A two-stage stochastic transportation problem with fixed handling costs and a priori selection of the distribution channels

In this paper, a transportation problem comprising stochastic demands, fixed handling costs at the origins, and fixed costs associated with the links is addressed. It is assumed that uncertainty is adequately captured via a finite set of scenarios. The problem is formulated as a two-stage stochastic program. The goal is to minimize the total cost associated with the selected links plus the expected transportation and fixed handling costs. A prototype problem is initially presented which is then progressively extended to accommodate capacities at the origins and multiple commodities. The results of an extensive set of computational tests are reported and discussed

The Single Period Coverage Facility Location Problem: Lagrangean heuristic and column generation approaches

In this paper we introduce the Single Period Coverage Facility Location Problem. It is a multi-period discrete location problem in which each customer is serviced in exactly one period of the planning horizon. The locational decisions are made independently for each period, so that the facilities that are open need not be the same in different time periods. It is also assumed that at each period there is a minimum number of customers that can be assigned to the facilities that are open. The decisions to be made include not only the facilities to open at each time period and the time period in which each customer will be served, but also the allocation of customers to open facilities in their service period. We propose two alternative formulations that use different sets of decision variables. We prove that in the first formulation the coefficient matrix of the allocation subproblem that results when fixing the facilities to open at each time period is totally unimodular. On the other hand, we also show that the pricing problem of the second model can be solved by inspection. We prove that a Lagrangean relaxation of the first one yields the same lower bound as the LP relaxation of the second one. While the Lagrangean dual can be solved with a classical subgradient optimization algorithm, the LP relaxation requires the use of column generation, given the large number of variables of the second model. We compare the computational burden for obtaining this lower bound through both models

Efecto del temperamento infantil en el peso del niño preescolar: una revisión sistemática

Background: Temperament is a variable that has recently been shown to be of interest as a risk factor for childhood obesity. Some studies indicate that difficult temperament is associated with weight gain in preschoolers.Objectives: The aim of the present study was to analyze the available literature on the association between the child's temperament and the BMI of the preschool child.Methods: We did a review of the literature about studies evaluating the association amoung temperament and body mass index in the preschool child. The search was carried since May to June of 2016 in databases such as Pubmed, EBSCO Host, Ovid, Springer Link and academic google. We included studies that had not more than 10 years of published and that complied criteria for inclusion, in addition the results of the studies had quality in the methodology and results, as reference for the evaluation of the studies, we used The Critical Apprasisal Skills Program English.Results: We found 784 articles, of which only nine were included for this review, six of the studies evaluated temperament based on attentional reactivity and / or traits, three evaluated temperament based on self-regulation of the child and only one Evaluated both emotional reactivity and self-regulation. It seems that negative reactivity and low self-regulation are factors associated with childhood obesity in the preschool age.Conclusions: The literature suggests that more research is needed to determine the temperament behavior around obesity in children.Antecedentes: El temperamento es una variable que recientemente ha resultado de interés por considerarse un factor de riesgo de la obesidad infantil. Algunos estudios señalan que el temperamento difícil se asocia al incremento del peso en los preescolares.  Objetivo: Analizar la literatura disponible sobre la asociación entre el temperamento infantil y el IMC del niño preescolar. Métodos: Se realizó una revisión de la literatura sobre estudios que evaluaran la asociación entre el temperamento e índice de masa corporal en el niño preescolar, la búsqueda se realizó en los meses de mayo y junio del 2016, en bases de datos como Pubmed, EBSCO host, Ovid, Springer Link y Google académico, se incluyeron estudios que no tuvieran más de 10 años de haberse publicado y que cumplieran con los criterios de inclusión y calidad en la metodología y resultados presentados, como referencia para la evaluación de los estudios se utilizó la guía Critical Apprasisal Skills Programme Español.Resultados: Se encontraron 784 artículos, de los cuales solo nueve se incluyeron para esta revisión, seis de los estudios evaluaban el temperamento en base a la reactividad atencional y/o rasgos, tres evaluaban el temperamento en base a la autorregulación del niño y solo uno evaluó tanto la reactividad emocional como la autorregulación. Pareciera que la reactividad negativa y la baja autorregulación son factores asociados a la obesidad infantil en la edad preescolar. Conclusiones: La literatura encontrada sugiere que es necesaria mayor investigación para determinar el comportamiento del temperamento en torno a la obesidad en los niños

