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501.
半球谐振陀螺控制电路的控制精度直接影响半球谐振陀螺仪的输出精度,而频率跟踪精度又直接影响了半球谐振陀螺控制电路的精度.传统的半球谐振陀螺数字控制电路采用过零比较的方法计算陀螺幅点信号的频率,此方法易受地线毛刺信号的干扰,频率跟踪精度不高.介绍了采用A/D转换采集数据估算陀螺幅点信号频率的方法,并对各种方法进行了优缺点比较,提出选用建议.这些方法既提升电路抗干扰能力,又大幅提升了频率跟踪精度,还省去了过零比较电路.分析及测试结果表明,采用该频率跟踪方法,半球谐振陀螺的频率跟踪精度可达0.002Hz,可大幅提升半球谐振陀螺控制电路的精度. 相似文献
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利用熔体超声处理、Sr/Ce复合变质及热处理相结合的方法提高铝合金的强韧性,通过金相组织分析及力学性能测试研究了固溶处理对A356合金组织和性能的影响。研究结果表明,熔体处理有利于改善α-Al枝晶和共晶硅相,铸态合金的抗拉强度和伸长率分别达到215 MPa和9.5%;T6热处理后,共晶硅的形态由纤维状转变成独立分布的颗粒状,而除了伸长率之外,合金的力学性能都显著提高;随着固溶时间的延长,共晶硅的等效直径呈现先减小后增大的趋势,而长径比逐渐减小,合金的拉伸性能和硬度均呈现先增大后减小的趋势;当固溶时间为4 h时,合金的综合力学性能达到最佳,其抗拉强度、屈服强度、伸长率和显微硬度分别达到300、240 MPa、8.0%和110HV。 相似文献
504.
栽机要求悬挂物必须实现GJB1188A中数据总线(GJB289A)的远程终端(RT)功能,同时实现GJB1188A中任务悬挂物投放允许等接口功能.描述了一种采用TMS320C6713B高速浮点DSP为核心的GJB1188A接口的实现方法,从硬件平台组成、控制逻辑实现、驱动软件结构三个方面来说明GJB289A(RT)功能的实现方法.介绍了任务悬挂物投放允许等接口的一种设计实现方法.从而将以往单一的GJB289A总线接口模块与嵌入式计算机结合在一起.满足了体积和成本上的要求.使嵌入式弹载计算机在GJB1188A接口的前提下实现与机载火控系统的通信、进行同步的数据采集与控制. 相似文献
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Ibtissame Bentahar Mohammed Raji 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2021,67(3):945-963
The eastern part of the Rich area consists of the massive Paleozoic and Meso-Cenozoic cover formations that present the geodynamic development of the study area, where is characterized by various carbonate facies of Jurassic age. The geographical characteristic of the study area leaves the zone difficult to map by conventional methods. The objective of this work focuses on the mapping of the constituent lithological units of the study area using multispectral data of Landsat OLI, ASTER, and Sentinel 2A MSI. The processing of these data is based on a precise methodology that distinguishs and highlights the limits of the different lithological units that have an approximate similarity of spectral signature. Three techniques were used to enhance the image including Principal Component Analysis (PCA), Minimum Noise Fraction (MNF), and Independent Component Analysis (ICA). Lithological mapping was performed using two types of supervised classification : Maximum likelihood classifier (MLC) and Support Vector Machine (SVM).The results of processing data show the effectiveness of Sentinel 2A data in mapping of lithological units than the ASTER and Landsat OLI data. The classification evaluation of two methods of the Sentinel 2A MSI image showed that the SVM method give a better classification with an overall accuracy of 93,93% and a Kappa coefficient of 0.93, while the MLC method present an overall accuracy of 82,86% and a Kappa coefficient of 0.80. The results of mapping obtained show a good correlation with the geological map of the study area as well as the efficiency of remote sensing in identification of different lithological units in the Central High Atlas. 相似文献
509.
