SAVCBS 2001 Proceedings: Specification and Verification of Component-Based Systems, Workshop at OOPSLA 2001

The goal of this workshop was to explore how formal (i.e., mathematical) techniques can be or should be used to establish a suitable foundation for specification and verification of component-based systems. Component-based systems are a growing concern for the object-oriented community. Specification and reasoning techniques are urgently needed to permit composition of systems from components, for which source code is unavailable. This report is the proceedings of the worksho

Algebraic Principles for Program Correctness Tools in Isabelle/HOL

This thesis puts forward a flexible and principled approach to the development of construction and verification tools for imperative programs, in which the control flow and the data level are cleanly separated. The approach is inspired by algebraic principles and benefits from an algebraic semantics layer. It is programmed in the Isabelle/HOL interactive theorem prover and yields simple lightweight mathematical components as well as program construction and verification tools that are themselves correct by construction. First, a simple tool is implemented using Kleeene algebra with tests (KAT) for the control flow of while-programs, which is the most compact verification formalism for imperative programs, and their standard relational semantics for the data level. A reference formalisation of KAT in Isabelle/HOL is then presented, providing three different formalisations of tests. The structured comprehensive libraries for these algebras include an algebraic account of Hoare logic for partial correctness. Verification condition generation and program construction rules are based on equational reasoning and supported by powerful Isabelle tactics and automated theorem proving. Second, the tool is expanded to support different programming features and verification methods. A basic program construction tool is developed by adding an operation for the specification statement and one single axiom. To include recursive procedures, KATs are expanded further to quantales with tests, where iteration and the specification statement can be defined explicitly. Additionally, a nondeterministic extension supports the verification of simple concurrent programs. Finally, the approach is also applied to separation logic, where the control-flow is modelled by power series with convolution as separating conjunction. A generic construction lifts resource monoids to assertion and predicate transformer quantales. The data level is captured by concrete store-heap models. These are linked to the algebra by soundness proofs. A number of examples shows the tools at work

QoS and trust prediction framework for composed distributed systems

The objective of this dissertation is to propose a comprehensive framework to predict the QoS and trust (i.e, the degree of compliance of a service to its specification) values of composed distributed systems created out of existing quality-aware services. We improve the accuracy of the predictions by building context-aware models and validating them with real-life case studies. The context is the set of environmental factors that affect QoS attributes (such as response time and availability), and trust of a service or a composed system. The proposed framework uses available context-QoS dependency information of individual services and information about the interaction patterns among the services to make predictions for the QoS and trust values of the composed system at the design phase of the development lifecycle. Such predictions made in the early phases of the system development lifecycle will reduce cost, time, and effort. We demonstrate the use of these predictions in selecting the optimum set of services to create composed systems using heuristic optimization algorithms. Additionally, the prediction model is used at runtime with fast heuristic techniques to build adaptable composed systems. The empirical results show the proposed context-dependent framework performs well in providing more accurate predictions than the prevalent approaches

Análisis de dispositivos de microondas con simetrías de primer y segundo orden mediante el Método de los Elementos Finitos 2D

Los dispositivos de microondas son la base sobre la cual se fundamentan los sistemas de comunicaciones, hoy en día omnipresentes como consecuencia del enorme crecimiento y popularización que han sufrido las Tecnologías de la Información (TI). Ámbitos como las comunicaciones inalámbricas ubicuas (como el 5G), el Internet de las Cosas (IoT, por sus siglas en inglés) y los sistemas de geolocalización (Galileo, GPS, GLONASS), así como otras recientes iniciativas privadas (Starlink de SpaceX, Proyecto Kuiper de Amazon) necesitan de nuevos dispositivos con capacidades y prestaciones potenciadas que atiendan las demandas de la industria. Entre las tecnologías más utilizadas en el ámbito de alta potencia y bajas pérdidas está la guía de onda, muy empleada, por ejemplo, en aplicaciones aeroespaciales. En el contexto de las antenas diseñadas en esta tecnología, también destacan las estructuras selectivas en frecuencia (FSS) y polarización (PSS), elaboradas mediante rejillas periódicas y capaces de ser fabricadas mediante manufacturación aditiva (impresión 3D). Para el diseño y optimización de estos dispositivos de microondas predominan hoy en día las herramientas basadas en el diseño asistido por ordenador (CAD, en inglés). Estas herramientas, versátiles y potentes, permiten hacer el análisis electromagnético de las estructuras basadas en las tecnologías antes descritas y muchas otras, obteniendo una gran precisión en los resultados. En este ámbito, destaca el Método de los Elementos Finitos (FEM, por sus siglas en inglés), basado en la división de una estructura en secciones finitas, para las que se obtiene un resultado discretizado que es una aproximación del real. Esta técnica, a pesar de ser potente y general, y precisamente por ello, puede ser muy costosa computacionalmente. En este proyecto, atendiendo a la demanda de crear herramientas de análisis más completas y eficientes, se ha tomado como punto de partida el Método de los Elementos Finitos, y se ha estudiado en casos particulares aplicados a guías de onda, FSS y PSS; tanto de análisis modal como de problemas de excitación, buscando optimizaciones que reduzcan el coste computacional y aporten información de interés basándose en las propiedades de simetría de dichas estructuras, tanto de primer como de segundo orden

