Дисертації з теми "Spatial and Temporal Documentation"
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1
Parker, Austin. "Spatial probabilistic temporal databases." College Park, Md.: University of Maryland, 2008. http://hdl.handle.net/1903/8728.
Повний текст джерелаАнотація:
Thesis (Ph. D.) -- University of Maryland, College Park, 2008.Thesis research directed by: Dept. of Computer Science. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Storey, Susan. "Spatial-temporal fish stock assessment." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28463.pdf.
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3
Slack, Marc G. "Spatial and temporal path planning." Thesis, This resource online, 1987. http://scholar.lib.vt.edu/theses/available/etd-04272010-020255/.
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4
Liu, Fang 1962. "Modeling spatial and temporal textures." Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/29131.
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Henderson, Jonathan. "Avian spatial and temporal cognition." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/14049.
Повний текст джерелаАнотація:
I investigated the spatial memory abilities of male rufous hummingbirds (Selasphorus rufus) on their breeding grounds, where birds can be readily trained to feed from artificial flowers presented in two- and three-dimensional arrays. I found that birds use height as a cue when encoding flower locations, preferring to visit taller flowers. Performance in three-dimensional arrays was not however consistently better than in 2-D arrays. I also examined the possibility that hummingbirds follow a fixed flight path when returning to an array of flowers, as has been seen in the Hymenoptera. By manipulating the number of doors by which a bird could enter an arena to feed on an array of flowers, I found some evidence that birds do use systematic movements when relocating rewarding sites. Rufous hummingbirds feed on floral nectar, a resource that varies in time as well as space. To determine whether these birds use time as a cue when foraging, I provided them with an array in which flowers were refilled after intervals of either ten or twenty minute. The birds were able to learn these intervals, as they returned to flowers on or shortly after their expected refill time. I used an analogous experiment to investigate timing abilities in coal tits (Parus ater), a food-storing species, and great tits (P. major), a non food-storing species, in the laboratory. Storers and non-storer might differ in their ability to time intervals due to the demands, on storers, of reliable cache recovery. Coal tits were able to track the availability of rewards in three different locations associated with reward schedules in the 30-120s range. I found no consistent differnces in the abilities of coal tits and great tits to time intervals in the 40-70s range. In conclusion, rufous hummingbirds were shown to use both spatial and temporal cues whilst foraging at flowers. Coal tits and great tits were able to time short intervals in the laboratory, but I found no overall differences in timing behaviour between the two species.
6
Zhou, Feng. "Spatial, Temporal and Spatio-Temporal Correspondence for Computer Vision Problems." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/410.
Повний текст джерелаАнотація:
Many computer vision problems, such as object classification, motion estimation or shape registration rely on solving the correspondence problem. Existing algorithms to solve spatial or temporal correspondence problems are usually NP-hard, difficult to approximate, lack flexible models and mechanism for feature weighting. This proposal addresses the correspondence problem in computer vision, and proposes two new spatio-temporal correspondence problems and three algorithms to solve spatial, temporal and spatio-temporal matching between video and other sources. The main contributions of the thesis are: (1) Factorial graph matching (FGM). FGM extends existing work on graph matching (GM) by finding an exact factorization of the affinity matrix. Four are the benefits that follow from this factorization: (a) There is no need to compute the costly (in space and time) pairwise affinity matrix; (b) It provides a unified framework that reveals commonalities and differences between GM methods. Moreover, the factorization provides a clean connection with other matching algorithms such as iterative closest point; (c) The factorization allows the use of a path-following optimization algorithm, that leads to improved optimization strategies and matching performance; (d) Given the factorization, it becomes straight-forward to incorporate geometric transformations (rigid and non-rigid) to the GM problem. (2) Canonical time warping (CTW). CTW is a technique to temporally align multiple multi-dimensional and multi-modal time series. CTW extends DTW by incorporating a feature weighting layer to adapt different modalities, allowing a more flexible warping as combination of monotonic functions, and has linear complexity (unlike DTW that has quadratic). We applied CTW to align human motion captured with different sensors (e.g., audio, video, accelerometers). (3) Spatio-temporal matching (STM). Given a video and a 3D motion capture model, STM finds the correspondence between subsets of video trajectories and the motion capture model. STM is efficiently and robustly solved using linear programming. We illustrate the performance of STM on the problem of human detection in video, and show how STM achieves state-of-the-art performance.
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Wang, Qian. "Characterizing InternetWorm Spatial-Temporal Infection Structures." FIU Digital Commons, 2010. http://digitalcommons.fiu.edu/etd/294.
Повний текст джерелаАнотація:
Since the Morris worm was released in 1988, Internet worms continue to be one of top security threats. For example, the Conficker worm infected 9 to 15 million machines in early 2009 and shut down the service of some critical government and medical networks. Moreover, it constructed a massive peer-to-peer (P2P) botnet. Botnets are zombie networks controlled by attackers setting out coordinated attacks. In recent years, botnets have become the number one threat to the Internet. The objective of this research is to characterize spatial-temporal infection structures of Internet worms, and apply the observations to study P2P-based botnets formed by worm infection. First, we infer temporal characteristics of the Internet worm infection structure, i.e., the host infection time and the worm infection sequence, and thus pinpoint patient zero or initially infected hosts. Specifically, we apply statistical estimation techniques on Darknet observations. We show analytically and empirically that our proposed estimators can significantly improve the inference accuracy. Second, we reveal two key spatial characteristics of the Internet worm infection structure, i.e., the number of children and the generation of the underlying tree topology formed by worm infection. Specifically, we apply probabilistic modeling methods and a sequential growth model. We show analytically and empirically that the number of children has asymptotically a geometric distribution with parameter 0.5, and the generation follows closely a Poisson distribution. Finally, we evaluate bot detection strategies and effects of user defenses in P2P-based botnets formed by worm infection. Specifically, we apply the observations of the number of children and demonstrate analytically and empirically that targeted detection that focuses on the nodes with the largest number of children is an efficient way to expose bots. However, we also point out that future botnets may self-stop scanning to weaken targeted detection, without greatly slowing down the speed of worm infection. We then extend the worm spatial infection structure and show empirically that user defenses, e.g., patching or cleaning, can significantly mitigate the robustness and the effectiveness of P2P-based botnets. To counterattack, we evaluate a simple measure by future botnets that enhances topology robustness through worm re-infection.
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Bai, Ping Truong Young K. Smith Richard L. "Temporal-spatial modeling for fMRI data." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1481.
Повний текст джерелаАнотація:
Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). "... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Statistics and Operations Research." Discipline: Statistics and Operations Research; Department/School: Statistics and Operations Research.
