• Progress in Superconductivity
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• 제8권1호
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• pp.122-126
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• 2006

This paper presents experimental and numerical investigation on heat generation of a bulk HTS for application to a 100 kWh Superconductor Flywheel Energy Storage System(SFES) bearing. An experimental device is manufactured to reproduce varying magnetic field conditions that a bulk HTS may experience during the operation of the 100 kWh SFES. The bulk HTS is directly cooled by a cryocooler while the heat is generated by the eddy currents created by varying magnetic fields induced by a coil. In order to design the cryocooling system for the 100 kWh SFES project, a preliminary experiment to investigate the actual cooling load variation under AC magnetic field has been carried out. In the experiment, two different copper holders were designed and tested. Several temperature sensors were installed on each component of the assembly and the temperatures were measured for several operating conditions of the 100 kWh SFES. The experimental investigation on the thermal response of the bulk HTS and its holder is considered to be a valuable step fur the successful materialization of a large-scale SFES.

• ETRI Journal
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• 제39권2호
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• pp.284-291
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• 2017

Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.323-326
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• 2001

NI$_2$MnGa-based ferromagnetic shape memory alloys (FSMA) are hoped to be used as robust actuators with high performance and power density, as a replacement of other actuation materials such as thermo-mechanical SMAs and mechanical-electric piezoelectrics. Recently, we have observed significant shape changes under magnetic field application when single- and poly-crystalline forms are used. In the present study, two mechanisms have been proposed to predict the magnetic field-induced shape change as a function of external magnetic field at temperatures below Mr and above Ar. In the case of the field-induced shape change at temperature below M$_{f}$, paired martensite variants are assumed to form by application of magnetic field. The direction of magnetization in martensites formed in austenite matrix is assumed to be parallel to the applied magnetic field in the case of shape change by application at temperature above Af. Various energies has been considered in the shape change under two mechanisms.s.

• 멤브레인
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• 제13권1호
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• pp.37-46
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• 2003

하전된 멤브레인 미세기공으로 유체가 흐르는 경우는 계면동전기 효과가 작용하게 된다. 비선형 Poisson-Boltzmann 전기장과 흐름에 의해 유발되는 전기장 사이의 정전상호작용을 운동방정식의 외부작용 힘으로 고려하였다. 유한차분법으로 정전위 분포를 우선 산출하고, 이어서 Green 함수로 슬릿형 기공에 대한 Navier-Stokes 식의 해석해를 구하였다. 계면동전기적 유동에 의한 흐름전위를 관련된 물리화학적 인자들의 함수로 유도되는 해석적인 명확한 표현으로 제시하였다. 전기이중층, 표면전위, 그리고 기공벽면의 하전조건의 영향에 따른 유속분포와 흐름전위 변화를 고찰하였다 계산결과, 전기이중층 두께나 표면전위가 증가함에 따라 평균유속은 감소하는 반면에 흐름전위는 증가하였다.

• 전기학회논문지
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• 제66권12호
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• pp.1844-1851
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• 2017

As the capacity of the wireless power transmission increases, a higher supply current which may induce current in nearby conductive parts requires. Induced current may affect electric shock to the human body and malfunction of the electrical equipment. In order to prevent such induced phenomena as a risk factor, shielding is required between the source of the wireless power transmission and the conductive parts. The resonance frequency for the large capacity wireless power transmission has the wavelength of several hundred meters, so most environments are included in the near-field area. By wave impedance, the electric field has higher density in the near-field area and needs to be analyze for protecting. For this purpose, it is necessary to select a substance having a larger electric conductivity and optimized shielding structure. In this paper, an aluminum base shielding structure was presented to conduct experiments on thickness, position, and heat dissipation. In the 35 kW, 60 kHz environments, the optimized 5T Al base shielding structure attenuates the induced current to 43 %.

