An effective method was proposed to establish the continuous cooling transformation（CCT） diagrams of aluminum alloys using in situ voltage measurement.The voltage change of samples with predefined dimension was reco...An effective method was proposed to establish the continuous cooling transformation（CCT） diagrams of aluminum alloys using in situ voltage measurement.The voltage change of samples with predefined dimension was recorded under the constant current state during continuous cooling.Solutionizing time,together with starting and finishing temperatures of phase transformation of the alloy can be obtained from relationships of voltage vs time and temperature.A critical cooling rate without detectable phase transition during continuous cooling can be determined.Continuous cooling transformation diagrams of tested samples can be established conveniently based on these results.Microstructure observation and differential scanning calorimetry（DSC） testing were applied to verify the reliability of continuous cooling transformation diagram.展开更多
To resolve the completeness and independence of an invariant set derived by the traditional method, a systematic method for deriving a complete set of pseudo-Zernike moment similarity （translation, scale and rotation...To resolve the completeness and independence of an invariant set derived by the traditional method, a systematic method for deriving a complete set of pseudo-Zernike moment similarity （translation, scale and rotation） invariants is described. First, the relationship between pseudo-Zernike moments of the original image and those of the image having the same shape but distinct orientation and scale is established. Based on this relationship, a complete set of similarity invariants can be expressed as a linear combination of the original pseudo-Zernike moments of the same order and lower order. The problem of image reconstruction from a finite set of the pseudo-Zernike moment invariants （PZMIs） is also investigated. Experimental results show that the proposed PZMIs have better performance than complex moment invariants.展开更多
The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different ci...The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different circuit parameters of the PWM buck converter have been analyzed. The method of using Fourier descriptor to extract output signals characteristics is put forward and proved to be a gist of identifying and classifying the behavior of DC DC converter. This method can establish a good foundation fo...展开更多
The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put...The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.展开更多
The transverse spin-2 Ising ferromagnetic model with a longitudinal crystal-field is studied within the mean-field theory based on Bogoliubov inequality for the Gibbs free energy. The ground-state phase diagram and th...The transverse spin-2 Ising ferromagnetic model with a longitudinal crystal-field is studied within the mean-field theory based on Bogoliubov inequality for the Gibbs free energy. The ground-state phase diagram and the tricritical point are obtained in the transverse field Ω/ zJ-longitudinal crystal D / zJ field plane. We find that there are the first order-order phase transitions in a very small range of D /zJ besides the usual first order-disorder phase transitions and the second order-disorder phase transitions,展开更多
We study the finite-size scaling behavior of velocity and central charge for different coupling constants and different phases in -dimensional lattice model in very short chains. Using XXZ spin 1/2 chains with 15 or f...We study the finite-size scaling behavior of velocity and central charge for different coupling constants and different phases in -dimensional lattice model in very short chains. Using XXZ spin 1/2 chains with 15 or fewer sites, we demonstrate the weak finite-size dependence of spinon velocity for any magnitude of coupling strength and the strong phase dependence of central charge. This behavior of velocity and central charge in different coupling constants and different phases gives a method to determine phase transitions of -dimensional models. This method is simple and efficient by utilizing only the ground state energy of very short finite-size chains. It is also general and powerful for various one-dimensional lattice models and it uncovers even the weakest Berezinski?Kosterlitz?Thouless phase transitions.展开更多
This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spread...This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spreading spectrum communication and chaotic cipher.展开更多
Using- the recursion method, we study the phase transitions of theAshkin-Teller model on the Bethe lattice, restricting ourselves to the case of ferromagneticinteractions. The isotropic Ashkin-Teller model and the ani...Using- the recursion method, we study the phase transitions of theAshkin-Teller model on the Bethe lattice, restricting ourselves to the case of ferromagneticinteractions. The isotropic Ashkin-Teller model and the anisotropic one are respectivelyinvestigated, and exact expressions for the free energy and the magnetization are obtained. It canbe found that each of the three varieties of phase diagrams, for the anisotropic Ashkin-Tellermodel, consists of four phases, i.e., the fully disordered paramagnetic phase Para, the fullyordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases 【 σ 】 and 【 σs】, while the phase diagram, for the isotropic Ashkin-Teller model, contains three phases, i.e., thefully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, andthe partially ordered ferromagnetic phase 【 σs 】.展开更多