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Bonsall, Michael B. "Temporal and spatial insect population dynamics." Thesis, Imperial College London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406839.
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Liddle, Elizabeth B. "Temporal and spatial attention in dyslexia." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/14422/.
Повний текст джерелаАнотація:
It was hypothesized that the deficits underlying reading impairment may arise from supra-modal deficits in temporal and spatial attention, disrupting, on the one hand, the ability to segment the temporally ordered phonemes of language and thus the acquisition of decoding skills, and, on the other, the ability to integrate spatially and temporally ordered orthographic information acquired from the fluent visual scanning of written text. Temporal and spatial attentional deficits in dyslexia were investigated using a lateralized visual temporal order judgment (TOJ) paradigm that allowed both sensitivity to temporal order and spatial attentional bias to be measured. Dyslexic and non-dyslexic participants were required to report the temporal order of two simple visual stimuli presented in either the same or different lateral hemifields. Findings indicated that dyslexic participants showed markedly impaired sensitivity to temporal order, and that the degree of impairment was correlated with the severity of their dyslexia. Furthermore, the findings suggested that at least three partially dissociated deficits may underlie both impaired TOJ task performance and reading disorder. One is a deficit associated with difficulty in reporting the temporal order of two visual stimuli, particularly when the first is presented in right hemifield; with slow word recognition and non-word reading; and with deficits in spelling and phonological skill. This constellation of deficits was interpreted as reflecting deficits in networks in left cerebral hemisphere implicated in phoneme-grapheme mapping and visual orienting. The second is a deficit that is associated with a rightward attentional bias; with inaccurate non-word reading that is worse than predicted by phonological skill or by word recognition; and with poor sustained attention. This constellation of impairments was interpreted as evidence of a deficit in right-lateralised networks implicated in the modulation of arousal, and possibly reflecting a “developmental left-neglect” syndrome. A third deficit was associated with impaired temporal order sensitivity, regardless of hemifield presentation; with symptoms of Attentional Deficit and Hyperactivity Disorder (ADHD); and with increased interference from distractor stimuli. This constellation of deficits suggests that the impaired network is implicated in executive control of attention, including conflict resolution and working memory. The results of the investigation as a whole suggests that the reading impairments of dyslexia may arise from attentional deficits that have with substantial overlap with those of ADHD, and include deficits in attentional networks implicated in orienting attention to temporally presented stimuli.
11
Kan, Jing. "Spatial-temporal source reconstruction for magnetoencephalography." Thesis, University of York, 2011. http://etheses.whiterose.ac.uk/1636/.
Повний текст джерелаАнотація:
Magnetoencephalography (MEG) is a new non-invasive technique for the functional imaging of the human brain. It has been widely used in both research and clinical applications, for it has several superior properties, including a high-temporal resolution with no interference from the bone or the head-like fluid to the signal spatial transformation. In this thesis, we aim to develop a framework for MEG spatial-temporal current course reconstruction by introducing classical methods from the pattern recognition theory into medical imaging. These applications provide a new angle for research in MEG source reconstruction with the solution for source reconstruction at a single point, and improvements of the reconstruction on spatially and temporally. The whole thesis is based on three topics, which are designed to be parts of an integrated reconstruction process, and each of them are interrelated, rather than independent from each other. We firstly introduce the source reconstructionmethod at a single time point using the basis function extraction. In light of the assumption that the Laplacian eigenvectors of mesh can be the analogous to the basis functions that represent the cortex mesh; we build a new model to describe the current source that is distributed on each mesh vertex. This model consists of analogous basis functions and unknown weighted coefficients. In terms of experiment results, this algorithm shows good reconstructed property to the single stimulus, as well as the supercial stimulus on the cortical surface. Secondly, with respect to the spatial reconstructed sources by basis function method from the last topic, we build a new solution for improving the spatial-resolution of MEG source reconstruction at a single time point by introducing a classical method ( the Bayesian super-resolution method) from the pattern recognition theory. Although the approach is designed based on the reconstruction from basis functions, it is also feasible for other spatial reconstruction methods to improve the spatial-resolution. From the numerical experiment results, it is apparent that the spatial resolution has been effectively improved. Then, the MEG measurement system in the temporal field is assumed to be a linear dynamic system where the classical methods, Kalman filter and Kalman smoother, are applied as the solution for the estimation of source in time course. The Kalman filter is used to estimate the dynamic state while the Kalman smoother is applied for correcting the source distribution of the hidden state with the EMalgorithm. This approach shows superior performance to solve the inverse problem. It extends the improvement in source reconstruction using the temporal field. We construct the synthetic data as well as apply the realMEG data throughout all the experimental test of my work. In summary, this thesis builds three algorithms, which aim to reconstruct the MEG source distribution on spatial and temporal field respectively aided by methods from pattern recognition. This work provides a new angle of using the pattern recognition theory for MEG source reconstruction. Meanwhile, we also explore a new direction for applying the theory of pattern recognition. This work not only provides a good integration between these two fields, but also encourage future interactions.
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Naylor, Susan J. "Spatial context effects on temporal and spatial factors in map memory /." Thesis, Connect to Dissertations & Theses @ Tufts University, 1999.
Знайти повний текст джерелаАнотація:
Thesis (Ph.D.)--Tufts University, 1999.Adviser: Holly A. Taylor. Submitted to the Dept. of Psychology. Includes bibliographical references (leaves 59-61). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Farr, Daniel. "Resolving the Temporal-Spatial Ambiguity With the Auroral Spatial Structures Probe." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/3728.
Повний текст джерелаАнотація:
The behavior of the electric and magnetic fields in the upper atmosphere of the Earth is scientifically interesting but difficult to study, since balloons and aircraft are unable to fly high enough to measure it directly. Sounding rockets, which make a one-time flight carrying instruments that measure the environment around them, have been successfully used to study the upper atmosphere. As the rocket flies through the upper atmosphere, it radios down data about the environment. When scientists on the ground use this data to construct a picture of the upper atmosphere, they run into a problem: the fields reported by the rocket change over time, but it is not clear whether this is because these fields are actually changing in time, or just because the rocket has moved to a different place where the fields are different. This inability to determine whether changes are happening in time or space is called the temporal-spatial ambiguity.
This thesis describes the Auroral Spatial Structures Probe (ASSP), a sounding rocket mission that attempts to resolve the temporal-spatial ambiguity by using multiple payloads flying in formation. Several payloads will pass through and measure the same point in space one after another, which will enable us to see how the fields are changing over time.
