985,807 research outputs found

    The integrated use of enterprise and system dynamics modelling techniques in support of business decisions

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    Enterprise modelling techniques support business process re-engineering by capturing existing processes and based on perceived outputs, support the design of future process models capable of meeting enterprise requirements. System dynamics modelling tools on the other hand are used extensively for policy analysis and modelling aspects of dynamics which impact on businesses. In this paper, the use of enterprise and system dynamics modelling techniques has been integrated to facilitate qualitative and quantitative reasoning about the structures and behaviours of processes and resource systems used by a Manufacturing Enterprise during the production of composite bearings. The case study testing reported has led to the specification of a new modelling methodology for analysing and managing dynamics and complexities in production systems. This methodology is based on a systematic transformation process, which synergises the use of a selection of public domain enterprise modelling, causal loop and continuous simulationmodelling techniques. The success of the modelling process defined relies on the creation of useful CIMOSA process models which are then converted to causal loops. The causal loop models are then structured and translated to equivalent dynamic simulation models using the proprietary continuous simulation modelling tool iThink

    An application of the individual channel analysis and design approach to control of a two-input two-output coupled-tanks system

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    Frequency-domain methods have provided an established approach to the analysis and design of single-loop feedback control systems in many application areas for many years. Individual Channel Analysis and Design (ICAD) is a more recent development that allows neo-classical frequency-domain analysis and design methods to be applied to multi-input multi-output control problems. This paper provides a case study illustrating the use of the ICAD methodology for an application involving liquid-level control for a system based on two coupled tanks. The complete nonlinear dynamic model of the plant is presented for a case involving two input flows of liquid and two output variables, which are the depths of liquid in the two tanks. Linear continuous proportional plus integral controllers are designed on the basis of linearised plant models to meet a given set of performance specifications for this two-input two-output multivariable control system and a computer simulation of the nonlinear model and the controllers is then used to demonstrate that the overall closed-loop performance meets the given requirements. The resulting system has been implemented in hardware and the paper includes experimental results which demonstrate good agreement with simulation predictions. The performance is satisfactory in terms of steady-state behaviour, transient responses, interaction between the controlled variables, disturbance rejection and robustness to changes within the plant. Further simulation results, some of which involve investigations that could not be carried out in a readily repeatable fashion by experimental testing, give support to the conclusion that this neo-classical ICAD framework can provide additional insight within the analysis and design processes for multi-input multi-output feedback control systems

    PREDICTING AVAILABILITY AND RESPONSE TIMES OF IT SERVICES

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    When IT service providers adapt their IT system landscapes because of new technologies or changing business requirements, the effects of changes to the quality of service must be considered to fulfill service level agreements. Analytical prediction models can support this process in the service design stages, but dependencies between quality aspects are not taken into account. In this paper, a novel approach for predicting availability and response time of an IT service is developed, which is simulation-based to support dynamic analysis of service quality. The correctness of the model as well as its applicability in a real case can be evaluated. Therefore, this work presents a step towards an analytical framework for predicting IT service quality aspects

    Managing coupled human and natural systems (CHANS) : the case of water

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    Many sustainability challenges of the 21st century are the result of poor management of coupled human and natural systems (CHANS). Limited understanding of the mechanisms that give rise to complex dynamics in CHANS has contributed to overexploitation and degradation of water and other natural resources around the globe, leading to unintended consequences of well-intentioned policies. This raises the question of whether the tools and methods currently used in environmental management and policy design meet the requirements of complex dynamic systems. In this thesis, qualitative and quantitative research approaches from the fields of systems thinking and simulation modelling were combined with the aim of improving understanding of the dynamics of CHANS, and human-water systems in particular, and developing better methods and tools to support more effective policy and management strategies in the future. The work included a systematic review, qualitative and quantitative system dynamics modelling case studies, method development, and agent-based modelling and simulation. The results showed that changes in CHANS are driven by observable and unobservable exchanges of energy, matter and information across space and time that give rise to constantly changing, nonlinear dynamics. Many contemporary tools and methods used in management and policy design are not suited to this dynamic complexity and, instead of embracing complexity, seek to reduce it by excluding structural drivers of endogenous behaviour. This can contribute to unsustainable water use and amplify impacts of climate change in coupled human and water systems. This thesis showed that system dynamics-based approaches can effectively complement conventional static management tools, to better account for dynamic complexity. By tapping into the collective intelligence of actors engaged in the system, the approaches can support more realistic models and more effective and sustainable management, leading to establishment of middle-range theories for management of CHANS

