DSpace Collection:
http://dspace.utpl.edu.ec/jspui/handle/123456789/17045
2024-03-29T14:44:57Z
2024-03-29T14:44:57Z
Comparative analysis between the techniques used in the Requirements Engineering, evaluating such techniques forehead to the characteristics of software projects
Valdivieso, D.
Jaramillo Hurtado, D.
http://dspace.utpl.edu.ec/jspui/handle/123456789/19311
2017-06-16T22:03:20Z
Title: Comparative analysis between the techniques used in the Requirements Engineering, evaluating such techniques forehead to the characteristics of software projects
Authors: Valdivieso, D.; Jaramillo Hurtado, D.
Abstract: It is tried to emphasize the importance of the Engineering of Requirements in the development of software, its model of processes and activities, also, to inform on the tools and techniques more used in the obtaining into requirements for the construction of projects or solutions for the clients, in addition, a comparative one between activities, projects and tools and techniques, that determine the best options to be used in the engineering of requirements. To define clear and needs to Engineering requirements and some its characteristics.
An ethnobotanical survey of medicinal plants used in Loja and Zamora-Chinchipe, Ecuador
Malagon Aviles, O.
Vidari, G.
Zaragoza, T.
Tene, V.
Armijos Riofrio, C.
Finzi, P.
http://dspace.utpl.edu.ec/jspui/handle/123456789/19314
2017-06-16T22:03:20Z
Title: An ethnobotanical survey of medicinal plants used in Loja and Zamora-Chinchipe, Ecuador
Authors: Malagon Aviles, O.; Vidari, G.; Zaragoza, T.; Tene, V.; Armijos Riofrio, C.; Finzi, P.
Abstract: This paper reports the results of an ethnobotanical survey on the uses of medicinal plants by inhabitants of two southern Ecuadorian provinces, namely, Loja and Zamora-Chinchipe. In this region, two surviving ethnic groups, the Saraguros and the Shuars, and the descendants of a now extinct culture, the Paltas, have been identified. The present study reports a total of 275 plant species, having 68 different therapeutical uses. © 2006 Elsevier Ireland Ltd. All rights reserved.
Microstructure and optical properties of alpha - Fe2 O3 containing F-centres
Rivera Escobar, R.
Stashans, A.
Gonzalez, S.
http://dspace.utpl.edu.ec/jspui/handle/123456789/19315
2017-06-16T22:03:20Z
Title: Microstructure and optical properties of alpha - Fe2 O3 containing F-centres
Authors: Rivera Escobar, R.; Stashans, A.; Gonzalez, S.
Abstract: Effects produced in the hematite (alpha-Fe2O3) crystal due to the presence of F-centre are reported in the present work. The results are based on the performed quantum-chemical modelling using the Hartree-Fock methodology. A supercell consisting of 120 atoms has been used throughout the computations. First, the required numerical parameters for the Fe atom are obtained by reproducing fairly well the main features of a pure material. Then, the neutral F-centre defect has been introduced and its influence upon the microstructure and electronic properties in the hematite is determined. The acquired atomic shifts around the F-centre imply the significance of the Coulomb interaction in this material. However, the defect-induced electron density redistribution has to be taken into consideration in order to explain explicitly the atomic relaxation. Presence of the F-centre induces a local energy level in gap between the upper valence band and the conduction band, which imparts to the absorption spectra of the material with two values, 0.9 eV and 3.6 eV. © 2009 Elsevier Ltd. All rights reserved.
Ti-doped alpha-Fe2O3 by quantum-chemical modeling
Rivera Escobar, R.
Stashans, A.
http://dspace.utpl.edu.ec/jspui/handle/123456789/19316
2017-06-16T22:03:20Z
Title: Ti-doped alpha-Fe2O3 by quantum-chemical modeling
Authors: Rivera Escobar, R.; Stashans, A.
Abstract: Structure and electronic properties of Ti-doped hematite (?-Fe 2O3) crystal have been studied using a quantum-chemical method based on the Hartree-Fock theory. A supercell model employing a system consisting of 120 atoms has been exploited throughout the investigation. The impurity presence produces defect-inward displacement for the majority of Fe atoms whereas the O atoms experience both defect-inward and defect-outward shifts depending on their original position in the crystal. A small reduction in the band-gap width due to the Ti incorporation is also observed which might lead to some increase in the electrical conductivity in concordance to the available experimental measurements. Two new phenomena are discovered according to results of our modeling, being those of electron density redistribution between different 3d Atomic Orbitals (AOs) within the same Fe atom and extra valence electron escape from the Ti-surrounding region towards far-situated Fe atoms. The latter presumably could explain some contradictory results on saturation magnetization in Ti-doped ?-Fe2O3 compounds. The atomic structure of Ti-doped hematite with pointers indicating lattice relaxation. Ti incorporation into the hematite crystal produces changes upon structural, electronic and electrical properties of this material. © 2010 Elsevier Masson SAS.