Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 54 for “"Grid cells."”.
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Theta oscillations, timing and cholinergic modulation in the rodent hippocampal circuit
… input from the medial septum. Entorhinal grid cells fire when an animal visits particular locations in the environment arranged on the corners of tightly packed, equilateral triangles. Grid cells show phase precession, in which neurons fire at progressively earlier phases relative to theta …
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A neural inspired grid cell aid for robot intertial navigation.
… model of map formation and localization with grid cells to aid dead reckoning with an accelerometer and gyroscope to show grid cells are a viable aid in idiothetic navigation. The results show that the grid cell aided navigation systems shows better performance with longer paths and higher …
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Heterogeneity effects on flow and transport within a shallow fluvial aquifer
… using stochastic, geostatistical models with grid cells on the order of several meters. It was found that river loss decreased directly with an increase in the extent of heterogeneity and that homogeneous approximations resulted in increased loss estimates. Heterogeneity effects on transport …
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Charting the hippocampal cognitive map: Investigating the emergence of grid cell and place cell firing patterns in novel and familiar environments
Hippocampal place cells comprise the main building blocks of the cognitive map which is used to encode our surroundings quickly and rapidly. Prominent theoretical models argue that place cells emerge via a linear summation of different grid cells from the medial entorhinal cortex. However, recent …
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A Grid based Indoor Radiolocation Technique Based on Spatially Coherent Path Loss Model
This thesis presents a grid-based indoor radiolocation technique based on a Spatially Coherent Path Loss Model (SCPL). SCPL is a path loss model which characterizes the radio wave propagation in an environment by solely using Received Signal Strength (RSS) fingerprints. The propagation of the radio …
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Comparing Spatial Measures of the Built Environment for Health Research
… and other arbitrary geographies, such as grid cells. There is a lack, however, of reports that describe the justifications or implications for using different methods. This research compares different forms and distances for measuring environmental variables surrounding residential …
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A Model for Simulating Soil-Zone Processes at the Regional Scale
… solution (0.014-0.052 RMSE) with only 6 grid cells and 0.11 seconds computation time compared to the 6250 grid cells and 40 seconds of computation time required for a stable solution to RE. MODFLOW-SZF solutions had negligible errors due to grid effects (<0.01 RMSE) however, RE solutions …
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From spatio-temporal data to a weighted and lagged network between functional domains: Applications in climate and neuroscience
… Such data are typically embedded in a grid with a resolution larger than the true dimensionality of the underlying system. One major task is to identify the distinct semi-autonomous functional components of the spatio-temporal system and to infer their interconnections. In this thesis, …
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Measurement and deduction of emissions of short-lived atmospheric organo-chloride compounds
… estimate of corrections factors for land-based grid cells presented here indicate that the RCEI emissions for trichloroethene and tetrachloroethene need to be increased by a factor of ~2 to explain the observations. Only anthropogenic sources of trichloromethane were gridded in the initial …
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Mechanisms underlying spatial navigation
… First, I investigate the information conveyed by grid cells, whose firing fields tile the environment in a hexagonal grid. In doing so, they are thought to provide a static map of space. Current models of navigation propose that this static grid cell map is used to support navigation behaviours. …
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Patterns in the landed catches and determinants of catch composition in the South African inshore trawl fishery
… trawl grounds were divided into 20' by 20' grid cells, which were used to aggregate the trawls and clustered into six groups at an 87% similarity. 7 | P a g e The landed catch composition per trip was influenced by the vessel (F(1, 21) = 32.7, p < 0.001, R2 = 0.31), year (F(1, 29) = 16.0, p …
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Dynamic grid adaption using the LPE equation
… and implementation of a dynamic adaptive grid method for general two and three dimensional static and transient fluid flow problems solved over structured grids. The technique automatically manipulates the location of grid points within the domain of interest to concentrate cells in …
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Mathematical modelling of flow and combustion in internal combustion engines
… in the solution procedure specific to moving grids, and combustion modelling. Two and three-dimensional computations of the in-cylinder turbulent flow in a diesel engine are described first, with emphasis on the modifications made to the standard k- model of turbulence to account for rapid …
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Spatial and non-spatial patterns of genetic diversity in Neotropical bats
… calculated from 66 geographically distributed grid cells. Using a map of bat occurrence data, I estimated the average nucleotide diversity across bat species from each 300 x 300 km grid cell that contained at least three sequences of the same OTU. Across the same grid cells, I also compared …
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3D ICEPIC simulations of pulsed relativistic magnetron with transparent cathode : a comparative study with 3D MAGIC simulations
… run on a parallel architecture with 64 CPUs at a grid resolution of 1mmx 1mmy 1mmz in the 3-dimensional Cartesian coordinate system. These simulations consisted of roughly 6 million active grid cells and 16 million particles. Results indicated agreement between results from ICEPIC and MAGIC to …
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The elevation pyramid: a method for compressing elevation data
A quadtree-like representation for storing gridded elevation data is described. In its simplest form, the data structure is a pyramid with each node containing a two bit code. The root of the pyramid has associated with it the minimum elevation for the grid and the range (the greatest power of 2 …
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Boundless Fluids Using the Lattice-Boltzmann Method
… to utilize a recursive run-length-encoded (RLE) grid data structure instead of the standard fixed array of grid cells, which reduces the amount of memory required for LBM simulations as well as allowing the domain to grow and shrink as necessary to accomodate a liquid surface. The modified LBM is …
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Analysis of distribution maps from bird atlas data: dissimilarities between species, continuity within ranges and smoothing of distribution maps
… are compared over all quarter degree grid cells. Existing coefficients are not suitable for the comparison of distributions with different total areas and species with different mean reporting rates. In each grid cell the reliability of the reporting rates depends on the number of …
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Little Sac Woods Metro Forest, a Land Management Methodology and Plan
… use of maps and the area was divided into 320 grid cells of 2.5 acres each. Land management goals were determined for the area and criteria developed for six goals. Each grid cell was rated as to its suitability for the goal. The computer played an important role in the methodology. The …
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Applying the RUSLE and SEDD Equations to an Agricultural Watershed in Southwest Virginia - A Case Study in Sediment Yield Estimation Using GIS
… In ArcGIS the watershed was broken into a raster grid of approximately 5,200 discrete 100 foot by 100 foot grid cells. The resulting watershed erosion model identified two main sources of sediment: a cluster of farms relatively close to and east of the duck pond, and a harvested timber site north …
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