Thermodynamic modeling of PVTx properties for several water/hydrocarbon systems in near-critical and supercritical conditions

Both the equation of state-excess Gibbs energy (EoS/G ^E ) model and the cubic plus association (CPA) equation of state (EoS) are compared in this study with respect to their accuracy in the correlation of PVTx for systems such as water/methanol, water/ethanol, water/benzene, water/toluene, water/methane, water/n-butane, water/n-pentane, water/n-hexane, water/heptane, and water/octane, in supercritical conditions within temperature and pressure ranges of (573–698 K) and (7.0–276.0 MPa), respectively. In the proposed EoS/G ^E model, Peng-Robinson (PR) equation of state, linear combination Vidal-Michelsen (LCVM) and Wong-Sandler (WS) mixing rules in conjunction with UNIQUAC activity coefficient model were used. Correlation of both CPA and EoS/G ^E models was evaluated by comparing the results with the experimental data. Average absolute relative deviation (AARD) for WS, LCVM, and CPA was found to be 2.99, 11.11 and 5.14%, respectively, indicating better correlation of WS model with the experimental data.     

A quantum mechanical transport approach to simulation of quadruple gate silicon nanowire transistor

In this paper we have used quantum mechanical transport approach to analyse electrical characteristics of silicon nanowire transistor and have compared the results with those obtained using semi classical Boltzmann transport model. The analyse employs a three dimensional simulation of Silicon nanowire transistor based on self consistent solution of Poisson, Schrodinger equations. Quantum mechanical transport model uses the non equilibrium Green's function (NEGF) while the semi classic model doesn't account for tunneling current. The results have shown that Quantum tunneling is significant in inversion condition especially when the channel length is short. For the long devices quantum modeling and semi classical model produce the same result, and tunneling is negligible.     

Analysis of pressure fluctuations in fluidized beds. II. Reconstruction of the data by the Fokker–Planck and Langevin equations

In this part of the sequel we develop a continuum representation of the pressure fluctuation time series p(t) for a fluidized bed (FB), analyzed in part I, by using stochastic methods based on the Markov processes. It is shown that the data may be represented by Markov series with a Markov time scale t_M that is estimated based on the data. Using the relation between the Markov processes and the Kramers–Moyal (KM) expansion that is a continuum equation that involves, in principle, an infinite number of coefficients, we represent the pressure fluctuation time series by a KM expansion. However, since the third and higher-order coefficients of the expansion are very small, the KM expansion reduces to a Fokker–Planck (FP) equation that represents p(t) in terms of a drift and a diffusion coefficients that are computed based on the data. The FP equation is, in turn, equivalent to a Langevin equation, which is used to reconstruct the data, i.e. generate the time series that mimic, in a statistical sense, the original data. Thus, the Langevin equation may also be used to make probabilistic predictions for the future values of the pressure over time scales that are of the order of the Markov time scale t_M. The accuracy of the reconstructed series and, hence, their continuum representation, is demonstrated. We also compute the frequency of level-crossing at a given level α, i.e. the relative frequency (probability) of occurrence of the event defined, for two times t_i−1 and t_i, by, , where P(x) is the probability of the event. Thus, yields the frequency that a given pressure fluctuation level may be expected. The average time that one should wait in order to observe the pressure at a given level again is also computed. The two quantities may be particularly important for modeling of the FBs. A relation is presented between the drift and diffusion coefficients of the FP equation and the Hurst exponent that has previously been used to describe the pressure fluctuation time series in terms of self-affine stochastic distributions.     

Evaluation of wool nanoparticles incorporation in chitosan/gelatin composite films

The aim of this work was to develop chitosan/gelatin composite films embedded with various amounts of wool nanoparticles, which were produced by an environmental friendly process. Films loaded with wool nanoparticles were subjected to physiochemical, biological, and mechanical characterization. The obtained results showed that incorporation of wool nanoparticles into chitosan/gelatin composite led to a reduction in swelling, moisture content and dissolution degree of the films. In vitro degradation test revealed that the nanoparticles‐embedded composites had a lower degradation rate than that of chitosan/gelatin composite. Besides, composite films containing wool nanoparticles showed an improvement in the stability in phosphate buffered saline. On the other hand, tensile strength and elongation at break decreased upon loading the films with wool nanoparticles. The biocompatibility of the produced composites was also confirmed by MTT test. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40294.     

