Here we consider the verification and semantic integration for the set of first-order time ontologies by Allen-Hayes, Ladkin, and van Benthem that axiomatize time as points, intervals, or a combination of both within an ontology repository environment. Semantic integration of the set of time ontologies is explored via the notion of theory interpretations using an automated reasoner as part of the methodology. We use the notion of representation theorems for verification by characterizing the models of the ontology up to isomorphism and proving that they are equivalent to the intended structures for the ontology. Provided is a complete account of the meta-theoretic relationships between ontologies along with corrections to their axioms, translation definitions, proof of representation theorems, and a discussion of various issues such as class-quantified interpretations, the impact of namespacing support for Common Logic, and ontology repository support for semantic integration as related to the time ontologies examined.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008. / Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 28, 2009) Includes bibliographical references.

Thesis (Ph. D.)--Carnegie Mellon University, 2005. / "May 2005." Includes bibliographical references.

Magnetocaloric materials with first-order magnetic (FOM) phase transitions are of interest as low-cost working materials in magnetic cycles. Hysteresis is a property associated with first order transitions, and is undesirable as it can reduce performance. Devices using FOMs in active magnetic refrigeration have shown performance comparable to more expensive second-order materials, so some degree of hysteresis appears to be acceptable; however, the amount of hysteresis that may be tolerated is still an unanswered question. Among the FOM, the family of MnP-based is one of the promising materials for magnetic heat pump applications near room temperature. The present study describes the experimental investigation of a single-layer MnFeP1-xSix active magnetic regenerator (AMR), under different test conditions and following a protocol of heating and cooling processes. The results for the FOM are compared with a Gd AMR that is experimentally tested following the same protocol, with the objective to study the irreversibilities associated with FOM. The experimental tests are performed in a PM I test apparatus at a fixed displaced volume of 5.09 cm3 and a fixed operating frequency of 1 Hz. The results indicated a significant impact of the hysteresis on the heating and cooling temperature span for FOM regenerator. For certain operating conditions, multiple points of equilibrium (MPE) exist for a fixed hot rejection temperature. It is shown that the existence of MPEs can affect the performance of an AMR significantly for certain operating conditions. The present work advances our understanding since the combined hysteresis and MPE are two significant features which can impact layered AMR performance using MnFeP1-xAsx FOM by systematic experimental testing. With this objective, three multilayer MnFeP1-xAsx FOM regenerator beds are experimentally characterized under a range of applied loads and rejection temperatures. Thermal performance and the impacts of MPE are evaluated via heating and cooling experiments where the rejection (hot side) temperature is varied in a range from 283 K to 300 K. With fixed operating conditions, we find multiple points of equilibrium for steady-state spans as a function of warm rejection temperature. The results indicate a significant impact of MPE on the heating and cooling temperature span for multilayer MnFeP1-xAsx FOM regenerator. Unlike single material FOM tests where MPEs tend to disappear as load is increased (or span reduced), with the layered AMRs, MPEs can be significantly even with small temperature span conditions. A third experimental study examines the performance of MnFeP1-xAsx multilayer active magnetic regenerators. Five different matrices are tested: (i) one with three layers; (ii) one with six layers; and (iii) three, eight layer regenerators where the layer thickness is varied. The tests are performed using a dual regenerator bespoke test apparatus based on nested Halbach permanent magnets (PM II test apparatus). Operating variables include displaced volume (3.8 - 12.65 cm3), operating frequency (0.5 - 0.8 Hz) and hot-side rejection temperature (293-313 K).The results are mainly reported in terms of zero net load temperature span as a function of rejection temperature; a few tests with non-zero applied load are also presented. A maximum temperature span of 32 K is found for an 8-layer regenerator, which is similar to a previous work performed with gadolinium in the same experimental apparatus. A 1D active magnetic regenerator model accounting for thermal and magnetic hysteresis is developed and compared to experimental data for both a Gd-based and MnFeP1-xSix based AMR. Magnetic and thermal hysteresis are quantified using measured data for magnetization and specific heat under isothermal and isofield warming and cooling processes. Hysteresis effects are then incorporated in the model as irreversible work and reduced adiabatic temperature change. Model results are compared to measured temperature spans for regenerators operating with different thermal loads. Simulated results for temperature span as a function of cooling power and rejection temperature show good agreement with experimental data. The irreversible work due to hysteresis is found to have a small impact on predicted spans, indicating that useful cooling power is well predicted using cyclic measurements of adiabatic temperature change. / Graduate

