• Composites Research
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• v.20 no.6
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• pp.8-14
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• 2007

Debonding failure characteristics of the composite skin-stiffener specimens were experimentally investigated. The influences of bonding methods, types of stiffener shape and various secondary bonding parameters were evaluated. Present test results combined with the previous test results[1] showed that the failure displacement of the skin-stiffener specimens well evaluates the skin-stiffener debonding failure strength of the composite stiffened panels. The specimens with an open type stiffener had lower bending stiffness and larger failure displacement than those with a closed type stiffener. Secondary bonding and co-curing with adhesive had better failure strength than co-curing without adhesive film. Secondary bonded specimens failed by adhesive failure and co-cured specimens failed by delamination failure. As the bondline thickness was thinner, the skin-stiffener specimens had higher failure strength. The fillets had no influence on failure strength of the specimens. The influence of the surface roughness was shown according to types of stiffener shape.

• Composites Research
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• v.21 no.1
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• pp.40-45
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• 2008

Rubber hose assembly for automotive hydraulic brake during operation is subject to combined stresses of cyclic pressure, cyclic bending and torsion as well as thermal load. The rubber hose is composed of ethylene-propylene diene monomer(EPDM) rubber layers reinforced by polyvinyl acetate(PVA) braided fabrics. A durability tester with loading rigs for inducing the above cyclic stresses was used to investigate failure mechanisms in the rubber hose assembly. Failure examination was performed at every 100 thousands cycles of bending and torsion. Hose samples were sectioned with a diamond-wheel cutter and then polished. The polished surface was observed by optical microscope and scanning electron microscope (SEM). Some interfacial delamination with a length of about 1mm along the interface between EPDM rubber and PVA fabrics was shown at the test cycles of 400,000. The delamination induced some cracking into the outer rubber skin layer to leading the final rupture of the hose.

• Korean Journal of Community Nutrition
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• v.28 no.3
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• pp.220-234
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• 2023

Objectives: This study aimed to assess the adherence to dietary guidelines among college students in the post-COVID-19 era and examine the changes in their dietary habits as the learning environment transitioned from remote to in-person classes. Methods: We conducted a survey involving 327 college students in Daejeon from March to April 2023. The survey questionnaires included various factors, including age, gender, type of residence, frequency of use of delivery food, convenience food, and eating out. In addition, we investigated the extent of adherence to the dietary guidelines for Koreans and the degree of dietary changes following the post-COVID-19 shift in class format were investigated. For comparative analysis of the level of adherence to dietary guidelines in relation to dietary habit changes, an ANOVA and a post hoc Scheffe test were employed. We also performed a multiple linear regression analysis to identify dietary factors influencing the level of adherence to dietary guidelines. Results: The study revealed a high rate of convenience food consumption and a low rate of homemade food intake among students. There was a marked increase in the consumption of processed foods, convenience foods, dining out, sweet foods, high-fat fried foods, beverages, and alcohol following the transition from online to in-person classes. When examining adherence to Korean dietary guidelines, the highest scored practice was 'Hydration', and the lowest was 'Breakfast habit'. Increased consumption of convenience foods, late-night snacks, and dining out were negatively correlated with adherence levels to dietary guidelines, specifically correlating with 'Healthy weight', 'Hydration', 'Breakfast habit', and the total score of adherence. The adoption of 'regular meals' was positively associated with increased adherence levels to dietary guidelines. Conclusions: The transition from remote to in-person classes post-COVID-19 led to increased intake of convenience foods, dining out, sweet foods, high-fat fried foods, and alcohol. The rise in convenience food and late-night snack consumption negatively influenced several aspects of the dietary guidelines adherence, thereby suggesting the need for strategies to encourage healthy dietary habits among college students.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1D
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• pp.35-43
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• 2008

This paper mainly deals with the performance evaluation of 33 asphalt sections of Korea Expressway Corporation Test Road (KECTR) during the past four years. Since the construction of the KECTR in December 2002, key performance indicators of asphalt pavements have been collected five times with an Automatic Road Analyzer (ARAN), and have been analyzed for permanent deformation, surface distress, and road roughness. Linear viscoelastic characteristics of four dense graded HMAs used in KECTR were investigated with a series of complex modulus test. The effect of air void in HMAs on dynamic modulus was investigate at two air void contents for a surface course HMA (19 mm Nominal Maximum Size of Aggregate). Layer densification due to traffic was estimated from air void contents of field cored samples, and was correlated with pavement distresses and performances. One of findings of this study was that both permanent deformation and cracking were suspectible to pavement temperatures, rather than traffic. However, it was found that road roughness was mostly affected by traffic loading.

