特殊情况下的圆曲线放样

本文主要解决了在无控制测量资料的情况下，圆曲线放样的方法．     

500百帕大气环流对云南地震的影响和震级的预测

本文用北半球５００百帕大气月均高度场资料，与云南地区每年发生的最大地震的震级作相关分析，选出其中影响地震的主要环流因子，分别构成每年上半年和下半年的最大震级预报方程。经三年的预报试验，效果尚好。     

一种地物点云数据栅格化分类新方法

激光技术的不断发展对利用点云数据进行地物分类的方法提出了更高的要求。基于此提出了一种结合遥感领域地物分类特点,利用地物反射率的不同来实现地物分类的方法。该方法首先提取数据的反射率信息,然后将其作为栅格化后的属性值,最后利用监督分类、非监督分类和支持向量机分类方法对栅格化后的栅格影像进行地物分类。通过实验表明,支持向量机方法在保持较高训练和分类速度的同时还具有较高的分类精度,总精度和Kappa系数达到了88.69%和0.86,为点云数据分类提供了一种新的途径。     

线元点位误差带的“纺锤形”模型

对当前GIS界流行的以点位误差描述线元位置不确定性的误差带理论提出相反的观点。最早提出的线元误差带理论为"ε-带"模型,后来又提出了"E-带"模型和在其基础上发展的"G-带"模型。后两者均认为以控制点点位误差描述的线元的误差带的基本形状呈"哑铃"形,即认为线元上端点的位置不确定性大于端点之间的点的位置不确定性。笔者的看法与此相反,笔者认为线元上两控制点之间的点的位置不确定性应大于控制点的位置不确定性,且在两控制点的中间达到最大,即线元误差带的基本形状应为"纺锤形"而不是"哑铃形"。     

The crystalline complexes of Hamadan (Sanandaj–Sirjan zone, western Iran): metasedimentary Mesozoic sequences affected by Late Cretaceous tectono-metamorphic and plutonic events

The Hamadan area is characterised by various metamorphic rocks where the slates yielded Jurassic fossils. The entire column, representing the Mesozoic from at least the Jurassic to the Mid-Cretaceous, has been affected by tectono-metamorphic events and the emplacement of Late Cretaceous granitic rocks. A timing of these events is based on the ⁴⁰K–⁴⁰Ar ages carried mainly on separated amphiboles, biotites and muscovites, and interpreted as the ages of their isotopic closure. Results are ranging between 91 and 70 Ma. To cite this article: A. Baharifar et al., C. R. Geoscience 336 (2004).

Résumé

La région de Hamadan expose des roches métamorphiques dont les termes les moins transformés contiennent des fossiles jurassiques. Au cours du Crétacé supérieur, elle a été affectée par un événement tectono-métamorphique régional et elle a été le siège d'une activité plutonique. Les résultats des datations ⁴⁰K–⁴⁰Ar des amphiboles et des micas séparés des roches métamorphiques et plutoniques qui s'étagent entre 91 et 70 Ma montrent l'importance de ces événements et leur étalement au cours du Crétacé supérieur. Pour citer cet article : A. Baharifar et al., C. R. Geoscience 336 (2004).     

Discovery of the largest impact crater field on Earth in the Gilf Kebir region, Egypt

Using orbital imaging radar, we have detected a large number of circular structures in the southwestern Egyptian desert, covering more than 4500 km² close to the Gilf Kebir plateau in sandstones of Upper Cretaceous. Fieldwork confirmed that it is a new impact crater field: 13 craters from 20 m to 1 km in diameter were studied. The impact origin is confirmed by the observation of shock-related structures, such as shatter cones and planar fractures in quartz grains of breccia. Considering the extension of the crater field, it was possibly created by several meteorites that broke up when entering the atmosphere. To cite this article: P. Paillou et al., C. R. Geoscience 336 (2004).