Starch sulfate as an efficient and biodegradable polymer catalyst for one‐pot,four‐component reaction of 2H‐indazolo[2,1‐b]phthalazine‐triones

A practical and green method for the synthesis of 2H‐indazolo[2,1‐b]phthalazine‐1,6,11(13H)‐trione derivatives using starch sulfate as a solid acid catalyst for the four‐component condensation reaction from hydrazinium hydroxide, phthalic anhydride, dimedone, and aromatic aldehydes under thermal solvent‐free conditions is described for the first time. Starch sulfate, a recyclable and easily handled catalyst has been demonstrated as a new catalyst for the synthesis of these classes of compounds.     

Biosurfactant-producing bacterium, Pseudomonas aeruginosa MA01 isolated from spoiled apples: physicochemical and structural characteristics of isolated biosurfactant

An extensive investigation was conducted to isolate indigenous bacterial strains with outstanding performance for biosurfactant production from different types of spoiled fruits, food-related products and food processing industries. An isolate was selected from 800 by the highest biosurfactant yield in soybean oil medium and it was identified by 16S rRNA and the two most relevant hypervariable regions of this gene; V3 and V6 as Pseudomonas aeruginosa MA01. The isolate was able to produce 12 g/l of a glycolipid-type biosurfactant and generally less efficient to emulsify vegetable oils compared to hydrocarbons and could emulsify corn and coconut oils more than 50%. However, emulsification index (E(24)) of different hydrocarbons including hexane, toluene, xylene, brake oil, kerosene and hexadecane was between 55.8% and 100%. The surface tension of pure water decreased gradually with increasing biosurfactant concentration to 32.5 mNm(-1) with critical micelle concentration (CMC) value of 10.1mg/l. Among all carbon substrates examined, vegetable oils were the most effective on biosurfactant production. Two glycolipid fractions were purified from the biosurfactant crude extracts, and FTIR and ES-MS were used to determine the structure of these compounds. The analysis indicated the presence of three major monorhamnolipid species: R(1)C(10)C(10), R(1)C(10)C(12:1), and R(1)C(10)C(12); as well as another three major dirhamnolipid species: R(2)C(10)C(10), R(2)C(10)C(12:1), and R(2)C(10)C(12). The strain sweep experiment for measuring the linear viscoelastic of biosurfactant showed that typical behavior characteristics of a weak viscoelastic gel, with storage modulus greater than loss modulus at all frequencies examined, both showing some frequency dependence.     

Flexural strength evaluations and fractography analyses of slip cast mesoporous submicron alumina

Mesoporous submicron α?Al₂O₃ green compacts were fabricated using slip casting of ultrafine alumina powders. The pre-sintered samples were sintered in air atmosphere at 1300 °C, 1350 °C, 1400 °C, and 1500 °C to obtain a variety of grain morphologies namely submicron equiaxed and micro rod structures. The resulting grain diameters lie between ～ 270 nm and ～ 1590 nm and total porosity fraction between 0.05% and 13%. The room temperature flexural strength (σ) evaluations and fractography analyses of sintered alumina samples were performed. It was observed that the total porosity fraction dictates the flexural strength as compared to grain diameter. Further, it was found that the flexural strength exhibited a decreasing trend for an increase in the total porosity fraction, and proved to be a better effective parameter than open porosity fraction. The fractography analyses suggest that samples sintered at 1300 °C and 1350 °C predominantly underwent intergranular fracture, while those sintered at 1400 °C and 1500 °C underwent a mixture of intergranular and transgranular fracture.     

