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이동기(Dong Kee Rhee),조영곤(Young Kon Cho) 한국경영학회 2001 經營學硏究 Vol.30 No.4
This paper examines the relationship between the ratio of outside directors in board composition and R&D spendings of firms in sample firms from U. S. R&D intensive industries. First, we find a positive relationship between the ratio of outside directors and R&D intensity, supporting that outside directorship can be a structural factor ensuring board independence. Second, we find that the relation-ship between the ratio of outside directors and R&D intensity is weaker in owner-controlled firms than in manager-controlled firms suggesting that the effectiveness of monitoring of outside directors are constrained due to information asymmetry arising from the entrepreneur mode of decision-making process in owner-controlled firms.
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.
근관형성 방법에 따른 근관변위와 잔존치질의 두께에 관한 연구
서병곤,조영곤 朝鮮大學校 口腔生物學硏究所 1991 口腔生物學硏究 Vol.15 No.-
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 curve mesial root canals of extracted human mandibular molars. Fourty - six clear polyesther blocks were made and randomly divided into two groups hand instrumentation group with D - Fles files and ultrasonic instrumentation group with Suprasson SP unit. All root canals were instrumented to a size corresponding to a #30 K - Flex file 1㎜ 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 stereomicroscope. 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 significant 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 both techmiques.