Grid in earth sciences     

M. Petitdidier  R. Cossu  P. Mazzetti  P. Fox  H. Schwichtenberg  W. Som de Cerff 《Earth Science Informatics》2009,2(1-2):1-3

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HR 4049: temporal variations in the structure of the circumstellar material     

J. J. Johnson  C. M. Anderson  K. S. Bjorkman †  A. D. Code  G. K. Fox  A. J. Weitenbeck  B. L. Babler  M. R. Meade  N. E. B. Zellner  O. L. Lupie 《Monthly notices of the Royal Astronomical Society》1999,306(3):531-537

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Basement geology beneath the northeast Thelon Basin,Nunavut: insights from integrating new gravity,magnetic and geological data   总被引：1，自引：0，他引：1       下载免费PDF全文

V. Tschirhart  C.W. Jefferson  W.A. Morris 《Geophysical Prospecting》2017,65(2):617-636

Current models for unconformity‐associated uranium deposits predict fluid flow and ore deposition along reactivated faults in >1.76 Ga basement beneath Mesoproterozoic siliciclastic basins. In frontier regions such as the Thelon Basin in the Kivalliq region of Nunavut, little is known about the sub‐basin distribution of units and structures, making exploration targeting very tenuous. We constructed a geological map of the basement beneath the unconformity by extrapolating exposed features into the subsurface. The new map is constrained by detailed geological, geophysical, and rock property observations of outcrops adjacent to the basin and by aeromagnetic and gravity data over the geophysically transparent sedimentary basin. From rock property measurements, it is clear that the diverse magnetic and density characteristics of major rock packages provide quantitative three‐dimensional constraints. Gravity profiles forward modelled in four cross sections define broad synforms of the Amer Belt and Archean volcanic rocks that are consistent with the structural style outside the basin. Major lithotectonic entities beneath the unconformity include: supracrustal rocks of the Archean Woodburn Lake group and Marjorie Hills meta sedimentary gneiss and associated mixed granitoid and amphibolitic gneiss; the Amer Mylonite Zone and inferred mafic intrusions oriented parallel and sub‐parallel; other igneous intrusions of 2.6 Ga, 1.83 Ga, and 1.75 Ga vintage; and the <2.3 Ga to >1.84 Ga Amer Group. Four main brittle regional fault arrays (040°–060°, 075°–90°, 120°, and 150°) controlled development and preservation of the basin. The reactivated intersections of such faults along fertile basement units such as the Rumble assemblage, Marjorie Hills assemblage, Nueltin igneous rocks, and Pitz formation are the best targets for uranium exploration.  相似文献   

Stormwater management network effectiveness and implications for urban watershed function: A critical review          下载免费PDF全文

Anne J. Jefferson  Aditi S. Bhaskar  Kristina G. Hopkins  Rosemary Fanelli  Pedro M. Avellaneda  Sara K. McMillan 《水文研究》2017,31(23):4056-4080

Deleterious effects of urban stormwater are widely recognized. In several countries, regulations have been put into place to improve the conditions of receiving water bodies, but planning and engineering of stormwater control is typically carried out at smaller scales. Quantifying cumulative effectiveness of many stormwater control measures on a watershed scale is critical to understanding how small‐scale practices translate to urban river health. We review 100 empirical and modelling studies of stormwater management effectiveness at the watershed scale in diverse physiographic settings. Effects of networks with stormwater control measures (SCMs) that promote infiltration and harvest have been more intensively studied than have detention‐based SCM networks. Studies of peak flows and flow volumes are common, whereas baseflow, groundwater recharge, and evapotranspiration have received comparatively little attention. Export of nutrients and suspended sediments have been the primary water quality focus in the United States, whereas metals, particularly those associated with sediments, have received greater attention in Europe and Australia. Often, quantifying cumulative effects of stormwater management is complicated by needing to separate its signal from the signal of urbanization itself, innate watershed characteristics that lead to a range of hydrologic and water quality responses, and the varying functions of multiple types of SCMs. Biases in geographic distribution of study areas, and size and impervious surface cover of watersheds studied also limit our understanding of responses. We propose hysteretic trajectories for how watershed function responds to increasing imperviousness and stormwater management. Even where impervious area is treated with SCMs, watershed function may not be restored to its predevelopment condition because of the lack of treatment of all stormwater generated from impervious surfaces; non‐additive effects of individual SCMs; and persistence of urban effects beyond impervious surfaces. In most cases, pollutant load decreases largely result from run‐off reductions rather than lowered solute or particulate concentrations. Understanding interactions between natural and built landscapes, including stormwater management strategies, is critical for successfully managing detrimental impacts of stormwater at the watershed scale.  相似文献   

