不确定系数多离散时滞的中立型系统的时滞相关鲁棒稳定性

研究了一类时变不确定系数多离散时滞中立型系统的时滞相关鲁棒稳定性问题.利用线性矩阵不等式技术,提出了一种计算该系统自由权矩阵和时滞上界的简化方法,并在系统中考虑了中立项时滞和离散时滞,得到了上述系统为稳定与鲁棒稳定的一些充分条件.最后,用数值例子说明了该方法的有效性和较小的保守性.     

具有时变时滞的数据采样无人船舵减摇系统稳定性分析

本文研究了基于数据采样的无人船舵减摇闭环控制系统的稳定性.考虑到采样过程存在延迟现象,引用动态时滞区间的方法,构造相应的Lyapunov-Krasovskii泛函（LKF）.此方法将固定时滞区间扩展成为动态时滞区间,不仅放宽了时滞区间上界和下界的限制,还能同时获得基于线性矩阵不等式（LMI）的更小保守性的相关稳定性判据.最终可以获得一个更宽松的标准来分析基于数据采样的无人船舵减摇闭环控制系统的稳定性.最后,举例说明了所提出方法的有效性.     

关于随机分布参数系统的变结构控制研究

研究了一类Itô型随机时滞分布参数系统的滑动模控制问题,设计了该系统的变结构控制器,证明了系统的滑动模运动的存在性,并分析了在滑动切换面上滑动模控制系统关于不确定量的不变性特征及运动稳定性.与相关论文相比,所获结论与扩散系数相关,在实际应用中更具实践意义.运用文中方法,类似论文结论均可进行改进.     

负相依索赔条件下带常数利率的风险模型在随机时间上的破产概率

研究了负相依索赔条件下带常数利率的风险模型在随机区间上的破产问题.假设随机埋单服从指数分布,通过分析随机时间与有限时间之间的关系,得到了该模型破产概率的渐近表达式.     

一类带马氏切换与时滞的未定权益模型的对冲策略

在风险资产服从一类带马尔科夫模式切换（马氏切换）的时滞随机微分方程模型的情形下,考虑了一个以上述风险资产为标的资产的欧式未定权益,利用Esscher变换找到了等价鞅测度,并在此基础上得到该权益价格过程的鞅表示.同时,在资产价格过程的系数满足一定条件的假设下,给出了在由马氏切换的出现而导致的不完备市场中,通过最小化残余风险而求得的最优连续对冲策略.     

一类非线性时变时滞随机大系统的稳定性

讨论了线性时滞随机系统平凡解的 几乎必然渐近稳定性&并推广到非线性 多时滞随机大系统的几乎必然渐近稳定 性''提出了非线性多时滞随机大系统几 乎必然渐近稳定性的代数判据''最后&用 仿真例子说明了主要结果的可行性与有 效性     

具有随机扰动和混合时滞的两层异质网络的同步研究

在现实生活中,很多复杂的系统不是由单个网络来表示,而是由一组相互依赖的网络系统来表示的.本文研究了具有随机扰动和混合时滞的两层异质网络的对应节点的同步控制问题.基于随机微分时滞方程的LaSalle不变原理和Lyapunov稳定性理论,采用牵制控制方法,对部分节点实施控制,给出了实现同步的充分条件.为了降低反馈控制的增益,结合自适应控制的方法,进一步弱化了两层异质网络实现同步的条件.最后,通过数值仿真,验证了理论结果的有效性.     

混杂随机微分方程理论概述

本文对混杂随机时滞微分方程的当前发展及最新的研究成果进行了概述.主要回顾了混杂随机微分方程解的存在唯一性定理、稳定性、鲁棒有界性以及离散时间反馈镇定性等部分对混杂随机微分方程的研究起到关键推动作用的成果.     

多智能体系统的有限时间与固定时间一致性

本文利用非连续的控制协议,研究了多智能体系统的有限时间一致性与固定时间一致性问题.基于集值映射、微分包含以及Lyapunov稳定性理论,在统一的框架下,给出了多智能体系统达到有限时间一致性和固定时间一致性的判别准则.通过数值仿真,验证了所给协议的有效性.     

随机马尔可夫跳变系统的弹性动态输出反馈控制

本文讨论了随机噪声影响下马尔可夫跳变系统的弹性动态输出反馈控制问题.在系统随机干扰和控制输入扰动的情况下,设计的弹性控制器可以确保闭环系统的依概率渐近稳定性.通过运用随机微分方程理论和线性矩阵不等式技术对系统进行稳定性分析,获得了系统依概率渐近稳定的充分条件和控制器增益.最后通过数值算例和直升机系统仿真验证了所提弹性动态输出反馈控制方法的有效性.     

EFFECTS OF THE AMBIENT TEMPERATURE GRADIENT ON DEVELOPMENT AND MOVEMENT OF TROPICAL DISTURBANCES

The effects of the ambient temperature gradient on the development and movement of tropical disturbanceshave been analysed through a two-layer model of the CISK.The results show that when the gradient exists inthe external area of disturbances and directs to their center,it is favourable to the development of distur-bances,but an unfavourable case occurs when the gradient exists not only in the external but also in theinternal areas of the disturbances.It is also shown that the gradient makes the disturbances tend to movetoward warm environments.These results coincide with the observational facts which take place when coldfronts approach typhoons or tropical cyclones.     

