The exact solution of fractional diffusion model with a location-independent source term used in the study of the concentration of fission product in spherical uranium dioxide （U02） particle is built. The adsorption...The exact solution of fractional diffusion model with a location-independent source term used in the study of the concentration of fission product in spherical uranium dioxide （U02） particle is built. The adsorption effect of the fission product on the surface of the U02 particle and the delayed decay effect are also considered. The solution is given in terms of Mittag-Leffler function with finite Hankel integral transformation and Laplace transformation. At last, the reduced forms of the solution under some special physical conditions, which is used in nuclear engineering, are obtained and corresponding remarks are given to provide significant exact results to the concentration analysis of nuclear fission products in nuclear reactor.展开更多
We investigate the transport properties of Dirac fermions through velocity-modulation structures,with the Fermi velocity inside the barriers larger than the one outside.It is shown that the transmission exhibits pseud...We investigate the transport properties of Dirac fermions through velocity-modulation structures,with the Fermi velocity inside the barriers larger than the one outside.It is shown that the transmission exhibits pseudo-periodicity with the incident angle below the critical transmission angle,but attenuates exponentially in the opposite situation.It is found that in the transmission,(1)the pseudo-periodicity turns to periodicity with suitable modulation;(2)line-type peaks appear in the exponential attenuation region for multiple velocity barriers;(3)peak splitting occurs with the number of the velocity barriers increasing.Some sharp oscillations with the falling-edge slopes close to infinity exist in the conductance profile.These novel transport properties suggest significant potential applications in graphene-based devices.展开更多
Highly excited vibrational dynamics of phosphaethyne(HCP)integrable system are investigated based on its dynamic potentials.Taking into consideration the 2:1 Fermi resonance between H–C–P bending vibrational mode an...Highly excited vibrational dynamics of phosphaethyne(HCP)integrable system are investigated based on its dynamic potentials.Taking into consideration the 2:1 Fermi resonance between H–C–P bending vibrational mode and C–P stretching vibrational mode,it is found that the effects of H–C stretching vibrational mode on vibrational dynamic features of the HCP integrable system are significant and regularly vary with Polyad numbers(P number).The geometrical profiles of the dynamic potentials and the corresponding fixed points are sensitive to the variation of H–C stretching vibrational strength when P numbers are small,but are not sensitive when P numbers become larger and the corresponding threshold values become lower.The phase space trajectories of different energy levels in a designated dynamic potential(P=28)were studied and the results indicated that the dynamic potentials govern the various dynamic environments in which the vibrational states lie.Furthermore,action integrals of the energy levels contained in dynamic potential(P=28)were quantitatively analyzed and elucidated.It was determined that the dynamic environments could be identified by the numerical values of the action integrals of trajectories of phase space,which is equivalent with dynamic potentials.展开更多
We compare the transport properties of electrons in monolayer graphene by modulating the Fermi velocity inside the barrier. A critical transmission angle is found only when the Fermi velocity in the barriers is larger...We compare the transport properties of electrons in monolayer graphene by modulating the Fermi velocity inside the barrier. A critical transmission angle is found only when the Fermi velocity in the barriers is larger than the one outside the barriers. It is shown that the transmission exhibits periodicity with the incident angle below the critical transmission angle, and attenuates exponentially in the opposite situation. For both situations, peak splitting occurs in the transmission as the number of the velocity barriers increases, and the characteristics of the transmission suggest an interesting application of an excellent band-pass filter. The dependence of the conductance on the Fermi energy through an identical velocity- modulation structure differs wildly with different Fermi velocities of the barrier. The counterpart of the peak splitting is the sharp oscillations in the conductance profile. Furthermore, some oscillations for the multiple barriers are so sharp that the structure may be used as an excellent sensor.展开更多
