A study of transient responses of a submerged spherical shell under shock waves

Based on a procedure which couples the finite element method with the doubly asymptotic approximation, this work addresses the problem of the transient responses of a submerged spherical shell subjected to strong, plane, incident shock waves, in which elastoplastic material behavior is considered. Simulation results indicate that the procedure adopted shows good agreement with related literature, which considered linear elastic behavior of the shell. Also presented herein are the time histories of surface pressure, radial velocity and von Mises stress of the shell. Moreover, deformation diagrams and spreading of the plastic zone of the shell are described as well.     

The free vibration analysis of submerged cantilever plates

Based on empirical added mass formulation, this work presents a simple procedure to determine the vibration frequencies and mode shapes of submerged cantilever plates. Once the added mass formulation is derived, the procedure can be used to analyze free vibration response easily. An analytical and numerical study is also performed for the vibrations of cantilever plates in air and in water, with these results compared with experimental and numerical data from pertinent literature. Besides, the frequency parameters of the submerged plate for various aspect ratios and thickness ratios are given in design data sheet form and are appropriate for engineering design applications.     

Transient dynamic response of submerged sphere shell with an opening subjected to underwater explosion

This investigation applies the time domain FEM/DAA coupling procedure to predict the transient dynamic response of submerged sphere shell with an opening subjected to underwater explosions. The elastic–plastic material behavior of the transient fluid–structure interaction relate to structural response equation also presented herein. This analysis also examines the transient responses of structures to different charge distances. The effects of standoff distance on pressure time history of the shell to underwater explosion (3001b TNT) are presented. Additionally, the transient dynamic responses to underwater explosion shockwaves in the sea and the air are compared.     

Correction to: The catastrophic landside in Maoxian County,Sichuan, SW China,on June 24, 2017

Natural Hazards - Due to an oversight, four references were cited incorrectly in the reference list of the original publication as well as in the text of the publication. The first names were used...     

A micromechanics-based elasto-plastic model for granular media combined with Cosserat continuum theory

Acta Geotechnica - This paper is devoted to the micromechanical model of granular materials based on the Cosserat continuum theory. The generalised stress–strain relationships of a...     

基于控制区间牵引算法的地下施工变形预测

变形是地下结构施工安全状态的重要评价指标。针对数据驱动变形预测方法中地下施工动态影响因素难以量化这一问题,提出了基于控制区间牵引算法的地下施工变形预测模型。以双向长短时记忆网络（Bi-LSTM）对变形监测时间序列进行预测,以数值模拟在关键施工阶段处的结果为牵引点。根据实测值随阶段更新牵引点,并基于注意力机制双向长短时记忆网络（Bi-LSTM-AM）以牵引点修正数据驱动模型在控制区间的预测结果,实现更准确、更智能的地下施工变形预测。设置牵引相对权重,使模型可自适应判断当前合理牵引程度,准确融合了Bi-LSTM与数值模拟的结果。通过相关历史案例与数据,验证了牵引预测模型的有效性。依托西安市西咸新区丰镐三路地下通道上跨地铁1号线自动化监测实例,采用牵引算法预测了地下结构变形。结果表明：在关键施工阶段处,牵引作用改善了数据驱动预测方法存在的滞后问题,各阶段误差平均降低了24.34%;不断优化的牵引点逐渐趋近真值,降低了数值模拟出现偏差时造成的影响。该方法可为地下施工变形预测问题提供新途径。     

Energy dissimilation characteristics and shock mechanism of coal-rock mass induced in steeply-inclined mining: comparison based on physical simulation and numerical calculation

Acta Geotechnica - In recent years, as the Urumqi mining area deepens, rockbursts induced by the instability of the coal-rock mass are becoming more serious in steeply-inclined coal seam mining....     

卫星定位导航系统在地震应急救援中的应用

在对地震灾害特点综合分析的基础上,分析了地震应急响应与救援决策中的关键性问题。认为震害的规模、程度、空间分布和灾情发展趋势,以及快速获取灾情信息已成为整个地震应急响应和救援决策的关键;而对灾情空间分布及其不同灾情程度位置的确定是救援决策的先导与重要环节。卫星定位导航技术在地震应急搜救的信息快速获取、应急响应、救援决策、指挥、搜索与营救等救援行动的整个过程中,都将发挥其强大的功能。建议研发中国北斗灾害应急救援导航与指挥决策系统,包括地震灾情快速获取、快速判定和决策定位导航技术系统、地震救援指挥调度技术系统和应急救援物流定位导航技术系统建设;研发北斗灾害应急救援导航装备,包括自主定位导航幸存者搜索和营救设备研发和国内外巨灾救援专用定位与导航系统研发。     

Size variation of the end Permian conodont <Emphasis Type="Italic">Neogondolella</Emphasis> at Meishan Section,Changxing, Zhejiang and its significance

This study is based on both a generic and species level investigation of the individual size of the latest Permian conodont Neogondolella Pa elements collected from Meishan Section A, Changxing, Zhejiang Province. In this study, an obvious size reduction of Neogondolella Pa elements within bed 24e of the upper Changxing Limestone is recognized. The size variation of the Neogondolella occurs simultaneously with some important events including the negative shift of δ ¹³C, change in the ratio of the abundance of cyanobacterial biomarkers versus that of other general bacterial biomarkers and the shallowing of the sea water. Through the investigation of the paleoenvironmental changes and the analysis of the paleoecology of the conodont genus Neogondolella, the authors propose that the major factors for the size reduction of species of the conodont genus Neogondolella are food shortages caused by the mass extinction, the shallowing of the sea water as well as the increase in opacity of the sea water during the end Permian. The same phenomenon of Neogondolella size reduction is also observed in preliminary research from the same horizon at Shangsi Section, Sichuan Province. All the evidence suggests that there was a mass extinction that occurred at the horizon of bed 24e, and the evidence supports the viewpoint of a multi-phase mass extinction during the Permian and Triassic transition in South China.