• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1994년도 Proceedings of the Korea Automatic Control Conference, 9th (KACC) ; Taejeon, Korea; 17-20 Oct. 1994
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• pp.100-105
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• 1994

In this paper, we discuss a method for design of an ambulance stretcher which call decrease blood pressure fluctuation caused by ambulance acceleration. Recently, a lot of stretchers which can isolate the vertical vibration to reduce body resonances (4-10 Hz) have been used during ambulance transport. However, we have found that blood pressure of a patient laying in the stretcher fluctuates when the ambulance accelerates or decelerates. Since the enforced change of the blood pressure may deteriorate the patent's condition, a stretcher to cancel head-to-foot acceleration and to decrease the blood pressure variation (BPV) is expected for safe transport. We propose a method to design a stretcher which is tilted according to an adequate angle to cancel head-to-foot acceleration by gravity when the ambulance accelerates or decelerates. A control method of the stretcher is constructed by means of simulation analysis using acceleration data measured during ambulance transport. It is confirmed that the active controlled stretcher proposed has good performance for the BPV reduction.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 1997년도 추계학술대회 발표논문집:21세기를 향한 정보통신 기술의 전망
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• pp.451-462
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• 1997

A 2-dimensional numerical analysis is presented for thermal-electron heat conduction effects upon the electron transport and the drain current-voltage characteristics of submicron GaAs MESFETs, based on the use of a nonstationary hydrodynamic transport model. It is shown that for submicron GaAs MESFETs, electron heat conduction effects are significant on their internal electronic properties and also drain current-voltage characteristics. Due to electron heat conduction effects, the electron energy is greatly one-djmensionalized over the entire device region. Also, the drain current decreases continuously with increasing thermal conductivity in the saturation region of large drain voltages above 1 V. However, the opposite trend is observed in the linear region of small drain voltages below 1 V. Accordingly, for a large thermal conductivity, negative differential resistance drain current characteristics are observed with a pronounced peak of current at the drain voltage of 1 V. On the contrary, for zero thermal conductivity, a Gunn oscillation characteristic is observed at drain voltages above 2 V under a zero gate bias condition.

• 한국습지학회지
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• 제5권1호
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• pp.67-78
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• 2003

The unsteady 2D convection and diffusion equation is solved numerically for the real-time simulation of suspended load propagation. The streamlined upwind scheme efficiently reduces numerical oscillations due to the high Peclet number in the convection dominant flow. By using the mixed boundary condition to express the external source terms or externally induced suspended load as a function of time in the algorithm, the model is capable of handling not only continuous load cases but also non-continuous suspended load influx. The suspended load transport modelwas verified using a case study for which an analytical exact solution is available and was applied to the real-time simulation of a suspended load influx case on the Mississippi River. The model algorithm can provide a framework upon which water quality as well as contaminant transport models can be built.

• 한국대기환경학회:학술대회논문집
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• 한국대기환경학회 2002년도 추계학술대회 논문집
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• pp.255-258
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• 2002

The vertical exchange of trace gases and aerosols in upper regions of the atmosphere is primarily controlled by the atmospheric conditions. The study of the vertical and temporal variation of the upward transport of $H_2O$ and the downward transport of $O_3$, NO$_2$, CO and other long-lived trace species will enable a better understanding of these transport mechanisms. (omitted)

• 세라미스트
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• 제23권2호
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• pp.145-165
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• 2020

Halide perovskites are promising photovoltaic materials due to their excellent optoelectronic properties like high absorption coefficient, low exciton binding energy and long diffusion length, and single-junction solar cells consisting of them have shown a high certified efficiency of 25.2%. Despite of high efficiency, perovskite photovoltaics show poor stability under actual operational condition, which is the mostly critical obstacle for commercialization. Given that the stability of the perovskite devices is significantly affected by charge-transporting layers, the use of inorganic charge-transporting layers with better intrinsic stability than the organic counterparts must be beneficial to the enhanced device reliability. In this review article, we summarized a number of studies on the inorganic charge-transporting layers of the perovskite solar cells, especially focusing on their effects on the enhanced device reliability.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2006년도 춘계학술대회
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• pp.81-84
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• 2006

To investigate the characteristics of water droplet on the gas diffusion layer from both upper-view and side-view of flow channel, a rig test apparatus was designed and fabricated with L-shape acryl plate in a $1mm{\times}1mm$ micro-channel. This experimental device is used to simulate the single droplet growth and its transport process under fuel cell operating condition. As a first step, we investigated the growth and transport of single water droplet with working temperature and air flow velocity. The contact angle and its hysteresis of water droplet at departing moment are measured and analyzed. It is expected that this study can provide the basic understanding of liquid water droplet behavior in gas flow channel and GDL interface during the PEM fuel cell operation.

