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Dissertations / Theses on the topic 'Spatial field'
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Haines, Ross. "Simultaneous reconstruction of spatial frequency fields and field sample locations." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:aa35073d-003b-4939-bf0e-8348243871b7.
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Classically, spatial smoothing methods such as kriging estimate smooth interpolating fields for features measured at well-located points. In this thesis, we make a simultaneous reconstruction of interpolating spatial fields and measurement locations. We give models, and sample-based Bayesian inference, for estimating locations of dialect samples on a map of England. The method exploits dialect-based spellings to locate these samples. The data are feature vectors extracted from written dialect samples. Just a fraction of the feature vectors ('anchors') have an associated spatial location. When coupled to a prior for the smoothly varying feature field, and the anchor texts, the unlocated feature vectors are jointly informative of their own location and the feature fields. The dataset is large, but sparse, since a given word has a large number of variant spellings which may appear in just a few documents. We report an analysis including Bayesian model fitting and validation on a large and representative subset of the data. The thesis has two main aims - to provide statistical tools for the linguists who collected the data, and to meet the computational and inferential challenge of simultaneously locating large numbers of feature vectors. The results presented in this thesis show that we have largely succeeded in meeting these challenges.
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Wealands, Stephen Russell. "Quantitative methods for hydrological spatial field comparison /." Connect to thesis, 2006. http://eprints.unimelb.edu.au/archive/00002722.
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Zuvela, Dominik. "Pretoria city : a spatial field in tension." Diss., University of Pretoria, 2010. http://hdl.handle.net/2263/30298.
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Architecture is a representation of our society’s aspirations and of our social, economic and political paradigms. Since 1994, has the city of Pretoria been successfully represented? Does the city succeed architecturally in creating space that is democratic and that embraces our country’s diversity? The large influx of people within the city of Pretoria has created a terrain consisting of a series of contradictions and conflicts. These conflicts and contradictions within the city are a result of social, economic, spatial, physical and historical tensions that exist within society's social, economic and political paradigms. Physical and spatial reactions have occurred as a result of these tensions that exist within the city of Pretoria. This dissertation will explore these urban spaces that are in tension and investigate what opportunities and limitations such spaces offer the city of Pretoria. The objective is to consider what architectural intervention will arise from the resolution, synthesis or conflict of these tensions. Can these spaces that are in tension within the city foster a new post-apartheid way of city-making.Dissertation (MArch(Prof))--University of Pretoria, 2011.
Architecture
unrestricted
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Rydén, Magnus. "Strategic Placing of Field Hospitals Using Spatial Analysis." Thesis, KTH, Geoinformatik och Geodesi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-34292.
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Humanitarian help organisations today may benefit on improving their location analysis when placing field hospitals in countries hit by a disasters or catastrophe. The main objective of this thesis is to develop and evaluate a spatial decision support method for strategic placing of field hospitals for two time perspectives, long term (months) and short term (weeks). Specifically, the possibility of combining existing infrastructure and satellite data is examined to derive a suitability map for placing field hospitals. Haut-Katanga in Congo is used as test area where exists a large variety of ground features and has been visited by aid organisations in the past due to epidemics and warzones. The method consists of several steps including remote sensing for estimation of population density, a Multi Criteria Evaluation (MCE) for analysis of suitability, and visualization in a webmap. The Population density is used as a parameter for an MCE operation to create a decision support map for locating field hospitals. Other related information such as road network, water source and landuse is also taken into consideration in MCE. The method can generate a thematic map that highlights the suitability value of different areas for field hospitals. By using webmap related technologies, these suitability maps are also dynamic and accessible through the Internet. This new approach using the technology of dasymetric mapping for population deprival together with an MCE process, yielded a method with the result being both a standalone population distribution and a suitability map for placing field hospitals with the population distribution taken into consideration. The use of dasymetric mapping accounted for higher resolution and the ability to derive new population distributions on demand due to changing conditions rather than using pre-existing methods with coarser resolution and a more seldom update rate. How this method can be used in other areas is also analysed. The result of the study shows that the created maps are reasonable and can be used to support the locating of field hospitals by narrowing down the available areas to be considered. The results from MCE are compared to a real field hospital scenario, and it is shown that the proposed method narrows down the localisation options and shortens the time required for planning an operation. The method is meant to be used together with other decision methods which involves non spatial factors that are beyond the scope of this thesis.
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Gyllingberg, Linnéa. "Mean field approximations of spatial models of evolution." Thesis, Uppsala universitet, Tillämpad matematik och statistik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295782.
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Zhang, Mi. "Study of Spatial Structure of Squeezed Vacuum Field." W&M ScholarWorks, 2016. https://scholarworks.wm.edu/etd/1499450043.
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Squeezed states of light, with field fluctuations smaller than the coherent state fluctuations (or shot noise), are used for improving accuracy of quantum-noise limited measurements, like the detection of gravitational waves. They are also essential resources for quantum information transfer protocols. We studied a squeezed vacuum field generated in hot Rb vapor via the polarization self-rotation effect. We studied the mode structure of the squeezed field by spatially-masking the laser beam after its interaction with the Rb atomic vapor. From analysis of the data we developed a multi-mode theory to simulate the mode composition of the squeezed vacuum field. Our experiments showed that the amount of observed squeezing may be limited by the complex mode structure due to the excitement of higher order spatial modes during the nonlinear atom-light interaction. We demonstrated that optimization of the spatial profile of the beam led to higher detected squeezing. Our studies are useful for enhancing precision metrology and quantum memory applications.
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Haag, Christian. "Temporal and spatial wind field distribution in Delaware Bay." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 9.11 Mb., 62 p, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:1430767.
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Thesis (M.E.E.)--University of Delaware, 2006.Principal faculty advisors: Kenneth E. Barner, Dept. of Electrical and Computer Engineering; and Mohsen Badiey, Dept. of Marine and Earth Studies. Includes bibliographical references.
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Rew, Lisa J. "Spatial and comparative aspects of arable field margin flora." Thesis, University of Reading, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333656.
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MacKinnon, James L. "Spatial dynamics of cyclic field vole, Microtus agrestis, populations." Thesis, University of Aberdeen, 1998. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU483789.
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1. Many ecologists have recently advocated the study of spatial patterns of abundance or growth rates as a means of better understanding population dynamics. In this study I described the spatial pattern of abundance of the field vole, Microtus agrestis, which has previously been shown to have cyclic temporal fluctuations of abundance in my study area in Kielder Forest, northern England. A combination of techniques was then used to investigate which processes determine the spatial pattern of dynamics in these vole populations.2. Previous analysis of spatial patterns in density of field voles from an area of approximately 80 km2 within Kielder forest over a 13-year period indicate that density varies as a periodic travelling wave moving across the landscape. I collected data on vole density from a larger area (approximately 600 km2) over a 2.5-year period and used the same analysis to show that the spatio-temporal variation in density was well explained by a travelling wave of density moving across the entire region. Estimates of the wave's speed of 14 kmyr-1 and direction of 66° from north were consistent with the estimates obtained from the data set covering a smaller spatial extent but spanning a longer temporal scale.3. Processes that determine population abundance do so by acting on vital demographic rates. Spatial patterns in demographic rates were therefore described to help identify potential causes of the spatial patterns of density. Eight 0.3 ha live-trapping grids were established within the study area and animals were trapped at monthly intervals during a period of extended low density and during a period of increasing densities. Capture-mark-recapture techniques were used to estimate abundance, juvenile recruitment rate, apparent survival rate and immigration rate at these sampling sites. The synchrony of changes in these parameters between sites was measured as the cross-correlation coefficient between the time series of each parameter and the spatial patterns in the synchrony of each demographic rate were described using Mantel correlations. Field vole abundance, juvenile recruitment rate and a derived estimate of mortality rate were most synchronous between the closest sites, however no directionality was found in these patterns and they could not therefore be related to the travelling wave pattern of density. I concluded that the process responsible for the wave probably only acted during the period of declining density and that therefore the factors causing spatial patterns in abundance could differ at different stages of the population cycle.
