• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1013-1019
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• 2007

Electronic wastes have increased tremendously. However, any reliable treatment methodologies have rarely been established. Electronic wastes have posed serious disposal problem due to their physico-chemical stability. This paper investigated the application possibility of pyrolysis for the purpose of recycling the p-CCL(phenol based Copper Clad Laminate). Thermogravimetric analysis(TGA) was used to investigate the thermal decomposition pattern of p-CCL. We elucidated the characteristics of pyrolysis by-products at operating temperatures of 280, 350 and $600^{\circ}C$. GC/MS and FT-IR were used to characterize the liquid by-products along with general characterization methods such as Ultimate Analysis, Proximate Analysis and Heating Value, whereas general characterization methods were only introduced for the solid by-products. At a heating rate of $5^{\circ}C$/min, TGA curves exhibited three decomposition stages: (1) low-temperature decomposition region$(<280^{\circ}C)$, (2) medium temperature region$(280\sim350^{\circ}C)$ and (3) high-temperature region$(>350^{\circ}C)$. The major compounds of liquid by-products at low- and medium-temperatures were accounted for by water and phenol, whereas branched phenols and furans were major compounds at high-temperatures. As the temperature increases, volatile quantities decreased but the fixed carbon increased. High heating values of solid by-products($7,400\sim7,600$ kcal/kg) would suggest that the solid by-products could be applicable as fuel. In addition, high fixed carbon but low ash content of the solid by-products offered an implication that they are capable of being upgradable for adsorbent after applying appropriate activating process.

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.4
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• pp.506-521
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• 2007

Statement of problem: The cumulative success rate of wide implant is still controversial. Some previous reports have shown high success rate, and some other reports shown high failure rate. Purpose: The aim of this study was to analyze, and compare the biomechanics in wide implant system embeded in different width of crestal bone under different occlusal forces by finite element approach. Material and methods: Three-dimensional finite element models were created based on tracing of CT image of second premolar section of mandible with one implant embedded. One standard model (6mm-crestal bone width, 4.0mm implant diameter central position) was created. Varied crestal dimension(4, 6, 8 mm), different diameter of implants(3.3, 4.0, 5.5, 6.0mm), and buccal position implant models were generated. A 100-N vertical(L1) and 30 degree oblique load from lingual(L2) and buccal(L3) direction were applied to the occlusal surface of the crown. The analysis was performed for each load by means of the ANSYS V.9.0 program. Conclusion: 1. In all cases, maximum equivalent stress that applied $30^{\circ}$ oblique load around the alveolar bone crest was larger than that of the vertical load. Especially the equivalent stress that loaded obliquely in buccal side was larger. 2. In study of implant fixture diameter, stress around alveolar bone was decreased with the increase of implant diameter. In the vertical load, as the diameter of implant increased the equivalent stress decreased, but equivalent stress increased in case of the wide implant that have a little cortical bone in the buccal side. In the lateral oblique loading condition, the diameter of implant increased the equivalent stress decreased, but in the buccal oblique load, there was not significant difference between the 5.5mm and 6.0mm as the wide diameter implant. 3. In study of alveolar bone width, equivalent stress was decreased with the increase of alveolar bone width. In the vertical and oblique loading condition, the width of alveolar bone increased 6.0mm the equivalent stress decreased. But in the oblique loading condition, there was not a difference equivalent stress at more than 6.0mm of alveolar bone width. 4. In study of insertion position of implant fixture, even though the insertion position of implant fixture move there was not a difference equivalent stress, but in the case of little cortical bone in the buccal side, value of the equivalent stress was most unfavorable. 5. In all cases, it showed high stress around the top of fixture that contact cortical bone, but there was not a portion on the bottom of fixture that concentrate highly stress and play the role of stress dispersion. These results demonstrated that obtaining the more contact from the bucco-lingual cortical bone by installing wide diameter implant plays an important role in biomechanics.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.17 no.1
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• pp.19-26
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• 2006

