Time filter

Source Type

buk, South Korea

Kim H.J.,Korea Aerospace Research Institute | Cha J.-P.,Poongsan Corporation | Song J.-K.,Korea Aerospace Research Institute | Ko Y.S.,Chungnam National University
Journal of Sound and Vibration | Year: 2010

An acoustic cavity was selected as a stabilization device to control high-frequency combustion instabilities in gas turbines or liquid rocket engine combustors, and the acoustic damping capacity of the acoustic cavity was investigated for various geometric configurations under atmospheric non-reacting conditions. The tuning frequency of the acoustic cavity and the acoustic responses of a model chamber with a single acoustic cavity were studied first. Damping capacity was initially quantified through the frequency width of two split modes and the amplitude-damped ratio. The results showed that the cavity with the largest orifice area or the shortest orifice length was the most effective in acoustic damping of the harmful resonant mode. The effect of the number of cavities on acoustic damping capacity was also studied. Damping capacity was improved by increasing the number of cavities. For a better evaluation of acoustic damping capacity, two quantified parameters; the acoustic absorption, meaning the damping efficiency, and acoustic conductance, meaning the acoustic power loss, were introduced. The case was observed that has had insufficient loss of acoustic power in spite of having the highest absorption efficiency. As a result, fine geometric tuning for the acoustic cavity is required for the sufficient passive control. Also, the choice of the number of cavities is important to optimize the damping efficiency and absolute damping loss in consideration of the restriction of the cavity volume. © 2010 Elsevier Ltd. All rights reserved.

Poongsan Corporation | Date: 2014-07-08

Rifle ammunition; bullets; air pistol bullets; ammunition and projectiles; bodies of shell; gunpowder; guns; rifles; firing platforms; cartridge cases; firearms.

A copper alloy material for electrical and electronic components and a method of preparing the same are disclosed. In particular, a copper alloy material with excellent mechanical strength characteristics, high electrical conductivity, and high thermal stability as a material for information transmission and electrical contact of connectors or the like for home appliances and automobiles, including semiconductor lead frames and a method of preparing the same are disclosed.

A copper alloy includes Si to facilitate deoxidation, and can be easily manufactured even when including elements such as Cr or Sn. The copper alloy has high conductivity and high workability without negatively affecting the tensile strength. The copper alloy consists of 0.2 to 0.4 wt % of Cr, 0.05 to 0.15 wt % of Sn, 0.05 to 0.15 wt % of Zn, 0.01 to 0.30 wt % of Mg, 0.03 to 0.07 wt % of Si, with the remainder being Cu and inevitable impurities. A method for manufacturing the copper alloy includes obtaining a molten metal having the described composition; obtaining an ingot; heating the ingot at a temperature of 900-1000 C. to perform a hot rolling process; cold rolling; performing a first aging process at a temperature of 400-500 C. for 2 to 8 hours; cold rolling; and performing a second aging process at a temperature of 370-450 C. for 2 to 8 hours.

Poongsan Corporation | Date: 2010-07-20

The present invention relates to a method of manufacturing a high purity copper (Cu) powder material useable in fabricating a sputtering target material for electronic industrial applications, for example a penetrator liner. The foregoing method has a configuration of using an apparatus composed of a raw material feeder, a plasma torch and a reactor to prepare a metal powder, and includes steps of passing a Cu powder having an average particle diameter of 30 to 450 m through the thermal plasma torch at an introduction rate of 2 to 30 kg/hr. to thereby fabricate a Cu powder having an average particle diameter of 5 to 300 m.

Discover hidden collaborations