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排序方式: 共有1417条查询结果,搜索用时 16 毫秒
981.
A new spherical macroporous epoxy-polyamide chelating resin was synthesized from epoxy resin by simple and rapid means and used for the preconcentration and separation of trace noble metal ions from solution samples. The acidity, flow rate, reusability, capacity and interference with the adsorption of ions on the resin as well as the conditions of desorption of these ions from the resin are discussed. The results show that the relative standard deviations for the determination of 50ng mL–1 Au(III), Pt(IV) and Pd(IV) by inductively coupled plasma atomic emission spectrometry are in the range of 0.5–3.6%. The procedure was applied to determine metal smelter samples with satisfactory results. 相似文献
982.
The tetrahydro-pyrano[3,4-b]indoles 6 were synthesized from 2-(2-trimethylsilanyl-1H-indol-3-yl)-ethanols 5 and various ketones or aldehydes through silicon-directed oxa-Pictet-Spengler cyclizations. An unusual reaction led to the dimeric products 7 when some of 5 was treated with acetone using BF(3) as the catalyst. 相似文献
983.
Feng Li Fan Ji Xinjie Lü Zhan Sui Jianjun Wang Kun Gao Jianping Xie Hai Ming 《Optics & Laser Technology》2007,39(6):1120-1124
Pulse stacking is an effective method to generate a long-shaped pulse from short pulses. In this paper, we study all-fiber coherent pulse stacking systematically; we show that the time delays and phase differences between the short pulses are the key parameters of the stacked pulse. The permitted variation of the time delay and phase difference are obtained. The ability of the stacker to produce arbitrary pulse shapes is discussed. 相似文献
984.
啁啾脉冲堆积用于光脉冲整形 总被引:7,自引:1,他引:7
报道了一种利用100 ps啁啾脉冲堆积产生2.2 ns任意整形脉冲的脉冲整形系统。采用掺Yb~(3 )光纤锁模振荡器得到稳定的锁模光脉冲序列,将该锁模脉冲通过啁啾光纤光栅展宽并通过1 nm带宽的高斯形光谱滤波器滤波,得到标准的100 ps高斯形啁啾脉冲序列,将此脉冲选单经过光纤延迟线组成的32路脉冲堆积器,得到了精度为32 bit的重复频率为1 Hz的2.2 ns任意整形光脉冲。研究了堆积脉冲的特性,分析了宽带啁啾堆积整形脉冲的光谱时间扫描特性对激光驱动惯性约束聚变打靶束匀滑的优化作用。实验测得了该系统输出的2.2 ns整形光脉冲具有小于50 ps的上升沿,与100 ps啁啾脉冲的时间抖动小于4 ps。 相似文献
985.
以自行研制的大能量单纵单横电光调Q激光系统作为抽运源,在小尺寸(2 cm×2 cm×4 cm)的熔融石英玻璃样品中实现了强烈发展的受激布里渊散射(SBS)过程,在工作介质无损伤的情况下,相位共轭波能量高达110 mJ,反射率约为60%.还研究了SBS能量反射率与入射角之间的关系,证实了此前提出的“自供种子光(self-Stokes-seeding)”效应的存在.提出了双棒串接的构型,得到了更为高效的SBS过程.
关键词:
受激布里渊散射
熔融石英玻璃
激光损伤
反射率 相似文献
986.
给出了光谱、时间、空间分辨的激光二极管(LD)抽运动力学模型,包括LD阵列输出的波长啁啾效应、输出功率随时间的瞬态变化,重点研究了不同吸收带宽的激光介质对大功率LD阵列输出的光谱选择吸收特性. 基于该模型,分析了三种典型激光增益介质Yb:YAG,Yb:S-FAP,Nd:YAG在脉冲储能运转方式下的抽运激发性能. 优化了不同增益介质所需的LD阵列的初始中心波长,并对三种介质对LD波长啁啾效应的敏感性进行了详细研究.
关键词:
激光二极管阵列
波长啁啾
抽运动力学
激光材料 相似文献
987.
X. Wang G. Yu B. Lei X. Wang C. Lin Y. Sui S. Meng M. Qi A. Li 《Journal of Electronic Materials》2007,36(6):697-701
The n-GaN films grown by metal-organic chemical vapor deposition (MOCVD) are etched in an inductively coupled plasma (ICP) reactor
chamber. Atomic-force microscopy (AFM) characterization shows an increase of the surface roughness after the etching. Furthermore,
Hall measurement and photoluminescence (PL) spectra highlight deterioration of the electrical and optical properties, respectively.
Attempts to recover the damage are carried out by nitrogen plasma treatments accompanied by thermal annealing at the growth
temperature in a molecular-beam epitaxy (MBE) chamber. Improved electrical and optical properties compared with those of the
as-etched GaN, evidenced in both Hall and PL measurements, show a pronounced decrease of the damage introduced by the ICP
etching. 相似文献
988.
989.
Xin Sui Baohui Wang Haiming Wu 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2018,92(2):304-309
The crystallization kinetics and morphology of CaCO3 crystals precipitated from the high salinity oilfield water were studied. The crystallization kinetics measurements show that nucleation and nuclei growth obey the first order reaction kinetics. The induction period of precipitation is extended in the high salinity solutions. Morphological studies show that impurity ions remain mostly in the solution phase instead of filling the CaCO3 crystal lattice. The morphology of CaCO3 precipitates can be changed from a smooth surface (calcite) to rough spheres (vaterite), and spindle rod bundles, or spherical, ellipsoid, flowers, plates and other shapes (aragonite). 相似文献
990.
In this study,the maleic anhydride(MAH)and styrene(St)dual monomers grafted polypropylene(PP)and poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS),i.e.PP-g-(MAH-co-St)and SEBS-g-(MAH-co-St)are prepared as multi-phase compatibilizers and used to compatibilize the PA6/PS/PP/SEBS(70/10/10/10)model quaternary blends.Both PS and SEBS are encapsulated by the hard shell of PP-g-(MAH-co-St)in the dispersed domains(about 2μm)of the PA6/PS/PP-g-(MAH-co-St)/SEBS(70/10/10/10)quaternary blend.In contrast,inside the dispersed domains(about 1μm)of the PA6/PS/PP/SEBS-g-(MAH-co-St)(70/10/10/10)quaternary blend,the soft SEBS-g-(MAH-co-St)encapsulates both the hard PS and PP phases and separates them.With increasing the content of the compatibilizers equally,the morphology of the PA6/PS/(PP+PP-g-(MAH-co-St))/(SEBS+SEBS-g-(MAH-co-St))(70/10/10/10)quaternary blends evolves from the soft(SEBS+SEBS-g-(MAH-co-St))encapsulating PS and partially encapsulating PP(about 1μm),then to PS exclusively encapsulated by the soft SEBS-g-(MAH-co-St)and then separated by PP-g-(MAH-co-St)inside the smaller domains(about 0.6μm).This morphology evolution has been well predicted by spreading coefficients and explained by the reaction between the matrix PA6 and the compatibilizers.The quaternary blends compatibilized by more compatibilizers exhibit stronger hierarchical interfacial adhesions and smaller dispersed domain,which results in the further improved mechanical properties.Compared to the uncompatibilized blend,the blend with both 10 wt%PP-g-(MAH-co-St)and 10 wt%SEBS-g-(MAH-co-St)has the best mechanical properties with the stress at break,strain at break and impact failure energy improved significantly by 97%,71%and 261%,respectively.There is a strong correlation between the structure and property in the blends. 相似文献