CSRH模拟接收机设计   总被引：1，自引：1，他引：0  

姬国枢  窦玉江  王威  刘飞  陈志军  张坚  颜毅华 《天文研究与技术》2006,3(2):135-142

本文叙述了日像仪实验的方案，双天线干涉仪中模拟接收机的结构，灵敏度，动态范围，噪声，增益的各级分配等问题，基于实验方案设计了日像仪模拟接收机。  相似文献   

Wisconsinan Late-glacial environmental change on the southeast Baffin shelf,southeast Baffin Island and northern Labrador     

J. T. Andrews 《第四纪科学杂志》1994,9(2):179-183

The importance of the Baffin-Labrador region is explained in terms of the channelling through this area of the mass flux of meltwater from the Laurentide Ice Sheet and the probable effects of this on the thermohaline circulation of the North Atlantic. The chronology of glaciation and deglaciation in the region is summarised. Reference is made to recent marine records from the Baffin Shelf. Isotopic changes recorded in foraminiferal assemblages obtained from marine sediments in the Baffin Shelf-Labrador Sea area indicate the timing and possible magnitude of meltwater fluxes during the period 14.0-11.0 ka BP.  相似文献   

时间频率溯源链的重要特性及其应用     

倪广仁  许录平  和康元 《天文研究与技术》2006,3(1):13-20

主要以美国国家技术标准研究院(NIST)的时间频率溯源链系统为典型,给出其方框图和技术指标,并述评了NIST的宗旨、任务,及时间频率溯源链的重要特征是:拥有高精度的铯喷泉原始频率基准(准确度、稳定度均~1.10-15);在时间频率传递方法和技术研究开发方面处于领先地位;在远程校准的频率测量和分析系统(FMAS),及溯源链系统的尖端装备的高集成化、自动化、智能化、轻量化品质方面均达到先进水平。并综述了高精度的时间频率同步系统在天文学测量、导弹发射、导航、定位等科学实验研究领域中的重要作用和目前达到的关键技术指标。  相似文献   

Secular Dynamics of Asteroids in the Inner Solar System     

Patrick Michel  Christiane Froeschlé  Paolo Farinella 《Celestial Mechanics and Dynamical Astronomy》1997,69(1-2):133-147

In the last three years we have carried out numerical and semi-analytical studies on the secular dynamical mechanisms in the region (semimajor axis a < 2 AU) where the NEA orbits evolve. Our numerical integrations (over a time span of a few Myr) have shown that: (i) the linear secular resonances with both the inner and the outer planets may play an important role in the dynamical evolution of NEAs; (ii) the apsidal secular resonance with Mars could provide an important dynamical transport mechanism by which asteroids in the Mars-crossing region eventually achieve Earth-crossing orbits; (iii) in this region, due to the interaction with the terrestrial planets, the Kozai resonance can occur at small inclinations, with the argument of perihelion ω librating around 0° or 180°, providing a temporary protection mechanism against close approaches to the planets. The location of the linear secular resonances in this zone has also been obtained by an automatic procedure using a semi-numerical method valid for all values of the inclinations and eccentricities of the small bodies, and also in the case of libration of the argument of perihelion. A map of the secular resonances in the (a, i) plane shows — in agreement with the numerical integrations — that all the resonances with the terrestrial and giant planets are present, and also that some of them overlap. Thus the way is now open to fully take into account secular resonances in modelling the dynamical evolution of NEAs. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

2015年广东开汛前后旱涝急转特征及成因分析     

于玲玲  麦健华  纪忠萍  张东 《热带气象学报》2021,(44):611-622

利用1961—2015年广东86站3—5月逐日降水资料、NCEP/NCAR再分析资料及NOAA的Hysplit后向轨迹模式资料和海温资料,分析了2015年广东开汛前后旱涝异常特征,旱涝急转前后的大气环流和水汽条件转变及成因。(1) 2015年5月第1候广东发生了严重的旱涝急转事件,旱涝急转前全省严重干旱,旱涝急转后广东大部地区降水异常偏多。(2) 旱涝急转前后,500 hPa中高纬度由“两槽两脊”转为“两脊一槽”和“两槽一脊”,副高持续加强,广东地区高层辐散和低层辐合加强,地面由冷空气控制广东转为冷暖空气在广东交汇;水汽输送通道由北部湾和长江中下游地区转为南海南部和中南半岛南部海面,广东低层水汽净流入增加。 (3) 黑潮区、北太平洋中部、Ni?o3、Ni?o4区及印度洋和南海的海温异常增暖造成了旱涝急转前后大气环流和水汽的转变。  相似文献   

