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1
Niedfeldt, John Clyde. "RapidSCAT Slice Spatial Response Function Contour Parameterization." BYU ScholarsArchive, 2016. https://scholarsarchive.byu.edu/etd/6260.
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The spatial response function (SRF) of the backscatter measurements for a radar scatterometer is often used in reconstruction. It has been found that in many cases the SRF can be approximated as a binary function that is 1 inside the - 6 dB contour of the SRF and 0 outside. This improves the computation speed of reconstruction. Computing the SRF contour can still be a lengthy computation, which can be simplified by precomputing and tabulating key SRF contours. The tabular parameterization for many spinning scatterometers, i.e., QuikSCAT, is straight-forward. For RapidSCAT, this estimation is more involved than other radars due to the irregular orbit of its host platform, the International Space Station (ISS). This thesis presents a process for parameterizing the slice contours for RapidSCAT that are acceptable for reconstruction purposes. This thesis develops a new process for parameterizing slice contours. First, RapidSCAT SRFs are calculated using XfactorRS3, and -6 dB slice contours are found using matplotlib. Then, a suitable filter is found for reducing noise present in slice contours due to quantization error and interpolation inaccuracies. Afterwards, the polygon comparison algorithm is used to determine a set of approximation points. With the approximation points selected, the 3-rd order linear approximation is calculated using parameters available in the L1B data files for RapidSCAT. Finally, analysis of the parameterization is performed. Overall, I developed a process that parameterizes RapidSCAT slice contours with an average root mean square (RMS) error of roughly 1.5 km. This is acceptable for the application of the slice parameterization algorithm and significantly reduces computation compared to fully computing the SRF.
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Bury, Samuel Gary. "The Estimation of the RapidScat Spatial Response Function." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6797.
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RapidScat is a pencil-beam wind scatterometer which operated from September 2014 to August 2016. Mounted aboard the International Space Station (ISS), RapidScat experiences significant altitude and attitude variations over its dataset. These variations need to be properly accounted for to ensure accurate calibration and to produce high resolution scatterometer images. Both the antenna pose and the one-way antenna pattern need to be validated. The spatial response function (SRF) is the two-way antenna pattern for a scatterometer combined with the processing and filtering done in the radar system electronics, and is dominated by the two-way pattern. To verify the pointing of the RapidScat antenna, the RapidScat SRF is estimated using on-orbit data. A rank reduced least squares estimate is used, which was developed previously for the Oceansat-2 (OSCAT) scatterometer [1]. This algorithm uses a small, isolated island as a delta function to sample the SRF. The island used is Rarotonga Island of the Cook Islands. The previously developed algorithm is updated to estimate the SRF in terms of beam azimuth and elevation angle rather than in kilometers on the ground. The angle-based coordinate system promotes greater understanding of how the SRF responds to biases and errors in antenna geometry. The estimation process is simulated to verify its accuracy by calculating the SRF for several thousand measurements in the region of Rarotonga. The calculated SRFs are multiplied by a corresponding synthetically created surface and integrated to yield simulated backscatter measurements, with added white noise. The SRF estimation algorithm is then performed. The results of the simulation show that the SRF estimation process yields a close estimate of the original SRF. The antenna pointing is validated by introducing a fixed offset in azimuth angle into the simulation and observing that the SRF is correspondingly shifted in the azimuth-elevation grid. The SRF computed from real data shows that there is an azimuth rotation angle bias of about 0.263 degrees for the inner beam and about 0.244 degrees for the outer beam. Since the SRF is dominated by the two-way antenna pattern, it can be modeled as the product of two identical one-way antenna patterns which are slightly offset from each other due to antenna rotation during the transmit/receive cycle. A method is developed based on this model to derive the one-way antenna pattern from the estimated SRF. Using a Taylor series expansion the one-way antenna pattern is computed from the SRF. The derived pattern recovers the SRF with small error, but there is significant error in the inferred one-way pattern when compared to the pre-launch estimated RapidScat one-way antenna pattern.
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Kim, Youngtae. "Spatial resolution limits for the reconstruction of acoustic source distribution by inverse techniques." Thesis, University of Southampton, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274706.
