DSpace Colección : El Instituto General de Investigación tiene por misión promover el desarrollo de la Investigación Científica y Tecnológica en la Universidad Nacional de Ingeniería.El Instituto General de Investigación tiene por misión promover el desarrollo de la Investigación Científica y Tecnológica en la Universidad Nacional de Ingeniería.http://hdl.handle.net/20.500.14076/30832024-03-28T14:03:13Z2024-03-28T14:03:13ZPrediction of compression strength of high performance concrete using artificial neural networksTorre, A.Garcia, F.Moromi, IsabelEspinoza, P.Acuña, L.http://hdl.handle.net/20.500.14076/41472019-03-13T14:48:56Z2015-01-01T00:00:00ZTítulo : Prediction of compression strength of high performance concrete using artificial neural networks
Autor : Torre, A.; Garcia, F.; Moromi, Isabel; Espinoza, P.; Acuña, L.
Resumen : High-strength concrete is undoubtedly one of the most innovative materials in construction. Its manufacture is simple and is carried out starting from essential components (water, cement, fine and aggregates) and a number of additives. Their proportions have a high influence on the final strength of the product. This relations do not seem to follow a mathematical formula and yet their knowledge is crucial to optimize the quantities of raw materials used in the manufacture of concrete. Of all mechanical properties, concrete compressive strength at 28 days is most often used for quality control. Therefore, it would be important to have a tool to numerically model such relationships, even before processing. In this aspect, artificial neural networks have proven to be a powerful modeling tool especially when obtaining a result with higher reliability than knowledge of the relationships between the variables involved in the process. This research has designed an artificial neural network to model the compressive strength of concrete based on their manufacturing parameters, obtaining correlations of the order of 0.94.2015-01-01T00:00:00ZEquivalence between p-cyclic quasimonotonicity and p-cyclic monotonicity of affine mapsOcaña, EladioCotrina, JohnBueno, Oresteshttp://hdl.handle.net/20.500.14076/41462017-12-27T19:54:34Z2014-03-01T00:00:00ZTítulo : Equivalence between p-cyclic quasimonotonicity and p-cyclic monotonicity of affine maps
Autor : Ocaña, Eladio; Cotrina, John; Bueno, Orestes
Resumen : We prove that the notions of -cyclic quasimonotonicity and -cyclic monotonicity are equivalent for affine maps defined on Banach spaces. First this is done in a finite dimensional space by using the index of asymmetry for matrices defined by J.-P. Crouzeix and C. Gutan. Then this equivalence is extended to general Banach spaces.2014-03-01T00:00:00ZFabrication of ultra-sharp tips from carbon fiber for scanning tunneling microscopy investigations of epitaxial graphene on 6H-SiC(0001) surfaceMorán Meza, José AntonioLubin, ChristopheThoyer, F.Villegas Rosales, Kevin AmilcarGutarra Espinoza, Abel AurelioMartin, F.Cousty, Jacqueshttp://hdl.handle.net/20.500.14076/41452019-03-27T14:36:28Z2015-05-01T00:00:00ZTítulo : Fabrication of ultra-sharp tips from carbon fiber for scanning tunneling microscopy investigations of epitaxial graphene on 6H-SiC(0001) surface
Autor : Morán Meza, José Antonio; Lubin, Christophe; Thoyer, F.; Villegas Rosales, Kevin Amilcar; Gutarra Espinoza, Abel Aurelio; Martin, F.; Cousty, Jacques
Resumen : The fabrication of ultra-sharp tips from carbon fiber (CF), which are mounted on a qPlus probe for combined dynamic scanning tunneling microscopy (STM) and frequency modulation atomic force microscopy (FM-AFM) experiments, is reported. The carbon fiber tips were electrochemically etched in a KOH or NaOH solution, using different electronic devices. CF tips with an apex radius ∼10 nm, as deduced from the measured slopes of the Fowler–Nordheim plots (kR < 70 nm for k ∼ 6), were routinely obtained with a homemade electronic device that controls the intensity of the etching current. Then, these conductive CF tips were also characterized by imaging the 6H-SiC(0 0 0 1) surface covered by an epitaxial graphene layer in ultra-high vacuum (UHV). The lattice of the R30° reconstruction was regularly imaged by STM working either in non-oscillating mode or in dynamic mode, which also maps the variations of the force gradient. From these measurements with a constant mean-tunneling-current of 20 pA, it was found that the STM tip suffered variations of the tip/surface force gradient in between 8.25 and 16.50 N/m when it scanned the epitaxial graphene layer on the reconstructed 6H-SiC(0 0 0 1) surface.2015-05-01T00:00:00ZInfluence of the spray pyrolysis seeding and growth parameters on the structure and optical properties of ZnO nanorod arraysRodríguez, JuanFeuillet, GuyDonatini, FabriceOnna, DiegoSanchez, LuisCandal, Roberto J.Marchi, María ClaudiaBilmes, Sara A.Chandezon, Frédérichttp://hdl.handle.net/20.500.14076/41442019-03-13T13:58:38Z2015-02-01T00:00:00ZTítulo : Influence of the spray pyrolysis seeding and growth parameters on the structure and optical properties of ZnO nanorod arrays
Autor : Rodríguez, Juan; Feuillet, Guy; Donatini, Fabrice; Onna, Diego; Sanchez, Luis; Candal, Roberto J.; Marchi, María Claudia; Bilmes, Sara A.; Chandezon, Frédéric
Resumen : ZnO nanorods (NRs) were grown on fluorine doped tin oxide (FTO) substrates at low temperatures (90 °C) from Zn2+ precursors in alkaline media previously seeded with ZnO nanoparticles. These were deposited onto the FTO substrate heated at 350 °C by spray pyrolysis of a Zn acetate solution in a water ethanol mixture. The structure of seeds was tuned by the ethanol to water ratio, Γ, which controls the solvent evaporation rate of drops impinging the substrate. From a detailed characterization using a combination of scanning electron microscopy, X-ray diffraction, UV–visible absorption and cathodoluminescence spectroscopies, the dependence of the morphology and optical properties of the ZnO NRs on the seeding conditions was demonstrated. NRs grown on seeds deposited from solutions with Γ in the 0.03–0.06 range – i.e. when the surface excess of ethanol in the water–ethanol mixture has a maximum – show thinner average diameters and stacking faults due to the presence of zinc blende domains embedded into an overall wurtzite NR. They furthermore exhibit blue-shifted near band edge emission peak and a high deep level emission in cathodoluminescence. All these findings support the use of spray pyrolysis as a simple and reproducible way to control the seeds deposition, influencing the growth, the structure and the optical properties of the final ZnO NRs.2015-02-01T00:00:00Z