Estudo, conceção e construção de um sistema pneumático de aplicação de carga cíclica para processo de soldadura “pressuring difussion welding”

The joining process carried out in the solid state, named Pressuring Diffusion Welding (PDW), is a modified version of Diffusion Welding (DW). In PDW, the load applied to the samples to be joined varies in a sine wave pattern during the whole process instead of being kept constant as in DW. The PDW process produces high strength joints, due to the fact that the load wave pattern enhances rupture of the oxide scales during the initial stages of the joining process. The main objective is to upgrade an existing vacuum furnace, used to produce joints by DW, in order to enable PDW joining; this apparatus should be capable of developing cycling loads between 70 N to 15 kN, with an operative frequency comprised between 0.5 and 5 Hz. This paper will present and discuss the results obtained so far in the design, development and construction of a pneumatic actuation system needed for applying cycling loads to process transient joints by PDW. The whole setup will be presented, which includes the actuator, the force sensor and acquisition system used to evaluate the performance of the pneumatic actuation. The obtained results will also be presented and discussed.O processo de união conduzido no estado sólido, designado por Pressuring Diffusion Welding (PDW), é uma variante da Soldadura por Difusão (SD). Nas juntas obtidas por PDW, a força aplicada aos materiais a ligar varia sinusoidalmente no decorrer do processo, em vez de ser mantida constante como na SD. O PDW produz juntas de elevada resistência mecânica, em virtude de promover a rotura da película superficial de óxidos durante os instantes iniciais do processo. Pretende-se assim efetuar um “upgrade” a um forno de vazio já existente, que é usado para SD, para efetuar PDW, devendo ser capaz de aplicar cargas cíclicas de 70 N a 15 kN a uma frequência de operação de 0.5 a 5 Hz. Este artigo apresenta e discute os resultados obtidos até esta altura relativamente à conceção, desenvolvimento e construção de um sistema de atuação pneumático dedicado à aplicação de cargas cíclicas para o processamento de juntas por PDW. O equipamento de ensaio será apresentado, o qual inclui o atuador propriamente dito, um sensor de força e o sistema de aquisição de dados usado para avaliar o desempenho da atuação pneumática. Os resultados obtidos nesta fase serão igualmente apresentados e discutido

Confronting the 95 GeV excesses within the UN2HDM

We consider the small excesses around 95 GeV found in several searches for a new scalar in $\gamma \gamma$, $\tau \tau$ and $b \bar b$ final states. Instead of trying to accommodate them all, as is usually done in the literature, in the context of a given Standard Model~(SM) extension, we investigate whether it would be possible that one or two of these excesses correspond to an actual new scalar, while the remaining ones are merely statistical fluctuations. To this end, we use as benchmark model the UN2HDM, a SM extension with one scalar doublet, one scalar singlet, and an extra $\text{U}(1)'$ symmetry, which has been previously studied in the context of multiboson cascade decays. We show that most of the possibilities where the excesses in one or two of these channels disappear in the future can be accommodated by type-I or type-III UN2HDMs.Comment: LaTeX 17 page

Metabolic profiling and biological capacity of Pieris brassicae fed with kale (Brassica oleracea L. Var. Acephala).

Vegetables of the Brassica group are the most commonly grown and consumed worldwide. Food plants with apparent cancer and cardiovascular di sease-preventing properties include several varieties of Brassica oleraceae. The majority of the herbivorous insect species are specialized feeders, for which the behavioral decision to accept a plant as food or oviposition substrate is mainly related with sensory information. Pieris insects (Lepidoptera: Pieridae) are specialist herbivores of cruciferous plants

Analysis and comparison of a hydraulic and pneumatic system using the Dymola software

This work addresses the modelling of a system using Modelica language and the Dymola software tool. Dymola is a modelling and simulation environment that uses the open Modelica language to map hardware components of physical systems directly into software components. Therefore, this modelling language allows the user to model a system in a physical form, rather than a mathematical fashion, through the use of general equations, objects, and links. This paper as an informative character about a tool for the development of mechatronic systems. The topics covered here are part of a more extensive modelling and simulation work on the dynamics of mechanical systems, within the scope of an Integrated Master in Mechanical Engineering. This study was carried out based on the comparison between pneumatic and hydraulic models of the same system. Therefore, it was modeled a system used in backhoe loaders that can be operated either using a hydraulic or a pneumatic cylinder. The activity focuses, essentially, on the analysis of parameters that describe the behaviour of the system, emphasizing the position, velocity, acceleration and loads observed in both cylinders. The goal is to introduce the reader to the Dymola environment and Modelica language by addressing the modelling of a system. This study also pretends to identify significant differences regarding the behaviour performance of the pneumatic and hydraulic approaches to model the selected system, and the causes that lead to such differences.(undefined)info:eu-repo/semantics/publishedVersio

Literacy(ies) and skills in times of digital education: Exploring communication and interaction in digitally mediated learning worlds