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Lindsley, Richard D. "Enhanced-Resolution Processing and Applications of the ASCAT Scatterometer." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5739.
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The ASCAT scatterometer measures the Earth surface microwave radar backscatter in order to estimate the near-surface winds over the oceans. While the spatial resolution of the conventional applications is sufficient for many purposes, other geoscience applications benefit from an improved spatial resolution. Specialized algorithms may be applied to the scatterometer data in order to reconstruct the radar backscatter on a high-resolution grid. Image reconstruction requires the spatial response function (SRF) of each measurement, which is not reported with the measurement data. To address this need, I precisely model the SRF incorporating (1) the antenna beam response, (2) the processing performed onboard ASCAT before telemetering to the ground, and (3) the Doppler shift induced by a satellite orbiting the rotating Earth. I also develop a simple parameterized model of the SRF to reduce computational complexity. The accuracy of both models is validated.Image reconstruction of the ASCAT data is performed using the modeled SRF. I discuss the spatial resolution of the reconstructed ASCAT images and consider the first- and second-order statistics of the reconstructed data. Optimum values for the parameters of the reconstruction algorithms are also considered. The reconstructed radar backscatter data may be used for enhanced-resolution wind retrieval and for geoscience applications. In this dissertation, the reconstructed backscatter data is used to map the surface extent of the 2010 Deepwater Horizon oil spill and in a study to quantify the azimuth angle anisotropy of backscatter in East Antarctica. Near-coastal ocean wind retrieval is also explored in this dissertation. Because near-coastal ocean measurements of backscatter may be “contaminated” from nearby land and introduce errors to wind retrieval, they must be discarded. The modeled SRF is used to quantify the land contamination, enabling enhanced-resolution wind retrieval much closer to the coasts. The near-coastal winds are validated against buoy measurements.
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Bradley, Joshua P. "Extending the QuikSCAT Data Record with the Oceansat-2 Scatterometer." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3435.
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Originally designed for wind velocity estimation over the ocean, scatterometers have since been applied to climate studies of the Earth's cryosphere and bioshere. As an integral part of climatological studies of the planet, the NASA Scatterometer Climate Record Pathfinder (SCP) supplies scatterometer-based products designed to aid researchers in climatological studies of the planet. In this thesis, necessary steps are taken to facilitate data from the Oceansat-2 Ku-band scatterometer (OSCAT) to be used in extending the Ku-band SCP dataset of conically scanning pencil-beam scatterometers begun by the Seawinds scatterometer flown on the QuikSCAT mission 1999-2009. As a standard SCP product, a temporal resolution enhancement technique for the scatterometer image reconstruction (SIR) algorithm is applied to OSCAT data. A relative cross-calibration method is developed to ensure consistency amongst datasets of conically scanning pencil-beam scatterometers in the SCP data time series. By application of the method, both raw data and SIR image data of OSCAT is cross-calibrated with QuikSCAT. To enable creation of SCP products requiring knowledge of the spatial response function (SRF) with OSCAT data, a method of estimating the SRF of pencil-beam scatterometers is developed. The estimation method employs rank-reduced least-squares to invert the radar equation using measurements over islands. A simulation is performed to validate the efficacy of the method and provide optimum choice of island size and number of singular values used in rank-reduced least-squares. The utility of the SRF estimates is demonstrated by applying an estimate of the OSCAT SRF to SIR image construction with OSCAT data.
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Foster, Collin David. "Spatial parameter estimation using measured frequency response functions." Thesis, University of Liverpool, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314556.
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Kornak, John. "Bayesian spatial inference from haemodynamic response parameters in functional magnetic resonance imaging." Thesis, University of Nottingham, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325718.
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Rincon, Rueda Diego Fernando. "Delphastus catalinae and the silverleaf whitefly, Bemisia tabaci biotype B, on tomato: modeling predation across spatial scales." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429788087.
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Rau, Christian, and rau@maths anu edu au. "Curve Estimation and Signal Discrimination in Spatial Problems." The Australian National University. School of Mathematical Sciences, 2003. http://thesis.anu.edu.au./public/adt-ANU20031215.163519.
