972 resultados para Phase change
Resumo:
The entrepreneurship and innovation have been gradually gaining ground in the academic community as a field of study. However, the interpretations surrounding fragmented, without a univocal definition. In last decades, tourism has received greater attention from researchers in various sciences, varying only by the different emphases considered: economic, social, cultural and environmental. As other emerging sectors in a modern economy, tourism is a dynamic and ever-changing industry. The study has as purpose to provide a better understanding regarding the essence of entrepreneurship: theoretical and practical implications from the perspective of tourism. Regarding the methodology used here, this is a conceptual paper with a literature review that brings together the major components of entrepreneurship and its implications tourist perspective and conceptual model of the dynamic nature of the Triggering Process and innovation (e.g. iTravey, Interactive Stores, Tourist Transportable Tower).
Resumo:
We propose new theoretical models, which generalize the classical Avrami-Nakamura models. These models are suitable to describe the kinetics of nucleation and growth in transient regime, and/or with overlapping of nucleation and growth. Simulations and predictions were performed for lithium disilicate based on data reported in the literature. One re-examined the limitations of the models currently used to interpret DTA or DSC results, and to extract the relevant kinetic parameters. Glasses and glass-ceramics with molar formulation 0.45SiO2? (0.45-x)MgO?xK2O?0.1(3CaO.P2O5) (0?x?0.090) were prepared, crystallized and studied as potential materials for biomedical applications. Substitution of K+ for Mg2+ were used to prevent devritification on cooling, to adjust the kinetics of crystallization and to modify the in vitro behaviour of resulting biomaterials. The crystallization of the glass frits was studied by DTA, XRD and SEM. Exothermic peaks were detected corresponding to bulk crystallization of whitlockite-type phosphate, Ca9MgK(PO4)7, at approximately 900ºC, and surface crystallization of a predominant forsterite phase (Mg2SiO4) at higher temperatures. XRD also revealed the presence of diopside (CaMgSi2O6 in some samples. The predominant microstructure of the phosphate phase is of the plate-type, seemingly crystallizing by a 2-dimensional growth mechanism. Impedance spectroscopy revealed significant changes in electrical behaviour, associated to crystallization of the phosphate phase. This showed that electrical measurements can be used to study the kinetics of crystallization for cases when DTA or DSC experiments reveal limitations, and to extract estimates of relevant parameters from the dependence of crystallization peak temperature, and its width at half height. In vitro studies of glasses and glass-ceramics in acelular SBF media showed bioactivity and the development of apatite layers The morphology, composition and adhesion of the apatite layer could be changed by substitution of Mg2+ by K+. Apatite layers were deposited on the surface of glass-ceramics of the nominal compositions with x=0 and 0.09, in contact with SBF at 37ºC. The adhesion of the apatite layer was quantified by the scratch test technique, having been related with SBF?s immersion time, with composition and structure of the glass phase, and with the morphology of the crystalline phase of the glass-ceramics. The structure of three glasses (x=0, 0.045 and 0.090) were investigated by MAS-NMR ( 29Si and 31P), showing that the fraction of Q3 structural units increases with the contents of Mg, and that the structure of these glasses includes orthophosphate groups (PO43-) preferentially connected to Ca2+ ions. Mg2+ ions show preference towards the silicate network. Substitution of Mg2+ by K+ allowed one to change the bioactivity. FTIR data revealed octacalcium phosphate precipitation (Ca8H2(PO4)6.5H2O) in the glass without K, while the morphology of the layer acquires the shape of partially superimposed hemispheres, spread over the surface. The glasses with K present a layer of acicular hidroxyapatite, whose crystallinity and needles thickness tend to increase along with K content.
Resumo:
ABSTRACTThis paper reports an empirical case study on the interface between microfinance and climate change actions. Climate change, which until recently seemed a luxury for the microfinance sector, now appears to be crucial for its future. For their low adaptive capacity, the millions of microfinance clients worldwide happen to be the most vulnerable to a changing climate. However, such an arena is still blurred from an academic viewpoint, and inexistent among Brazilian academia. Therefore, by investigating Brazil’s largest rural MFI, Agroamigo, we aim at providing an empirical contribution to green microfinance. The main conclusion is that, albeit Agroamigo offers important links to climate change initiatives, it will need to take better account of specific vulnerabilities and risks to protect its portfolio and clients better from climate change impacts.