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Zhou, Sichao. "Complex Optical Fields Generation Using a Vectorial Optical Field Generator." University of Dayton / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1461689435.
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Neagu, Teodora. "Is there a relationship between spatial orientation ability, and field of study and gender?" Thesis, Umeå universitet, Institutionen för psykologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-184031.
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Spatial ability has been studied in relation to education and gender previously, concluding that men outperform women in any field of study in spatial tasks and test batteries. For that reason, the present study aims to confirm such differences through a spatial orientation task and the Santa Barbara Sense of Direction Scale (SBSOD). The study was conducted online with 106 participants of which 58 were men and 44 women, distributed in two groups (STEM and No-STEM). An analysis of variance (ANOVA) and t-test concluded that overall men outperform women in both the task and the test, however, there is no difference between field of study. Further research should focus on the limitations of the present study, regarding the sample size and task design.Spatial förmåga har tidigare studerats med avseende på både studieinriktning och kön, där slutsatsen har varit att män presterar bättre än kvinnor oavsett studieinriktning vid test av spatial förmåga. Av den anledningen riktar den här studien in sig på att styrka det sambandet med hjälp av en spatial orienteringsuppgift och Santa Barbara Sense of Direction Scale (SBSOD). Studien genomfördes online med 106 deltagare där 58 var män och 44 kvinnor, fördelade i två grupper baserat på studieinriktning (Naturvetenskaplig och icke- naturvetenskaplig). En variansanalys (ANOVA) och ett t-test gav resultatet att män generellt presterar bättre än kvinnor i både uppgiften och testet, men det finns däremot ingen skillnad mellan studieinriktningar. Ytterligare forskning bör fokusera på begränsningarna i denna studie, avseende antal deltagare och utformning av uppgiften.
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Price, Oliver Richard. "Spatial variation in pesticide/soil interactions at the field scale." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409062.
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Martin, Patrick Dov. "Place field plasticity and directionality in a spatial memory task." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243291.
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Benitez, Lionel Ernesto Donatti. "SPATIAL VARIATION OF PHYSICAL PROPERTIES IN AN IRRIGATED FIELD (ARIZONA)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275402.
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Yukutake, Yohei. "Spatial change in the stress field around large earthquake faults." 京都大学 (Kyoto University), 2006. http://hdl.handle.net/2433/144197.
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Kyoto University (京都大学)0048
新制・課程博士
博士(理学)
甲第12114号
理博第3008号
新制||理||1448(附属図書館)
23950
UT51-2006-J109
京都大学大学院理学研究科地球惑星科学専攻
(主査)助教授 飯尾 能久, 教授 平原 和朗, 教授 橋本 学
学位規則第4条第1項該当
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Gair, Sinclair. "3-D spatial field and force distributions in axial field machines using a computed tomography method." Thesis, Heriot-Watt University, 1990. http://hdl.handle.net/10399/852.
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Durban, Reguera Maria L. "Modelling spatial trends and local competition effects using semiparametric additive models." Thesis, Heriot-Watt University, 1998. http://hdl.handle.net/10399/1287.
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Wood, Gillian Ann. "Field arrangements in the West Riding of Yorkshire in the High Middle Ages." Thesis, University of Leeds, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275806.
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Glenn, Dickins, and glenn dickins@dolby com. "Applications of Continuous Spatial Models in Multiple Antenna Signal Processing." The Australian National University. Research School of Information Sciences and Engineering, 2008. http://thesis.anu.edu.au./public/adt-ANU20080702.222814.
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This thesis covers the investigation and application of continuous spatial models for multiple antenna signal processing. The use of antenna arrays for advanced sensing and communications systems has been facilitated by the rapid increase in the capabilities of digital signal processing systems. The wireless communications channel will vary across space as different signal paths from the same source combine and interfere. This creates a level of spatial diversity that can be exploited to improve the robustness and overall capacity of the wireless channel. Conventional approaches to using spatial diversity have centered on smart, adaptive antennas and spatial beam forming. Recently, the more general theory of multiple input, multiple output (MIMO) systems has been developed to utilise the independent spatial communication modes offered in a scattering environment.¶
Underlying any multiple antenna system is the basic physics of electromagnetic wave propagation. Whilst a MIMO system may present a set of discrete inputs and outputs, each antenna element must interact with the underlying continuous spatial field. Since an electromagnetic disturbance will propagate through space, the field at different positions in the space will be interrelated. In this way, each position in the field cannot assume an arbitrary independent value and the nature of wave propagation places a constraint on the allowable complexity of a wave-field over space. To take advantage of this underlying physical constraint, it is necessary to have a model that incorporates the continuous nature of the spatial wave-field. ¶This thesis investigates continuous spatial models for the wave-field. The wave equation constraint is introduced by considering a natural basis expansion for the space of physically valid wave-fields. This approach demonstrates that a wave-field over a finite spatial region has an effective finite dimensionality. The optimal basis for representing such a field is dependent on the shape of the region of interest and the angular power distribution of the incident field. By applying the continuous spatial model to the problem of direction of arrival estimation, it is shown that the spatial region occupied by the receiver places a fundamental limit on the number and accuracy with which sources can be resolved. Continuous spatial models also provide a parsimonious representation for modelling the spatial communications channel independent of specific antenna array configurations. The continuous spatial model is also applied to consider limits to the problem of wireless source direction and range localisation.
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Pearson, Frank. "The formulation and development of instruments to measure field dependence-field independence using spatial and verbal modalities." Thesis, Oxford Brookes University, 2013. https://radar.brookes.ac.uk/radar/items/8f6bb6a1-48db-4e2c-af7c-117374df8ad4/1/.
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The thesis gives a description of the formulation and development of an Embedded Shapes Test which was subsequently used as a method of measuring the construct/cognitive style of field dependence – field independence, using a spatial modality. Two additional methods of measuring field dependence – field independence were also formulated and developed, which used a verbal modality, in the form of a Sense Word Test (SWT) and Non-Sense Word Test (NSWT). Each of the above field dependence – field independence 'tests' were used in a series of pilot studies and studies, as part of their development and application. With two of the studies, of which there were four, additional ‘tests’ were used to measure cognitive attributes considered to have some association with those inherent in the measurement of field dependence – field independence. These included the Chronological Order Integration Test (COIT) and the Gestalt Picture Completion Test (GPCT) in Study Three; and the GPCT; British Ability Scales (BASI)/Short Form IQ; and the Cognitive Styles Analysis (CSA) in Study Four. The COIT in Study Three provided a framework to measure field dependence – field independence using a verbal modality through the medium of text. Therefore, this enabled comparisons to be made within a verbal modality through the medium of words and non-sense words by the SWT and NSWT, as well as a spatial modality by the EST. The inclusion of the GPCT, in Studies Three and Four enabled the process of measuring field dependence – field independence to be compared with a process that appeared to be opposite to it, i.e. an integration – synthesis process, or putting together pieces of information, instead of a segregated – analytical process, or taking apart a piece of information, respectively. The BASI/Short Form IQ was included in Study Four to provide a measure of cognitive ability. Since an argument directed at the concept and measurement of field dependence – field independence is that it is measuring cognitive ability rather than cognitive style, a comparison was made between field dependence – field independence and cognitive ability/intelligence as measured by the BASI/Short Form IQ. A further comparison with measurements of field dependence – field independence was made possible by the inclusion of the CSA in terms of a Wholistic or Analytic perception of information, as well as a propensity, on the part of the individual, to think spatially or verbally, i.e. in the Imager or Verbaliser mode of the CSA. The inclusion of school subject performance/attainment levels, in each of the four studies, was to enable comparisons to be made between the various measurements of field dependence – field independence, i.e. EST, SWT, NSWT and COIT, and GPCT, BASI/Short form IQ, CSA, and the characteristics of the different school subjects themselves. This enabled the exploration as to whether or not the characteristics of particular school subjects have an affinity to field dependence – field independence in terms of cognitive style and/or cognitive ability. This exploration was augmented in Study Three by the inclusion of GCSE subject grades for the sample members. In Chapter 14 (Comparisons of the Outcomes from the Four Studies), Witkin’s Group Embedded Figures Test (GEFT) was introduced to provide a comparison of reliability between the EST3, SWT2 and NSWT1, using the Cronbach Alpha statistic. The sample used for each of the pilot studies and studies consisted of Year 8, male and female, students of mixed ability, from Comprehensive and Middle Schools. The sample sizes for each of the two pilot studies were thirty, but varied for the four studies from 62 to 224 to increase the statistical validity and to decrease the standard error. Within each of the four studies, means; standard deviations; Multivariate Analysis of Variance (MANOVA); correlations (Pearson Product Moment) and Cronbach Alpha statistics were used to analyse the data. The EST3, SWT2 and NSWT1 were used in each of the four studies and produced a high level of construct validity across the four studies. A number of significant F ratios and correlations were obtained between the variables in each of the four studies. In particular, significant F ratios were obtained for EST3; Sex; Test Type (SWT2 and NSWT1), e.g. (F = 4.00; df 2, 56; p = 0.05 – Study 1); School Subjects and GCSE Subjects; and significant correlations between EST3 and Science (General), e.g. r = 0.4006; p = 0.05 – Study 1; Modern Language (French); COIT A and S; COIT B and S; and IQ within the corresponding that included these variables. Correlations (r) between EST3, SWT2 and NSWT1 within each study produced a number of high reliability values (See Chapter 14, Table 14.4 for full details). In addition, the Cronbach Alpha values for the EST3, SWT2 and NSWT1 gave a high reliability, i.e. 0.84263, 0.92799, 0.91946 for Study One; 0.90281, 0.93720, 0.88725 for Study Two; 0.89441, 0.94493, 0.92713 for Study Three; and 0.84942, 0.93779, 0.91099 for Study Four, respectively. The Cronbach Alpha value for the EST3 was greater than that for the GEFT, i.e. 0.93544 and 0.89234, respectively. Similar values were obtained for the SWT2 and NSWT1 when compared to the GEFT, i.e. 0.97891 and 0.96411, respectively.
