Liner shipping network design with sensitive demand

Purpose: This paper aims to examine containership routing and speed optimization for maritime liner services. It focuses on a realistic case in which the transport demand, and consequently the collected revenue from the visited ports depend on the sailing speed. Design/methodology/approach: The authors present an integer non-linear programming model for the containership routing and fleet sizing problem, in which the sailing speed of every leg, the ports to be included in the service and their sequence are optimized based on the net line's profit. The authors present a heuristic approach that is based on speed discretization and a genetic algorithm to solve the problem for large size instances. They present an application on a line provided by COSCO in 2017 between Asia and Europe. Findings: The numerical results show that the proposed heuristic approach provides good quality solutions after a reasonable computation time. In addition, the demand sensitivity has a great impact on the selected route and therefore the profit function. Moreover, the more the demand is sensitive to the sailing speed, the higher the sailing speed value. Research limitations/implications: The vessel carrying capacity is not considered in an explicit way. Originality/value: This paper focuses on an important aspect in liner shipping, i.e. demand sensitivity to sailing speed. It brings a novel approach that is important in a context in which sailing speed strategies and market volatility are to be considered together in network design. This perspective has not been addressed previously. © 2020, Pacific Star Group Education Foundation

Development of a dynamic optimization framework for waste management systems

Waste to energy (WTE) technologies have emerged as an alternative solution to municipal solid waste management. WTE systems provide major environmental and economic benefits by converting waste into accessible energy, as part of an integrated solid waste management (ISWM) strategy. However, previous studies showed that establishing an ISWM strategy based on a single type of WTE systems does not necessarily realize maximum benefits. Hence, optimizing the selection of WTE systems as part of a hybrid waste management strategy can potentially achieve maximum benefits and minimize negative impacts. However, such task is challenging due to the various alternatives and objectives, particularly those related to the material and energy recovery systems. This article presents the methods used to develop a systematic optimization framework that identifies the most beneficial set of ISWM systems through mathematical modelling. The methods include the procedures of the established framework, including base model computations, as well as the comprehensive modelling and optimization methods. • The energy recovery, carbon footprint, and financial profitability are computed for selected WTE facilities. • The multi-objective mathematical programming is solved using the weighted comprehensive criterion method (WCCM). • The model is implemented in CPLEX software using mathematical programming language (OPL). © 2021 The Author

Comprehensive quantity discount model for dynamic green supplier selection and order allocation

We model and solve a deterministic multi-period single-product green supplier selection and order allocation problem in which the considered suppliers’ availability, cost, and green performance change from one period to another in the planning horizon. Moreover, the available suppliers may offer an all-unit or an incremental quantity discount (QD) scheme, resulting in three problem configurations. In one configuration, all suppliers offer all-unit QD. In the second, all suppliers offer incremental QD. In the third, some suppliers offer all-unit QD, and others offer incremental QD. The problem is modelled using a bi-objective integer linear programming formulation that maximizes the total green value of the purchased items from all the suppliers and minimizes their total corresponding cost, including the fixed cost, variable cost, inventory holding cost, and shortage cost. The proposed bi-objective model is scalarized and solved using the branch-and-cut algorithm and a population-based heuristic. A numerical analysis is conducted, which allows first to validate the heuristic approach using small-size instances by comparing its results with those of the exact approach. Moreover, an extensive comparison between the exact and heuristic solution approaches is carried out. The results reveal different findings. First, the economic and environmental solutions of an instance are different, and the environmental solution is independent of the suppliers’ pricing schemes. Second, the maximum difference between the heuristic approach and the exact approach in terms of the bi-objective function value is 4.72%, which makes the proposed heuristic recommended for large-size instances due to its short computation time and good accuracy. Third, there is no difference in terms of the heuristic performance between the combined model and the models with a single type of discount. Fourth, the all-unit discount scheme seems to be generally better in terms of the trade-off between the green value of purchasing and cost

Air Traffic Flow Management Under Emission Policies: Analyzing the Impact of Sustainable Aviation Fuel and Different Carbon Prices

