Journal La Multiapp <p>International <strong>Journal La Multiapp</strong> ISSN 2721-1290 (Online) and ISSN 2716-3865 (Print) includes all the areas of research activities in all fields Engineering, Technology, Computer Sciences, A<span class="tlid-translation translation" lang="en"><span class="" title="">rchitect</span></span>, Applied Biology, Applied Chemistry, Applied Physics, Material Engineering, Civil Engineering, Military and Defense Studies, Photography, Cryptography, Electrical Engineering, Electronics, Environment Engineering, Computer Engineering, Software Engineering, Electromechanical Engineering, Transport Engineering, Mining Engineering, Telecommunication Engineering, Aerospace Engineering, Food Science, Geography, Oil &amp; Petroleum Engineering, Biotechnology, Agricultural Engineering, Food Engineering, Material Science, Earth Science, Geophysics, Meteorology, Geology, Health and Sports Sciences, Industrial Engineering, Information and Technology, Social Shaping of Technology, Journalism, Art Study, Artificial Intelligence, and other Applied Sciences.</p> Newinera Publisher en-US Journal La Multiapp 2716-3865 Glass Foam Made with Silicon Nitride and Manganese Oxide by Microwave Irradiation <p><em>A high mechanical strength (6.1 MPa) glass foam was produced by sintering/foaming at 830 ºC in an experimental 0.8 kW-microwave oven. The basic raw material was a colorless flat glass waste and the foaming agent was Si3N4 powder (2 wt.%). As an oxygen supplying agent, a MnO2 powder (3.1 wt.%) was used. The main physical, mechanical, thermal and morphological characteristics of the optimal sample were: apparent density of 0.47 g/cm3, porosity of 77.6%, thermal conductivity of 0.105 W/m·K, compressive strength of 6.1 MPa and pore size between 0.15-0.40 mm. The optimal glass foam sample has the required characteristics of a thermal insulation material usable under mechanical stress conditions in civil engineering. The originality of the paper is the application of the unconventional microwave heating technique, faster and more economical, unlike the other papers in the same area published in the literature, followers of the traditional conventional heating technique.</em></p> Marius Florin Dragoescu Lucian Paunescu Sorin Mircea Axinte Copyright (c) 2021 Journal La Multiapp 2021-04-30 2021-04-30 2 2 1 9 10.37899/journallamultiapp.v2i2.325 Fault Diagnostic Methodology for Grid-Connected Photovoltaic Systems <p>This research focuses on the design of a fault diagnosis methodology to contribute to the improvement of efficiency, maintainability and availability indicators of Grid-Connected Photovoltaic Systems. To achieve this, we start from the study of the mathematical model of the photovoltaic generator, then, a procedure is performed to quantify the operational losses of the photovoltaic generator and adjust the mathematical model of this to the real conditions of the system, through a polynomial adjustment. A real system of nominal power 7.5 kWp installed in the Solar Energy Research Center of the province of Santiago de Cuba is used to evaluate the proposed methodology. Based on the results obtained, the proposed approach is validated to demonstrate that it successfully supervises the system. The methodology was able to detect and identify 100% of the simulated failures and the tests carried out had a maximum false alarm rate of 0.22%, evidencing its capacity.</p> Proenza Y. Roger Camejo C. José Emilio Ramos H. Rubén Copyright (c) 2021 Journal La Multiapp 2021-04-30 2021-04-30 2 2 10 30 10.37899/journallamultiapp.v2i2.339