Which is more appropriate: a multi-perspective comparison between systems dynamics and discrete event simulation

System Dynamics (SD) and Discrete Event Simulation (DES) are two established simulation tech-niques for simulating the dynamics of a system. Both have been widely used in modelling business de-cisions. This paper presents meta-comparison between the two approaches based on literature survey. Upon reviewing the existing literature it has been identified that existing comparisons could be classi-fied under three main perspectives: Systems perspective, Problems perspective and Methodology per-spective. The nature of system and nature of problem have been argued as primary factors for decid-ing modelling methodology. Therefore SD and DES comparisons have been classified on the basis of systems, problems and inherent aspects and capabilities of both modelling methods. It has been ar-gued that development of sound models need fit between system, problem and methodology. The suc-cess of model depends on it’s technical soundness as well as it’s successful implementation. In order to develop successful models this vision has been further extended to incorporate stakeholders, re-sources and time

Managing Vulnerabilities of Tactical Wireless RF Network Systems: A Case Study

Organisations and individuals benefit when wireless networks are protected. After assessing the risks associated with wireless technologies, organisations can reduce the risks by applying countermeasures to address specific threats and vulnerabilities. These countermeasures include management, operational and technical controls. While these countermeasures will not prevent all penetrations and adverse events, they can be effective in reducing many of the common risks associated with wireless RF networks. Among engineers dealing with different scaled and interconnected engineering systems, such as tactical wireless RF communication systems, there is a growing need for a means of analysing complex adaptive systems. We propose a methodology based on the systematic resolution of complex issues to manage the vulnerabilities of tactical wireless RF systems. There are is a need to assemble and balance the results of any successful measure, showing how well each solution meets the system’s objectives. The uncertain arguments used and other test results are combined using a form of mathematical theory for their analysis. Systems engineering thinking supports design decisions and enables decision‐makers to manage and assess the support for each solution. In these circumstances, complexity management arises from the many interacting and conflicting requirements of an increasing range of possible parameters. There may not be a single ‘right’ solution, only a satisfactory set of resolutions which this system helps to facilitate. Smart and innovative performance matrixes are introduced using a mathematical Bayesian network to manage, model, calculate and analyse all the potential vulnerability paths in wireless RF networks

Approaches to integrated strategic/tactical forest planning

Traditionally forest planning is divided into a hierarchy of planning phases. Strategic planning is conducted to make decisions about sustainable harvest levels while taking into account legislation and policy issues. Within the frame of the strategic plan, the purpose of tactical planning is to schedule harvest operations to specific areas in the immediate few years and on a finer time scale than in the strategic plan. The operative phase focuses on scheduling harvest crews on a monthly or weekly basis, truck scheduling and choosing bucking instructions. Decisions at each level are to a varying degree supported by computerized tools. A problem that may arise when planning is divided into levels and that is noted in the literature focusing on decision support tools is that solutions at one level may be inconsistent with the results of another level. When moving from the strategic plan to the tactical plan, three sources of inconsistencies are often present; spatial discrepancies, temporal discrepancies and discrepancies due to different levels of constraint. The models used in the papers presented in this thesis approaches two of these discrepancies. To address the spatial discrepancies, the same spatial resolution has been used at both levels, i.e., stands. Temporal discrepancies are addressed by modelling the tactical and strategic issues simultaneously. Integrated approaches can yield large models. One way of circumventing this is to aggregate time and/or space. The first paper addresses the consequences of temporal aggregation in the strategic part of a mixed integer programming integrated strategic/tactical model. For reference, linear programming based strategic models are also used. The results of the first paper provide information on what temporal resolutions could be used and indicate that outputs from strategic and integrated plans are not particularly affected by the number of equal length strategic periods when more than five periods, i.e. about 20 year period length, are used. The approach used in the first paper could produce models that are very large, and the second paper provides a two-stage procedure that can reduce the number of variables and preserve the allocation of stands to the first 10 years provided by a linear programming based strategic plan, while concentrating tactical harvest activities using a penalty concept in a mixed integer programming formulation. Results show that it is possible to use the approach to concentrate harvest activities at the tactical level in a full scale forest management scenario. In the case study, the effects of concentration on strategic outputs were small, and the number of harvest tracts declined towards a minimum level. Furthermore, the discrepancies between the two planning levels were small

