4,803 research outputs found
An ab initio study of the magnetic and electronic properties of Fe, Co, and Ni nanowires on Cu (001) surface
No full textMagnetic moment and magnetic anisotropy of linear and zigzag 4d and 5d transition metal nanowires: First-principles calculations
No full textAb initio studies of spin-spiral waves and exchange interactions in 3d transition metal atomic chains
No full textMagnetic anisotropy and spin-spiral wave in V, Cr and Mn atomic chains on Cu (0 0 1) surface: first principles calculations
No full textRecent ab intio studies of the magnetic properties of all 3d transition metal (TM) freestanding atomic chains have predicted that these nanowires could have a giant magnetic anisotropy energy (MAE) and might support a spin-spiral structure, thereby suggesting that these nanowires would have technological applications in, e.g. high-density magnetic data storage. In order to investigate how the substrates may affect the magnetic properties of the nanowires, here we systematically study V, Cr and Mn linear atomic chains on a Cu(0 0 1) surface based on the density functional theory with the generalized gradient approximation. We find that V, Cr and Mn linear chains on the Cu(0 0 1) surface still have a stable or metastable ferromagnetic state. However, the ferromagnetic state is unstable against the formation of a noncollinear spin-spiral structure in the Mn linear chains and also the V linear chain on the atop sites on the Cu(0 0 1) surface, due to the frustrated magnetic interactions in these systems. Nonetheless, the presence of the Cu(0 0 1) substrate does destabilize the spin-spiral state already present in the freestanding V linear chain and stabilizes the ferromagnetic state in the V linear chain on the hollow sites on Cu(0 0 1). When spin–orbit coupling (SOC) is included, the spin magnetic moments remain almost unchanged due to the weakness of SOC in 3d TM chains. Furthermore, both the orbital magnetic moments and MAEs for V, Cr and Mn are small, in comparison with both the corresponding freestanding nanowires and also the Fe, Co and Ni linear chains on the Cu(0 0 1) surface.</jats:p
Produção de biodiesel por processo não catalítico com etanol supercrítico a partir do óleo de tungue (Vernicia fordii) bruto e in situ
Full text linkTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2015.O trabalho teve como objetivo avaliar o rendimento de biodiesel produzido a partir da transesterificação não catalítica do óleo de tungue bruto e in situ sob condições supercríticas do etanol, bem como verificar a influência das condições operacionais sobre o perfil dos ésteres etílicos de ácidos graxos (FAEE). Para executar as reações de transesterificação com etanol supercrítico foi desenvolvida uma unidade experimental multipropósito com reator batelada (500 ml) e sistema de aquisição e monitoramento da pressão, temperatura e tempo de reação. O planejamento fatorial 23 completo com ponto central foi empregado com o intuito de avaliar a influência das condições operacionais. Quando foi utilizado o óleo bruto, avaliou-se o efeito da razão molar de óleo/álcool (1/18 e 1/42), temperatura (290 oC e 330 oC) e tempo de reação (5 min e 55 min), e quando o óleo in situ (semente) foi a matéria-prima, foram avaliados a razão da massa por volume (1/10 e 1/30), temperatura (270 oC e 310 oC) e granulometria (8-10 mesh e inteira). A caracterização e quantificação dos FAEE foi realizada por cromatografia gasosa acoplada a detector de ionização em chama (GC-FID). Foram determinadas as curvas analíticas para os ésteres etílicos dos ácidos: láurico, mirístico, palmítico, palmitoleico, esteárico, oleico, linoleico, linolênico e araquidônico. As condições operacionais exerceram grande influência sobre o rendimento do biodiesel de tungue. A transesterificação a partir do óleo bruto propiciou rendimentos de até 95,7% na condição de ponto central (1/30, 310 oC e 30 min) e a análise de variância ao nível de 95% indicou que o tempo de reação não exerce influência significativa na faixa investigada. Em relação ao perfil de FAEE, o teste Tukey ao nível de 5% de probabilidade indicou diferenças significativas entre as médias. Ésteres etílicos de ácidos graxos saturados são influenciados positivamente pelo acréscimo da temperatura e tempo de reação, aumentando seus teores, enquanto que, os teores de insaturados decrescem. A transesterificação in situ do óleo de tungue proporcionou atingir rendimentos de até 94,0%. As análises estatísticas indicaram que a granulometria investigada não exerce influência sobre o rendimento e perfil de FAEE. A biomassa residual de tungue, obtida após o processo de transesterificação in situ, possui elevado valor energético, com poder calorífico superior de 8.124 kcal/kg.Abstract : The objective of this study was to evaluate the yield of biodiesel produced from non-catalytic transesterification of raw crude tung oil and in situ oil, under supercritical conditions of ethanol, as well to determine the influence of the operating conditions on the profile of ethyl esters of fatty acids (FAEE). To perform the transesterification reactions with supercritical ethanol it developed a multipurpose experimental unit with batch reactor (500 ml) and system of the acquisition and monitoring of pressure, temperature and reaction time. A 23 factorial design with central point