Pyrolysis Temperature and Time Dependence of Electrical Conductivity Evolution for Electrostatically Generated Carbon Nanofibers

Carbon nanofibers were produced from polyacrylonitrile/N, N-Dimethyl Formamide (PAN/DMF) precursor solution using electrospinning and vacuum pyrolysis at temperatures from 773-1273 K for 0.5, 2, and 5 h, respectively. Their conductance was determined from I – V curves. The length and cross-section area of the nanofibers were evaluated using optical microscope and scanning probe microscopes, respectively, and were used for their electrical conductivity calculation. It was found that the conductivity increases sharply with the pyrolysis temperature, and increases considerably with pyrolysis time at the lower pyrolysis temperatures of 873, 973, and 1073 K, but varies, less obviously, with pyrolysis time at the higher pyrolysis temperatures of 1173 and 1273 K. This dependence was attributed to the thermally activated transformation of disordered to graphitic carbons

Electronic Transport Properties of Incipient Graphitic Domains Formation in PAN Derived Carbon Nanofibers

The carbon nanofibers used in this work were derived from a polyacrylonitrile (PAN)/N, N-dimethyl formamide (DMF) precursor solution using electrospinning and vacuum pyrolysis techniques. Their conductivity, σ, was measured at temperatures between 1.9 and 300 K and transverse magnetic field between -9 and 9 T. Zero magnetic field conductivity σ(0,T) was found to increase monotonically with the temperature with a convex σ(0,T) versus T curve. Conductivity increases with the external transverse magnetic field, revealing a negative magnetoresistance at temperatures between 1.9 and 10 K, with a maximum magnetoresistance of - 75 % at 1.9 K and 9 T. The magnetic field dependence of the conductivity and the temperature dependence of the zero-field conductivity are best described using the two-dimensional weak localization effect

Tin oxide micro/nano fibers from electrostatic deposition

SnO2 micro/nano fibers in the rutile structure were synthesized using electrospinning and metallorganic decomposition techniques. Fibers were electrospun using two different precursor solutions, one based on SnCl4 and the other on C22H44O4Sn. The fibers were sintered in air for two hours at 400, 500, 600, 700 and 800ºC. SEM, AFM, XRD, XPS and Raman microspectrometry were used to characterize the sintered fibers. The results showed that the fibers were composed of SnO2 and that the SnCl4 precursor led to better results in terms of uniformity/continuity of the fibers

Utilização de diferentes equações e métodos a estimativa do gasto energético basal e total de praticantes de atividade física adultos

Introduction and Aims: The BEC (Basal Energy Cost /GEB) is the energy used by every cell in the human body for the maintenance of its operation. The Energy Expenditure with Physical Activities (GAF), added to the GEB and determine the GET. To estimate the GET physically active individuals is necessary to know the type of exercise performed, the frequency of training, duration and intensity. This study aimed to evaluate the different equations to estimate the GET, compare the results and point out the possible differences. Methods: A study carried out in two stages, the first part consists of a literature review and the second evaluated the GET two adult volunteers (one male and one female) regularly physically active. Results: We found in the literature five equations that estimate the GEB, WHO (1985), FAO / WHO / UNU (1985), Schofield (1985), Mifflin-St Jeor (1990) and Harris Benedict (1919), from these equations the calculations of GEB, GET and GAF for each volunteer were performed. Discussion: When selecting an equation to estimate the GEB and GET gender, the variables (weight, height and age), factor activity and METs are important requirements to determine the energy requirement. All equations had higher estimates for males. The method of Harris-Benedit gave an estimation of the GEB, GET and REE + MET larger than the other methods. Conclusion: It was found that there were no relevant differences between the equations, so all are suitable for use.Universidade São Caetano do Sul-USCS, Curso de Nutrição e Educação Física, Sao Paulo, BrazilUniversidade Federal de Sao Paulo, Nutrição Clínica e em Cuidados Integrativos, Sao Paulo, BrazilCentro Universitário São Camilo, curso de Nutrição, Sao Paulo, BrazilUniversidade Federal de Sao Paulo, Nutrição Clínica e em Cuidados Integrativos, Sao Paulo, BrazilWeb of Scienc

Tourist tracking and monitoring: a study of the technologies used

Introdução: O presente estudo teve o propósito de analisar artigos científicos relacionados as tecnologias para rastreamento de turistas procurando catalogar as tecnologias mais utilizadas, utilizando uma revisão sistemática dos artigos publicados dos últimos cinco anos Método: Para o desenvolvimento deste trabalho foi realizada uma revisão sistemática através de um protocolo de pesquisa levando em consideração as publicações científicas nas bases de dados de periódicos ACM, IEEE, Science Direct e Scopus. O processo foi realizado em duas etapas: busca nas bases de dados de periódicos e a análise sistemática através da leitura dos artigos relacionados ao tema da pesquisa. Resultados: Foram pesquisados 761 artigos, dos quais 47 foram selecionados para a leitura e extração de dados. Temas como: tecnologias para rastreamento e contagem de turistas, turismo inteligente, tecnologia da informação, gestão e sustentabilidade apontam como destaque nas pesquisas. Conclusão: O presente estudo serviu para responder a pergunta; “Quais são as tecnologias para rastreamento de turistas mais utilizadas?”, sendo assim pode-se afirmar que as 5 principais tecnologias utilizadas com base nesta revisão sistemática são: GPS, Aplicativos, Sensores, Mídias Sociais e RFID.Introduction: Introduction: Tourism is an element that has a significant contribution to the development and renovation of cities and according to the Paraná Turístico 2026 plan a new approach to smart destinations on the temporal and spatial behavior of tourists using new technologies for tracking or counting can serve as a key factor in improving the sustainable management of tourism. Following this trend, this study seeks to carry out a systematic review of the literature on the topic of tourist movement, aiming to classify the most used. Method: Systematic literature review, analyzing scientific publications in ACM, IEEE, Science Direct and Scopus journals databases in the last 5 years. Results: 761 articles were found, of which 47 were selected for reading and data extraction, and then the most cited technologies in the literature were classified and generated, where the technologies used in each article are presented. Topics such as: technologies for tracking and counting tourists, smart tourism, information technology, management and sustainability are highlighted in the surveys. Conclusion: The present study served to answer the question; “What are the most used technologies for tracking tourists?”, thus, it can be said that the objective of this study was achieved by classifying the 5 main technologies most used being: GPS, Applications, Sensors, Social Media and RFID followed by others of equal relevance for further studies. It was found that the technologies raised, mostly, are free technologies, in which it is possible to develop innovative projects with low execution cost.

Synthesis and characterization of tin oxide microfibres electrospun from a simple precursor solution

Tin oxide (SnO2) microfibres in the rutile structure were synthesized using electrospinning and metallorganic decomposition techniques. Fibres were electrospun from a precursor solution containing 20 mg poly(ethylene oxide) (molecular weight 900 000), 2 ml chloroform and 1 ml dimethyldineodecanoate tin, and sintered in the air for 2 h at 400, 600 and 800 \ufffdC, respectively. Scanning electron microscopy, x-ray diffraction and Raman microspectrometry were used to characterize the sintered fibres. The results showed that the synthesized fibres are composed of SnO2.NRC publication: Ye