High order compact schemes for gradient approximation

In this paper, we propose three gradient recovery schemes of higher order for the linear interpolation. The first one is a weighted averaging method based on the gradients of the linear interpolation on the uniform mesh, the second is a geometric averaging method constructed from the gradients of two cubic interpolation on macro element, and the last one is a local least square method on the nodal patch with cubic polynomials. We prove that these schemes can approximate the gradient of the exact solution on the symmetry points with fourth order. In particular, for the uniform mesh, we show that these three schemes are the same on the considered points. The last scheme is more robust in general meshes. Consequently, we obtain the superconvergence results of the recovered gradient by using the aforementioned results and the supercloseness between the finite element solution and the linear interpolation of the exact solution. Finally, we provide several numerical experiments to illustrate the theoretical results.     

A new finite element of C cubic splines

In this paper, we give a new finite element with dimension 16 of C¹ cubic splines which have interpolation schemes on the Morgan-Scott construction ₀ of a triangle.     

CONSTRAINED RATIONAL CUBIC SPLINE AND ITS APPLICATION

1. IntroductionDesign of high quality, manufacturable surfaces, such as the outer shape of a ship, car oraeroplane, is an important yet challenging task in today's manufacturing industries. Althoughsignificam progress has been made in the last decade in developing and commercializing pro--duction quality CAD tools, demand for more effective tools is still high due to the ever increajsein model complexity and the needs to address and incorporate manufacturing requirements inthe early stage of …     

Discrete time Galerkin approximations to the nonlinear filtering solution

This paper concerns discrete time Galerkin approximations to the solution of the filtering problem for diffusions. Two families of schemes approximating the unnormalized conditional density, respectively, in an “average” and in a “pathwise” sense, are presented. L² error estimates are derived and it is shown that the rate of convergence is linear in the time increment or linear in the modulus of continuity of the sample path.     

单调光滑函数的样条插值

ELI Passow在[1]中提出了X={x_i}(x_(i-1)相似文献   

分数年龄生存函数的估计

本文主要讨论了生存函数的插值问题,使用了非节点端点的三次样条插值和α-power插值两种方法对生存函数进行了插值,并与传统的三种插值假设：死亡均匀分布假设、常数死亡力假设、Balducci假设做了比较.另外,我们对α-power插值中的α进行了拟合,并通过误差分析表明先对α拟合后再进行α-power插值,其插值的误差将会变得非常小,几乎与样条插值相仿.     

双立方插值和二元三次样条插值在心磁图像处理中的应用

心磁图是根据人体心脏跳动产生的微弱磁场测量信号计算得到的医学图像,它较心电图诊断心脏疾病具有更高的灵敏度和准确性.为了提高心磁图的成像精度,通常需要对心磁检测数据进行插值处理.提供了双立方插值和二元三次样条插值两种插值方法,应用实例的结果表明,三次样条插值的效果比双立方插值效果好,基本能达到应用的要求.     

Matrix-valued symmetric templates for interpolatory surface subdivisions: I. Regular vertices

The objective of this paper is to introduce a general procedure for deriving interpolatory surface subdivision schemes with “symmetric subdivision templates” (SSTs) for regular vertices. While the precise definition of “symmetry” will be clarified in the paper, the property of SSTs is instrumental to facilitate application of the standard procedure for finding symmetric weights for taking weighted averages to accommodate extraordinary (or irregular) vertices in surface subdivisions, a topic to be studied in a continuation paper. By allowing the use of matrices as weights, the SSTs introduced in this paper may be constructed to overcome the size barrier limited to scalar-valued interpolatory subdivision templates, and thus avoiding the unnecessary surface oscillation artifacts. On the other hand, while the old vertices in a (scalar) interpolatory subdivision scheme do not require a subdivision template, we will see that this is not the case for the matrix-valued setting. Here, we employ the same definition of interpolation subdivisions as in the usual scalar consideration, simply by requiring the old vertices to be stationary in the definition of matrix-valued interpolatory subdivisions. Hence, there would be another complication when the templates are extended to accommodate extraordinary vertices if the template sizes are not small. In this paper, we show that even for C² interpolatory subdivisions, only one “ring” is sufficient in general, for both old and new vertices. For example, for 1-to-4 split C² interpolatory surface subdivisions, we obtain matrix-valued symmetric interpolatory subdivision templates (SISTs) for both triangular and quadrilateral meshes with sizes that agree with those of the Loop and Catmull–Clark schemes, respectively. Matrix-valued SISTs of similar sizes are also constructed for C² interpolatory and subdivision schemes in this paper. In addition to small template sizes, an obvious feature of matrix-valued weights is the flexibility for introducing shape-control parameters. Another significance is that, in contrast to the usual scalar setting, matrix-valued SISTs can be formulated in terms of the coefficient sequence of some vector refinement equation of interpolating bivariate C² splines with small support. For example, by modifying the spline function vectors introduced in our previous work [C.K. Chui, Q.T. Jiang, Surface subdivision schemes generated by refinable bivariate spline function vectors, Appl. Comput. Harmon. Anal. 15 (2003) 147–162; C.K. Chui, Q.T. Jiang, Refinable bivariate quartic and quintic C²-splines for quadrilateral subdivisions, Preprint, 2004], C² symmetric interpolatory subdivision schemes associated with refinement equations of C² cubic and quartic splines on the 6-directional and 4-directional meshes, respectively, are also constructed in this paper.     

