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981.
3维地理信息系统技术综述 总被引:23,自引:1,他引:22
文中对3维地理信息系统技术进行综述性介绍,扼要地讨论了国内外有关3维地球空间信息的获取、管理、分析与可视化等技术的进展与动态,并分别探讨了它们的优势和局限。 相似文献
982.
Sebastian Wolf 《Astrophysics and Space Science》2008,313(1-3):109-112
Theoretical investigations show that planet-disk interactions cause structures in circumstellar disks, which are usually much
larger in size than the planet itself and thus more easily detectable. The specific result of planet-disk interactions depends
on the evolutionary stage of the disk. Exemplary signatures of planets embedded in disks are gaps and spiral density waves
in the case of young, gas-rich protoplanetary disks and characteristic asymmetric density patterns in debris disks. Numerical
simulations convincingly demonstrate that high-resolution imaging performed with observational facilities which are already
available or will become available in the near future will allow to trace these “fingerprints” of planets in protoplanetary
and debris disks. These observations will provide a deep insight into specific phases of the formation and early evolution
of planets in circumstellar disks.
In this context, the Atacama Large Millimeter Array (ALMA) will play a crucial role by allowing to trace features in disks
which are indicative for various stages of the formation and early evolution of planets in circumstellar disks. 相似文献
983.
At present, there are few laboratory spectra of analogs of astrophysical interest in the far-infrared range (FIR). Laboratory infrared (IR) spectra of simple ices and its mixtures obtained at low temperature and pressure are found mainly up to 25 μm, and few up to 200 μm. On the other hand, there are some spectra for carbonaceous material and silicates up to 2000 μm. Our laboratory is equipped with an IR spectrometer that integrates a Michelson interferometer with a resolution better than 0.25 cm−1 and that operates under vacuum conditions of 10−1 mbar. There is also a silicon bolometer, a very high-sensitivity detector in comparison with the standard deuterated triglycine sulfate (DTGS) detectors. The use of the bolometer and the possibility of working under vacuum conditions inside the optics and the sample compartment of the spectrometer allow obtaining high-sensitivity spectra free from H2O vapor and CO2 gas bands. Those conditions are necessary to obtain high-quality spectra in the FIR where absorption bands are much less intense than those in the mid-IR region. In our laboratory there is also a high-vacuum chamber that allows different studies on ices deposited onto a cold finger. We have already carried out experiments on the study of ice density as a function of temperature, UV irradiation of ices, temperature-programmed desorption (TPD) and UV-vis reflectance. In this work, we present the design of the experimental setup we are building to carry out different experiments simultaneously on the same ice sample, including spectra measurements in the mid-IR range (MIR) and the FIR. This design integrates jointly the IR spectrometer, the high-vacuum chamber and the silicon bolometer. Lastly, we show a spectrum we have obtained of a solid of astrophysical interest such as crystalline forsterite grains by using the polyethylene pellet technique. 相似文献
984.
土钉支护现场测试及三维数值模拟分析 总被引:12,自引:3,他引:9
在进行土钉轴力和边坡位移测试的基础上 ,进行了土钉支护的三维数值模拟研究 ,对边坡位移、土钉轴力、塑性区分布等分别作了较为深入的探讨 ,认识到土钉与土体相互作用形成了一个完整的支护体系 ;基坑失稳破坏并非传统意义上的土体和土钉的破坏 ,而是土钉支护体系的整体性破坏 ;土钉支护体系的形成正是通过土钉的分担作用、应力传递与扩散作用来实现的 ,这是土钉支护作用的实质. 相似文献
985.
C.M. Lisse 《Icarus》2008,195(2):941-944
This response is to address the comments made by Drs. J. Crovisier and D. Bockelee-Morvan concerning the spectral analysis of Lisse et al. [Lisse, C.M., Kraemer, K.E., Nuth, J.A., Li, A., Joswiak, D., 2007. Icarus 187, 69-86] of the mid-IR ISO SWS spectrum of Comet Hale-Bopp 1995 O1 taken on October 6, 1996, and to support the conclusions made in Lisse et al. concerning the positive detection of PAHs in this comet. We also present some additional information determined from the Deep Impact and STARDUST missions, demonstrating the presence of PAHs in other comets, to support the plausibility of the Hale-Bopp PAH detection. 相似文献
986.
