Preparation and characterization of Mo/W bimetallic carbides by using different synthesis methods

Molybdenum and tungsten bimetallic oxides were synthetized according to the following methods: Pechini, coprecipitation and solid state reaction (SSR). After the characterization, those solids were carbureted at programmed temperature. The carburation process was monitored by checking the consumption of carburant hydrocarbon and CO produced. The monitoring process permits to avoid or to diminish the formation of pirolytic carbon.

Banana as Adjunct in Beer Production: Applicability and Performance of Fermentative Parameters

Traditionally, the raw materials for beer production are barley, hops, water, and yeast, but most brewers use also different adjuncts. During the alcoholic fermentation, the contribution of aroma compounds from other ingredients to the final beer flavor depends on the wort composition, on the yeast strain, and mainly on the process conditions. In this context, banana can also be a raw material favorable to alcoholic fermentation being rich in carbohydrates and minerals and providing low acidity. In this work, the objective was to evaluate the performance of wort adjusted with banana juice in different concentrations. For this, static fermentations were conducted at 15 degrees C at pilot scale (140 L of medium). The addition of banana that changed the concentration of all-malt wort from 10 degrees P to 12 and 15 degrees P were evaluated (degrees P is the weight of the extract or the sugar equivalent in 100 g solution, at 20 degrees C). The results showed an increase in ethanol production, with approximately 0.4 g/g ethanol yield and 0.6 g/L h volumetric productivity after 84 h of processing when concentrated wort was used. Thus, it was concluded that banana can be used as an adjunct in brewing methods, helping in the development of new products as well as in obtaining concentrated worts.

Ecodesign methods focused on remanufacturing

Understanding the product`s `end-of-life` is important to reduce the environmental impact of the products` final disposal. When the initial stages of product development consider end-of-life aspects, which can be established by ecodesign (a proactive approach of environmental management that aims to reduce the total environmental impact of products), it becomes easier to close the loop of materials. The `end-of-life` ecodesign methods generally include more than one `end-of-life` strategy. Since product complexity varies substantially, some components, systems or sub-systems are easier to be recycled, reused or remanufactured than others. Remanufacture is an effective way to maintain products in a closed-loop, reducing both environmental impacts and costs of the manufacturing processes. This paper presents some ecodesign methods focused on the integration of different `end-of-life` strategies, with special attention to remanufacturing, given its increasing importance in the international scenario to reduce the life cycle impacts of products. (C) 2009 Elsevier Ltd. All rights reserved.

A Study on Unconditionally Stable FDTD Methods for the Modeling of Metamaterials

We assess the performance of three unconditionally stable finite-difference time-domain (FDTD) methods for the modeling of doubly dispersive metamaterials: 1) locally one-dimensional FDTD; 2) locally one-dimensional FDTD with Strang splitting; and (3) alternating direction implicit FDTD. We use both double-negative media and zero-index media as benchmarks.

Aerodynamic study of three-dimensional larynx models using finite element methods

The airflow velocities and pressures are calculated from a three-dimensional model of the human larynx by using the finite element method. The laryngeal airflow is assumed to be incompressible, isothermal, steady, and created by fixed pressure drops. The influence of different laryngeal profiles (convergent, parallel, and divergent), glottal area, and dimensions of false vocal folds in the airflow are investigated. The results indicate that vertical and horizontal phase differences in the laryngeal tissue movements are influenced by the nonlinear pressure distribution across the glottal channel, and the glottal entrance shape influences the air pressure distribution inside the glottis. Additionally, the false vocal folds increase the glottal duct pressure drop by creating a new constricted channel in the larynx, and alter the airflow vortexes formed after the true vocal folds. (C) 2007 Elsevier Ltd. All rights reserved.

Noise reduction in biomedical speech signal processing based on time and frequency Kalman filtering combined with spectral subtraction

The goal of this paper is to study and propose a new technique for noise reduction used during the reconstruction of speech signals, particularly for biomedical applications. The proposed method is based on Kalman filtering in the time domain combined with spectral subtraction. Comparison with discrete Kalman filter in the frequency domain shows better performance of the proposed technique. The performance is evaluated by using the segmental signal-to-noise ratio and the Itakura-Saito`s distance. Results have shown that Kalman`s filter in time combined with spectral subtraction is more robust and efficient, improving the Itakura-Saito`s distance by up to four times. (C) 2007 Elsevier Ltd. All rights reserved.

