• Journal of the Korea Academia-Industrial cooperation Society
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• 제21권10호
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• pp.393-405
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• 2020

Various geotechnical information is required to evaluate the stability of the ground and a foundation once liquefaction occurs due to earthquakes, such as the soil strength and groundwater level. The results of the Standard Penetration Test (SPT) conducted in Korea are registered in the National Geotechnical Information Portal System. If geotechnical information for a non-drilled area is needed, geostatistics can be applied. This paper is about the feasibility of obtaining ground information by the Empirical Bayesian Kriging (EBK) method and the Inverse Distance Weighting Method (IDWM). Esri's ArcGIS Pro program was used to estimate these techniques. The soil strength parameter of the drilling area and the level of groundwater obtained from the standard penetration test were cross-validated with the results of the analysis technique. In addition, Multichannel Analysis of Surface Waves (MASW) was conducted to verify the techniques used in the analysis. The Buk-gu area of Pohang was divided into 1.0 km×1.0 km and 110 zones. The cross-validation for the SPT N value and groundwater level through EBK and IDWM showed that both techniques were suitable. MASW presented an approximate section area, making it difficult to clearly grasp the distribution pattern and groundwater level of the SPT N value.

• Proceedings of the Korean Information Science Society Conference
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• 한국정보과학회 2003년도 봄 학술발표논문집 Vol.30 No.1 (B)
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• pp.371-373
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• 2003

웹 문서를 분류하는 목적은 특정 주제별로 중요한 문서들을 구분하려는 것과 사용자의 선호도를 바탕으로 개인화를 하려는 것으로 나누어 볼 수 있다. 특히, 웹의 효율적인 탐색을 위해 사용자가 관심 있어 할 웹 문서를 분류하는 것은 중요하다 일반적으로 하나의 웹 문서는 특징 추출방법에 의해 문서 벡터로 표시되며 사용자의 선호여부나 주제번호를 클래스로 삼는다. 사용자가 선호도를 표시한 웹 문서를 사용하여 새로운 웹 문서의 선호 여부를 예측하기 위해 자기 구성지도(SOM)를 사용하면, 시각적으로 구조를 보여주어 데이터 사이의 관계를 효과적으로 이해할 수 있다. 그러나 SOM은 노드의 개수와 구조를 자동적으로 결정하지 못하는 단점이 있기 때문에, SOM의 장점을 활용하면서 자동적으로 구조를 결정하기 위해 구조적응 자기구성지도(SASOM)를 이용한다. 보다 나은 성능과 다양한 해석을 위해, 여러 개의 SASOM을 서로 다른 특징추출 방법을 이용하여 학습시킨 후 사용자가 주관적으로 분류기의 중요도를 결정할 수 있는 퍼지적분을 사용하여 결합하였다. UCI Syskill & Webert 데이터에 대한 실험결과 기존의 DT, MLP, naive Bayes 분류기 보다 향상된 성능을 보였다.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2009년도 학술발표회 초록집
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• pp.996-1000
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• 2009

