The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time （ t ） using microwave electromagnetic parameters analysis techniques. The results show that the ...The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time （ t ） using microwave electromagnetic parameters analysis techniques. The results show that the imaginary part of intrinsic dynamic permeability （ ui ） of the ball- milled panicles is much bigger than that of raw powders. ui strongly depends on t and exhibits several slightly damped ferromagnetic resonances. These phenomena are in qualitative agreement with the formation of the corresponding microstructure or the Aharoni ＇ s model of non-uniform exchange resonance modes. The present microwave permeabilhy behavior indicates that nanocrystalline materials with the same grain size may exhibit different properties that depend upon the microstructure, which provides a possibility for manufacturing high performance microwave absorber.展开更多
Microwave remote sensing has become the primary means for sea-ice research, and has been supported by a great deal of field experiments and theoretical studies regarding sea-ice microwave scattering. However, these st...Microwave remote sensing has become the primary means for sea-ice research, and has been supported by a great deal of field experiments and theoretical studies regarding sea-ice microwave scattering. However, these studies have been barely carried in the Bohai Sea. The sea-ice microwave scattering mechanism was first developed for the thin sea ice with slight roughness in the Bohai Sea in the winter of 2012, and included the backscattering coefficients which were measured on the different conditions of three bands（L, C and X）, two polarizations（HH and VV）, and incident angles of 20° to 60°, using a ground-based scatterometer and the synchronous physical parameters of the sea-ice temperature, density, thickness, salinity, and so on. The theoretical model of the sea-ice electromagnetic scattering is obtained based on these physical parameters. The research regarding the sea-ice microwave scattering mechanism is carried out through two means, which includes the comparison between the field microwave scattering data and the simulation results of the theoretical model, as well as the feature analysis of the four components of the sea-ice electromagnetic scattering. It is revealed that the sea-ice microwave scattering data and the theoretical simulation results vary in the same trend with the incident angles. Also, there is a visible variant in the sensitivity of every component to the different bands.For example, the C and X bands are sensitive to the top surface, the X band is sensitive to the scatterers, and the L and C bands are sensitive to the bottom surface, and so on. It is suggested that the features of the sea-ice surfaces and scatterers can be retrieved by the further research in the future. This experiment can provide an experimental and theoretical foundation for research regarding the sea-ice microwave scattering characteristics in the Bohai Sea.展开更多
基金Funded by the 863 High Technology Research Project ( No.2001AA339020 and 2002AA305302) fromthe Ministry of Scienceand Technology of China , and the Excellent Young Teachers Pro-gramof MOE(2002[350]) ,China
文摘The microwave magnetic properties of the ball milled FeCo panicles were investigated as functions of ball milling time （ t ） using microwave electromagnetic parameters analysis techniques. The results show that the imaginary part of intrinsic dynamic permeability （ ui ） of the ball- milled panicles is much bigger than that of raw powders. ui strongly depends on t and exhibits several slightly damped ferromagnetic resonances. These phenomena are in qualitative agreement with the formation of the corresponding microstructure or the Aharoni ＇ s model of non-uniform exchange resonance modes. The present microwave permeabilhy behavior indicates that nanocrystalline materials with the same grain size may exhibit different properties that depend upon the microstructure, which provides a possibility for manufacturing high performance microwave absorber.
基金The National Science Foundation for Young Scientists of China under contract No.41306193the National Special Research Fund for Non-Profit Marine Sector under of China under contract No.201105016the European Space Agency-Ministry of Science and Technology of the People’s Republic of China(ESA-MOST)Dragon 3 Cooperation Programme under contract No.10501
文摘Microwave remote sensing has become the primary means for sea-ice research, and has been supported by a great deal of field experiments and theoretical studies regarding sea-ice microwave scattering. However, these studies have been barely carried in the Bohai Sea. The sea-ice microwave scattering mechanism was first developed for the thin sea ice with slight roughness in the Bohai Sea in the winter of 2012, and included the backscattering coefficients which were measured on the different conditions of three bands（L, C and X）, two polarizations（HH and VV）, and incident angles of 20° to 60°, using a ground-based scatterometer and the synchronous physical parameters of the sea-ice temperature, density, thickness, salinity, and so on. The theoretical model of the sea-ice electromagnetic scattering is obtained based on these physical parameters. The research regarding the sea-ice microwave scattering mechanism is carried out through two means, which includes the comparison between the field microwave scattering data and the simulation results of the theoretical model, as well as the feature analysis of the four components of the sea-ice electromagnetic scattering. It is revealed that the sea-ice microwave scattering data and the theoretical simulation results vary in the same trend with the incident angles. Also, there is a visible variant in the sensitivity of every component to the different bands.For example, the C and X bands are sensitive to the top surface, the X band is sensitive to the scatterers, and the L and C bands are sensitive to the bottom surface, and so on. It is suggested that the features of the sea-ice surfaces and scatterers can be retrieved by the further research in the future. This experiment can provide an experimental and theoretical foundation for research regarding the sea-ice microwave scattering characteristics in the Bohai Sea.
