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In this paper an analysis of the present stress field near the Meiling arcuate faults in Beijing area is made. Based on the in situ stress measurements, petrofabric analysis and model experiments, it has been found that this local stress field is a rotational shear stress field. It has been active from the late Yenshanian up to the present with the outer side rotating clockwise. The features of the local stress field are different from those of the present regional stress field characteristic of the Neocathaysian system. The trajectories of the maximum principal compressive stresses of the former show an arcuate pattern converging towards SE and diverging towards NW. However, those of the latter extend approximately in the NWW direction. 相似文献
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A progressive processing method for breast cancer detection via UWB based on an MRI-derived model 总被引:1,自引:0,他引:1 下载免费PDF全文
Ultra-wideband (UWB) microwave imaging is a promising method for breast cancer detection based on the large contrast of electric parameters between the malignant tumor and its surrounded normal breast organisms. In the case of multiple tumors being present, the conventional imaging approaches may be ineffective to detect all the tumors clearly. In this paper, a progressive processing method is proposed for detecting more than one tumor. The method is divided into three stages: primary detection, refocusing and image optimization. To test the feasibility of the approach, a numerical breast model is developed based on the realistic magnetic resonance image (MRI). Two tumors are assumed embedded in different positions. Successful detection of a 3.6 mm-diameter tumor at a depth of 42 mm is achieved. The correct information of both tumors is shown in the reconstructed image, suggesting that the progressive processing method is promising for multi-tumor detection. 相似文献
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提出了一种基于自主设计小型超宽带天线的微波稳健波束形成(RCB)成像肿瘤检测系统.仿真结果表明,该检测系统对肿瘤反射信号有很高的敏感度.在简单平面模型和核磁共振成像图(MRI)导出模型中进行仿真检测实验,并将天线阵列接收信号用RCB算法进行成像处理.从乳房重构图像中能够得到正确的肿瘤位置及大小信息,实现了平面模型中最小直径3 mm和MRI导出模型中最小直径4 mm的肿瘤检测,证实了该检测系统用于早期乳腺肿瘤检测的可行性. 相似文献
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