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Vincart-Emard, Alexandre. "Numerical investigation of spatial inhomogeneities in gravity and quantum field theory." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62607.
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Many interesting phenomena, such as high-temperature superconductivity and the quark-gluon plasma, still lack a satisfyingly predictive theoretical description. However, recent advances have revealed a curious connection between quantum field theories at strong coupling and classical gravity. This correspondence, known as the gauge/gravity duality or holographic correspondence, offers a promising perspective for investigating strongly correlated systems. In this thesis, we focus on using these new tools to examine the consequences of breaking translational invariance in such systems.
We first use this duality to study the holographic realization of a spatially inhomogeneous condensed matter device known as a Josephson junction. We do so by constructing the gravitational equivalent of two superconductors separated by a weak metallic link, from which we then extract various field-theoretic quantities of interest. These include the spontaneously generated Josephson current, the superconducting order parameter, as well as a novel quantity we refer to as edge currents, which are indicative of gapless chiral modes localized at the interfaces between phases.
We then investigate the more abstract construct of entanglement entropy in holographic theories. We model the fast local injection of energy in a 2+1 dimensional field theory and study the resulting thermalization of quantum entanglement. We achieve this objective by numerically evolving the geometry dual to a local quench from which we then compute the area of various minimal surfaces, the holographic proxy for entanglement entropy. We observe the appearance of a lightcone featuring two distinct regimes of entanglement propagation and provide a phenomenological explanation of the underlying mechanisms at play.
Finally, we turn our attention to spatial inhomogeneities in gravitational systems themselves. We use an approximation of general relativity in which the number of spacetime dimensions is infinite to investigate the Gregory-Laflamme instability of higher-dimensional charged black branes. We argue that charged branes are always unstable in this new language, and push the approximation to next-to-leading order to compute the critical dimension below which the instability results in horizon fragmentation. We also examine the stability properties of two-dimensional black membranes and find that the triangular lattice minimizes brane enthalpy.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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Hill, Bryony J. "An orientation field approach to modelling fibre-generated spatial point processes." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/49422/.
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This thesis introduces a new approach to analysing spatial point data clustered along or around a system of curves or fibres with additional background noise. Such data arise in catalogues of galaxy locations, recorded locations of earthquakes, aerial images of minefields, and pore patterns on fingerprints. Finding the underlying curvilinear structure of these point-pattern data sets may not only facilitate a better understanding of how they arise but also aid reconstruction of missing data. We base the space of fibres on the set of integral lines of an orientation field. Using an empirical Bayes approach, we estimate the field of orientations from anisotropic features of the data. The orientation field estimation draws on ideas from tensor field theory (an area recently motivated by the study of magnetic resonance imaging scans), using symmetric positive-definite matrices to estimate local anisotropies in the point pattern through the tensor method. We also propose a new measure of anisotropy, the modified square Fractional Anisotropy, whose statistical properties are estimated for tensors calculated via the tensor method. A continuous-time Markov chain Monte Carlo algorithm is used to draw samples from the posterior distribution of fibres, exploring models with different numbers of clusters, and fitting fibres to the clusters as it proceeds. The Bayesian approach permits inference on various properties of the clusters and associated fibres, and the resulting algorithm performs well on a number of very different curvilinear structures.
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McCormick, John. "The use of secondary spatial transforms in near field antenna measurements." Thesis, Open University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311859.
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Getachew, T. (Tibebu). "Spatial-temporal structure and distribution of the solar photospheric magnetic field." Doctoral thesis, Oulun yliopisto, 2019. http://urn.fi/urn:isbn:9789526224367.
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Abstract I have made a detailed study of the fundamental properties of the solar photospheric magnetic field, which helps in better understanding the Sun’s radiative and particle outputs that affect the Earth’s near-space environment, as well as the entire heliosphere. Photospheric magnetic field is an essential parameter for space weather and space climate. The photospheric magnetic field includes a wide range of large-scale and small-scale structures, but the contribution of weak, small-scale fields to the total flux on the solar surface is dominant. This thesis discusses the spatial-temporal structure and long-term evolution of the solar photospheric magnetic field. Particularly, the thesis presents, for the first time, the spatial distribution of the asymmetry of weak field values and its evolution in solar cycles 21–24. I found that the asymmetry (also called shift) of the distribution of positive and negative weak-field values is a real physical phenomenon. I also found that the shifts are most effectively produced at the supergranulation scale. I studied the asymmetry of the distribution of weak field values separately in the two solar hemispheres. My results show that the shifts of weak-field field distributions in the two solar hemispheres have always the same sign as the new polarity of the polar field in the respective hemisphere and solar cycle. I also found that the hemispheric shifts change their sign in the late ascending to maximum phase of the solar cycle and attain their maximum in the early to mid-declining phase. This evolution of the hemispheric weak-field gives a new signal of the solar magnetic cycle. We also studied the long-term spatial-temporal evolution of the weak-field shift and skewness of the distribution of photospheric magnetic field values during solar cycles 21–24 in order to clarify the role and relation of the weak field values to the overall magnetic field evolution. Our results give evidence for the preference of even the weakest field elements toward the prevailing magnetic polarity since the emergence of an active region, and for a systematic coalescence of stronger magnetic fields of opposite to produce weak fields during the poleward drift of the surgeOriginal papers Original papers are not included in the electronic version of the dissertation. Getachew, T., Virtanen, I., & Mursula, K. (2017). Structure of the Photospheric Magnetic Field During Sector Crossings of the Heliospheric Magnetic Field. Solar Physics, 292(11). https://doi.org/10.1007/s11207-017-1198-9 http://jultika.oulu.fi/Record/nbnfi-fe201802083259 Getachew, T., Virtanen, I., & Mursula, K. (2019). Asymmetric Distribution of Weak Photospheric Magnetic Field Values. The Astrophysical Journal, 874(2), 116. https://doi.org/10.3847/1538-4357/ab0749 http://jultika.oulu.fi/Record/nbnfi-fe2019061320447 Getachew, T., Virtanen, I., & Mursula, K. (2019). A New Signal of the Solar Magnetic Cycle: Opposite Shifts of Weak Magnetic Field Distributions in the Two Hemispheres. Geophysical Research Letters, 46(16), 9327–9333. https://doi.org/10.1029/2019gl083339 Mursula, K., Getachew, T., & Virtanen, I. (2019). Spatial-temporal evolution of photospheric weak-field shifts in solar cycles 21-24. Astron. Astrophys., submitted
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Morphet, William James. "Simulation, Kriging, and Visualization of Circular-Spatial Data." DigitalCommons@USU, 2009. https://digitalcommons.usu.edu/etd/386.
