Generalized dynamic analysis of structural single rocking walls (SRWs)

The investigation of structural single rocking walls (SRWs) continues to gain interest as they produce self-centering lateral load responses with reduced structural damage. The simple rocking model with modifications has been shown to capture these responses accurately if the SRW and its underlying base are infinitely rigid. This paper advances previous rocking models by accounting for (1) the inelastic actions at or near the base of the SRW and (2) the flexural responses within the wall. Included in the proposed advancements are hysteretic and inherent viscous damping associated with these two deformation components so that the total dynamic responses of SRWs can be captured with good accuracy. A system of nonlinear equations of motion is developed, in which the rocking base is discretized into fibers using a zero-length element to locate the associated compressive deformations and damage. The flexural deformations of the rocking body are captured using an elastic term, while the impact events are modeled using impulse-momentum equations. Comparisons with experiments of structural precast concrete and masonry SRWs show that the proposed approach accurately estimates the dynamic responses of different SRWs with and without unbonded posttensioning, for various dynamic excitations and degrees of hysteretic action. Using the proposed approach, a numerical investigation employs different configurations of structural SRWs to quantify the various sources of energy loss, including hysteretic action and impact damping, during various horizontal ground motions.     

内蒙古中部深成侵入岩谱系单位及构造岩浆活动初探──以苏尼特左旗等8幅1：5万区域地质调查为例

摘要：内蒙古苏尼特左旗地区大面积出露各地质时代的深成侵入体,它们的详细划分和归并对探讨整个内蒙古中部地区的地质发展史具有重要的意义。本文在简单描述各种侵入岩的地质特征、岩石化学特征和稀土元素地球化学特征的基础上,将它们归并为６个超单元和３个独立侵入体,并进一步探讨了它们的演化特征和形成环境。首次从岩石学的角度探讨了区域构造岩浆活动史。同时,简要报道了在该区首次发现的碱性花岗岩、Ｓ型花岗岩和堆晶角闪辉长岩。     

Empirical model for estimating Fourier amplitude spectra of ground acceleration in Taiwan region

A collection of ground‐motion recordings (1070 acceleration records) of moderate (5.1⩽M_L⩽6.5) earthquakes obtained during the execution of the Taiwan Strong Motion Instrumentation Program (TSMIP) since 1991 was used to study source scaling model and attenuation relations for a wide range of earthquake magnitudes and distances and to verify the models developed recently for the Taiwan region. The results of the analysis reveal that the acceleration spectra of the most significant part of the records, starting from S‐wave arrival, can be modelled accurately using the Brune's ω‐squared source model with magnitude‐dependent stress parameter Δσ, that should be determined using the recently proposed regional relationships between magnitude (M_L) and seismic moment (M₀) and between M₀ and Δσ. The anelastic attenuation Q of spectral amplitudes with distance may be described as Q=225 ƒ^1.1 both for deep (depth more than 35 km) and shallow earthquakes. The source scaling and attenuation models allow a satisfactory prediction of the peak ground acceleration for magnitudes 5.1⩽M⩽6.5 and distances up to about 200 km in the Taiwan region, and may be useful for seismic hazard assessment. Copyright © 2000 John Wiley & Sons, Ltd.     

荧光光谱向量空间距离模式识别法鉴别海面溢油源

采用向量空间距离模式识别法鉴别海面溢油源,研究出4个激发波长和4个发射波长用作数据处理的信息点.对未风化的和风化过的原油,燃料油和润滑油数据进行了研究.并采集了十多条船上的油品验证了方法的可靠性.给出了实验条件下的最小向量空间距离,建立了荧光光谱鉴别海面溢油源的新技术.     

利用高分辨率水体反射地震资料研究吕宋海峡以东黑潮区混合

混合过程是海洋中普遍存在的一种形式, 对气候变化、物质分布等起到了重要作用。地震海洋学是近十多年发展起来的一门新兴学科, 被广泛应用到物理海洋学问题的研究中, 具有高空间分辨率的突出优点。文章利用反射地震资料, 通过斜率谱方法, 分别获得了吕宋海峡以东黑潮区湍流段与内波段的耗散率及扩散率。结果显示, 在剖面深度200~800m的平均耗散率为10 ^-7.0W·kg ^-1, 平均扩散率为10 ^-3.3m ²·s ^-1, 比大洋统计均值10 ^-5.0m ²·s ^-1高约1~2个量级, 与前人在吕宋海峡的观测结果相一致。湍流段和内波段的扩散率空间分布差异较大: 湍流段扩散率高值区对应强流区域, 推测这里是中尺度涡边缘, 其次中尺度不稳定过程引起扰动增强, 进而引起湍流混合的加强; 内波段扩散率高值区出现在吕宋岛弧附近, 推测是内波遇到岛弧地形发生破碎, 进而引起强的内波混合。     

