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781.
M. Koch-Müller P. Dera Y. Fei H. Hellwig Z. Liu J. Van Orman R. Wirth 《Physics and Chemistry of Minerals》2005,32(5-6):349-361
We synthesized superhydrous phase B (shy-B) at 22 GPa and two different temperatures: 1200°C (LT) and 1400°C (HT) using a
multi-anvil apparatus. The samples were investigated by transmission electron microscopy (TEM), single crystal X-ray diffraction,
Raman and IR spectroscopy. The IR spectra were collected on polycrystalline thin-films and single crystals using synchrotron
radiation, as well as a conventional IR source at ambient conditions and in situ at various pressures (up to 15 GPa) and temperatures
(down to −180°C). Our studies show that shy-B exists in two polymorphic forms. As expected from crystal chemistry, the LT
polymorph crystallizes in a lower symmetry space group (Pnn2), whereas the HT polymorph assumes a higher symmetry space group (Pnnm). TEM shows that both modifications consist of nearly perfect crystals with almost no lattice defects or inclusions of additional
phases. IR spectra taken on polycrystalline thin films exhibit just one symmetric OH band and 29 lattice modes for the HT
polymorph in contrast to two intense but asymmetric OH stretching bands and at least 48 lattice modes for the LT sample. The
IR spectra differ not only in the number of bands, but also in the response of the bands to changes in pressure. The pressure
derivatives for the IR bands are higher for the HT polymorph indicating that the high symmetry form is more compressible than
the low symmetry form. Polarized, low-temperature single-crystal IR spectra indicate that in the LT-polymorph extensive ordering
occurs not only at the Mg sites but also at the hydrogen sites. 相似文献
782.
地震灾害预测和应急模拟系统的设计与应用——以永安市城市应急系统为例 总被引:1,自引:0,他引:1
城市防震减灾是地震潜在频发区提高自然灾害防治能力建设的重要方面。本文结合福建省永安市城市防震减灾信息管理系统的建设,探讨设计防震减灾数值模型,分析模型集成的关键技术,构建了地震风险评估、建筑物易损性评价、生命与财产损失估算、救援与救灾管理调度等模型和基于GIS开发的震害预测和应急模拟系统。该系统在福建省永安市的实际应用表明,通过对地震灾害预测结果的分析,可加强城市抗震中的薄弱环节,为灾区政府应急响应和制订对策提供决策支持辅助信息,从而显著提高城市防震减灾的综合能力。 相似文献
783.
本文利用2001-2003年南极中山站175天全天空摄像机观测,对午后多重极光弧的出现率及其与Kp指数的关系进行了统计分析,结果表明午后多重极光弧出现率呈一单峰分布,最大发生率出现在1445UT(1645MLT),其位置在1500MLT极光热点(1300-1700MLT)近夜侧的部分。与地磁活动指数Kp的相关统计分析表明,Kp值为2-3之间时多重极光弧有较大的出现率,这说明中等地磁活动情形下午后多重极光弧有较高的出现率。事件分析表明多重极光弧的强度变化与地磁Pc5脉动具有较高的相关性,并且有类似的频谱特征,这说明午后多重极光弧可能与同时出现的Pc5地磁脉动有关。 相似文献
784.
浙江磐安蕨类植物资源及其开发利用 总被引:5,自引:0,他引:5
调查统计,磐安共有蕨类植物112种,隶属于60属、34科。地理成分分析表明,种的地理成分以东亚分布,特别是中国一日本分布为主,区系显示出较明显的亚热带一暖温带过渡的特征。同时从水平分布、垂直分布和生态分布三种分布型分析了磐安蕨类植物资源的分布规律,并根据其用途,划分为药用植物资源、食用植物资源、观赏植物资源等。在以上研究的基础上,提出了合理开发利用磐安蕨类植物资源的一些建议。 相似文献
785.
不同浓度的Na2SO4水溶液的拉曼光谱显示了SO42-的四个拉曼活性带:980 cm-1处的SO42-的对称伸缩振动模式v1带,1 106 cm-1处的反对称伸缩振动模式v3带,448 cm-1处的变形振动模式v2带和617 cm-1处的变形振动模式v4带。482 cm-1处的肩膀峰是由于NaSO4-离子对的形成对448 cm-1的v2带的影响而形成的SO42-的一个新的振动峰。浓Na2SO4水溶液中,水共享离子对[Na+.H2O.SO42-]-是主要的离子对物种。随着Na2SO4水溶液浓度的增加,Na+和SO42-的相互作用增强,NaSO4-离子对所占的摩尔分数增加。 相似文献
786.
787.
788.
Using raw regional climate model outputs for quantifying climate change impacts on hydrology 下载免费PDF全文
General circulation model outputs are rarely used directly for quantifying climate change impacts on hydrology, due to their coarse resolution and inherent bias. Bias correction methods are usually applied to correct the statistical deviations of climate model outputs from the observed data. However, the use of bias correction methods for impact studies is often disputable, due to the lack of physical basis and the bias nonstationarity of climate model outputs. With the improvement in model resolution and reliability, it is now possible to investigate the direct use of regional climate model (RCM) outputs for impact studies. This study proposes an approach to use RCM simulations directly for quantifying the hydrological impacts of climate change over North America. With this method, a hydrological model (HSAMI) is specifically calibrated using the RCM simulations at the recent past period. The change in hydrological regimes for a future period (2041–2065) over the reference (1971–1995), simulated using bias‐corrected and nonbias‐corrected simulations, is compared using mean flow, spring high flow, and summer–autumn low flow as indicators. Three RCMs driven by three different general circulation models are used to investigate the uncertainty of hydrological simulations associated with the choice of a bias‐corrected or nonbias‐corrected RCM simulation. The results indicate that the uncertainty envelope is generally watershed and indicator dependent. It is difficult to draw a firm conclusion about whether one method is better than the other. In other words, the bias correction method could bring further uncertainty to future hydrological simulations, in addition to uncertainty related to the choice of a bias correction method. This implies that the nonbias‐corrected results should be provided to end users along with the bias‐corrected ones, along with a detailed explanation of the bias correction procedure. This information would be especially helpful to assist end users in making the most informed decisions. 相似文献
789.
Spatial information on soil properties is an important input to hydrological models. In current hydrological modelling practices, soil property information is often derived from soil category maps by the linking method in which a representative soil property value is linked to each soil polygon. Limited by the area‐class nature of soil category maps, the derived soil property variation is discontinuous and less detailed than high resolution digital terrain or remote sensing data. This research proposed dmSoil, a data‐mining‐based approach to derive continuous and spatially detailed soil property information from soil category maps. First, the soil–environment relationships are extracted through data mining of a soil map. The similarity of the soil at each location to different soil types in the soil map is then estimated using the mined relationships. Prediction of soil property values at each location is made by combining the similarities of the soil at that location to different soil types and the representative soil property values of these soil types. The new approach was applied in the Raffelson Watershed and Pleasant Valley in the Driftless Area of Wisconsin, United States to map soil A horizon texture (in both areas) and depth to soil C horizon (in Pleasant Valley). The property maps from the dmSoil approach capture the spatial gradation and details of soil properties better than those from the linking method. The new approach also shows consistent accuracy improvement at validation points. In addition to the improved performances, the inputs for the dmSoil approach are easy to prepare, and the approach itself is simple to deploy. It provides an effective way to derive better soil property information from soil category maps for hydrological modelling. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
790.