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지르코니아-유리복합체용 글래스의 조성에서 MgO의 함량 변화가 강도에 미치는 영향
이규선,이창완,이채현,Lee, Kyu-Sun,Lee, Chang-Wan,Lee, Chae-Hyun 대한치과기공학회 2007 대한치과기공학회지 Vol.29 No.1
The quantity of MgO in the Zirconia of 20wt% Frit has been varied and the sintering temperature has been differentiated to monitor the changes in the mechanical features. The rise of sintering temperature from 1100$^{\circ}C$ to 1300$^{\circ}C$ was followed by higher sintering density. And, at a sintering temperature, the increase of the quantity of MgO was followed by lower sintering density. The bending strength has been lowered as the quantity of MgO increases in the Zirconia of 20wt% Frit, which seems to be because the MgO functions as impurities degrading the mechanical features. In terms of micro-structure analysis, the pore has been greatly enlarged, while the density varied very little, when the MgO of 3wt% was added. The size of pore became smaller as the added quantity of MgO increased larger in the sequence of 5wt% and 7wt%. But, the pore-generating rate became higher as the added quantity of MgO increased in the sequence of 3wt%, 5wt% and 7wt%. Thus, it is possible to summarize that the small quantity of MgO, say, of 3wt%, promotes the grain growth, and the large quantity of MgO, say, of 7wt%, hinders the grain growth. Also, if the quantity of MgO exceeds some level, the MgO hinders substances from moving, which, ultimately, keeps blowholes from becoming enlarged or extinct, and makes pores small and dispersed in broad area. In conclusion, the study on the change in the size of pore shows that the larger the quantity of MgO is, the more the micro pores are, thereby degrading the mechanical features.
이규선(Lee Kyu-Sun),박희성(Park Hee-Sung) 대한토목학회 2011 대한토목학회논문집 D Vol.31 No.3D
공정관리의 원활한 수행은 프로젝트의 성패와 직접적인 관계를 가지고 있다. 이에 최근에 효율적인 공정관리업무를 수행을 위해 새로운 공정관리기술의 도입에 대한 필요성이 제기되고 있다. 따라서 본 연구는 도로건설 현장의 공정관리 업무 및 활용기법의 현황을 조사 · 분석하여 문제점 및 린 건설이론의 현장 적용정도를 파악하였다. 그리고 공정관리 측면에서 린 건설 도입방안을 도출함으로써 도로 현장의 효율적인 공정관리를 위한 개선방안을 제시하였다. 이는 현장에서 효율적인 공정계획을 수립하는데 도움이 될 것이며 추후 현장 현황을 고려한 공정관리 시스템 개발을 위한 기초연구로 유용할 것으로 사료된다. 또한 이러한 개선방안 및 도입방안을 현장에 적용하여 성과를 분석하는 연구가 추후에 수행되어져야 할 것으로 기대한다. There is a relationship between effective time management and project success. Therefore, advanced time management techniques have recently been introduced. This paper investigates the current time management practices for road construction sites and proposes lean construction practices to effectively implement time management. This would be helpful to establish an effective schedule plan. Also, an efficient construction site time management system can be developed base on this fundamental research. Furthermore, future research should be performed to investigate the performance of lean construction.
소규모 제조업 남성 근로자의 수면의 질, 직무 스트레스 및 피로가 우울수준에 미치는 영향
이규선(Lee, Kyu-Sun),강정숙(Kang, Jeong-Suk),권인선(Kwon, In-Sun),조영채(Cho, Young-Chae) 한국산학기술학회 2011 한국산학기술학회논문지 Vol.12 No.5
본 연구는 소규모 제조업 사업장 남성 근로자들의 수면의 질, 직무스트레스 및 피로가 우울수준 에 미치는 영향을 규명하고자 50인 미만의 소규모 제조업 사업장에 종사하고 있는 남성 근로자 856명을 대상으로 2010년 4월1 일부터 6월 30일까지의 기간 동안에 자기기입식 설문조사(self-administrated questionnaire)를 실시하였다. 연구결과 조 사대상자의 우울군(CES-D 21점 이상)의 분포는 44.3%를 차지하였으며, 우울수준은 직무스트레스(r=0.538, p<0.01), 피 로(r=0.533, p<0.01) 및 수면의 질(r=-0.399, p<0.01)과 유의한 양의 상관관계를 보였다. 공분산 구조분석 결과 직무스 트레스는 수면의 질이나 피로수준보다 우울수준에 더 큰 영향을 미쳤으며, 직무스트레스 및 피로수준이 증가할수록, 수면의 질이 낮을수록 우울수준을 증가시키는 효과가 있는 것으로 나타났다. 따라서 근로자들의 우울수준을 감소시키 기 위해서는 작업환경 및 직무내용의 개선을 위한 노력이 필요할 것으로 생각된다. This study was performed to determine the depression and its association with sleep quality, occupational stress and fatigue among small-scale manufacturing male workers. The self-administered questionnaires were given to 856 workers under 50 members of manufacturing industries during the period from April 1st to June 30th, 2010. As a results, the distribution of depression group(21 point and over at CES-D score) among all subjects were 44.3%, and it was positively correlated with occupational stress, fatigue and quality of sleep. With the analysis of covariance structure, occupational stress(KOSS) was more influential on the depression than quality of sleep and fatigue. It was found to have the inter-relational effects that the higher the occupational stress(KOSS) and fatigue(MFS), and the lower the quality of sleep, the higher the depression. Thus the effective strategy for depression reduction among workers requires the efforts to improve the work environment and job contents.
반구형 전극계에서 뇌임펄스전압에 의한 토양의 종류별 이온화 특성
李圭善(Kyu-Sun Lee),朴建勳(Geon-Hun Park),金會九(Hoe-Gu Kim),李福熙(Bok-Hee Lee) 대한전기학회 2009 전기학회논문지 Vol.58 No.1
This paper deals with the characteristics of soil ionization affecting the dynamic performance of grounding systems under lightning impulse voltage. A concentric hemispherical electrode system was employed in order to facilitate the field calculation and analysis of the experimental results. The parameters such as the ionization threshold and breakdown field intensity, the pre-ionization and the post-ionization resistances, the time-lag to ionization, the transient impedance, the equivalent ionized radius for various soil media were measured and analyzed. The dynamic characteristics of ionization processes under lightning impulse voltage are strongly dependent on the types of soil and water content. As a result, a soil ionization reduces the ground resistance and there is a little effect of applied impulse polarity on the soil ionization threshold field intensity. Although the ionization threshold field intensity of wet clay with 30 % water content is the highest, its ionized zone was found to be the smallest amongst the test samples.