• 디지털융복합연구
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• 제10권4호
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• pp.265-270
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• 2012

최근 기간망의 전송속도는 괄목할 만한 성장을 이루고 있으나 가입자 전송망의 전송속도는 이전 수준에 비교해서 진정이 없는 상태이다. 그래서 가입자 접속 구간은 다수의 LAN과 백본망 사이에 병목지점으로 지적되고 있다. 현재 가입자 구간은 VOD, 양방향게임, 양방향 영상회의와 같은 새로운 대용량 멀티미디어 서비스를 수용하기에 충분한 대역폭을 제공하지 못하고 있다. 그런 가운데 저가의 이더넷 장비와 광선로 인프라를 융합한 EPON(Ethernet Passive Optical Network)이 차세대 가입자 접속망에 가장 적합하다. 하지만 이러한 우수성을 가진 EPON도 안정적인 대용량 멀티미디어 서비스를 제공하기에는 부족함을 가지고 있다. EPON에서 ONU가 수신할 수 있는 대역폭은 1GBPS이지만 송신하기 위한 대역폭은 모든 ONU가 공유해야 하므로 부족하다. 따라서 양방향 초고속 가입자 접속망을 위해 FTTx를 지원하는 EPON의 부족한 상향 전송 대역폭을 충족시키는 상향 대역폭 할당 방법이 필요하다. 본 논문에서는 EPON의 상향 트래픽에 대한 QoS를 보장하기 위한 우선순위 큐를 고려한 가중치 기반의 차등대역폭 할당 방식을 제안한다.

• 한국지능시스템학회논문지
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• 제14권3호
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• pp.310-315
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• 2004

야간에 비디오카메라로 촬영시 열악한 주위 환경과 영상 전송에 기인하여 다양한 잡음에 의하여 왜곡되고 흐린 저대비 (low contrast)영상을 가질 수 있다. 본 논문에서는 획득한 저대비 영상을 대비 향상시켜주는 기법을 제안한다. MPEG-2는 인간의 시각 특성상 색차(chrominance)신호보다 밝기(luminance)신호에 더 민감하기 때문에 밝기신호와 색차신호를 분리하여 압축한다. 본 논문에서는 밝기신호만을 추출하여, K-means 알고리듬을 사용하여 교차점을 자동으로 선정하는 방법을 사용한다. 이 최적의 교차점을 선정하는 과정은 획득한 영상을 물체와 배경으로 분리하는 두 개의 클래스 문제로 보고 K-means 알고리듬을 적용하였다. 구한 교차점을 사용하여 영상을 양분하고 양분된 영상의 각각에 히스토그램 평활화 방법을 적용하였다. 본 논문에서는 퍼지성 지수(index of fuzziness)를 사용하여 향상의 정도를 측정하였다. 제안된 기법을 저대비 영상에 적용하였으며 그 결과를 히스토그램 평활화 기법의 결과와 비교하였다.

• Steel and Composite Structures
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• 제33권4호
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• pp.569-581
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• 2019

Corrugated steel plate shear wall (CSPSW) as an innovative lateral load resisting system provides various advantages in comparison with the flat steel plate shear wall, including remarkable in-plane and out-of-plane stiffnesses and stability, greater elastic shear buckling stress, increasing the amount of cumulative dissipated energy and maintaining efficiency even in large story drifts. Employment of low yield point (LYP) steel web plate in steel shear walls can dramatically improve their structural performance and prevent early stage instability of the panels. This paper presents a comprehensive structural performance assessment of corrugated low yield point steel plate shear walls having circular openings located in different positions. Accordingly, following experimental verification of CSPSW finite element models, several trapezoidally horizontal CSPSW (H-CSPSW) models having LYP steel web plates as well as circular openings (for ducts) perforated in various locations have been developed to explore their hysteresis behavior, cumulative dissipated energy, lateral stiffness, and ultimate strength under cyclic loading. Obtained results reveal that the rehabilitation of damaged steel shear walls using corrugated LYP steel web plate can enhance their structural performance. Furthermore, choosing a suitable location for the circular opening regarding the design purpose paves the way for the achievement of the shear wall's optimal performance.

