• 한국세라믹학회지
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• 제34권7호
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• pp.693-698
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• 1997

The refractive index and dispersion in the (100-x)(0.6CaO.0.4Al2O3).xSiO2(x=0~30) glasses were investigated. As the amount of SiO2 increased, the refractive index decreased. The change of refractive index was attributed to the change of the molar refraction rather than the molar volume. When the amount of SiO2 was smaller than 20 mol%, the average electronic transition energy gaps(E0) and the electronic oscillator strengths(Ed) were about 10.9($\pm$0.1) nd 18($\pm$0.5)eV, respectively. However E0 and Ed of the glass (CAS30) with 30 mol% SiO2 increased to 12.63 and 19.89eV, respectively. The similar results was observed in the variation of Abbe Number. Abbe number of the glass in the range of 0~20 mol% SiO2 was about 46 and that of CAS30 increased to 60. The zero-material dispersion wavelength({{{{ lambda }}0) of pure calcium aluminate glass was 1.8 ${\mu}{\textrm}{m}$. As the amount of SiO2 increased, the zero-material dispersion wavelength shifted to a shorter wavelength. {{{{ lambda }}0 of CAS30 was 1.5 ${\mu}{\textrm}{m}$, that is currently using for the optical telecommunication system.

• 한국음향학회지
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• 제27권1호
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• pp.33-39
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• 2008

공기방울에 의한 음속 확산 (sound speed dispersion)을 측정하여 잘피 서식지에서 광합성시 발생되는 기공률을 추정하였다. 해상 실험은 니질로 구성된 거머리말 서식지에서 광합성이 활발한 주간과 상대적으로 덜 활발한 야간에 실시되었고 120 kHz 정현파 음원을 이용하여 잘피 서식지로부터 후방산란된 음향 신호를 획득하였다. 실험 결과 잘피 서식지로부터 수신된 신호의 도달 시간이 주/야간 차이가 있음을 확인하였고 도달 시간의 변화는 잘피의 광합성에 의해서 발생되는 공기방울에 의한 음속 확산이 원인임을 추정할 수 있었다.

• 한국산업보건학회지
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• 제34권3호
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• pp.247-253
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• 2024

Objectives: The purpose of this study is to establish a method for the production of standard samples of crystalline silica and to assess its feasibility for the future application in non-mandatory quality control. Methods: We dispersed crystalline silica in 2-propanol to prepare a 1 mg/mL dispersion solution. Between 50-200 uL of the dispersion solution was taken with a pipette, injected onto PVC filters, air-dried, and used as samples. The variation and homogeneity of the quartz concentrations were confirmed by FTIR analysis. Analytical proficiency testing was conducted across 30 voluntary participants. Results: The coefficient of variation was lower for samples prepared using supernatant (settled for 16 hours) compared to those made with dispersion solution. The contamination level after using the pipette tip one to five times was 8.13-9.89% of the solution's concentration. Homogeneity was confirmed within the concentration of 0.0223-0.0431 mg/mL, but it was not at the higher concentration of 0.0553 mg/mL. In the analytical proficiency testing, the coefficient of variation for each level ranged from 24.6% to 28.3%, with a compliance rate of 90.0% to 96.7%. Conclusions: This study was conducted to produce standard samples of crystalline silica. The homogeneity of the samples was confirmed at low concentrations. However, further investigations on the applicability of wider range of concentrations are needed.

• 한국재료학회지
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• 제26권3호
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• pp.136-142
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• 2016

To study the dispersion factors of silica sol prepared from fumed silica powder, we prepared silica sol under an aqueous system using a batch type bead mill. The dispersion properties of silica sol have a close relationship to dispersion factors such as pH, milling time and speed, the size and amount of zirconia beads, the solid content of fumed silica, and the shape and diameter of the milling impellers. Especially, the silica particles in silica sol were found to show dispersion stability on a pH value above 7, due to the electrostatic repulsion between the particles having a high zeta potential value. The shape and diameter of the impellers installed in the bead mill for the dispersion of fumed silica was very important in reducing the particle size of the aggregated silica. The median particle size ($D_{50}$) of silica sol obtained after milling was also optimized according to the variation of the size and amount of the zirconia beads that were used as the grinding medium, and according to the solid content of fumed silica. The dispersion properties of silica sol were investigated using zeta potential, turbiscan, particle size analyzer, and transmission electron microscopy.

• 한국물환경학회지
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• 제28권1호
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• pp.115-120
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• 2012

Different colloidal particles generally co-exist in the water and wastewater. Thus, there needs to identify practical electrokinetic characteristics of the particles, comparing with the case when each colloidal material is independently distributed. In this study, changes of overall zeta potential was examined through mixed dispersions of $TiO_{2}$ and $MnO_{2}$. The mixing ratios were classified into 3-type in order to distinguish the effects of the proportions of each particle from those of total concentration in colloidal suspensions. The types are single colloidal dispersions of $TiO_{2}$ and $MnO_{2}$ (1:0, 0:1), mixed dispersions at different ratios (0.75:0.25, 0.5:0.5, 0.25:0.75), and a mixed dispersion with doubled concentration (1:1), respectively. It showed that the overall variation of zeta potential as a function of pH was intensified in a colloidal dispersion with the ratio of 1:1. It was concerned that the double action of ion would contribute to this result. On the one hand, the zeta potentials of each colloidal dispersion commonly decreased at the state of strong acid and base under the influence of compression of the electric double layer. The changing patterns were also considered through calculating total interaction energy between colloidal particles based on DLVO theory and measuring turbidity of the colloidal dispersions.

