Pound-Drever-Hall稳频方法的Multisim建模分析

Pound-Drever-Hall(PDH)稳频方法涉及光学和电学2个部分,综合仿真较为困难。针对该问题,设计了PDH的电路部分。根据器件的工作原理,采用电路模型搭建光学元件。在此基础上进行了器件的单独仿真和开环PDH光、电综合仿真,仿真使用长度为15 cm,腔镜反射率为0.97的Fabry-Pérot腔(F-P腔),并采用20 MHz的调制频率。仿真结果表明:器件模型搭建合理;激光器在无频率漂移时,系统输出较小幅度的零漂移信号;在频率漂移为5 MHz,10 MHz,15 MHz时,系统输出较为理想的误差信号。最后对仿真结果进行了讨论,并提出了改进方案。     

一种新型无人机机载计算机同步策略研究

机载计算机是无人机的核心部件,其可靠性高低直接决定了系统的安全。余度技术作为机载计算机可靠性设计的一项重要手段,对提高系统的应变能力,实现故障隐蔽以消除故障,改善系统性能有十分重要的作用。但是在余度技术中不同通道之间会存在一定的时钟误差,如果不进行处理将会使其无法达到无缝切换,从而影响系统的安全。在对机载计算机内部通道间不同步的原因进行详细分析的基础上,提出了一种软、硬件相结合的同步算法,并以三余度机载计算机为例进行了实际测试。测试结果证明该策略实现简单、同步效果好,异步度完全满足系统要求且付出的软、硬件代价小,显著提高了全系统的可靠性及可维护性。     

Effect of ZnAl2O4 coating on the compressive behaviors of aluminum borate whiskers-reinforced aluminum composites at elevated temperatures

Aluminum borate whiskers (ABOw) with or without ZnAl₂O₄ coating reinforced pure aluminum composites (ABOw/Al, ABOw/ZnAl₂O₄/Al) were fabricated by squeeze casting. The effects of ZnAl₂O₄ coating on the compressive behaviors, microstructures, and matrix textures of the composites were investigated at different temperatures and strain rates. The results indicate that the maximum compressive flow stress of the composites almost linearly decreases with the increase in temperature. The maximum compressive flow stress of ABOw/ZnAl₂O₄/Al composite is higher than that of ABOw/Al composite at the same temperature when the strain rate is larger, however, it is reversed when the strain rate is smaller. It is more serious for the fracture of whiskers in ABOw/ZnAl₂O₄/Al composite than that in ABOw/Al composite at the high compressive strain rate. However, the average length of whiskers in ABOw/ZnAl₂O₄/Al composite is larger than that in ABOw/Al composite at the low compressive strain rate. The strong matrix texture in ABOw/ZnAl₂O₄/Al composite appears at the high compressive strain rate, however, it is observed in ABOw/Al composite at the low compressive strain rate.     

(2+1)-Dimensional Fermion Determinant in a Constant Background Field at Finite Temperature and Density

We evaluate exactly both the nonrelativistic and relativistic fermion determinant in 2+1 dimensions in a constant background field at finite temperature. The effect of finite chemical potential is also considered. In both cases, the systems are decoupled into an infinite number of 1+1 fermions by Fourier transformation in the -variable. The total effective actions demonstrate nonextensiveness in the -dimension.     

PUMP-TUNING KTP OPTICAL PARAMETRIC OSCILLATOR WITH CONTINUOUS OUTPUT WAVELENGTH PUMPED BY A PULSED TUNABLE Ti:SAPPHIRE LASER

We report on the implementation of a KTP optical parametric oscillator pumped by a pulsed tunable Ti:sapphire laser. Two major improvements were achieved, including the connection of the signal and idler tuning ranges and the high-output conversion efficiency through the signal and idler tuning ranges. Both in the signal and idler, the continuous output wavelength from 1.261 to 2.532μm was obtained by varying the pump wavelength from 0.7 to 0.98μm. The maximum output pulse energy was 27.2mJ and the maximum conversion efficiency was 35.7% at 1.311μm (signal).     

镜象电流选择的唯一性

利用稳恒磁场边值问题解答的唯一性定量和维尔斯特拉斯定理讨论了镜象电流选择的唯一性。     

在线单模光纤偏振控制器研究

利用Ｐｏｉｎｃａｒｅ球理论首次全面分析了在线全光纤偏振控制器。结果发现该偏振器可以有八种不同路径，实现任意偏振态之间的转化，最后通过实验验证了其工作性能。     

2，5─哌嗪二酮与α，β─不饱和醛反应研究

综合运用了多种波谱学方法及化学手段确证并归属了２，５－哌嗪二酮与α，β－不饱和醛在超声波分散金属钾及双季铵盐作用下反应产物的立体化学与核磁共振信号，为研究这个反应提供了有用的信息．     

Novel Image Optimization Method for Joint Photoacoustic Tomography

The distribution of speed of sound （SOS） in biomedical tissue and delay compensation （DC） have significant impact on the image quality of photoacoustic tomography （PAT）. When imaging human peripheral joints, using fixed SOS and DC can only ensure that the reconstructed images are focused in a limited depth range, whereas they are defoeused at other depths, which cause severe artifacts and blurring. In this work, a linear-DC based reconstruction approach is proposed to focus the whole PAT image region. It is proved by two in vivo experiments that, compared with traditional delay-and-sum back projection algorithms, the proposed method can effectively optimize the image quality of articular tissues in PAT.     

Back focal plane imaging of Tamm plasmons and their coupled emission

The unique optical properties of Tamm plasmons (TPs) – such as flexible wavevector matching conditions including inplane wavevector within the light line, and existing both S‐ and P‐polarized TPs − facilitate them for direct optical excitation. The Tamm plasmon‐coupled emission (TPCE) from a combined photonic–plasmonic structure sustaining both surface plasmons (SPs) and TPs is described in this paper. The sensitivity of TPCE to the emission wavelength and polarization is examined with back focal plane imaging and verified with the numerical calculations. The results reveal that the excited probe can couple with both TPs and SPs, resulting in surface plasmon‐coupled emission (SPCE) and TPCE, respectively. The TPCE angle is strongly dependent on the wavelength allowing for spectral resolution using different observation angles. These Tamm structures provide a new tool to control the optical emission from dye molecules and have many potential applications in fluorescence‐based sensing and imaging.