• 대한기계학회논문집A
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• 제21권1호
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• pp.12-21
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• 1997

A model for analysis of the crushing mechanism of thin-walled rectangular tube is presented. The crushing modes of rectangular tubes may be characterized as either compact or noncompact and the model presented only considers compact modes. The unloading process in the crushing are categorized into three different stages where the distinction is based on the ratio of outward to inward fold length. Using the kinematic relations and the energy conservation principle, the instantaneous crush load is derived. An approximate equation that considers the rolling behavior is also given so that the crush load history may be established. The equation is experimentally proved.

• Earthquakes and Structures
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• 제12권3호
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• pp.321-332
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• 2017

The reverse fault is a dangerous geological hazard faced by buried steel pipelines. Permanent ground deformation along the fault trace will induce large compressive strain leading to buckling failure of the pipe. A hybrid pipe-shell element based numerical model programed by INP code supported by ABAQUS solver was proposed in this study to explore the strain performance of buried X80 steel pipeline under reverse fault displacement. Accuracy of the numerical model was validated by previous full scale experimental results. Based on this model, parametric analysis was conducted to study the effects of four main kinds of parameters, e.g., pipe parameters, fault parameters, load parameter and soil property parameters, on the strain demand. Based on 2340 peak strain results of various combinations of design parameters, a semi-empirical model for strain demand prediction of X80 pipeline at reverse fault crossings was proposed. In general, reverse faults encountered by pipelines are involved in 3D oblique reverse faults, which can be considered as a combination of reverse fault and strike-slip fault. So a compressive strain demand estimation procedure for X80 pipeline crossing oblique-reverse faults was proposed by combining the presented semi-empirical model and the previous one for compression strike-slip fault (Liu 2016). Accuracy and efficiency of this proposed method was validated by fifteen design cases faced by the Second West to East Gas pipeline. The proposed method can be directly applied to the strain based design of X80 steel pipeline crossing oblique-reverse faults, with much higher efficiency than common numerical models.

• 대한전자공학회논문지SD
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• 제44권4호
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• pp.32-42
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• 2007

[ $0.35{\mu}m$ ]twin-well non-epitaxial CMOS 공정에서의 substrate noise에 의한 아날로그 회로의 성능 저하를 예측하기 위하여 substrate 저항을 모델링하였다. Substrate 저항 모델 방정식은 P+ guard-ring isolation에 적용되어 측정값과 일치함을 확인하였다. Substrate 저항을 네 가지 형태로 구분하고 각각에 대하여 semi-empirical 모델 방정식을 확립하여, 측정값과 비교하여 rms 오차가 10% 미만이 되었다. 이 substrate 저항 모델을 guard-ring에 의한 isolation 구조에 적용하기 위하여 모델 방정식과 ADS(Advanced Design System) 회로 시뮬레이션에 의한 결과와 Network Analyzer의 측정 결과를 비교하였고, 비교적 잘 일치함을 확인하였다.

• 한국항공우주학회지
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• 제48권11호
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• pp.849-859
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• 2020

반경험식과 상용 전산해석도구를 이용하여 비행 속도 및 챔버 압력에 따른 유도무기의 기저항력을 예측하였으며, 두 해석 결과는 대체적으로 일치함을 보였다. 노즐에 의한 분사 제트의 과대/과소 팽창에 따라 기저부의 유동 특성과 기저항력의 차이가 관찰되었다. 과대팽창 조건에서는 기저부 상단에 팽창파가 발생되면서 기저부의 압력이 감소하였으며, 외부 자유류의 마하수가 증가함에 따라 팽창파의 강도가 강해지면서 기저부 압력 더욱 감소하였다. 과소 팽창 조건에서는 노즐 후류의 영향으로 기저부 주위에 충격파가 발생하고 이로 인해 기저부 압력이 증가하였으며, 챔버의 압력이 증가할수록 그 영향이 크게 나타났다. 동일 챔버 압력 조건에서는 자유류 마하수가 증가함에 따라 기저부에서 생성되는 충격파가 하류로 이동하면서 기저 압력이 감소하는 특성이 관찰되었다.

