• Magazine of the Korea Concrete Institute
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• v.10 no.6
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• pp.291-301
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• 1998

In this paper, two dimensional and three dimentional modeling techniques are proposed for the failure analysis of deteriorated reinforced concrete T-girder bridge subjected to cyclic loading up to failure. For the nonlinear failure anaysis, a tension stiffening model which can consider degradation of bond between reinforcement and surrounding concrete due to corrision of rebars in old bridge is proposed and a modeling technique for the supports conditions of the bridges which can consider degradation of bearing at supports in old bridge is also proposed, The analysis results along with comparisons with full-scale failure-test results confirm that finite element modeling techniques in this paper can be well applied to the failure analyses of in-situ old reinforced concrete T-girder bridges subjected to cyclic loading and the support condition modeling especially affects the bridge strength significantly.

• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.72-74
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• 2005

전력선통신은 현재 홈 네트워크 및 검침기술과 같은 다양한 분야에서 활발하게 응용이 되고 있는 기술이다. 이러한 전력선 통신을 위한 전송선로는 통신을 위한 정보데이터를 전송하는 기능과 더불어 선로상의 전력 부하들을 위한 전력 공급용으로서의 용도도 가지고 있다. 그러므로 선로상의 부하변동은 다양한 형태의 임 펄스 잡음을 야기 시키고 이러한 임펄스성 잡음은 전송 데이터에 군집에러를 발생시킴으로써 통신성능을 크게 열화 시키는 요인이 되고 있다. 따라서 효율적인 전력선 통신시스템을 위해서는 전력 선로상의 임펄스 잡음의 특성을 명확히 분석하고, 그에 따른 에러제거기법을 적용하는 것이 필수적이라고 할 수 있다. 이러한 관점에서 본 논문에서는 새롭게 가정의 전력 선로에 연결되는 부하들의 동작 및 변동에 따른 임펄스 잡음 특성을 다양한 부하의 유형별로 디지털 하드웨어를 이용하여 실측 및 분류한 후, 새롭게 도출한 임펄스 잡음 모델을 기반으로 순방향 오류정정방식(FEC;Forward Error Correction)인 컨벌루션 부호화(Convolution Coding) 및 인터리빙(Interleaving) 방식을 가미하여 시스템의 비트오율 개선효과를 확인하였다. 본 논문에서 수행된 새로운 실측기반의 임펄스 잡음이 반영된 채널부호화 방식에 의한 성능평가 결과는 향후 홈네트워크기반의 전력선 통신시스템의 실질적인 참고데이터로서 유용하게 활용되리라 기대된다.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1008-1014
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• 2003

In this paper, we propose the image retrieval method based on object regions using bidirectional round filter in the wavelet transform domain. A conventional method that includes unnecessary background information reduce retrieval efficiency, because of the extraction of feature vectors from the whole region of subband. On proposed method, it extracts accurate feature vectors and keep certainly retrieval efficiency in case of reduced feature vectors, because of the extraction of feature vectors from the only extracted object region. Furthermore, it improve retrieval efficiency by removing unnecessary background information. Consequently, the retrieval efficiency is improved with 2.5%∼5.5% values, which have a little chances to vary according to characteristics of image.

• Journal of Radiation Protection and Research
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• v.17 no.2
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• pp.49-59
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• 1992

A new model was developed in order to investigate the effects of chelating agents on the migration of a radionuclide in the form of ion or chelate. The migration behavior of the chelated radionuclide was analyzed by formulating a convective-dispersion transport equation which included a degradation of chelating agent and chelated radionuclide. The mathematical model was analytically solved and checked with the existing retardation factor. The results show that the migration velocity of the chelated radionuclide was much faster than the ionic one due to the decreased retardation. Therefore, it was concluded that a new remedial action should be developed to reduce the generation and release of chelating agents from the nuclear power plant into the environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.7A
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• pp.682-688
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• 2006

In this paper, a soft-decision method for initial PN code acquisition in pilot-channel aided Direct Sequence Code Division Multiple Access (DS-CDMA) systems is proposed in order to improve the acquisition performance. We apply this technique to the conventional hybrid search algorithm and analyze it in terms of mean code acquisition time. For the analysis, we present mathematical model of proposed algorithm and also perform the simulation under IMT-2000 channel models. Numerical results show that our proposed scheme outperforms the conventional one by 0.2 - 0.4 sec with respect to the mean code acquisition time because the soft decision technique can mitigate the possible decline in search performance caused by the use of a hard-decision technique.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.41 no.1
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• pp.80-82
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• 2016

