Tesi: "Root modelling"

1

Moore, Simon Patrick Merewether. "Spatiotemporal modelling of hormonal crosstalk in the Arabidopsis root". Thesis, Durham University, 2018. http://etheses.dur.ac.uk/12624/.

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Plant development, growth and response to varying environmental conditions, involves a complex network of overlapping interactions between plant signalling hormones and gene expression, known as ‘CROSSTALK’, which controls cell proliferation, elongation and differentiation. Hormone response, concentrations and gene expression levels vary through the root tip and display patterning, which ultimately drives development; however, little is known about how this is established. Models have been constructed to explain patterning, including a ‘physical’ auxin flux model in a simple rectangular 2-D multicellular Arabidopsis root which excludes crosstalk (Grieneisen et al., 2007), and a single cell ‘biological crosstalk’ model of multiple hormone and protein interactions in WT and mutants (Liu et al., 2010; Liu et al., 2013). The project goal was to combine these approaches by embedding the single cell biological crosstalk relationships into a 2-D multicellular root structure to reproduce experimentally observed hormone and gene expression patterning. An initial model was constructed and parameter values calibrated to meet fit criteria and produce a WT parameter set. The model proved robust to parameter variation, indicating that results did not rely on unique parameter value selections. Model results were compared to experimental data to test predictive capability and matched experimentally observed patterning and concentration trends for most species and mutants. A more realistic digital root map was then developed with additional auxin carriers to allow improved comparison between model and experimental images at a cell-scale level. The roles of auxin influx and efflux carriers in regulating auxin patterning were investigated by developing a ‘Recovery Principle’, where pattern perturbations due to changes in one carrier set could be recovered by adjustments to the other carrier set. Finally, using additional experimental data from the literature, the crosstalk network was revised to produce more representative cytokinin patterning. The model provides an explanation of crosstalk control of gene expression and patterning, and forms a foundation for future expansion of hormonal crosstalk and gene expression modelling in the Arabidopsis root. In summary, this project has developed predictive models to further explore hormone and gene expression levels and spatiotemporal pattern formation in the Arabidopsis thaliana root tip.

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2

Livingstone, D. "Modelling cell proliferation in a structured tissue". Thesis, University of Reading, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379764.

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3

Thor, Magnus. "Heterobasidion root rot in Norway spruce : modelling incidence, control efficacy and economic consequences in Swedish forestry /". Uppsala : Department of Forest Mycology and Pathology, Swedish University of Agricultural Sciences, 2005. http://epsilon.slu.se/200505.pdf.

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4

Mao, Zhun. "Temporal and spatial modelling of root reinforcement in natural montane and subalpine forests". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20118.

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Il est généralement admis que la végétation peut stabiliser les pentes naturelles et artificielles contre les glissements de terrain superficiel. Par rapport au rôle mécanique, les racines renforcent le sol d'une pente en fournissant une cohésion additionnelle (cr). La quantification des cr est une étape essentielle pour évaluer la stabilité des pentes, quantifiée par le facteur de sécurité (FoS, défini par le ratio entre les forces de la résistance et les forces motrices sur une pente). La plupart des modèles prédictifs de cr existants ne prennent pas en compte la dynamique racinaire à l'échelle spatiale et temporelle qui peut conduire à une hétérogénéité de renforcement des racines. Ainsi, cette thèse vise à caractériser, quantifier et modéliser la répartition spatiale et temporelle de la dynamique racinaire ainsi que son impact sur la cr estimée. La distribution, croissance et mortalité racinaire ont été échantillonnées à l'aide de monolithes et de rhizotrons à deux altitudes dans des forêts mixtes et naturellement régénérées dans les Alpes françaises, composées d'îlots et de trouées. Avec les méthodes de modélisation statistique, une série de facteurs abiotiques et biotiques affectant la dynamique racinaire ont été étudiés. Pour quantifier les cr, une méta-analyse a été effectuée et les divers algorithmes de modélisation ont été employés et leurs résultats comparés. Cette étude a montré que: (i) dans un écosystème à espèces mixtes, la densité racinaire influence davantage les cr que les propriétés de la qualité racinaire; (ii) tous les facteurs abiotiques (altitude, paysage écologique, profondeur du sol et mois) peuvent faire varier la densité racinaire selon des conditions différentes du sol ; (iii) lors de l'observation de 1,5 ans à l'aide de rhizotrons, le cr augmente continuellement, rapidement dans la saison active et lentement pendant la saison dormante, mais cette augmentation est dépendante de la profondeur du sol, de l'altitude et du patch écologique ; (iv) malgré le fait que les racines les plus fines (]0, 1] mm en diamètre) soient les plus actives dans le cycle de nutritions et de carbone (selon des publications précédentes), elles contribuent peu au renforcement mécanique de terrain. Cette étude a permis d'élargir et d'approfondir nos connaissances sur le rôle des racines dans l'éco-ingénierie
It is largely recognized that vegetation can stabilize artificial and natural slopes against shallow landslides. Mechanically, plant roots reinforce soil on a slope by providing an additional cohesion (cr). Quantification of cr is a key step to estimate the stability of a given slope, usually quantified by the Factor of Safety (FoS, deﬁned as the ratio between resisting forces and the driving forces on a slope). Most existing cr predictive models do not take into consideration spatial and temporal root dynamics which result in heterogeneous root reinforcement along a vegetated slope. Therefore, this thesis aims to characterize, quantify and model the spatial and temporal patterns in root dynamics and their impact on the estimation of cr. Root distribution, growth and mortality were measured using monoliths and rhizotrons installed at two altitudes in naturally regenerated mixed forests in the French Alps. These forests are composed of trees growing in groups (tree islands) with large gaps between the islands. Using statistical modeling approaches, abiotic and biotic factors affecting root dynamics were investigated. For quantifying cr, a meta-analysis was performed and different modeling algorithms were employed and results compared. Based on these studies, the following conclusions were made: (i) in a mixed, mature forest ecosystem root density influenced cr more than root mechanical properties; (ii) all abiotic factors (altitude, type of vegetation patch, soil depth and month) significantly affected root quantity to different degrees, depending on soil conditions; (iii) during the 1.5 years' observations in rhizotron, cr increased rapidly during the growing season and more slowly in the dormant season but the increment increase was largely dependent on soil depth, altitude and vegetation patch. (iv) The finest roots (]0, 1] mm in diameter), which are considered the most important for nutrient and carbon cycling, contributed little to mechanical reinforcement of the soil. Results are discussed with regard to ecological engineering strategies for unstable slopes

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5

Mellor, Nathan L. "Multiscale modelling of plant hormone signalling : auxin regulated lateral root emergence". Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/30420/.

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The formation of lateral roots is an important post-embryonic developmental process that allows plants to adapt to their environment via exploitation of soil mineral resources. New lateral roots initiate as lateral root primordia (LRP) in the pericycle cell layer adjacent to the central vascular tissue in the primary root, and must pass through the outer cell layers of endodermis, cortex and epidermis to emerge as mature roots. A key regulator of emergence is the plant hormone auxin and it has been shown previously that in Arabidopsis the auxin induced expression of the auxin influx carrier LAX3 in specific cortical cells over LRP is required for emergence to occur, as this leads to the expression of cell wall remodelling enzymes such as polygalacturonase (PG). By developing mathematical models of auxin transport and LAX3 expression the work in the thesis aims to test the existing conceptual models for lateral root emergence, and provide testable hypotheses for the existence of additional gene regulatory components. An initial single cell model demonstrates that hysteresis and bistability may explain the experimentally observed 'all-or-nothing' LAX3 spatial expression pattern in cortical cells containing a gradient of auxin concentrations. By fitting model parameters against experimental data, the model is then used to show that some auxin homeostasis mechanism is present, with both endogenous and exogenous sources of homeostasis investigated. The single cell model also investigates the validity of several alternative gene regulatory networks for LAX3, and its apparent repression by a key mediator of the auxin response, ARF19. Finally, the model is extended to a multicellular context, in which the auxin distribution from a simulated LRP source cell is used as a basis for the expression of LAX3, leading to the expression of PG in specific cells between which the LRP must pass.

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6

Tsegaye, Tezera. "Modelling the effect of variable soil impedance on pea root growth". Thesis, University of Aberdeen, 1992. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU045142.

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Experiments were conducted: (i) to investigate varietal differences in pea (Pisum sativum L.) root response to mechanical impedance, (ii) to study the effect of mechanical impedance on root growth and morphology and (iii) to predict root growth in soils whose mechanical impedance varied temporally and spatially by adapting the Diggle (1988), ROOTMAP, model. Pea varieties whose root growth rates did not differ under unimpeded conditions had their root growth rates reduced by significantly different proportions in response to mechanical impedance. Highly significant correlations between first order lateral elongation rate and diameter were observed for pea roots grown in moist vermiculite. There was also evidence that regular stimulation of the root tip is required to trigger lateral emergence. An experimental procedure for obtaining ROOTMAP input parameters was devised and the growth and distribution of pea roots grown for 29 days in soil whose mechanical impedance varied with time and depth as a result of soil drying out, was successfully predicted. These findings highlight the potential that exists for selecting and breeding varieties based on root characters that confer insensitivity of response to mechanical impedance and for using ROOTMAP to investigate the growth response of different crop varieties in realistic soil scenarios.

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7

Brassett, P. R. "Computer simulation of the take-all disease of winter wheat with particular reference to methodology". Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233678.

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The theory and the practical application of the simulation of root infection of winter wheat by the take-all fungus, Gaeumannomyces graminis var. tritici, are critically evaluated with respect to field epidemics and to infection of seedlings within controlled environments. Several simple models for disease progress in field epidemics are evaluated with respect to field data, including a generalized logistic equation and systems of simple non-linear differential equations, with and without algebraic solutions. An investigation is made of disease heterogeneity in the field and transect data derived from sampling 11,000 plants are analysed for the presence of significant pattern. The effect of the observed spatial heterogeneity on the precision of field data is also empirically investigated. The use of a controlled-environment experiment to model the effect of volunteer infestation on inoculum survival in the field is demonstrated, and a simple model is used to quantitatively estimate the effect of volunteer infestation on inoculum multiplication. Data for a seedling disease epidemic are simulated by three mathematically and computationally diverse simulators derived from a single underlying theoretical model. The first is a complex simulator written in FORTRAN and run on a mainframe computer which resolves the infection process into a number of detailed submodels. The second simulator is written in BBCBASIC and 6502 machine code and makes use of a discrete root map to hold information on host growth and infection. In the third simulator the model is expressed as a series of rate equations and is run on a simulation package on the BBC microcomputer. The simulation techniques used are discussed and evaluated with respect to model development and the descriptive accuracy of the simulators. In conclusion a strategy is proposed for the development of a comprehensive model for field epidemics of take-all by means of controlled-environment experimentation.

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8

Cropp, Roger Allan, e R. Cropp@griffith edu au. "A Biogeochemical Modelling Analysis of the Potential For Marine Ecosystems to Regulate Climate By the Production of Dimethylsulphide". Griffith University. Australian School of Environmental Studies, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030703.101310.

