• The Journal of Korean Academy of Prosthodontics
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• v.39 no.3
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• pp.260-272
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• 2001

All-ceramic restorations have had a more limited life expectancy than metal ceramic restorations because of their low strength. Their relatively lower strength and resistance to fracture have restricted the use of all-ceramic crowns to anterior applications where occlusal loads are lower. But there has been increasing interest in all-ceramic restorations because patients are primarily concerned with improved esthetics. Many efforts have been made to in prove the mechanical properties of dental ceramics. This study was designed to elucidate the influence of the luting agent on the strength of the Empress 2 crown (staining technique) cemented on human teeth. Seventy extracted human permanent molar teeth were chosen. Teeth were prepared for Empress 2 crowns with milling machine on a surveyor. A dental bur was placed in the mandrel that was positioned so that the long axis of the bur was perpendicular to the surveyor base. Dimensions of the Empress 2 crown preparation were $6^{\circ}$ taper on each side, $1.5{\pm}0.1mm$ shoulder margin, and 4mm crown height. The luting cements used in this study were as follow: 1. Uncemented 2. Zinc phosphate cements (Confi-Dental) 3. Conventional glass ionomer cement : Fuji 1 (GC) 4. Resin-modified glass ionomer cements : Fuji plus (GC) 5. Adhesive cements : Panavia F (Kuralay), Variolink II (Vivadent), Choice (Bisco). Fracture test using Instron. The crowns were loaded in compressive force to evaluate the effect of these cements on the breaking strength of these all-ceramic crowns. A steel ball with a diameter of 4mm was placed on the occlusal surface and load was applied to the steel ball by a cylindrical bolt with a crosshead speed of 0.5mm per minute until fracture occurred. The fractured surface was examined using Scanning Electron Microscopic Image (SEM) to discover the correlation between fracture strength and bonding capacity. Within the limitation of this in vitro study design, the results were as follows : 1. fomentations significantly increased the fracture resistance of Empress ceramic crowns compared to control. Uncemented (206.9 N): ZPC (812.9 N): Fuji 1 (879.5 N): Fuji Plus (937.7 N): Choice (1105.4 N): Variolink II (1221.1 N): Panavia F (1445.2 N). 2. Resin luting agent, treated by a silane bond enhancing agents, yielded a significant increase in fracture resistance. In some of the Panavia F group, a fracture extended into dentin. 3. According to SEM images of fractured Empress crowns, the stronger the bond at both interfaces(crown and die), the more fracture strength was acquired.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.27 no.4
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• pp.269-282
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• 2017

Objectives: Currently, masks against yellow dust and fine particulates are being certified with no consideration of facial dimensional variations among children and adults. The aims of this study were to develop masks against yellow dust and fine particulates for children in Korea and provide basic data to suggest new test methods for mask certification that consider the breathing capacity of children. Methods: A total of 730 study participants aged from six to 13 years old were recruited in the Seoul, Gyeonggi, and Incheon region. This study used a 3D scanning instrument to obtain 16 facial anthropometric data points. Literature reviews, a comparison of breathing capacity between adults and children, and analysis of children's pulmonary physiological data were conducted in order to suggest new test standards for certifying children's masks against yellow dust and fine particulates. In addition, types of children's masks, choice of wearing a mask or not, and reasons for not wearing masks were surveyed. Results: Based on a clustering analysis of participants' facial dimensions, facial shapes were classified into three groups: small, medium, and large. The sizes of children's masks were subtracted by using 3D sketch techniques(Large: $121.25mm{\times}89.46mm$, Medium: $111.92mm{\times}78.55mm$, Small: $102.13mm{\times}72.87mm$). In certifying children's mask, flow rates of $60{\ell}/m$ for the filtering efficiency test and $20{\ell}/m$ for the breathing resistance test were recommended, since children's pulmonary physiological capacity is about 60-70% of adults' pulmonary capacity. Conclusions: The results of this study suggest that three mask sizes for children would be sufficient and practical for providing protection against yellow dust and fine particulates. Revising current test methods for certifying respiratory protective devices for children is important, since children's pulmonary physiological capacity substantially differs from that of adults. Therefore, it is recommended that new test standards for certifying children's masks be promulgated in the near future.