Objectives : The object of this study was to examine computer game playing patterns and psychopathologies related to computer game addiction in school-age children. Methods : The subjects were 533 elementary school students (4th to 6th grade) in Kangdonggu, Seoul. We evaluated computer playing patterns of all subjects using computer game playing pattern questionnaire, and determined the risk group of computer game addiction by internet game addiction scale score. We evaluated subscale score of K-CBCL from parents of all subjects, and conducted correlation analysis and logistic regression analysis between computer game addiction and subscale score of K-CBCL. Results : In 488 responders, 10.2% of started playing computer game in preschool age, and 67.2% started at low grade of elementary school. The mean frequency of computer game play per week was 3.66 days. Mean time spent playing computer games per day was 1.89 hours. 'Simply for fun' was the most common reason far playing computer games (40.8%). Male subjects showed statistically significant differences in age of starting computer game, frequency of computer game play per week, reasons for playing computer game and computer game addiction scale scores. There were significant correlations between computer game addiction scale scores and academic performance, somatic complaints, attention problems, and internalizing problems in K-CBCL. But In logistic regression analysis, only attention problems among K-CBCL subscales showed significant predictability to computer game addiction. Conclusion : Upper grade elementary school students experienced computer game playing at the very early age, and spend much time in playing computer games. There were significant correlation and predictability between computer game addiction and attention problems.

• Journal of The Korean Association For Science Education
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• v.38 no.4
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• pp.495-504
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• 2018

This study was conducted to develop items to measure scientific core competency based on statements of scientific core competencies presented in the 2015 revised national science curriculum and to identify the validity and reliability of the newly developed items. Based on the explanations of scientific reasoning, scientific inquiry ability, scientific problem-solving ability, scientific communication ability, participation/lifelong learning in science presented in the 2015 revised national science curriculum, 25 items were developed by five science education experts. To explore the validity and reliability of the developed items, data were collected from 11,348 students in elementary, middle, and high schools nationwide. The content validity, substantive validity, the internal structure validity, and generalization validity proposed by Messick (1995) were examined by various statistical tests. The results of the MNSQ analysis showed that there were no nonconformity in the 25 items. The confirmatory factor analysis using the structural equation modeling revealed that the five-factor model was a suitable model. The differential item functioning analyses by gender and school level revealed that the nonconformity DIF value was found in only two out of 175 cases. The results of the multivariate analysis of variance by gender and school level showed significant differences of test scores between schools and genders, and the interaction effect was also significant. The assessment items of science core competency based on the 2015 revised national science curriculum are valid from a psychometric point of view and can be used in the science education field.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.1-11
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• 2009

Statement of problem: There are two methods of color choice for the esthetic restoration. One is visual shade matching which draws a comparison between shade guide and teeth in dentist's own eye and the other is using a digital shade analysis system recently introduced. Although the visual shade matching has a lot of problems, decision of color by this visual shade matching and the ways of expression for the decided color are still applicable to clinical dentistry. Purpose: This study is designed to investigate shade guides used in the dental clinics and laboratories have the same value using ShadeEye-$NCC^{(R)}$ dental chroma meter (Shofu Inc., Kyoto, Japan) using shade guide are evaluated. Material and methods: At the first experiment, eight Vita Lumin Vacuum shade guides (Vident Inc., California, USA) were collected from the dental clinics. A1 and B1 shade tabs are chosen and the colors are analyzed five times each in both tooth and porcelain modes by digital shade analysis system, ShadeEye-$NCC^{(R)}$. In the second experiment, twelve Vita shade guides using practically in the dental clinics and laboratories were collected and also A1 and B1 shade tabs are chosen and the colors of A1 and B1 are analyzed one time each in both tooth and porcelain modes by ShadeEye-$NCC^{(R)}$. Results and conclusion: There were significant differences among eight shade guides in terms of shade (chroma), value and hue in both of A1 and B1 (P<.05). Shade guides using in present both dental clinics and laboratories did not show significant differences, except A1 in the porcelain mode, it showed significant differences (P<.05) in the shade even though the shade tab has the same name.

• The Journal of Korean Academy of Prosthodontics
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• v.47 no.1
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• pp.29-38
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• 2009

Statement of problem: A casting connection technique is widely used for repair, correction and addition to base metal framework. However, a casting connection technique may increase the risk of failure in clinical situations when high stresses exist. Purpose: The purpose of this study was to investigate the mechanical retentive groove design comparatively to increase the joint strength by using the three-dimensional finite element analysis model of a 3-unit fixed partial denture. Material and methods: Ten finite element models were constructed. (Model A: One retentive groove, Model B: Two retentive grooves, Model C: Three retentive grooves, Model D: Four retentive grooves, Model E: One horizontal groove and two vertical grooves, Model F: Two horizontal grooves and one vertical groove, Model G: One groove with the enlarged dimension, Model H: Two grooves with the enlarged dimension, Model I: One groove with the increased height, Model J: One groove with the increased width of base). The vertical force was applied to the mesial and the distal fossa to the casting connection of mandibular first molar. Results: The main factors, affecting joint strength of casting connection were both the retention between the primary cast and the secondary cast and the thickness of the primary cast remaining after preparing retentive groove. The increase of retentive force, according to the numbers and the dimension of retentive groove had an effect on distributing stress. However, in some cases, the increase of retentive force resulted in the increase of stress by reducing thickness of the primary cast in the connection area. Conclusion: The design of retentive groove that limits number of retentive groove for metal thickness and increases the depth of retentive groove for retention is highly recommended.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.293-302
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• 2014

