Theoretical description of improving measurement accuracy for incoherence Mie Doppler wind lidar

For the nonlinearity of Fabry-Perot interferometer(FPI) transmission spectrum,the measurement uncertainty of incoherent Mie Doppler wind lidar based on it increases evidently with the increase of backscattering signal Doppler shift.A method of repeating the use of the approximate linear part of FPI transmission spectra for reducing the high uncertainty of a big Doppler shift is proposed.One of the ways of realizing this method is discussed in detail,in which the characteristics of FPI transmission spectrum changing with thickness and incident angle are utilized simultaneously.Under different atmosphere conditions,it has been proved theoretically that the range of measurement uncertainty drops to one-sixth while its minimum has no serious change.This method can be used not only to guide the new system design,but also as a new working way for the fabricated system.     

Simulating regular wave propagation over a submerged bar by boundary element method model and Boussinesq equation model

Numerical models based on the boundary element method and Boussinesq equation are used to simulate the wave transform over a submerged bar for regular waves.In the boundary-element-method model the linear element is used,and the integrals are computed by analytical formulas.The Boussinesq-equation model is the well-known FUNWAVE from the University of Delaware.We compare the numerical free surface displacements with the laboratory data on both gentle slope and steep slope,and find that both the models simulate the wave transform well.We further compute the agreement indexes between the numerical result and laboratory data,and the results support that the boundary-element-method model has a stable good performance,which is due to the fact that its governing equation has no restriction on nonlinearity and dispersion as compared with Boussinesq equation.     

Stability analysis and control synthesis of uncertain Roesser-type discrete-time two-dimensional systems

We study the stability analysis and control synthesis of uncertain discrete-time two-dimensional(2D) systems.The mathematical model of the discrete-time 2D system is established upon the well-known Roesser model,and the uncertainty phenomenon,which appears typically in practical environments,is modeled by a convex bounded(polytope type) uncertain domain.The stability analysis and control synthesis of uncertain discrete-time 2D systems are then developed by applying the Lyapunov stability theory.In the processes of stability analysis and control synthesis,the obtained stability/stabilzaition conditions become less conservative by applying some novel relaxed techniques.Moreover,the obtained results are formulated in the form of linear matrix inequalities,which can be easily solved via standard numerical software.Finally,numerical examples are given to demonstrate the effectiveness of the obtained results.     

Two new discrete integrable systems

In this paper,we focus on the construction of new(1+1)-dimensional discrete integrable systems according to a subalgebra of loop algebra A 1.By designing two new(1+1)-dimensional discrete spectral problems,two new discrete integrable systems are obtained,namely,a 2-field lattice hierarchy and a 3-field lattice hierarchy.When deriving the two new discrete integrable systems,we find the generalized relativistic Toda lattice hierarchy and the generalized modified Toda lattice hierarchy.Moreover,we also obtain the Hamiltonian structures of the two lattice hierarchies by means of the discrete trace identity.     

Average consensus of multi-agent systems with communication time delays and noisy links

In this paper,we consider the average-consensus problem with communication time delays and noisy links.We analyze two different cases of coupling topologies:fixed and switching topologies.By utilizing the stability theory of the stochastic differential equations,we analytically show that the average consensus could be achieved almost surely with the perturbation of noise and the communication time delays even if the time delay is time-varying.The theoretical results show that multi-agent systems can tolerate relatively large time delays if the noise is weak,and they can tolerate relatively strong noise if the time delays are low.The simulation results show that systems with strong noise intensities yield slow convergence.     

Adaptive control of bifurcation and chaos in a time-delayed system

In this paper, the stabilization of a continuous time-delayed system is considered. To control the bifurcation and chaos in a time-delayed system, a parameter perturbation control and a hybrid control are proposed. Then, to ensure the asymptotic stability of the system in the presence of unexpected system parameter changes, the adaptive control idea is introduced, i.e., the perturbation control parameter and the hybrid control parameter are automatically tuned according to the adaptation laws, respectively. The adaptation algorithms are constructed based on the Lyapunov-Krasovskii stability theorem. The adaptive parameter perturbation control and the adaptive hybrid control methods improve the corresponding constant control methods. They have the advantages of increased stability, adaptability to the changes of the system parameters, control cost saving, and simplicity. Numerical simulations for a well-known chaotic time-delayed system are performed to demonstrate the feasibility and superiority of the proposed control methods. Besides, comparison of the two adaptive control methods are made in an experimental study.     

High frequency forcing on nonlinear systems

High-frequency signals are pervasive in many science and engineering fields.In this work,the effect of high-frequency driving on general nonlinear systems is investigated,and an effective equation for slow motion is derived by extending the inertial approximation for the direct separation of fast and slow motions.Based on this theory,a high-frequency force can induce various phase transitions of a system by changing its amplitude and frequency.Numerical simulations on several nonlinear oscillator systems show a very good agreement with the theoretic results.These findings may shed light on our understanding of the dynamics of nonlinear systems subject to a periodic force.     

基于隐藏故障和竞争失效的多态系统视情维修策略

针对具有隐藏故障和竞争失效模式的多态系统维修策略问题,提出了一种综合考虑隐藏故障损失成本、竞争失效模式、不完美检测、不完美维修等因素的多态系统维修建模方法。首先,描述了多态系统及其失效准则,并给出具体的视情维修策略;其次,推导了系统因隐藏故障而导致的损失成本,并对缺陷状态的不完美检测和不完美维修情形进行了数学描述;然后,分析计算了竞争失效模式下系统的两种更新情形及其发生概率,并基于此构建了多态系统的维修模型-期望成本率;最后,通过数值算例验证了所构建维修模型的有效性,分析结果表明,通过优化维修模型能够找到系统的最佳检测策略,从而有效降低维修成本。     

小麦品质近红外检测系统的设计与试验研究

为实现快速无损地检测小麦品质设计了基于光栅技术的近红外检测系统,测试了该系统的准确性、重复性和稳定性,选取MPA光谱仪为参比仪器,分别采集56份小麦样品的光谱,建立偏最小二乘回归模型并验证。该系统的四个模型的决定系数R2分别为92.38%,93.48%,93.16%,94.44%,交叉验证标准差RESECV为0.405,0.374,0.383,0.346,相对分析误差RPD为3.62,3.39,3.82,4.24;预测集验证模型的R2为96.97%,94.22%,96.62%,96.34%,预测标准差RMSEP为0.221,0.305,0.233,0.243。MPA光谱仪的建模结果R2 为95.99%,RESECV 为0.293,RDP为5;预测集验证模型的R2为98.31%,RMSEP为0.165。实验表明：小麦品质近红外检测系统所得模型具有良好的预测性,稳定性和重复性;所得光谱波长与吸光度具有重现性;其模型对平均光谱的预测效果优于单张光谱;该系统工作稳定,性能优良,可应用于小麦品质质量检测。     

N-型四能级系统的EIT和MOLLOW谱分析

构建双耦合场作用下的N-型四能级系统,详细讨论系统的探测吸收特性随两个耦合场Rabi频率取不同值时的变化规律,得到EIT、Mollow和Autler-Townes双峰效应及其它们之间的相互转化规律。通过找出N-型四能级系统中的多个跃迁通道,将系统按跃迁通道拆分成多个子系统,不同的拆分方法实现了不同跃迁通道之间的量子干涉,从而使系统呈现出三种产生条件和物理本质不同的非线性效应。