Optimización de los movimientos de tierras en proyectos de obras lineales mediante técnicas de programación lineal: modelo basado en rendimientos de construcción

Las operaciones de movimiento de tierras representan una de las partidas más importantes en el presupuesto de cualquier obra lineal, e influyen de forma relevante tanto en el proceso de planificación como en el plazo de la obra. El estudio detallado y la optimización de estas operaciones son aspectos importantes a considerar durante la redacción de un proyecto de obra lineal. La asignación de los volúmenes de materiales que deben transportase desde los centros de producción (desmontes y préstamos) a los centros de consumo (terraplenes y vertederos) es un problema relativamente complejo, para cuya resolución se han propuesto en la literatura científica básicamente dos grupos de metodologías: una más tradicional, basada en el denominado diagrama de masas; y otras más novedosas, que se apoyan en técnicas de optimización. Mediante el diagrama de masas se establece una compensación longitudinal de los materiales, y se limita a informar sobre distancias medias de transporte. En relación al segundo grupo de metodologías, en las últimas décadas se han desarrollado diferentes procedimientos basados en programación lineal, en su forma particular del problema del transporte. Estas técnicas permiten optimizar de forma más precisa las operaciones de movimiento de tierras si bien no se ha estudiado con detalle la manera de generar o definir los centros de producción y consumo considerando aspectos relacionados con la planificación. En este artículo se desarrolla un procedimiento para la optimización de los movimientos de tierras en obras lineales mediante técnicas de programación lineal, en el cual los centros de producción y consumo son obtenidos a partir de los rendimientos de construcción de los equipos disponibles por el contratista. El procedimiento permite obtener tanto el coste mínimo de las operaciones de movimiento de tierras como el plazo de ejecución de las obras. Finalmente, se presentan los resultados de la aplicación a un caso real de una carretera

Numerical Analysis of Bicycle Helmet under Blunt Behavior

This study evaluates various safety aspects of standardized impacts that cyclists may suffer while wearing a bicycle helmet, by combining a partially validated finite element model of the cranio-cervical region and a newly developed commercial bicycle helmet model. Under EN 1078 standardized impact conditions, the results of simulated impact tests show that the helmet can absorb 40% to 50% of the total impact energy at impact velocities above 4 m/s. Further, based on a relationship between the head injury criterion and the risk of injury from field data, the results of the simulations suggest that minor injuries may occur at impact velocities of 10 km/h, serious injuries at 15 km/h, and severe injuries at 20 km/h. Fatal injuries will likely occur at impact velocities of 30 km/h and higher.This work has been carried out within the framework of the research project DPI2017-88166- of FEDER program financed by the Ministerio de Economía, Industria y Competitividad and the Spanish Ministry of Education, Culture and Sports for the professor’s mobility program José Castillejo’s 2018 grant (CAS18/00292)

Experimental and numerical study of the thermo-viscoplastic behavior of nicro 12.1 for perforation tests

Dynamic impact tests using thin metal plates for ballistic characterization have received significant attention in recent years. The Johnson–Cook (J–C) model is extensively used in numerical modeling of impact and penetration in metals. The AISI (American Iron and Steel Institute) 301 steel family presents good impact behavior, excellent formability, and high corrosion resistance. Thus, NICRO (Nickel and Hard Chrome Plated Steel) 12.1 (part of the AISI 301 steel family) was chosen in this work, although parameters of the J–C model or impact results were not found in the literature. In this work, NICRO 12.1 steel plates, were characterized in ballistics with an initial impact velocity up to 200 m/s and three shape nose projectiles. The Johnson–Cook parameters for the NICRO 12.1 steel were calculated for a large range of temperatures and strain rates. Impact tests were carried out using three projectiles: conical, hemispherical, and blunt. The ballistic curves, failure mode, and maximum deformation obtained with each projectile, experimentally and numerically, were compared, and a good correlation was obtaine

Ballistic performance of aramid composite combat helmet for protection against small projectiles

