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51.
Matthias R. Aellig Alan J. Lazarus Justin C. Kasper Keith W. Ogilvie 《Astrophysics and Space Science》2001,277(1-2):305-307
The Triana PlasMag Faraday Cup (FC) will be able to determine speed, flow angles, temperature, and density of the main solar
wind ion species with a time resolution of better than one second. Thus, the Triana PlasMag FC will enable resolution of spatial
structures as small as a few hundred kilometers as the structures convect past the spacecraft. Under typical solar wind conditions,
that size is comparable to a few proton gyroradii.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
52.
K. O'Brien Keith Horne B. Boroson † M. Still ‡ R. Gomer J.B. Oke P. Boyd S.D. Vrtilek 《Monthly notices of the Royal Astronomical Society》2001,326(3):1067-1075
We present Keck II spectroscopy of optical mHz quasi-periodic oscillations (QPOs) in the light curve of the X-ray pulsar binary Hercules X-1. In the power spectrum it appears as 'peaked noise', with a coherency ∼2, a central frequency of 35 mHz and a peak-to-peak amplitude of 5 per cent. However, the dynamic power spectrum shows it to be an intermittent QPO, with a lifetime of ∼100 s, as expected if the lifetime of the orbiting material is equal to the thermal time-scale of the inner disc. We have decomposed the spectral time series into constant and variable components and used blackbody fits to the resulting spectra to characterize the spectrum of the QPO variability and constrain possible production sites. We find that the spectrum of the QPO is best fitted by a small hot region, possibly the inner regions of the accretion disc, where the ballistic accretion stream impacts on to the disc. The lack of any excess power around the QPO frequency in the X-ray power spectrum, created using simultaneous light curves from RXTE , implies that the QPO is not simply reprocessed X-ray variability. 相似文献
53.
Christopher A. Airriess Wei Li Karen J. Leong Angela Chia-Chen Chen Verna M. Keith 《Geoforum》2008,39(3):1333-1346
This research examines the role of social capital and networks to explain the evacuation, relocation, and recovery experiences of a Vietnamese American community in New Orleans, Louisiana in the aftermath of Hurricane Katrina. As the single largest community institution, the parish church’s complex bonding and bridging social capital and networks proved particularly critical in part because of its historically based ontological security. The process of evacuation, but especially relocation and recovery, was dependent on deploying co-ethnic social capital and networks at a variety of geographical scales. Beyond the local or community scale, extra-local, regional, and national scales of social capital and networks reproduced a spatially redefined Vietnamese American community. Part of the recovery process included constructing discursive place-based collective-action frames to successfully contest a nearby landfill that in turn engendered social capital and networks crossing ethnic boundaries to include the extra-local African American community. Engaging social capital and networks beyond the local geographical scale cultivated a Vietnamese American community with an emergent post-Katrina cultural and political identity. 相似文献
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Victor Fernandez Nascimento Nazli Yesiller Keith C Clarke Jean Pierre Henry Balbaud Ometto Pedro R. Andrade Anahi Chimini Sobral 《地理信息系统科学与遥感》2017,54(5):657-677
??The proper management of solid waste (SW) is a global environmental challenge. A major issue is the proper disposal of SW while balancing a wide range of criteria and working with different spatial data. In this study, we used geographic information system as a tool to perform multi-criteria decision analysis with an analytical hierarchy process to develop an environmental impact susceptibility model (EISM) for landfills. The model was applied to the state of California, USA and results are presented herein. In particular, the EISM considers factors such as geology, pedology, geomorphology, water resources, and climate as represented by 13 associated environmental indicators. The results of the EISM indicate that more than 75% of California’s territory is situated in areas with very low, low, and medium environmental impact susceptibility categories. However, in the remaining 25% of the state’s land, 61 landfills are located in the high and very high categories. These results are alarming because during the period from 2000 to 2015, these 61 landfills received approximately 308 million tons of SW, which corresponds to more than 57% of all SW disposed in California. The model results can be used toward mitigating the environmental impacts of these facilities. 相似文献
56.
