Some metals, such as Ti-6Al-4V, have a high elongation to failure when strained at certain rates and temperatures. Superplastic forming is the utilisation of this property, and it can be used to form thin, geometrically complex components. Superplastic forming is a slow process, and this is one of the reasons why it is an expensive manufacturing process. Localised thinning occurs if the specimen is strained too quickly, and components with locally thin wall thickness fail prematurely. The goal of this study is to find a technique that can be used to minimise the forming time while limiting the minimum final thickness. The superplastic forming process is investigated with the finite element method. The finite element method requires a material model which describes the superplastic behaviour of the metal. Several material models are investigated in order to select a material model that can show localised thinning at higher strain rates. The material models are calibrated with stress-strain data, grain size-time data and strain rate sensitivity-strain data. The digitised data from literature is for Ti-6Al-4V with three different initial grain sizes strained at different strain rates at 927 C. The optimisation of the forming time is done with an approximate optimisation algorithm. This algorithm involves fitting a metamodel to simulated data, and using the metamodels to find the optimum instead of using the finite element model directly. One metamodel is fitted to the final forming time results, and another metamodel is fitted to the final minimum thickness results. A regressive radial basis function method is used to construct the metamodels. The interpolating radial basis function method proved to be unreliable at the design space boundaries due to non-smooth finite element results. The non-smooth results are due to the problem being path dependent. The final forming time of the superplastic forming of a rectangular box was successfully minimised while limiting the final minimum thickness. The metamodels predicted that allowing a 4% decrease in the minimum allowable thickness (1.0 mm to 0.96 mm) and a 1 mm gap between the sheet and the die corner the forming time is decreased by 28.84%. The finite element verification indicates that the final minimum thickness reduced by 3.8% and that the gap between the sheet and the die corner is less than 1 mm, resulting in the forming time being reduced by 28.81%. / Dissertation (MEng)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / MEng / Unrestricted

This study uses numerical design optimization with advanced metamodeling techniques to investigate the effects of material substitution and dummy models on crashworthiness characteristics of automotive structures. A full-scale Dodge Neon LS-DYNA finite element model is used in all structural analysis and optimization calculations. Optimization is performed using vehicle-based responses for multiple crash scenarios and occupant-based responses for one crash scenario. An AZ31 magnesium alloy is substituted for the baseline steel in twenty-two vehicle parts. Five base metamodels and an Optimized Ensemble metamodel are used to develop global surrogate models of crash-induced responses. Magnesium alloy is found to maintain or improve vehicle crashworthiness with an approximate 50% reduction in selected part mass using vehicle-based responses while dummy-based designs show less percentage decrease in weight. Vehicle-based responses selected to approximate dummy injury metrics do not show the same relative change compared to dummy-based responses.

As engineering technologies continue to grow and improve, the complexities in the engineering models which utilize these technologies also increase. This seemingly endless cycle of increased computational power and demand has sparked the need to create representative models, or metamodels, which accurately reflect these complex design spaces in a computationally efficient manner. As research into metamodeling and using advanced metamodeling techniques continues, it is important to remember design engineers who need to use these advancements. Even experienced engineers may not be well versed in the material and mathematical background that is currently required to generate and fully comprehend advanced complex metamodels. A metamodeling environment which utilizes an advanced metamodeling technique known as Gaussian Process is being developed to help bridge the gap that is currently growing between the research community and design engineers. This tool allows users to easily create, modify, query, and visually/numerically assess the quality of metamodels for a broad spectrum of design challenges.

