Showing papers in "International Journal of Simulation Modelling in 2012"

Comparison of dispatching rules in job-shop scheduling problem using simulation: a case study

Abstract: This paper focuses on the development of EQNML which is an extended queuing modelling and markup language. We discuss the DSML metamodel and its XML-based exchange format which represent the cornerstone of the development process. EQNML enhances interoperability between a wide range of analytical solvers and simulation tools dealing with systems performance evaluation and based on the extended queuing theory. Furthermore, the Model Driven Engineering approach allows automatic generation of modelling environments and simulation/analytical codes which improve productivity and quality. Our aim is to induce discussion on and contributions for elaborating the whole metamodel and providing a starting point for the development of a standard inter-change format. 19 refs. (Received in February 2011, accepted in April 2012. This paper was with the authors 2 months for 2 revisions.)

Optimization of cutting inserts geometry using DEFORM-3D: Numerical simulation and experimental validation

Abstract: In this research work an attempt has been made to minimize flank wear of uncoated carbide inserts while machining AISI 1045 steel by finite element analysis. Tool wear is the predominant factor that causes poor surface finish and is responsible for the dimensional accuracy of the machined surface. The quality of component produced decides the effectiveness and competitiveness of any manufacturing industry. In this analysis, the effect of tool geometries on performance measures of flank wear, surface roughness and cutting forces generated are evaluated. Three levels of cutting insert shape, relief angle and nose radius are chosen. Taguchi’s Design of experiment (DOE) is used to design the experiments. For three parameters and three levels a suitable L9 Orthogonal array is selected. Based on the designed experiment, simulation analysis is carried out using DEFORM-3D, a machining simulation and analysis software and the output quality characteristics are analysed by statistical techniques like Signal-to-Noise (S/N) ratio and Analysis of Variance (ANOVA). A validation finite element simulation is conducted with the obtained optimum tool geometry, which is also verified experimentally. It is observed that the performance of the determined tool geometry provides satisfactory results. (Received in August 2011, accepted in November 2011. This paper was with the authors 1 month for 1 revision.)

Heat transfer enhancement for natural convection flow of water-based nanofluids in a square enclosure

Abstract: Numerical analysis is performed to examine the heat transfer enhancement of Au, Al 2 O 3 , Cu and TiO 2 water-based nanofluids. The analysis uses a two-dimensional enclosure under natural convection heat transfer conditions and has been carried out for the Rayleigh number range 10 3 < Ra ≤ 10 5 , and for the nanoparticles' volume fraction range 0 ≤ ϕ < 0,10. The governing equations were solved with the standard finite-volume method and the hydrodynamic and thermal fields were coupled together using the Boussinesq approximation. Highly accurate numerical results are presented in the form of average Nusselt number and heat transfer enhancement. The results indicate clearly that the average Nusselt number is an increasing function of both, Rayleigh number and volume fraction of nanoparticles. The results also indicate that heat transfer enhancement is possible using nanofluids in comparison to conventional fluids, resulting in the compactness of many industrial devices. However, low Rayleigh numbers show more enhancement compared to high Rayleigh numbers.

Design of modern hydraulic tank using fluid flow simulation

Abstract: Hydraulic power units are one of the most commonly used power sources in industry. The progress in recent years has offered high efficiency and reliable hydraulic components, yet the hydraulic tank design is often neglected part of the development. The paper presents the development of industrial 400 litre hydraulic tank. In order to reduce oil swirling and improve stability of fluid flow, CFD simulations of oil flow inside hydraulic tank were made. Several variations of new hydraulic tank designs are compared with standard industrial tank. Furthermore, to achieve steady flow through the entire reservoir and reduce the phenomenon of oil swirling, newly-developed diffuser is used. Consequently a full scale hydraulic power unit was built according to obtained results. (Received in September 2011, accepted in February 2012. This paper was with the authors 1 month for 1 revision.)

Analysis of a Three-Stage Supply Chain with Level Constraints

Abstract: Many companies have enjoyed a significant success due to the unique ways in which they have organized their supply chains, which are one of the best ways to compete in today's marketplaces. For make-to-stock production systems the production plans and activities are based on demand forecasting. This is one of the key causes of the bullwhip effect. The bullwhip effect (BE) is the inherent increase in demand fluctuation up the supply chain. In the paper we experimented (by simulating) with a special case of a simple three-stage supply chain using seasonal and deseasonalized time series of the market demand data in order to identify, illustrate and discuss the impacts of different level constraints on the BE. The results are presented for different overall equipment effectiveness (OEE) and constrained inventory policies. At higher OEE level there is less variability in production processes, but at inventory limitations the impact is more complex. (Received in December 2011, accepted in July 2012. This paper was with the authors 2 months for 2 revisions.)