一类时滞不确定离散系统的鲁棒自适应滑模控制

主要研究一类具有不确定项和外部扰动的离散时滞系统的鲁棒自适应控制,假设扰动和不确定项是有界的,而扰动和关于状态的不确定项的边界是不必知道的.设计了自适应控制器以保证系统能在有限时间内到达切换面,并且收敛到包含原点的一定的有界区域内.仿真的结果说明了该方法的有效性.     

Statistical performances of various deterministic and stochastic models for rainfall series disaggregation

This paper compares the performance of seven disaggregation models, based on various approaches and/or concepts, for the generation of 10-min time step rainfall series from hourly rainfall series. The so-called constant disaggregation model and a linear model based on the external temporal pattern of rainfall are first considered. The other models are stochastic: the first ones are based on a given probability density function applying for the 10-min rainfall amounts of the hour to disaggregate. This probability density function is either uniform or derived from the external temporal pattern of rainfall. The other stochastic models are scaling models using canonical or microcanonical multiplicative random cascades. The comparison of the models is based on their ability to reproduce some important statistical characteristics of the observed time series: variance, skewness coefficient, wet/dry properties of 10-min rainfall amounts; rainfall amounts quantiles for different return periods; autocorrelation of 10-min rainfall amounts. A continuous hydrological simulation is next applied to produce for each generated rainfall series a continuous discharge series used afterwards for a retention design. The ability of the different disaggregation models to produce rainfall time series resulting in the same retention design than the one obtained with the observed rainfall series is finally analysed. Deterministic models as well as simpler stochastic models have rather bad performances when compared to the others. Because it is non-conservative, the model based on a microcanonical random cascade performs also very poorly. It significantly overestimates all studied statistics. Models based on microcanonical random cascades achieve the best performance. They perform reasonably well for the reproduction of rainfall statistics and almost perfectly for the reproduction of runoff and storage design variables. Results finally highlight the interest of including in the disaggregation scheme information related to the external temporal pattern of rainfall.     

Topographic effects on solitary Rossby waves

The model for baroclinic solitary waves previously described by Flierl is developed to include effects of bottom variations.Topographic disturbances are shown to act, through their first and second derivatives, on both the phase speed correction and the maximum horizontal amplitude.The combined effects of mean shear flow steepening and bottom variations are considered; an equation is derived, showing the relative importance of each effect.     

积云团对大气层结影响的模拟研究

文中设计了一个二维完全弹性的积云团数值模式 .模式中考虑了水平均一和时间定常的大尺度抬升速度的影响 .大度抬升速度只对热力学方程和水汽守恒方程有影响 .积云团的启动方式采用冷池和随机扰动相结合的方法 .文中对一个给定温湿层结和大尺度抬升速度情况下 ,就不同扰动结构、水平环境切变、模式区域大小和冷池强度等进行了 1 1个模拟试验 .结果表明 ,在不同扰动结构、是否有水平环境风切变、模式区域不同以及不同云型谱时 ,给定温湿层结和大尺度抬升速度下的积云团活动使得温湿层结向着同一温湿层结调整 .这说明大气由于积云团活动达到准平衡状态 ,这个准平衡状态主要依赖于初始温湿层结和大尺度抬升速度 .这与 Betts积云参数化方案的假设相一致 .     

The random force theory: Application to meso- and large-scale atmospheric diffusion

The physical basis for the random force theory of atmospheric diffusion is briefly reviewed. The random force equation has usually been introduced as an atmospheric analogy to Brownian motion. Here it is derived by assuming a type of Rayleigh friction in the Lagrangian equations of atmospheric motion. Consequences, including the Lagrangian correlation and spectrum, the particle-particle intercorrelation, and cluster and plume dispersion and meandering, are derived and compared with atmospheric observations. The characteristic time-scale of atmospheric diffusion is shown to be governed by the Coriolis effect, a result in good agreement with meso- and large-scale observations.     

Phillips模式的斜压不稳定的非线性饱和问题:能量情形

A conservation law for the Phillips model is derived. Using this law, the nonlinear saturation of purely baroclinic instability caused by the vertical velocity shear of the basic flow in the Phillips model-the case of energy-is studied within the context of Arnold's second stability theorem. Analytic upper bounds on the energy of wavy disturbances are obtained. For one unstable region in the parameter plane, the result here is a second-order correction in ε to Shepherd's; For another unstable region, the analytic upper bound on the energy of wavy disturbances offers an effective constraint on wavy (nonzonal) disturbances φ'i at any time.     

2006年夏季川渝高温干旱分析

2006年夏季,我国重庆、四川等地持续高温少雨,遭遇特大伏旱,影响严重。初步分析表明,2006年盛夏川渝的异常高温事件可能是受全球变暖和天气扰动共同作用的结果,但以天气扰动的影响为主。大气环流异常,北方南下冷空气活动偏弱,西北太平洋副高脊线偏北以及冬季青藏高原积雪偏少是导致该地区2006年严重高温干旱的直接原因。     

基于LMI的不确定时滞非线性系统鲁棒镇定研究

研究了一类不确定时滞非线性系统的鲁棒镇定问题.不确定参数是时变未知有界的,但不一定满足所谓的匹配条件.利用线性矩阵不等式,一些充分条件被获得,保证了相应闭环系统的鲁棒稳定性,并在此基础上得出了相应的状态反馈控制器.最后,通过一个数值例子说明了该方法的有效性.