Resumo:
Revista Lusófona de Ciências Sociais
Resumo:
RESUMO: Com a globalização e as mudanças provenientes da mesma, o ser humano vem sofrendo com o estresse ao tentar se adaptar e acompanhar tais acontecimentos seja no âmbito familiar, social, afetivo e profissional. Para desempenhar as funções docentes do ensino superior, são exigidas diversas condições, e o professor sofre um desgaste físico e psicológico ao tentar suprir determinadas demandas, o que em muitos casos, ocasiona o estresse ocupacional. Com o propósito de aprofundar conhecimentos sobre a relação existente entre o estresse e a atividade docente, fizemos o seguinte questionamento: quais os sintomas de estresse apresentados em professores do ensino superior? Com Objetivo geral de estudar os sintomas e níveis de estresse, relacionando-os à carreira docente do ensino superior, com as variáveis: regime de trabalho, vínculo institucional, idade, sexo, tempo de trabalho, tipo de IES, em uma população específica pertencente a duas Instituições de Ensino Superior -IES da cidade de Teresina, Estado do Piauí- Brasil, sendo uma pública e uma privada. Visando atingir os objetivos propostos, utilizamos da metodologia de caráter exploratório e descritivo, com abordagem quantitativa dos dados recorrendo à estatística descritiva. O instrumento de coleta de dados utilizado foi o “Inventário de Sintomas de Stress Lipp – ISSL” da autora Marilda Lipp (2000), aplicado em uma amostra de cem (100) professores, com idade entre 22 e 55 anos de idade. Mediante a análise dos dados, pode-se verificar que apesar das diferenças existentes entre IES públicas e privadas, a maioria dos resultados foram semelhantes. Em ambas as IES houve presença de estresse nos docentes, prevalecendo a fase de alerta, logo após a fase de resistência, em seguida a fase de quase-exaustão,Houve um predomínio de sintomas psicológicos, onde na IES privada se destacam: aumento súbito de motivação e entusiasmo súbito. E como sintomas físicos: boca seca e nó no estômago. Na IES públicas os sintomas psicológicos foram: entusiasmo súbito e aumento súbito de motivação. E físicos: tensão muscular e nó no estômago. Em relação as co-variáveis que apresentaram maior relação com o estresse pode-se apresentar na IES privada o sexo masculino e feminino possuem a mesma representatividade, a faixa etária de 31 a 39 anos, estado civil casado, tempo de serviço de 7 a 13 anos, jornada de trabalho integral e vínculo efetivo. Já na IES pública verifica-se relação com o sexo feminino, idade variando de 31 a 39 anos, estado civil solteiro, tempo de serviço de 7 a 13 anos, jornada de trabalho parcial e vínculo substituto. De acordo com o que foi analisado, percebe-se que os docentes do ensino superior, independente do tipo de IES ao qual estão vinculados, estão sujeitos ao estresse e que estes não devem ser responsabilizados pelo mesmo, nem por adoção de medidas preventivas, visto que toda a IES sofre as conseqüências, e tem condições de auxiliar o professor com situações preventivas, de controle a partir do conhecimento, interpretação e mudança de hábitos do professor no ambiente universitário. ABSTRACT: With globalization and its changes, the human being has suffered from stress while trying to adapt and monitor such events, within family, social, emotional or professional scope. To play as teacher in higher education, they are required various conditions and the teacher suffers physical and psychological wear trying to meet certain demands, which in many cases leads to occupational stress.Aiming to deepen knowledge about the relationship between stress and teaching activities, we made the following question: what are the symptoms of stress presented by higher education teachers? With the general objective of study the symptoms and the stress levels, linking them to the teaching career in higher education, using the following variables: working regime, institutional link, age, sex, working time, type of HEI, in a specific population belongs to two Higher Education Institutions HEI - of Teresina, Piauí, Brazil, one public and one private. Aiming to achieve the proposed objectives, we used a exploratory - descriptive study, with quantitative approach of data using graphs and tables. The data collection instrument used was the "Lipp Stress Symptoms Inventory - ISSL" by the author Marilda Lipp (2000), applied to a sample of a hundred (100) teachers, between 22 and 55 years of age. Through data analysis, despite the differences between public and private HEIs, we can see that the most results were similar. In both HEIs, the results revealed that the alert phase of stress had prevailed, followed by resistance and almost-exhaustion phases. A small number presented stress in exhaustion phase and another group did not present stress. There was a predominance of psychological symptoms, which in private HEIs stands out: increase of motivation and enthusiasm suddenly. And as physical symptoms: dry mouth and stomached. In public HEI, psychological symptoms were sudden enthusiasm and increse of motivation. And physical symptoms: muscle tension and stomached. In relation to the co-variables that showed a greater relationship with stress, in private HEIs males and females have the same representation, between 31-39 years, married, working time of 7-13 years, full working day and effective link. Already in public HEIs, female, between 31-39 years, unmarried, working time of 7-13 years, partial working day and substitute link had prevailed. According to analysis, we find that teachers in higher education, regardless of the HEI to which they are linked, are subject to stress. And they should not be blamed for the onset of stress, neither by adopting preventive measures, since all the HEI suffers the consequences, and it is able to help teachers with preventive measures based on the knowledge, interpretation and change habits of the teacher in the university environment.
