Selection of regression models for predicting strength and deformability properties of rocks using GA

Recently, many regression models have been presented for prediction of mechanical parameters of rocks regarding to rock index properties. Although statistical analysis is a common method for developing regression models, but still selection of suitable transformation of the independent variables in a regression model is difficult. In this paper, a genetic algorithm (GA) has been employed as a heuristic search method for selection of best transformation of the independent variables (some index properties of rocks) in regression models for prediction of uniaxial compressive strength (UCS) and modulus of elasticity (E). Firstly, multiple linear regression (MLR) analysis was performed on a data set to establish predictive models. Then, two GA models were developed in which root mean squared error (RMSE) was defined as fitness function. Results have shown that GA models are more precise than MLR models and are able to explain the relation between the intrinsic strength/elasticity properties and index properties of rocks by simple formulation and accepted accuracy.     

An Efficient Hybrid Approach to Solve Bi-objective Multi-area Dynamic Economic Emission Dispatch Problem

Abstract

Single period economic dispatch cannot handle the intertemporal constraints in multi-period environment. To cope with this issue, the extension of economic dispatch over multiple time intervals (i.e., dynamic economic dispatch) has been introduced that considers the intertemporal constraints between different time intervals. Another issue is determining the most economical generation dispatch that could supply the area demand without violating the tie-line capacity, which cannot be solved by conventional economic dispatch problems. However, this study shows that the most economic schedule of power generation cannot satisfy echo-system expectation; therefore, making a compromise between fuel cost and environmental issues, a hot-button subject in industrialized nations, seems to be crucial. To reach the goals a bi-objective multi-area dynamic economic dispatch approach, which can handle intertemporal and multi-area constraints concurrently, is proposed to assist power system operators more and more. Finally, a hybrid algorithm, namely gray wolf optimizer-particle swarm optimization is introduced to solve the proposed problem and also a set of benchmark problems. By implementing the proposed approach on two small (10-unit, three areas) and large (40-unit, four areas) scale test systems, about 3.1% and 3.3% improvement in generation cost is obtained, respectively compare to the best reported results in the literature.     

Sensitivity Investigation of SW-B80N80 Nanotube to Polychlorinated Biphenyl-153 (PCB-153): DFT Methods

Polychlorinated biphenyls (PCBs) is one of the most persistent organic pollutants that exist in the atmosphere and can be concentrated in lithosphere and hydrosphere. Because of low biodegradability and lipophilicity, PCBs accumulate in fatty tissues and through oxidative stress could lead to cancers and central nervous system disorders. Currently, degradation of these synthetic pollutants is one of the environmental issues. The aim of this study is to provide a sensor for detection of PCB-153 (PCB-153). Nano boron nitride compounds (B_nN_m) are magic materials with high stability that can be used as a sensor for detection of chlorinated aromatic compounds. In this study, sensitivity of B₈₀N₈₀ as a form of single-walled boron nitride nanotubes (SW-B₈₀N₈₀ nanotube (8,8)) to PCB-153 has been investigated. The PCB-153 is closed to the SW-B₈₀N₈₀ nanotube and electron exchanges between them have been evaluated using density functional calculations by B3LYP/6–31G^* method. The calculation of the electronic properties has shown that SW-B₈₀N₈₀ nanotube is very sensitive to the presence of PCB-153 molecules. The HOMO/LUMO and gap energy (E_g) changes were considerable. Gap energy decreased from 4.214 eV to 2.022 eV during the formation of complex PCB-153-SW-B₈₀N₈₀ nanotube that leads to conversion of PCB-153 into the other products. According to thermodynamic parameter calculation through the IR-DFT method, it is expected that SW-B₈₀N₈₀ nanotube will be a suitable candidate in the elimination of PCB-153, as well as a gas sensor.     

Application of ZnO and TiO<Subscript>2</Subscript> nanoparticles coated onto montmorillonite in the presence of H<Subscript>2</Subscript>O<Subscript>2</Subscript> for efficient removal of cephalexin from aqueous solutions

This study considers the feasibility of uptake of cephalexin, an emerging contaminant, from aqueous solutions by using green local montmorillonite (GLM), montmorillonite coated with ZnO (ZnO/GLM) and montmorillonite coated with TiO₂ (TiO₂/GLM) in the presence of H₂O₂. Batch adsorption experiments were carried out as a function of pH, initial concentration of the cephalexin, adsorbent dosage, contact time, and temperature. Finally, the adsorbents were characterized by XRD, SEM and FTIR analyses. XRD patterns showed dramatic changes in the adsorbents after loading with the nanoparticles, confirming successful placing of the nanoparticles onto GLM. The GLM mineral surface after nanoparticle loading appears to be fully exposed and more porous with irregular shapes in particles diameters of 1-50 microns. FTIR analyses also confirmed dramatic changes in surface functional groups after modification with these nanoparticles. The results showed that the removal efficiency of cephalexin was better at lower pH values. Totally, the removal efficiency increased with increase in adsorbent dosage and contact time and decreased with concentration and temperature increase. The thermodynamics values of ΔG ^o and ΔH ^o revealed that the adsorption process was spontaneous and exothermic. In isotherm study, the maximum adsorption capacities (qm) were obtained to be 7.82, 17.09 and 49.26 mg/g for GLM, ZnO/GLM and TiO₂/GLM, respectively. Temkin constant (B _T ) showed that adsorption of cephalexin from solution was exothermic for all three adsorbents.     

