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Surface Models (surface + models)
Kinds of Surface Models Selected AbstractsACIDIC ELECTROLYZED WATER PROPERTIES AS AFFECTED BY PROCESSING PARAMETERS AND THEIR RESPONSE SURFACE MODELSJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 1 2004GABRIEL O. I. EZEIKE Several studies of acidic electrolyzed (EO) water demonstrated the efficacy of EO water for inactivation of different foodborne pathogens and reported on the chemical species present in EO water. This study was conducted to investigate the effect of production parameters (voltage, NaCl concentration, flow rate, and temperature) on the properties of EO water and to model the complex reactions occurring during the generation of EO water. At 0.1% salt concentration, EO water was produced at 2, 10, and 28 V. However, due to high conductivity of the electrolyte at 0.5% salt concentration, the voltage applied across the cell was limited to 7 V. The electrolyte flow rate was set at 0.5, 2.5, and 4.5 L/mn. For pH and oxidation-reduction potential (ORP), NaCl concentration was the most significant factor followed by voltage, electrolyte flow rate and temperature, respectively. However, in the case of residual chlorine, flow rate was relatively more important than voltage. Response surface methodology yielded models to predict EO water properties as functions of the process parameters studied, with very high coefficients of determination (R2= 0.872 to 0.938). In general, the higher the NaCl concentration and voltage, the higher the ORP and residual chlorine of EO water. Increased electrolyte flow rate will produce EO water with lower ORP and residual chlorine due to the shorter residence time in the electrolytic cell. [source] Simplified intersubject averaging on the cortical surface using SUMAHUMAN BRAIN MAPPING, Issue 1 2006Brenna D. Argall Abstract Task and group comparisons in functional magnetic resonance imaging (fMRI) studies are often accomplished through the creation of intersubject average activation maps. Compared with traditional volume-based intersubject averages, averages made using computational models of the cortical surface have the potential to increase statistical power because they reduce intersubject variability in cortical folding patterns. We describe a two-step method for creating intersubject surface averages. In the first step cortical surface models are created for each subject and the locations of the anterior and posterior commissures (AC and PC) are aligned. In the second step each surface is standardized to contain the same number of nodes with identical indexing. An anatomical average from 28 subjects created using the AC,PC technique showed greater sulcal and gyral definition than the corresponding volume-based average. When applied to an fMRI dataset, the AC,PC method produced greater maximum, median, and mean t -statistics in the average activation map than did the volume average and gave a better approximation to the theoretical-ideal average calculated from individual subjects. The AC,PC method produced average activation maps equivalent to those produced with surface-averaging methods that use high-dimensional morphing. In comparison with morphing methods, the AC,PC technique does not require selection of a template brain and does not introduce deformations of sulcal and gyral patterns, allowing for group analysis within the original folded topology of each individual subject. The tools for performing AC,PC surface averaging are implemented and freely available in the SUMA software package. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source] Global perspective on hydrology, water balance, and water resources management in arid basinsHYDROLOGICAL PROCESSES, Issue 2 2010Yanjun Shen Abstract Arid and semiarid regions comprise a large part of the world's terrestrial area and are home to hundreds of millions of people. Water resources in arid regions are rare and critical to society and to ecosystems. The hydrologic cycle in arid and semiarid regions has been greatly altered due to long-term human exploitation. Under conditions of global warming, water resources in these regions are expected to be more unstable and ecosystems likely will suffer from severe water stress. In the current special issue contributed to understanding ecohydrologic processes and water-related problems in arid regions of western China, this paper provides a global perspective on the hydrology and water balance of six major arid basins of the world. A number of global datasets, including the state-of-the-art ensemble simulation of land surface models by GSWP2 (Global Soil Wetness Project II, a project by GEWEX), were used to address the water balance terms in the world's major hydroclimatic regions. The common characteristics of hydrologic cycles and water balance in arid basins are as follows: strong evapotranspiration characterizes the hydrological cycle in arid basins; and in water use sectors irrigation consumes a large amount of water, resulting in degradation of native vegetation. From the ecohydrology viewpoint, a comprehensive study of hydrological and ecological processes of water utilization