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1.
本文根据直升机应召搜潜的基本原理,描述了直升机搜潜设备搜索潜艇目标的运动状态,建立了直升机搜潜设备探测装置与潜艇相对运动的搜索模型,给出了直升机最优搜索运动航线,解决了直升机应召搜潜时如何快速搜潜的难题。  相似文献   

2.
非线性最优化算法主要包括两个步骤:一是利用目标函数和约束函数的导数或相关信息来确定搜索方向,二是利用一维搜索和信赖域方法来确定沿搜索方向步长.一维直线搜索在各种教科书及参考文献中被广泛地讨论过,而另一种搜索方法弧搜索方法,在某些情况下更有效却鲜为人知.本文讨论弧搜索方法的一些细节及在各种最优化问题中的应用,并指出弧搜索技术比直线搜索对某些问题更具优越性.  相似文献   

3.
对求解无约束规划的超记忆梯度算法中线搜索方向中的参数,给了一个假设条件,从而确定了它的一个新的取值范围,保证了搜索方向是目标函数的充分下降方向,由此提出了一类新的记忆梯度算法.在去掉迭代点列有界和Armijo步长搜索下,讨论了算法的全局收敛性,且给出了结合形如共轭梯度法FR,PR,HS的记忆梯度法的修正形式.数值实验表明,新算法比Armijo线搜索下的FR、PR、HS共轭梯度法和超记忆梯度法更稳定、更有效.  相似文献   

4.
宋健  邓雪 《运筹与管理》2018,27(9):148-155
针对模糊不确定的证券市场,用可能性均值、下可能性方差和协方差分别替换了投资组合模型中概率均值、方差和协方差,构建了双目标均值-方差投资组合模型。然后采用线性加权法将双目标模型转化为单目标模型,进而提出了一个PSO-AFSA混合算法对其求解。该混合算法中,将粒子群算法搜索的结果作为人工鱼群算法初始鱼群,进一步搜索,这样能有效的避免粒子群算法陷入局部最优。同时,将人工鱼群中的最好位置反馈到粒子群算法的速度更新公式中,指引粒子运动,加快算法收敛。最后,进行实例分析,结果表明:PSO-AFSA混合算法是有效的,混合算法搜索到的全局最优值好于基本粒子群算法搜索到的全局最优值。  相似文献   

5.
了目标搜索区域的确定方法以及失事飞机在目标搜索区域的初始概率分布,得到发现概率的计算公式。以发现概率为目标,构造了一个求解最优搜寻策略的Max Max化规划模型,模型可以动基于贝叶斯方法,提出了一个失事飞机的发现概率模型,利用飞机失联前后的信息数据,给出态地对坠机点的概率分布进行更新,使下一步搜寻任务得到及时的修正和调整。考虑到洋流对坠机点的影响,本文还提出了一个关于基点先验概率分布的重构策略。此外,对任务搜索区域最优路径的选取问题做了进一步探讨,给出了一个任务搜索区域上搜寻路径的选取方法  相似文献   

6.
本文提出了两种搜索方向带有扰动项的Fletcher-Reeves (abbr. FR)共轭梯度法.其迭代公式为xk 1=xk αk(sk ωk),其中sk由共轭梯度迭代公式确定,ωk为扰动项,αk采用线搜索确定而不是必须趋于零.我们在很一般的假设条件下证明了两种算法的全局收敛性,而不需要目标函数有下界或水平集有界等有界性条件.  相似文献   

7.
一个新的无约束优化超记忆梯度算法   总被引:3,自引:0,他引:3  
时贞军 《数学进展》2006,35(3):265-274
本文提出一种新的无约束优化超记忆梯度算法,算法利用当前点的负梯度和前一点的负梯度的线性组合为搜索方向,以精确线性搜索和Armijo搜索确定步长.在很弱的条件下证明了算法具有全局收敛性和线性收敛速度.因算法中避免了存贮和计算与目标函数相关的矩阵,故适于求解大型无约束优化问题.数值实验表明算法比一般的共轭梯度算法有效.  相似文献   

8.
为了有效积累和重用直升机事故案例蕴含的宝贵知识,从而提升通用航空安全水平,提出了一种基于本体的直升机事故案例建模与检索方法.首先基于运营决策支持和安全信息应用这一目标建立了直升机事故案例建模与检索的系统框架结构;然后分析了直升机事故案例特征,进而设计了基于本体的直升机事故案例表示;在此基础上,面向不同应用需求,设计了不同的检索索引,并提出了语义属性和数值属性的相似性计算方法,从而实现多尺度的案例检索.开发的原型系统及其应用表明,直升机事故案例建模与检索实现了案例知识的积累和应用,为通用航空安全信息处理提供了系统的解决方案.  相似文献   

9.
模糊度搜索空间的大小是影响模糊度解算效率的关键因素之一.针对传统确定模糊度搜索空间的方法较为保守,致使搜索空间过大,提出了一种基于最小二乘模糊度降相关平差法(LAMBDA)的改进方法.首先对目前模糊度搜索空间确定方法给予了介绍和深入的分析比较,评价了这些经典方法的优缺点.在此基础上,定义了搜索空间的一个影响因子η,并结合LAMBDA方提出了确定模糊度搜索空间的修正公式.基于仿真和实测数据对修正方法进行实验,结果表明方法在保证获得期望模糊度组数的前提下,其确定的模糊度搜索空间包含的整数点个数更小,可保证90%以上实际模糊度组数接近于期望值.  相似文献   

