The Project Scheduling Problem with Non-Deterministic Activities Duration: A Literature Review

Purpose: The goal of this article is to provide an extensive literature review of the models and solution procedures proposed by many researchers interested on the Project Scheduling Problem with nondeterministic activities duration. Design/methodology/approach: This paper presents an exhaustive literature review, identifying the existing models where the activities duration were taken as uncertain or random parameters. In order to get published articles since 1996, was employed the Scopus database. The articles were selected on the basis of reviews of abstracts, methodologies, and conclusions. The results were classified according to following characteristics: year of publication, mathematical representation of the activities duration, solution techniques applied, and type of problem solved. Findings: Genetic Algorithms (GA) was pointed out as the main solution technique employed by researchers, and the Resource-Constrained Project Scheduling Problem (RCPSP) as the most studied type of problem. On the other hand, the application of new solution techniques, and the possibility of incorporating traditional methods into new PSP variants was presented as research trends. Originality/value: This literature review contents not only a descriptive analysis of the published articles but also a statistical information section in order to examine the state of the research activity carried out in relation to the Project Scheduling Problem with non-deterministic activities duration.Peer Reviewe

Catalytic Applications of Metal-Organic Frameworks

In recent years, metal organic frameworks (MOF) have received considerable interest due to their physicochemical properties, such as structures’ flexibility, high surface area, tunable pore size, and topologies, among others, which have lead to promising applications, particularly in the area of catalysis. In this chapter, we present the most important results of research conducted with MOF in catalytic applications; mainly in the design of its structure, synthesis, characterization, and possible limitations

Procesos comunicativos implementados por el metro Medellín durante la construcción del metrocable línea P

Analizar las percepciones que tienen los habitantes del barrio la Paralela de Medellín frente a los procesos comunicativos del Metro de Medellín que conllevan la construcción del proyecto Metrocable línea P, durante el primer semestre del 2019.Este estudio examina el proceso comunicativo que se implementó en el barrio la paralela por parte del metro de Medellín, durante la construcción del metrocable línea P, por medio de entrevistas realizadas a una profesional 1 de la dirección de comunicaciones del metro y 7 habitantes del barrio la paralela de la ciudad de Medellín, se analizan las herramientas de comunicación que se implementaron en la comunidad para informar sobre el proyecto que se iba a llevar a cabo y a su vez poder dar espacio a los habitantes de este sector un espacio para compartir sus opiniones frente al proyecto. Los datos analizados sugieren que durante la planeación de un proyecto en este caso de transporte urbano, es necesario llevar un buen proceso de comunicación por las partes implicadas, en donde la participación de la comunidad es fundamental, dado que a raíz de esto puede depender el éxito de un proyecto y la aceptación por parte de la comunidad

Stratigraphy, provenance, and syn-orogenic evolution of the Gibbett Hill and Quidi Vidi formations (lower Signal Hill Group), Avalon Peninsula (Newfoundland)

Sedimentologic and provenance studies of the syn-orogenic Ediacaran lower Signal Hill Group (Gibbett Hill and Quidi Vidi formations) in the Avalon Peninsula, Newfoundland, Canada, were conducted to test structural and depositional models related to late Ediacaran West Avalonian orogenesis. Two facies associations corresponding to delta front and delta plain environments were identified from five stratigraphic sections. The presence of an unconformity between these facies near the location of a previously proposed thrust-related paleo-high and changes in sedimentary patterns reflecting shoreline regression supports hypothetical syn-sedimentary uplift and reveals coeval base level fall. Framework petrography, detrital geochronology, and detrital heavy mineral analysis indicate sediment sourcing from hinterlands of West Avalonian igneous and metamorphic basement. Changes in provenance were noted between the delta front and delta plain facies coeval with regression of the Signal Hill delta that suggests coeval thrusting of volcanic cover sequences over previously exhumed plutonic sources and the exhumation of higher-grade metamorphic rocks in the hinterlands. Detrital zircon U-Pb maximum depositional ages of the delta front and delta plain facies yield 557 ± 9 Ma and 556 ± 22 Ma, respectively, constraining this episode of West Avalonian hinterland exhumation, wedge-top foreland basin deformation, and forced regression to ca. 556 Ma

On weights and quotas for weighted majority voting games

In this paper, we analyze the frequency distributions of weights and quotas in weighted majority voting games (WMVG) up to eight players. We also show different procedures that allow us to obtain some minimum or minimum sum representations of WMVG, for any desired number of players, starting from a minimum or minimum sum representation. We also provide closed formulas for the number of WMVG with n players having a minimum representation with quota up to three, and some subclasses of this family of games. Finally, we complement these results with some upper bounds related to weights and quotas.Peer ReviewedPostprint (published version

