A Note on a Parameterization of the Sea Drag     

V. K. Makin 《Boundary-Layer Meteorology》2003,106(3):593-600

A new parameterization of the sea drag is based on a wind-over-wavescoupling theory. The parameterization accounts for the wind speed, wave ageand finite depth dependencies of the sea drag. The latter two are introducedthrough the integral parameters of the wind-wave field: the dominant waveheight and the wavenumber at the spectral peak, and the water depth. Theparameterization is checked against the wind-over-waves model results andtwo field datasets obtained in a wide range of the wind speed and wave age.The comparison is encouraging. The parameterization is aimed for use inoperational ocean-state and atmosphere models.  相似文献   

Silicic arc volcanism in Central Luzon, the Philippines: Characterization of its space, time and geochemical relationship   总被引：1，自引：0，他引：1  

Graciano P. Yumul  Jr  Carla B. Dimalanta  Rodolfo A. Tamayo  Jr    Herve Bellon 《Island Arc》2003,12(2):207-218

Abstract   The silicic volcanic rocks in Central Luzon show a temporal and spatial relationship with its geochemistry. Volcanic centers dated to approximately 5 Ma are silicic in geochemical composition whereas those between <5–1 Ma expose basaltic to andesitic rocks. Volcanic centers dated <1 Ma are characterized by a wide range of geochemistry encompassing basaltic through andesitic to dacitic signatures. Aside from changes in geochemistry through time, the areas (i.e. fore-arc to back-arc region) where the volcanic centers are formed also vary. The shift in the location of the volcanic centers in Central Luzon is attributed to changes in the dip of subduction of the South China Sea crust along the Manila Trench. Flat subduction resulted from the subduction of the Scarborough Seamount Chain, an oceanic bathymetric high along the Manila Trench west of northern Luzon. However, collision of Luzon with Taiwan in the north and Palawan in the south resulted in steepening of the subduction angle. The silicic volcanic centers in the forearc (Ce/Yb = 20–140) and back-arc (Ce/Yb = 20–60) regions are generally characterized by higher Ce/Yb compared to the basaltic-andesitic volcanic rocks in the main volcanic arc (Ce/Yb = 20) and back-arc (Ce/Yb = 20–30) regions. This across-arc geochemical variation highlights the contributions from the slab, mantle and crust coupled with the effects of geochemical processes that include partial melting, fractionation, magma mixing and mantle–melt interaction.  相似文献   

Discovery of the copper deposits with features of the Keweenawan type in the border area of Yunnan and Guizhou provinces   总被引：1，自引：0，他引：1  

朱炳泉  胡耀国  张正伟  常向阳 《中国科学D辑(英文版)》2003,46(Z1)

There existed intense Cu anomaly on the northeastern side of the geochemical boundary with NW strike in the border area between the Yunnan and Guizhou provinces. Through field observation, ore bodies of high-grade native coppers have been found. The copper mineralization was constrained by the ancient volcanic vents of Permian basalt eruption and the overlain strata of carbonaceous argillites. Native coppers with flaky, net veined and impregnated occurrences, fine-grained tenorites and massive chalcocites widely occur in volcanic breccias, tuffs, carbonaceous-siliceous argillites and siliceous bitumen rocks with bed thickness of about 15-80 m. Cu contents vary from 0.5% to 20%. The copper mineralization was tightly related to actinolite-tremolitization, zeolitization and bituminization and involved in extensive reduction environments. Continental flood basalts erupted in mantle plume environments usually have high Cu concentrations (～170 ×10-6 in the Emeishan basalts), which provided a copper source of mineralization. Thus, metallogenesis of the native copper deposits in the Yunnan-Guizhou border area is tightly associated with intensive crust-mantle and organic-inorganic interactions. The tremolitization and chalcocitization indicate that the metallogenic temperatures are in a range of 400-100℃. The geologic background and characteristics of ore and alteration for the native copper deposits in this area are somewhat similar to those of the Keweenawan native copper deposit in Michigan, USA.  相似文献   

Evaluation of vertical seismic response for a large‐scale beam‐supported aqueduct     

Yuchun Li  Menglin Lou  Danguan Pan 《地震工程与结构动力学》2003,32(1):1-14

By the theories of potential flow and structural vibration, the formulae for evaluating the ‘wet’ (with water) frequencies and mode shapes of the beam‐supported aqueduct are derived through a simplified fluid‐structure interaction analysis. The time‐history formulae of structural responses to the vertical seismic excitation are obtained. Applying the response‐spectrum principle, the equivalent vertical earthquake load exerted on the beam and the corresponding effects are also derived. Several illustrative examples are conducted. The analytical results show that: (i) The ‘wet’ frequencies of the structure are lower than the corresponding ‘dry’ (without water) frequencies due to the participating water mass, but the ‘wet’ mode shapes are identical to the corresponding ‘dry’ ones. (ii) The water mass plays an important role in the vertical seismic response, which varies with the different geological sites. For the different seismic inputs, the deeper the water is, the greater are the structural responses. (iii) The vertical seismic effects on the beam are generally not too small to be neglected and should be considered in the structural designs of a beam‐supported aqueduct. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Influence of free field variability on linear soil–structure interaction (SSI) by indirect integral representation     

