As we begin to analyze and construct extremely complex systems, a theory for understanding and designing the underlying architecture becomes very important. To move in the direction of a precise theory of architecture, this thesis will provide some concrete tools to analyze and design complex systems with a given network structure. The first main result of this thesis analyzes the vulnerability of a system and shows that a system's vulnerability depends on its network structure. We will consider destabilization attacks acting on a single link in a system's logical interconnection structure. The concept of a vulnerable link is characterized and necessary and sufficient conditions for identifying these links are provided. The vulnerability of various system architectures are then characterized by the vulnerability of their weakest link, and it is shown that every transfer function has a completely secure architecture with no vulnerable links. The second part of this thesis focuses on synthesizing controllers with a specified network structure. It presents a new approach to distributed controller design that exploits the dynamical structure function representation of linear time invariant systems to characterize the structure of a system. The design technique sequentially constructs each link in an arbitrary controller signal structure, and the main theorem proves that either the resulting controller is stabilizing or that no controller with the desired structure can stabilize the system.

This thesis presents the development and validation of a novel interface modelling methodology integrated with a system architectural analysis framework that emphasises the need to manage the integrity of deriving and allocating requirements across multiple levels of abstraction in a structured manner. The state of the art review in this research shows that there is no shared or complete interface definition model that could integrate diverse interaction viewpoints for defining system requirements with complete information. Furthermore, while existing system modelling approaches define system architecture with functions and their allocation to subsystems to meet system requirements, they do not robustly address the importance of considering well-defined interfaces in an integrated manner at each level of systems hierarchy. This results in decomposition and integration issues across the multiple levels of systems hierarchy. Therefore, this thesis develops and validates following: -Interface Analysis Template as a systematic tool that integrates diverse interaction viewpoints for modelling system interfaces with intensive information for deriving requirements. -Coupling Matrix as an architecture analysis framework that not only allocates functions to subsystems to meet requirements but also promotes consistent consideration of well-defined interfaces at each level of design hierarchy. Insights from the validation of developed approach with engineering case studies within an automotive OEM are discussed, reflecting on the effectiveness, efficiency and usability of the methods.

Monitoring the health status of coral reefs is a crucial activity in protecting the environment. One way is by conducting "Manta tow surveys." For a long time, these surveys were conducted by a diver holding a board being towed by a boat. In this thesis, we propose a new vehicle design that works as a platform to help conduct the "towboard" activities for underwater coral reef surveys. It utilizes paravane or depressor features which is a common tool used by fishermen to catch fish at a specified depth. The vehicle offers a compact size, modular design, and control surfaces to maneuver around and close to reef walls. The thesis describes the architecture of the overall system and its components, the design decisions, the mechanical interfaces, and a brief description of the dynamics. An experiment is conducted to validate the design and verify system performance, measuring pressure, speed, and orientation. The prototype is presented as a proof of concept.

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This thesis describes an adaptable component level machinery system weight and size estimation tool used in the context of a ship distributed system architecture framework and ship synthesis model for naval ship concept design. The system architecture framework decomposes the system of systems into three intersecting architectures: physical, logical, and operational to describe the spatial and functional relationships of the system together with their temporal behavior characteristics. Following an Architecture Flow Optimization (AFO), or energy flow analysis based on this framework, vital components are sized based on their energy flow requirements for application in the ship synthesis model (SSM). Previously, components were sized manually or parametrically. This was not workable for assessing many designs in concept exploration and outdated parametric models based on historical data were not sufficiently applicable to new ship designs. The new methodology presented in this thesis uses the energy flow analysis, baseline component data, and physical limitations to individually calculate sizes and weights for each vital component in a ship power and energy system. The methodology allows for new technologies to be quickly and accurately implemented to assess their overall impact on the design. The optimized flow analysis combined with the component level data creates a higher fidelity design that can be analyzed to assess the impact of various systems and operational cases on the overall design. This thesis describes the SSM, discusses the AFO's contribution, and provides background on the component sizing methodology including the underlying theory, baseline data, energy conversion, and physical assumptions. / Master of Science / This thesis describes an adaptable component level machinery system weight and size estimation tool used in the context of a preliminary ship system design and naval ship concept design. The system design decomposes the system of systems into three intersecting areas: physical, logical, and operational to describe the spatial and functional relationships of the system together with their time dependent behavior characteristics. Following an Architecture Flow Optimization (AFO), or energy flow analysis based on this system design, vital components are sized based on their energy flow requirements for application in the ship synthesis model (SSM). Previously, components were sized manually or with estimated equations. This was not workable for assessing many designs in concept exploration and outdated equation models based on historical data were not sufficiently applicable to new ship designs. The new methodology presented in this thesis uses the energy flow analysis, baseline component data, and physical limitations to individually calculate sizes and weights for each vital component in a ship power and energy system. The methodology allows for new technologies to be quickly and accurately implemented to assess their overall impact on the design. The optimized flow analysis combined with the component level data creates a more accurate design that can be analyzed to assess the impact of various systems and operational cases on the overall design. This thesis describes the SSM, discusses the AFO’s contribution, and provides background on the component sizing methodology including the underlying theory, baseline data, energy conversion, and physical assumptions.

