Mode field converter based on embedded photonic crystal fiber

Six high-index cores are embedded around the central solid core of the photonic crystal fiber to form a fiber embedded photonic crystal fiber （FEPCF）, which is investigated based on the beam propagation method. In this structure, the Gaussian mode could be transferred to the ring mode. So FEPCF could used as a mode convertor.     

岩石压剪断裂过程中的超声波波谱特性研究

岩石破裂过程中的声发射特性不仅与岩石种类有关 ,而且与受到的载荷和破裂进展密切相关 ,岩石受载时的声发射波谱中含有大量与微断裂有关的信息。本文通过岩石压剪加载时峰值前的声发射波谱特性分析 ,探讨了岩石压剪时的微断裂机理 ,揭示了岩石在压剪加载不同阶段的波谱特性与岩石初始非线性、线性响应和临界裂纹扩展之间的相关关系。实验结果表明 ,声发射波谱参数的变化对岩石微断裂进展的响应比载荷本身更为敏感。这一结论为岩石边坡稳定性分析 ,岩爆预测和采矿工程的安全性评估提供了十分有意义的实验依据。     

新桥DDN网管系统的路由功能

介绍了天津DDN本地网网管系统的路由功能,其中引入了“域”的概念。     

聚合物表面滴状冷凝传热寿命的实验研究

在滴状冷凝传热寿命测试装置上，对采用离子束动态混合注入（DIMI）技术制备的聚四氟乙烯（PTFE）表面的商状冷凝传热寿命进行了间歇实验测试。满状冷凝已维持约500h（间歇操作总时间为1，000h），实验现象及传热性能趋于基本稳定。同时表明聚合物与金属基体具有较强的结合力。     

新型非均匀有源层掺杂分布改善功率GaAs MESFET的线性度

<正> 在功率GaAs MESFET及其放大器迅速发展的今天,人们已不再满足于仅利用均匀的有源层掺杂分布模型对器件的基本特性进行分析,以及利用近似均匀分布的GaAs材料来制作功率GaAs MESFET。研究非均匀有源层掺杂分布对GaAs MESFET性能的影响已有一些报道。人们对正斜率型、负斜率型、高斯型的有源层分布进行了比较,并采用分析模型对高斯型分布器件的直流I—V特性作了分析。结果表明:改善器件跨导g_m的均匀性,能够提高GaAs MESFET大信号应用时的输出信号线性度。对于低噪声器件,均匀的跨导能使器件获得更低的噪声。因此,研究有源层掺杂分布对于改善功率GaAs MESFET的线性问题意义十分重大。     

Transition to Antispirals in the Complex Ginzburg-Landau Equation

We report a continuous transition from outwardly rotating spiral waves to antispirals in the complex GinzburgLandau equation. Numerical simulations demonstrate that the normal spiral to antispiral transition is fulfilled through a rest spiral wave with zero propagation speed. The propagation direction of spiral waves and the power law behaviour close to the transition boundary are examined.     

一维模型原子在组合脉冲辐照下的高次谐波发射

本文采用SMT（sknple man’s theory）仔细分析了一维普薛耳-特勒势（P—T势）模型原子在高、低频组合强激光脉冲辐照下电子的动力学行为。并且，在此基础上，着力讨论了电离电子在激光脉冲策动下回核并与之复合从而发射高次谐波的平台结构，采用一种特殊设计的高、低频脉冲组合方案。使谐波发射效率较之于只用单一低频激光时的谐波发射效率提高两个数量级。     

蛋白质与线性DNA片断结合过程中的末端效应

各种体外实验技术被广泛地用来研究DNA-蛋白质之间的相互作用, 但体外和体内实验一个最明显的区别是实验使用的DNA片段远远短于基因组DNA, 因而多出了大量线性DNA分子末端. 末端问题曾倍受关注, 若干研究小组在不同系统中对其进行了研究, 但结果却并不一致, 甚至完全相反. 本文利用表面等离子共振技术(SPR)对一系列不同长度非特异DNA和Mnt阻遏蛋白结合和解离过程进行实时监测, 结果表明该蛋白在线性DNA分子末端有比内部位点更高的解离速率. 通过考察在不同位点含有特异序列的DNA与Mnt阻遏蛋白的结合过程, 发现线性DNA分子末端在一定距离内会直接影响DNA与该蛋白的特异性结合.     

Ultrahigh Harmonic Generation from an Atom with Superposition of Ground State and Highly Excited States

We investigate the high-order harmonic generation from an atom prepared in a superposition of ground state and highly excited state. When the atom is irradiated by an ultrashort pulse, the cutoff position of the plateau in the harmonic spectrum is largely extended compared with the case that the atom is initially in the ground state. The physics of the extension of the high-order harmonic plateau can be interpreted by the spatial structure of the atomic initial wave packet. We can optimize the generation of high-order harmonics by substituting the excited state for a particular coherent superposition of some highly excited states to form a spatially localized excited wave packet.     

Fabrication of fiber-embedded multi-core photonic crystal fibers

A novel fabrication method of multi-core photonic crystal fibers is proposed on the basis of a fiber-embedded technique. A taper tower is used to modify the structures of the fiber preform, and four steps of fiber fabrication and different structures of fiber samples are given. The mode structures and beating characteristics of a photonic crystal fiber sample with two successive cores are investigated in detail with the help of a supercontinuum light source, a charge-coupled device （CCD） camera, and an optical spectrum analyzer. The test results show a clear beating phenomenon between two orthotropic polarization modes with a 2.8-nm peak interval in wavelength.