Correction of atmospheric effect on ADEOS/OCTS ocean color data: Algorithm description and evaluation of its performance

This paper first describes the atmospheric correction algorithm for OCTS visible band data used at NASDA/EOC. Sharing a basic structure with Gordon and Wang’s Sea WiFS algorithm, it uses 10 candidate aerosol models including the “Asian dust model” introduced in consideration of the unique feature of aerosols over the east Asian waters. Based on the observations at 670 and 865 nm bands, the algorithm selects a pair of aerosol models that account best for the observed spectral reflectances, and synthesizes the aerosol reflectance used for the atmospheric correction. Two different schemes for determining the value of the parameter for the aerosol model selection are presented and their anticipated estimation error is analyzed in terms of retrieved water reflectance at 443 nm. The results of our numerical simulation show that the standard deviation of the estimation error of the “weighted average” scheme is mostly within the permissible level of ±0.002, reducing the error by 18% on average compared to the “simple average” scheme. The paper further discusses the expected error under the old CZCS-type atmospheric correction, which assumes constant aerosol optical properties throughout the given image. Although our algorithm has a better performance than the CZCS algorithm, further analysis shows that the error induced by the assumption taken in the algorithm that the water-leaving radiance at 670 nm band is negligibly small may be large in high pigment concentration waters, indicating the necessity for future improvements.     

红树林孢粉-气候因子转换函数恢复古环境的可行性初探

红树林是一种对温、盐、流及土质等均具严格要求的植被类型，对定量化研究热带，亚热带沿海地区古环境具有重要的意义，通过对广西英罗湾、北海洞尾的红树林表土中孢粉的研究，初步建立起红树林植物孢粉-气候因子的转换函数，将之运用到位于英罗湾的典型钻孔D325的孢粉资料中，获得该孔所记录的年平均温度，最高温度，最低温度，年降雨量以及最高盐度等气候环境指标的变化，同时，与由孢粉分析获得的D325孔记录的全新世以来的7个气候变化阶段相对比，发现具有很好的对应关系，说明利用对环境反映灵敏的红树林孢粉为信息源，建立与环境气候因子的关系，定量恢复环境具可行性。     

Impacts of confining pressure and safety thickness on water and mud inrush in weathered granite

Abstract

Due to the strong disintegration and water erosion of completely weathered granite, water and mud inrush disasters are apt to take place in this zone during underwater tunnel construction. The pore, compactness, seepage path length, fracture geometries and their interconnections for water and mud transfer are strongly influenced by confining pressure and waterproof-resistant slab safety thickness. In order to inspect the influence, a series of experiments based on a self-designed testing system and non-Darcy testing method were performed. The results indicated that the water and mud inrush evolution increased with the increase of confining pressure and decreased with the increase of safety thickness. In particular, the confining pressure mainly influences the initial evolution stage, and a critical safety thickness to prevent water and mud inrush is obtained. Besides, the non-Darcy testing method results shows that the water and mud inrush evolution affects the influence of non-Darcy flow. For example, while the safety thickness was smaller than the critical value, the evolution was large and unstable and its behavior transferred into nonlinear. In this case, the flow changed to non-Darcy flow.     

火山活动状态及其机理的初步探讨

根据火山喷发实例总结了火山喷发在不同阶段的活动状态,并探讨了可能的物理机理。火山活动从岩浆补给到岩浆喷发的物理过程可分为3个阶段:1)岩浆补给阶段,岩浆囊压力差或过剩压力的大小决定了火山活动是否休眠或扰动,岩浆补给速率对压力差起了决定性的作用;2)通道形成阶段,当过剩压力超过围岩破裂强度时,围岩开始破裂,之后水热活动起了重要的作用;3)岩浆运移与失稳喷发阶段,主要是岩浆运移与地壳盖层的相互作用与失稳的过程。文中还讨论了火山活动状态与火山喷发危险性等级之间的关系,7个危险性等级分别对应于火山活动的7种状态,即休眠、平静、扰动、动荡、临界、活动、灾变     

暴雨作用下排土场平台–边坡系统土壤侵蚀过程模拟研究

为了探究冻融循环作用对土体结构和力学性质的影响机理,以内蒙古元宝山露天煤矿内排土场典型黏土为研究对象,采用室内冻融循环试验和MatDEM数值模拟,进行土体内部温度场、水分场和应力场的模拟分析。结果表明：排土场土料经过冻融循环后发生冻缩现象;低围压时应力−应变曲线呈现应变软化型,发生剪切破坏,围压升高后向应变硬化型转变,发生剪胀破坏;抗剪强度的劣化受前3次冻融作用的影响最为显著,在第3次达到最低值;温度的传递过程可划分为温度快速下降、缓慢相变过程、继续降温、温度稳定4个阶段;水分运移主要在温度传递的前2个阶段发生,且第二阶段的水分运移量居多;颗粒受冻融作用后整体半径缩小、分散性增大;温度和水分运移引起的颗粒胀缩、冰−水相变、冷生结构的形成等,导致颗粒的大小、位置、连接状态和颗粒间的应力等反复变化,共同驱动土体产生不可逆的结构性损伤,进而造成强度劣化。水分运移不仅为冷生构造的生长提供水源条件,还产生溶蚀、冲刷破坏,与水的相变共同成为冻融循环作用导致土体发生结构调整和应力场变化的主要原因。通过离散元法模拟冻融循环,有助于了解土体内部的力学特征和强度劣化机理,为冻区露天煤矿内排土场边坡及其他工程建设的稳定性研究提供参考。

     

水溶性污染物在土壤中转化的原位实验方法

建立了一种研究水溶性污染物在土壤中运转化的原位实验方法，该方法已成功地应用于研究黄土中氨氮的运移转化规律，克服了土柱实验存在的破坏土壤结构及氧化还原电位发生变化等所引起的实验误差。     

Massive star formation in galaxies: radiative transfer models of the UV to millimetre emission of starburst galaxies

We present illustrative models for the UV to millimetre emission of starburst galaxies which are treated as an ensemble of optically thick giant molecular clouds (GMCs) centrally illuminated by recently formed stars. The models follow the evolution of the GMCs owing to the ionization-induced expansion of the H  ii regions and the evolution of the stellar population within the GMC according to the Bruzual & Charlot stellar population synthesis models. The effect of transiently heated dust grains/PAHs on the radiative transfer, as well as multiple scattering, is taken into account.
The expansion of the H  ii regions and the formation of a narrow neutral shell naturally explain why the emission from PAHs dominates over that from hot dust in the near- to mid-infrared, an emerging characteristic of the infrared spectra of starburst galaxies.
The models allow us to relate the observed properties of a galaxy to its age and star formation history. We find that exponentially decaying 10⁷–10⁸ yr old bursts can explain the IRAS colours of starburst galaxies. The models are also shown to account satisfactorily for the multiwavelength data on the prototypical starburst galaxy M82 and NGC 6090, a starburst galaxy recently observed by ISO . In M82 we find evidence for two bursts separated by 10⁷ yr. In NGC 6090 we find that at least part of the far-infrared excess may be due to the age of the burst (6.4×10⁷ yr). We also make predictions about the evolution of the luminosity of starbursts at different wavelengths which indicate that far-infrared surveys may preferentially detect older starbursts than mid-infrared surveys.