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과산화수소 , 무수피로인산나트륨 및 불화나트륨을 배합한 특수세치제의 치아미백효과에 관한 실용실험연구
정세환,배광학,이원재,문혁수,백대일,김종배 대한구강보건학회 2001 大韓口腔保健學會誌 Vol.25 No.2
The purpose of this study was to evaluate the effects of therapeutic toothpaste containing tetrasodium pyrophosphate, vitamin-E and hydrogen peroxide on the whitening. 55 adult male and female subjects aged 20 to 29 year-olds completed 2-week, double-blind clinical study. Subjects were divided by two balanced groups according to baseline tooth brightness. Trubyte Bioform shade guide was used to score the tooth brightness. There was statistical significance of the brightness changes between the therapeutic toothpaste and the control toothpaste after 2 weeks(P<0.05). This result suggest that therapeutic toothpaste containing tetrasodium pyrophosphate, vitamin-E, and hydrogen peroxide be effective on improving tooth whitening.
비형식교육기관의 환경교육 프로그램의 개발 및 적용(무인도를 이용한 체험활동 프로그램 사례)
정세환,박영신 대한지구과학교육학회 2015 대한지구과학교육학회지 Vol.8 No.3
The ultimate goal of environment education plays an important role in forming knowledge, skill, attitude and a point of value along with sustainable development in the regions. Recently, however, environment education is comparatively despised due to college-entrance-exam-focused education policy. Ironically, environment education is more actively implemented at informal institutes rather than formal ones. Environment education at schools is based on the school curriculum, but at informal educational institutes enjoy much more freedom in choosing learners, places and programs. Among them, the place is one of the most important factors of environment education. Therefore, in order to maximize the goal of environment education in this study, a specified program was developed and applied to a certain place to investigate its features and effects. Also the program was checked if it reflexes the environment education goal by using environment education program analysis frame. The results are as follows; according to the analysis of the program, the program was most effective for the two goals of offering hands-on experience and presenting motivations. The second most effective result of the program lied in the goal of knowledge, functions, value and attitude. And the teachers who used this program concluded that, when the program was applied to unmanned islands, offered stronger motivation due to their natural surroundings. Furthermore, direct experience is recommended because it can give us better conditions to collect data and to enhance interpretation ability.
Reverse Bending을 통한 CTOD 시험 예비균열 형상균일화에 관한 연구
정세환,박동환,김현수,신상범,박태종,Jeong, Sehwan,Park, Dong-Hwan,Kim, Hyeon-Su,Shin, Sang-Beom,Park, Tae-Jong 대한용접접합학회 2015 대한용접·접합학회지 Vol.33 No.2
This study investigates the appropriate range of reverse bending load for the CTOD test of thick weld by observing improvement of pre-crack shape and determination of the limit applicable load. In order to do it, the effect of the amount of the reverse bending load on the maximum deviation of the pre-crack length was investigated by the extensive tests, and the variation of plastic zone size in way of the crack tip under reverse bending load were evaluated by FEA. With the results obtained by the experiments and FEA, the proper range of reverse bending load was suggested. The effectiveness of the reverse bending method was verified by examining the pre-crack straightness after CTOD tests of thick weld specimens with various thickness and strength.