Optimisation of strength and ductility of Cu–Cr–Zr by combining severe plastic

The microstructure and mechanical behaviour of a Cu–Cr–Zr alloy has been examined after severe plastic deformation, and giving both prior and subsequent age hardening treatments. Dislocation subgrain structures are produced by deformation leading to high strength and reduced ductility. Mild annealing following deformation leads to slight substructural coarsening, some loss of dislocations, and simultaneous precipitation, resulting in an increase of strength with some improvement of ductility. The same heat treatments for precipitation before deformation lead to finer substructures, with shear reducing particle size and leading to partial dissolution. Strength and ductility are analysed in terms of the deformation substructures and the role of precipitate particlesfinancial support of the Spanish Ministry of Education and Science under project number MAT2009- 07342. and CSIC for financial support within the confines of a JAE scholarshipPeer reviewe

Recovery of deformation substructure and coarsening of particles on annealing severely plastically deformedAl–Mg–Si alloy and analysis of strengthening mechanisms

An Al–Mg–Si alloy was annealed to various solutionized and aged states and was then severely plastically deformed by equal channel angular pressing (ECAP). These materials were subsequently annealed for a range of times and temperatures to induce precipitation, dislocation recovery, and grain growth, with changes of mechanical behavior followed by tensile testing. Precipitation of excess solute was seen to occur in all cases, independent of the initial heat treated state, but the particles present appear to play only a small role in stabilizing the deformation substructure, at least until significant particle and grain coarsening has occurred, when discontinuous grain coarsening can be provoked. The strength of materials is examined, and the respective contributions of loosely arranged dislocations, many grain boundaries, and dispersed particles are deduced. It is shown that dislocation strengthening is significant in as-deformed, as well as lightly annealed materials, with grain boundary strengthening providing the major contribution thereafterComunidad de Madrid (CAM) under Contract No. 07N/0087/2002Peer reviewe

Effect of Equal Channel Angular Pressing (ECAP) on microstructure and properties of Al-FeAlCr intermetallic phase composites

An aluminium matrix composite was prepared by mixing commercial aluminium powders and 15 vol % of FeAlCr powders and consolidation by hot extrusion. The extruded composite was subjected to severe plastic deformation by equal channel angular pressing (ECAP) at room temperature and at 150°C. The extruded composite presents a uniform distribution of particles although some defects are observed such as residual pores and particle agglomerates. The particle distribution does not show a significant change due to ECAP. The extruded composite exhibits a relatively fine grain size of the order of 1-2 μm that was refined to 550 nm after three ECAP passes at room temperature by route A and to 636 nm after four passes at 150°C by route Bc. The yield stress of the composites was increased by 140 to 180% after ECAP as compared with the extruded condition.Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Spanish Ministry of Education and ScienceUniversidade Federal de São Paulo (UNIFESP) Instituto de Ciência e TecnologiaUNIFESP, Instituto de Ciência e TecnologiaFAPESP: 2012/ 07536-0Spanish Ministry of Education and Science: MAT2009-07342SciEL

Matrix grain refinement in Al-TiAl composites by severe plastic deformation: influence of particle size and processing route

The microstructure and mechanical behaviour of Al-based composites reinforced with TiAl intermetallic particles has been examined in the as-extruded state and after processing by equal channel angular pressing (ECAP). The latter produces a grain size reduction in the aluminium matrix to values of 500 nm, using route A, and 750 nm, using route C. The ECAP produces up to a 75% increase in the yield stress of the composites, being more rapid when route A is used. The strengthening effect by ECAP is much larger than that obtained by increasing the volume fraction of reinforcement particles from 25 to 50% in these compositesThanks to the Spanish Ministry of Education and Science for financing this study under project number MAT2003-01540.Peer reviewe

Kinetics of Intramolecular Chemical Exchange by Initial Growth Rates of Spin Saturation Transfer Difference Experiments (SSTD NMR)

We report here the Initial Growth Rates SSTD NMR method, as a new powerful tool to obtain the kinetic parameters of intramolecular chemical exchange in challenging small organic and organometallic molecules

Elaboración del catálogo musical descriptivo: Cien años de música coral para niños en el Perú

Entre sus múltiples beneficios, la práctica coral infantil es también una oportunidad para que nuestros niños conozcan las expresiones artísticas propias de nuestros pueblos. En un país pluricultural como el nuestro, esa diversidad nos enriquece como individuos, como Nación. Es, a su vez, fuente de saber e inspiración para nuestros músicos y compositores. Al ser así, se hace imprescindible la inclusión de sus obras, destinadas a las llamadas voces blancas, en el repertorio coral infantil de nuestro país. El presente trabajo describe el proceso de realización del Catálogo musical descriptivo: Cien años de música coral para niños en el Perú, sobre las obras corales para niños —de compositores peruanos— escritas en el periodo comprendido entre 1921 y 2021; el cual incluye, también, los aportes de las publicaciones realizadas por importantes directores y pedagogos musicales, a favor del repertorio coral en las escuelas. Se indagó y se recopiló información de diversas fuentes bibliográficas, se contactó a la mayor cantidad de compositores nacionales, o a sus familiares (en el caso de compositores ya desaparecidos); lo cual permitió generar una red de contactos tanto a nivel nacional como internacional. A raíz de ello, se tuvo acceso a información relevante sobre sus composiciones y arreglos para coros de niños que, estoy seguro, permitirá ampliar el repertorio coral infantil y adolescente de nuestro país; así como su difusión y su empleo para fines didácticos o de investigación

COVID-19 attributed mortality and ambient temperature: a global ecological study using a two-stage regression model

