As a highly efficient absorbing boundary condition, Perfectly Matched Layer (PML) has been widely used in Finite Difference Time Domain (FDTD) simulation of Ground Penetrating Radar (GPR) based on the first order elec...As a highly efficient absorbing boundary condition, Perfectly Matched Layer (PML) has been widely used in Finite Difference Time Domain (FDTD) simulation of Ground Penetrating Radar (GPR) based on the first order electromagnetic wave equation. However, the PML boundary condition is difficult to apply in GPR Finite Element Time Domain (FETD) simulation based on the second order electromagnetic wave equation. This paper developed a non-split perfectly matched layer (NPML) boundary condition for GPR FETD simulation based on the second order electromagnetic wave equation. Taking two-dimensional TM wave equation as an example, the second order frequency domain equation of GPR was derived according to the definition of complex extending coordinate transformation. Then it transformed into time domain by means of auxiliary differential equation method, and its FETD equation is derived based on Galerkin method. On this basis, a GPR FETD forward program based on NPML boundary condition is developed. The merits of NPML boundary condition are certified by compared with wave field snapshots, signal and reflection errors of homogeneous medium model with split and non-split PML boundary conditions. The comparison demonstrated that the NPML algorithm can reduce memory occupation and improve calculation efficiency. Furthermore, numerical simulation of a complex model verifies the good absorption effects of the NPML boundary condition in complex structures.展开更多
Dear Editor,Although effective vaccines and antiviral therapies are available,hepatitis B virus(HBV)infection is still a serious global health threat.Persistent HBV infection remains the principal cause of liver cirrh...Dear Editor,Although effective vaccines and antiviral therapies are available,hepatitis B virus(HBV)infection is still a serious global health threat.Persistent HBV infection remains the principal cause of liver cirrhosis and hepatocellular carcinoma(HCC).HBV is a small DNA virus,owning a~3.2 kb genome that encodes several proteins:viral DNA polymerase,core antigen(HBcAg),E antigen(HBeAg),three surface antigens(PreS1/PreS2/HBsAg),and a regulatory X protein(HBx)(Lamontagne et al.,2016).X protein,named for its lack of homology with any known proteins,is a 154 aa protein that plays an essential role in HBV biology and regulates the development of HCC(Yang et al.,2022).Although previous studies have strongly expanded our understanding of HBx,the regulation of HBx is not completely elucidated.展开更多
A triple-objective optimal design method for AC filters in high voltage direct current(HVDC)system based on an improved multi-objective evolutionary algorithm based on decomposition(MOEA/D)is proposed.A triple-objecti...A triple-objective optimal design method for AC filters in high voltage direct current(HVDC)system based on an improved multi-objective evolutionary algorithm based on decomposition(MOEA/D)is proposed.A triple-objective optimisation mathematical model including total harmonic distortion(THD)on AC side voltage,investment cost of AC filters and telephone harmonic form factor(THFF)is established.An improved MOEA/D is proposed to realise the triple-objective optimal design for AC filters more efficiently.The improved MOEA/D adds a particular mutation operator,which can not only to prevent MOEA/D from getting stuck at local optimum but also accelerate the convergence to the optimum solution while the algorithm approaches the neighbourhood of the optimum solution.A three-dimensional fuzzy evaluation system is designed to select the optimum solution of the triple-objective optimisation.A case of±500 kV HVDC system is simulated.Taking the±500 kV HVDC system as the prototype system,a dynamic simulation experimental platform of the rectification system of the direct current transmission system with AC filters is designed and established based on the similarity principle.Both the simulation and experimental results verify that the proposed method have excellent performance.展开更多
文摘As a highly efficient absorbing boundary condition, Perfectly Matched Layer (PML) has been widely used in Finite Difference Time Domain (FDTD) simulation of Ground Penetrating Radar (GPR) based on the first order electromagnetic wave equation. However, the PML boundary condition is difficult to apply in GPR Finite Element Time Domain (FETD) simulation based on the second order electromagnetic wave equation. This paper developed a non-split perfectly matched layer (NPML) boundary condition for GPR FETD simulation based on the second order electromagnetic wave equation. Taking two-dimensional TM wave equation as an example, the second order frequency domain equation of GPR was derived according to the definition of complex extending coordinate transformation. Then it transformed into time domain by means of auxiliary differential equation method, and its FETD equation is derived based on Galerkin method. On this basis, a GPR FETD forward program based on NPML boundary condition is developed. The merits of NPML boundary condition are certified by compared with wave field snapshots, signal and reflection errors of homogeneous medium model with split and non-split PML boundary conditions. The comparison demonstrated that the NPML algorithm can reduce memory occupation and improve calculation efficiency. Furthermore, numerical simulation of a complex model verifies the good absorption effects of the NPML boundary condition in complex structures.
基金funded by the National Science and Technology Innovation 2030 Major Project of China(No.2021ZD0203900)the Ministry of Science and Technology of China(No.2019YFA0802103)+3 种基金the National Natural Science Foundation of China(No.92253302)the Department of Science and Technology of Zhejiang Province(No.2021C03104)the Guangzhou Science Innovation and Development Program(No.201803010092)athe Shenzhen-Hong Kong Institute of Brain Science(No.NYKFKT2019006).
文摘Dear Editor,Although effective vaccines and antiviral therapies are available,hepatitis B virus(HBV)infection is still a serious global health threat.Persistent HBV infection remains the principal cause of liver cirrhosis and hepatocellular carcinoma(HCC).HBV is a small DNA virus,owning a~3.2 kb genome that encodes several proteins:viral DNA polymerase,core antigen(HBcAg),E antigen(HBeAg),three surface antigens(PreS1/PreS2/HBsAg),and a regulatory X protein(HBx)(Lamontagne et al.,2016).X protein,named for its lack of homology with any known proteins,is a 154 aa protein that plays an essential role in HBV biology and regulates the development of HCC(Yang et al.,2022).Although previous studies have strongly expanded our understanding of HBx,the regulation of HBx is not completely elucidated.
文摘A triple-objective optimal design method for AC filters in high voltage direct current(HVDC)system based on an improved multi-objective evolutionary algorithm based on decomposition(MOEA/D)is proposed.A triple-objective optimisation mathematical model including total harmonic distortion(THD)on AC side voltage,investment cost of AC filters and telephone harmonic form factor(THFF)is established.An improved MOEA/D is proposed to realise the triple-objective optimal design for AC filters more efficiently.The improved MOEA/D adds a particular mutation operator,which can not only to prevent MOEA/D from getting stuck at local optimum but also accelerate the convergence to the optimum solution while the algorithm approaches the neighbourhood of the optimum solution.A three-dimensional fuzzy evaluation system is designed to select the optimum solution of the triple-objective optimisation.A case of±500 kV HVDC system is simulated.Taking the±500 kV HVDC system as the prototype system,a dynamic simulation experimental platform of the rectification system of the direct current transmission system with AC filters is designed and established based on the similarity principle.Both the simulation and experimental results verify that the proposed method have excellent performance.
