The phonon dispersion relation of the commensurate quantum Frenkel-Kontorova model is studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction for the parti...The phonon dispersion relation of the commensurate quantum Frenkel-Kontorova model is studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction for the particles. The single-particle state is taken to be a frozen Jackiw-Kerman wavefunction. Under the condition of minimum uncertainty, equations of motion for the particle expectation values are derived to obtain the phonon dispersion relation. It is shown that the strength of the substrate potential and the phonon excitation gap are reduced due to the quantum fluctuations in comparison with those of the classical model. We also compare our results with those previously obtained by using the path-integral molecular dynamics.展开更多
A side band power re-injection locked （SBPRIL） magnetron is presented in this paper. A tuning stub is placed between the external injection locked （EIL） magnetron and the circulator. Side band power of the EIL mag...A side band power re-injection locked （SBPRIL） magnetron is presented in this paper. A tuning stub is placed between the external injection locked （EIL） magnetron and the circulator. Side band power of the EIL magnetron is reflected back to the magnetron. The reflected side band power is reused and pulled back to the central frequency. A phase-locking model is developed from circuit theory to explain the process of reuse of side band power in SBPRIL magnetron. Theoretical analysis proves that the side band power is pulled back to the central frequency of the SBPRIL magnetron, then the amplitude of the RF voltage increases and the phase noise performance is improved. Particle-in-cell （PIC） simulation of a 10-vane continuous wave （CW） magnetron model is presented. Computer simulation predicts that the frequency spectrum＇s peak of the SBPRIL magnetron has an increase of 3.25 dB compared with the free running magnetron. The phase noise performance at the side band offset reduces 12.05 dB for the SBPRIL magnetron. Besides, the SBPRIL magnetron experiment is presented. Experimental results show that the spectrum peak rises by 14.29% for SBPRIL magnetron compared with the free running magnetron. The phase noise reduces more than 25 dB at 45-kHz offset compared with the free running magnetron.展开更多
The transport of a walker in rocking feedback-controlled ratchets is investigated. The walker consists of two coupled ＂feet＂ that allow the interchange of the order of particles while the walker moves. In the underd...The transport of a walker in rocking feedback-controlled ratchets is investigated. The walker consists of two coupled ＂feet＂ that allow the interchange of the order of particles while the walker moves. In the underdamped case, tile deterministic dynamics of the walker in a tilted asymmetric ratchet with an external periodic force is considered. It is found that delayed feedback ratchets with a switching-on- and-off dependence of the states of the system can lead to absolute negative mobility. In such a novel phenomenon, the particles move against tile bias. Moreover, the walker can acquire a series of resonant steps for different values of the current. It is interesting to find that the resonant currents of the walker are induced by tile phase locked motion that corresponds to the synchronization of the motion with the change in the frequency of the external driving. These resonant steps can be well predicted in terms of time-space symmetry analysis, which is in good agreement with dynamics simulations. The transport performances can be optimized and controlled by suitably adjusting the parameters of tile delayed-feedback ratchets.展开更多
We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are invest...We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.展开更多
The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FG...The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FGCM-1.0 is capable of producing the interannual variability of the tropical Pacific, such as the ENSO phenomenon. The mechanism of the ENSO events in the coupled model can be explained by “delayed oscillator” and “recharge-discharge” hypotheses. Compared to the observations, the simulated ENSO events show larger amplitude with two distinctive types of phase-locking： one with its peak phase-locked to boreal winter and the other to boreal summer. These two types of events have a similar frequency of occurrence, but since the second type of event is seldom observed, it may be related to the biases of the coupled model. Analysis show that the heat content anomalies originate from the central south Pacific in the type of events peaking in boreal summer, which can be attributed to a different background climatology from the normal events. The mechanisms of their evolutions are also discussed.展开更多
文摘The phonon dispersion relation of the commensurate quantum Frenkel-Kontorova model is studied by means of the time-dependent variational approach combined with a Hartree-type many-body trial wavefunction for the particles. The single-particle state is taken to be a frozen Jackiw-Kerman wavefunction. Under the condition of minimum uncertainty, equations of motion for the particle expectation values are derived to obtain the phonon dispersion relation. It is shown that the strength of the substrate potential and the phonon excitation gap are reduced due to the quantum fluctuations in comparison with those of the classical model. We also compare our results with those previously obtained by using the path-integral molecular dynamics.