Résumé

À partir d'images satellites issues de systèmes radar, nous avons détecté un grand nombre de structures circulaires dans le Sud-Ouest du désert égyptien, s'étendant sur plus de 4500 km² à l'est du plateau du Gilf Kebir, dans des grès du Crétacé supérieur. Une étude sur le terrain a permis de vérifier qu'il s'agit d'un champ d'impacts météoritiques jusque là inconnu : 13 structures, d'un diamètre compris entre 20 m et 1 km, ont été reconnues comme cratères d'impact. La présence d'un grand nombre de cônes de percussion et de brèches dans lesquelles des quartz choqués à structures planaires ont été observés confirment l'hypothèse de l'impact. Considérant l'extension du champ d'impact, il a probablement été créé par plusieurs météorites qui se sont fragmentées dans l'atmosphère terrestre. Pour citer cet article : P. Paillou et al., C. R. Geoscience 336 (2004).     

Static compression of α-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>: linear incompressibility of lattice parameters and high-pressure transformations

The high-pressure behavior of -Fe₂O₃ has been studied under static compression up to 60 GPa, using a laser-heated diamond anvil cell. Synchrotron-based angular-dispersive X-ray diffraction shows that the sample remains in the corundum structure up to 50 GPa, but with the appearance of coexisting diffraction lines from a high-pressure phase at pressures above 45 GPa. A least-squares fit of low-pressure phase data to an Eulerian finite-strain equation of state yields linear incompressibilities of K _{a 0}=749.5 (± 18.4) GPa and K _{c 0}= 455.7 (± 21.4) GPa, differing by a factor of 1.6 along the two directions. The enhanced compressibility of the c axis may lead to breaking of vertex- or edge-sharing bonds between octahedra, inducing the high-pressure phase transformation at 50 GPa. Analysis of linear compressibilities suggests that the high-pressure phase above 50 GPa is of the Rh₂O₃ (II) structure. Continuous laser heating reveals a new structural phase transformation of -Fe₂O₃ at 22 GPa, to an orthorhombic structure with a=7.305(3) Å, b=7.850(3) Å, and c=12.877(14) Å, different from the Rh₂O₃ (II) structure.     

转换波的静校正

横向不均匀风化层和甚低速剪切波使得P—SV转换波静校正量大且横向变化剧烈。这种大的静校正量不可能通过常规的P波折射静校正得到消除。采用模型相关和曲线圆滑消除接收点静校正量。其步骤为：(1)利用优化共接收点叠加道确定总的接收点静校正量;(2)利用圆滑的方法得到对构造起伏的估计;(3)总的接收点静校正量减去构造起伏便得到了接收点的静校正量。     

A general model for modifying Stokes’ formula and its least-squares solution

Today the combination of Stokes formula and an Earth gravity model (EGM) for geoid determination is a standard procedure. However, the method of modifying Stokes formula varies from author to author, and numerous methods of modification exist. Most methods modify Stokes kernel, but the most widely applied method, the remove compute restore technique, removes the EGM from the gravity anomaly to attain a residual gravity anomaly under Stokes integral, and at least one known method modifies both Stokes kernel and the gravity anomaly. A general model for modifying Stokes formula is presented; it includes most of the well-known techniques of modification as special cases. By assuming that the error spectra of the gravity anomalies and the EGM are known, the optimum model of modification is derived based on the least-squares principle. This solution minimizes the expected mean square error (MSE) of all possible solutions of the general geoid model. A practical formula for estimating the MSE is also presented. The power of the optimum method is demonstrated in two special cases. AcknowledgementsThis paper was partly written whilst the author was a visiting scientist at The University of New South Wales, Sydney, Australia. He is indebted to Professor W. Kearsley and his colleagues, and their hospitality is acknowledged.     

The Performance of Atmospheric Component Model R42L9 of GOALS／LASG

This paper examines the performance of an atmospheric general circulation model (AGCM) developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics (LASG/IAP). It is a spectral model truncated at R42(2.8125°long×1.66°lat) resolution and with nine vertical levels, and referred to as R42L9/LASG hereafter. It is also the new version of atmospheric component model R15L9 of the global ocean-atmosphere-land system (GOALS/LASG). A 40-year simulation in which the model is forced with the climatological monthly mean sea surface temperature is compared with the 40-year (1958-97) U.S. National Center for Environmental Prediction (NGEP) global reanalysis and the 22-year (1979-2000) Xie-Arkin monthly precipitation climatology. The mean DJF and JJA geographical distributions of precipitation, sea level pressure, 500-hPa geopotential height, 850-hPa and 200-hPa zonal wind, and other fields averaged for the last 30-year integrat