A simple yet effective technique is used to obtain a numerical stability criteria for explicit time-marching algorithms in elastic-viscoplasticity. The resulting stability criteria are capable of accounting for non-associative and work hardening viscoplasticity for a wide variety of constitutive laws of the Perzyna-type. Conservative estimates for maximum permissible time step are obtained. This thesis investigates the level of conservativeness by considering different problems exhibiting various levels of constraint. Using the proposed stability criterion, assuming a linear flow function, non-hardening and uniform material properties, it is shown that the initial strain algorithm for plasticity and the initial strain viscoplastic algorithms are numerically the same. The intuitive approach used to obtain an estimate of maximum permissible time step was also used to develop an unconditionally stable implicit time marching scheme which avoids expensive matrix inversions. / Thesis / Master of Engineering (ME)

No / Visual impairment is an important risk factor for falls, but relatively little is known about how it affects stair negotiation. The present study determined how medio-lateral (ML) dynamics of stepping and single limb support stability when stepping up or down to a new level were affected by blurring the vision of healthy elderly subjects. Twelve elderly subjects (72.3±4.2years) were analysed performing single steps up and single steps down to a new level (7.2, 14.4 and 21.6cm). Stepping dynamics were assessed by determining the ML ground reaction force (GRF) impulse, lateral position of the centre of mass (CM) relative to the supporting foot (average horizontal ML distance between CM and CP during single support) and movement time. Stability was determined as the rms fluctuation in ML position of the centre of pressure (CP) during single support. Differences between optimal and blurred visual conditions were analysed using a random effects model. Duration of double and single support, and the ML GRF impulse were significantly greater when vision was blurred, while the average CM¿CP ML distance and ML stability was reduced. ML stability decreased with increasing step height and was further decreased when stepping down than when stepping up. These findings indicate that ML balance during stepping up and down was significantly affected by blurring vision. In particular, single limb support stability was considerably reduced, especially so during stepping down. The findings highlight the importance of accurate visual feedback in the precise control of stepping dynamics when stepping up or down to a new level, and suggest that correcting common visual problems, such as uncorrected refractive errors and cataract may be an important intervention strategy in improving how the elderly negotiate stairs.

No / PURPOSE: The risk of falling increases dramatically with age, and visual impairment is known to be an important risk factor. Therefore, it is highly pertinent to assess the effects of age and vision on the performance of everyday tasks linked to falling, such as stepping from one level to another. METHODS: Nine young (age, 26 +/- 4 years) and ten elderly (age, 72 +/- 5 years) subjects performed a stepping-up task of three different heights. Their stepping strategies with blurred and optimally corrected vision were compared. Center of mass (CM), center of pressure (CP) dynamics (in the mediolateral and anteroposterior directions), and foot clearance parameters were determined, and statistical regression modeling was applied. RESULTS: Elderly subjects spent 20% more time (P = 0.03) than young subjects during double support and they had reduced anteroposterior CM-CP divergence (P < 0.001) during double support and slower anteroposterior (P < 0.001) and mediolateral (P = 0.002) CM velocities during initiation of movement and single limb support. Blur caused similar adaptations, such as increased toe clearance, across both age groups, though mediolateral (ML) CM-CP divergence in elderly subjects was significantly more reduced than in young subjects (P < 0.001). CONCLUSIONS: Findings indicate, in general, that older subjects used a more cautious and controlled stepping strategy. However, the lack of significant age differences in toe clearance suggests this strategy was mainly aimed at reducing ML instability rather than increasing margins of safety regarding toe clearance.

No / This study utilises a rarely examined biomechanical parameter – the free vertical moment to determine age-related differences in rotational kinetics of the body about the vertical-axis when stepping down from a stationary position. Ten older and 10 young adults completed step-downs from three heights. Free vertical moment impulse and peak during step-initiation double-support and the subsequent step-execution phase, and vertical-axis pelvis angular displacement and velocity at instant of landing were compared. The free vertical moment during double-support was directed away from the intended leadlimb side, producing a change in vertical-axis rotational momentum that moved the lead-limb in a forwards- medial direction about the stationary support/trailing limb during the subsequent step-execution phase. The free vertical moment during step-execution was directed towards the lead-limb side and acted to slow/halt the body’s vertical-axis rotation away from lead-limb side. Free vertical moment impulse and peak during double-support were similar between groups (P > 0.05), but during step-execution were significantly reduced in older adults (P = 0.002). As a result older adults had greater verticalaxis pelvis angular displacement and velocity at instant of landing (directed away from lead-limb side), with significant (P < 0.001) group-by-step height interactions indicating that differences between groups became more pronounced with increasing step-height. These findings highlight that older adults were unable to exert the same vertical-axis control during single-support as young subjects did. Findings also highlight that the analysis of free vertical moment data can be a useful biomechanical tool to highlight age-related differences in how steps/stairs are negotiated.

