Modern warfare demands weapons capable of penetrating substantial structures,which presents sig-nificant challenges to the reliability of the electronic devices that are crucial to the weapon's perfor-mance.Due to...Modern warfare demands weapons capable of penetrating substantial structures,which presents sig-nificant challenges to the reliability of the electronic devices that are crucial to the weapon's perfor-mance.Due to miniaturization of electronic components,it is challenging to directly measure or numerically predict the mechanical response of small-sized critical interconnections in board-level packaging structures to ensure the mechanical reliability of electronic devices in projectiles under harsh working conditions.To address this issue,an indirect measurement method using the Bayesian regularization-based load identification was proposed in this study based on finite element(FE)pre-dictions to estimate the load applied on critical interconnections of board-level packaging structures during the process of projectile penetration.For predicting the high-strain-rate penetration process,an FE model was established with elasto-plastic constitutive models of the representative packaging ma-terials(that is,solder material and epoxy molding compound)in which material constitutive parameters were calibrated against the experimental results by using the split-Hopkinson pressure bar.As the impact-induced dynamic bending of the printed circuit board resulted in an alternating tensile-compressive loading on the solder joints during penetration,the corner solder joints in the edge re-gions experience the highest S11 and strain,making them more prone to failure.Based on FE predictions at different structural scales,an improved Bayesian method based on augmented Tikhonov regulariza-tion was theoretically proposed to address the issues of ill-posed matrix inversion and noise sensitivity in the load identification at the critical solder joints.By incorporating a wavelet thresholding technique,the method resolves the problem of poor load identification accuracy at high noise levels.The proposed method achieves satisfactorily small relative errors and high correlation coefficients in identifying the mechanical response of local interconnections in board-level packaging structures,while significantly balancing the smoothness of response curves with the accuracy of peak identification.At medium and low noise levels,the relative error is less than 6%,while it is less than 10%at high noise levels.The proposed method provides an effective indirect approach for the boundary conditions of localized solder joints during the projectile penetration process,and its philosophy can be readily extended to other scenarios of multiscale analysis for highly nonlinear materials and structures under extreme loading conditions.展开更多
A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method a...A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.展开更多
The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in t...The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in the central Nepal,we discovered exotic thrust packages of the Middle Proterozoic rocks,which has been regarded as the Siwalik Group or post\|collisional sediments correlatable with the Subathu or Murree Formation in India.The thrust belt,called the Bagmati Belt,is narrowly distributed in the Siwalik Belt,22km to the north of the Main Frontal Thrust (MFT or HFF) that is an active fault and considered to be the deformation front of the Himalayan orogen.The Main Boundary Thrust (MBT) which separates the Siwalik Belt from the Lesser Himalayan Belt runs 7km to the north of the thrust packages.Within the belt,tectonic slices of 400m to 1km in thickness are repeated three to five times due to thrusts,sandwiching a thin slice of the Siwalik beds.The thrust package consists of the pre\|Siwalik sedimetary rocks and sills of dolerite,and named as the Bagmati Group.The thickness is only about 800m due to tectonic repition by thrust,although the group has been considered to be a continuous sequence attaining 2200m in thickness.We divided the Bagmati Group into three formations,each of which shows an upward\|coarsening and thickening sequence of 200 to 350m in thickness.All sequence is composed of red\|brown orthoquartzite,pink quartzite,micaceous shale and thin sandstone interbed and rhythmite,mottled hematite and hematitic pisolite.We interpret that the Bagmati Group was deposited in shallow lacustrine and desert environments.展开更多
The magnetic resonance spectroscopy(MRS)results are greatly influenced by reconstruction of the spectrum and quantitative analysis.Because of this requirement a number of programs dedicated to MRS data analysis were d...The magnetic resonance spectroscopy(MRS)results are greatly influenced by reconstruction of the spectrum and quantitative analysis.Because of this requirement a number of programs dedicated to MRS data analysis were developed.The selection and use of appropriate software is crucial not only in clinical procedures,but also while carrying out scientific research.The choice of the software to suit the user's needs should be based on the analysis of the functionality of the program.It is particularly important from the user's viewpoint to identify what data can be loaded and processed in the program.The specific programs allow the user different degree of control over analysis parameters.Moreover,the programs for MRS data analysis differ in terms of the applied signal processing algorithms.The aim of this work,therefore,is to review available packages designed for MRS data analysis,taking into account their capabilities and limitations.展开更多
Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed...Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed into the product of block bidiagonal triangular matrix and its transpose by means of Cholesky decomposition. Then an algorithm for solving systems of block bidiagonal triangular linear equations was given, which is not necessary to treat with the zero elements out of banded systems. A fast algorithm for solving the systems of symmetry block tridiagonal linear equations was deduced, which can quicken the speed of ray-tracing. Finally, the simulation based on this algorithm for ray-tracing in three dimensional media was carried out. Meanwhile, the segmentally-iterative ray-tracing method and banded method for solving the systems of block tridiagonal linear equations were compared in the same model mentioned above. The convergence condition was assumed that the L-2 norm summation for mk, 1 and mk. 2 in the whole ray path was limited in 10-6. And the calculating speeds of these methods were compared. The results show that the calculating speed of this algorithm is faster than that of conventional method and the calculated results are accurate enough. In addition, its precision can be controlled according to the requirement of ray-tracing.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52475166,52175148)the Regional Collaboration Project of Shanxi Province(Grant No.202204041101044).
文摘Modern warfare demands weapons capable of penetrating substantial structures,which presents sig-nificant challenges to the reliability of the electronic devices that are crucial to the weapon's perfor-mance.Due to miniaturization of electronic components,it is challenging to directly measure or numerically predict the mechanical response of small-sized critical interconnections in board-level packaging structures to ensure the mechanical reliability of electronic devices in projectiles under harsh working conditions.To address this issue,an indirect measurement method using the Bayesian regularization-based load identification was proposed in this study based on finite element(FE)pre-dictions to estimate the load applied on critical interconnections of board-level packaging structures during the process of projectile penetration.For predicting the high-strain-rate penetration process,an FE model was established with elasto-plastic constitutive models of the representative packaging ma-terials(that is,solder material and epoxy molding compound)in which material constitutive parameters were calibrated against the experimental results by using the split-Hopkinson pressure bar.As the impact-induced dynamic bending of the printed circuit board resulted in an alternating tensile-compressive loading on the solder joints during penetration,the corner solder joints in the edge re-gions experience the highest S11 and strain,making them more prone to failure.Based on FE predictions at different structural scales,an improved Bayesian method based on augmented Tikhonov regulariza-tion was theoretically proposed to address the issues of ill-posed matrix inversion and noise sensitivity in the load identification at the critical solder joints.By incorporating a wavelet thresholding technique,the method resolves the problem of poor load identification accuracy at high noise levels.The proposed method achieves satisfactorily small relative errors and high correlation coefficients in identifying the mechanical response of local interconnections in board-level packaging structures,while significantly balancing the smoothness of response curves with the accuracy of peak identification.At medium and low noise levels,the relative error is less than 6%,while it is less than 10%at high noise levels.The proposed method provides an effective indirect approach for the boundary conditions of localized solder joints during the projectile penetration process,and its philosophy can be readily extended to other scenarios of multiscale analysis for highly nonlinear materials and structures under extreme loading conditions.
文摘A new seismic ray-tracing method is put forward based on parabolic travel-time interpolation(PTI) method, which is more accurate than the linear travel-time interpolation (LTI) method. Both PTI method and LTI method are used to compute seismic travel-time and ray-path in a 2-D grid cell model. Firstly, some basic concepts are introduced. The calculations of travel-time and ray-path are carried out only at cell boundaries. So, the ray-path is always straight in the same cells with uniform velocity. Two steps are applied in PTI and LTI method, step 1 computes travel-time and step 2 traces ray-path. Then, the derivation of LTI formulas is described. Because of the presence of refraction wave in shot cell, the formula aiming at shot cell is also derived. Finally, PTI method is presented. The calculation of PTI method is more complex than that of LTI method, but the error is limited. The results of numerical model show that PTI method can trace ray-path more accurately and efficiently than LTI method does.
