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Modelling
Kinds of Modelling Terms modified by Modelling Selected AbstractsINTEGRATED MODELLING OF WATER POLICY SCENARIOS IN THE GREAT BARRIER REEF REGIONECONOMIC PAPERS: A JOURNAL OF APPLIED ECONOMICS AND POLICY, Issue 3 2005Alexander Smajgl The Reef Water Quality Protection Plan defined a landmark in the political discussion on water use in the Great Barrier Reef (GBR) region. In order to develop a decision support tool that integrates market values and non-market values we combine Computable General Equilibrium (CGE) modelling with multi-attribute utility theory (MAUT) to integrate socio-economic, ecological and hydrological aspects of water use. In two scenarios the applied modelling approach of this paper is explained. [source] AN EMPIRICAL SURVEY OF RESIDENTIAL WATER DEMAND MODELLINGJOURNAL OF ECONOMIC SURVEYS, Issue 5 2008Andrew C. Worthington Abstract The increased reliance on demand-side management policies as an urban water consumption management tool has stimulated considerable debate among economists, water utility managers, regulators, consumer interest groups and policymakers. In turn, this has fostered an increasing volume of literature aimed at providing best-practice estimates of price and income elasticities, quantifying the impact of non-price water restrictions and gauging the impact of non-discretionary environmental factors affecting residential water demand. This paper provides a synoptic survey of empirical residential water demand analyses conducted in the last 25 years. Both model specification and estimation and the outcomes of the analyses are discussed. [source] MATHEMATICAL MODELLING OF THIN-LAYER DRYING OF KIWIFRUIT SLICESJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2009M DOYMAZ ABSTRACT The effect of temperature on the drying kinetics of kiwifruit was investigated. The drying process was carried out at temperatures of 50, 55 and 60C, air velocity of 2.4 m/s and relative humidity between 10,25%. Drying time decreased considerably with increased air temperature. Drying process took place in the falling rate period. Twelve mathematical models available in the literature were fitted to the experimental data. The models were compared by four statistical parameters; i.e., determination of coefficient, mean relative percent error, reduced chi-square and root mean square error, and the best-fit model was selected. The modified Henderson and Pabis and Verma et al. models were given the best results in describing thin-layer drying of kiwifruits. The effective diffusivity of water during air-drying varied from 1.743 to 2.241 × 10,10 m2/s over the temperature range investigated, with activation energy equal to 22.48 kJ/mol. PRACTICAL APPLICATIONS Drying can be described as an industrial preservation method in which water content and activity of agricultural products are decreased by heated air to minimize biochemical, chemical and microbiological deterioration. Kiwifruit has a very short life because of softening and vitamin loss during cold storage. The use of drying prolongs the shelf-life of the kiwifruit, as the water content reduction slows down deterioration reactions. In this study, drying characteristics of kiwifruits were studied in a convectional hot-air dryer. The objectives of the present study were to determine experimentally the thin-layer drying characteristics and rehydration capacity of samples, and to fit the experimental data to 12 mathematical models available from the literature. [source] PETROLEUM MIGRATION, FAULTS AND OVERPRESSURE, PART I: CALIBRATING BASIN MODELLING USING PETROLEUM IN TRAPS , A REVIEWJOURNAL OF PETROLEUM GEOLOGY, Issue 3 2006D.A. Karlsen This paper considers the principles of deciphering basin-scale hydrocarbon migration patterns using the geochemical information which is present in trapped petroleum. Petroleum accumulations in subsiding basins can be thought of as "data archives" within which stored information can help us to understand aspects of hydrocarbon formation and migration. This information can impart a time-resolved picture of hydrocarbon migration in a basin in response to processes associated with progressive burial, particularly in the context of the occurrence and periodic activity of faults. This review, which includes a series of tentative models of migration-related processes in the extensional Halten Terrace area, offshore mid-Norway, illustrates how we can use information from the migrating mobile hydrocarbon phase to improve our knowledge of the static geological system. Of particular importance is the role of sub-seismic heterogeneities and faults in controlling migration processes. We