Approach for preventive maintenance planning of machine tools

This paper addresses a common problem to manufacturing companies: the maintenance of machine tools and their components. Preventive maintenance has always been a great challenge for companies, due to the need of predicting failures or production shutdowns, which requires knowledge and resources. However, the planning of machine tools maintenance presents itself as an even more complex problem due to the distinct lifetimes of their components. Age-based preventive replacement and Block replacement models define optimal replacement intervals for one item based on associated maintenance costs. A machine tool can be seen as a serial system of components or items. The concepts of group technology and clustering can be used to group components together in order to define common preventive maintenance intervals and reduce the number of production stops. In the literature, some contributions are found. However, the defined groups are static as well as the preventive maintenance intervals. This paper presents a conceptual model for the definition of dynamic clusters and intervals. It also presents an application to record the inputs, data collected in real time, needed to group components and set up preventive maintenance intervals. The developed application is being implemented in a metalworking company.We would like to thank the companies that are involved in the project and express our appreciation for the commitment of the employees involved. This work has been supported by Norte 010247 FEDER 017833 – TechParts I&D

A importância da consciência fonológica na escrita.

Relatório apresentado para cumprimento dos requisitos necessários à obtenção do grau de Mestre em Educação Pré Escolar e Ensino do 1º ciclo do Ensino Básico

Planning process for an operational management platform for a public transport

This work addresses the planning process of a public passenger transport operator, including the generation of schedules and services for vehicles and drivers, in the framework of a previously agreed service. This problem will be studied in the context of all stages of the planning process: parameterization, preparation, production of performance indicators and the generation of results for different operational scenarios.info:eu-repo/semantics/publishedVersio

Planning process for an operational management platform for a public transport

This work addresses the planning process of a public passenger transport operator, including the generation of schedules and services for vehicles and drivers, in the framework of a previously agreed service. This problem will be studied in the context of all stages of the planning process: parameterization, preparation, production of performance indicators and the generation of results for different operational scenarios.info:eu-repo/semantics/publishedVersio

Task scheduling characterisation in enterprise application integration

Cloud computing allows enterprises to incorporate applications and computational resources as services, and thus, enterprises can concentrate on their business processes, without concerning the development, configuration and maintenance of these applications and resources. Integration platforms are one of these services that allow enterprises to integrate applications in order to reduce the maintenance costs and operations of the integration of on-premises platforms. However, high performance on resources offered by the cloud, demands improvement in task scheduling of integration platforms. Our literature review has identified a lack of studies in the field of enterprise application integration, focusing on specificities and vulnerabilities of the task scheduling of integration processes. This is a pioneer work regarding the characterisation of the scheduling of tasks of integration processes. We propose a ranking according to their conceptual models and apply this ranking to five integration processes. Then, we have statistically analysed the influence of each component of their conceptual models on the performance of the execution of these integration processes. We characterise the task scheduling of integration processes and presented a mathematical equation for the makespan as a function of the components of this characterisation. This study can guide software engineers in the optimal task scheduling for integration processes, which can improve the performance runtime systems regarding using the computational resources and result in minimisation of costs of companies.info:eu-repo/semantics/acceptedVersio

Queue-priority optimized algorithm: a novel task scheduling for runtime systems of application integration platforms

The need for integration of applications and services in business processes from enterprises has increased with the advancement of cloud and mobile applications. Enterprises started dealing with high volumes of data from the cloud and from mobile applications, besides their own. This is the reason why integration tools must adapt themselves to handle with high volumes of data, and to exploit the scalability of cloud computational resources without increasing enterprise operations costs. Integration platforms are tools that integrate enterprises’ applications through integration processes, which are nothing but workflows composed of a set of atomic tasks connected through communication channels. Many integration platforms schedule tasks to be executed by computational resources through the First-in-first-out heuristic. This article proposes a Queue-priority algorithm that uses a novel heuristic and tackles high volumes of data in the task scheduling of integration processes. This heuristic is optimized by the Particle Swarm Optimization computational method. The results of our experiments were confirmed by statistical tests, and validated the proposal as a feasible alternative to improve integration platforms in the execution of integration processes under a high volume of data.info:eu-repo/semantics/acceptedVersio

