A non-contact geomatics technique for monitoring membrane roof structures

This thesis presents research carried out to monitor the behaviour of membrane structures, using the non-contact geornatics techniques of terrestrial laser scanning and videogrammetry. Membrane structures are covers or enclosures in which fabric surface is pre-tensioned to provide a stable shape under environmental loads. It is most often adopted by structural engineers as the solution to the roof of a building. Membrane structures resist extemally-imposed loads by a combination of curvature and tension of the highly flexible fabric membrane. However, collapse may occur if the real deflections exceed the designed tolerances. In order to avoid such failures in the future, a generic monitoring system, incorporating in-house software for observing and analysing the behaviour of existing membrane structures, was developed. This system has been applied to observe three different types of as-built membrane structures, with two primary issues investigated and resolved. The first aspect of the research was devoted to determining differences which exist between the designed model and the finished structure. To address this issue, terrestrial laser scanning was applied to generate the as-built model of the membrane structure. Statistical comparisons were then performed between the resultant scanned model and the designed mathematical model. The disparities were determined, allowing the factors causing these differences to be further explored. The second research issue investigated the effects of loading on the displacement of the membrane roof. A videogrammetric monitoring system employing stereo CCD video cameras was used to observe the movements of the membrane roofs. In order to accommodate constraints at the test site, a non-contact control method and structured light targeting were adopted in the monitoring scheme. Once the processing was completed, displacements occurring over time were determined. Investigations on the three types of finished membrane structures have been successfully achieved, proving the system to be a viable metrology tool for structural engineers involved in monitoring real-world membrane structures. The system effectively fulfilled the requirements for understanding the interaction of membrane surface geometry, applied loads and structural response. The information acquired by the system offers great potential to collaborating engineers who are involved in the design and refinement of such structures.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Methods for coastal monitoring and erosion risk assessment: two Portuguese case studies

Coastal zones are naturally dynamic and mobile systems exposed to natural (river flows, waves and storms) as well as human interventions that continuously reshape their morphology. Erosion phenomena related to extreme weather events and sediment scarcity are common, threatening buildings and infrastructures, as well as beaches, ecosystems and valuable wetland; conditions that pose challenges to coastal security and defence. Regular monitoring of coastal areas, assessment of their morphodynamics and identification of the processes influencing sediment transport are thus increasingly important for a better understanding of changes and evolutionary trends in coastal systems. This demands a multi-disciplinary approach involving researchers with expertise in coastal processes and state-of-the-art observation technologies. In this paper state-of-the-art surveying methods for an efficient quantification of changes in coastal environments are described and evaluated, and two NW-Portuguese case studies are presented. Survey methods included: topographic surveys based on terrestrial videogrammetric mobile mapping and aerial photogrammetry; sub-tidal bathymetry with sonar imagery using an Autonomous Surface Vehicle (ASV); as well as field observations, with sediment sampling and beach characterisation. In the first case study erosion/accretion patterns in the Douro estuary sand spit are analysed, considering its breakwater, river flow, wave and wind effects. Prior to the construction of a detached breakwater, the spitâ s morphodynamics was related to extreme river flow events, wave and wind conditions; afterwards the spit stabilized its shape and increased its area and volume. In the second case study the coast of Vila Nova de Gaia was broadly analysed, including the shoreface, foreshore and dunes, the characterization of major features and a short-period analysis of installed dynamics. Results obtained from field data, topographical surveys and numerical wave models were combined for the erosion risk assessment, using a methodology specifically developed for the study area. Both monitoring programs achieved their proposed objectives and provided valuable information to the local authorities, as gathered and processed information constitutes a valuable database for coastal planning and for ICZM purposes. They demonstrate the potential of several approaches, supported by advanced technologies, for the study of complex coastal morphodynamic processes.Zonas costeiras são sistemas naturalmente dinâmicos e móveis, expostos a fatores naturais (fluxos de rios, ondas e tempestades) e intervenções humanas, que alteram continuamente a sua morfologia. Fenómenos de erosão relacionados com temporais e escassez de sedimentos são comuns. Eles ameaçam construções e infraestruturas, praias, ecossistemas e zonas húmidas, o que constitui um desafio para a segurança e defesa costeiras. Uma monitorização regular de áreas costeiras, com avaliação da sua morfodinâmica e identificação dos processos que influenciam o transporte de sedimentos, visando uma melhor compreensão das alterações e tendências evolutivas nos sistemas costeiros, torna-se portanto cada vez mais importante. Para tal necessita-se de uma abordagem multidisciplinar e investigadores especializados em processos costeiros e tecnologias de observação de ponta. O presente trabalho descreve e avalia métodos de monitorização de última geração para uma quantificação eficiente de alterações em ambientes costeiros e apresenta dois estudos de caso Portugueses. Os métodos de observação incluem: levantamentos topográficos terrestres em modo cinemático baseados em videogrametria; levantamentos topográficos aéreos baseados em fotogrametria; batimetria sub-tidal e imagens de fundo obtidas com sonar a partir de um veículo autónomo de superfície; e observações de campo com análise de sedimentos e caracterização de praias. O primeiro caso de estudo referese à análise de padrões de erosão e acreção na restinga do estuário do Douro, tendo em conta efeitos causados pelo molhe, o caudal do rio, ondas e vento. Antes da construção de um molhe destacado, a morfodinâmica da restinga estava relacionada com eventos extremos de caudal, agitação marítima e vento. Após a construção, a forma da restinga estabilizou e observou-se um aumento da sua área e do seu volume. No segundo caso de estudo, a costa de Vila Nova de Gaia foi amplamente estudada, incluindo shoreface, foreshore e dunas, com a caracterização dos principais atributos e uma análise de curto-período da dinâmica instalada. Os resultados obtidos a partir de dados de campo, dos levantamentos topográficos e de modelos numéricos de ondas foram combinados numa análise de risco com métodos especificamente desenvolvidos para a área de estudos. Ambos os programas de monitorização atingiram os seus objetivos e geraram informação relevante para as autoridades locais. A informação recolhida e processada constitui uma base de dados valiosa para o planeamento costeiro e a Gestão Integrada de Zonas Costeiras. Os estudos demonstram o potencial das diversas abordagens, apoiadas por tecnologias avançadas, para o estudo dos processos complexos de morfodinâmica costeira.This research was partially supported by the European Regional Development Fund (ERDF) through the COMPETE – Operational Competitiveness Programme and national funds through FCT – Foundation for Science and Technology, under the project “Pest-C/ MAR/LA0015/2013”, and partially funded by the Project ECORISK (reference NORTE-07-0124-FEDER- 000054), co-financed by the North Portugal Regional Operational Programme (ON.2 – O Novo Norte), under the National Strategic Reference Framework (NSRF), through the European Regional Development Fund (ERDF). Wave climate analyses were supported by the FCT-funded RAP project (PTDC/MAR/111223/2009)

