To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the c...To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.展开更多
Surface tension and filling ability of molten metal play an important role on the shaping of the molten metal. The surface tension was calculated from wetting angles of the molten metal by the sessile drop method. The...Surface tension and filling ability of molten metal play an important role on the shaping of the molten metal. The surface tension was calculated from wetting angles of the molten metal by the sessile drop method. The specimen for filling ability was designed and the filling ability experiments under the alternative electromagnetic field were performed. The results show that the intensity and frequency of the alternative electromagnetic field have significant effects on the surface tension of the molten metal. The surface tension of Al-6%Si alloy decreases with increasing the intensity of the electromagnetic field. For pure Sn, the surface tension decreases gradually when the frequency of electromagnetic field is reduced. The filling ability is improved by applying the alternative electromagnetic field.展开更多
With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are inve...With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.展开更多
In order to obtain cast metal of high quality, an investigation was carried out by simultaneous imposition of multi electromagnetic fields from the outside of a cold crucible copper mold. Sn 4.5%Pb as a simulator of h...In order to obtain cast metal of high quality, an investigation was carried out by simultaneous imposition of multi electromagnetic fields from the outside of a cold crucible copper mold. Sn 4.5%Pb as a simulator of high melting point metal was continuously cast under different conditions. The results show that multi electromagnetic fields can eliminate surface defects, and coarse columnar grains of the solidification structure is turned into equiaxed crystal with the increase of magnetic flux density. Moreover, finer equiaxed crystal structure is obtained when rapidly solidified sheet is fed into the mold during continuous casting.[展开更多
New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, mac...New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining.展开更多
Considering the Lagrangian density of the electromagnetic field, a 4 × 4 transformation matrix is found which can be used to include two of the symmetrized Maxwell’s equations as one of the Euler-Lagrange equati...Considering the Lagrangian density of the electromagnetic field, a 4 × 4 transformation matrix is found which can be used to include two of the symmetrized Maxwell’s equations as one of the Euler-Lagrange equations of the complete Lagrangian density. The 4 × 4 transformation matrix introduces newly defined vector products. In a Theorem the surface integral of one of the newly defined vector products is shown to be reduced to a line integral.展开更多
5182 Al alloy ingots with the diameters of 100 mm are produced by conventional and combined electromagnetic fields (CEMF) horizontal direction chill (HDC) cast- ing process. The effect of CEMF on the ingot surface...5182 Al alloy ingots with the diameters of 100 mm are produced by conventional and combined electromagnetic fields (CEMF) horizontal direction chill (HDC) cast- ing process. The effect of CEMF on the ingot surface quality and floating grains is investigated. The results show that the CEMF is effective in reducing the segregation layer in both top and bottom sub-surfaces. Big floating grains with coarse dendrite arms mainly distribute in the crescent-shaped area near the bottom in the conven- tional HDC casting ingot. With the application of the CEMF, they disappear in the whole cross section of the HDC casting ingot and the equiaxed grains are significantly refined.展开更多
The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on ...The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on the surface quality of billet. However, few public reports on the surface quality of LFEC magnesium billets could be found. Therefore, a new crystallizer with a metal internal sleeve to-gether with a kind of lubricant was designed aiming at lowing surface turning quantity, and the effects of casting velocity, electromagnetic condition and lubrication on the surface quality of magnesium billets were investigated. The results indicate that LFEF together with the lubricate condition would be responsible for the surface quality of the billets, and the high surface quality billets could be achieved by optimizing the casting conditions.展开更多
The combination of electromagnetic field is applied in the Horizontal Direct Chill(HDC)casting process to produce 3004 aluminum alloy ingot.The effect of combination of electromagnetic field on the ingot surface quali...The combination of electromagnetic field is applied in the Horizontal Direct Chill(HDC)casting process to produce 3004 aluminum alloy ingot.The effect of combination of electromagnetic field on the ingot surface quality and inner structure was investigated by macro and micro-structure observation.The results show that the combination of electromagnetic field can improve the ingot surface quality and inner structure effectively.The thickness of segregation layer decreased with the application of combination of electromagnetic field.In addition,the combination of electromagnetic field can effectively improve the as-casting structure.Under the function of combination of electromagnetic field,coarse columnar grains transfer to fine equiaxed grains.展开更多