Mathematical model for maintenance planning of machine tools

Preventive maintenance planning of machine tools may be a complex task for tools with multiple components. For manufacturing processes with high setup and downtime costs, components replacement should be combined to avoid too many production stoppages and therefore reduce costs. The combination that minimizes costs should take into account the lifetime distribution and the age of each component at the replacement time. Replacing too soon may imply a high number of replacements for a given component, while replacing too late may imply a high number of failures that lead to shutdowns, increasing costs. In this paper, a tool is seen as a series system, which means that whenever a component fails, a corrective action is needed and at least the failed component has to be replaced. In the literature, some of the models and heuristics for maintenance planning of series systems consider that a minimal repair is made when a component fails, while other models propose static approaches, i.e., the same combination and the same interval is used over time regardless of the ages of the components involved. This paper aims to propose a dynamic approach and presents a mathematical model to determine both the next time to perform a preventive maintenance task and the components that should be replaced in order to minimize the total cost. The model also intends to determine the components to be replaced preventively when unexpected events occur (such as the failure of a tool component or the machine, the shortage of raw material, etc.) or during planned stoppages (such as the end of a production order, machine preventive maintenance task, etc.).We would like to thank the companies associated with the project and express our appreciation for the commitment of the employees involved.This work has been supported by Norte 010247 FEDER 017833 – TechParts I&D

Progress and perspective on different strategies to achieve wake-up-free ferroelectric hafnia and zirconia-based thin films

In the last decade orthorhombic hafnia and zirconia films have attracted tremendous attention arising from the discovery of ferroelectricity at the nanoscale. However, an initial wake-up pre-cycling is usually needed to achieve a ferroelectric behaviour in these films. Recently, different strategies, such as microstructure tailoring, defect, bulk and interface engineering, doping, NH3 plasma treatment and epitaxial growth, have been employed to obtain wake-up free orthorhombic ferroelectric hafnia and zirconia films. In this work we review recent developments in obtaining polar hafnia and zirconia-based thin films without the need of any wake-up cycling. In particular, we discuss the rhombohedral phase of hafnia/ zirconia, which under a constrained environment exhibits wake-up-free ferroelectric behaviour. This phase could have a strong impact on the current investigations of ferroelectric binary oxide materials and pave the way toward exploiting ferroelectric behaviour for next-generation memory and logic gate applications.This work was supported by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Funding Contract UIDB/04650/2020 and by DST-SERB, Govt. of India through Grant Nr. ECR/2017/00006. R. F. Negrea and L. Pintilie acknowledge funding through project CEPROFER/ PN-III-P4-ID-PCCF-2016-0047 (contract 16/2018, funded by UEFISCDI). J.L.M-D. thanks the Royal Academy of Engineering Chair in Emerging Technologies Grant, CIET1819_24, the EPSRC grant EP/T012218/1- ECCS – EPSRC, and the grant EU-H2020-ERC-ADG # 882929, EROS

Hyperbaric Oxygen Therapy in Retinal Arterial Occlusion: Epidemiology, Clinical Approach, and Visual Outcomes

PURPOSE: To evaluate the efficacy and safety of hyperbaric oxygen therapy (HBOT) in patients with acute retinal artery occlusion (RAO). Secondarily, to analyse the epidemiology and the clinical approach. METHODS: Retrospective study of 13 patients submitted to HBOT between 2013 and 2018. The analysed parameters consisted of: systemic history, time between symptoms onset and treatment, initial approach, number of HBOT sessions, complications of HBOT and best corrected visual acuity-BCVA (of the total sample, central RAO-CRAO-group, and branch RAO-BRAO group). RESULTS: Arterial hypertension was the most prevalent systemic risk factor (53.8%). Initial therapies were 100% normobaric oxygen administration, topical and oral hypotensive medication, eye massage and aspirin. CRAO was observed in 69.2% and BRAO in 30.8% of the cases, with clinically significant visual improvement (a decrease in logMAR of 0.3) in 55.5% and 75%, respectively. Time between symptoms onset and treatment had a median of 9 hours. The median number of HBOT sessions was 7, without complications. CONCLUSIONS: HBOT provide BCVA improvement in patients with RAO, when it is performed in an early time after the symptom onset. It seems to be an effective and safe therapeutic option for a pathology that still remains without approved treatment.info:eu-repo/semantics/publishedVersio

The apicomplexan parasite Toxoplasma gondii

PTDC/CVT-CVT/31840/2017EXPL/CVT-EPI/1945/2013Toxoplasma gondii is a ubiquitous zoonotic parasite with an obligatory intracellular lifestyle. It relies on a specialized set of cytoskeletal and secretory organelles for host cell invasion. When infecting its felid definitive host, T. gondii undergoes sexual reproduction in the intestinal epithelium, producing oocysts that are excreted with the feces and sporulate in the environment. In other hosts and/or tissues, T. gondii multiplies by asexual reproduction. Rapidly dividing tachyzoites expand through multiple tissues, particularly nervous and muscular tissues, and eventually convert to slowly dividing bradyzoites which produce tissue cysts, structures that evade the immune system and remain infective within the host. Infection normally occurs through ingestion of sporulated oocysts or tissue cysts. While T. gondii is able to infect virtually all warm-blooded animals, most infections in humans are asymptomatic, with clinical disease occurring most often in immunocompromised hosts or fetuses carried by seronegative mothers that are infected during pregnancy.info:eu-repo/semantics/publishedVersio