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Transition dynamics have been studied widely in two-mode Bose–Einstein condensate systems with linear coupling effects. Nonlinear interaction between atoms would induce a nonlinear Josephson oscillation, which admits an oscillation form different from the classical Josephson oscillation. Similar extensions for the Rosen–Zener transition and the Landau–Zener transition also suggest that a strong nonlinear strength would induce nonlinear-type transition dynamics, which is in sharp contrast to the linear process. Interestingly, here we show a standard Josephson oscillation that has a constant linear coupling strength, no matter how great the nonlinear interaction strength is. This characteristic is in sharp contrast to the nonlinear Josephson oscillation reported before in nonlinear coupled systems. By manipulating the linear coupling strength with the RF field, we demonstrate that the Rosen–Zener transition particles, with an invariant distribution profile, can be managed well under exponential and periodic forms. The nonlinear interaction strength is found to have no effect on the transition rate between atoms in the two components for the case where the inter- and intra-atomic interaction strengths are equal. Furthermore, we test the robustness of the transition dynamics against parameter deviations and noises in the initial condition. These results are helpful for controllable quantum state preparations.

We study the relations between modulational instability and several well-known nonlinear excitations in a nonlinear fiber such as bright soliton, nonlinear continuous wave, Akhmediev breather, Peregrine rogue wave, and Kuznetsov–Ma breather. We present a quantitative correspondence between them based on the dominant frequency and propagation constant of each perturbation on a continuous-wave background. We especially demonstrate that rogue wave comes from modulational instability with the resonance perturbation on continuous-wave background. The numerical simulations are performed to test these theoretical results. These results will deepen our understanding of rogue wave excitation and be helpful for controllable nonlinear wave excitations in nonlinear fiber and other nonlinear systems.

A binary Mg-4Zn alloy was fabricated as a potential degradable biomaterial. To improve the corrosion resistance of Mg-4Zn alloy, an amorphous micro-arc oxidation (MAO) coating was prepared on the Mg-4Zn substrate. Electrochemical measurements and immersion tests were employed to evaluate the corrosion resistance of the specimen in simulated body fluid (SBF). Electrochemical measurements show that the Mg-4Zn alloy covered with a MAO coating has a much lower corrosion current density and a much greater polarization resistance. Immersion tests suggest that the degradation of Mg-4Zn substrate is relatively serious during the initial 8 h of immersion although it has been protected by a MAO coating. When most micro-pores within the MAO coating have been filled with precipitates resulted from the corrosion of the metal substrate, the degradation of the Mg-4Zn substrate is significantly delayed.

We investigate the properties of phase transitions in a weakly coupled ultracold atom-molecule boson system based on the phase space analysis approach. We identify the pure molecular and mixed atom-molecule phases of the system by different values of the time average of molecular population. When applying a periodic modulation on the energy detuning, we find that the atom-molecule mixing dynamics can be well controlled. For both high- and low-frequency modulations, it is shown that the transition points can be shifted effectively by choosing parameters of the periodic modulation appropriately. The analytical expressions for the dependence of the transition parameters on the modulation parameters are also obtained for the two cases. In particular, when the modulation with a frequency near the atom-molecule transition frequency is applied, the resonance between the periodic modulation and atom-molecule Rabi oscillation will emerge, which can affect the atom-molecule mixing dynamics dramatically and lead to the complex chaos phenomenon.

We study optical rogue waves (RWs) in a nonlinear graded-index waveguide with variable coefficients. An exact RW solution on Gaussian background beam is presented, in contrast to the previous studies about RWs, on plane wave background. It is shown that the characteristics of RWs are maintained on Gaussian background beam and that the beam’s width is even a bit smaller than the RWs scale. These results may raise the possibility of related experiments and potential applications in nonlinear optics.

We find that diverse nonlinear waves, such as soliton, Akhmediev breather, and rogue waves (RWs), can emerge and interplay with each other in a two-mode coupled system. It provides a good platform to study interaction between different kinds of nonlinear waves. In particular, we obtain dark RWs analytically for the first time in the coupled system, and find that two RWs can appear in the temporal-spatial distribution. Possible ways to observe these nonlinear waves are discussed.

One new type metastable β-titanium-alloy for biomedical applications Ti-25Nb-2Mo-4Zr (wt %) with lower elastic modulus was designed based on the d-electron alloy design method and prepared in this study. The microstructure and basic mechanical properties of designed alloy were investigated in this paper. The test results show that the Yang’s modulus is 65GPa and the tensile strength is 863MPa of designed alloy after solution treatment at 700℃ for 0.5 h; the Yang’s modulus is 68GPa and the tensile strength is 1032MPa for the designed alloy after aging treatment at 500℃ for 2 h. The designed alloy with lower Yang’s modulus is expected to have good prospects for implant biomaterials for its excellent biomechanical compatibility.

We present a series of chirp-free and chirped analytical nonautonomous soliton solutions to the generalized nonlinear Schrödinger equation with distributed coefficients by Darboux transformation from a trivial seed. For a chirp-free nonautonomous soliton, the dispersion management term can change the motion of a nonautonomous soliton and does not affect its shape at all. Specifically, the classical optical soliton can be presented with a variable dispersion term and nonlinearity when there is no gain. For a chirped nonautonomous soliton, dispersion management can meanwhile affect the shape and motion of nonautonomous solitons. The periodic dispersion term can be used to control its “breathing” shape, and it does not affect the trajectory of a nonautonomous soliton center with a certain condition.

Magnesium and its alloys are potential biodegradable materials due to their outstanding biological performance, but their poor corrosion resistance greatly limits their applications as bone implants. This paper investigates the influence of in situ magnesium oxide coating on corrosion resistance of pure magnesium in normal saline. It was discovered by SEM that rough and porous oxide coatings were obtained on the surface of the pure magnesium after heat-treated at 400~500°C and the samples were severely corroded after immersion in 0.9 wt.% NaCl solution for 3 days. It also showed that the weight loss rates of the treated pure magnesium (TPM) samples were about 5~6 times higher than that of the untreated pure magnesium (UPM) sample. Electrochemical measurements showed that the corrosion current density (icorr) of the TPM samples was one order of magnitude higher than that of the UPM sample.