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The potential for life to control its environment was first suggested by Lovelock (1972). Charlson et al (1987) proposed a role for marine planktonic ecosystems in global climate regulation via the production and ventilation to the atmosphere of dimethylsulphide (DMS), a by-product of phytoplankton metabolism. Once in the atmosphere DMS contributes to the formation of cloud condensation nuclei, and increases the amount and brightness of cloud. This affects the albedo of the planet, reflecting more incident sunlight back into space, and cooling the earth. In common with many other 'hypotheses' regarding complex adaptive systems, the hypothesis proposed by Charlson et al (1987) is not experimentally testable. The production and ventilation to the atmosphere of DMS is the result of complex interactions between biological, chemical and physical processes. Consequently, increasing use is being made of mathematical models that simulate these processes to advance understanding of it (Archer et al. 2002). This study examines one of the fundamental mechanisms proposed by the Charlson et al (1987) hypothesis, that increasing global temperatures will lead to increased ventilation of DMS from the ocean to the atmosphere. The study develops one-dimensional biogeochemical models of DMS production by upper ocean ecosystems, based on the model proposed by Gabric et al. (1993b). The models are examined to elucidate their fundamental mathematical properties, and are subjected to sensitivity analysis to identify important processes and parameters. These investigations identify a simpler model that can reproduce the predictions of the Gabric et al. (1993b) model. Predictions derived from model simulations forced by climatologies of measured physical data are compared to a global database of measurements of sea surface DMS concentrations, and to observed depth profiles of DMS in the upper ocean. These comparisons confirm that all models are in good qualitative agreement with measured data. The fifteen global climate prediction models currently in use around the globe all predict substantial warming effects from the ventilation of anthropogenic carbon dioxide to the atmosphere. A simplified DMS model is calibrated to climatologies of Antarctic chlorophyll and DMS data and reproduces the data with great precision. The calibrated model is applied in global warming scenarios to 'test' the efficacy of the mechanism proposed by the Charlson et al (1987) hypothesis. This simulation provides evidence that the response predicted by the hypothesis is indeed feasible, and that substantial increases (up to 45%) in the ventilation of DMS to the atmosphere could be possible in some circumstances. The results of the modelling study provide impetus for further examination of field data. If couplings between marine biota and atmosphere are feasible, then they may be operating contemporarily, and may be detectable. Atmospheric DMS is oxidised to form aerosols (Miller et al. 2002) that influence the aerosol optical depth of the atmosphere. Archives of remote sensed ocean chlorophyll a concentration and aerosol optical depth are examined for evidence of the biologically mediated couplings. A clear coupling between aeolian dust and marine phytoplankton is evident from this analysis, suggesting that the deposition of dust from the atmosphere is a major factor controlling phytoplankton growth in many parts of the ocean. A second coupling between marine phytoplankton and atmospheric aerosols is also detected. This coupling is apparently not related to dust and is symmetrical about the equator, despite the substantial differences in the atmospheres and oceans of each hemisphere. It is speculated that this coupling may reflect the influence of the ventilation of DMS produced by marine phytoplankton on the atmosphere. This thesis provides new evidence supporting the important role of marine ecosystems in global climate regulation by the production of DMS. This evidence is principally obtained from a biogeochemical modelling approach, but is supported by analyses of empirical data. The concordance of results obtained from different approaches suggests that the contribution of marine ecosystems to global climate regulation is real, important and currently active.

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Saario, Seppo Aukusti, e n/a. "FDTD Modelling For Wireless Communications: Antennas and Materials". Griffith University. School of Microelectronic Engineering, 2003. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20030602.101319.

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The application of the finite-difference time-domain (FDTD) method for the numerical analysis of complex electromagnetic problems related to wireless communications is considered. Since exact solutions to many complex electromagnetic problems are difficult, if not impossible, the FDTD method is well suited to modelling a wide range of electromagnetic problems. Structures considered include single and twin-slot antennas for millimetre-wave applications, monopole antennas on mobile handsets and chokes for the suppression of currents on coaxial cables. Memory efficient techniques were implemented for the split-field perfectly matched layer (PML) absorbing boundary condition. The frequency-domain far-field transformations were used for the calculation of far-field radiation patterns. Dipole, slot and mobile handset antenna benchmark problems verified the accuracy of the FDTD implementation. The application of slot antennas for millimetre-wave imaging arrays was investigated. An optimal feed network for an offset-fed single-slot antenna was designed for the X band with numerical and experimental results in excellent agreement. A twin-slot antenna structure reduced surface wave coupling by 7.6 dB in the substrate between coplanar waveguide-fed slot antenna elements in a planar array. The reduction of substrate surface waves for the twin-slot antenna allows for closer element spacings with less radiation pattern degradation in array applications. Suppression techniques for currents flowing on the exterior surface of coaxial cables were investigated. These include the use of ferrite beads and a quarter-wave sleeve balun. The frequency dependent behaviour of ferrite based chokes showed highly resonant effects which resulted in less than 5 dB of isolation at the resonant frequencies of the bead. An analysis of air-gaps between the ferrite bead and cable are shown to be extremely detrimental in the isolation characteristics of ferrite bead chokes. An air-gap of 0.5 mm can reduce the isolation effectiveness of a bead by 20 dB. The first rigorous analysis of a quarter-wave sleeve balun is presented, enabling an optimal choke design for maximum isolation. A standard 0.25[symbols] sleeve balun achieved 10.9 dB isolation with [symbols]=4, whereas a choke of optimal length 0.232[symbols] had an isolation of better than -20 dB. Several techniques for the measurement of antenna characteristics of battery powered handsets were compared and perturbation effects associated with the direct connection of a coaxial cable to a mobile handset was quantified. Significant perturbation in both return loss and radiation pattern can occur depending on cable location on the handset chassis. The effectiveness of ferrite chokes in any location was marginal. However, the application of an optimal quarter-wave sleeve balun in the centre of the largest plane of the handset, orthogonal to the primary polarisation resulted in minimal perturbation of both radiation patterns and return loss.

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Pham, Duc Nghia, e n/a. "Modelling and Exploiting Structures in Solving Propositional Satisfiability Problems". Griffith University. Institute for Integrated and Intelligent Systems, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20070216.143447.

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Recent research has shown that it is often preferable to encode real-world problems as propositional satisfiability (SAT) problems and then solve using a general purpose SAT solver. However, much of the valuable information and structure of these realistic problems is flattened out and hidden inside the corresponding Conjunctive Normal Form (CNF) encodings of the SAT domain. Recently, systematic SAT solvers have been progressively improved and are now able to solve many highly structured practical problems containing millions of clauses. In contrast, state-of-the-art Stochastic Local Search (SLS) solvers still have difficulty in solving structured problems, apparently because they are unable to exploit hidden structure as well as the systematic solvers. In this thesis, we study and evaluate different ways to effectively recognise, model and efficiently exploit useful structures hidden in realistic problems. A summary of the main contributions is as follows: 1. We first investigate an off-line processing phase that applies resolution-based pre-processors to input formulas before running SLS solvers on these problems. We report an extensive empirical examination of the impact of SAT pre-processing on the performance of contemporary SLS techniques. It emerges that while all the solvers examined do indeed benefit from pre-processing, the effects of different pre-processors are far from uniform across solvers and across problems. Our results suggest that SLS solvers need to be equipped with multiple pre-processors if they are ever to match the performance of systematic solvers on highly structured problems. [Part of this study was published at the AAAI-05 conference]. 2. We then look at potential approaches to bridging the gap between SAT and constraint satisfaction problem (CSP) formalisms. One approach has been to develop a many-valued SAT formalism (MV-SAT) as an intermediate paradigm between SAT and CSP, and then to translate existing highly efficient SAT solvers to the MV-SAT domain. In this study, we follow a different route, developing SAT solvers that can automatically recognise CSP structure hidden in SAT encodings. This allows us to look more closely at how constraint weighting can be implemented in the SAT and CSP domains. Our experimental results show that a SAT-based mechanism to handle weights, together with a CSP-based method to instantiate variables, is superior to other combinations of SAT and CSP-based approaches. In addition, SLS solvers based on this many-valued weighting approach outperform other existing approaches to handle many-valued CSP structures. [Part of this study was published at the AAAI-05 conference]. 3. Finally, we propose and evaluate six different schemes to encode temporal reasoning problems, in particular the Interval Algebra (IA) networks, into SAT CNF formulas. We then empirically examine the performance of local search as well as systematic solvers on the new temporal SAT representations, in comparison with solvers that operate on native IA representations. Our empirical results show that zChaff (a state-of-the-art complete SAT solver) together with the best IA-to-SAT encoding scheme, can solve temporal problems significantly faster than existing IA solvers working on the equivalent native IA networks. [Part of this study was published at the CP-05 workshop].

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11

Angelov, Nikolay. "Essays on unit-root testing and on discrete-response modelling of firm mergers /". Uppsala : Department of Economics, Uppsala University, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6358.

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12

Udono, Ken, e n/a. "Modelling Seawater Desalination With Waste Incineration Energy Using Dynamic Systems Approach". Griffith University. School of Information and Communication Technology, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20070110.164750.

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Water shortage issues have been growing concerns in many cities around the world in recent years, especially in Eastern cities of Australia, which is the driest continent on the earth. The aim of this PhD thesis is a development of a model to study the use of waste incineration energy supplemented by alternative energy to power seawater desalination. It is to aid the freshwater supply of a drought stricken city in Eastern Australia. My work contributes to a development of efficient model in a simpler understandable way to reduce efforts required for modelling complex multi domain problems. This research is motivated by the successive severe drought conditions that affected many Australian cities in the past few years, compounded with an additional strain from a fast growing population. While we dump our waste into the Australian landscape, in more densely populated cities in Europe and Asia, the waste is incinerated to obtain thermal energy for various purposes. The waste is used as an energy source while at the same time reducing the amount of space needed for landfill. Seawater desalination has been uccessfully practiced for quite some time particularly in the Middle Eastern countries. To deal with increasing water shortage crisis, many cities around the world have opted or are considering seawater desalination to supplement their freshwater supply. The combination of both - waste incineration and seawater desalination - has rarely been studied. This is a twofold problem that requires modelling the problem of water demand and supply together with waste incineration to find a sustainable solution. This is a complex task. The effort needed for this can be reduced by using a modelling approach that is more efficient than the traditionally used statistical approaches. In this thesis, I present a comprehensive model developed using a dynamic system approach combined with artificial neural networks. It simulates water demand and supply as well as the possible amount of the desalinated water that can be produced using the energy from clean city waste incineration. This is done while taking in various influential factors including population growth and irregular weather patterns. This research comprises a literature review on seawater desalination and waste incineration, the establishment of water demand and supply dynamics of Gold Coast City as my case study and identifying any modelling difficulties that need to be overcome. This is followed by the development of a comprehensive model and its components, model calibration and simulation experiments. It was found that with the energy of waste incineration, up to 60% of the freshwater demand could be fulfilled by seawater desalination in a sustainable way.

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Pham, Tien Duc, e n/a. "A new approach to regional modelling: an Integrated Regional Equation System (IRES)". Griffith University. School of International Business and Asian Studies, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20041022.083520.

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This thesis develops a new structure that explicitly combines two CGE models, a national and a regional, in an integrated structure that gives the thesis model the name IRES, in short for the Integrated Regional Equation System. The typical features of the integrated structure are the adding-up conditions and the two-way linkages between the national and the regional modules facilitated by the interface shifters. The adding-up conditions ensure the two modules produce consistent results and updated databases. The inclusion of the interface shifters on the one hand plays a role in ensuring compatibility of results of the two modules, i.e. no distortion occurs because technical or taste changes are transferred across modules. On the other hand, the interface shifters assist the operation of IRES in different modes: the model can be used as a top-down model, a bottom-up model or an integrated model where national and regional shocks can be introduced at the same time. Hence, IRES has more flexibility in its application than a regional model or a national model alone, as IRES can make use of availability of data at any levels in the economy. IRES has a new labour market in which regional migration is no longer the only factor that settles the labour market as in the original setting of the MMRF model. Regional unemployment and regional participation rates are modelled to response to changes in regional employment growth using elasticities estimated econometrically in this thesis. IRES implements historical patterns of regional migration so that results of regional migration are consistent with observed patterns. Altogether, regional migration, regional unemployment and participation rates determine the equilibrium of the labour market. IRES adopts new approaches to modelling margin demands and indirect taxes. These new approaches are very effective in reducing the size of IRES but they do not compromise the use of the model. These approaches are readily applicable to any other regional CGE models.

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Hellström, Jörgen. "Count data modelling and tourism demand". Doctoral thesis, Umeå universitet, Institutionen för nationalekonomi, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-82168.

