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研究一类具有不连续治疗策略和非线性发生项的SIR模型.首先运用右端不连续的微分方程理论定义模型的Filippov解,然后证明该模型的全局行为由阈值R0确定,即当R0≤1时,无病平衡点全局渐近稳定. 相似文献
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文章讨论了具有时滞的SIR模型的渐近性态.利用Liapunov-Lasalle原理得到R0=1是疾病消除与流行的阈值.并且得到了地方病平衡点全局稳定的条件. 相似文献
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研究了一类具有垂直传染和因病死亡的SIR传染病模型,得到了地方病平衡点存在的阈值R0*.当R0*<1时,仅存在无病平衡点且局部渐近稳定;当R0*>1时,除存在不稳定的无病平衡点外,还存在唯一的正地方病平衡点且局部渐近稳定. 相似文献
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一类具饱和治愈率和垂直传染的传染病模型的研究 总被引：1，自引：1，他引：0
考虑了一类具有饱和治愈率和垂直传染的SIR传染病模型,通过计算得到基本再生数R0,并研究了无病平衡点和地方病平衡点全局渐近稳定性.通过构造Dulac函数,得到了该模型在正向不变集上闭轨线不存在的充分条件. 相似文献
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建立了一类考虑钉螺总数变化的血吸虫病动力学模型,利用谱半径的方法计算得到基本再生数R0,证明了当R0<1时无病平衡点全局渐近稳定,当R0>1时地方病平衡点全局渐近稳定. 相似文献
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《赣南师范学院学报》2013,(3):60-62
通过黄龙病在柑橘中的传播机理,建立了一个媒介传染病动力学模型.利用LaSalle不变性原理,Ben-dixson-Dulac定理证明了当R0≤1时无病平衡点全局渐近稳定,当R0>1时地方病平衡点全局渐近稳定. 相似文献
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研究了n个斑块间人口流动的疫苗接种的SVIR模型的全局稳定性。首先利用下一代矩阵的方法求得基本再生数R0。其次,应用非负矩阵以及非主对角元非负矩阵的相关知识给出了当R0<1时,无病平衡点是局部渐近稳定的,当R0>1时,无病平衡点是不稳定的;并且运用Lasalle不变原理证明了当R0<1时,无病平衡点的全局渐近稳定性。最后应用李雅普诺夫函数法、Lasalle不变原理并结合图论的方法证明了当R0>1时,疾病是一致持续存在的,同时地方病平衡点唯一存在且是全局渐近稳定的。 相似文献
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讨论了一类具有非线性传染率的SEIS流行病模型,当基本再生数R0<1时,无病平衡点全局渐近稳定;基本再生数R0>1时,地方平衡点全局渐近稳定. 相似文献
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研究了一类具有阶段结构和logistic输入的SIR传染病模型.将种群分为成年、幼年,并且假定只有成年个体可以染病.通过Hurtwiz判据、Bendixson-Dulac判别法及构造恰当的Lyapunov函数,获得了疾病的无病平衡点和地方病平衡点的局部渐近稳定性和全局渐近稳定性.研究表明:当基本再生数R01且满足一定的条件时,疾病将被消除;当基本再生数R01时,疾病持续流行并将成为一种地方病. 相似文献
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给出了无疾病潜伏期的传染病动力学模型的基本形式，通过对SIR有垂直传染且康复者的新生儿不具免疫力模型和SIR无垂直传染而引入疫苗接种模型的阈值和再生数分析，说明了阈值和再生数R0=1的差异。 相似文献
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《海外英语》2007,(5):10-11
Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help? 相似文献
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罗艳萍 《读与写:教育教学刊》2008,5(6)
The communication of people partially is the communication of cultures. Culture has a direct effect on international commercial activities in all aspects. Different conceptions about time, space, equality, law and the like, lead people to deal with things in different ways. So to know cultures of the counterpart is to facil-itate our enterprises so as to have a smooth and successful communication in commercial activity. 相似文献
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《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
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Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
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Richard Denner 《海外英语》2007,(4):14-15
Rosco and I wait for the fishermen to return.I sit at a wooden bench near the store at Mt.Baker Resort and watch the clouds change shape. Rosco has my belt around his neck and an eight foot tow chain hooked to a tree. Dogs must be on a leash. Ducks and rabbits are loose. 相似文献
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Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
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RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献