Discrete-Event Simulation

This paper proposes to combine the 'systems approach' technique with process-oriented modelling and simulation. The process-oriented modelling concept, in which a system is decomposed into a set of component classes, each with a specific data structure, processes and mutual interactions fits well to the general concept of 'systems approach'. The advantages of this are that during the design phase the modelling can be 'problem oriented' and furthermore a hierarchical structure can be designed. Combining this approach with a modern software platform provides opportunities for flexible modelling an reuse of component classes. As an example the modelling of part of a container terminal is shown. An absolute demand on a simulation tool for practice is its speed and the capability to manage large-scale models. A simple benchmark has been worked out in a process-oriented package 'TOMAS', the kernel of which is a fast sequencing mechanism for managing...

Model-based design methodologies are commonly used in industry for the development of complex cyber-physical systems (CPSs). There are many different languages, tools, and formalisms for model-based design, each with its strengths and weaknesses. Instead of accepting some weaknesses of a particular tool, an alternative Communicated by Prof. J. Sztipanovits, M. Broy, and H. Daembkes. This work is partially based on previous work published by the authors [7,8,15], but the contributions presented in this article stand on their own. is to embrace heterogeneity, and to develop tool integration platforms and protocols to leverage the strengths from different environments. A fairly recent attempt in this direction is the functional mock-up interface (FMI) standard that includes support for co-simulation. Although this standard has reached acceptance in industry, it provides only limited support for simulating systems that mix continuous and discrete behavior, which are typical of CPS. This paper identifies the representation of time as a key problem, because the FMI representation does not support well the discrete events that typically occur at the cyber-physical boundary. We analyze alternatives for representing time in hybrid co-simulation and conclude that a superdense model of time using integers only solves many of these problems. We show how an execution engine can pick an adequate time resolution, and how disparities between time representations internal to co-simulated components and the resulting effects of time quantization can be managed. We propose a concrete extension to the FMI standard for supporting hybrid co-simulation that includes integer time, automatic choice of time resolution, and the use of absent signals. We explain how these extensions can be implemented modularly within the frameworks of existing simulation environments.

Tank truck loading operations in fuel distribution terminals have particular characteristics which are challenging to simulate. Demands for different fuel types are correlated rather than independent. In addition, queuing policies which do not address the current state of the terminal may increase equipment idleness and trucks' lead time. We propose a decomposition of the joint probability distribution of fuel types and a procedure to simulate it. We also propose a new queuing policy aimed at reducing equipment idleness and trucks' lead time. The procedures are tested and validated through a discrete-event simulation model of a real fuel distribution terminal. We simulate alternative scenarios in which we increase fuel flow rate as well as the number of loading arms and test a new queuing policy. Results show the effectiveness of the simulation procedure in replicating real performance indicators. Moreover, the proposed idleness-based queuing policy resulted in lower idleness and lead time compared with a first-come-first-served policy.

Abstract: JavaScript is an interpreted language where the important techniques of Object Oriented Programming can be utilized. Some of them are not included directly, so they need additional support. For example inheritance has to be programmed explicitly. A JavaScript programmer is thus making use of a modern language that, together with HTML, supports creation of documents that can contain user-friendly input of validated data, any kind of data processing, and lucid presentation of results. Solutions based on JavaScript and HTML are typically placed on the web and made thus available literally to everybody who has a browser supporting particular versions of these two languages. These capabilities have been applied to create various web-hosted problemsolving tools. Such tools can contain simple and medium-scale simulation models. Several simulation models have already been implemented and placed on the web with very encouraging response. Routines used to create these models, includ...

Mathematics plays a critical role in many modeling and simulation applications, and whenever detailed representations of combat phenomenon are required (e.g., attrition, detection, etc.). The required mathematics can seem daunting, but a wealth of problems relevant to the M&S community can be addressed with efficient numerical algorithms and heuristics. We shall present a small sampling of these methods and relevant examples of their usage. Examples include combat attrition, target engagement, detection, and missile defense. Most of these can be implemented with a spreadsheet for demonstration.

Background and Purpose: The aim of this paper is to present the influence of Industry 4.0 on the development of the new simulation modelling paradigm, embodied by the Digital Twin concept, and examine the adoption of the new paradigm via a multiple case study involving real-life R&D cases involving academia and industry.

