Thermoelectric properties of plasma sprayed of calcium cobaltite (Ca2Co2O5)

The thermoelectric properties of calcium cobaltite deposits produced by the plasma spray process are investigated from room-temperature to 873 K. Synthesis of Ca₃Co₂O₆ and Ca₂Co₂O₅ powders were prepared by the solid-state reaction from CaO and CoO_x starting powders. During their subsequent plasma spray Ca particles experience preferential evaporation within the plasma, resulting in a complex interplay among process conditions, stoichiometry, and resultant phases. The as-sprayed material predominantly contains amorphous and secondary phases. Upon annealing, the deposits show sensitivity to phase evolution and therefore thermoelectric properties. Through screening studies, optimal annealing conditions were identified which show a p-type Seebeck coefficient value of 180 μV K^?1, electrical conductivity of 1.09 × 10⁴ S m^?1, thermal conductivity of 1.16 W m^-1 K^-1 at 873 K. The resultant figure of merit value reached 0.266 for this combination of processing and thermal treatment and is in line with data reported from other techniques for this system.     

Predicting cetane number,kinematic viscosity,density and higher heating value of biodiesel from its fatty acid methyl ester composition

Biodiesel is a renewable bio-fuel derived from natural fats or vegetable oils, and it is considered as a promising alternative to substitute diesel fuels. Cetane number, viscosity, density, and higher heating value are important properties to affect the utilization of biodiesel fuels, because they are involved in the definition of fuel quality and are required as input data for predictive engine combustion models. This work presents the characterization of two biodiesel samples made from beef tallow and soybean oil through their fatty acid methyl esters (FAMEs) profile. Empirical equations were developed to estimate four physical properties of methyl esters; and an average absolute deviation (AAD) of 5.95%, 2.57%, 0.11% and 0.21% for the cetane number, kinematic viscosity, density, and higher heating value were founded. Cetane number, viscosity, and higher heating value increases because of the increase of molecular weight and these physical properties decrease as the number of double bonds increases. Unlike that of above properties, density decreases as molecular weight increases and density increases as the degree of unsaturation increases. Two general mixing rules and five biodiesel samples were used to study the influence of FAMEs over the physical properties of biodiesel. The prediction of the cetane number, kinematic viscosity, density and higher heating value of biodiesel is very close to the experimental values.     

Synthesis and analysis of phase segregation of polystyrene-block-poly(methyl methacrylate) copolymer obtained by Steglich esterification from semitelechelic blocks of polystyrene and poly(methyl methacrylate)

Here, an alternative route to successfully synthesize polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) is reported. Steglich esterification was used as an effective, metal free approach for coupling carboxylic terminated PS and the hydroxyl end-functionalized PMMA chains obtained by nitroxide-mediated polymerization and atom transfer radical polymerization, respectively. α-Functionalization was obtained using 4,4′-azobis(4-cyanovaleric acid) and 2,2,2-tribromoethanol as initiators. The synthesis of PS-b-PMMA was confirmed by gel permeation chromatography and nuclear magnetic resonance (NMR), while the dependence of the diffusion coefficients of the polymers (PS, PMMA, PS/PMMA blend, and PS-b-PMMA) with their corresponding molecular weights was discussed based on the results of atomic force microscopy-based infrared spectroscopy, differential scanning calorimetry, and spectra of diffusion-ordered NMR spectroscopy. Differently from PS-b-PMMA, a partial segregation was observed for the PS/PMMA blend, affecting its thermal behavior and diffusion coefficient. The study here presented provides an easier and efficient strategy for the synthesis of PS-b-PMMA and new insights into the diffusion of polymers.     