    Distributed Renewable Power Sources in Weak Grids — Analysis and Control

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    This chapter describes the main aspects about distributed generation (DG) systems and investigates the operation of DG systems based on static power converters connected to weak grids. Initially, the concept of DG is discussed, and the main topologies for the connection of DG systems to the grid are covered. Converters used in such applications are also introduced. When connected to weak grids, DG systems based on static power converters suffer with problems related to the total harmonic distortion (THD) at the connection point. To address this issue, initially, a definition of weak grid is presented. Then, the dynamic behaviour of the most common small DG system when connected to a weak grid and the relation between the voltage harmonic distortion and the weak grid impedance are analyzed. Aiming to comply with the THD requirements, the main topologies of passive filter used in the connection of inverter-based DG units with weak grids are also discussed. Finally, a controller design that considers the grid side impedance in its formulation is developed. Experimental results are provided to support the theoretical analysis and to illustrate the performance of the grid-connected DG in a weak grid case operation scenario

    Design and Implementation of Role-based Architectural Event Modules

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    This diploma thesis attempts to improve the language-support for coping with the problem of negative emergence in dynamic Systems-of-Systems (SoS). Negative emergence is understood to be the emergence of unintended behaviour among constituent systems of a SoS in response to certain changes to the composition of constituent systems in the SoS. The architecture description language (ADL) "EventArch 2.0" approaches this problem by allowing the SoS-manager to define certain rules to manipulate the original behaviour of certain constituent systems at certain critical points of execution of the SoS to prevent unintended behaviour ("coordination rules"). This thesis approaches a solution to the following problem: to prevent the introduction of unintended behaviour through overly- or underly-restrictive coordination rules, more- or less-restrictive variants of a coordination rule would have to be applied to the SoS depending on the current composition of constituent systems in the SoS. This thesis has the goal to approach this problem by devising a mechanism to dynamically exchange a coordination rule depending on the current composition of constituent systems in the SoS. To achieve that goal, the ADL "EventArch 2.0" is extended to support the dynamic application of a coordination rule to a System-of-Systems. The dynamic application is achieved by connecting coordinators and constituent systems at runtime. As a special characteristic, each coordinator is dedicated to a specific constituent system and is responsible for achieving compliance of that system with respect to a specific coordination rule. It is shown that this architectural setup can be nicely modeled using concepts from the field of "role-based modeling". The solution does therefore employ concepts that are central to the "role-based modeling"-approach: "Role", "Base", and "Compartment". The applicability of the extended language to practical coordination-problems is shown by applying it to a constructed use case in the field of energy-efficient computing.:1 Introduction 1 1.1 Motivation and Problem Statement 1 1.2 Overview 2 2 Background 4 2.1 System of Systems 4 2.2 EventArch 2.0 8 2.2.1 Concepts 8 2.2.2 Implementation 10 2.2.3 Diagrams 15 2.3 Role-based Modeling 19 2.4 Coupling Strategies 22 3 Related Work 25 3.1 Requirements 25 3.2 Features 28 3.3 OT/J 29 3.4 Other Role-based Languages 31 3.5 Areas of Improvement 35 3.5.1 OT/J 35 3.5.2 Other Role-based Languages 40 4 Concepts of EventArch 3.0 45 4.1 Base, Role, and Compartment 45 4.2 Dynamic Composite AEM and Role-Binder 46 4.3 Inner Roles and Atomic Block 48 4.4 Diagrams 49 5 Internal Design of EventArch 3.0 55 5.1 Implementation of the Concepts 55 5.1.1 Base, Role, and Compartment 56 5.1.2 Dynamic Composite AEM and Role-Binder 58 5.1.3 Inner Roles and Atomic Block 60 5.1.4 Other Concepts 62 5.2 Further Discussion and Design Alternatives 63 6 Evaluation of EventArch 3.0 66 6.1 Advantages 66 6.2 Disadvantages 74 6.3 Reflections on the Fulfillment of the Requirements 77 6.4 Use case 81 6.5 Application to the Example Use case 83 6.5.1 Presentation of the implementation 83 6.5.2 Advantages shown by the implementation 90 7 Conclusion 93 7.1 Future Work 95 8 Appendix 99 8.1 Additional Source-Code 99 8.1.1 OT/J source-code 99 8.1.2 “State”-coordination rule 105 8.2 Internal Design of EventArch 2.0 109 8.2.1 Abstract 109 8.2.2 Detailed 116 8.3 Grammar of EventArch 3.0 . 