• Journal of the Korean Institute of Telematics and Electronics D
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• v.36D no.9
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• pp.50-55
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• 1999

In this paper we proposed a variable optical attenuator using the side polished fiber coupled with a refractive index matching liquid. Small variation of refractive index of matching liquid can induce very large change of optical loss due to the coupling between the fiber mode and radiation mode. The thermo-optic effect of matching liquid was used to ontrol the optical attenuation. The side polished fiber block was fabricated using the silicon V gloove. Experimental results showed that $5^{\circ}C$ temperature variation was enough to adjust full range attenuation. The polarization dependent loss and insertion loss of the fabricated devices were 0.5dB and 0.2dB respectively.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.9
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• pp.111-117
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• 1998

This paper presents a polarity changing method without dead time of a cycloconverter with an LC resonant circuit. According to the proposed method, dead time to prevent short circuit for the polarity changing is not required. Therefore the delay of control and the harmonic components of output currents can be decreased. And the proposed method can be expanded for the other natural commutated cycloconverters of noncirculating current type. In this paper, the switching method of the proposed polarity changing without dead time is studied, and in order to confirm the validity of the proposed method the experiment is carried out with a cycloconverter with an LC resonant circuit.

• KSBB Journal
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• v.8 no.1
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• pp.83-88
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• 1993

Lipase was separated using reverse mlcelles in a spray column. The 50 mM AOT-Isooctane solution was used as reverse micellar solution for the extraction of lipase (crude containing 25% Protein). Ionic strength was controlled by KCl(0.1M KCl for extraction, 0.5M KCl for back exlractlon). Acetate buffer and phosphate buffer were used for control of pH. The efficiencies of extraction and stripping were 30% and 50%. An increase of circulation did not change the efficiency of extraction in forward extraction. The optimum flow rate was around 0.10ml/sec.

• Broadcasting and Media Magazine
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• v.27 no.4
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• pp.79-90
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• 2022

'스마트 기술(smart tech)'과 '도시화(urbanization)'라는 두 메가트렌드(megatrends)를 융합해 탄생한 스마트시티(smart city)가 전 세계적인 화두다. 스마트시티의 성장 가운데서 핵심적인 요소가 바로 '도시의 다양한 요소가 미디어(媒體, media)의 기능을 하는 커뮤니케이션이 중심이 된 도시'라는 점이다. 특히 메타버스 기술이 스마트시티에 접목되고 있음에 주목해야 한다. '초월'이라는 의미의 '메타(meta)'와 우주를 뜻하는 '유니버스(universe)'의 합성어인 메타버스(Metaverse)는 1992년 닐 스티븐슨(Neal Stephenson)의 소설 《스노우 크래쉬》에서 유래한 개념이라고 알려져 있다[1]. 메타버스는 정의하는 연구자에 따라서 크게 다르지만 흔히 '가상의 것(virtual thing)'으로 한정하는 경향이 있다. 하지만 최근에는 메타버스가 정치·경제·사회·문화 전반적 측면에서 오프라인의 현실과 온라인의 비현실 모두 공존할 수 있는 생활형·게임형 가상 융합 세계라는 의미로 보다 광의적으로 사용되고 있다. 최근 스마트시티의 변화를 보면 도시 운영이 고도로 지능화되고 다양한 콘텐츠가 증강되면서 <<도시 공간에서의 온라인과 오프라인의 경계 구분>>을 파괴하고 있음을 발견할 수 있다. 우리는 과거와 다름없이 물리적 도시 공간을 걷고 있지만 이제는 지형지물과 연결된 공간정보를 스마트폰으로 확인하고 또 도심의 디지털 사이니지(digital signage)를 통해 실시간 공공 및 상업 정보에 항시적으로 접하고 있다. 도시의 지향점으로 간주되는 스마트시티는 이제 일종의 '도시민 생활 플랫폼'으로 메타버스 기술과 융합 콘텐츠를 통해 도시민의 생활을 촘촘하게 연결한다. 본고에서는 '스마트시티가 메타버스 미디어 공간으로 기능하는 현상'을 '테코레이션(Tecoration: Technology + Decoration: 디지털 미디어 기술을 통한 도시 공간구축)'이라고 명명하려고 한다. 본고는 '메타버스 미디어 공간으로서 스마트시티 그리고 디지털 사이니지 테코레이션'을 주제로 '디지털 사이니지가 만들어 가는 스마트시티의 소통'과 관련된 주요 이슈를 다루려고 한다.

