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81.
Yakovenchuk Victor N. Ivanyuk Gregory Yu. Pakhomovsky Yakov A. Panikorovskii Taras L. Britvin Sergei N. Krivovichev Sergey V. Shilovskikh Vladimir V. Bocharov Vladimir N. 《Mineralogy and Petrology》2018,112(1):111-121
Mineralogy and Petrology - Kampelite, Ba3Mg1.5Sc4(PO4)6(OH)3·4H2O, is a new Ba-Sc phosphate from the Kovdor phoscorite-carbonatite complex (Kola Peninsula, Russia). It is orthorhombic, Pnma,... 相似文献
82.
Victor L. Vinograd Benjamin P. Burton Neil L. Allan 《Geochimica et cosmochimica acta》2007,71(4):974-983
Thermodynamic mixing properties and subsolidus phase relations of the rhombohedral carbonate system, (1 − x) · CaCO3 − x · MgCO3, were modelled in the temperature range of 623-2023 K with static structure energy calculations based on well-parameterised empirical interatomic potentials. Relaxed static structure energies of a large set of randomly varied structures in a 4 × 4 × 1 supercell of calcite (a = 19.952 Å, c = 17.061 Å) were calculated with the General Utility Lattice Program (GULP). These energies were cluster expanded in a basis set of 12 pair-wise effective interactions. Temperature-dependent enthalpies of mixing were calculated by the Monte Carlo method. Free energies of mixing were obtained by thermodynamic integration of the Monte Carlo results. The calculated phase diagram is in good agreement with experimental phase boundaries. 相似文献
83.
Lapperre Rimbaud E. Bense Victor F. Kasse Cornelis van Balen Ronald T. 《Hydrogeology Journal》2022,30(4):1233-1257
Hydrogeology Journal - Faults in the Roer Valley Rift System (Netherlands, Belgium, and Germany) act as barriers to lateral groundwater flow in unconsolidated sedimentary aquifers. This causes a... 相似文献
84.
Ayugi Brian Shilenje Zablon Weku Babaousmail Hassen Lim Kam Sian Kenny T. C. Mumo Richard Dike Victor Nnamdi Iyakaremye Vedaste Chehbouni Abdelghani Ongoma Victor 《Natural Hazards》2022,113(2):1151-1176
Natural Hazards - The ongoing global warming has caused unprecedented changes in the climate system, leading to an increase in the intensity and frequency of weather and climate extremes. This... 相似文献
85.
Xavier Bruna Catarino Egydio-Silva Marcos Sadowski Georg Robert de Assis Silva Bruno Takara Victor Junji 《Geotechnical and Geological Engineering》2022,40(3):1345-1361
Geotechnical and Geological Engineering - To optimize the prediction of structural geological conditions in the underground as of data collected at the surface, due to the usual great uncertainties... 相似文献
86.
Victor Birman 《Ocean Engineering》1986,13(6)
This paper presents an exact solution of the problem of free nonlinear rolling or pitching motion of a submerged vehicle. The nondimensional frequency-amplitude relationship of free uncoupled roll or pitch is universal, i.e. the single curve describes the behavior of any vehicle. This relationship is softening, i.e. the decreasing frequencies correspond to larger amplitudes of roll or pitch. The amplitudes of vibrations in the region of frequencies corresponding to the resonance are very sensitive to small variations of the frequency. These conclusions, i.e. the softening nonlinearity and the high sensitivity of the amplitudes to small variations of the vibration frequency are valid also for the problem of forced nonlinear roll or pitch motion of submerged vehicles. 相似文献
87.
