Removal of Reactive Red 198 from aqueous solution by combined method multi-walled carbon nanotubes and zero-valent iron:Equilibrium,kinetics, and thermodynamic

Dyes often include toxic,carcinogenic compounds and are harmful to humans' health.Therefore,removal of dyes from textile industry wastewater is essential.The present study aimed to evaluate the efficiency of the combination of zero valent iron(ZVI) powder and multi-walled carbon nanotubes(MWCNTs) in the removal of Reactive Red 198(RR198) dye from aqueous solution.This applied research was performed in a batch system in the laboratory scale.This study investigated the effect of various factors influencing dye removal,including contact time,p H,adsorbent dose,iron powder dose,initial dye concentration,and temperature.The equilibrium adsorption data were analyzed using three common adsorption models:Langmuir,Freundlich and Temkin.Besides,kinetic and thermodynamic parameters were used to establish the adsorption mechanism.The results showed,in pH =3,contact time = 100 min,ZVI dose = 5000 mg·L~(-1),and MWCNTs dose = 600 mg·L~(-1)in 100 mg·L~(-1)dye concentration,the adsorption efficiency increased to 99.16%.Also,adsorption kinetics was best described by the pseudo-second-order model.Equilibrium data fitted well with the Freundlich isotherm(R2= 0.99).The negative values of ΔG0and the positive value of ΔH0(91.76) indicate that the RR198 adsorption process is spontaneous and endothermic.According to the results,the combination of MWCNTs and ZVI was highly efficient in the removal of azo dyes.     

Segmental mobility in the vicinity of Tg in PS/SBR blends: Nanodomain size prediction of the dispersed phase

The blends of polystyrene (PS) and styrene‐butadiene rubber (SBR) are melt‐blended at different ratios to form physical thermoplastic elastomers. This polymeric blend is expected to behave more or less similar to chemically synthesized block copolymers such as styrene‐butadiene block copolymers (SBS). In this study, mechanical and the thermomechanical properties of this blend are investigated and compared to those of SBS copolymer. As far as morphology is considered, the blend shows a two‐phase morphology with an interface, which shows very weak interactions. According to the observed morphology and the domain size of dispersed phase the blends are of good integrity. The mechanical properties of the blends confirm the integrity of the blend and effective interface stress transfer. The tensile and Izod impact properties of the blends shows improvements upon increase in SBR content of the blend. As SBR content augments the elongation at break increases, whereas tensile dissipated energy and impact resistance go through a maximum. Therefore, blend with SBR‐content in 60–75% range can be considered as preferred one. In a wide range of concentration a phase inversion was observed and T_g‐depression was detected also for the SBR phase. This T_g‐depression was correlated to the changes in dynamics of segments (segmental mobility) near the surfaces. Using the proposed relationships between T_g‐depression and the thickness of the thin films, it was tried to calculate domain size of SBR inclusions in PS matrix. A rough correlation between SBR domain sizes in SEM images and calculated thicknesses using T_g‐depression in thin films was found. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Lipase-Mediated Conversion of Protecting Group Silyl Ethers: An Unspecific Side Reaction

Silyl ether protecting groups are important tools in organic synthesis, ensuring selective reactions of hydroxyl functional groups. Enantiospecific formation or cleavage could simultaneously enable the resolution of racemic mixtures and thus significantly increase the efficiency of complex synthetic pathways. Based on reports that lipases, which today are already particularly important tools in chemical synthesis, can catalyze the enantiospecific turnover of trimethylsilanol (TMS)-protected alcohols, the goal of this study was to determine the conditions under which such a catalysis occurs. Through detailed experimental and mechanistic investigation, we demonstrated that although lipases mediate the turnover of TMS-protected alcohols, this occurs independently of the known catalytic triad, as this is unable to stabilize a tetrahedral intermediate. The reaction is essentially non-specific and therefore most likely completely independent of the active site. This rules out lipases as catalysts for the resolution of racemic mixtures of alcohols through protection or deprotection with silyl groups.     

Improved modeling for the reheat phase in thermoforming through an uncertainty treatment of the key parameters

This work focuses on the treatment of parameter uncertainty in the simulation of the sheet reheat phase of the thermoforming process. The approach aims to improve the quality of predictions through more accurate evaluation of the input parameters. First, the modeling approach is employed to perform a sensitivity analysis on the reheat phase. Then, a series of specialized experiments with heat flux and temperature sensors are performed on a thermoforming machine. The key parameters identified through the sensitivity analysis are the subject of these experiments. The natural convective heat transfer coefficients are evaluated by two different approaches. Through treatment of the uncertainty associated with the input parameters, the prediction of sheet reheat phase is significantly improved.     

