International Journal of Simulation and Process Modelling (25 papers in press)
A new semantic annotation approach for software vulnerability source code
by Chi Zhang, Jinfu Chen, Lei Zhang
Abstract: An efficient semantic annotation approach is proposed to annotate software vulnerability source code based on the Vulnerability Code Semantic Description Language (VCSDL) in this paper. A set of general annotation frameworks is proposed for two basic components: basic description information of vulnerability and vulnerability source code description information in the language. Specific annotation methods are studied for these two components, according to the annotation method of the basic description information of vulnerability. Also, the corresponding attribute in the VCSDL document structure is extracted to determine the labelling of the basic information of the vulnerability. While, according to the vulnerability source code information, the semantic annotation of the source code information of the vulnerability is implemented. The experimental results show that the proposed semantic annotation approach has a better effectiveness on the annotation of datasets with a simple code structure and a smaller scale. The success rate and accuracy of the proposed annotation are higher and the false positive rate and false negative rate are lower.
Keywords: software vulnerability; semantic annotation; vulnerability source code; vulnerability detection.
Path-based modelling of business processes
by Wilhelm Nüßer
Abstract: Modelling business processes as stochastic processes has a long tradition. Most models focus on the dynamics of the complete state of the process. In this article we propose an approach that concentrates on the stochastic paths of measurable quantities such as KPIs. Using this concept, a strong analogy to current results in statistical physics is exposed that leads to a general expression for the entropy of a business process as well as results quantifying the performance loss in processes due to fluctuations. Finally, path probabilities and averages of KPIs of a process are given in terms of business constraints expressed as variational principles.
Keywords: stochastic processes; business processes modelling; simulation; entropy; path probabilities; fluctuations.
Numerical simulation for fractional Phi-4 equation using homotopy Sumudu approach
by Abedel-Kareem Alomari, Gufran Darabseh, Mohammad Al-Jamal, Ramzi AlBadarneh
Abstract: In this study, we use the homotopy analysis method and the Sumudu transform to find the solution of fractional order partial differential equations. We focus primarily on the employment of the method for solving the fractional Phi-4 equation in one-dimensional spatial domain. The method can be extended easily for more general nonlinear equations. Convergence and error analysis are given. Numerical experiments show that the method is both effective and accurate, and suits such type of applications.
Keywords: Sumudu transform; homotopy analysis method; Phi-4 equation; convergence; unique solution.
A new transformation approach for complex systems modelling and simulation: application to an industrial control system
by Noureddine Seddari, Sofiane Boukelkoul, Abdelghani Bouras, Mohamed Belaoued, Mohammed Redjimi
Abstract: Owing to the increasing importance of complex systems, the problem of modelling and simulation of these systems, their approaches and solutions has been studied extensively these last years. In this paper, we present a novel approach to modelling and simulation of discrete event dynamic systems (DEDS), based on the combination of DEVS (Discrete Event Systems Specification) and AGR (Agent Group Role). In this study, the DEVS atomic models are transformed into agents and the DEVS coupled models into groups of agents. Thus, we provide a set of procedures and functions that allow the systematic transformation from DEVS into AGR models in order to be implemented in multiagent platforms. The proposed approach is validated by a case study, an application in the water supply used in natural gas liquefaction process.
Keywords: complex systems; discrete event dynamic systems; discrete event systems specification; modelling and simulation; agent/group/role model.
