Study of the performance of dry methane reforming in a microchannel reactor using sputtered Ni/Al2O3 coating on stainless steel

In this study, a microchannel reactor was designed, its catalytic performance in dry methane reforming (DRM) was assessed, and the results were compared with those observed in a conventional fixed bed reactor. The catalyst was prepared in two forms, including catalyst pellets and catalyst-coated plate. The microchannel reactor had thin films of Ni/Al₂O₃ coated on stainless steel substrate via radio frequency (RF) magnetron sputtering method in various sputtering times. The fall-off rate of the catalyst-coated plates can be neglected after putting the plates under the high-temperature DRM reaction, due to the formation of firm active catalyst coatings. The performance of the samples was evaluated at different temperatures from 700 to 800 °C, at P = 1 atm, with a CH₄:CO₂ ratio of 1. The results of XRD showed that with increasing the sputtering time, there was an increase in crystallinity. As observed in FESEM images, the sample prepared with 5 min of sputtering was dense and uniform. The results of EDX not only proved the dispersion of the samples observed in XRD and FESEM analysis, but also verified the presence of the utilized elements. The temperature of 800 °C and the sample with 5 min sputtering time were selected as the optimum condition that provided the best performance. Catalytic performance was investigated in fixed bed reactor at the same GHSV; based on the results there were no significant conversions in the fixed bed reactor. The results of the stability test in the microchannel reactor showed a good performance during 30 h on stream. Therefore, Ni/Al₂O₃ thin films had a satisfactory performance in the designed microchannel. Our study shows that this type of reactor has many advantages in terms of performance, compactness, and economic concerns.     

Design,modeling, and optimization of a dual reflector parabolic trough concentration system

The aim of the present work is to enhance the thermal management avoiding the high-thermal stress on the outer surface of the parabolic trough receiver (PTR) derived from nonuniform concentrated solar flux distribution. A parabolic trough concentrating (PTC) system with second homogenizing reflector (HR) is numerically designed and optimized to ensure a uniform concentrated solar flux on the PTR walls. For this purpose, a three-dimensional optical model has been developed to analyze quantitatively the improvement made by the HR using the optical efficiency and qualitatively basing on the uniformity of the solar flux density distribution over the entire surface of the PTR. The validation of the numerical tool is presented, and the algorithm of the design process has been proposed and detailed. As a preliminary trait, it was revealed that the peak of the designed system performance is achieved with a rim angle of 68° avoiding simultaneously the aberration and the blocking effects. Despite the optical efficiency decrease by about 7% compared with the conventional PTC design, the uniformity of the solar flux distribution has been strongly improved such that the maximum local solar flux density gradient is decreased from 80 to 11 kW/m² equivalent to a decrease of 86.25% with respect to the conventional PTC and the average local density is about 25.5 kW/m².     

DFNS/PEI/Cu Nanocatalyst for Reduction of Nitro-aromatic Compounds

Catalysis Letters - Nitro-aromatic pollution in industrial waste streams threat wellbeing of water resources. This study investigates the performance of a copper-based nano catalyst to reduce...     

Fault‐tolerant control of distributed systems by information pattern reconfiguration

Given a fault‐tolerance strategy and a distributed control system, the set of recoverable faults depends on the information pattern that is implemented. This paper shows that fault‐tolerance can be achieved, when possible, by the reconfiguration of the information pattern. A necessary and sufficient recoverability condition is provided, and sub‐optimal solutions are developed for actuator and sensor faults under system reconfiguration. Copyright © 2014 John Wiley & Sons, Ltd.     

