Past Challenges and the Future of Discrete Event Simulation

The American scientist Carl Sagan once said: “You have to know the past to understand the present.” We argue that having a meaningful dialogue on the future of simulation requires a baseline understanding of previous discussions on its future. For this paper, we conduct a review of the discrete event simulation (DES) literature that focuses on its future to understand better the path that DES has been following, both in terms of who is using simulation and what directions they think DES should take. Our review involves a qualitative literature review of DES and a quantitative bibliometric analysis of the Modeling and Simulation (M&S) literature. The results from the bibliometric study imply that demographics of the M&S community are rapidly changing, both in terms of the nations that use M&S and the academic disciplines from which new simulationists hail. This change in demographics has the potential to help aid the community face some of its future challenges. Our qualitative literature review indicates that DES still faces some significant challenges: these include integrating human behavior; using simulation for exploration, not replication; determining return on investment; and communication issues across a splitting community

A Review of Approaches for Sensing, Understanding, and Improving Occupancy-Related Energy-Use Behaviors in Commercial Buildings

Buildings currently account for 30–40 percent of total global energy consumption. In particular, commercial buildings are responsible for about 12 percent of global energy use and 21 percent of the United States’ energy use, and the energy demand of this sector continues to grow faster than other sectors. This increasing rate therefore raises a critical concern about improving the energy performance of commercial buildings. Recently, researchers have investigated ways in which understanding and improving occupants’ energy-consuming behaviors could function as a cost-effective approach to decreasing commercial buildings’ energy demands. The objective of this paper is to present a detailed, up-to-date review of various algorithms, models, and techniques employed in the pursuit of understanding and improving occupants’ energy-use behaviors in commercial buildings. Previous related studies are introduced and three main approaches are identified: (1) monitoring occupant-specific energy consumption; (2) Simulating occupant energy consumption behavior; and (3) improving occupant energy consumption behavior. The first approach employs intrusive and non-intrusive load-monitoring techniques to estimate the energy use of individual occupants. The second approach models diverse characteristics related to occupants’ energy-consuming behaviors in order to assess and predict such characteristics’ impacts on the energy performance of commercial buildings; this approach mostly utilizes agent-based modeling techniques to simulate actions and interactions between occupants and their built environment. The third approach employs occupancy-focused interventions to change occupants’ energy-use characteristics. Based on the detailed review of each approach, critical issues and current gaps in knowledge in the existing literature are discussed, and directions for future research opportunities in this field are provided

Network Simulation Cradle

This thesis proposes the use of real world network stacks instead of protocol abstractions in a network simulator, bringing the actual code used in computer systems inside the simulator and allowing for greater simulation accuracy. Specifically, a framework called the Network Simulation Cradle is created that supports the kernel source code from FreeBSD, OpenBSD and Linux to make the network stacks from these systems available to the popular network simulator ns-2. Simulating with these real world network stacks reveals situations where the result differs significantly from ns-2's TCP models. The simulated network stacks are able to be directly compared to the same operating system running on an actual machine, making validation simple. When measuring the packet traces produced on a test network and in simulation the results are nearly identical, a level of accuracy previously unavailable using traditional TCP simulation models. The results of simulations run comparing ns-2 TCP models and our framework are presented in this dissertation along with validation studies of our framework showing how closely simulation resembles real world computers. Using real world stacks to simulate TCP is a complementary approach to using the existing TCP models and provides an extra level of validation. This way of simulating TCP and other protocols provides the network researcher or engineer new possibilities. One example is using the framework as a protocol development environment, which allows user-level development of protocols with a standard set of reproducible tests, the ability to test scenarios which are costly or impossible to build physically, and being able to trace and debug the protocol code without affecting results

Serious Games as a Validation Tool for Decision Support System in Disaster Management—Case of PREDIS

Validation of Decision Support System (DSS) through simulation games or serious game is one way of validating the cognitive capability models through expert opinion. Here, this technique is used to validate PREDIS as a model for DISaster response supplier selection (PREDIS), previously introduced by authors. This DSS is a combination of a PREDictive component (PRED) for predicting the disaster human impact, an estimation component to Estimate the DISaster (EDIS) needs and optimised for supplier based resource allocation. This paper aims to test the suitability of the PREDIS model further for decision-making in the disaster situation. A quasi-experiment design embedded in a participatory simulation game is conducted to compare the opinion of equal sample of 22 experts and non-experts. The following questions are put forward. First, “Does PREDIS model assists the decision makers to make the same decisions faster”. Second, “Does the PREDIS model assist the non-experts as simulated decision makers to decide like an expert”. Using AHP weights of decision makers’ preference as well as borda counts, the decisions are compared. The result shows that PREDIS helps to reduce the decision making time by experts and non-experts within 6 h after the disaster strike, instead of 72 h. It also assist 71% of the non-expert to make similar de-cision as experts. In summary, the PREDIS model has two major capabilities. It enables the experts and non-experts to predict the disaster results immediately and using the widely available data. It also enables the non-experts to decide almost the same as the experts; either in predicting the human impact of the disaster and estimating the needs or in selecting suitable suppliers