This thesis examines the migrationary processes of graduates leaving their home country and their post-migration experiences and aspirations in a receiving state. Using the case study of England, findings are presented from qualitative research with Polish graduates born between the late 1970s and early 1980s, and who moved to England after 2004. It is argued that this generation of Polish migrants is particularly important given the profound impacts of socio-cultural and economic transformation in Poland, tied to the emergence of capitalism, the preparation for accession of Poland to the European Union (EU) and EU citizenship in 2004, on current debates on the geographies of graduate migration within and beyond Europe. Several important findings are revealed by the research. First, it is asserted that perspectives of migration which focus on structure-agency relations (Halfacree, 1995) need to encompass the economic and political aspects of participants sending state at the time of migration, as well as the historical influences on migration decision-making processes. Second, the discussion shows that graduate migration to another country leads to differing approaches to career and life trajectory development after migration and this thesis conceptualises these using the following typology: Continuers , Switchers and Late Awakeners , with dynamism and slippage across the groupings. Third, the findings expose graduate migrant perceptions of becoming and being highly-skilled, and the role of university preparation, and other forms of post-graduate training and potentially strategic acquisitions of citizenship for labour market confidence to compete and undertake professional jobs in Poland and England. Fourth, the thesis stresses that migration is often a first step in graduate migrants life trajectories and it emphasises the importance of a stepping-stone migration , both socially and spatially, and which is embedded within individuals' life-phases and perceptions of home and place. It is argued that this conceptual and geographic contribution to wider studies of graduate migration across countries may have wider resonance to other graduate migrant groups in Europe and beyond.