was applied in order to evaluate the influence of operating conditions. When the crude oil was used as raw material were evaluated the molar ratio of oil/alcohol (1/18 and 1/42), temperature (290 oC and 330 oC) and reaction time (5 min and 55 min). When used in situ oil was evaluated the mass/volume ratio (1/10 and 1/30), temperature (270 ºC to 310 ºC) and particle size (8-10 mesh and whole). The characterization and quantification of esters were performed by gas chromatography coupled with a flame ionization detector employing the method of internal standardization with methyl heptadecanoate. Were determined the analytical curves for the ethyl esters of fatty acids: lauric, myristic, palmitic, palmitoleic, stearic, oleic, linoleic, linolenic and arachidonic. Operational conditions have exerted great influence on the yield of biodiesel of tung. The transesterification from crude oil afforded yields of up to 95.7% in the central point of condition (1/30, 310 ºC and 30 min) and the analysis of variance at 95% indicated that the reaction time had no influence significantly in the investigated range. Regarding the profile of FAEE, the Tukey test at 5% probability indicated significant differences between means. Ethyl esters of saturated acids are positively influenced by increased temperature and reaction time, while the content of the unsaturated decrease. The in situ transesterification of tung oil afforded achieve yields of up to 94.0%. Statistical analysis indicated that the particle size investigated had no influence on yield and FAEE profile. The residual biomass tung originated from the process of the in situ transesterification possesses high energetic value, with superior calorific power of 8,124 kcal/kg
J.C. Steyn Collection index
No full textThis index describes the J. C. Steyn collection which includes background material for 3 biographies by J.C. (Jaap) Steyn namely N.P. van Wyk Louw, P.J. Cillié and MER (M.E. Rothman). Prof. J.C. Steyn (1939-) is an educationist, linguist and author. Correspondence ; clippings ; photographs ; book reviews ; articles ; speeches ; varia compiled in 23 pamphlet boxes
Product Innovation Knowledge Transfer for Developing Countries: Towards a systematic Transfer Approach
No full textThe transfer of knowledge on product innovation to small- and medium-sized enterprises and local knowledge institutions in developing countries is expected to be one of the key drivers for competiveness and economical growth, and a part of the solution to environmental and social challenge. In that respect, this PhD study focuses on how the process of the current knowledge transfer takes place and how it can be improved. A combination of literature review and empirical research has resulted into a conceptual framework to describe the complex and dynamic process of product innovation knowledge transfer to developing countries. In order to improve this process, a systematic approach has been developed and operationalized by a needs assessment tool and a design manual: The UNEP Design for Sustainability for Developing Economies (D4S-DE) Manual (www.d4s-de.org). Both tools have been tested in practice by practitioners and have been evaluated by an academic review board.Design EngineeringIndustrial Design Engineerin
Where do we draw lines: professional relationship boundaries and the child and youth care practitioner
No full textThe question of professional relationship boundaries is a poignant one, in light of the many boundary grey-zones that are created by the variety of young people’s needs, practice settings and professional relationship contexts within the field of child and youth care. In order to support practitioners’ development of critical thought and awareness of professional boundaries, this paper applies a professional relationship boundaries conceptual framework to child and youth care work, and the literature is consulted to explore the impacts of boundary violations, influences on individual’s boundaries, cues to indicate blurring boundaries, and key strategies to maintain balanced boundaries
Anthropometry of the Beaver, Sekani, and Carrier Indians:
Full text linkby J.C. Boileau GrantBulletin (National Museum of Canada) ; 81. Bulletin (National Museum of Canada). Anthropological series. ; 18
J.C. Painter letter to Benjamin Lundy
No full textLetter from J.E. Painter to (presumably) Benjamin Lundy, answering a request for information about the history and operations of the Underground Railroad. Letter includes details of a story of an ex-slave transported on the Underground Railroad through Ohio and stories of the plight of other fugitive slaves crossing the Ohio River.
Benjamin Lundy (1789-1839) was a prominent Quaker abolitionist best known for his development of abolitionist periodicals. His "Genius of Universal Emancipation" was first published in 1821 from his home in Mt. Pleasant, Ohio, and enjoyed a wide circulation across the antebellum United States. In the 1820s, the young William Lloyd Garrison came to work for The Genius. Benjamin Lundy traveled widely seeking subscriptions to The Genius, giving talks about the anti-slavery movement, and observing and documenting the conditions of enslaved people across the Americas. He was also involved in the establishment of freed slave colonies in Mexico
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