This article seeks to explore the notions of literacy(ies) and competences in times of digital education. The aim of the study was to understand, from perspectives of experts, what literacy(ies) and competences are in digital teaching-learning contexts, how they are operationalised, which strategies can be used for their development, and what are the opportunities and challenges for their application in digital education. Through a qualitative approach, four experts were interviewed as privileged informants in their areas of expertise. The individuals interviewed are academics with extensive research in the areas of literacy(ies), digital and infocommunication skills and digital education. The interviews were conducted during the first quarter of 2023, as part of a larger ongoing study - digital and infocommunicational competences in virtual learning environments: practices in e-learning curricular units in Portuguese Higher Education. According to these experts, digital is largely responsible for the recent changes in the world, but the most important thing is not learning or teaching digital: it is developing citizens' skills or competences, exploring communication and interaction in digitally mediated learning worlds. This demands the mobilization of competences to search and exchange information, and to interact with another people in digital environments. This can help citizens become more confident, critical, and open-minded users of today’s technologies.info:eu-repo/semantics/acceptedVersio

Um esquema de elementos finitos para ondas dispersivas unidireccionais

Apresenta-se um Método de Elementos Finitos (MEF) com uma formulação de Petrov-Galerkin para a resolução numérica da equação Regularized Long Wave (RLW). O esquema proposto recorre à discretização por elementos finitos no espaço e no tempo. Introduz-se uma correcção da dispersão numérica bem como um mecanismo dissipativo altamente selectivo, através de termos adicionais upwind nas funções de peso. A integração no tempo recorre a um esquema do tipo predictor-corrector com três passos correctores. A formulação permite uma precisão de quarta ordem na forma linear, sendo condicionalmente estável. Ilustra-se a apresentação com três experiências numéricas, cujos resultados são comparados com casos similares presentes na literatura: propagação de uma onda solitária; colisão de duas ondas solitárias; propagação e break-up de um impulso de Maxwell. Conclui-se que o esquema possui boas propriedades conservativas e elevada precisão

Synthesis of red mud derived M-type barium hexaferrites with tuneable coercivity

Hexagonal ferrites can be employed in a multitude of applications, the most common hexaferrites are the M ferrites such as BaFe12O19 (barium hexaferrite, BaM). It is known that if Fe3+ is substituted with a combination of Ti4+/Co2+ the coercivity of BaM can be reduced to produce soft M ferrites with easily switchable magnetisation. They can be utilised as powders, films or bulk ceramics, and can be manufactured from a wide variety of synthesis methods. The production of hexaferrites usually requires commercial raw materials, but if an industrial waste can be utilised, this will help to ease waste disposal and storage costs, valorise a waste material and encourage circular economy. In this study, bauxite residue (red mud) from the production of alumina was used to synthesise M-type hexaferrites, using a simple ceramic process. BaCO3, or BaCO3+Co3O4, were added to the red mud, blended and heated at 1000 °C to produce the M-type hexaferrites. Without cobalt addition up to 81.1 wt% M ferrite was produced, and with Co addition up to 74.3 wt% M ferrite was formed. Without cobalt, the M ferrite phase closely resembled BaFe9Al3O19, and was a hard ferrite with a magnetisation of 12–19 A m2/kg for the whole powder (up to 23.6 A m2/kg for the M ferrite phase) and a coercivity of ~290 kA/m. When cobalt was added, secondary titanate phases vanished, and Ti4+/Co2+ partially substituted very soft M ferrite was formed with a low coercivity of ~16 kA/m but a higher magnetisation of 24.5 A m2/kg for the whole powder (up to 34.9 A m2/kg for the M ferrite phase). Therefore, not only can good quality magnetic materials be easily produced from this common waste material, but its magnetic properties can be tuned by varying the 2 + ions added during the process

Unravelling the Affinity of Alkali-Activated Fly Ash Cubic Foams towards Heavy Metals Sorption

In this work, alkali-activated fly ash-derived foams were produced at room temperature by direct foaming using aluminum powder. The 1 cm3 foams (cubes) were then evaluated as adsorbents to extract heavy metals from aqueous solutions. The foams’ selectivity towards lead, cadmium, zinc, and copper ions was evaluated in single, binary, and multicomponent ionic solutions. In the single ion assays, the foams showed much higher affinity towards lead, compared to the other heavy metals; at 10 ppm, the removal efficiency reached 91.9% for lead, 83.2% for cadmium, 74.6% for copper, and 64.6% for zinc. The greater selectivity for lead was also seen in the binary tests. The results showed that the presence of zinc is detrimental to cadmium and copper sorption, while for lead it mainly affects the sorption rate, but not the ultimate removal efficiency. In the multicomponent assays, the removal efficiency for all the heavy metals was lower than the values seen in the single ion tests. However, the superior affinity for lead was preserved. This study decreases the existing knowledge gap regarding the potential of alkali-activated materials to act as heavy metals adsorbents under different scenarios