The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thaw...The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thawing experiment was conducted with Lanzhou loess(LZL)and Qinghai-Tibet Plateau silty clay(QSC)using a novel layered nuclear magnetic resonance approach.During LZL freezing,the unfrozen water content first increased and then decreased with decreasing temperature near the freezing front,but decreased with decreasing temperature in other layers,whereas during the freezing of QSC,the unfrozen water content in different layers(including the freezing front)decreased with decreased temperature.Notably,the increased liquid water near the freezing front during LZL freezing was primarily adsorbed water.In addition to the temperature gradient,the squeezing action during soil freezing was another important factor affecting water migration,especially at the early stage of soil freezing.However,which of the two factors,squeezing action and temperature gradient,was the dominant one causing water migration depended on soil structure.At the early stage of soil freezing,the squeezing action had a significant effect on the water migration of LZL,but no significant effect on that of QSC.Furthermore,water accumulation of LZL near the freezing front due to squeezing action at the early stage of freezing limited the formation and growth of segregation ice.This study provided an improved understanding for ice segregation and water migration during soil freezing.展开更多
The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics simulations.It is found that the phase transition of water molecules in nanochannels occu...The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics simulations.It is found that the phase transition of water molecules in nanochannels occurs by changing the frequency of the varying electric field.Water molecules maintain the ice phase when the frequency of the varying electric field is less than 16 THz or greater than 30 THz,and they completely melt when the frequency of the varying electric field is 24 THz.This phenomenon is attributed to the breaking of hydrogen bonds when the frequency of the varying electric field is close to their inherent resonant frequency.Moreover,the study demonstrates that the critical frequency varies with the confinement situation.The new mechanism of regulating the phase transition of water molecules in nanochannels revealed in this study provides a perspective for further understanding of the phase transition of water molecules in nanochannels,and has great application potential in preventing icing and deicing.展开更多
The brain neural system is often disturbed by electromagnetic and noise environments, and research on dynamic response of its interaction has received extensive attention. This paper investigates electrical activity o...The brain neural system is often disturbed by electromagnetic and noise environments, and research on dynamic response of its interaction has received extensive attention. This paper investigates electrical activity of Morris-Lecar neural systems exposed to sinusoidal induced electric field(IEF) with random phase generated by electromagnetic effect. By introducing a membrane depolarization model under the effect of random IEF, transition state of firing patterns, including mixed-mode oscillations(MMOs) with layered inter-spike intervals(ISI) and intermittency with a power law distribution in probability density function of ISI, is obtained in a single neuron. Considering the synergistic effects of frequency and noise, coherence resonance is performed by phase noise of IEF under certain parameter conditions. For the neural network without any internal coupling, we demonstrate that synchronous oscillations can be induced by IEF coupling, and suppression of synchronous spiking is achieved effectively by phase noise of IEF. Results of the study enrich the dynamical response to electromagnetic induction and provide insights into mechanisms of noise affecting information coding and transmission in neural systems.展开更多
The structure, spectroscopic properties and chemical stability of [VS4-(CuPPh3)3 (CuCl)Br2] in CDCl3 solution have been studied by multinuclear NMR tech-nique. Two peaks with relative intensity of 1: 4 are found in th...The structure, spectroscopic properties and chemical stability of [VS4-(CuPPh3)3 (CuCl)Br2] in CDCl3 solution have been studied by multinuclear NMR tech-nique. Two peaks with relative intensity of 1: 4 are found in the31P-{1H} spectra.Some 13C-{1H} and 1H NMR peaks have the same integral intensity ratio. These com-plemented the results of 31P-{1H} NMR. The experimental results demonstrates that the PPh3 ligand bound to Cu(6) is not equivalent with the four PPh3 ligands bound toCu(2) ~Cu (5 )- It affords an evidence that the title compound in the solution keepssimilar structure to solid state.展开更多
