• Title/Summary/Keyword: 분산반경

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Characteristics of Electrospun Poly(methyl methacrylate) Nanofibers Embedding Multi-Walled Carbon Nanotubes(MWNTs) (다중벽 탄소 나노튜브가 분산된 Poly(methyl methacrylate) 고분자 용액의 전기방사연구)

  • Kim Dong Ouk;Lee Dai-Hoi;Yoon Seong-sik;Lee Sun-Ae;Nam Jae Do
    • Polymer(Korea)
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    • v.30 no.1
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    • pp.90-94
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    • 2006
  • An electrospinning process was used to fabricate poly(methyl methacrylate) (PMMA) nanofibers embedding multi-walled carbon nanotubes(MWNTs). SEM images showed that the nanofiber surface and structural morphology depended on solvent types (dimethyl formamide, chlor-form and toluene) and carbon nanotube contents (0.5 and $3.0\;wt\%$). Nano-fiber alignments could be controlled by adjusting the electrodes configuration at collector sites. Relationship between carbon nanotube and PMMA nanofiber was studied with radius of gyration of polymer chain and carbon nanotube sizes. As the carbon nanotube content ratio increased, the number of bead increased.

A Dual Beaconing Scheme for Effective Context Awareness in Vehicular Ad Hoc Networks (차량 애드혹 네트워크에서 효과적인 상황 인지를 위한 이중 비콘 전송 기법)

  • Joo, Jhihoon;Lee, Heechang;Kim, Jungjoon;Han, Dong Seog
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.39B no.2
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    • pp.114-122
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    • 2014
  • Beacon transmission is one of the fundamental mechanisms in vehicular ad hoc networks. Variety services including context awareness can be embodied by exchanging beacons in each vehicle. In this paper, we propose dual beacon transmission instead of traditional single beacon transmission for beaconing mechanism. dual beacon transmission divides beacon into two functions and operates two beaconing process independently. We verified the superiority of dual beacon transmission by comparing beacon packet delivery ratio with single beacon transmission. In conclusion, dual beacon transmission can reduce channel load and have both wider communication range and effective context awareness. In addition, implementing dual beacon transmission has less complexity and appliable with conventional adaptive beaconing schemes.

Development and Properties of Carbon monoxide Detector for Ambient Air monitoring (대기오염 측정용 일신화 탄소 검출기의 제작 및 특성)

  • Cho, Kyung-Haeng;Lee, Sang-Wha;Lee, Joung-Hae;Choi, Kyong-Sik
    • Analytical Science and Technology
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    • v.13 no.2
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    • pp.222-228
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    • 2000
  • A detector for monitoring carbon monoxide (CO) in ambient air by nondispersive infrared (NDIR) spectroscopy has been developed and investigated its sensitivity and stability. The essential parts of the absorption cell are three spherical concave mirrors so as to improve the sensitivity by increasing the light path length in the cell. The radius and center of curvature of mirrors and position in the cell was calculated by computer simulation in order that the light path length may be 16m into the 50cm cell. The number of traversals and optical path properties were confirmed by laser beam alignment in transparent absorption cell. The photoconductive type lead selenide (PbSe) was used as CO sensing material, which was cooled to increase the responsibility by thermoelectric cooling method. The detection limit and span drift of the developed CO detector was 0.24ppm and 0.03ppm(v/v) respectively.

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Study on Microstructure and Physical Properties of PUF by the Impeller Type of Agitator (교반기의 임펠러 형태에 따른 폴리우레탄 폼의 미세구조와 물성 연구)

  • Lee, Chae-Rim;Kim, Jung Soo;Park, Byeongho;Um, Moon-Kwang;Park, Teahoon
    • Composites Research
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    • v.34 no.1
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    • pp.16-22
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    • 2021
  • Polyurethane foam (PUF) can be manufactured in soft, semi-rigid, and hard forms, so it is used in various fields industrially. Among them, rigid PUF has excellent mechanical properties and low thermal conductivity, and is used as a thermal insulation material for buildings and as a cold insulation material in the natural gas transportation field. In this field, there is a steady demand on higher mechanical strength and lower thermal conductivity. In this study, a rigid PUF was manufactured, and the microstructure and physical properties were studied according to the impeller type (propeller, dispersed turbine) of the agitator. Through FE-SEM and Micro-CT analysis, it was confirmed that the average pore size of the foam manufactured with the dispersed turbine was 21.5% smaller than that of the pore made by the propeller. The compressive strength was improved by 15.4%, and the thermal conductivity decreased by 3.1% in the foam with small pores. This result can be utilized for fabricating PUF composites.