Calibrating a System Dynamic Model Within an Integrative Framework to Test Foreign Policy Choices

Political science uses international relations (IR) theory to explain state-actor political behavior. Research suggests that this theoretical framework can inform a predictive model incorporating features of systems dynamics (SD) and agent based (AB) modeling. The Foreign Policy Model (ForPol) herein applies Alexander Y. Lubyansky\u27s (2014) SD model for macro-political behavior to represent behaviors between real systems and mental models. While verifying and validating the resulting SD/AB/IR holistic model requires an extensive comprehensive research agenda, the present work will take a closer examination at input parameter calibration and conducting typical runs of the SD portion of the model as a first step in the testing, verification and validation process of the proposed integrative model. This thesis proposes incorporating an AB paradigm drawn from work by Claudio Cioffi-Revilla (2009), Edward P. MacKerrow (2003), David L. Rousseau (2006), Joshua M. Epstein and Robert Axtell (1996) as a future hybrid extension. The model applies a SD approach for the modeling of macro-political aggregate behavior. Therefore, the deep analysis of the SD portion of ForPol is modeled and calibrated in Vensim, using empirical data from the 1967 Arab-Israeli Six Day War as a pilot. Interactions within the model actualize Choucri, et. al. (2006), definition of state stability and agent behavior aspects of Cioffi-Revilla\u27s (2009) SimPol polity model. Following calibration results discussion, the present work closes with consideration of future research directions

Air Force Institute of Technology Research Report 2013

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems Engineering and Management, Operational Sciences, Mathematics, Statistics and Engineering Physics

MODELLING VIRTUAL ENVIRONMENT FOR ADVANCED NAVAL SIMULATION

This thesis proposes a new virtual simulation environment designed as element of an interoperable federation of simulator to support the investigation of complex scenarios over the Extended Maritime Framework (EMF). Extended Maritime Framework is six spaces environment (Underwater, Water surface, Ground, Air, Space, and Cyberspace) where parties involved in Joint Naval Operations act. The amount of unmanned vehicles involved in the simulation arise the importance of the Communication modelling, thus the relevance of Cyberspace. The research is applied to complex cases (one applied to deep waters and one to coast and littoral protection) as examples to validate this approach; these cases involve different kind of traditional assets (e.g. satellites, helicopters, ships, submarines, underwater sensor infrastructure, etc.) interact dynamically and collaborate with new autonomous systems (i.e. AUV, Gliders, USV and UAV). The use of virtual simulation is devoted to support validation of new concepts and investigation of collaborative engineering solutions by providing a virtual representation of the current situation; this approach support the creation of dynamic interoperable immersive framework that could support training for Man in the Loop, education and tactical decision introducing the Man on the Loop concepts. The research and development of the Autonomous Underwater Vehicles requires continuous testing so a time effective approach can result a very useful tool. In this context the simulation can be useful to better understand the behaviour of Unmanned Vehicles and to avoid useless experimentations and their costs finding problems before doing them. This research project proposes the creation of a virtual environment with the aim to see and understand a Joint Naval Scenario. The study will be focusing especially on the integration of Autonomous Systems with traditional assets; the proposed simulation deals especially with collaborative operation involving different types of Autonomous Underwater Vehicles (AUV), Unmanned Surface Vehicles (USV) and UAV (Unmanned Aerial Vehicle). The author develops an interoperable virtual simulation devoted to present the overall situation for supervision considering also the sensor capabilities, communications and mission effectiveness that results dependent of the different asset interaction over a complex heterogeneous network. The aim of this research is to develop a flexible virtual simulation solution as crucial element of an HLA federation able to address the complexity of Extended Maritime Framework (EMF). Indeed this new generation of marine interoperable simulation is a strategic advantage for investigating the problems related to the operational use of autonomous systems and to finding new ways to use them respect to different scenarios. The research deal with the creation of two scenarios, one related to military operations and another one on coastal and littoral protection where the virtual simulation propose the overall situation and allows to navigate into the virtual world considering the complex physics affecting movement, perception, interaction and communication. By this approach, it becomes evident the capability to identify, by experimental analysis within the virtual world, the new solutions in terms of engineering and technological configuration of the different systems and vehicles as well as new operational models and tactics to address the specific mission environment. The case of study is a maritime scenario with a representation of heterogeneous network frameworks that involves multiple vehicles both naval and aerial including AUVs, USVs, gliders, helicopter, ships, submarines, satellite, buoys and sensors. For the sake of clarity aerial communications will be represented divided from underwater ones. A connection point for the latter will be set on the keel line of surface vessels representing communication happening via acoustic modem. To represent limits in underwater communications, underwater signals have been considerably slowed down in order to have a more realistic comparison with aerial ones. A maximum communication distance is set, beyond which no communication can take place. To ensure interoperability the HLA Standard (IEEE 1516 evolved) is adopted to federate other simulators so to allow its extensibility for other case studies. Two different scenarios are modelled in 3D visualization: Open Water and Port Protection. The first one aims to simulate interactions between traditional assets in Extended Maritime Framework (EMF) such as satellite, navy ships, submarines, NATO Research Vessels (NRVs), helicopters, with new generation unmanned assets as AUV, Gliders, UAV, USV and the mutual advantage the subjects involved in the scenario can have; in other word, the increase in persistence, interoperability and efficacy. The second scenario models the behaviour of unmanned assets, an AUV and an USV, patrolling a harbour to find possible threats. This aims to develop an algorithm to lead patrolling path toward an optimum, guaranteeing a high probability of success in the safest way reducing human involvement in the scenario. End users of the simulation face a graphical 3D representation of the scenario where assets would be represented. He can moves in the scenario through a Free Camera in Graphic User Interface (GUI) configured to entitle users to move around the scene and observe the 3D sea scenario. In this way, players are able to move freely in the synthetic environment in order to choose the best perspective of the scene. The work is intended to provide a valid tool to evaluate the defencelessness of on-shore and offshore critical infrastructures that could includes the use of new technologies to take care of security best and preserve themselves against disasters both on economical and environmental ones