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This thesis consists of four papers concerning modelling of count data and tourism demand. For three of the papers the focus is on the integer-valued autoregressive moving average model class (INARMA), and especially on the ENAR(l) model. The fourth paper studies the interaction between households' choice of number of leisure trips and number of overnight stays within a bivariate count data modelling framework. Paper [I] extends the basic INAR(1) model to enable more flexible and realistic empirical economic applications. The model is generalized by relaxing some of the model's basic independence assumptions. Results are given in terms of first and second conditional and unconditional order moments. Extensions to general INAR(p), time-varying, multivariate and threshold models are also considered. Estimation by conditional least squares and generalized method of moments techniques is feasible. Monte Carlo simulations for two of the extended models indicate reasonable estimation and testing properties. An illustration based on the number of Swedish mechanical paper and pulp mills is considered. Paper[II] considers the robustness of a conventional Dickey-Fuller (DF) test for the testing of a unit root in the INAR(1) model. Finite sample distributions for a model with Poisson distributed disturbance terms are obtained by Monte Carlo simulation. These distributions are wider than those of AR(1) models with normal distributed error terms. As the drift and sample size, respectively, increase the distributions appear to tend to T-2) and standard normal distributions. The main results are summarized by an approximating equation that also enables calculation of critical values for any sample and drift size. Paper[III] utilizes the INAR(l) model to model the day-to-day movements in the number of guest nights in hotels. By cross-sectional and temporal aggregation an INARMA(1,1) model for monthly data is obtained. The approach enables easy interpretation and econometric modelling of the parameters, in terms of daily mean check-in and check-out probability. Empirically approaches accounting for seasonality by dummies and using differenced series, as well as forecasting, are studied for a series of Norwegian guest nights in Swedish hotels. In a forecast evaluation the improvements by introducing economic variables is minute. Paper[IV] empirically studies household's joint choice of the number of leisure trips and the total night to stay on these trips. The paper introduces a bivariate count hurdle model to account for the relative high frequencies of zeros. A truncated bivariate mixed Poisson lognormal distribution, allowing for both positive as well as negative correlation between the count variables, is utilized. Inflation techniques are used to account for clustering of leisure time to weekends. Simulated maximum likelihood is used as estimation method. A small policy study indicates that households substitute trips for nights as the travel costs increase.

Härtill 4 uppsatser.

digitalisering@umu

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Randall, Marcus Christian, e n/a. "A General Modelling System and Meta-Heuristic Based Solver for Combinatorial Optimisation Problems". Griffith University. School of Environmental and Applied Science, 1999. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051116.120133.

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There are many real world assignment, scheduling and planning tasks which can be classified as combinatorial optimisation problems (COPs). These are usually formulated as a mathematical problem of minimising or maximising some cost function subject to a number of constraints. Usually, such problems are NP hard, and thus, whilst it is possible to find exact solutions to specific problems, in general only approximate solutions can be found. There are many algorithms that have been proposed for finding approximate solutions to COPs, ranging from special purpose heuristics to general search meta-heuristics such as simulated annealing and tabu search. General meta-heuristic algorithms like simulated annealing have been applied to a wide range of problems. In most cases, the designer must choose an appropriate data structure and a set of local operators that define a search neighbourhood. The variability in representation techniques, and suitable neighbourhood transition operators, has meant that it is usually necessary to develop new code for each problem. Toolkits like the one developed by Ingber's Adaptive Simulated Annealing (Ingber 1993, 1996) have been applied to assist rapid prototyping of simulated annealing codes, however, these still require the development of new programs for each type of problem. There have been very few attempts to develop a general meta-heuristic solver, with the notable exception being Connolly's General Purpose Simulated Annealing (Connolly 1992). In this research, a general meta-heuristic based system is presented that is suitable for a wide range of COPs. The main goal of this work is to build an environment in which it is possible to specify a range of COPs using an algebraic formulation, and to produce a tailored solver automatically. This removes the need for the development of specific software, allowing very rapid prototyping. Similar techniques have been available for linear programming based solvers for some years in the form of the GAMS (General Algebraic Modelling System) (Brooke, Kendrick, Meeraus and Raman 1997) and AMPL (Fourer, Gay and Kernighan 1993) interfaces. The new system is based on a novel linked list data structure rather than the more conventional vector notation due to the natural mapping between COPS and lists. In addition, the modelling system is found to be very suitable for processing by meta-heuristic search algorithms as it allows the direct application of common local search operators. A general solver is built that is based on the linked list modelling system. This system is capable of using meta-heuristic search engines such as greedy search, tabu search and simulated annealing. A number of implementation issues such as generating initial solutions, choosing and invoking appropriate local search transition operators and producing suitable incremental cost expressions, are considered. As such, the system can been seen as a good test-bench for model prototypers and those who wish to test various meta-heuristic implementations in a standard way. However, it is not meant as a replacement or substitute for efficient special purpose search algorithms. The solver shows good performance on a wide range of problems, frequently reaching the optimal and best-known solutions. Where this is not the case, solutions within a few percent deviation are produced. Performance is dependent on the chosen transition operators and the frequency with which each is applied. To a lesser extent, the performance of this implementation is influenced by runtime parameters of the meta-heuristic search engine.

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Brena-Medina, Victor Francisco. "Modelling initiation of plant root hairs : a reaction-diffusion system in a non-homogenous environment". Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619139.

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A reaction-diffusion system, which can be considered as a generalised Schnakenberg-like model, is studied mathematically in 1D and 2D. This system models an initiation process within a root-hair cell which involves biochemical interactions of the G-proteins, known as Rho of Plants, or ROPs. These proteins attach to the cell membrane prompting a localised patch which, in consequence, induces cell wall softening and subsequently hair growth. This model assumes that the auxin provided is the key catalyst. Auxin is a plant hormone which is known to because of many different features in plant morphogenesis. Also, this hormone is experimentally known to enter the cell including a spatially dependent gradient.. Numerical bifurcation analysis is carried on in order to explore solutions which resemble all features that the G-proteins and auxin arc known to cause. The main bifurcation parameters arc taken to be the overall auxin rate, and the cell length. The analysis is backed up by full numerical simulations and asymptotic analysis using semi-strong interaction theory. The asymptotics not only provides existence of solutions and explains numerical properties, but also sheds light on transition mechanisms via the theory of competition instability and transverse instability of homoclinic stripes. The analytical results are found to agree favourably with numerical simulations, and to give further explanation of the agreement between the model and biological data for different scenarios. From a mathematical point of view, pattern formation of non-homogeneous reaction-diffusion systems is a subject that is not yet well understood. However, upon using the theory of semi-strong interactions, light is shed on the dynamics and instabilities that. spatially dependent coefficients bring about. As a consequence, transitions between different spot-like patterns and the dynamics of their location can be explored and theoretically explained.

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Smit, Robin, e n/a. "An Examination of Congestion in Road Traffic Emission Models and Their Application to Urban Road Networks". Griffith University. School of Environmental Science, 2007. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20070724.155421.

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The level of air pollution in urban areas, which is largely affected by road traffic, is an issue of high political relevance. Congestion is most prevalent in urban areas and a common and increasingly present phenomenon worldwide. The first four chapters of this study have investigated how and to what extent models, which are used to predict emissions on road links in urban road networks, include the effects of congestion on emissions. In order to make this assessment, traffic engineering literature and empirical studies have been examined and used as a basis to review (current) emission models that exist or have been used around the world. Congestion causes changes in driving patterns of individual vehicles in a traffic stream, and these changes are subsequently reflected in changes in congestion indicators and changes in emission levels. This consideration and a literature review has led to a proposed 'congestion typology' of emission models, which reflects the different ways in which and the extent to which congestion has been incorporated in these models. The typology clarifies that six of in total ten families of emission models that were investigated in this thesis explicitly consider congestion in the modelling process (i.e. model variables are related to congestion), although this is done in different ways. For the remaining four families of emission models it was not possible to determine the extent to which congestion has been incorporated on the basis of literature review alone. Two families fell beyond the scope of this work since they cannot be used to predict emission on road links. For the other two families it became clear in the course of the thesis that the extent can be determined through analysis of driving pattern data (and other information with respect to e.g. data collection) that were used in the model development. A new methodology is presented in this thesis to perform this analysis and to assess the mean level of congestion in driving patterns (driving cycles). The analysis has been carried out for one important family of emission models, the so-called travel speed models ('average speed models'), which are used extensively in urban network modelling. For four current models (COPERT III, MOBILE 6, QGEPA 2002, EMFAC 2000), it is concluded that these models implicitly (i.e. congestion is inherently considered) take varying levels of congestion into account, but that this conclusion is subject to a number of limitations. It became clear in the course of this study that prediction of (the effects of) congestion in both traffic models and emission models is generally restricted to certain modelling dimensions. As a consequence, the effects of congestion are only partially predicted in current air emission modelling. Chapter 5 has attempted to address the question whether congestion is actually an important issue in urban network emission modelling or not. It also addressed the question if different types of emission models actually predict different results. On the basis of a number of selection criteria, two types of models were compared, i.e. one explicit model (TEE-KCF 2002) and two implicit models (COPERT III, QGEPA 2002). The research objectives have been addressed by applying these emission models to a case-study urban network in Australia (Brisbane) for which various model input attributes were collected from different sources (both modelled and field data). The findings are limited by the fact that they follow from one urban network with particular characteristics (fleet composition, signal settings, speed limits) and application of only a few particular emission models. The results therefore indicate that: 1. Changes in traffic activity (i.e. distribution of vehicle kilometres travelled on network links) over the day appear to have the largest effect on predicted traffic emissions. 2. Congestion is an important issue in the modelling of CO and HC emissions. This appears not to be the case for NOx emissions, where basic traffic composition is generally a more important factor. For the most congested parts in the urban network that have been investigated, congestion can more than double predicted emissions of CO and HC. 3. Different types of emission models can produce substantially different results when absolute (arithmetic) differences are considered, but can produce similar results when relative differences (ratio or percent difference) are considered.

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Passot, Sixtine. "Exploration du système racinaire du mil et ses conséquences pour la tolérance à la sécheresse". Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT160/document.

