Дисертації: "Spatial multiplier"

1

Acar, Alper. "Optimal Urban Planning and Housing Prices : a Spatial Analysis." Electronic Thesis or Diss., Bourgogne Franche-Comté, 2024. http://www.theses.fr/2024UBFCG008.

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La thèse étudie l'impact de l'aménagement urbain optimal surla diffusion des prix des logements dans un marché immobilier local. À travers une analyse du champ de la localisation optimale et de l'économétrie spatiale, cette étude vise à considérer comment les propriétés des graphes et les modèles de localisation optimale peuvent contribuer à mieux comprendre et à évaluer les impacts des effets de multiplicateur spatial dans l'économie. Pour ce faire, la recherche s'appuie sur une méthodologie combinant la création d'outils d'aide à la décision et l'étude des prix immobiliers par un modèle économétrique spatiale hiérarchique. Les résultats démontrent que la prise en compte des relations spatiales optimales permet une étude plus précise des impacts de l'aménagement urbain sur la diffusion des prix. A contrario, la considération de relations spatiales “classiques" sur ou sous-estime les impacts
This dissertation studies the effect of optimal urban planning on housing prices diffusion in local real-estate markets. The study uses facility location theory and spatial econometrics to investigate how graph properties and optimal location models can contribute to a better understanding and evaluation of the impact of spatial multiplier effects in the economy. To this end, the research is based on a methodology that combines the creation of decision-support tools and the study of real estate prices using hierarchical spatial econometric models. The results states that using optimal spatial relationships enables a more precise analysis of the impacts of urban planning on the diffusion of prices. Conversely, the consideration of “classical” spatial relationships either underestimates or overestimates the spatial impacts

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2

Hory, Marie-Pierre. "Essais sur la politique budgétaire : Multiplicateurs et interactions budgétaires." Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE0506/document.

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Cette thèse étudie les déterminants de l’efficacité de la politique budgétaire, et en analyse les modalités de mise en oeuvre. Le premier chapitre compare la valeur du multiplicateur budgétaire dans les économies émergentes (EMEs)et dans les avancées (AEs). Le multiplicateur est plus faible dans les EMEs que dans les AEs, et si les déterminants du multiplicateur y sont similaires, leur impact et leur hiérarchisation y sont différents. Dans les EMEs, l’amélioration de l’efficacité de la politique budgétaire semble devoir passer par des changements structurels relatifs aux institutions.D’après le chapitre 2, le multiplicateur décroit avec la part de la dette des firmes libellée en monnaie étrangère qui se trouve être particulièrement élevée dans les EMEs. Des mesures limitant les prêts en monnaie étrangère et favorisant le développement du système financier local devraient permettre de recouvrer l’efficacité de la politique budgétaire. Le troisième chapitre montre que les gouvernements européens interagissent entre eux pour fixer leurs politiques budgétaires: ils s’imitent avec un an de délai. Ces interactions sont dues à de la concurrence par comparaison. L’objectif électoral des politiques budgétaires peut en réduire l’efficacité. Aussi, davantage d’institutions seraient nécessaires pour garantir une certaine coordination budgétaire en Europe. Les interactions décalées dans le temps témoignent d’un phénomène de leader-suiveur en Europe, et le chapitre 4 montre que l’Allemagne occupe la place de leader. L’Allemagne pourrait donc amorcer une certaine coordination budgétaire en Europe
This thesis analyzes the determinants of fiscal policy efficiency and the way fiscal policy is implemented. The first chapter compares the fiscal multiplier in emerging market economies (EMEs) with the one in advanced economies(AEs): the fiscal multiplier is smaller in EMEs than in AEs. While the determinants of fiscal multipliers are similar in both groups, their weights differ across groups. To improve fiscal policy efficiency EMEs seem to need structural policies to better their institutional quality. Chapter 2 empirically and theoretically shows that the fiscal multiplier decreases with the share of firms’ indebtedness that is denominated in foreign currency. EMEs have large debt denominated in foreign currency. Fostering the use of local currency to finance activity, for example via quotas on foreign loans, shall allow EMEs to improve the efficiency of their fiscal policies. Chapter 3 shows that European governments mimic each other in the implementation of fiscal policy with one year delay. These interactions are due to yardstick competition.The electoral objectives of governments may reduce fiscal policy efficiency and the incentive of governments to fiscally cooperate. If we believe in fiscal cooperation as a force to enhance fiscal policy efficiency, more institutions should be set up to foster cooperation in Europe. Moreover, the delayed interactions found are consistent with a leader-follower process, and Chapter 4 shows that Germany is the leader: European countries follow Germany in the implementation of fiscal policy. Hence, the push for fiscal cooperation could come from Germany

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3

Raboun, Oussama. "Multiple Criteria Spatial Risk Rating." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLED066.

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La thèse est motivée par une étude de cas intéressante liée à l’évaluation du risque nucléaire. Le cas d’étude consiste à évaluer l’impact d’un accident nucléaire survenu dans le milieu marin. Ce problème comporte des caractéristiques spatiales, différents enjeux économiques et environnementaux, des connaissances incomplètes sur les potentiels acteurs et un nombre élevé de scénarios d’accident possibles. Le cas d’étude a été résolu en utilisant différentes techniques d’analyse décisionnelle telles que la comparaison des loteries et les outils MCDA (Multiple Criteria Decision Analysis).Une nouvelle méthode de classification ordinale, nommée Dynamic-R, est née de cette thèse, visant à fournir une notation complète et convaincante. La méthode développée a fourni des résultats intéressants au cas d’étude et des propriétés théoriques très intéressantes qui sont présenté dans les chapitres 6 et 7 de ce manuscrit
The thesis is motivated by an interesting case study related to environmental risk assessment. The case study problem consists on assessing the impact of a nuclear accident taking place in the marine environment. This problem is characterized by spatial characteristics, different assets characterizing the spatial area, incomplete knowledge about the possible stakeholders, and a high number of possible accident scenarios. A first solution of the case study problem was proposed where different decision analysis techniques were used such as lotteries comparison, and MCDA (Multiple Criteria Decision Analysis) tools. A new MCDA rating method, named Dynamic-R, was born from this thesis, aiming at providing a complete and convincing rating. The developed method provided interesting results to the case study, and very interesting theoretical properties that will be presented in chapters 6 and 7 of this manuscript

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4

Younis, Abdelhamid. "Spatial modulation : theory to practice." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8990.

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Spatial modulation (SM) is a transmission technique proposed for multiple–input multiple– output (MIMO) systems, where only one transmit antenna is active at a time, offering an increase in the spectral efficiency equal to the base–two logarithm of the number of transmit antennas. The activation of only one antenna at each time instance enhances the average bit error ratio (ABER) as inter–channel interference (ICI) is avoided, and reduces hardware complexity, algorithmic complexity and power consumption. Thus, SM is an ideal candidate for large scale MIMO (tens and hundreds of antennas). The analytical ABER performance of SM is studied and different frameworks are proposed in other works. However, these frameworks have various limitations. Therefore, a closed–form analytical bound for the ABER performance of SM over correlated and uncorrelated, Rayleigh, Rician and Nakagami–m channels is proposed in this work. Furthermore, in spite of the low–complexity implementation of SM, there is still potential for further reductions, by limiting the number of possible combinations by exploiting the sphere decoder (SD) principle. However, existing SD algorithms do not consider the basic and fundamental principle of SM, that at any given time, only one antenna is active. Therefore, two modified SD algorithms tailored to SM are proposed. It is shown that the proposed sphere decoder algorithms offer an optimal performance, with a significant reduction of the computational complexity. Finally, the logarithmic increase in spectral efficiency offered by SM and the requirement that the number of antennas must be a power of two would require a large number of antennas. To overcome this limitation, two new MIMO modulation systems generalised spatial modulation (GNSM) and variable generalised spatial modulation (VGSM) are proposed, where the same symbol is transmitted simultaneously from more than one transmit antenna at a time. Transmitting the same data symbol from more than one antenna reduces the number of transmit antennas needed and retains the key advantages of SM. In initial development simple channel models can be used, however, as the system develops it should be tested on more realistic channels, which include the interactions between the environment and antennas. Therefore, a full analysis of the ABER performance of SM over urban channel measurements is carried out. The results using the urban measured channels confirm the theoretical work done in the field of SM. Finally, for the first time, the performance of SM is tested in a practical testbed, whereby the SM principle is validated.

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5

Ramalingam, Chitra. "Modeling Multiple Granularities of Spatial Objects." Fogler Library, University of Maine, 2002. http://www.library.umaine.edu/theses/pdf/RamalingamC2002.pdf.

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6

Tamè, Luigi. "Multiple Spatial Representations for Haptic Perception." Doctoral thesis, Università degli studi di Trento, 2010. https://hdl.handle.net/11572/368662.

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In everyday life, our body gets in contact with multiple tactile stimuli from the outside world. How our somatosensory system identifies and localises these multiple stimuli entering in contact with our body surface, is the general framework to which the researches of the present thesis belong. Tactile stimuli on our body can be spatially coded and represented by using multiple reference frames. Touch is initially encoded into a sensory-space within primary somatosensory map and then further stages of processing can represent the location of tactile event with respect to the overall body structure (body-space) or to the outside world (external-space). In the present thesis we report first a series of behavioural experiments aimed at investigating which spatial reference frame is adopted in a special context of sensory stimulation, namely the double simultaneous stimulation (DSS). Then, we used functional magnetic resonance (fMRI) as a tool for delineating the neural bases of the cognitive processes sub-serving the elaboration and representation of concurrent stimuli for conscious tactile perception. In a first behavioural study using the tactile DSS paradigm, we defined the spatial coding used by observers when tactile stimuli are delivered with different fingers combinations (i.e., within vs. between hands) and hand postures (i.e., hands palm-down vs. palm-up). In a second behavioural work we tested the influence of different visual modulations (e.g., seeing body parts or objects) and visual-proprioceptive conflict (e.g., seeing body parts in a different position with respect to one adopted by the participant) on the spatial representation of touch. Furthermore, we investigated the effect of changes to the visual structural morphology of a body part on the spatial representation of touch. Finally, using a fMRI adaptation paradigm for touches at the fingers, we aimed to define the neural bases of tactile perception in a repeated stimulations context. In particular, we assessed the mutual interaction between tactile stimuli located at body parts that are clearly distinct in terms of the body-space (e.g., left and right index fingers), but proximal in terms of neural representations (due to some bilateral responses of the somatosensory cortices).

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7

Tamè, Luigi. "Multiple Spatial Representations for Haptic Perception." Doctoral thesis, University of Trento, 2010. http://eprints-phd.biblio.unitn.it/168/1/Luigi_Tam%C3%A8_PhD_Thesis.pdf.

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In everyday life, our body gets in contact with multiple tactile stimuli from the outside world. How our somatosensory system identifies and localises these multiple stimuli entering in contact with our body surface, is the general framework to which the researches of the present thesis belong. Tactile stimuli on our body can be spatially coded and represented by using multiple reference frames. Touch is initially encoded into a sensory-space within primary somatosensory map and then further stages of processing can represent the location of tactile event with respect to the overall body structure (body-space) or to the outside world (external-space). In the present thesis we report first a series of behavioural experiments aimed at investigating which spatial reference frame is adopted in a special context of sensory stimulation, namely the double simultaneous stimulation (DSS). Then, we used functional magnetic resonance (fMRI) as a tool for delineating the neural bases of the cognitive processes sub-serving the elaboration and representation of concurrent stimuli for conscious tactile perception. In a first behavioural study using the tactile DSS paradigm, we defined the spatial coding used by observers when tactile stimuli are delivered with different fingers combinations (i.e., within vs. between hands) and hand postures (i.e., hands palm-down vs. palm-up). In a second behavioural work we tested the influence of different visual modulations (e.g., seeing body parts or objects) and visual-proprioceptive conflict (e.g., seeing body parts in a different position with respect to one adopted by the participant) on the spatial representation of touch. Furthermore, we investigated the effect of changes to the visual structural morphology of a body part on the spatial representation of touch. Finally, using a fMRI adaptation paradigm for touches at the fingers, we aimed to define the neural bases of tactile perception in a repeated stimulations context. In particular, we assessed the mutual interaction between tactile stimuli located at body parts that are clearly distinct in terms of the body-space (e.g., left and right index fingers), but proximal in terms of neural representations (due to some bilateral responses of the somatosensory cortices).

