• Elastomers and Composites
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• v.58 no.4
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• pp.208-215
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• 2023

In this study, the properties of polyurethane-polydimethylsiloxane (PU-PDMS) hybrid foams containing different types and contents of physical blowing agents (PBAs) were investigated. Two types of blowing agents, namely physical blowing agents and thermally expandable microspheres (TEM), were applied. The apparent density was measured using precisely cut foam samples, and the pore size was measured using image software. In addition, the microstructure of the foam was confirmed via scanning electron microscopy and transmission electron microscopy. The thermal conductivities related to the microstructures of the different foams were compared. When 0.5 phr of the hydrocarbon-based PBA was added, the apparent density and pore size of the foam were minimal; however, the pore size was larger than that of neat foam. In contrast, the addition of 3 phr of TEM effectively reduced both the apparent density and pore size of the PBAs. The increase in resin viscosity owing to TEM could enhance bubble production stability, leading to the formation of more uniform and smaller pores. These results indicate that TEM is a highly efficient PBA that can be employed to decrease the weight and pore size of PU-PDMS hybrid foams.

• Journal of the Korean Society of Clothing and Textiles
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• v.33 no.5
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• pp.711-720
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• 2009

Leaf fibers have many good properties; they are strong, long, cheap, abundant and bio-degradable. Since they, however, contain a great quantity of non-cellulose components, they have been used for the materials of mats, ropes, bags and nets rather than those of clothing. In this study, we investigated the characteristics of leaf fibers in order to promote the use of leaf fibers for the materials of clothing as well as develop the high value-added textile fibers. Leaf fiber plants including New Zealand Flax, Henequen and Banana plant, which have various nature and shape, were used. New Zealand Flax and Henequen leaves were cut from lower part of plants. Banana leaves and pseudo-stems were peeled and cut from the stem of Banana plants. First, the thin outer skins like film of leaves, veins and stems were removed before retting. The chemical retting had been processed for 1hour, at 100 in 0.4% $H_2SO_4$ aqueous solution(liquid ratio 50:1). Then, the retted leaf fibers had been soaked for 1hour, at room temperature in 0.5% NaClO solution(v/v) to remove the miscellaneous materials. We investigated the physical characteristics of three leaf fibers including the transversal and longitudinal morphology, the contents(%) of pectin, lignin and hemicellulose, the length and diameter of fibers, the tensile strength of the fiber bundles, and the fiber crystallinity and the moisture regain(%). The lengths of fiber from three leaf fibers were similar to their leaf lengths. The fiber bundles were composed of the cellulose paralleled to the fiber axis and the non-cellulose intersecting at right angle with the fiber axis. The diameters of New Zealand Flax, Henequen and Banana fibers were $25.13{\mu}m$, $18.16{\mu}m$ and $14.01{\mu}m$, respectively and their tensile strengths were 19.40 Mpa, 32.16 Mpa and 8.45 Mpa, respective. The non-cellulose contents of three leaf fibers were relatively as high as 40%. If the non-cellulose contents of leaf fibers might be controlled, leaf fibers could be used for the materials of textile fiber, non-wovens and Korean traditional paper, Hanjee.

• The Mathematical Education
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• v.41 no.1
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• pp.59-78
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• 2002

In a globalization and information society in the 21st century, the emphasis of education is on producing people who can create intellectual value. To meet the purpose in mathematics education, students should be taught to be able to understand basic logics and principles and exchange mathematical information each other. Also they had better be guided to study on their own at home in an effective way. In reality, however, most of the home study does not go beyond confirming the same homework. It is very difficult for students to plan systematic preparation and review of their lessons and study on their own. Moreover there seems to be no integration between the lessons students receive at school and in private classes. Therefore the need for more systematic home study in relation to school lessons is high to maximize the teaming effect. Studying through Web has little restriction in terms of time and space. Students can collect useful information inexpensively and share their learning assignment with each other. But mathematics education through Web has not yet been developed in such a way as to see a positive result from it. This research intends to develop a web site where students can study mathematics systematically in a self-guided way. The research methods applied included survey, student discussion and online home study. The questionnaires were designed to figure out students'and parents'changes in their concept of mathematics home study. The research also tried to look for ways to cut down the burden of expensive private lessons in mathematics. The student discussions were made up of problem-making and problem-solving. The discussion procedure was analysed so as to check if students used their creativity while they were working. As stated above, the research aims to develop a web site to support effective home study, enhance students' mathematical ability and reduce the burden of private lessons.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.266-283
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• 2022

