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알칼리 프리계 급결제를 사용한 강섬유 보강 숏크리트의 성능 평가
백철우,박찬기,전언중,원종필,Baek, Chul-Woo,Park, Chan-Gi,Jun, Oun-Jung,Won, Jong-Pil 한국농공학회 2004 한국농공학회논문집 Vol.46 No.3
Modern underground and tunnel works that the wet type shotcrete is getting widely designed and applied in a large scale project. Further to its applications, the needs of improving the performance of the shotcrete, such as new and developed additives and accelerators fur increasing the performance of shotcrete, become the most important issue in the field. The main objective of this study evaluated to performance of steel fiber reinforced shotcrete using alkali free based accelerator for the durability and high quality of shotcrete. The major test variables are accelerator type and its dosage. One type silicate based accelerator and one type aluminate based accelerator and one type alkali free based accelerator were used. The dosage of accelerators is determined by the manufactures and laboratory test condition. Compressive strength test results showed that the dosage of silicate and aluminate based accelerators caused reduction of mechanical properties of shotcrete. Compressive strength of alkali free based accelerator is more stable than of silicate and aluminate based accelerators. Also, according to the compressive strength and flexural test results, it was found that steel fiber reinforced shotcrete used alkali free based accelerator could attain significant improvement in the mechanical and flexural performance.
백철우 한국혁신학회 2020 한국혁신학회지 Vol.15 No.1
Since 2008, a feasibility study has been accumulating cases of cost-benefit analysis for national R&D programs, and the methodology for estimating benefits has been advanced. However, due to the nature of R&D, the performance and its spillover paths are diverse, and the uncertainty of the data is so large that it is more difficult to estimate benefits than social overhead capital. This study examines the following four issues in the estimation of the benefits of national R&D programs and proposes methods for upgrading the analysis methodology. First, unlike conventional product life cycles where the benefits go through the introduction, growth, maturity, and decline phases, the estimated benefit tends increase over time, so we can consider applying the R&D contribution rate differentially over time to solve it. Second, the R&D investment elasticity value of total factor productivity estimated at the macro level is applied as the R&D contribution ratio. In order for the R&D contribution rate to meet its original meaning, it is necessary to estimate the portion of R&D investment that contributes to the creation of added value at the micro level, and this figure needs to be differentiated according to the technology readiness level. Third, it is necessary to include substantial indirect effects with relatively clear spillover paths and possible monetization in benefit. Fourth, the benefit estimation method of the technology non-designated (free public offering) program needs to be replaced with an alternative benefit estimation method through objective data because there is a possibility of overresponse of potential beneficiaries. 2008년부터 예비타당성조사를 통해 국가연구개발사업에 대한 비용편익분석 사례가 축적되고 편익 추정 방법론도 고도화되고 있다. 하지만 R&D의 특성상 성과와 그 파급경로가 다양하고 자료의 불확실성이 커서 사회간접자본에 비해 편익 추정의 어려움이 크다. 본 연구는 국가연구개발사업의 편익추정에 있어서 다음과 같이 4가지 이슈를 점검하고 분석방법론 고도화를 위한 방안들을 제안하였다. 첫째, 도입기-성장기-성숙기-쇠퇴기를 거치는 일반적인 제품수명주기와 달리 시간에 따라 편익이 점증하는 현재 방식의 문제를 해결하기 위해 시간에 따라 R&D 기여율을 차등적용하는 방안을 고려할 수 있다. 둘째, 거시수준에서 추정한 총요소생산성의 R&D 투자탄력성 수치를 R&D 기여율로 적용하고 있는데, 본래의 의미에 부합하도록 미시적 수준에서 R&D 투자가 부가가치 창출에 기여하는 부분을 추정하고 이 수치도 기술준비단계에 따라 차별화할 필요가 있다. 셋째, 비교적 파급경로가 명확하고 화폐화가 가능한 실질적인 간접효과는 편익에 포함하는 것이 필요하다. 넷째, 기술비지정(자유공모형) 사업의 편익추정 방식은 잠재적 수혜기업의 과잉응답의 가능성이 존재하기 때문에 객관적 자료를 통한 편익추정 방식을 대안으로 고려할 수 있다.