• 한국전자파학회논문지
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• 제13권9호
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• pp.937-946
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• 2002

본 논문에서는 도체로부터의 안정된 전자기 산란 응답을 계산하는 새로운 해법을 제안한다. 이 방법은 기존의 MOT (marching-on in time) 기법을 이용하지 않고, 가중 라게르 (Laguerre) 다항식으로 유기전류의 과도 응답을 표현하여 시간 영역의 적분방정식을 푼다. 이 시간 영역의 기저함수를 사용함으로써 적분식의 미분항을 해석적으로 처리하여 과도 응답을 구할 수 있다. 또한 적용되는 이 기저함수는 시간이 진행함에 따라 영으로 수렴하는 특성 때문에, 유기전류의 과도응답도 후기 진동을 가지지 않고 영으로 수렴한다. 제안되는 방법의 타당성을 보이기 위하여 시간 영역 전장 적분방정식의 해를 MOT 및 해석해와 주파수 영역으로부터 구한 해의 이산 푸리에 역변환 (inverse discrete Fourier transform, IDFT)과도 비교한다.

• Bulletin of the Korean Chemical Society
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• 제28권8호
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• pp.1405-1409
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• 2007

The potential-induced charge transfer of the dye (Bu4N)2[Ru(dcbpyH)2-(NCS)2] (N719) on Au, Ag, and Cu electrode surfaces has been examined by surface-enhanced Raman scattering (SERS) in the applied voltage range between 0.0 and ?0.8 V. N719 is assumed to have a relatively perpendicular geometry with its bipyridine ring on the metal surfaces. A strong appearance of the carboxylate band at ~1370 cm-1 indicates that the carboxyl group will likely be deprotonated on the metal surfaces. As the electric potential is shifted from ?0.8 to 0.0 V, the ν (NCS) band at ~2100 cm-1 on the electrode surfaces appears to undergo a shift in frequency and intensity change. This indicated that the charge transfer between the dye and metal electrode surfaces had occurred. Electric-field-dependent charge transfer differs somewhat depending on the type of metal surfaces as suggested from the dissimilar frequency positions of the ν (NCS) band.

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권3호
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• pp.81-85
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• 2003

This paper describes the results of experiments made to examine the behavior of water droplet on the polymer surface and influence of the charge. In this experiment, water droplet was put on the polymer surface in an applied AC electric field and the investigations of its behavior were done with a high-speed video camera. It can be observed that the droplet elongates and vibrates with being pulled towards the positive electrode in a wave synchronism with the frequency of the power source. The volume and conductivity of water droplet are shown to have a marked effect on the mode of discharge development. These behaviors may be caused by the change of electric field of applied AC voltage and induced charges in/on the water droplet.

• KIEE International Transactions on Power Engineering
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• 제3A권2호
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• pp.109-114
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• 2003

This paper presents observations made on four-bundled conductor transmission lines concerning the behavior of conductors under the effect of natural winds. To know the wind-induced vibration status and how to control it, wind-induced vibrations have been recorded and analyzed from the real transmission lines. From the field observation and analysis results, subspan oscillation was found to be the main type of vibration. In addition, the data also revealed some common characteristics of the observation sites with high maintenance rates. The results will be used in controlling the subspan oscillations and protecting the conductors.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
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• pp.57-58
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• 2009

The dynamics of nano or micro sized-particles in liquid crystal (LC) medium under an external electric field is of theoretical and technological interest. A fullerene of 10 wt% was doped into the LC medium and its electric field induced motion was controlled by both in-plane and vertical electric fields. In the proposed device, pixel electrode I and pixel electrode II were designed consecutively on the bottom substrate and common electrode on the top of the substrate. When the electric field was applied, the fullerenes start to move in direction of applied electric field. The dark, grey and white states in the proposed device can be obtained by suitable combination of the polarity of applied electric field at pixel electrode I, pixel electrode II and common electrode. The dynamical motions of fullerene particles in LC medium suggest that fullerene can be designed for electronic-paper like displays.