For the purpose of computer calculation to evaluate time-dependent quantum properties in finite temperature, we propose new numerical method expressed in the forms of simultaneous differential equations. At first we d...For the purpose of computer calculation to evaluate time-dependent quantum properties in finite temperature, we propose new numerical method expressed in the forms of simultaneous differential equations. At first we derive the equation of motion in finite temperature, which is found to be same expression as Heisenberg equation of motion except for the c-number. Based on this equation, we construct numerical method to estimate time-dependent physical properties in finite temperature precisely without using analytical procedures such as Keldysh formalism. Since our approach is so simple and is based on the simultaneous differential equations including no terms related to self-energies, computer programming can be easily performed. It is possible to estimate exact time-dependent physical properties, providing that Hamiltonian of the system is taken to be a one-electron picture. Furthermore, we refer to the application to the many body problem and it is numerically possible to calculate physical properties using Hartree Fock approximation. Our numerical method can be applied to the case even when perturbative Hamiltonians are newly introduced or Hamiltonian shows complex time-dependent behavior. In this article, at first, we derive the equation of motion in finite temperature. Secondly, for the purpose of verification and of exhibiting the usefulness, we show the derivation of gap equation of superconductivity and of sum rule of electrical conductivity and the application to the many body problem. Finally we apply this method to these two cases: the first case is most simplified resonance charge transfer neutralization of an ion and the second is the same process but impurity potential is newly introduced as perturbative Hamiltonian. Through both cases, it is found that neutralization process is not so sensitive to temperature, however, impurity potential as small as 10 meV strongly influences the neutralization of ion.展开更多
In order to know about the rheological properties of rock in a long range of the time scale,method of increasing temperature was brought forward to accelerate the rheological process of rock,which could extend the tim...In order to know about the rheological properties of rock in a long range of the time scale,method of increasing temperature was brought forward to accelerate the rheological process of rock,which could extend the time scale of experimental test data.Firstly,based on the generalized linear viscoelastic constitutive equation with temperature variable,the creep behavior of rock was divided into three types according to the different strain dependences of the time,that is,Hookean deformation,Newtonian flow,and retarded elasticity.Then the general equivalence relationship between time parameter and temperature parameter was derived for each type of strain.Finally,the relation between time parameter and temperature parameter in the whole creep was considered and the general theory of time-temperature equivalence effect(TTEE) of rock was established.This research reveals: ①The temperature effect on the instantaneous strain could be modified through vertical shift.②The key point of the TTEE of Newtonian flow depends on whether in the study of linear viscoelastic behavior of rock change of temperature is completely equivalent to a shift of the logarithmic time scale or not.③By plotting the results of a creep experiment performed at different temperatures and comparing the curves obtained,one can decide whether the rock considered have TTEE.④The TTEE of the whole creep should satisfy that the horizontal shift function of Newtonian flow and retarded elasticity is consentaneous.展开更多
The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on ino...The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on inorganic binder-bonded sands no matter the test items or the atmospheric protection, while the instrumentss specially designed for resin-bonded sand are not yet available. A new instrument for testing the hightemperature performance of resin sand was designed including the confirmation of the testing parameters, loading, measurement and control systems, and the design of the frame shape and heating furnace. This instrument can test the compressive strength, heat tolerance time and restraining load of phenol-formaldehyde resin coated sand, self-hardened furan resin sand, and trimethylamine(TEA)-based resin bonded sand at high temperatures. The developed instrument has a high accuracy offering smaller than 0.3% deviation at a full scale in the measurement of the high temperature compressive strength and the restraining load over the range of 0-6.8 MPa and 0-2,000 N, respectively. The high temperature heat tolerance time range is 0-300 s and its measurement accuracy is ±1 s.展开更多
From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a t...From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a time-dependent failure assessment diagram (TDFAD) isdeveloped on the basis of the time dependent crack tip parameter J integral. According to theproposed TDFAD method, detailed crack initiation and creep crack growth analysis is avoided insafety assessments of high temperature structures by performing simple calculations of stressintensity factor and limit load. To evaluate the creep toughness parameter K_(mat), three differentexpressions are suggested on the basis of experimental load-line displacement, creep crackinitiation and growth parameters as well as the isochronous stress-strain curve. The influence ofservice factors such as temperature and service-time on the proposed TDFAD is discussed by using theproperties of 2.25CrlMo steel and an example is also presented to illustrate the approach.展开更多
