We studied the compressional wave event in Pc5 frequency range observed in the dawn-side magnetic equator on 9 March 1998 by Grad-Shafranov(GS) reconstruction method for the first time. To test the effectiveness of ap...We studied the compressional wave event in Pc5 frequency range observed in the dawn-side magnetic equator on 9 March 1998 by Grad-Shafranov(GS) reconstruction method for the first time. To test the effectiveness of application of GS method on Pc5 compressional wave, we benchmarked our procedure by applying it to a one-dimensional current sheet model first. Excluding the left-hand corners, the average error magnitude was less than 10%. The reconstruction of actual data showed that we obtained the 2-D map of compressional wave without suffering model constraints for the first time. The magnetic filed lines density cyclical changed, and the wavelength was about 2-4 times earth radius. The reconstructed magnetic topology had a shape very similar to the empirical 2-dimensional standing wave model proposed by the former workers. Besides, we also recovered the plasma thermal pressure and current density of the wave quantitatively.展开更多
Recent advances in molecular genetics techniques have made dense marker maps available, and the prediction of breeding value at the genome level has been employed in genetics research. However, an increasingly large n...Recent advances in molecular genetics techniques have made dense marker maps available, and the prediction of breeding value at the genome level has been employed in genetics research. However, an increasingly large number of markers raise both statistical and computational issues in genomic selection （GS）, and many methods have been developed for genomic prediction to address these problems, including ridge regression-best linear unbiased prediction （RR-BLUP）, genomic best linear unbiased prediction, BayesA, BayesB, BayesCπ, and Bayesian LASSO. In this paper, these methods were compared regarding inference under different conditions, using real data from a wheat data set and simulated scenarios with a small number of quantitative trait loci （QTL） （20）, a moderate number of QTL （60, 180） and an extreme number of QTL （540）. This study showed that the genetic architecture of a trait should be fully considered when a GS method is chosen. If a small amount of loci had a large effect on a trait, great differences were found between the predictive ability of various methods and BayesCπ was recommended. Although there was almost no significant difference between the predictive ability of BayesCπ andBayesB, BayesCπ is more feasible than BayesB for real data analysis. If a trait was controlled by a moderate number of genes, the absolute differences between the various methods were small, but BayesA was also found to be the most accurate method. Furthermore, BayesA was widely adaptable and could perform well with different numbers of QTL. If a trait was controlled by an extreme number of minor genes, almost no significant differences were detected between the predictive ability of various methods, but RR-BLUP slightly outperformed the others in both simulated scenarios and real data analysis, thus demonstrating its robustness and indicating that it was quite effective in this case.展开更多
We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations fo...We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations following the branches of the "academic family tree" rooted on Prof. Bengt U. ? Sonnerup, the inventor of the GS method. Special attentions are paid to validations of the GS reconstruction results via(1) the direct validation by co-spatial in-situ measurements among multiple spacecraft, and(2) indirect validation by implications and interpretations of the physical connection between the structures reconstructed and other related processes. For the latter, the inter-comparison and interconnection between the large-scale magnetic flux ropes(i.e., Magnetic Clouds) in the solar wind and their solar source properties are presented. In addition, we also summarize various GS-type(or-like) reconstruction and an extension of the GS technique to toroidal geometry. In particular,we point to a possible advancement with added complexity of "helical symmetry" and mixed helicity, in the hope of stimulating interest in future development. We close by offering some thoughts on appreciating the scientific merit of GS reconstruction in general.展开更多
Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference devi...Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently, the computational demands and the accuracy of sparse source reconstruction are improved simultaneously. The simulation results demonstrate that the FGS method is capable of reconstructing sparse equivalent current sources using the magnetic field data generated by a single current source with varying orientation or multiple current sources generated randomly. In addition, we analyze the cardiac current source reconstructed with real MCG data at typical instants and discuss the electrical excitation conduction during the QRS complex based on moving sparse source imaging.展开更多
文摘We studied the compressional wave event in Pc5 frequency range observed in the dawn-side magnetic equator on 9 March 1998 by Grad-Shafranov(GS) reconstruction method for the first time. To test the effectiveness of application of GS method on Pc5 compressional wave, we benchmarked our procedure by applying it to a one-dimensional current sheet model first. Excluding the left-hand corners, the average error magnitude was less than 10%. The reconstruction of actual data showed that we obtained the 2-D map of compressional wave without suffering model constraints for the first time. The magnetic filed lines density cyclical changed, and the wavelength was about 2-4 times earth radius. The reconstructed magnetic topology had a shape very similar to the empirical 2-dimensional standing wave model proposed by the former workers. Besides, we also recovered the plasma thermal pressure and current density of the wave quantitatively.