The critical behaviors of a mixed spin-1/2 and spin-sB Ising system with a transverse crystal field are studiedby use of the effective-field theory with correlations. The effect of the transverse crystal field on tran...The critical behaviors of a mixed spin-1/2 and spin-sB Ising system with a transverse crystal field are studiedby use of the effective-field theory with correlations. The effect of the transverse crystal field on transition temperaturesis investigated numerically for the honeycomb (z = 3) and square (z = 4) lattices. The results show that there is notricritical point for the system.展开更多
Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the st...Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the strain fields accurately and graphically.Strain distribution of the CT specimen was predicted by finite element method(FEM).Good agreement is observed between the surface strain fields measured by DIC and predicted by FEM,which reveals that the proposed method is practical and effective to determine the strain fields of CT specimens.Moreover,strain fields of the CT specimens with various compressive loads and notch diameters were studied by DIC.The experimental results can provide effective reference to usage of CT specimens in triaxial creep test by appropriately selecting specimen and experiment parameters.展开更多
This paper presented a registration method based on Fourier transform for multi-band images which is involved in translation and small rotation. Although different band images differ a lot in the intensity and feature...This paper presented a registration method based on Fourier transform for multi-band images which is involved in translation and small rotation. Although different band images differ a lot in the intensity and features, they contain certain common information which we can exploit. A model was given that the multi-band images have linear correlations under the least-square sense. It is proved that the coefficients have no effect on the registration progress if two images have linear correlations. Finally, the steps of the registration method were proposed. The experiments show that the model is reasonable and the results are satisfying.展开更多
文摘An effective method was proposed to establish the continuous cooling transformation（CCT） diagrams of aluminum alloys using in situ voltage measurement.The voltage change of samples with predefined dimension was recorded under the constant current state during continuous cooling.Solutionizing time,together with starting and finishing temperatures of phase transformation of the alloy can be obtained from relationships of voltage vs time and temperature.A critical cooling rate without detectable phase transition during continuous cooling can be determined.Continuous cooling transformation diagrams of tested samples can be established conveniently based on these results.Microstructure observation and differential scanning calorimetry（DSC） testing were applied to verify the reliability of continuous cooling transformation diagram.
基金The National Natural Science Foundation of China(No.61071192,61073138)
文摘To resolve the completeness and independence of an invariant set derived by the traditional method, a systematic method for deriving a complete set of pseudo-Zernike moment similarity （translation, scale and rotation） invariants is described. First, the relationship between pseudo-Zernike moments of the original image and those of the image having the same shape but distinct orientation and scale is established. Based on this relationship, a complete set of similarity invariants can be expressed as a linear combination of the original pseudo-Zernike moments of the same order and lower order. The problem of image reconstruction from a finite set of the pseudo-Zernike moment invariants （PZMIs） is also investigated. Experimental results show that the proposed PZMIs have better performance than complex moment invariants.
文摘The precondition of realizing feedback controlling DC DC converter to avoid chaotic state is to judge the behavior of the converter and take corresponding measures. In this paper, the output signals under different circuit parameters of the PWM buck converter have been analyzed. The method of using Fourier descriptor to extract output signals characteristics is put forward and proved to be a gist of identifying and classifying the behavior of DC DC converter. This method can establish a good foundation fo...
基金Project (IP08-092009) supported by Sino Swiss Science and Technology Cooperation (SSSTC)Project (50971136) supported by the National Natural Science Foundation of ChinaProject (1343-71134001013) supported by the Scholarship Award for Excellent Doctoral Student granted by Ministry of Education of China
文摘The Fe-Ti binary system was re-assessed using the CALPHAD method in order to improve the capability of being extrapolated to a ternary or higher-order system. Compared with previous assessments, the main focus was put on the thermodynamic description of the two intermetallic compounds Fe2Ti and FeTi. The C14_Laves phase Fe2Ti was described by the two-sublattice model, which is widely used at present. By checking the homogeneity range on the boundary of the ternary systems involving the binary, the phase boundary of this compound was further confirmed. The FeTi phase with a BCC_B2 crystal structure was treated as the ordered phase of the BCC_A2 phase and a unified Gibbs energy function was used to describe both the ordered and disordered phases. Reproduction of the specific heat capacities of these compounds was another aspect paid particular attention to. Comprehensive comparisons of the calculated and experimental results regarding the phase diagram and thermodynamic properties show a good agreement between them and prove the validity of the present thermodynamic description.
