• 한국작물학회지
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• 제55권2호
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• pp.98-104
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• 2010

논을 밭으로 1년 전환 후 다시 논으로 복원한 논에서의 벼의 생육촉진 및 질소흡수 증가의 효과를 살펴보기 위하여 복원논 1년 및 2년차인 2006년 및 2007년에 복원논 및 연작논을 대상으로 질소비료를 0, 3, 6 kg $10a^{-1}$ 시용하여 벼의 생육량, 질소흡수량, 쌀의 수량 및 단백질 함량 등을 조사하였는데 결과는 다음과 같다. 연작논에 비해 복원논에서 복원 1년 및 2년차 모두 벼의 초기생육이 크게 증가하여 유수형성기 건물중 및 질소함량이 증가하였으며, 복원논에서도 질소시비량 증가에 따라 건물중 및 질소량이 증가하여 질소시비량 6 kg $10a^{-1}$까지 질소시비 효과가 뚜렷이 나타났는데, 복원논 1년차 및 2년차의 질소무비구의 건물중 및 질소흡수량은 각각 연작논의 질소시비량 6 및 3 kg $10a^{-1}$와 동일한 값을 나타내었다. 수확기에서의 벼의 건물중 및 질소흡수량도 유수형성기와 비슷한 경향을 보였으며, 질소시비 방법으로는 같은 량의 질소시비량이라도 전량을 기비로 시용한 것보다 유수형성기에 추비로 3 kg $10a^{-1}$를 시용한구가 질소흡수량이 다소 높았다. 수량구성요소에서는 연작논에 비해 복원논에서 벼의 수당립수가 증가하는 경향이었으며, 질소시비량이 많아질수록 등숙율이 감소하였는데, 특히 질소흡수량이 많았던 복원논-질소시비량 6 kg $10a^{-1}$ 구에서의 등숙비율이 많이 감소하였다. 벼의 수량도 복원논이 연작논에 비해 복원 1년차 및 2년차 모두 연작논보다 증가하였는데, 복원 1년차는 질소시비량간 벼수량의 차이가 없었지만, 복원 2년차에는 무질소시비구에서 벼의 수량이 다소 감소하였다. 현미 및 백미의 단백질 함량은 복원논이 연작논보다, 질소시비량이 증대할수록 높아졌는데, 질소시비방법에서는 질소시비량 모두 3, 6 kg $10a^{-1}$ 모두 유수형성기에서 추비로 3 kg $10a^{-1}$를 준 구에서 높아 질소흡수량이 많은 복원논에서 질소를 추비로 줄 때 단백질함량이 증대할 위험성이 높았다.

• International Journal of Automotive Technology
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• 제7권6호
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• pp.757-762
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• 2006

Reliability of automotive parts has been one of the most interesting fields in the automotive industry. Especially, a small DC motor was issued because of the increasing adoption for passengers' safety and convenience. For several years, small DC motors have been studied and some problems of a life test method were found out. The field condition was not considered enough in the old life test method. It also needed a lot of test time. For precise life estimation and accelerated life test, new life test procedure was developed based on measured field condition. The vibration condition on vehicle and latent force on fan motor shaft were measured and correlated with each other. We converted the acceleration data into the load data and calculated the equivalent load from integrated value. We found the relationship which can be used for accelerated life test without changing the severity by using different loading factors.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.199-201
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• 2011

NACA0012 Airfoil was simulated with Computational Fluid Dynamics(CFD) and the aerodynamic characteristics was analyzed for various far-field boundary distances ranging from 10 airfoil chord to 50 chord Drag coefficient distribution was dependent on the far-field distance and circulation, integrated along the loop inside the flow region, was also dependent. It was turned out that some corrections based on the circulation should be added to the far-field boundary condition for accurate airfoil simulation.

• 대한수학회지
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• 제50권4호
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• pp.899-916
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• 2013

We develop a version of dipolar conformal field theory in a simply connected domain with the Dirichlet-Neumann boundary condition and central charge one. We prove that all correlation functions of the fields in the OPE family of Gaussian free field with a certain boundary value are martingale-observables for dipolar SLE(4).

• 대한수학회보
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• 제43권1호
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• pp.77-80
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• 2006

Let K be a number field, $K_n$ its ray class field with conductor n and L a Galois extension of K containing $K_n$. We prove that $L/K_n$ has a relative integral basis (RIB) under certain simple condition. Also we reduce the problem of the existence of a RIB to a quadratic extension of $K_n$ under some condition.

