As an additive manufacturing technique,the laser-aided direct energy deposition(L-DED)method has been widely used for component repair(also called laser repair).With significant differences from traditional manufactur...As an additive manufacturing technique,the laser-aided direct energy deposition(L-DED)method has been widely used for component repair(also called laser repair).With significant differences from traditional manufacturing techniques,the laser repair process has the characteristics of point-by-point deposition and has a high-temperature gradient in the repair area,resulting in the formation of heterogeneous thermal deformation and residual stress after cooling.High stress may lead to the appearance of cracks in the repair area and may seriously influence the bearing capacity of the repaired parts.Therefore,the characterization of the temperature and deformation fields of the components during laser repair is important for the analysis of the mechanism of damage evolution in the repair area,optimization of the process parameters,and improvement of the mechanical properties of the repaired components.Because of the demand for the simultaneous measurement of the temperature and deformation fields,using a multispectral camera and a self-designed three-peak filter,a temperature-deformation field measurement technique was developed and applied to in situ monitoring during the L-DED manufacturing process.In the actual measurement process,the synchronous measurement of the temperature field of the laser molten pool and the deformation field of the side surface of the repaired component were realized using the images of multiple channels in the multispectral camera.The experimental results verify that a three-peak filter can effectively eliminate the influences of glare and overexposure on the recorded multispectral images.Moreover,the amplitude of the displacement field and the temperature gradient of the repaired component will increase with the increase in laser power,which may affect the final molding of the repaired component.This work extends the function of the multispectral camera to measure the temperature and deformation fields and provides a new measurement method for further optimizing the process parameters of 展开更多
文中对准连续波雷达信号处理算法进行了多处改进,合理设计多级滤波器抽取比,使A/D采样直流延拓分量影响最小化;通过简单移位及加法运算实现抑制度达80 d B以上的高通滤波器;为提高系统抗干扰性,创新性的设计了具有免混频系数特性的双数...文中对准连续波雷达信号处理算法进行了多处改进,合理设计多级滤波器抽取比,使A/D采样直流延拓分量影响最小化;通过简单移位及加法运算实现抑制度达80 d B以上的高通滤波器;为提高系统抗干扰性,创新性的设计了具有免混频系数特性的双数字下变频方案。基于Xilinx公司XC4VSX55器件,整个设计完成了所有雷达信号处理算法及对外接口控制功能,资源占用情况比传统方案减少30%以上,同时依然保持良好的性能,尤其适合低复杂度小型弹载雷达系统。展开更多
.A non-intrusive reduced order model(ROM)that combines a proper orthogonal decomposition(POD)and an artificial neural network(ANN)is primarily studied to investigate the applicability of the proposed ROM in recovering....A non-intrusive reduced order model(ROM)that combines a proper orthogonal decomposition(POD)and an artificial neural network(ANN)is primarily studied to investigate the applicability of the proposed ROM in recovering the solutions with shocks and strong gradients accurately and resolving fine-scale structures efficiently for hyperbolic conservation laws.Its accuracy is demonstrated by solving a high-dimensional parametrized ODE and the one-dimensional viscous Burgers’equation with a parameterized diffusion coefficient.The two-dimensional singlemode Rayleigh-Taylor instability(RTI),where the amplitude of the small perturbation and time are considered as free parameters,is also simulated.An adaptive sampling method in time during the linear regime of the RTI is designed to reduce the number of snapshots required for POD and the training of ANN.The extensive numerical results show that the ROM can achieve an acceptable accuracy with improved efficiency in comparison with the standard full order method.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12032013 and 11972209)the National Key Research and Development Program of China(Grant No.2017YFB1103900)。
文摘As an additive manufacturing technique,the laser-aided direct energy deposition(L-DED)method has been widely used for component repair(also called laser repair).With significant differences from traditional manufacturing techniques,the laser repair process has the characteristics of point-by-point deposition and has a high-temperature gradient in the repair area,resulting in the formation of heterogeneous thermal deformation and residual stress after cooling.High stress may lead to the appearance of cracks in the repair area and may seriously influence the bearing capacity of the repaired parts.Therefore,the characterization of the temperature and deformation fields of the components during laser repair is important for the analysis of the mechanism of damage evolution in the repair area,optimization of the process parameters,and improvement of the mechanical properties of the repaired components.Because of the demand for the simultaneous measurement of the temperature and deformation fields,using a multispectral camera and a self-designed three-peak filter,a temperature-deformation field measurement technique was developed and applied to in situ monitoring during the L-DED manufacturing process.In the actual measurement process,the synchronous measurement of the temperature field of the laser molten pool and the deformation field of the side surface of the repaired component were realized using the images of multiple channels in the multispectral camera.The experimental results verify that a three-peak filter can effectively eliminate the influences of glare and overexposure on the recorded multispectral images.Moreover,the amplitude of the displacement field and the temperature gradient of the repaired component will increase with the increase in laser power,which may affect the final molding of the repaired component.This work extends the function of the multispectral camera to measure the temperature and deformation fields and provides a new measurement method for further optimizing the process parameters of
文摘文中对准连续波雷达信号处理算法进行了多处改进,合理设计多级滤波器抽取比,使A/D采样直流延拓分量影响最小化;通过简单移位及加法运算实现抑制度达80 d B以上的高通滤波器;为提高系统抗干扰性,创新性的设计了具有免混频系数特性的双数字下变频方案。基于Xilinx公司XC4VSX55器件,整个设计完成了所有雷达信号处理算法及对外接口控制功能,资源占用情况比传统方案减少30%以上,同时依然保持良好的性能,尤其适合低复杂度小型弹载雷达系统。
基金funding support of this research by the National Natural Science Foundation of China(11871443)Shandong Provincial Qingchuang Science and Technology Project(2019KJI002)the Ocean University of China for providing the startup funding(201712011)that is used in supporting this work.
文摘.A non-intrusive reduced order model(ROM)that combines a proper orthogonal decomposition(POD)and an artificial neural network(ANN)is primarily studied to investigate the applicability of the proposed ROM in recovering the solutions with shocks and strong gradients accurately and resolving fine-scale structures efficiently for hyperbolic conservation laws.Its accuracy is demonstrated by solving a high-dimensional parametrized ODE and the one-dimensional viscous Burgers’equation with a parameterized diffusion coefficient.The two-dimensional singlemode Rayleigh-Taylor instability(RTI),where the amplitude of the small perturbation and time are considered as free parameters,is also simulated.An adaptive sampling method in time during the linear regime of the RTI is designed to reduce the number of snapshots required for POD and the training of ANN.The extensive numerical results show that the ROM can achieve an acceptable accuracy with improved efficiency in comparison with the standard full order method.
