• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.151-156
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• 2011

The influence of thickness on magnetic interaction and magnetic properties in electrodeposited CoPt magnetic films was investigated from the analysis of the magnetic remanence curves and the magnetic hysteresis loops. As the thickness of the CoPt film is increased, the perpendicular coercivity and the saturation magnetization are increased but the squareness is considerably decreased. The analysis results of the magnetic remanence curves and the magnetic hysteresis loops exhibited that the dipolar interaction is the main interaction mechanism for all samples, but the strength of the dipolar interaction gradually increased with increasing sample thickness.

• Journal of the Korean Magnetics Society
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• v.7 no.4
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• pp.191-195
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• 1997

$Co_{84}Hf_{16}$ (1300$\AA$, 2150$\AA$) thin films were prepared by dc magnetron sputtering method. To investigate the uniaxial anisotrpy of the sample, the saturation and effective magnetization of the thin films were measured by VSM and FMR, respectively. The spectroscopic splitting g factor were estimated from the ferromagnetic resonance curves. For 1300$\AA$, 2150$\AA$, the effective magnetization was measured at the temperatures from T=77K to T=300K. The results were analyzed in terms of Bloch's law $M_s(T)=M_s(0)(1BT^{3/2}CT^{5/2}$. The Bloch coefficient B and C were determined by fitting. $M_{eff}(0)$ was obtained by extrapolating $M_{eff}$ to 0 K. From this result, the spinwave stiffness constants D was also determined and the exchange stiffness constants $A_{eff}$ were calculated by Kittel's resonance conditions.

• Journal of Wetlands Research
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• v.20 no.1
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• pp.63-71
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• 2018

The particle filtration mechanisms in an infiltration trench should be varying due to the different hydraulic conditions during stormwater runoff. The understanding of these variations associated with different filtration mechanisms and their effect on the particle removal efficiency is of vital importance. Therefore, a LID (Low Impact Development) system comprising of an infiltration trench packed with gravel and woodchip was investigated during the monitoring of several independent rainfall events. A typical rainfall event was divided into separate regimes and their corresponding flow conditions as well as filtration mechanisms in the trench were analyzed. According to hydraulic conditions, it was found out that filtration changes between vertical and horizontal flows as well as between unsaturated, saturated, and partially-saturated flows. Particle separation efficiency was high (55-76%) and was mainly governed by physical straining during the unsaturated period. It was then enhanced by diffusion during the saturated period (75-95%). When the trench became partially saturated at the end of the rainfall event, the efficiency decreased which was believed to be due to the existence of a negatively charged air-water interface which limited the removal to positively charged particles.

• The Journal of Engineering Geology
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• v.32 no.2
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• pp.209-219
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• 2022

To experimentally investigate the variation of soil characteristics in slope during rainfall and the shape of slope failure, the model test was performed using soil box and artificial rainfall simulator. The model test of slope formed by the homogenous sand was performed, and the saturation pattern in the model slope due to rainfall infiltration was observed. The slope model with the inclination of 35° was set up on the slope of 30°, and the rainfall intensity of 50 mm/hr was applied in the test. The soil depth of 35 cm was selected by considering the size of soil box, and the TDR (time domain reflectometry) sensors were installed at various depths to investigate the change of soil characteristics with time. As the result of model test, the slope model during rainfall was saturated from the soil surface to the subsurface, and from the toe part to the crest part due to rainfall infiltration. That is, the toe part of slope was firstly saturated by rainfall infiltration, and then due to continuous rainfall the saturation range was enlarged from the toe part to the crest part in the slope model. The failure of slope model was started at the toe part of slope and then enlarged to the crest part, which is called as the retrogressive failure. At the end of slope failure, the collapsed area increased rapidly. Also, the mode of slope failure was rotational. Meanwhile, the slope failure was occurred when the matric suction in the slope was reached to the air entry value (AEV) estimated in soil-water characteristic curve (SWCC).

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1812-1818
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• 2005

Even though SMA actuators have high power to volume ratio, there exist disadvantages such as hysteresis and saturation. So the model identification for SMA actuators is very difficult. For the qualitative model identification, we described the behavior of SMA actuators using a so-called diagonal model, which can readily expect the turning point of an incomplete phase transformation. For the quantitative model identification, we developed the general dynamics of SMA actuators using the modified Liang's model. Using this dynamics we can describe the hysteresis and the saturation very well. It is also very important to notice that the modified Liang's model maintains a continuous martensite fraction at the change of the phase transformation but the original model cannot.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.90-94
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• 2005

