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ZHANG Xiao-song DONG Xiao-yi LIU Yan-ge KAI Gui-yun WANG Zhi LI Lan HAN Xu LI Yan 《光电子快报》2007,3(5):337-338
PbS quantum dots were prepared in the aqueous medium from readily available precursors. The shape of the particles isapproximately spherical, and the average particle size observed from HRTEM image was 7-8 nm. We applied PbS quantumdots and PMMA polymer to fabricate PbS quantum dots-PMMA composites, and investigate the photoluminescence PbSquantum dots in PMMA matrix with different mass ratio. PbS quantum dots in PMMA matrix have broad emission be-tween 900 nm and 1 500 nm and photoluminescence peak at 1 179 nm. Additionally, the photoluminescence intensityincreases with increasing the dopant concentration. PbS quantum dots-PMMA polymer composites can be potentially usedfor polymer optical fiber and electroluminescence (EL) in optical communication. 相似文献
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针对现有多图像加密算法只能同时加密多张同类型同大小的图像,适用范围不广、实用性差等问题,提出一种基于图像重组和比特置乱的多图像加密算法.该算法通过将任意数量、不同大小和不同类型的图像重新组合成新多灰度图,一次完成同时加密,极大提高了加密效率和适用范围.首先,依次提取所有待加密图像像素值重新组合出N张m×n新灰度图,并将其转化成m×n×8N二进制矩阵.然后,采用3D比特置乱方式,对高位页进行行列比特置乱,低位页进行整页比特置乱.最后,进行异或扩散操作,得到密文图像.高低位分开置乱提高了算法的抗噪声能力,最终密文信息熵达到7.999以上,很好地掩盖了明文的统计特性.构造一种新型Logistic与广义三阶Fibonacci级联的混沌系统产生随机序列,增加了初值和控制参数范围,扩大了密钥空间,使其达到8×10^84以上,极大地提高了抗穷举攻击能力.既提高了序列随机性,又同时保留了低维混沌系统的快速性.结合明文哈希值(SHA-256)产生密钥,明文像素值发生微小改变后密文像素值变化率达到0.996以上,极大地提高了的明文敏感性和算法抗选择明文攻击的能力.实验分析表明,提出的多图像加密算法安全性高、实用性强. 相似文献
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G.Trevisi R Frigeri M. Minelli P. Allegri V. Avanzini S. Franchi 《光电子快报》2007,3(3):161-164
This work deals with the study of optical and morphological properties of InGaAs/AlGaAs quantum dot (QD) structures grown by molecular beam epitaxy (MBE). Photoluminescence (PL) emission energies, activation energies of PL quenching and QD sizes are studied as functions of the Al content in the AlyGal-yAs confining layers (CL). We show that the PL emission energy of In(Ga)As/AlyGal-yAs QD structures increases with increasing y and that the sizes of InAs/AlyGal-yAs QDs decrease with increasing y. By the comparison of the experimental results with those of an effective-mass model developed to calculate the QD fundamental transition energies, we show that the blueshift of emission energy has to be ascribed not only to the increase in barrier discontinuities that confine the carriers into QDs but even to effects related to changes of the QD morphology dependent on CL composition. Moreover, we show that the Al content in the barriers determines also the activation energy of thermal quenching of PL, which depends on the thermal escape of carriers from QD levels. These studies resulted in the preparation of structures with efficient light-emission in the 980 nm spectral window of interest for lightwave communications. 相似文献
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详细介绍了LTE中基于3C结构的密钥生成算法SFHA-256(SHA-256的改进),并针对由于计算分支f'包括f的一个分支,存在部分算法重复的嫌疑,对SFHA-256进行了优化,最后通过仿真验证优化的SFHA-256在抗冲突性和均匀分布方面都得到了改善。 相似文献
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介绍了单向散列函数特性和SHA-256算法原理.基于C语言实现SHA-256算法的程序设计,在Visual C++6.0环境下仿真测试结果,对该算法的单向散列函数特性进行了分析.对24组1 024 bit测试数据测试分析,结果表明,SHA-256算法具有理想的单向散列函数特性. 相似文献
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在室内/热点区域场景下,由于终端与基站之间信道质量良好,因此可以考虑引入高阶星座调制以提高频谱效率。基于一种MCS/TBS/CQI配置,对多种Small Cell场景进行引入256QAM的系统级仿真,并通过仿真结果来对比在不同场景中,引入256QAM和采用原有调制方式对用户吞吐量、频谱效率等多项指标的影响。仿真结果初步表明,在Small Cell scenario 3稀疏场景下,引入256QAM后将对系统产生较大增益。 相似文献
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摩托罗拉16位单片机MC9S12DP256在汽车电子中的应用 总被引:5,自引:0,他引:5
介绍了摩托罗拉16位单片机MC9S12DP256的结构、特点及其区别于其它单片机的优势。通过MC9S12DP256在汽车电子门控汽车电子系统的应用实例 ,简单介绍了MC9S12DP256单片机在汽车电子领域的应用方法 相似文献
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单片开关电源具有性价比高、外围电路简单、效率高、功耗低等显著特点,文中介绍了TNY256的性能特点、工作原理,并给出了TNY256的典型应用电路。 相似文献