• 한국컴퓨터정보학회논문지
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• 제3권3호
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• pp.107-112
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• 1998

본 논문에서는 마이크로스트립 선로로 제작이 쉽고, 스터브를 사용한 필터보다 적은 공간을 차지하는 Hi-Z, Low-Z 필터를 사용하여 마이크로스트립 필터를 설계.제작하였다. 이 필터는 선로의 전기적 길이가 매우 짧은 경우. 즉 Bl＜$\pi$/4의 조건에서, 저역통과기본형의 직렬 인덕터일 때 고 임피던스 선로부로 병렬 커패시터를 저 임피던스 선로부로 대치할 수 있다. 이렇게 대치된 각 단을 마이크로스트립 선로로 설계하기 위해 주어진 마이크로스트립의 실효 유전율을 구해서 각 단의 폭과 길이를 계산하고 필터 설계에 사용하였다. 또한, 설계된 필터를 Touchstone의 이론치와 제작된 필터의 실험치를 비교하여 응답특성을 분석하였다.

• 한국수소및신에너지학회논문집
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• 제26권2호
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• pp.184-191
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• 2015

As the power electronics system increases the frequency, the power loss and thermal management are paid more attention. This research presents a real time model of dissipation power with junction temperature response for 120kw IGBT inverter which is applied to the thermal management of high power IGBT inverter. Since the computational time is critical for real time simulation, look-up tables of IGBT module characteristic curve are implemented. The power loss from IGBT provides a clue to calculate the temperature of each module of IGBT. In this study, temperature of each layer in IGBT is predicted by lumped capacitance analysis of layers with convective heat transfer. The power loss and temperature of layers in IGBT is then communicated due to mutual dependence. In the dynamic model, PWM pulses are employed to calculation real time IGBT and diode power loss. Under Matlab/Simulink$^{(R)}$ environment, the dynamic model is validated with experiment. Results showed that the dynamic response of power loss is closely coupled with effective thermal management. The convective heat transfer is enough to achieve proper thermal management under guideline temperature.

• 전기학회논문지
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• 제59권5호
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• pp.860-865
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• 2010

When a circuit breaker is opened, a large capacitance around the buses, the circuit breaker and the potential transformer (PT) might cause PT ferroresonance. During PT ferroresonance, the iron core repeats saturation and unsaturation even though the supplied voltage is a rated voltage. This paper describes an analytical analysis of PT ferroresonance in the transient-state. To analyze ferroresonance analytically, the iron core is modelled by a simplified two-segment core model in this paper. Thus, a nonlinear ordinary differential equation (ODE) for the flux linkage is changed into a linear ODE with constant coefficients, which enables an analytical analysis. In this simplified model, each state, which is either saturated or unsaturated state, corresponds to one of the three modes, i.e. overdamping, critical damping and underdamping. The flux linkage and the voltage in each state are obtained analytically by solving the linear ODE with constant coefficients. The proposed transient analysis is effective in the more understanding of ferroresonance and thus can be used to design a ferroresonance prevention or suppression circuit of a PT.

• 마이크로전자및패키징학회지
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• 제16권4호
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• pp.5-8
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• 2009

In this paper, a high-quality low-temperature co-fired ceramic (LTCC) solenoid inductor using a solder ball and an air cavity on a silicon wafer for three-dimensional (3-D) system-in-package (SiP) is proposed. The LTCC multi-layer solenoid inductor is attached using Ag paste and solder ball on a silicon wafer with the air cavity structure. The air cavity is formed on a silicon wafer through an anisotropic wet-etching technology and is able to isolate the LTCC dielectric loss which is equivalent to a low k material effect. The electrical coupling between the metal layer and the LTCC dielectric layer is decreased by adopting the air cavity. The LTCC solenoid inductor using the solder ball and the air cavity on silicon wafer has an improved Q factor and self-resonant frequency (SRF) by reducing the LTCC dielectric resistance and parasitic capacitance. Also, 3-D device stacking technologies provide an effective path to the miniaturization of electronic systems.

• 대한전자공학회논문지SD
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• 제40권4호
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• pp.74-84
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• 2003

기존의 테스트 알고리즘은 대부분 셀간의 고장에 중심이 맞추어져 있어 메모리의 집적도의 증가와 더불어 일어나는 word-line 과 bit-line 결합 잡음에 의한 고장을 효과적으로 테스트 할 수 없다 본 논문에서는 word-line 결합 capacitance에 의한 고장의 가능성을 제시하고 새로운 고장 모델인 WLSFs(Word-Line Sensitive Faults)을 제안하였다. 또한 word-line 과 bit-line 결합 잡음을 동시에 고려한 알고리즘을 제시하여 고장의 확률을 높였고 고장의 원인을 기존의 고장 모델로는 되지 않음을 보여준다. 제안된 알고리즘은 기존의 기본적인 고장인 고착고장, 천이고장, 그리고 결합고장을 5개의 이웃셀 내에서 모두 검출할 수 있음을 보여준다.