물순환계를 종합적으로 관리하기 위해서는 물순환계의 모니터링과 해석모형의 구축이 필요하다. 실측자료만으로는 복잡 다양한 물순환계 구조 및 인과관계를 규명할 수 없기 때문에 시간적 공간적으로 변화하는 다양한 수문현상을 일관된 하나의 시스템으로 이해하기 위해 물순환 해석모델을 구축하여 검토할 필요가 있다. CAT(Catchment hydrologic cycle Analysis Tool)은 수문학적으로 균일하게 판단되는 범위를 소유역으로 분할하여 지형학적 요인에 의한 유출 특성을 객관적으로 반영할 수 있게 하며, 토양층에 따라 침투, 증발, 지하수 흐름 등의 모의가 가능하도록 하는 Link-Node 모형으로, 증발산은 기준 증발산을 외부에서 직접 입력하거나, Penman-Monteith 방법을 선택할 수 있으며, 침투는 토양의 수리전도도에 따른 연직방향 침투 및 사면방향 복귀류를 고려할 수 있다. 노드의 지하수 유거를 고려하여 기존 노드-링크 방식 모형의 장기 유출 해석시 제한점을 보완하였으며, Muskingum, Muskingum-Cunge, Kinematic wave 방법을 이용하여 하도추적을 모의할 수 있다. 또한 GUI를 통해 사용자가 손쉽게 모형을 적용하고 관리 할 수 있도록 하고, 여러 시나리오를 적용함에 있어서 편리하도록 개발 중인 모형이다. 본 연구에서는 개발중인 CAT 모형을 평가 하기위해 시험 유역으로 운영 중인 설마천 유역에 적용하여 소유역 분할(노드수), 계산 시간 간격(일/시단위) 등에 따른 적용성을 평가하였다. 관측 자료를 통해 구축 가능한 물리적 매개변수를 통해 해당 유역을 단일 노드 및 다중 노드로 간단히 모형화할 수 있었으며, 모의 결과, 관측 유량과 적절히 일치하는 결과를 얻을 수 있었다. 1시간 단위에 대한 모의에서도 유출을 적절히 모의할 수 있었으며, 소규모 유역에 대한 정밀한 물순환 해석이 가능할 것으로 평가되었다.

• Geophysics and Geophysical Exploration
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• 제5권4호
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• pp.299-308
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• 2002

We have derived an analytical expression for the sensitivity of the frequency domain small-loop electromagnetic (EM) surveys over a two-layer earth in order to estimate the depth of investigation with an instrument having the source-receiver separation of about 2 m. We analyzed the sensitivities to the lower layer normalized by those to the upper half-space and estimated the depth of investigation from the sensitivity analyses and the mutual impedance ratio. The computational results showed that the in-phase components of the sensitivity to the lower layer dominates those to the upper layer when the thickness of the upper layer is less than 20 m, while the quadrature components are not sensitive to the lower layer over the entire frequency range. Hence we confirmed that the accurate measurement of the in-phase component is essential to increase the depth of investigation in the multi-frequency small-loop EM survey. When conductive basement of 10 ohm-m underlies the upper layer of 100 ohm-m, an accurate measurement of the in-phase components ensures the depth of the investigation more than 10 m even accounting a noise effect, from which we conclude that the small-loop EM survey is quite effective in imaging the conductive plume down to a considerable depth. On the other hand, in the presence of the resistive basement of 1,000 ohm-m, the depth of investigation may not exceed 5 m considering the instrumental accuracy, which implies that the application of the small-loop EM survey is not recommended over the resistive environment other than detecting the buried conductor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제34권6호
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• pp.67-74
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• 2006

In this paper, a tiled display system is developed to get a high-resolution image in visualization of large-scale structural analysis data with low-resolution display devices and low-cost cluster computer system. Concerning the hardware system, some of the crucial points are investigated, and a new beam-projector positioner is designed and manufactured to resolve the keystone phenomena which result in distorted image. In the development of tiled display software, Qt and OpenGL are utilized for GUI and rendering, respectively. To obtain the entire tiled image, LAM-MPI is utilized to synchronize the several sub-images produced from each cluster computer node.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제17권5호
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• pp.25-33
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• 2017

NOMA (Non-orthogonal multiple access) system becoming a strong candidate for 5G cellular system of its high spectral efficiency. This paper considers an optimal power allocation scheme to minimize the outage probability of a user relay based cooperative NOMA system. We first derive the outage probabilities of the relay user (RU) and the destination user (DU) with selection combining. Based on these probabilities, the outage probability of the cooperative NOMA system is obtained. The analytical results are verified by Monte Carlo simulation. It is noticed that the outage probability of cooperative NOMA system has a convex function, the optimum power allocation coefficient, which satisfied the minimum outage probability, is calculated. Numerical examples show that the optimal power allocation coefficient increases with the required capacity of DU. While the capacity of DU is fixed, we noticed that the increase of the required capacity of RU decreases the optimal power allocation coefficient.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제17권5호
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• pp.35-42
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• 2017

