Comparing Industry and Academic Perspectives on Cross-docking Operations

This paper performs a comparative analysis on the industry and academic perspectives on cross-docking operations. Detailed descriptions are provided for three typical cross-dock settings by means of case illustrations. The purpose of these descriptions is to inspire break-through innovations in future cross-docking research by identifying constraints, decision problems, and performance indicators that are thoroughly anchored in current practice

School timetabling problem under disturbances

School timetables are one or multiple times per year generated to assign class-teacher combinations to class rooms and timeslots. Post-publication disturbances such as absence of teachers typically pose a need for schedulers to rapidly implement some minor changes to avoid empty periods in the timetable. In this paper our aim is to define methods to efficiently solve the school timetabling problem under disturbances. We present three types of solution methods, namely a simple rule-of-thumb, a heuristic and an optimization approach. Exhaustive numerical experiments have been performed with data from five high schools in The Netherlands, each with their unique characteristics in number of classes, number of teachers and number of daily meetings. For each of the three methods we show advantages and disadvantages as well as the effects of resulting changes in the schedules.<br/

Maritime Location Decisions for Lng Bunkering Facilities

Liquefied natural gas (LNG) is one of the upcoming fuels to be used for more sustainable shipping activities in the maritime sector. For a widespread adoption by end-users, a refuelling network requiring capital intensive investments, needs to be in place. From a macro perspective of suppliers of LNG, it makes sense to develop the infrastructure at strategic locations that capture as many vessels and ships as possible. The goal of this research is to develop a facility location model that can contribute to the location selection of LNG facilities in a new fuelling network. The new model will fit the maritime sector and specifically the LNG transition. Experiments, with data obtained from expert interviews, have been performed to study facility location decisions in the North Sea areas

Planning and Control Concepts for Material Handling Systems

Iris Vis was born in 1974 in Leidschendam. May 2002 - Assistant professor at the School of Economics and Business Administration, Vrije Universiteit Amsterdam 1999, Visiting scholar at Georgia Institute of Technology, School of Industrial and Systems Engineering, october - december September 1997 - May 2002, Ph.D. candidate at the Rotterdam School of Management/Faculteit Bedrijfskunde, Erasmus University Rotterdam Research Areas logistics, material handling systems, cross-docking centres, number of vehicles, scheduling, storage and retrieval, container terminalsThe purpose of this research is the development of new concepts for different planning and control problems within material handling centres, like warehouses and container terminals. Problems discussed, are, for example: (i) the determination of the number of vehicles required to transport all loads in time (ii) scheduling of storage and retrieval requests. Techniques from Operations Research are used to model and solve above mentioned problems. Firstly, a polynomial time algorithm (minimum flow algorithm) is developed to solve the problem of the determination of the minimum number of vehicles to transport all loads at known time instants. An extension of this problem is the determination of the minimum number of vehicles required if every job has a time window. In this case, a release time and a due time are given for every job. This problem can be formulated as an integer linear programming model and a set partitioning model. A dynamic programming model is developed to solve the scheduling of retrieval and storage requests for a storage and retrieval machine working in multiple parallel aisles. All developed methods will be applied within a semi-automated container terminal. For the internal transportation of containers from ship to stack (storage) and vice versa and for inter terminal transport Automated Guided Vehicles (AGVs) will be used. Also stacking will be done in an automatic way by Automated Stacking Cranes (ASCs). Simulation studies are performed to test the methods developed

Design of Cross-chain Internet Order Fulfillment Centres

Many consumers have embraced the option of ordering via the Internet, which has resulted in an enormous increase in direct orders compared to the times when direct ordering was done by catalogue and phone. The fulfillment process in the supply chain is an important factor for these consumers impacting how long they must wait between ordering and delivery. This fact has significantly increased the importance of the back-end fulfillment process. We present a novel supply chain design to enable cross-chain coordination of order fulfillment operations for internet sales. Shared warehousing facilities are used more and more to achieve competitive advantage. This situation asks for new models to enable a smooth warehousing process for each web shop, but at the same time to ensure overall efficiency and effectiveness. This paper introduces a layout model for shared operations under one roof by simultaneously optimizing the overall facility layout and the area layout

