Assessing aeolian beach‐surface dynamics using a remote sensing approach     

Irene Delgado‐Fernandez  Robin Davidson‐Arnott  Bernard O. Bauer  Ian J. Walker  Jeff Ollerhead  Hosahng Rhew 《地球表面变化过程与地形》2012,37(15):1651-1660

A remote sensing technique for assessing beach surface moisture was used to provide insight into beach‐surface evolution during an aeolian event. An experiment was carried out on 21 October 2007 at Greenwich Dunes, Prince Edward Island National Park, Canada, during which cameras were mounted on a mast on the foredune crest at a height of about 14 m above the beach. Maps of beach surface moisture were created based on a calibrated relationship between surface brightness from the photographs and surface moisture content measured in situ at points spaced every 2.5 m along a transect using a Delta‐T moisture probe. A time sequence of maps of surface moisture content captured beach surface evolution through the transport event at a spatial and temporal resolution that would be difficult to achieve with other sampling techniques such as impedance probes. Erosion of the foreshore and berm crest resulted in an increase in surface moisture content in these areas as the wetter underlying sediments were exposed. Flow expansion downwind of the berm crest led to sand deposition and a consequent decrease in surface moisture content. Remote sensing systems such as the one presented here allow observations of the combined evolution of beach surface moisture, shoreline position, and fetch distances during short‐term experiments and hence provide a comprehensive rendering of sediment erosion and transport processes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

The SCUBA HAlf Degree Extragalactic Survey – VI. 350-μm mapping of submillimetre galaxies     

Kristen Coppin  Mark Halpern  Douglas Scott  Colin Borys  James Dunlop  Loretta Dunne  Rob Ivison  Jeff Wagg  Itziar Aretxaga  Elia Battistelli  rew Benson  rew Blain  Scott Chapman  Dave Clements  Simon Dye  Duncan Farrah  David Hughes  Tim Jenness  Eelco van Kampen  Cedric Lacey  Angela Mortier  Alexandra Pope  Robert Priddey  Stephen Serjeant  Ian Smail  Jason Stevens  Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,384(4):1597-1610

A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich  ( M _dust≃ 9 × 10⁸ M_⊙)  , luminous  ( L _FIR≃ 2 × 10¹² L_⊙)  star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of  ≃400 M_⊙ yr⁻¹  . We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N ₃₅₀(>25 mJy) ∼ 200–500 deg⁻².  相似文献   

Thermocline bulk shear analysis in the northern North Sea     

Shengli Chen  Jeff A. Polton  Jianyu Hu  Jiuxing Xing 《Ocean Dynamics》2016,66(4):499-508

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A New Zonation Algorithm with Parameter Estimation Using Hydraulic Head and Subsidence Observations     

Meijing Zhang  Thomas J. Burbey  Vitor Dos Santos Nunes  Jeff Borggaard 《Ground water》2014,52(4):514-524

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Tidally induced mean flow over bathymetric features: a contemporary challenge for high-resolution wide-area models     

Jeff A. Polton 《地球物理与天体物理流体动力学》2015,109(3):207-215

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Diamond formation episodes at the southern margin of the Kaapvaal Craton: Re–Os systematics of sulfide inclusions from the Jagersfontein Mine     

Sonja Aulbach  Steven B. Shirey  Thomas Stachel  Steven Creighton  Karlis Muehlenbachs  Jeff W. Harris 《Contributions to Mineralogy and Petrology》2009,157(4):525-540

Sulfide inclusions in diamonds from the 90-Ma Jagersfontein kimberlite, intruded into the southern margin of the Kaapvaal Craton, were analyzed for their Re–Os isotope systematics to constrain the ages and petrogenesis of their host diamonds. The latter have δ¹³C ranging between −3.5 and −9.8‰ and nitrogen aggregation states (from pure Type IaA up to 51% total N as B centers) corresponding to time/temperature history deep within the subcontinental lithospheric mantle. Most sulfides are Ni-poor ([Ni + Co]/Fe = 0.05–0.25 for 15 of 17 inclusions), have elevated Cu/[Fe + Ni + Co] ratios (0.02–0.36) and elemental Re–Os ratios between 0.5 and 46 (12 of 14 inclusions) typical of eclogitic to more pyroxenitic mantle sources. Re–Os isotope systematics indicate two generations of diamonds: (1) those on a 1.7 Ga age array with initial ¹⁸⁷Os/¹⁸⁸Os (¹⁸⁷Os/¹⁸⁸Os_i) of 0.46 ± 0.07 and (2) those on a 1.1 Ga array with ¹⁸⁷Os/¹⁸⁸Os_i of 0.30 ± 0.11. The radiogenic initial Os isotopic composition for both generations of diamond suggests that components with high time-integrated Re–Os are involved, potentially by remobilization of ancient subducted oceanic crust and hybridization of peridotite. A single sulfide with higher Os and Ni content but significantly lower ¹⁸⁷Os/¹⁸⁸Os hosted in a diamond with less aggregated N may represent part of a late generation of peridotitic diamonds. The paucity of peridotitic sulfide inclusions in diamonds from Jagersfontein and other kimberlites from the Kaapvaal craton contrasts with an overall high relative abundance of diamonds with peridotitic silicate inclusions. This may relate to extreme depletion and sulfur exhaustion during formation of the Kaapvaal cratonic root, with the consequence that in peridotites, sulfide-included diamonds could only form during later re-introduction of sulfur.  相似文献   