A coordinated physicomathematical model for the propagation of a soliton-like electromagnetic pulse in a heterogeneous medium is developed in the presence of strong discontinuities in the electromagnetic field. The mo...A coordinated physicomathematical model for the propagation of a soliton-like electromagnetic pulse in a heterogeneous medium is developed in the presence of strong discontinuities in the electromagnetic field. The model is based on the reduction of Maxwell’s equations to the well-studied wave equation. When the electromagnetic pulse was specified, its amplitude modulation was taken into account, as was the nonstationary broadening of the spectral line. Conditions for matching the momentum for the first initial boundary-value problem are obtained. The time dispersion of the electrical induction is taken into account in terms of the function of signal conditioning which takes account of the broadening of its spectral line and integration over the continuous spectrum. With this approach, it is not necessary to neglect spatial derivatives, and also to use spatial nonlocal relations to take account of the effect of surface charge, surface current, and spatial dispersion of electrical induction at the interfaces of adjacent media.展开更多
We describe the synthesis of three-dimensional(3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico–chemical method. The surface-enhanced Raman scattering(SERS) performance of the 3D multilayer Zn O@Ag/SiO2@Ag...We describe the synthesis of three-dimensional(3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico–chemical method. The surface-enhanced Raman scattering(SERS) performance of the 3D multilayer Zn O@Ag/SiO2@Ag nanorod arrays is studied by varying the thickness of dielectric layer SiO2 and outer-layer noble Ag. The 3D Zn O@Ag/SiO2@Ag nanorod arrays create a huge number of SERS "hot spots" that mainly contribute to the high SERS sensitivity. The great enhancement of SERS results from the electron transfer between ZnO and Ag and different electromagnetic enhancements of Ag nanoparticles(NPs) with different thicknesses. Through the finite-difference time-domain(FDTD) theoretical simulation, the enhancement of SERS signal can be ascribed to a strong electric field enhancement produced in the 3D framework. The simplicity and generality of our method offer great advantages for further understanding the SERS mechanism induced by the surface plasmon resonance(SPR) effect.展开更多
The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface tempera...The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface temperature(LST)retrieval and environmental monitoring.Before data application,quality assessment is an essential procedure for a new instrument.In this paper,based on the data collected by the scanner near the Yellow River in Henan Province,the geometric and radiometric qualities of the images are first evaluated.The absolute geolocation accuracy of the ten bands of the scanner is approximately 5.1 m.The ground sampling distance is found to be varied with the whisk angles of the scanner and the spatial resolution of the images.The band-to-band registration accuracy between band one and the other nine bands is approximately 0.25 m.The length and angle deformations of the ten bands are approximately 0.67%and 0.3°,respectively.The signal-to-noise ratio(SNR)and relative radiometric calibration accuracy of bands 4,9,and 10 are relatively better than those of the other bands.Secondly,the radiative transfer equation(RTE)method is used to retrieve the LST from the data of the scanner.Measurements of in situ samples are collected to evaluate the retrieved LST.Neglecting the samples with unreasonable retrieved LST,the bias and RMSE between in situ LST measured by CE312 radiometer and retrieved LST are−0.22 K and 0.94 K,and the bias and RMSE are 0.27 K and 1.59 K for the InfReC R500-D thermal imager,respectively.Overall,the images of the Large Field of View Airborne Infrared Scanner yield a relatively satisfactory accuracy for both LST retrieval and geometric and radiometric qualities.展开更多
Contacting state between molten metal and a mold and initial solidification process of continuously cast metals can be controlled by imposing an intermittent magnetic field.In this study, effect of the intermittent ma...Contacting state between molten metal and a mold and initial solidification process of continuously cast metals can be controlled by imposing an intermittent magnetic field.In this study, effect of the intermittent magnetic field on the initial solidification ofcontinuoasly cast metals was investigated by measuring the temperature distribution in the melt pool and the initial solidification starting position of shells. It was found that under the condition with intermittent magnetic field, the melt near meniscns is in slow cooling state, the initial solidification starting position descends, initial solidification shell thickens and the liquid-solid interface becomes smooth.展开更多