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Mahdi, Walid. "Macro-segmentation sémantique des documents audiovisuels à l'aide des indices spatio-temporels." Ecully, Ecole centrale de Lyon, 2001. http://www.theses.fr/2001ECDL0011.
Повний текст джерелаАнотація:
Suite a une convergence rapide de l'informatique et l'audiovisuel, nous assistons a l'heure actuelle a une profusion de documents audiovisuels (dav). Cependant, l'appropriation d'informations visuelles dans le contexte actuel, par une recherche et une navigation intelligente, est difficile. Il est necessaire de proposer des outils, par la creation de tables des matieres ou d'index, permettant aux utilisateurs de maitriser cette abondance d'informations. Dans cette these, nous nous somme principalement interesses au probleme de la segmentation semantique, connue encore sous le nom de macro-segmentation, des documents audiovisuels. L'objectif ici est de mettre en place des techniques permettant d'aider a la creation automatique des tables de matieres, appelees aussi storyboard, associees aux davs en explicitant la structure hierarchique de ceux-ci, en plans, en scenes et en sequences. Notre contribution principale est la mise au point d'une nouvelle methode most (methode spatio-temporel) de macro-segmentation en scenes par une analyse du canal d'images d'un dav en nous focalisant sur des films de fiction. Notre approche trouve son originalite dans la prise en compte des indices spatio-temporels contenus dans un dav, des regles basees sur des conventions du langage audiovisuels reconnues par le spectateur (les ponctuations et le rythme), et aussi des regles basees sur des principes de perception (classification des plan selon le lieu exterieur ou interieur, le temps jour ou nuit). Les resultats experimentaux de notre methode most sur un corpus significatif de sequences video sont tres satisfaisants et tres proches d'une segmentation manuelle realisee par des expertsMore and more AudioVisual Document (DAV) are available in digital form, in various places around the world. Unfortunately, the full use of this media is currently limited by the opaque character of the video which prevents content-based access. To facilitate video navigation and borwsing, it is essential to allow non-linear access, especially for long programs. This can be achieved by identifying story structure to generate the storyboard of index of a DAV which can be captured both by visual content and temporal organization of composing elements within a video. Our principal contribution is a new method "Most" (Spatial- Temporal MethOd) of scences macro-segmentation by analyzing images canal of a DAV. The originality of our technique is to combine the analysis of many main video features, including spatial-temporal clues embedded within a DAV, som rules used in the cinematrographic language such as punctuation and rhythm and other rules based on perception principle (Exterior/Interior shot classification, Day/Night shot classification). The experimental results on more than 90 minutes from different movies, show that our method "Most" performs very well, leading to an automatic segmentation of scenes which is close to a manual expert-based segmentation
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Greenlee, Jordan. "Temporal and spatial modeling of analog memristors." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41215.
Повний текст джерелаАнотація:
As silicon meets its performance limits, new materials and methods for advancing computing and electronics as a whole are being intensely researched, as described in Chapter 1. Memristors are a fusion of these two research areas, with new materials being pursued concurrently to development of novel architectures to take advantage of these new devices. A background of memristors and an overview of different memristive developments in the field are reviewed in Chapter 2.
Chapter 3 delves into the physical mechanisms of analog memristors. To investigate and understand the operation of analog memristors, a finite element method model has been developed.
More specifically, the devices simulated include a simple memristor simulation where the lithium ions (dopants) are confined to the device, but allowed to move in response to a voltage applied across the device. To model a more physical memristor, charge carrier mobility dependence on dopant levels was added to the device, resulting in a simulated device that operates similarly to the first simulation. Thereafter, the effect of varying geometries was modeled, and it was determined that both the speed and the resistance change of the device were improved by increasing the ratio of the top and bottom metal contact lengths in a restrictive flow geometry. Finally, the effect of dopant removal was investigated. It was determined that if the greatest change in resistance is required, then the removal of dopants is the optimal operating regime for an analog memristor.
Through a greater understanding of analog memristors developed by the simulation described herein, researchers will be able to better harness their power and implement them in bio-inspired systems and architectures.
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Fairbairn, Jonathan Paul. "Spatial and temporal dynamics of entomopathogenic nematodes." Thesis, University of Stirling, 2001. http://hdl.handle.net/1893/26685.
Повний текст джерелаАнотація:
The life-history and infection parameters of the entomopathogenic nematodes Steinernema feltiae (Filipjev)(Nematoda:Rhabditida) and Heterorhahditis megidis (Poinar, Jackson & Klein)(Nematoda:Rhabditida) were examined to provide specific details for the construction of mathematical SI models for biological control of soil insect pests. Laboratory experiments using the Greater Waxmoth, Galleria mellonella as the model host were undertaken to specifically examine the transmission behaviour of infective juvenile nematodes. The proportion of infective juveniles of S. feltiae which infected hosts was dependent on time. Previous studies declared that the proportion of infective juveniles which can infect is static, however, over a period of 5 days most of the infective juveniles infected hosts, demonstrating that the proportion infecting is dynamic. Infection of hosts by both species of nematode was compared using two mathematical representations of the transmission rate. Whereas the most parsimonious form of transmission for H. megidis was the linear Mass Action function, it was evident that, when measured at the individual nematode scale, S. feltiae transmission was non-linear. I postulated that this functional difference is due to the biology of the two species of nematodes. The subsequent effect of including the non-linear response on model predictions were investigated and it was demonstrated that the dynamics of the host nematode interaction became less stable. Spatial models of S. feltiae infection were parameterised from laboratory experiments, and control prediction of these models examined. The horizontal rate of dispersal through sand columns was determined in the presence and absence of hosts. Infective juveniles were found to disperse preferentially towards hosts. The predicted dynamics of pest control using the spatial moqel were highly dependent on the degree of nematode dispersal, host dispersal and the attraction of nematode infective juveniles towards hosts. The overall findings of this thesis have been placed in the context of epidemiological models created elsewhere, and predict that entomopathogenic nematodes may be targeted to specific pest systems with a high degree of success. An understanding of the infection biology of these nematode species is crucial in determining how and when pests may be controlled, and equally importantly, which systems successful control is not predicted.
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Xia, Jianhong, and not supplied. "Modelling the spatial-temporal movement of tourists." RMIT University. Mathematical and Geospatial Sciences, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080110.161021.