Calibration of low-pressure MEMS gas sensor for detection of hydrogen gas

Detection of hydrogen by sensors are significant for improvement and safe usage of hydrogen gas as an energy source. In this paper, the application of the MEMS gas sensor for detection of hydrogen gas is numerically studied to develop the application of this device in different industrial applications. The flow feature and force generation mechanism inside a rectangular enclosure with heat and cold arms as the non-isothermal walls are inclusively discussed. In this study, the pressure of hydrogen is varied from 62 to 1500 pa correspond to Knudsen number from 0.1 to 4.5 to investigate all characteristics of the thermal-driven force inside the MEMS sensor. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equations are applied to obtain high precision results. To solve these equations, Direct Simulation Monte Carlo (DSMC) approach is used as a robust method for the non-equilibrium flow field. The effects of length, thickness and temperature of arms are comprehensively investigated in different ambient pressures. In addition, the effect of various hydrogen concentrations on the Knudsen force is studied. Our findings show that maximum Knudsen force occurs at P = 387 pressure and intensifies when the length of the arms is increased from 50 μm to 150 μm. In addition, the obtained results demonstrate that the generated force is highly sensitive to hydrogen gas species and this enables device for detection of hydrogen gas.     

Fast and Ultraclean Approach for Measuring the Transport Properties of Carbon Nanotubes

In this work, a fast approach for the fabrication of hundreds of ultraclean field‐effect transistors (FETs) is introduced, using single‐walled carbon nanotubes (SWCNTs). The synthesis of the nanomaterial is performed by floating‐catalyst chemical vapor deposition, which is employed to fabricate high‐performance thin‐film transistors. Combined with palladium metal bottom contacts, the transport properties of individual SWCNTs are directly unveiled. The resulting SWCNT‐based FETs exhibit a mean field‐effect mobility, which is 3.3 times higher than that of high‐quality solution‐processed CNTs. This demonstrates that the hereby used SWCNTs are superior to comparable materials in terms of their transport properties. In particular, the on–off current ratios reach over 30 million. Thus, this method enables a fast, detailed, and reliable characterization of intrinsic properties of nanomaterials. The obtained ultraclean SWCNT‐based FETs shed light on further study of contamination‐free SWCNTs on various metal contacts and substrates.     

A robust scheduling for the multi-mode project scheduling problem with a given deadline under uncertainty of activity duration

The problem of this paper deals with the multi-mode project scheduling problem under uncertainty of activity duration where only the renewable resources are taken into account and a given deadline has to be met at the cost of recruiting additional resources. A heuristic algorithm is employed to solve this problem, and to maintain the robustness of the baseline schedule, the concept of critical chain project management (CCPM) is applied in which a new definition to resource buffer is considered. A simulation methodology is used to determine the size and location of resource buffers in the schedules in which three different buffer sizes and three different uncertainty levels are considered. Results and analysis of the simulation outcomes illustrate that resource buffers are useful and should be simulated by the CCPM schedules, as they help to decrease the total duration of the project during implementation and meet the deadline of the project with more assurance.     

Optical and photocatalytic properties of the Fe-doped TiO2 nanoparticles loaded on the activated carbon

In this work, Fe-doped (1?wt%) TiO₂ loaded on the activated carbon nano-composite was prepared using a sol-gel method. A prepared nano-composite was characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), BET surface area, Fourier transform infrared spectroscopy (FTIR), photoluminescence (PL) spectroscopy and UV–Vis diffuse reflectance spectroscopy (DRS). The photocatalytic activity of the nano-composite was evaluated through degradation of synthetic textile wastewater, reactive red 198, under visible light irradiations. The XRD result indicated that the TiO₂ nano-composite contained only anatase phase. The surface area of the TiO₂ increased from 48?m²/g to 100?m²/g through the fabrication of the nano-composite. The FE-SEM results indicate that the TiO₂ particles with an average particle size of 35–70?nm can be deposited homogeneously on the activated carbon surface. DRS showed that the Fe doping in the TiO₂ -activated carbon nano-composite induced a significant red shift of the absorption edge and then the band gap energy decreased from 3.3 to 2.9?eV. Photocatalytic results indicated that the photocatalytic activity of the Fe doped TiO₂ increased under visible light irradiation in the presence of the activated carbon.