• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.673-675
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• 2011

본 연구에서는 매립 구간의 길이가 유도초음파 신호 강도에 미치는 영향을 분석하였다. 유도초음파 모드 해석을 통해 가진 모드와 주파수를 결정하였으며, 유도초음파의 가진 및 수진은 경사각 입사 방식의 Pitch-Catch 법을 이용하였다. 또한, 비 매립된 배관에서 유도초음파 신호를 획득하여, 이를 기준으로 매립된 배관에서 획득한 유도초음파 신호를 분석하였다. 실험 결과 매립 구간의 길이가 유도초음파의 신호 강도에 매우 큰 영향을 미칠 뿐만 아니라, 매립 구간의 길이와 신호 강도의 변화가 선형 비례적인 관계를 보이지 않는다는 것을 확인할 수 있었다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.9
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• pp.859-866
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• 2008

A guidance scheme for controlling the relative geometry of multiple flight vehicle formation flying is proposed. Each flight vehicle in the formation takes the roles of leader and follower simultaneously except for the formation leader. In this scheme, the flight commands for a leader are shared by all the followers and this leaders to a synchronized flight of all flight vehicles comprising the formation. Lyapunov stability theorem is used to obtain the guidance law. High fidelity nonlinear simulation results are presented to show the effectiveness of the proposed guidance law using a reconnaissance and surveillance mission example.

• Applied Biological Chemistry
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• v.36 no.1
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• pp.1-6
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• 1993

Chitinase was induced in rice cell suspension culture with treatment of chitooligosaccharides mixture. Among eleven isozymes found in 10% polysacrylamide gel electropherogram, four isozymes were identified as induced enzymes. Acidic chitinase fraction separated in DEAE-cellulose column chromatography, includes three induced chitinase, while basic fraction contains only one induced isozyme. Treatment of chitooligosaccharides mixture enhanced the contents in both protein and chitinase activity in cell suspension culture media, but increase in chitinase activity was much higher than in protein.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.203-211
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• 2006

This paper presents a new, effective torsional constant for thin-waled open beams under concentrated and uniformly distributed torques. The proposed constant can be used directly, instead of the St. Venant torsional constant, for any generic comemrcial finite-element program, without modifying the algorithm. The derived torsional constant accounts for both the pure torsion and the warping torsion, and is equal to the St. Venant torsion constant times a correction factor. It is also shown, in the case of the St. Venant torsion, that the derived constant is identical to the torsional constant. The derived effective torsional constant is different from the one given by Elhelbawey et al. The pure torsional shear stress, the warping shear stress, and the warping normal stress were also determine d, using the maximum twisting angle. The accuracy of the proposed torsional constant was validated by comparing the numerical results with the closed-form solutions or other numerical results available in the literature.

• Journal of Life Science
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• v.29 no.1
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• pp.18-28
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• 2019

Recent studies reported that obesity upregulated the expression of neuronal nitric oxide synthase (nNOS) and regulated particular behavior patterns in animal models. They also reported that ameliorated the increase in nNOS expression and decreased depression and anxiolytic effects. Thus, exercise seems to be an effective strategy for improving brain function by downregulating nNOS. However, the immune response differs greatly, depending on the exercise intensity. The aim of the present study was to investigate differences in brain nNOS expression in obese C57BL/6 mice that performed exercise of different intensities. Obesity was induced in 6-wks-old mice (n=35) by feeding a 60%-fat diet for 6-wks. A control (CON) group (n=14) was fed a normal diet. At the end of the induction 6-wks period of obesity, seven animals in the CON group and obesity-induced group were sacrificed to confirm obesity induction (preliminary experiments and confirmation of visceral fat accumulation). The remaining animals were then used in an 8-wks exercise intervention. Other than the CON (n=7), the obesity-induced animals were divided into the following groups: high-fat diet (HFD, n=7), HFD-low intensity (HFD-LI, n=7, 12 m/min for 75 min), HFD-moderate intensity (HFD-MI, n=7, 15 m/min for 60 min), and HFD-high intensity (HFD-HI, n=7, 18 m/min for 50 min). The exercise was performed on an animal treadmill. The expression of the nNOS protein in the hippocampus was significantly higher in the HFD group as compared with that in the CON group (p<0.01). However, there was no difference in the hippocampal expression of the nNOS protein in the other exercise groups as compared with that in the CON group. In contrast, nNOS expression in the HFD-HI group was significantly lower than that in the HFD-LI group (p<0.05). The expression of phosphorylated Akt (pAkt) was significantly higher in all the exercise groups as compared with that in the CON and HFD groups. There was no difference in the expression of pAkt in the cerebral cortex among groups, and the expression of pAkt in the cerebellum was significantly higher in the HFD-HI group as compared with that in the CON group (p<0.05). There were also no between-group differences in pAkt expression in the cerebellum among the various exercise groups. In conclusion, nNOS seems to be overexpressed in response to obesity, and it appears to be downregulated by exercise. Relatively high-intensity exercise may be effective in improving brain function by downregulating nNOS.

