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31.
Filter-free ultra-wideband (UWB) doublet pulse generation is experimentally demonstrated in the optical domain based on cross-gain modulation (XGM) in semiconductor optical amplifier (SOA) and UWB-over-fiber technology is implemented by exploiting dispersion-induced pulse broadening effect in single-mode fiber (SMF). In our proposed system, the SOA generates a polarity-inversed Gaussian pulse train with respect to the injected one through the XGM. After a piece of SMF, the bandwidth of polarity-reversed Gaussian pulse broadens due to the induced dispersion. After the combination of the two light waves with a suitable time delay between them, UWB pulse is obtained. The key parameters for UWB pulse, including central frequency, 10 dB bandwidth, as well as fractional bandwidth are experimentally obtained with 8 GHz, 9.9 GHz and 123% respectively. The generated UWB doublet pulse conforms with the UWB definition of Federal Communications Commission (FCC).  相似文献   
32.
<正>The first-principles calculations are performed to investigate the adsorption of O2 molecules on an Sn(111) 2×2 surface.The chemisorbed adsorption precursor states for O2 are identified to be along the parallel and vertical channels, and the surface reconstructions of Sn(lll) induced by oxygen adsorption are studied.Based on this,the adsorption behaviours of O2 on X(111)(X=Si,Ge,Sn,Pb) surfaces are analysed,and the most stable adsorption channels of O2 on X(111)(X=Si,Ge,Sn,Pb) are identified.The surface reconstructions and electron distributions along the most stable adsorption channels are discussed and compared.The results show that the O2 adsorption ability declines gradually and the amount of charge transferred decreases with the enhancement of metallicity.  相似文献   
33.
We investigate the crossover from three to two dimensions for harmonically trapped hard-sphere Bose gases by varying the aspect ratio of the trapping potential. The diffusion Monte Carlo method is used to calculate both the ground-state energy and structural properties. The effect of trap anisotropy, interparticle interaction, and number of particles on the ground-state properties is discussed. Our results show that the minimum value of the aspect ratio at which the system reaches an asymptotic equilibrium distribution in the weakly confined direction decreases with increasing scattering length, while the minimum value of the aspect ratio at which the system enters the quasi-two-dimensional (2D) regime increases as both the scattering length and the number of particles increase. Additionally, the role played by particle correlations is proved to be more pronounced in the quasi-2D system than in the three-dimensional (3D) system by directly comparing the ground-state properties for the two cases.  相似文献   
34.
Some 13C chemical shifts of the CHn groups in the aliphatic side chains of Im-cyt c have been determined for the first time based on the H chemical shifts of their attached protons with the aid of heteronuclear multiple-quantum coherence (HMQC) spectroscopy. Comparison of chemical shifts of these specifically assigned 13C and H resonances from Im-cyt c with those from cyt c indicates that 13C-NMR spectra may provide an opportunity to probe the electronic structure and conformational changes induced by axial ligand substitution.  相似文献   
35.
微谐振环结构体内太赫兹增强效应   总被引:1,自引:0,他引:1       下载免费PDF全文
基于严格电磁场理论,给出了微型谐振环形和Fishnet结构体内太赫兹波的严格表达式,并利用电磁场的边界条件分析了太赫兹波在微型谐振环形和Fishnet结构体内空间分布的增强效应。数值模拟结果表明:谐振环金属条附近的电场大于磁场,金属条附近的电场相对其他区域明显要强得多,开口处表现更为突出,太赫兹波在Fishnet结构体内电磁场的峰位处电场和磁场分布关于x对称;电场的极值出现在大十字架的上下四个角,而磁场的极值则出现在小十字架的上下两端点。同时用电磁场传输线理论对该现象作出一定的物理解释。收稿日期:; 修订日期:  相似文献   
36.
37.
A diode-pumped acousto-optically Q-switched intracavity frequency-doubled Nd:GdVO4/KTP green laser formed with a flat–flat resonator was demonstrated. 3.05 W of average green output power at pulse repetition frequency (PRF) of 40 kHz was obtained with an optical conversion efficiency of 18.4%, the effective intracavity frequency-doubling efficiency was 57%. At the incident pump power of 15 W, the shortest laser pulse occurred at PRF of 25 kHz with FWHM width of 14 ns, yielding the highest peak power of 7.44 kW; while the largest pulse energy of 0.14 mJ was achieved at PRF of 15 kHz.  相似文献   
38.
小功率高转速蒸汽透平试验研究和优化邵振麒(同济大学汽车工程系上海200092)关键词:小蒸汽透平,效率,优化1前言回收能量和工业装置的余热及利用太阳能等新能源是节能和环保的重要措施,由此产生的机械能可供发电,气体增压等多种用途。在一些废热量不大且不宜...  相似文献   
39.
The X-ray spectra of Nb surface induced by Ar q+ (q = 16,17) ions with the energy range from 10 to 20 keV/q were studied by the optical spectrum technology. The experimental results indicate that the multi-electron excitation occurred as a highly charged Ar16+ ion was neutralized below the metal surface. The K shell electron of Ar16+ was excited and then de-excited cascadly to emit K X-ray. The intensity of the X-ray emitted from K shell of the hollow Ar atom decreased with the increase of projectile kinetic energy. The intensity of the X-ray emitted from L shell of the target atom Nb increased with the increase of projectile kinetic energy. The X-ray yield of Ar17+ is three magnitude orders larger than that of Ar16+. Supported by the National Natural Science Foundation of China (Grant Nos.10774149 and 10405025)  相似文献   
40.
A new high-performance laser scanning system is designed. In this system, a scanning arm consisting of a pentagonal prism and a scanning object lens is used to replace the traditional Fθ lens, and a circular imaging plate transmission mechanism is specially designed in order to meet the requirement of the scanning arm. At the same time, the stimulation fluorescence can be obtained by the scanning arm. Some main factors that influence the spatial resolution and the performance of the laser scanner system are analyzed, and the analysis results are presented, which is helpful for further optimization design of the system. Experimental results indicate that the images obtained by the system have good visual effects and can meet the requirements of industrial inspection.  相似文献   
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