New 3-d video methods reveal novel territorial drift-feeding behaviors that help explain environmental correlates of Chena River chinook salmon productivity

Thesis (Ph.D.) University of Alaska Fairbanks, 2014.Chinook salmon (Oncorhynchus tshawytscha) are critical to subsistence and commerce in the Yukon River basin, but several recent years of low abundance have forced devastating fishery closures and raised urgent questions about causes of the decline. The Chena River subpopulation in interior Alaska has experienced a decline similar to that of the broader population. To evaluate possible factors affecting Chena River Chinook salmon productivity, I analyzed both population data and the behavior of individual fish during the summer they spend as fry drift feeding in the river. Using a stereo pair of high definition video cameras, I recorded the fine-scale behavior of schools of juvenile Chinook salmon associated with woody debris along the margins of the Chena River. I developed a software program called VidSync that recorded 3-D measurements with sub-millimeter accuracy and provided a streamlined workflow for the measurement of several thousand 3-D points of behavioral data (Chapter 1). Juvenile Chinook salmon spent 91% of their foraging attempts investigating and rejecting debris rather than capturing prey, which affects their energy intake rate and makes foraging attempt rate an unreliable indicator of foraging success (Chapter 2). Even though Chinook salmon were schooling, some were highly territorial within their 3-D school configurations, and many others maintained exclusive space-use behaviors consistent with the population regulatory effects of territoriality observed in other salmonids (Chapter 3). Finally, a twenty-year population time series from the Chena River and neighboring Salcha River contained evidence for negative density dependence and a strong negative effect of sustained high summer stream discharge on productivity (Chapter 4). The observed territoriality may explain the population's density dependence, and the effect of debris on foraging efficiency represents one of many potential mechanisms behind the negative effect of high stream discharge. In combination, these findings contribute to a statistically and mechanistically plausible explanation for the recent decline in Chena River Chinook salmon. If they are, in fact, major causes of the decline (other causes cannot be ruled out), then we can be tentatively hopeful that the population may be experiencing a natural lull in abundance from which a recovery is possible.General Introduction -- Chapter 1: Measuring fish and their habitats: Versatile 2-D and 3-D video techniques with user-friendly software -- Chapter 2: Mechanisms of drift-feeding behavior in juvenile Chinook salmon and the role of inedible debris in a clear-water Alaskan Stream -- Chapter 3: Territoriality within schools: dynamic competition of drift-feeding juvenile Chinook salmon in 3-dimensional space -- Chapter 4: Low productivity of Chinook salmon strongly correlates with high summer stream discharge in two Alaskan rivers in the Yukon drainage

