Diffraction of plane sh waves in a half-space     

A. H. Shah  K. C. Wong  S. K. Datta 《地震工程与结构动力学》1982,10(4):519-528

Scattering of antiplane shear waves (SH) in two dimensions by surface and near-surface defects in a homogeneous, isotropic elastic semi-infinite medium has been studied. Attention has been focused here in the range of medium to long wavelengths. A combined finite element and analytical technique has been used to study the problems of scattering by semi-circular and triangular canyons. The results for the former case are compared with the known exact solution and those for the latter case are compared with some available approximate solutions. Finally a problem of multiple scattering by a triangular canyon and a nearby circular tunnel is studied. Numerical results are presented showing the effects of multiple scattering and different angles of incidence. These results are of interest in earthquake engineering.  相似文献   

Effects of CO₂-H₂O and oblique collision on orogenesis—the european hercynides as an example     

How Kin Wong  Egon T. Degens 《Tectonophysics》1983,95(3-4)

The European Hercynides are considered the collisional result of Baltica and the microcontinents of Southern Europe, after subduction destroyed the intervening Rheic Ocean during the early Paleozoic. Their geotectonic development is assumed to consist of four overlapping stages:

1. (1) lithospheric thinning, upwelling of hot asthenospheric material, subsidence along listric faults, and basinal and geosynclinal development on the opposing shelves of the Rheic Ocean starting in pre-Devonian time;

2. (2) intermittent subduction of the Rheic Ocean interspersed with episodes of fracturing, volcanism, local uplift and subsidence, and basement reactivation as a result of compression with dextral megashear, particularly since the earliest Devonian;

3. (3) several phases of folding with a northward vergence, and thrusting and overthrusting along listric surfaces, the true orogenic stage;

4. (4) post-orogenic stage of massive granite intrusions and subsequent volcanism in the Permo-Triassic

.The high clastic content (as opposed to carbonates) of the sedimentary sequences involved in the subduction and folding processes and the consequent release of large amounts of meteoric water are held responsible for the synorogenic and post-orogenic magma rise, and for the wide zone of anatectic granites and migmatites. The dominant dextral megashear, the constant re-adjustment of the microcontinents of Southern Europe (oblique collision) and the scarcity of back-arc basins, oceanic plateaus and microcontinents led to the poor preservation of ophiolites and ultrabasic rocks, and to a wide (over 1500 km) Hercynian Foldbelt.During the Paleozoic, the depositional center of the Rhenish Massif shifted from south polar latitudes in the early Ordovician to tropical positions within a period of about 100 m.y. The sediment facies reflects this paleogeographic development.  相似文献   

Defining the geochemical baseline: a case of Hong Kong soils     

H. B. Zhang  Y. M. Luo  M. H. Wong  Q. G. Zhao  G. L. Zhang 《Environmental Geology》2007,52(5):843-851

A geochemical baseline provides the means to distinguish between the pedogenic origin and the anthropogenic origin of the trace element in the environmental compartments. We collected 271 soil samples representative of different parent rocks and soil types from the whole territory of Hong Kong and analyzed the composition of clay mineralogy and the contents of 15 chemical elements (Fe, Cd, As, etc.) for these samples. The baseline was predicted with the method of the normalization procedure combined with the relative cumulative frequency curve. The result indicated that Fe was the best reference element for the normalization procedure among the five potential reference elements (Fe, Al, Sc, Ti, and Mn), followed by Sc and Ti. A poor correlation was found between Sc, Ti, and Cu. The predicted baseline was much lower than the A-value of the Dutch List used usually in screening the polluted soil of Hong Kong, implying that the extent of heavy metal pollution might have been underestimated with respect to local lands. We also applied the cluster analysis to distinguish the geochemical associations of the trace elements due to its importance to the baseline. Approximately three major associations including the Fe–Mn-oxides related, Al oxides or Al-bearing-clay-mineralogy related and sulfide- related associations were observed from the dendrogram.  相似文献   

将C/S移植到CICS三层次结构的方法技术研究   总被引：2，自引：0，他引：2  

赵太银  李正文 《物探化探计算技术》2002,24(3):279-283

由于其低成本和易于编程，两层次的C／S结构是目前流行的体系结构。但因为两层次C／S结构固有的局限性，当系统大到一定程度时，我们必须要采用多层次的体系结构，而IBM公司的CICS是开发大型分布式应用系统的主流代表之一。作者在本文中介绍了将PowerBuider开发的两层次C／S结构移植到CICS三层次结构的简单方法。  相似文献   