Volumetric properties of polymer blends from Tao–Mason equation of state

The present study is an improvement of previous work (Yousefi and Karimi, Ionics 18:135–142, 17) concern to the assessment of the ability of the Tao–Mason equation of state to predict pressure–volume–temperature (PVT) of melting polymers. The present paper, focus on the modeling of volumetric properties of polymer blends based on melting temperature (T _m) and melting point density (ρ _m), as scaling constants. The calculation of second Virial coefficients (B ₂), effective van der Waals co-volume (b) and correction factor (α) are required for judgment about applicability of this model. The new correlations were used to predict the PVT behavior of polymer blends containing poly(propylene glycol) + poly(ethylene glycol) (PEG-200), poly(ethylene glycol) methyl ether(PEGME-350) + PEG-200, PEGME-350 + PEG-600, poly(2,6-dimethyl-1,4-phenylene oxide) + poly styrene(PS), and PS + poly(vinylmethylether) in different temperatures, pressures, and mole fractions. A collection of 5,397 data points has been examined for the aforementioned polymers in the temperature in the range of 298.15–605.05 K and pressures up to 200 MPa. The average absolute deviation between the calculated and experimental densities is of the order of 0.78 %.     

运用人工神经网络关联二元混合物中气液相平衡

In this paper, a back propagation artificial neural network （BP-ANN） model is presented for the simultaneous estimation of vapour liquid equilibria （VLE） of four binary systems viz chlorodifluoromethan-carbondioxide, trifluoromethan-carbondioxide, carbondisulfied-trifluoromethan and carbondisulfied-chlorodifluoromethan. VLE data of the systems were taken from the literature for wide ranges of temperature （222.04-343.23K） and pressure （0.105 to 7.46MPa）. BP-ANN trained by the Levenberg-Marquardt algorithm in the MATLAB neural network toolbox was used for building and optimizing the model. It is shown that the established model could estimate the VLE with satisfactory precision and accuracy for the four systems with the root mean square error in the range of 0.054-0.119. Predictions using BP-ANN were compared with the conventional Redlich-Kwang-Soave （RKS） equation of state, suggesting that BP-ANN has better ability in estimation as compared with the RKS equation （the root mean square error in the range of 0.115-0.1546）.     

Modeling of complex parison formation in extrusion blow molding: Effect of medium to large die heads and fuel tank geometry

This work presents the effect of die geometry and die gap opening on the extrudate swell phenomenon, in complex parison formation using the vertical wall distribution system (VWDS) and partial wall distribution system (PWDS). The BlowParison^© software from IMI is used to predict the parison formation for a combined VWDS/PWDS system, accounting for swell, sag, and nonisothermal effects. This software couples a fluid mechanics approach to represent the die flow, with a solid mechanics approach to represent the parison behavior outside the die, and a mathematical swell model to account for the pronounced elongational and shear stresses at high Weissenberg numbers. The emphasis is placed on experimental validation of the predicted parison dimensions using four diverging die geometries and different sets of VWDS/PWDS profiles. The experimental and predicted weight profiles for a dissected fuel tank are also presented. Both experimental and simulation results suggest a strong dependence of extrudate swell to the die geometry in the die land zone. The results also demonstrate the validity of the numerical predictions for part design purposes given the multitude of experimental validations presented in this work. POLYM. ENG. SCI., 2009. Published by the Society of Plastics Engineers     

Exergoeconomic optimization of a 1000 MW light water reactor power generation system

A typical 1000 MW pressurized water reactor nuclear power plant is considered for optimization. The thermodynamic modeling is performed based on the energy and exergy analysis, while an economic model is developed according to the total revenue requirement method. The objective function based on the exergoeconomic analysis is obtained. The exergoeconomic optimization process with 10 decision variables is performed using a hybrid stochastic/deterministic search algorithm namely as genetic algorithm. The results that are obtained using optimization process are compared with the base case system and the discussion is presented. Copyright © 2009 John Wiley & Sons, Ltd.     

Sparsity aware consistent and high precision variable selection

Variable selection is fundamental while dealing with sparse signals that contain only a few number of nonzero elements. This is the case in many signal processing areas extending from high-dimensional statistical modeling to sparse signal estimation. This paper explores a new and efficient approach to model a system with underlying sparse parameters. The idea is to get the noisy observations and estimate the minimum number of underlying parameters with acceptable estimation accuracy. The main challenge is due to the non-convex optimization problem to be solved. The reconstruction stage deals with some suitable objective function in order to estimate the original sparse signal by performing variable selection procedure. This paper introduces a suitable objective function in order to simultaneously recover the true support of the underlying sparse signal while still achieving an acceptable estimation error. It is shown that the proposed method performs the best variable selection compared to the other algorithms, while approaching the lowest least mean squared error in almost all the cases.     

Thermorheological analysis of blend of high- and low-density polyethylenes

The effect of temperature on dynamic viscoelastic properties of high density polyethylene and low density polyethylene blends with different weight fractions was investigated in the molten state by means of small amplitude oscillatory shear rheometry. It was found that the blends at various compositions do follow well the time-temperature superposition principle and show thermorheologically simple behavior. This behavior is attributed to both similarity in glass-transition temperature of the constituents and phase stability in the blends at various temperatures. The latter was suggested via coincidence of G′-G′′ plots and δ-G^* plots at different temperatures. That was furthur supported using G′ vs. temperature curves which showed no breakdown in the linear relation. Horizontal shift factors, which reflect temperature dependence of relaxation times, obtained to draw G′ and G′′ master curves, followed an Arrhenius equation with temperature. Analysis of terminal relaxation times of components revealed that terminal dynamics of components is similar at limited particular temperatures but different at others. Moreover, depending to test temperature, dynamics of a given component in the blend may be faster or slower than in the pure state.