Повний текст джерелаАнотація:
Tourism is one of the most rapidly developing industries in the world. The study of spatio-temporal movement models of tourists are undertaken in variety of disciplines such as tourism, geography, mathematics, economics and artificial intelligence. Knowledge from these different fields has been difficult to integrate because tourist movement research has been conducted at different spatial and temporal scales. This thesis establishes a methodology for modelling the spatial-temporal movement of tourists and defines the spatial-temporal movement of tourists at both the macro and micro level. At the macro level, the sequence of tourist movements is modelled and the trend for tourist movements is predicted based on Markov Chain theory (MC). Log-linear models are then adopted to test the significance of the movement patterns of tourists. Tourism market segmentation based on the significant movement patterns of tourists is implemented using the EM (Expectation-Maximisation) algorithm. At the micro level, this thesis investigates the wayfinding decision-making processes of tourists. Four wayfinding models are developed and the relationships between the roles of landmarks and wayfinding decision-making are also discussed for each type of the wayfinding processes. The transition of a tourist movement between the macro and micro levels was examined based on the spatio-temporal zooming theory. A case study of Phillip Island, Victoria, Australia is undertaken to implement and evaluate the tourist movement models established in this thesis. Two surveys were conducted on Phillip Island to collect the macro and micro level movement data of tourists. As results show particular groups of tourists travelling with the same movement patterns have unique characteristics such as age and travel behaviours such as mode of transport. Effective tour packages can be designed based on significant movement patterns and the corresponding target markets. Tourists with various age groups, residency, gender and different levels of familiarity with physical environment have different wayfinding behaviours. The results of this study have been applied to tourism management on Phillip Island and the novel methods developed in this thesis have proved to be useful in improving park facilities and services provided to tourists, in designing tour packages for tourism market promotion and in understanding tourist wayfinding behaviours.
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Osnas, Erik E. "Temporal and spatial structure of waterfowl communities." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ30815.pdf.
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Geberl, Cornelia. "Spatial and temporal resolution of bat sonar." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-160582.
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Chorley, N. "Spatial and temporal analysis of sunspot oscillations." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/47200/.
Повний текст джерелаАнотація:
Sunspots are the most conspicuous feature seen on the solar photosphere and are manifestations of the solar magnetic field. Their study, then, may provide us with a greater understanding of the dynamo mechanism thought to be responsible for the generation of this field. In this thesis, the oscillations of sunspots are studied by making use of observational data from two instruments: the Nobeyama Radioheliograph (NoRH) and the Solar Optical Telescope (SOT) on board the Hinode spacecraft. First, a study of long period oscillations was undertaken in which two long period peaks (P > 10 min) were identified in the power spectra of time series generated from sets of images of 3 sunspots observed with NoRH. In addition, by using the techniques of period, power, correlation and lag mapping, it was found that the power in each of these peaks was concentrated over the umbral regions and that there were two regions of approximately equal size oscillating in anti-phase with each other. It was suggested that these properties could be signatures of a "shallow" sunspot. A follow-up study was then performed, in which the lifetimes of the long period oscillations were investigated over a period of 9 days. These oscillations were seen to dominate the spectra during this interval and the periods and amplitudes were stable during that time. A simple model of a damped, driven simple harmonic oscillator (in which the driving term was nonlinear) was proposed to explain the generation and support of the oscillations. Finally, a study of the spatial properties of the 3 minute oscillations was performed by applying the mapping techniques mentioned above to Hinode/SOT data. The distributions of power and lag of maximum correlation coefficient were found to be non-uniform over the sunspots under study and this may be indicative of inhomogeneities of the physical quantities in the structures.
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Richardson, Thomas Owen. "Spatial and temporal organisation within ant societies." Thesis, University of the West of England, Bristol, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.557142.
Повний текст джерелаАнотація:
In this thesis the organisation of colonies of the ant, Temnothorax albipennis, is investigated with a special focus on their spatial and temporal statistics. Individual-based modelling combined with analyses of experimental data are used extensively to infer the mechanisms that govern individual and collective behaviour. The unequal allocation of labour amongst different individuals, as manifested in skewed distributions of activity, is ubiquitous within the social insects. Early non-spatial individual-based models demonstrated that such skewed divisions of labour can self- organise through the interaction of fluctuating levels of stimuli associated with a task, with differentially sensitive agents that perform work upon the stimulus. Here, that modelling framework is extended by explicitly including space. This modification induces a 'percolation' effect, in which small differences amongst agents in their response thresholds, are related to large differences in their probabilities of performing work. The extension of the original fixed-threshold models of Division of Labour to include space means that they can be treated as a special case of diffusion in disordered media - a well studied branch of statistical mechanics. Staying at home to care for young or leaving to find food is one of the most fundamental divisions of labour. Here the rate of departures from ant nests and the collective activity of the individuals within the nest, are experimentally quantified. Both the rate of nest-leaving, and the inside-nest activity showed a non-linear decline over time. This and other results indicates that fluctuating record signals and repulsive ant-ant interactions play a significant role in colony organisation. A record signal is a new 'high water mark' in the history of a system. The dynamics of several complex but purely physical systems are also based on record signals but this is the first time they have been experimentally shown in a biological system. Finally, the generation of spatial pattern formation is experimentally investigated In the context of resilience to perturbations. The brood within the ant colony is often sorted into an intricate annular pattern, according to the developmental stage of the various rood types. Even after the pattern is completely destroyed, the workers are able to re-establish the pattern. The dynamics of this process of re-emergence is quantified in detail. Lastly, the possible utility of the pattern as a spatial cue to the workers is discussed.
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White, Andrew. "Temporal and spatial dynamics of ecological systems." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338459.
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Alqarni, M. S. "Spatial temporal distribution of helical gyrotactic swimmers." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3024800/.
Повний текст джерелаАнотація:
We consider a spherical swimmer that undergoes helical motion due to the existence of a propulsive torque which is not parallel to a propulsive force that pulls the cell through the fluid. In addition, the cell is bottom-heavy; the centre of gravity is offset from the centre of buoyancy which generates a gravitational torque. In the presence of shear, fluid viscosity generates a further torque. Because cells swim at low Reynolds number, these torques are balanced. This thesis extends the model developed in Bearon (2013) in two distinct directions. Firstly, we consider an extension to the case of a flow where the shear varies with position. We consider a downward flow in a vertical channel. We observe that depending on the parameters, cells may exhibit the classical accumulation towards the centre of the channel or display a new focussing away from the centre. Secondly, we develop the model to describe randomness associated with changes in cell orientation. This is done by developing a Fokker-Planck equation for helical swimmers in terms of Euler angles. The classical Fokker-Planck equation obtained by Pedley and Kessler (1992) is a special case of the equation derived in this thesis. To implement this model numerically as an individual based model, we derive the corresponding stochastic differential equations. The Fokker-Planck equation and stochastic differential equation are extended to examine the spatial-temporal distribution of helical swimmers. We explore in detail how the horizontal distribution of cells in channel flow evolves to an equilibrium state, and how the evolution depends on the model parameters. For non-helical swimmers, we compare the result of the model to the recent experiments of Croze et al (2017).
