Processing of Ni-WC-8Co MMC casting through microwave melting

The melting and casting of nickel-based powder metal matrix composites (MMCs) through microwave energy is carried out in the present work. The nickel powder was mixed with 5% and 10% volume fraction of the WC-8Co reinforcement powder and processed in a microwave oven at 2.45?GHz and 900?W. The developed castings revealed complete melting of the nickel powder within 25 minutes of microwave exposure. The processing mechanism of MMC castings through microwave is explained and the developed castings were subjected to the microstructure and mechanical characterizations. The results of XRD analysis revealed the formation of some hard intermetallics such as NiSi and Cr₂₃C₆. The back-scattered scanning electron microscopy images of castings microstructures revealed the formation of nearly equiaxed grains of the matrix. It was observed that WC particles within the matrix were in agglomerated patterns, which were randomly dispersed. The presence of hard phases of WC reinforcement and formed intermetallic carbides enhanced the microhardness (788?±?52?HV) of the developed composites.     

Synthesis,structural and optical properties of Ag doped ZnO nanoparticles with enhanced photocatalytic properties by photo degradation of organic dyes

In present paper chemical route based synthesis of Ag doped ZnO nanoparticles (NPs) by co-precipitation method is reported to develop ZnO NPs for photo catalytic application. XRD confirms the structural purity of ZnO NPs. FESEM and TEM study reveals the surface and ultra structure morphology of NPs. EDAX study confirms the purity and homogeneity of NPs. The Ag/ZnO NPs with different weight percentage of Ag relative to ZnO were applied under visible light irradiation for evaluating heterogeneous photo catalytic degradation of methylene blue (MB) and Brilliant blue (BB) respectively. The presence of Ag in ZnO enhance MB and BB dye degradation effectiveness from 96.78 to 98.66 and 82.15 to 97.36% for pure ZnO and maximum Ag doped ZnO (x?=?0.1) respectively. In comparison of MB and BB final degradation ability, MB dyes have more effective photo catalytic efficiency towards different oxidizing species to degradation process.     

Investigation of Microwave Processing Parameters on Development of Ni-40Cr3C2 Composite Clad and Their Characterization

Metallurgical and Materials Transactions A - The chromium carbide (Cr3C2)-reinforced Ni-based composite clad on austenitic stainless steel (SS-316) substrate was successfully developed by the...     

Design and performance analysis of low power LNA with variable gain current reuse technique

This paper presents a CMOS low power Variable Gain Low Noise Amplifier for 26–34 GHz in 45 nm process technology, which composes of cascaded complimentary common gate (CCG) stage and digital current steering amplifier. First stage is CCG stage, which helps in achieving the low power consumption and less area. Second stage is variable gain amplifier, uses current reuse technique as well as g_m-boost technique and has constant dc current to make the input impedance stable. Source degeneration technique cancel out MOS parasitic capacitance help in achieving linearity. Simulated maximum peak gain is 13.139 dB at 30.57 GHz and lowest peak gain is 7.75 dB at 26 GHz i.e. approximately flat over the entire band. Lowest NF is 3.08 dB at 32.6 GHz. Process corner simulation has been done for all four corners (S–S, S–F, F–S, F–F) showing robustness of LNA. Input return loss has value less than ? 9.58 dB while output return loss has less than ? 2.6 dB showing good matching; power consumption is 16 mW for dc current of 16 mA at 1 V. MOS active chip area is 76.727 µm².

     

Experimental study for the enhancement of heat transfer characteristics and development of thermal correlations of a roughened solar collector

The thermal performance of the flat plate solar collector is very low. The most beneficial and worthwhile method for increasing the thermal performance of a solar-powered air heater (SPAH) is to include a roughness element in the working zone of heat transfer that is located beneath the shear layer of the absorber surface. In this research work, efforts are made to enhance thermal performance and develop thermal correlations for the estimation of the Nusselt number and friction factor of a roughened SPAH. Experiments are performed for various ranges of flow, Reynolds numbers, and roughness parameters. The experimental technique of liquid crystal thermography is utilized to assess the dispersal of Nusselt number over the roughened surface for all roughness parameters. A maximum thermal performance enhancement index of 2.69 is obtained with the optimum value of the roughness parameter at a relative roughness pitch (RRP) of 9, a relative staggering distance (RSD) of 4, and a relative roughness length (RRL) of 6.15. Second, a mathematical correlation is developed using a regression model to estimate the Nusselt number and friction factor in terms of nondimensional roughness and flow parameters operated as RRP, RSD, RRL, and Re. The degree of discrepancy between the established the relationships and the findings from the experiment reveals incredibly satisfying results. Hence employing twisted V-ribs as an artificial roughness element no doubt increases the Nusselt number, and thermohydraulic performance enhancement index, but it also exerts less frictional power across the SPAH duct.     