focus on how the secondary migration process can be enhanced in a multi-source rock basin such as the Halten Terrace, thereby increasing prospectivity. [source] DISTRIBUTION OF SOURCE ROCKS AND MATURITY MODELLING IN THE NORTHERN CENOZOIC SONG HONG BASIN (GULF OF TONKIN), VIETNAMJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2005C. Andersen The northern offshore part of the Cenozoic Song Hong Basin in the Gulf of Tonkin (East Vietnam Sea) is at an early stage of exploration with only a few wells drilled. Oil to source rock correlation indicates that coals are responsible for the sub-commercial oil and gas accumulations in sandstones in two of the four wells which have been drilled on faulted anticlines and flower structures. The wells are located in a narrow, structurally inverted zone with a thick predominantly deltaic Miocene succession between the Song Chay and Vinh Ninh/Song Lo fault zones. These faults are splays belonging to the offshore extension of the Red River Fault Zone. Access to a database of 3,500 km of 2D seismic data has allowed a detailed and consistent break-down of the geological record of the northern part of the basin into chronostratigraphic events which were used as inputs to model the hydrocarbon generation history. In addition, seismic facies mapping, using the internal reflection characteristics of selected seismic sequences, has been applied to predict the lateral distribution of source rock intervals. The results based on Yükler ID basin modelling are presented as profiles and maturity maps. The robustness of the results are analysed by testing different heat flow scenarios and by transfer of the model concept to IES Petromod software to obtain a more acceptable temperature history reconstruction using the Easy%R0 algorithm. Miocene coals in the wells located in the inverted zone between the fault splays are present in separate intervals. Seismic facies analysis suggests that the upper interval is of limited areal extent. The lower interval, of more widespread occurrence, is presently in the oil and condensate generating zones in deep synclines between inversion ridges. The Yükler modelling indicates, however, that the coaly source rock interval entered the main window prior to formation of traps as a result of Late Miocene inversion. Lacustrine mudstones, similar to the highly oil-prone Oligocene mudstones and coals which are exposed in the Dong Ho area at the northern margin of the Song Hong Basin and on Bach Long Vi Island in Gulf of Tonkin, are interpreted to be preserved in a system of undrilled NW,SE Paleogene half-grabens NE of the Song Lo Fault Zone. This is based on the presence of intervals with distinct, continuous, high reflection seismic amplitudes. Considerable overlap exists between the shale-prone seismic facies and the modelled extent of the present-day oil and condensate generating zones, suggesting that active source kitchens also exist in this part of the basin. Recently reported oil in a well located onshore (BIO-STB-IX) at the margin of the basin, which is sourced mainly from "Dong Ho type" lacustrine mudstones supports the presence of an additional Paleogene sourced petroleum system. [source] BURIAL HISTORY RECONSTRUCTION AND THERMAL MODELLING AT KUH-E MOND, SW IRANJOURNAL OF PETROLEUM GEOLOGY, Issue 4 2003M. R. Kamali At the Kuh-e Mond anticline (Fars Province, SW Iran) and in nearby offshore structures, large volumes of natural gas are reservoired in the Permian , Early Triassic Dehram Group while heavy oil has been discovered in the Cretaceous Sarvak and Eocene Jahrum Formations. In this paper, we use data from six exploration wells and from nearby surface exposures to reconstruct the burial history at Kuh-e Mond. Regional observations show that the thick sedimentary fill in this part of the Zagros Basin was subjected to intense tectonism during the Zagros Orogeny, with a paroxysmal phase during the late Miocene and Pliocene. Thermal modelling and geochemical data from Kuh-e Mond and adjacent fields allows possible hydrocarbon generation and migration mechanisms to be identified. Maturities predicted using Lopatin's TTI model are in accordance with maturities obtained from vitrinite reflectance measurements. We show that formations which have source potential in the nearby Dezful Embayment (including the Pabdeh, Gurpi, Gadvan and Kazhdumi Formations) have not reached the oil window in the Mond wells. Moreover, their organic carbon content is very low as they were deposited in oxic, shallow-water settings. Underlying units (including the Ordovician and Cambrian) could have reached the gas window but contain little organic matter. Silurian shales (Sarchahan Formation), which