An experimental study on the wave-induced pore water pressure change and relative influencing factors in the silty seabed

In this study, a flume experiment was designed to investigate the characteristics of wave-induced pore water pressure in the soil of a silty seabed with different clay contents, soil layer buried depths and wave heights respectively. The study showed that water waves propagating over silty seabed can induce significant change of pore water pressure, and the amplitude of pore pressure depends on depth of buried soil layer, clay content and wave height, which are considered as the three influencing factors for pore water pressure change. The pressure will attenuate according to exponential law with increase of soil layer buried depth, and the attenuation being more rapid in those soil layers with higher clay content and greater wave height. The pore pressure in silty seabed increases rapidly in the initial stage of wave action, then decreases gradually to a stable value, depending on the depth of buried soil layer, clay content and wave height. The peak value of pore pressure will increase if clay content or depth of buried soil layer decreases, or wave height increases. The analysis indicated that these soils with 5% clay content and waves with higher wave height produce instability in bed easier, and that the wave energy is mostly dissipated near the surface of soils and 5% clay content in soils can prevent pore pressure from dissipating immediately.     

Study on virtual source method under complex overburden in horizontal well

In conventional seismic exploration,complex overburden prevents us from imaging the deeper under- ground structure,because near-surface velocity model cannot be efficiently simplified and accurately estab- lished． The virtual source method provides a promising solution,which images below a complex overburden without the knowledge of overburden velocities and near-surface changes． In this paper,the authors simulate the forward modeling under complex overburden with sources on the surface and receivers in the horizontal well, and reset the real sources into the horizontal well using the virtual source method,which subtly avoid the distor- tion effects of the complex overburden． Finally the underground structure can be imaged using Kirchhoff migra- tion,so the feasibility and advantages of the virtual source method are verified．     

Comparison of the Different Classifiers in Vegetation Species Discrimination Using Hyperspectral Reflectance Data

Feature selection methods play an important role in Hyperspectral Remote Sensing applications, especially in classification. This paper proposed a new Feature selection strategy for Hyperspectral dataset. This strategy was designed to help refine vegetation classification of 4 categories with 13 species vegetation which are the most common species in central China. An ASD field spectrometer (Analytical Spectral Device) was used to collect spectrum information of plant leaves from each species through 400 nm to 900 nm with 1 nm spectral resolution. Firstly, correlation between the physical/chemical characteristics of the leaves and the separability of each vegetation species was tested. Then, two feature selection methods, spectral angle and spectral distance, and the feature parameters extracted from spectral curves (FPESC) were used to build the feature space which would be the input space for the classifiers. At last, two linear classifiers, mahalanobis distance (MDC), and fisher linear discriminate analysis (FLDA), and a quadratic classifier, maximum likelihood (MLC), were used for vegetation species refine classification. The results showed that (1) there were no significant differences among 13 species on the leaf dry weight (physical parameter) and leaf chlorophyll content (chemical parameter); (2) FPESC of 13 species have distinctive differences and could be ideal features to discriminate these species; (3) The linear classifiers, MDC and FLDA, have better classification results in the experiments compared to the quadratic classifier MLC, where MDC has the highest classification accuracy which is above 96.2 %.     

基于OGR的交换格式数据驱动的设计与实现

交换格式是测绘行业部门为实现与其他行业部门进行信息交换与共享而设计的一种明码文件格式,需要根据不同的GIS软件开发不同的处理程序进行数据处理。针对这一情况,提出基于OGR库开发一个交换格式数据驱动,实现交换格式数据与商用GIS数据格式之间的自由转换,以提高交换格式数据使用的效率,降低数据使用成本,扩大数据使用的范围与影...     

光学遥感图像植被信息抑制通用方法

植被是影响岩石信息提取的主要因素之一.为此,采用一种通用的光学遥感图像增强方法,即植被信息掩模抑制方法,对植被信息进行抑制处理.该方法主要包括掩模、强迫不变及整体色调调整等3个步骤.通过对浙江省杭州市、云南省富宁县、江西省荣塘镇和广东省中西部等4个地区的实验结果表明,该方法对不同光谱、不同空间分辨率光学遥感图像上的植被...     

基于影像交叉学习的CBERS CCD波段模拟

与TM/ETM+相比,CBERS CCD缺少2个红外波段(波段5和波段7),这便导致了许多针对TM/ETM+数据的图像处理方法难以直接应用于CBERS CCD图像.为此,采用基于影像交叉学习的波段模拟方法,即以ETM+数据作为先验知识,通过支持向量回归( Support Vector Regression,SVR),拟...     

遥感影像融合技术方法研究

分析多种遥感影像融合方法的特点、存在的问题及其应用.应用Brovey变换、乘积变换、主成分变换、HIS变换、小波变换等五种方法对SPOT和TM图像进行影像融合实例验证.最后,对试验结果进行目视效果分析及定量分析评价.     

局部区域数据纳入ITRF的新方法

在相同历元下,忽略速度和转换参数变率的影响,实现了坐标协方差阵的严密框架转换。通过这种方法,能够使局部区域数据不必重新处理就能纳入ITRF框架,方便利用国际上已有的数据成果。实例表明,使用该种方法,转换后的坐标偏差优于0.1 mm,完全能够满足框架之间转换的要求。     

城市化发展对达拉特旗局地气候影响

通过对达拉特旗国家一般气象站1959—2008年的有关气象观测资料,分析了达拉特旗近50a来气温、风、降水气象要素的变化趋势和特点,探讨了城市化发展对达拉特旗局地气候变化产生的影响。分析表明:(1)近50a来,达拉特旗年平均温度呈明显上升趋势,趋势强度在不断加强,年极端最低气温也呈上升趋势。(2)不断增多、增密的建筑物对气流阻滞作用,使当地年平均风速呈减小趋势。同时,随着达拉特旗城市化的快速发展和进程的加快,已经对局地气候产生了重要影响,城市化进程对平均气温、风速的影响比对其降水量的影响更为显著、直接。     

Modelling the biological half-life and seasonality of ¹⁴C in Fucus vesiculosus from the east coast of Ireland: implications for the estimation of future trends

Radiocarbon levels were recorded in Fucus vesiculosus samples collected on a monthly basis over a three-year period at a site on the east coast of Ireland. The resulting data was analysed using a numerical model which estimates the transit times from the Sellafield plant to the sampling location, and the mean availability time of ¹⁴C in seaweed. With the inclusion of a model parameter allowing for seasonal variability in uptake by the Fucus, good correlation was observed between the predicted and measured concentrations. Future temporal trends of ¹⁴C Fucus concentrations along the eastern Irish coastline were modelled with the application of three possible prospective discharge scenarios, predicting ¹⁴C Fucus concentrations to reduce to ambient background levels within 2.5-years of discharges being set to zero. Such projections may prove helpful in assessing the consequences of discharge management and policy making in the context of the OSPAR convention.