On alternative mixed integer programming formulations and LP-based heuristics for lot-sizing with setup times

We address the multi-item, capacitated lot-sizing problem (CLSP) encountered in environments where demand is dynamic and to be met on time. Items compete for a limited capacity resource, which requires a setup for each lot of items to be produced causing unproductive time but no direct costs. The problem belongs to a class of problems that are difcult to solve. Even the feasibility problem becomes combinatorial when setup times are considered. This difculty in reaching optimality and the practical relevance of CLSP make it important to design and analyse heuristics to nd good solutions that can be implemented in practice. We consider certain mixed integer programming formulations of the problem and develop heuristics including a curtailed branch and bound, for rounding the setup variables in the LP solution of the tighter formulations. We report our computational results for a class of instances taken from literature

Corporate sustainability interactions: A game theoretical approach to sustainability actions

Recent global developments lead companies to include into their strategic plans not only economic sustainability but environmental and social sustainability as well. Companies have been investing in environmental and social sustainability to meet stakeholder demand and/or regulatory demands. Considering this as a market mechanism, we view the sustainability actions of companies as interrelated strategic decisions and propose a Stackelberg game to model the effects of competition for sustainability and sustainability spillovers over the sustainability outcomes of companies. We provide equilibrium solutions for the one leader, two followers game over different intervals of competition levels and spillover rates. Using a numerical example, we observe how the sustainability investments and net benefits change as competition levels and spillover rates change and identify the competition-spillover regions, where each player invests the most and has the advantage in terms of benefit. We discuss implications for both the companies and the policy makers

Increasing Biofuel Proliferation via the Optimal Use of Government Incentives

With the increasing public awareness on global warming, the demand for low greenhouse gas emission (GHG) transportation fuel, such as biofuel, is growing rapidly. In the U.S., like many other countries, the government is providing monetary incentives for biofuel displacement of fossil fuel. From the standpoint of biofuel proliferation, it is important that biofuel producers utilize these incentives in the most effective way, because better utilizations of incentives will lead to reduced costs for producers, which in turn will lower biofuel retail prices. Currently, however, biofuel producers are not taking full advantage of these incentives. This industry note introduces a new approach that allows U.S. biofuel producers to improve their practice of using an incentive program called the LCFS (California Low Carbon Fuel Standard). Our method, which is relatively simple, is based on a recent research project conducted with a biofuel manufacturing firm, which aimed to maximize the benefit gained from the LCFS incentive program. We show, by performing numerical experiments with realistic settings, that the method matches or outperforms the current practice, in terms of maximizing gains extracted from the incentive program, under all conditions

The value of quality grading in remanufacturing under quality level uncertainty

In remanufacturing, variability in quality levels of available cores (end-of-life products) has an impact on both the process cost and the process time. While previous research suggests that quality grading adds value, there are also concerns raised regarding how reliably the grades can be identified. We argue that uncertainty is inherent to the grading process and investigate the value of grading by taking into account the underlying uncertainty. We develop a robust optimisation model for remanufacturing planning, where both the per-unit cost and resource requirement to remanufacture a core are uncertain parameters that are assumed to reside in two different uncertainty sets; box and ellipsoidal. We analyse both uncapacitated and capacitated cases, and based on extensive numerical analysis, conclude that while on average, there is still value in grading, it becomes significantly smaller when the inherent uncertainty is accounted for. For the capacitated case, we also consider a cost for grading and find that it may cause a significant deterioration in the value of grading, if not rendering the grading totally useless. We show the validity of our approach through extensive numerical analyses.This accepted article is published Yanıkoğlu, İ., & Denizel, M. (2020). The value of quality grading in remanufacturing under quality level uncertainty. International Journal of Production Research, 59(3), 839–859. https://doi.org/10.1080/00207543.2020.1711983. Posted with permission

An efficient system of incentivizing truck drivers to accept night loads

Night deliveries are increasingly used by motor carriers to cut costs, but many carriers struggle to secure night truck drivers because many drivers dislike night driving. Monetary incentives are offered to drivers to accept night loads, but the incentive system currently used in practice is inefficient, as it not only pays more incentives than necessary but also does not incentivize the right drivers, both of which increase costs. This paper develops a new incentive system that allows carriers to secure night drivers at lower costs. Based on the interviews conducted with seven motor carriers, as well as the analysis of large night delivery data, we propose a bi-level programming approach that (1) generates a unique incentive for each driver based on his/her night driving performance, and (2) implicitly aligns the incentive paid to each driver with his/her reservation price. Simulation experiments conducted with real-world data showed that by using our approach carriers can not only avoid over-incentivizing drivers, but also (1) incentive only the right set of drivers who can bring cost savings and (2) encourage other drivers to improve night driving. Results also showed that our approach may give cost savings of up to 2.5% over the current system.This accepted article is published as Suzuki, Y., & Denizel, M. (2023). An efficient system of incentivizing truck drivers to accept night loads. International Journal of Production Research, 62(11), 3819–3834. https://doi.org/10.1080/00207543.2023.2250008. Posted with permission

