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131.
Calculation of the Spatio-Temporal Dynamics of Q-switched Yb^3+:YAG Laser with an Unstable Cavity and a Super-Gaussian Mirror 下载免费PDF全文
A numerical simulation used to compute the spatio-temporal dynamics of pulse formation of diode-pumped Q- switched Yb: YA G laser is carried out. The model takes the laser amplification and gain saturation, the properties of the laser cavity, and the diffractive effects of the laser disc into account. The numerical calculation is performed for a confocal positive-branch unstable resonator with a super Gaussian coupling mirror. The simulation results show that the laser pulse starts from a Gaussian intensity distribution and becomes rapidly non-Gaussian. The corresponding beam quality M^2 factor is seen to vary approximately from 1.5 at the beginning of the formation of pulse to more than 10 in the tail of the pulse, with a value of 11.6 at the peak of the pulse. 相似文献
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A 5.35-μm-thick ZnO film is grown by chemical vapour deposition technique on a sapphire (0001) substrate with a GaN buffer layer. The surface of the ZnO film is smooth and shows many hexagonal features. The full width at half maximum of ZnO (0002) u-rocking curve is 161 arcsec, corresponding to a high crystal quality of the ZnO film. From the result of x-ray diffraction 0 - 20 scanning, the stress status in ZnO film is tensile, which is supported by Raman scattering measurement. The reason of the tensile stress in the ZnO film is analysed in detail. The lattice mismatch and thermal mismatch are excluded and the reason is attributed to the coalescence of grains or islands during the growth of the ZnO film. 相似文献
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A kind of ruthenium oxide with smaller particles and higher porosity was prepared by a sol-gel process with RuCl3·xH2O and NaHCO3 solution. Several details concerning this new material, including crystal structure,particle size as functions of the temperature, and electrochemical properties were also reported. The optimal annealing temperature was 210 ℃ and the powder annealed at this temperature had a rate capacitance of 541 F/g. In addition, the rate capacitance of the composite electrode reached 802 F/g after 10% carbon black was added, much higher than any previously reported value. High energy density supercapacitors were built with the newly discovered electrode material. Energy densities as high as 67 J/g were obtained based on the RuO2 ·xH2O alone. By introducing the highly porous carbon black into the electrode, energy densities great than 100 J/g could be achieved. The power density of the capacitor was enhanced significantly. 相似文献
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研究了980 nm激发下β-NaYF4:Yb3+,Er3+纳米片在不同温度下的上转换发光。在不同温度下,观察到了较强的绿色和红色上转换发光,分别对应于Er3+的(2H11/2,4S3/2)→4I15/2和4F9/2→4I15/2能级跃迁。随着温度的升高,520 nm的绿色发光带和660 nm的红色发光带强度逐渐增大,545 nm的绿色发光带呈现出先增强(84~204 K)后减弱的趋势(204~483 K)。分析了样品上转换发光随温度变化的原因,并用三能级模型对样品的上转换发光随温度的变化规律进行了理论分析。 相似文献
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由双-(β-酮苯胺)镍(Ⅱ)/MAO新型催化体系催化聚合制得苯乙烯聚合物,用^1H NMR、^13C NMR、FT—IR、DSC及WAXD等技术对聚合物进行了结构和性能的表征。通过^1H NMR、^13C NMR分析,证实该体系催化聚合得到无规聚苯乙烯(aPS);DSC结果表明,聚合物的玻璃化温度为Tg=66.6℃;WAXD结果分析表明,所得聚苯乙烯为非晶态,但在较短范围内表现出有序的特征。所有聚合物均可溶于氯仿、2-丁酮、丙酮、甲苯、四氢呋喃、氯苯、邻-二氯苯等有机溶剂中。 相似文献
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电化学阴极沉积制备氧化镍/碳纳米管复合电极的准电容特性 总被引:4,自引:0,他引:4
采用催化裂解的方法制备了碳纳米管,其比容量为12F/g.采用碳纳米管作为电极基体,采用阴极电化学还原Ni(NO3)2的方法在碳纳米管基体表面均匀的沉积了纳米氧化镍颗粒并由此制备了氧化镍碳纳米管复合电极材料.采用循环伏安、恒流充放电、交流阻抗及扫描电镜等方法考察了复合电极材料的容量特性、阻抗特性、自放电特性以及电极表观特征.实验表明复合电极具有良好的电化学特性,碳纳米管基体在明显降低氧化镍材料的阻抗的同时还提高了电极材料的电化学容量并拓宽了电极材料的有效工作电位窗,复合电极在6mol/LKOH电解液中比容量达到25F/g且表现了良好的电化学可逆性.与碳纳米管基电容器相比,采用氧化镍复合电极材料组装的电容器具有较低的自放电率. 相似文献
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