MATHEMATICAL MODELLING OF MACROSEGREGATION IN INGOT CASTING

The occurrence of macrosegregation in alloys produced by ingot casting can adversely affect the quality of the final product. Macrosegregation can be described as a severe variation on the macroscopic scale of the chemical species that compose the alloy, and the ability of computational simulations to predict such defects remains far from perfect. Therefore, this research focuses on the development of a two-dimensional mathematical model that - through computational simulations - could be applied to study and predict the formation of macrosegregation in the ingot casting of binary alloys. Once accomplished, this work can establish the framework to new studies that will tackle more advanced problems, e.g., for actual ingot geometries, three-dimensional models and industrially-important ternary alloys

Thermal Effects on Photon-Induced Quantum Transport

We theoretically investigate laser induced quantum transport in a two-level quantum dot attached to electric contacts. Our approach, based on nonequilibrium Green function technique, allows to include thermal effects on the photon-induced quantum transport and excitonic coherent dynamics. By solving a set of coupled integrodifferential equations, involving correlation and propagator functions, we obtain the photocurrent and the dot occupations as a function of time. The characteristic coherent Rabi oscillations are found in both occupations and photocurrent, with two distinct sources of decoherence: incoherent tunneling and thermal fluctuations. In particular, for increasing temperature the dot becomes more thermally occupied which shrinks the amplitude of the Rabi oscillations, due to Pauli blockade. Finally, due to the interplay between photon and thermal induced electron populations, the photocurrent can switch sign as time evolves and its stationary value can be maximized by tunning the laser intensity.Comment: 5 pages, 4 figure

Efeitos do cloreto de sódio na germinação e vigor de plântulas de arroz.

Este trabalho teve como objetivo avaliar os efeitos delet&ios do NaU na germinação e vigor das cultivares de arroz (Oryza saliva L.) IAC-25, IAC-47, IAC-165, CNA-796019, Lebonnet, IRAT-112 e CICA-8. Amostras de sementes foram colocadas para germinar em solução de NaU com potenciais osmóticos de - 0,4 e - 0,8 Megapascal (MPa). As cultivares IAC-25 e IAC-47 foram consideradas tolerantes à salinidade atá - 0,4 MPa de NaCl; Lebonnet, CNA-796019 e CICA-8 foram consideradas moderadamente tolerantes; a IAC-165 e IRAT-112 pouco tolerantes. Entretanto, a -0,8 MPa, em que todo material foi severamente afetado pela salinidade, as cultivares IAC-25, IAC-47 e CNA-796019 foram as menos sensíveis. A cultivar IAC-25, de maneira geral, foi a mais tolerante à salinidade imposta e a IAC-165 foi a mais sensíve

Estresse salino e hídrico na germinação e vigor do arroz.

O objetivo deste trabalho foi avaliar os efeitos do estresse salino provocado pelo cloreto de sódio (NaCI) e pelo sulfato de sódio (Na 2SO4), bem como os efeitos, do estresse hídrico induzido pelo polietileno glicol 6000 (PEG 6000) na germinação e vigor do arroz (Oryza saliva L.) cv. IAC 25. O potencial osrnótico das soluções variou de 0,0 a - 1,2 Megapascal (MPa). A germinação foi mais afetada pelos sais, enquanto que o PEG 6000 induziu grande redução na parte aérea. A germinação e o crescimento das plântulas foram mais afetados pelo Na 2SO4 e os sais tiveram ação mais tóxica do que osmótica, enquanto o PEG 6000 apresentou efeito exclusivamente osmótico. O potencial osmótico a - 0,8 MPa de NaCl ou Na2SO4 pode ser considerado crítico para a germinação e crescimento da cultivar IAC 25, ao passo que o PEG 6000 só foi altamente prejudicial a - 1,2 MPa

Effect of minor impurities on the electrical properties of Se and Se containing glasses

A number of selenium glasses doped with halogens (Cl, Br, I), in the range of few p.p.m. up to U at %, were prepared in an oxygen-free atmosphere by melt quenching. D.C. conductivity as a function of the temperature was measured and for the higher impurity concentration samples the measurement of the thermoelectric power, D.C. photoconductivity, electron spin resonance and optical absorption coefficient was also undertaken. Other supporting experiments included infrared spectrometry, differential scanning calorimetry, energy dispersive analysis of X-Rays and field effect. X-Ray diffraction was used to check the lack of long-range order in each sample. A general review of amorphous semiconductors is included with particular reference to their electronic and optical properties and the importance of defect states. Results demonstrate the large effect of halogens on conductivity and that the conduction remains p-type with no observable E.S.R. signal. Data obtained are compared with those available in the literature and discussed within the framework of the CFQ-Mott theory. Tentative interpretation of the results is made via a "dangling bonds model" assuming a single particle acceptor level. Additional complementary studies of a number of chalcogenide glasses doped with Br are also included. The effect of several other additives (Ag, Cu, Tl, Na, Sb, Al, Bi) on the D.C. conductivity and other properties of vitreous selenium is briefly investigated

The role of project-based learning in engineering curriculum: the case of the industrial engineering and management program at the University of Minho

One of the key questions arising from literature in Higher Education is the mismatch between curriculum and professional practice. This work presents an analysis of an engineering program, based on a model of curriculum development that includes three dimensions: professional profile, curriculum elements and framework of competences. These dimensions were considered in the methodological approach that involves a case study of the Industrial Engineering and Management (IEM) program at the University of Minho, Portugal. Data were collected through a combination of methods, including a survey, narratives, interviews and focus group. The aim was to get to know the perceptions of students and teachers of IEM program and professionals working in this engineering field. The findings highlight the relevance of projectbased learning within the engineering curriculum in so far as it provides students with opportunities to develop both technical and transversal competences related to their professional practice. This implies developing learning situations in which it is possible to solve engineering problems, linking theory and practice based upon an interdisciplinary approach. Furthermore, the implementation of project-based learning have implications for curriculum development, namely in regard to the definition of the assessment (e.g. milestones, feedback, etc.), coordination and communication between the faculty, content selection according to the problem to be solved, amongst other issues with impact in teaching practice.CIEC - Centro de Investigação em Estudos da Criança, IE, UMinho (UI 317 da FCT), PortugalFundos Nacionais através da FCT (Fundação para a Ciência e a Tecnologia) e cofinanciado pelo Fundo Europeu de Desenvolvimento Regional (FEDER) através do COMPETE 2020 – Programa Operacional Competitividade e Internacionalização (POCI) com a referência POCI-01-0145-FEDER-007562info:eu-repo/semantics/publishedVersio