A simulated τCDM cosmology cluster catalogue: the NFW profile and the temperature–mass scaling relations     

P. A. Thomas  Orrarujee Muanwong  F. R. Pearce  H. M. P. Couchman  A. C. Edge  A. Jenkins  L. Onuora 《Monthly notices of the Royal Astronomical Society》2001,324(2):450-462

We have extracted over 400 clusters, covering more than two decades in mass, from three simulations of the τ CDM cosmology. This represents the largest uniform catalogue of simulated clusters ever produced. The clusters exhibit a wide variety of density profiles. Only a minority are well-fitted in their outer regions by the widely used density profile of Navarro, Frenk & White (NFW), which is applicable to relaxed haloes. Others have steeper outer density profiles, show sharp breaks in their density profiles, or have significant substructure. If we force a fit to the NFW profile, then the best-fitting concentrations decline with increasing mass, but this is driven primarily by an increase in substructure as one moves to higher masses. The temperature–mass relations for properties measured within a sphere enclosing a fixed overdensity all follow the self-similar form, T ∝ M ^2/3; however, the normalization is lower than the value inferred for observed clusters. The temperature–mass relations for properties measured within a fixed physical radius are significantly steeper then this. Both can be accurately predicted using the NFW model.  相似文献   

Performance of ground penetrating radar in root detection and its application in root diameter estimation under controlled conditions     

Shan Wing Yeung  Wai Man Yan  Chi Hang Billy Hau 《中国科学:地球科学(英文版)》2016,59(1):145-155

A plant is stabilized by its root system. In congested urban cities such as Hong Kong, ground trenching is frequently seen due to the installation of utility lines along the roadside. Soil nailing, which involves soil coring in slopes, is a common solution to improve the slope stability. However, both activities inevitably pose a risk to the integrity of any root systems present, and thus reduce the root anchorage. To prevent or minimize such damage, a careful design of the excavation/drilling location is of prime importance. Ground penetrating radar (GPR) provides a non-destructive method for locating roots by examining the contrast between the dielectric properties of the roots and the surrounding soil. To examine the performance of GPR and promote its use in Hong Kong, a test bed was prepared using local materials to create a controlled environment in which to conduct a series of systematic tests evaluating the performance of a 900 MHz GPR. The reflected radargrams were subject to the influence of the following factors: size and depth of roots, horizontal distance between roots, and contrast between the root and soil water content. Correlations between root size and a number of waveform parameters were also explored. Limiting values for root size, root embedded depth, horizontal separation distance between roots, and water content contrast between root and soil were obtained. A significant correlation was found between the root diameter and time travel parameter T ₂ (p<0.001, r=0.795). Because GPR root detection is highly site-specific, this study provides a local reference for GPR performance in the Hong Kong environment. The findings demonstrate that the 900 MHz GPR is applicable in Hong Kong for the detection of main roots.  相似文献   

Near-infrared evolution of brightest cluster galaxies in the most X-ray luminous clusters since  z= 1      

J. P. Stott  A. C. Edge  G. P. Smith  A. M. Swinbank  H. Ebeling 《Monthly notices of the Royal Astronomical Society》2008,384(4):1502-1510

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Tidal gravity and ocean tide loading in Europe     

T. F. Baker  R. J. Edge  G. Jeffries 《Geophysical Journal International》1991,107(1):1-11

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The results are presented from tidal gravity measurements at five sites in Europe using LaCoste and Romberg ET gravimeters. Improvements that we have made to the accuracies of these gravimeters are discussed. It is shown that the 'standard' calibration of the International Center for Earth Tides, used for worldwide tidal gravity profiles, is 1.2 per cent too high. The M₂ and O₁ observations are compared with model calculations of the Earth's body tide and ocean tide loading and it is shown that there is a very significant improvement in the agreement between observations and models compared to that obtained with previous tidal gravity measurements. For O₁, where the ocean tide loading and attraction in central Europe is only 0.4 per cent of the body tide, our measurements verify that the Dehant-Wahr anelastic body tide model gravimetric factor is accurate to 0.2 per cent. It is also shown that the effects of lateral heterogeneities in Earth structure on tidal gravity are too small to explain the large anomalies in previously published tidal gravity amplitudes. The observations clearly show the importance of conserving tidal mass in the Schwiderski ocean tide model. For sites in central Europe, the M₂ and O₁ observations and the models are in agreement at the 0.1 μgal (10⁻⁹ m s⁻²) level and tidal corrections to this accuracy can now be made to absolute gravity measurements.  相似文献   

A ROSAT study of the cores of clusters of galaxies — I. Cooling flows in an X-ray flux-limited sample     

C. B. Peres  A. C. Fabian  A. C. Edge  S. W. Allen  R. M. Johnstone  & D. A. White 《Monthly notices of the Royal Astronomical Society》1998,298(2):416-432

