Bending localization of nitrous oxide under anharmonicity and Fermi coupling: the dynamical potential approach

This paper studies the vibrational nonlinear dynamics of nitrous oxide with Fermi coupling between the symmetric stretching and bending coordinates by classical dynamical potential approach. This is a global approach in the sense that the overall dynamics is evidenced by the classical nonlinear variables such as the fixed points and the focus are on a set of levels instead of individual ones. The dynamics of nitrous oxide is demonstrated to be not so much dependent on the excitation energy. Moreover, the localized bending mode is shown to be ubiquitous in all the energy range studied.     

Flow localization in fissure eruptions

 During a basaltic fissure eruption heat transfer from the hot magma to the surrounding rock causes a dramatic increase in the magmatic viscosity and solidification at the margins. Both viscosity contrast and solidification can amplify initial variations in the flow rate and lead to localization of the flow along the strike of the fissure. However, for typical parameters, amplification driven by solidification is slower and significantly weaker than amplification driven by viscosity variations. In fact, for the parameters examined, the amplification due to solidification is so weak that its effect is almost insignificant, whereas viscosity variation provides a strong active mechanism for flow localization. Laboratory experiments illustrate viscous localization and suggest that this mechanism is robust. The dependence of viscosity on temperature can cause a small change in the pressure of the magma chamber to lead to a large jump in the flow rate of magma through the fissure. Received: 13 March 1998 / Accepted: 27 September 1998     

考虑塑性应变率梯度的单轴压缩岩样轴向响应

基于剪切应变率梯度格式,采用解析方式研究了岩石材料在单轴压缩条件下的应变软化的结构响应。根据非局部连续介质模型,提出了一维二阶剪切应变率梯度格式。非局部剪切应变率与局部剪切应变率及其二阶梯度有关。将经典塑性理论中的局部剪切应变率替换为非局部剪切应变率,可以直接得到局部剪切应变率的封闭解析解,而不必通过将局部剪切应变对时间求导获得。通过对局部剪切应变率积分,得到了沿剪切带方向的相对剪切速度。试件峰值强度后的端部速度由弹性及塑性两部分构成。前一部分由虎克定律描述;后一部分与相对剪切速度有关。对弹性及塑性两部分速度求和,得到了单轴压缩岩样剪切破坏问题轴向响应的解析式。研究表明：试样高度越大、内部长度越小、剪切软化模量越大及泊松比越小,则岩样的轴向响应倾向于脆性。根据岩样与矿柱的相似性,岩样响应倾向于脆性,意味着矿柱将失去稳定性,发生矿柱岩爆。目前的基于剪切应变率梯度格式的主要优点是简洁。     

A phenomenological constitutive model for rocks with shear failure mode

In this paper, a phenomenological constitutive model is proposed to simulate the stress–strain behaviours of intact rocks with shear failure mode. The model captures a wide range of behaviours of rock material such as elastic, plastic, strain softening, ‘Class II’, strain localization, elastic modulus degradation, etc. The sensitivity of the stress–strain relation on the parameters is also investigated. Typical results obtained by testing a number of granite and marble specimens are used to validate the proposed model. Copyright © 2001 John Wiley & Sons, Ltd.     

A new approach to numerical simulation of source development of earthquake

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Identification of damage in reinforced concrete structures from earthquake records- optimal location of sensors

A method for the localization of structural damage in seismically excited reinforced concrete (RC) structures using a measured acceleration response time series is presented. From the measured response of some or all storeys, the two lowest smoothed eigenfrequencies and mode shape coordinates are estimated. These estimated values are used as an input to a developed substructure iteration method where local storey damages are estimated in such a way that these smoothed values are reproduced. The local damage indicator of a substructure is defined as the average reduction of the stiffness matrix of the initial undamaged substructure. The method is applied to simulated data of a six-storey, two-bay test frame (scale 1:5) that is to be tested at the Structural Laboratory of Aalborg University, Denmark. The simulations are performed using the non-linear finite element program SARCOF. Special emphasis is put on the investigation of the optimal location of measurement sensors, i.e. at which locations along the structure is the most information about the damage distribution gained. In all cases it is assumed that measurements are performed at top storey and ground surface, and the investigations are concentrated on putting one or two more measurement points in between. The two cases where the structure is excited in the first and second mode are investigated, and it is found that in general the sensors should be placed in the lower part of the structure. Furthermore, it is found that the method provides good results even when only the measurements at top storey and ground surface are used.     

