The Role of Discrete Event Simulation Techniques in Finite Capacity Scheduling

Discrete event simulation is becoming an established tool in finite capacity scheduling. However, recent work on scheduling systems has concentrated on the development of different modelling approaches and tools, without proper examination of how they can be used to meet business objectives. This paper examines the role of scheduling in improving business performance and suggests possible considerations in the development and implementation of a finite capacity scheduler. It reviews the advantages and limitations of discrete event simulation as a modelling technique for scheduling, and argues the need for further research to develop more versatile tools. A simulation-based scheduling system incorporating bottleneck planning principles to maintain throughput with low inventory is described, as are the experiences gained during its implementation in a medium-sized press shop.     

Competitive dynamics in pharmaceutical markets: A case study in the chronic cardiac disease market

A modelling project involved system dynamics simulation of chronic cardiac disease in Bulgaria, examining the dynamic behaviour of a cardiac drug molecule in the market. The system dynamics model was calibrated using market data sourced from the Bulgarian National Health Care Fund, the Bulgarian Generic Pharmaceutical Association and a market research firm. The main results of the study showed that the timing of access to market was a critical driver in reducing prices and providing wider, as well as more affordable, access for patients to medicinal therapy. Our findings indicate that healthcare authorities may obtain savings while, at the same time, they may provide conditions for more patients to be treated depending on the timing of access to market of new generic drugs.     

A multiple criteria information system for pedagogical evaluation and professional development of teachers

Information systems for the evaluation of pedagogical practices aim to improve teaching activity and encourage the pedagogical development of teachers. The implementation of these systems has been interpreted in different ways, depending on each school’s administration board and/or the person responsible for the evaluation process. This ambiguity (and inherent subjectivity) is a barrier to the principles of transparency, equity and fairness in the pedagogical performance evaluation of teachers. From this premise, the main objective of this paper consists in proposing a multiple criteria information system to support the evaluation of pedagogical practices. By combining cognitive mapping and the measuring attractiveness by a categorical based evaluation technique (MACBETH), our framework allows for the conception of a more transparent evaluation system, bringing new insights to the pedagogical appraisal and professional development of teachers. The strengths and weaknesses of our framework are also discussed.     

Simulation for business process re-engineering: case study of a database management system

This paper describes the use of discrete event simulation in the resource, throughput and content analysis and improvement of a business process in the Iranian Information and Documentation Centre (IRANDOC). The process was initially mapped using Data Flow Diagrams (DFD), and the objectives of the study for a range of users were captured using the Delphi method. The time taken for the tasks in the process were estimated by work study, and the simulation was developed in ServiceModel?. The simulation was valuable in understanding why the current systems were not performing satisfactorily and led to a number of proposals for improvement. This mixed use of hard (simulation) and soft (Delphi) methods proved a fruitful way to gain process improvements and could be employed in other organisations.     

Complex economic dynamics: Chaotic saddle, crisis and intermittency

Complex economic dynamics is studied by a forced oscillator model of business cycles. The technique of numerical modeling is applied to characterize the fundamental properties of complex economic systems which exhibit multiscale and multistability behaviors, as well as coexistence of order and chaos. In particular, we focus on the dynamics and structure of unstable periodic orbits and chaotic saddles within a periodic window of the bifurcation diagram, at the onset of a saddle-node bifurcation and of an attractor merging crisis, and in the chaotic regions associated with type-I intermittency and crisis-induced intermittency, in non-linear economic cycles. Inside a periodic window, chaotic saddles are responsible for the transient motion preceding convergence to a periodic or a chaotic attractor. The links between chaotic saddles, crisis and intermittency in complex economic dynamics are discussed. We show that a chaotic attractor is composed of chaotic saddles and unstable periodic orbits located in the gap regions of chaotic saddles. Non-linear modeling of economic chaotic saddle, crisis and intermittency can improve our understanding of the dynamics of financial intermittency observed in stock market and foreign exchange market. Characterization of the complex dynamics of economic systems is a powerful tool for pattern recognition and forecasting of business and financial cycles, as well as for optimization of management strategy and decision technology.     

The effect of the nature of the liabilities on the solvency and maturity payouts of a UK life office fund: a stochastic evaluation

Several studies have shown that a simulation model of participating life insurance business must reflect explicitly the major decisions which are left to the discretion of management. In the UK these decisions include asset allocation and bonus distribution. It is also common in the UK to use premium bases which do not explicitly account for the expectation that a terminal bonus will be paid, while using a uniform system of reversionary bonus for business of all terms. Here, we show that this results in short-term business being at much greater risk of insolvency than long-term business, under a variety of investment strategies. Our main purpose is to study the effect of small changes to the parameters of the investment model used on the outcomes described above. For this purpose we compare results using two versions of the Wilkie model (Wilkie, A.D., 1986. A stochastic investment model for actuarial use. Transactions of the Faculty of Actuaries 39, 341–403, Wilkie, A.D., 1995. More on a stochastic asset model for actuarial use. British Actuarial Journal 1, 1–168.) We show that small changes in the variances of the economic series modelled have a marked impact on solvency, while changes in maturity values are mostly the result of a small change in the rate of real dividend growth.     

