Paul Young | Dublin City University (original) (raw)

Papers by Paul Young

2008 Winter Simulation Conference, 2008

This paper presents a new batch scheduling heuristic-the Time-Limited Next Arrival heuristic for ... more This paper presents a new batch scheduling heuristic-the Time-Limited Next Arrival heuristic for batch processing and setup reduction (TLNA). This heuristic has been defined for a batch processing machine group in a re-entrant manufacturing environment where setups are sequencedependent. When making the scheduling decision, TLNA takes into account future arrivals based on a user-defined wait time. A series of experiments is conducted on a discrete event simulation model to determine the impact of this wait time. A total cost function is used to combine two conflicting performance measures (total item queuing time and total machine running time) into one. All TLNA wait time scenarios are compared to the Next Arrival Control Heuristic for Multiple products and Multiple machines (NACHMM). The experiments presented show that there is a wait time that minimises the total operational cost. TLNA outperforms NACHMM with regard to all performance measures except total queuing time.

Production Planning & Control: The Management of Operations, Aug 8, 2013

This article interweaves the widely published empirical frameworks with a new paradigm proposing ... more This article interweaves the widely published empirical frameworks with a new paradigm proposing stochastic dynamic decision-making tools that could be employed for capturing the trade-offs among multiple and conflicting-in-nature criteria so as to provide a design of a resilient shock absorber (RSA) for disrupted supply chain network (SCN). Modern SCNs encounter ‘excursion events’ of different kinds mainly due to uncertain and turbulent markets, catastrophes, accidents, industrial disputes/strikes in organisations, terrorism and asymmetric information. An ‘excursion event’ is an unpredictable event that effectively shuts down or has a relatively large negative impact on the performance of at least one member of a system for a relatively long amount of time. In this article, design of an analytical framework has been conceptualised that allows an SCN to avoid propagating the ill effects of the ‘excursion events’ further and maintains the network at a desired equilibrium level. A broad analytical view of econophysics has been conceptualised using the definition of a ‘system’ from physics. An example derived from the 9/11 case has been delineated in order to illustrate the efficacy of the proposed design. The devised RSA facilitates the assessment of resiliency strategies for SCNs prone to excursion events that are characterised by low probability of occurrence and high impact. The shock-dampening fortification framework also enables practitioners to identify and assess quantitatively the islands of the excursion events in SCN.

Modelling & Simulation, …, Jan 1, 2009

This paper conceptualises an analytical framework meant for resiliency of supply-chain networks b... more This paper conceptualises an analytical framework meant for resiliency of supply-chain networks by assessing excursion events. Modern Supply-Chain Networks (SCNs) face excursion events of various kinds mainly due to uncertain and turbulent markets, catastrophes, accidents, industrial disputes/strikes in organisations and terrorism. An "excursion event" is an unpredictable event that effectively shuts-down or negatively impacts the performance of at least one node/member of a system for a relatively long amount of time. In this paper, an analytical framework has been conceptualised that prevents a SCN to propagate the effects of the "excursion events" further and maintains the network at desired equilibrium level. The gestated quantitative decision-support approach facilitates the assessment of resilient strategies for SCNs prone to excursion events that are characterised by Low Probability of occurrence and High Impact (LPHI).

Journal of Materials Processing Technology, 2004

Semiconductor manufacturing facilities are migrating to 300mm technology, necessitating the imple... more Semiconductor manufacturing facilities are migrating to 300mm technology, necessitating the implementation of automated material handling systems (AMHS) for a variety of ergonomic and safety considerations. A predictive tool, such as software simulation, is needed at the planning stage to estimate the performance of these relatively new systems. Two forms of AMHS are in general use in industry one which handles

Conceptual Modeling for Discrete-Event Simulation, 2010

First published in September 2007, the Systems Modeling Language (SysML) is a recent language for... more First published in September 2007, the Systems Modeling Language (SysML) is a recent language for systems modeling that has a growing community of users and advocates in the field of systems engineering. This chapter gives an overview of SysML, identifies why it is ...

