International Journal of Simulation and Process Modelling (13 papers in press)
- Real-Time Simulation of DEVS Models in CD++
by Gabriel Wainer
Abstract: The CD++ toolkit was developed in order to implement the theoretical concepts specified by the DEVS formalism. The tool allows the execution of both DEVS and Cell-DEVS models. In this work, we present the definition and implementation of a real-time simulator. In such simulations, events must be handled timely and time constraints can be stated and validated accordingly. The new simulation technique allows the interaction between the model and its surrounding environment. Additionally, a non-hierarchical simulation approach is presented and introduced to CD++ in order to reduce the communication overhead.
Keywords: DEVS, real-time DEVS, real-time systems, CD++ toolkit.
- Construction resource scheduling with chaotic particle swarm optimisation
by Zenghui Huang, Hongbo Zhao
Abstract: The traditional methods, such as critical path method and linear programming, have difficulty solving more general scheduling problems, such as resource constrained scheduling problems. Emerging techniques, such as particle swarm optimisation (PSO), have shown advantages in addressing this problem. However, the performance of simple PSO is greatly dependent on its parameters, and bad selection of the parameters often leads to the problem of being trapped in local optima which causes premature convergence. By introducing chaos mapping into the PSO algorithm, we present an updated PSO method addressing the construction resource rescheduling problems. In the proposed approach, the parameters of chaotic PSO have little influence on the performance of the algorithm, and thus make the algorithm more robust. The new method has been examined and tested on a practical problem. The results indicate that the new approach solves the problem at a faster convergence rate and with a better precision, as well.
Keywords: construction management; project management; scheduling; artificial intelligence; particle swarm optimisation
- Simulation of autonomous systems in the extended marine domain
by Alberto Tremori, Angelo Ferrando, Matteo Agresta
Abstract: This paper is focused on the characteristics and goals of an integrated architecture that aims at reproducing joint interoperability among autonomous systems; the paper proposes an experimentation over a scenario developed for the maritime context that uses an innovative simulator. The authors' goal, during such research, consists of identifying requirements related to these simulators so that they accurately take into account the most important elements affecting real operative context. This analysis addresses training and engineering, and it could be further developed for supporting or operation supervision. The general architecture is devoted to integrating such simulators within a federation, together with the approach that has been used in order to carry out this operation, and represent the subjects of this paper. The mission environment has been created with the only goal to test the federation, and similarly simulation architecture and conceptual models are validated through proposed preliminary activities.
Keywords: autonomous systems, simulation, interoperability, intelligent agents
- Infrastructure protection based on heterogenous networks
by Marina Massei, Agostino Bruzzone, Simonluca Poggi
Abstract: This paper presents a modelling approach for mapping cyber defence issues with respect to heterogeneous networks; the research is devoted to develop an agent-driven simulation environment able to analyse this problem considering different layers, including CIS capabilities, operational issues, system architecture, management processes and human factors. The paper analyses a specific case study to validate and verify the proposed modelling approach; the scenario is focused on an heterogeneous network applied to extended maritime environment including Autonomous Underwater Vehicles (AUV), sensors, platforms, vessels, satellites and relevant military assets and threats. The present document uses this case study as example of System of Systems to be simulated including cyber warfare issues to evaluate their impact on operations.
Keywords: cyber defence, interoperable simulation, maritime simulation, heterogeneous networks, autonomous systems
- Modelling and evaluation of investment strategies in human resource for logistics improvement
by Amrita Jhawar, S.K. Garg, Shikha.N. Khera
Abstract: Logistics cost is an important factor that affects the competitiveness of nations as well as firms. High logistics costs and low levels of service are a barrier to trade and foreign direct investment and thus to economic growth. Shortening of production cycles, amplification of competition globally, sharing and outsourcing of production processes, shorter delivery times and a plethora of choices for customers has made logistics as a source of competitive advantage. The success of logistics depends on the quality, qualification, skills and commitment of the employees and to excel in future, firms need to attract, retain and develop individuals with the right skills and capabilities. The paper evaluates various investment strategies for investment in human resources by an Indian-based logistics firm, using system dynamics modelling to study the effect of improvement in human resources on the logistics performance index.
Keywords: system dynamics, simulation, human resources, logistics performance index, modelling, investment, causal loop diagram, reliability, flexibility, safety, delivery time, logistics cost.
