• 한국전산유체공학회지
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• 제16권1호
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• pp.36-41
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• 2011

Numerical simulation of air-launched rockets from a helicopter was conducted to investigate the aerodynamic interference between air-launched rocket and helicopter. For this purpose, a three-dimensional inviscid flow solver has been developed based on unstructured meshes. An overset mesh technique was used to describe the relative motion between rocket and rocket launcher. The flow solver was coupled with six degree-of-freedom equation to predict the trajectory of free-flight rockets. For the validation, calculations were made for the impinging jet with inclined plate. The rotor downwash of helicopter was calculated and applied to simulation of air-launched rocket. It is shown that the rotor downwash has non-negligible effect on the air-launched rocket and its plume development.

• 대한전기학회논문지:전력기술부문A
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• 제55권7호
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• pp.290-296
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• 2006

If the three phases are not balanced, the current in neutral wire is not zero. Then, the induced voltage can be generated in communication line. The KEPCO's rule about unbalanced current for one step type in distribution pole is a twenty percent of phase current. But the unbalanced current for two step type in distribution pole can't decide the rule because there are many different views. This paper presents the calculation and analysis technique of neutral current in distribution poles using equivalent circuit analysis and EMTP simulation.

• 한국자동차공학회논문집
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• 제6권6호
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• pp.88-97
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• 1998

Compliance elements such as bushings of a suspension system play a crucial role in determining the ride and handling characteristics of the vehicle. In this paper, a general procedure is proposed for the optimum design of compliance elements to meet various design targets. Based on the assumption that the displacements of elastokinematic behavior of a suspension system under external forces are very small, linearized elastokinematic equations in terms of infinitesimal displacements and joint reaction forces are derived. Directly differentiating the linear elastokinematic equations with respect to design variables associated with bushing stiffness, sensitivity equations are obtained. The design process for determining the bushing stiffness using sensitivity analysis and optimization technique is demonstrated.

• 천문학회지
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• 제50권2호
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• pp.29-39
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• 2017

We investigate two abnormal CME-Storm pairs that occurred on 2014 September 10 - 12 and 2015 March 15 - 17, respectively. The first one was a moderate geomagnetic storm ($Dst_{min}{\sim}-75nT$) driven by the X1.6 high speed flare-associated CME ($1267km\;s^{-1}$) in AR 12158 (N14E02) near solar disk center. The other was a very intense geomagnetic storm ($Dst_{min}{\sim}-223nT$) caused by a CME with moderate speed ($719km\;s^{-1}$) and associated with a filament eruption accompanied by a weak flare (C9.1) in AR 12297 (S17W38). Both CMEs have large direction parameters facing the Earth and southward magnetic field orientation in their solar source region. In this study, we inspect the structure of Interplanetary Flux Ropes (IFRs) at the Earth estimated by using the torus fitting technique assuming self-similar expansion. As results, we find that the moderate storm on 2014 September 12 was caused by small-scale southward magnetic fields in the sheath region ahead of the IFR. The Earth traversed the portion of the IFR where only the northward fields are observed. Meanwhile, in case of the 2015 March 17 storm, our IFR analysis revealed that the Earth passed the very portion where only the southward magnetic fields are observed throughout the passage. The resultant southward magnetic field with long-duration is the main cause of the intense storm. We suggest that 3D magnetic field geometry of an IFR at the IFR-Earth encounter is important and the strength of a geomagnetic storm is strongly affected by the relative location of the Earth with respect to the IFR structure.

• Carbon letters
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• 제5권4호
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• pp.159-163
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• 2004

The polymer-ceramic hybrid, known as 'ceramer', was synthesized by a sol-gel process by incorporating different amount of alkoxide as source of silicon in resorcinol-formaldehyde in presence of basic catalyst to get different percentage of silicon in ultimate carbonized composites. FTIR of the ceramer confirms that it is a network of Si-O-Si, Si-O-$CH_2$ and Si-OH type groups linked with benzene ring. Different amount of silicon in the ceramer exhibits varying temperature of thermal stability and lower coefficient of thermal expansion as compared to pure resorcinol-formaldehyde resin. The lower value of CTE in ceramer is due to existence of silica and resorcinol -formaldehyde in co-continuous phase. Unidirectional composites prepared with ceramer matrix and high-strength carbon fibers show lower value of flexural strength at polymer stage as compared to those prepared with resorcinol-formaldehyde resin. However, after heat treatment to $1450^{\circ}C$, the ceramer matrix composites show large improvement in the mechanical properties, i.e. with 7% silicon in the ceramer, the flexural strength is enhanced by 100% and flexural modulus value by 40% as compared to that of pure resorcinol-formaldehyde resin matrix composites.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.275-278
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• 2005

This study has focused on manufacturing technique of powder injection molding of watch case which made from zirconia powder. A series of computer simulation process was applied to prediction of the flow pattern in the inside of the mould and defects as weld line. The material properties of melted feedstock inclusive of the PVT graph and thermal viscosity flowage properties were measured for obtaining the input data in computer simulation. Also, molding experiment was conducted and the results of experiment showed that good agreement with simulation results far flow pattern and weld line location. On the other hand, gravity and inertia effect have an influence on velocity of melt front because of high density of ceramic powder particles in powder injection molding against the polymer injection molding process. In the experiment, the position of melt front was compared with upper gate and lower gate position. The gravity and inertia effect could be confirmed in the experimental results.

