• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.294-301
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• 2020

This study evaluated the burnability and hydration reaction of clinker burned with high Al₂O₃ content OPC to apply large amounts of industrial by-products in the cement manufacturing process. Specifically, after preparing a clinker with a high C₃A content by burning the OPC raw material with a high content of Al₂O₃ in a laboratory electric furnace, the burnability of the clinker was evaluated through XRD Rietveld analysis and polarization microscopy, and clinker hydration reactivity was reviewed through the Isothermal conduction calorimetry analysis and the cement compressive strength. As a result, the kiln burning temperature for the production of high Al₂O₃ content clinker lower, and the compressive strength was equal to or higher than OPC. Therefore it was confirmed the possibility to manufacturing energy-saving high Al₂O₃ content clinker using a large amount of industrial by-products.

• The Korean Journal of Financial Management
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• v.25 no.3
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• pp.1-32
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• 2008

This study examines the changes and determinants of cash to assets ratios(cash ratios) by analyzing 14,016 Korean manufacturing firms sample for the period of $1999{\sim}2004$. The major findings can be summarized as follows. First, the average cash ratios for Korean manufacturing firms have increased from 4.7 percent of 1999 to 5.2 percent of 2004. In addition, the average cash holdings per firm also have increased from 4.3 billion Won to 8.0 billion Won during the same period. However, the capital expenditures relative to cash ratios or operating cash flow have decreased significantly, confirming the notion that physical investment of Korean manufacturing sector has been shrinking recently. Second, in regression tests with panel data, the coefficients of target adjustment variables show the expected negative signs, but coefficients of the deficit of fund variables show the unexpected positive signs. Thus, the evidence seems to be supportive of static tradeoff model of cash holdings. Third, in regression tests to find the determinants of cash ratios, most of the variables show similar results as the previous studies. However, in terms of adjusted coefficient of determination and F-statistic, the firm-characteristic variables suggested by static trade-off theory have more explanatory power than the variables suggested by pecking order theory.

• Journal of Electrochemical Science and Technology
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• v.1 no.1
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• pp.19-24
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• 2010

Alloying degree is an important structural factor of PtRu catalysts for direct methanol fuel cells (DMFC). In this work, carbon supported PtRu catalysts were synthesized by reduction method using anhydrous ethanol as a solvent and $NaBH_4$ as a reducing agent. Using anhydrous ethanol as a solvent resulted in high alloying degree and good dispersion. The morphological structure and crystallanity of synthesized catalysts were characterized by X-ray diffraction (XRD), high resolution transmission electron microscope (HR-TEM). CO stripping and methanol oxidation reaction were measured. Due to high alloying degree catalyst prepared in anhydrous ethanol, exhibited low onset potential for methanol oxidation and negative peak shift of CO oxidation than commercial sample. Consequently, samples, applying ethanol as a solvent, exhibited not only enhanced CO oxidation, but also increased methanol oxidation reaction (MOR) activity compared with commercial PtRu/C (40 wt%, E-tek) and 40 wt% PtRu/C prepared in water solution.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.2
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• pp.208-213
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• 2011

This paper analyzes potential interference effects of Ultra Wide Band(UWB) on Global Positioning System(GPS) which is providing safety service. For the interference analysis, positioning error method is used to determine the minimum protection distance to meet positioning error of 2.5 m below and Minimum Coupling Loss(MCL) method is used to determine the required protection ratio(I/N) from the protection distance of UWB transmitter and GPS receiver to meet positioning error of 2.5 m below. In a result, the minimum protection distance to meet positioning error of 2.5 m below was about 10 m and the protection ratio to meet positioning error 2.5 m below was -20 dB. The protection ratio proposed in this paper is the same value of the protection ratio of safety service proposed by ITU-R. The obtained protection ratio can be used for the protection standard of domestic GPS system for the safe of life service.