Service-oriented architecture-based design of bank-ATM and its verification with Petri net
by Amar Nath, Santanu Kumar Rath
Abstract: In the present era, IT-enabled business applications are very much observed to be pervasive and felt to be essential to manage an organisation. An organisation needs to update and upgrade its strategies to meet the challenges by adopting an IT-enabled solution to meet the agile customer requirements and market demand. An organisation has to embrace and underline technology that can be updated and modified without any severe bottlenecks. Service-Oriented Architecture (SOA) is one of the various architectural styles that provide agility to the organisation. SOA can help to meet different changes in requirements, viz., service composition, model-driven development, and service virtualisation. This paper illustrates the application of SOA in designing and implementing Automated Teller Machine (ATM) services, helpful in banking transactions. An ATM is a unit in the banking system, which is an embedded system that works on a distributed architecture. The incorporation of various services and their orchestration is implemented by using the Business Process Execution Language (BPEL) module under the OpenESB framework. However, in a complex and dynamic network environment, it is not easy to guarantee the quality of the BPEL process. So, it is very much essential to develop a proper BPEL process and validate it. In this study, the validation of the BPEL model is carried out by using the Petri net tool. The verification and validation activities are often considered essential to ensure the correctness of the system. The verification results obtained in this study are quite encouraging and prove validity.
Keywords: design of bank-ATM; improving bank-ATM performance; service-oriented architecture; orchestration of bank's services; verification with Petri net.
Miniaturised structure design, modelling and simulation process for active engine mounts
by Pu Wang, Rang-Lin Fan, Zeng-Yao Xing, Wei-Cun Zhang, Quan-Fa Wu
Abstract: Active engine mounts (AEMs) provide an effective solution to further improve the dynamic comfort of passenger cars in noise and vibration, and tend to be miniaturised to reduce the space occupation. This paper focuses on the miniaturised structure design process and the corresponding modelling and simulation. Two types of electromagnetic AEM with oscillating coil actuator or solenoid actuator were compared in space occupation, sealing performance, cost, static load capacity and dynamic performance, and their advantages and disadvantages were summarised, then the optimal design of the miniaturised structure was carried out using finite element modelling and lumped parameter modelling and simulations. The final design of the miniaturised AEM had small dimensions and similar performance to those ordinary AEMs. The miniaturised design and simulation process shown in this article can improve the use of space of AEM while ensuring no performance degradation.
Keywords: active engine mount; miniaturised structure design; oscillating coil actuator; solenoid actuator; finite element model; finite element analysis; performance simulation; powertrain mounting system; automotive.
Simulation-based improvement and modification for performances of hospitals: a case study
by Mohammad Mahdi Ershadi, Ahmad Shafaeizadeh
Abstract: It is necessary to improve the process of service provided to patients owing to increased patient referrals and the variety of patients visiting hospitals. Besides, patients satisfaction is affected by admission methods of the hospital, availability of its resources, admission waiting time, resource wastes, and patient feedback analysis. Therefore, hospital managers need to find current prioritised problems of the hospital and make efforts to solve various therapeutic processes about defined problems using appropriate planning. The prioritised problems are changed after every improvement scenario implementation. Besides, some results are unpredictable owing to the complexity of the hospital. Therefore, a simulation model for all departments of the hospital is proposed with a mathematical model and Taguchi method based on the real data obtained from a hospital. Decreasing resource wastes, the number of patients in the queue, and waiting time in different departments and increasing value-added time, use of resources, and productivity are considered in a mathematical model. All improvement scenarios are evaluated using the proposed model before implementation. Besides, FMEA is used to find the priority of problems and guide improvement teams. By analyzing these scenarios and examining their appropriate combination, a suitable plan designed for prioritised problems. The best improvement scenarios and their effects are defined using the proposed model in this paper. After the actual implementation of them, the difference between reality and the expected condition was less than 10%.
Keywords: discrete event simulation; multi-objective model; hospitals; healthcare system; failure modes and effects analysis.
Multilevel model of spatially allocated time use for takeout food ordering behaviour: a case study
by Jingyao Li, Shengchuan Zhao, Junyi Zhang
Abstract: The development of food delivery services in China has affected peoples space choice of dining. However, few studies have explored the influence of food delivery services in both space and time dimensions. To explore the activity decision-making mechanism which contains space and time dimensions, weekly panel data of spatially allocated time use was collected from undergraduate students. A multilevel spatially allocated time use model was built and based on the principle of utility maximisation. The research results prove that the spatially allocated time use in a whole day is a comprehensive decision-making process under the constraints of cross-sections of multiday survey, life circles and individual attributes. Takeout food ordering behaviour decreases travel demand for dining and other non-essential activities. It is concluded that takeout food ordering behaviour affects individual decision-making of spatially allocated time use in the whole day for both activity content and activity space.