The effect of substrate temperature on microstructural evolution and hardenability of tungsten carbide coating in hot filament chemical vapor deposition

Effect of substrate temperature on microstructural evolution and hardenability of tungsten carbide coating produced by hot filament chemical vapor deposition (HFCVD) process was studied. Annealed sheets of 316L stainless steels were used as the substrate. HFCVD technique, with substrate temperatures of 400 and 500°C, was used to deposit tungsten carbide coating on these sheets. Field Emission Scanning Electron Microscope (FE‐SEM) was used to study the evolution of microstructure. X‐Ray Diffraction spectroscopy was used to analyze the phases formed and Raman spectroscopy was employed to differentiate molecular composition of the coatings. The amount of the porosity of the coatings was measured and Vickers hardness measurement was used for hardness assessment. Results show that the tungsten carbide coatings have a honeycomb structure and increasing the temperature of the substrate increases the amount of porosity of the coating. XRD results showed that 3 different crystalline structures containing W, WC, and W₂C were formed in the coating deposited on the 316L stainless steel. Increasing the temperature of the deposition has increased the intensity of the peaks in the XRD results. Raman spectroscopy results indicated the presence of a carbon in the tungsten carbide coatings. Finally, microhardness of the tungsten carbide coating increases with increasing the temperature of the substrate.     

Feed-reflector design for large adaptive reflector antenna (LAR)

A novel feed-reflector system for large Cassegrain antennas of radio astronomy and deep-space communication applications is investigated. This feed-reflector is used to illuminate a hyperboloid subreflector with a 5-10 m diameter located 500 m above the ground. Because the subreflector is located in the near field of the feed-reflector antenna, a theory based on the near field focusing properties of paraboloid reflectors is established. The focusing at near distance is formed by moving the feed horn away from the focal point of the feed-reflector. In this theory, the properties of axial defocused paraboloid reflectors at near distance are investigated in more detail. By using equivalence path law, the subreflector shape is obtained. It is found that the hyperbola can approximate the subreflector well. A detailed ray tracing is performed on the entire system which reveals that the feed system uses some part of the subreflector three times. The gain, side lobe level, cross polarization, and aperture distribution are calculated for different feed horn locations and taper at the edge of the feed-reflector and also for different sizes and eccentricities of the subreflector. Peak efficiency in excess of 74.8% and side lobe level around -20 dB are obtained for an unshaped system. The performance of the system over the operating band (1-22 GHz) is also studied and shown that the lower-frequency limit is dependent on subreflector and feed-reflector sizes     

Cold plasma as a tool for the elimination of food contaminants: Recent advances and future trends

Abstract

Food contaminants are challenging the food industry due to the inefficiency of conventional decontamination techniques. Cold plasma as an emerging technique for the degradation of food contaminants attracted notable attention. The current study overviews the plasma-induced degradation of food contaminants, discusses the mechanisms involved, points its benefits and drawbacks out, highlights the research needed in this area, and explores future trends. According to the literature, cold plasma efficiently degraded many common pesticides (e.g. parathion, paraoxon, omethoate, dichlorvos, malathion, azoxystrobin, cyprodinil, fludioxonil, cypermethrin, and chlorpyrifos) and food allergens (e.g. tropomyosin, b-conglycinin, glycinin, trypsin inhibitor, and Kunitztype trypsin inhibitor). These degradations occurred primarily due to the presence of reactive oxygen species (ROS) and reactive nitrogen species (RNS) in the plasma that attack the chemical bonds of food contaminants. The type of pesticide degrades are highly dependent on the concentrations of plasma-generated ROS and RNS. Research showed that several parameters, such as plasma generation device, plasma exposure time, plasma power, and the carrier gas composition, influence the type and concentration of reactive species (e.g. ROS and RNS) and the overall efficiency of cold plasma degradation for a specific pesticide or allergen.

• Highlights

• Cold plasma can be used for degradation of many types of pesticides and allergens.

• Plasma-generated reactive species and UV can interact with pesticides and allergens.

• The scaled up removal of pesticides and allergens by plasma can be challenging.

     

Comparison of Various Estimation and Simulation Methods for Orebody Grade Variations Modeling

Journal of Mining Science - Estimation of iron ore grade distribution has been done using geostatistics and Artificial Neural Network (ANN) models for an iron ore body in Central Iran. The methods...     

Deposition of CuWO4 nanoparticles over g-C3N4/Fe3O4 nanocomposite: Novel magnetic photocatalysts with drastically enhanced performance under visible-light

Novel g-C₃N₄/Fe₃O₄/CuWO₄ nanocomposites, as magnetic visible-light-driven photocatalysts, fabricated through a simple refluxing-calcination process. The synthesized photocatalysts were characterized by a series of techniques including XRD, EDX, SEM, TEM, HRTEM, FT-IR, TGA, BET, UV–vis DRS, PL, and VSM. The results showed that heterojunctions are formed between g-C₃N₄, Fe₃O₄, and CuWO₄, which favor suppression of the photogenerated electron/hole pairs from recombination. The resultant g-C₃N₄/Fe₃O₄/CuWO₄ (30%) sample exhibited superior photocatalytic performance. The degradation rate constants on the g-C₃N₄/Fe₃O₄/CuWO₄ (30%) nanocomposite were almost 10.5, 17, 12.5, and 42.5 times higher than those of the pristine g-C₃N₄ for degradations of RhB, MB, MO, and fuchsine, respectively. Moreover, the photocatalyst was magnetically separated and recycled with negligible loss in the activity, which is important for the sustainable photocatalytic processes. Thus, the ternary nanocomposite could have potential applications in different photocatalytic processes.