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Ibague, Colombia

This paper presents a study on the behavior of the temperature field and the profile of residual stresses that appear in a type cruciform welded joint during post weld cooling phase. A 3D model and an analysis of nonlinear transient heat transfer by the finite elements are used. Corroboration of the simulations were done experimentally, achieved by constructing welded cruciform specimen geometry using the SMAW process, using as a base contribution metal plates HR ASTM A36 structural steel and metal electrodes corresponding to E6013 contribution. Specimens were subjected to three cooling conditions: water, oil, and air. A field defined initial temperature according to thermo-graphics data that were obtained experimentally during the construction of not standardized specimens, which were made from three different hick welding sizes, while plate thickness where kept constant. Very good correspondence between bothcooling curves obtained experimentally and by numerical simulations was found. This work shows that the size of the region affected by residual stresses and peak magnitudes are influenced by the cooling medium. High cooling medium produce high cooling rates, generating residual stresses regions of bigger magnitudes. Furthermore, an increase in the residual stress along the welding hick was observed. © 2016, Universidad de Tarapaca. All rights reserved. Source

Alfonso R.A.,University of Ibague
Proceedings of 2011 IEEE International Conference on Grey Systems and Intelligent Services, GSIS'11 - Joint with the 15th WOSC International Congress on Cybernetics and Systems | Year: 2011

An experience of a profound change in the structure of a small non-for-profit private university in Colombia will be used to show the relationship between organizational learning and the need to improve its management of complexity [Beer 1979; 1985; Espejo 1992; Espejo & Reyes 2011]. © 2011 IEEE. Source

Da Silva D.S.,University of Sao Paulo | Naranjo L.P.,University of Ibague | Kassab L.R.P.,Sao Paulo State Technological College | De Araujo C.B.,Federal University of Pernambuco
Applied Physics B: Lasers and Optics | Year: 2012

We report the first observation of photolumines-cence enhancement in Er 3+ doped GeO 2-Bi 2O 3 glasses containing silicon nanocrystals (Si-NCs) excited by a laser operating at 980 nm. The growth of ≈ 200% in the intensity of the Er 3+ transition 4S 3/2 → 4I 15/2 (545 nm) and of ≈ 100% for transitions 2H 11/2 → 4I 15/2 (525 nm), 4F 9/2 → 4I 15/2 (660 nm), and 4I 5/2 → 4I 13/2 (1530 nm) was observed in comparison with a reference sample that does not contain Si-NCs. The results open a new road for obtaining efficient Stokes and anti-Stokes emissions in germanate composites doped with rare-earth ions. © Springer-Verlag 2012. Source

The aim of the study was to relate the basic dimensions of personality formulated by the model of the big five factors with problematic Internet use in a sample of 411 Colombian youngsters, 18-28 years of age, attending three private universities. Online survey questionnaires were administered for: socio-demographics and Internet usage habits, the Big Five Inventory (John, Donahue and Kentle, 1991), to assess personality, and the Internet Addiction Test (Young, 1998), to determine the degree of use of the Internet (controlled, problematic or addictive). The results revealed that 9.7% of the sample has a problematic Internet use. Among them, the majority were male (χ2= 12.93, p= 0.01) and performing communication and leisure activities. The problematic use correlates positively with neuroticism and negatively with friendliness and responsibility. On the other hand, is not related to extraversion and openness to experience. Being female and the responsibility dimension are protective factors from problematic use, while neuroticism predicts it. In conclusion, the study data provides empirical evidence of the relationship between personality and problematic Internet use. Source

Mena N.P.,University of Chile | Garcia-Beltran O.,University of Ibague | Lourido F.,University of Chile | Urrutia P.J.,University of Chile | And 4 more authors.
Biochemical and Biophysical Research Communications | Year: 2015

Abundant evidence indicates that iron accumulation, oxidative damage and mitochondrial dysfunction are common features of Huntington's disease, Parkinson's disease, Friedreich's ataxia and a group of disorders known as Neurodegeneration with Brain Iron Accumulation. In this study, we evaluated the effectiveness of two novel 8-OH-quinoline-based iron chelators, Q1 and Q4, to decrease mitochondrial iron accumulation and oxidative damage in cellular and animal models of PD. We found that at sub-micromolar concentrations, Q1 selectively decreased the mitochondrial iron pool and was extremely effective in protecting against rotenone-induced oxidative damage and death. Q4, in turn, preferentially chelated the cytoplasmic iron pool and presented a decreased capacity to protect against rotenone-induced oxidative damage and death. Oral administration of Q1 to mice protected substantia nigra pars compacta neurons against oxidative damage and MPTP-induced death. Taken together, our results support the concept that oral administration of Q1 is a promising therapeutic strategy for the treatment of NBIA. © 2015 Elsevier Inc. Source

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