Evaluation of manufacturing tolerance using a statistical method and experimentation

Abstract: This paper proposes a study of a milling process planning to determine the tolerancing for manufacturing using statistical tool. The deviation between the machined surface and the surface corresponding to the nominal one due to combined errors is expressed in terms of the small displacement torsor parameters. These parameters are considered as random variables, displacements are expresses as variances. Experimentation is realised on a set of manufactured parts which consists of measuring various defects on machine-tool. The experimental results and the simulation results are compared in this paper. (Received in March 2011, accepted in August 2011. This paper was with the authors 1 month for 1 revision.)

Reducing Delay in Healthcare Delivery at Outpatients Clinics Using Discrete Event Simulation

Abstract: Outpatient clinics are demanding more consideration to enhance their performance and quality of care. This paper presents a thorough exploration of the outpatient clinics’ environment at a local hospital. The ophthalmology outpatient clinic was selected for a case study. To this end, the total visit time and service times at stations were collected and fed into a Discrete Event Simulation (DES) model. The model was validated through a statistical comparison with the performance of the real system. Various improvement alternatives were then proposed and investigated using the DES model. Key performance indicators of the system, including expected waiting time and expected visit length, were traced. Findings indicated that many improvement scenarios could be applied with significant amounts of reduction in waiting time up to 29 % and visit length up to 19 % without investing in new resources. (Received in November 2011, accepted in April 2012. This paper was with the authors 1 month for 2 revisions.)

Optimising flow stress input for machining simulations using taguchi methodology

Abstract: Flow stress is a vital input data for successful simulation of a machining process. However the flow stress data obtained from experiments do not represent the practical machining conditions which induce errors in the simulated output. In this research work the flow stress of Ti6Al4V titanium alloy is improved through a new integrated Taguchi – Finite element optimisation technique. The finite element (FE) outputs for cutting force, feed force and chip thickness ratio are compared with the results from the orthogonal machining process and an optimum set of material parameters of the Johnson – Cook (JC) flow stress equation is identified. The optimised flow stress is found to improve the simulated cutting forces by 3-16 %, feed forces by 2-25 %, chip thickness ratio by 0-19 % over flow stress computed from conventional JC model parameters. The yield strength parameter of the JC model impacts the simulation results the most and the JC material constitutive law is found to be robust in flow stress characterisation with the optimized parameters. (Received in March 2011, accepted in September 2011. This paper was with the authors 1 month for 1 revision.)

Simulation-Based Environmental Cost Analysis for Work-in-Process

Abstract: Under the modern manufacturing environment-oriented, both productivity and green environmental consideration are made in diverse phases of production operations. In this paper, in order to dynamically analyse and control changes of Work-In-Process (WIP) inventory level, a centralized fuzzy control method is proposed. Additionally, a new environmental management accounting method, Material Flow Cost Accounting (MFCA), is adopted to find and calculate environmental waste hiding in the production processes. Moreover, a simulation model integrated with these methods above is constructed. Based on the simulation data, sensitivity analysis between control factors of WIP inventory level and negative product costs ratio is made. To achieve a reasonable productivity as well as green environmental performance for this case, a corresponding optimized solving measure is put forward by means of OptQuest in the Arena simulation system. Through studying, the proposed control approach of WIP can reduce the green environmental cost, and improve production capacity. (Received in February 2012, accepted in August 2012. This paper was with the author 2 months for 1 revision.)

Magnetic device simulation modelling and optimisation for scale control

Abstract: The paper presents model devices for magnetic water treatment, optimized for scale control at water capacities up to a few m/h. Different arrangements of permanent magnets were investigated and simulated at different water-flow capacities to yield the proper magnetic field distribution and the required magnetic flux density, using the computational program OPERA 15R1 (Vector Fields Software) with the finite-element method, considering the real 3Dgeometry, non-linearity of magnetic properties of construction materials, and the interaction of neighbouring poles. (Received in October 2011, accepted in April 2012. This paper was with the authors 2 months for 1 revision.)