NOMA (Non-orthogonal multiple access) system is the most promising multiple access technology to satisfy the requirements of the spectral efficiency and the performance of 5G cellular systems. NOMA system simultaneously serves multiple users in the power domain, and adapts SIC (Successive interference cancellation) at the receivers to cancel the interference from multiple users. Since in a realistic wireless fading channel the perfect SIC is impossible, the study of the effect of the imperfect SIC to a NOMA system is necessary. This paper considers a cooperative NOMA system with SIC error, and the performance of the system is analytically derived. And the optimum power allocation to minimize the system performance is obtained. When the transmit power is fixed, the distances between a base station and the relay is considered for different SIC errors. The derived analytical results are verified through Monte Carlo simulation, and the results are perfectly matched.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• 제18권5호
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• pp.69-75
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• 2018

Recently, Non-orthogonal multiple access (NOMA) has been focused for the next generation multiple access, which has more spectral efficiency under the limited spectrum bandwidth. Moreover, the spectrum efficiency can be improved by cognitive radio in which the unlicensed secondary users can access the spectrum that is used by the licensed primary user under the limited interference. Hence, we consider the combination of NOMA and cognitive radio, and derive the performance of the cognitive cooperative NOMA system. For the cooperation, a relay is selected among near users, and the selection combining is assumed at a far user. The outage probability of the selected relay and the far user is derived in closed-form, respectively. The provided numerical results are matched well with the Monte Carlo simulation. Numerical results showed that the performance of the relay is affected from the power allocation coefficient, the minimum outage probability is observed at 0.86 of the power allocation coefficient for far user under the given conditions. More than 15 dB of signal-to-noise ratio is required to meet the outage probability of $1{\times}10^{-13}$ for the far user with the frequency acquisition probability of 0.5 compared to that of 1. It shows that the performance of the far user is very sensitive to the acquisition probability of the cognitive relay.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• 제5권2호
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• pp.29-38
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• 1994

The denser and higher speed telecommunication systems get, the more electromagnetic waves and more heat they throw off. With power predictions lastly for the upcoming systems, they need the enforced method to optimize the technologies between shielding effectiveness and cooling characteristics. In the present study, the shielding effectiveness and cooling characteristics for en- closures with multiapertures considered as fundamental solution in telecommunication systems are performed both of experimentally and unmerically. The shielding effectiveness measured from ex- perimental work is compared with both of the analytical data for flat plates with multi-apertures and the cooling characteristics by the numerical solution. As results, the most significant influence on the shielding effectiveness of enclosures is determined by the porosities of apertures, and it is found that shielding effectiveness and cooling capabilities are significant varied, reciprocally,at which porosity is more than 80%.

• Proceedings of the KIPE Conference
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.183-184
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• 2012

본 논문에서는 출력 인덕터 리플과 2차 측 정류기의 공진 전압을 저감할 수 있는 다중 위상천이 풀 브리지 컨버터를 제안한다. 제안된 회로는 총 8개의 스위치가 사용되며, 각 4개의 스위치가 하나의 위상천이 풀 브리지 인버터 부를 구성하는 구조이다. 기존 위상천이 풀 브리지 컨버터의 경우, 진상레그와 지상레그의 위상차이를 조절하여 출력전압을 제어하는데 반해, 제안된 회로는 진상레그와 지상레그의 위상차이 뿐만 아니라 각 풀 브리지 인버터 부의 위상차이를 동시에 조절하여 출력전압을 제어하는 것이 특징이다. 이를 통하여 제안회로는 출력 인덕터 전류 리플 및 2차 측정류기의 공진 전압을 크게 저감시킬 수 있어 고 효율화에 유리하다. 본 논문에서는 제안된 회로의 이론적 해석 및 PSIM 모의실험을 수행하며, 450W급 시작품을 제작하여 제안회로의 타당성을 검증하였다.