• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.37-40
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• 2001

This paper presents the modeling methodology of Zinc diffusion process applied for high-speed avalanche photodiode fabrication using neural networks. Three process factors (sealing pressure, amount of Zn$_3$P$_2$ source per volume, and doping concentration of diffused layer) are examined by means of D-optimal design experiment. Then, diffusion rate and doping concentration of Zinc in diffused layer are characterized by a static response model generated by training fred-forward error back-propagation neural networks. It is observed that the process models developed here exhibit good agreement with experimental results.

• 한국농공학회지
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• 제45권1호
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• pp.102-114
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• 2003

The objectives of the paper are to evaluate cell based pollutant loadings for different storm events, to monitor the hydrology and water quality of the Baran HP#6 watershed, and to validate AGNPS with the field data. Simplification was made to AGNPS in estimating storm erosivity factors from a triangular rainfall distribution. GIS-AGNPS interface model consists of three subsystems; the input data processor based on a geographic information system. the models. and the post processor Land use patten at the tested watershed was classified from the Landsat TM data using the artificial neural network model that adopts an error back propagation algorithm. AGNPS model parameters were obtained from the GIS databases, and additional parameters calibrated with field data. It was then tested with ungauged conditions. The simulated runoff was reasonably in good agreement as compared with the observed data. And simulated water quality parameters appear to be reasonably comparable to the field data.

• Bulletin of the Korean Chemical Society
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• 제28권9호
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• pp.1477-1484
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• 2007

Artificial neural networks (ANNs), for a first time, were successfully developed for the prediction partial molar heat capacity of aqueous solutions at infinite dilution for various polar aromatic compounds over wide range of temperatures (303.55-623.20 K) and pressures (0.1-30.2 MPa). Two three-layered feed forward ANNs with back-propagation of error were generated using three (the heat capacity in T = 303.55 K and P = 0.1 MPa, temperature and pressure) and six parameters (four theoretical descriptors, temperature and pressure) as inputs and its output is partial molar heat capacity at infinite dilution. It was found that properly selected and trained neural networks could fairly represent dependence of the heat capacity on the molecular descriptors, temperature and pressure. Mean percentage deviations (MPD) for prediction set by the models are 4.755 and 4.642, respectively.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.195-198
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• 2006

One of the major sources of error in precise GPS positioning since the turn-off the Selective Availability(SA) is the ionospheric propagation delay. For the last decades, a lot of the ionospheric researches based on a GPS network have been implemented throughout the world. Especially researches of the ionospheric modeling for Wide Area Argumentation System(WAAS) have been undertaken and published. In mid-latitude regions, typical spatial and temporal variations in ionospheric models delay tend to minimal. The developed ionospheric model calls for a 1.25 degree grid at latitudes and a 2.5 degree grid at longitudes. The precise grid TEC estimated by the inversion technique is also compared with global ionosphere maps(GIMs) which have been provided by several analysis centers(ACs). The results of initial investigations into the suitability of the proposed ionospheric modeling scheme in north-east Asia are presented.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 International Symposium on GPS/GNSS Vol.2
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• pp.199-202
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• 2006

One of the major sources of error in precise GPS positioning since the turn-off the Selective Availability(SA) is the ionospheric propagation delay. For the last decades, a lot of the ionospheric researches based on a GPS network have been implemented throughout the world. Especially researches of the ionospheric modeling for Wide Area Argumentation System(WAAS) have been undertaken and published. In mid-latitude regions, typical spatial and temporal variations in ionospheric models delay tend to minimal. The developed ionospheric model calls for a 1.25 degree grid at latitudes and a 2.5 degree grid at longitudes. The precise grid TEC estimated by the inversion technique is also compared with global ionosphere maps(GIMs) which have been provided by several analysis centers(ACs). The results of initial investigations into the suitability of the proposed ionospheric modeling scheme in north-east Asia are presented.

• 한국항해항만학회지
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• 제32권8호
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• pp.589-596
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• 2008

선박의 접안운동을 자동화하기 위하여 인공신경망(Artificial Neural Network, 이하 ANN)에 의한 제어를 수행하였다. ANN은 시스템의 비선형성이 표현 가능하므로 접안운동과 같은 비선형성이 강한 조종운동에 적합하다. 입력층과 출력층 사이에 하나 이상의 중간층이 존재하는 다층 인식자(Multi-layer perceptron)를 사용하였고, 교사 데이터(Teaching data)와 역전파(Back-Propagation) 알고리즘을 사용하여 신경망의 출력값과 목표 출력값 사이의 오차가 최소가 되도록 신경망 학습을 수행하였다. 접안 시 저속조종 수학모델을 사용하여 접안 시뮬레이션을 수행하였으며, ANN의 입력층 성분(unit)이 8개인 구조와 6개인 구조의 접안 제어를 비교하였다. 시뮬레이션 결과, 두 ANN에 의하여 접안 경로 선택에 차이가 나타났으나 접안 조건은 모두 만족하였다.