generate gas at Kuh-e Gahkum and Kuh-e Faraghan (north of Bandar Abbas) and in Saudi Arabia and elsewhere in the Middle East, are absent from the Mond structure. The absence of source rocks suggests that the gas and heavy oil accumulations at Kuh-e Mond and at nearby fields have most probably undergone long-distance lateral migration from distant source kitchens. [source] CYCLOSPORIN DOSING IN CHILDREN FOLLOWING RENAL TRANSPLANTATION: POPULATION PHARMACOKINETIC MODELLINGNEPHROLOGY, Issue 3 2000McTaggart Sj [source] MODELLING THE SLOW MEAN-REVERSION OF THE CENTRAL AND EASTERN EUROPEAN COUNTRIES' REAL EXCHANGE RATES,THE MANCHESTER SCHOOL, Issue 1 2008GILLES DUFRENOT In this paper we propose a new modelling approach of the exchange rate misalignments in four transition countries: Hungary, Poland, Slovakia and Slovenia. We provide an empirical framework that takes into account two characteristics of these misalignments: while the fundamentals and policies adjust to restore equilibrium towards the long-term exchange rate, there are factors that hinder a fast mean-reverting dynamics. When the exchange rates adjust slowly to their equilibrium long-run values, the standard regressions that assume zero-mean misalignments present some drawbacks and one needs a model that helps to capture the time-varying aspects of the misalignment dynamics. The model proposed in this paper reproduces well the periods of overvaluation and undervaluation observed in the four countries. [source] MACROECONOMETRIC MODELLING WITH A GLOBAL PERSPECTIVE,THE MANCHESTER SCHOOL, Issue 2006M. HASHEM PESARAN This paper provides a synthesis and further development of a global modelling approach introduced in Pesaran et al. (Journal of Business and Economic Statistics, Vol. 22 (2004), pp. 129,162), where country-specific models in the form of VARX* structures are estimated relating a vector of domestic variables, xit, to their foreign counterparts, , and then consistently combined to form a global vector autoregression. It is shown that the VARX* models can be derived as the solution to a dynamic stochastic general equilibrium model where overidentifying long-run theoretical relations can be tested and imposed if acceptable. This gives the system a transparent long-run theoretical structure. Similarly, short-run overidentifying theoretical restrictions can be tested and imposed if accepted. Alternatively, if one has less confidence in the short-run theory the dynamics can be left unrestricted. The assumption of the weak exogeneity of the foreign variables for the long-run parameters can be tested, where variables can be interpreted as proxies for regional and global factors. Rather than using deviations from ad hoc statistical trends, the equilibrium values of the variables reflecting the long-run theory embodied in the model can be calculated. The paper also provides some new results on the relative importance of external shocks for the UK and the Euro area economies. [source] TOWARDS A NEW APPROACH TO ARCHAEOMAGNETIC DATING IN EUROPE USING GEOMAGNETIC FIELD MODELLING*ARCHAEOMETRY, Issue 2 2009A. LODGE We introduce a new approach to producing secular variation curves for archaeomagnetic dating, using global geomagnetic field modelling techniques. Using published palaeosecular variation curves for five European locations as input, and a previous global model for regularization, we produce a model for the period ad 0,1900, which reproduces the input curves within their 95% confidence intervals, and successfully fits data from other regions in Europe. Our global model performs as well as a previous regional model, but additionally ensures consistency with physical constraints. We show that the curves currently used for dating are not mutually consistent, and therefore that in the future this new approach will provide more reliable curves for archaeomagnetic dating. [source] A SEMIPARAMETRIC BAYESIAN APPROACH TO NETWORK MODELLING USING DIRICHLET PROCESS PRIOR DISTRIBUTIONSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 3 2010Pulak Ghosh Summary This paper considers the use of Dirichlet process prior distributions in the statistical analysis of network data. Dirichlet process prior distributions have the advantages of avoiding the parametric specifications for distributions, which are rarely known, and of facilitating a clustering effect, which is often applicable to network nodes. The approach is highlighted for two network models and is conveniently implemented using WinBUGS software. [source] LEVERAGE ADJUSTMENTS FOR DISPERSION MODELLING IN GENERALIZED NONLINEAR MODELSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2009Gordon K. Smyth Summary For normal linear