Shake table testing and numerical simulation of a self‐centering energy dissipative braced frame

The self‐centering energy dissipative (SCED) brace is a new steel bracing member that provides both damping to the structure and a re‐centering capability. The goal of this study was to confirm the behavior of SCED braces within complete structural systems and to confirm the ability to model these systems with both a state‐of‐the‐art computer model as well as a simplified model that would be useful to practicing engineers. To these ends, a three‐story SCED‐braced frame was designed and constructed for testing on a shake table. Two concurrent computer models of the entire frame were constructed: one using the opensees nonlinear dynamic modeling software, and a simplified model using the commercial structural analysis software sap2000 . The frame specimen was subjected to 12 significant earthquakes without any adjustment or modification between the tests. The SCED braces prevented residual drifts in the frame, as designed, and did not show any significant degradation due to wear. Both numerical models were able to predict the drifts, story shears, and column forces well. Peak story accelerations were overestimated in the models; this effect was found to be caused by the absence of transitions at stiffness changes in the hysteretic model of the braces. Copyright © 2013 John Wiley & Sons, Ltd.     

迁安紫苏花岗岩的~(40)Ar/~(39)Ar年龄谱

对采自河北省迁安县水厂地区的紫苏花岗岩中的黑云母和紫苏辉石进行了~(40)Ar/~(39)Ar年龄测定,分别给出了18.7亿年和19.6亿年的~(40)Ar保存年龄。这两种矿物的年龄谱的视年龄的梯度变化表明,紫苏花岗岩形成后是缓慢冷却的。3.9亿年左右的一次热事件,造成了放射成因~(40)Ar的丢失。根据热历史和封闭温度的研究,从27亿年(侵入到该区紫花岗岩中的花岗闪长岩的锆石U-Pb年龄)到19.6亿年,紫苏花岗岩岩体的抬升速率为6.5m/Ma,但从19.6亿年到18.7亿年,其抬升速率高达111m/Ma,具有明显的构造抬升作用。     

Seasonal variability of community structure and breeding activity in marine phytal harpacticoid copepods on Ulva pertusa from Pohang,east coast of Korea

Seasonal changes in community structure and reproductive status of phytal harpacticoid copepods in the shallow sublittoral bottom at two sites (Masan-ri and Guryongpo) in Pohang (Korea) are described monthly over a period of 1 year (October 1996 to September 1997). A total of 36 harpacticoid species was identified and the numerically dominant copepods were made up of the families Porcellidiidae and Tisbidae. Although the number of species did not show a seasonal trend, total harpacticoid density revealed a favorable distribution for the warmer season (spring and summer) at both sites. Multiple linear regression analyses showed that univariate indices such as density, evenness and diversity are closely associated with certain environmental parameters. For example, the dominant species fluctuated seasonally in abundance and their maximum densities were found to be temperature- (+ with Porcellidium ofunatense) and nutrient-dependent (+ with Scutellidium longicauda acheloides, + with Zaus unisetosus, and ? with P. wandoensis). In addition, the dominant species appeared to breed year round and their reproductive indices are significantly correlated with some environmental parameters such as temperature (?), pH (+), and phosphate (+). Three species (S. l. acheloides, P. wandoensis, and P. ofunatense) showed maximum density two or three months after their reproductive activity reached a maximum. Overall, the seasonal changes in a phytal harpacticoid community could be explained by combinations of environmental parameters supporting the complexity and biodiversity for this specific group of species in coastal ecosystems.     

决策树在遥感影像分类中的应用

在充分了解决策二叉树分类过程的基础上, 以西藏波密地区的TM遥感影像为研究对象, 提取并分析各种典型地物的反射光谱特征, 利用不同地物的光谱差异并结合人工目视判读建立了一组能够精确、快速划分遥感影像的分类规则。用ENVI建立分类决策树对实验区遥感影像进行分类, 并将分类结果和传统的最大似然法相比较。结果表明:决策树分类的总体精度和Kappa分别为97.15%和0.9644, 优于传统的最大似然法, 取得了较为满意的分类结果。     

Southwestward intrusion of korea strait bottom cold water observed in 2003 and 2004

Hydrographic surveys were carried out four times in the western channel of the Korea Strait in March and August 2003 and in June and November 2004. The bottom cold water, which was lower than 10°C, appeared in the channel trough except in March 2003. It flowed southwestward along the shelf of Korean coasts in August 2003 and in November 2004. The width and the maximum speed of the intrusion current were about 20 km and approximately 25 cm s^-1, respectively, off Ulsan, Korea. The volume transport of the bottom cold water was estimated 0.019 Sv (Sv≡10⁶ m³ s^-1) in August 2003 and 0.026 Sv in November 2004.     

