Application of an improved semi-Lagrangian procedure to fully-nonlinear simulation of sloshing in non-wall-sided tanks     

《Applied Ocean Research》2015

The semi-Lagrangian procedure is widely used for updating the fully-nonlinear free surface in the time domain. However, this procedure is only available to cases when the body surface is vertical near the waterline. Present study introduces an improved semi-Lagrangian procedure which removes this ‘vertical-wall’ limitation. Coupling with the boundary element method, the improved semi-Lagrangian procedure is applied to the simulation of fully-nonlinear sloshing waves in non-wall-sided tanks. From the result comparison with the open source CFD software OpenFOAM, it is confirmed that this numerical scheme could guarantee a sufficient accuracy. Further series studies on 2D and 3D fully-nonlinear sloshing waves in wedged tanks are performed. Featured phenomena are observed which are distinct from those in wall-sided tanks.  相似文献   

Diagenetic evolution of the upper Cretaceous limestone and sandstone exhumed reservoirs in the western Basque–Cantabrian Basin,North Spain     

《Marine and Petroleum Geology》2015

The Basque–Cantabrian Basin (NE Spain) has been considered one of the most interesting areas for hydrocarbon exploration in the Iberian Peninsula since the 60th to 70th of last century. This basin is characterized by the presence of numerous outcrops of tar sands closely associated with fractures and Triassic diapirs. The aims of this work is to establish the diagenetic evolution of the Upper Cretaceous reservoir rocks with special emphasis in the emplacement of oil and their impact on reservoir quality. The studied rocks are constituted of carbonates and sandstones that contain massive quantities of bitumen filling vugs and fractures.Petrographic results indicate that the carbonate rocks from Maestu outcrops are bioclastic grainstones and wackestones, whereas the tar sandstones from Atauri and Loza outcrops are dominated by quartzarenites and subordinated subarkoses. The paragenetic sequence of the main diagenetic phases and processes include, pyrite, bladed and drusy calcite cement, calcite overgrowths, silicification of bioclasts and microcrystalline rhombic dolomite cement, and first stage of oil emplacement, blocky calcite cement, coarse crystalline calcite cement, calcitized dolomite, calcite veins, saddle dolomite and stylolites filled by the second phase of oil entrance. Together with the above mentioned diagenetic alterations, the arenites are affected by early kaolinitization of feldspars and the scarce formation of clay rim and epimatrix of illite. All sandstones and dolomitized carbonate rocks show high intercrystalline and intergranular porosity which is full by biodegraded hydrocarbons (solid bitumen). The biodegradation affects alkanes, isoprenoids and partially hopanes and steranes saturated hydrocarbons. Aromatics hydrocarbons, like naphthalenes, phenanthrenes, dibenzothiophenes and triaromatics are also affected by biodegradation. Results indicate that the first HC emplacement corresponds to early stage of calcite and dolomite cementation, and the second and more important emplacement is related to fracturation processes resulting in the formation of excellent reservoirs.  相似文献   

Visualizing spatiotemporal trajectories of mobile social media users using space–time cube     

Chen Xu  Han Qin  Manzhu Yu 《制图学和地理信息科学》2015,42(4):75-83

The implementation of social network applications on mobile platforms has significantly elevated the activity of mobile social networking. Mobile social networking offers a channel for recording an individual’s spatiotemporal behaviors when location-detecting capabilities of devices are enabled. It also facilitates the study of time geography on an individual level, which has previously suffered from a scarcity of georeferenced movement data. In this paper, we report on the use of georeferenced tweets to display and analyze the spatiotemporal patterns of daily user trajectories. For georeferenced tweets having both location information in longitude and latitude values and recorded creation time, we apply a space–time cube approach for visualization. Compared to the traditional methodologies for time geography studies such as the travel diary-based approach, the analytics using social media data present challenges broadly associated with those of Big Data, including the characteristics of high velocity, large volume, and heterogeneity. For this study, a batch processing system has been developed for extracting spatiotemporal information from each tweet and then creating trajectories of each individual mobile Twitter user. Using social media data in time geographic research has the benefits of study area flexibility, continuous observation and non-involvement with contributors. For example, during every 30-minute cycle, we collected tweets created by about 50,000 Twitter users living in a geographic region covering New York City to Washington, DC. Each tweet can indicate the exact location of its creator when the tweet was posted. Thus, the linked tweets show a Twitter users’ movement trajectory in space and time. This study explores using data intensive computing for processing Twitter data to generate spatiotemporal information that can recreate the space–time trajectories of their creators.  相似文献   

Remote sensing and geophysical survey applications for delineating near-surface palaeochannels and shallow aquifer in the United Arab Emirates     

