• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 춘계학술대회 논문집
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• pp.1303-1307
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• 2004

MAGLEV is the vehicle which can run in levitated condition by the electro-magnets, and the vehicle can run without any contact condition. In MAGLEV system achieving a high magnetic field for minimum weight is a noteworthy goal. Unfortunately the two aspects of this goal high field and low weight are contradictory. Suitable designs must be sought using optimization techniques. In this paper, magnet attraction force is calculated and conformed by experimental data for designing a electro-magnet.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2003년도 춘계학술대회 논문집
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• pp.439-443
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• 2003

MAGLEV is the vehicle which can run in levitated condition by the electro-magnets, and the vehicle can run without any contact condition. In MAGLEV system achieving a high magnetic field for minimum weight is a noteworthy goal. Unfortunately the two aspects of this goal high field and low weight are contradictory. Suitable designs must be sought using optimization techniques. In this paper is a technique for designing a electro-magnet in terms of simple equation.

• 진공이야기
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• 제2권2호
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• pp.24-28
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• 2015

The brightness of an electron source, along with the aberrations of an objective lens, determines the image resolution and beam current on samples, which are two important parameters for evaluating the performance of an electron microscope. Here we introduce thermal electron source, Schottky emitter and cold field electron emitter. Thermal electron source is the cheapest and stable electron source but it has the lowest brightness. Schottky emitter is 10000 times brighter than tungsten thermal electron source, but requires ultrahigh vacuum operating condition. Cold field electron emitter is 10 times brighter than Schottky emitters, but it is rather unstable and its operation requires most stringent vacuum condition, hindering its widespread use.

• 한국초지조사료학회지
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• 제31권2호
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• pp.119-126
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• 2011

본 시험은 논에서 배수조건에 따라 벼 대체 여름 사료작물인 수수류를 논 재배하여 생육 특성과 수량에서 우수한 품종을 선발할 목적으로 2007년부터 2008년까지 충남 아산과 천안농가 포장에서 수행하였다. 비출수형 2품종과 출수형 4 품종 등 총 6 품종을 시험한 결과 불량한 논에 재배하였을 경우에는 배수 양호한 논에 재배시의 66.4%로 건물수량이 감소하였고, 배수가 불량한 논에서는 SS405 품종이 습해에 비교적 강하고 줄기가 굵으며 건물수량이 ha 당 12.9톤으로 최고의 수량을 보였으며 소르단 79 품종은 배수 양호한 논에서 재배한 성적에 비해 배수가 불량한 논에 재배시에 공시 품종 중에서 수량 감소가 가장 컸으며, 수량 감소가 가장 작은 품종은 점보로 약 2 톤 정도의 감소를 보였다. 또한 사료가치는 ADF, NDF, CP 등에서 약간의 차이를 보였는데 SS405 품종은 배수 불량한 논에 재배시에만 조단백질이 1.1% 증가 하였고 다른 특성들간에 차이는 없었다.

• Journal of Astronomy and Space Sciences
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• 제37권2호
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• pp.77-84
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• 2020

We performed high-resolution three-dimensional global magnetohydrodynamic (MHD) simulations to study the interaction between the Earth's magnetosphere and a prolonged steady southward interplanetary magnetic field (IMF) (Bz = -2nT) and slow solar wind. The simulation results show that dayside magnetic reconnection continuously occurs at the subsolar region where the magnetosheath magnetic field is antiparallel to the geomagnetic field. The plasmoid developed on closed plasma sheet field lines. We found that the vortex was generated at the magnetic equator such as (X, Y) = (7.6, 8.9) R_E due to the viscous-like interaction, which was strengthened by dayside reconnection. The magnetic field and plasma properties clearly showed quasiperiodic variations with a period of 8-10 min across the vortex. Additionally, double twin parallel vorticity in the polar region was clearly seen. The peak value of the cross-polar cap potential fluctuated between 17 and 20 kV during the tail reconnection.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.257-261
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• 2000

The value of I$_c$(critical current) in HTS (High Temperature Superconductor) tape has a great influence on B${\bot}$(vertical field). Therefore, in shape design of field coil for the HTSG(High Temperature Superconducting Generator), a method to reduce the B${\bot}$ should be considered in order to maintain the stability and substantial improvement on the performance. On the basis of the magnetic field analysis, this paper deals with various field coil shape according to the iron plate to obtain small B${\bot}$ by using Biot-Savart's law, image method and 2D FEA(2 Dimensional Finite Element Analysis) considering the stress condition of HTS. Moreover, the analysis is verified by comparison with experimental results. And also this paper presents the advanced model by using 3D FEA, in which flux density at armature is calculated in 5kVA class HTSG.

