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Keywords = fine-grained river ice

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28 pages, 12085 KiB  
Article
Reconstructing the Fluvial History of the Lilas River (Euboea Island, Central West Aegean Sea) from the Mycenaean Times to the Ottoman Period
by Matthieu Ghilardi, Tim Kinnaird, Katerina Kouli, Andrew Bicket, Yannick Crest, François Demory, Doriane Delanghe, Sylvian Fachard and David Sanderson
Geosciences 2022, 12(5), 204; https://doi.org/10.3390/geosciences12050204 - 11 May 2022
Cited by 4 | Viewed by 4554
Abstract
This paper aims to reconstruct the alluvial activity for the Lilas river, the second-largest catchment of Euboea Island (Central Western Aegean Sea), for approximately the last three and a half millennia. The middle reaches (Gides basin) exhibit several historical alluvial terraces that were [...] Read more.
This paper aims to reconstruct the alluvial activity for the Lilas river, the second-largest catchment of Euboea Island (Central Western Aegean Sea), for approximately the last three and a half millennia. The middle reaches (Gides basin) exhibit several historical alluvial terraces that were first recognised in the 1980s but have remained poorly studied, resulting in uncertain chronological control of palaeofluvial activity. In order to reconstruct the past fluvial dynamics of the Lilas river, a ca. 2.5 m thick stratigraphic profile has been investigated for granulometry and magnetic parameters. Absolute dating of the sediments was possible by applying Optically Stimulated Luminescence (OSL). The results reveal: (i) two coarse-grained aggradational episodes dated from the Mycenaean/Early Iron Age and the Roman periods, respectively, (ii) a phase of rapid fine-grained vertical accretion corresponding to the Late Byzantine to early Venetian periods, (iii) potential evidence for final alluvial deposition from the Little Ice Age/Ottoman period, and (iv) two major incision episodes inferred from Ancient Greek times and most of the Byzantine period. Based on the published core material, the paper also evaluates the direct impacts of the Late Holocene alluviation recorded mid-stream on the fluvial system situated downstream in the deltaic area. Sediment sourcing is attempted based on the magnetic properties of the catchment lithology and of alluvium collected upstream along the main stream bed. Finally, the present paper discusses the possible links between Late Holocene hydroclimatic oscillations and the aggradational/incision phases revealed in the Gides basin. Correlations are attempted with regional palaeoclimate records obtained for the Aegean. In addition to climatic variability, anthropogenic factors are considered: specific land use for agricultural purposes, in particular during the Mycenaean period, the Roman and the Late Byzantine/Early Venetian periods, might have enhanced sediment deposition. Archaeological information and pollen records were also evaluated to reconstruct regional land-use patterns and possible impacts on soil accumulation over the last 3.5 millennia. Full article
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17 pages, 6801 KiB  
Article
ICENETv2: A Fine-Grained River Ice Semantic Segmentation Network Based on UAV Images
by Xiuwei Zhang, Yang Zhou, Jiaojiao Jin, Yafei Wang, Minhao Fan, Ning Wang and Yanning Zhang
Remote Sens. 2021, 13(4), 633; https://doi.org/10.3390/rs13040633 - 10 Feb 2021
Cited by 23 | Viewed by 3396
Abstract
Accurate ice segmentation is one of the most crucial techniques for intelligent ice monitoring. Compared with ice segmentation, it can provide more information for ice situation analysis, change trend prediction, and so on. Therefore, the study of ice segmentation has important practical significance. [...] Read more.
Accurate ice segmentation is one of the most crucial techniques for intelligent ice monitoring. Compared with ice segmentation, it can provide more information for ice situation analysis, change trend prediction, and so on. Therefore, the study of ice segmentation has important practical significance. In this study, we focused on fine-grained river ice segmentation using unmanned aerial vehicle (UAV) images. This has the following difficulties: (1) The scale of river ice varies greatly in different images and even in the same image; (2) the same kind of river ice differs greatly in color, shape, texture, size, and so on; and (3) the appearances of different kinds of river ice sometimes appear similar due to the complex formation and change procedure. Therefore, to perform this study, the NWPU_YRCC2 dataset was built, in which all UAV images were collected in the Ningxia–Inner Mongolia reach of the Yellow River. Then, a novel semantic segmentation method based on deep convolution neural network, named ICENETv2, is proposed. To achieve multiscale accurate prediction, we design a multilevel features fusion framework, in which multi-scale high-level semantic features and lower-level finer features are effectively fused. Additionally, a dual attention module is adopted to highlight distinguishable characteristics, and a learnable up-sampling strategy is further used to improve the segmentation accuracy of the details. Experiments show that ICENETv2 achieves the state-of-the-art on the NWPU_YRCC2 dataset. Finally, our ICENETv2 is also applied to solve a realistic problem, calculating drift ice cover density, which is one of the most important factors to predict the freeze-up data of the river. The results demonstrate that the performance of ICENETv2 meets the actual application demand. Full article
(This article belongs to the Special Issue Computer Vision and Deep Learning for Remote Sensing Applications)
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16 pages, 3208 KiB  
Article
Analysis of the Physical Properties of Hydrate Sediments Recovered from the Pearl River Mouth Basin in the South China Sea: Preliminary Investigation for Gas Hydrate Exploitation
by Bin Wang, Peng Huo, Tingting Luo, Zhen Fan, Fanglan Liu, Bo Xiao, Mingjun Yang, Jiafei Zhao and Yongchen Song
Energies 2017, 10(4), 531; https://doi.org/10.3390/en10040531 - 13 Apr 2017
Cited by 44 | Viewed by 5073
Abstract
Laboratory based research on the physical properties of gas hydrate hosting sediment matrix was carried out on the non-pressurized hydrate-bearing sediment samples from the Chinese Guangzhou Marine Geological Survey 2 (GMGS2) drilling expedition in the Pearl River Mouth (PRM) basin. Measurements of index [...] Read more.
Laboratory based research on the physical properties of gas hydrate hosting sediment matrix was carried out on the non-pressurized hydrate-bearing sediment samples from the Chinese Guangzhou Marine Geological Survey 2 (GMGS2) drilling expedition in the Pearl River Mouth (PRM) basin. Measurements of index properties, surface characteristics, and thermal and mechanical properties were performed on ten sediment cores. The grains were very fine with a mean grain size ranging from 7 to 11 μm throughout all intervals, which provide guidance for the option of a screen system. Based on X-ray Computed Tomography (CT) and SEM images, bioclasts, which could promote hydrate formation, were not found in the PRM basin. However, the flaky clay might be conducive to hydrate formation in pore spaces. The measured sediment thermal conductivities are relatively low compared to those measured at other mines, ranging from 1.3 to 1.45 W/(m·K). This suggests that thermal stimulation may not be a good option for gas production from hydrate-bearing sediments in the PRM basin, and depressurization could exacerbate the problems of gas hydrate reformation and/or ice generation. Therefore, the heat transfer problem needs to be considered when exploiting the natural gas hydrate resource within these areas. In addition, the results of testing the mechanical property indicate the stability of hydrate-bearing sediments decreases with hydrate dissociation, suggesting that a holistic approach should be considered when establishing a drilling platform. Both the heat-transfer characteristic and mechanical property provide the foundation for the establishment of a safe and efficient production technology for utilizing the hydrate resource. Full article
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