Keywords: multilevel spatially allocated time use model; takeout food ordering behaviour; life circle; panel data of time use; undergraduate students.
Simulation-based decision support for production improvement using ntegrated ergonomic and productivity performance indicators
by Regina Dias Barkokebas, Chelsea Ritter, Mohamed Al-Hussein, Xinming Li
Abstract: Workers in the construction manufacturing industry are exposed to labour-intensive tasks with ergonomic risks, such as forceful exertion and repetitive motion. Owing to increased productivity and repetitive motions resulting from improvement initiatives implemented in offsite construction manufacturing, the investigation of ergonomic risks associated with these changes is needed. In this context, this paper explores an existing panelised floor production line aiming to minimise its ergonomic risks while improving its current productivity rate. Information pertaining to human body motion and productivity is extracted from video recordings. The ergonomic risks associated with specific tasks are identified using two existing ergonomic risk assessment methods: the rapid entire body assessment and the rapid upper limb assessment. A simulation model is used to evaluate various process improvements from the perspective of both ergonomic risks and productivity to support the decision-making process and the prioritisation of process changes in the factory.
Keywords: simulation; process modelling; decision support systems; integrated decision-making processes; production improvements; ergonomics; ergonomic risk assessments; Rapid Entire Body Assessment; REBA; Rapid Upper Limb Assessment; RULA; productivity performance indicators; productivity; offsite construction.
A novel energy conservation method for office building lighting system
by Xinyin Xu, Zhengtian Wu, Baochuan Fu
Abstract: There is a trade-off between human visual performance and energy cost. With an open office as the research object, personalised control with demand and daylight adaptation is considered in a lighting system with multiple illumination devices. Each luminaire and workspace is equipped with illumination sensors and intelligent units. The intelligent dimming model of the lighting system is established, and the optimal dimming value of the luminaire is determined by the constraint control algorithm. The summation of the power consumed by all LED lights and the other devices is used as the objective function. A simulation study was conducted in this research work with DIALux to verify the lighting system and control method. The simulation results show that the proposed control strategy can automatically adjust illumination in real time according to the change of daylight and personal demand.
Keywords: energy conservation; lighting system; constraint control; daylight; simulation.
Middleware for running and debugging Taverna workflows utilising RESTful web services
by Kasikrit Damkliang, Pichaya Tandayya
Abstract: Scientific workflows composed of independent distributed web services allow a user to easily orchestrate dataflows and processing tasks, and handle interoperations with ever more intricate workflows. Typically, these integrated workflows are complex, tightly-coupled, and computational and data intensive because of the workflow invocation management. One side effect is the increase in no-response states as unpredictable events and infrastructure inconsistencies interrupt invocations and cause failure, which are hard and heavy work to manually debug. We propose middleware for running and debugging integrated workflows called RDW utilising the Taverna Server invocation engine which helps the user investigate complex tightly-coupled workflows. Two debugging modes, sequential and parallel, are provided for inspecting the sub-workflows of these integrated workflows. Also, interactions between the user and the server are orchestrated seamlessly by the RDW which manages workflow invocations and provides running and debugging logs. The execution time of our RDW is slightly less than the standard workbench, although the sequential and parallel RDW debugging modes have slightly different running times. RDW offers stable workflow invocation which can significantly reduce the total execution times. The middleware is freely available from our website (http://bioservices.sci.psu.ac.th).
Keywords: invocation management; debugging workflows; result inspection; sequential and parallel debugging; invocation request and handling; scientific workflows; RESTful service.