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8

Pokhrel, Prafulla. "TOWARDS IMPROVED IDENTIFICATION OF SPATIALLY-DISTRIBUTED RAINFALL RUNOFF MODELS." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194356.

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Distributed rainfall runoff hydrologic models can be highly effective in improving flood forecasting capabilities at ungauged, interior locations of the watershed. However, their implementation in operational decision-making is hindered by the high dimensionality of the state-parameter space and by lack of methods/understanding on how to properly exploit and incorporate available spatio-temporal information about the system. This dissertation is composed of a sequence of five studies, whose overall goal is to improve understanding on problems relating to parameter identifiability in distributed models and to develop methodologies for their calibration.The first study proposes and investigates an approach for calibrating catchment scale distributed rainfall-runoff models using conventionally available data. The process, called regularization, uses spatial information about soils and land-use that is embedded in prior parameter estimates (Koren et al. 2000) and knowledge of watershed characteristics, to constrain and reduce the dimensionality of the feasible parameter space.The methodology is further extended in the second and third studies to improve extraction of `hydrologically relevant' information from the observed streamflow hydrograph. Hydrological relevance is provided by using signature measures (Yilmaz et al 2008) that correspond to major watershed functions. While the second study applies a manual selection procedure to constrain parameter sets from the subset of post calibrated solutions, the third develops an automatic procedure based on a penalty function optimization approach.The fourth paper investigates the relative impact of using the commonly used multiplier approach to distributed model calibration, in comparison with other spatial regularization strategies and also includes investigations on whether calibration to data at the catchment outlet can provide improved performance at interior locations. The model calibration study conducted for three mid sized catchments in the US led to the important finding that basin outlet hydrographs might not generally contain information regarding spatial variability of the parameters, and that calibration of the overall mean of the spatially distributed parameter fields may be sufficient for flow forecasting at the outlet. This then was the motivation for the fifth paper which investigates to what degree the spatial characteristics of parameter and rainfall fields can be observable in catchment outlet hydrographs.

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9

Francisco-Revilla, Luis. "Multi-model adaptive spatial hypertext." Texas A&M University, 2004. http://hdl.handle.net/1969.1/1444.

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Information delivery on the Web often relies on general purpose Web pages that require the reader to adapt to them. This limitation is addressed by approaches such as spatial hypermedia and adaptive hypermedia. Spatial hypermedia augments the representation power of hypermedia and adaptive hypermedia explores the automatic modification of the presentation according to user needs. This dissertation merges these two approaches, combining the augmented expressiveness of spatial hypermedia with the flexibility of adaptive hypermedia. This dissertation presents the Multi-model Adaptive Spatial Hypermedia framework (MASH). This framework provides the theoretical grounding for the augmentation of spatial hypermedia with dynamic and adaptive functionality and, based on their functionality, classifies systems as generative, interactive, dynamic or adaptive spatial hypermedia. Regarding adaptive hypermedia, MASH proposes the use of multiple independent models that guide the adaptation of the presentation in response to multiple relevant factors. The framework is composed of four parts: a general system architecture, a definition of the fundamental concepts in spatial hypermedia, an ontological classification of the adaptation strategies, and the philosophy of conflict management that addresses the issue of multiple independent models providing contradicting adaptation suggestions. From a practical perspective, this dissertation produced WARP, the first MASH-based system. WARPs novel features include spatial transclusion links as an alternative to navigational linking, behaviors supporting dynamic spatial hypermedia, and personal annotations to spatial hypermedia. WARP validates the feasibility of the multi-model adaptive spatial hypermedia and allows the exploration of other approaches such as Web-based spatial hypermedia, distributed spatial hypermedia, and interoperability issues between spatial hypermedia systems. In order to validate the approach, a user study comparing non-adaptive to adaptive spatial hypertext was conducted. The study included novice and advanced users and produced qualitative and quantitative results. Qualitative results revealed the emergence of reading behaviors intrinsic to spatial hypermedia. Users moved and modified the objects in order to compare and group objects and to keep track of what had been read. Quantitative results confirmed the benefits of adaptation and indicated a possible synergy between adaptation and expertise. In addition, the study created the largest spatial hypertext to date in terms of textual content.

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10

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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11

Morrison, Wendy Elizabeth. "Aquatic plant-herbivore interactions across multiple spatial scales." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34734.

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For decades scientists believed that herbivory had minimal impact on freshwater ecosystems. We now know that herbivory in freshwater systems equals or exceeds herbivory in terrestrial and marine systems. In extreme cases, herbivores can change clear, macrophyte dominated ecosystems into turbid plankton dominated ecosystems. Even though research on plant-herbivore interactions in freshwater systems has increased, there is still much that is unknown. This thesis is comprised of four studies investigating freshwater plant-herbivore interactions across multiple spatial scales. The first study investigated how induced chemical defenses in Cabomba caroliniana suppress herbivore consumption and growth as well as how this herbivore-generated change in plant chemistry affects the growth of plant associated microbes. At the spatial scale of individual ponds or lakes, consumers that induce their host plants may also be indirectly affecting other consumers and microbial pathogens via changes in this shared resource. The second study moves to an ecosystem scale and investigates how exotic versus native apple snails may impact Everglades' habitats. We investigated plant preference, consumption, growth and conversion efficiencies in the singly native apple snail to occur in the U.S. (Pomacea paludosa) versus four introduced species (P. canaliculata, P. insularum, P. haustrum and P. diffusa). We found that even though plant preferences are similar, invasive snails tend to eat more, grow more rapidly, and sometimes more efficiently than natives. This suggests that invasive species could have a large impact on the environment, especially the abundance of submerged plants. The third study investigated how palatability of freshwater plants varies with latitude (i.e. geographic scale). Increased herbivory at lower latitudes is hypothesized to select for increased plant defenses, which has been shown to be true for tropical forests, salt marshes, and seaweeds. When we contrasted eight confamilial plants collected in Indiana versus Southern Florida, three of four herbivores significantly preferred northern plants. When we evaluated a second set of plants collected from Indiana versus Central Florida, only one of three herbivores preferred the northern plants. Overall, our results suggest a preference for northern plants, but the strength of this relationship was variable. We hypothesize that this variability may be driven by 1) local variance in herbivore pressure that creates variance in plant defenses, and/or 2) the effect of winter length on the survival and feeding rate of herbivores. The final study expanded to a world scale, and investigated herbivore preference for native vs exotic plants. We found that both N. American crayfish and S. American snails preferred exotic plants over confamilial natives, despite responding to different plant characteristics. The single species of apple snail that occurs in N. American showed no preference for native or exotic plants from a N. American perspective, but instead exhibited preferences that correlated with its history of evolution in S. America. As the N. American species is a sister species of the S. American snails, feeding by the N. American snail appears more affected by its S. American lineage than its recent history in N. America. This suggests that phylogenetic legacy will affect choices of the herbivore as well as resistance or susceptibility of plants.

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12

Bogdanski, Bryan E. C. "Economics of multiple-use forest management : spatial considerations." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0015/NQ56508.pdf.

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13

Ventrucci, Massimo <1980&gt. "Multiple testing in spatial epidemiology: a Bayesian approach." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1564/1/tesi_Massimo_Ventrucci.pdf.

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In this work we aim to propose a new approach for preliminary epidemiological studies on Standardized Mortality Ratios (SMR) collected in many spatial regions. A preliminary study on SMRs aims to formulate hypotheses to be investigated via individual epidemiological studies that avoid bias carried on by aggregated analyses. Starting from collecting disease counts and calculating expected disease counts by means of reference population disease rates, in each area an SMR is derived as the MLE under the Poisson assumption on each observation. Such estimators have high standard errors in small areas, i.e. where the expected count is low either because of the low population underlying the area or the rarity of the disease under study. Disease mapping models and other techniques for screening disease rates among the map aiming to detect anomalies and possible high-risk areas have been proposed in literature according to the classic and the Bayesian paradigm. Our proposal is approaching this issue by a decision-oriented method, which focus on multiple testing control, without however leaving the preliminary study perspective that an analysis on SMR indicators is asked to. We implement the control of the FDR, a quantity largely used to address multiple comparisons problems in the eld of microarray data analysis but which is not usually employed in disease mapping. Controlling the FDR means providing an estimate of the FDR for a set of rejected null hypotheses. The small areas issue arises diculties in applying traditional methods for FDR estimation, that are usually based only on the p-values knowledge (Benjamini and Hochberg, 1995; Storey, 2003). Tests evaluated by a traditional p-value provide weak power in small areas, where the expected number of disease cases is small. Moreover tests cannot be assumed as independent when spatial correlation between SMRs is expected, neither they are identical distributed when population underlying the map is heterogeneous. The Bayesian paradigm oers a way to overcome the inappropriateness of p-values based methods. Another peculiarity of the present work is to propose a hierarchical full Bayesian model for FDR estimation in testing many null hypothesis of absence of risk.We will use concepts of Bayesian models for disease mapping, referring in particular to the Besag York and Mollié model (1991) often used in practice for its exible prior assumption on the risks distribution across regions. The borrowing of strength between prior and likelihood typical of a hierarchical Bayesian model takes the advantage of evaluating a singular test (i.e. a test in a singular area) by means of all observations in the map under study, rather than just by means of the singular observation. This allows to improve the power test in small areas and addressing more appropriately the spatial correlation issue that suggests that relative risks are closer in spatially contiguous regions. The proposed model aims to estimate the FDR by means of the MCMC estimated posterior probabilities b i's of the null hypothesis (absence of risk) for each area. An estimate of the expected FDR conditional on data (\FDR) can be calculated in any set of b i's relative to areas declared at high-risk (where thenull hypothesis is rejected) by averaging the b i's themselves. The\FDR can be used to provide an easy decision rule for selecting high-risk areas, i.e. selecting as many as possible areas such that the\FDR is non-lower than a prexed value; we call them\FDR based decision (or selection) rules. The sensitivity and specicity of such rule depend on the accuracy of the FDR estimate, the over-estimation of FDR causing a loss of power and the under-estimation of FDR producing a loss of specicity. Moreover, our model has the interesting feature of still being able to provide an estimate of relative risk values as in the Besag York and Mollié model (1991). A simulation study to evaluate the model performance in FDR estimation accuracy, sensitivity and specificity of the decision rule, and goodness of estimation of relative risks, was set up. We chose a real map from which we generated several spatial scenarios whose counts of disease vary according to the spatial correlation degree, the size areas, the number of areas where the null hypothesis is true and the risk level in the latter areas. In summarizing simulation results we will always consider the FDR estimation in sets constituted by all b i's selected lower than a threshold t. We will show graphs of the\FDR and the true FDR (known by simulation) plotted against a threshold t to assess the FDR estimation. Varying the threshold we can learn which FDR values can be accurately estimated by the practitioner willing to apply the model (by the closeness between\FDR and true FDR). By plotting the calculated sensitivity and specicity (both known by simulation) vs the\FDR we can check the sensitivity and specicity of the corresponding\FDR based decision rules. For investigating the over-smoothing level of relative risk estimates we will compare box-plots of such estimates in high-risk areas (known by simulation), obtained by both our model and the classic Besag York Mollié model. All the summary tools are worked out for all simulated scenarios (in total 54 scenarios). Results show that FDR is well estimated (in the worst case we get an overestimation, hence a conservative FDR control) in small areas, low risk levels and spatially correlated risks scenarios, that are our primary aims. In such scenarios we have good estimates of the FDR for all values less or equal than 0.10. The sensitivity of\FDR based decision rules is generally low but specicity is high. In such scenario the use of\FDR = 0:05 or\FDR = 0:10 based selection rule can be suggested. In cases where the number of true alternative hypotheses (number of true high-risk areas) is small, also FDR = 0:15 values are well estimated, and \FDR = 0:15 based decision rules gains power maintaining an high specicity. On the other hand, in non-small areas and non-small risk level scenarios the FDR is under-estimated unless for very small values of it (much lower than 0.05); this resulting in a loss of specicity of a\FDR = 0:05 based decision rule. In such scenario\FDR = 0:05 or, even worse,\FDR = 0:1 based decision rules cannot be suggested because the true FDR is actually much higher. As regards the relative risk estimation, our model achieves almost the same results of the classic Besag York Molliè model. For this reason, our model is interesting for its ability to perform both the estimation of relative risk values and the FDR control, except for non-small areas and large risk level scenarios. A case of study is nally presented to show how the method can be used in epidemiology.

