石油勘探电磁层析成像在复杂岩层的应用仿真

对石油岩层进行勘探时,是通过电磁波形成稳定图像,对石油岩层进行勘探.由于石油区域的岩层结构密集和稀松部分分布不均匀,电磁层析成像在分布不均匀的岩石结构中,电磁波回波过程发生不定衰减,导致电磁析图像发生局部变异.传统的石油勘探电磁层析成像技术在图像局部变异下,会严重影响后期的成像效果,成像信息失真明显.提出采用加权小波分析的石油勘探中电磁层析成像复杂结构声波过滤方法.用非线性方程描述所有的石油勘探中电磁层析成像结构声波,选取一组成像信号作为样本数据,计算成像信号的权重,获取所有成像信号在声波过滤过程中的重要程度.针对上述结果进行小波变换处理,完成成像信号的分解,将所有的因子进行重构,实现声波过滤.实验结果表明,利用改进算法进行石油勘探中电磁层析成像复杂结构声波过滤,能够极大的提高过滤准确性,得到清晰的成像信号.     

基于方向Snake模型的心脏磁共振图像左心室内外膜分割

针对心脏磁共振图像(MRI)左心室内膜与外膜边缘方向不同的特点,提出一种基于曲线演化框架的方向主动轮廓模型进行左心室内外膜分割。曲线演化方程中包含基于图像边缘与区域灰度特征的混合几何流。几何流中的边缘信息项由经Fast Marching方法扩展后的动态方向梯度矢量流场（DDGVF）构成,用以引导曲线向具有不同方向的目标边缘运动,而区域灰度信息项则由Chan-Vese (CV)模型构成,用以防止曲线在演化过程中受其他边缘成分的影响而发生泄漏。最终的曲线演化方程采用水平集方法求解。实验结果表明,所提方法能够较为准确地分割出心脏MRI图像中的左心室内外膜并具有较好的鲁棒性,对于实现基于心脏MRI图像的左心室心肌区域自动快速分割和心脏功能分析与评价具有一定的应用价值。     

Inversion of the Baseline Incline Angle for Tiangong-2 Interferometric Imaging Radar Altimeter

Tiangong-2 Interferometric Imaging Radar Altimeter(InIRA) is the first wide-swath radar altimeter adopting small incidences angles with short baseline.The knowledge of the roll angle of the baseline is crucial for measuring the wide-swath Sea Surface Height(SSH) with centimeter-level accuracy.In this work,we aim to validate the technique of baseline angle determination from spaceborne nadir interferometric echoes which has been tested by airborne experiment.According to the observation geometry,the interferometric phases of nadir echoes acquired by Tiangong-2 Imaging Radar Altimeter(InIRA) are related to the roll angle of the baseline,so it should be possible for us to retrieve the incline angle from the interferometric phases under some ocean conditions not so high.In order to do so,the Tiangong-2 was tilted about 5° so as to realize a 0° baseline and in this way,a lot of data was collected.In this paper,we present the retrieved roll angles and compare them with the measured angles by the platform.Due to the Earth is an ellipsoid,and the control of the Tiangong-2 is referring to the Earth center,while the retrieved roll angle is referring to the nadir point on the Earth surface,there is a systematic error related to the orbit,and after calibration of which,the expected results are obtained：two measurements agree with each other very well not only for the measured trend but also for the standard bias between them.     

一种新的LOG算子对SAR图像的边缘检测能力

在对SAR图像的分析和识别中,边缘的检测信息十分重要。针对传统的LOG算子的缺陷,本文提出了一种基于自适应中值滤波的改进LOG算子对SAR图像的边缘检测方法,在平滑图像内部区域的同时保留了更多的细节,提高了LOG算子对SAR图像的弱边缘检测能力,是一种有效的方法。     

Integration of MODIS-derived metrics to assess interannual variability in snowpack, lake ice, and NDVI in southwest Alaska

