International Journal of Simulation and Process Modelling (24 papers in press)
Intelligent cloud-based monitoring system of electricity demand of fused magnesium furnace process
by Jie Yang, Shaowen Lu, Liangyong Wang, Quan Xu
Abstract: We introduce a monitoring system of electricity demand of the fused magnesium furnace (FMF) process. Fused magnesia is commonly used in producing fire-resistant material. The manufacturing process of fused magnesia in an electric arc melting furnace is highly energy intensive. The main purpose of monitoring the electricity power demand is to avoid the demand spikes that may break the limit imposed by local grid operators. We present a data-driven approach to forecasting the event of demand threshold breakout. The monitoring system proposed in this paper employs cloud computing technology to support remote and mobile monitoring. Also, a three-dimensional visual simulation of the manufacturing scene is provided as an auxiliary monitoring function.
Keywords: cloud computing; 3D scene simulation; demand monitoring; fused magnesium furnaces.
The research of net carbon reduction model for CCS-EOR projects and case studies
by D.Y. Zhao
Abstract: This paper develops a calculation model of net carbon reduction for CCS-EOR （CO2 capture and sequestration, Enhanced Oil Recovery）, which is calculated by 1 minus the new generation CO2 by energy consumption during the processes of capture, transportation, injection and the recovery, meanwhile adding the re-injection CO2 content. By taking the CCS-EOR projects with the capacity of 0.5 million tons CO2 per year in the coal-fired power plant, coal chemical plant and chemical fertiliser plant as examples, we calculate the actual emission reductions and energy consumption per ton of CO2 with reference to the current mainstream technology level. The results show that the net carbon reduction values in the two situations without and with recovery process of associated gas are, respectively, 0.4965 and 0.3951, 0.7624 and 0.6610 , 0.7815 and 0.68 tons CO2 with 1 ton CO2 injection, and the energy consumption values are 5.7405 and 6.6117, 2.7095 and 3.5807, 2.49185 and 3.36305 GJ with 1 ton CO2 injection in the three different plants.
Keywords: modelling; CO2 capture and storage process; enhanced oil recovery; net emission reductions.
Modelling and simulation of complex repetitive construction operations
by Essam Zaneldin
Abstract: In an effort to improve productivity and optimise resource use, a simplified activity-on-arrow (AOA) approach is used in this paper to model and simulate real-world repetitive construction operations of high-rise buildings. The objective of the paper is to use simulation to find the optimum combination of construction resources to improve construction productivity and minimise operational cost. In order to achieve the goals of the study, a simulation model for typical floor finishes activities of a high-rise building project was developed. The model was validated through a predefined construction operation. Several model runs were then conducted using different resource combinations. The results were tabulated to arrive at the optimum combination that improves productivity and reduces the operational cost. In addition, the developed model was used to experiment with different resource alternatives and overtime options for one floor and for repetitive floors in order to arrive at the best resource alternatives that provide the optimum solution. The potential of using this approach for resource optimisation of large infrastructure networks was investigated, and possible future extensions to the present study were then discussed.
Keywords: simulation; construction; high-rise buildings; productivity; cost.
Numerical simulation and experimental validation for design improvement of packer rubber
by Hanxiang Wang, Shengshan Chen, Yanxin Liu, Lijun Zhang, Zhenning Zhang
Abstract: As the packer plays an important role in the exploration of low permeability reservoirs, the sealing property of the dual-channel packer is studied in this paper. The finite element analysis software ABAQUS is used to optimise the sealing unit structure of the dual-channel packer. The influences of inner groove shape and structure of shoulder protection on the sealing property are investigated. Based on simulation results, the best inner groove shape and structure of shoulder protection are confirmed. Furthermore, the validity of the simulation results is confirmed by performing experiments, which shows that the dual-channel packer with optimised sealing unit can work reliably in 70 MPa and 170 degree Celsius.
Keywords: packer rubber; sealing property; numerical simulation; experimental validation.
The information age combat model: a vision for a discrete event simulation approach
by Mahmoud Khasawneh, Nevan Shearer, Ghaith Rabadi, Shannon Bowling
Abstract: Network Centric Operations (NCO) has been dubbed the most significant revolution in military affairs (RMA) in the past 200 years. The promise of NCO is based on the notion that information sharing and connectivity is fundamental to the effectiveness of a combat force. This is due to the ability of a properly networked force to self-synchronise as it engages enemy forces. The information age combat model (IACM) is a popular representation of NCO. Previous research at modelling the IACM has focused solely on using agent-based modelling. That work produced significant contributions to the IACM literature. However, it has proven to be computationally expensive. IACM simulations must be sustainable as research into IACM evolves and more NCO complexities are introduced. This research will propose a discrete-event simulation (DES) approach to model the IACM. The paper will present the basis upon which DES was selected for this purpose and will illustrate how the DES approach can provide significant improvements in terms of the time and computational power needed to run IACM simulations.
