Effect of aligned carbon nanotubes on electrical conductivity behaviour in polycarbonate matrix

This article reports effects of alignment of embedded carbon nanotubes in a polycarbonate polymer matrix under magnetic, direct and alternating current electric fields on the electrical properties of the resulting nanocomposites. Composites consisting of different quantities of carbon nanotubes in a polycarbonate matrix have been prepared using a solution casting technique. The effects of field strength and nanotube concentration on the resulted network structure and conductivity of the composites were studied by in situ optical microscopy, transmission electron microscopy and four-point probe technique. The results showed that the composites prepared in the presence of field had better conductivity than those of as-prepared composites. It was also concluded that the application of alternating current electric field and magnetic field in this system led to the formation of relatively continuing networks while direct current electric field only prevented agglomeration of the carbon nanotubes in the polycarbonate matrix and created relatively uniform distribution of nanotubes in the matrix.     

High velocity impact of metal sphere on thin metallic plate using smooth particle hydrodynamics (SPH) method

The modeling of high velocity impact is an important topic in impact engineering. Due to various constraints, experimental data are extremely limited. Therefore, detailed numerical simulation can be considered as a desirable alternative. However, the physical processes involved in the impact are very sophisticated; hence a practical and complete reproduction of the phenomena involves complicated numerical models. In this paper, we present a smoothed particle hydrodynamics (SPH) method to model two-dimensional impact of metal sphere on thin metallic plate. The simulations are applied to different materials (Aluminum, Lead and Steel); however the target and projectile are formed of similar metals. A wide range of velocities (300, 1000, 2000, and 3100 m/s) are considered in this study. The goal is to study the most sensitive input parameters (impact velocity and plate thickness) on the longitudinal extension of the projectile, penetration depth and damage crater.     

Structural features of bionanocomposite derived from novel designed poly(ester-imide) based on natural amino acids with hydroxyl segments tailored for better dispersion of TiO 2 nanofiller

Deliberately inorganic nanoparticles (NP)s in polymer matrices significantly affect their characteristics and therefore their applications, but key factor to achieve the expected efficiency is well dispersion of the NPs in polymer matrix. The work presented here deals with the polymerization of amino acid-based monomer to synthesize optically active poly(ester-imide) (PEI) with hydroxyl terminated groups, using tosyl chloride/pyridine/N,N-dimethylformamide system as a condensing agent. The synthesized polymer was used for the preparation of bionanocomposite (BNC) containing modified titanium dioxide (TiO₂) NPs using ultrasonic irradiation. With the aim of γ-amidopropyl-triethoxylsilicane as a coupling agent, the surface of nanoscale TiO₂ was modified to decrease aggregation of the NPs in polymer matrix. The obtained PEI/TiO₂ BNCs were characterized with fourier transfer infrared (FT–IR), thermogravimetric analysis, field emission scanning electron microscopy (FE–SEM), X-ray diffraction and transmission electron microscopy (TEM) techniques. Morphology study of resulting PEI/TiO₂ BNCs by FE–SEM and TEM analyses demonstrated that the hydroxyl-terminated polymer chains reduced aggregation of the NPs and thus lead to better dispersion of the NPs in the polymer matrix.     

Synthesis and optical characterization of copper nanoparticles prepared by laser ablation

The remarkable size-tunable properties of nanoparticles (NPs) make them a hot research topic with applications in a wide range of fields. Hence, copper (Cu) colloidal NPs were prepared using laser ablation (Nd:YAG, 1064 nm, 7 ns, 10 Hz, 6000 pulses) of a copper metal plate at different laser fluences (LFs) in the range of 1–2.5 J cm^?2 in ethylene glycol (EG), at room temperature. Analysis of NPs was carried using different independent techniques such as ultraviolet–visible (UV–vis) spectroscopy; transmission electron microscopy (TEM) and Fourier transform infrared (FTIR) spectroscopy. TEM analysis showed that the NPs were spherical with a bimodal distribution and an average particle size of 5 and 16 nm influence of 1.2 J cms^?2, and 9 and 22 nm at 2 J cm^?2. The UV–vis spectra of colloidal NPs revealed the maximum absorbance at around 584 nm, indicating the formation of Cu NPs, which supported using FTIR spectra. Furthermore, the absorption spectra confirmed the metallic nature of Cu NPs. FTIR spectroscopy was utilized to verify information about the NPs surface state and chemical bonds constructed in the atom groups apparent on their surface.     

