查询词典 method of difference

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。

In chapter 2,all kinds of numerical methods of computational fracturemechanics are summarized,the development histories and present situation ofboundary collocation method,boundary integral method,finite difference method,boundary element method and finite element method are expounded,and theapplication of finite element method in fracture mechanics are emphaticallydiscussed.

第二章 总结了计算断裂力学中各种数值方法，论述了边界配位法、边界积分法、有限差分法、边界元法及有限元法的发展历史和现状，并着重讨论了有限元法在断裂力学中的应用。

Among used machine learning methods, the gradient descent method is widely used to train various classifiers, such as Back-propagation neural network and linear text classifier. However, the gradient descent method is easily trapped into a local minimum and slowly converges. Thus, this study presents a gradient forecasting search method based on prediction methods to enhance the performance of the gradient descent method in order to develop a more efficient and precise machine learning method for Web mining.However, a prediction method with few sample data items and precise forecasting ability is a key issue to the gradient forecasting search method. Applying statistic-based prediction methods to implement GFSM is unsuitable because they require a large number of data items to model a prediction model. In the contrast with statistic-based prediction methods, GM(1,1) grey prediction model does not need a large number of data items to build a prediction model, and it has low computational load. However, the original GM(1,1) grey prediction model uses a mathematical hypothesis and approximation to transform a continuous differential equation into a discrete difference equation in order to model a forecasting model.

其中梯度法是一个最常被使用来实现机器学习的方法之一，然而梯度法具有学习速度慢以及容易陷入局部最佳解的缺点，因此，本研究提出一个梯度预测搜寻法则(gradient forecasting search method， GFSM)来改善传统梯度法的缺点，用来提升一些以梯度学习法则为基础的分类器在资讯探勘上的效率与正确性；而一个所需资料量少、计算复杂度低且精确的预测模型是梯度预测搜寻法能否有效进行最佳解搜寻之关键因素，传统统计为基础之预测方法的缺点是需要较大量的数据进行预测，因此计算复杂度高，灰色预测模型具有建模资料少且计算复杂度低等优点，然而灰色预测理论以连续之微分方程式为基础，并且透过一些数学上的假设与近似，将连续之微分方程式转换成离散之差分方程式来对离散型资料进行建模及预测，这样的作法不尽合理，且缺乏数学理论上的完备性，因为在转换过程中已经造成建模上的误差，且建模过程仅考虑相邻的两个资料点关系，无法正确反应数列未来的变化趋势。

In this paper, based on an optimum difference operator for spatial differential given by Holberg, an optimum difference method of modeling crosswell elastic wavefield is put forward, which adopts the staggered-grid technique and calculates the wavefield at different grid points. When the half length of optimum difference operator is taken as four to six points, the required number of grid points per wavelength equals to three, crosshole elastic wavefield numerical modeling can attain satisfied accuracy.

本文以Holberg提出的一种空间微分的最佳差分算子为基础，采用交错网格技术，提出了一种模拟井间弹性波场的最佳差分法，该方法能在大空间网格点上得到精确的波场值，当最佳差分算子的半长度取4～6个点，每个波长只采3个样点时，井间弹性波场的模拟就可以得到满意的精度，其计算速度比常规有限差分法至少快一个数量级。

In this paper,the variable space finite difference method of lines is presented on the basis of equal space finite difference method of lines.

在等步长有限差分线法的理论基础上，构造出变步长的有限差分线法格式，并对其进行了误差分析。

The plane adopts the joint method of both the finite element and the finite difference to divide plane domain by means of irregular triangular net in order to fit topography and coastal line complicated sea zone; Vertical application σcoordinate conversion and the finite difference method.

平面采用有限元法和有限差分法相结合的方法，用不规则三角形网格剖分计算域，以适应地形和岸线复杂的海区；垂向应用σ-坐标变换及有限差分法。

The anteroposterior projectionof the foot, utilized to examine the foot disease in the past was referred as to the freely-stressed method. However, most of the patients on suspicion of Hallux Valgus get pains while standing with weight-bearing. Additionally, the patients' real conditions can not be diagnosed without standing. it is helpful for us to apply both the foot weight-bearing and the foot non weight-bearing so as to probe the individual difference between the HVA and the IMA 1(superscript * intermetatarsal angle and further to provide the informative resources concerning the assessment of performing surgery operation. The study include 40 patients who we having Hallux Valgus of different degree, The findings have revealed the significant difference among 40 patients after the method-weight-bearing AP of the foot projection given.

