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排序方式: 共有342条查询结果,搜索用时 171 毫秒
321.
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介绍了超短波电台自动检测系统与故障诊断系统的功能,并根据功能要求进行了硬件电路的设计,采取面向信号的ATLAS语言进行软件设计和建立在专家知识输入故障推理模型.该系统经使用证明,检测结果精确,检测效率较高. 相似文献
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An equatorial coronal hole has been observed on 18 and 19 October 1996 with SOHO-CDS and with the Nancąy Radioheliograph (RH).
The CDS EUV line intensities are used to determine the coronal hole Differential Emission Measure (DEM); in turn this is used
to compute the radio brightness temperature Tb at the observed frequencies, leaving the coronal electron temperature and density as free parameters. EUV line intensities,
calculated from the derived models, show a good agreement with EUV observations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
325.
建立了基于数字射频存储器技术构建雷达标校器的方法.该雷达标校器可灵活实现目标运动模拟、多普勒频率加载、目标RCS模拟、多目标模拟等功能,较传统的基于光纤延迟实现的雷达标校器更具有应用价值.针对实际应用需求提出了解决频率捷变的方案,给出了典型模拟策略所需数学模型.应用研究表明,基于数字射频存储器技术的雷达标校器具有较强的... 相似文献
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327.
Torsten Schmidt Jens WickertAntonia Haser 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2010
Recently, Lewis (2009) introduced a new method for the identification of tropopause heights (TPHs) from GPS radio occultation (RO) bending angles (α). The method uses a covariance transform to identify transitions in a ln(α) profile. Lewis validates the results with lapse rate tropopause (LRT) heights from one year of FORMOSAT-3/COSMIC data and radiosondes. In this study we apply the new method to the RO data sets from CHAMP/GRACE (2001–2009) and FORMOSAT-3/COSMIC (2006–2009). These results are the basis for TPH trend estimations for the time period between May 2001 and August 2009 (100 months) based on zonal monthly mean GPS RO data from CHAMP (2001–2008), GRACE (since 2006) and FORMOSAT-3/COSMIC (since 2006). Further, we compare the α based TPH trends with LRT height trends and discuss the differences, which are largest in the subtropical regions (20°–40°) on both the northern and southern hemisphere. A global increase of the TPH between 5 and 9 m/yr is found for both methods and different data sets (CHAMP/GRACE alone and CHAMP/GRACE plus FORMOSAT-3/COSMIC). The results for the TPH trends are linked with bending angle and temperature trends in the upper troposphere and lower stratosphere region. Generally, an upper tropospheric warming (bending angle decrease) and a lower stratospheric cooling (bending angle increase) is noted. 相似文献
328.
R. Chandra N. Gopalswamy P. Mäkelä H. Xie S. Yashiro S. Akiyama W. Uddin A.K. Srivastava N.C. Joshi R. Jain A.K. Awasthi P.K. Manoharan K. Mahalakshmi V.C. Dwivedi D.P. Choudhary N.V. Nitta 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
We present a comparative study of the properties of coronal mass ejections (CMEs) and flares associated with the solar energetic particle (SEP) events in the rising phases of solar cycles (SC) 23 (1996–1998) (22 events) and 24 (2009–2011) (20 events), which are associated with type II radio bursts. Based on the SEP intensity, we divided the events into three categories, i.e. weak (intensity < 1 pfu), minor (1 pfu < intensity < 10 pfu) and major (intensity ? 10 pfu) events. We used the GOES data for the minor and major SEP events and SOHO/ERNE data for the weak SEP event. We examine the correlation of SEP intensity with flare size and CME properties. We find that most of the major SEP events are associated with halo or partial halo CMEs originating close to the sun center and western-hemisphere. The fraction of halo CMEs in SC 24 is larger than the SC 23. For the minor SEP events one event in SC23 and one event in SC24 have widths < 120° and all other events are associated with halo or partial halo CMEs as in the case of major SEP events. In case of weak SEP events, majority (more than 60%) of events are associated with CME width < 120°. For both the SC the average CMEs speeds are similar. For major SEP events, average CME speeds are higher in comparison to minor and weak events. The SEP event intensity and GOES X-ray flare size are poorly correlated. During the rise phase of solar cycle 23 and 24, we find north–south asymmetry in the SEP event source locations: in cycle 23 most sources are located in the south, whereas during cycle 24 most sources are located in the north. This result is consistent with the asymmetry found with sunspot area and intense flares. 相似文献
329.
月球背面能够有效屏蔽来自地球并同时遮挡来自太阳的射电信号干扰,拥有太阳系中近乎最安静的电磁环境,是开展空间超长波天文观测的最佳选择区域。在立足完成空间干涉实验的基本任务目标基础、并力争实现重大科学发现的研究思路基础上,研制并发射两颗微卫星,搭载"嫦娥4号"任务进入地月转移轨道,自主完成地月转移、近月制动,在有效燃料约束下形成环月大椭圆轨道编队,构建环月超长波天文干涉仪。说明了系统的工作模式,对数据处理与科学分析方法进行了论述,包括数据预处理、干涉成像与全天功率谱获取角度,进而从支持服务模块和科学载荷模型两个方面对微卫星方案进行了简要概述,凝练了项目任务解决的关键科学与技术问题。月球轨道编队超长波天文观测微卫星的实施将通过全球首个绕月近距编队飞行系统,构建全球首个星–星干涉射电天文观测系统,进而打开人类认识宇宙的新窗口。 相似文献
330.
导航信号同步技术是无线电导航系统的关键技术.本文介绍了"北斗"陆基增强系统的技术方案,对该系统导航信号同步技术进行了分析.利用"北斗"单向授时技术实现导航台时钟同步;采用CPLD器件设计同步脉冲提取电路及同步调整电路;利用直接频率合成技术产生高精度、高稳定度的扩频伪码时钟.实测数据分析表明,通过"北斗"授时可以保证陆基增强系统的导航台链具有较高的时钟同步精度. 相似文献