Improving the vacuum-infusion process to manufacture high quality structural composite for the aeronautic market

In last years, the vacuum-infusion processing method is being replacing successfully autoclave technologies to manufacture advanced composite structures, namely, the carbon-fibre reinforced plastic (CFRP) ones, for aeronautical and aerospace applications. The high investment associated with autoclave “prepreg” manufacturing has prompted interest in the use of alternative vacuum-infusion technologies that proven to be much more cost-effective processing methods. The present work presents, describes and discusses improvements and developments made on an existing vacuum-infusion process to obtained high quality and reliable CRFP structural components to the aircraft industry. The first aim is to use the developed technology to produce wing elevators for an unmanned aerial vehicle (UAV), commonly known as “drone”, expected to be used in firefighting and policing civilian operations. An additional heating stage was enhanced to the initial standard vacuum process to increase the quality and reliability of the final manufactured composite parts, namely in terms of void reduction and control of fibre content and orientation. A prototype part was manufactured by using this improved vacuum-infusion process to be tested and validate the developed technology. This paper will present and discuss the results obtained in the manufacturing and characterization tests made on the produced prototypes.FCT projeto UID/CTM/50025/201

POLQUAL : measuring service quality in police traffic services

Purpose The purpose of this paper is to build a customer quality assessment scale for use in the field of policing – POLQUAL. It adapts and applies a modified SERVQUAL approach to police traffic services in Portugal. Design/methodology/approach Original data was collected by means of telephone interviews over a three‐month period. The proposed scale's reliability and validity are assessed. Findings The study shows how it is possible to implement a SERVQUAL‐based approach in police traffic services. The adapted scale – POLQUAL – includes all five original dimensions plus another new dimension “promptitude”. The most negative gaps found are for the dimensions of reliability and tangibles. There was evidence that perceived quality of service decreases as the level of education of the driver increases. The paper did not find a difference between perceived quality of service provided between requested services and imposed services, respectively, represented by the accident service and radar service. Research limitations/implications The results are based on a specific police services context – that of out of office traffic services in Portugal. Practical implications The study provides the police traffic services with a tool for measuring quality of service which can provide information for focusing improvement efforts. Social implications Often the user cannot choose to interact with police services. However, in a democratic society good quality of service is essential for maintaining trust in the police services. Originality/value The study provides police traffic services with a valid and reliable tool to assess quality of service from the user's perspective.info:eu-repo/semantics/publishedVersio

Efeitos das alterações climáticas e da subida do nível do mar nos aquíferos costeiros

Neste trabalho descrever-se-ão os efeitos da subida do nível do mar no planeamento e gestão dos sistemas de captação da água doce disponível nas regiões costeiras. Recordar-se-ão as leis que regem o escoamento subterrâneo nos aquíferos do litoral e as metodologias para a procura das melhores políticas de extracção da água doce. Apresenta-se o modelo de gestão que é composto pela associação de uma técnica de optimização e de modelos de simulação do comportamento do aquífero. O modelo de optimização-simulação determina as extracções máximas permitidas a um conjunto de captações para cada cenário de subida do nível do mar, do escoamento natural no aquífero, do local de implantação e da distância de segurança entre o pé da interface água doce / água salgada e o ponto de controlo. Os efeitos na redução das extracções face à projectada subida do nível do mar e da diminuição do escoamento natural no aquífero, para que seja mantida a distância de segurança pretendida, são diversos em função do local de implantação. As superfícies e as curvas das extracções máximas em função da subida do nível do mar e do local de implantação evidenciam a necessidade dum adequado planeamento dos locais de construção das captações que antecipadamente evite os efeitos das alterações climáticas.Fundação para a Ciência e a Tecnologia (FCT

Surface photochemistry: benzophenone as a probe for the study of silica and reversed-phase silica surfaces

This work reports the use of benzophenone, a very well characterized probe, to study new hosts: two reversed-phase silicas. Laser-induced room temperature luminescence of argon purged solid powdered samples of benzophenone adsorbed onto the two different reversed-phase silicas, RP-18 and RP-8, revealed the existence of a low energy emission band in contrast with the benzophenone adsorbed on 60 A pore silica, where only triplet benzophenone emits. This low energy emission band was identified as the fluorescence of the ketyl radical of benzophenone, which is formed as the result of a hydrogen atom abstraction reaction of the triplet excited benzophenone from the alkyl groups of the surface of the reversed silicas. Such emission does not exist for benzophenone adsorbed onto 60 A pore silica. Room temperature phosphorescence was obtained in argon purged samples for all the surfaces under use. The decay times of the benzophenone emission vary greatly with the alkylation of the silica surface when compared with "normal" silica surface. A lifetime distributions analysis has shown that the shortest lifetimes for the benzophenone emission exist in the former case. Triplet-triplet absorption of benzophenone was detected in all cases and is the predominant absorption in the case of 60 A pore silica, while benzophenone ketyl radical formation occurs in the case of the reversed silicas. Diffuse reflectance laser. ash photolysis and gas chromatography-mass spectrometry techniques provided complementary information, the former about transient species and the latter regarding the final products formed after laser irradiation, both at 266 nm or 355 nm. Product analysis and identification show that the degradation photoproducts are dependent on the excitation wavelength, the photochemistry being much more rich and complex in the 266 nm excitation case, where an alpha-cleavage reaction occurs. A detailed mechanistic analysis is proposed