Vipin K. Yadav Nandita Srivastava S.S. Ghosh P.T. Srikar Krishnamoorthy Subhalakshmi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2018,61(2):749-758
The Aditya-L1 is first Indian solar mission scheduled to be placed in a halo orbit around the first Lagrangian point (L1) of Sun-Earth system in the year 2018–19. The approved scientific payloads onboard Aditya-L1 spacecraft includes a Fluxgate Digital Magnetometer (FGM) to measure the local magnetic field which is necessary to supplement the outcome of other scientific experiments onboard. The in-situ vector magnetic field data at L1 is essential for better understanding of the data provided by the particle and plasma analysis experiments, onboard Aditya-L1 mission. Also, the dynamics of Coronal Mass Ejections (CMEs) can be better understood with the help of in-situ magnetic field data at the L1 point region. This data will also serve as crucial input for the short lead-time space weather forecasting models.The proposed FGM is a dual range magnetic sensor on a 6?m long boom mounted on the Sun viewing panel deck and configured to deploy along the negative roll direction of the spacecraft. Two sets of sensors (tri-axial each) are proposed to be mounted, one at the tip of boom (6?m from the spacecraft) and other, midway (3?m from the spacecraft). The main science objective of this experiment is to measure the magnitude and nature of the interplanetary magnetic field (IMF) locally and to study the disturbed magnetic conditions and extreme solar events by detecting the CME from Sun as a transient event. The proposed secondary science objectives are to study the impact of interplanetary structures and shock solar wind interaction on geo-space environment and to detect low frequency plasma waves emanating from the solar corona at L1 point. This will provide a better understanding on how the Sun affects interplanetary space.In this paper, we shall give the main scientific objectives of the magnetic field experiment and brief technical details of the FGM onboard Aditya-1 spacecraft. 相似文献
510.
N.C. Patel S.P. Karia K.N. Pathak 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(6):1860-1881
This paper investigated the performance of the latest International Reference Ionosphere model (IRI-2016) over that of IRI-2012 in predicting total electron content (TEC) at three different stations in the Indian region. The data used were Global Positioning System (GPS) data collected during the ascending phase of solar cycle 24 over three low-latitude stations in India namely; Bangalore (13.02°N Geographic latitude, 77.57°E Geographic longitude), Hyderabad (17.25°N Geographic latitude, 78.30°E Geographic longitude) and Surat (21.16°N Geographic latitude, 72.78°E Geographic longitude). Monthly, the seasonal and annual variability of GPS-TEC have been compared with those derived from International Reference Ionosphere IRI-2016 and IRI-2012 with two different options of topside electron density: NeQuick and IRI01-corr. It is observed that both versions of IRI (i.e., IRI-2012 and IRI-2016) predict the GPS-TEC with some deviations, the latest version of IRI (IRI-2016) predicted the TEC similar to those predicted by IRI-2012 for all the seasons at all stations except for morning hours (0500 LT to 1000?LT). This shows that the effect of the updated version is seen only during morning hours and also that there is no change in TEC values by IRI-2016 from those predicted by IRI-2012 for the rest of the time of the day in the Indian low latitude region. The semiannual variations in the daytime maximum values of TEC are clearly observed from both GPS and model-derived TEC values with two peaks around March-April and September-October months of each year. Further, the Correlation of TEC derived by IRI-2016 and IRI-2012 with EUV and F10.7 shows similar results. This shows that the solar input to the IRI-2016 is similar to IRI 2012. There is no significant difference observed in TEC, bottom-side thickness (B0) and shape (B1) parameter predictions by both the versions of the IRI model. However, a clear improvement is visible in hmF2 and NmF2 predictions by IRI-2016 to that by IRI-2012. The SHU-2015 option of the IRI-2016 gives a better prediction of NmF2 for all the months at low latitude station Ahmedabad compare to AMTB 2013. 相似文献