Structural integrity of Ellisolandia elongata reefs: A mechanical approach to compare tensile strengths in natural and controlled environments

Geniculate coralline algae are oases of biodiversity, providing nursery areas and shelter for the species that live amongst their fronds. The key to their success in the inter‐tidal is the ability to withstand hydrodynamic forces. Under culturing conditions most of the physical and ecological stressors such as intense hydrodynamic forces and grazing are extremely reduced, thus affecting species mechanical properties and their response to external threats. The aim of the present study was to investigate tensile mechanical properties of clusters of fronds of Ellisolandia elongata from natural (sheltered and exposed reef) and culturing conditions (after 1 month of culturing). The tensile test showed that the first failure stress (σ_I) was not significantly different between the natural and culturing conditions, indicating that the two reefs (sheltered and exposed) were characterized by the same distribution of pre‐existing, inherent structural flaws. Interestingly, the σ_max (maximum stress before rupture) was significantly different between the two conditions, with the culturing condition being more resistant to average load compared to the natural conditions. The maximum stress before rupture (σ_max) showed the influence of the environment in reducing the strength and elasticity of the fronds.     

自然延伸概念及相关地质要素在海域划界中的影响效力分析

The United Nations Convention on the Law of the Sea entitled the coastal States to naturally extend the continental shelf, which has caused more drastic disputes of maritime delimitation. This paper devotes to clarifying the significant concept of natural prolongation through an effect method combing the legal principles and technical analysis. Firstly, the classic samples with respect of the development of geological features are traced. Based on these samples, the classification with a model is proposed in order to affirm the concept''s significance under certain geomorphologic situations. Lastly, scientific analysis is used to present two potential prolongation situations and emphasize that all the technical analysis on maritime delimitation should be complied with international law and protect the common interest of all the mankind.     

Experimental and theoretical methods on determination of stress-dependent natural frequency of marine sedimentary clay

Excited by the vibration sources in dynamic engineering, the natural frequency and damping factor of the saturated marine sedimentary clay are key dynamic parameters that influence the responses under cyclic loads. Experimental and theoretical methods are proposed in this paper to analyze the natural frequency and the stress-dependent nonlinearity. The experimental method shows that the natural frequency of soils with specific stress state subjected to large cyclic shear strain can be estimated from the data of dynamic triaxial tests based on the amplitude–frequency response curve. Trial and error by the criterion from the half-power bandwidth method is used to determine the optimal fitting. The results of a theoretical study on the free vibration of soil layers are then presented to derive the analytic solution of natural frequency. In addition to the two frequency-independent elements (a lumped mass matrix and a stiffness matrix), the system’s equivalent damping coefficient matrix is iteratively determined based upon the forced vibration experimentally. Finally, the impacts of the resonance phenomenon on the dynamic shear modulus and hysteretic loop are discussed.     

1730年夏季黄淮地区暴雨极端事件研究

1730年（清雍正八年）7—8月,我国黄淮地区连续暴雨17 d,引起黄河、大运河和淮河暴涨、决堤的大范围洪涝灾害。这是小冰期中相对温暖时段气候背景下的极端气候事件。本文依据历史文献记载复原了1730年夏季暴雨时段的天气实况,绘制了暴雨区域图显示强降雨中心移动动态和水灾地域分布图,概述当年气候特点,指出暴雨事件与台风活动的关联。1730年是太阳活动周极小年的前3年、有重大火山活动,是极强的厄尔尼诺事件后的第2年。这些天气特点和背景条件与现代罕见的1975年河南“75?8暴雨”相似。     

Finite‐element analysis of laminated rubber bearing of building frame under seismic excitation

Finite element analysis is carried out for a building frame supported by laminated rubber bearings to simultaneously investigate global displacement and local stress responses under seismic excitation. The frame members and the rubber bearings are discretized into hexahedral solid elements with more than 3 million degrees of freedom. The material property of rubber is represented by the Ogden model, and the frame is assumed to remain in elastic range. It is shown that the time histories of non‐uniform stress distribution and rocking behavior of the rubber bearings under a frame subjected to seismic excitation can be successfully evaluated, and detailed responses of base and frame can be evaluated through large‐scale finite element analysis. Copyright © 2015 John Wiley & Sons, Ltd.     