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Le mil est une céréale d’importance majeure pour la sécurité alimentaire dans les régions arides d’Afrique et d’Inde. Pourtant, elle a fait l’objet de relativement peu d’efforts d’amélioration variétale par rapport à d’autres céréales. En particulier, l’amélioration de son système racinaire pourrait permettre une amélioration de la tolérance de cette plantes aux contraintes physiques qu’elle subit (sécheresse et faible disponibilité en nutriments) et ainsi un accroissement substantiel de la production. L’objectif de ce travail est de caractériser ce système racinaire, en vue de produire des connaissances nécessaires à l’amélioration variétale, axée principalement sur la tolérance à la sécheresse en début de cycle.Dans un premier temps, nous avons décrit précisément la morphologie du système racinaire dans les premiers stades de développement, la dynamique de mise en place des différents axes racinaires ainsi que l’anatomie des différents types de racines. Ce travail a mis en évidence l’existence de trois types anatomiques distincts pour les racines latérales. Nous avons également mis en évidence l’existence de variabilité dans la dynamique de mise en place précoce du système racinaire au sein d’un panel de diversité issu de variétés cultivées, ce qui ouvre la possibilité d’utiliser cette variabilité existante pour l’amélioration du système racinaire. Notre étude a aussi révélé une grande variabilité des profils de croissances au sein des racines latérales.Pour analyser plus avant cette diversité, la croissance d’un grand nombre de racines latérales a été mesurée quotidiennement et un modèle statistique a permis de classer ces racines latérales en trois grandes tendances, selon leurs profils de croissance. Ces trois catégories distinguent des racines avec des forts taux de croissance, et dont la croissance se poursuit après la fin du suivi, des racines avec des taux de croissance intermédiaires et des racines au taux de croissance faible, qui cessent rapidement de pousser. Ces différents types de racines sont répartis aléatoirement le long de la racine primaire et il ne semble pas y avoir d’influence des types racinaires sur les intervalles entre racines latérales successives. Les trois types cinétiques correspondent, imparfaitement cependant, aux trois types anatomiques mis en évidence dans le premier chapitre. Un travail similaire a été effectué sur le maïs, ce qui a permis de comparer ces deux céréales phylogénétiquement proches.Enfin, nous avons recherché de marqueurs génétiques associés à la croissance de la racine primaire, un trait racinaire supposément impliqué dans la tolérance à la sécheresse précoce. Ce travail a nécessité le phénotypage du trait racinaire en question sur panel de lignées de mil fixées, ce qui a confirmé la présence d’une grande variabilité existante pour ce trait. Ces lignées ont ensuite été génotypées par séquençage. Les analyses d’association génotype/phénotype sont en cours.Ce travail de thèse a permis de caractériser plus précisément le système racinaire du mil, relativement mal connu jusqu’à ce jour. Il a fourni des données utiles pour la paramétrisation et le test de modèles fonctionnels de croissance et de transport d’eau. La caractérisation cinétique précise des types de racines latérales est une approche originale et pourra être utilisée chez d’autres céréales. Enfin, les données acquises par génétique d’association devraient pouvoir servir à une meilleure compréhension de la mise en place de ce système racinaire et ouvrent la voie à l’amélioration assistée par marqueurs génétiques pour des traits racinaires chez le mil
Pearl millet plays an important role for food security in arid regions of Africa and India. Nevertheless, it lags far behind other cereals in terms of genetic improvement. Improving its root system could improve pearl millet tolerance to abiotic constraints (drought and low nutrient availability) and lead to a significant increase in production. The objective of this work is to characterize pearl system root system development in order to produce knowledge for breeding, mainly targeted on tolerance to drought stress occurring at the early growth stages.First, we described the dynamics of early pearl millet root system development and the anatomy of the different root types. This work revealed the existence of three anatomically distinct types for lateral roots. We also showed the existence of variability in primary root growth and lateral root density in a diversity panel derived from cultivated varieties, which opens the possibility to use this existing variability in root system breeding. Our study also revealed a large variability among the growth profiles of lateral roots.To further analyze this diversity, the growth rates of a large number of lateral roots were measured daily and a statistical model developed to classify these lateral roots into three main trends, according to their growth profiles. These three categories distinguish roots with high growth rate that keep on growing after the end of the experiment, roots with intermediate growth rates and roots with low growth rates that quickly stop growing. These different lateral root types are randomly distributed along the primary root and there seem to be no influence of root types on the intervals between successive lateral roots. The three growth types correspond, though imperfectly, to the three anatomical types evidenced in the first chapter. A similar work has been performed on maize, which was used to compare these two phylogenetically close cereals.Finally, we searched for genetic markers associated to primary root growth, a root trait potentially involved in early drought stress tolerance. A large panel of genetically fixed pearl millet inbred lines was phenotyped, confirming the presence of a large variability existing for this trait. These lines were then genotyped by sequencing. Analyses of association between phenotype and genotype are underway.This work provides a precise description of pearl millet root system that was little studied to date. Our data were used for parameterization and testing of functional structural plant models simulating root growth and water transport. The statistical tool developed for the characterization of the different lateral root growth types is an original approach that can be used on other cereals. Finally, results from our association study will reveal new information on the genetic control of root growth and open the way to marker assisted selection for root traits in pearl millet

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Sayin, Ipek. "Modelling Electricity Demand In Turkey For 1998-2011". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615515/index.pdf.

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This thesis estimates the quarterly electricity demand of Turkey. First of all proper seasonal time series model are found for the variables: electricity demand, temperature, gross domestic product and electricity price. After the right seasonal time series model are found Hylleberg, Engle, Granger and Yoo (1990) test is applied to each variable. The results of the test show that seasonal unit roots exist for the electricity price even it cannot be seen at the graph. The other variables have no seasonal unit roots when the proper seasonal time series model is chosen. Later, the cointegration is tested by looking at the vector autoregressive model. As the cointegration is seen vector error correction model is found. There is long-run equilibrium when the price is the dependent variable and independent variable is gross domestic product. Temperature is taken as exogenous variable and demand is not statistically significant.

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Raybould, Michael, e n/a. "Attitudes and Information Effects in Contingent Valuation of Natural Resources". Griffith University. Australian School of Environmental Studies, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20061009.150949.

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This thesis investigated the effects of photographic and text information on respondents' attitudes and willingness-to-pay for a proposed beach protection scheme in the erosion prone Gold Coast region on the east coast of Australia. The research developed two alternative expectancy-value attitude-behaviour models to test residents' attitudes toward relevant targets and behavioural intention, expressed through stated willingness-to-pay, and compared the proposed models with one established attitude-behaviour model. The thesis set out to investigate three central research questions; one question relating to the effects of information on attitudes and willingness-to-pay, and two questions relating to the relationships between attitudes and willingness-to-pay. It was hypothesised that photographs that depicted severe erosion damage would result in more positive attitudes toward, and greater willingness-to-pay for, beach protection than photographs that showed only mild levels of erosion damage. Positive relationships were hypothesised between variables representing attitudes toward beach erosion, attitude toward beach protection, attitude toward paying for beach protection, and willingness-to-pay. Finally, it was hypothesised that the relationships between attitudes and willingness-to-pay could be adequately explained by the proposed attitude-behaviour models. The thesis describes how seven information treatments and eight attitude measurement scales were developed and tested in a pilot experiment before use in a survey of homeowners in the region of interest. Analysis of variance showed that, while respondent's attitude toward beach protection was affected by the information treatments, their willingness-to-pay for the proposed program was insensitive to information. There were no significant effects that could be attributed exclusively to text descriptions of the good but there were significant effects that could be attributed to photographic information treatments. However, none of the effects on attitudes resulted in significant effects on the behavioural intention expressed in stated willingness-to-pay. Analysis of respondents with low previous knowledge of the proposed good revealed more extensive information effects on attitudes, but still not on willingness-to-pay, and this suggests that high levels of previous knowledge in a large proportion of the sample had a moderating effect on attitude change caused by the information treatments. Regression analysis showed that seven of the eight attitude and behaviour variables in the proposed attitude-behaviour model were significant predictors of willingness-to-pay. In the final phase of the analysis, goodness-of-fit indices, estimated using Structural Equation Modelling, indicated a good fit between the data and the attitude-behaviour models tested. Standardised coefficients on the model indicated that perceived behavioural control, expected utility of outcomes, and subjective norms all had strong direct relationships with stated willingness-to-pay, and strong indirect relationships on willingness-to-pay via attitudes toward payment. These results are consistent with the relationships proposed in attitude-behaviour models and the moderating effects of these variables explain why significant information treatment effects were observed on attitude to beach protection but not on willingness-to-pay. This research showed that respondent's willingness-to-pay in a contingent valuation experiment is quite insensitive to photographic treatments when previous knowledge is high and that costly and time consuming testing procedures, recommended by authorities, may not be necessary under these conditions. It also demonstrated that measures of attitude, consistent with an attitude-behaviour model, can be collected easily in a contingent valuation study and can contribute to understanding of participant responses and to identification of protest responses.

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Thornton, John Richard, e n/a. "Constraint Weighting Local Search for Constraint Satisfaction". Griffith University. School of Computing and Information Technology, 2000. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20050901.142439.

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One of the challenges for the constraint satisfaction community has been to develop an automated approach to solving Constraint Satisfaction Problems (CSPs) rather than creating specific algorithms for specific problems. Much of this work has concentrated on the development and improvement of general purpose backtracking techniques. However, the success of relatively simple local search techniques on larger satisfiability problems [Selman et a!. 1992] and CSPs such as the n-queens [Minton et al. 1992] has caused interest in applying local search to constraint satisfaction. In this thesis we look at the usefulness of constraint weighting as a local search technique for constraint satisfaction. The work is based on the clause weighting ideas of Selman and Kautz [1993] and Moths [1993] and applies, evaluates and extends these ideas from the satisfiability domain to the more general domain of CSPs. Specifically, the contributions of the thesis are: 1. The introduction of a local search taxonomy. We examine the various better known local search techniques and recognise four basic strategies: restart, randomness, memory and weighting. 2. The extension of the CSP modelling framework. In order to represent and efficiently solve more realistic problems we extend the C SP modelling framework to include array-based domains and array-based domain use constraints. 3. The empirical evaluation of constraint weighting. We compare the performance of three constraint weighting strategies on a range of CSP and satisflability problems and with several other local search techniques. We find that no one technique dominates in all problem domains. 4. The characterisation of constraint weighting performance. Based on our empirical study we identiIS' the weighting behaviours and problem features that favour constrtt weighting. We conclude weighting does better on structured problems where the algorithm can recognise a harder sub-group of constraints. 5. The extension of constraint weighting. We introduce an efficient arc weighting algorithm that additionally weights connections between constraints that are simultaneously violated at a local minimum. This algorithm is empirically shown to outperform standard constraint weighting on a range of CSPs and within a general constraint solving system. Also we look at combining constraint weighting with other local search heuristics and find that these hybrid techniques can do well on problems where the parent algorithms are evenly matched. 6. The application of constraint weighting to over constrained domains. Our empirical work suggests constraint weighting does well for problems with distinctions between constraint groups. This led us to investigate solving real-world over constrained problems with hard and soft constraint groups and to introduce two dynamic constraint weighting heuristics that maintain a distinction between hard and soft constraint groups while still adding weights to violated constraints in a local minimum. In an empirical study, the dynamic schemes are shown to outperform other fixed weighting and non-weighting systems on a range of real world problems. In addition, the performance of weighting is shown to degrade less severely when soft constraints are added to the system, suggesting constraint weighting is especially applicable to realistic, hard and soft constraint problems

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Chapala, Usha Kiran, e Sridhar Peteti. "Continuous Video Quality of Experience Modelling using Machine Learning Model Trees". Thesis, Blekinge Tekniska Högskola, Institutionen för datavetenskap, 1996. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17814.

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Adaptive video streaming is perpetually influenced by unpredictable network conditions, whichcauses playback interruptions like stalling, rebuffering and video bit rate fluctuations. Thisleads to potential degradation of end-user Quality of Experience (QoE) and may make userchurn from the service. Video QoE modelling that precisely predicts the end users QoE underthese unstable conditions is taken into consideration quickly. The root cause analysis for thesedegradations is required for the service provider. These sudden changes in trend are not visiblefrom monitoring the data from the underlying network service. Thus, this is challenging toknow this change and model the instantaneous QoE. For this modelling continuous time, QoEratings are taken into consideration rather than the overall end QoE rating per video. To reducethe user risk of churning the network providers should give the best quality to the users. In this thesis, we proposed the QoE modelling to analyze the user reactions change over timeusing machine learning models. The machine learning models are used to predict the QoEratings and change patterns in ratings. We test the model on video Quality dataset availablepublicly which contains the user subjective QoE ratings for the network distortions. M5P modeltree algorithm is used for the prediction of user ratings over time. M5P model gives themathematical equations and leads to more insights by given equations. Results of the algorithmshow that model tree is a good approach for the prediction of the continuous QoE and to detectchange points of ratings. It is shown that to which extent these algorithms are used to estimatechanges. The analysis of model provides valuable insights by analyzing exponential transitionsbetween different level of predicted ratings. The outcome provided by the analysis explains theuser behavior when the quality decreases the user ratings decrease faster than the increase inquality with time. The earlier work on the exponential transitions of instantaneous QoE overtime is supported by the model tree to the user reaction to sudden changes such as video freezes.

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Huber, Katrin [Verfasser]. "The role of soil heterogeneity on field scale evapotranspiration : 3D integrative modelling and upscaling of root water uptake / Katrin Huber". Bonn : Universitäts- und Landesbibliothek Bonn, 2015. http://d-nb.info/1079273409/34.

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Keyes, Samuel. "X-ray computed tomography and image-based modelling of plant, root and soil systems, for better understanding of phosphate uptake". Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/364786/.