The Impact of Petri Nets on System-of-Systems Engineering

The successful engineering of a large-scale system-of-systems project towards deterministic behaviour depends on integrating autonomous components using international communications standards in accordance with dynamic requirements. To-date, their engineering has been unsuccessful: no combination of top-down and bottom-up engineering perspectives is adopted, and information exchange protocol and interfaces between components are not being precisely specified. Various approaches such as modelling, and architecture frameworks make positive contributions to system-of-systems specification but their successful implementation is still a problem. One of the most popular modelling notations available for specifying systems, UML, is intuitive and graphical but also ambiguous and imprecise. Supplying a range of diagrams to represent a system under development, UML lacks simulation and exhaustive verification capability. This shortfall in UML has received little attention in the context of system-of-systems and there are two major research issues: 1. Where the dynamic, behavioural diagrams of UML can and cannot be used to model and analyse system-of-systems 2. Determining how Petri nets can be used to improve the specification and analysis of the dynamic model of a system-of-systems specified using UML This thesis presents the strengths and weaknesses of Petri nets in relation to the specification of system-of-systems and shows how Petri net models can be used instead of conventional UML Activity Diagrams. The model of the system-of-systems can then be analysed and verified using Petri net theory. The Petri net formalism of behaviour is demonstrated using two case studies from the military domain. The first case study uses Petri nets to specify and analyse a close air support mission. This case study concludes by indicating the strengths, weaknesses, and shortfalls of the proposed formalism in system-of-systems specification. The second case study considers specification of a military exchange network parameters problem and the results are compared with the strengths and weaknesses identified in the first case study. Finally, the results of the research are formulated in the form of a Petri net enhancement to UML (mapping existing activity diagram elements to Petri net elements) to meet the needs of system-of-systems specification, verification and validation

A review of approaches and tools for collaborative networks simulation

Collaborative networks (CN) are characterised by being complex systems, highlighting the need of considering simulation approaches to support the resolution of CN models. Simulation approaches are seen as a supporting tool to analyse the formal model of a supply network. Three relevant simulation approaches are identified for its application in the context of CN models: Discrete Events Simulation, System Dynamics and Agent Based Simulation. Each simulation approach is briefly described and compared with each other, according to a group of relevant features, with the main aim of aiding the modellers in the task of selecting the most appropriate simulation approach to address the modelling process in the context of CN. Besides, a group of commercial and academic tools are listed for each simulation approach.Andres, B.; Poler, R. (2016). A review of approaches and tools for collaborative networks simulation. Brazilian Journal of Operations and Production Management. 13(3):232-242. doi:10.14488/BJOPM.2016.v13.n3.a1S23224213

Modelo de estratégia e coordenação genérico para sistemas multi-agente

Estágio realizado na Universidade de Aveiro e orientado pelo Prof. Doutor Jose Nuno Panelas Nunes LauTese de mestrado integrado. Engenharia Electrotécnica e de Computadores. Faculdade de Engenharia. Universidade do Porto. 200

Re-use of an ontology for modelling urban energy systems

The use of ontologies for the interoperability of software models is widespread, with many applications also in the energy domain. By formulating a shared data structure and a definition of concepts and their properties, a language is created that can be used between modellers and - formalised in an ontology - between model components. When modelling energy systems, connections between different infrastructures are critical, e.g. the interaction between the gas and electricity markets or the need for various infrastructures including power, heat, water and transport in cities. While a commonly shared ontology of energy systems would be highly desirable, the fact is that different existing models or applications already use dedicated ontologies, and have been demonstrated to work well using them. To benefit from linking data sources and connecting models developed with different ontologies, a translation between concepts can be made. In this paper a model of an urban energy system built upon one ontology is initialised using energy transformation technologies defined in another ontology, thus illustrating how this common perspective might benefit researchers in the energy domain. ©2010 IEEE