文摘The transverse spin-2 Ising ferromagnetic model with a longitudinal crystal-field is studied within the mean-field theory based on Bogoliubov inequality for the Gibbs free energy. The ground-state phase diagram and the tricritical point are obtained in the transverse field Ω/ zJ-longitudinal crystal D / zJ field plane. We find that there are the first order-order phase transitions in a very small range of D /zJ besides the usual first order-disorder phase transitions and the second order-disorder phase transitions,
文摘We study the finite-size scaling behavior of velocity and central charge for different coupling constants and different phases in -dimensional lattice model in very short chains. Using XXZ spin 1/2 chains with 15 or fewer sites, we demonstrate the weak finite-size dependence of spinon velocity for any magnitude of coupling strength and the strong phase dependence of central charge. This behavior of velocity and central charge in different coupling constants and different phases gives a method to determine phase transitions of -dimensional models. This method is simple and efficient by utilizing only the ground state energy of very short finite-size chains. It is also general and powerful for various one-dimensional lattice models and it uncovers even the weakest Berezinski?Kosterlitz?Thouless phase transitions.
基金National Natural Science Fundation of China(Grant No. 69735101)
文摘This letter presents a new one-dimensional chaotic map with infinite collapses. Theoretical analyses show that the map has complicated dynamical behavior and ideal distribution.The map can be applied in chaotic spreading spectrum communication and chaotic cipher.
文摘Using- the recursion method, we study the phase transitions of theAshkin-Teller model on the Bethe lattice, restricting ourselves to the case of ferromagneticinteractions. The isotropic Ashkin-Teller model and the anisotropic one are respectivelyinvestigated, and exact expressions for the free energy and the magnetization are obtained. It canbe found that each of the three varieties of phase diagrams, for the anisotropic Ashkin-Tellermodel, consists of four phases, i.e., the fully disordered paramagnetic phase Para, the fullyordered ferromagnetic phase Ferro, and two partially ordered ferromagnetic phases 【 σ 】 and 【 σs】, while the phase diagram, for the isotropic Ashkin-Teller model, contains three phases, i.e., thefully disordered paramagnetic phase Para, the fully ordered ferromagnetic phase Baxter Phase, andthe partially ordered ferromagnetic phase 【 σs 】.
基金The project supported by Science Foundation of the Ministry of Education of China under Grant No.99026
文摘The critical behaviors of a mixed spin-1/2 and spin-sB Ising system with a transverse crystal field are studiedby use of the effective-field theory with correlations. The effect of the transverse crystal field on transition temperaturesis investigated numerically for the honeycomb (z = 3) and square (z = 4) lattices. The results show that there is notricritical point for the system.
基金Projects(51575347,51405297,51204107)supported by the National Natural Science Foundation of China
文摘Surface strain fields of the designed compact tension(CT)specimens were investigated by digital image correlation(DIC)method.An integrative computer program was developed based on DIC algorithms to characterize the strain fields accurately and graphically.Strain distribution of the CT specimen was predicted by finite element method(FEM).Good agreement is observed between the surface strain fields measured by DIC and predicted by FEM,which reveals that the proposed method is practical and effective to determine the strain fields of CT specimens.Moreover,strain fields of the CT specimens with various compressive loads and notch diameters were studied by DIC.The experimental results can provide effective reference to usage of CT specimens in triaxial creep test by appropriately selecting specimen and experiment parameters.
基金Shanghai Science and Technology Devel-opm ent Funds ( No.0 2 DZ15 0 0 1)
文摘This paper presented a registration method based on Fourier transform for multi-band images which is involved in translation and small rotation. Although different band images differ a lot in the intensity and features, they contain certain common information which we can exploit. A model was given that the multi-band images have linear correlations under the least-square sense. It is proved that the coefficients have no effect on the registration progress if two images have linear correlations. Finally, the steps of the registration method were proposed. The experiments show that the model is reasonable and the results are satisfying.
