Geostationary secular dynamics revisited: application to high area-to-mass ratio objects

The long-term dynamics of the geostationary Earth orbits (GEO) is revisited through the application of canonical perturbation theory. We consider a Hamiltonian model accounting for all major perturbations: geopotential at order and degree two, lunisolar perturbations with a realistic model for the Sun and Moon orbits, and solar radiation pressure. The long-term dynamics of the GEO region has been studied both numerically and analytically, in view of the relevance of such studies to the issue of space debris or to the disposal of GEO satellites. Past studies focused on the orbital evolution of objects around a nominal solution, hereafter called the forced equilibrium solution, which shows a particularly strong dependence on the area-to-mass ratio. Here, we i) give theoretical estimates for the long-term behavior of such orbits, and ii) we examine the nature of the forced equilibrium itself. In the lowest approximation, the forced equilibrium implies motion with a constant non-zero average `forced eccentricity', as well as a constant non-zero average inclination, otherwise known in satellite dynamics as the inclination of the invariant `Laplace plane'. Using a higher order normal form, we demonstrate that this equilibrium actually represents not a point in phase space, but a trajectory taking place on a lower-dimensional torus. We give analytical expressions for this special trajectory, and we compare our results to those found by numerical orbit propagation. We finally discuss the use of proper elements, i.e., approximate integrals of motion for the GEO orbits.Comment: Accepted for publication in CMD

Always watchful of your arrival and departure, baggage handlers wait to serve you how baggage handling in an airport can entail in biomechanical risks

Baggage handling is a high risk job that presents awkward postures, overexertion and repetition in their activities. Ergonomic studies have used biomechanical and psychophysical approaches to evaluate the level of risk of MSDs in baggage handlers. Most of the studies target the activities in the aircraft baggage compartment. The objective of this study was to determine the risk level of MSDs in baggage handlers of the Quito airport through the application of biomechanical risk factors identification tools, in order to propose control strategies that could reduce the mentioned risk. The study analyzed the manual handling activities performed in the baggage tunnel. Four activities were identified and 95 baggage handlers of the Quito airport were evaluated using the RULA. Also, the Maximum Acceptable Weight of Lift (MAWL) was applied to determine the lift capacity of baggage handlers in the Quito airport. The RULA analysis determined a total score of 7, Action Level 4, for each of the activities evaluated, for the 100% of the baggage handlers. The activities performed by TAME and ANDES were found to be equal, but their lifting frequencies were not. On the other hand, the MAWL for the population of male baggage handlers in the Quito airport was determined to be 7 kg, which compared to the actual average weight of the bags lifted is much lower. Therefore, this study determined that baggage handling activities performed in the baggage tunnel present a high risk of developing an upper MSD, and work conditions should be changed immediately. Finally, administrative and engineering controls were proposed in order to reduce the biomechanical risk level that result from baggage handling activities

From order to chaos in Earth satellite orbits

We consider Earth satellite orbits in the range of semi-major axes where the perturbing effects of Earth's oblateness and lunisolar gravity are of comparable order. This range covers the medium-Earth orbits (MEO) of the Global Navigation Satellite Systems and the geosynchronous orbits (GEO) of the communication satellites. We recall a secular and quadrupolar model, based on the Milankovitch vector formulation of perturbation theory, which governs the long-term orbital evolution subject to the predominant gravitational interactions. We study the global dynamics of this two-and-a-half degrees-of-freedom Hamiltonian system by means of the fast Lyapunov indicator (FLI), used in a statistical sense. Specifically, we characterize the degree of chaoticity of the action space using angle-averaged normalized FLI maps, thereby overcoming the angle dependencies of the conventional stability maps. Emphasis is placed upon the phase-space structures near secular resonances, which are of first importance to the space debris community. We confirm and quantify the transition from order to chaos in MEO, stemming from the critical inclinations, and find that highly inclined GEO orbits are particularly unstable. Despite their reputed normality, Earth satellite orbits can possess an extraordinarily rich spectrum of dynamical behaviors, and, from a mathematical perspective, have all the complications that make them very interesting candidates for testing the modern tools of chaos theory.Comment: 30 pages, 9 figures. Accepted for publication in the Astronomical Journa

