구치부에서의 심미적 수복

조영곤 대한치과의사협회 1998 대한치과의사협회지 Vol.36 No.8

Foreign Investors' Block Acquisition, Purpose of Acquisition and Firm Value

조영곤,서민교,설원식 한국무역학회 2008 Journal of Korea trade Vol.12 No.3

This paper examines the announcement effect of block acquisitions of foreign investors on firm value and the differences in market responses by the type of the purpose of acquisition using the event study methodology. The results show that the disclosures of foreign investors' block acquisitions do not significantly influence market value of target firms in general. But, for the disclosure that the purpose of an acquisition is for influencing corporate policy, we find positive and significant CARs around the announcement date. On the other hand, CARs are not significant at all for disclosures in which the purpose of acquisition is for investment only. In addition, excess financial resources, ownership of existing outside blockholders, and firm size are found to influence on the choice of the purpose of acquisition announced at the disclosure whether foreign investors have the intention of influencing corporate policy or not.

근관형성 방법에 따른 근관변위와 잔존치질의 두께에 관한 연구

조영곤,서병곤 大韓齒科保存學會 1992 Restorative Dentistry & Endodontics Vol.17 No.2

The purpose of this study was to evaluate the root canal transportation and remaining dentin/ cementum thickness after using hand and ultrasonic instrumentation in the urved mesial root canals fo extracted human mandibular molars. Fourty-six clear polyether blocks were made and reandomly divided into two troups : hand instrumentation group with K-Flex files and ultrasonic instrumentation group with Suprasson SP unit. All root canals were instrumented to a size corresponding to a #30 K-Flex file 1mm short from the radiographic apex. The roots were then sectioned perpendicular to the long axis so the apical and middle third could be evaluated with the Zoom steremoicroscope. The results were as follows: 1. In the total amount of removed dentin at middle third level, there was not significant difference between the hand instrumentation and ultrasonic instrumentation (P>0.05). 2. In the total amount of removed dentin at apical third level, there was more removed by the ultrasonic instrumentation than hand instrumentation(P>0.005). 3. In the transportation width, there was not signficant difference between the two groups at both sectioned levels(P>0.05). 4. It was suggested that the canal was transported distally at middle third level and mesially at apical third level by booth techniques. The purpose of this study was to compare the effectiveness of hand instrumentation with K-file and ultrasonic instrumentation and irrigation system in removing pulpal debris and canal wall planing. 20 mandibular molar teeth were instrumented to size 30 K-file and 20 teeth were instrumented with ultrasonic Suprasson. And Nomal Saline and 2.5% NaOCl were used as irrigation solution. All specimens were viewed at the coronal, middle, and apical third of the root canals for the evaluation of the cleaning effect under the multiview microscope. The result were as follows ; 1. All of the technique and irrigation solution was efficient in the debris removal and canal wall planing at the cervical and middle thirds of the root canal. 2. All of the techniques and irrigation solutions was less efficient in the debris removal and canal planing at the apical third of the root canal. 3. The debris removal and canal wall planing was depended more on the anatomical variations of the root canal than on the techniques and irrigation solutions.

국제합작투자의 소유구조와 경영통제 및 협력관계의 질에 관한 연구

조영곤 한국국제경영관리학회 2006 국제경영리뷰 Vol.10 No.3

본 연구에서는 국제합작투자의 소유구조와 경영통제 및 협력관계의 질을 중국에 투자한 한ㆍ중 합작투자기업을 대상으로 실증분석 하였다. 실증분석 결과 소유구조는 전반적 경영통제 수준과 정(+)의 상관관계를 가지나 선택적 통제와는 유의적인 관계를 가지지 않았다. 또한 균등지분구조는 비균등지분구조에 비해 절차적 공정성이 높은 것으로 나타났다. 이러한 실증결과는 소유지분은 합작투자의 경영통제와 협력관계의 질에 영향을 미칠 수 있는 구조적 요인이 될 수 있음을 시사하고 있다. This study empirically investigates the relationships among ownership, control and quality of cooperative relationship in international joint venture in China. The results show that ownership has an positive effect on overall control while it does not have a significant effect on selective control. the degree of procedural justice is found to be higher in shared controlled firms than dominant controlled ones. These imply that ownership can be a structural factor, which has a relation with the performance of international joint venture.