This study was carried out to develop rain shelter which can make an appropriate size and environment for Chinese cabbage rainproof cultivation. Fifty three farms with chinese cabbage rainproof cultivation system have been investigated to set up width and height of rain shelter. Mostly the width of 6m was desired for rain shelter and the height of 1.6m for their eaves, so these values were chosen as the dimensions for rain shelter. After an analysis of their structural safety and installation costs by the specifications of the rafter pipe, Ø$25.4{\times}1.5t$ and 90cm have been set as the size of rafter that such size costs the least. This size is stable with $27m{\cdot}s^{-1}$ of wind velocity and 17cm of snow depth. Therefore it is difficult to apply this dimension to area with higher climate load. In order to sort out such problem, the rain shelter has been designed to avoid damage on frame by opening plastic film to the ridge. Once greenhouse band is loosen by turning the manual switch at the both sides of rain shelter and open button of controller is pushed then switch motor rises up along the guide pipe and plastic film is opened to the ridge. Chinese cabbage can be damaged by insects if rain shelter is opened completely as revealed a field. To prevent this, farmers can install an insect-proof net. Further, the greenhouse can be damaged by typhoon while growing Chinese cabbage therefore the effect of an insect-proof net on structural safety has been analyzed. And then structural safety has been analyzed through using flow-structure interaction method at the wind condition of $40m{\cdot}s^{-1}$. And it assumed that wind applied perpendicular to side of the rain shelter which was covered by insect-proof net. The results indicated that plastic film was directly affected by wind therefore high pressure occurred on the surface. But wind load on insect-proof net was smaller than on plastic film and pressure distribution was also uniform. The results of structural analysis by applying pressure data extracted from flow analysis indicated that the maximum stress occurred at the end of pipe which is the ground part and the value has been 54.6MPa. The allowable stress of pipe in the standard of structural safety must be 215 MPa or more therefore structural safety of this rain shelter is satisfied.

• Journal of The Korean Society of Inherited Metabolic disease
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• v.17 no.3
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• pp.85-91
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• 2017

Purpose: The aim of this study was to describe the clinical and biochemical features as well as the molecular analysis of a newly diagnosed illustrative case with ML II and to analyze the clinical features of 11 Korean patients with ML II/III. Method: Including a newly diagnosed patient, total 11 patients in 10 families were diagnosed as ML II (n=7) or ML III (n=4) were enrolled in the study. A diagnosis of ML II or III was made by demonstrating increased lysosomal enzyme activities in the plasma and sequence analysis of GNPTAB with characteristic clinical features. Result: A illustrative case of ML II patient was a 17 month-old boy showing characteristic facial appearance, multiple joint contractures with cardiac involvements. The enzyme assay showed increased lysosomal enzyme activities in the plasma. We identified compound heterozygous mutations in GNPTAB sequence analysis, including a frameshift (c.3428dupA [pAsn1143Lysfs*3]) and a nonsense variant c.673C>T (p.Gln225*). In total 11 patients with ML II/III, the patients with ML II showed severe growth retardation (height standard deviation score -3.2 [${\pm}1.5$]), compare to patients with ML III. Furthermore, patients with ML II patients had serious cardiac problem (n=4), hepatomegaly (n=3) and underwent tracheostomy (n=3) with further respiratory support due to respiratory distress. To improve osteoporosis and bone pain, all patients with ML III and four of 7 patients with ML II treated with intravenous pamidronate. Conclusion: Here we showed a newly diagnosed case of ML II and clinical features of 11 Korean patients with ML II or III. These data could be helpful for further diagnosis of mucolipidosis, a rare inherited metabolic disease, in Korea.