Keywords: network centric operations; information age combat model; discrete event simulation.
Simulation of microstructure evolution of AZ31 magnesium alloy during indenten-flatten compound deformation technology based on cellular automata
by Zhongtang Wang, Lingyi Wang, Shengdong Gao
Abstract: Indenten-flatten compound deformation technology (IFCDT) is defined, and the characteristics of IFCDT are discussed. Microstructure evolution of dynamic recrystallisation of AZ31 magnesium alloy during IFCDT was simulated by cellular automaton (CA) method. Dynamic recrystallisation of AZ31 magnesium alloy deformed by IFCDT is analysed. Grain shape, distribution, orientation and size are analysed. When holding time is constant, the grain size increases significantly with increasing of deformation temperature. When deformation temperature is constant, the grain size increases slightly with increase of holding time. With the increase of reduction, the grain size clearly decreases. When the reduction is 2 mm, dynamic recrystallisation does not appear. Comparing simulation results with those of experiment, the maximum relative error is 15.4%. It is proved that the CA method may be used to predict the microstructure evolution of AZ31 magnesium alloy during IFCDT.
Keywords: magnesium alloy; AZ31; IFCDT; microstructure evolution; cellular automata.
Crowd evacuation simulation based on emotion contagion
by Xuemei Du, Wu He, Yan Mao
Abstract: Simulation study on evacuation scenarios has an important influence on public safety. Unfortunately, the traditional evacuation-drill approach for emergency situations focuses on the physiological interaction between individuals/crowds, but ignores psychological interaction. In this paper, we present an emotion contagion model that associates components, such as physiological demand, security requirement and personality traits with individual agents comprising a crowd, and produces emergent behaviours in the crowd as a whole. The emotion contagion model realises the interaction of physiological and psychological factors. Personality traits are associated with emotions by using the OCEAN, OCC and PAD models. To reflect the complexity of emotion contagion of crowd, we consider three processes: contagion, update, and decay. We also consider the effect of emotions on the movement. Testing results demonstrate that the proposed method is effective and realistic for simulating the movement of a heterogeneous crowd in emergency situations.
Keywords: simulation; emergency; emotion contagion; OCEAN model; OCC model; PAD model.
Supporting collaborative business processes: a BPaaS approach
by Lai Xu, Paul De Vrieze
Abstract: Collaborative business processes are increasingly driven by business flexibility and agility. Cloud-based business process management services have provided small and medium enterprises (SMEs) with a pay-per-use manner for their daily business needs, i.e. some simple business process applications, e.g. salesforce provides cloud-based CRM to boost SMEs' sales. This raises the question of how cloud-based business process management solutions can support the fast pace of change of business collaborations among business partners. For example, collaborative processes for managing industrial incidents are short term, low frequency processes. This paper proposes an architecture meta-model, which is used to design the concrete architecture and to further analyse the performance of the proposed solution. A real world case of collaborative processes for incident and maintenance notifications is used to explain the design and implementation of the cloud-based solution for supporting collaborative business processes. Service improvement of the new solution and computing power costs are analysed accordingly.
Keywords: business process as a service; incident management; business process mashup; cloud computing; service-oriented computing.
Special Issue on: The Latest Technologies for Building a Smart City
A novel visible-infrared image fusion framework for smart cities
by Zhinqin Zhu, Guanqiu Qi, Yi Chai, Hongpeng Yin, Jian Sun
Abstract: Image fusion technology is widely used in different areas and can integrate complementary and relevant information of source images captured by multiple sensors into a unitary synthetic image. Image fusion technology, as an efficient way to integrate information from multiple images, plays a more and more important role in smart cities. The quality of the fused image affects the accuracy, efficiency, and robustness of the related applications. Existing sparse representation-based image fusion methods consist of overly complete and redundant dictionary learning and sparse coding. However, overly complete and redundant dictionary does not consider the discriminative ability of dictionaries that may seriously affect the image fusion. A good dictionary is the key to a successful image fusion technique. To construct a discriminative dictionary, a novel framework that integrates an image-patches clustering and online dictionary learning methods is proposed for visible-infrared image fusion. The comparison experiments with existing solutions are used to validate and demonstrate the effectiveness of the proposed solution for image fusion.