With the rapid development of autonomous vehicle technology, unexpected accidents are occurring. Therefore, it is necessary to minimize user accident damage through the development of autonomous traffic safety education. Since edge cases, accident type, and risk factor analysis are important for realistic education, overseas case studies and demonstrations were carried out, and based on this, two curriculum for service providers and general users were developed. The service provider curriculum consisted of OEDR, sudden stop, cut-in, take-over, defensive driving, system malfunction, policy and information security education, and the general user curriculum consisted of attention duty, take-over, operating design domain, accidents type, laws, functions, information security education.

• Asian Spine Journal
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• v.12 no.6
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• pp.1085-1091
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• 2018

Study Design: Case-control. Purpose: To determine optimal cut-off value for body mass index (BMI) in predicting surgical success in patients with lumbar spinal canal stenosis (LSCS). Overview of Literature: BMI is an essential variable in the assessment of patients with LSCS. Methods: We conducted a prospective study with obese and non-obese LSCS surgical patients and analyzed data on age, sex, duration of symptoms, walking distance, morphologic grade of stenosis, BMI, postoperative complications, and functional disability. Obesity was defined as BMI of ${\geq}30kg/m^2$. Patients completed the Oswestry Disability Index (ODI) questionnaire before surgery and 2 years after surgery. Surgical success was defined as ${\geq}30%$ improvement from the baseline ODI score. Receiver operating characteristic (ROC) analysis was used to estimate the optimal cut-off values of BMI to predict surgical success. In addition, correlation was assessed between BMI and stenosis grade based on morphology as defined by Schizas and colleague in total, 189 patients were eligible to enter the study. Results: Mean age of patients was $61.5{\pm}9.6years$. Mean follow-up was $36{\pm}12months$. Most patients (88.4%) were classified with grades C (severe stenosis) and D (extreme stenosis). Post-surgical success was 85.7% at the 2-year follow-up. A weak correlation was observed between morphologic grade of stenosis and BMI. Rates of postoperative complications were similar between patients who were obese and those who were non-obese. Both cohorts had similar degree of improvement in the ODI at the 2-year followup. However, patients who were non-obese presented significantly higher surgical success than those who were obese. In ROC curve analysis, a cut-off value of ${\leq}29.1kg/m^2$ for BMI in patients with LSCS was suggestive of surgical success, with 81.1% sensitivity and 82.2% specificity (area under the curve, 0.857; 95% confidence interval, 0.788-0.927). Conclusion: This study showed that the BMI can be considered a parameter for predicting surgical success in patients with LSCS and can be useful in clinical practice.

• FLOWER RESEARCH JOURNAL
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• v.26 no.4
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• pp.209-215
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• 2018

The survey conducted with 120 florists in Korean domestic flower shops to investigate the use and awareness of floral preservatives in Korea. As a result, only 19.8% of the domestic florists use floral preservatives frequently in their shops, whereas 45.5% do not use them at all, suggesting very low use frequency. Korean domestic florists considered the use of floral preservatives mostly for storing cut flowers to preventing bacteria growth. For the reasons not to use floral preservatives, 51.4% of the Korean domestic florists did not value its usefulness, showing a lack of awareness of floral preservatives. However, 44.2% of the florists who had the experience with floral preservatives satisfied with the effect of floral preservatives, and 49.5% of the respondents positively answered to recommend floral preservatives to others. General awareness on floral preservatives among Korean domestic florists was positive. 50.5% of the florists with the experience with the floral preservative had the high intention to re-purchase the flower preservatives. The low use frequency and lack of recognition of floral preservatives in Korea were likely due to very few floral preservative brands and little advertising. However, the high satisfaction level and repurchase intention rate shown by the florists indicates that increasing advertising and education for the floral preservatives would improve the accessibility and awareness of the products and their effects increasing the opportunity to use floral preservatives among Korean domestic florists, further enhancing consumers' satisfaction by improving the cut flower quality and its vase life.

