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101.
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103.
This paper describes the ocean loading tides corrections of GPS stations in Antarctica, such as the Great Wall station and Zhongshan station. Based on the theory of ocean loading tides, the displacement corrections of ocean loading tides on GPS stations in Antarctica are calculated by using the CRS4.0 ocean loading tides model. These corrections are also applied to GPS data processing. The GPS data are analyzed by the GAMIT software with and without these corrections. We compared and analyzed the GPS baseline components to get the differences. The results show that the ocean tidal displacement corrections have obvious effects upon GPS baseline components. Therefore, we should not ignore the ocean loading tides corrections of GPS stations in Antarctica to obtain precise and reliable results. 相似文献
104.
海洋上部水体垂向结构变化对于理解热带海区在全球气候变化中的作用有着重要意义。通过分析印度尼西亚穿越流(ITF)出口处东印度洋帝汶海区SO18480-3孔中的浮游有孔虫表层种Globigerinoides ruber和温跃层种Pulleniatina obliquiloculata壳体氧碳同位素,并借助12个AMS14C测年数据重建了末次盛冰期(LGM)以来该区温跃层深度和营养盐水平的演化序列。壳体氧同位素(δ18O)记录表明温跃层古海洋学特征的变化幅度要大于表层海水,其差值(Δδ18O(P-G))有效地反映了温跃层深度的变化,即冰消期和晚全新世温跃层较浅,LGM和早中全新世温跃层较深;并揭示出与全新世相比,LGM期间ITF总流量未显著减小,ITF对该区上部水体结构的影响受到了东西太平洋之间不对称性的调节。碳同位素(δ13C)记录则表明该区的古海洋学变化在不同程度上受到了南大洋的影响,并受本区上部水体垂向结构的控制,其差值(Δδ13(G-P))在一定程度上反映了该区上部水体营养盐水平的变化。 相似文献
105.
对渤海GNSS-R机载试验进行了海面风场反演.结果表明,风速精度优于1 m/s,风向精度优于20°. 相似文献
106.
We study the aspect of unstable behavior (like strain localization bands) in elastic solids as a consequence of micro-fracturing.
A two-scale approach of computational homogenization is considered. The macroscopic behavior is investigated by finite element
computations on a unit cell. At the micro-level, we consider a granular structure with elastic grains. The inter-granular
boundaries are modeled with cohesive laws, friction and unilateral contact. We show that decohesion between grains gives rise
to macro-instabilities, indicated by the loss of ellipticity, typical for deformation localization bands. The relation between
the microscopic softening on inter-granular boundaries and the onset of macro-instabilities is studied through numerical examples.
The influence of the cohesive law and friction parameters is analyzed. For periodic distributions of granular structures,
we prove the loss of periodicity by failure and the corresponding size dependence effect in the homogenized response. We present
numerical examples of bifurcation of solutions for granular cell structures and of particular solutions specific to elementary
volumes with periodic cell distribution. Size dependence appears in the unstable regime and is strongly influenced by cohesion
and friction parameters. 相似文献
107.
The present paper deals with the specification of bed erosion flux that accounts for the effects of sediment-induced stratification in the water column. Owing to difficulties in measuring the bed shear stress b and the erosive shear strength s, we suggest a series of methods that combine laboratory and numerical experiments. A simplified turbulent transport model that includes these effects helps to quantify b and s. Focusing on soft stratified beds, the present study considers erosion rate formulas of the form =f exp {[Tb-Ts]} where is a model constant (=1 for Gularte's (1978) formula and =1/2 for Parchure's (1984) formula). First, the bed erosive strength profile s(Z) is adjusted by forcing the turbulent transport model with measured erosion rates. Second, three procedures are suggested to determine the erosion rate formula coefficients f and : a global procedure and two different layer-by-layer procedures. Each procedure is applied to an erosion experiment conducted in a rotating annular flume by Villaret and Paulic (1986). The use of the layer-by-layer procedure based on a least squares fitting technique provides a closer fit than the global procedure. The present study points out the complementarity of experimental and numerical approaches and also suggests possible improvements in laboratory test procedures. 相似文献
108.
Weak and strong ground motions were numerically predicted for three stations of the Ashigara Valley test site. The prediction was based on the records from a rock-outcrop station, one weak-motion record from a surface-sediments station, and the standard geotechnical model. The data were provided by the Japanese Working Group on the Effects of Surface Geology as a part of an international experiment. The finite-difference method for SH waves in a 2-D linear viscoelastic medium (a causalQ model) was employed.Comparison with the real records shows that at two stations the predictions fit better than at the third one. Strangely, the two better predictions were for stations situated at larger distances from the reference rock station (one station was on the surface, the other in a borehole). The strong ground motion (the peak acceleration of about 200 cm s–2) was not predicted qualitatively worse than the weak motion (8 cm s–2). A less sophisticated second prediction (not submitted during the experiment), in which we did not attempt to fit the available weak-motion record at the sedimentary station, agrees with the reality significantly better. 相似文献
109.
M. Varvayanni C. G. Helmis G. T. Amanatidis D. N. Asimakopoulos J. G. Bartzis A. Soilemes K. H. Papadopoulos H. D. Kambezidis 《Pure and Applied Geophysics》1993,140(4):681-720
Field measurements of wind, air temperature and humidity were taken at the eastern part of the Attika district in June 1991, to examine the topographic influences exerted on the local sea breezes. These influences are due either to the elongated Evia island, faced by the northern half of Attica coastline some tens of kilometers offshore, or to the coast-parallel range of Hymettos mountain, rising steeply 12 km onshore. The instrumentation consisted mainly of three tethered meteorological balloons released at characteristic sires (i.e., the coast, a location between shoreline and mountain foot and the mountain top) and three autographic ground-based anemometers operating at selected locations. Data from the ground-based and upper air stations of the Hellenic National Meteorological Service, as well as the diurnal weather maps were also obtained and analyzed. Observations were made under different synoptic wind and the latter was found to determine remarkably the significance of the topographic effects. A preliminary two-dimensional numerical approach was also made concerning the sea breeze capability to reach the Hymettos mountain top in the case of a weak opposing geostrophic flow. 相似文献
110.
Santschi Peter H. Honeyman Bruce D. Quigley Matthew S. 《Aquatic Sciences - Research Across Boundaries》1993,55(4):230-239
In 1975 Paul Schindler produced the first oceanic trace metal scavenging model to explicitly include the role of surface chemistry as a control on trace metal water column residence times. The eighteen years that have elapsed since the publication of Schindler's seminal paper have seen the development of a variety of oceanic scavenging models; yet, the fundamental insight of his Zero-order Model remains the benchmark. This paper describes the role of Paul Schindler's work on surface chemistry in providing a framework for the current generation of trace element scavenging models. 相似文献