As part of the global efforts to make aviation activities more environmentally friendly, the worldwide goal is to achieve a 50% reduction in the 2005 emissions by 2050. In this context, aviation emissions represent a critical challenge to aviation activities, especially with the increasing travel demand up to the beginning of the COVID-19 crisis, starting in 2020. One of the potential drivers that would help the aviation industry reduce its emissions is the use of sustainable aviation fuel (SAF). In this study, we analyzed the impact of SAF from an air traffic flow management (ATFM) perspective, considering delay and re-routing costs. We developed an optimization model that considers, in addition to the traditional ATFM costs, fuel costs and carbon dioxide emissions. We investigated the impact of accounting for these two new aspects, that is, fuel costs and emissions, on ATFM performance, and we compared SAF with conventional fuel. The analysis of a real case study revealed that, in addition to delay and re-routing costs, fuel cost should be included in the ATFM model so that the resulting solution becomes economically and environmentally realistic for airlines. The increase in the fuel cost and network delays when using SAF requires setting an appropriate carbon price under an emission policy, such as the carbon offsetting and reduction scheme for international flights policy, to make SAF more attractive. Furthermore, flexible re-routing programs for flights operated using SAF make it advantageous from an ATFM perspective

Central authority controlled air traffic flow management: An optimization approach.

Despite various planning efforts, airspace capacity can sometimes be exceeded, typically due to disruptive events. Air traffic flow management (ATFM) is the process of managing flights in this situation. In this paper, we present an ATFM model that accounts for different rerouting options (path rerouting and diversion) and pre-existing en-route flights. The model proposes having a central authority to control all decisions, which is then compared with current practice. We also consider inter-flight and inter-airline fairness measures in the network. We use an exact approach to solve small-to-medium-sized instances, and we propose a modified fix-and-relax heuristic to solve large-sized instances. Allowing a central authority to control all decisions increases network efficiency compared to the case where the ATFM authority and airlines control decisions independently. Our experiments show that including different rerouting options in ATFM can help reduce delays by up to 8% and cancellations by up to 23%. Moreover, ground delay cost has much more impact on network decisions than air delay cost, and network decisions are insensitive to changes in diversion cost. Furthermore, the analysis of the trade-off between total network cost and overtaking cost shows that adding costs for overtaking can significantly improve fairness at only a small increase in total system cost. A balanced total cost per flight among airlines can be achieved at a small increase in the network cost (0.2 to 3.0%) when imposing airline fairness. In conclusion, the comprehensiveness of the model makes it useful for analyzing a wide range of alternatives for efficient ATF