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14

Ventrucci, Massimo <1980&gt. "Multiple testing in spatial epidemiology: a Bayesian approach." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/1564/.

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Анотація:

In this work we aim to propose a new approach for preliminary epidemiological studies on Standardized Mortality Ratios (SMR) collected in many spatial regions. A preliminary study on SMRs aims to formulate hypotheses to be investigated via individual epidemiological studies that avoid bias carried on by aggregated analyses. Starting from collecting disease counts and calculating expected disease counts by means of reference population disease rates, in each area an SMR is derived as the MLE under the Poisson assumption on each observation. Such estimators have high standard errors in small areas, i.e. where the expected count is low either because of the low population underlying the area or the rarity of the disease under study. Disease mapping models and other techniques for screening disease rates among the map aiming to detect anomalies and possible high-risk areas have been proposed in literature according to the classic and the Bayesian paradigm. Our proposal is approaching this issue by a decision-oriented method, which focus on multiple testing control, without however leaving the preliminary study perspective that an analysis on SMR indicators is asked to. We implement the control of the FDR, a quantity largely used to address multiple comparisons problems in the eld of microarray data analysis but which is not usually employed in disease mapping. Controlling the FDR means providing an estimate of the FDR for a set of rejected null hypotheses. The small areas issue arises diculties in applying traditional methods for FDR estimation, that are usually based only on the p-values knowledge (Benjamini and Hochberg, 1995; Storey, 2003). Tests evaluated by a traditional p-value provide weak power in small areas, where the expected number of disease cases is small. Moreover tests cannot be assumed as independent when spatial correlation between SMRs is expected, neither they are identical distributed when population underlying the map is heterogeneous. The Bayesian paradigm oers a way to overcome the inappropriateness of p-values based methods. Another peculiarity of the present work is to propose a hierarchical full Bayesian model for FDR estimation in testing many null hypothesis of absence of risk.We will use concepts of Bayesian models for disease mapping, referring in particular to the Besag York and Mollié model (1991) often used in practice for its exible prior assumption on the risks distribution across regions. The borrowing of strength between prior and likelihood typical of a hierarchical Bayesian model takes the advantage of evaluating a singular test (i.e. a test in a singular area) by means of all observations in the map under study, rather than just by means of the singular observation. This allows to improve the power test in small areas and addressing more appropriately the spatial correlation issue that suggests that relative risks are closer in spatially contiguous regions. The proposed model aims to estimate the FDR by means of the MCMC estimated posterior probabilities b i's of the null hypothesis (absence of risk) for each area. An estimate of the expected FDR conditional on data (\FDR) can be calculated in any set of b i's relative to areas declared at high-risk (where thenull hypothesis is rejected) by averaging the b i's themselves. The\FDR can be used to provide an easy decision rule for selecting high-risk areas, i.e. selecting as many as possible areas such that the\FDR is non-lower than a prexed value; we call them\FDR based decision (or selection) rules. The sensitivity and specicity of such rule depend on the accuracy of the FDR estimate, the over-estimation of FDR causing a loss of power and the under-estimation of FDR producing a loss of specicity. Moreover, our model has the interesting feature of still being able to provide an estimate of relative risk values as in the Besag York and Mollié model (1991). A simulation study to evaluate the model performance in FDR estimation accuracy, sensitivity and specificity of the decision rule, and goodness of estimation of relative risks, was set up. We chose a real map from which we generated several spatial scenarios whose counts of disease vary according to the spatial correlation degree, the size areas, the number of areas where the null hypothesis is true and the risk level in the latter areas. In summarizing simulation results we will always consider the FDR estimation in sets constituted by all b i's selected lower than a threshold t. We will show graphs of the\FDR and the true FDR (known by simulation) plotted against a threshold t to assess the FDR estimation. Varying the threshold we can learn which FDR values can be accurately estimated by the practitioner willing to apply the model (by the closeness between\FDR and true FDR). By plotting the calculated sensitivity and specicity (both known by simulation) vs the\FDR we can check the sensitivity and specicity of the corresponding\FDR based decision rules. For investigating the over-smoothing level of relative risk estimates we will compare box-plots of such estimates in high-risk areas (known by simulation), obtained by both our model and the classic Besag York Mollié model. All the summary tools are worked out for all simulated scenarios (in total 54 scenarios). Results show that FDR is well estimated (in the worst case we get an overestimation, hence a conservative FDR control) in small areas, low risk levels and spatially correlated risks scenarios, that are our primary aims. In such scenarios we have good estimates of the FDR for all values less or equal than 0.10. The sensitivity of\FDR based decision rules is generally low but specicity is high. In such scenario the use of\FDR = 0:05 or\FDR = 0:10 based selection rule can be suggested. In cases where the number of true alternative hypotheses (number of true high-risk areas) is small, also FDR = 0:15 values are well estimated, and \FDR = 0:15 based decision rules gains power maintaining an high specicity. On the other hand, in non-small areas and non-small risk level scenarios the FDR is under-estimated unless for very small values of it (much lower than 0.05); this resulting in a loss of specicity of a\FDR = 0:05 based decision rule. In such scenario\FDR = 0:05 or, even worse,\FDR = 0:1 based decision rules cannot be suggested because the true FDR is actually much higher. As regards the relative risk estimation, our model achieves almost the same results of the classic Besag York Molliè model. For this reason, our model is interesting for its ability to perform both the estimation of relative risk values and the FDR control, except for non-small areas and large risk level scenarios. A case of study is nally presented to show how the method can be used in epidemiology.

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15

Stavridis, Athanasios. "On the energy efficiency of spatial modulation concepts." Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/15951.

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Spatial Modulation (SM) is a Multiple-Input Multiple-Output (MIMO) transmission technique which realizes low complexity implementations in wireless communication systems. Due the transmission principle of SM, only one Radio Frequency (RF) chain is required in the transmitter. Therefore, the complexity of the transmitter is lower compared to the complexity of traditional MIMO schemes, such as Spatial MultipleXing (SMX). In addition, because of the single RF chain configuration of SM, only one Power Amplifier (PA) is required in the transmitter. Hence, SM has the potential to exhibit significant Energy Efficiency (EE) benefits. At the receiver side, due to the SM transmission mechanism, detection is conducted using a low complexity (single stream) Maximum Likelihood (ML) detector. However, despite the use of a single stream detector, SM achieves a multiplexing gain. A point-to-point closed-loop variant of SM is receive space modulation. In receive space modulation, the concept of SMis extended at the receiver side, using linear precoding with Channel State Information at the Transmitter (CSIT). Even though receive space modulation does not preserve the single RF chain configuration of SM, due to the deployed linear precoding, it can be efficiently incorporated in a Space Division Multiple Access (SDMA) or in a Virtual Multiple-Input Multiple-Output (VMIMO) architecture. Inspired by the potentials of SM, the objectives of this thesis are the evaluation of the EE of SM and its extension in different forms of MIMO communication. In particular, a realistic power model for the power consumption of a Base Station (BS) is deployed in order to assess the EE of SM in terms of Mbps/J. By taking into account the whole power supply of a BS and considering a Time Division Multiple Access (TDMA) multiple access scheme, it is shown that SM is significantly more energy efficient compared to the traditional MIMO techniques. In the considered system setup, it is shown that SM is up to 67% more energy efficient compared to the benchmark systems. In addition, the concept of space modulation is researched at the receiver side. Specifically, based on the union bound technique, a framework for the evaluation of the Average Bit Error Probability (ABEP), diversity order, and coding gain of receive space modulation is developed. Because receive space modulation deploys linear precoding with CSIT, two new precoding methods which utilize imperfect CSIT are proposed. Furthermore, in this thesis, receive space modulation is incorporated in the broadcast channel. The derivation of the theoretical ABEP, diversity order, and coding gain of the new broadcast scheme is provided. It is concluded that receive space modulation is able to outperform the corresponding traditional MIMO scheme. Finally, SM, receive space modulation, and relaying are combined in order to form a novel virtual MIMO architecture. It is shown that the new architecture practically eliminates or reduces the problem of the inefficient relaying of the uncoordinated virtual MIMO space modulation architectures. This is undertaken by using precoding in a novel fashion. The evaluation of the new architecture is conducted using simulation and theoretical results.

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16

Fukuzono, Hayato. "Spatial Signal Processing on Distributed MIMO Systems." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/217206.

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17

Fletcher, David. "Biological invasion risk assessment, considering adaptation at multiple scales : the case of topmouth gudgeon Pseudorasbora parva." Thesis, Montpellier, 2018. http://www.theses.fr/2018MONTG029/document.