매복된 상악견치를 수술로 노출시켜 교정치료한 후의 치주 상태에 대한 연구
백철우,김경호,임성빈,정진형,Baek, Chul-Woo,Kim, Kyung-Ho,Lim, Sung-Bin,Chung, Chin-Hyung 대한치주과학회 1999 Journal of Periodontal & Implant Science Vol.29 No.3
The present study examines the effects of orthodontic treatment of surgically exposed impacted upper canines or ectopically erupted upper canines to periodontal condition and whether various opening procedures have significant difference in postoperative periodontal status. The subjects included 23 orthodontic patients(7 men, 16 women) with unilateral upper canine impaction treated either with closed eruption technique(group I), with apically positioned flap procedure (group II), and those with canines ectopically erupted through keratinized gingiva (group III). In each subject, the ectopic canine was orthodontically aligned, and changes in periodontal tissue were assessed by measuring keratinized gingival width, attached gingival width, probing depth and bone probing depth. In all three groups, the width of keratinized gingiva was preserved while showed no signs of detrimental periodontal condition such as gingival recession. In all three groups, no significant difference in periodontal pocket depth from control was observed. The width of attached gingiva was significantly greater in patients treated with apically positioned flap procedure(group II) than in patients on other groups.
CAD/CAM 세라믹 인레이에 대한 3종의 레진 시멘트의 전단결합강도에 관한 연구
백철우,박철우,박준섭,류재준,Baek, Chul-Woo,Park, Cheol-Woo,Park, Jun-Sub,Ryu, Jae-Jun 대한치과보철학회 2013 대한치과보철학회지 Vol.51 No.1
연구 목적: 본 연구는 최근 심미수복에 주로 사용되는 CAD/CAM 세라믹 인레이와 각종 레진 시멘트간의 결합강도를 알아보고자 하였다. 연구 재료 및 방법: 원기둥 모양의 세라믹 블록(높이: 5 mm, 직경: 3 mm)을 Cerec3로 제작하고, 총 90개의 우식이 없는 대구치의 상아질 표면에 세 종류의 레진 시멘트(Unicem$^{(R)}$, Biscem$^{(R)}$, Variolink II$^{(R)}$)를 사용하여 각각 제조업체의 지시에 따라 접착했다. 90개의 시편을 레진 시멘트의 종류에 따라 3개의 군으로 나누고, 각 군의 절반은 $5-55^{\circ}C$, 5,000 cycle 조건 하에서 thermocycling을 시행하였고, 다른 절반은 시행하지 않았다. 모든 시편은 결합강도를 측정하기 전에 $37^{\circ}C$ 생리 식염수에 24시간 동안 보관되었다. 전단결합강도는 만능시험기를 이용하여 0.5 mm/min의 cross head speed로 측정하였다. 결과 값은 t-test 및 one-way ANOVA를 사용하여 통계 분석하였다. 결과: Unicem$^{(R)}$ 군의 전단결합강도가 thermocycling 후에 약간 감소했으나 3 개의 군 중 가장 높은 결합 강도를 보였다. Unicem$^{(R)}$ 및 Valiolink II$^{(R)}$ 군의 전단결합강도가 thermocycling에 영향을 받았지만 Biscem$^{(R)}$은 영향을 받지 않았다(P<.05). Thermocyling 전에는 3개의 군 간의 결합강도에 유의한 차이가 없었지만, thermocyling 후에는 Unicem$^{(R)}$과 Valiolink II$^{(R)}$ 군 간에 유의한 차이가 있었다(P<.05). 결론:CAD/CAM 세라믹 인레이 수복물을 치아에 접착할 때, etch-and-rinse 레진 시멘트인 Valiolink II$^{(R)}$ 대신self-adhesive 레진 시멘트인 Unicem$^{(R)}$과 Biscem$^{(R)}$을 사용해도 임상적으로 유용하다. Purpose: The purpose of this study was to evaluate the bond strengths between the latest CAD/CAM ceramic inlay and various resin cements which are used primarily for esthetic restoration. Materials and methods: Cylindrical ceramic blocks(Height: 5 mm, diameter: 3 mm) were fabricated by using Cerec3 and bonded on the dentin of the ninety extracted caries-free molars using three different kinds of resin cement(Unicem$^{(R)}$, Biscem$^{(R)}$, and Variolink II$^{(R)}$) according to the manufacturer's instructions. Ninety specimens were divided into 3 groups according to three different kinds of resin cement. Half of each group were conducted thermocycling under the conditions of the $5-55^{\circ}C$, 5,000 cycle but the other half of them weren't. All specimens were kept in normal saline $37^{\circ}C$, for 24 hours before measuring the bond strength. The