Revealing hidden symmetries and gauge invariance of the massive Carroll-Field-Jackiw model

In this paper we have analyzed the improved version of the Gauge Unfixing (GU) formalism of the massive Carroll-Field-Jackiw model, which breaks both the Lorentz and gauge invariances, to disclose hidden symmetries to obtain gauge invariance, the key stone of the Standard Model. In this process, as usual, we have converted this second-class system into a first-class one and we have obtained two gauge invariant models. We have verified that the Poisson brackets involving the gauge invariant variables, obtained through the GU formalism, coincide with the Dirac brackets between the original second-class variables of the phase space. Finally, we have obtained two gauge invariant Lagrangians where one of them represents the Stueckelberg form.Comment: revised version. To appear in Europhysics Letter

Rendimento de massa e características morfológicas de Crotalaria ochroleuca em populações de plantas.

JIPE 2013

Ventilation and energy efficiency of buildings

O presente artigo sustenta-se numa síntese de conhecimentos sobre ventilação e eficiência energética, num contexto social de maior procura de condições de conforto no interior dos mesmos. Nas últimas décadas tem aumentado a preocupação com o consumo excessivo de energias nos edifícios, o que conduziu ao desenvolvimento e implementação legislação de modo a controlar o problema. A par disso, têm-se desenvolvido diversos tipos de edifícios com elevada eficiência energética, tirando partido do meio em que se inserem e integrando princípios da arquitetura sustentável. Por outro lado, a qualidade de ar interior tem sido uma preocupação constante dos projetistas pois, atualmente, grande parte do dia é passado em espaços fechados e com concentrações de poluentes acima dos recomendados. Estas concentrações devem-se ao aumento da preocupação com a diminuição das infiltrações sem acautelar os valores de renovação de ar adequados. Atualmente, a legislação relativa ao desempenho energético dos edifícios veio evidenciar uma evolução ao nível das exigências regulamentares relativas aos vãos envidraçados, mostrando o forte impacto que estes elementos têm nas condições de conforto interior e por consequência nos consumos energéticos dos mesmos. Os vãos envidraçados são um elemento intermediário nas trocas de energia entre o interior e o exterior, representando também pontos de infiltração não controlada de ar. Torna-se vantajoso a reabilitação dos vãos envidraçados de modo a maximizar a qualidade do ar interior e as condições de conforto, sem aumentar os consumos energéticos.This article is based on a synthesis of knowledge regarding ventilation and energy efficiency, in a social context of greater demand for comfort conditions inside them. In recent decades there has been a growing concern about the excessive consumption of energy in buildings, which has led to the development and implementation of legislation to control the problem. In addition, several types of buildings have been developed with high energy efficiency, taking advantage of the environment in which they integrate and with integrating principles of sustainable architecture. On the other hand, the quality of indoor air has been a constant concern of the project engineer because, today, a large part of the day is spent in enclosed spaces and with concentrations of pollutants above those recommended. These concentrations are due to the rising concern with the reduction of infiltrations without taking in consideration the adequate air renewal values. Currently, the legislation on the energy performance of buildings has shown an evolution in the regulatory requirements for glazed sills, showing the strong impact that these elements have on the interior comfort conditions and consequently on the energy consumptions of themselves. Glazed sills are an intermediate element in energy exchanges between the interior and exterior, also representing points of uncontrolled infiltration of air. It is advantageous to rehabilitate glazed sills in order to maximize indoor air quality and comfort conditions without increasing energy consumption.info:eu-repo/semantics/publishedVersio

Déficit hídrico severo afeta as reservas orgânicas do cafeeiro.

