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91.
Having formulated the Clairaut second-order differential equations up to the fourth order in superficial distortion due to Hensen's coefficients in the previous article (El-Sharawyet al., 1989 III, hereafter denotes by SM3), we are now in a position to solve them. In this paper we shall discuss the methods of solving the Clairaut theory, to give an explicit form about the distortion of the surfaces of Jupiter and Saturn, numerically up to the fourth-order. 相似文献
92.
Marie Ekström 《Geografiska Annaler: Series A, Physical Geography》2002,84(2):113-126
Wind direction conditions during the 20th century in Scania, southern Sweden, are investigated using an estimated series of monthly wind vector components (east–west u component and north–south v component). The series is developed from a regression relationship between pairwise (1973 to 1997) monthly averages of 10–m surface wind from Scania and a monthly geostrophic wind, based on mean sea level (MSL) pressure data from the National Center of Atmospheric Research (NCAR). The wind conditions during the 20th century are dominated by winds from southwesterly and westerly directions, particularly during summer and autumn. From the 1980s onwards, increased frequencies of westerly winds are evident in spring and summer; however, similarly large frequencies of westerly winds are also found during the early part of the 20th century. Analysis of the estimated wind series indicates large variation in wind direction during the investigated time period, particularly during 1930 to 1960 when large increases of easterly winds are evident in spring. Increased frequencies of easterly winds were also found in other months during this period but not to the same extent as during the spring season. Thus, the presence of periods with quite different wind characteristics suggests that the overall atmospheric circulation has experienced some shifts in this region during the 20th century. 相似文献
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94.
Marie Grace Pamela G. Faylona Claire E. Lazareth Anne‐Marie Smah Sandrine Caquineau Hugues Boucher Wilfredo P. Ronquillo 《Geoarchaeology》2011,26(6):888-901
Tridacnidae shells, a valuable archive of past environments, are common in the Balobok Rockshelter archaeological site on Sanga‐Sanga Island in the south Philippines. This site was occupied during the mid‐Holocene (ca. 5000–8800 14C yr B.P.), a period of Neolithic cultural expansion in the Philippines. This paper focuses on the preservation of two shell specimens, Hippopus hippopus and Tridacna maxima, unearthed from two mid‐Holocene layers within the rockshelter. The shells' mineralogy and microstructure (prismatic and crossed‐lamellar) were studied using micro‐Fourier transform infrared spectroscopy and scanning electron microscopy to determine if the samples were suitable as paleoenvironmental records. Both shells are still aragonitic but aragonite crystals of both microstructure types are partly dissolved. This dissolution, characteristic of meteoric water alteration, precludes their utility in paleoenvironmental geochemical studies. Nevertheless, these shells are abundant in archaeological sites in the region and may be better preserved in other depositional contexts; more studies on Philippine Tridacnidae shell diagenesis are needed. © 2011 Wiley Periodicals, Inc. 相似文献
95.
Alex Brown Rowena Banerjea Amanda Dawn Wynne Normunds Stivrins Marc Jarzebowski Lisa‐Marie Shillito Aleks Pluskowski 《Geoarchaeology》2015,30(6):511-527
Slavic and German colonization of the southern Baltic between the 8th and 15th centuries A.D. is well‐documented archaeologically and historically. Despite the large number of pollen profiles from Poland, few palaeoecological studies have examined the ecological impact of a process that was central to the expansion of European, Christian, societies. This study aims to redress this balance through multiproxy analysis of lake sediments from Radzyń Chełminski, Northern Poland, using pollen, element geochemistry (Inductively Coupled‐Optical Emission Spectroscopy [ICP‐OES]), organic content, and magnetic susceptibility. The close association between lake and medieval settlements presents the ideal opportunity to reconstruct past vegetation and land‐use dynamics within a well‐documented archaeological, historical, and cultural context. Three broad phases of increasing landscape impact are visible in the pollen and geochemical data dating from the 8th/9th, 10th/11th, and 13th centuries, reflecting successive phases of Slavic and German colonization. This involved the progressive clearance of oak‐hornbeam dominated woodland and the development of an increasingly open agricultural landscape. Although the castles and towns of the Teutonic Order remain the most visible signs of medieval colonization, the palynological and geochemical data demonstrate that the major phase of woodland impact occurred during the preceding phase of Slavic expansion; Germans colonists were entering a landscape already significantly altered. 相似文献
96.
97.
Simone Fontana Fadi Henri Nader Sadoon Morad Andrea Ceriani Ihsan Shakir Al‐Aasm Jean‐Marc Daniel Jean‐Marie Mengus 《Sedimentology》2014,61(3):660-690
An integrated approach consisting of fracture analysis, petrography, carbon, oxygen and strontium‐isotope analyses, as well as fluid‐inclusion micro‐thermometry, led to a better understanding of the evolution of fluid–rock interactions and diagenesis of the Upper Permian to Upper Triassic carbonates of the United Arab Emirates. The deposited carbonates were first marked by extensive early dolomitization. During progressive burial, the carbonates were affected by dolomite recrystallization as well as precipitation of vug and fracture‐filling dolomite, quartz and calcite cements. After considerable burial during the Middle Cretaceous, sub‐vertical north–south oriented fractures (F1) were cemented by dolomite derived from mesosaline to hypersaline fluids. Upon the Late Cretaceous maximum burial and ophiolite obduction, sub‐vertical east–west fractures (F2) were cemented by dolomite (Dc2) and saddle dolomite (Ds) derived from hot, highly saline fluids. Then, minor quartz cement has precipitated in fractures from hydrothermal brines. Fluid‐inclusion analyses of the various diagenetic phases imply the involvement of increasingly hot (200°C) saline brines (20 to 23% NaCl eq.). Through one‐dimensional burial history numerical modelling, the maximum temperatures reached by the studied rocks are estimated to be in the range of 160 to 200°C. Tectonically‐driven flux of hot fluids and associated diagenetic products are interpreted to have initiated during the Late Cretaceous maximum burial and lasted until the Oligocene–Miocene compressional tectonics and related uplift. The circulation of such hydrothermal brines led to partial dissolution of dolomites (Dc2 and Ds) and to precipitation of hydrothermal calcite C1 in new (mainly oriented north–south; F3) and pre‐existing, reactivated fractures. The integration of the obtained data confirms that the diagenetic evolution was controlled primarily by the interplay of the burial thermal evolution of the basin and the regional tectonic history. Hence, this contribution highlights the impacts of regional tectonics and basin history on diagenetic processes, which may subsequently affect reservoir properties. 相似文献
98.
Annie Marie de Grosbois 《Environmental Geology》2007,53(2):471-476
99.
100.