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221.
Introduction The tidal variation signals of the solid Earth recorded with the modern measuring techniques can be used to provide effectively the means to cognize the Earths motion, deformation and structure character, especially to monitor the material motion in the Earths interior. In the recent 20 years, the distribution character of the global gravity field has made great progress since the continuous and deep theoretical studies in geophysics and geodesy domains. The successful manufactur… 相似文献
222.
Episodic dune formations during the Quaternary are found in many deserts of China. The causes of desert expansions on different time scales are not the same. Desert extension at about 1.1 and 0.9 Ma ago were the response to the active tectonic movements, whereas the desert evolutions on the ten-thousand years time scale were the response to the orbital scale climatic changes. Spatial scale studies on desert evolution indicate that desert margins shifted greatly during the last glacial maximum (LGM) and the Holocene optimum, its changing from 125°E of the LGM to 105°E of the climatic optimum. Historical desertification in the semiarid China is not a response to climate drought but largely associated with the human impacts (mainly over-cultivation) since about 2300 years ago, which leads to the reworking of the underlying LGM sands. 相似文献
223.
现代地裂缝在世界许多国家普遍存在 ,已成为当今世界范围内的主要地质灾害之一。本文在详尽分析了山西榆次地裂缝的各个致灾因子的基础上 ,利用GIS技术建立了地质学意义上的专题层 ;然后采用人工神经网络技术构建出了地裂缝灾害活动性的评价模型 ,并建立了地裂缝活动性的评价系统 ,对榆次地裂缝进行了灾害活动性评价 ,为榆次市城建和国土规划等部门的正确决策提供了重要的科学依据 相似文献
224.
科学的进步使地形变监测事业得到长足发展,市场经济的繁荣催生出形变监测行业独有的管理之道。形变监测行业是个介于科研、IT及服务行业三者之间的特殊行业,因此,它的发展必须具有一定的科学性、前瞻性和服务性。 相似文献
225.
Study of the Earth’s free core nutation by tidal gravity data recorded with international superconducting gravimeters 总被引:2,自引:0,他引:2
By stacking high-precision tidal gravity observations obtained with superconducting gravimeters at six stations in China,
Japan, Belgium, France, Germany and Finland, the local systematical discrepancies in the parameter fitting, caused by atmospheric,
oceanic tidal loading and the other local environmental perturbations, are eliminated effectively. As a result, the resonance
parameters of the Earth’s free core nutation are accurately determined. In this study, the eigenperiod of free core nutation
is given as 429.0 sidereal days, which is in agreement with those published in the previous studies. It is about 30 sidereal
days less than those calculated in theoretical models (about 460 sidereal days), which confirms the real ellipticity of the
fluid core of the Earth to be about 5% larger than the one expected in assumption of hydrostatic equilibrium. The quality
factor (Q value) of free core nutation is given as about 9543, which, compared with those determined before based on the body
tide observations, is much larger, but more close to those obtained using the VLBI observations. The complex resonance strength
is also determined as (−6.10×10−4, −0.01 ×10−4)°/h, which can principally describe the deformation characteristics of an anelastic mantle. 相似文献
226.
Lower Cretaceous red sedimentary rocks from the depositional basin of East Qilian fold belt have been collected for a paleomagnetic study. Stepwise thermal demagnetization reveals two or three components of magnetization from dark red sandstones. Low-temperature magnetic component is consistent with the present Earth Field direction in geographic coordinates. High-temperature magnetic components are mainly carried by hematite. The mean pole of 19 sites for high-temperature magnetic components after tilt-correction is λ=62.2°N, φ=193.4°E, A95=3.2°, and it passes fold tests at 99% confidence level and reversal tests at 95% confidence level. The paleopole is insignificantly different from that of Halim et al. (1998) from the same sampling area at the 95% confidence level. Compared with paleomagnetic results for North China, South China, and Eurasia, our results suggest that no significant relative latitudinal displacement has taken place between Lanzhou region and these blocks since Cretaceous time. Remarkably, the pole of Lanzhou shows a 20° clockwise rotation with respect to those of North China, South China, and Eurasia. Geological information indicates that the crustal shortening in the western part of Qilian is greater than that in eastern part. In this case, the clockwise rotation of sampling area was related to India/Eurasia collision, and this collision resulted in a left-lateral strike-slip motion of the Altun fault in north Tibetan Plateau after the Cretaceous. 相似文献
227.
县级农用地分等评价单元划分方法评析 总被引:2,自引:0,他引:2
叠置法、地块法、详查图斑法和动态网格法是划分农用地分等评价单元的四种主要方法。该文结合实例 ,对以上四种划分方法作了介绍 ,并逐一比较、评析了其优缺点、适用地域和注意事项 相似文献
228.
新时期我国区域经济地理学发展问题初探 总被引:4,自引:0,他引:4
我国新时期的区域经济地理学在取得全面发展的同时,在理论体系,研究方法和实践领域等方面还需要进一步的发展,文章根据学习和实践区域经济地理学的体会,初步提出基础理论和应用理论,思维方法和技术方法等方面发展见解,并指出区域创新系统和国际经济技术合作等学科应注意拓展的重要实践领域,最后提出我国区域经济地理学科发展的建议。 相似文献
229.
230.
成都市民消费结构与休闲活动关系研究 总被引:6,自引:0,他引:6
城市居民消费水平,消费结构会影响其休闲消费能力,消费意愿,消费方式,消费态度和休闲时空结构,文章以成都市7个城区歌舞,茶棋牌,电影及城市公园休闲活动调查为基础,探讨了城市居民消费结构及其变化与休闲活动特征的关系。研究结果表明,城市居民消费结构的改变对歌舞,茶棋牌娱乐活动影响最大。 相似文献