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111.
基于空间采样法的齿轮调相振动信号解调 总被引:1,自引:0,他引:1
在对机械设备的齿轮部件进行振动监测时,由于载荷以及转速波动等因素的影响,会引起振动信号的相位调制,使得频谱严重失真.通过对调相现象的理论分析和数值仿真计算,提出了基于空间采样的齿轮振动调相信号的解调方法,结果表明,该方法可以获得有价值的振动信号,从而进行有效的齿轮故障诊断. 相似文献
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电磁弹射用直线永磁无刷直流电机的永磁体动子具有开断结构,使动子边端的磁场分布发生变形。当采用霍尔元件检测磁场实现换相时,这种边端效应就会影响换相时机。分析了这类电机的换相机理和动子开断结构对换相时机的影响,指出这类边端效应受极弧系数影响显著,并提出了利用不对称滞环比较器或简易单限比较器对霍尔输出信号进行处理从而消除这类边端效应影响的方法,实验验证了简易单限比较器方案的可行性。 相似文献
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长基线下,受伪距多径和电离层残差影响,传统的CIR法解算载波相位宽巷模糊度时某些历元无法得到正确的结果,基础载波模糊度的搜索范围也较大。分析了CIR法的模糊度误差,提出了基于载波相位平滑伪距并且消除电离层时延的改进的CIR算法,分析了其误差方差,最后利用Compass系统实测数据对短基线和长基线两种情况下CIR法和改进CIR法的解算结果进行比较。实测数据表明,本文提出的算法能够单历元解算超宽巷模糊度和宽巷模糊度,并且能够大大缩小基础载波模糊度的搜索空间。 相似文献
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Vadim Kolnogorov 《战略研究杂志》2013,36(2):339-359
Few issues were as contentious in the development of the Soviet Navy as the role of aircraft carriers and sea-based aviation. Despite the continued insistence by the highest naval authorities and scientific experts that surface combatants simply could not be protected in the open ocean without the support of ship-borne aviation, Soviet leaders – for a variety of reasons – resisted aircraft carrier development until the final decades of the Cold War. In examining one of the most defining and telling asymmetries of the Cold War at sea, the author argues that while the USSR was economically and technologically capable of building aircraft carriers of any class, bureaucratic infighting, misperceptions of cost and practicality, and the inherent flaws of a totalitarian system ultimately created an impossible gap in capabilities between the two sides. The priorities and direction of Soviet weapons and defense technology development during the Cold War was largely a factor of the military-political situation taking shape at home, and in the world. As a rule, the navy was assigned missions that corresponded to its capabilities at a given point in time, rather than the other way around. Often, the navy lacked the material resources needed to implement its core mission. The availability of these resources, in turn, depended on the country's economic situation, its scientific potential, the technological state of its industry, as well as the subjective influence of political and military leaders on the priorities of technological development. The impact of the country's socioeconomic imperatives was undoubtedly also felt in the sluggish pace of development of ship-borne aviation and aircraft carriers in the USSR. 相似文献
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航母编队兵力配置是航母编队作战运用的基础内容,从作战任务的角度来研究航母编队兵力配置问题。航母编队基本作战样式可分为对空作战、对海作战、对潜作战和对岸作战4种,航母编队通过基本作战样式的组合来达成作战任务。基于每种作战样式下航母编队兵力执行的作战任务,确定了兵力配置的原则和方法。为研究航母编队兵力配置问题提供了一种可借鉴的思路。 相似文献
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基于传输方程空化模型的定常自然空化流场数值计算 总被引:3,自引:0,他引:3
采用基于传输方程的空化模型,应用自主开发的软件对水翼和水下回转体定常自然空化流场进行了数值计算。采用基于压力修正和多块结构化网格的有限体积方法数值求解Favre平均的NS方程,运用k-ε两方程加壁函数的湍流模式封闭雷诺应力。计算结果与已有实验结果符合较好。 相似文献
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This paper considers a discrete time, single item production/inventory system with random period demands. Inventory levels are reviewed periodically and managed using a base‐stock policy. Replenishment orders are placed with the production system which is capacitated in the sense that there is a single server that sequentially processes the items one at a time with stochastic unit processing times. In this setting the variability in demand determines the arrival pattern of production orders at the queue, influencing supply lead times. In addition, the inventory behavior is impacted by the correlation between demand and lead times: a large demand size corresponds to a long lead time, depleting the inventory longer. The contribution of this paper is threefold. First, we present an exact procedure based on matrix‐analytic techniques for computing the replenishment lead time distribution given an arbitrary discrete demand distribution. Second, we numerically characterize the distribution of inventory levels, and various other performance measures such as fill rate, base‐stock levels and optimal safety stocks, taking the correlation between demand and lead times into account. Third, we develop an algorithm to fit the first two moments of the demand and service time distribution to a discrete phase‐type distribution with a minimal number of phases. This provides a practical tool to analyze the effect of demand variability, as measured by its coefficient of variation, on system performance. We also show that our model is more appropriate than some existing models of capacitated systems in discrete time. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007 相似文献
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