International Journal of Modern Physics B

Piezoelectric actuators are widely used in the field of high-precision positioning control. However, due to the inherent hysteresis nonlinearity of piezoelectric actuators, it can seriously affect their accuracy in tracking and positioning systems, and even cause system instability. In order to suppress the hysteresis characteristics of piezoelectric, based on the analysis of piezoelectric characteristics and the characteristics of classical Bouc–Wen model, a Bouc–Wen model is adopted to describe the hysteresis characteristics of piezoelectric actuators, an artificial bee colony (ABC) algorithm is used to identify Bouc–Wen. The maximum error of the model is 2.49%. According to the established hysteresis model, its inverse model is obtained as the feedforward controller, and the inverse model compensation method is used to realize the open-loop control of the system. Since the feedforward controller based on the inverse model cannot eliminate the modeling errors and external disturbances of the inverse model, a fractional-order controller is designed on the basis of inverse compensation, and a compound control method combining feedforward control and feedback control is adopted. Experiments show that the fractional-order control system has fast response speed, small steady-state error and simple structure compared with other nonlinear controllers, positioning error is about 3%.

ZrO₂ thin films are deposited by the sol–gel dip-coating technique where the thermal annealing temperature and the number of deposited layers determine the properties of this material concerning the application in field-effect transistor (FET) devices in conjunction with SnO₂ layer, also produced by sol–gel dip-coating. The best annealing temperature for the ZrO₂ film was found as 400°C, along with a small number of layers and the position of the layer inside the oven, which determines the dominant heat transport mechanism of conduction or convection phenomena. The electrical insulating property of ZrO₂ layers was confirmed with the current in the order of pA, even for layers about 100 nm thick. The temperature of 400°C also leads to a lower leak current through the gate in the device, which is three orders of magnitude lower than the source-drain current (in the order of a tenth of $\mu$A).

The paper presents the results of a study of the optical properties of CdS on the basis of the band anticrossing theory (BAC) with the involvement of the wider source data to the analysis results. Depending on the growth conditions, the presence and change in the concentration of oxygen and intrinsic point defects, which determine the composition of the crystals, have been taken into account. Data from studies of the structural features of crystals have also been used. The concept of nonuniform distribution of oxygen isoelectronic centers in the CdS volume due to their predominant segregation in layers of stacking faults (SFs) and also on dislocations has been introduced.

To analyze the optical data, the capabilities of the method for constructing band models, which collect extensive and multilateral information about specific samples have been used. A refined model multizone of $\mathrm{\text{CdS}}\cdot \mathrm{\text{O}}$ with SFs, which determines the spectrum of edge emission, has been presented.

The nature of the edge emission A₂B₆ crystals with a small deviation from stoichiometry (CdS type) was explained as a spectrum of bound excitons at oxygen centers in SF layers. The article gives recommendations for the diagnostics of CdS crystals, suitable for creating stable luminescent systems or lasers.

With the growing demand for energy, the importance of oil as a major energy resource is increasingly evident, and trade has become the key to balancing energy supply and demand. We construct the evolving international oil trade network (iOTN) and analyze the structure and evolution characteristics of the network. Meanwhile, we identify different oil market states by applying the sequential clustering method, combined with relevant network indicators. We find an increase in bilateral cooperation among economies in the oil market, closer trade ties and an upward trend in network reciprocity. The iOTN is heterogeneous, and economies with widely differing trade positions are more likely to cooperate. Trade cooperation with significant trade volumes is more irreplaceable and stable. The changes of oil market state in 1990, 2004 and 2014 indicate that major international events significantly impact the structure of energy systems and trade networks. The division of the oil trade market state by sequential clustering can reflect the reality. Our study clarifies the structural attributes of the iOTN, explores the evolution of the oil trade pattern from the network level, and accurately identifies the state changes in the international oil market.