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Walford, Hannah Louise. "Spatial and temporal variation of African epeirogeny." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620082.
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Crema, E. R. "Spatial and temporal models of Jomon settlement." Thesis, University College London (University of London), 2013. http://discovery.ucl.ac.uk/1382589/.
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The Jomon culture is a tradition of complex hunter-gatherers which rose in the Japanese archipelago at the end of the Pleistocene (ca. 13,000 cal BP) and lasted until the 3rd millennium cal BP. Recent studies increasingly suggest how this long cultural persistence was characterised by repeated episodes of change in settlement pattern, primarily manifested as cyclical transitions between nucleated and dispersed distributions. Although it has been suggested that these events correlate with population dynamics, shifts in subsistence strategies, and environmental change, to date there have been very few attempts to provide a quantitative analysis of spatio-temporal change in Jomon settlement and its possible causes. This thesis is an attempt to fill that lacuna by adopting a twin-track approach to the problem. First, two case studies from central Japan have been examined using a novel set of methods, which have been specifically designed to handle the intrinsic chronological uncertainty which characterises most prehistoric data. This facilitated the application of a probabilistic framework for quantitatively assessing the available information, making it possible to identify alternating phases of nucleated and dispersed pattern during a chronological interval between 7000 and 3300 cal BP. Second, computer simulation (by means of an agent-based model) has been used to carry out a formal inquiry into the possible underlying processes that might have triggered the observed changes in the settlement pattern. The aim of this simulation exercise was two-fold. First, it has been used as a theory-building tool, combining several models from behavioural ecology and cultural transmission theory in order to provide explicit expectations in relation to the presence and absence of environmental disturbances. Second, the outcome of the simulation has been used as a template for linking the observed patterns to possible underlying socio-ecological processes suggested by the agent-based model. This endeavour has shown how some of the largest changes in the empirically observed settlement patterns can be simulated as emerging from the internal dynamics of the system rather than necessarily being induced by external changes in the environment.
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Jiang, Bihan. "Spatial and temporal analysis of facial actions." Thesis, Imperial College London, 2014. http://hdl.handle.net/10044/1/25002.
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Facial expression recognition has been an active topic in computer vision since 90s due to its wide applications in human-computer interaction, entertainment, security, and health care. Previous works on automatic analysis of facial expressions have focused mostly on detecting prototypic expressions of basic emotions like happiness and anger. In contrast, the Facial Action Coding System (FACS) is one of the most comprehensive and objective ways to describe facial expressions. It associates facial expressions with the actions of the muscles that produce them by defining a set of atomic movements called Action Units (AUs). The system allows any facial expressions to be uniquely described by a combination of AUs. Over the past decades, extensive research has been conducted by psychologists and neuroscientists on various applications of facial expression analysis using FACS. Automating FACS coding would make this research faster and more widely applicable, opening up new avenues to understanding how we communicate through facial expressions. Morphology and dynamics are the two aspects of facial actions, that are crucial for the interpretation of human facial behaviour. The focus of this thesis is how to represent and learn the rich facial texture changes in both the spatial and temporal domain. The effectiveness of spatial and spatio-temporal facial representations and their roles in detecting the activation and temporal dynamics of facial actions are explored. In the spatial domain, a novel feature extraction strategy is proposed based on a heuristically defined regions from which a separate classifier is trained and fused in the decision-level. In the temporal domain, a novel dynamic appearance descriptor is presented by extending the static appearance descriptor Local Phase Quantisation (LPQ) to the temporal domain by using the Three Orthogonal Planes (TOP). The resulting dynamic appearance descriptor LPQ-TOP is applied to detect the latent temporal information representing facial appearance changes and explicitly model facial dynamics of AUs in terms of their temporal segments. Finally, a parametric temporal alignment method is proposed. Such strategy can accommodate very flexible time warp functions and is able to deal with both sequence-to-sequence and sub-sequence alignment. This method also opens up a new approach to the problem of AU temporal segment detection. This thesis contributes to facial action recognition by modelling the spatial and temporal texture changes for AU activation detection and AU temporal segmentation. We advance the performance of state-of-the-art facial action recognition systems and this has been demonstrated on a number of commonly used databases.
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Monteiro, Fernando C. "Region-based spatial and temporal image segmentation." Doctoral thesis, Universidade do Porto, Faculdade de Engenharia, 2008. http://hdl.handle.net/10198/1835.
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This work discusses region-based representations for image and video sequence segmentation. It presents effective image segmentation techniques and demonstrates how these techniques may be integrated into algorithms that solve some of the motion segmentation problems. The region-based representation offers a way to perform a first level of abstraction and to reduce the number of elements to process with respect to the classical pixel-based representation.
Motion segmentation is a fundamental technique for the analysis and the understanding of image sequences of real scenes. Motion segmentation 'describes' the sequence as sets of pixels moving coherently across one sequence with associated motions. This description is essential to the identification of the objects in the scene and to a more efficient manipulation of video sequences.
This thesis presents a hybrid framework based on the combination of spatial and motion information for the segmentation of moving objects in image sequences accordingly with their motion. We formulate the problem as graph labelling over a region moving graph where nodes correspond coherently to moving atomic regions. This is a flexible high-level representation which individualizes moving independent objects. Starting from an over-segmentation of the image, the objects are formed by merging neighbouring regions together based on their mutual spatial and temporal similarity, taking spatial and motion information into account with the emphasis being on the second. Final segmentation is obtained by a spectral-based graph cuts approach.
The initial phase for the moving object segmentation aims to reduce image noise without destroying the topological structure of the objects by anisotropic bilateral filtering. An initial spatial partition into a set of homogeneous regions is obtained by the watershed transform. Motion vector of each region is estimated by a variational approach. Next a region moving graph is constructed by a combination of normalized similarity between regions where mean intensity of the regions, gradient magnitude between regions, and motion information of the regions are considered. The motion similarity measure among regions is based on human perceptual characteristics. Finally, a spectral-based graph cut approach clusters and labels each moving region.
The motion segmentation approach is based on a static image segmentation method proposed by the author of this dissertation. The main idea is to use atomic regions to guide a segmentation using the intensity and the gradient information through a similarity graph-based approach. This method produces simpler segmentations, less over-segmented and compares favourably with the state-of-the-art methods. To evaluate the segmentation results a new evaluation metric is proposed, which takes into attention the way humans perceive visual information.