Rozdział prezentuje charakterystykę i zastosowanie obiektowej biblioteki CSL# przeznaczonej do budowy modeli układów zdarzeń dyskretnych. Biblioteka CSL# wspomaga tworzenie modeli w zakresie: generacji liczb pseudolosowych, operowania na kolekcjach danych, zarządzania czasem symulacji, wyznaczania statystycznej oceny zmiennych modelu. Przydatność i poprawność narzędzia zweryfikowano realizując symulacje prostych systemów masowej obsługi i komunikacyjnych protokółów sieciowych poprzez porównanie wyników symulacji z rezultatami uzyskanymi analitycznie

Hospitals across the country attempt to evaluate their emergency department patients within 30minutes of arrival. However, wait times often exceed this goal in the late afternoon or during a busy flu season. For very high-volume hospitals in Texas especially metropolitan cities like Dallas, Arlington, Fort Worth, Plano the average wait time before being admitted is 298 minutes while national average is 332 minutes according to U.S Center for Medicare Services.

The nascent wave of disruptive competition in the current business environment brought about by the fourth industrial revolution (Fashion 4.0 or Apparel 4.0) is enormous. Therefore, it is paramount important to apparel industry to be flexible enough to respond quickly to the unstable customers' demand through continuous improvement of their process efficiency and productivity. This study aims at achieving an optimal trouser assembly line balancing using simulation-based optimization via design of experiment. The empirical study is conducted at Southern Range Nyanza Limited (NYTIL) garment facility and a complex trouser assembly line with 72 operations is considered. The discrete event simulation of the trouser assembly line is developed using Arena simulation software. The local optimal solution is obtained from simulation experimentation and is adopted for the optimization process. The OptQuest tool is utilized to solve a single objective function (throughput) optimization problem. The results show that average throughput increases from the existing design (490 pieces per day) to local optimal design (638) and global optimal design (762). Consequently, the line efficiency increases from 61.2% to 79.7% to 95.2% respectively. The high increase in line efficiency and average throughput confirms the suitability assembly line balancing using simulation-based optimization via design of experiment.

Pada tahun 2014, sebuah terminal baru telah dibangun dengan mengusung konsep baru. Terminal tersebut adalah terminal pelabuhan Teluk Lamong. Teluk Lamong adalah pelabuhan pertama dan satu-satunya di Indonesia yang menggunakan konsep “green port”. Salah satu dari konsep tersebut ialah lapangan penyimpanan peti kemas yang menggunakan twin-automatic stacking cranes untuk mengendalikan keseluruhan perpindahan peti kemas di lapangan penyimpanan. Bagaimanapun pertumbuhan arus perpindahan peti kemas di Indonesia secara cepat mengalami peningkatan yaitu mencapai 27,2% sejak tahun 2010-2013. Oleh karena itu, Teluk Lamong ditutut untuk mampu memprediksi jumlah lapangan penyimpanan yang optimum melayani permintaan peti kemas secara akurat, mengingat biaya yang dibutuhkan untuk berinvestasi demi mengembangkan lahan dan membeli twin-ASC baru terbilang sangat mahal. Di samping, Teluk Lamong harus mencegah shortage yang disebabkan container yard tidak dapat menampung peti kemas yang datang. Pada penelitian ini akan dievaluasi kondisi lapangan peti kemas internasional pada saat ini dengan pendekatan simulasi diskrit yang mengakomodasi kompleksitas dan sifat keacakan dari kedatangan peti kemas dan kapal pengangkut. Sehingga, Teluk Lamong dapat memprediksi jumlah lapangan penyimpanan yang optimum dan juga twin-ASC dengan mempertimbangkan turnaround time kapal. Hasilnya menunjukkan bahwa PT Terminal Teluk Lamong sebaiknya menambah 2 unit quay cranes pada saat volume peti kemas internasional mencapai 148416 TEUs per tahun dan beberapa container yard pada saat fase 2

A strategy for adaptive control and energetic optimization of aerobic fermentors was implemented, with both air flow and agitation speed as manipulated variables. This strategy is separable in its components: control, optimization, estimation. We optimized parameter’s estimation (from the usual KLa correlation) using sinusoidal excitation of air flow and agitation speed. We have implemented parameter’s estimation trough recursive least squares algorithm with forgetting factor. We carried separate essays on control, optimization and estimation algorithms. We carried our essays using an original computational simulation environment, with noise and delay generating facilities for data sampling and filtering.

Our results show the convergence and robustness of the estimation algorithm used, improved with use of both forgetting factor and KLa dead-band facilities. Control algorithm used in our work compares favorably with PID using the integrated area criteria for deviation between oxygen molarity and critical molarity (set point). Optimization algorithm clearly reduces energetic consumption, respecting critical molarity. Integration of control, optimization and adaptive algorithms was implemented, but future work is needed for stability. Methods were defined and implemented for stability improvement. We have implemented data acquisition and computer manipulation of air flow and agitation speed for actual fermentors.