The influences of the cooling style and static magnetic field on the air film casting process were investigated. Ingots of 6063 aluminum alloy were produced by AIRSOL VEIL casting with double-layer cooling water and s...The influences of the cooling style and static magnetic field on the air film casting process were investigated. Ingots of 6063 aluminum alloy were produced by AIRSOL VEIL casting with double-layer cooling water and static magnetic field. Surface segregation, hot crack and variation of solute content along the radius direction of ingot were examined. The results showed that double-layer cooling water can improve the surface quality and avoid of hot crack, which created conditions to increase the casting speed. The electromagnetic casting process can effectively improve the surface quality in high speed casting process, and static magnetic field has a great influence on solute distribution along the radius direction of ingot.展开更多
基金supported by the Major State Basic Research and Development Project of China (No.2005CB623707)the Innovative Research Team Project of Northeastern University (No.N090109001)
文摘To improve the quality of 7050 aluminum alloy ingots, low-frequency electromagnetic (LFE) field was applied during the conventional hot-top casting process. Macrostructures and microstructures of the ingots by the conventional and LFE hot-top casting processes were studied. The experimental results show that when the LFE field is turn off during the hot-top casting process, cold folding appears, and the as-cast structure becomes very coarse. Additionally, the thickness of the shell zone is much thinner during the low-frequency electromagnetic hot-top casting process than that during the conventional hot-top casting process. Some reasons for low-frequency electromagnetic field improving the surface quality, refining the structure of the ingot, and minimizing the thickness of the shell zone have been studied.
文摘Surface tension and filling ability of molten metal play an important role on the shaping of the molten metal. The surface tension was calculated from wetting angles of the molten metal by the sessile drop method. The specimen for filling ability was designed and the filling ability experiments under the alternative electromagnetic field were performed. The results show that the intensity and frequency of the alternative electromagnetic field have significant effects on the surface tension of the molten metal. The surface tension of Al-6%Si alloy decreases with increasing the intensity of the electromagnetic field. For pure Sn, the surface tension decreases gradually when the frequency of electromagnetic field is reduced. The filling ability is improved by applying the alternative electromagnetic field.
基金Project supported by the Science Foundation of Shanghai Municipal Commission of Education (Grant No.04AB30)
文摘With the air gap magnetic field distribution of surface mounted permanent magnet (PM) motors obtained using an analytical technique, the instantaneous electromagnetic torque and its corresponding components are investigated with the Maxwell stress tensor method. Accurate results can easily be achieved using the proposed method without using the tedious finite element analysis (FEA). In this paper, the electromagnetic torque of a surface mounted PM motor with two phases energized is decomposed into four torque components. This technique is useful not only for the design and optimization of the permanent magnet motor, but also for the choice of control strategy.
文摘In order to obtain cast metal of high quality, an investigation was carried out by simultaneous imposition of multi electromagnetic fields from the outside of a cold crucible copper mold. Sn 4.5%Pb as a simulator of high melting point metal was continuously cast under different conditions. The results show that multi electromagnetic fields can eliminate surface defects, and coarse columnar grains of the solidification structure is turned into equiaxed crystal with the increase of magnetic flux density. Moreover, finer equiaxed crystal structure is obtained when rapidly solidified sheet is fed into the mold during continuous casting.[
文摘New theories and technology in the electromagnetic field were put forward about DC casting of Al alloys, including the fundamental research works, i.e, effects of the electromagnetic field on solidus and liquidus, macrosegregation of the main alloying elements, microstructures, content of alloying elements in grains and grain size after solidification under electromagnetic field, and also including a new process DC casting under low frequency electromagnetic field(LFEMC), which can refine microstructure, eliminate macrosegregation, increase the content of alloying elements within grains, decrease the residual stress, avoid cracks and improve surface quality, and another new process DC casting under low frequency electromagnetic vibration(LFEVC), which is a high effective method for grain refining.