• 설비공학논문집
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• 제9권3호
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• pp.343-353
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• 1997

This paper presents a theoretical model for predicting transient behaviors during storage process of the cool storage system using the R141b clathrate. Introduction of the lumped capacitance method along with a brine reservoir having large thermal capacity yields a set of simplified energy equations. Based on the Arrhenius equation and the known experimental findings, the formation rate of clathrate for which the degree of subcooling is properly accounted is newly developed. An effective nondimensionalization of the model equations facilitates the closure of modeling as well as parametric study. Calculated results for a specific case not only simulate a typical pattern of temperautre variation in the tank successfully, but also agree reasonably well with available data. The effect of each characteristic parameter on the system performance is also investigated. It is revealed that the dominant among relevant parameters are the activation energy of reaction, the degree of subcoling and the initial mass fraction of refrigerant. Finally, the uncertainty associated with modeling of the shaft work variation appears to need further studies.

• 마이크로전자및패키징학회지
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• 제11권4호
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• pp.61-67
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• 2004

알루미늄 유전체의 표면적 증가에 의한 정전용량 값을 증가시키기 위하여, 1 M의 염산 에칭용액에 첨가제를 사용했을 때 나타나는 알루미늄 표면의 에칭특성의 변화를 조사하였다. 에칭액으로서 염산을 사용한 경우 알루미늄 표면에서 생성되는 에치피트의 형상과 단위 면적당 생성밀도가 균일하지 못하였다. 염산용액에 에틸렌글리콜이 첨가된 혼합용액에서 에칭을 실시했을 경우, 알루미늄 기지 표면에 미세하고 균일한 에치피트가 형성되어 표면적 증가의 효과가 크게 나타났다. 에틸렌글리콜이 첨가된 에칭액에서 제조된 유전체는 표면적 증가에 의한 효과로 높은 정전용량 값을 나타냈다.

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.183-190
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• 2019

Here, we introduce porous graphene balls (PGB) showing superior electrochemical properties as supercapacitor electrode materials. PGB was fabricated via activation of graphene oxides (GO) by H₂O₂ and aerosol spray drying in series. Effect of activation on the morphology, specific surface area, pore volume, and electrochemical properties were investigated. As-prepared PGB showed spherical morphology containing pores, which lead to the effective prevention of restacking in graphene sheets. It also exhibited a large surface area, unique porous structures, and high electrical conductivity. The electrochemical properties of the PGB as electrode materials of supercapacitor are investigated by using aqueous KOH under symmetric two-electrode system. The highest specific capacitance of PGB was 279 F/g at 0.1 A/g. In addition, the high rate capability (93.8% retention) and long-term cycling stability (92.2%) of the PGB were found due to the facilitated ion mobility between the porous graphene layers.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 추계학술대회 논문집 Vol.18
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• pp.30-32
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• 2005

The effects of mole ratio and Ti-ion on the dielectric properties and microstructure of modified $CaZrO_3$ composition such as $(Ca_{0.7}Sr_{0.3})_m(Ti_yZr_{1-y})O_3$ were investigated. Ti ions substituted on Zr-sites in these modified $CaZrO_3$ composition strongly affect the sintering density and microstructure of the fired ceramic body. With increasing the amount of Ti substituted on Zr-sites, the sintered density rapidly increased and the dense microstructures were obtained for the compositions having mole ratio of 1.01, whereas the sintered density and microstructures are nearly constant with the content of Ti-ion for the compositions having mole ratio of 0.99. With increasing the content of Ti ion, the curve of TCC (temperature coefficient of capacitance) as a function of temperature rotated clockwise and satisfied the COG characteristics for both of compositions with mole ratio of 0.99 and 1.01. The content of Ti ion seems to be more effective than mole with respect to the controlling of firing and TCC.

• International Journal of Precision Engineering and Manufacturing
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• 제9권4호
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• pp.3-10
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• 2008

Micro-electrical discharge machining (micro-EDM) is an effective method for machining all types of conductive materials regardless of hardness. Since micro-EDM is an electro-thermal process, the energy supplied by the pulse generator is an important factor in determining the effectiveness of the process. In this study, an investigation was conducted on the micro-EDM of tungsten carbide (WC) to compare the performance of transistor and resistance/capacitance (RC) pulse generators in obtaining the best quality micro-hole. The performance was measured by the machining time, material removal rate, relative tool wear ratio, surface quality, and dimensional accuracy. The RC generator was more suited for minimizing the pulse energy, which is a requirement for fabricating micro-parts. The smaller-sized debris formed by the low-discharge energy of RC micro-EDM could be easily flushed away from the machined zone, resulting in a surface free of burrs and resolidified molten metal. The RC generator also required much less time to obtain the same quality micro-hole in WC. Therefore, RC generators are better suited for fabricating micro-structures, producing good surface quality and better dimensional accuracy than the transistor generators, despite their higher relative tool wear ratio.