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1.
Smoothed particle hydrodynamics (SPH) is a useful meshless method. The first and second orders are the most popular derivatives of the field function in the mechanical governing equations. New methods were proposed to improve accuracy of SPH approximation by the lemma proved. The lemma describes the relationship of functions and their SPH approximation. Finally, the error comparison of SPH method with or without our improvement was carried out. Foundation item: The National Natural Science Foundation of China (No. 50778111); The Key Project of Fund of Science and Technology Development of Shanghai (No. 07JC14023)  相似文献   

2.
The smoothed particle hydrodynamics (SPH), as a fully Lagrangian particle method, has been successfully applied to astrophysical problems and extended to elastic dynamics and computational fluid dynamics.High order derivatives have to be approximated when elastic dynamics problems are modeled. However, the approximation errors in SPH could lead to computational failure in the case that the order of derivative is high.A novel method was proposed in order to improve the accuracy of SPH method, which shows the relationship between the selected functions and their SPH approximations. The entire involved system was represented by a finite number of particles that carry individual mass and occupy individual space, and the integral interpolation was approximated by a summation interpolation. In addition, error comparison was made between SPH method with and without the present improvement.  相似文献   

3.
This paper described an approach to make inferences on Chinese information using first order predicate logic, which could be used in the semantic query of Chinese. The predicates of the method were derived from the natural language using rule based LFT, the axiom set was generated by extracting lexicon knowledge from HowNet, and the first order predicate inferences were made through symbol connection of center words. After all these were done, the evaluation and possible improvements of the method were provided. The experiment result shows a higher precision rate than that traditional methods can reach.  相似文献   

4.
光滑离子流体动力学(SPH)法是一种纯拉格朗日(Lagrange)无网格方法,近年来发展日趋成熟.对SPH法的基本原理、核函数及控制方程离散格式、边界处理方法等进行了介绍.在此基础上建立了数值水槽模型,模拟了立面二维溃坝流动问题,并将所得结果与VOF法及模型试验得到的结果进行比较,结果表明:SPH法能够捕捉到流体的飞溅及融合现象,适于模拟具有瞬时极大变形等物理力学问题.  相似文献   

5.
在非线性滤波系统中,线性化误差和系统误差是影响滤波精度的两个主要因素.提出联合粒子滤波方法,在减少线性化误差的同时,能够实时估计系统误差的大小并自适应地消除其影响.说话人跟踪仿真实验结果验证了此方法的有效性.  相似文献   

6.
在非线性滤波系统中,线性化误差和系统误差是影响滤波精度的两个主要因素.提出联合粒子滤波方法,在减少线性化误差的同时,能够实时估计系统误差的大小并自适应地消除其影响.说话人跟踪仿真实验结果验证了此方法的有效性.  相似文献   

7.
提出了一种采用两级喷射器混药的植保机,利用风机产生压缩空气,利用射流泵进行水和药液的一级混合,利用喷射器进行压缩空气与药液和水混合流体的二级混合,使药液、水、气达到均匀混合的目的,基于流体力学基本定律和射流泵设计理论,建立了流体力学参数设计方程,用数值算例验算了所述理论的实用性.  相似文献   

8.
针对桥式起重机桥架结构设计计算,采用一阶优化分析方法对其桥架结构的约束条件以及目标函数进行优化处理,研究结构的强度、刚度等静态特性,并对优化后的结果与优化之前的数值进行对比分析,充分地验证了一阶优化方法的优越性。  相似文献   

9.
ITS��Ŀ�������Ķ����Ż������о�   总被引:1,自引:0,他引:1  
智能交通系统(ITS)是缓解城市交通矛盾的一条新途径,然而我国智能交通系 统的建设还刚起步,一方面需要建设的项目多、项目投资大,另一方面又客观存在资金、人才、技术等各方面的约束,因而必须运用科学的理论和方法对ITS项目进行事前评价,科学地安排ITS项目的建设次序.由于缺乏基础数据,通过精确地计算智能交通系统的成本、效益等数据来确定项目的重要程度还存在较大的困难.本文基于层次分析法,建立了ITS项目实施序列优化模型,并尝试将其用于上海市公路网交通信息化与智能化规划研究.应用该方法,可以客观地推荐项目建设次序,避免主观臆断.  相似文献   

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