• Journal of the Korea Institute of Building Construction
• /
• v.11 no.4
• /
• pp.371-378
• /
• 2011

Concrete is affected by various deterioration factors, such as $CO_2$ and chloride ions from the sea, which cause carbonation and salt attack on concrete. These deterioration phenomena cause steel corrosion in RC structures. Although a great deal of research has been carried out in this area thus far, it is difficult to know the point at which corrosion will occur to a reinforced bar. As the diffusion of deterioration factors depends on the water content in concrete, it is imperative to assess the condition of absorbed water content. A mass measuring method was applied to calculate the absorbed water diffusion coefficient, as well as non-linear finite element method(FEM) analysis. As a result, it was found that W/C and unit water content in concrete mixture affect the diffusion coefficient decision.

• Journal of the Korea Concrete Institute
• /
• v.25 no.2
• /
• pp.145-153
• /
• 2013

Recently, accelerated chloride diffusion coefficients are used for an evaluation of chloride behavior. Similar as apparent diffusion coefficients, accelerated diffusion coefficients decrease with time. In this study, decrease in diffusion coefficient with time is simulated with porosity. Utilizing DUCOM-program, porosities from 15 mix proportions are obtained and diffusion coefficients are modelled with regression analysis of porosity for 270 days. Considering non-linear binding capacity which means the relation between free and bound chloride ion, chloride behavior in high performance concrete is evaluated. Through utilizing the previous test results for concrete under chlorides for 180 days, the applicability of the proposed technique is verified. The proposed technique is evaluated to reasonably predict the chloride behavior in concrete with various w/c (water to cement) ratios and mineral admixtures (GGBFS and FA). It is also shown that decrease in chloride diffusion should be considered for chloride prediction in concrete with mineral admixture since it has very clear decrease in diffusivity with time.

• Journal of the korean Society of Automotive Engineers
• /
• v.14 no.3
• /
• pp.115-125
• /
• 1992

혼합 대류 이상 유동 시스템에 부유된 슈트와 미분탄과 같은 고흡수, 방사하는 입자의 열확산적 입자이동에 대한 복사 및 부력효과를 수치적으로 검토하였다. 기체 및 입자유동의 지배방정식 들은 Euler 관점의 two-fluid model의 근간에서 수행되었으며, 에너지 보존식의 비선형 복사 생 성항은 P-1 근사방법에 의해 계산되었다. 혼합 대류 유동에서의 입자의 열확산 현상은 복사 열 전달과 커플링되며, 복사효과의 증가는 부력효과를 상대적으로 감소시켜 부력효과에 의한 입자 부착율을 완화시켰다. 복사효과가 무시될 때 Grashof 수의 증가에 따라 입자의 확산효과는 감 소되었으며, 복사효과가 함께 작용될 때 입자 부착율은 증가됨을 보였다.

• Journal of the Korea Concrete Institute
• /
• v.14 no.6
• /
• pp.883-891
• /
• 2002

The chloride penetration in concrete structures is influenced by many factors such as types of cement and admixture proportion. Therefore, the effects of these factors on chloride diffusion must be correctly considered. The conventional diffusion analysis also neglected the existence of reinforcing bar in concrete structures. The purpose of the present paper is therefore to investigate the effect of reinforcing bar on the chloride diffusion in concrete structures. For this purpose, a comprehensive finite element analyses have been conducted to obtain chloride penetration profile. The results indicate that the chlorides are accumulated in front of a reinforcing bar and that the accumulation is much larger for the case of large diameter bars. The higher accumulation of chloride at bar location causes much faster corrosion of reinforcing steel. It can be concluded from the present study that the effects of reinforcing bars must be considered in chloride diffusion analysis for more realistic prediction of durable life of concrete structures.

• Proceedings of the Korea Institute of Convergence Signal Processing
• /
• 2003.06a
• /
• pp.300-303
• /
• 2003

In this paper, a baseband module of the spread spectrum system with FPGA is designed. A spread spectrum system spreads the signal bandwidth necessary for information transmission. We focused on the design of FEC decoder, especially the convolutional code fo constraint length K=3, rate R=l/2, is designed. For the VHDL design the Xilinx Foundation 3.1 is used. As results, a spread spectrum modem with convolutional coding is designed and we have plan to apply this modem to short distances wireless communication.

