• ETRI Journal
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• 제40권3호
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• pp.330-336
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• 2018

Free-space optical (FSO) systems have attracted much attention from both research and application perspectives owing to their many benefits, such as license-free operation, low-cost, and high data rates. This paper investigates the ergodic capacity of FSO systems, which is an important metric of system performance. The stochastic temporary laser-beam blockage, pointing errors, and atmospheric turbulence are simultaneously considered. The results illustrate that the link blockage causes a decreased ergodic capacity. We show that to maximize the ergodic capacity, there is an optimal value of the laser-beam radius at the waist, which largely depends on pointing errors; however, it is independent of the atmospheric turbulence and the probability of link blockage.

• 열처리공학회지
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• 제20권6호
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• pp.293-298
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• 2007

Influences of aluminum carbide ($Al_4C_3$) addition on microstructure and damping capacity of Mg-3%Al casting alloy have been investigated based on experimental results of optical micrography, scanning electron microscopy with energy-dispersive spectrometry analysis and damping capacity measurement at RT. The addition of $Al_4C_3$ particles results in an efficient grain refinement. The damping capacity shows an increasing tendency with an increase in $Al_4C_3$ content. The damping value associated with $Al_4C_3$ particles is linearly dependent on the volume fraction of $Al_4C_3$ particles to the 2/3 power, $f_{2/3}$, which corresponds to the total surface area of the particles.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.126-129
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• 1999

In this paper, it is assumed that a mobile radio channel is a Rayleigh distributed multipath fading channel and Erlang capacity and equivalent channel numbers are calculated for the reverse link of a imperfect power controlled DS/CDMA cellular system considering both shadowing and multipath fading. The DS/CDMA blocking probability is calculated based on a new analysis method that considers Erlang capacity and ICF(interference correction factor) using the median value of $E_{b(i)}$/ $I_{o}$ corresponding to each reverse link user. It is showed that the effect of multipath fading must not be ignored in Erlang capacity of the IS-95 DS/CDMA cellular system and the Erlang capacity is decreased according to the increase of the deviation of the imperfect power control, to the decrease of the processing gain, to the increase of the voice activity.y.

• 콘크리트학회논문집
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• 제12권5호
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• pp.101-110
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• 2000

A practical approach of calculating the ultimate strength of composite beams with unreinforced web opning is proposed through shear behavioral tests. In this method, the slab shear contribution at the opening is calculated as the smaller value of the pullout capacity of shear connector at the high moment end and the one way shear capacity of slab. A simple interaction equation is used to predict the ultimate strength under simultaneous bending moment and shear force. Strength prediction by the proposed method is compared with previous test results and the predictions by other analytical methods. The comparison shows that the proposed method predicts the ultimate capacity with resonable accuracy.

• Geomechanics and Engineering
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• 제9권3호
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• pp.287-311
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• 2015

The ultimate bearing capacity and failure mechanism of square footings resting on a sand layer over clay soil have been investigated numerically by performing a series of three-dimensional non-linear finite element analyses. The parameters investigated are the thickness of upper sand layer, strength of sand, undrained shear strength of lower clay and surcharge effect. The results obtained from finite element analyses were compared with those from previous design methods based on limit equilibrium approach. The results proved that the parameters investigated had considerable effect on the ultimate bearing capacity and failure mechanism occurring. It was also shown that the thickness of upper sand layer, the undrained shear strength of lower clay and the strength of sand are the most important parameters affecting the type of failure will occur. The value of the ultimate bearing capacity could be significantly different depending on the limit equilibrium method used.

• Geomechanics and Engineering
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• 제15권6호
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• pp.1193-1205
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• 2018

A footing located on slopes possess relatively lower bearing capacity as compared to the footing located on the level ground. The bearing capacity further reduces under seismic loading. The adverse effect of slope inclination and seismic loading on bearing capacity can be minimized by proving sufficient setback distance. Though few earlier studies considered setback distance in their analysis, the range of considered setback distance was very narrow. No study has explored the critical setback distance. An attempt has been made in the present study to comprehensively investigate the effect of setback distance on footing under seismic loading conditions. The pseudo-static method has been incorporated to study the influence of seismic loading. The rate of decrease in seismic bearing capacity with slope inclination become more evident with the increase in embedment depth of footing and angle of shearing resistance of soil. The increase in bearing capacity with setback distance relative to level ground reduces with slope inclination, soil density, embedment depth of footing and seismic acceleration. The critical value of setback distance is found to increase with slope inclination, embedment depth of footing and density of soil. The critical setback distance in seismic case is found to be more than those observed in the static case. The failure mechanisms of footing under seismic loading is presented in detail. The statistical analysis was also performed to develop three equations to predict the critical setback distance, seismic bearing capacity factor ($N_{{\gamma}qs}$) and change in seismic bearing capacity (BCR) with slope geometry, footing depth and seismic loading.

