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Item type:Publication, Access status: with files , Flexibility in manufacturing system design: A review of recent approaches from operations research(Elsevier, 2024-06-01); ; Due to increasing demand uncertainty and product variety, manufacturing systems must continually adapt to maintain productivity. Generally, decision-makers can maintain flexibility to account for these adaptations efficiently already in the design phase of manufacturing systems. Consequently, over the past few decades, a significant body of literature has addressed manufacturing system design associated with various manufacturing paradigms, claiming to provide the ‘right’ level of flexibility. Advanced analytical methods from Operations Research are frequently used in this domain to support decision-making. However, articles on the manufacturing paradigms remain in disjunct literature streams. In this article, we review literature from the last two decades that focuses on the application of Operations Research methods in manufacturing system design. The analyzed articles were selected from peer-reviewed scientific literature in a systematic search and screening process. To unite literature on different manufacturing paradigms, the concept of manufacturing flexibility is adapted, focusing on flexibility types required and considered in manufacturing systems’ design phases. The reviewed articles frequently employ mixed-integer linear programming or propose heuristic procedures. Most contributions evaluate static and deterministic settings, overlooking short- or long-term uncertainties in the design of manufacturing systems. Predominantly, flexibility is maintained to enhance economic or performance-oriented objectives. The consideration of social or ecological indicators, however, is barely found. Therefore, research perspectives from this analysis include integrating social and ecological indicators into multi-objective decision-making methods, anticipating neighboring planning problems during design, and applying systematic procedures to address uncertainty.Publicationtype: Review ArticleScopus© Citations 3 70 381 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Vessel velocity decisions in inland waterway transportation under uncertainty(2022-01-16); ; Recent studies have concentrated on environmental and economic impacts of ships. In this regard, fuel and CO2 emission is considered as one of the important factors for such impacts. In particular, the sailing speed of the vessels affects the fuel consumption and therefore the emission directly. In this study, we consider a speed optimization problem in inland waterway, which is characterized by stochastic waiting times at the lock caused by uncertainty in lock processing time estimations of other vessels. The objective is to minimize fuel consumption of an approaching ship, such that it traverses the river segment in a set deadline. We introduce a mathematical model for this problem and evaluate the effectiveness and attractiveness of two solution approaches: an optimal solution and a simple heuristic. This creates intuitive guidelines for skippers based on information provision to select an appropriate speed decision approach to minimize the total expected fuel consumption and CO2 emission of inland waterway transportation.Publicationtype: Journal Article51 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Inland waterway efficiency through skipper collaboration and joint speed optimizationWe address the problem of minimizing the aggregated fuel consumption by the vessels in an inland waterway, e.g., a river, with a single lock. The fuel consumption of a vessel depends on its velocity and the slower it moves, the less fuel it consumes. Given entry times of the vessels into the waterway and the deadlines before which they need to leave the waterway, we start from the optimal velocities of the vessels that minimize their private fuel consumption, where we assume selfish behavior of the skippers. Presence of the lock and possible congestion on the waterway make the problem computationally challenging. First, we prove that in general, a Nash equilibrium might not exist, i.e., if there is no supervision on the vessels’ velocities, there might not exist a strategy profile from which no vessel can unilaterally deviate to decrease its private fuel consumption. Next, we introduce simple supervision methods to guarantee the existence of a Nash equilibrium. Unfortunately, though a Nash equilibrium can be computed, the aggregated fuel consumption of such a stable solution can be high compared to the social optimum, where the total fuel consumption is minimized. Therefore, we propose a mechanism involving payments between vessels, guaranteeing a Nash equilibrium while minimizing the fuel consumption. This mechanism is studied for both the offline setting, where all information is known beforehand, and online setting, where we only know the entry time and deadline of a vessel when it enters the waterway.Publicationtype: Journal Article38 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Operations research for sustainability assessment of products: a review(Elsevier, 2019-04-01); ; ; The environmental and social impacts of products are being increasingly scrutinized. This necessitates systematic assessment methods. Life Cycle Sustainability Assessment (LCSA) provides a framework to addresses diverse sustainability issues over the product's life cycle, but its application is complicated. Major challenges, such as the selection of relevant indicators, multi-criteria comparisons of alternatives, the treatment of uncertainties, or the integration of spatially differentiated data, can be facilitated by adopting advanced analytical methods from Operations Research. This paper reviews 142 articles that use Operations Research methods for product-related sustainability assessments. The articles were selected from peer-reviewed scientific literature in a systematic search and screening process. Descriptive analysis shows that related publication output is growing over time and originates mainly in journals related to Environmental Management. While ecological indicators are considered by most articles, the integration of economic and social indicators is emerging. Focusing on the contributions of Operations Research, a detailed analysis shows that more than half of the articles adopt methods from Multi-Attribute Decision Making (MADM), followed by Data Envelopment Analysis (DEA) and Multi-Objective Decision Making (MODM). Uncertainties with regard to inventory data and decision makers’ preferences are addressed using fuzzy logic, stochastic models, or sensitivity analysis. The use of spatially differentiated data is not frequently found in the reviewed articles. Research needs derived from this analysis comprise the integration of qualitative and semi-quantitative (social) indicators, the simultaneous consideration of global and local sustainability objectives, and the application of systematic procedures to address uncertainty.Publicationtype: Journal Article50 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Improved integrality gap upper bounds for TSP with distances one and twoPublicationtype: Journal Article106 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Remarks on "A measure of risk and a decision-making model based on expected utility and entropy" by Jiping Yang and Wanhua Qiu (EJOR 164 (2005), 792-799)Yang and Qiu [Yang, J., Qiu, W., 2005. A measure of risk and a decision-making model based on expected utility and entropy. European Journal of Operational Research 164, 792-799] suggest a new concept for decision making under risk. This concept relies on a combination of the well-known expected utility criterion and the so-called entropy. The authors claim that the approach might be used as a descriptive as well as a normative decision model. In this paper, the theoretical soundness of the concept of entropy is critically examined. The analysis is underpinned by a discussion of the properties of the respective entropy function. Furthermore, normative and descriptive features of the concept are discussed and it is shown that the usefulness with respect to both aspects is questionable.Publicationtype: Journal Article107