BBOⅠ类相位匹配光参量放大中群速失配的补偿

描述了在BBOⅠ类相位匹配的飞秒光参量放大（OPA）中，利用非共线结构和倾斜抽运光的脉 冲波面来完全补偿三波群速失配的方法.理论计算了三波群速匹配时，非共线角、相位匹配 角、抽运光的脉冲波面倾斜角随信号光波长的变化，并分析了对抽运光光斑尺寸的要求和对 空间走离长度的影响.结果表明，利用该方法不仅能够实现最大的参量带宽，而且能够完全 补偿飞秒OPA中三波的群速失配.此外，选取合适的抽运光光斑尺寸和非线性晶体的长度对提 高参量增益也至关重要. 关键词： 群速匹配 非共线相位匹配 脉冲波面倾斜 飞秒光参量放大     

高功率LED热特性测试方法研究与应用

叙述了利用动态电学测试方法测量高功率LED热阻和结温的原理、试验装置、测量步骤和影响测试结果的因素.研究结果表明,该方法具有测试结构简单、稳定性高等特点,可作为高功率LED热阻和结温的一种测试方法.     

Fermions in Odd Space-Time Dimensions: Back to Basics

It is a well-known feature of odd space-time dimensions d that there exist two inequivalent fundamental representations A and B of the Dirac gamma matrices. Moreover, the parity transformation swaps the fermion fields living in A and B. As a consequence, a parity-invariant Lagrangian can only be constructed by incorporating both the representations. Based upon these ideas and contrary to long-held belief, we show that in addition to a discrete exchange symmetry for the massless case, we can also define chiral symmetry provided the Lagrangian contains fields corresponding to both the inequivalent representations. We also study the transformation properties of the corresponding chiral currents under parity and charge-conjugation operations. We work explicitly in 2 + 1 dimensions and later show how some of these ideas generalize to an arbitrary number of odd dimensions.     

Studies on Fast Algorithm for the Scattering of a Large Array of Waveguide-Fed Wide-Slot Antennas in Millimeter Wave Region

We present an effective numerical technique to characterize the scattering of wide-slot antennas fed by waveguides with arbitrary terminations in terms of the method of moment (MoM) and the mixed potential integral equation (MPIE). In particular, the precorrected-fast Fourier transform (P-FFT) eliminates the need to generate and store the usual square impedance matrix andthus leads to speed up the matrix-vector multiplication in the resultant system. This property makes the Rao-Wilton-Glisson (RWG) functions to be useful in simulating electrically large-scale problems. In addition, the scattering from the finite ground surfaces is accounted for in the total scattered field by using the method of equivalent edge currents. The numerical results are presented and compared with both the traditional method of moment results obtained using the entire-domain basis functions and the experimental results, to demonstrate the proposed method to be a good candidate for study on the scattering of arbitrary wide-slot large array.     

On the boundary slip of fluid flow

For hundreds of years, in all the textbooks of classical fluid mechanics and lubrica- tion mechanics it is assumed that there was no wall slip (boundary slip) at a liquid-solid interface, i.e. no relative motion between liquid and solid at the interface. This is the no-slip boundary condition. It has been widely applied to engineering and experiments and to almost all the rheology or viscosity measurements of fluids. Rheology is one of the most important bases for fluid mechanics and lubricati…     

基于RBR和PCA的2.4米风洞故障诊断系统应用研究

为解决2.4米风洞试验装备的故障监测与诊断（FDD）问题,设计了一种基于规则推理（RBR）和主元分析（PCA）的并行故障诊断系统。对试验流程和因果关系较强的单一装备故障,采用RBR诊断方法;而对控制过程和重要传感器的故障,通过构建PCA模型,根据平方预报误差（SPE）实现系统故障的诊断。运行效果表明：该系统实时性好、诊断结果与实际相符合、且对过程故障具有较强的针对性。     

衍射法测量金属丝的杨氏模量

本文提出了一种新的测量金属丝杨氏模量的方法--夫琅禾费单缝衍射法.平行光遇到由金属丝被拉伸形变而形成的单缝,产生衍射,用CCD光强分布测量仪接收衍射光信号,用示波器定标方法测量衍射角,可以精确计算金属丝的杨氏模量.最后与普通光杠杆放大法比较,对可能引入的误差来源做了分析,结果证明,本方法测量精度更高、相对误差更小.     

The influence of fiber dispersion on the code form of the optical mm-wave signal generated by single sideband intensity-modulation

We have theoretically investigated the transmission performance of the optical mm-wave generation by using an external modulator based on single sideband (SSB) intensity modulation. Though the SSB millimeter (mm)-wave can immune the fading effect, the baseband signals with a high bit rate are degraded greatly after transmission along fiber. The main reason is that the fiber dispersion causes the time shift of the code edges; therefore the maximum transmission distance of the baseband signals is limited. The experimental and simulation results agree well with our theoretical analysis. We also propose a novel scheme to extend the transmission distance. In this novel scheme, the data signals are modulated only onto one of the two optical carriers; hence the shift of the code edges in the down-converted signals after transmission is eliminated.     

The optical properties of planar waveguides in LiB3O5 crystals formed by Cu implantation

A planar optical waveguide has been formed in a LiB₃O₅ crystal using 6.0 MeV Cu⁺-ions with a dose of 1 × 10¹⁵ ions/cm² at room temperature. Possible propagating modes were measured at a wavelength of 633 nm using the prism-coupling method. The refractive index profiles of the waveguide were reconstructed by an effective refractive index method and the beam propagation method was used to investigate the properties of the propagation modes in the formed waveguide. The results suggest that the fundamental TE₀ and TM₀ modes may be well-confined and propagate a longer distance inside the waveguide. The implantation process was also simulated using the transport of ions in matter code (TRIM), which indicates that the nuclear energy deposition may be the main factor for the refractive index change.