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91.
Atmospheric aerosols are a crucial link in the physical processes, involved in the formation and growth of precipitating clouds. Extensive aerosol measurements in surface air and in the lower troposphere were made at inland and coastal stations of different regions in India. At inland stations, the hygroscopic fraction of the total aerosol content is found to be a useful characteristic for distinguishing between the monsoon and summer airflow, as well as an indicator for a good or a badly developed monsoon. At coastal stations, however, this feature is not observed.Measurements as a function of height brought out that the aerosol varied widely in air over different seasons. During monsoon, the hygroscopic fraction was found highest at the cloud base level and was closely linked to the development of rain. Details of these investigations are presented. 相似文献
92.
Mössbauer fractions f are reported for various ferrous- and/or ferric-containing oxides, hydroxides, silicates, and phosphates to extend the list previously reported by De Grave and Van Alboom (1991). The f fractions were evaluated from the experimental temperature dependencies of their center shifts, assuming the Debye model for the lattice vibrations. For most Fe2+ sites the characteristic Mössbauer or lattice temperatures ΘM are in the range 300–400 K, while those for Fe3+ sites are close to or exceed 500 K, implying significantly higher f fractions for Fe3+ than for Fe2+, in particular at room temperature. A correlation between ΘM and the coordination type, or, for a given valence state and coordination type, between ΘM and the mineral type is, however, not obvious. 相似文献
93.
The concept of polynomial‐fraction approximation is explored in this article to develop a nested type of systematic lumped‐parameter model for unbounded soil. Based on the optimal coefficients determined from the flexibility formulation, the reciprocal of the polynomial‐fraction is first taken to represent the dynamic stiffness function of foundation and then decomposed into a linear polynomial and another polynomial‐fraction. The nested division introduced in this study is operated to generate a nested form for this decomposed polynomial‐fraction, which directly corresponds to a nested discrete‐element model. The nested type of lumped‐parameter model is then easily constructed by connecting this nested discrete‐element model in series with another simple discrete‐element model corresponding to the linear polynomial. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
94.
目前观点认为,自然生态条件下的非固氮植物-土壤体系中,根据分解供给是土壤中氮的主要来源。研究植物-土壤体系中氮素的分布转化规律是评估土壤中氮素有效性的重要基础。笔者选取黄土高原这一典型西北生境中植物-土壤样品,通过测定样品氮含量与同位素自然丰度组成变化,来说明不同粒级土壤中氮素的分解水平与潜力。
结果表明,植物在分解过程中氮同位素产生3‰-5‰不等的分馏,在粒级由大到小变化的土壤组份中,随着可分解氮素的减少,土壤总氮同位素比值表现不同程度的偏正趋势,并于小粒级中趋于稳定,这与含量测量中表现出的矿化氮含量增加规律一致。氮的同位素自然丰度组成对于植物分解程度的灵敏响应,使其可以作为一种指示植物-土壤体系中氮素转化程度与趋势以及评估土壤中氮的有效性的指标,应用于自然生态研究。 相似文献
95.
96.
Hisham T. Eid 《Geotechnical and Geological Engineering》2006,24(6):1695-1713
The influence of sample preparation procedure on the measured classification indices such as clay-size fraction, liquid limit,
and plastic limit of shales was investigated. Shale samples covering a wide range of composition and plasticity were tested
using standard and modified preparation procedures to yield quantitative data required for this investigation. The study specifies
the range of shale plasticity in which the measured values of clay-size fraction and liquid limit are sensitive to hydrometer
specimen size and rehydration time, respectively. The study also revealed that the degree of shale particle disaggregation
has an important influence on the measured clay-size fraction and liquid limit. This influence is maximized for shales with
intermediate plasticity and can be interpreted in terms of particle size and shape. Correlations were established between
classification indices derived from standard and modified sample preparation procedures. It is recommended to use these correlations
to adjust shale classification indices derived from standard sample preparation procedures usually utilized by commercial
laboratories. Such correlations help in creating a universally followed procedure for better estimation of shale engineering
properties and reliable interpretation of case histories involving shale formations. 相似文献
97.
介绍了毛细管气相色谱和原子发射光谱联用仪(GC_AED)在石油馏分分析中的几个应用实例。结果表明,利用GC_AED的高选择性和高灵敏度,能够快速、有效地解决石油分析中的一些复杂问题,准确度、精密度满足应用要求。 相似文献
98.
地质样品中稀土总量的X射线荧光分析法测定 总被引:1,自引:0,他引:1
本文研究了稀土元素Ce的质量分数wCe与由Ce至Lu12元素质量分数之和w12(Nd除外)间的关系,发现wCe和w12间存在明显一致的线性相关性。回归w12-ICe标准工作曲线,实现了w12的直接测定。方法采用直接粉末压片制样,光谱仪测定wCe,wLa,wNd,wY,w12参数条件实现与稀土总量的转换。按本法对标准物质进行单项测定,结果令人满意 相似文献
99.
100.
利用HR-768型便携式光谱仪,测定了不同大豆残茬覆盖度下的地面光谱,利用照相法获取对应的大豆残茬覆盖度。采用线性回归方法分析了单波段反射率、反射率一阶导数、归一化指数、比值指数与大豆残茬覆盖度的相关性,获取了不同覆盖度水平下大豆残茬的光谱响应特征,并结合MODIS、TM、HJ-1B星的波段响应函数建立了大豆残茬覆盖度最优估算模型。结果表明,在2050—2150nm和2250—2350nm两个波段范围内,大豆残茬与裸土的光谱差异最显著,可用于二者的区分;大豆残茬的光谱特征与玉米、小麦残茬的光谱特征相似,仅在920—967nm范围内存在特殊的吸收峰;以高光谱数据为数据源,941.6nm处的反射率、2151.8nm处反射率一阶导数、1461.3nm和2404.4nm反射率构建的归一化指数以及2247nm和608.6nm反射率构建的比值指数适宜用于作物残茬覆盖度估算,以宽波段数据为数据源,短波红外与红波段反射率构建的比值指数适宜用于大豆残茬覆盖度估算。 相似文献