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1.
一类不确定时滞系统的K-稳定性   总被引:1,自引:1,他引:0  
研究了一类不确定时滞系统:x(t)=Ax(t) Bx(1-τ(t) f(t,x(t) g(t,x(t-τ(t))),t≥0,x(t)=φ(t),-τ≤t≤0的K-全局渐近稳定性和K-全局指数稳定性,通过使用不等式技巧和微分方程性质,得到了这类系统K-稳定性的时滞相关充分条件,最后举例阐述了它的有效性。  相似文献   

2.
时滞细胞神经网络模型的渐近性态分析   总被引:1,自引:0,他引:1  
对具有时滞的神经网络模型xi(t)=-Cixi(t) ∑j=1^n aijfj(xj(t)) ∑j=1^n bijfj(xj(t-τj)) Ii,i=1,2,…,n,在非线性神经元激励函数满足Lipachitz连续的条件下通过构造适当的泛函,研究了这类模型的渐近性态,获得了这类模型全局吸引和平衡点的全局指数稳定易于验证的充分条件.  相似文献   

3.
时滞细胞神经网络模型的全局吸引性和全局指数稳定性   总被引:6,自引:4,他引:6  
借助于Liapunov第二方法 ,对具有时滞的细胞神经网络系统x′i(t) =-Cixi(t) ∑nj=1aijfj(xj(t) ) ∑nj=1bijfj(xj(t-τj) ) Ii, i=1,2 ,… ,n ,在非线性神经元激励函数满足Lipschitz连续的条件下 ,研究了这类模型全局吸引和平衡点全局指数稳定的问题 ,获得了易于验证的充分条件  相似文献   

4.
研究非线性时滞系统 X(t) =f(t,X(t) ) +g(t,X(t -τ(t) ) ) , t 0 ,X(t) =Φ(t) ,  -τ t 0的K 稳定性 ,通过使用不等式技巧和微分方程性质 ,得到了这类系统的K 全局渐近稳定性与K 全局指数稳定性的易于验证的时滞相关充分条件 .  相似文献   

5.
造血模型正平衡解的全局吸引性   总被引:1,自引:0,他引:1  
作者得到造血模型dN(t)/dt=-δN(t) βθ^nN(t-τ)/θ^n N^n(t-τ),dN(t)/dt=-δN(t)-βθ^n(t)/θ^n N^n(t) 2βθ^nN(t-τ)/θ^n N(t-τ)e-π,正平衡解全局吸引的充分条件。这里δ,β,θ,r,τ∈(0, ∞),n∈(0,1]。  相似文献   

6.
考虑具周期系数非线性时滞差分方程xn 1-xn pnxn-k=pnf(x[n/τ]τ-l),n=0,1,2,…,其中{pn}为T周期正数列,即Pn τ=pn,k=sT,k,s,T为自然数,通过讨论对应的齐次线性差分方程的性质,获得了关于零解全局渐近稳定的充分必要条件。  相似文献   

7.
利用不动点理论和时延不等式的方法研究了具有时滞的Cohen Grossberg神经网络模型dui(t)dt=ai(ui(t))bi(ui(t))-∑nj=1Tijfj(uj(t-τj)),i=1,2,…,n平衡点的稳定性问题.给出判定模型平衡点存在唯一性和全局指数稳定性的几个充分条件,这些条件取消了权矩阵(Tij)n×n对称性的假设,推广了已知文献的一些结果,使模型的应用范围更加广泛.  相似文献   

8.
研究了具有变时滞的细胞神经网络系统nx.i(t)=-cixi(t)+∑nj=1aijfj(xj(t))+∑nj=1bijfj(xj(t-τj(t)))+Ii,i=1,2,…,n.在非线性神经激励函数满足Lipschitz条件下,借助于推广的Halanay时滞微分不等式等方法,得到了该系统的平衡点是全局指数稳定的条件.  相似文献   

9.
本文利用Lyapunov泛函及不等式,研究了一类变时滞线性中立型泛函微分方程[x(t)-m∑i=1aix(t-τi)]'=bx(t)+n∑j=1+cjx(t-δj(t))的稳定性,并得到其零解渐进稳定性的充分条件.  相似文献   

10.
研究了其时滞是在更一般的时间变量的函数情况下的Hopfield网络系统:(*)/(x)i(t)=-cixi(t)+∑n j=1aijfj(xj(t))+∑n j=1bijfj(xj(t-τj(t)))+Ii,i=1,2,...,n.在非线性神经激励函数满足较弱的Lipschitz条件下,引入Lyapunov函数,利用不等式技巧和泛函的单调性等,研究了具有变时滞的Hopfield网络系统的稳定性,得到了对每一个输出响应函数fj(*)在R上有定义,且连续的情况下,系统有唯一的平衡点X=X*,并且该平衡点是全局指数稳定的一个易于判定的充分条件.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
何延凌 《科技信息》2008,(4):258-258
Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women's language from these perspectives: pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women's language, more attention should be paid to language use in social context. What's more, the linguistic phenomena in a speaking community can be understood more thoroughly.  相似文献   

13.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

14.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

15.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

16.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

17.
王慧 《科技信息》2008,(10):240-240
Wuthering Heights, Emily Bronte's only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.  相似文献   

18.
The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.  相似文献   

19.
In the 19th century the society was controlled by men, and women were just appendants of them, they had not any rights and freedom. But Jane was an exception, she showed some characteristics of early feminist. Jane showed her characteristics of feminism in three aspects: rebellion, equality, and independence. These characteristics were helpful to her success, and feminism is the only way out for women of that time.  相似文献   

20.
1 Rise of studies on climate change's effects on biodiversity
Until the 1980s, climate change and biodiversity were studied as two independent disciplines for more than a century. In 1992, the Ecological Society of America's annual report named climate change, biodiversity, and the sustainable ecological system as the three major global environmental issues of the twenty-first century [1].  相似文献   

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