本文对非线性Sobolev方程采用低阶的协调混合元(Q11+Q01×Q10)方法进行分析.利用单元的高精度结果、平均值技巧和插值后处理技术,在半离散格式下,分别导出精确解u的H1-模和中间变量p的L2-模意义下的超逼近性质和整体超收敛.进一步,利用Bramble-Hilbert引理得到三个新的渐近误差展开式.同时,通过构造合适的辅助问题,运用Richardson外推格式,得到具有精度为O(h3)阶的外推结果.
In this paper, low order conforming mixed finite element (Q11+Q01×Q10) method is adopted for nonlinear Sobolev equation. By utilizing the high precision results of the element, meanvalue techniques and Interpolation postprocessing approach, the superclose properties and the global superconvergence for the primitive solution u in Hi-norm and the intermediate variable p in L^2-norm are obtained respectively in semi-discrete scheme. Furthermore, three new asymptotic error expansions are deduced through Bramble-Hilbert Lemma. At the same time, through constructing a suitable ayxiliary Droblem and Richardson extrapolation, the extrapolation results with order O(h^3) ave derived.