巨灾保险机制研究——新西兰、土耳其、美国加州、中国台湾、日本案例分析

分析总结了新西兰、土耳其、美国加州、中国台湾地区和日本等国家和地区地震保险制度的特点,依据分析提出:中国需要建立巨灾保险制度,政府要在其中承担主导性职责,同时,巨灾保险需要民营保险公司和政府的分工合作。     

Winkler弹性地基板梁的自由振动分析

中短型轨道板的几何构型介于梁、板之间,属于宽梁结构。从Mindlin板理论出发,退化得到适用于宽梁的Mindlin板梁控制方程;引入Winkler地基刚度系数,推导得到位移和转角的模态函数表达式。考虑两端简支的边界条件,得到弹性地基板梁的自由振动特征方程。通过无量纲数值算例求解出弹性地基板梁的自振频率,并与Timoshenko梁理论和Mindlin板理论进行对比。研究高跨比、泊松比和弹性地基刚度等参数对结构自振特性的影响,总结出弹性地基板梁方程的特点及适用范围,即宽度效应显著且泊松比较大的宽梁结构。     

青海木里三露天天然气水合物分布与储层特征

根据在青海木里三露天施工完成的14 口天然气水合物钻孔揭露的地质信息,从天然气水合物产出、赋存、空间展布3个方面介绍工作区天然气水合物基本特征。此外,文章还以岩性特征、空间展布、裂隙、岩石物性多元控制因素 间相互制约和促进的内在联系为桥梁建立了天然气水合物储层这一研究对象。从储层方面分析,受岩相的控制作用三露天天然气水合物在空间上的分布有一定的选择性、延展性和可追索性, 即其储层具有相对稳定性;三露天天然气水合物在储层内部的分布除了受有利储层产状变化限制外,还受到裂隙产状的控制,致使其在空间上分布既不规则、又往往突然消失或突然出现。     

青海木里三露天天然气水合物钻孔岩心构造裂隙特征

通过对三露天井田天然气水合物钻孔岩心观察与统计分析,从线密度、倾角、充填程度等方面对裂隙的特征进行讨论,明确研究区天然气水合物赋存类型以及构造裂隙的基本特征,最后讨论了裂隙对天然气水合物形成的作用。结果表明：井田内 天然气水合物绝大多数赋存于粉砂岩、暗色泥岩、油页岩中,其中62.5%赋存于构造裂隙中;研究区构造裂隙以低倾角(占50.37%)、未被充填裂隙为主(占73.68%),且水合物上覆地层裂隙 密度均不同程度减小。研究区裂隙的发育特征对天然气水合物成藏起到重要的作用：研究区73.68%的裂隙为未充填,为烃类气体的运移和聚集提供了空间;50.37%的裂隙为低倾角,垂直方 向上的渗透率值较小,不同层位的连通性差,极大地限制了烃类气体向上扩散,使其得以聚集保存;最后,裂隙发育程度的降低,同样抑制了烃类气体向上扩散,起到了相对“盖层”的作用 。     

鄂尔多斯盆地北部泊尔江海子断裂对上古生界天然气成藏的控制

为了揭示泊尔江海子断裂对鄂尔多斯盆地北部杭锦旗地区上古生界天然气成藏的控制作用,应用地震和钻井资料,在断裂活动性分析的基础上,根据断层泥比率和断层连通概率法对泊尔江海子断裂的侧向和垂向封闭性进行半定量评价,探讨断裂和天然气富集区的关系。结果表明：泊尔江海子断裂呈现3次明显的活动高峰期,分别为加里东期-早海西期的断裂形成期、印支期-早燕山期的挤压逆断裂活动期、中晚燕山期的走滑撕裂活动期,而中晚燕山期的走滑撕裂控制了上古生界天然气主要成藏期。断裂的封闭性具有“横向分段、纵向分层”的特点;横向上,以断层泥比率(SGR)等于0.3为界将泊尔江海子断裂分为侧向优势输导区和侧向封闭区;纵向上,在石千峰组和上石盒子组断裂启闭系数基本都小于1.0,断裂垂向封闭,在下石盒子组和山西组断裂启闭系数主要集中在4.0~10.0,断裂垂向开启。在断裂侧向优势输导区,断裂南部主力烃源区生成的天然气,经断裂发生垂向和侧向运移,易在断裂北部地区富集成藏;在侧向封闭区,则易在断裂南部地区富集成藏。