1、应数学系吴勃英教授、王春程副教授邀请，南方科技大学教授王学锋教授将于2017年5月15日访问002全讯白菜网数学系，并作学术报告。欢迎感兴趣的老师和同学参加。

报告时间：2017年5月15日，格物楼503，上午10:00-11:00

报告题目：Using effective boundary conditions to model fast diffusion on a road in a large field

报告摘要：We consider a logistic diffusion equation on the plane consisting of two components, a straight "road" and a "field", in each of which the diffusion rate differs significantly. Compared to the size of the field, the width of the road is assumed to be small. Thus in this diffusion equation multiple scales appear in two places: the spatial variable and the diffusion parameter. Such an equation is not easy to solve numerically, and it is not easy to see the effects of the road. Recently, Berestycki, Roquejoffre and Rossi provide a model which is meant to resolve these issues. In this paper we first use the idea of effective boundary conditions (EBCs) to propose,rigorously,a different model: we study the limit of the solution of the original logistic equation as the width of the road approaches zero, obtaining a limiting model, in which the road now is the horizontal line with EBCs imposed on it. This effective problem has no multiple scales and hence should be easier to solve numerically. Moreover, to see the effects of the road, we further investigate the asymptotic propagation speed of the effective model, showing that the road indeed enhances the spreading speed along its direction, provided that the diffusion rate on the road is of the order of the reciprocal of the width of the road.

报告人简介：王学锋，南方科技大学数学系教授，广东省数学学会常务理事，Communications on Pure and Applied Analysis杂志副主编。1984年获得北京大学学士学位，1990年在美国明尼苏达大学获得博士学位，1991-2015年间在美国Tulane大学工作，2016年任南方科大数学系教授。王学锋教授主要研究领域是偏微分方程及其应用，在Transactions of the American Mathematical Society，Communications on Pure and Applied Mathematics，Archive for Rational Mechanics and Analysis，SIAM Journal on Mathematical Analysis，Journal of Differential Equations国际著名期刊上发表40余篇学术论文。

个人主页：http://math.sustc.edu.cn/people_all/WANGXuefeng.html

2、应数学系王春程副教授邀请，美国威廉玛丽学院史峻平教授将于2017年5月15日访问002全讯白菜网数学系，并作学术报告。欢迎感兴趣的老师和同学参加。

报告时间：2017年5月15日，格物楼503，下午13:30-14:30

报告题目：A mathematical model of interaction of pelagic algae, benthic algae and nutrients in an oligotrophic shallow aquatic ecosystem

报告摘要：A coupled system of ordinary differential equations and partial differential equations is proposed to describe the interaction of pelagic algae, benthic algae and one essential nutrient in an oligotrophic shallow aquatic ecosystem with ample supply of light. The existence, uniqueness and stability of non-negative steady states are shown, and these results characterize some threshold conditions for the regime shift. The influence of environmental parameters on algal biomass density is also considered, which is an important indicator of algal blooms. This is a joint work with Jimin Zhang (Heilongjiang University) and Xiaoyuan Chang (Harbin University of Science and Technology).

报告人简介：史峻平，美国威廉玛丽学院教授。1990-93年南开大学学习，1998年毕业于美国杨百翰大学，获博士学位。主要研究方向为偏微分方程，动力系统，分歧理论，非线性泛函分析，生物数学。现主持美国国家科学基金会基金项目1项，参加美国国家科学基金会基金项目1项，主持完成美国国家科学基金会项目3项。参加中国国家自然科学基金项目3项。获得黑龙江省科技奖2项。主持组织国际学术会议10多次，在国际学术会议做大会报告/邀请报告200余次。担任两个国际知名SCI刊物编委，为60多种数学、物理、生物刊物审稿人。发表学术论文120余篇，被SCI杂志引用1000余次。在偏微分方程，分歧理论方面的研究工作受到国际上广泛重视。另外在生物数学，包括种群模型，生物化学反应，形态生成，生态系统稳定性等方面都有研究。

个人主页：http://jxshix.people.wm.edu/

3.  应数学系魏俊杰教授、王春程副教授邀请，加拿大Alberta大学Hao Wang教授将于2017年5月15日访问002全讯白菜网数学系，并作学术报告。欢迎感兴趣的老师和同学参加。

报告时间：2017年5月15日，格物楼503，下午14:30-15:30

报告题目：A New Algorithm to Recover the Time Dependent Transmission Coefficient from Infection Data

报告摘要：The transmission rate of many acute infectious diseases varies significantly in time, but the underlying mechanisms are usually uncertain. They may include seasonal changes in the environment, contact rate, immune system response, etc. The transmission rate has been thought difficult to measure directly. We present a new algorithm to compute the time-dependent transmission rate directly from prevalence data, which makes no assumptions about the number of susceptible or vital rates. The algorithm follows our complete and explicit solution of a mathematical inverse problem for SIR-type transmission models. We prove that almost any infection profile can be perfectly fitted by an SIR model with variable transmission rate. This clearly shows a serious danger of overfitting such transmission models. We illustrate the algorithm with historic UK measles data and our observations support the common belief that measles transmission was predominantly driven by school contacts. We apply this method to pre-vaccination and post-vaccination measles data in Liverpool and London. The comparison leads to some insightful observations.

报告人简介：Hao Wang，加拿大Alberta大学数学系副教授，以及该校生物数学中心顾问委员会成员。2006年在美国Arizona State University获得博士学位。Hao Wang教授主要研究领域是生物数学，在Journal of Dynamics and Differential Equations，SIAM Journal on Applied Mathematics，Journal of Mathematical Biology, Bulletin of Mathematical Biology国际著名期刊上发表40余篇学术论文。