Reconstruction of four-dimensional rockfall trajectories using remote sensing and rock-based accelerometers and gyroscopes

This work focuses on the in-depth reconstruction of the full set of parameters of interest in single-block rockfall trajectories. A comprehensive understanding of rockfall trajectories holds the promise to enhance the application of numerical models for engineering hazard analysis. Such knowledge is equally important to investigate wider cascade problems in steep terrain. Here, we present a full four-dimensional trajectory reconstruction of the “Chant Sura” rockfall experiment performed with EOTA221 norm rocks. The data analysis allows a complete kinematic description of a rock's trajectory in real terrain and underscores the physical complexity of rock–ground interactions. In situ accelerometer and gyroscope data are combined with videogrammetric and unmanned aerial-systems mapping techniques to understand the role of rock rotations, ground penetration and translational scarring in rockfall motion. The exhaustive trajectory reconstruction provides information over the complete flight path such as translational velocity vectors, angular velocities, impact duration and forces, ballistic jump heights, and lengths. The experimental data provide insight into the basic physical processes detailing how rotating rocks of general shape penetrate, rebound and scar ground terrain. In future, the data will serve as a calibration basis to enhance numerical rockfall modelling.</p

Analysis of finger movement coordination during the Variable Dexterity Test and comparative activities of daily living

Background/Aims: This study aimed to analyse and compare finger coordination patterns during the performance of the Variable Dexterity Test (VDT) and comparative daily tasks. Methods: An optoelectronic system was used to record the joint angles of 10 healthy participants performing the VDT and daily tasks. Joint angles from digits 1 to 5 were cross-correlated across the tasks, providing a measure of the degree of finger movement coordination. Results: Correlation coefficients showed identifiable coordination patterns among the finger movements under analysis. Low correlation coefficients suggested the presence of independent finger movements during the performance of the selected tasks. Conclusions: Finger movement coordination patterns observed during activities of daily living are comparable with the patterns observed during performance of the Variable Dexterity Test for the three grasping patterns analysed in the stud

Differences in EMG burst patterns during grasping dexterity tests and activities of daily living

The aim of this study was to characterize the muscle activation patterns which underlie the performance of two commonly used grasping patterns and compare the characteristics of such patterns during dexterity tests and activities of daily living. EMG of flexor digitorum and extensor digitorum were monitored from 6 healthy participants as they performed three tasks related to activities of daily living (picking up a coin, drinking from a cup, feeding with a spoon) and three dexterity tests (Variable Dexterity Test-Precision, Variable Dexterity Test-Cylinder, Purdue Pegboard Test). A ten-camera motion capture system was used to simultaneously acquire kinematics of index and middle fingers. Spatiotemporal aspects of the EMG signals were analyzed and compared to metacarpophalangeal joint angle of index and middle fingers. The work has shown that a common rehabilitation test such as the Purdue Pegboard test is a poor representation of the muscle activation patterns for activities of daily living. EMG and joint angle patterns from the Variable Dexterity Tests which has been designed to more accurately reflect a range of ADl's were consistently comparable with tasks requiring precision and cylinder grip, reaffirming the importance of object size and shape when attempting to accurately assess hand function

Analysing finger interdependencies during the Purdue Pegboard Test and comparative activities of daily living

Study Design: Bench, Cross-sectional Introduction: Information obtained from dexterity tests is an important component of a comprehensive examination of the hand. Purpose of the Study: To analyse and compare finger interdependencies during the performance of the Purdue Pegboard Test and comparative daily tasks. Methods: A method based on the optoelectronic kinematic analysis of the precision grip style and on the calculation of cross-correlation coefficients between relevant joint angles, which provided measures of the degree of finger coordination, was conducted on 10 healthy participants performing the Purdue Pegboard Test and two comparative daily living tasks. Results: Daily tasks showed identifiable interdependencies patterns between the metacarpophalangeal joints of the fingers involved in the grip. Tasks related to activities of daily living resulted in significantly higher cross-correlation coefficients across subjects and across movements during the formation and manipulation phases of the tasks (0.7-0.9), while the release stage produced significantly lower movement correlation values (0.3-0.7). Contrarily, the formation and manipulation stages of the Purdue Pegboard Test showed low finger correlation across most subjects (0.2-0.6), while the release stage resulted in the highest values for all relevant movements (0.65-0.9). Discussion: Interdependencies patterns were consistent for the activities of daily living, but differ from the patterns observed from the Purdue Pegboard Test. Conclusions: The Purdue Pegboard Test does not compare well with the whole range of finger movements that account for hand performance during daily tasks