a b s t r a c tForecasting future sales is one of the most important issues that is beyond all strategic and planning decisions in effective operations of retail businesses. For profitable retail businesses, accurate demand forecasting is crucial in organizing and planning production, purchasing, transportation and labor force. Retail sales series belong to a special type of time series that typically contain trend and seasonal patterns, presenting challenges in developing effective forecasting models. This work compares the forecasting performance of state space models and ARIMA models. The forecasting performance is demonstrated through a case study of retail sales of five different categories of women footwear: Boots, Booties, Flats, Sandals and Shoes. On both methodologies the model with the minimum value of Akaike's Information Criteria for the in-sample period was selected from all admissible models for further evaluation in the out-of-sample. Both one-step and multiple-step forecasts were produced. The results show that when an automatic algorithm the overall out-of-sample forecasting performance of state space and ARIMA models evaluated via RMSE, MAE and MAPE is quite similar on both one-step and multi-step forecasts. We also conclude that state space and ARIMA produce coverage probabilities that are close to the nominal rates for both one-step and multi-step forecasts.
One of the challenges in a kidney exchange program (KEP) is to choose policies that ensure an effective and fair management of all participating patients. In order to understand the implications of different policies of patient allocation and pool management, decision makers should be supported by a simulation tool capable of tackling realistic exchange pools and modeling their dynamic behavior. In this paper, we propose a KEP simulator that takes into consideration the wide typology of actors found in practice (incompatible pairs, altruistic donors, and compatible pairs) and handles different matching policies. Additionally, it includes the possibility of evaluating the impact of positive crossmatch of a selected transplant, and of dropouts, in a dynamic environment. Results are compared to those obtained with a complete information model, with knowledge of future events, which provides an upper bound to the objective values. Final results show that shorter time intervals between matches lead to higher number of effective transplants and to shorter waiting times for patients. Furthermore, the inclusion of compatible pairs is essential to match pairs of specific patient-donor blood type. In particular, O-blood type patients benefit greatly from this inclusion.
Competitiveness in the Oil and Gas (O&G) sector has required high technological investments for datacentric decisions. One of the trends is the adoption of Digital Twins (DTs), which use virtual spaces and advanced analytical services to monitor and improve physical spaces. Central to the interconnection of these systems is a Data Fusion Core (DFC) component, which provides data management capabilities. Although the literature has proposed data management functionality in the scope of specific O&G DT applications, different joint efforts towards standardization can be found to deal with data integration and interoperability in the industry. The Open Subsurface Data Universe (OSDU) data platform is an initiative by several partners members of The Open Group consortium created to eliminate data silos in the O&G ecosystem and leverage innovation through a data-driven approach. In this article, we look at the convergence of this effort in providing data management functionalities for digital twins, highlighting strengths, gaps, and opportunities. We investigated the extent to which the OSDU data platform meets the needs of a DFC implementation, with a focus on interoperability, integration, governance, and data lineage. We also propose additional resources for data management in this context, namely data enrichment, workflows, and data lineage. Our main contributions are: (i) analysis of possible data management capabilities for creating a working DFC for an O&G DT and (ii) initial ideas on the complementary role of OSDU data representation and ontologies and how this semantic enrichment can be leveraged in a DFC of a DT.
In this work we present a metaheuristic method based on tabu search for solving the permutation flow shop scheduling problem with sequence dependent setup times, with the objective of minimizing total weighted tardiness. The problem is well known for its practical applications and for the difficulty in obtaining good solutions. The tabu search method proposed is based on the insertion neighborhood, and is characterized, at each iteration, by the selection and evaluation of a small subset of this neighborhood; this has consequences both on diversification and on speeding up the search. We also propose a speed-up based on book keeping information of the current solution, used for the evaluation of its neighbors.
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