S-wave Velocity Structure Beneath the KS31 Seismic Station in Wonju, Korea Using the Joint Inversion of Receiver Functions and Surface-wave Dispersion Curves and the H-κ Stacking Method (수신함수와 표면파 분산곡선의 복합역산 및 수신함수 H-κ 중첩법을 이용한 원주 KS31 지진관측소 하부의 S파 지각 속도구조)

  • Jeon, Tae-Hyeon;Kim, Ki-Young;Park, Yong-Cheol;Kang, Ik-Bum
    • Geophysics and Geophysical Exploration
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    • v.15 no.1
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    • pp.8-15
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    • 2012
  • To estimate the S-wave velocity structure beneath the KS31 broad-band station in Wonju, Korea, we used $H-{\kappa}$ stacking and joint inversion of receiver functions and surface-wave dispersion curves derived from 297 teleseismic events (Mw > 5.5) recorded during the period between 2002 and 2009. We thereby determined that the average depth to a nearly flat Moho is $32.4{\pm}0.5\;km$ within tens of kilometer radius of the seismic station. For the crust at this location, we estimate an average shear-wave velocity of 3.69 km/s and a ratio of P- to S-wave velocities, $V_p/V_s$, of $1.72{\pm}0.04$, as is typical for continental crust. A negative phase in the receiver functions at 1 s indicates the presence of a shearwave low velocity layer in a depth interval of 10 to 18 km in the upper crust beneath the KS31 station.

An analysis on the mask play music composition - focuscing on the Bonsandaenori mask play - (가면극 음악구성의 원리 - 본산대놀이계통 가면극을 중심으로 -)

  • Im, Hyejung
    • (The) Research of the performance art and culture
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    • no.33
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    • pp.97-128
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    • 2016
  • According to the findings of the study, the music composition of the mask play is deeply related to the main characteristics of the scene. The first scene of the play starts with the Byeoksa dance. This particular dance part represents the evil spirit expel ritual. The instrumental accompaniment like and are played for the dance. The last part of the play starts with the Halmi and Yeonggam scene. This scene is played in both the instrumental and vocal music. For the instrumental part , for the vocal part and songs are played. and songs are played on the part of the Halmi's funeral ceremony scene. The instrumental and are played in various scenes for the accompaniment of the dance part. The musical structure of the mask play is flexible. This kind of flexibility of scene structure mainly concerned with the way of musical composition. The main structure of the mask play can be classified into two main styles according to the allocation of the vocal music. In first style, the vocal music is evenly dispersed. In second style, the vocal parts are concentrated in the rear section. As I mentioned earlier, no logical association is found in the matter of the scene arrangement. A scene arrangement has a deep connection with the arrangement of the music in each scene. In conclusion, the mixed arrangement of the scene in mask play is mainly concerned with the matter of the music arrangement in order to maintain the tension of the drama.

The Effect of the Packing Materials on the Pressure Fluctuations in Fluidized Bed (유동층 연소로에서 충전물이 압력 요동 특성에 미치는 영향)

