• The Journal of Korean Institute of Communications and Information Sciences
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• v.14 no.5
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• pp.571-577
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• 1989

In this paper, the double-refractive index profile, which is generalized a trapezoidal index profile, is proposed to study the characteristics of a optical fiber in the wave length 1.55um. Being compared with a triangle profile, it has many advantages over an optimum core radius, the minimum refractive index difference and the change of chromati dispersion characteristics with wavelength. Though the value of a varies from 2 to infinite, the same results are approximately obtained. Therefore, in fabrication of a fiber, the step part of trapezoidal index profile can replace the profile of a-power refractive index. Because the refractive index presented in this paper varies with a, it can be applied to multiple cladding fiber or segmented core fiber. And it is expected that the characteristics of the fiber are obtained.

• Proceedings of the Korean Geotechical Society Conference
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• 2000.03b
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• pp.365-372
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• 2000

현장상황에 대한 불충분한 자료와 파괴 메커니즘에 대한 불완전한 이해로 인해 발생하는 가변성(variability)과 불확실성(uncertainty)은 암반사면공학뿐만 아니라 지반공학에서 흔히 접하게 되는 문제점이다. 특히 암반사면공학에서는 이러한 가변성과 불확실성이 불연속면의 방향 및 기하학적 특성, 그리고 실내실험 결과의 분산으로 나타난다. 그러나 안전율(factor of safety)의 개념을 기초로 하는 전통적인 결정론적 해석방법(deterministic analysis)은 이러한 분산을 고려하지 않은 채 단일 대표 값만을 이용하여 구조물의 안정성을 판단하여 왔다. 확률론적 해석방법(probabilistic analysis)은 이러한 가변성과 불확실성을 효과적으로 정량화하여 해석에 이용할 수 있는 방법 중의 하나로 제안되었다. 이러한 해석방법은 불연속면의 기하학적 특성과 강도 특성을 확률변수(random variable)로 취급하여 신뢰성이론(reliability theory)과 확률이론(probability theory)을 근거로 분석하였으며 이를 기초로 하여 Monte Carlo Simulation과 같은 해석법을 이용, 구조물의 붕괴가능성을 확률로 표현하였다. 확률론적 해석 방법은 기존의 안전율을 대체하여 구조물의 안정성을 붕괴확률(probability of failure)로 제안하였으며 이 붕괴확률은 안전율의 확률분포함수 (probability density function)에서 안전율이 1보다 작을 가능성을 확률로 나타낸 수치이다. 본 논문에서는 확률론적 해석방법을 이용하여 불연속면 특성들의 확률특성을 고찰하였으며 이를 기초로 하여 암반사면의 안정성 해석에 응용했다.

• Korean Journal of Soil Science and Fertilizer
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• v.13 no.2
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• pp.65-70
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• 1980

This experiment was aimed at selecting the most suitable dispersing agent to the Korean soils. The particle size distribution of 18 soil samples representing the great soil groups in Korea was analysed with 5 different dispersing agents by pipette-method. Passing percent of 0.05, 0.02 and 0.002mm in diameter was used for the comparision of the dispersion capacity of chemical agents. The results obtained are as follows; 1. The influence of chemical agents on dispersion seemed to be greater to finer soil particles. The passing percents of 0.002mm showed a great differences according to the chemical agents used, while little differences was observed in those of 0.05mm. 2. It was showed that sodium pyrophosphate had the highest dispersion capacity for the most of Korean soils, the dispersion capacity of sodium hexametaphosphate was also high enough except for volcanic ash soils. 3. It was recommendable that sodium hexametaphosphate could widely be used as a dispersing agent in the routine analysis of soil particle size distribution except for the Volcanic ash soils. 4. The dispersion of Volcanic ash soils was rather poor when chemical agents used. Therefore, special care should be taken for the dispersion of allophane soils.

• The Korean Journal of Applied Statistics
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• v.14 no.2
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• pp.429-437
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• 2001

단순 이단계 표본 추출의 경우에 최적 선택률은 Hansen과 Hurwitz(1949)에 의하여 구하여졌다. 그러나 통계청에서 실시하는 표본조사등은 층화 이단계 추출을 한다. 따라서 실제적인 필요성에 의하여 층화 2단계 표본 설계를 시도 하였다. 층화 이단계 표본추출시에 주어진 비용아래서 모총계의 추정량의 분산을 최소로 하는 최적의 선택확률(optimum selection probability), 표본추출율과 부차 표본추출율을 Lagrangean 승수법에 의하여 구한다.

• The Journal of the Acoustical Society of Korea
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• v.17 no.2
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• pp.63-70
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• 1998

특정 기지국에 호가 집중하는 경우, 통화차단율 증가로 인한 가입자에 대한 서비스 의 저하를 해결할 수 없다. 따라서 근접 기지국에 할당된 채널의 상당부분을 특정 기지국이 공용하도록 함으로서 채널이용률을 최대화하고 통화차단율을 최소화할 수 있는 중계망 구성 에 대한 연구가 절실히 요구된다. 본 논문에서는 특정 기지국에 발생하는 집중호를 근접 기 지국에 균등 분배케 함으로서 통화차단율을 최소화하고 가입자에 대한 통화서비스를 향상시 킬 수 있는 중계망 운용 알고리듬을 제안하고 컴퓨터 시뮬레이션을 통해 그 개선 정도를 확 인한다.