The high demand for building digital libraries by non-experts requires a simplified modeling process and rapid generation of digital libraries. To enable rapid generation, digital libraries should be modeled with descriptive languages. A visual modeling tool would be helpful to non-experts so they may model a digital library without knowing the theoretical foundations and the syntactical details of the descriptive language. In this thesis, we describe the design and implementation of a domain-specific visual modeling tool, 5SGraph, aimed at modeling digital libraries. 5SGraph is based on a metamodel that describes digital libraries using the 5S theory. The output from 5SGraph is a digital library model that is an instance of the metamodel, expressed in the 5S description language (5SL). 5SGraph presents the metamodel in a structured toolbox, and provides a top-down visual building environment for designers. The visual proximity of the metamodel and instance model facilitates requirements gathering and simplifies the modeling process. Furthermore, 5SGraph maintains semantic constraints specified by the 5S metamodel and enforces these constraints over the instance model to ensure semantic consistency and correctness. 5SGraph enables component reuse to reduce the time and efforts of designers. The results from a pilot usability test confirm the usefulness of 5SGraph. / Master of Science

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-11-13T10:34:43Z No. of bitstreams: 2 Dissertação - Marcelo Barros de Azevedo Vieira - 2018.pdf: 2090852 bytes, checksum: cea29f7c5b0e3e434fef63a6866bc625 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-11-13T11:09:32Z (GMT) No. of bitstreams: 2 Dissertação - Marcelo Barros de Azevedo Vieira - 2018.pdf: 2090852 bytes, checksum: cea29f7c5b0e3e434fef63a6866bc625 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-11-13T11:09:32Z (GMT). No. of bitstreams: 2 Dissertação - Marcelo Barros de Azevedo Vieira - 2018.pdf: 2090852 bytes, checksum: cea29f7c5b0e3e434fef63a6866bc625 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-10-09 / The technological advances in recent years have allowed the development of new applications for communication. These applications allow multiple types of media to be switched between their users, with lower latency providing a better experience for the user. However, the development of applications for communication using general purpose languages has as a focus the development of the application and not the solution of the problems in a domain. In this way, domain-specific modeling languages, originated in Model-Driven Engineering, raise the level of abstraction and reduce the complexity of software development. Specificaly, modeling languages for the real-time communication domain aim to model applications that allow real-time communication among users, not only reducing the development time but also offering users the possibility of creating their own applications. The objective of this work was to propose a new communication modeling language, RBCML, which enables the definition of communication applications based on the roles that users play in a communication session, as well as their requirements in terms of the types of media and data that they can exchange. An implementation of the language was developed on top of the standards-based WebRTC platform in order to carry out evaluation experiments to demonstrate its usability and performance. / Os avanços tecnológicos ocorridos nos últimos anos, permitiram o desenvolvimento de novas aplicações para comunicação. Essas aplicações permitem que diversos tipos de mídia sejam usadas na comunicação entre os usuários, com menor latência e proporcionando uma melhor experiência para o usuário. No entanto, o desenvolvimento de aplicações para comunicação utilizando linguagens de propósito geral tem como característica o foco no desenvolvimento da aplicação e não na resolução de problemas no domínio. Isso motivou o surgimento de linguagens de modelagem específicas de domínio, originadas na Engenharia Dirigida por Modelos, que elevam o nível de abstração e reduzem a complexidade do desenvolvimento de software. Linguagens de modelagem específicas para o domínio de comunicação em tempo real têm como objetivo modelar aplicações que permitam a comunicação em tempo real, reduzindo o esforço no desenvolvimento deste tipo de aplicação e permitindo que os usuários criem suas próprias aplicações. O objetivo deste trabalho foi propor uma nova linguagem de comunicação, RBCML, que permite a definição de aplicações de comunicação com base nos papéis que os usuários desempenham nas sessões de comunicação, bem como em seus requisitos com respeito aos tipos de mídia e dados por meio dos quais a comunicação ocorre. Uma implementação da linguagem foi desenvolvida usando o padrão WebRTC para permitir a realização de experimentos para demonstrar sua usabilidade e desempenho.

Today, business process modelling is important part of analysis and design of the information systems. There is number of standards, which is concerned with process modelling, whereas each of them represents a little different approach. The project Opensoul created general metamodel, which defines basic elements and their mutual associations, which all standards should meet. In other words, it defines basic rules for process modelling. The goal of this thesis is to compare chosen standards of process modelling with Business process metamodel of Opensoul initiative. The results of this comparison would have provide basis to answer the question, which standard supports in the best way the rules of process modelling defined by metamodel through the system of elements and their associations. This goal requires specifying the method, on which basis the comparison will be made. This method comprises the extension of metamodel with new elements and their relations to other elements, and the extension of some elements with some workflow patterns defined by Workflow Patterns initiative. That is the main benefit of this thesis.

