Browsing by Author "Guzman, D."

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    Evolution of synthesis of FCC nanocrystalline solid solution and amorphous phase in the Ti-Ta based alloy by high milling energy
    (2021) Aguilar, C.; Pio, E.; Medina, A.; Martinez, C.; Sancy, M.; Guzman, D.
    Pure Ti and Ti-based alloys exhibit two equilibrium phases: at lower temperatures they have a hexagonal close packed (alpha-Ti) crystalline structure while at higher temperatures they possess a body-centered cubic (beta-Ti) structure. However, in special conditions, they could exhibit a metastable face-centered cubic (gamma-Ti) crystalline structure. This paper aims to investigate the influence of Sn amount and milling time on the formation of gamma-Ti phase on the Ti-Ta based alloy. Four alloys with compositions Ti-13Ta-xSn (x: 3, 6, 9 and 12 at. %) were obtained by high energy milling. The alloys were analyzed by X-ray diffaction patterns, transmission and scanning electron microscopy. For the Ti-13Ta-3Sn alloy, the beta-Ti phase is formed in greater quantity, similar to 70% at 100 h. For the Ti-13Ta-6Sn and Ti-13Ta-9Sn alloys, the phase that is in greater quantity is gamma-Ti, around 100% at 100h. The Ti-13Ta-6Sn alloy shows a greater tendency to form the gamma-Ti phase, since the quantity is close to 100% at 50 h milling time. Thermodynamic calculations are comparable with experimental data. The calculations were made using the MAAT software based on Miedema's model. The MAAT is a free software that can be download from www.rpm.usm.cl. (C) 2020 Elsevier B.V. All rights reserved.
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    Open-loop tomography with artificial neural networks on CANARY: on-sky results
    (2014) Osborn, J.; Guzman, D.; de Cos Juez, F. J.; Basden, A. G.; Morris, T. J.; Gendron, E.; Butterley, T.; Myers, R. M.; Guesalaga, A.; Sanchez Lasheras, F.; Gomez Victoria, M.; Sanchez Rodriguez, M. L.; Gratadour, D.; Rousset, G.
    We present recent results from the initial testing of an artificial neural network (ANN)-based tomographic reconstructor Complex Atmospheric Reconstructor based on Machine lEarNing (CARMEN) on CANARY, an adaptive optics demonstrator operated on the 4.2 m William Herschel Telescope, La Palma. The reconstructor was compared with contemporaneous data using the Learn and Apply (L&A) tomographic reconstructor. We find that the fully optimized L&A tomographic reconstructor outperforms CARMEN by approximately 5 per cent in Strehl ratio or 15 nm rms in wavefront error. We also present results for CANARY in Ground Layer Adaptive Optics mode to show that the reconstructors are tomographic. The results are comparable and this small deficit is attributed to limitations in the training data used to build the ANN. Laboratory bench tests show that the ANN can outperform L&A under certain conditions, e.g. if the higher layer of a model two layer atmosphere was to change in altitude by similar to 300 m (equivalent to a shift of approximately one tenth of a subaperture).
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    Powder Metallurgy Production of Ti-2 Wt Pct Si Alloy : Structural, Mechanical, and Electrochemical Characterization of the Sintered Material
    (2020) Guzman, D.; Muranda, D.; Soliz, A.; Aguilar, C.; Guzman, A.; Sancy, Mamié; Pineda Parra, Fabiola Makarena; Rojas, P.