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排序方式: 共有404条查询结果,搜索用时 46 毫秒
1.
脉冲压缩光栅光路调节新方法研究 总被引:2,自引:1,他引:1
介绍了一种简单而实用的大口径脉冲压缩光栅光路调节方法,有效解决了普通光路调节方法中轴向调节精度不高的问题。首先由全息透镜(光栅)成像公式出发,推导出了该光路调节的基本原理。并从光栅记录系统与光栅衍射波像差的关系,结合初级像差理论推导得出叠栅条纹像差为0.4786λ,大约是光栅衍射波像差(0.25λ)的两倍,利用此关系也可对光栅衍射波像差进行实时监测。从数值模拟结果可知,利用叠栅条纹法调节光路可将光栅波像差减至0.06λ,相应的轴向误差量为0.007 mm,可有效提高了轴向调节精度。 相似文献
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用原子吸收分光光度计石墨炉法分析了公路附近的蔬菜中铅的含量。结果表明,蔬菜中铅的含量还与其距离公路的远近有关,蔬菜与空气接触程度也有关;不同种类蔬菜中的铅污染有差异。 相似文献
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Hu J Zhang Y Liu B Liu J Zhou H Xu Y Jiang Y Yang Z Tian ZQ 《Journal of the American Chemical Society》2004,126(31):9470-9471
In this communication, gold nanoparticles with a tadpole shape were synthesized by a simple aqueous-phase chemical method. The unusual three-dimensional and crystallized structures were demonstrated by TEM, AFM, and HRTEM methods. The SEM and UV-visible absorption measurements and electrophoresis experiments revealed that the tadpoles had novel optical and electrical properties. These attractive structures and properties are expected to find uses in many fields such as electrics, optics, electrochemistry, and biological sensing. 相似文献
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The anodic reaction of Ni in an alkaline solution was studied by the tip–substrate voltammetry mode of scanning electrochemical microscopy (SECM) and cyclic voltammetry (CV). A platinum microdisc electrode was selected as the tip electrode, which functioned as a pH sensor with transient response capability. The pH value of the solution near the Ni electrode surface varied while the Ni substrate oxidation reaction occurred, and the pH variation could be detected by the tip faradic current. The cyclic voltammogram results showed that two types of hydroxides: i.e. α‐Ni(OH)2 and β‐Ni(OH)2 were formed during Ni oxidation in the lower potential region. In the proceedings of α‐Ni(OH)2 → γ‐NiOOH and β‐Ni(OH)2 → β‐NiOOH, the process of OH? concentration decrease in the solution was ahead and behind of electron transfer in the solid phase, respectively. These results indicate that the OH? adsorption process occurs as an elementary step in the former reaction and the H+ diffusion process from the inner to the outer layer of the solid phase occurs as a subsequent step in the latter reaction. The results also revealed that the oxide film on the Ni surface has a two‐layer structure. The real potential of the oxygen evolution reaction (OER) on the Ni surface with different cycles is also analyzed in the paper. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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对聚苯醚(PPO)进行了苯环溴代、甲基溴代以及胺交联,发现苯环溴代可提高O_2、N_2透过率(P),而选择性(α)基本不变。甲基溴代则相反,P降低、α有明显提高。调节两者比例可得到P、α兼优的O_2、N_2分离膜。甲基溴代后进一步胺交联可得到α更高、耐溶剂的膜材料。 相似文献
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Nolde F Qu J Kohl C Pschirer NG Reuther E Müllen K 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(13):3959-3967
Two new synthetic approaches to terrylenediimides, highly photostable fluorescent dyes, are described. For the first time terrylenediimide has been synthesised in a straightforward procedure that makes large quantities available. The second route includes an efficient cross-coupling reaction followed by a cyclodehydrogenation. Monofunctionalisation of the imide structure allows terrylenediimides now to be coupled with a variety of compounds, for example, by Suzuki cross-coupling, which can lead to an array of terrylenediimides with new functional groups such as hydroxy, amino, or carboxy groups needed to link up with other molecules. The functionalisation in the bay region is used to tune the properties of terrylenediimides and extend the range of applications, for example, by introducing water solubility. These tetrasubstituted terrylenediimides offer, depending on the substituents used, exciting features such as good solubility in common organic solvents, water solubility, or NIR absorption. 相似文献