Modelo dinámico de un sistema de control de par por cuatro giróscopos

The dynamic model of a Four Control Moment Gyroscope (4-CMG) is traditionally obtained after computing the derivative of the angular momentum equation. Although this approach leads to a simple dynamic model, new models have been introduced due to terms not taken into account during the computation of the angular momentum equation. In this paper, a new dynamic model for a 4-CMG based on the Newton-Euler algorithm, which is well accepted in Robotics, was developed. This new approach produces a complete dynamic model. © The authors; licensee Universidad Nacional de Colombia

Mental health among children and adolescents: Construct validity, reliability, and parent-adolescent agreement on the ‘Strengths and Difficulties Questionnaire’ in Chile

The Strengths and Difficulties Questionnaire (SDQ) is a screening tool used to measure psychological functioning among children and adolescents. It has been extensively used worldwide, but its psychometric properties, such as internal structure and reliability, seem to vary across countries. This is the first study exploring the construct validity and reliability of the Spanish version of SDQ among early adolescents (self-reported) and their parents in Latin America. A total of 1, 284 early adolescents (9–15 years) and their parents answered the SDQ. We also collected demographic variables. A confirmatory factor analysis was conducted to assess the latent structure of the SDQ. We also used the multitrait-multimethod analysis to separate the true variance on the constructs from variance resulting from measurement methods (self-report vs. parent report), and evaluated the agreement between adolescents and their parents. We found that the original five-factor model was a good solution and the resulting sub-scales had good internal consistency. We also found that the self-reported and parental versions of SDQ provide different information, which are complementary and provide a better picture of the emotional, social, and conduct problems of adolescents. We have added evidence for the construct validity and reliability of the Spanish self-reported and parental SDQ versions in a Chilean sample

QCD sum rules and thermal properties of Charmonium in the vector channel

The thermal evolution of the hadronic parameters of charmonium in the vector channel, i.e. the J/psi resonance mass, coupling (leptonic decay constant), total width, and continuum threshold is analyzed in the framework of thermal Hilbert moment QCD sum rules. The continuum threshold $s_0$, as in other hadronic channels, decreases with increasing temperature until the PQCD threshold s_0 = 4, m_Q^2 is reached at T \simeq 1.22T_c (m_Q is the charm quark mass) and the J/psi mass is essentially constant in a wide range of temperatures. The other hadronic parameters behave in a very different way from those of light-light and heavy-light quark systems. The total width grows with temperature up to T \simeq 1.04T_c beyond which it decreases sharply with increasing T. The resonance coupling is also initially constant beginning to increase monotonically around T \simeq T_c. This behavior strongly suggests that the J/psi resonance might survive beyond the critical temperature for deconfinement, in agreement with lattice QCD results.Comment: 4 pages, two figures, contribution to QCD 10, Montpellier 28th June-2nd July 201

Resultados de la enseñanza de estrategias de lectura y escritura en la alfabetización temprana de niños con riesgo social

Introducción: La evidencia científica reciente destaca la importancia de la alfabetización temprana como fundamento del aprendizaje lector posterior, especialmente en niños en riesgo social, pero no existen las condiciones adecuadas para alcanzar su desarrollo. El objetivo del estudio fue evaluar los resultados de una intervención focalizada en el aprendizaje temprano de la lectura y la escritura de niños con riesgo social (5 años 3 meses promedio). Material y Métodos: Se evaluaron 339 niños(as) (132 grupo intervención/207 grupo comparación), al inicio y al fin del año escolar. Los profesores del grupo de intervención participaron en un programa de desarrollo profesional de un año que incluyó capacitación y acompañamiento para la aplicación de estrategias de enseñanza de la alfabetización temprana. Resultados: Se observó un resultado positivo en el conocimiento del alfabeto, la escritura emergente y el reconocimiento visual de palabras, no en comprensión oral. Discusión: Se contrastan los resultados con otros programas de intervención en niños con riesgo social, resaltando la importancia de la capacitación y el acompañamiento a los educadores

Sixteen years of social and ecological dynamics reveal challenges and opportunities for adaptive management in sustaining the commons