Business process modeling plays an important role for the documentation and analysis of organizational processes and for the specification of requirements for information systems. Currently, there are many standards for process modeling, and each represents a different approach to modeling and provides different opportunities for creating models. Thus, same models created in different modeling languages differ in terms of their expressiveness, according to each standard. The goal of this thesis is to evaluate the effectiveness of selected business process modeling standards. The effectiveness of standards will be evaluated on two levels. First, in terms of their semantics and second, in terms of their syntax. Evaluation of standards in terms of their semantics will be based on the comparison of standards with a business process metamodel created within the project Opensoul. This model defines a set of basic elements and their associations at a basic level of process modeling. Evaluation of standards in terms of their syntax will be based on the comparison of standards with a framework proposed by Moody and Hillegersberg. The results of this comparison should show which standard best supports defined criteria. The evaluation framework will be applied on the following process modeling standards: BPMN, EPC and IDEF3. Based on the results obtained their strength and weaknesses will be discussed. The main contribution of this thesis can be seen both in the analysis of the element set of selected process modeling standards and further in the comparison of standards according to the evaluation framework.

The diploma thesis is focused on create an optimization methodology for CFD issues or any other computationally demanding software. Optimization method is applied on simplified model of car, where improves its aerodynamic properties

It is well-recognized among computer scientists that prospective informatics systems will become more and more complex and will increasingly accumulate non-linear behaviour that is difficult to orchestrate, to configure, and to reason about. Certainly, large-scale mobile computing systems will challenge our understanding, similar to climate systems, bio-chemical systems, physical systems, or social networks. This suggests a rigorous formalization and study of non-trivial computational systems. In this regard, bigraphs are a groundbreaking novel theory for distributed and parallel systems, treating mobile locality and mobile interaction as first-class citizens. The theory was devised by Robin Milner as a process algebra with rewrite capabilities based on graph equations and an algebraic type system. Bigraphs have been the subject of extensive investigation from various perspectives, including agent-based modelling, cyber-physical games, language construction, graph rewriting, and as a unifying metamodel for other rewrite theories and process calculi, but particularly in the context of the categorical reactive system approach. In this approach, a labelled transition system, over which bisimilarity is a congruent equivalence relation, is generated from reduction semantics that can be freely specified. The bigraph theory treats two-dimensional graphs as arrows and their interfaces as objects while category theory provides the underlying mathematical framework for their axiomatization. Fortunately, category theory makes the theory future-proof, competitive and extensible. The recently developed categorical concepts of relative and idempotent pushouts facilitate the categorical construction of minimal context labels enabling the development of a behavioural theory, where bisimulation is a congruence. The metamodel character of bigraphs enables the comparison of other formalisms and algebraic theories of concurrent computation at a very abstract level, thus, regaining their behavioural theory and computational notion, with the ultimate goal of exploiting synergies. Indeed, bigraphs are much more than a computational model for understanding, analysing, and verifying systems. They provide both a formal and practical foundation for context-oriented reactive system modelling and programming languages. Consequently, the development of software solutions based on the bigraph theory necessitates suitable tools, frameworks, and