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Afin de quantifier les risques d’invasion chez le goujon Asiatique Pseudorasbora parva, un petit cyprinidae d’eau douce, j’ai tout d’abord testé une approche corrélative de modélisation de la niche climatique dans laquelle j’ai intégré un proxy relatif à la probabilité d’introduction. Cette approche s’appuie sur des assomptions relatives à l’adaptation des organismes aux conditions environnementales locales ou régionales. J’ai ensuite comparé la niche climatique mesurée de deux lignées génétiques majeures à la fois dans les aires natives et envahies. Puis dans un second temps, par une approche expérimentale j’ai comparé la réponse aux variations de température, des traits d’histoire de vie de populations vivant dans des zones climatiques contrastées. Finalement, je me suis intéressé à la dispersion des goujons Asiatiques afin de mieux comprendre si les populations situées sur les fronts d’invasions avaient des capacités de colonisation plus importante. J’ai donc quantifié et comparé le long d’un gradient d’invasion, le potentiel de dispersion des individus ainsi que des traits pouvant y être liés (activité et morphologie). L’étude des risques d’invasions a montré que de nombreuses zones – au delà des zones déjà envahies - étaient climatiquement favorables au goujon Asiatique. C’était le cas en particulier pour certaines zones comme l’Australie, l’Amérique du Sud et du Nord, indiquant que l’invasion de cette espèce pourrait encore s’étendre. Après avoir pris en compte les probabilités d’introduction, cette étude a montré que l’Amérique du Nord était la zone la plus à risques. Par contre, la niche climatique entre les différentes lignées dans les zones géographiques envahies est très similaire, ce qui laisse à penser qu’il n’y a pas de patrons d’adaptation locale chez cette espèce. Pour autant, la niche climatique observée dans la zone envahie est très différente de celle observée dans la zone native, ce qui suggère un shift climatique important au cours de l’invasion. Les réponses thermiques des traits d’histoire de vie du goujon Asiatique testés expérimentalement n’ont pas varié significativement entre les populations originaires de conditions climatiques continentales et maritime-tempérées. Par exemple, l’effort reproductif global des femelles n’a pas varié entre les températures testées (15-25°C) mais la stratégie temporelle de reproduction a beaucoup varié. L’effort reproductif était plus cours et plus intense à forte température, alors qu’il était plus étalé et avec des pics reproductifs moins forts à faible température. Pour ailleurs, il semble qu’il existe un gradient morphologique fort entre les populations situées à différentes distances du front d’invasion ce qui suggère une forte plasticité morphologique mais qui ne serait pas liée à la capacité de dispersion de ces populations. En effet, cette dernière ne variant pas significativement le long du gradient d’invasion. La capacité de dispersion serait principalement liée à la taille du corps de goujon Asiatique, les individus les plus grands ayant une probabilité plus élevée de disperser.Bien que les prédictions générales du modèle de niche puissent être affectées par de potentielles adaptations à l’échelle de la population ou de la lignée évolutive, les résultats suggèrent qu’une certaine incertitude liée à ces prédictions persiste puisque la distribution native ne prédisait que très mal la distribution actuelle dans les zones envahies. Par ailleurs, mes travaux expérimentaux à plus fine échelle suggèrent que cette espèce est extrêmement adaptable et tolère une large gamme environnementale, ce qui pourrait expliquer son caractère invasif. Les connaissances produites au cours de cette thèse constituent donc des ressources extrêmement pertinentes pour développer des stratégies de gestion visant à contrôler les invasions futures du goujon Asiatique
In this thesis I set out to quantify the risk of invasion from the invasive freshwater fish, Pseudorasbora parva, at a global extent, using traditional correlative ecological niche modelling approaches with the integration of surrogate data representing introduction likelihood (Chapter I). These correlative approaches rely upon key assumptions relating to the presence or absence of local or regional adaptations, and so I subsequently tested for evidence of such adaptations in genetic lineages and in individual populations. This was achieved through analyzing climatic niche differentiation of key genetic lineages in the native and invasive ranges (Chapter II) and by conducting lab experiments comparing thermal responses of important life history traits in populations from contrasting climates (Chapter III). The initial risk assessment did not account for a key factor in invasions; namely, natural dispersal. Natural dispersal has been observed to be subject to selection in vanguard populations of invasive species, and adaptation of dispersal traits can infer additional invasive vigor, allowing the species to spread across the landscape quicker. For this reason, I quantified dispersal, activity and morphological differences, often associated with differential dispersal ability, in populations along a distance-gradient from an invasion front, in order to identify if P. parva is capable of such adaptations.The initial risk mapping study showed that large areas, beyond the current distribution of the species, are climatically suitable. These areas are mainly in North and South America, Australia and New Zealand, and constitute significant scope for spread and impact of this species. When introduction likelihood was included, N. America appears most at risk. I found no evidence to suggest that native genetic lineages represented local adaptations to their respective native climates - there was little or no differentiation of the lineages’ climatic niches in the invasive range. It was also apparent, from the niche comparisons, that the climatic niche in the invaded range constituted a significant shift, compared to the native range. The thermal responses of P. parva life history traits did not differ significantly between populations from a strongly seasonal continental climate and a mild temperate maritime climate. The overall reproductive output of females did not vary according to breeding season temperature, however, temporal reproductive strategy showed a strong response, with lower temperatures inducing a protracted breeding season and higher temperatures inducing rapid and intense reproductive output. The dispersal and morphology-related study identified a strong gradient of morphological change, corresponding with distance from invasion front. This demonstrates a high degree of plasticity in P. parva’s morphology in an invasion context, however this was not linked to either dispersal or activity levels, neither of which was significantly linked to distance from invasion front. Dispersal was best explained by body size, with larger fish more likely to disperse further.Whilst I found no evidence to suggest that the model predictions (Chapter I) were hampered by differentiation at either lineage or population levels, the findings of Chapter II do highlight the uncertainties surrounding the degree of conservatism in such predictions, mainly owing to the fact that past, native, distribution did not accurately predict the current invaded distribution. The results of Chapters II-IV show broad tolerances and great plasticity in P. parva, which likely underpin this species success as a pan-continental invader. The knowledge produced in this thesis provides a useful new resource for the development of management strategies for P. parva and could be usefully enhanced by the additional of analogous studies on native populations, which could help elucidate the source of the observed plasticity

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18

Anderson, Casey C. "GIS spatial analysis of multiple scenes in criminal homicides." [Tampa, Fla] : University of South Florida, 2009. http://purl.fcla.edu/usf/dc/et/SFE0002967.

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19

Mokh, Ali. "Receive and Transmit Spatial Modulation Techniques for Low Complexity Devices." Thesis, Rennes, INSA, 2018. http://www.theses.fr/2018ISAR0020.

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L'Internet des objets est l'un des concepts clefs stimulant l'évolution des réseaux mobiles dans le but de leur donner de nouvelles fonctionnalités de communication et de gestion d'objets dits connectés. Comparativement aux terminaux mobiles standards, les usages associés à ces objets connectés sont en général caractérisés par des débits modestes et de faibles ressources en capacité de calcul et en énergie. Les techniques de modulation spatiale (SM) sont proposées comme une solution prometteuse pour assurer les débits des objets connectés tout en maîtrisant le critère de la consommation énergétique. L'objectif de cette thèse est d'étudier les performances de différents schémas de transmission basés sur le concept SM mis en oeuvre en transmission ou en réception. Nous avons notamment proposé un système global de communication en liaisons montante (SM en transmission) et descendante (SM en réception) entre une station de base et un objet, dans lequel l'essentiel de la complexité de calcul est concentré à la station de base. Par ce système, une liaison avec un objet peut être établie en limitant les traitements au sein de l'objet à di simples fonctions d'activation/désactivation d'antenne et de détection à seuil. Par ailleurs, nous avons proposé des schémas SM étendus grâce auxquels l'efficacité spectrale atteignable devient égale au nombre d'antennes au sein de l'objet. Les expressions analytiques de la probabilité d'erreur binaire ont été développées pour l'ensemble des systèmes étudiés en utilisant différentes méthodes de détection. L'impact de la connaissance imparfaite de l'état des canaux de propagation ainsi que l'effet des corrélations entre antennes ont également été incorporés dans l'étude des performances des schémas SM de réception. Dans une dernière partie, nous avons proposé d'adapter les schémas SM de réception dans un environnement de propagation en ondes millimétriques en utilisant une formation de faisceau hybride analogique/numérique au niveau de l'émetteur
Internet of Things is one of the keyword that represents the evolution in 5G that is able to connect the so-called Connected Devices (CD) to the network. These CDs are expected to require modest data rates and will be characterized by low resources in terms of both computation and energy consumption compared to other mobile multi-media devices. Spatial Modulation (SM) is proposed to be a promising solution to boost the data rate of the CD with a small ( or no) increase in energy consumption. Inspired by the advantages of SM, the objective of this thesis is to study the performance of different transmission scheme based on the SM concept at the transmitter and at tht receiver, for respectively an uplink and a downlink transmission between a BS and a CD. We proposed a global system where the higher computational complexity remains at the BS: The transmit SM is used for uplink, and the receive SM for downlink. It is shown that with SM, an ONOFF keying for uplink and Single Tap detector for downlink could be sufficient for the transmission a the CD. Also, with Extended SM schemes, we increased the spectral efficiency of SM to be equal t< the number of antennas of CD in both uplink and downlink transmission. A framework for the derivation of the Bit Error Probability (BEP) is developed for all schemes with different detection methods. Impact of imperfect CSIT transmission has been studied when linear precoding is implemented for the receive spatial modulation, as well as the effect of antenna correlations. Finally we proposed to adapte the spatial modulation at the receiver with the mmWave environment, using hybrid beamformina at the transmitter

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20

Ben, Abbes Mohamed Aymen. "La sélection attentionnelle et le traitement multiples dans la Mémoire Visuelle à Court-Terme." Thesis, Aix-Marseille, 2012. http://www.theses.fr/2012AIXM3014.

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Ce travail est divisé en deux parties : la première partie concerne l'évaluation de la sélection attentionnelle dans une tâche de Mémoire visuelle à Court-Terme. Nous avons testé, dans cette partie, la capacité des participants à sélectionner et mémoriser des cibles parmi des distracteurs. Nos résultats ont mis en évidence la capacité à mémoriser quatre objets sélectionnés parmi un ensemble de distracteurs sans l'intervention de mécanismes physiologiques tels que les saccades oculaires. En outre, nous avons montré que cette capacité est sensible à l'organisation spatiale des cibles parmi les distracteurs. A travers plusieurs expériences manipulant l'organisation spatiale des objets, le niveau d'exigence de la tâche, la différence entre l'objet test et celui présenté préalablement à la même localisation, nous avons mis en évidence l'impact de l'organisation spatiale des objets d'une part sur l'allocation attentionnelle sur les localisations et d'autre part sur le traitement des cibles apparaissant dans ces localisations. La proximité spatiale des objets serait un facteur facilitateur lors de l'allocation attentionnelle mais elle rendrait le traitement plus difficile. Dans la deuxième partie, nous avons combiné la méthode de prévisualisation des distracteurs avec le paradigme de report partiel pour examiner l'effet du nombre des localisations servant d'indices sur la capacité d'allocation attentionnelle et l'effet du nombre des cibles indicées sur la capacité de traitement
The aim of this thesis is twofold : the first dealt with the assessment of the attentional selection in a Visual Short Term-Memory task. We tested the capacity of the participants in selecting and memorizing targets among distractors. Our results provided evidence for the capacity to memorize four selected objects among a set of distractors without the involvement of physiological mechanisms like eye-movements. Furthermore, we showed that this capacity is sensitive to the spatial organization of targets among distractors. In further experiments, we manipulated the spatial organization of objects, the requirement of the task, the difference between the test object and the object previously presented at the same location. The results highlighted the impact of the spatial organization of objects on the attentional allocation over locations and the processing of targets appearing at these locations. The spatial proximity of objects greatly facilitated the attentional allocation but made the processing more difficult. The second aim dealt with the combination of the preview of distractors method with the partial report paradigm to examining i) the effect of the number of locations serving as cues on the attentional allocation capacity and ii) the effect of the number of objects on the processing capacity. We showed that the division of attention over several objects is limited by the difficulties associated with attentional allocation beyond two selected locations and the difficulties associated with processing beyond two encoded objects

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21

Dayton, Gage Hart. "Community assembly of xeric-adapted anurans at multiple spatial scales." Texas A&M University, 2005. http://hdl.handle.net/1969.1/3296.

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The distribution and abundance of organisms is influenced by historical, abiotic, and biotic factors. The goal of my dissertation was to determine the distribution of anurans in the Big Bend region of the Chihuahuan Desert and to examine how abiotic and biotic factors shape the composition and structure of anuran communities at multiple spatial scales. My approach relied on extensive field surveys, laboratory and field experiments, and GIS modeling. Results from field surveys and reciprocal transplant studies of tadpoles indicate that abiotic conditions of the breeding site most likely do not play a significant role in causing the segregation of species among individual breeding pools. I used laboratory and mesocosm experiments to test for indirect and direct effects of predators on growth and survival of S. couchii tadpoles. I found that S. couchii tadpoles do not alter their behavior in the presence of predators and are very susceptible to predation. Although tadpoles reared with predators suffered high mortality rates, they metamorphosed significantly faster than tadpoles reared without predators. The reduced time to metamorphose is likely a result of the thinning of intraspecific competitors. Because the primary cause of death for S. couchii tadpoles is desiccation due to pond drying, predators may play an important role in facilitating metamorphosis by decreasing competitors and thus increasing per capita resources, therefore decreasing time to metamorphosis for the surviving tadpoles. At the landscape level anuran distributions seem to be influenced by environmental factors that influence the survival of the adult stage. At the level of the breeding site, microhabitat and abiotic components of the aquatic environment do not seem to play an important role in influencing breeding site use by different species. Rather, it seems likely that predation on tadpoles by predators is important in limiting the distribution of some species and that the fast-developing S. couchii may exclude other species from using sites via oophagy and predation on small tadpoles. My research elucidates the fact that in order to understand factors important in regulating ecological communities it is important to examine both abiotic and biotic factors at multiple spatial scales.

