Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured ...Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured data away from the edge of a geometric discontinuity. Photoelastic data are hybridized with complex variable/mapping techniques to calculate photoelastic stress-field around a circular hole or an elliptical hole in plates under uniaxial tensile loading. This method determines full-field stresses in perforated finite tensile plates containing either a circular or an elliptical hole. The second one is a fringe phase shift method to separate isochromatics and isoclinics from photoelastic fringes of a circular disk under diametric compression by use of phase shift method. Digitally determined isochromatics and isoclinics are agreed well with those of manual measurements.展开更多
In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calcula...In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calculates the scattering phase shift instead of scattering matrix elements in order to simplify the calculation. As an illustration, this method is used to calculate the broadening and shift coefficients of the absorption lines of alkali metal atom Rb, as it collides with buffer gas He and Ar, in a temperature range from 150 K to 800 K. With a comparison with other calculations and experiment measurements, the reasonable agreements in all cases demonstrate the validity and simplicity of this method.展开更多
Based on the transfer matrix method,a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating(FBG)is investigated.Temporal responses of the double-phase-shifted FBG to optical pulse are an...Based on the transfer matrix method,a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating(FBG)is investigated.Temporal responses of the double-phase-shifted FBG to optical pulse are analyzed and the influence of the two phase-shifts’position on the reflected output pulse is evaluated.Results demonstrate that very different temporal pulse waveforms can be achieved by adjusting the length ratio(α=L2/L1).Specifically,a transform-limited Gaussian input optical pulse can be shaped into flat-top square pulse(α=1.81)or two identical optical pulse sequences(α=1.93).展开更多
The Haicheng region,Liaoning,China,likely hosts a conjugate fault system comprising the NW-trending Haichenghe fault and NE-trending secondary faults.On February 4,1975,at 19:36 CST,an earthquake of M_(S)7.3 and inten...The Haicheng region,Liaoning,China,likely hosts a conjugate fault system comprising the NW-trending Haichenghe fault and NE-trending secondary faults.On February 4,1975,at 19:36 CST,an earthquake of M_(S)7.3 and intensity(MMI)IX hit the city of Haicheng,Liaoning,China.Although deep seismic profiling was previously conducted along the Haichenghe fault,the limited horizontal resolution in the shallow part prevented the recognition of kilometer-scale anomalies.The velocity structure characteristics of the Haichenghe fault and its NE-trending conjugate faults remain unclear.Using the extended range phase shift method,the high-resolution S-wave velocity structures are obtained by deploying a long,dense linear array of 55 short-period seismometers across the fault and NE-trending conjugate faults.The array length was 32 km and inter-station spacing was approximately 600 m,facilitating the collection of approximately 22 days of continuous waveform data.Employing the Extended Range Phase Shift(ERPS)method enabled the extraction of broadband 0.2–5 s Rayleigh wave phase velocity dispersion curves.The broadband dispersion data were used for inversion of the high-resolution S-wave velocity structure to a depth of 8 km from the surface.The velocity structure characteristics and seismicity of the Haichenghe fault and NE-trending conjugate faults were analyzed and compared with nearby fault gas measurements.Results show(1)shallow S-wave velocities show a low-high-low horizontal distribution,corresponding to basin-uplift-basin topography;(2)significant velocity contrasts occur across the Haichenghe fault:its SW segment(0–17 km)exhibits high velocities consistent with Paleoproterozoic crystalline basement(Pt_(1)),while the NE segment(17–32 km)shows low velocities related to Yanshanian intrusions(γ_(5))and Quaternary sediments.NE-trending conjugate faults display sharp velocity gradients marking fracture locations,with all faults being near-vertical to~8 km depth;(3)seismicity at 1–6 km depth mainly clusters in high-velocity zones;at 6–8 km depth,it concentrates beneath the Haichenghe fault in low-velocity areas and along NE-trending faults;(4)the seismic activity characteristics and fault zone width of the Haicheng he fault reflected by velocity imaging results are basically consistent with those obtained by the fault gas measurement method.展开更多
This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe ana...This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.展开更多
Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper p...Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.展开更多
文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间...文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间,从而达到提升图像质量和深度测量精度的效果。在运动模糊测试平台上对改善效果进行一系列测试。结果表明,该方法能显著提高ToF相机在动态场景下的深度图像质量,在测试装置转速为100~200 r/min内时,由运动模糊产生的错误像素数减少百分比可达35%以上,最高可达41.46%。通过实验验证,基于增益标定的ToF相机运动模糊矫正方法能有效提升图像质量和深度信息的准确性,展现了其在动态环境下的广泛应用潜力。展开更多
文摘Photoelastic fringe patterns for stress analysis are investigated by use of hybrid technique and fringe phase shift method. The first one is a hybrid method which combines the conformal mapping technique and measured data away from the edge of a geometric discontinuity. Photoelastic data are hybridized with complex variable/mapping techniques to calculate photoelastic stress-field around a circular hole or an elliptical hole in plates under uniaxial tensile loading. This method determines full-field stresses in perforated finite tensile plates containing either a circular or an elliptical hole. The second one is a fringe phase shift method to separate isochromatics and isoclinics from photoelastic fringes of a circular disk under diametric compression by use of phase shift method. Digitally determined isochromatics and isoclinics are agreed well with those of manual measurements.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.11405077 and 11575073)
文摘In this work, a new full quantum method is proposed to calculate the broadening and shift coefficients of the D1 line in neutral collision. Based on the variable phase approach and Baranger theory, this method calculates the scattering phase shift instead of scattering matrix elements in order to simplify the calculation. As an illustration, this method is used to calculate the broadening and shift coefficients of the absorption lines of alkali metal atom Rb, as it collides with buffer gas He and Ar, in a temperature range from 150 K to 800 K. With a comparison with other calculations and experiment measurements, the reasonable agreements in all cases demonstrate the validity and simplicity of this method.