川南大村区块五峰—龙马溪组页岩气成藏条件及勘探前景

近年来,深海大洋钻探已证实在洋陆俯冲带的浅部,板块边界断裂高度集中在特征性岩层中,然而对于这种断裂高度集中化现象是否发生在俯冲带深部仍然缺乏充分的认识,因此对日本中部侏罗纪燧石-碎屑岩杂岩体中一个露头宽度约50 m的断裂带进行了调查。该断裂带沿古俯冲带深部的板块边界延伸而出的逆冲断层发育,断裂带中的剪切变形集中在数层黑色有机质黏土岩中,表现为沿交织鳞片状叶理的分散剪切,剪切方向分为左行走滑和逆冲走滑,可能形成于俯冲带中的滑动分异或左行斜俯冲过程。体现滑动集中化的拆离面切割了黑色有机质黏土岩层,拆离面表现为左行滑动。利用碳物质拉曼光谱测量了拆离面上及黑色有机质黏土岩层中的碳物质。结果表明,相对于黑色有机质黏土岩,拆离面中的碳物质具有更高的成熟度,表明在左行滑动过程中产生了快速的摩擦升温。野外观测和实验结果表明,这一古断裂带记录的俯冲带深部板块边界断裂高度集中在黑色有机质黏土岩层中,发育于其中的拆离面的左行剪切可能产生于深部地震性滑动。     

Modeling of rocking frames under seismic loading

A novel modeling approach for the seismic response assessment of rocking frames is presented. Rocking frames are systems with columns that are allowed to fully, or partially, uplift. Despite the apparent lack of a mechanism to resist lateral forces, they have a remarkable capacity against earthquake loading. Rocking frames are found in old structures, for example, ancient monuments, but it is also a promising design concept for modern structures such as bridges or buildings. The proposed modeling can be implemented in a general-purpose structural analysis software, avoiding the difficulties that come with the need of formulating and solving specifically tailored differential equations, or the use of detailed computational models. Different configurations of a rocking portal frame problem are examined. The model is based on rigid, or flexible, beam elements that describe the members of the frame. Negative-stiffness rotational springs are smartly positioned at the rocking interfaces in order to simulate the rocking restoring moment, while the mass and the rotational moment of inertia are considered either lumped or distributed. Both the cases of rigid and flexible piers/columns are discussed, while it is shown that frames with restrained columns can be considered in a straightforward manner. A simple alternative based on an equivalent oscillator that follows the generalized rocking equation of motion is also investigated. The efficiency and the accuracy of the proposed modeling is demonstrated with the aid of carefully chosen case studies.     

Monte carlo simulation of in situ gamma-spectra recorded by NaI (Tl) detector in the marine environment

To develop a Na I(Tl) detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Carlo N-Particle( MNCP) code were performed to provide the response spectra of some interested radionuclides and the background spectra originating from the natural radionuclides in seawater recorded by a Na I(Tl) detector. A newly developed 75 mm × 75 mm Na I(Tl) detector was calibrated using four reference radioactive sources 137 Cs, 60 Co, 40 K and 54 Mn in the laboratory before the field measurements in seawater. A simulation model was established for the detector immersed in seawater. The simulated spectra were all broadened with Gaussian pulses to reflect the statistical fluctuations and electrical noise in the real measurement. The simulated spectra show that the single-energy photons into the detector are mostly scattering low-energy photons and the high background in the low energy region mainly originates from the Compton effect of the high energy γ-rays of natural radionuclides in seawater. The simulated background spectrum was compared with the experimental one recorded in field measurement and they seem to be in good agreement. The simulation method and spectra can be used for the accurate analysis of the filed measurement results of low concentration radioactivity in seawater.     

沿海滩涂大米草叶绿素含量的高光谱估算模型

以沿海滩涂大米草为研究对象,测试其叶片水平的反射光谱和叶绿素含量;基于反射光谱提取多变量和单变量参数,并分析其与叶绿素含量的相关性;应用线性回归和非线性模拟的方法构建大米草叶绿素含量的高光谱估算模型。结果表明:叶绿素a,b和(a+b)含量与487 nm的导数光谱相关系数最高,分别为-0.615,-0.572和-0.613;应用多元逐步线性回归构建的叶绿素a和(a+b)含量的高光谱估算模型精度最高,调整后的R2分别为0.449和0.407;应用二次函数法构建的叶绿素b含量的高光谱估算模型精度最高,调整后的R2为0.387。