Performance evaluation of MAC transmission power control in wireless sensor networks.

In this paper we provide a method to analytically compute the energy saving provided by the use of Transmission Power Control (TPC) at the MAC layer in Wireless Sensor Networks (WSN). We consider a classical TPC mechanism: data packets are transmitted with the minimum required power to achieve a given packet error probability, whereas the additional MAC control packets are transmitted with the nominal (maximum) power. This scheme has been chosen because it does not modify the network topology, since control packet transmission range does not change. This property also allow us to compute analytically the expected energy savings. Besides, this type of TPC can be implemented in the current sensor hardware, and can be applied directly to several MAC protocols already proposed for WSN. The foundation of our analysis is the evaluation of L ratio, defined as the total energy consumed by the network using the original MAC protocol divided by the total energy consumed if the TPC mechanism is employed. In the L computation we emphasize the basic properties of sensor networks. Namely, the savings are calculated for a network that is active a very long time, and where the number of sensors is supposed to be very large. The nodes position is assumed to be random -for the sake of example a normal bivariate distribution is assumed in the paper- and no node mobility is considered. In the analysis we stress the radio propagation and the distribution of the nodes in the network, that will ultimately determine the performance of the TPC. Under these conditions we compute the mean value of L. Finally, we have applied the method to evaluate the benefits of TPC for TDMA and CSMA with two representative protocols, L-MAC and S-MAC using their implementation reference parameters. The conclusion is that, while S-MAC does not achieve a significant improvement, LMAC may reach energy savings up to 10-20%

Simulation scalability issues in wireless sensor networks.

The formidable growth of WSN research has opened challenging issues about their performance evaluation. Despite the steady increase in mathematical analysis and experimental deployments, most of the community has chosen simulation for their study. Although it seems straightforward, this approach becomes a quite delicate matter. Complexity is caused by several issues. First, the large number of nodes heavily impacts simulation performance and scalability. Second, credible results demand an accurate characterization of the sensor radio channel. New aspects, inherent in WSN, must be included in simulators, e.g. a physical environment and an energy model, leading to different degrees of accuracy versus performance. Moreover, many necessary models are in the continuous-time domain (e.g. heat transmission, battery discharge), being complex to integrate into discrete event network simulators. These issues result in an exponential growth of the overall network state information. Through this survey we review these problems both quantitatively and qualitatively while depicting a common suitable simulation model. We also briefly describe the most significant simulation frameworks available.This work has been funded by the Economy, Industry and Innovation Council, with the SOLIDMOVIL project (2I04SU044), by Fundacion Seneca with the ARENA Project (00546/PI/04), both of them from the Region of Murcia, and by the Spanish Research Council with the ARPaq project (TEC2004-05622-C04-02/TCM)

La prevención de los riesgos laborales en Argentina. Aportes del modelo español

115 páginas.Trabajo Fin de Curso de Experto Universitario en Derecho del Trabajo y Gestión Laboral. Directora: María Teresa Igartua Miro. El objetivo principal del trabajo es alertar sobre la mala técnica legislativa utilizada en Argentina para legislar sobre la prevención de riesgos del trabajo y destacar los aportes que el modelo español puede otorgar para mejorar la eficacia preventiva. A tal fin se describe el sistema legal argentino sobre la materia. Luego, se desarrollan las críticas a la legislación Argentina, haciendo hincapié en la falta de medidas para estimular a los distintos sujetos a tomar medidas preventivas con respecto a los riesgos del trabajo. A continuación, se destacan los aportes que el modelo español con miras de mejorar la eficacia preventiva en Argentina. Se destaca: la decisión de legislar la prevención de los riesgos por separado de la reparación, la comparación entre el rol preventivo de las mutuas colaboradoras con la seguridad social en España y las aseguradoras de riesgos del trabajo en Argentina, el papel de la responsabilidad administrativa, penal y civil para estimular actitudes preventivas de los riesgos del trabajo. Por último, se desarrollan propuestas legislativas y/o medidas activas tendentes a mejorar la eficacia de la legislación que regula la prevención de los riesgos laborales en Argentina

La transición del Paleolítico Medio al Superior en el Suroeste de Europa en base a las dataciones radiocarbónicas

