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DAN MATSUMOTO HAJIME NARUSE SHIGEHIRO FUJINO APICHART SURPHAWAJRUKSAKUL THANAWAT JARUPONGSAKUL NORIHIKO SAKAKURA MASAFUMI MURAYAMA 《Sedimentology》2008,55(6):1559-1570
This study reveals the three‐dimensional morphology and syn‐sedimentary formation processes of a deformation structure termed ‘truncated flame structures’ which is found in a terrestrial tsunami deposit in southern Thailand that formed during the 2004 Indian Ocean Tsunami. The structure was found at the boundary between a lower fine‐grained layer and an upper coarse‐grained layer that are related to two runup events. In order to confirm the morphology of the structure, the authors excavated two trenches and an opencast pit. When viewed in a cross‐section oriented parallel to the direction of the runup current, the deformed boundary has an irregularly bulging profile, similar to that observed in flame structures. The protruding structures are inclined towards the downstream direction of the runup current, and are truncated horizontally along their upper surface by parallel laminations in the overlying layer. When viewed in a cross‐section oriented perpendicular to the current direction, it appears that parts of the upper layer descend into the lower layer as lobate masses. In places, these masses are completely detached from the main part of the upper layer, forming circular or elliptical shapes. The contact between the lower layer and the main part of the upper layer is a planar truncation surface. Opencast excavation of the contact surface revealed that the deformed structures have flat, sinuous horseshoe crests that open in a downstream direction. It is possible for the runup current to generate shear stress such that it deforms the boundary into a truncated flame structure. Moreover, the observations made in this study indicate the syn‐sedimentary development of the structure: deformation and truncation occurred simultaneously in association with the runup current that formed the upper layer. Truncated flame structures can be used as a criterion in identifying the syn‐sedimentary deformation of substrate: the structures are indicative of unidirectional flow with sufficiently high shear velocity to deform unconsolidated substrate. As in the present case, the truncated flame structures may be characteristic of tsunami events that involve strong unidirectional currents on land due to the extraordinarily long wave period of tsunamis, rather than other events such as storm surges or flooding. 相似文献
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This paper proposes the Linear-Saturation (LS) control as a new and suitable control algorithm for buildings with an Active Mass Damper (AMD) system. It takes into account the physical constraints on the AMD system and uncertainties in the loading. The LS control consists of a low-gain linear control when the system is close to the zero state and bang-bang control otherwise. This paper provides a precise formulation of the saturation control and presents optimal solutions which can be implemented in the state space. A numerical scheme to synthesize the switching surface which is needed to implement the bang-bang control is developed. Furthermore, a method to demarcate the region for linear control is proposed. The effectiveness of the LS control is verified through numerical simulations with one- and multi-storey buildings subjected to earthquakes. It is shown that the LS control provides better performance compared to even the gain-scheduled LQ control. 相似文献
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