The purpose of this thesis is to characterize, compare and contrast four network-centric software architectures, namely Client-Server Architecture (CSA), Distributed Objects Architecture (DOA), Service-Oriented Architecture (SOA) and Peer-to-Peer Architecture (PPA) and seven associated frameworks consisting of .NET, Java EE, CORBA, DCOM, Web Services, Jini and JXTA with respect to a set of derived criteria. Network-centric systems are gaining in popularity as they have the potential to solve more complex problems than we have been able to in the past. However, with the rise of SOA, Web Services, a set of standards widely used for implementing service-oriented solutions, is being touted as the "silver bullet" to all problems afflicting the software engineering domain with the danger of making other architectures seem obsolete. Thus, there is an urgent need to study the various architectures and frameworks in comparison to each other and understand their relative merits and demerits for building network-centric systems. The architectures studied here were selected on the basis of their fundamentality and generality. The frameworks were chosen on the basis of their popularity and representativeness to build solutions in a particular architecture. The criteria used for comparative assessment are derived from a combination of two approaches — by a close examination of the unique characteristics and requirements of network-centric systems and then by an examination of the constraints and mechanisms present in the architectures and frameworks under consideration that may contribute towards realizing the requirements of network-centric systems. Not all of the criteria are equally relevant for the architectures and frameworks. Some, when relevant, are relevant in a different sense from one architecture (or framework) to another. One of the conclusions that can be drawn from this study is that the different architectures are not completely different from each other. In fact, CSA, DOA and SOA are a natural evolution in that order and share several characteristics. At the same time, significant differences do exist, so it is clearly possible to judge/differentiate one from the other. All three architectures can coexist in a single system or system of systems. However, the advantages of each architecture become apparent only when they are used in their proper scope. At the same time, a sharp difference can be perceived between these three architectures and the peer-to-peer architecture. This is because PPA aims to solve a totally different class of problems than the other three architectures and hence has certain unique characteristics not observed in the others. Further, all of the frameworks have certain unique architectural features and mechanisms not found in the others that contribute towards achieving network-centric quality characteristics. The two broad frameworks, .NET and Java EE offer almost equivalent capabilities and features; what can be achieved in one can be achieved in the other. This thesis deals with the study of all the four architectures and their related frameworks. The criteria used, while fairly comprehensive, are not exhaustive. Variants of the fundamental architectures are not considered. However, system/software architects seeking an understanding of the tradeoffs involved in using the various architectures and frameworks and their subtle nuances should benefit considerably from this work. / Master of Science

Research in the area of autonomous mobile robots has increased over the last several years. Autonomous mobile robots are now being used in a wide variety of applications, including nuclear plant maintenance, interplanetary exploration, military missions and smart highway systems. This thesis is a survey of recent publications, 1990-1996, of wheeled autonomous mobile robots for harsh environments. Various sensing, navigation, and motion control strategies commonly used on autonomous mobile robots are compared. The integration of all three systems in a system architecture is also presented. Following a general discussion of autonomous mobile robot technology, vehicles that have entered the Unmanned Ground Robotics Competition are presented as a focused study of the application of this broad field of research. / Master of Science

The integration of mobile and sensor technologies, and the design and implementation of different web-enabled visualizations to support inquiry learning in different educational scenarios encompass the main research efforts carried out in this thesis. These challenges are addressed from the perspectives of mobile and web engineering, visualization and technology-enhanced learning (TEL). Thus, the main research question investigated in this thesis relates to the identification of the main features that can guide the design and implementation of web and mobile applications to support inquiry learning in different contexts. This thesis consists of a collection of four publications that describe the research efforts conducted during a period of three years in relation to the Learning Ecology through Science with Global Outcomes (LETS GO) research project. The research questions investigated and the implemented technological solutions reported in these publications are closely related to the main goals and challenges of this thesis. The design and implementation of the proposed software system was guided, deployed and refined having the following aspects in mind: (1) System Requirements and Architectural Design, (2) System Implementation and Deployment, and (3) System Assessment and Web Usability Testing. During the three years of development efforts, three software prototypes were implemented utilizing service-oriented approaches. These efforts have been tested with more than 200 users in connection to several trials that took place during this period. The user trials allowed testing the software application throughout three development iterations on authentic settings, while new requirements continuously emerged in these activities. This process made it possible to verify that user requirements were adequately addressed while satisfying their needs. The outcomes of these activities led to the design and implementation of a system architecture that relies on service-oriented approaches and open standards. The main outcomes of this thesis are presented in the form of Architectural Concepts, as they can be used to guide the design and implementation of web and mobile applications to support inquiry learning. The idea behind architectural concepts is to provide a set of tools for supporting the overall life cycle of a software development process, such as requirements, design, implementation, deployment and testing while coping with rapid changes of technological implementations. Some of the architectural concepts identified in this thesis correspond well with the kind of support that inquiry-learning activities require. They provide solid foundations in terms of possibilities to tackle the requirements for supporting inquiry learning in a flexible manner.