In the present paper we systematically evaluate the radiometric database underlying the Middle to Upper Palaeolithc transition in southwestern Europe.The different models which attempt to explain the demographical processes underlying this transition rely to a large degree on radiocarbon chronology. We observe that: 1) with increasing age, dates on bone samples show large offsets against those on charcoal, often underestimating these for several thousand years BP and; 2) there is no proof for a persistence of Middle Palaeolithic industries into the time of the earliest Aurignacian in SW Europe. These data contradict the “Ebro- Frontier” model that distinguishes Late Middle Palaeolithic industries in the SW of the Iberian Peninsula from early Aurignacian ones in the NE. On the contrary, our data 3) imply a model of interregional shifts of populations contracting during severe cold and arid phases and expanding under warmer, interstadial conditions, raising ideas on a regional in situ development of the SW European Aurignacian out of Latest Middle Palaeolithic industries made by Neanderthals some 40.0 kyr cal BC.Se presenta un estudio sistemático sobre la información radiometrica disponible para la transición Paleolítico Medio-Paleolítico Superior en el Suroeste de Europa. Los diferentes modelos para explicar el proceso demográfico que subyace en esta transición dependen en gran medida de la cronología radiocarbónica. Se observa que: 1) a mayor antiguedad las fechas sobre hueso muestran una mayor desvisación frente a las muestras sobre carbón, a menudo infravalorando estas varios miles de años BP y 2) que no hay pruebas de perduración de industrias de Paleolítico Medio durante las fases tempranas del Auriñaciense en el SW de Europa. Estos datos contradicen el modelo de “frontera del Ebro” que distingue industrias de Paleolítico Medio Tardío en el SW de la Península Ibérica de las industrias del Auriñaciense temprano en el NE. Por el contrario, 3) nuestros datos implican un modelo de cambios de población interregional que se contrae durante las fases aridas y de frío severo y que se expande durante las fases más calidas de los interestadios, surgiendo la idea de un desarrollo regional del Auriñaciense del SW europeo a partir de las industrias del Paleolítico Medio Tardío realizadas por los Neanderthales hace 40 kyr cal BC

Revisión del estado de investigación formativa en monografías del programa en Licenciatura en Educación Física Recreación y Deportes de la Corporación Universitaria Minuto de Dios Sede Principal.

Caracterizar la investigación formativa del programa por medio de las monografías de los estudiantes que optan por el título en el programa de Licenciatura en Educación Física, Recreación y Deportes de la Corporación Universitaria Minuto de Dios.El presente trabajo se realiza en la Corporación Universitaria Minuto de Dios por el programa de Licenciatura en Educación Física Recreación y Deporte, donde los estudiantes de dicho programa tienen distintas opciones de grado para obtener el título del programa una de ellas con más relevancia a realizar es la monografía esta es la base fundamental de esta investigación. Este tipo de investigación no se ha realizado en el programa, según “anexo1” el cual hace referencia a los requisitos que se sustentan en el programa de educación FEDU estas monografías deben contar con originalidad donde no se copia o imita el proyecto de otros, novedad parte de adquirir un nuevo conocimiento o destacar algo poco tratado, rigurosidad académica donde se refleja localidad del pensamiento, claridad de expresión para encontrar una lectura adecuada al lector, estar adscrito a una línea de investigación de la facultad. Continuando con el desarrollo de este proyecto se realizó una revisión documental por medio del repositorio virtual de la biblioteca nacional de Rafael García Herreros así poder extraer un total de 139 monografías que se entregaron a partir del año 2014 hasta el 2017 las cuales son entregadas para optar por el título de dicho programa resaltando los ítems en investigación que se basan en Tendencia (educación física, recreación, actividad física, inclusión, deporte) enfoque (cuantitativo, cualitativo o mixto), metodología, instrumento de investigación y líneas de investigación. Así por medio de los análisis, la discusión y las conclusiones, se busca que el lector adquiera el conocimiento tratado en la caracterización de la investigación formativa del programa de Licenciatura en educación física recreación y deporte

A Stochastic Model for Chain Collisions of Vehicles Equipped With Vehicular Communications