Hybrid nanofluid is deployed to optimize the heat transfer features of an axisymmetric magnetohydrodynamic (MHD) flow exterior to a rotating cylinder. Hybrid nanofluids contain composite nanoparticles, which improve thermal conductivity. Here, two distinct particles single and multi-walled carbon nanotubes (CNTs) are taken and mixed to form hybrid nanoparticles, and water is taken as the working fluid. The energy transport phenomenon is examined by incorporating the Joule heating effect. The axial pressure gradient is generated as a consequence of the torsional motion of the cylinder, which results in the wall jet phenomenon on the axial axis. The governing equations are transformed into an ordinary differential system in view of the similarity group. The numerical approach bvp4c is employed to solve the problem. The graphical results for flow and thermal energy transport with a comparison of nanofluid and hybrid nanofluid are analyzed. The axial component of velocity escalates by augmenting Reynolds number, while the azimuthal components of velocity and thermal profile decline. Moreover, the numerical outcomes of wall stresses and Nusselt number enhance for higher Reynolds number. The temperature field declines by increasing the Prandtl number because of less thermal diffusivity.

The radiative recombination rate is greatly enhanced by the conversion of GaN last quantum barrier (LQB) into aluminium gallium nitride (AlGaN) LQB and further into graded AlGaN electron blocking layer (EBL) in GaN-based yellow light-emitting diode (LED) with emission between 510 nm and 580 nm. Our simulation results reveal an increase in carrier concentration and, therefore, reduction in electron-hole asymmetry in multiple quantum wells (MQWs). The proposed structure demonstrates that in MQWs, the chance of the electron-hole (e-h) overlapping increases. When compared to conventional LED, the radiative recombination increases by 70%, while the hole concentration increases by 20%. In our proposed structure, the turn-on voltage is also decreased from 3.2 V to 2.9 V

The enhancement of the heat transfer of fluids is a very important task in engineering and technology which can be accomplished through the hybrid nanoparticles. In this theoretical investigation, the natural convection flow of nanoliquid through a square container is examined under the impacts of thermal boundary conditions. The considered nanoliquid is a combination of titanium alloy Ti6Al4V (class of titanium) and aluminum alloy AA7075 (class of aluminum) nanoparticles and water as a base fluid. Aluminum alloys are commonly used in household wiring and manufacturing of wheels, etc. The titanium alloy Ti6Al4V is commonly acknowledged as the “workhorse” of titanium which is extensively used in aerospace and biomedical engineering. The mathematical model is developed in the form of nonlinear partial differential equations and later transformed into dimensionless form. The resultant dimensionless set of equations is simulated numerically by using the eminent finite element method (FEM). The iterative Newton’s Raphson method is used to get the optimal solutions. The stream function and temperature contours are displayed against the Rayleigh number and nanoparticle volume friction. The variation of local and average Nusselt numbers is also plotted. The outcomes revealed that water-based titanium alloy is the best choice to enhance the heat transfer rate in the cavity. The results obtained in this investigation are very important in engineering research, academic, and discussion about the heat transfer analysis with these two types of alloy nanoparticles inside the cavity flows.

In this paper, we explore the dynamics of quantum correlations in an isolated physical quantum dot under the influence of intrinsic decoherence (ID). We characterize quantum correlations in the quantum dot system using Concurrence to capture the amount of entanglement, and we use Trace Distance Discord (TDD) and Local Quantum Uncertainty (LQU) to measure nonclassical correlations. Likewise, we investigate the effect of ID on the temporal evolution of these quantifiers. In particular, the behavior of the two discord-like quantifiers in terms of the system parameters and the ID rate is investigated and analyzed in detail. We found that TDD and LQU behave similarly for different parameters characterizing the considered system and that TDD is more resistant than Concurrence and LQU against the ID effects. Our results also show that the robustness of quantum correlations can be modulated by adjusting the ID rate, quantum dot physical properties and initial conditions.

In this paper, we obtain novel solutions of a coupled ${\varphi }^4$, a coupled nonlinear Schrödinger equation and a coupled modified Korteweg de Vries equation which can be re-expressed as a linear superposition of either the sum or the difference of two hyperbolic pulse solutions or the sum of either a two-kink or a kink and an antikink solution. These results demonstrate that the notion of superposed solutions extends to coupled nonlinear equations as well.

Morphogen gradient possesses stem cells’ spatial information to control these cells’ differentiation toward distinct directions. In embryos, the formation of this gradient is a dynamic process with time. However, how the information during the process of forming morphogen gradient is measured remains unsolved. Here, according to the theory of information geometry, the information length based on Fisher information is introduced to measure the change in the information from morphogen gradient’s initial state to its steady state. We find that morphogen’s diffusion rate, degradation rate and production rate have important effects on the information length. Specially, morphogen gradation’s degradation rate and diffusion rate have opposite effects on the information length. Our results enrich the current ones about morphogen gradients.