• 마이크로전자및패키징학회지
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• 제17권4호
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• pp.83-88
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• 2010

복합전기도금은 도금 중 반응성이 없는 물질을 첨가하여 도금층 내부에 함께 존재하도록 함으로써 이루어진다. 퍼멀로이는 철과 니켈의 합금을 말하는 것으로써 높은 투자율를 나타내기 때문에 산업 여러 분야에 응용된다. 복합도금을 통해 제품의 미세경도를 향상시킬 수 있으며 이는 제품의 수명과 연관된다. 하지만 실리카 나노분말 표면의 수산화기는 표면을 수분에 취약하게 만들고 이는 나노분말의 응집을 발생시켜 균일한 도금층의 형성을 어렵게 하는 요인이 된다. 본 연구에서는 실리카 나노분말의 응집을 줄이기 위하여 첨가제의 변화, 초음파 처리 시간의 변화를 살펴보았다. 초음파 처리시간의 증가시 입자의 분산효과가 좋았고 조성의 변화가 발생하였다. 첨가제에 따라 표면 형상과 공석되는 실리카 나노입자의 함량 차이가 나타났다. 염기성 도금용액에서 sodium lauryl sulfate를 사용하였을 경우 표면이 매끄럽고 공석되는 실리카 나노분말의 양도 높았다.

• Journal of the Optical Society of Korea
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• 제15권4호
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• pp.398-402
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• 2011

In this paper, we have proposed a principle to design wideband, low dispersion and temperature stabilized slow light structure in slotted photonic crystal waveguide (SPCW). The infiltration of the silicon photonic crystal with polymer will enhance the slow light and increase the group index, whereas the different signs of thermo-optic coefficients of polymer and silicon make the proposed structure stable on temperature variation over $60^{\circ}C$ and improves the group index-bandwidth products of the designed structure. The SPCW structure is modified to maximize the slow light effect and minimize the dependence of the group index and hence the group velocity dispersion to temperature.

• Journal of the Optical Society of Korea
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• 제12권4호
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• pp.249-254
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• 2008

In this paper we present an electronic domain solution for chromatic dispersion (CD) monitoring algorithm based on the estimated time domain channel in electronic domain using channel estimation methods. The proposed scheme utilizes kurtosis as a CD measurement, directly computed from the estimated inter-symbol-interference (ISI) channel due to the CD distortion. Hence, the proposed scheme exhibits robust performance under OSNR variation, in contrast to the existing electronic domain approach based on minimum mean squared error (MMSE) fractionally-spaced equalizer taps [1]. The simulation results verify the CD monitoring ability of the proposed scheme.

• 한국염색가공학회지
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• 제25권1호
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• pp.37-46
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• 2013

This paper surveys the ESD characteristics of the PANI added PU/MWNT film according to the manufacturing conditions such as variation of the loading contents of PANI and the mixture ratio of 2 dispersion solutions. For this purpose, PANI added PU/MWNT ground films were made with IPA/MWNT 3wt% dispersion solution and PANI/DMF dispersion solutions(5, 10, 15, 20, 25, and 30wt% contents of the PANI) by the mixture ratio of dispersion solution(10/50, 20/40, 30/30, 40/20, and 50/10part) in the PU (972DF) 100g, which was treated with 500rpm for 30min in the stirrer with condition of the dry temperature $120^{\circ}C$ for 2min. Totally, 36 kinds of PANI added PU/MWNT film specimens were prepared. The physical properties of the PANI added PU/MWNT films such as electrical resistivity, absorbancy by UV-Vis spectrometer, and triboelectricity were measured and discussed with surface characteristics of the PANI added PU/MWNT films by SEM. The dispersion property of PANI to the DMF showed best dispersion at the 25% of PANI content. The surface electrical resistivity of the PANI added PU/MWNT films was decreased with increasing the weight content of PANI/DMF dispersion solution, and it showed the lowest value $10^6{\Omega}$ at the mixing condition of PANI/DMF 20part and MWNT/IPA 40part with 30% PANI. Furthermore, it was shown that the electrical and physical properties of the PANI added PU/MWNT film such as electrical resistivity, and triboelectricity were better than those of PU/MWNT film prepared with no PANI, which was result obtained in previous paper.

• 대한지하수환경학회지
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• 제2권2호
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• pp.49-57
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• 1995

지하수에 대한삼중수소농도의 측정치가 발표된 충청남도 청양, 제주도 지역 및 미국 조지아지역에 대해 평균체제시간을 계산하는 지하수연령측정 모델인 PFM, CMM, DBM과 평균체제시간과 분산매개변수를 동시에 계산하는 DNM, DM( $C_{FF}$ )모델을 적용하여 그 결과를 비교하였다. 입력자료인 강우의 삼중수소 농도의 부족한 측정자료를 보완하기 위하여 한국의 포항, 카나다의 오타와지역의 강수자료를 이용하여 입력함수를 작성하였다. 내재적으로 적은 분산을 가정하는 PFM과 DBM모델에 의한 결과는 유사하게 계산되었으며, 동일한 지역에서도 특이하게 높은 농도를 보이는 지점은 CMM에 의한 계산이 되지 않았다. 평균체제시간과 분산매개변수가 동시에 계산된 DNM과 DM( $C_{FF}$ )모델의 결과는 PFM, CMM, DBM의 결과를 이용하여 매개변수값을 한정시켰다. 동일지역에서도 삼중수소농도의 변화가 큰 경우는 각 지점마다 특징적인 지하수유동특성을 보이는 것으로 판단되어, 전 지 역에 걸쳐 동일한 모델을 일률적으로 적용하는 것은 바람직하지 않은 것으로 사료된다.