Keywords: image fusion; sparse representation; dictionary learning; sub-space clustering; smart city.
Container-as-a-service architecture for business workflow
by Ye Tao, Xiaodong Wang, Xiaowei Xu, Guozhu Liu
Abstract: The massive amount of data makes the work of building a smart city more and more data-driven. However, data collection and its analysis in such a large system are often separated and executed by different vendors. Owing to volume, security and privacy reasons, data migration can be difficult. To build a bridge between data owners and data analysers, service migration is applied, which forms the infrastructures, applications and services for different vendors. This paper presents a Container-as-a-Service (CaaS) framework for data processing in a smart city environment. We design and implement a multi-layered container service construction and deployment environment, and we employ the business workflow orchestration technologies in this environment. By using containers, local cluster resources are virtualised and isolated to simplify the creation and deployment of multiple applications autonomously across multiple vendor systems. Inside a container, computational tasks and worker processes are encapsulated into web services, in order to leverage service-based workflow technologies to develop timely and effective workflows for a smart city environment. A use case of smart transportation is studied to validate the usefulness and evaluate the performance of the presented architecture. Results show that the approach can be beneficial to the scientific tasks in regard to its flexibility and re-usability.
Keywords: container; service computing; scientific workflow; BPEL for web services; Hadoop.
Software behaviour analysis method based On behaviour template
by Yingxu Lai, Zenghui Liu, Tao Ye
Abstract: This paper proposes a software behaviour analysis method based on behaviour template (SABT) which, according to the context of source code, builds a behaviour template to detect software malicious behaviour based on a function transfer map and minimum function blocks. Many methods use state transfer diagrams to build software behaviour models. Our method is based on the corresponding relationship between the functions and system call sequence, which ensures accurate detection of malicious behaviour. Compared with traditional methods, such as N-gram, FSA, and Var-gram, SABT can get higher cover rate of code and detect abnormal behaviour more effectively and efficiently.
Keywords: software behaviour, software interrupt, behaviour template, minimum function block
Boundary estimating of urban road network for traffic impact analysis when reconstructing intersections: methodology and evaluation
by Yingying Ma, Ying Zeng
Abstract: Intersections are major points of conflict for road users and the key parts of urban road networks. It is necessary to reconstruct some intersections to improve capacity and safety. A methodology to estimate the boundary of a road network for traffic impact analysis of intersection improvements is discussed in this paper. Firstly, models are presented for two types of degree of correlation. The degree of saturation and free-flow travel time are considered in the model for the degree of correlation between two adjacent intersections, and the degree of correlation between any two intersections in the network is analysed using a Laplacian matrix algorithm. Secondly, a new method to estimating a road network boundary is proposed. Thirdly, two measures are adopted to evaluate the boundary of road networks: the minimum average cut degree of correlation and the minimum traffic influence on intersections outside the boundary. Finally, the method is demonstrated using a city road network. The results of the case study confirm the validity of the proposed approach.
Keywords: boundary estimating, traffic impact analysis, intersection reconstruction, Laplacian matrix
Knowledge extraction based on linked open data for clinical documentation
by Mazen Alobaidi, Khalid Mahmood, Susan Sabra
Abstract: Smart cities are becoming a reality in the near future to transform many sectors and activities in our lives. Smart city systems, such as healthcare systems, will have new functionality to improve the quality of life of its citizens. Electronic health records are an essential component of healthcare systems. They are valuable for medical research, but much of the information is recorded as unstructured free text. Knowledge extraction from unstructured text in electronic health records is a problem that is well-documented but still not totally resolved. Knowledge extraction is very challenging because medical language has ungrammatical and fragmented constructions. We have implemented a unique framework knowledge extraction based on linked open data for clinical documentation (KE-LODC) that generates accurate and high quality triples transforming unstructured text from clinical documentation into well-defined and ready-to-use linked open data for diagnosis and treatment. We used Name Entity Recognition and Disambiguation (NERD) because it proved to be highly more precise than other available tools in entity recognition. Our framework proved to produce highly qualified big number of triple candidates, which improves the likelihood of better classification. Also, we evaluate our framework by comparing its precision and recall with two benchmark algorithms. The results show that KE-LODC performs better.
