Biomass Burning in Southern Africa: Individual Particle Characterization of Atmospheric Aerosols and Savanna Fire Samples   总被引：2，自引：0，他引：2  

Xiande Liu  Piet Van Espen  Freddy Adams  Jan Cafmeyer  Willy Maenhaut 《Journal of Atmospheric Chemistry》2000,36(2):135-155

Ambient atmospheric aerosols and savanna fireparticulate emission samples from southern Africa werecharacterised in terms of particle classes and theirnumber abundance by electron probe X-ray microanalysis(EPXMA). About ten particle classes were identifiedfor each sample. The major classes werealuminosilicates and sea salts for ambient coarse(2–10 m equivalent aerodynamic diameter (EAD))samples, and K-S and S-only particles for ambient fine(<2 m EAD) samples. The K-S particles are oneof the major products of biomass burning. The EPXMAresults were found to be consistent with the resultsfrom bulk analyses on a sample by sample basis. Forsavanna fire fine samples, quantitative EPXMA revealedthat many particles had a composition of simple saltssuch as KCl. Some particles had a deviatingcomposition in the sense that more ionic species wereinvolved in sustaining the balance between cations andanions, and they were composite or mixed salts.Because of extensive processing during the atmospherictransport, the composition of the K-S particles in theambient samples was different from K₂SO₄,and such particles were enriched with S. The finepyrogenic KCl particles and the fine sea-saltparticles were much depleted in chlorine.  相似文献   

Reliability of rayleigh wave dispersion curve obtained from f–k spectral analysis of microtremor array measurement     

Juan C. Tokeshi  Madan B. Karkee  Yoshihiro Sugimura 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):163-174

The paper utilizes previously developed microtremor simulation technique to evaluate the reliability of Rayleigh wave dispersion curve estimated by f–k spectral analysis of microtremor array measurement. The simulated microtremors are obtained for a fictitious (TEST) site. Attempt is also made to obtain the dispersion curve for two real sites (OHDATE and SKC) by inverse analysis of the microtremor array measurement using f–k spectra method. The estimated dispersion curve from simulated microtremors (TEST site) compares well with the theoretical dispersion curve, demonstrating the reliability of f–k spectra method and indicating that the estimated dispersion curve from microtremor measurements could be adequately used as the target for inverse analysis purposes. It is also demonstrated that the dispersion curve from microtremor measurements can be utilized to estimate the soil profile at OHDATE and SKC sites by inverse analysis. Results show that the theoretical dispersion curve of the fundamental mode of Rayleigh wave after the end of inverse analysis are in good agreement with the dispersion curve obtained by f–k spectral analysis of microtremor array measurement.  相似文献   

即时合成层状双氢氧化物处理酸性大红GR染料实验研究   总被引：3，自引：0，他引：3  

庆承松  陈天虎  王志光  樊明德  陈岗  孙捷 《矿物学报》2006,26(1):8-14

印染废水是重要的工业污染源之一,研究新的印染废水脱色技术是水污染控制技术领域重要课题之一。以酸性大红GR为典型代表,初步研究了镁-铝盐水解共沉淀法即时合成层状双氢氧化物(LDH)处理阴离子型染料溶液的效果、影响因素和染料去除机理。结果表明,镁-铝盐水解共沉淀法即时合成LDH对酸性大红GR染料溶液有非常好的脱色效果,影响处理效果的主要因素是Mg/Al比和pH值。在pH值8.5~10.0,Mg/Al比2∶1~4∶1,都可以获得较好的净化效果,酸性大红GR染料浓度0.65 mmol/L时,染料去除率达99%。其净化机理是,当在染料溶液中投加Mg2 、Al2 溶解盐和NaOH时,Mg2 、Al3 水解共沉淀形成LDH的同时,染料阴离子以平衡LDH结构电荷的形式进入LDH结构层间,含有染料的LDH通过沉淀分离从溶液中去除。  相似文献   

Relationships between three dispersion measures used in flood frequency analysis     

I. Markiewicz  W. G. Strupczewski  K. Kochanek  V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(6):391-405

Three dispersion measures of a random variable, i.e., the standard deviation, the mean deviation (MD) about the mean and the second L-moment, are analyzed in terms of their properties and mutual relationships. Emphasis is placed on the MD, as it is less recognized than two other dispersion measures. The relationships between the dispersion measures are derived for distributions commonly applied in flood frequency analysis (FFA). For distributions that are unbounded, there is a distribution-dependent constant value of the ratio of dispersion measures, or equivalently of respective coefficients of variation. For two-parameter distributions that are lower-bounded, the relationship between the coefficients of variation is also distribution dependent and is not linear. For lower-bounded three-parameter distributions, the dispersion measure ratios, or equivalently the ratios of coefficients of variation, depend on the coefficient of skewness and show a strong distributional dependence. For selected distributions, the three dispersion measures are compared both in terms of the robustness to the largest samples element and the accuracy of upper quantile estimation. The MD statistics may be highly competitive to the two other dispersion measure statistics if applied in FFA for parameters estimation.  相似文献   

A Large-Eddy Simulation and Lagrangian Stochastic Study of Heavy Particle Dispersion in the Convective Boundary Layer   总被引：4，自引：1，他引：4  