Procedia CIRP, 2014

The cost of acquiring commercial simulation packages is considerably high and this might explain ... more The cost of acquiring commercial simulation packages is considerably high and this might explain why organisations are often reluctant to make further investments on training and retraining of employees on simulation modelling. Ironically, the level of benefit derived from simulation is highly dependent on experimental, analytical and statistical skills of the user. These cost and skill requirements make simulation an unattractive decision support tool to SMEs and small multinational organisations. Proposed in this study is ManPy, a semantic-free opensource approach to discrete event simulation (DES), such that users with different levels of skills can derive considerable benefits from simulation. ManPy eradicates the high investments required for simulation modelling by making it possible for low skilled users to benefit from readily available generic modelling objects which are contributed to an open source platform by highly skilled simulation practitioners, statisticians and academics. Another benefit of ManPy is the ability to integrate with other enterprise planning tools for system knowledge extraction and real time simulation input data. Some of these benefits are demonstrated through the implementation of ManPy in a SME that specialises in rapid prototyping and rapid tooling.

Procedia CIRP, 2014

ABSTRACT This paper describes a test implementation of the Core Manufacturing Simulation Data (CM... more ABSTRACT This paper describes a test implementation of the Core Manufacturing Simulation Data (CMSD) information model and the integration and initialisation of a simulation model in a newly developed Simulation Engine. The cost of developing, implementing and using simulation technology is high. The costs of integrating simulation models with other manufacturing applications are even higher. There is always a need to enable data exchange and sharing between simulation applications and other software applications. The idea of the CMSD effort is to facilitate the above using neutral, reusable data structures for managing actual production operations and for simulating the performance of the manufacturing system. To address the problem of time consuming pre-coding for DES projects, a knowledge extraction tool is currently being developed. The knowledge extraction tool will read data from several resources of an organisation and output it in a format that is applicable for simulation purposes. The format that we adopted follows the CMSD standard in order to describe simulation related data. In this paper we present the modelling of a complex production line of our industrial partner with the CMSD standard and the development of the translator in ManPy so that it can read the CMSD information model and run the simulation.

The Job-shop scheduling is one of the most important industrial activities, especially in manufac... more The Job-shop scheduling is one of the most important industrial activities, especially in manufacturing planning. The problem complexity has increased along with the increase in the complexity of operations and product-mix. To solve this problem, numerous approaches have been developed incorporating discrete event simulation methodology. The scope and the purpose of this paper is to present a survey which covers

A computational study has been developed to obtain optimal / near optimal solution for the flow s... more A computational study has been developed to obtain optimal / near optimal solution for the flow shop scheduling problem with make-span minimization as the primary criterion and the minimization of either the mean completion time, total waiting time or total idle time as the secondary criterion. The objective is to determine a sequence of operations in which to process ‘n’

The current trend in semiconductor manufacturing is characterized by expanding product variety, d... more The current trend in semiconductor manufacturing is characterized by expanding product variety, decreasing lead times from order to delivery, exacting standards of quality, and competitive prices. One possible means of achieving this is in the form of increased flexibility. Providing flexibility is typically an expensive proposition so, industrial engineers aim to provide more economic approaches to enable flexible manufacturing cells

Production Planning & Control, 2013

This article interweaves the widely published empirical frameworks with a new paradigm proposing ... more This article interweaves the widely published empirical frameworks with a new paradigm proposing stochastic dynamic decision-making tools that could be employed for capturing the trade-offs among multiple and conflicting-in-nature criteria so as to provide a design of a resilient shock absorber (RSA) for disrupted supply chain network (SCN). Modern SCNs encounter ‘excursion events’ of different kinds mainly due to uncertain

