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Metalens for improving optical coherence tomography
Guo Songming,Feng Weibin,Long Yong,Liu Zhihao,Fu Xiao,Liang Haowen,Li Juntao 한국물리학회 2022 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.81 No.1
Optical coherence tomography is one of the most attractive new tomographic techniques, especially in the detection and imaging of biological tissues. For the detection and imaging of human corneas, the current ultra-high-resolution optical coherence tomography technology faces the challenge that the depth of focus is too short to scan the entire human cornea in a single amplitude scan. Here, we propose and design a silicon metalens to replace the objective lens in the sample arm of the optical coherence tomography system. In our simulation, a uniform focused beam with a depth of focus of 886 μm, an axial resolution of 3.1 μm and a lateral resolution of 2.2 μm can be generated by the metalens, which is under the excitation of broadband Gaussian light with wavelength coverage from 800 to 900 nm. This metalens fully satisfies the depth of focus and resolution requirements of the ultra-high-resolution optical coherence tomography system for human corneas, hence expands the application of optical coherence tomography in medical science for the benefit of mankind.
Shear strength of match-cast-free dry joint in precast girders
Haibo Jiang,Jiahui Feng,Jie Xiao,Mingzhu Chen,Weibin Liang 사단법인 한국계산역학회 2020 Computers and Concrete, An International Journal Vol.26 No.2
Shear keys in precast concrete segmental bridges (PCSBs) are usually match-casting which is very labour intensive. In this research, an innovative match-casting-free construction was proposed by leaving small gap between the convex and the concave castellated shear keys in the joints of PCSBs. Specimen experiment, shear strength analysis and numerical simulation were conducted, investigating the loading performance of this new type of dry joints, the gap dry joints. Compared with matchcasting joint specimens, it has been found from experiment that shear capacity of gap joint specimens significantly decreased ranging from 17.75% to 42.43% due to only partially constrained and contacted in case of gap dry joints. Through numerical simulation, the effects of bottom contacting location, the heights of the gap and the shear key base were analyzed to investigate strength reduction and methods to enhance shear capacity of gap joint specimens. Numerical results proved that shear capacity of gap dry joints under full contact condition was higher than that under partial contact. In addition, left contact destroyed the integrity of shear keys, resulting in significant strength reduction. Larger shear key base remarkably increased shear capacity of the gap joint. Experimental tests indicated that AASHTO provision underestimated shear capacity of the match-casting dry joint specimens, while the numerical results for the gap dry joint showed that AASHTO provision underestimated shear capacity of full contact specimens, but overestimated that of left contact specimens.
Zhihuang Shen,Bin Yao,Weibin Teng,Wei Feng,Weifang Sun 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.1
This work presents a digital graphic scanning (DGS) method, based on computer scanning graphics, to generate a grinding profile avoiding the difficulties appeared from the complex equations of the contact line. First the enveloping surface between the forming tool (rotor) profile and its corresponding cutting locus was developed, then based on Bresenham algorithm, the best possible pixels of the enveloping surface in the pixel matrix of screen were demonstrated using a specified color. Finally, the grinding profile data of the rotor (forming tool) were collected by scanning the pixel matrix of screen, capturing the coordinates of the indicated color of the best possible pixels. Comparing the analytical gearing envelope method and the DGS method, the feasibility of the DGS method was indicated. The DGS method was shown as a precise, rapid, efficient and stable computing tool to generate a grinding profile. In addition, such an approach can be applied in designing other similarly conjugated products such as gears, perpetual screws and milling cutters.