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The circular dataimage is defined by displaying direction as the color at the same direction in a color wheel composed of a sequence of two-color gradients with color continuity between gradients. The resulting image of circular-spatial data is continuous with high resolution. Examples include ocean wind direction, Earth's main magnetic field, and rocket nozzle internal combustion flow. The cosineogram is defined as the mean cosine of the angle between random components of direction as a function of distance between observation locations. It expresses the spatial correlation of circular-spatial data. A circular kriging solution is developed based on a model fitted to the cosineogram. A method for simulating circular random fields is given based on a transformation of a Gaussian random field. It is adaptable to any continuous probability distribution. Circular random fields were implemented for selected circular probability distributions. An R software package was created with functions and documentation.
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Smith, Alison B. "Multiplicative mixed models for the analysis of multi-environment trial data /." Title page, contents and abstract only, 1999. http://web4.library.adelaide.edu.au/theses/09PH/09phs64221.pdf.
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Poth, Michaela [Verfasser], and Andreas [Akademischer Betreuer] Herz. "Spatial representation in the mammalian brain : field-to-field variability of grid cells / Michaela Poth ; Betreuer: Andreas Herz." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2020. http://d-nb.info/1219852023/34.
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Reiter, Bettina. "Temporal and spatial receptive field characteristics of tectal neurons in zebrafish larvae." [S.l.] : [s.n.], 2005. http://edoc.ub.uni-muenchen.de/archive/00005153.
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Wells, Susan K. "Temporal and spatial decorrelation scales of the Yellow Sea thermal field[s] /." Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA288617.
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Thesis (M.S. in Meteorology and Physical Oceanography) Naval Postgraduate School, September 1994.Thesis advisor(s): Peter Chu, Steven D. Haeger. "September 1994." Bibliography: p. 45-47. Also available online.
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Reiter, Bettina. "Temporal and spatial receptive field characteristics of tectal neurons in zebrafish larvae." Diss., lmu, 2006. http://nbn-resolving.de/urn:nbn:de:bvb:19-51537.
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Manggala, Putra. "On Markov random field models for spatial data: towards a practitioners toolbox." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=114270.
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In the era of big data, data sets have been growing very large, and interest for algorithms and computation framework that handle such large scales is increasing. The number of computing cores per chip has also increased. Instead of developing ingenious ways of speeding up convergences and obtaining better approximations for a smaller subclass of the problems, it is interesting to simply "throw more cores" at exact algorithms and get a speed-up which scales accordingly. This allows practitioners who are not specialists to use the algorithms more efficiently. The MapReduce framework is one of the most widely used paradigms for parallel computation, and we show how to cast the exact deterministic algorithms for our customized spatial model in this framework. Higher-order Markov random fields, i.e., Markov random fields with higher-order interactions, have been shown to be able to represent large-scale properties of typical spatial scenes via MCMC simulation. We present a Markov random field parametrization such that the specification of clique configurations that include higher-order interactions is included in a methodical fashion. This ought to be useful for a practitioner with respect to specifying the type of images desired. The general Markov random field model commonly requires approximation techniques due to its intractable normalization constant, and inference and simulation techniques for models with high dependence via MCMC tend to be time-consuming and may involve algorithms with sensitive convergence criteria. These algorithms are not suitable for practitioners or spatial modellers who are not well-versed in MCMC, and it is therefore more desirable for them to work with models that are able to reproduce spatial structures, while still being easier to wield. We construct variants of the Markov random field that seek to achieve the same goal, but whose inference and simulation is tractable without MCMC, and cast the latter in the MapReduce framework. We also consider the MapReduce formulation of MCMC simulation algorithms for Markov random fields in order to leverage the power of parallel computing.Dans cette époque du "big data", les fichiers de données atteignent des tailles très importantes, et il y a un intérêt grandissant pour les algorithmes et les infrastructures de calcul adaptés à de telles quantités de données. Le nombre d'unités de calcul par puce électronique va lui aussi en grandissant. Au lieu de développer des méthodes ingénieuses pour accélérer la convergence et obtenir de meilleures approximations pour des classes de problèmes plus restreintes, il est intéressant de combiner l'utilisation d'algorithmes exacts avec une simple augmentation du nombre de coeurs ("cores") de microprocesseurs dédiés aux caluls et d'obtenir ainsi une accélération proportionelle. Ceci permet à des utilisateurs qui ne sont pas des spécialistes d'utiliser les algorithmes avec plus d'efficacité. Le "framework" MapReduce est un des paradigmes les plus utilisés pour le calcul parallèle. Nous montrons comment formuler les algorithmes de notre modèle spatial spécialisé dans cette infrastructure. On sait que les champs aléatoires de Markov avec des intéractions d'ordre élevé peuvent être utilisés pour représenter les propriétés à grande échelle de motifs spatiaux typiques par la simulation MCMC (Markov Chain Monte Carlo). Nous présentons une paramétrisation des champs aléatoires markoviens telle que la spécification des configurations de cliques qui comprennent des intéractions d'ordre supérieur à deux est prise en compte méthodiquement. Ceci sera utile à l'utilisateur qui voudra spécifier le type d'images qu'il désire produire. L'utilisation d'un champ aléatoire de Markov général requiert des approximations à cause de la constante de normalisation difficilement calculable en pratique, et les techniques d'inférence et de simulation pour les modèles avec dépendances d'ordre élevé par MCMC ont tendance à demander des temps de calculs prohibitifs, et sont parfois basées sur des algorithmes dont les critères de convergence sont sensibles aux données. Ces algorithmes ne sont pas adaptés aux besoins des utilisateurs et modélisateurs sans connaissances approfondies du MCMC. Il est donc préférable pour eux de travailler avec des modèles qui peuvent reproduire les structures spatiales, tout en étant plus faciles d'utilisation. Nous construisons des variantes du champ de Markov aléatoire avec les mêmes objectifs, mais pour lesquelles l'inférence et la simulation peuvent être accomplies sans recours au MCMC, et nous adaptons ces dernières au framework MapReduce. Nous nous intéressons également à la formulation dans MapReduce des algorithmes de simulation MCMC pour les champs aléatoires de Markov pour pouvoir faire usage de la puissance du calcul parallèle.
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Aplin, Paul. "Fine spatial resolution satellite sensor imagery for pre-field land cover classification." Thesis, University of Southampton, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297413.
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Berry, Sam. "Ultra-high spatial and temporal resolution using Scanning Near-field Optical Microscopy." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/348102/.
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Scanning near-field optical microscopy (SNOM) is a system that can image beyond the conventional diffraction limit. It does this by collecting the information contained within evanescent fields. This unique ability to image using evanescent fields also enables SNOM to directly measure the electric field distribution in waveguides, where light is guided by total internal reflection. When SNOM is used with a spectrally resolving detector, local temporal phenomena can be detected by analysing spectral interference in the spectra collected by the probe. This spectrally resolving configuration was used to directly measure inter-modal group velocity difference in a multimode ridge waveguide and, using the modes’ spatial profiles to experimentally determine the mode amplitude coefficient ratio. Such an ability to provide measurements on the local dispersion characteristics and relative modal amplitudes of guided light establishes SNOM as a route for investigating the conversion of current single mode photonic devices into multimode devices. The spectrally resolving SNOM system was also used to investigate the sources of temporal delays created by a quasi disordered scattering sample, which was based on John H. Conway’s pinwheel tiling. Whilst the measurements do not create a complete picture of the scattering phenomena in this work, suggestions for improvement are offered with the aim establishing spectrally resolving SNOM systems as tools for mapping localised temporal phenomena in disordered scattering systems.