• Journal of Periodontal and Implant Science
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• v.32 no.1
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• pp.89-112
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• 2002

The earliest reports of the use of electrical energy to directly stimulate bone healing seem to be in 1853 from England, the techniques involved the introduction of direct current into the non-united fracture site percutaneously via metallic needles, with subsequent healing of the defect. One endpoint of the periodontal therapy is to generate structure lost by periodontal diseases. Several procedural advances may support regeneration of attachment, however, regeneration of alveolar bone does not occur consistently. Therefore, factors which stimulate bone repair are areas for research in periodontal reconstructive therapy. Effects of cytokines or growth factors on bone repair are examples of such areas. Another one is electrical current which occurs in bone naturally, so that such bone may be particularly susceptible to electrical therapy. The purposes of this study were to observe the effects of electrical stimulation on the normal periodontium, to determine whether the electricity is the useful means for periodontal regeneration or not. Forty rats weighted about 100 gram were used and divided into 4 groups, the first group, there was no electrical stimulation with the connection of electrodes only. In the second group, there was stimulated by the 10 mA during 10 minutes per a day, in the third group was stimulated by the 25 mA , and the fourth by the 50 mA. At 3, 5, 10 and 15 days post-appliance , two rats in each group were serially sacrificed. and the maxillae and the mandible processed to paraffin, and the specimens were prepared with Hematoxylin-Eosin stain for the light microscopic evaluation. The results of this study were as follows : 1. There was the distinct reversal line on the lingual alveolar crest, whereas a little changes in the labial alveolarcrest to the duration and amount of currents. 2. In 50 mA group, the cells were highly concentrated at the apex of anterior teeth, and was observed the necrotic tissue. In posterior root apex, the hypercementosis was appeared, and newly formed cementum layer has been increased continuously with the time. 3. The periodontal ligament fiber and Sharpey's fiber were arranged in order, and the bone trabeculae were increased as the experiment proceeded by, relatively the bone marrows were decreased. 4. In the pulp tissue, the blood vessels were increased with blood congestion in the experimetal specimens remarkably, and the dentinal tubules were obstructed . 5. The osteoblasts in alveolar bone proper had been showed highly activity, and also observed the formation of bone trabeculea. In the conclusion, it was suggested that the electrical stimulation has influence on the periodontium and the pulp tissue. However, there might be the injurious effects.

• Journal of Periodontal and Implant Science
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• v.36 no.1
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• pp.113-123
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• 2006

연구배경 IgG에 대한 $Fc{\gamma}$ 수용기는 치주병인균에 대한 숙주 반응에 있어서 중요한 역할을 하는데, 이 중 $Fc{\gamma}RIIIa$는 NK 세포, 대식세포, 단핵구, ${\gamma}{\delta}T$세포에서 발현되며, EC2 도메인에서 158 아미노산 부위의 valine (V)-phenylalanine (F)의 유전자다형성을 보인다. $Fc{\gamma}RIIIb$는 특이적으로 중성구에 발현되는데, extracellular (ECl) Ig-like 도메인 내 4개의 아미노산 치환(substitutions)에 의한 NA1-NA2 유전자다형성을 보인다. 이 연구의 목적은 한국인에서 급진성 치주염 환자와 $Fc{\gamma}III$ 수용기의 유전자다형성과의 관련성을 알아보는 것이다. 연구방법 및 재료 치주적으로 건강한 90명 (대조군, 남자 64명, 여자 26명)과 서울대학교 치과병원 지주과에 내원하여 급진성 치주염으로 진단된 환자 43명 (aggressive periodontitis patients: AgP, 남자 30명, 여자 13명)을 대상으로 하였다. 모든 실험 대상자는 임상 실험에 대해 동의 하였고, 초진 시 전자 탐침(Florida Probe(R) Co. Gainesville, FL)을 이용하여 탐침 시 치주낭 깊이 (PPD), 임상부착수준 (CAL), 치태지수(PI), 탐침 후 출혈지수 (BOP)를 측정하였다. 또한 이들의 정맥혈에서 추출한 DNA를 PCR법, 전기영동법 등을 이용하여 $Fc{\gamma}RIIIa$, $Fc{\gamma}RIIIb$의 대립 유전자의 존재여부를 확인하였다. 이를 바탕으로 $Fc{\gamma}RIII$ 복합 유전형을 확인하여 각 군 간을 비교하였다. 연구 결과 1. $Fc{\gamma}RIIIa$에 대한 유전자다형성 연구 결과 대조군과 급진성 치주염 환자 군(AgP)사이에서는 대립 유전자 분포가 서로 유의성 있는 차이를 나타내었고 (P<0.05), $Fc{\gamma}RIIIb$에서는 유의성 있는 차이를 발견할 수 없었다. (P>0.05) 2. $Fc{\gamma}RIIIa$ 158F 대립형질이 급진성 치주염 환자에서 유의성 있게 많이 발견되어졌다. (P<0.05) 결론 이 연구를 통하여 $Fc{\gamma}RIIIa$ 유전자의 분석이 한국인의 급진성 치주염에 대한 감수성의 위험요소의 표지자로 활용할 수 있을 것으로 사료되며, 향 후 더 많은 환자를 대상으로 히는 추가 연구가 필요하다고 생각된다.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.671-681
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• 2004

