Characterization of soil's structural crust by spectral reflectance in the SWIR region (1.2–2.5 μm)     

N. Goldshleger  E. Ben-Dor  Y. Benyamini  M. Agassi  & D. G. Blumberg 《地学学报》2001,13(1):12-17

Structural crust is a thin layer formed on the soil surface after a rainstorm. The crust is the result of a physical segregation and rearrangement of soil particles in a way that affects some of the soil properties, such as infiltration, runoff and soil erosion. In practice, there is no rapid, in situ method for monitoring, assessing and mapping crust intensity and quality. In this study, a controlled spectral investigation of the structural crust across the NIR–SWIR spectral region was conducted on three selected Israeli soils, to study the potential of reflectance radiation to detect structural crust in soils. Two major factors served as the driving forces for this study: (1) there is no valid method for in situ assessment of the crust's characteristics in the agriculture field, and (2) the crust might bias thematic remote sensing of soils, because the thin layer of crust blocks photon–matter interaction, which represents the relevant soil body. Through the use of a laboratory rainfall simulator and a sensitive spectrometer, it was revealed that for three selected soils, significant spectral differences occurred between the crust and its bulk soil. The spectral information was found to be related to changes in particle size distribution and texture at the surface of the soil. This conclusion was based on indications of absorption of OH in clay lattice, OH in adsorbed water and CO₃ in carbonates. It was concluded that the structural crust is a phenomenon that should not be ignored by remote-sensing users. In fact, in the field of agriculture, the spectral properties of crust can be used as tools for estimating the crust's intensity.  相似文献   

Magnetic anomaly map for Northern,Western, and Eastern Europe*     

Thomas Wonik  Klaus Trippler  Helmut Geipel  Siegfried Greinwald  Inna Pashkevitch 《地学学报》2001,13(3):203-213

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Microboudin structures of piemontite along the Sambagawa metamorphic belt, Japan: implications for lateral variation of differential stress during regional metamorphism     

T. Masuda  T. Shibutani  T. Ochiai  S. Akagi  H. Yamaguchi  Y. Kugimiya  N. Kimura  T. Miyake 《Journal of Metamorphic Geology》2004,22(3):199-205

Evidence is presented of a lateral variation in differential stress during metamorphism along a regional metamorphic belt on the basis of the proportion of microboudinaged piemontite grains (p) in a quartz matrix in metacherts. It is proposed that p is a practical indicator of relative differential stress. Analysis of 123 metacherts from the 800 km long Sambagawa metamorphic belt, Japan, reveals that p‐values range from < 0.01 to 0.7 in this region. Most samples from Wakayama in the mid‐belt area have p‐values of 0.4–0.6, whereas those from western Shikoku have p‐values of < 0.1. This difference cannot be explained by variations in metamorphic temperature, and is instead attributed to a regional, lateral variation in differential stress during metamorphism.  相似文献   

Neutron background in large-scale xenon detectors for dark matter searches     

M. J. Carson  J. C. Davies  E. Daw  R. J. Hollingworth  V. A. Kudryavtsev  T. B. Lawson  P. K. Lightfoot  J. E. McMillan  B. Morgan  S. M. Paling  M. Robinson  N. J. C. Spooner  D. R. Tovey 《Astroparticle Physics》2004,21(6):667-687

Simulations of the neutron background for future large-scale particle dark matter detectors are presented. Neutrons were generated in rock and detector elements via spontaneous fission and (α,n) reactions, and by cosmic-ray muons. The simulation techniques and results are discussed in the context of the expected sensitivity of a generic liquid xenon dark matter detector. Methods of neutron background suppression are investigated. A sensitivity of 10⁻⁹–10⁻¹⁰ pb to WIMP-nucleon interactions can be achieved by a tonne-scale detector.  相似文献   

A Fabry-Pérot etalon as fourier tachometer     

I. E. Kozhevatov  E. H. Kulikova  N. P. Cheragin 《Solar physics》1996,168(2):251-258

A tachometer for measuring the displacements of the center of gravity of spectral line profiles is developed. The implementation of the device, basically a Fabry-Pérot etalon, is given. The spectral shifts are determined, using the frequency of a laser as reference.  相似文献   

Magnetic Reconnection and Extraplanar Diffuse Ionized Gas     

Guido T. Birk  Harald Lesch  Thomas Neukirch 《Astrophysics and Space Science》2004,289(3-4):359-362

Photoionization by stars cannot be the only cause for the diffuseionized gas component in the distant halos of galaxies.Quasistationary localized magnetic reconnection can efficientlycontribute to the ionization of the extraplanar halo gas. The gas isheated and re-ionized in numerous current filaments fast enough tocompensate recombination. The necessary magnetic energy is provided bythe disk activity.  相似文献   

Simultaneous operation of the Sea Beam multibeam echo-sounder andthe SeaMARC II bathymetric sidescan sonar system     

de Moustier  C. Lonsdale  P.F. Shor  A.N. 《Oceanic Engineering, IEEE Journal of》1990,15(2):84-94

An experiment aboard the Scripps Institution of Oceanography's RV Thomas Washington has demonstrated the seafloor mapping advantages to be derived from combining the high-resolution bathymetry of a multibeam echo-sounder with the sidescan acoustic imaging plus wide-swath bathymetry of a shallow-towed bathymetric sidescan sonar. To a void acoustic interference between the ship's 12-kHz Sea Beam multibeam echo-sounder and the 11-12-kHz SeaMARC II bathymetric sidescan sonar system during simultaneous operations, Sea Beam transmit cycles were scheduled around SeaMARC II timing events with a sound source synchronization unit originally developed for concurrent single-channel seismic, Sea Beam, and 3.5-kHz profile operations. The scheduling algorithm implemented for Sea Beam plus SeaMARC II operations is discussed, and the initial results showing their combined seafloor mapping capabilities are presented  相似文献   

Analysis of submerged platform breakwater by Eigenfunction expansion method   总被引：1，自引：0，他引：1  

Hin-Fatt Cheong  N.Jothi Shankar  S Nallayarasu 《Ocean Engineering》1996,23(8):649-666

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A comparison of type II shock speeds     

R. J. Thompson  J. A. Kennewell  N. P. Prestage 《Solar physics》1996,166(2):371-378

Type II radio bursts are produced by material moving outwards in the solar atmosphere. Their drift in frequency allows the calculation of the radial speed with which the shock is moving- very basic information in assessing the likelihood that the shock will reach the Earth and its time of arrival. This paper compares the shock speeds derived from radio bursts observed by the Swept Frequency Interferometric Radiometer (SFIR) equipment at the US Air Force Radio Solar Telescope Network (RSTN) of observatories with those measured with the Culgoora radiospectrograph operated by IPS Radio and Space Services. The SFIR shock speeds are found to be 1.5–3.0 times larger than the Culgoora values which are consistent with earlier results. This difference appears to originate from the incorrect interpretation of events as a result of the smaller frequency range of the SFIR equipment.  相似文献   

The Hubble constant from the gravitational lens CLASS B0218+357 using the Advanced Camera for Surveys     

T. York  N. Jackson  I. W. A. Browne  O. Wucknitz  J. E. Skelton † 《Monthly notices of the Royal Astronomical Society》2005,357(1):124-134

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