Radial basis function Hermite collocation approach for the solution of time dependent convection–diffusion problems

This work presents a meshless numerical approach for the solution of time dependent convection–diffusion problems in terms of a Hermite radial basis function interpolation numerical scheme. To test the proposed scheme several numerical examples are analysed including problems with variable convective velocity and reaction coefficient. Comparisons are made with available analytical solutions.     

DEBH: detecting and eliminating black holes in mobile ad hoc network

Security in mobile ad hoc network (MANET) is one of the key challenges due to its special features e.g. hop-by-hop communications, dynamic topology, and open network boundary that received tremendous attention by scholars. Traditional security methods are not applicable in MANET due to its special properties. In this paper, a novel approach called detecting and eliminating black holes (DEBH) is proposed that uses a data control packet and an additional black hole check table for detecting and eliminating malicious nodes. Benefiting from trustable nodes, the processing overhead of the security method decreases by passing time. Ad hoc on-demand distance vector (AODV) routing protocol is used as the routing protocol in our design. After finding the freshest path using AODV, our design checks the safety of selected path. In case of detecting any malicious node, it is isolated from the entire network by broadcasting a packet that contains the ID of malicious nodes. Simulation results show that DEBH increases network throughput and decreases packet overhead and delay in comparison with other studied approaches. Moreover, DEBH is able to detect all active malicious nodes which generates fault routing information.     

Doping effect of M (M = Nb,Ce, Nd,Dy, Sm,Ag, and/or Na) on the growth of pulsed-laser deposited V2O5 thin films

V₂O₅ thin films were prepared by using a pulsed-laser deposition technique. We investigate the doping effect of elements such as Nb, Ce, Nd, Dy, Sm, Ag, and/or Na, on the growth of V₂O₅ films. X-ray photoelectron spectroscopy results indicate that the oxidation state of vanadium is almost highest. X-ray diffraction study reveals that the doping of Nb urges to crystallize the V₂O₅ films. The Raman measurement shows that the doping of rare earth elements leads to the shift from 146 to 149 cm^?1 about –O–V–O–O–V– bond and from 995 to 998 cm^?1 about VO double bond. The optical measurement study reveals that the doping effect on the VO double bond is classified into two types. The addition of Nb, Ce, Nd, Sm, and/or Dy results in an increase of band gap, while those of Ag, and/or Na decreases a band gap. The electrochromic parameters of V₂O₅ films doped with Nb, and/or Na are superior to that of other elements as an electrochromic device (ECD).     

Semicompletion time of carbon dioxide uptake in the process of gas hydrate formation in presence and absence of SDS and silver nanoparticles

Carbon dioxide emission to the atmosphere is one of the main causes of the current global warming. Therefore, capturing this greenhouse gas is very important. The effect of sodium dodecyl sulfate (SDS) and silver nanoparticles on semicompletion time (t_95%) of carbon dioxide uptake in the process of gas hydrate formation is investigated in this communication. The tests were performed at temperatures of 273.65 and 275.65 K and initial pressures of 2 and 3 MPa in a 460 cm³ stirred batch reactor. Experimental measurements show that utilization of SDS and silver nanoparticles decreases the semicompletion time of carbon dioxide uptake considerably. The addition of SDS with concentration of 500 ppm and silver nanoparticles with concentration of 45 μM at p = 2 MPa and T = 275.65 K, respectively, decreases the semicompletion time of carbon dioxide uptake 136.09% and 152.88%, compared to pure water. Investigating the effect of temperature on the amount of t_95% in the presence and absence of tested additives shows that this kinetic parameter decreases by increasing the temperature from 273.65 to 275.65 K.     

