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Non-linear discrete-time observer design by sliding modeAlgarawi, Mohammed January 2007 (has links)
Research into observer design for non-linear discrete-time systems has produced many design methods. There is no general design method however and that provides the motivation to search for a new simple and realizable design method. In this thesis, an observer for non-linear discrete-time systems is designed using the sliding mode technique. The equation of the observer error is split into two parts; the first part being a linearized model of the system and the second part an uncertain vector. The sliding mode technique is introduced to eliminate the uncertainty caused by the uncertain vector in the observer error equation. By choosing the sliding surface and the boundary layer, the observer error is attracted to the sliding surface and stays within the sliding manifold. Therefore, the observer error converges to zero. The proposed technique is applied to two cases of observers for nonlinear discrete-time systems. The second case is chosen to be a particular practical system, namely the non-linear discrete-time ball and beam system. The simulations show that the sliding mode technique guarantees the convergence of the observer error for both systems.
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Citizen science data quality: Harnessing the power of recreational SCUBA divers for rockfish (Sebastes spp.) conservationGorgopa, Stefania M. 30 August 2018 (has links)
Monitoring rare or elusive species can be especially difficult in marine environments, resulting in poor data density. SCUBA-derived citizen science data has the potential to improve data density for conservation. However, citizen science data quality may be perceived to be of low quality relative to professional data due to a lack of ‘expertise’ and increased observer variability. We evaluated the quality of data collected by citizen science scuba divers for rockfish (Sebastes spp.) conservation around Southern Vancouver Island, Canada. An information-theoretic approach was taken in two separate analyses to address the overarching question: ‘what factors are important for SCUBA-derived citizen science data quality?’. The first analysis identified predictors of variability in precision between paired divers. We found that professional scientific divers did not exhibit greater data precision than recreational divers. Instead, precision variation was best explained by study site and divers’ species identification or recreational training. A second analysis identified what observer and environmental factors correlated with higher resolution identifications (i.e. identified to the species level rather than family or genus). We found divers provided higher resolution identifications on surveys when they had high species ID competency and diving experience. Favorable conditions (high visibility and earlier in the day) also increased taxonomic resolution on dive surveys. With our findings, we are closer to realizing the full potential of citizen science to increase our capacity to monitor rare and elusive species. / Graduate
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Observer error in identifying species using indirect signs: analysis of a river otter track survey techniqueEvans, Jonah Wy 17 September 2007 (has links)
Indirect signs of species presence (e.g., tracks, scats, hairs) are frequently used to
detect target species in occupancy, presence/absence, and other wildlife studies. Indirect
signs are often more efficient than direct observation of elusive animals, making such
signs well suited for long-term and broad-scale monitoring programs. However, error
associated with misidentification of indirect signs can be high, and should be measured
if meaningful inferences about population parameters are to be made. This study
addressed the need for systematic approaches to estimate and minimize variation due to
observer error in identifying indirect signs. I reanalyzed data from 4 replicates of a
presence/absence survey of northern river otters (Lontra canadensis) that had been
conducted by Texas Parks and Wildlife Department (1996-2003). Sixteen observers had
recorded tracks at sample points under bridges (n = 250) distributed throughout 27
counties in the Piney-Woods ecoregion of east Texas. My objectives were to 1)
determine if observers were a source of bias in the survey, 2) estimate the proportion of
error associated with track identification skill, and 3) evaluate the use of an international
certification procedure that measured observer tracking skill. The null hypothesis that observers had no effect on the variation in reported sign was rejected. Indeed, binary
logistic regression tests indicated that observers were significantly associated with
variation in reported track presence. Observers were not randomly distributed among
bridge sites, and therefore were significantly correlated with 4 habitat variables that may
have influenced heterogeneity in otter occupancy and probability of detection
(watershed, vegetation-type, water-type, bridge-area). On average, experienced
observers (n = 7) misidentified 44% of otter tracks, with a range of 0% to 100% correct
detection. Also, 13% of the tracks of species determined to be 'otter-like' were
misidentified as belonging to an otter. During the certification procedure, participants
misidentified the tracks of 12 species as otter. Inaccurate identification of indirect signs
is a likely source of error in wildlife studies. I recommend that observer skill in
identification of indirect signs be measured in order to detect and control for observer
bias in wildlife monitoring.
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