Abstract

Abstract
A common pattern for enterprise applications, particularly in small and medium businesses, is the reliance on an integrated traditional relational database system that provides persistence and where the relational aspect underlies the core logic of the application. While several solutions are proposed for scaling out such applications, database replication is key if the relational aspect is to be preserved. However, it is worrisome that because proposed solutions for database replication have been evaluated using simple synthetic benchmarks, their applicability to enterprise applications is not straightforward: the performance of conservative solutions hinges on the ability to conveniently partition applications while optimistic solutions may experience unacceptable abort rates, compromising fairness, particularly considering long-running transactions. In this thesis, we address these challenges. First, by performing a detailed evaluation of the applicability of database replication protocols based on conservative concurrency control to enterprise applications. Results invalidate the common assumption that real-world databases can be easily partitioned. Then, we tackle the issue of unacceptable abort rates in optimistic solutions by proposing a novel transaction scheduler, AJITTS, which uses an adaptive mechanism that by reaching and maintaining the optimal level of concurrency in the system, minimizes aborts and improves throughput.;Um padrão comum no que toca a aplicações empresariais, particularmente em pequenas e médias empresas, é a dependência de um sistema de base dados relacional integrado que garante a persistência dos dados e no qual o aspeto relacional é parte integral da logica da aplicação. Embora várias soluções tenham sido propostas para dotar este tipo de aplicações de escalabilidade horizontal, a replicação de base de dados é a solução se o aspeto relacional deve ser preservado. No entanto, é preocupante que, dado que as soluções existentes para replicação de base de dados têm sido avaliadas utilizando testes de desempenho sintéticos e simples, a aplicabilidade destes a aplicações empresariais não é directa: o desempenho de soluções conservadoras está intimamente ligado à capacidade de particionar a aplicação convenientemente, enquanto que soluções optimistas podem sofrer de taxas de insucesso inaceitáveis o que compromete a equidade das mesmas, em particular no caso de transações especialmente longas. Nesta tese, abordamos estes desafios. Primeiro, através de uma avaliação detalhada da aplicabilidade de protocolos de replicação de base de dados baseados em controlo de concorrência conservador a aplicações empresariais. Os resultados obtidos invalidam o pressuposto comum de que bases de dados reais podem ser facilmente particionadas. Assim sendo, abordámos o problema das possíveis taxas de insucesso inaceitáveis em soluções optimistas propondo um novo escalonador de transações, o AJITTS, que utiliza um mecanismo adaptativo que ao atingir e manter o nível ótimo de concorrência no sistema, minimiza a taxa de insucesso e melhora o desempenho do mesmo.

Abstract
The paper presents a tuning method for PID controllers which substantially improves closed-loop disturbance rejection performance while keeping the tracking performance. The tuning method is based on the internal disturbance compensator which parameters are calculated according to the Magnitude Optimum criterion. The results of experiments show that the proposed model-based approach gives superior disturbance-rejection response and lower controller activity when compared to Disturbance Rejection Magnitude Optimum tuning method. © Springer International Publishing Switzerland 2017.

Abstract
This works intends to be a reduced, but complete literature review about the role of the implementation process in the new technological paradigm for manufacturing, called "Industry 4.0". This is a very recent subject that already generated a wide range of literature and discussion, although it had not yet been studied in-depth, making the term "industry 4.0" and its related concepts blurrier than concrete. The expression "implementation of industry 4.0" is too wide, since it is the result of the implementation of "industry 4.0" technologies and not the paradigm per se. The main objective of this work is to study what is known until now about the implementation of "industry 4.0". With that objective, this paper starts by presenting a definition of what is "industry 4.0" and contextualizing it in today's manufacturing environment. Then some preconditions that are required for the implementation of "industry 4.0" are presented, followed by the specificities that some particular technologies have.

Abstract
The organizational impacts of adopting social media have been on the top key concerns of organizations entering these environments. Organizations are, in fact, allocating time, effort, skills, human resources and technology and this raises the constant need to measure the ROI and legitimize the use of social media in the context of organizational development. However, how can organizations attempt to measure the efficiency and return on investments on a social media content approach that has not been strategically designed? In this paper, we report on previous research which we have further developed into a more comprehensive and solid analysis of types of social media content strategies that are being implemented in the Higher Education Sector, using clustering to group analogue content strategies and social media KPI to measure the efficiency of each of the main i. This work is based on a previously proposed editorial model for the design of social media content strategies for Higher Education Institutions, and results show which are the most relevant strategic areas of communication and corresponding return, in terms of publics' engagement, that organizations can obtain. (C) 2017 The Authors. Published by Elsevier B.V.

Abstract
In a high-volume production environment it is particularly important to ensure that key process variables and parameters are within the specification limits. Often, adjustments and changes to the process are required to ensure all applicable quality requirements. In most cases, problems are not caused by an isolated factor. In fact, they are the result of interactions between several factors, including quality ingredients, parameter settings and other processing conditions. In the biscuit manufacturing industry, the thickness and weight of the biscuit are two of the most important product's quality characteristics. Regardless of the product purchased by the customer, the declared weight is considered a specification, so any deviation of these characteristics from their nominal values leads to a change in the weight of the packages. In this paper, we explore a six-sigma approach in the improvement of an industrial biscuit production.