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A major constraint to crop growth is the poor bioavailability of edaphic nutrients, especially phosphate (P). Improving the nutrient acquisition efficiency of crops is crucial in addressing pressing global food-security issues arising from increasing world population, reduced fertile land and changes in the climate. Despite the undoubted importance of root architecture and root/soil interactions to nutrient uptake, there is a lack of approaches for quantifying plant roots non-invasively at all scales. Mathematical models have allowed our understanding of root and soil interactions to be improved, but are almost invariably reliant on idealised geometries or virtual root growth models. In order to improve phenotyping of advantageous traits for low-P conditions and improve the accuracy of root growth and uptake models, more sophisticated and robust approaches to in vivo root and soil characterisation are needed. Microfocus X-ray Computed Tomography (�-CT) is a methodology that has shown promise for noninvasive imaging of roots and soil at various scales. However, this potential has not been extended to consideration of either very small (rhizosphere scale) or large (mature root system scale) samples. This thesis combines discovery experiments and method development in order to achieve two primary objectives: • The development of more robust, well-described approaches to root and soil �-CT imaging. Chapters 2 and 3 explore the potential of clinical contrasting methods in root investigation, and show how careful consideration of imaging parameters combined with development of user invariant image-processing protocol can improve measurement of macro-porous volume fraction, a key soil parameter. • Chapter 4 develops an assay for first-time 3D imaging of root hairs in situ within the rhizosphere. The resulting data is used to parameterise an explicit P uptake model at the hair scale, suggesting a different contribution of hairs to uptake than was predicted using idealised geometries. Chapter 5 then extends the paradigm for root hair imaging and model generation, building a robust, modular workflow for investigating P dynamics in the rhizosphere that can accommodate non-optimal soil-water states.

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Radanielson, Mariot Ando. "Identification de nouveaux traits de sélection pour améliorer la productivité en situation de déficit hydrique chez le tournesol". Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0013/document.

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Le développement de variétés productives et adaptées aux conditions de déficit hydrique est toujours au cœur du défi de l'amélioration variétale chez le tournesol. Pour une nouvelle orientation de la sélection, ce travail se propose d'identifier de nouvelles cibles phénotypiques au travers d'une démarche couplant le phénotypage écophysiologique, la modélisation biophysique et la génétique quantitative. Les cibles potentielles ont été identifiées sur la base de leur variabilité génotypique, leur impact sur le rendement, leur héritabilité et leur facilité de mesure. Des paramètres génotypiques du modèle SUNFLO-CLIMATOR relatifs à la phénologie, l'architecture foliaire et l'accès aux réserves hydriques du sol ont été testés. 19 lignées et 125 hybrides ont été phénotypés au champ et sous serre. La structure génétique des populations d'hybrides a permis d'évaluer l'héritabilité des paramètres génotypiques et leur mode de transmission.La date thermique de la floraison a présenté la variabilité génotypique la plus restreinte, mais l'héritabilité la plus élevée (H²=0.78). Ce trait est un bon indicateur de la précocité de la floraison mais peu pertinent pour améliorer la précocité à la maturité. La date de la maturité physiologique a présenté un déterminisme environnemental important et une amélioration de sa représentation dans le modèle est nécessaire. Les traits caractéristiques de l'architecture ont présenté la plus grande variabilité génotypique. Leur héritabilité était par contre peu élevée (0.20 ≤ H² ≤ 0.39). L'interaction des traits architecturaux était plus importante que leur contribution individuelle dans la variabilité de la productivité. Des investigations plus approfondies sur l'interaction des traits d'architecture devraient apporter plus de précision sur la stratégie d'intégration de ces caractères en sélection. L'utilisation du trait, position de la plus grande feuille, A2gen, et surface foliaire de la plus grande feuille, A3gen, en sélection sur valeur propre des lignées, peut cependant déjà permettre une amélioration de l'efficience d'interception des hybrides durant la phase reproductive et particulièrement dans des conditions de déficit hydrique en fin de cycle. Le trait Indice d'extraction de l'eau IEgen caractéristique de la capacité d'extraction de l'eau du sol, constitue le trait le plus prometteur. Il présente une héritabilité élevée (0.77 ≤ H² ≤ 0.83). La réponse du rendement à sa variabilité est linéaire, avec un gain de 0.8 à 1.5 q ha-1 pour une augmentation de 1 % de la teneur en eau minimale d'extraction de l'eau.La recherche de marqueurs moléculaires pour ces paramètres génotypiques d'intérêt peut être faite et dans le but d'une stratégie de sélection assistée par la modélisation biophysique et le marquage moléculaire
This work was an attempt to assist sunflower breeding program by crop physiology knowledge to sustain and to improve productivity under water deficit. The approach was based on using SUNFLO-CLIMATOR, a biophysical crop modelling to identify the limiting factors to plant productivity. These factors were considered as potential new traits for breeding program. Their assessment for this objective corresponded to four criteria: genotypic variability, impact on plant productivity, heritability and simplified phenotyping method. Thus, traits related to genotypic parameters of three processes were analysed: phenology, architecture and soil water uptake. Their variability was evaluated on field and greenhouse experiments carried out with 19 inbred lines and 125 hybrids. Sensitivity analysis of plant yield, simulated with SUNFLO-CLIMATOR model, was then done to estimate the impact of the parameter variability among the studied genotypes. Quantitative genetic analyses were used to evaluate their heritability and the combining ability of the parental inbred lines.Large phenotypic variability was observed for each parameter with a significant “genotype” effect. Thermal time for flowering displayed high heritability about H² = 0.78. Thermal time to physiological maturity (M3) displayed high environmental effect on its variability. Its genotypic variability would probably need new way of modelling such as the development of a seed growth module. Architectural traits related to canopy size and shape presented also lower heritability (0.20 ≤ H² ≤ 0.39) and their impact on plant productivity depends on their interaction. However the trait position of the largest leaf A2gen and its leaf area A3gen could be yet used to screen the best inbred lines for improving radiation interception efficiency of the hybrids during the grain-filling phase.Root depth is a relevant trait for deeper soil. Its access remains difficult and time consuming. For shallower or medium depth soil, higher water extraction capacity seemed allow higher plant yield with linear relationship about 0.8 – 1.5 q ha-1 more per 1% decrease of soil water content minimal for water extraction. The index of water extraction (IEgen) displayed high value of heritability (0.77 ≤ H² ≤ 0.83). The genotypic parameters A2gen, A3gen, IEgen were confirmed with genetic resources to enhance plant productivity under water deficit. Research for their molecular marker would be a next step for this work and an issue for a new selection assisted by marker molecular and plant modelling

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Mira, Sébastian. "Caractérisation et analyse prospective de la contribution de l'effet rhizosphère aux performances du blé (Triticum aestivum) en contexte de polyculture-élevage". Electronic Thesis or Diss., Rennes, Agrocampus Ouest, 2023. http://www.theses.fr/2023NSARD101.

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Face aux enjeux sociétaux, environnementaux et d’érosion de la biodiversité, la reconception des systèmes de cultures mobilisant les interactions écologiques en place des intrants est cruciale à développer. L’interface sol-plante présente un intérêt majeur car elle héberge une diversité de processus impliqués dans la nutrition et la santé des plantes. L’effet rhizosphère induit par les plantes est très dynamique, et influencé non seulement par le type de sol ou l’espèce cultivée mais également par les pratiques agricoles. Dans une approche combinant expérimentation et modélisation statistiques par équation structurale, cette thèse a permis de développer des indicateurs de fonctionnement de la rhizosphère du blé (Triticum aestivum var Absalon) au cours du cycle de développement de la plante.La méthodologie appliquée a permis de mettre en avant des effets synergiques de la diversification des cultures au cours de la succession avec le travail réduit du sol afin de promouvoir l’effet rhizosphère. Enfin, ce travail a permis de mettre en évidence un schéma structurel causal commun entre les conditions contrôlées et le terrain grâce à la modélisation par équation structurales. En conclusion, ce travail de thèse menée en collaboration avec les adhérents de trois coopératives permet d’ouvrir des perspectives de conception et d’évaluation des systèmes de cultures agroécologiques à bas intrants basés sur l’effet rhizosphère
Faced with societal and environmental challenges and loss of biodiversity, the redesign of cropping systems mobilizing ecological interactions instead of synthetic inputs is crucial to develop. The soil-plant interface influenced by root activities is of major interest because it harbors a diversity of processes involved in plant nutrition and health. However, the rhizosphere effect induced by plants is very dynamic, and influenced not only by soil type or crop species but also by agricultural practices. In an approach combining experimentation and statistical modeling by structural equations, indicators of rhizosphere functioning in wheat (Triticum aestivum var Absalon) were developped.The applied methodology allowed to put forward synergistic effects of crop diversification during the succession with reduced tillage in order to promote the rhizosphere effect. Finally, we highlighted a common scheme of causal structure between controlled conditions and the field by structural equation modeling that pave the way for further development of rhizosphere indicators. In conclusion, this thesis work carried out in collaboration with the members of three cooperatives opens perspectives for the design and evaluation of low-input agroecological cropping systems

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Crawford, Alistair, e n/a. "Bad Behaviour: The Prevention of Usability Problems Using GSE Models". Griffith University. School of Information and Communication Technology, 2006. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20061108.154141.

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Abstract (sommario):

The aim of Human Computer Interaction or HCI is to both understand and improve the quality of the users' experience with the systems and technology they interact with. Recent HCI research requirements have stated a need for a unified predictive approach to system design that consolidates system engineering, cognitive modelling, and design principles into a single 'total system approach.' At present, few methods seek to integrate all three of these aspects into a single method and of those that do many are extensions to existing engineering techniques. This thesis, however proposes a new behaviour based approach designed to identify usability problems early in the design process before testing the system with actual users. In order to address the research requirements, this model uses a new design notation called Genetic Software Engineering (GSE) in conjunction with aspects of a cognitive modelling technique called NGOMSL (Natural GOMS Language) as the basis for this approach. GSE's behaviour tree notation, and NGOMSL's goal orientated format are integrated using a set of simple conversion rules defined in this study. Several well established design principles, believed to contribute to the eventual usability of a product, are then modelled in GSE. This thesis addresses the design of simple interfaces and the design of complex ubiquitous technology. The new GSE approach is used to model and predict usability problems in an extensive range of tasks from programming a VCR to making a video recording on a modern mobile phone. The validity of these findings is tested against actual user tests on the same tasks and devices to demonstrate the effectiveness of the GSE approach. Ultimately, the aim of the study is to demonstrate the effectiveness of the new cognitive and engineering based approach at predicting usability problems based on tangible representations of established design principles. This both fulfils the MCI research requirements for a 'total system approach' and establishes a new and novel approach to user interface and system design.

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28

AIDOO, ERIC. "MODELLING AND FORECASTING INFLATION RATES IN GHANA: AN APPLICATION OF SARIMA MODELS". Thesis, Högskolan Dalarna, Statistik, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:du-4828.

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Abstract (sommario):

Ghana faces a macroeconomic problem of inflation for a long period of time. The problem in somehow slows the economic growth in this country. As we all know, inflation is one of the major economic challenges facing most countries in the world especially those in African including Ghana. Therefore, forecasting inflation rates in Ghana becomes very important for its government to design economic strategies or effective monetary policies to combat any unexpected high inflation in this country. This paper studies seasonal autoregressive integrated moving average model to forecast inflation rates in Ghana. Using monthly inflation data from July 1991 to December 2009, we find that ARIMA (1,1,1)(0,0,1)12 can represent the data behavior of inflation rate in Ghana well. Based on the selected model, we forecast seven (7) months inflation rates of Ghana outside the sample period (i.e. from January 2010 to July 2010). The observed inflation rate from January to April which was published by Ghana Statistical Service Department fall within the 95% confidence interval obtained from the designed model. The forecasted results show a decreasing pattern and a turning point of Ghana inflation in the month of July.

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29

Larrey, Mathieu. "Analysis of the root system architecture responses to reserves availability in grapevine rootstocks using the Archisimple model". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0448.

