The Hyperbolic Forest Owner

This paper examines the implications of quasi-hyperbolic inter-temporal preferences to the Faustman model. The use of decreasing discount rates leads to dynamically inconsistent behavior. To solve this problem a two-stages optimization decision model is developed. The resulting actual cutting time will be anticipated compared to the Faustman optimal cutting time. If, alternatively, the equivalent constant rate of discount is the empirically observed discount rate, then the optimal cutting time is the same, but the present value of profits for the hyperbolic forest owner is always higher than the one resulting from the equivalent constant discount rate. All these results apply to both the single and the multiple rotation problems.Hyperbolic discounting; time preference; dynamic inconsistency; Faustman model; optimal rotation

Robowiki: um recurso para a robótica educativa em língua portuguesa

Nos anos mais recentes, a Robótica Educativa (RE) tem-se afirmado como uma alternativa às abordagens pedagógicas tradicionais no ensino/aprendizagem de diversos conteúdos curriculares e na aquisição das respectivas competências. No entanto, são ainda relativamente escassos os recursos ao dispor da comunidade educativa, para uma implementação da RE nas salas de aula, um cenário que se agrava quando se considera apenas a língua portuguesa. Este trabalho pretende contribuir para colmatar esta lacuna ao apresentar o sítio RoboWiki, um portal de RE onde se apresentam alguns recursos importantes, nomeadamente: (i) conjunto de planificações de sessões para um curso de introdução à RE usando kits Lego Mindstorms; (ii) planificações de sessões para abordagem de conteúdos curriculares; (iii) sugestões de projectos multidisciplinares; (iv) documentação em língua portuguesa sobre a programação de kits Lego Mindstorms. Actualmente, todos estes grupos incluem já recursos elaborados pelos autores no âmbito de trabalho em curso, convidando-se adicionalmente a comunidade educativa a contribuir para este projecto.Fundação para a Ciência e a Tecnologia (FCT

Ionic liquids in the solvent extraction of platinum-group metals : how far can they go?

ABSTRACT: Ionic liquids (ILs) are molten salts that are liquid at room temperature. Although their existence has been known from the beginning of the 20th century, only at the end of the 80's - beginning of 90´s their characteristic properties and potential advantages began to be widely explored. Nowadays there is no doubt that ILs have become a major subject of research for modern chemistry, and the industry progressively starts to include ILs in chemical processes. This communication presents and discusses some relevant results found in literature concerning the application of ILs to recover platinum-group metals (PGMs) from complex leaching solutions by solvent extraction (SX). Based on the available data, an evaluation about the forthcoming of ILs to recover PGMs from real leaching solutions of spent catalysts will be assessed.info:eu-repo/semantics/publishedVersio

First report of Meloidogyne naasi parasitizing turfgrass in Portugal

In an exploratory sampling of a football field in Porto, Portugal, the root-knot nematode, Meloidogyne naasi, previously unreported from the Iberian Peninsula, was detected. Diagnosis was based on the analysis of perineal patterns and esterase phenotypes of females excised from grass roots, morphometrics and molecular analysis (PCR with specific primers and analysis of partial 28S sequences obtained by amplification using the primers D2A/D3B) of second- stage juveniles (J2) extracted from soil. When collected in water, J2 aggregated into a worm-star. Endospores of Pasteuria penetrans were frequently found attached to the J2. To our knowledge, this is the first report of M. naasi in Portugal and in the Iberian Peninsula, and the first report of worm-star formation in Meloidogyne.The authors would like to thank Dr. M. Luísa Moura and José F. Azevedo for collaboration in sampling and sample processing. This work was supported by the strategic program UID/BIA/04050/2019 (POCI01-0145-FEDER-007569), funded by national funds through the Portuguese Foundation For Science and Technology (FCT) I.P. and by the ERDF through the COMPETE2020 – Programa Operacional Competitividade e Internacionalização (POCI)

Recovery of palladium from a spent automobile catalyst leaching solution by a thiodiglycolamide derivative

In the sequence of previous research on the development of novel liquid-liquid amidetype compounds to efficiently and selectively extract platinum-group metals (PGMs) from concentrated hydrochloric acid media, a specific thiodiglycolamide derivative – N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) – has been applied for the recovery of palladium(II) from a spent automobile catalyst leaching solution, containing palladium(II) and rhodium(III) as PGMs. The results obtained are rather promising, since the DMDCHTDGA behavior towards the two PGMs is similar to that observed for hydrochloric acid aqueous media studied before, simulating the real leaching phases. Within eleven metal elements co-existing in solution, the majority in high fold-excesses, only aluminum(III) and cerium(III) interfere in the palladium(II) liquid-liquid extraction process, requiring further optimization

Recovery of platinum(IV) and palladium(II) from complex hydrochloric acid matrices by a thiodiglycolamide derivative

The solvent extraction performance of N,N’-dimethyl-N,N’-dicyclohexylthiodiglycolamide (DMDCHTDGA) towards Pt(IV) and Pd(II) in HCl solutions has recently been published. It was shown that these two platinum-group metals (PGMs) are efficiently extracted from 8 M HCl aqueous phases, being subsequently separated by sequential strippings: 1 M HCl allows Pt(IV) recovery, whereas Pd(II) is only back-extracted by thiourea in HCl. In this work, selectivity tests were carried out to evaluate the performance of DMDCHTDGA towards the recovery of both PGMs, from 8 M HCl aqueous phases, when in presence of Rh(III), Fe(III), Ni(II), Zn(II), Al(III), Ce(III) and Zr(IV), simulating the leaching solutions that may result from the hydrometallurgical treatment of spent automobile catalytic converters. It was generally observed that the additional metal ions do not affect the recovery of Pd(II) and Pt(IV) by DMDCHTDGA. Fe(III), Zn(II) and Zr(IV) are co-extracted with Pt(IV) and Pd(II); Fe(III) and Zn(II) were efficiently scrubbed with water, whereas Zr(IV) was removed by an acidified aqueous solution. Inversely, Ni(II) is not extracted, and Rh(III) and Ce(III) appear only traceably in the loaded organic phase. Al(III) is a concern, as it is appreciably extracted, and none of the tested backextraction solutions was able to strip it

