一类带有非线性传染率的传染病模型的全局性态

假设潜伏者与染病者都具有传染性且染病者恢复后对该病具有终身免疫力,建立了一类带有非线性传染率（γαE／（1＋bE^n）＋λaI／（1＋bI^n））的SEIR传染病模型,得到了疾病是否会成为地方病的基本再生数,讨论了无病平衡点和地方病平衡点的全局稳定性．     

一类带有非线性传染率的SEIR传染病模型的全局分析

通过假设潜伏者与染病者都具有传染性且染病者恢复后对该病具有终身免疫力,建立了一类带有非线性传染率的SEIR传染病模型.得到了疾病是否会成为地方病的基本再生数,以及无病平衡点和地方病平衡点的全局稳定性.     

具有脉冲接种的传染病模型的渐近分析

研究具有比例接种和脉冲接种的传染病模型的渐近性态，给出了对疾病传播有重要影响的再生数，得到了比例接种模型无病平衡点和地方病平衡点的全局渐近稳定性及脉冲接种模型无病周期解的全局稳定性，比较了接种效果，并对一定的参数进行了数值模拟。     

一类手足口病模型的全局稳定性分析

研究具有隐性传染和隔离措施的手足口病模型,计算模型的基本再生数.结果表明,当基本再生数小于1时,模型仅有唯一的无病平衡点,利用线性化方法和Lyapunov函数方法,讨论无病平衡点的全局渐近稳定性.当基本再生数大于1时,无病平衡点不稳定,模型还存在唯一的地方病平衡点,通过构造合适的Lyapunov函数证明地方病平衡点的全局渐近稳定性.     

一类多种预防控制策略的SVIQR流行病模型研究

研究一类带有接种、剔除和隔离等多种混合策略的SVIQR模型.研究了在多种控制策略下预防和控制流行病模型,针对一些接种期比较长的流行病,把接种者群体看作一类特殊群体.利用微分方程有关定性稳定性理论分析了该模型,得到了疾病绝灭与否的基本再生数R0,证明了当R01时,无病平衡点E0全局渐近稳定,疾病最终会消失;当R01时,E0不稳定,惟一的地方病平衡点E*全局渐近稳定,疾病最终得到流行.最后对接种、剔除和隔离策略进行了讨论和比较,针对流行病的具体情况采取不同的预防和控制策略.     

一类恒化器模型正平衡解的稳定性

在齐次Neumann条件下研究一类具有能量维持扩散的恒化器模型的稳定性.首先利用最大值原理和Harnack不等式给出平衡态方程正解的先验估计;其次利用谱分析和特征值理论证明正常数平衡解的一致渐近稳定性;最后借助构造Lyapunov函数来证明正常数平衡解的全局渐近稳定性.     

人与人传染的有媒体影响因子的禽流感模型

建立人与人之间相互传染的有媒体影响因子的SI-SIR禽流感模型,并研究其动力学性态,得到判断疾病传播与否的阈值R_a和R_0.利用Lyapunov函数、Dulac函数以及LaSalle不变原理等证明了当R_a1且R_01时,无病平衡点E_0~*是全局渐近稳定的;当R_a1且R_01时,边界平衡点E_1~*是全局渐近稳定的;当R_a1时,系统的正平衡点E_2~*是全局渐近稳定的.     

双时滞种群-传染病模型的稳定性分析

建立了一类双时滞两种群捕食与被捕食传染病模型,得到了无病平衡点稳定与否的阀值条件.当时滞经过某一临界值时,Hopf分支在有病的边界平衡点发生,并利用Rouche定理得到了有病平衡点关于两时滞的稳定区间.     

一类带隔离项的具非线性传染率的SIQ模型的全局分析

研究了一类带有隔离项的具有非线性传染率的SIQ传染病模型的全局稳定性.得到了基本再生数R0,利用Lasalle不变集原理,证明了无病平衡点的全局稳定性.利用零点定理及方程根的分布特点.证明了地方病平衡点的存在性及唯一性.同时,借助多元函数微分学关于极值判断定理及Lyapunov函数,证明了地方病平衡点的全局稳定性.     

一类带有非线性传染率的SEIR模型的全局分析

建立了一类带有非线性传染率βSφ（I）的SEIR传染病模型,得到了疾病是否会成为地方病的基本再生数,利用Lassalle不变原理证明了无病平衡点的全局渐进稳定和地方病平衡点的渐进稳定性.     

SEIS流行病模型中各类人群的指数变化率

针对类似丙肝这种具有较长慢性阶段的流行病问题,依据仓室建模思想,建立并研究了一类具有变化的总人口数的含有易感者类、潜伏期类、染急性病者类和染慢性病者类的SEIS流行病模型.借助基本再生数R0和基本取代率R1,讨论了上述4类人群的指数变化率.     

一类具有群体感应机理的传染病模型渐近分析

考虑病菌的群体感应机理,建立了一类具有一般作用率反应病菌与免疫系统竞争的传染病数学模型. 分析了模型平衡点的存在性及渐近稳定性. 特别地,利用中心流形定理研究退化平衡点的稳定性. 最后,数值模拟验证所得理论结果,为传染病的控制和预防提供了理论基础和数值依据.     

US news media coverage of tobacco control issues

Objective

To characterise the relative amount and type of daily newspaper, local and national TV newscast, and national news magazine coverage of tobacco control issues in the United States in 2002 and 2003.

Design

Content analysis of daily newspapers, news magazines, and TV newscasts.

Subjects

Items about tobacco in daily newspapers, local and national TV newscasts, and three national news magazines in a nationally representative sample of 56 days of news stratified by day of week and season of the year, from 2002 and 2003.

Main outcome measures

Story theme, tobacco topics, sources, story prominence, story valence (orientation), and story type.

Results

Tobacco coverage was modest over the two‐year period as estimated in our sample. Only 21 TV stories, 17 news magazine stories, and 335 daily newspaper stories were found during the two‐year sampling period. Noteworthy results for the newspaper data set include the following: (1) government topics predominated coverage; (2) government action and negative health effects topics tended not to occur together in stories; (3) tobacco stories were fairly prominently placed in newspapers; (4) opinion news items tended to favour tobacco control policies, while news and feature stories were evenly split between positive and negative stories; and (5) tobacco coverage in the southeast, which is the country''s major tobacco producing region, did not differ from the rest of the country.

Conclusion

Results suggest mixed support in news coverage for tobacco control efforts in the United States. The modest amount of news coverage of tobacco is troubling, particularly because so few news stories were found on TV, which is a more important news source for Americans than newspapers. When tobacco was covered, government themed stories, which often did not include mentions of negative health effects, were typical, suggesting that media coverage does not reinforce the reason for tobacco control efforts. However, some results were encouraging. For example, when newspapers did cover tobacco, they accorded the stories relatively high prominence, thus increasing the chance that readers would see tobacco stories when they were published.     

具有饱和接触率和垂直感染的SIR模型全局分析

研究了一类具有饱和接触率和垂直感染的SIR模型,得到了疾病绝灭的阈值R0.通过构造V函数和Dulac函数,证明了当R0≤1时,无病平衡点全局渐近稳定;当R01时,存在惟一地方病平衡点,且全局渐近稳定.