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基于有向图的二维约束求解算法研究 总被引:1,自引:0,他引:1
针对过约束、几何完全定义状态判定和约束求解效率等问题,提出了基于约束图,利用自由度理论和约束冲突机制,通过反向约束方向平衡约束,进而通过排序进行约束求解的算法。算法采用约束图记录约束和几何的关系;通过约束平衡的方法进行过约束和几何完全定义的判定;采用排序求解方法,将庞大计算问题转化为一组相对简单的计算问题。算法已得到初步应用,对过约束和几何完全定义状态的判定有明显的效果,而且提高了约束求解效率。 相似文献
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根据已知变量概率信息的不同,概率信息不完全系统可分为子类I、子类II和子类III。现有的统计矩点估计法可以方便地用于概率信息完全系统和概率信息不完全系统子类I,但是对可能出现的概率信息不完全系统子类II和子类III无能为力。为此,该文在重点研究子类III的等效相关系数求解方法的同时给出了子类II等效相关系数的简化方法,并发展了适用于一般概率信息不完全系统的广义Nataf变换;在此基础上,结合多变量函数的单变量降维近似模型,提出了概率信息不完全系统的统计矩估计方法,并讨论了参考点选择、变量排序等对计算效率的影响;最后,通过算例对建议方法进行了系统的验证。算例结果表明:该文建议的等效相关系数求解方法准确有效、变量排序策略切实可行,统计矩估计法具有广泛适用性且对于低阶矩具有较理想的精度。 相似文献
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本文提出一种基于知识的高精度机械工程图二维重建方法,在研究中充分利用图纸中所蕴含的知识型信息,并注重模糊推理及模糊识别技术的应用,通过尺寸驱动及约束求解方法,实现了对图形的几何信息用拓扑信息和尺寸信息进行智能校正。 相似文献
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图的拓扑结构在化学分子结构中有重要的意义,并且图的各种矩阵都蕴含了图的拓扑结构信息.在本文中,我们根据距离谱的定义以及四类图形的构造特点,对四类双日冕图进行了距离谱的刻画,通过数学归纳法得到对应的距离矩阵.在此基础上,本文构建了分块矩阵(超日冕距离矩阵),根据矩阵特征值的唯一性,对超日冕距离矩阵进行特征值以及特征向量的求解,并验证了结论准确性及可靠性.进一步,当 $G$ 为完全图且 $G_{1}, G_{2}$ 为正则图时,研究了四类特殊的双日冕图 $G^{(S)}\circ\{G_{1},G_{2}\}$, $G^{(Q)}\circ\{G_{1},G_{2}\}$, $G^{(R)}\circ\{G_{1},G_{2}\}$, $G^{(T)}\circ\{G_{1},G_{2}\}$ 的距离谱. 相似文献
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基于空间收缩的并行演化算法 总被引:5,自引:2,他引:5
提出了一种基于空间收缩的求解MINLP问题的新算法。算法应用了快速有效的不完全演化搜索较优解的分布信息,通过分布信息定位最优解的可能分布,再由精英个体信息决定下次搜索空间。仿真结果表明该算法在搜索效率、应用范围、解的精确性和鲁棒性上都优于其他现存演化算法。 相似文献
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针对突发事件下城市轨道交通车站的客流疏散问题,考虑乘客的不完全理性决策行为,提出基于前景理论的疏散客流分配方法。首先,将车站内部结构网络化为有向图,利用图的深度优先遍历算法求解得到有效路径集合。然后考虑乘客的不完全理性行为,建立基于前景理论的疏散客流分配模型,并利用连续平均法进行求解。最后以成都太升南路地铁站为例,设置应急疏散场景进行模型应用,并利用AnyLogic将基于前景理论的配流结果和基于乘客完全理性的用户均衡配流结果进行仿真对比。结果表明,基于前景理论的客流分配方法得到的配流结果更符合实际应急疏散结果。 相似文献
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一种用实验模态数据识别结构系统支承刚度的新方法 总被引:9,自引:2,他引:7
本文给出了一种直接利用在系统可测自由度上获得的不完全模态参数识别结构系统支承刚度的方法。本文详细地给出了方法的理论推导过程和识别求解的计算方法,整个识别过程采用迭代求解的方式有效地克服了测量误差和模态截断的影响。算例表明本文方法简便,能合理地利用实验数据,结果可靠,具有实际应用的价值。 相似文献
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研究社区支持农业体系中投资型消费者的风险规避度对生鲜农产品公司收益和决策以及其合作机制的影响。构建了新鲜度和价格共同影响的需求函数和风险规避的投资型消费者效用函数,以及生鲜农产品公司和投资型消费者的收益共享函数,通过求解得到完全和不完全信息情况下最优的分红比例、投入的保鲜努力以及各参与者的利润,并对其进行了数值仿真。发现在完全信息情况下,存在帕累托最优结果;在不完全信息情况下,存在均衡解且随着投资型消费者风险规避度的增加,消费者的收益逐渐减少,公司的收益和投入的保鲜努力都增大。在面对风险规避的消费者时,其风险规避度越大公司应投入的保鲜努力也越大,以此来保证和消费者的长久合作,保障社区支持农业的发展。 相似文献
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Replenishment and pricing decisions are of great importance to firms. Traditionally replenishment and pricing strategies are determined by separate units of a firm, the former by production and the latter by marketing. In determining these two strategies, firms frequently have to face two challenges. One stems from a lack of coordination between production and marketing, which leads to revenue loss or excess inventory. The other is caused by lack of information when making these two decisions. That is, firms usually have to make decisions when market information is poor. We consider the joint effects of coordination and information when market demand becomes more variable in the sense of a specific mean preserving transformation. We have three main findings. First, when these two strategies are coordinated by the Headquarters (HQ) of the firm, the HQ uses pricing and inventory as two instruments to manage uncertainty. How exactly increasing demand variability affects the decisions depends on the type of demand uncertainty faced. In particular, for additive demand uncertainty, both price and service level decrease in demand variability, whereas for multiplicative demand uncertainty, they both increase in demand variability. Second, the value of information increases with the level of demand variability, suggesting that it is more beneficial to have information when demand is more variable. The impact of demand variability on the value of coordination, however, is indeterminate. Furthermore, perfect information has more value than perfect coordination if and only if demand variability is high. Third, coordinating these two decisions reduces the value of obtaining the demand information and similarly coordination is more valuable when the demand information is unavailable than otherwise. 相似文献