2023 - The Fourth Annual Fall Symposium of Student Scholars

The full program book from the Fall 2023 Symposium of Student Scholars, held in November 2023. Includes abstracts from the presentations and posters.https://digitalcommons.kennesaw.edu/sssprograms/1028/thumbnail.jp

Passivity enforcement via chordal methods

Orientador: Prof. Dr. Gustavo Henrique da Costa OliveiraTese (doutorado) - Universidade Federal do Paraná, Setor de Tecnologia, Programa de Pós-Graduação em Engenharia Elétrica. Defesa : Curitiba, 27/08/2019Inclui referências: p. 164-175Resumo: Neste documento são propostos três algoritmos inéditos associados aos problemas subsequentes de aferição e imposição da passividade, a qual é uma propriedade qualitativa, geral e fundamental na modelagem matemática de transitórios eletromagnéticos de sistemas elétricos passivos, como transformadores. Esses algoritmos baseiam-se numa combinação de teoria dos grafos e otimização convexa. O primeiro deles consiste na aferição de subsistemas passivos contidos num sistema não passivo, intuitivamente busca-se partes passivas contidas num todo não passivo. Já na etapa de imposição de passividade, o segundo algoritmo é consequência natural do primeiro: retendo apenas os parâmetros associados às partes passivas e descartando os demais, parte-se de um sistema passivo parcialmente especificado para se determinar novos parâmetros em substituição àqueles descartados de modo que o sistema como um todo seja passivo. A possibilidade de determinação dos novos parâmetros depende de uma propriedade topológica de um grafo associado às matrizes de parâmetros do modelo, tal propriedade é denominada cordalidade. O terceiro algoritmo aborda novamente a questão de imposição da passividade e também faz uso da cordalidade, não mais como condição de existência de solução, mas sim como uma forma de explorar a esparsidade das matrizes de parâmetros. O problema de imposição da passividade encerra dois desafios no seu processo de solução, a saber: (i) compensação de parâmetros resultando na degradação do modelo bem como (ii) longos tempos de solução. Os algoritmos ora propostos são uma resposta a essas questões e os resultados obtidos demonstraram-se comparáveis àqueles já existentes na literatura especializada, em alguns casos apresentando melhorias, seja em termos de aproximação ou tempo computacionais. Os algoritmos foram testados a partir de dados de medição de um Transformador de Potencial Indutivo bem como de um Transformador de Potência. Palavras-chave: Macro-modelagem Passiva. Teoria de Sistemas. Álgebra Linear Aplicada. Análise de Transitórios. Transformadores.Abstract: Three novel algorithms are herein proposed to solve passivity assessment and enforcement problems. Passivity is a general, qualitative and fundamental property pertaining to the modeling associated with electromagnetic transients in passive power systems, such as transformers. These algorithms make combined use of Graph Theory and Convex Optimization. The first algorithm is concerned with passivity assesment. In particular, it searches for passive subsystems embedded into a larger nonpassive system and eventually specifies a partially specified passive system. Focusing on the subsequent step, algorithm two is a natural consequence of the preceeding one: retaining only the parameter set associated with passive subsystems as determined before, this partially specified passive system is used to further determine the remaining parameters so that the entire system be fully specified and passive. The existence condition for finding a fully specified system hinges on the fulfillment of a topological property of the graph associated the parameter matrices, namely chordality. The third algorithm also solves the passivity enforcement problem by making use of chordality, not as an existence condition, but rather by exploiting chordal sparsity patterns obtained with the parameter matrices. Solving passivity enforcement problems entails two persisting challenges, namely: (i) passivity compensations to parameters prompting increased model degradation as well as (ii) large computation times. The algorithms herein proposed tackle these issues and yield results comparable to those already in use, sometimes resulting in improved performance in terms of either approximation accuracy or runtime. These results herein reported entail data from actual measurements of an Inductive Voltage Transformer and a Power Transformer. Keywords: Passive Macromodeling. System Theory. Applied Linear Algebra. Transient Analysis. Transformers