New maps of martian water vapor and hydrogen peroxide have been obtained in November-December 2005, using the Texas Echelon Cross Echelle Spectrograph (TEXES) at the NASA Infra Red Telescope facility (IRTF) at Mauna Kea Observatory. The solar longitude Ls was 332° (end of southern summer). Data have been obtained at 1235-1243 cm−1, with a spectral resolution of 0.016 cm−1 (R=8×104). The mean water vapor mixing ratio in the region [0°-55° S; 345°-45° W], at the evening limb, is 150±50 ppm (corresponding to a column density of 8.3±2.8 pr-μm). The mean water vapor abundance derived from our measurements is in global overall agreement with the TES and Mars Express results, as well as the GCM models, however its spatial distribution looks different from the GCM predictions, with evidence for an enhancement at low latitudes toward the evening side. The inferred mean H2O2 abundance is 15±10 ppb, which is significantly lower than the June 2003 result [Encrenaz, T., Bézard, B., Greathouse, T.K., Richter, M.J., Lacy, J.H., Atreya, S.K., Wong, A.S., Lebonnois, S., Lefèvre, F., Forget, F., 2004. Icarus 170, 424-429] and lower than expected from the photochemical models, taking in account the change in season. Its spatial distribution shows some similarities with the map predicted by the GCM but the discrepancy in the H2O2 abundance remains to be understood and modeled. 相似文献
987.
Comet 73P-B/Schwassmann-Wachmann 3 was observed with IRCS/Subaru at geocentric distance of 0.074 AU on UT 10 May 2006. Multiple H2O emission lines were detected in non-resonant fluorescence near 2.9 μm. No significant variation in total H2O production rate was found during the (3 h) duration of our observations. H2O rotational temperatures and ortho-to-para abundance ratios were measured for several positions in the coma. The temperatures extracted from two different time intervals show very similar spatial distributions. For both, the rotational temperature decreased from ∼110 to ∼90 K as the projected distance from the nucleus increased from ∼5 to ∼30 km. We see no evidence for OPR change in the coma. The H2O ortho-para ratio is consistent with the statistical equilibrium value (3.0) for all spatially resolved measurements. This implies a nuclear spin temperature higher than ∼45 K. 相似文献
988.
Athena Coustenis Donald E. Jennings Yves Bénilan Sandrine Vinatier Gordon L. Bjoraker Ronald C. Carlson 《Icarus》2008,197(2):539-548
We report here the first detection of mono-deuterated acetylene (acetylene-d1, C2HD) in Titan's atmosphere from the presence of two of its emission bands at 678 and 519 cm−1 as observed in CIRS spectral averages of nadir and limb observations taken between July 2004 and mid-2007. By using new laboratory spectra for this molecule, we were able to derive its abundance at different locations over Titan's disk. We find the C2HD value () to be roughly constant with latitude from the South to about 45° N and then to increase slightly in the North, as is the case for C2H2. Fitting the 678 cm−1ν5 band simultaneously with the nearby C2H2 729 cm−1ν5 band, allows us to infer a D/H ratio in acetylene on Titan with an average of the modal values of 2.09±0.45×10−4 from the nadir observations, the uncertainties being mainly due to the vertical profile used for the fit of the acetylene band. Although still subject to significant uncertainty, this D/H ratio appears to be significantly larger than the one derived in methane from the CH3D band (upper limit of 1.5×10−4; Bézard, B., Nixon, C.A., Kleiner, I., Jennings, D.E., 2007. Icarus, 191, 397-400; Coustenis, A., Achterberg, R., Conrath, B., Jennings, D., Marten, A., Gautier, D., Bjoraker, G., Nixon, C., Romani, P., Carlson, R., Flasar, M., Samuelson, R.E., Teanby, N., Irwin, P., Bézard, B., Orton, G., Kunde, V., Abbas, M., Courtin, R., Fouchet, Th., Hubert, A., Lellouch, E., Mondellini, J., Taylor, F.W., Vinatier, S., 2007. Icarus 189, 35-62). From the analysis of limb data we infer D/H values of (at 54° S), (at 15° S), (at 54° N) and (at 80° N), which average to a mean value of 1.63±0.27×10−4. 相似文献
989.
We present the first spectra of Neptune taken with the Spitzer Space Telescope, highlighting the high-sensitivity, moderate-resolution 10-20 μm (500-1000 cm−1) spectra. We report the discovery of methylacetylene (CH3C2H) and diacetylene (C4H2) with derived 0.1-mbar volume mixing ratios of (1.2±0.1)×10−10 and (3±1)×10−12 respectively. 相似文献
990.
季节性Kendall检验及其在三门峡水库水质趋势分析中的应用 总被引:4,自引:0,他引:4
选择1997—2002年三门峡库区的龙门、潼关和三门峡3个断面的水质监测资料,运用季节性Kendall检验方法分析三门峡水库水质趋势,结果显示:龙门断面,CODMn、NO2-N及Hg的变化趋势不明显,NH3-N呈显著上升趋势,As、Cd和Cu呈显著下降趋势,而Pb则呈高度显著下降趋势;潼关断面,NH3-N、NO2-N和Hg的变化趋势不明显,CODMn呈显著上升趋势,As、Cd和Pb呈显著下降趋势,而Cu则呈高度显著下降趋势;三门峡断面,CODMn、NO2-N、As及Hg的变化趋势不明显,NH3-N污染呈显著上升趋势,Cd呈显著下降趋势,而Cu和Pb则呈高度显著下降趋势。 相似文献