• Nuclear Engineering and Technology
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• v.24 no.1
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• pp.40-51
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• 1992

One of the important irradiation performance characteristics of the silicide dispersion fuel element in research reactors is the diameteral increase resulting from fuel swelling. This paper, will attempt to develop a physical model for the fuel swelling, DFSWELL, by analyzing the basic irradiation behaviours and some experimental evidences. From the experimental evidences, it was shown that the volume changes in irradiated U$_3$Si-Al were strongly dependent on temperature and fission rate. The quantitative-amount of swelling for silicide fuel is estimated by considering temperature, fission rate, solid fission product build-up and gas bubble behavior. The swelling for the silicide fuel is comprised of three major components : i ) a volume change due to the formation of an interfacial layer between the fuel particle and matrix. ii ) a volume change due to the accumulation of gas bubble nucleation iii ) a volume change due to the accumulation of solid fission products The DFSWELL model which takes into account the above three major physical components predicts well the absolute magnitude of silicide fuel swelling in accordance with the power histories in comparison with the experimental data.

• Journal of Broadcast Engineering
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• v.16 no.1
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• pp.144-154
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• 2011

In this paper, we propose a parallel LDPCA encoding method for fast transform-domain Wyner-Ziv video encoding which is suitable in an ultra fast and low power video encoding. The conventional transform-domain Wyner-Ziv video encoding performs LDPCA channel coding of quantized transform coefficients in bitplane-serial fashion, which takes about 60% of total encoding time, and this computational complexity becomes severer as the bitrate increases. The proposed method binds several bitplanes into one packed message and carries out the LDPCA encoding in parallel. The proposed LDPCA encoding method improves the encoding speed by 8 ~ 55 times. In the experiment, the proposed Wyner-Ziv encoder can encode 700 ~ 2,300 QCIF size frames per second with GOP=64. The method can be applied to the pixel-domain Wyner-Ziv encoder using LDPCA, and has a wide scope of application.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.6
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• pp.48-57
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• 2003

In this paper, An 8${\times}$l ID-IDCT processor with adder-based distributed arithmetic(DA) and bit-serial method Is presented. To reduce hardware cost and to improve operating speed, the proposed 8${\times}$1 ID-IDCT used the bit-serial method and DA method. The transform of coefficient equation results in reduction in hardware cost and has a regularity in implementation. The sign extension computation method reduces operation clock. As a result of logic synthesis, The gate count of designed 8${\times}$1 1D-IDCT is 17,504. The sign extension processing block has gate count of 3,620. That is 20% of total 8${\times}$1 ID-IDCT architecture. But the sign extension processing block improves more than twice in throughput. The designed IDCT processes 50Mpixels per second and at a clock frequency of 100MHz.

• Journal of the Korea Society of Computer and Information
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• v.10 no.4 s.36
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• pp.93-102
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• 2005

Excessive traffic of P2P applications in the limited communication environment is considered as a network bandwidth problem. Moreover, Though P2P systems search a resource in the phase of search using weakly connected systems(peers' connection to P2P overlay network is very weakly connected), it is not guaranteed to download the very peer's resource in the phase of download. In previous P2P search algorithm (1), we had adopted the heuristic peer selection method based on Random Walks to resolve this problems. In this paper, we suggested an adaptive P2P search algorithm based on the previous algorithm(1) to reform the node distribution rate which is affected in unit peer ability. Also, we have adapted the discriminative replication method based on a query ratio to reduce traffic amount additionally. In the performance estimation result of this suggested system, our system works on a appropriate point of compromise in due consideration of the direction of searching and distribution of traffic occurrence.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.138-139
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• 2010

본 논문은 저복잡도 비디오 부/복호화를 위한 엔트로피 부호화 기반의 분산 비디오 코딩 방법을 제안한다. 제안하는 엔트로피 부호화 기반의 분산 비디오 코딩은 복호기의 복잡도를 줄이기 위하여 기존의 분산 비디오 코딩에서 사용하는 채널코딩을 이용하는 것이 아니라 엔트로피 코딩을 이용하여 부호화를 수행한다. 제안하는 방법에서 복호가는 움집임 추정을 수행하고 그 결과인 움직임 백터를 부호기로 전송하며, 부호기는 전송받은 움직임 백터를 초기 움직임 백터로 하여 움직임 백터 값의 갱신을 수행한다. 제안한 방법의 성능을 평가하기 위하여 기존의 분산 비디오 코딩 방법과 복호기 복잡도를 비교한 결과 99%의 복잡도 감소가 있었고, H.264/AVC의 All Intra 방법과 비교하여 20.3%의 비트율 감소가 있었다.