models, it is generally accepted that residual maximum likelihood estimation is appropriate when covariance components require estimation. This paper considers generalized linear models in which both the mean and the dispersion are allowed to depend on unknown parameters and on covariates. For these models there is no closed form equivalent to residual maximum likelihood except in very special cases. Using a modified profile likelihood for the dispersion parameters, an adjusted score vector and adjusted information matrix are found under an asymptotic development that holds as the leverages in the mean model become small. Subsequently, the expectation of the fitted deviances is obtained directly to show that the adjusted score vector is unbiased at least to,O(1/n). Exact results are obtained in the single-sample case. The results reduce to residual maximum likelihood estimation in the normal linear case. [source] HIGH-DIMENSIONAL PARAMETRIC MODELLING OF MULTIVARIATE EXTREME EVENTSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2009Alec G. Stephenson Summary Multivariate extreme events are typically modelled using multivariate extreme value distributions. Unfortunately, there exists no finite parametrization for the class of multivariate extreme value distributions. One common approach is to model extreme events using some flexible parametric subclass. This approach has been limited to only two or three dimensions, primarily because suitably flexible high-dimensional parametric models have prohibitively complex density functions. We present an approach that allows a number of popular flexible models to be used in arbitrarily high dimensions. The approach easily handles missing and censored data, and can be employed when modelling componentwise maxima and multivariate threshold exceedances. The approach is based on a representation using conditionally independent marginal components, conditioning on positive stable random variables. We use Bayesian inference, where the conditioning variables are treated as auxiliary variables within Markov chain Monte Carlo simulations. We demonstrate these methods with an application to sea-levels, using data collected at 10 sites on the east coast of England. [source] SCALE MIXTURES DISTRIBUTIONS IN STATISTICAL MODELLINGAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 2 2008S.T. Boris Choy Summary This paper presents two types of symmetric scale mixture probability distributions which include the normal, Student t, Pearson Type VII, variance gamma, exponential power, uniform power and generalized t (GT) distributions. Expressing a symmetric distribution into a scale mixture form enables efficient Bayesian Markov chain Monte Carlo (MCMC) algorithms in the implementation of complicated statistical models. Moreover, the mixing parameters, a by-product of the scale mixture representation, can be used to identify possible outliers. This paper also proposes a uniform scale mixture representation for the GT density, and demonstrates how this density representation alleviates the computational burden of the Gibbs sampler. [source] HIERARCHICAL BAYESIAN MODELLING OF SOCIAL VARIATION IN THE AGE DEPENDENCE OF DISABILITY PREVALENCEAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 4 2005Patrick Graham Summary Motivated by a study of social variation in the relationship of functional limitation prevalence to age, this paper examines methods for modelling social variation in health outcomes. It is argued that, from a Bayesian perspective, modelling the dependence of functional limitation prevalence on age separately for each social group, corresponds to an implausible prior model, in addition to leading to imprecise estimates for some groups. The alternative strategy of fitting a single model, perhaps including some age-by-group interactions but omitting higher-order interactions, requires a strong prior commitment to the absence of such effects. Hierarchical Bayesian modelling is proposed as a compromise between these two analytical approaches. Under all hierarchical Bayes analyses there is strong evidence for an ethnic group difference in limitation prevalence in early- to mid-adulthood among tertiary-qualified males. In contrast, the single-model approach largely misses this effect, while the group-specific analyses exhibit an unrealistically large degree of heterogeneity in gender-education-specific ethnicity effects. The sensitivity of posterior inferences to prior specifications is studied. [source] SPACE,TIME MODELLING OF SYDNEY HARBOUR WINDSAUSTRALIAN & NEW ZEALAND JOURNAL OF STATISTICS, Issue 1 2005Edward Cripps Summary This paper develops a space-time statistical model for local forecasting of