Recent advances on graphical evaluation and review techniques

Graphical evaluation and review techniques (GERT) is a technique to study the stochastic nature of networks consists of different branches. In GERT, all branches are explained in terms of the probability that the branch is traversed and the tile to traverse the branch in case it is realized. This paper presents recent advances of the implementation of GERT in various industries. The study presents a comprehensive description of GERT and recent advances on the implementation of GERT in various industries over the period 2002-2017.Peer reviewedFinal article published.Network designGERTGraphical evaluation and review technique

Determination of Criticality Indexes in the Remanufacturing Process: A GERT-based Simulation Approach

In this paper one of the important “end of life options” (remanufacturing) has been analysed. Among the related studies surveyed the various remanufacturing aspects, less attention has been paid to the stochastic process routing. In this regard, a remanufacturing process routing with stochastic activities is modelled as a GERT network. One of the efficient ways to analyse a remanufacturing process is the identification of most effective activities based on the cost and time of the process during the process implementation. Criticality indexes are suitable scales for this purpose. Therefore, to analyse the important aspects of the remanufacturing process, four criticality indexes are developed in this paper. These indexes measure the cost and time of the process and its activities to identify the activities with high importance in terms of cost and time. On the other hand, simulation is an efficient tool to cope with the uncertainties in the production problems. Hence a Monte Carlo approach (which is developed using Arena software) has been adopted to analyse the GERT based model and to calculate the criticality indexes. In addition, a mathematical approach using Moment Generation Functions has been adopted to calculate the expected value of the criticality indexes. In addition, a numerical example (lathe spindle remanufacturing) has been solved using both proposed approaches. Results show the acceptable performance of the proposed GERT based simulation approach

A Case-Based Reasoning Method for Remanufacturing Process Planning

Remanufacturing is a practice of growing importance due to its increasing environmental and economic benefits. Process planning plays a critical role in realizing a successful remanufacturing strategy. This paper presents a case-based reasoning method for remanufacturing process planning, which allows a process planner to rapidly retrieve, reuse, revise, and retain the solutions to past process problems. In the proposed method, influence factors including essential characteristics, failure characteristics, and remanufacturing processing characteristics are identified, and the local similarity of influence factors between the new case and the past cases is determined by nearest neighbor matching method, and then the vector of correction factor for local similarity is utilized in the nearest neighbor algorithm to improve the accuracy and effectiveness of case searching. To assess the usefulness and practicality of the proposed method, an illustrative example is given and the results are discussed

Performance evaluation of reverse logistics enterprise – an agent-based simulation approach

Reverse logistics (RL) has been applied in many industries and sectors since its conception. Unlike forward logistics, retracing consumer goods from the point of consumption to the point of inception is not a well-studied process. It involves many uncertainties such as time, quality and quantity of returns. The returned products can be remanufactured, have parts harvested, or be disposed safely. It is important to implement these activities in a cost-effective manner. The aim of this research is to measure the performance of the RL enterprise with the help of an agent-based simulation model. The major entities in the RL network are considered as Agents that can act independently. There are several different agents: collector agent, sorting-cum-reuse agent, remanufacturing agent, recycler agent, supplier agent and distributor agent. The individual performances of the agents are measured and recommendations are given to improve their performance, leading to the enhancement of the total performance of the RL enterprise. The approach is applied to a case study involving cell phone remanufacturing

Shunting of Passenger Train Units in a Railway Station

In this paper we introduce the problem of shunting passenger trainunits in a railway station. Shunting occurs whenever train units aretemporarily not necessary to operate a given timetable. We discussseveral aspects of this problem and focus on two subproblems. Wepropose mathematical models for these subproblems together with asolution method based on column generation. Furthermore, a newefficient and speedy solution technique for pricing problems in columngeneration algorithms is introduced. Finally, we present computationalresults based on real life instances from Netherlands Railways.logistics;column generation;railway optimization;real world application

Studying the impact of merged and divided storage policies on the profitability of a remanufacturing system with deteriorating revenues

Peer ReviewedMerging capacity for a remanufacturing system is studied in this paper. In the system under study, there are two streams for returns and each stream has its dedicated processing line. However, the storage space is merged between the streams. Two strategies are investigated and compared in this paper. The first strategy is to divide the storage space between the two streams in the way that each type of return has its predetermined space in the storage area (divided capacity). In the second strategy, storage space is not split between the two streams and each unit of return, independent of its type, is admitted if there is vacant space (merged capacity). In both strategies, the value of remanufactured products decreases over time by a known factor called the decay rate. Mathematical models to maximize the total profit in each strategy is presented and also verified by a simulation model. From a practical point of view, selecting the correct strategy is an important decision for the remanufacturers because choosing the wrong policy leads to lost profits. Numerical experiments reveal that neither of the scenarios is always preferred to the other one and the choice of the optimal strategy depends on the parameters' values and product types. For instance, increasing the remanufacturing cost of the superior product, or increasing the sale price of the inferior product make the merged storage strategy more desirable. On the contrary, increasing the remanufacturing cost of the inferior product, or increasing the sale price of the superior product make the divided storage policy more appealing

Shunting of Passenger Train Units in a Railway Station

In this paper we introduce the problem of shunting passenger train units in a railway station. Shunting occurs whenever train units are temporarily not necessary to operate a given timetable. We discuss several aspects of this problem and focus on two subproblems. We propose mathematical models for these subproblems together with a solution method based on column generation. Furthermore, a new efficient and speedy solution technique for pricing problems in column generation algorithms is introduced. Finally, we present computational results based on real life instances from Netherlands Railways

Determining The Optimal Order Picking Batch Size In Single Aisle Warehouses

This work aims at investigating the influence of picking batch size to average time in system of orders in a one-aisle warehouse under the assumption that order arrivals follow a Poisson process and items are uniformly distributed over the aisle's length. We model this problem as an M/G[k]/1 queue in which orders are served in batches of exactly orders. The average time in system of the M/G[k]/1 queue is difficult to obtain for general service times. To circumvent this obstacle, we perform an extensive numerical experiment on the average time in system of the model when the service time is deterministic (M/D[k]/1) or exponentially distributed (M/M[k]/1). These results are then compared with the corresponding times in system of the actual model taken from simulation runs. A variance analysis is carried out and its result elicits that the M/D/[k]/1 queue is a very good approximation for the average time in system of orders. Correspondingly, the optimal picking batch size of the real system ca

Performance Evaluation of a Reverse Logistics Enterprise - An Agent-Based Modelling Approach

Reverse Logistics (RL) has been applied in many industries and sectors ever since its conception. Unlike Forward Logistics retracing consumer goods from the point of consumption to the point of inception is not a well-studied process. It involves many uncertainties such as time, quality and quantity of return. It is important to address these uncertainties to meet the economic, ecological and social challenges. The returned products can be remanufactured, can have parts harvested, or can be disposed safely. It is important to implement these activities in a cost-effective manner. The aim of this research is to measure the performance of the RL enterprise with the help of an Agent-based Modeling technique. The major entities in the RL network are considered as Agents that can act independently. There are several different agents: Collector Agent, Sorting-Cum-Reuse Agent, Remanufacturing Agent, Recycler Agent, Supplier Agent, and Distributor Agent. The individual performances of each agent are measured and recommendations are given to improve their performance, leading to the enhancement of the total performance of the RL enterprise. The solution approach is applied to a case study involving cell-phone remanufacturing