Soil pipe flow tracer experiments: 2. Application of a streamflow transient storage zone model          下载免费PDF全文

Yan Zhou  G. V. Wilson  G.A. Fox  J.R. Rigby  S.M. Dabney 《水文研究》2016,30(8):1280-1291

Soil pipes are important subsurface flow pathways in many soil erosion phenomena. However, limited research has been performed on quantifying and characterizing their flow and transport characteristics. The objectives of this research were to determine the applicability of a streamflow model with transient storage in deriving flow and transport characteristics of soil pipes. Tracer data from pulse inputs were collected in four different soil pipes after a fluorescein dye was injected in the upstream end of each soil pipe network in three branches (west, middle, and east) of a main catchment and a back catchment in Goodwin Creek Experimental Watershed in Mississippi. Multiple sampling stations were positioned along each soil pipe network. The transient storage zone model OTIS‐P was executed inversely to estimate transport parameters by soil pipe reach such as the soil pipe cross‐sectional area (A), soil storage zone cross‐sectional area (A_s), and exchange rate between the soil pipe and the soil storage zone (α_s). Model convergence was achieved, and simulated breakthrough curves of the reaches were in good agreement with actual tracer data for eight of the nine reaches of the three branches of the Main Catchment and five of the seven reaches of the Back Catchment soil pipe. Simulation parameters for the soil pipe networks were similar to the range of values reported for flow and transport characteristics commonly observed in streams. Inversely, estimated soil pipe flow velocities were higher with increased tortuosity, which led to a smaller cross‐sectional areas predicted for the soil pipe flowpaths, while other parameters were not sensitive to tortuosity. In general, application of One‐Dimensional Transport with Inflow and Storage‐P to this unique soil pipe condition suggested larger transient storage (A_s and α_s) compared with most stream systems. This was hypothesized to be because of relatively higher ratio of the wetted perimeter to flow area in the soil pipe, the hydraulic roughness of the soil pipe, potential retention in collapsed portions of the pipe, and interaction with smaller preferential flow systems. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Ground truthed performance of single‐and dual‐polarized radar rain rates at large ranges          下载免费PDF全文

Micheal J. Simpson  Jason A. Hubbart  Neil I. Fox 《水文研究》2016,30(20):3692-3703

Radar accuracy in estimating qualitative precipitation estimation at distances larger than 120 km degrades rapidly because of increased volume coverage and beam height. The performance of the recently upgraded dual‐polarized technology to the NEXRAD network and its capabilities are in need of further examination, as improved rainfall estimates at large distances would allow for significant hydrological modelling improvements. Parameter based methods were applied to radars from St. Louis (KLSX) and Kansas City (KEAX), Missouri, USA, to test the precision and accuracy of both dual‐ and single‐polarized parameter estimations of precipitation at large distances. Hourly aggregated precipitation data from terrestrial‐based tipping buckets provided ground‐truthed reference data. For all KLSX data tested, an R(Z,ZDR) algorithm provided the smallest absolute error (3.7 mm h^?1) and root‐mean‐square‐error (45%) values. For most KEAX data, R(ZDR,KDP) and R(KDP) algorithms performed best, with RMSE values of 37%. With approximately 100 h of precipitation data between April and October of 2014, nearly 800 and 400 mm of precipitation were estimated by radar precipitation algorithms but was not observed by terrestrial‐based precipitation gauges for KLSX and KEAX, respectively. Additionally, nearly 30 and 190 mm of measured precipitation observed by gauges were not detected by the radar rainfall estimates from KLSX and KEAX, respectively. Results improve understanding of radar based precipitation estimates from long ranges thereby advancing applications for hydrometeorological modelling and flood forecasting. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Book reviews     

Colin Woodroffe  R.W. Young  Marilyn Fox  David Mercer  Paul S. Kench  J.M. Powell 《The Australian geographer》1996,27(2):279-285

