Getting to the Bottom of It: Tools,Techniques, and Discoveries of Deep Ocean Geography     

Dawn J. Wright 《The Professional geographer》1999,51(3):426-439

The initial impetus for developing a specialty in ocean geography resulted from the need to resolve applied problems in coastal resources, as opposed to development of oceanographic research methods and concepts. However, the development in the last 10 to 20 years of sophisticated technologies for ocean data collection and management holds tremendous potential for mapping and interpreting the ocean environment in unprecedented detail. With the understanding that ocean research is often very costly, yet deemed extremely important by large funding agencies, geographers now have the opportunity to perform coastal and marine studies that are more quantitative in nature, to formulate and test basic hypotheses about the marine environment, and to collaborate with geographers working in corollary subdisciplines (e.g., remote sensing, GIS, geomorphology, political geography as pertaining to the Law of the Sea, etc.), as well as with classically-trained oceanographers. This article reviews, for the non-specialist, the newest advances in mapping and management technologies for undersea geographic research (particularly on the ocean floor) and discusses the contributions that geographers stand to make to a greater understanding of the oceans.  相似文献   

Laboratory and Field Investigation of Surfactant Sorption Using Single-Well, "Push-Pull" Tests     

J.D. Istok  J.A. Field  M.H. Schroth  T.E. Sawyer  M.D. Humphrey 《Ground water》1999,37(4):589-598

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2009年3月28日山西原平4．2级地震现场考察报告     

山西原平.级地震现场工作队 《山西地震》2009,(3):1-7

2009年3月28日19时11分,在山西省原平市苏龙口镇发生4．2级地震。地震后,由山西省地震局、忻州市地震局联合组成的现场工作队,对此次地震进行了现场考察。经调查,宏观震中位于原平市苏龙口镇下政化村代县新高乡沿村之间,截止到3月30日08时共发生余震67次,宏观震中最大烈度为Ⅴ度,地震有感范围涉及忻州市大部分地区和太原、朔州、阳泉、大同等4市的部分县区,总面积约30000m^2。  相似文献   

Dependence of eelgrass (Zostera marina) light requirements on sediment organic matter in Massachusetts coastal bays: Implications for remediation and restoration     

W.J. Kenworthy  C.L. Gallegos  Charles Costello  Donald Field  Giuseppe di Carlo 《Marine pollution bulletin》2014

Using a calibrated bio-optical model we determined that the optical water quality conditions in several nitrogen-impaired embayments and in one unimpaired system were within the range of values known to support eelgrass growth. We also used the model to identify a range of light requirements for eelgrass (Zostera marina). Higher eelgrass light requirements, expressed as a percentage of surface-incident irradiance, corresponded with higher sediment organic matter content. These results corroborated findings by previous studies which indicate a generalized relationship: seagrasses growing in turbid conditions with poorer water and sediment quality have higher light requirements than those growing in less degraded conditions. The mechanistic reason for the variation in light requirements is still not completely explained and cannot be attributed to a single independent variable. Varying light requirement have important implications for eelgrass protection and should be considered when setting restoration targets for eelgrass in water quality and nitrogen remediation programs.  相似文献   

Resolved OH megamaser emission in the nuclear region of the ultraluminous infrared galaxy Markarian 273     

J. A. Yates  A. M. S. Richards  M. M. Wright  J. L. Collett  M. D. Gray  D. Field  R. J. Cohen 《Monthly notices of the Royal Astronomical Society》2000,317(1):28-36

We present high angular resolution MERLIN observations of the 18-cm OH maser and continuum emission associated with the active core of the ultraluminous infrared galaxy Markarian 273. The continuum emission comes from three distinct regions in the central arcsecond of the galaxy. The brightest region of emission has a double-peaked structure which is spatially coincident with similar structures observed at 6 cm and 2.2 μm. The peak of the OH maser emission is spatially coincident with the peak in the continuum. For the first time the maser emission is spatially resolved, allowing us to measure the gas motion within the central 100 pc of the galaxy. Maser emission is found in both the 1665- and 1667-MHz lines, with no systematic offset found in the spatial locations of the two lines. The brighter component of the maser emission shows ordered motion and is aligned along the axis of the double-peaked structure in the brightest continuum region. The gas motion enables us to estimate the central mass density to be 850±50 M_⊙ pc⁻³, which corresponds to a total mass of ≈1.5×10⁸ M_⊙.  相似文献   

On the Basis for the 0.1 mg/L Water Quality Objective for “Taste and Odor” for Diesel in Groundwater          下载免费PDF全文

Dawn A. Zemo  Kirk T. O'Reilly 《Ground Water Monitoring & Remediation》2016,36(3):88-90

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On the meaning and inapplicability of the Zeldovich relations of magnetohydrodynamics     