in arid basins is urgently needed. Copyright © 2009 John Wiley & Sons, Ltd. [source] Octree-based reasonable-quality hexahedral mesh generation using a new set of refinement templatesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 13 2009Yasushi Ito Abstract An octree-based mesh generation method is proposed to create reasonable-quality, geometry-adapted unstructured hexahedral meshes automatically from triangulated surface models without any sharp geometrical features. A new, easy-to-implement, easy-to-understand set of refinement templates is developed to perform local mesh refinement efficiently even for concave refinement domains without creating hanging nodes. A buffer layer is inserted on an octree core mesh to improve the mesh quality significantly. Laplacian-like smoothing, angle-based smoothing and local optimization-based untangling methods are used with certain restrictions to further improve the mesh quality. Several examples are shown to demonstrate the capability of our hexahedral mesh generation method for complex geometries. Copyright © 2008 John Wiley & Sons, Ltd. [source] Numerical derivation of contact mechanics interface laws using a finite element approach for large 3D deformationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 2 2004Alex Alves Bandeira Abstract In this work a homogenization method is presented to obtain by numerical simulation interface laws for normal contact pressure based on statistical surface models. For this purpose and assuming elastic behaviour of the asperities, the interface law of Kragelsky et al. (Friction and Wear,Calculation Methods, Pergamon, 1982) is chosen for comparison. The non-penetration condition and interface models for contact that take into account the surface micro-structure are investigated in detail. A theoretical basis for the three-dimensional contact problem with finite deformations is shortly presented. The augmented Lagrangian method is then used to solve the contact problem with friction. The algorithms for frictional contact are derived based on a slip rule using backward Euler integration like in plasticity. Special attention was dedicated to the consistent derivation of the contact equations between finite element surfaces. A matrix formulation for a node-to-surface contact element is derived consisting of a master surface segment with four nodes and a contacting slave node. It was also necessary to consider the special cases of node-to-edge contact and node-to-node contact in order to achieve the desired asymptotic quadratic convergence in the Newton method. A numerical example is selected to show the ability of the contact formulation and the algorithm to represent interface law for rough surfaces. Copyright © 2003 John Wiley & Sons, Ltd. [source] Multi-objective turbomachinery optimization using a gradient-enhanced multi-layer perceptronINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 6 2009M. C. Duta Abstract Response surface models (RSMs) have found widespread use to reduce the overall computational cost of turbomachinery blading design optimization. Recent developments have seen the successful use of gradient information alongside sampled response values in building accurate response surfaces. This paper describes the use of gradients to enhance the performance of the RSM provided by a multi-layer perceptron. Gradient information is included in the perceptron by modifying the error function such that the perceptron is trained to fit the gradients as well as the response values. As a consequence, the back-propagation scheme that assists the training is also changed. The paper formulates the gradient-enhanced multi-layer perceptron using algebraic notation, with an emphasis on the ease of use and efficiency of computer code implementation. To illustrate the benefit of using gradient information, the enhanced neural network model is used in a multi-objective transonic fan blade optimization exercise of engineering relevance. Copyright © 2008 John Wiley & Sons, Ltd. [source] Development of a hydrometeorological forcing data set for global soil moisture estimationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2005A. A Berg Abstract Off-line land surface modeling simulations require accurate meteorological forcing with consistent spatial and temporal resolutions. Although reanalysis products present an attractive data source for these types of applications, bias to many of the reanalysis fields limits their use for hydrological modeling. In this study, we develop a global 0.5° forcing data sets for the time period 1979,1993 on a 6-hourly time step through application of a bias correction scheme to reanalysis products. We then use this forcing data to drive a land surface model for global estimation of soil moisture and other hydrological states and fluxes. The simulated soil moisture estimates are compared to in situ measurements, satellite observations and to a modeled data set of root zone soil moisture produced within a separate land surface model, using a different data set of hydrometeorological forcing. In general, there is good agreement between anomalies in modeled and observed (in situ) root zone soil