Ciencias Exactas y Ciencias de la Salud

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Routing and storage assignment for the precedence-constrained order picking process
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2022-06-20) Pineda Romero, Valeria Viridiana; REGIS HERNANDEZ, FABIOLA; 331834; Regis Hernández, Fabiola; puelquio/mscuervo; Espinoza García, Juan Carlos; School of Engineering and Sciences; Campus Monterrey; Murrieta Cortés, Beatriz
Order picking is retrieving items from the warehouse to fulfill customers’ orders. It is considered the most labor-intensive and time-consuming operation in a warehouse and composes almost half of the total operating costs. Thus, developing efficient routing sequences for order pickers has been one of the main focus projects of managers. In addition, in real-warehouse environments, routing is frequently influenced by precedence constraints. Precedence constraints arise when certain products need to be collected before others due to a particular physical characteristic of the items. For instance, precedence constraints may be defined by the products’ fragility, weight, or size, among others. Even though many warehouses face such constraints, they have often been neglected in the scientific literature. This dissertation is inspired by a practical case of a Mexican Company that stores perishable products, which are considered sensitive items; this means that they are easily deformed if a certain weight is placed on them. This situation arises the problem that the warehouse under study must consider Unit of Measurement and Load constraints. The Unit of Measurement constraint prevents box-packed items from being placed on top of individual units. Load constraint allows only a limited number of boxes to be placed on top of another box. To develop a solution to this concern, we propose a mathematical model to formulate the problem. Due to its complexity, the implementation of an approximate method was mandatory. Indeed, a Genetic Algorithm was designed to meet this problem’s requirements. In addition, we propose three Storage Assignment strategies to analyze if these further improve the traveling distance of the resulting routing sequences. These were applied to a set of instances obtained from the Company’s Warehouse Management System observations. We assess the picker routing and storage assignment strategies’ performance and obtain essential knowledge for this type of problem.
A two-phase optimization model that considers risk and accessibility for vaccine allocation and health-care units location
(Instituto Tecnológico y de Estudios Superiores de Monterrey, 2021-12-03) Martínez Fantini, Linda Sofía; REGIS HERNANDEZ, FABIOLA; 331834; Regis Hernández, Fabiola; puemcuervo, emipsanchez; Mora Ochomogo, Elma Irais; School of Engineering and Sciences; Campus Monterrey; Mora Vargas, Jaime
In December 2019, the novel virus SARS-CoV-2 appeared causing the COVID-19 pandemic. Healthcare systems globally were primary affected by it due to the increase on medical attention and Intensive Care Units (ICUs) demand. Particularly, Mexico belonged among the top 10 coun- tries with the highest number of confirmed cases, and within the top 5 in global deaths. These indicators required federal authorities to mount complex response actions to eradicate it. One of the concerns to deal with hospitals overload is an effective vaccination plan. For this, we propose a two-phase model to prioritize the Mexican entities with higher levels of vulnerability and risk of hospitalization to address the demand allocation problem in an equitable way. The vulnerability index is obtained through data analysis of a Mexican open database, and the model considers a two-dose vaccination program, and a monthly time horizon. The second phase con- sists of a Maximal Covering Location problem that maximizes a set of accessibility indicators to locate the facilities to cover the maximum Mexican population possible. The models are solved in Gurobi Optimizer commercial software and provides the optimal solution within seconds. The results obtained in the allocation model showed that the first vaccine lots are assigned to Ciudad de Me ́xico which is the entity with highest risk of exposure, and, by August 2021 at least 71% of the population is immunized with vaccine. The second model exposes that when enabling 100% of the available facilities, only 57% of the municipalities has access to vaccination. Moreover a sensitivity analysis is employed to evaluate the effect of the radii and the weights in the solution. For future work, we propose the implementation of mobile units to enhance the accessibility. This way providing an effective and equitable solution for Mexico.

Ciencias Exactas y Ciencias de la Salud

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