179 research outputs found

    Observations and analysis of two type IIP supernovae: the intrinsically faint object SN 2005cs and the ambiguous object SN 2005ay

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    Aims: To derive observational properties and physical parameters of the progenitor stars of type IIP supernovae SN 2005ay and SN 2005cs from their U,B,V,R,I CCD photometry, and to define their velocity behaviour. Methods: Light curves are analysed, and the velocities and spectral characteristics of SN 2005cs are obtained using synthetic spectra modeling. Results: Both supernovae are found to be fainter than the average SN IIP, with SN 2005cs being more subluminous and showing slight brightening in the second half of plateau stage in the V,R,I bands and a low expansion velocity. The effects of two different plausible distance moduli on the derived physical parameters of SN 2005ay are considered. Two approaches are used to recover the amounts of the ejected 56Ni, indicating masses of the order of 0.02 Msun, although late luminosities might indicate a higher amount for SN 2005ay, especially for the large distance case. Constraints on the progenitor properties are also presented, based on empirical analytical models. Two approaches are used to estimate the expansion velocities at the middle of the plateau phase. SN 2005cs represents an example of where all 3 physical parameters, velocity, energy and 56Ni mass are lower than average, a correlation not always observed in SNe IIP. SN 2005ay may belong to the same class if the shorter distance possibility is adopted. Furthermore, the estimated mass range for SN 2005cs is in agreement with limits established by using pre-supernova imaging.Comment: 8 pages, 6 figures, to be published in A&A vol.460, issue 3, December 200

    Calibrating hydrogen-rich core-collapse supernovae for their use as distance indicators independently of type Ia supernovae

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    Using our new general-relativistic, radiation hydrodynamics, Lagrangian code, we computed a rather extended grid of hydrogen-rich core-collapse supernova (CC-SN) models and explored the potentials of their "standardization" as distance indicators. We discuss the properties of some calibrations previously reported in the literature and present new correlations based on the behavior of the light curve, that can be employed for calibrating hydrogen-rich CC-SNe using only photometric data.Comment: 2 pages, 3 figures, to appear in Proceedings of IAU Symp. 281, Binary Paths to Type Ia Supernovae Explosions, ed. R. Di Stefano and M. Ori

    Synthesis, characterization and ionic conductivity of MgAl2O4

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    Magnesium aluminate nanoparticles have been synthesized by a citrate sol-gel route. X-ray diffraction and IR spectroscopy study confirmed the formation of MgAl2O4 cubic spinel structure without presence of any secondary phase. Crystallite size of the synthesized nanoparticles was found to be equal to 24 nm. The ac conductivity of MgAl2O4 was studied using complex impedance spectroscopy technique in the frequency range from 5 Hz to 13 MHz and temperature range from 673 to 798 K. The temperature and frequency dependence of ac conductivity were highlighted and the activation energies of, respectively, ac conduction and relaxation processes were also calculated

    Multipoint Relay Selection based on Stability of Spatial Relation in Mobile Ad hoc Networks

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    Increasing stability is one of the main objectives in designing routing protocols for Mobile Ad-Hoc Network (MANETS). Various research schemes have been addressed to this challenge and to support it. In fact, some papers have considered modifications to MPRs selection mechanism in OLSR. In this paper, the author proposes a new mechanism to elect stable and sustainable nodes relay between all nodes in MANETs. In this mechanism, a mobility function is used as the main selection criterion based on the calculation of the spatial relation of a node relative to its neighbor. This mechanism is applied in OLSR protocol to choose stable and supportable MPRs nodes. This mechanism significantly finds more stable MPRs and it promises QoS metrics such as lost packets and delay. Simulation results reveals a significant performance gains and it motivates further examinations to develop the mechanism in order to improve the routing protocol requirements. Performances are evaluated based on Random Waypoint model and network simulator ns3

    Effective Detection of Parkinson’s Disease at Different Stages using Measurements of Dysphonia

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    This paper addressees the problem of multiclass of Parkinson’s disease by the characteristic features of person’s voice. So we computed 22 dysphonia measures from 375 voice samples of healthy and people suffer from PD. We used the particle swarm optimization (PSO) feature selection method, with random forest and the linear discriminant analysis (LDA) along with the 4-fold cross validation analysis to classify the subjects in 4 classes according to the severity of symptoms. With a classification accuracy score of 95.2%. Promisingly, the proposed diagnosis system might serve as a powerful tool for diagnosing PD, and could also extended for other voice pathologies

    Construir con la naturaleza: el agua como infraestructura del paisaje urbano de Fez

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    El Agua es el material fundamental en la creación de espacios, recorridos y paisajes tanto urbanos como naturales. En Fez, una de las ciudades imperiales de Marruecos, el Agua viene representada por el río Oued Fez que forma una arteria fluvial viva que atraviesa la ciudad y la alimenta de agua. Con el crecimiento urbano incontrolado de la ciudad se fueron invadiendo espacios ribereños que pertenecían al régimen fluvial del río y por lo tanto la ciudad sufrió importantes inundaciones a nivel de los barrios cercanos a las riberas del Oued Fez. Este elemento natural que sigue generando problemas a la ciudad podría convertirse en una infraestructura verde-azul que responderá a los actuales conflictos y ayudará a la gente desarrollar una cultura ambiental importante y ofrecer a la ciudad espacios verdes que ayudan a la interacción con la naturaleza. Esta investigación tiene la finalidad de estudiar las oportunidades que tiene el Oued Fez y la viabilidad de construir un corredor verde-azul a lo largo de este río. A través de un análisis diagnóstico basado en tres sistemas principales: hidráulico, ambiental y sociocultural, estos tres sistemas nos permitirán entender bien el funcionamiento del Oued Fez para luego localizar los espacios de oportunidad que tiene este río. Y con la ayuda de las estrategias de intervención en ríos urbanos que se han desarrollado en diferentes países del mundo, se podrá visualizar el potencial que tiene el Oued Fez en la mejora del paisaje natural y urbano de Fez.Award-winnin

    Voice Assessments for Detecting Patients with Parkinson’s Diseases in Different Stages

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    Recently, a wide range of speech signal processing algorithms (dysphonia measures) aiming to detect patients with Parkinson’s disease (PD). So we have computed 19 dysphonia measures from sustained vowels collected from 375 voice samples from healthy and people suffer from PD. All the features are analysed and the more relevant ones are selected by the Principal component analysis (PCA) to classify the subjects in 4 classes according to the UPDRS (unified Parkinson’s disease Rating Scale) score. We used k-folds cross validation method with (k=4) validation scheme; 75% for training and 25% for testing, along with the Support Vector Machines (SVM) with its different types of kernels. The best result obtained was 92.5% using the PCA and the linear SVM
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