Keywords: healthcare, smart city, linked open data; semantic web; knowledge extraction;
Special Issue on: ACECS-2016 Advances and Applications of Process Modelling and Simulation
Modelling and hardware co-simulation of a quadrotor unmanned aerial vehicle
by Soufiene Bouallegue, Rabii Fessi
Abstract: This paper deals with the modelling and hardware (HW) co-simulation of a Quadrotor Vertical Take-Off and Landing (VTOL) type of Unmanned Aerial Vehicle (UAV). The developed HW co-simulation platform is based on a reconfigurable I/O (RIO) board of National Instruments (NI) Company, called sbRIO-9636, and a host PC with a Real-Time Operating System (RTOS). The Control Design and Simulation (CDSim) module of LabVIEW environment, as well as an established Network Streams data communication protocol, are used to emulate and co-simulate all flight dynamics within a Processor-In-the-Loop (PIL) framework. The flight motion principle of the quadrotor, i.e. lift, rotation and translation, is firstly described as a function of changes in the angular speed of the rotors. All aerodynamic forces and moments of such a vehicle are then described within an inertial earth frame, and a nonlinear dynamical model is established thanks to the Newton-Euler formalism. The dynamics of the propellers' brushless DC motors, accelerometer and gyroscope types of sensor are also modelled and co-simulated in order to complete the established model of the studied VTOL rotorcraft. HW simulations are carried out and compared with those obtained with software (SW) simulations in order to show the effectiveness of the proposed PIL co-simulation strategy.
Keywords: quadrotor UAV; modelling; aerodynamic effects; rotors and sensors dynamics; Newton-Euler equations; PIL co-simulation; NI single-board RIO; LabVIEW.
Artificial neural networks for acquisition and processing of sensors data in a radiotherapy application
by Kheireddine Lamamra
Abstract: This paper presents a practical aspect of work that we have planned for several steps. It describes the acquisition and processing of coded data from temperature sensors of type MS6503 used in radiotherapy rooms of the hospital PMCC (Hospital Pierre and Marie Curie Centre). The aim is to acquire and check remotely the temperatures of rooms to trigger alarms and their control thereafter in order to avoid mistakes of manipulation which are deadly for patients if they happen or arise. For this, a system modelling is made before proceeding to the implementation in practice. During the implementation, several problems have occurred such as the legibility of the received data that has been encrypted. To overcome this problem, an artificial neural networks type of Multi-Layer Perceptron (MLP) is used to acquire and decrypt the temperature data received from the sensors placed in the treatment rooms. The obtained results show that the neural network used has decrypted well the received data, hence this technique has been implemented in the realised solution.
Keywords: data acquisition and processing; temperature sensor; radiotherapy room control; artificial neural network; modelling.
Continuous Petri nets and hybrid automata: two bisimilar models for the simulation of positive systems
by Latefa Ghomri, Hassane Alla
Abstract: Petri nets (PNs) are a well-known modelling tool for discrete event systems. Continuous PN were introduced in order to avoid the combinatory explosion of the number of states, when considering real life systems. The constant speed continuous Petri nets (CCPN) where constant maximal firing speeds are associated with transitions allow very fast simulations. They can be used to model discrete events systems; in that case, they constitute an approximation, which is often satisfactory. They can also model positive continuous systems. Hybrid automata (HA) are a less compact and expressive model, but, they can be used to perform powerful analysis. In this paper, we first present the continuous PN and its modelling advantages. Then we present the main contribution of this paper, that is a structural translation algorithm from a CCPN into a HA. The goal of this translation algorithm is to combine advantages of both tools. The first one is an elegant modelling tool; with the second one, it is possible to compute the reachable state space. The translation algorithm is structural in the sense that it does not depend on the initial marking of the Petri net. We present the principal characteristics of the CCPN and the HA, and we prove the timed bisimilarity between the two models. Then it will be possible to deduce properties of the CCPN from the HA. An example of a manufacturing system is used throughout the paper to illustrate the different results, and a water supply system is presented as a more complex example.
Keywords: discrete event systems modelling; constant speed continuous Petri nets; hybrid automata; bisimulation.
