Cang-Long Wang

Dust negative ion acoustic shock waves considering dust size distribution effect

A multi-ion dusty plasma containing hot isothermal electrons, ions (light positive ions and heavy negative ions), and extremely and negatively charged dust grains is studied in the present paper. The dust negative ion acoustic shock waves have been investigated by employing the reductive perturbation method. How the dust size distribution affects the height and the thickness of the nonlinear shock wave is studied. It is noted that the different dust size distribution has different shock wave form and different moving speed.

The effect of dust size distribution on the damping of the solitary waves in a dusty plasma

The effect of the dust size distribution on the damping rate of the solitary wave in a dusty plasma is investigated in the present paper. It is found that the damping rate increases as either the mean radius of dust grains increases or as the total number density of the dust grains increases. The damping rate is less for usual dusty plasma (about which the number density of the smaller dust grains is larger than that of the larger dust grains) than that of the unusual dusty plasma (about which the number density of the larger dust grains is larger than that of the smaller dust grains).

Investigation of superlubricity in a two-dimensional Frenkel-Kontorova model with square lattice symmetry

A two-dimensional Frenkel–Kontorova model with a square symmetry substrate potential for a square lattice layer driven by an external driving force with an arbitrary direction α and an arbitrary misfit angle θ between upper and lower layers is presented in this paper. The effects of the system parameters have been investigated. The application of our results to the tribology is discussed and the dependence of the static friction force on the system parameters is studied. How to make the material with superlubricity is suggested.

Influence of charging process and size distribution of dust grain on the electric conductivity of dusty plasma

The effects of dust size distribution and charging process of dust grains on the complex electric conductivity of dusty plasmas have been investigated in the present paper. Comparisons are made between real dusty plasma in which there are many different dust grain species and the mono-sized dusty plasma (MDP) in which there is only one kind of dust grain whose size is the average dust size. In some cases the complex electric conductivity of real dusty plasma is larger than that of MDP, while in other cases it is smaller than that of MDP, it depends on the dust size distribution function.

The collision effect between dust grains and ions to the dust ion acoustic waves in a dusty plasma

Damping solitary wave in dusty plasma is studied by considering the collision effect between dust grains and ions. It can be described by a KdV type equation in which a damping term of φ2 exist. It is found that both the amplitude and propagation velocity of the solitary wave decrease with time exponentially. Our results are compared with another KdV type equation with the damping term of φ. It is noted that the damping rate of the KdV type equation with the damping term of φ2 is larger than that with the term of φ. It is found that the damping rate is proportional to the collision frequency between dust grains and ions.

The stability and the growth rate of the electron acoustic traveling wave under transverse perturbations in a magnetized quantum plasma

Theoretical and numerical studies are carried out for the stability of the electron acoustic waves under the transverse perturbation in a magnetized quantum plasma. The Zakharov-Kuznetsov (ZK) equation of the electron-acoustic waves (EAWs) is given by using the reductive perturbation technique. The cut-off frequency is obtained by applying a transverse sinusoidal perturbation to the plane soliton solution of the ZK equation. The propagation velocity of solitary waves, the real cut-off frequency, as well as the growth rate of the higher order perturbation to the traveling solitary wave are obtained.

Hysteresis in the pinning-depinning transition in underdamped two-dimensional Frenkel-Kontorova model

Hysteretic phenomenon is studied in the 2D Frenkel-Kontorova model system. In the depinning process, two critical points Fs1 and Fs2 are found. In the pinning process, two critical points Fb1 and Fb2 are also found. The dependence of four critical forces Fs1, Fs2, Fb1, Fb2 on the system parameters such as external driving force, misfit angle, winding number, interatomic strength is investigated. The winding number b/a substantially affect the depinning forces of Fs1 and Fs2, but not the pinning forces of both Fb1 and Fb2. The pinning force of Fb2 linearly increases as the interatomic interaction strength (K) increase. The dependence of both Fb1 and Fb2 on the misfit angle θ is not in fractal structure which is different from the depinning force of Fs1.

Contribution of the Dust Grains to the Damping of the Electromagnetic Waves Propagating in Plasma

Explanation for the damping of electromagnetic (EM) waves propagating in a plasma is given. Comparisons of the damping rates between a general plasma (with no dust grains) and a dusty plasma are given. It is found that, in a certain range of the EM waves, the damping rate in the dusty plasma is much larger than that in a general plasma. The damping rate mainly depends on the number density of the dust grains and the frequency of the EM waves.

Ratchet effect and amplitude dependence of phase locking in a two-dimensional Frenkel-Kontorova model

We demonstrate the ratchet and phase locking effects in a two-dimensional overdamped Frenkel-Kontorova model with a square symmetric periodic substrate when both a longitudinal dc drive and a circular ac drive are applied. Besides the harmonic steps, the large half integer steps can also clearly be seen in the longitudinal (x) direction. These half integer steps are directly correlated to the appearance of positive and negative ratchet effects in the transverse (y) direction due to the symmetry breaking in the combination of the dc and ac drives. The angle between the net displacement and the longitudinal direction is analytically obtained in a single period of the ac drive. In the examination of the amplitude dependence of the ac drive, the maxima decrease monotonically with the amplitude, while the anomalies occur for the critical depinning force and the harmonic steps due to the spatial symmetry breaking of orbits in the presence of the ac drive.

Frictional Dynamics in a Two Dimensional Frenkel-Kontorova Model with Square Lattice Symmetry

A two-dimensional (2D) Frenkel-Kontorova (FK) model with a square symmetry substrate potential for a square lattice layer driven by an external driving force with an arbitrary direction α and an arbitrary misfit angle θ between upper and lower layers is presented. Both the theoretical and the numerical study of the lock-to-sliding transition for this 2D FK model are given. The results show that both the misfit angle θ and the direction (cosα, sinα) of the external driving force play crucial roles in the scenario of the lock-to-sliding transition and the determination of the structure of the sliding state. The effects of the system parameters such as the magnitude of the adhesive force between the two layers, the stiffness of the interatomic bonds, and the viscous damping constant to the lock-to-sliding transition have also been investigated. The application of our results to the tribology is discussed and the dependence of the static friction force on the system parameters is studied. It is noted that the parameters of both θ and α play important roles in the magnitude of the static friction force Fs. The numerical results show that the possibility to obtain superlubricity is larger between two same material layers than that for different materials. How to make the material with superlubricity is suggested.