液相介质对水平气液间歇流动压降的影响

研究了水平管内不同液相介质(水、油和不同浓度的CMC溶液)对气液两相间歇流动压降的影响.实验管道为内径50mm的透明有机玻璃管,从入口到分离器长约30 m,实验段由2个长3 m的水平管组成.共记录了320组不同表观流速下的压降信号:油相0.17～1.85 m/s,水相0.17～2.48 m/s,CMC溶液0.17～1.42 m/s,气相0.06～3.40 m/s.结果表明,液相为牛顿流体(油或水)的气液流动,随着表观气相流速的增大,压降呈增加趋势;非牛顿幂率流体(不同浓度的CMC溶液)的管道流动,当流动指数低于一定值时,压降随气相流量的增加呈降低趋势,并且低于单液相流动的压降.Lockhart-Martinelli模型过高地预测了气-非牛顿幂率流体两相的压降.

Computer simulation of influence of sedimentation on rapid coagulation

A computer simulation was performed to explore the features and effects of sedimentation on rapid coagulation. To estimate the accumulated influence of gravity on coagulation for dispersions, a sedimentation influence ratio is defined. Some factors possibly related to the influence of sedimentation were considered in the simulation and analysed by comparing the size distribution of aggregates, the change in collision number, and coagulation rates at different gravity levels (0 g, 1 g and more with g being the gravitational constant).

任意阶隐式指数时程差分多步法及其在非线性系统中的应用

对非线性系统提出了任意阶隐式指数时程差分多步法 ,实现了任意阶次指数时程差分预测 校正算法 .发展完善了指数时程差分法 .将新算法应用于非线性系统 ,取得了较好的效果 .数值结果表明隐式指数时程差分多步法很好地修正了显式指数时程差分多步法 ,隐式指数时程差分多步法是一种高精度、高效率的方法

EVALUATION OF FILM-SUBSTRATE ADHESION VIA IMPACT USING COATED BULLETS

A method was devised to evaluate the adhesion between a film and a substrate. A front-end coated bullet is accelerated by a gas gun and hits the substrate of the specimen under test. The impact generates a compressive stress pulse that propagates toward the film. After transmission through the interface, part of the pulse is reflected on the free surface of the film, and tensile stress arises at the film-substrate interface, possibly inducing debonding of the film. This dynamic process was demonstrated analytically and simulated numerically by the finite element method. The results validate the initial concept and lay the foundation for further optimization of this method.

激光同步辐射作为阿秒X射线辐射源的特性研究

研究了逆流相对论电子与激光脉冲相互作用获得激光同步辐射的频率上移、微分散射截面等特性.发现逆流相对论电子与短脉冲激光相互作用,可以获得阿秒X射线辐射脉冲.短脉冲激光条件下得到的后向散射光的频率上移与长脉冲激光条件下得到的后向散射光的频率上移是完全一致的,同时发现随着入射电子初始能量的增加,散射光的准直性越来越好,后向散射光脉冲的脉宽越来越短.

Study of the transmitter antenna gain for intersatellite laser communications

The gain of a transmitter for intersatellite communications is closely related to the performance of all the links. We calculate the transmitter telescope's gain with the help of the rigorous scalar diffraction theory and equivalent optical layout method. Furthermore, a comparison is performed with the conventional imaging method. The results show that the stop inside the telescope can affect the gain of the telescope. Finally, the gain is calculated under the condition of the aberrations. We find that different aberrations cause different effects. (C) 2006 Society of Photo-Optical Instrumentation Engineers.

基于正交频率变换的高功率蓝绿全固态激光器

对多横模全固态激光器使用正交频率变换进行了分析,计算了频率转换效率与激光发散角的关系。使用双KTP晶体正交倍频的方法,对Nd∶YAG激光器输出的含有高阶横模的激光进行倍频实验研究。在1064 nm Nd∶YAG激光基波功率密度为121 MW/cm2时,其谐波转换效率达到75.5%。研究表明,对于光束质量较差的基波激光,采用正交频率变换的方式,适当选择晶体参数,同样可以获得较高效率的二次谐波输出。

Near infrared broadband emission of bismuth-doped aluminophosphate glass

Near infrared broadband emission characteristics of bismuth-doped aluminophosphate glass have been investigated. Broad infrared emissions peaking at 1210nm, 1173nm and 1300nm were observed when the glass was pumped by 405nm laser diode (LD), 514nm Ar+ laser and 808nm LD, respectively. The full widths at half maximum (FWHMs) are 235nm, 207nm and 300nm for the emissions at 1210nm, 1173nm and 1300nm, respectively. Based on the energy matching conditions, it is suggested that the infrared emission may be ascribed to P-3(1) --> P-3(0) transition of Bi+. The broadband infrared luminescent characteristics of the glasses indicate that they are promising for broadband optical fiber amplifiers and tunable lasers. (C) 2005 Optical Society of America.

