复合调制长周期光栅耦合器的研究

从麦克斯韦方程出发,推导了长周期光栅耦合器在折射率、增益、损耗复合调制下完整的耦合理论模型。在此基础上,详细分析了该复合调制长周期光栅耦合器直通与交叉臂间的功率耦合和多波长滤波特性。结果表明,当增益/损耗调制与折射率调制作用相等时,复合调制长周期光栅耦合器具有单向非互易的功率耦合特性,而且随着多波长复用信号输入光纤和输入方向的不同,具有不同的上下话路滤波特性。在增益调制作用下,满足相位匹配条件的信号不仅可有效地耦合到交叉臂下话路输出,还能得到明显的放大;但当损耗调制时,直通与交叉臂中的信号功率均保持各自的初值,而且不再具备波长选择滤波能力。     

一种60GHz毫米波全双工光纤无线通信系统

为了实现有线信号和无线信号的同时传输,采用将有线信号和无线信号分别在两个正交的偏振态中构造混合网络的方法,用非对称输入的双臂马赫-曾德尔调制器来产生无线信号中的毫米波;利用相位调制器实现差分相位键控调制格式,以便在上行链路中实现载波重用有线信号,分别将调制后两个正交偏振态信号耦合到同一光波长上经过光纤传输至基站。在基站处将两个正交偏振态的信号分离,携带无线信号光载波经光电检测放大后由天线传输出去,而携带有线信号光载波分为两路,一路经过平衡检测器检测得到有线信号,另外一路应用到上行链路中实现载波重用。通过OPTICSYSTEM软件进行了理论分析和实验验证,得到了10Gbit/s有线信号和60GHz无线信号通过光纤传输50km后的眼图。结果表明,该方案传输效果很好。     

星载Ka频段波束赋形波纹喇叭天线设计

提出一种具有稀疏波纹结构的波纹喇叭天线,仅有2圈波纹,结构简单,易于设计加工。通过对天线参数的设计优化,可实现平顶波束赋形,在±40°的波束赋形范围内增益优于5 dBi,天线副瓣优于-30 dB,整个工作频段内驻波比(VSWR)优于1.8,适用于高轨卫星星间通信。通过对一个Ka频段样品的加工、测试和结果比对,验证了该设计方案的正确性。     

跨模态医学图像预测综述

医学影像技术与设备的进步在生物医学领域的各项研究中发挥着重要作用.跨模态医学图像预测旨在由一种模态图像预测另一种模态图像.本文详细综述了由MRI预测CT图像、7T-Like图像重构、PET预测及其他医学模态预测研究,阐述了各类模态预测的必要性及存在的挑战,说明各类预测方法的特点并进行性能比较,最终得出结论：基于深度学习的跨模态预测在预测精度和预测时间两方面更具优势.     

基于混合域的SAR回波快速算法

该文提出了一种基于混合域的SAR回波快速算法。该算法利用空变的系统传递函数参与计算,沿距离时域积分计算回波信号2维频谱,从而实现了回波信号的精确仿真。复杂度和性能分析表明,该算法不仅能够在保证较高相位精度情况下有效提高回波仿真速度,而且在2维时域内易于添加运动误差模型。最后针对点阵和面目标进行了仿真,验证了算法的有效性。     

Ångstrom‐Scale Silver Particles as a Promising Agent for Low‐Toxicity Broad‐Spectrum Potent Anticancer Therapy

Cancer incidence is rising, and the efficacy of current available anticancer agents is limited by severe dose‐limiting toxicities and drug resistance problems. Nanoparticles are heralded as the next frontier in cancer treatment. Here, a pure physical method is used to efficiently fabricate very small silver particles even approaching the Ångstrom (Ång) dimension. Fructose is used as a dispersant and stabilizer to coat the Ång‐scale silver particles (AgÅPs). Functional and mechanistic studies demonstrate that fructose‐coated AgÅPs (F‐AgÅPs) can enter and accumulate in multiple cultured cancer cell lines to induce apoptotic death, whereas most normal cells are resistant to the efficacious dose of F‐AgÅPs; in vivo, intravenous administration of F‐AgÅPs potently inhibits the growth of pancreatic and lung cancer xenografts in nude mice, without inducing notable toxic effects on the healthy tissues. The results suggest the promising potential of F‐AgÅPs as a potent, safe, and broad‐spectrum agent for the cancer treatment.     

Ultrathin Highly Luminescent Two‐Monolayer Colloidal CdSe Nanoplatelets

Surface effects in atomically flat colloidal CdSe nanoplatelets (NLPs) are significantly and increasingly important with their thickness being reduced to subnanometer level, generating strong surface related deep trap photoluminescence emission alongside the bandedge emission. Herein, colloidal synthesis of highly luminescent two‐monolayer (2ML) CdSe NPLs and a systematic investigation of carrier dynamics in these NPLs exhibiting broad photoluminescence emission covering the visible region with quantum yields reaching 90% in solution and 85% in a polymer matrix is shown. The astonishingly efficient Stokes‐shifted broadband photoluminescence (PL) emission with a lifetime of ≈100 ns and the extremely short PL lifetime of around 0.16 ns at the bandedge signify the participation of radiative midgap surface centers in the recombination process associated with the underpassivated Se sites. Also, a proof‐of‐concept hybrid LED employing 2ML CdSe NPLs is developed as color converters, which exhibits luminous efficacy reaching 300 lm W_opt^?1. The intrinsic absorption of the 2ML CdSe NPLs (≈2.15 × 10⁶ cm^?1) reported in this study is significantly larger than that of CdSe quantum dots (≈2.8 × 10⁵ cm^?1) at their first exciton signifying the presence of giant oscillator strength and hence making them favorable candidates for next‐generation light‐emitting and light‐harvesting applications.     

基于BTV正则项的图像超分辨率重建改进算法

文章在最大后验概率(MAP)随机正则化理论框架下,采用L1范数来构造数据保真项,同时为了更好的保持重建图像边缘,在结合双边滤波(BTV)正则项的基础上,提出了一种能有效利用图像梯度大小和方向信息的正则化模型.实验结果表明,此方法与L1范数结合BTV正则项经典算法相比,能更好的抑制噪声和保持边缘,且在视觉效果和客观评价两...     

基于业务预测的同目的汇聚波带交换

提出了一种新的多粒度交换结构,在这种结构中,波带交换平面与波长交换平面相互独立,适合于采用同目的汇聚的波带疏导算法。为了提高波带业务疏导算法的效率,将业务预测技术引入疏导的计算。仿真结果表明,采用业务预测后,同目的汇聚业务疏导算法的阻塞率可以减少20％以上。     

一种基于MRI图像的脑肿瘤组合分割法

从模糊的MRI脑肿瘤的图像中准确找出肿瘤,供医学临床使用。分别采用了2种分割方法：一种是改进的阈值方法,即在进行最大方差阈值法之前首先采用手动阈值法;另一种是采用圆形结构元素作为种子的形态学分割方法。这2种方法均实现了从低对比度MRI脑图像提取目标的要求。灵活使用阈值法和形态学分割方法与医学图像中,具有一定的临床实用价值。