Development of color density concept with color difference formulas in respect to human vision system

The aims of this study are to develop the color density concept and to propose the color density based color difference formulas.The color density is defined using the metric coefficients that are based on the discrimination ellipses and the locations of the colors in the color space.The ellipse sets are the MacAdam ellipses in the CIE 1931 xy-chromaticity diagram and the chromaticity-discrimination ellipses in the CIELAB space.The latter set was originally used to develop the CIEDE2000 color difference formula.The color difference can be calculated from the color density for the two colors under consideration.As a result,the color density represents the perceived color difference more accurately,and it could be used to characterize a color by a quantity attribute matching better to the perceived color difference from this color.Resulting from this,the color density concept provides simply a correction term for the estimation of the color differences.In the experiments,the line element formula and the CIEDE2000 color difference formula performed better than the color density based difference measures.The reason behind this is in the current modeling of the color density concept.The discrimination ellipses are typically described with three-dimensional data consisting of two axes,the major and the minor,and the inclination angle.The proposed color density is only a one-dimensional corrector for color differences;thus,it cannot capture all the details of the ellipse information.Still,the color density gives clearly more correct estimations to perceived color differences than Euclidean distances using directly the coordinates of the color space.

LEIBNIZ′FORMULA OF GENERALIZED DIFFERENCE WITH RESPECT TO A CLASS OF DIFFERENTIAL OPERATORS AND RECURRENCE FORMULA OF THEIR GREEN′S FUNCTION

In this paper, Leibniz' formula of generalized divided difference with respect to a class of differential operators whose basic sets of solutions have power form, is considered. The recurrence formula of Green function about the operators is also given.

NEWTON'S THEOREM WITH RESPECT TO A LOT OFCENTERS AND THEIR APPLICATIONS

In this paper we shall extend the paper [1] to a separate Taylor's Theorem with respect to a lot of centers, namely Newton's Theorem Of a lot of centers. From it we obtain the analogous results in the paper [2]. namely an interpolation formula of the difference of higher order. Finally we give their applications.

Semi-Implicit Interior Penalty Discontinuous Galerkin Methods for Viscous Compressible Flows

We deal with the numerical solution of the Navier-Stokes equations describing a motion of viscous compressible fluids.In order to obtain a sufficiently stable higher order scheme with respect to the time and space coordinates,we develop a combination of the discontinuous Galerkin finite element(DGFE)method for the space discretization and the backward difference formulae(BDF)for the time discretization.Since the resulting discrete problem leads to a system of nonlinear algebraic equations at each time step,we employ suitable linearizations of inviscid as well as viscous fluxes which give a linear algebraic problem at each time step.Finally,the resulting BDF-DGFE scheme is applied to steady as well as unsteady flows and achieved results are compared with reference data.

ANALYSIS OF A FULLY DISCRETE FINITE ELEMENT METHOD FOR PARABOLIC INTERFACE PROBLEMS WITH NONSMOOTH INITIAL DATA

This article concerns numerical approximation of a parabolic interface problem with general L 2 initial value.The problem is discretized by a finite element method with a quasi-uniform triangulation of the domain fitting the interface,with piecewise linear approximation to the interface.The semi-discrete finite element problem is furthermore discretized in time by the k-step backward difference formula with k=1,...,6.To maintain high-order convergence in time for possibly nonsmooth L 2 initial value,we modify the standard backward difference formula at the first k−1 time levels by using a method recently developed for fractional evolution equations.An error bound of O(t−k nτk+t−1 n h 2|log h|)is established for the fully discrete finite element method for general L 2 initial data.

A SECOND ORDER UNCONDITIONALLY CONVERGENT FINITE ELEMENT METHOD FOR THE THERMAL EQUATION WITH JOULE HEATING PROBLEM

In this paper,we study the finite element approximation for nonlinear thermal equation.Because the nonlinearity of the equation,our theoretical analysis is based on the error of temporal and spatial discretization.We consider a fully discrete second order backward difference formula based on a finite element method to approximate the temperature and electric potential,and establish optimal L^(2) error estimates for the fully discrete finite element solution without any restriction on the time-step size.The discrete solution is bounded in infinite norm.Finally,several numerical examples are presented to demonstrate the accuracy and efficiency of the proposed method.

A Robust, Fully Adaptive Hybrid Level-Set/Front-Tracking Method for Two-Phase Flows with an Accurate Surface Tension Computation

We present a variable time step,fully adaptive in space,hybrid method for the accurate simulation of incompressible two-phase flows in the presence of surface tension in two dimensions.The method is based on the hybrid level set/front-tracking approach proposed in[H.D.Ceniceros and A.M.Roma,J.Comput.Phys.,205,391-400,2005].Geometric,interfacial quantities are computed from front-tracking via the immersed-boundary setting while the signed distance(level set)function,which is evaluated fast and to machine precision,is used as a fluid indicator.The surface tension force is obtained by employing the mixed Eulerian/Lagrangian representation introduced in[S.Shin,S.I.Abdel-Khalik,V.Daru and D.Juric,J.Comput.Phys.,203,493-516,2005]whose success for greatly reducing parasitic currents has been demonstrated.The use of our accurate fluid indicator together with effective Lagrangian marker control enhance this parasitic current reduction by several orders of magnitude.To resolve accurately and efficiently sharp gradients and salient flow features we employ dynamic,adaptive mesh refinements.This spatial adaption is used in concert with a dynamic control of the distribution of the Lagrangian nodes along the fluid interface and a variable time step,linearly implicit time integration scheme.We present numerical examples designed to test the capabilities and performance of the proposed approach as well as three applications:the long-time evolution of a fluid interface undergoing Rayleigh-Taylor instability,an example of bubble ascending dynamics,and a drop impacting on a free interface whose dynamics we compare with both existing numerical and experimental data.

A Comparison of Semi-Lagrangian and Lagrange-Galerkin hp-FEM Methods in Convection-Diffusion Problems

We perform a comparison in terms of accuracy and CPU time between second order BDF semi-Lagrangian and Lagrange-Galerkin schemes in combination with high order finite element method.The numerical results show that for polynomials of degree 2 semi-Lagrangian schemes are faster than Lagrange-Galerkin schemes for the same number of degrees of freedom,however,for the same level of accuracy both methods are about the same in terms of CPU time.For polynomials of degree larger than 2,Lagrange-Galerkin schemes behave better than semi-Lagrangian schemes in terms of both accuracy and CPU time;specially,for polynomials of degree 8 or larger.Also,we have performed tests on the parallelization of these schemes and the speedup obtained is quasi-optimal even with more than 100 processors.