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Suryan, Varun. "Learning a Spatial Field in Minimum Time with a Team of Robots." Thesis, Virginia Tech, 2018. http://hdl.handle.net/10919/93735.
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We study an informative path planning problem where the goal is to minimize the time required to learn a spatial field. Specifically, our goal is to ensure that the mean square error between the learned and actual fields is below a predefined value. We study three versions of the problem. In the placement version, the objective is to minimize the number of measurement locations. In the mobile robot version, we seek to minimize the total time required to visit and collect measurements from the measurement locations. A multi-robot version is studied as well where the objective is to minimize the time required by the last robot to return back to a common starting location called depot. By exploiting the properties of Gaussian Process regression, we present constant-factor approximation algorithms that ensure the required guarantees. In addition to the theoretical results, we also compare the empirical performance using a real-world dataset with other baseline strategies.M. S.
We solve the problem of measuring a physical phenomenon accurately using a team of robots in minimum time. Examples of such phenomena include the amount of nitrogen present in the soil within a farm and concentration of harmful chemicals in a water body etc. Knowing accurately the extent of such quantities is important for a variety of economic and environmental reasons. For example, knowing the content of various nutrients in the soil within a farm can help the farmers to improve the yield and reduce the application of fertilizers, the concentration of certain chemicals inside a water body may affect the marine life in various ways. In this thesis, we present several algorithms which can help robots to be deployed efficiently to quantify such phenomena accurately. Traditionally, robots had to be teleoperated. The algorithms proposed in this thesis enable robots to work more autonomously.
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Zacharias, Sebastian. "Modeling Spatial Variability of Field-Scale Solute Transport in the Vadose Zone." Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30775.
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Spatial heterogeneity in the soil system has a profound influence on the flow of water and chemicals in the unsaturated zone. Incorporating intrinsic soil variability and extrinsic variability into root zone leaching models will provide a better representation of pollutant distribution in natural field conditions.
In this study, a stochastic framework (SF) was developed to represent spatial variability of soil properties in one-dimensional solute transport models, and implemented with two existing root zone leaching models, Opus and GLEAMS. The accuracy of soil water, bromide and pesticide transport predictions from Opus-SF and GLEAMS-SF was evaluated using field-measured soil water content, bromide and pesticide mass data from a 3.9-ha agricultural field in the Dougherty Plain of Georgia and a 0.05-ha field plot in Nomini Creek watershed in Virginia. Results from the rate-based Opus-SF and capacity-based GLEAMS-SF were compared to determine if there were significant differences in their predictions.
In the stochastic approach, the heterogeneous field is conceptualized as a collection of vertical, non-interacting soil columns differing in soil properties. The horizontal variations of soil hydraulic and retention properties in each horizon are treated as random functions of zero transverse spatial correlation length, after accounting for any spatial trends. The spatially variable parameters were generated using the Latin hypercube sampling method, and the stochastic simulation of the model was performed using Monte-Carlo simulation techniques.
Statistical tests indicated that Opus-SF and GLEAMS-SF did not predict the central tendency and distribution of depth-averaged soil water content and total pesticide mass observed in the field on most sampling dates. But their predictions were sufficiently accurate for most management-type applications. Soil hydraulic and retention properties derived from texture data at the Nomini Creek site substantially reduced the variability in soil water content predictions from both models, but had less impact on bromide and pesticide mass predictions from both models.
The mean values predicted by Opus-SF and GLEAMS-SF were similar, but not equal to those predicted by the deterministic version of the models. Soil water and solute transport predictions from Opus-SF and GLEAMS-SF were not substantially different from corresponding results from the traditional Monte-Carlo approach, although soil water predictions from the two modeling approaches were significantly different for the first 150 days of simulation. Comparison between results from Opus-SF and GLEAMS-SF showed that the distributions and medians of soil water content predicted by the two models were significantly different on most sampling dates. The distributions and medians of pesticide mass predicted by the two models were closer than soil water content, but were significantly different on more than half of the field sampling dates.
The more functional GLEAMS-SF model was able to simulate depth-averaged soil water content in the root zone better than the more physically based Opus-SF, although GLEAMS-SF was not able to simulate the depth distribution of soil water as accurately as Opus-SF. GLEAMS-SF was also able to predict solute movement at least as well as Opus-SF. GLEAMS-SF was able to simulate spatial variations of depth-averaged soil water content and pesticide mass in the field with reasonable accuracy employing fewer parameters that exhibit relatively lesser spatial variability.Ph. D.
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Zhang, Xi. "SPATIAL ESTIMATION OF HYDRAULIC PROPERTIES IN STRUCTURED SOILS AT THE FIELD SCALE." UKnowledge, 2019. https://uknowledge.uky.edu/pss_etds/117.
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Improving agricultural water management is important for conserving water during dry seasons, using limited water resources in the most efficient way, and minimizing environmental risks (e.g., leaching, surface runoff). The understanding of water movement in different zones of agricultural production fields is crucial to developing an effective irrigation strategy. This work centered on optimizing field water management by characterizing the spatial patterns of soil hydraulic properties. Soil hydraulic conductivity was measured across different zones in a farmer’s field, and its spatial variability was investigated by using geostatistical techniques. Since direct measurement of hydraulic conductivity is time-consuming and arduous, pedo-transfer functions (PTFs) have been developed to estimate hydraulic conductivity indirectly through more easily measurable soil properties. Due to ignoring soil structural information and spatial covariance between soil variables, PTFs often perform unsatisfactorily when field-scale estimations of hydraulic conductivity are needed. The performance of PTFs in estimating hydraulic conductivity in the field was therefore critically evaluated. Due to the presence of structural macro-pores, saturated hydraulic conductivity (Ks) showed high spatial heterogeneity, and this variability was not captured by texture-dominated PTF estimates. However, the general spatial pattern of near-saturated hydraulic conductivity can still be reasonably generated by PTF estimates. Therefore, the hydraulic conductivity maps based on PTF estimates should be evaluated carefully and handled with caution. Recognizing the significant contribution of macro-pores to saturated water flow, PTFs were further improved by including soil macro-porosity and were proven to perform much better in estimating Ks compared with established PTFs tested in this study. Additionally, the spatial relationship between hydraulic conductivity and its potential influencing factors were further quantified by the state-space approach. State-space models outperformed current PTFs and effectively described the spatial characteristics of hydraulic conductivity in the studied field. These findings provided a basis for modeling water/solute transport in the vadose zone, and sitespecific water management.
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Ensini, Davide. "Spatial computing per smart devices." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amslaurea.unibo.it/7990/.
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Magic Carpet, nato come un middleware orientato a una dimostrazione sullo spatial computing, che inizialmente coinvolgeva solo smart devices ed un tappeto di tag NFC, è il punto di partenza per uno studio sulle tecnologie abilitanti in tale campo.
Il prodotto finale è una toolchain per lo sviluppo e la distribuzione, su dispositivi connessi, di applicazioni di spatial computing. Essa comprende un interprete per un DSL basato su un core calculus formalizzato, Field Calculus, e un middleware che supporta l'astrazione curando, a basso livello, le comunicazioni con il vicinato e le percezioni ambientali.
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Carbonell, Leal Miguel. "Complex spatial shaping of femtosecond pulses with phase-only spatial light modulators." Doctoral thesis, Universitat Jaume I, 2020. http://hdl.handle.net/10803/668541.