Genomic Project 이후로 다양한 질환에 있어서 유전적인 영향에 관한 연구가 진행되고 있다. 이 연구의 목적은 한국인 치주질환 환자에서 Fc ${\gamma}R$ 유전자의 유전자다형성과 치주질환 특성과의 관련성을 알아보는 것이다. 치주적으로 건강한 한국인 90명(대조군, 남자64명, 여자26명), 중도 만성 치주염환자 40명(severe chronic periodontitis patients; severe CP, 남자 24명, 여자 16명)을 대상으로 임상지수(치주낭 깊이, 입상부착소실, 치은지수, 치태지수, 탐침 후 출혈지수, 치조골소실)를 측정하였다. 또한 이들의 정맥혈에서 추출한 DNA를 PCR(Polymerase Chain Reaction)법, 전기영동법 등을 이용하여 Fc ${\gamma}RIIIa$ , Fc ${\gamma}RIIIb$의 대립유전자의 존재여부를 확인하였다. 이를 바탕으로 각 유전자의 다형성 및 Fc ${\gamma}R$ 복합유전자형 (Fc ${\gamma}R$ composite genotype)을 확인하여, 각 군 간을 비교하였다. 치주질환의 특성과 유전자 다형성과의 관련성을 알아보기 위하여 Fc ${\gamma}R$ 유전자에 대한 유전자다형성을 조사한 결과 다음과 같은 결과를 얻을 수 있었다. 1. Fc ${\gamma}RIIla$에 대한 유전자다형성 연구결과 대조군과 severe CP, AgP군 사이에서, severe CP와 AgP군 사이에서는 대립유전자분포가 서로 유의성 있는 차이를 나타내었지만(p<0.05), Fc ${\gamma}RIIlb$에서는 유의성 있는 차이를 보이지 않았다(p>0.05). 2. Fc ${\gamma}R$ 복합유전자형간의 비교에서 유의성 있는 차이를 발견할 수 없었다(p>0.05). 이와 같은 결과를 종합하여 볼 때 실험대상 한국인 치주염환자에서 Fc ${\gamma}R$ 유전자에 대한 다형성분석에서 Fc ${\gamma}RIIIa$ 대립유전자가 치주염에 대한 감수성과 관련되어 있다고 생각된다. 이 연구의 결과는 유전자의 차이가 치주질환의 감수성 판단의 자료로 활용할 수 있는 가능성을 보여주고 있다.

• Journal of Periodontal and Implant Science
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• v.34 no.3
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• pp.623-637
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• 2004