Alignment of Partnering with Construction IT

Supply Chain Management (SCM) and Building Information Modelling (BIM) are seen as innovations that can manage complexities in construction by focusing on integrating processes and products respectively. Whereas these two innovations have been considered compatible, their practical combination has been mainly anecdotal. The Netherlands was the locale of this study, where both SCM and BIM have been popular approaches. The research objective is to explore their real-world combination and propose strategies for the alignment of SCM and BIM, by viewing Supply Chain (SC) partnering as the inter-organisational proxy of SCM. The main question is: “How to align the SCM philosophy with BIM technologies to achieve integration in the construction industry? What aspects contribute to this alignment?”. The methodology was mixed and both qualitative and quantitative data were analysed. The overarching method was case study research and the unit of analysis was the firm, also referred to as ‘actor’.After a semi-chronological review of the relevant literature, the two constructs of SCM and BIM were found interdependent in product-, process-, and actor-related (P/P/A) dimensions. The study consisted of four other consecutive studies. First, empirical insights into the practical implementation of SC partnering and BIM were obtained via the exploration of five cases. Second, a conceptual model for the quantitative analysis of the product-, process-, and actor-related dimensions was designed. Third, this model and mixed methods were applied to two polar (extreme) cases to analyse the contractual (typically SC-related), digital (typically BIM-related), and informal interactions among the involved actors. Fourth, an additional theoretical exploration of the BIM-enabled SC partnerships took place with focusing also on intra-organisational relations within the involved firms. After the four studies, the findings were systematically combined to create the theoretical synthesis, i.e. generate theory. Three consecutive steps of ‘construct’, ‘internal’, and ‘external’ validity took place after the synthesis, to define the transferability of findings. The systematic combination of findings deduced two routes to achieve SC integration in construction: (a) product-related (emphasis on BIM tools), and (b) actor-related (emphasis on SCM philosophy).The two observed routes to SC integration emerged from the data of the polar cases. Two complementary sets of strategies for SC integration were derived afterwards. These strategies could ease the identification of which route is the ‘closest fit’ to SC integration, and then support the decision-making of how to pursue it. As the concept of BIM is currently a hot topic, it might be wise to undertake a ‘product-related’ route to integration and gradually introduce strategies from the ‘actor-related’ route. However, the ‘actor-related’ route could attain long-term integration and thus, long-lasting relations among the multi-actor networks. The key aspects of the alignment of partnering with construction IT for BIM-enabled SC partnerships are: - The identification of whether the SC complexity is of process-, product- or actor-related nature; - The deployed BIM collaboration patterns, i.e. ad-hoc, linear or distributed; - The SC coordination mechanisms, e.g. centralised or decentralised; - The relation between formal and informal aspects, e.g. symmetric or asymmetric; - The emerging intra-organisational relations due to BIM and SCM implementation; - The hierarchical level that BIM-enabled SC partnership decision-making pertains. As the construction industry evolves into an information-driven sector, the alignment of construction IT with inter-organisational management is preeminent for managing the inherent complexities of the industry. In parallel, embracing inter-organisational approaches for information management such as BIM is a promisingway forward for SCM and construction management

Engage D2.2 Final Communication and Dissemination Report

This deliverable reports on the communication and dissemination activities carried out by the Engage consortium over the duration of the network. Planned activities have been adapted due to the Covid-19 pandemic, however a full programme of workshops and summer schools has been organised. Support has been given to the annual SESAR Innovation Days conference and there has been an Engage presence at many other events. The Engage website launched in the first month of the network. This was later joined by the Engage ‘knowledge hub’, known as the EngageWiki, which hosts ATM research and knowledge. The wiki provides a platform and consolidated repository with novel user functionality, as well as an additional channel for the dissemination of SESAR results. Engage has also supported and publicised numerous research outputs produced by PhD candidates and catalyst fund projects