A seawater RO desalination process driven by dynamic pressure of high-speed seawater droplets
by Yi Xiang, Hui Lu, Qingfen Ma, Mengnan Hao
Abstract: Seawater reverse osmosis (RO) desalination requires driving pressure of 5~8 MPa which is usually offered by the high-pressure pump, the standard device employed in the commercial application, accompanied by a series of problems. To replace the high-pressure pump, a seawater RO desalination technique driven by the dynamic pressure of high-speed seawater droplets is proposed. By theoretical calculation and computational fluid dynamic (CFD) simulation, the required operating conditions for the acquisition of effective impacting seawater droplets were investigated. The results showed that the velocity of the seawater droplets should exceed 70 m/s to achieve the driving pressure of 5 MPa, and simultaneously the air flow velocity should exceed 70 m/s to act as the accelerating medium. The proper size of the accelerated droplets at different air flow velocity within the range of 70~100 m/s was determined not only considering the final velocity of the droplets but also their gravitational settling limitation. In addition, five structures of the RO membrane module were designed and tested, in which the ring-shaped and semicircle-shaped structure exhibited good performance with droplet trap rate greater than 90%. Furthermore, the energy balance of the whole system was analysed, and some constructive suggestions are provided to reduce the energy consumption.
Keywords: seawater desalination; RO technique; dynamic pressure; micro droplets.
Staff scheduling in restaurants where hall staff and robots cooperate
by Takashi Tanizaki, Takeshi Shimmura, Nobutada Fujii, Antonio Oliveira Nzinga Rene
Abstract: The number of companies introducing robots as part of their workforce has been increasing in the recent years. One aim of such companies is to have robots perform low value-added work, and humans perform high value-added work. This objective also generally applies to the service industry. Increasing the number of repeat customers and improving profitability are required in the restaurant business. Furthermore, customer satisfaction (CS), employee satisfaction (ES) and management satisfaction (MS) must be simultaneously improved. However, these three indices are in a trade-off relationship. Based on the abovementioned background, this study proposes the modelling of the staff scheduling problem in restaurants to maximise the weighted sum of the CS, ES, and MS values, where hall staff and robots cooperate, as a set covering problem. The simulation results show that increasing the utilisation of robots for low value-added work and hall staff for high value-added work with customer contact contributes to improvements in CS, ES, and MS in restaurants.
Keywords: staff scheduling; set covering problem; customer satisfaction; employee satisfaction; management satisfaction; process modelling; robot; service industry; restaurant business; simulation.
Simulation-based trajectory tracking coordination of intelligent vehicle with explicit model prediction
by Xingyuan Xu, Liyang Xie, Yin Zhang
Abstract: In this paper a novel approach to trajectory tracking problem of intelligent vehicle is presented. A model-based optimisation algorithm for steering systems with multiple physical constraints is designed. A simplified linear vehicle model is designed in order to improve its real-time ability. Moreover, an offline solving method based on explicit model predictive control (EMPC) is presented to improve the computation speed. The simulation results show the offline solving method has the same tracking performance compared with the online solving problem by YALMIP toolbox. The computation speed is significantly increased.
Keywords: trajectory tracking; explicit model predictive control; EMPC; vehicle modelling; fast solving.
Special Issue on: I3M 2018 Virtual and Augmented Reality in Industry and Logistics
Effectiveness of acoustic AR-TA agent using localised footsteps corresponding to audience members' participating attitudes
by Yuki Kitagishi, Tomoko Yonezawa
Abstract: We investigated an acoustic augmented reality teaching assistant agent (AATA) that walks according to the participating attitudes of the audience members in one-to-many communications. If participants are not focused on the lecture, it is difficult to make them pay attention. To improve such audience members' attitudes, or to draw their attention to the appropriate target, we propose an AATA expressed by moving the localised footsteps using a direction-controllable parametric speaker. We conducted the experiment to evaluate the effectiveness of the AATA. As the results, the participants felt as though someone, the teaching assistant or the lecturer, was walking around them when they perceived the movement of the localised footsteps, and they felt the changes in the AATA's attention and intention to them when the AATA's walking pattern was changed. Accordingly, it is proposed that the AATA's movement can deliver an implicit message to the audience members.