Os fotoassimilados, produzidos na parte aérea durante o processo de fotossíntese, são translocados para toda a planta a fim de suprir a demanda de energia que irá ser responsável pela formação de novos tecidos. A intensidade da produção, translocação e uso desses carboidratos depende entre outros fatores, da carga pendente de frutos e do status hídrico das plantas. Esse trabalho teve por objetivo verificar ao efeito do déficit hídrico nas reservas orgânicas de cafeeiros com diferentes níveis de produtividade. Os resultados mostram que os efeitos da seca afetaram em maior intensidade os níveis de reservas orgânicas das plantas e o crescimento de radicelas do que a carga pendente da cultura

Considering the stiffness of the forming tools in the numerical analysis of the ironing process

Ironing can occur in cylindrical cup drawing whenever the thickness of the drawn flange is larger than the gap between the punch and the die. This is particularly relevant for materials that present r-values lower than 1.0, such as the aluminium alloys, since they tend to present more thickening of the flange. The aim of this study is to evaluate numerically the impact of the elastic deformation of the forming tools on the final cup geometry, i.e., the earing profile and the evolution of thickness along the circumferential direction, at different heights. Different contact conditions are also analysed since they strongly affect both the thickness strain and the earing profile. The process conditions considered are the ones from EXACT, the ESAFORM Benchmark 2021, enabling the comparison with experimental results. Considering the deformation of the forming tools mainly impacts the ironing stage, enabling predicting wall thickness values larger than the gap between the punch and the die.The authors gratefully acknowledge the financial support of the Portuguese Foundation for Science and Technology (FCT) under projects with reference 2022.08459.PTDC, UIDB/00285/2020 and LA/P/0112/2020

Influence of the orthotropic behaviour on defects prediction in cup drawing, reverse redrawing and expansion

Finite elements analysis is commonly used in the cans tool design since it allows predicting different sheet metal defects and instabilities that significantly affect the efficient production of beverage cans. These defects include caring, due to the material orthotropic behaviour, thinning and fracture. The numerical prediction of these kind of defects is more complex when different combinations of strain paths are involved. The process conditions considered in this work involve the drawing of a cylindrical cup, the reverse redrawing and the expansion. The two materials under analysis are an AA5352 aluminium alloy and a TH330 steel. The materials orthotropic plastic behaviour is modelled with a non-quadratic yield criterion. The results show that changes in the yield surface lead to slight changes in the caring profile and in the location were strain localization occurs. Moreover, the numerical model must describe in detail the process conditions, since they may affect the formability prediction.The authors would like to acknowledge the funding from of the Foundation for Science and Technology (FCT) under projects with reference PTDC/EME-EME/30592/2017 and PTDC/EME-EME/31243/2017 and by European Regional Development Fund (ERDF) through the Portugal 2020 program and the Centro 2020 Regional Operational Programme (CENTRO-01-0145-FEDER-031657) under project MATIS (CENTRO-01-0145-FEDER-000014) and UID/EMS/00285/2020

Study on the influence of the strain rate sensitivity on the springback of the AA5086 alloy under warm forming conditions

Warm forming processes have been successfully applied to overcome some important drawbacks of the aluminium alloys, such as poor formability and large springback. The virtual try-out of this type of processes requires the accurate prediction of springback. The process conditions considered in this work are the ones established for the benchmark 3 - Springback of an Al-Mg alloy in warm forming conditions, proposed under the Numisheet 2016 international conference. The material under analysis is the AA5086-H111 aluminium alloy. Its mechanical behaviour is described by a Hockett-Sherby hardening law and an orthotropic yield function. The numerical analysis of the warm forming process is performed considering different yield criteria, using a strain rate-dependent flow rule. Although the material presents a positive strain rate sensitivity at 240 degrees C, the influence of the punch velocity on the punch force evolution is negligible due to the impact of the punch velocity on the temperature distribution in the cup. Since the hoop stress distribution on the ring (before splitting) is only slightly influenced by the punch velocity, the impact of the punch velocity on the springback is also negligible.The authors would like to acknowledge the funding from of the Foundation for Science and Technology (FCT) under projects with reference PTDC/EME-EME/30592/2017 and PTDC/EME-EME/31657/2017 and by European Regional Development Fund through the Portugal 2020 program and the Centro 2020 Regional Operational Programme under the project MATIS and UIDB/00285/2020