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.

다량의 혼화재를 사용한 고강도 콘크리트의 역학적 특성

백철우,박조범,최성우,조현태,류득현,Baek, Chul-Woo,Park, Cho-Bum,Choi, Sung-Woo,Jo, Hyun-Tae,Ryu, Deuk-Hyun 한국건설순환자원학회 2014 한국건설순환자원학회 논문집 Vol.2 No.3

본 연구에서는 시멘트 사용량을 저감하고 다량의 혼화재를 사용하여 고강도 콘크리트 제조 과정에서 시멘트에 의한 $CO_2$ 발생량을 감소시킬 목적으로 혼화재 및 무기계 자극제를 사용한 고강도 콘크리트의 역학적 특성을 평가하였으며, HVMA 결합재 도출과 W/B 변화 및 양생온도에 따른 HVMA 고강도 콘크리트를 실험하였다. 실험결과, 다량의 혼화재와 무기계 자극제인 열병합애시와 무수석고를 혼합 사용한 HVMA 결합재 배합을 설계하였으며, 설계된 HVMA 결합재를 사용할 경우 W/B 26% 수준에서 HVMA 고강도 콘크리트 배합이 유동특성과 역학적 특성이 양호한 것으로 나타났다. 또한 HVMA 결합재를 사용한 고강도 콘크리트의 양생온도 영향을 검토한 결과, 양생온도 $20^{\circ}C$ 이상 확보한 경우에는 50MPa 이상의 고강도 HVMA 고강도 콘크리트 제조가 실용화 가능성이 높은 것으로 나타났다. The purpose of this study is to evaluate on the mechanical properties of High Volume Mineral Admixture(HVMA) high strength concrete to reduce the amount use of Ordinary Potland Cement, to discover the optimized HVMA binder and to test HVMA concrete based on the change of W/B and curing temperature. The results were shown as follows: The HVMA binder using the mixture of combined heat power plant fly ash and anhydrous gypsum known as inorganic activators with the mixture of blast furnace slag and fly ash was optimized. The mixture of HVMA high strength concrete at 26% of W/B ratio had a good result on flow characteristic and mechanical properties. High strength HVMA concrete over 50MPa is possibly manufactured over curing temperature $20^{\circ}C$.

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.

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.

액상형 흄드실리카 대체율별 페이스트 특성 평가

백철우(Baek, Chul Woo),김완수(Kim, Wan Su),박창건(Park, Chang Gun),박조범(Park, Cho-Bum),최성우(Choi, Sung Woo),류득현(Ryu, Deuk Hyun) 한국콘크리트학회 2023 한국콘크리트학회 학술대회 논문집 Vol.35 No.1

질적성과를 고려한 R&D 효율성 분석연구

백철우 ( Chul Woo Baek ),이순배 ( Sun Bae Lee ) 한국생산성학회 2010 生産性論集 Vol.24 No.4

This study explores the application of Data Envelopment Analysis(DEA) for the evaluation of R&D project with the consideration of qualitative performance. DEA is considered as the best methodology for R&D efficiency in that (i) it can consider multiple outputs, (ii) it does not require prior information on the function and (iii) it can provide benchmarking information to improve efficiency. Among previous DEA models, Range Adjusted Measure(RAM) is the most appropriate because (i) it assumes flexible production frontier, (ii) it does not require restriction on the direction of either inputs or outputs and (iii) it can separately consider qualitative performance from quantitative performance. In this study, we applied RAM to the evaluation of R&D project funded by ministry of information and communication.

아시아 국가의 기술혁신 환경요인이 R&D 효율성에 미치는 영향 분석

백철우(Chul Woo Baek),권명화(Myung Hwa Kwon),유승훈(Seong Hoon Yoo) 한국아시아학회 2009 아시아연구 Vol.12 No.2

본 연구에서는 한국, 일본, 중국, 싱가폴, 대만 등 아시아 5개국의 R&D 효율성을 자료포락분석(Data Envelopment Analysis)을 이용하여 측정하였고, 토빗(Tobit) 모형을 통해 개방성, 지식재산권 보호정도, 반독점정책, 학연협력, 벤처캐피털 시장 발전정도 등의 기술혁신 환경요인이 아시아 국가의 R&D 효율성에 미친 영향을 분석하였다. 분석결과 2003년 이후 아시아 5개국의 R&D 효율성이 비아시아권의 선진국 수준으로 급성장하였으며, 2003년 이후 한국, 일본, 중국이 R&D를 효율적으로 수행하는 국가로 자리매김하고 있는 것을 확인하였다. 또한 아시아 5개 국가에 있어서는 기술혁신 환경이 다른 선진국과 다르게 R&D 효율성에 영향을 미치고 있었다. 비아시아 국가와는 달리 개방성과 지식재산권 보호가 강화될수록 아시아 국가의 효율성은 저하되며, 벤처캐 피털 시장의 발전도 R&D 효율성에 음(-)의 영향을 미치고 있었다. 이상의 논의는 아시아 국가가 기존의 선진국의 논리에 함몰되기 보다는 각 국의 제도적·지리적·문화적 특성을 감안하여 기술혁신 환경을 구축할 것을 시사한다. This research measures R&D efficiency of five Asian countries such as Korea, Japan, China, Singapore and Taiwan by using Data Envelopment Analysis, and analyses the effect of innovation environment factors - openness, intellectual property right, co-research between university and research institute and venture capital market- on R&D efficiency by using Tobit regression. Results shows that rapid increase in R&D efficiency of five Asian countries since 2003 is observed and Korea, Japan and China are evaluated as R&D efficient countries since 2003. Moreover, it is remarkable that innovation environment factors differently effected on R&D efficiency of Asian countries compared with other advanced countries. Contrary to non-asia countries, the reinforcement of openness, intellectual property right and venture capital market caused decrease in R&D efficiency. This implies that Asian countries should improve their own environment factors for innovation considering institutional, geographical and cultural characteristics.

리젝트애쉬를 사용한 콘크리트 특성

백철우(Baek, Chul-Woo),김호수(Kim, Ho-Soo),박조범(Park, Cho-Bum),류득현(Ryu, Deuk-Hyun) 한국콘크리트학회 2006 한국콘크리트학회 학술대회 논문집 Vol.2006 No.5

고강도 HVMA 콘크리트 성능평가를 위한 Mock Up Test

백철우(Baek, Chul Woo),김훈상(Kim, Hoon Sang),박조범(Park, Cho Bum),최성우(Choi, Sung Woo),조현태(Jo, Hyun Tae),류득현(Ryu, Deuk Hyun) 한국콘크리트학회 2014 한국콘크리트학회 학술대회 논문집 Vol.2014 No.5

기업의 개방형 혁신전략의 R&D 효율성 제고 효과

백철우 ( Chul Woo Baek ),노민선 ( Mean Sun Noh ) 한국생산성학회 2013 生産性論集 Vol.27 No.4

This study examines the contribution of firms` open innovation strategies to R&D efficiency at the firm level. R&D efficiency is measured by using Data Envelopment Analysis. Then Tobit regression identifies the effect of open innovation strategies - R&D outsourcing, external funding and introduction of foreign technologies - on R&D efficiency. Results imly that R&D outsourcing strategy is very effective to improve R&D efficiency and large-sized enterprises and low technology industries have larger effect than the others. On the other hand, external funding fails to improve R&D efficiency even though it contributes to expansion of R&D scale. Last, introduction of foreign technologies has negative effect to R&D efficiency in large-sized enterprises and low technology industries.