• 한국군사과학기술학회지
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• 제23권4호
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• pp.407-416
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• 2020

Recent complex battle field demands Network Centric Warfare(NCW) ability to control various parts into a cohesive unit. In path planning filed, the NCW ability increases complexity of path planning algorithm, and it has to consider a communication coverage map as well as traditional parameters such as minimum radar exposure and survivability. In this paper, pros and cons of various propagation models are summarized, and we suggest a coverage map generation method using a Longley-Rice propagation model. Previous coverage map based on line of sight has significant discontinuities that limits selection of path planning algorithms such as Dijkstra and fast marching only. If there is method to remove discontinuities in the coverage map, optimization based path planning algorithms such as trajectory optimization and Particle Swarm Optimization(PSO) can also be used. In this paper, the Longley-Rice propagation model is used to calculate continuous RF strengths, and convert the strength data using smoothed leaky BER for the coverage map. In addition, we also suggest other types of rough coverage map generation using a lookup table method with simple inputs such as terrain type and antenna heights only. The implemented communication coverage map can be used various path planning algorithms, especially in the optimization based algorithms.

• 한국통신학회논문지
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• 제38A권9호
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• pp.765-772
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• 2013

본 논문에서는 인천공항 Concourse 지역에서 항공정보통신 무선 채널의 경로 손실 모델에 관해 연구하였다. 항공정보통신 주파수 밴드인 VHF/UHF 채널 중에 두 개의 주파수에 대해 전파 측정을 수행하였다. 현재 운영 중인 송신 사이트에서 변조 신호를 제거한 캐리어 파워를 송신하였으며, 전파 측정을 위해 수신기를 장착한 이동 차량을 이용하여 Concourse 지역에서 전파 측정을 수행하였다. 송신 파워, 주파수, 안테나 위치 등은 현재 운용 조건과 같다. 경로 손실 계수 및 실험적인 경로 손실 식은 기본적인 경로 손실 모델 및 하타 모델 등을 이용하여 추출하였다. Concourse 지역에서 추출된 LOS/NLOS 경로 손실 계수는 128.2MHz 및 269.1MHz에서 각각 3.1/3.13 및 3.01/3.38이었고 예측 에러의 편차는 각각 2.77/3.17 및 4.01/3.66이었다. 추출된 경로 손실 계수를 이용하여 Concourse 지역에서 전파 경로 손실식과 실험적인 경로 손실 계수를 도출하였으며 또한 다른 전파 패스 모델과 비교하였다. 이러한 결과는 항공정보통신 사이트 최적 위치 선정 및 항공정보통신 서비스 평가에 도움이 될 것이다.

• 대기
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• 제21권2호
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• pp.163-172
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• 2011

Numerical forecasting depends on the initial condition error strongly because numerical model is a chaotic system. To calculate the sensitivity of some forecast aspects to the initial condition in the Korea Meteorological Administration (KMA) Unified Model (UM) which is originated from United Kingdom (UK) Meteorological Office (MO), an algorithm to calculate adjoint sensitivities is developed by modifying the adjoint perturbation forecast model in the KMA UM. Then the new algorithm is used to calculate adjoint sensitivity distributions for typhoon DIANMU (201004). Major initial adjoint sensitivities calculated for the 48 h forecast error are located horizontally in the rear right quadrant relative to the typhoon motion, which is related with the inflow regions of the environmental flow into the typhoon, similar to the sensitive structures in the previous studies. Because of the upward wave energy propagation, the major sensitivities at the initial time located in the low to mid- troposphere propagate upward to the upper troposphere where the maximum of the forecast error is located. The kinetic energy is dominant for both the initial adjoint sensitivity and forecast error of the typhoon DIANMU. The horizontal and vertical energy distributions of the adjoint sensitivity for the typhoon DIANMU are consistent with those for other typhoons using other models, indicating that the tools for calculating the adjoint sensitivity in the KMA UM is credible.

• 한국해안·해양공학회논문집
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• 제30권6호
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• pp.263-269
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• 2018

해저에서 지진 및 산사태 등에 기인하는 수심변화는 자유수면의 변동을 유발한다. 이러한 자유수면의 변동은 해안으로 전파하고 천수현상에 의해 파고가 상승하면서 큰 피해를 야기한다. 지진해일의 생성 및 전파과정을 모의하기 위해 다양한 수치해석모형이 개발된 바 있다. 대부분의 지진해일모형은 해저 지반의 움직임이 수면에 즉시적이고 동일하게 전달된다는 가정하에 초기수면을 결정한다. 하지만, 이 접근 방법은 시간적 및 공간적 차이를 지니고 발생하는 해저지진의 특성을 고려하지 못하며, 이는 그대로 해석오차에 반영된다. 본 연구에서는 Hammack(1973)의 해석해를 응용하여 수심이 시간차를 가지고 변할 때 이로 인한 초기 자유수면의 변동과 이렇게 변화된 수면의 전파 특성을 모의하고 그 결과를 검토하였다. 이는 다양한 유형의 지반운동과 자유수면 형성과의 인과관계 및 상승된 자유수면의 이동속도 등의 관계규명에 도움이 될 것이다.