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991.
We propose a universal and practical scheme to realize polarization-free second-order nonlinear frequency-conversion processes, including sum-frequency generation, difference-frequency generation, and optical parametric amplification. This scheme is based on the optical superlattice with a noncritical phase-matching condition, which is suitable for optical integration. A chirped dual-period structure is proposed to ensure the efficiency and stability of the conversions. 相似文献
992.
Accurate method for measuring the thermal coefficient of group birefringence of polarization-maintaining fibers 总被引:1,自引:0,他引:1
We present a method to accurately measure the group birefringence variation with temperature in high-birefringence polarization-maintaining (PM) fibers using a distributed polarization analyzer. By analyzing polarization cross-talk peaks purposely induced at both ends of a PM fiber, the temperature coefficient of group birefringence can be accurately obtained. We confirm the theoretical prediction that the group birefringence of PANDA and TIGER PM fibers decrease linearly with temperature from -40 °C to 80 °C, and find that the temperature coefficients are -5.93 × 10(-7) °C(-1) and -5.29 × 10(-7) °C(-1) for two types of PANDA fibers, and -5.36 × 10(-7) °C(-1) for a TIGER fiber. 相似文献
993.
Indirect measurement of the intensity of incident light by the light transmission fluctuation method
The light transmission fluctuation method is a simple and useful method for in situ and in-line measurement of particle size and concentration. To accomplish the measurement, it is necessary to know the intensity of incident light or background signal I(0). However, measuring I(0) during in-line applications is hard. In this Letter, an algorithm is proposed to indirectly measure I(0) based on the variation of transmitted light signals. Experiments have been carried out to verify the algorithm and the maximum deviation between premeasured I(0) and indirectly measured I(0)' is less than 2.5%. 相似文献
994.
Zhengzheng Shao Liaoyong WenDongmin Wu Xueao ZhangShengli Chang Shiqiao Qin 《Applied Surface Science》2011,257(11):4919-4922
We have demonstrated a high performance piezoelectric nanogenerator by scanning a diamond-coated conductive tip on ZnO nanorod arrays in an AFM system with contact-mode. About 95% ZnO nanorods generate piezoelectric current due to the excellent mechanical and electrical properties of the tip. The tip's nitrogen-doped diamond coating is the key factor to maintain effective physical contact and electrical contact to ZnO nanorods, leading to efficient piezoelectric generation. Rectifying n+-n heterojunction is formed when the nitrogen-doped diamond tip contacted with a ZnO nanorod, which plays an important role in accumulating and releasing piezoelectric charges of the piezoelectric nanogenerator. Our research indicates that conductive diamond film is an ideal electrode for this type of piezoelectric nanogenerator. 相似文献
995.
Lihui SunHongwei Qin Feng GaoEnsi Cao Kai FanJifan Hu 《Applied Surface Science》2011,257(7):2633-2636
The adsorption of CO, NH3 and O2 gas molecules on Fe site of La0.875Sr0.125FeO3 (0 1 0) surface has been investigated based on the density functional theory (DFT) with the spin polarized generalized gradient approximation (GGA). The optimal adsorption orientations as well as the adsorption energies for these molecules adsorption on Fe site of La0.875Sr0.125FeO3 (0 1 0) surface are derived. Results show that adsorption configurations with C-down for CO, N-down for NH3 are stable. For the O2 molecule adsorption, the mode with an angle about 120° between the oxygen molecule and La0.875Sr0.125FeO3 (0 1 0) surface is stable. 相似文献
996.
R. Qin D.Y. Ding C.Q. NingH.G. Liu B.S. ZhuM. Li D.L. Mao 《Applied Surface Science》2011,257(14):6308-6313
Self-organized Ni-Ti-O nanotube arrays were fabricated through a direct anodization of NiTi shape memory alloy in glycerol-based electrolyte. The growth of Ni-doped TiO2 nanotube arrays was mainly affected by anodization voltage and temperature. Higher anodization voltage facilitated the growth of uniform nanotube arrays. Large-area open-ended Ni-Ti-O nanotube arrays could form on the surface of the shape memory alloy under a higher anodization temperature. The oxide nanotubes had a gradually changed composition along the growth direction of the nanotube and presented a thermal stability up to 400 °C. The nanotubular oxide demonstrated a much better hydrophilic behavior than that of the traditional oxide layer grown on NiTi substrate through air oxidization. The successful fabrication of Ni-doped TiO2 nanotube arrays here makes it feasible to further explore excellent physical and chemical as well as biomedical properties of the nanotube-modified surfaces of the NiTi shape memory alloy. 相似文献
997.
998.
高光谱技术分析茶树叶片中叶绿素含量及分布 总被引:4,自引:0,他引:4
植物叶片叶绿素含量及分布是植物营养信息表达的一个重要指标.以茶树为研究对象,利用高光谱技术分析茶树叶片中叶绿素含量及其分布.通过采集茶树鲜叶的高光谱图像,利用7种不同的算法从高光谱数据中提取相应的特征参数,并根据特征参数和叶绿素含量的参考测量值分别拟合出相应的预测模型.结果显示,二次土壤调节植被指数算法提取的特征参数最... 相似文献
999.
针对不确定多属性决策中的属性信息分布不均匀,且评价信息多数为二维信息的情况,本文提出了二维区间密度加权算子(TDIDW算子)的属性信息集结方法.依据密度算子的集结过程特点,文章首先定义了二维区间密度加权算子及其合成算子,然后介绍了基于灰色区间聚类法的评价信息分组方法以及基于非线性模型的密度加权向量确定方法,最后进行了算例验证.验证结果表明,该方法可以有效地解决由于属性信息分布不均匀而导致评价结果不准确的问题. 相似文献
1000.
Qinhua Wei Hongsheng Shi Xiaofeng Cheng Laishun Qin Guohao Ren Kangying Shu 《Journal of Crystal Growth》2010,312(11):1883-1885
The growth and scintillation properties of the Na2W2O7 crystal are reported. The solid reaction between Na2CO3 and WO3 is used to synthesise the Na2W2O7 material. The Na2W2O7 single crystal has been grown by the Bridgman method. And the Na2W2O7 single crystal with sizes 14×7×6 mm3 has been achieved. The transmission spectra, the Ultraviolet fluorescence spectra and the X-ray excited luminescence spectra of the Na2W2O7 crystal are measured. The measurement results show that the Na2W2O7 crystal is a promising intrinsic scintillator. 相似文献