The suitability of geologic frameworks for extrapolating hydraulic conductivity (K) to length scales commensurate with hydraulic data is difficult to assess. A novel method is presented for evaluating assumed relations between K and geologic interpretations for regional-scale groundwater modeling. The approach relies on simultaneous interpretation of multiple aquifer tests using alternative geologic frameworks of variable complexity, where each framework is incorporated as prior information that assumes homogeneous K within each model unit. This approach is tested at Pahute Mesa within the Nevada National Security Site (USA), where observed drawdowns from eight aquifer tests in complex, highly faulted volcanic rocks provide the necessary hydraulic constraints. The investigated volume encompasses 40 mi3 (167 km3) where drawdowns traversed major fault structures and were detected more than 2 mi (3.2 km) from pumping wells. Complexity of the five frameworks assessed ranges from an undifferentiated mass of rock with a single unit to 14 distinct geologic units. Results show that only four geologic units can be justified as hydraulically unique for this location. The approach qualitatively evaluates the consistency of hydraulic property estimates within extents of investigation and effects of geologic frameworks on extrapolation. Distributions of transmissivity are similar within the investigated extents irrespective of the geologic framework. In contrast, the extrapolation of hydraulic properties beyond the volume investigated with interfering aquifer tests is strongly affected by the complexity of a given framework. Testing at Pahute Mesa illustrates how this method can be employed to determine the appropriate level of geologic complexity for large-scale groundwater modeling. 相似文献
57.
Community‐Derived Standards for LA‐ICP‐MS U‐(Th‐)Pb Geochronology – Uncertainty Propagation,Age Interpretation and Data Reporting 下载免费PDF全文
Matthew S. A. Horstwood George Gehrels Simon E. Jackson Noah M. McLean Chad Paton Norman J. Pearson Keith Sircombe Paul Sylvester Pieter Vermeesch James F. Bowring Daniel J. Condon Blair Schoene 《Geostandards and Geoanalytical Research》2016,40(3):311-332
The LA‐ICP‐MS U‐(Th‐)Pb geochronology international community has defined new standards for the determination of U‐(Th‐)Pb ages. A new workflow defines the appropriate propagation of uncertainties for these data, identifying random and systematic components. Only data with uncertainties relating to random error should be used in weighted mean calculations of population ages; uncertainty components for systematic errors are propagated after this stage, preventing their erroneous reduction. Following this improved uncertainty propagation protocol, data can be compared at different uncertainty levels to better resolve age differences. New reference values for commonly used zircon, monazite and titanite reference materials are defined (based on ID‐TIMS) after removing corrections for common lead and the effects of excess 230Th. These values more accurately reflect the material sampled during the determination of calibration factors by LA‐ICP‐MS analysis. Recommendations are made to graphically represent data only with uncertainty ellipses at 2s and to submit or cite validation data with sample data when submitting data for publication. New data‐reporting standards are defined to help improve the peer‐review process. With these improvements, LA‐ICP‐MS U‐(Th‐)Pb data can be considered more robust, accurate, better documented and quantified, directly contributing to their improved scientific interpretation. 相似文献
58.
59.
Keith Fitchett 《The Australian geographer》1987,18(1):1-7
Detailed aerial photograph analysis of the effects of hurricane Bebe (21 October 1972) on Funafuti atoll using ‘before and after’ photos plus ground truthing give a detailed picture of wind and water motions during passage of the cyclone. Interpretation of damage to coconut palms, motu (cay) and reef‐flat structures together with other directional indicators show that hurricane Bebe passed to the east of the atoll. Average wind and water‐flow directions were substantially different; wind directions changed during the cyclone's movement while wave and surge generated water flows remained more constant. A model showing wind and water motion associated with the storm is presented. 相似文献
60.