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Satisfactory Accuracy (satisfactory + accuracy)
Selected AbstractsDetailed chemical kinetic modeling of pyrolysis of ethylene, acetylene, and propylene at 1073,1373 K with a plug-flow reactor modelINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 4 2008Koyo Norinaga This study examines the predictive capability of our recently proposed reaction mechanism (Norinaga and Deutschmann, Ind Eng Chem Res 2007, 46, 3547) for hydrocarbon pyrolysis at varying temperature. The conventional flow reactor experiments were conducted at 8 kPa, over the temperature range 1073,1373 K, using ethylene, acetylene, and propylene as reactants to validate the mechanism. More than 40 compounds were identified and quantitatively analyzed by on- and off-line gas chromatography. The chemical reaction schemes consisting of 227 species and 827 reactions were coupled with a plug-flow reactor model that incorporated the experimentally measured axial temperature profile of the reactor. Comparisons between the computations and the experiments are presented for more than 30 products including hydrogen and hydrocarbons ranging from methane to coronene as a function of temperature. The model can predict the compositions of major products (mole fractions larger than 10,2) in the pyrolysis of three hydrocarbons with satisfactory accuracies over the whole temperature range considered. Mole fraction profiles of minor compounds including polycyclic aromatic hydrocarbons (PAHs) up to three ring systems, such as phenanthrene, anthracene, and phenylnaphthalene, are also fairly modeled. At temperatures lower than 1273 K, larger PAHs were underpredicted and the deviation became larger with decreasing temperature and increasing molecular mass of PAHs, while better agreements were found at temperatures higher than 1323 K. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 199,208, 2008 [source] Soil frost effects on soil water and runoff dynamics along a boreal transect: 2.HYDROLOGICAL PROCESSES, Issue 6 2001Simulations Abstract A physically based SVAT-model was tested with soil and snow physical measurements, as well as runoff data from an 8600 m2 catchment in northern Sweden in order to quantify the influence of soil frost on spring snowmelt runoff in a moderately sloped, boreal forest. The model was run as an array of connected profiles cascading to the brook. For three winter seasons (1995,98) it was able to predict the onset and total accumulation of the runoff with satisfactory accuracy. Surface runoff was identified as only a minor fraction of the total runoff occurring during short periods in connection with ice blocking of the water-conducting pores. Little surface runoff, though, does not mean that soil frost is unimportant for spring runoff. Simulations without frost routines systematically underestimated the total accumulated runoff. The possibility of major frost effects appearing in response to specific combinations of weather conditions were also tested. Different scenarios of critical initial conditions for the winter, e.g. high water saturation and delayed snow accumulation leading to an increased frost penetration, were tested. These showed that under special circumstances there is potential for increased spring runoff due to soil frost. Copyright © 2001 John Wiley & Sons, Ltd. [source] Explaining qualifications in audit reports using a support vector machine methodologyINTELLIGENT SYSTEMS IN ACCOUNTING, FINANCE & MANAGEMENT, Issue 4 2005Michael Doumpos The verification of whether the financial statements of a firm represent its actual position is of major importance for auditors, who should provide a qualified report if they conclude that the financial statements fail to meet this requirement. This paper implements support vector machines (SVMs) to develop models that may support auditors in this task. Linear and non-linear models are developed and their performance is analysed using training samples of different size and out-of-sample/out-of-time data. The results show that all SVM models are capable of distinguishing between qualified and unqualified financial statements with satisfactory accuracy. The performance of the models over time is also explored. Copyright © 2005 John Wiley & Sons, Ltd. [source] Eight-node shell element based on incompatible modesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 2 2009Desheng Xu Abstract This paper concerns the shell element formulation used for linear analysis. Introduction of hierarchical incompatible modes into the ordinary 8-node solid element is very effective to obtain the rational deflection,rotation relationship. An efficient revision scheme without using numerical volume integration is developed to ensure the satisfaction of