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This thesis is focused on spatial manipulation of laser beams with a single phase only SLM. To achieve it, it is essential to arbitrarily modify a complex field with this kind of devices. In addition, it is intended to introduce new methods to improve existing techniques. In that sense, the experimental implementation of a method known as double-phase is improved and optimized. With that goal in mind, the behavior of SLMs is studied in order to adapt, as far as possible, the experimental response of these devices. Finally, the optimized method is used in several applications to obtain real results comparable to other well-known optical methods.La posibilidad de definir, de forma arbitraria, parámetros como el patrón de irradiancia o la fase de un haz láser ha contribuido a adecuar las fuentes de luz a los requisitos concretos de cada usuario para sus distintas aplicaciones. Como resultado, el desarrollo de nuevas técnicas que permitan realizar este tipo de control se ha convertido en un tema esencial que beneficia a gran cantidad de aplicaciones. Los moduladores espaciales de luz (SLMs por sus siglas en inglés) son dispositivos que permiten control directo de estas propiedades. Generalmente, los SLMs son capaces de modular en tiempo real y de forma programable uno de estos parámetros (amplitud o fase). No obstante, para controlar los dos parámetros al mismo tiempo es necesario el empleo de varios dispositivos o el desarrollo de alguna técnica que permita realizar este control con un solo dispositivo.
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Hama, Rash Shwan. "Consequences of spatial variability in the field on the uniformity of barley seed." Thesis, University of Reading, 2018. http://centaur.reading.ac.uk/77709/.
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Spatial variation in seed and grain quality was investigated in uniformly-managed commercial winter barley crops in the south-east of England in order to assess scope for precision agriculture (PA) and management of seed crops. Within-field spatial variation in barley seed quality, yield and protein content was investigated at different spatial scales to determine scale-dependence of variation and relationships with environmental factors. Two fields were studied, one in 2013 and one in 2014, using unbalanced nested sampling designs with five spatial scales between 1 and 81 m and 138-150 sampling points per field. Spatially-correlated variation in seed moisture content, thousand grain weight (TGW) and protein content was moderate and the variograms of most variables increased with lag distance to a sill. Scale-dependent correlations of seed and grain quality with pedo-climaticbiotic variables were stronger over long (> 20 m) than over short (< 20 m) distances. Interestingly, some correlations changed from positive to negative or vice versa at different spatial scales implying scale-dependent processes. Although spatial variability in seedling vigour was unlikely to be of agronomic importance for PA in either field, it provides an example of different scale dependent processes. In one field, high seedling vigour was associated with high canopy temperature over an 81 m scale, but it was correlated with lower temperatures over a 3 m spatial scale. It is suggested that in general higher canopy temperatures promoted better seed development, more rapid drying and reduced seed dormancy accounting for the long distance correlation. At high temperatures, however, too high a temperature could become supra-optimal and detrimental to seed viability and vigour, and in locations with higher canopy temperatures, there could be a negative correlation over short distances. Spatial dependence was, however, low for seed germination, partly because germination percentage was high, averaging 95-97% across the fields and at least 90% at all sampling points. No PA interventions, therefore, needed to be considered for germination. Such variation in germination as did occur, was at a shorter spatial scale than the minimum sampled (i.e. <1m) and is probably accounted for by intrinsic variation in seed development between individual plants and tillers. By contrast, PA for seed quality could be envisaged in the two fields studied for seed moisture content (SMC), thousand grain weight (TGW) and grain protein content, which varied highly over longer distances (> 20 m). Management strategies of zones of high and low TGW is, however, unlikely to be of economic value; for protein it might be relevant for malting barley. For seed moisture content, zones >17% could be harvested separately either for dedicated drying of moister seeds or else postponing their harvest. An economic analysis suggests drying costs would be reduced through such a strategy, but un costed advantages are likely to include optimal use of drying facilities and avoiding heat damage to seeds which do not need drying. For such zones to be usable by farmers, they need to be predictable. Spatially-correlated variation in seed moisture occurred such that high seed moisture was associated with areas of higher soil moisture from anthesis to maturation. Higher soil moisture areas were associated with and might be predictable from soil texture, soil organic matter, soil EC and to some extent canopy variables, but further research is needed both to validate these recommendations in other fields and seasons and to assess factors likely to influence adoption of zone management at harvest.
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Anjasmara, Ira Mutiara. "Spatio-temporal analysis of GRACE gravity field variations using the principal component analysis." Thesis, Curtin University, 2008. http://hdl.handle.net/20.500.11937/957.
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Gravity Recovery and Climate Experiment (GRACE) mission has amplified the knowledge of both static and time-variable part of the Earth’s gravity field. Currently, GRACE maps the Earth’s gravity field with a near-global coverage and over a five year period, which makes it possible to apply statistical analysis techniques to the data. The objective of this study is to analyse the most dominant spatial and temporal variability of the Earth’s gravity field observed by GRACE using a combination of analytical and statistical methods such as Harmonic Analysis (HA) and Principal Component Analysis (PCA). The HA is used to gain general information of the variability whereas the PCA is used to find the most dominant spatial and temporal variability components without having to introduce any presetting. The latter is an important property that allows for the detection of anomalous or a-periodic behaviour that will be useful for the study of various geophysical processes such as the effect from earthquakes. The analyses are performed for the whole globe as well as for the regional areas of: Sumatra- Andaman, Australia, Africa, Antarctica, South America, Arctic, Greenland, South Asia, North America and Central Europe. On a global scale the most dominant temporal variation is an annual signal followed by a linear trend. Similar results mostly associated to changing land hydrology and/or snow cover are obtained for most regional areas except over the Arctic and Antarctic where the secular trend is the prevailing temporal variability.Apart from these well-known signals, this contribution also demonstrates that the PCA is able to reveal longer periodic and a-periodic signal. A prominent example for the latter is the gravity signal of the Sumatra-Andaman earthquake in late 2004. In an attempt to isolate these signals, linear trend and annual signal are removed from the original data and the PCA is once again applied to the reduced data. For a complete overview of these results the most dominant PCA modes for the global and regional gravity field solutions are presented and discussed.
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Illerstam, Fredrik. "Quality Assurance of the Spatial Accuracy of Large Field of View Magnetic Resonance Imaging." Thesis, KTH, Skolan för teknik och hälsa (STH), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-148815.
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In todays Radiotherapy Treatment Planning, RTP, it is common to use Computed Tomography, CT, together with Magnetic Resonance Imaging, MRI, where CT provides electron density information and a geometrical reference, and where MRI provides superior soft tissue contrast. To sim- plify the workflow and improve treatment accuracy, research groups have demonstrated how to exclude CT and use a MRI-only approach. In this thesis, a method for spatial distortion analysis, ultimately enabling quality assurance, QA, of the spatial accuracy of MRI, was defined, tested and evaluated. A phantom was built to cover the entire clinical Field Of View, FOV, and 6mm-diameter fluid filled paintball markers were placed in a well-defined geometrical pattern within the phantom, and used as positive contrast. The phantom was imaged with a 3D Fast Gradient Echo sequence and a 3D Fast Spin Echo sequence. The markers were identified in the image data by a MATLAB-algorithm, and the location of the center of mass was calculated for each marker and compared to a theoretical reference. The location error was defined as the spatial distortion - a measurement of the spatial accuracy. Imaging parameters were altered and the effect on the spatial accuracy was analyzed. The spatial distortions were successfully measured within the entire (maximal) clinical FOV. It was shown that high readout bandwidth reduced distortions in the frequency encoding direction. These distortions could thus be attributed to B0-inhomogeneities. It was also determined that increasing the readout bandwidth to the maximum value reduced the maximum distortions in the frequency encoding direction to the same level as the maximum distortions in the other two phase-encoding directions of the 3D acquisitions. The voxel size had a very small effect on the spatial accuracy, enabling large voxelsize to be used when imaging the phantom, to decrease the scan time. The method was deemed capable of serving as a basis for QA of the spatial accuracy of large FOV MRI, which is needed in future MRI-only RTP approaches.