Improvement of traffic safety by cooperative vehicular applications is one of the most promising benefits of vehicular ad hoc networks (VANETs). However, to properly develop such applications, the influence of different driving parameters on the event of vehicle collision must be assessed at an early design stage. In this paper, we derive a stochastic model for the number of accidents in a platoon of vehicles equipped with a warning collision notification system, which is able to inform all the vehicles about an emergency event. In fact, the assumption of communications being used is key to simplify the derivation of a stochastic model. The model enables the computation of the average number of collisions that occur in the platoon, the probabilities of the different ways in which the collisions may take place, as well as other statistics of interest. Although an exponential distribution has been used for the traffic density, it is also valid for different probability distributions for traffic densities, as well as for other significant parameters of the model. Moreover, the actual communication system employed is independent of the model since it is abstracted by a message delay variable, which allows it to be used to evaluate different communication technologies. We validate the proposed model with Monte Carlo simulations. With this model, one can quickly evaluate numerically the influence of different model parameters (vehicle density, velocities, decelerations, and delays) on the collision process and draw conclusions that shed relevant guidelines for the design of vehicular communication systems, as well as chain collision avoidance applications. Illustrative examples of application are provided, although a systematic characterization and evaluation of different scenarios is left as future work.This work was supported in part by the MICINN/FEDER project under Grant TEC2010-21405-C02-02/TCM (CALM) and in part by Fundación Seneca RM under Grants 00002/CS/08 FORMA and 04549/GERM/06. The work of J. Garcia-Haro was supported by Grant PR2009-0337. The work of E. Egea was supported by the Universidad Politécnica de Cartagena under Grant PMPDI-UPCT-2011. The work of J. Tomas- Gabarron was supported by Grant AP2008-02244. The work of C. Garcia-Costa was supported by Grant 12347/FPI/09

OBIWAN: wireless sensor networks with OMNET++

Simulation is essential in WSN study. However, the nature of WSN makes it an unexpectedly complex task. The extremely large number of nodes, the need for an environment model, and the cross-layer dependencies of the models are some of the reasons for this complexity. Many of the existing simulation tools do not properly handle these issues. In this paper, OBIWAN, a new simulator for WSN is presented. In its design, critical issues like reusability, scalability and cross-layer dependencies have been addressed. The results on its capabilities and performance are provided through a case study involving several thousand nodes and an environment modelThis, work has been funded by the Economy,Industry and Innovation Council,with the SOLIDMOVIL project(2I04SU044),by Fundación Séneca both from the Region of Murcia with the ARENA Project(00546/PI/04)and by the Spanish Research Council with the ARPaq project(TEC2004-05622-C04-02/TCM)and CSI-RHET project(TEC2005-08068–C04-01/TCM)

Simulation of the carbon dioxide hydrate-water interfacial energy

Hypothesis: Carbon dioxide hydrates are ice-like nonstoichiometric inclusion solid compounds with importance to global climate change, and gas transportation and storage. The thermodynamic and kinetic mechanisms that control carbon dioxide nucleation critically depend on hydrate-water interfacial free energy. Only two independent indirect experiments are available in the literature. Interfacial energies show large uncertainties due to the conditions at which experiments are performed. Under these circumstances, we hypothesize that accurate molecular models for water and carbon dioxide combined with computer simulation tools can offer an alternative but complementary way to estimate interfacial energies at coexistence conditions from a molecular perspective. Calculations: We have evaluated the interfacial free energy of carbon dioxide hydrates at coexistence conditions (three-phase equilibrium or dissociation line) implementing advanced computational methodologies, including the novel Mold Integration methodology. Our calculations are based on the definition of the interfacial free energy, standard statistical thermodynamic techniques, and the use of the most reliable and used molecular models for water (TIP4P/Ice) and carbon dioxide (TraPPE) available in the literature. Findings: We find that simulations provide an interfacial energy value, at coexistence conditions, consistent with the experiments from its thermodynamic definition. Our calculations are reliable since are based on the use of two molecular models that accurately predict: (1) The ice-water interfacial free energy; and (2) the dissociation line of carbon dioxide hydrates. Computer simulation predictions provide alternative but reliable estimates of the carbon dioxide interfacial energy. Our pioneering work demonstrates that is possible to predict interfacial energies of hydrates from a truly computational molecular perspective and opens a new door to the determination of free energies of hydrates.We thank Pedro J. Pérez for the critical reading of the manuscript. We also acknowledge Centro de Supercomputación de Galicia (CESGA, Santiago de Compostela, Spain) and MCIA (Mésocentre de Calcul Intensif Aquitain) of the Universités de Bordeaux and Pau et Pays de l’Adour (France) for providing access to computing facilities. We thank financial support from the Ministerio de Economía, Industria y Competitividad (FIS2017- 89361-C3-1-P), Junta de Andalucía (P20-00363), and Universidad de Huelva (P.O. FEDER UHU-1255522), all three cofinanced by EU FEDER funds. J.A. acknowledges Contrato Predoctoral de Investigación from XIX Plan Propio de Investigación de la Universidad de Huelva and a FPU Grant (Ref. FPU15/03754) from Ministerio de Educación, Cultura y Deporte. J. A., J. M. M., and F. J. B. thankfully acknowledge the computer resources at Magerit and the technical support provided by the Spanish Supercomputing Network (RES) (Project QCM- 2018–2- 0042). Funding for open access charge: Universidad de Huelva / CBU