文摘Considering the Lagrangian density of the electromagnetic field, a 4 × 4 transformation matrix is found which can be used to include two of the symmetrized Maxwell’s equations as one of the Euler-Lagrange equations of the complete Lagrangian density. The 4 × 4 transformation matrix introduces newly defined vector products. In a Theorem the surface integral of one of the newly defined vector products is shown to be reduced to a line integral.
基金supported by the National Natural Science Foundation of China(Nos.51204053 and 51074048)Research Fund for the Doctoral Program of Higher Education of China(No.20090042120001)+2 种基金Central University Basic R&D Operating Expenses(No.N100409006)China Postdoctoral Science Foundation(No.20110491518)National Basic Research Program of China(973Program)(No.2012CB619506)
文摘5182 Al alloy ingots with the diameters of 100 mm are produced by conventional and combined electromagnetic fields (CEMF) horizontal direction chill (HDC) cast- ing process. The effect of CEMF on the ingot surface quality and floating grains is investigated. The results show that the CEMF is effective in reducing the segregation layer in both top and bottom sub-surfaces. Big floating grains with coarse dendrite arms mainly distribute in the crescent-shaped area near the bottom in the conven- tional HDC casting ingot. With the application of the CEMF, they disappear in the whole cross section of the HDC casting ingot and the equiaxed grains are significantly refined.
基金Supported by the 11th Five-Year Plan of China (Grant No. 2006BAE04B01-5)the National Basic Research Program of China ("973") (Grant No. 2007CB613702)
文摘The microstructures of the magnesium billets could be improved markedly by low-frequency electro-magnetic casting (LFEC) processing. In fact, the low-frequency electromagnetic field (LFEF) also has favorite effect on the surface quality of billet. However, few public reports on the surface quality of LFEC magnesium billets could be found. Therefore, a new crystallizer with a metal internal sleeve to-gether with a kind of lubricant was designed aiming at lowing surface turning quantity, and the effects of casting velocity, electromagnetic condition and lubrication on the surface quality of magnesium billets were investigated. The results indicate that LFEF together with the lubricate condition would be responsible for the surface quality of the billets, and the high surface quality billets could be achieved by optimizing the casting conditions.
基金Item Sponsored by Natural Science Foundation (5107404) the Ministry of Education New Teachers Fund Project (20090042120001) +1 种基金Central University Basic R&D Operating Expenses (N100409006) China Postdoctoral Science Foundation (20110491518)
文摘The combination of electromagnetic field is applied in the Horizontal Direct Chill(HDC)casting process to produce 3004 aluminum alloy ingot.The effect of combination of electromagnetic field on the ingot surface quality and inner structure was investigated by macro and micro-structure observation.The results show that the combination of electromagnetic field can improve the ingot surface quality and inner structure effectively.The thickness of segregation layer decreased with the application of combination of electromagnetic field.In addition,the combination of electromagnetic field can effectively improve the as-casting structure.Under the function of combination of electromagnetic field,coarse columnar grains transfer to fine equiaxed grains.
文摘A coordinated physicomathematical model for the propagation of a soliton-like electromagnetic pulse in a heterogeneous medium is developed in the presence of strong discontinuities in the electromagnetic field. The model is based on the reduction of Maxwell’s equations to the well-studied wave equation. When the electromagnetic pulse was specified, its amplitude modulation was taken into account, as was the nonstationary broadening of the spectral line. Conditions for matching the momentum for the first initial boundary-value problem are obtained. The time dispersion of the electrical induction is taken into account in terms of the function of signal conditioning which takes account of the broadening of its spectral line and integration over the continuous spectrum. With this approach, it is not necessary to neglect spatial derivatives, and also to use spatial nonlocal relations to take account of the effect of surface charge, surface current, and spatial dispersion of electrical induction at the interfaces of adjacent media.
基金This work was financially supported by the National Natural Science Foundation of China (NSFC) (61675169, 61377055 and 11634010), the National Key R&D Program of China (2017YFA0303800), and the Fundamental Research Funds for the Central Universities (3102017zy021, 3102017HQZZ 022).