Keywords: one-to-many communication; acoustic AR-TA agent; AATA; lecturer support; audience attention; ambient interaction; parametric speaker; presence of agent; localised sound; education technology.
Enabling outdoor MR capabilities for head mounted displays: a case study
by Christoph Praschl, Oliver Krauss, Gerald A. Zwettler
Abstract: This research work covers generic approaches to determine the outdoor position and orientation of an augmented reality device due to the lack of outdoor capability of depth-sensor or environmental recognition-sensor-based devices currently available on the market. The determination of the orientation is primarily achieved with an attitude heading reference system (AHRS) for a rough estimation. Based on a connected/built-in video camera the accuracy at minor changes of the orientation is enhanced by applying registration to assess the differences in orientation between two video frames, compensating for gyroscope drift errors. The position determination is achieved using GPS with a rover and base station real time kinematic beacon system to achieve enhanced precision. Results show that due to sensor application AR hardware considered for indoor use can be retooled to properly work outdoors, at large distances and even inside running vehicles. Thus, future implementation of applications in various domains is facilitated.
Keywords: mixed reality; outdoor capabilities; orientation; positioning; image registration; modelling MR training scenarios; head mounted displays.
Augmented reality-based solar system for e-magazine with 3-D audio effect
by K. Martin Sagayam, Alex J. Timothy, Chiung Ching Ho, Lawrence Edward Henesey, Robert Bestak
Abstract: Augmented reality (AR) is the newest technology that can be applied to computer vision, audio, video and other sensor-based input projects into 3D vision. It is the backbone for all specialisation of science, medical and engineering concepts. Currently, the reading and learning method through AR-based approaches are quite highly intensive than the existing methods such as papers, books and magazines. This strategy is more expensive but it is more interactive to the user in understanding the root concepts in an effective manner. This paper explores the experiment on solar system revolution pattern along with 3D audio effect in spatial dimension. This novel idea inculcates more vibrancy in the current generation of students to understand the concepts with the clear illustrations and demonstrations.
Keywords: augmented reality; solar system; 3D vision; computer vision; 3D audio effect; 3D modelling.
Interactive design and architecture by using virtual reality, augmented reality and 3D printing
by Nora Argelia Aguilera Gonzalez, Fernando Suarez-Warden, Hector Nahun Quintero Milian, Samira Hosseini
Abstract: New methods of teaching architectural design consider the elements of religion, spirituality, modernism, history and other cultural factors to address the physical, spatial and emotional needs of society. This article presents an educational training that emphasises on these critical elements. This paper describes a basic design course taught to second-semester students in the design and architecture course using virtual reality (VR), augmented reality (AR), and 3D printing to incorporate inner sensations and feelings of a human being in the designs. Applied techniques have transformed the classrooms into interactive spaces where the professors use strategies requiring the participants to work together to achieve the objectives of the course. Acquiring skills to create two-dimensional (2D) and three-dimensional (3D) representations facilitated the final products that meet the needs of the users in multitude of manners. The results of this project demonstrated an increase in spatial visualisation, analysis, and critical thinking among the students. Additionally, 100% of the students showed high level of satisfaction with the course and the experience of using these technological tools in the design and architecture course.
Keywords: educational innovation; spatial visualisation; virtual reality; augmented reality; 3D printing; design process; cultural elements in architectural design.
