查询词典 fractional derivative

Therefore, a similarity solution of velocity distribution exists in such unsteady Navier-Stokes equations; In chapter 3, the unsteady flow of a viscoelastic fluid with the fractional derivative Maxwell model in rectangular tube is studied.

因而，给出了不定常Navier-Stokes方程速度分布的一相似性解；第三章研究了具有分数阶Maxwell模型的粘弹性流体在矩形管内的不定常流动。

Using difference method, the first-order and the second-order differential equations of fractional derivative can become the first-order ordinary differential equation, and the high precision direct integration can be used for the solution.

所论方法首先引入差分格式，将含有分数阶导数的一阶和二阶微分方程变为一阶的常微分方程，然后再用精细积分方法逐步积分进行求解。

The dynamic stability of simple supported viscoelastic column, subjected to a periodic axial force, is investigated. The viscoelastic material was assumed to obey the fractional derivative constitutive relation.

研究简支的受轴向周期激励的粘弹性柱动力稳定性，柱的材料满足分数导数型本构关系。

The method can beused to solve the integro-differential equation included fractional integral orfractional derivative in a long history and the difficulty of storing all history data isovercome and the error can be controlled.Two numerical examples are presented.

利用该方法可对包含分数积分和微分的积分-微分方程进行较长时间的数值模拟，克服了存储全部历史数据的困难，并能对计算误差进行控制。

In the third chapter,the Lévy-Feller advection-dispersion equation describing anomalous diffusion,with asymmetric fractional derivative,is considered.

更多程不同的是，在三维情形中，分数阶导数的复杂性使得在构造差分格式时所添加的摄动项也非常复杂，由此所构造差分格式的理论分析也变得比较复杂。

The analysis results show clearly that the fractional derivative Maxwell model can embody both the creeping and the relaxing of the viscoelastic materials.

通过分析分数微分Maxwell模型的复模量，证实该模型具有广适性。

This method was applied to preprocess the 2-D seismic data of Shengli oilfield, showing that the fractional order derivative profile can effectively describe the unconformity and reflect the lateral changes of actual interface.

对胜利油田某区块实际二维地震资料进行了试处理，结果表明分数阶导数剖面能很好地描述不整合面，反映实际界面的横向变化。

According to the fractional derivative model of viscoelastic damper and force-deformation-slip relation of friction element,a precise finite element model of FVD is constructed,and the method for forming element stiffness matrix and control force vector of FVD is deduced.

针对粘弹性材料的分数导数模型和摩擦单元的力-位移-滑移量的矩阵关系式，建立了FVD精确的有限元模型，推导了FVD单元刚度矩阵和控制力向量计算公式和求解方法；根据钢筋混凝土框架结构的非线性特性，建立了设置FVD非线性钢筋混凝土框架结构地震反应时程分析的控制方法。

Comparing with classical viscoelastic models, fractional derivative models describe not only the constitutive of viscoelastic material and the related mechanics properties accurately in wide range, but also need less model parameters.

分数导数模型与其他经典模型相比不但能够精确地描述粘弹性材料的本构关系及其力学特性，而且确定模型所需实验参数少、能够在较宽的频率范围内描述材料的力学行为。

Pole-placement and Inner model tuning methods are discussed finally;(2) For the linear derivative action, several different tracker-differentiators are presented to improve the quality of the derivative signals;(3) A neural network tuning method is given for the nonlinear PID controller which includes the above tracker-differentiator;(4) For the linear integral action, a nonlinear pre-phase integrator is studied in order to decrease the phase delay problem; Simulation results show that the nonlinear PID controller including the pre-phase integrator posseses better performance in both fast and stable property, and strong ability of anti-disturbance;(5) A simple optimal criteria is introduced to optimize the parameters of the nonlinear PID controller based on the pre-phase integrator.

仿真研究表明，由此形成的非线性复合积分PID控制系统，具有快速而平稳的过渡过程和超强的干扰抑制能力；(5)采用物理意义简单明确的目标函数的优化设计方法，对上述非线性PID控制器进行参数整定，达到了满意控制典型工业过程的目的。通过对直线电机伺服系统的仿真研究，表明该种非线性控制器具有同时跟踪多个目标的优越性能。

Salt is good, but if the salt becomes flat and tasteless, with what do you season it?

14：33 盐本是好的，盐若失了味，可用什么叫它再咸呢？

He reiterated that the PLA is an army of the people under the leadership of the Communist Party of China.

他重申，人民解放军是在中国共产党领导下的人民军队。