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排序方式: 共有378条查询结果,搜索用时 15 毫秒
251.
《防务技术》2014,10(2):131-140
This paper deals with the issue of preparation of the aiming angles with the use of tabular firing tables and needed determination of the ballistic elements μB (ballistic wind wB, wxB, wZB, ballistic (virtual) temperature τB, ballistic density ρB) from the standardized met messages. The weighting factors are used for the calculation of ballistic elements μB that are incorporated into the trajectory calculations characteristics of weapon and ammunition. Two different methodologies practically used in the praxis are analysed and compared. For the comparison of the two methodologies the reference height of trajectory determined from the weighting factor functions is employed. On the basis of the analyses conducted, the potential for further increase in accuracy of these aiming angles preparation methods is pointed out. 相似文献
252.
Wieslaw
Kubiak Yanling Feng Guo Li Suresh P. Sethi Chelliah Sriskandarajah 《海军后勤学研究》2020,67(4):272-288
Job shop scheduling with a bank of machines in parallel is important from both theoretical and practical points of view. Herein we focus on the scheduling problem of minimizing the makespan in a flexible two-center job shop. The first center consists of one machine and the second has k parallel machines. An easy-to-perform approximate algorithm for minimizing the makespan with one-unit-time operations in the first center and k-unit-time operations in the second center is proposed. The algorithm has the absolute worst-case error bound of k − 1 , and thus for k = 1 it is optimal. Importantly, it runs in linear time and its error bound is independent of the number of jobs to be processed. Moreover, the algorithm can be modified to give an optimal schedule for k = 2 . 相似文献
253.
254.
基于尾流自导鱼雷的制导原理、弹道和自导开机过程,提出了最小开机距离的概念。分析指出了影响尾流自导鱼雷最小开机距离的主要因素是设定的鱼雷深度、鱼雷的航行精度和目标运动参数散布等。建立了最小开机距离的计算模型,并在不同攻击态势下进行了仿真计算和统计分析,得出了有益的结论:在一定的攻击条件下,不同的设定深度、使用不同的鱼雷速制以及不同的目标运动要素误差、鱼雷航行精度,将使鱼雷的最小开机距离不同,即鱼雷的最小开机距离实际上是关于各种因素的函数。通过最小开机距离可以进一步计算出鱼雷自导开机的最大距离,若在工程中予以实现,将对提高潜艇攻击的隐蔽性和鱼雷作战效能具有重要意义。 相似文献
255.
旋转调制式捷联惯导误差分析 总被引:2,自引:0,他引:2
系统级旋转自补偿技术可以使捷联惯性导航系统的误差发散得到一定程度的抑制,是在现有元件水平不变的情况下提高系统精度的有效方法.对于不同的误差项,旋转补偿技术具有不同的调制效果.针对目前研究较为广泛的8位置双轴转位调制方素,对被调制后的误差公式进行了推导和分析,分析发现:常值零偏、逐次启动漂移以及缓变漂移都可以得到较好的调... 相似文献
256.
研究了星载SAR天线阵面形变对波束输出的影响及形变补偿方法.针对未来星载SAR将采用的柔性阵面,提出了一种用于星载SAR天线的空间形变实时测量与控制的闭环系统,建立了阵面形变下阵列流形误差模型,得出小幅度形变主要影响波束的旁瓣输出,通过求解补偿形变权值的最小二乘解,使阵列形变补偿后波束输出与期望波束输出最佳逼近,并给出用于阵列误差补偿的阵列形变测量精度要求.仿真结果验证了本文方法结论的正确性与有效性. 相似文献
257.
258.
基于遗传算法的航向测量误差分析 总被引:9,自引:3,他引:6
提出了一种基于遗传算法的高精度航向测量误差分析的方法,测量模型由2台全站仪组成.通过最佳保留策略和带约束条件的遗传算子,保证该算法具有全局搜索能力.分析结果表明,遗传算法的搜索空间仅为整个搜索空间的0.03%,该模型在现有码头条件下航向测量的精度可达到4″,满足对舰船导航设备高精度航向标校的要求. 相似文献
259.
In this work, we extend the recently proposed adaptive phase field method to model fracture in orthotropic functionally graded materials (FGMs). A recovery type error indicator combined with quadtree decomposition is employed for adaptive mesh refinement. The proposed approach is capable of capturing the fracture process with a localized mesh refinement that provides notable gains in computational efficiency. The implementation is validated against experimental data and other nu-merical experiments on orthotropic materials with different material orientations. The results reveal an increase in the stiffness and the maximum force with increasing material orientation angle. The study is then extended to the analysis of orthotropic FGMs. It is observed that, if the gradation in fracture properties is neglected, the material gradient plays a secondary role, with the fracture behaviour being dominated by the orthotropy of the material. However, when the toughness increases along the crack propagation path, a substantial gain in fracture resistance is observed. 相似文献
260.
For the case that two pursuers intercept an evasive target, the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target, which performs a bang For the case that two pursuers intercept an evasive target, the cooperative strategies and state estimation methods taken by pursuers can seriously affect the guidance accuracy for the target, which performs a bang-bang evasive maneuver with a random switching time. Combined Fast multiple model adaptive estimation (Fast MMAE) algorithm, the cooperative guidance law takes detection configuration affecting the accuracy of interception into consideration. Introduced the detection error model related to the line-of-sight (LOS) separation angle of two interceptors, an optimal cooperative guidance law solving the optimization problem is designed to modulate the LOS separation angle to reduce the estimation error and improve the interception performance. Due to the uncertainty of the target bang-bang maneuver switching time and the effective fitting of its multi-modal motion, Fast MMAE is introduced to identify its maneuver switching time and estimate the acceleration of the target to track and intercept the target accurately. The designed cooperative optimal guidance law with Fast MMAE has better estimation ability and interception performance than the traditional guidance law and estimation method via Monte Carlo simulation. 相似文献