Inexpe nsive copper nano particles are generally thought to possess weak and broad localized surface plasm on resonance(LSPR).The,present experimental and theoretical studies show that tailoring the Cu nanoparticle to...Inexpe nsive copper nano particles are generally thought to possess weak and broad localized surface plasm on resonance(LSPR).The,present experimental and theoretical studies show that tailoring the Cu nanoparticle to a cubic shape results in a single intense,narrow,and asymmetric LSPR line shape,which is even superior to round-shaped gold nanoparticles.In this study,the dielectric function of copper is decomposed into an interband transition component and a free-electron component.This allows interband transition-induced plasmon damping to be visualized both spectrally and by surface polarization charges.The results reveal that the LSPR of Cu nanocubes originates from the comer mode as it is spectrally separated from the interb and transitions.In additi on,the interband tran sitions lead to severe damping of the local electromagnetic field but the cubic corner LSPR mode survives.Cu nanocubes display an extinction coefficient comparable to the dipole mode of a gold nanosphere with the same volume and show a larger local electromagnetic field enhancement These results will guider-development of in expensive plasmonic copper-based nano materials.展开更多
Results of theoretical researches of the saturated absorption resonance shape in a method of the probing field on V-type of transitions are represented. It is shown that in case of opposite circulary polarized optical...Results of theoretical researches of the saturated absorption resonance shape in a method of the probing field on V-type of transitions are represented. It is shown that in case of opposite circulary polarized optical fields the resonance is shown in the form of cross, and its form strongly depends on relaxation constants of levels and it can be represented as in the form of a dip, and absorption peak. Thus the peak form has exclusively coherent character. Atomic transitions are offered, on which observation of the given effect is possible.展开更多
According to the resonance transition between propagating surface plasmon and localized surface plasmon, we demonstrate a design of beam splitter that can split terahertz wave beams in a relatively broad frequency ran...According to the resonance transition between propagating surface plasmon and localized surface plasmon, we demonstrate a design of beam splitter that can split terahertz wave beams in a relatively broad frequency range. The transmission properties of the beam splitter are analyzed utilizing the finite element method. The resonance transition between two kinds of plasmons can be explained by a model of coherent electron cloud displacement.展开更多
The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurem...The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurement have been avoided and the experimental precision has been improved by using this method. The optical oscillator strength density spectrum corresponding to the 1S n’P transitions and ionization of helium has been measured in the energy loss range of 21 - 26 eV. And the same work corresponding to the autoionization resonance region has been done in energy loss ranges of 59-67 eV and 69-74 eV. The above results have also been compared with those of the previous work.展开更多
By employing the normal form theory, the Hopf bifurcation and the transition boundary of an autonomous double pendulum with 1:1 internal resonance at the critical point is studied. The results are compared with numeri...By employing the normal form theory, the Hopf bifurcation and the transition boundary of an autonomous double pendulum with 1:1 internal resonance at the critical point is studied. The results are compared with numerical solutions. Further, by numerical methods, the road to chaos of a non-autonomous system is presented in the end.展开更多
基金supported by the Key Project of the Natural Science Foundation of China(No.41630636)the National Natural Science Foundation of China(No.41501072)+1 种基金the Independent Foundation of State Key Laboratory of Frozen Soil Engineering,China(No.SKLFSE-ZT-202107)the Natural Science Foundation of Gansu,China(No.22JR5RA057).
文摘The formation and growth of segregation ice dominate the frost heave during soil freezing,which is closely related to water migration.To analyze segregation ice during soil freezing for different soils,a freezing-thawing experiment was conducted with Lanzhou loess(LZL)and Qinghai-Tibet Plateau silty clay(QSC)using a novel layered nuclear magnetic resonance approach.During LZL freezing,the unfrozen water content first increased and then decreased with decreasing temperature near the freezing front,but decreased with decreasing temperature in other layers,whereas during the freezing of QSC,the unfrozen water content in different layers(including the freezing front)decreased with decreased temperature.Notably,the increased liquid water near the freezing front during LZL freezing was primarily adsorbed water.In addition to the temperature gradient,the squeezing action during soil freezing was another important factor affecting water migration,especially at the early stage of soil freezing.However,which of the two factors,squeezing action and temperature gradient,was the dominant one causing water migration depended on soil structure.At the early stage of soil freezing,the squeezing action had a significant effect on the water migration of LZL,but no significant effect on that of QSC.Furthermore,water accumulation of LZL near the freezing front due to squeezing action at the early stage of freezing limited the formation and growth of segregation ice.This study provided an improved understanding for ice segregation and water migration during soil freezing.
