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The influence of three elastic contact models on the dynamics of the drilling module is studied by representing the percussive drilling process as a drifting oscillator. The Kelvin-Voigt, Hertz stiffness and nonlinear stiffness and damping models were considered. The local dynamics of the system were found to be almost identical for the three models. Hence the Kelvin-Voigt system adequately describes the local dynamics of the system. However, for larger frequency and higher damping the behaviour of the three models differed. Experimental indentation studies were carried out on sandstones samples using static and dynamic loading. A force penetration relation was obtained for the loading and unloading phases of the indentation using a conical and spherical indenter under quasi-static conditions. Conical indentation tests were carried out in dynamic conditions. Both experiments showed that the force penetration relationship that could describe the contact model were closer to that obtained for the elastic-plastic indentation of ductile materials. The dynamic model for the drilling module was developed using an elastic plastic model for conical and spherical indenter. In addition, the model’s parameters were modified to those obtained from the experiments and used for the comparison with the results obtained for the elastic plastic model. The result obtained suggested a topological similarity between the experimental and theoretical parameters. It was also noted that the results suggested that the conical indenter appeared to be more efficient of the two indenter types considered. Finally, the rock fracture as a result of its contact with the drill-bit insert was investigated. For simplicity, the inserts are considered as flat punch and the contact problem is treated as a plane strain problem. Experimental studies were also carried out to determine the crack initiation angle in sandstone.

We study the following geometric representation problem: Given a graph whose vertices correspond to axis-aligned rectangles with fixed dimensions, arrange the rectangles without overlaps in the plane such that two rectangles touch if the graph contains an edge between them. This problem is called Contact Representation of Word Networks (Crown) since it formalizes the geometric problem behind drawing word clouds in which semantically related words are close to each other. Crown is known to be NP-hard, and there are approximation algorithms for certain graph classes for the optimization version, Max-Crown, in which realizing each desired adjacency yields a certain profit. We present the first O(1)-approximation algorithm for the general case, when the input is a complete weighted graph, and for the bipartite case. Since the subgraph of realized adjacencies is necessarily planar, we also consider several planar graph classes (namely stars, trees, outerplanar, and planar graphs), improving upon the known results. For some graph classes, we also describe improvements in the unweighted case, where each adjacency yields the same profit. Finally, we show that the problem is APX-complete on bipartite graphs of bounded maximum degree.

Systematic pre cleaning, disinfection and sterilization of medical equipment used in examination and treatment of patients are very important for safe care of the patients and the staff handling these instruments. Due to the technical properties of stainless steel, its hygienic experience and the sophisticated look of the stainless steel, it has dominated the medical health care environments for decades. The wetting properties of stainless steel surfaces are presumed to be essential for the process of clean ability and for a wide variety of bio compatibility.In collaboration with the topical company for this thesis, the idea is to find the correlation between the surface properties of various stainless steel in relation to their wetting and spreading ability to enable efficient cleaning of the surface. For a substrate surface to be thoroughly cleaned of any debris or soil, it should be able to allow proper adherence of the liquid across its surface to a certain degree good enough to ensure good wettability of the surface and conversely easy and proper removal of any attached soil on the surface. Higher demand on cleaning, disinfection and sterilization processes became more and more pressing due the development of complex medical equipment.Different stainless steel (316L) surface finishes and some surgical equipment are investigated using the state of the equipment at Halmstad University. Using the imaging interferometer and mapping software, Mountain Map, the results obtained is controlled readings and classification of the various surface parameters. Contact angle measurements were carried out on each surface with three polar (Distilled water, Glycerol and Ethylene glycol) and one non polar (Olive Oil) probe liquids with a drop volume of 3μm using Theta Optical Tensiometer and One Attention Software for the analysis. The impact and correlations of the surface parameters on wettability was later compared from the measurements obtained.