Typescript (Photocopy) / Digitized by Kansas Correctional Industries

A fragmentação de hábitats, e conseqüente isolamento de populações animais e vegetais, tem sido apontada como uma das principais ameaças à biodiversidade. Os elementos de conexão são estruturas que favorecem o deslocamento de organismos pela paisagem fragmentada. Um destes elementos, os trampolins ecológicos, também chamados de pontos de ligação ou stepping stones, são pequenas áreas de hábitat dispersas na matriz de não habitat, que potencialmente podem aumentar a conectividade na paisagem, reduzindo a probabilidade de extinção de diversas espécies. Este trabalho foi desenvolvido nos municípios de Teodoro Sampaio e Euclides da Cunha, localizados na região do Pontal do Paranapanema, Estado de São Paulo. Foram selecionadas duas paisagens com situações distintas no que se refere à presença dos elementos de conexão: Paisagem da Água Sumida (AS) e Paisagem da Ponte Branca (PB). Para a amostragem da avifauna utilizou-se o método do ponto fixo, no qual os pontos foram alocados distantes pelo menos 200m uns dos outros e o tempo de observação foi de 10 minutos por ponto. A coleta de dados em campo ocorreu nos meses de novembro e dezembro de 2003 e janeiro de 2004. Em cada paisagem foram realizadas quatro visitas. Em função deste levantamento, foi calculado o Índice Pontual de Abundância (IPA) para cada espécie em todos os pontos amostrados. Diversos bosques agroflorestais foram estudados, a fim de se verificar se eram utilizados pela avifauna, o que seria um indicativo da potencialidade destes bosques como trampolim ecológico. Foram também incluídos a matriz de pasto e os elementos de conexão: corredores ecológicos e pequenos fragmentos naturais. Os dados obtidos foram comparados com outro estudo conduzido nos fragmentos grandes. Foi observada uma diferença na composição da avifauna entre os diversos tipos de hábitats considerados, mas que ainda pouco deve refletir no aumento de fluxo pela paisagem das espécies florestais. Estas espécies na maior parte das vezes foram somente observadas nos fragmentos grandes e, aparentemente, não usam os bosques ou qualquer outro elemento de conexão, provavelmente devido ao elevado grau de isolamento destes e à hostilidade da matriz. Apesar de ter sido observado que os sistemas agroflorestais ainda não beneficiam grande parte da avifauna dependente de floresta, os resultados apontam que as ações de manejo nos assentamentos rurais começam a ter reflexos na diversidade na escala da paisagem da região, além de fornecer sustento para as famílias assentadas. Estes benefícios provavelmente serão maximizados com a intensificação dos processos de implantação de novos bosques agroflorestais, recuperação das matas ciliares e melhoramento da qualidade da vegetação dos remanescentes florestais. / Habitat fragmentation and consequent isolation of fauna and flora populations have been mentioned as one of the most critical threat for the biodiversity. The landscape elements are structures that increase the biota movements throw landscape. One of these elements is the stepping stones, which are small portions of habitat spread in matrix, and potentially could increase landscape connectivity, reducing extinction probability of a number of species. This study was conducted in Pontal do Paranapanema, State of São Paulo, Brazil, in two different areas concerning the presence or absence of some of the landscape elements: Landscape of Água Sumida (AS) and Landscape of Ponte Branca (PB). Field work had happened from November 2003 to January 2004. Avifauna was surveyed by point counts, where birds were registered for 10 minutes. The points were located at least 200m far from another, and each point was visited four times. Punctual Abundance Index (IPA) were calculated for birds species in all surveyed points. Some agro-forest patches were surveyed to verify the avifauna presence, which would be an indication of the potentially effect of stepping stones. Matrix of pasture, corridors and smalls fragments of native forest were also surveyed. The data obtained were compared to big fragments data of another study. There were differences of birds species compositions among all kinds of habitat considered, but it does not indicate increase of movements of forest species throw landscape. These species were most of the time registered into the large forest fragments, and they did not use agro-forest patches nor landscape elements, probably due the isolation caused by matrix hostility. Despite agro-forest system still do not increase movements of forest birds, the results suggests that environment management in settleland areas interfere on the biodiversity in landscape scale in this region, besides provide support for settled families. These benefits probably will be optimized with implantation of new agro-forest patches, revegetation of riparian areas and quality improvement of vegetation of residual woodlots.

Thesis (M.E.) -- University of Adelaide, Department of Electrical Engineering, 1978. / Typescript (photocopy).

