• Journal of the Korean Electrochemical Society
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• v.22 no.3
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• pp.128-137
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• 2019

A lithium is the lightest metal on the earth. It has some attractive characteristics as a negative electrode material such as a low reduction potential (-3.04 V vs. SHE) and a high theoretical capacity ($3,860mAh\;g^{-1}$). Therefore, it has been studied as a next generation anode material for high energy lithium batteries. The thin lithium electrode is required to maximize the efficiency and energy density of the battery, but the physical roll-press method has a limitation in manufacturing thin lithium. In this study, thin lithium electrode was fabricated by electrodeposition under various conditions such as compositions of electrolytes and the current density. Deposited lithium showed strong relationship between process condition and its characteristics. The concentration of electrolyte affects to the shape of deposited lithium particle. As the concentration increases, the shape of particle changes from a sharp edged long one to a rounded lump. The former shape is favorable for suppressing dendrite formation and the elec-trode shows good stripping efficiency of 92.68% (3M LiFSI in DME, $0.4mA\;cm^{-2}$). The shape of deposited particle also affected by the applied current density. When the amount of current applied gets larger the shape changes to the sharp edged long one like the case of the low concentration electrolyte. The combination of salts and solvents, 1.5M LiFSI + 1.5M LiTFSI in DME : DOL [1 : 1 vol%] (Du-Co), was applied to the electrolyte for the lithium deposition. The lithium electrode obtained from this electrolyte composition shows the best stripping efficiency (97.26%) and the stable reversibility. This is presumed to be due to the stability of the surface film induced by the Li-F component and the DOL effect of providing film flexibility.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.44 no.3
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• pp.211-218
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• 2018

Instant face lifting cosmetics contain various film forming agents for stretching the wrinkles on the skin surface. But, most of the film-forming polymers have sticky feels. And they are easily scrubbed out when skin is rubbed on. In this study, we focused on the influence of sodium silicate that has rapid film forming effect on skin surface and immediate wrinkle reducing effect. Sodium silicate, also known as water glass or soluble glass, is a compound containing sodium oxide and silica. Sodium silicate is a white powder that is readily soluble in water, producing an alkaline solution. Sodium silicate is stable in neutral and alkaline solutions. The sodium silicate solution hardens by drying in air and rapidly forms a thin film. When the solution is applied to the skin, the fine membrane coating is formed by water evaporation and ionic bond re-formation. It also makes the strong siloxane (Si-O) bonding on the skin surface. When these fixation properties are applied to cosmetics, they can give remarkable skin tightening effect. The sodium silicate solution can provide the lifting effect by forming a film on skin at a proper concentration. But, skin irritation may be caused with too high concentration of sodium silicate. We studied a desirable range of the sodium silicate concentration and combination with other fixatives for skin care formulation that has no sticky feels and no scrubbing out phenomenon. Immediate lifting gel was developed by using sodium silicate and various thickening systems. Among of the various thickeners, aluminum magnesium silicate showed the best compatibility with sodium silicate for rapid lifting effect. This instant physical lifting gel was confirmed as a low stimulating formula by skin clinical test.

• Applied Chemistry for Engineering
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• v.9 no.1
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• pp.44-51
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• 1998

In this work, the in-situ viscoelastic characteristics of electropolymerized polypyrrole (PPy) thin film were investigated in the electrolyte solutions of $NaClO_4$, $LiClO_4$, and $KClO_4$ by using quartz crystal analyzer (QCA). One side of quartz crystal was used as a working electrode mounted in a special fabricated QCA electrochemical ceil. The resonant frequency and resonant resistance diagram (F-R diagram) was used to interpret the viscoelastic characteristics of Pby thin film and compared with AFM photograph. The resonant frequency, resonant resistance, and current were measured to analyze the redox reaction behaviors when the cyclic voltammetry was performed using AT-cut quartz crystal electrode coated with galvanostatically polymerized Ppy film. The result suggests that the Ppy film polymerized onto the crystal behaves as a rigid elastic layer at the initial stage of electropolymerization, while the film becomes a viscoelastic layer the polymerization proceeds further. At the same time, the film thickness increases and some morphological changes take place due to the penetration of electrolyte solution into the film. These phenomena take place when cyclic voltammetry was performed using different electrolyte solution compared with polymerization process.