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Améliorer le taux de reprise des jeunes plants greffés/soudés afin de limiter leur dépérissement futur au vignoble est un enjeu majeur pour la pépinière viticole. Cela passe notamment par une meilleure compréhension des capacités d'enracinement et de la mise en place de l'architecture racinaire après implantation, en lien avec l'efficacité des racines à coloniser le sol et prélever les ressources hydro-minérales. De nombreux facteurs génétiques, physiologiques ou environnementaux modifient ces processus chez la vigne. Parmi eux, le statut nutritionnel du matériel végétal initial pourrait être déterminant. Cette thèse a pour objectif de caractériser, chez la jeune vigne en conditions contrôlées, l'influence de la disponibilité initiale en réserves carbonées et azotées sur la rhizogenèse, la croissance et la plasticité des traits morphologiques du système racinaire pour différents génotypes de porte-greffes, contrastés en termes de développement racinaire. Il sera notamment recherché si les processus d'émission, d'élongation et de ramification racinaire sont différemment impactés par la teneur locale en sucres et la nature du greffon. Ces données serviront également à calibrer un premier modèle de développement racinaire pour la vigne
Improving the recovery rate of young grafted grapevines in order to limit their future decline in vineyards is a major challenge for nurseries and grape growers. This requires a better understanding of their rooting capacities and the establisment of their root system architecture (RSA) after implantation, in particular in relation to their efficiencies in soil prospection and soil resources capture. Many genetic, physiological or environmental factors modify these processes in grapes. Among them, the nutritional status of the mother plant material could be decisive. The aim of this thesis is to characterize, in young vines mostly under controlled conditions, the influence of the initial availability of carbon and nitrogen reserves on rhizogenesis, growth and plasticity of the morphological traits of the root system for different Vitis rootstock genotypes contrasted in terms of root development. In particular, it will be investigated whether the processes of root emission, elongation and branching are differently affected by the local carbohydrates content and the nature of the graft. These data will also be used to calibrate a first model of root system development for the vine. Such functional-structural root model is a promising way to overcome in situ root phenotyping issues and can serve as a basis for the development of root ideotypes in silico by highlighting the underlying genetic mechanisms and parameters that are most likely influence RSA

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30

Bouteillé, Marie. "Control of shoot and root growth by water deficit in Arabidopsis thaliana : a parallel analysis using artificial and natural mapping populations". Thesis, Montpellier, SupAgro, 2011. http://www.theses.fr/2011NSAM0017/document.

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Le maintien de la croissance foliaire en situation de déficit hydrique résulte du maintien de l´absorption racinaire et de la production de biomasse au niveau foliaire. Pour optimiser les deux processus, la plante ajuste la croissance de ses organes, et la répartition de la biomasse produite, entre les différents organes (root/shoot ratio) ou au sein de chaque organe (surface foliaire spécifique, longueur racinaire spécifique). Les principaux objectifs de ce travail de thèse étaient (i) d´évaluer l´impact des modifications de répartition de biomasse sur le maintien de la croissance foliaire en situation de déficit hydrique, (ii) de relier la réponse de la croissance d´un génotype aux caractéristiques de son habitat d´origine, and (iii) d´identifier les régions du génome responsables de la variation des croissances foliaires et racinaires en situation de déficit hydrique. Différent types de populations d´Arabidopsis thaliana ont été utilisés, une population de lignées recombinantes, ainsi que différents groupes d´accessions collectées dans des environnements naturels contrastés. Une analyse des relations allométriques entre les variables foliaires et racinaires en conditions de culture optimales puis en situation de déficit hydrique a permis de mettre en évidence le rôle clé de la surface foliaire spécifique dans l´amélioration de la tolérance au déficit hydrique. Une caractérisation détaillée du climat des régions dans lesquelles les accessions avaient été collectées a permis de faire le lien entre la tolérance accrue de certains génotypes et la faible balance climatique dans laquelle ils évoluaient. Enfin, en utilisant ces génotypes, une analyse de génétique quantitative (combinant recherche de QTL et génétique d´association) a été menée. Les régions génomiques controllant les croissances foliaires et racinaires étaient très liées, en particulier en situation hydrique optimale, mais le calcul de variables utilisant la croissance de la plante comme cofacteur a permis d´identifier des régions spécifiques de la croissance racinaire, dont une a été confirmée en utilisant des lignées quasi isogéniques. En situation de contrainte hydrique, les déterminants génétiques des croissances foliaires et racinaires étaient moins liés, et plusieurs régions très fortement associées spécifiquement aux variations de croissance racinaire ou foliaire ont été détectées. Des régions associées au maintien de la croissance foliaire en situation de déficit hydrique ont pu être mises en évidence, et la précision des études de génétique d´association a permis de réveler la présence de gènes d´intéret dans ces régions
Growth maintenance under water deficit mainly results from the maintenance of water uptake at the root level,and assimilates production by leaves. To optimize both processes, plant need to adjust organ growth and biomassallocation patterns between roots and shoots (root/shoot ratio), but also within the organs, through specific leaf areaand specific root length variations. The main objectives of this study were (i) to evaluate the impact of growth andbiomass allocation patterns modifications on growth maintenance under drought conditions, (ii) to rely the genotypicresponses to water deficit conditions and the climatic features of the natural environment in which they evolved, and(iii) to identify the key genetic regions responsible for shoot and root growth variation in response to water deficitconditions. We used different sets of genotypes, a population of recombinant inbred lines, and different sets ofaccessions of Arabidopsis thaliana, collected in a wide range of environments. An analysis of the allometricrelationships between shoot and root growth related variables under both well watered and water deficit conditionsallowed to highlight the importance of specific leaf area plasticity to maintain plant growth under water deficit. Adetailed climatic characterization of the natural habitats of the accessions studied, combined to the evaluation ofgrowth response to water deficit in these accessions allowed connecting low climatic water balance to better toleranceto water deficit conditions in specific regions, suggesting that this climatic feature could have shaped the evolution ofgenotypes in certain regions. Finally, using these two sets of genotypes, joint linkage and linkage disequilibriumanalysis were performed on growth related traits under well watered and water deficit conditions. Some genetic regionsinvolved in the control of root and shoot related traits were strongly coupled, especially in well watered experiments,but we managed to identify root specific regions using calculated variables that takes global plant growth as a cofactor.Under water deficit, the regions controlling root and shoot growth were less associated, and very strong QTL weredetected, specifically associated to one or the other part. Genomic regions associated to growth response to waterdeficit were also detected, and the accuracy of association mapping enabled to identify target genes that could be playa role in growth maintenance under drought

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31

Ji, Jinnan. "Finite elements modelling and analysis of the effect of vegetation on forested slopes stability". Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20213.

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L'ingénierie écologique, qui est décrite comme «la gestion de la nature», a d'abord été proposée par Odum en 1971. Dans les dernières décennies, l'ingénierie écologique a été largement consacrée à lutter contre l'érosion des sols et les mouvements de masse, tout en permettant d'assurer la durabilité des écosystèmes. L'objectif de cette thèse est d'évaluer l'impact de peuplements forestiers sur la stabilité de pentes de dimension finie, en considérant à la fois les effets mécaniques et hydrologiques des racines peu profondes contre les glissements de terrain. Deux sites forestiers monospécifiques et équiennes, plantés respectivement de Robinia pseudoacacia et Platycladus orientalis, ont été sélectionnés sur le Plateau du Loess en Chine et utilisés comme sites d'étude. Le Facteur de Sécurité (FoS) de ces pentes ont été calculées en utilisant un modèle éléments finis 2D qui prend en compte la distribution des racines dans les couches superficielles du sol.Des mesures de terrain et des tests de laboratoire ont été effectués afin d'estimer les principaux paramètres du modèle, à savoir la distribution des surfaces relatives de racines dans le sol (Root Area Ratio), la résistance à la traction des racines, ainsi que les propriétés mécaniques et hydrologiques du sol nu. La contribution des racines à la résistance au cisaillement du sol a été considérée par l'intermédiaire d'une « cohésion additionnelle » calculée à l'aide de modèles fournis par la littérature. Six modèles existants ont été testés. Cette thèse est composée de deux chapitres principaux portant sur: (1) l'effet mécanique de l'hétérogénéité spatiale de la distribution des racines à l'échelle de pente; (2) l'influence de la distribution des racines sur le couplage entre la diffusion de l'eau interstitiel et les contraintes mécaniques dans le sol et son impact sur la stabilité des pentes.Les simulations amènent aux conclusions principales suivantes: (1) les pentes en terrasse sont en théorie 20% plus stables que les pentes rectilignes, sans tenir compte des effets hydrologiques; (2) le FoS atteint une valeur asymptotique lorsque l'on augmente la cohésion des racines; (3) les variations de la cohésion des racines observées sur le terrain ont peu d'effet sur la stabilité des pentes. Toutefois le renforcement de la partie basse des pentes, où les racines ont un plus grand impact positif sur le FOS, peut permettre de diminuer le risque de glissement; (4) l'effet des fortes précipitations sur la stabilité de la pente pourrait probablement être atténué par la présence de racines, mais cet effet dépend des caractéristiques des racines et de leur influence sur le débit d'eau dans le sol
Ecological engineering, which is described as ‘the management of nature', was first proposed by Odum in 1971. In the past few decades, ecological engineering has been largely devoted to combat soil erosion and mass movement all over the world, because of its benefit on sustainable ecosystems. The objective of this thesis is to evaluate the impact of forest stands on the stability of finite slopes, considering both the mechanical and hydrological effects of roots against shallow landslides. Two monospecific and even-aged forest sites planted with Robinia pseudoacacia and Platycladus orientalis respectively were selected on the Loess Plateau of China and used as study sites. Slope Factors of Safety were calculated using a 2D finite element model that takes into account the distribution of roots in the shallow layers of soil.Field site experiments and laboratory tests were performed in order to estimate the main parameters of the model, i.e. distribution of root area ratio within the soil, root tensile strength, as well as bare soil mechanical and hydrological properties. The contribution of roots to soil shear strength was considered through an additional cohesion calculated with models provided by the literature. Six existing models were tested. This thesis is composed of two main chapters that make the focus on : (1) the mechanical effect of the spatial heterogeneity of root distribution at the slope scale; (2) the influence of root distribution on the coupling between pore fluid diffusion and mechanical stress and its impact on slope stability. This study brings to the following main conclusions: (1) terraced slopes were 20% more stable than rectilinear slopes, disregarding the differences in hydrological regimes between the two sites; (2) FoS could reach an asymptotic value when increasing root additional cohesion; (3) variations of the actual root cohesion do not affect much slope stability. However more attention should be given to the reinforcement of the bottom part of the actual slopes, where roots have a larger positive impact on the FoS; (4) the effect of heavy precipitations on slope stability could probably be overcome or at least mitigated by root system network, but this depends on root characteristics and their resulting effect on soil water flow

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32

Saint, Cast Clément. "Modélisation du développement architectural, de l'acclimatation au vent dominant et de l'ancrage du système racinaire du pin maritime". Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0018/document.