室温下光纤耦合二极管泵浦Tm：YAP激光器

为实现室温下小型化、高效率的1.9μm激光输出,采用793.5 nm激光二极管泵浦Tm：YAP晶体,晶体采用热电制冷及风冷的方式控制在18℃,采用1∶1的聚焦耦系统,获得功率为2.2 W、中心波长为1928 nm的激光输出,光光转换效率为31%,斜率效率达41%。对影响激光输出的耦合输出率、腔型、腔长、晶体工作温度等因素进行了实验分析,实验结果表明：输出功率的变化与温度基本成线性关系,当增加激光谐振腔长时,由于高阶模式损耗加大以及晶体热透镜效应的加重导致腔内损耗加大,输出功率和斜率效率都有所下降。

水杉的分类、历史地理分布及其与古气候变迁的关系

本文所用标本为采自中国东北晚白垩世或古新世黑龙江省嘉荫县乌云组和早始新世辽宁省抚顺市西露天矿古城子组和计军屯组的水杉植物化石。标本包括营养结构如两种小枝，生殖结构如雄花枝和雌球果。本论文对水杉的形态结构包括叶表皮及在雄球花苞叶的上下表皮结构及花粉结构作了详细的研究。 水杉属目前已建立21个种，由于保存的原因，多数种建立在保存下来的都分器的特征上。通过对中国东北材料与曾建立的14个种M. milleri，M. glyptostroboides, M. disticha, M. japonica, M. chinensis, M. cuneata, M. papillapollenites, M. miocenica, M. kimurae, M. onukii, M. europaea, M. asiatica, M. nathorstii, M. occidentalis 之间进行的详细对比，发现这些种之间存在着极大的相似性。现代水杉M. glyptostroboides的研究非常详细，且化石种缺乏足够的特征与其相对比，因此现代水杉可作为一个生活种而存在。M. milleri和M. glyptostroboides相比较表明：二者的雄球花及木材的解剖结构特征不同，以上其他的化石种由于保存的局限性，不具有可与M. milleri对此的相应的解剖特征，认为化石种M. milleri成立。M. disticha, M. japonica, M. chinensis, M. cuneata, M. papillapolenites, M. miocenica, M. kimurae, M. onukii, M. europaea, M. asiatica, M. nathorstii 11个化石种均归于M. occidentalis。由于M. wigginsii, M. neosibirica, M. krysthofovichi, M. spitzbergensis, M. paradoxa 5个种仅建立在具有互生叶的小枝或叶表皮的基础上，M. sibirica和M. klerkiana两个种仅建立在木材解剖的结构特征上,故此7个种有待于进一步研究.因此,水杉属下确定存的有3个种:1个现代种:M. glyptostroboides;2个化石种:M. occidentalis和M. Milleri. 本文还通过收集水杉栽培状况的资料,对水杉生长的环境和生长状况统计分析,得出水杉生存繁衍的气候条件要求范围:年降水量为1000.0 - 1865.5 mm,年均温为13-16 ℃, 一月均温为-3.1至4.2 ℃,极端低温为-12 ℃, 七月均温为17.7 - 27.9 ℃。这一条件也是水杉在地质克史时期分布区应该具备的气候限制因素。本文通过收集大量的文献资料得到水杉从晚白垩世至今在全球范围内的分布状况，发现：由于自晚白垩世以来气候逐渐转冷的变化，水杉的分布范围也在逐渐变小，最后仅自然分布于中国中部湘鄂川三省的交界。以时间为横轴，水杉分布的纬度为纵轴得到水杉分布的纬度变化曲线，从各个时期最北界为点建立的曲线的起伏变化表明，除从古新世至始新世曲线稍微升高外，晚白垩世以来曲线大都在下降，反映了气温在古新世晚期略微升高，其它时期都在下降之中，这一结论与氧同位素的结论基本一致。