• Korean Chemical Engineering Research
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• v.47 no.1
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• pp.31-37
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• 2009

A zwitterionic surfactant shows not only detergency but also mildness effect since it shows characteristics of a nonionic or an anionic surfactant above an isoelectric point, while showing characteristics of a cationic surfactant below an isoelectric point. Therefore, a zwitterionic surfactant can serve as a dual function surfactant by a single molecule through the interconversion of cleaning and softening effects depending on pH variations of the aqueous solution. In this study, physical properties of betaine surfactant such as CMC, surface tension, interfacial tension, contact angle and viscosity were measured and phase behavior study was performed. Also dual function characteristics of betaine zwitterionic surfactant were investigated by measuring an isoelectric point using QCM(quartz crystal microbalance) and zeta potential measurement. The CMC of betaine surfactant was near $10^{-4}mol/L$ and the surface tension at CMC was about 32 mN/m. The interfacial tension between 1 wt% aqueous solution and n-decane measured by spinning drop tensiometer at pH 2~10 resulted in an increase in interfacial tension until pH 5 and a decrease with pH after 5 and equilibration time showed the similar trend with an increase in pH. The isoelectric point of betaine surfactant measured by QCM experiment was found to exist between 3.0 and 3.3, which is the same as the result determined by zeta potential measurement.

• Resources Recycling
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• v.17 no.4
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• pp.37-46
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• 2008

In view of the increasing importance of the waste recycling to meet the strict environmental regulations, the present investigation reports an adsorption process using cationic exchanger DOWEX G-26 for the recovery of copper from the synthetic sulphate solutions containing copper 0.3 to 0.5 mg/ml, similar to the CMP waste effluent of electronic industry. Various process parameters viz. contact time, solution pH, resin dose, and A/R ratio for elution were investigated to recover copper from the effluents. Complete adsorption of copper from the solution was achieved at equilibrium pH 2.5 and aqueous I resin (A/R) ratio of 100 ml/g in 14 minutes contact time. The adsorption of copper on DOWEX G-26 resin was found to follow the Langmuir isotherm and second order reaction. The copper was eluted from loaded resin with dilute sulphuric acid to produce copper-enriched solution.

• Resources Recycling
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• v.27 no.3
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• pp.8-15
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• 2018

Solvent extraction behavior of light rare earth elements (Pr, Nd) and medium rare erath elements (Tb, Dy) in the HCl-PC88A-kerosene extraction system was investigated in order to separate high-purity light rare earths (Pr, Nd) and medium rare earths (Tb, Dy) in the mixed rare earth chloride solution. In the batch test step, it was confirmed that the separation efficiency was good when the extractant concentration (PC88A) was 0.5 M, the equilibrium pH after extraction was 0.8 to 1.0 (initial pH 1.3 of the feed), the concentrations of hydrochloric acid in scrubbing solution was set as 0.1 M, the concentrations of hydrochloric acid in stripping solution was set as 2.0 M or more. Based on the experimental data obtained from the batch test, the mixer-settler was composed as follows; 4 stages of extraction, 8 stages of scrubbing, 4 stages of stripping, and 3 stages of pickling organic solution. The Mixer-settler was operated for 180 hours, and the operating conditions were continuously adjusted to obtain the high-purity light/medium rare earths. Finally, the purity of light (Pr, Nd) and medium rare earth elements (Tb, Dy) was reached as 3 N class.

• Archives of design research
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• v.14
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• pp.163-178
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• 1996

