and p less than 0.05 respectively) groups. The maximum A-P propulsive force correlated strongly with 5 metre time for the first step (rs = -0.670, p less than 0.01), second step (rs = -0.621, p less than 0.01) and the addition of the first and second steps (rs = -0.678, p less than 0.01) across all the sprinters. Whereas, the A-P propulsive impulse correlated strongly with 5 metre time for the first step (rs = -0.525, p less than 0.01), second step (rs = -0.592, p less than 0.01) and the addition of the first and second steps (rs = -0.584, p less than 0.01). Three A-P GRF patterns were observed during the first and second foot contacts of the sprinters examined in this study. A braking-propulsive (B-P) pattern was the most frequently observed followed by a propulsive-braking-propulsive (P-B-P) and a no braking (NB) pattern 82.7%, 15.4% and 1.9% respectively. The P-B-P and NB patterns, which have not been described previously, appeared most frequently in the least experienced sprinters. In the past, some sprinters and their coaches have tried to minimise the braking phase and maximise the propulsive phase of the first two foot contacts after exiting the blocks during sprinting. This study suggests that increasing the maximum propulsive force is the best way to increase performance over the first 5 metres of the acceleration phase. The research also suggests that there will be little benefit gained from trying to increase performance by focusing on the braking phase during these first two steps after exiting the blocks. As such, sprinters and coaches should focus their attention primarily on producing a large A-P propulsive force during the first two steps of a sprint.

Les contacts électriques, utilisés dans les contacteurs et les disjoncteurs, sont des composants fortement sollicités dont le comportement influence la durée de vie des appareils. Les pastilles de contacts électriques, en matériaux composites à matrice d'argent, sont actuellement élaborées par des opérations classiques de métallurgie des poudres avant d'être assemblées par soudage sur des supports contacts. Un procédé envisagé pour le remplacement de la méthode classique d'élaboration est celui de la projection dynamique par gaz froid communément appelé cold spray. Dans ce procédé, des particules de poudre sont accélérées au moyen d'une tuyère de Laval avant d'aller s'écraser sur un substrat en formant un dépôt par empilement. L'objectif de ce travail est de démontrer le potentiel de ce procédé pour la réalisation de contacts électriques. La démarche retenue s'appuie sur le triplet élaboration, caractérisation et simulation numérique. La souplesse du procédé cold spray a rendu possible l'élaboration d'une large gamme de microstructures composites en ayant optimisé au préalable la projection de la matrice d'argent. La caractérisation de ces microstructures a été menée à différentes échelles, notamment fine pour quantifier la porosité par microtomographie et très fine pour élucider les mécanismes interfaciaux d'adhésion et de déformation survenant lors de l'impact par microscopie électronique en transmission. Ces investigations poussées sont nécessaires pour comprendre le comportement de la matrice d'argent dans un premier temps. Les dépôts composites font l'objet d'études complémentaires, les données disponibles dans la bibliographie étant rares. D'un point de vue plus macroscopique, les microstructures ont été éprouvées par des moyens d'essais classiques ou développés pour les besoins de cette étude en s'appuyant notamment sur les effets engendrés par une impulsion laser. Parallèlement, des calculs par éléments finis ont permis de mieux comprendre les phénomènes induits par un tir laser et donc, par extension, par un arc électrique. Pour compléter cette démarche, une simulation numérique originale basée sur un modèle d'empilement faisant appel à la morphologie mathématique propose de relier microstructure réelle et microstructure simulée, le but étant de prévoir la morphologie d'une microstructure uniquement à partir de la caractérisation de quelques particules. L'ensemble des résultats obtenus a permis d'identifier les facteurs dont dépendent les propriétés d'un dépôt (granulométrie des poudres, taille de grains,...) et ainsi de choisir des microstructures en vue de la réalisation de contacts électriques. L'endurance de prototypes de contacts fabriqués par cold spray a été déterminée sur banc d'essais de contacteurs industriels. Elle a été montrée comme largement compétitive avec celle des contacts industriels actuels réalisés par métallurgie des poudres classiques.