The LaFe11.4Si1.6 compounds are prepared by arc-melting and then annealed at different high temperatures from 1323 K （5 h） to 1623 K （2 h）. The powder X-ray diffraction （XRD） and microstructure observations show...The LaFe11.4Si1.6 compounds are prepared by arc-melting and then annealed at different high temperatures from 1323 K （5 h） to 1623 K （2 h）. The powder X-ray diffraction （XRD） and microstructure observations show that large amount of 1：13 phase begins to appear in the LaFe11.4Si1.6 compound annealed at 1423 K （5 h）. In the temperature range from 1423 K to 1523 K, the α-Fe and LaFeSi phases rapidly decrease to form 1：13 phase. The LaFeSi phase is rarely observed by XRD when the as-cast compound is annealed at 1523 K （5 h）. With annealing temperature increasing to 1573 K, LaFeSi phase is detected again in LaFe11.4Si1.6 compound. In LaFe11.4Si1.6 compounds annealed at 1523 K （5 h）, at 1373 K （2 h）＋1523 K （5 h）, and 1523 K （7 h）＋1373 K （2 h）, the impurity phases including small amount of α-Fe and LaFeSi phase reduce in turn. The magnetic measurement shows that LaFe11.4Si1.6 compounds annealed by above three processes keep the first-order of magnetic transition behavior, and Tc are both at about 200 K. But the values of the maximal ASM（T, H） of has large difference, they are 9.94, 12.66, and 13.96 J/（kg.K） under a magnetic field of 0- 2 T, respectively.展开更多
The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and ...The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.展开更多
文摘For the purpose of computer calculation to evaluate time-dependent quantum properties in finite temperature, we propose new numerical method expressed in the forms of simultaneous differential equations. At first we derive the equation of motion in finite temperature, which is found to be same expression as Heisenberg equation of motion except for the c-number. Based on this equation, we construct numerical method to estimate time-dependent physical properties in finite temperature precisely without using analytical procedures such as Keldysh formalism. Since our approach is so simple and is based on the simultaneous differential equations including no terms related to self-energies, computer programming can be easily performed. It is possible to estimate exact time-dependent physical properties, providing that Hamiltonian of the system is taken to be a one-electron picture. Furthermore, we refer to the application to the many body problem and it is numerically possible to calculate physical properties using Hartree Fock approximation. Our numerical method can be applied to the case even when perturbative Hamiltonians are newly introduced or Hamiltonian shows complex time-dependent behavior. In this article, at first, we derive the equation of motion in finite temperature. Secondly, for the purpose of verification and of exhibiting the usefulness, we show the derivation of gap equation of superconductivity and of sum rule of electrical conductivity and the application to the many body problem. Finally we apply this method to these two cases: the first case is most simplified resonance charge transfer neutralization of an ion and the second is the same process but impurity potential is newly introduced as perturbative Hamiltonian. Through both cases, it is found that neutralization process is not so sensitive to temperature, however, impurity potential as small as 10 meV strongly influences the neutralization of ion.
基金Supported by the Long-term evolution of stability and permeability of high-level radioactive waste repository surrounding rock under THMC coupling process
文摘In order to know about the rheological properties of rock in a long range of the time scale,method of increasing temperature was brought forward to accelerate the rheological process of rock,which could extend the time scale of experimental test data.Firstly,based on the generalized linear viscoelastic constitutive equation with temperature variable,the creep behavior of rock was divided into three types according to the different strain dependences of the time,that is,Hookean deformation,Newtonian flow,and retarded elasticity.Then the general equivalence relationship between time parameter and temperature parameter was derived for each type of strain.Finally,the relation between time parameter and temperature parameter in the whole creep was considered and the general theory of time-temperature equivalence effect(TTEE) of rock was established.This research reveals: ①The temperature effect on the instantaneous strain could be modified through vertical shift.②The key point of the TTEE of Newtonian flow depends on whether in the study of linear viscoelastic behavior of rock change of temperature is completely equivalent to a shift of the logarithmic time scale or not.③By plotting the results of a creep experiment performed at different temperatures and comparing the curves obtained,one can decide whether the rock considered have TTEE.④The TTEE of the whole creep should satisfy that the horizontal shift function of Newtonian flow and retarded elasticity is consentaneous.
