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São José dos Campos, Brazil

Edwards E.R.,Sao Paulo State University | Antunes E.F.,National Institute for Space Research | Antunes E.F.,Aeronautical Institute of Technology | Botelho E.C.,Sao Paulo State University | And 2 more authors.
Applied Surface Science

A detailed analysis by X-ray photoelectron spectroscopy was carried out on multi-walled carbon nanotube (MWCNT) surfaces after non-oxidative and oxidative purification treatments in liquid-phase. The MWCNT were produced by pyrolysis of camphor and ferrocene, that provides a high yield but with high iron contamination (∼15% wt). The elimination and/or oxidation of iron nanoparticles were monitored by Fe2p and O1s core level. Oxygen-based functional groups attachment was also investigated by C1s fitting. The effectiveness of each treatment in iron removal was evaluated by thermogravimetric analysis (TGA) and atomic absorption spectroscopy (AAS). The integrity of the MWCNT structure was verified by Raman spectroscopy (RS) and transmission electron microscopy (TEM). A purity degree higher than 98% was achieved only with non-oxidative treatments using sonification process. © 2011 Elsevier B.V. All rights reserved. Source

Oliveira D.L.,Aeronautical Institute of Technology | Lussari E.,Mectron Corporation
Proceedings of the 2011 7th Southern Conference on Programmable Logic, SPL 2011

Contemporary digital systems must necessarily be based on the "System-on-Chip - SoC" concept. An interesting style for SoC design is the GALS (Globally Asynchronous, Locally Synchronous) paradigm, which can be used to implement circuits in FPGAs (Field Programmable Gate Array). Although these devices have the benefits of low-cost and short development time, there's a major drawback which is implementing Asynchronous Interfaces (AI) in FPGA devices. There's a typical AI design style which is based on asynchronous controllers that provides communication between modules (called ports), but Port controllers are subject to essential-hazard when implemented FPGAs. This paper proposes a method based on direct mapping to implement these ports. It begins with an MBG (multi-burst graph) specification and makes use of the essential signal concept to check if the resulting circuit is hazard-free, or to point potential essential-hazard problems in the circuit. By satisfying the essential signal condition, this method is capable of providing robust ports, i.e. essential-hazard-free. © 2011 IEEE. Source

Zanatta A.M.,Aeronautical Institute of Technology | Bressan J.D.,Santa Catarina State University | de Oliveira Gomes J.,Aeronautical Institute of Technology | Origo F.D.,Institute Estudos Avancados | Damiao A.J.,Institute Estudos Avancados
Advanced Materials Research

The present work investigates the surface finishing of two mould tool steels (WNr 1.2738~P20 and WNr 1. 4305) after polishing by conventional method and automatic laboratory equipment. These steels are employed in the fabrication of polymer injection moulds due to its good machinability, homogeneous microstructure and hardness. The polishing process was performed in laboratory by manual and automated processes. The surface finishing was measured by mechanical and optical methods. In the manual polishing, SiC paper grit 320, 600 and 1200 was used. Final polishing was carried out with polishing cloth containing 0.3 μm alumina suspension or 6 μm and 1 μm diamond suspension. Alternately, polishing of steel specimens in the specially developed laboratory automatic equipment was performed using a large rotating disc at 140 rpm, nominal pressures of 0.013 Pa, 0.139 Pa and 0.244 Pa and diamond paste with particle size 1 μm. Surface finish of specimens were compared as a function of the particle size and polishing time by three methods: the roughness parameter Rz (mean of maximum roughness depth) using a stylus probe, light reflectance with an integrating sphere connected to a spectrophotometer, and reflected diffuse light intensity analysis of a He-Ne laser. Specimen surface images were also obtained by an optical microscope to compare the topography after polishing. From the plot of roughness measurements versus particle size and intensity of diffuse light versus particle size, it was observed that both roughness parameter Rz and the intensity of diffuse light decreased linearly with the abrasive particle size for the manual polishing method. The method of light reflectance measurements shows an approximately constant value of 55% for all particle size. Therefore, the better methods to assess surface finish of tool steels are the roughness parameter Rz and the intensity of diffuse light by laser method. For the automatic polishing, the results show that there is an optimized time for minimum roughness which is 5 minute. Other relevant aspects of surface finish by particle abrasion are also discussed. © (2013) Trans Tech Publications, Switzerland. Source

Santos L.B.,Aeronautical Institute of Technology | Striebeck M.V.,University of Buenos Aires | Crespi M.S.,Sao Paulo State University | Ribeiro C.A.,Sao Paulo State University | De Julio M.,Aeronautical Institute of Technology
Journal of Thermal Analysis and Calorimetry

Recently, biochar was introduced as a bioadsorbent material to remove various contaminants in effluents, such as pigments, dyes, heavy metals, naphthalene, 1-naphthol, atrazine, phosphorus and some macro- and micronutrients. Therefore, biochar of biomass residue pellet obtained for slow pyrolysis was evaluated as an alternative process for the potential utilization as chemical contaminant remover with low cost. Thus, the main objective of this work was to produce biochar from pine residue pellet for subsequent use of the same as a potential adsorbent for effluent treatment. In order to perform the characterization, samples of biochar from pine pellet were produced using several heating rates (5-30 °C min-1), residence temperatures (200, 280 and 570 °C) and residence times (1 h and half an hour). The process adopted led to a rapid degradation of the raw material (pine pellet) associated with an intense generation of volatile compounds, conditions that led to a reduction in density and establishment of porous structure. Biochars had basic character (pH 8.47), predominance of aromatic structures, low moisture content (0.9-1.8 %), low ash content (1.25-1.80 %) and high thermal stability. Low humidity favors the adsorption and an improvement in the conservation during transport and storage. © 2015 Akadémiai Kiadó, Budapest, Hungary. Source

Da Silva A.L.,Federal University of ABC | Paglione P.,Aeronautical Institute of Technology | Yoneyama T.,Aeronautical Institute of Technology
Journal of Aerospace Engineering

A cruising autopilot is developed for a nonlinear flexible aircraft based on the model-following method. The autopilot controller, called the outer loop, is designed for a rigid body approximation of the flexible aircraft. The model-following control, named the inner loop, approximates the input-output behavior of the flexible aircraft to a rigid body. The autopilot is applied to the flexible aircraft with a model-following inner loop. This inner loop controls the flexible modes and the outer loop, which are the rigid body dynamics. The model-following control is a suboptimal linear quadratic formulation with output feedback. This technique can stabilize the flexible modes and keep their amplitudes acceptable. The autopilot is a speed and altitude tracker with a wing leveler. It is designed via a robust H∞ with static output feedback. An aircraft model with nine flexible modes is used to evaluate the method. It is a conceptual medium size jet, like an Embraer 190/190 or Boeing 737-200/300. Simulations are performed in the presence of a stochastic Dryden turbulence model combined with a 1-cosine (1-cos) shape wind gust. The model-following inner loop is validated via a comparison with an internal loop of flexible mode stabilization, designed via a standard linear quadratic regulator with output feedback. © 2014 American Society of Civil Engineers. Source

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