• Geotechnical Engineering
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• v.14 no.6
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• pp.113-125
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• 1998

At the end of 1997 about 3 million tons of coal ash was produced as byproducts from the coal fired electrical power plants in Korea. Only about 27% of that byproducts was utilized as the admixtures of cement and concrete industry. But the large quantity of coal fired fly-ash has been used as the soil improvement materials in other countries. So the aim of this study is the estimation of the applicability of the coal fired fly-ash as microfine grouting materials by admixing the superfine particles which were separated from the coal fired fly-ash for the higher values. The 6 types of specimens were manufactured in the laboratory for the purpose of estimating the chemical and physical properties of cement and grouts. These specimens consisted of 2 specific surfaces of 6, 000 and 8, 000$cm^2$/g in Elaine method. And these specimens are devide into 3 ratios (30%, 50%, 70%) of fly-ash by weight. From the estimated properties of the coal fired fly-ash microflne cements and grouts, 50% fly-ash is the most suitable ratio for grouting materials. However, further study of durability is necessary for using fly-ash grouts practically at the field projects. The higher content of the unburned carbon of fly-ash increases the thinner layer of carbon on the surface of solution of grouts, and requires more quantity of surface active agent. As a results of this study, it is found that the microfine fly-ash is very useful as a good grouting material if 50% of fly-ash is added with the microfine portland cement. So, in the near future, if the coal fired fly-ash is able to be used as grouting material in Korea, the demand of fly-ash will increase rapidly.

• Journal of the korean academy of Pediatric Dentistry
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• v.38 no.3
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• pp.262-269
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• 2011

Ameloblastic fibroma is rare true benign mixed odontogenic tumor. Most of these tumors occur in the posterior region of the mandible under 20 years of age. It develops generally associated with unerupted tooth and grows slowly on the surface of alveolar bone, therefore interferes normal tooth eruption. These lesions rarely showing a little bony expansion, are usually asymptomatic and are discovered incidentally on routine dental exam. It is similar to amleoblastic fibroodontoma and ameloblastic fibrodentinoma clinically and roentgenographically but represents no dental hard tissue formation histologically. Enucleation and curettage of surrounding bone are generally recommended options for treatment. Even though there are some reports of recurrence and malignant transformation and more aggressive treatment options like block resection are suggested sometimes, but in most cases, recurrence is unusual because it is well encapsulated and easily separated from adjucent bony socket. In these cases, we did conservative treatment such as enucleation and curettage to the patients who were visited for ameloblastic fibroma associated with delayed eruption of lower first molar. After regular check-ups, we found relatively natural eruption process of combined teeth.

• Journal of the korean academy of Pediatric Dentistry
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• v.35 no.1
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• pp.73-82
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• 2008

Dental caries is an infectious disease caused by mutans streptococci, and is a primary etiologic agent of dental caries in humans. The molecular pathogenesis of mutans streptococcal-associated dental caries occurs in three phases. Firstly, S. mutans attaches to tooth surface via a cell surface adhesion termed antigen I/II. In the second phase, the glucosyltransferase(GTFs) synthesize polymers like glucans in the presence of sucrose. In the third phase, the multivalent glucans interacts with glucan binding proteins (GBPs) and they make dental plaque and accumulation of microorganisms. Many studies and clinical trials have indicated that a mucosal immune response to these antigens(Ag I/II, GTFs, GBPs) of S. mutans can influence the pathogenesis of dental caries. So these antigens can be important vaccine candidates for immunologic intervention against dental caries. In this study, we cloned the genes for GTFb, GTFc, GTFd from S. mutans GS-5 and did the nucleotide sequence analysis. And the recombinant proteins of GTFd and N-terminus of GTFd were expressed. Intact GTF which we get from this experiment can be used for antibody production specific for any GTF activity domain through animal experiment.

• Journal of the korean academy of Pediatric Dentistry
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• v.33 no.3
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• pp.401-410
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• 2006

Dental caries results from localized demineralization of tooth enamel by acids of bacterial origin produced from the fermentation of dietary sugars. A group of related oral bacteria, collectively known as mutans streptococci, are implicated as the primary etiological agents of human caries. Within this group, Streptococcus mutans has been known as a causative agent for dental caries. As well as acid production yielding the demineralization of tooth enamel, adherence and colonization of S. mutans to the teeth are also important for their virulence Cell-surface fibrillar proteins, which mediate adherence to the salivary pellicle are virulence components of mutans streptococci, and primary candidates for a human caries vaccine. Here we report that the AgI/II gene from S. mutans GS-5 were cloned by PCR amplification of the bacterial chromosomal DNA and the integrity of cloned genes were confirmed by nucleotide sequencing. Sequence analyses showed the sequence alignment of 280 nucleotides between the cloned AgI/II and the reported sequence of S. mutans GS-5 showed the perfect match The cloned genes which signal nucleotide was truncated, were transferred into bacterial expression vector and the recombinant proteins were purified as His-tag fusion proteins In order to generate polyclonal antibodies against the recombinant proteins, AgI/II mr, some $100{\mu}g$ of the proteins was injected into mice three times. It can be used for an effective vaccine production to prevent dental caries caused by pathogenic S. mutans.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2391-2400
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• 2015