• Journal of Soil and Groundwater Environment
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• v.8 no.1
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• pp.48-56
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• 2003

A geophysical conductivity logging technique has been adopted to determine hydraulic constants using a simplified physical model that depicts the borehole condition. An experiment has been made by monitoring the conductivity change within the model hole using borehole environment water and incoming-outgoing water of different salinity, under the state of constant flow rate by maintaining balance between inflow and outflow. Conductivity variation features were observed that depended on flow rate, salinity contrasts between fluid within the hole and incoming-outgoing fluid, and density contrasts between fluid conductivity within the hole and incoming fluid. The results of the experiment show the uniform change of fluid conductivity within the hole with time, a fairly good correlation between the flow rate and the conductivity change rate. The geophysical conductivity logging technique can be an efficient tool for determining hydraulic constants if the model equation is verified by henceforward experiments.

• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.45-45
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• 2020

하천 횡단구조물 하류부에서는 고유속 및 ±압력에 의해 하상재료가 유실되는 세굴현상이 발생한다. 이러한 세굴을 방지하기 위해 횡단구조물 하류부에는 석재, 콘크리트 및 콘크리트 블록 등을 설치 및 포설하여 하상보호공을 설치한다. 하상보호공을 설치하면 설치된 부분은 세굴이 방지 되지만, 하상보호공 끝단 이후에는 지반이 노출되어 있어 노출된 지반에서 고유속 흐름 및 압력변화에 의한 세굴이 발생하는 경우가 많다. 이에 본 연구에서는 하상보호공 끝단 즉, 하상이 노출된 지반에서 압력변화에 따라 하상재료가 유실되므로 압력에너지를 감쇄시키기 위한 하상보호장치를 개발하였다. 개발한 하상보호장치는 본래 다수개가 열을 지어 메트릭스 형태로 설치되도록 하여야 하지만 실험 여건상 단일체로 수리실험을 진행하였다. 하상보호장치는 상판과 하판이 조립된 형태이며 상판과 하판 사이에 이격공간이 구비되어있다. 하상보호장치 검증을 위해 상판과 하판에 쓰이는 판은 수로재질과 같은 아크릴로 제작하였으며, 하상재료의 공극률을 반영하여 다공성 판으로 제작하였다. 다공판의 전체 구멍 면적 대비 판 면적은 35 % 로 동일하다. 상판 구멍 지름 15.0 mm, 4.5 mm 2가지로 제작하였으며, 하판 구멍 지름 3.0 mm 으로 동일하다. 압력변화가 큰 곳에서 작은 곳으로 물이 이동하게 되므로 고유속 수리조건에서 상판과 하판 사이에서의 압력변화를 측정하기 위해 판 중간에 압력계를 설치하였다. 하상보호장치 설치지점 앞 0.3 m 부근에 PIV를 설치하여 유속을 측정하였다. 실험결과 상판의 구멍 직경(15.0 mm)이 클 경우 상판부 압력이 하판부로 전달되어 하판에서 측정되는 압력이 증폭 되었으며, 상판의 다공성 구멍 직경(4.5 mm)이 작을 경우 상판부에서 하판부로 전달되는 압력이 감소하여 하판에서 측정되는 압력이 감소하였다. 상판과 하판의 다공성 구멍의 직경을 적절한 사이즈로 조절하면 상판부의 압력이 하판부로 전달되는 것을 막고 압력에 의해 하상에서 흡출되는 유사를 막을 수 있는 것으로 판단되며 추후 상판과 하판의 다공성판 구멍 직경의 상대적 차이에 따른 압력 감소효율에 관한 연구가 필요하다고 판단된다.