Assessment approaches to logistics for offshore wind energy installation

AbstractOffshore wind farm installation planning is highly complex, due to the high dependency on weather and the oversized components that impose specific constraints in areas such as transportation and lifting. Currently, there is very little transparency vis-à-vis the logistics challenges in the industry. We extend the literature by creating an overall view of the coherency between logistical methods and project performance. We develop knowledge about how to use the various approaches by analyzing different logistical solutions. A holistic view of the coherency between the approaches in terms of logistics and project performance, taking into consideration the external influence of weather, is provided through analysis of actual projects in the North Sea region. Case study findings reveal the major factors to be pre-assembly, vessel load, and the distance to shore. We suggest a pre-assembly strategy comprised of a minimum number of components for installation onsite and a maximum number of turbines to be loaded on a vessel. These findings are especially important for the new wind farms being positioned further offshore. We show by means of a case study, with specific characteristics and weather conditions, that the appropriate strategies can be arrived at by using a simulation-based decision-support tool we developed

The pickup and delivery traveling salesman problem with handling costs

This paper introduces the pickup and delivery traveling salesman problem with handling costs (PDTSPH). In the PDTSPH, a single vehicle has to transport loads from origins to destinations. Loading and unloading of the vehicle is operated in a last-in-first-out (LIFO) fashion. However, if a load must be unloaded that was not loaded last, additional handling operations are allowed to unload and reload other loads that block access. Since the additional handling operations take time and effort, penalty costs are associated with them. The aim of the PDTSPH is to find a feasible route such that the total costs, consisting of travel costs and penalty costs, are minimized. We show that the PDTSPH is a generalization of the pickup and delivery traveling salesman problem (PDTSP) and the pickup and delivery traveling salesman problem with LIFO loading (PDTSPL). We propose a large neighborhood search (LNS) heuristic to solve the problem. We compare our LNS heuristic against best known solutions on 163 benchmark instances for the PDTSP and 42 benchmark instances for the PDTSPL. We provide new best known solutions on 52 instances for the PDTSP and on 15 instances for the PDTSPL, besides finding the optimal or best known solution on 102 instances for the PDTSP and on 23 instances for the PDTSPL. The LNS finds optimal or near-optimal solutions on instances for the PDTSPH. Results show that PDTSPH solutions provide large reductions in handling compared to PDTSP solutions, increasing the travel distance by only a small percentage

Integration of returns and decomposition of customer orders in e-commerce warehouses

In picker-to-parts warehouses, order picking is a cost- and labor-intensive operation that must be designed efficiently. It comprises the construction of order batches and the associated order picker routes, and the assignment and sequencing of those batches to multiple order pickers. The ever-increasing competitiveness among e-commerce companies has made the joint optimization of this order picking process inevitable. Inspired by the large number of product returns and the many but small-sized customer orders, we address a new integrated order picking process problem. We integrate the restocking of returned products into regular order picking routes and we allow for the decomposition of customer orders so that multiple batches may contain products from the same customer order. We thereby generalize the existing models on order picking processing. We provide Mixed Integer Programming (MIP) formulations and a tailored adaptive large neighborhood search heuristic that, amongst others, exploits these MIPs. We propose a new set of practically-sized benchmark instances, consisting of up to 5547 to be picked products and 2491 to be restocked products. On those large-scale instances, we show that integrating the restocking of returned products into regular order picker routes results in cost-savings of 10 to 15%. Allowing for the decomposition of the customer orders' products results in cost savings of up to 44% compared to not allowing this. Finally, we show that on average cost-savings of 17.4% can be obtained by using our ALNS instead of heuristics typically used in practice.Comment: Authors' preprin