This letter presents seafloor classification study results of a hybrid artificial neural network architecture known as learning vector quantization. Single beam echo-sounding backscatter waveform data from three different seafloors of the western continental shelf of India are utilized. In this letter, an analysis is presented to establish the hybrid network as an efficient alternative for real-time seafloor classification of the acoustic backscatter data. 相似文献
The Vilarelho da Raia-Chaves region, located in northern Portugal adjacent to the Spanish border, is characterized by both
hot and cold CO2-rich mineral waters issuing from springs and drilled wells. The present paper updates the conceptual circulation model of
the Vilarelho da Raia cold CO2-rich mineral waters. Vilarelho da Raia mineral waters, dominated by Na and HCO3 ions, have formed mainly by interaction with CO2 of deep-seated mantle origin. The δ18O, δ2H and 3H values indicate that these waters are the result of meteoric waters infiltrating into Larouco Mountain, NW of Vilarelho
da Raia, circulating at shallow depths in granitic rocks and moving into Vilarelho da Raia area. The conceptual geochemical
and geophysical circulation model indicates that the hot and cold CO2-rich mineral waters of Chaves (76 °C) and Vilarelho da Raia (17 °C) should be considered manifestations of similar but not
the same geohydrological systems.
Electronic Publication 相似文献
Dynamic aspects of the long runout Ontake-san debris avalanche are evaluated by a comparison of several models. An unsteady numerical model assumes two-dimensional flow of an incompressible biviscous or Newtonian fluid, represented as a continuum with a free surface. Internal deformation of the flowing mass is considered, as well as boundary resistances. Thus flow thinning and deposit shape as well as flow kinematics may be modeled. Parameters are adjusted to match observed runout, with additional constraints on velocity and emplacement time. With abundant constraints for Ontake-san, from careful field investigations by Japanese research teams, our analysis indicates that a substantial decrease in flow resistance occurred as a function of displacement. Constant-property models that match runout tend to overestimate the peak velocities and to underestimate the emplacement times. A staged increase in mobility in both constant volume and variable volume models leads to results consistent with field data. Runout in a channel overflow area was also modeled. Qualitatively similar results have been obtained by other researchers using simple sliding block models with empirical parameters, a slide block model with rational parameter selection, a modified flood simulation, and a multi-element frictional slide model. The relative merits of these models are compared.
The field mechanisms associated with this mobility increase with displacement are poorly understood, but the question is now identified as a target for future research at debris avalanche sites, and some plausible mechanisms are considered. The main reason probably involves the entrainment of river water and saturated sediment, leading to enhanced efficiency of fluid pressure mechanisms with undrained shear; in addition, progressive shearing reduced the mean particle size and angularity, and the cohesion and friction (and apparent viscosity) of avalanche debris near the wetted perimeter. Hydroplaning — the shearing of water films and slurries — may have occurred locally. 相似文献
Flow-type landslides are an important hazard that can cause great destruction due to the rapid flow velocity and large disaster area. This paper presents a catastrophic flowslide that recently occurred at a landfill in Shenzhen, China. This disaster involved an area about 1100 m in length and 630 m in maximum width, and caused the death of 77 people and the destruction of 33 buildings. The precise reason for the landfill’s failure is still unknown, and therefore we try to contribute an increased understanding of the event for future prevention. In this study, the failure mechanism of the studied slope was analyzed and described under partially saturated condition. The solid–fluid transition during the flowslide occurrence was described using a unified constitutive model. The model was used to perform the hydro-elasto-plastic modeling in the pre-failure stage, the viscous modeling in the post-failure stage, and the second-order work criterion was introduced in between to model the solid–fluid transition. The consistent evolution of the flowslide, including initiation, propagation, and deposit stages, was simulated and analyzed using the finite element method with Lagrangian integration points after careful calibration of the viscous parameters. The numerical results were compared with the real case and used to explain the failure mechanism. 相似文献
Physical modelling of cracked/fractured media using downscaled laboratory experiments has been used with great success as a useful alternative for understanding the effect of anisotropy in the hydrocarbon reservoir characterization and in the crustal and mantle seismology. The main goal of this work was to experimentally verify the predictions of effective elastic parameters in anisotropic cracked media by Hudson and Eshelby–Cheng's effective medium models. For this purpose, we carried out ultrasonic measurements on synthetic anisotropic samples with low crack densities and different aspect ratios. Twelve samples were prepared with two different crack densities, 5% and 8%. Three samples for each crack density presented cracks with only one crack aspect ratio, whereas other three samples for each crack density presented cracks with three different aspect ratios in their composition. It results in samples with aspect ratio values varying from 0.13 to 0.26. All the cracked samples were simulated by penny‐shaped rubber inclusions in a homogeneous isotropic matrix made with epoxy resin. Moreover, an isotropic sample for reference was constructed with epoxy resin only. Regarding velocity predictions performed by the theoretical models, Eshelby–Cheng shows a better fit when compared with the experimental results for samples with single and mix crack aspect ratio (for both crack densities). From velocity values, our comparisons were also performed in terms of the ε, γ, and δ parameters (Thomsen parameters). The results show that Eshelby–Cheng effective medium model fits better with the measurements of ε and γ parameters for crack samples with only one type of crack aspect ratio. 相似文献