Sources, Fates and Consequences of Pollutants in the Great Barrier Reef     

Pat Hutchings  David Haynes 《Marine pollution bulletin》2000,41(7-12):265-266

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The insensitivity of the cosmic ray galactic anisotropy to heliomagnetic polarity reversals     

K. Nagashima  S. Sakakibara  A.G. Fenton  J.E. Humble 《Planetary and Space Science》1985,33(4):395-405

Using the cosmic ray sidereal and anti-sidereal diurnal variations observed underground in London and Hobart during the period 1958–1983, it is demonstrated that: (1) the phase changes of the apparent sidereal diurnal variation observed only in the Northern Hemisphere cannot be attributed to the change of the heliomagnetospheric modulation of galactic cosmic ray anisotropy caused by the polarity reversal of the solar magnetic field, but that they are due to the fluctuation of the spurious sidereal variation produced from the anisotropy responsible for the solar semi-diurnal variation; (2) the spurious sidereal variation can be eliminated from the apparent variation by using the observed anti-sidereal diurnal variation; and (3) after the elimination, the sidereal diurnal variations in the Northern and Southern Hemispheres almost coincide with each other and are stationary throughout the period, regardless of the polarity reversal of the heliomagnetosphere. The origin of the corrected sidereal variation is discussed.  相似文献   

Port surveys for introduced marine species--and the fate of the material collected     

Hutchings P  Glasby C 《Marine pollution bulletin》2004,48(11-12):1009-1011

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Monterey Fan: Growth pattern control by basin morphology and changing sea levels     

William R. Normark  C. E. Gutmacher  T. E. Chase  Pat Wilde 《Geo-Marine Letters》1983,3(2-4):93-99

Monterey Fan is the largest modern fan off the California shore. Two main submarine canyon systems feed it via a complex pattern of fan valleys and channels. The northern Ascension Canyon system is relatively inactive during high sea-level periods. In contrast, Monterey Canyon and its tributaries to the south cut across the shelf and remain active during high sea level. Deposition on the upper fan is controlled primarily by the relative activity within these two canyon systems. Deposition over the rest of the fan is controlled by the oceanic crust topography, resulting in an irregular fan shape and periodic major shifts in the locus of deposition.  相似文献   

Metal accumulation in four molluscs     

Paul B Lobel  Pat Mogie  Dave A Wright  B.L Wu 《Marine pollution bulletin》1982,13(5):170-174

Specimens of mussels (Mytilus edulis), winkles (Littorina littorea), dogwhelks (Nucella lapillus) and limpets (Patella vulgata) were collected from the north-east coast of England in 1980–1981 in order to analyse the dried whole soft tissue for zinc, copper and iron. In each case, only a narrow size range of organisms was collected from a small environmentally homogeneous site and sex was taken into account. Most of the frequency distributions of metal concentrations obtained were found to show significant positive skewness. This skewness could not be explained either by the degree of mobility or type of feeding mechanism of the organisms or by any other known parameter, e.g. size, sex, habitat variation. Some individual mussels were found to be extremely good regulators of their zinc concentrations. On the other hand, other individual mussels had the ability to accumulate unusually high levels of zinc.  相似文献   

Interpretation of the complex dune morphology on Mars: dune activity,modelling and a terrestrial analogue     

S. Silvestro  L. K. Fenton  T. I. Michaels  A. Valdez  G. G. Ori 《地球表面变化过程与地形》2012,37(13):1424-1436

In this work we analyze a dark erg on Mars that could be considered a mega‐dune (draa) where secondary dunes of different morphology are superposed over a main crescent‐shaped bedform (primary dune). The presence of a complex, multi‐directional wind regime is indicated as one of the main causes for the accumulation of a tall draa, presenting an analogy to the Great Sand Dunes in Colorado. In both cases, main regional winds from the SW blow in opposition to winds from the NE which are enhanced by the topography. Such a complex wind regime leads to the development of star and reversing dunes and is accurately predicted by atmospheric models on a regional and local scale. Signs of activity in the form of grainflow scars are also noted over the slip faces of many dunes, suggesting that easterly winds are actively shaping the study draa in the present‐day climatic setting. The presence of this draa on Mars suggests a complex interaction between regional and local topographically controlled flows and a consistent availability of sand. The future study of an analogue terrestrial site such as the Great Sand Dunes could be fundamental for understanding the evolution of similar Martian dune fields. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Site amplification in the Kathmandu Valley during the 2015 <Emphasis Type="Bold">M</Emphasis>7.6 Gorkha,Nepal earthquake     

