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991.
一个外国人看中国地图学教育──中国的高等地图学教育[俄]A.M.Berlyant编者按:俄国莫斯科大学教授A.M.Berlysnt在访问武测科大和南京大学等单位后,写成此文。从一个侧面反映了我国地图学教育的成就。译文中个别字句稍有删节。地图学在中国源... 相似文献
992.
陆下和洋底脊橄榄岩单斜辉石中的Na.Al^IV和Al^VI:地幔中不同熔融… 总被引:1,自引:0,他引:1
把从大西洋洋中脊采集的无斜长石的尖晶石二辉橄缆岩和方辉橄缆岩中的单斜辉石的Na-Al^IV和Al^VI浓度与陆下和前大洋的无斜长石的尖晶石橄榄岩的数据进行了比较。单斜辉石的Al2O3含量在洋底橄缆岩组和陆下橄缆岩组中的同一范围内发生变化,从高铝至贫铝。然而,洋底橄缆岩中单斜辉石的Na含量(0.02 ̄0.6wt%Na2O)和Al^VI/Al^IV比值(0.3 ̄1)都低于陆下橄缆岩单斜辉石的Na含量( 相似文献
993.
994.
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
995.
苏联国家地质委员会各机关的勘探和普查固体矿产时,钻探费用约占地质勘探总投资的20%。 相似文献
996.
Ikeda M Maezawa H Ito T Saito G Sekimoto Y Yamamoto S Tatematsu K Arikawa Y Aso Y Noguchi T Shi SC Miyazawa K Saito S Ozeki H Fujiwara H Ohishi M Inatani J 《The Astrophysical journal》1999,527(1):L59-L62
Large-scale mapping observations of the 3P1-3P0 fine-structure transition of atomic carbon (C i, 492 GHz) and the J=3-2 transition of CO (346 GHz) toward the Orion A molecular cloud have been carried out with the Mount Fuji submillimeter-wave telescope. The observations cover 9 deg2 and include the Orion Nebula M42 and the L1641 dark cloud complex. The C i emission extends over almost the entire region of the Orion A cloud and is surprisingly similar to that of 13CO (J=1-0). The CO (J=3-2) emission shows a more featureless and extended distribution than C i. The C i/CO (J=3-2) integrated intensity ratio shows a spatial gradient running from the north (0.10) to the south (1.2) of the Orion A cloud, which we interpret as a consequence of the temperature gradient. On the other hand, the C i/13CO (J=1-0) intensity ratio shows no systematic gradient. We have found a good correlation between the C i and 13CO (J=1-0) intensities over the Orion A cloud. This result is discussed on the basis of photodissociation region models. 相似文献
997.
Lieu R Bonamente M Mittaz JP Durret F Dos Santos S Kaastra JS 《The Astrophysical journal》1999,527(2):L77-L80
The EUV excess emission from the clusters A2199 and A1795 remains an unexplained astrophysical phenomenon. There has been many unsuccessful attempts to "trivialize" the findings. In this Letter, we present direct evidence proving that the most recent of such attempts, which attributes the detected signals to a background nonuniformity effect, is likewise excluded. We address the issue by a reobservation of A2199 that features a new filter orientation, usage of a more sensitive part of the detector, and, most crucially, the inclusion of a background pointing at approximately 2 degrees offset-the first in situ measurement of its kind. We first demonstrate quantitatively two facts: (1) the offset pointing provides an accurate background template for the cluster observation, while (2) data from other blank fields do not. We then performed a point-to-point subtraction of the in situ background from the cluster field, with an appropriate propagation of errors. The resulting cluster radial profile is consistent with that obtained by our original method of subtracting a flat asymptotic background. The emission now extends to a radius of 20&arcmin;; it confirms the rising prominence of EUV excess beyond approximately 5&arcmin; as previously reported. 相似文献
998.
We consider the thermal properties of cold, dense clouds of molecular hydrogen and atomic helium. For cloud masses below 10-1.7 M middle dot in circle, the internal pressure is sufficient to permit the existence of particles of solid or liquid hydrogen at temperatures above the cosmic microwave background temperature. Optically thin thermal continuum emission by these particles can balance cosmic-ray heating of the cloud, leading to equilibria that are thermally stable even though the heating rate is independent of cloud temperature. For the Galaxy, the known heating rate in the disk sets a minimum mass of order 10-6 M middle dot in circle necessary for survival. Clouds of this type may in principle comprise most of the dark matter in the Galactic halo. However, we caution that the equilibria do not exist at redshifts z greater, similar1 when the temperature of the microwave background was substantially larger than its current value; therefore, the formation and the survival of such clouds to the present epoch remain open questions. 相似文献
999.
1000.