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11.
随着全球变暖,极端天气事件逐渐增加,影响着社会经济发展,揭示区域极端降水时空变化对防洪减灾具有重要意义。基于1960—2019年的逐日降水,通过MK趋势检验、小波分析、重标极差以及克里金插值方法,从强度、频率和持续性三方面分析里下河地区的极端降水指数,并进一步探究其未来趋势变化。结果表明:(1)里下河地区多年平均降水为1017.25 mm,呈不显著增加趋势;空间分布差异明显,总体呈自西北向东南逐渐增加的分布。(2)研究区内各站点极端降水指数变化不同,总体而言,极端降水强度、频率均呈现增加趋势,持续性呈减少趋势。(3)极端降水指数变化过程中存在3类尺度的周期性变化,在整个时间尺度上存在3个偏多中心和2个偏少中心。(4)除R10mm和R20mm未来变化趋势与过去趋势相反且呈弱持续性,其他极端降水指数未来变化趋势与过去相一致,且过去总体趋势对未来趋势的影响时间长度在9~16年左右。研究结果为里下河地区科学合理应对气象灾害、合理配置水资源提供依据。 相似文献
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L. Kaml 《Astronomische Nachrichten》1998,319(3):183-185
CCD photometry of possible standard stars, in Cousins B, V, R and I, in a field in the region of NGC 188 is presented. 相似文献
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C.J. Mooney W.R.J. Rolleston F.P. Keenan P.L. Dufton D.L. Pollacco H.R. Magee 《Monthly notices of the Royal Astronomical Society》2001,326(3):1101-1109
We present a model-atmosphere analysis for the bright ( V ∼13) star ZNG-1, in the globular cluster M10. From high-resolution ( R ∼40 000) optical spectra we confirm ZNG-1 to be a post-asymptotic giant branch (post-AGB) star. The derived atmospheric parameters are T eff =26 500±1000 K and log g =3.6±0.2 dex . A differential abundance analysis reveals a chemical composition typical of hot post-AGB objects, with ZNG-1 being generally metal poor, although helium is approximately solar. The most interesting feature is the large carbon underabundance of more than 1.3 dex. This carbon deficiency, along with an observed nitrogen enhancement relative to other elements, may suggest that ZNG-1 evolved off the AGB before the third dredge-up occurred. Also, iron depletions observed in other similar stars suggest that gas–dust fractionation in the AGB progenitor could be responsible for the observed composition of these objects. However, we need not invoke either scenario since the chemical composition of ZNG-1 is in good agreement with abundances found for a Population II star of the same metallicity. 相似文献
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In recent years many fuller ship hull forms have been designed and constructed in various shipbuilding countries, but the data available for the development of the fuller forms are inadequate from the point of view of preliminary ship design. In this paper the authors describe how they have systematically tested vessel forms of block coefficients ranging from 0.80 to 0.90. The analysis and presentation of the test results have been made in such a manner that designers can produce hull forms like those of tankers and other bulk carriers quickly and reliably. 相似文献
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Leitzinger M Odert P Kulikov YN Lammer H Wuchterl G Penz T Guarcello MG Micela G Khodachenko ML Weingrill J Hanslmeier A Biernat HK Schneider J 《Planetary and Space Science》2011,59(13):1472-1481
We present thermal mass loss calculations over evolutionary time scales for the investigation if the smallest transiting rocky exoplanets CoRoT-7b (∼1.68REarth) and Kepler-10b (∼1.416REarth) could be remnants of an initially more massive hydrogen-rich gas giant or a hot Neptune-class exoplanet. We apply a thermal mass loss formula which yields results that are comparable to hydrodynamic loss models. Our approach considers the effect of the Roche lobe, realistic heating efficiencies and a radius scaling law derived from observations of hot Jupiters. We study the influence of the mean planetary density on the thermal mass loss by placing hypothetical exoplanets with the characteristics of Jupiter, Saturn, Neptune, and Uranus to the orbital location of CoRoT-7b at 0.017 AU and Kepler-10b at 0.01684 AU and assuming that these planets orbit a K- or G-type host star. Our findings indicate that hydrogen-rich gas giants within the mass domain of Saturn or Jupiter cannot thermally lose such an amount of mass that CoRoT-7b and Kepler-10b would result in a rocky residue. Moreover, our calculations show that the present time mass of both rocky exoplanets can be neither a result of evaporation of a hydrogen envelope of a “Hot Neptune” nor a “Hot Uranus”-class object. Depending on the initial density and mass, these planets most likely were always rocky planets which could lose a thin hydrogen envelope, but not cores of thermally evaporated initially much more massive and larger objects. 相似文献
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本文提出比值R分析计算方法,用其求解时间序列数据矩平差和标准差结构的分形,目的的于判定地震预报指标,作为实例,宁夏区和同心区的地震频度,最大震级,以及同心地办水氡观测数据的比值R随时间的分形变化进行了初步分析,证明本方法能为我国提供可信的震情信息。 相似文献