E. Savin 《地震工程与结构动力学》2003,32(1):49-69

An integral equation for the representation of the response of a structure impinged by an incident wave field including soil–structure interaction is proposed. It requires the knowledge of the fundamental solution for the overall soil–structure domain when a unit load is applied to the structure. This fundamental solution is obtained by means of a substructuring technique and boundary integral equations using the Green tensors for homogeneous or horizontally stratified soil media. The effects of a non‐stationary modulated random incident field are addressed in terms of the instantaneous power spectral density of the structural response of interest for a given coherency function of the free field. Several applications of the proposed procedure are presented. The first one considers kinematic interaction of a rigid circular foundation and is used to validate the numerical implementation. The second one considers a complex structure on a stiff stratified soil and the last one considers the pounding effect between two adjacent, identical structures resting on a thin soft soil layer. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Experimental identification of the vibration modes of liquid‐filled conical tanks and validation of a numerical model     

A. M. I. Sweedan  A. A. El Damatty 《地震工程与结构动力学》2003,32(9):1407-1430

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Assessment of seismic performance of extended pile‐shafts     

Y. H. Chai  S. T. Song 《地震工程与结构动力学》2003,32(12):1937-1954

The seismic performance of extended pile‐shafts subjected to the current level of displacement ductility demand is assessed for different soil conditions. Local curvature ductility demand is compared with the curvature ductility capacity provided by the current level of confining steel. Parameters in the assessment of extended pile‐shafts include the undrained shear strength of cohesive soils, relative density of cohesionless soils, aboveground height, longitudinal reinforcement ratio, axial force level and pile diameter. Results indicate that the curvature ductility demand in the pile decreases with increased soil stiffness but increases with increased aboveground height. The curvature ductility demand however is not sensitive to the longitudinal reinforcement ratio or axial force level, and is independent of the pile diameter. Results further indicate that the curvature ductility capacity available from the current level of confining steel may not be adequate for tall extended pile‐shafts, especially for piles with large longitudinal reinforcement ratio and embedded in soft or loose soils. Limits on the maximum longitudinal reinforcement ratio are suggested in the paper. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

大别苏鲁地区层状地幔反射体及其解释   总被引：15，自引：2，他引：15       下载免费PDF全文

杨文采 《地球物理学报》2003,46(2):191-196

深反射地震虽然己广泛应用于地壳上地幔调查，然而，来自地幔的反射体在全世界 都还比较少见，尤其是尚未有发现上地幔中多层水平反射体的报道. 近年来，作者用24s 的 深反射地震记录揭示了在大别苏鲁地区岩石圈地幔内存在5组水平的反射体, 表明该区具有 特殊演化作用形成的上地幔组构, 它们可随深度增加分别命名为M1到M5 . 这些反射体不仅 可在地震叠加剖面上看到，有时还可在野外单炮记录上看到. 反射体M1对应Moho面，而M5大 概与现今岩石圈底界对应，根据地热资料，苏鲁热岩石圈厚度约为78km. 其他3个反射体可 能是中生代岩石圈减薄诱发的壳幔作用的结果. 根据岩石学与地球化学的数据，在晚中生代 中国东部岩石圈的厚度约从150km减薄到约60km，在新生代又略微加厚到平均 78km. 这一减 薄作用引起岩浆底侵并在下地壳产生麻粒岩层，而早侏罗纪扬子克拉通向北的陆-陆俯冲又 在上地幔产生榴辉岩层. 在双程走时12s处的反射体M2 则是麻粒岩层与榴辉岩层的边界，它 也是古生代的 Moho面. 反射体 M3 出现在14s 前后，看来是榴辉岩层的底面, 它的下面应 保存有残留的古生代上地幔. 由于新老岩石圈地幔成分不同，其界面产生反射体 M4. 这种 多层岩石圈地幔反射体的存在表明，所研究地区的地幔结构与中国东部中生代岩石圈减薄作 用有关. 同时，由于20世纪80年代以来一直认为上地幔在反射地震上是相对透明的，多层反 射体的发现对这一认识是新的挑战, 表明采用爆炸震源与地震反射新技术有可能揭露岩石圈 地幔内部结构细节，这些细节也是地幔动力学作用的产物.  相似文献   

结构随机地震响应分析的复模态法     

李创第  邹万杰  李暾  陈俊忠 《地震工程与工程振动》2003,23(6):44-49

本文对多自由度基础平动结构随机地震响应问题进行了系统研究。针对用第1振型近似代表上部结构所得方程为非经典阻尼和非对称结构情况。用复模态法解耦。获得了以第1振型表示的结构地震响应的解析解。对单自由度体系。此解即为结构响应的精确解。本文方法也可用于带TMD减震结构等的随机地震响应分析与优化设计。  相似文献   

U-Pb isotopic geochemistry of the post-collisional mafic-ultramafic rocks from the Dabie Mountains——Crust-mantle interaction and LOMU component     

黄方  李曙光  周红英  李惠民 《中国科学D辑(英文版)》2003,46(4)

Geochronological studies of mafic-ultramafic intrusions occurrence in the northern Dabie zone (NDZ) suggest that these pyroxenite-gabbro intrusions formed 120—130 Ma ago should be post-collisional magmatic rocks[1—4]. These mafic-ultramafic rocks provid…  相似文献