Modelling and simulation of analytical approach to handle real-time traffic in VoIP network
by Sakshi Kaushal, Harish Kumar, Sarbjeet Singh, Sundarapandian Vaidyanathan, Jasleen Kaur, Shubhani Aggarwal
Abstract: In recent years, Internet Protocol (IP) has become a good choice over Public Switched Telephone Network (PSTN). A Voice over IP (VoIP) communication supports a number of users with an acceptable voice quality. VoIP implementation uses hard IP phones and soft IP phones, does not rely on a traditional PBX and uses Softswitch for call signalling, access control, etc. The Erlang B model is used to determine the number of trunks in a circuit-switched network and find traffic intensity and grade of service. This paper uses an extension of the Erlang B model for traffic engineering of VoIP, i.e., Extended Erlang B model. The main purpose for Extended Erlang B is that has better efficiency to handle the percentage of blocked calls by choosing a threshold value (). We propose a new measurement scheme based on an extended Erlang B model using FreeSWITCH to simulate and analyse VoIP traffic. Simulations are done in the QualNet 7.3 Network simulator using SIP protocol for VoIP traffic. We compare our version with the original definition of the Erlang B model and present further results from simulations. Experiments are conducted based on different voice codecs such as G.711, G.729A and G.723.1 for measuring packetisation intervals and for calculating bandwidth. The proposed scheme is also analysed for other QoS parameters, i.e, jitter, end-to-end delay and mean opinion score.
Keywords: VoIP; SIP; Softswitch; call admission control; traffic load measurement; Erlang B model.
Special Issue on: Integrating Modelling and Simulation Tools and Methodologies in Real-World Complex Systems for Solving Multidisciplinary Problems
Computer-aided support for the temperature control in buildings
by Borut Zupančič
Abstract: The paper briefly describes the Modelica model of a cubic room with one window. The 'physical' model was then implemented as a Modelica (Dymola) block in Matlab-Simulink environment. Simulink was used for the realisation of different control schemes, which were 'manually' and 'automatically' optimised. The experiments show that the synergetic combination of Matlab-Simulink and Dymola-Modelica environments is an efficient and powerful approach giving the possibility to realise several important goals: realisation preserving modelling in Modelica, efficient simulation with Simulink and many possibilities for control system design and optimisation using basic Matlab and appropriate Matlab toolboxes. However, the experiences with Modelica modelling taught us that Modelica models become rather complex, and therefore model reduction techniques in order to obtain usable and efficient models are desired. The last part of the paper briefly describes some research activities in this area and also our contributions.
Keywords: object oriented modelling; multi-domain modelling; thermal flows; radiation flows; temperature control; control design; PID control; optimisation; model reduction; Modelica
A divide and conquer approach for simulating an airport system
by Paolo Maria Scala, Miguel Mujica Mota, Nico Ed Bock
Abstract: Airport capacity, expressed as the maximum number of air traffic movements
that can be accommodated during a given period of time under given conditions, has
become a hard constraint to the air transportation, owing to the scarcity of resources on the ground and restrictions in the airspace. Usually the problem of capacity at airports is studied by separating airspace operations from ground operations, but it is evident that the two areas are tied to each other. This work aims at developing a simulation model that takes into account both airspace and ground operations. The approach used is a divide and conquer approach, which allows the combination of four different models. The four models refer to the airside, and airspace operations. This approach allows to evaluate the system from different angles depending on the scope of the study, the results show the analytic potential of this approach.
Keywords: simulation model; airport ground operations; airspace operations; divide and conquer approach; data driven decisions.
Extending Sim# for simulation-based optimisation of semi-automated machinery
by Johannes Karder, Andreas Scheibenpflug, Andreas Beham, Stefan Wagner, Michael Affenzeller
Abstract: Model building is a fundamental task in simulation-based optimisation. In this paper we demonstrate the application of Sim# in combination with HeuristicLab to optimise semi-automated machinery. On top of Sim#, custom simulation extensions have been implemented and are used to create a simulation model of real world machinery. These extensions enable the design of simulation components that can be reused within different simulation models. This allows to easily create multiple model implementations that reflect different designs of a machine by using a combination of already existing and adapted components. The resulting model is used as an evaluation function for single- and multi-objective optimisation using HeuristicLab. Results for different optimisation targets, e.g. job order, and quality criteria such as set-up time are compared.
