Estimation of dispersion in estuaries by a self-consistent method     

D.J. Gunn  O. Yenigun 《Estuarine, Coastal and Shelf Science》1985,21(2):257-272

Longitudinal and transverse dispersion in estuaries may be determined in principle by measuring the change in time of the concentration field of a water soluble dye. In practice, measurements may take the form of several sampling runs crossing the dye patch. The coefficients of dispersion are usually estimated from the second moments of the concentration field; the use of second moments, in particular, introduces errors because measurements at long times or distance are unduly emphasized.A self-consistent method, free of the disadvantages inherent in the use of higher moments, is described in which the distribution of concentration in space is related to the zeroth spatial moment of concentration. In this formulation, based upon sampling runs across the dye patch, the concentration field in the estuary may be directly and simply related to the dispersion coefficients in both the intercept and gradient of a linear graph.The methods are illustrated by the characterization of a series of experiments in the Inner Estuary of Milford Haven.  相似文献   

Change in cloud-top temperatures over Europe     

Devasthale  A. Kruger  O. Grassl  H. 《Geoscience and Remote Sensing Letters, IEEE》2005,2(3):333-336

Long-term measurements from Advanced Very High Resolution Radiometer (AVHRR) onboard the National Oceanic and Atmospheric Administration satellites were evaluated to assess variability in cloud-top temperatures over central and eastern Europe that saw radical infrastructural changes after the fall of the East Bloc in 1989 that has affected the pollution levels and hence cloud albedo. Four years in the late 1980s (1985-1988) and in the late 1990s (1997-2000) were chosen, as these are distinctively marked as episodes of very high and lower air pollution (sulphates and particulate matter). During the late 1980s, low- and medium-level clouds were colder by more than 2 K and convective clouds even by 4 K. Cloud-tops over and around polluted regions are higher, and their temperatures showed stronger variability, suggesting an indirect aerosol effect in the thermal spectral range as well.  相似文献   

Elastic solutions for stresses in a transversely isotropic half‐space subjected to three‐dimensional buried parabolic rectangular loads     

Cheng‐Der Wang  Jyh‐Jong Liao 《国际地质力学数值与分析法杂志》2002,26(14):1449-1476

In many areas of engineering practice, applied loads are not uniformly distributed but often concentrated towards the centre of a foundation. Thus, loads are more realistically depicted as distributed as linearly varying or as parabola of revolution. Solutions for stresses in a transversely isotropic half‐space caused by concave and convex parabolic loads that act on a rectangle have not been derived. This work proposes analytical solutions for stresses in a transversely isotropic half‐space, induced by three‐dimensional, buried, linearly varying/uniform/parabolic rectangular loads. Load types include an upwardly and a downwardly linearly varying load, a uniform load, a concave and a convex parabolic load, all distributed over a rectangular area. These solutions are obtained by integrating the point load solutions in a Cartesian co‐ordinate system for a transversely isotropic half‐space. The buried depth, the dimensions of the loaded area, the type and degree of material anisotropy and the loading type for transversely isotropic half‐spaces influence the proposed solutions. An illustrative example is presented to elucidate the effect of the dimensions of the loaded area, the type and degree of rock anisotropy, and the type of loading on the vertical stress in the isotropic/transversely isotropic rocks subjected to a linearly varying/uniform/parabolic rectangular load. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

A chum scale pattern analyzer and stock identification based onscale patterns by discriminant function and power spectrum analysis     

Watarai  O. Igarashi  M. 《Oceanic Engineering, IEEE Journal of》1992,17(3):280-287

An optoelectronic instrument has been developed to analyze the scales and scale patterns of chum salmon. This device, with specially developed software, has been used to study populations of salmon. Fish from two different rivers approximately 200 km apart from each other were grouped with an accuracy of 82% or more. Machine-measured ages coincided with those derived from visual estimation in approximately 80% of the fish sampled. These results suggest the proposed system could be of practical use for measuring and analyzing the scale patterns that allow one to accurately measure both natural and farmed populations of salmon  相似文献   

Examples of clustering around high redshift radio-galaxies     

J. M. Deltorn  O. Le Fèvre 《Astrophysics》1995,38(4):379-381

Published in Astrofizika, Vol. 38, No. 4, pp. 677–680, October–December, 1995.  相似文献   

Observational Selection of Comet Discoveries     

Kalinicheva  O. V. 《Solar System Research》2002,36(3):260-266

The distribution of perihelion distances of nearly periodic comets was studied using different assumptions about comet discovery probabilities. It was shown that the concentration of perihelia at small heliocentric distances cannot be explained solely by the influence of visibility conditions.  相似文献   

