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量子随机数发生器 被引量:7
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作者 周泓伊 曾培 《信息安全研究》 2017年第1期23-35,共13页
利用量子物理中的基本原理可以产生真随机数,它们在许多应用尤其是密码学中起到重要作用.对一个量子系统进行测量得到的真随机性揭示了量子特性——相干性,这是一个区分量子力学和经典力学的重要特性.根据对设备的信赖程度,量子随机数... 利用量子物理中的基本原理可以产生真随机数,它们在许多应用尤其是密码学中起到重要作用.对一个量子系统进行测量得到的真随机性揭示了量子特性——相干性,这是一个区分量子力学和经典力学的重要特性.根据对设备的信赖程度,量子随机数发生器可以被分为三大类:第1类是实用化的量子随机数发生器,这类发生器需要充分信任设备并建立适当的物理模型对设备进行描述,通常可以有很高的随机数产生率;第2类是自检测量子随机数发生器,可以在不信任设备的条件下产生随机数;第3类是半自检测量子随机数发生器,它是介于前2类之间的一类方案,通过部分地信任设备来获得相对较高的随机数产生率. 展开更多
关键词 量子相干性 量子随机数发生器 实用化 自检测 半自检测
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Comparative study on the performance of textural image features for active contour segmentation
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作者 MORARU Luminita MOLDOVANU Simona 《Science China(Life Sciences)》 SCIE CAS 2012年第7期637-644,共8页
We present a computerized method for the semi-automatic detection of contours in ultrasound images. The novelty of our study is the introduction of a fast and efficient image function relating to parametric active con... We present a computerized method for the semi-automatic detection of contours in ultrasound images. The novelty of our study is the introduction of a fast and efficient image function relating to parametric active contour models. This new function is a combination of the gray-level information and first-order statistical features, called standard deviation parameters. In a comprehensive study, the developed algorithm and the efficiency of segmentation were first tested for synthetic images. Tests were also performed on breast and liver ultrasound images. The proposed method was compared with the watershed approach to show its efficiency. The performance of the segmentation was estimated using the area error rate. Using the standard devia- tion textural feature and a 5x5 kernel, our curve evolution was able to produce results close to the minimal area error rate (namely 8.88% for breast images and 10.82% for liver images). The image resolution was evaluated using the con- trast-to-gradient method. The experiments showed promising segmentation results. 展开更多
关键词 active contour model image feature area error rate
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