• Korean Journal of Community Nutrition
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• v.28 no.5
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• pp.404-413
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• 2023

Objectives: This study compared serum lipid concentration according to drinking habits. Methods: We analyzed data from the 7th Korea National Health and Nutrition Examination Survey (KNHANES VII). The study included 8,525 adults (3,651 males and 4,874 females), aged 30 - 59 years. Results: There were differences in age, gender, education level, smoking status, physical activity, and waist circumference between drinkers and abstainers. The serum low-density lipoprotein-cholesterol (LDL-C) level of the drinkers was lower than those of the abstainers (P < 0.05). The serum triglyceride (TG) and high-density lipoprotein-cholesterol (HDL-C) concentrations were highest in the group that consumed alcohol 'more than twice a week' relative to the other groups (P < 0.001). The LDL-C and atherogenic index (AI) levels were lowest in the 'more than twice a week' drinking group compared to the other groups (P < 0.001). The serum TG and HDL-C concentrations were the highest in the '7 glasses/time' group (P < 0.001). The serum LDL-C concentration was the lowest in the '7 glasses/time' group (P < 0.001). Notably, the higher the frequency of binge drinking (7 glasses or more), the higher the concentration of TG (P < 0.001). The serum HDL-C concentration was significantly higher in the 'no binge' and 'more than once a week' groups compared to the other groups (P < 0.001). The serum LDL-C concentration and AI score were the lowest in the 'more than once a week' group (P < 0.001). Conclusions: As the quantity and frequency of drinking increased, the serum TC concentration increased. Moreover, an increase in the serum HDL-C concentration led to a decrease in AI. The factors exacerbating cardiovascular disease increased simultaneously due to drinking. Our results suggest that for individuals with hypertriglyceridemia and patients with low HDL-cholesterolemia, separate guidelines based on the quantity and frequency of alcohol consumption are warranted.

• Korean Journal of Community Nutrition
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• v.28 no.5
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• pp.392-403
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• 2023

Objectives: This study was intended to investigate adults' health behaviors and eating habits according to their levels of social media use. Methods: From May 27 to July 11, 2022, an online survey was conducted of 452 male and female social media users in their 20s and 30s, and their eating habits and health behaviors were compared and analyzed according to their degree of social media use. For each of the three levels of food content use, the frequency of social media content use, and the total score range of average social media viewing time per day were divided into three parts, and a group with a score of less than 2 points was classified as low-use; a group with a score of 2 or more and less than 3 points was classified as middle-use; and a group with a score of 3 points or more was classified as high-use. Results: The use of food content was higher in women than in men (P < 0.001), and higher in those in their 20s than in those in their 30s (P < 0.001). The group with a high level of food content use showed a higher rate of post-use hunger than the group with a low level (P < 0.01). The experience of eating after using food content was also higher in the group with a high level of use than in the group with a low level of use (P < 0.001). The group with a normal or high level of food content use had more negative eating habits than the group with a low level. Conclusions: The study highlighted the need to provide desirable food content to people in their 20s and 30s with negative eating habits and to promote them so that they can use the right healthy nutrition-related content.

• Korean Journal of Community Nutrition
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• v.29 no.2
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• pp.156-170
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• 2024

Objectives: This study aimed to investigate the association between how often Korean adolescents watch Mukbang and Cookbang videos and their dietary habits. Methods: Data from the 18th Korea Youth Risk Behavior Survey conducted in 2022 was analyzed for this study. The study included 51,850 middle and high school students and assessed various aspects, including demographics, frequency of watching Mukbang and Cookbang videos per week, dietary habits, health behaviors, and mental health factors. Results: Nearly a third (29.3%) of Korean adolescents watched Mukbang and Cookbang videos one to four times a week, while 13.5% watched them more than five times weekly. Females, those with lower academic achievement, and those from lower socioeconomic backgrounds were significantly more likely to be frequent viewers (P < 0.001). Increased viewing frequency was associated with poorer dietary habits. Adolescents who watched more frequently were less likely to eat breakfast and consume fruits and milk, while their consumption of fast food, high-caffeine drinks, sugary drinks, and late-night snacks increased (P < 0.001). Higher viewing frequency correlated with increased feelings of stress, depression, and loneliness (P < 0.001). Logistic regression analysis confirmed these associations. More frequent viewers were significantly less likely to eat breakfast (odds ratio (OR), 0.63; 95% confidence interval (CI), 0.58-0.68), and more likely to consume fast food (OR, 1.85; 95% CI, 1.69-2.02), high-caffeine drinks (OR, 1.43; 95% CI, 1.30-1.56), sugary drinks (OR, 1.54; 95% CI, 1.41-1.67), and late-night snacks (OR, 1.37; 95% CI, 1.25-1.51). Conclusions: Our findings suggest that frequent exposure to Mukbang and Cookbang content is linked to unhealthy dietary habits in adolescents. Educational programs may be necessary to mitigate the potential for these videos to negatively influence dietary choices.

