一类具有双线性发生率的SEIR流行病传播数学模型

利用Lasalle不变集原理探讨系统的渐近性态,研究了一类具有双线性发生率且染病期传染的SEIR流行病传播数学模型的动力学性质.得到了疾病绝灭与持续的阈值-基本再生数,证明了无病平衡点的全局渐近稳定性和地方病平衡点的全局渐近稳定性,揭示了潜伏期传染的影响.     

潜伏期和染病期均传染的SEIS模型的分析

研究了潜伏期和染病期均传染的SEIS模型.给出了各类平衡点存在的条件阈值,证明了无病平衡点全局渐近稳定性的条件,并且利用第二加性复合矩阵给出了地方平衡点的存在性和全局渐近稳定性的充分条件.     

一类潜伏期和染病期均传染且具一般接触率的SEIS模型

研究了一类潜伏期和染病期均传染且具有一般接触率的SEIS流行病模型,确定了各类平衡点存在的阈值,讨论了各类平衡点的稳定性,揭示了潜伏期和染病期传染对流行病发展趋势的共同影响.     

一类潜伏期和染病期均传染的SEIS模型

研究了一类具有非线性传染率且潜伏期和染病期均传染的SEIS传染病模型,得到了决定疾病绝灭和持续的阈值,证明了在无因病死亡的情形下,极限系统的地方病平衡点只要存在就一定是全局渐近稳定的.     

一类具有常数迁入且潜伏期和染病期均传染的流行病模型

讨论了一类有常数迁入且潜伏期和染病期均传染,潜伏期和染病期传染率相同的SEIS模型.确定的基本再生数R0,如果R0≤1,则无痛平衡点是全局渐进稳定的,当尺R0>1时疾病消除平衡点是不稳定的,地方病平衡点是局部渐进稳定的.     

预防接种情况下潜伏期和染病期均具有传染力的SEIR传染病模型的全局分析

讨论了一类在连续预防接种情况下具有垂直传染的潜伏期和染病期均有传染力的SEIR传染病模型,通过计算得到了基本再生数R0。当R01时,仅存在无病平衡点且全局渐近稳定;当R01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全局渐近稳定。     

一类具有线性传染力的SIRS传染病动力系统的分析与控制

面对传染病对人类身体健康的严重威胁,医学工作者以及数学工作者在使用数学模型研究传染病的传染规律、趋势预测以及预防控制等方面做了大量的研究工作。主要对一类具有线性传染力的SIRS传染病模型进行了平衡点的稳定性分析,并将控制理论应用于传染病的控制,即对染病者施加控制以使疾病最终消除,对于具有线性传染力的SIRS传染病的控制有一定的实际应用意义。首先,根据疾病消除平衡点和地方病平衡点存在的条件定义阈值;然后,用Lyapunov方法和LaSalle不变原理证明了不同阈值下疾病消除平衡点和地方病平衡点的全局渐近稳定性,根据系统对染病者施加有效的控制以使疾病消除平衡点全局渐近稳定,并对控制器的设计加以解释;最后,以数字例子进行系统仿真以说明控制的有效性。     

基于潜伏期有传染力的SEIR传染病模型的控制策略

研究了潜伏期和染病期均有传染力的SEIR传染病模型,在连续接种和治疗不同策略下平衡点的稳定性,获得了疾病消除的阈值.通过比较两种控制策略的有效性,说明接种比治疗更能有效地控制疾病,同时应用两种控制策略比单独应用一种更加有效.     

一类潜伏期和染病期均传染SEIS模型的渐近定性分析

研究了一类潜伏期、染病期均传染且具有不同饱和接触率C1（N）和C2（N）的SEIS传染病模型,得到了疾病流行的基本再生数R0.运用Liapunov函数方法,证明了当R0〈1时,无病平衡点P0全局渐近稳定,疾病最终消失;利用Hurwitz判据定理,证明了当R0〉1时,P0不稳定,地方病平衡点P＊局部渐近稳定;当因病死亡率为零时,极限系统的地方病平衡点P＊全局渐近稳定.     

一类潜伏期具有传染性的流行病模型的稳定性

研究一类潜伏期和染病期均具有传染性和康复可能的SEIQ流行病模型,确定了疾病流行与否的阈,利用Routh-Hurwitz判据和LaSalle不变集原理得到无病平衡点的全局渐近稳定性,并借助广义Bendixson-Dulac定理得到地方病平衡点的全局渐近稳定性,最后将隔离率作为控制变量,用范数指标函数作为衡量控制变量的标准,得出该模型最优控制元的存在惟一性.     

Markedness and its Interpretation in Language Use

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.     

Features of Women's language

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.     

Characterization of Ordovician carbonate reservoirs, southeastern Saskatchewan, Canada

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.     

低渗透非均质砂岩油藏启动压力梯度研究

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。     

On Tragic Consciousness In The Works By Ernest Hemingway

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.     

A computer generator for randomly layered structures

AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…     

An Index mechanism for multi-scale view in spatial databases

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.     

Jane Eyre——A Feminist In The 19th Century

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.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-