Dans de nombreux projets de végétalisation, le sol est la principale entrave à l’implantation des végétaux. Il est donc fondamental de connaitre la manière dont les systèmes racinaires se mettent en place dans le sol. La mise en place du système racinaire dans le milieu souterrain correspond à l’expression du patrimoine génétique guidé par les contraintes du sol. A travers ce document nous avons tout d’abord présenté la mise en place des systèmes racinaires des espèces herbacées résultant du patrimoine génétique puis nous avons présenté sa plasticité face à certaines contraintes du sol. Les espèces ne possèdent pas forcément un simple système racinaire mais une combinaison de systèmes racinaires qui se met progressivement en place. Nous présentons dans ce document une typologie et une classification de ces systèmes racinaires selon leur localisation et l’implication de l’organe-support dans la multiplication de l’espèce. Nous nous intéressons aussi à l’effet des contraintes du sol sur la mise en place de l’architecture racinaire : la résistance à la pénétration qui est une contrainte récurrente même dans les terres cultivées et la porosité grossière qui est une contrainte présente dans les sols remaniés. Des expérimentations ont été menées sur une diversité d’espèces herbacées afin de comparer leur architecture racinaire en présence ou non une zone de contrainte. Concernant la résistance à la pénétration, nous retrouvons et généralisons les résultats obtenus par d’autres chercheurs sur d’autres espèces herbacées tels que la diminution du taux de croissance ou l’augmentation du diamètre des racines au niveau de la contrainte. De même, nous retrouvons des traits prédictifs de capacité de pénétration tels que le diamètre apical racinaire et le taux de croissance racinaire et nous mettons en avant la teneur en matière sèche du système racinaire avec une corrélation négative. Concernant la porosité grossière, nous observons un effet sur la croissance racinaire, le diamètre apical racinaire et le développement de primordia lorsque la porosité est très grossière / In many revegetation projects, the soil is the main obstacle to the establishment of plants. It is therefore essential to know how the root systems are set up in the ground. The root systems establishment is the expression of the genetic heritage guided by the constraints of the environment. In this document we first presented the root systems development of herbaceous species resulting from genetic and then we presented its plasticity face to soil constraints. The species do not have a single root system, but a combination of root systems that are implemented gradually. We present here a typology and classification of root systems depending on their location and on the bearing-organ involvement in the vegetative multiplication of the species. We are also interested in the effect of soil constraints on the development of root architecture: the penetration resistance is a recurring stress even in cultivated land and the gross porosity is a stress present in soils reworked. Experiments were conducted on a variety of herbaceous species to compare their root architecture with or without a stress zone. Regarding the penetration resistance, we find and generalize the results obtained by other researchers on other herbaceous species such as the decreasing root growth rate or the increasing root diameter at the level of the stress. Similarly, we find the traits predicting the penetration such as root apical diameter and root growth rates and we highlight the root dry matter content with a negative correlation. Regarding the gross porosity, we observe an effect on root growth rate, root apical diameter and primordia development when the porosity is very gross

Robustness of a system has been defined in various ways and a lot of work has been done to model the robustness of a system, but quantifying or measuring robustness has always been very difficult. In this research, we develop a framework for robust system architecture. We consider a system of a linear estimator (multiple tap filter) and then attempt to model the system performance and robustness in a graphical manner, which admits an analysis using the differential geometric concepts. We compare two different perturbation models, namely the gradient with biased perturbations (sub-optimal model) of a surface and the gradient with unbiased perturbations (optimal model), and observe the values to see which of them can alternately be used in the process of understanding or measuring robustness. In this process we have worked on different examples and conducted many simulations to find if there is any consistency in the two models. We propose the study of robustness measures for estimation/prediction in stationary and non-stationary environment using differential geometric tools in conjunction with probability density analysis. Our approach shows that the gradient can be viewed as a random variable and therefore used to generate probability densities, allowing one to draw conclusions regarding the robust- ness. As an example, one can apply the geometric methodology to the prediction of time varying deterministic data in imperfectly known non-stationary distribution. We also compare stationary to non-stationary distribution and prove that robustness is reduced by admitting residual non-stationarity. We then research and develop a robust iterative handoff algorithm, relating generally to methods, devices and systems for reselecting and then handing over a mobile communications device from a first cell to a second cell in a cellular wireless communications system (GPRS, W-CDMA or OFDMA). This algorithm results in significant decrease in amount of power and/or result is a decrease of break in communications during an established voice call or other connection, in the field, thereby outperforming prior art.