文摘The mechanical properties of resin-bonded sand mixtures at high temperatures significantly affect the quality of casting. However, the existing instruments for high-temperature performances testing mainly focus on inorganic binder-bonded sands no matter the test items or the atmospheric protection, while the instrumentss specially designed for resin-bonded sand are not yet available. A new instrument for testing the hightemperature performance of resin sand was designed including the confirmation of the testing parameters, loading, measurement and control systems, and the design of the frame shape and heating furnace. This instrument can test the compressive strength, heat tolerance time and restraining load of phenol-formaldehyde resin coated sand, self-hardened furan resin sand, and trimethylamine(TEA)-based resin bonded sand at high temperatures. The developed instrument has a high accuracy offering smaller than 0.3% deviation at a full scale in the measurement of the high temperature compressive strength and the restraining load over the range of 0-6.8 MPa and 0-2,000 N, respectively. The high temperature heat tolerance time range is 0-300 s and its measurement accuracy is ±1 s.
文摘From the idea of failure of defective structures at high temperature beingcontrolled by two mechanisms: fast fracture due to creep crack growth initiating at the crack tipand creep rupture on the weakened section, a time-dependent failure assessment diagram (TDFAD) isdeveloped on the basis of the time dependent crack tip parameter J integral. According to theproposed TDFAD method, detailed crack initiation and creep crack growth analysis is avoided insafety assessments of high temperature structures by performing simple calculations of stressintensity factor and limit load. To evaluate the creep toughness parameter K_(mat), three differentexpressions are suggested on the basis of experimental load-line displacement, creep crackinitiation and growth parameters as well as the isochronous stress-strain curve. The influence ofservice factors such as temperature and service-time on the proposed TDFAD is discussed by using theproperties of 2.25CrlMo steel and an example is also presented to illustrate the approach.
基金supported by the Key Project of National Natural Science Foundation of China (Nos.50731007 and 51176050)the National High Technical Research and Development Programme of China (No.2007AA03Z440)
文摘The LaFe11.4Si1.6 compounds are prepared by arc-melting and then annealed at different high temperatures from 1323 K （5 h） to 1623 K （2 h）. The powder X-ray diffraction （XRD） and microstructure observations show that large amount of 1：13 phase begins to appear in the LaFe11.4Si1.6 compound annealed at 1423 K （5 h）. In the temperature range from 1423 K to 1523 K, the α-Fe and LaFeSi phases rapidly decrease to form 1：13 phase. The LaFeSi phase is rarely observed by XRD when the as-cast compound is annealed at 1523 K （5 h）. With annealing temperature increasing to 1573 K, LaFeSi phase is detected again in LaFe11.4Si1.6 compound. In LaFe11.4Si1.6 compounds annealed at 1523 K （5 h）, at 1373 K （2 h）＋1523 K （5 h）, and 1523 K （7 h）＋1373 K （2 h）, the impurity phases including small amount of α-Fe and LaFeSi phase reduce in turn. The magnetic measurement shows that LaFe11.4Si1.6 compounds annealed by above three processes keep the first-order of magnetic transition behavior, and Tc are both at about 200 K. But the values of the maximal ASM（T, H） of has large difference, they are 9.94, 12.66, and 13.96 J/（kg.K） under a magnetic field of 0- 2 T, respectively.
文摘The CaCu3Ti4O12(CCTO) ceramic was prepared through conventional solid-state method. The effects of synthesis process(synthesis temperature and synthesis time) of powder on ceramic microstructures, CuO segregation and electrical properties were investigated. The phase composition was determined by X-ray diffraction and the microstructure was examined by SEM. The dielectric constant, dielectric loss, and resistance of the ceramic were also determined by a precision impedance tester. The results show that, as the synthesis temperature increases, the CCTO ceramic grain size decreases and the stoichiometric ratio of Cu/Ca at the grain boundary increases, the dielectric constant increases and the dielectric loss decreases(40 < f < 10 kHz). In addition, when the synthesis time is shorter than 12 h, the Cu/Ca ratio of CCTO decreases and the dielectric constant increases with time increase. However, when the synthesis time exceeds 12 h, this trend is just the opposite. It is further proved that Cu at the grain boundary is not conducive to the dielectric constant of CCTO.
