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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
521

Průmysl 4.0 ve vybraném klastru / Industry 4.0 in a selected cluster

Hykyšová, Zuzana January 2017 (has links)
This diploma thesis focuses on industry clusters and their relation to industry 4.0. The aim is to propose improvements of a selected cluster with prerequisites for transition to industry 4.0. For this purpose, a cluster maturity model will be developed in order to determine the current level of cluster readiness for industry 4.0 in predefined dimensions. This model will be based on an analysis of current maturity models and specific features and clusters´s restrictions. An analysis of the OMNIPACK cluster and the subsequent application of the maturity model to this cluster will be also part of the work. The benefit of this diploma thesis will be wider application of the defined maturity model in Czech cluster organizations.
522

The Distribution and Ages of Star Clusters in the Small Magellanic Cloud: Constraints on the Interaction History of the Magellanic Clouds

Bitsakis, Theodoros, González-Lópezlira, R. A., Bonfini, P., Bruzual, G., Maravelias, G., Zaritsky, D., Charlot, S., Ramírez-Siordia, V. H. 26 January 2018 (has links)
We present a new study of the spatial distribution and ages of the star clusters in the Small Magellanic Cloud (SMC). To detect and estimate the ages of the star clusters we rely on the new fully automated method developed by Bitsakis et al. Our code detects 1319 star clusters in the central 18 deg(2) of the SMC we surveyed (1108 of which have never been reported before). The age distribution of those clusters suggests enhanced cluster formation around 240 Myr ago. It also implies significant differences in the cluster distribution of the bar with respect to the rest of the galaxy, with the younger clusters being predominantly located in the bar. Having used the same setup, and data from the same surveys as for our previous study of the LMC, we are able to robustly compare the cluster properties between the two galaxies. Our results suggest that the bulk of the clusters in both galaxies were formed approximately 300 Myr ago, probably during a direct collision between the two galaxies. On the other hand, the locations of the young (<= 50 Myr) clusters in both Magellanic Clouds, found where their bars join the H I arms, suggest that cluster formation in those regions is a result of internal dynamical processes. Finally, we discuss the potential causes of the apparent outside-in quenching of cluster formation that we observe in the SMC. Our findings are consistent with an evolutionary scheme where the interactions between the Magellanic Clouds constitute the major mechanism driving their overall evolution.
523

The HST Large Programme on ω Centauri. II. Internal Kinematics

Bellini, Andrea, Libralato, Mattia, Bedin, Luigi R., Milone, Antonino P., Marel, Roeland P. van der, Anderson, Jay, Apai, Dániel, Burgasser, Adam J., Marino, Anna F., Rees, Jon M. 25 January 2018 (has links)
In this second installment of the series, we look at the internal kinematics of the multiple stellar populations of the globular cluster omega Centauri in one of the parallel Hubble Space Telescope (HST) fields, located at about 3.5 hal-flight radii from the center of the cluster. Thanks to the over 15 yr long baseline and the exquisite astrometric precision of the HST cameras, well-measured stars in our proper-motion catalog have errors as low as similar to 10 mu as yr(-1), and the catalog itself extends to near the hydrogen-burning limit of the cluster. We show that second-generation (2G) stars are significantly more radially anisotropic than first-generation (1G) stars. The latter are instead consistent with an isotropic velocity distribution. In addition, 1G stars have excess systemic rotation in the plane of the sky with respect to 2G stars. We show that the six populations below the main-sequence (MS) knee identified in our first paper are associated with the five main population groups recently isolated on the upper MS in the core of cluster. Furthermore, we find both 1G and 2G stars in the field to be far from being in energy equipartition, with eta(1G) = -0.007 +/- 0.026 for the former and eta(2G) = 0.074 +/- 0.029 for the latter, where eta is defined so that the velocity dispersion sigma(mu) scales with stellar mass as sigma(mu) proportional to m(-eta). The kinematical differences reported here can help constrain the formation mechanisms for the multiple stellar populations in omega Centauri and other globular clusters. We make our astro-photometric catalog publicly available.
524

Galaxy cluster luminosities and colours, and their dependence on cluster mass and merger state