Modèles d'optimisation pour le management de flux de trafic aérien

Les retards et les émissions CO2 sont des sujets critiques dans l’industrie aéronautique. Les principales sources de retard sont le déséquilibre entre la demande et la capacité, la dotation en personnel des contrôleurs du traffic aérien et les conditions météorologiques extrêmes. Dans certains cas, les compagnies aériennes peuvent choisir d’augmenter la vitesse de l’avion au delà de celle programmée, ce qui engendre une augmentation des émissions. Plusieurs projets ont été lancés pour améliorer le partage d’informations et, par conséquent, la prise de décision au profit de tous les acteurs ou toutes les parties prenantes de l’aviation et réduire les retards et les émissions.Dans cette thèse de doctorat, nous visons à étudier le problème de la gestion des flux du trafic aérien (Air Traffic Flow Management (ATFM)) du point de vue de la recherche opérationnelle / management des opérations. Nous étudions le modèle ATFM largement utilisé dans la littérature et l’analysons. Nous corrigeons les lacunes de formulation de la littérature et étendons la conception du réseau et les fonctionnalités considérées pour atteindre une meilleure représentation du réseau réel. Dans cette extension, nous considérons plusieurs types de vols et plusieurs décisions, comme le changement de trajectoire et d’aéroport d’atterrissage. L’objectif de de ce travail peut être résumé dans les points suivants.(1) Étudier l’impact de la centralisation du processus de prise de décision dans le problème ATFM par rapport à la situation actuelle où les décisions de l’autorité ATFM et des compagnies aériennes sont prises indépendamment.1(2) Analyser l’équité inter-vols et inter-compagnies dans le problème ATFM.(3) Construire un modèle de capacité météorologique de décision pour les aéroports et développer des arbres de scénarios pour les réseaux ATFM stochastiques basés sur des données réelles.(4) Intégrer la configuration dynamique de l’espace aérien dans le problème ATFM et analyser son impact.(5) Tenir compte des émissions CO2 et des différents types de carburant dans l’ATFM.Nous développons dous cette thèse plusieurs extensions du modèle ATFM pour analyser ces problématiques. Tout d’abord, nous proposons un modèle ATFM déterministe qui centralise les décisions de l’autorité ATFM et des compagnies aériennes, et qui considère différentes options de réacheminement. Ensuite, nous formulons un modèle ATFM stochastique qui tient compte des incertitudes météorologiques du traffic aérien. La relation météo-capacité et les arbres de scénarios stochastiques sont élaborés à l’aide des rapports d’aérodrome météorologiques, de la base de données AirportCorner et de la technique de regroupement des k-means. Ensuite, nous nous concentrons sur l’optimisation de la configuration de l’espace aérien en même temps que le problème ATFM en minimisant la capacité totale de l’espace aérien inutilisé et le coût total du réseau. Enfin, nous intégrons les émissions CO2 dans la modélisation ATFM à travers un modèle d’optimisation bi-objectif. Le modèle permet d’étudier l’impact des émissions de CO2 sur le coût du réseau et l’effet du type de combustible sur les décisions du réseau. Les modèles développés sont résolus en utilisant l’approche exacte, et dans le cas de temps de calcul longs, une heuristique du type fix-and-relax.Les modèles proposés peuvent aider les décideurs à analyser l’impact des décisions à prendre sur le réseau et les acteurs impliqués. Par conséquent, les conséquences et les coûts associés pourront être calculés. En outre, ces modèles aident les décideurs à affiner et à vérifier les résultats de plusieurs projets et initiatives ATFM. Ils suggèrent également aux décideurs comment les plans de vol peuvent être mis à jour en cas de perturbation du réseau et les coûts associés aux changements.Delays and emissions are critical topics in the aviation industry. The major delay sources are imbalanced demand and capacity, air traffic controller staffing, and severe weather conditions. In some cases, flights can choose to fly at a higher speed than the scheduled one, which increases emissions. Moreover, several projects have been initiated to improve information sharing, and consequently, decision making in order to benefit all aviation parties and reduce delays and emissions.In this Ph.D. thesis, we aim at studying the air traffic flow management (ATFM) problem from an operations research/operations management perspective. We study the ATFM model, a widely used model in the literature, and analyze it. We correct the formulation deficiencies, and we extend the network design and the considered features to reach a better representation of the real-life network. In this extension, we consider several types of flights and several decision options, such as changing the path or the landing airport. The objectives of this research can be summarized in the following points.(1) To study the impact of centralizing the decision-making process in the ATFM problem compared to the current situation where decisions by ATFM authority and airlines are made independently.(2) To analyze the inter-flight and inter-airline fairness in the ATFM problem.(3) To construct a weather-capacity model for airports and develop scenario trees for stochastic ATFM networks based on real data.(4) To integrate dynamic airspace configuration in the ATFM problem and to analyze the impact.(5) To account for CO2 emissions and different fuel types in the ATFM.Therefore, we develop several extensions to the ATFM model to accommodate these issues. First, we propose a deterministic ATFM model that centralizes the decisions of the ATFM authority and the airlines, and that considers different rerouting options. Then, we formulate a stochastic ATFM model that accounts for airports' weather uncertainties. The weather-capacity relationship and the stochastic scenario trees are developed using meteorological aerodrome reports, the AirportCorner database, and the k-means clustering technique. After that, we focus on optimizing the airspace configuration simultaneously with the ATFM problem by minimizing the total unused airspace capacity and the total network cost. Finally, we integrate the CO2 emissions in the ATFM model through a bi-objective optimization approach. The model is used to study the CO2 emissions' impact on the network's cost and the effect of fuel type on the network decisions. The developed models are solved using the exact approach, and in the case of long computational times, a fix-and-relax heuristic is used.The proposed models can help decision-makers through analyzing the impact of the decisions to be made on the network and the stakeholders involved. Therefore, the consequences and the associated costs can be calculated. In addition, these models help decision-makers fine-tune and verify findings of several ATFM projects and initiatives. They also suggest to decision makers how flight plans can be updated in cases of network disturbance and the associated costs of the changes