Robotics in child storytelling

Although the field of Educational Robotics (ER) has been growing over the last few years and its usefulness has been shown in many studies, its use in basic or elementary school levels has been scarce. This work intends to address the issue of demonstrating that ER makes a very useful tool at the elementary levels of learning, proposing a project-oriented approach, where interdisciplinary work uses children's stories and their imagination. The project involved the use of Lego Mindstorms robotics kits by students with ages between 9 and 12 years old. It involved the construction and programming of robots, addressing the dramatization of the popular tales "Little Red Riding Hood" and "The Three little pigs" as the final goal. Also, other groups of students implemented fashion and dancing shows, also with robots. Each of the robots performed as one of the characters of the story/ show, following a set of steps according to the script that was programmed by the students. The work involved also a previous step where the robots were built and dressed according to its role. The final results show the applicability of ER to this level of learning/ teaching. The students were able to successfully complete the project, achieving the proposed aims and also showing high levels of motivation and enthusiasm through its whole duration. The work culminated with public shows thatUniversidade do Minho. Centro de Investigação em Educação (CIEd-UMINHO

Characterisation of the progression of salts in walls of earthen architecture heritage

Two hundred years (1750–1950) of earthen architecture represents an important period of construction in the central region of Portugal. Earthen architecture is usually built close to the coast or to rivers and placed in sandy ground. The impact of rising damp is a general problem and efflorescences are a common cause of damage decay. This problem was studied in a building with two types of earthen construction, adobe masonry walls and formed masonry walls. The aim of this research was to characterise the conditions for the appearance and phase transitions of thénardite and mirabilite, and determine how to prevent progression of salt effects in the two types of wall to support future conservation measures. Laboratory capillarity and porosimetry tests with dolomitic air lime mortar and hygrothermal monitoring were pursued along with in situ tests. Visual assessment showed that the progression of salts depends on the composition of the earthen materials. To understand these differences, all crystalline solid phases were analysed by powder X-ray diffraction, and building interior hygrothermal conditions were monitored. An investigation into the influence of surface lime water painting and sacrificial mortar application on the crystallisation of sodium sulfates concluded that these also depend on the wall's composition. Data allowed us to conclude that inside the building the temperature and humidity [relative humidity (RH = 100 pw/p°w > 70)] conditions led to the adobe breakdown by the fast conversion from thénardite to mirabilite. Therefore, contact with wet atmospheres should be avoided and interior hygrothermal conditions should be controlled. Laboratory and in situ tests showed that the environmental conditions of the spaces had effects on the results. The results contribute to understanding of the salt progression and pattern of decay, as well as supporting future recommendations for building conservation, based on the identification of environmental conditions proper to their occurrence.publishe

A proposal for the evaluation of educational robotics in basic schools

Educational Robotics (ER) is increasingly used to boost student performance in several subjects, being reported successful attempts to introduce ER as a non-conventional way to help students in learning mathematics, sciences or even arts and to implement novel learning approaches, such as constructivism, project-based and problem-based learning. ER has been used to promote multidisciplinarity and collaborative work, to foster students’ motivation, imagination, creativity and logical thinking. However, available studies are mainly descriptive and qualitative. Indeed, fundamental questions, such as “Is ER a suitable tool for basic school students?” or “What are the contents/skills that can be taught/learned using ER?” remain largely unanswered. This paper proposes a methodology to conduct studies that provide an answer to those questions. Our proposal has two distinct components: (i) the planning of a set of ER sessions to conduct with the students; (ii) validation instruments to apply, for quantitative and qualitative evaluation of ER as a pedagogical tool. An example is provided for subjects related to the concepts of multiplication/ division in 4th grade Mathematics.Universidade do Minho. Centro de Investigação em Educação (CIEd)Fundação para a Ciência e a Tecnologia (FCT

A robótica educativa como ferramenta pedagógica na resolução de problemas de matemática no Ensino Básico

A Robótica Educativa (RE) tem sido apontada nos últimos anos como uma das ferramentas educativas emergentes de maior potencial. Entre as várias características que lhe são atribuídas, realça-se a sua adequação a uma aprendizagem baseada na resolução de problemas concretos cujos desafios criados promovem o raciocínio e o pensamento crítico de uma forma activa, elevando também os níveis de interesse e motivação dos alunos por matérias por vezes complexas. Estas características tornam a RE especialmente apelativa para o ensino/aprendizagem da Matemática e das ciências naturais. Neste trabalho, disponibilizam-se um conjunto de sessões usando a RE que podem ser usadas para trabalhar a resolução de problemas relacionados com as operações de multiplicação e divisão na área da Matemática para alunos do 4º ano do Ensino Básico. Estas permitem ao professor trabalhar estes conteúdos de uma forma alternativa ao ensino tradicional. Os recursos apresentados neste trabalho são enquadrados num contexto mais amplo de um portal de RE, onde se podem encontrar outros recursos úteis para a implementação da RE no Ensino Básico.Fundação para a Ciência e Tecnologia (FCT) - Bolsa de Doutoramento SFRH/BD/36919/2007