languages for putting bigraphs into practice. These tools are essential for evaluating the model’s effectiveness in both academic research and the software industry. Only this permits rigorous testing of the theory. But moreover, reaching this goal is the result of the motivation to lower the barrier to entry for model-driven context-adaptive programming using the bigraph theory. So far, several tools and libraries have been developed to model and simulate bigraphical reactive systems. These tools can roughly be referred to as bigraphical calculators and are meant for experimentation and comprehension of the theory. Without them, this work could not have been written. However, we elevate the initial efforts to a level more conducive to enable advanced bigraphical software engineering practises. Therefore, the Bigraph Toolkit Suite was developed—a collection of tools and methods for the research and development of reactive systems for real-world applications. The suite consists of model-based integration frameworks, architectural guidelines, integrated development environments, command-line tools, and an uncomplicated language engineering workbench with an extensible grammar and interpreter. Each product of the Bigraph Toolkit Suite serves a distinct function, ranging from the manipulation and simulation of bigraphs to bigraphical language engineering and distributed storage of bigraph models. The tools are finely tuned to each other via a common metamodel, which facilitates implementation of novel bigraphical tool chains as well as the integration of arbitrary tools and public programming interfaces. Certainly, the following ambient question paved the path of this research: Is there a formalism or theory that supports context modelling, computation and verification, and that can be used as a programming language? The work shows that bigraphs can be used to lay such a foundation to regain the understanding of new informatics systems, with model-driven engineering contributing to this. According to this, the latent objective of this work is the cross-fertilization process of model-driven engineering and bigraphical reactive systems on a practical basis. A discussion is developed of whether there is evidence to support the view that the presence of MDE-related model operations and practices may be related to bigraph operations and vice versa. A relation can be established by a consistent and complete canonical mapping on the x-axis based on a systematic four-layer metamodelling framework; and on the y-axis between three different yet interoperable technical spaces. Thus, the result of this thesis is developed along two axes from a strict software engineering perspective. On the one hand, practical observations of the bigraph theory are provided about other graph structures, categories and model-driven operations. On the other, a novel software ecosystem for bigraphical reactive systems is provided together with several generic experimental approaches such as event-based execution of sub-bigraphical reactive systems. The theory already stimulated much other research works and therefore advancing fundamental computer science, this work may additionally—hopefully, the reader will agree—solidify and advance bigraphical research.:1 Introduction 1.1 Background and Motivation 1.1.1 Typical Application Scenarios 1.1.2 The Dilemma of Complex Reactive Systems 1.2 Field of Work 1.2.1 Reactive Systems 1.2.2 Model-driven Engineering 1.2.3 Context Adoption in Software: A Novel Taxonomy 1.3 Research Project 1.3.1 Hypothesis 1.3.2 Research Aim 1.3.3 Research Objectives 1.3.4 Contributions 1.4 Outline 2 The Theory of Bigraphical Reactive Systems for Software Engineers 2.1 Graph Theory: Basic Notation 2.2 Categories for Context-adaptive Software 2.2.1 Elementary Category Theory 2.2.2 Reactive System Categories: s-category and spm category 2.2.3 Type Graphs and Type Morphisms 2.2.4 Observations 2.3 On the Static Structure of Bigraphs 2.3.1 Signatures 2.3.2 Pure Bigraphs: Place Graphs and Link Graphs 2.3.3 Compositional Structures: Interfaces and Operators 2.3.4 Algebra of Bigraphs 2.3.5 Graphical s-categories 2.4 Type Systems and Sortings 2.4.1 Basic Terminology 2.4.2 Sortings and Bigraphs 2.5 Dynamics of Reactive Systems 2.5.1 Operational Semantics