본 연구의 목적은 현 국내 홍수 예경보시스템에 사용되고 있는 저류함수모형의 매개변수 변화에 따른 유량해석의 불확실성을 평가하는데 있다. 적용 대상지점으로는 개진을 출구로 하는 낙동강 회천유역($747.5km^2$)이며 비교적 양호한 수문자료를 가지고 있는 단일 호우사상을 선정하였다. 불확실성 평가에 사용된 매개변수는 관측수문곡선을 비교적 정확하게 모의하는 경험적인 값을 기준으로 Monte Carlo 기법을 이용하여 각각의 매개변수(K, P, $T_{1},\;f_{l},\;R_{sa}$)에 대한 정규분포를 가지는 100개의 난수를 발생시켜 저류함수 모형으로 모의되는 유량 앙상블을 평가하였다. 최적화된 매개변수를 이용하여 유량해석을 실시한 결과, 각각의 매개변수가 유출해석에 미치는 영향을 파악할 수 있었으며, 그 중 저류상수 K와 포화누가우량 Rsa가 불확실성이 제일 큰 매개변수로 나타났고, 이들의 혼합 앙상블 유출결과도 매우 큰 불확실성을 내포하는 것으로 나타났다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2011.07a
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• pp.528-531
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• 2011

본 논문은 3차원 TV에 있어서, 인간의 색 순응에 근거하여 3차원 재생 방식에서도 2차원 재생 방식의 색상을 재현하기 위한 색상 톤 매핑 연산자를 제안한다. 이를 위하여 각 재생 방식에 따라 동일한 128단계의 무채색 색표를 이용한 색상 요소 입출력 관계 곡선을 측정 및 모델링하였고, 그 오차를 보정하기 위한 색상 톤 매핑 연산자를 도출하였다. 또한 도출된 색상 톤 매핑 연산자에 의한 색 포화 및 색 대비 왜곡을 완화하기 위하여 동적 영역 정규화를 실시하였다. 이를 통해 기존 3차원 영상 대비 10.13dB의 PSNR 개선 효과를 확인 할 수 있었다.

• Electrical & Electronic Materials
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• v.1 no.3
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• pp.269-277
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• 1988

P형 Si(100)로 제작한 MOS 커패시터에 $Co^{60}$-.gamma.선을 주사한 후 고주파 C-V특성 곡선으로 부터 방사선 조사에 의해 유발된 산화막안의 트랩전하의 거동 및 Si- $SiO_{2}$계면에서의 트랩밀도 분포의 변화를 검토하였다. 산화막 느랩전하는 .gamma.선 흡수선량 증가와 더불어 증가하다가 $10^{7}$ rad 부근에서부터 서서히 포화하는 경향이 나타났으며 게면트랩밀도의 분포모양은 흡수선량의 증가와 더불어 전형적인 이그러진 W자형에서 넓혀진 V자형 분포로 변화하였으나 최소값은 항상 진성페르미준위( $E_{i}$)부근에 있었으며 그 밀도는 1.0*$10^{11}$~7.5*$10^{11}$[개/$cm^{2}$/eV]로 계산되었다. 또한, 일정 바이어스전압하에서의 조사선량에 따른 $V_{fb}$ 의 변화는 현저하지는 않았으나 바이어스 전압을 +12V로 인가할 때 변화방향의 반전상태가 관측되었다. 그 이유로는 Si측의 계면 부근에서 일어난 눈사태 전자가 산화막내로 주입됨에 따라 도너형 양전하의 수가 감소되기 때문으로 추정되었다.되었다.

• Korean Journal of Materials Research
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• v.7 no.5
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• pp.381-385
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• 1997

PEMOCVD에 의해서 SrBi$_{2}$Ta$_{2}$O$_{9}$밥막이 낮은 온도에서 성공적으로 Pt/Ti/SiO$_{2}$Si위에 증착되었다. 5$50^{\circ}C$에서 증착된 200nm박막은 치밀하고 작은 결정립을 보였으며 3V의 인가전압하에서 이력곡선은 포화되기 시작하였다. 3V에서 박막은 잔류분극 (P$_{r}$)과 항전계(E$_{c}$)는 각각 15$\mu$/$\textrm{cm}^2$과 50kV/cm이었다. 6V bipolar square pulse의 피로측정에서 박막은 1.0x$10^{11}$cycles까지 피로 현상을 보이지 않았다. PEMOCVD에 의해서 5$50^{\circ}C$에서 증착된 SBT박막은 비휘발성 기억소자에 충분히 활용할 수 있다.다.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.74-77
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• 2001

The saturated winding inductances of a transformer are determined using the instantaneous magnetic saturation curve. The instantaneous curve is obtained from no load saturation curve in rms form by a direct piecewise linearized approach, then it is represented by a four-term ploynominal approximation. The saturated differential, effective and apparent winding inductances are computed from this curve, and these inductances are compared with the measured magnetizing inductance. The results show that the relation of $L_d<L_e<L_a$ exists and the computed apparent inductance is more close to the measured inductance.