Band 75, Heft 7

An efficient method for the large-scale fabrication of composite polyvinyl alcohol polymer nano fibers loaded with magnetic nanoparticles and methotrexate is reported in this study. We have demonstrated that nonwoven textile formed by needleless electro spinning is effective in immobilization and triggered the release of drugs, which is achieved by an alternating magnetic field induced heating of magnetic nanoparticles. This smart stimuli-responsive release ability, biocompatibility, and ultra-lightweight property render enormous potential for this electrospun nano fiber mat to be used as an anti-psoriatic drugs release platform, which may have far-reaching applications in dermatology.

A relatively simple chaotic hyperjerk circuit, which is the modified chaotic hyperjerk system [Dalkiran and Sprott, IJBC 2016] is proposed and investigated in this paper. Only one semiconductor diode modelled the nonlinear function capable of rich and complex dynamical behaviours of the system. We investigate a new kind of behaviours name “bubbles of bifurcation’’ (referred as BsB hereafter) observed here for the first time in the hyperjerk system. An interesting phenomenon of mixed-mode bursting oscillations (MMBOs) is also investigated. The complex dynamics of the novel oscillator (such as MMBOs, BsB, offset boosting and multistability) with respect to its parameters and initial conditions are uncovered using bifurcation diagrams, Lyapunov exponents (LE) and phase portraits. As another interesting property of this circuit, some parameter regions are determined for the existence of coexisting BsB and the coexistence of asymmetric mixed-mode bursting oscillations. Let us emphasized that the complex phenomena observed in this work is very rare in the literature and henceforth merit dissemination. Finally, a physical circuit is constructed to demonstrate some experimental observation of MMBOs.

In community ecology, the stability of a predator–prey system is a considerably desired issue; as a result, population control of a predator–prey system is very important. The dynamics of continuous-time models with Z-type control is studied earlier. But, the effectiveness of the Z-type control mechanism in a discrete-time set-up is lacking. First, we consider a Lotka–Volterra type discrete-time predator–prey model. We observe that without control, the system exhibits rich dynamical behaviors including chaotic oscillations. We apply the Z-control mechanism in both direct and indirect ways to the system and observe that in both cases, controllers have the property to drive the populations of the system to the desired state. We conduct numerical simulation as supporting evidence of our analytical results.

This paper presents an approximate analytical solution for the vertical dynamic impedance and shaft resistance of rectangular closed diaphragm walls (RCDWs) embedded in a homogeneous soil medium and resting on rock base. The vertical continuous displacement model for the steady-state response of RCDWs is proposed to ensure proper RCDWs-soil contact and satisfy the boundary condition of soil at infinite horizontal distance. The soil horizontal displacement is neglected and the effect is indirectly taken into account by the modification of soil modulus. The functional of system potential and kinetic energies is established via the soil and RCDWs displacement functions. The governing equations of the system and the relevant conditions are obtained and the vertical shaft resistance of RCDWs is established by employing Hamilton’s variational principle for RCDWs-soil system and thin layer element, respectively. Some representative numerical examples are presented to portray the influences of soil core ratio, height–width ratio, diaphragm wall-soil stiffness ratio, and aspect ratio of RCDWs cross sections on the dynamic impedances and stiffness of the shaft resistance.

Consideration is given to the shallow-water equations, a hyperbolic system modeling the propagation of long waves at the surface of an incompressible inviscible fluid of constant depth. It is well known that the solution of the Riemann problem associated to this system may feature dry states for some configurations of the Riemann data. This article will discuss various scenarios in which the Riemann problem for the shallow water system arises in a physically reasonable sense. In particular, it will be shown that if certain physical assumptions on the disposition of the Riemann data are made, then dry states can be avoided in the solution of the Riemann problem.

Considering the slip boundary condition, the rotating electro-osmotic flow of a third grade fluid in a channel formed by two parallel plates is investigated in the present study. The charge distribution is treated with the Debye–Hückel approximation analytically. Based on the finite difference method, the velocity profile for rotating electro-osmotic flow of third grade fluid is obtained numerically. It is shown that the non-Newtonian parameter of third grade fluid and the velocity slip factor play the important roles for the rotating electro-osmotic flow. The increasing non-Newtonian parameter slows down the flow and decreases the velocity magnitude, and the increasing slip parameter β has the similar influence on the velocity profile. Furthermore, the effect of the inclusion of third grade on the velocity profile is more conspicuous in the area near the walls.

The present study is devoted to ultrasonic characterization of Si-oil based magneto-rheological (MR) fluid. Initially, the structural, morphological and magnetic properties of carbonyl iron powder have been carried out by its X-ray diffraction (XRD), scanning electron microscope (SEM), SEM-energy dispersive X-ray analyser (SEM-EDX) and vibrating sample magnetometer (VSM) measurements. The cubic structure with lattice parameter 2.841 Å of powdered material is confirmed by XRD study while spherical particle content is confirmed by SEM measurement. The VSM measurement of powder endorses the smooth magnetization and demagnetization with no remnance and coercivity. The rheological and ultrasonic properties are measured for pure Si-oil and four synthesized MR fluids having 10–40 wt% of carbonyl iron powder. The density and viscosity of synthesized MR fluid is found to enhance with weight percentage of carbonyl iron powder. In absence of magnetic field, the longitudinal ultrasonic velocity is found to decay with temperature and concentration. In presence of magnetic field, the longitudinal ultrasonic velocity is found to enhance while velocity measured at transverse magnetic field is found to decay for each MR fluid. The change in ultrasonic velocity with concentration at fixed temperature or magnetic field resembles the magnetization characteristics of disperse powder in MR fluid. The study opens a new dimension for its characterization through ultrasonic non-destructive technique.

In this study, the propagation characteristics of electromagnetic waves in a parity-time (PT)-symmetrical 1D photonic crystal comprising dispersed silver layers are investigated. Based on the transmission matrix theory, the total reflection and transmission coefficients of the structure are obtained. It was found that, due to the PT-symmetrical structure, the reflections of the left and right incident waves are nonreciprocal. Numerical simulations indicated that the width of the band gap decreases with the increase in the gain and loss factor ρ in the PT medium, and the band gap ultimately disappears when ρ reaches a critical value, i. e., ρ P T ${\rho }_{PT}$ . With the increase in ρ > ρ P T $\rho { >}{\rho }_{PT}$ , anomalous transmittance and reflection occur within the original bang gap. As the gain and loss factor ρ continue to increase, the abnormal transmittance and reflectivity exhibit a trend of oscillatory decline, and perfect transmission can be achieved at larger values of ρ .

An analysis of the self-focusing of highly intense chirped pulse laser under exponential plasma density ramp with higher order value of axial electron temperature has been done. Beam width parameter is derived by using paraxial ray approximation and then solved numerically. It is seen that self-focusing of chirped pulse laser is intensely affected by the higher order values of axial electron temperature. Further, influence of exponential plasma density ramp is studied and it is concluded that self-focusing of laser enhances and occurs earlier. On the other hand defocusing of beam reduces to the great extent. It is noticed that the laser spot size reduces significantly under joint influence of the density ramp and the axial electron temperature. Present analysis may be useful for the analysis of quantum dots, the laser induced fusion and etc.