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Noise Barrier with 2-D Partition Lattice
Sung Soo Jung,S. I. Cho,W. S. Lee,Y. B. Lee 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.51
Noise barrier with a 2-D partition lattice of rectangular plate assembled on its top edge was developed. Its acoustical characteristics were investigated by using the boundary element method (BEM). The insertion loss calculated with the BEM was compared with the measured values obtained from the reduced scale model test. The results showed that the insertion loss of the noise barrier with a 2-D partition array was similar to that of the noise barrier with a 3-D partition lattice. Finally, a eld test was performed at the test track of the Korea high speed train, Korea Train Express (KTX). When the insertion loss of the new noise barrier was compared to that of a simple noise barrier with the same height, an average 2.3-dB additional noise reduction was observed.
A complementary method to determine the effective flow resistivity of the flat ground states
Sung Soo Jung,Cheol-Ho Hwang 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.4
A complementary method to keep a speaker and microphones vertical for determining the sound pressure level dierence was proposed to determine the eective ow resistivities of several ground states. The method could be well applied to at ground and the sound pressure level dierences measured had less scattering than those obtained by using the ordinary method which kept the speaker and the microphones horizontal. The ow resistivity of a cabbage farm was newly estimated as 200 cgs rayls. In the case of a rice plant, we estimated a ow resisitivity of 2 cgs rayls with the new analysis.
Level Gauge by Using Acoustic Resonance Frequency
Sung Soo Jung,Cheon-Woo Kim,Seung Il Cho,김용태 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.43 No.51
An acoustic level gauge which is based on the acoustic resonance in a waveguide was developed. Its stability was tested by measuring the rst resonance frequency spectrum, and good agreement between the measured and the theoretically predicted values was obtained. As testing materials, distilled water was used as the liquid and wheat our, sugar, or salt as the loose materials. In the cases of loose materials, the air-loose material contact surface could no longer act as a rigid boundary. The measured resonance frequency was lower than the theoretical one because the sound was able to radiate into the loose material and a virtual boundary was formed not at the real airmaterial contact surface but at some location in the loose material. An acoustic level gauge which is based on the acoustic resonance in a waveguide was developed. Its stability was tested by measuring the rst resonance frequency spectrum, and good agreement between the measured and the theoretically predicted values was obtained. As testing materials, distilled water was used as the liquid and wheat our, sugar, or salt as the loose materials. In the cases of loose materials, the air-loose material contact surface could no longer act as a rigid boundary. The measured resonance frequency was lower than the theoretical one because the sound was able to radiate into the loose material and a virtual boundary was formed not at the real airmaterial contact surface but at some location in the loose material.
InfluenceoftheWaterVaporContentontheHydrogenReductionProcessofNanocrystallineNiO
( Sung Soo Jung ),( Hyo Sang An ),( Jai Sung Lee ) 대한금속재료학회 ( 구 대한금속학회 ) 2010 대한금속·재료학회지 Vol.48 No.4
In this study, the hydrogen reduction behavior of ball-milled NiO nanopowder was investigated depending on the partial pressure of water vapor. The hydrogen reduction behavior was analyzed by thermogravimetry and hygrometry under heating to 873 K in hydrogen. In order to change the partial pressure of the water vapor, the dew point of hydrogen was controlled in the range of 248 K~293 K by passing high-purity hydrogen through a saturator that contained water. Interestingly, with the increase in the dew point of the hydrogen atmosphere, the first step of thehydrogen reduction process decreased and the second step gradually increased. After the first step, apore volume analysis revealed that the pore size distribution in the condition with ahigher water vapor pressure shifted to a larger size, whereasthe opposite appearedat a lower pressure. Thus, it was found that the decrease in the pore volume during the chemical reaction controlled process at a dew point of 248 K caused a reduction in retardation in the diffusion controlled process. (Received November 18, 2009)
Sound Absorption of Micro-Perforated Panel
Sung Soo Jung,Doo Hee Lee,Ho Chul kim,이종규,Seung Il Cho,Yong Tae Kim 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.4
Theoretical sound absorption coefficient and profile of micro-perforated single-, double-, and triple-layer systems with varying panel parameters were calculated by using the lumped and the distributed models for acoustic impedances. The sound absorption levels and profiles predicted by using the distributed model with Maa’s acoustic impedance showed a close agreement for all panel systems with those obtained experimentally by using impedance-tube and reverberation-room tests.
Sung Soo Jung,Duckwhan Kim,Kim Ho Chul,Su Hyun Shin,Yong Bong Lee,Yong Tae Kim 한국물리학회 2006 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.49 No.5I
An acoustic velocity sensor, micro-flown, was used to monitor the vibration signal in measurements of the resonance frequency, the loss factor, and the dynamic Young’s modulus of structural steel and polycarbonate by using a resonance method. The results showed that the measured loss factors of the structural steel and polycarbonate used in the present specimen were 0.0023 and 0.056, respectively, and the Young’s moduli were 198.4 GPa and 2.4 GPa. The values measured with micro-flown agreed with those obtained with a conventional displacement sensor and with the theoretically estimated and reference values. The agreements ensure the reliability of the use of a micro-flown acoustic velocity sensor in measuring the resonance frequency, the loss factor, and the dynamic Young’s modulus.