香豆素440/荧光素钠/藏红混合染料体系的光谱研究

通过对C440/Fl.Na/Saf.-T三元混合染料体系的荧光光谱研究,了解到这三种染料之间有较充分的能量转移。又通过对C440/Fl.Na和Fl.Na/Saf.-T两个混合染料体系的荧光寿命测量,讨论了分子间能量转移过程和机理,并做了一些定量的分析。

Microstructure and mechanical behaviour of a SiC particles reinforced Al-5Cu composite under dynamic loading

The mechanical behaviour of a composite of Al–5Cu matrix reinforced with 15% SiC particles was studied at different strain rates from 1×10−3 to 2.5×103 s−1 using both a conventional universal testing machine (for low strain-rate tests) and a split Hopkinson bar (for tests at dynamic strain rates). Whilst the yield stress of the composite increases as the strain rate increases, the maximum flow stresses, 440 MPa for compression and 450 MPa for tension, are independent of strain rate. The microstructures and defect structures of the deformed composite were studied with both scanning electron microscopy and transmission electron microscopy and were correlated to the observed mechanical behaviour. Fracture surface studies of samples after dynamic tensile testing indicates that failure of the composite is controlled by ductile failure of the aluminium matrix by the nucleation, growth and coalescence of voids.

Stress-distribution at the rigid circular-arc inclusion end

The elastic plane problem of a rigid co-circular arc inclusion under arbitrary loads is dealt with. Applying Schwarz's reflection principle integrated with the analysis of the singularity of complex stress functions, the general solution of the problem is found and several closed-form solutions to some problems of practical importance are given. Finally, the stress distribution at the arc inclusion end is examined and a comparison is made with that of the rigid line inclusion end to show the effect of curvature.

配置环形线电极的单极机中的磁流体力学流动

给出配置了环形线电极的单极机中的磁流体力学解析解.由于问题是线性的,求解可简化为基本解的叠加,可利用单极机在两个区域中的基本解的衔接来求得解析解.讨论了基本解的性质.利用非完全电极可改善Hartmann边界层、增加装置中的质量流量.应用基本解讨论了连续电极的单极机.

估算等离子体效应对类氢离子束缚态能级能量影响的新公式

在均匀电子气模型下，通过求解Dirac方程，计算了类氢离子束缚态能级能量与等离子体密度的关系，得到了能近似估算能级能量随等离子体密度变化的新拟合公式，该公式同样可以用以估算不同束缚态能级发生压致电离时的临界电子密度．通过与自洽场离子球模型计算结果的比较，作为一种简单和快捷的计算方法，均匀电子汽模型在近似计算束缚态能级能量及压致电离临界电子密度方面是自洽场离子球模型得很好近似方法．

Temperature dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials

The dependence of thermal properties of Ag8In14Sb55Te23 phase-change memory materials in crystalline and amorphous states on temperature was measured and analyzed. The results show that in the crystalline state, the thermal properties monotonically decrease with the temperature and present obvious crystalline semiconductor characteristics. The heat capacity, thermal diffusivity, and thermal conductivity decrease from 0.35 J/g K, 1.85 mm(2)/s, and 4.0 W/m K at 300 K to 0.025 J/g K, 1.475 mm(2)/s, and 0.25 W/m K at 600 K, respectively. In the amorphous state, while the dependence of thermal properties on temperature does not present significant changes, the materials retain the glass-like thermal characteristics. Within the temperature range from 320 K to 440 K, the heat capacity fluctuates between 0.27 J/g K and 0.075 J/g K, the thermal diffusivity basically maintains at 0.525 mm(2)/s, and the thermal conductivity decreases from 1.02 W/m K at 320 K to 0.2 W/m K at 440 K. Whether in the crystalline or amorphous state, Ag8In14Sb55Te23 are more thermally active than Ge2Sb2Te5, that is, the Ag8In14Sb55Te23 composites bear stronger thermal conduction and diffusion than the Ge2Sb2Te5 phase-change memory materials.

高功率光纤激光器研究进展

高功率掺镱双包层光纤激光器由于在效率、散热和光束质量方面的优势,在工业加工、医疗和国防等领域具有广泛的应用前景,是目前国际上激光技术研究的热点之一.首先综述了国际上高功率光纤激光器的研究进展情况,然后重点介绍了中国科学院上海光学精密机械研究所在连续光纤激光和脉冲光纤激光方面所取得的进展,采用双端泵浦技术,在15 m的国产双包层光纤中获得440 W的连续输出,采用MOPA方式,以4 m长的国产光纤作为放大介质,在100 kHz时,获得了133 W的平均功率输出.

Dy^3＋掺杂Ge-Ga-Se硫系玻璃的性质(英文)

实验制备了Dy^3+掺杂Ge-Ga—Se系统硫系玻璃样品，测试了玻璃的密度、显微硬度、可见-红外透射光谱、荧光光谱以及荧光寿命。根据玻璃的密度计算了玻璃的摩尔体积以及致密度。讨论了玻璃的这些性能随系统平均配位数的变化关系。实验结果表明：该系统中配位数大于2．67的玻璃在1．3μm具有较好的发光性能，荧光寿命在440-530μs之间，当玻璃组成位于化学门槛即平均配位数为2．73时玻璃的发光强度最强。

Ultrabroad infrared luminescences from Bi-doped alkaline earth metal germanate glasses

We report on ultrabroad infrared (IR) luminescences covering the 1000-1700-nm wavelength region, from Bi-doped 75GeO(2) 20RO-5Al(2)O(3) 1B(2)O(3) (R = Sr, Ca, and Mg) glasses. The full width at half-maximum of the IR luminescences excited at 980 nm increases (315 -> 440 -> 510 nm) with the change of alkaline earth metal (Mg2+ -> Ca2+ -> Sr2+). The fluorescence lifetime of the glass samples is 1725, 157, and 264 mu s when R is Sr, Ca, and Mg, respectively. These materials may be promising candidates for broad-band fiber amplifiers and tunable laser resources.

Spectral properties of Ho : GdVO4 single crystal

Absorption and emission spectral properties of GdVO4 single crystal doped with Ho3+ ions were investigated at room temperature. Polarized absorption cross section is calculated in the range of 400-2200nm. Results were analyzed and parameters were calculated based on Judd-Ofelt theory, the emission spectrum shows that the emission intensity around the wavelength of 546 nm associated with transition S-5(2) -> I-5(8) is much stronger than other bands in the observed range and potentially enable the green light output around this emission band in this crystal. (c) 2006 Elsevier B.V. All rights reserved.