考虑心理因素和饱和治疗的H7N9禽流感动力学模型分析

研究了一种带治疗的病媒传播疾病的流行模型.得到了模型的基本再生数R_0,模型的平衡点和阈值由R_0确定.利用Bendixson-Dulac定理,证明了当R_01时,该模型的唯一正平衡点是全局稳定的.该结果可以帮助探索控制媒介传染病传播的方法.最后对模型进行了数值模拟,验证了该结论.     

多项式微分系统的不变直线的不同斜率的最大个数

本文证明了公式β（ｎ）＝σ（ｎ－１）＋１其中α（ｎ－１）是ｎ－１次多项式微分系统的不为直线的最多条数，βｎ）是ｎ次多项式微分系统的不变直线的不同斜率的最大个数。这里假设所讨论的多项式系统只有限条不变直线。     

Nonmonotonic logics and algebras

Several nonmonotonic logic systems together with their algebraic semantics are discussed. NMalgebra is defined. An elegant construction of an NMalgebra starting from a Boolean algebra is described which gives rise to a few interesting algebraic issues.     

Improvement of warm formability of Al-Mg sheet alloys containing coarse second-phase particles

Several alloying elements involving Zr,Cu,Zn and Sc were added to Al-Mg sheet alloys in order to obtain an excellent combination of high strength and good high-temperature formability.Microstructural examination showed that coarse intermetallic particles were formed in the microstructure and their amounts changed with variations of the alloying elements. During warm rolling of thermomechanical treatments prior to warm deformation,the coarse particles initiated cracks,decreasing the warm formability.For healing the crack damage and further improving the warm formability,a process of hot isothermal press was developed and optimized to the sheet alloys.With this process,the biaxial stretch formability at 350°C was improved by 22%for an aluminum alloy containing a large amount of coarse particles.