• Proceeding of EDISON Challenge
• /
• 2016.03a
• /
• pp.102-107
• /
• 2016

본 연구에서는 동역학적 격자기반 대정준 Monte Carlo (Kinetic Lattice Grand Canonical Monte Carlo, KLGCMC) 모의실험 방법을 이용하여 비정상 몰분율 효과 (Anomalous mole fraction effect)에 대해서 알아보고자 하였다. 이를 위해 양이온 선택성을 가진 이온채널 모델에서 $NH_4{^+}$와 $Rb^+$의 혼합물에 대하여 몰분율의 변화에 따른 이온전도도를 KLGCMC 모의실험을 이용하여 계산하고, 이를 평균장 이론인 Poisson-Nernst-Planck (PNP)의 결과와 비교해 봄으로써 비정상 몰분율 효과에 대하여 심도 있게 이해하고자 하였다. 본 연구 결과로부터 비정상 몰분율 효과는 이온채널의 이온 선택성에 의해서 발생함을 확인할 수 있었다. 즉, 두 종류 이상의 이온들이 채널 내부로 이동할 때, 이온채널의 이온 선택성에 의해서 각 이온들과 채널 간에 서로 상이한 상호작용을 하게 되고, 이로 인해서 이온 혼합물 조성의 변화, 즉 몰분율의 변화에 대해서 이온 전류가 선형적이 아닌 비선형적으로 변하게 됨을 알 수 있었다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.31 no.2C
• /
• pp.191-199
• /
• 2006

In this paper, we propose a method to implement a predistorter of the $rho$-th order inverse filter structure to prevent signal distortion and spectral re-growth due to the high PAPR (peak-to-average ratio) of the OFDM signals and the non-linearity of high-power amplifiers. We model the memory-less non-linearity of the high-power amplifier with a polynomial model and utilize the inverse of the model, the $rho$-th order inverse filter, for the predistorter. Once the non-linearity is modeled with a polynomial, since we can determine the $rho$-th order inverse filter only with the coefficients of the polynomial, large memory is not required. To update the coefficients of the non-linear high-power amplifier model, we can use LMS or RLS algorithms. The convergence speed is high since the number of coefficients is small, and the computation is simple since manipulation of complex numbers is not necessary.

• Proceedings of the Korean Society of Broadcast Engineers Conference
• /
• 2018.06a
• /
• pp.267-269
• /
• 2018

인공신경망의 확산 및 보급에 따라 적용 영역이 확대되고 있으며 여러 분야에서 획기적인 성능 향상을 이루고 있다. 영상 압축 분야의 기술개발은 기존 코덱 구조 내 각 요소기술의 성능향상을 위한 인공신경망 기술 분야와 기존 코덱 구조가 아닌 end-to-end 학습을 통한 인공신경망 기반 기술 분야로 나뉘어 진행되고 있다. 본 논문에서는 end-to-end 학습을 통한 인공신경망 기술의 비선형 변환 계층 중 GDN(generalized divisive normalization) 계층이 영상 압축에 미치는 영향을 분석한다.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.35 no.8A
• /
• pp.777-784
• /
• 2010

Recently, the necessity of underwater communication and demand for transmitting and receiving various data such as voice or high resolution image data are increasing as well. The performance of underwater acoustic communication system is influenced by characteristics of the underwater communication channels. Especially, ISI(inter symbol interference) occurs because of delay spread according to multi-path and communication performance is degraded. In this paper, we study the OFDM technique to overcome the delay spread in underwater channel and by using CP, we compensate for delay spread. But PAPR which OFDM system has problem is very high. Therefore, we use DFT-spread OFDM method to avoid nonlinear distortion by high PAPR and to improve efficiency of amplifier. DFT-spread OFDM technique obtains high PAPR reduction effect because of each parallel data loads to all subcarrier by DFT spread processing before IFFT. In this paper, we show performance about delay spread through OFDM system and verify method that DFT spread OFDM is more suitable than OFDM for underwater communication. And we analyze performance according to two subcarrier mapping methods(Interleaved, Localized). Through the simulation results, performance of DFT spread OFDM is better about 5~6dB at $10^{-4}$ than OFDM. When compared to BER according to subcarrier mapping, Interleaved method is better about 3.5dB at $10^{-4}$ than Localized method.

• 전기의세계
• /
• v.53 no.7
• /
• pp.19-23
• /
• 2004

정보화시대를 맞이하여 수용가측의 전력품질에 대한 관심이 나날이 높아지고 있고, 특히 공장자동화 및 컴퓨터의 보급 확산으로 배전계통에 비선형 부하의 사용이 늘어나고 있다. 공장제어기 및 인버터 마이크로 프로세서와 같은 기기들은 전력품질에 매우 민감하므로, 이들 기기를 보호하기 위해 전력품질 보상기기인 DVR, D-STATCOM과 같은 전력품질 향상기기가 개발되어 사용되고 있다. 이들 기기의 정확한 적용효과 분석 및 용량, 위치 선정 등을 위해서는 설치 개소의 부하특성 및 전력품질이 반영되어야 한다. 본 고에서는 국내의 계절별, 지역별, 용도별 부하구성비를 살펴보고, 실계통에 계측기를 설치하여 취득된 전압변동 데이터를 분석하였다. (중략)