弱双折射光纤布喇格光栅反射偏振对温度响应特性的研究

理论分析了切趾弱双折射光纤布喇格光栅反射偏振相关特性与温度之间的关系.数值模拟了切趾弱双折射光纤光栅的反射谱、偏振相关损耗和差分群时延随波长变化曲线.实验测出了不同温度下反射谱、偏振相关损耗和差分群时延随波长变化曲线.根据实验结果对偏振相关损耗和差分群时延的变化情况作出了分析.反射偏振相关损耗呈现两个峰值,随温度增加两峰漂移程度相同,表明偏振相关损耗无明显差异.差分群时延最大值随温度增加成线性向长波方向漂移,证明了光纤光栅正交模损耗变化的等同性.综合理论分析与实验结果表明:切趾弱双折射光纤布喇格光栅的偏振特性随温度产生明显的变化,其正交模变化呈现等比例特性.     

The scaled universe II

In an earlier paper we had pointed out that quantum mechanical type effects are seen at different scales in the macrouniverse also. In this paper we obtain a rationale for this, which lies in the picture of bound material systems, spanning a Compton wavelength type extent, separated by much larger and relatively much less dense distances.     

Etude cristallographique et par résonance magnétique nucléaire du bismuthooctadécatungstate Na7[H2BiW18O60]·24H2O

The heteropolytungstate [H_nBiW₁₈O₆₀]^(9-n)- crystallized in a rhombohedral space group (R3, a = 19.575(4), c = 18.112(4) A) with seven sodium cations identified by X-ray diffraction. Electroneutrality implies the occurrence of two protons per molecule hence the formula Na₇[H₂BiW₁₈O₆₀]·24H₂O. Proton magnetic resonance with triiodomethane as standard also led to two protons per molecule of bismuthooctadecatungstate. They showed up at 6.18 ppm with respect to tetramethylsilane.     

A unique Janus PdZn-Co catalyst for enhanced photocatalytic syngas production from CO2 and H2O

The development of excellent catalyst to achieve photocatalytic syngas production from CO₂ and H₂O is a prospective and sustainable strategy to alleviate environment and energy crisis. In this study, a unique Janus PdZn-Co catalyst is prepared by annealed the Pd/IRMOF-3(Co, Zn) precursor. Due to the strong interaction, the electron transfers from PdZn terminal to Co terminal in the Janus structure. The electron-received Co terminal facilitates Co sites coordinate with the electrophilic C atom of CO₂ and the electron-donated PdZn center is easier to coordinate with nucleophilic O atoms of H₂O or CO bonds. The charge redistribution enhances the absorption of CO₂ and H₂O, which promotes H₂ evolution and CO production. In addition, the carbon shell effectively suppresses the metal core agglomeration and facilitates the electron transmission from photosensitizer to metallic active sites. Meanwhile, the ratio of CO/H₂ can be regulated (∼3:1 to 2:1) by adjusting the proportion of Co and PdZn. The Janus structure and graphite carbon synergistically play a profound impact on improving the photocatalytic performance. The optimized PdZn-Co catalyst exhibits a superior photocatalytic CO production rate (20.03 µmol/h) and the H₂ generation rate (9.90 µmol/h) with a ratio of CO/H₂ = 2.02.