The hypersonic environment: Required operating conditions and design challenges

Hypersonic flight powered by airbreathing engines offers the potential for faster response time at long ranges, and reduced cost for access-to-space. In the present paper the operating environment of typical hypersonic vehicles are discussed, including results for the radiation equilibrium wall temperature of external vehicle surfaces and the flow properties through three sample engines spanning the range of hydrocarbon-fueled Mach 4-8 flight and hydrogen-fueled flight at speeds up to Mach 17. Flow conditions at several locations through the sample engines were calculated to provide indications of the required operating flow environment. Additional system consideration such a seals, joints, vehicle integration and in-service engineering are addressed.     

Solution of the problem of determination of the density of heat flow due to high-pressure gas quenching by the finite-element method

The density of the heat flow due to quenching in high-pressure gas (nitrogen) is computed with the help of the finite-element method and FLUENT software based on a mathematical model of turbulent flow. The effects of temperature and pressure on the characteristics of the nitrogen medium and the variation of the thermal radiation properties of metallic materials as a function of the temperature are considered. __________ Translated from Metallovedenie i Termicheskaya Obrabotka Metallov, No. 5, pp. 12–17, May, 2006.     

Magnetic field control of a supersonic nitrogen flow

Magnetohydrodynamic impact on a cold supersonic nitrogen flow with external magnetic field was realized in an experimental complex based on the Big Shock Tube at the Ioffe Physicotechnical Institute. A pulsed supersonic flow with a Mach number of M=4 and steady phase duration of about 1.5 ms was created by expansion of the shock-heated nitrogen flow from a supersonic nozzle. The gas was ionized by pulsed discharge between two electrodes mounted on the nozzle wall so that an electric current of up to ∼500 A passed in the direction perpendicular to the gas flow at the dielectric wall. External magnetic field ∼0.3 T was perpendicular to the gas flow and the current direction. It is established that the magnetic field significantly modifies the shock wave structure in the flow.     

Effect of high-fat cholesterol enriched diets on hypolipemic action of Oenothera paradoxa oil in rats. Part 1. Blood serum and liver lipids

The effect on Oenothera paradoxa oil on blood serum and liver lipids metabolism in rats fed a semisynthetic high-fat cholesterol enriched diets was investigated. The source of fats was sunflower oil or lard in 15% quantities and the source of protein was soybean protein isolate in 27% quantity. The diets were enriched with 0.5% cholesterol. This dietary experiment was carried on for 8 weeks. For the first 4 weeks rats were fed standard diet and for the next 4 weeks Oe. paradoxa oil (300 mg/day/rat) was additionally given by stomach-tube. At the end of experiment the contents of total cholesterol, HDL-cholesterol, triglycerides and free fatty acids in blood serum as well as cholesterol and triglycerides level in liver were determined. It was found, that the addition of cholesterol to the diet decreased the hypocholesterolemic and hypotriglyceridemic effects of Oe. paradoxa oil both in blood serum and liver. It have not had any significant effect on the free fatty acid concentration in blood serum decrease by Oe. paradoxa oil intake.     

Influence of deposited metal structures on the failure mechanisms of silicon-based components

Miniaturised silicon-based multilayer chips are nowadays widespread as semiconductor components for the mobile device technology. The use of special processing and integration procedures requires such materials to possess a definite mechanical strength to ensure the functionality of the entire device. The strength and mechanical reliability of such components can be described by the Weibull theory, and is highly influenced by the geometry of the metallisation and other near-surface functional layers. In this work, we attempt to clarify the mechanisms leading to the failure of the metallised side of Si-chip components. The combined use of Finite Elements (FE) and Focused Ion Beam (FIB) analyses allowed recognising that cracks are induced in the metal-oxide-silicon interfacial area well before complete failure of the component. Such cracks have a crucial role in the lower strength and higher Weibull modulus observed on the metallised side.     

Grafting of poly(acrylic acid) on polyamide yarn

Graft copolymerization of acrylic acid onto PA6 yarn was examined in this study. Prior to the grafting process, the fibers were activated with a benzene solution of benzoyl peroxide. Next, the fibers were put into a bath containing acrylic acid, a dispersing agent, and the activator of reaction. The effects of the main process parameters and auxiliary additives on the degree of grafting, quantity of the homopolymer formed during grafting, effectiveness of grafting, extent of conversion, and grafting ratio were determined. Using calculation factors such as the reaction efficiency, the extent of reaction, and the ratio of grafting, the conditions of grafting were found that made possible the reduction or elimination of the by‐product. Also determined were the influence of the degree of grafting on the moisture sorption and the swelling of modified fibers. In addition, the value of apparent activation energy was calculated (49.123 kJ/mol). © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1914–1919, 2001