Higher Order Approximation to the Hill Problem Dynamics about the Libration Points

An analytical solution to the Hill problem Hamiltonian expanded about the libration points has been obtained by means of perturbation techniques. In order to compute the higher orders of the perturbation solution that are needed to capture all the relevant periodic orbits originated from the libration points within a reasonable accuracy, the normalization is approached in complex variables. The validity of the solution extends to energy values considerably far away from that of the libration points and, therefore, can be used in the computation of Halo orbits as an alternative to the classical Lindstedt-Poincar\'e approach. Furthermore, the theory correctly predicts the existence of the two-lane bridge of periodic orbits linking the families of planar and vertical Lyapunov orbits.Comment: 28 pages, 8 figure

Student interactions in online discussion forums: their perception on learning with business simulation games

Digital technology offers new teaching methods with controversial results over learning. They allow students to develop a more active participation in their learning process although it does not always drive to unequivocal better learning outcomes. This study aims to offer additional evidence on the contribution of business simulation games to students' learning outcomes, considering student interactions in online discussion forums. We conducted a qualitative research with the online discussion forums of 5 different courses at bachelor and master levels, which involves 41 students' teams. The final sample was composed of 3681 messages posted by the students. The results reveal that some generic and specific managerial skills exert a positive influence on learning outcomes. Students mostly highlighted teamwork, decision-making, information processing, reaching agreements, and dealing with uncertainty as the most relevant contributions of the game towards their learning. These results have instructional and pedagogical implications for determining the best way to enhance students' motivation and learning outcomes when using digital technology methods, which involves recommendations that affect their design and monitoring

La comunicación aplicada a la gestión de prácticas profesionales en 2011: caso facultad de ciencias de la comunicación- U.A.N.L.

El objetivo general que guía el estudio es analizar los procesos de comunicación aplicada a la gestión de prácticas profesionales realizados en 2011 y conocer la forma en que ésta se desempeña conforme a su estructura organizacional. Los hallazgos obtenidos formarán parte de una investigación más amplia, que estará dividida en varias etapas, la primera será el estudio de 2011, que ya está en proceso y subsecuentemente los años de 2012 y 2013

El estilo de inserción laboral de las mujeres salvadoreñas: patriarcado, división sexual del trabajo y discriminación

El autor considera que este artículo constituye un esfuerzo por reflexionar sobre el estilo de inserción laboral de las mujeres salvadoreñas. El autor plantea que los dos factores que condicionan tal estilo es, por un lado, la división sexual del trabajo y, por otro, el proceso de desvalorización de la fuerza de trabajo femenina. Estos factores son vistos a partir de tres indicadores: tasa de desempleo, participación laboral de las mujeres y brechas salariales

On the 3D structure of the mass, metallicity, and SFR space for SF galaxies

We demonstrate that the space formed by the star-formation rate (SFR), gas-phase metallicity (Z), and stellar mass (M), can be reduced to a plane, as first proposed by Lara-Lopez et al. We study three different approaches to find the best representation of this 3D space, using a principal component analysis, a regression fit, and binning of the data. The PCA shows that this 3D space can be adequately represented in only 2 dimensions, i.e., a plane. We find that the plane that minimises the chi^2 for all variables, and hence provides the best representation of the data, corresponds to a regression fit to the stellar mass as a function of SFR and $Z$, M=f(Z,SFR). We find that the distribution resulting from the median values in bins for our data gives the highest chi^2. We also show that the empirical calibrations to the oxygen abundance used to derive the Fundamental Metallicity Relation (Nagao et al.) have important limitations, which contribute to the apparent inconsistencies. The main problem is that these empirical calibrations do not consider the ionization degree of the gas. Furthermore, the use of the N2 index to estimate oxygen abundances cannot be applied for ~8.8 because of the saturation of the [NII]6584 line in the high-metallicity regime. Finally we provide an update of the Fundamental Plane derived by Lara-Lopez et al.Comment: ApJ, accepted. 15 pages, 13 figure

«Quién dice que la ausencia causa olvido» (Cinco poemas inéditos y un ensayo de aproximación critica).

Sin resume

Effect of cleaning products on upholstery leather finishes

The main objective of the project is to investigate the effects of cleaning products on upholstery leather finishes. Focusing on products applicable to upholstery leather cleaning, non-typical leather cleaners (and possible contaminants) or ink removers, in order to find out their behaviour, understanding how they work and if they are suitable for their purpose. Moreover an initial investigation about mechanism of soiling is proposed, in order, in the future, to avoid the soiling or develop an anti-soiling system making an improvement on the durability and maintainability in the leather types and producing an increase of the leather quality.The work reported in this document discusses the cleaning products used to clean upholstery leather finishes. The products examined range from leather cleaners, non-typical leather cleaners such as washing up liquids, furniture polishes, leather dressings, etc. Possible contaminants e.g. hair spray and finally ink removers. As a section of the project, an initial trial examining the mechanism of soiling of upholstery leather surfaces was carried out. The techniques discussed include optical microscope, scanning electron microscope and attenuated total reflectance

Numerical study on propulsion of flapping flight at low Reynolds number

Along the history, innumerable studies about the kinematics that govern flapping flight at high Reynolds number can be found. Although the literature of this kind of flight at low Reynolds number is also huge, the unsteadiness in the aerodynamics, is still really complex to predict due to the amount of parameters involved in it. This bachelor thesis aims to study the best configuration of parameters involved in the kinematics of a flapping airfoil, to achieve the maximum propulsive efficiency and thrust as possible, without penalizing the generated lift. To make the study possible, the Navier Stokes equations, for an incompressible flow around an airfoil, are solved by means of Direct Numerical Simulations, where an Immersed Boundary Method is implemented. In the process 48 cases are simulated. The immersed body selected is a NACA 0012 profile. Due to the unmanageable number of parameters that affects to the kinematics of the problem, some of them are kept fixed while other varies. A Reynolds number of Re = 500, a reduced frequency of k = 1.41, a phase shift between pitching and heaving of ϕ = 90o and a heaving amplitude of h/c = 1 are selected. Feathering parameter (χ) is going to be studied in the range of values between 0 and 1, where propulsive forces appears. The selected values of χ have their associated values of pitching amplitude (θ0) and the mean pitch angle (θm) is adjusted according to the equations of motion to achieved some desired values of mean lift coefficient in the range of values between 0 and 1.5. It is observed, how at χ ≃ 0.5 maximum values of thrust are obtained while at χ ≃0.7 maximum values of propulsive efficiency are achieved. Moreover, it is included a comparison of the results obtained in the actual project with the ones of a companion project (Yuste 2017).Ingeniería Aeroespacia