应6163银河线路检测中心张达治、郭志昌老师邀请，中国科学技术大学数学科学学院徐岩教授作学术报告，欢迎感兴趣的师生参加！

【报告题目】：Higher order structure-preserving numerical schemes for nonlinear time-dependent problems

【报告时间】：2020年6月20日，下午14：00

【报告平台】：腾讯会议

点击链接直接加入会议：https://meeting.tencent.com/s/48pPrE7KTm1b

【会议ID】：449 736 329

【报告摘要】：In this talk, we discuss local discontinuous Galerkin (LDG) method for solving the nonlinear equations which contain nonlinear high order derivatives. The discretization results in an extremely local, element based discretization, which is beneficial for parallel computing and maintaining high order accuracy on unstructured meshes. We also develop a novel semi-implicit spectral deferred correction (SDC) time marching method. The method can be used in a large class of problems, especially for highly nonlinear ordinary differential equations (ODEs) without easily separating of stiff and non-stiff components, which is more general and efficient comparing with traditional semi-implicit SDC methods. The proposed semi-implicit SDC method is based on low order time integration methods and corrected iteratively. The order of accuracy is increased for each additional iteration.  This SDC method is intended to be combined with the method of lines, which provides a flexible framework to develop high order semi-implicit time marching methods for nonlinear partial differential equations (PDEs). Coupled with the LDG spatial discretization, the fully discrete schemes are all high order accurate in both space and time, and stable numerically with the time step proportional to the spatial mesh size. Using Lagrange multipliers the conditions imposed by the positivity preserving limiters are directly coupled to a DG discretization combined with implicit time integration method. The positivity preserving DG discretization is then reformulated as a Karush-Kuhn-Tucker (KKT) problem. We therefore develop an efficient active set semi-smooth Newton method that is suitable for the KKT formulation of time-implicit positivity preserving DG discretizations. Convergence of this semi-smooth Newton method is proven using a specially designed quasi-directional derivative of the time-implicit positivity preserving DG discretization. Numerical experiments are carried out to illustrate the accuracy and capability of the proposed method.

【报告人简介】：徐岩，中国科学技术大学数学科学学院教授。2005年于中国科学技术大学数学系获计算数学博士学位。2005-2007年在荷兰Twente大学从事博士后研究工作。2009年获得德国洪堡基金会的支持在德国Freiburg大学访问工作一年。主要研究领域为高精度数值计算方法。研究工作主要涉及高精度离散格式的设计、分析、及其应用等方面，特别侧重于间断有限元方法及其在流体力学、相场模型、相变问题、水波问题的应用。2008年度全国优秀博士学位论文奖，2017年获国家自然科学基金委“优秀青年基金”。徐岩教授入选了教育部新世纪优秀人才计划，主持国家自然科学基金面上项目、德国洪堡基金会研究组合作计划(Research Group Linkage Programme)、霍英东青年教师基础研究课题等科研项目。