Kakadu: natural and cultural heritage and management

E.J. Press, D.A.M. Lea, A. Webb & A. Graham (eds), 1995

Australian Nature Conservation Agency & North Australia Research Unit, Australian National University, Darwin

17 × 25 cm, xviii + 318 pp., ISBN 0–7315–2171–4, A$29.95 (soft)

The landforms of England and Wales

A. Goudie, 1993 (first published in hardcover in 1990)

Blackwell, Oxford

23 × 15 cm, xi + 394 pp., ISBN 0–631–16367–0, A$45.00 (soft)

Technological change and the city

P.N. Troy (ed.), 1995

Federation Press, Sydney

14 × 21 cm, vi + 202 pp., ISBN 1–86287–184–1, A$35.00 (soft)

Oceanic islands

P.D. Nunn, 1994

Blackwell, Oxford

17 × 25 cm, xv + 413 pp., ISBN 0–631–17811–7, A$90.00 (soft)

Aotearoa and New Zealand: a historical geography

A. Grey, 1994

Canterbury University Press, Christchurch

14 × 21 cm, xix + 476 pp., ISBN 0–908812–34–5, NZ$29.95 (soft)  相似文献   

Solar atmospheric model including OH-continuum opacity     

P. W. Fox  S. P. Tarafdar 《Solar physics》1978,60(2):241-250

Flux-constant model has been constructed for solar atmosphere, including OH-bound-free opacity, but without any line opacity, atomic, ionic or molecular. A comparison between the theoretical and observed intensity and flux shows that OH-opacity can account for the missing solar opacity, except at those wavelengths where the intensity shows the presence of numerous absorption lines, provided the unknown oscillator strength of the transition is 0.3. The T – relation, however gives larger temperatures at smaller depths than those by the empirical model. This and the large theoretical flux in the spectral region with heavy line absorption indicate the importance of line opacity.On leave from Tata Institute of Fundamental Research, Bombay-400005, India.  相似文献   

A multi‐asperity plastic‐contact crack plane model for geomaterials     

I. C. Mihai  A. D. Jefferson 《国际地质力学数值与分析法杂志》2013,37(11):1492-1509

A mechanistic constitutive model for fully formed cracks in geomaterials, such as concrete and rock, is presented. A three‐dimensional characterisation of the crack morphology is employed in which the crack surface is idealised as a series of conical teeth and corresponding recesses of variable height and slope. Based on this geometrical characterisation, an effective contact function is derived to relate the contact stresses that develop on the sides of the teeth to the net stresses on a crack plane. Plastic embedment and frictional sliding are simulated using a local plasticity model in which the plastic surfaces are expressed in terms of the contact surface function in cylindrical relative displacement space. Finally, the performance of the model is assessed against several sets of experimental data from direct shear tests, and it is concluded that the model is able to capture key characteristics of the behaviour of fully formed cracks in geomaterials. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Benthic control upon the morphology of transported fine sediments in a low‐gradient stream          下载免费PDF全文

James Fox  William Ford  Kyle Strom  Gabriele Villarini  Michelle Meehan 《水文研究》2014,28(11):3776-3788

The structure of fluvial sediments in streams has environmental implications to contaminant fate, nutrient budgeting and the carbon flux associated with fine particulate organic matter (FPOM). However, the influence of sediment structure is lacking in environmental predictive models. To this end, the present study links field‐based results of sediment aggregate structure to seasonal biological functions in the surface fine‐grained laminae (SFGL) of a low‐gradient stream. Fluvial sediment collection, microscopy and image analysis are used to show that aggregates collected over a 20 month time period support the concept that aggregate structure can vary seasonally in low‐gradient streams where temporarily stored sediment is prominent. Results show that the structure of the transported aggregates is more irregular in the summer with the structure being elongated about the long axes. In the winter, the aggregate structure is compacted and more spherical. Statistical analysis and results suggest that heterotrophic and autotrophic biological activity within the SFGL exhibits seasonal control upon the morphology of transported sediments. Implications of this research are highlighted through calculations of the reactive surface area of the transported suspended sediment load. The surface area of transported sediment is estimated to be 40% greater in the summer as compared to the winter time period, which implies that (i) the affinity of sediments to sorb contaminants is higher in summer months and (ii) the downstream reactivity of FPOM in large rivers, lakes and estuaries is not just a function of microbial drivers but also the seasonally dependent structure of transported FPOM derived from low‐order streams. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献