Technical review: Improvement of mechanical properties and suitability towards armor applications – Alumina composites

Ceramic Matrix Composites (CMCs) have many interesting properties, mainly light weight, cost efficiency, low density, high compressive strength, high hardness and durability. Hence, they emerged as a boon to the development of personnel armors in the past. The current work aims to review various new methodologies adapted for the reinforcement of Alumina (Al₂O₃) CMCs in recent times, including some of the interesting results obtained with respect to mechanical properties, suitability of the synthesized composites for armor applications, and the upcoming reinforcement trends. Finally, studies related to reinforcement in Al₂O₃ CMCs, specifically towards armor applications have been consolidated to arrive at some of the important inferences for concluding reasonably.     

Hybrid Metamodel—NSGA-III—EDAS Based Optimal Design of Thin Film Coatings

In this work, diamond-like carbon (DLC) thin film coatings are deposited on silicon substrates by using plasma-enhanced chemical vapour deposition (PECVD) technique. By varying the hydrogen (H₂) flow rate, CH₄−Argon (Ar) flow rate and deposition temperature (T_d) as per a Box-Behnken experimental design (BBD), 15 DLC deposition experiments are carried out. The Young’s modulus (E) and the coefficient of friction (COF) for the DLCs are measured. By using a second-order polynomial regression approach, two metamodels are built for E and COF, that establish them as functions of H₂ flow rate, CH₄-Ar flow rate and T_d. A non-dominated sorting genetic algorithm (NSGA-III) is used to obtain a set of Pareto solutions for the multi-objective optimization of E maximization and COF minimization. According to various practical scenarios, evaluation based on distance from average solution (EDAS) approach is used to identify the most feasible solutions out of the Pareto solution set. Confirmation experiments are conducted which shows the efficacy of the polynomial regression—NSGA-III—EDAS hybrid approach. The surface morphology of the DLCs deposited as per the optimal predictions is also studied by using atomic force microscopy.     

Electric field induced enhancement in the interfacial charge transfer kinetics of a solid polymer electrolyte

A novel electrostatic method for preparing modified solid polymer electrolytes (SPEs) is reported. Application of an electric field on an evaporating mixture of KYNAR, ethylene carbonate (EC), propylene carbonate (PC) and LiPF₆ dissolved in tetra hydro furan (THF) resulted in a solid polymer electrolyte whose charge transfer resistance was at least an order of magnitude lower than that formed without the application of an electric field. We believe that the observed enhancement is probably due to an electric field induced orientation of dipoles in the polymer chain.     

Optimization of hybrid laser–TIG welding of 316LN stainless steel using genetic algorithm

Determination of optimum hybrid laser–TIG welding process variables for achieving the maximum depth of penetration (DOP) in type 316LN stainless steel has been carried out using a genetic algorithm (GA). Nd:YAG pulsed laser and the TIG heat source were coupled at the weld pool to carry out hybrid welding. Design of experiments approach was used to generate the experimental design matrix. Bead-on-plate welds were carried out based on the design matrix. The input variables considered were laser power, pulse frequency, pulse duration, and TIG current. The response variable considered was the DOP. Multiple-regression model was developed correlating the process variables with the DOP using the generated data. The regression model was used for evaluating the objective function in GA. GA-based model was developed and it produced a set of solutions. Tournament and roulette wheel selection methods were used during the execution of GA. It was found that both the selection methods identified similar welding process parameters for achieving the maximum DOP. Excellent agreement was observed between the target DOP and the DOP values obtained in the validation experiments during hybrid laser–TIG welding.     

Influence of PVP on Bi25FeO40 microcubes for Supercapacitors and Dye-Sensitized Solar Cells applications

Journal of Materials Science: Materials in Electronics - Polyvinylpyrrolidone (PVP)-assisted Bi25FeO40 microcubes have been synthesized through hydrothermal technique and the effect of morphology...     