Keywords: simulation-based optimisation, genetic algorithms, machinery, Sim#, HeuristicLab
Modular construction of compact Petri net models
by Juan Ignacio Latorre-Biel, Emilio Jimenez-Macias, Jorge Luis Garcia-Alcaraz, Juan Carlos Saenz-Díez Muro, Julio Blanco-Fernandez, Mercedes Perez De La Parte
Abstract: The use of modelling formalisms for the design of discrete event systems presents many advantages, such as the possibility of structural analysis of the model or performance evaluation. However, the difficulty of the process to obtain an appropriate model of the system requires the use of methodologies to ease the work of the designers. In this paper, two main subjects are discussed. On the one hand, the modular construction of Petri nets alleviates the design process by the use of blocks that can be assembled to build up a complete Petri net model. On the other hand, the development of decision support systems may require the assessment of the performance and properties of complete models obtained from different combinations of modular blocks. The formalism of the alternatives aggregation Petri net may help in the development of compact and efficient models that may reduce the use of scarce computer resources.
Keywords: modular Petri nets; alternatives aggregation Petri nets; decision support systems; performance evaluation.
The Industrial Internet of Things and technological innovation in its applications for resources optimisation
by Albino Ribeiro Neto, Maira Fernanda Gizotti Ribeiro, Gerson Gomes Cunha, Luiz Landau
Abstract: This paper presents a study on the use of the Industrial Internet of Things (IIoT), the use of IIoT in the current Brazilian industry context, its basic differences from the Internet of Things (IoT) and its expansion possibilities, pointing out some challenges related to a new approach within industry. The complex interconnection that is made possible through the IIoT is able to optimise resources and reduce exponentially the costs of production processes in most stages and is gradually changing the direction of society in labour relations. These advances in manufacturing processes are feasible as the IIoT is not simply inserting intelligence into equipment, but allowing interconnection, reconfiguring functions and anticipating loss of productivity or failures that might occur in real time. Within this context, the IIoT can be understood as a broad and complex concept that encompasses asset and performance management areas, availability of increased data and intelligent corporate control. To implement this, it is necessary to integrate the most diverse devices, standards, technologies and systems efficiently. All this automation is called 'smart manufacturing' and enables continuous improvement in processes, increased productivity by eliminating gaps and through the use of modelling and simulation, which enables operators to test and optimise processes and products still in the design phase, consequently decreasing costs and time of creation.
Keywords: Industrial Internet of Things; Internet of Things; radiofrequency identification; interconnection; network; sensors; industry; devices; big analogue data; wireless; cloud computing; digital services; smart manufacturing.
An intelligent serious game for a multi-device cultural heritage experience
by Francesco Longo, Letizia Nicoletti, Antonio Padovano, Marco Vetrano
Abstract: To date, digital technologies applied to cultural heritage have been mainly devoted to the reconstruction of the original appearance of artefacts and of the museum itself, thus implementing the mere concept of a virtual museum. Apart from some isolated cases, museums, and cultural institutions in general, are not so inclined to open out to virtual reality (VR) technologies because they offer the user a detached look at the art collection without actually delivering any cultural and educational content. This research work aims at presenting an innovative multi-device application based on the concept of Intelligent Serious Games (ISG). The combination of the educational potential of Serious Games (SG) with Intelligent Agents (IA), which will drive the evolution of the played scenario in accordance with the initial users' profiling and to the sequence of events generated during the museum tour, will create new patterns and promote new strategies for cultural content dissemination and fruition.
Keywords: cultural heritage; serious games; intelligent agents; museums; virtual reality; education.
Special Issue on: Integrating Modeling & Simulation tools and methodologies in real-world complex systems for solving multidisciplinary problems
An empirical investigation of comparative performance of approximate and exact corrections of the bias in Crostons method in forecasting lumpy demand
by Adriano Solis, Francesco Longo, Somnath Mukhopadhyay, Letizia Nicoletti
Abstract: A positive bias in Crostons method, which had been developed to forecast intermittent demand, was reported by Syntetos and Boylan. They proposed an approximate correction. Subsequently, Shale, Boylan, and Johnston proposed an exact correction. Both corrections were derived analytically. The mathematical analysis establishes the superiority of the exact correction over both Crostons method and the approximate correction. We empirically investigate whether or not there are significant improvements in statistical forecast accuracy as well as inventory control performance obtained by applying the approximate or exact correction when forecasting lumpy demand. Using extensive simulation experiments, we find overall superior forecast accuracy of the bias correction methods over both simple exponential smoothing and Crostons methods. However, the exact correction yielded the same or only marginally better accuracy measures compared with the approximate correction. Moreover, in terms of inventory control performance, we observe marginal differences in inventory on hand and backlogs.
Keywords: forecasting; time series; inventory; modelling and simulation; lumpy demand.