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Calibration Process (calibration + process)
Selected AbstractsThe measurement and modelling of rill erosion at angle of repose slopes in mine spoilEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2008G. R. Hancock Abstract The process of rill erosion causes significant amounts of sediment to be moved in both undisturbed and disturbed environments and can be a significant issue for agriculture as well as mining lands. Rills also often develop very quickly (from a single rainfall event to a season) and can develop into gullies if sufficient runoff is available to continue their development. This study examines the ability of a terrestrial laser scanner to quantify rills that have developed on fresh and homogeneous mine spoil on an angle of repose slope. It also examines the ability of the SIBERIA erosion model to simulate the rill's spatial and temporal behaviour. While there has been considerable work done examining rill erosion on rehabilitated mine sites and agricultural fields, little work has been done to examine rill development at angle of repose sites. Results show that while the overall hillslope morphology was captured by the laser scanner, with the morphology of the rills being broadly captured, the characteristics of the rills were not well defined. The digital elevation model created by the laser scanner failed to capture the rill thalwegs and tops of the banks, therefore delineating a series of ill defined longitudinal downslope depressions. These results demonstrate that an even greater density of points is needed to capture sufficient rill morphology. Nevertheless, SIBERIA simulations of the hillslope demonstrated that the model was able to capture rill behaviour in both space and time when correct model parameters were used. This result provides confidence in the SIBERIA model and its parameterization. The results demonstrate the sensitivity of the model to changes in parameters and the importance of the calibration process. Copyright © 2007 John Wiley & Sons, Ltd. [source] Three-dimensional flow modelling and sediment transport in the River KlarälvenEARTH SURFACE PROCESSES AND LANDFORMS, Issue 7 2004Bijan Dargahi Abstract A three-dimensional ,ow model that uses the RNG k - , turbulence model and a non-equilibrium wall function was applied to the River Klarälven in the southwest part of Sweden. The objectives were to study the nature of the ,ow in the river bifurcation and to investigate the short-term sediment transport patterns in the river. The effectiveness of three-dimensional ,ow models depends upon: (1) how well the river geometry and it surface roughness are modelled; and (2) the choice of the closure model. Improvements were obtained by modelling the river in two parts: the entire river reach, and a selected part. Composite Manning coef,cients were used to account for roughness properties. The method requires a calibration process that ensures the water surface pro,les match the ,eld data. The k - , model under-predicted both the extent of ,ow separation zones and the number of secondary ,ow regions having a spiral motion, in comparison with the RNG k - , model. The 3-D model could predict with good accuracy both the general and secondary ,ow ,elds in the river. The results agreed well with the 3-D velocity measurements using an acoustic Doppler current pro,ler. A conceptual model was developed that accounts for the development of secondary ,ows in a river bifurcation having two bends. The main ,ow feature in the river cross-sections was the existence of multiple counter-rotating spiral motions. The number of spiral motions increased as the river bends were approached. The river bends also caused vorticity intensi,cation and increased the vertical velocities. The application of the 3-D ,ow model was extended by solving the sediment continuity equation. The sediment transport patterns were related to the secondary ,ow ,elds in the river. The sediment transport patterns at the river bifurcations are characterized by the growth of a sandbank. Copyright © 2004 John Wiley & Sons, Ltd. [source] Comparison of Linear Regression Models for Quantitative Geochemical Analysis: An Example Using X-Ray Fluorescence SpectrometryGEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 3 2005Mirna Guevara calibration analytique; régression linéaire; matériaux de référence en géochimie; géochimie analytique; loi de propagation d'erreurs This paper presents statistical aspects related to the calibration process and a comparison of different regression approaches of relevance to almost all analytical techniques. The models for ordinary least-squares (OLS), weighted least-squares (WLS), and maximum likelihood fitting (MLF) were evaluated and, as a case study, X-ray fluorescence (XRF) calibration curves for major elements in geochemical reference materials were used. The results showed that WLS and MLF models were statistically more consistent in comparison with the usually applied OLS approach. The use of uncertainty on independent and dependent variables during the calibration process and the calculation of final uncertainty on individual results using error propagation equations are the novel aspects of our work. Cet article présente les aspects statistiques liés au processus de calibration et fait une comparaison des différents calculs de régression utilisés dans pratiquement toutes les techniques