Neural nets in a group decision process

In recent years there has been some interest in applying Artificial Adaptive Agents (AAA) to the study of complex adaptive systems, especially economic systems. Neural networks are frequently employed as AAA. Artificial neural nets mimic certain aspects of the physical structure and information processing of the human brain and their most attractive characteristic is their ability to learn a pattern from a given set of examples. In this study, we investigated the ability of neural nets to model human behavior in a group decision process. The context was a market entry game with a linear payoff function and binary decisions. The players had to decide, for each trial, whether or not to enter a market whose capacity is public knowledge. Human behavior in this situation has been modeled and empirically validated by the Nash equilibrium for noncooperative n-person games. A simulation of the game was performed with neural nets instead of human subjects. The nets were trained using the results of the games in which they participated. The simulation with groups of neural nets exhibits phenomena very similar to those observed in groups of human players. Received February 2000     

Examining prospective mathematics teachers' pedagogical content knowledge on fractions in terms of students' mistakes

The aim of the study is to examine prospective mathematics teachers’ pedagogical content knowledge in terms of knowledge of understanding students and knowledge of instructional strategies which are the subcomponents of pedagogical content knowledge. The participants of this research consist of 98 prospective teachers who are studying in two universities in Turkey. The participants were selected with the purposive sampling method which is one of the non-random sampling methods. Case study method, which is based on the qualitative research approach, was used. The answers given by secondary school students to fraction-related open-ended questions in the study of Soylu and Soylu were used as the data collection tool. The obtained data were analyzed via the content analysis technique. The analyses showed that the prospective mathematics teachers’ pedagogical content knowledge on fractions was not at an adequate level in identifying and correcting students’ errors. However, it was observed that the prospective teachers experienced more difficulty in the knowledge of instructional strategies compared to the knowledge of understanding students.     

SIMULEX — a multiattribute DSS to solve rescheduling problems

Knowledge-based systems (KBS) can help to make simulation available to a large group of users. We want to exemplify this by describing a decision support system (DSS) for short term rescheduling in manufacturing called SIMULEX. It couples expert systems, simulation, and a multiattribute decision making (MADM) procedure to assist the production manager. After an introduction to simulation as a problem solving tool, the current problems in production control and the goals of the project are described. Then, the various components of SIMULEX are explained in some detail. Some results and a short outlook conclude the article.     

Development of a miniature robot based on experience that is inspired by nature

In this paper, using nature as inspiration, micro robot is designed. Utilizing the basic principles of the biological systems motion and modern software tools Matlab Simulink and SolidWorks a mathematical analysis and simulation of its mechanism for movement are developed. It will be shown that the Bionics along with use of modern software can be a powerful engineering tool. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Using economic X control chart design methodology to estimate and optimize machine efficiency in the case of multimachine assignments

Estimation and optimization of machine efficiency in the case of multi machine assignments is a difficult issue for some industries such as textile industry, due to the machine interference. Although the problem is not new, the solutions proposed are not full satisfactory. For example, the analytical formulas are not suitable for high number of machines; queuing theory approaches are complex and impractical for mill managers. On the other hand, simulation methodology seems to be a perfect tool to estimate and analyze; however, the simulation package programs are expensive and are not suitable for systematic optimization. In this paper, Duncan's economic control chart design methodology is proposed as an alternative way for one of the oldest industrial problems. This study shows that this new approach is a more efficient solution to this stochastic problem. Copyright © 2009 John Wiley & Sons, Ltd.     

The Use of Soft Systems Methodology in the Development of a Simulation of Out-patient Services at Watford General Hospital

The effective and efficient provision of out-patient services may be assisted by the appropriate use of discrete event simulation. Resource use must be carefully monitored and suitable control actions must be taken, if service level and quality are to be maintained, whilst keeping cost increases to a minimum. In itself, simulation provides no means by which system activities may be identified. The use of soft systems methodology as a tool to aid in activity identification for simulation modelling is being explored. The investigation focuses on the effects the participative nature of soft systems methodology has on the acceptability of a simulation model. This case study forms part of a research objective of developing a generic approach to link soft systems methodology and simulation. Its aim is to provide analysts and managers with a process which may assist in planning strategies for health care.     

Reducing the graphical user interface of a dynamic geometry system

Graphical user interfaces (GUIs) of dynamic or interactive geometry software (DGS) allow users to interact with the DGS by using a computer mouse. Clicking on a GUI icon performs an action like choosing a construction tool or manipulating an object. For novices, it may be difficult to recognize and recall the icons needed for a task. Learning mathematics and learning the use of a dynamic geometry system at the same time could lead to cognitive overload. Several DGS systems try to solve this problem by offering different GUIs: expert users can choose between a wide range of icons, while for novice users only the most basic icons are presented. By preselecting a specific set of icons, a teacher can adapt a DGS to create a tool, which meets specific pedagogical demands. Two experiments were conducted to investigate the effects of reducing GUIs of a DGS. In experiment 1, which was carried out with full and reduced interfaces of the DGS Cinderella, the eye movements and gaze points of the users were recorded by an eye tracker. The time taken by users to find given icons in different types of interfaces was measured. In experiment 2, students measured the angle sums of polygons using the DGS Cinderella with a full or a reduced interface. No significant effects of GUI reduction were found in both experiments. The results are discussed and ideas for future research are presented.     