- Simulation of lateral transshipment in order delivery under e-commerce environment
by Haibin Liu
Abstract: In this research, we apply a discrete event simulation approach to explore how enterprises on the Chinese mainland make a successful operation with the aid of e-commerce. This paper examines the effects of four proposed kinds of transshipment operation network structures on the performance and service level of organisation under different policies of transshipment and inventory allocation through a series of simulation experiments. Results show that: (1) transshipment can bring a level of profit and service; (2) inventory allocation influences the operating performance; (3) TBA (transshipment based on availability) policy can produce a high level of service, and TIE ((transshipment based on the inventory equalisation)) policy can give high profits; (4) adoption of TBA policy or TIE policy is contingent on different stages of development; (5) an optimal service level and performance can both be acquired at the same time by adjusting the transshipping structure; (6) the 'complete link' transshipping structure is the best in improving the service level, but it can cause more transshipment cost and activity; (7) the 'small-world' transshipping structure is optimal because it can produce the higher profits than any other structure and also approach the service level of 'complete link'; (8) the 'scale-free' transshipping structure should be averted forming in operation.
Keywords: lateral transshipment, discrete event simulation, TBA, TIE
Special Issue on: "I3M 2014 "Modelling and Applied Simulation for the 3rd Millennium Enhancements in Traditional Approaches and Moving towardsÂ Simulation as Service,"
- A simulation optimisation-based approach for team building in cyber security
by Pasquale Legato, Rina Mary Mazza
Abstract: In this study we present a simulation optimisation (SO) approach based on direct search methods applied to cyber security. The problem consists in investigating if and when human resources (i.e. analysts) in a company should i) work alone or ii) work in consultation with teammates when responding to different attack rates and types targeting a predefined set of company cyber assets. The objective of the study is to evaluate overall attack tolerance with respect to system performance degradation and both resource training and knowledge gain. Numerical examples and experiments related to resource assignment and team formation are presented to show how the SO model can support company managers when grappling with a very common decision: make or buy cyber security knowhow.
Keywords: simulation optimisation, cyber security, team formation and collaboration
Special Issue on: "Recent Trends in Process Modelling, Simulation and Control,"
- Modelling and simulation of predictive handover control mechanisms for fast-moving mobile nodes in wireless networks
by Raman Kumar Goyal, Sakshi Kaushal
Abstract: Nowadays, with the growth of wireless technology, the internet can be accessed by small hosts such as cell phones, tablets, etc. Users are engaged in different types of internet applications, such as video and audio streaming and browsing applications, that require continuous connectivity to the internet. When a mobile node (MN) moves to another network, the connection gets interrupted owing to a change in IP address and signal loss. Terminal mobility includes the ability of the network to identify and locate the MN, and the MN should be able to access the services while moving. It consists of location management and handover management. When the MN is moving at high speed from one network to another network, the performance of the Mobile IP (MIP) is degraded as the MN cannot complete the handover within the required time owing to delayed triggering of the handover request. To ensure seamless connectivity without performance degradation, the traditional handover mechanism needs to be enhanced. In this paper, a Media Independent Handover (MIH)-based handover triggering scheme is proposed, based on the mobility prediction of the MN. Router discovery time in MIPv6 is also removed by defining new MIH primitives. The scanning process required for traditional MIH networks is eliminated using an Information Server (IS) that estimates the Received Signal Strength (RSS) of candidate networks based on the location of the MN. Simulation results show that the proposed scheme reduces the handover latency and improves the throughput in homogeneous networks at varying velocities of the MN.
Keywords: communication, MIH, mobility prediction, MIPv6, handover, RSS, LET
- Comparison of subspace and prediction error methods of system identification for cement grinding process
by Venkatesh Sivanandam, Ramkumar Kannan, Seshadhri Srinivasan, Guruprasath Muralidharan
Abstract: Maintaining product quality in the cement grinding process in the presence of clinker heterogeneity is a challenging task. Model Predictive Controllers (MPC) are argued to be one possible solution to handle the variability, and the lack of models that relate clinker heterogeneity with product quality makes the MPC design challenging. This investigation addresses the suitability of two data-driven modelling approaches for cement grinding process - prediction error and subspace identification methods. Data collected from the cement grinding process is used to build a model of the same. The collected data is used to build different candidate state-space models using the prediction error and subspace identification methods. The candidate models were validated using Akaikes information criterion and mean square error to study the suitability of these modelling techniques. The validation tests are used to identify the most suitable candidate models for the prediction error and subspace methods. The models developed in this investigation are inputs to design predictive controllers for cement industries and to assure product quality in the presence of clinker grindability variations.
