Iterated monoidal categories

We develop a notion of an n-fold monoidal category and show that it corresponds in a precise way to the notion of an n-fold loop space. Specifically, the group completion of the nerve of such a category is an n-fold loop space, and free n-fold monoidal categories give rise to a finite simplicial operad of the same homotopy type as the classical little cubes operad used to parametrize the higher H-space structure of an n-fold loop space. We also show directly that this operad has the same homotopy type as the n-th Smith filtration of the Barratt-Eccles operad and the n-th filtration of Berger's complete graph operad. Moreover, this operad contains an equivalent preoperad which gives rise to Milgram's small model for when n=2 and is very closely related to Milgram's model of for n>2.     

KNbO3：Fe晶体的时间微分效应及图像追踪

本文观察到了KNbO_3:Fe晶体的时间微分效应,并用这个微分效应进行了图像追踪的演示,为KNbO_3:Fe晶体在光折变器件领域的应用进行了有益的探索。     

The Influence of Window Parameters on the Transmission Characteristics of Millimeter Waves

This work reports about the influence of some window parameters, such as the mechanical tolerance of disk thickness, the variation of distance between two disks, and the frequency drift during gyrotron operation on the transmission characteristics of millimeter waves. Detailed calculations of the transmission characteristics for a single-disk gyrotron window and frequency tunable double-disk plasma fusion torus windows have been performed. The geometry of the window units has been optimized in order to obtain a suitable transmission characteristic, i.e. power reflection less than –20 dB within a frequency bandwidth of about 1 GHz around the chosen frequencies.     

Semiclassical approximation for transmission through open Sinai billiards

We use a semiclassical approximation to study the transport through the weakly open chaotic Sinai quantum billiards which can be considered as the schematic of a Sinai mesoscopic device,with the diffractive scatterings at the lead openings taken into account.The conductance of the ballistic microstructure which displays universal fluctuations due to quantum interference of electrons can be calculated by Landauer formula as a function of the electron Fermi wave number,and the transmission amplitude can be expressed as the sum over all classical paths connecting the entrance and the exit leads.For the Sinai billiards,the path sum leads to an excellent numerical agreement between the peak positions of power spectrum of the transmission amplitude and the corresponding lengths of the classical trajectories,which demonstrates a good agreement between the quantum theory and the semiclassical theory.     

多单元光纤激光阵列的倾斜控制实验研究

本文结合光纤激光阵列技术的发展趋势,介绍一种基于大模场面积光纤的自适应光纤光源准直器的研制进展,搭建七单元光纤激光阵列,进行平行发射体系下阵列间的倾斜控制实验,并初步探索了基于目标在回路的共形发射体系下阵列间的倾斜控制.最后,在三级全光纤放大链路的主振荡-功率放大系统中,完成了两路10W量级光纤激光阵列的倾斜控制及锁相.为在实际大气环境下应用光纤激光阵列技术提供了参考.     

基于背景光调制的复合光傅里叶变换轮廓术

提出一种基于背景光调制的用于傅里叶变换轮廓术测量范围的复合光栅,该光栅通过调制一正弦条纹和不含任何相位信息的背景光来抑制零频,较基于相移技术的复合光栅有更大的优势:背景光只含直流分量,使得复合光栅的频谱更加简单,有利于滤出载波信息,提高测量精度;对从复合光栅中解调出来的背景光只涉及平均值校准,校准过程更为简单;解调出的背景光与物体表面的反射率成正比,具有潜在的应用价值。采用Matlab程序对该复合光栅进行了数值模拟,并对该光栅实用性进行了实验研究,结果证实了该光栅用于抑制零频、扩大傅里叶变换轮廓术测量范围的有效性,且提高了测量精度。     

基于0-1稀疏循环矩阵的测量矩阵分离研究

当前压缩感知中测量矩阵的优化是测量阶段和重构阶段采用同一矩阵的事前优化。采用了以行变换为主的测量矩阵优化算法和过渡矩阵将压缩感知的测量矩阵和重构矩阵相分离,在测量阶段采用单像素相机的0-1稀疏矩阵,在重构阶段采用近似矩阵,这是区别于传统思路的测量数据和测量矩阵的事后优化方法。理论分析和实验结果表明,优化矩阵的性能好于稀疏循环矩阵,近似矩阵和优化矩阵具有相近的性能。研究成果降低了测量矩阵工程设计和实现的难度。     

时间延迟积分型面阵CMOS图像传感器MTF速度失配模型研究

研究了时间延迟积分型面阵互补金属氧化物半导体(CMOS)图像传感器调制传递函数(MTF)速度失配特性,在分析累加级数、像素尺寸、镜头放大倍数、行周期及电机运动速度失配等影响因素的基础上,建立了MTF速度失配模型。基于现场可编程门阵列(FPGA)开发板,搭建面阵CMOS图像传感器实现线阵时间延时积分(TDI)的CMOS测试系统。实验结果表明,在光强为3lx,速度失配M(ΔV/V)<2,8级时间延迟积分与面阵成像相比,MTF值提高50%;当累加级数为8级,速度失配满足M(ΔV/V)=2的速度失配容限时,奈奎斯特频率处的MTF值下降10%,当速度失配达到M(ΔV/V)=10时,MTF值下降35%。     

空气开关等离子体干涉条纹图像的处理

利用Mach-Zehnder干涉仪测量了空气开关中等离子体电子密度分布,使用高速分幅相机拍摄记录不同时延下的干涉条纹图像。针对实验获得的干涉条纹图像的特点,提出了一种首先进行频域FFT滤波去噪,然后进行空域二值化、细化的处理方法。该方法能够很好的消除图像噪声的影响,提取出单像素的亮条纹中心线,从而能够准确读取条纹坐标信息,再通过对干涉条纹偏移量进行Abel逆变换,得到等离子体电子密度分布。     

带有增益介质层的混合脊状等离子体波导的传输特性

在传统脊状等离子体波导的基础上设计了一种带有增益介质层的新型混合脊状等离子体波导,其结构中的介质层部分包含两个区域:前区为单一介质,后区的脊是由2种介质构成的双层脊区。采用二维时域有限差分方法分析了波导结构的传输特性,得到了TM模下的电场分布图,并对输出功率以及传输损耗与结构参数和介质折射率的变化规律进行了讨论。结果表明,在波导中引入的增益介质材料磷化铟后其损耗达到-6 dB/μm。此种波导结构对于光集成芯片的研究与制作具有重要意义。