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排序方式: 共有398条查询结果,搜索用时 15 毫秒
1.
Lucas May Petry Camila Leite Da Silva Andrea Esuli Chiara Renso Vania Bogorny 《International journal of geographical information science》2020,34(7):1428-1450
ABSTRACT The increasing popularity of Location-Based Social Networks (LBSNs) and the semantic enrichment of mobility data in several contexts in the last years has led to the generation of large volumes of trajectory data. In contrast to GPS-based trajectories, LBSN and context-aware trajectories are more complex data, having several semantic textual dimensions besides space and time, which may reveal interesting mobility patterns. For instance, people may visit different places or perform different activities depending on the weather conditions. These new semantically rich data, known as multiple-aspect trajectories, pose new challenges in trajectory classification, which is the problem that we address in this paper. Existing methods for trajectory classification cannot deal with the complexity of heterogeneous data dimensions or the sequential aspect that characterizes movement. In this paper we propose MARC, an approach based on attribute embedding and Recurrent Neural Networks (RNNs) for classifying multiple-aspect trajectories, that tackles all trajectory properties: space, time, semantics, and sequence. We highlight that MARC exhibits good performance especially when trajectories are described by several textual/categorical attributes. Experiments performed over four publicly available datasets considering the Trajectory-User Linking (TUL) problem show that MARC outperformed all competitors, with respect to accuracy, precision, recall, and F1-score. 相似文献
2.
Continental (fluvial) strata of the Pinjor Formation (Siwalik Group), northwestern Himalayas, India, contain an invertebrate trace fossil assemblage containing Planolites beverleyensis, Palaeophycus isp., Scoyenia gracilis, Taenidium barretti and other undifferentiated traces. The traces are found in an \(\sim \)26 m thick interval of alternating pinkish red siltstone, which is intercalated with mudstone, and thickly-bedded buff and greenish coloured sandstone. These sediments are interpreted as the deposits of floodplains and channel-bars of fluvial environments and low-energy overbank floodplain deposits. The trace fossils studied here are the first well documented ichnofossil assemblage from the vast, late Cenozoic Siwalik depositional system. They are not only of palaeoenvironmental significance, but they add to the growing ichnofossil database in facies of fluvial origin and should be an impetus to further ichnological studies of the Siwalik Group. 相似文献
3.
Quintana Gonzalo Iñaki Tandeo Pierre Drumetz Lucas Leballeur Laurent Pavec Marc 《Natural Hazards》2021,108(3):2905-2917
Natural Hazards - This paper studies different machine learning methods for solving the regression problem of estimating the marine surge value given meteorological data. The marine surge is... 相似文献
4.
Hydro-geochemistry of groundwater and surface water in Dschang town(West Cameroon): Alkali and alkaline-earth elements ascertain lithological and anthropogenic constraints 下载免费PDF全文
Yemeli Elida Joelle Temgoua Emile Kengni Lucas Ambrosi Jean-Paul Momo-nouazi Mathieu Silatsa-Tedou Francis Brice Wamba Franck Robean Tchakam-Kamtchueng Brice 《地下水科学与工程》2021,9(3):212-224
This study focuses on the sources of alkali and alkaline-earth elements based on the geochemistry of groundwater and surface water in Dschang concerning environmental and anthropogenic constraints. A comprehensive set of 50 samples from groundwater and surface water were analyzed by ICPMS and processed by spatial interpolation in a GIS environment. The results highlight a geochemical anomaly at the center of the densely inhabited area subject to a profusion of open dumps discharges. This anomaly with the highest spatial contents of Be(Cs, Rb, Mg) suggests an anthropogenic source that demarcates with the lowest alkali and alkaline-earth elements on the peripheral area of Dschang. Other findings include lithological constraints with volcanic rocks being the main source compared to granitoid.The study points out good correlations between Be, Cs, Rb and Mg spatial distributions and physicochemical parameters of waters(K, EC, TDS), and inversely with the lowest p H. p H is established as the most functioning physico-chemical constraint of alkali and alkaline-earth mobility in Dschang. The p H lowest values within the geochemical anomaly also highlight the impact of human activities on water acidity, which later enhance elements mobility and enrichment. Despite low elements contents relative to WHO standards, our findings point out an example of anthropogenic impact on water geochemistry linked to solid waste pollution; it also demonstrates significant anthropogenic changes of environmental physicochemical parameters of prime importance in the mobility and distribution of elements in the study area.Similar assessments should be extended in major towns in Cameroon. 相似文献
5.
Filho Hugo Carlos Scheuermann Martins Carlos Guilherme Menezes Ricardo José Wink Dornelles Lucas Eduardo Consoli Nilo Cesar 《Geotechnical and Geological Engineering》2021,39(7):5395-5404
Geotechnical and Geological Engineering - Dispersive soils are susceptible to phenomena of internal and external erosion when in contact with relatively pure water due to its particle’s... 相似文献
6.
