2,344,563 research outputs found
CU Tenancingo invita al Diplomado en Enología
No full textCU Tenancingo invita al Diplomado en Enologí
Strength modelling of Al-Cu-Mg Type alloys
No full textAge hardening of Al-Cu-Mg type alloys occurs in two stages separated by a constant hardness plateau when the alloys are aged at 110°C to 240?C after solution treatment and quenching. This work aims to develop a physically based two-stage hardening model to predict the yield strength of Al-Cu-Mg alloys with compositions in the (?+S) phase region. Experiments by means of hardness and tensile tests, differential scanning calorimetry and transmission electron microscopy (TEM) have been carried out to provide the relevant information for the calibration and validation of the model. The model considers a simplified precipitation sequence which involves a pre-precipitate structure followed by S phase. This pre-precipitate structure is referred to as Cu-Mg co-clusters instead of GPB zones based on atom probe and TEM studies from collaborators and a review of the literature. The competition between the Cu-Mg co-clusters and the S phase is modelled by assuming S phase forms at the expense of Cu-Mg co-clusters. In the model, the solvi of the Cu-Mg co-clusters and the S phase are calculated, the evolution of precipitates in terms of volume fraction, average size and the solute concentration in the matrix are described and the superposition of various contributions from precipitation strengthening, solution strengthening and dislocation strengthening are modelled. Strengthening by Cu-Mg co-clusters and S phase is described by the modulus strengthening mechanism and the Orowan bypassing mechanism, respectively. The predicted contributions to the critical resolved shear stress show that strengthening in the alloys is mainly due to the Cu-Mg co-clusters in the first stage of hardening and due to the S phase in the second stage of hardening. The model takes account of the composition dependency of precipitation rate for Cu-Mg co-clusters formation as well as the amount of Cu and Mg present in undissolved intermetallic phases. With a training root mean square error of 12MPa on an artificially aged 2024 alloy, the modelling accuracy on unseen yield strength data of two other alloys is 16MPa. Using a single set of parameters, the model has been applied to predict the hardness of a 2024-T351 alloy artificially aged at low temperature followed by short term underageing at higher temperature and then room temperature ageing. Good agreement between the predictions and the experiments indicates that the hardness changes during these multi-stage heat treatments can be well interpreted by considering Cu-Mg co-cluster dissolution, S precipitation and Cu-Mg co-cluster re-formation. Application to Al-xCu-1.7Mg alloys (x=0.2, 0.5, 0.8 and 1.1at.%) has shown good predictive capabilities of the model for the first stage of hardening. It is also shown that the model is applicable to Al-Cu-Mg alloys with Si contents at levels of 0.1-0.2wt.%. Modelling results of various Al-Cu-Mg alloys during natural ageing, artificial ageing and multi-stage heat treatments indicate that the model is capable of predicting the evolution of microstructure and the yield strength as a function of composition and heat treatments, and can provide a predictive tool for predicting the strength of Al-Cu-Mg based welds.<br/
Magnetotransporte em sistemas nanoestruturados de Co/Cu
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro de Ciências Físicas e Matemáticas. Programa de Pós-Graduação em Física.As propriedades magnetorresistivas de nanoestruturas de Co/Cu eletrodepositadas é investigada para diferentes geometrias. Na primeira parte, multicamadas de Co/Cu estruturadas na forma de válvulas de spin são investigadas em termos da magnetorresistência gigante (GMR). Apresenta-se um processo de otimização do efeito GMR em função do potencial de deposição, espessura das camadas e uso de surfactantes. Na segunda parte, uma técnica de nanoestruturação baseada em litografia de nanoesferas é apresentada e usada na fabricação de multicamadas porosas lamelares de Co/Cu. Suas propriedades magnéticas e de magnetotransporte são apresentadas e interpretadas qualitativamente
HAXPES spectra for Cu
No full textHAXPES spectra for Cu measured at BL15XU of SPring-8. This dataset is a part of "HAXPES spectra for elemental solids" MDR collection https://doi.org/10.48505/nims.370
Study of Cu(In,Al)Se2 thin films prepared by selenisation of sputtered metallic precursors for application in solar cells
No full textCu-In, Cu-Al and Cu-In-Al metallic precursor layers were deposited using radio-frequency magnetron sputtering and selenised to produce thin films of CuInSe2 (CIS), CuAlSe2 (CAS) and CuIn1-xAlxSe2 (CIAS), respectively. The selenisation stage of this 2-stage process was carried out in a tube furnace (TF) or a rapid thermal processor (RTP) in the presence of elemental Se, either deposited on top of the precursor film or provided from an external source in the chamber, in order to fabricate the chalcopyrite material. The aim was to produce single phase, device quality CIS, CAS and CIAS for use as an absorber layer material in thin film photovoltaic solar cells. Profilometry performed on the as-deposited Cu-In-Al metallic precursors showed an important increase in surface roughness compared to the Cu-In and Cu-Al precursors. This was found to be due to the preferential formation of Cu9(In,Al)4, which stoichiometry led the excess In to