Switching between windows on a computer is a frequent activity, but finding and switching to the target window can be inefficient. This thesis aims to better understand and support window switching. It explores two issues: (1) the lack of knowledge of how people currently interact with and switch between windows and (2) how window switching can be supported better. Having a good understanding of how users interact with windows is important for informing the design of new and improved window management tools. However, there have been relatively few empirical studies of window manipulation on commonly used operating systems, and those that do exist may no longer reflect current use. To address this lack of knowledge a three week log-based longitudinal study of window use by 25 participants was conducted using the custom-made tool PyLogger, which recorded actual window switching behaviour. However, the analysis of longitudinal log data, such as the data gathered by PyLogger, is problematic as it is difficult to extract meaningful characterisations. Therefore, this thesis also presents a visualisation tool called Window Watcher that assists understanding and interpreting the low level event logs of window use generated by PyLogger. Window Watcher’s design objectives are described, and examples demonstrate the ways that it summarises and elucidates window use. The results of the PyLogger study provide an empirical characterisation of interaction with windows, and results include the following: (1) the participants had fewer windows open and visible than in previous studies; (2) window switching is a frequent activity; (3) several findings related to specific window switching tools, including that acquiring a particular window by navigating through application-grouped items on the Taskbar is slow, and that Alt+Tab is seldom used for retrieving anything other than the most recently used window; (4) an updated classification of stereotypical window management styles (pilers, maximisers, near maximisers, and splatterers); and (5) there are strong window and application revisitation patterns. Finally, implications of the results of the log study for the design of window switching tools are discussed. The findings from the PyLogger study led to the development of a new window switcher called SCOTZ (for Spatially Consistent Thumbnail Zones). SCOTZ is a window switching interface which shows all windows grouped by application and allocates more space to the most frequently revisited applications. The two design objectives of SCOTZ are (1) to provide a spatially stable layout of applications and windows, and (2) to support revisitation to recently and frequently used windows. Additional design objectives are to support various display sizes, to support both keyboard and mouse input, to provide possibilities for application launching and to provide options for end-user customisation. The design and features of SCOTZ are described, followed by theoretical and empirical validation of its underlying design principles. Findings include that (1) spatially stable layouts allow for faster acquisition of targets than recency and random layouts, (2) the instability inevitably caused by size morphing does not severely impact user performance, (3) size morphing leads to an overall performance advantage because of the Fitts’ Law targetting time advantage of increased target size, and (4) size morphing facilitates finding items because of guided search. Also, findings from an empirical study demonstrate that SCOTZ yields performance and preference benefits over existing window switching tools. Finally, as SCOTZ employs a treemap algorithm to generate the layout of the application zones the suitability of various treemap algorithms for the purpose of SCOTZ is explored, particularly in terms of spatial stability. In previous work, many different treemap algorithms have been proposed, often with the aim being to optimise performance across several criteria, including spatial stability. However, none of the existing treemaps are stable when data updates, and when items are added/deleted, and when many changes have taken place (i.e., the cumulative effect of data changes). Therefore, this thesis introduces the novel ‘Hilbert’ and ‘Moore’ treemap algorithms, which are designed to achieve high spatial stability. Their performance is theoretically assessed in comparison to other treemaps by using various metrics, including a novel ‘location drift’ metric to better capture spatial stability than the commonly used ‘distance change’ metric. The theoretical evaluation demonstrates that Hilbert and Moore treemaps perform well across all stability metrics. An empirical study examines the validity and usefulness of the location drift metric, showing that location drift can explain some effects on user performance that distance change alone can not.

<p>Different techniques have been employed through the years to predict hydrodynamic instabilities on high speed liquid jets. In this work, a local linear stability analysis (LSA) has been chosen to estimate streamwise wavelengths on the jet surface near the jet exit.  Data for 0.24 to 0.5 diameters downstream in a high speed water jet issuing into air, given by Reynolds number based momentum thickness between 240 and 600, for validation of the method.  </p> <p>The hypothesis is: near the exit of the jet nozzle, for high speed liquid jets, the local velocity profile evolves based on the momentum thickness and, because of large inertia effects, the flow may be considered as inviscid for instability purposes. Therefore, the approach in this work is based on the Rayleigh equation and with the momentum thickness scaling, both non-dimensional and dimensional values of the most unstable wavelengths are obtained.</p> <p>The key aspect of the  approach is the relevance of the momentum thickness as the scaling factor for calculation purposes on dimensional values of wavelengths.</p> <p>Also, a hyperbolic tangent velocity profile is assumed for the Linear Stability Analysis based on the Rayleigh equation. Numerical restrictions and comparisons, using the Riccati transformation, are specified and described in detail to generalize this approach.</p> <p>Results show that analytical estimates of the most unstable streamwise wavelengths are close to the experimental measurements published by Portillo et al. in 2011.  The agreement using this new approach is often within the experimental uncertainty.</p> <p><br></p>

