Hierarchical 3D starfish-like Ni3S4–NiS on reduced graphene oxide for high-performance supercapacitors

In this research, Ni₃S₄–NiS with starfish morphology was synthesized with a simple hydrothermal method and then hybridized with reduced graphene oxide (rGO) as a material for high-performance supercapacitors. The crystal structure and morphology of the as-prepared materials were studied by X-ray diffraction spectroscopy and electron microscopy. Uniform distribution of Ni₃S₄–NiS on rGO was observed from electron microscopy images. The results showed that Ni₃S₄–NiS/rGO with a specific capacitance of 1578 Fg^-1 and discharge time of 603 s at the current density of 0.5 Ag^-1 has more capacity and stability relative to Ni₃S₄–NiS. The cyclic stability after 5000 cycles showed that the Ni₃S₄–NiS/rGO electrode is stable, and 91% of its corresponding initial capacitance retained at the end of 5000 cycles. The good results in capacitance and stability of this electrode can be regarded as an improvement for the development of highly efficient and economic supercapacitors for portable electronic devices.     

PHENOLIC WASTEWATER TREATMENT BY SUPPORTED LIQUID MEMBRANE USING DIFFERENT COOKING OILS AS LIQUID MEMBRANE

Transport of phenol through a flat sheet supported liquid membrane (SLM) containing cooking oil as liquid membrane (LM) was investigated. Factors affecting permeation of phenol such as membrane phase, support material, feed phase pH, stripping phase concentration, stirring speed, and initial concentration of phenol were studied. It was found that these parameters strongly influence phenol removal efficiency; PTFE membrane as support material, grape seed oil as liquid membrane, feed pH of 2.0, initial phenol concentration of 100 mg/L, stirring speed of 350 rpm, and 0.2 M sodium hydroxide as effective stripping agent were found as the best conditions for greater phenol transport. Under these conditions, permeability was found to be 7.46 × 10^?6 m/s. After 10.5 h, phenol was completely removed from the feed phase to strip phase. According to stability experiments, it was observed that the SLM is stable after 22 h. Thus, the use of cheap, nontoxic, and naturally oil as a novel and green membrane for recovery of phenol from wastewater was demonstrated.     

Modelling-based Optimisation of the Direct Synthesis of Dimethyl Ether from Syngas in a Commercial Slurry Reactor

In the present study, we developed a multi-component one-dimensional mathematical model for simulation and optimisation of a commercial catalytic slurry reactor for the direct synthesis of dimethyl ether (DME) from syngas and CO₂, operating in a churn-turbulent regime. DME productivity and CO conversion were optimised by tuning operating conditions, such as superficial gas velocity, catalyst concentration, catalyst mass over molar gas flow rate (W/F), syngas composition, pressure and temperature. Reactor modelling was accomplished utilising mass balance, global kinetic models and heterogeneous hydrodynamics. In the heterogeneous flow regime, gas was distributed into two bubble phases: small and large. Simulation results were validated using data obtained from a pilot plant. The developed model is also applicable for the design of large-scale slurry reactors.     

An Update to “Recent Trends in the Processing of Enargite Concentrates”

An update is presented to the paper “Recent trends in the processing of enargite concentrates” by Safarzadeh, Moats, and Miller (2014). Publications which were not included in the initial review paper, primarily to avoid redundancy, are presented and discussed here. Thus, roasting, atmospheric acidic and alkaline leaching, the dissolution of enargite in low-melting point salts, bioleaching, and pressure leaching are presented. For the first time, the modified phase stability (Kellogg) diagram and the E_h-pH diagram for the Cu-As-S system including sinnerite (Cu₆As₄S₉) have been established. According to the results from different treatment options discussed in our earlier review and also in this paper, it is evident that the most recent research activities for the treatment of enargite concentrates are centered around roasting, alkaline sulfide leaching, and high temperature pressure oxidation. Taking into account the advantages and disadvantages of the mentioned processing options, and the numerous preliminary experiments performed, the acid bake-leach process has been identified and is being studied at the University of Utah. It has been found that enargite transforms to water-soluble copper sulfate, arsenic trioxide and elemental sulfur by sulfuric acid baking of enargite at 200°C, with less than 1% of the arsenic being released to the gas phase. This process strategy provides a new possibility for the treatment of enargite concentrates.     

