• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.35.3-35.3
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• 2018

Incorporating the fully quantum mechanical computation of scattering cross-section and statistical moment analysis of absorption profiles, we investigate the Lyman line asymmetry of extremely high column density systems. Recent high redshift observations detected strong damped Lyman alpha systems (DLAs) whose column density is larger than N_HI ~ [10]^21.3 cm^(-2). Absorption profiles of these DLAs are characterized by the broad and asymmetric damping wing. For accurate description of radiation damping, the second-order time-dependent perturbation theory is adopted. To quantitatively address line asymmetry, we define a distribution function for each Lyman line, and compute statistical moments (mean, standard deviation, skewness and kurtosis) regarding column densities N_HI > [10]^18 cm^(-2). In this work, we present statistical properties of the intrinsic line profiles, and compare them with the Lorentzian cases.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.5
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• pp.94-100
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• 2004

In order to improve the frontal crash performance of an Aluminum Space Frame Vehicle, this presents a systematic optimal design process to maximize the crush energy absorption capacity of side-members while satisfying the maximum displacement constraint. In this study, five design types are studied for selecting a good collapse initiator. Then, for the selected collapse initiator type, 7 design variables are defined to represent cross section shape, thickness and bead interval. The systematic optimization processor, R-INOPL uses DOE, RSM and numerical optimization techniques. R-INOPL uses only 14 analyses to solve the 7 design variable optimization problem the final design can improve 103.9% of the internal energy and reduce 13.9% of the maximum displacement.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.12
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• pp.1082-1086
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• 2007

Optical characteristics of $YCOB(YCa_4B_3O_{10})$, known as a crystal of self frequency doubling, was investigated when Yb and Er ions were co-doped 20 % and 2 %, respectively. The absorption cross section of Er,Yb:YCOB crystal at $1.0\;{\mu}m$ was larger than that of Yb:YCOB, which means that the former was profitable for more energy absorption than the latter. The fluorescent lifetime at $1.5\;{\mu}m$ was measured to be 1.27 ms at room temperature, and lengthened to 1.54 ms and 1.62 ms at low temperatures of 77 K and 6 K, respectively. The line widths of fluorescent spectrum at $1.5\;{\mu}m$ were getting narrower as lowering temperature. However, we didn't observe a temperature dependent peak wavelength shift.

• Journal of the East Asian Society of Dietary Life
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• v.2 no.2
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• pp.277-282
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• 1992

This study was designedto investigate changes in phsicochemical properties of rice extrudate with added glycerin fatty acid ester extruded by single screw extruder. According to emulsifier content, expansion ratio and water solubility index were represented minimum in rice extrudate with added 2.0% and 2.5% glycerin fatty acid ester. Extrudate with added 1.5% emulsifier revealed lowest break strength and bulk density, so got a tender and light texture. Meanwhile water absorption index was showed maximum at 1.5% emulsifier content. As emulsifier content increased, lightness raised. By the microstructure obsorved with image analyzer, addition of emulsifier had decreased area and fractarea of air cells of cross section of extrudates. On the results of this research, quality of extrudate with added 1.5% glycerin fatty acid ester was considered very well than 100% rice extrudate, because of tender and light texture, highest water absorption indexand fine structure with higher lightness.

• Proceedings of the Optical Society of Korea Conference
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• 2000.08a
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• pp.252-253
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• 2000

본 실험에서는 수 MW/$ extrm{cm}^2$ 의 매우 낮은 영역의 세기에서 순수한 GaAs의 bulk에 대하여 실험한 결과 비선형 흡수가 나타남을 관찰 하였으며, 더불어 자유전하 흡수 계수를 여러 가지 세기의 빛에서 측정한 결과 자유전하 흡수 단면적이 빛의 세기에 따라 변화하는 것을 관찰하였다.$^{(1)}$ GaAs의 굴절률이 3.6으로 매우 커서 Fabry-Perot 효과가 나타나므로 시료의 한쪽 면을 SiN로 무반사 코팅을 하여 실험 하였다. GaAs의 표면은 쉽게 레이저 빛에 의해 손상을 입는 것을 고려하여 같은 자리에서 여러 번의 실험을 하여 같은 결과가 나오는 것을 확인하여 실험 결과를 얻었다. 사용된 레이저는 Nd:YAG 레이저로서 1.064 $mu extrm{m}$의 파장에서 7 나노초의 펄스를 방출한다. 빛의 세기는 편광기와 half wave plate를 이용하여 변화 시켰다. (중략)