This paper focuses on the ballistic performance of aramid composite combat helmet commonly worn by military and security corps, against small projectiles threat. We propose a numerical finite element model for aramid composite protections, considering a multi-layer architecture, able to predict its ballistic behaviour and damage extension. The aim is determining the minimum number of layers required for a correct protection against a given ballistic thread. The constitutive aramid behaviour has been calibrated by means of experimental tests with FSP (Fragment Simulate Projectiles) projectiles and steel spheres on aramid flat plates. Once calibrated, a predictive numerical model of the helmet against different small projectiles and impacted localisations was developed and compared with experimental tests performed in the real head protection. The results calculated for the absorbed impact energy by the helmet and the induced damage due to small projectiles at different impact location, are in good agreement with experimental results and postmortem helmet analysis, validating the proposed numerical model. The numerical model is thus validated for the design of optimized head protections based on aramid compositeThe authors acknowledge the Ministry of Economy and Competitiveness of Spain and the European Regional Development Fund, (FEDER) program under the Project RTC-2015-3887-8 and the Project DPI2017-88166-R for the financial support of the work

Energy absorption analysis of aramid composite during blunt projectile impact

In this work, a numerical model for aramid composites is experimentally validated in terms of permanent deformation, energy absorption and damage mechanisms for ballistic applications. Novel experimental and numerical results of non-perforating ballistic impacts with blunt projectiles are presented. The resistance forces and absorption energy by the specimen are measured for different impact velocities. A post-mortem analysis of the failure mechanisms is performed using computed tomography and a profilometer device. The numerical model is used to analyse the influence of impactor mass and impact velocity below the ballistic limit.The authors acknowledge the Ministry of Economy and Competitiveness of Spain and FEDER program under the Project DPI2017-88166-R for the financial support of the work. Prof. A. Rusinek acknowledges the financial support from the program UC3M-Santander Chair of Excellence in additive manufacturing

Consistency of expert product reviews: an application to wine guides

Purpose. The purpose of this study is to examine the internal consistency of wine guides by comparing the judgements of experts who taste and review wines. It further classifies the wines into categories to establish whether expert reviews of similar wines are coherent. Design/methodology/approach. Sentiment analysis based on natural language processing techniques was used to compare quantitative and qualitative reviews between experts. In addition, a finite mixture model was used to classify wines into categories to analyse internal consistency between ratings. Findings. The results for a sample of more than 200,000 Wine Enthusiast ratings reveal significant differences between the experts’ reviews, which shows that there are no standard criteria for reviewing the wines included in the guide. Originality. Wine guides are amongst the most widely used marketing resources in the wine industry. They provide a signal to consumers about the quality of wines, guiding their purchase decisions, whilst also influencing the reputation of brands and the performance of the companies producing these wines. Thus, the main contribution of this study is to improve comparisons of the assessments by wine guide experts in relation to the wines they taste. This analysis will make it possible to verify their effectiveness as a source of information for consumers and will allow wine producers to make more accurate assessments of the potential impact of experts on their performance

Evaluation of Combat Helmet Behavior under Blunt Impact

This article belongs to the Special Issue Armour and Protection SystemsNew threats are a challenge for the design and manufacture of modern combat helmets. These helmets must satisfy a wide range of impact velocities from ballistic impacts to blunt impacts. In this paper, we analyze European Regulation ECE R22.05 using a standard surrogate head and a human head model to evaluate combat helmet performance. Two critical parameters on traumatic brain analysis are studied for different impact locations, i.e., peak linear acceleration value and head injury criterion (HIC). The results obtained are compared with different injury criteria to determine the severity level of damage induced. Furthermore, based on different impact scenarios, analyses of the influence of impact velocity and the geometry impact surface are performed. The results show that the risks associated with a blunt impact can lead to a mild traumatic brain injury at high impact velocities and some impact locations, despite satisfying the different criteria established by the ECE R22.05 standard. The results reveal that the use of a human head for the estimation of brain injuries differs slightly from the results obtained using a surrogate head. Therefore, the current combat helmet configuration must be improved for blunt impacts. Further standards should take this into account and, consequently, combat helmet manufacturers on their design process.This work has been carried out within the framework of the research project DPI2017-88166-R of the FEDER program financed by the Ministerio de Economía, Industria y Competitividad and the Spanish Ministry of Education, Culture and Sports for the professor's mobility program José Castillejo's 2018 grant (CAS18/00292)

Lateral absorption measurements of InAs/GaAs quantum dots stacks: Potential as intermediate band material for high efficiency solar cells