The adsorption behaviors of radioactive strontium and silver nuclides on the graphite surface in a high-temperature gas-cooled reactor are studied by first-principles theory using generalized gradient approximation(GG...The adsorption behaviors of radioactive strontium and silver nuclides on the graphite surface in a high-temperature gas-cooled reactor are studied by first-principles theory using generalized gradient approximation(GGA)and local density approximation(LDA)pseudo-potentials.It turns out that Sr prefers to be absorbed at the hollow of the carbon hexagonal cell by 0.54 eV(GGA),while Ag likes to sit right above the carbon atom with an adsorption energy of almost zero(GGA)and 0.45 eV(LDA).Electronic structure analysis reveals that Sr donates its partial electrons of the 4𝑝and 5𝑠states to the graphite substrate,while Ag on graphite is a physical adsorption without any electron transfer.展开更多
We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors （the two-dimensional electron gas （2DEG））. It is elucidated that the...We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors （the two-dimensional electron gas （2DEG））. It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene. However, resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene, which do not occur in the 2DEG. Furthermore, there are tunneling and forbidden regions in the transmission spectrum for each material, and the division of the two regions has been given in the work. The tunneling region covers a wide range of the incident energy for the two graphene systems, but only exists under specific conditions for the 2DEG. The counterparts of the transmission in the conductance profile are also given for the three materials, which may be used as high-performance devices based on the bilayer graphene.展开更多
An algorithm has been introduced to calculate molecular bond polarizabilities of thiourea, which supply essential electronic information about the nonresonant Raman excited virtual states. The main dynamical behaviour...An algorithm has been introduced to calculate molecular bond polarizabilities of thiourea, which supply essential electronic information about the nonresonant Raman excited virtual states. The main dynamical behaviour of the excited virtual states of thiourea is that the Raman excited electrons tend to flow to the N-H bonds and C-N bonds from the S-C bonds because of the electronic repulsion effect. The difference in Raman excited electron relaxation time of thiourea under 514.5-nm and 325-nm excitations has been observed, which quantitatively shows that the Raman scattering process is dependent on the wavelength of the pumping laser. Finally, the distribution of the electrons at the final stage of relaxation is given out through the comparison between the bond electronic densities of the ground states and the bond polarizabilities after deexcitation.展开更多
Two kinds of approaches are built to solve the fission products diffusion models(Fick's equation)based on sphere fuel particles and sphere fuel elements exactly.Two models for homogenous TRISO-coated fuel particle...Two kinds of approaches are built to solve the fission products diffusion models(Fick's equation)based on sphere fuel particles and sphere fuel elements exactly.Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented,respectively.The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system,a modification of the diffusion coefficient from D to D/Гis made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element.Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.展开更多
An algorithm is employed to calculate molecular bond polarizabilities of p-hydroxybenzoic acid,which supplies essential electronic information of the nonresonant Raman excited virtual states.The main dynamical behavio...An algorithm is employed to calculate molecular bond polarizabilities of p-hydroxybenzoic acid,which supplies essential electronic information of the nonresonant Raman excited virtual states.The main dynamical behavior of the excited virtual states of p-hydroxybenzoic acid with 514.5 nm excitation is such that the Raman excited electrons tend to flow to the C–C connected with–OH and–COOH from the benzene ring because of the electronic repulsion effect.The distribution of the electrons at the final stage of relaxation is given out through the comparison between the bond electronic densities of the ground states and the bond polarizabilities after de-excitation.Furthermore,the relaxation characteristic times of bond polarizabilities shows that the transport of electrons on–COOH is distinct.展开更多
基金Supported by the National S&T Major Project under Grant No.ZX06901
文摘The exact solution of fractional diffusion model with a location-independent source term used in the study of the concentration of fission product in spherical uranium dioxide （U02） particle is built. The adsorption effect of the fission product on the surface of the U02 particle and the delayed decay effect are also considered. The solution is given in terms of Mittag-Leffler function with finite Hankel integral transformation and Laplace transformation. At last, the reduced forms of the solution under some special physical conditions, which is used in nuclear engineering, are obtained and corresponding remarks are given to provide significant exact results to the concentration analysis of nuclear fission products in nuclear reactor.
