Design Synchronization in Distributed Collaborative Design - Design Change in Product-Process Design Across Global Enterprises

Ph.DDOCTOR OF PHILOSOPH

Survey on Additive Manufacturing, Cloud 3D Printing and Services

Cloud Manufacturing (CM) is the concept of using manufacturing resources in a service oriented way over the Internet. Recent developments in Additive Manufacturing (AM) are making it possible to utilise resources ad-hoc as replacement for traditional manufacturing resources in case of spontaneous problems in the established manufacturing processes. In order to be of use in these scenarios the AM resources must adhere to a strict principle of transparency and service composition in adherence to the Cloud Computing (CC) paradigm. With this review we provide an overview over CM, AM and relevant domains as well as present the historical development of scientific research in these fields, starting from 2002. Part of this work is also a meta-review on the domain to further detail its development and structure

Graph BI & analytics: current state and future challenges

In an increasingly competitive market, making well-informed decisions requires the analysis of a wide range of heterogeneous, large and complex data. This paper focuses on the emerging field of graph warehousing. Graphs are widespread structures that yield a great expressive power. They are used for modeling highly complex and interconnected domains, and efficiently solving emerging big data application. This paper presents the current status and open challenges of graph BI and analytics, and motivates the need for new warehousing frameworks aware of the topological nature of graphs. We survey the topics of graph modeling, management, processing and analysis in graph warehouses. Then we conclude by discussing future research directions and positioning them within a unified architecture of a graph BI and analytics framework.Peer ReviewedPostprint (author's final draft

Study of lightweighting structural design considering 3D printing constraints

One of the current challenges of the aerospace industry is the exploration of new lightweighting structures to reduce fuel consumption and limiting the environmental impact. The use of numerical methods concerning topology optimization techniques allows the obtaining of such weight reduction, also minimizing both design time and costs, and hence accelerating the design process. Nevertheless, current structural optimization leads to the apparition of complex shapes and volumes with unintuitive holes, thus needing the use of additive manufacturing constraints - minimum length scales and overhanging - to ensure manufacturability. Considering the background exposed above, the aim of this project is to study the feasibility of heuristic designs concerning lightweighting structures, materialized with additive manufacturing and considering 3D printing constraints. The design stage will be developed by means of topology optimization techniques, applied to anisotropic filtering. The methodology employed has considered all details concerning Computational Solid Mechanics (CSM) techniques used in structures optimization, as well as additive manufacturing techniques, different case studies definition and their feasibility study. More specifically, in the context of CSM, the use of Finite Element Methods (FEM) in the classical elastic problem is reviewed, as well as current topology optimization techniques, so as to implement FEM in optimization algorithms. Thus, theoretical basis in additive manufacturing techniques are reviewed, along with the mathematical formulation of length scale and overhang constraints. Lastly, the programming stage is performed by previously defining the working environment, consisting in the use of Object-Oriented Programming within the git Version Control System, and hence establishing the computational domain definition for all cases, the meshing process and the simulation setup. In the end, the present project has accomplished the main objectives, giving a positive answer to the creation of lightweighting structures and fulfillment of 3D printing constraints. Indeed, FEM combined with topology optimization techniques has led to the obtaining of optimized designs, fulfilling an objective function and a set of constraints, considering both design variables approaches, density and level set. Besides, an additional shape functional has been defined as a penalty contribution to the main cost function in order to fulfill 3D printing constraints - the anisotropic perimeter - being the evolution of the standard isotropic one, both applied to total and relative perimeters. This shape functional self-penalizes length scale constraints and keeps control in overhanging phenomena by orienting the topologies with the definition of a virtual anisotropic stiffness matrix. Results obtained show that the apparition of local features with small length scales has been avoided when including either isotropic or anisotropic perimeter as a penalty term. Furthermore, vertical tendency orientation of topologies has been generally obtained with the anisotropic cases, along with penalization of horizontal features. Overall, this project has become clearly relevant for the exploration of new lightweighting structures, achieving weight reduction with topology optimization techniques. Further exploration remains in the course of PhD professionalization, specially when considering phase-field models, high-performance computing and large-scale optimization inside the non-linear regime