Mulroy, Sarah L., McGee, Sean L., Gillman, Steven, Smith, Graham P., Haines, Chris P., Démoclès, Jessica, Okabe, Nobuhiro, Egami, Eiichi 12 1900 (has links)
We study a sample of 19 galaxy clusters in the redshift range 0.15 < z < 0.30 with highly complete spectroscopic membership catalogues (to K < K*(z) + 1.5) from the Arizona Cluster Redshift Survey, individual weak-lensing masses and near-infrared data from the Local Cluster Substructure Survey, and optical photometry from the Sloan Digital Sky Survey. We fit the scaling relations between total cluster luminosity in each of six bandpasses (grizJK) and cluster mass, finding cluster luminosity to be a promising mass proxy with low intrinsic scatter sigma ln (L|M) of only similar to 10-20 per cent for all relations. At fixed overdensity radius, the intercept increases with wavelength, consistent with an old stellar population. The scatter and slope are consistent across all wavelengths, suggesting that cluster colour is not a function of mass. Comparing colour with indicators of the level of disturbance in the cluster, we find a narrower variety in the cluster colours of 'disturbed' clusters than of 'undisturbed' clusters. This trend is more pronounced with indicators sensitive to the initial stages of a cluster merger, e.g. the Dressler Schectman statistic. We interpret this as possible evidence that the total cluster star formation rate is 'standardized' in mergers, perhaps through a process such as a system-wide shock in the intracluster medium.
525

Atypical Mg-poor Milky Way Field Stars with Globular Cluster Second-generation-like Chemical Patterns

Fernández-Trincado, J. G., Zamora, O., García-Hernández, D. A., Souto, Diogo, Dell’Agli, F., Schiavon, R. P., Geisler, D., Tang, B., Villanova, S., Hasselquist, Sten, Mennickent, R. E., Cunha, Katia, Shetrone, M., Prieto, Carlos Allende, Vieira, K., Zasowski, G., Sobeck, J., Hayes, C. R., Majewski, S. R., Placco, V. M., Beers, T. C., Schleicher, D. R. G., Robin, A. C., Mészáros, Sz., Masseron, T., Pérez, Ana E. García, Anders, F., Meza, A., Alves-Brito, A., Carrera, R., Minniti, D., Lane, R. R., Fernández-Alvar, E., Moreno, E., Pichardo, B., Pérez-Villegas, A., Schultheis, M., Roman-Lopes, A., Fuentes, C. E., Nitschelm, C., Harding, P., Bizyaev, D., Pan, K., Oravetz, D., Simmons, A., Ivans, Inese I., Blanco-Cuaresma, S., Hernández, J., Alonso-García, J., Valenzuela, O., Chanamé, J. 23 August 2017 (has links)
We report the peculiar chemical abundance patterns of 11 atypical Milky Way (MW) field red giant stars observed by the Apache Point Observatory Galactic Evolution Experiment (APOGEE). These atypical giants exhibit strong Al and N enhancements accompanied by C and Mg depletions, strikingly similar to those observed in the so-called second-generation (SG) stars of globular clusters (GCs). Remarkably, we find low Mg abundances ([Mg/Fe]. < 0.0) together with strong Al and N overabundances in the majority (5/7) of the metal-rich ([Fe/H] greater than or similar to-1.0) sample stars, which is at odds with actual observations of SG stars in Galactic GCs of similar metallicities. This chemical pattern is unique and unprecedented among MW stars, posing urgent questions about its origin. These atypical stars could be former SG stars of dissolved GCs formed with intrinsically lower abundances of Mg and enriched Al (subsequently self-polluted by massive AGB stars) or the result of exotic binary systems. We speculate that the stars Mg-deficiency as well as the orbital properties suggest that they could have an extragalactic origin. This discovery should guide future dedicated spectroscopic searches of atypical stellar chemical patterns in our Galaxy, a fundamental step forward to understanding the Galactic formation and evolution.
526

