NSPMF-EB耦合模型及其在近岸波浪计算中的应用

提出通过耦合透水介质的流体运动方程(NSPMF模型)和改良Boussinesq方程(EB模型)来描述近岸水波现象的数学模型。NSPMF模型的优越性在于它能描述波浪破碎、越浪以及波浪和各种结构物(包括透水性结构物)之间的相互作用等伴随着复杂流动结构的局部波动现象;EB模型则可用于求解广阔海域内非线性不规则波浪的运动和变形过程。耦合模型兼有二者的优势,具有广阔的应用前景。验证计算的结果表明本文建议的耦合方法是有效的。     

Fixed Points and Asymptotic Properties of Neutral Stochastic Delay Differential Equations

This paper discusses a linear neutral stochastic differential equation with variable delays. By using fixed point theory, the necessary and sufficient conditions are given to ensure that the trivial solution to such an equation is pth moment asymptotically stable. These conditions do not require the boundedness of delays, nor derivation of delays. An example was also given for illustration.     

考虑航行姿态变化的的高速船阻力性能预报

为了精确获得高速船的航行阻力,计及航行姿态变化对其阻力的影响。基于CFD理论,本文通过耦合求解计及黏性的RANS和船体运动方程的方式实时预报船体受力,船体根据受力进行姿态调整,最终达到平衡,以此预报船舶在高速运动稳定后的航行姿态及阻力。并将一系列的数值计算结果与试验数据对比分析,数值计算结果和实验数据吻合良好。船舶设计工作者可以参考数值计算结果辅助船体型线设计,其具有重要的工程应用价值。     

基于 mN LS方程的周期波群非线性演化数值模拟研究

论文基于控制深水复波包络演化的修正的四阶非线性薛定谔方程（mNLS）建立模型,利用离散时间步长的虚拟频谱方法（split‐step pseudospectral method）进行求解,模拟了周期波群的非线性演化,对演化过程中复包络幅值、波面位移、谱成分能量以及模态值的变化进行分析。结果表明：该模型可以有效地模拟周期波群的非线性演化。     

固结拉索近似频率方程求解条件的对比研究

利用文献[1]得出的近似频率方程和求解条件,结合Rayleigh定理和经典弦的频率公式,推导拉索近似频率方程的求解条件及其参考值,扩大近似频率方程的使用范围。通过数值算例,将文献[1]和本文求解条件的合理性和可靠性进行对比研究,其结果可用于快速测试拉索索力。     

Nonlinear optimal integrated vehicle control using individual braking torque and steering angle with on-line control allocation by using state-dependent Riccati equation technique

This paper proposes the solution of state-dependent Riccati equation as a nonlinear optimal regulator to stabilise the motion dynamics of the vehicle model subjected to sudden disturbance inputs in the lateral direction. The proposed nonlinear regulator coordinates individually actuated wheel braking torque and steering wheel angle simultaneously in an optimal manner. Performance criteria are satisfied by solving the Riccati equation based on the given cost function subjected to the nonlinear vehicle dynamics. On-line control allocation in terms of optimal brake torque distribution enhanced by optimal wheel steering angle input is achieved. Furthermore, the proposed optimal nonlinear regulator is an active fault-tolerant control system against partial by-wire actuator failures while guaranteeing stability with good performance due to its capability to allocate the individual control inputs in an optimal way. The main aim is to stabilise the motion dynamics of the vehicle model during short-term emergency situations along the desired straight trajectory manageable by average drivers and to provide vehicle stability and handling predictability through the interaction of individual wheel braking and steering actuators. Simulation results are used to illustrate the effectiveness of the proposed methodology.     

低信噪比下非线性调频信号瞬时频率估计

多项式Wigner-Vill分布(PWVD)能很好地对非线性调频信号进行分析.利用PWVD平面七的尖峰值作为非线性调频信号的瞬时频率的估计.在PWVD上,对估计的瞬时频率进行差分,利用信号差分方程的特征,结合直方图统计方法在低信噪比情况中从PWVD平面提取方差很小的瞬时频率点,从而达到精确估计的目的.     

三弯矩方程的改进及在船舶轴系动态校中中的应用

针对船舶轴系静态校中计算的缺点，对船舶轴系动态校中计算进行了理论分析，并对传统的连续梁三弯矩方程进行了改进，提出了对轴系同时进行垂直平面和水平平面校中计算的方法；同时，利用改进的三弯矩方程，开发了基于VB的计算软件，通过对实船轴系的校中计算与测试，证明是完全正确的。     

LD-pumped Ho, Tm： YLF microchip laser

A simple rate equation model for 2μm Tm, Ho:YLF laser is given to study laser dynamics. Under low pump power, the explicit formulae for the threshold pump power and the relation between output power and incident power are obtained. The present model provides a straightforward procedure to design the laser resonator and the optical coupling system for optimization. At the same time, the experimental results are reported. At room temperature the slope efficiency is 22.4% and the typical lasing threshold is about 328mW. The theory is in good agreement with experiment.