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181.
慢刀伺服车削技术是一种特殊的创成加工方法,采用C轴、X轴、Z轴联动的方式在极坐标或圆柱坐标内可车削加工自由曲面光学元件。但是由于各种误差因素的影响,使用慢刀伺服技术仅加工一次获得的光学元件可能不满足精度指标。为此需要研究能够进一步提升慢刀伺服车削加工精度的误差补偿技术。Zernike多项式是面形分析与光学分析之间的理想接口工具,因此本文使用Zernike多项式拟合的方法处理慢刀伺服车削加工的误差,并根据慢刀伺服加工技术的特点,建立慢刀伺服车削加工的误差补偿算法。实验结果表明,基于Zernike多项式拟合的慢刀伺服车削加工误差补偿技术可有效地针对加工中产生的特定误差进行补偿,从而提高自由曲面车削加工精度。 相似文献
182.
随着消防法的修订颁布,目前各地适用的地方性消防法规的相关规定已经不适应新形势下消防法制建设的需要,亟待重新修订。通过对消防法、相关法律以及部门消防规章与地方性消防法规之间关系的审视和分析,为地方性消防法规的修订提供参考。 相似文献
183.
一般武器-目标分配问题,是使武器发挥最大效能而使目标遭受最大毁伤的最优化问题.遗传算法广泛用于解决最优化问题.提出一种具有贪心优化机制的局部搜索方法,以提高遗传算法的搜索效率,从而迅速找到全局最优解.应用于炮兵武器-目标分配问题的仿真试验结果表明,此算法比现有的其他搜寻算法具有更好的求解效率. 相似文献
184.
任耀峰 《海军工程大学学报》2003,15(3):14-16
利用特殊半鞅的收敛定理和一般形式的Kronecker引理,给出了特殊半鞅和非负特殊半鞅强大数定律的一般形式,推广和完善了已有的结果. 相似文献
185.
Andrew Phiri 《Defence and Peace Economics》2019,30(4):474-487
Using annual data collected from 1988 to 2015, this study provides evidence of a non-linear relationship between military spending, economic growth and other growth determinants for the South African economy. The empirical study is based on estimates of a logistic smooth transition regression (LSTR) model and our empirical results point to an inverted U-shaped relationship between military spending and economic growth for the data. Furthermore, our empirical results suggest that the current levels of military spending, as a component of total government expenditure, are too high in the South African economy and need to be transferred towards more productive non-military expenditure in order to improve the performance of economic growth and other growth determinants. 相似文献
186.
Approximation schemes for single‐machine scheduling with a fixed maintenance activity to minimize the total amount of late work
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We consider the problem of scheduling n independent and simultaneously available jobs without preemption on a single machine, where the machine has a fixed maintenance activity. The objective is to find the optimal job sequence to minimize the total amount of late work, where the late work of a job is the amount of processing of the job that is performed after its due date. We first discuss the approximability of the problem. We then develop two pseudo‐polynomial dynamic programming algorithms and a fully polynomial‐time approximation scheme for the problem. Finally, we conduct extensive numerical studies to evaluate the performance of the proposed algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 172–183, 2016 相似文献
187.
In this article, we define two different workforce leveling objectives for serial transfer lines. Each job is to be processed on each transfer station for c time periods (e.g., hours). We assume that the number of workers needed to complete each operation of a job in precisely c periods is given. Jobs transfer forward synchronously after every production cycle (i.e., c periods). We study two leveling objectives: maximin workforce size () and min range (R). Leveling objectives produce schedules where the cumulative number of workers needed in all stations of a transfer line does not experience dramatic changes from one production cycle to the next. For and a two‐station system, we develop a fast polynomial algorithm. The range problem is known to be NP‐complete. For the two‐station system, we develop a very fast optimal algorithm that uses a tight lower bound and an efficient procedure for finding complementary Hamiltonian cycles in bipartite graphs. Via a computational experiment, we demonstrate that range schedules are superior because not only do they limit the workforce fluctuations from one production cycle to the next, but they also do so with a minor increase in the total workforce size. We extend our results to the m‐station system and develop heuristic algorithms. We find that these heuristics work poorly for min range (R), which indicates that special structural properties of the m‐station problem need to be identified before we can develop efficient algorithms. © 2016 Wiley Periodicals, Inc. Naval Research Logistics 63: 577–590, 2016 相似文献
188.
局部特征提取在点云相关应用中具有十分重要的作用,因此提出一种用于点云局部特征表示的扩展点特征直方图描述子。针对邻域点的两两点对提出一系列不变量;在特征点上构建一个局部参考坐标框架以获得特征描述子对旋转和平移的不变性;将关键点局部邻域划分成多个子空间,并依据每个子空间中的点对不变量构建一个直方图;将所有直方图串联起来得到扩展点特征直方图特征描述子。采用Bologna公共数据集对扩展点特征直方图特征描述子的性能进行测试,并与多个现有算法进行对比。结果表明,扩展点特征直方图特征描述子获得了良好的性能,其结果优于多个现有的特征描述子。 相似文献
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190.
Previous work has documented a negative correlation between internal conflict and state capacity. We attempt to shed light on mechanisms that underlie this relationship, using data for Colombian municipalities. We rely on identifying heterogeneous effects of different types of violent events on state capacity, taking advantage of variability across municipalities in the prevalence of specific manifestations of conflict and their intensity. Our findings suggest that events making civilians feel targeted affect the state’s capacity to collect taxes, while those reflecting a stronger military capacity of illegal armies, in particular their large-scale attacks, affect the state’s capacity to provide public goods. 相似文献