Surface structural and solar absorptance features of nitrate-based copper-cobalt oxides composite coatings: Experimental studies and molecular dynamic simulation

The copper and cobalt oxides composites coatings on aluminum substrates have been successfully synthesized via sol-gel method using nitrate-based sol precursors. The composites were characterized by X-ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Field Emission Scanning Electron Microscopy (FESEM), Atomic Force Microscopy (AFM), and UV–Vis–NIR spectrophotometry. The sol-gel reactions were discussed and Molecular Dynamics (MD) simulation was integrated into the study to predict molecules assembly properties. The XRD analyses revealed that the CuO and the Co₃O₄ composites were formed after the annealing process with the average difference of the calculated lattice parameters compared to ICDDs was 1.17%. The surface electronic structure was mainly consisted of tetrahedral Cu(I), octahedral Cu(II), tetrahedral Co(II), octahedral Co(III) as well as surface, sub-surface and lattice oxygen O^?. The XRD, XPS and MD simulation results showed that there was minimal (or possibly non-existing) indication of copper-cobalt mixed phase oxides formations. FESEM and AFM surveys revealed that the coating had a porous surface composed of interlinked nanoparticles in the range of ~?10 to ~?40?nm. UV–Vis–NIR reflectance spectra showed that the sol precursors concentration and the dip-drying cycle significantly influenced the absorptance value with optimum absorptance (α) of 88.7% exhibited by coating synthesized using sol concentration of 0.1?M and 10 dip-drying cycles. High absorptance value and simplicity in the synthesis process render the coatings to be very promising candidates for solar selective absorber (SSA) applications.     

Backstepping - Sliding Mode Controllers Applied to a Fixed-Wing UAV

This paper deals with the design of five controllers, based on Backstepping and Sliding Modes, which are applied to a fixed-wing unmanned aerial vehicle (UAV). We are interested to realize a comparative analysis of such methodologies in order to know what controller has a better performance when they are used to the autonomous flight (altitude, yaw and roll) of a fixed-wing UAV. The designed controllers are: Backstepping, Sliding Mode control (SMC), Backstepping with Sliding Mode control, Backstepping with two Sliding Mode control, and Backstepping with high order Sliding Mode (HOSM) control. Simulation results are obtained in order to analyze the controllers performance. We finally present an experimental result, in open-loop, with the purpose of validate the magnitude of the control signals obtained in the simulations.     

Adaptive control for a radio‐controlled helicopter in a vertical flying stand

In this paper, we focus on the design and implementation of a controller for a two degree‐of‐freedom system. This system is composed of a small‐scale helicopter which is mounted on a vertical platform. The model is based on Lagrangian formulation and the controller is obtained by classical pole‐placement techniques for the yaw dynamics and adaptive pole‐placement for the altitude dynamics. Experimental results show the performance of such a controller. Copyright © 2004 John Wiley & Sons, Ltd.     

Porous ceramics with controllable properties prepared by protein foaming-consolidation method

A new protein foaming-consolidation method for preparing porous alumina was developed using egg yolk both as consolidating and foaming agent. This method allows the control of properties of porous alumina not only by varying alumina-to-yolk ratio but also by managing the foaming process. After drying, the green bodies were burned at 600 °C for 1 h to remove the pore creating agent, followed by sintering at 1,550 °C for 2 h. The porous alumina ceramics with pore sizes of 25–1,000 μm and relative density of 29–50% were obtained. The compressive strength of the sintered samples varied within the range of 1.1–5.7 MPa, corresponding to porosity of 40–71%. The addition of dispersant with different concentration into alumina slurries shifted the rheological properties from shear thinning behavior to a Newtonian fluid, which resulted in changes in the pore sizes of the resulting ceramics. The main advantages of the process are the simplicity of the process and the low-cost processing equipment/materials needed. These results have opened a novel preparative way for porous ceramics especially alumina-based porous materials designed for biomedical applications.     

Real-time Implementation and Flight Tests using Linear and Nonlinear Controllers for a Fixed-wing Miniature Aerial Vehicle (MAV)

International Journal of Control, Automation and Systems - This work presents the real-time implementation of four linear controllers and one nonlinear control technique (known as backstepping),...     

Dehydration of potato slices following brief dipping in osmotic solutions: Effect of conditions and understanding the mechanism of water loss

A novel variant of osmotic dehydration, named here as postdipping dehydration—where a material is dipped in a salt or sugar solution for a very short time followed by simple exposure to ambient conditions was explored with the aim of lowering water content of potato slices but at the same time not gain a high level of sugar/salt. The rate of water loss, which was rapid initially, was found to approach equilibrium. This article also explored whether the water loss process could subsequently be kick started once again, by employing a multistage process, where each stage consisted of osmotic solution dipping followed by ambient holding of the potato slices that had reached equilibrium in the earlier stage. Water loss values comparable to conventional osmotic dehydration could be achieved thus, but with significantly lower overall solid gain (<50%)—which can potentially yield a significantly healthy product option.     

Stabilization and Trajectory Tracking of a Quad-Rotor Using Vision

We propose a vision-based position control method, with the purpose of providing some level of autonomy to a quad-rotor unmanned aerial vehicle. Our approach estimates the helicopter X-Y-Z position with respect to a landing pad on the ground. This technique allows us to measure the position variables that are difficult to compute when using conventional navigation systems, for example inertial sensors or Global Positioning Systems in urban environment or indoor. We also present a method to measure translational speed in a local frame. The control strategy implemented is based on a full state feedback controller. Experimental results validate the effectiveness of our method.