"Color" education aimed at cultivating creativeness and expressive techniques in the education of visual art, in the college of art and design, should be balanced with "form" education; nevertheless, the present situation at Korean universities is such that the overall environments of "color" education are far too inferior to those of "form" education.The problem is, among other things, that the curriculum of visual art education is centered around formal education; in addition, color education courses consist mostly of theoretical issues, not experimental, first-hand-experience-oriented activities that are best suited for the characteristics of the language of color as a visual language, thereby making it difficult to expect the efficiency of education.Particularly, it is a serious problem that the courses dealing with color are not offered in a step by step fashion, from the most elementary, to the intermediate, working up to the most advanced level. Another problem is that those people involved in color education seldom have an expertise in their area; furthermore, the educational environment, educational tools, and the content of the texbooks are far from being ideal.Moreover, it is a grim reality that most color theory courses that have been offered end up being a lecture of "general, basic" color theories, ignoring the students' diverse specialization areas.As a way of normalizing color education, rationalizing the curriculum and initiating the professorship exclusively teaching color education have to be introduced, so that we can increase the depth of color education and individualize the contents of color education according to the students' needs. It is believed that the introduction of the "color-education-only" professorship will greatly facilitate our effort to devise an efficient educational method, to determine the scope of individualized color education, and to improve the ovarial educational environment (such as facilities, instruments, and teaching materials) necessary for an in-depth education.ments, and teaching materials) necessary for an in-depth education.

• Journal of the Korea Organic Resources Recycling Association
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• v.4 no.2
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• pp.55-62
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• 1996

The purpose of this study is the evaluation of adsorption capacity of casts for heavy metals comparing with the activated carbon. The casts was obtained from vermicomposting of the mixed organic sludges which were generated from the treatment facilities for leather wastewater and cattle wastewater. The physico-chemical characteristics of cast was investigated. Also, the batch adsorption experiments of cast and activated carbon for heavy metals were carried out, and the results were analyzed by Freundlich isotherm. The buffering capacity to the acidic wastewater was founded in the cast, and the cation exchange capacity of cast impling adsorption capacity for soluble substances was evaluated as about 55me/100g. Those were implied that the cast have a large potential as a good adsorbent for soluble pollutants in wastewater. From the results of batch experiments, the removal efficiencies of tested various heavy metals including Pb, Cu, Cd, and Cr were very high value as 89-98% for the activated car-bon, and 80~95% for the casts except for Zn. The adsorption equilibriums for the two materials were achieved within 90 minutes. The order of preferable metals in the adsorption was found to be Pb>Cu>Cd>Cr>Zn on the cast and to be Pb>Cd>Cu>Cr>Zn on the activated carbon, respectively. From the above results, it might be con-cluded that cast is effectively available as a good adsorbent to treating the heavy metal bearing wastewater.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2006.04a
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• pp.247-252
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• 2006

오염 퇴적물내 중금속의 방출과 이에 따른 생이용성(bioavalability)은 기존의 가역 평형관계로써 설명하기에 불충분한 것으로 알려져 있다. 최근 연구결과에 의하면 이러한 탈착 저항성을 설명하기 위한 비가역적 모델에 의해 퇴적물내 중금속의 탈착저항성 부분이 존재함이 밝혀졌다. 탈착저항성에 대해서는 아직 충분한 규명이 이루어지지 않았으나, 오염물질의 노화(aging)에 의해 일단 탈착저항성을 띠게 되면 생이용성(bioavailability)이 감소되는 것으로 알려져 있다. 본 연구에서는 노화(aging)가 연안 퇴적물 내 납과 카드뮴의 흡/탈착 특성에 미치는 영향을 알아보기 위해 연속 탈착실험과 biphasic 탈착모델을 적용함으로써 납과 카드뮴의 탈착저항성을 규명하고자 하였다. 그리고 연속 추출 실험을 통해서 노화(aging)에 따른 퇴적물 내 납과 카드뮴의 흡착 기작을 규명하고자 하였다. 연속탈착 실험 결과 시간이 경과함에 따라 탈착저항성부분의 크기가 증가하였으며, 연속추출 실험 결과 납의 경우 carbonate fraction에서 추출된 납이 가장 많았으며, 노화(aging) 따라 exchangeable fraction에서 추출된 납이 감소하는 반면 reducible, organic material, residual fraction에서 추출된 납의 양이 증가하였다. 카드뮴의 경우 가장 많은 양이 추출된 단계는 exchangeable fraction이였으며, organic material fraction에서는 카드뮴이 추출되지 않았다. 노화(aging) 따라 reducible fraction과 residual fraction에서의 추출량이 증가하는 경향을 보였으나 그 양은 매우 적은 것으로 나타났으며, 노화(aging)에 따른 exchangeable fraction과 carbonate fraction에서의 추출량은 큰 변화가 없었다. 대해서는 북한지역의 분포상황을 밝혔다.것을 알 수 있었으며, 크롬과 비소의 경우는 초기에 많이 용출되고, 구리의 경우는 꾸준히 용출되는 것을 알 수 있었다. 3년 된 통나무집이 8년 된 통나무집보다. 용출양이 더 컸으며, 이는 CCA성분이 초기에 많이 용출된다는 것을 의미한다. 억제 효과를 나타내었고 Hep3B에서는 부탄을 분획물 (1 mg/mL)에서 82%의 비교적 높은 성장억제효과를 나타내었다.as a "front" and "back". Thus, Germany′s private space may face a genuine public space and street, which is rare in the Korean housing. Although the layout of indoor space in the korean housing tends to be open, such an openness may be outstanding in living and dining spaces, kitchen and various accesses to rooms. In the case of Germany, such indoor spaces are usually closed to each other. Thus corridors act to separate these spaces. Such differences are analysed to be due to the different perceptions of interpersonal and socio-cultural attributes as intra-family and inter-neighbor relationships or communications. 알 수 있었다.도 질소와 인산처럼 토양지지대가 있는 경우가 낮은 함량을 유지하였다.pe from the daily life, to fantasize and daydre

