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针对无尾布局超声速航向静稳定性不足的问题,提出一种基于超声速压缩/膨胀流动的后体超声速航向气动增稳设计方法。首先通过无尾布局扁平后体和常规后体方案航向静稳定性和表面流场差异的对比,明确了后体超声速航向增稳设计思路。然后基于后体参数化外形分析了后体型面对于布局超声速航向静稳定性的影响规律。最后通过评估典型后体方案的综合气动特性验证了后体超声速航向增稳设计方法的可行性。研究表明:重心后侧向投影面积增量、后体脊线以及后体截面曲线是影响后体型面超声速航向增稳能力的3个主要参数。与常规后体型面相比,通过超声速航向增稳设计获得的后体型面能够在布局阻力变化不大的情况下,显著改善无尾布局在跨声速和超声速状态的航向静不稳定性。 相似文献
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《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(1):306-315
We investigate the geomagnetic and ionospheric effects of seismic activity during 1954 Sun spotless days (SSL) from 1995 to 2020. Two subsets of earthquakes (EQ) are evaluated for 676 events observed with the depth D1 ≤ 30 km and 1278 events with D2 > 30 km and the total set SSL. Newly developed 1 h geomagnetic index Hpo and the ionospheric WEQ index are used for the comparisons with the daily peak earthquake. The ionosphere WEQ index is derived at the EQ epicenter from JPL GIM-TEC map within the cell of 2.5°×5°, in latitude φ and longitude λ surrounding the epicenter at radius of about 200 km. We use the method of superposed epoch with the zero epoch time t0 taken at EQ to extract peak values of Hpo and WEQ during t0-24 h ≤ t < t0 (preEQ) and t0 < t ≤ t0 + 24 h (postEQ). It is found that the magnitude of Hpo(t0) is less that the both peaks of Hpo(preEQ) and Hpo(postEQ) in 91 % of events independent of EQ’s depth. Similar effect is observed with the peak of the positive/negative ionosphere indices and the absolute values of |W(preEQ)| and |W(postEQ)| the both exceeding |WEQ| in 77 % of events. The seismic activity tends to increase towards the solar minimum when SSLs occur. Our results provide evidence that EQ-related geomagnetic and ionospheric activities experience decline of intensity at the time of EQ under SSL. 相似文献
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钟敬武 《海军航空工程学院学报》2014,29(5):481-485
综合考虑了大型复杂设备生产厂家各种类型的部件来源与需求,构建了复杂设备部件生产库存控制模型。模型以费用作为目标,通过权衡生产成本、库存成本以及缺货成本,从而确定合理的部件生产库存控制策略。 相似文献
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基于2微米全天巡天(2MASS)短波红外巡天点源星表,分别从白天可探测恒星分布、天空背景辐射与大气传输、传感器性能和光学系统视场大小等方面,分析了短波红外波段相对于可见光波段,在大气层内白天观星实现全天时天文导航的优势,并展望了其发展方向。 相似文献