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Search Results: 1 - 10 of 6721 matches for " Esteban Egea-Lopez "
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Distributed and Fair Beaconing Congestion Control Schemes for Vehicular Networks
Esteban Egea-Lopez,Pablo Pavon-Mari?o
Computer Science , 2014,
Abstract: Cooperative inter-vehicular applications rely on the exchange of broadcast single-hop status messages among vehicles, called beacons. The aggregated load on the wireless channel due to periodic beacons can prevent the transmission of other types of messages, what is called channel congestion due to beaconing activity. In this paper we approach the problem of controlling the beaconing rate on each vehicle by modeling it as a Network Utility Maximization (NUM) problem. This allows us to formally define the notion of fairness of a beaconing rate allocation in vehicular networks. The NUM model provides a rigorous framework to design a broad family of simple and decentralized algorithms, with proved convergence guarantees to a fair allocation solution. In this context, we propose the Fair Adaptive Beaconing Rate for Intervehicular Communications (FABRIC) algorithm, which uses a particular scaled gradient projection algorithm to solve the dual of the NUM problem. Simulation results validate our approach and show that, unlike recent proposals, FABRIC converges to fair rate allocations in multi-hop and dynamic scenarios.
Optimization of Vehicular Trajectories under Gaussian Noise Disturbances
Juan-Bautista Tomas-Gabarron,Esteban Egea-Lopez,Joan Garcia-Haro
Future Internet , 2013, DOI: 10.3390/fi5010001
Abstract: Nowadays, research on Vehicular Technology aims at automating every single mechanical element of vehicles, in order to increase passengers’ safety, reduce human driving intervention and provide entertainment services on board. Automatic trajectory tracing for vehicles under especially risky circumstances is a field of research that is currently gaining enormous attention. In this paper, we show some results on how to develop useful policies to execute maneuvers by a vehicle at high speeds with the mathematical optimization of some already established mobility conditions of the car. We also study how the presence of Gaussian noise on measurement sensors while maneuvering can disturb motion and affect the final trajectories. Different performance criteria for the optimization of such maneuvers are presented, and an analysis is shown on how path deviations can be minimized by using trajectory smoothing techniques like the Kalman Filter. We finalize the paper with a discussion on how communications can be used to implement these schemes.
Desafios da acidez na catálise em estado sólido
Moreno, Esteban Lopez;Rajagopal, Krishnaswamy;
Química Nova , 2009, DOI: 10.1590/S0100-40422009000200044
Abstract: this study explores the similarities between solid and liquid acid catalysts highlighting the advantages and the main challenges of heterogeneous catalytic processes. we describe the main developments in technical procedures like selection of compounds and reaction models involved in: increasing acidity, characterization of solid acidity and in coke formation.
Offside Detection System Using an Infrared Camera Tracking System  [PDF]
Esteban Lopez, Peter E. Jenkins
World Journal of Mechanics (WJM) , 2019, DOI: 10.4236/wjm.2019.96011
Abstract: This paper describes an experimental offside detection system that will be capable of detecting offside passes during a game of soccer. Soccer is the world’s most popular and most televised sport. In recent years, FIFA has implemented goal line technology in order to end controversial goals/missed goals during high profile competitive matches. The most contentious aspect of the sport is the offside rule and its many controversial calls or lack of calls. Sometimes the linesmen cannot see the passage of playing fast enough to make a correct decision. Being similar to goal line technology, people have requested offside technology to help the linesmen and to reduce the number of incorrect offside calls in a game. This paper describes a working offside detection system that can accurately detect offside passes. Positional data was exported from a VICON infrared motion tracking camera system and a MATLAB script was written so that it can analyze the positions of the players and the ball and determine if a pass was offside.
