Special Issue "Design and Optimization of Production Lines"

The classical models for designing production lines follow the objective of balancing the line so as to improve the throughput [...

Electrical Transport Features of SiNWs Random Network on Si Support After Covalent Attachment of New Organic Functionalities

Modification of the electrical transport of a random network of silicon nanowires assembled on n‐silicon support, after silicon nanowires functionalization by chlorination/alkylation procedure , is here described and discussed. We show that the organic functionalities induce charge transfer at single SiNW and produce doping‐like effect that is kept in the random network too. The SiNWs network also presents a surface recombination velocity lower than that of bulk silicon. Interestingly, the functionalized silicon nanowires/n‐Si junctions display photo‐yield and open circuit voltages higher than those including oxidized silicon nanowire networks. Electrical properties stability in time of junctions embedding propenyl terminated silicon nanowires network and transport modification after secondary functionalization is also shown. These results suggest a possible route for the integration of functionalized Si nanowires, although randomly distributed, in stable large area photovoltaic or molecule sensitive based devices

Otimização e simulação da programação de projetos em estaleiros nacionais considerando restrições de conteúdo local

The growth of oil exploration and production in Brazil, especially after the pre-salt oil reserves discovery, implied in ships, rigs and platforms construction demand increase. In this context, the activities planning and scheduling in Brazilian shipyards has become a challenging task to minimize exposure to fines for local content non-compliance clauses and, at the same time, meet the demand of the national oil industry. In order to support the decision-making process of allocating projects to shipyards and dimensioning the exposure to foreign content, this work proposes a mixed integer programming model, based on the classic resource constrained project scheduling problem. Due to the historical delays in the completion of activities by the national shipbuilding industry, a robust model was developed to address the anticipation of possible delays. The parameter known as degree of conservatism was scaled according to the activities lateness probabilities, based on the historical data. Finally, an event discrete simulation model is proposed for sensitivity analysis and delays dimensioning in the projects delivery, and the opportunity cost in the oil production delay.Com o crescimento das atividades de exploração e produção de óleo e gás no país, principalmente com a descoberta das reservas de petróleo na camada do Pré-sal, houve aumento na demanda por construção de navios, sondas e plataformas. Nesse contexto, o planejamento e programação de atividades nos estaleiros nacionais tornou-se uma tarefa desafiadora, visando minimizar a exposição a multas por não atendimento de cláusulas de conteúdo nacional e, ao mesmo tempo, atender a demanda da indústria petrolífera nacional. Para apoiar o processo decisório de alocação de projetos a estaleiros e dimensionamento da exposição ao conteúdo estrangeiro, foi proposto um modelo de programação inteira mista, baseado no problema clássico de programação de projetos com restrição de recursos. Devido aos atrasos históricos na conclusão das atividades pela indústria naval nacional, uma modelagem robusta foi desenvolvida para tratar a antecipação de possíveis atrasos. O parâmetro conhecido como grau de conservadorismo foi dimensionado de acordo com as probabilidades de atrasos das atividades, baseadas nos dados históricos. Por fim, foi proposto um modelo de simulação para análise de sensibilidade e dimensionamento de atrasos na entrega dos projetos, e do custo de oportunidade no atraso na produção de óleo

Reflectance and photoluminescence characterization of CdS and CdSe heteroepitaxial films deposited by laser ablation technique

Optical properties of CdSe and CdS films, deposited on sapphire substrate by means of pulsed laser ablation technique, have been investigated in order to study the effect of such a transparent substrate on the photoluminescence efficiency of the deposited epilayers. CdSe and CdS films present intrinsic (excitonic) emission at low temperature, differently from the same films deposited on quartz. The temperature dependence of the excitonic energy has been analyzed taking into account the contribution of both the thermal dilatation and electron-phonon interaction

Formation of TiO2 nanostructures modified Eumelanin films with enhanced properties for biopolymer implementations

Thin films of hybrid melanin-TiO2 nanoparticles (eumelanin: TiO2) deposited from solution by electro-spray were accurately inspected to unveil modified structural and electronic properties for device implementations. Based on the reorganization of the melanin electronic valence orbital, among other interesting behaviors, we observed up to a two orders increase in the absorption coefficient in the visible range. Furthermore the redshifted absorption features, disclose that the extended π- stacking of oligomers is mainly responsible for the tunability of the optical gap as confirmed by photoluminescence. TiO2 nanostructures via oxidative polymerization, further improve the oligomeric character observed by means of Raman scattering. Finally, the photocatalytic activity of TiO2 nanoparticles helps the saturation of shallow trap states in melanin structure and consequently enhances the charge carrier transport

Use of lipid bilayers as support for biomolecules integration in OTFT biosensors

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thermoluminescence in lif crystals and the role of impurities

Eight nominally pure lithium fluoride crystals, obtained from a single LiF crystal containing less than 100 ppm impurities, were irradiated by gamma-rays from a 60 Co source at room temperature, with doses from 8.4 to 2.5 x 10 5 Gy, but one at -60 °C. Optical density measurements were performed to investigate the radiation-induced color centres (CCs) and to evaluate their concentrations. Thermoluminescence (TL) glow curves were collected and simulated by a first-order kinetics approach, and from the best-fit procedure ten glow peaks (GPs) spanning from 100 to 450 °C were highlighted. A comparative analysis of GP intensities and CC concentrations as a function of the irradiation dose has questioned their association as obtained in previous measurements, showing the impurities, less than 10 18 cm -3 , still playing a predominant role in TL spectra. New measurements on LiF crystals more pure, at least an order of magnitude, are required to establish for sure the association of GPs to CCs