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22

Werner, Jeffery Ross. "Habitat specificity among ground squirrel populations at multiple spatial scales." Thesis, University of British Columbia, 2016. http://hdl.handle.net/2429/60189.

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The arctic ground squirrel (Urocitellus parryii; AGS) comprised 17% of the herbivore biomass in the Yukon boreal forest during the summer months from 1987 to 1996 and accounted for 23% of the energy flow at the herbivore level. By 2000 these ground squirrel populations had collapsed to nearly zero and today they comprise ~1% of the herbivore biomass in this zone. Most forest populations (~95%) are extirpated, whereas only 65% of low-elevation meadow populations are extirpated. AGS remain abundant in alpine (93% occupancy) and in human altered habitats (97% occupancy). During spring, postpartum females in forests weighed less and were in poorer condition than females in meadows. However, by onset of hibernation, forest squirrels had reached parity with meadow squirrels in mass and condition. For squirrels in formerly occupied boreal forests a) poor spring body condition likely decreased reproductive success, and b) achieving compensatory growth, via increased foraging, may result in higher predation risk. These costs likely contributed to the recent local extinctions of AGS in boreal forest habitat. Population densities of AGS and snowshoe hares were estimated over a 25-year period encompassing two snowshoe hare cycles. A hyperbolic curve best describes the per capita rate of increase of ground squirrels relative to their population size, with a single stable equilibrium and a lower critical threshold below which populations drift to extinction. The crossing of this unstable boundary resulted in the subsequent uncoupling of ground squirrel and hare abundance following their mutual declines in 1998. Sustained top-down control of AGS, via a Type II predator response, probably led to their local extinction. Fine scale habitat features of 138 AGS colonies were measured over a 25,000 km² region of the southern Yukon, 2013-2015. Logistic regression models were constructed to determine which food, soil, and visibility characteristics best explain colony persistence. Habitat characteristics associated with food, predation risk, and overwinter survival jointly influence the distribution of colony extinctions over large spatial scales. Evidence for multi-factor control of the distribution of this important northern herbivore at the southern portion of its range indicate that numerical responses to environmental change will not be uniform.
Science, Faculty of
Zoology, Department of
Graduate

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23

Au, Carmen E. "Integrating multiple views to improve scene understanding and spatial awareness." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104479.

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The way humans visualize and interact with visual data affects how that data is processed. The current most prevalent paradigm for displaying visual content is a two dimensional display that suffers from a number of shortcomings. One shortcoming is that the display is a flat 2D display. As such, displaying collections of images that have been acquired from widely differing viewpoints becomes a challenge. With the pervasiveness of cameras, there is an abundance of these collections of images. These images are mostly stored and displayed as disparate images, and the information that they share and how the images relate is lost. Another shortcoming of the current display paradigm is that the display can only act as a peephole into a much larger visual space, thereby filtering out a lot of the visual information. This particular shortcoming is especially pronounced with displays on mobile devices, which are relatively small in size. On mobile device displays, even 2D visual spaces, such as maps, a lot of information is filtered out, since only a small portion of the 2D space can be seen at any given time. Each of these small portions becomes like an individual view of the map, and in exploring the visual space, the views of the space change; information of how these views relate is therefore lost. In this thesis, we examine the ways in which we can relate seemingly disparate views in order to improve scene understanding and spatial awareness.We present two approaches to relating views: a passive and an active approach. In the passive approach, users do not interact with the display; rather, we integrate images such that images from widely differing viewpoints can be displayed in a natural way that maintains their spatial relationships. Our approach is called Virtual Mirroring because we place virtual mirrors on the scene and overlay images onto them. For example, if we had a picture of both the front and the back of a person, we can assume that a virtual mirror is behind the person, and overlay onto it the image of the back of the person. In so doing, we can see both the front view and the back view, by way of a virtual mirror. Subsequently, we present a psychophysical experiment that we performed, which validates our belief that by presenting users with integrated images of a scene rather than non-integrated images, the users are better able to understand that scene. Our active approach involves users interacting with the display. We tie user motor actions to display changes, such that the display scrolls in the direction that the mobile device has been tilted. We then perform a psychophysical experiment to investigate whether such a coupling between user motor actions and display changes can result in better learning of the visual space. Our findings support such an active approach to the learning of visual information. Finally, we present an application for our work. One activity, in which better spatial understanding is crucial, is navigation. We create a system, MirrorMap, that incorporates the Virtual Mirroring technique to provide users of the system with alternate views of the environment they are navigating. For examples, video feeds from traffic cameras with better views of an intersection, can be overlaid onto virtual mirrors and then displayed to the user in a manner that preserves the spatial relationship between the camera and the user's locations.
La façon dont les humains visualisent et interagissent avec les données visuelles affecte la manière dont elles sont traitées. Le paradigme le plus courant présentement utilisé pour représenter du contenu visuel est un affichage en deux dimensions qui possède de nombreux désavantages. L'un de ces désavantages est que l'affichage est plat et en 2D. Ainsi, l'affichage de collections d'images acquises de points de vue grandement différents devient un défi. Avec l'omniprésence des appareils photos, il y a abondance de ces collections d'images. Ces images sont surtout emmagasinées et affichées en images disparates, et l'information qu'elles partagent et les rapports entre les images sont perdus. Un autre désavantage du paradigme d'affichage courant est que l'affichage peut seulement agir comme une petite ouverture vers un espace visuel beaucoup plus grand, ce qui a pour effet de filtrer beaucoup d'information visuelle. Ce désavantage est particulièrement prononcé sur des appareils portatifs, qui sont relativement de petite taille. Sur des appareils portatifs, même des espaces visuels en 2D comme des cartes filtrent beaucoup d'information, puisqu'une petite partie seulement peut être vue à tout moment. Chacune de ces petites parties devient comme une vue individuelle de la carte. Dans l'exploration de l'espace visuel, les vues de l'espace changent ce qui fait en sorte que la façon dont ces vues se rapportent l'une à l'autre est perdu. Dans cette thèse, nous examinons comment nous pouvons rapporter l'une à l'autre des vues disparates pour améliorer la compréhension de la scène et la sensibilisation à l'espace.Nous présentons deux approches pour rapporter les images : l'une passive et l'autre active. Dans l'approche passive, les utilisateurs n'interagissent pas avec l'affichage; nous intégrons plutôt des images de façon à ce que les images de points de vue grandement différents puissent être affichées d'une manière naturelle qui maintient leurs points communs dans l'espace. Notre approche se nomme Réflexion Virtuelle parce que nous plaçons des miroirs virtuels sur la scène et transposons des images sur eux. Par exemple, si nous avions une photographie du devant et du dos d'une personne, nous pouvons penser qu'un miroir virtuel est derrière la personne et y superposer l'image du dos de la personne. De cette façon, nous pouvons voir la vue de face et celle de dos, avec l'aide d'un miroir virtuel. Ensuite, nous présentons une expérience psychologique que nous avons effectuée qui valide notre hypothèse que la présentation d'images intégrées d'une scène aux utilisateurs -plutôt que des images non intégrées- facilite la compréhension de la scène. Notre approche active implique que les utilisateurs interagissent avec l'affichage. Nous lions les actions motrices de l'utilisateur pour démontrer les changements de façon à ce que l'affichage défile dans la direction où l'appareil portatif a été incliné. Nous effectuons ensuite une expérience psychologique pour vérifier si la combinaison des actions motrices avec le changement d'affichage peut amener à un meilleur apprentissage de l'information visuelle. Finalement, nous présentons une application pour notre travail. Une activité pour laquelle une meilleure compréhension de l'espace est cruciale est la navigation. Nous créons un système, MirrorMap, qui incorpore la technique de Réflexion Virtuelle pour fournir aux utilisateurs du système des points de vue alternatifs de l'environnement qu'ils naviguent. Par exemple, des vidéos de caméras de trafic routier avec de meilleures vues de l'intersection peuvent être superposées sur des miroirs virtuels et ensuite exposés à l'utilisateur de façon à préserver la relation spatiale entre la caméra et la location de l'utilisateur.

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24

Bradter, Ute. "The distribution of upland breeding waders at multiple spatial scales." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550525.

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Species distribution models are a valuable tool in conservation and research. This thesis addressed three common constraints of such models: the lack of detailed vegetation data for large areas. the inclusion of variables at arbitrary spatial scales which can lead to wrong conclusions as processes are scale dependent. 3) the potentially large number of variables and associated problems in variable selection when models include the landscape context. A novel technique combining a multiple scale species distribution model with image interpretation classified 24 detailed vegetation communities and an additional class for trees and bushes of the Yorkshire Dales at a high resolution (5 m) with overall high accuracies (87 - 92%). A novel selection procedure was developed capable of selecting important variables at appropriate spatial scales from a large number of variables. Models were presented on the example of curlew (Numenius arquata) and lapwing (Vanellus vanellus) in the Yorkshire Dales. Predictive ability of most resulting • models was moderate to high (AUC = 0.84 - 0.97). Lapwing presence was positively associated with gentle slopes and negatively with soil of low fertility at a large scale (10 km) while locally (250 - 500 m) lapwing preferred soil with impeded drainage and acid grassland. Curlew presence was negatively associated with westerly facing slope and curlew density positively with south facing slope (above a threshold of 14%) at large scales (9 - 10 km). Curlew presence was negatively associated with freely draining soil and settlements and positively with bogs at small scales (250 - 750 m). Near paths, density of curlew was higher if less of the path was in view at a small scale (250 m). Hatching success of curlew was strongly negatively related with settlements within 1 km. At nests, curlew preferred vegetation of intermediate height (ea. 40 cm).

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25

Feinstein, Larry M. "Microbial Functional Activity and Diversity Patterns at Multiple Spatial Scales." Kent State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=kent1341967745.

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26

Whitman, Elizabeth Rose. "Factors Affecting Green Turtle Foraging Ecology Across Multiple Spatial Scales." FIU Digital Commons, 2018. https://digitalcommons.fiu.edu/etd/3870.