moisture. Similarly, for the surface soil wetness state, modeled estimates and satellite observations are in general statistical agreement; however, correlations decline with increasing vegetation amount. Comparisons to a modeled data set of soil moisture also demonstrates that both simulations present estimates that are well correlated for the soil moisture in the anomaly time series, despite being derived from different land surface models, using different data sources for meteorological forcing, and with different specifications of the land surfaces properties. Copyright © 2005 Royal Meteorological Society [source] The evolution of, and revolution in, land surface schemes designed for climate modelsINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 5 2003A. J. Pitman Abstract The land surface is a key component of climate models. It controls the partitioning of available energy at the surface between sensible and latent heat, and it controls the partitioning of available water between evaporation and runoff. The land surface is also the location of the terrestrial carbon sink. Evidence is increasing that the influence of the land surface is significant on climate and that changes in the land surface can influence regional- to global-scale climate on time scales from days to millennia. Further, there is now a suggestion that the terrestrial carbon sink may decrease as global temperatures increase as a consequence of rising CO2 levels. This paper provides the theoretical background that explains why the land surface should play a central role in climate. It also provides evidence, sourced from climate model experiments, that the land surface is of central importance. This paper then reviews the development of land surface models designed for climate models from the early, very simple models through to recent efforts, which include a coupling of biophysical processes to represent carbon exchange. It is pointed out that significant problems remain to be addressed, including the difficulties in parameterizing hydrological processes, root processes, sub-grid-scale heterogeneity and biogeochemical cycles. It is argued that continued development of land surface models requires more multidisciplinary efforts by scientists with a wide range of skills. However, it is also argued that the framework is now in place within the international community to build and maintain the latest generation of land surface models. Further, there should be considerable optimism that consolidating the recent rapid advances in land surface modelling will enhance our capability to simulate the impacts of land-cover change and the impacts of increasing CO2 on the global and regional environment. Copyright © 2003 Royal Meteorological Society [source] The regional scale impact of land cover change simulated with a climate modelINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 3 2002Mei Zhao Abstract A series of 17-year integrations using the NCAR CCM3 (at about 2.8° × 2.8° resolution) were performed to investigate the regional-scale impact of land cover change. Our aim was to determine the impact of historical land cover change on the regional-scale climate over the regions where most change occurred: Europe, India and China. The change from natural to current land cover was estimated using BIOME3 to predict the natural vegetation type, and then using remotely sensed data to estimate the locations where land cover had been changed through human activity. Results show statistically significant changes in the 15-year averaged 1000 hPa wind field, mean near-surface air temperature, maximum near-surface air temperature and the latent heat flux over the regions where land cover change was imposed. These changes disappeared if the land cover over a particular region was omitted, indicating that our results cannot be explained by model variability. An analysis of changes on an averaged monthly time scale showed large changes in the maximum daily temperature in (Northern Hemisphere) summer and little change in the minimum daily temperature, resulting in changes in the diurnal temperature range. The change in the diurnal temperature range could be positive or negative depending on region, time of year and the precise nature of the land cover changes. Our results indicate that the inclusion of land cover change scenarios in simulations of the 20th century may lead to improved results. The impact of land cover changes on regional climates also provides support for the inclusion of land surface models that can represent future land cover changes resulting from an ecological response to natural climate variability or increasing carbon dioxide. Copyright © 2002 Royal Meteorological Society. [source] Models for the adsorption and self-assembly of ethanol and 1-decanethiol on Au(111) surfaces.INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2010A comparative study by computer simulation Abstract Results from computer simulations, based on different models to study theadsorption and self-assembly of the ethanol and 1-decanethiol on gold surfaces, Au(111), are presented. Canonical ensemble Monte Carlo simulations were performed at 298 K using