Experimental Investigation on Noise Suppression in Supersonic Jets from Convergent-Divergent Nozzles with Baffles

The acoustic properties of supersonic jet noise from a convergent-divergent nozzle with a baffle have been studied experimentally over the range of nozzle pressure ratios from 2.0 to 8.0. Acoustic measurements were conducted in a carefully designed anechoic room providing a free-field environment. A new approach for screech noise suppression by a cross-wire is proposed. Schlieren photographs were taken to visualize the shock wave patterns in the supersonic jet with and without the cross-wire. The effects of the baffle and the cross-wire on acoustic properties are discussed. It is shown that the baffle has little effect on the screech frequency for the underexpanded supersonic jet without the cross-wire. Also, the cross-wire introduced in supersonic jets is found to lead to a significant reduction in overall sound pressure level.     

Analysis of Particle Behavior in High-Velocity Oxy-Fuel Thermal Spraying Process

This paper analyzes the behavior of coating particle as Well as the gas flow both of inside and outside the High-Velocity Oxy-Fuel (HVOF) thermal spraying gun by using quasi-one-dimensional analysis and numerical simulation. The HVOF gun in the present analysis is an axisymmetric convergent-divergent nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. In the present analysis it is assumed that the influence of the particles injected in the gas flow is neglected, and the interaction between the particles is also neglected. The gas flow in the gun is assumed to be quasi-one-dimensional adiabatic flow. The velocity, temperature and density of gas in the jet discharged from the barrel exit are predicted by solving Navier-Stokes equations numerically. The particle equation of motion is numerically integrated using three-step Runge-Kutta method. The drag coefficient of the particle is calculated by linear interpolation of the experimental data obtained in the past. Particle     

Preservation of freshness of rainbow trout fillets packaged with carbon dioxide-nitrogen gas mixture (studies on gas-exchange packaging of fresh fish,part 2)

Gas-exchange packaging was applied to preserve freshness of rainbow trout fillets. The fillets were packaged in pouches of coextruded laminate (ethylene vinyl acetate/ polyvinylidene chloride-polyolefin) with a carbon dioxide-nitrogen gas mixture (N₂ : CO₂ = 6 : 4). Other fillets were wrapped with polyvinyl chloride film as a reference group. Changes in sensory score of colour and flavour, K-value and bacterial counts of the fillets were investigated during storage at 5°C. After 2 days the fillets wrapped with polyvinyl chloride film lost their gloss. In addition, an amine-like odour was detected after 3 days. The gas-packaged fillets, however, showed little change in colour, flavour and bacterial counts, and retained their fresh appearance for 3 days.     

A four-pulp flap technique for creating nail folds in the separation of a mid-digital mass in a patient with Apert's disease

Apert's disease is distinguished from other acrocephalosyndactylys by bilateral and symmetrical deformities, including symphalangism of the hands, which is commonly present in the index, long, and ring fingers. In the correction of the Apert hand, simple separation and skin grafting may be used to create a five-digit hand. However, this technique may result in narrow, atrophic fingertips, and pulp pads. In this paper, a simple technique to create nail folds and pulps for each finger with four transposition flaps from the common pulp is described. During the past 3 years, four Apert hand deformities in 2 patients were treated with this procedure. At a mean follow-up of 32 months, good results were obtained.     

Announcement

Content to volume 269     

Fine structures and fracture processes in plastic-rubber two-phase polymer systems III. Temperature dependence of Charpy impact strength

Notched Charpy impact strengths of a series of plasticrubber two-phase polymer systems were measured over a wide range of temperatures. Blends of polyvinylchloride and rubbers with varying chemical structures, and several ABS polymers were investigated. In all systems, Charpy impact strength began to increase near the T_g of the rubber component followed by a logarithmic increase with increasing temperature. The trend is expressed by the following empirical relation: where I is Charpy impact strength, A and B are constants, and T is the absolute temperature. This equation is applicable between the T_g's of the plastic and the rubber components. The increasing tendency of impact strength, i.e. the B value of the above equation, is depressed mainly by the decrease of the compatibility and/or the interfacial adhesive force between the two phases. Toughening mechanism and the ways of increasing toughness are discussed based on the craze formation mechanism.     

Ammonium hexafluorosilicate increased acid resistance of bovine enamel and dentine

Although diamine silver fluoride (AgF: (NH₃)₂AgF) stains teeth black, it is known as a very effective agent to prevent the dental caries progress. In order to find another fluoride that has a similar anticariogenic effect without changing tooth color, we prepared ammonium hexafluorosilicate (SiF: (NH₄)₂SiF₆), in which the silver of AgF is replaced with silicon. In this study, the anticariogenic effect of SiF was evaluated using bovine teeth. Fluoride solutions, SiF, AgF, acidulated phosphate fluoride (APF), and sodium fluoride (NaF), were applied to bovine enamel and dentine blocks, and the depth of demineralization was measured after exposure to a demineralizing solution for 24 h. Also, fluoride was applied to a simulated dentine caries specimen to evaluate the caries progress-preventing ability. For the dentine specimens, mineral loss ( Z) was also measured with microradiography. We found that SiF treated enamel showed better acid resistance than specimens treated with NaF or APF. AgF treated enamel also showed similar acid resistance, but was stained black. SiF and AgF treated caries-affected dentine showed reduced demineralization when exposed to a demineralization solution for 24 h. Mineral loss ( Z) was reduced to 85% and 75%, respectively. Although the acid resistance of the SiF treated teeth was inferior to that of the AgF treated teeth, we consider that SiF has good potential as anticariogenic agent, since it increased acid resistance without changing tooth color.     

Met 235 Thr polymorphism of angiotensinogen in Indonesians

PURPOSE: To report a previously undescribed cause of bilateral macular hole formation. METHOD: Case report. RESULTS: Septic emboli were noted at the center of the macula in both eyes of a 32-year-old man with acute bacterial endocarditis. Bilateral full-thickness macular holes later developed at the site of these retinal lesions. CONCLUSION: This case represents the first report of fundus lesions in septicemia resulting in full-thickness macular hole formation.