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The hierarchical levels at which resource selection occurs can have important consequences for individual and population energy budgets and structure the impacts of a forager on its ecosystem. Assessing factors affecting resource selection of large marine herbivores across scales is important because of their potentially large impacts on seagrass community dynamics and historical and current changes in their population sizes and those of their potential predators. I explored the factors (predation risk, resource abundance, quality and identity) affecting resource use of large marine herbivores (green turtles, Chelonia mydas) from the scale of habitat patches to forage species within patches. I used a combination of in-water surveys, aerial drone video transects, baited camera surveys, and seagrass community and nutrient content analyses to provide insights into resource use by turtles in multiple ecological contexts. In Abaco, The Bahamas I found relatively intact shark populations, including apex predators, relative to other parts of the Caribbean. In the context of healthy predator populations in Abaco, I tested a priori predictions rooted in Ideal Free Distribution (IFD) theory. Green turtles off Abaco deviated from predictions of an IFD determined by the standing stocks of seagrass. Instead, distributions are consistent with predictions of the foraging arena hypothesis with turtles largely restricted to safe habitat patches and selecting locations within these where seagrass N content is relatively high. Marine invasive species can have detrimental effects on coastal ecosystems and economies. Therefore, understanding the effects of, and factors influencing the rate of spread of the invasive seagrass Halophila stipulacea in the Caribbean is important. In the French West Indies (Guadeloupe, Martinique and St. Martin), I investigated foraging preferences for native versus invasive seagrass species and whether green turtles might facilitate or attenuate the invasion through their choice of habitats and feeding patterns. Green turtle distributions were correlated with native seagrass distributions. Also, despite similar nutrient contents, turtles preferred feeding on native seagrasses irrespective of their relative abundance within a patch. These results suggest that, as predicted by the Enemy Release Hypothesis, green turtles likely facilitate the invasion and spread of the invasive seagrass that may reduce energy flow into turtle populations.

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27

CARUSO, ALICE. "Investigation of the factors controlling hyporheic exchangeat multiple spatial scales." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2707514.

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Hyporheic exchange is the mixing between stream water and sediment pore water occurring vertically through the riverbed and laterally through the riverbanks. This mixing between water coming from the river and water coming from the aquifer, with very different physical and chemical characteristics, creates a unique environment in which important biogeochemical reactions occur and rich communities of microorganisms and macroinvertebrates flourish. The occurrence of the hyporheic exchange significantly influences the quality of the stream water and the nutrient cycling, playing a crucial role in hydrological, biogeochemical, and ecological processes. Although hyporheic fluxes are driven by the local morphology of the streambed, they are strongly affected by the large-scale groundwater system, which obstructs the penetration of stream water into the sediments and limits the intensity of hyporheic exchange. The present thesis aims to: i) investigate the role of the regional groundwater flow system on hyporheic exchange, analyzing the factors controlling the spatial variability of groundwater discharge patterns along the river corridor and ii) study the effect of microbial growth on exchange fluxes and nutrient reactions within the hyporheic sediments. The work is divided into five Chapters. Chapter 1 presents a general overview on groundwater-surface water interactions, with a description of the multiple scales involved in these processes. The main aspects for which these interactions are important are recalled and a brief review on the modeling,of river-aquifer interactions is presented. The attention is then focused on hyporheic processes, analyzing the main hydraulic and biogeochemical features characterizing these processes. The impact that the groundwater flow system has on these local processes is discussed. Finally, the main research topics investigated in the thesis are outlined. In Chapter 2, the role of groundwater table structure at basin scale on the spatial patterns of groundwater discharge to the stream network and, consequently, on hyporheic exchange was investigated. Specifically, we determined the spatial structure of the groundwater upwelling along the stream network in order to investigate the effect of large-scale groundwater flow on local hyporheic flow velocity. A semi-analytical method for the estimation of the three-dimensional groundwater flow field was adopted, based on an approximation between the groundwater head distribution and the landscape topography. Results highlight that the complex topographic conformation of a basin determines a strong spatial variability of the groundwater flow field that, in turn, translates into a fragmentation of the hyporheic zone. Chapter 3 is in line with the study developed in Chapter 2, looking at the groundwater-surface water interactions induced by large-scale hydrogeological characteristics. A more complex numerical model was adopted, allowing us to remove some simplifications on which the previous semi-analytical model was based on. The influence of some topographic and hydrogeological factors on determining the spatial variability of groundwater discharge patterns was investigated. Results indicate that the geological heterogeneity of the aquifer is the main control of river-aquifer exchange patterns and the structure of subsurface flow patterns is marginally affected by other modeling assumptions. Chapter 4 shifts the focus on biogeochemical processes occurring at smaller scales and deals with the existing coupling between hydrodynamic processes, solute transport, and microbial metabolism within the hyporheic zone. A flow and reactive transport model was coupled with a microbial biomass model where two microbial components representing autotrophic (nitrifying) bacteria and heterotrophic (facultative anaerobic) bacteria were considered. The aim was to investigate how the filling of sediment pore space induced by biomass growth (i.e. bioclogging) alters hyporheic flow patterns and transformation rates of nitrogen, oxygen, and organic carbon within hyporheic sediments. Results show how the bioclogging-induced biogeochemical zonation of hyporheic zone strongly influences coupled nitrogen, carbon, and oxygen dynamics. Finally, Chapter 5 presents general conclusions of the work.

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28

Ferrari, Marika. "Spatial assessment of multiple ecosystem services in an Alpine region." Doctoral thesis, Università degli studi di Trento, 2014. https://hdl.handle.net/11572/367721.

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Ecosystem Services (ESs) are the goods and services supplied by ecosystems. In order to fully understand their contribution to human wellbeing, there is a need to identify them, assess their supply, recognise areas where they appear together repeatedly and analyse the interactions that may exist among them. Most of these tasks are also specifically required by the European Biodiversity Strategy for 2020, which asks Member States, by 2014, to identify key ESs and to spatially assess their supply and demand (European Commission, 2011). Nevertheless, these are difficult tasks and to date they have been only partly performed: existing studies in fact have typically focused on a small sub-set of ESs and made use of information that poorly reflects the actual variability of the ESs distribution across a region. The present research aims to fill these gaps, by developing methods involving a wide set of ESs and providing a detailed ESs assessment, based on spatial and statistical analyses. The methods have been tested on an Alpine region of Italy, Trentino. The Alps present a heterogeneous landscape, resulting from the combination of natural and urbanized environments, that allows the supply of a wide range of ESs. The research has four specific objectives. The first objective focuses on the selection and the representation over specific spatial units of the real supply of multiple ESs. Operatively, 51 experts from the local administrative offices and research institutes have been involved in the selection of the most important ESs and spatial indicators for the case study. The experts identified 25 ESs and 57 representative spatial indicators (1 to 5 indicators for each service), and provided data for indicators mapping. To consider the heterogeneity of the ESs supply across the region, indicators were mapped over 20 different spatial units, including: land cover classes, cadastral parcels, fishing zones and catchments.The second objective is to develop and test a statistical method for identifying key indicators that are spatially-explicit and able to measure the biophysical, socio-cultural and economic values of ESs (both in terms of stock and flow). Spearman pairwise correlation analysis was performed among the indicators of the same service in order to identify the highly correlated ones, hence deemed to provide redundant information. Key indicators were selected among the lowly correlated ones. 35 indicators were selected for the case study (out of the 57 initial indicators). The analysis showed that there is a minimum number of key indicators for each ES. Accordingly, three general rules were identified for the selection: (i) if the supply of an ES is regulated, both its biophysical-stock and biophysical-flow indicators must be selected, (ii) if multiple stock (flow) biophysical indicators for a single ES are mapped over different spatial units, all stock (flow) indicators must be maintained, (iii) socio-cultural or economic indicators are always selected as key indicators. The third objective is to develop and test a statistical method for defining bundles of ESs, as sets of spatially correlated services. Principal Component Analysis was used to summarize the information of the 35 indicators, while hierarchical clustering was applied to identify 11 ESs clusters. Clusters were turned into bundles by analyzing the spatial variability of the services due to biophysical (e.g. morphological conditions) and human (e.g. land use) factors. The results of the analysis show that in Trentino multiple ESs can be grouped in a few number of bundles with a complex shape. In particular, areas with poor ESs supply are grouped in one single bundle and the largest bundle follows the spatial distribution of a single land cover class: i.e. forest.The fourth objective is to develop a method to study interactions among ESs, by combining statistical and spatial analyses. In fact, the supply of a given ES is correlated with the supply of other ESs and it is affected by multiple external factors. Correlations may be positive when an increase in the supply of one service corresponds to higher supplies of other services (i.e. synergies), or negative when an increase in the supply of one service corresponds to lower supplies of other services (i.e. tradeoffs). The degree of interactions among 35 key indicators is determined by performing a Spearman pairwise correlation analysis. The latter enabled to identify six patterns of ESs interactions, one pattern of tradeoffs and five of synergies. The analysis showed that the local land use management has not compromised the capacity of ecosystems to provide regulating services while supplying the provisioning ones. The external factors causing the variability of the services across the region were identified and explained by means of spatial and Spearman correlation analyses among the ESs principal components. Principal components were turned into drivers of change by analyzing the spatial variability of the ESs due to biophysical (e.g. forest density) and human (e.g. land use) factors. Land use management was found as the external factor that causes the greatest variability of the ESs distribution across the region. Within forest areas, forest management activities that involve loss of vegetation were found as the main drivers of ESs change. This research aimed to consider a wide set of ESs and information able to reflect the actual variability of the services distribution across a region. It proposed a scientifically sound methodology to deal with the main issues of the ESs spatial assessment, that may reveal efficiently applicable in other geographical areas where ESs are heterogeneously supplied.

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29

Ferrari, Marika. "Spatial assessment of multiple ecosystem services in an Alpine region." Doctoral thesis, University of Trento, 2014. http://eprints-phd.biblio.unitn.it/2758/1/PhDThesis_MarikaFerrari.pdf.

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Анотація:

Ecosystem Services (ESs) are the goods and services supplied by ecosystems. In order to fully understand their contribution to human wellbeing, there is a need to identify them, assess their supply, recognise areas where they appear together repeatedly and analyse the interactions that may exist among them. Most of these tasks are also specifically required by the European Biodiversity Strategy for 2020, which asks Member States, by 2014, to identify key ESs and to spatially assess their supply and demand (European Commission, 2011). Nevertheless, these are difficult tasks and to date they have been only partly performed: existing studies in fact have typically focused on a small sub-set of ESs and made use of information that poorly reflects the actual variability of the ESs distribution across a region. The present research aims to fill these gaps, by developing methods involving a wide set of ESs and providing a detailed ESs assessment, based on spatial and statistical analyses. The methods have been tested on an Alpine region of Italy, Trentino. The Alps present a heterogeneous landscape, resulting from the combination of natural and urbanized environments, that allows the supply of a wide range of ESs. The research has four specific objectives. The first objective focuses on the selection and the representation over specific spatial units of the real supply of multiple ESs. Operatively, 51 experts from the local administrative offices and research institutes have been involved in the selection of the most important ESs and spatial indicators for the case study. The experts identified 25 ESs and 57 representative spatial indicators (1 to 5 indicators for each service), and provided data for indicators mapping. To consider the heterogeneity of the ESs supply across the region, indicators were mapped over 20 different spatial units, including: land cover classes, cadastral parcels, fishing zones and catchments.The second objective is to develop and test a statistical method for identifying key indicators that are spatially-explicit and able to measure the biophysical, socio-cultural and economic values of ESs (both in terms of stock and flow). Spearman pairwise correlation analysis was performed among the indicators of the same service in order to identify the highly correlated ones, hence deemed to provide redundant information. Key indicators were selected among the lowly correlated ones. 35 indicators were selected for the case study (out of the 57 initial indicators). The analysis showed that there is a minimum number of key indicators for each ES. Accordingly, three general rules were identified for the selection: (i) if the supply of an ES is regulated, both its biophysical-stock and biophysical-flow indicators must be selected, (ii) if multiple stock (flow) biophysical indicators for a single ES are mapped over different spatial units, all stock (flow) indicators must be maintained, (iii) socio-cultural or economic indicators are always selected as key indicators. The third objective is to develop and test a statistical method for defining bundles of ESs, as sets of spatially correlated services. Principal Component Analysis was used to summarize the information of the 35 indicators, while hierarchical clustering was applied to identify 11 ESs clusters. Clusters were turned into bundles by analyzing the spatial variability of the services due to biophysical (e.g. morphological conditions) and human (e.g. land use) factors. The results of the analysis show that in Trentino multiple ESs can be grouped in a few number of bundles with a complex shape. In particular, areas with poor ESs supply are grouped in one single bundle and the largest bundle follows the spatial distribution of a single land cover class: i.e. forest.The fourth objective is to develop a method to study interactions among ESs, by combining statistical and spatial analyses. In fact, the supply of a given ES is correlated with the supply of other ESs and it is affected by multiple external factors. Correlations may be positive when an increase in the supply of one service corresponds to higher supplies of other services (i.e. synergies), or negative when an increase in the supply of one service corresponds to lower supplies of other services (i.e. tradeoffs). The degree of interactions among 35 key indicators is determined by performing a Spearman pairwise correlation analysis. The latter enabled to identify six patterns of ESs interactions, one pattern of tradeoffs and five of synergies. The analysis showed that the local land use management has not compromised the capacity of ecosystems to provide regulating services while supplying the provisioning ones. The external factors causing the variability of the services across the region were identified and explained by means of spatial and Spearman correlation analyses among the ESs principal components. Principal components were turned into drivers of change by analyzing the spatial variability of the ESs due to biophysical (e.g. forest density) and human (e.g. land use) factors. Land use management was found as the external factor that causes the greatest variability of the ESs distribution across the region. Within forest areas, forest management activities that involve loss of vegetation were found as the main drivers of ESs change. This research aimed to consider a wide set of ESs and information able to reflect the actual variability of the services distribution across a region. It proposed a scientifically sound methodology to deal with the main issues of the ESs spatial assessment, that may reveal efficiently applicable in other geographical areas where ESs are heterogeneously supplied.

