Discussion on: A mathematical model of permeability alteration around wells     

J. D. McKinley  M. D. Bolton 《国际地质力学数值与分析法杂志》1992,16(12):887-890

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Sublittoral seaweed communities on natural and artificial substrata in a high-latitude coral community in South Africa     

L Gersun  JR Hart  GW Maneveldt  JJ Bolton 《African Journal of Marine Science》2016,38(3):303-316

Coral mortality may result in macroalgal proliferation or a phase shift into an alga-dominated state. Subtidal, high-latitude western Indian Ocean coral communities at Sodwana Bay on the KwaZulu-Natal coast, South Africa, have experienced some mortality because of warm-water anomalies, storms and other causes, but the response of the macroalgae is unknown. We investigated the abundance and diversity of benthic algae on different hard natural substrata (dead digitate, brain and plate corals and beach rock) on Two-Mile Reef, Sodwana Bay. We also compared algal communities colonising ceramic, marble and pretreated ceramic tiles placed on the reef for six months. We identified 95 algae (14 Chlorophyta, 11 Phaeophyceae, 69 Rhodophyta and one cyanobacterium). Assemblages on natural and artificial substrata were dominated by the brown alga Lobophora variegata (Lamouroux) Womersley ex Oliveira and non-geniculate corallines (Rhodophyta, Corallinaceae). Cluster and ordination analyses revealed that the algae showed no affinity for particular substrata, whether natural or artificial. Algal cover was occasionally higher on rougher tiles and crustose corallines were significantly more abundant on marble than ceramic tiles. Two-Mile Reef had 23.1% dead and 48.4% live scleractinian coral cover, where dead corals were colonised indiscriminately by many small algal species, but there was no evidence of algal proliferation. The results provide a baseline for monitoring this high-latitude reef system.  相似文献   

Soil-structure interaction with Rayleigh waves     

Alberto Gmez-Mass  John Lysmer  Jian-Chu Chen  H. Bolton Seed 《地震工程与结构动力学》1983,11(4):567-583

Presented is a plane-strain method for soil-structure interaction analysis consisting of the superposition of the free field motions and the interaction motions in a generalized seismic environment. The free field is modelled as a horizontally layered viscoelastic medium and the seismic environment may consist of a combination of S, P and Rayleigh waves. The soil-structure system is modelled with viscoelastic finite elements, transmitting boundaries, viscous boundaries and a three-dimensional simulation. Comparative analyses of the same structure are conducted for an input of R waves and for vertically propagating S and P waves in a rock site and sand site. In the rock site the R waves produce higher peak horizontal spectral acceleration up to 25 per cent, and a significant rocking effect at points away from the centre of gravity of the structure. However, the S and P waves show higher peak vertical spectral acceleration by up to 15 per cent at the centre of the structure. Very similar horizontal response, but higher vertical response only at the centre of the structure for S and P waves, is obtained for the sand site.  相似文献   

The observed ionization rate of the intergalactic medium and the ionizing emissivity at z≥ 5: evidence for a photon-starved and extended epoch of reionization     

James S. Bolton  Martin G. Haehnelt 《Monthly notices of the Royal Astronomical Society》2007,382(1):325-341

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华北克拉通南缘中条山-嵩山地区1.78Ga基性岩墙群的地球化学特征及构造环境   总被引：8，自引：6，他引：2  

胡国辉  胡俊良  陈伟  赵太平 《岩石学报》2010,26(5):1563-1576

幔源岩浆侵位产生的基性岩墙群是地壳伸展裂解的重要标志。华北克拉通南缘中条山-嵩山地区出露有大量的中元古代基性岩墙群,对其研究将有助于深入了解华北克拉通中元古代构造演化特征。其岩石类型以辉绿岩为主,少量辉长辉绿岩和辉绿玢岩;主要造岩矿物为斜长石和单斜辉石,其它矿物包括角闪石、Fe-Ti氧化物、磷灰石、黑云母、碱性长石和石英。锆石SHRIMPU-Pb年龄为1785±18Ma,代表岩墙的结晶年龄。岩石K2O+Na2O含量为3.63%～6.18%,K2O/Na2O比值为0.73～1.38,FeOT含量较高(10.03%～13.59%),属于拉斑玄武岩系列。岩石的稀土元素含量高(142×10-6～381×10-6),亏损Nb、Ta、Zr、Hf等高场强元素,富集Rb、Ba、La等大离子亲石元素,全岩εNd(t)值为-6.2～-8.1。岩墙的固结指数(SI)和MgO含量呈明显的正相关关系,说明幔源岩浆发生过明显的结晶分异作用。地球化学分析表明,研究区基性岩墙属于板内拉斑玄武岩系列,与熊耳群火山岩有相似的地球化学特征;基于两者紧密的产出关系,我们认为该区岩墙可能是熊耳群火山岩的通道岩墙,共同代表了华北克拉通东、西陆块碰撞后伸展事件。  相似文献   