the patch test. A lot of numerical tests are carried out for the validation of the present element. Numerical results show that the element can give satisfactory accuracy and convergence, especially for moderately thick shells. Copyright © 2008 John Wiley & Sons, Ltd. [source] Comparison of two wave element methods for the Helmholtz problemINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2009T. Huttunen Abstract In comparison with low-order finite element methods (FEMs), the use of oscillatory basis functions has been shown to reduce the computational complexity associated with the numerical approximation of Helmholtz problems at high wave numbers. We compare two different wave element methods for the 2D Helmholtz problems. The methods chosen for this study are the partition of unity FEM (PUFEM) and the ultra-weak variational formulation (UWVF). In both methods, the local approximation of wave field is computed using a set of plane waves for constructing the basis functions. However, the methods are based on different variational formulations; the PUFEM basis also includes a polynomial component, whereas the UWVF basis consists purely of plane waves. As model problems we investigate propagating and evanescent wave modes in a duct with rigid walls and singular eigenmodes in an L-shaped domain. Results show a good performance of both methods for the modes in the duct, but only a satisfactory accuracy was obtained in the case of the singular field. On the other hand, both the methods can suffer from the ill-conditioning of the resulting matrix system. Copyright © 2008 John Wiley & Sons, Ltd. [source] Tests of radial basis functions in the 3D DRM-MDINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 1 2006Bruno Natalini Abstract Several global as well as compactly supported radial basis functions were tested in the boundary element dual reciprocity method-multi domain approach (DRM-MD) applied to 3D potential problems. Compactly supported radial basis functions (CS-RBFs) showed the highest accuracy, while the augmented thin plate splines (ATPS) showed the highest consistency in terms of accuracy and convergence for the two examples considered, the Poisson and the advection,diffusion equations. A problem for implementation of the CS-RBFs is the lack of guidelines in choosing the size of the support, which showed to have large influence on the accuracy and convergence when these types of RBFs are used. The ATPS showed satisfactory accuracy and since its use does not involve any extra parameters, at the moment it is this function that is the choice of the authors for use in the DRM-MD. Copyright © 2005 John Wiley & Sons, Ltd. [source] An optimally convergent discontinuous Galerkin-based extended finite element method for fracture mechanicsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 6 2010Yongxing Shen Abstract The extended finite element method (XFEM) enables the representation of cracks in arbitrary locations of a mesh. We introduce here a variant of the XFEM rendering an optimally convergent scheme. Its distinguishing features are as follows: (a) the introduction of singular asymptotic crack tip fields with support on only a small region around the crack tip (the enrichment region), (b) only one and two enrichment functions are added for anti-plane shear and planar problems, respectively and (c) the relaxation of the continuity between the enrichment region and the rest of the domain, and the adoption of a discontinuous Galerkin (DG) method therein. The method is provably stable for any positive value of a stabilization parameter, and by weakly enforcing the continuity between the two regions it eliminates ,blending elements' partly responsible for the suboptimal convergence of some early XFEMs. Moreover, the particular choice of enrichment functions results in a surprisingly sparse stiffness matrix that remains reasonably conditioned as the mesh is refined. More importantly, the stress intensity factors can be extracted with a satisfactory accuracy as primary unknowns. Quadrature strategies required for the optimal convergence are also discussed. Finally, the DG method was modified to retain stability based on an inf-sup condition. Copyright © 2009 John Wiley & Sons, Ltd. [source] Lyapunov spectrum determination from the FEM simulation of a chaotic advecting flowINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN FLUIDS, Issue 5 2006Philippe CarričreArticle first published online: 7 SEP 200 Abstract The problem of the determination of the Lyapunov spectrum in chaotic advection using approximated velocity fields resulting from a standard FEM method is investigated. A fourth order Runge,Kutta scheme for trajectory integration is combined with a third order Jacobian matrix method with QR -factorization. After checking the algorithm on the standard Lorenz and coupled quartic oscillator systems, the method is applied to a model 3-D steady flow for which an analytical expression is known. Both linear and quadratic approximated velocity fields succeed in predicting the Lyapunov exponents as well as describing the chaotic or regular regions inside the flow with satisfactory accuracy. A more realistic flow is then studied in order to delineate the possible limitations of the approach. Copyright © 2005 John Wiley & Sons, Ltd. [source] Hybrid kernel learning via genetic optimization for TS fuzzy system identificationINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 1 2010Wei Li Abstract This paper presents a new TS fuzzy system identification approach based on hybrid kernel learning and an improved genetic algorithm (GA). Structure identification is achieved by using support vector regression (SVR), in which a hybrid kernel function is adopted to improve regression performance. For multiple-parameter selection of SVR, the proposed GA is adopted to speed up the search process and guarantee the least number of support vectors. As a result, a concise model structure can be determined by these obtained support vectors. Then, the premise parameters of fuzzy rules can be extracted from results of SVR, and the consequent parameters can be optimized by the least-square method. Simulation results show that the resulting fuzzy model not only achieves satisfactory accuracy, but also takes on good generalization capability. Copyright © 2008 John Wiley & Sons, Ltd. [source] The effect of viscosity on surface tension measurements by the drop weight methodJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007T. Kaully Abstract Viscosity is one of the parameters affecting the measured surface tension, as fluid mechanics affects the measurement process using conventional methods. Several methods including the selected planes (SPM) and WDSM which combines the weight drop method (WDM) and SPM, are applied to surface tension measurement of high viscous liquids. Yet, none of them treats the viscosity effect separately. The current publication presents a simple, easy to apply empirical approach of satisfactory accuracy, for evaluation of surface tension of liquids having wide range of viscosities up to 10 Pa s. The proposed method is based on Tate's law and the "drop weight" method using calibration curves of known liquids having similar surface tensions but different viscosities. Drop weight of liquids having viscosity ,0.05 Pa s, was found to be significantly affected by the liquid viscosity. The shape factor, f, of high viscosity liquids was found to correlate linearly with the logarithm of viscosity, pointing the importance of viscosity correction. The experimental correlation presented in the current work can be used as a tool for the evaluation of surface tension for high viscosity liquids such as prepolymers. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Dry film method with ytterbium as the internal standard for near infrared spectroscopic plasma glucose assay coupled with boosting support vector regressionJOURNAL OF CHEMOMETRICS, Issue 1-2 2006Yan-Ping Zhou Abstract A novel near infrared (NIR) spectroscopic measurement technique, dry film method, has been proposed for the determination of glucose in plasma. Rare earth element ytterbium (Yb) has been taken in the dry film method as the internal standard to compensate for the thickness variation of the dry films. This technique circumvents the interference from water absorption and requires only 50 µl of sample. Support vector regression (SVR) as a multivariate calibration method has been combined with boosting for the development of a boosting support vector regression (BSVR) method for the dry film measurement modeling. The introduction of boosting drastically enhances the performance of individual SVR model. The results show that the glucose in plasma can be determined over the 0.4,20,mmol/L concentration range with satisfactory accuracy using the dry film technique coupled with the BSVR method. Moreover, the performance of BSVR was compared favorably with that of the conventional SVR and PLS. Copyright © 2006 John Wiley & Sons, Ltd. [source] Study of peptide conformation in terms of the ABEEM/MM methodJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 1 2006Zhong-Zhi Yang Abstract The ABEEM/MM model (atom-bond electronegativity equalization method fused into molecular mechanics) is applied to study of the polypeptide conformations. The Lennard,Jones and torsional parameters were optimized to be consistent with the ABEEM/MM fluctuating charge electrostatic potential. The hydrogen bond was specially treated with an electrostatic fitting function. Molecular