基金supported by the National Basic Research Program of China(2011CB100100)the Priority Academic Program Development of Jiangsu Higher Education Institutions+4 种基金the National Natural Science Foundations(31391632,31200943,and31171187)the National High-tech R&D Program(863 Program)(2014AA10A601-5)the Natural Science Foundations of Jiangsu Province(BK2012261)the Natural Science Foundation of the Jiangsu Higher Education Institutions(14KJA210005)the Innovative Research Team of Universities in Jiangsu Province
文摘Recent advances in molecular genetics techniques have made dense marker maps available, and the prediction of breeding value at the genome level has been employed in genetics research. However, an increasingly large number of markers raise both statistical and computational issues in genomic selection （GS）, and many methods have been developed for genomic prediction to address these problems, including ridge regression-best linear unbiased prediction （RR-BLUP）, genomic best linear unbiased prediction, BayesA, BayesB, BayesCπ, and Bayesian LASSO. In this paper, these methods were compared regarding inference under different conditions, using real data from a wheat data set and simulated scenarios with a small number of quantitative trait loci （QTL） （20）, a moderate number of QTL （60, 180） and an extreme number of QTL （540）. This study showed that the genetic architecture of a trait should be fully considered when a GS method is chosen. If a small amount of loci had a large effect on a trait, great differences were found between the predictive ability of various methods and BayesCπ was recommended. Although there was almost no significant difference between the predictive ability of BayesCπ andBayesB, BayesCπ is more feasible than BayesB for real data analysis. If a trait was controlled by a moderate number of genes, the absolute differences between the various methods were small, but BayesA was also found to be the most accurate method. Furthermore, BayesA was widely adaptable and could perform well with different numbers of QTL. If a trait was controlled by an extreme number of minor genes, almost no significant differences were detected between the predictive ability of various methods, but RR-BLUP slightly outperformed the others in both simulated scenarios and real data analysis, thus demonstrating its robustness and indicating that it was quite effective in this case.
基金supported by National Aeronautics and Space Administration (NASA) and National Science Foundation (NSF) (Grants Nos. AGS-1062050, NNG04GF47G, NNG06GD41G, NNX12AF97G, NNX12AH50G, NNH13ZDA001N, and NNX14AF41G)
文摘We review and summarize the applications of the Grad-Shafranov(GS) reconstruction technique to space plasma structures in the Earth's magnetosphere and in the interplanetary space. We organize our presentations following the branches of the "academic family tree" rooted on Prof. Bengt U. ? Sonnerup, the inventor of the GS method. Special attentions are paid to validations of the GS reconstruction results via(1) the direct validation by co-spatial in-situ measurements among multiple spacecraft, and(2) indirect validation by implications and interpretations of the physical connection between the structures reconstructed and other related processes. For the latter, the inter-comparison and interconnection between the large-scale magnetic flux ropes(i.e., Magnetic Clouds) in the solar wind and their solar source properties are presented. In addition, we also summarize various GS-type(or-like) reconstruction and an extension of the GS technique to toroidal geometry. In particular,we point to a possible advancement with added complexity of "helical symmetry" and mixed helicity, in the hope of stimulating interest in future development. We close by offering some thoughts on appreciating the scientific merit of GS reconstruction in general.
基金supported by the National Natural Science Foundation of China(60771030)the National HighTechnology Research and Development Program of China(2008AA02Z308)+2 种基金the Shanghai Science and Technology Development Foundation(08JC1421800)Shanghai Leading Academic Discipline Project(B004)the Open Project of State Key Laboratory of Function Materials for Information(Shanghai Institute of Microsystem and Information Technology,Chinese Academy of Sciences)
文摘Cardiac current source reconstruction is investigated by a fast greedy sparse(FGS) method applied to simulated and real magnetocardiography(MCG) data measured using 61-channel superconducting quantum interference device. The approach reduces the size of the lead field matrix based on a priori knowledge of dipolar magnetic field map. Consequently, the computational demands and the accuracy of sparse source reconstruction are improved simultaneously. The simulation results demonstrate that the FGS method is capable of reconstructing sparse equivalent current sources using the magnetic field data generated by a single current source with varying orientation or multiple current sources generated randomly. In addition, we analyze the cardiac current source reconstructed with real MCG data at typical instants and discuss the electrical excitation conduction during the QRS complex based on moving sparse source imaging.
