Transmission network expansion planning considering weighted transmission loading relief nodal indexes

En este artículo se presenta un modelo y método de solución para el problema de la expansión de la red de transmisión, que integra restricciones de seguridad dadas a través de los índices nodales ponderados de alivio de carga en transmisión. Estos índices integran factores de inyección y distribución de potencia que permiten estimar la severidad de sobrecargas en condiciones normales y bajo contingencias simples. Adicionalmente, se ha considerado la inclusión de generación a pequeña escala, como complementaria a las soluciones del problema de expansión de la red de transmisión. El modelo propuesto es solucionado mediante la metaheurística NSGA-II (Non-dominated Sorting Genetic Algorithm II), permitiendo encontrar un conjunto de soluciones que representan un compromiso entre el costo del plan de expansión y su nivel de seguridad. Se encontró que la inclusión de generación a pequeña escala en nodos estratégicos permite reducir los costos de los planes de expansión y aumenta sus niveles de seguridad ante contingencias simples.This paper presents a model and a solution approach for the transmission network expansion planning (TNEP) problem that integrates security constraints given by weighted transmission loading relief (WTLR) indexes. Such indexes integrate shift and power distribution factors and allow to measure the severity of overloads in normal conditions and under any single contingency. Furthermore, the inclusion of small-scale generation was considered as complementary to TNEP solutions. The proposed model was solved by means of the metaheuristic NSGA-II (Non-dominated Sorting Genetic Algorithm II), which enabled to find a set of solutions that represent a trade-off between the cost of the expansion plan and its security level. Several tests were performed on the 6-bus Garver system and the IEEE 24-bus reliability test system, thus showing the applicability of the proposed approach. It was found that the inclusion of small-scale generation in strategic nodes allows to reduce the cost of expansion plans and increases their level of security for single contingencies

Determinación de movimientos propios de un grupo de estrellas variables de la clase R Coronae Borealis

En base a posiciones fotográficas actuales obtenidas en Córdoba y tomando en cuenta todas las posiciones anteriores disponibles (fotográficas y meridianas) se determinaron movimientos propios anuales en el sistema FK4 para las estrellas UW Cen, Y Mus, S Aps, RB Tel y RY Sqr, pertenecientes a la clase R CrB. Las estrellas R CrB, XX Cam y U Aqr también se incluyeron en la discusión con valores tomados directamente de la literatura. En general los movimientos propios que resultan de este trabajo son relativamente pequeños, como corresponde a estrellas de este brillo; nuestros valores para Rs Tel y Ry Sqr muestran un acuerdo razonable con los obtenidos por otros autores, aunque para Ry Sqr se obtienen distintos valores según se consideran las posiciones fotográficas o las meridianas.Asociación Argentina de Astronomí

Propiedades cinemáticas de las estrellas del tipo R Coronae Boralis

Se presentan resultados que sugieren que estas estrellas no participan completamente de la rotación galáctica. Este hecho, sumado a su distribución y velocidades espaciales, indica que las estrellas R CrB son objetos "suavemente" del halo de la Galaxia, en un sentido similar a como las estrellas extremas de He lo son.Asociación Argentina de Astronomí

Evidence for subaerial development of the Caribbean oceanic plateau in the Late Cretaceous and palaeo-environmental implications

The formation of oceanic plateaus in the Pacific in the Mesozoic has been proposed to create major environmental impacts, including global anoxic events OAE-1 in the Aptian (ca. 120 Ma) and OAE-2 in the Cenomanian–Turonian (ca. 90 Ma). However, our understanding of the formation of these large volcanic systems and their environmental effects are strongly limited by difficulties in accessing them and characterising their volcanic evolution. In particular, it remains significant to determine whether Pacific oceanic plateaus experience a phase of subaerial volcanic activity as this has critical implications in terms of their environmental impacts. Herein we provide the first unequivocal evidence for an emergent volcanic phase of the Caribbean oceanic plateau in the Late Cretaceous. This subaerial phase is evidenced by accreted oceanic sequences in Colombia that include fallout tuffs with accretionary lapilli and lahar deposits. This facies assemblage, recognised for the first time in an oceanic plateau, reflects phreatomagmatic eruptions coeval with subaerial erosion on an oceanic island. This result, combined with previous evidence of subaerial development of the Ontong Java Plateau and Shatsky Rise, suggests that syn-volcanic emergence of oceanic plateaus was common in the Pacific during the Mesozoic. Although temporal and spatial scales of these emergences remain poorly constrained it confirms that emergence of the Caribbean plateau in the Late Cretaceous (ca. 90 Ma) could have actively contributed to atmospheric changes and the establishment of OAE-2. Significantly, emergence of the Caribbean plateau occurred synchronously to the beginning of its tectonic displacement between the Americas. We propose that this unusual volcanic and tectonic evolution led to drastic reduction of the flow of Pacific oxygenated bottom waters into the early Atlantic basin, leading to a series of regional anoxic events previously documented between the Coniacian and Santonian (OAE-3, ca. 89 to 84 Ma). In addition, emergence of the Caribbean Plateau in the early inter-American seaway could have facilitated migration of terrestrial organisms between the Americas in the Late Cretaceous. The formation of the Caribbean plateau had therefore a large range of possible environmental effects, from atmospheric to palaeo-oceanographic and biotic impacts