分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： Investigating the CKM matrix in different parametrization schemes, it is noticed that those schemes can be divided into a few groups where the sine values of the CP phase for each group are approximately equal. Using those relations, several approximate equalities among the elements of CKM matrix are established. Assuming them to be exact, there are infinite numbers of solutions and by choosing special values for the free parameters in those solutions, several textures presented in literature are obtained. The case can also be generalized to the PMNS matrix for the lepton sector. In parallel, several mixing textures are also derived by using presumed symmetries, amazingly, some of their forms are the same as what we obtained, but not all. It hints existence of a hidden symmetry which is broken in the practical world. The nature makes its own selection on the underlying symmetry and the way to break it, while we just guess what it is.
分类： 化学 >> 物理化学 提交时间： 2017-11-05 合作期刊: 《结构化学》
摘要： The adsorption process and hydrogenation mechanisms of 2-methylthiophene on the Pt(111) surface have been elucidated using density functional theory (DFT). The optimal adsorption sites of reactants, intermediates, and products as well as the activation energy and reaction energy of each elementary reactions were investigated. The results turned out that the 2-methylthiophene tilt to the Pt(111) catalyst with the C1–C2 double bond at the top site was the most stable. During the hydrogenation process, the heat of reaction almost located at the negative side, so dropping the temperature is good for the occurrence of hydrogenation process. The hydrogenation steps of mechanism take place along C2→C3→C1→C4→S→C1 to generate the product of pentane-2-thiol, in which the first step with the highest energy barrier is the rate-determining step.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Zhongjin Lin
Yanmei Lin
Hao Li
Mengyue Xu
Mingbo He
Wei Ke
Zhaohui Li
Dawei Wang
X. Steve Yao
Siyuan Yu
Xinlun Cai
摘要： High-speed polarization management is highly desirable for many applications, such as remote sensing, telecommunication, and medical diagnosis. However, most of the approaches for polarization management rely on bulky optical components that are slow to respond, cumbersome to use, and sometimes with high drive voltages. Here, we overcome these limitations by harnessing photonic integrated circuits based on thin-film lithium niobate platform. We successfully realize a portfolio of thin-film lithium niobate devices for essential polarization management functionalities, including arbitrary polarization generation, fast polarization measurement, polarization scrambling, and automatic polarization control. The present devices feature ultra-fast control speed, low drive voltages, low optical losses and compact footprints. Using these devices, we achieve high fidelity polarization generation with a polarization extinction ratio up to 41.9 dB, fast polarization scrambling with a scrambling rate up to 65 Mrad/s, and endless polarization control with a tracking speed up to 10 Krad/s, all of which are best results in integrated optics. The demonstrated devices unlock a drastically new level of performance and scales in polarization management devices, leading to a paradigm shift in polarization management.
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