Quantum interference effects on the probe amplification without and with inversion in a four-level system

A four-level system driven by two coherent fields is considered. It is shown that in the presence of an incoherent pump, the probe gain at a short wavelength can be achieved due to the quantum interference. Our density matrix calculation provides the conditions for probe amplification from different origins, including gain without population inversion on any state basis, gain with population inversion on the dressed-state basis, and gain with population inversion on the bare-state basis. Also, by controlling the Rabi frequency of the coupling field a total change from non-inversion to inversion can be achieved which does not depend on the intensity of the incoherent pump.     

Bursty events and incremental diffusion in a local diffusion and multi—scale convection system

A one-dimensional cellular automaton is defined without the critical gradient rule (Δh>Δh_c) which is essential to the existence of avalanches in self-organized criticality (SOC) models. Instead, only the local diffusion rule is used, however, the characteristics of SOC, such as the bursty behaviour, power-law decay in fluctuation spectra, self-similarity over a broad range of scales and long-time correlations, are still observed in these numerical experiments. This numerical model is established to suggest that the bursty events and the incremental diffusion observed universally in fusion experiments do not necessarily imply the submarginal dynamics.     

含有柠檬酸配体的钼硫配合物的合成、光谱及电子结构

含有柠檬酸配体的钼硫配合物的合成、光谱及电子结构;钼硫化合物;柠檬酸;性质;电子结构     

Yield strengths and stress induced crackles in copper films：effects of substrate and passivated layer

Yield strengths in unpassivated and 530 nm TiN passivated Cu films deposited on Ti, high-speed steel and Ni substrates have been measured by x-ray diffraction (XRD) in combination with the four-point bending method. The results show that, although the texture and average grain size, investigated by XRD and transmission electron microscopy respectively, do not vary with different substrate, the yield strength of the Cu film increases obviously when a thin passivated layer is present and varies slightly with substrates. Many crackles appear in the passivated Cu film on Ti substrate but do not appear in other samples. The experimental results have been explained satisfactorily with an expression for the yield strength of thin films given previously.     

High-speed 2×2 silicon-based electro-optic switch with nanosecond switch time

A 2× 2 electro-optic switch is experimentally demonstrated using the optical structure of a Mach--Zehnder interferometer (MZI) based on a submicron rib waveguide and the electrical structure of a PIN diode on silicon-on-insulator (SOI). The switch behaviour is achieved through the plasma dispersion effect of silicon. The device has a modulation arm of 1~mm in length and cross-section of 400~nm× 340~nm. The measurement results show that the switch has a V_πL_π figure of merit of 0.145~V\cdot cm and the extinction ratios of two output ports and cross talk are 40~dB, 28~dB and -28~dB, respectively. A 3~dB modulation bandwidth of 90~MHz and a switch time of 6.8~ns for the rise edge and 2.7~ns for the fall edge are also demonstrated.     

基于状态观测器的扰动补偿在转台控制中的应用

为了减小干扰力矩对转台性能的影响,提出了基于观测器的扰动补偿控制来抑制干扰力矩的方法.首先采用传递函数的方法分析了状态观测器中各观测状态与观测器输入之间的关系,利用观测器获得角加速度信号构造扰动补偿器对外部扰动进行补偿控制,设计了具有扰动补偿的转台控制系统,并分析了加入扰动补偿后对控制系统的影响.分析和试验结果表明,此基于状态观测器的扰动补偿可以对低频的扰动进行有效的抑制,能够显著的提高转台低频小信号振动时的失真度和三轴联动精度,同时对瞬态扰动也有一定的抑制作用.     

Epoxidation of allyl chloride with H_2O_2 on Ti-ZSM-5 prepared by the isomorphous substitution

The epoxidation of allyl chloride with H2O2 on Ti-ZSM-5 prepared by isomorphous substitution of HZSM-5 with TiCl4 gas was studied. The results show that Ti-ZSM-5 has a high catalytic efficiency for the epoxidation of allyl chloride. The H2O2 utilization reaches 99.50% when the allyl chloride/H2O2 molar ratio is > 1. The effect of solvent species, catalyst concentration, H2O2 and allyl chloride concentration and reaction temperature on the epoxidation was investigated simultaneously. It is found that methanol is the best solvent for the reaction. The reaction rate equation with v = k[Cat. ] [H2O2]1/2-[C3H5Cl] and the apparent activation energy with Ea = 63.462 kJ/mol are obtained according to the kinetics study.     

镉的硫族化合物半导体纳米线阵列的模板法

以多孔氧化铝为模板,用交流电分别通过含有相应的ＣｄＣｌ２、ＺｎＣｌ２、单质Ｓ、Ｓｅ等的二甲亚砜（ＤＭＳＯ）溶液,沉积ＣｄＳ、ＣｄＣｅ以及ＣｄｘＺｎ１－ｘＳ半导体纳米线阵列并研究其紫外可见吸收光谱。实验结果表明,当半导体纳米线的直径小于２５ｎｍ时,其吸收边相对于体相的吸收边产生蓝移,而且蓝移的幅度随着半民体纳米线直径的减小而增加,显示了明显的量子限域效应。     

补充富硒小麦和富硒玉米对大鼠血硒状态影响的对比观察

给克山病病区粮喂养６周的大鼠补充富硒小麦或富硒玉米,观察了大鼠血硒和血ＣＳＨ－Ｐｘ活性的变化。结果显示,补充富硒小麦和富硒玉米均可有效地升高大鼠血浆硒、红细胞硒和红细胞ＧＳＰ－Ｐｘ活性,且两种形式硒的作用效果相同;停止补硒后,补充富硒小麦组大鼠的红细胞和红细胞ＧＳＨ－Ｐｘ活性均显著高于补充富硒玉米组大鼠。表明给大鼠补充富硒小麦较补充富硒玉米好。     

冲击高度对半封闭紊流冲击射流流场影响的实验研究

采用热线风速仪给出了在半封闭、雷诺数为23000时四种不同的冲击高度下紊流冲击射流流场的详细的测量结果,并与文献结果作了比较。表明壁面的“阻尼”影响主要集中在近壁面0.5D以内,在径向上流动既有顺压梯度,又有逆压梯度。小板间距时径向速度曲线下降得比大板间距时明显要快,且曲线的峰值也稍大;在r/D≤1.0的区间内,板间距为2和4时紊动能的数值大小和分布趋势与板间距为6和8时的不同,在其它位置紊动能的分布趋势基本一致,只是大板间距下的值较大;流动结构在z4和z6之间发生了较大的变化,这种变化与势流核心区有关,在势流核心区的顶端以及下游的一段距离内紊流度都很高。