Does the Pi strip method allow assessment of the available soil P?: Comparison against the reference isotope method

Experiments have been carried out in acid soils developed under tropical climates with and without phosphate rock (PR) addition to assess the ability of the Pi strip method to extract available soil P compared with the Isotopic Exchange Kinetics method (IEK). In the Pi strip method strips of filter paper, previously impregnated with iron hydroxide acting as a sink for phosphate ions from soil components, are added to an aqueous soil suspension. The extracted phosphate ions are eluted in diluted sulfuric acid and quantified by a colorimetric method. Available soil P, defined as the amount of phosphate ions that can move from the soil particles to soil solution, is described by three factors: an intensity factor, a quantity factor and a capacity factor. These three factors were determined by the IEK-method. Following the addition of carrier-free ³²PO₄-ions to soil, the ability of the Pi strip to extract available soil P was assessed: (i) by comparing the quantity of instantaneously exchangeable P (E₁) to the quantity extracted with the Pi strip; (ii) by determining the fraction of ³²P extracted with the Pi strip, and (iii) by comparing the specific activity (SA) of P present as phosphate ions extracted by the Pi strip to the specific activity of P in the soil solution. It was observed that (i) E₁ and the amount extracted with the Pi strip are highly correlated, (ii) the recovery of ³²P extracted by the Pi strip varies between 17 and 66%, and (iii) the specific activity of P extracted by the Pi strip is of the same order of magnitude as that of P in the soil solution. In acid soils low in available P, part of the P in aqueous KCl-extracts is presumably not only present as free phosphate ions but also occluded in the form of a soluble complex, whose isotopic exchangeability is significantly lower than that of phosphate ions transferred to the Pi strip. It is concluded from the results that the Pi strip method can be recommended in routine analysis for the determination of the quantity factor. However, this method cannot provide intensity or capacity factors and therefore needs to be complemented by the IEK-method for full characterization of the available soil P status.     

Electrical Characterization of a Joined Electroceramic, La0.85Sr0.15MnO3

Pieces of saw-cut La_0.85Sr_0.15MnO₃ were joined at 1150° and 1250°C under a compressive stress. The strains to form the joints were ∼0.1. Joints formed by plastic deformation were examined using scanning electron microscopy, and they were indistinguishable from the bulk. The room-temperature direct-current resistivity of the joined pieces was identical to that measured in the bulk material. This indicated that a sound, electrically conducting joint could be formed using plastic deformation (grain-boundary sliding) with little surface preparation.     

CFD as an approach to understand flammable dust 20 L standard test: Effect of the ignition time on the fluid flow

A computational study based on the Euler–Lagrange approach was developed for the characterization of flammable dusts in the 20 L sphere standard test. The aim of the study was to analyze some parameters that might affect the experimental data (e.g., cold turbulence and particle size). The turbulence of a wheat starch cloud was described with the Detached Eddy Simulation model. Both the pressure of the system and the RMS velocity were compared with the flow patterns established with a particle image velocimetry analysis. It was concluded that the rebound nozzle forms a cloud that is composed by clumps. This fact implies dissimilarities between the local concentrations and the nominal value. Finally, a granulometric analysis established that the mean diameter of the particle size distribution (PSD) decreased by 69% during the dispersion. Thus, it is suggested to consider the PSD at the ignition zone rather than the PSD of the sample. © 2017 American Institute of Chemical Engineers AIChE J, 63: 42–54, 2018     

An adaptive color similarity function suitable for image segmentation and its numerical evaluation

In this article, we present an adaptive color similarity function defined in a modified hue‐saturation‐intensity color space, which can be used directly as a metric to obtain pixel‐wise segmentation of color images among other applications. The color information of every pixel is integrated as a unit by an adaptive similarity function thus avoiding color information scattering. As a direct application we present an efficient interactive, supervised color segmentation method with linear complexity respect to the number of pixels of the input image. The process has three steps: (1) Manual selection of few pixels in a sample of the color to be segmented. (2) Automatic generation of the so called color similarity image (CSI), which is a gray level image with all the gray level tonalities associated with the selected color. (3) Automatic threshold of the CSI to obtain the final segmentation. The proposed technique is direct, simple and computationally inexpensive. The evaluation of the efficiency of the color segmentation method is presented showing good performance in all cases of study. A comparative study is made between the behavior of the proposed method and two comparable segmentation techniques in color images using (1) the Euclidean metric of the a* and b* color channels rejecting L* and (2) a probabilistic approach on a* and b* in the CIE L*a*b* color space. Our testing system can be used either to explore the behavior of a similarity function (or metric) in different color spaces or to explore different metrics (or similarity functions) in the same color space. It was obtained from the results that the color parameters a* and b* are not independent of the luminance parameter L* as one might initially assume in the CIE L*a*b* color space. We show that our solution improves the quality of the proposed color segmentation technique and its quick result is significant with respect to other solutions found in the literature. The method also gives a good performance in low chromaticity, gray level and low contrast images. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 156–172, 2017     