  • Kim, Mi Young;Jo, Byung Yeol;Park, Sang Chan;Lee, Dong Kyu;Kim, Eui Sik
    • Applied Chemistry for Engineering
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    • v.9 no.6
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    • pp.852-856
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    • 1998
  • Effects of packing materials on the pressure fluctuations in a fluidized bed have been analysed using statistical method to interpret fluidized bed behavior. The experiments were carried out in a fluidized bed of 6.7cm - ID, and the experimental variables were particle size and its distributions, fluidizing velocity, aspect ratio, and packing materials, etc. Screen packings are used as packing material, the properties of the pressure fluctuations in the fluidized bed were measured by a differential pressure transducer. The measured properties for the pressure fluctuations were the mean, the standard deviation, and the major frequency of the power spectral density functions, etc. The standard deviations of the pressure fluctuations have been slightly affected in the radial directions of fluidized bed, and almost constant in axial directions the height above 4.5cm of the distributor of fuidized bed without packing materials. The major frequency decreased with increaing packing size, whereas it showed maximum at 10% of packing materials. It has been found that the standard deviation of the pressure fluctuations can effectively explain the fluidized phenomena, and the packing materials severely affected the properties of the pressure fluctuations.

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Methodology for Determining RSE Spacing for Vehicle-Infrastructure Integration(VII) Based Traffic Information System (Focused on Uninterrupted Traffic Flow) (차량-인프라 연계(VII) 기반 교통정보시스템의 RSE 설치간격 결정 방법론 (연속류를 중심으로))

  • Park, Jun-Hyeong;O, Cheol;Im, Hui-Seop;Gang, Gyeong-Pyo
    • Journal of Korean Society of Transportation
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    • v.27 no.6
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    • pp.29-44
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    • 2009
  • A variety of research efforts, using advanced wireless communication technologies, have been made to develop more reliable traffic information system. This study presents a novel decentralized traffic information system based on vehicle infrastructure integration (VII). A major objective of this study was also to devise a methodology for determining appropriate spacing of roadside equipment (RSE) to fully exploit the benefits of the proposed VII-based traffic information system. Evaluation of travel time estimation accuracy was conducted with various RSE spacings and the market penetration rates of equipped vehicle. A microscopic traffic simulator, VISSIM, was used to obtain individual vehicle travel information for the evaluation. In addition, the ANOVA tests were conducted to draw statistically significant results of simulation analyses in determining the RSE spacing. It is expected that the proposed methodology will be a valuable precursor to implementing capability-enhanced next generation traffic information systems under the forthcoming ubiquitous transportation environment.

