The Effect of Ti on Mechanical Properties of Extruded In-Situ Al-15 pct Mg2Si Composite

This work was carried out to investigate the effect of different Ti concentrations as a modifying agent on the microstructure and tensile properties of an in-situ Al-15 pctMg₂Si composite. Cast, modified, and homogenized small ingots were extruded at 753 K (480 °C) at the extrusion ratio of 18:1 and ram speed of 1 mm/s. Various techniques including metallography, tensile testing, and scanning electron microscopy were used to characterize the mechanical behavior, microstructural observations, and fracture mechanisms of this composite. The results showed that 0.5 pctTi addition and homogenizing treatment were highly effective in modifying Mg₂Si particles. The results also exhibited that the addition of Ti up to 0.5 pct increases both ultimate tensile strength (UTS) and tensile elongation values. The highest UTS and elongation values were found to be 245 MPa and 9.5 pct for homogenized and extruded Al-15 pctMg₂Si-0.5 pctTi composite, respectively. Fracture surface examinations revealed a transition from brittle fracture mode in the as-cast composite to ductile fracture in homogenized and extruded specimens. This can be attributed to the changes in size and morphology of Mg₂Si intermetallic and porosity content.     

Application of dielectric barrier discharge (DBD) plasma packed with glass and ceramic pellets for SO2 removal at ambient temperature: optimization and modeling using response surface methodology

Air pollution is a major health problem in developing countries and has adverse effects on human health and the environment. Non-thermal plasma is an effective air pollution treatment technology. In this research, the performance of a dielectric barrier discharge (DBD) plasma reactor packed with glass and ceramic pellets was evaluated in the removal of SO₂ as a major air pollutant from air in ambient temperature. The response surface methodology was used to evaluate the effect of three key parameters (concentration of gas, gas flow rate, and voltage) as well as their simultaneous effects and interactions on the SO₂ removal process. Reduced cubic models were derived to predict the SO₂ removal efficiency (RE) and energy yield (EY). Analysis of variance results showed that the packed-bed reactors (PBRs) studied were more energy efficient and had a high SO₂ RE which was at least four times more than that of the non-packed reactor. Moreover, the results showed that the performance of ceramic pellets was better than that of glass pellets in PBRs. This may be due to the porous surface of ceramic pellets which allows the formation of microdischarges in the fine cavities of a porous surface when placed in a plasma discharge zone. The maximum SO₂ RE and EY were obtained at 94% and 0.81 g kWh⁻¹, respectively under the optimal conditions of a concentration of gas of 750 ppm, a gas flow rate of 2 l min⁻¹, and a voltage of 18 kV, which were achieved by the DBD plasma packed with ceramic pellets. Finally, the results of the model's predictions and the experiments showed good agreement.     

From Feather Waste to Valuable Nanoparticles

Feather is a waste product generated in large quantities from industrial poultry processing. Recycling of this renewable source of biopolymers has been the objective of many researches due to its high protein content, biodegradability, and biocompatibility. This study investigates the feasibility of producing nanoparticles from feather waste by enzymatic hydrolysis, followed by ultrasonic treatment. The effects of enzyme concentration, hydrolysis time and substrate concentration on particles size were evaluated to optimize the best condition in order to attain the smallest particles by a Box-Behnken Design. The optimum hydrolysis conditions were found to be: enzyme concentration: 3.6%, substrate concentration: 5 g/l and hydrolysis time: 243 h. Scanning electron micrographs indicated fiber fibrillation and degradation as it was progressively converted into particles form. The results of particle size analysis indicated the positive effect of sonication on reducing particles size. Fourier transform infrared spectra showed no remarkable changes in the chemical composition of treated samples. Moreover, crystallinity and thermal stability of feather nanoparticles enhanced upon enzymatic hydrolysis and ultrasonic treatment.     