• 한국결정성장학회지
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• 제29권3호
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• pp.140-142
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• 2019

자외선 LED용 기판소재로 응용가능한 AlN(질화알루미늄) 단결정을 물리기상이동법(Physical Vapor Transport Method)으로 성장하기 위해 성장 거동을 조사하였다. 다결정의 종자결정을 사용하였으며, 직경은 3인치급이었고, 120시간 동안 성장공정을 수행하여 길이 약 4 mm의 다결정상을 얻었다. 본 연구에서는 성장 조건과 대형의 도가니를 사용하였을 경우의 성장 거동에 대하여 고찰하여 보고자 하였다.

• 한국결정성장학회지
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• 제26권2호
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• pp.84-88
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• 2016

PVT(Physical vapor transport)법을 이용하여 AlN 단결정을 성장시켰으며 유도 코일의 위치를 변화시켜가면서 핫존의 위치가 달라짐에 따라 변화하는 결과를 비교하였다. 그라파이트 도가니가 사용되었으며 그 규격은 ${\Phi}90{\times}H120$이었다. 온도는 $1950{\sim}2050^{\circ}C$이며 챔버 압력은 150에서 1 Torr까지 사용되었다. 또한 핫존은 실험 회차에 따라 변화를 주었으며 이 결과가 비교되었다. 핫존의 위치가 AlN 단결정 응축 위치에서부터 충분히 아래쪽(> 40 mm)인 경우 성장된 결정 사이즈는 다른 조건들에 비해 양호했지만(${\sim}300{\mu}m/hr$), 조건 재현성은 상당히 떨어졌다. 반대로 핫존과 AlN 성장 위치간의 거리가 가까워질수록 성장된 결정의 크기는 작아지고 결정의 핵이 생성되는 빈도는 낮아지면서 성장된 결정의 질의 안정성은 증가했다. 성장 속도와 품질 두 가지 면에서 초기 핫존 코일의 위치가 결정 성장 위치로부터 20 mm 정도일 때가 가장 우수했다. 핫존의 위치는 매우 민감한 결과를 주었고 이것에서 더 나아가 코일의 이동 속도 또한 최적으로 컨트롤 되어야만 최적의 성장 조건이 설정될 수 있다.

• 대한전자공학회논문지TC
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• 제48권11호
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• pp.73-82
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• 2011

무선 인터넷 사용자의 증가, IPTV 확산, 개인 멀티미디어 플랫폼의 다양화 등으로 IP 기반의 패킷 서비스에 대한 요구가 증가함에 따라 TDM 기술을 사용하는 회선 기반의 전송방식에서 이더넷 기반의 패킷 전송방식으로 기술이 진화하고 있다. 본 논문에서는 PBB-TE 기술 및 MPLS-TP 기술을 적용한 패킷 전송망에 대해 소개하고, 패킷 전송망에서 사용자의 다양한 요구조건에 만족하는 서비스 품질 관리 방안을 제시한다. 제안된 플로우 기반의 QoS 관리 방안에서는 입력 프레임을 플로우 별로 구분하여 PTL 터널에 매핑하고 각 플로우 및 PTL 터널 별 대역관리를 수행함으로써 대역충돌 상황에서도 설정된 서비스 품질을 완벽히 보장해 줄 수 있다. 제안된 방안의 성능분석을 위해 각 입력 프레임 별 플로우 및 PTL 터널을 정의하고 각 플로우 및 PTL 터널 별 QoS 파라메터를 설정하였으며 OPNET modeler를 사용하여 모의시험을 수행 하였다.

• Journal of Applied Biological Chemistry
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• 제43권1호
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• pp.25-30
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• 2000

The main form of nitrogen fertilizer applied to lowland rice is urea, but little is known about its transport in waterlogged soil. This study was conducted to investigate the transport of urea in waterlogged soil column using WAVE (simulation of the substances Water and Agrochemicals in the soil, crop and Vadose Environment) model which includes the parameters for urea adsorption and hydrolysis, The adsorption distribution coefficient and hydrolysis rate of urea were measured by batch experiments. A transport experiment was carried out with the soil column which was pre-incubated for 45 days under flooded condition. The urea hydrolysis rate (k) was $0.073h^{-1}$. Only 5% of the applied urea remained in soil column at 4 days after urea application. The distribution coefficient ($K_d$) of urea calculated from adsorption isotherm was $0.21Lkg^{-1}$, so it was assumed that urea that urea was a weak-adsorbing material. The maximum concentration of urea was appeared at the convective water front because transport of mobile and weak-adsorbing chemicals, such as urea, is dependent on water convective flow. The urea moved down to 11 cm depth only for 2 days after application, so there is a possibility that unhydrolyzed urea could move out of the root zone and not be available for crops. A simulated urea concentration distribution in waterlogged soil column using WAVE model was slightly different from the measured concentration distribution. This difference resulted from the same hydrolysis rate applied to all soil depths and overestimated hydrodynamic dispersion coefficient. In spite of these limitations, the transport of urea in waterlogged soil column could be predict with WAVE model using urea hydrolysis rate (k) and distribution coefficient ($K_d$) which could be measured easily from a batch experiment.