Integrating simulation modelling and GIS: spatial decision support systems for evacuation planning

A prototype spatial decision support system (SDSS) has been designed for contingency planning for emergency evacuations which combines simulation techniques with spatial data handling and display capabilities of a geographical information system (GIS). It links together the topographical support and analysis provided by the GIS–ARC/INFO, with a simulation model designed to simulate the dynamics of an evacuation process in detail. Our aim has been to design a SDSS so that it provides an interactive evacuation simulator with dynamic graphics that allows for experimentation with policies by providing rapid feedback from the simulation. The idea is that emergency planners will be able to use the SDSS to experiment with emergency evacuation plans in order to plan for different contingencies. This paper concentrates on the issues involved in designing an effective integration link interface between the GIS and the simulation model when building a SDSS of this type.     

Agent-based simulation of innovation diffusion: a review

Mathematical modeling of innovation diffusion has attracted strong academic interest since the early 1960s. Traditional diffusion models have aimed at empirical generalizations and hence describe the spread of new products parsimoniously at the market level. More recently, agent-based modeling and simulation has increasingly been adopted since it operates on the individual level and, thus, can capture complex emergent phenomena highly relevant in diffusion research. Agent-based methods have been applied in this context both as intuition aids that facilitate theory-building and as tools to analyze real-world scenarios, support management decisions and obtain policy recommendations. This review addresses both streams of research. We critically examine the strengths and limitations of agent-based modeling in the context of innovation diffusion, discuss new insights agent-based models have provided, and outline promising opportunities for future research. The target audience of the paper includes both researchers in marketing interested in new findings from the agent-based modeling literature and researchers who intend to implement agent-based models for their own research endeavors. Accordingly, we also cover pivotal modeling aspects in depth (concerning, e.g., consumer adoption behavior and social influence) and outline existing models in sufficient detail to provide a proper entry point for researchers new to the field.     

Agent-based modeling and simulation of community collective efficacy

Community collective efficacy is an important concept in studying various community problems and in developing community well-beings. While existing research on collective efficacy mainly focuses on building analytical or statistical models from informant survey data, this paper develops a complexity science-informed agent-based model to study the dynamic process of collective efficacy formation in a community. We model the individual level cognitive process for participating in community tasks and simulate the emergent spatial patterns of agents’ collective efficacies in a community. The developed model is based on the self-efficacy theory and Theory of Planned Behavior. Interesting patterns such as spatial segregation has been observed through simulations, and an application of the developed model is presented.     

Agent-based simulation for computational experimentation: Developing an artificial labor market

This paper discusses the creation of an artificial labor market (ALM) as an agent-based simulation model. We trace the development of the ALM by adapting the traditional simulation life cycle into two main parts: the model phase and the simulation phase. In the modeling phase of the life cycle, we focus upon agent representation and specification within the virtual world. In the simulation phase, we discuss the use of scenario planning as the experimentation vehicle. Throughout, we use military recruit market as an example to illustrate the methodology. The benefits of the ALM are (1) it provides a virtual world for continuous computational experimentation, (2) it supports market segmentation by allowing “drilldowns” to finer and finer levels of granularity, and (3) when connected via a common OLAP interface to a “real world” counterpart, it facilitates a tightly integrated, persistent, “sense and respond” decision support functionality.     

Numerical simulation of building evacuation in emergency conditions

In the present work, pedestrian behaviour in crowds is assumed to be a coupled phenomena. Therefore, the use of continuousand individual-models in different regions according to its local density is suggested. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Conceptual modelling for simulation Part II: a framework for conceptual modelling

Following on from the definition of a conceptual model and its requirements laid out in a previous paper, a framework for conceptual modelling is described. The framework consists of five iterative activities: understanding the problem situation, determining the modelling and general project objectives, identifying the model outputs, identify the model inputs, and determining the model content. The framework is demonstrated with a modelling application at a Ford Motor Company engine assembly plant. The paper concludes with a discussion on identifying data requirements from the conceptual model and the assessment of the conceptual model.     

Object-oriented modelling and simulation of a motorcycle

The design of a control oriented motorcycle model for the simulation of two-wheeled vehicles is widely recognized to be a very challenging task, as a complete analytical model is not directly available, due to its complexity and its high sensitivity to parameters' variations. Accordingly, a reliable model should be based on multibody modelling tools endowed with automated symbolic manipulation capabilities. This paper presents a simulation model for the dynamic behaviour of a motorcycle based on the object-oriented modelling paradigm developed in Modelica, within the Dymola environment. Specifically, we illustrate the modular approach to motorcycle modelling and discuss the tire-road interaction model, which is the crucial part of the proposed model. The validity of the proposed simulation model is assessed on real data, measured on an instrumented test vehicle. Further, to perform the verification phase a virtual driver model has been implemented, which allows to track both a roll angle and a target speed profile during different maneuvers. In particular, the behaviour of the driver is modelled as an inverse pendulum, with a rotational degree of freedom along the forward axis. This allows accounting for the driver lean angle, which is necessary to fully capture the real driving behaviour and its effects on the overall vehicle dynamics.     

Conceptual modelling for simulation Part I: definition and requirements

Conceptual modelling is probably the most important aspect of a simulation study. It is also the most difficult and least understood. Over 40 years of simulation research and practice have provided only limited information on how to go about designing a simulation conceptual model. This paper, the first of two, discusses the meaning of conceptual modelling and the requirements of a conceptual model. Founded on existing literature, a definition of a conceptual model is provided. Four requirements of a conceptual model are described: validity, credibility, utility and feasibility. The need to develop the simplest model possible is also discussed. Owing to a paucity of advice on how to design a conceptual model, the need for a conceptual modelling framework is proposed. Built on the foundations laid in this paper, a conceptual modelling framework is described in the paper that follows.     