of Reactive Systems 2.5.2 Reactive System Theory: General Categories 2.5.3 Bigraphical Reactive Systems 2.5.4 Labelled Transition Systems 2.5.5 Behavioural Equivalences 2.5.6 Observations 2.6 Formal Verification 2.6.1 Model Checking in Detail 2.6.2 Properties of Sequential and Parallel Programs 2.6.3 State-Space Explosion Problem 3 Model-driven Concepts in Bigraphs 3.1 A Canonical Mapping: From Bigraphs to Ecore 3.1.1 The Four-layer Metamodelling Framework Revisited 3.1.2 Formal Relations between Bigraphs, Type Graphs and Ecore 3.1.3 Model Constraints at the 𝑀1 and 𝑀0 layer 3.1.4 Design Level Variability and Extensibility 3.2 Bigraphical Models: Specification and Generation 3.2.1 Typing and Subtyping via (Un-)Sorted Signatures and their Instantiation from Metamodels 3.2.2 Bigraphs and their Instantiation from Metamodels 3.2.3 Observations 3.3 Modelling Techniques: A Bigraphical Perspective 3.3.1 Bigraphs and UML Class Diagrams 3.3.2 Signature Operations 3.3.3 Abstraction 3.3.4 View Modelling with Place Graphs 3.4 Design Patterns for Implementing Variation Points 3.5 Summary 4 Bigraph Toolkit Suite: A Complete Software Development Ecosystem 4.1 The Bigraphical Tool Landscape 4.1.1 High-level Architecture 4.1.2 Overview of the Constituents 4.1.3 Design Qualities 4.1.4 Project Organisation 4.2 Modelling and Visualization 4.2.1 Programmatic Approach: Builders and Operators 4.2.2 Domain-specific Language 4.2.3 Converters: Model Translations 4.2.4 Visual Modelling: Bigellor 4.3 Simulation and Verification 4.3.1 Specification of BRSs 4.3.2 Implementation Aspects: Entity Classes 4.3.3 Implementation Aspects: Business Classes 4.3.4 Model Checking Algorithm 4.3.5 Coordination of BRSs: Higher-order Execution Strategies 4.3.6 Error Handling: Chain of Responsibility and Exceptions 4.4 Bigraphical Domain-specific Language 4.4.1 Overview of BDSL’s Grammar 4.4.2 Language Features 4.4.3 Interpreter: Decoupling the Grammar from Application-Specific Code 4.4.4 BDSL-CLI: A Command-line Interpreter Tool for BDSL 4.4.5 Theia: An Integrated Development Environment for BDSL 4.5 Persistence: Distributed Model Storage 4.5.1 Basic Filesystem Storage Facilities 4.5.2 Spring Data CDO: Spring Data and Connected Data Objects 4.5.3 Arbitrary Hierarchical Layouts for Bigraphical Models 4.5.4 Event Listeners 4.6 Performance and Quality Analysis 4.6.1 Functional Tests 4.6.2 Dependency Analysis 4.6.3 Runtime Analysis 4.7 Summary 5 Related Work: The Bigraphical Tool Landscape 5.1 A Lightweight Qualitative Comparison Framework 5.1.1 Conceptual Foundations 5.1.2 Considerations 5.2 Method and Tool Candidates 5.2.1 Selection Process 5.2.2 Excluded Tool Candidates 5.2.3 Tool Overview 5.3 Results 5.3.1 jLibBig 5.3.2 bigraphspace 5.3.3 BigRED 5.3.4 BigM 5.3.5 BigraphER 5.3.6 BigMC 5.3.7 BPL Tool 5.3.8 BiGMTE 5.3.9 DBtk 5.4 Evaluation and Discussion 5.4.1 Assessment Criteria 5.4.2 Comparison of Non-Functional Aspects 5.4.3 Comparison of Functional Aspects 5.4.4 Term Language 5.4.5 Interoperability 5.4.6 Accessibility 5.5 Summary 6 Conclusion List of Figures List of Tables List of Listings Bibliography Online Resources Appendices A Theoretical Addendum B Design Patterns, Techniques and Technologies C Code Listings: Related Work Abbreviations

Für eine konsistente Rechtevergabe in betrieblichen Anwendungssystemen ist die Einbeziehung umfassender intra- und interorganisationeller Strukturen unabdingbar. Die Kernproblematik aktueller Ansätze beruht auf der inkonsistenten Zuweisung von Aufgabenträgern bei der Rechtevergabe. Die Problematik fällt speziell bei aufbauorganisatorischen Änderungen, wie der Einstellung, der Versetzung und dem Ausscheiden von Aufgabenträgern in Unternehmen, ins Gewicht. Das Resultat der inkonsistenten Rechtevergabe ist die Verletzung von (Sicherheits-)Richtlinien in den Unternehmen. Der Neuheitswert der Arbeit basiert vorrangig auf der Entwicklung eines aufbauorganisatorischen Metamodells und einer korrespondierenden deklarativen Anfragesprache. Diese Komposition ermöglicht die konsistente Rechtevergabe und damit einhergehend die Einhaltung der (Sicherheits-)Richtlinien in den betrieblichen Anwendungssystemen. Des Weiteren wird der Wartungsaufwand in den betrieblichen Anwendungssystemen bei den erwähnten aufbauorganisatorischen Änderungen reduziert.