Volume 76, Issue 5

Previous studies of the gold-nanoparticles-covered U-type medical optical fiber sensor with millimeter size were mainly confined to the experimental aspect, while the corresponding theoretical studies were only for bare fibers based on geometrical optics or those for micron level photonic crystal fibers based on wave optics. Combining wave and geometrical optics, the gold-nanoparticles-covered U-type optical fiber sensor was simulated with millimeter size. The localized surface plasmon resonance absorption peak near 540 nm is obtained in the simulation, very close to that (≈560 nm) of the experimental value for the gold nanoparticles of 37 nm size. Compared with the refractive index (RI) sensitivity (≈7.10/RIU) for the plain, U-type optical fiber (≈43.50/RIU) exhibits more than 610% enhancement in the gold-nanoparticles-covered sample. Present studies would be helpful to the further simulation and design for various noble metal nanoparticles covered optical fiber sensors with different shapes.

As an important technology of the quantum detection, the quantum synchronization detection is always used in the detection or measurement of some quantum systems. A probing model is established to describe the probing of a qubit system in the cavity field and to reveal the effect of the environment (cavity) on the quantum synchronization occurrence, as well as the interactions among environment, a qubit system, and probing equipment. By adjusting the frequency of the probe, the in-phase, anti-phase, and out-of-phase synchronization can be achieved. Simultaneously, the effect of γ3${\gamma }_{3}$ which describes the interaction strength between the probe and environments for quantum synchronization is discussed under different Ohmic dissipation index s . Finally, the machine learning method is applied to present an optimization for classification and regression of synchronization transition dependent on s and γ3${\gamma }_{3}$.

We have studied the photodetachment dynamics of the H − ion in a harmonic potential confined in a quantum well for the first time. The closed orbits of the detached electron in a confined harmonic potential are found and the photodetachment spectra of this system are calculated. It is interesting to find that the photodetachment spectra depend sensitively on the size of the quantum well and the harmonic frequency. For smaller size of the quantum well, the harmonic potential can be considered as a perturbation, the interference effect between the returning electron wave bounced back by the quantum well and the initial outgoing wave is very strong, which makes the photodetachment spectra exhibits an irregular saw-tooth structure. With the increase of the size of the quantum well, the photodetachment spectra oscillates complicatedly in the higher energy region. For very large size of the quantum well, the photodetachment spectra approach to the case in a free harmonic potential, which is a regular saw-tooth structure. In addition, the harmonic frequency can also affect the photodetachment spectra of this system greatly. Our work provides a new method for the study of spatially confined low-dimensional systems and may guide the future experimental research for the photodetachment dynamics in the ion trap.

A system of partial differential equations describing the one-dimensional motion of an inviscid self-gravitating and spherical symmetric dusty gas cloud, is considered. Using the method of the kinematics of one-dimensional motion of shock waves, the evolution equation for the spherical shock wave of arbitrary strength in interstellar dusty gas clouds is derived. By applying first order truncation approximation procedure, an efficient system of ordinary differential equations describing shock propagation, which can be regarded as a good approximation of infinite hierarchy of the system. The truncated equations, which describe the shock strength and the induced discontinuity, are used to analyze the behavior of the shock wave of arbitrary strength in a medium of dusty gas. The results are obtained for the exponents from the successive approximation and compared with the results obtained by Guderley’s exact similarity solution and characteristic rule (CCW approximation). The effects of the parameters of the dusty gas and cooling-heating function on the shock strength are depicted graphically.

In this study, free vibration analysis of nanobeams under various non-ideal supports have presented. Size effect of nanobeams has applied by utilizing modified couple stress theory. Hamilton’s principle has been used to derive the equation of motion. Governing equation has subjected to non-ideal boundary conditions which are modeled as linear functions including an introduced weighting factor ( k ). Obtained numerical results have verified by comparing with the published results. Results show that fundamental resonance frequencies of non-ideal clamped nanobeams are significantly decreased when it is compared to ideal supports. However, non-ideal simply supports creates a minor increase effect on fundamental frequencies with respect to clamped ones. Also, nano-size effect has investigated for non-ideal supports. It has found that, the smaller cross-sectional size of nanobeam causes increasing effect of non-ideal supports on fundamental frequencies.