Supplier selection and order allocation with green criteria: An MCDM and multi-objective optimization approach

International audienc

Apparent mass of the standing human body when using a whole-body vibration training machine: Effect of knee angle and input frequency

Several studies have investigated the transmission of vibration from the vibrating plate of a whole-body vibration training machine (WBVTM) to different locations on the human body. No known work has investigated the interface force between the vibrating plate of the machine and the human body. This paper investigates the effect of bending the knees and the vibration frequency on the interface force (presented as apparent mass (AM)) between the vibrating plate and the body. Twelve male subjects stood with four different knee angles (180, 165, 150 and 135°) and were exposed to sinusoidal vertical vibration at eight frequencies in the range of 17–42 Hz. The vertical acceleration and the interface force between the body and the vibrating plate were measured and used to calculate the AM. The acceleration and force depended on the frequency and were found to vary with both the adopted posture and subject. The AM generally decreased with increasing the frequency but showed a peak at 24 Hz which was clearer when the knees were bent. Bending the knees showed an effect similar to increasing the damping of a system with base excitation; increasing the damping reduced the AM in the resonance region but increased the AM at higher frequencies. Users of WBVTMs have to be careful when choosing the training posture: although, as shown in previous studies, bending the knees reduces the transmission of vibration to the spine, it increases the interface forces which might indicate increased stresses on the lower legs and joints. © 2018 Elsevier Lt

Power absorbed by the standing human body during whole-body vibration training

Absorbed power (AP) is a biodynamic response that is directly related to the magnitude and duration of vibration. No work has previously investigated the power absorbed by the standing human body during the exposure to vibration training conditions or otherwise. This article reports the power absorbed by the standing human body under whole-body vibration (WBV) training conditions. In this work, the force and acceleration used to calculate the apparent mass by Nawayseh and Hamdan (2019, "Apparent Mass of the Standing Human Body When Using a Whole-Body Vibration Training Machine: Effect of Knee Angle and Input Frequency," J. Biomech., 82, pp. 291-298) were reanalyzed to obtain the AP. The reported acceleration was integrated to obtain the velocity needed to calculate the AP. The effects of bending the knees (knee angles of 180 deg, 165 deg, 150 deg, and 135 deg) and vibration frequency (17-42 Hz) on the power absorbed by 12 standing subjects were investigated. Due to the different vibration magnitudes at different frequencies, the AP was normalized by dividing it by the power spectral density (PSD) of the input acceleration to obtain the normalized AP (NAP). The results showed a dependency of the data on the input frequency as well as the knee angle. A peak in the data was observed between 20 and 24 Hz. Below and above the peak, the AP and NAP tend to increase with more bending of the knees indicating an increase in the damping of the system. This may indicate the need for an optimal knee angle during WBV training to prevent possible injuries especially with prolonged exposure to vibration at high vibration intensities. © 2020 Wolters Kluwer Medknow Publications. All rights reserved

Effect of car speed on the transmission of vibration through the seat pan and backrest: Field study

This study investigates the effect of car speed on the vibration transmitted to the passenger through both the seat pan and backrest. Ten male subjects sat in the front passenger seat of a sedan car and were driven at three different speeds (60, 80 and 100 km/h). During each ride, the vibration dose value (VDV) was measured in the x, y and z-directions on the seat pan and at the backrest. The results showed an increase in the VDV in all directions with increasing the car speed. The VDVs at the backrest were found as high as, or even higher than, those measured on the seat depending on the speed and the measurement axis. Hence, it is recommended that vibration in road vehicles be assessed using more than one speed while taking into consideration measurement at the backrest. Copyright © 2019 Inderscience Enterprises Ltd