Journal of Materials Processing Technology, 2004

The pressures on semiconductor manufacturers due to cost considerations, rapid growth of process ... more The pressures on semiconductor manufacturers due to cost considerations, rapid growth of process technology, quality constraints, feature size reduction, and increasingly complex products are requiring ever higher efficiency from manufacturing facilities. The complexity of manufacturing high capacity semiconductor devices means that it is impossible to analyze the process control parameters and the production configurations using traditional analytical models. There is, therefore, an increasing need for effective models of each manufacturing process, characterizing and analyzing the process in detail, allowing the effect of changes in the production environment on the process to be predicted. The photolithography process is one of the most complex processes in semiconductor manufacturing. Using state-of-the-art computer simulation and a structured modelling methodology a generic model of photolithography flexible manufacturing cells has been developed and used to mimic the actual performance of the tools. Comparison of the output from the model with data from the plant shows the quality of the model. This paper discusses the technique used to develop the simulation model and includes a details on the structured modelling approach employed to develop reusable generic model for optimizing photolithography process parameters.

Exergy analysis has been applied to desalination membrane processes in an effort to characterise ... more Exergy analysis has been applied to desalination membrane processes in an effort to characterise energy consumption and to optimise energy efficiency. Several models have been used to this end in the literature. One assumption that is common in these analyses is that of ideal solution behavior. However, seawater and other aqueous solutions of interest do not behave ideally. Indeed, even when ideal behavior is not assumed, there are several approaches to calculate these activity values, which are typically a function of the molality and ionic strength of the electrolytic solution. What is not clear from the published literature is the impact that the choice of activity calculation model has on the exergy analysis results. The objective of this research was to undertake the exergy analysis of a seawater membrane desalination plant using the Szargut chemical exergy approach and to compare the activity calculation approaches. The chemical exergy of the seawater was calculated using seve...

Desalination, 2015

ABSTRACT In the literature, several exergy analysis approaches have been proposed to investigate ... more ABSTRACT In the literature, several exergy analysis approaches have been proposed to investigate desalination processes. It is not clear, however, which approach is the most appropriate or indeed whether all approaches are valid. The objective of this paper is to review the various methods and to critically assess their assumptions, limitations, advantages and disadvantages. The main focus of this work is the chemical exergy term. Several exergy calculation models were examined and compared using a dataset from the literature. In addition, an accurate approach to calculate the chemical exergy of electrolyte solutions, based on the Pitzer equations, was proposed. The models assessed were: (1) the ideal mixture model (NaCl and water), (2) the ideal mixture model (seawater salt and water), (3) the Sharqawy seawater functions, and (4) the electrolyte solution model (Pitzer equations, NaCl and water), (5) the model used by Drioli et al. and (6) the dissociated ion approach (NaCl and water). Four of the six approaches produced very similar results. Moreover, one other exergy calculation method was found to have serious limitations. The findings presented here show that the choice of exergy model can have a significant impact on the results obtained and that considerable care must be taken to select the most suitable approach.

Proceedings of the 36th conference on Winter …, 2004

Scheduling of a semiconductor manufacturing facility is one of the most complex tasks encountered... more Scheduling of a semiconductor manufacturing facility is one of the most complex tasks encountered. Confronted with a high technology product market, semiconductor manufacturing is increasingly more dynamic and competitive in the introduction of new products in shorter time intervals. Photolithography, being one of the processes repeated often, is a fabrication bottleneck. Lot scheduling within photolithography is a challenging activity where substantial improvements in factory performance can be made. The proposed scheduling methodology integrates two common approaches, simulation and artificial intelligence. Using detailed simulation modeling within a structured modeling method, a comprehensive model to characterize the photolithography process was developed. An artificial intelligence scheduler was then developed and integrated with the model with the goal of reducing Work-In-Process (WIP), setup time, and throughput time. The results have shown a significant improvement in lot cycle time as well as tool utilization, improved the throughput time by an average of 15% and is currently in use for scheduling the photolithography process.

