Evolutionary Design Model for the design of complex engineered systems : Masdar City as a case study

Thesis (S.M.)--Massachusetts Institute of Technology, Computation for Design and Optimization Program, 2009."September 2009." Cataloged from PDF version of thesis.Includes bibliographical references (p. 150-157).This thesis develops a framework for constructing an Evolutionary Design Model (EDM) that would enhance the design of complex systems through an efficient process. The framework proposed is generic and suggests a group of systematic methodologies that eventually lead to a fully realized and integrated design model. Within this model, complexities of the design are handled and the uncertainties of the design evolution are managed. Using the framework, vast design spaces can be searched while solutions are intelligently modified, their performance evaluated, and their results aggregated into a compatible set for design decisions. The EDM is composed of several design states as well as design evolving processes. A design state describes a design at a particular point in time and maps the system's object to the system's requirements and identifies its relation to the context in which the system will operate. A design evolving process involves many sub-processes which include formulation, decomposition, modeling, and integration. These sub-processes are not always carried out in a sequential manner, but rather a continuous move back and forth to previous and subsequent stages is expected. The resulting design model is described as an evolutionary model that moves a system's design from simple abstract states to more complex and detailed states throughout its evolution.(cont.) The framework utilizes system modeling methodologies that include both logical and mathematical modeling methods. The type of model used within the EDM's evolving processes is highly dependent on and driven by design needs of each process. As the design progresses a shift from logical models to mathematical models occurs within the EDM. Finally, a partial EDM is implemented within the context of a computational design system for Masdar city to demonstrate the application of the proposed framework.By Anas Alfaris.S.M

Emergence through conflict : the Multi-Disciplinary Design System (MDDS)

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Architecture, 2009.Includes bibliographical references (p. 413-430).This dissertation proposes a framework and a group of systematic methodologies to construct a computational Multi-Disciplinary Design System (MDDS) that can support the design of complex systems within a variety of domains. The way in which the resulting design system is constructed, and the capabilities it brings to bare, are totally different from the methods used in traditional sequential design. The MDDS embraces diverse areas of research that include design science, systems theory, artificial intelligence, design synthesis and generative algorithms, mathematical modeling and disciplinary analyses, optimization theory, data management and model integration, and experimental design among many others. There are five phases to generate the MDDS. These phases involve decomposition, formulation, modeling, integration, and exploration. These phases are not carried out in a sequential manner, but rather in a continuous move back and forth between the different phases. The process of building the MDDS begins with a top-down decomposition of a design concept. The design, seen as an object, is decomposed into its components and aspects, while the design, seen as a process, is decomposed into developmental levels and design activities. Then based on the process decomposition, the architecture of the MDDS is formulated into hierarchical levels each of which comprises a group of design cycles that include design modules at different degrees of abstraction. Based on the design object decomposition, the design activities which include synthesis, analysis, evaluation and optimization are modeled within the design modules.(cont.) Subsequently through a bottom-up approach, the design modules are integrated into a data flow network. This network forms MDDS as an integrated system that acts as a holistic structured functional unit that explores the design space in search of satisfactory solutions. The MDDS emergent properties are not detectable through the properties and behaviors of its parts, and can only be enucleated through a holistic approach. The MDDS is an adaptable system that is continuously dependent on, and responsive to, the uncertainties of the design process. The evolving MDDS is thus characterized a multi-level, multi-module, multi-variable and multi-resolution system. Although the MDDS framework is intended to be domain-independent, several MDDS prototypes were developed within this dissertation to generate exploratory building designs.by Anas Alfaris.Ph.D

City.Net IES: A sustainability-oriented energy decision support system

A city's energy system processes, as well as the interactions of the energy system with other systems in a city are imperative in creating a comprehensive energy decision support system due to the interdependencies between critical segments of the system. City.Net is a sustainability-oriented decision support system that represents the energy, water, waste, transportation and building systems in a city while taking into consideration the integration and interdependencies that exist between these systems. This paper, which is focused on the integrated energy infrastructure system of a sustainable city, builds on the previous work which employs hierarchical decomposition and multi-domain formulation for the design of complex sustainable systems. The City.Net energy system encompasses the generation, transmission, distribution and consumption of energy in different forms, in several domains and at diverse scales in a city. Also, the interactions of the energy system with other aforementioned systems are incorporated in City.Net. The result is a scalable and flexible energy decision support system which can be simulated and used as a sustainability-analysis tool, encompassing environmental, social and economic sustainability

If It Looks Like a Spammer and Behaves Like a Spammer, It Must Be a Spammer

Spam in online social networks (OSNs) is a systemic problem that imposes a threat to these services in terms of undermining their value to advertisers and potential investors, as well as negatively affecting users’ engagement. As spammers continuously keep creating newer accounts and evasive techniques upon being caught, a deeper understanding of their spamming strategies is vital to the design of future social media defense mechanisms. In this work, we present a unique analysis of spam accounts in OSNs viewed through the lens of their behavioral characteristics. Our analysis includes over 100 million messages collected from Twitter over the course of 1 month. We show that there exist two behaviorally distinct categories of spammers and that they employ different spamming strategies. Then, we illustrate how users in these two categories demonstrate different individual properties as well as social interaction patterns. Finally, we analyze the detectability of spam accounts with respect to three categories of features, namely content attributes, social interactions, and profile properties