Resumo:
RESUMO: O presente estudo teve como objectivo investigar os principais impedimentos que ocorrem nos estabelecimentos de ensino relativamente à aplicabilidade dos Programas Nacionais de Educação Física (PNEF). Considerando as particularidades do grupo disciplinar, as instalações da escola ou o meio cultural envolvente, pretende-se perceber as razões para que no panorama nacional, a grande maioria das escolas resista a esse processo de mudança, não criando condições para o desenvolvimento de iguais oportunidades na disciplina de educação física no currículo de todos os alunos. Este estudo ambiciona ser um contributo para que a educação física (EF) dê um passo no desenvolvimento qualitativo da realidade educativa, ao destacar os pontos comuns e mais importantes reunidos nas escolas de referência que aplicam os PNEF. A metodologia desenvolvida apresenta duas fases na análise de dados, sendo que a primeira extrai os pontos em comum e personalizados do grupo de professores entrevistados pertencentes ao grupo A, constituído pelos autores dos PNEF e por uma especialista na área de desenvolvimento curricular. A segunda fase, segue a lógica anterior para o grupo B, grupo que reúne professores em contacto directo no dia-a-dia das escolas. A consciência e o conhecimento dos problemas apresentados nas escolas que não seguem os programas, torna-se importante pois possibilita a procura de soluções para esses mesmos problemas. Desta forma será possível desenvolver as inovações escolares, proporcionando aos alunos a oportunidade de crescer no seio das inúmeras qualidades que a disciplina de educação física pode oferecer e desenvolver. Um crescimento baseado na autonomia, na cooperação e no desenvolvimento de hábitos de vida saudável enquanto futuros cidadãos. ABSTRACT: This study aimed to investigate the main issues that prevent the physical education programs to be applied on the Portuguese schools. Considering the disciplinary group particularities, the school facilities or the environment, we intend to understand the reasons that may explain why the majority of the Portuguese schools resist to this change process, not creating conditions for the development of equal opportunities on the physical education of every student. This study intend to be a contribute for the physical education development on the educational reality, highlighting the common factors of the reference schools that apply the physical education programs. The method integrates two phases of development: the first one extracts the common and custom factors between the Group A professors, consisting of physical education programs authors and one expert in the field of curriculum development. The second phase follows the previous logic for the Group B, a group that meets professors with direct contact of schools day-to-day. The consciousness and knowledge about the existing problems in schools that don‟t apply physical education programs it‟s important, because it enables the search for solutions. This will allow innovations development, giving students the opportunity to grow within the many qualities that the discipline of physical education can provide and develop. Growth based on autonomy, cooperation and development of healthy lifestyle habits as future citizens.
Resumo:
We examine the instability behavior of nanocrystalline silicon (nc-Si) thin-film transistors (TFTs) in the presence of electrical and optical stress. The change in threshold voltage and sub-threshold slope is more significant under combined bias-and-light stress when compared to bias stress alone. The threshold voltage shift (Delta V-T) after 6 h of bias stress is about 7 times larger in the case with illumination than in the dark. Under bias stress alone, the primary instability mechanism is charge trapping at the semiconductor/insulator interface. In contrast, under combined bias-and-light stress, the prevailing mechanism appears to be the creation of defect states in the channel, and believed to take place in the amorphous phase, where the increase in the electron density induced by electrical bias enhances the non-radiative recombination of photo-excited electron-hole pairs. The results reported here are consistent with observations of photo-induced efficiency degradation in solar cells.