• Proceedings of the Korean Institute of Building Construction Conference
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• 2020.11a
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• pp.161-162
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• 2020

In this study, as part of securing related data, water droplets were dropped on the upper part of the wooden board for flooring in an environment such as floor heating, and the degree of absorption according to the surface temperature change was tested. The test results showed that the contact angle of the surface was low (25℃→40℃) or the droplet was absorbed into the small plate and disappeared. The contact angle of the OSB and MDF was decreased within 30 minutes, but the surface water droplet was maintained longer than the plywood. This is because the surface is coated with hydrophobicity unlike the plywood, but moisture absorption in the cross section after the second processing will not be prevented and it will lead to defect occurrence problem.

• Journal of the Optical Society of Korea
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• v.1 no.1
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• pp.10-14
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• 1997

Single pulse laser excitation at 656 nm and successive pulse excitation at 635.2 and 648.4 nm produced blue emission at 480 nm by two-step upconversion process in Tm/sup 3+/:LaF/sub 3/. The excited-state absorption cross-section of the /sup 3/F/sub 4/ to /sup 1/G/sub 4/ transition was estimated by a looping mechanism with cross-relaxation processes. The dynamics of up-conversion andthe possibility of the photon avalanche by a pulse laser excitation were studied by numerical simulation with the rate equation model.

• The Journal of the Acoustical Society of Korea
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• v.37 no.4
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• pp.181-187
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• 2018

In this paper, sound absorption of micro-perforated elastic plates installed in an impedance tube of a circular cross-section is discussed using an analytic method. Vibration of the plates and sound pressure fields inside the duct are expressed in terms of an infinite series of modal functions, where modal functions in the radial direction is given in terms of the Bessel functions. Under the plane wave assumption, a low frequency approximation is derived by including the first few plate modes, and the sound absorption coefficient is given in terms of an equivalent impedance of a single surface. The sound absorption coefficient using the proposed formula is in excellent agreement with the result by the FEM (Finite Element Method), and shows dips and peaks at the natural frequencies of the plate. When the perforation ratio is very small, the sound absorption coefficient is dominated by the vibration effect. However, when the perforation ratio reaches a certain value, the sound absorption is mainly governed by the rigid MPP (Micro-Perforated Plate), while the vibration effect becomes very small.

• Composites Research
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• v.19 no.1
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• pp.29-35
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• 2006

The avoidance of enemy's radar detection is very important issue in the modem electronic weapon system. Researchers have studied to minimize reflected signals of radar. In this research, two types of radar absorbing structure (RAS), 'C'-type shell and 'U'-type shell, were fabricated using fiber-reinforced composite materials and their radar cross section (RCS) were evaluated. The absorption layer was composed of glass fiber reinforced epoxy and nano size carbon-black, and the reflection layer was fabricated with carbon fiber reinforced epoxy. During their manufacturing process, undesired thermal deformation (so called spring-back) was observed. In order to reduce spring-back, the bending angle of mold was controlled by a series of experiments. The spring-back of parts fabricated by using compensated mold was predicted by finite element analysis (ANSYS). The RCS of RAS shells were measured by compact range and predicted by physical optics method. The measured RCS data was well matched with the predicted data.

• Journal of The Korean Astronomical Society
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• v.47 no.5
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• pp.187-193
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• 2014

Recent cosmological observations indicate that the reionized universe may have started at around z = 6, where a significant suppression around $Ly{\alpha}$ has been observed from the neutral intergalactic medium. The associated neutral hydrogen column density is expected to exceed $10^{21}cm^{-2}$, where it is very important to use the accurate scattering cross section known as the Kramers-Heisenberg formula that is obtained from the fully quantum mechanical time-dependent second order perturbation theory. We present the Kramers-Heisenberg formula and compare it with the formula introduced in a heuristic way by Peebles (1993) considering the hydrogen atom as a two-level atom, from which we find a deviation by a factor of two in the red wing region far from the line center. Adopting a representative set of cosmological parameters, we compute the Gunn-Peterson optical depths and absorption profiles. Our results are quantitatively compared with previous work by Madau & Rees (2000), who adopted the Peebles approximation in their radiative transfer problems. We find deviations up to 5 per cent in the Gunn-Peterson transmission coefficient for an accelerated expanding universe in the red off-resonance wing part with the rest wavelength ${\Delta}{\lambda}{\sim}10{\AA}$.