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In many instances arising prominently, but not exclusively, in imaging problems, it is important to condense the salient information so as to obtain a low-dimensional approximant of the data. This thesis is concerned with two basic situations which call for such a dimension reduction. The first of these is the statistical recovery of smooth edges in regression and density surfaces. The edges are understood to be contiguous curves, although they are allowed to meander almost arbitrarily through the plane, and may even split at a finite number of points to yield an edge graph. A novel locally-parametric nonparametric method is proposed which enjoys the benefit of being relatively easy to implement via a `tracking' approach. These topics are discussed in Chapters 2 and 3, with pertaining background material being given in the Appendix. In Chapter 4 we construct concomitant confidence bands for this estimator, which have asymptotically correct coverage probability. The construction can be
likened to only a few existing approaches, and may thus be considered as our main contribution.
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Chapter 5 discusses numerical issues pertaining to the edge and confidence band estimators of Chapters 2-4. Connections are drawn to popular topics which originated in the fields of computer vision and signal processing, and which surround edge detection. These connections are exploited so as to obtain greater robustness of the likelihood estimator, such as with the presence of sharp corners.
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Chapter 6 addresses a dimension reduction problem for spatial data where the ultimate objective of the analysis is the discrimination of these data into one of a few pre-specified groups. In the dimension reduction step, an instrumental role is played by the recently
developed methodology of functional data analysis. Relatively standar non-linear image processing techniques, as well as wavelet shrinkage, are used prior to this step. A case study for remotely-sensed navigation radar data exemplifies the methodology of Chapter 6.
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Garris, Heath William. "Restructuring of Wetland Communities in Response to a Changing Climate at Multiple Spatial and Taxonomic Scales." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1383312022.
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Dul, Emilie. "Monte Carlo simulation of the spatial response function of a SPECT measurement device for nuclear fuel bundles." Thesis, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-148686.
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The PGET device is currently being developed for partial-defect verication purposes on nuclear fuel assemblies. It Comprises CdTe detector elements in a heavy tungsten-alloy collimator, for which collimator slit openings define the field-of-view. This study aims at calculating the spatial response function of this device for further deployment in tomographic reconstruction algorithms. In this work, the detector response for 2 dierent sources (662 keV from Cesium-137 and 1274 keV from Europium-154) was simulated using the MCNPX software package. In the simulations, energy windows used in measurements with the PGET device were deployed. The results show the expected characteristics with strong response for a source position directly in front of the collimator slit opening and decreasing response as the source is moved into the penumbra and umbra region. The uncertainty of the simulated response function was less than 3.5 % for both sources. Separate simulations were made to quantify contributions from septal penetration and scattering from the collimator material into the detector for the energy windows covering the full -energy peak. These contributions were found to be around3% for the source of Cesium-137 and 6% for the source of Europium-154.
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Anderson, Morgan. "Wolf responses to spatial variation in moose density in northern Ontario." Thesis, 2012. http://hdl.handle.net/10214/3544.
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Forty-four wolves in 3 boreal forest sites in Ontario were monitored via GPS radiotelemetry during 2010 and 2011 to examine spatial responses to variation in prey density. Home ranges were defined using a Brownian bridge utilization distribution, and a resource utilization function was calculated for each pack in winter and summer, based on habitat, topography, and prey density. Wolf territories were smaller where moose density was higher. Third order selection (within home range) varied by pack and season. Wolves generally selected for sloping areas, areas near water, and stands with deciduous or regenerating forest, but selected against areas with dense conifer cover. Roads were most important in summer, especially in those territories with large road networks. Habitat use in a mild winter was similar to habitat use in summer. Variable resource selection among packs emphasizes the adaptable, generalist nature of wolves even in the relatively homogenous the boreal shield.National Science and Engineering Research Council, Ontario Graduate Scholarships, Ontario Ministry of Natural Resources - Wildlife Research and Development Section, Center for Northern Forest Ecosystem Research, Ontario Ministry of Natural Resources, Canadian Forest Service, Forest Ecosystem Science Cooperative
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Ferdous, Nazneen. "A new estimation approach for modeling activity-travel behavior : applications of the composite marginal likelihood approach in modeling multidimensional choices." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-08-4224.
