We present an improved digital image processing(DIP)method to calculate the widths of single slits.Different from the traditional laser Fraunhofer diffraction experiment in college physical experiments,by performing f...We present an improved digital image processing(DIP)method to calculate the widths of single slits.Different from the traditional laser Fraunhofer diffraction experiment in college physical experiments,by performing fast Fourier transform,inverse fast Fourier transform and the nonlinear leastsquare fitting on the diffraction pattern taken by a camera,the DIP method can quickly return an analytic expression,whose period is used to calculate widths of single slits.By comparing the measured results by the DIP method and the successional difference(SD)method,we find that for a single slit whose width is 60372μm,the DIP method is more accurate.Experimental results show that for single slits with widths between 40μm and 160μm,the relative error of the DIP method is less than 2.78%.Also,the DIP method can be used to measure the diameter of filament and fibres online in real time.展开更多
As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the ...As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the same total nozzle outlet area.A numerical simulation study on the effect of various parameters on the atomization in the annular slit atomizer was carried out by coupling both the large eddy simulation(LES)and volume of fluid(VOF)model,which is based on the applicability of LES in capturing the breakup behavior of transient liquid droplets and the advantage of VOF method in directly capturing the phase interface.The simulation results showed that the increase in the atomization pressure makes the gas gain higher momentum,while the increase in the nozzle intersection angle decreases the distance between the nozzle exit and the computational domain axis.The increase in these two variables results in enhancing the gas-liquid interaction in the primary atomization zone and the formation of more aluminum droplets simultaneously.It is considered that the atomization effect becomes better when atomization pressure is 2.5 MPa,and the nozzle intersection angle is 60°.Industrial tests showed that the aluminum powder prepared by the optimized annular slit atomizer has a finer mean particle size and a higher yield of fine powder.The numerical simulation results agree well with the industrial test data of the powder particle size.展开更多
随着光学镜头在工业自动化检测领域中的广泛应用,快速且准确地评价镜头的成像质量具有重要意义。为满足这一需求,调制传递函数(Modulation Transfer Function,MTF)测量仪已经得到研发并投入使用。其测量方法主要有垂直狭缝法和倾斜刃边...随着光学镜头在工业自动化检测领域中的广泛应用,快速且准确地评价镜头的成像质量具有重要意义。为满足这一需求,调制传递函数(Modulation Transfer Function,MTF)测量仪已经得到研发并投入使用。其测量方法主要有垂直狭缝法和倾斜刃边法,但垂直狭缝法需保证狭缝与传感器严格对齐,在实际操作难以实现。而倾斜刃边法在测量过程中由于其微分过程导致噪声放大且无法避免,从而影响测量结果。为了应对这些挑战,提出了一种改进的倾斜狭缝法。该方法解决了倾斜刃边法中的噪声放大问题,同时适用于倾斜狭缝的情况,从而实现精确的MTF测量。该方法在去噪方面采用多帧图像像素平均的方法去除随机噪声得到狭缝图;截取图像部分纯背景区域求像素均值作为背景噪声的值,用该图减去该值去除背景噪声。此外,针对此狭缝图引入了一种新的求质心方法。首先以图像的一行或一列的线扩散函数(Line Spread Function,LSF)中最高像素值为中心,遍历其左右像素以确定有效狭缝区域,对此区域数据应用三次样条插值算法,得到亚像素级的质心位置。以当前行或列获得的质心位置为中心,以相机像元尺寸的0.25倍亚像素间距对各像素位置进行离散采样并归档,将沿着狭缝方向对落入同档位的像素值进行均值计算,从而得到4倍超采样的亚像素级线扩散函数。倾斜狭缝法不仅能精确计算狭缝的倾斜角度,而且能精确测量镜头的MTF。对实验中影响MTF测试精度的因素进行了详细分析,结果表明,与国外先进仪器的对比中,该方法在超采样前的奈奎斯特频率以内,MTF值的测量误差小于1%;超采样后,在2.6倍奈奎斯特频率以内,测量误差小于1.3%。实验结果验证了该方法的有效实用性,表明其能够满足工业生产的需求。这一方法的应用可以有效解决购买国外先进MTF测试仪昂贵和难以自主控制的问题。展开更多
基金National Natural Science Foundtion of China(No.11435011)Young Teachers Fund of Nanjing Institute of Technology,China(Nos.QKJ201907 and QKJ201908)+2 种基金China Scholarship Council(No.201708320319)Postgraduate Research and Practice Innovation Program of Jiangsu Province,China(No.KYZZ16-0349)Qing Lan Project of Jiangsu Province,China。
文摘We present an improved digital image processing(DIP)method to calculate the widths of single slits.Different from the traditional laser Fraunhofer diffraction experiment in college physical experiments,by performing fast Fourier transform,inverse fast Fourier transform and the nonlinear leastsquare fitting on the diffraction pattern taken by a camera,the DIP method can quickly return an analytic expression,whose period is used to calculate widths of single slits.By comparing the measured results by the DIP method and the successional difference(SD)method,we find that for a single slit whose width is 60372μm,the DIP method is more accurate.Experimental results show that for single slits with widths between 40μm and 160μm,the relative error of the DIP method is less than 2.78%.Also,the DIP method can be used to measure the diameter of filament and fibres online in real time.
