Alex Grasas

Journal of Simulation (JOS) publishes articles, technical notes, case studies and tutorials in the field of simulation, with a particular focus on the applications of simulation and modelling. Journal of Simulation is an official journal of the OR Society.

Background and Objective: Recent studies suggest that transfusion of old red blood cell (RBC)s, mainly those close to the 42‐day maximum shelf life (MSL), is associated with increased morbi‐mortality. Although there is no formal proof supporting a causal relationship, the precautionary principle asks for corrective interventions whenever they do not bring about other risks or unjustified costs. Here, we investigated the feasibility of reducing the MSL.Materials and Methods: A trace simulation model was used to analyse the repercussions of several MSLs on a large regional blood system. The baseline model was fed with real input and output data from years 2009 to 2010 and validated against real inventory data. Shortage and outdate rates and inventory levels for each blood group were derived assuming 42‐, 35‐, 28‐, 21‐ and 14‐day MSLs, as well as several distribution rules and supply shocks (periods without blood collections).Results: The model shows that MSL could be reduced to 28–35 days without major increases in the shortage or outdate rates, even after supply shocks. At the 21‐day MSL, the inventory capability to compensate supply shocks was severely reduced and translated into large shortage rates. The later were higher for group O and Rh‐negative RBCs as compared to group A and Rh‐positive, respectively.Conclusion: Reductions of MSL to 28–35 days seem feasible and riskless and do not require major changes in the inventory management policies. Consequently, and giving preponderance to the precautionary principle, the Catalan Blood Agency has decided to reduce the MSL of RBCs from 42 to 35 days.

Blood samples are usually collected daily from different collection points, such hospitals and health centers, and transported to a core laboratory for testing. This paper presents a project to improve the collection routes of two of the largest clinical laboratories in Spain. These routes must be designed in a cost-efficient manner while satisfying two important constraints: (i) two-hour time windows between collection and delivery, and (ii) vehicle capacity.

This paper presents several experiences regarding Operations Research (OR) and Simulation education activities in three master programs, each of them offered at a different university. The paper discusses the importance of teaching these contents in most managerial and engineering masters. After a brief overview of existing related work, the paper provides some recommendations-based on our own teaching experiences-that instructors should keep in mind when designing OR/Simulation courses, either in traditional face-to-face as well as in pure online learning models. The case studies exposed here include students from business management, computer science, and aeronautical management degrees, respectively. For each type of student, different OR/Simulation tools are employed in the courses, ranging from easy-to-use optimization and simulation software to simulation-based algorithms developed from scratch using a programming language.

To understand whether retailers should consider consumer returns when merchandising , we study how the optimal assortment of a retailer is influenced by its return policy. The retailer selects its assortment from an exogenous set of horizontally differentiated products. Consumers make purchase and keep/return decisions in nested multinomial logit fashion. Our main finding is that the optimal assortment has a distinct structure for relatively strict return policies: it is optimal to offer a mix of the most popular and most eccentric products when the refund amount is sufficiently low, which can be viewed as a form of risk sharing between the retailer and consumers. In contrast, if the refund is sufficiently high or when returns are disallowed, the optimal assortment is composed of only the most popular products (a common finding in the literature). We provide preliminary empirical evidence for one of the key drivers of our results: more eccentric products have higher probability of return—conditional on purchase. In light of our analytical findings and managerial insights, we conclude that retailers should take returns into account when merchandising.

In this article we present a Vehicle Routing Problem (VRP) faced by a large distribution company in the Northeast of Spain. The company distributes products from its central facilities to a chain of around 400 stores all over the country. One of the peculiarities of the VRP of this company – which is common among real-life VRPs – is the presence of a heterogeneous fleet where vehicles with different capacities can make multiple trips during a single day. This variant of the problem, which we refer as Heterogeneous Fleet and Multi-trip VRP, has been barely studied in the literature. To solve the problem, we use an algorithm based on the well-known savings heuristic with a biased-randomization effect and three local search operations. Our approach is simple to implement as it needs few parameters and no fine-tuning processes, which are usually cumbersome and require experts’ involvement. We obtain savings of around 12 per cent in transportation costs, which represent around €30 000 saved per week.