Finite Element Modeling Driven by Health Care and Aerospace Applications

This thesis concerns the development, analysis, and computer implementation of mesh generation algorithms encountered in finite element modeling in health care and aerospace. The finite element method can reduce a continuous system to a discrete idealization that can be solved in the same manner as a discrete system, provided the continuum is discretized into a finite number of simple geometric shapes (e.g., triangles in two dimensions or tetrahedrons in three dimensions). In health care, namely anatomic modeling, a discretization of the biological object is essential to compute tissue deformation for physics-based simulations. This thesis proposes an efficient procedure to convert 3-dimensional imaging data into adaptive lattice-based discretizations of well-shaped tetrahedra or mixed elements (i.e., tetrahedra, pentahedra and hexahedra). This method operates directly on segmented images, thus skipping a surface reconstruction that is required by traditional Computer-Aided Design (CAD)-based meshing techniques and is convoluted, especially in complex anatomic geometries. Our approach utilizes proper mesh gradation and tissue-specific multi-resolution, without sacrificing the fidelity and while maintaining a smooth surface to reflect a certain degree of visual reality. Image-to-mesh conversion can facilitate accurate computational modeling for biomechanical registration of Magnetic Resonance Imaging (MRI) in image-guided neurosurgery. Neuronavigation with deformable registration of preoperative MRI to intraoperative MRI allows the surgeon to view the location of surgical tools relative to the preoperative anatomical (MRI) or functional data (DT-MRI, fMRI), thereby avoiding damage to eloquent areas during tumor resection. This thesis presents a deformable registration framework that utilizes multi-tissue mesh adaptation to map preoperative MRI to intraoperative MRI of patients who have undergone a brain tumor resection. Our enhancements with mesh adaptation improve the accuracy of the registration by more than 5 times compared to rigid and traditional physics-based non-rigid registration, and by more than 4 times compared to publicly available B-Spline interpolation methods. The adaptive framework is parallelized for shared memory multiprocessor architectures. Performance analysis shows that this method could be applied, on average, in less than two minutes, achieving desirable speed for use in a clinical setting. The last part of this thesis focuses on finite element modeling of CAD data. This is an integral part of the design and optimization of components and assemblies in industry. We propose a new parallel mesh generator for efficient tetrahedralization of piecewise linear complex domains in aerospace. CAD-based meshing algorithms typically improve the shape of the elements in a post-processing step due to high complexity and cost of the operations involved. On the contrary, our method optimizes the shape of the elements throughout the generation process to obtain a maximum quality and utilizes high performance computing to reduce the overheads and improve end-user productivity. The proposed mesh generation technique is a combination of Advancing Front type point placement, direct point insertion, and parallel multi-threaded connectivity optimization schemes. The mesh optimization is based on a speculative (optimistic) approach that has been proven to perform well on hardware-shared memory. The experimental evaluation indicates that the high quality and performance attributes of this method see substantial improvement over existing state-of-the-art unstructured grid technology currently incorporated in several commercial systems. The proposed mesh generator will be part of an Extreme-Scale Anisotropic Mesh Generation Environment to meet industries expectations and NASA\u27s CFD visio

Resource Orchestration in Softwarized Networks

Network softwarization is an emerging research area that is envisioned to revolutionize the way network infrastructure is designed, operated, and managed today. Contemporary telecommunication networks are going through a major transformation, and softwarization is recognized as a crucial enabler of this transformation by both academia and industry. Softwarization promises to overcome the current ossified state of Internet network architecture and evolve towards a more open, agile, flexible, and programmable networking paradigm that will reduce both capital and operational expenditures, cut-down time-to-market of new services, and create new revenue streams. Software-Defined Networking (SDN) and Network Function Virtualization (NFV) are two complementary networking technologies that have established themselves as the cornerstones of network softwarization. SDN decouples the control and data planes to provide enhanced programmability and faster innovation of networking technologies. It facilitates simplified network control, scalability, availability, flexibility, security, cost-reduction, autonomic management, and fine-grained control of network traffic. NFV utilizes virtualization technology to reduce dependency on underlying hardware by moving packet processing activities from proprietary hardware middleboxes to virtualized entities that can run on commodity hardware. Together SDN and NFV simplify network infrastructure by utilizing standardized and commodity hardware for both compute and networking; bringing the benefits of agility, economies of scale, and flexibility of data centers to networks. Network softwarization provides the tools required to re-architect the current network infrastructure of the Internet. However, the effective application of these tools requires efficient utilization of networking resources in the softwarized environment. Innovative techniques and mechanisms are required for all aspects of network management and control. The overarching goal of this thesis is to address several key resource orchestration challenges in softwarized networks. The resource allocation and orchestration techniques presented in this thesis utilize the functionality provided by softwarization to reduce operational cost, improve resource utilization, ensure scalability, dynamically scale resource pools according to demand, and optimize energy utilization

Model-driven engineering of software architecture viewpoints

Ankara : The Department of Computer Engineering and the Graduate School of Engineering and Science of Bilkent University, 2012.Thesis (Master's) -- Bilkent University, 2012.Includes bibliographical references.A common practice in software architecture design is to apply so-called architectural views to design software architecture for the various stakeholder concerns. Architectural views are usually developed based on architectural viewpoints which define the conventions for constructing, interpreting and analyzing views. So far most architectural viewpoints seem to have been primarily used either to support the communication among stakeholders, or at the best to provide a blueprint for the detailed design. In this thesis, we provide a software language engineering approach to define viewpoints as domain specific languages. This enhances the formal precision of architectural viewpoints and leads to executable views that can be interpreted and analyzed by tools. We illustrate our approach for defining domain specific languages for the viewpoints of the Views and Beyond framework. The approach is implemented as an Eclipse plug-in, SAVE-Bench tool, which can be used to define different views based on the predefined software architecture viewpoints. The tool also supports automatic generation of architecture documentation from view models.Demirli, ElifM.S