<p>Nickel based coatings were deposited on copper substrates by two different sputtering techniques from a nickel alloy based target. The substrates used were commercially available copper based substrates for low duty electrical contacts. The coatings were analyzed and evaluated as copper diffusion barriers for electrical contact applications. In addition two types of commercially available electroplated nickel coatings (referred to as type A electroplated coatings and type B electroplated coatings) were characterized for comparison. The Technique I sputtered coatings were deposited using three different substrate bias voltages and two different working gas pressures. The Technique II coatings were deposited using two different substrate bias voltages and two different working gas pressures. All sputtered coatings were deposited at a temperature of 200° C. The quality of the barriers was investigated by analyzing their composition, microstructure, stress, mechanical properties , and surface roughness. The results show that sputtered coatings have polycrystalline structures while the two plated films had (200) orientation and (111) orientation. Both plated coatings contained impurities that originate from chemicals used in the plating baths. The surface of the sputtered coatings reflects the substrate surface, while the electroplated samples on the same substrate (type A coatings) show a smooth mirror like surface and the type B electroplated coatings show a rough surface.</p><p>Technique II sputtered coatings showed the highest hardness in the amount of 13 GPa, followed by electroplated type A coatings with a hardness of about 9 GPa while the Technique I coatings showed hardness of 6-8 GPa. All sputtered coatings exhibited compressive stress while the electroplated type A coatings exhibited tensile stress of almost twice the magnitude.</p><p>In this study it is shown that sputtered nickel based coatings sputtered nickel based coatings are a promising more environmental friendly alternative to electroplated nickel coatings.</p>

Notre étude a cherché à comprendre comment des acteurs locaux se connectent au transnational, quelle est la contribution de ces échanges au processus de développement local et quelle perspective peut en être envisagée. Comme cadre, elle a porté principalement sur les micro-commerçants de Butembo, au Nord-Est du Congo. L'objectif général a été d'analyser l'articulation entre rapports sociaux et rapports marchands dans les échanges transnationaux et l'impact de cette dynamique sur le processus de développement local. Notre étude s'inspire du courant de pensée néo-braudélien en histoire économique et sociale, qui établit qu'historiquement, l'économie ne procède pas uniquement de principes économiques mais aussi de rapports sociaux. Ce genre d'approche permet de reconnaître que pour le développement des échanges, le réseau de socialité est tout aussi important que la rationalité mise en avant par un certain individualisme méthodologique. D'autre part il contribue également à adopter une autre vision du secteur dit informel et de l'économie populaire, en termes d'articulation d'acteurs. En partant des pratiques d'acteurs qui s'adonnent aux échanges transnationaux, il y a lieu d'analyser autrement le commerce extérieur. Nous parlons de "transnational" plutôt que d'international, pour mettre en exergue la dimension d'ignorance des systèmes nationaux par ces marchands dont les opérations traversent différents espaces nationaux. Nous ne parlons pas de l'"informel transnational" au sens des mouvements qui transgressent les cadres étatiques car dans ce cas il s'identifierait à l'illégal. Mais nous faisons plutôt référence aux flux des personnes, des services et des biens à travers des espaces de plusieurs Etats, qui évoluent malgré les institutions de ces Etats, au travers de leurs cadres. Les acteurs y évoluent grâce à d'autres institutions, d'autres pratiques qui peuvent apparaître atypiques. C'est le cas du parrainage, des contacts réticulaires personnalisés. Les réseaux sont locaux et transnationaux. Des acteurs locaux pour effectuer des opérations transnationales, ont besoin des contacts dans d'autres pays. Dans la mesure où ces différents acteurs sont interconnectés, nous sommes en présence de réseaux. Le réseau assume ainsi une fonction d'intermédiation pour connecter le local au transnational. L'insertion dans le réseau est liée aux relations basées sur l'appartenance religieuse, les rapports familiaux ou amicaux, le village de provenance, la confiance, le parrainage. Les opérations