1,981 research outputs found

    A 3D stereo camera system for precisely positioning animals in space and time

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    PLT was supported by the Scottish Funding Council (grant HR09011) through the Marine Alliance for Science and Technology for Scotland.Here, we describe a portable stereo camera system that integrates a GPS receiver, an attitude sensor and 3D stereo photogrammetry to rapidly estimate the position of multiple animals in space and time. We demonstrate the performance of the system during a field test by simultaneously tracking the individual positions of six long-finned pilot whales, Globicephala melas. In shore-based accuracy trials, a system with a 50-cm stereo baseline had an average range estimation error of 0.09 m at a 5-m distance increasing up to 3.2 at 50 m. The system is especially useful in field situations where it is necessary to follow groups of animals travelling over relatively long distances and time periods whilst obtaining individual positions with high spatial and temporal resolution (up to 8 Hz). These positions provide quantitative estimates of a variety of key parameters and indicators for behavioural studies such as inter-animal distances, group dispersion, speed and heading. This system can additionally be integrated with other techniques such as archival tags, photo-identification methods or acoustic playback experiments to facilitate fieldwork investigating topics ranging from natural social behaviour to how animals respond to anthropogenic disturbance. By grounding observations in quantitative metrics, the system can characterize fine-scale behaviour or detect changes as a result of disturbance that might otherwise be difficult to observe.PostprintPeer reviewe

    Repair of metallic components using hybrid manufacturing

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    Many high-performance metal parts users extend the service of these damaged parts by employing repair technology. Hybrid manufacturing, which includes additive manufacturing (AM) and subtractive manufacturing, provides greater build capability, better accuracy, and surface finish for component repair. However, most repair processes still rely on manual operations, which are not satisfactory in terms of time, cost, reliability, and accuracy. This dissertation aims to improve the application of hybrid manufacturing for repairing metallic components by addressing the following three research topics. The first research topic is to investigate and develop an efficient best-fit and shape adaption algorithm for automating 3D models\u27 the alignment and defect reconstruction. A multi-feature fitting algorithm and cross-section comparison method are developed. The second research topic is to develop a smooth toolpath generation method for laser metal deposition to improve the deposition quality for metallic component fabrication and repair. Smooth connections or transitions in toolpath planning are achieved to provide a constant feedrate and controllable deposition idle time for each single deposition pass. The third research topic is to develop an automated repair process could efficiently obtain the spatial information of a worn component for defect detection, alignment, and 3D scanning with the integration of stereo vision and laser displacement sensor. This dissertation investigated and developed key technologies to improve the efficiency, repair quality, precision, and automation for the repair of metallic components using hybrid manufacturing. Moreover, the research results of this dissertation can benefit a wide range of industries, such as additive manufacturing, manufacturing and measurement automation, and part inspection --Abstract, page iv

    Establishing a Quantifiable Model of Whale Shark Avoidance Behaviours to Anthropogenic Impacts in Tourism Encounters to Inform Management Actions

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    As the world's largest living fish, the whale shark has received much scientific attention in recent years, although despite this a great deal is still unknown on the life history and behavioural ecology of these majestic sharks. Whale shark related tourism has exploded in the last two decades from only a few sites in the 1990s to more than 12 sites internationally, allowing it to become a highly lucrative industry based upon this Vulnerable species. This study assesses the effects of anthropogenic impact on the sharks’ avoidance behaviours within modern day tourism encounters, and provides recommendations on how to control and reduce unnecessary disturbance to the species. By means of stereo-photogrammetry, continuous high definition videos of human-animal interactions were recorded and analyzed for behavioural changes against pre-selected independant variables. The use of Stereo-photogrammetry imagery also allowed for the accumulation of repeatable, proximity measurements of swimmer distance to the shark, permitting more precise and accurate results. Avoidance behaviours of 33 individual whale sharks were monitored during typical tourism encounters (n=75). A total of 192 search hours were documented over the collection periods, which incorporated three-aggregation sites spanning the Indian Ocean (the Seychelles, the Philipines & Mozambique). A generalized linear model demonstrated that proximity of swimmers to the shark was found to be significant (p=0.0295) in explaining the probability of the whale sharks showing disturbed behaviour. A proportional odds plot for proximity was developed to give an indication of the animals disturbance level in tourism interactions. At recommended distances of three metres from the sides of the shark, there is on average a 42% chance of disturbance, while at the distance of four metres from the tail area results showed a 31% chance of overall disturbance. The true estimate for either distance is likely to lie between 22-53% respectively with regards to the uncertainty around the mean predictions. Whale shark tourism is viewed as a potential means of protecting this threatened species, while also providing a sustainable livelihood for local communities and tourism providers. Management recommendations presented offer suggestions on how to tackle concerns over proximity distances and links to disturbance. Additionally judgments for future research endeavors into assessing both the impacts of uncontrolled tourism and participants behaviour

    Computational Imaging Approach to Recovery of Target Coordinates Using Orbital Sensor Data

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    This dissertation addresses the components necessary for simulation of an image-based recovery of the position of a target using orbital image sensors. Each component is considered in detail, focusing on the effect that design choices and system parameters have on the accuracy of the position estimate. Changes in sensor resolution, varying amounts of blur, differences in image noise level, selection of algorithms used for each component, and lag introduced by excessive processing time all contribute to the accuracy of the result regarding recovery of target coordinates using orbital sensor data. Using physical targets and sensors in this scenario would be cost-prohibitive in the exploratory setting posed, therefore a simulated target path is generated using Bezier curves which approximate representative paths followed by the targets of interest. Orbital trajectories for the sensors are designed on an elliptical model representative of the motion of physical orbital sensors. Images from each sensor are simulated based on the position and orientation of the sensor, the position of the target, and the imaging parameters selected for the experiment (resolution, noise level, blur level, etc.). Post-processing of the simulated imagery seeks to reduce noise and blur and increase resolution. The only information available for calculating the target position by a fully implemented system are the sensor position and orientation vectors and the images from each sensor. From these data we develop a reliable method of recovering the target position and analyze the impact on near-realtime processing. We also discuss the influence of adjustments to system components on overall capabilities and address the potential system size, weight, and power requirements from realistic implementation approaches

    Development of a handheld fiber-optic probe-based raman imaging instrumentation: raman chemlighter

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    Raman systems based on handheld fiber-optic probes offer advantages in terms of smaller sizes and easier access to the measurement sites, which are favorable for biomedical and clinical applications in the complex environment. However, there are several common drawbacks of applying probes for many applications: (1) The fixed working distance requires the user to maintain a certain working distance to acquire higher Raman signals; (2) The single-point-measurement ability restricts realizing a mapping or scanning procedure; (3) Lack of real-time data processing and a straightforward co-registering method to link the Raman information with the respective measurement position. The thesis proposed and experimentally demonstrated various approaches to overcome these drawbacks. A handheld fiber-optic Raman probe with an autofocus unit was presented to overcome the problem arising from using fixed-focus lenses, by using a liquid lens as the objective lens, which allows dynamical adjustment of the focal length of the probe. An implementation of a computer vision-based positional tracking to co-register the regular Raman spectroscopic measurements with the spatial location enables fast recording of a Raman image from a large tissue sample by combining positional tracking of the laser spot through brightfield images. The visualization of the Raman image has been extended to augmented and mixed reality and combined with a 3D reconstruction method and projector-based visualization to offer an intuitive and easily understandable way of presenting the Raman image. All these advances are substantial and highly beneficial to further drive the clinical translation of Raman spectroscopy as potential image-guided instrumentation

    Underwater Photogrammetry for Archaeology

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