• 동력기계공학회지
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• 제9권1호
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• pp.70-75
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• 2005

The damping property of Fe-12Cr-22Mn-X alloys has been investigated to develop high damping and high strength alloy. Particularly, the effect of the phase of austenite, alpha and epsilon martensite, which constitute the structure of the alloys Fe-12Cr-22Mn-X alloys, on the damping capacity at room temperature has been investigated. Various fraction of these phases were formed depending on the alloy element and cold work degree. The damping capacity is strongly affected by ${\varepsilon}$ martensite while the other phase, such as ${\alpha}'$ martensite, actually exhibit little effect on damping capacity. In case of Fe-12Cr-22Mn-3Co alloy, the large volume fraction of ${\varepsilon}$ martensite formed at about 30% cold rolling, and in case of Fe-12Cr-22Mn-1Ti alloy, formed at about 20% cold rolling and showed the highest damping capacity. Damping capacity showed higher value in Fe-12Cr-22Mn-1Ti alloy than one in Fe-12Cr-22Mn-3Co alloy.

• 동력기계공학회지
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• 제8권4호
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• pp.31-37
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• 2004

The damping capacity and strength of Fe-2Al-26Mn alloys have been studied for the development of new materials with high strength and damping capacity. Particularly, the effect of ${\alpha}'\;and\;{\varepsilon}$ martensite phase, which constitutes the microstructure of cold rolled Fe-Al-Mn alloys, has been investigated in terms of the strength and damping capacity of the alloys. The damping capacity rises with increasing the degree of cold rolling and reveals the maximum value at 25% reduction. The damping capacity is strongly affected by the volume fraction of ${\varepsilon}$ martensite, while the other phases, such as ${\alpha}'$ martensite and austenite phase, actually exhibit little effect on damping capacity. Considering that tensile strength increases and elongation decreases with increasing the volume fraction of ${\alpha}'$ martensite, it is proved that tensile strength is mainly affected by the amount of ${\alpha}'$ martensite.

• 한국경제지리학회지
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• 제22권4호
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• pp.488-512
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• 2019

본 연구는 동아시아의 외부 선진 경제권과의 디커플링 가설을 최신 부가가치 교역통계를 활용하여 지역과 국가간 교역패턴 변화를 중심으로 검증하였다. 분석방법으로 부품이나 중간재 교역비중 등을 통한 간접 측정방법이 아닌 실제 부가가치의 역내외 배분 정도를 직접 측정할 수 있는 부가가치 창출능력 지표를 활용했다. 분석 결과, 첫째, 2000년대 중반까지 동아시아 성장엔진으로 작용했던 최종수요와 수출의 역내 부가가치 창출능력이 국제금융위기 이후 급격히 감소하여 정체상태에 머물고 있는 현상이 확인되었다. 둘째, 지역내 국가간 부가가치 배분 패턴의 변화에서 GVC 발전을 통해 미래 성장동력 배양을 기대할 수 있는 후발 개도국의 기부능력이나 수혜능력에 의미 있는 변화가 발견되지 않았다. 마지막으로 동아시아 중심국으로 기능하고 있는 중국의 역내 부가가치 기부능력이 2000년대 중반 이후 현저히 감소한 반면 수혜능력은 크게 늘어나면서 경쟁관계에 있는 역내 선진 경제국의 부가가치 수혜능력이 상대적으로 줄어드는 등 중국의 역내 부가가치 창출능력이 제한적임을 발견하였다.

• 한국유기농업학회지
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• 제20권1호
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• pp.71-80
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• 2012

본 실험은 중부 지방에서 Rye(곡우)와 Triticale(신영)의 단, 혼파 실험을 통하여 생산성, 사료가치 및 가축사육능력을 조사하여 중부지방에 적합한 초종을 선별하고자 하였으며, 결과를 요약하면 다음과 같다. 동계 사료작물의 건물수량은 밭토양에서는 R+R이 5.20ton/ha로 가장 많았으나 R, T+R과 유의한 차이는 없었고, 논토양에서는 R+H가 5.20ton/ha로 가장 많았지만 T+H, R과의 유의한 차이는 없었다. 또한 모든 시험구에서 단파구에 대한 혼파구의 상대수량이 1.00보다 높아 혼파효과가 입증되었다. 상대사료가치는 밭토양, 논토양 모두 Triticale 혼파구에서 다른 시험구와 유의한 차이를 보였다. 가축사육능력은 $K_{CP}$와 $K_{TDN}$의 평균값으로 비교해 보았을 때, 밭토양에서는 R+R이 2.75, 논토양에서는 T+H가 2.84로서 가장 높은 값을 보였다. 이상의 결과로 볼 때 중부 지방에서 동계 사료작물 생산에 있어서 가장 적합한 초종은 밭토양에서는 Rye+Red clover 혼파이며, 논토양에서는 Triticale+Hairy vetch 혼파라고 판단된다.