복합레진 수복물의 변연 미세누출에 관한 Biscover™ 전색제의 효과

조영곤,,최희영 大韓齒科保存學會 2005 Restorative Dentistry & Endodontics Vol.30 No.5

본 연구는 복합레진을 광조사하기 전과 광조사한 후에 표면 전색제인 Biscover를 적용하여 이들에 대한 변연 미세누출을 평가하고, 또한 표면 전색제를 적용하지 않는 복합레진 수복물과의 미세누출 차이를 비교하기 위하여 시행하였다. 30개의 발거된 대구치의 협면 치경부에 5급 와동을 형성하여 다음과 같이 3개의 군으로 분류하였다; 대조군은 복합레진 표면에 Biscover를 적용하지 않은 군, 1군은 복합레진을 광조사하고 마무리한 후 Biscover를 적용한 군, 2군은 복합레진을 광조사하지 않고 Biscover를 적용한 군. 각 군의 시편은 실온의 증류수에 48시간 동안 보관한 후 5℃와 55℃에서 1,000회의 열 순환을 시행하고 2% methylene blue 용액에 4시간 동안 침적시켰다. 20배율의 광학 입체현미경 하에서 각 군의 교합면측과 치은측 변연의 색소 침투 정도를 관찰하여 미세누출 점수를 얻은 후, 각 군 간의 유의성을 검정하여 다음과 같은 결과를 얻었다. 1. 2군은 1군보다 교합면측과 치은측 변연 모두에서 높은 미세누출을 보였으나 통계학적으로 유의한 차이는 없었다 (p > 0.05). 2. 대조군은 교합면측 변연에서 1군과 2군보다 약간 높은 미세누출을 보였으며, 치은측 변연에서 1군보다 약간 높게 그리고 2군과 비슷한 미세누출을 보였다. (p>0.05). 3. 대조군과 2군은 교합면측 보다 치은측 변연에서 통계학적으로 높은 미세누출을 보였으며 (p<0.05). 1군은 교합면측과 치은측의 변연 미세누출 간에 통계학적인 차이를 나타내지 않았다 (p>0.05). 본 연구를 종합하면, Biscover는 중합된 복합레진 표면에 적용할 경우 치은측 변연의 미세누출을 감소시키는데 효과적이었다. The purpose of this study was to compare the effect on marginal leakage of a resin surface sealant (Biscover) applied before or after polymerization of composite resin to unsealed composite restorations. Thirty Class V cavities with the occlusal margin in enamel and cervical margin in dentin or cementum were prepared on the buccal surfaces of sound extracted molars and restored with a microfilled light-cured composite resin (Micronew) . Restorations were randomly assigned into one of three equal groups (n = 10): a control group - no surface sealing, group 1 - applied Biscover after polymerization of the composite resin, and group 2 - applied Biscover before polymerization of the composite resin. Specimens were thermocycled, immersed in a 2% methylene blue solution for 4 hours, sectioned longitudinally, and analyzed for leakage at the occlusal and gingival margins. The results of this study were as follows; 1. In sealed group, group 2 showed higher microleakage than group 1 at both occlusal and gingival margins, but there was no significant difference between two groups (p > 0. 05). 2. Unsealed control group showed a little higher microleakage than sealed group at occlusal marglns, and a little higher or similar microleakage than sealed group at gingival margins (p > 0. 05). 3. Control group and group 2 showed significantly less microleakage at the occlusal margins, but group 1 showed no significantly difference between microleakage at the occlusal and gingival margins.

