沉积物孔隙毛细管压力与甲烷水合物饱和度关系研究   总被引：1，自引：1，他引：0  

孙始财  刘昌岭  业渝光  刘玉峰 《海洋学报(英文版)》2014,33(10):30-36

To better understand the relationship between the pore capillary pressure and hydrate saturation in sediments, a new method was proposed. First, the phase equilibria of methane hydrate in fine-grained silica sands were measured. As to the equilibrium data, the pore capillary pressure and saturation of methane hydrate were calculated. The results showed that the phase equilibria of methane hydrates in fine-grained silica sands changed due to the depressed activity of pore water caused by the surface group and negatively charged characteristic of silica particles as well as the capillary pressure in small pores together. The capillary pressure increased with the increase of methane hydrate saturation due to the decrease of the available pore space. However, the capillary-saturation relationship could not yet be described quantitatively because of the stochastic habit of hydrate growth.  相似文献   

A GIHS-based spectral preservation fusion method for remote sensing images using edge restored spectral modulation     

《ISPRS Journal of Photogrammetry and Remote Sensing》2014

High spatial resolution and spectral fidelity are basic standards for evaluating an image fusion algorithm. Numerous fusion methods for remote sensing images have been developed. Some of these methods are based on the intensity–hue–saturation (IHS) transform and the generalized IHS (GIHS), which may cause serious spectral distortion. Spectral distortion in the GIHS is proven to result from changes in saturation during fusion. Therefore, reducing such changes can achieve high spectral fidelity. A GIHS-based spectral preservation fusion method that can theoretically reduce spectral distortion is proposed in this study. The proposed algorithm consists of two steps. The first step is spectral modulation (SM), which uses the Gaussian function to extract spatial details and conduct SM of multispectral (MS) images. This method yields a desirable visual effect without requiring histogram matching between the panchromatic image and the intensity of the MS image. The second step uses the Gaussian convolution function to restore lost edge details during SM. The proposed method is proven effective and shown to provide better results compared with other GIHS-based methods.  相似文献   

Coupled hydro-mechanical model for partially saturated soils predicting small strain stiffness     

《Computers and Geotechnics》2014

In the paper, we present newly developed hydro-mechanical hypoplastic model for partially saturated soils predicting small strain stiffness. Hysteretic void ratio dependent water retention model has been incorporated into the existing hypoplastic model. This required thorough revision of the model structure to allow for the hydro-mechanical coupling dependencies. The model is formulated in terms of degree of saturation, rather than of suction. Subsequently, the small strain stiffness effects were incorporated using the intergranular strain concept modified for unsaturated conditions. New features included degree of saturation-dependent size of the elastic range and an updated evolution equation for the intergranular strain. The model has been evaluated using two comprehensive data sets on completely decomposed tuff from Hong-Kong and Zenos Kaolin from Iran. It has been shown that the modified intergranular strain formulation coupled with the hysteretic water retention model correctly reproduces the effects of both the stress and suction histories on small strain stiffness evolution. The model can correctly predict also different other aspects of partially saturated soil behaviour, starting from the very small strain range up to the asymptotic large-strain response.  相似文献   

Distributed discharge and sediment concentration predictions in the sub‐humid Ethiopian highlands: the Debre Mawi watershed          下载免费PDF全文

Seifu A. Tilahun  Christian D. Guzman  Assefa D. Zegeye  Dessalegn C. Dagnew  Amy S. Collick  Birru Yitaferu  Tammo S. Steenhuis 《水文研究》2015,29(7):1817-1828

