Thermoanalytical and rheological characterization of automotive mineral lubricants after thermal degradation

This work aims to characterize thermal degradation process of automotive mineral lubricants, in relation to its rheological and thermoanalytical properties. Lubricants were degraded at temperatures varying from 150 to 210 °C, and times of 1–48 h. After degradation, oils were characterized by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (NMR), rheologic measurements and thermal analysis (TG/DSC). IR and NMR spectra indicated oxidation reaction products. TG curves indicated a decrease in the temperature of decomposition start after degradation. DSC curves indicated a decrease in the peak related to hydrocarbon combustion after degradation. In general, the increase in degradation temperature led to an increase of the lubricants viscosity, besides thixotropy appearance for some samples.     

Worker evaluation of a macroergonomic intervention in a Brazilian footwear company

This article presents a macroergonomic intervention in a Brazilian footwear company and its evaluation by the workers. Using participatory ergonomics, the traditional Taylor/Ford production system was transformed into a socio-technical one and tested by 100 volunteers working during 3.5 years in a pilot production line. Multiskilling and teamwork were the major changes promoted to enlarge and enrich work and make it more flexible. The workers' evaluation pre- and post-intervention showed an increase in overall satisfaction with the work and more commitment to the results and company targets.     

Hardware-In-the-Loop Simulation with X-Plane of Attitude Control of a SUAV Exploring Atmospheric Conditions

The attitude control law for fixed-wing small unmanned aircraft proposed in this paper is constructed based on two phases of a flight: stable flight and maneuvering flight. In the maneuvering flight, the aircraft deflects the main control surfaces (ailerons and elevator), whereas on the stable flight only the trim tabs are deflected. The switch between the two flights is done when the aircraft enters a zone in which the difference between the aircraft’s attitude and the reference value that the airplane needs to reach is greater than a predetermined value. The control laws are implemented on an on-board computer and are validated though Hardware-In-the-Loop (HIL) simulations, between the hardware and the flight simulator X-Plane, which simulates the unmanned aircraft dynamics, sensors, and actuators. The paper proves that this implementation can reduce the rise time and the overshoot, compared with traditional PID implementations. In order to analyze the behavior of the SUAV in these situations, it was performed simulations with Wind Gust and levels of Turbulence, using the X-Plane features.     

Compatibilization of nitrile‐butadiene rubber/ethylene‐propylene‐diene monomer blends by mercapto‐modified ethylene‐vinyl acetate copolymers

Mercapto‐modified ethylene‐vinyl acetate (EVASH) has been employed as a reactive compatibilizing agent for nitrile‐butadiene rubber (NBR)/ethylene‐propylene‐diene monomer (EPDM) blends vulcanized with a sulfur/2,2′‐dithiobisbenzothiazole (MBTS) single accelerator system and a (sulfur/MBTS/tetramethylthiuram disulfide (TMTD) binary accelerator system. The addition of 5.0 phr EVASH resulted in a significant improvement in the tensile properties of blends vulcanized with the sulfur/MBTS system. In addition to better mechanical performance, these functionalized copolymers gave rise to a more homogeneous morphology and, in some cases, better aging resistance. The compatibilization was not efficient in blends vulcanized with the S/MBTS/TMTD binary system, probably because of the faster vulcanization process occurring in this system. The good performance of these EVASH samples as compatibilizing agents for NBR/EPDM blends is attributed to the higher polarity of these components that is associated with their lower viscosity. Dynamic mechanical analysis also suggested a good interaction between the phases in the presence of EVASH. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1404–1412, 2004     

白于山井区长4 5_2油组储层沉积微相研究

通过对构造背景、岩心、古生物特征、测井资料的综合分析,查明了鄂尔多斯盆地白于山井区长4 52油组的沉积特征和沉积微相的平面展布规律,认为白于山井区长4 52油组储集体发育的是一套三角洲前缘亚相砂体,其沉积微相可进一步划分为水下分流河道、河口砂坝、远砂坝和支流间湾微相。根据不同沉积微相的测井响应特征,研究了沉积相在平面上的分布特征,并总结出研究区的相层序。     

Dynamic selection of classifiers—A comprehensive review

This work presents a literature review of multiple classifier systems based on the dynamic selection of classifiers. First, it briefly reviews some basic concepts and definitions related to such a classification approach and then it presents the state of the art organized according to a proposed taxonomy. In addition, a two-step analysis is applied to the results of the main methods reported in the literature, considering different classification problems. The first step is based on statistical analyses of the significance of these results. The idea is to figure out the problems for which a significant contribution can be observed in terms of classification performance by using a dynamic selection approach. The second step, based on data complexity measures, is used to investigate whether or not a relation exists between the possible performance contribution and the complexity of the classification problem. From this comprehensive study, we observed that, for some classification problems, the performance contribution of the dynamic selection approach is statistically significant when compared to that of a single-based classifier. In addition, we found evidence of a relation between the observed performance contribution and the complexity of the classification problem. These observations allow us to suggest, from the classification problem complexity, that further work should be done to predict whether or not to use a dynamic selection approach.     