two different force fields. One from DFT calculations, where the gold electrode has an explicit structure (corrugated electrode), and the other representing an electrode, in which the structure is taken into account on an average way (flat electrode). The behavior of the ethanol adsorption on gold surfaces, with and without the 1-decanethiol presence, is analyzed. The introduction of molecular flexibility is also discussed. The relative surface density for the ethanol oxygen, adsorbed on gold, and the density profiles, in different conditions, show that the structure of the surface has a fundamental role on the way the adsorption takes place, not only on the preferential adsorption sites of the surface but also on the ethanol distribution over the electrodes. Potentials of mean force have also been calculated for the two surface models, giving the free energy barriers to the 1-decanethiol crossing of the solvent adsorption layers. The average tilt angle, obtained with a single thiol molecule in the simulation box, presents the values: ,26° for the rigid molecule model and 74° ± 18° for the flexible one. These differences are analyzed. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [source] Analysis and prediction of protein folding rates using quadratic response surface modelsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 10 2008Liang-Tsung Huang Abstract Understanding the relationship between amino acid sequences and folding rates of proteins is an important task in computational and molecular biology. In this work, we have systematically analyzed the composition of amino acid residues for proteins with different ranges of folding rates. We observed that the polar residues, Asn, Gln, Ser, and Lys, are dominant in fast folding proteins whereas the hydrophobic residues, Ala, Cys, Gly, and Leu, prefer to be in slow folding proteins. Further, we have developed a method based on quadratic response surface models for predicting the folding rates of 77 two- and three-state proteins. Our method showed a correlation of 0.90 between experimental and predicted protein folding rates using leave-one-out cross-validation method. The classification of proteins based on structural class improved the correlation to 0.98 and it is 0.99, 0.98, and 0.96, respectively, for all-,, all-,, and mixed class proteins. In addition, we have utilized Baysean classification theory for discriminating two- and three-state proteins, which showed an accuracy of 90%. We have developed a web server for predicting protein folding rates and it is available at http://bioinformatics.myweb.hinet.net/foldrate.htm. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Sequential Quadratic Programming for Development of a New Probiotic Dairy Tofu with Glucono-,-LactoneJOURNAL OF FOOD SCIENCE, Issue 7 2004M.-J. Chen ABSTRACT: The purpose of this research was to evaluate the effects of various concentrations of glucono-,-lactone (GDL) and skim milk powder, as well as the addition of prebiotics, on the rheology and probiotic viabilities of dairy tofu. Additionally, modern optimization techniques were applied to attempt to determine the optimal processing conditions and growth rate for the selected probiotics (Lactobacillus. acidophilus, L. casei, Bifidobacteria bifidum, and B. longum). There were 2 stages in this research to accomplish the goal. The 1st stage was to derive surface models using response surface methodology (RSM); the 2nd stage performed optimization on the models using sequential quadratic programming (SQP) techniques. The results were demonstrated to be effective. The most favorable production conditions of dairy tofu were 1% GDL, 0% peptides, 3% isomaltooligosaccharides (IMO), and 18% milk, as confirmed by subsequent verification experiments. Analysis of the sensory evaluation results revealed no significant difference between the probiotic dairy tofu and the GDL analog in terms of texture and appearance (P < 0.05). The viable numbers of probiotics were well above the recommended limit of 106 CFU/g for the probiotic dairy tofu throughout the tested storage period. [source] An integrated visualization system for surgical planning and guidance using image fusion and an open MRJOURNAL OF MAGNETIC RESONANCE IMAGING, Issue 6 2001David T. Gering MS Abstract A surgical guidance and visualization system is presented, which uniquely integrates capabilities for data analysis and on-line interventional guidance into the setting of interventional MRI. Various pre-operative scans (T1- and T2-weighted MRI, MR angiography, and functional MRI (fMRI)) are fused and automatically aligned with the operating field of the interventional MR system. Both pre-surgical and intra-operative data may be segmented to generate three-dimensional surface models of key anatomical and functional structures. Models are combined in a three-dimensional scene along with reformatted slices that are driven by a tracked surgical device. Thus, pre-operative data augments interventional imaging to expedite tissue characterization and precise localization and targeting. As the surgery progresses, and anatomical changes subsequently reduce the relevance of pre-operative