The influence of a non‐associated flow rule on the calculation of the factor of safety of soil slopes     

Yu‐Jie Wang  Jian‐Hua Yin  C. F. Lee 《国际地质力学数值与分析法杂志》2001,25(13):1351-1359

This paper presents a method that incorporates a non‐associated flow rule into the limit analysis to investigate the influence of the dilatancy angle on the factor of safety for the slope stability analysis. The proposed method retain's the advantage of the upper bound method, which is simple and has no stress involvement in the calculation of the energy dissipation and the factor of safety. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Abundance and isotopic composition of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite     

Teruyuki MARUOKA  Jun‐ichi MATSUDA  Gero KURAT 《Meteoritics & planetary science》2001,36(5):597-609

Abstract— Abundances and isotopic compositions of noble gases in metal and graphite of the Bohumilitz IAB iron meteorite were measured. The abundance ratios of spallogenic components in metal reveal a ³He deficiency which is due to the diffusive loss of parent isotopes, that is, tritium (Tilles, 1963; Schultz, 1967). The diffusive loss likely has been induced by thermal heating by the Sun during cosmic‐ray exposure (～160 Ma; Lavielle et al, 1999). Thermal process such as impact‐induced partial loss may have affected the isotopic composition of spallogenic Ne. The ¹²⁹Xe/¹³¹Xe ratio of cosmogenic components in the metal indicates an enhanced production of epi‐thermal neutrons. The abundance ratios of spallogenic components in the graphite reveal that it contained small amounts of metal and silicates. The isotopic composition of heavy noble gases in graphite itself was obtained from graphite treated with HF/HCl. The isotopic composition of the etched graphite shows that it contains two types of primordial Xe (i.e., Q‐Xe and El Taco Xe). The isotopic heterogeneity preserved in the Bohumilitz graphite indicates that the Bohumilitz graphite did not experience any high‐temperature event and, consequently, must have been emplaced into the metal at subsolidus temperatures. This situation is incompatible with an igneous model as well as the impact melting models for the IAB‐IIICD iron meteorites as proposed by Choi et al. (1995) and Wasson et al (1980).  相似文献   

The Geminid Meteor Stream Activity Profile     

Ryabova  G. O. 《Solar System Research》2001,35(2):151-157

The existence of two maxima of the activity of the Geminid meteor stream and the general shape of the stream activity (rate curve) are discussed. The data of visual and radar observations are compared to the results of mathematical simulation. The distribution of the orbits of meteoroids, which are observed on the Earth, is determined from the mathematical model. This distribution cannot as yet be confirmed or disproved because of the absence of appropriate experimental data.  相似文献   

Starburst activity in a ROSAT narrow emission-line galaxy     

Katherine F. Gunn  I. M. MHardy  O. Almaini  T. Shanks  T. J. Sumner  T. W. B. Muxlow  A. Efstathiou  L. R. Jones  S. M. Croom  J. C. Manners  A. M. Newsam  K. O. Mason  S. B. G. Serjeant  M. Rowan-Robinson 《Monthly notices of the Royal Astronomical Society》2001,324(2):305-312

We present multiwaveband photometric and optical spectropolarimetric observations of the R =15.9 narrow emission-line galaxy R117_A which lies on the edge of the error circle of the ROSAT X-ray source R117. The overall spectral energy distribution of the galaxy is well modelled by a combination of a normal spiral galaxy and a moderate-strength burst of star formation. The far-infrared and radio emission is extended along the major axis of the galaxy, indicating an extended starburst.
On positional grounds, the galaxy is a good candidate for the identification of R117, and the observed X-ray flux is very close to what would be expected from a starburst of the observed far-infrared and radio fluxes. Although an obscured high-redshift QSO cannot be entirely ruled out as contributing some fraction of the X-ray flux, we find no candidates to K =20.8 within the X-ray error box, and so conclude that R117_A is responsible for a large fraction, if not all, of the X-ray emission from R117.
Searches for indicators of an obscured AGN in R117_A have so far proven negative; deep spectropolarimetric observations show no signs of broad lines to a limit of 1 per cent and, for the observed far-infrared and radio emission, we would expect 10 times greater X-ray flux if the overall emission were powered by an AGN. We therefore conclude that the X-ray emission from R117 is dominated by starburst emission from the galaxy R117_A.  相似文献