具脉冲和时滞影响的非线性抛物系统边值问题的振动结果

研究一类具非线性扩散项的脉冲时滞抛物偏微分系统解的振动性,借助Green公式、垂直相加法和脉冲时滞微分不等式,获得了该类系统在Robin边值条件下振动的充分性条件.所得结果充分反映了脉冲和时滞在系统振动中的影响作用.     

具正负系数的二阶中立型时滞差分方程的振动和非振动准则

研究了一类具有正负系数的二阶非线性中立型时滞差分方程的振动性,利用Banach空间的不动点原理,结合Riccati变换,获得了该类方程存在非振动解的一些新的准则,并同时得到了该类方程振动的判别准则,这些准则改善了对方程的条件限制,所得结论推广并改进了现有文献中的一系列结果.     

一类脉冲时滞抛物方程组边值问题的振动准则

考虑了一类带强迫项的脉冲时滞抛物方程组,利用脉冲时滞微分不等式,获得了该类方程组的解强迫振动的若干充分判据.     

具有连续分布偏差变元的双曲型微分方程振动准则的进一步结果(英文)

A class of hyperbolic equations with continuous distributed deviating arguments is considered and its oscillation theorems are discussed.These theorems are of higher degree of generality and deal with the cases which are not covered by the known criteria.Particularly,these criteria extend and unify a number of existing results.     

A REMARK FOR “ASYMPTOTIC BEHAVIOR OF DELAY 2-D DISCRETE LOGISTIC SYSTEMS”

In this remark,we shall show some counter examples for the main results of the recent paper "Asymptotic Behavior of Delay 2-D Discrete Logistic Systems" (IEEE Trans.Circuits Systems,49(2002),1677-1682.)     

Theoretical investigation of effects of flow oscillations on ultrasound Doppler velocity measurements

Effects of flow oscillations on spectrum of Ultrasound Doppler Velocimetry (UDV) signals were investigated theoretically and numerically. A laminar pipe flow with a superimposed oscillating component was considered. Negative impact of oscillation on the ultrasound signal hence on the flow images was observed in the form of spreading of spectral ultrasound signal energy around mean component, leading to image artifacts. Both analytical and numerical results revealed the strong effect of a group of parameters including Doppler frequency, flow oscillation amplitude and frequency. Exceeding a particular value of the group, 1.45, resulted in artifacts in the flow images. Revealing the mechanisms involved in the deteriorations associated with the flow oscillations is potentially useful in UDV studies involving random flow fluctuations such as turbulence.     

均匀展宽增益介质中超光速饱和现象的研究

根据饱和增益理论分析可知,不同抽运光功率对应着介质不同的吸收和增益状态. 在吸收介质中,相干布居振荡效应导致光脉冲经历饱和吸收,光脉冲传输延迟;在增益介质中, 相干布居振荡效应导致光脉冲经历增益饱和,光脉冲传输超前. 本文由铒离子的亚稳态速率方程出发,建立了掺铒光纤中超光速传输的理论模型, 同时得到时间超前的数值解析表达式;讨论了低频率段超光速的饱和现象, 即超光速在低频段并不随着抽运光功率的增强而加强,而在高频率段随抽运光功率的增加而加强.     

时间尺度上具阻尼项的二阶半线性时滞动力方程振动性的新结果

本文讨论一类具阻尼项的二阶半线性时滞动力方程解的振动性质, 利用广义Riccati 变换和不等式技巧, 在一定条件下, 建立了4 个新的振动准则, 其结果改进和推广了已知的一些结果.     

一类寄生虫模型解的性态研究

本文研究了一类寄生虫模型解的性态, 给出了该模型的解具有持久性和振动性的一些充分条件,回答了Dynamics of Second Order Difference Equation 一书中的一个公开的研究建议.