By incorporating spatial and motion information simultaneously in a region-based framework, we can visually obtain meaningful segmentation results. Experimental results of the proposed technique performance are given for different image sequences with or without camera motion and for still images. In the last case a comparison with the state-of-the-art approaches is made.
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Smith, Elizabeth M. "Spatial and temporal regulation of IL4Rα expression". Doctoral thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/3117.
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Includes abstract.In this study, we generated a new mouse model, which allows both inducible and cell-specific deletion and reconstitution of IL-IL4Rα expression. This model has the potential to add a new dimension to our understanding of IL4Rα biology. This has been achieved by using the established Tet System (Goosen and Bujard, 1992) where the crossing of two complementary transgenic mouse lines enable the generation of the final double transgenic model. The first line expresses the transactivator, tTA, from the Tet-Off expression cassette driven by the Vav hemapoeitic specific promoter (Wiesner et al., 2005).
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Loach, Daniel. "Inhibitory processes in temporal selection." Thesis, Bangor University, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275136.
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Ralley, Richard. "Spatial constraints on attention." Thesis, University of Hertfordshire, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302301.
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Bränd, Stefan. "Using Rigid Landmarks to Infer Inter-Temporal Spatial Relations in Spatio-Temporal Reasoning." Thesis, Linköpings universitet, Artificiell intelligens och integrerad datorsystem, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-124064.
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Spatio-temporal reasoning is the area of automated reasoning about space and time and is important in the field of robotics. It is desirable for an autonomous robot to have the ability to reason about both time and space. ST0 is a logic that allows for such reasoning by, among other things, defining a formalism used to describe the relationship between spatial regions and a calculus that allows for deducing further information regarding such spatial relations. An extension of ST0 is ST1 that can be used to describe the relationship between spatial entities across time-points (inter-temporal relations) while ST0 is constrained to doing so within a single time-point. This allows for a better ability of expressing how spatial entities change over time. A major obstacle in using ST1 in practise however, is the fact that any observations made regarding spatial relations between regions is constrained to the time-point in which the observation was made, so we are unable to observe inter-temporal relations. Further complicating things is the fact that deducing such inter-temporal relations is not possible without a frame of reference. This thesis examines one method of overcoming these problems by considering the concept of rigid regions which are assumed to always be unchanging and using them as the frame of reference, or as landmarks. The effectiveness of this method is studied by conducting experiments where a comparison is made between various landmark ratios with respect to the total number of regions under consideration. Results show that when a high degree of intra-temporal relations are fully or partially known, increasing the number of landmark regions will reduce the percentage of inter-temporal relations to be completely unknown. Despite this, very few inter-temporal relations can be fully determined even with a high ratio of landmark regions.
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Heuermann, Heike. "Spatial and temporal factors in visual auditory interaction." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=967796601.
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Haakonsen, Trond Arve. "Temporal and Spatial Analyses of Continuous GPS Observations." Doctoral thesis, Norwegian University of Science and Technology, Department of Civil and Transport Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-663.
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The objective of this thesis is to increase the understanding of land motion, using statistical analysis of the available three-dimensional (3-D) time series from Continuously operated Global Positioning System stations (CGPS). A primary goal has been to search for new procedures and determine a spectrum of univariate CGPS time series. A new program package has been developed for adjustment and spectral analysis of the CGPS time series for possible future studies. This will take into account the possibility of weighting and managing, non-stationary and time series with missing data. The least squares spectrum and its relation to covariance and correlation functions are explained in detail. Different estimation methods of such functions that are used to visualise temporal correlations have been tested. A challenge of the work has been the handling data jumps revealed in the numerical investigations, that vitally affect the estimation of correlation functions and spectra.
The work has also included numerical analyses of two independently pre-processed data sets from a Norwegian and a European network of CGPS. The spectral analysis has shown large contributions of annual cycles for most series. In addition semi-annual and three-month cycles have been found. After the removal of these effects, the resulting spectra estimated from the residual series of CGPS time series shows similarities with Markov-processes that are closely related to white noise processes. The detection of a Chandler-like period is more surprising because this period should have been corrected for in the pre-processing stage of CGPS time series. A Principal Component Analysis (PCA) has been implemented to determine the spatial pattern of CGPS data. So far this has not been performed either for a network of Norwegian CGPS stations or for a network covering the whole of Europe. The results from both analyses confirm that the first mode obtained up to 50 percent of the overall variance in all station series. In addition to a high inter-station correlation, only slightly decreasing as a function of distance, this implies at least one common effect for the entire network. The spatial and partially temporal pattern for the first three modes in CGPS data show similarity with corresponding modes extracted from predictions of atmospheric loading of surface displacements. These relations have been further investigated for the purpose of deriving possible model relations. Numerical investigations using the derived models to correct the CGPS data for the atmospheric loading effect have shown a possible sample variance reduction of up to 10 percent for the vertical component of CGPS data.
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Thompson, Phil. "The spatial and temporal evolution of submarine channels." Thesis, University of Aberdeen, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549064.
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Johnson, David. "The spatial and temporal variability of nearshore currents." University of Western Australia. Centre for Water Research, 2004. http://theses.library.uwa.edu.au/adt-WU2004.0067.
Повний текст джерелаАнотація:
The nearshore current field, defined here as the residual horizontal flow after averaging over the incident wave period, exhibits variability at a range of time and space scales. Some of the variable currents are low frequency gravity wave motions. However, variable, rotational (in the sense of possessing vertical vorticity) flow can also exist as part of the overall nearshore current field. A field and numerical modelling investigation of these variable rotational currents has been carried out. Drifters, which were developed for surfzone use, enabled measurement of the nearshore current structure; the design and testing of these new instruments is described. Two sets of field measurements, using the new drifters and Eulerian instruments were carried out for conditions with swell perpendicular to a plane beach and in strong longshore currents. In the perpendicular swell conditions, an interesting and well-defined feature of the measured trajectories was the development of transient rip currents. Discrete vortices were also observed. In the longshore current case, trajectories with the longshore current displacement removed had complex meandering paths. Lagrangian data were used to make estimates of length scales and dispersion, both of which provide strong evidence that the current field cannot be due to low frequency gravity waves alone. Under the assumption of equipartition of kinetic and potential energy for low frequency gravity waves, Eulerian measurements of velocities and pressure show significant energy due to non-divergent, rotational flow in both the perpendicular swell and longshore current case. A numerical model that can simulate horizontal flow with a directionally spread, random wave field incident on a plane beach was implemented. The model developed transient rip currents that are qualitatively very similar to those seen in the drifter trajectories from the field. The number and intensity of rip currents in the model depended on the beach slope and incident wave spectra. The energy content and cross-shore flux (and hence transport of material) of the rotational current flow component in the simulated flow fields is comparable to that due to low frequency gravity waves. The modelling also provided some evidence that there may be universal characteristics of the rotational currents. The field results and modelling show that variable rotational currents are ubiquitous in the field even when longshore currents and hence shear waves are not present. The term “infragravity turbulence” is suggested to describe the general class of nearshore hydrodynamics not directly associated with shear waves, which is largely disorganised, but contains well defined features such as transient rips currents and large scale horizontal vortices. The results have important implications in the understanding of the transport of material, including sediment, biological material, pollution, and sometimes bathers, in the nearshore zone.