基金the National Natural Science Foundation of China under Grant Nos 11104156 and 21271114the Postdoctoral Science Foundation of China under Grant No 2012M510405+1 种基金the Independent Research and Development Fund of Tsinghua University under Grant Nos 20121087948 and 20111080982the Beijing Key Lab of Fine Ceramics Opening Fund under Grant No 2012200110.
文摘We investigate the transport properties of Dirac fermions through velocity-modulation structures,with the Fermi velocity inside the barriers larger than the one outside.It is shown that the transmission exhibits pseudo-periodicity with the incident angle below the critical transmission angle,but attenuates exponentially in the opposite situation.It is found that in the transmission,(1)the pseudo-periodicity turns to periodicity with suitable modulation;(2)line-type peaks appear in the exponential attenuation region for multiple velocity barriers;(3)peak splitting occurs with the number of the velocity barriers increasing.Some sharp oscillations with the falling-edge slopes close to infinity exist in the conductance profile.These novel transport properties suggest significant potential applications in graphene-based devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11505027 and 11104156)the Open Foundation of Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation(Grant No.JXMS201605)+1 种基金the Science and Technology Project of Education Department of Jiangxi Province in2016the National High Technology Research and Development Program of China(Grant No.2014AA052701)
文摘Highly excited vibrational dynamics of phosphaethyne(HCP)integrable system are investigated based on its dynamic potentials.Taking into consideration the 2:1 Fermi resonance between H–C–P bending vibrational mode and C–P stretching vibrational mode,it is found that the effects of H–C stretching vibrational mode on vibrational dynamic features of the HCP integrable system are significant and regularly vary with Polyad numbers(P number).The geometrical profiles of the dynamic potentials and the corresponding fixed points are sensitive to the variation of H–C stretching vibrational strength when P numbers are small,but are not sensitive when P numbers become larger and the corresponding threshold values become lower.The phase space trajectories of different energy levels in a designated dynamic potential(P=28)were studied and the results indicated that the dynamic potentials govern the various dynamic environments in which the vibrational states lie.Furthermore,action integrals of the energy levels contained in dynamic potential(P=28)were quantitatively analyzed and elucidated.It was determined that the dynamic environments could be identified by the numerical values of the action integrals of trajectories of phase space,which is equivalent with dynamic potentials.
基金Project supported by the National Natural Science Foundation of China (Grant No. 11104156)the Postdoctoral Science Foundation of China (CPSF) (Grant No. 2012M510405)+1 种基金the Independent Research and Development Fund of Tsinghua University (Grant No. 20121087948)Beijing Key Laboratory of Fine Ceramics Opening Fund (Grant No. 2012200110)
文摘We compare the transport properties of electrons in monolayer graphene by modulating the Fermi velocity inside the barrier. A critical transmission angle is found only when the Fermi velocity in the barriers is larger than the one outside the barriers. It is shown that the transmission exhibits periodicity with the incident angle below the critical transmission angle, and attenuates exponentially in the opposite situation. For both situations, peak splitting occurs in the transmission as the number of the velocity barriers increases, and the characteristics of the transmission suggest an interesting application of an excellent band-pass filter. The dependence of the conductance on the Fermi energy through an identical velocity- modulation structure differs wildly with different Fermi velocities of the barrier. The counterpart of the peak splitting is the sharp oscillations in the conductance profile. Furthermore, some oscillations for the multiple barriers are so sharp that the structure may be used as an excellent sensor.
基金Supported by the National Science and Technology Major Project of China under Grant No 2008ZX06901the National Natural Science Foundation of China under Grant No 50871057+1 种基金the Independent Research and Development Fund of Tsinghua University under Grant No 20111080982the Beijing Key Lab of Fine Ceramics Opening Fund under Grant No 2012200110.