Massive star formation in Wolf-Rayet galaxies. III: Analysis of the O and WR populations
Angel R. Lopez-Sanchez,Cesar Esteban
Physics , 2010, DOI: 10.1051/0004-6361/200913434
Abstract: (Abridged) We perform a comprehensive multiwavelength analysis of a sample of 20 starburst galaxies that show the presence of a substantial population of Wolf-Rayet (WR) stars. In this paper we present the analysis of the O and WR star populations. We study the spatial localization of the WR-rich clusters via the detection of the blue WR bump (broad He II 4686) and the red WR bump (broad C IV 5808). We perform a detailed fitting of the nebular and broad emission lines within these broad features and derive the numbers of WN, WC and O stars using (i) the standard assumption of constant WR luminosities and (ii) considering metallicity-dependent WR luminosities. We then compare our results with the predictions given by evolutionary synthesis models and with previous empirical results. Aperture effects and the exact positioning of the slit onto the WR-rich bursts play a fundamental role in their detection. As expected, the total number of WR stars increases with increasing metallicity, but objects with 12+log(O/H)<8.2 show a rather constant WR/(WR+O) ratio. The computed WCE/WNL ratios are different than those empirically found in nearby star-forming galaxies, indicating that the observed galaxies are experiencing a strong and very short burst. Considering metallicity-dependent WR luminosities, our data agree with a Salpeter-like IMF in all regimes. We consider that the contribution of the WCE stars is not negligible at low metallicities. Although available models reproduce fairly well the WR properties at high metallicities, new evolutionary synthesis models for young starbursts including all involved parameters (age, metallicity, star-formation history, IMF and WR stars properties such as metallicity-dependent WR luminosities, stellar rotation and the WR binnary channel) are absolutely needed to perform an appropriate comparison with the observational data.
Massive star formation in Wolf-Rayet galaxies: IV b. Using empirical calibrations to compute the oxygen abundance
Angel R. Lopez-Sanchez,Cesar Esteban
Physics , 2010,
Abstract: We have performed a comprehensive multiwavelength analysis of a sample of 20 starburst galaxies that show a substantial population of very young massive stars, most of them classified as Wolf-Rayet (WR) galaxies. We have analysed optical/NIR colours, physical and chemical properties of the ionized gas, stellar, gas and dust content, star-formation rate and interaction degree (among many other galaxy properties) of our galaxy sample using multi-wavelength data. We compile 41 independent star-forming regions --with oxygen abundances between 12+log(O/H) = 7.58 and 8.75--, of which 31 have a direct estimate of the electron temperature of the ionized gas. This paper, only submitted to astro-ph, compiles the most common empirical calibrations to the oxygen abundance, and presents the comparison between the chemical abundances derived in these galaxies using the direct method with those obtained through empirical calibrations, as it is published in Lopez-Sanchez & Esteban (2010b). We find that (i) the Pilyugin method (Pilyugin 2001a,b; Pilyugin & Thuan 2005) which considers the R23 and the P parameters, is the best suited empirical calibration for these star-forming galaxies, (ii) the relations between the oxygen abundance and the N2 or the O3N2 parameters provided by Pettini & Pagel (2004) give acceptable results for objects with 12+log(O/H)>8.0, and (iii) the results provided by empirical calibrations based on photoionization models (McGaugh, 1991; Kewley & Dopita, 2002; Kobulnicky & Kewley, 2004) are systematically 0.2 -- 0.3 dex higher than the values derived from the direct method. These differences are of the same order that the abundance discrepancy found between recombination and collisionally excited lines. This may suggest the existence of temperature fluctuations in the ionized gas, as exists in Galactic and other extragalactic HII regions.