• Tribology and Lubricants
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• 제36권6호
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• pp.385-390
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• 2020

It rains heavily, such as long rain and typhoons, during a typical rainy season in Korea. In this season, several fuel contamination accidents by water and vehicular problems caused by water contaminated fuel occur. Many research groups have studied the effects of water contaminated fuel on vehicles and environment. However the characteristics of water contaminated fuel have not been studied. In this study, we prepared diesel samples with a constant ratio of water (0~30 volume %) using an emulsifier. Then, we analyzed these diesel samples for their representative fuel properties. In the analytical results, diesel with 30% water showed an increase in fuel properties such as density (823→883 kg/㎥), kinematic viscosity (2.601→6.345 ㎟/s), flash point (47→56℃), pour point (-22→2℃), CFPP (cold filter plugging point) (-17→20℃) and copper corrosion number (1a→2a). The low temperature characteristics, such as low pour point and CFPP, blocks the fuel filter in the cold season. In addition, water contaminated diesel decreases lubricity (190→410 ㎛) under high frequency reciprocating rig (HFRR) and derived cetane number (54.81→34.25). The low lubricity of fuel causes vehicle problem such as pump and injector damage owing to severe friction. In addition, the low cetane diesel fuel increases exhaust gases such as NOx and particulate matters (PM) owing to incomplete combustion. This study can be used to identify the problems caused by water contamination to vehicle and fuel facilities.

• The Journal of Korean Physical Therapy
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• 제14권4호
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• pp.398-411
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• 2002

Objectives: The purpose of present study was to investigate the experience and point prevalence rate and factors related with Low Back Pain (LBP) in train egineers. Methods: Questionnaires were completed by 324 train engineers in Daejeon railroad administration from May 2002. The information was used to estimate odds ratio (OR) and 95$\%$ confidence intervals (CI) for factors relation to LBP. A retrospective study design was used. Results: The experience rate for LBP was 67.9$\%$, 54$\%$ in one year interval prevalence, 53.4$\%$ in 6 months interval prevalence, and 47.8$\%$ in a point prevalence rate. Variables significantly associated with LBP experience were age (p=0.0327), train vibration(p=0.0015), labour hour(p=0.0034), and pay(p=0.0534). As subjects got older, the higher experience for LBP was (OR=1.1, 95$\%$ CI 1.0-1.2). LBP experience rate for people who had felt train vibration was a higher than those who did not (OR=2.5, 95$\%$ CI 1.4-4.4, OR=2.3 95$\%$ CI 1.3-4.0 in a point prevalence). The people who worked for long hour was a higher than those who did not (OR=2.8, 95$\%$ CI 1.4-5.6, OR=2.2, 95$\%$ CI 1.1-4.5 in a point prevalence). The people who were not satisfied with pay was a higher than those who were (OR=1.7, 95$\%$ CI 1.0-3.0). Factors related to a point prevalence rate were train vibration(p=0.0027), chair vibration (p=0.0444), and labour hour(p=0.0340). LBP a point prevalence rate for people who had felt the vibration of train chair was a higher than those who did not (OR=1.8 95$\%$ CI 0.7-2.0). Conclusions: Results from present study indicated that a statistically significant factors associated with LBP experience were age, train vibration, labour hour, and pay, Factors related to a point prevalence rate were also train vibration, the vibration of train chair, and labour hour.

• Journal of Biosystems Engineering
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• 제17권2호
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• pp.156-170
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• 1992