Special Issue on: I3M 2018 Modelling and Simulation for Sustainable Development in Energy, Industry and Logistics
The cost analysis of a leading optics business in Saudi Arabia
by Ahmed Bakhsh
Abstract: Changing economic situations impose multiple challenges to industries, pushing decision-makers to optimise their processes better than their competitors. Discrete event simulation (DES) is one of the effective tools used by business leaders to enhance organisational performance. The present study used DES to minimise the processing cost of a leading optics business in Saudi Arabia. Data is collected from three branches located in Jeddah city to calculate the operating cost and delivery time of the products. A proposed solution is developed to replace three technical workshops inside every branch with one central workshop in the city. A number of replications are carried out to reach the optimal solution. Cost analysis is done to compare the process cost, delivery time and idle working hours of the two options. A significant reduction is observed in the process cost and delivery time of the products besides increasing the idle working hours of the technicians. These extra working hours can be used in receiving orders from the remaining branches of the organisation to enhance its productivity and profitability.
Keywords: DES; simulation; optics; decision-making.
Discrete-event simulation and data analysis for process flow improvements in a cabinet manufacturing facility
by Osama Mohsen, Sina Abdollahnejad, Narges Sajadfar, Yasser Mohamed, Simaan AbouRizk
Abstract: Project uniqueness and high degrees of customisation have always been challenging characteristics of construction projects and many related operations. This paper describes the simulation of a production line in a cabinet manufacturing facility carried out with the aim of better understanding and improving the production processes particularly associated with mass customisation. Discrete event simulation (DES) using Simphony.NET, a simulation modelling tool developed at the University of Alberta, is used to investigate and analyse an existing facility process. The purpose is to optimise productivity, reduce work-in-progress, and decrease idle time. The cabinet manufacturing factory in the presented study operates multiple production lines, produces different product types, and uses varying materials and finishings. In this specific case study, the simulation model is used to explore the challenges associated with increasing production to satisfy the rising demand for customised products. The result of the simulation study provides valuable information to achieve this goal.
Keywords: discrete-event simulation; cabinet manufacturing; mass customization; construction manufacturing; workflow improvement; modelling; simulation; data analysis.
Dynamic bond graph modelling of a two-phase cooling system with experimental analysis
by Mohamed Kebdani, Geneviève Dauphin-Tanguy
Abstract: The power electronics components are a significant source of heat power, which must be managed in spite of the limitations of conventional cooling systems. In order to surpass these restrictions, an innovative heat transfer system is here investigated: Two-phase Loop Mechanically Pumped (TLMP). An instrumented test rig is built with temperatures, pressures and mass flow rate sensors to analyse the flow response in both steady and transient states. In this work, we focus on the pump-pipes subsystem. The results confirm the systems ability to manage heat power dissipation by maintaining a stable power electronics temperature. In addition, the experiment results validate a thermo-hydraulic model based on bond graph theory. The variables used to simulate phase-change phenomena are: mass enthalpy, temperature and pressure. This modelling allows estimating the influence of external conditions on loop operation. Moreover, it offers sizing prospects for this kind of loop development on-board future missiles.
Keywords: cooling systems; thermal control; bond graphs; dynamic systems modelling; phase change; heat transfers; convection; conduction; turbomachines.
Special Issue on: I3M 2019 Simulation and Process Modelling of Tomorrow How 4.0 is Affecting R&D in Multiple Domains
Mesoscopic simulation model of the logistics system of concentrated sets of urban delivery locations
by David Lajos Sardi, Krisztian Bona
Abstract: In city logistics, the examination of the urban concentrated sets of delivery locations is an important new area. In these sets, there are a relatively large number of stores with significant goods traffic, which generates significant customer traffic, while their logistics systems are not properly designed. Despite all this, city logistics research projects do not specifically target this field. Earlier, only a few subsystems have been examined, so we started to study and model the concentrated sets of delivery locations generally. In our research, a mesoscopic level mathematical and a simulation model was developed in MS Excel, which can clearly show the performances and the costs in the current city logistics system, and the possible savings in the case of new, consolidation-based city logistics systems of the concentrated sets of delivery locations. Based on the results of the simulation runs performed by this model, it is clear that the performances and the emissions can be significantly reduced in the new systems, and the logistics costs of the new system will be less too. Additionally, this simulation model can be applied for the sizing of the city logistics junctions of the new systems and for ranking of these sets.