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采用数值方法研究转速对转子-轴承-密封系统非线性动力学特性的影响,采用Muszynska非线性密封力模型和Capone圆轴承油膜力模型,建立超超临界汽轮发电机组高压端转子-轴承-密封系统的非线性动力模型。通过数值方法,研究转速对转子-轴承-密封动力学特性的影响,计算不同转速下的转子时间历程图、轴心轨迹图、Poincare图和频谱图,揭示了转速变化对转子非线性振动的影响规律。 相似文献
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On the connection between microstructure and surface roughness of brass sheets and their formability 总被引:1,自引:0,他引:1
F. Stachowicz 《Acta Mechanica》2016,227(1):253-262
The aim of this work was the analysis of the relationships between material properties and forming limits of a sheet, caused by the strain localization in the groove. In particular, we aim at the replacement of a nonmeasurable inhomogeneity coefficient of the material, the value of which has to be taken a priori, by measurable coefficients. In the proposed model, it is assumed that the material heterogeneity is a result of surface roughness and presence of internal defects (voids). The value of inhomogeneity coefficients changes with increasing strain. The experiments were carried out for M85 brass sheets, annealed to produce different microstructures. The measured values of some material parameters: strain-hardening constants n and C, normal anisotropy factors, inhomogeneity coefficients (surface roughness and volume fraction of voids) as well as forming limit curve demonstrated their dependence on the grain size. As a result of the experimental work, original equations were proposed, describing the relationship between inhomogeneity coefficients and effective strain and grain size. These equations were used in the theoretical calculation of the forming limit diagram. The theoretical calculations of the strain limits of the tested sheets were based on the associated flow rules, assuming strain-hardening and strain-softening process (Shima–Oyane equation and equations based on the Gurson theory). The analysis of the influence of different material parameters on the forming limit diagram has shown that in the case of the material tested, the value of limit strains depends decisively on the values of the inhomogeneity coefficients and grain size. The postulates showing proportional relationship between the value of a strain-hardening exponent and limit strains were not confirmed. 相似文献
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Columns made of a linear three-element model material and with initial lateral deflections, referred to as ‘imperfections’, are analyzed by the dynamic and static approaches. Both analyses provide approximately the same time-deflection response for the structure. It is shown that imperfections may be regarded as a special class of disturbances which do not affect the value of the viscoelastic critical load. However, the influence of such ‘permanent’ disturbances on the rate of deformation is much more severe than that due to disturbances acting on a perfect column. Consequently, any possible safe operational period, related to the so-called ‘critical time,’ for the imperfect structure is much shorter than a corresponding period obtained from an analysis of the perfect column. 相似文献
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为了讨论楔形端承摩擦桩在扭矩
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