A hierarchical production planning system simulator

Abstract: This research develops and demonstrates a Hierarchical Production Planning System Simulator (HPPSS) for the analysis of feedback-and-control mechanisms between linear programming models at two levels within a Hierarchical Production Planning (HPP) system. This work focuses on planning levels dealing with tactical decisions. Three areas distinguish it from prior research. First, the HPPSS allows explicit examination of the effects of different information exchanges between the levels of a hierarchical model. Second, the HPPSS allows examination of the problems for which a given feedback-and-control mechanism performs well. Finally, the HPPSS allows the effects of a rolling horizon implementation on the hierarchical models of the production planning problem to be investigated. The significance is that a more thorough understanding of the costs and benefits of various mechanisms for information exchange between the levels of hierarchical models of planning problems over time will lead to improved hierarchical decision-making techniques that may influence organizational design. (Received in May 2011, accepted in October 2011. This paper was with the author 1 month for 1 revision.)

Semi-discrete events and models in categorical language

Abstract: Some problems related to discrete event simulation and model validation are discussed. The validity of models with simultaneous events is discussed. The basic concepts of the theory of categories are recalled and applied to model construction process. The language of the theory of categories is used to treat some problems in modelling and simulation of discrete event, namely the ambiguity that may appear when simultaneous events occur. It is pointed out that the theory of categories may be useful as a unified language for model description. In particular, the categorical point of view can be useful while treating the model validity. Using this language we can get a high level of abstractions in model building.

Modelling and control of tinning line entry section using neural networks

Abstract: The objective of this paper is the development of a mathematical model and the design of the control of the drives of a tinning line entry section, using artificial neural networks. The first part of the paper describes the mathematical models of the individual sections of the processing line: a decoiler and four traction rolls joined together by a steel strip creating a flexible linkage. The drive models have been supplemented by neural controllers in such a way as to satisfy the requirements specified for the individual drives and determined by the sheet metal tinning technology. The paper is concluded with a description of the whole model of the tinning line entry section together with the neural controllers and with an evaluation of the achieved simulation results. (Received in November 2011, accepted in March 2012. This paper was with the authors 1 month for 1 revision.)

Ontology Development and Agent Communication in Agent-Based Simulation of AGVS

Abstract: For effective information exchange in agent-based systems, domain-specific ontology is strongly needed, which is the vocabulary representing facts and relations of objects in the domain. In this paper, a semi-formal domain-specific ontology for shop floor focusing on Automated Guided Vehicle Systems (AGVS) is presented. The domain-specific ontology is developed on Protégé, a leading frame-based ontology editor, and is further converted into JADETM (Java Agent DEvelopment Framework) compliant java classes. The developed ontology has been used in agent-communication of a simulator known as agent-based shop floor simulator (ABSFSim). Agent communication used in the ABSFSim is discussed. Agentbased simulation model of a sample manufacturing system is built with ABSFSim and the working of the model is verified and validated by comparing the output with an equivalent model developed in ProModel. The ontology development process presented in this paper is useful for developing agent-based models in different sections of manufacturing and also for developing high level agent-based software platforms for manufacturing systems. (Received in February 2011, accepted in June 2012. This paper was with the authors 2 months for 2 revisions.)

SimSum1: a general optimisation via simulation approach for 0-1 programming models

Abstract: The current study develops a new general heuristic approach to address a special class of combinatorial problems, efficiently. The approach combines discrete event simulation together with relaxation techniques to solve a special class of 0-1 programming models including a constraint that restricts the summation of all variables to be 1. Three well-known combinatorial problems -including such a constraintsuch as Dynamic Facility Layout Problem (DFLP), Graph Labelling Problem (GLP) and Travelling Salesman Problem (TSP) have been addressed and could be solved efficiently by the proposed algorithm. Several experiments have been carried out to show the efficiency of the algorithm. The results show that the proposed algorithm can be used for several real world applications while according to the best knowledge of the author, at least for DFLP and GLP, it is the fastest algorithm which has been developed in the literature. (Received in October 2011, accepted in April 2012. This paper was with the author 2 months for 3 revisions.)

Towards a metamodel for extended queuing networks

Abstract: This paper focuses on the development of EQNM 2 L which is an extended queuing modelling and markup language. We discuss the DSML metamodel and its XML-based exchange format which represent the cornerstone of the development process. EQNM 2 L enhances interoperability between a wide range of analytical solvers and simulation tools dealing with systems performance evaluation and based on the extended queuing theory. Furthermore, the Model Driven Engineering approach allows automatic generation of modelling environments and simulation/analytical codes which improve productivity and quality. Our aim is to induce discussion on and contributions for elaborating the whole metamodel and providing a starting point for the development of a standard interchange format.