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Miller, Kelsey, Olivier Guyon, and Jared Males. "Spatial linear dark field control: stabilizing deep contrast for exoplanet imaging using bright speckles." SPIE-SOC PHOTO-OPTICAL INSTRUMENTATION ENGINEERS, 2017. http://hdl.handle.net/10150/626442.
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Direct imaging of exoplanets requires establishing and maintaining a high-contrast dark field (DF) within the science image to a high degree of precision (10(-10)). Current approaches aimed at establishing the DF, such as electric field conjugation (EFC), have been demonstrated in the lab and have proven capable of high-contrast DF generation. The same approaches have been considered for the maintenance of the DF as well. However, these methods rely on phase diversity measurements, which require field modulation; this interrupts the DF and consequently competes with the science acquisition. We introduce and demonstrate spatial linear dark field control (LDFC) as an alternative technique by which the high-contrast DF can be maintained without modulation. Once the DF has been established by conventional EFC, spatial LDFC locks the high-contrast state of the DF by operating a closed loop around the linear response of the bright field (BF) to wavefront variations that modify both the BF and the DF. We describe the fundamental operating principles of spatial LDFC and provide numerical simulations of its operation as a DF stabilization technique that is capable of wavefront correction within the DF without interrupting science acquisition. (c) The Authors.
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Zive, Kevin. "Integration of visual and auditory spatial stimuli in the blind field of hemispherectomy patients." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0002/MQ44327.pdf.
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Zive, Kevin. "Integration of visual and auditory spatial stimuli in the blind field of hemispherectomy patients." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20615.
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The effect of multisensory integration in the blind field of hemispherectomy patients was investigated in order to examine the possible involvement of the superior colliculus in blindsight. The superior colliculus may be responsible for residual abilities in the blind field because of its predominant subsidiary visual connections with the retina. Ten normal subjects and four patients with a temporal lobe removal served as controls for four experimental subjects (two hemispherectomized and two partial hemispherectomized). The experiment tested three tasks that measured reaction time and localization accuracy: (1) visual target only; (2) auditory target only; (3) simultaneous auditory and visual (aud/vis) stimuli at the same location. Only reaction time was measured in the condition where simultaneous presentations of aud/vis stimuli were made at different locations. The existence of blindsight was substantiated for localization, but not for reaction time in the blind field of hemispherectomy patients. None of the subjects demonstrated multisensory integration for reaction time and localization accuracy. Our results indicate that multisensory integration did not take place, at least with the types of stimuli used here. A role of the superior colliculus in blindsight remains possible since the hemispherectomy subjects still showed unconscious residual visual abilities in their blind field.
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Cowan, Nicholas Jon. "Spatial variability of nitrous oxide flux measurements at the plot, field and farm scale." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10442.
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Nitrous oxide (N2O) is a potent greenhouse gas (GHG) which is released naturally into the atmosphere as a by-product of the microbial processes of nitrification and denitrification. Agricultural activities are believed to account for up to 80% of anthropogenic N2O emissions at a global scale; however, these estimates are prone to large uncertainties due to the large temporal and spatial variability associated with flux measurements. This thesis contains five studies which aimed to improve the ability to measure and predict N2O emissions from agricultural activities. A closed loop dynamic chamber was developed using a quantum cascade laser (QCL). This method provided high precision chamber measurements of N2O flux from soils with a detection limit below 4 μg N2O-N m-2 h-1. Using the dynamic chamber method allowed for a detailed investigation of uncertainties in individual measurements including contributions from regression fitting, temperature and pressure. The lack of negative fluxes measured that were outwith the detection limits of the methodology (0.3% of all measurements) highlighted that the uptake of N2O reported in some previous literature is likely to have been the result of detection limits of measurement methods applied. Spatial variability of N2O flux was investigated at the plot, field and farm scale. Fluxes were measured from a grassland field plot before and after a tillage event. These measurements highlighted the large spatially variability present in N2O fluxes from agricultural soils. Fluxes varied by up to three orders of magnitude over distances less than 5 metres after the tillage event. A field scale experiment carried out on grazed grassland investigated relationships between soil properties and N2O flux. This study found that N2O emissions correlated strongly with available nitrogen content in the soil and that animal waste was likely responsible for the spatial variability of N2O flux observed at the field scale. A farm scale inventory of N2O emissions was carried out investigating several large point sources of N2O and emissions from the wider field coverage. The inventory estimates that nitrogen fertiliser application is the single largest N2O source from the livestock farm accounting for 49% of annual emissions.
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Nijbroek, Ravic. "Understanding and simulating spatial soil water and yield variability in an irrigated soybean field." [Florida] : State University System of Florida, 1999. http://etd.fcla.edu/etd/uf/1999/amp7403/nijbroek.pdf.
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Thesis (M.E.)--University of Florida, 1999.Title from first page of PDF file. Document formatted into pages; contains xvi, 151 p.; also contains graphics. Vita. Includes bibliographical references (p. 148-150).
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Schlegel, Jennifer Lynn. "Imaging the spatial variation of dielectric constant in materials using microwave near field microscopy." Available to US Hopkins community, 2003. http://wwwlib.umi.com/dissertations/dlnow/3080759.
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Lavinsky, D. V. "Structural analysis of the technological systems under electromagnetic field action." Thesis, Center of educational literature, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/22372.
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Painter, Michael Scott. "Characterizing the Role of Magnetic Cues Underlying Spatial Behavior." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/74049.
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In the 50+ years since the discovery of magnetic compass orientation by migratory songbirds, evidence for the use of magnetic cues has been obtained for a range of taxonomic groups, including several classes of vertebrate and invertebrate taxa. Surprisingly, however, the biophysical mechanisms and biological substrate that underlie magnetic sensing are still not fully understood. Moreover, while use of magnetic cues for compass orientation is intuitive, the functional significance of other forms of behavioral responses mediated by magnetic cues, such as spontaneous magnetic alignment, is less clear. The following research was carried out to investigate the mechanisms underlying magnetic orientation in vertebrates and invertebrates. This involved the modification of existing experimental systems to characterize responses to magnetic cues in laboratory animals (flies, mice) and the development of novel techniques for studying the role of magnetic cues in the spatial behavior of free-living animals (red foxes). Chapter II examines magnetic orientation in wild-type Drosophila melanogaster larvae. We show that three strains of larvae reared under non-directional ultraviolet (UV) light exhibit quadramodal spontaneous orientation along the anti-cardinal compass directions (i.e. northeast, southeast, southwest, northwest) when tested in a radially symmetrical environment under UV light. Double-blind experiments cancelling the horizontal component of the magnetic field confirmed that the response is dependent on magnetic cues rather non-magnetic features of the test environment. Furthermore, we argue that the larval quadramodal pattern of response is consistent with properties of magnetic compass orientation observed in previous studies of adult Drosophila and laboratory mice, both of which have been proposed to be mediated by a light-dependent magnetic compass mechanism. Chapter III explores the use of novel biologging techniques to collect behavioral and spatial data from free-roaming mammals. Specifically, a previous observational study of free- roaming red foxes found a 4-fold increase in the success of predatory 'mousing' attacks when foxes were facing ~north-northeast, consistent with magnetic alignment responses reported for a range of terrestrial animals. The authors propose that the magnetic field may be used to increase accuracy of mousing attacks. Using tri-axial accelerometer and magnetometer bio-loggers fitted to semi-domesticated red foxes, we created ']magnetic ethograms' from behavioral and magnetic machine learning algorithms 'trained'] to identify three discrete behaviors (i.e. foraging, trotting, and mousing-like jumps) from raw accelerometer signatures and to classify the magnetic headings of mousing-like jumps into 45° sectors from raw magnetometer data. The classifier's ability to accurately identify behaviors from a separate fox not used to train the algorithm suggests that these techniques can be used in future experiments to obtain reliable magnetic ethograms for free-roaming foxes. We also developed the first radio-frequency emitting collar that broadcasts in the low MHz frequency range shown to disrupt magnetic compass responses in a host of animals. The radio-frequency collars coupled with biologgers will provide a powerful tool to characterize magnetic alignment responses in predatory red foxes and can be adapted for use in studies of magnetic alignment and magnetic compass orientation in other free-roaming mammals. Chapter 3 discusses findings from a magnetic nest building assay involving male labratory mice. Mice trained to position nests in one of four directions relative to the magnetic field exhibited both learned magnetic compass responses and fixed magnetic nest positioning orientation consistent with northeast-southwest spontaneous magnetic alignment behavior previously reported for wild mice and bank voles. This is the first mammalian assay in which both learned magnetic compass orientation and spontaneous magnetic alignment were exhibited in the same species, and suggests that the use of magnetic cues in rodents may be more flexible that previously realized.Ph. D.