Sustainable Biorefineries: What was Learned from the Design, Analysis and Implementation

Bioeconomies need sustainable technologies and strategies for biomass processing. One of the best ways to do that is to consider biorefineries as a practical way to achieve real developments in the industry for integral production of energy, food, feed and chemicals under an ideal dream of replacing today’s crude-oil and basically using the accessible biomass in the world as much as possible. Additionally, the existent biofuel facilities are constantly adding new processing lines without integral design strategies, and possibly repeating the past design and implementation errors in refineries based on crude-oil. In recent years, more as a fashion or tendency, these processing lines from biofuels industry have been integrated in a system called “biorefinery” and many sectors have supported this idea through policies to incentivize the development of the bio-based economies adopting this concept. The design of biorefineries is presented as a relevant topic due to the multiple processing paths that could be available to obtain a set of desirable products. However, after many scientific efforts in design through well validated methodologies the biorefineries currently are not working properly or are more close to a conventional standalone biomass processing. Some big facilities already implemented today as biorefineries are closed or working just as standalone process (biofuels plant), but not through a promising multiproduct biorefinery configuration for which the resulting design was developed. In this work, 13 biorefineries were analysed including 4 industrial cases that were implemented after specific design and different industrial plants that use different raw materials of renewable origin. To achieve this, different strategic cases were considered: raw materials with inherent logistics restrictions, technical, economic, environmental assessments together with social considerations and finally market restrictions. As a result, and based on different case studies (where these process engineering strategies where applied through conceptual design using Aspen Plus and Potential Environmental Impacts) the positive and negative lessons are discussed in detail. The main result is an overall learning from different cases of study for future design, analysis and implementation of new biorefineries with a real sustainability and avoiding a repetition of the same evolution that risky and controversial crude-oil refineries had

Identificación y modelamiento matemático, a partir de datos entrada-salida de un sistema de presión de aire

Este artículo presenta dos metodologías para determinar el modelo matemático de un sistema de presión de aire a través de los datos de entrada y salida de una planta cuando no es posible encontrarlo por medio de las ecuaciones fundamentales de la física. En este trabajo se implementan dos metodologías, la primera a través del análisis de la gráfica obtenida de los datos de presión del sistema respecto al tiempo y la segunda utilizando un modelo de estimación por variables instrumentales. Como prueba experimental, se realiza el modelamiento del sistema físico con ambos métodos. El sistema de presión de aire fue construido para operar en un rango de presiones de 0-40 mmHg. Los resultados de los modelos obtenidos fueron evaluados a través de la comparación directa de la salida modelada contra la señal real del sistema

Identificación y modelamiento matemático, a partir de datos entrada-salida de un sistema de presión de aire

Este artículo presenta dos metodologías para determinar el modelo matemático de un sistema de presión de aire a través de los datos de entrada y salida de una planta cuando no es posible encontrarlo por medio de las ecuaciones fundamentales de la física. En este trabajo se implementan dos metodologías, la primera a través del análisis de la gráfica obtenida de los datos de presión del sistema respecto al tiempo y la segunda utilizando un modelo de estimación por variables instrumentales. Como prueba experimental, se realiza el modelamiento del sistema físico con ambos métodos. El sistema de presión de aire fue construido para operar en un rango de presiones de 0-40 mmHg. Los resultados de los modelos obtenidos fueron evaluados a través de la comparación directa de la salida modelada contra la señal real del sistema

Evaluation of Natural Rubber Specific Heat Capacity at High Pressures from DSC Experimental Data at Atmospheric Pressure

[EN] The natural rubber specific heat capacity dependence on pressure was estimated on thermodynamic grounds on the basis of the values empirically determined from differential scanning calorimetry data, (in the temperature range of 70 to 50 C), and by means of the Tait equation of state (in the pressure range of 0.1 240 MPa). It was found that the specific heat capacity decreases with pressure, being the dependency more pronounced at low pressures.This work was financially supported by the DGCYT through Grant MAT2008-06725-C03 and by Generalitat Valenciana through Grant No. ACOMP/2010/204.Ortiz Serna, MP.; Díaz Calleja, R.; Sanchis Sánchez, MJ. (2012). Evaluation of Natural Rubber Specific Heat Capacity at High Pressures from DSC Experimental Data at Atmospheric Pressure. Journal of Applied Polymer Science. 128(4):2269-2272. doi:10.1002/app.38118S22692272128