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Distributions of Amplitude and Phase Around C-points: Lemon, Mon-Star, and Star
Renlong Yu,Dong Ye,Yu Xin,Yanru Chen,Qi Zhao 한국광학회 2016 Current Optics and Photonics Vol.20 No.1
The distributions of (or constraints for) amplitude and phase around C-points, including Lemon,Mon-Star and Star, are studied. A Cartesian coordinate system with origin at the C-point is established. Four curves, where the azimuthal angles of polarization ellipses are 0°, 45°, 90°, and 135° respectively,are used to determine the distributions. Discussions of these constraints illustrate why Mon-Star is rarerthan Lemon or Star in experiments. The transformation relationships between these three polarizationsingularities (PSs) are also discussed. We construct suitable functions for amplitude and phase accordingto their constraints, and simulate several PSs of particular shapes. With the development of modulationtechniques for amplitude and phase, it is clear that this work is helpful for generating arbitrarily shapedC-points in experiments.
Calibration of Measurement of Multiple Polarization Singularities
Renlong Yu,Yu Xin,Shuan Zhao,Qi Zhao,Yanru Chen 한국광학회 2015 Current Optics and Photonics Vol.19 No.4
In this paper, we propose a method used to measure the polarization state of a field with multiplepolarization singularities (PSs), such as an array of PSs and PSs in vector speckle. A checkerboard isused to construct characteristic points, which makes it possible to calibrate the mismatches between picturesobtained during the rotation of a quarter-wave plate and a polarizer. Using this method a field with anarray of PSs is measured. The experimental result is compared with the numerical simulation. We alsocarry out some data analysis. The comparison and analysis emphasize the necessity and feasibility of thismethod to measure the PSs
Ghost Imaging with Different Speckle Sizes of Thermal Light
Jue Wang,Renlong Yu,Yu Xin,Yanming Shao,Yanru Chen,Qi Zhao 한국광학회 2016 Current Optics and Photonics Vol.20 No.1
In this paper, we theoretically and experimentally analyze the impact of speckle size of pseudo-thermallight source on ghost imaging. A larger size of speckle can bring improvements in SNR and visibility. At the same time, the edge blur of the retrieved image will become more serious. We also present a setupwhich can mitigate the edge blur of larger speckle while maintaining the advantages of higher SNR andvisibility by changing the speckle size of the object beam with a concave lens.
Changfa Guo,Yue Xiao,Renlong Xin 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.9
In this work, we statistically investigate the texture effect on twinning behavior in rolling of an AZ31 Mg alloy by electronbackscatter diffraction technique and evaluate it by a generalized Schmid factor (GSF). The results show that twinningnucleation and area fraction are promoted significantly with the c-axis of grains rotating from the transverse direction to therolling direction. More importantly, twin propensity and the selection of twin variants can be well explained by the GSFthat is calculated based on an estimated stress state for rolling. The present results provide some insights into controlling themicrostructure and texture of Mg alloys by rolling processes.
Bo Song,Huaizhi Zhao,Linjiang Chai,Ning Guo,Hucheng Pan,Hongbing Chen,Renlong Xin 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5
Extruded AZ31 Mg alloy rods were subject to free-end torsion deformation at room temperature. The microstructure features of the torsion deformed samples were characterized using electron backscatter diffraction technique. Mg rods with gradient microstructure can be fabricated by torsion deformation. Inhomogeneous distribution of microstructure along the radial direction of the twisted rods is attributed to the linearly increasing strain accumulation and strain rate from core to surface. With increasing equivalent strain, both the amount of {10- 12} twins and dislocation density increase and the c-axes of texture tend to rotate towards torsion axis. Although both dislocation slips and {10-12} twinning can be activated during torsion, dislocation slips are considered as the dominated deformation mechanism and responsible for the change of macro-texture for present torsion deformation. {10-12} twins and dislocations in the twisted samples can generate refinement hardening and dislocation hardening, respectively, to increase the hardness value.
Tension-Compression Asymmetry of a Rolled Mg-Y-Nd Alloy
Bo Song,Hucheng Pan,Weijie Ren,Ning Guo,Zehong Wu,Renlong Xin 대한금속·재료학회 2017 METALS AND MATERIALS International Vol.23 No.4
In this work, tension and compression deformation behaviors of rolled and aged Mg-Y-Nd alloys were investigated. The microstructure evolution and plastic deformation mechanism during tension and compression wereanalyzed by combined use of electron backscatter diffraction and a visco-plastic self-consistent crystal plasticitymodel. The results show that both rolled and aged Mg-Y-Nd sheets show an extremely low yield asymmetry. Elimination of yield asymmetry can be ascribed to the tilted basal texture and suppression of {10-12} twinning. The rolled sheet has almost no yield asymmetry, however exhibits a remarkable strain-hardening behavior asymmetry. Compressed sample shows lower initial strain hardening rate and keeps higher strain hardening rate at thelater stage compared with tension. The strain-hardening asymmetry can be aggravated by aging at 280 C. It is consideredthe limited amount of twins in compression plays the critical role in the strain hardening asymmetry. Finally, the relevant mechanism was analyzed and discussed.