一类时滞Liénard方程同宿解存在性问题

本文首先利用Mawhin重合度拓展定理对任意正整数k探讨了一类时滞Liénard方程2kT-周期解uk(t)存在性问题,由此获得周期函数集合{uk(t)},然后证明了该集合{uk(t)}在Cl1oc(R,R)中的极限点就是所讨论方程的同宿解.     

不变子空间在周期解析信号中的应用

利用后移不变子空间,给出了周期解析信号与共轭周期解析信号的乘积仍为周期解析信号的充要条件。特别地,当周期解析信号对应的Z变换过圆周解析时,其对应的共轭周期解析信号为有理函数且有理函数的极点恰为周期解析信号对应的Z变换的零点。作为上述结论的应用,考虑了具有长度为n的Fourier级数的周期解析信号保持幅度不变的条件。     

环面自映射ω-极限集轨道的渐近性

给出了环面上连续自映射f的ω-极限集的如下结果：若 （x,y）∈X,则（1）ωf（x,y）=ωfn（x,y）;（2）（x,y）AP（f）蕴涵ωf（x,y）不可数;（3）ωf（x,y）或是由厂的一条周期轨道组成,或不可数;（4）ωf（x,y）=n-1∪i=0ωfn（f（x,y））f（ωfnf（x,y）））=ωfn（fi＋1（x,y））,f（ωfn（fn-1（x,y）））=ωfn（x,y）。     

周期法测G实验中磁场对扭秤周期的影响

磁场波动是周期法测G实验中的一个误差来源,作用到扭秤上的周期性变化磁场力矩会影响扭秤的运动周期.把磁场作用力矩当作噪声来处理,并利用非线性最小方差拟合法来提取扭秤周期.根据实验给出的相关参数值,利用数值模拟得到了周期性变化磁场力矩所引起扭秤周期的变化δT约为3.8×10-6s.     

一类多种群非线性捕食-竞争系统的持久性

研究一类多种群概周期系数非线性关系的捕食-竞争系统,得到系统持久性的充分性条件. 所得结果推广了李传荣,卢松坚等学者的相应结果.     

一类多种群非线性捕食-竞争系统的持久性

研究一类多种群概周期系数非线性关系的捕食-竞争系统,得到系统持久性的充分性条件.所得结果推广了李传荣,卢松坚等学者的相应结果.     

一类浮游生物植化相克时滞系统的概周期解的存在性

研究了一类浮游生物植化相克时滞概周期系统,运用概周期系统的性质与Lyapunov-Razuminkhin技巧,给出了其存在严格正概周期解的充分条件.     

一类二阶时滞泛函微分方程周期解的存在与唯一性

我们利用Mawhin重合度拓展定理,研究了一类二阶时滞泛函微分方程x″(t) f(t,x(t),x(t-τ))=p(t)周期解的存在唯一性问题,得到了其周期解存在唯一的新的结果.     

Seasonal cycle of the zonal land-sea thermal contrast and East Asian subtropical monsoon circulation

Based on analysis of the climatic temperature latitudinal deviation on middle troposphere, its seasonal cycle suggests that due to the rapid warming from eastern China continent to the east of Tibetan Plateau and the heating of Tibetan Plateau in spring, seasonal transition of the thermal difference between East Asia continent and West Pacific first takes place in the subtropical region with greatest intensity. On the accompanying low troposphere, the prevailing wind turns from northerly in winter to southerly in summer with the convection precipitation occurring at the same time. This maybe indicates the onset of the East Asian subtropical summer monsoon. Consequently, we advice that the seasonal cycle formed by the zonal thermal contrast between Asian continent and West Pacific may be an independent driving force of East Asian subtropical monsoon.     

An endpoint damage oriented model for life cycle environmental impact assessment of buildings in China

The midpoint impact assessment methodology and several weighting methods that are currently used by most building Life cycle assessment （LCA） researchers in China, still have some shortcomings. In order to make the evaluation results have better temporal and spatial applicability, the endpoint impact assessment methodology was adopted in this paper. Based on the endpoint damage oriented concept, four endpoints of resource exhaustion, energy exhaustion, human health damage and ecosystem damage were selected according to the situation of China and the specialties of the building industry. Subsequently the formula for calculating each endpoint, the background value for normalization and the weighting factors were defined. Following that, an endpoint damage oriented model to evaluate the life cycle environmental impact of buildings in China was established. This model can produce an in- tegrated indicator for environmental impact, and consequently provides references for directing the sustainable building design.