This paper focusses upon passenger flow issues within airport terminals and includes all activities occurring between curb-side and boarding. To improve passenger flow and associated planning activities, a simulation framework is developed using Discrete-Event Simulation (DES). The DES is built using ExtendSim V9.2 simulator software from Imagine That. The model can be used to evaluate the efficiency of the outbound operational processes including check-in, security screening, immigration & custom and boarding. It can also assist management to identify potential bottlenecks in the system. The main input of the model is the flight schedule. A case study of the Brisbane international airport was analysed.

The nature of the healthcare system is crucial and requires health authorities worldwide to ensure every decision is made correctly and efficiently. Simulation modeling which is among the decision-making techniques, is generally used to represent the real systems of healthcare for the authorities to evaluate prior to any modification. A holistic understanding of the issues related to simulation types in healthcare is required. This paper reviews and summarizes publications related to various types of computer simulation tools in the healthcare domain, using the Scopus database. Based on healthcare applications and issues, this paper finalized five main types of simulations: 1) discrete-event simulation; 2) system dynamics; 3) agent-based modeling; 4) Monte Carlo simulation; and 5) hybrid systems. All of these types have continued to contribute to healthcare simulation modelling in recent years and more are expected in the future. In general, this review argues that future studies should focus on framework development that will support the selection of simulation types based on the problem.

This paper presents the extension to an ontology-based data model supporting the design and performance evaluation of production systems. This extension aims to link the modeling of the spatial representation of physical objects with the characterization of their states and behavior. Furthermore, the formalization of the performance history of a production system and its components is addressed to capture both the spatial and state evolution of the objects. Such history can be provided by simulation runs or gathered from a monitoring system. A test case is described and then used to show how different software tools can be integrated to support the integrated design and evaluation of a production system.

This case study will focus on human trafficking interventions, but will specifically concentrate on prosecution, which is one particular aspect of the “3P paradigm – Prosecution, Protection, and Prevention, which continues to serve as the fundamental framework used around the world to combat human trafficking” (Trafficking in Persons Report. 2016. 7). This case study is intended to assist in the identification and disruption of organized human trafficking networks, specifically the process of moving victims through border crossings by traffickers by analyzing existing patterns of movements by the traffickers, which can then be used to guide disruptive and intervention strategies by border monitoring organizations.
    This poses the question, can existing crime theories, along with game theory simulations be used to create predictive models of trafficker movements which can be used to predict and then disrupt human trafficking networks?  By using a combination of rational choice theory, agent-based modeling, and discrete event simulation, predictive models can be developed to simulate trafficker movements across a border and to forecast changes in trafficker behaviors and the numbers of victims identified and intercepted by varying the number of monitors, time of day and days of the ​week. This case study is focused on the international border between Nepal and India

JAPROSIM is a well designed library, free and open source that adopts the popular process-interaction worldview. It is implemented in Java programming language allowing deep access to its powerful features and can serve as a basis for the development of dedicated object-oriented simulation environments. The paper presents architecture and major components of the library. The process-interaction world view adopted by JAPROSIM is discussed. A modeling example is given in order to highlight JAPROSIM capabilities. Important features of JAPROSIM are summarized and suggestions for improving our work are given.

Conceptual modeling is of great importance not only to Information Systems and Software Engineering, but also to Simulation Engineering. It is concerned with identifying, analyzing and describing the essen- tial concepts and constraints of a real-world domain with the help of a (diagrammatic) modeling language that is based on a set of basic modeling concepts (forming a metamodel). In this tutorial, we introduce the ontologically well-founded conceptual modeling language Onto-UML and show how to use it for making conceptual simulation models as the basis of model-driven simulation engineering.

Discrete event simulation models define a state transition system, using some form of transition rules, or transition functions. In this paper we propose an ontological account of transition rules based on disposi- tions and causal laws. This account extends our previous presentation of DESO, a foundational ontology of objects and events for discrete event simulation modeling. We also show how the ontological concepts of dispositions and causal laws provide a semantics for the concept of transition rules in conceptual simu- lation modeling languages corresponding to transition functions in simulation languages.

This paper describes important features of JAPROSIM, a free and open source simulation library implemented in Java programming language. It provides a framework for building discrete event simulation models. The process interaction world view adopted by JAPROSIM is discussed. We present the architecture and major components of the simulation library. In order to ascertain important features of JAPROSIM, examples are given. Further motivations are discussed and suggestions for improving our work are given.