Experimental research in the Ethiopian highlands found that saturation excess induced runoff and erosion are common in the sub‐humid conditions. Because most erosion simulation models applied in the highlands are based on infiltration excess, we, as an alternative, developed the Parameter Efficient Distributed (PED) model, which can simulate water and sediment fluxes in landscapes with saturation excess runoff. The PED model has previously only been tested at the outlet of a watershed and not for distributed runoff and sediment concentration within the watershed. In this study, we compare the distributed storm runoff and sediment concentration of the PED model against collected data in the 95‐ha Debre Mawi watershed and three of its nested sub‐watersheds for the 2010 and 2011 rainy seasons. In the PED model framework, the hydrology of the watershed is divided between infiltrating and runoff zones, with erosion only taking place from two surface runoff zones. Daily storm runoff and sediment concentration values, ranging from 0.5 to over 30 mm and from 0.1 to 35 g l^?1, respectively, were well simulated. The Nash Sutcliffe efficiency values for the daily storm runoff for outlet and sub‐watersheds ranged from 0.66 to 0.82, and the Nash–Sutcliffe efficiency for daily sediment concentrations were greater than 0.78. Furthermore, the model uses realistic fractional areas for surface and subsurface flow contributions, for example between saturated areas (15%), degraded areas (30%) and permeable areas (55%) at the main outlet, while close similarity was found for the remaining hydrology and erosion parameter values. One exception occurred for the distinctly greater transport limited parameter at the actively gullying lower part of the watershed. The results suggest that the model based on saturation excess provides a good representation of the observed spatially distributed runoff and sediment concentrations within a watershed by modelling the bottom lands (as opposed to the uplands) as the dominant contributor of the runoff and sediment load. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

液氮溶浸对不同煤阶含水煤样渗流特性的影响     

张磊  田苗苗  曾世攀  郭鲁成  卢硕  唐俊 《岩土力学》2022,43(11):3015-3026

中国包含多种煤阶煤层,由于煤质、地质条件等差异,不同煤层中的水分赋存情况也具有较大差异性。煤阶、饱水度作为影响液氮低温致裂效果的两个重要因素,有必要对其进行深入研究。为此,分别选择褐煤、烟煤与无烟煤3种煤阶煤样,并制备得出饱水度分别为0%、33%与99%的煤样进行液氮溶浸处理,使用摄像机定点拍摄、观察煤样表面宏观裂隙处理前后的演化规律,并对煤样进行氮气渗流试验。试验结果表明：液氮溶浸后褐煤因产生的一条与多条贯穿裂隙发生整体结构上的断裂,烟煤表面有新裂隙产生,原生宏观裂隙有一定的扩展与延伸,无烟煤表面宏观裂隙无明显发育;煤样饱水度越高,液氮的致裂增透效果越显著;液氮溶浸对3种煤阶煤样的致裂增透效果关系为：褐煤>烟煤>无烟煤,在完全干燥状态下,由于热应力不足以破坏颗粒间链接,烟煤与无烟煤的增透效果近似相等;对于褐煤,液氮溶浸处理对完全干燥状态下的煤体即产生有效致裂,渗透率平均增幅高达559.35%,对于烟煤,在饱水度为33%和99%的状态下,液氮溶浸对煤体具有明显致裂效果,渗透率平均增幅分别为330.60%和448.77%,对于无烟煤,在饱水度为99%的状态下液氮溶浸处理才能对煤体产生有效致裂,渗透率平均增幅为185.53%。  相似文献   

Refined conceptualization of TOPMODEL for shallow subsurface flows     

M. Todd Walter  Tammo S. Steenhuis  Vishal K. Mehta  Dominique Thongs  Mark Zion  Elliot Schneiderman 《水文研究》2002,16(10):2041-2046

The TOPMODEL framework was used to derive expressions that account for saturated and unsaturated flow through shallow soil on a hillslope. The resulting equations were the basis for a shallow‐soil TOPMODEL (STOPMODEL). The common TOPMODEL theory implicitly assumes a water table below the entire watershed and this does not conceptually apply to systems hydrologically controlled by shallow interflow of perched groundwater. STOPMODEL provides an approach for extending TOPMODEL's conceptualization to apply to shallow, interflow‐driven watersheds by using soil moisture deficit instead of water table depth as the state variable. Deriving STOPMODEL by using a hydraulic conductivity function that changes exponentially with soil moisture content results in equations that look very similar to those commonly associated with TOPMODEL. This alternative way of conceptualizing TOPMODEL makes the modelling approach available to researchers, planners, and engineers who work in areas where TOPMODEL was previously believed to be unsuited, such as the New York City Watershed in the Catskills region of New York State. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Multiple scattering of seismic waves, variable gas saturation and ZODs: theoretical considerations and an observational methodology     