过去一般常用诊断足部疾病的足部摄影(anteroposterior projection of the foot； AP projection of the foot)是指未施加压於病人足部的拍摄方法，然而多大脚趾外翻的病患常於站负重时感觉疼痛舒服，而未负重摄影却无法呈现出病人站时的真实态，因此我们用足部前后位负重摄影(weight-bearing AP projection of the foot)与足部未负重摄影(non weight-bearing AP projection of the foot)的影像比较其大脚趾外翻角(Hallux valgus angle， HVA)及第一跖骨间的角1(上标 st intermetatarsal angle， IMA的差，进而提供外科手术的估评。

In the functional mechanism, we should use the technique "use the DNA Microarray to build the gene expression difference chart" to lead to the combination of Traditional Chinese Pharmacy and gene expression difference chart to study. Meanwhile,we can establish a totally new method of screening modern Traditional Chinese Pharmacy based on the gene expression difference chart, it can really make the modernization and internationalization of Traditional Chinese Pharmacy.

在中药作用机制方面，应采用&利用基因芯片建立基因表达差异谱&技术，将中药与基因表达差异谱有机地结合起来进行研究，同时以基因表达差异谱为基础建立一种全新的现代中药筛选方法，使中药真正实现现代化、国际化。

This course is an attempt to give the students the basic idea and method of forest management in order to prepare the management plan; Place of forest management in forestry; Content of forest management; Guide principles of forest management; Sustained working; Silvicultural system; Forest yield; Increment; Volume increment; Quality increment; Price increment; Total price increment; Forest maturity; Indicating percent; Productive stage; Physical rotation; Technical rotation; Rotation of maximum volume yield; Highest forest rent rotation; Financial rotation; Cutting cycle of selection system; Normal forest; Normal distribution of age classes; Normal arrangement of stands; Normal increment; Normal growing stock; Normal yield; Improvement of actual forest; Reserve forest; Reserve fund; Planning and plan of forest management; Forest regulation; Area allotment; Volume allotting method; Volume frame work; Area-volume combined frame work; Growing stock; Utilization percent method; Difference method; Pure age-class; Growth method; Control method; Forest subdivision; Forest surveying; Forest survey; Certainty of future policy of forest; Selection of species; Decision of silvicultural system; Decision of rotation; Regulation of future yield; Preparation of management plan; Working the plan; Control and revision of management

本课程之目的为使学生了解森林经营之基本观念及方法，以期编订经营计划，课程包括森林经营学在林学上之地位、森林经营学之内容、森林经营之指导原则、保续作业、森林作业法、森林收获、生长、材积生长、形质生长、腾贵生长、总价格生长、林木成熟期、指率、生产期、自然轮伐期、工艺轮伐期、材积收获最多轮伐期、森林纯益最大之轮伐期、财政轮伐期、择伐林之回归期、法正林、法正龄级分配、法正林分排列、法正生长、法正蓄积、法正伐采额、现时林之改良、预备林、预备金、森林经营上之规划及计划、收获预定、面积配分法、材积配分法、材积平分法、折衷平分法、蓄积法、利用率法、较差法、纯粹龄级法、生长量法、稽核法、森林区划、森林测量、森林调查、将来森林经营方针之确定、树种之选定、作业法之决定、轮伐期之判定、将来收获之预定、经营管理计划之编订、计划之执行、经营管理计划之稽核与检订。

This paper reviews and summarizes the progress in this field as follows: the mathematical model and the difficulty of the analytical solutions is introduced; discusses the latest progress of the numerical solutions is discussed; the finite difference method, the Godunov method, the Boltzmann method, and the KFVS method of one-dimensional dam-break problem are introduced; the TVD method, the discontinuous finite element method, the finite volume method and characteristic method of two-dimensional dam-break problem are discussed; the applicability, the advantage and the disadvantage of each method are analyzed; and the progress in the numerical calculations of flow of fluid with free surface are presented.

回顾和总结了国内外对溃坝水流演进问题的研究进展：介绍了溃坝水流的数学模型及解析解法存在的困难，进而讨论了数值解法的最新进展；论述了求解溃坝水流一维问题的有限差分法、近似黎曼解的Godunov格式法、Boltzmann法、KFVS法和二维问题的TVD格式法、间断有限元法、有限体积法、特征线法，并分析了各种方法的适用范围和优缺点，及讨论了限制函数的使用；介绍了利用自由水面追踪方法计算溃坝水流的研究进展，并根据目前存在的不足和实际工程的需要，提出了进一步研究的方向和发展趋势。

Neither the killing of Mr Zarqawi nor any breakthrough on the political front will stop the insurgency and the fratricidal murders in their tracks.

在对危险的南部地区访问时，他斥责什叶派民兵领导人对中央集权的挑衅行为。

In fact,I've got him on the satellite mobile right now.

实际上 我们已接通卫星可视电话了