文摘The Siwalik Belt is a frontal fold\|thrust belt of the Himalayas and composed of thick sequence of foreland basin sediments derived from the Himalayas during the last 15 to 17 million years.From this Miocene belt in the central Nepal,we discovered exotic thrust packages of the Middle Proterozoic rocks,which has been regarded as the Siwalik Group or post\|collisional sediments correlatable with the Subathu or Murree Formation in India.The thrust belt,called the Bagmati Belt,is narrowly distributed in the Siwalik Belt,22km to the north of the Main Frontal Thrust (MFT or HFF) that is an active fault and considered to be the deformation front of the Himalayan orogen.The Main Boundary Thrust (MBT) which separates the Siwalik Belt from the Lesser Himalayan Belt runs 7km to the north of the thrust packages.Within the belt,tectonic slices of 400m to 1km in thickness are repeated three to five times due to thrusts,sandwiching a thin slice of the Siwalik beds.The thrust package consists of the pre\|Siwalik sedimetary rocks and sills of dolerite,and named as the Bagmati Group.The thickness is only about 800m due to tectonic repition by thrust,although the group has been considered to be a continuous sequence attaining 2200m in thickness.We divided the Bagmati Group into three formations,each of which shows an upward\|coarsening and thickening sequence of 200 to 350m in thickness.All sequence is composed of red\|brown orthoquartzite,pink quartzite,micaceous shale and thin sandstone interbed and rhythmite,mottled hematite and hematitic pisolite.We interpret that the Bagmati Group was deposited in shallow lacustrine and desert environments.
文摘The magnetic resonance spectroscopy(MRS)results are greatly influenced by reconstruction of the spectrum and quantitative analysis.Because of this requirement a number of programs dedicated to MRS data analysis were developed.The selection and use of appropriate software is crucial not only in clinical procedures,but also while carrying out scientific research.The choice of the software to suit the user's needs should be based on the analysis of the functionality of the program.It is particularly important from the user's viewpoint to identify what data can be loaded and processed in the program.The specific programs allow the user different degree of control over analysis parameters.Moreover,the programs for MRS data analysis differ in terms of the applied signal processing algorithms.The aim of this work,therefore,is to review available packages designed for MRS data analysis,taking into account their capabilities and limitations.
基金Project(40674071) supported by the National Natural Science Foundation of ChinaProject(KFAS2002-2003) supported by the Korea Foundation for Advanced Studies
文摘Beginning with the method of whole path iterative ray-tracing and according to the positive definiteness of the coefficient matrix of the systems of linear equations, a symmetry olock tridiagonal matrix was decomposed into the product of block bidiagonal triangular matrix and its transpose by means of Cholesky decomposition. Then an algorithm for solving systems of block bidiagonal triangular linear equations was given, which is not necessary to treat with the zero elements out of banded systems. A fast algorithm for solving the systems of symmetry block tridiagonal linear equations was deduced, which can quicken the speed of ray-tracing. Finally, the simulation based on this algorithm for ray-tracing in three dimensional media was carried out. Meanwhile, the segmentally-iterative ray-tracing method and banded method for solving the systems of block tridiagonal linear equations were compared in the same model mentioned above. The convergence condition was assumed that the L-2 norm summation for mk, 1 and mk. 2 in the whole ray path was limited in 10-6. And the calculating speeds of these methods were compared. The results show that the calculating speed of this algorithm is faster than that of conventional method and the calculated results are accurate enough. In addition, its precision can be controlled according to the requirement of ray-tracing.
