• Korean Journal of Optics and Photonics
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• v.10 no.4
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• pp.328-334
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• 1999

Methylene blue-sensitized photopolymerizable material based on acrylamide is investigated with two-wave energy coupling experiments. Differently from other studies, self-diffraction oscillations are observed and the grating phase is determined without applying external electric fields, moving nonlinear materials, and phase shifting one of two writing beams. The phase grating showed a phase shift of $\pm$50$^{\circ}$ with respect to the intensity grating. Modified Kogelnik's coupled wave equation considering the mixed gratings of phase and absorption gratings and nonzero spatial phase shifts of the gratings with respect to the intensity interference patterns formed during the two-wave energy coupling is discussed in detail to understand these phenomenon.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.20 no.3
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• pp.1083-1095
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• 1996

Shock wave/boundary layer interaction frequently causes the shock wave to oscillate violently and thus the global flow field to unstabilize. In order to stabilize the shock wave system in the diffuser of a supersonic wind tunnel, the present study attempted to control the shock oscillations by using a passive control. A porous wall with the porosity of 19.6% was mounted on a shallow cavity. Experiment was made by means of schlieren optical observation and wall pressure measurements. The flow Mach number just upstream the shock system and Reynolds number based on the turbulent boundary layer thickness were 2.1 and 1.8 * 10$\^$6/, respectively. The results show that the present passive control method on the shock wave/boundary layer interaction in the supersonic diffuser can significantly suppress the oscillations of shock system, especially when the shock system locates at the porous wall.

• Journal of Energy Engineering
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• v.13 no.3
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• pp.205-213
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• 2004

Usefulness of an optical fiber was demonstrated by detecting the generation of self-excited combustion oscillations. OH chemiluminescence intensity detected by the optical fiber showed mostly excellent agreement with those obtained by high speed CCD camera measurements when combustion oscillations were strong. Symptoms of self-excited combustion oscillation were also studied in order to predict the onset of combustion oscillation before it proceeded to a catastrophic failure. For the purpose, we have found and proposed unique measures to tell the onset of self-excited combustion oscillations based on the careful statistics of fluctuating properties in flames, such as pressure or omission of OH radicals.

• The Bulletin of The Korean Astronomical Society
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• v.12
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• pp.7.3-8
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• 1987

• 한국전기화학회:학술대회논문집
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• 2002.07a
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• pp.171-174
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• 2002

• 한국전기화학회:학술대회논문집
• /
• 2002.07a
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• pp.25-28
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• 2002

• 한국전산유체공학회:학술대회논문집
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• 2008.08a
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• pp.53.2-53.2
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• 2008

• Bulletin of the Korean Space Science Society
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• 2006.04a
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• pp.63-63
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• 2006

• 대한약리학회:학술대회논문집
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• 2006.11a
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• pp.59-59
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• 2006

• Kyungpook Mathematical Journal
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• v.32 no.2
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• pp.159-166
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• 1992