• Progress in Superconductivity
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• 제8권2호
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• pp.152-157
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• 2007

Uniaxial square Helmholtz coils for testing SQUID sensors were designed and their field distributions were calculated. Optimum parameters for maximizing the uniform region in the Helmholtz mode were obtained for different uniformity tolerances. The coil system consists of 2 pairs of identical square loops, a Helmholtz pair for generating uniform fields and the other for the 2nd-order gradient fields in combination with the Helmholtz pair. Full expressions of the axial component of the field were calculated by using Biot-Savart's law. To understand the behavior of the field near the coil center, analytical expressions were obtained up to the 4th-order in the midplane and along the coil axis. The Helmholtz condition for generating uniform fields was calculated to be $d/{\alpha}=0.544505643$, where 2d is the inter-coil distance and $2{\alpha}$ is the side length of the coil square. Maximized uniform range can be obtained for a given nonuniformity tolerance by choosing $d/{\alpha}$ slightly lower than the Helmholtz condition. The pure second-order gradient field can be generated by subtracting the Helmholtz field from the field of the 2nd pair with equal magnitudes of the center fields of the two pairs. The coil system is useful for testing balance and sensitivity of SQUID gradiometers.

• 천문학회보
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• 제39권1호
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• pp.69.1-69.1
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• 2014

We perform an MHD simulation combined with observed vector field data to clarify an eruptive dynamics in the solar flare. We first extrapolate a 3D coronal magnetic field under a Nonlinear Force-Free Field (NLFFF) approximation based on the vector field, and then we perform an MHD simulation where the NLFFF prior to the flare is set as an initial condition. Vector field was obtained by the Soar Dynamics Observatory (SDO) at 00:00 UT on February 15, which is about 90 minutes before the X2.2-class flare. As a result, the MHD simulation successfully shows an eruption of strongly twisted lines whose values are over one-turn twist, which are produced through the tether-cut magnetic reconnection in strongly twisted lines of the NLFFF. Eventually, we found that they exceed a critical height at which the flux tube becomes unstable to the torus instability determining the condition that whether a flux tube might escape from the overlying field lines or not. In addition to these, we found that the distribution of the observed two-ribbon flares is similar to the spatial variance of the footpoints caused by the reconnection of the twisted lines being resided above the polarity inversion line. Furthermore, because the post flare loops obtained from MHD simulation well capture that in EUV image taken by SDO, these results support the reliability of our simulation.

• 한국초지조사료학회지
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• 제31권1호
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• pp.47-54
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• 2011

본 시험은 논에서 가뭄조건에 따른 여름 사료작물인 옥수수의 생육특성과 수량성을 알아보기 위해서 2008년부터 2009년까지 2년간에 걸쳐 전남 영광과 천안의 농가 포장에서 수행하였다. 국내육성 5품종과 도입품종 5품종 등 10품종을 시험한 결과 강다옥 품종이 생육특성과 수량성에서 우수한 결과를 보였고 가뭄에 대해 비교적 수량 감소가 적은 것으로 나타났다. 표준조건 재배에서는 강다옥의 건물수량은 21.8 톤/ha이었고 가뭄조건에서 국산품종인 강다옥의 건물수량이 5,548 kg/ha 으로 공시품종 중에서 최고의 수량을 보였다. 또한 사료가치는 표준조건보다 가뭄조건에서 떨어지는 경향을 보였는데 ADF 함량은 17.8% 증가하였으나 조단백질 함량은 27.4%로 최고의 감소를 보였다. 따라서 본 연구결과를 토대로 볼 때 사일리지용 옥수수를 논에 재배하기 위해서는 가뭄시에 충분히 관수를 하고 가뭄에 강한 품종을 재배하는 것이 중요하다는 사실이다.

• 한국농림기상학회지
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• 제25권3호
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• pp.218-225
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• 2023

영농형 태양광 시스템은 노지 작물 경작과 동일한 토지 상부에 설치된 태양광 패널을 통한 발전을 동시에 하는 시스템이다. 지금까지 영농형 태양광은 에너지와 식량의 양자구도로만 집중되어있다. 영농환경 중 하나인 토양수분은 강우 또는 관개수로 증발 및 유출⋅침투로 손실된 수분을 공급받아 노지 작물 생산에 기여한다. 본 연구는 식량, 에너지와 함께 물의 개념을 포함하여 영농형 태양광 시설을 보고자 하였으며, 미기상 관측을 통해 봄 기간 동안 휴경논에서 영농형 태양광 시설 하부의 토양수분과 지온의 변화를 분석하였다. 영농형 태양광 하부는 패널로 인한 부분차광 조건으로 지면에 입사되는 광 에너지량이 감소하여 지온이 낮아질 뿐만 아니라 토양수분 손실이 적어 대조구인 노지에 비해 습윤한 조건을 보인다. 또한, 태양광 하부는 에너지 제한 환경이며, 상대적으로 지온이 높은 노지는 수분 제한 환경으로 설명된다. 노지와 태양광 하부의 상이한 토양수분 환경은 필연적으로 작물에 영향을 미칠 것이며, 농업 환경과 농촌 경제를 고려한 지속가능한 대처가 필요하겠다.