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We propose an efficient scheme for optimizing the optical memory of a sequence of signal light pulses in a system of ultracold atoms in Λ configuration. The memory procedure consists of write-in, storage, and retrieval phases. By applying a weak microwave field in the storage stage, additional phase-dependent terms are included, and the contrast of the output signal pulses can be dynamically controlled (enhanced or suppressed) through manipulating the relative phase φ between optical and microwave fields. Our numerical analysis shows that the contrast is enhanced to the most extent when φ=1.5π. In addition, the contrast is in proportion to the Rabi frequency of the microwave field with a certain relative phase. 相似文献
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We propose an efficient scheme for optimizing the optical memory of a sequence of signal light pulses in a system of ultracold atoms in ∧ configuration.The memory procedure consists of write-in,storage,and retrieval phases.By applying a weak microwave field in the storage stage,additional phase-dependent terms are included,and the contrast of the output signal pulses can be dynamically controlled(enhanced or suppressed) through manipulating the relative phase φ between optical and microwave fields.Our numerical analysis shows that the contrast is enhanced to the most extent when φ = 1.5π.In addition,the contrast is in proportion to the Rabi frequency of the microwave field with a certain relative phase. 相似文献
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采用PCA和PSNR的医学图像配准 总被引:1,自引:0,他引:1
医学图像配准是医学图像融合的前提,是目前医学图像处理中的热点,具有重要的临床诊断和治疗价值.利用图像矩计算医学图像的质心,根据图像坐标矩阵主分量分析(PCA)的特征矢量旋转不变性,计算参考图像和浮动图像的倾斜角,获得配准初始值;在寻找最优几何变换参数时,采用峰值信噪~(PSNR)作为参考图像和浮动图像的相似性测度.实验时,采用单纯形法作为多参数寻优方法.实验结果表明,该方法计算简单,运算量少,配准速度快,精度高,而且克服了容易陷入局部最优的问题.该方法既可用于单模态图像配准,也可以用于多模态配准. 相似文献
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探讨用多变量统计分析方法对激光诱导的SD大鼠结肠组织5-ALA-PpⅨ荧光光谱进行分类,以诊断结肠早癌。对20只DMH诱导的SD大鼠,12只诱导鼠的第二代鼠,8只正常SD大鼠,按25 mg·kg-1体重剂量尾静脉注射5-ALA,150 min后进行活体激光检测,钛宝石激光器激发波长370 nm。将343条3类组织谱线分为训练组和预测组,经预处理,再采用主成分分析法提取4个主成分变量。利用训练组建立逐步多变量Logistic回归模型,并对预测组预测。3类组织病理类型两两结合,共构建3个回归方程。正常组织与早癌及进展期癌识别的特异性分别为100%, 98.4%,敏感性分别为96%, 100%,准确率分别为98%, 99.2%。在光敏剂5-ALA的辅助作用下,对370 nm激光诱导的结肠组织荧光光谱,采用主成分变量压缩与逐步多变量Logistic回归分析方法相结合,可以获得较高的正常组织对早癌及进展期癌组织识别特异性和敏感性,是一种较有潜力的结肠早癌无损诊断方法。 相似文献
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半导体设备与工艺技术的现状及新技术 总被引:2,自引:0,他引:2
简要介绍了半导体的有关工艺技术和生产设备的发展动向。首先对光刻技术、干蚀刻技术、清洗技术、氧化?扩散技术、快速高温处理(RTP)技术、离子注入技术、化学气相沉积(CVD)技术、物理气相沉积(PVD)技术以及化学机械研磨(CMP)技术等分别加以介绍,然后对未来的发展动向提出一些建议。 相似文献
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利用傅里叶方法得到了非齐次中子扩散方程格林函数的解析形式,通过格林函数计算了当外源在堆芯任意位置时的中子通量密度分布,分析了在次临界反应堆系统中,次临界倍增系数ks 与外源位置和相同次临界深度下堆芯尺寸的依赖关系。发现,ks 随着堆芯尺寸的增加而减小,这点变化虽小,但能量增益对ks 以及堆芯尺寸是相当敏感的,加速器驱动的次临界系统(ADS) 设计时应必须予以考虑。The analytical form of the Green’s functions of the inhomogeneous diffusion equation for neutrons are obtained using the Fourier method. The neutron flux distributions with the external neutron source locatedat arbitrary positions are calculated from the Green’s functions. In a subcritical system, the ependences of the subcritical multiplication factor ks on the source position and the core size with the fixed subcriticality keff are analyzed based on the series solution. It is found that ks decreases with the core size. Although this variation is small, the energy gain is sensitive to ks and then the core size, which has to be taken into account in the design of the source driven subcritical system. 相似文献
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由于砷化镓肖特基栅场效应晶体管的输入输出阻抗比双极晶体管高,设计宽带放大器有一定的困难。本报告用如下的结构实现了宽带化。首先,利用有限长的50欧姆线路将设计在中心频率的场效应晶体管输入输出阻抗变成纯电阻,其次,用二级阶梯变换器变成电阻值,最后,利用二级阶梯变换器变为50欧姆。在场效应晶体管输入输出阻抗的纯电阻变换回路中,使用有限长的50欧姆线路时,从图1可知,变换回路的传输量G(ω~2)表示如下 相似文献