Characterization of polyurethane resins by FTIR,TGA, and XRD

Fourier Transformed Infrared Spectroscopy, Thermogravimetric Analysis, and X‐ray Diffractometry have been used to investigate the rigid, semi rigid, and soft polyurethane (PU) forms, which were developed by the Group of Analytic Chemistry and Technology of Polymers ‐ USP ‐ São Carlos. The –NCO/–OH ratios were 0.6, 0.5, and 0.3% for rigid, semi rigid, and soft PUs, respectively, showing that different ratios cause differences in thermal behaviors and crystalline structures of the synthesized PU resins. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Stakeholder management influence on trust in a project: A quantitative study

This article aims to analyze the influence of stakeholder management on trust in project environments. Data was collected from 130 project professionals in companies from several national and multinational segments operating in Brazil. PLS-PM was applied for treatment and for data analysis. The results show that the relational stakeholder management influence on the three types of trust is relevant and significant. Therefore, it is important that the project manager not fail to consider actions such as communication with empathy as of the beginning of the project.     

On the invariant reactions in the Mo-rich portion of the Mo-Si system

The Mo-Si system presents two invariant reactions (eutectic and peritectic) in the Mo-rich region; these reactions involve the Liquid, Mo_ss, Mo₃Si, and Mo₅Si₃ phases. The results presented in the literature show disagreement about the specific reactions, with two proposals being reported: (1) L + Mo_ss ⇔ Mo₃Si and L ⇔ Mo₃Si + Mo₅Si₃; and (2) L + Mo₅Si₃ ⇔ Mo₃Si and L ⇔ Mo_ss + Mo₃Si. In order to contribute to this subject, we have produced several Mo-Si alloys (21 to 29 at.% Si) via arc melting and evaluated the as-cast microstructures through x-ray diffraction (XRD), scanning electron microscope/backscattered electron image (SEM/BSEI), and energy dispersive x-ray analysis (EDS). The primary phases identified in the different samples were Mo_ss, Mo₃Si, and Mo₅Si₃. The results have indicated clearly the existence of a eutectic reaction involving the phases Mo₃Si and Mo₅Si₃, confirming the existence of the L + Mo_ss ⇔ Mo₃Si and L ⇔ Mo₃Si + Mo₅Si₃ invariant reactions. In addition, alloys with composition 26 at.% Si and 27 at.% Si presented Mo₃Si and Mo₅Si₃ as primary phases, respectively, indicating that the liquid eutectic composition is located between those values.     

A differential evolution approach for solving constrained min–max optimization problems

Many problems occurring in engineering can be formulated as min–max optimization problems, for instance, in game theory, robust optimal control and many others. Min–max problems are considered difficult to solve, specially constrained min–max optimization problems. Approaches using co-evolutionary algorithms have successfully been used to solve min–max optimization problems without constraints. We propose a novel differential evolution approach consisting of three populations with a scheme of copying individuals for solving constrained min–max problems. Promising results have been obtained showing the suitability of the approach.     

Review of Benthic Invertebrate Fauna in Extremely Acidic Environments (pH ≤ 3)

Some benthic invertebrate species are able to colonise habitats in extremely acidic waters. We compiled a list of acid-resistant benthic invertebrates from the literature and extended it by studying extremely acidic mining lakes in eastern Germany. Acid-resistant species were registered for some habitats with pH ≤ 3, such as volcanic lakes, acid strip streams, and acidic mining lakes. Twenty nine taxa were found in waters with pH below 3. Diptera comprised 48.3% of the total number of taxa, followed by Coleoptera with 10.3%, Trichoptera 10.3%, Ephemeroptera, Megaloptera, and Plecoptera each with 6.9%, and Odonata, Hirudinea, and Acari each with 3.5%. Chironomus (Diptera: Chironomidae) were the most common genus in extremely acidic environments with 9 species. In Germany, Chironomus crassimanus was found to be the most abundant species in extremely acidic mining lakes. Generally, aquatic insects were the most common group of benthic invertebrates.     

<Superscript>1</Superscript>H NMR and Multivariate Calibration for the Prediction of Biodiesel Concentration in Diesel Blends

In this work, the use of ¹H-NMR spectroscopy and a statistical approach to the analysis of biodiesel concentrations in blends with conventional diesel is described. For this, we performed ¹H-NMR analyses using distinct mixtures of biodiesel from soybean and castor oil in mineral diesel, in concentrations ranging from 0.5 to 30%, and then we applied partial least squares regression (PLS) and principal components regression (PCR) to such data. So, six models were designed and they were evaluated through statistical parameters and through the analysis of four samples prepared in the laboratory. Briefly, a PLS model, obtained through the selection of aromatic, aliphatic and methoxy spectral regions, was quite suitable for the prediction of biodiesel concentrations greater than 2.0%. Deviations of real and predicted values were found to B2 commercial blends, indicating that this model can only be applied to blends exceeding a 2.0% level of biodiesel in petroleum diesel. In conclusion, the ¹H-NMR-PLS method is fairly useful for the quality control of biodiesel–diesel blends, whose commercialisation has increased in the last few years.     

Optical fibre nanotaper sensors

This paper reviews the work carried out in the recent years on sensors which exploit optical fibre nanotapers (OFN). After a brief introduction on the morphology, fabrication and properties of OFN, this paper will review the various OFN sensors. This type of sensors are extremely compact and relatively robust, are usually unperturbed by electromagnetic interference and can be interrogated remotely. In this review sensors will be grouped in three categories according to their morphology: linear sensors, resonant sensors and tip sensors. While linear and resonant sensors exploit the fraction of power propagating in the evanescent field (outside the nanotaper physical boundary), tip sensors exploit light confined within the nanotaper to excite/detect variations within a very limited area.     

Special purpose processor for parameter identification of CNC second order servo systems on a low-cost FPGA platform

The parameter identification process has an important role in servo systems tuning on computer numerical control (CNC) machine tools. The parameter identification is mostly done off-line due to the high computational load carried by the identification algorithms. In this work, we present a novel hardware architecture for an application specific processor implementing the recursive least-squares algorithm for the on-line identification. The developed processor is simulated and tested with the necessary elements to perform the CNC machine servo system control. The system was implemented in a low-cost FPGA, getting a maximum sample frequency of 40 kSps.     

Experimental investigation of bidensity slurries on an incline

We investigate the dynamics of bidensity slurries on an incline. The particle-fluid mixture consists of two species of negatively buoyant particles that have roughly the same size but significantly variant densities. This mismatch in particle densities induces or prevents settling depending on the relative amount of heavy to light particles, leading to complex regimes also found in the monodisperse case. In addition, when settling effects dominate within the thin film, we observe the phase separation down the incline between the particles and the liquid, as well as between two particle types.