Submitted by (lucia.rodrigues@ufrpe.br) on 2016-10-14T14:40:26Z No. of bitstreams: 1 Valdemir de Paula e Silva Junior.pdf: 1674024 bytes, checksum: fa219e683d9e8d4feb594943a85825eb (MD5) / Made available in DSpace on 2016-10-14T14:40:26Z (GMT). No. of bitstreams: 1 Valdemir de Paula e Silva Junior.pdf: 1674024 bytes, checksum: fa219e683d9e8d4feb594943a85825eb (MD5) Previous issue date: 2015-02-03 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Soil water content has an important role for agricultural practices, influencing water movement and storage within the soil. In semiarid regions, knowledge concerning soil water content holds great relevance, mainly due to precipitation’s high spatial-temporal variability and high evapotranspiration indices, bringing about soil water deficit. The aim of this study was to evaluate spatial and temporal stability of soil water content under different cover crop conditions and soil types, in order to identify a representative point for soil water content readings. Additionally, it was evaluated the use of infrared thermography as a tool to estimate non-saturated hydraulic conductivity at a representative watershed, located in Pesqueira, in the semiarid region of Pernambuco. A grid of points for soil water content measurement was monitored, using a capacitive probe. In the first chapter, the soil water content data was evaluated on a hillslope with six measuring points, under natural vegetation and pasture with the same type of soil (Red Yellow Ultisol). According to temporal stability concept, the technique for relative mean differences and standard deviations was applied in order to investigate the point, which is capable of representing the mean temporal behavior of the other measuring points, and the correlation among soil water content points. In the second chapter, temporal variation patterns were analyzed for seventeen soil water content points distributed along the watershed, under two different soil types: Yellow Ulitsol and Regolithic Entisol, and two cover crop conditions, being used the mean relative differences technique and correlation among points in order to validate if the stable point would be the same found for the hill experiment. In the third chapter, published in the Quantitative Infrared Thermography Journal, v.11, 2:2014, p.161-169, infrared thermography technique was used to estimate soil hydraulic conductivity. The study was performed in a laboratory of the Coimbra University, using a slope soil channel and three types of soil and a thermographic video camera to record the images. Estimated hydraulic conductivity data with the infrared thermography technique were correlated to the values obtained with the aid of a constant-head permeameter, by statistical indices and regression analysis. For the fourth chapter, the thermography technique was used under field condition to estimate non-saturated hydraulic conductivity, in the Mimoso watershed, for two soil types: Yellow Ultisol and Fluvic Entisol. Four different hydraulic heads were applied to soil surface, with three replications and seven tests for each soil type under different initial conditions of soil temperature and thermal records using a thermographic camera. Thermal records were correlated to non-saturated soil hydraulic conductivity, which presented high correlations. Water content dynamics technique allowed the identification of a point of stability in the watershed. Thermal records enabled the distinction between the studied soil types, when subjected to different hydraulic heads, being related with the respective non-saturated hydraulic conductivities. It was verified that the thermography is an innovative technique capable of estimating non-saturated hydraulic conductivity, enabling the mapping of soil surface conditions. / A umidade do solo tem grande importância para as atividades agrícolas, influenciando o movimento da água no solo e no seu armazenamento. Em regiões de clima semiárido, o conhecimento da umidade no solo tem grande relevância, principalmente por causa da grande variabilidade espacial e temporal da precipitação e dos altos índices de evapotranspiração, provocando déficit de umidade no solo. O objetivo desse estudo foi avaliar a estabilidade temporal e espacial da umidade do solo sob diferentes condições de cobertura vegetal e tipos de solo a fim de identificar um ponto que representativo para leitura da umidade e a aplicação da termografia por infravermelho, para estimativa da condutividade hidráulica não saturada do solo em uma bacia hidrográfica representativa, localizada na região de Pesqueira, semiárido pernambucano. Foi monitorada uma rede de pontos de medição de umidade, utilizando uma sonda capacitiva. No primeiro capítulo, os dados de umidade foram avaliados em uma encosta com seis pontos de monitoramento, com cobertura de vegetação natural e pastagem paro o mesmo tipo de solo um Argissolo Vermelho Amarelo. De acordo com o conceito de estabilidade temporal, foi aplicada a técnica de diferenças relativas médias e desvios padrão, para investigar o ponto que fosse capaz de representar o comportamento temporal da média dos demais locais de monitoramento, e a correlação entre os pontos de umidade. No segundo capítulo analisaram-se os padrões de variação temporal em dezessete pontos monitorados de umidade distribuídos em escala de bacia, avaliados para dois tipos de solo: Argissolo Amarelo e Neossolo Regolítico, com duas condições de cobertura do solo, sendo aplicada a técnica de diferenças relativas médias e correlação desses pontos, validam-se o ponto estável seria o mesmo encontrado para encosta. No terceiro capítulo, publicado na revista Quantitative Infrared Thermography Journal, v.11, 2:2014, p.161-169, foi utilizada a técnica da termografia de infravermelho para estimativa da condutividade hidráulica do solo. O estudo foi realizado em laboratório na Universidade de Coimbra, utilizando um canal de terra com declividade e três tipos de solo e uma câmera de vídeo termográfica para registros das imagens. Os dados de condutividade hidráulica estimados com a técnica da termografia infravermelha foram correlacionados com os valores medidos obtidos com um permeâmetro de carga constante, por meio de índices estatísticos e análises de regressão. Para o quarto capítulo, a técnica da termografia foi utilizada em campo para estimativa da condutividade hidráulica não saturada, na bacia do Mimoso para dois tipos de solo, Argissolo Amarelo e o Neossolo Flúvico. Foram aplicadas no solo quatro cargas hidráulicas distintas na superfície do solo, com três repetições e sete ensaios em cada solo em diferentes condições iniciais de temperatura do solo e registros térmicos utilizando uma câmera termográfica. Os registros térmicos foram correlacionados com a condutividade hidráulica não saturada do solo onde apresentaram correlações elevadas. A técnica da dinâmica da umidade permitiu identificar um ponto de estabilidade na bacia. Os registros térmicos permitiram distinção no solo estudado, quando submetidos a diferentes cargas hidráulicas, estando correlacionados com as respectivas condutividades hidráulicas não saturadas. Verificou-se que termografia é uma técnica inovadora capaz de estimar características da condutividade hidráulica não saturada, possibilitando mapeamento das condições de superfície do solo.