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我是一个走上教育岗位刚两年的化学教师。初三化学已教过两次,每次都有不同的体会。初三的同学是第一次上化学课,这一课上的好坏就直接关系到同学们以后学习化学的兴趣和态度。第一课是“绪言”,教时往往有困难。现在刚开学,又要教“绪言”了,我且把我的意见写出来供大家研究。 相似文献
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Analysis of Nanostructural Waveguides Using Fourth-Order Accurate Finite Difference Methods with Nonuniform Scheme 下载免费PDF全文
We successfully apply fourth-order accurate finite difference methods with nonuniform scheme to analysis the symmetric slot waveguides. The results of numerical simulations show that the present nonuniform formula offers the results more accurate than the previously presented second order schemes. 相似文献
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We report the stimulated emission from a dye doped polymer plane waveguide with TiO2 particles. This waveguide consists of a poly (methylmethacrylate) (PMMA) film containing laser dye DCM as a gain medium. The emission spectrum of the film pumped by the Nd:YAG laser is different from the amplified spontaneous emission of the dye-doped film without particles. It is shown that when the excitation intensity reaches the threshold 9.6 μJ, the broad band emission spectrum narrows into multiple separate peaks with central wavelength of 608 nm. The linewidth of the sharp peak is 0.5 nm. According to our analyses, this phenomenon is due to the multiscattering of the disordered TiO2 particles inside the gain polymer film. 相似文献
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一种通带平坦的粗波分复用/解复用器件的研制 总被引:3,自引:4,他引:3
随着粗波分复用(CWDM)系统在城域网和接入网中日益广泛的应用,人们对粗波分复用/解复用器的研究也逐渐展开。报道了一种8通道波长间隔为20nm的粗复用/解复用器。该器件基于阵列波导光栅(AWG)原理设计,利用平面光波导技术(PLC)制作,采用多模干涉输入结构和“S”形阵列波导结构,实现了较宽的通带宽度和较低的串扰。实验测得1dB带宽大于10nm,相邻串扰大于24dB,非相邻串扰大于32dB。介绍了其设计原理和制作过程,给出了光束传播法(BPM)数值模拟结果,并和实验结果进行了对比。 相似文献
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引伸仪是测量拉伸试件的伸长变形,用以确定材料的一些重要的力学性能的仪器.我们研制了一种新型的引伸仲仪-球铰式引伸仪.它 ... 相似文献
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The synthesis of zinc oxide (ZnO) nanowires is achieved by vapor phase transportation (VPT) method. The designed quartz tube, whose both ends are narrow and the middle is wider, is used to control the growth of ZnO nanowires. Dielectrophoresis (DEP) method is employed to align and manipulate ZnO nanowires which are ultrasonic dispersed and suspended in ethanol solution. Under the dielectrophoretic force, the nanowires are trapped on the pre-patterned electrodes, and further aligned along the electric field and bridge the electrode gap. The dependence of the alignment yield on the applied voltage and frequency is investigated. 相似文献
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选用五种样品试剂三氟乙酸、四氢呋喃、甲酸、乙腈、60%乙腈/5%三氟乙酸和两种不同的制样方法,采用基质辅助激光解吸电离飞行时间质谱(MALDI-TOF MS)表征难溶性聚合物聚对苯二甲酸己二酰胺(PA6T)的结构和分子量。发现以60%乙腈/5%三氟乙酸为样品试剂所得谱图的分子质量范围和信噪比最大,且溶剂法一步点样优于无溶剂法制样。获得了离子液体中合成产物PA6T的链结构,表明其主链为线性,未发现环状聚合物的存在,存在三种端基结构聚合体: 两端均为氨基或羧基、或一端为氨基另一端为羧基。采用MALDI-TOF MS和SEC两种方法对比测量了PA6T的平均分子量和分子量分布指数,表明MALDI-OF MS测得的平均分子量低于SEC法,分子量分布指数也低于SEC法,这是由于MS处理数据时忽略了低分子量部分,且高分子量部分因难以离子化而无法得到引起的。对于难溶的聚芳酰胺类聚合物的结构和分子量及其分布表征,MALDI-TOF MS仍不失为一个好方法。 相似文献
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NO,NO_2性质的演示装置必须显示出: ①NO不溶于水, ②NO遇氧很易生成红棕色的NO_2, ③NO_2很易溶于水。④NO_2溶于水后显酸性。根据这些要求设计了上图的演示装置。甲为圆底烧瓶带有三孔橡皮塞,其中一孔插长玻璃管,玻管一端直至瓶底,另一端伸入乙瓶,也伸至瓶底;另二孔插入两根短的弯玻管,再套以橡皮管与启普发生器丙、丁相连。乙瓶为与甲瓶同容积的平底烧瓶,带有二孔橡皮塞,其中一孔即插由甲瓶来的玻管如前所述,另一孔插一短的弯玻管3。丙、丁均为启普发生器,在此处用作储气瓶。(收集气体时可先将整个发生器充满了水,然后将气体从发生器出气嘴处压入,水即进入顶上漏斗中。) 相似文献