Weather proof steels are used for steel bridges due to its high corrosion resistance under atmospheric conditions. However, instead of forming stabilized rust layers, general rust occurs on weather proof steels under high humidity condition close to seawater or shady places. In Japan, therefore, they perform rust stabilization treatment instead of unpainted treatment due to severe atmospheric conditions. However, most of domestic weather proof steels were constructed unpainted in the form of closed box-girder, which makes the periodical repetition of dry and wet hard to occur. For the steel bridges constructed on the Han river, the evaporation of water, dew condensation due to temperature change, and stagnant water due to rain affect harmfully on the formation of passive film on weather proof steels. Thus, in this research, in order to analyze corrosion properties inside the closed box-girder for the unpainted weather proof steel bridge in the waterworks safety zone, multiple ways of analysis such as observation with eyes, cellophane-tape test, steel thickness measurement, surface corrosion potential measurement, electron microscope analysis, and X-ray diffraction analysis of the rust were performed. As a result, unstable rust layer was observed inside the closed box-girder, and severe corrosion was observed on the top and bottom of the flanges due to the effects of stagnant water caused by rain, dew condensation, and de-icing materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.210-210
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• 2013

그래핀은 뛰어난 기계적, 화학적, 광학적, 전기적 특성을 가지고 있는 2차원 물질로, 대면적 합성법과 전사 공정을 통해 다양한 기판에서의 사용이 가능해지면서 차세대 전자 소자로 활용하기위한 활발한 연구가 이루어지고 있다. 디스플레이, 태양전지의 전극과 전계 효과 트랜지스터의 채널로 적용한 연구에서 우수한 결과들을 보이고 있다. 특히, 금속/금속 산화물 전극은 염료 감응형 태양전지와 유기 발광 다이오드 구조에서 화학적으로 불안정할 뿐 아니라 일함수가 고정되어 쇼트키 접촉이 형성되면 저항을 낮추기 어렵지만, 그래핀은 금속/금속 산화물 전극보다 화학적으로 안정하고 일함수의 조절이 가능해 옴 접촉 형성에 용이하다. 그래핀의 일함수를 조절하는 연구는 크게 공유결합과 비공유 결합을 이용한 방법이 시도된다. 공유 결합을 이용한 방법은 합성과정에서 그래핀의 구조에 내재된 결함 혹은 새로운 결함을 형성하여 다른 원소를 첨가하는 방법이다. 이러한 방법은 그래핀의 결함 영역에서 작용하기 때문에 그래핀 전자 구조의 높은 수준 조절을 위해선 그래핀 구조의 파괴가 동반된다. 반면, 비공유 결합을 이용한 방법은 전하 이동 도핑 효과를 이용해 그래핀의 전자 구조를 제어하는 방법으로, 금속/금속산화물/기능기와 그래핀의 적층으로 복합 구조를 형성하는 방법이다. 금속/금속 산화물과의 복합구조는 안정적인 p-형 도핑이 보고되었지만, n-형 도핑은 대기중의 수분, 산소 그리고 기판과의 상호작용에 의해 대기중에서 불안정해 추가적인 피막공정이 요구된다. 기능기를 이용한 적층 구조는 그래핀과 기판사이의 상호작용 혹은 그래핀 전자 구조를 다양한 기능기를 이용해 제어하는 것으로, 이극성을 가진 자기정렬 단일층(self-assembled monolayers)이 대표적인 방법이다. 공간기(spacer)의 길이나 말단기(end group)의 종류로 p-형과 n-형의 도핑 수준을 제어할 수 있지만, 흡착기(chemisorbing groups)의 반응성이 기판의 화학적, 물리적 표면상태에 의존하기때문에 기판 선택이 제약되며 전처리 공정이 요구될 수 있는 한계가 있다. 본 연구에서는 다양한 기판에 적용가능한 용액 공정을 이용해 그래핀과 고분자를 적층하였고, 안정적이고 효과적으로 일함수를 낮추는 구조를 확인하였다.

• Korean journal of applied entomology
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• v.44 no.4 s.141
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• pp.299-306
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• 2005

Soybean seed injury was analyzed in the experiments that soybean pods were allowed to be sucked by adults of the bean bug, R. clavatus, and were picked with a specimen pin. While attack by the bean bug at podding stage of soybean caused the increase of empty pods and completely-undeveloped seeds, attack at full seed stage caused the increase of seeds wi distinct injury mark on seed-coat. The ratio of deformed seed was lower than those of injury-marked seed and undeveloped seed when attacked during all stages. In at full bloom stage hardly produced injury-marked seeds and deformed seeds. When the injured seeds were dyed with acid-fuchsine solution, stylet sheaths of R. clavatus formed on seed-coat were observed in 83% of undeveloped seeds formed under attack during podding stage and in 91% of injury-marked seeds formed during full seed stage. In pods injured with a specimen pin at full seed and full maturity stages, no healthy seeds could be obtained from the pods. And the more picked at full seed stage, the more deformed seeds were produced and the higher weight reduction of injury-marked seed occurred. However, pin-injury at full maturity stage didn't give rise to weight reduction of seeds.