Calibrating the Planck cluster mass scale with CLASH

Penna-Lima, M., Bartlett, J. G., Rozo, E., Melin, J.-B., Merten, J., Evrard, A. E., Postman, M., Rykoff, E. 14 August 2017 (has links)
We determine the mass scale of Planck galaxy clusters using gravitational lensing mass measurements from the Cluster Lensing And Supernova survey with Hubble (CLASH). We have compared the lensing masses to the Planck Sunyaev-Zeldovich (SZ) mass proxy for 21 clusters in common, employing a Bayesian analysis to simultaneously fit an idealized CLASH selection function and the distribution between the measured observables and true cluster mass. We used a tiered analysis strategy to explicitly demonstrate the importance of priors on weak lensing mass accuracy. In the case of an assumed constant bias, b(SZ), between true cluster mass, M-500, and the Planck mass proxy, M-PL, our analysis constrains 1 - b(SZ) = 0.73 +/- 0.10 when moderate priors on weak lensing accuracy are used, including a zero-mean Gaussian with standard deviation of 8% to account for possible bias in lensing mass estimations. Our analysis explicitly accounts for possible selection bias effects in this calibration sourced by the CLASH selection function. Our constraint on the cluster mass scale is consistent with recent results from the Weighing the Giants program and the Canadian Cluster Comparison Project. It is also consistent, at 1.34 sigma, with the value needed to reconcile the Planck SZ cluster counts with Planck's base Lambda CDM model fit to the primary cosmic microwave background anisotropies.
527

Magellan/M2FS Spectroscopy of Galaxy Clusters: Stellar Population Model and Application to Abell 267

Tucker, Evan, Walker, Matthew G., Mateo, Mario, Olszewski, Edward W., Bailey, John I., Crane, Jeffrey D., Shectman, Stephen A. 29 August 2017 (has links)
We report the results of a pilot program to use the Magellan/M2FS spectrograph to survey the galactic populations and internal kinematics of galaxy clusters. For this initial study, we present spectroscopic measurements for 223 quiescent galaxies observed along the line of sight of the galaxy cluster Abell 267 (z similar to 0.23). We develop a Bayesian method for modeling the integrated light from each galaxy as a simple stellar population, with free parameters that specify the redshift (v(los)/c) and characteristic age, metallicity ([Fe/H]), alpha-abundance ([alpha/Fe]), and internal velocity dispersion (sigma(int)) for individual galaxies. Parameter estimates derived from our 1.5 hr observation of A267 have median random errors of sigma(vlos) = 20 km s(-1), sigma(Age) = 1.2 Gyr, sigma([Fe/H]) = 0.11 dex, sigma([alpha/Fe]) = 0.07 dex, and sigma(sigma int) = 20 km s(-1). In a companion paper, we use these results to model the structure and internal kinematics of A267.
528

An Approach to Defend Against Black hole Attacks in Ad Hoc Networks: Node Clustering AODV Protocol (CAODV)

Alnaghes, Mnar Saeed 09 October 2015 (has links)
The flexibility of Mobile Ad hoc networks (MANET) and its characteristics introduce new security risks. One possible attack is the Black Hole attack which received recent attention. In the Black Hole attack, a malicious node uses the routing protocol to declare itself as having the shortest path to the node whose packets it wants to intercept. It is needed to understand this risk with a view to extract preventive and corrective protections against it. We introduce an approach that could stop this attack from happening in such a network by using an algorithm which controls the communications between nodes and let each node becomes identified and authorized in a group of nodes. In this algorithm, stable nodes, which called leaders, are responsible for routing and forwarding packets from source to destination nodes. This research reviews the black hole attack, and, explains the algorithm that helps throughput to be increased as a consequence. / Graduate / manar.alnaghes@hotmail.com
529

Weak-lensing mass calibration of redMaPPer galaxy clusters in Dark Energy Survey Science Verification data

