Improved method for modelling sediment transport on unpaved roads using KINEROS2 and dynamic erodibility     

Alan D. Ziegler  Thomas W. Giambelluca  Ross A. Sutherland 《水文研究》2002,16(15):3079-3089

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Gemini observations of disks and jets in young stellar objects and in active galaxies     

Peter McGregor  Michael Dopita  Ralph Sutherland  Tracy Beck  Thaisa Storchi-Bergmann 《Astrophysics and Space Science》2007,311(1-3):223-230

We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] λ 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H₂ lines, in accordance with the model advocated by Pyo, T.-S., et al., Astrophys. J. 570, 724 (2002).  相似文献   

Vanadium-rich ruby and sapphire within Mogok Gemfield,Myanmar: implications for gem color and genesis     

Khin Zaw  Lin Sutherland  Tzen-Fu Yui  Sebastien Meffre  Kyaw Thu 《Mineralium Deposita》2015,50(1):25-39

Rubies and sapphires are of both scientific and commercial interest. These gemstones are corundum colored by transition elements within the alumina crystal lattice: Cr³⁺ yields red in ruby and Fe²⁺, Fe³⁺, and Ti⁴⁺ ionic interactions color sapphires. A minor ion, V³⁺ induces slate to purple colors and color change in some sapphires, but its role in coloring rubies remains enigmatic. Trace element and oxygen isotope composition provide genetic signatures for natural corundum and assist geographic typing. Here, we show that V can dominate chromophore contents in Mogok ruby suites. This raises implications for their color quality, enhancement treatments, geographic origin, exploration and exploitation and their comparison with rubies elsewhere. Precise LA-ICP-MS analysis of ruby and sapphire from Mogok placer and in situ deposits reveal that V can exceed 5,000 ppm, giving V/Cr, V/Fe and V/Ti ratios up to 26, 78, and 97 respectively. Such values significantly exceed those found elsewhere suggesting a localized geological control on V-rich ruby distribution. Our results demonstrate that detailed geochemical studies of ruby suites reveal that V is a potential ruby tracer, encourage comparisons of V/Cr-variation between ruby suites and widen the scope for geographic typing and genesis of ruby. This will allow more precise comparison of Asian and other ruby fields and assist confirmation of Mogok sources for rubies in historical and contemporary gems and jewelry.  相似文献   

The measurement of sand transport in two inlets of Venice lagoon,Italy     

C.L. Amos  M. Villatoro  R. Helsby  C.E.L. Thompson  L. Zaggia  G. Umgiesser  V. Venturini  D. Are  T.F. Sutherland  A. Mazzoldi  F. Rizzetto 《Estuarine, Coastal and Shelf Science》2010

Sand transport in Lido and Chioggia inlets was measured using modified Helley–Smith sand traps equipped with 60-micron nets. The traps had an efficiency of about 4% only but provided enough material for analysis. Very fine sand (0.07 < d < 0.11 mm) only was collected in the traps. Transport of sand was greatest in the bottom 10% of the water column and followed a Rouse profile. Sand extended to a height of about 4 m above the bed during peak flows corresponding to the estimated thickness of the boundary layer; and observed in synoptic ADCP profiles. The sand in the benthic boundary layer was largely inorganic (>95%); above this layer, organic content varied widely and was greatest near the surface. The movability number Ws/U_∗$W_s/U_{\ast }$ showed a linear relationship to dimensionless grain diameter (D_*): (Ws/U_∗)=(D_∗/10)$\left(W_s/U_{\ast }\right)=\left(D_{\ast }/10\right)$; D_* < 10. Sand concentration in suspension was simulated by a mean Rouse parameter of −2.01 ± 0.66 (Lido inlet) and −0.82 ± 0.27 (Chioggia inlet). The β parameter ( Hill et al., 1988) was correlated with D_* and movability number in the form: β=2.07−2.03D_∗+59(Ws/U_∗)²$\beta =2.07-2.03D_{\ast }+59{\left(W_s/U_{\ast }\right)}^2$ (r² = 0.42). Von Karman's constant was back-calculated from a Law of the Wall relationship as a test on the accuracy of U_* estimates; a mean value of 0.37 ± 0.1 (compared to the accepted value of 0.41) suggest U_* was accurate to within 10%. The constant of proportionality (γ = 3.54 × 10⁻⁴) between reference concentration (C_a) and normalized excess bed shear stress was in line with the published literature.  相似文献   

Radio sources in the 2dF Galaxy Redshift Survey – II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz     

Elaine M. Sadler  Carole A. Jackson  Russell D. Cannon  Vincent J. McIntyre  Tara Murphy  Joss Bland-Hawthorn  Terry Bridges  Shaun Cole  Matthew Colless  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2002,329(1):227-245

We have cross-matched the 1.4-GHz NRAO VLA Sky Survey (NVSS) with the first 210 fields observed in the 2dF Galaxy Redshift Survey (2dFGRS), covering an effective area of 325 deg² (about 20 per cent of the final 2dFGRS area). This yields a set of optical spectra of 912 candidate NVSS counterparts, of which we identify 757 as genuine radio identifications – the largest and most homogeneous set of radio source spectra ever obtained. The 2dFGRS radio sources span the redshift range     to 0.438, and are a mixture of active galaxies (60 per cent) and star-forming galaxies (40 per cent). About 25 per cent of the 2dFGRS radio sources are spatially resolved by NVSS, and the sample includes three giant radio galaxies with projected linear size greater than 1 Mpc. The high quality of the 2dF spectra means we can usually distinguish unambiguously between AGN and star-forming galaxies. We make a new determination of the local radio luminosity function at 1.4 GHz for both active and star-forming galaxies, and derive a local star formation density of         .  相似文献   