CORRELATION AND PREDICTION OF VLE OF WATER + CONGENER MIXTURES FOUND IN ALCOHOLIC BEVERAGES USING AN ARTIFICIAL NEURAL NETWORK

Artificial neural networks have been used for the correlation and prediction of vapor-liquid equilibrium data of binary water mixtures found in alcoholic beverage production. The main interest of the study is the accurate modeling of the bubble pressure and concentration of congeners in the vapor phase (substances different from ethanol and water), considered to be an important enological parameter in the alcoholic industry. Nine binary water + congener mixtures were considered for analysis. Vapor-liquid equilibrium data of these systems were taken from the literature (333 data points for training and 111 data points for testing), the artificial neural network results were compared with available literature data, and the accuracy of the modeling is discussed. The study shows that the neural network model is a good alternative method for the estimation of phase equilibrium properties for this type of mixture.

Supplemental materials are available for this article. Go to the publisher's online edition of Chemical Engineering Communications to view the free supplemental file. http://www.informaworld.com/smpp/title~db=all~content=t713454788     

Horizontal reactive distillation for multicomponent chiral resolution

A novel horizontal reactive distillation apparatus and a new overall process scheme are proposed for continuous multicomponent chiral resolution via reversible enantioselective acylation of a chiral (racemic) substrate by a chiral (racemic) acyl donor. The process enables simultaneous production of up to four enantiomers with enhanced chiral purity. Kinetic studies, miniplant experiments, and process simulation results are described for a model lipase‐catalyzed reaction: (R)‐enantioselective transesterification of (R,S)‐1‐n‐butoxy‐2‐propanol with (R,S)‐1‐methoxy‐2‐acetoxypropane to produce (R)‐1‐n‐butoxy‐2‐acetoxypropane, (R)‐1‐methoxy‐2‐propanol, and the two unreacted (S)‐enantiomers of the (R,S)‐reagents. A horizontal, compartmentalized reactive distillation vessel is specified instead of a conventional reactive distillation column to provide longer liquid‐phase residence time needed for adequate conversion. Low vapor‐traffic pressure drop allows operation under vacuum at reduced temperatures for good enzyme stability and enantioselectivity. The general technology has potential as a means to producing a wide range of chiral synthons used in asymmetric syntheses of chiral pharmaceuticals and other biologically active products. © 2013 American Institute of Chemical Engineers AIChE J, 59: 2603–2620, 2013     

Assessment of production efficiency,physicochemical properties and storage stability of spray-dried propolis,a natural food additive,using gum Arabic and OSA starch-based carrier systems

The aim of this work was to obtain propolis in a powder, alcohol-free, water-dispersed and shelf-stable form. Propolis extract was spray-dried using gum Arabic and octenyl succinic anhydride (OSA) starch as carriers in two different weight ratios (1:4 and 1:6). Spray-dried propolis samples were evaluated for morphology, moisture, water activity, water dispersibility, hygroscopicity, particle size, particle distribution, entrapping efficiency, stability, isotherms and antioxidant properties. The spray-drying process produced round particles with sizes ranging from 15 to 24 μm. This process preserved the antioxidant activity of propolis and also allowed propolis to be obtained in a powder form, which was stable during storage at room temperature, had low hygroscopicity and was highly dispersible in cold water. The application of this technology could increase the use of propolis in various industrial applications, such as an antimicrobial and as an antioxidant in food.