중증 만성 치주염과 1L-1B+3954 및 1L-1A+4845 유전자의 대립유전자 2 보유 유전자 다변성이 관련된다고 보고되었다. 그러나 이러한 1L-1 복합유전자 다변성과 만성 치주염 및 급진성 치주염과의 관련성에 대해서는 상반되게 보고되고 있는데 이는 인종적 배경과 질환특성의 차이에 기인한 것으로 보인다. 이 연구는 한국인에서 경도, 중등도와 중증의 만성 치주염 그리고 급진성 치주염 환자를 대상으로 하여 1L-1A+4845, 1L-1B+3954, 1L1B-511, 1L-1 RN intron 2 (VNTR) 유전자 다변성의 분포를 평가하고, 치주질환의 심도와 유형에 관련되는지 알아보고자 시행되었다. 전남대학교 병원 치주과에서 검진과 치료를 받은 100명의 치주질환자를 대상으로 하였고 질환군은 치주낭 깊이, 부착 소실, 골 소실을 기준으로 하여 경도, 중등도, 중증의 만성 치주염, 급진성 치주염군으로 분류하였다. 대조군으로는 전남대학교 병원 소아치과에 내원한 전신적으로 건강한 92명의 아동을 포함하였다. 각 대상 환자에서 채취된 협점막상피에서 genomic DNA를 얻어 1L-1A+4845, 1L-1B+3954, 1L-1B-511 genotype은 중합효소 연쇄반응을 시행한 후 제한 효소분해과정을 거쳐 전기영동 후 분리한 결과를 해석하였으며 1L-1 RN(VNTR) 유전형은 중합효소연쇄반응 후 분리한 결과를 해석하여 다음의 결과를 얻었다. 대립유전자 2 보유자 비율은 치주질환자에서 1L-1A+4845, 1L-1B+3954, 1L-1B-511, 1L-1 RN이 각각 61%, 13%, 76.6%, 34%였으며 대조군에서는 76.9%, 7.7%, 62.2%, 19.1%였다. 1L-1B+3954과 1L-1A+4845 대립유전자 2 보유자인 양성유전자형 비율은 경도, 중등도, 중증의 만성치주염, 급진성 치주염환자에서 각각 10%, 7.9%, 22.2%, 12% 였으며 치주질환자의 13%, 대조군의 7.7%에서 양성 복합유전자형(positive genotype)을 보였다. IL-1B-511 유전자 다변성은 치주질환자에서 대조군에 비하여 높았으며 급진성 치주염환자에서 대립유전자 2 보유자율이 유의하게 높았다(p<0.01). IL-1 RN intron 2 유전자 다변성은 중등도 및 중증 만성 치주염환자에서 대립유전자 2 보유자율이 유의하게 증가하였다. 이러한 결과는 IL-1 gene cluster의 유전형이 한국인에서도 치주염의 유형과 질환 심도에 관련될 수 있음을 시사하였다.

• Journal of the Korean Society of Food Science and Nutrition
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• v.43 no.1
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• pp.86-92
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• 2014

Cordycepin is the major functional component of Cordyceps species and is widely used in traditional oriental medicine. Cordycepin has been shown to possess many pharmacological properties, such as enhancement of immune function along with anti-inflammatory, antioxidant, anti-aging, and anti-cancer effects. Here, we investigated the inhibitory effects of cordycepin on cell migration and invasion, which are two critical cellular processes that are often deregulated during metastasis, using HCT116 human colorectal carcinoma cells. According to our data, cordycepin at non-cytotoxic concentrations markedly inhibited the motility and invasiveness of HCT116 cells in a time-dependent manner. RT-PCR and Western blotting results indicated that cordycepin reduced the levels of claudin proteins, which are major components of tight junctions (TJs), and induced tightening of TJs. Cordycepin also attenuated the expression and activities of matrix metalloproteinases (MMPs)-2 and -9, whereas levels of tissue inhibitor of metalloproteinases (TIMPs)-1 and -2 were simultaneously elevated. These findings suggest that cordycepin reduces the migration and invasion of HCT116 cells by modulating the activities of TJs and MMPs.

• Journal of the Korean GEO-environmental Society
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• v.13 no.6
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• pp.91-100
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• 2012

Wireless monitoring system for the structural health evaluation has a limit to the reliability of measured response. The objective of this study is to evaluate an effective measurement range of the wireless monitoring system on the analyzed data. For the wireless monitoring system, Bluetooth and Wi-Fi are applied to datalogger-receiver and receiver-personal computer, respectively. For the model of the monopile structure response, a laboratory-scale monopile is manufactured with Mono Cast Nylon and a lateral loading is applied by hammer impacting. Strain gauges attached on the model monopile are connected with the datalogger. The distances of datalogger-receiver and receiver-personal computer are changed for the evaluation of the measurement range. Experimental results show that the receiving rates of the response remain almost constant within limited distance, while the receiving rates dramatically decrease out of effective range. In addition, the receiving rates affect on the measured natural frequencies of the model monopile. This study suggests that the effective range evaluation of the wireless monitoring system may be used for the determination of a monitoring distance to the monopile installed in the offshore wind farm.