应用非定常分区算法研究超声速流射流不稳定结构

近年来，超声速射流混合研究之所以受到人们的广泛重视，这是由于下一代高速旅客运输机（HSPT）飞机采用超燃冲压发动机（SCRAMIJET）技术，需要研究燃料和空气的快速混合，其中首先需要解决的是超声速快速混合问题，以提高整个推进系统的性能。改进射流介质与环境介质混合的措施，不仅可以提高超燃冲压发动机性能，还可以加快射流介质与外界流体的起始混合，能够加速射流流出物的浸没消散，或者减弱射流噪声的强度，以及减弱羽流的红外信号强度等等。另外，超声速射流的激波啸叫（Sereech）是另一个重要课题，它是高速非完全膨胀射流产生的强烈的离散频率噪声。激波啸叫不仅引起环境噪声污染，而且还会造成机体结构的破坏。加世纪50年代以来，人们对有关问题进行了深入的研究，取得了重大进展，但是有一些重要问题依然没有得到很好解决。非圆形喷口射流之所以引起人们的特别研究兴趣，是由于与圆形喷口射流的混合效果相比，这种改变喷口形状的被动控制技术能在多个方面改进混合流谱的特征：第一是由于喷流结构的涡轴转变能够增强大尺度涡相干结构的混合。第二，由于其顶角区域的扰动增强了小尺度混合的效率。第三，远下游流动的混合作用明显比通常的圆形喷口的混合效果增强了，这是由于非圆形射流流场的涡结构中流向涡较强，加快了流动的混合与转挟。深入研究可压缩剪切层中的大尺度涡相干结构，实行有效的主动控制和被动控制技术改变剪切层的厚度增长率，了解剪切层中拟序运动的流场参数的变化等是解决超声速混合的关键。超声速射流流场的流动特性研究，尤其是欠膨胀射流的流场流动特征非常复杂，包含有多激波栅格和剪切层，其中有规则反射激波、马赫盘、弓形激波和接触间断等结构。超声速射流的激波栅格结构与射流压比n值有关：当射流压比n比较低（n＜2）时，超声速射流形成规则反射波系；当射流压比n超过某临界值以后，流场中便出现正激波或马赫盘。这种激波反射结构和流形的不稳定性对射流混合有着一定作用。本文通过数值模拟和实验研究相结合的途径，研究了超声速气体射流流动的不稳定结构问题。包括：（l）本文理论上对非定常激波解进行了分析，数值模拟的Sod激波问题计算结果与精确解作了比较分析。（2）本文研究发展了一种计算非定常激波动力学问题的分区方法，及其相应的分区内边界处理方法。应用非定常分区算法，模拟计算二维运动激波在楔形体和菱形体固体边界上的反射和激波衍射的问题，计算结果在分区的内边界上无扰动，并与文献上的46“夹角的楔形体和NACA0018翼型的基准实验结果作了比较。（3）应用非定常分区算法，模拟计算了二维和三维、正方形和长方形的超声速射流。数值模拟了随超声速射流压比增加激波栅格结构从规则反射到马赫反射的变化，观察到了非圆形射流当压比足够高时，呈现出了祸轴转变现象。（4）本文设计、加工了流场显示的实验设备，设计了相应的先进实验手段。流场实验显示结果表明，圆孔射流实验中观测到了激波规则反射结构和马赫反射结构。相同实验条件下，方孔和长方孔实验中仅有激波规则反射结构。射流的多种激波反射结构和流形是不稳定的。本文对非定常激波动力学流场进行了理论分析，流场显示实验研究和数值模拟的计算研究。并为以后研究组进行爆轰激波气体动力学研究和并行计算平台的研制和开发打下了基础。

高等断裂力学

《高等断裂力学》系统论述断裂力学的基本概念、理论基础、力学原理、分析方法以及断裂力学的实验测定和工程应用。深入阐明了断裂力学各个重要发展阶段的新颖学术思想和原创性工作，同时融会贯通地介绍了国内学者在作者熟悉的若干领域内的创造性贡献。　　《高等断裂力学》共14章。第1章介绍断裂力学的历史背景和发展脉络；第2～5章介绍线弹性断裂力学；第6～8章论述弹塑性断裂力学；第9及第10章分别介绍疲劳裂纹扩展和界面裂纹；第11～14章阐述裂纹体弹性动力学和裂纹动态扩展。　　《高等断裂力学》适合从事断裂力学研究和应用的科技工作者及工程师使用和参考，也可供力学专业的高年级本科生和研究生阅读参考.

