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981.
A subsurface radar using a multi-frequency signal has been developed. It is designated for surveying building structures and works. The characteristic feature of this device is the possibility of obtaining sounding plane radio images featuring a high resolution attaining 1…2 cm. The main applications of this device includes the survey of building structures to reveal their heterogeneities and defects and the investigation of premises to detect bugging devices  相似文献   
982.
The available data describing the incompressible zero-pressure-gradient boundary layer are reviewed in association with a range of studies which are either new or, to date, not very generally available. The new data cover a Reynolds number range 2.5 < Reδ2 × 10−3 < 58 and include measurements of all three turbulence perlurbations and the Reynolds shear stress. They are assessed in relation to data in the range 0.4 < Reδ2 × 10−3 < 211 using established scaling laws. In common with other investigators we find that while scaling the mean flow leads to a high degree of apparent similarity, scaling of the turbulence quantities is in general not so satisfactory.  相似文献   
983.
984.
We present a photometric study of the luminous early-type star Car. The star's secular brightness increase is due largely to the expansion of the Homunculus. Car is a LBV with a possible B0.5V companion. The combined effect of Balmer-line emission, and of warm and cold dust radiation explains the star's other light variations.  相似文献   
985.
The diverse populations of icy bodies of the outer Solar System (OSS) give critical information on the composition and structure of the solar nebula and the early phases of planet formation. The two principal repositories of icy bodies are the Kuiper belt or disk, and the Oort Cloud, both of which are the source regions of the comets. Nearly 1000 individual Kuiper belt objects have been discovered; their dynamical distribution is a clue to the early outward migration and gravitational scattering power of Neptune. Pluto is perhaps the largest Kuiper belt object. Pluto is distinguished by its large satellite, a variable atmosphere, and a surface composed of several ices and probable organic solid materials that give it color. Triton is probably a former member of the Kuiper belt population, suggested by its retrograde orbit as a satellite of Neptune. Like Pluto, Triton has a variable atmosphere, compositionally diverse icy surface, and an organic atmospheric haze. Centaur objects appear to come from the Kuiper belt and occupy temporary orbits in the planetary zone; the compositional similarity of one well studied Centaur (5145 Pholus) to comets is notable. New discoveries continue apace, as observational surveys reveal new objects and refined observing techniques yield more physical information about specific bodies.  相似文献   
986.
THE DIGITAL WAVE-PROCESSING EXPERIMENT ON CLUSTER   总被引:1,自引:0,他引:1  
The wide variety of geophysical plasmas that will be investigated by the Cluster mission contain waves with a frequency range from DC to over 100 kHz with both magnetic and electric components. The characteristic duration of these waves extends from a few milliseconds to minutes and a dynamic range of over 90 dB is desired. All of these factors make it essential that the on-board control system for the Wave-Experiment Consortium (WEC) instruments be flexible so as to make effective use of the limited spacecraft resources of power and telemetry-information bandwidth. The Digital Wave Processing Experiment, (DWP), will be flown on Cluster satellites as a component of the WEC. DWP will coordinate WEC measurements as well as perform particle correlations in order to permit the direct study of wave/particle interactions. The DWP instrument employs a novel architecture based on the use of transputers with parallel processing and re-allocatable tasks to provide a high-reliability system. Members of the DWP team are also providing sophisticated electrical ground support equipment, for use during development and testing by the WEC. This is described further in Pedersen et al. (this issue).  相似文献   
987.
Radial pulsation periods are calculated for models of variables in the lower Cepheid instability strip. Evolution tracks in several diagrams are constructed and used for comparisons with observed periods, period ratios, and effective temperatures. These comparisons are simpler and more direct than in earlier studies with separate evolution and pulsation calculations.  相似文献   
988.
An increasing number of high-resolution spacecraft observations provide access to details of energetic electron and ion velocity-space distribution structures. Since resonant wave-particle interaction processes depend considerably on the distribution function details, space plasma modeling is of particular interest for studies of a variety of plasma environments as planetary magnetospheres, the interplanetary medium or solar flares. After summarizing the most popular particle acceleration processes we focus on wave-powered energization mechanisms induced by Landau interaction and demonstrate from a time-evolutionary scenario that power-law distributions, highly favored by observations in recent years, are generated resonantly by an Alfvén wave spectrum and possibly saturate. This process is further stimulated in non-uniform magnetic field configurations where multiple wave packets at different phase velocities provide the energy source for a continuous acceleration process. Moreover, in this conjunction we demonstrate that in particular κ-distributions are a consequence of a generalized entropy concept, favored by nonextensive statistics, which provides the missing link for power-law plasma models from fundamental physics. With regard to in situ space observations examples are provided illuminating that for non-thermal plasma characteristics the particular structure of the velocity-space distribution dominates as regulating mechanism for the wave-particle interaction process over effects related to changes in space plasma parameters. This revised version was published online in August 2006 with corrections to the Cover Date.  相似文献   
989.
The behavior, in an oxygen atmosphere, of shocked drops of nitromethane, 1- and 2- nitropropane, ethyl and propyl nitrate, decane, and heptane was studied. Results suggest a new mode of ignition for nitrates at high incident shock Mach numbers (M 3.7). At the high incident shock strengths ignition occurs in the boundary layer, but no blast wave develops as is the case for lower shock strengths. Since ignition delay times are very short under these conditions, the absence of blast waves is attributed to the lack of time for the accumulation of fuel in the wake. Gas phase studies of the shock decomposition of fuel molecules were undertaken to determine if gas phase data could be used to explain the trends in the drop ignition observations. Nitromethane and the nitrates were mainly used in this effort. Alternative explanations for the role of gas phase kinetics in the ignition of drops are presented.  相似文献   
990.
In 2003, geomagnetic activity was found to be considerably higher than in any other year of the current solar cycle. This was caused by the time coincidence of large low-latitude coronal holes and a significant burst of the flare and eruptive activity of the Sun. The features of recent intensification of the activity are discussed, and the long-period behavior of indices of the geomagnetic activity in the 23rd and previous cycles is compared. The large magnetic storms in October–November 2003 are analyzed in more detail.Translated from Kosmicheskie Issledovaniya, Vol. 42, No. 6, 2004, pp. 563–573.Original Russian Text Copyright © 2004 by Belov, Gaidash, Ivanov, Kanonidi.  相似文献   
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