Efforts to confront the challenges of environmental change and uncertainty include attempts to adaptively manage social–ecological systems. However, critical questions remain about whether adaptive management can lead to sustainable outcomes for both ecosystems and society. Here, we make a contribution to these efforts by presenting a 16-y analysis of ecological outcomes and perceived livelihood impacts from adaptive coral reef management in Papua New Guinea. The adaptive management system we studied was a customary rotational fisheries closure system (akin to fallow agriculture), which helped to increase the biomass of reef fish and make fish less wary (more catchable) relative to openly fished areas. However, over time the amount of fish in openly fished reefs slowly declined. We found that, overall, resource users tended to have positive perceptions about this system, but there were negative perceptions when fishing was being prohibited. We also highlight some of the key traits of this adaptive management system, including 1) strong social cohesion, whereby leaders played a critical role in knowledge exchange; 2) high levels of compliance, which was facilitated via a “carrot-and-stick” approach that publicly rewarded good behavior and punished deviant behavior; and 3) high levels of participation by community actors

Quaternionic and Octonionic Spinors. A Classification

Quaternionic and octonionic realizations of Clifford algebras and spinors are classified and explicitly constructed in terms of recursive formulas. The most general free dynamics in arbitrary signature space-times for both quaternionic and octonionic spinors is presented. In the octonionic case we further provide a systematic list of results and tables expressing, e.g., the relations of the octonionic Clifford algebras with the $G_2$ cosets over the Lorentz algebras, the identities satisfied by the higher-rank antisymmetric octonionic tensors and so on. Applications of these results range from the classification of octonionic generalized supersymmetries, the construction of octonionic superstrings, as well as the investigations concerning the recently discovered octonionic $M$-superalgebra and its superconformal extension.Comment: 24 pages, LaTe

[Accepted Manuscript] Psychometric Evaluation of the Adolescent Health Promotion Scale in Chile: Differences by Socioeconomic Status and Gender.

The promotion of healthy behaviors is a relevant issue worldwide, especially among adolescent populations, as this is the developmental stage where most unhealthy behaviors become ingrained. The aim of this study was to analyze the psychometric properties of the Spanish version of the Adolescent Health Promotion Scale (AHPS) in a Chilean sample of early adolescents. The sample was composed of 1,156 adolescents aged 10-14 years from schools in San Felipe, Chile. Item structure was assessed using exploratory and confirmatory factor analyses; reliability was measured using Cronbach's alpha; and differences in terms of gender, age, and socioeconomic status (SES) were established using analysis of variance. The analyses of item structure identified all of the six original factors (nutrition behaviors, health responsibility, social support, life appreciation, stress management and exercise behavior) as significant. However, eight items did not fit the Chilean population well. Therefore, the AHPS in Chile has been reduced to 32 items. The Cronbach's alpha of the 32-item Chilean AHPS was .95, with the subscale coefficients ranging from .76 to .94. In addition, female subjects performed better than male subjects, and individuals of higher SES scored higher than the middle and lower socioeconomic groups. No differences on AHPS scores were found in different age groups. The AHPS appears to have good psychometric properties in terms of item structure and reliability. Consistent with studies carried out in other countries, health promotion behavioral differences were observed in association with gender and SES. The results support the Chilean version of the AHPS as an appropriate instrument for measuring the health promotion behaviors of early adolescents in Chile and for comparing results with those from other countries

Direct flux and current vector control for induction motor drives using model predictive control theory

The study presents the direct flux and current vector control of an induction motor (IM) drive, which is a relatively newer and promising control strategy, through the use of model predictive control (MPC) techniques. The results highlight that the fast flux control nature of direct flux control strategy is further enhanced by MPC. Predictive control is applied in two of its variants, namely the finite control set and modulated MPC, and the advantages and limitations of the two are underlined. This work also highlights, through experimental results, the importance of prioritising the flux part of the cost function which is particularly significant in the case of an IM drive. The performance of the MPC-based approach is compared with the proportional-integral controller, which also prioritises the flux control loop, under various operating regions of the drive such as in the flux-weakening regime. Simulations show the performance expected with different control strategies which is then verified through experiments