This is the first part of a study of the detailed X-ray properties of the cores of nearby clusters. We have used the flux-limited sample of 55 clusters listed by Edge et al., and archival and proprietary data from the ROSAT observatory. In this paper an X-ray spatial analysis based on the surface-brightness-deprojection technique is applied to the clusters in the sample with the aim of studying their cooling flow properties. We determine the fraction of cooling flows in this sample to be 70–90 per cent, and estimate the contribution of the flow region to the cluster X-ray luminosity. We show that the luminosity within a strong cooling flow can account for up to 70 per cent of a cluster X-ray bolometric luminosity. Our analysis indicates that about 40 per cent of the clusters in the sample have flows depositing more than 100 M⊙ yr⁻¹ throughout the cooling region, and that these possibly have been undisturbed for many Gyr, confirming that cooling flows are the natural state of cluster cores. New cooling flows in the sample are presented, and previously ambiguous ones are clarified. We have constructed a catalogue of some intracluster medium properties for the clusters in this sample. The profiles of the mass deposited from cooling flows are analysed, and evidence is presented for the existence of breaks in some of the profiles. Comparison is made to recent optical and radio data. We cross-correlate our sample with the Green Bank, NVSS and FIRST surveys, and with the volume-limited sample of brightest cluster galaxies presented by Lauer &38; Postman. Although weak trends exist, no strong correlation between optical magnitude or radio power of the brightest cluster galaxy and the strength of the flow is found.  相似文献   

Trace element study of high- and low-refractive index Muong Nong-type tektites from Indochina     

Billy P. Glass  Christian Koeberl 《Meteoritics & planetary science》1989,24(3):143-146

Abstract— Previous work indicates that Muong Nong-type tektites from Indochina with low refractive indices and high silica contents contain relict mineral grains while those with high refractive indices and low silica contents do not. Instrumental Neutron Activation Analysis (INAA) was used to determine selected trace element concentrations for four Muong Nong-type tektites with high refractive indices and no relict mineral inclusions and one with low refractive index and relict inclusions, to determine if there are any systematic differences in trace element compositions between the two groups. The data also were compared with published trace element data for sixteen Muong Nong-type tektites which have low refractive indices and, therefore, should contain relict inclusions. Except for Ta which had lower concentrations in the high refractive index group, there is no consistent difference in trace element compositions between the two groups. We interpret these results to indicate a single, slightly heterogeneous source for the Muong Nong-type tektites, rather than different source regions.  相似文献   

A bucket wheel dredge system for offshore tin mining beyond the 50 m water depth     

A. Albar  R. E. Randall  B. Dwibarto  B. L. Edge 《Ocean Engineering》2002,29(14):1751-1767

A bucket wheel dredge (BWD) for offshore tin mining is part of the long term plan of PT Timah Tbk to identify new dredging technologies for mining in greater than 50 m water depths. Measured tin-ore physical properties are used in a new BWD computer model to investigate deep water tin mining. The model simulates the cutting and hydraulic transport of submerged tin-ore. The results show that hydraulic tin mining beyond water depths of 50 m is feasible. It is best to employ hydraulic transport for lifting the tin-ore from the ocean floor to the surface and to use barges to transport the tin-ore to land processing plants.  相似文献   

Cohesive sediment transport in the 3D-hydrodynamic-baroclinic circulation model,: study case for idealized tidal inlet     

Wahyu W. Pandoe  Billy L. Edge 《Ocean Engineering》2004,31(17-18):2227-2252

This work provides a general hydrodynamic circulation model that can be used to understand density driven flows, which may arise in the case of suspension of fine-grained materials. The research is expected to provide a better understanding of the characteristics of spatial and temporal variability of current, which is associated with the period of ebb and flood tidal cycles.The model development includes extending the existing three-dimensional (3D) ADCIRC model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for cohesive type sediment. In the case of an idealized tidal inlet in stratified water, the inclusion of baroclinic term can demonstrate the prevailing longshore sediment transport. It is shown that the model has application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast.  相似文献   

Three-dimensional hydrodynamic model, study cases for quarter annular and idealized ship channel problems     

W. W. Pandoe  B. L. Edge 《Ocean Engineering》2003,30(9):1117-1135

An extended version of the three-dimensional hydrodynamic model, ADCIRC 3D-DSS, was utilized to simulate both horizontal and vertical flows in a (quarter) annular harbor (QATP and ATP) and rectangular basin with an idealized ship channel (RBSC). Comparison of horizontal and vertical solutions to the analytical solution and results of other researchers are in good agreement. The vertical velocity solution is highly sensitive to the horizontal velocity solutions. The presence of the sidewall boundary may also affect the vertical solutions. Around the sloping bank of RBSC channel with one-third gradient, the vertical velocity becomes important. The maximum vertical velocity approaches ±50% of the sediment fall velocity of fine sand.  相似文献   

A necessary voice: Climate change and lived experiences of youth in Rigolet,Nunatsiavut, Canada     

Joanna Petrasek MacDonald  Sherilee L. Harper  Ashlee Cunsolo Willox  Victoria L. Edge 《Global Environmental Change》2013,23(1):360-371

Globally, youth voices and their experiences, observations, and perceptions about climatic and environmental change and variability are relatively absent in the published literature to date. To address this gap, the goal of this research was to explore the observations and perceptions of climate change held by youth (12–25 years old) in the Inuit community of Rigolet, Nunatsiavut, Canada. Twenty in-depth interviews were conducted with youth in Rigolet to gather data about climatic and environmental changes young people have observed, and the subsequent impacts of these changes on their lives, culture, and community. Youth reported observing and experiencing climatic and environmental changes throughout their lives, with reported impacts falling within five main themes: changing travel conditions and access to hunting; challenges to Inuit culture; a concern for Elder and senior well-being; strong climate-related emotional responses; and youth-identified potential adaptation strategies. More broadly, this research demonstrated that young people have valuable knowledge and perspectives to offer. In particular, researchers, community leaders, and policy makers are encouraged to meaningfully engage youth as crucial stakeholders in future climate change work, research, dialogue, and policy.  相似文献