分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Pulsar timing arrays (PTAs) consisting of widely distributed and well-timed millisecond pulsars can serve as a galactic interferometer to measure gravitational waves. With the same data acquired for PTAs, we propose to develop pulsar polarization arrays (PPAs), to explore astrophysics and fundamental physics. As in the case of PTAs, PPAs are best suited to reveal temporal and spatial correlations at large scales that are hard to mimic by local noise. To demonstrate the physical potential of PPAs, we consider detection of ultralight axion-like dark matter (ALDM), through cosmic birefringence induced by its Chern-Simon coupling. Because of its tiny mass, the ultralight ALDM can be generated as a Bose-Einstein condensate, characterized by a strong wavy nature. Incorporating both temporal and spatial correlations of the signal, we show that PPAs have a potential to probe the Chern-Simon coupling up to $\sim 10^{-14}-10^{-17}$GeV$^{-1}$, with a mass range $\sim 10^{-27} - 10^{-21}$eV.
分类： 心理学 >> 实验心理学 提交时间： 2021-03-08
摘要： Panum’s limiting case is a typical phenomenon of monocular occlusion in binocular vision. It occurs naturally when one object is occluded by another object for one eye, but in the other eye the two objects are located in different directions. Only recently has it been found that in addition to horizontal disparity, the vertical disparity gradient and cue conflict are two important determinants for double fusion. Therefore, the current study aims to determine the relationship between the two determinants and perceptual learning in Panum’s limiting case. Twenty-six observers were trained for five days. Meanwhile, the RTs and duration of double fusion was measured when the participants viewed several versions of Panum’s configuration. In these stimuli, vertical disparity gradient was varied from 0.1 to 0.6 and cue conflict was manipulated from low to high. The results revealed that for each level of these factors, the RTs of double fusion decreased and the duration of double fusion increased with each training session. Moreover, there were significant differences among different levels of vertical disparity gradient and cue conflict. Lastly, there was also a significant interaction effect between the two determinants in Panum’s limiting case. These results suggest that there is perceptual learning for each level of the two determinants in monocular occlusion and these factors jointly affect the sensitivity and stability of double fusion.
分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 分类： 材料科学 >> 纳米科学和纳米技术 提交时间： 2017-02-23
摘要： The hexagonal boron nitride (h-BN) nanosheets are synthesized by the liquid-phase exfoliation method and transferred onto the microfiber by optical deposition method. The h-BN-deposited microfiber exhibits dual-function, that is, saturable absorption and high-nonlinearity. To check the laser performance by using the proposed h-BN device, it is inserted into an erbium-doped fiber laser (EDFL). In experiment, we demonstrate a tunable, switchable dual-wavelength soliton pulse by properly adjusting the pump power and the polarization state in the EDFL. The dual-wavelength soliton laser has a pump threshold of 50 mW at 976 nm, pulse energy of up to 3.4 nJ, peak power of about 2.62 kW, and pulse duration of about 1.3 ps. Additionally, we also demonstrate switchable operation of single-wavelength soliton pulse located at 1531.5 and 1557.5 nm, respectively. Our finding unambiguously implies that apart from its fantastic electric and thermal property, h-BN nanosheets may also possess attractive optoelectronic property for nonlinear photonics, such as mode-locker, Q-switcher, optical limiter and so on.
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