Multichannel analysis of surface wave method with the autojuggie   总被引：2，自引：0，他引：2  

Gang Tian  Don W. Steeples  Jianghai Xia  Richard D. Miller  Kyle T. Spikes  Matthew D. Ralston 《Soil Dynamics and Earthquake Engineering》2003,23(3):61-65

The shear (S)-wave velocity of near-surface materials and its effect on seismic-wave propagation are of fundamental interest in many engineering, environmental, and groundwater studies. The multichannel analysis of surface wave (MASW) method provides a robust, efficient, and accurate tool to observe near-surface S-wave velocity. A recently developed device used to place large numbers of closely spaced geophones simultaneously and automatically (the ‘autojuggie’) is shown here to be applicable to the collection of MASW data. In order to demonstrate the use of the autojuggie in the MASW method, we compared high-frequency surface-wave data acquired from conventionally planted geophones (control line) to data collected in parallel with the automatically planted geophones attached to steel bars (test line). The results demonstrate that the autojuggie can be applied in the MASW method. Implementation of the autojuggie in very shallow MASW surveys could drastically reduce the time required and costs incurred in such surveys.  相似文献   

Hg and As Minerals in Fluid Inclusions from the Williams Mine,Hemlo,and Their Genetic Implications   总被引：1，自引：0，他引：1  

卢焕章 《中国地球化学学报》2002,21(1):1-18

The Hemlo mineralization is enigmatic compared to general Archean lode gold deposits based on the fact that is characterized by an exotic mineralogy containing elements such as As,Hg,Sb,Ba,V and Mo.The genetic concepts range from syngenetc to epigenetic types of mineralization.This reconnaissance study was designed to examine the relationshp of Hg-As minerals with respect of fluid inclusions in the Williams mine(formerly known as the Page Williams mine)covering the A and C ore zones.  相似文献   

Conflicting rights to the city in New York's community gardens   总被引：1，自引：0，他引：1  

Lynn A. Staeheli  Don Mitchell  Kristina Gibson 《GeoJournal》2002,58(2-3):197-205

In the mid-1990s, New York City initiated what would prove to be a long, highly visible struggle involving rights claims related to property, housing, and public space in the form of community gardens. The competing discourses of rights were part of a struggle over the kind of city that New York was to become, and more specifically, whether it would be one in which difference is accepted and in which access to the city and the public realm would be guaranteed. Using interviews with participants in the conflict over community gardens, we evaluate how the resolution to the gardens crisis, which in part occurred through the privatization of what are often taken to be public or community rights to land, transform not only the legal status of the gardens but also, potentially, their role as places where different `publics' can both exercise their right to the city and solidify that right in the landscape.  相似文献   

Permafrost science and secondary education: direct involvement of teachers and students in field research     

Anna E. Klene  Frederick E. Nelson  John Nevins  Don Rogers  Nikolay I. Shiklomanov 《Geomorphology》2002,47(2-4)

Permafrost and periglacial geomorphology are absent from the science curriculum in most secondary schools in the United States. This is an unfortunate situation given the recent increases in development and environmental concerns in northern latitudes and high-mountain areas, and the interesting examples of basic scientific principles found in the history of research on periglacial geomorphology and permafrost. In 1997 and 1998, a University of Delaware research group studying permafrost and periglacial geomorphology in northern Alaska participated in the National Science Foundation's (NSF) Teachers Experiencing the Antarctic and Arctic (TEA) Program. In each of these years, a high school teacher and a student traveled as part of the research team to the North Slope of Alaska. They learned about the landscape, collected active-layer thickness and temperature measurements, and assisted in data analysis. Results from studies of active-layer thickness variability and ground temperature contributed to a series of long-term observations and international research on the impacts of global climate change. Since their expeditions, the teachers have shared their experiences with their classrooms and communities in several ways, including public lectures and the Internet. Classroom activities are available to the public through the TEA web site (http://tea.rice.edu). This experience may heighten public awareness of permafrost and contribute to it becoming a useful part of the secondary curriculum.  相似文献   

Results from the Wide Angle Search for Planets Prototype (WASP0) – III. Planet hunting in the Draco field     

Stephen R. Kane †  rew Collier Cameron  Keith Horne  David James  T. A. Lister  Don L. Pollacco  Rachel A. Street  Yiannis Tsapras 《Monthly notices of the Royal Astronomical Society》2005,364(3):1091-1103

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Linking large-parallax Spitzer–CFHT–VLT astrometry of asteroids     

Mikael Granvik  Karri Muinonen  Lynne Jones  Bidushi Bhattacharya  Marco Delbo  Laura Saba  Alberto Cellino  Edward Tedesco  Don Davis  Victoria Meadows 《Icarus》2007,192(2):475-490