surface-level wind fields in a coastal region with complex topography. The statistical model makes use of output from deterministic numerical weather prediction models which are able to produce forecasts of surface wind fields on a spatial grid. When predicting surface winds at observing stations, errors can arise due to sub-grid scale processes not adequately captured by the numerical weather prediction model, and the statistical model attempts to correct for these influences. In particular, it uses information from observing stations within the study region as well as topographic information to account for local bias. Bayesian methods for inference are used in the model, with computations carried out using Markov chain Monte Carlo algorithms. Empirical performance of the model is described, illustrating that a structured Bayesian approach to complicated space-time models of the type considered in this paper can be readily implemented and can lead to improvements in forecasting over traditional methods. [source] ACCOUNTING FOR POPULATION AGEING IN TAX MICROSIMULATION MODELLING BY SURVEY REWEIGHTING,AUSTRALIAN ECONOMIC PAPERS, Issue 1 2006LIXIN CAI This paper investigates the use of sample reweighting, in a behavioural tax microsimulation model, to examine the implications for government taxes and expenditure of population ageing in Australia. First, a calibration approach to sample reweighting is described, producing new weights that achieve specified population totals for selected variables. Second, the performance of the Australian Bureau of Statistics' (ABS) weights provided with the 2000,2001 Survey of Income and Housing Cost (SIHC) was examined and it was found that reweighting does not improve the simulation outcomes for the 2001 situation, so the original ABS weights were retained for 2001. Third, the implications of changes in the age distribution of the population were examined, based on population projections to 2050. A ,pure' change in the age distribution was examined by keeping the aggregate population size fixed and changing only the relative frequencies in different age-gender groups. Finally, the effects of a policy change to benefit taper rates in Australia were compared for 2001 and 2050 population weights. It is suggested that this type of exercise provides an insight into the implications for government income tax revenue and social security expenditure of changes in the population, indicating likely pressures for policy changes. [source] BIOMOD , optimizing predictions of species distributions and projecting potential future shifts under global changeGLOBAL CHANGE BIOLOGY, Issue 10 2003Wilfried ThuillerArticle first published online: 9 OCT 200 Abstract A new computation framework (BIOMOD: BIOdiversity MODelling) is presented, which aims to maximize the predictive accuracy of current species distributions and the reliability of future potential distributions using different types of statistical modelling methods. BIOMOD capitalizes on the different techniques used in static modelling to provide spatial predictions. It computes, for each species and in the same package, the four most widely used modelling techniques in species predictions, namely Generalized Linear Models (GLM), Generalized Additive Models (GAM), Classification and Regression Tree analysis (CART) and Artificial Neural Networks (ANN). BIOMOD was applied to 61 species of trees in Europe using climatic quantities as explanatory variables of current distributions. On average, all the different modelling methods yielded very good agreement between observed and predicted distributions. However, the relative performance of different techniques was idiosyncratic across species, suggesting that the most accurate model varies between species. The results of this evaluation also highlight that slight differences between current predictions from different modelling techniques are exacerbated in future projections. Therefore, it is difficult to assess the reliability of alternative projections without validation techniques or expert opinion. It is concluded that rather than using a single modelling technique to predict the distribution of several species, it would be more reliable to use a framework assessing different models for each species and selecting the most accurate one using both evaluation methods and expert knowledge. [source] A moving planar mirror based approach for cultural reconstructionCOMPUTER ANIMATION AND VIRTUAL WORLDS (PREV: JNL OF VISUALISATION & COMPUTER ANIMATION), Issue 3-4 2004Kyung Ho Jang Abstract Modelling from images is a cost-effective means of obtaining virtual cultural heritage models. These models can be effectively constructed