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Plus de la moitié des pertes de bois dans les forêts européennes sont dues aux tempêtes. Une connaissance des mécanismes impliqués dans la stabilité mécanique des arbres est alors capitale. L’ancrage de l’arbre dans le sol constitue l’une des composantes principales du maintien mécanique de l’arbre. Il est principalement déterminé par l’architecture du système racinaire et son interaction mécanique avec le sol. Au cours de son développement, l’arbre modifie ses dimensions et se complexifie. Plus particulièrement, le système racinaire semble s’acclimater (ex : croissance en diamètre plus importante) aux déformations engendrées par le vent. L’ensemble de ces modifications conduit à une évolution des mécanismes à l’origine de l’ancrage au cours du développement de l’arbre. L’étude expérimentale de cette fonction est compliquée car les racines sont difficilement mesurables en continu dans le sol. Nous avons alors mis au point une approche numérique pour décrire la croissance du système racinaire et la distribution des déformations dues au vent. Une grande base de données structurée en chronoséquence de systèmes racinaires numérisés (Pinus pinaster) a été mobilisée. Comme l’étude de la structure et des fonctions des racines est plus efficiente quand la différentiation entre racines est prise en compte, nous avons d’abord formalisé les types racinaires du système racinaire du pin maritime à partir d’une technique de classification (« k-means clustering ») réalisée avec quatre variables. La classification des racines latérales du pin maritime nous a permis d’identifier 5 types racinaires au cours du développement du pin maritime. Ce regroupement explique 70% de la variabilité de notre base de données. Chaque système racinaire est caractérisé par trois grosses racines horizontales émises par la souche. Les racines montrent une forte différentiation pour leur tropisme, avec une direction de croissance soit horizontale soit verticale. La structure de la partie centrale du système racinaire est pratiquement complète dès l'âge de 4 ans. Sur la base des types racinaires identifiés, nous avons calibré un modèle architectural (RootTyp ; Pagès et al. 2004) pour le pin maritime. Treize paramètres pour chaque type racinaire ont été estimés par l’intermédiaire de la base de données, d’informations issues de la littérature et d’une procédure d'optimisation. Une modélisation réaliste du système racinaire jusqu'à 50 ans n’a pu être obtenue qu'en implémentant au modèle RootTyp de nouveaux processus biologiques : la diminution de la ramification avec la croissance de la racine et la diminution de la vigueur des racines avec l'ordre de ramification. Malgré ces améliorations, les systèmes racinaires de la base de données présentent des diamètres plus importants à proximité de la souche par rapport aux systèmes racinaires simulés. Ce biais systématique est principalement attribué à l’acclimatation des racines au vent dominant. Les altérations de croissance dues aux contraintes pédologiques ont également été implémentées grâce à l’amélioration du module de sol du modèle architectural.Enfin, pour comprendre les mécanismes à l’origine de l’acclimatation des racines nous avons combiné plusieurs modèles pour prédire la distribution spatiale des déformations dans des maquettes simplifiées de systèmes racinaires à 4, 6 et 13 ans, pour trois régimes de vent spécifiques à la région étudiée. D’après les simulations, les déformations des racines sous l'effet du vent diminuent avec l’âge, en raison de l’augmentation de la rigidité des racines. Cela suggère une plus forte réponse thigmomorphogénétique aux stades jeunes. Les modifications structurelles et anatomiques du système racinaire par acclimatation au vent s’expliquent principalement par les distributions des déformations et des contraintes dans les racines
Storms cause more than 50% of the timber loss in European forests. However, forest tree anchorage mechanisms throughout their lifespan are not fully understood, especially the strong acclimation of root systems to common winds. This lack of knowledge is mainly due to technical difficulties: neither the root structure nor the mechanical contribution of the roots could be characterized continually. Thus we set up a numerical approach to model the development of the root system and to describe the strains resulting from common winds. This generic approach has been developed using Pinus pinaster grown in sandy soils as model species.Seven datasets of excavated root systems from 0 to 50 years were employed. The assessment of root structure and functions is more powerful if the differentiation of root system in several root types is considered. We first proposed an automatic classification of roots with the k-means clustering algorithm. Four root traits were chosen as classifiers, including three geometric architectural traits, which can be precisely assessed whatever the tree/root age. Clustering yielded similar five groups of laterals roots at all ages, explaining 70% of the variability. The three largest lateral roots per tree were all horizontal roots branching from stump and the other lateral roots show a large differentiation for tropism: nearly all the roots were horizontal or vertical roots. The framework of the central part of the root system can be almost completed in 4-year-old trees (3.5 cm collar diameter). We then calibrated the existing RootTyp (Pagès et al. 2004) architectural model for P. pinaster for each of the root types defined by the cluster analysis. We used the database combined with a literature review and an optimization method to get accurate values for 13 parameters by root types. We devoted effort to validate our model calibration. In order to model architecture of the root system, damping properties had to be implemented to yield realistic outputs up to the mature stage. Branching varied as a function of distance from the root base, and growth capacity decreased with branching order. Nevertheless, the root diameters of simulated root systems were generally underestimated. This was certainly due to root growth plasticity to the prevailing wind, an acclimation facet not taken into account at this calibration step. Growth alterations due to a cemented horizon were reproduced using the new calibrated soil module. Then, the wind acclimation of roots was numerically investigated by examining the root mechanical stimuli due to wind. A chain of biomechanical models was used to predict the spatial distribution of stress and strain in simplified root systems at 4, 6 and 13-year-old as a result of three levels of usual winds. According to simulations, the strain amplitude decreased with tree growth due to the increasing root system stiffness. This suggests larger thigmomorphogenetic responses at young stages. The modifications of the structural and wood root properties related to wind acclimation were largely explained by the stress and strain distribution in the root system

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33

Kamanu, Timothy Kevin Kuria. "Location-based estimation of the autoregressive coefficient in ARX(1) models". Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_9551_1186751947.

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Abstract (sommario):

In recent years, two estimators have been proposed to correct the bias exhibited by the leastsquares (LS) estimator of the lagged dependent variable (LDV) coefficient in dynamic regression models when the sample is finite. They have been termed as &lsquo
mean-unbiased&rsquo
and &lsquo
medianunbiased&rsquo
estimators. Relative to other similar procedures in the literature, the two locationbased estimators have the advantage that they offer an exact and uniform methodology for LS estimation of the LDV coefficient in a first order autoregressive model with or without exogenous regressors i.e. ARX(1).

However, no attempt has been made to accurately establish and/or compare the statistical properties among these estimators, or relative to those of the LS estimator when the LDV coefficient is restricted to realistic values. Neither has there been an attempt to
compare their performance in terms of their mean squared error (MSE) when various forms of the exogenous regressors are considered. Furthermore, only implicit confidence intervals have been given for the &lsquo
medianunbiased&rsquo
estimator. Explicit confidence bounds that are directly usable for inference are not available for either estimator. In this study a new estimator of the LDV coefficient is proposed
the &lsquo
most-probably-unbiased&rsquo
estimator. Its performance properties vis-a-vis the existing estimators are determined and compared when the parameter space of the LDV coefficient is restricted. In addition, the following new results are established: (1) an explicit computable form for the density of the LS estimator is derived for the first time and an efficient method for its numerical evaluation is proposed
(2) the exact bias, mean, median and mode of the distribution of the LS estimator are determined in three specifications of the ARX(1) model
(3) the exact variance and MSE of LS estimator is determined
(4) the standard error associated with the determination of same quantities when simulation rather than numerical integration method is used are established and the methods are compared in terms of computational time and effort
(5) an exact method of evaluating the density of the three estimators is described
(6) their exact bias, mean, variance and MSE are determined and analysed
and finally, (7) a method of obtaining the explicit exact confidence intervals from the distribution functions of the estimators is proposed.

The discussion and results show that the estimators are still biased in the usual sense: &lsquo
in expectation&rsquo
. However the bias is substantially reduced compared to that of the LS estimator. The findings are important in the specification of time-series regression models, point and interval estimation, decision theory, and simulation.

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34

Niglis, Anton, e Per Öberg. "Modelling High-Fidelity Robot Dynamics". Thesis, Linköpings universitet, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-119640.

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The field of robotics is in continuous development. Driving forces for the development are higher demands on robot accuracy and being more cost effective in the development process. To reduce costs, product development is moving towards virtual prototyping to enable early analysis and testing. This process demands realistic models and modelling is therefore of utmost importance. In the process of modelling high fidelity robot dynamics many different physical aspects have to be taken into account. Phenomena studied in this thesis stretch from where to introduce flexibilities, mechanical and dynamical coupling effects, and how to describe friction. By using a bottom up approach the effects are analysed individually to evaluate their contribution both to accuracy and computationalcomplexity. A strategy for how to model a flexible parallel linkage manipulator by introducing some crucial simplifications is presented. The elastic parameters are identified using a frequency domain identification algorithm developed in [Wernholt, 2007] and shows that the presented method works well up to a certain level of fidelity. Friction is modelled using empirically derived static and dynamic models. Evaluation of accuracy is conducted through identification of friction models for a real manipulator and it is seen that to capture all existing phenomena in low velocities a dynamic model is needed. It is also seen that friction characteristics vary with temperature and a Kalman filter is suggested to adaptively estimate friction parameters. Finally an implementation of a flexible manipulator model using the software MapleSim is presented. The tool severely simplifies the process of modelling manipulators and enables for export to other environment such as simulation, optimization and control.

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35

Hernández, González Francisco. "Planar Robot Arm Modelling and Control". Thesis, Mälardalens högskola, Akademin för innovation, design och teknik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-14883.

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The thesis objective is to model a one link robotic arm mounted on a sliding mobile platform and to investigate different control strategies under the effect of gravity and external force disturbance. For simplicity the robotic set up can be modelled and controlled as an inverted pendulum moving on a non constant sloping surface. Firstly the control is done on level ground. This lower mathematical complexity will be taken as an advantage to approach the analysis on aspects more related with control theory: several control techniques and observers, steady state error study, etcetera. Afterwards the control is generalized for sloping grounds. This chapter will seek situations closer to reality, the purpose is to design something with practical interests, like model a Segway.

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36

Adam, George K. "Modelling robot tasks in interactive workcells". Thesis, University of Strathclyde, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306981.

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37

Oxnard, Stephen. "Efficient hybrid virtual room acoustic modelling". Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/17459/.

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This thesis investigates approaches to virtual room acoustic modelling and auralisation in order to a develop hybrid modelling solution that is capable of efficient and accurate simulation of enclosed sound propagation. Emphasis is placed on the advantages and disadvantages of state of the art numerical and geometric acoustic modelling methods. Numerical methods have been shown to preserve important sound wave characteristics such as diffraction and room modes, and are considered more accurate for low frequency acoustic modelling than geometric techniques which fail to preserve such wave effects. However, the implementation of numerical acoustic models inherently requires large computational effort compared to more efficient geometric techniques such as ray-tracing. This is particularly problematic for simulations of large-scale 3D acoustic environments and for high spatio-temporal sampling rates. A novel acoustic modelling solution is presented, which seeks to circumvent the disadvantageous computational requirements of 3D numerical models while producing a suitable approximation to low frequency sound behaviour. This modelling technique incorporates multiple planar cross-sectional 2D Finite Difference schemes that are utilised in combination to synthesise low frequency wave propagation throughout the target acoustic field. In this way a subset of prominent low frequency sound wave characteristics may be emulated with low computational cost compared to 3D numerical schemes. These low-frequency results can then be combined with the high-frequency output from efficient geometric simulations to create a hybrid model providing accurate broadband results at a relatively low computational cost. Investigation of room impulse response rendering for a series of theoretic and real spaces demonstrates advantages of this new hybrid acoustic modelling technique over purely ray-based methods in terms of low frequency accuracy, and over 3D numerical methods in terms of computational efficiency. Conclusions are drawn from objective measurements obtained from simulation results of the virtual models produced. Results demonstrate the applicability of the novel hybrid approach to the enhancement of purely ray-based room impulse response rendering by which a more realistic representation of low frequency wave phenomena may be simulated in an efficient manner, improving the theoretical accuracy of objective and audible results. This study contributes towards research and design of high-speed, interactive virtual acoustic simulations appropriate for industrial and creative virtual reality applications.

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38

Luh, Cheng-Jye 1960. "Hierarchical modelling of mobile, seeing robots". Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/276998.

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Abstract (sommario):

This thesis describes the implementation of a hierarchical robot simulation environment which supports the design of robots with vision and mobility. A seeing robot model applies a classification expert system for visual identification of laboratory objects. The visual data acquisition algorithm used by the robot vision system has been developed to exploit multiple viewing distances and perspectives. Several different simulations have been run testing the visual logic in a laboratory environment. Much work remains to integrate the vision system with the rest of the robot system.

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39

Theodoridis, Theodoros. "Modelling criminal behaviours for intelligent robot surveillance". Thesis, University of Essex, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537948.