Preparation and characterization of novel derivatives of chitosan and trimethyl chitosan conjugated with dipeptides and vitamin B12 as candidates for oral delivery of insulin

Chitosan and its derivatives are widely used in drug delivery systems due to their bio-degradebility, bio-compatibility and absorption enhancing properties. Many peptide and protein derived therapeutics cannot be administered through oral rout because of the proteolytic condition of gastro-intestinal tract and their low bio-availability. Insulin is a peptide drug which is widely used in diabetics as repeated daily injection. Due to the fact that there are receptors for didpeptides and vitamine B12 in small intestine, in this research work novel derivatives of chitosan and trimethyl chitosan conjugated with glycyl-glycine, alanyl-alaninie and vitamine B12 were synthesized and characterized. The structure of conjugates as well as substitution of different functional groups was confirmed by different instrumental analytical methods such as Fourier transform infrared, magnetic resonance, and X-ray diffraction spectroscopy. Nano-particles of aforementioned loaded with insulin were prepared and their size, surface electrical charge and morphology characterized and their release profile were studied. The results are promising and reveal that these new chitosan and trimethyl chitosan derivatives are potential vehicles for protein and peptide drug molecules.     

Phase evolution in mechanical alloying and spark plasma sintering of AlxCoCrCuFeNi HEAs

ABSTRACT

Al_xCoCrCuFeNi high-entropy alloys were synthesised through mechanical alloying and spark plasma sintering. Different alloys were produced by varying the aluminium content (x?=?0.5, 1.5, 2.5 and 4). The influences of the milling duration on the evolution of microstructure, constituent phases and morphology were studied. Increasing milling time resulted in grain refinement and higher solid solution homogenisation characterised by a high internal strain. As a consequence of aluminium addition, the microstructure of materials evolved from face centered cubic (FCC) and body centered cubic (BCC) phases to FCC, BCC and ordered BCC phases. Both mechanical alloying and SPS conditions as well as aluminium content led to grain refinement and variations of mechanical properties. In particular, hardness increased with increasing aluminium content. The aluminium percentage and the evolution of consequent phases are responsible for the microstructural stability at high temperatures. In addition, with Al content increase, the further synergy of strength and ductility along with a more pronounced strain hardening was obtained.     

Perfect forward secrecy in VoIP networks through design a lightweight and secure authenticated communication scheme

With the growth of the internet, development of IP based services has increased. Voice over IP (VoIP) technology is one of the services which works based on the internet and packet switching networks and uses this structure to transfer the multimedia data e.g. voices and images. Recently, Chaudhry et al., Zhang et al. and Nikooghadam et al. have presented three authentication and key agreement protocols, separately. However, in this paper, it is proved that the presented protocols by Chaudhry et al. and also Nikooghadam et al. do not provide the perfect forward secrecy, and the presented protocol by Zhang et al. not only is vulnerable to replay attack, and known session-specific temporary information attack, but also does not provide user anonymity, re-registration and revocation, and violation of fast error detection. Therefore, a secure and efficient two-factor authentication and key agreement protocol is presented. The security analysis proves that our proposed protocol is secure against various attacks. Furthermore, security of proposed scheme is formally analyzed using BAN logic and simulated by means of the AVISPA tool. The simulation results demonstrate security of presented protocol against active and passive attacks. The communication and computation cost of the proposed scheme is compared with previously proposed authentication schemes and results confirm superiority of the proposed scheme.

     

Binary nanocomposite of Fe3O4/MWCNTs for adsorption of Reactive Violet 2: Taguchi design,kinetics and equilibrium isotherms