from classical Structure from Motion algorithm. However, it's too difficult to reconstruct whole scenes using SFM method since general oriental historic sites contain a very complex shapes and brilliant colours. To overcome this difficulty, the current paper proposes a new reconstruction method based on a moving planar mirror. We devise the mirror posture instead of scene itself as a cue for reconstructing the geometry. That implies that the geometric cues are inserted into the scene by compulsion. With this method, we can obtain the geometrical details regardless of the scene complexity. For this purpose, we first capture image sequences through the moving mirror containing the interested scene, and then calibrate the camera through the mirror's posture. Since the calibration results are still inaccurate due to the detection error, the camera pose is revised using frame-correspondence of the corner points that are easily obtained using the initial camera posture. Finally, 3D information is computed from a set of calibrated image sequences. We validate our approach with a set of experiments on some cultural heritage objects. Copyright © 2004 John Wiley & Sons, Ltd. [source] Embedded Implicit Stand-Ins for Animated Meshes: A Case of Hybrid ModellingCOMPUTER GRAPHICS FORUM, Issue 1 2010D. Kravtsov Abstract In this paper, we address shape modelling problems, encountered in computer animation and computer games development that are difficult to solve just using polygonal meshes. Our approach is based on a hybrid-modelling concept that combines polygonal meshes with implicit surfaces. A hybrid model consists of an animated polygonal mesh and an approximation of this mesh by a convolution surface stand-in that is embedded within it or is attached to it. The motions of both objects are synchronised using a rigging skeleton. We model the interaction between an animated mesh object and a viscoelastic substance, which is normally represented in an implicit form. Our approach is aimed at achieving verisimilitude rather than physically based simulation. The adhesive behaviour of the viscous object is modelled using geometric blending operations on the corresponding implicit surfaces. Another application of this approach is the creation of metamorphosing implicit surface parts that are attached to an animated mesh. A prototype implementation of the proposed approach and several examples of modelling and animation with near real-time preview times are presented. [source] Affective Modelling: Profiling Geometrical Models with Human Emotional ResponsesCOMPUTER GRAPHICS FORUM, Issue 7 2009Cheng-Hung Lo Abstract In this paper, a novel concept, Affective Modelling, is introduced to encapsulate the idea of creating 3D models based on the emotional responses that they may invoke. Research on perceptually-related issues in Computer Graphics focuses mostly on the rendering aspect. Low-level perceptual criteria taken from established Psychology theories or identified by purposefully-designed experiments are utilised to reduce rendering effort or derive quality evaluation schemes. For modelling, similar ideas have been applied to optimise the level of geometrical details. High-level cognitive responses such as emotions/feelings are less addressed in graphics literatures. This paper investigates the possibility of incorporating emotional/affective factors for 3D model creations. Using a glasses frame model as our test case, we demonstrate a methodological framework to build the links between human emotional responses and geometrical features. We design and carry out a factorial experiment to systematically analyse how certain shape factors individually and interactively influence the viewer's impression of the shape of glasses frames. The findings serve as a basis for establishing computational models that facilitate emotionally-guided 3D modelling. [source] A Time Model for Time-Varying VisualizationCOMPUTER GRAPHICS FORUM, Issue 6 2009M. Wolter I.3.6 [Computer Graphics]: Methodology and Techniques; I.6.6 [Simulation and Modelling]: Simulation Output Analysis Abstract The analysis of unsteady phenomena is an important topic for scientific visualization. Several time-dependent visualization techniques exist, as well as solutions for dealing with the enormous size of time-varying data in interactive visualization. Many current visualization toolkits support displaying time-varying data sets. However, for the interactive exploration of time-varying data in scientific visualization, no common time model that describes the temporal properties which occur in the visualization process has been established. In this work, we propose a general time model which