Even–odd analysis on a complex shoreline     

Todd L. Walton  Jr 《Ocean Engineering》2002,29(6):711-719

An even–odd signal decomposition is performed on a complex shoreline having a longshore sediment transport gradient. The expected impact of erosion due to a navigation channel and structures is discussed and implications of the transport gradient on the decomposed shoreline signal are noted.  相似文献   

Hydrous olivine alteration on Mars and Earth     

Zoltn Vci  Carl B. Agee  Christopher D. K. Herd  Erin Walton  Oliver Tschauner  Karen Ziegler  Vitali B. Prakapenka  Eran Greenberg  Sylvia Monique‐Thomas 《Meteoritics & planetary science》2020,55(5):1011-1030

Hydrous alteration of olivine macrocrysts in a Martian olivine phyric basalt, NWA 10416, and a terrestrial basalt from southern Colorado are examined using SEM, EPMA, TEM, and µXRD techniques. The olivines in the meteorite contain linear nanotubes of hydrous material, amorphous areas, and fluid dissolution textures quite distinct from alteration identified in other Martian meteorites. Instead, they bear resemblance to terrestrial deuteric alteration features. The presence of the hydrous alteration phase Mg‐laihunite within the olivines has been confirmed by µXRD analysis. The cores of the olivines in both Martian and terrestrial samples are overgrown by unaltered rims whose compositions match those of a separate population of groundmass olivines, suggesting that the core olivines are xenocrysts whose alteration preceded crystallization of the groundmass. The terrestrial sample is linked to deep crustal metasomatism and the “ignimbrite flare‐up” of the Oligocene epoch. The comparison of the two samples suggests the existence of an analogous relatively water‐rich magmatic reservoir on Mars.  相似文献   

A New Model for the Dilation of Brittle Rocks Based on Laboratory Compression Test Data with Separate Treatment of Dilatancy Mobilization and Decay     

G. Walton  M. S. Diederichs 《Geotechnical and Geological Engineering》2015,33(3):661-679

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Aspects of Groundwater Supply Sustainable Yield   总被引：1，自引：0，他引：1  

William C. Walton  Charles F. McLane 《Ground water》2013,51(2):158-160

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The relationship between African easterly waves and daily rainfall over West Africa: observations and regional climate simulations     

Julien Crétat  Edward K. Vizy  Kerry H. Cook 《Climate Dynamics》2015,44(1-2):385-404

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Public Support for Land Acquisition: A Key Instrument for Successful Land Conservation,Governance and Management     

Beatrice Frank  Michael Walton  Rick Rollins 《社会与自然资源》2019,32(6):720-729

While it is recognized that protected areas are important for biodiversity conservation and human wellbeing, governments struggle to establish and/or enlarge protected areas. Land acquisition and the challenges encountered by governing institutions in funding protected area systems expansion is discussed in this paper using the Capital Regional District (CRD) Land Acquisition Fund as a case study. We briefly discuss land acquisition in British Columbia and in the CRD, and offer an overview of the CRD Land Acquisition Fund and the public participation process that led to its establishment. We emphasize the importance of developing political and citizen support, and a shared vision about expanding protected areas systems - a key element for nearly doubling the parkland base of CRD Regional Parks in less than 20?years. We conclude by offering the lessons learned through the case study and provide guidance for policy and governance directions with regard to land acquisition.  相似文献   

High spatial resolution Galactic 3D extinction mapping with IPHAS     

Stuart E. Sale  J. E. Drew  Y. C. Unruh  M.J. Irwin  C. Knigge  S. Phillipps  A. A. Zijlstra  B. T. Gänsicke  R. Greimel  P. J. Groot  A. Mampaso  R. A. H. Morris  R. Napiwotzki  D. Steeghs  N. A. Walton 《Monthly notices of the Royal Astronomical Society》2009,392(2):497-513

We present an algorithm (MEAD, for 'Mapping Extinction Against Distance') which will determine intrinsic  ( r '− i ')  colour, extinction, and distance for early-A to K4 stars extracted from the IPHAS   r '/ i '/Hα  photometric data base. These data can be binned up to map extinction in three dimensions across the northern Galactic plane. The large size of the IPHAS data base (∼200 million unique objects), the accuracy of the digital photometry it contains and its faint limiting magnitude  ( r '∼ 20)  allow extinction to be mapped with fine angular (∼10 arcmin) and distance (∼ 0.1 kpc) resolution to distances of up to 10 kpc, outside the solar circle. High reddening within the solar circle on occasion brings this range down to ∼2 kpc. The resolution achieved, both in angle and depth, greatly exceeds that of previous empirical 3D extinction maps, enabling the structure of the Galactic Plane to be studied in increased detail. MEAD accounts for the effect of the survey magnitude limits, photometric errors, unresolved interstellar medium (ISM) substructure and binarity. The impact of metallicity variations, within the range typical of the Galactic disc is small. The accuracy and reliability of MEAD are tested through the use of simulated photometry created with Monte Carlo sampling techniques. The success of this algorithm is demonstrated on a selection of fields and the results are compared to the literature.  相似文献   