E. G. Blackman  G. B. Field 《Astronomische Nachrichten》2005,326(6):386-392

Considering a plasma with an initially weak large scale field subject to nonhelical turbulent stirring, Zeldovich (1957), for two‐dimensions, followed by others for three dimensions, have presented formulae of the form 〈b²〉 = f(R_M) . Such “Zeldovich relations” have sometimes been interpreted to provide steady‐state relations between the energy associated with the fluctuating magnetic field and that associated with a large scale or mean field multiplied by a function f that depends on spatial dimension and a magnetic Reynolds number R_M. Here we dissect the origin of these relations and pinpoint pitfalls that show why they are inapplicable to realistic, dynamical MHD turbulence and that they disagree with many numerical simulations. For 2D, we show that when the total magnetic field is determined by a vector potential, the standard Zeldovich relation applies only transiently, characterizing a maximum possible value that the field energy can reach before necessarily decaying. In 3D, we show that the standard Zeldovich relations are derived by balancing subdominant terms. In contrast, balancing the dominant terms shows that the fluctuating field can grow to a value independent of R_M and the initially imposed , as seen in numerical simulations. We also emphasize that these Zeldovich relations of nonhelical turbulence imply nothing about the amount mean field growth in a helical dynamo. In short, by re‐analyzing the origin of the Zeldovich relations, we highlight that they are inapplicable to realistic steady‐states of large R_M MHD turbulence. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

Cartoblography: Experiments in Using and Organising the Spatial Context of Micro‐blogging     

Kenneth Field  James O'Brien 《Transactions in GIS》2010,14(Z1):5-23

Blogs, micro‐blogs and online forums underpin a more interconnected world. People communicate ever more and are increasingly keen to explain and illustrate their lives; showing where they are and what they are doing. Desktop, online and mobile mapping landscapes have never been as rich or diverse yet this challenges cartography to adapt and remain relevant in the modern mapping world. We explore the spatial expression and potential value of micro‐blogging and Twitter as a social networking tool. Examples of “twitter maps” are reviewed that leverage the Twitter API and online map services to locate some component of the “tweet”. Scope, function and design are illustrated through development of two proof‐of‐concept map mashups that support collaborative real‐time mapping and the organisation and display of information for mass user events. Through the experiments in using and organising data in this way we demonstrate the value of “cartoblography”– a framework for mapping the spatial context of micro‐blogging.  相似文献   

Dimensionless and unbiased CPT interpretation in sand     

Dawn Shuttle  Michael Jefferies 《国际地质力学数值与分析法杂志》1998,22(5):351-391

The cone penetration test (CPT) is widely used, and although initially developed as a stratigraphic logging tool its excellent repeatability and accuracy offers a benchmark quantitative test for sand in particular. A continuing difficulty, however, is that the CPT does not measure any soil property directly, so that parameters of interest must be recovered from solution of an inverse boundary value problem, which is difficult. To date most CPT interpretations in sand have been based on very limited calibration testing carried out in large chambers on a few sands from which mappings are developed. But there are differences in the CPT response from one sand to another leaving the interpretation imprecise (and arguably even speculative) because these differences remain poorly understood. In this paper we use the familiar spherical cavity expansion analogy to the CPT including large strains and a good, critical-state-based, soil model to develop a pattern of behaviour which we then compare to some of the reference chamber test data. We find that one of the issues of dispute in the empirical interpretation methods, the so-called stress-level effect, is caused by neglect of elasticity and that there are several additional parameters of first-order significance to cavity expansion in sands. More generally, we show that the difference in CPT response between various chamber sands in predicted. Our results are cast in dimensionless form and the inversion illustrates that extreme care is required in interpreting CPT data if the in situ sand state is to be determined with precision approaching that suggested as achievable by the repeatability of the CPT data itself. Aspects requiring particular care in interpreting CPT data in sand are discussed. © 1998 John Wiley & Sons, Ltd.  相似文献   

Introduction to “Northern Gulf of Mexico ecosystem change and hazards susceptibility”     

John C. Brock  Dawn L. Lavoie  Richard Z. Poore 《Geo-Marine Letters》2009,29(6):343-347

The northern Gulf of Mexico and its diverse natural resources are threatened by population and development pressure, and by the impacts of rising sea level and severe storms. In the wake of the devastating 2005 hurricane season, and in response to the complex management issues facing the region, the U.S. Geological Survey organized the multidisciplinary “Northern Gulf of Mexico Ecosystem Change and Hazards Susceptibility” project. This special issue of Geo-Marine Letters hosts a few of the early results in the form of 11 papers covering three themes: (1) the control exerted by the underlying geologic framework on geomorphology and nearshore processes and features; (2) impact of human activities on nearshore water quality; and (3) hurricanes and associated effects.  相似文献