data, interventional data is refreshed for software navigation in true real time. The system has been applied in 45 neurosurgical cases and found to have beneficial utility for planning and guidance. J. Magn. Reson. Imaging 2001;13:967,975. © 2001 Wiley-Liss, Inc. [source] Influence of water activity and temperature on conidial germination and mycelial growth of ochratoxigenic isolates of Aspergillus ochraceus on grape juice synthetic medium.JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 10 2005Predictive models Abstract The first stages in the development of Aspergillus ochraceus, an ochratoxin A-producing fungus that infects grapes and may grow on them, have been studied on a synthetic nutrient medium similar to grape in composition. Spore germination and mycelial growth have been tested over a water activity (aw) and temperature range which could approximate to the real conditions of fungal development on grapes. Optimal germination and growth were observed at 30 °C for all three isolates tested. Maximal germination rates were detected at 0.96,0.99 aw at 20 °C, while at 10 and 30 °C the germination rates were significantly higher at 0.99 aw. Although this abiotic factor (aw) had no significant influence on mycelial growth, growth rates obtained at 0.98 aw were slight higher than those at other aw levels. Predictive models for the lag phase before spore germination as a function of water activity and temperature have been obtained by polynomial multiple linear regression, and the resulting response surface models have been plotted. Copyright © 2005 Society of Chemical Industry [source] Numerische Modellierung von Holz und Verbindungselementen in Holz-Beton-VerbundkonstruktionenBAUTECHNIK, Issue 6 2005Marco Grosse Dipl.-Ing. Durch die Anwendung der FEM können auch komplexe Strukturen berechnet werden, die sich nicht mehr als Stab- oder Flächentragwerke abbilden lassen. Es ist daher naheliegend, auch das Tragverhalten von Bauteilen oder Bauteilkomponenten in Abhängigkeit von verschiedenen Einflußparametern mit Hilfe von FE-Modellen zu simulieren. Um dabei aber Versagensmechanismen abbilden zu können, ist es notwendig, das Materialverhalten der Baustoffe im Nachbruchbereich zu berücksichtigen. Es wird ein konstitutives Materialmodell für den Werkstoff Holz vorgestellt, welches das räumlich anisotrope und vom Beanspruchungsmodus abhängige, nichtlineare Tragverhalten einbezieht. Durch die Kombination mit einem leistungsfähigen Betonmodell ist es möglich, Holz-Beton-Verbundkonstruktionen zu untersuchen. Anhand der Simulationen von Scherversuchen mit verschiedenen Schubverbindungselementen soll die Leistungsfähigkeit solcher numerischer Modelle verdeutlicht werden. Numerical modelling of timber and connection elements used in timber-concrete composite structures. Complex load carrying structures that can not be reproduced as framework ore simple surface models can be calculated using the Finite Element Method. Therefore it seems desirable to simulate the structural behaviour of members or components considering several influence parameters with the help of FE-models too. However, to model the failure mechanism it is necessary to take into account the material behaviour in the critical and post critical range. An adequate numerical model for timber that considers the specific anisotropic and load dependent strength and degradation behaviour is introduced. In combination with an capable model for concrete it is possible to examine timber concrete composite structures. The effectiveness of such models is verified by simulations of shear tests with several fastener elements. [source] Response Surface Designs for Experiments in BioprocessingBIOMETRICS, Issue 2 2006Steven G. Gilmour Summary Many processes in the biological industries are studied using response surface methodology. The use of biological materials, however, means that run-to-run variation is typically much greater than that in many experiments in mechanical or chemical engineering and so the designs used require greater replication. The data analysis which is performed may involve some variable selection, as well as fitting polynomial response surface models. This implies that designs should allow the parameters of the model to be estimated nearly orthogonally. A class of three-level response surface designs is introduced which allows all except the quadratic parameters to be estimated orthogonally, as well as having a number of other useful properties. These subset designs are obtained by using two-level factorial designs in subsets of the factors, with the other factors being held at their middle level. This allows their properties to be easily explored. Replacing some of the two-level designs with fractional replicates broadens the class of useful designs, especially with five or more factors, and sometimes incomplete subsets can be used. It is very simple to include a few two- and four-level factors in these designs by excluding subsets with these factors at the middle level. Subset designs can be easily modified to include factors with five or more levels by allowing a different pair of levels to be used in different subsets. [source] | |||||||||||||