Keywords: cement grinding process, system identification, state space model, prediction error method, subspace method
Special Issue on: "I3M 2014 "New Advances in Simulation and Process Modelling Integrating New Technologies and Methodologies to Enlarge Simulation Capabilities,"
- Combining DEVS and model-checking: concepts and tools for integrating simulation and analysis
by Bernard Zeigler, James Nutaro, Chungman Seo
Abstract: Our objectives here are to discuss the development of a formal framework that exploits the advantages of the Discrete Event System Specification (DEVS) formalism and builds upon recent extensive work on verification combining DEVS and model checking for hybrid systems. The mathematical concepts within the DEVS formalism encompass a broad class of systems that includes multi-agent discrete event components combined with continuous components such as timed automata, hybrid automata, and systems described by constrained differential equations. Moreover, DEVS offers the ability, via mathematical transformations called system morphisms, to map a system expressed in a formalism suitable for analysis (e.g., timed automata or hybrid automata) into the DEVS formalism for the purpose of simulation. Conversely, it is also possible to go from DEVS to formalism suitable for analysis for the purposes of model checking, symbolic extraction of test cases, reachability, among other analysis tasks. We discuss a probabilistic extension of the FD-DEVS formalism that enables a set of model classes and tools derived from Markov-type models. The MS4 modeling environment provides a suite of tools that support this extension, called FP-DEVS. In this paper we describe these tools and concepts underlying them. We also provide examples of application of these concepts and discuss the open opportunities for research in this direction.
Keywords: DEVS , model-checking, verification, simulation, modeling and simulation tools, Markov models
- Application of mobile devices within distributed simulation-based decision making
by Josef Brozek, Martin Jakes
Abstract: As a consequence of the development of the market with information technology, where users are increasingly inclined towards mobile devices at the expense of conventional stand-alone devices, increasing user literacy in the use of smartphones and tablets, and the increasing computing performance of mobile devices, a study has been created that addresses the potential of using mobile devices in a distributed simulation. The study also focuses on the possibility of applying the various technologies and architectures in a context of using mobile devices in simulation. This article provides overview information about the study itself, but it is strongly focused on technologies and paradigms that were identified as highly perspective. The paper also explains fundamental themes so that the readers could also apply the information in their home environment. Part of the work is an extensive case study carried out in collaboration with a commercial entity.
Keywords: simulation, tablet, smartphone, mobile device, distributed simulation, heterogenic simulation, HLA, simulation-based decision making, decision making.
Special Issue on: "Simulation Modelling and Optimisation of Large-scale Systems,"
- An iterative parametric estimation method for Hammerstein large-scale systems: a simulation study of hydraulic process
by Elloumi Mourad, Kamoun Samira
Abstract: This paper aims at developing an iterative method that permits to estimate the parameters of Single-Input Single-Output (SISO) large-scale nonlinear systems, described by Hammerstein mathematical models. We particularly focus on the dynamic large-scale nonlinear systems, which are made up of several interconnected nonlinear monovariable subsystems. Each subsystem can operate in a stochastic environment and is described by a discrete-time Hammerstein mathematical model with known structure variables (order, delay) and unknown time-varying parameters. The problem formulation is achieved based on the prediction error method and the least-squares techniques. The convergence analysis of the recursive algorithm is provided using the differential equation approach and its performance is illustrated by treating two simulation examples.
Keywords: large-scale nonlinear systems; Stochastic systems; mathematical modelling; Hammerstein models; parametric estimation; convergence analysis; simulation; hydraulic process.
- Hybrid clustering technique of PCA-SM-GHSOM for abnormal and normal classification with quarterly financial ratios of the listed TCM company sector
by Ruicheng Yang
Abstract: By combining principal component analysis (PCA) and the similarity matching (SM) method with growing hierarchical self-organising map (GHSOM), this paper provides a hybrid technique PCA-SM-GHSOM for clustering the quarterly financial data into normal and abnormal groups. For evaluating the performance of this hybrid method, we give some empirical analysis for the listed traditional Chinese medicine (TCM) companies in China. Three stages are proposed for the clustering experiment. First, we use the PCA method to reduce the high dimensions of financial ratios into low dimensions. Secondly, we adopt the cosine similarity computation method to measure the similarity between the considered company and the other companies of the same TCM sector. According to the similarity values, we choose the three best matching companies, and further get the deviation dataset of the considered company. Finally, we put the deviation dataset into the GHSOM system and derive the clustering results. Furthermore, we derive the empirical clustering results with other different techniques that are single GHOM, combination of PCA-GHSOM, combination of SM, and GHSOM. By comparing these experiment results with that of the hybrid technique PCA-SM-GHSOM, we find that the proposed hybrid technique can improve greatly the accuracy for clustering the data into normal and abnormal groups.
Keywords: PCA-SM-GHSOM; cosine similarity; financial ratios; TCM