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11.
Yan Huang Xiang-Ping Wu Quan Guo Qian Zheng Bi-Ying Li Huan-Yuan Shan Ke-Jia Lee Hai-Guang Xu 《天文和天体物理学研究(英文版)》2021,(10):17-26
We present a conceptual design study of external calibrators in the 21 cm experiment towards detecting the globally averaged radiation of the epoch of reionization(EoR). Employment of external calibrator instead of internal calibrator commonly used in current EoR experiments allows removing instrumental effects such as beam pattern, receiver gain and instability of the system if the conventional three-position switch measurements are implemented in a short time interval. Furthermore, in the new design the antenna system is placed in an underground anechoic chamber with an open/closing ceiling to maximally reduce the environmental effect such as RFI and ground radiation/reflection. It appears that three of the four external calibrators proposed in this paper, including two indoor artificial transmitters and one outdoor celestial radiation(the Galactic polarization), fail to meet our purpose. Diurnal motion of the Galactic diffuse emission turns out to be the most probable source as an external calibrator, for which we have discussed the observational strategy and the algorithm of extracting the EoR signal. 相似文献
12.
????????????????д????????ò???????????????????????????ε??????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????????硢??????????????????Ч??????????????????????????????????????????С?? 相似文献
13.
本文通过对铁炉坪银、铅矿床围岩蚀变的研究,划分出6种基本蚀变类型,3种蚀变带。各蚀变带以矿体为中心对称分布,各带之间呈渐变过渡关系。并指出由蚀变作用引起围岩化学成分及微量元素含量的变化,岩石化学成分与矿物成分变化相一致,成矿与围岩蚀变相辅相成。还指出了围岩蚀变的找矿意义。 相似文献
14.
郭遂红 《广东海洋大学学报》2002,22(2):78-81
随着我国改革开放的进展 ,跨国度、跨文化之间的交往越来越频繁。由于文化因素上的差异 ,交际行为在不同的文化中往往产生不同的意义 ,语用迁移难免会造成理解失误或交际失败。因而外语教学在培养学生整体语言技能的同时 ,应注意文化因素的渗透 ,提高学生的跨文化交际能力 相似文献
15.
16.
?????????????????????????ο??????????????????????????????????????????????????????????NGA?????????????????????????飬??????????????????????о?????????????????????????????????????????2012?????4.7??????????е?????????????????????????????????????PGA??????S??a??T???????б????о?????????????????????????????????????????????????????????????????????????????????????????????? 相似文献
17.
介绍了气候生态监测服务系统建设的必要性、当前发展的状况和未来趋势.并就存在的问题、今后改进气候生态监测网络建设和加强相关部门间合作、奠定合作基础等问题进行了探讨. 相似文献
18.
The Luzon Strait is the only deep channel that connects the South China Sea(SCS) with the Pacific.The transport through the Luzon Strait is an important process influencing the circulation,heat and water budgets of the SCS.Early observations have suggested that water enters the SCS in winter but water inflow or outflow in summer is quite controversial.On the basis of hydrographic measurements from CTD along 120° E in the Luzon Strait during the period from September 18 to 20 in 2006,the characteristics of t... 相似文献
19.
The West Kunlun orogenic belt is located at the conjunction of the paleo-Asian tectonic system and the Tethys tectonic system.
Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case
the metamorphism reached low-temperature granulate facies, the typical mineral assemblage is biotite-garnet-silimanite-K feldspar-plagioclase-quartz.
The peak metamorphic temperatures are within the range of 720–740°C and the pressure is 0.6 GPa ±. Three types of metamorphic
zircon have been detected in the metamorphic rocks: the complex inclusion-bearing type ; the early relic zircon inclusion-bearing
type; and the inclusion-free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that
these zircons were formed principally during 400–460 Ma, indicating that pre-Cambrian metamorphic surface crust rocks underwent
low-temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of
this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type
A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there
were accompanied with tectonic deformation at deep levels and medium- to high-grade metamorphism. This study provided important
chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun
Early Paleozoic.
Part of the results from the research project “ Research on the West Kunlun pre-Cambrian tectonic events” under the program
“ Research on the important geological problems of China’ s pre-Cambrian” (No. 200113900070) sponsored by the China National
Geological Surveying Bureau. 相似文献
20.