dipole moments, dimerization energies, and hydrogen bond lengths of complexes are reasonably achieved by our model, compared to ab initio results. The ABEEM/MM fluctuating charge model reproduces both the peptide conformational energies and structures with satisfactory accuracy with low computer cost. The transferability is tested by applying the parameters of our model to the tetrapeptide of alanine and another four dipeptides. The overall RMS deviations in conformational energies and key dihedral angles for four di- or tetrapeptide, is 0.39 kcal/mol and 7.7°. The current results agree well with those by the accurate ab initio method, and are comparable to those from the best existing force fields. The results make us believe that our fluctuating charge model can obtain more promising results in protein and macromolecular modeling with good accuracy but less computer cost. © 2005 Wiley Periodicals, Inc. J Comput Chem 27: 1,10, 2006 [source] ADSORPTION CHARACTERISTICS OF FUNCTIONAL SOY PROTEIN PRODUCTSJOURNAL OF FOOD PROCESS ENGINEERING, Issue 6 2003ZHONGLI PAN ABSTRACT The moisture adsorption characteristics of three commercial functional soy protein products (two isolates and one concentrate) in the temperature range of 10 to 40C were studied. The temperature showed significant effect on both the change of moisture content during adsorption and equilibrium moisture content. The rate of moisture adsorption of a soy protein isolate at water activity of 0.84 increased, but its equilibrium moisture content decreased with the increase of temperature. The suitability of Peleg and GAB equations for modeling the change of moisture content during adsorption and adsorption isotherms was respectively examined, and the constants in both equations were determined. In the temperature range of 10C to 40C, the relative errors of predicted change in moisture content at water activity of 0.84 and predicted isotherms of a soy protein isolates were ranged from 1.36% to 4.85% and 2.80% to 3.63%, respectively. The two equations can be used to predict the change in moisture content during adsorption and isotherms of functional soy protein products at different temperatures with satisfactory accuracy. [source] High sensitivity determination of valproic acid in mouse plasma using semi-automated sample preparation and liquid chromatography with tandem mass spectrometric detectionRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2005Vincenzo Pucci A high-throughput liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) assay using automated sample preparation has been developed for the determination of valproic acid (VPA) in mouse plasma. A liquid-handling system was programmed to prepare calibration standard solutions in plasma, as well as quality controls and clinical samples. Plasma protein precipitation was performed on a 96-well plate, and the collected supernatant was directly injected into a reversed-phase LC/ESI-MS/MS system in the negative ionization mode. The calibration curve for VPA was linear over a dynamic range of 0.15,100,µg/mL. The limit of detection was 75,ng/mL and the lower limit of quantitation was 150,ng/mL. Intra- and inter-day validation assays of the semi-automated plasma analysis showed satisfactory accuracy and precision. Copyright © 2005 John Wiley & Sons, Ltd. [source] Determination of 3,,4,,5,,5,7-pentamethoxyflavone in the plasma and intestinal mucosa of mice by HPLC with UV detectionBIOMEDICAL CHROMATOGRAPHY, Issue 4 2009Hong Cai Abstract In a preliminary experiment 3,,4,,5,,5,7-pentamethoxyflavone (PMF) inhibited adenoma development in ApcMin mice, a model of the human heritable condition familial adenomatous polyposis. An HPLC method for tricin was modified and validated to permit measurement of PMF in mouse plasma and intestinal mucosa. HPLC analysis was carried out on a Hypersil-BDS C18 column with detection at 324 nm and tricin as internal standard. The assay was linear in the range of 100,2000 ng/mL plasma and 1.0,40 µg/mL mucosa. PMF in plasma was efficiently extracted using solid-phase columns. In the case of mucosa organic solvent protein precipitation displayed satisfactory accuracy and precision. The assay recovery at low, medium and high concentrations was between 85 and 103% for both biomatrices, with a relative standard deviation of <15%. The lower limits of quantitation for plasma and mucosa were 100 ng/mL and 1.0 µg/mL, respectively. This method allowed measurement of PMF steady-state median concentrations in plasma (1.08 nmol/mL, n = 11; 10th and 90th percentiles: 0.633 and 2.385 nmol/mL) and mucosa (108.5 nmol/g, n = 9; 10th and 90th percentiles: 38.9 and 164.4 nmol/g) in mice which had received PMF (0.2%, w/w) with their diet. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||