Kinetics of (TBAF + CO2) semi-clathrate hydrate formation in the presence and absence of SDS

In this communication, the impacts of adding SDS (sodium dodecyl sulfate), TBAF (tetra-n-butylammonium fluoride) and the mixture of SDS + TBAF on the main kinetic parameters of CO₂ hydrate formation (induction time, the quantity and rate of gas uptake, and storage capacity) were investigated. The tests were performed under stirring conditions at T = 5 ℃ and P = 3.8 MPa in a 169 cm³ batch reactor. The results show that adding SDS with a concentration of 400 ppm, TBAF with a concentration of 1–5 wt%, and the mixture of SDS + TBAF, would increase the storage capacity of CO₂ hydrate and the quantity of gas uptake, and decrease the induction time of hydrate formation process. The addition of 5 wt% of TBAF and 400 ppm of SDS would increase the CO₂ hydrate storage capacity by 86.1% and 81.6%, respectively, compared to pure water. Investigation of the impact of SDS, TBAF and their mixture on the rate of gas uptake indicates that the mixture of SDS + TBAF does not have a significant effect on the rate of gas uptake during hydrate formation process.     

Hydrothermal synthesis of CuMn2O4/CuO nanocomposite without capping agent and study its photocatalytic activity for elimination of dye pollution

The problem of water pollution is a great concern. Elimination of dye pollution from the solvent phase by adsorption is a necessary aspect of research. In this work, Cu-based spinel nanocomposites were synthesized without using any surfactant, via a hydrothermal method at 180 °C for 12 h, they can help us to solve the waste disposal problem. The Cu (II) and Mn (II) nitrates with a stoichiometry ratio of 1:2 were used as precursors. This method involves the hydrolysis of Mn and Cu salts in aqueous solution using ammonia as a pH regulator. In order to optimization the morphology and structural characterization of the nanocomposites, effects of the reaction time and temperature were investigated. XRD patterns confirmed formation CuMn₂O₄/CuO nanocomposites. VSM showed an antiferromagnetic behavior for the nanocomposites in high fields. It is due to the super exchange interactions between the Mn ions. Also, VSM displayed a moderate ferromagnetic behavior with a coercivity of 134 Oe in low fields. The photocatalytic performance of the nanocomposites was examined against the organic dyes of malachite green, eriochrome black T, and methyl orange. CMO NCs exhibited their higher photocatalytic activity in the presence of 0.07 g CMO NC for the degradation of MG solution with 10 ppm concentration. MG contaminant photodegradation was 73.27% after 90 min in this condition.     

Heat and Hydrogen Management Strategies in an Integrated Autothermal Radial Flow Reactor for Enhancement of Olefin Production

Theoretical Foundations of Chemical Engineering - Autothermal configurations are recognized as a novel concept in process intensification. The main objective of this study is modeling and...     

Investigation of photocatalytic,electrochemical, optical and magnetic behaviors of rare-earth double perovskites using combustion synthesized Gd2NiMnO6 nanostructures in the presence of different saccharides

This paper reports combustion synthesis of Gd₂NiMnO₆ nanostructures (GNMO NSs), for the first time, through reaction between metal nitrates in the presence of different saccharides, as capping and reducing agents. Analysis of XRD, FT-IR, EDS, along with TEM and SEM images and also VSM and DRS spectra were applied to study the NSs. The VSM showed an antiferromagnetic behavior. The DRS spectroscopy ascertained semiconducting behavior of GNMO NSs with E_g = 3.05 eV for optimum sample prepared in the presence of glucose at 1000 °C. The CV was used to investigation of electrochemical property of the NSs. For the first time, the photocatalytic behavior of the GNMO NSs was evaluated, using the degradation of organic dyes under UV irradiation. The photodegradation of EDT was almost similar to that of ES, except for initial times of the irradiation. The degradation percentage of EBT and ES in the presence of GNMO NSs was large, whereas that of MV was little in the time range.     

Refined first-order reliability method using cross-entropy optimization method

Engineering with Computers - Generally, the first-order reliability method (FORM) is an efficient and accurate reliability method for problems with linear limit state functions (LSFs). It is showed...