économiques sont ainsi portées par des relations sociales. L'analyse en termes de réseau permet de sortir d'une approche de dépersonnalisation des relations économiques. Par ailleurs, si l'économie officielle a cessé de faire vivre la population, n'est-il pas pertinent de changer d'échelle et de prendre suffisamment en considération les initiatives d'autoprise en charge à la base ? En effet, des processus de développement sont en œuvre à Butembo comme sans doute ailleurs en Afrique. Une conception universaliste et modernisatrice du développement fausse le regard sur ces processus. Le développement local fait référence à un processus de prise en charge individuelle et collective des initiatives en vue de l'amélioration de la qualité de vie et du cadre de vie pour les individus et la communauté à l'échelle locale. En Afrique, ces initiatives n'attendent souvent pas un cadre et des institutions formelles pour s'exprimer. En l'absence de l'État comme moteur du développement, l'associatif a pris le relais au niveau local dans le cadre d'une responsabilisation locale et contribue au renforcement du lien social. Généralement, ces initiatives ne pèsent pas lourd, du point de vue quantitatif. Mais, à l'échelle locale, il s'agit des petits pas du processus de développement. Les travaux d'infrastructures, qui constituent un des aspects sur lesquels portent les initiatives locales, nécessitent des moyens qui sont souvent mobilisés dans le cadre des associations d'acteurs, parmi lesquelles les groupements des commerçants. Ces associations constituent ainsi des cadres de redistribution au service des initiatives locales. Ces dernières traduisent une demande de maîtrise des choix de développement par les populations elles-mêmes, à l'échelle locale. Les pratiques locales imposent donc de nous rendre compte de l'importance de l'ancrage local des processus de développement et de la nécessité de les consolider en vue d'y baser des politiques à long terme. Enfin dans le débat sur "l'économie informelle" et "populaire", l'approche en termes d'acteurs plutôt que de secteur, contribue, par la compréhension de leurs pratiques, à montrer l'importance de leur articulation historique au sein d'un espace et son rôle pour une conceptualisation du rapport entre commerce et développement.

In this thesis, the problem of controlling a surgical masterand slave system with force reflection is studied. The problemof stiff contacts between the slave and the environment isgiven specific attention. The work has been carried out at KTHbased on an initial cooperation with Karolinska Sjukhuset. Theaim of the over all project is to study the possibilities forintroduction of a force reflective teleoperator in neurologicalskullbase operations for the particular task of bone millingand thereby, hopefully, increase patient safety, decreasesurgeon workload and cost forthe society. The main contributions of this thesis are: Derivation of a dynamical model of the master andoperator’s finger system and, experimental identificationof ranges on model parameter values. Based on this model, theinteraction channel controllers optimized for transparency arederived and modified to avoid the influence of the uncertainmodel parameters. This results in a three channel structure. Todecrease the influence of the uncertain parameters locally atthe master, a control loop is designed such that the frequencyresponse of the reflected force is relatively unaffected by theuncertainties, a result also confirmed in a transparencyanalysis based on the H-matrix. The developed teleoperatorcontrol structure is tested in experiments where the operatorcould alter the contact force without facing any problems aslong as the slave is in contact with the environment. As a result of the severe difficulties for the teleoperatorto move from free space motion to in-contact manipulationwithout oscillative behaviour, a new detection algorithm basedon passivity theory is developed. The algorithm is able todetect the non-passive behaviour of the actual teleoperatorinduced by the discrete change in system dynamics occurring atthe contact instant. A stabilization controller to be activatedby the detection algorithm is designed and implemented on themaster side of the teleoperator. The detection algorithm andthe stabilization controller are shown highly effective in realexperiments. All major research results presented in the thesis have beenverified experimentally. KeywordsTeleoperator, Force Feedback, Passivity, StiffContacts, Control, Robustness, Transparency, Bone Milling,Uncertainty