We show that the new ephemeris-space multiple-address-comparison (eMAC) method solves asteroid linking problems despite large parallaxes by applying the method to astrometric asteroid observation sets obtained nearly simultaneously with the Spitzer space telescope, the Canada–France–Hawaii Telescope (CFHT), and European Southern Observatory's Very Large Telescope (VLT). For main-belt asteroids, the parallax between Spitzer and the Earth-based telescopes is approximately one degree which is large as compared to a typical parallax for solely Earth-based telescopes in the arcseconds regime. In the eMAC method, we reduce the initially huge amount of possible linkages between observation sets by comparing samples of ephemerides that have been computed separately for all sets at, say, three common dates. If the non-zero ephemeris probability densities overlap at all common dates, we try to find an orbit solution for these so-called trial linkages. If there exists an orbit which reproduces all the astrometric observations assuming predefined observational errors, we call it a linkage. Known asteroids are independently identified among Spitzer, CFHT, and VLT astrometry, and comparing the identified observations to the linkages found shows that the method found all known correct linkages present in the data. In addition, we also found five previously unpublished linkages between Spitzer astrometry and Earth-based astrometry. Based on our simulations, we found virtually all Spitzer-related linkages between two single-night observation sets, and more than 99.4% of linkages between two single-night observation sets obtained by Earth-based observatories. Virtually all correct linkages consisting of at least three single-night sets were also detected. The results show that large-parallax discovery observations made from a spacecraft can be linked to Earth-based follow-up observations to ensure that the objects are not lost. Furthermore, we compute the heliocentric and Spitzer-centric distances as well as the corresponding solar phase angles at the dates of Spitzer observations. Based on comparisons to simulated geocentric observations, we also show that, for typical nearly-simultaneous observations, the parallax reduces the distance uncertainties by several orders of magnitude.  相似文献   

Mapping Paleo‐Fire Boundaries from Binary Point Data: Comparing Interpolation Methods     

Amy Hessl  Jennifer Miller  James Kernan  David Keenum  Don McKenzie 《The Professional geographer》2007,59(1):87-104

Fire history studies have traditionally emphasized temporal rather than spatial properties of paleo‐fire regimes. In this study we compare four methods of mapping paleo‐fires in central Washington from binary point data: indicator kriging, inverse distance weighting, Thiessen polygons, and an expert approach. We evaluate the results of each mapping method using a test (validation) dataset and receiver operating characteristic plots. Interpolation methods perform well, but results vary with fire size and spatial pattern of points. Though all methods involve some subjectivity, automated interpolation methods perform well, are replicable, and can be applied across varying landscapes.  相似文献   

Halogen diffusion in a basaltic melt   总被引：2，自引：0，他引：2  

Marina Alletti  Don R. Baker  Carmela Freda 《Geochimica et cosmochimica acta》2007,71(14):3570-3580

The diffusion of the halogens fluorine, chlorine and bromine was measured in a hawaiitic melt from Mt. Etna at 500 MPa and 1.0 GPa, 1250 to 1450 °C at anhydrous conditions; the diffusion of F and Cl in the melt was also studied with about 3 wt% of dissolved water. Experiments were performed using the diffusion-couple technique in a piston cylinder. Most experiments were performed with only one halogen diffusing between the halogen-enriched and halogen-poor halves of the diffusion couple, but a few experiments with a mixture of halogens (F, Cl and Br) were also performed in order to investigate the possibility of interactions between the halogens during diffusion. Fluorine and chlorine diffusivity show a very similar behavior, slightly diverging at low temperature. Bromine diffusion is a factor of about 2-5 lower than the other halogens in this study. Diffusion coefficients for fluorine range between 2.3 × 10⁻¹¹ and 1.4 × 10⁻¹⁰ m² s⁻¹, for chlorine between 1.1 × 10⁻¹¹ and 1.3 × 10⁻¹⁰ and for bromine between 9.4 × 10⁻¹² and 6.8 × 10⁻¹¹ m² s⁻¹. No pressure effect was detected at the conditions investigated. In experiments involving mixed halogens, the diffusivities appear to decrease slightly (by a factor of ∼3), and are more uniform among the three elements. However, activation energies for diffusion do not appear to differ between experiments with individual halogens or when they are all mixed together. The effect of water increases the diffusion coefficients of F and Cl by no more than a factor of 3 compared to the anhydrous melt (D_F = 4.0 × 10⁻¹¹ to 1.6 × 10⁻¹⁰ m² s⁻¹; D_Cl = 3.0 × 10⁻¹¹ to 1.9 × 10⁻¹⁰ m² s⁻¹). Comparing our results to the diffusion coefficients of other volatiles in nominally dry basaltic melts, halogen diffusivities are about one order of magnitude lower than H₂O, similar to CO₂, and a factor of ∼5 higher than S. The contrasting volatile diffusivities may affect the variable extent of volatile degassing upon melt depressurization and vesiculation, and can help our understanding of the compositions of rapidly grown magmatic bubbles.  相似文献   

Evaluation of TCE and MTBE in situ Biodegradation: Integrating Stable Isotope, Metabolic Intermediate, and Microbial Lines of Evidence     

Jennifer R. McKelvie  Sarah K. Hirschorn  Georges Lacrampe-Couloume  Jon Lindstrom  Joan Braddock  Kevin Finneran  Don Trego  Barbara Sherwood Lollar 《Ground Water Monitoring & Remediation》2007,27(4):63-73

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Progress in NTHMP Hazard Assessment     

Frank I. González  Vasily V. Titov  Harold O. Mofjeld  Angie J. Venturato  R. Scott Simmons  Roger Hansen  Rodney Combellick  Richard K. Eisner  Don F. Hoirup  Brian S. Yanagi  Sterling Yong  Mark Darienzo  George R. Priest  George L. Crawford  Timothy J. Walsh 《Natural Hazards》2005,35(1):89-110

The Hazard Assessment component of the U.S. National Tsunami Hazard Mitigation Program has completed 22 modeling efforts covering 113 coastal communities with an estimated population of 1.2 million residents that are at risk. Twenty-three evacuation maps have also been completed. Important improvements in organizational structure have been made with the addition of two State geotechnical agency representatives to Steering Group membership, and progress has been made on other improvements suggested by program reviewers.  相似文献