Design and Cost Analysis of Rapid Aquifer Restoration Systems Using Flow Simulation and Quadratic Programming   总被引：2，自引：0，他引：2  

L. Jeff Lefkoff  Steven M. Gorelick 《Ground water》1986,24(6):777-790

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Predictions of hydrothermal alteration within near-ridge oceanic crust from coordinated geochemical and fluid flow models     

Laura Reiser Wetzel  Jeff P. Raffensperger  Everett L. Shock   《Journal of Volcanology and Geothermal Research》2001,110(3-4)

Coordinated geochemical and hydrological calculations guide our understanding of the composition, fluid flow patterns, and thermal structure of near-ridge oceanic crust. The case study presented here illustrates geochemical and thermal changes taking place as oceanic crust ages from 0.2 to 1.0 Myr. Using a finite element code, we model fluid flow and heat transport through the upper few hundred meters of an abyssal hill created at an intermediate spreading rate. We use a reaction path model with a customized database to calculate equilibrium fluid compositions and mineral assemblages of basalt and seawater at 500 bars and temperatures ranging from 150 to 400°C. In one scenario, reaction path calculations suggest that volume increases on the order of 10% may occur within portions of the basaltic basement. If this change in volume occurred, it would be sufficient to fill all primary porosity in some locations, effectively sealing off portions of the oceanic crust. Thermal profiles resulting from fluid flow simulations indicate that volume changes along this possible reaction path occur primarily within the first 0.4 Myr of crustal aging.  相似文献   

A Travel Cost Study of Duck Hunting in the Upper South East of South Australia     

Stuart M. Whitten  Jeff W. Bennett 《The Australian geographer》2002,33(2):207-221

Wetlands in the Upper South East (USE) of South Australia yield a range of values to their owners and to the wider community. One such value is that generated by duck hunting in the region. Wetland owners receive private benefits from hunting fees, while hunters gain a non-monetary consumers' surplus. These non-monetary benefits received by duck hunters through their enjoyment of hunting in wetlands are the primary focus of this paper. In order to estimate these values, a 'travel cost' survey of duck hunters participating in an organised shoot held by Wetlands and Wildlife in February 2000 was undertaken. The extent of the private recreation benefits so estimated is assessed in terms of their potential to stimulate the provision of wetlands for both private and social benefits.  相似文献   

A detailed study of the distribution of heat flow and radioactivity in New Hampshire (U.S.A.)     

Claude Jaupart  Jeff R. Mann  Gene Simmons 《Earth and Planetary Science Letters》1982,59(2):267-287

We present a set of 39 new determinations of heat flow and radiogenic heat production for several different geological environments in the State of New Hampshire (U.S.A.). With the extensive data set now available for the state, the linear relation of heat flow and heat production appears as a very useful generalization for the study of the heat flow field of a geological province. Our measurements indicate that the vertical distribution of radiogenic heat production is similar in plutonic and metasedimentary rocks. Our data are compatible with the linear relationship established earlier by F. Birch and his co-workers in 1968. Young granites are markedly enriched in radioactive elements and those which do not outcrop are revealed by anomalies in the general relation of heat flow versus radioactivity.Heat flow is high for plutons by low elsewhere. The mean heat flow through metasedimentary formations is 1.15 μcal/cm² s (48 mW/m²), a value near the mean heat flow for old cratons. The lowest heat flow measured is 0.76 μcal/cm² s (32 mW/m²) for a unit poor in radioactivity. The heat flow field grades smoothly into the low heat flow regions of the Canadian Shield.The New Hampshire region is in thermal equilibrium: its heat flow is in secular equilibrium with the heat generated by crustal sources and that supplied from the mantle. In this area, the thermal perturbations due to orogenic events decrease below the detection level in less than 200–275 Ma. The thickness of the layer which is thermally affected during continent-continent collision-type orogenies cannot be greater than about 190 km.  相似文献