S.?Tallett-WilliamsEmail author  B.?Gosh  S.?Wilkinson  C.?Fenton  P.?Burton  M.?Whitworth  S.?Datla  G.?Franco  A.?Trieu  M.?Dejong  V.?Novellis  T.?White  T.?Lloyd 《Bulletin of Earthquake Engineering》2016,14(12):3301-3315

The 25th April 2015 M7.6 Gorkha earthquake caused significant damage to buildings and infrastructure in both Kathmandu and surrounding areas as well as triggering numerous, large landslides. This resulted in the loss of approximately 8600 lives. In order to learn how the impact of such events can be reduced on communities both in Nepal and elsewhere, the Earthquake Engineering Field Investigation Team (EEFIT) reconnaissance mission was undertaken, aiming to look at damage patterns within the country. Passive, microtremor recordings in severely damaged areas of the Kathmandu Valley, as well as at the main seismic recording station in Kathmandu (USGS station KATNP) are used to determined preliminary shear wave velocity (V_s) profiles for each site. These profiles are converted into spectral acceleration using the input motion of the Gorkha earthquake. The results are limited, but show clear site amplification within the Siddhitol Region. The resulting ground motions exceed the design levels from the Nepalese Building Codes, indicating the need for site-specific hazard analysis and for revision of the building code to address the effect of site amplification.  相似文献   

On the efficient estimation of small failure probability in slopes     

Jinsong Huang  Gordon Fenton  D. V. Griffiths  Dianqinq Li  Chuangbing Zhou 《Landslides》2017,14(2):491-498

The random finite element method (RFEM) combines the random field theory and finite element method in the framework of Monte Carlo simulation. It has been applied to a wide range of geotechnical problems such as slope stability, bearing capacity and the consolidation of soft soils. When the RFEM was first developed, direct Monte Carlo simulation was used. If the probability of failure (p _f ) is small, the direct Monte Carlo simulation requires a large number of simulations. Subset simulation is one of most efficient variance reduction techniques for the simulation of small p _f . It has been recently proposed to use subset simulation instead of direct Monte Carlo simulation in RFEM. It is noted, however, that subset simulation requires calculation of the factor of safety (FS), while direct Monte Carlo requires only the examination of failure or non-failure. The search for the FS in RFEM could be a tedious task. For example, the search for the FS of slope stability by the strength reduction method (SRM) usually requires much more computational time than a failure or non-failure checking. In this paper, the subset simulation is combined with RFEM, but the need for the search of FS is eliminated. The value of yield function in an elastoplastic finite element analysis is used to measure the safety margin instead of the FS. Numerical experiments show that the proposed approach gives the same level of accuracy as the traditional subset simulation based on FS, but the computational time is significantly reduced. Although only examples of slope stability are given, the proposed approach will generally work for other types of geotechnical applications.  相似文献   

Ostracods and Foraminifera from the Pleistocene Knocknasilloge Member,County Wexford,Ireland     

David J. Horne  Pat Kerr 《Geological Journal》1989,24(1):71-74

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A mesh deformation algorithm for free surface problems     

Gordon A. Fenton  D. V. Griffiths 《国际地质力学数值与分析法杂志》1997,21(12):817-824

Employing the simple iterative technique of adjusting the element positions using computed potentials to locate the free surface can lead to finite elements with large aspect ratios as the free surface drops towards the base of the mesh. In particular, free surface modelling of earth dams with base drains suffer from this problem. The paper suggests a number of steps which can be taken to alleviate mesh distortion problems and improve the numerical stability of the iterative finite element analysis. This leads to a mesh deformation algorithm which adjusts element widths in a simple fashion depending on the free surface height as the iterations proceed. The algorithm is specialized to the sloped earth dam problem, but may find application to other geometries. © 1997 by John Wiley & Sons, Ltd.  相似文献