Investigation of spatial variability of SPT data in Mashhad City (NE Iran) using a geostatistical approach

Bulletin of Engineering Geology and the Environment - Precisely investigating subsurface conditions is a major concern for both geotechnical and geological engineers. In recent years, growing...     

Mathematical modelling of CO2 facilitated transport through liquid membranes containing amines as carrier

An approximate analytical solution for the facilitated transport of carbon dioxide across a liquid membrane containing aqueous primary and secondary amine solutions has been developed in which the reversible reaction A(CO₂) + 2B(amine) AB(carbamate) + BH(protonated amine) occurs inside the liquid membranes. The current approximate analytical solution predicts the facilitated factor of CO₂ through the membrane and is based on the dimensionless, nonlinear diffusion‐reaction transport problem. The approximate analytical solution predicts the facilitation factors for the range from the moderate reaction rate to the equilibrium chemical reaction regime, allowing unequal diffusivities of complexes and carrier and cases of zero and nonzero permeate side solute concentrations. In the present mathematical model, a constant free carrier concentration is assumed throughout the membrane phase. In comparison with the numerically calculated results, the results obtained were found to be in well agreement.     

Dibenzothiophene removal from model fuel using an acid treated activated carbon

Sulfur containing compounds are one of the most concerning pollutants in fossil fuels. The increasing rate of fuel consumption around the globe reveals the necessity of further purification of the fuels. In this study, application of adsorption process in removing dibenzothiophene from a model fuel is investigated. A granular activated carbon is treated with aqueous solution of nitric acid and implemented as the sorbent. Treatment of the activated carbon with nitric acid resulted in increasing the adsorption capacity of the activated carbon. Freundlich and TÓth isotherms are capable of sufficiently describing the equilibrium data. Investigation of the kinetics of the process is carried out using the homogeneous surface diffusion model. Internal and external mass transfer coefficients are 9.3917 × 10^-6?m²/min and 1.4153 × 10^-2?m/min for the virgin activated carbon (VAC) and 4.8738 × 10^-6?m²/min and 5.2529 × 10^-2?m/min for acid treated activated carbon (AAC), respectively.     

An Enhanced LVRT Scheme for DFIG-based WECSs under Both Balanced and Unbalanced Grid Voltage Sags

Due to the latest grid codes, wind energy conversion systems (WECSs) are required to remain connected to grid under grid voltage sags and supply reactive power into the grid. So, this paper proposes an enhanced scheme to improve low-voltage ride through (LVRT) capability of doubly fed induction generator (DFIG)-based WECSs under both balanced and unbalanced grid voltage sags. The proposed scheme is composed of active and passive LVRT compensators. The active compensator is performed by controlling the rotor- and grid-side converters of the DFIG to decrease the stator flux oscillations and inject reactive power into the grid. The passive compensator is based on a three-phase stator damping resistor (SDR) located in series with the stator windings. The proposed scheme decreases the negative effects of grid voltage sags in the DFIG system including the rotor over-currents, electromagnetic torque oscillations, and DC-link over-voltage and also injects reactive power into grid to support the grid voltage. So, the LVRT capability of DFIG is enhanced and new grid code requirements are addressed. Simulation results on a 1.5-MW DFIG-based WECS using MATLAB/Simulink demonstrate the effectiveness of the proposed LVRT scheme under both balanced and unbalanced grid voltage sags.     

Optimization of encapsulation of maltogenic amylase into a mixture of maltodextrin and beeswax and its application in gluten-free bread

In this work maltogenic amylase (MAase) was encapsulated into the mixture of maltodexrin and beeswax (BW) for retarding staling of gluten-free bread. The effects of maltogenic amylase (MAase) concentration (8.2, 45, and 82 mg/ml), maltodextrin with dextrose equivalent (DE) 4–7 (MD) (1, 2.5, and 4%) and, BW (1, 2.5, and 4%) on the encapsulation efficiency (EE) of encapsulated enzyme were optimized using RSM. The optimized formulation was MAase with 8.2 mg/ml, MD 4% and BW 1%, leading to the highest EE (79.35%), thus chosen for subsequent experiments. The prepared particles were 1,190.50 nm with PDI of 0.336 and zeta potential of −8.30 mV. Surface morphologies of produced particles were almost spherical with layered appearance. Batter with this formulation led to higher cross over point in frequency sweep than free enzyme-loaded batter. Lower weight loss, higher volume index, darker crust color, whiter crumb color, more aerated microstructure, less hardness in crumb, and higher sensorial acceptability on the first day and during storage period in the breads containing encapsulated MAase was observed.     

