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질소분압에 따른 TaNx coating층의 미세조직 연구
김선화,최용락 순천향대학교 부설 산업기술연구소 1998 순천향 산업기술연구소논문집 Vol.3 No.3
TaNx film were fabricated for this research by the reactive magnetron sputtering process. In order to improve TCR, it was investigated the transformation of coated TaNx film. The variables were the N₂/Ar fraction and the thermal heat-treatment. The electrical resistance and the TCR of specimen were measured. It was observed the microstructure change under thermal heat-treatment by XRD experiment. Also the morphology of TaNx film was observed by SEM. As a result, TCR was stabilized when N₂/Ar fraction were 0.166 to 0.25. The phases of as-coated TaNx film were Ta, TaN, β-Ta and amorphous. The new phases, Ta₄N and Ta₃N?? were formed after thermal heat-treatment. As the ratio of nitrogen gas was increased, the morphology of the layer was changed to a discontinuous island particle. These results were consistent with results of electrical resistance change.
Improving Database System Performance by Applying NoSQL
( Yong Lak Choi ),( Woo Seong Jeon ),( Seok Hwan Yoon ) 한국정보처리학회 2014 Journal of information processing systems Vol.10 No.3
Internet accessibility has been growing due to the diffusion of smartphones in today``s society. Therefore, people can generate data anywhere and are confronted with the challenge that they should process a large amount of data. Since the appearance of relational database management system (RDBMS), most of the recent information systems are built by utilizing it. RDBMS uses foreign-keys to avoid data duplication. The transactions in the database use attributes, such as atomicity, consistency, isolation, durability (ACID), which ensures that data integrity and processing results are stably managed. The characteristic of RDBMS is that there is high data reliability. However, this results in performance degradation. Meanwhile, from among these information systems, some systems only require high-performance rather than high reliability. In this case, if we only consider performance, the use of NoSQL provides many advantages. It is possible to reduce the maintenance cost of the information system that continues to increase in the use of open source software based NoSQL. And has a huge advantage that is easy to use NoSQL. Therefore, in this study, we prove that the leverage of NoSQL will ensure high performance than RDBMS by applying NoSQL to database systems that implement RDBMS.
Evolution and Mechanical Effect of S`-Phase in ECA Pressed Al-3.8Cu-1.2Mg-0.5Mn Alloys
( Yong Lak Choi ),( Seon Hwa Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2008 METALS AND MATERIALS International Vol.14 No.6
The composition, morphology, and distribution of an Al-3.8Cu-1.2Mg-0.5Mn alloy precipitate formed during the ECAP process was investigated using XRD and TEM, and its mechanical properties were estimated via a SP test. A texture structure was formed at the initial state of the ECAP process, but an equiaxed structure was formed as the process progressed. The grain size was refined to around 100 nm through the ECAP process, and the morphology of the S` phase at the initial state is characterized by a rod shape in the grain boundary. As the number of passes increased, the S` phase assumed a spherical shape, with a diameter of 10 nm to 20 nm, and it was uniformly distributed in the internal grain boundary. Growth of the S` phase was also observed, and is thought to be due to Ostwald ripening. The results of the SP test show that the maximum load increased to above 60 %, indicating that changes in the size and distribution of the S` phase affect the alloy`s tensile strength.
Improving Database System Performance by Applying NoSQL
Choi, Yong-Lak,Jeon, Woo-Seong,Yoon, Seok-Hwan Korea Information Processing Society 2014 Journal of information processing systems Vol.10 No.3
Internet accessibility has been growing due to the diffusion of smartphones in today's society. Therefore, people can generate data anywhere and are confronted with the challenge that they should process a large amount of data. Since the appearance of relational database management system (RDBMS), most of the recent information systems are built by utilizing it. RDBMS uses foreign-keys to avoid data duplication. The transactions in the database use attributes, such as atomicity, consistency, isolation, durability (ACID), which ensures that data integrity and processing results are stably managed. The characteristic of RDBMS is that there is high data reliability. However, this results in performance degradation. Meanwhile, from among these information systems, some systems only require high-performance rather than high reliability. In this case, if we only consider performance, the use of NoSQL provides many advantages. It is possible to reduce the maintenance cost of the information system that continues to increase in the use of open source software based NoSQL. And has a huge advantage that is easy to use NoSQL. Therefore, in this study, we prove that the leverage of NoSQL will ensure high performance than RDBMS by applying NoSQL to database systems that implement RDBMS.