Optical gain at 1550 nm from colloidal solution of Er3+-Yb3+ codoped NaYF4 nanocubes

We demonstrated optical amplification at 1550 nm with a carbon tetrachloride solution of Er3+-Yb3+ codoped NaYF4 nanocubes synthesized with solvo-thermal route. Upon excitation with a 980 nm laser diode, the nanocube solution exhibited strong near-infrared emission by the I-4(13/2) -> I-4(15/2) transition of Er3+ ions due to energy transfer from Yb3+ ions. We obtained the highest optical gain coefficient at 1550 nm of 0.58 cm(-1) for the solution with the pumping power of 200 mW. This colloidal solution might be a promising candidate as a liquid medium for optical amplifier and laser at the optical communication wavelength. (C) 2009 Optical Society of America

Optical spectroscopy and energy transfer of Er3+/Ce3+ in B2O3-doped bismuth-silicate glasses

Ce3+ and B2O3 are introduced into erbium-doped Bi2O3-SiO2 glass to enhance the luminescence emission and optic spectra characters of Er3+. The energy transfer from Er3+ to Ce3+ will obviously be improved with the phonon energy increasing by the addition of B2O3. Here, the nonradiative rate, the lifetime of the I-4(11/2) -> I-4(3/2) transition, and the emission intensity and bandwidth of the 1.5 mu m luminescence with the I-4(13/2) -> I-4(5/2) transition of Er3+ are discussed in detail. The results show that the optical parameters of Er3+ in this bismuth-borate-silicate glass are nearly as good as that in tellurite glass, and the physical properties are similar to those in silicate glass. With the Judd-Ofelt and nonradiative theory analyses, the multiphonon decay and phonon-assisted energy-transfer (PAT) rates are calculated for the Er3+/Ce3+ codoped glasses. For the PAT process, an optimum value of the glass phonon energy is obtained after B2O3 is introduced into the Er3+/Ce3+ codoped bismuth-silicate glasses, and it much improves the energy-transfer rate between Er3+ I-4(11/2)-I-4(13/2) and Ce3+ F-2(5/2) -> F-2(7/2), although there is an energy mismatch. (c) 2007 Optical Society of America.

掺铒碲酸盐玻璃中的浓度猝灭机理研究

测试了掺铒碲酸盐玻璃在不同掺杂浓度下的荧光特性．根据Dexter能量转移理论计算了Er^3+在碲酸盐玻璃中发生浓度猝灭的临界距离R0及Er^3+间相互作用参数CEr-Er，并与其他基质玻璃中CEr-Er数值进行了比较．最后建立了Er^3+基于OH^-作为猝灭中心下碲酸盐玻璃中的浓度猝灭模型．

CE3+对ER3+/Yb3+共掺TeO2-WO3-ZnO玻璃发光性能的影响

Ce3+ ions were introduced into the Er3+/Yb3+ -codoped TeO2-WO3-ZnO glasses, and the effect of Ce3+ on the emission properties at 1.5 mu m band and the upconversion luminescence of Er3+ in the glasses was investigated. With the increasing of Ce3+ concentration, the emission intensity of Er3+ at 1.5 mu m band increases firstly, and then decreases. The optimal doping concentration of Ce3+ is about 2.07 x 10(20)/cm(3). As for the Er3+ emission at 1.5-mu m band, the fluorescence lifetime decreases a little from 3.4ms to 3.0ms, while the full width at half maximum (FWHM) hardly changes with the increase of Cc 3+ concentration. Due to the effective cross relaxation between Ce3+ and Er3+ : Er3+ (I-4(11/2)) + Ce3+ (F-2(5/2)) -> Er3+ (I-4(13/2)) + Ce3+ (F-2(7/2)), the upconversion emission intensity of Er3+ is reduced greatly. But when Ce3+ -doping concentration is too high, the other cross relaxation between Ce3+ and Er3+ : Er3+ (4I(13/2)) + Ce3+ (F-2(5/2)) -> Er3+ (I-4(15/2)) + Ce3+ (F-2(7/2)) happens, which depopulates the I-4(13/2) level of Er3+ and results in the decrease of the emission intensity and fluorescence lifetime of Er3+ at 1.5 mu m band.

掺铒高硅氧玻璃光谱性质的研究

应用Judd-Oflet理论计算了新型掺铒高硅氧玻璃中铒离子的强度参量Ωt（t=2，4，6），Ω2=8．15×10^-20,Ω4=1．43×10^-20,Ω6=1．22×10^-20，相比于其他氧化物玻璃，表现出较大的Ω2,6值，反映了铒离子周围的近邻结构不对称性和Er-O键的离子键成分较高．利用McCumber理论计算得到了能级4I13/2→4I15/2跃迁的受激发射截面为σc=O．51pm^2．这种高硅氧玻璃掺铒离子浓度尽管高于石英光纤的掺杂浓度10倍左右，其荧光寿命和量子效率仍达到6．0ms和66．

铒离子浓度对掺Er^3＋碲酸盐玻璃的Judd-Ofelt理论参数的影响

制备了四种不同铒离子掺杂浓度的碲酸盐玻璃，通过测定吸收光谱计算了吸收谱线的振子强度，根据Judd-Ofelt理论计算了不同浓度下Er^3＋离子发光光谱的强度参数Ω（i=2，4，6），计算了自发辐射电偶和磁偶跃迁概率、辐射寿命、荧光分支比等参数，讨论了Er^3＋离子浓度变化对以上这些参数的影响。测试了Er^3＋：^4I13／2→^4I15／2跃迁对应的荧光光谱和Er^3＋：^4I13／2能级荧光寿命。最后应用McCumber理论计算了玻璃中Er^3＋：^4I13／2→^4I15／2跃迁对应的受激发射截面大小