Kinetics and Mechanism of the Simultaneous Carbothermic Reduction of FeO and MnO from High-Carbon Ferromanganese Slag

The carbothermic reduction of 38.7 pct MnO-12.1 pct CaO-5.4 pct MgO-9.3 pct Al₂O₃-24.1 pct SiO₂-10.4 pct FeO slag in Ar at 1600 °C was studied using the sessile drop wettability technique. Pure graphite, coke, and charcoal were used as the carbon material substrates. The reduction rates were evaluated by sampling at different reduction times and by analyzing the chemical compositions of the reduced slag and the produced metal. The carbothermic FeO reduction from slag is initially fast followed by a much slower reduction rate. However, the rate of the MnO reduction is slow in the fast FeO reduction stage, and it starts to increase significantly during the slow FeO reduction stage. The kinetics of FeO and MnO reduction are affected by the type of carbonaceous materials. Moreover, the rate of the carbon dissolution/transfer into the produced metal phase and the amount of the transferred manganese to the metal phase depend on the type of carbon. Based on the experimental observations and the thermodynamic calculations, a mechanism for MnO reduction was proposed. According to this mechanism, MnO is mainly reduced through a metallothermic reduction by Fe and the rate of MnO reduction is controlled by the rate of the consumption of FeO from the slag, which takes place simultaneously. In contrast, the rate of FeO reduction in the fast initial reduction stage is controlled by the rate of the carbon dissolution/transfer into the metal phase. However, at the second slow FeO reduction stage, it is reduced mainly by the solid carbon.     

Piecewise fractional Legendre functions for nonlinear fractional optimal control problems with ABC fractional derivative and non-smooth solutions

In this study, to solve fractional problems with non-smooth solutions (which include some terms in the form of piecewise or fractional powers), a new category of basis functions called the orthonormal piecewise fractional Legendre functions is introduced. The upper bound of the error of the series expansion of these functions is obtained. Two explicit formulas for computing the Riemann–Liouville and Atangana–Baleanu fractional integrals of these functions are derived. A direct method based on these functions and their fractional integral is proposed to solve a family of optimal control problems involving the ABC fractional differentiation whose solutions are non-smooth in the above expressed forms. By the proposed technique, solving the original fractional problem turns into solving an equivalent system of algebraic equations. The established method accuracy is studied by solving some examples.     

Aqueous dye-sensitized solar cell based on new ruthenium diphenyl carbazide complexes

The major challenge of the operation of every solar cell based on dye including water splitting solar cell (WSSC) and dye sensitized solar cell (DSSC) is the using organic solvent medium which causes to decompose the solar cell structure, resulting environmental impact. Here, we synthesized and characterized two new ruthenium complexes with nitrogen and oxygen donor ligands for DSSC application which show good stability on TiO₂ surface in water solvent. Interestingly, the DSSC based on [Ru(dcbpy)₂(DPC)]Cl, where dcbpy = 4,4-dicarboxilic acid 2,2-bipyridin and DPC = diphenylcarbazide, was shown better efficiency in water than methanol dye loading as well as N3 as a benchmark sensitizer in the same condition. The DPC-based exhibited open circuit voltage (V_oc) of 0.63 V, short-circuit current density (J_sc) of 2.5 mA/cm² and fill factor (FF) of 70%, resulting an overall power efficiency of 1.12%. The incident-photon-to-current conversion efficiency (IPCE) value is also reached to 45% for [Ru(dcbpy)₂(DPC)]Cl in the same condition It is proposed that the ruthenium complex containing nitrogen and oxygen donor ligands is more stability on TiO₂ and prevent the decomposition of TiO₂ porous under water solvent condition.     

Fuzzy calibration of a magnetic compass for vehicular applications

In a strapdown compass on a vehicle, three-axis magnetometers measure the Earth's magnetic field vector along the body axes of the vehicle to determine its heading angle. Owing to the local magnetic effects, the measurements frequently deviate from the geomagnetic field vector coordinated in the body frame. Therefore, online calibration of the compass should be considered to satisfy the requirements of the vehicle navigation system. In this paper, a new intelligent method is developed to implement online calibration of the compass system. First, a regression model is proposed to increase the convergence probability of the calibration process using the attitude angles in the measurement equations. Second, based on the knowledge of expert engineers, a Mamdani type fuzzy batch least-square (FBLS) algorithm is designed to estimate the calibration bias and scaling parameters. Generalized likelihood ratio (GLR) and the changes of estimated parameters are considered as the main information of the fuzzy system in which the length of data batch and the associated weighting factor are updated continuously. The results of simulations and experiments reveal the superiority of the proposed approach to the non-fuzzy methods.     

Synthesis of Zn-SBA-15 as a new pigment for spacecraft white thermal control coatings

Thermal control coatings (TCCs) help to maintain the thermal equilibrium of spacecraft at a level acceptable for vital components, usually around 20°C. This is done by either minimizing the solar absorbance or maximizing the thermal emittance. In the present study, with the aim of introducing new TCCs with enhanced optical properties, two TCCs were prepared by incorporating presynthesized pigments including SBA-15 (mesoporous material) and Zn-SBA-15 into potassium silicate binder. After application and drying, the TCC containing SBA-15 showed very low hiding power, so optical tests for this TCC were not done. The results of solar absorptance measurements revealed that the TCC containing Zn-SBA-15 was a proper reflector in the ultraviolet (UV) radiation range, making it much less susceptible to solar radiation in comparison with conventional TCCs. Also, thermal emittance tests demonstrated that the surface of this TCC had greater ability to emit heat. Furthermore, lower pigment-to-binder ratio and dry film thickness were attainable with this TCC, leading to weight reduction, improvement of mechanical properties, and lower porosity.