Biological control is an environmentally sound and effective means of reducing or mitigating pests and pest effects through the use of natural enemies. In this talk, we propose and analyze a model on biological control, which is based on the abundance of pest and a simple predator-prey model. We first study the existence and stability of equilibria. It turns out that backward bifurcation occurs with the migration rate as the bifurcation parameter. The stability of the trivial equilibrium and the boundary equilibrium is delay-independent. However, the stability of the positive equilibrium may be delay-dependent. Moreover, delay can switch the stability of the positive equilibrium. When the positive equilibrium loses stability, Hopf bifurcation can occur.

报告人：张同华 教授Swinburne University of Technology, Australia题目：Delay-induced Turing instability时间：5月29日 下午3:00-4:00地点：数学系致远楼102欢迎各位老师和同学参加！张同华教授，澳大利亚斯威本科技大学（Swinburne University of Technology）数学系博士生导师。2005年－2010年就职于澳大利亚科廷大学（助理研究员，研究员）。2004年以来发表SCI论文40余篇；出版专著《Computation of Mathematical Models...

Talk Title and AbstractOn the study of the first order Melnikov functionnear homoclinic and heteroclinic loops韩茂安Shanghai Normal University, ChinaIn this talk, we introduce some advances on the expansion of the first order Melnikov function appearing by perturbing a Hamiltonian or integrable system with a homoclinic or heteroclinic loop. We obtain formulas for computing the first coefficient...

拓扑学青年学者论坛程序册(Program)5月15日星期五 上午8:50-9:00欢迎词梁汉营9:00-9:50Witten Rigidity on Odd Dimensional Manifolds韩飞梁汉营9:50-10:15拍照10:15-11:05TBA王诗宬赵学志11:10-12:00Matrix group actions on CAT(0) spaces and Spheres叶圣奎12:00-2:30午餐5月15日星期五 下午时间报告(致远楼107)报告人主持人2:30-3:00实moment-angle流形的上同调环蔡力潘生亮3:20-3:50self-dual codes and simple polytopes...

报告人：肖冬梅 (上海交通大学教授，杰出青年基金获得者)题目：Traveling waves for a nonlocal diffusion population model with spatio-temporal delays时间： 5月7日（星期四），下午3:30-4:30地点：数学系致远楼102欢迎各位参加

学术报告报告人：徐洪坤教授（第三世界科学院院士，杭州电子科技大学特聘教授）题目: Proximal Methods for Nonconvex Optimization Problems时间：2015年4月30日(星期四)下午4：00—5：00地点：数学系致远楼102欢迎各位参加

学术报告 题 目：复杂数据的在线监控与诊断报告人：王兆军教授 (南开大学统计研究院副院长，长江学者）【王兆军教授简历】现任南开大学统计研究院副院长，教育部长江特聘教授，国务院学位委员会第七届学科评议组成员（统计学）；中国现场统计研究会副理事长，中国现场统计研究会生存分析分会副理事长，中国现场统计研究会高维数据统计分会副理事长，中国工业统计学教学研究会副理事长，天津市现场统计研究会理事长,全国应用统计...

We discuss unique solvability of the equality-constraint quadratic programming problem, establish a class of preconditioned alternating variable minimization with multiplier (PAVMM) methods for iteratively computing its solution, and demonstrate asymptotic convergence property of these PAVMM methods. We also discuss an algebraic derivation of the PAVMM method by making use of matrix splitting.