I. Lerche 《Geophysical Journal International》1986,86(2):241-261

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罗布泊地区凝结水对潜卤水资源量评价的影响分析          下载免费PDF全文

顾新鲁  余绍文  汪玉松  颜辉  于咏梅  李明  刘小星  丁光发 《盐湖研究》2012,20(4):1-7,35

新疆罗布泊地区属于极端干旱气候地区,大气降水对地下水的补给极其有限,长期以来,众多学者认为凝结水量是罗布泊干盐湖潜卤水的重要补给来源之一。本次通过在罗北凹地地区开展的凝结水试验,较准确地计算了其补给资源量,指出尽管研究区凝结水总生成量较大,但真正能入渗补给到潜卤水饱水带的量却极少,绝大多数凝结水都以难以开发利用的土壤水形式短暂保存,被蒸发散失到大气中,对潜卤水资源量评价影响较小。  相似文献   

A Study of Surface Humidity Changes in China During the Recent 50 Years   总被引：2，自引：1，他引：1       下载免费PDF全文

SONG Yafang  LIU Yanju  DING Yihui 《Acta Meteorologica Sinica》2012,26(5):541-553

This paper analyzes in detail the characteristics of surface humidity changes in China under the background of global warming in the recent 50 years by using the observation data compiled by the National Meteorological Information Center of China. The results reveal that (1) with the increase of temperature,surface saturation specific humidity (qs) shows basically an exponential growth, according to the Clausius-Clapeyron equation. The nationwide average moistening rate in winter is obviously less than the annual average rate and the summer rate. There are some regional differences in qstrends in different regions of China. For example, qsin central and eastern parts of China exhibits a reducing trend in summer, consistent with the weakening trend of temperature in these areas; (2) except parts of South China and Jianghuai Region in eastern China, unanimously increasing trends of annual and winter specific humidity (q) are found in most of China, especially in western China. In summer, except parts of Northeast China, Northwest China, and some areas over the Qinghai-Tibetan Plateau, the decreasing and drying trends are significant in most of China, which is not consistent with the global mean situation; (3) the surface relative humidity(RH) in most of China shows a reducing trend. One of the major reasons for the reduction of RH is that the increasing rates of q are smaller than those of qs. Nonetheless, upward trends of RH in central and eastern China mainly due to the cooling temperature and rising q in these regions are observed in summer, leading to more precipitation. From about 2003 or so, qshas remarkably increased while q has sharply decreased in most parts of China; therefore, RH has reduced to a great extent. This may be closely related to the persistent growth of drought areas in China in the recent 10 years.  相似文献   

西北地区MODIS-NDVI指数饱和问题分析   总被引：6，自引：0，他引：6  

杨嘉  郭铌  黄蕾诺  贾建华 《高原气象》2008,27(4)

为了了解西北地区MODIS-NDVI和MODIS-EVI两种植被指数的特点,本文利用美国NASA LP DAAC(Land Process Distributed Active Archive Center)2004年1~12月的250 m分辨率16天植被指数合成的MOD13 Q1数据集,对西北地区不同类型植被NDVI和EVI的特征进行分析,并对西北地区MODIS-NDVI饱和问题进行了初步研究。结果表明:NDVI和EVI对干旱—半干旱气候区植被覆盖度不高的植被类型描述能力相似,月际变化趋势一致。西北地区各种植被类型NDVI比EVI高,NDVI与EVI的差异总体上呈现从半荒漠、草原、农区到林区,随NDVI值的增加而增大的规律。对植被度覆盖度高的阔叶林和针叶林,在植被生长旺盛期,NDVI总在0.8附近波动,NDVI随植被的生长增加的很小,一直维持在一个高且平的范围内,不再能看出植被生长变化的现象,即饱和现象严重;而EVI表现良好,随着植被的生长而增加,能明显地反映出植被生长的季节变化。西北高寒草甸和陕西关中农业区NDVI也出现有不同程度的饱和,饱和时间因植被的不同从1~2月不等。0.8可作为NDVI饱和的阈值。NDVI饱和问题对卫星监测植被的研究和应用会产生误差,EVI能较好地解决NDVI的饱和问题。  相似文献