Conceptual design of an e-marketplace for small and medium enterprises in the Turkish machinery industry

This paper reports on the results of a study carried out in the Turkish machinery industry. The purpose of the study was to identify the benefits the sector can seize from e-business and to develop a conceptual framework for potential e-business applications. We analysed the current state of e-business use in the machinery industry in order to understand the future requirements and application opportunities and to come up with a conceptual e-business design that would suit both the needs and the characteristics of the sector. The study included those companies, which are members of the Machine Manufacturers’ Association (MMA) in Turkey. Information about the existing applications and future requirements was obtained from the results of a survey conducted among the member companies. Statistically adequate number of responses was obtained to make the results representative of the machine industry. Web sites of the member companies were also reviewed for further information gathering. Results indicated that most of the companies are Small and Medium Enterprises(SME) and it would be better for them to carry out certain operations through an e-market specifically designed for the sector. The proposed conceptual e-market design is based on the characteristics of the industry emerging from the survey

Examining Firms’ Sustainability Frontier: Efficiency in Reaching the Triple Bottom Line

Sustainability has become a significant concern worldwide in recent decades. There seems to be implicit competition among firms for better sustainability performance. Like any other firm activity, sustainability undertakings require resources and their efficient use to achieve the desired performance. Firms may hesitate to undertake sustainability initiatives due to the underlying costs, leading to the question of how efficient they are in their sustainability practices. Relying on data from CSRHub and COMPUSTAT, we employed data envelopment analysis to evaluate the sustainability efficiency of 1141 large U.S. manufacturing firms from 2009 to 2018. We measured the sustainability efficiency of each firm relative to those on the efficient frontier for all the firms in our sample and also separately for each industry. The analysis results indicate that firms’ sustainability efficiency varies across years and industries. Furthermore, we show a quadratic relationship between sustainability performance and sustainability efficiency. This finding implies a process that begins with firms struggling to streamline their sustainability efforts and decreasing their efficiency as sustainability performance increases. Sustainability efficiency starts increasing only after a certain threshold is reached in sustainability performance. Our findings offer valuable insights for firms and stakeholders in their efforts to achieve desired levels of sustainability efficiency.This article is published as Zhuang, Y.; Denizel, M.; Montabon, F. Examining Firms’ Sustainability Frontier: Efficiency in Reaching the Triple Bottom Line. Sustainability 2023, 15, 8871. https://doi.org/10.3390/su15118871 © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https://creativecommons.org/licenses/by/4.0/)

Drift or shift? Continuity, change, and international variation in knowledge production in OR/MS

With the aim of contributing to the debate around OR/MS as a discipline, this study provides a historical comparative investigation of publicly available knowledge production in the field. The empirical investigation is based on a content analysis of 300 randomly selected articles from six major journals in the field. We have found: (1) since the late 1950s to the present day there has been no significant change in the types of published research in OR/MS in North America; (2) from the late 1950s to the present day, there have been significant differences in types of published research in OR/MS internationally. The imputed imbalance between theory and applications in published work had already occurred in the early stages of the development of OR/MS in North America and has since remained very much the same. Furthermore, research in the United Kingdom has been distinctly different from that dominant in North America and elsewhere. There are also indications that outside North America and the United Kingdom there is an emerging turn towards applications-oriented research. Over the last two or three decades there has been a significant increase overall in the share of articles published by academic authors

Toward the Physical Internet—Logistics Service Modularity and Design Implications

The Physical Internet (PI) is a modularization of logistics services: standardized protocols, full interoperability and standardized packaging, PI‐containers, and encapsulated freight. The PI‐containers are a core component of the PI; however, previous PI studies have not addressed those containers’ repositioning, despite its importance and effect on the PI network efficiency. In this paper, we analyze how the PI‐containers’ design and characteristics will determine the containers’ flows in a domestic network context. The flows are studied strategically using a linear programming model minimizing flow imbalances between hubs and simulating the effect of PI‐container compatibility. The model is tested using inter‐regional freight data from Sweden, and the results are framed using modularity theory. Our analysis reveals that PI‐container compatibility in terms of forward and reverse flows determines whether PI presents increased or decreased empty runs compared with the existing conventional logistics system. Departing from modularization theory, we discuss our results, emphasizing not only the importance of keeping synergistic specificity low but also how the characteristics will affect the urgency of technology use. Our implications are important to supply chain managers and policymakers for the future research on the Physical Internet, PI‐container repositioning and routing, and packaging design