국제합작투자의 파트너간 문화적 거리 지분구조가 경영성과에 미치는 영향

조영곤 한국국제경영관리학회 2004 국제경영리뷰 Vol.8 No.2

ONE-STEP 접착제의 상아질 접착에 관한 연구

조영곤,박성택,박광수 大韓齒科保存學會 1998 Restorative Dentistry & Endodontics Vol.23 No.1

The purpose of this study was to oberve the morphologic change of dentinal surface. adhesion in interface between dentin and bonding agents, and penetration pattern of resin tags into dentinal tubles according to bonding procedure of ONE-STEP universal adhesive system. Ten extracted human molars were mounted in dental stone and sectioned to expose midcoronal occlusal dentin and again sectioned tooth drown apically. Specimens were randomly assigned to three groups for dentin conditiong with 32% phoshoric acid. two coats of bonding agents after dentin conditioning, and bond of composite resin. The surface of dentin were treated with etchant and applied bonding agent, and bonded composite resin according to the directions of manufactruer. Specimens which were boned composite were sectioned longitudinally for observing interfaces between in 6 N HCL for 30 second and 1% NaOCL for 12 hours to partially demineralize and deproteinize the dentin substrate. Each specimen was mounted on a brass stub, sputter-coated with gold and observed under SEM. The result were as follows : 1. On the dentinal surface which was conditional with 32% phosphoric acid, the smear layer was completely removed, orifices of dentinal tubules were opened 3-5㎛ wide, and dentinal surface was irregular. 2. On the dentinal surface which was applied ONE-STEP bonding agent, resin particles were observed on the orifices of dentinal tubules and intertubular dentin. 3. There were close adaptation between dentin and resin and were the pattern which composite invaded into dentin. 4. 1-3㎛ wide hybrid layer was visible in the interface between dentin and resin. 5. Long and funnel shaped resin tags were observed in demineralized specimens, and the surfaces of tags were rough.

외국인 주주와 연구개발투자: 중국 상장기업을 대상으로

조영곤 한국국제경영관리학회 2016 국제경영리뷰 Vol.20 No.4

본 연구는 중국 상장기업에서 외국인 투자자가 연구개발투자에 미치는 영향을 규명하기 위해 2009년부터 2014년까지 중국 증권거래소(상해 또는 심천)에 상장되어 있는 371개 기업의 5년간 패널자료를 이용하여 GMM 추정 방식의 동적 패널분석을 실시하였다. 실증분석의 주요 결과는 다음과 같다. 첫째, 중국 국내 상장 외국인 지분율은 연구개발투자(연구개발투자/매출액, 연구개발투자/종업원 수)에 정(+)의 유의미한 영향을 미치는 것으로 나타났다. 그러나 외국인 지분율과 기업의 성장잠재력의 교차 분석에서는 추가적으로 유의적인 관계는 존재하지 않았다. 본 결과는 중국 국내 상장 외국인 투자자는 지분 보유 기업을 대상으로 적극적인 감시 활동을 전개하여 연구개발투자를 촉진하도록 영향을 미치고 있음을 시사하고 있다. 둘째, 해외 상장 외국인 지분율은 연구개발투자에 직접적인 영향을 미치지 않는 것으로 나타났다. 그러나 해외 상장 외국인 지분율과 기업의 성장잠재력 간의 교차 분석에서는 양자 간에 정(+)의 유의적인 관계가 확인되었다. 본 결과는 해외 상장 외국인 투자자는 성장잠재력이 높은 기업을 대상으로 적극적인 감시 활동을 전개하여 연구개발투자를 촉진하도록 영향을 미치고 있음을 시사하고 있다. 전체적으로 본 실증 결과는 외국인 투자자의 유형과 연구개발투 자의 측정 방법에 따라 실증결과가 일부 상이하지만 중국 상장기업에서 외국인 투자자는 지분 투자 기업을 대상으로 경영 감시 활동을 전개하여 연구개발투자를 촉진하도록 직, 간접적인 영향을 미치고 있음을 지지하고 있다. The paper aims to explore the relationship between foreign ownership and firms' R&D investment in Chinese listed firms. Using five-year longitudinal data of 371 firms during the period of 2009-2013, this study finds that when foreign ownership in domestic listed stocks of firms have positive effects on firms' R&D investment in terms of R&D expenditure over firms sales as well as R&D expenditure per employee, suggesting that foreign shareholders exercise active monitoring roles in targed firms, by exerting pressure on them to increase the amount of risky investment. On the other hand foreign ownership do not have moderating effects on firms' R&D investment with respect to their growth potential. The study also finds that foreign ownership in oversea listed stocks of firms do not have significant effects on firms' R&D investment. On the other hand foreign ownership have positive moderating effects on R&D investment of firms which have high growth potential, suggesting that foreign shareholders exert active monitoring roles in targed firms, demanding them, which are in high need of investment in risky projects due to their high growth potential, to increase the amount of risky investment to capture them. Though the relations between foreign ownership and firms' R&D investment is slightly different according to its measurements, the results, in general, support that foreign shareholders exercise active monitoring roles in Chinese listed firms, demanding them to increase the amount of R&D investment directly or indirectly, which contribute to the mitigation of agency problem between managers and shareholders on the decision of risky projects in Chinese listed firms.