form island-shaped In phases at the surface of the bulk, while only Cu2In and CuIn2 formed in Cu-In precursors. Regarding the selenisation, temperatures ranging from 250°C to 550°C were used, and the resulting samples were investigated using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), secondary ion mass spectroscopy (SIMS) and glow-discharge optical emission spectroscopy (GD-OES). Thin films of single phase CIS and CAS were successfully produced with energy band gaps of 0.99 eV and 2.68 eV, respectively. However the incorporation of Al proved to be difficult. The results showed that no incorporation of the Al into the chalcopyrite lattice was achieved in the samples selenised in the RTP, which was believed to be due to the oxidation of the element Al into amorphous Al2O3. In the tube furnace, possibly due to lower levels of oxidation, incorporation occurred more readily but Al and In segregated towards the back and front of the layer, respectively. The causes of the segregation were studied and solutions to avoid it developed, resulting under certain conditions in successful production of CuIn1-xAlxSe2. Samples were tested in a photoelectrochemical cell and showed (apparent) external quantum efficiency values comparable to a CuInSe2 (CIS) sample used as a standard
rebeccaorourke-cu/Mosimann_Prummel_et_al_2021: Mosimann.Prummel.2021
No full textNo description provided
The impacts of social media on destination branding. Case study based on Hanoi city – the capital of Vietnam.
No full textThe purpose of the thesis was to discover the current situation of social media in destination branding with a use case of a developing city in Vietnam while weighing the impacts of social media marketing brings to advertise the destination.
In the theoretical chapters of the thesis, the author aimed to understand the general state of social media at the moment. Moreover, the author wanted to understand the impacts that social media has on the image of Hanoi. So that he could utilize the advantages and minimize the disadvantages affecting directly to the image of Hanoi. There were a few studies that only focus on the general picture of the relationship between social media marketing and destination branding. However, they did not concentrate on the specific purpose of the effectiveness of social media marketing in a destination. According to the data which was collected after six interviews, the author had an overview of the current impacts of social media marketing and the ways of improving them from the experts in this field.
Combined with previous studies, the influences of social media on the destination have been seen. Besides, there are more suitable proposals to improve and promote the image of Hanoi in the future. At the end chapter of the thesis, the author also gave a few pieces of advice as a guideline to build an effective social media marketing plan
Wettability of molten Sn-Bi-Cu solder on Cu substrate
No full textThe wetting behavior of a new Sn-Bi-Cu Pb-firee solder on Cu substrate was investigated by sessile drop method under an Ar-H(2) flow in the temperature range from 493 K to 623 K. The contact angle curves tested at 548 K and 623 K are found to fit exponential rule very well. However. the contact angle curve tested under493 K is not well consistent with exponential rule, for which the spreading course may be classified into three stages. Equilibrium contact angles between Sn-Bi-Cu solder and Cu substrate decrease monotonously with the increase in temperature, which are 28 degrees, 24 degrees and 18 degrees at 493 K. 548 K and 623 K, respectively. The results show that 69.5Sn30Bi-0.5Cu/exhibits good wettability on Cu substrate. Intermetallics formed at the 69.5Sn-30Bi-0.5Cu/Cu interface are identified as Cu(6)Sn(5) adjacent to the solder and Cu(3)Sn adjacent to the Cu substrate, respectively. Formation of intermetallic seems to improve strong wetting of the substrate by the solder. (C) 2009 Elsevier B.V. All rights reserved
Growth rate and superconducting properties of Gd-Ba-Cu-O bulk superconductors melt processed in air
No full textA generic Mg-doped Nd-Ba-Cu-O seed crystal has been developed recently for the fabrication of any type of rare earth (RE) based (RE)-Ba-Cu-O single grain bulk superconductor in air. The new generic seed simplifies significantly the top seeded melt growth (TSMG) process for light rare earth based (Nd, Sm, Gd, or mixed rare earth elements) bulk superconductors, in particular. GdBCO single grains have been fabricated successfully in air using the new seed in a cold-seeding process. In this study, precursor powders were enriched with different amounts of BaO2 to investigate the extent of substitution of Gd for Ba in the Gd1+xBa2-xCu3O7-delta solid solution phase. The growth process of large single grains in air was investigated at various growth temperatures under isothermal processing conditions. Crystal growth rate as a function of under-cooling and BaO2 content has been determined from these experiments. The spatial variation of Tc and transition temperature width for applied field aligned along the a/b and c-axis of grains fabricated with different BaO2 content has also been investigated in order to understand the extent of the formation of Gd/Ba solid solution with varying growth temperature and precursor composition. These results have been used to establish the optimum conditions for fabricating solid solution-free, large single grains of GdBCO in air
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