A double-exposure fabrication method without any intensity shadow mask to fabricate arbitrarily apodized fiber Bragg gratings（ FBGs） with narrow bandwidth is demonstrated by controlling the total ultra violet （UV）...A double-exposure fabrication method without any intensity shadow mask to fabricate arbitrarily apodized fiber Bragg gratings（ FBGs） with narrow bandwidth is demonstrated by controlling the total ultra violet （UV） irradiation along the grating by varying the speed of a translation stage. The UV source used is a stable continuous intracavity frequency-doubled argonion laser. The parameters （such as length, apodization profile, average index change）of FBGs can be easily changed with this method. The total UV irradiation is kept constant in the doubleexposure process because of the precise control of the exposure time, which ensures that the apodized FBG＇s bandwidth can be extremely narrow. The full width at half maximum （FWHM） bandwidth of the 2-cm-long apodized FBG fabricated by this method is 0. 15 nm with a maximum reflectivity of more than 95%.展开更多
During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly...During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly, the backward roller paths of hemispherical parts with aluminum alloy 2024-O are analyzed. Finite element model with parameterized conventional spinning roller paths, which are based on quadratic Bezier curves, is developed to explore the evolution of the stress, strain and thinning during the backward processes. Analysis of the simulation results reveals stress and strain features of backward pass spinning. According to the findings, the application of the backward pass can obviously improve the uniformity of wall thickness. Furthermore, references of the parameters in future backward path design are provided.展开更多
Spray performance downward the plain orifice injector was numerically simulated by using Fluent. The primary breakup and the secondary breakup were both focused. To capture the instantaneous interface of two-phase flo...Spray performance downward the plain orifice injector was numerically simulated by using Fluent. The primary breakup and the secondary breakup were both focused. To capture the instantaneous interface of two-phase flow and multiscale structure of liquid spray more accurately,an adaptive mesh refinement(AMR) method was adopted. Firstly,the velocity distribution and jet structure were obtained. Then,with different coupled VOF(Volume of Fluid)-DPM(Discrete Phase model)strategies,the jet trajectory,the column breakup point,and the time-average SMD distribution were analyzed and compared. Meanwhile,the experimental data and several empirical formulas were applied to verify the numerical value. The results suggested that the numerical simulation could accord well with experimental data and a certain formula.展开更多
基金The Natural Science Foundation of Jiangsu Province(No.BK2004207)
文摘A double-exposure fabrication method without any intensity shadow mask to fabricate arbitrarily apodized fiber Bragg gratings（ FBGs） with narrow bandwidth is demonstrated by controlling the total ultra violet （UV） irradiation along the grating by varying the speed of a translation stage. The UV source used is a stable continuous intracavity frequency-doubled argonion laser. The parameters （such as length, apodization profile, average index change）of FBGs can be easily changed with this method. The total UV irradiation is kept constant in the doubleexposure process because of the precise control of the exposure time, which ensures that the apodized FBG＇s bandwidth can be extremely narrow. The full width at half maximum （FWHM） bandwidth of the 2-cm-long apodized FBG fabricated by this method is 0. 15 nm with a maximum reflectivity of more than 95%.
基金Project(2014CB046601)supported by the National Basic Research Program of ChinaProject(51675333)supported by the National Natural Science Foundation of China
文摘During multi-pass conventional spinning, roller paths combined with the forward and the backward pass are usually used to improve the material formability. In order to understand the backward spinning process properly, the backward roller paths of hemispherical parts with aluminum alloy 2024-O are analyzed. Finite element model with parameterized conventional spinning roller paths, which are based on quadratic Bezier curves, is developed to explore the evolution of the stress, strain and thinning during the backward processes. Analysis of the simulation results reveals stress and strain features of backward pass spinning. According to the findings, the application of the backward pass can obviously improve the uniformity of wall thickness. Furthermore, references of the parameters in future backward path design are provided.
基金supported by the National Natural Science Foundation of China(No. 91741118)
文摘Spray performance downward the plain orifice injector was numerically simulated by using Fluent. The primary breakup and the secondary breakup were both focused. To capture the instantaneous interface of two-phase flow and multiscale structure of liquid spray more accurately,an adaptive mesh refinement(AMR) method was adopted. Firstly,the velocity distribution and jet structure were obtained. Then,with different coupled VOF(Volume of Fluid)-DPM(Discrete Phase model)strategies,the jet trajectory,the column breakup point,and the time-average SMD distribution were analyzed and compared. Meanwhile,the experimental data and several empirical formulas were applied to verify the numerical value. The results suggested that the numerical simulation could accord well with experimental data and a certain formula.
