光纤通信技术发展特点及现状

光纤通信是以其传输频带宽、通信容量大、中继距离长、损耗低特点,并具有抗电磁干扰能力强,保密性好的优势,在通信的主干线路中、电力通信控制系统中以及军事领域的用途越来越广泛。光纤通信技术正朝着超大容量、超长距离传输和交换、全光网络方向发展。     

光电互感器的原理及在数字化变电站的应用

本文介绍了光电电流互感器和光电电压互感器的类型及原理,并将它们与传统互感器进行比较。在此基础上,提出一些关于光电互感器存在的问题和发展前景的观点。     

高压触点光纤测温技术

本文介绍了各种高压电气测温方式,着重说明了光纤式测温的优点及局限性。     

Si代P点缺陷对KDP晶体光学质量的影响

通过基于第一性原理的CASTEP计算发现,KDP晶体中Si代P点缺陷的形成能约是12．18eV,比较难在晶体中形成。模拟了此种点缺陷形成前后晶体的电子结构和能态密度,发现Si替代P后,晶体带隙宽度几乎没有变化,说明这种点缺陷不会引起晶体对光的额外吸收。Si替代P点缺陷仅使其周围的晶格及电子结构发生轻微畸变,对晶体整体结构影响不大。     

Investigation and conservation of Anne Marie Carl-Nielsen's wax models

Abstract

The Danish sculptor Anne Marie Carl-Nielsen (1863–1945) often prepared three-dimensional models in wax before producing her works of art. The Carl Nielsen Museum in Odense keeps a unique collection of around 200 of the artist's fragile wax models. In 2008 the entire collection was examined, documented, X-ray radiographed, photographed, and conserved. Analyses of five figurines by attenuated total reflectance-Fourier transform infrared spectroscopy, optical microscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy showed two different kinds of wax mixtures, one containing beeswax and potato or maize starch as filler, and the other consisting of gypsum, zinc stearate, and a greasy substance. During the examination a specific deterioration phenomenon was noticed in the areas where the wax models had been strengthened with internal metal armatures. A chemical reaction between the wax mixture and the copper containing armature has caused an intense greenish colouring of the wax as well as creating a soft and almost liquid consistency and formation of copper(II) carboxylate salts. Based on an original recipe from Anne Marie Carl-Nielsen, a replica of one of the wax mixtures was produced and examined with respect to its infrared spectrum and its modelling properties.     

Science Teachers and Science‐Related Attitudes

Summaries

English

Science teachers’ perceptions of affective‐domainobjectives were gathered through interview procedures. A sample of teachers in Western Australian high schools were the subjects of the study.

For the purpose of analysis, a distinction is drawn between attitudes to science (such as ‘enjoyment of science lessons’ and ‘interest in science') and scientific attitudes (such as ‘honesty in reporting data’and ‘tolerance of the views of others').

Analysis of teachers’ views revealed confusion and lack of clarity regarding these science‐related attitudes. However, it is argued that curriculum writers are no clearer in their views.

It is suggested that a much clearer, more explicit justification for attitude objectives (of both kinds) needs to be made by curriculum writers. Science teachers need to be provided with greater assistance in clarifying the role of these attitude objectives, as well as assistance with techniques for their assessment.     

Meat quality traits of four Chinese indigenous chicken breeds and one commercial broiler stock

Meat quality traits of four genotypes of Chinese indigenous chicken [Ninghai chicken (NC), frizzle chicken (FC), Ninghai xiang chicken (XC), and Zhenning loquat chicken (LC)] and one genotype of commercial broiler [Arbor Acres plus broiler (AAB)] were analyzed. The indigenous chickens were raised before the commercial chickens in order to achieve the same final processed days. Indigenous chickens of NC, FC, XC, and LC showed significantly higher inosine-5′-monophosphate (IMP) content, shorter fiber diameter, and lower shear force than those of AAB (P<0.05). In the indigenous genotypes, NC and FC had significantly shorter fiber diameters and lower shear forces than XC and LC (P<0.05), and NC and XC had a higher IMP content than FC and LC (P<0.05). Moreover, the indigenous genotype of LC significantly displayed the highest protein content (P<0.05) in the five genotypes of birds, and no significant differences of protein content were found between the other genotypes of NC, FC, XC, and AAB (P>0.05). The indigenous chickens from FC displayed the highest total lipid content in the five bird genotypes (P<0.05). Significant differences of pH, color values of L* and a*, and drip loss for the five genotypes of birds were also observed. In conclusion, there were significant differences in the meat quality traits of the bird breeds selected in this study, and the indigenous chickens, especially the NC genotype, produced better quality meat as far as the IMP content, fiber diameters, and shear forces were concerned.     

基于四波混频效应的光纤参量放大器的设计

利用一组非线性耦合方程,在理论上推导出了双泵浦、级联结构光纤参量放大器的增益表达式。研究表明,在双泵浦情况下,光纤参量放大器的增益与光纤长度、非线性系数以及泵浦光功率呈指数关系。采用多段光纤级联的结构,可以均衡光纤参量放大器增益的不平坦性,理论上得到了带宽达160nm、起伏小于1．5dB的理想增益。     

从玩器到科学——欧洲光学玩具在清朝的流传与影响

17、18世纪,一批欧洲光学玩具通过耶稣会士等途径流传到大清国,不仅被带入宫廷,而且在民间也得到广泛传播。它们同眼镜、望远镜一起在清朝的社会文化中留下了明显的印记,并促进了中国早期光学工业的诞生。更有趣的是,这些玩具最终还变成了科学研究对象,导致了一种独特的中国式光学系统的建立。