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The research in the field of travel demand modeling is driven by the need to understand individuals’ behavior in the context of travel-related decisions as accurately as possible. In this regard, the activity-based approach to modeling travel demand has received substantial attention in the past decade, both in the research arena as well as in practice. At the same time, recent efforts have been focused on more fully realizing the potential of activity-based models by explicitly recognizing the multi-dimensional nature of activity-travel decisions. However, as more behavioral elements/dimensions are added, the dimensionality of the model systems tends to explode, making the estimation of such models all but infeasible using traditional inference methods. As a result, analysts and practitioners often trade-off between recognizing attributes that will make a model behaviorally more representative (from a theoretical viewpoint) and being able to estimate/implement a model (from a practical viewpoint).
An alternative approach to deal with the estimation complications arising from multi-dimensional choice situations is the technique of composite marginal likelihood (CML). This is an estimation technique that is gaining substantial attention in the statistics field, though there has been relatively little coverage of this method in transportation and other fields. The CML approach is a conceptually and pedagogically simpler simulation-free procedure (relative to traditional approaches that employ simulation techniques), and has the advantage of reproducibility of the results. Under the usual regularity assumptions, the CML estimator is consistent, unbiased, and asymptotically normally distributed.
The discussion above indicates that the CML approach has the potential to contribute in the area of travel demand modeling in a significant way. For example, the approach can be used to develop conceptually and behaviorally more appealing models to examine individuals’ travel decisions in a joint framework. The overarching goal of the current research work is to demonstrate the applicability of the CML approach in the area of activity-travel demand modeling and to highlight the enhanced features of the choice models estimated using the CML approach. The goal of the dissertation is achieved in three steps as follows: (1) by evaluating the performance of the CML approach in multivariate situations, (2) by developing multidimensional choice models using the CML approach, and (3) by demonstrating applications of the multidimensional choice models developed in the current dissertation.text
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de, Kerckhove Derrick Tupper. "The Spatial Ecology of Predator-prey Relationships in Lakes." Thesis, 2014. http://hdl.handle.net/1807/65654.
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The pelagic zone of lakes is defined as the water column over the area of the lake benthos that does not receive enough light from the sun to allow macrophytes to grow. The four chapters of this thesis explore the spatial ecology of predator-prey interactions between schooling fish and their fish predators in this featureless environment. We first developed novel hydroacoustics methods to study fish and fish school swimming behaviour in the pelagic zone (Chapter 1 and 2). Then we characterized our in-situ school formation and prey movement observations using an ideal gas model to better understand the mechanisms that lead to fish and school densities during the daytime (Chapter 2 and 3). With this model we estimated the functional relationship between the schooling prey densities and predator encounter rates, and verified with empirical data a counterintuitive relationship that encounter rates decreased as overall prey densities increased (Chapter 3). The encounter rates suggested that predation within the pelagic zone might be greatly influenced by external forces if they provide spatial structure which encourages greater degrees of prey aggregation in predictable locations. In this regard we examined the predator-prey dynamics under wind and found large redistributions of prey and predators under windy conditions leading to greater aggregations in downwind locations. Further, we found that our study fish were larger in lakes that were oriented into the wind, perhaps demonstrating a benefit to fish growth under windy conditions (Chapter 4).
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"Grain-dependent habitat selection in white-tailed deer (Odocoileus virginianus)." Thesis, 2014. http://hdl.handle.net/10388/ETD-2014-10-1811.
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A fundamental problem in ecology is determining what factors affect the distribution of organisms across a landscape. Landscapes are by their nature heterogeneous and different habitat types confer different fitness benefits and costs to organisms that inhabit them. Ecologists are now aware of the importance of examining multiple spatial scales when designing studies quantifying animal resource selection. Scale of analysis has been shown to be important, since ecological pressures relating to the establishment of a home range differ from those relating to the use of resources within the home range. Most studies that examine multiple spatial scales examine the effect of modifying extent. Here, I examine the role of grain, an underappreciated component of scale, on our interpretation of habitat selection patterns and functional response.