Abandoned shorelines are an important archive used to constrain past fluctuations in the hydrological balance of lakes around the globe. Within Australia, the shorelines preserved at Lake George, NSW, form one of the few shoreline archives in the south-east of the continent that record palaeoenvironmental conditions throughout the late Quaternary. Here, we examined and tested the lake-level record for Lake George constructed in the 1970s by dating a well-preserved shoreline sequence at Luckdale, on the lake's eastern shore, using single-grain optically stimulated luminescence (OSL) dating. Ten stratigraphic units were identified, and these suggest a late Quaternary highstand for Lake George in MIS 3, with fluctuations superimposed upon an overall drying trend throughout MIS 2 and into the present. At Luckdale, the highest four shoreline-associated units were deposited ~13 to 19 m above lake base and date to between 39 ± 2 and 29 ± 1 ka ago. Our study pushes back the timing of maximum lake depth at Lake George to at least MIS 3, rather than MIS 2. The overall drying trend is supported by similar reductions in both Riverine Plain fluvial activity and other associated lake-level records from within the Murray basin. 相似文献
7.
Tracing variability of run‐off generation in mountainous permafrost of semi‐arid north‐eastern Mongolia 下载免费PDF全文
The headwaters of mountainous, discontinuous permafrost regions in north‐eastern Mongolia are important water resources for the semi‐arid country, but little is known about hydrological processes there. Run‐off generation on south‐facing slopes, which are devoid of permafrost, has so far been neglected and is totally unknown for areas that have been affected by recent forest fires. To fill this knowledge gap, the present study applied artificial tracers on a steppe‐vegetated south‐facing and on two north‐facing slopes, burned and unburned. Combined sprinkling and dye tracer experiments were used to visualize processes of infiltration and water fluxes in the unsaturated zone. On the unburned north‐facing slope, rapid and widespread infiltration through a wet organic layer was observed down to the permafrost. On the burned profile, rapid infiltration occurred through a combusted organic and underlying mineral layer. Stained water seeped out at the bottom of both profiles suggesting a general tendency to subsurface stormflow (SSF). Ongoing SSF could directly be studied 24 h after a high‐intensity rainfall event on a 55‐m hillslope section in the burned forest. Measurements of water temperature proved the role of the permafrost layer as a base horizon for SSF. Repeated tracer injections allowed direct insights into SSF dynamics: A first injection suggested rather slow dispersive subsurface flow paths; whereas 18 h later, a second injection traced a more preferential flow system with 20 times quicker flow velocities. We speculate that these pronounced SSF dynamics are limited to burned slopes where a thermally insulating organic layer is absent. On three south‐facing soil profiles, the applied tracer remained in the uppermost 5 cm of a silt‐rich mineral soil horizon. No signs of preferential infiltration could be found, which suggested reduced biological activity under a harsh, dry and cold climate. Instead, direct observations, distributed tracers and charcoal samples provided evidence for the occurrence of overland flow. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
8.
9.
Influence of flooding on groundwater flow in central Cambodia 总被引:2,自引:1,他引:1
Cambodia is affected by flooding from the Mekong, Tonle Sap and Bassac rivers every year, which harms human populations and
damages property, as well as alters the water quality in aquifer systems. The objective of this paper is to highlight the
effects of river flooding on groundwater flow using numerical simulation. A two-dimensional groundwater flow model coupled
with a groundwater recharge model was applied to the research area in central Cambodia. River level variation was included
in model processes, and flood areas and periods were assigned. The results showed that during flooding periods, floodwater
from the three rivers played an important role in recharging groundwater. During the dry season, Tonle Sap River received
groundwater supply from the northwest, and levels in the Bassac and Mekong River dropped to lower than the groundwater level.
This study improves understanding of the surface water and groundwater flow system in the study area. 相似文献
10.
C.A. Mériaux J.A. Mansour L.N. Moresi R.C. Kerr D.A. May 《Physics of the Earth and Planetary Interiors》2011,184(1-2):63-79
The rise of an initially horizontal, buoyant cylinder of fluid through a denser fluid at low Reynolds number is used to look at the ascent of strongly tilted mantle plumes through the mantle. Such ascents are characterized by (1) the growth of instabilities and (2) the development of a thermal wake downstream. Three-dimensional numerical experiments were carried out to examine these features. An hybrid particle-in-cell finite element method was used to look at the rise of non-diffusing cylinders and, a standard finite element method was used to look at the diffusing case. First the experiments show that the timescale of the fastest growing instability vary with the Rayleigh number and the viscosity ratio. In particular the growth rate decreases as the Rayleigh number decreases, in agreement with our analysis of the laboratory experiments of Kerr et al. (2008). Second the experiments show that the length of the thermal wake increases with the Rayleigh number but the change in viscosity has almost no influence on the wake length. Applied to strongly tilted mantle plumes we conclude that such plumes cannot be unstable given the plume timescales. We also discuss the application of this conclusion to weakly tilted plumes. Besides, this study allows to predict that mantle plumes are unlikely to have developed a significant thermal wake by the time they reach the surface. Finally, the resolution that is required to allow for the growth of mantle plume tails by combined diffusion and thermal entrainment is shown to represent a challenge for the large scale mantle convection simulations. 相似文献