Noise levels of the three subway lines of Busan city have been investigated. Averaged cabin noise of the train has been measured during the train trip for each station. It has been measured with separation of day time (9:00~18:00) and night time (18:00~22:00) measurements but there was no big difference on the measured data. Repeating for the measured data has been confirmed with twice measurements in May and June 2010. Several noise effects to the subway noise levels of Busan are explained. Those are screen door effect, rail road surface condition, subway train type and curvature of railway. Among three subway lines of Busan city, the line 2 is relatively noisy and its reasons are studied. It has been shown that the screen door effect is 10 dB(A) and S shape of sharp curve contributes in high noise level
Polypropylene was treated with low pressure glow discharge plasma for the introduction of functional groups in its surface using plasma of different types. For this purpose plasma containing nitrogen and hydrogen and coating by deposition of thin plasma polymerized layers of functional group carrying monomer with NH 2 on it were used. The surface elemental composition was changed stoichiometrically by adjusting the plasma conditions depending on the feeding and plasma density. The optimum power plays an important role in the control of surface reactions between surface reactive species and plasma reactive species. Plasma-Polymerized-Allylamine (PPAa) thin film prepared with r.f. continuous and pulse wave power was characterized to study surface amine functionality. The surface amine content of PPAa at r.f. pulse wave power could be retained more efficiently than that of PPAa at r.f. continuous wave power because of less fragment of monomer. The stability test of r.f. pulse wave plasma polymerization indicated that the deposits of PPAa at the high r.f. pulse wave power were more stable than those at low r.f. pulse wave power after soaking it in tetrahydrofuran (THF).
To solve the combustion instability, especially chuffing phenomena, happened during development process of a drive-away motor that was required for cold launch system of missile, various technical approaches have been performed through ground firing tests. The ignition energy or its supply system, generally closely related with the chuffing phenomena, does not affect suppression of the chuffing, but the increase of characteristic length(L*) as well as the addition of 2% ZrC as a damping material is effective to suppress the chuffing. Therefore we could have a typical experience on the combustion instability in double base propellant.
The combustion pressure and thrust of aft-igniter were measured to investigate the characteristics of ignition charge. Granule and pellet shape ignition charge of BKNO3 and MTV(Magnesium-Teflon-Viton) were used for igniters. Ignitions with granule charges show abrupt increases of combustion pressure and thrust compared to those of pellet charge. BKNO3 igniter shows higher combustion pressure than MTV igniter due to higher combstion rate.Mg particle size affects the combustion pressure of MTV igniter.
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