Massive star formation in Wolf-Rayet galaxies. IV: Colours, chemical composition analysis and metallicity-luminosity relations
Angel R. Lopez-Sanchez,Cesar Esteban
Physics , 2010, DOI: 10.1051/0004-6361/201014156
Abstract: (Abridged) We performed a multiwavelength analysis of a sample of starburst galaxies that show the presence of a substantial population of very young massive (WR) stars. Here we present the global analysis of the derived photometric and chemical properties. We compare optical/NIR colours and the physical properties (reddening coefficient, equivalent widths of the emission and underlying absorption lines, ionization degree, electron density, and electron temperature) and chemical properties with previous observations and galaxy evolution models. Attending to their absolute B-magnitude many of them are not dwarf galaxies, but they should be during their quiescent phase. We found that both C(Hb) and Wabs increase with increasing metallicity. We detected a high N/O ratio in objects showing strong WR features. The ejecta of the WR stars may be the origin of the N enrichment in these galaxies. We compared the abundances provided by the direct method with those obtained using empirical calibrations, finding that (i) the Pilyugin method is the best suitable empirical calibration, (ii) the relations between the oxygen abundance and the N2 or the O3N2 parameters provided by Pettini & Pagel (2004) give acceptable results for objects with 12+log(O/H)>8.0, and (iii) the results provided by empirical calibrations based on photoionization models are systematically 0.2-0.3 dex higher than the values derived from the direct method. The O and N abundances and the N/O ratios are related to the optical/NIR luminosity; the dispersion is consequence of the differences in the star-formation histories. Galaxies with redder colours tend to have higher oxygen and nitrogen abundances. Our detailed analysis is fundamental to understand the nature of galaxies showing strong starbursts, as well as to know their star formation history and the relationships with the environment.
Massive star formation in Wolf-Rayet galaxies: II. Optical spectroscopy results
Angel R. Lopez-Sanchez,Cesar Esteban
Physics , 2009, DOI: 10.1051/0004-6361/200912042
Abstract: (Abridged) We have performed a comprehensive multiwavelength analysis of a sample of 20 starburst galaxies that show the presence of a substantial population of very young massive stars. In this paper, the second of the series, we present the results of the analysis of long-slit intermediate-resolution spectroscopy of star-formation bursts for 16 galaxies of our sample. We study the spatial localization of the WR stars in each galaxy. We analyze the excitation mechanism and derive the reddening coefficient, physical conditions and chemical abundances of the ionized gas. We study the kinematics of the ionized gas to check the rotation/turbulence pattern of each system. When possible, tentative estimates of the Keplerian mass of the galaxies have been calculated. Our analysis has revealed that a substantial fraction of the galaxies show evidences of perturbed kinematics. With respect to the results found in individual galaxies, we remark the detection of objects with different metallicity and decoupled kinematics in Haro 15 and Mkn 1199, the finding of evidences of tidal streams in IRAS 08208+2816, Tol 9 and perhaps in SBS 1319+579, and the development of a merging process in SBS 0926+606 A and in Tol 1457-262. All these results reinforce the hypothesis that interactions with or between dwarf objects is a very important mechanism in the triggering of massive star formation in starburst galaxies, specially in dwarf ones. It must be highlighted that only deep and very detailed observationscan provide clear evidences that these subtle interaction processes are taking place.
Garment Counting in a Textile Warehouse by Means of a Laser Imaging System
Alejandro Santos Martínez-Sala,Juan Carlos Sánchez-Aartnoutse,Esteban Egea-López
Sensors , 2013, DOI: 10.3390/s130505630
Abstract: Textile logistic warehouses are highly automated mechanized places where control points are needed to count and validate the number of garments in each batch. This paper proposes and describes a low cost and small size automated system designed to count the number of garments by processing an image of the corresponding hanger hooks generated using an array of phototransistors sensors and a linear laser beam. The generated image is processed using computer vision techniques to infer the number of garment units. The system has been tested on two logistic warehouses with a mean error in the estimated number of hangers of 0.13%.
Análise estatística e optimiza??o de perfis de redu??o termoprogramada (TPR)
Nele, Marcio;Moreno, Esteban Lopez;Andrade, Heloysa Martins Carvalho;
Química Nova , 2006, DOI: 10.1590/S0100-40422006000400003
Abstract: the effect of operational variables and their interaction in tpr profiles was studied using a fractional factorial experimental design. the heating rate and the reducing agent concentration were found to be the most important variables determining the resolution and sensitivity of the technique. they showed opposite effects. therefore, they should be manipulated preferentially in order to obtain optimized tpr profiles. the effect of sample particle size was also investigated. the tests were carried out within a cu/zn/al2o3 catalyst used for the water-gas shift reaction that presented two distinct species of cu2+ in tpr profiles.
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