Caracterização dinâmica da ponte Luiz Bandeira em Sejães

A Ponte Luiz Bandeira, localizada na N333-3 sobre o Rio Vouga próxima da localidade de Sejães (Oliveira de Frades), é hoje considerada como a mais antiga ponte de betão armado em utilização no nosso país, e uma das mais velhas da Europa. Recentemente foram realizados na Ponte Luiz Bandeira um conjunto de ensaios de inspecção e diagnóstico estrutural que incluíram, entre outros, uma identificação dinâmica para a determinação das frequências naturais, modos de vibração e coeficientes de amortecimento. Para a elaboração da campanha experimental, primeiramente foi efectuada uma análise numérica de sensibilidade da resposta dinâmica da ponte, que permitiu melhor definir os procedimentos de ensaio em campo. Na ponte foram efectuados dois tipos de ensaios dinâmicos: ensaios com ruído ambiente e ensaios para a determinação dos coeficientes de amortecimento com recurso à passagem de um automóvel sobre uma prancha no pavimento a diferentes velocidades. Posteriormente, os resultados da identificação dinâmica foram utilizados para a calibração do modelo numérico que permitiu aferir, juntamente com os restantes ensaios de inspecção e diagnóstico, o estado de conservação estrutural da ponte Luiz Bandeira. A presente comunicação apresenta e descreve detalhadamente todas as fases de estudo referentes à caracterização dinâmica da ponte

A Review of Heat Treatments on Improving the Quality and Residual Stresses of the Ti–6Al–4V Parts Produced by Additive Manufacturing

Additive manufacturing (AM) can be seen as a disruptive process that builds complex components layer upon layer. Two of its distinct technologies are Selective Laser Melting (SLM) and Electron Beam Melting (EBM), which are powder bed fusion processes that create metallic parts with the aid of a beam source. One of the most studied and manufactured superalloys in metal AM is the Ti–6Al–4V, which can be applied in the aerospace field due to its low density and high melting point, and in the biomedical area owing to its high corrosion resistance and excellent biocompatibility when in contact with tissues or bones of the human body. The research novelty of this work is the aggregation of all kinds of data from the last 20 years of investigation about Ti–6Al–4V parts manufactured via SLM and EBM, namely information related to residual stresses (RS), as well as the influence played by different heat treatments in reducing porosity and increasing mechanical properties. Throughout the report, it can be seen that the expected microstructure of the Ti–6Al–4V alloy is different in both manufacturing processes, mainly due to the distinct cooling rates. However, heat treatments can modify the microstructure, reduce RS, and increase the ductility, fatigue life, and hardness of the components. Furthermore, distinct post-treatments can induce compressive RS on the part’s surface, consequently enhancing the fatigue lifeinfo:eu-repo/semantics/publishedVersio

Design, development and construction of a medical wrist rehabilitation device

This project consisted on the design, development and construction of a medical device for the rehabilitation of the wrist. The construction of the actual prototype was carried out with off-the-shelf components. The objective was to develop a functional and low cost device. The system is divided into two main components, one for the rehabilitation of the wrist and the other one to perform proprioception exercises, providing relaxation of the patient’s pain due to injuries on the wrist. All the hardware is assembled in one portable support, capable to carry out vertical and horizontal adjustments. Both systems are fully controlled through a software specially designed for being used by both physiotherapists and patients, allowing at the same time the control over the progress of rehabilitation

Design of a control system for a medical wrist rehabilitation device

The development of a new control system for a medical wrist rehabilitation device consists basically in the design of an intuitive controllable mechanism that aims to accept the parameters defined by the user and to respond adequately to that request. Two motors (a brushless motor “AEO A2830” and a stepper motor “Superior Electric M062”) are controlled by an Arduino development board, which receives and processes the instructions for the motors as well as for the acquisition software developed in LabVIEW (by National Instruments™). Two methods were used to define the interface between the user and therehabilitation mechanism, one of which is oriented to the electronic hardware and other one to the data acquisition software: the commands and instructions are addressed to the first one, while all the information is collected and registered on the second one. Since such rehabilitation mechanisms already exist, it is intended that the drawbacks of such equipment should also be addressed in the purpose of this study, complementing a gap in the health area

A control strategy for a three-phase four-wire shunt active filter

This paper presents a control strategy for a three- phase four-wire shunt active filter. The shunt active filter is a custom-power device capable to compensate, in real time, harmonics, unbalances and power factor in an electrical installation. In this work the power circuit is based on a three-leg IGBT inverter, with the dc-link composed by two capacitors connected in split. Thus the neutral point is connected directly to the midpoint of the dc-link capacitors. Its control system is composed by an algorithm based on the active and non-active currents together with a synchronizing circuit, and a novel algorithm to keep the voltages of the dc-link capacitors balanced and regulated. Due to the applied power-inverter topology, it is imperative to keep these voltages of the dc-link capacitors balanced in order to avoid malfunctioning of the active filter. To validate the proposed control strategy, simulation and experimental results are presented