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30

Ganji, Saichand. "Space-Time Block Coding to Achieve Spatial Diversity in a Multiple Input Multiple Output System." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1534432423784957.

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31

Uhl, Brecken. "Direct Spatial Antenna Modulation for Wideband Phase Control." International Foundation for Telemetering, 2010. http://hdl.handle.net/10150/604278.

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ITC/USA 2010 Conference Proceedings / The Forty-Sixth Annual International Telemetering Conference and Technical Exhibition / October 25-28, 2010 / Town and Country Resort & Convention Center, San Diego, California
Direct spatial antenna modulation (DSAM) is a new approach to phased array control that opens up new "smart antenna" architecture possibilities. The DSAM technique leverages the inherent spatial differences of excitation in an antenna in a novel way to achieve the equivalent of conventional modulation and beam control effects. Smart antenna techniques are of potentially increasing importance to test range operations given a trend toward more flexible, internetworked, and autonomous test activities. The DSAM technique has been demonstrated through several generations of analysis, simulation, and prototyping, but has previously only been applied to narrowband antenna designs. Furthermore, the IQ DSAM approach in particular has not been previously implemented in hardware. This paper details the application of IQ DSAM to achieve wideband phase control using a commercial off the shelf (COTS) antenna. The phase control performance of IQ DSAM over a range of 1.5 GHz to 4 GHz is measured across relative field control angles of +/- 45 degrees. The measured IQ DSAM performance is compared to what could be expected from a conventional phased array element control architecture.

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32

Sabade, Sagar Suresh. "Integrated circuit outlier identification by multiple parameter correlation." Diss., Texas A&M University, 2004. http://hdl.handle.net/1969.1/267.

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Semiconductor manufacturers must ensure that chips conform to their specifications before they are shipped to customers. This is achieved by testing various parameters of a chip to determine whether it is defective or not. Separating defective chips from fault-free ones is relatively straightforward for functional or other Boolean tests that produce a go/no-go type of result. However, making this distinction is extremely challenging for parametric tests. Owing to continuous distributions of parameters, any pass/fail threshold results in yield loss and/or test escapes. The continuous advances in process technology, increased process variations and inaccurate fault models all make this even worse. The pass/fail thresholds for such tests are usually set using prior experience or by a combination of visual inspection and engineering judgment. Many chips have parameters that exceed certain thresholds but pass Boolean tests. Owing to the imperfect nature of tests, to determine whether these chips (called "outliers") are indeed defective is nontrivial. To avoid wasted investment in packaging or further testing it is important to screen defective chips early in a test flow. Moreover, if seemingly strange behavior of outlier chips can be explained with the help of certain process parameters or by correlating additional test data, such chips can be retained in the test flow before they are proved to be fatally flawed. In this research, we investigate several methods to identify true outliers (defective chips, or chips that lead to functional failure) from apparent outliers (seemingly defective, but fault-free chips). The outlier identification methods in this research primarily rely on wafer-level spatial correlation, but also use additional test parameters. These methods are evaluated and validated using industrial test data. The potential of these methods to reduce burn-in is discussed.

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33

Corkum, Cristine V. "Response of small mammals to landscape structure at multiple spatial scales." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ47018.pdf.

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34

Fortin, Daniel. "Foraging decisions at multiple spatial and temporal scales, a bison perspective." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ56280.pdf.

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35

Canessa, Rosaline Regan. "Towards a coastal spatial decision support system for multiple-use management." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ32737.pdf.

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36

Harmouche, Rola. "Bayesian multiple sclerosis lesion classification modeling regional and local spatial information." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99411.

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This thesis presents a fully automatic Bayesian method for multiple sclerosis lesion classification. Traditionally, human experts locate lesions, which are diseased tissue, on magnetic resonance images (MRI). However, manual classification methods are particularly subjective, as experts locate lesions differently, particularly around the borders of these structures. The proposed approach classifies voxels from MRIs into regular tissue and lesions, thus allowing for an objective and consistent way to locate lesions in order to help track their size and count. Previous automatic classification approaches do not model the variation of the MRI tissue intensities in the brain, so as to accurately locate lesions in the posterior fossa, where the intensities vary significantly from the rest of the brain. To this end, the posterior probability distribution is used to determine MRI voxel labels for background, cerebrospinal fluid, grey matter, white matter, as well as labels for two lesion types which differ due to their appearance on MRIs: T1-hypointense lesions (also called black holes) and T2-hyperintense lesions excluding black holes. Furthermore, the proposed method provides neuropathology experts with a confidence level in the classification, which has not been provided in previous work. Spatial variability in intensity distributions over the brain is explicitly modeled by (1) segmenting the brain into distinct anatomical regions, (2) building the likelihood distributions of each tissue class in each region and (3) modeling each distribution as a multidimensional Gaussian using intensities from multimodal MRIs. Local smoothness is enforced by incorporating Markov random fields in the prior probability and thus taking into account neighboring voxel tissue classes. Qualitative and quantitative validation is performed for both lesion classes on real data from 10 patients with multiple sclerosis. Validation on ten patients for both lesion types has not been performed by previous works. Lesion classification results are compared to classifications performed by several experts and two other automatic classification techniques, using volume count and overlap. Automatic classification results are comparable to manual classifications, thus providing a more consistent and time effective alternative to manual classification. In addition, the proposed method has the advantage of providing a more accurate classification in the posterior fossa, which is a region of the brain that is difficult to classify, and where no other automatic method reports success.

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37

Zhang, Xiongbo, and 張雄波. "3D trajectory recovery in spatial and time domains from multiple images." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/195966.

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Recovering 3D structure from multiple 2D images is a fundamental problem in computer vision. Most of existing methods focus on the reconstruction of static points in 3D space; however, the reconstruction of trajectories which are resulted from moving points should also have our full attention due to its high efficiency in structure modeling and description. Depending on whether points are moving in spatial domain or in time domain, trajectory recovery turns out to be a curve reconstruction problem or a non-rigid structure recovery problem respectively. This thesis addresses several issues that were not considered in existing approaches in both of the two problems. For the curve reconstruction problem, we propose a dedicated method for planar curve reconstruction and an optimization method for general curve reconstruction. In the planar curve reconstruction method, measured projected curves that are typically represented by sequences of points are fitted using B-splines before reconstruction, enabling the occlusion problem to be handled naturally. Also, an optimization algorithm is developed to match the fitted curves across images while enforcing the planarity constraint, and the algorithm is guaranteed to converge. In the general curve reconstruction method, Non-Uniform Rational B-Spline (NURBS) is employed for curve representation in 3D space, which improves the flexibility in curve description while maintaining the smoothness of a curve at the same time. Starting with measured point sequences of projected curves, a complete set of algorithms are developed and evaluated, including curve initialization and optimization of the initialized curve by minimizing the 2D reprojection error that is defined to be the 2D Euclidean distance from measured points to reprojected curves. Experiments show that the proposed methods are robust and efficient, and are excellent in producing high-quality reconstruction results. For the non-rigid structure recovery problem, we proposed two methods for the recovery of non-rigid structures together with a strategy that automates the process of non-rigid structure recovery. Compared with existing methods using synthetic datasets, both of the two proposed methods perform significantly better than existing methods when there are noise contaminations in measurements, and are capable to recover the ground truth solution when the measurements are noise free whereas no existing method is capable of achieving this so far. In the first method, namely factorization-based method, the available constraints in non-rigid structure from motion are analyzed and the ambiguity of the solution space of the proposed method is clarified, leading to a straightforward approach that requires only solution to several linear equations in least-squares sense instead of having to solve non-linear optimization problems in existing methods. In the second method, namely bundle adjustment method, a modified trajectory basis model that is demonstrated to be more flexible for non-rigid structure description is proposed. The method seeks for optimal non-rigid structure and camera matrices by alternately solving a set of linear equations in least square sense. Experiments on real non-rigid motions show that the method improves the quality of reconstruction significantly.
published_or_final_version
Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy

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38

Taschler, Bernd. "Spatial point process models for MRI lesion data in multiple sclerosis." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/93636/.

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Over the past three decades neuroimaging techniques in general and magnetic resonance imaging (MRI) in particular have made large contributions to the understanding of human brain function and to the diagnosis and treatment of neurological diseases. One area of wide-spread clinical use of MRI is in the assessment of multiple sclerosis (MS). MS patients present with lesions – areas of decreased neuronal conductivity, akin scarred tissue – that occur across the brain and spinal cord. There has been growing interest to use quantitative measures of lesion incidence, exact lesion location and the shape of lesions in the analysis of MRI-based lesion data. Our objective is to address some of the limitations of current methods which rely on particular assumptions about the data and mostly ignore any spatial correlation and structure in the data. In this work we explore several ways of incorporating multiple sources of information into models that can be used for classification and prediction purposes. We compare and assess different machine learning and Bayesian spatial models in a classification task based on MS lesion data. Furthermore, we propose an extended doubly-stochastic spatial point process model based on Gamma random fields that includes non-imaging data as well as location-specific measures attached to xyz-coordinates, and use both simulated and real data to evaluate our methods.

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39

Lian, Zhengyi. "Discontinuous Galerkin solution of the Boltzmann equation in multiple spatial dimensions." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41560.