• Journal of Electrical Engineering and Technology
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• 제3권2호
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• pp.213-217
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• 2008

The flux-lock type superconducting fault current limiter(SFCL) can apply the magnetic field into the high-$T_C$ superconducting(HTSC) element by adopting the magnetic field coil in its third winding. To apply the magnetic field into the HTSC element effectively, the capacitor for LC resonance is connected in series with the magnetic field coil. However, the current waveform of third winding for the application of the magnetic field is affected by the LC resonance condition for the frequency of the source voltage and can affect the waveform of the limited fault current. In this paper, the current waveform of the third winding in the flux-lock type SFCL according to LC resonance condition during a fault period was analyzed. From the differential equation for its electrical circuit, the current equation of the third winding was derived and described with the natural frequency and the damping ratio as design parameters. Through the analysis according to the design parameters of the third winding, the waveform of the limited fault current was confirmed to be influenced by the current waveform of the third winding and the design condition for the stable fault current limiting operation of this SFCL was obtained.

• Journal of Electrical Engineering and Technology
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• 제12권2호
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• pp.665-673
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• 2017

This paper proposes a field weakening control method for operating an induction motor with a variable DC input voltage condition. In the variable DC voltage condition such as a battery, the field weakening method are required for the maximum output power. The conventional field weakening control methods can be used for operating the induction motor over the rated speed in a constant DC-link voltage condition. However, the conventional methods for operating the motor with the variable DC voltage is not suitable for the maximum output power. To overcome this problem, this paper proposes the optimized field weakening control method to extend the operating range of the induction motor with a rated power in a limited thermal and a wide DC input voltage conditions. The optimized d-axis and q-axis current equations are derived according to the field weakening region I and II to extend the operating region. The experimental results are presented to verify the effectiveness of the proposed method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1552-1553
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• 2011

The HVDC transformer which is one of the main equipments for HVDC(High Voltage Direct Current) electric power transmission systems is exposed to not only AC voltage but also the inflowing DC voltage which comes from the DC-AC converter systems. Therefore, the HVDC transformer insulation system is required to withstand the electric field stress under AC, DC and DC polarity reversal conditions. However the electric field distributions under those conditions are different because the AC electric field and DC electric field are governed by permittivity and conductivity, respectively. In this study, the changes of electric potential and electric field of conventional AC transformer insulation system under DC polarity reversal test condition were analyzed by FEM(Finite Element Method). The DC electric field stress was concentrated in the solid insulators while the AC electric field stress was concentrated in the mineral oil. In addition, the electric stress under that condition which is affected by the surface charge accumulation at the interfaces between insulators was evaluated. The stress in some parts could be higher than that of AC and DC condition, during polarity reversal test. The result of this study would be helpful for the HVDC transformer insulation system design.

• 센서학회지
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• 제29권1호
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• pp.45-50
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• 2020

Magnetoelectric (ME) composites were designed using the PMN-PZT single crystal and Ni foils; the properties and magnetic-field sensitivities of ME composites with different piezoelectric vibration modes (i.e., 31, 32, and 36 modes that depend on the crystal orientation of the single crystal) were compared. In the off-resonance condition, the ME coupling properties of the ME composites with the 32 and 36 piezoelectric vibration modes were better than those of the ME composites with the 31 piezoelectric vibration mode. However, in the resonance condition, the ME coupling properties of the ME composites were almost similar, irrespective of the piezoelectric vibration mode. Additionally, in the off-resonance condition (at 1 kHz), the magnetic-field sensitivity of the ME composites with the 36 piezoelectric vibration mode was up to 2 nT and those of the ME composites with the 31 and 32 piezoelectric vibration modes were up to 5 nT. These magnetic-field sensitivities are similar to those offered by conventional high-sensitivity magnetic-field sensors; the potential of the proposed sensor to replace costly and bulky high-sensitivity magnetic field sensors is significant.

• 전기학회논문지
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• 제64권2호
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• pp.331-337
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• 2015

The power flow analysis of electrified railway is required complicated calculation, because of variable load. Train runs trough rail supplied by electric power therefore, the load value in electrified railway system fluctuates along time. The power flow algorithm in electrified railway system is different from general power system, and the power flow simulation is peformed by the particular simulation software. Powerail is simulation software for analysis of traction power supply system developed by KRRI, in 2008. This consists of load forecasting module, including TPS and time scheduling, and power flow module. This software was verified by measured current under normal feeding condition, however, has not been verified by voltage on the condition of extended feeding. This paper presents the verification of PowerRail based on voltage drop under extended feeding condition. This is performed by comparing simulation result with field test. Field test and simulation is done in commercial railway line.