123 8.4 EventArch 3.0 Diagrams 126 Bibliography 134Die vorliegende Diplomarbeit ist mit der Verbesserung der Sprachunterstützung zur Vermeidung negativer Emergenz in dynamischen Systems-of-Systems (SoS) befasst. Negative Emergenz wird dabei als unerwünschtes Verhalten von an einem SoS beteiligten Systemen verstanden, welches auf Grund von Änderungen in der Zusammensetzung des SoS (d.h. auf Grund des Eintritts oder Austritts von konstituierenden Systemen) aufgetreten ist. Die Architekturbeschreibungssprache "EventArch 2.0" unterstützt den SoS-manager bei der Lösung dieses Problems durch die Möglichkeit das Verhalten der beteiligten Systeme in bestimmten Ausführungsmomenten durch die Definition von Koordinationsregeln zu manipulieren und auf diesem Wege das Auftreten negativer Emergenz zu vermeiden. Die Diplomarbeit ist ein Beitrag zur Lösung des folgenden Problems: Um die Einführung von unerwünschtem Verhalten durch übermäßig- oder unzureichend restriktive Koordinationsregeln zu verhindern, müssten unterschiedliche Varianten einer Koordinationsregel, die sich im Grade ihrer Restriktivität unterscheiden, auf das SoS angewendet werden. Diese Anwendung müßte in Abhängigkeit der aktuellen Zusammensetzung des SoS aus konstituierenden Systemen erfolgen. In der vorliegenden Diplomarbeit wird eine Möglichkeit entwickelt um eine Koordinationsregel zur Laufzeit in Abhängigkeit der aktuellen Zusammensetzung des SoS aus konstituierenden Systemen auszutauschen. Sie leistet damit einen Beitrag zur Lösung des vorgenannten Problems. In der Arbeit wird die Architekturbeschreibungssprache "EventArch 2.0" um die Möglichkeit des dynamischen Austausches von Koordinationsregeln erweitert. Dabei werden Koordinationsregeln angewendet durch die gezielte Verbindung von Koordinatoren und konstituierenden Systemen. Die Besonderheit des Ansatzes besteht darin, dass jedem konstituierenden System ein persönlicher Koordinator zugeordnet wird, d.h. ein Koordinator der ausschließlich für die Anpassung des Verhaltens des jeweiligen Systems an eine bestimmte Koordinationsregel verantwortlich ist. In der Arbeit wird gezeigt, dass dieser architektonische Ansatz durch zentrale Konzepte des Modellierungsansatzes "rollenbasierte Modellierung" modelliert werden kann. In der entwickelten Spracherweiterung werden daher die Konzepte "Rolle", "Basis" und "Compartment" verwendet. Die Anwendbarkeit der erweiterten Sprache, wird durch deren Anwendung auf einen konstruierten Anwendungsfall aus dem Bereich der Energie-effizienten Berechnung gezeigt.:1 Introduction 1 1.1 Motivation and Problem Statement 1 1.2 Overview 2 2 Background 4 2.1 System of Systems 4 2.2 EventArch 2.0 8 2.2.1 Concepts 8 2.2.2 Implementation 10 2.2.3 Diagrams 15 2.3 Role-based Modeling 19 2.4 Coupling Strategies 22 3 Related Work 25 3.1 Requirements 25 3.2 Features 28 3.3 OT/J 29 3.4 Other Role-based Languages 31 3.5 Areas of Improvement 35 3.5.1 OT/J 35 3.5.2 Other Role-based Languages 40 4 Concepts of EventArch 3.0 45 4.1 Base, Role, and Compartment 45 4.2 Dynamic Composite AEM and Role-Binder 46 4.3 Inner Roles and Atomic Block 48 4.4 Diagrams 49 5 Internal Design of EventArch 3.0 55 5.1 Implementation of the Concepts 55 5.1.1 Base, Role, and Compartment 56 5.1.2 Dynamic Composite AEM and Role-Binder 58 5.1.3 Inner Roles and Atomic Block 60 5.1.4 Other Concepts 62 5.2 Further Discussion and Design Alternatives 63 6 Evaluation of EventArch 3.0 66 6.1 Advantages 66 6.2 Disadvantages 74 6.3 Reflections on the Fulfillment of the Requirements 77 6.4 Use case 81 6.5 Application to the Example Use case 83 6.5.1 Presentation of the implementation 83 6.5.2 Advantages shown by the implementation 90 7 Conclusion 93 7.1 Future Work 95 8 Appendix 99 8.1 Additional Source-Code 99 8.1.1 OT/J source-code 99 8.1.2 “State”-coordination rule 105 8.2 Internal Design of EventArch 2.0 109 8.2.1 Abstract 109 8.2.2 Detailed 116 8.3 Grammar of EventArch 3.0 . 123 8.4 EventArch 3.0 Diagrams 126 Bibliography 13