Determinants of Inflation in a Dollarized Economy: The Case of Ecuador

In this paper we estimate a structural VAR model to identify the causes of inflation in Ecuador. To examine the VAR dynamics, we use the decomposition of the variance because it provides information about the relative importance of each shock to the variables in the VAR. We differ from previous studies because we are able not only to identify the impact of each exogenous variable on the inflation rate but also to estimate the inflation rate from the exogenous variables in the model. We found that on the first quarter of 2008 the annual inflation rate in Ecuador was mainly caused by international prices, exchange rates and public policy.VAR, SVAR, Inflation, Time Series

Análisis de las nuevas resoluciones de la Junta Bancaria sobre las reservas técnicas del sistema asegurador.

The Superintendence of Banks and Insurance Companies of Ecuador through the years has issued several resolutions that control the system of technical reserves, equity and solvency of the insurance companies and reinsurance companies in the country, in order to strengthen the sector and allow insurance companies to have an adequate level of solvency preventing failure and bankruptcy of enterprises caused by catastrophic events. The present work aims to analyze first the entire Ecuadorian system based on the major components of the balance sheet. Also, it was analyzed the growth of premiums and claims that have occurred. Main financial indicators of the company QBE Seguros Colonial in contrast with the total of the system were also compared. Second, it was conducted a study of the latest resolutions of the Banking Board, according to the constitution of technical reserves and changes of them over time. Finally, it was performed a comparative analysis of the Ecuadorian insurance market and Latin American economies very similar but more developed such as: Colombia and Mexico.La Superintendencia de Bancos y Seguros del Ecuador a través de los años ha emitido varias resoluciones que regulan el sistema de las reservas técnicas, patrimonio y solvencia de las entidades aseguradoras y reaseguradoras del país, con la finalidad de fortalecer el sector y permitir que las compañías de seguros cuenten con un nivel de solvencia adecuado previniendo la insolvencia y la quiebra de las empresas causado por eventos de índole catastrófica. El presente trabajo tiene como objetivo analizar, primero, todo el sistema asegurador ecuatoriano en base a los principales componentes del balance general. También, se analizó el crecimiento de las primas y siniestros ocurridos; además se comparó los principales indicadores financieros de la compañía QBE Seguros Colonial en contraste con el total del sistema. Segundo, se realizó el estudio de las últimas resoluciones de la Junta Bancaria, con respeto a la constitución de reservas técnicas y cambios de las mismas a través del tiempo. Por último, se realizó un análisis comparativo entre el mercado asegurador ecuatoriano y el de otras dos economías latinoamericanas muy parecidas pero más desarrolladas tales como: Colombia y México

Vegetation groups from life-history traits for the management of savannah-forest mosaic

This study defined ecological groups of tree species based on species life-history traits within the savannah-forest mosaic of the Lopé National Park, Gabon in order to understand the connection between different types of forest within this study area. Three life-history traits were the most efficient at discriminating species groups within the floristic assemblage, namely, functional guild, dispersal type and phytogeographic type. The combination of dispersal potential and functional guild enabled us to rank the 169 studied species on gradient of forest types. A species classification into functional groups based on similar biological traits was proposed for the purpose of conservation management and development of new conservation areas. This first classification distinguished between canopy species and understorey species, thus suggesting the existence of two separate dynamics for tree species and three functional groups. These results are useful to set conservation priorities to achieve management plans. (Résumé d'auteur

Empresas familiares entendiendo la sucesión a las siguientes generaciones para lograr sostenibilidad en el mercado