When centers can fail: a close second opportunity

This paper presents the p-next center problem, which aims to locate p out of n centers so as to minimize the maximum cost of allocating customers to backup centers. In this problem it is assumed that centers can fail and customers only realize that their closest (reference) center has failed upon arrival. When this happens, they move to their backup center, i.e., to the center that is closest to the reference center. Hence, minimizing the maximum travel distance from a customer to its backup center can be seen as an alternative approach to handle humanitarian logistics, that hedges customers against severe scenario deteriorations when a center fails. For this extension of the p-center problem we have developed several different integer programming formulations with their corresponding strengthenings based on valid inequalities and variable fixing. The suitability of these formulations for solving the p-next center problem using standard software is analyzed in a series of computational experiments. These experiments were carried out using instances taken from the previous discrete location literature.Peer ReviewedPostprint (author’s final draft

A computational comparison of several formulations for the multi-period incremental service facility location problem

The Multi-period Incremental Service Facility Location Problem, which was recently introduced, is a strategic problem for timing the location of facilities and the assignment of customers to facilities in a multi-period environment. Aiming at finding the strongest formulation for this problem, in this work we study three alternative formulations based on the so-called impulse variables and step variables. To this end, an extensive computational comparison is performed. As a conclusion, the hybrid impulse–step formulation provides better computational results than any of the other two formulations

Vacuna BNT162b2 en el personal sanitario: ¿Qué posibilidad hay de desarrollar efectos adversos?

Introducción/Objetivos Evaluar la aparición de efectos adversos a corto plazo y los factores de riesgo tras recibir la vacuna BNT162b2 en el personal sanitario del Hospital Clínico San Cecilio de Granada. Material y Métodos Estudio observacional, longitudinal, con sentido hacia delante y prospectivo en el que se analizaron las historias clínicas de 1492 profesionales sanitarios que notificaron reacciones adversas en el periodo comprendido entre el 27 de diciembre de 2020 y el 1 de septiembre de 2021. Se aplicaron test T de Student y chi-cuadrado para buscar asociación con la edad, sexo, dosis completa e infección previa por COVID-19. Finalmente, se realizó un análisis multivariante de regresión logística para analizar el efecto de las asociaciones ajustadas por posibles factores de confusión. Resultados Solo el 3.8% de los participantes presentaron alguna reacción adversa. Las más frecuentes fueron malestar general (2.2%), fiebre (1.9%) y artromialgias (1.8%). No se encontró asociación entre presentar reacción adversa y la edad, el sexo o la categoría MIR/EIR. Por el contrario, sí se encontró asociación, de acuerdo con el modelo de regresión logística ajustado, entre reacción adversa y la categoría enfermería (OR = 2.59, IC95%: 1.29 - 5.69), la pauta completa (OR = 0.11, IC95%: 0.02 - 0.77) y la infección COVID-19 previa (OR = 2.22, IC95%: 1.15 - 4.06). Conclusiones La frecuencia de efectos adversos fue reducida entre el personal sanitario. La infección previa y ser enfermero se relacionaron con mayor riesgo de notificar reacción adversa. Los efectos adversos que se notificaron fueron leves, lo que apoya el uso de la vacuna BNT162b2 ante posibles dosis de refuerzo a este colectivo. Aun así, es necesario seguir evaluando la seguridad de esta vacuna y realizar más estudios

Network flow based approaches for the pipelines routing problem in naval design

In this paper we propose a general methodology for the optimal automatic routing of spatial pipelines motivated by a recent collaboration with Ghenova, a leading Naval Engineering company. We provide a minimum cost multicommodity network flow based model for the problem incorporating all the tech- nical requirements for a feasible pipeline routing. A branch-and-cut approach is designed and different matheuristic algorithms are derived for solving efficiently the problem. We report the results of a battery of computational experiments to assess the problem performance as well as a case study of a real-world naval instance provided by our partner company.Ministerio de Ciencia Y Tecnología (MCYT). España PID2020-114594GB-C21European Commission (EC). Fondo Europeo de Desarrollo Regional (FEDER) US-1256951Junta de Andalucía P18-FR-1422Junta de Andalucía CEI-3-FQM331Junta de Andalucía B-FQM-322-UGR2

An optimization model for line planning and timetabling in automated urban metro subway networks

In this paper we present a Mixed Integer Nonlinear Programming model that we developed as part of a pilot study requested by the R&D company Metrolab in order to design tools for finding solutions for line planning and timetable situations in automated urban metro subway networks. Our model incorporates important factors in public transportation systems from both, a cost-oriented and a passenger-oriented perspective, as time-dependent demands, interchange stations, short-turns and technical features of the trains in use. The incoming flows of passengers are modeled by means of piecewise linear demand functions which are parameterized in terms of arrival rates and bulk arrivals. Decisions about frequencies, train capacities, short-turning and timetables for a given planning horizon are jointly integrated to be optimized in our model. Finally, a novel Math-Heuristic approach is proposed to solve the problem. The results of extensive computational experiments are reported to show its applicability and effectiveness to handle real-world subway networksComment: 30 pages, 6 figures, 9 table