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La dynamique du geste reste peu exploitée dans le domaine de l’interaction hommemachinealors qu’elle permet de définir des critères simples d’analyse de l’intention desutilisateurs. Sa principale utilisation porte sur les fonctions de transfert des périphériquesisotoniques. Ces fonctions permettent d’établir une relation entre le geste de l’utilisateureffectué dans l’espace moteur avec le périphérique de pointage (i.e. souris) et le mouvementdu pointeur dans l’espace visuel. Les fonctions de transfert utilisées par les systèmesd’exploitation modernes restent cependant fortement méconnues même si des études ontmontré qu’elles ont un impact sur les performances des utilisateurs. Pour caractériser cesfonctions, nous avons développé un périphérique électronique qui simule une souris réelleet qui permet d’obtenir les fonctions de transfert de tout système. Nous avons ainsi puobtenir les fonctions des systèmes Windows, Linux et Mac et nous avons observé des différencesnotables entre ces fonctions. Nous avons ensuite cherché à optimiser ces fonctionsen réduisant au maximum le nombre de leurs degrés de liberté. En faisant varier de manièreexhaustive ces paramètres, nous avons ainsi pu observé des différences significativesqui montrent qu’il existe une famille de fonctions pour lesquelles les performances sontoptimales. Enfin, nous nous sommes intéressés à l’utilisation de la dynamique du gestedans un autre contexte, celui de la génération d’événements discrets, pertinent dans lecadre des interfaces sans contact de type Kinect. Nous avons ainsi montré qu’il est possiblede distinguer la sélection du déplacement dans une tâche d’interaction 3D. La techniquedéveloppée est ensuite améliorée dans le cas des cibles de petites tailles et son applicationdans un contexte d’interaction 2D est évaluée. / The dynamic of the gesture is not used a lot in the domain of human-computer interaction,while it can help to define some simple heuristics to analyze the intents of users.Its first use is related to transfer functions for isotonic devices. Those functions establisha relationship between the gesture of the user, executed in motor space with the pointingdevice (i.e. a mouse), and the movement of the pointer in the visual space. The transferfunctions used by modern operating systems are still not well known, even if somestudies have shown they have an impact on user’s performance. To characterize thosefunctions, we have developed an electronic device which simulates a real mouse, and thatcan retrieve the transfer functions of any system. We have then exposed the functions ofthe Windows, Linux and Mac systems, and we observed some visible differences betweenthose functions. We have then tried to optimize those functions by reducing their numberof degrees of freedom. By varying those parameters in an exhaustive way, we have thenobserved some significant differences that show there is a family of functions for whichperformances are optimal. Finally, we were interested in the use of the dynamic of thegesture in another context : the generation of discrete events, useful when dealing withcontact-less interfaces, like the Kinect. We have shown that it is possible to distinguishbetween picking and drag’n’drop in a 3D interaction task. The technique is then improvedin the case of small size targets, and its application in a 2D interaction context isevaluated.

This thesis explores the practice of family mediators when screening for domestic violence during mediation. Mediation Information and Assessment Meetings (MIAMs) and Joint Mediation Meetings (JMs) were recorded between April 2010 and January 2011, by four mediators who mediate for National Family Mediation (NFM) affiliated services in the South of England. These meetings were analysed from the mother’s perspective, using qualitative and quantitative analysis. The themes for analysis were taken from the Duluth Domestic Abuse Intervention Programme (DDAIP). It was found that mediators did initially screen for domestic violence during the MIAM, using the guidelines published by NFM; that screening was focused on the clients perception of the abuse and not the mediators interpretation of the abuse. The published expectation for screening to be ongoing throughout mediation was explored during the analysis of the joint meetings. There was evidence that abusive behaviours were alleged or inferred during those meetings and there was also evidence that the abusive behaviours and the emotions expressed by the mothers were managed by the mediators. There was no clear evidence that the mediators were proactively screening for domestic violence during the joint meetings save for reacting to and managing the impact and effect of the negative behaviours. This study concludes that mediators do not routinely screen for domestic violence during joint meetings, therefore guidance and training for ongoing screening during joint mediation meetings is needed. The current guidance and policy for screening needs to be reviewed.