A negative correlation between ambient temperature and COVID-19 mortality has been observed. However, the World Meteorological Organization (WMO) has reinforced the importance of government interventions and warned countries against relaxing control measures due to warmer temperatures. Further understanding of this relationship is needed to help plan vaccination campaigns opportunely. Using a two-stage regression model, we conducted cross-sectional and longitudinal analyses to evaluate the association between monthly ambient temperature lagged by one month with the COVID-19 number of deaths and the probability of high-level of COVID-19 mortality in 150 countries during time t = 60, 90, and 120 days since the onset. First, we computed a log-linear regression to predict the pre-COVID-19 respiratory disease mortality to homogenize the baseline disease burden within countries. Second, we employed negative binomial and logistic regressions to analyze the linkage between the ambient temperature and our outcomes, adjusting by pre-COVID-19 respiratory disease mortality rate, among other factors. The increase of one Celsius degree in ambient temperature decreases the incidence of COVID-19 deaths (IRR = 0.93; SE: 0.026, p-value<0.001) and the probability of high-level COVID-19 mortality (OR = 0.96; SE: 0.019; p-value<0.001) over time. High-income countries from the northern hemisphere had lower temperatures and were most affected by pre-COVID respiratory disease mortality and COVID-19 mortality. This study provides a global perspective corroborating the negative association between COVID-19 mortality and ambient temperature. Our longitudinal findings support the statement made by the WMO. Effective, opportune, and sustained reaction from countries can help capitalize on higher temperatures’ protective role including the timely rollout of vaccination campaigns

Propuesta de mejora del proceso de abastecimiento para evitar el quiebre de stock de medicamentos en la botica Libertad - Trujillo 2021

El presente trabajo de investigación tuvo como objetivo elaborar una propuesta de mejora en el proceso de abastecimiento para evitar el quiebre de stock de medicamentos en la Botica Libertad. Se realizó un estudio transversal tipo aplicada y de grado pre experimental. Como técnicas se empleó la encuesta a 21 colaboradores y la observación para el control del tiempo de respuesta a los clientes; como instrumento se aplicó el cuestionario de 25 preguntas debidamente alineadas a cada dimensión de las variables en estudio, los cuales permitieron conocer su sistema de abastecimiento de medicamento en el que no siempre utilizan un modelo técnico de reabastecimiento lo que redunda en quiebres de stock de sus medicinas de mayor de demanda. En relación a las propuestas de mejoras en el proceso de abastecimiento de medicamentos, se inició con la selección de proveedores aplicando la técnica de factores ponderados; el cual deben dar prioridad de compra a la Distribuidora y Droguería las Américas SAC (395 puntos) porque obtuvo el máximo puntaje de selección y como última opción se tiene a la empresa distribuidora Jenfarma Perú SAC por haber obtenido el mínimo puntaje de selección (300 puntos). Luego se aplicó el modelo económico de pedidos (EOQ) para determinar las cantidades óptimas (Q*) el cual se obtuvo un promedio de 1,768 unidades; número de pedidos (N), estos oscilaron entre 22 y 25 veces al año; tiempo entre pedidos (T), que osciló entre 12 y 15 días; punto de reorden que osciló entre 617 unidades como mínimo y 763 unidades como máximo. El tiempo que demoran los proveedores en enviar los medicamentos es de 4 a 5 días. Se determinó el stock de seguridad valorizado de los principales medicamentos; se determinó el tiempo de respuesta durante el proceso de ventas. Así mismo, se determinó la frecuencia de rotación de los medicamentos con mayor demanda para dar una ubicación preferencial y estratégica en el almacén.The objective of this research work was to elaborate a proposal for improvement in the supply process to avoid the stock break of medicines in the Botica Libertad. A cross sectional applied study of a pre-experimental grade was carried out. The techniques used were the survey of 21 employees and observation to control the response time to customers; As an instrument, the questionnaire of 25 questions duly aligned to each dimension of the variables under study was applied, which allowed to know their drug supply system in which they do not always use a technical replenishment model, which results in stock breaks of their medicines of greater demand. In relation to the proposals for improvements in the drug supply process, it began with the selection of suppliers applying the weighted factor technique; which must give priority of purchase to the Distribuidora y Droguería las Américas SAC (395 points) because it obtained the maximum selection score and as a last option there is the distribution company Jenfarma Perú SAC for having obtained the minimum selection score (300 points). Then the economic ordering model (EOQ) was applied to determine the optimal quantities (Q *), which resulted in an average of 1,768 units; number of orders (N), these ranged between 22 and 25 times a year; time between orders (T), which ranged between 12 and 15 days; reorder point that ranged from a minimum of 617 units to a maximum of 763 units. The time it takes for providers to ship medications is 4-5 days. The valued safety stock of the main drugs was determined; the response time was determined during the sales process. Likewise, the frequency of rotation of the drugs with the highest demand was determined to give a preferential and strategic location in the warehouseTesi

Plasticity analysis by synchrotron radiation in a Mg97Y2Zn1 alloy with bimodal grain structure and containing LPSO phase

© 2015 Acta Materialia Inc. All rights reserved. Deformation behaviour has been examined by synchrotron radiation diffraction in an extruded magnesium - long-period-stacking-order phase alloy comprising three components of microstructure. The variation of internal strains and intensities of the important crystallographic planes of the two phases has been examined during compression at several temperatures. The long-period-stacking-order phase remains elastic to stresses beyond the macroscopic yield stress while deformation in the magnesium matrix is dominated by twinning and basal slip, with the coarse-grained regions deforming plastically at stresses well below the macroscopic yield stress while regions with fine grain size deform plastically only at much higher stresses.We would like to acknowledge financial support of the Spanish Ministry of Education and Science under project number MAT2012-34135. We would like to acknowledge the expert support of Miguel Acedo and Edurne Laurin for assistance with the extrusion processing and the metallographical preparation, respectively.Peer Reviewe