2008 Winter Simulation Conference, 2008

This paper presents a new batch scheduling heuristic-the Time-Limited Next Arrival heuristic for ... more This paper presents a new batch scheduling heuristic-the Time-Limited Next Arrival heuristic for batch processing and setup reduction (TLNA). This heuristic has been defined for a batch processing machine group in a re-entrant manufacturing environment where setups are sequencedependent. When making the scheduling decision, TLNA takes into account future arrivals based on a user-defined wait time. A series of experiments is conducted on a discrete event simulation model to determine the impact of this wait time. A total cost function is used to combine two conflicting performance measures (total item queuing time and total machine running time) into one. All TLNA wait time scenarios are compared to the Next Arrival Control Heuristic for Multiple products and Multiple machines (NACHMM). The experiments presented show that there is a wait time that minimises the total operational cost. TLNA outperforms NACHMM with regard to all performance measures except total queuing time.

Production Planning & Control: The Management of Operations, Aug 8, 2013

This article interweaves the widely published empirical frameworks with a new paradigm proposing ... more This article interweaves the widely published empirical frameworks with a new paradigm proposing stochastic dynamic decision-making tools that could be employed for capturing the trade-offs among multiple and conflicting-in-nature criteria so as to provide a design of a resilient shock absorber (RSA) for disrupted supply chain network (SCN). Modern SCNs encounter ‘excursion events’ of different kinds mainly due to uncertain and turbulent markets, catastrophes, accidents, industrial disputes/strikes in organisations, terrorism and asymmetric information. An ‘excursion event’ is an unpredictable event that effectively shuts down or has a relatively large negative impact on the performance of at least one member of a system for a relatively long amount of time. In this article, design of an analytical framework has been conceptualised that allows an SCN to avoid propagating the ill effects of the ‘excursion events’ further and maintains the network at a desired equilibrium level. A broad analytical view of econophysics has been conceptualised using the definition of a ‘system’ from physics. An example derived from the 9/11 case has been delineated in order to illustrate the efficacy of the proposed design. The devised RSA facilitates the assessment of resiliency strategies for SCNs prone to excursion events that are characterised by low probability of occurrence and high impact. The shock-dampening fortification framework also enables practitioners to identify and assess quantitatively the islands of the excursion events in SCN.

Modelling & Simulation, …, Jan 1, 2009

This paper conceptualises an analytical framework meant for resiliency of supply-chain networks b... more This paper conceptualises an analytical framework meant for resiliency of supply-chain networks by assessing excursion events. Modern Supply-Chain Networks (SCNs) face excursion events of various kinds mainly due to uncertain and turbulent markets, catastrophes, accidents, industrial disputes/strikes in organisations and terrorism. An "excursion event" is an unpredictable event that effectively shuts-down or negatively impacts the performance of at least one node/member of a system for a relatively long amount of time. In this paper, an analytical framework has been conceptualised that prevents a SCN to propagate the effects of the "excursion events" further and maintains the network at desired equilibrium level. The gestated quantitative decision-support approach facilitates the assessment of resilient strategies for SCNs prone to excursion events that are characterised by Low Probability of occurrence and High Impact (LPHI).

Journal of Materials Processing Technology, 2004

Semiconductor manufacturing facilities are migrating to 300mm technology, necessitating the imple... more Semiconductor manufacturing facilities are migrating to 300mm technology, necessitating the implementation of automated material handling systems (AMHS) for a variety of ergonomic and safety considerations. A predictive tool, such as software simulation, is needed at the planning stage to estimate the performance of these relatively new systems. Two forms of AMHS are in general use in industry one which handles

Conceptual Modeling for Discrete-Event Simulation, 2010

First published in September 2007, the Systems Modeling Language (SysML) is a recent language for... more First published in September 2007, the Systems Modeling Language (SysML) is a recent language for systems modeling that has a growing community of users and advocates in the field of systems engineering. This chapter gives an overview of SysML, identifies why it is ...

Procedia CIRP, 2014

The cost of acquiring commercial simulation packages is considerably high and this might explain ... more The cost of acquiring commercial simulation packages is considerably high and this might explain why organisations are often reluctant to make further investments on training and retraining of employees on simulation modelling. Ironically, the level of benefit derived from simulation is highly dependent on experimental, analytical and statistical skills of the user. These cost and skill requirements make simulation an unattractive decision support tool to SMEs and small multinational organisations. Proposed in this study is ManPy, a semantic-free opensource approach to discrete event simulation (DES), such that users with different levels of skills can derive considerable benefits from simulation. ManPy eradicates the high investments required for simulation modelling by making it possible for low skilled users to benefit from readily available generic modelling objects which are contributed to an open source platform by highly skilled simulation practitioners, statisticians and academics. Another benefit of ManPy is the ability to integrate with other enterprise planning tools for system knowledge extraction and real time simulation input data. Some of these benefits are demonstrated through the implementation of ManPy in a SME that specialises in rapid prototyping and rapid tooling.

Procedia CIRP, 2014

ABSTRACT This paper describes a test implementation of the Core Manufacturing Simulation Data (CM... more ABSTRACT This paper describes a test implementation of the Core Manufacturing Simulation Data (CMSD) information model and the integration and initialisation of a simulation model in a newly developed Simulation Engine. The cost of developing, implementing and using simulation technology is high. The costs of integrating simulation models with other manufacturing applications are even higher. There is always a need to enable data exchange and sharing between simulation applications and other software applications. The idea of the CMSD effort is to facilitate the above using neutral, reusable data structures for managing actual production operations and for simulating the performance of the manufacturing system. To address the problem of time consuming pre-coding for DES projects, a knowledge extraction tool is currently being developed. The knowledge extraction tool will read data from several resources of an organisation and output it in a format that is applicable for simulation purposes. The format that we adopted follows the CMSD standard in order to describe simulation related data. In this paper we present the modelling of a complex production line of our industrial partner with the CMSD standard and the development of the translator in ManPy so that it can read the CMSD information model and run the simulation.

The Job-shop scheduling is one of the most important industrial activities, especially in manufac... more The Job-shop scheduling is one of the most important industrial activities, especially in manufacturing planning. The problem complexity has increased along with the increase in the complexity of operations and product-mix. To solve this problem, numerous approaches have been developed incorporating discrete event simulation methodology. The scope and the purpose of this paper is to present a survey which covers

A computational study has been developed to obtain optimal / near optimal solution for the flow s... more A computational study has been developed to obtain optimal / near optimal solution for the flow shop scheduling problem with make-span minimization as the primary criterion and the minimization of either the mean completion time, total waiting time or total idle time as the secondary criterion. The objective is to determine a sequence of operations in which to process ‘n’

The current trend in semiconductor manufacturing is characterized by expanding product variety, d... more The current trend in semiconductor manufacturing is characterized by expanding product variety, decreasing lead times from order to delivery, exacting standards of quality, and competitive prices. One possible means of achieving this is in the form of increased flexibility. Providing flexibility is typically an expensive proposition so, industrial engineers aim to provide more economic approaches to enable flexible manufacturing cells

Production Planning & Control, 2013

This article interweaves the widely published empirical frameworks with a new paradigm proposing ... more This article interweaves the widely published empirical frameworks with a new paradigm proposing stochastic dynamic decision-making tools that could be employed for capturing the trade-offs among multiple and conflicting-in-nature criteria so as to provide a design of a resilient shock absorber (RSA) for disrupted supply chain network (SCN). Modern SCNs encounter ‘excursion events’ of different kinds mainly due to uncertain

Journal of Materials Processing Technology, 2004

The pressures on semiconductor manufacturers due to cost considerations, rapid growth of process ... more The pressures on semiconductor manufacturers due to cost considerations, rapid growth of process technology, quality constraints, feature size reduction, and increasingly complex products are requiring ever higher efficiency from manufacturing facilities. The complexity of manufacturing high capacity semiconductor devices means that it is impossible to analyze the process control parameters and the production configurations using traditional analytical models. There is, therefore, an increasing need for effective models of each manufacturing process, characterizing and analyzing the process in detail, allowing the effect of changes in the production environment on the process to be predicted. The photolithography process is one of the most complex processes in semiconductor manufacturing. Using state-of-the-art computer simulation and a structured modelling methodology a generic model of photolithography flexible manufacturing cells has been developed and used to mimic the actual performance of the tools. Comparison of the output from the model with data from the plant shows the quality of the model. This paper discusses the technique used to develop the simulation model and includes a details on the structured modelling approach employed to develop reusable generic model for optimizing photolithography process parameters.

Exergy analysis has been applied to desalination membrane processes in an effort to characterise ... more Exergy analysis has been applied to desalination membrane processes in an effort to characterise energy consumption and to optimise energy efficiency. Several models have been used to this end in the literature. One assumption that is common in these analyses is that of ideal solution behavior. However, seawater and other aqueous solutions of interest do not behave ideally. Indeed, even when ideal behavior is not assumed, there are several approaches to calculate these activity values, which are typically a function of the molality and ionic strength of the electrolytic solution. What is not clear from the published literature is the impact that the choice of activity calculation model has on the exergy analysis results. The objective of this research was to undertake the exergy analysis of a seawater membrane desalination plant using the Szargut chemical exergy approach and to compare the activity calculation approaches. The chemical exergy of the seawater was calculated using seve...

Desalination, 2015

ABSTRACT In the literature, several exergy analysis approaches have been proposed to investigate ... more ABSTRACT In the literature, several exergy analysis approaches have been proposed to investigate desalination processes. It is not clear, however, which approach is the most appropriate or indeed whether all approaches are valid. The objective of this paper is to review the various methods and to critically assess their assumptions, limitations, advantages and disadvantages. The main focus of this work is the chemical exergy term. Several exergy calculation models were examined and compared using a dataset from the literature. In addition, an accurate approach to calculate the chemical exergy of electrolyte solutions, based on the Pitzer equations, was proposed. The models assessed were: (1) the ideal mixture model (NaCl and water), (2) the ideal mixture model (seawater salt and water), (3) the Sharqawy seawater functions, and (4) the electrolyte solution model (Pitzer equations, NaCl and water), (5) the model used by Drioli et al. and (6) the dissociated ion approach (NaCl and water). Four of the six approaches produced very similar results. Moreover, one other exergy calculation method was found to have serious limitations. The findings presented here show that the choice of exergy model can have a significant impact on the results obtained and that considerable care must be taken to select the most suitable approach.

Proceedings of the 36th conference on Winter …, 2004

Scheduling of a semiconductor manufacturing facility is one of the most complex tasks encountered... more Scheduling of a semiconductor manufacturing facility is one of the most complex tasks encountered. Confronted with a high technology product market, semiconductor manufacturing is increasingly more dynamic and competitive in the introduction of new products in shorter time intervals. Photolithography, being one of the processes repeated often, is a fabrication bottleneck. Lot scheduling within photolithography is a challenging activity where substantial improvements in factory performance can be made. The proposed scheduling methodology integrates two common approaches, simulation and artificial intelligence. Using detailed simulation modeling within a structured modeling method, a comprehensive model to characterize the photolithography process was developed. An artificial intelligence scheduler was then developed and integrated with the model with the goal of reducing Work-In-Process (WIP), setup time, and throughput time. The results have shown a significant improvement in lot cycle time as well as tool utilization, improved the throughput time by an average of 15% and is currently in use for scheduling the photolithography process.