• Journal of the Korean Magnetics Society
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• v.8 no.5
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• pp.261-269
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• 1998

Induced anisotropy with the energy of $6{\times}10^4\; J/m^3$ is obtained in amorphous Sm-Fe based thin films which are fabricated by rf magnetron sputtering under a magnetic field of 500~600 Oe. Compared with conventional thin films, the anisotropic thin films exhibit a similar "saturation" magnetostriction, but show a very large anisotropy in magnetorstiction which is of significant practical importance due to increased strain at a particular direction. It is shown from a systematic investigation over a wide composition range for binary Sm-Fe alloys that anisotropy is also induced, though small, during a normal sputtering procedure due to the stray field, and the largest anisotropy is observed in the composition range of 25~30 at.% Sm. Furthermore, induced anisotropy is also found to be formed by magnetic annealing, but the anisotropy energy is much smaller than that by magnetic sputtering. This may be because the volume diffusion by which atoms move during magnetic annealing to from induced anisotropy is much slower than the surface diffusion which is expected to be a dominant factor during magnetic sputtering.puttering.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.49 no.8
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• pp.627-636
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• 2021

This paper deals with a study for the guidance control of reusable launch vehicle. For this purpose, modeling of the equation of motion of a reusable launch vehicle with 6 degrees of freedom was performed. With this model, an optimal re-entry path was created and a path-following guidance control simulation was performed to follow the optimal re-entry path. For the design of the path-following guidance controller, the attitude controller applying a time-delay technique that is resistant to modeling uncertainty, disturbance and failure. And the nonlinear path-following guidance law were used. Guidance control simulation using a classical PD controller was performed and compared with the guidance control simulation of a reusable launch vehicle applying a time delay technique.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.2
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• pp.127-136
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• 2007

In this paper, the equations of the scaled boundary finite element method are derived for non-homogeneous half plane and analyzed numerically In the scaled boundary finite element method, partial differential equations are weaken in the circumferential direction by approximation scheme such as the finite element method, and the radial direction of equations remain in analytical form. The scaled boundary equations of non-homogeneous half plane, its elastic modulus varies as power function, are newly derived by the virtual work theory. It is shown that the governing equation of this problem is the Euler-Cauchy equation, therefore, the logarithm mode used in the half plane problem is not valid in this problem. Two numerical examples are analysed for the verification and the feasibility.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.57-57
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• 2011

저차원 나노구조인 자발형성 양자점은 그 우수한 전기적, 광학적 특성으로 많은 주목을 받고 있다. 이미 양자점을 이용한 소자들의 우수성이 입증이 되고 있다. 그러나 양자점의 형성은 단결정 기판 위에서 Stranski-Krastanow 성장 방법을 통해 일어나기 때문에 성장표면에 존재하는 표면 계단구조 등의 국부적인 표면 불균일성에 의해서 모두 동시에 형성되는 것은 아니다. 표면 핵생성의 시간차에 의해 양자점의 크기 불균일성이 나타나게 되며 이는 양자점의 우수성을 저해하는 요인이 된다. 특히, 비정상적으로 크게 성장된 양자점은 내부에 전위 등의 결정결함을 내포하게 되고, 양자점의 우수한 광특성을 손상시키는 주 요인이 된다. 양자점의 우수한 광특성을 소자로 응용하기 위해서는 이러한 비정상적으로 큰 양자점이 없으면서 균일한 양자점을 성장하는 것이 매우 필요하다. 본 발표에서는 그 동안 본 연구실에서 제안한 새로운 양자점 성장 방법에 대한 소개를 하고자 한다. 유기화학금속화학성장(Metal Organic Chemical Vapor Deposition) 도중에 V족 소스가스인 $AsH_3$의 주입을 주기적으로 끊어 주는 새로운 성장 방법(Periodic Arsine Interruption; PAI)을 제안하였다. 이 방법을 통해서 비정상적으로 형성되는 큰 양자점을 완전히 제거할 수 있었다. $AsH_3$을 끊어주는 시간 동안에 표면에서 As의 탈착을 유도하여 표면을 In-rich 쪽으로 유도하였고, 이렇게 함으로써 성장 표면에너지를 높은 쪽으로 바꾸어 줌으로써 핵생성을 위한 표면 roughening이 시작되는 것을 억제하였다. 이렇게 함으로써 미리 핵생성이 되어 비정상적으로 크게 성장하는 양자점으로 억제하면서 거의 동시에 모든 양자점이 핵생성되게 유도하였다. $AsH_3$의 주입 방법의 변화에 따른 양자점의 형성 거동을 연구함으로써 PAI 의 메카니즘을 이해할 수 있었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.16 no.2
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• pp.1-13
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• 2012

Seismic fragility functions are derived for probabilistic evaluation of seismic control performance of energy dissipation devices installed in reinforced concrete structures. Displacement-dependent dampers are added to the nonlinear single-degree-of-freedom systems with different natural periods and hysteretic characteristics of which stiffness and strength has uncertainty. Nonlinear time history analysis is conducted for those SDOF systems and the result is processed statistically to obtain seismic fragility functions in the form of log normal distribution. Variation of seismic fragility functions for different parameters of SDOF systems and dampers are investigated and the seismic control performance is assessed probabilistically.