• Journal of the Korean Geotechnical Society
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• v.19 no.4
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• pp.265-275
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• 2003

In this study, shaking table tests were conducted to estimate dynamic interface properties between geosynthetics such as geomembrane, geotextile and geosynthetic clay liner. Accelerations of both shaking table and upper box, and relative displacements between geosynthetics under dynamic loading were measured. Also, the influence of normal stress, frequency of excitation and dry/wet conditions were investigated through the analyses of test results. from the test results, it was found that there is a limited acceleration below which dynamic farce can be transmitted between geosynthetics without the loss of horizontal acceleration. Dynamic interface friction angle between geosynthetics could be calculated through the limited acceleration. Relative displacements induced along geosynthetic interfaces under dynamic loading were not consistent depending on the type of interface and test conditions. The maximum slip displacements between geosynthetics are normalized and normalized slip equations were developed for each interface. By using the normalized slip equation, maximum slip displacements for the geosynthetic interface could be predicted for the given base acceleration and frequency of excitation.

• Journal of Korean Society of Environmental Engineers
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• v.39 no.6
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• pp.371-376
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• 2017

The effect of vortex finder confiqurations on the PM-10 collection efficiencies has been investigated using 7 different types of cyclones. Cyclone inlet velocities were calculated by computational fluid dynamics analysis and PM-10 collection efficiencies were measured from experimental apparatus. The inlet velocities of normal, P and A type cyclones were calculated 15.48 m/sec, 16.03 m/sec and 15.9 m/sec, respectively while experimental results show that PM-10 collection efficiencies were increased 4% for P type and 7% for A type cyclones compared to normal cyclone. Also it was found that there exist optimum parallel head lengths for both P and A type cyclones to maximize the PM-10 collection efficiencies.

• Korean Journal of Plant Tissue Culture
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• v.22 no.4
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• pp.217-221
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• 1995

This experiment was carried out to determine the effects of genotyes (cultivars) and kinds of cytokinins and concentrations on shoot multiplication of roses (Rosa hybrida) by nodal culture. The results from this study were summarized as follows. Shoot multiplication was significantly affected by genotypes. Most shoots were produced from 'Carl Red 'rather than two other cultivars, 'Golden Emblem' and 'Tineke'. Among 3 cytokinins, BA was more significantly effective for multiplication than two other cytokinins, 2iP and kinetin. However subsequent shoot growth after multiplication was more enhanced by 2iP and kinetin rather than BA. An optimal concentration of cytokinin for shoot multiplication was 1 mg/L in this study but BA at 1-5 mg/L was considered optimal for multiplication ratio itself. Subsequent shoot growth was significantly inhibited by increases in cytokinin concentrations, regardless of kinds of cytokinin.

• Journal of the Korean Geotechnical Society
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• v.24 no.6
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• pp.69-75
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• 2008

Shear tests were carried out on interface between two concrete eco-blocks which comprise segmental retaining wall. Three interface conditions were considered : 1) direct contact of two blocks, 2) placing rubber pad between two blocks, 3) placing rubber pad and shear key between two blocks. According to shear tests, shear load-shear displacement relationship which was obtained from direct contact of two blocks was similar to elastic-perfectly plastic behavior. Ductile behavior of shear load-shear displacement relationship was observed for the interface condition of placing rubber pad. Apparent minimum shear capacities and apparent friction angles for the interface conditions of direct contact of two blocks, placing rubber pad between two blocks, placing rubber pad and shear key were 1.7 kN/m, $27.6^{\circ}$ and 4.2 kN/m, $26.2^{\circ}$ and 20.9 kN/m, $26.0^{\circ}$ respectively.