Flat boundaries and their effect on sand testing     

G. Marketos  Malcolm D. Bolton 《国际地质力学数值与分析法杂志》2010,34(8):821-837

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Convection driven by centrifugal bouyancy in a rotating annulus     

M. A. Azouni  E. W. Bolton  F. H. Busse 《地球物理与天体物理流体动力学》2013,107(1-4):301-317

Abstract

Drift rates and amplitudes of convection columns driven by centrifugal bouyancy in a cylindrical fluid annulus rotating about a vertical axis have been measured by thermistor probes. Conical top and bottom boundaries of the annular fluid region are responsible for the prograde Rossby wave like dynamics of the convection columns. A constant positive temperature difference between the outer and the inner cylindrical boundaries is generated by the circulation of thermostatically controled water. Mercury and water have been used as converting fluids. The measurements extend the earlier visual observations of Busse and Carrigan (1974) and provide quantitative data for an eventual comparison with nonlinear theories of thermal Rossby waves. The measured drift frequencies are in general agreement with linear theory. Of particular interest is the decline of the amplitude of convection with increasing Rayleigh number in a region beyond the onset of convection.  相似文献   

The radio source population at high frequency: follow-up of the 15-GHz 9C survey     

R. C. Bolton  G. Cotter  G. G. Pooley  J. M. Riley  E. M. Waldram  C. J. Chandler  B. S. Mason  T. J. Pearson  A. C. S. Readhead 《Monthly notices of the Royal Astronomical Society》2004,354(2):485-521

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Finite element analysis of a centrifuge model of a retaining wall embedded in a heavily overconsolidated clay     

M. D. Bolton  A. M. Britto

W. Powrie

T. P. White 《Computers and Geotechnics》1989,7(4):289-318

The current study is aimed at the behaviour right upto collapse of a retaining wall embedded in overconsolidated clay. It is found that the excess pore pressures generated due to the excavation are fairly well simulated. The rupture lines on the passive side in the centrifuge model test were closely matched by two lines along which the stress state was reaching the critical state in the analysis. The displacements on the active side were not well matched especially the vertical settlements near to the wall. The bending moments were significantly overpredicted. The prop force due to excavation was also overpredicted. This is to be expected because the prop was modelled as rigid in the analysis.  相似文献   

Earth Dam-foundation interaction during earthquakes     

I. M. Idriss  J. M. Mathur  H. Bolton Seed 《地震工程与结构动力学》1973,2(4):313-323

Several significant parameters that could affect interaction in a dam-foundation system are discussed. These parameters are: (1) Fundamental periods of the dam and the foundation layer. (2) Lateral extent of the dam. (3) The material properties of the dam and the foundation layer. Five cases are analysed to illustrate the influence of these parameters on interaction. An interaction ratio, R₁, relating the response of the dam-foundation system at the base of the dam to the free field response is introduced and interaction effects are expressed in terms of this ratio; the smaller this ratio, the less are the interaction effects. For very small values of R₁, it is shown that the dam-foundation system could be decoupled The results of the studies presented in the paper suggest that the interaction effects cannot be uniquely related to either the ratio of the period of the dam to the period of the foundation layer, or to the material properties of the dam and foundation layer. However, for the limited number of cases investigated, the interaction effects were found to be uniquely related to the ratio D/B, where D is the depth of the foundation layer and B is the width of the dam section. For values of D/B less than unity, strong interaction effects were obtained and the dam-foundation system could only be analysed as a coupled system. For values of D/B greater than unity, the interaction appeared negligible and the dam and its foundation layer could be decoupled. It should be noted, however, that for very small values of D/B the interaction effects would decrease becaase as D approaches zero, there would be no interaction The use of the interaction ratio, R₁, and the parameter D/B should aid in assessing the need for analysing the response of the dam-foundation as a coupled or as a decoupled system.  相似文献