• 한국환경과학회지
• /
• 제17권11호
• /
• pp.1203-1210
• /
• 2008

Flow resistance in a natural stream is caused by complex factors, such as the grains on the bed, vegetation, and bed-form, reach profile. Flow resistance in a generally stable gravel bed stream is due to protrudent grains from bed. Therefore, the flow resistance can be calculated by equivalent roughness in gravel bed stream, but estimation of equivalent roughness is difficult because nonuniform size and irregular arrangement of distributed grain on natural stream bed. In previous study, equivalent roughness is empirically estimated using characteristic grain size. However, application of empirical equation have uncertainty in stream that stream bed characteristic differs. In this study, we developed a model using an analytical method considering grain diameter distribution characteristics of grains on the bed and also taking into account flow resistance acting on each grain. Also, the model consider the protrusion height of grain.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2003년도 봄 학술발표회 논문집
• /
• pp.569-576
• /
• 2003

Based on the equivalent uniform stress concept Presented by Seed and Idriss, sinusoidal cyclic loads which simplified earthquake loads have been applied in evaluating the liquefaction resistance strength experimentally. However, the liquefaction resistance strength of soil based on the equivalent uniform stress concept can not exactly reflect the dynamic characteristics of the irregular earthquake motion. The liquefaction assessment method which was invented by using the equivalent uniform stress concept is suitable for the severe earthquake region such as Japan or USA, so the proper method to Korea is needed. In this study, estimation of the resistance to liquefaction was conducted by applying real earthquake loading to the cyclic triaxial test. From the test results, the characteristics of the fine sand under moderate earthquake were analyzed and compared with the results under strong earthquakes. Typically real earthquake loads used in this study are divided into two types - impact type and vibration type. Furthermore, results of the liquefaction resistance strength based on the equivalent uniform stress concept and tile concept using real earthquake loading were compared.

• 한국해안·해양공학회논문집
• /
• 제21권3호
• /
• pp.216-223
• /
• 2009

수면보다 높은 사각기둥 저항체가 등간격으로 배치되어 있는 경우의 상당저항계수 식의 횡방향에 따른 항력상호작용계수를 연구하여 제안하였다. 저항체의 횡방향 이격거리에 따른 에너지 손실이 오리피스의 공극률에 따른 에너지 손실과 동일하다고 가정하고 오리피스의 에너지 손실계수를 차용하여 횡방향 항력상호작용계수를 제안하였다. 이 항력상호작용계수를 사용하는 상당저항계수 식을 김 등(2008)에 의해 사용된 수리조건에 대해 그 해석능력이 검증된 FLOW-3D를 이용하여 수치실험한 결과와 비교하였다. 그 결과가 잘 일치하였고 이로부터 바닥마찰뿐만 아니라 수면보다 높은 정방형 다열기둥의 종방향 및 횡방향 이격거리에 따라 변화되는 저항정도를 고려할 수 있는 제안된 상당저항계수 식의 타당성을 검증하였다.

• 한국화재소방학회논문지
• /
• 제17권2호
• /
• pp.10-16
• /
• 2003

본 연구의 목적은 성능위주의 화재안전설계법에 따른 구획실 용도별 요구내화시간산정을 실시함으로써 현행 내화성능기준의 문제점도출 및 개선방향을 제시하는 것이다. 내화성능기준에 대한 검토를 위해 본 연구에서는 현재 국내의 시방규정에 의해 결정된 요구내화시간과 등가시간공식에 의해 산정된 화재노출상응시간과 비교하였고, 화재노출상응시간을 산정하기 위해 화재하중밀도, 환기계수, 구조재료의 열적특성 그리고 구획실 형상치수 등을 조사하였다.

• Transactions on Electrical and Electronic Materials
• /
• 제8권3호
• /
• pp.131-134
• /
• 2007

An $ITO/Alq_3/Al$ structure was used to study complex impedance of $Alq_3$ based organic light-emitting diodes. Equivalent circuit was analyzed in a device structure of $ITO/Alq_3/Al$ with a thickness layer of $Alq_3$ of 100 nm. The obtained impedance was able to be fitted using equivalent circuit model of parallel combination of resistance $R_p$ and capacitance $C_p$ with a small series resistance of $R_s$.