classifies the time frames of simulation phenomena and the connections between different time scales in the analysis process. This model is designed for intuitive interaction with time in visualization applications for the domain expert as well as for the developer of visualization tools. We demonstrate the benefits of our model by applying it to two use cases with different temporal properties. [source] Implicit Surface Modelling with a Globally Regularised Basis of Compact SupportCOMPUTER GRAPHICS FORUM, Issue 3 2006C. Walder We consider the problem of constructing a globally smooth analytic function that represents a surface implicitly by way of its zero set, given sample points with surface normal vectors. The contributions of the paper include a novel means of regularising multi-scale compactly supported basis functions that leads to the desirable interpolation properties previously only associated with fully supported bases. We also provide a regularisation framework for simpler and more direct treatment of surface normals, along with a corresponding generalisation of the representer theorem lying at the core of kernel-based machine learning methods. We demonstrate the techniques on 3D problems of up to 14 million data points, as well as 4D time series data and four-dimensional interpolation between three-dimensional shapes. Categories and Subject Descriptors (according to ACM CCS): I.3.5 [Computer Graphics]: Curve, surface, solid, and object representations [source] Recent Developments and Applications of Haptic DevicesCOMPUTER GRAPHICS FORUM, Issue 2 2003S. D. Laycock Abstract Over recent years a variety of haptic feedback devices have been developed and are being used in a number of important applications. They range from joysticks used in the entertainment industry to specialised devices used in medical applications. This paper will describe the recent developments of these devices and show how they have been applied. It also examines how haptic feedback has been combined with visual display devices, such as virtual reality walls and workbenches, in order to improve the immersive experience. ACM CSS: H.5.2 Information Interfaces and Presentation,Haptic I/O; I.3.8 Computer Graphics,Applications; I.6 Simulation and Modelling,Applications [source] On the Modelling of a Nonequilibrium Spherical Microwave Discharge at Atmospheric PressureCONTRIBUTIONS TO PLASMA PHYSICS, Issue 3 2007I. R. Rafatov Abstract The work presents results of calculation of a spherical microwave discharge characteristics in an argon at atmospheric pressure against the external parameters (the mode, frequency and power of the applied electromagnetic field and the size of the discharge chamber). Model assumes a thermal and ionization non-equilibrium of discharge plasma and takes into account first three modes of incident electromagnetic waves. Calculation results are compared with the results for the ionization equilibrium model. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Gyrofluid Turbulence Modelling of the Linear Device VINETACONTRIBUTIONS TO PLASMA PHYSICS, Issue 7-9 2006G. N. Kervalishvili Abstract The two-moment version of the three-dimensional gyrofluid code GEM3 has been adapted for the simulation of drift-wave turbulence in the linear device VINETA [1]. In the modified GEM3 code gyrofluid equations for the density and parallel velocity of electrons and ions are solved for the cylindrical annulus. Computations are done for the electrostatic case using an exponential background density profile observed experimentally. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Experimental Study and Modelling of Formation and Decay of Active Species in an Oxygen DischargeCONTRIBUTIONS TO PLASMA PHYSICS, Issue 1 2005A.-M. Diamy Abstract A microwave (2.45 GHz) oxygen discharge (3 hPa, 150 W, 50 mL.min,1) is studied by optical emission spectroscopy of O(5P) (line 777.4 nm) and of the atmospheric system of O2(head-line 759.4 nm). Calibration of the spectral response of the optical setup is used to determine the concentrations of O(5P) and O2(b). The concentration of the O(5P) atoms is in the range 108,109 cm,3 and the concentration of the O2(b) molecules is in the range 1014 , 2 × 1014 cm,3 along the discharge tube. An attempt is made to simulate the experimental results by using coupling the Boltzmann equation, homogeneous energy transfer V-V and V-T, heterogeneous reactions on the walls (energy transfer and recombination of atoms) and a kinetic scheme (electronic transfer and chemical reactions). The Boltzmann equation includes momentum transfer, inelastic and superelastic processes and e-e collisions. V-V and V-T transfer equations are obtained from