Crystal habits of LiMn2O4 and their influence on the electrochemical performance

Crystal habits of LiMn₂O₄ prepared through a sol-gel method using different starting materials (metal acetates and metal nitrates) are studied using a crystal shape algorithm. Density functional theory (DFT) as implemented in VASP is employed to study the thermodynamic stabilities and the electronic structure of the different hkl planes of LiMn₂O₄, as identified by the crystal shape algorithm. The crystal habit of lithium manganate prepared through the metal acetate route, LiMn₂O₄ (A), seems to possess a higher thermodynamic stability compared to the metal nitrate route viz. LiMn₂O₄ (N). Electrochemical cycling measurements show that the capacity retention in LiMn₂O₄ (A) is better than LiMn₂O₄ (N) at low (C/10) as well as at higher (5C) rates.     

Antibacterial and free radical scavenging activity of a medicinal plant Solanum xanthocarpum

The present study describes the phytochemical profiles, antibacterial, and antioxidant properties of different solvent extracts of Solanum xanthocarpum leaves. Phytochemical analysis results revealed the presence of terpenoids, tannins, steroids, and phenols. Methanolic extract of plant had a maximum quantity of phenol (28.3 ± 2.0 mg) and flavonoids (25.2 ± 1.2 mg) than others. Similarly, the methanolic extract showed excellent antibacterial activity and exhibited the highest inhibitory effect against Pseudomonas aeruginosa (12 ± 0.5 mm), Salmonella typhi (10 ± 0.6 mm), Staphylococcus aureus (9 ± 1.0 mm), and Escherichia coli (7 ± 1.3 mm). The average minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values were reported in the range of 3.2 to 6.9 µg/ml (for MIC) and 6.0 to 14.5 µg/ml (for MBC), respectively. The remarkable antioxidant activity was observed in chloroform and methanol extract on the DPPH radical scavenging activity with the lowest IC₅₀ value of 197.245 μg/ml (chloroform) and 201.04 μg/ml (methanol) and compared with control (ascorbic acid 239.36 μg/ml). GC-MS analysis revealed the presence of six major bioactive compounds as follows; 2,Octylcyclopropene-1-Heptanol (42.81%), Hexadecanoic acid (26.63%), 1-methylene-2b Hydroxymethyl-3,3-Dimethyl-4b-(3Methylbut-2enyl)-C (9.3%), Phytol (7.5%), (1,3,3-Trimethyl-2-Hydroxymethyl-3,3-Dimethyl-4–3-Methylbut-2-Enyl)-C (7.2%). 3,7,11,15-Tetramethyl-2-Hexadecen-1-Ol (6.3%). The FT-IR spectrum reflected the presence of the twelve peaks at the range of 3746.38 cm-1 (O-H stretch alcohols), 3424.18 cm-1 (O-H stretch phenols), 2926.01 cm-1 (C-H stretch alkanes), 2857.55 cm-1 (C-H stretch alkanes), 2084.04 cm-1 (-C = C stretch alkynes), 1595.76 cm-1 (N-H bend primary amines), 1402.49 cm-1 (C-C stretch in ring aromatics) and others. This study suggests S. xanthocarpum as a potential candidature for having better antibacterial and antioxidant property and identified several bioactive compounds by GC-MS analysis.     

Shield Techniques for Application Layer DDoS Attack in MANET: A Methodological Review

In today’s world of wireless networks the mobile ad-hoc networks are widely preferred as a communication medium as these are infrastructure less networks. The application layer of these networks is targeted by attackers because it is responsible for actual data exchange with end users. As human dependency on wireless networks is increasing the DDoS attacks i.e. distributed denial of service attack which becomes a nightmare for the researchers. This attack is one of the most devastating attacks that can be executed on web-servers and congest the network keys like socket connections, CPU cycles, and memory database. In this current mobile computing world the necessity of DDOS attack management is significantly increased because this attack can degrade the entire web experience. Further, this DDOS attack is commenced along with the legitimate requests so it is also important to differentiate DDoS attack from other similar Events. This review endeavors to explore with more emphasis on application layer DDoS attack and its management stages like prevention, detection, mitigation and Differentiation along with comparative statement of prominent techniques discovered in each stage. This methodological survey report shall lead the way to researchers and network designers to suit the specific management scheme to provide the complete protection of wireless networks from DDoS attack.