氢化丁苯共聚物结构的核磁共振波谱表征Ⅱ.微观结构的定量计算

在氢化丁苯共聚物¹³C-NMR谱脂肪碳部分谱带归属的基础上,根据各谱带的主要来源,推导出六个二单元浓度的计算公式。计算出二单元、一单元的相对含量,各结构单元的数均序列长度、嵌段含量和其它结构参数。加氢前后的¹H-和¹³C-NMR谱的组成计算结果基本一致。初步探讨了作为粘度指数改进剂的氢化丁苯共聚物微观结构与性能的关系,为合成提供了依据。     

Polytetrafluoroethylene and metal structure convective-flow CO laser

A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity.     

用于机械振动实时监测的光纤光栅有源传感装置

把一对中心反射波长分别为1562.11nm和1562.71nm的光纤光栅粘贴在均质、等厚、等腰三角形悬臂梁上下表面作为环形腔光纤激光器端镜，当机械振动激励自由端时，通过观测激光输出脉冲，地施加于自由端的机械振动的频率进行了实时监测；观察两光栅波长漂移量差值的变化，可在0～6.1mm的范围内判断所测振动的振幅。低于100Hz时，实验结果与实际值基本吻合。     

单光子态的产生与测量

报道了通过自发参量下转换产生单光子态的实验研究,使用中心波长425 nm的飞秒脉冲泵浦Ⅰ类非共线相位匹配的BBO晶体,在实验上得到单光子计数率为2.978×10-4,并分析了实验中的相关问题.     

大口径光束波前采样器(孔栅)的研制

应用平面波角谱理论，分析了采样器对光波场采样和分光的基本原理以及对空间采样频率的选择规则，描述了实际研制的大口径采样器的结构设计，并通过数值方法和高能激光大气传输实验研究了高能激光经采样器前／后的远场光斑分布关系。结果表明：利用光束波前采样器能高保真地实现对高能激光束的分光。     

用于激光推进的高功率激光器的选择

 从激光推进的要求出发，阐述了用于激光推进的高功率激光器的选择原则，即激光器必须满足：（1）高的平均功率和峰值功率；（2）高的单脉冲能量；（3）高的重复频率；（4）优良的大气传输特性。主要分析了目前YAG固体激光器、自由电子激光器和TEA脉冲CO₂激光器的特点，通过上述4个方面性能的比较，认为在目前水平下，TEA脉冲CO₂激光器是进行激光推进的首选强激光源，其优点表现在：功率可达10kW量级，单脉冲能量可达0.5~1kJ，重复频率为20~40Hz；激光波长处于大气传输窗口，对大气变化不敏感；工作物质快速流动，不存在热透镜效应和破坏阈值；相关光学元件易于制造；光束质量较好；运行成本低。     

Performance of a CW pumped Nd:YVO4 amplifier with kHz pulses

Until recently, simple and reliable high repetition-rate laser sources with nanosecond pulses much shorter than from conventional A-O Q-switch lasers were not available. However over the past 2 years we have developed such lasers based on proprietary fast E-O switching technology, which allows designs delivering 1 ns pulses and subnanosecond jitter for good synchronisation. The technology provides pulses with multi-kW peak power and repetition-rates to >100 kHz.Most recently, the performance of these short pulse lasers has been developed further by implementing oscillator/amplifier (master oscillator and power amplifier, MOPA) technology which increases the output to >1 W average power. Here we report on a simple model that has been used to predict the performance of the CW pumped Nd:YVO₄ amplifier used in the MOPA laser. The model is based on the well-known expressions for the saturated gain applying to laser pulses, but more usually applied to pulse-excited amplifiers. The model is shown to allow a good interpretation of the amplifier behaviour for kHz pulses and to be a useful tool for predicting the performance of the MOPA laser.     

Electronic molecule-like spectrum of quantum wells in crossed fields

We show that an electron confined to a single finite parabolic quantum well in crossed electric and magnetic fields can behave as a double quantum well system. The magnetic field is parallel to the heterostructure layers and the electric field is perpendicular to those. For a suitable choice of both fields and quantum well width, the electron can be confined to a double quantum well effective potential that is very similar to the electronic potential model for diatomic molecules. The double quantum well spectrum is calculated using a numerical algorithm based on semiclassical methods. A physical interpretation of this quantum system is given based on the analogy to the electrons bound to diatomic molecules.     

Inner bounds for the spectrum of quasinormal operators

A linear operator in a separable Hilbert space is called a quasinormal one if it is a sum of a normal operator and a compact one. In the paper, bounds for the spectrum of quasinormal operators are established. In addition, the lower estimate for the spectral radius is derived. Under some restrictions, that estimate improves the well-known results. Applications to integral operators and matrices are discussed. Our results are new even in the finite-dimensional case.