Resumo:
The modelling of the experimental data of the extraction of the volatile oil from six aromatic plants (coriander, fennel, savoury, winter savoury, cotton lavender and thyme) was performed using five mathematical models, based on differential mass balances. In all cases the extraction was internal diffusion controlled and the internal mass transfer coefficienty (k(s)) have been found to change with pressure, temperature and particle size. For fennel, savoury and cotton lavender, the external mass transfer and the equilibrium phase also influenced the second extraction period, since k(s) changed with the tested flow rates. In general, the axial dispersion coefficient could be neglected for the conditions studied, since Peclet numbers were high. On the other hand, the solute-matrix interaction had to be considered in order to ensure a satisfactory description of the experimental data.
Resumo:
A área de comercialização de energia eléctrica conheceu uma profunda mudança após a liberalização do sector eléctrico, que levou à criação de algumas entidades, as quais gerem os mercados de electricidade europeus. Relativamente a Portugal e Espanha, durante esse processo de liberalização, deu-se também um acordo que os levou à criação de um mercado conjunto, um mercado Ibérico (MIBEL). Dentro deste mercado estão contemplados dois operadores, sendo que um deles representa o pólo Português (OMIP) e o outro representa o pólo Espanhol (OMEL). O OMIP contempla os mercados a prazo, ou futuros, normalmente apresenta contratos de energia comercializada com durabilidade de semanas, meses, trimestres, semestres ou mesmo anos. Diariamente estes contratos poderão vencer no OMEL, que engloba os mercados, diário e intradiário. Este, ao contrário do OMIP negoceia para o dia seguinte (mercado diário) ou para uma determinada altura do dia (mercado intra diário). O mercado diário será o exemplo usado para a criação do simulador interactivo do mercado de energia eléctrica. Este será composto por diversos utilizadores (jogadores), que através de uma plataforma HTML irão investir em centrais de energia eléctrica, negociar licitações e analisar o funcionamento e resultados deste mercado. Este jogo subdividir-se-á então em 3 fases: 1. Fase de investimento; 2. Fase de venda (licitações); 3. Fase de mercado. Na fase do investimento, o jogador terá a possibilidade de adquirir unidades de geração de energia eléctrica de seis tipos de tecnologia: 1. Central a Carvão; 2. Central de Ciclo Combinado; 3. Central Hídrica; 4. Central Eólica; 5. Central Solar; 6. Central Nuclear. Com o decorrer das jogadas o jogador poderá aumentar a sua capacidade de investimento, com a venda de energia, sendo o vencedor aquele que mais saldo tiver no fim do número de jogadas previamente definidos, ou aquele que mais depressa atingir o saldo definido como limite pelo administrador do jogo. A nível pedagógico este simulador é muito interessante pois para além de o utilizador ficar a conhecer as tecnologias em causa e as vantagens e desvantagens das centrais de energia renovável e das centrais a combustíveis fósseis, este ganha igualmente uma sensibilidade para questões de nível ambiental, tais como o aumento dos gases de estufa e o degelo resultante do aquecimento global provocado por esses gases. Para além do conhecimento adquirido na parte de energia eléctrica este jogo dará a conhecer ao utilizador o funcionamento do mercado da energia eléctrica, bem como as tácticas que este poderá usar a seu favor neste tipo de mercado.
Resumo:
The spectral response and the photocurrent delivered by entirely microcrystalline p-i-n-Si:H detectors an analysed under different applied bias and light illumination conditions. The spectral response and the internal collection depend not only on the energy range but also on the illumination side. Under [p]- and [n]-side irradiation, the internal collection characteristics have an atypical shape. It is high for applied bias and lower than the open circuit voltage, shows a steep decrease near the open circuit voltage (higher under [n]-side illumination) and levels off for higher voltages. Additionally, the numerical modeling of the VIS/NIR detector, based on the band discontinuities near the grain boundaries and interfaces, complements the study and gives insight into the internal physical process.
Resumo:
Electrical resistivity, transverse magnetoresistance and thermoelectric power measurements were performed on CuS high quality single crystals in the range 1.2-300 K and under fields of up to 16 T. The zero field resistivity data are well described below 55 K by a quasi-2D model, consistent with a carrier confinement at lower temperatures, before the transition to the superconducting state. The transverse magnetoresistance develops mainly below 30 K and attains values as large as 470% for a 16 T field at 5 K, this behaviour being ascribed to a band effect mechanism, with a possible magnetic field induced DOS change at the Fermi level. The transverse magnetoresistance shows no signs of saturation, following a power law with field Delta rho/rho(0) proportional to H(1.4), suggesting the existence of open orbits for carriers at the Fermi surface. The thermoelectric power shows an unusual temperature dependence, probably as a result of the complex band structure of CuS.