• Korean Journal of Childcare and Education
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• v.10 no.2
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• pp.319-335
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• 2014

The purpose of this study was to examine the effects of variables of interest on mothers' choices of infant care. The variables of interest in this study were categorized into the following three areas: 1) demographic characteristics of mothers and infants, 2) structural and procedual dimensions of infant care facilities, and 3) maternal beliefs on child-rearing. The subjects of this study were mothers whose infants were currently cared by at infant care facilities(n=185) and those who were on the waiting list to use non-maternal infant care(n=53). The main results of this study were as follows. First, mothers of this study preferred to select a type of center-based subsidized infant care over other types of care(family day care) due to quality of the program. Second, the mothers who were not using infant care and cared for their infants at homes reported that there were limitations in their choices of types of infant care due to accessibility and availability of public subsidized infant care facilities, and their child rearing goals were more likely to emphasize learning achievement and maturity than character education or personality. The mothers were more likely to choose a family home care over center-based public subsidized care when they were employed, had younger infants, had longer period of time on waiting lists, and emphasized structural dimensions of infant care than center-based care users. Implications for research and practices were discussed along with the main results of this study.

• Korean journal of food and cookery science
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• v.27 no.6
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• pp.825-838
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• 2011

The main purposes of this study were to assess coffee shop use and to identify the influence of physical environment of a coffee chop on customer behavioral intention. The survey was administered from April to May 2011, targeting twenties college students in Seoul, Gyeonggi Province. A total of 174 copies of the questionnaire were collected for the data analyses such as frequency test, descriptive analysis, chi-square analysis, reliability test, factor analysis, ANOVA, Duncan's multiple range test and multiple regression analysis using SPSS 17.0 program. The main results of this study were as follows: The number of visits was once or twice a week. Students went with their friends to the coffee shop. Most of the students answered that they visit the coffee shop at any time. The main purpose of visit was to have time to relax. The main source in choosing a coffee shop was recommendation from others. The main criterion for the selection of the coffee shop was atmosphere. Americano was a favorite drink. Coffee was drunk with a cake. Expenditure per visit was 3,000~5,000 won. The choice of the coffee shop was selected by the student. The factor analysis identified seven underlying dimensions of coffee shop physical environment perceptions (seating comfort, attractiveness, cleanliness, harmony, ambient condition, congestion, amenity) and one dimension of customer behavioral intention. Through multiple regression analyses, four determinants (attractiveness, cleanliness, amenity, ambient condition) were found to have the greatest impact on customer behavioral intention.

• Journal of the Economic Geographical Society of Korea
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• v.19 no.1
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• pp.122-142
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• 2016

This paper examines the implications of North Korea's Special Economic Zone (SEZ) strategy since the early 1990s in terms of the shifts in both North Korea's economic system and geopolitical order on the Korean peninsula. Specifically, it analyzes the shifts in North Korea's SEZ policy in three different aspects-North Korea's unique territorial logic, stress on decentralization, and comparison with Chinese reform and opening-up. Based upon this analysis, this paper criticizes a linear approach to understand North Korea's economic transformation from isolation to opening-up, and explores the dynamics of North Korea SEZ strategy in various dimensions. It contends that North Korea's SEZ strategy is neither an inevitable choice from economic difficulty nor an adoption of Chinese model of reform and opening up. Rather this paper focuses on the geopolitical logic and local development imperatives underlying SEZ strategy.

• Journal of the Korea Convergence Society
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• v.11 no.6
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• pp.269-279
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• 2020

The leader has an indispensable role in the enterprise. This article takes transformational leadership as the research object and introduces job satisfaction and job performance as variables. It is aimed to explore the impact of various dimensions of transformational leadership on employee performance and satisfaction, and to try to find the acting mechanism of the effect of transformational leadership on employee performance. The study used a questionnaire survey method and SPSS23.0 for statistical analysis. Through the analysis of 378 questionnaire surveys, it was found that the four constituent variables of transformational leadership would have different degrees of influence on job performance and satisfaction. Enterprise leaders should put emphasis on the choice of leadership style and pay special attention to the work attitude of employees. This study provides useful enlightenment for companies to carry out human resource management work. However, this study did not verify whether job satisfaction has an intermediary role in between transformational leadership and job performance, which is also an area that needs to be further studied in the future.

