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41.
Aurelian Andrei Radu Tatiana Angelescu Valentin Curtef Florin Delia Daniel Felea Ioana Goia Dumitru Ha?egan Bogdan Lucaschi Ancuta Manea Vlad Popa Ioan Rali?? Radu V?c?reanu 《Experimental Astronomy》2012,34(1):31-42
Around the world, several scientific projects share the interest of a global network of small Cherenkov telescopes for monitoring observations of the brightest blazars??the DWARF network. A small, ground based, imaging atmospheric Cherenkov telescope of last generation is intended to be installed and operated in Romania as a component of the DWARF network. To prepare the construction of the observatory, two support projects have been initiated. Within the framework of these projects, we have assessed a number of possible sites where to settle the observatory. In this paper we submit a brief report on the general characteristics of the best four sites selected after the local infrastructure, the nearby facilities and the social impact criteria have been applied. 相似文献
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We have reanalyzed the Voyager radio occultation data for Titan, examining two alternative approaches to methane condensation. In one approach, methane condensation is facilitated by the presence of nitrogen because nitrogen lowers the condensation level of a methane/nitrogen mixture. The resulting enhancement in methane condensation lowers the upper limit on surface relative humidity of methane obtained from the Voyager occultation data from 0.7 to 0.6. We conclude that in this case the surface relative humidity of methane lies between 0.08 and 0.6, with values close to 0.6 indicated. In the other approach, methane is allowed to become supersaturated and reaches 1.4 times saturation in the troposphere. In this case, surface humidities up to 100% are allowed by the Voyager occultation data, and thus the upper limit must be set by other considerations. We conclude that if supersaturation is included, then the surface relative humidity of methane can be any value greater than 0.08--unless a deep ocean is present, in which case the surface relative humidity is limited to less than 0.85. Again, values close to 0.6 are indicated. Overall, the tropospheric lapse rate on Titan appears to be determined by radiative equilibrium. The lapse rate is everywhere stable against dry convection, but is unstable to moist convection. This finding is consistent with a supersaturated atmosphere in which condensation-and hence moist convection-is inhibited. 相似文献
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The soil properties of a vegetation chronosequence in Hong Kong involving a grassland, a 22-year mixed woodland, a 52-year forest and two graduation 150-year old climax ( feng shui ) forests were examined. The objectives were to test the three hypotheses: (1) there are no significant differences in soil chemical properties between different climax forests, (2) exotic species are inferior to native species in soil amelioration; and (3) organic carbon, nitrogen and cation nutrients tend to accumulate in the soils during successional development of the vegetation. The results show that the soils along the vegetation chronosequence are strongly acidic in reaction, contained moderate to high levels of organic carbon, high exchangeable acidity, and low levels of mineral nitrogen (NH⊂4⊂> and NO⊂3⊂), available phosphorus and cation nutrients. All the three hypotheses are rejected. While the feng shui forests differed markedly in soil properties, exotic species were superior to native species in augmenting soil organic carbon, mineral nitrogen and exchangeable Ca. There was no accumulation of organic carbon, nitrogen and cation nutrients with ecological succession, due to the influence of patchy fire, species composition, parent materials and distance from the sea. 相似文献
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Elastic waves, such as Rayleigh and mode‐converted waves, together with amplitude versus offset variations, serve as noise in full waveform inversion using the acoustic approximation. Heavy preprocessing must be applied to remove elastic effects to invert land or marine data using the acoustic inversion method in the time or frequency domains. Full waveform inversion using the elastic wave equation should be one alternative; however, multi‐parameter inversion is expensive and sensitive to the starting velocity model. We implement full acoustic waveform inversion of synthetic land and marine data in the Laplace domain with minimum preprocessing (i.e., muting) to remove elastic effects. The damping in the Laplace transform can be thought of as an automatic time windowing. Numerical examples show that Laplace‐domain acoustic inversion can yield correct smooth velocity models even with the noise originating from elastic waves. This offers the opportunity to develop an accurate smooth starting model for subsequent inversion in the frequency domain. 相似文献
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J.M. Retterer Ronald Ilma M.C. Kelley Jorge L. Chau C.E. Valladares L.C. Gentile K. Groves 《Journal of Atmospheric and Solar》2010,72(4):350-357
The storm period of 8–12 November 2004 offers an opportunity for insight into the phenomena of low-latitude ionospheric structure during geomagnetically disturbed times because of the strength of the disturbances, the timing of the storms, and the instrumentation that was operating during the interval. We will take advantage of these factors to model the ambient ionosphere and the plasma turbulence responsible for radio scintillation within it, using the AFRL low-latitude ambient/turbulent ionospheric model and the storm-time model features described in the companion paper [Retterer, J.M., Kelley, M.C., 2009. Solar-wind drivers for low-latitude ionospheric models during geomagnetic storms. J. Atmos. Solar-Terr. Phys., this issue]. The model plasma densities show very good agreement with the densities measured by the Jicamarca ISR as well as with the total electron content (TEC) measured by the Boston College South American chain of GPS receivers. The detection by the radar of coherent returns from plasma turbulence match well the times of predicted ionospheric instability. The predicted geographic extent of the occurrence of equatorial plasma bubbles was matched by DMSP satellite observations and our forecasts of scintillation strength were validated with measurements of S4 at Ancon and Antofagasta by stations of the AFRL SCINDA network. 相似文献
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