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There exist a large class of acoustic sources which have an underlying periodic phenomenon. Unlike the well-studied Bearings-Only Tracking(BOT) of an aperiodic acoustic source,this paper considers the problem of tracking a periodic acoustic source. For periodic acoustic tracking, the signal emission time is known. However, the true measurement reception time is unknown because it is corrupted by noise due to propagation delay. We augment the sensor’s signal reception time onto bearing measuremen... 相似文献
264.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(5):2140-2154
After deployment from a rocket, a CubeSat is detumbled using magnetorquer rods bringing the norm to the point where the reaction wheels take over to reduce the angular velocity to null. Therefore, utilizing reaction wheels for satellite detumbling at higher initial velocities is vital but they are heavy and occupy significant space on a spacecraft having challenging control. To address this challenge, this paper features a disruptive approach that conducts the control only by the PCB-integrated magnetorquers with various geometries using a diverse non-unity track width ratio. The trace widths are parametrized such that the optimal torque to power dissipation ratio is investigated. The optimizations are then simulated for various geometric distributions and validated through comprehensive measurement setups that establish a framework for selecting the best-case coil configuration according to mission requirements. The detumbling rates of multiple asymmetric coil configurations are compared with the embedded designs in published literature and state of the art. It is found that the proposed asymmetric embedded magnetorquers can detumble the vehicle at high initial angular velocities. Lastly, the simulation results of thermal analysis are validated for selecting the application-specific optimal coils configuration. At the end, the proposed system is compared with the embedded magnetorquers available in the literature and commercial attitude control systems. 相似文献
265.
《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2023,71(3):1397-1417
An evaluation of the hydromorphological condition of the Mahananda-Balason River system of the sub-Himalayan foothills, West Bengal, India was attempted using a multiparameter-based Hydromorphological Quality Index (HQI). After segmenting these rivers based on continuity, bed material and channel planform, a total of 18 indicators, divided into 3 subgroups Continuity (C), Planform (P), and Floodplain Morphology (FM), were quantified reach-wise and scaled upon the level of alteration (1 for highly altered and 5 for no alteration). The derived overall HQI (3.6) exhibited a moderate hydromorphological quality of the system, however, significant differences between the HQIs of confined and unconfined reaches were witnessed. Students ‘t-test and Multiple Correspondence Analysis both portrayed vast dissimilarities among the confined and unconfined reaches and the clustering was depending on their confinement. The deviations measured from the system’s mean and least altered conditions portrayed that the confined reaches with lesser human interventions were in comparatively more pristine hydromorphological conditions. Conversely, unconfined reaches showed moderate to very poor hydromorphological conditions chiefly due to intense human-induced alterations regarding urbanization, embanking and sediment extraction. Restorations on these aspects should initiate with immediate effect to avoid a shortage of riverine resources such as fluvial sediment, fish and groundwater. Overall, this methodology was found suitable for continuous monitoring of the river systems along with the precise identification of areas and aspects to be restored for upgrading the hydromorphological quality. More testing of this methodology would eventually help in validating the hydromorphological quality assessment protocol for Indian rivers. 相似文献
266.
为增强卫星的自主生存能力,研究了基于卫星轨道软件平台的自主导航计算方法。由星载导航部件获取导航参数,应用数值或解析法进行自主导航计算,以实时获得精确的轨道参数。理论分析和仿真结果表明,读方法正确可行,具有较高的工程应用价值。 相似文献
267.
高等学校是航空航天原始创新的重要发源地,在航空航天技术发展和进步中发挥了重要作用。为了分析我国高等学校在航空航天领域的发展情况,以JCR收录的航空航天工程类期刊为数据源,选取2011—2020年我国高等学校发表论文,利用CiteSpace软件对航空航天领域的论文发表情况、机构合作关系、关键词共现、关键词聚类等进行可视化分析,总结我国高等学校在航空航天领域的研究现状、合作关系以及未来研究前沿。通过梳理我国高等学校关于航空航天领域的研究情况,本文研究为我国航空航天事业的规划布局、创新发展提供一定参考价值。 相似文献
268.
《中国航空学报》2023,36(5):1-17
Serpentine nozzles are widely used in combat aircraft to realize strong stealth characteristics. Based on the layout characteristics within a confined space, a series of double serpentine nozzles with spanwise offsets are established. Using computational fluid dynamics and Taguchi method, the influence mechanisms of the Distribution of Area (DA), Distributions of Centerline for the first and second ‘S’ sections in the Vertical direction (DCV1 and DCV2), and Distribution of Centerline in the Spanwise direction (DCS) are analyzed. The impact of these factors on the total pressure recovery coefficient can be ranked as DA > DCV2 > DCS > DCV1, whereas their impacts on the discharge coefficient and axial thrust coefficient can be ranked as DCV2 > DCS > DA > DCV1. Considering the statistical significance of these factors, a nozzle in which DA changes rapidly at the exit and DCV1, DCV2, and DCS change rapidly at the entrance gives the best aerodynamic performance. Compared to the worst configuration, the total pressure recovery coefficient, discharge coefficient, and axial thrust coefficient are improved by 1.6%,3.5% and 3.6%, respectively. DA influences the gas flow acceleration in the entire serpentine channel, resulting in different wall shear stress and friction losses. The various centerline distributions influence the gas flow acceleration effects and form complex wave structures in the constant-area extension section, resulting in different local and friction losses. 相似文献
269.
旋转部件转动诱导振动信号检测与分析 总被引:1,自引:0,他引:1
阐述了一个典型旋转部件振动时产生诱导振动信号的检测方法。介绍了测试系统,旋转部件振动测点布置和振动信号采集。根据两个样机的实测结果,认为旋转部件的诱导振动信号与旋转部件生产质量、安装精度密切相关,对旋转部件轴承固有特征的理论计算值和实测频谱进行了比较,进而判断轴承是否存在故障,并分析了上、下轴承间振动信号的相关性。 相似文献