Análisis de viscocidad en lubricantes mediante diseño factorial con tres factores

In the field of statistics, the experimental design becomes an analysis tool to establish the ideal conditions of a very important process and / or product, analysis of variance it is very useful in cases where there are a series of controllable factors and that affect a complex process in order to optimize them, in the specific case, it is sought to give a solution to a lubricants analysis using a factorial design. For the development of the following document, it is proposed to show the analysis performed on lubricant samples by means of a 3 x 22 factorial design with 9 replicas. The analysis was performed on 108 samples, taking into account three different types of lubricants; which were subjected to a temperature of 40 degrees Celsius by kinematic viscocity test. It was observed in the analysis that taking into account the factors that interacted in the design (types of lubricant, parts, brands), only one of them showed significant interaction. The use of the design of factorial experiments is considered pertinent, since this can be useful in making maintenance decisions when buying a specific lubricant brand. The experiment design was carried out with StatGraphics statistical software. © 2018 Latin American and Caribbean Consortium of Engineering Institutions. All rights reserved

Substitutional effects of in by Cu in CeIn2

We have investigated the evolution of the magnetic properties on the Ce(In1'xCux)2 (0 < x ≤ 0.3) series of alloys. The orthorhombic structure of the CeIn2 alloy (Imma) changes into the hexagonal AlB2-type (P6/mmm) for x = 0.05 and, then, into the hexagonal CaIn2-type (P63/mmm) for higher Cu concentrations, up to x = 0.3. The dc (ac) magnetic susceptibility shows an abrupt decrease of the magnetic transition temperature from 22 K to 5.4 K (x = 0.05). The results indicate the influence of the crystallographic type of structure and disorder effects on the magnetic behavior along the series. © Owned by the authors, published by EDP Sciences, 2014

Carbon and oxygen in HII regions of the Magellanic Clouds: abundance discrepancy and chemical evolution

We present C and O abundances in the Magellanic Clouds derived from deep spectra of HII regions. The data have been taken with the Ultraviolet-Visual Echelle Spectrograph at the 8.2-m VLT. The sample comprises 5 HII regions in the Large Magellanic Cloud (LMC) and 4 in the Small Magellanic Cloud (SMC). We measure pure recombination lines (RLs) of CII and OII in all the objects, permitting to derive the abundance discrepancy factors (ADFs) for O^2+, as well as their O/H, C/H and C/O ratios. We compare the ADFs with those of other HII regions in different galaxies. The results suggest a possible metallicity dependence of the ADF for the low-metallicity objects, but more uncertain for high-metallicity objects. We compare nebular and B-type stellar abundances and we find that the stellar abundances agree better with the nebular ones derived from collisionally excited lines (CELs). Comparing these results with other galaxies we observe that stellar abundances seem to agree better with the nebular ones derived from CELs in low-metallicity environments and from RLs in high-metallicity environments. The C/H, O/H and C/O ratios show almost flat radial gradients, in contrast with the spiral galaxies where such gradients are negative. We explore the chemical evolution analysing C/O vs. O/H and comparing with the results of HII regions in other galaxies. The LMC seems to show a similar chemical evolution to the external zones of small spiral galaxies and the SMC behaves as a typical star-forming dwarf galaxy.Comment: Accepted for publication in MNRAS, 17 pages, 11 figures, 8 table

Relationship between dental age, chronological age and cervical vertebral maturation in children and adolescents from Bucaramanga, Colombia.

Abstract: Objective: To determine the relationship between chronological age and dental age using Demirjian’s method and Baccetti’s method of cervical vertebral maturation in radiographs of children and adolescents aged 5 to 16 years in the city of Bucaramanga, Colombia. Methods: An analytical observational cross-sectional study was performed in 1385 cephalometric and panoramic radiographs of 775 females and 610 males. Sex, dental age according to the Demirjian’s method, chronological age and degree of maturation of the cervical vertebrae according to Baccetti’s method were analyzed. The univariate analysis included the calculation of measures of central tendency for quantitative variables, and frequencies and proportions for qualitative variables. Spearman correlation coefficients were calculated in the bivariate analysis. In the multivariate analysis a multiple linear regression was performed. A value of p&lt;0.05 was considered statistically significant. Results: The mean chronological age was 10.8±3.3 years [Median: 11; 95% CI:10.6-10.6]. There was no statistically significant difference according to sex (p=0.3409). The mean of the differences between dental age and chronological age was 0.60±1.44 years. There was a strong and positive correlation between dental age and chronological age with each stage of maturation. Females reached skeletal maturity at an earlier age. Conclusions: Chronological age shows a direct and positive relationship with dental age and stages of skeletal maturation in a Colombian population

The planetary nebula IC 4776 and its post-common-envelope binary central star

We present a detailed analysis of IC 4776, a planetary nebula displaying a morphology believed to be typical of central star binarity. The nebula is shown to comprise a compact hourglass-shaped central region and a pair of precessing jet-like structures. Time-resolved spectroscopy of its central star reveals periodic radial velocity variability consistent with a binary system. While the data are insufficient to accurately determine the parameters of the binary, the most likely solutions indicate that the secondary is probably a low-mass main sequence star. An empirical analysis of the chemical abundances in IC 4776 indicates that the common-envelope phase may have cut short the AGB evolution of the progenitor. Abundances calculated from recombination lines are found to be discrepant by a factor of approximately two relative to those calculated using collisionally excited lines, suggesting a possible correlation between low abundance discrepancy factors and intermediate-period post-common-envelope central stars and/or Wolf-Rayet central stars. The detection of a radial velocity variability associated with binarity in the central star of IC 4776 may be indicative of a significant population of (intermediate-period) post-common-envelope binary central stars which would be undetected by classic photometric monitoring techniques.Comment: Accepted for publication in MNRA

Waste clay materials as pozzolanic additions

En: 1st Spanish National Conference on Advances in Materials Recycling and Eco – Energy Madrid, 12-13 November 2009.-- Editors: F. A. López, F. Puertas, F. J. Alguacil and A. Guerrero.-- 4 pages, 3 figures.The building materials industries have made improvements in manufacturing processes. However, with the implementation of quality systems, more compliance, with new standard more restrictive, and especially by the competition between products, it is inevitable that industries deemed a rejection of material unsuitable for marketing or materials waste. The wastes from the ceramic industry (ceramic waste) may have characteristics suitable for use as pozzolanic materials, as it is known that the first materials used as pozzolans were heat-treated clays, material like clay products.This research was funded by a Science and Technology Commission (CICYT) (Research Project AMB96-1095).Peer reviewe