On Hankel and Mellin transforms

The development of three positively evaluated social science computer simulations is reviewed as a basis for comments on current debates about the utility of social simulations: Colby's treatment of neurotic belief dynamics, the Abelson‐Bernstein simulation of fluoridation controversies and Alker's projected computer model of United Nations parliamentary diplomacy.

In each case, the non‐analytical nature of the computer model is not due to unusual mathematical ineptitude but derived from evidence contradicting the empirical validity of more elegant formalizations employing, respectively, formal logics and graph theory, differential equation systems, game theory and statistical models. Several analytically challenging problems concerning validity assessment, the nature of deep structure, and the policy‐relevant performance characteristics of complex models are mentioned.

Moral, political, philosophical and pedagogical issues derive from the empirically provisional nature of all simulation versions of frequently controversial social theories, the frequent mystification of mathematical/computerized ‘results’, and the uneven practical utility and accessibility of social simulations. Conflicts between the ethical perspectives of doctors, public officials, citizens and natural scientists are suggested in terms of a humanoid interpretation of complex simulation systems. The pedagogical use of mixed or complementary developmental, philosophical, mathematical and scientific approaches is advocated to minimize potential abuses of social simulation research.

     

浙江交通运输与经济发展的相关性分析

本文运用灰色系统建模理论和数量经济的方法对浙江省交通运输与经济发展之间的关系进行相关性分析,研究交通运输业内各重要指标对经济发展的内在联系.这对充分发挥交通运输对经济活动中的重要作用,研究交通运输与经济的协调发展都将提供必要的参考依据.     

Application of stochastic analytic hierarchy process within a domestic appliance manufacturer

The stochastic analytic hierarchy process (SAHP) provides a mechanism for achieving more effective selection of alternatives in the form of considering multi and conflicting criteria using quantitative and qualitative information under uncertainty. In contrast to the traditional analytic hierarchy process, the SAHP uses probabilistic distributions to incorporate uncertainty that people have in converging their judgements of preferences into a Likert scale. The vector of priorities is calculated using Monte Carlo simulation, the final rankings are analysed for rank reversal using statistical analysis, and managerial aspects are introduced systematically. The present paper demonstrates an application of the SAHP in a world-class domestic appliance manufacturer. The case study was carried out by strictly following a disciplined and organized methodology for applying the SAHP developed by the authors. The results of this study were encouraging to key personnel within the company, establishing a greater opportunity to explore the applications of the SAHP in other core business processes.     

Nonlinear dynamical analysis and demonstration on Chinese business cycle

This paper is devoted to the study of a generalized Chinese business cycle by nonlinear dynamical method. Firstly, we establish a Chinese economic cycle model based on Goodwin model, and then discuss the point estimation and confidence interval of the model’s parameter values based on the historical data. At last, we study the bifurcation and chaotic behavior of the model. The results show that the marginal consumption has great influence on the development of Chinese economic. The Chinese economic development will run into the stable periodic wave when the marginal consumer is greater than 0.5. Furthermore, the greater the marginal consumption is, the more stable the economic development is.     

Impact of the cost of the time resource on efficiency of economic processes

The objective of the paper is to simulate behavior of economic agents with a special emphasis on the use of the time resource in economic processes. The case studied is from the fishing industry. With simulations, the study analyzes the behavior of economic agents as they lead their processes through time. The paper estimates the value of time in a fishery operation, and shows that the time cost is essential in clarifying some phenomena in the economic behavior of agents. Among the conclusions is that the difference in economic efficiency between strong and weak ownership is due to difference in time costs. The secondary goal of the paper is to develop a simulation tool for analyzing a range of problems in the fishing industry, ranging from decision situations onboard fishing vessels to serving as a tool for fishery managers and legislators.     

A generic environment for modelling future launch operations—GEM-FLO: a success story in generic modelling

Several NASA programs have been established to study and improve the current launch capability to meet the need for more aggressive space exploration in the future. Numerous launch systems have been proposed by different government and commercial organizations with the potential goal of replacing the Space Shuttle. NASA must evaluate new designs and technologies with the objective of improving upon today's Shuttle cost, performance, and turnaround time, before the government or commercial organizations pursue the large undertaking of a new launch system. To address this issue, the Generic Simulation Environment for Modelling Future Launch Operations (GEM-FLO) was developed to accurately predict processing turnaround times and other effectiveness criteria and support making key business and program decisions. GEM-FLO utilizes a generic modelling paradigm to provide a single platform for modelling different designs, which helped significantly cut the cost of these studies. This paper documents a success story in generic simulation modelling.