反应溅射沉积技术制备燃料电池催化层的模拟

反应溅射沉积技术(RSDT)可以生成纳米大小的颗粒并有效溅射形成性能稳定的催化层,是一项崭新的催化层制备技术。为从理论上研究RSDT过程的复杂物理化学过程,本文提出了RSDT过程的三维综合数学模型,模型描述了流体流动、热/质传递,并与燃料气的化学反应和液滴的燃烧相耦合。RNGκ-ε模型用于描述湍动燃烧气流,液滴的跟踪和分析在拉格朗日框架下进行,并利用Monte Carlo方法生成了催化层的表面结构。计算结果可以为该技术的优化提供一定的参考。     

Oscillation conditions of cw simultaneous dual-wavelength Nd：YAG laser for transitions 4F3／2-4I9／2 and 4F3／2-4I11／2

The operating condition of a cw simultaneous dual-wavelength Nd:YAG laser for both {}^4F_{3/2}-{}^4I_{9/2} (quasi-three-level system) and {}^4F_{3/2}-{}^4I_{11/2}(four-level system) transitions is studied. According to this condition, the cw simultaneous dual-wavelength at 1.06μm and 946 nm in Nd:YAG crystal has been realized experimentally through an adaptive coating design of the cavity mirrors. A total power output of 2.5W of the dual-wavelength at 946nm and 1.06μm has been achieved with an optical conversion efficiency 14.3%. The experimental results are in good agreement with the theoretical analysis.     

BaTiO3自泵浦相位共轭镜

首次报道用国产光折变晶体BaTiO_6制成的反射率大于30%的自泵浦相位共轭镜(SPPCM).并使用它成功地完成了畸变像复原实验.文中给出了自泵浦相位共轭信号的建立与入射光强度.入射光和晶体晶轴夹角的依赖关系及其擦洗速率的实验结果.文中还首次提出了一种使用单块BaTiO_3晶体,使多束入射光同时获得各自相位共轭波的方法.     

The mechanism research of the Cr^4＋Nd^3＋：YAG laser

The 946nm diode-pump microchip self-Q-switched laser of a chromium and neodymium codoped yttrium aluminum garnet crystal material (Cr^{4+}Nd^{3+}:YAG) is studied, especially about its physical mechanism of operation. The {}^4F_{3/2}→{}^4I_{9/2} transition of Nd^{3+} ion is beneficial to achieving laser oscillation in a quasi-three-level system based on coating the cavity mirrors of the microchip with films that suppress the 1064nm operation and enhance the 946nm laser. The Cr^{4+} ion is a saturable absorber. The initial loss N_{t1} is high, which acts as the threshold for laser oscillation. The stable loss N_{t2} is low because the Cr^{4+} ion is acceleratively bleached by the fast enhancement of the oscillating laser. The high N_{t1}, small N_{t2} and fast progresses permit the oscillating laser of the Cr^{4+}Nd^{3+}:YAG to have a good self-Q-switched property whose full width at half maximum is about 4.2ns. Its highest laser power is about 5.7mW. Its peak power is about 150W. Its good fundamental transverse TEM_{00} mode results from the absorption bleaching established by both the pump and oscillating lasers, which suppress other transverse mode and allow the oscillation only in the fundamental transverse TEM_{00} mode.     

走近物理学大师--宾尼格印象记

多年来在海外访问工作，有幸会面了不少物理学大师，他们的音容笑貌至今萦回耳畔脑际；其中印象最深的当数宾尼格（Gerd Binnig）先生．     

两种电路N_2激光器的输出特性

一、引 言 我们已经在 Blumlein型电路中采用瓷介电容器作为储能元件研制成体积小而输出高的N2激光器,这种电路N2激光器的激光脉冲宽度一般是3—5ns.考虑到大部分N2激光器是用作染料激光器的泵源,显然除了对激光脉宽有特殊需求外,为了提高抽运染料的效率,在相同的输出能量下,增     

Remotely pumped EDFA-based 40-Gb/s downstream and 10-Gb/s upstream long-reach WDM PON employing RSOA and FBG equalizer

We propose a remotely pumped Er-doped fiber amplifier （EDFA）-based 40-Gb/s downstream and 10- Gb/s upstream transmission long-reach wavelength division multiplexing passive optical network （WDM- PON） scheme with downstream and upstream transmission implemented by quadrature phase-shift keying （QPSK） transceiver and reflective semiconductor optical amplifier （RSOA）-based intensity modulation direct detection （IM-DD）. Transmissions of the 40-Gb/s QPSK downstream, using a Mach-Zehnder mod- ulator, and the 10-Gb/s non-return-to-zero on-off keying （NRZ-OOK） upstream, using a 1.2-GHz RSOA equalized by fiber Bragg grating （FBG）, are demonstrated with 40-km fiber transmission.     

Nd:YAG Lasers Operating at 1064nm and 946nm by Direct Pumping and Thermally Boosted Pumping

We demonstrate a 1064nm Nd：YAG laser by directly pumping into the upper lasing level with a tunable Ti：sapphire laser. The valid wavelength is demonstrated at 868.3nm, 875.2nm, 883.8nm, and 885.5nm, respectively. To our knowledge, this is the first time that 1064nm Nd：YAG laser pumped by 875.2nm laser. In addition, laser wavelength at 946 nm is also generated by direct pumping together with traditional pumping.     

Orbit and attitude control of spacecraft formation flying

Formation flying is a novel concept of distributing the functionality of large spacecraft among several smaller, less expensive, cooperative satellites. Some applications require that a controllable satellite keeps relative position and attitude to observe a specific surface of another satellite among the cluster. Specially, the target space vehicle is malfunctioning. The present paper focuses on the problem that how to control a chaser satellite to fly around an out-of-work target satellite closely in earth orbit and to track a specific surface. Relative attitude and first approximate relative orbital dynamics equations are presented. Control strategy is derived based on feedback linearization and Lyapunov theory of stability. Further, considering the uncertainty of inertia, an adaptive control method is developed to obtain the correct inertial ratio. The numerical simulation is given to verify the validity of proposed control scheme.     

基于稀土上转换纳米粒子制作指示牌标识的研究

采用热解法制备NaYF4∶ Yb,Er纳米粒子,并通过TEM和XRD对纳米粒子的形貌和结构进行表征,结果表明制备的NaYF4:Yb,Er是β相纳米粒子,形态均一,尺寸约24 nm.并对Er3+典型的绿色上转换荧光的产生机制和荧光光谱进行了研究.进一步搭建指示牌标识成像系统,基于制备的NaYF4∶Yb,Er纳米粒子作为荧光标记材料,利用Er3+的2H11/2/4S3/2-4I15/2跃迁产生绿色上转换荧光对指示牌标识进行成像,得到了高对比度的荧光成像.