Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by...Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.展开更多
The phase behavior of a monolayer of dipolar hard spheres under an external field, which makes all dipoles of the monolayer orientate along its direction, is investigated. Using integral equation theory in the referen...The phase behavior of a monolayer of dipolar hard spheres under an external field, which makes all dipoles of the monolayer orientate along its direction, is investigated. Using integral equation theory in the reference hypemetted chain （RHNC） approximation we calculate the correlation functions, which are used to obtain the response matrix of grand potential with respect to density fluctuations. The smallest eigenvalue of this response matrix determines the stability of the monolayer. When the smallest eigenvalue approaches zero, the monolayer becomes unstable and the corresponding eigenvector characterizes this instability. At dilute densities, with decreasing temperature the dipoles of the monolayer begin to form chains and simultaneously condensate. At medium and high densities, however, the dipoles of the monolayer have a stronger tendency to form dipolar chains with decreasing temperature and there is no condensation. The part of specific heat related to potential energy is investigated and found to increase sharply near the temperature of dipolar chain formation. This is in accordance with a sharp decrease in potential energy induced by the formation of a dipolar chain.展开更多
The SMM properties of the spatially closed Dy（Ⅲ） double-decker Pc complex Dy（obPc）2 （1）, which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal latti...The SMM properties of the spatially closed Dy（Ⅲ） double-decker Pc complex Dy（obPc）2 （1）, which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal lattice in the monoclinic space group P22/n and was isomorphous with Tb（obPc）2 （3）, which is arranged in a dimer structure along the b axis. The intermetallic Dy-Dy distance was determined to be 0.756 nm. ZMT versus T plots for 1 decreased with a decrease in T, which suggests the existence of an antiferromagnetic （AF） interaction between the Dy3＋ ions. The M-H curve for 1 at 1.8 K showed magnetic hysteresis. In ac susceptibility measurements on a powder sample of 1, which were dependent on the applied ac field, indicating that 1 is an single molecule magnet （SMM）, a maximum appeared at 22 K at an ac frequency 09 of 1488 Hz. The shape of the peaks dras- tically changed, and the peaks did not shift when an Hd~ large enough to suppress the quantum tunneling of the magnetization （QTM） was applied. The energy barrier （A/hc） was estimated to be 44 cm-1 with a pre-exponential factor （r0） of 1.6 × 10-5 s from an Arrhenius plot. Our results suggest that the SMM/magnetic properties of 1 significantly change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM.展开更多
A new ultrasonic transducer with multi-belts coil for generating and receiving longitudinal guided wave in ferromagnetic material pipes is proposed.The theory backgrounds and transduction principle of the proposed tra...A new ultrasonic transducer with multi-belts coil for generating and receiving longitudinal guided wave in ferromagnetic material pipes is proposed.The theory backgrounds and transduction principle of the proposed transducer are presented and ana- lyzed.To verify the performance of the transducer,several experiments are performed.The performance of inspecting crack, frequency-tuned characteristic,effect of bias static magnetic field and dynamic magnetic field,lift-off effect and effect of the period number of the exciting current are investigated.The results show that the proposed coils not only could tune the center frequency but also could improve the amplitude and signal-to-noise(SNR)of the detected signals.Bias static magnetic field and dynamic magnetic field are two important factors influencing the amplitude of the longitudinal guided wave.The amplitude of the longitudinal guided wave is exponentially decreased versus the lift-off distance of the transmitter and receiver.Period number of excitation signal could influence the amplitude and wave width of the ultrasonic wave.The proposed transducer could easily control the wave modes and would be a better choice for pipes’monitoring and inspection compared to traditional single-belt coil transducer.展开更多
A novel magnetic field sensor based on optical fiber Mach-Zehnder interferometer(MZI) coated by magnetic fluid(MF) is proposed. The MZI consists of two spherical structures formed on standard single mode fiber(SMF). T...A novel magnetic field sensor based on optical fiber Mach-Zehnder interferometer(MZI) coated by magnetic fluid(MF) is proposed. The MZI consists of two spherical structures formed on standard single mode fiber(SMF). The interference wavelength and the power of the sensing structure are sensitive to the external refractive index(RI). Since RI of the MF is sensitive to the magnetic field, the magnetic field measurement can be realized by detecting the variation of the interference spectrum. Experimental results show that the wavelength and the power of interference dip both increase with the increase of magnetic field intensity.展开更多
Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are...Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency （RF） field. Both electrom^gnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.展开更多
We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyze...We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.展开更多
基金Supported by the Ph.D. Start-up Fund of Beijing University of Technology (No.127-00227).
文摘Simulations of heat transfer and oxygen transport during a Czochralski growth of silicon with and without a cusp magnetic field were carried out. A finite volume method with a low-Reynolds number K-e model proposed by Jones-Launder was employed. The numerical results were compared with the experimental data in the literature. It is found that the calculated results are in good agreement with the experimental data.