10.
本文提出了一种新的求解无约束优化问题的混合共轭梯度算法.通过构造新的β_k公式,并由此提出一个不同于传统方式的确定搜索方向的方法,使得新算法不但能自然满足下降性条件,而且这个性质与线性搜索和目标函数的凸性均无关.在较弱的条件下,我们证明了新算法的全局收敛性.数值结果亦表明了该算法的有效性.  相似文献   

11.
The paper reports some simulation results for models of the types of search that might be conducted by a rescue helicopter when looking for a walker who is lost in the desert and wants to be found. The walker has a smaller speed than the helicopter, but the walker can detect the helicopter at a greater distance than the helicopter can detect the walker. Possible search strategies include those in which the helicopter flies in a decreasing spiral or sweeps back and forth across a region. The walker may remain stationary, move randomly or walk towards the helicopter when he hears it. Simulation work suggests the types of strategies that may do best.  相似文献   

12.
If two searchers are searching for a stationary target and wish to minimize the expected time until both searchers and the lost target are reunited, there is a trade off between searching for the target and checking back to see if the other searcher has already found the target. This note solves a non-linear optimization problem to find the optimal search strategy for this problem.  相似文献   

13.
向多个供应商采购的存贮模型研究   总被引:6,自引:0,他引:6  
本文研究当需求量巨大、单一供应商无法满足供货要求情况下的多供应商采购-库存问题,建立了一个向多个有能力约束的供应商采购的库存模型;将模型简化以后用Kuhn-Tucker条件分析了其松弛问题的最优解的必要条件及其相应的搜索算法;随后给出了模型的整数近似解算法,最后给出本文结论以及未来的研究方向。  相似文献   

14.
In this paper we have calculated the average number of comparisons required when searching in a general sequence search tree, which is an extension of the concept of binary and ternary sequence search trees. The analysis uses recurrence relations and illustrates how useful such techniques are in this type of problem.  相似文献   

15.
In many computer experiments, surrogates are used to assist in searching for certain target points. If the surrogates are defined by response function values evaluated by costly iterative processes, the computational burdens may impede the efficiency of regular surrogate-assisted methods. Instead of computing the fully convergent response function values, we propose to control the function evaluation iterations dynamically to save time on function evaluations without degrading the overall performance. Our new algorithms adaptively determine whether each of the function evaluation iterations should be paused, kept running, or restarted; we then use the approximate function values with various levels of accuracy to construct the surrogates. The numerical results show that the proposed algorithms achieve significant savings when solving super-level set searching problems that involve identifying positive Lyapunov exponents of a dynamical system.  相似文献   

16.
Time-dependent reliability-based design optimization with both probabilistic and interval uncertainties is a cost-consuming problem in engineering practice which generally needs huge computational burden. In order to deal with this issue, a sequential single-loop optimization strategy is established in this work. The established sequential single-loop optimization strategy converts the original triple-loop optimization into a sequence of deterministic optimization, the estimations of time instant and interval value that corresponding to the worst case scenario, and the minimum performance target point searching. Two key points in the sequential single-loop optimization strategy guarantee the high efficiency of the proposed strategy. One is that no iterative searching step is needed to find the minimum performance target point at each iteration in the proposed sequential single-loop optimization strategy. The other is that only the correction step needs the reliability analysis to correct the design parameter solutions. In the example section, four minimum performance target point searching techniques are combined with the sequential single-loop optimization strategy to solve the corresponding optimization problems so to illustrate the effectiveness of the established strategy.  相似文献   

17.
This article analyses firms’ efforts to find a suitable partner for a technology cooperation. Although more theoretical studies acknowledge that search costs are an essential part of transaction costs, empirical research on interfirm co‐operation neglects searching. This paper explicitly addresses this lacuna. Hypotheses on the search behavior of firms are derived by applying considerations of transaction cost economics and arguments concerning the social embeddedness of firms to a search model widely used in economics. It is argued that on the one hand the problem potential of co‐operation, which is determined by the co‐operation's volume and the involved relation‐specific investments and uncertainty, affects the benefits a firm can gain from searching. On the other hand, the social embeddedness of a firm influences the costs of searching. Further, I consider the size and homogeneity of the pool of potential partners in the analysis. The derived hypotheses are tested on a dataset of 94 technology cooperations within five Dutch multinationals. The results clearly show that transaction cost economics does explain the search efforts of firms. In addition, I find evidence that the social embeddedness also affects searching.  相似文献   

18.
This article asks the following: How does a teacher use a metaphor in relation to a prototypical image to help students remember a set of theorems? This question is analyzed through the case of a geometry teacher. The analysis uses Duval's work on the apprehension of diagrams to investigate how the teacher used a metaphor to remind students about the heuristics involved when applying a set of theorems during a problem-based lesson. The findings show that the teacher used the metaphor to help students recall the apprehensions of diagrams when applying several theorems. The metaphor was instrumental for mediating students’ work on a problem and the proof of a new theorem. The findings suggest that teachers’ use of metaphors in relation to prototypical images may facilitate how they organize students’ knowledge for later retrieval.  相似文献   

19.
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