基金supported by the Foundation of Beijing Municipal Committee of CPC Organization Department(No.2012D005002000001)the Talents of North China University of Technology(No.CCXZ201307)the Importation and Development of High-Caliber Talents Project of Beijing Municipal Institutions(No.CIT&TCD201304001)
文摘Based on the transfer matrix method,a detailed theoretical and numerical study on double-phase-shifted fiber Bragg grating(FBG)is investigated.Temporal responses of the double-phase-shifted FBG to optical pulse are analyzed and the influence of the two phase-shifts’position on the reflected output pulse is evaluated.Results demonstrate that very different temporal pulse waveforms can be achieved by adjusting the length ratio(α=L2/L1).Specifically,a transform-limited Gaussian input optical pulse can be shaped into flat-top square pulse(α=1.81)or two identical optical pulse sequences(α=1.93).
基金supported by the Special Fund of the Institute of Geophysics,China Earthquake Administration,(No.DQJB21B34).
文摘The Haicheng region,Liaoning,China,likely hosts a conjugate fault system comprising the NW-trending Haichenghe fault and NE-trending secondary faults.On February 4,1975,at 19:36 CST,an earthquake of M_(S)7.3 and intensity(MMI)IX hit the city of Haicheng,Liaoning,China.Although deep seismic profiling was previously conducted along the Haichenghe fault,the limited horizontal resolution in the shallow part prevented the recognition of kilometer-scale anomalies.The velocity structure characteristics of the Haichenghe fault and its NE-trending conjugate faults remain unclear.Using the extended range phase shift method,the high-resolution S-wave velocity structures are obtained by deploying a long,dense linear array of 55 short-period seismometers across the fault and NE-trending conjugate faults.The array length was 32 km and inter-station spacing was approximately 600 m,facilitating the collection of approximately 22 days of continuous waveform data.Employing the Extended Range Phase Shift(ERPS)method enabled the extraction of broadband 0.2–5 s Rayleigh wave phase velocity dispersion curves.The broadband dispersion data were used for inversion of the high-resolution S-wave velocity structure to a depth of 8 km from the surface.The velocity structure characteristics and seismicity of the Haichenghe fault and NE-trending conjugate faults were analyzed and compared with nearby fault gas measurements.Results show(1)shallow S-wave velocities show a low-high-low horizontal distribution,corresponding to basin-uplift-basin topography;(2)significant velocity contrasts occur across the Haichenghe fault:its SW segment(0–17 km)exhibits high velocities consistent with Paleoproterozoic crystalline basement(Pt_(1)),while the NE segment(17–32 km)shows low velocities related to Yanshanian intrusions(γ_(5))and Quaternary sediments.NE-trending conjugate faults display sharp velocity gradients marking fracture locations,with all faults being near-vertical to~8 km depth;(3)seismicity at 1–6 km depth mainly clusters in high-velocity zones;at 6–8 km depth,it concentrates beneath the Haichenghe fault in low-velocity areas and along NE-trending faults;(4)the seismic activity characteristics and fault zone width of the Haicheng he fault reflected by velocity imaging results are basically consistent with those obtained by the fault gas measurement method.
基金Project supported by the National Natural Sciences Foundation of China (No. 10572102).
文摘This paper deals with the mode I crack problem of a cracked rubber sheet under plane stress condition using the delicate digital moiré technique. Through the four step phaseshifting method of automated fringe analysis, the displacement fields in the Cartesian coordinate system are given. By the coordinate-transform equation, the radial and circular displacement distributions in the polar coordinate system are obtained. The displacement isoline distributions and displacement vector distributions near the crack tip are discussed. The strain isoline distributions near the crack tip are also analyzed in this paper. Finally, the distribution rules for the mechanical fields near the crack tip are discussed with the sector division method.
文摘Unintentional islanding phenomenon has been one of the most important problems of gridconnected photovoltaic inverters. To prevent this phenomenon, all kinds of anti-islanding methods have been discussed. This paper presents a combined active islanding detection method, which consists of active frequency drift method and automatic phase-shift method. The traditional active anti-islanding methods of grid-connected PV inverters bear nondetection zone possibilities for certain paralleled RLC loads. The combined method shows islanding detection ability effectively, and it can eliminate nondetection zones even in the worst case conditions. Simulation in different load conditions is performed for verification.
文摘文章旨在减轻Time of Flight(ToF)相机在动态场景中产生的运动模糊,以提升图像质量和深度信息的准确性。提出了一种基于增益标定的矫正方法,通过增益标定精确测定每个像素的增益系数,并引入深度解算原理中的四位相移法以此优化曝光时间,从而达到提升图像质量和深度测量精度的效果。在运动模糊测试平台上对改善效果进行一系列测试。结果表明,该方法能显著提高ToF相机在动态场景下的深度图像质量,在测试装置转速为100~200 r/min内时,由运动模糊产生的错误像素数减少百分比可达35%以上,最高可达41.46%。通过实验验证,基于增益标定的ToF相机运动模糊矫正方法能有效提升图像质量和深度信息的准确性,展现了其在动态环境下的广泛应用潜力。