基金the financial support provided by the National Natural Science Foundation of China(U21A20317)supported by High-Performance Computing Center of Wuhan University of Science and Technology.
文摘As the width-thickness ratio of the discrete nozzle atomizer’s discrete hole greatly influences the loss of atomizing gas flow rate,the discrete nozzle atomizer was transformed into an annular slit atomizer with the same total nozzle outlet area.A numerical simulation study on the effect of various parameters on the atomization in the annular slit atomizer was carried out by coupling both the large eddy simulation(LES)and volume of fluid(VOF)model,which is based on the applicability of LES in capturing the breakup behavior of transient liquid droplets and the advantage of VOF method in directly capturing the phase interface.The simulation results showed that the increase in the atomization pressure makes the gas gain higher momentum,while the increase in the nozzle intersection angle decreases the distance between the nozzle exit and the computational domain axis.The increase in these two variables results in enhancing the gas-liquid interaction in the primary atomization zone and the formation of more aluminum droplets simultaneously.It is considered that the atomization effect becomes better when atomization pressure is 2.5 MPa,and the nozzle intersection angle is 60°.Industrial tests showed that the aluminum powder prepared by the optimized annular slit atomizer has a finer mean particle size and a higher yield of fine powder.The numerical simulation results agree well with the industrial test data of the powder particle size.
文摘随着光学镜头在工业自动化检测领域中的广泛应用,快速且准确地评价镜头的成像质量具有重要意义。为满足这一需求,调制传递函数(Modulation Transfer Function,MTF)测量仪已经得到研发并投入使用。其测量方法主要有垂直狭缝法和倾斜刃边法,但垂直狭缝法需保证狭缝与传感器严格对齐,在实际操作难以实现。而倾斜刃边法在测量过程中由于其微分过程导致噪声放大且无法避免,从而影响测量结果。为了应对这些挑战,提出了一种改进的倾斜狭缝法。该方法解决了倾斜刃边法中的噪声放大问题,同时适用于倾斜狭缝的情况,从而实现精确的MTF测量。该方法在去噪方面采用多帧图像像素平均的方法去除随机噪声得到狭缝图;截取图像部分纯背景区域求像素均值作为背景噪声的值,用该图减去该值去除背景噪声。此外,针对此狭缝图引入了一种新的求质心方法。首先以图像的一行或一列的线扩散函数(Line Spread Function,LSF)中最高像素值为中心,遍历其左右像素以确定有效狭缝区域,对此区域数据应用三次样条插值算法,得到亚像素级的质心位置。以当前行或列获得的质心位置为中心,以相机像元尺寸的0.25倍亚像素间距对各像素位置进行离散采样并归档,将沿着狭缝方向对落入同档位的像素值进行均值计算,从而得到4倍超采样的亚像素级线扩散函数。倾斜狭缝法不仅能精确计算狭缝的倾斜角度,而且能精确测量镜头的MTF。对实验中影响MTF测试精度的因素进行了详细分析,结果表明,与国外先进仪器的对比中,该方法在超采样前的奈奎斯特频率以内,MTF值的测量误差小于1%;超采样后,在2.6倍奈奎斯特频率以内,测量误差小于1.3%。实验结果验证了该方法的有效实用性,表明其能够满足工业生产的需求。这一方法的应用可以有效解决购买国外先进MTF测试仪昂贵和难以自主控制的问题。
