• Environmental Analysis Health and Toxicology
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• 제24권3호
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• pp.231-240
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• 2009

We explored collective behaviors of indicator species to elucidate the effect of the chemical stress. After the treatments of an insecticide, diazinon, at low concentrations (1.0 and 10.0 ${\mu}g/L$), spatial dispersion patterns of Daphnia magna were checked in a test chamber. The I-index was used to characterize the movement data before (0~1 h) and after (1~2 h) the treatments in laboratory conditions. The slopes of the frequency distribution of I-index in semi-log scale decreased significantly, and the test populations appeared to be more dispersed with a lower degree of aggregation after the treatments. The index was feasible in indicating decrease in the ability of the specimens to keep desirable distances with neighbor individuals under chemical stress and showed a possibility of monitoring presence of toxic chemicals in environment through group behavior measurement.

• 한국분말재료학회지
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• 제24권3호
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• pp.216-222
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• 2017

Synthesized monocrystalline nanodiamond (nD) particles are heat-treated at various temperatures to produce highly structured diamond crystals. The heat-treated nDs show different weight loss ratios during thermogravimetric analysis. The crystallinities of the heat-treated nDs are analyzed using Raman spectroscopy. The average particle sizes of the heat-treated nDs are measured by a dynamic light scattering (DLS) system and direct imaging observation methods. Moreover, individual dispersion behaviors of the heat-treated nD particles are investigated based on ultrasonic dispersion methods. The average particle sizes of the dispersed nDs according to the two different measurement methods show very similar size distributions. Thus, it is possible to produce highly crystallized nD powder particles by a heat-treatment process, and the nD particles are relatively easy to disperse individually without any dispersant. The heat-treated nDs can lead to potential applications such as in nanocomposites, quantum dots, and biomedical materials.

• 한국광학회지
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• 제9권2호
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• pp.123-126
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• 1998

길이가 15 km이고, 상온에서의 영분산 파장이 1550 nm인 분산천이광섬유(DSF)에 대해 온도에 따른 영분산 파장의 변화를 이론적으로 유도하였고, 이것을 4광파혼합현상을 이용하여 측정하였다. 상온($22^{\circ}C$)에서 $59^{\circ}C$까지의 범위의 온도 변화에서 측정된 분산천이광섬유의 영분산파장 변화는 1.19 nm였다. 이로부터 온도 변화에 대한 영분산파장의 변화율은 0.032 nm/$^{\circ}C$가 됨을 알 수 있었다. 또한 온도 변화에 따른 영분산 파장의 변화가 4광파 혼합 효율에 미치는 영향을 계산하여 그 결과가 실험 결과와 유사함을 알아보았다.

• 한국세라믹학회지
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• 제47권5호
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• pp.387-393
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• 2010

To improve concrete quality one of the most widely used chemical admixtures is polycarboxylate type superplasticizer. Unlike lignosulfonate and naphthalene-sulfonate, it has high dispersion property and excellent sustainable dispersion property for cement and concrete. Thus, polycarboxylate type superplasticizer has been widely used as a high-performance water reducing admixture together with silica fume in high-performance concrete and other applications for the dispersion of high-strength concrete over 100 MPa. However, even though there have been many studied on the dispersion of concrete by the structure of polycarboxylate type superplasticizer, there have a few studied that clarified the relationships between its rheological properties and microstructure properties in the early hydration behavior of ordinary portland cement. To investigate the correlations between the rheological properties and microstructure of cementitious materials with polycarboxylate type superplasticizer, this study experimented on the rheology, pore structure, heat evolution, and consistency in early hydration as well as on the compressive strength by early dispersion characteristics.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.392-393
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• 2006

Direct Printing Process is a suitable fabrication technique to develope pigment components whose dimensions are in nano. The success of this process depends on the sysmatic preparation of pigment millbase. Conventional millbase dispersions are constituted of the organic pigments, monomer, dispersant and solvents. An experimental study on the rheology of millbase dispersions is presented.

