首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 922 毫秒
1.
众所周知,求解微分方程(组)常用的数值方法有有限差分法,有限元素法等,这些方法都是将微分方程(组)分离散化后求解.若将网格划分得粗了,则求解精度不高,不能满足工程实际需要,若将网格划分得细了,则所需计算机内存量和计算量都太大.为解决上述问题,本文给出微分方程(组)的解的概率表达式的一种新的数值解法──概率数值解法.  相似文献   

2.
PHOENICS求解非稳态导热对流及辐射换热耦合问题   总被引:2,自引:0,他引:2  
分析了采用大型通用计算程序PHOENICS(1.4版本)求解有内热源的非稳态导热与对流换热及辐射换热的耦合问题,发现由于该程序所求解的能量方程实际上是比焓方程,若求解域中不同物质(固体、流体)的质量热容相差很大时,采用整体求解法将得出错误的结果,并使结果发散。为了解决这个问题,发展了原有虚拟密度法,新方法可以同时求解非稳态的能量方程、动量方程及连续性方程,从而使利用PHOENICS(1.4版本)求解非稳态耦合换热问题变得简单可靠。  相似文献   

3.
本文采用变尺度法(DFP)求解承受横向载荷的纤维增强层合板弯曲挠度的优化设计.这是无约束的优化问题,一维搜索使用0.618法,用FORTRAN语言编制了计算程序。  相似文献   

4.
卫星舱布局优化设计问题数学上属NP-hard问题.较有效的求解途径之一是研究混合算法,为此构造了并行混合PGA-Powell-蚁群算法(简称PGPAHA).该算法以并行遗传算法为基本框架,根据各子群体收敛速率的快慢来决定它们之间迁移的时机,在收敛后期加入Powell法作为并行遗传算法的算子来加快收敛速度,并利用蚁群优化算法提高计算的精度.最后应用该算法求解了简化的三维带性能约束的国际商用通讯卫星的卫星舱布局设计问题,数值实验结果表明,该算法与并行遗传算法(PGA)相比,在计算精度、计算效率及计算稳定性方面较优。  相似文献   

5.
通过修改流体-结构界面处流体域的边界条件并引入松耦合方法,改进了一种求解气动弹性问题的数值计算方法.该数值计算方法的网格生成、流场求解、结构求解和数据交换四个过程相互独立,因而有可能利用现有的发展比较成熟的商用网格生成器、CFD(computational fluid dyllamics)求解器和CSD(computational structural dymrmcs)求解器分别完成这些功能.通过对折减阻尼比为0.0208的圆柱涡激振动问题在雷诺数为100条件下的计算结果进行分析,表明该方法是可行的.  相似文献   

6.
对外贴FRP(纤维增强复合材料)加固钢筋混凝土梁抗弯极限承载力的求解问题,ACI440F规范及我国CECS146:2003规程都给出了相应的求解公式,但均为验算形式.这在面向设计,即计算给定目标承载力下的FRP用量时,并不方便.针对矩形截面形式,通过引入原构件配筋特征参数和FRP配筋特征参数,推导出量纲-形式的弯矩增量与参数之间的关系表达式,并给出显式求解FRP用量的计算方法.在此基础上,进一步通过定义截面形状系数,将这一显式求解方法推广至T形及更为一般性的截面形式.  相似文献   

7.
Darcy渗流量计算的等效结点流量法   总被引:9,自引:0,他引:9  
Darcy渗流量计算的等效结点流量法朱岳明(河海大学水利水电工程学院南京210098)1基本原理1.1Darcy稳定渗流场的有限单元法求解在只有第一、二类边界条件的Darcy稳定渗流场的有限单元法水头协调模型中,水头的插值公式、求解的泛函Π(H)及...  相似文献   

8.
本文通过对源区电场求解过程的分析,指出了产生源区电场求解的奇异性是由于不适当的微、积分算子交换次序所形成的.PV法并不能解决数值计算的奇异性困难.进而,提出了对电流分布J(r)无任何限制且无奇异的新的电场积分公式  相似文献   