A new approach to obtain mesoporous-activated carbon via hydrothermal carbonization of Brazilian Cerrado biomass combined with physical activation for bisphenol-A removal

Abstract

The worrying hydric crisis and the increasing water contamination by emerging pollutants around the world stimulate the development of activated carbons (AC) for the removal of endocrine disruptors, including bisphenol-A (BPA). For this reason, a new approach for the synthesis of AC from hydrochar produced through hydrothermal carbonization (HTC) of Brazilian Cerrado biomass (Magonia pubescens–Sapindaceae) and physical activation using water vapor is highlighted. Compared to the traditional method of physical activation after pyrolysis, HTC was found to be better option to develop the specific surface area, porosity, and yield of the ACs, which presented mesoporous structure and carbon content higher than 80%. The BPA adsorption was evaluated by varying the contact time, BPA concentration, and pH. The Langmuir, Freundlich, and Redlich–Peterson isotherms were used to model the adsorption behavior. In the preliminary test to verify the adsorption efficiency, the AC obtained from hydrochar treated at 180?°C presented better results compared to commercial AC. The BPA adsorption data of the best treated hydrochar correlated well with the pseudo first-order model and the Langmuir isotherm (Q_max = 21.26?mg g^?1). The results of the studies indicated the combination of HTC and physical activation with steam to be an efficient way to prepare an ecologically sound adsorbent for removal of Bisphenol-A from water with lower temperature and without chemical reagents. The ACs obtained can also be potential materials for other applications, such as in the field of catalysis and environmental remediation.     

Electrochemical oxidation of an acid dye by active chlorine generated using Ti/Sn<Subscript>(1−<Emphasis Type="Italic">x</Emphasis>)</Subscript>Ir<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>O<Subscript>2</Subscript> electrodes

The generation of active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes, with different compositions of Ir (x = 0.01, 0.05, 0.10 and 0.30 ), was investigated by controlled current density electrolysis. Using a low concentration of chloride ions (0.05 mol L⁻¹) and a low current density (5 mA cm⁻²) it was possible to produce up to 60 mg L⁻¹ of active chlorine on a Ti/Sn_0.99Ir_0.01O₂ anode. The feasibility of the discoloration of a textile acid azo dye, acid red 29 dye (C.I. 16570), was also investigated with in situ electrogenerated active chlorine on Ti/Sn_(1−x)Ir _x O₂ anodes. The best conditions for 100% discoloration and maximum degradation (70% TOC reduction) were found to be: NaCl pH 4, 25 mA cm⁻² and 6 h of electrolysis. It is suggested that active chlorine generation and/or powerful oxidants such as chlorine radicals and hydroxyl radicals are responsible for promoting faster dye degradation. Rate constants calculated from color decay versus time reveal a zero order reaction at dye concentrations up to 1.0 × 10⁻⁴ mol L⁻¹. Effects of other electrolytes, dye concentration and applied density currents also have been investigated and are discussed.     

Graft copolymers of poly(methyl methacrylate) backbone and poly(propylene oxide-b-ethylene oxide) branches

Summary Two mono-functional macromonomers of poly (propylene oxide-b-ethylene oxide) were synthesized by reaction with methacryloyl chloride. The macromonomers have the same molecular weight and ratio of ethylene oxide and propylene oxide sequences. The reactive methacrylate group can be linked to the ethylene oxide (BuPPOPEO) or to the propylene oxide (BuPEOPPO). These macromonomers showed self-gelling in one week even at low temperature and under a dry atmosphere. Graft copolymers were obtained by reaction of these macromonomers with methyl methacrylate upon free-radical initiation and they were characterized by GPC, VPO, IR and ¹H NMR spectra.     

Study of the hypophosphite effect on the electrochemical reduction of nitrobenzene on Ni

The effect of the hypophosphite ion on the electrochemical reduction of nitrobenzene on Ni was evaluated from a cyclic voltammetric study and from constant potential electrolysis in an aqueous-ethanol alkaline medium. The results were compared with the data obtained in an hypophosphite-free solution. It was found that in an hypophosphite containing solution an unusual selective reduction of nitrobenzene to nitrosobenzene occurs. It is the first time that nitrosobenzene is detected as the reaction product of the nitrobenzene electrochemical reduction in an aqueous-ethanol solution. It is proposed that the Ni modified surface which is formed upon hypophosphite oxidation is responsible for the non reducibility of nitrosobenzene. The effect of the electrode potential on the nitrobenzene electrolysis on a Ni modified electrode was analysed. It was concluded that the highest nitrosobenzene yield (33%) and selectivity (82%) is achieved at −1.1 V. It was also found that the formation of nitrosobenzene leads to an electrode poisoning effect in the electrolysis process.