Computational magneto-hydrodynamic modeling of hypersonic flows with resolved shock wave diffusion

The present model describes magneto-hydrodynamic (MHD) effects on diffusing shock waves in compressible flows. The accurateness and the robustness of these new density-based numerical algorithm in his ideal form was tested on a series of benchmark numerical experiments like the present MHD shock tube [1]. Interpolation schemes are used for interpolation of density, temperature, velocity and the magnetic field. For the discretization of laplacian terms with diffusion coefficient for polyhedral meshes, we make use of the Gauss linear uncorrected schemes to deal with the case that the consecutive cell faces are non-orthogonal. The approach described above and developed in the present project has been coupled with semi-discrete central schemes (e.g. Greenshields et al. [2]). All computational results are validated with verified data and analytical results. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Linear multi-secret sharing schemes based on multi-party computation

In multi-secret sharing schemes, publishing shares during the process of reconstructing partial secrets may leak some information of the secrets unrecovered yet. By using a multi-party computation (MPC) protocol, we solve this problem for any linear multi-secret sharing scheme (MSSS). We also show that LMSSS usually involve more complicated reconstruction algorithms than “direct sum” schemes, but from the point of reducing share expansion, the former is preferred.     

The bidimensional interproximation problem and mixed splines

Interproximation methods for surfaces can be used to construct a smooth surface interpolating some data points and passing through specified regions. In this paper we study the use of mixed splines, that is smoothing splines with additional interpolation constraints, to solve the interproximation problem for surfaces in the case of scattered data. The solution is obtained by solving a linear system whose structure can be improved by using “bell-shaped” thin plate splines.     

利用近似能量极小构造平面C1三次Hermite插值曲线

研究了利用近似能量极小构造平面$C^1$三次Hermite插值曲线的方法.该方法的主要的目是求出$C^1$三次Hermite插值曲线的最佳切矢.通过将应变能、曲率变化能和组合能的近似函数极小化,得到了求解最佳切矢的线性方程组.通过求解发现,近似曲率变化能极小不存在唯一解, 而近似应变能极小和近似组合能极小由于方程系统的系数矩阵为严格对角占优故都存在唯一解.最后, 通过实例表明了本文方法构造平面$C^1$三次Hermite插值曲线的有效性.     

Characters of table algebras and applications to association schemes

Hanaki [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] generalized many properties of characters of finite groups to characters of association schemes. In this paper we show that many of these properties also hold for table algebras. Our approach is not to generalize the proofs in [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] to table algebras, but to prove many stronger properties, and then obtain results in [A. Hanaki, Representations of association schemes and their factor schemes, Graphs Combin. 19 (2003) 195-201; A. Hanaki, Characters of association schemes and normal closed subsets, Graphs Combin. 19 (2003) 363-369] as direct consequences.     

Central-upwind scheme for shallow water equations with discontinuous bottom topography

Finite-volume central-upwind schemes for shallow water equations were proposed in [A. Kurganov and G. Petrova, Commun. Math. Sci., 5 (2007), 133–160]. These schemes are capable of maintaining “lake-at-rest” steady states and preserving the positivity of the computed water depth. The well-balanced and positivity preserving features of the central-upwind schemes are achieved, in particular, by using continuous piecewise linear interpolation of the bottom topography function. However, when the bottom function is discontinuous or a model with a moving bottom topography is studied, the continuous piecewise linear approximationmay not be sufficiently accurate and robust.     

A simple rational spline and its application to monotonic interpolation to monotonic data

Summary We shall consider a class of simple rational splines and their application to monotonic interpolation to monotonic data. Our method is situated between interpolation with the usual cubic splines and with monotone quadratic splines. A selection of numerical results is presented in Figs. 4–11.     

Phase lag analysis of variational integrators using interpolation techniques

In the present work we derive higher order variational integrators and combine them with phase lag properties for the numerical integration of systems with oscillatory solutions. The discrete Lagrangian in any time interval is defined as a weighted sum of the evaluation of the continuous Lagrangian at intermediate time nodes. The expressions used for configurations and velocities use linear interpolation, cubic spline interpolation or interpolation via trigonometric functions. The new methods depend on a frequency, which needs to be chosen appropriately. Results show that the energy error of the integration method is decreased for good frequency estimates. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Convexity control and approximation properties of interpolating curves

A constrained rational cubic spline with linear denominator was constructed in [1]. In the present paper, the sufficient condition for convex interpolation and some properties in error estimation are given.     

Sharp Lebesgue constants for bounded cubic interpolation ℒ-splines

We construct the Lebesgue function and find sharp Lebesgue constants for bounded cubic interpolation ℒ-splines with equally spaced interpolation nodes and discontinuities of the second derivative chosen so that the cubic ℒ-splines satisfy a certain extremal property with respect to the functions under interpolation.     

Conservative semi‐Lagrangian finite volume schemes

Semi‐Lagrangian finite volume schemes for the numerical approximation of linear advection equations are presented. These schemes are constructed so that the conservation properties are preserved by the numerical approximation. This is achieved using an interpolation procedure based on area‐weighting. Numerical results are presented illustrating some of the features of these schemes. © 2001 John Wiley & Sons, Inc. Numer Methods Partial Differential Eq 17:403–425, 2001     

On bicompact grid-characteristic schemes for the linear advection equation

A set of grid-characteristic schemes for the linear advection equation is considered. Depending on the behavior of the solution, hybrid compact difference schemes of second–third order accuracy are proposed as based on interpolation polynomials. The schemes produce monotone solutions and only slightly smear discontinuities.