• Journal of Korea Multimedia Society
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• v.16 no.11
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• pp.1288-1296
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• 2013

The prominent line at the singe image is the important fact for understanding spatial structure or estimating aesthetic scoring. According to this thesis, the abstraction of the background line helps analyzing vanishing point, reconstitution of 3 dimensions, and determining of image sloppiness. It also makes easy to calculate the rule of thirds. This thesis is composed of section hough transform mapping, prioritizing of the prominent line, and selection of the prominent line. These technologies are departmentalized to be applied abstraction of traffic lane, analyzing of building structure, abstraction of vanishing point, and abstraction of straight line documentation. This gives the choice that users are able to compose technology by considering characteristic of objects and luminous environment. This thesis also can be applied to abstract circle. The interval hough transform is able to select the number of prominent line which users want to abstract. It can analyze important prominent line numbers at the image and then abstract the lines, too. Results of prominent lines by experiments would be show at this thesis.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1141-1146
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• 2004

The antenna array for receiving satellite broadcasting of Koreasat III is proposed. A cavity-backed slot antenna array is proposed to reduce feed line loss, increase the radiation efficiency, and make the feed network simple. A sub-array consists of $2{\times}4$ slot elements backed by a single cavity. By proper choice of dimensions it is shown that the proposed antenna has characteristics of the high radiation efficiency and the broad frequency bandwidth. Antenna characteristics for the array antenna with 256 elements are measured in Ku-band. A single cavity backed-sub-array has the gain of 18 dEi. The gam of the total antenna array(256 elements) is Over 33 dEi.

• The Mathematical Education
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• v.59 no.3
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• pp.237-254
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• 2020

The current study investigated the relationships between mathematical knowledge for teaching and the mathematical quality in instruction in order to gain insight about teacher education for secondary teachers in South Korea. We collected and analyzed twelve high school teachers' scores of the multiple-choice assessment for mathematical knowledge for teaching developed by the Measures of Effective Teaching project. Their instruction was video recorded and analyzed with the mathematical quality in instruction developed by the Learning Mathematics for Teaching project. We also interviewed the teachers about how they planned and assessed their instruction by themselves in order to gain information about their intention and interpretation about instruction. There was a statistically significant and positive association between the levels of mathematical knowledge for teaching and the mathematical quality in instruction. Among three dimensions of the mathematical quality in instruction, mathematical richness seemed most relevant to mathematical knowledge for teaching because subject matter knowledge plays an important role in mathematical knowledge for teaching. Furthermore, working with students and mathematics as well as students participation were critical to decide the quality of instruction. Based on these findings, the current study discussed offering opportunities to learn mathematical knowledge for teaching and philosophy about how teachers need to consider students in high schools particularly in terms of constructivism.

• Lingua Humanitatis
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• v.2 no.1
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• pp.7-42
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• 2002

This paper reexamines ideas about linguistic relativity in the light of new interest in the theoretical climate. The original idea is based on the incommensurability of the semantic structures of different languages. On this view, language, thought, culture are deeply interconnected, so that each language might be associated with it a distinctive world view. Throughout this work I utilize the historico-epistemological standpoint to dissect the conceptual structure of this principle. In the introduction I will of for a justification of choice of the theme. Section 1 will address some essential definition of the linguistic principle and insist on the necessity to elaborate a typological spectrum of relativism and universalism. In the second section some important landmarks of linguistic relativity were marked from Plato to Humboldt via Condillac and Herder. 1 will subdivide the relativity hypothesis into 3 theses which are interlated. In the final section the epistemological structure of the linguistic principle will be analysed in some detail by providing my exposition of Sapir-Whorf hypothesis. By way of conclusion I will present the works of Wierzbicka who demonstrated the lexicons of different languages suggest different conceptual universes. By rejecting analytical tools derived from the English language she proposed instead a natural semantic metalanguage based on lexical universals, which is made up of universal semantic primitives. In this paper we attempted to construct a general problematics of linguistic relativity, focolizing on the Sapir-Whorf hypothesis. We devided this very problematic question into its ontological and epistemological dimensions. In particular the ambivalance of Whorf's relativity is discussed in some detail. Also, an archeological survey of this subtle question on the relation between language, thinking and culture was provided. (from Aristotle to Humboldt, via Condillac and Nitzche). In conclusion this investigation underlines the necessity of preparing the cultural linguistics to enlarge the scope of contempory linguistics.