An investigation of reaction furnace temperatures and sulfur recovery

In a modern day sulfur recovery unit (SRU), hydrogen sulfide (H₂S) is converted to elemental sulfur using a modified Claus unit. A process simulator called TSWEET has been used to consider the Claus process. The effect of the H₂S concentration, the H₂S/CO₂ ratio, the input air flow rate, the acid gas flow of the acid gas (AG) splitter and the temperature of the acid gas feed at three different oxygen concentrations (in the air input) on the main burner temperature have been studied. Also the effects of the tail gas ratio and the catalytic bed type on the sulfur recovery were studied. The bed temperatures were optimized in order to enhance the sulfur recovery for a given acid gas feed and air input. Initially when the fraction of AG splitter flow to the main burner was increased, the temperature of the main burner increased to a maximum but then decreased sharply when the flow fraction was further increased; this was true for all three concentrations of oxygen. However, if three other parameters (the concentration of H₂S, the ratio H₂S/CO₂ and the flow rate of air) were increased, the temperature of the main burner increased monotonically. This increase had different slopes depending on the oxygen concentration in the input air. But, by increasing the temperature of the acid gas feed, the temperature of the main burner decreased. In general, the concentration of oxygen in the input air into the Claus unit had little effect on the temperature of the main burner (This is true for all parameters). The optimal catalytic bed temperature, tail gas ratio and type of catalytic bed were also determined and these conditions are a minimum temperature of 300°C, a ratio of 2.0 and a hydrolysing Claus bed.     

Methanol to propylene: the effect of iridium and iron incorporation on the HZSM-5 catalyst

The effect of iridium and iron impregnation of HZSM-5 zeolite on the methanol to propylene reaction (MTP) was investigated. The selectivities of propylene and other hydrocarbons, and the conversion of methanol were compared by performing MTP in a small pilot plant. The results indicate that HZSM-5 zeolite modified by iron and iridium increased propylene selectivity by 6.3% and 8%, respectively. The selectivity of propylene was higher for Ir/H-ZSM-5 than for Fe/H-ZSM-5, where Fe/H-ZSM-5 was more stable than Ir/H-ZSM-5. Analytic techniques, including X-ray diffraction, BET surface area, temperature-programmed desorption of ammonia, and inductively coupled plasma atomic emission spectroscopy, were used to characterize the modified zeolites as well as the parent zeolites.     

Finite element simulation for elastic dislocation of the North-Tehran fault: The effects of geologic layering and slip distribution for the segment located in Karaj

The present study uses the finite element method for simulating the crustal deformation due to the dislocation of a segment of the North-Tehran fault located in the Karaj metropolis region. In this regard, a geological map of Karaj that includes the fault segment is utilized in order to create the geometry of finite element model. First, finite element analysis of homogeneous counterpart of the fault’s domain with two different sections was performed, and the results were compared to those of Okada’s analytical solutions. The fault was modeled with the existing heterogeneity of the domain having been considered. The influences of both uniform and non-uniform slip distributions were investigated. Furthermore, three levels of simplification for geometric creation of geological layers’ boundaries were defined in order to evaluate the effects of the geometric complexity of the geological layering on the displacement responses obtained with the finite element simulations. In addition to the assessment of slip distribution, layering complexity and heterogeneity, the results demonstrate both the capability and usefulness of the proposed models in the dislocation analysis for the Karaj segment of North-Tehran fault.     

Predicting lateral displacement caused by seismic liquefaction and performing parametric sensitivity analysis: Considering cumulative absolute velocity and fine content

Lateral displacement due to liquefaction (D_H) is the most destructive effect of earthquakes in saturated loose or semi-loose sandy soil. Among all earthquake parameters, the standardized cumulative absolute velocity (CAV₅) exhibits the largest correlation with increasing pore water pressure and liquefaction. Furthermore, the complex effect of fine content (FC) at different values has been studied and demonstrated. Nevertheless, these two contexts have not been entered into empirical and semi-empirical models to predict D_H. This study bridges this gap by adding CAV₅ to the data set and developing two artificial neural network (ANN) models. The first model is based on the entire range of the parameters, whereas the second model is based on the samples with FC values that are less than the 28% critical value. The results demonstrate the higher accuracy of the second model that is developed even with less data. Additionally, according to the uncertainties in the geotechnical and earthquake parameters, sensitivity analysis was performed via Monte Carlo simulation (MCS) using the second developed ANN model that exhibited higher accuracy. The results demonstrated the significant influence of the uncertainties of earthquake parameters on predicting D_H.     

Numerical investigation of the velocity field and separation efficiency of deoiling hydrocyclones

Three-dimensional simulation of a multiphase flow is performed using the EulerianEulerian finite volume method in order to evaluate the separation efficiency and velocity field of deoiling hydrocyclones.The solution is developed using a mass conservation-based algorithm(MCBA) with collocated grid arrangement.The mixture approach of the Reynolds stress model is also employed in order to capture features of turbulent multiphase swirling flow.The velocity field and separation efficiency of two different configurations of deoiling hydrocyclones are compared with available experimental data.The comparison shows that the separation efficiency can be predicted with high accuracy using computational fluid dynamics.The velocity fields are also in good agreement with available experimental velocity measurements.Special attention is drawn to swirl intensity in deoiling hydrocyclones and it is shown that the differences in velocity and volume fraction fields of different configurations are related to swirl distribution.