Novel mixed solar cooker: Experimental,energy, exergy,and economic analysis

This work focuses on the structure, working, and testing of a new mixed solar cooker using a linear Fresnel collector, evacuated tube and box-type cooker. The low-cost components used in the construction of this cooker can help it satisfy the needs of both urban and rural inhabitants who need steady cooking temperatures above 140°C. A family of five can prepare four meals using this modified solar cooker, which costs about $250. The designed solar cooker was tested by conducting no-load and full-load tests. For the no-load test, the maximum temperature of the absorber plate and oil for the new mixed cooker was recorded as 160.26°C and 172.72°C, respectively. The absorber plate of the new mixed cooker and its oil both reached their highest temperatures during the full-load test at 141.14°C and 157°C, respectively. The energy efficiency of the new cooker is 58.776%, while its exergy efficiency is 13%. The heat transfer coefficient increased to 100.16 W/m² °C. This cooker provides an additional time savings of 60 min. An improvement of 27.5% in the highest temperature reached was seen when the developed cooker's performance was compared with those reported in the literature. Additionally, the new cooker's heat-storing capability enables up to 3 h of autonomy. The Levelized Cost of Cooking a Meal for the innovative mixed solar cooker is $0.034 per meal.     

Preparation and luminescence properties of novel K2ZnP2O7: Mn2+ green phosphor

Novel green-emitting phosphors K₂Zn_1???xP₂O₇: x mol% Mn²⁺ have been successfully prepared using classical solid-state reaction method in air atmosphere, doped by different Mn²⁺ ion contents, namely x?=?0.5, 1, 1.25 and 1.5 mol%. The samples were characterized by the thermogravimetric (ATD/ATG/DSC), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), steady and time-resolved photoluminescence techniques. It was found that all K₂Zn_1???xP₂O₇: x mol% Mn²⁺ samples crystallize in the tetragonal phase with P4₂/mnm space group. Upon 425 nm excitation, K₂ZnP₂O₇: Mn²⁺ exhibits an intense broad green asymmetric emission band peaking at 520 nm, owing to the ⁴T₁→⁶A₁(⁶ S) transition of Mn²⁺ ion in K₂ZnP₂O₇. In addition, it is suggested that Mn²⁺ ions occupy more than one symmetry site in the host K₂ZnP₂O₇. The optimal Mn²⁺ ion concentration in K₂ZnP₂O₇:Mn²⁺ phosphor is 1 mol % and with the lifetime 9.81 ms.

     

Feedback linearisation control of an induction machine augmented by single-hidden layer neural networks

We consider adaptive output feedback control methodology of highly uncertain nonlinear systems with both parametric uncertainties and unmodelled dynamics. The approach is also applicable to systems of unknown, but bounded dimension. However, the relative degree of the regulated output is assumed to be known. This new control strategy is proposed to address the tracking problem of an induction motor based on a modified field-oriented control method. The obtained controller is then augmented by an online neural network that serves as an approximator for the neglected dynamics and modelling errors. The network weight adaptation rule is derived from the Lyapunov stability analysis, that guarantees boundedness of all the error signals of the closed-loop system. Computer simulations of an output feedback controlled induction machine, augmented via single-hidden-layer neural networks, demonstrate the practical potential of the proposed control algorithm.