No description available.

No description available.

No description available.

This thesis provides a specification theory with strong algebraic and compositionality properties, allowing for the systematic construction of new components out of existing ones, while ensuring that given properties continue to hold at each stage of system development. The theory shares similarities with the interface automata of de Alfaro and Henzinger, but is linear-time in the style of Dill's trace theory, and is endowed with a richer collection of operators. Components are assumed to communicate with one another by synchronisation of input and output actions, with the component specifying the allowed sequences of interactions between itself and the environment. When the environment produces an interaction that the component is unwilling to receive, a communication mismatch occurs, which can correspond to run-time error or underspecification. These are modelled uniformly as inconsistencies. A linear-time refinement preorder corresponding to substitutivity preserves the absence of inconsistency under all environments, allowing for the safe replacement of components at run-time. To build complex systems, a range of compositional operators are introduced, including parallel composition, logical conjunction and disjunction, hiding, and quotient. These can be used to examine the structural behaviour of a system, combine independently developed requirements, abstract behaviour, and incrementally synthesise missing components, respectively. It is shown that parallel composition is monotonic under refinement, conjunction and disjunction correspond to the meet and join operations on the refinement preorder, and quotient is the adjoint of parallel composition. Full abstraction results are presented for the equivalence defined as mutual refinement, a consequence of the refinement being the weakest preorder capturing substitutivity. Extensions of the specification theory with progress-sensitivity (ensuring that refinement cannot introduce quiescence) and real-time constraints on when interactions may and may not occur are also presented. These theories are further complemented by assume-guarantee frameworks for supporting component-based reasoning, where contracts (characterising sets of components) separate the assumptions placed on the environment from the guarantees provided by the components. By defining the compositional operators directly on contracts, sound and complete assume-guarantee rules are formulated that preserve both safety and progress. Examples drawn from distributed systems are used to demonstrate how these rules can be used for mechanically deriving component-based designs.

In this dissertation, an innovative approach combining continuum mechanics and atomistic simulations is exposed to develop a nanomechanics theory for modeling and predicting the macroscopic behavior of nanomaterials. This nanomechanics theory exhibits the simplicity of the continuum formulation while taking into account the discrete atomic structure and interaction near surfaces/interfaces. There are four primary objectives to this dissertation. First, theory of interfaces is revisited to better understand its behavior and effects on the overall behavior of nanostructures. Second, atomistic tools are provided in order to efficiently determine the properties of free surfaces and interfaces. Interface properties are reported in this work, with comparison to both theoretical and experimental characterizations of interfaces. Specifically, we report surface elastic properties of groups 10 11 transition metals as well as properties for low-CSL grain boundaries in copper. Third, we propose a continuum framework that casts the atomic level information into continuum quantities that can be used to analyze, model and simulate macroscopic behavior of nanostructured materials. In particular, we study the effects of surface free energy on the effective modulus of nano-particles, nanowires and nano-films as well as nanostructured crystalline materials and propose a general framework valid for any shape of nanostructural elements / nano-inclusions (integral forms) that characterizes the size-dependency of the elastic properties. This approach bridges the gap between discrete systems (atomic level interactions) and continuum mechanics. Finally this continuum outline is used to understand the effects of surfaces on the overall behavior of nano-size structural elements (particles, films, fibers, etc.) and nanostructured materials. More specifically we will discuss the impact of surface relaxation, surface elasticity and non-linearity of the underlying bulk on the properties nanostructured materials.