A fragmentação de hábitats, e conseqüente isolamento de populações animais e vegetais, tem sido apontada como uma das principais ameaças à biodiversidade. Os elementos de conexão são estruturas que favorecem o deslocamento de organismos pela paisagem fragmentada. Um destes elementos, os trampolins ecológicos, também chamados de pontos de ligação ou stepping stones, são pequenas áreas de hábitat dispersas na matriz de não habitat, que potencialmente podem aumentar a conectividade na paisagem, reduzindo a probabilidade de extinção de diversas espécies. Este trabalho foi desenvolvido nos municípios de Teodoro Sampaio e Euclides da Cunha, localizados na região do Pontal do Paranapanema, Estado de São Paulo. Foram selecionadas duas paisagens com situações distintas no que se refere à presença dos elementos de conexão: Paisagem da Água Sumida (AS) e Paisagem da Ponte Branca (PB). Para a amostragem da avifauna utilizou-se o método do ponto fixo, no qual os pontos foram alocados distantes pelo menos 200m uns dos outros e o tempo de observação foi de 10 minutos por ponto. A coleta de dados em campo ocorreu nos meses de novembro e dezembro de 2003 e janeiro de 2004. Em cada paisagem foram realizadas quatro visitas. Em função deste levantamento, foi calculado o Índice Pontual de Abundância (IPA) para cada espécie em todos os pontos amostrados. Diversos bosques agroflorestais foram estudados, a fim de se verificar se eram utilizados pela avifauna, o que seria um indicativo da potencialidade destes bosques como trampolim ecológico. Foram também incluídos a matriz de pasto e os elementos de conexão: corredores ecológicos e pequenos fragmentos naturais. Os dados obtidos foram comparados com outro estudo conduzido nos fragmentos grandes. Foi observada uma diferença na composição da avifauna entre os diversos tipos de hábitats considerados, mas que ainda pouco deve refletir no aumento de fluxo pela paisagem das espécies florestais. Estas espécies na maior parte das vezes foram somente observadas nos fragmentos grandes e, aparentemente, não usam os bosques ou qualquer outro elemento de conexão, provavelmente devido ao elevado grau de isolamento destes e à hostilidade da matriz. Apesar de ter sido observado que os sistemas agroflorestais ainda não beneficiam grande parte da avifauna dependente de floresta, os resultados apontam que as ações de manejo nos assentamentos rurais começam a ter reflexos na diversidade na escala da paisagem da região, além de fornecer sustento para as famílias assentadas. Estes benefícios provavelmente serão maximizados com a intensificação dos processos de implantação de novos bosques agroflorestais, recuperação das matas ciliares e melhoramento da qualidade da vegetação dos remanescentes florestais. / Habitat fragmentation and consequent isolation of fauna and flora populations have been mentioned as one of the most critical threat for the biodiversity. The landscape elements are structures that increase the biota movements throw landscape. One of these elements is the stepping stones, which are small portions of habitat spread in matrix, and potentially could increase landscape connectivity, reducing extinction probability of a number of species. This study was conducted in Pontal do Paranapanema, State of São Paulo, Brazil, in two different areas concerning the presence or absence of some of the landscape elements: Landscape of Água Sumida (AS) and Landscape of Ponte Branca (PB). Field work had happened from November 2003 to January 2004. Avifauna was surveyed by point counts, where birds were registered for 10 minutes. The points were located at least 200m far from another, and each point was visited four times. Punctual Abundance Index (IPA) were calculated for birds species in all surveyed points. Some agro-forest patches were surveyed to verify the avifauna presence, which would be an indication of the potentially effect of stepping stones. Matrix of pasture, corridors and smalls fragments of native forest were also surveyed. The data obtained were compared to big fragments data of another study. There were differences of birds species compositions among all kinds of habitat considered, but it does not indicate increase of movements of forest species throw landscape. These species were most of the time registered into the large forest fragments, and they did not use agro-forest patches nor landscape elements, probably due the isolation caused by matrix hostility. Despite agro-forest system still do not increase movements of forest birds, the results suggests that environment management in settleland areas interfere on the biodiversity in landscape scale in this region, besides provide support for settled families. These benefits probably will be optimized with implantation of new agro-forest patches, revegetation of riparian areas and quality improvement of vegetation of residual woodlots.

Background. Fluid simulation is an area of ongoing research. In recent years, simulators have become more realistic and stable, partly by employing the condition of having divergence-free velocity fields. A divergence-free velocity field is a strict constraint that requires a high level of correctness in a simulation. Another recent development is in the subject of performance optimization, where asynchronous time integration is used. Asynchronous time integration means integrating different parts of a fluid with varying time step sizes. Doing so leads to overall larger time step sizes, which improves performance. This thesis combines the divergence-free velocity field condition with asynchronous time stepping in a particle-based simulator. Objectives. This thesis aims to achieve a performance speedup by implementing asynchronous time integration into an existing particle-based simulator that assures the velocity field is divergence-free. Methods. With an open source simulator employing a divergence-free velocity field as a starting point, asynchronous time integration is implemented. This is achieved by dividing the fluid into three regions, each with their own time step sizes. Introducing asynchronous time integration means significantly lowering the stability of a simulation. This is countered by implementing additional steps to increase stability. Results. Roughly a 40\% speedup is achieved in two out of three scenes, with similar visual results as the original synchronous simulation. In the third scene, there is no performance speedup as the performance is similar to that of the original simulation. The two first scenes could be sped up further with more aggressive settings for asynchronous time integration. This is however not possible due to stability issues, which are also the cause for the third scene not resulting in any speedup. Conclusions. Asynchronous simulation is shown to be a valid option even alongside a divergence solver. However, occasional unrealistic behavior resembling explosions among the particles do occur. Besides from being undesirable behavior, these explosions also decrease performance and prevent more aggressive performance settings from being used. Analysis of their cause, attempted solutions and potential future solutions are provided in the discussion chapter.