A dynamic two phase flow model for a pilot scale sodium borohydride hydrogen generation reactor

A two-dimensional, non-isothermal, and dynamic model was developed to describe a sodium borohydride/hydrogen re-actor for stationary use. All relevant transport phenomena were treated in detail and the kinetic model developed previ-ously by the authors was introduced into the algorithm. In this paper the reactive solution was modeled as a two phase flow; with this approach the impact of the hydrogen production on the solution stirring could be observed and quantified. Results showed that not all ruthenium deposited on the nickel foam was used efficiently as catalyst. In fact, most of the reaction occurred in the surface of the catalyst foam and around 70% of the deposited catalyst was not used. It was also demonstrated the importance of the two phase flow approach for a correct simulation of the solution stirring and heat transfer

Graviton resonances on two-field thick branes

This work presents new results about the graviton massive spectrum in two-field thick branes. Analyzing the massive spectra with a relative probability method we have firstly showed the presence of resonance structures and obtained a connection between the thickness of the defect and the lifetimes of such resonances. We obtain another interesting results considering the degenerate Bloch brane solutions. In these thick brane models, we have the emergence of a splitting effect controlled by a degeneracy parameter. When the degeneracy constant tends to a critical value, we have found massive resonances to the gravitational field indicating the existence of modes highly coupled to the brane. We also discussed the influence of the brane splitting effect over the resonance lifetimes.Comment: 15 pages, 8 figure

Control of uncertain compartmental systems

\ A study of the performance of mass control for compartmental systems, under the presence of uncertainties, is presented. Bounds for the asymptotical mass offset are derived as a functional of the uncertainty bounds. The obtained results are illustrated by simulations for the case of neuromuscular blockade control of patients undergoing surgery

Strategic partnerships in the renewable energy sector in Portugal

This paper focuses on the strategic partnerships established by firms operating in the renewable energy technologies sector in Portugal. The analysis aims at contributing to deepen the knowledge about the types and forms of partnerships in the renewables sector. The goal is to uncover the factors that explain the success of these partnerships and draw conclusions on the way they contributed to building a renewables cluster in Portugal.info:eu-repo/semantics/acceptedVersio

Strategic partnerships of the renewable energy firms in Portugal

This paper focuses on the strategic partnerships established by firms operating in the renewable energy technologies sector in Portugal. The analysis aims at contributing to deepen the knowledge about the types and forms of partnerships in the renewables sector. The goal is to uncover the factors which explain the success of these partnerships and draw conclusions on the way they contributed to building a renewables cluster in Portugal.FC

Encurralados na pandemia de COVID-19: o efeito da preocupação com o risco e das emoções no burnout nos profissionais de saúde

The COVID-19 pandemic poses critical challenges for the health care workers (HCWs) around the world due to the increasing demands imposed on health care systems. This study aims to investigate how risk concern impacts burnout via positive and negative affect. Further, the moderating role of risk exposure (low, medium, and high) in this parallel mediation model is examined. A sample of 257 Portuguese HCWs answered a questionnaire. Structural equation modeling (SEM) analysis was applied. Results showed that risk concern positively influences negative affect – but not positive affect – and, consequently, burnout. Contrary to our expectations, this indirect effect was not greater for individuals in the high-risk group (vs. low-risk group), which can be explained by individual and organizational factors' buffering role. These findings draw healthcare organizations' attention to the hazardous effects of risk concern on HCWs' well-being.info:eu-repo/semantics/publishedVersio

Self-Similarity of Friction Laws

The change of the friction law from a mesoscopic level to a macroscopic level is studied in the spring-block models introduced by Burridge-Knopoff. We find that the Coulomb law is always scale invariant. Other proposed scaling laws are only invariant under certain conditions.}Comment: Plain TEX. Figures not include