• Journal of the Korean Society of Radiology
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• v.11 no.3
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• pp.171-175
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• 2017

In the non-destructive inspection field, we invest a lot of time and resources in developing the radiation source system to ensure the safety of the workers. However, the probability of accidents is still high. In order to prevent potential radiation accidents in advance, it is necessary to directly verify the position of the radiation source, but the research is still insufficient. In this study, we developed a monitoring system that can detect the position of the radiation source in the source guide tube in the gamma-ray irradiator. The characteristics of the radiation detector are estimated by monte carlo simulation. As a result, the radiation detector for Ir-192 gamma-ray energy was analyzed to have secondary electron equilibrium at $150{\mu}m$ regardless of the semiconductor material. Also, it is expected that the gamma ray response characteristic is the best in $HgI_2$. These results are expected to be used as a basis for determining the optimal thickness of the radiation detector located in the detection part of the future monitoring system. In addition, when developing a monitoring system based on this, radiation workers can easily recognize the danger and secure safety, as well as prevent and preemptively respond to potential radiation accidents.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.08a
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• pp.264-265
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• 2010

최근, nanorod나 nanowire와 같은 1차원의 나노구조가 나노디바이스로 각광을 받고 있다. [1] 특히 InN는 3족 질화물 반도체 중 가장 작은 밴드갭 에너지와 뛰어난 수송 특성을 가지고 있어 나노디바이스로의 응용에 적합한 물질이다. [2] 그러나 InN는 큰 평형증기압을 가지므로 쉽게 인듐과 질소로 분해되는 특성이 있어 나노구조로의 성장이 쉽지 않음이 알려져 있다. [3] 최근 연구결과에 따르면, InN 나노구조는 금속 catalyst를 사용한 방법이나, 기판 위 패턴을 이용하여 성장하는 방법, 염소를 사용한 방법이 널리 쓰이고 있다. [4,5,6] 그러나 이 방법들은 의도치 않은 불순물의 원인이 되거나 다른 추가적인 과정을 필요로 한다는 문제점도 일부 가지고 있다. 본 연구에서는 catalyst-free 유기 금속 화학 증착법 (MOCVD)를 이용하여 $Al_2O_3$ (0001)면 위에 InN nanostructure를 성장하였다. InN nanostructure 성장 시 트리메틸인듐(TMIn)과 암모니아($NH_3$) 를 전구체로 사용하였으며, 캐리어 가스로는 질소를 사용하였다. 또한 모든 샘플의 성장시간은 60분으로 고정하였으나, 성장 시 온도의 의존성을 보기 위해 $680-710^{\circ}C$ 의 온도범위에서 성장을 진행하였다. 그 결과 InN는 본 실험에서 적용된 성장온도범위 내에서 온도가 증가함에 따라 초기에는 columnar구조로 성장된 박막의 형태에서 wall이 배열된 형태로 변화하며 결국 $710^{\circ}C$ 의 온도에서 nanorod로 성장하게 된다. 성장된 InN의 나노구조는 X-선 회절 측정법, 주사 전자 현미경 그리고 투과 전자 현미경을 이용하여 각각의 구조적 특성을 분석하였다. X-선 회절 측정법과 주사 전자 현미경을 통한 분석결과에서는 이들 nanorods가 대부분 c 방향으로 수직하게 정렬되어 있음을 확인 할 수 있었다. 또한, $690^{\circ}C$ 에서 60분간 성장된 InN의 wall 구조의 두께는 200 nm, 길이는 $2-2.5\;{\mu}m$로 관찰되었으며, $710^{\circ}C$에서 60분간 성장된 InN nanorod의 지름은 150 nm, 길이는 $3\;{\mu}m$ 정도로 관찰되었다. 이를 통하여 볼 때 성장 온도가 InN의 나노구조 형성 시 표면의 모폴로지변화에 중요한 변수로 작용함을 알 수 있다. 본 발표에서는 이러한 표면 형상 및 구조 변화가 성장온도에 따른 관계성을 가짐을 InN의 분해와 성장의 경쟁적인 관계에 의해 논의할 것이다.

• Journal of Soil and Groundwater Environment
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• v.8 no.2