Family businesses have been considered as the basis of the economic system for many years and in many countries are the source of employment as well as an element of social cohesion. This type of company has been defined as an organization controlled by one or more family members. There are several models that attempt to explain the dynamics and functioning of these companies such as the model of the three circles, three-dimensional evolutionary model, and model the five circles. Throughout history, it has been found that family businesses face a lot of uncertainty in the change from generation to generation in which many of them have ended their course. This happens for not having a clear structure and a suitable family protocol. For this reason, the best option for the preservation of the company is to establish a vision in which all generations can support. In Ecuador, family businesses are a vital part of the economy, being the most important companies in the country.Las empresas familiares han sido consideradas como la base del sistema económico debido a que desde hace muchos años y en muchos países son fuente generadora de la mayor parte de empleo así como un elemento de cohesión social. Este tipo de empresa ha sido definida como una organización controlada por uno o varios miembros de la familia. Existen varios modelos que intentan explicar la dinámica y funcionamiento de estas compañías como son el modelo de los tres círculos; modelo evolutivo tridimensional; y modelo de los cinco círculos. A lo largo de la historia, se ha visto que las empresas familiares enfrentan un proceso difícil y de mucha incertidumbre en el cambio de generación a generación en el cual muchas de ellas han terminado su funcionamiento. Esto se da por no tener una estructuración clara y un protocolo familiar adecuado. Por este motivo, lo mejor para la continuidad de la empresa es tener una visión establecida en la cual todas las generaciones se puedan apoyar. En el Ecuador, las empresas familiares son una parte fundamental para el motor de la economía, siendo estas las más importantes dentro del país

Macroeconomic Consistency Framework for the Ecuadorian Economy: Getting Back to Fundamentals

This document presents a Macroeconomic Consistency Model for a dollarized economy such as Ecuador. Based on a simply accounting framework that combined the social accounting matrix with the flow of funds, we integrate the different sectors of the economics through a matrix of income, expenditure, saving, and asset and liability accumulation. This is done by using Easterly's (1989) Consistency Accounting Matrix which specifies the linkages between sources and uses of funds as well as between institutional sector accounts. This approach ensures the numerical consistency of data drawn from different sources in such a way that, both, the sectoral budget constraints as well as the overall economy-wide budget constraints are simultaneously satisfied. From this model we were able to estimate the liquidity of the economy, the actual amount of government subsidies, and the gaps in the Ecuadorian economy.Macroeconomics, Financial Programing, Macroeconomic Consistency

Ductile damage parameters identification for cold metal forming applications

International audienceDuctile damage mechanics is essential to predict failure during cold metal forming applications. Several damage models can be found in the literature. These damage models are coupled with the mechanical behavior so as to model the progressive softening of the material due to damage growth. However, the identification of damage parameters remains an issue. In this paper, an inverse analysis approach is set-up to identify ductile damage parameters, based on different kind of mechanical tests and observables. The Lemaitre damage model is used and damage is coupled with the material behavior. The Efficient Global Optimization (EGO) method is used in a parallel environment. This global algorithm based on kriging meta-model enables the identification of a set of damage parameters based on experimental observables. Global and local observables are used to identify these parameters and a special attention is paid to the computation of the cost function. Finally, an identification procedure based on displacement field measurements is presented and applied for damage parameters identification

La lutte biologique contre d'ambroisie à feuilles d'armoise illustrée par l'exemple d'Ophraella communa : quels intérêts et quelles limites ?

Introduite en France il y a plus de 150 ans, la progression sur le territoire d'Ambrosia artemisiifolia (ambroisie à feuilles d'armoise) semble inexorable. La biologie particulière de cette annuelle estivale pose des problèmes nouveaux aux gestionnaires des différents milieux où l'on retrouve la plante. La réduction ou l'impossibilité d'utiliser des moyens de lutte traditionnelle dans certaines conditions environnementales amène à envisager la lutte biologique comme un des seuls recours possibles pour ralentir, voire faire reculer la distribution de cette plante envahissante et allergisante. A travers l'exemple d'Ophraella communa est présentée la réflexion qui peut être faite sur la balance " bénéfice-risque " de l'introduction d'un insecte exotique pour la gestion d'une envahissante à fort impact sur la santé humaine. Le cas de l'ambroisie pourrait servir de modèle aux différentes espèces envahissantes à effet sur la santé humaine visée dans le nouveau projet de loi santé. (Résumé d'auteur