• Membrane Journal
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• v.15 no.2
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• pp.121-131
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• 2005

Separation and purification of lysozyme from chicken egg white was studied using ultrafiltration. We have obtained experimental data through the cellulose membranes with the molecular weight cut off (MWCO) of 10 kDa, 30 kDa and 100 kDa in a stirred ultrafiltration device. Certain amounts of egg white were dissolved into 20 mM phosphate buffers of pH 6, 7 and 8 to make protein solutions of $1\%,\;2\%,\;3\%\;and\;10\%$ concentration. Permeation flux increased with increasing MWCO of the membrane. Permeation flux increased with increasing transmembrane pressure (TMP) and decreasing the protein concentration. As the MWCO of membrane decreased, the selectivity increased. The selectivity increased with increasing TMP and protein concentration of the solution.

• Journal of Practical Engineering Education
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• v.15 no.2
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• pp.519-528
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• 2023

Recently, for the preservation and transmission of cultural heritage, various researches and content development based on technologies such as virtual reality, augmented reality, and extended reality, which are the core technologies of the 4th industrial revolution era, are being conducted. Intangible cultural heritage is variable, unlike tangible cultural heritage, so it changes greatly depending on time and space, and as a result, it is in danger of being discontinued due to the aging and death of the inheritors. In this study, the current status and cases of related realistic content production were collected and analyzed, focusing on statistical data, intangible cultural heritage training centers through search portals, and platform cases. As a result of the analysis, it was found that overall, there were very few cases of use in content and transfer education using intangible cultural heritage. Through this study, we will consider ways to revitalize the effective transfer education of intangible cultural heritage that is on the verge of being cut off from transmission.

• Korean Journal of Health Education and Promotion
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• v.3 no.1
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• pp.29-42
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• 1985

The purpose of this study was to evaluate the educatconal function of the health related articles. The health articles of the four major daily newspapers from Jan. 1st, 1980 to Dec. 31th, 1984 were used and examined for the study. Editorials were excluded. The major results were summarized as follows: 1. The total number of the health articles subjected to the study in the four major daily newspapers was 4,431. On the whole, the health articles were appeared most frequently in 1981. As for monthly distribution, the health articles were appeared most frequently on June.(9.3%). As for weekly distribution, the health articles were appeared most frequently on wednesday and saturday(50.8%). As for the subjects of content; the health articles related to the health & disease management were appeared most frequently(52.8%), but the health articles on industrial health were showed least frequently(0.6%). 2. Reviewing the chronological trend of the health articles, the frequency of appearance of the public health administration was tended to increase year by year, whereas that of enviornmental health, industrial health and population decrease relatively. As for appealing method, it was observed that the articles providing health information were steadily increasing. As for the motives of writing the health articles, there was a tendency that seasonal motive, symphosium & seminar and compaign were increasing, but motive of legislative action and administrative action were gradually decreasing. As for type of the health articles, it was observed that interpretation and research result were steadily increasing. As for the writer of the health articles, there was a tendency that writing by reporter was increasing, whereas writing by experts was decreasing. As for tone of head, the health articles written by identification statement was tended to increase. As for the appearance of photograph & cut, it was observed that the health articles excluding photograph & cut were increasing. 3. When contents were analyzed by subjects, for the purpose of providing information was used most frequently as appealing method for all subjects. As for the motive of writing, "from the interest of writers" was most frequent. As for the type of articles, interpretation type was most prevalent for the public health administration, enviornmental health, food hygrene & nutrition, population and health behavior, while contribution by experts was most frequent for the health & disease management. As for the size of articles, all subjects except the population were appeared most frequently on the column. size between 100㎠ and 199㎠.

• Journal of the Korean earth science society
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• v.26 no.6
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• pp.461-468
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• 2005

The purpose of this study is to investigate the abilities of 6th grade students to assess the relationship between spatial capability, concept of celestial motion, and science process skills, which can help find a better teaching strategy for students in understanding the concept of celestial motion. The results are as follows. First, in terms of level of accomplishment of these three skills, male students show higher level of accomplishment than female students, but significant differences are found. Second, according to the analysis of the effect of spatial capability and concept of the movement of heavenly bodies, the former has a stronger influence on the students' cognition of celestial motion. Minor elements of spatial capability that influence the conception of celestial motion are device analogy, calculation of wood cut, and revolving light. Third, spatial capability is very influential on the level of accomplishment in science process skills. Among the minor elements of spatial capability that is influential to science process skills, calculation of wood cut is the highest, especially when various elements are interactively related to each other.