Prototypes based on InAs/GaAs QDs have been manufactured in order to realize the theoretically predicted high efficiency intermediate band solar cells (IBSCs). Unfortunately, until now, these prototypes have not yet demonstrated the expected increase in efficiency when compared with reference samples without IB material. One of the main arguments explaining this performance is the weak photon absorption in the QD-IB material, arising from a low density of QDs. In this work, we have analyzed the absorption coefficient of the IB material by developing a sample in an optical wave-guided configuration. This configuration allows us to illuminate the QDs laterally, increasing the path length for photon absorption. Using a multi-section metal contact device design, we were able to measure an absorption coefficient of ∼100 cm−1 around the band edge (∼1 eV ) defined by the transition in InAs/GaAs QD-IB materials. This figure, and its influence on the IBSC concept, is analyzed for this system

Calcinación de huesos: análisis de cambios de color con fines forenses

Introducción: Los cambios morfológicos que experimentan los huesos sometidos a elevadas temperaturas presentan un reto para los laboratorios forenses y antropológicos. El cambio producido en ellos puede verse influenciado por la temperatura y tiempo de exposición al calor. Objetivo: correlacionar cambios del color en el hueso con la temperatura de incineración. Material y métodos. Un total de 32 huesos largos de 5 centímetros de longitud fueron calcinados en un horno de mufla. Ocho de ellos fueron sometidos a 200 °C: 4 durante 30 minutos y otros 4 durante 60 minutos. Otros 8 se expusieron a 400 °C: 4 durante 30 minutos y los otros 4 durante 60 minutos. Ocho más se sometieron a 600 °C: 4 durante 30 minutos y 4 durante 60 minutos. Los 8 restantes se sometieron a 800 °C e igualmente divididos en un grupo de 4 sometido durante un tiempo de 30 minutos y otros 4 durante 60 minutos Además, 4 se utilizaron como control. Con ayuda de lupas y fotografías se realizó un examen visual donde se describió el color de la cortical y medula del hueso. También, se midió el cambio de color con un espectrofotómetro portátil. Finalmente se realizó estudio de correlación entre los cambios de color y la exposición a la temperatura y tiempos. Resultados. Los huesos sometidos a 200 ºC mostraron un color marrón mientras que a 400 el color fue negro en el 100% de casos. A 600 y 800 ºC viraban a gris y blanco con tonos azulados. Los resultados mostraron alteraciones del color significativas en los valores de Blanqueamiento (WI) y Crominancia (y). Además, se observa correlación significativa entre el color y la temperatura tanto en los huesos sometidos durante 30 como a 60 minutos en los mismos parámetros anteriores. . Conclusión. De acuerdo con estos resultados, el análisis colorimétrico de los huesos incinerados puede ayudar a estimar la temperatura de exposición siendo la temperatura el factor más influyente.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Calcinación de dientes y huesos: estudio morfológico con fines forenses

INTRODUCCIÓN: Los cambios físicos y morfológicos (macro y microscópicos) que experimentan los dientes y huesos sometidos a altas temperaturas han sido motivo de nuestros estudios en los últimos años. El cambio producido en ellos pueden verse influenciados por una serie de factores externos como la temperatura y el tiempo en el que han permanecido expuestos. Por ello, el objetivo de este estudio es conocer los cambios morfológicos que se originan en la calcinación de dientes y huesos a diferentes temperaturas. MATERIAL Y MÉTODOS: Diez muestras mineralizadas (4 dientes y 6 huesos largos) divididas en dos grupos se someten a 200 y 400 ºC durante 30 minutos en un horno de mufla (Nabertherm LT 40/12, Nabertherm GmbH, Germany). Posteriormente, se observaron mediante un Microscopio Multizoom Nikon modelo AZ 100 con objetivo 2 y zoom 1 asociado a un a un ordenador (PC) donde está instalado el programa Nis-Elements diseñado para la captación, almacenaje y tratamiento de fotografías. RESULTADOS: Las fisuras longitudinales se inician en el 100% de los dientes sometidos a 200 ºC durante 30 minutos tanto a nivel coronal como radicular. A esta misma temperatura y tiempo no se observa fisuras en los huesos largos. A 400 ºC se originan fracturas “en casquete” del esmalte en el molar y fractura radicular y coronal en el premolar. Además, se inician las fisuras a nivel medular de los huesos. CONCLUSIONES: Según este estudio, ante la misma temperatura y tiempo de calcinación los dientes se fisuran y fracturan antes que los huesos largos.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech