Reggie Davidrajuh | University of Stavanger (original) (raw)

Papers by Reggie Davidrajuh

Drilling operation is the major cost factor for the industry. Appropriately designed operations a... more Drilling operation is the major cost factor for the industry. Appropriately designed operations are essential for successful drilling. Optimized drilling operations also allow enhanced drilling performance and reduce the drilling cost. This is achieved by increasing the bit life (minimizing premature bit wear), drilling faster that allows reducing drilling time, and also reducing tripping operations. The paper presents two parts. The first part compares the parametric physic-based swab and surge simulation results obtained from Bingham Plastic, Power Law, and Robertson and Stiff models. The aim is to show how the model predictions deviate from each other. Two 80-20 Oil Water ratios (OWR) and two 90-10 OWR oil-based drilling fluids with 1.96 sg and 2.0 sg were considered in vertical- and deviated wells. Simulation results analysis revealed that the deviations depend on the drilling fluid’s physical and rheological parameters as well as the well trajectory. Moreover, the model’s predi...

2022 26th International Conference on Circuits, Systems, Communications and Computers (CSCC)

2022 14th International Conference on Computational Intelligence and Communication Networks (CICN)

Applied Sciences, 2022

Swab and surge pressure fluctuations are decisive during drilling for oil. The axial movement of ... more Swab and surge pressure fluctuations are decisive during drilling for oil. The axial movement of the pipe in the wellbore causes pressure fluctuations in wellbore fluid; these pressure fluctuations can be either positive or negative, corresponding to the direction of the movement of the pipe. For example, if the drill string is lowering down in the borehole, the drop is positive (surge pressure), and if the drill string is pulling out of the hole, the drop is negative (swab pressure). The intensity of these pressure fluctuations depends on the speed of the lowering down (tripping in) or withdrawing the pipe out (tripping out). High tripping speed corresponds to higher pressure fluctuations and can lead to fracturing the well formation. Low tripping speed leads to a slow operation, causing non-productive time, thus increasing the overall well budget. Researchers used mathematical equations and physics to understand the phenomena and have provided many empirical, mathematical, and phy...

Discrete event dynamic systems (DEDS) are prevalent in many areas of engineering, like manufactur... more Discrete event dynamic systems (DEDS) are prevalent in many areas of engineering, like manufacturing, maintenance, distributed computing, etc. Activities or discrete events in DEDS are generally large in numbers, highly parallel, distributed, and highly intertwined. Modeling DEDS systems are further complicated by the fact that the decisions to be made from the model may incorporate inference engines that uses advanced statistical analysis on massive data and may also include fuzzy decisions. This paper talks about development of a new tool for modeling and simulation of DEDS that can satisfy the characteristics mentioned above; the new tool is called General purpose Petri net Simulator (GPenSIM). This paper further presents a recent extension to the new tool, which is the real-time simulation capability.

SpringerBriefs in applied sciences and technology, 2018

This chapter discusses performance evaluation of discrete-event systems with GPenSIM. The topics ... more This chapter discusses performance evaluation of discrete-event systems with GPenSIM. The topics such as P/T Petri nets, marked graphs, and strongly connected components are presented. Also, some of the GPenSIM functions that are available for performance evaluation are presented. These functions can be used to find the flow rate, the existence of bottlenecks and deadlocks, etc.

SpringerBriefs in applied sciences and technology, 2018

This chapter presents two of the functions (tools) that are available in the GPenSIM for the anal... more This chapter presents two of the functions (tools) that are available in the GPenSIM for the analysis of Petri nets: coverability tree and firing sequences. In coverability tree analysis, we determine the states that are reachable from a given initial state. The firing sequence is executing a sequence of transitions, to study the state space generated by the firings.

SpringerBriefs in applied sciences and technology, 2018

This chapter introduces the processor files of the GPenSIM. With the processors, many real-life d... more This chapter introduces the processor files of the GPenSIM. With the processors, many real-life discrete-event systems could be modeled as Petri nets. The processors also give GPenSIM the flexibility it is well known for and the potential for making hybrid Petri net models by combining Petri nets with the other MATLAB Toolboxes (e.g., Fuzzy Logic, Control Systems).

SpringerBriefs in applied sciences and technology, 2018

This chapter presents some of the extensions and restrictions to the P/T Petri nets. GPenSIM supp... more This chapter presents some of the extensions and restrictions to the P/T Petri nets. GPenSIM supports some of these extensions (e.g., colored Petri net, Petri net with inhibitor arc, enabling functions, transitions with priorities) and restrictions (marked graphs, state machines). Due to its flexibility, it is easy to implement the other extensions and restrictions too in GPenSIM.

Lecture notes in mechanical engineering, Oct 20, 2017

In the paper, the production process of liquid soap is analyzed using simulation method. The purp... more In the paper, the production process of liquid soap is analyzed using simulation method. The purpose of the study is to assess the impact of production system modernization. First, the liquid soap production process is modeled after studying the characteristics of the processes. Then, two simulation experiments are conducted based on the developed simulation models of the production line. The results of the experiments are presented and discussed.

Abstract This paper presents a model for greener power generation to satisfy electricity needs of... more Abstract This paper presents a model for greener power generation to satisfy electricity needs of North-east Sri Lanka (NE-SL). With the absence of indigenous fossil fuel and large-scale hydrologic resources, NE-SL depends on the import of fossil fuel for electricity ...

제어로봇시스템학회 국제학술대회 논문집, Aug 1, 2009

Theory of Connection is based on geometry, and has been used to solve many problems in engineerin... more Theory of Connection is based on geometry, and has been used to solve many problems in engineering, economics, and in management. In this paper, firstly, the theory of connection is introduced. Secondly, a toolbox of functions for modeling and simulation is presented; the toolbox is developed for MATLAB platform. Thirdly, a case study is presented on the application of the theory to solve material flow problems. The scope of this paper is limited to introducing and applying the theory of connection. The major contribution of the paper is the introduction of the toolbox with which mathematical modeling and simulations can be done efficiently on an operating platform like MATLAB.

Petri Net Markup Language (PNML) is an XML based interchange format that allows exchange of Petri... more Petri Net Markup Language (PNML) is an XML based interchange format that allows exchange of Petri net models between Petri net tools, thus PNML capability is an inevitable part of newer Petri Net Tools. General Purpose Petri Net Simulator (GPenSIM) is a new Petri net simulator. In addition to the usual Petri Net functions, GPenSIM also possess capabilities like cost calculation and real-time control. However, until recently, GPenSIM did not possess PNML capability. In addition, GPenSIM lacked graphical user interface (GUI) for creating the initial Petri Net model, thus, model creation was done by writing special MATLAB M-files using GPenSIM language. This works presents some scientific details on how PNML capability was incorporated into GPenSIM. This work also shows how the PNML capability enhanced the usefulness of GPenSIM for modeling and simulation of discrete event dynamics systems.

Information Society can be loosely defined as a society integrated by complex communication netwo... more Information Society can be loosely defined as a society integrated by complex communication networks that rapidly develop and exchange information. Information society is becoming an earthly phenomenon and the goal of every country is to ensure that their people achieve the status of information society. Norway is one of the richest countries in the world. But, is Norway also an information society? If so, to what extend? Analyzing these two questions is the scope of this paper. This paper first develops a simple measuring tool and then uses the tool to measure the strength of Norway as an information society. The paper shows that Norway has achieved mixed results in ensuring that its people achieve the status of the digital citizens of an information society.

International journal of simulation: systems, science and technology, May 14, 2022

International journal of simulation: systems, science and technology, Sep 30, 2017

Activity-Oriented Petri Nets (AOPN) is a convenient way of modeling and simulation of discrete ev... more Activity-Oriented Petri Nets (AOPN) is a convenient way of modeling and simulation of discrete event systems when a large number of resources are involved. By the AOPN approach, Petri net models are created by focusing only on the activities and by pushing the resources into the background. As a result, the Petri net obtained by this approach works on a virtual platform and the places of this Petri net seemingly has no relevance to the real-world buffers. In case the places are supposed to represent the buffers, this paper explains how the places can be aligned with the buffers. As this paper focuses on a unique problem in AOPN, it is written in a tutorial style, keeping literature study and relevant works to a minimum.

International journal of simulation: systems, science and technology, Jun 30, 2017

Petri net is a family of modeling formalism; Place-Transition net-the original member of this fam... more Petri net is a family of modeling formalism; Place-Transition net-the original member of this family-though useful as a modeling tool, it often fails to model real-life discrete event systems. This is because it lacks modeling power. There are many extensions proposed to increase the modeling power; however, these extensions while increasing the modeling power they also decrease the decision (analytical) power. Cohesive Place-Transition net with Inhibitor Arcs (CPTI) is an extension which increases the modeling power while retaining the decision power. Hence, to enjoy the analysis capabilities of CPTI nets, one has to first determine whether a given Petri net model satisfies the CPTI constrains. General Purpose Petri Net Simulator (GPenSIM) is a toolbox running on MATLAB platform that is easy to use and extensible. The aim of this paper is to present the data structures and algorithms for implementation of CPTI in GPenSIM.

International journal of simulation: systems, science and technology, Mar 30, 2019

This paper presents an efficient Alpha-algorithm for process mining. Firstly, a short literature ... more This paper presents an efficient Alpha-algorithm for process mining. Firstly, a short literature review is given on the available algorithms for process mining. Secondly, a new polynomial-time algorithm is proposed, which is efficient as it takes only O(LT2 + T3) time, where L and T are the number of traces (rows) of the event log and the total number of unique tasks, respectively. Also, this algorithm is elegant and easy to understand as it mainly manipulates four simple matrices (such as Serial Binary Matrix, Parallel Binary Matrix, input incidence matrix, and output incidence matrix). The operations performed on these matrices are also simple. Thirdly, a case study is given as a proof-of-concept showing the Alpha-algorithm in action. In the case study, from a medium-sized event log, a Petri net model is generated by the proposed algorithm, which is implemented using the General-purpose Petri Net Simulator (GPenSIM).

Advances in intelligent systems and computing, Aug 18, 2017

This paper presents a new approach for modeling discrete manufacturing systems using Petri nets. ... more This paper presents a new approach for modeling discrete manufacturing systems using Petri nets. Starting with the literature review of the classical approaches, this paper describes the new approach known as Activity-Oriented Petri Nets (AOPN). The AOPN approach provides expressive Petri net models that are powerful enough for modeling complex and large-scale manufacturing systems. The AOPN approach provides compact Petri net model too when a large number of resources are used in the manufacturing system. GPenSIM is a software implementation of AOPN on MATLAB platform. Using a flexible manufacturing system as a running example, this paper also shows how a real-life manufacturing system can be modeled and simulated with the GPenSIM software using AOPN approach.

Drilling operation is the major cost factor for the industry. Appropriately designed operations a... more Drilling operation is the major cost factor for the industry. Appropriately designed operations are essential for successful drilling. Optimized drilling operations also allow enhanced drilling performance and reduce the drilling cost. This is achieved by increasing the bit life (minimizing premature bit wear), drilling faster that allows reducing drilling time, and also reducing tripping operations. The paper presents two parts. The first part compares the parametric physic-based swab and surge simulation results obtained from Bingham Plastic, Power Law, and Robertson and Stiff models. The aim is to show how the model predictions deviate from each other. Two 80-20 Oil Water ratios (OWR) and two 90-10 OWR oil-based drilling fluids with 1.96 sg and 2.0 sg were considered in vertical- and deviated wells. Simulation results analysis revealed that the deviations depend on the drilling fluid’s physical and rheological parameters as well as the well trajectory. Moreover, the model’s predi...

2022 26th International Conference on Circuits, Systems, Communications and Computers (CSCC)

2022 14th International Conference on Computational Intelligence and Communication Networks (CICN)

Applied Sciences, 2022

Swab and surge pressure fluctuations are decisive during drilling for oil. The axial movement of ... more Swab and surge pressure fluctuations are decisive during drilling for oil. The axial movement of the pipe in the wellbore causes pressure fluctuations in wellbore fluid; these pressure fluctuations can be either positive or negative, corresponding to the direction of the movement of the pipe. For example, if the drill string is lowering down in the borehole, the drop is positive (surge pressure), and if the drill string is pulling out of the hole, the drop is negative (swab pressure). The intensity of these pressure fluctuations depends on the speed of the lowering down (tripping in) or withdrawing the pipe out (tripping out). High tripping speed corresponds to higher pressure fluctuations and can lead to fracturing the well formation. Low tripping speed leads to a slow operation, causing non-productive time, thus increasing the overall well budget. Researchers used mathematical equations and physics to understand the phenomena and have provided many empirical, mathematical, and phy...

Discrete event dynamic systems (DEDS) are prevalent in many areas of engineering, like manufactur... more Discrete event dynamic systems (DEDS) are prevalent in many areas of engineering, like manufacturing, maintenance, distributed computing, etc. Activities or discrete events in DEDS are generally large in numbers, highly parallel, distributed, and highly intertwined. Modeling DEDS systems are further complicated by the fact that the decisions to be made from the model may incorporate inference engines that uses advanced statistical analysis on massive data and may also include fuzzy decisions. This paper talks about development of a new tool for modeling and simulation of DEDS that can satisfy the characteristics mentioned above; the new tool is called General purpose Petri net Simulator (GPenSIM). This paper further presents a recent extension to the new tool, which is the real-time simulation capability.

SpringerBriefs in applied sciences and technology, 2018

This chapter discusses performance evaluation of discrete-event systems with GPenSIM. The topics ... more This chapter discusses performance evaluation of discrete-event systems with GPenSIM. The topics such as P/T Petri nets, marked graphs, and strongly connected components are presented. Also, some of the GPenSIM functions that are available for performance evaluation are presented. These functions can be used to find the flow rate, the existence of bottlenecks and deadlocks, etc.

SpringerBriefs in applied sciences and technology, 2018

This chapter presents two of the functions (tools) that are available in the GPenSIM for the anal... more This chapter presents two of the functions (tools) that are available in the GPenSIM for the analysis of Petri nets: coverability tree and firing sequences. In coverability tree analysis, we determine the states that are reachable from a given initial state. The firing sequence is executing a sequence of transitions, to study the state space generated by the firings.

SpringerBriefs in applied sciences and technology, 2018

This chapter introduces the processor files of the GPenSIM. With the processors, many real-life d... more This chapter introduces the processor files of the GPenSIM. With the processors, many real-life discrete-event systems could be modeled as Petri nets. The processors also give GPenSIM the flexibility it is well known for and the potential for making hybrid Petri net models by combining Petri nets with the other MATLAB Toolboxes (e.g., Fuzzy Logic, Control Systems).

SpringerBriefs in applied sciences and technology, 2018

This chapter presents some of the extensions and restrictions to the P/T Petri nets. GPenSIM supp... more This chapter presents some of the extensions and restrictions to the P/T Petri nets. GPenSIM supports some of these extensions (e.g., colored Petri net, Petri net with inhibitor arc, enabling functions, transitions with priorities) and restrictions (marked graphs, state machines). Due to its flexibility, it is easy to implement the other extensions and restrictions too in GPenSIM.

Lecture notes in mechanical engineering, Oct 20, 2017

In the paper, the production process of liquid soap is analyzed using simulation method. The purp... more In the paper, the production process of liquid soap is analyzed using simulation method. The purpose of the study is to assess the impact of production system modernization. First, the liquid soap production process is modeled after studying the characteristics of the processes. Then, two simulation experiments are conducted based on the developed simulation models of the production line. The results of the experiments are presented and discussed.

Abstract This paper presents a model for greener power generation to satisfy electricity needs of... more Abstract This paper presents a model for greener power generation to satisfy electricity needs of North-east Sri Lanka (NE-SL). With the absence of indigenous fossil fuel and large-scale hydrologic resources, NE-SL depends on the import of fossil fuel for electricity ...

제어로봇시스템학회 국제학술대회 논문집, Aug 1, 2009

Theory of Connection is based on geometry, and has been used to solve many problems in engineerin... more Theory of Connection is based on geometry, and has been used to solve many problems in engineering, economics, and in management. In this paper, firstly, the theory of connection is introduced. Secondly, a toolbox of functions for modeling and simulation is presented; the toolbox is developed for MATLAB platform. Thirdly, a case study is presented on the application of the theory to solve material flow problems. The scope of this paper is limited to introducing and applying the theory of connection. The major contribution of the paper is the introduction of the toolbox with which mathematical modeling and simulations can be done efficiently on an operating platform like MATLAB.

Petri Net Markup Language (PNML) is an XML based interchange format that allows exchange of Petri... more Petri Net Markup Language (PNML) is an XML based interchange format that allows exchange of Petri net models between Petri net tools, thus PNML capability is an inevitable part of newer Petri Net Tools. General Purpose Petri Net Simulator (GPenSIM) is a new Petri net simulator. In addition to the usual Petri Net functions, GPenSIM also possess capabilities like cost calculation and real-time control. However, until recently, GPenSIM did not possess PNML capability. In addition, GPenSIM lacked graphical user interface (GUI) for creating the initial Petri Net model, thus, model creation was done by writing special MATLAB M-files using GPenSIM language. This works presents some scientific details on how PNML capability was incorporated into GPenSIM. This work also shows how the PNML capability enhanced the usefulness of GPenSIM for modeling and simulation of discrete event dynamics systems.

Information Society can be loosely defined as a society integrated by complex communication netwo... more Information Society can be loosely defined as a society integrated by complex communication networks that rapidly develop and exchange information. Information society is becoming an earthly phenomenon and the goal of every country is to ensure that their people achieve the status of information society. Norway is one of the richest countries in the world. But, is Norway also an information society? If so, to what extend? Analyzing these two questions is the scope of this paper. This paper first develops a simple measuring tool and then uses the tool to measure the strength of Norway as an information society. The paper shows that Norway has achieved mixed results in ensuring that its people achieve the status of the digital citizens of an information society.

International journal of simulation: systems, science and technology, May 14, 2022

International journal of simulation: systems, science and technology, Sep 30, 2017

Activity-Oriented Petri Nets (AOPN) is a convenient way of modeling and simulation of discrete ev... more Activity-Oriented Petri Nets (AOPN) is a convenient way of modeling and simulation of discrete event systems when a large number of resources are involved. By the AOPN approach, Petri net models are created by focusing only on the activities and by pushing the resources into the background. As a result, the Petri net obtained by this approach works on a virtual platform and the places of this Petri net seemingly has no relevance to the real-world buffers. In case the places are supposed to represent the buffers, this paper explains how the places can be aligned with the buffers. As this paper focuses on a unique problem in AOPN, it is written in a tutorial style, keeping literature study and relevant works to a minimum.

International journal of simulation: systems, science and technology, Jun 30, 2017

Petri net is a family of modeling formalism; Place-Transition net-the original member of this fam... more Petri net is a family of modeling formalism; Place-Transition net-the original member of this family-though useful as a modeling tool, it often fails to model real-life discrete event systems. This is because it lacks modeling power. There are many extensions proposed to increase the modeling power; however, these extensions while increasing the modeling power they also decrease the decision (analytical) power. Cohesive Place-Transition net with Inhibitor Arcs (CPTI) is an extension which increases the modeling power while retaining the decision power. Hence, to enjoy the analysis capabilities of CPTI nets, one has to first determine whether a given Petri net model satisfies the CPTI constrains. General Purpose Petri Net Simulator (GPenSIM) is a toolbox running on MATLAB platform that is easy to use and extensible. The aim of this paper is to present the data structures and algorithms for implementation of CPTI in GPenSIM.

International journal of simulation: systems, science and technology, Mar 30, 2019

This paper presents an efficient Alpha-algorithm for process mining. Firstly, a short literature ... more This paper presents an efficient Alpha-algorithm for process mining. Firstly, a short literature review is given on the available algorithms for process mining. Secondly, a new polynomial-time algorithm is proposed, which is efficient as it takes only O(LT2 + T3) time, where L and T are the number of traces (rows) of the event log and the total number of unique tasks, respectively. Also, this algorithm is elegant and easy to understand as it mainly manipulates four simple matrices (such as Serial Binary Matrix, Parallel Binary Matrix, input incidence matrix, and output incidence matrix). The operations performed on these matrices are also simple. Thirdly, a case study is given as a proof-of-concept showing the Alpha-algorithm in action. In the case study, from a medium-sized event log, a Petri net model is generated by the proposed algorithm, which is implemented using the General-purpose Petri Net Simulator (GPenSIM).

Advances in intelligent systems and computing, Aug 18, 2017

This paper presents a new approach for modeling discrete manufacturing systems using Petri nets. ... more This paper presents a new approach for modeling discrete manufacturing systems using Petri nets. Starting with the literature review of the classical approaches, this paper describes the new approach known as Activity-Oriented Petri Nets (AOPN). The AOPN approach provides expressive Petri net models that are powerful enough for modeling complex and large-scale manufacturing systems. The AOPN approach provides compact Petri net model too when a large number of resources are used in the manufacturing system. GPenSIM is a software implementation of AOPN on MATLAB platform. Using a flexible manufacturing system as a running example, this paper also shows how a real-life manufacturing system can be modeled and simulated with the GPenSIM software using AOPN approach.