Zinc blende GaAsSb nanowires grown by molecular beam epitaxy

We report the growth of GaAsSb nanowires (NWs) on GaAs(111)B substrates by Au-assisted molecular beam epitaxy. The structural characteristics of the GaAsSb NWs have been investigated in detail. Their Sb mole fraction was found to be about?25%. Their crystal structure was found to be pure zinc blende (ZB), in contrast to the wurtzite structure observed in GaAs NWs grown under similar conditions. The ZB GaAsSb NWs exhibit rotational twins around their [111]B growth axis, with twin-free segments as long as 500?nm. The total volumes of GaAsSb segments with twinned and un-twinned orientations, respectively, were found to be equal by x-ray diffraction analysis of NW ensembles.     

Density and Dynamic Viscosity of Sn,Sn–Ag,and Sn–Ag–Cu Liquid Lead-Free Solder Alloys

Powder Metallurgy and Metal Ceramics - Traditionally, the soldering process was carried out, applying mainly lead-based solder materials. However, the prohibition against using lead (Pb) in...     

Synthesis and in vitro Study of Artemisinin/Synthetic Peroxide-Based Hybrid Compounds against SARS-CoV-2 and Cancer

The newly emerged severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) cause life-threatening diseases in millions of people worldwide, in particular, in patients with cancer, and there is an urgent need for antiviral agents against this infection. While in vitro activities of artemisinins against SARS-CoV-2 and cancer have recently been demonstrated, no study of artemisinin and/or synthetic peroxide-based hybrid compounds active against both cancer and SARS-CoV-2 has been reported yet. However, the hybrid drug's properties (e. g., activity and/or selectivity) can be improved compared to its parent compounds and effective new agents can be obtained by modification/hybridization of existing drugs or bioactive natural products. In this study, a series of new artesunic acid and synthetic peroxide based new hybrids were synthesized and analyzed in vitro for the first time for their inhibitory activity against SARS-CoV-2 and leukemia cell lines. Several artesunic acid-derived hybrids exerted a similar or stronger potency against K562 leukemia cells (81–83 % inhibition values) than the reference drug doxorubicin (78 % inhibition value) and they were also more efficient than their parent compounds artesunic acid (49.2 % inhibition value) and quinoline derivative (5.5 % inhibition value). Interestingly, the same artesunic acid-quinoline hybrids also show inhibitory activity against SARS-CoV-2 in vitro (EC₅₀ 13–19 μm ) and no cytotoxic effects on Vero E6 cells (CC₅₀ up to 110 μM). These results provide a valuable basis for design of further artemisinin-derived hybrids to treat both cancer and SARS-CoV-2 infections.     

Steady-state analysis of self-excited induction generators using genetic algorithm approach under different operating modes

The main focus of this paper is the steady-state analysis of self-excited induction generators (SEIGs). It employs the genetic algorithm approach (GAA) to estimate the steady-state performance of these machines. Further, the GAA is used for the solution of problems related to the operation of a number of SEIGs running in parallel. GA-based modelling is found to be effective to determine the generated voltage and frequency. Experimental results validate the proposed methodology.     

Development of an automated system for continuous monitoring of powered roof support in longwall panel

Described the development of an Intrinsically Safe System for continuous monitoring of load and convergence of powered roof supports installed at longwall faces. The system developed for monitoring of behavior of a powered support in a mechanized longwall sublevel caving face. The logging system can be programmed for logging the data from the sensors at different logging intervals ranging from 16 h to 1 ms for logging variation in hydraulic pressures in legs and convergence of the support during progressive face advance. For recording dynamic loads, the data logger can be programmed to start fast logging, say at 10 ms intervals, when the pressure in a leg reaches a pre-specified threshold value, and continue fast logging until the pressure drops below this threshold value. This fast logging automatically stops when the pressure drops below this threshold value.