• 한국자기학회지
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• 제6권1호
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• pp.28-35
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• 1996

자기 테이프 제조용 초미립 자성 철 분말의 분산 거동을 파악하기 위하여 vinyl계 바이더, polyurethane 바인더, 윤활제등 첨가제 종류 및 양에 따른 분산 거동 및 물리특성들을 조사하였다. 분산성은 바인더의 funtional group의 종류, 자성체와 바인더의 비율등에 크게 영향을 받았으며 적정 조건의 선택으로 분산성은 종래보다 20% 증가하 였다. 이에 따라 자기 특성중 포화 자화는 종래의 경우보다 200 Gauss 증가하였으며, 전자 변환 특성중 휘도 S/N (signal to noise ratio)은 2dB 증가하였다. 적절한 윤활제의 종류및 양에 따라 tape의 마찰계수는 0.15 감소하였으며, 이에 따라 tape의 내구성중 휘도 S/N 열화특성이 4dB 이상 향상되었다.

• International Journal of Automotive Technology
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• 제6권3호
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• pp.215-219
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• 2005

Liquefied petroleum gas (LPG) has been used as motor fuel due to its low emissions and low cost. A liquid direct injection system into a cylinder was suggested as a next generation system to maximize a fuel economy as well as a power. This study addresses the analysis of the LPG spray injecting from single hole injector. Two different test conditions are given, which are a fully developed spray case with various injection pressures and a developing spray case with ambient pressure variation. The LPG spray photographs are compared with the sprays of gasoline and diesel fuel at the same conditions, and the spray angles and penetration lengths are also compared, and then the spray behavior is analyzed. The LPG spray photos show that the dispersion characteristic depends very sensitively on the ambient pressure soon after injection. The spray angle is very wide in a low ambient pressure condition until the saturated pressure, but the angle is quickly reduced at the condition over the pressure. However, the down stream of the LPG spray shows much wider dispersion and less penetration than those of gasoline and diesel sprays regardless ambient pressure condition.

• Carbon letters
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• 제12권4호
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• pp.194-206
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• 2011

Carbon nanomaterials in organic photovoltaic (OPV) cells have attracted a great deal of interest for the development of high-efficiency, flexible, and low-cost solar cells. Due to the complicated structure of OPV devices, the electrical properties and dispersion behavior of the carbon nanomaterials should be controlled carefully in order for them to be used as materials in OPV devices. In this paper, a fundamental theory of the electrical properties and dispersion behavior of carbon nanomaterials is reviewed. Based on this review, a state-of-the-art OPV device composed of carbon nanomaterials, along with issues related to such devices, are discussed.

• 대한토목학회논문집
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• 제39권1호
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• pp.195-201
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• 2019

장대케이슨은 1함당 작용하는 평균파력이 감소하는 파력의 평활화 효과로 인해 케이슨의 활동파괴에 대한 구조안정성을 향상시킬 수 있으나, 장대케이슨은 제작 및 시공상의 이유로 사용하는데 어려움이 있다. 이에 대한 대안으로 개별 케이슨을 인접한 케이슨과 서로 인터로킹시켜 파력을 분산시키는 인터로킹 케이슨에 대한 연구가 되고 있다. 본 연구에서는 케이슨의 장대화가 가능한 전단키형 인터로킹 케이슨을 제안하고, 해석적 방법을 통해 전단키에 의한 파력분산효과를 평가하였다. 해석결과, (1) 전단키형 인터로킹 케이슨은 좌우비대칭 형상으로 인해 구조물 거동 및 파력분산효과 또한 좌우비대칭으로 나타난다. (2) 파력분산효과는 전단키의 전단경사각, 높이, 전단길이비 등 전단키의 형상보다는 각 케이슨에 작용하는 파력 분포 및 특성에 더 큰 영향을 받는다. (3) 장대화된 인터로킹 케이슨 방파제는 완전일체형 방파제와 거의 유사한 거동 및 파력분산효과를 나타낸다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2002년도 학술발표회 논문집(I)
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• pp.389-393
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• 2002