基金Project supported by the National Basic Research Program of China(Grant No.2013CB328902)the National Natural Science Foundation of China(Grant No.61501311)
文摘A side band power re-injection locked （SBPRIL） magnetron is presented in this paper. A tuning stub is placed between the external injection locked （EIL） magnetron and the circulator. Side band power of the EIL magnetron is reflected back to the magnetron. The reflected side band power is reused and pulled back to the central frequency. A phase-locking model is developed from circuit theory to explain the process of reuse of side band power in SBPRIL magnetron. Theoretical analysis proves that the side band power is pulled back to the central frequency of the SBPRIL magnetron, then the amplitude of the RF voltage increases and the phase noise performance is improved. Particle-in-cell （PIC） simulation of a 10-vane continuous wave （CW） magnetron model is presented. Computer simulation predicts that the frequency spectrum＇s peak of the SBPRIL magnetron has an increase of 3.25 dB compared with the free running magnetron. The phase noise performance at the side band offset reduces 12.05 dB for the SBPRIL magnetron. Besides, the SBPRIL magnetron experiment is presented. Experimental results show that the spectrum peak rises by 14.29% for SBPRIL magnetron compared with the free running magnetron. The phase noise reduces more than 25 dB at 45-kHz offset compared with the free running magnetron.
基金This work was supported by the National Natural Science Foundation of China （Grant Nos. 11475022 and 11347003）, the Scientific Research Funds of Huaqiao University, and the Excellent Talents Program of Shenyang Normal University （Grant No. 91400114005）.
文摘The transport of a walker in rocking feedback-controlled ratchets is investigated. The walker consists of two coupled ＂feet＂ that allow the interchange of the order of particles while the walker moves. In the underdamped case, tile deterministic dynamics of the walker in a tilted asymmetric ratchet with an external periodic force is considered. It is found that delayed feedback ratchets with a switching-on- and-off dependence of the states of the system can lead to absolute negative mobility. In such a novel phenomenon, the particles move against tile bias. Moreover, the walker can acquire a series of resonant steps for different values of the current. It is interesting to find that the resonant currents of the walker are induced by tile phase locked motion that corresponds to the synchronization of the motion with the change in the frequency of the external driving. These resonant steps can be well predicted in terms of time-space symmetry analysis, which is in good agreement with dynamics simulations. The transport performances can be optimized and controlled by suitably adjusting the parameters of tile delayed-feedback ratchets.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61072012,60901035,and 50907044)
文摘We develop a model of CA3 neurons embedded in a resistive array to mimic the effects of electric fields from a new perspective. Effects of DC and sinusoidal electric fields on firing patterns in CA3 neurons are investigated in this study. The firing patterns can be switched from no firing pattern to burst or from burst to fast periodic firing pattern with the increase of DC electric field intensity. It is also found that the firing activities are sensitive to the frequency and amplitude of the sinusoidal electric field. Different phase-locking states and chaotic firing regions are observed in the parameter space of frequency and amplitude. These findings are qualitatively in accordance with the results of relevant experimental and numerical studies. It is implied that the external or endogenous electric field can modulate the neural code in the brain. Furthermore, it is helpful to develop control strategies based on electric fields to control neural diseases such as epilepsy.
文摘The mean climatology and the basic characteristics of the ENSO cycle simulated by a coupled model FGCM-1.0 are investigated in this study. Although with some common model biases as in other directly coupled models, FGCM-1.0 is capable of producing the interannual variability of the tropical Pacific, such as the ENSO phenomenon. The mechanism of the ENSO events in the coupled model can be explained by “delayed oscillator” and “recharge-discharge” hypotheses. Compared to the observations, the simulated ENSO events show larger amplitude with two distinctive types of phase-locking： one with its peak phase-locked to boreal winter and the other to boreal summer. These two types of events have a similar frequency of occurrence, but since the second type of event is seldom observed, it may be related to the biases of the coupled model. Analysis show that the heat content anomalies originate from the central south Pacific in the type of events peaking in boreal summer, which can be attributed to a different background climatology from the normal events. The mechanisms of their evolutions are also discussed.
