Six-Fold Degenerate Dark States in a Four-Level Atomic System

With all driving fields on Raman resonance, a tripod-type atomic system quickly evolves into a dark state decoupled from the lossy excited level. The dark state depends strongly on field Rabi frequencies, spontaneous decay rates, and the initial atomic population in a complicated way. Analytical results reveal that it is a sixfold degenerate dark state with its three components superposed both coherently and incoherently due to population redistribution from spontaneous emission.     

堆焊熔敷层表面纳米晶层摩擦磨损性能研究

用预压力滚压技术在堆焊修复层表面制备纳米晶层.利用TEM、SEM分析技术研究表面纳米晶层微观结构,利用CETR-3型多功能摩擦磨损试验机考察在干摩擦条件下堆焊层表面纳米晶层的摩擦磨损性能.结果表明堆焊修复层表面经表面纳米化处理后,表面形成厚度约为10μm(晶粒尺寸小于100 nm)的纳米晶层,最表面层平均晶粒尺寸约为10 nm.纳米压痕试验表明纳米晶层的硬度提高,最表面纳米晶层的硬度约为原始堆焊层硬度的3倍.与原始堆焊试样相比,表面纳米化试样的摩擦系数降低了10%,磨损体积降低了25%~30%左右.表面纳米化样品的磨损机制由原始堆焊层的磨粒磨损和黏着磨损转变为磨粒磨损,分析表明晶粒细化导致的高硬度、低塑性是摩擦磨损性能改善和磨损机制改变的主要原因.     

MICROSTRUCTURE AND FRACTAL FORMATION OF ANNEALED Ge-Au FILM AND Ge-Au/Au BILAYER FILMS

The as-deposited and annealed Ge-Au film and Ge-Au/Au bilayer films have been observed by transmission electron microscopy. The bilayer with a composition of Ge-5at%Au film is amorphous, while the Ge-22at%Au film is polycrystalline. Higher concentration of Au raises the structural heterogeneity and instability. Fractals can be observed in the Ge-5at%Au/Au bilayer samples annealed at 60-100℃. The difference of the fractal patterns generated from Ge-Au/An and a-Ge/Au films call be attributed to the higher heterogeneity and instability in Ge-Au/An bilayers.     

An analysis of seismic attenuation in random porous media

The attenuation of seismic wave in rocks has been one of the interesting research topics, but till now no poroelasticity models can thoroughly explain the strong attenuation of wave in rocks. In this paper, a random porous medium model is designed to study the law of wave propagation in complex rocks based on the theory of Biot poroelasticity and the general theory of stochastic process. This model sets the density of grain, porosity, permeability and modulus of frame as random parameters in space, and only one fluid infiltrates in rocks for the sake of better simulation effect in line with real rocks in earth strata. Numerical simulations are implemented. Two different inverse quality factors of fast P-wave are obtained by different methods to assess attenuation through records of virtual detectors in wave field (One is amplitude decay method in time domain and the other is spectral ratio method in frequency domain). Comparing the attenuation results of random porous medium with those of homogeneous porous medium, we conclude that the attenuation of seismic wave of homogeneous porous medium is far weaker than that of random porous medium. In random porous media, the higher heterogeneous level is, the stronger the attenuation becomes, and when heterogeneity σ = 0.15 in simulation, the attenuation result is consistent with that by actual observation. Since the central frequency (50 Hz) of source in numerical simulation is in earthquake band, the numerical results prove that heterogeneous porous structure is one of the important factors causing strong attenuation in real stratum at intermediate and low frequency.     

交通产业链上企业工程项目成本控制的影响因素研究

一些企业以轨道交通产业为纽带形成了交通产业链,轨道交通产业链上的企业要注重对相关工程项目实施全过程中的成本控制.从产业链的视角出发,围绕财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个方面,构建了评价指标体系和成本控制指标体系.运用层次分析法和模糊综合评价法进行评价和分析,找出了影响轨道交通产业链上企业工程项目成本控制的主要因素.研究表明,有55%的人认为财务指标、内部业务流程指标、客户指标、学习与成长能力指标这4个因素对轨道交通工程项目成本控制的影响较大.     

A study on the real-time radiation dosimetry measurement system based on optically stimulated luminescence

The optically stimulated luminescent (OSL) radiation dosimeter technically surveys a wide dynamic measurement range and a high sensitivity. Optical fiber dosimeters provide capability for remote monitoring of the radiation in the locations which are difficult-to-access and hazardous. In addition, optical fiber dosimeters are immune to electrical and radio-frequency interference. In this paper, a novel remote optical fiber radiation dosimeter is described. The optical fiber dosimeter takes advantage of the charge trapping materials CaS:Ce, Sm that exhibit OSL. The measuring range of the dosimeter is from 0.1 to 100 Gy.     

强脉冲电磁场对金属凝固组织影响的研究

提出了用强脉冲磁场和电流细化金属凝固组织的新工艺.与未经磁场或电流处理的凝固样品相比,强脉冲电磁场能够显著地改善LY12铝合金的凝固组织,使晶粒明显细化、球化;电磁场的强度愈强,这种改善效果愈明显.对该新工艺的细化机理进行了理论分析,同时,指出了实验中的新现象和新问题. 关键词：     

Statistical Fluctuation of Linear-System Driven by Colored Noise

The Brownian motion driven by colored noise in the harmonic oscillator potential is studied, and the "best Fokker-Planck equationn" is proposed. The analytical formulse of the second moments of coordinate and velocity are obtained. The fluctuation behavior of a system under influence of the correlation time of colored noise is discussed.     

高压X光机发射谱的测量与研究

本文描述了测量高压Ｘ光机发射谱的技术,并成功地测量了１４０ｋＶ高压Ｘ光机的发射谱。研究了滤波片对Ｘ光机发射谱特性的影响,在此基础上提出了可根据不同的测试目的和条件,用不同的滤波片可形成高强度的准单能,双能等Ｘ光激发源及其可能的应用领域。     

ConFlo III - an interface for high precision delta(13)C and delta(15)N analysis with an extended dynamic range

A newly developed interface coupling a CHN combustion device (elemental analyser 'EA') to an isotope ratio mass spectrometer is described and evaluated. The purpose of the device is to extend the dynamic range of delta(13)C and delta(15)N analysis from less than 2 orders of magnitude to more than 3 orders of magnitude. Carbon isotope ratio measurements of atropine as a model compound have been performed analysing between 1 μg to 5 mg C with acceptable to excellent precision (0.6 to 0.06 per thousand, delta-notation). The correction due to the blank signal is critical for sample amounts smaller than 4 μg C. The maximum sample weight is determined by the combustion capacity of the EA. Larger sample amounts are measured using dilution of a small part of the EA effluent with helium. The dilution mechanism works virtually free of isotope fractionation. Copyright 1999 John Wiley & Sons, Ltd.