Data Mining Applied to Harmonic Current Sources Identification in Residential Consumers

This work proposes a method based on both preprocessing and data mining with the objective of identify harmonic current sources in residential consumers. In addition, this methodology can also be applied to identify linear and nonlinear loads. It should be emphasized that the entire database was obtained through laboratory essays, i.e., real data were acquired from residential loads. Thus, the residential system created in laboratory was fed by a configurable power source and in its output were placed the loads and the power quality analyzers (all measurements were stored in a microcomputer). So, the data were submitted to pre-processing, which was based on attribute selection techniques in order to minimize the complexity in identifying the loads. A newer database was generated maintaining only the attributes selected, thus, Artificial Neural Networks were trained to realized the identification of loads. In order to validate the methodology proposed, the loads were fed both under ideal conditions (without harmonics), but also by harmonic voltages within limits pre-established. These limits are in accordance with IEEE Std. 519-1992 and PRODIST (procedures to delivery energy employed by Brazilian`s utilities). The results obtained seek to validate the methodology proposed and furnish a method that can serve as alternative to conventional methods.

Thermal diffusivity of polymers by modified angstrom method

The nature of the molecular structure of plastics makes the properties of such materials markedly temperature dependent. In addition, the continuous increase in the utilization of polymeric materials in many specific applications has demanded knowledge of their physical properties, both during their processing as raw material, as well as over the working temperature range of the final polymer product. Thermal conductivity, thermal diffusivity and specific heat, namely the thermal properties, are the three most important physical properties of a material that are needed for heat transfer calculations. Recently, among several different methods for the determination of the thermal diffusivity and thermal conductivity, transient techniques have become the preferable way for measuring thermal properties of materials. In this work, a very simple and low cost variation of the well known Angstrom method is employed in the experimental determination of the thermal diffusivity of some selected polymers. Cylindrical shaped samples 3 cm diameter and 7 cm high were prepared by cutting from long cylindrical commercial bars. The reproducibility is very good, and the results obtained were checked against results obtained by the hot wire technique, laser flash technique, and when possible, they were also compared with data found in the literature. Thermal conductivity may be then derived from the thermal diffusivity with the knowledge of the bulk density and the specific heat, easily obtained by differential scanning calorimetry. (C) 2009 Elsevier Ltd. All rights reserved.

Assessment of the Performance of Acoustic and Mass Balance Methods for Leak Detection in Pipelines for Transporting Liquids

On-line leak detection is a main concern for the safe operation of pipelines. Acoustic and mass balance are the most important and extensively applied technologies in field problems. The objective of this work is to compare these leak detection methods with respect to a given reference situation, i.e., the same pipeline and monitoring signals acquired at the inlet and outlet ends. Experimental tests were conducted in a 749 m long laboratory pipeline transporting water as the working fluid. The instrumentation included pressure transducers and electromagnetic flowmeters. Leaks were simulated by opening solenoid valves placed at known positions and previously calibrated to produce known average leak flow rates. Results have clearly shown the limitations and advantages of each method. It is also quite clear that acoustics and mass balance technologies are, in fact, complementary. In general, an acoustic leak detection system sends out an alarm more rapidly and locates the leak more precisely, provided that the rupture of the pipeline occurs abruptly enough. On the other hand, a mass balance leak detection method is capable of quantifying the leak flow rate very accurately and of detecting progressive leaks.

Experimental Analysis of Structural Change and Rheological Behavior of Macromolecular Solutions with Guar and Xanthan Gums in Crossflow Microfiltration Processing

The present paper reports on the structural change and rheological behavior of mixtures of macromolecular suspensions (guar and xanthan gums) in crossflow microfiltration processing. Mixtures in suspension of guar and xanthan gums at low concentrations (1,000 ppm) and different proportions were processed by microfiltration with membrane of nominal pore size of 0.4 mu m. The rheological behavior of the mixtures was investigated in rotational viscometers at two different temperatures, 25 and 40 C, at the beginning and at the end of each experiment. The shear stress (t) in function of the shear rate (gamma) was fitted and analyzed with the power-law model. All the mixtures showed flow behavior index values (n) lower than 1, characterizing non-Newtonian fluids (pseudoplastic). The samples of both mixtures and permeates were also analyzed by absorbency spectroscopy in infrared radiation. The absorbency analysis showed that there is good synergism between xanthan and guar gums without structure modifications or gel formation in the concentration process by microfiltration.

