Generation of picosecond soliton pulses with tunable repetition rate by modulational instability

Picosecond soliton pulse train has been obtained from a passively mode locked erbium-doped ring fiber laser. The passive mode-locking mechanism that is at play in this laser relies on the modulational instability (MI) theory. By accurately adjusting the polarization setting of the circulating cavity light, the repetition rate can be tuned from 58 to 114 GHz. Theoretical explanations has also been given.     

Study on the drain bias effect on negative bias temperature instability degradation of an ultra-short p-channel metal-oxide-semiconductor field-effect transistor

This paper studies the effect of drain bias on ultra-short p-channel metal-oxide-semiconductor field-effect transistor (PMOSFET) degradation during negative bias temperature (NBT) stress. When a relatively large gate voltage is applied, the degradation magnitude is much more than the drain voltage which is the same as the gate voltage supplied, and the time exponent gets larger than that of the NBT instability (NBTI). With decreasing drain voltage, the degradation magnitude and the time exponent all get smaller. At some values of the drain voltage, the degradation magnitude is even smaller than that of NBTI, and when the drain voltage gets small enough, the exhibition of degradation becomes very similar to the NBTI degradation. When a relatively large drain voltage is applied, with decreasing gate voltage, the degradation magnitude gets smaller. However, the time exponent becomes larger. With the help of electric field simulation, this paper concludes that the degradation magnitude is determined by the vertical electric field of the oxide, the amount of hot holes generated by the strong channel lateral electric field at the gate/drain overlap region, and the time exponent is mainly controlled by localized damage caused by the lateral electric field of the oxide in the gate/drain overlap region where hot carriers are produced.     

Dynamic instability of collective myosin Ⅱ motors

Some kinds of muscles can oscillate spontaneously,which is related to the dynamic instability of the collective motors.Based on the two-state ratchet model and with consideration of the motor stiffness,the dynamics of collective myosin Ⅱmotors are studied.It is shown that when the motor stiffness is small,the velocity of the collective motors decreases monotonically with load increasing.When the motor stiffness becomes large,dynamic instability appears in the forcevelocity relationship of the collective-motor transport.For a large enough motor stiffness,the zero-velocity point lies in the unstable range of the force-velocity curve,and the motor system becomes unstable before the motion is stopped,so spontaneous oscillations can be generated if the system is elastically coupled to its environment via a spring.The oscillation frequency is related to the motor stiffness,motor binding rate,spring stiffness,and the width of the ATP excitation interval.For a medium motor stiffness,the zero-velocity point lies outside the unstable range of the force-velocity curve,and the motion will be stopped before the instability occurs.     

Viscosity,heat conductivity,and Prandtl number effects in the Rayleigh–Taylor Instability

The two-dimensional Rayleigh–Taylor instability problem is simulated with a multiple-relaxation-time discrete Boltzmann model with a gravity term. Viscosity, heat conductivity, and Prandtl number effects are probed from macroscopic and nonequilibrium viewpoints. In the macro sense, both viscosity and heat conduction show a significant inhibitory effect in the reacceleration stage, which is mainly achieved by inhibiting the development of the Kelvin–Helmholtz instability. Before this, the Prandtl number effect is not sensitive. Viscosity, heat conductivity, and Prandtl number effects on nonequilibrium manifestations and the degree of correlation between the nonuniformity and the nonequilibrium strength in the complex flow are systematically investigated.     

Nonlinear acoustic waves in a collisional self-gravitating dusty plasma

Using the reductive perturbation method,we investigate the small amplitude nonlinear acoustic wave in a collisional self-gravitating dusty plasma.The result shows that the small amplitude dust acoustic wave can be expressed by a modified Korteweg-de Vries equation,and the nonlinear wave is instable because of the collisions between the neutral gas molecules and the charged particles.     

Investigation of fast pitch angle scattering of runaway electrons in the EAST tokamak

This paper reports that an experimental investigation of fast pitch angle scattering(FPAS) of runaway electrons in the EAST tokamak has been performed.From the newly developed infrared detector(HgCdTe) diagnostic system,the infrared synchrotron radiation emitted by relativistic electrons can be obtained as a function of time.The FPAS is analysed by means of the infrared detector diagnostic system and the other correlative diagnostic systems(including electron-cyclotron emission,hard x-ray,neutrons).It is found that the intensity of infrared synchrotron radiation and the electron-cyclotron emission signal increase rapidly at the time of FPAS because of the fast increase of pitch angle and the perpendicular velocity of the energetic runaway electrons.The Parail and Pogutse instability is a possible mechanism for the FPAS.     

Neutrino beam plasma instability

We derive relativistic fluid set of equations for neutrinos and electrons from relativistic Vlasov equations with Fermi weak interaction force. Using these fluid equations, we obtain a dispersion relation describing neutrino beam plasma instability, which is little different from normal dispersion relation of streaming instability. It contains new, nonelectromagnetic, neutrino-plasma (or electroweak) stable and unstable modes also. The growth of the instability is weak for the highly relativistic neutrino flux, but becomes stronger for weakly relativistic neutrino flux in the case of parameters appropriate to the early universe and supernova explosions. However, this mode is dominant only for the beam velocity greater than 0.25c and in the other limit electroweak unstable mode takes over.     

Solitary Wave Solutions of Discrete Complex Ginzburg-Landau Equation by Modified Adomian Decomposition Method

In this paper, exact and numerical solutions are calculated for discrete complex Ginzburg-Landau equation with initial condition by considering the modified Adomian decomposition method （mADM）, which is an efficient method and does not need linearization, weak nonlinearity assumptions or perturbation theory. The numerical solutions are also compared with their corresponding analytical solutions. It is shown that a very good approximation is achieved with the analytical solutions. Finally, the modulational instability is investigated and the corresponding condition is given.     

周期调制结构平面薄膜电爆炸实验研究

在金属层表面引入微结构以实现对Z箍缩等离子体形成和发展过程中不稳定性的调控具有重要研究价值.在“强光一号”装置上(峰值电流~1.4 MA,上升时间~100 ns),开展了针对具有一维周期性凹槽调制结构的金属薄膜的电爆炸实验研究.实验负载采用外推型平面结构,基底为30μm厚铝膜,刻蚀周期为2 mm,刻蚀深度约为10μm.通过激光阴影成像、激光干涉成像和可见光自辐射成像等系统进行联合诊断.实验结果表明刻蚀结构对等离子体发展过程的不稳定性特征产生了明显调制作用,原本征波长也受到抑制,微结构周期对不稳定结构波长产生趋同效应;未刻蚀一侧边界层同样受刻蚀层结构的影响,在不稳定结构上表现出相似形貌,且内外侧不稳定性特征的耦合关联性增强;刻蚀凹槽处在爆炸过程中膨胀更为迅速,形成的表面等离子体结构与初始结构反相;在刻蚀结构的几何突变处会形成细长的等离子体喷流,在二分之一刻蚀波长处出现波谱特征峰.理论分析表明电流密度调制造成电热不稳定性分布改变是调控作用产生的重要原因.     

Modeling of cascaded high isolation bidirectional amplification in long-distance fiber-optic time and frequency synchronization system

We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs), no spontaneous lasing even with high gain, in longdistance fiber-optic time and frequency(T/F) synchronization system. It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design, but the amplified spontaneous emission(ASE) noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise, the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773 × 10-13/1 s. And the instability caused by asymmetry is 2.6064 × 10-16/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m. The intensity noises originating from the laser and detector, the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied. The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis. In summary, the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift, while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.