DT—1016型阴离子交换树脂分离富集金铂钯   总被引：17，自引：5，他引：17  

甘树才  段太成等 《岩矿测试》2002,21(2):113-116

研究了DT－1016型阴离子交换树脂对超痕量Au,Pt,Pd的吸附性能及条件。在0.025mol/L HCl介质中，流出速度为0.5-1.0mL/min时，Au,Pt和Pd的富集效果最佳，吸附率分别为99.72％，99.06％和97.95％，共存离子无显著性影响。用等离子体质谱测定标准物质中Au，Pt和Pd，其结果与标准值基本相符。检出限Au为0.27μg/L，Pt为0.40μg/L，Pd为0.19μg／L。对GBW 07294铂族元素国家标准物质进行精密度试验，RSD（n=8）Au为19．2％，Pt为28.1％，Pd为15.6％。  相似文献   

江西安远路迳金伯利质煌斑岩筒的Rb-Sr同位素年龄及其地质意义   总被引：1，自引：2，他引：1  

叶松  杨眉  叶德隆  邰道乾  任迎新 《地质科技情报》2001,20(2):27-29

报道了赣南安远县路迳金伯利质煌斑岩筒的 Rb-Sr等时线地质年龄 :t=( 3 7.6± 2 .2 ) Ma,初始值 [n( 87Sr) / n( 86Sr) ] i=0 .70 5 17± 0 .0 0 0 12。  相似文献   

水--煤层气两相流体在煤层中的渗流规律   总被引：1，自引：1，他引：1  

张永利  邰英楼  王来贵 《地质灾害与环境保护》2001,12(4):63-66

采用煤体承受有效应力、水-气混合流动及固一流相互作用的基本原理，建立了煤层气开采过程中水-煤层气两相流渗的基本方程，通过自行设计的实验装置，测定了煤层中水-煤层气共同流动时的两相流体的流量，渗透率及随水的饱和度变化关系，并据此模拟出了反映水-煤层气渗透基本规律，从而为煤层气开采提供了理论基础。  相似文献   

Living with floods: victims' perceptions in Beijiang, Guangdong, China   总被引：2，自引：0，他引：2  

Koon-Kwai Wong  & Xiaobin Zhao 《Area》2001,33(2):190-201

This study revealed the collective values of the flood victims in the Beijiang area, Guangdong, China, as a result of a hazardous flood in 1994. The victims were sceptical of large flood-prevention engineering structures. They believed that flooding was unavoidable, but by extending support networks, applying hazard-resistant designs, and developing loss-sharing adjustments the disastrous effects of a flood could be mitigated. Seemingly, victims were prepared to live with floods and adopted functional adjustments to lessen flood impact.  相似文献   

Long-term changes in water quality and phytoplankton characteristics in port shelter, Hong Kong, from 1988-1998.   总被引：6，自引：0，他引：6  

Y K Yung  C K Wong  K Yau  P Y Qian 《Marine pollution bulletin》2001,42(10):981-992

This study analysed monthly physico-chemical and phytoplankton data collected from 10 marine monitoring stations in Port Shelter Hong Kong, from 1988 to 1998. Cluster analysis based on all water quality parameters measured shows that the 10 monitoring stations can be grouped into three clusters: Cluster I consists of stations located in Outer Port Shelter; Cluster II consists of stations located in Inner Port Shelter and Cluster III consists of a single station in Hebe Heaven, a well-sheltered Bay in Inner Port Shelter. Factor analysis shows high positive loadings for nutrients and nutrient ratios in the first two factors of the three clusters, which indicates that the stations of the three clusters were primarily grouped according to their respective nutrient conditions. In Inner Port Shelter, and particularly Station PM5 in the sheltered Hebe Haven, the influence of surface runoff and pollution loading from the surrounding catchment area was apparent. Five stations located along a transect from Inner to Outer Port Shelter were selected for trend analysis. An increasing trend for temperature and a decreasing trend for pH are observed in all Stations except PM10 which is at the mouth of Port Shelter. The results of canonical analysis revealed that temperature and pH could also play an important role in determining the density and biovolume of the minor algal groups in Port Shelter.  相似文献   

Evaluation of response and energy in actively controlled structures     

Kevin K. F. Wong  Rong Yang 《地震工程与结构动力学》2001,30(10):1495-1510

A computational method of energy evaluation is derived to study the elastic responses and energy distribution of actively controlled single‐degree‐of‐freedom (SDOF) structures during earthquakes. Contrary to the common perception that applying active control force pumps energy into the structure, the applied control force can actually reduce the energy in the structure by reducing the input energy from earthquakes to the structure. In addition, applying control force can dissipate a large amount of energy in the structure when this control force is applied in the direction opposite to the displacement and velocity responses. To demonstrate this energy mechanism in active controlled structures, the two most popular control algorithms, optimal linear control (OLC) and instantaneous optimal control (IOC) algorithms, are used to calculate the control response and energy spectra. One‐step time delay is incorporated into the algorithms to take into consideration the practical aspect of active control. The effects of different earthquakes and damping ratios on control energy and response spectra are studied. These studies show that both OLC and IOC are very effective in reducing the structural displacement and velocity responses by reducing the input earthquake energy as well as dissipating a large amount of energy in the structure. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献