the SSH theory and the kinetic scheme includes 65 reactions with 17 species [electrons e, ions O, and O2,, fundamental electronic neutral species O(3P), O2, O2(X,v), O3 and excited neutral species O2(a), O2(b), O2(A), O(1D), O(1S), O(5P), O(4d 5Do), O(5s 5So), O(3d 5Do) and O(4s 5So)]. A fair agreement between experimental results and modelling is obtained with the following set of fitting values: , heterogeneous deactivation coefficient for O2(b) , = 2.6 × 10,2; , rate constant of reaction [O(1D) + O(3P) , 2 O(3P)] k34 = 1.4 × 10,11 cm3.s,1; , electron concentration in the range 1010 , 1011 cm,3. Modelling shows that the recombination coefficient for oxygen atoms on the silica wall (range 1.4 × 10,3 , 0.2 × 10,3) is of the same order as the values obtained in a previous paper and that the ratio ([O] / 2 [O2]initial) is about 33,50%. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Hydrodynamic and Kinetic Modelling of Dust Free and Dusty Radio-Frequency DischargesCONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-6 2004W. J. Goedheer Abstract In this paper hydrodynamic and kinetic approaches to model low pressure capacitively coupled radio-frequency discharges are discussed. In particular approaches and results for power modulated discharges in a mixture of silane and hydrogen and for discharges containing a considerable amount of dust particles will be presented. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Present and potential distribution of invasive garlic mustard (Alliaria petiolata) in North AmericaDIVERSITY AND DISTRIBUTIONS, Issue 4 2002Erik Welk Abstract. This paper demonstrates the use of a bioclimatic model mapped over geographical regions as a tool for spatially refined risk assessment for the establishment of non-indigenous plants with invasive behaviour. Drawing on the relationship between plant distribution and climate, the approach uses gridded spatial interpolated monthly means of temperature and precipitation linked with accurate maps of general native distribution ranges to predict the long-term potential of a plant species to invade a certain region. The ascertained potential for establishment is illustrated by the example of garlic mustard (Alliaria petiolata[M. Bieb.] Cavara & Grande) in North America. The first step is to calculate and visualize the number of populated grid cells along climatic gradients in frequency diagrams for the general native distribution range. Interpretations of the response curves recorded are used for assessing apparent climatic range boundaries. Modelling was gradually optimized based on the results of experience-based interpretations and by examining omission and over-representation errors. The obtained climatic model of the range of A. petiolata shows considerable congruencies with its mapped, native Eurasian range. Degrees of climatic similarity between North America and the native range of A. petiolata were calculated with the help of GIS methodology and were used to assess the regionally different likelihood of establishment in North America of the invasive species under consideration. [source] Risk assessment for nonindigenous pests: 2.DIVERSITY AND DISTRIBUTIONS, Issue 5 2001Accounting for interyear climate variability Abstract The paper firstly discusses the importance of accounting for interyear variability when assessing the likelihood of establishment of an alien pest. The potential establishment of Colorado beetle (Leptinotarsa decemlineata) is used as an illustration within the geographical context of England and Wales. An aggregate risk index is introduced as a probabilistic representation of the likelihood that a pest might complete a single generation over a 30-year period (1961,90). Data for individual years were used to compute, objectively, the interyear distribution of risk across the landscape. The standard deviation in area at risk (26 800 km2) was high relative to the average proportion of the landscape potentially at risk (95 700 km2). In 40% of years, the area at risk was estimated to be higher than ,average'. Secondly, the paper demonstrates multiple indices of risk that reflect different aspects of pest risk assessment. Viewing risk from a variety of perspectives provides a means of gauging the consistency and therefore reliability of the results. This contrasts with current practice, where a single mapped output is commonly presented to decision makers. Modelling using a daily time step allowed the use of indices to investigate the long-term probabilities of biotic and abiotic events of short duration. These indices include estimates of pest activity and flight potential. [source] | |||||||||||||||||||||||||||||||||||||||||||||||||||||||