基金supported in part by the National Natural Science Foundation of China(Grant No. 10835005)
文摘The phase behavior of a monolayer of dipolar hard spheres under an external field, which makes all dipoles of the monolayer orientate along its direction, is investigated. Using integral equation theory in the reference hypemetted chain （RHNC） approximation we calculate the correlation functions, which are used to obtain the response matrix of grand potential with respect to density fluctuations. The smallest eigenvalue of this response matrix determines the stability of the monolayer. When the smallest eigenvalue approaches zero, the monolayer becomes unstable and the corresponding eigenvector characterizes this instability. At dilute densities, with decreasing temperature the dipoles of the monolayer begin to form chains and simultaneously condensate. At medium and high densities, however, the dipoles of the monolayer have a stronger tendency to form dipolar chains with decreasing temperature and there is no condensation. The part of specific heat related to potential energy is investigated and found to increase sharply near the temperature of dipolar chain formation. This is in accordance with a sharp decrease in potential energy induced by the formation of a dipolar chain.
基金financially supported by a Grant-in-Aid for Scientific Research(s) (20225003) from the Ministry of Education, Culture, Sports,Science, and Technology, Japan
文摘The SMM properties of the spatially closed Dy（Ⅲ） double-decker Pc complex Dy（obPc）2 （1）, which is equivalent to a pseudo dinuclear complex, are reported. Complex 1 crystallized with ethanol in the crystal lattice in the monoclinic space group P22/n and was isomorphous with Tb（obPc）2 （3）, which is arranged in a dimer structure along the b axis. The intermetallic Dy-Dy distance was determined to be 0.756 nm. ZMT versus T plots for 1 decreased with a decrease in T, which suggests the existence of an antiferromagnetic （AF） interaction between the Dy3＋ ions. The M-H curve for 1 at 1.8 K showed magnetic hysteresis. In ac susceptibility measurements on a powder sample of 1, which were dependent on the applied ac field, indicating that 1 is an single molecule magnet （SMM）, a maximum appeared at 22 K at an ac frequency 09 of 1488 Hz. The shape of the peaks dras- tically changed, and the peaks did not shift when an Hd~ large enough to suppress the quantum tunneling of the magnetization （QTM） was applied. The energy barrier （A/hc） was estimated to be 44 cm-1 with a pre-exponential factor （r0） of 1.6 × 10-5 s from an Arrhenius plot. Our results suggest that the SMM/magnetic properties of 1 significantly change in a dc magnetic field. These relaxation mechanisms are related to the energy gap of the ground state and to QTM.
基金supported by the National Natural Science Foundation of China(Grant No.10974115)
文摘A new ultrasonic transducer with multi-belts coil for generating and receiving longitudinal guided wave in ferromagnetic material pipes is proposed.The theory backgrounds and transduction principle of the proposed transducer are presented and ana- lyzed.To verify the performance of the transducer,several experiments are performed.The performance of inspecting crack, frequency-tuned characteristic,effect of bias static magnetic field and dynamic magnetic field,lift-off effect and effect of the period number of the exciting current are investigated.The results show that the proposed coils not only could tune the center frequency but also could improve the amplitude and signal-to-noise(SNR)of the detected signals.Bias static magnetic field and dynamic magnetic field are two important factors influencing the amplitude of the longitudinal guided wave.The amplitude of the longitudinal guided wave is exponentially decreased versus the lift-off distance of the transmitter and receiver.Period number of excitation signal could influence the amplitude and wave width of the ultrasonic wave.The proposed transducer could easily control the wave modes and would be a better choice for pipes’monitoring and inspection compared to traditional single-belt coil transducer.
基金supported by the National Training Programs of Innovation and Entrepreneurship for Undergraduates of China(No.201310060015)Education Program(No.YB11-32)
文摘A novel magnetic field sensor based on optical fiber Mach-Zehnder interferometer(MZI) coated by magnetic fluid(MF) is proposed. The MZI consists of two spherical structures formed on standard single mode fiber(SMF). The interference wavelength and the power of the sensing structure are sensitive to the external refractive index(RI). Since RI of the MF is sensitive to the magnetic field, the magnetic field measurement can be realized by detecting the variation of the interference spectrum. Experimental results show that the wavelength and the power of interference dip both increase with the increase of magnetic field intensity.
基金Supported by the Science Foundation of Guizhou Province under Grant Nos.LKM(2013)19 and (2014)2090
文摘Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency （RF） field. Both electrom^gnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40804031, 41074114, 40921063)the Specialized Research Fund for State Key Laboratories
文摘We have studied 172 field-aligned currents （FACs） cases observed by the ClusterlI satellites when they crossed the plasma sheet boundary layer （PSBL） in the magnetotail from July to October 2001. We mainly analyzed the relationship between the characteristic of FACs at the PSBL in magnetotail and the Kp index. The main results indicated the followings： 1） In the different geomagnetic activity levels, the relative occurrence of FACs in PSBL increased monotonically with geomagnetic activity. 2） The density of FACs in PSBL increased monotonically with Kp index. In the storm main phase, the density of FACs increased dramatically, the maximum FACs approximately equaled 19.05 nA m-2 while Kp equaled 5.3） The variation of FACs density in PSBL was consistent with the variation of the Kp index. However, when AE〈800 nT, FACs density in PSBL increased with increasing AE, and when AE〉800 nT, it decreased with increasing AE. Therefore, our results suggested that the FACs density in PSBL had a closer correlation with Kp index.