shear bond strength was measured by Universal testing machine with a cross head speed of 0.5 mm/min. The results were analyzed statistically by t-test and one-way ANOVA. Results: Unicem$^{(R)}$ group showed the highest shear bond strength despite a slight decline by thermocycling. The shear bond strength of Unicem$^{(R)}$ group and ValiolinkII$^{(R)}$ group were significantly influenced by thermocycling, whereas Biscem$^{(R)}$ group was not influenced (P<.05). There were no significant differences in the bond strength between the three groups without thermocycling, but there was significant differences between Unicem$^{(R)}$ group and Valiolink II$^{(R)}$ group with thermocycling(P<.05). Conclusion: It has been shown to be clinically effective when the self-adhesive resin cements Unicem$^{(R)}$ and Biscem$^{(R)}$ were used instead of the etch-and-rinse resin cement Valiolink II$^{(R)}$ during the bonding of CAD/CAM ceramic inlay restorations with teeth.
산업 수준의 파생수요함수를 활용한 제조업 전력수요의가격탄력성 분석
백철우 한국혁신학회 2022 한국혁신학회지 Vol.17 No.3
As Korea's manufacturing share is higher than that of its competitors, electricity consumption is also high. However, due to the recent increase in oil prices caused by the war between Ukraine and Russian, and rising costs to respond to climate change, there is a lot of pressure to increase electricity rates. The price elasticity of electricity demand is an important indicator to check how sensitive electricity consumers are to changes in electricity rates. All previous studies estimated the price elasticity of electricity demand through the general demand function. However, in the case of manufacturing, electricity is not consumed as a final product. Instead the production that maximizes profit is determined and then the optimal power consumption is determined through adjustment between input factors, which implies the demand of electricity in manufacturing sector is the derived demand. Therefore, in this study, the price elasticity of electricity demand for each manufacturing sector was estimated through the demand derived from the translog production function. As analysis data, the ‘Mining and Manufacturing Survey’ of the National Statistical Office, which surveyed all 10 or more manufacturing employees, was used. As a result of the analysis, it was confirmed that the price elasticity of electricity demand was less than -1 in all manufacturing sectors, so that electricity demand was very sensitive to electricity rates. This suggests that it is necessary to reflect the cost incurred in the carbon-neutral process in the electricity price at an appropriate level, because even if the electricity price rises in the future carbon-neutral process, it will not significantly impair the competitiveness of manufacturing companies. 한국은 경쟁국 대비 제조업 비중이 높음에 따라 전력사용량도 높은 수준이다. 하지만 최근 우크라이나-러시아 간 전쟁으로 인한 유가 상승, 기후변화 대응을 위한 비용 상승 등으로 인해 전기요금 인상의 압박이 크다. 전력수요의 가격탄력성은 전력소비자들이 전기요금 변화에 얼마나 민감하게 반응하는지 확인할 수 있는 중요한 지표이다. 기존 연구는 모두 일반수요함수를 통해 전력수요의 가격탄력성을 추정하였으나, 제조업은 전기를 최종재로 소비하는 것이 아니라 이윤을 극대화하는 생산량을 정하고 이후에 투입요소 간 조정을 통해 최적 전력소비량을 결정하기 때문에 제조업의 전력수요는 파생수요에 해당한다. 따라서 본 연구에서는 트랜스로그 생산함수의 파생수요함수를 통해 제조업 중분류별 전력수요의 가격탄력성을 추정하였다. 분석 자료로 제조업 10인 이상 전수를 조사한 통계청의 ‘광업제조업조사’를 활용하였다. 분석결과 제조업 모든 업종에서 전력수요의 가격탄력성이 –1보다 작아 전력수요가 전기요금에 매우 민감함을 확인하였다. 이는 향후 탄소중립 추진 과정에서 전기요금이 상승하여도 장기적으로 제조기업의 경쟁력을 크게 저해하지 않을 것이기 때문에 탄소중립 과정에서 발생하는 비용을 적정 수준에서 전력가격에 반영하는 것이 필요함을 시사한다.
