查询词典 difference equation

The fundamental and higher-order harmonic ultrasound fields of a zeroth-order Bessel ultrasound field and focused Gaussian field in absorbing medium are computed and simulated by solving the KZK equation using a frequency domain finite difference method.

通过频域有限差分方法求解KZK方程，对吸收媒质中的零阶Bessel超声场、Gauss聚焦超声场进行计算，得到基波和高次谐波声场的数值解和仿真图，计算仿真结果验证了上述的理论结论。

In the light of the complex, high-level and non-linear feature of the mathematical model which describe the transport of the coalbed methane, this paper study the fully-implicit solving method of the mathematical model in detail. Based on the complexity of the algebraic equations which are formed eventually, according to the alternating direction implicit difference pattern, this paper use the iterative method and the fully main element Gauss-Jordan eliminating method to solve equations, which is to use the iterative method to determine coefficient matrix and use the fully main element Gauss-Jordan method to solve th linear algebraic equation group, at the same time of studying the solving method of the mathematical model, according to the devising requirement of FORTRAN77 program structure, this paper draw up computer program and form the corresponding computer model, and verify the validity and reliability of the model in theory by operating the model.

重点研究了模型内、外边界及有关参数的处理，针对描述煤层甲烷运移的数学模型是一个复杂、高阶非线性数学模型的特点，详细研究了模型的全隐式求解方法，根据最后形成的代数方程组的复杂性，按交替方向隐式差分格式，采用迭代与全选主元高斯约当消去法相结合的方法求解方程：即确定系数矩阵采用迭代法，求解线性方程组时采用全选主元高斯约当消去法，在研究模型解法的同时按FORTRAN结构化程序设计的要求，编制计算机程序，形成相应的CBMRS计算机模型，并通过模型的运行从理论上证明了模型的正确性与可靠性。

Based on the second- and fourth-order compact difference formulas for second-order derivatives and the idea of weighted average, two classes of the alternating direction implicit method are proposed for solving two-dimensional wave equation. The methods are of accuracy O (T^2+h^4) and O (T^4+h^4) respectively. Stability conditions are obtained by Fourier analysis method.

基于二阶微商的四阶紧致差商逼近公式及加权平均思想，提出了数值求解二维波动方程的2种精度分别为O(т^2+h^4)和O(т^4+h^4)的交替方向隐式格式，以及与其相匹配的第一个时间层的同阶离散格式，并且通过Foulier方法分析了格式的稳定性。

In the method of numerical analysis, the spatial part of equation system in strong conservation form is first discretized by conventional central finite-difference approximation and then the system of partial differential equations becomes a system of ordinary difference equations.

本文所建数值方法的基本空间离散格式是中心差分，并用源于Jameson的标量耗散模型抑制数值波动；采用经典四阶龙格—库塔法积分经过空间离散后得到的常微分方程组当残差足够小时的解为稳态解。

The initial-boundary value problem of dispersive equation is a kind of mathematical model, in this paper, it has been followed the ways of other scholars and used a new method and got a new difference scheme. It was a three layers ten-point implicit difference schemes.

色散方程的初边值问题是在孤立波这样的物理现象中抽象出来的一类数学模型，在前人构造的众多差分格式的基础上，使用新的构造方法，给出了该问题的三层十，点隐式差分格式。

Based on the analysis of the traditional absolute difference positioning th eory, the relative pseudorange difference positioning technique was researched and the equation of state which solves r elative position was given.

在对传统的绝对差分定位原理进行分析的基础上，研究了相对伪距差分定位技术，得到了求解相对位置的状态方程。

In this paper, by considering higher order approximation to the interaural phase difference, a more general localization equation for stereo sound image with interchannel phase difference is derived.

考虑双耳根位差的高级近似，得到了具有更普遍意义的、重发通路间存在相位差时的立体声声像定位公式。

Result Richards Model and Monodic Quadratic Equation could properly describe grain dry matter growing process and the change process of grain filling rate with days after anthesis. There was big difference in average grain filling rate, maximum grain filling rate under different planting density. Average grain filling rate 1.26 mg/ and maximum grain filling rate 2.44 mg/ of T7 were the quickest, and the average grain filling rate 0.94 mg/ and maximum grain filling rate 1.99 mg/ of T12 were the slowest, and the maximum difference percentage of the average grain filling rate and maximum grain filling rate among different density were 33.98%, 22.61%. There was significant correlation between average grain filling rate, maximum grain filling rate, grain filling active duration, rapid increasing stage and thousand grain weight, and the correlation coefficients were 0.628*, 0.630*, 0.849**, 0.739**. Active grain filling duration contributed mostly to TGW.

结果不同密度处理间千粒重、单位面积穗数、穗粒数、单株穗数、单位面积籽粒产量均存在显著差异；不同密度处理冬小麦的籽粒灌浆均符合慢－快－慢的&S&型生长特性，用Richards模型能很好地模拟冬小麦籽粒增重过程，用一元二次抛物线方程能较好地模拟冬小麦灌浆速率随花后时间变化过程；不同密度处理间平均灌浆速率、最大灌浆速率有较大差异，最大差异率分别为33.98%、22.61%，T7的平均灌浆速率1.26mg/及最大灌浆速率2.44mg/均最大，T12的平均灌浆速率0.94mg/及最大灌浆速率1.99mg/均最小；平均灌浆速率、最大灌浆速率、灌浆活跃期、灌浆快增期与千粒重显著或极显著正相关，相关系数分别为0.628*、0.630*、0.849**、0.739**；通径分析表明，灌浆活跃期对千粒重的贡献最大。

Equations are differenced by control volume algorithm , convection term is differenced by up wind difference algorithm , diffusion term and continuity equation are differenced by central difference algorithm .

采用控制容积法对控制方程组进行离散，对流项采用迎风差分格式，扩散项、连续方程采用中心差分格式。

2Similar to other shrimps, artificial pond culture Penaeus monodon also had difference in growth between female and male. At early culture period, the difference between them was not distinct, but the female would grow more quickly than male after the fifty-ninth day. The body weight growth turning point of the male appeared at the 144.5 days, and at the 195. 3 days for the female.(3) By using Von Bertallanffy growth equation, the growth equations of Penaeus monodon were abtained.

养殖前期，雌、雄虾的体长、体重生长差异不明显，雄虾略高于雌虾，在59.6d后，雌虾体长生长速度高于雄虾；雄虾体重的生长拐点出现在144.5d左右，雌虾体重的生长拐点出现在195.3d左右；(3)采用von Bertallanffy生长方程，拟合出池塘养殖斑节对虾体长、体重生长方程为：。

In the United States, chronic alcoholism and hepatitis C are the most common ones.

在美国，慢性酒精中毒，肝炎是最常见的。

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如果有任何问题，你可以随时联系我。