Carrier Envelope Phase Effect of a Long Duration Pulse in the Low Frequency Region

Using the characteristic of small energy difference between two high Rydberg states, we theoretically investigate the carrier envelope phase （CEP） effect in a bound-bound transition of an atom in a low-frequency long laser pulse with tens of optical cycles. Particularly, we first prepare a Rydberg state of a hydrogen-like atom by a laser field with the resonant frequency between this state and the ground state. Then by using a low-frequency long laser pulse interacting with this Rydberg atom, we calculate the population of another Rydberg state nearby this Rydberg state at the end of the laser pulse and find that the population changes dramatically with the CEP of the low-frequency pulse. This CEP effect is attributed to the interference between the positive-frequency and negative-frequency components in one-photon transition. These results may provide a method to measure the CEP value of a long laser pulse with low frequency.     

Optimization of Single or Range of Harmonics by Using Two Gas Jets

The interference of high-order harmonics generated by two successive gas jets within a single laser pulse is discussed by a modeling with the inclusion of macroscopic propagation of the fundamental and harmonic fields in an ionizing medium. Based on the interference, we show that one can extract the laser Rayleigh range from the interference of harmonics and the accuracy of retrieve is independent of carrier-envelope phase while dependent on the pulse duration. Moreover~ we demonstrate that it is possible to optimize the single or range of harmonics with a high ratio relative to the adjacent orders by changing the separation of two gas jets, which is unavailable by using a single gas jet and linear polarized laser pulse.     

Passively Q-Switched Tm,Ho：YVO4 Laser with Cr：ZnS Saturable Absorber at 2 μm

A stable diode-pumped passively Q-switched Tm,Ho：YVO4 laser with Cr：ZnS saturable absorber is reported. The shortest pulse duration of -500 ns with the central wavelength of 2041 nm is obtained at the pump power of 7.4 W, corresponding to the pulse energy of 3.5 μd at repetition rate of 65 kHz.     

质子交换膜燃料电池多时间尺度下的动态特性

目前对质子交换燃料电池动态性能的研究多针对于运行参数对系统的影响,未涉及多时间尺度下电池的动态特性和相应多时间尺度模型的研究.为探明质子交换膜燃料电池动态变化时系统内各因素在不同时间尺度下对输出性能的影响效力,利用质量扩散方程及理想气体状态方程求得氧气和氢气有效分压,根据能量守恒定律、热力学定律、电化学反应方程建立动态模型.通过设置载荷突变(大、中、小时间尺度动态时长分别为0.6 s, 165 s, 16 min)研究负载电流突变时电压立即突变的机理,从作用于动态性能时长的时间常数着手,控制变量分析双层电荷层效应的电容C、燃料氧化剂的延迟时间常数τe、热力学特性(温度T)对动态性能的影响(变量初值为C=4 F,τe=80 s, T=307.7 K),明确其在不同时间尺度下的作用强度,借助Matlab/Simulink平台仿真呈现研究结果并验证所建模型的正确性和有效性.仿真结果表明:负载突变时电压突变是由于开路电压和欧姆极化电阻的作用且欧姆电阻占主导(欧姆过电压变化值2 V,开路电压变化0.05 V),小时间尺度(ms)下C对动态性能起主导作用,中时间尺度(s)下τe对动态特性影响较大,...     

噪声对滑动移除近似熵的影响

受外强迫和仪器本身的测量误差等因素的影响, 观测数据中经常包含噪声和扰动等一些虚假的信息. 针对这一问题, 本文研究了各种不同噪声对滑动移除近似熵的影响. 研究结果表明, 滑动移除近似熵的检测结果受尖峰噪声和高斯白噪声的影响较小, 意味着其具有很强的抗噪能力, 这为该方法在实际观测资料中的广泛应用提供了坚实的实验基础.     

Development of all-solid coherent Doppler wind lidar

A 1 064-nm pulsed coherent Doppler lidar (CDL) prototype is developed to measure short range wind speed in the lower altitude troposphere layer. The CDL system adopts an injection-seeded Nd:YAG laser with the pulse duration of 80 ns, single pulse energy of 0.5 mJ, and pulse repetition rate of 200 Hz. Speed calibration experiments are implemented to obtain a speed accuracy of 0.3 m/s using a hard target. Data analysis results show that the CDL system can obtain a line-of-sight wind velocity at a range of 30 to 500 m with the range resolution of 40 m and 38 pulses accumulation.     

Graphene-based Q-switched pulsed fiber laser in a linear configuration

A pulsed laser system is realized with graphene employed as a Q-switch.The graphene is exfoliated from its solution using an optical deposition and the optical tweezer effect.A fiber ferrule that already has the graphene deposited on it is inserted into an erbium-ytterbium laser(EYL)system with linear cavity configuration.We successfully demonstrate a pulsed EYL with a pulse duration of approximately 5.9μs and a repetition rate of 20.0 kHz.     

岩体应力应变曲线转型的孔压效应与降雨滑坡的机制分析

从宏观与微观机制方面探讨了孔隙水压力对岩体脆－延性转变的影响。定义了一个峰后破坏割线模量Epost来表征孔隙水压力对岩体应力应变曲线转型的效应,并结合突变理论得到的斜坡失稳的刚度判据,进一步分析了孔隙水压力对应力应变曲线峰后斜率的影响,随孔隙水压力的增加,峰后曲线斜率变陡,峰后刚度增大,即材料的均匀性、脆性增大与刚度比k减小。因此在系统内部条件不变时,刚度比k=1时就存在一个临界孔隙水压力pwcritical,即降雨等涨落因素引起滑面介质中的孔隙水压力大于这个临界值时斜坡就易于发生突变失稳。从而深化认识了降雨等外部涨落因素对斜坡系统失稳的重要触发作用。     

基于突变理论的液化评估方法

作为众多突变类型的一种形式,尖点突变模型由于其优良的性质而广泛应用于生物学和社会科学,近年来又有越来越多的学者用尖点突变模型来研究工程实际问题。本文基于地震液化的基本机理和突变理论的特点,以土体的抗液化能力和土体得到的地震能量为控制变量,以孔隙水压力发展为状态变量,建立了地震诱导的孔隙水压力发展模型。宏观震害调查结果和本文的计算结果对比表明,本文建议的方法方便、可靠,是一种理想的液化评估方法。     

乳状液的转相特性研究

本文总结了乳状液转相的基本理论和近年来的研究进展。影响乳液转相的因素主要有配方变量、组成变量和乳化方案,其中由配方变量引起的转相称为过渡转相,而由组成变量引起的转相称为突变转相。可以用综合变量（SAD或HLD）来描述不同配方变量对乳液物理化学配方的影响。通过绘制配方-组成关系图,可以通过图中的标准转相线或动态转相线来研究乳液的转相特性。与标准转相线相比较,乳液的动态转相线存在明显的滞后现象。乳液的突变动态转相有两种形式：从反常乳液到正常乳液的转相和从正常乳液到反常乳液的转相。Pickering乳液的转相不存在明显的滞后现象。目前,乳液转相技术已被广泛应用于纳米乳液和高内相黏度、高内相体积分数乳液的制备工艺中。此外,在原油/稠油的开采和输送工艺中,乳液转相技术也有着重要应用。