国际气候治理中的公正转型议题：概念辨析与治理进展     

张莹  姬潇然  王谋 《气候变化研究进展》2021,17(2):245-254

国际气候治理中的公正转型议题涉及就业、关乎民生,是各国都很关注的政策领域之一,因此也被视为是支持应对气候变化的一种重要社会机制。近年来,国际社会积极推动建设气候治理公正转型制度体系,各国也在所制定的国家应对气候变化战略和规划中越来越多地提出与公正转型和就业相关的目标与措施。公正转型议题在国际气候治理进程中主流化的趋势给中国参与和引领全球气候治理带来了新的机遇与挑战。中国应加强关于该问题的基础性研究;在国内应对气候变化的行动中充分考虑该问题,保障受影响就业群体获得社会公正对待;总结具体实践经验;在政策领域协调上做好新的布局;积极参与《联合国气候变化框架公约》下公正转型治理体系的构建中。  相似文献   

基于Kriging方法的空间数据插值研究   总被引：11，自引：0，他引：11  

曾怀恩  黄声享 《测绘工程》2007,16(5):5-8

介绍了Kriging插值方法及其实质,提出一种变异函数理论模型参数估计的新方法,给出变异函数理论模型有效性评定的统计指标,并通过算例予以验证。最后,通过实例与反距离加权法相比较,证实Kriging插值的优越性。  相似文献   

实物地质资料二次开发利用在矿山深边部找矿中的作用          下载免费PDF全文

高建伟  任香爱  邓会娟  李秋玲  李英康  赵国春 《地质找矿论丛》2018,33(1):156-160

随着多年的开采,我国许多矿山成为危机矿山,外围及深部的找矿工作迫在眉睫。在前人研究的基础上,笔者总结了矿山二次利用实物地质资料进行找矿预测的方法,并将其归纳为成果及原始资料的重新分析、成矿预测方法的正确选择、实物地质资料的重新利用、找矿思路的重新确定、成矿规律的重新认识5个方面内容,以期望生产矿山加强实物地质资料二次开发力度,开辟深边部找矿的新局面。  相似文献   

“Source to Sink”: A Review of Tectonics-Erosion-Sedimentation Interactions in the Analogue Experiments of Accretionary WedgeEI北大核心CSCD     

Deng B.  Huang R.  Ma H.  He Y.  Lai D.  Jiang L.  Liu S. 《大地构造与成矿学》2018,(3):431-444

It is believed that the tectonics-erosion-sedimentation interaction in the analogue experiments was essentially improved by the theory of “from source to sink”. In particular, the widespread uplift and exhumation in the western China occurred in Cenozoic can be considered to be a typical natural laboratory in the world. Here we review our current understanding from tectonic sandbox models of tectonics-erosion-sedimentation and their interactions, as well as from natural laboratory. As we known, there are widespread erosion occurred predominantly at hinterland of the accretionary wedge, in contrast to the sedimentation occurred widely at foreland of the wedge. Therefore, fold-and-thrust belts with low syntectonic sedimentation and erosion would evolve in a self-similar fashion to produce a narrow accretionary wedge, while high syntectonic sedimentation and erosion would produce accretionary wedge with very active hinterland thrusts, and a large width. Furthermore, the critically tapered wedge model suggests that the crust-scale thrust-and-fold belts under a horizontal compressive force would come into a self-similar growth of a forward-tapering wedge when it reaches a critical taper angle of the combined angles of the base dip and the wedge slope. Such a process has important influence on the tectonics-erosion- sedimentation and their interactions both in accretionary wedges and their analogue experiments. Although there is a significant similarity between the analogue experiments and natural accretionary wedges in the surface processes of tectonics- erosion-sedimentation and their interactions, it is difficult to get more universal parameters between them. It should be noted that sandbox models of the accretionary wedges in the natural laboratory would improve significantly our understanding of the theory of the tectonics-erosion-sedimentation interactions and “from source to sink”. © 2018, Science Press. All right reserved.  相似文献   

准噶尔盆地南缘小渠子背斜T/P 同构造不整合几何学、运动学特征及地质意义   总被引：1，自引：0，他引：1       下载免费PDF全文

马德龙潘建国  张虎权王宏斌王彦君  魏彩茹陈雪珍 《地质科学》2018,(1):146-154

为探讨准噶尔盆地南缘二叠纪-三叠纪盆地构造性质及构造演化过程,笔者对盆地南缘小渠子背斜保存较完整的T/P 不整合进行了几何学、运动学和沉积韵律旋回特征的分析。T/P 不整合具有同构造不整合的特点,表现为不整合之下削蚀、之上超覆,是由于盆地南缘经历晚二叠世-早三叠世区域性挤压作用造成的。通过对小渠子地区深层地质结构的分析,认为晚二叠世-早三叠世的构造演化过程与早石炭世伸展断陷的反转密切相关。  相似文献