The force-deformation relationship gives the basic physical properties of the fruits such as the bioyield point, the rupture point, and the deformations at the bioyield point and the rupture point. These informations are very important to study the stress-strain relationships of the fruits. This study was conducted to analyze those physical properties according to the sampling position of the fruits, and to determine the bioyield point, the rupture point, and the deformations at the bioyield point and the rupture point of the fruits for two different storage conditions(low temperature and normal temperature) and the storage period, and to investigate the effect of loading rate on those physical properties, the hysteresis on the loading-unloading condition and the degree of elasticity of the fruits. The results of the study were as follows : 1. The physical properties(BS, US, BD, and RD) of the test specimen selected from the different sampling positions were quite different. The values of the physical properties were shown smallest ones at the cheek of the fruits, and the statistical test results of the physical properties between the cheek from the other two positions of the fruits showed that there were significant difference at the 1 % level between them. 2. The effect of loading rate on the physical properties of the fruits was relatively large, all the considered physical propertis of the fruits increased with the loading rate, but the hysteresis loss decreased with it. 3. The physical properties of the fruits according to the storage conditions and period showed different, and the bioyield deformation and the rupture deformation of the fruits increased with the storage period, but the bioyield strength and the ultimate strength of the fruits decreased with it. The effect of the storage conditions on the those physical properties showed that the normal temperature storage condition was a little higher than the low temperature storage condition. 4. As a whole, it was shown that the bioyield strength and the ultimate strength of the pear decreased a little faster than those of the apple, and the bioyield deformation and rupture deformation of the pear increased a little faster than those of apple at the two storage conditions.

• 소성∙가공
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• 제24권4호
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• pp.241-247
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• 2015

In order to prevent shape defects such as fluting and stretcher strains during press forming of aged low carbon steel sheets, roller leveling conditions for reducing yield point elongation were studied. Yield point elongations of leveled sheets were determined as a function of leveling, which is defined as the plastic fraction or the ratio of plastically deformed part in sheet thickness section to the whole thickness of the sheet. By adjusting this plastic fraction during leveling to more than 78%, yield point elongation in the leveled sheets was reduced so no fluting occurred during subsequent tangential bending. Stretcher strains can be avoided by leveling the sheet to an 84% plastic fraction condition.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2000년도 춘계학술대회 논문집 전자세라믹스 센서 및 박막재료 반도체재료 일렉트렛트 및 응용기술
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• pp.35-38
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• 2000

In this study, the rise throughput and the stability in fabrication of device can be obtained by applying of CMP process to STI structure in 0.l8um semiconductor device. Through reverse moat pattern process, reduced moat density at high moat density, STI CMP process with low selectivity could be to fit polish uniformity between low moat density and high moat density. Because this reason, in-situ motor current end point detection method is not fit to the current EPD technology with the reverse moat pattern. But we use HSS without reverse moat pattern on STI CMP and take end point current sensing signal.[1] To analyze sensing signal and test extracted signal, we can to adjust wafer difference within $110{\AA}$.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 봄 학술발표회 논문집
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• pp.154-159
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• 1995

Cold weather concrete presents the many characteristic variation of quality, according to the mixing and cooling point, the cooling time and the quantity of air besides the compressive strength of concrete. Thus, in this study to verify the character of cold-weather concrete we make the concrete specimens at laboratory and cool them at cooling-melting machine and then test the 7days compressive strength of them, with the variation of compressive strength of concrete, cooling point, cooling time, cooling weather and air quantity. At the results, the compressive strength of concrete decrease in the case of early cooling point, long cooling time, low cooling temperature and the low design compressive strength

• 전기학회논문지
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• 제58권6호
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• pp.1241-1245
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• 2009

As FFT(Fast Fourier Transform) processor is used in OFDM(Orthogonal Frequency Division Multiplesing) system. According to increase requirement about mobility and broadband, Research about low power and low area FFT processor is needed. So research concern in reduction of memory size and complex multiplier is in progress. Increasing points of FFT increase memory area of FFT processor. Specially, SRU(Signal Reordering Unit) has the most memory in FFT processor. In this paper, we propose a reduced method of memory size of SRU in FFT processor. SRU of 64, 1024 point FFT processor performed implementation by VerilogHDL coding and it verified by simulation. We select the APEX20KE family EP20k1000EPC672-3 device of Altera Corps. SRU implementation is performed by synthesis of Quartus Tool. The bits of data size decide by 24bits that is 12bits from real, imaginary number respectively. It is shown that, the proposed SRU of 64point and 1024point achieve more than 28%, 24% area reduction respectively.