In this letter, we evaluate the performances of both GOOK and GFSK de/modulation techniques which are candidates for ULP communications in WPAN systems. For the performance evaluation, we define the system model for each of GOOK and GFSK de/modulations and perform computer simulations based on the proposed models. From the computer simulations, we show that GOOK de/modulation technique has 15 dB out-of-band emission gain and is robust over frequency offsets in terms of BER compared to GFSK de/modulation technique.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.12
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• pp.1777-1783
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• 2021

The use of drones is gradually increasing for the efficient maintenance of large-scale renewable energy power generation complexes. For a long time, photovoltaic panels have been photographed with drones to manage panel loss and contamination. Various approaches using artificial intelligence are being tried for efficient maintenance of large-scale photovoltaic complexes. Recently, semantic segmentation-based application techniques have been developed to solve the image classification problem. In this paper, we propose a classification model using semantic segmentation to determine the presence or absence of failures such as arcs, disconnections, and cracks in solar panel images obtained using a drone equipped with a thermal imaging camera. In addition, an efficient classification model was implemented by tuning several factors such as data size and type and loss function customization in U-Net, which shows robust classification performance even with a small dataset.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.4
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• pp.421-431
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• 2023

Sewer deterioration models can offer important information on prediction of future condition of the asset to decision makers in their implementing sewer pipe networks management program. In this study, Markov chain model was used to estimate sewer deterioration trend based on the historical structural condition assessment data obtained by CCTV inspection. The data used in this study were limited to Hume pipe with diameter of 450 mm and 600 mm in three sub-catchment areas in city A, which were collected by CCTV inspection projects performed in 1998-1999 and 2010-2011. As a result, it was found that sewers in sub-catchment area EM have deteriorated faster than those in other two sub-catchments. Various main defects were to generate in 29% of 450 mm sewers and 38% of 600 mm in 35 years after the installation, while serious failure in 62% of 450 mm sewers and 74% of 600 mm in 100 years after the installation in sub-catchment area EM. In sub-catchment area SN, main defects were to generate in 26% of 450 mm sewers and 35% of 600 mm in 35 years after the installation, while in sub-catchment area HK main defects were to generate in 27% of 450 mm sewers and 37% of 600 mm in 35 years after the installation. Larger sewer pipes of 600 mm were found to deteriorate faster than smaller sewer pipes of 450 mm by about 12 years. Assuming that the percentage of main defects generation could be set as 40% to estimate the life expectancy of the sewers, it was estimated as 60 years in sub-catchment area SN, 42 years in sub-catchment area EM, 59 years in sub-catchment area HK for 450 mm sewer pipes, respectively. For 600 mm sewer pipes, on the other hand, it was estimated as 43 years, 34 years, 39 years in sub-catchment areas SN, EM, and HK, respectively.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.299-310
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• 2009

In this paper, we proposed a new method to correct the zoom lens distortion for the video sequence captured by the zoom lens. First, we defined the nonlinear zoom lens distortion model which is represented by the focal length and the lens distortion using the characteristic that lens distortion parameters are nonlinearly and monotonically changed while the focal length is increased. Then, we chose some sample images from the video sequence and estimated a focal length and a lens distortion parameter for each sample image. Using these estimated parameters, we were able to optimize the zoom lens distortion model. Once the zoom lens distortion model was obtained, lens distortion parameters of other images were able to be computed as their focal lengths were input. The proposed method has been made experiments with many real images and videos. As a result, accurate distortion parameters were estimated from the zoom lens distortion model and distorted images were well corrected without any visual artifacts.

• Korean Journal of Construction Engineering and Management
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• v.8 no.5
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• pp.71-79
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• 2007

It is common that the analysis of VE/LCC is performed in design phase of quay wall structures. The analysis is mainly executed based on experience and engineering sense of expert considering the selection of construction method, construction and maintenance cost. Recently there are increasing demands on the analysis that includes uncertainty and vulnerability of input parameters, for this purpose, fuzzy reliability based probabilistic VE/LCC analysis model for quay wall structures is suggested. In VE/LCC analysis for quay wall structures, the application of probabilistic analysis method give very similar results compare with those of deterministic analysis method. It is anticipated that the methodology proposed in this paper can also be utilized in the design and maintenance phase of other facilities where decision making is made for the probabilistic life cycle cost and value analysis.