9.
将功的互等定理法(MRT)推广于求解在集中简谐干扰力矩作用下四边简支矩形板的稳态响应.给出了一系列封闭解以及一些有实用价值的图.  相似文献   

10.
对结构进行空间整体分析,并通过结构系统总势能二阶交分为零(δΠ=0)推导出结构屈曲方程.文中采用目前求解特征值问题最有效、精度最好的反幂法来求解结构的临界荷载,同时编制出应用于实际工程的计算程序.  相似文献   

11.
Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.  相似文献   

12.
The discovery of the prolific Ordovician Red River reservoirs in 1995 in southeastern Saskatchewan was the catalyst for extensive exploration activity which resulted in the discovery of more than 15 new Red River pools. The best yields of Red River production to date have been from dolomite reservoirs. Understanding the processes of dolomitization is, therefore, crucial for the prediction of the connectivity, spatial distribution and heterogeneity of dolomite reservoirs.The Red River reservoirs in the Midale area consist of 3~4 thin dolomitized zones, with a total thickness of about 20 m, which occur at the top of the Yeoman Formation. Two types of replacement dolomite were recognized in the Red River reservoir: dolomitized burrow infills and dolomitized host matrix. The spatial distribution of dolomite suggests that burrowing organisms played an important role in facilitating the fluid flow in the backfilled sediments. This resulted in penecontemporaneous dolomitization of burrow infills by normal seawater. The dolomite in the host matrix is interpreted as having occurred at shallow burial by evaporitic seawater during precipitation of Lake Almar anhydrite that immediately overlies the Yeoman Formation. However, the low δ18O values of dolomited burrow infills (-5.9‰~ -7.8‰, PDB) and matrix dolomites (-6.6‰~ -8.1‰, avg. -7.4‰ PDB) compared to the estimated values for the late Ordovician marine dolomite could be attributed to modification and alteration of dolomite at higher temperatures during deeper burial, which could also be responsible for its 87Sr/86Sr ratios (0.7084~0.7088) that are higher than suggested for the late Ordovician seawaters (0.7078~0.7080). The trace amounts of saddle dolomite cement in the Red River carbonates are probably related to "cannibalization" of earlier replacement dolomite during the chemical compaction.  相似文献   

13.
理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。  相似文献   

14.
AcomputergeneratorforrandomlylayeredstructuresYUJia shun1,2,HEZhen hua2(1.TheInstituteofGeologicalandNuclearSciences,NewZealand;2.StateKeyLaboratoryofOilandGasReservoirGeologyandExploitation,ChengduUniversityofTechnology,China)Abstract:Analgorithmisintrod…  相似文献   

15.
As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.  相似文献   

16.
There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.  相似文献   

17.
本文叙述了对海南岛及其毗邻大陆边缘白垩纪到第四纪地层岩石进行古地磁研究的全部工作过程。通过分析岩石中剩余磁矢量的磁偏角及磁倾角的变化,提出海南岛白垩纪以来经历的构造演化模式如下:早期伴随顺时针旋转而向南迁移,后期伴随逆时针转动并向北运移。联系该地区及邻区的地质、地球物理资料,对海南岛上述的构造地体运动提出以下认识:北部湾内早期有一拉张作用,主要是该作用使湾内地壳显著伸长减薄,形成北部湾盆地。从而导致了海南岛的早期构造运动,而海南岛后期的构造运动则主要是受南海海底扩张的影响。海南地体运动规律的阐明对于了解北部湾油气盆地的形成演化有重要的理论和实际意义。  相似文献   

18.
19.
The elongation method,originally proposed by Imamura was further developed for many years in our group.As a method towards O(N)with high efficiency and high accuracy for any dimensional systems.This treatment designed for one-dimensional(ID)polymers is now available for three-dimensional(3D)systems,but geometry optimization is now possible only for 1D-systems.As an approach toward post-Hartree-Fock,it was also extended to  相似文献   

20.
Various applications relevant to the exciton dynamics,such as the organic solar cell,the large-area organic light-emitting diodes and the thermoelectricity,are operating under temperature gradient.The potential abnormal behavior of the exicton dynamics driven by the temperature difference may affect the efficiency and performance of the corresponding devices.In the above situations,the exciton dynamics under temperature difference is mixed with  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号