• 한국전산유체공학회지
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• 제11권1호
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• pp.29-35
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• 2006

A code is developed to analyze a spherically symmetric underwater explosion. The arbitrary Lagrangian-Eulerian(ALE) Godunov scheme for two-phase flow is used to calculate numerical fluxes through moving control surfaces. For detonation gas of TNT and liquid water, the Jones-Wilkins-Lee(JWL) equation of states and the isentropic Tait relation are used respectively. It is suggested to use the Godunov variable to estimate the velocity of a material interface. The code is validated through comparisons with other results on the gas-water shock tube problem. It is shown that the code can handle generation of discontinuity and recovering of continuity in the normal velocity near the material interface during shock waves interact with the material interface. The developed code is applied to analyze a spherically symmetric underwater explosion. Repeated transmissions of shock waves are clearly captured. The calculated period and maximum radius of detonation gas bubble show good agreements with experimental and other numerical results.

• Advances in aircraft and spacecraft science
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• 제4권5호
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• pp.503-514
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• 2017

The attitude control of an aircraft is usually fulfilled by means of thrusters at high altitudes. Therefore, the possibility of using also aerodynamic surfaces would produce the advantage of reducing the amount of fuel for the thrusters to be loaded on board. For this purpose, Zuppardi already considered some aerodynamic problems linked to the use of a wing flap in a previous paper. A NACA 0010 airfoil with a trailing edge flap of 35% of the chord, in the range of angle of attack 0-40 deg and flap deflections up to 30 deg was investigated. Computer tests were carried out in hypersonic, rarefied flow by a direct simulation Monte Carlo code at the altitudes of 65 and 85 km of Earth Atmosphere. The present work continues this subject, considering the same airfoil and free stream conditions but two flap extensions of 45% and 25% of the chord and two flap deflections of 15 and 30 deg. The main purpose is to compare the influence of the flap dimension with that of the flap deflection. The present analysis is carried out in terms of: 1) percentage variation of the global aerodynamic coefficients with respect to the no-flap configuration, 2) increment of pressure and heat flux on the airfoil lower surface due to the Shock Wave-Shock Wave Interaction (SWSWI) with respect to the same quantities with no SWSWI or in no-flap configuration, 3) flap hinge moment. Issues 2) and 3) are important for the design of the mechanical and thermal protection system and of the flap actuator, respectively. Under the above mentioned test and geometrical conditions, the flap deflection is aerodynamically more effective than the flap extension, because it involves higher variation of the aerodynamic coefficients. However, tests verify that a smaller deflection angle involves the advantage of a smaller increment of pressure and heat flux on the airfoil lower surface, due to SWSWI, as well as a smaller hinge moment.

• EDISON SW 활용 경진대회 논문집
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• 제5회(2016년)
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• pp.604-609
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• 2016

슬롯판을 이용한 경사충격파와 경계층 간섭유동 제어에서, 슬롯판 아래에 있는 공동부의 형상을 바꾸어 가며 제어 성능을 비교하는 수치적 연구가 수행되었다. 공동형상 직사각형 5개, 사다리꼴 3개를 선정하여 shock 뒤에서 경계층 안정성, 전압손실을 기준으로 제어 성능을 평가하였다. 수치해석 결과 모든 형상에 대해 제어하지 않은 상태보다 좋은 성능을 얻었다. 그 중 경계층 안정성 측면에서는 형상 L과 R, 전압손실 감소 측면에서는 형상 M과 A가 효과적임을 확인하였고, 종합적으로 슬롯의 끝 면과 공동의 길이방향 끝 면이 일치하는 형상에서 상대적으로 좋은 결과를 얻음을 확인했다. 또한 슬롯과 공동 내부유동을 분석하면서 경계층 안정성과 전압손실 감소에 영향을 미치는 것은 separation 영역을 얼마 원활히 흡입하는지의 여부임을 알 수 있었고, 상류 슬롯에서 발생하는 shock에 대한 추후 해결 연구도 필요함을 알 수 있었다.

• 한국재료학회지
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• 제29권2호
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• pp.106-115
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• 2019

Recently, metal cases are widely used in smart phones for their luxurious color and texture. However, when a metal case is used, electric shock may occur during charging. Chip capacitors of various values are used to prevent the electric shock. However, chip capacitors are vulnerable to electrostatic discharge(ESD) generated by the human body, which often causes insulation breakdown during use. This breakdown can be eliminated with a high-voltage chip varistor over 340V, but when the varistor voltage is high, the capacitance is limited to about 2pF. If a chip capacitor with a high dielectric constant and a chip varistor with a high voltage can be combined, it is possible to obtain a new device capable of coping with electric shock and ESD with various capacitive values. Usually, varistors and capacitors differ in composition, which causes different shrinkage during co-firing, and therefore camber, internal crack, delamination and separation may occur after sintering. In addition, varistor characteristics may not be realized due to the diffusion of unwanted elements into the varistor during firing. Various elements are added to control shrinkage. In addition, a buffer layer is inserted in the middle of the varistor-capacitor junction to prevent diffusion during firing, thereby developing a co-fired product with desirable characteristics.