Impacts of global climate change are expected to result in greater variation in the seasonality of snowpack, lake ice, and vegetation dynamics in southwest Alaska. All have wide-reaching physical and biological ecosystem effects in the region. We used Moderate Resolution Imaging Spectroradiometer (MODIS) calibrated radiance, snow cover extent, and vegetation index products for interpreting interannual variation in the duration and extent of snowpack, lake ice, and vegetation dynamics for southwest Alaska. The approach integrates multiple seasonal metrics across large ecological regions.Throughout the observation period (2001-2007), snow cover duration was stable within ecoregions, with variable start and end dates. The start of the lake ice season lagged the snow season by 2 to 3 months. Within a given lake, freeze-up dates varied in timing and duration, while break-up dates were more consistent. Vegetation phenology varied less than snow and ice metrics, with start-of-season dates comparatively consistent across years. The start of growing season and snow melt were related to one another as they are both temperature dependent. Higher than average temperatures during the El Niño winter of 2002-2003 were expressed in anomalous ice and snow season patterns. We are developing a consistent, MODIS-based dataset that will be used to monitor temporal trends of each of these seasonal metrics and to map areas of change for the study area.     

基于贪婪算法成像侦察卫星调度方法研究

成像侦察卫星的调度问题需要考虑大量互相联系的约束条件,实现全面调度的难度比较大,特别是在作战的情况下,很难满足快速战略决策的要求,而且各种干扰因素将会对卫星的状态产生影响,需要优越的初始调度方案作为基础.针对以上提出的实际问题,首先对成像侦查卫星约束条件进行分析,在简单假设的基础上对问题进行描述,建立卫星调度的约束模型,基于贪婪算法原理,通过软件实现调度模型求解,得到成像侦查卫星的快速调度方案,为卫星任务状态变化的二次调度和满足快速战略决策提供比较令人满意的调度基础解.     

岩石实验室反射光谱的相似系数聚类分析

以n维向量空间中的向量夹角为分类依据,对内蒙乌拉尔山地区53个岩石实验室反射光谱进行相似系数聚类分析,揭示出0.4～2.5μm岩石谱形的总体相似性差异。结果表明,岩石的电磁波属性不同于岩石学的分类属性,提出按谱形的相似性对岩石进行归类的方法及其意义。同时分析了成像光谱技术中光谱角度填图方法的优劣及改善措施,为成像光谱图像处理方法提供了十分有意义的光谱依据。     

合成孔径雷达中点目标模拟的干涉现象分析

用稀疏天线阵的观点解释了对均匀分布的点目标进行SAR成像模拟时幅度图像中出现的明暗条纹现象。在条纹的亮区,图像的信噪比和清晰度都很高,相位信息也得到很好保持;但在条纹的暗区,图像的幅度信息和相位信息都受到严重破坏。明暗条纹出现的位置和宽度与雷达观测角度、距离向分辨率、以及雷达工作频率等有关。用使均匀分布的点目标的高度有一个很小程度的随机分布的方法来破坏均匀分布,达到了消除明暗条纹的目的。消除明暗条纹后的雷达图像的清晰度和分辨率都比消除前有所降低,但却符合具有相应分辨率的雷达系统的成像效果。     

太赫兹成像系统控制软件设计

设计并实现了一套基于热释电面阵探测器的太赫兹成像软件。该软件基于VC．NET的强大功能，通过对Active控件接口的二次开发和数字图像处理技术，完成了太赫兹图像的采集、处理、显示、更替和被测物品的机械位移控制。该软件在连续太赫兹实时成像系统中运行良好。     

多模态网络融合在轻度认知障碍分类中的应用

针对早期轻度认知障碍（MCI）根据医学诊断认知量表评估极有可能无法判断的问题,提出了一种多模态网络融合的MCI辅助诊断分类方法。基于图论的复杂网络分析方法在神经影像领域的应用已得到广泛认可,但采用不同模态的成像技术研究脑部疾病对大脑网络拓扑结构属性的影响会产生不同结果。首先,使用弥散张量成像（DTI）与静息态功能磁共振成像（rs-fMRI）数据构建大脑结构和功能连接的融合网络。然后,融合网络的拓扑属性被施以单因素方差分析（ANOVA）,选择具有显著差异的属性作为分类特征。最后,利用支持向量机（SVM）留一法交叉验证对健康组和MCI组分类,估算准确率。实验结果表明,所提方法的分类结果准确率达到94.44%,相较单一模态数据法的分类结果有明显提高。所提方法诊断出的MCI患者在扣带回、颞上回以及额叶和顶叶部分区域等许多脑区表现出显著异常,与已有研究结果基本一致。