文摘The adsorption behaviors of radioactive strontium and silver nuclides on the graphite surface in a high-temperature gas-cooled reactor are studied by first-principles theory using generalized gradient approximation(GGA)and local density approximation(LDA)pseudo-potentials.It turns out that Sr prefers to be absorbed at the hollow of the carbon hexagonal cell by 0.54 eV(GGA),while Ag likes to sit right above the carbon atom with an adsorption energy of almost zero(GGA)and 0.45 eV(LDA).Electronic structure analysis reveals that Sr donates its partial electrons of the 4𝑝and 5𝑠states to the graphite substrate,while Ag on graphite is a physical adsorption without any electron transfer.
基金the National Natural Science Foundation of China(Grant No.11104156)the Postdoctoral Science Foundation of China(Grant No.2012M510405)+1 种基金the Independent Research and Development Fund of Tsinghua University,China(Grant No.20121087948)the Beijing Key Lab of Fine Ceramics Opening Fund,China(Grant No.2012200110)
文摘We studied and compared the transport properties of charge carriers in bilayer graphene, monolayer graphene, and the conventional semiconductors （the two-dimensional electron gas （2DEG））. It is elucidated that the normal incidence transmission in the bilayer graphene is identical to that in the 2DEG but totally different from that in the monolayer graphene. However, resonant peaks appear in the non-normal incidence transmission profile for a high barrier in the bilayer graphene, which do not occur in the 2DEG. Furthermore, there are tunneling and forbidden regions in the transmission spectrum for each material, and the division of the two regions has been given in the work. The tunneling region covers a wide range of the incident energy for the two graphene systems, but only exists under specific conditions for the 2DEG. The counterparts of the transmission in the conductance profile are also given for the three materials, which may be used as high-performance devices based on the bilayer graphene.
基金supported by the National Science and Technology Major Project (Grant No. ZX06901)
文摘An algorithm has been introduced to calculate molecular bond polarizabilities of thiourea, which supply essential electronic information about the nonresonant Raman excited virtual states. The main dynamical behaviour of the excited virtual states of thiourea is that the Raman excited electrons tend to flow to the N-H bonds and C-N bonds from the S-C bonds because of the electronic repulsion effect. The difference in Raman excited electron relaxation time of thiourea under 514.5-nm and 325-nm excitations has been observed, which quantitatively shows that the Raman scattering process is dependent on the wavelength of the pumping laser. Finally, the distribution of the electrons at the final stage of relaxation is given out through the comparison between the bond electronic densities of the ground states and the bond polarizabilities after deexcitation.
基金Supported by the National S&T Major Project of China under Grant No ZX06901.
文摘Two kinds of approaches are built to solve the fission products diffusion models(Fick's equation)based on sphere fuel particles and sphere fuel elements exactly.Two models for homogenous TRISO-coated fuel particles and fuel elements used in pebble-bed high temperature gas-cooled reactors are presented,respectively.The analytical solution of Fick's equation for fission products diffusion in fuel particles is derived by variables separation.In the fuel element system,a modification of the diffusion coefficient from D to D/Гis made to characterize the difference of diffusion rates in distinct areas and it is shown that the Laplace and Hankel transformations are effective as the diffusion coefficient in Fick's equation is dependant on the radius of the fuel element.Both the solutions are useful for the prediction of the fission product behaviors and could be programmed in the corresponding engineering calculations.
基金Supported by the National Natural Science Foundation under Grant No 11104156.
文摘An algorithm is employed to calculate molecular bond polarizabilities of p-hydroxybenzoic acid,which supplies essential electronic information of the nonresonant Raman excited virtual states.The main dynamical behavior of the excited virtual states of p-hydroxybenzoic acid with 514.5 nm excitation is such that the Raman excited electrons tend to flow to the C–C connected with–OH and–COOH from the benzene ring because of the electronic repulsion effect.The distribution of the electrons at the final stage of relaxation is given out through the comparison between the bond electronic densities of the ground states and the bond polarizabilities after de-excitation.Furthermore,the relaxation characteristic times of bond polarizabilities shows that the transport of electrons on–COOH is distinct.