Interactions between serpentinite devolatilization, metasomatism and strike-slip strain localization during deep-crustal shearing in the Eastern Alps

The Greiner shear zone in the Tauern Window, Eastern Alps, changes from a zone of distributed (dominantly sinistral) shear in supracrustal rocks to a series of narrow, gully forming dextral splays where it enters basement gneisses. Within these splays, granodiorite is transformed into quartz‐poor biotite and/or chlorite schists, reflecting hydration, removal of Si, Ca and Na, and concentration of Fe, Mg and Al. Stable isotope analyses show a prominent increase in δD and a decrease in δ¹⁸O from granodiorite into the shear zones. These changes indicate significant channelized flow of an externally derived, low‐δ¹⁸O, high‐δD fluid through the shear zones. The shear zone schists are chemically similar to blackwall zones developed around serpentinite bodies elsewhere in the Greiner zone and the stable isotope data support alteration via serpentinite‐derived fluid. Monazite in schist from one shear zone yields spot dates of 29–20 Ma, indicating that the fluid influx and switch from sinistral to dextral shear occurred at or shortly after the thermal peak of the Alpine orogeny (c. 30 Ma). We suggest that Alpine metamorphism of serpentinites released large amounts of high‐δD, low‐δ¹⁸O, Si‐undersaturated, Fe + Mg‐saturated fluids that became channelized along prior zones of weakness in the granodiorite. Infiltration of this fluid facilitated growth of chlorite and biotite, which in turn localized later dextral strain in the narrow splays via cleavage‐parallel slip. This dextral strain event can be linked to other structures that accommodated tectonic escape of major crustal blocks during dextral transpression in the Eastern Alps. This study shows that serpentinite devolatilization can play an important role in modifying both the chemistry and rheology of surrounding rocks during orogenesis.     

Seismic strain rates and distributed continental deformation in the northern Andes and three-dimensional seismotectonics of northwestern South America

Remote sensing and field studies of several extensional basins along the northern margin of the Gulf of Aden in Yemen show that Oligocene–Miocene syn-rift extension trends N20°E on average, in agreement with the E–W to N120°E strike of main rift-related normal faults, but oblique to the main trend of the Gulf (N70°E). These faults show a systematic reactivation under a 160°E extensional stress that we interpret also as syn-rift. The occurrence of these two successive phases of extension over more than 1000 km along the continental margin suggests a common origin linked to the rifting process. After discussing other possible mechanisms such as a change in plate motion, far-field effects of Arabia–Eurasia collision, and stress rotations in transfer zones, we present a working hypothesis that relates the 160°E extension to the westward propagation since about 20 Ma of the N70°E-trending, obliquely spreading, Gulf of Aden oceanic rift. The late 160°E extension, perpendicular to the direction of rift propagation, could result from crack-induced extension associated with the strain localization that characterises the rift-to-drift transition.     

环南海区域发展特征与一体化经济区建设前景

《区域全面经济伙伴关系协定》（RCEP）合作框架正催化全球经济版图格局发生剧烈演变,为应对“百年未有之大变局”,中国需要以“一带一路”倡议为契机,以环南海区域为战略基点,在深入研究区域发展特征的基础上,探讨建设“中国+东南亚”战略性一体化经济区的可能性并付诸实施。本文以环南海区域为重点,结合区域发展重点指标描述了其整体发展特征,利用产业结构相似度指数和贸易结构重合度指数,对环南海区域产业与对外贸易的结构性特征进行了剖析,并刻画了环南海区域核心增长区域的空间网络特征,最后讨论了环南海区域构建多元一体化经济区的前景并提出政策建议。结果表明：① 2000—2017年环南海区域主要发展指标增长态势强劲,发展速度和质量远超全球同期平均水平。② 在全球产业转移周期阶段与空间路径的双重驱动下,环南海区域形成了“澳新港—粤闽台文马—滇桂琼泰印菲越—缅老柬”四大梯级发展格局。③ 环南海区域11个国家间产业结构相似度指数和贸易结构重合度指数均处于较高水平,兼具“横向一体化”和“纵向梯级化”复合特征;产业结构与全球贸易商品结构呈现出“高端化”和“低端化”并举的态势。④ 环南海区域已经形成九大核心增长区域,增长极的极化与扩散效应使得不同区域之间的优势产业和出口商品类型呈现相似性和互补性。⑤ 展望未来,新一轮全球产业转移及其引致的全球价值链重组将构建起深度匹配地区资源禀赋特征的区域一体化生产—消费网络,而城市群、高速交通等空间实体所构建的“点—轴”空间网络和“内—外”开放合作政策平台也将更好保障一体化经济区的构建与发展。