Can stress-strain relationships be obtained from indentation curves using conical and pyramidal indenters?

Applying the scaling relationships developed recently for conical indentation in elastic-plastic solids with work-hardening, we examine the question of whether stress-strain relationships of such solids can be uniquely determined by matching the calculated loading and unloading curves with that measured experimentally. We show that there can be multiple stress-strain curves for a given set of loading and unloading curves. Consequently, stress-strain relationships may not be uniquely determined from loading and unloading curves alone using a conical or pyramidal indenter.

载流条形薄板的非线性应力与变形分析

在所建立的载流条形薄板的非线性磁弹性基本方程——运动方程、几何方程、物理方程和电动力学方程的基础上,通过变量代换,整理成含有10个基本未知函数的标准柯西型方程。采用差分及准线性化方法,将含有10个基本未知函数的偏微分方程组,变换成能用离散正交法编程求解的准线性微分方程组。由此计算分析两边简支条形薄板在电磁场和机械载荷耦合作用下的应力与变形,研究侧向电流和外磁场强度对载流条形薄板的磁弹性效应。

火箭剩余推进剂排放过程的分析与模拟

为了减少空间碎片的产生，星箭分离后，需要在轨排放火箭末级贮箱内的剩余推进剂．分析表明，排放条件下的推进剂射流进入太空后，立即失稳破碎为大量液滴；液滴在高真空环境下扩散，它们的表面不断有气体分子蒸发，逐渐在箭体周围形成了一个由液滴和蒸气分子组成的羽流场．采取Lagrange方法追踪该流场中每个液滴的运动轨迹以及表面蒸发冷凝过程，利用直接模拟Monte Carlo方法计算蒸气分子的运动和碰撞，然后通过微观量的统计平均获得感兴趣的宏观流场、箭体表面的压力和剪应力分布等．为了检验稀薄蒸气算法、模型和程序，模拟了真空水射流周围水蒸气羽流场，获得的径向Pitot压力分布与Fuchs和Legge的实验数据的符合．在此基础上，分别模拟了CZ-4B火箭末级剩余燃料偏二甲肼在不同排放方式下的三维稀薄蒸气与液滴羽流场．计算表明：原排放方式的扰动力矩相当大，超出了火箭姿控范围，新排放方式的扰动力矩很小，处于火箭姿控范围之内．这些预测得到了飞行遥测数据的支持．

Optimization of optical parametric chirped pulse amplification with different pump wavelengths

Optical parametric chirped pulse amplification with different pump wavelengths was investigated using LBO crystal, at signal central wavelength of 800 nm. According to our theoretical simulation, when pump wavelength is 492.5 nm, there is a maximal gain bandwidth of 190 nm. centered at 805 nm in optimal noncollinear angle using LBO. Presently, pump wavelength of 492.5 nm can be obtained from second harmonic generation of a Yb:Sr-5(PO4)(3)F laser. The broad gain bandwidth can completely support similar to 6 fs with a spectral centre of seed pulse at 800 nm. The deviation from optimal noncollinear angle can be compensated by accurately tuning crystal angle for phase matching. The gain spectrum with pump wavelength of 492.5 nm is much better than those with pump wavelengths of 400, 526.5 and 532 nm, at signal centre of 800 nm. (c) 2005 Elsevier B.V. All rights reserved.

透射型光折变体全息光栅对超短脉冲激光光束衍射的特性

在Kogelnik耦合波理论的基础上，考虑光栅记录介质的色散效应的影响，研究了光折变体全息光栅对不同偏振状态的超短脉冲激光光束衍射的性质，讨论了高斯型入射脉冲激光光束的谱宽与光栅的有效衍射谱宽之比不同时，衍射和透射光束的光谱宽度、时间宽度、波形和衍射效率的变化。结果表明，光栅的有效衍射谱宽受光栅参量及入射条件的影响，对衍射性质的影响很大，且在考虑光栅记录介质的色散效应时减小。当入射脉冲的偏振方向垂直于入射面时，光栅的有效衍射谱宽大于偏振方向平行于入射面的情形，衍射效率在入射脉冲宽度较大时小于偏振方向平行于

Femtosecond optical Kerr effect study of Ge(10)AS(40)S(30)Se(20) film

The results of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultrafast pulses in amorphous Ge10As40S30Se20 film is reported in this paper. The film shows an optical non-linear response of: 200 fs under ultrafast 80 fs-pulse excitation and the values of real and imaginary parts of non-linear susceptibility chi((3)) were 9.0 X 10(-12) and -4.0 X 10(-12) esu, respectively. The large third-order non-linearity and ultrafast response are attributed to the ultrafast distortion of the electron orbits surrounding the average positions of the nucleus of Ge, As, S and Se atoms. This Ge10As40S30Se20 chalcogenide glass would be expected as a promising material for optical switching technique. (c) 2005 Elsevier Ltd. All rights reserved.

Non-resonant third-order non-linear optical properties of amorphous GeSe2 film

The real and imaginary parts of third-order susceptibility of amorphous GeSe2 film were measured by the method of the femtosecond optical heterodyne detection of optical Kerr effect at 805 nm with the 80 fs ultra fast pulses. The results indicated that the values of real and imaginary parts were 8.8 x 10(-12) esu and -3.0 x 10(-12) esu, respectively. An amorphous GeSe2 film also showed a very fast response within 200 fs. The ultra fast response and large third-order non-linearity are attributed to the ultra fast distortion of the electron orbits surrounding the average positions of the nucleus of Ge and Se atoms. (c) 2005 Elsevier B.V. All rights reserved.

