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In this work we investigate the stability properties of a convex symmetric timeinvariant third order matrix's polytope depending on a real positive parameter r. We apply the obtained results to the calculation of the real stability radius of a third order matrix under a certain class of affine perturbations.Keywords: Polytope, stability radius, matrix analysis, Hurwitz stability. ResumenEn este trabajo estudiamos las propiedads de estabilidad de un politopo simétrico y convexo de matrices de tercer orden invariantes en el tiempo, este politopo depende de un parámetro real positivo r. Los resultados que se obtienen son aplicados al cálculo de radio real de estabilidad, no dependiente del tiempo, de una matriz cuadrada de tercer orden sometida a cierta multiperturbación afin.

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The aim of this paper is to implement an algorithm that facilitates the application of fundamental result obtained previously about the asymptotic stability of the solutions of a certain class of interconnected systems (switched linear systems). We also intend to reaffirm the possibility of finding new points of contact between the qualitative theory of ordinary differential equations and study electrical and mechanical properties of certain electrical machines.

This article presents the results of the comparison between the CFD simulation and temperature measurements, both in the time domain, at a certain point of interest within a specific closed space (cubicle) of the institutional library of the Salesian Polytechnic University (UPS), at its headquarters in the city of Cuenca, Republic of Ecuador. In this specific case, solar radiation is considered as the main heat transfer mechanism, which is why it was considered in the applied simulation method. An acceptable relative error was obtained between the simulated and measured temperature values. During the summer period, the thermal conditions inside the cubicle are not suitable for the comfort of the users. The study developed can constitute a basic tool for possible future research related to the implementation of climate conditioning for the cubicle, the library in general and any other site with similar constructive and operational characteristics.

The value spectrum for the Module of Elasticity of the long cortical bovine bone is ample, according to the consulted specialized bibliography. The studies made to 4494 Efrén Vázquez Silva et al. reach those values have been developed under non controlled conditions, and that fact could have affected the biological and structural conditions of the observed samples. In addition, the methodology used to perform the testing has not been mentioned, either. In the present study, a mechanical-experimental analysis of the cortical bovine bone tissue under controlled conditions is exposed (destructive tests of flexure in three points), which guarantees a significant conservation degree of the biological characteristics of the bone. Additionally, the speed of the improvement of the load is controlled to study the behavior of the long bones as structural elements. Tests in six angles of the action of the load were performed, and a value of 2.23 GPa was obtained for the Module of Elasticity.