Optimization of a telescope movable support structure by means of Volumetric Displacements

Ortega, Nestor F.,Robles, Sandra I. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.31 No.4

The Purpose of this paper is to show the applicability of a methodology, developed by the authors, with which to perform the mechanical optimization of space truss structures strongly restricted. This methodology use a parameter call "Volumetric Displacement", as the Objective Function of the optimization process. This parameter considers altogether the structure weight and deformation whose effects are opposed. The Finite Element Method is employed to calculate the stress/strain state and the natural frequency of the structure through a structural linear static and natural frequency analysis. In order to show the potentially of this simple methodology, its application on a large diameter telescope structure (10 m) considering the strongly restriction that became of its use, is presented. This methodology, applied in previous works on continuous structures, such as shell roof and fluid storage vessels, is applied in this case to a space truss structure, with the purpose of generalize its applicability to different structural topology. This technique could be useful in the morphology design of deployable and retractable roof structures, whose use has extensively spread in the last years.

Regression models generated by gamma random variables with long-term survivors

Ortega, Edwin M.M.,Cordeiro, Gauss M.,Hashimoto, Elizabeth M.,Suzuki, Adriano K. The Korean Statistical Society 2017 Communications for statistical applications and me Vol.24 No.1

We propose a flexible cure rate survival model by assuming that the number of competing causes of the event of interest has the Poisson distribution and the time for the event follows the gamma-G family of distributions. The extended family of gamma-G failure-time models with long-term survivors is flexible enough to include many commonly used failure-time distributions as special cases. We consider a frequentist analysis for parameter estimation and derive appropriate matrices to assess local influence on the parameters. Further, various simulations are performed for different parameter settings, sample sizes and censoring percentages. We illustrate the performance of the proposed regression model by means of a data set from the medical area (gastric cancer).

Beams affected by corrosion influence of reinforcement placement in the cracking

Ortega, Nestor F.,Rivas, Irene E.,Aveldano, Raquel R.,Peralta, Maria H. Techno-Press 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.37 No.2

The results of experimental and numerical investigations on reinforced concrete beams, with different longitudinal rebars affected by corrosive processes are presented in this paper. Different diameters and/or different distributions of longitudinal rebars were employed keeping constant the total section in each analyzed case, (maintaining a constant stirrup diameter and distribution). The rebars were subjected to accelerated corrosion in the experimental study. Electrochemical monitoring of the process, periodic measuring of the cover cracking and gravimetry of the rebars were performed through the test. Some building recommendations are obtained in order to be considered by designers of concrete structures. The numerical simulation was carried out through the application of the Finite Element Method (FEM), employing plane models, and using linear-elastic material model. The cracking process was associated with the evolution of the tensile stresses that were originated. This numerical methodology allows the monitoring of the mechanical behavior until the beginning of the cracking.

Theoretical model to determine bond loss in prestressed concrete with reinforcement corrosion

Ortega, Nestor F.,Moro, Juan M.,Meneses, Romina S. Techno-Press 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.65 No.1

This paper reviews the mechanical effects produced by reinforcement corrosion of prestressed concrete beams. Specifically, modifications in the bonding of the tendon to the concrete that reduce service life and load bearing capacity are studied. Experimental information gathered from previous works has been used for the theoretical analysis. Relationships between bond stress loss and reinforcement penetration in the concrete, and concrete external cracking were established. Also, it was analysed the influence that has the location of the area affected by corrosion on the loss magnitude of the initial prestress.

TWO CONDITIONS ON THE RICCI TENSOR OF A REAL HYPERSURFACE OF COMPLEX PROJECTIVE SPACE

ORTEGA, MIGUEL,PE´REZ, JUAN DE DIOS,SUH, YOUNG JIN 경북대학교 위상수학 기하학연구센터 1999 硏究論文集 Vol.8 No.-

We study two conditions on the Ricci tensor of a real hypersurface of complex projective space that allows us to characterize certain real hypersurfaces. We also introduce a new kind of such real hypersurfaces.

A new extended Birnbaum-Saunders model with cure fraction: classical and Bayesian approach

Ortega, Edwin M.M.,Cordeiro, Gauss M.,Suzuki, Adriano K.,Ramires, Thiago G. The Korean Statistical Society 2017 Communications for statistical applications and me Vol.24 No.4

A four-parameter extended fatigue lifetime model called the odd Birnbaum-Saunders geometric distribution is proposed. This model extends the odd Birnbaum-Saunders and Birnbaum-Saunders distributions. We derive some properties of the new distribution that include expressions for the ordinary moments and generating and quantile functions. The method of maximum likelihood and a Bayesian approach are adopted to estimate the model parameters; in addition, various simulations are performed for different parameter settings and sample sizes. We propose two new models with a cure rate called the odd Birnbaum-Saunders mixture and odd Birnbaum-Saunders geometric models by assuming that the number of competing causes for the event of interest has a geometric distribution. The applicability of the new models are illustrated by means of ethylene data and melanoma data with cure fraction.