Increasing the Value of Data in Production Systems

A digital transformation is taking place, where information is available about almost anything, changing how work is performed and anticipated. More digitized information enabled by the digital technologies is supporting businesses to measure more about their processes and thereby also to know more. The same transformation is taking place in the manufacturing domain, which is referred to as the fourth industrial revolution. There are numerous national initiatives to approach the fourth industrial revolution and the aim is to make the manufacturing industry more digitalized and increase competitiveness. Digitalization is making more information about processes available, but it is first when data is informing decisions in an organization it will add value.\ua0 Along with all the benefits and potential values of the digital transformation, much of the attention has been on the technologies and systems that can enable the digitalization. Less focus has been spent on how the technologies and systems should be put into practice in the organizations to fulfill the needs of the manufacturing domain. New knowledge about digital technologies in combination with already existing expertise about manufacturing processes is needed. The aim of the thesis is to identify the value of data for decision-making. The approach outlined in this thesis will identify the values gained from the raw data itself and from the further processed data to provide decision support. The distinction between these two forms of data, raw data and further processed data, is important because it is believed that these can provide different values and that they involve different challenges for the organization. 5G telecommunication and 3D laser scanning serve as digital technologies in this thesis to enable more data in digital form on a production system. 5G was used for connecting a machine enabling the collection of data about critical machine components. 3D laser scanning was used to collect the spatial data in a factory environment. The results show that more data available about the connected machine provide values to the organization to know the status of the machine, be able to compare the designed system against the behavior in the real-world setting, a better understanding of the process and to learn from data. Spatial data provide values by being able to represent the production system as-is in a very accurate and photorealistic way. The values identified from having more data available for the decision support were in the daily operations to know the condition of the machine, for the manufacturing organization to plan proactive actions, and for the production engineer to understand the behavior of the designed system in the real-world context. The spatial data could both support when making changes to the physical setup and when planning the design of the factory environment in an offline mode.The initial studies presented in this thesis supported to build the understanding of the current practice of data as decision support in the production organization. The understanding that data should support decision-making was high, but the data availability in the current state was scarce or of poor quality. This strengthens the aim of the thesis, to provide results that can show the value of data for decision-making. “To measure more is to know more” (McAffee and Brynjolfsson, 2012) is a statement serving as a cornerstone throughout this thesis and has also been justified by the results presented to answer research question 1 and 2. Data enabled by digital technologies can support multiple roles in the manufacturing organization throughout the different phases of the production system, for example in daily operations and maintenance

Earth resources: A continuing bibliography with indexes (issue 47)

This bibliography lists 524 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1 and September 30, 1985. Emphasis is placed on the use of remote sensing and geophysical instrumentation in spacecraft and aircraft to survey and inventory natural resources and urban areas. Subject matter is grouped according to agriculture and forestry, environmental changes and cultural resources, geodesy and cartography, geology and mineral resources, hydrology and water management, data processing and distribution systems, instrumentation and sensors, and economical analysis