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• pp.55-61
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• 2003

The objective of this study was to investigate the characteristics of nitrate removal by conducting the column test in order to see the performance of surfactant modified zeolite (SMZ) as a permeable reactive barrier material. The prediction of nitrate removal was tested using the one-dimensional advective-dispersive model fitted to the experimental breakthrough curve. A methodology for scaling up to in-situ permeable reactive barrier was also proposed. The breakthrough of nitrate in the column packed with SMZ was well predicted using linear equilibrium adsorption model. The breakthrough time and half-life obtained by breakthrough experiment with variation of flowrates were decreased with the increase of flowrates. When 10㎥/day of groundwater containing the 50 mg/l of nitrate is to be treated to satisfy the potable water quality criteria (10 mg/l) by SMZ reactive barrier, 300 tons of SMZ and about 6 years of breakthrough time will be required, suggesting that 165 million wons are needed as barrier material expenses in each 6 years besides the initial design and construction expenses and the minimal monitoring and maintenance expenses.

• Journal of the Korean Wood Science and Technology
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• v.38 no.1
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• pp.17-26
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• 2010

Recently, yellow poplar (Liriodendron tulipifera L.) is getting attention in Korea due to the fast growing and high yield and quality of lumber. But, it is thought that the color difference between heartwood and sapwood may restrict the practical use of it. This study was aimed to enhance the value of yellow poplar lumber by the color control using high temperature heat-treatment, which had been tried for domestic cedar (Kim et al., 2009). The material properties including surface color of yellow poplar lumber were evaluated according to heat treatment conditions. The difference of color between sapwood and heartwood could be reduced by heat treatment at a temperature about $200^{\circ}C$. Long heating time was more effective in reducing the difference. The Equilibrium Moisture Content (EMC) of heat-treated wood was as low as 50 percent of the control. The result obviously indicates that heat-treated wood is more dimensionally stable in the change of moisture condition. The durability against wood rotting fungi also increased by the heat-treated, but it was not so effective as the case of cedar. The changes of mechanical properties of heat-treated yellow poplar were very similar to that of heat-treated cedar. In order to develop new use of heat-treated yellow poplar, the changes of mechanical properties should be considered. There were no significant changes in microscopic structure which may cause changes in mechanical properties. Further study of heat-treated wood is needed to scrutinize the causes of changes of material properties.