The article presents the study of the evolutionary behavior of plane and cylindrically symmetric acceleration discontinuities along the characteristic path under the effect of dust particles in a non-ideal magnetogasdynamic flow. Implications regarding the propagation of disturbances in planar and cylindrically symmetric flows have been shown. Using the characteristics of the governing quasilinear system as a reference coordinate system, we transform the fundamental equations and find the solution. It is explored how the dust particles, along with the nonideal parameter, will influence the steepening or flattening of the propagating waves in magnetic and nonmagnetic cases. The transport equation leading to the evolution of acceleration discontinuities is determined, which provides the relation for the occurrence of shock. The impact of non-idealness of the gas and dust on the evolutionary process of propagating waves for the magnetic and nonmagnetic cases are discussed. The comparison between the flow patterns and distortion of the propagating waves for planar and cylindrically symmetric flows is demonstrated under the various parameter effects.

The head-on collision between two ion-acoustic solitons (IASs) is studied in pair ions plasmas with hybrid Cairns–Tsallis-distributed electrons. The chosen model is inspired from the experimental studies of Ichiki et al. [Phys. Plasmas 8, 4275 (2001)]. The extended Poincaré–Lighthill–Kuo (PLK) method is employed to obtain the phase shift due to the IASs collision. Both analytical and numerical results reveal that the magnitude of the phase shift is significantly affected by the nonthermal and nonextensive parameters ( α and q ), the number density ratios ( μ and υ ) as well as the mass ratio σ . For a given mass ratio σ≃0.27$\sigma \simeq 0.27$ (Ar + , SF6−${\text{SF}}_{6}^{-}$), the magnitude of the phase shift ΔQ(0)${\Delta}{Q}^{\left(0\right)}$ decreases slightly (increases) with the increase of q ( α ). The effect of α on ΔQ(0)${\Delta}{Q}^{\left(0\right)}$ is more noticeable in the superextensive distribution case ( q  < 1). As σ increases [σ≃0.89$\sigma \simeq 0.89$ (Xe + , SF6−${\text{SF}}_{6}^{-}$)], the phase shift becomes wider. In other terms, the phase shift was found to be larger under the effect of higher densities of the negative ions. Our findings should be useful for understanding the dynamics of IA solitons’ head-on collision in space environments [namely, D -regions (H+${\text{H}}^{+}$, O2−${\text{O}}_{2}^{-}$) and F-regions (H + , H − ) of the Earth’s ionosphere] and in laboratory double pair plasmas [namely, fullerene (C + , C − ) and laboratory experiment (Ar + , F − )].

Using Sagdeev pseudo-potential technique, we have studied the arbitrary amplitude ion acoustic solitons, double layers and supersolitons in a collisionless plasma consisting of adiabatic warm ions, non-thermal hot electrons and isothermal cold electrons immersed in an external uniform static magnetic field. We have used the phase portraits of the dynamical system describing the non-linear behaviour of ion acoustic waves to confirm the existence of different solitary structures. We have found that the system supports (a) positive potential solitons, (b) negative potential solitons, (c) coexistence of both positive and negative potential solitons, (d) negative potential double layers, (e) negative potential supersolitons and (f) positive potential supersolitons. Again, we have seen that the amplitude of the positive potential solitons decreases or increases with increasing n ch according to whether 0<nch<nch(c)$0{< }{n}_{ch}{< }{n}_{ch}^{\left(c\right)}$ or nch(c)<nch≤1${n}_{ch}^{\left(c\right)}{< }{n}_{ch}\le 1$, where nch${n}_{ch}$ is the ratio of isothermal cold and non-thermal hot electron number densities, and nch(c)${n}_{ch}^{\left(c\right)}$ is a critical value of n ch . Also, we have seen that the amplitude of the positive potential solitons decreases with increasing β e , where β e is the non-thermal parameter. We have also investigated the transition of different negative potential solitary structures: negative potential soliton (before the formation of negative potential double layer) → negative potential double layer → negative potential supersoliton → negative potential soliton (after the formation of negative potential double layer) by considering the variation of θ only, where θ is angle between the direction of the external uniform static magnetic field and the direction of propagation of the ion acoustic wave.