查询词典 approximation methods in physics

By using slowly-varying envelope approximation, a family of solutions of the paraxial wave equation are found in theory, which represents a new family of ultrashort pulsed beams called ultrashort pulsed complex argument Sinc-Gaussian beams.

杨振峰 河北科技大学经济管理学院，石家庄 050018杨振军河北师范大学物理学院，石家庄 050016胡巍华南师范大学传输光学实验室，广州 510631利用理论解析推导的方法，在傍轴近似条件下，给出了一组新的超短脉冲光束的解析解，称为超短脉冲复宗量辛格高斯光束。

We establish mathematical models of optimal operation schema, and to solve them by feasible direction method and linear approximation.

在管网布局的基础上，以管网投资净现值为目标，建立了管网结构参数优化模型，并充分考虑了输气量、管径、输气压力、管长、增压比、压缩机数目之间的关系，采用混合变量优化方法进行求解。

This thesis is concerned with metric Diophantine approximation for formal Laurent series over a finite base field.

我们将在本论文中探讨有限体下正规Laurent级数上的Diophantine逼近。

The absorbing performance of one dimensional PML is theoretically analyzed and numerically simulated in view of the error caused by finite difference approximation, respectively, whose results show that this theoretical analysis can exactly indicate practical circumstances.

在计及有限差分近似造成的误差下，理论分析和数值模拟了一维理想匹配层的吸收性能，结果表明这种理论分析能完全反映实际情况。

Numerical dispersion characteristic and impedance relationship of three dimensional perfectly matched layers are analyzed under finite difference approximation in this paper, respectively, which show that numerical dispersion relationship of PML is different from that of the FDTD equations and the impedance of homogeneous PML medium is the same as that of free space.

本文分别分析了有限差分近似下三维理想匹配层的数值色散特性和阻抗关系，分析表明，理想匹配层的数值色散关系有别于时域有限差分方程的数值色散关系；有限差分近似下，均匀理想匹配层媒质的阻抗和自由空间的阻抗相同。

The estimation errors, including the finite difference approximation error, the instrumentation channel mismatch error, and the error caused by ambient noise, are studied systematically.

文中基于声信号的空间互谱分析，给出了声强向量阵的定向原理，并系统分析了其定向误差，包括有限差分误差、通道失配误差和环境噪声引起的误差。

On the aspect of error compensation, the system using the geometric average sound pressure instead of the arithmetic average sound pressure to get the sound pressure of the measurement point. This method not only reduces the high frequency error in the sound intensity measurement, which compensates the finite difference approximation error, but also greatly reduces the computation of the sound pressure spectrum.

误差补偿方面，课题采用几何平均声压代替通常的算术平均声压来计算双传声器法的声场声压值，这样不仅可以有效的减少声强测量中的高频误差，对有限差分误差起到了补偿作用，而且还大大减小了声压谱计算中的计算量。

This model used the finite—difference approximation to the advection— dispersion equation. The spatial derivatives in the flow equation are approximated by central difference written about grid—block boundaries and time derivatives are approximated by a fully implicit backward scheme.

水流方程的空间导数采用中心差分格式离散，时间导数采用隐式差分格式离散，建立了土壤水分和污染物在各种饱和度的条件下迁移转化方程耦合求解的二维数值计算模型。

The tether was modeled using finite difference approximation. The balloon was modeled using rigid-body dynamic model including the static derivative, dynamic derivative and added mass.

缆绳采用有限差分法，球体采用经典的六自由度方程，其中气动力导数以静导数、动导数和附加质量表示。

A new scheme for approximating the solution of 2D Maxwell's equations-the high order symplectic scheme is proposed to overcome the shortcoming of the conventional finite difference time domain. The scheme is obtained by discretizing the Maxwell's equations in time domain based on symplectic scheme with high order, and then evaluating the equation in spatial domain with second or fourth order finite difference approximation.

为克服标准时域有限差分方法的缺陷，引入一种新的数值计算方法－高阶辛算法求解Maxwell方程，即在时间上用高阶辛差分格式离散，空间分别采用二阶及四阶精度的差分格式离散。

We were cousins—his grandfather was King of Scots,and his great-grandfather was Henry VII of England.

我们是堂姐弟——他的祖父曾是苏格兰国王，他的曾祖父是英格兰的亨利二世。

I do want to help you, but I am in a quandary now!

我是想帮你，但是我现在左右为难啊！