    Light Water Sustainability Program: Optimizing Information Automation Using a New Method Based on System-Theoretic Process Analysis

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    This report describes the interim progress for research supporting the design and optimization of information automation systems for nuclear power plants. Much of the domestic nuclear fleet is currently focused on modernizing technologies and processes, including transitioning toward digitalization in the control room and elsewhere throughout the plant, along with a greater use of automation, artificial intelligence, robotics, and other emerging technologies. While there are significant opportunities to apply these technologies toward greater plant safety, efficiency, and overall cost-effectiveness, optimizing their design and avoiding potential safety and performance risks depends on ensuring that human-performance-related organizational and technical design issues are identified and addressed. This report describes modeling tools and techniques, based on sociotechnical system theory, to support these design goals and their application in the current research effort. The report is intended for senior nuclear energy stakeholders, including regulators, corporate management, and senior plant management. We have developed and employed a method to design an optimized information automation ecosystem (IAE) based on the systems-theoretic constructs underlying sociotechnical systems theory in general and the Systems-Theoretic Accident Modeling and Processes (STAMP) approach in particular. We argue that an IAE can be modeled as an interactive information control system whose behavior can be understood in terms of dynamic control and feedback relationships amongst the system’s technical and organizational components. Up to this point, we have employed a Causal Analysis based on STAMP (CAST) technique to examine a performance- and safety-related incident at an industry partner’s plant that involved the unintentional activation of an emergency diesel generator. This analysis provided insight into the behavior of the plant’s current information control structure within the context of a specific, significant event. Our ongoing analysis is focused on identifying near-term process improvements and longer-term design requirements for an optimized IAE system. The latter analyses will employ a second STAMP-derived technique, System-Theoretic Process Analysis (STPA). STPA is a useful modeling tool for generating and analyzing actual or potential information control structures. Finally, we have begun modeling plantwide organizational relationships and processes. Organizational system modeling will supplement our CAST and STPA findings and provide a basis for mapping out a plantwide information control architecture. CAST analysis findings indicate an important underlying contributor to the incident under investigation, and a significant risk to information automation system performance, was perceived schedule pressure, which exposed weaknesses in interdepartmental coordination between and within responsible plant organizations and challenged the resilience of established plant processes, until a human caused the initiating event. These findings are discussed in terms of their risk to overall system performance and their implications for information automation system resilience and brittleness. We present two preliminary information automation models. The proactive issue resolution model is a test case of an information automation concept with significant near-term potential for application and subsequent reduction in significant plant events. The IAE model is a more general representation of a broader, plantwide information automation system. From our results, we have generated a set of preliminary system-level requirements and safety constraints. These requirements will be further developed over the remainder of our project in collaboration with nuclear industry subject matter experts and specialists in the technical systems under consideration. Additionally, we will continue to pursue the system analyses initiated in the first part of our effort, with a particular emphasis on STPA as the main tool to identify weak or weakening ontrol structures that affect the resilience of organizations and programs. Our intent is to broaden the scope of the analysis from an individual use case to a related set of use cases (e.g., maintenance tasks, compliance tasks) with similar human-system performance challenges. This will enable more generalized findings to refine the Proactive Issue Resolution and IAE models, as well as their system-level requirements and safety constraints. We will use organizational system modeling analyses to supplement STPA findings and model development. We conclude the report with a set of summary recommendations and an initial draft list of system-level requirements and safety constraints for optimized information automation systems