Xuhui Cai  Rui Zhang  Yan LI 《Boundary-Layer Meteorology》2006,120(3):413-435

Large-eddy simulation and Lagrangian stochastic dispersion models were used to study heavy particle dispersion in the convective boundary layer (CBL). The effects of various geostrophic winds, particle diameters, and subgrid-scale (SGS) turbulence were investigated. Results showed an obvious depression in the vertical dispersion of heavy particles in the CBL and major vertical stratification in the distribution of particle concentrations, relative to the passive dispersion. Stronger geostrophic winds tended to increase the dispersion of heavy particles in the lower CBL. The SGS turbulence, particularly near the surface, markedly influenced the dispersion of heavy particles in the CBL. For reference, simulations using passive particles were also conducted; these simulation results agreed well with results from previous convective tank experiments and numerical simulations.  相似文献   

从高铝粉煤灰中提取非晶态SiO2的实验研究   总被引：5，自引：0，他引：5  

张战军  孙俊民  姚强  赫英  马鸿文 《矿物学报》2007,27(2):137-142

为了有效提高高铝粉煤灰的Al/Si比,为提取氧化铝奠定基础,研究了用NaOH从高铝粉煤灰中提取非晶态SiO2的最佳工艺条件,并对提硅反应的机理进行了探讨。首先根据高铝粉煤灰的化学与物相组成特点,确立了利用NaOH提取非晶态SiO2的基本技术路线;然后用正交实验法确定了提硅的最佳条件:NaOH的浓度25%,灰碱质量比1∶0.5,反应温度95℃,反应时间4 h。经最佳条件反应之后,SiO2的提取率达到了41.8%,灰中Al2O3的含量由48.5%增加到了57.38%,Al2O3/SiO2质量比由1.29提高到了2.39。  相似文献   

土壤、大气尘中晶体的组成及其物源指示意义——以长沙、株洲和湘潭地区为例     

张广平吴堑虹  戴塔根方建武张建新  徐海珍苏调红 《地质通报》2007,26(11):1459-1462

基于长沙、株洲和湘潭地区大气尘(可吸入颗粒和近地表积尘)和表层土壤的X-射线衍射(XRD)分析数据,采用微量相鉴定方法获得的结果显示,大气尘和表层土壤中包含石英、石膏、方解石、白云石、硫酸镉等自然矿物及SiS_2、NiTi、Cd_3As_2、FeOCl等非自然源晶体。比较了长沙、株洲、湘潭地区大气尘与表层土壤的晶体组成,分析了大气尘矿物及非自然源晶体的空间分布,探讨了其环境指示意义。  相似文献   

Solubility of FeO in (Mg,Fe)SiO₃ perovskite and the post-perovskite phase transition     

Shigehiko Tateno  Kei Hirose  Nagayoshi Sata  Yasuo Ohishi 《Physics of the Earth and Planetary Interiors》2007,160(3-4):319-325

Phase relations in Mg_0.5Fe_0.5SiO₃ and Mg_0.25Fe_0.75SiO₃ were investigated in a pressure range from 72 to 123 GPa on the basis of synchrotron X-ray diffraction measurements in situ at high-pressure and -temperature in a laser-heated diamond-anvil cell (LHDAC). Results demonstrate that Mg_0.5Fe_0.5SiO₃ perovskite is formed as a single phase at 85–108 GPa and 1800–2330 K, indicating a high solubility of FeO in (Mg,Fe)SiO₃ perovskite at high pressures. Post-perovskite appears coexisting with perovskite in Mg_0.5Fe_0.5SiO₃ above 106 GPa at 1410 K, the condition very close to the post-perovskite phase transition boundary in pure MgSiO₃. The coexistence of perovskite and post-perovskite was observed to 123 GPa. In addition, post-perovskite was formed coexisting with perovskite also in Mg_0.25Fe_0.75SiO₃ bulk composition at 106–123 GPa. In contrast to earlier experimental and theoretical studies, these results show that incorporation of FeO stabilizes perovskite at higher pressures. This could be due to a larger ionic radius of Fe²⁺ ion, which is incompatible with a small Mg²⁺ site in the post-perovskite phase.  相似文献   

Rayleigh波的频散方程高频近似分解和多模式激发数目   总被引：4，自引：4，他引：4       下载免费PDF全文

凡友华  陈晓非  刘雪峰  刘家琦  陈小宏 《地球物理学报》2007,50(1):233-239

对于在Rayleigh波勘探中经常提取到的多模式频散曲线，如何在理论上对其特征进行描述是一个很有意义的问题. 本文根据Rayeigh波频散方程中传递矩阵具有的高频近似特征，提出了传递矩阵的高频近似分解公式，据此导出了频散方程的高频近似分解公式，并在此基础上，定义了Rayleigh波的4种基本模式(R模、S模、R型周期模和S型周期模). 根据频散方程具有的周期性特征，给出了周期模频散曲线之间的平均间隔近似公式，以及在任意频率和相速度段内频散方程根的数目（即多模式的激发数目）的预测公式. 在这些结果的基础上，本文最后提出了频散方程数值搜根的一种新方法.  相似文献   

肺炎性假瘤的CT诊断与鉴别诊断     

毕纯龙  万霞  杨立国  张慰 《CT理论与应用研究》2007,16(1):77-80

目的: 分析肺炎性假瘤的CT表现.方法: 对32例经手术病理证实的肺炎性假瘤的CT及临床资料进行回顾性分析.结果: 病灶多位于肺胸膜下,广基地与胸膜相连;多呈圆形或类圆形,边缘光滑,直径2-5cm,密度均匀;边缘可见粗长毛刺,棘状突起或浅分叶;可有淋巴结肿大.结论: 全面综合地分析肺炎性假瘤的CT表现特征,结合肺内感染病史,肺炎性假瘤的正确诊断与鉴别诊断是很有帮助.  相似文献