analytiques. Les modèles des moindres carrés ordinaires (MCO) et pondérés (MCP), et d'ajustement de maximum de vraisemblance (AMV) ont étéévalués et appliqués aux courbes de calibration d'éléments majeurs obtenues en analyse par fluorescence X (XRF) de matériaux certifiés de référence. Les résultats obtenus avec les modèles MCP et AMV sont plus cohérents statistiquement que ceux obtenus la méthode classique des MCO. L'utilisation de l'incertitudes sur des variables indépendantes ou dépendantes durant la procédure de calibration et le calcul de l'incertitude finale sur chaque résultat à partir des lois de propagation d'erreur sont des aspects novateurs de ce travail. [source] Comparative assessment of two distributed watershed models with application to a small watershedHYDROLOGICAL PROCESSES, Issue 11 2006Latif Kalin Abstract Distributed watershed models are beneficial tools for the assessment of management practices on runoff and water-induced erosion. This paper evaluates, by application to an experimental watershed, two promising distributed watershed-scale sediment models in detail: the Kinematic Runoff and Erosion (KINEROS-2) model and the Gridded Surface Subsurface Hydrologic Analysis (GSSHA) model. The physics behind each model are to some extent similar, though they have different watershed conceptualizations. KINEROS-2 was calibrated using three rainfall events and validated over four separate rainfall events. Parameters estimated by this calibration process were adapted to GSSHA. With these parameters, GSSHA generated larger and retarded flow hydrographs. A 30% reduction in both plane and channel roughness in GSSHA along with the assumption of Green-Ampt conductivity KG-A = Ks, where Ks is the saturated conductivity, resulted in almost identical hydrographs. Sediment parameters not common in both models were calibrated independently of KINEROS-2. A comparative discussion of simulation results is presented. Even though GSSHA's flow component slightly overperformed KINEROS-2, the latter outperformed GSSHA in simulations for sediment transport. In spite of the fact that KINEROS-2 is not geared toward continuous-time simulations, simulations performed with both models over a 1 month period generated comparable results. Copyright © 2006 John Wiley & Sons, Ltd. [source] Calibration of a discrete element model for intact rock up to its peak strengthINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 5 2010Yuannian Wang Abstract When three dimensional, bonded discrete element models (DEMs) are deployed to model intact rock, a basic question is how to determine the micro parameters that control macro properties of the modeled rock. After briefly describing the authors' DEM code, this paper describes algorithms to calibrate the model's micro parameters against standard laboratory tests, such as uniaxial and triaxial tests. Sensitivity analysis is used to identify the deformability micro parameters by obtaining relationships between microscopic and macroscopic deformability properties. The strength model parameters are identified by a global optimization process aimed at minimizing the difference between computed and experimental failure envelopes. When applied to the experimental results of Lac du Bonnet granite, this calibration process produced a good agreement between simulated and experimental results for both deformability and strength properties. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experience in calibrating the double-hardening constitutive model MonotINTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2003M. A. Hicks The Monot double-hardening soil model has previously been implemented within a general purpose finite element algorithm, and used in the analysis of numerous practical problems. This paper reviews experience gained in calibrating Monot to laboratory data and demonstrates how the calibration process may be simplified without detriment to the range of behaviours modelled. It describes Monot's principal features, important governing equations and various calibration methods, including strategies for overconsolidated, cemented and cohesive soils. Based on a critical review of over 30 previous Monot calibrations, for sands and other geomaterials, trends in parameter values have been identified, enabling parameters to be categorized according to their relative importance. It is shown that, for most practical purposes, a maximum of only 5 parameters is needed; for the remaining parameters, standard default values are suggested. Hence, the advanced stress,strain modelling offered by Monot is attainable with a similar number of parameters as would be needed for some simpler, less versatile, models. Copyright © 2003 John Wiley & Sons, Ltd. [source] Surrogate model-based strategy for cryogenic cavitation model validation and sensitivity evaluationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 9 2008Tushar Goel Abstract The study of cavitation dynamics in cryogenic environment has critical implications for the performance and safety of liquid rocket engines, but there is no established method to estimate cavitation-induced loads. To help develop such a computational capability, we employ a multiple-surrogate model-based approach to aid in the model validation and calibration process of a transport-based, homogeneous cryogenic cavitation model. We assess the role of empirical parameters in the cavitation model and