    Teaching Construction in the Virtual University: the WINDS project

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    This paper introduces some of the Information Technology solutions adopted in Web based INtelligent Design Support (WINDS) to support education in A/E/C design. The WINDS project WINDS is an EC-funded project in the 5th Framework, Information Society Technologies programme, Flexible University key action. WINDS is divided into two actions: ·The research technology action is going to implement a learning environment integrating an intelligent tutoring system, a computer instruction management system and a set of co-operative supporting tools. ·The development action is going to build a large knowledge base supporting Architecture and Civil Engineering Design Courses and to experiment a comprehensive Virtual School of Architecture and Engineering Design. During the third year of the project, more than 400 students all over Europe will attend the Virtual School. During the next three years the WINDS project will span a total effort of about 150 man-years from 28 partners of 10 European countries. The missions of the WINDS project are: Advanced Methodologies in Design Education. WINDS drives a breakdown with conventional models in design education, i.e. classroom or distance education. WINDS implements a problem oriented knowledge transfer methodology following Roger Schank's Goal Based Scenario (GBS) pedagogical methodology. GBS encourages the learning of both skills and cases, and fosters creative problem solving. Multidisciplinary Design Education. Design requires creative synthesis and open-end problem definition at the intersection of several disciplines. WINDS experiments a valuable integration of multidisciplinary design knowledge and expertise to produce a high level standard of education. Innovative Representation, Delivery and Access to Construction Education. WINDS delivers individual education customisation by allowing the learner access through the Internet to a wide range of on-line courses and structured learning objects by means of personally tailored learning strategies. WINDS promotes the 3W paradigm: learn What you need, Where you want, When you require. Construction Practice. Construction industry is a repository of ""best practices"" and knowledge that the WINDS will profit. WINDS system benefits the ISO10303 and IFC standards to acquire knowledge of the construction process directly in digital format. On the other hand, WINDS reengineers the knowledge in up-to-date courses, educational services, which the industries can use to provide just-in-time rather than in-advance learning. WINDS IT Solutions The missions of the WINDS project state many challenging requirements both in knowledge and system architecture. Many of the solutions adopted in these fields are innovative; others are evolution of existing technologies. This paper focuses on the integration of this set of state-of-the-art technologies in an advanced and functionally sound Computer Aided Instruction system for A/E/C Design. In particular the paper deals with the following aspects: Standard Learning Technology Architecture The WINDS system relies on the in progress IEEE 1484.1 Learning Technology Standard Architecture. According to this standard the system consists of two data stores, the Knowledge Library and the Record Database, and four process: System Coach, Delivery, Evaluation and the Learner. WINDS implements the Knowledge Library into a three-tier architecture: 1.Learning Objects: ·Learning Units are collections of text and multimedia data. ·Models are represented in either IFC or STEP formats. ·Cases are sets of Learning Units and Models. Cases are noteworthy stories, which describes solutions, integrate technical detail, contain relevant design failures etc. 2.Indexes refer to the process in which the identification of relevant topics in design cases and learning units takes place. Indexing process creates structures of Learning Objects for course management, profile planning procedures and reasoning processes. 