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171.
本文通过比较太阳直射表和太阳光度计探测的大气柱气溶胶光学厚度,分析了从太阳直射表探测的全波段太阳直射光强信息确定大气柱气溶胶光学厚度的误差,并应用北京观象台的太阳直射表观测资料,反演得到了 1990—1993年北京大气柱气溶胶光学厚度,分析了该光学厚度月与年变化规律以及1991年菲律宾皮纳图博火山爆发对北京大气气溶胶含量的影响。本文还提出了关于有效水汽含量的一个经验关系式,用于确定水汽对太阳辐射的吸收率。 相似文献
172.
1987年1月8日甘肃迭部5.9级地震与地形变特征 总被引:1,自引:0,他引:1
根据1987年1月8日甘肃迭部5.9级地震前,该区域的地壳形变中长期背景和定点台站连续观测资料的震反应异常,分析研究了这此异常的变化特征。 相似文献
173.
174.
浅谈自动气象站的防雷设计要点 总被引:2,自引:0,他引:2
运用当代防雷领域中的有关理论,对自动气象站容易遭受雷击的原因和途径进行分析,提出了自动气象站的防雷设计要点。 相似文献
175.
中小震近场地震动估计中地震动衰减关系的适用性分析 总被引:9,自引:1,他引:9
核工程场地设计基准地震动确定中涉及弥散地震的地震动估计,这导致中小震近场地震动估计成为被关注的研究课题。本文基于一些中小震近场地震动记录资料,分析和探讨了国内外多种地震动衰减关系对中小震近场地震动估计的适用性问题,并结合我国几个核工程地震问题研究工作的实践对中小震近场地震动衰减关系确定的思路和原则提出了建议。 相似文献
176.
介绍了地质科学应用程序从Basic向Visual Basic(简称VB,下同)移植的基本技巧,并结合实际开发经验对变量定义、数据读取、成果输出和存储等开发、移植过程做了说明. 相似文献
177.
Wang Xiuxi Li Jijun Song Chunhui Zhang Jun Zhao Zhijun Gao Junping Pan Meihui 《Frontiers of Earth Science》2007,1(3):304-308
The Cenozoic sedimentation in the Tianshui basin, which is located at the junction of the liupanshan and West Qinling, northeast
margin of the Tibetan plateau, provides a record for the regional tectonism and exhumation history of the surrounding mountains.
Thermochronologic study on the detrital apatite grains from sandstones at Yaodian, near Tianshui, has revealed two rapid tectonic
uplift-exhumation events of the source area, which happened at 23.7 and 14.1 Ma, respectively. The fast exhumation (0.34 mm/a)
at 23.7 Ma, which recorded the tectonic uplift of West Qinling, led to the formation of the Neogene Tianshui basin and initiated
the reception of alluvial deposits. This event is most likely in response to the synchronous tectonism of the Tibetan plateau.
The source region experienced another rapid exhumation (1.05 mm/a) at 14.1 Ma, when the Tianshui basin began to depress broadly
and fluvial-lacustrine sediments dominated the Late Miocene.
Translated from Acta Sedimentologica Sinica, 2006, 24(6): 783–789 [译自: 沉积学报] 相似文献
178.
Twenty broadband seismographs were deployed along Hongyuan, Sichuan to Wuwei, Gansu. 81 teleseismic events were recorded in one year. We computed receiver functions from teleseismic waveform data and obtained S wave velocity structure beneath each station along the profile by using receiver function inversion method. The results revealed that the crustal structure is very complex and crustal average S wave velocity is to be on the low side. Low velocity structure generally exists in the depth range of 10~40 km in the crust between Aba arc fault and northern edge fault of Qinling earth's axis and it is a tectonic feature of complex geological process such as ancient A'nyemaqen Tethys ocean from closing and side colliding to subducted plate exhumed or thrust rock slice lifted. The Moho is about 50 km depth along the profile and is slightly deeper in the south than in the north. 相似文献
179.
We investigate the estimation of interfacial areas, curvatures, and common curve lengths in multiphase porous medium systems. Algorithms are developed to obtain estimates of these quantities based upon a variety of potential data sources and estimation approaches. The accuracy of the derived approximations are evaluated as a function of the data type and resolution of the data. The methods advanced improve upon standard approaches now in use and show excellent accuracy at resolutions on the order of five lattice points per minimum radius of curvature of the object being resolved. Finally, we suggest a promising class of extensions that could lead to further improvements in the accuracy of such methods. 相似文献
180.
Precipitation is often the sole source of water replenishment in arid and semi‐arid areas and, thus, plays a pertinent role in sustaining desert ecosystems. Revegetation over 40 years using mainly Artemisia ordosica and Caragana korshinskii at Shapotou Desert Experimental Research Station near Lanzhou, China, has established a dwarf‐shrub and microbiotic soil crust cover on the stabilized sand dunes. The redistribution of infiltrated moisture through percolation, root extraction, and evapotranspiration pathways was investigated. Three sets of time‐domain reflectometry (TDR) probes were inserted horizontally at 5, 10, 15, 20, 30 and 40 cm depths below the ground surface in a soil pit. The three sets of TDR probes were installed in dwarf‐shrub sites of A. ordosica and C. korshinskii community with and without a microbiotic soil crust cover, and an additional set was placed in a bare sand dune area that had neither vegetation nor a microbiotic soil crust present. Volumetric soil moisture content was recorded at hourly intervals and used in the assessment of infiltration for the different surface covers. Infiltration varied greatly, from 7·5 cm to more than 45 cm, depending upon rainfall quantity and soil surface conditions. In the shrub community area without microbiotic soil crust cover, infiltration increased due to preferential flow associated with root tunnels. The microbiotic soil crust cover had a significant negative influence on the infiltration for small rainfall events (~10 mm), restricting the infiltration depth to less than 20 cm and increasing soil moisture content just beneath the soil profile of 10 cm, whereas it was not as strong or clear for larger rainfall events (~60 mm). For small rainfall events, the wetting front depth for the three kinds of surface cover was as follows: shrub community without microbiotic soil crust > bare area > shrub community with microbiotic soil crust. In contrast, for large rainfall events, infiltration was similar in shrub communities with and without microbiotic soil crust cover, but significantly higher than measured in the bare area. Soil water extraction by roots associated with evapotranspiration restricted the wetting front penetration after 1 to 3 h of rainfall. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献