Determination of Fluorine in Eighty International Geochemical Reference Samples by Proton Induced Gamma Ray Emission Spectrometry (PIGE)     

Iwan ROELANDTS  Guy ROBAYE  Georges WEBER  Jeanne-Marie DELBROUCK 《Geostandards and Geoanalytical Research》1985,9(2):191-192

Fluorine content has been determined non destructively in eighty international geochemical reference samples (GRS) including rocks, soils, sediments, minerals and ores, by proton induced gamma ray emission spectrometry (PIGE) using the nuclear reaction ¹⁹F(p,αγ) ¹⁶O. Under our operating conditions, the detection limit is around 25 ppm. Our analytical results are compared with the presently preferred values when available or with other published data. The general agreement between this work and reported values is reasonably good. The present paper includes results on several GRS for which existing data are rather scarce or even inexistant.  相似文献   

Geochemical Reference Sample Bibliography for 1985     

Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1986,10(2):265-280

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1982 Compilation of Elemental Concentrations in Eleven United States Geological Survey Rock Standards     

Ernest S. GLADNEY  Colleen E. BURNS  Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1983,7(1):3-6

Elemental composition data on eight older (AGV-1, BCR-1, DTS-1, G-1, G-2, GSP-1, PCC-1 and W-1) and three newer (BIR-1, DNC-1 and W-2) USGS rock standards have been collected from institutional reports and journal articles from 1972–1981. This collection was combined with data from previous compilations and "consensus values" for up to 79 elements determined by comparing overall means, medians, and individual means based on analytical techniques.  相似文献   

Geochemical Reference Sample: BIBLIOGRAPHY FOR 1991     

Iwan ROELANDTS 《Geostandards and Geoanalytical Research》1992,16(2):343-362

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GeostandaRef Corner Geochemical Reference Sample Bibliography for 1997     

Iwan Roelandts 《Geostandards and Geoanalytical Research》1998,22(2):257-284

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What kind of countryside do the public want: community visions from Wales UK?     

Alister J. Scott  James Shorten  Rosalind Owen  Iwan Owen 《GeoJournal》2011,76(4):417-436

This paper assesses how far community led rural visions accord with the current thrust of rural planning policy delivery in the UK. Adapting conventional visioning methods, qualitative techniques were used on eight different communities across urban, exurban and rural Wales to elicit views relating to the kind of local countryside(s) that were desired. The results show that the communities’ visions reflect an emerging consensus around local countryside priorities: multifunctionality, integration, wider countryside protection, development based on need, and local distinctiveness according with the thrust of current planning policy at national and local levels. However, there is a clear dichotomy between this and the reality of what communities actually experienced in developments affecting their countryside. Here, universal criticism was encountered over the type, pace and scale of development, the lack of rural specificity and the failure to take account of local community needs and priorities. It is hypothesized that tensions between national and local politics and stakeholder power relations are playing a crucial role in distorting the delivery of town and country planning. It is recommended that rural policy delivery must become more “joined up” and rural proofed at national and local levels concomitant with a change in the operational culture of agencies at the forefront of rural delivery. Essentially, effective engagement of top down approaches synergising with bottom up community led ideas is long overdue.  相似文献   

GeostandaRef Corner Geochemical Reference Sample Bibliography for 1999     

Iwan Roelandts 《Geostandards and Geoanalytical Research》2000,24(2):281-302

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Prediction of hydrodynamic forces on submarine pipelines using an improved Wake II Model     

Iwan R. Soedigdo  K.F. Lambrakos  Billy L. Edge 《Ocean Engineering》1998,26(5):431-462

The hydrodynamic force model for prediction of forces on submarine pipelines as described includes flow history effect (wake effects) and time dependence in the force coefficients. The wake velocity correction is derived by using a closed-form solution to the linearized Navier–Stokes equations for oscillatory flow. This is achieved by assuming that the eddy viscosity in the wake is only time dependent and of a harmonic sinusoidal form. The forces predicted by the new Wake (Wake II) Model have been compared to Exxon Production Research Company Wake Model in terms of time histories (force shape) and magnitudes of peak forces. Overall, the model predictions by the Wake II Model are satisfactory and represent a substantial improvement over the predictions of the conventional models. The conventional force models representing adaptations of Morison's equation with ambient velocity and constant coefficients give predictions that are in poor agreement with the measurements especially for the lift force component. The Wake II Force Model can be used for submarine pipeline on-bottom stability design calculations for regular waves with various pipe diameters.  相似文献   

An investigation of meteors in early April     

Terrance R. Arter  Iwan P. Williams 《Earth, Moon, and Planets》1995,68(1-3):141-153

In conducting a search through the IAU Meteor Catalogue at Lund, a peak in activity on April 8th, not corresponding to any known shower was discovered. Analysis of the orbit shows that a subset of those meteors originated on very coherent orbits. It is suggested that there could either represent a hither to unidentified stream or that they are meteoroids which, like the April Lyrids, were ejected from Comet Thatcher but have arrived onto their current orbits as a consequence primarily of Poynting - Robertson drag.  相似文献   

The Dynamics of Objects in the Inner Edgeworth–Kuiper Belt     

Daniel C. Jones  Iwan P. Williams  Mario D. Melita 《Earth, Moon, and Planets》2005,97(3-4):435-458

Objects in 3:2 mean motion resonance with Neptune are protected from close encounters with Neptune by the resonance. Bodies in orbits with semi-major axis between 39.5 and about 42 AU are not protected by the resonance; indeed due to overlapping secular resonances, the eccentricities of orbits in this region are driven up so that a close encounter with Neptune becomes inevitable. It is thus expected that such orbits are unstable. The list of known Trans-Neptunian objects shows a deficiency in the number of objects in this gap compared to the 43–50 AU region, but the gap is not empty. We numerically integrate models for the initial population in the gap, and also all known objects over the age of the Solar System to determine what fraction can survive. We find that this fraction is significantly less than the ratio of the population in the gap to that in the main belt, suggesting that some mechanism must exist to introduce new members into the gap. By looking at the evolution of the test body orbits, we also determine the manner in which they are lost. Though all have close encounters with Neptune, in most cases this does not lead to ejection from the Solar System, but rather to a reduced perihelion distance causing close encounters with some or all of the other giant planets before being eventually lost from the system, with Saturn appearing to be the cause of the ejection of most of the objects.  相似文献