D.C. 마그네트론 스퍼터법으로 제조한 ITO 박막의 미세조직과 투명 전극 특성 변화에 관한 연구(1)
최용락 ( Yong Lak Choi ),김선화 ( Seon Hwa Kim ) 대한금속재료학회 ( 구 대한금속학회 ) 2006 대한금속·재료학회지 Vol.44 No.8
ITO thin films were deposited on corning 1737 glass using a D.C. magnetron sputtering. The morphology, the crystallinity and the electrical properties of ITO thin films were investigated by XRD, FESEM and 4 point probe system. The morphology of ITO particles changed from round island to polygonal shape as the O2 flow rate increased. In the first stage of the growth of ITO thin films, amorphous phase occurred. As O2 flow rate increased, ITO thin film grew to the crystalline with preferred orientation of (400) and (440). The sheet resistance of ITO thin films decreased to 9Ω/_ when the substrate temperature was 350℃. In this study, preferred orientation of (400) and coarse island particle of ITO thin films were critical factor.
산림경영의 3차 산업화를 위한 휴양림 이용자 추정모형 - 전라북도를 중심으로 -
최용락 ( Yong-lak Choi ),박희정 ( Hee-jung Park ),이상현 ( Sang-hyun Lee ) 전북대학교 농업과학기술연구소 2016 농업생명과학연구 Vol.47 No.1
The purpose of this study is to provide information for reasonable management of recreational forests in Jeollabuk-do by responding to the social needs for various functions of forest and to find ways of vitalizing and maximizing public values of forests. Annual visitors in the future were predicted using Gompertz marginal models based on the visitors statistics of recreational forests in Jeollabuk-do and its inter-temporal characteristics. As the result of this study, visitors were in constant rising tendency, expecting 624,028 visitors in 2015, 852,148 visitors in 2020 and 1,034,644 visitors in 2024. These result suggests that supported by increasing visitors, operation of various kinds of programs relating history, culture and education should be introduced. Also the goal of invigoration of forestry activities could be answered by solving the problem of small-sized ownership of private-owned forests through continuous management on recreational forests, tertiary industrialization of forest management, effective utilization of public values and positive governmental supports.
최용락(Yong-Lak Choi),서완석(Wan-Seok Seo),성형모(Hyung-Mo Sung),구본훈(Bon-Hoon Koo),김경근(Kyung-Keun Kim),김소연(So-Yeun Kim),최소정(So-Jeong Choi),이종훈(Jong-Hun Lee) 대한생물치료정신의학회 2009 생물치료정신의학 Vol.15 No.1
Objectives:This study was conducted to investigate various social and environmental factors related to children’s sleep and to know how these factors may affect sleep duration and patterns. Methods:Total 2,958 students of three elementary school in Daegu, Korea were enrolled in this study. We investigated various factors related to children’s sleep using Sleep questionnaires for Korean Children(SKC) for two days. The factors that we investigated were classified into sleep-related factors, daily life factors, environmental factors. We also evaluated correlations between these factors and children’s sleep duration. Results:When identifying various factors related to children’s sleep in three elementary school groups, group A showed significantly later bedtime(F=103.683, p<.001), longer sleep latency(F=6.30, p<.05), shorter total sleep duration(F=5.93, p<.05), and shorter nap duration(F=141.94, p<.001) compared to other group B and C. Also, group A showed significantly earlier time of returning home(F=71.073, p<.001), shorter amount of TV viewing (F=108.45, p<.001), earlier time of stopping TV viewing(F=24.01, p<.001), shorter amount of computer use(F=67.10, p<.001), earlier time of attending school(F=5.40, p<.05), longer hours in private institute(F=15.57, p<.001), smaller number of family(F=11.00, p<.001), longer father’s years of education(F=311.82, p<.001), and longer mother’s years of education(F=334.87, p<.001) compared to other two groups. Conclusion:Group A was associated with late bedtime, long sleep latency, short total sleep duration despite relatively short nap duration, short amount of TV viewing, short amount of computer use, early time of stopping TV viewing, small number of family, long mother’s years of education. This result suggests that total amount of hours in private institute and parents’ academic demands might be a contributing factor for children’s sleep duration.