산화철 폐촉매를 사용한 NiZn-페라이트웨 합성 및 자기적 특성

  • Park, Sang-Il;Hwang, Yeon;Lee, Hyo-Sook
    • Proceedings of the Korea Crystallographic Association Conference
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    • 2003.05a
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    • pp.26-26
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    • 2003
  • 산업 폐기물로서 전량 매립되고 있는 styrene monomer (SM) 공정에서 발생되는 산화철 폐촉매를 사용하여 NiZn-페라이트를 합성하였고, 그 자기적 특성을 조사하였다. 평균입경 0.5㎛로 미분쇄된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소한후 1230℃에서 5시간 동안 소결하여 스핀넬형 페라이트 소결체를 얻었다. Ni/sub x/Zn/ub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66) 및 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 초투자율을 측정하였다. S-parameter를 측정하여 반사 감쇄량을 계산하였다. Ni/sub 0.5/Zn/sub 0.5/fe₂O₄ 조성의 경우 밀도 5.38 g/㎤ kHz에서의 초투자율이 59인 특성을 얻었다. 산화철 폐촉매를 이용하여 X-band 주파수 영역에서 높은 전자파 흡수능을 갖는 전파흡수체를 제조할 수 있음을 확인하였다. Ni/sub 0.5/Zn/sub 0.5/Fe₂O₄ 조성에 대하여 1100℃에서 하소한 분말을 사용하여 실리콘 고무에 복합시킨 후 전파흡수능을 측정하였다. 폐촉매에는 산화철 이외에 CeO₂가 주된 첨가물로 함유되어 있어서 페라이트의 합성 후에도 2차상으로서 존재하였다. 출발 원료인 산화철 폐촉매에 존재하는 K₂O 및 CeO₂를 제거하기 위하여 산처리와 분산제를 이용한 CeO₂ 분리과정을 행하였다. 정제된 산화철 폐촉매에 NiO 및 ZnO를 혼합하여 900℃에서 하소하여 스핀넬형 페라이트를 합성하고 1325℃에서 5시간 소결하였다. 위와 마찬가지로 Ni/sub x/Zn/sub 1-x/Fe₂O₄(x=0.36, 0.50, 0.66)과 (Ni/sub 0.5/Zn/sub 0.5/)/sub 1-y/Fe/sub 2+y/O₄(y=-0.02, 0, 0.02) 조성에 대하여 자기적 특성을 조사하였다.화된 중성자빔으로 측정하였다 BPC-Si를 구부려 슬랩의 곡률반경을 변화시키면서 단색기-시료-검출기가 평행파 반평행배치일 때 Cu(111), (200), (220), (311), (331), (420)면의 회절선을 측정하여 각 조건에서 분해능과 강도를 평가하였다.료의 가시적 변화를 통해 illumination angle 1.25mrad(Dose rate : 334 × 10³ e/sup -//sec·n㎡)일 경우 약 3초 이내에 비정질화가 시작됨을 알 수 있었고 이는 약 1 × 10/sup 6/ e/sup -//sec·n㎡ 의 전자선량에 해당되며 이를 기준으로 각각의 illumination angle에 대한 임계전자선량을 평가할 수 있었다. 실질적으로 Cibbsite와 같은 무기수화물의 직접가열실험 시 전자빔 조사에 의해 야기되는 상전이 영향을 배제하고 실험을 수행하려면 illumination angle 0.2mrad (Dose rate : 8000 e/sup -//sec·n㎡)이하로 관찰하고 기록되어야 함을 본 자료로부터 알 수 있었다.운동횟수에 의한 영향으로써 운동시간을 1일 6시간으로 설정하여, 운동횟수를 결정하기 위하여 오전, 오후에 각 3시간씩 운동시키는 방법과 오전부터 6시간동안 운동시키는 두 방법을 이용하여 품질을 비교하였다. 각 조건에 따라 운동시킨 참돔의 수분함량을 나타낸 것으로, 2회(오전 3시간, 오후 3시간)에 나누어서 운동시키기 위한 육의 수분함량은 73.37±2.02%를 나타냈으며, 1회(6시간 운동)운동시키기 위한 육은 71.74±1.66%을 나타내었다. 각각의 운동조건에서 양식된 참돔은 사육초기에는 큰 변화가 없었으나, 사육 5일 이후에는 수분함량이 증가하여 15일에는 76.40±0.14, 75.62±0.98%의 수분함량을 2회와 1회 운동시킨 참돔의 육에서 각각 나타났다. 운동횟수에 따른 지질함량은 2회 운동시킨 참돔은 5.83±2.08, 1회 운

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The Effects of Toddlers' Characteristics and Child Care Environments on Toddlers' Behaviors in Child Care Center (영아특성 및 보육환경(보육시설과 교사)변인이 영아의 놀이실 행동에 미치는 영향)

  • Choi, Ji Hyun;Park, Hye Won
    • Korean Journal of Childcare and Education
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    • v.1 no.1
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    • pp.103-124
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    • 2005
  • This study aims to investigate and analyze how toddlers' characteristics and child care center's environments including facilities and care-givers' characteristics affect toddlers' behavior in child care center using observational methods. Total 40 toddlers in same numbers of boys and girls participated in this study. Average age of tollers were the 31.7 months ranging from 27 months to 35 months. The toddlers were observed with the observation schedule modified from observation categories of Holloway and Reichhart-Erickson(1988). Data were analysed by Pearson's correlation, t-test, one away ANOVA, Duncan Test and stepwise regression using the SPSSWIN Version. The results of the study were as follow: First, the toddlers' behaviors were related to all the toddlers' characteristics. Second, the toddlers' behaviors were related to all the characteristics of the child care facilities such as the types of facilities, the class size and the caregiver-toddler ratio. Third, the toddler' behaviors were related to caregivers' variables such as the total care experience in centers, the experience with toddler care, the martial status, the certificate types except the child rearing experience and the educational level. Fourth, the toddlers' characteristics were more significantly related to the behavior of them than those of child care centers' environment.

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