基金Project supported by the Fund from the Science and Technology Department of Jilin Province,China(Grant No.20170520108JH)the Beihua University Youth Nurtural Fund,China(Grant No.2017QNJJL15)+1 种基金the Beihua University PhD Research Start-up Fund,China(Grant No.202116140)the Undergraduate Innovation Project,China(Grant No.220718100)
文摘We describe the synthesis of three-dimensional(3D) multilayer ZnO@Ag/SiO2@Ag nanorod arrays by the physico–chemical method. The surface-enhanced Raman scattering(SERS) performance of the 3D multilayer Zn O@Ag/SiO2@Ag nanorod arrays is studied by varying the thickness of dielectric layer SiO2 and outer-layer noble Ag. The 3D Zn O@Ag/SiO2@Ag nanorod arrays create a huge number of SERS "hot spots" that mainly contribute to the high SERS sensitivity. The great enhancement of SERS results from the electron transfer between ZnO and Ag and different electromagnetic enhancements of Ag nanoparticles(NPs) with different thicknesses. Through the finite-difference time-domain(FDTD) theoretical simulation, the enhancement of SERS signal can be ascribed to a strong electric field enhancement produced in the 3D framework. The simplicity and generality of our method offer great advantages for further understanding the SERS mechanism induced by the surface plasmon resonance(SPR) effect.
基金supported by the National Natural Science Foundation of China(Grant Nos.42171363,41804166,and 41971299)High-Resolution Earth Observation Major Special Aviation Observation System(No.30-H30C01-9004-19/21)+1 种基金the Shanghai Municipal Science and Technology Major Project(No.2021SHZDZX0100)the Shanghai Municipal Commission of Science and Technology Project(No.19511132101).
文摘The Large Field of View Airborne Infrared Scanner is a newly developed multi-spectral instrument that collects images from the near-infrared to long-wave infrared channels.Its data can be used for land surface temperature(LST)retrieval and environmental monitoring.Before data application,quality assessment is an essential procedure for a new instrument.In this paper,based on the data collected by the scanner near the Yellow River in Henan Province,the geometric and radiometric qualities of the images are first evaluated.The absolute geolocation accuracy of the ten bands of the scanner is approximately 5.1 m.The ground sampling distance is found to be varied with the whisk angles of the scanner and the spatial resolution of the images.The band-to-band registration accuracy between band one and the other nine bands is approximately 0.25 m.The length and angle deformations of the ten bands are approximately 0.67%and 0.3°,respectively.The signal-to-noise ratio(SNR)and relative radiometric calibration accuracy of bands 4,9,and 10 are relatively better than those of the other bands.Secondly,the radiative transfer equation(RTE)method is used to retrieve the LST from the data of the scanner.Measurements of in situ samples are collected to evaluate the retrieved LST.Neglecting the samples with unreasonable retrieved LST,the bias and RMSE between in situ LST measured by CE312 radiometer and retrieved LST are−0.22 K and 0.94 K,and the bias and RMSE are 0.27 K and 1.59 K for the InfReC R500-D thermal imager,respectively.Overall,the images of the Large Field of View Airborne Infrared Scanner yield a relatively satisfactory accuracy for both LST retrieval and geometric and radiometric qualities.
文摘Contacting state between molten metal and a mold and initial solidification process of continuously cast metals can be controlled by imposing an intermittent magnetic field.In this study, effect of the intermittent magnetic field on the initial solidification ofcontinuoasly cast metals was investigated by measuring the temperature distribution in the melt pool and the initial solidification starting position of shells. It was found that under the condition with intermittent magnetic field, the melt near meniscns is in slow cooling state, the initial solidification starting position descends, initial solidification shell thickens and the liquid-solid interface becomes smooth.
基金supported by the Key Fundamental Research Program of China (No.2005CB623707)the Project for Talents Cultivation Fund (No.704015)
文摘The influences of the cooling style and static magnetic field on the air film casting process were investigated. Ingots of 6063 aluminum alloy were produced by AIRSOL VEIL casting with double-layer cooling water and static magnetic field. Surface segregation, hot crack and variation of solute content along the radius direction of ingot were examined. The results showed that double-layer cooling water can improve the surface quality and avoid of hot crack, which created conditions to increase the casting speed. The electromagnetic casting process can effectively improve the surface quality in high speed casting process, and static magnetic field has a great influence on solute distribution along the radius direction of ingot.