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Clubb, Bryan H. "Spatial and temporal distribution of perinuclear actin shells." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq31094.pdf.
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White, Gentry. "Bayesian semiparametric spatial and joint spatio-temporal modeling." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4450.
Повний текст джерелаАнотація:
Thesis (Ph.D.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (May 2, 2007) Vita. Includes bibliographical references.
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Zhang, Xin. "Spatial and temporal phosphoregulation of MCAK during mitosis." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3264319.
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Thesis (Ph.D.)--Indiana University, Dept. of Biology, 2007.Source: Dissertation Abstracts International, Volume: 68-05, Section: B, page: 2766. Adviser: Claire E. Walczak. "Title from dissertation home page (viewed Jan. 24, 2008)."
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Bamatraf, Abdurhman Mohamed. "Temporal and spatial relationships of canopy spectral measurements." Diss., The University of Arizona, 1986. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1986_25_sip1_w.pdf&type=application/pdf.
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Hostetter, Michael. "Analogical representation in temporal, spatial, and mnemonic reasoning." Thesis, This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-03242009-040545/.
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Owens, Eli Thomas. "Investigating Granular Structure with Spatial and Temporal Methods." Thesis, North Carolina State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3538538.
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This dissertation reports studies of the internal structure of jammed granular materials and how granular sound propagation and vibrational modes are influenced by disorder in particle positions and contact forces. We investigate the role of particle scale forces on sound amplitude and speed, how to characterize the bulk pressure via the density of states, and force network modularity. We perform our experiments on a vertical, 2D, photoelastic granular material. Acoustic waves are excited from the bottom of the system and observed via particle scale sensors and a high speed camera. This novel combination of spatial and temporal measurements allows us to observe the role of force chains in sound propagation. The sound amplitude is largest through particles with strong contact forces, and we see that sound travels fastest along high force paths, giving rise to multiple sound speeds. Combining acoustic excitations with a method from thermal physics, we developed a new method to measure the density of modes, D(f). From D( f), we define a critical frequency, fc, that scales with the bulk pressure, and comparing D( f) to Debye scaling, we find an excess of low frequency modes. Disorder in the force chain network and particle configurations plays a crucial role in D(f), as Debye scaling is only recovered for high pressure, hexagonally ordered packings. Finally, we characterize the force network by dividing it into modules of highly connected nodes. These communities become progressively more ordered as the pressure on the system is increased and the force chains become more uniform. Together, these studies illustrate the importance of the force chains in understanding static and dynamic granular properties.
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Pan, Feifei. "Spatial and temporal structures of soil moisture fields." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/32842.
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Barry, Jon. "Spatial and temporal statistics in the environmental sciences." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337435.
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Richardson, Jennifer. "Topics in statistics of spatial-temporal disease modelling." Thesis, Durham University, 2009. http://etheses.dur.ac.uk/2122/.
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This thesis is concerned with providing further statistical development in the area of space-time modelling with particular application to disease data. We briefly consider the non-Bayesian approaches of empirical mode decomposition and generalised linear modelling for analysing space-time data, but our main focus is on the increasingly popular Bayesian hierarchical approach and topics surrounding that. We begin by introducing the hierarchical Poisson regression model of Mugglin et al. [36] and a data set provided by NHS Direct which will be used to illustrate our results through-out the remainder of the thesis. We provide details of how a Bayesian analysis can be performed using Markov chain Monte Carlo (MCMC) via the software LinBUGS then go on to consider two particular issues associated with such analyses. Firstly, a problem with the efficiency of MCMC for the Poisson regression model is likely to be due to the presence of non-standard conditional distributions. We develop and test the 'improved auxiliary mixture sampling' method which introduces auxiliary variables to the conditional distribution in such a way that it becomes multivariate Normal and an efficient block Gibbs sampling scheme can be used to simulate from it. Secondly, since MCMC allows modelling of such complexity, inputs such as priors can only be elicited in a casual way thereby increasing the need to check how sensitive our output is to changes to the prior. We therefore develop and test the 'marginal sensitivity' method which, using only one MCMC output sample, quantifies how sensitive the marginal posterior distributions are to changes to prior parameters
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Addison, W. D. "Blind source separation using spatial and temporal priors." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.525254.
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Dimitriou-Fakalou, Chrysoula. "Statistical inference for spatial and spatio-temporal processes." Thesis, London School of Economics and Political Science (University of London), 2006. http://etheses.lse.ac.uk/2006/.
Повний текст джерелаАнотація:
First, the time series analysis was widely introduced and used in the statistical world. Next, the analysis of spatio-temporal processes has followed, which is taking into account not only when, but also where the phenomenon under observation is taking place. We mainly focus on stationary processes that are assumed to be taking place regularly over both time and space. We examine ways of estimating the parameters involved, without the risk of coming up with a very large bias for our estimators; the bias is the typical problem of estimation for the parameters of stationary processes on Zd, for any d > 2. We particularly study the cases of spatio-temporal ARMA processes and spatial auto-normal formulations on Zd. For both cases and any positive integer d, we propose estimators that are consistent, asymptotically unbiased and normal, if certain conditions are satisfied. We do not only study the spatio-temporal processes that are observed regularly over space, but also those, for which we have recordings on a fixed number of locations anywhere. We might follow the route of a multivariate time series methodology then. Thus, the asymptotic behavior of the estimators proposed might be analyzed as the number of recordings over time only tends to infinity.
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Shou, Yutao Sindy, and 壽玉濤. "Efficient query processing for spatial and temporal databases." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2004. http://hub.hku.hk/bib/B29853655.
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Kiyosugi, Koji. "Temporal and Spatial Analysis of Monogenetic Volcanic Fields." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4101.