• Journal of Power Electronics
• /
• 제7권1호
• /
• pp.38-43
• /
• 2007

An External Electrode Fluorescent Lamp (EEFL) has longer lifespan, higher power efficiency and higher luminance than a Cold Cathode Fluorescent Lamp (CCFL). Moreover, it is easy to drive them in parallel. Therefore, the EEFL is expected to quickly replace the CCFL in LCD backlight systems. However, the EEFL has more complex characteristics than the CCFL with a resistive component, because it has both a resistive component by plasma and a capacitive component by external electrode. In this paper, values of resistance and capacitance are measured at several power levels and at several operating frequencies. They are expressed by a numeral formula based on a linear approximation that represents the equivalent resistance and capacitance as a function of power. Then we made block diagram of the equivalent circuit model using numerical expressions. Simulation waveforms and experimental results are presented to verify the feasibility of the equivalent model.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2008년도 International Meeting on Information Display
• /
• pp.446-449
• /
• 2008

Organic light emitting diodes (OLEDs) with multiple organic layers were fabricated to obtain and to evaluate an equivalent resistance and an equivalent capacitance of OLED device. The staircase voltage with an increasing period and a constant period was designed and applied to the OLED. The resistance of OLED was found to decrease from $270\;k{\Omega}$ to $2\;K{\Omega}$ as applied voltage increased after turn on. The equivalent capacitance of OLED maintained unchanged at low voltage level and deceased after showing peak value as the applied voltage increased.

• 센서학회지
• /
• 제4권4호
• /
• pp.29-40
• /
• 1995

본논문(本論文)에서는 정전유도(靜電誘導) 트랜지스터의 잡음원인분석(雜音原因分析)을 위하여 직류(直流) 및 잡음특성(雜音特性), 잔존성분(殘存成分), 입력용량등(入力容量等)의 정무화(定武化)에 필요(必要)한 잡음(雜音) 등가회로(等價回路)를 제안(提案)하였다. 가장 단순(單純)한 잡음(雜音) 등가회로(等價回路)는 정전유도(靜電誘導) 트랜지스터의 동작원리(動作原理)에 의한 모델이며, 이 모델에 의한 실측치(實測値)가 산탄(shot) 잡음(雜音)보다 작게 나타났다. 소스 저항(抵抗)이 삽입(揷入)된 등가회로(等價回路)에서는 소스 저항(抵抗)의 부귀환효과(負歸還效果)에 의하여 산탄 잡음(雜音)이 저감(低減)됨을 확인(確認)하였다. 정확(正確)한 잡음저감원인(雜音低減原因)을 분석(分析)하기 위하여 소스 저항(抵抗)과 드레인 저항(低抗)의 계산식(計算式)을 유도(誘導)하기 위한 등가회로(等價回路)를 제안(提案)하였다. 등가회로(等價回路) 확인(確認) 실험(實驗)에서는 잔존성분(殘存成分)에 대한 신호원저항(信號源抵抗)과 출력부하저항(出力負荷抵抗)의 영향(影響)은 작으며, 잔존성분(殘存成分)은 입력환산등가잡음저항(入力換算等價雜音抵抗)으로 나타낼 수 있다. 또한, 입력용량(入力容量)은 부하저항(負荷抵抗)이 $0{\Omega}$일 때 13.6pF이며, 게이트 배선등(配線等) 정전유도(靜電誘導) 트랜지스터 동작(動作)에 직접(直接) 관여(關與)하지 않는 용량(容量)은 10pF정도(程度)이다.

• Journal of Magnetics
• /
• 제17권4호
• /
• pp.280-284
• /
• 2012

This paper presents a method for evaluating interior permanent magnet synchronous motor (IPMSM) performance over the entire operation region. Using a d-q axis equivalent circuit model consisting of motor parameters such as the permanent magnetic flux, copper resistance, core loss resistance, and d-q axis inductance, a conventional mathematical model of an IPMSM has been developed. It is well understood that in IPMSMs, magnetic operating conditions cause cross saturation and that the iron loss resistance - upon which core losses depend - changes according to the motor speed; for the sake of convenience, however, d-q axis machine models usually neglect the influence of magnetic cross saturation and assume that the iron loss resistance is constant. This paper proposes an analysis method based on considering a magnetic cross saturation and estimating a core loss resistance that changes with the operating conditions and speed. The proposed method is then verified by means of a comparison between the computed and the experimental results.

• 전기학회논문지P
• /
• 제59권4호
• /
• pp.358-363
• /
• 2010

This paper proposes a step-by-step method of determining the parameters of equivalent circuit which is considered the no load losses for the single phase induction motor which has the starting winding. This method is comprised of three steps, and the stator resistance which is measured by the method of voltage drop is treated as constant and the stator and the rotor leakage reactances are assumed to be the same in every step. The test results of no load and locked rotor test are used in the 1st and 2nd step, and the ratings of name plate of the motor are needed in the 3rd step. In the 1st step, the traditional equivalent circuit parameters are directly calculated by no load and locked rotor conditions. In the next step, five nonlinear simultaneous equations for five unknown parameters can be set up by no load and locked rotor equivalent circuits. These equations are solved by using the initial parameters obtained by the 1st step parameters. In the final step, three nonlinear simultaneous equations for rotor winding resistance, leakage reactance and no load losses component resistance can be set up by equivalent circuit under the rated operation. Three parameters are solved by using the 2nd step parameters. Thus, equivalent circuit parameters are gradually refined step by step. The validity of the proposed method is evaluated by comparing the computed values obtained by the equivalent circuit parameters with the experimental values of the load test.