Guilherme Pereira

Simulation as a tool for planning a material delivery system to manufacturing lines

This paper describes the procedures used during the planning of a material delivery system for the manufacturing lines of an electronic company. The paper describes the simulation experiments of a material delivery system for the manufacturing lines, using a logistic train. The main objective of this study is to make simulation experiments, regarding different amounts of equipment and logistic train programming methods, in order to identify and to propose changes that may lead to greater efficiency and precision of the logistic train functioning. The developed models were implemented with Arena simulation software. Experimental results are presented. Conclusions are discussed.

Solving the Team Orienteering Problem: Developing a Solution Tool Using a Genetic Algorithm Approach

Nowadays, the collection of separated solid waste for recycling is still an expensive process, specially when performed in large-scale. One main problem resides in fleet-management, since the currently applied strategies usually have low efficiency. The waste collection process can be modelled as a vehicle routing problem, in particular as a Team Orienteering Problem (TOP). In the TOP, a vehicle fleet is assigned to visit a set of customers, while executing optimized routes that maximize total profit and minimize resources needed. The objective of this work is to optimize the waste collection process while addressing the specific issues around fleet-management. This should be achieved by developing a software tool that implements a genetic algorithm to solve the TOP. We were able to accomplish the proposed task, as our computational tests have produced some challenging results in comparison to previous work around this subject of study. Specifically, our results attained 60% of the best known scores in a selection of 24 TOP benchmark instances, with an average error of 18.7 in the remaining instances. The usage of a genetic algorithm to solve the TOP proved to be an efficient method by outputting good results in an acceptable time.

Using simio for the specification of an integrated automated weighing solution in a cement plant

This paper focuses on the use of a discrete simulation tool (SIMIO) in the logistic system design of a cement plant. This research project specifies a proposal of using Discrete Event Simulation (DES) and innovative logistic methods for the correct specification of an integrated weighing solution in a cement plant. This specification will then help the design phase of the whole plant and will contribute for the rationalization of the use of cement plant resources. The proposed monitoring weighing system (Cachapuz - SLV Cement) together with the simulation model will evaluate different scenarios as far as the logistic system is concerned and will support important decisions in the design phase of a cement plant, contributing to the best use of the best set of resources.

A warehouse design decision model — Case study

Todaypsilas competitive and volatile market requires flexibility, quality and efficiency from the logistics operations. In this context, warehouses are an important link of the logistic chain and warehouse management plays an important role over customerpsilas service. Throughout this work we analyze a mathematical model aiming to support warehouse management decisions. A case study is used for that purpose and the model jointly identifies product allocation to the functional areas in the warehouse, as well as the size of each area. This case study also evaluates the performance of the model when real data is used. Model is solved using LINGO 9.0 mixed-integer commercial solver, and potential savings achieved using the proposed technique are discussed.

Layout and process optimisation : using computer-aided design (CAD) and simulation through an integrated systems design tool

The design of production and logistic systems is a process of managing both technical and organisational variants in order to identify the best solution for a given system. This paper discusses design issues of production systems that are applied to an internal logistic system in the automotive industry. As far as the production systems design (PSD) is concerned, three basic classes of software tools usually pertain: computer-aided design (CAD), process simulation, and information systems. However, these software tools have been used with low levels of integration. Vik et al. (2010b, 2010c) proposed integrating these software resources in production systems and developed an advanced tool called integrated design of systems (IDS). The proposed IDS tool involves a wide set of functions for the most common tasks of PSD, from conceptualisation to implementation, including systems analysis (P-Q, cluster, and material flow analysis), automatic generation of simulation models, generation of alternatives for the layout of facilities and factories, material flows display, transportation system design, and iterative buffer size specification. The IDS approach takes advantage of simulation, CAD systems, and their integration. This paper will demonstrate the concept and functionalities of the proposed tool in a real industrial case study.

Non Emergency Patients Transport - A Mixed Integer Linear Programming

Fundacao para a Ciencia e Tecnologia; project GATOP - Genetic Algorithms for Team Orienteering Problem (Ref PTDC/EME- GIN/120761/2010), financed by national funds by FCT / MCTES, and co-funded by the European Social Development Fund (FEDER) through the COMPETE - Programa Operacional Fatores de Competitividade (POFC) Ref FCOMP-01-0124- FEDER-020609. This work has been partially supported by FCT – Fundacao para a Ciencia e Tecnologia within the Project Scope: PEst-OE/EEI/UI0319/2014 The authors would like to thank the NEOS Server at the University of Wisconsin in Madison for providing support to this study

An Integrated Simulation and Business Intelligence Framework for Designing and Planning Demand Responsive Transport Systems

Transportation planners, analysts and decision-makers usually make use of simulation tools in order to accurately predict the performance of new practices and policies before their implementation. Additionally, most of them, recently introduced new auxiliary Business Intelligence decision support tools in order to transform their available huge amount of real operating data into timely and accurate information for their decisions. However, although both of those types of automated decision support are valuable, very few attempts were already made by researchers to integrate them into a unified tool.

State probabilities of a float system

Purpose – The purpose of this paper is to determine the state probabilities for a float system when overhauls are performed periodically.Design/methodology/approach – First, a model is developed to express the relationship between the rate of occurrence of failure and time interval between overhauls. Then, a methodology is defined to develop differential equations for each system state in order to calculate corresponding system state probabilities.Findings – Since it is considered that units requiring an overhaul stay in operation until replacement, the possibility of failure of those units has to be included. Then, the determination of system state probabilities has to be done iteratively.Practical implications – The methodology proposed in this paper enables comparison of different designs for a float system submitted to periodic overhauls through some different performance measures. System state probabilities can also be used to determine the idle time of units, which is essential to obtain the cost of...

Micro Simulation to Evaluate the Impact of Introducing Pre-signals in Traffic Intersections

The resolution of problems related to the saturation of traffic intersections usually consists in the construction of infrastructure such as bridges or tunnels. These represent the most costly type of solutions. As such, it becomes necessary to ponder other types of solution, of lower cost. Thus, this paper intends to provide a way to significantly improve the performance of a traffic intersection, by using pre-signals, on its approaches. For this purpose, a traffic micro simulation model was developed, using Simio. The simulation experiments show that the implementation of pre-signals result in an increase of the intersection flows upper ceiling in over 10%, a decrease in the average waiting time per vehicle in 1 minute and a decrease of the queues average size. In addition, it was also found that there is always gain in the space occupied by the queues, taking into consideration the space investment needed to implement pre-signals.

Warehouse design and planning: a mathematical programming approach

The dynamic nature of todays competitive markets compels organizations to an incessant reassessment in an effort to respond to continuous challenges. Therefore, warehouses as an important link in most supply chains, must be continually re-evaluated to ensure that they are consistent with both markets demands and managements strategies. A number of warehouse decision support models have been proposed in the literature but considerable difficulties in applying these models still remain, due to the large amount of information to be processed and to the large number of possible alternatives. In this paper we discuss a mathematical programming model aiming to support some warehouse management and inventory decisions. In particular a large mixed-integer nonlinear programming model (MINLP) is presented to capture the trade-offs among the different inventory and warehouse costs in order to achieve global optimal design satisfying throughput requirements.