Amplitude-dependent phenomena of filler-reinforced rubber: Experiments,modelling and simulation

It's a matter of common knowledge, that carbon black-or silica-loaded elastomers show a pronounced nonlinearity when excited with dynamic deformation amplitudes, namely the Payne-effect. Furthermore, several experiments prove a very complex history-dependence and significant recovery-behaviour of this effect. In the present paper, a few experimental results of dynamical measurements on filler-loaded rubber are shown with importance attached to the complicated history dependence. In order to describe the depicted phenomena, a model, based on intrinsic time scales is presented with corresponding simulation results. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Discrete-event modelling of an urban transportation system

The modelling of an urban transportation system is addressed. The transportation network is modelled as an oriented graph in which nodes represent single-mode or intermodal stations, integrating different transportation services. Its characteristics make it suitable to model the network as a Discrete Event System. In introducing the model proposed, attention is paid to the definition of all its components, but particular care is necessary for the identification of the probability distributions of the stochastic variables. The validation procedure performed to check the reliability of the model is described in detail. Some numerical results about a case study are presented and discussed.     

The theory of self-organization and modelling complex urban systems

In this article we focus on the problem the social scientist is confronted with when trying to model the complex and dynamic world he lives and works in, and on the different scientific paradigms of the ‘hard sciences’ which are at his disposition. We further concentrate our attention on the EMUS (=Evolutionary Models of Urban Systems) models which we developed using the concepts of the theory of Self-Organization and which we believe to be capable of unravelling some of the complexity of the real world. We will not dwell on the mathematical foundations of the model, but concentrate on the philosophical basis, some practical considerations about modelling and forecasting and on results we obtained on different spatial scales and in different socio-economic contexts.     

Conceptual modelling and the project process in real simulation projects: a survey of simulation modellers

A survey was used to obtain information on the processes and methods used by simulation experts in real projects. The 102 survey respondents answered questions about their most recent simulation project. This paper presents some of the survey results, focussing mainly on conceptual modelling and the pattern of time allocation to different topics. There are a wide range of findings that include the modellers making changes to the initial conceptual model during subsequent tasks in most of the projects usually by adding complexity, model coding taking on average about twice the time of other topics, and the topics generally occurring in single blocks of time (at the resolution of the survey data collection) but with considerable overlaps. The results give an insight into the way experts approach simulation projects and their problem solving strategies. A potential application is in training novice modellers, particularly in developing ‘craft skills’. The results also provide an empirical basis for further research, especially in conceptual modelling.     

Brief note: thoughts about the essentials of simulation modelling

During the past few years, I have been involved, in one way or another, with developing courses on simulation methods, simulation methodology, and applications of simulation techniques to real world problems. In the course of developing and teaching such courses, a reasonable step-by-step approach to the simulation of real world systems has evolved. This paper represents an attempt to present a “kernel” on the subject and it is not offered as a definitive treatment of the subject, but rather, it is offered in the hopes of stimulating further thinking and refinement.     

System dynamic modelling and simulation of hydrodynamic machines

A graph-theoretic framework for the dynamic simulation of hydrodynamic (both axial and radial flow) machines is presented in this article. The physics based analytical models are developed by considering the dynamics of the hydraulic fluid flow and its interaction with the mechanical components. A linear graph is used to capture the topology of the system and the interconnection of the constituent components. Using the graph-theoretic framework, a dynamic model of an automotive hydrodynamic torque converter is developed to simulate its behaviour under different flow conditions. The ability of the model to capture different features of the torque converter will also be demonstrated by simulation. The simulation results are compared with and validated by experimental results in the literature.     

On the relative leadership property of Stackelberg strategies

The relative leadership property of Stackelberg strategies has been investigated via a scalar nonzero-sum, two-person differential game problem. It is shown that, depending on the parameters of the game, there exist three different types of solutions for his class of games.This work was partially supported by the National Science Foundation, Grant No. GK-31511, and the U.S. Office of Naval Research under the Joint Services Electronics Program, Contract No. N00014-67-A-0298-0006. The author would like to thank Professor Y. C. Ho for several valuable discussions.     

Individual-based modelling and simulation of microbial processes: yeast fermentation and multi-species composting

Controlled microbial activity is the core of many industrial processes. Such dynamic microbial processes must be carefully studied to optimize their application. They are usually tackled by means of continuous mathematical modelling at the population level (top-down). An alternative approach is individual-based modelling (IbM) (bottom-up). INDISIM is a discrete and spatially explicit IbM. It sets the rules that govern each microbe and its interaction with its local environment, as well as the significant environmental processes. Then it performs simulations that include a large number of microbes, and the behaviour of the whole system emerges. The rules are changed to reproduce the behaviour of microbes depending on the system to be studied. Two adaptations of INDISIM to study yeast fermentations and multi-species composting are presented in this article (INDISIM-YEAST and INDISIM-COMP), proof of INDISIM's versatility. A few representative results are also shown.     

Multiscale modelling and simulation of micro machining of titanium

The microscale morphology of micro machined component surfaces is directly connected to the heterogeneous microstructure. The deformation depends on the crystal structure, in case of the considered cp-titanium, the hcp crystal structure. In a first approach the crystal plastic deformation is modeled with isotropic hardening. A visco-plastic evolution law accounts for the rate dependency. The concept of configurational forces is used with the framework of crystal plasticity to model the cutting process of cp-titanium. The setting is implemented into the finite element method. The examples show the effect of the material heterogeneity on the deforamtion behavior and on the related configurational forces. (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)