Samy Ismail Elmahdy  Mohamed Mostafa Mohamed 《国际地球制图》2015,30(7):723-736

This study integrates remote sensing data and geoelectrical dipole–dipole resistivity to delineate near-surface palaeochannels and shallow aquifer in the northern part of Abu Dhabi Emirate, United Arab Emirates. The shuttle imaging radar images and shuttle radar topographic mission DEM were used to delineate near-surface palaeochannels visually based on the contrast between bright and dark tone and automatically using the eight-direction flow model. The delineated palaeochannels were validated by comparing the textural features evident from advanced land observing satellite-phased array type L-band synthetic aperture radar images and determining whether these patterns were different. Field observation and geoelectrical dipole–dipole resistivity method was used to define the depth of palaeochannels and lithology of the shallow aquifer. The remote sensing and geophysical investigations in the UAE, including the study area, indicate the presence of buried palaeochannels with south-west and north-west flow directions from Oman Mountain. The study area can be of economic importance to the local population.  相似文献   

Dinosaur ichnofauna of the Upper Jurassic/Lower Cretaceous of the Paraná Basin (Brazil and Uruguay)     

《Journal of South American Earth Sciences》2015

Upper Jurassic and Lower Cretaceous sedimentary layers are represented in the Brazilian Paraná Basin by the fluvio–aeolian Guará Formation and the Botucatu Formation palaeoerg, respectively, overlapped by the volcanic Serra Geral Formation. In Uruguay, the corresponding sedimentary units are named Batoví and Rivera Members (both from the Tacuarembó Formation), and the lava flows constitute the Arapey Formation (also in Paraná Basin). Despite the lack of body fossils in the mentioned Brazilian formations, Guará/Batoví dinosaur fauna is composed of theropod, ornithopod and wide–gauge sauropod tracks and isolated footprints, as well as theropod teeth. In turn, the Botucatu/Rivera dinosaur fauna is represented by theropod and ornithopod ichnofossils smaller than those from the underlying units. The analysis of these dinosaur ichnological records and comparisons with other global Mesozoic ichnofauna indicates that there is a size reduction in dinosaur fauna in the more arid Botucatu/Rivera environment, which is dominated by aeolian dunes. The absence of sauropod trackways in the Botucatu Sandstone fits with the increasingly arid conditions because it is difficult for heavy animals to walk on sandy dunes, as well as to obtain the required amount of food resources. This comparison between the Upper Jurassic and Lower Cretaceous dinosaur fauna in south Brazil and Uruguay demonstrates the influence of aridization on the size of animals occupying each habitat.  相似文献   

Age,composition, and source of continental arc- and syn-collision granites of the Neoproterozoic Sergipano Belt,Southern Borborema Province,Brazil     

《Journal of South American Earth Sciences》2015

The Sergipano belt is the outcome of collision between the Pernambuco-Alagoas Domain (Massif) and the São Francisco Craton during Neoproterozoic assembly of West Gondwana. Although the understanding of the Sergipano belt evolution has improved significantly, the timing of emplacement, geochemistry and tectonic setting of granitic bodies in the belt is poorly known. We recognized two granite age groups: 630–618 Ma granites in the Canindé, Poço Redondo and Macururé domains, and 590–570 Ma granites in the Macururé metasedimentary domain. U–Pb SHRIMP zircon ages for granites of first age group indicated ages of 631 ± 4 Ma for the Sítios Novos granite, 623 ± 7 Ma for the Poço Redondo granite, 619 ± 3.3 Ma for the Lajedinho monzodiorite, and 618 ± 3 Ma for the Queimada Grande granodiorite. These granitoids are dominantly high-K calc-alkaline, magnesian, metaluminous, mafic enclave-rich (Queimada Grande and Lajedinho), or with abundant inherited zircon grains (Poço Redondo and Sitios Novos). Geochemical and isotope data allow us to propose that Sítios Novos and Poço Redondo granites are product of partial melting of Poço Redondo migmatites. Sr-Nd isotopes of the Queimada Grande granodiorite and Lajedinho monzodiorite suggest that their parental magma may have originated by mixing between a juvenile mafic source and a crustal component that could be the Poço Redondo migmatites or the Macururé metasediments. Other 630–618 Ma granites in the belt are the mafic enclave-rich Coronel João Sá granodiorite and the Camará tonalite in the Macururé sedimentary domain. These granites have similar geochemical and isotopic characteristics as the Lajedinho and Queimada Grande granitoids. We infer for the Camará tonalite and Coronel João Sá granodiorite that their parental magmas have had contributions from mafic lower crust and felsic upper crust, most probably from underthrust São Francisco Craton, or Pernambuco-Alagoas Domain. The younger 590–570 Ma granite group is confined to the Macururé metasedimentary domain. Although these granites do not show typical features of S-type granites, their U–Pb age, field relationships, geochemical and Sr-Nd data suggest that their parental magmas have originated from high degree melting of the Macururé micaschists. Field observations support a model in which the Macururé domain, limited by the Belo Monte-Jeremoabo and São Miguel do Aleixo shear zones, behaved as a ductile channel flow for magma migration and emplacement during the Neoproterozoic, very much like the channel flow model proposed for emplacement of leucogranites in the Himalayas.  相似文献   