• 한국해안해양공학회지
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• 제13권4호
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• pp.319-326
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• 2001

본 논문에서는 경사형 방파제 설계시 최소 중량으로 외부 조건에 충분히 견딜 수 있는 사석 크기를 결정하는 방법을 제시한다. 기존의 방파제 설계에 있어 사석 중량 산정에 이용된 Iribarren, Hudson, Van der Meer 식 등은 단지 차원 해석에 의하여 파력이 중력과 파고의 곱에 비례하는 관계를 이용하였는데, 이번 연구에서는 파력이 파입자의 수표면 최대 속도와 밀접한 관계가 있음을 이용하였다. 또한 파고가 사석 중량 산정에 중요 요소인 것은 여러 논문을 통해서도 알 수 있는데, 이번 연구에서는 선형파 이론을 이용하여 새로운 매개 변수를 추출하였다. 이렇게 구한 경험식을 van der Meer 관측자료에 적용하여 경험계수 산정식을 결정하였다.

• E2M - 전기 전자와 첨단 소재
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• 제9권2호
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• pp.174-179
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• 1996

We present a new physically based analytical equation for electron effective mobility in MOS inversion layers. The new semi-empirical model is accounting expicitly for surface roughness scattering and screened Coulomb scattering in addition to phonon scattering. This model shows excellent agreement with experimentally measured effective mobility data from three different published sources for a wide range of effective transverse field, channel doping and temperature. By accounting for screened Coulomb scattering due to doping impurities in the channel, our model describes very well the roll-off of effective mobility in the low field (threshold) region for a wide range of channel doping level (Na=3.0*10$^{14}$ - 2.8*10$^{18}$ cm$^{-3}$ ).

• 설비공학논문집
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• 제12권9호
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• pp.835-842
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• 2000

Film boiling heat transfer of the subcooled turbulent liquid film flow on a horizontal plate was investigated by theoretical and experimental studies. In the theoretical analysis, by solving the integral energy and momentum equations analytically, some generalized expressions for Nusselt number was deduced. Next, by comparing the deduced equations with the experimental data on the turbulent film boiling heat transfer of the subcooled thin liquid film flow, the semi-empirical relation between the Nusselt number based on the modified heat transfer coefficient and the Reynolds number was obtained. The correlating equation was very similar to that of the turbulent heat transfer in a single phase flow, and it was found that the heat transfer was dissipated to increase the liquid temperature.

• 패션비즈니스
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• 제20권6호
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• pp.66-78
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• 2016

Hygroscopic knitted cotton fabric was found to spontaneously absorb water showing a significantly wide concentration gradient in the absorption direction. A semi-empirical diffusion model was introduced to describe how the wicking behavior compared to the classical capillary model (Washburn's equation), which has been widely used in the textiles industry. The capillary sorption curve and the permeability coefficient, which are key variables for the model equations, were measured using an electronic balance. The concentration profile as a function of the wicking distance and the elapsed time was derived, based on the diffusion model. From the concentration profile, the wicking distance detectable by the human eye or a digital camera with the aid of an image-analysis system, could be described realistically as a function of the time. The classical capillary model could be modified by introducing the tortuous correction factor to match the diffusion model. Wicking models and data-processing techniques in the work could provide useful tools for objectively evaluating the textile's wicking performances.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1490-1493
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• 2007

Aerodynamic noise generated from wind turbines is predicted by it's classified source mechanisms using computational method. BPF noise according to the blade passing motion, is modelled on monopole and dipole sources. They are predicted by Farassat 1A equation. Airfoil self noise and turbulence ingestion noise are modelled upon quadrupole sources and are predicted by semi-empirical formulas composed on the groundwork of Brooks et al. and Lowson. Retarded time is considered, not only in low frequency noise prediction but also in turbulence ingestion noise and airfoil self noise prediction. Wind turbine noise emission of a 3MW wind turbine and a 600 kW wind turbine, standing for large and middle sized wind turbines, is analyzed.

• Nuclear Engineering and Technology
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• 제29권2호
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• pp.99-109
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• 1997

A dynamic model for hydrogen generation by Fuel-Coolant Interactions(FCI) is developed with separate models for each FCI stage, coarse mixing and stratification. The model includes the physical concept of FCI, semi-empirical heat and mass transfer correlation and the concentration diffusion equation with the general non-zero boundary condition. The calculated amount of hydrogen, which is mainly generated in stratification, is compared with the FITS experiments. The model developed in this study shows a good agreement within a range of 10 % fuel oxidation rate and predicts the controlled mechanism of the chemical reaction very well. And this model predicts more accurately than the previous works. It is shown from the sensitivity study that the higher initial temperature of fuel particle is, the larger the reaction rate is. Up to 2700 K of temperature of the particle, the reaction rate increases rapid, which can lead to metal ignition.