Binary nanocomposite of magnetite/multi-walled carbon nanotubes (Fe₃O₄/MWCNTs) was synthesized through the chemical reduction method at room temperature and employed for adsorptive removal of Reactive Violet 2 (RV2) from aqueous solutions. The experiments were carried out based on a Taguchi experimental design with four variables of the adsorbent dosage, pH, contact time and ionic strength. Analysis of variance (ANOVA) showed that the adsorbent dosage with contribution of 79.14% was the most effective factor on the process efficiency. Percent contributions of solution pH and contact time were found to be 9.85 and 6.16, respectively. The ionic strength showed no considerable contribution to the response. The optimal dye removal conditions were determined as the adsorbent dosage of 2.0?g?L^?1, pH = 6, contact time of 30?minutes and ionic strength of 0.1?mol?L^?1 which resulted in the average efficiency of 98.23% for RV2 removal. The results showed that RV2 adsorption onto Fe₃O₄/MWCNTs followed the pseudo-second order kinetic model. Moreover, the intraparticle diffusion model suggested a two-step adsorption process, including macropore diffusion of about 94% of RV2 molecules into the nanocomposite surface during ～10?minutes and a micropore diffusion as the rate-limiting step. Fitting of the experimental data to six isotherms (Langmuir, Harkins-Jura, Freundlich, Tempkin, Halsey and Redlich-Peterson) was also investigated and Redlich-Peterson and Halsey isotherms provided the best quality of fitting for the dye-nanocomposite system with R² values of 0.9992 and 0.9906, respectively.     

Nonlocal static analysis of a functionally graded material curved nanobeam

This article is concerned with the analytical solution for a curved nanobeam based on nonlocal elasticity. The structure is made of functionally graded (FG) material, and its property varies in accordance with a power law function through the thickness. To obtain the displacement function, the static differential equations for a curved FG beam are combined with the nonlocal Eringen stress equations. By using the direct method for solving the nonlocal force–strain and moment–curvature relations covering the distributed loads, the explicit expressions of nonlocal strains are achieved. The strain-displacement relations are also employed to find displacement field. Numerical examples with different types of boundary conditions are carried out in order to investigate the effects of nonlocal parameters, the nonhomogeneity index, and geometric characteristics.     

Novel electro-conductive nanocomposites based on electrospun PLGA/CNT for biomedical applications

Electro-conductive nanocomposites have several applications in biomedical field. Development of a biocompatible electro-conductive polymeric materials is therefore of prime importance. In this study, electro-conductive nanofibrous mats of PLGA/CNT were fabricated through different methods including blend electrospinning, simultaneous PLGA electrospinning and CNT electrospraying and ultrasound-induced adsorption of CNTs on the electrospun PLGA nanofibers. The morphology and diameter of fibers were characterized by SEM and TEM, showing the lowest average diameters of 477?±?136?nm for PLGA/MWCNT blend nanocomposites. MWCNT-sprayed PLGA specimens showed significant lower water contact angle (83°), electrical resistance (3.0?×?10⁴?Ω) and higher mechanical properties (UTS: 5.50?±?0.46?MPa) compared to the untreated PLGA scaffolds. Also, results of PC12 cell study demonstrated highest viability percentage on the MWCNT-sprayed PLGA nanofibers. We propose that the conductive nanocomposites have capability to use as tool for the neural regeneration and biosensors.

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IoT-Enabled Autonomous System Collaboration for Disaster-Area Management

Timely investigating post-disaster situations to locate survivors and secure hazardous sources is critical, but also very challenging and risky. Despite first responders putting their lives at risk in saving others, human-physical limits cause delays in response time, resulting in fatality and property damage. In this paper, we proposed and implemented a framework intended for creating collaboration between heterogeneous unmanned vehicles and first responders to make search and rescue operations safer and faster. The framework consists of unmanned aerial vehicles (UAVs), unmanned ground vehicles (UGVs), a cloud-based remote control station (RCS). A light-weight message queuing telemetry transport (MQTT) based communication is adopted for facilitating collaboration between autonomous systems. To effectively work under unfavorable disaster conditions, antenna tracker is developed as a tool to extend network coverage to distant areas, and mobile charging points for the UAVs are also implemented. The proposed framework’s performance is evaluated in terms of end-to-end delay and analyzed using architectural analysis and design language (AADL). Experimental measurements and simulation results show that the adopted communication protocol performs more efficiently than other conventional communication protocols, and the implemented UAV control mechanisms are functioning properly. Several scenarios are implemented to validate the overall effectiveness of the proposed framework and demonstrate possible use cases.