高层钢框架-支撑结构二阶非线性随机地震响应分析

针对常用的高层钢框架－支撑结构，考虑材料非线性和几何非线性，建立了框架部分、支撑部分的二阶动力分析模型。用等效线性方法对结构进行非线性随机地震响应分析，结合工程算例，论述不同场地土、不同层数、不同支撑情况下，二阶效应对结构地震响应统计量的影响。     

Parameter identification for lined tunnels in a viscoplastic medium

This paper is dedicated to the identification of constitutive parameters of elasto‐viscoplastic constitutive law from measurements performed on deep underground cavities (typically tunnels). This inverse problem is solved by the minimization of a cost functional of least‐squares type. The exact gradient is computed by the direct differentiation method and the descent is done using the Levenberg–Marquardt algorithm. The method is presented for lined or unlined structures and is applied for an elastoviscoplastic constitutive law of the Perzyna class. Several identification problems are presented in one and two dimensions for different tunnel geometries. The used measurements have been obtained by a preliminary numerical simulation and perturbed with a white noise. The identified responses match the measurements. We also discuss the usage of the sensitivity analysis of the system, provided by the direct differentiation method, for the optimization of in situ monitoring. The sensitivity distribution in space and time assess the location of the measurements points as well as the time of observation needed for reliable identification. Copyright © 2002 John Wiley & Sons, Ltd.     

Exploration and Study on Deep Crust Structural Characteristics in the Jiashi-Artux Seismic Region

The data from two deep seismic sounding profiles was processed and studied comprehensively. The results show that crnst-mantle structures in the investigated region obviously display layered characteristics and velocity structures and tectonic features have larger distinction in different geological structure blocks. The boundary interface C between the upper and lower crust and Moho fluctuate greatly. The shallowest depths of C (30.0km) and Moho (45.5km) under Jiashi deepen sharply from Jiashi to the western Kunlun mountain areas, where the depths of C and Moho are 44.0km and 70.0km, respectively. The higher velocity structures in the Tarim massif determine its relatively “stable“ characteristics in crust tectonics. The phenomenon in the Jiashi region, where the distribution of earthquake foci mostly range from 20kin to 40kin in depth, may infer that the local uplift of C and Moho interface, anomalonsly lower velocity bodies and deep large faults control earthquake occurrence and seismogenic processes in the Jiashi strong earthquake swarm.     

System identification of linear structures based on Hilbert–Huang spectral analysis. Part 2: Complex modes

A method, based on the Hilbert–Huang spectral analysis, has been proposed by the authors to identify linear structures in which normal modes exist (i.e., real eigenvalues and eigenvectors). Frequently, all the eigenvalues and eigenvectors of linear structures are complex. In this paper, the method is extended further to identify general linear structures with complex modes using the free vibration response data polluted by noise. Measured response signals are first decomposed into modal responses using the method of Empirical Mode Decomposition with intermittency criteria. Each modal response contains the contribution of a complex conjugate pair of modes with a unique frequency and a damping ratio. Then, each modal response is decomposed in the frequency–time domain to yield instantaneous phase angle and amplitude using the Hilbert transform. Based on a single measurement of the impulse response time history at one appropriate location, the complex eigenvalues of the linear structure can be identified using a simple analysis procedure. When the response time histories are measured at all locations, the proposed methodology is capable of identifying the complex mode shapes as well as the mass, damping and stiffness matrices of the structure. The effectiveness and accuracy of the method presented are illustrated through numerical simulations. It is demonstrated that dynamic characteristics of linear structures with complex modes can be identified effectively using the proposed method. Copyright © 2003 John Wiley & Sons, Ltd.     

The dynamic characteristics and migration of a pyramid dune

The results of wind tunnel experiments and field observations show that when the intersection angle between airflow direction and dune crest (ridge) line is > 30°, a reverse vortex is formed. Because of the convergence of sand streams from the windward and lee slopes at the crest, sand accumulates in the crestal region, causing vertical growth. Nevertheless, studies also show that the common asymmetry of the two slopes of a dune may significantly influence the evolution of arms of a pyramid dune. The migration rates of pyramid dunes are mediated by the interplay of their arms moving transversely and the vertical growth in response to the variations in wind regimes. Comparing the effects of airflow transverse to a given arm with longitudinal airflow, it is indicated that the transverse airflow is more significant in controlling the arms of pyramid dunes. The whole body of the studied pyramid dune, particularly the upper quarter section, migrated SE direction during the monitoring period. The patterns of wind erosion and deposition change alternately with seasonal variations in wind directions. The W, NE and SE sides undergo constant erosion, deposition and both erosion and deposition, respectively. The results of long-term monitoring of a pyramid dune show that southerly winds, resulting from a local circulation, markedly affect the transverse migration of the whole pyramid dune.     

山东省鄄城陨石中的金属矿物及组构特征

1997年降落在山东省鄄城县的陨石雨,是橄榄石-古铜辉石球粒陨石。该陨石中的金属矿物主要为铁纹石和陨硫铁,其次为镍纹石,金属矿物呈填隙状分布于以橄榄石和古铜辉石为主的硅酸盐矿物粒间及球粒周围。陨石中可见由铁纹石和镍纹石组成的显微蠕虫状连晶,是陨石中金属矿物在降温冷却过程中发生固溶体分离作用而成。陨石中金属矿物的分布特征表明,金属Fe-Ni和硫化物（FeS）应该是星云凝聚不同阶段的产物。陨石中金属矿物的成分和组构特征及陨石中出现的球粒结构、橄榄石的炉条结构等特征表明,该球粒陨石是星云物质快速冷却的产物。     

危机矿山接替资源勘查实践——以安庆铜矿为例

总结了国家危机矿山接替资源勘查项目在安庆铜矿的工作实践,强调了接替资源勘查的重要性和科学性。简介了在现有矿山范围找矿勘查工作的一般原则和方法步骤,并取得了初步勘查成果。     

新疆博格达山分段及深浅构造转换关系

研究表明 ,天山及邻区自中生代以来一直处于热衰减状态 ,博格达山新生代再造山具有“冷隆升”性 ,盆山边界断裂多限于上地壳内 ,而非直通中地壳低速体甚至上地幔的“深大断裂”。造山带内的韧性剪切带是在古生代形成的 ,而不是再造山期的断裂 ,它对造山带隆升及盆山耦合无贡献 ,博格达山的隆升为复式背斜构造所支持。博格达山与准东的关系为背斜北翼与盆地平缓基底构成的挠曲构造 ,而不是被深大断裂分隔的断块。博格达山具有独特鲜明的分段性 ,造山带的两个弧形构造与新生代再生前陆盆地构成独特的“斜方对称”分布样式。以板条观点为指导 ,从盆山单元的平面配置关系和深浅构造转换关系入手 ,探讨了博格达山板内造山阶段的几何学和运动学分段性的成因 ,构建了盆山耦合模式     

橄榄岩中尖晶石的氧同位素继承性与晶体结构转变

根据激光探针分析含尖晶石橄榄石中矿物的氧同位素组成,反应增量法计算矿物对氧同位素分馏曲线,得到正尖晶石－矿物对氧同位素温度高于含尖晶石橄榄岩的相平衡温度,而用反尖晶石－矿物的对计算的氧同位素温度则很接近含尖晶石橄榄岩的相平衡温度,较为合理,因此地幔橄榄岩中镁铝尖晶石的氧同位素组成继承了其母体反尖晶石特征,即与橄榄石,单斜辉石和斜方辉石平衡的是反结构尖晶石,在其发生相变作用变成正结构尖晶石时未发生氧