This study was to carry out phytochemical screening, to determine the total phenolic and flavonoid content as well as to evaluate the antioxidant properties of methanolic extract of root of Asparagus racemosus. Antioxidant properties were determined by 1,1-diphenyl,2-picrylhydrazyl (DPPH), hydroxyl radical, superoxide radical, hydrogen peroxide assay and total antioxidant activity by the phosphomolybdenum assay. The result showed that the powdered roots of A. racemosus were extracted with methanol and the percentage of yield was 29.2%. The total phenolic and flavonoid contents of the extracts were 12.90 ± 0.002 mg/g and 0.80 ± 0.001 mg/g dry weight respectively. The plant sample possesses high free radical scavenging activity and phytochemical constituents which might be useful for further studies to fight against oxidative stress.

In recent times, gas foil bearings have become popular for commercial use in the aircraft and space industry, turbocompressors, turbine generators and in the more complex fields of turbochargers and turboexpanders. The gain in popularity for gas foil bearings is due to their features such as contamination-free zone, wide temperature range, higher stability and higher reliability characteristics as compared to other types of bearings. However, several challenges have come across while analysing the gas foil bearing behaviour at different working conditions. The current paper presents an overview of the work done in the past few decades for developing numerical models and listing the efforts of several researchers around the world to conduct the experimental investigation for predicting and analysing thermohydrodynamic behaviour of gas foil bearings at different operating conditions. It is expected that the current paper will help readers to thoroughly understand the hydrodynamic and thermal aspects of gas foil bearings.

Gas foil bearings are often used in high-speed turbomachinery such as turboexpanders and turbochargers due to their merits over simple gas-lubricated bearings. The merits of gas foil bearings include their ability to tailor dynamic parameters such as stiffness and damping. Gas foil bearings usually have low clearance and operate at a high rotational speed, which eventually leads to velocity slip at the solid–fluid interface. This article investigates the effect of slip flow on various parameters of gas foil thrust bearings. A numerical model is formulated to predict pressure, film thickness and temperature distribution of helium lubricated gas foil thrust bearing at high rotating speed. The Reynolds equation is modified by assuming first-order slip coupled with the structural (compliant) and energy equation. The temperature-dependent viscosity and density of the fluid are also considered in the Reynolds equation to predict the thermohydrodynamic behaviour of gas foil thrust bearings. The numerical model thus developed uses a finite-difference method and the Newton–Raphson method to solve the Reynolds equation,whereas the successive over-relaxation method is used to solve the energy equation. Various performance parameters are compared for slip and no-slip conditions for gas foil thrust bearings. The results show a considerable difference between the two phenomena. Also, the conventional Reynolds equation tends to overestimate the load-carrying capacity.

In this study, a rubber pressure molding (RPM) technique is developed to prepare fiber-reinforced plastic components (FRP) using glass fiber and epoxy resin. The technique is based on the matching die set, where the die is made of hard metal-like steel and the punch from flexible rubber-like materials. The use of a flexible rubber punch helps to intensify and uniformly redistribute pressure (both the operating pressure and developed hydrostatic pressure due to the flexible rubber punch) on the surface of the product. A split steel die and rubber punch are designed and fabricated to prepare the FRP components. The same split die is also used to cast the rubber punch. Silicone rubber is used to prepare the rubber punch in this investigation. Burn test, coin test, scanning electron microscopy, and mechanical tests like interlaminar fracture toughness, interlaminar shear test (ILST), tension test, etc. are carried out to know the fiber content, void content, presence of delamination, bonding between fiber and resin, microstructure, and mechanical properties of the composite materials. These properties are also compared with the FRP components made by the conventional technique to evaluate its performances in structural applications.

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