Modeling nonlinear wave–wave interactions with the elliptic mild slope equation     

《Applied Ocean Research》2014

An approach is developed to simulate wave–wave interactions using nonlinear elliptic mild-slope equation in domains where wave reflection, refraction, diffraction and breaking effects must also be considered. This involves the construction of an efficient solution procedure including effective boundary treatment, modification of the nonlinear equation to resolve convergence issues, and validation of the overall approach. For solving the second-order boundary-value problem, the Alternating Direction Implicit (ADI) scheme is employed, and the use of approximate boundary conditions is supplemented, for improved accuracy, with internal wave generation method and dissipative sponge layers. The performance of the nonlinear model is investigated for a range of practical wave conditions involving reflection, diffraction and shoaling in the presence of nonlinear wave–wave interactions. In addition, the transformation of a wave spectrum due to nonlinear shoaling and breaking, and nonlinear resonance inside a rectangular harbor are simulated. Numerical calculations are compared with the results from other relevant nonlinear models and experimental data available in literature. Results show that the approach developed here performs reasonably well, and has thus improved the applicability of this class of wave transformation models.  相似文献   

Mixed sand–mud bedforms produced by transient turbulent flows in the fringe of submarine fans: Indicators of flow transformation     

Megan L. Baker  Jaco H. Baas 《Sedimentology》2020,67(5):2645-2671

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Evolutionary biogeography on Ophiocordyceps sinensis:An indicator of molecular phylogeny to geochronological and ecological exchanges     

《地学前缘(英文版)》2020,11(3):807-820

The fungus Ophiocordyceps sinensis is endemic to the vast region of the Qinghai-Tibetan plateau(QTP).The unique and complex geographical environmental conditions have led to the "sky island" distribution structure of O.sinensis.Due to limited and unbalanced sample collections,the previous data on O.sinensis regarding its genetic diversity and spatial structure have been deemed insufficient.In this study,we analyzed the diversity and phylogeographic structures of O.sinensis using internally transcribed spacer region(ITS) and 5-locus datasets by a large-scale sampling.A total of 111 haplotypes of ITS sequences were identified from 948 samples data of the fungus O.sinensis,with representing high genetic diversity,and 8 phylogenetic clades were recognized in O.sinensis.Both the southeastern Tibet and the northwestern Yunnan were the centers of genetic diversity and genetic differentiation of the fungus,and they were inferred as the glacial refugia in the Quaternary.Three distribution patterns were identified to correspond to the 8 clades,including but not limited to the coexistence of widely and specific local distributive structures.It also revealed that the differentiation pattern of O.sinensis did not fit for the isolation-by-distance model.The differentiation into the 8 clades occurred between 1.56 Myr and6.62 Myr.The ancestor of O.sinensis most likely originated in the late Miocene(6.62 Myr) in the northwestern Yunnan,and the Scene A-C of the Qinghai-Tibetan movements may have played an important role in the differentiation of O.sinensis during the late Miocene-Pliocene periods.Our current results provide a much clearer and detailed understanding of the genetic diversity and geographical spatial distribution of the endemic alpine fungus O.sinensis.It also revealed that the geochronology resulting from paleogeology could be cross-examined with biomolecular clock at a finer scale.  相似文献   

Mesozoic–Cenozoic stress field magnitude in Sichuan Basin,China and its adjacent areas and the implication on shale gas reservoir: Determination by acoustic emission in rocks     

《China Geology》2020,3(4):591-601

The Sichuan Basin is one of the vital basins in China, boasting abundant hydrocarbon reservoirs. To clarify the intensity of the tectonic stress field of different tectonic episodes since the Mesozoic and to identify the regional dynamic background of different tectonic movements in the Sichuan Basin and its adjacent areas, the characteristics of the acoustic emission in rocks in different strata of these areas were researched in this paper. Meanwhile, the tectonic stress magnitude in these areas since the Mesozoic was restored. The laws state that the tectonic stress varied with depth was revealed, followed by the discussion of the influence of structural stress intensity on structural patterns in different tectonic episodes. These were conducted based on the paleostress measurement by acoustic emission method and the inversion principle of the stress fields in ancient periods and the present, as well as previous research achievements. The results of this paper demonstrate that the third episode of Yanshanian Movement (Yanshanian III) had the maximum activity intensity and tremendously influenced the structural pattern in the study area. The maximum horizontal principal stress of Yanshanian III varied with depth as follows: 0.0168 x + 37.001 (MPa), R² = 0.8891. The regional structural fractures were mainly formed in Yanshanian III in Xujiahe Formation, west Sichuan Basin, of which the maximum paleoprincipal stress ranging from 85.1 MPa to 120.1 MPa. In addition, the law stating the present maximum horizontal principal stress varies with depth was determined to be 0.0159 x+10.221 (MPa), R²=0.7868 in Wuling Mountain area. Meanwhile, it was determined to be 0.0221 x+9.4733 (MPa), R²=0.9121 in the western part of Xuefeng Mountain area and 0.0174 x+10.247 (MPa), R²=0.8064 in the whole study area. These research results will not only provide data for the simulation of stress field, the evaluation of deformation degree, and the prediction of structural fractures, but also offer absolute geological scientific bases for the elevation of favorable shale gas preservation.  相似文献