Keywords: logistics; city logistics; urban logistics; consolidation; modelling; simulation; Excel; mathematical model; topological model.
Integrating physical and virtual game-based simulation for operators training to enhance learning effectiveness: an application in hazardous industrial spaces
by Francesco Longo, Antonio Padovano, Lucia Gazzaneo, Giovanni Mirabelli, Alessandra Ferraro, Marco Pirozzi, Luciano Di Donato
Abstract: Inadequate training and lack of risk awareness are among the main causes of work-related accidents in industrial facilities and during hazardous tasks. Although new learning methods and technological tools, such as Virtual Reality (VR), have been largely deployed, they still do not find implementation on a large scale owing to different shortcomings. As opposed to traditional role-playing games based on long storyboards the trainee needs to complete, this research proposes the concept of 'virtual training pills' (VTPs), i.e. delivering learning content in the form of short educational games by using a common technological platform based on virtual, interactive and immersive reality. An application study has been conducted in the case of 'dead chambers' of a decommissioned nuclear power plant, which are classified as confined and pollution-suspected spaces. These areas represent a crucial and challenging environment for maintenance, regulation, installation of mechanical parts, cleaning, and other activities that in other industrial scenarios would have been normally conducted. The results of a randomised controlled experiment conducted with 14 subjects who were administered a Game Experience Questionnaire (GEQ) at the end of their training session proved the potential of this novel game-based learning approach. Short 'learning pills' have much higher effectiveness and are much more valuable than traditional role-playing games with long storyboards. This work also discusses the benefits of workforce training based on VTPs integrated with live exercises.
Keywords: confined space; game-based learning; virtual reality; simulation; process modelling.
Building a digital twin for IoT smart stores: a case in the retail and apparel industry
by Yasmina Maizi, Ygal Bendavid
Abstract: A Digital Twin (DT) is a digital representation of a physical object, process or system across its lifecycle, creating two similar systems (twins) connected by a permanent real-time data exchange to enable understanding, learning and decision taking. Today DTs are among the highest technological trends and have moved from concept to reality. Although the first implementations were conducted in the manufacturing sector as an enabler of Industry 4.0, their evolution is expected to transform the face of several industries. Even though there has been a considerable growth of interest among the scientific community in the DT concept, its application remains at a cradle stage and research in other sectors such as retail is very limited. Additionally, since an increasing number of companies are implementing Internet of Things (IoT) technologies, they may deploy a DT in the next years, and knowing the realistic impacts of DT on operations management is therefore of great interest. In this research paper, we aim to develop a DT prototype for service-oriented organisations in the retail sector. More specifically, we study the case of implementing a DT in smart stores and assess its impact on daily operations management performance using simulation.
Keywords: digital twin; simulation; retail; RFID technology; IoT.
Simulation-based optimisation for worker cross-training
by Johannes Karder, Andreas Beham, Viktoria A. Hauder, Klaus Altendorfer, Michael Affenzeller
Abstract: Worker cross-training is a problem arising in many companies that involve human work. To perform certain activities, workers are required to possess certain skills. Cross-trained workers possess multiple skills, which enables a more flexible deployment, but also incurs higher costs. Thus, companies seek to balance the available skills such that customer deadlines can be met in a cost-efficient way. In this work, we compare solution approaches for a simulation-based problem formulation with three objectives. We apply evolutionary multi-objective optimisation to a production system scenario with two lines and six workstations. Their performance is compared for a hard scenario where cross-training is essential to achieve high service levels. Results indicate that the algorithms are able to solve this three-objective formulation quite well using the described encoding and operators. Employing this technology at companies could lead to better qualification strategies and a better contribution of qualification efforts to company goals.
Keywords: worker cross-training; workforce qualification; encoding; multi-objective optimisation; NSGA-II; MOEA/D.