Anaerobic pretreatment and aerobic post-treatment of municipal wastewater is being used more frequently. Recent investigations in this field using an AFBR/aeration chamber combination demonstrated the technical feasibility of this process. The investigation presented herein describes the use of a combined UASB/aeration chamber system for the treatment of municipal wastewater and attempts to demonstrate the technical feasibility of using the UASB process as both a pretreatment unit and a waste activated sludge digestion system. The results indicate that the UASB reactor has a TSS removal efficiency of about 37%. Of the solids removed by the unit, 33% were degraded by the action of microorganisms, and 4.6% were accumulated in the reactor. The results also show that accumulation of solids in the UASB reactor took place in the upper zone of the sludge bed.

Interracial contact in South Africa continues to be fraught with tension. Many investigators have used the contact hypothesis to explore the relationship between contact and prejudice in South African samples, which has revealed the highly complex character of interracial contact. With much of the research on interracial contact being quantitative in nature and comparatively little qualitative work being done, few studies have looked at perceptions of interracial contact and none can be found which have used Q-methodology as the method of investigation. The aim of the study was to uncover groups of people who have similar perceptions about interracial contact in South Africa through the factor analytic process inherent in Q-methodology. Q-methodology is a comprehensive way of looking at people’s views, attitudes, opinions and beliefs on a topic and has both qualitative as well as quantitative dimensions, making it unique method which can shed a different kind of insight into the subjectivities of interracial contact compared to traditional research methods. Q-methodology is explained in some detail and supported as the best approach for exploring perceptions of interracial contact in South Africa given the country’s history of racial segregation and complexity of intergroup dynamics. The study used a non-probability, volunteer sample of 55 undergraduate students at the University of the Witwatersrand. A centroid factor analysis was performed on the data followed by a varimax rotation, which yielded four groups (“factors”) of people with similar patterns of subjectivities on the topic of interracial contact in South Africa. The groups were labelled the experientialists, ethnocentrists, segregationists, and integrationists based on their distinct patterns of perceptions of interracial contact in South Africa.

Faculty of Science School of Geography,Archaeolgy and Enviromental Studies 9408209v brandoornum@nmsa.org.za / While the Iron Age sequence of the Shashe-Limpopo region of Limpopo Province has been the subject of much research in the past, little is known about the huntergatherer sequence of the area. I begin to address this lack through the description of three new hunter-gatherer sites: Tshisiku Shelter, Balerno Main Shelter and Balerno Shelter 2. I examine how hunter-gatherer spaces, places and identity changed with the movement of different groups of farmers (including Zhizo, K2 and Mapungubwe period farmers) into the Shashe-Limpopo region over the last 2000 years. I also investigate how hunter-gatherer / farmer proximity impacted on interaction, and what social structures, boundaries, and constructed identities underlie interaction in the region. The pre-contact and contact periods are compared in order to determine whether changes in the hunter-gatherer sequence were due to the arrival, and continued presence, of farmers. Ethnographic and archaeological interaction case studies are used to construct a model of interaction for the Shashe-Limpopo. Based on data from Tshisiku Shelter, Balerno Main Shelter, Balerno Shelters 2 and 3, and Little Muck Shelter, a new sequence is proposed for hunter-gatherer occupation in the Shashe-Limpopo region: · An early pre-contact phase (11 120 – 10 890 BC; 6000 – 1220 BC) · A late pre-contact phase (1220 BC - AD 100) · An early contact phase (AD 100 – AD 900) · A late contact phase divided into two periods: - The Zhizo period (AD 900 – AD 1000 / 1200) - The K2 / Mapungubwe period (AD 1000 – AD 1300) Finally, a late second millennium phase of Late Iron Age farmer utilisation of hunter- gatherer sites occurs in the recent past (AD 1600 – AD 1900). iv My research suggests that: · A hunter-gatherer presence occurs significantly earlier in the region than initially hypothesised. · Differences in farmer social structure and identity play a role in how farmers interact with hunter-gatherers, and vice versa. · Finally, due to the differences between farmer groups and decreasing space on the landscape, a range of hunter-gatherer reactions to the presence of farmers occurred throughout the last two millennia in the Shashe-Limpopo region.