基金partially supported by the National Natural Science Foundation of China (Nos. 12172334 and 12274110)the Zhejiang Provincial Natural Science Foundation of China (No. LR21A020001)
文摘The phase transition of water molecules in nanochannels under varying external electric fields is studied by molecular dynamics simulations.It is found that the phase transition of water molecules in nanochannels occurs by changing the frequency of the varying electric field.Water molecules maintain the ice phase when the frequency of the varying electric field is less than 16 THz or greater than 30 THz,and they completely melt when the frequency of the varying electric field is 24 THz.This phenomenon is attributed to the breaking of hydrogen bonds when the frequency of the varying electric field is close to their inherent resonant frequency.Moreover,the study demonstrates that the critical frequency varies with the confinement situation.The new mechanism of regulating the phase transition of water molecules in nanochannels revealed in this study provides a perspective for further understanding of the phase transition of water molecules in nanochannels,and has great application potential in preventing icing and deicing.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11672233, 11672231)the NPU Foundation for Fundamental Research (Grant No. 3102017AX008)+1 种基金the Seed Foundation of Innovation and Creation for Graduate Student in Northwestern Polytechnical University (Grant No. ZZ2018173)the Qian Xuesen Laboratory of Space Technology Seed Fund (Grant No. QXS-ZZJJ-02)
文摘The brain neural system is often disturbed by electromagnetic and noise environments, and research on dynamic response of its interaction has received extensive attention. This paper investigates electrical activity of Morris-Lecar neural systems exposed to sinusoidal induced electric field(IEF) with random phase generated by electromagnetic effect. By introducing a membrane depolarization model under the effect of random IEF, transition state of firing patterns, including mixed-mode oscillations(MMOs) with layered inter-spike intervals(ISI) and intermittency with a power law distribution in probability density function of ISI, is obtained in a single neuron. Considering the synergistic effects of frequency and noise, coherence resonance is performed by phase noise of IEF under certain parameter conditions. For the neural network without any internal coupling, we demonstrate that synchronous oscillations can be induced by IEF coupling, and suppression of synchronous spiking is achieved effectively by phase noise of IEF. Results of the study enrich the dynamical response to electromagnetic induction and provide insights into mechanisms of noise affecting information coding and transmission in neural systems.
文摘The structure, spectroscopic properties and chemical stability of [VS4-(CuPPh3)3 (CuCl)Br2] in CDCl3 solution have been studied by multinuclear NMR tech-nique. Two peaks with relative intensity of 1: 4 are found in the31P-{1H} spectra.Some 13C-{1H} and 1H NMR peaks have the same integral intensity ratio. These com-plemented the results of 31P-{1H} NMR. The experimental results demonstrates that the PPh3 ligand bound to Cu(6) is not equivalent with the four PPh3 ligands bound toCu(2) ~Cu (5 )- It affords an evidence that the title compound in the solution keepssimilar structure to solid state.
文摘Inexpe nsive copper nano particles are generally thought to possess weak and broad localized surface plasm on resonance(LSPR).The,present experimental and theoretical studies show that tailoring the Cu nanoparticle to a cubic shape results in a single intense,narrow,and asymmetric LSPR line shape,which is even superior to round-shaped gold nanoparticles.In this study,the dielectric function of copper is decomposed into an interband transition component and a free-electron component.This allows interband transition-induced plasmon damping to be visualized both spectrally and by surface polarization charges.The results reveal that the LSPR of Cu nanocubes originates from the comer mode as it is spectrally separated from the interb and transitions.In additi on,the interband tran sitions lead to severe damping of the local electromagnetic field but the cubic corner LSPR mode survives.Cu nanocubes display an extinction coefficient comparable to the dipole mode of a gold nanosphere with the same volume and show a larger local electromagnetic field enhancement These results will guider-development of in expensive plasmonic copper-based nano materials.
文摘Results of theoretical researches of the saturated absorption resonance shape in a method of the probing field on V-type of transitions are represented. It is shown that in case of opposite circulary polarized optical fields the resonance is shown in the form of cross, and its form strongly depends on relaxation constants of levels and it can be represented as in the form of a dip, and absorption peak. Thus the peak form has exclusively coherent character. Atomic transitions are offered, on which observation of the given effect is possible.
文摘According to the resonance transition between propagating surface plasmon and localized surface plasmon, we demonstrate a design of beam splitter that can split terahertz wave beams in a relatively broad frequency range. The transmission properties of the beam splitter are analyzed utilizing the finite element method. The resonance transition between two kinds of plasmons can be explained by a model of coherent electron cloud displacement.
基金State Science and Technology Commission of ChinaNational Natural Science Foundation of ChinaChinese Academy of Science,and University of Science and Technology of China.
文摘The optical oscillator strengths of helium have been studied by a high-resolution dipole (e, e) method on the recently built high-resolution fast-electron energy-loss spectrometer. The difficulties of optical measurement have been avoided and the experimental precision has been improved by using this method. The optical oscillator strength density spectrum corresponding to the 1S n’P transitions and ionization of helium has been measured in the energy loss range of 21 - 26 eV. And the same work corresponding to the autoionization resonance region has been done in energy loss ranges of 59-67 eV and 69-74 eV. The above results have also been compared with those of the previous work.
文摘By employing the normal form theory, the Hopf bifurcation and the transition boundary of an autonomous double pendulum with 1:1 internal resonance at the critical point is studied. The results are compared with numerical solutions. Further, by numerical methods, the road to chaos of a non-autonomous system is presented in the end.