Melchior, P., Gruen, D., McClintock, T., Varga, T. N., Sheldon, E., Rozo, E., Amara, A., Becker, M. R., Benson, B. A., Bermeo, A., Bridle, S. L., Clampitt, J., Dietrich, J. P., Hartley, W. G., Hollowood, D., Jain, B., Jarvis, M., Jeltema, T., Kacprzak, T., MacCrann, N., Rykoff, E. S., Saro, A., Suchyta, E., Troxel, M. A., Zuntz, J., Bonnett, C., Plazas, A. A., Abbott, T. M. C., Abdalla, F. B., Annis, J., Benoit-Lévy, A., Bernstein, G. M., Bertin, E., Brooks, D., Buckley-Geer, E., Carnero Rosell, A., Carrasco Kind, M., Carretero, J., Cunha, C. E., D’Andrea, C. B., da Costa, L. N., Desai, S., Eifler, T. F., Flaugher, B., Fosalba, P., García-Bellido, J., Gaztanaga, E., Gerdes, D. W., Gruendl, R. A., Gschwend, J., Gutierrez, G., Honscheid, K., James, D. J., Kirk, D., Krause, E., Kuehn, K., Kuropatkin, N., Lahav, O., Lima, M., Maia, M. A. G., March, M., Martini, P., Menanteau, F., Miller, C. J., Miquel, R., Mohr, J. J., Nichol, R. C., Ogando, R., Romer, A. K., Sanchez, E., Scarpine, V., Sevilla-Noarbe, I., Smith, R. C., Soares-Santos, M., Sobreira, F., Swanson, M. E. C., Tarle, G., Thomas, D., Walker, A. R., Weller, J., Zhang, Y. 08 1900 (has links)
We use weak-lensing shear measurements to determine the mean mass of optically selected galaxy clusters in Dark Energy Survey Science Verification data. In a blinded analysis, we split the sample of more than 8000 redMaPPer clusters into 15 subsets, spanning ranges in the richness parameter 5 <= lambda <= 180 and redshift 0.2 <= z <= 0.8, and fit the averaged mass density contrast profiles with a model that accounts for seven distinct sources of systematic uncertainty: shear measurement and photometric redshift errors; cluster-member contamination; miscentring; deviations from the NFW halo profile; halo triaxiality and line-of-sight projections. We combine the inferred cluster masses to estimate the joint scaling relation between mass, richness and redshift, M(lambda, z). M-0 lambda(F) (1 + z)(G). We find M-0 equivalent to M-200m vertical bar lambda = 30, z = 0.5 = [2.35 +/- 0.22 (stat) +/- 0.12 (sys)] x 10(14) M circle dot, with F = 1.12 +/- 0.20 (stat) +/- 0.06 (sys) and G = 0.18 +/- 0.75 (stat) +/- 0.24 (sys). The amplitude of the mass-richness relation is in excellent agreement with the weak-lensing calibration of redMaPPer clusters in SDSS by Simet et al. and with the Saro et al. calibration based on abundance matching of SPT-detected clusters. Our results extend the redshift range over which the mass-richness relation of redMaPPer clusters has been calibrated with weak lensing from z <= 0.3 to z <= 0.8. Calibration uncertainties of shear measurements and photometric redshift estimates dominate our systematic error budget and require substantial improvements for forthcoming studies.
530

A Novel Method to Automatically Detect and Measure the Ages of Star Clusters in Nearby Galaxies: Application to the Large Magellanic Cloud

Bitsakis, T., Bonfini, P., González-Lópezlira, R. A., Ramírez-Siordia, V. H., Bruzual, G., Charlot, S., Maravelias, G., Zaritsky, D. 11 August 2017 (has links)
We present our new, fully automated method to detect and measure the ages of star clusters in nearby galaxies, where individual stars can be resolved. The method relies purely on statistical analysis of observations and Monte-Carlo simulations to define stellar overdensities in the data. It decontaminates the cluster color-magnitude diagrams and, using a revised version of the Bayesian isochrone fitting code of Ramirez-Siordia et al., estimates the ages of the clusters. Comparisons of our estimates with those from other surveys show the superiority of our method to extract and measure the ages of star clusters, even in the most crowded fields. An application of our method is shown for the high-resolution, multiband imaging of the Large Magellanic Cloud. We detect 4850 clusters in the 7 deg(2) we surveyed, 3451 of which have not been reported before. Our findings suggest multiple epochs of star cluster formation, with the most probable occurring similar to 310 Myr ago. Several of these events are consistent with the epochs of the interactions among the Large and Small Magellanic Clouds, and the Galaxy, as predicted by N-body numerical simulations. Finally, the spatially resolved star cluster formation history may suggest an inside-out cluster formation scenario throughout the LMC, for the past 1 Gyr.

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