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961.
W. M. Davis E. R. Cespedes L. T. Lee J. F. Powell R. A. Goodson 《Environmental Geology》1997,29(3-4):228-237
The Site Characterization and Analysis Penetrometer System (SCAPS) was used to investigate subsurface petroleum contamination
at Aberdeen Proving Ground, Maryland. The SCAPS is a rapid site-screening tool developed by the Tri-Services (U.S. Army, Navy,
and Air Force) to reduce the cost of installation restoration activities. The system, consisting of a geophysical cone penetrometer
fitted with a laser-induced fluorescence petroleum sensor, is capable of simultaneous, real-time delineation of subsurface
stratigraphy and petroleum contamination. Onsite processing of the SCAPS data allows three-dimensional visualization of both
subsurface stratigraphy and petroleum contaminant distribution. The site investigation described herein successfully identified
three distinct areas of subsurface petroleum contamination caused by leaking underground storage tanks containing No. 2 healing
oil. The SCAPS petroleum sensor response was verified by obtaining 20 soil samples and performing onsite and conventional
laboratory analyses for petroleum contaminants. Verification sample results indicate a strong correlation between the SCAPS
fluorescence data and conventional measures of petroleum contamination. This investigation illustrates the capabilities of
the SCAPS for rapid site characterization.
Received: 27 November 1995 · Accepted: 11 December 1995 相似文献
962.
Marcin Jankiewicz Roman V. Buniy Thomas W. Kephart Thomas J. Weiler 《Astroparticle Physics》2004,21(6):651-666
It has been proposed that propagation of cosmic-rays at extreme-energy may be sensitive to Lorentz-violating metric fluctuations (“foam”). We investigate the changes in interaction thresholds for cosmic-rays and gamma-rays interacting on the CMB and IR backgrounds, for a class of stochastic models of space–time foam. The strength of the foam is characterized by the factor (E/MP)a, where a is a phenomenological suppression parameter. We find that there exists a critical value of a (dependent on the particular reaction: acrit3 for cosmic-rays, 1 for gamma-rays), below which the threshold energy can only be lowered, and above which the threshold energy may be raised, but at most by a factor of two. Thus, it does not appear possible in this class of models to extend cosmic-ray spectra significantly beyond their classical absorption energies. However, the lower thresholds resulting from foam may have signatures in the cosmic-ray spectrum. In the context of this foam model, we find that cosmic-ray energies cannot exceed the fundamental Planck scale, and so set a lower bound of 108 TeV for the scale of gravity. We also find that suppression of p→pπ0 and γ→e−e+ “decays” favors values aacrit. Finally, we comment on the apparent non-conservation of particle energy–momentum, and speculate on its re-emergence as dark energy in the foamy vacuum. 相似文献
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Since the discovery of quasars, it has been recognized that these objects must have either an extraordinary intrinsic brightness or a nonlinear redshift. The most widely accepted current belief incorporates a linear (Hubble) redshift- distance relation and time evolution within a Big Bang model. We reconsider the possibility of a nonlinear (de Sitter) redshift-distance relation and find quasar intrinsic brightness to be not at all extraordinary. Given a de Sitter law, intrinsic brightness is found to be independent of redshift over five orders of magnitude. 相似文献
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967.
Thomas G. Müller 《Meteoritics & planetary science》2002,37(12):1919-1928
Abstract— Visual photometry, which measures reflected solar radiation, can be combined with infrared radiometry, which measures absorbed and re‐radiated solar energy, to determine key properties of small solar system objects. This method can be applied via thermophysical model concepts not only for albedo and diameter determination, but also for studies of thermal parameters like thermal inertia, surface roughness or emissivity. Hence, a detailed analysis of the asteroid surface is possible and topics like surface mineralogy, the density of the regolith or the presence of a rocky surface, lightcurve influences due to shape or albedo, porosity of the surface material, etc. can be addressed. The “radiometric technique” based on a recently developed thermophysical model is presented. The model was extensively tested against observations from the infrared space observatory, including spectroscopic and photometric measurements at infrared wavelengths between 2 and 200 μm of more than 40 asteroids. The possible model applications are discussed in terms of the different levels of knowledge for individual asteroids. The effects of the thermal parameters are illustrated and methods are presented as to how to separate different aspects. Possibilities and limitations are evaluated for the possible transfer of this model to near‐Earth asteroids. In the long run, this kind of study of near‐Earth asteroids may provide answers to questions about their surface properties which are crucial to develop mitigation scenarios. 相似文献
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