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991.
Volker D. Burkert 《中国物理 C》2009,33(12):1043-1050
Recent measurements of nucleon resonance transition form factors with CLAS at Jefferson Lab are discussed. The new data confirm the assertion of the symmetric constituent quark model of the Roper as the first radial excitation of the nucleon. The data on high Q2 nπ+ production better constrain the branching ratios liNK and [3Nn. For the first time, the longitudinal transition amplitude to the S11(1535) was extracted from the nπ+ data. Also, new results on the transition amplitudes for the D13(1520) resonance are presented showing a rapid transition from helicity 3/2 dominance seen at the real photon point to helicty 1/2 dominance at higher Q2. I also discuss the status of the search for new excited nucleon states. 相似文献
992.
In optical parametric chirped pulse amplification (OPCPA), the degradation of temporal contrast of the compressed signal pulse mainly results from spectral clipping in the grating stretcher with finite size of the optics, parametric fluorescence (PF) and the spectral variations transferred from temporal fluctuation of the pump pulse. The temporal contrast of the recompressed amplified pulse in the OPCPA system is studied numerically and a number of solutions are considered and optimized to achieve the highest temporal contrast. 相似文献
993.
Acceptor Concentration Effects on Photovoltaic Response in the La1-xSrxMnO3/SrNbyTi1-yO3 Heterojunction 下载免费PDF全文
Photovoltaic response in the heterojunction of La1-x SrxMnO3/SrNby Ti1-yO3 (LSMO/SNTO) is analyzed theoretically based on the drift-diffusion model. It is found that the decrease of acceptor concentration in the La1-xSrxMnO3 layer of hereto junction can increase the peak value of photovoltaic signal and the speed of photovoltaic response, whereas the changing of donor concentration in the SrNby Ti1-yO3 layer has no such evident effect. Furthermore, the result also indicates that the modulation of Sr doping in La1-xSrxMnO3 is an effective method to accommodate the sensitivity and the speed of photovoltaic response for LSMO/SNTO photoelectric devices. 相似文献
994.
Generally, dipole mode is a doubly degenerate mode. Theoretical calculations have indicated that the single dipole mode of two-dimensional photonic crystal single point defect cavity shows high polarization property. We present a structure with elongated lattice, which only supports a single y-dipole mode. With this structure we can eliminate the degeneracy, control the lasing action of the cavity and demonstrate the high polarization property of the single dipole mode. In our experiment, the polarization extinction ratio of the y-dipole mode is as high as 51:1. 相似文献
995.
Super-High Resolution Time Interval Measurement Method Based on Time-Space Relationships 总被引:1,自引:0,他引:1 下载免费PDF全文
Based on the principle of quantized delay-time, a super-high resolution time interval measurement method is proposed based on time-space relationships. Using the delay-time stability that time and frequency signal travel in a specific medium, the measured time interval can be quantized. Combined with the phase coincidence detection technique, the measurement of time can be changed into the measurement of space length. The resolution and the stability of the measurement system are easily improved. Experimental results show that the measurement resolution of the measured time interval depends on the length difference of the double delay-time unit. When the length difference is set up on millimeter level or sub-millimeter level, super-high measurement resolution from hundreds of picosecond to tens of picosecond can be obtained. 相似文献
996.
差分吸收激光雷达回波信号统计模型的研究 总被引:3,自引:0,他引:3
差分吸收激光雷达回波信号统计模型是研究差分吸收激光雷达系统的基础,但是现有的统计模型中均没有考虑大气湍流导致的激光闪烁对回波信号的影响。针对已有统计模型的缺陷和应用需要,综合考虑了大气湍流导致的激光闪烁、目标反射斑纹、接收噪声以及发射功率波动对回波信号统计特性的影响,提出了一种改进的长程差分吸收激光雷达回波信号统计模型,分析了该模型的统计特性。仿真结果表明大气湍流导致的激光闪烁对回波信号统计特性的影响十分显著,同时也验证了该统计模型比已有统计模型更精确、更符合实际。 相似文献
997.
998.
999.
TiAl3 和Ti/TiAl3 非合金化电极n型GaN欧姆接触的实现 总被引:1,自引:0,他引:1
在不进行合金化的情况下,首次直接采用TiAl3合金材料作为金属接触电极.在蓝宝石衬底上生长的n型载流子浓度为2×1018 cm-3的GaN上,成功地得到低接触电阻的欧姆接触,并由环形传输线模型方法测得比接触电阻率为3×10-5 Ω*cm2.与通常n型欧姆接触采用的Ti/Al双层结构比较,TiAl3合金结构更容易形成非合金化的n型欧姆接触.在此实验基础上,进一步分析了N空位和界面层处的TiAl3在形成非合金化或低温退火欧姆接触中发挥的作用,由此设计的Ti/TiAl3/Ni/Au接触结构,在TiAl3合金结构基础上明显地降低了接触电阻率. 相似文献
1000.
本文介绍了带有STC功能的接收机中频组件的设计,它动态范围宽,输出饱和电平大,选择性好,响应时间快.同时,对系统的电磁干扰加以讨论,并介绍了抗干扰的有效措施. 相似文献