• 대한의용생체공학회:의공학회지
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• 제41권5호
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• pp.203-209
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• 2020

As the number of people with gait disorders increases, the demand for using wheelchairs increases and the area of a ctivity for people with disabilities expands, thereby they increasing the demand for riding comfortability in various driving environments. Therefore, this study is to develop an entry-level active suspension system that apply to wheelchairs and to evaluate its usability. The suspension applied in this paper consists of a coil spring, a shock absorber, a control module to control the strength of the shock absorber, and a road surface condition monitoring system. A wheelchair occupant secures the riding comfort by adjusting the coil strength of the shock absorber in 12 steps according to various road conditions. Therefore, the mechanical properties were evaluated through the structural analysis of the suspension system, and the tendency toward the magnitude of the road surface vibration attenuated according to the rigidity of the suspension through the vibration test was attempted. In conclusion, as a result of structural analysis of the suspension system, stress in a range lower than the yield strength of the material was generated, and the vibration test showed the effect of attenuating the vibration generated from the road surface when the stiffness of the suspension was adjusted.

• 한국양식학회지
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• 제8권3호
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• pp.159-170
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• 1995

참전복의 3배체 유도를 위하여 수정 12분후 및 32분 후에 저온$(0^{\circ}C\;,\;3^{\circ}C)$해수 혹은 고온$(35^{\circ}C\;,\;40^{\circ}C)$ 해수 속에서 여러 처리 지속 시간으로 3배체 유도 실험을 한 결과, 수정율은 실험군 사이에 유의한 차가 없었다. (P>0.05). 그러나 부화율과 정상발생율은 3배체구간 2배체 대조구보다 유의하게 낮았다. (P<0.05). $40^{\circ}C$의 고온처리구에서 수정율은 매우 낮았고$(0\~2.7\%)$ 부화되는 유생은 없었다. 3배체 유도율은 염색체수를 직접 계수해서 구했는데 가장 높은 3배체 유도율은 수정 12분 후에 $3^{\circ}C$ 해수에 15분 동안 처리했을 때 $(84.0\%)$였다. 참전복 2배체의 염색체 수는 2n=36이었고 3배체의 염색체 수는 3n=54이었다.

• 약학회지
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• 제44권5호
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• pp.470-477
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• 2000

WooHwangChungSimWon is a traditional medicine for treatment of hypertension, arteriosclerosis, coma, and stroke in China, Korea, and Japan. In the new prescription of WooHwangChungSimWon, the civet is substituted for the musk, the major component of WooHwangChungSimwon, because of the prohibition law about the musk. We have made a comparative study of the effects on the central nervous system between the musk containing and civet containing WooHwangChungSimWon. In order to investigate the effects on the central nervous system, we have examined spontaneous motor activities, anti-convulsion activities induced by chemicals or electric shock, sleep induced by hexobarbital, and antistress effects. In the examination of anti-convulsion effects against the electric shock and injection of pentetrazol, only the civet containing WooHwangChungSimWon showed the anti-convulsion effects, i.e. the duration of convulsion by electric shock was decreased (control: 104.0 seconds, low dose of civet containing WooHwangChungSimWon: 60.7 seconds) and the duration of suppression against pentetrazol induced convulsion was increased (control: 392.3 seconds, low dose of civet containing WooHwangChungSimWon: 574.0 seconds, high dose of civet containing WooHwangChungSimWon: 561.4 seconds). In the other examinations, all kinds of WooHwangChungSimWon showed sedation, anti-convulsion activities, and induction of sleeping. These results suggest that there are no significant differences between the musk containing and civet containing WooHwangChungSimWon except the anti-convulsion effects against the convulsions induced by electric shock and pentetrazol.

• Journal of Microbiology and Biotechnology
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• 제15권4호
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• pp.831-837
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• 2005

Low-temperature adaptation and cryoprotection were studied in Leuconostoc mesenteroides SYl, a strain isolated from Kimchi. L. mesenteroides SY1 cells grown in exponential growth phase at $30^{\circ}C$ were exposed to $15^{\circ}C,\;10^{\circ}C$, and $5^{\circ}C$ for 2, 4, and 6 h, respectively, and then frozen at $- 70^{\circ}C$ for 24 h. Survival ratio was measured after the cells were thawed. The freezing-thawing cycles were repeated four times. Preadapted cells survived better than non-adapted control cells, and the highest survival ratio ($96\%$) was observed for cells preadapted for 2 h at $5^{\circ}C$, whereas control cells showed only $22\%$. The 2D gel showed that two proteins (spots A and B) were induced in cells preadapted at lower temperatures. Spots A and B have the same molecular weight (7 kDa), but the pI was 4.6 for spot A and 4.3 for spot B. The first 29 and 15 amino acid sequences from spots A and B were determined, and they were identical, except for one amino acid. A csp gene was cloned, and nucleotide sequencing confirmed that the gene encoded spot A cold shock protein.

• 대한기계학회논문집A
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• 제40권9호
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• pp.801-805
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• 2016

플러그인 하이브리드 전기자동차는 내연기관과 전기모터를 동력원으로 사용하며 주행 상황에 따라 다양한 주행 모드을 갖는다. 주행 모드에는 전기모터로만 주행하는 EV 모드(전기주행), 내연기관으로 주행하는 엔진 운전 모드, 두 개의 동력원을 이용하는 HEV 모드(하이브리드 주행)가 있다. 특히 병렬형 구조를 갖는 하이브리드 전기자동차는 모드변환에 따라 엔진 클러지가 접합되거나 해제되는데, 클러치 접합 시 나타나는 충격은 차량의 승차감에 영향을 주기 때문에 중요하다. 본 논문에서는 플러그인 하이브리드 전기자동차의 성능 시뮬레이터를 MATLAB/Simulink를 이용하여 개발하고, 시뮬레이션 결과를 통해 엔진 클러치 접합 시 나타나는 충격 특성을 분석하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2005년도 창립60주년 기념 추계 학술대회
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• pp.82.1-82.1
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• 2005