Ultrafast optical Kerr effect in amorphous Ge10As40S30Se20 film induced by ultrashort laser pulses

The results of the femtosecond optical heterodyne detection of optical Kerr effect at 805 am with the 80 fs ultrafast pulses in amorphous Ge10As40S30Se20 film is reported in this Letter. The film shows an optical nonlinear response of 200 fs under ultrafast 80 fs-pulse excitation, and the values of real and imaginary parts of nonlinear susceptibility chi((3)) were 9.0 x 10(-12) esu and -4.0 x 10(-12) esu respectively. The large third-order nonlinearity and ultrafast response are attributed to the ultrafast distortion of the electron orbits surrounding the average positions of the nucleus of Ge, As, S and Se atoms. This Ge10As40S30Se20 chalcogenide glass would be expected as a promising material for optical switching technique.

Frequency upconversion fluorescence emission of Er3+-doped oxychloride germanate glass

Frequency upconversion fluorescence property of Er3+-doped oxychloride germanate glass is investigated. Intense green and red emissions centred at 525, 546, and 657nm, corresponding to the transitions H-2(11/2) -> I-4(15/2), S-4(3/2) -> 4I(15/2), and F-4(9/2) -> I-4(15/2), respectively, were simultaneously observed at room temperature. The quadratic dependence of the 525, 546, and 657nm emissions on excitation power indicates that a two-photon absorption process occurs under 975nm laser diode (LD) excitation. The Raman spectrum investigation indicates that oxychloride germanate glass has the maximum phonon energy at similar to 805 cm(-1). The thermal stability of this oxychloride germanate glass is evaluated by differential scanning calorimetry, and thermal stability factor Delta T (Delta T = T-x-T-g) is 187 degrees C. Intense upconversion luminescence and good thermal stability indicate that Er3+-doped oxychloride germanate glass is a promising upconversion laser material.

Growth, etching morphology and spectra of LiAlO2 crystal

gamma-LiAlO2 single crystal was successfully grown by Czochralski method. The crystal quality was characterized by X-ray rocking curve and chemical etching. The effects of air-annealing and vapor transport equilibration (VTE) on the crystal quality, etch pits and absorption spectra of LiAlO2 were also investigated in detail. The results show that the as-grown crystal has very high quality with the full width at half maximum (FWHM) of 17.7-22.6 arcsec. Dislocation density in the middle part of the crystal is as low as about 3.0 x 10(3) cm(-2). The VTE-treated slice has larger FWHM value, etch pits density and absorption coefficient as compared with those of untreated and air-annealed slices, which indicates that the crystal quality became inferior after VTE treatment. (C) 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

毛乌素沙地两种蜜源植物羊柴和角蒿的传粉生物学研究

本论文从传粉生物学的角度出发，运用野外观察、室内测定和生物统计学方法，对毛乌素沙地的两种蜜源植物羊柴（Hedysarum leave）和角蒿（Incarvillea sinensis var. sinensis）的开花物候、花生物学特性、传粉昆虫行为以及繁育系统进行了研究，得出如下结论： 1．在自然居群中，存在着开白色花和紫红色花的两种羊柴植株，其中白色花植株仅占5.5±1.56%左右。白色花和紫红色花植株的花期存在明显的重叠，白色花植株的花期集中在8月中旬到9月上旬，而紫红色花植株的花期从7月中旬持续到9月中旬。在整个花期内，单个白色花植株的生产的总花数为125±11.33朵，明显少于紫红色花植株的372±30.38朵，两者存在极显著差异。 2． 羊柴白色花和紫红色花的单花花粉量、胚珠数和P/O值都存在显著差异。在单花开放的整个过程中，白色花的花蜜分泌量显著地高于紫红色花，但白色花和紫红色花的花蜜糖分浓度变化趋势相似，即都具有两个花蜜浓度高峰值。 3. 羊柴白色花植株稳定且访花频率较高的传粉者是散熊蜂、白脸条蜂和意大利蜂，而紫红色花植株稳定且访花频率较高的传粉者有散熊蜂、白脸条蜂、意大利蜂和海切叶蜂。传粉昆虫在白色花上的单花停留时间比紫红色花的稍长，两者存在显著差异。 4. 羊柴白色花植株和紫红色花植株自花授粉的结实率（白色花：4.31±0.34%;紫红色花：4.58±0.53%），相对于人工异花授粉的结实率（白色花：19.77±2.31%;紫红色花：21.03±3.02%）较低。自然结实率（白色花：25.93±2.30%;紫红色花：25.24±1.61%）没有显著性差异（F=0.25;P=0.80）。此外，羊柴不存在无融合生殖现象。 5. 角蒿花期从7月中旬持续到9月初，单花开放时间为5-9h;单花花粉量为18816.27±326.70、在花开放后3-4h时，花粉活力达到最大值71.98±1.23%，胚珠数为180.80±5.30，P/O值为104.7。在花开放后3-4h时，花蜜量达到最大值1.41±0.35ul。角蒿的传粉昆虫仅有散熊蜂和四条无垫蜂。在花开放过程中，花粉活力动态和花蜜分泌动态都与传粉昆虫的行为不吻合。 6. 角蒿自花授粉和人工异花授粉的结实率和结籽率均无显著差异。自然结实率为85.93±1.63%，显著地低于自花授粉和人工异花授粉，但是，自花授粉、人工异花授粉及自然对照的结籽率无显著差异。在开放传粉的情况下，被去雄的花结实率仅为48.90±5.37%，说明昆虫传粉仅贡献一部分结实率。角蒿不存在无融合生殖。