A solid-like FEM for geometrically non-linear 3D frames

This study presents a solid-like finite element formulation to solve geometric non-linear three-dimensional inhomogeneous frames. To achieve the desired representation, unconstrained vectors are used instead of the classic rigid director triad; as a consequence, the resulting formulation does not use finite rotation schemes. High order curved elements with any cross section are developed using a full three-dimensional constitutive elastic relation. Warping and variable thickness strain modes are introduced to avoid locking. The warping mode is solved numerically in FEM pre-processing computational code, which is coupled to the main program. The extra calculations are relatively small when the number of finite elements. with the same cross section, increases. The warping mode is based on a 2D free torsion (Saint-Venant) problem that considers inhomogeneous material. A scheme that automatically generates shape functions and its derivatives allow the use of any degree of approximation for the developed frame element. General examples are solved to check the objectivity, path independence, locking free behavior, generality and accuracy of the proposed formulation. (C) 2009 Elsevier B.V. All rights reserved.

A comparison between neodymium doped alumina samples obtained by Pechini and sol-gel methods using thermo-stimulated luminescence and SEM

Neodymium doped and undoped aluminum oxide samples were obtained using two different techniques: Pechini and sol-gel. Fine grained powders were produced using both procedures, which were analyzed using Scanning Electron Microscopy (SEM) and Thermo-Stimulated Luminescence (TSL). Results showed that neodymium ions incorporation is responsible for the creation of two new TSL peaks (125 and 265 degrees C) and, also, for the enhancement of the intrinsic TSL peak at 190 degrees C. An explanation was proposed for these observations. SEM gave the dimensions of the clusters produced by each method, showing that those obtained by Pechini are smaller than the ones produced by sol-gel; it can also explain the higher emission supplied by the first one. (C) 2010 Elsevier B.V. All rights reserved.

Thermoplastic starch modified during melt processing with organic acids: The effect of molar mass on thermal and mechanical properties

Thermoplastic starch (TPS) was modified with ascorbic acid and citric acid by melt processing of native starch with glycerol as plasticizer in an intensive batch mixer at 160 degrees C. It was found that the molar mass decreases with acid content and processing time causing the reduction in melting temperature (T(m)). As observed by the results of X-ray diffraction and DSC measurements, crystallinity was not changed by the reaction with organic acids. T(m) depression with falling molar mass was interpreted on the basis of the effect of concentration of end-chain units, which act as diluents. FTIR did not show any appreciable change in starch chemical compositions, leading to the conclusion that the main changes observed were produced by the variation in molar mass of the material. We demonstrated that it is possible to decrease melt viscosity without the need for more plasticizer thus avoiding side-effects such as an increase in water affinity or relevant changes in the dynamic mechanical properties. (C) 2010 Elsevier B.V. All rights reserved.

Compatible Ternary Blends of Chitosan/poly(vinyl alcohol)/poly(lactic acid) Produced by Oil-in-Water Emulsion Processing

Ternary compatible blends of chitosan, poly(vinyl alcohol), and poly(lactic acid) were prepared by an oil-in-water (O/W) emulsion process. Solutions of chitosan in aqueous acetic acid, poly(vinyl alcohol) (PVA) in water, and poly(lactic acid) (PLA) in chloroform were blended with a high shear mixer. PVA was used as an emulsifier to stabilize the emulsion and to reduce the interfacial tension between the solid polymers in the blends-produced. It proved to work very well because the emulsions were stable for periods of days or weeks and compatible blends were obtained When PVA was added. This effect was attributed to a synergistic effect of PVA and chitosan because the binary blends PVA/PLA and chitosan/PLA were completely incompatible; The blends were characterized by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal mechanical analysis (TMA), stress strain tests, and Fourier transform infrared spectroscopy (FTIR). The results indicated that despite the fact that the system contained distinct phases some degree of molecular miscibility occurred when the three components were present in the blend.

Methane generation in tropical landfills: Simplified methods and field results

This paper deals with the use of simplified methods to predict methane generation in tropical landfills. Methane recovery data obtained on site as part of a research program being carried Out at the Metropolitan Landfill, Salvador, Brazil, is analyzed and used to obtain field methane generation over time. Laboratory data from MSW samples of different ages are presented and discussed: and simplified procedures to estimate the methane generation potential, L(o), and the constant related to the biodegradation rate, k are applied. The first order decay method is used to fit field and laboratory results. It is demonstrated that despite the assumptions and the simplicity of the adopted laboratory procedures, the values L(o) and k obtained are very close to those measured in the field, thus making this kind of analysis very attractive for first approach purposes. (C) 2008 Elsevier Ltd. All rights reserved.