• Korean Journal of Psychosomatic Medicine
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• v.20 no.1
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• pp.22-31
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• 2012

Objectives : We investigated the prevalence and functional impairment of premenstrual dysphoric disorder (PMDD) and premenstrual syndrome(PMS) in young women. Methods : A total of 1063 female college students were recruited from two urban areas(Seoul and Suwon) of Korea. Questionnaires for sociodemographic data and risk factors of PMDD, attitude about menstruation, and the Premenstrual Symptoms Screening Tool(PSST) were applied. Results : The prevalence of severe moderate to severe PMS and PMDD were 16.9% and 11.7%, respectively. There were differences in the alcohol and coffee consumption, severity of menstrual cramp, and family history of PMS among the moderate to severe PMS, PMDD, and no/mild PMS groups. Although some participants did not fulfill diagnostic criteria for PMDD, they showed significant functional impairment. Participants with negative attitude about menstruation reported premenstrual symptoms more frequently than those with positive or ambivalent attitude about menstruation. Conclusion : These results suggest that PMS and PMDD were prevalent and associated with functional impairment in young females. Some participants reported significant functional impairments although they did not meet the full DSM-IV diagnostic criteria for PMDD. Negative attitude about menstruation was associated with more premenstrual symptoms experiences.

• Journal of Korean Ophthalmic Optics Society
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• v.18 no.1
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• pp.53-59
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• 2013

Purpose: This study calculated the prevalence of cataract in Korean and examined corrected eyesight with different types of opacification of crystalline lens. Methods: Using the data of the national health and nutrition examination survey (NHANES), population-based and cross-sectional research were designed in this study. After dividing total 4,977 persons into different groups by age, from 40 to 95 and by sex, the prevalence of cataract with different types of opacification was investigated. The average age of the total subjects was $58.28{\pm}12.07$, and the number of men and women were 2,142(43.0%) and 2,835(57.0%), repectively. Eyesight was calculated when it was less than 0.63. Results: Among total 4,977 subjects, 40.6% (men 17.5%, women 23.1%) had cataract. Different prevalence rates were found with different types of cataract; nuclear cataract (56.3%), cortical cataract (23.4%), mixed cataract (16.2%), anterior subcapsular(3.0%), and posterior subcapsular (1.1%) in order. There was no difference among men and women by the types. And those in their 40's showed a higher prevalence of cortical cataract than those in the other age groups. Most of subjects whose corrected eyesight is less than 0.63 had anterior subcapsular cataract. Conclusions: The type of cataract having the highest prevalence was nuclear opacity. Moreover, epidemiologic investigation and prevention policy with different type of lens opacity seems to be required.

• Korean Journal of Plant Taxonomy
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• v.41 no.1
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• pp.16-34
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• 2011

Scirpus L. s.l. of Cyperaceae has been regarded as a monophyletic group, but the taxa of Scirpus s.l. were rearranged into the five independent genera in recent molecular phylogenetic research: Bolboschoenus (Asch.) Palla, Schoenoplectus (Rchb.) Palla, Schoenoplectiella Lye, Scirpus L., and Trichophorum Pers. In this study, we examined the morphological characteristics and presented the delineation of the five genera of Scirpus s.l., including 21 taxa from South Korea. As a result of our investigation and analysis of domestic collections and those from abroad, the each taxon could be identified using key characteristics of the rhizome features; a cross-section of culm; the degree of development and the width of leaves; the shapes of the membranous region of leaf sheath; and the shapes and size of inflorescence, bract, floral scale, and achene. These major characteristics are illustrated and artificial keys are suggested in this study. In addition, we suggest a new combination for an unrecorded taxon of Schoenoplectiella that was discovered in Gangwon-do, Goseong-gun and give it the Korean name, as 'a-do-song-i-go-raeng-i'.