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Self-powered energy management circuits make energy harvesting converters more efficient and more reliable. This paper presents an improvement of a Maximum Power Point Tracking (MPPT) technique applied on a Parallel Synchronized Switch Harvesting on Inductor (P-SSHI) technique for piezoelectric vibration converters. The aims are to detect the unstable vibrational state, optimize the output voltage and maximize the output power of the piezoelectric transducer.First, the P-SSHI technique is implemented without an MPPT technique. Then, an MPPT technique based on Fractional Open Circuit (FOC) voltage method is implemented. An improvement of the FOC method is proposed to enhance the capability of the Piezoelectric Energy Harvesting (PEH) system. The comparison between different simulation results shows that by using the same input parameters, the maximum efficiency for the PEH system based on the P-SSHI technique implemented without MPPT is 8.82 % whereas the maximum efficiency of the system based on the (FOC) voltage MPPT method is 13.77 %. A significant improvement of the PEH system is obtained by using the modified (FOC) method, where the efficiency reached 24.59 %.

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Zn and Zn-Ni alloy coatings were electrode-posited on mild steel from sulfate-based bath containing Sn as additive. The effect of Ni content on the microstructure, morphology, micro hardness and the tribological behavior of these coatings were studied and discussed. Adding Sn in the sulfate bath had a significant effect on the surface morphology, particularly on the Zn-8 wt% Ni coatings. By increasing the Ni concentration from 8 to 14 wt%, the X-ray patterns showed that the phase structure of Zn-Ni alloy coatings was changed from g-phase Ni 3 Zn 22 to c-phase Ni 5 Zn 21 . The plastic deformation and delamination were found to be wear mechanisms for the investigated coatings. While the Zn-14 wt% Ni alloys had the best wear resistance, Zn films had the most severe wear volume loss and the highest friction coefficient.