Victor B. MAGLAMBAYAN † Daizo ISHIYAMA Toshio MIZUTA Akira IMAI Yohei ISHIKAWA 《Resource Geology》1998,48(2):87-104
Abstract: The Bulawan deposit is located in the porphyry copper belt of southwest Negros island, Philippines. Propylitic, K–feldspar, sericitic, and carbonate alteration types can be distinguished in the deposit. Propylite alteration occurs mainly in Cretaceous-Eocene andesitic lavas and agglomerates while K–feldspar, sericite and carbonate alteration types occur mostly in the Middle Miocene dacite porphyry breccia pipes and stocks which were intruded into the andesites. K-feldspar zones occur in the inner parts of the sericitized zone. Sericite alteration overprinted the propylitized and K-feldspar alteration zones, at lower temperature than epidote and chlorite in the propylitized zone. Carbonate alteration is associated with the mineralization in the center of the breccia pipes and along faults. Mineralization consists of gold-silver telluride ores that are hosted by the carbonate– and sericite-altered dacite porphyry breccia pipes. The Bulawan ores occur mainly as disseminations, but unlike many epithermal gold deposits, lack classical epithermal colloform and crustiform quartz veins. The ore minerals are sphalerite, galena, chalcopyrite, pyrite and tetrahedite-tennantite with minor amounts of electrum, calaverite, petzite, sylvanite, hessite, tellurobismuthite, coloradoite, altaite, and rucklidgeite. Electrum and telluride minerals are associated mostly with calcite and dolomite-ankerite minerals. Fluid inclusions in quartz and calcite in clasts of propylitized andesite in the breccia pipes homogenize from about 300° to 400°C while fluid inclusions in quartz, calcite and sphalerite within the dacite porphyry breccia pipes homogenize between 300° to 310°C. The ores were formed around 300°C from hydrothermal solutions with salinity of about 6. 6 wt % NaCl equivalent. The presence of sylvanite and calaverite as intergrowths with each other, and the Ag content of calaverite are consistent with the above temperature estimate. Based on paragenesis, the Bulawan deposit formed in a pyrite-stable environment, with pH between 3. 4 and 5. 5, fO2 between 10-32 to 10-30 atm, fS2 between 10-9.8 to 10-7.8 atm, fTe2 between 10-8.9 to 10-6.5 atm, and total sulfur content about 10-2.8 molal. The dominant reduced sulfur species in the ore solutions may have been H2S(aq), and the likely aqueous tellurium species were H2Te(aq) and H2TeO3(aq). The ore minerals in the Bulawan deposit were probably formed by mixing of slightly saline and low salinity fluids. 相似文献
88.
Andreas Fries Rütger Rollenbeck Fabian Bayer Victor Gonzalez Fernando Oñate-Valivieso Thorsten Peters Jörg Bendix 《Meteorology and Atmospheric Physics》2014,126(1-2):13-29
The precise estimation of precipitation quantities in tropical mountain regions is in great demand by ecological and hydrological studies, due to the heterogeneity of the rainfall distribution and the lack of meteorological station data. This study uses radar images and ground station data to provide the required high-resolution precipitation maps. Also wind data are taken into account, due to its influence on the precipitation formation and to demonstrate the relation between synoptic wind, topography and the precipitation distribution inside small mountain valleys. The study analyses the rainfall distribution and amounts of 4 days inside the San Francisco Valley, a small catchment in the tropical Andes of southern Ecuador, representing different seasons and the typical atmospheric flows, which are correlated to the annual precipitation map. The results show that the rainfall distribution and amounts are generally defined by the wind direction and velocity, besides the topographic location in relation to the main barriers and pathways. The dominant wind direction causes a division of the catchment in a wetter eastern and a dryer western part. Moreover, the annual seasons are reversed; the main rainy season for the eastern part occurs between June and August, while the western part reaches the precipitation maximum between January and March. This may have influence on the species composition at the different slopes and the annual hydrological cycle inside the catchment. 相似文献
89.
Estuarine soft sediments support a diverse group of eukaryotic and prokaryotic organisms though the role of the sediment per se for the functioning of these organisms remains largely unknown. The present study aimed to test the effect of sediment grain size on the grazing activities of harpacticoid copepods. In controlled experiments, two common intertidal harpacticoid species (Paramphiascella fulvofasciata and Nitokra spinipes) were each offered a mix of two benthic diatom species (Navicula phyllepta and Seminavis robusta) in different sedimentary conditions. Several microcosms were created using a variety of sediment types, including fine silt (<63 microm), coarser grained sands (125-250, 250-450, 100-300 microm), artificial 'sediments' of glass beads (250-500, 2000 microm) and even the absence of sediment was tested. The diatoms were enriched in the stable carbon (13)C to facilitate tracing in the harpacticoids. Both copepod species were able to graze on the diatoms with highest uptake when sediment was absent. In contrast, both harpacticoid species showed no uptake in silty conditions. In general, grazing was favoured when mean sediment grain size increased. The strong negative effect of fine grains on the grazer's efficiency can be explained by the resulting differences in the structure (and accessibility) of the diatom biofilm on the one hand and the mobility of the grazer on the other hand. In view of the subtle equilibrium between primary producers and grazers, these results might have important implications for the effect of siltation of tidal flats due to, e.g., human activities. 相似文献
90.