Made available in DSpace on 2014-06-12T15:48:50Z (GMT). No. of bitstreams: 2 arquivo2717_1.pdf: 481883 bytes, checksum: bb9d70f42c1cda245b5340284b5dc431 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2011 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Nesta tese, provamos que todo domínio infinito finitamente gerado é bi-interpretável com a estrutura dos números naturais. Usando este argumento, demonstramos que todo anel f.g. R que tem um ideal primo nilpotente I tal que R/I é um domínio é Quase-Finitamente Axiomatizável

Background: Community resilience to a disaster is a complex phenomenon studied using a variety of research lenses, such as psychological and ecological, resulting in a lack of consensus about what the key factors are that make a community resilient. Formally representing this knowledge will allow researchers to better understand the links between the knowledge generated using different lenses and help to integrate new findings into the existing body of knowledge. Objective: Using ontology engineering methods to represent this knowledge will provide a tool to aid researchers in the field. Methods: An ontology is a structured way of organizing and representing knowledge in the field of community resilience to a disaster. The model created using this method can be read by a computer, which allows a reasoner to manipulate and infer new knowledge. Results: When using these methods to structure community resilience knowledge some of the complexities and ambiguities were identified. These included semantic ambiguities, such as two distinct factors being used interchangeably or two terms being used to describe the same factor, making the distinction between what are the factors and the characteristics of those factors, and finally, the inherited characteristics and relationships associated with hierarchical relationships. Conclusions: Having the knowledge about community resilience to a disaster represented in an ontology will aid researchers when operationalizing this knowledge in the future.

This study is concerned with the development and implementation of a preconditioner for a set of hyperbolic partial differential equations resulting from a new 5-moment closure for the prediction of gas flows both in and out of local equilibrium. This new 5-moment closure offers a robust and efficient system of first-order hyperbolic partial differential equations that has proven to provide an accurate treatment of one-dimensional gases, both in and for significant departures from local thermodynamic equilibrium. However, numerical computations using this model have proven to be difficult as a result of a singularity in the closing flux of the system. This also causes infinitely large wavespeeds in the system. The main goal of this work is to mitigate these numerical issues. Since the solution of a hyperbolic system is characterized by the waves of the system, one could suggest to scale these wavespeeds to remove the arbitrarily large speeds without altering the solution of the system. To accomplish this, this work starts with a detailed study of the behaviour of the system’s wavespeeds, given by the eigenvalues of the flux Jacobian of the system. Since, it is not possible to solve for these eigenvalues explicitly, it is suggested to approximate them by interpolation between the few states at which these waves can be solved for explicitly. With an estimate for the wavespeeds, the nature of the singularity in the system can be analyzed mathematically. The results of this mathematical analysis are used to develop a preconditioner matrix to remove the singularity from the model. To implement the proposed preconditioned model numerically, a centred-difference scheme with artificial dissipation is proposed. A dual-time-stepping strategy is developed and implemented with implicit Euler time marching for both physical and pseudo time iteration. This dual-time treatment allows the preconditioned system to remain applicable to time-accurate problems and is found to greatly increase the robustness of the solution of the steady-state problems. Solutions to several canonical problems for both continuum and non-equilibrium flow are computed and comparisons are made to classical models.

Thesis. 1976. Ph.D.--Massachusetts Institute of Technology. Dept. of Philosophy. / Microfiche copy available in Archives and Humanities. / Bibliography: leaves 165-170. / Ph.D.

No description available.

It is a common practice when designing a system to apply safety factors to the critical failure load or event. These safety factors provide a buffer against failure due to the random or un-modeled behavior, which may lead the system to exceed these limits. However these safety factors are not directly related to the likelihood of a failure event occurring. If the safety factors are poorly chosen, the system may fail unexpectedly or it may have a design which is too conservative. Reliability-Based Design Optimization (RBDO) is an alternative approach which directly considers the likelihood of failure by incorporating a reliability analysis step such as the First-Order Reliability Method (FORM). The FORM analysis requires the solution of an optimization problem however, so implementing this approach into an RBDO routine creates a double-loop optimization structure. For large problems such as Reliability-Based Topology Optimization (RBTO), numeric sensitivity analysis becomes computationally intractable. In this thesis, a general approach to the sensitivity analysis of nested functions is developed from the Lagrange Multiplier Theorem and then applied to several Reliability-Based Design Optimization problems, including topology optimization. The proposed approach is computationally efficient, requiring only a single solution of the FORM problem each iteration. / Master of Science