• Korean Journal of Child Education & Care
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• v.18 no.2
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• pp.85-102
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• 2018

The purpose of this study is to determine the working conditions and demands of the assistant workforce at childcare centers, and to provide suggestions on policies for childcare teachers. To achieve the purpose of the study, a total of 190 assistant teachers, nursing helpers, alternative teachers and others were surveyed online during the month of August 2017. The survey examined the employment route and working motives, working conditions and environment, job and educational difficulties for analyzing the work conditions and demands of ancillary staff. For the analysis method, SPSS 12.0 was used to analyze frequency and difference. The main findings are as follows. First, childcare center assistants were able to work at their respective times, making it mandatory for them to enter the workforce, and making job openings for ancillary teachers. Second, 73.7% said the daily working hours were '4 hours to 8 hours' under the conditions and 57.9% said 'More than 510,000 won to less than 1 million won.' Average amount of rest time per day was about 30 minutes, and 17% had no rest periods. Third, based on the job and education status, ancillary personnel performed "infant and child guidance and interaction", "Cleaning and cleanliness related tasks" most actively, and "care for cleaning and cleanliness" and "care for morning and night care". Fourth, in the job trouble and difficulty, ancillary staff found it difficult to satisfy with wage related complaints and job insecurity, and the reason for agreeing to the non-regular workforce becoming a regular worker was found to be due to the stability of employment. Lastly, the most urgent tasks to solve the problem of non-regular workers were to fill the wage gap between regular and irregular workers, shorten the working hours and improve the working conditions. The policy implications are presented based on the above findings.

• Hwankyungkyoyuk
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• v.7 no.1
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• pp.106-122
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• 1994

The purpose of this study to investigate the awareness of environmental management knowledge and behavior and the effect of independent variables (The environmental management behavior of housewives are composed of five activities-clothing, eating, housing, buying, family management. The independent variables are composed of objective variable and subjective variable). The Research Questions are as follows; 1. Are there significant differences in the housewife's awareness of the environmental management knowledge according to the objective variable and the subjective variable? 2. How much are the effects of related variables on the awareness of environmental management knowledge? 3. Are there significant differences in the housewife's environmental management behavior according to objective variable and subjective variable and awareness of environmental management knowledge? 4. How much are effects of related variables on the housewife's environmental management behavior? For these purpose, a theoretical framework was developed by literature review and applied to empirical test. The data was collected through the questionnaire those respondents were 477 housewives in seoul. It was analyzed by various statistical methods such as Frequency. Percentile, GLM, F-test, T-test, Duncan's Multiple Range Test, Pearson's Correlations Analysis Simple Regression Analysis, and Multiple Regression Analysis. The results of this research are as follows; 1. The awareness of environmental management knowledge had significant differences according to the variables such as housewife's age, husband's job, family number, education experience of environment, frequencies of contracting mass media, the perceived adequacy of resources, social-altruistic orientation. 2. Among all of these variables affecting the awareness of environmental management knowledge, the perceived adequacy of resources had the highest effects and the next were family number, social-altruistic, type of residence in order. 3. Total Environmental management behavior of housewives had significant differences according to the variables such of environment, frequencies of contracting mass media, the satisfaction of household labor, the perceived adequacy of resources, biospheric orientation, social-altruistic orientation, egoism orientation, the awareness of environmental management knowledge. The clothing, eating, housing, family management behavior had the high level, the buying management behavior had the average level. The clothing, eating, housing, buying, family management behavior had significant differences according to the variables such as the satisfaction of household labor, the perceived adequacy of resources, biospheric orientation, social-altruistic orientation, egoism orientation, the awareness of environmental management knowledge. In particular, the clothing, eating, housing, buying management behavior had significant differences according to the variables such as education experience of environment. And the housing, buying management behavior had significant differences according to the variables such as frequencies of contracting mass media. 4. Among all of theses variables affecting environmental management behavior, the most influence variables was awareness of environmental management knowledge and the next were influence of housewife's job, biospheric orientation, the satisfaction of household labor, education experience of environment, frequencies of contraction mass media, egoism orientation in order. Among all of theses variables effecting the clothing, eating, housing, buying management behavior the variables affecting the family management behavior, the most influences variables was housewife's job. In the result of analysing the housewife's environmental management behavior and awareness of environmental management knowledge, influences of education experience of environment had the highest effect and frequencies of contracting mass media may more influencial than other variables. And Concrete and systematic knowledge and technique of environmental education is requisite. The result of this study could be attributed to develop the efficient environmental information. More emphasis should be given to environmental education and a long range environmental policy. in particular, environmental education be effectively related to environmental behavior, life-education and systematic support must be provided. In addition, further study of environmental problem is needed for and application of various theoretical approaches and research method.