uncertainties in material properties via global sensitivity analysis coupled with multiple surrogates including polynomial response surface, radial basis neural network, kriging, and a predicted residual sum of squares-based weighted average surrogate model. The global sensitivity analysis results indicate that the performance of cavitation model is more sensitive to the changes in model parameters than to uncertainties in material properties. Although the impact of uncertainty in temperature-dependent vapor pressure on the predictions seems significant, uncertainty in latent heat influences only temperature field. The influence of wall heat transfer on pressure load is insignificant. We find that slower onset of vapor condensation leads to deviation of the predictions from the experiments. The recalibrated model parameters rectify the importance of evaporation source terms, resulting in significant improvements in pressure predictions. The model parameters need to be adjusted for different fluids, but for a given fluid, they help capture the essential fluid physics with different geometry and operating conditions. Copyright © 2008 John Wiley & Sons, Ltd. [source] A RAPID METHOD OF QUANTIFYING THE RESOLUTION LIMITS OF HEAT-FLOW ESTIMATES IN BASIN MODELSJOURNAL OF PETROLEUM GEOLOGY, Issue 2 2008A. Beha Deterministic forward models are commonly used to quantify the processes accompanying basin evolution. Here, we describe a workflow for the rapid calibration of palaeo heat-flow behaviour. The method determines the heat-flow history which best matches the observed data, such as vitrinite reflectance, which is used to indicate the thermal maturity of a sedimentary rock. A limiting factor in determining the heat-flow history is the ability of the algorithm used in the software for the maturity calculation to resolve information inherent in the measured data. Thermal maturation is controlled by the temperature gradient in the basin over time and is therefore greatly affected by maximum burial depth. Calibration, i.e. finding the thermal history model which best fits the observed data (e.g. vitrinite reflectance), can be a time-consuming exercise. To shorten this process, a simple pseudo-inverse model is used to convert the complex thermal behaviour obtained from a basin simulator into more simple behaviour, using a relatively simple equation. By comparing the calculated "simple" maturation trend with the observed data points using the suggested workflow, it becomes relatively straightforward to evaluate the range within which a best-fit model will be found. Reverse mapping from the simple model to the complex behaviour results in precise values for the heat-flow which can then be applied to the basin model. The goodness-of-fit between the modelled and observed data can be represented by the Mean Squared Residual (MSR) during the calibration process. This parameter shows the mean squared difference between all measured data and the respective predicted maturities. A minimum MSR value indicates the "best fit". Case studies are presented of two wells in the Horn Graben, Danish North Sea. In both wells calibrating the basin model using a constant heat-flow over time is not justified, and a more complex thermal history must be considered. The pseudo-inverse method was therefore applied iteratively to investigate more complex heat-flow histories. Neither in the observed maturity data nor in the recorded stratigraphy was there evidence for erosion which would have influenced the present-day thermal maturity pattern, and heat-flow and time were therefore the only variables investigated. The aim was to determine the simplest "best-fit" heat-flow history which could be resolved at the maximum resolution given by the measured maturity data. The conclusion was that basin models in which the predicted maturity of sedimentary rocks is calibrated solely against observed vitrinite reflectance data cannot provide information on the timing of anomalies in the heat-flow history. The pseudo inverse method, however, allowed the simplest heat-flow history that best fits the observed data to be found. [source] SENSITIVITY CONSIDERATIONS WHEN MODELING HYDROLOGIC PROCESSES WITH DIGITAL ELEVATION MODEL,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 4 2001Sung-Mm Cho ABSTRACT: The purpose of this paper is to investigate the sensitivity of a hydrologic models to the type of DEM used. This was done while modeling basin water quality with 1:24,000 and 1:250,000 U.S. Geological Survey DEMs as input to model hydrological processes. The manner in which the model results were sensitive to the choice of raster cell size (scale) is investigated in this study. The Broadhead watershed, located in New Jersey, USA, was chosen as a study area. Curve numbers were estimated by a trial and error to match simulated and observed total discharge. Monthly runoff for the watershed was used in the calibration process. Higher runoff volumes were simulated by the model when the 1:24,000 DEM were used as input data, probably due to the finer resolution which simulated increased average slope and hence higher estimated runoff from the watershed. As the simulated slope of the watershed is flatten with the 1:250,000 DEM, the response of stream flow was delayed and simulated less runoff volume. (KEY TERMS: DEM; curve number; sensitivity analysis; runoff volume; water quality; calibration.) [source] | |||||||||||||