• 패션비즈니스
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• 제16권4호
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• pp.88-99
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• 2012

Recently the hair style of Michelle Obama, the world's most recognized First Lady of the United States has been loved by the public with her optimistic confidence and as a fashion leader. For Michelle Obama's hair styles by length, a medium-short cut style was expressed in various ways to show her strong will by exposing the forehead, an elegant image by asymmetry hair, or a progressive image by a short volume hair cut. A medium cut style expressed an elegant and intelligent image in shoulder-length and a trendy image using a side parting. A updo hair style produced young, womanly, and casual images using twisting, binding, typing up, and rolling technique according to situations. For hair styles associated with her roles, when participating as a diplomatic delegate, she expressed the President's helpful partner by a soft and womanly image using bobbed hair and half updo technique. For the participation in state occasions, her hair styles were examined in three situations. First of all, she mainly had a neat style, exposing her forehead in official schedules as a political partner to create an intelligent and high-class image. Second, she expressed a strong will with a medium-short style during an election campaign. Finally, she showed an elegant and refined hair style in consideration of T.P.O. during social activity. Michelle Obama overcame her hair's handicap, grasped her images associated with hair length, and expressed hair strategically according to her roles as the first African-American First Lady of the United States.

• 생명과학회지
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• 제32권8호
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• pp.595-600
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• 2022

Oenanthe javanica와 O. javanica var. japonica 한국 내 식용미나리이다. Cicuta virosa는 독미나리로 시큐톡신을 함유하고 있다. 미나리에 대한 RAPD 마크에 의한 분자적 변이를 조사하였다. RAPD 분석을 위해 10개 올리고프라이머(오페론, OPB)로 6개 집단을 분석하였다. 6개 집단에서 72개 DNA 분절(밴드)을 찾았다. 72 밴드 중 61개(84.7%) 밴드는 다형현상을 나타내었다. 한국 내 독미나리 자연 집단은 작고 격리되어 패치 분포를 이루고 있지만 높은 유전적 다양도를 가지고 있었다. 반면에, 재배종 미나리(Oenanthe javanica var. japonica) 집단은 채소용으로 논에서 광범위한 분포를 나타내지만 독미나리와 야생종 미나리에 비해 낮은 유전적 다양도를 나타내었다. 비록 야생집단이 재배집단에 비해 다양도가 높지만 유의한 차이는 없었다. 전체 유전적 다양도(H_T)는 0.342였다. 집단 내 유전적 다양도(H_S)는 0.201이였다. 유전자 좌위에 근거한 집단 간 분화에서 전체 유전적 다양도의 비율(G_ST)은 0.414이므로 전체 변이의 41.4%는 집단 간에 있었다. 결론으로 RAPD기법은 독미나리와 식용미나리의 동정에 유용하였다. 또, RAPD의 OPB 마크는 미나리의 다른 자원과 식품 자원을 식별하는 데 도움이 될 수 있는 분자 마크임을 보여주었다.

• 한국초전도ㆍ저온공학회논문지
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• 제10권1호
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• pp.10-14
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• 2008

Differently from BSCCO tapes which are fabricated by powder-in-tube method, the coated conductors are made by the evaporation of YBCO on metal substrate. Due to this structural merit, although the coated conductors are generally used for large current transportation, they are expected to be favorable to the purpose of the fault current limitation as well. In this study, using YBCO coated conductor having copper stabilizer formed by plating technique(produced by Superpower Co.), we investigated the over-current characteristics of the coated conductor. The coated conductors had 85 A $I_c$ and 90 K $T_c$. The resistance of the conductor was 0.93 $m{\Omega}/cm$ at 300 K and 0.17 $m{\Omega}/cm$ at the temperature right above $T_c$. To the coated conductors, we applied the voltages of the range from 150 $V_{rms}$ to 230 $V_{rms}$ and measured the V-I curves using four probe method. From the results, we could analyze the electric behavior of the coated conductor in flux flow state. As the current exceed $I_c$, the currents were distributed into the superconductor and metal stabilizer. The amounts of the currents shared through both current paths were calculated under the assumption that the ,Joule heating was perfectly eliminated by $LN_2$ surrounding the conductor. Finally, the condition for the stable current flowing state which does not affect the conductor was established from the analysis on the over-current characteristics.

• 한국재료학회지
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• 제15권6호
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• pp.413-418
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• 2005

Perovskite $Pb(Ni_{1/3}Nb_{2/3})O_3-Pb(Zr,Ti)O_3[PNN-PZT]$ ceramics were synthesized by conventional ceramic processing technique. In order to modify piezoelectric properties for sensor application in this system, NiO addition was considered to provide $Ni^{+2}$ as an acceptor, which was known to occupy with B site in the structure. The effect of NiO addition up to $8\;mol\%$ on the following piezoelectric properties as well as sintering properties was investigated. When NiO added more than $1\;mol\%$, average grain size was decreased and second phase was found to form. Moreover, the second phase caused decrease in relative dielectric constant $(\varepsilon_{33}T/\varepsilon0)$, electro-mechanical coupling factor $(k_p)$, and piezoelectric charge constant $(d_{33})$, while increasing mechanical quality factor $(Q_m)$. When $1\;mol\%$ NiO was added, density, dielectric properties and piezoelectric properties were abruptly increased.