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40

Tubsuwan, Kantitut. "Thermal modelling of the green roof substrate". Thesis, Heriot-Watt University, 2017. http://hdl.handle.net/10399/3388.

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This research aims to improve the accuracy of a green roof thermal simulation by linking the moisture transfer in the substrate with the conduction heat transfer. The improved simulation is divided into two phases, which are the absorption and evaporation. For the absorption, this research applies the Sharp Front theory to predict the position of the boundary between the saturated and dry zones. The theory of evaporation from a porous medium is used to predict the moisture content in different substrate layers during evaporation. After the moisture content in each layer is determined, this moisture content data can be converted into thermal conductivity, and the time dependent effective thermal resistance can be calculated, which is used in the conduction heat flux calculation for the thermal simulation. Having developed the simulation of heat conduction through the substrate as a result of absorption and evaporation, the results are applied to a case study building to compare a green roof substrate in three moisture conditions (dry, saturated, and the varying simulated moisture content). The results confirm that it is possible to include the effect of water absorption and evaporation from a green roof substrate in the thermal simulation of building performance using the two theories. The improved simulation makes it possible to model an intensive green roof, where the depth of the substrate is likely to produce a greater distribution of moisture content in service. The simulation is an improvement over previous models and the case study shows that, assuming the substrate to be dry (as in existing models), underestimates the heat loss, whilst assuming it is saturated slightly overestimates the heat loss. The small, but significant, effect of moisture variation in service is important for designers of green roofs. If it is not taken into account it would be preferable to assume that the roof is continuously saturated as this gives a conservative estimate of the heat loss from a building.

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41

Mattsson, Tobias. "The Roots of a Magma Chamber, the Central Intrusion, Rum, NW-Scotland". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-238320.

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The island of Rum in the Inner Hebrides, NW-Scotland, hosts a central volcanic complex that is part of the British-Irish Palaeogene Igneous Province situated in NE- Ireland and NW- Scotland. On Rum, rocks from several stages of Palaeogene magmatic activity have been exposed by millions of years of erosion. Rum is best known amongst geologists because of the famous layered ultrabasic intrusion that covers the SSE part of the island, which is amongst the world’s most studied non-active (fossil) volcanoes. The Long Loch Fault traverses Rum with an N-S direction and has been proposed to represent the feeder zone to the layered ultrabasic intrusion. The area close to the Long Loch Fault has been named the Central Intrusion, and was formed by interaction of the plutonic rocks with the Long Loch Fault. There are two end-member theories for the origin of the Central Intrusion: (i) formation by wholesale subsidence (graben formation) of layered ultrabasic units or (ii) by intrusion of new material in-between the Western and Eastern Layered Intrusions (brecciating and fracturing blocks of material from the layered suite) and so causing pulses of uplift and subsequent collapse. To test how the Long Loch Fault influenced magma emplacement on Rum, field work was conducted including structural mapping, and rock-sampling. The data collected in the field were processed by structural 3D modelling (Move Software suite) and complemented by petrography, FTIR, Electron Microprobe analysis and thermobarometry modelling. The results reveal that several fault splays cut the Central Intrusion, which furthermore provide evidence of a transtensional graben situated above the fault zone and into which the layered units collapsed. This collapse was associated with the intrusion of Ca-rich feldspathic peridotite at zones of weakness in the layered rocks (e.g. bedding planes, unit contacts and fractures), producing smaller fault blocks and acting as a lubricant in-between blocks. FTIR and barometry results show that the intruding feldspathic peridotite magma was water-rich and that the clinopyroxenes in the magma crystallised at approximately 15 km of depth. Consequently, a combination of both theories for the creation of the Central Intrusion appears most reasonable. The combination of data gathered allows to formulate a model in which the tectonic activity of the Long Loch fault repetitively opened and closed the magma conduit, causing pressure build-up in the underlying magma reservoir(s) when the conduit was shut. When the pressure was released, e.g. during fault movement, dense (phyric) and wet ultrabasic magma ascended rapidly and spread out into the shallow crustal magma chamber, thus supplying the growing ultrabasic pluton with pulses of magma from depth.
Ön Rum är en del av ö-gruppen Inre Hebridéerna i Nordvästra Skottland och består till stor del av magmatiska bergarter som härrör från en vulkan som var aktiv för cirka 60 miljoner år sedan. Vulkanen tillhör den Britiska Paleogena Magmatiska Provinsen och är skapad av mantelplymen som för nuvarande befinner sig under Island. Den nu eroderade vulkanen har en ikonisk status bland geologer världen över på grund av att den minerallagrade magmakammaren som utgör stora delar av ön, alltså själva hjärtat av vulkanen. Long Loch förkastingen delar Rum i två delar och har föreslagits vara huvudledaren av magma in i magmakammaren. Området på ön i anknytning till förkastningen har påverkats mycket av dess rörelser och har namngets den Centrala Intrusionen. Det finns två vitt skilda teorier om hur den Centrala Intrusionen har skapats: (i) den Centrala Intrusionen har skapats genom sättningar i magmakammaren och bildat en gravsänka, eller (ii) nytt material tränger i magmakammaren, vilket leder till upplyftning av magmakammar golvet som följs av sättning och bildar en gravsänka. I denna masteravhandling testades hypotesen ’Long Loch förkastningen var den primära magmaledaren till magmakammaren idag exponerad på Rum’ genom fältarbete, 3D modellering, petrografi, och geokemiska analyser (FTIR, Mikrosond och barometri). Resulatet visar att den Centrala Intrusionen genomskärs av flera förskastningsgrenar till Long Loch förkastningen vilka tillsammans formar ett tulpan mönster (en typ av gravsänka) som indikerar att en zon av flytande magma (magmaledare) låg under den Centrala Intrusionen när vulkanen var aktiv. Magman från zonen underlättade gravsänka bildandet genom att dela minerallagren i stora block och att intrudera mellan lager och fungera som glidmedel, vilket betyder att båda teorierna kan appliceras på bildandet av den Centrala intrusionen. FTIR och barometri analyserna visar att den intruderade magma var mycket vattenrik och och kom från en magmakammere på 15 km djup. Long Loch förkastningens rörelser stängde och öppnade magmakanalen, vilket orsakade att kristallrik magma intruderade i pulser.

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42

Murphy, Damian Thomas. "Digital waveguide mesh topologies in room acoustics modelling". Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313846.

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43

Reggente, Matteo. "Statistical gas distribution modelling for mobile robot applications". Doctoral thesis, Örebro universitet, Institutionen för naturvetenskap och teknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-37896.

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In this dissertation, we present and evaluate algorithms for statistical gas distribution modelling in mobile robot applications. We derive a representation of the gas distribution in natural environments using gas measurements collected with mobile robots. The algorithms fuse different sensors readings (gas, wind and location) to create 2D or 3D maps. Throughout this thesis, the Kernel DM+V algorithm plays a central role in modelling the gas distribution. The key idea is the spatial extrapolation of the gas measurement using a Gaussian kernel. The algorithm produces four maps: the weight map shows the density of the measurements; the confidence map shows areas in which the model is considered being trustful; the mean map represents the modelled gas distribution; the variance map represents the spatial structure of the variance of the mean estimate. The Kernel DM+V/W algorithm incorporates wind measurements in the computation of the models by modifying the shape of the Gaussian kernel according to the local wind direction and magnitude. The Kernel 3D-DM+V/W algorithm extends the previous algorithm to the third dimension using a tri-variate Gaussian kernel. Ground-truth evaluation is a critical issue for gas distribution modelling with mobile platforms. We propose two methods to evaluate gas distribution models. Firstly, we create a ground-truth gas distribution using a simulation environment, and we compare the models with this ground-truth gas distribution. Secondly, considering that a good model should explain the measurements and accurately predicts new ones, we evaluate the models according to their ability in inferring unseen gas concentrations. We evaluate the algorithms carrying out experiments in different environments. We start with a simulated environment and we end in urban applications, in which we integrated gas sensors on robots designed for urban hygiene. We found that typically the models that comprise wind information outperform the models that do not include the wind data.

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44

Yu, Hongnian. "Modelling and robust adaptive control of robot manipulators". Thesis, King's College London (University of London), 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.720361.

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45

Manessis, A. "3D reconstruction from video using a mobile robot". Thesis, University of Surrey, 2001. http://epubs.surrey.ac.uk/844129/.

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An autonomous robot able to navigate inside an unknown environment and reconstruct full 3D scene models using monocular video has been a long term goal in the field of Machine Vision. A key component of such a system is the reconstruction of surface models from estimated scene structure. Sparse 3D measurements of real scenes are readily estimated from N-view image sequences using structure-from-motion techniques. In this thesis we present a geometric theory for reconstruction of surface models from sparse 3D data captured from N camera views. Based on this theory we introduce a general N-view algorithm for reconstruction of 3D models of arbitrary scenes from sparse data. Using a hypothesise and verify strategy this algorithm reconstructs a surface model which interpolates the sparse data and is guaranteed to be consistent with the feature visibility in the N-views. To achieve efficient reconstruction independent of the number of views a simplified incremental algorithm is developed which integrates the feature visibility independently for each view. This approach is shown to converge to an approximation of the real scene structure and have a computational cost which is linear in the number of views. Surface hypothesis are generated based on a new incremental planar constrained Delaunay triangulation algorithm. We present a statistical geometric framework to explicitly consider noise inherent in estimates of 3D scene structure from any real vision system. This approach ensures that the reconstruction is reliable in the presence of noise and missing data. Results are presented for reconstruction of both real and synthetic scenes together with an evaluation of the reconstruction performance in the presence of noise.

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46

Macaro, Gianmarco. "Dynamical modelling and control of a flexible serial robot". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018.

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The main goals of the work are the renewal of the mechanical design of the serial elastic robot ELBROB of the INSTITUTE OF ROBOTICS (Linz) and the building of two models of the robot: one that considers the members of the robot as rigid and another one that contemplate the elasticity of the bodies. The mechanical design consists in the choice and adaptation of a new gearmotor on the first axe of the robot due to malfunctions in the previous transmission and in a new design for the angular plates supporting the gearmotor of the third axe. A simple PD control is then implemented on both models. Both the elastic and rigid models of the robot are obtained with the energetic method of the Projection Equation in subsystem representation (the deformation of elastic members is modelled thanks to Ritz method). The subsystems are then combined in order to form a complete system in minimal form. On the real robot the control logic is developed using the Stateflow toolbox in MatLab/SimuLink, that covers safety monitoring and all the tasks performed by the robot. Thanks to the control logic developed in MatLab/SimuLink R it is possible to use the software ControlDesk from dSPACE to design an interface that allows to initialize the robot, make the robot perform desired trajectories and to monitor input and output signals in real time. Once the control logic is written it is possible to design trajectories in Cartesian space. Finally, the signals from the strain gauges are compared to the ones predicted with the rigid body models that was developed, in order to validate it.

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47

Rundgren, Joel. "Modelling, Control and Simulation of a Jet Printer Robot". Thesis, KTH, Reglerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-55973.

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This thesis was carried out at Micronic Mydata AB in Stockholm in cooperation with the Automatic Control Laboratory at Royal Institute of Technology (KTH). The company develops and produces robots to attach components onto Printed Circuit Boards (PCBs). The focus of this thesis is a Jet Printer robot called MY500 which applies solder paste dots onto PCBs. The purpose is to build a realistic model of the robot including its controller structure in the Matlab toolboxes Simulink and SimMechanics. An analysis of the controller performance and comparison to a linear quadratic regulator is also considered and conclusions are made based on simulation results and performance logs from the company's laboratory.

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48

Syed, Mohammad Athar. "Modelling and control of a parallel-actuated robot manipulator". Thesis, Cardiff University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388459.

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49

Albagul, Abdulgani. "Dynamic modelling and control of a wheeled mobile robot". Thesis, University of Newcastle Upon Tyne, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327239.

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50

Lichon, Mariusz. "Modelling and multiarm robot manipulation of non-rigid materials". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393957.

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Tesi sul tema "Root modelling"

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