Influence of B‐Site Disorder on the Properties of Unpoled Bi1/2Na1/2TiO3‐0.06Ba(ZrxTi1‐x)O3 Piezoceramics

The influence of B‐site disorder on the dielectric, microstructural, and structural characteristics of unpoled, lead‐free (Bi_1/2Na_1/2)TiO₃‐0.06Ba(Zr_xTi_1‐x)O₃ piezoelectric ceramics with x = 0.02, 0.10, and 0.15 was investigated. The low and medium doping level introduced a stabilization of polar nanoregions reflected in the shift of the dispersive permittivity anomalies to higher temperatures and the development of lamellar rhombohedral domains embedded in the prevalent tetragonal nanodomain matrix. For higher Zr level, the regions of lamellar domains remain, but the dielectric characteristics indicate a reduction in the previous stabilization effect. This behavior is rationalized by a reduction in the correlation length due to the increasing amount of nonpolar sample volume with increasing Zr addition.     

Exciton-related nonlinear optical properties in cylindrical quantum dots with asymmetric axial potential: combined effects of hydrostatic pressure, intense laser field, and applied electric field

ABSTRACT: The exciton binding energy of an asymmetrical GaAs-Ga1-xAlxAs cylindrical quantum dot is studiedwith the use of the effective mass approximation and a variational calculation procedure. Theinfluence on this quantity of the application of a direct-current electric field along the growthdirection of the cylinder, together with that of an intense laser field, is particularly considered. Theresulting states are used to calculate the exciton-related nonlinear optical absorption and opticalrectification, whose corresponding resonant peaks are reported as functions of the external probes,the quantum dot dimensions, and the aluminum molar fraction in the potential barrier regions.     

Adaptive output‐feedback stabilisation of an uncertain second‐order linear systems

The adaptive stabilisation of uncertain second‐order linear systems is addressed, under a lack of information from both states and parameters. The only standard assumptions are no zeros and the sign of the high frequency gain known. To the best of the authors' knowledge, there has been only an explicit solution proposed in the literature so far with proven stability. Despite the simplicity of the system, it does not fit in any of the standard nonlinear control methodologies available. Thus, this work is a complementary contribution providing a mixed control design strategy based on a reduced‐order observer, adaptive Immersion & Invariance and Backstepping approaches. Hence, this solution depicts a transversal outlook of those nonlinear control strategies and provides a breakthrough for the generalisation of this non‐trivial control problem. Numerical simulations are reported to assess the effectiveness of the adaptive strategy. Copyright © 2016 John Wiley & Sons, Ltd.     

Ant Colony Optimization Inspired Algorithm for 3D Object Segmentation into its Constituent Parts

Neural Processing Letters - This work focuses on the use of an Ant colony optimization (ACO) based approach to the problem of 3D object segmentation. The ACO metaheuristic uses a set of agents...     

Size and Velocity Characteristics of Droplets Generated by Thin Steel Slab Continuous Casting Secondary Cooling Air-Mist Nozzles

Direct spray impingement of high temperature surfaces, 1473 K to 973 K (1200 °C to 700 °C), plays a critical role in the secondary cooling of continuously cast thin steel slabs. It is known that the spray parameters affecting the local heat flux are the water impact flux w as well as the droplet velocity and size. However, few works have been done to characterize the last two parameters in the case of dense mists (i.e., mists with w in the range of 2 to 90 L/m²s). This makes it difficult to rationalize how the nozzle type and its operating conditions must be selected to control the cooling process. In the present study, particle/droplet image analysis was used to determine the droplet size and velocity distributions simultaneously at various locations along the major axis of the mist cross section at a distance where the steel strand would stand. The measurements were carried out at room temperature for two standard commercial air-assisted nozzles of fan-discharge type operating over a broad range of conditions of practical interest. To achieve statistically meaningful samples, at least 6000 drops were analyzed at each location. Measuring the droplet size revealed that the number and volume frequency distributions were fitted satisfactorily by the respective log-normal and Nukiyama–Tanasawa distributions. The correlation of the parameters of the distribution functions with the water- and air-nozzle pressures allowed for reasonable estimation of the mean values of the size of the droplets generated. The ensemble of measurements across the mist axis showed that the relationship between the droplet velocity and the diameter exhibited a weak positive correlation. Additionally, increasing the water flow rate at constant air pressure caused a decrease in the proportion of the water volume made of finer droplets, whereas the volume proportion of faster droplets augmented until the water flow reached a certain value, after which it decreased. Diminishing the air-to-water flow rates ratio, particularly below 10, resulted in mists of bigger and slower droplets with low impinging Weber numbers. However, increasing the air pressure maintaining a constant water flow rate caused a greater proportion of finer and faster drops with Weber numbers greater than 80, which suggests an increased probability of wet drop contact with a hot surface that would intensify heat extraction.     

A new swing-up law for the Furuta pendulum

In this paper the swing-up problem for the Furuta pendulum is solved applying Fradkov's speed-gradient (SG) method to a dimension 4 model of the system. The new law is compared with the conventional Åström-Furuta strategy, based on a dimension 2 model. A comparative analysis, including simulations and experiments, whereby the advantages and effectiveness of the new law for swinging the pendulum up are shown, is included.