The goal of this thesis was to examine how grain size affects the interpretation of animal resource selection and functional response across multiple habitats. The perceptual range of an individual is known to change with habitat, therefore I hypothesized that resource selection and functional response would be both grain- and habitat-dependent, and that resource selection functions computed using different grains for different resources would be more predictive than models computed using only a single grain.
I used GPS-collared white-tailed deer (Odocoileus virginianus) to quantify resource selection functions at various grains and used generalized linear mixed effects modelling and multi-model inference techniques to examine how resource selection patterns changed with spatial scale across habitat types. I used selection ratios to examine functional response across grains. Model coefficients changed with grain and the strength of selection varied by habitat type. Multi-grain resource selection functions had lower AIC values and better cross-validation scores than single grain models. Functional response varied with scale and habitat type, displaying a unique relationship for each habitat. My results suggest that spatial memory and habitat-dependent perceptual range play an important role in resource selection. I conclude that the examination of multiple grains in the study of animal habitat selection and functional response represents a step forward in our ability to understand what drives the distribution and abundance of organisms.
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Wang, Chain-Ji, and 王前智. "Functional responses of Amblyseius ovalis (Acari: Phytoseiidae) preying on Tetranychus uritcae (Acari: Tetranychidae) and their spatial distribution." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/28913271129707660990.
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碩士國立中興大學
昆蟲學系
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The population distributions of Amblyseius ovalis (Evans) and Tetranychus urticae Koch were evaluated by the values of indices and their distribution─uniform, random, and aggregative distribution types, according to the hypotheses of (1) index of dispersion (ID), (2) Green''''s coefficient of dispersion (Cx), (3) Lloyd''''s mean crowding index (mc), (4) Lloyd''''s patchiness index (mc/m), (5) Morisita''''s coefficient of dispersion ( Iδ, Iβ), (6)Taylor''''s power law regression with intercept (㏒a) and sloped (7) Iwao''''s patchiness regression (α, β). The frequencies of distribution types of mites'''' populations mearsured by week or by stages were accordingly rearranged and utilized to assess the appropriate type of distributions. A. ovalis and T. urticae population in the field were either aggregative or random type. Predator-prey relationship was demostrated by A. ovali feeding on T. urticae. The responses of daily predation rate and predation rate curve of A. ovalis on 8 prey densities of T. urticae showed a Holling'''' s typeΠ and type Ⅲ responses─functional responses of predator. Non-linear regression model was used to fit daily predation rates on the different prey densities and found 43 functional response equations which included the independent variables of (1) predator''''s stages, sexes, and feeding history prey'''' s species, stages, and sexes, (3) habitat substrates and sizes, and (4) temperatures. The fitted regression equations were used to find out the theoretical attack rates (a) and handling time (Th) under different tested conditions. Those a'''' s and Th''''s were also variate with the tested conditions by which the interactions and relations between the predator and the prey were interpreted and discussed.
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(10703055), Guodong Jiang. "INTERPLAY OF GEOMETRY WITH IMPURITIES AND DEFECTS IN TOPOLOGICAL STATES OF MATTER." Thesis, 2021.
Find full textAbstract:
The discovery of topological quantum states of matter has required physicists to look beyond Landau’s theory of symmetry-breaking, previously the main paradigm forstudying states of matter. This has led also to the development of new topological theories for describing the novel properties. In this dissertation an investigation in this
frontier research area is presented, which looks at the interplay between the quantum geometry of these states, defects and disorder. After a brief introduction to the topological quantum states of matter considered herein, some aspects of my work in this area are described. First, the disorder-induced band structure engineering of topological insulator surface states is considered, which is possible due to their resilience from Anderson localization, and believed to be a consequence of their topological origin.
Next, the idiosyncratic behavior of these same surface states is considered, as observed in experiments on thin film topological insulators, in response to competition between
hybridization effects and an in-plane magnetic field. Then moving in a very different direction, the uncovering of topological ‘gravitational’ response is explained: the
topologically-protected charge response of two dimensional gapped electronic topological states to a special kind of 0-dimensional boundary – a disclination – that encodes spatial curvature. Finally, an intriguing relation between the gravitational response of quantum Hall states, and their response to an apparently unrelated perturbation – nonuniform electric fields is reported.