Soft segment composition and its influence on phase-separated morphology of PCL/PEG-based poly(urethane urea)s

A composition-dependent microphase separation of segmented poly(urethane urea)s (PUUs), based on a mixture of two hydrophobic (polycaprolactone) and hydrophilic (polyethylene glycol) polyols, is investigated. Synthesis of PUUs was carried out through the reaction of in situ generated AB-type macromonomers, prepared from the reaction of NCO-terminated urethane prepolymers, with benzoic acid in dimethyl sulfoxide as solvent/reagent at 40–80 °C. The segmented PUUs were characterized by different methods including FTIR and NMR spectroscopies, gel permeation chromatography, differential scanning calorimetry and dynamic mechanical analysis. Microphase separation in the synthesized PUUs was monitored using atomic force microscopy (AFM) to find a better insight into structure–property relationship of PUUs consisting of mixed polyols. Thermal analysis of the polymers revealed that by introducing poly(ethylene glycol) (PEG) in PUU backbone, a well-defined glass transition was obtained. The results of AFM showed that PCL-based poly(urethane urea) has a morphology in which hard segment domains were homogeneously distributed in the soft segment matrix. In the samples based on PCL/PEG, the hard segment domains aggregates were connected to each other and were inhomogeneously distributed in the matrix. Comparison of the overall data revealed that the differences in soft segment compositions had a marked effect on the molecular structure and the mechanical properties of PUUs.     

Phase transformation of FeCr2O4 to (Fe,Cr)2O3 solid solution pigment powders: Effect of post-heating temperature

Iron chromite powders were synthesized via solution combustion route using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, as well as glycine–urea, glycine–citric acid, and glycine–ethylene glycol mixtures as fuels. The effect of postheating at different temperatures on the structure, molecular, microstructure, and chromatic properties of powders and tiles colored by in-glaze powders was studied. The X-ray diffraction patterns showed that as-synthesized powders were obtained in crystalline FeCr₂O₄ phases moreover, postheating of the powders led to d-space shift and oxidation and formation of (Fe,Cr)₂O₃ solid solution phase regardless of fuel type. Phase transformation of FeCr₂O₄ to (Fe,Cr)₂O₃ solid solution was observed at 500/750°C depending on the dominant phase of as-synthesized particles. Fourier transform infrared analysis illustrated that the band positions of octahedral M–O and tetrahedral M–O bonds were shifted due to Fe cations movement from their position and lattice shrinkage by increasing of post-heating temperature. Moreover, scanning electron micrographs showed that Fe_0.7Cr_1.3O₃ semispherical fine particles were formed from porous spongy FeCr₂O₄ particles due to oxidation and phase transformation during the postheating. Furthermore, chromatic properties of the samples were represented. The color properties of the pigments showed that the formation of brown pigments is provided with the phase transformation from FeCr₂O₄ to (Fe,Cr)₂O₃ at a temperature of up to 750°C. Moreover, increasing the color purity to this temperature is related to the removal of residual carbonaceous matters. The chromatic properties of the glazed tiles colored using the pigments showed that postheating between 250 and 500°C led to more brown appearance.     

Synthesis of (Fe,Cr)2O3 solid solution pigment powders for ink application

Iron chromite pigment was synthesized via solution combustion using iron(III) nitrate nonahydrate and chromium(III) nitrate nonahydrate as starting materials, and glycine, urea, citric acid, and ethylene glycol as fuels. The effect of postheating temperature on the structure, microstructure, and chromatic properties of the synthesized powders was also studied. X-ray diffraction patterns showed that the as-synthesized powders were amorphous to crystalline FeCr₂O₄ phases, depending on fuel type. Moreover, regardless of the fuel type, postheating led to the d-space shift and oxidation and formation of (Fe,Cr)₂O₃ solid solution. Phase transformation of FeCr₂O₄ to (Fe,Cr)₂O₃ solid solution was observed at 500/750°C depending on the dominant phase present in the as-synthesized particles. Fourier transform infrared analysis illustrated a shift in the band position of octahedral M–O and tetrahedral M–O bonds due to the movement of Fe cations and the lattice shrinkage by increasing the postheating temperature. Moreover, scanning electron micrographs showed that Fe_0.7Cr_1.3O₃ semispherical fine particles consisted mainly of porous and spongy FeCr₂O₄ particles due to the oxidation and phase transformation during postheating. According to chromatic measurements, the ink prepared by using the powders synthesized in the presence of glycine and post-heated at 500°C showed reddish-brown color which could be considered a promising candidate for tile decoration application. Furthermore, rheology studies revealed that the prepared ink showed non-Newtonian shear thinning behavior.