Elastic lateral dynamic impedance functions for a rigid cylindrical shell type foundation

Elastic lateral dynamic impedance functions are defined as the ratio of the lateral dynamic force/moment to the corresponding lateral displacement/rotation at the top ending of a foundation at very small strains. Elastic lateral dynamic impedance functions have a defining influence on the natural frequencies of offshore wind turbines supported on cylindrical shell type foundations, such as suction caissons, bucket foundations, and monopiles. This paper considers the coupled horizontal and rocking vibration of a cylindrical shell type foundation embedded in a fully saturated poroelastic seabed in contact with a seawater half‐space. The formulation of the coupled seawater–shell–seabed vibration problem is simplified by treating the shell as a rigid one. The rigid shell vibration problem is approached by the integral equation method using ring‐load Green's functions for a layered seawater‐seabed half‐space. By considering the boundary conditions at the shell–soil interface, the shell vibration problem is reduced to Fredholm integral equations. Through an analysis of the corresponding Cauchy singular equations, the intrinsic singular characteristics of the problem are rendered explicit. With the singularities incorporated into the solution representation, an effective numerical method involving Gauss–Chebyshev method is developed for the governing Fredholm equations. Selected numerical results for the dynamic contact load distributions, displacements of the shell, and lateral dynamic impedance functions are examined for different shell length–radius ratio, poroelastic materials, and frequencies of excitation. Copyright © 2016 John Wiley & Sons, Ltd.     

SDINS/GPS in-flight alignment using GPS carrier phase rate

The alignments of the strapdown inertial navigation system (SDINS) utilizing GPS carrier phase rate measurements is introduced. In this paper, a measurement model of GPS carrier phase rate under two antenna configurations is derived in order to be used for the SDINS alignment process. For in-flight alignment, the performance of the proposed SDINS/GPS integration method is analyzed using the covariance analysis and the overall performance is briefly confirmed by the navigation result of a van test. Furthermore, we find that during in-flight alignment the proposed SDINS/GPS integrated system using GPS carrier phase rate measurements can be implemented in real time because the integer ambiguity problem resulting from carrier phase measurements is avoided.     

A Laboratory Model for the Flow in Urban Street Canyons Induced by Bottom Heating

Water tank experiments are carried out to investigate the convection flow induced by bottom heating and the effects of the ambient wind on the flow in non-symmetrical urban street canyons based on the PIV (Particle Image Visualization) technique. Fluid experiments show that with calm ambient wind,the flows in the street canyon are completely driven by thermal force, and the convection can reach the upper atmosphere of the street canyon. Horizontal and vertical motions also appear above the roofs of the buildings. These are the conditions which favor the exchange of momentum and air mass between the street canyon and its environment. More than two vortices are induced by the convection, and the complex circulation pattern will vary with time in a wider street canyon. However， in a narrow street canyon， just one vortex appears. With a light ambient wind, the bottom heating and the associated convection result in just one main vortex. As the ambient wind speed increases, the vortex becomes more organized and its center shifts closer to the leeward building.     

准噶尔盆地玛湖凹陷西斜坡三叠系百口泉组扇三角洲优质储集层预测

针对准噶尔盆地玛湖凹陷西斜坡风南地区三叠系百口泉组扇三角洲砂岩物性空间变化大、优质储集层(孔隙度大于7.4%,渗透率大于0.05×10^-3μm²)预测难的问题,在沉积岩石学、地震沉积学以及地震反演和解释理论指导下,综合利用测井、岩心和三维地震等资料开展了高精度层序地层划分、沉积微相描述和优质储集层地震反演研究。建立了风南井区四级层序地层格架,明确了扇三角洲多期水进水退的充填过程,指出SSQ3和SSQ5是优质储集层的发育层系;识别出扇三角洲平原分流河道、河道间和扇三角洲前缘水下分流水道、河口坝、席状砂等沉积微相,指出扇三角洲平原是优质储集层发育相带;通过应用高分辨层序地层纵向边界和沉积相横向边界约束,进行分层相控叠后地震波阻抗反演,提升储集层预测精度,在SSQ3和SSQ5预测5个优质储集层发育区,提出3口井的井位建议,钻探均获工业油流。