Modern glacier characteristics as a basis for inferring former climates with particular reference to the Loch Lomond Stadial     

Donald G. Sutherland 《Quaternary Science Reviews》1984,3(4):291-309

Studies of the mass balance of modern glaciers have indicated that the equilibrium line altitude (ELA) is the most critical parameter in the link between glaciers and climate. Average accumulation on a glacier includes components derived from direct precipitation on the glacier surface as well as wind-drifting and avalanching of snow, and approximates closely to accumulation at the equilibrium line. Ablation is most usefully predicted by mean summer temperature and there is a close, non-linear relationship between accumulation and mean summer temperature at the equilibrium line. Following discussion of methods of reconstructing former glaciers and calculating their equilibrium line altitudes, the application of the above relationships to the Loch Lomond Readvance glaciers of Highland Britain is considered and an outline of the precipitation pattern and the mean summer temperature of the Loch Lomond Stadial is given.  相似文献   

The topology of the IRAS Point Source Catalogue Redshift Survey     

A. Canavezes  V. Springel  S. J. Oliver  M. Rowan-Robinson  O. Keeble  S. D. M. White  W. Saunders  G. Efstathiou  C. S. Frenk  R. G. McMahon  S. Maddox  W. Sutherland  & H. Tadros 《Monthly notices of the Royal Astronomical Society》1998,297(3):777-793

We investigate the topology of the new Point Source Catalogue Redshift Survey (PSCz) of IRAS galaxies by means of the genus statistic. The survey maps the local Universe with approximately 15 000 galaxies over 84.1 per cent of the sky, and provides an unprecedented number of resolution elements for the topological analysis. For comparison with the PSCz data we also examine the genus of large N -body simulations of four variants of the cold dark matter (CDM) cosmogony. The simulations are part of the Virgo project to simulate the formation of structure in the Universe. We assume that the statistical properties of the galaxy distribution can be identified with those of the dark matter particles in the simulations. We extend the standard genus analysis by examining the influence of sampling noise on the genus curve and introducing a statistic able to quantify the amount of phase correlation present in the density field, the amplitude drop of the genus compared to a Gaussian field with identical power spectrum. The results for PSCz are consistent with the hypothesis of random-phase initial conditions. In particular, no strong phase correlation is detected on scales ranging from 10 to 32 h ⁻¹ Mpc, whereas there is a positive detection of phase correlation at smaller scales. Among the simulations, phase correlations are detected in all models at small scales, albeit with different strengths. When scaled to a common normalization, the amplitude drop depends primarily on the shape of the power spectrum. We find that the constant-bias standard CDM model can be ruled out at high significance, because the shape of its power spectrum is not consistent with PSCz. The other CDM models with more large-scale power all fit the PSCz data almost equally well, with a slight preference for a high-density τCDM model.  相似文献   

Accurate free–free Gaunt factors for astrophysical plasmas     

Ralph S. Sutherland 《Monthly notices of the Royal Astronomical Society》1998,300(2):321-330

New calculations of free–free transition matrix element integrals are performed using modern symbolic computing techniques to evaluate the hypergeometric functions with complex arguments. The results are presented in both graphical and tabular form including accurate extrapolation methods. The results are accurate to the level of ∼ 10⁻⁴, beyond which relativistic corrections would be needed, which are not included. The results are also computed over a very wide range of scaled ionic temperature (γ²) and wavelength, extending earlier results to new regimes encountered in highly photoionized and non-equilibrium ionization plasmas. These results will be useful in the spectral range from submillimetre to hard X-ray wavelengths and temperatures from 10 to 10⁹ K.  相似文献   

Influence of area on winter wheat climatic models     

D. M. Greene  S. M. Sutherland  M. B. Kirkham 《Climatic change》1979,2(1):21-32

Two areal scales were used to determine the effect of land size on wheat yield estimates from climatic data. The larger scale was the state of Oklahoma and the smaller scale included five crop reporting districts within the state. Two multilinear regression models were developed. One used unadjusted, and the other square-root adjusted, climatic data. Any comparative advantage of district modeling over a state model was judged upon the correlation coefficients of the model and its estimation capability over a five year trial period. When state and district models were compared in estimation capability, the state model achieved more accurate yield estimates of district wheat yields than did the individual district models.  相似文献   

Some theoretical aspects of optimizing complex mineral separation systems     

A. Jowett  D.N. Sutherland 《International Journal of Mineral Processing》1985,14(2):85-109

The use of the concept of maximum technical efficiency as a criterion for optimum setting of a mineral separation stage is discussed. The graphical assessment of an optimum is illustrated by the use of minerals separation curves for flotation of pentlandite and chalcopyrite.For multi-stage circuits it is shown that in some circumstances an often used recycle rule requiring matching streams is in accord with optimizing criteria. However, the rule cannot always be applied, and in the case of flotation systems it may be misleading. Also for flotation, distinctions between optimum setting of a stage and optimum setting of a system are important.An attempt is made to analyze some commonly occurring flowsheet features in terms of optimizing by maximizing technical efficiency. Specifically, cleaner-scavenger operation, bulked recycle streams and open-circuit re-treat systems are assessed by reference to some operations in Australia. The assessment suggests that (within analysis limitations imposed by use of simple optimizing criteria) it may be best to stay with well-established conventional circuitry.  相似文献