近似方法

Bifurcation behaviour of nonlinear systems under the resonance condition isstudied when there are parametric and external excitations at the same time.

本文提出的映射迭代法可以有效地用于强非线性系统的定性分析，且对于弱非线性系统，其一次近似的平均方程与其它方法等价。

Results of analysis show that Generalized Paris Law can consider the complex crack propagation in the material of the pavement structure. The fatigue life of the pavement increases with increasing thickness of surface layer in a power function. Use of a thicker surface layer may extend the service life of the asphalt pavement. The fatigue life increases with decreasing modulus of surface layer in a power function with a negative exponent. However, since reduced modulus would scarify the structural strength and might cause rutting-related distress, caution should be taken when using low modulus materials for improving fatigue performance of asphalt pavements. The fatigue life increases with increasing modulus of base material in a power function. However, the fatigue life can not infinitely increases with increasing modulus of the base.

计算与分析表明：广义Paris公式可以考虑沥青路面结构内材料复杂的裂缝扩展：沥青面层的疲劳寿命随着面层厚度的增加以幂函数的形式增加，适当增加沥青面层厚度可以提高路面的使用寿命；沥青面层的疲劳寿命随着面层材料模量的降低以负指数的幂函数形式增加；由于材料模量的降低将牺牲路面的整体强度并可能引起路面车辙类损坏，以此提高疲劳寿命的方法应慎重对待；沥青面层的疲劳寿命随着基层材料模量的增加呈幂函数的形式增加，但由疲劳方程可以看出，寿命并不是随基层材料模量的增加而无限的增加，疲劳曲线在经过一个上升段后，逐渐趋于一个常数值，这说明，这时基层模量对寿命已不作关键性贡献；随着底基层厚度的增加，面层的疲劳寿命近似地呈线性函数增加，但效果并不很明显。

It is based on the theory of light scattering by small particles.

该方法所依据的是小颗粒散射光的衍射近似原理。

For some intrinsic shortcomings in traditional methods, the attribute significance is defined scientificly on the base of two approximate quality of rough set, which is as a objective weights in comprehensive estimation according to the thought of information granularity.

由于常用方法存在诸多缺点，为此根据信息具有粒度的思想，基于粗糙集两个近似精度来科学定义属性的重要性，并将之作为综合评判中的客观权重。

The main results of this thesis are as follows:1. The critical properties of the spin-1 Heisenberg system with DM interactions on the simple cubic lattice are investigated.

本文应用二自旋集团平均场近似的方法研究了具有DM相互作用的量子自旋系统的相变和热力学性质。

After several years analysis and research in practice,this paper uses approximate equilateral triangle method,by the way of sine theorem,last according to tagent formule to calculate the REM ,this method is ssimple,its accuracy is high,the method applies to any circumstance to measure REM .

本文经过实践多年分析研究，采用近似正三角形法通过正弦定理、长边推短边，最后按正切公式让算获得悬高，方法简便，精度高，适用于任何条件下的悬高测量。

Using the elasticity and the singular integral equation method,an analysis of a pure bending beam containing a rigid linear inclusion is carried out under the Saint-Venant s approximation.

使用弹性力学和奇异积分方程方法，在Saint-Venant近似的精度下，对带有刚性线夹杂的纯弯曲直梁作了分析，求得了夹杂两侧的干扰界面应力及夹杂端点的应力强度因子，结果对带夹杂零件的强度设计有参考价值。

When the sojourn time of deteriorating state, inspection interval and maintenance time are the stochastic variables which follow the general distribution, the phase-type approach is proposed to preserve the analytical tractability of the transition probability matrix. To solve the problem that the PH distribution changes the state space of system, the value iteration algorithm for the semi-Markov decision process is improved to get the optimal inspection and maintenance policy.

针对模型中劣化阶段停留时间满足一般分布的情况，提出了一类基于位相型分布拟合的近似处理方法，将物理意义上的状态进行概率扩展，简化了维修决策的求解过程，并给出了对应的改进迭代算法，同时从理论上证明了该算法的收敛性。

The major implementations of the developed model include: Pseudo-spectral and finite-difference schemes are employed to approximate the spatial-differential operators in the horizontal and vertical directions, respectively. A second-order Runge-Kutta method is adopted to integrate in time for the velocity field and the free-surface elevation. The solenoidal condition of the velocity field is satisfied by solving the transformed pressure Poisson equation. A modified secant method is used to accelerate the iterative solution of the non-separable Poisson equation.

模式的主要数值方法包括：分别以拟频谱法以及二阶有限差分法近似控制方程与边界条件中的水平与垂直导数；以二阶Runge-Kutta法进行非稳态的自由液面位移与流场速度的时间积分；利用改良式割线叠代法求解计算区间中不可分离的压力Poisson方程式，以满足不可压缩流条件。

In consideration of large computational efforts of Deodatis simulation,a modified spectral representation method was proposed for simulating the fluctuating wind field of long span bridges.

针对现有Deodatis方法模拟大跨度桥梁空间脉动风场中存在的计算量问题，通过对谱分解矩阵引入插值近似，减少谱分解的次数，从而提高该谐波合成法的计算效率，并节省内存花费，实现了对三维空间脉动风场的有效模拟。

The split between the two groups can hardly be papered over.

这两个团体间的分歧难以掩饰。

This approach not only encourages a greater number of responses, but minimizes the likelihood of stale groupthink.

这种做法不仅鼓励了更多的反应，而且减少跟风的可能性。