掺铒碲酸盐玻璃的热力学稳定性和光谱性质的研究

分析了掺Er^3+碲酸盐玻璃的热力学稳定性能，研究了掺Er^3+碲酸盐玻璃的吸收和荧光光谱性质；应用Judd-Ofelt理论计算了碲酸盐玻璃中Er^3+离子的强度参数Ω(Ω2=4．79×10^-20cm^2,Ω4=1．52×10^-20cm^2，Ω6=0．66×10^-20cm^2)，计算了离子的自发跃迁几率，荧光分支比；应用McCumber理论计算了Er^3+的受激发射截面(σe=10．40×10^-21cm^2)、Er^3+离子^4I13／2→^4I15／2发射谱的荧光半高宽(FWHM=65．5nm)

掺铒碲钨酸盐玻璃及其平面波导

研制了一种用于宽带波导放大器的掺铒碲钨酸盐激光玻璃材料，对玻璃热稳定性、光谱性质进行了表征，并在其上采用离子交换法制作了平面光波导．掺铒碲钨酸盐玻璃的转变温度Tg和析品开始温度Tx分别为377．1和488．5℃；荧光半高宽为52nm；应用McCumber理论，计算得出Er^3+离子4I13／2→^4I15／2跃迁在峰值波长1532nm的受激发射截面为0．91×10^-20cm^2．不同条件下制作了在632．8nm处多模的平面光波导，通过拟合得到Ag^+离子在300℃的有效扩散系数De为2．82×10^-1

977nm抽运下掺铒碲酸盐基氧卤玻璃的光谱特性

研究了掺铒TeO2-ZnO-PbCl2碲酸盐基氧卤玻璃在977nm激光二极管抽运下的发光和上转换发光特性，结果发现除红外1．53μm^4I13.2→^4I15/2发光外(荧光半高宽高达69nm)，该玻璃还存在很强的^2H11/2→^4I15/2(527nm)，^4S3/2→^4I15/2(549nm)和^4R9/2→^4I15/2(666nm)可见上转换发光．应用Judd-Ofelt理论计算得到玻璃强度参数Ω1(t=2，4，6)分别为Ω2=5．87×10^20cm^2,Ω4=2．08×10^2-cm^2，

一种新型掺铒碲酸盐玻璃的光谱性质研究

研究了一种新型掺Er^3+碲酸盐玻璃的光谱性质；应用Judd-Ofelt理论计算了碲酸盐玻璃中Er^3+离子的强度参数Ω(Ω2=4．79×10^-20cm^2，Ω4=1．52×10^-20cm^2，Ω6=0．66×10^-20cm^2)，计算了离子的自发跃迁概率，荧光分支比；应用McCumber理论计算了Er^3+的受激发射截面(σe=10．40×10^-21cm^2)，Er^3+离子^4I13/2→^4I15/2发射谱的荧光半高宽(FWHM=65．5nm)及各能级的荧光寿命(^4I13/2能级为τrad

Effect of lithium-potassium mixed alkali on spectroscopic properties of Er3+-doped aluminophosphate glasses

Er3+-doped lithium-potassium mixed alkali aluminophosphate glasses belonging to the oxide system xK(2)O-(15x)Li2O-4B(2)O(3)-11Al(2)O(3)-5BaO-65P(2)O(5) are obtained in a semi-continuous melting quenching process. Spectroscopic properties of Er3+-doped glass matrix have been analysed by fitting the experimental data with the standard Judd-Ofelt theory. It is observed that Judd-Ofelt intensity parameters-Omega(t)(t=2, 4 and 6) of Er3+ change when the second alkali is introduced into glass matrix. The variation of line strength S-ed[I-4(13/2),I-4(15/2)] follows the same trend as that of the Omega(6) parameter. The effect of mixed alkali on the spectroscopic properties of the aluminophosphate glasses, such as absorption cross-section, stimulated emission cross-section, spontaneous emission probability, branching ratio and the radiative lifetime, has also been investigated in this paper.

Spectroscopic properties of fluorophosphate glass with high Er(3+)supercript stop concentration

Fluorophosphate glass with 4 mol.% ErF3 content was prepared. The different scanning calorimetry was conducted. Raman spectrum, infrared transmission spectrum, absorption spectrum were measured. Fluorescence spectrum and lifetime of emission around 1.53 mu m were measured under 970 nm laser diode excitation. The metaphosphate content in the composition is limited, but the maximum phonon energy of glass amounts to 1290 cm- 1, and is comparatively high. The full width at half maximum is about 56 nm, and is wider than for most of the materials investigated. The measured lifetime of I-4(13/2) -> I-4(15/2) transition, contributed by the high phonon energy, inefficient interaction of Er3+ ions, and low water content, amounts to no less than 7.36 ms though the Er3+ concentration is high. This work might provide useful information for the development of compact optical devices.