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Achieving an understanding of the nature of monogenetic volcanic fields depends on identification of the spatial and temporal patterns of volcanism in these fields, and their relationships to structures mapped in the shallow crust and inferred in the deep crust and mantle through interpretation of geochemical, radiometric and geophysical data.
We investigate the spatial and temporal distributions of volcanism in the Abu Monogenetic Volcano Group, Southwest Japan. E-W elongated volcano distribution, which is identified by a nonparametric kernel method, is found to be consistent with the spatial extent of P-wave velocity anomalies in the lower crust and upper mantle, supporting the idea that the spatial density map of volcanic vents reflects the geometry of a mantle diapir. Estimated basalt supply to the lower crust is constant. This observation and the spatial distribution of volcanic vents suggest stability of magma productivity and essentially constant two-dimensional size of the source mantle diapir.
We mapped conduits, dike segments, and sills in the San Rafael sub-volcanic field, Utah, where the shallowest part of a Pliocene magmatic system is exceptionally well exposed. The distribution of conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. The comparison of San Rafael conduit distribution and the distributions of volcanoes in several recently active volcanic fields supports the use of statistical models, such as nonparametric kernel methods, in probabilistic hazard assessment for distributed volcanism.
We developed a new recurrence rate calculation method that uses a Monte Carlo procedure to better reflect and understand the impact of uncertainties of radiometric age determinations on uncertainty of recurrence rate estimates for volcanic activity in the Abu, Yucca Mountain Region, and Izu-Tobu volcanic fields. Results suggest that the recurrence rates of volcanic fields can change by more than one order of magnitude on time scales of several hundred thousand to several million years. This suggests that magma generation rate beneath volcanic fields may change over these time scales. Also, recurrence rate varies more than one order of magnitude between these volcanic fields, consistent with the idea that distributed volcanism may be influenced by both the rate of magma generation and the potential for dike interaction during ascent.
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Robinzonov, Nikolay. "Advances in boosting of temporal and spatial models." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-153382.
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Boosting is an iterative algorithm for functional approximation and numerical optimization which can be applied to solve statistical regression-type problems. By design, boosting can mimic the solutions of many conventional statistical models, such as the linear model, the generalized linear model, and the generalized additive model, but its strength is to enhance these models or even go beyond. It enjoys increasing attention since a) it is a generic algorithm, easily extensible to exciting new problems, and b) it can cope with``difficult'' data where conventional statistical models fail. In this dissertation, we design autoregressive time series models based on boosting which capture nonlinearity in the mean and in the variance, and propose new models for multi-step forecasting of both.
We use a special version of boosting, called componentwise gradient boosting, which is innovative in the estimation of the conditional variance of asset returns by sorting out irrelevant (lagged) predictors. We propose a model which enables us not only to identify the factors which drive market volatility, but also to assess the specific nature of their impact. Therefore, we gain a deeper insight into the nature of the volatility processes. We analyze four broad asset classes, namely, stocks, commodities, bonds, and foreign exchange, and use a wide range of potential macro and financial drivers. The proposed model for volatility forecasting performs very favorably for stocks and commodities relative to the common GARCH(1,1) benchmark model. The advantages are particularly convincing for longer forecasting horizons. To our knowledge, the application of boosting to multi-step forecasting of either the mean or the variance has not been done before.
In a separate study, we focus on the conditional mean of German industrial production. With boosting, we improve the forecasting accuracy when compared to several competing models including the benchmark in this field, the linear autoregressive model. In an exhaustive simulation study we show that boosting of high-order nonlinear autoregressive time series can be very competitive in terms of goodness-of-fit when compared to alternative nonparametric models.
Finally, we apply boosting in a spatio-temporal context to data coming from outside the econometric field. We estimate the browsing pressure on young beech trees caused by the game species within the borders of the Bavarian Forest National Park ``Bayerischer Wald,'' Germany. We found that using the geographic coordinates of the browsing cases contributes considerably to the fit. Furthermore, this bivariate geographic predictor is better suited for prediction if it allows for abrupt changes in the browsing pressure.
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Soybali, Hasan Huseyin. "Temporal and spatial aspects of tourism in Turkey." Thesis, Bournemouth University, 2005. http://eprints.bournemouth.ac.uk/451/.
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Tourism supply and demand varies from one region to another and from one season to another in many destination countries. These variations provide certain benefits as well as problems and disadvantages. The developing countries need balanced development more than others as they need scarce resources of tourism, such as the natural environment, today as well as in the future, to be able to sustain the economy and the nation. The first chapter explains the need for this study, its aims and objectives together with detailed information about general outlook of Turkey and tourism development. As a developing country, despite its short history of mass tourism movements, Turkey has experienced massive growth in tourism and the effects of variations in time and place since the 1980s.Spatial and temporal variations in Turkish tourism have increased and tourism movements are concentrated increasingly in the coastal regions of the Mediterranean and Aegean and in the peak season between May and October since the late 1980s,while other regions and off-season are neglected. This reflects partly the basic structure of tourism demand towards Turkey and most importantly a lack of a national tourism policy and the failure of present policy and strategies to combat the potentially damaging effects of tourism on social and environmental resources and increase and spread the benefits of tourism as much as possible The second chapter tries to put temporal and spatial imbalance in general and in Turkey into perspective. Turkey has great unspoiled natural,cultural and historical resources and potential which will allow Turkey to develop supply-led tourism products as well as demand-led products and to combine both products in order to create market-led products, improving the uneven temporal and spatial distribution of tourism. After describing the methodology in the third chapter, the fourth chapter identifies the demographic and motivational characteristics and the reasons behind their seasonal and spatial preferences which indicate that each shoulder and each destination has its own segment. Regional tourism development policies, strategies and plans with goals to reduce both spatially and seasonally uneven distribution of tourism should be introduced. The tourism industry indicates great importance for Turkey and specifically for less-developed tourism regions of Turkey due to its unique advantages. The fifth chapter discusses the effects of temporal and spatial disparity in Turkey, explores the development and marketing options available for developing tourism destinations to follow, such as, encouraging tourism in certain regions by giving incentives, completing infra- and super-structure and promoting and marketing currently available and potential tourism products in those regions or encouraging tourism in all regions regardless of the type and location of products. It is obvious that there is a relationship between temporal and spatial imbalance. Therefore, understanding these relationships can and will help to achieve better balanced tourism development and management in Turkey, as well as other developing destinations.The development of Turkish tourism is still at its early stage and appropriate actions against present and future problems can prevent or avoid tomorrow's difficulties. This study aims to identify and diagnose spatial and temporal problems and the relationships between these two problems and contribute to the tourism industry by developing effective development and marketing strategies.