聚-10,12-二十五碳双炔酸Langmuir-Schaefer膜的非线性光学性质

通过飞秒脉冲激光单光束Z 扫描方法研究了聚 10,12 二十五碳双炔酸Langmuir Schaefer膜在非共振吸收区的三阶非线性光学特性。钛蓝宝石激光器的输出脉宽为60～70fs、波长为800nm,在入射光平均功率为145mW时测得其三阶非线性极化率为5.33×10-9esu。这一结果较该类材料的有掺杂的薄膜明显增强,与微晶和单晶达到同样的量级,对此进行了分析和讨论。     

喇曼自由电子激光器布拉格腔设计

本文介绍一种可用于喇曼自由电子激光器的布拉格腔实用化设计。如果激光器的互作用区漂移管波纹满足布拉格条件，则其分布反馈机理构成了类似于普通激光谐振腔的布拉格腔。该腔既可有效地选定中心频率，又可望提高准单模运转的喇曼自由电子激光器电子效率及其输出功率。     

The effect of loading on disturbance sounds of the Atlantic croaker Micropogonius undulatus: air versus water

Physiological work on fish sound production may require exposure of the swimbladder to air, which will change its loading (radiation mass and resistance) and could affect parameters of emitted sounds. This issue was examined in Atlantic croaker Micropogonius chromis by recording sounds from the same individuals in air and water. Although sonograms appear relatively similar in both cases, pulse duration is longer because of decreased damping, and sharpness of tuning (Q factor) is higher in water. However, pulse repetition rate and dominant frequency are unaffected. With appropriate caution it is suggested that sounds recorded in air can provide a useful tool in understanding the function of various swimbladder adaptations and provide reasonable approximation of natural sounds. Further, they provide an avenue for experimentally manipulating the sonic system, which can reveal details of its function not available from intact fish underwater.     

The axiomatic closure of the class of discriminating groups

In [6] squarelike groups were defined to be those groups G universally equivalent to their direct squares G × G. In that paper it was shown that G is squarelike if and only if G is universally equivalent to a discriminating group in the sense of [3]. Further it was shown that the class of squarelike groups is first-order axiomatizable while the class of discriminating groups is not. In this paper, we prove that the class of squarelike groups is the least axiomatic class containing the discriminating groups.Received: 18 August 2003     

On Turner’s theorem and first-order theory

A theorem of E.C. Turner states that if F is a finitely generated free group, then the test words are precisely the elements not contained in any proper retract. In this paper, we examine some ideas in model theory and logic related to Turner’s characterization of test words and introduce Turner groups, a class of groups containing all finite groups and all stably hyperbolic groups satisfying this characterization. We show that Turner’s theorem is not first-order expressible. However, we prove that every finitely generated elementary free group is a Turner group.     

以阳离子聚合物为介孔模板合成多级孔 TS-1

分别以阳离子聚季铵盐-7和聚季铵盐-6为介孔模板,通过水热法合成了多级孔TS-1沸石,采用X射线衍射、紫外可见光谱、扫描电镜、透射电镜及N2吸附-脱附等手段对所得样品进行了表征,并考察了其催化苯并噻吩及噻吩氧化反应性能.结果表明,聚季铵盐-7的加入对多级孔TS-1的晶化、钛物种的配位状态及晶粒形貌的影响不大;而随着聚季...     

波长1O64nm脉冲激光高阈值反射膜的研制

研究 Ｈｆ Ｏ２／ Ｓｉ Ｏ２ 高反射膜的制备工艺及其激光诱导损伤阈值的比较测试,分别采用了反应蒸镀 Ｈｆ Ｏ２、反应离子辅助蒸镀 Ｈｆ Ｏ２、反应离子辅助蒸镀金属 Ｈｆ 的源材料形成 Ｈｆ Ｏ２ 薄膜。采用这三种工艺制备了 Ｈｆ Ｏ２ ／ Ｓｉ Ｏ２ 高反射膜,在中心波长 １０６４ｎｍ 处,反射率 Ｒ≥９９．５％ ,其中反应蒸镀 Ｈｆ Ｏ２ ／ Ｓｉ Ｏ２ 高反射膜损伤阈值最高,可达 ６０ Ｊ／ｃｍ ２（１０６４ｎｍ ,５ｎｓ）。     

超高阈值Pick-off反射镜的研制

 采用水中抛光技术抛制了90mm×60mm×10 mm的K₉玻璃基片,表面粗糙度达1nm。在APS1504镀膜机上,摸索了电子束蒸发镀膜的最佳工艺条件,较稳定地在该超光滑玻璃表面上镀制了对波长1054 nm、入射角45°、反射率R≥99.5%的反射膜。膜层的抗激光损伤阈值可达26 J/cm²(1054nm, 1ns),镀膜后该玻璃基片反射波前可达l /10(p-v),最终制备了超高阈值Pick-off反射镜。