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????????????????y?????GOCE???????????10??60??ε?????????????????GOCE??гλ????в?????????????????????????????????з????????30°??Χ????????仯??????????GOCE??????????????B????(-75°, 250°)???????仯??-9.15 cm/a????B???????????????????     

改进的均衡滤波器在位场数据边界识别中的应用

边界识别是进行位场数据解释时一项必不可少的任务.现有的边界识别滤波器存在识别边界发散和深部地质体边界模糊的缺点.本文提出增强型均衡滤波器,可有效地改善上述缺点.该滤波器是利用不同阶导数之间的组合来进行地质体边界的识别,并在运算中引入一种计算高阶垂直导数的稳定算法.通过理论模型试验证明增强型均衡滤波器能使浅部与深部地质体的边界同时清晰地显示,且相对于其它边界识别滤波器能更加准确和清晰地识别出地质体的边界.最后将增强型均衡滤波器应用于实测位场数据的解释,根据其识别结果可容易地划分出断裂的水平位置及不同地层之间的界线,并能发现更多的细节信息.     

The response of saltation to wind speed fluctuations

The response time of saltation to spatial or temporal wind speed fluctuations constitutes an important control parameter for aeolian sediment transport and deposition. In this paper, we present direct measurements of the response time obtained from several field experiments. The sand transport was studied using six small microphones arranged in a vertical profile and collocated with a sonic anemometer, a webcam and a cup anemometer tower. The webcam was coupled with the sonic anemometer via a personal computer and provides information on creeping and saltating grains with a sampling rate of 10 Hz. Sediment transport measurements were obtained over four periods. The Wiener filter, a signal processing technique, is used to obtain a discrete transfer function that relates the horizontal wind speed and the non‐intermittent sand transport. The transfer function can be established using an exponential function with a time constant or characteristic response time τ without time shift. The response time fluctuated between zero and 1·5 seconds depending on the turbulence intensity, the saltation activity, the measuring height and sampling rates. The Wiener filter coefficients suggest that the response of saltation to wind speed alterations is determined by more than one process. Copyright © 2012 John Wiley & Sons, Ltd.     

Steerable Pyramid分解在储层断裂检测中的应用

在隐蔽油气藏勘探中,正确刻画储层断裂对于油气勘探和开发都有着至关重要的作用.储层断裂在地震数据中表现为边缘特征.但现今多尺度边缘检测的基本理论和方法都有其本身的局限性.本文详细阐述了Steerable Pyramid分解用于储层断裂检测的基本原理和方法.输入的三维地震切片经过Steerable Pyramid分解后,不仅可以分析不同尺度不同方向上断裂的特征及走向,还可以通过重构得到经S函数控制的断裂信息,该断裂信息不仅仅是断裂的边缘检测,而是增强的断裂本身.将该算法应用于实际地震切片的断裂检测,得到了清晰的断裂信息,完整细致地展现了这些地质类型的特征,为构造解释、地震相表征及储层预测提供了有用信息.     

探讨高频检波器与低截处理的替代关系

地震检波器是实现把机械振动转换为电信号的传感器,不同检波器具有不同的相位特性和频率特性。从检波器的振动理论方程着手,分析了地震资料反射品质与检波器特性的关系。结合地质任务和技术指标要求,在相同采集因素条件下,执行特定的试验内容,考核了不同检波器类型及其性能,对资料进行了有益的处理方法尝试,获得实用而有意义的结论。在目的层较浅的探区,试验数据表明采用自然频率较低的检波器和特殊的低截处理方法同样能够实现高分辨率的地震勘探效果。     

持久性有机污染物在森林生态系统中的环境行为研究

持久性有机污染物(POPs)具有环境持久性和半挥发性, 可以在区域及全球范围内传输和分布。森林植被和林下土壤富含有机质, 森林生态系统因此成为POPs主要的储存库之一。植被叶片可快速吸附大气POPs, 并通过叶片凋落、雨水冲刷和干沉降等过程加强或加速大气POPs 向地面的沉降, 并使森林土壤成为POPs 的“汇”, 从而形成所谓的“森林过滤效应”, 进而影响POPs 在全球的分布。进入森林的POPs 在森林生态系统中将经历一系列的环境过程。本文简要介绍了森林过滤效应的特征和影响因素, 综述了叶片对大气POPs 的吸附、叶片凋落和干湿沉降、POPs 在土壤中的迁移和损失等3 个主要环境过程的研究进展, 报道了松针、树皮和苔藓作为被动采样器反映的森林POPs空间分布趋势。最后, 提出了森林POPs研究中亟待解决的科学问题, 并指出未来中国森林POPs研究的可能方向。     

一种改进的SAR影像边缘检测方法

由于SAR影像具有乘性相干斑噪声,某些对光学影像有较好检测性能的边缘检测算子,对于SAR影像并不适用,因此本文提出了一种将改进后的Ratio算子与Canny算子相组合的新方法。首先采用多种客观评价指标,得出经典方法中的Lee滤波能有效去除噪声,且最大限度保留了梯度信息,适用于边缘检测;然后对边缘检测具有恒虚警特性的Ratio算子进行改进,改进后的算子更利于影像归一化处理;最后利用改进后的Ratio算子与Canny算子组合成新方法。试验结果证明,组合后的新方法显著提高了边缘检测正确率和定位精度,改善了边缘连续性,具有一定的有效性和实用性。     

A network model to assess base-filter combinations

Granular filters retain base material within the narrowest constrictions of their void network. A direct comparison of the base material particle size distribution (PSD) and the filter constriction size distribution (CSD) cannot easily be used to assess filter-base compatibility. Here a conceptually simple random-walk network model using a filter CSD derived from discrete element modelling and base PSD is used to assess filter-base compatibility. Following verification using experimental data the model is applied to assess empirical ratios between filter and base characteristic diameters. The effects of filter density, void connectivity and blocking in the first few filter layers are highlighted.     

Multi-directional modeling for prediction of fabric anisotropy in sand liquefaction

Anisotropy in the onset of liquefaction and post liquefaction under cyclic loading condition causes the change in response behavior of the soil. The proposed model operates within the integration of sliding/opening/closing framework of 17 predefined planes as local deformation. This leads to the use of better stress/strain multilaminate histories with many directional effects on soil behavior specifically internal mechanism during pre and post-liquefaction. The ability of multilaminate model for fabric anisotropy has been proven by comparison with the experimental results under drain and undrained conditions and monotonic and cyclic loading. The effects of induced anisotropy was also investigated.     

基于多因子及泰勒级数的滑坡变形预测模型研究

将滑坡的变形看作时间、月降雨量、气温的函数,使用泰勒级数建立它们的函数关系,并将泰勒级数展开至二次项,建立卡尔曼滤波模型,用于滑坡变形的预测预报。实例计算表明,卡尔曼滤波模型的拟合效果和预测效果良好,可用于土质滑坡变形的短期预测预报。