3.Courses are taxonomies of either Learning Units or a design task and Course Units. Knowledge Representation WINDS demonstrates that it is possible and valuable to integrate a widespread design expertise so that it can be effectively used to produce a high level standard of education. To this aim WINDS gathers area knowledge, design skills and expertise under the umbrellas of common knowledge representation structures and unambiguous semantics. Cases are one of the most valuable means for the representation of design expertise. A Case is a set of Learning Units and Product Models. Cases are noteworthy stories, which describe solutions, integrate technical details, contain relevant design failures, etc. Knowledge Integration Indexes are a medium among different kind of knowledge: they implement networks for navigation and access to disparate documents: HTML, video, images, CAD and product models (STEP or IFC). Concept indexes link learning topics to learning objects and group them into competencies. Index relationships are the base of the WINDS reasoning processes, and provide the foundation for system coaching functions, which proactively suggest strategies, solutions, examples and avoids students' design deadlock. Knowledge Distribution To support the data stores and the process among the partners in 10 countries efficiently, WINDS implements an object oriented client/server as COM objects. Behind the DCOM components there is the Dynamic Kernel, which dynamically embodies and maintains data stores and process. Components of the Knowledge Library can reside on several servers across the Internet. This provides for distributed transactions, e.g. a change in one Learning Object affects the Knowledge Library spread across several servers in different countries. Learning objects implemented as COM objects can wrap ownership data. Clear and univocal definition of ownerships rights enables Universities, in collaboration with telecommunication and publisher companies, to act as "education brokers". Brokerage in education and training is an innovative paradigm to provide just-in-time and personally customised value added learning knowledg

    On the design of multi-platform parallel mechanisms

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    Parallel mechanisms have been examined in more and more detail over the past two decades. Parallel mechanisms are essentially the same design layout, a base, multiple legs/limbs, and a moving platform with a single end-effector to allow the mechanism to complete its desired function. Recently, several research groups have begun looking into multiple-platform parallel mechanisms and/or multiple end-effectors for parallel mechanisms. The reason for the research in this new form of parallel mechanism stems from multiple sources, such as applications that would require multiple handling points being accessed simultaneously, a more controlled gripper motion by having the jaws of the gripper being attached at different platforms, or to increasing the workload of the mechanism. The aim of the thesis is to modify the design process of parallel mechanisms so that it will support the development of a new parallel mechanism with multiple platforms capable of moving relative to each other in at least 1-DOF and to analyse the improvements made on the traditional single platform mechanism through a comparison of the power requirements for each mechanism. Throughout the thesis, a modified approach to the type synthesis of a parallel mechanism with multiple moving platforms is proposed and used to create several case study mechanisms. Additionally, this thesis presents a new series of methods for determining the workspace, inverse kinematic and dynamic models, and the integration of these systems into the design of a control system. All methods are vetted through case studies where they are judged based on the results gained from existing published data. Lastly, the concepts in this thesis are combined to produce a physical multi-platform parallel mechanism case study with the process being developed at each stage. Finally, a series of proposed topics of future research are listed along with the limitations and contributions of this work
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