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991.
根据钻孔的倾角(直孔或斜孔)和导向器在钻孔中的位置,在定向钻进过程中可能有以下三种人工弯曲情况:1.向垂直钻孔中下放导向器时,通常是向安置导向器的方向偏斜。 相似文献
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993.
Warren HP Bookbinder JA Forbes TG Golub L Hudson HS Reeves K Warshall A 《The Astrophysical journal》1999,527(2):L121-L124
The ability of the Transition Region and Coronal Explorer (TRACE) to image solar plasma over a wide range of temperatures (Te approximately 104-107 K) at high spatial resolution (0&farcs;5 pixels) makes it a unique instrument for observing solar flares. We present TRACE and Yohkoh observations of an M2.4 two-ribbon flare that began on 1999 July 25 at about 13:08 UT. We observe impulsive footpoint brightenings that are followed by the formation of high-temperature plasma (Te greater, similar10 MK) in the corona. After an interval of about 1300 s, cooler loops (Te<2 MK) form below the hot plasma. Thus, the evolution of the event supports the qualitative aspects of the standard reconnection model of solar flares. The TRACE and Yohkoh data show that the bulk of the flare emission is at or below 10 MK. The TRACE data are also consistent with the Yohkoh observations of hotter plasma (Te approximately 15-20 MK) existing at the top of the arcade. The cooling time inferred from these observations is consistent with a hybrid cooling time based on thermal conduction and radiative cooling. 相似文献
994.
"This paper provides interpretation of the changing patterns of internal migration in Spain at the inter-provincial scale, and new analysis of age-specific migration during the 1980s using a 10% sample of anonymised records from the 1991 census. Schedules of age-specific gross migration rates are constructed and classified according to their shape and level relative to the national schedule, and the relationships between in-migration and out-migration rates are examined for four selected age groups to demonstrate how aggregate patterns of inter-provincial migration conceal a wide diversity of age specific experience." 相似文献
995.
LIU Cheng LIU Ruiliang ZHOU Pengcheng LU Chun YANG Zengxin A. Mark POLLARD Peter HOMMEL MA Jian CUI Jianfeng Peter BRAY TONG Jianyi Jessica RAWSON 《《地质学报》英文版》2020,94(3):594-602
Tianshanbeilu is the largest Bronze Age site in eastern Xinjiang, China. Stretching across the entire second millennium BC, it performed a prominent role in connecting the Hexi corridor, Central China and the steppe. A further insight into the metallurgical tradition and the metal supply network is of vital importance to improve our understanding of its multi-connected nature. This paper offers a new set of chemical and isotopic data on the copper-based objects at Tianshanbeilu, including alloying elements, trace elements (impurities) and lead isotopes. Combining the concentrations of arsenic and antimony reveals that arsenic was introduced to copper partially due to the use of specific minerals tethrahedrite-tennantite. Lead isotopes demonstrate that multiple sources of copper were employed at Tianshanbeilu and a majority of them are characterized by common lead, which appears rather different from those of the Central Plains and the Hexi corridor, but highly consistent with local ores. Surprisingly, one object at Tianshanbeilu contains the well-known highly radiogenic lead. This object undoubtedly marks the westernmost boundary of the distribution of the highly radiogenic lead. We also anticipate that more lead isotopic analyses in NW China will further contribute to the study of the highly radiogenic lead in Central China. 相似文献
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998.
地球物理工作在石油工业中已获得了公认,并在普查和勘探油田的综合地质勘探工作中居于牢固而称职的地位.三十七年前,苏联就开始了第一次勘探地球物理工作,最初是用来研究库尔斯克磁力异常上的鉄矿床.1919年根据列宁的指示在库尔斯克地区开始了磁力测量.1925年在乌拉尔-恩巴油区开始了第一次用地球物理勘探石油的工作,旨在寻找盐丘构造. 相似文献
999.