백철우 한국에너지학회 2014 에너지공학 Vol.23 No.3
Korean government has been investing more than 400 billion KRW in R&D on renewable energy. This paper aims to measure the R&D efficiency of national R&D program in the field of renewable energy, and to identify the sources of inefficiency. 4,213 R&D projects supported by Korean government during 2009-2011 are analyzed by using Data Envelopment Analysis and statistical tests. Results implies as follows. First, hydrogen, bio, fuel cell, photovoltaic have higher R&D efficiency than other renewable energies. Second, universities conducted national R&D program more efficiently than firms did, and small and medium sized enterprises are more efficient than large sized enterprises. Third, R&D inefficiency is mainly caused by the lacks of patent performance rather than excessive R&D investment or academic paper performance.
Non-parametric Measurement of Consumption Efficiency with DEA Framework
백철우,이정동,강민성 한국혁신학회 2014 한국혁신학회지 Vol.9 No.1
Data Envelopment Analysis (DEA), a representative non-parametric methodology in production economics, is applied in the measurement of consumption efficiency. By considering the direction of the Generalized Axiom of Revealed Preference (GARP), some obstacles in the application of DEA to the consumption area are overcome. Experimental simulation verifies that the DEA efficiency index outperforms Afriat’s efficiency index in both accuracy and credibility.
백철우,노민선 한국혁신학회 2014 한국혁신학회지 Vol.9 No.2
This research examines the effect of firms' R&D strategies - (i) self-implementingR&D, (ii) R&D outsourcing, (iii) introduction of overseas technologies - on firms’growth rate and profitability using panel data during 2001-2009. Results show that the increase 1% in the ratio of internal R&D to sales resultsin the 0.491% increase of sales growth and 0.004% increase of ROA. However,the increase 1% in the ratio of R&D outsourcing to sales, causes 0.389% declineof sales growth, and no significant effect on ROA. Introduction of overseastechnologies does not show any significant influences on sales growth andprofitability, neither. Open R&D strategies turn out to be invalid in our R&D environment. To reducetransaction cost in R&D outsourcing and introduction of overseas technologies, wesuggest the promotion of R&D service industry, supply of standards contract form,and reinforcement of intermediary function for overseas technologies. 본 연구는 (i) 자체수행 R&D, (ii) R&D 아웃소싱 (iii) 해외기술 도입이라는 기업의 세 가지 R&D 투자전략이 기업의 성장성과 수익성에 미치는 영향을 2001-2009년 패널데이터를 활용하여 분석하였다. 분석 결과, 매출액 대비 자체 R&D 투자를 1% 증가시키면, 매출액은 0.491%, ROA(Return on Asset)은 0.004% 증가하는 것으로 나타났다. 하지만, 매출액 대비 R&D 아웃소싱 1% 증가는 매출액을 0.389% 감소시키는 동시에 ROA에는 유의미한 영향을 미치지 못하였다. 해외기술 도입도 기업의 성장과 수익성 모두에 기여하지 못하는 것으로 분석되었다. 상기 결과는 개방형 혁신이 우리의 R&D 환경에서는 기업 성과에 긍정적으로 작용하지 못하고 있음을 시사한다. R&D 아웃소싱과 해외기술 도입에 따른 거래비용을 줄이기 위기 R&D 서비스업 활성화, 연구개발서비스 표준계약서 보급, 해외기술 중계기능 강화를 제안하였다.