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Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2007.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaves 77-79).
This thesis focuses on the numerical solution of a kinetic description of small scale dilute gas flows when the Navier-Stokes description breaks down. In particular, it investigates alternative solution techniques for the Boltzmann equation typically used when the Knudsen number (ratio of molecular mean free path to characteristic length scale of flow) exceeds (approximately) 0.1. Alternative solution methods are required because the prevalent Boltzmann solution technique, Direct Simulation Monte Carlo (DSMC), experiences a sharp rise in computational cost as the deviation from equilibrium decreases, such as in low signal flows. To address this limitation, L. L. Baker and N. G. Hadjiconstantinou recently developed a variance reduction technique [5] in which one only simulates the deviation from equilibrium. This thesis presents the implementation of this variance reduction approach to a Runge-Kutta Discontinuous Galerkin finite element formulation in multiple spatial dimensions. Emphasis is given to alternative algorithms for evaluating the advection operator terms, boundary fluxes and hydrodynamic quantities accurately and efficiently without the use of quadrature schemes. The collision integral is treated as a source term and evaluated using the variance-reduced Monte Carlo technique presented in [10, 9]. For piecewise linear (p = 1) and quadratic (p = 2) solutions to the Boltzmann equation in 5 spatial dimensions, the developed algorithms are able to compute the advection operator terms by a factor of 2.35 and 2.73 times faster than an algorithm based on quadrature, respectively; with the computation of hydrodynamic quantities, the overall performance improvement is a factor of 8.5 and 10, respectively.
(cont.) Although the collision integral takes up to 90% or more of the total computation cost, these improvements still provide tangible efficiency advantages in steady-flow calculations in which less expensive transient collision-operator calculation routines are used during a substantial part of the flow development. High order convergence in physical space has been verified by applying the implemented RKDG method on a test problem with a continuous solution. Furthermore, when applied to pressure driven Poiseuille flow through a rectangular channel, the steady state mass flux in the collisionless limit (where exact results exist) agrees within 0.5%, 0.8% and 1.2% of that obtained by Sone and Hasegawa [14] for aspect ratios of 1, 2 and 4 respectively under a spatial resolution of 52 x103 . For Kn = 0.2, 1 and 10, our results agree with those obtained by Sone and Hasegawa [14] from solutions of the linearized Boltzmann-Krook-Welander(BKW) equation by comparing them at an "equivalent" Knudsen number of 1.27Kn [21]. These results validate the implementation and demonstrate the feasibility of the variance-reduced RKDG method for solving the full Boltzmann equation in multiple spatial dimensions. To pursue higher accuracy for this pressure driven flow problem, a p = 1 scheme was found to be more efficient than a p = 2 scheme at a coarser spatial discretization. This can be achieved by using finer spatial discretization and non-uniform spacing to generate more elements near regions of discontinuities or large variations in the molecular distribution function.
by Zhengyi Lian.
S.M.

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40

Histed, Mark H. "Multiple spatial memories in the brain : decoding and modification using microstimulation." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33173.

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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2005.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (leaves 87-97).
Sequential processing --- using multiple sensory stimuli to plan and control a set of ordered movements --- is a central aspect of human behavior. Because previous and future movements must be stored during the execution of any movement in a sequence, memory is an indispensable aspect of sequential behavior. To study how memory is used to link sensory inputs to sequential motor outputs, we have used the oculomotor system as a model. We trained monkeys to remember the location of two spatial cues over a brief delay, and then make two eye movements to the remembered locations in the order that they appeared. We explored the role of two different frontal eye movement areas, the frontal and supplementary eye fields (FEF and SEF) during this memory delay. While both the FEF and SEF have shown to be important for sequential behavior, their individual roles are unknown. Here, using physiology, we show that the FEF is important for storing the location of multiple cues and their order in memory. In the SEF, we show that memory period stimulation can affect the order of a sequence, changing the goal of the entire sequence but not the individual movement components.
(cont.) Thus, both areas appear to play complementary roles in sequential planning: the FEF stores target locations, while the SEF appears to control the order of a response sequence, coding entire sequences without affecting the locations of the intermediate targets. This work bears on several outstanding questions in the field. It clarifies the individual roles of the FEF and SEF during sequencing: the FEF may serve as a buffer for multiple memories while the SEF plays a role in organizing movement sequences. It relates several prior SEF results, suggesting that a primary role of SEF may be to specify movements by their goal. Finally, we suggest that this goal-centered scheme may be a fundamental way that many different types of movements are encoded.
by Hark H. Histed.
Sc.D.

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41

Mahoney, Peter J. "Spatial Ecology of Coyotes and Cougars: Understanding the Influence of Multiple Prey on the Spatial Interactions of Two Predators." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/5658.

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The extent to which predators regulate prey populations remains a subject of debate. Yet, when predator control is employed as a management strategy, it is often assumed that predators can and do regulate prey populations. From 2011 through 2015, I monitored the demography and space use of coyotes (Canis latrans) and cougars (Puma concolor) on Monroe Mountain in Fishlake National Forest, Utah as part of a larger collaboration investigating the impacts of coyote aerial control on mule deer (Odocoileus hemionus) neonate survival. My primary objective was to assess the impacts of anthropogenic regulation on the respective populations and identify any cascading effects relevant to mule deer management. To meet this objective, I established a monitoring program for both predators by deploying radio-telemetry collars (VHF and GPS) on each, documented predation events, established surveys for small mammals and lagomorphs to monitor primary prey populations during deer parturition (June – August), and collected data on the location and demographic composition of winter-removed coyotes. I analyzed these data primarily in a community-based, animal movement and resource selection framework permitting the integration of data from multiple sources. When evaluating coyote aerial removal as a management strategy, I identified a spatial dependency in the ability to match removals with indices of deer recruitment as Wildlife Services Operations personnel were primarily limited by terrain and tree cover. Thus, matching treatment with deer fawning was highly variable with only a small number of sites where removals were effective. In addition, I found that coyotes selected for sites with the highest densities of lagomorphs while avoiding areas with a high probability of encountering cougars. Coyotes did not select for mule deer fawning sites, although individual coyotes that occupied resource-poor home ranges were more likely to do so. Cougars strongly selected for mule deer high use areas throughout much of the year, only switching to elk (Cervus elaphus) during the cougar harvest season (i.e., winter). Data from cougar kill site investigations match the observed patterns in cougar space use. My results suggest that predator-prey processes are multi-dimensional and dynamic through time, which likely contribute to the lack of resolution regarding the efficacy of predator control and the regulatory potential of predators in general.

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42

Huang, Fang. "Modeling patterns of small scale spatial variation in soil." Link to electronic thesis, 2006. http://www.wpi.edu/Pubs/ETD/Available/etd-011106-155345/.

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Thesis (M.S.)--Worcester Polytechnic Institute.
Keywords: spatial variations; nested random effects models; semivariogram models; kriging methods; multiple logistic regression models; missing; multiple imputation. Includes bibliographical references (p. 35-36).

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43

Heisswolf, Annette. "The distribution of leaf beetles on multiple spatial scales causes and consequences /." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981698301.

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44

Fu, Liqun. "Spatial statistics and their application to neuroimaging studies of multiple sclerosis patients." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0028/NQ50166.pdf.

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45

Fu, Liqun 1964. "Spatial statistics and their application to neuroimaging studies of multiple sclerosis patients." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35704.

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Proton Magnetic Resonance Spectroscopy (MRS) is an effective technology for imaging axonal damage in the brains of multiple sclerosis (MS) patients. This is based on decreases in signals from N-acetyl groups, which come primarily from the neuronal marker, N-acetylaspartate (NAA). Magnetic Resonance Spectroscopic Imaging (MRSI) visualizes the spatial distribution of the NAA intensities in the brains of MS patients. It can be combined with conventional Magnetic Resonance Imaging (MRI) and other clinical information in order to better understand the disease pathology.
This thesis comprises three independent but interconnected manuscripts concerning the application of MRSI and MRI to clinical researches in MS. (1) In the first, a statistical analysis strategy for multimodal analysis of MR spectroscopic images was developed. This method allowed for quantification of differences in images of different subgroups of MS patients and the relationship between chemical pathology, clinical disability, duration of disease, and lesions on T2-weighted MRI. (2) The statistical method was applied to serially collected MRSI data from 28 patients with MS (11 relapsing remitting (RR) and 17 secondary progressive (SP)) and 12 normal controls. Results showed that the NAA intensity was lower in the normal appearing white matter (NAVM) of MS patients than that in normal controls and the NAA intensity was 8.2% lower (p < 0.01) in the NAWM of SP than of RR patients. The decrease in NAA in NAWM over time correlated strongly (p < 0.001) with changes in disability in the RR subgroup. These results highlighted an association between axonal damage or loss and increasing disability in MS and suggested that accumulation of secondary axonal damage in the NAWM might be an important mechanism of functional impairment with this disease. (3) Finally, a computer package integrating spatial statistical methodologies adopted in this project and other image processing methods was developed. This package can also serve as a tool for medical imaging data organization, visualization, and manipulation. It will be used by researchers in the field to analyze functional imaging data.

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46

Macke, Benjamin Tyler. "CHARACTERIZATION OF AN ELECTRON GUN CONTROLLED MULTIPLE SPATIAL REGION PIEZOELECTRIC THIN FILM." UKnowledge, 2003. http://uknowledge.uky.edu/gradschool_theses/312.

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Piezoelectric bimorph thin films may hold solutions for many future applications, such as lightweight deployable mirrors and inflatable struts. Non-contact actuation by an electron gun has shown promise in preventing issues that arise from attaching many wire leads to a thin film surface. This study investigates piezoelectric bimorph thin film response to electron gun actuation when covered with multiple spatial regions of control. Desired parameter ranges are found that will lead to predictable control under certain circumstances. Under such circumstances, film response is influenced almost solely by the primary electrons incident on the film, and secondary electrons have negligible effect. Such information is vital before attempting closed loop control of a thin-film piezoelectric mirror with multiple electrodes.

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47

Schloss, Robert Perry. "External cavity laser with coherent amplifier array and multiple slit spatial filter." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/15185.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1986.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.
Bibliography: leaves 181-184.
by Robert Perry Schloss.
Ph.D.

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48

Adeane, Jaime. "Spatial diversity in wireless communications : multiple antenna systems and virtual antenna arrays." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613069.

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49

Verschut, Thomas Alexander. "Searching for food in complex environments : Integrating processes at multiple spatial scales." Doctoral thesis, Stockholms universitet, Institutionen för ekologi, miljö och botanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-141762.

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Resources are often unevenly distributed through the environment, resulting in a challenging task for insects to locate food, mates and oviposition sites. Consequently, there is an ongoing need to unravel how insects rely on behavioural and sensory traits while searching for resources in heterogeneous environments. In the first part of this thesis, I addressed this issue by studying how neighbouring resources can affect the likelihood of insects finding their preferred host resources. These effects of neighbouring resources are commonly referred to as associational effects, and are expected to result from limitations in the sensory physiology of insects. Such limitations constrain the insect’s ability to correctly evaluate resource quality at the different steps involved in insect search behaviour. Furthermore, I determined whether the physiological state of an insect, and sensory experiences made during larval stages, can affect host search behaviour in heterogeneous environments. By comparing the behaviour of Drosophila melanogaster in environments with single and multiple resources, I found that the presence of neighbouring recourses increased the selection rates for attractive resources, while it decreased the selection rates for less attractive resources. These effects are referred to as associational susceptibility and associational resistance respectively. Furthermore, by studying oviposition behaviour, I found that during these small-scale behavioural decisions, associational effects are mainly governed by gustatory mediated selection and less by olfactory mediated selection. The oviposition assay eliminated potential misinterpretations of resource quality along the different steps of search behaviour, hence the results suggested that associational effects rely on distinctive selection behaviour between resource types rather than on sensory constraints. In the second part of this thesis I determined whether natal experiences can be used by insects as sensory shortcuts to find host resources, and whether this leads to better larval performance on those selected host resources. For this purpose, I studied the interactions between the larval parasitoid Asecodes lucens and the oligophagous leaf beetle Galerucella sagittariae. The results showed that the relationship between oviposition preference and larval performance, of both insect species, depends on an interactive effect between the insects’ natal origin and the quality of the different host resources. Moreover, I found that the natal origin was a better predictor for the adult host preference, rather than for larval performance. This suggests that, aside from the actual quality of the host resources, locating any suitable host might be even more limiting for the female’s fitness.

At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted. Paper 3: Submitted.

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50

Vasques, Gustavo de Mattos. "Spatial and spectral models of soil carbon at multiple scales in Florida." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024803.

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