Exergy based performance analysis of a solid oxide fuel cell and steam injected gas turbine hybrid power system

This paper presents exergy analysis of a hybrid solid oxide fuel cell and gas turbine (SOFC/GT) system in comparison with retrofitted system with steam injection. It is proposed to use hot gas turbine exhaust gases heat in a heat recovery steam generator to produce steam and inject it into gas turbine. Based on a steady-state model of the processes, exergy flow rates are calculated for all components and a detailed exergy analysis is performed. The components with the highest proportion of irreversibility in the hybrid systems are identified and compared. It is shown that steam injection decreases the wasted exergy from the system exhaust and boosts the exergetic efficiency by 12.11%. Also, 17.87% and 12.31% increase in exergy output and the thermal efficiency, respectively, is demonstrated. A parametric study is also performed for different values of compression pressure ratio, current density and pinch point temperature difference.     

Causes of variability in concentrations of polychlorinated biphenyls and polybrominated diphenyl ethers in indoor air

Airborne concentrations of PCBs and PBDEs were measured in offices, homes, public environments, and cars. Variations in concentrations between different rooms in the same domestic and office buildings, showed some intra-building variability for both compound groups. Stepwise multiple linear regression analysis revealed no clear and consistent relationships between log-normalized concentrations of PCBs and PBDEs in homes and offices and factors such as the number of personal computers. This is considered to reflect the complexity of relationships between indoor air contamination and microenvironment characteristics. The influence of personal computers was demonstrated when PBDE concentrations in one office fell appreciably following the exchange of a computer constructed in 1998 for one dating from 2003. Concentrations of PCBs in buildings constructed between 1950 and 1979 were significantly higher (p < 0.001) than in those constructed since. When two of the most contaminated cars were omitted as outliers, a significant (p < 0.01) positive linear relationship was detected between PBDE concentrations and vehicle age. Concentrations of PCBs and PBDEs were monitored throughout a calendar year in four homes and four offices. Although concentrations in warmer months usually exceeded those in colder months, seasonal variability in indoor contamination appears less significant than observed previously for outdoor air.     

Multi-objective optimization of solid oxide fuel cell/gas turbine combined heat and power system: A comparison between particle swarm and genetic algorithms

Many studies have attempted to optimize integrated Solid Oxide Fuel Cell-Gas Turbine (SOFC-GT), although different and somehow conflicting results are reported employing various algorithms. In this study, Multi-Objective Optimization (MOO) is employed to approach the optimal design of SOFC-GT considering all prevailing factors. The emphasis is placed on the evaluation of the Particle Swarm Optimization (PSO) and Genetic Algorithm (GA) performance as two effective approaches for solving the multi-objective and non-linear optimization problems. Multi- objective optimization is carried out on two vital objectives; the electrical efficiency and the overall output power of the system. The considerable achievements are the set of optimal points that aim to identify the system optimal performance which provides a practical basis for the decision-makers to choose the appropriate target functions. For the studied conditions, the two algorithms nearly exhibit similar performance, while the PSO is faster and more efficient in terms of computational effort. The PSO appears to achieve its ultimate parameter values in fewer generations compared to the GA algorithm under the examined circumstances. It is found that the maximum power of 410 kW is accomplished employing the GA optimization method with an efficiency of 64%, while PSO method yields the maximum power of 419.19 kW at the efficiency of 58.9%. The results stress that PSO offers more satisfactory convergence and fidelity of the solution for the SOFC-GT MOO problems.     

Effect of hydrogen on H2/CH4 flame structure of MILD combustion using the LES method

Large eddy simulation (LES) method is employed to investigate the effect of the hydrogen content of fuel on the H₂/CH₄ flame structure under the moderate or intense low-oxygen dilution (MILD) condition. The turbulence–chemistry interaction of the numerically unresolved scales is modelled using the PaSR method, where the full mechanism of GRI-2.11 represents the chemical reactions. The influence of hydrogen concentration on the flame structure is studied using the profiles of temperature, CH₂O and OH mass fractions and the diffusion profiles of un-burnt fuel through the flame front. Furthermore, more details are investigated by contours of OH, HCO and CH₂O radicals in an area near the nozzle exit zone. Results show that increasing the hydrogen content of fuel reinforces the MILD combustion zone and increases the peak value of the flame temperature and OH mass fraction. This increment also increases the flame thickness and reduces the OH oscillations and diffusion of the un-burnt fuel through the flame front.     

Frame rate computing and aggregation measurement toward QoS/QoE in Video-SAR systems for UAV-borne real-time remote sensing

The Journal of Supercomputing - This research aims to introduce some new findings toward multimedia and communication aspects of Video-SAR imaging systems. The first suggestion is a modified frame...