상아질에 대한 단일 단계 접착제의 미세인장 결합강도

조영곤,기영재 大韓齒科保存學會 2005 Restorative Dentistry & Endodontics Vol.30 No.4

본 연구는 상아질에 대한 3종의 단일 단계 접착제의 미세인장 결합강도를 상호 비교하였다. 15개의 발거된 상·하악 대구치의 교하면측에 있는 표충 상아질을 노출시킨 후, 사용된 접착제에 따라 3개의 군 (Xeno 군-Xeno Ⅲ, Prompt군-Adper Prompt L-Pop, AQ군-AQ Bond)으로 분류하여 복합레진을 축조하였다. 각 시편을 막대모양으로 제작하였고, 각 군 당 20개의 시편을 이용하여 미세인장 결합강도를 측정하여 다음과 같은 곁과를 얻었다. 1. 상아질에 대한 각 관의 미세인장 결합강도는 Xeno 군에서 48.78±9.83 ㎫, Prompt 군에서 30.22±4.52 ㎫, AQ군에서 26.31±7.07 ㎫로 나타났다. 2. Xeno 군은 Prompt 군과 AQ 군보다 통계학적으로 높은 미세인장 결합강도를 나타냈다 (p<0.05). 3. Prompt 군과 AQ 군의 미세인장 결합강도 간에는 통계학적으로 유의차가 없었다 (p>0.05). This study compared the microtensile bond strength (μTBS) of three single step adhesives to dentin. Occlusal superficial dentin was exposed in fifteen human molars. They were assigned to three groups by used adhesives: Xeno group (Xeno Ⅲ), Prompt group (Adper Prompt L-Pop), AQ group (AQ Bond). Each adhesive was applied to dentin surface, and composite of same manufacturer was constructed. The bonded specimens were sectioned into sticks with an interface area approximately 1 ㎟, and subjected to μTBS testing with a crosshead speed of 1 mm/minute. The results of this study were as follows: 1. The μTBS to dentin was 48.78±9.83 ㎫ for Xeno Ⅲ, 30.22±4.52 ㎫ for Adper Prompt L-Pop, and 26.31±7.07 ㎫ for AQ Bond. 2. The mean μTBS of Xeno group was significantly higher than that of Prompt group and AQ group (p<0.05), 3. There was no significant difference between the μTBS of Prompt group and AQ group.[J kor Acad Cons Dent 30(4):312-315,2005]

복합레진 laminate veneer

조영곤 대한치과의사협회 1997 대한치과의사협회지 Vol.35 No.5