Solution of the MoMaS reactive transport benchmark with MIN3P—model formulation and simulation results     

K. Ulrich Mayer  Kerry T. B. MacQuarrie 《Computational Geosciences》2010,14(3):405-419

This paper summarizes the governing equations as implemented in the MIN3P multicomponent flow and reactive transport code (Mayer et al., Water Resour Res 38:1174, 2002) and introduces the equations in discretized form. Linearization and solution methods are presented including adaptive time stepping and update modification schemes. Code-specific details for the implementation of the GdR MoMaS benchmark simulations (Carrayrou et al., Comput Geosci, 2009) are presented. The standard version of the MIN3P code was used to solve the Easy, Medium, and Hard Test Cases, in one and two spatial dimensions, for both advection- and diffusion-dominated conditions. An analysis of the sensitivity of the solution in relation to spatial and temporal discretization parameters is provided for the Easy Test Case, selected results are presented for the Medium and Hard Test Cases, and the performance of the code as a function of discretization parameters is evaluated for all test cases.  相似文献   

The integration of thermal infrared imaging,discharge measurements and numerical simulation to quantify the relative contributions of freshwater inflows to small estuaries in Atlantic Canada     

Serban Danielescu  Kerry T. B. MacQuarrie  Russell N. Faux 《水文研究》2009,23(20):2847-2859

Nutrient fluxes from developed catchments are often a significant factor in the declining water quality and ecological functioning in estuaries. Determining the relative contributions of surface water and groundwater discharge to nutrient‐sensitive estuaries is required because these two pathways may be characterized by different nutrient concentrations and temporal variability, and may thus require different remedial actions. Quantifying the volumetric discharge of groundwater, which may occur via diffuse seepage or springs, remains a significant challenge. In this contribution, the total discharge of freshwater, including groundwater, to two small nutrient‐sensitive estuaries in Prince Edward Island (Canada) is assessed using a unique combination of airborne thermal infrared imaging, direct discharge measurements in streams and shoreline springs, and numerical simulation of groundwater flow. The results of the thermal infrared surveys indicate that groundwater discharge occurs at discrete locations (springs) along the shoreline of both estuaries, which can be attributed to the fractured sandstone bedrock aquifer. The discharge measured at a sub‐set of the springs correlates well with the area of the thermal signal attributed to each discharge location and this information was used to determine the total spring discharge to each estuary. Stream discharge is shown to be the largest volumetric contribution of freshwater to both estuaries (83% for Trout River estuary and 78% for McIntyre Creek estuary); however, groundwater discharge is significant at between 13% and 18% of the total discharge. Comparison of the results from catchment‐scale groundwater flow models and the analysis of spring discharge suggest that diffuse seepage to both estuaries comprises only about 25% of the total groundwater discharge. The methods employed in this research provide a useful framework for determining the relative volumetric contributions of surface water and groundwater to small estuaries and the findings are expected to be relevant to other fractured sandstone coastal catchments in Atlantic Canada. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

About time: An integrative approach to effective environmental policy     

David J. Hardisty  Ben Orlove  David H. Krantz  Arthur A. Small  Kerry F. Milch  Daniel E. Osgood 《Global Environmental Change》2012,22(3):684-694

Intertemporal trade-offs are ubiquitous in environmental decision-making and policy, yet comprehensive, practical guides are lacking. This paper introduces an adaptive, iterative approach to environmental policy, combining the insights of economics, psychology, and anthropology. We first summarize the major paradigms of each discipline, including models, concepts of time preference, strengths, and blind spots. Subsequently, we illustrate the integrative approach through four real-world environmental examples: a shopper purchasing a light bulb, an organization doing building renovations, a community considering a new source of renewable energy, and international organizations developing index insurance for farmers in the Horn of Africa. One-dimensional approaches are ill-suited to real-world challenges such as these, because each discipline only tackles one facet of the issue. In contrast, with each discipline informing the others, the integrative approach is more than the sum of its parts. This paper provides a concise guide for applied researchers and policy makers alike.  相似文献