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Baptista, Rita Gomes. "The relationship between field-determined putative territorial strategies and spatial and non-spatial learning in males of Carbonell's wall lizard, Podarcis Carbonelli berlengensis." Master's thesis, Instituto Superior de Psicologia Aplicada, 2007. http://hdl.handle.net/10400.12/340.
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Dissertação de Mestrado em EtologiaA maioria dos animais poderá demonstrar uma aprendizagem espacial quando procuram refúgio, parceiros, forrageiam ou mesmo quando fogem de predadores. No seu ambiente natural, os répteis demonstram que conseguem aprender e recordar tarefas espaciais. Foi sugerido que o contexto social poderá funcionar como uma vantagem selectiva para mecanismos espaciais cognitivos e desta forma seria de esperar que uma variação intrasexual pudesse influenciar uma cognição espacial. Num contexto espacial, os animais poderão usar uma estratégia espacial, na qual relacionam diversas pistas com o objectivo, ou possuírem uma flexibilidade comportamental para responder a diversas alterações do ambiente de forma a alcançar o objectivo. Esta flexibilidade comportamental é bastante importante, pois os animais que possuem uma flexibilidade elevada poderão alternar a sua resposta comportamental mesmo quando as pistas, o objectivo ou ambos, se alteram de uma forma inesperada. Neste trabalho estudei a variação intrasexual dos machos da lagartixa de Carbonell num teste de estratégia espacial (aprendizagem espacial) e num teste de flexibilidade comportamental (aprendizagem não-espacial). No campo, apesar de não ter testado completamente o comportamento territorial, observei durante algum tempo, o uso de espaço por cada macho e considerei um macho putativamente territorial quando ocupava uma área de ± 4 m2 e um macho putativamente não-territorial quando ocupava uma área superior. Neste estudo, refiro-me aos putativamente territoriais como machos territoriais e aos putativamente não-territoriais como machos não-territoriais. Se a variação intrasexual afecta uma cognição espacial, seria de esperar que os machos territoriais possuíssem um melhor desempenho que os machos não-territoriais. Se, na verdade, as lagartixas machos se orientam através do uso de uma flexibilidade comportamental, então seria de esperar que os machos não territoriais tivessem melhor desempenho na experiência de aprendizagem não-espacial. Tanto a experiência de aprendizagem espacial como a de aprendizagem não-espacial foram feitas numa arena circular com tampo metálico coberto por areia. Por baixo desse tampo, existiam 4 lâmpadas. No entanto, somente uma das lâmpadas era acesa por sessão o que gerava um quadrante aquecido que denominei de quadrante objectivo. Na experiência de estratégia espacial utilizei três pistas pretas: quadrado, circulo e triângulo. O círculo situava-se sempre no quadrante aquecido. Esta experiência teve uma duração de 16 dias em que, a partir do 7 dia, o círculo foi degradado a 50% (foi removido uma determinada quantidade do preto do círculo mantendo sempre a mesma forma); no décimo dia o círculo foi degradado a 75% e ao décimo terceiro dia o círculo foi removido. Para testar uma aprendizagem espacial, baseada nas pistas visuais, realizei um dia de teste em que a pista triangular e a pista quadrangular foram trocadas. Na experiência de estratégia não-espacial usei duas pistas pretas em que uma assinalava o reforço positivo (quadrante aquecido) e outra assinalava um reforço negativo (quadrante não-aquecido). A experiência teve uma duração de oito dias em que nos últimos quatro dias as pistas foram trocadas (a pista que assinalava anteriormente o reforço positivo passou a assinalar o reforço negativo). As observações foram analisadas com os programas Measuring in Motion, R, SPSS e JMP. Usei ANOVA factorial de medidas repetidas para analisar os efeitos de grupo, dia e territorialidade e pista, e também para comparar o último dia de treino e o primeiro dia de teste. Só apresentei as médias dos ângulos que apresentavam uma tendência direccional. Na experiência de estratégia espacial os machos não apresentaram um padrão de movimento aleatório na arena e mostraram aprendizagem, pois a latência diminuiu ao longo dos dias. Neste trabalho cronometrei a latência desde os primeiros movimentos dos quadris da lagartixa até parar pelo menos durante 30 segundos para termorregular. Não observei nenhuma alteração entre o último dia de treino e o teste. Os machos territoriais apresentaram aparentemente um desempenho melhor, no entanto só observei uma diferença estatística entre os machos territoriais e não-territoriais nas frequências de uso de quadrantes e desvio padrão da latência na experiência de aprendizagem espacial. Quando analisei os ângulos isoladamente, os dados mostraram que as lagartixas não se orientavam para o quadrante aquecido. Na experiência de estratégia não-espacial não observei uma alteração da latência ao longo dos dias. No entanto os machos mostraram uma preferência pelo uso da quadrante aquecido. Tanto na experiência de aprendizagem espacial como na de aprendizagem não-espacial, os machos de lagartixas de Carbonell não demonstraram uma aprendizagem baseada nas pistas visuais. No entanto, os machos não utilizaram uma estratégia aleatória e demonstraram aprendizagem espacial, Deste modo sugiro que as lagartixas usam um modelo de deslocação, pois reduziram ao longo dos dias o comprimento do seu trajecto até ao quadrante aquecido. Neste trabalho as lagartixas poderão não ter associado cada uma das pista à localização do quadrante aquecido devido à posição das mesmas, por variarem em cada sessão e porque o gradiente de temperatura poderá desviar a atenção às pistas. Estes resultados diferem dos que foram obtidos com tartarugas e cobras, mas não diferem dos de outras lagartixas. Este facto poderá ser devido a diferenças fisiológicas e fílogenéticas entre os animais e diferenças metodológicas entre os estudos. Neste estudo não observei a flexibilidade comportamental, pois os machos não conseguiram utilizar a informação potencialmente dada por cada pista e assim não perceberam quando as pistas foram invertidas. O facto de outros estudos, com répteis, terem observado uma flexibilidade comportamental poderá ser explicado devido às diferenças acima mencionadas. Os machos territoriais apresentaram um melhor desempenho geral em ambas as experiências. No entanto só observei uma diferença estatística nas frequências e no desvio padrão da latência, na experiência de estratégia-espacial. Não observei diferença estatística de latência e frequências entre os machos territoriais e não-territoriais. O facto da comparação entre os machos territoriais e não-territoriais ser confusa poderá ser devido a estes animais terem estado isolados um mês antes da experiências o que poderá ter confundido as características que influenciam as estratégias espaciais de cada grupo. Um modo de evitar a perda de algumas destas características em cativeiro seria o implantar as lagartixas com hormonas, já que as hormonas têm um efeito na capacidade cognitiva espacial e também no tamanho da área vital. Em conclusão, seria interessante testar em mais espécies de lagartixas o modelo de deslocação e averiguar especificamente se as lagartixas possuem ou não uma aprendizagem tigmotáctica. Neste trabalho a aprendizagem tigmotáctica foi dificultada devido ao quadrante aquecido variar aleatoriamente em cada sessão. Seria também interessante testar se as hormonas influenciam ou não o desempenho em tarefas de aprendizagem espacial e não-espacial de lagartixas, Palavras-chave: Lagartixa de Carbonell, estratégias putativas territoriais, aprendizagem espacial e aprendizagem não-espacial.