Differences Between Winning and Losing Teams in Youth Basketball Games (14-16 Years Old)

( Ortega E. ),( Cardenas D. ),( Sainz De Baranda P. ),( Palao J. M. ) 한국스포츠정책과학원(구 한국스포츠개발원) 2006 International Journal of Applied Sports Sciences Vol.18 No.2

Match analysis is common in performance sport to guide training and competition. However, it is not as common at the youth level. Most studies about match analysis have studied the variables of technique and tactics in relation to final actions of a team`s ball possession. However, a few studies have analyzed participation variables of technique and tactics. The purpose of this study was to determine the differences in final and participatory actions of technique and tactics in relation to winning and losing teams, ball possession, and type of attack phase in youth basketball games. The sample consisted of 184 male players from 16 teams with an average age of 15.6 ± 0.2 years. The twenty-four games were analyzed from the men`s under-16 finals of the Championship of Andalusia (Spain). The variables studied were: game result (win or loss), variables related to type of ball possession, and variables related to pattern of play. Two groups of three observers were utilized (one group observed terminal events of each possession and the other observed possession time and pattern of play). The minimum inter-observer correlation was 0.94. The results found significant differences between winning and losing teams in the following variables: winning teams had higher values than losing teams in the following variables: 2-point field goals made, free throws made, dribbling opposed, time of movement, dribble time, use of screens, fast breaks, attack phases from 1-5 seconds, attack phases in which 2 players participated, and attack phases in which 5 players participated. The results showed that the winning teams have patterns of play that use less dribbling, in general, and less dribbling with displacement, in particular; and they used fast attack phases (1-5 s) in which two players participate. Winning patterns of play were those that used either fast breaks or a long attack phase in which all players participated.

Consequences of Post-grazing Residues Control and Birth Season on the Body Traits, Reproductive Performance and Offspring's Growth of Suckling Goats and Ewes Reared at Pasture in Guadeloupe (FWI)

Ortega-Jimenez, E.,Alexandre, G.,Arquet, R.,Coppry, O.,Mahieu, M.,Xande, A. Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.8

In Guadeloupe small ruminants (SR) are reared for meat production under pasture conditions. Intensive rotational grazing systems (irrigated, fertilised and high stocked) allow reasonable levels of production but generate high post-grazing residues. Experiments were designed to control them. A system in which residuals were mown (RM) was tested in comparison to the control system (Residuals Remained, RR). The same design was carried out for two years with Creole goat (G) and Martinik sheep (S). An accelerated reproductive rate (3 parturitions over 2 years) was carried out. Systems were compared at three parturition seasons per year(dry, intermediate and rainy seasons). Each group was composed of 20 goats ($36.0{\pm}2.5kg$) or 20 ewes ($46.8{\pm}2.4kg$). The female body traits did not vary according to pasture management and seasons. The stocking rate averaged 1,400 kg LW/ha. The mean fertility rate for does varied significantly (p<0.05) within the kidding season, from $80.4{\pm}0.5%$ to $93.7{\pm}2.9%$ while the mean litter size was $2.30{\pm}0.07$ total kids born. No effect of pasture system was observed. Corresponding values for ewes were $83.2{\pm}12.8%$ vs. $75.6{\pm}12.5%$ (p<0.05) and $2.43{\pm}0.24$ vs. $2.03{\pm}0.29$ (p<0.01) total lambs born for SRM and SRR ewes, respectively. A seasonal effect was observed upon ewe performances. The preweaning mortality of kids and lambs averaged 16.3% and 14.4%, respectively. It was 7 and 9 percentage points more (p<0.01) for RR than for RM kids and lambs, respectively. For both species, weaning took place at an average age of $81.4{\pm}3.6days$. In Creole kids, live weight at birth and at weaning were $1.9{\pm}0.2kg$ and $8.9{\pm}0.8kg$, respectively. In the Martinik sheep, the traits averaged $2.9{\pm}0.2kg$ and $18.9{\pm}0.9kg$. For both traits in both species, significant (p<0.05) group${\times}$season interactions were recorded. The consequences of elimination of post-grazing residues varied according to the SR species, the environmental conditions and the animal physiological status. The forage characteristics were not limiting factors since forage availability in the RM systems (2,300 and 2,600 kg DM/ha, respectively) and chemical composition were at satisfactory levels (CP content averaged 12 and 10%). It is recommended to develop new grazing system which would allow the use of post-grazing residues instead of mowing the refusals.

스페인의 외국인 근로자 정책

Nieves Ortega-Perez 한국노동연구원 2007 국제노동브리프 Vol.5 No.8

En torno a los Orígenes de La Guerra del Pacífico

Luis Ortega(루이스 오르테가) 한국라틴아메리카학회 2006 라틴아메리카연구 Vol.19 No.4

After a year of deterioration in their diplomatic relations, in April 1879 Chile, on one side, and Bolivia and Peru, on the other, went to war for the second time in 42 years. The outcome was a resounding victory for Chile and the loss of considerable territory by her opponents. Even though hostilities ceased in 1884, ever since then relations between the three countries have been difficult, particularly, although not exclusively due to Bolivia’s claim for a sovereign access to the sea, which she lost during the war. This article analyses some of the economic factors which were crucial in the series of events that the led to the outbreak of hostilities. It is a view from the side of the winners that is to say from Chile’s viewpoint, since it was constructed mainly with documents and bibliography originating in that country.