• Nutrition Research and Practice
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• v.15 no.3
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• pp.329-345
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• 2021

BACKGROUD/OBJECTIVES: Evidence has suggested an association between serum vitamin D and metabolic syndrome (MetS), but prospective studies are very limited. The objective was to assess the dose-response association between serum vitamin D concentration and MetS risk using a systematic review and meta-analysis of updated observational studies. MATERIALS/METHODS: Using MEDLINE, PubMed, and Embase, a systematic literature search was conducted through February 2020 and the references of relevant articles were reviewed. A random-effects model was used to estimate the summary odds ratio/relative risk and 95% confidence interval (CI). Heterogeneity among studies was evaluated with I² statistic. In total, 23 observational studies (19 cross-sectional studies, and four cohort studies) were included in the meta-analysis. RESULTS: The pooled estimates (95% CI) for MetS per 25-nmol/L increment in serum vitamin D concentration were 0.80 (95% CI, 0.76-0.84; I² = 53.5) in cross-sectional studies, and 0.85 (95% CI, 0.72-0.98; I² = 85.8) in cohort studies. Similar results were observed, irrespectively of age of study population, study location, MetS criteria, and adjustment factors. There was no publication bias for the dose-response meta-analysis of serum vitamin D concentrations and MetS. CONCLUSIONS: Dose-response meta-analysis demonstrated that a 25-nmol/L increment in the serum vitamin D concentration was associated with 20% and 15% lower risks of MetS in cross-sectional studies and cohort studies, respectively.

• Korean Journal of Community Nutrition
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• v.25 no.6
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• pp.512-519
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• 2020

Objectives: A cross-sectional study was conducted to investigate the associations between food groups and hearing loss. Methods: Data of 1,312 individuals were used from the Korea National Health and Nutrition Examination Survey 2013. Hearing loss was determined with a pure tone average (PTA) of greater than 25 dB in either ear. The PTA was measured as the average hearing threshold at speech frequencies of 0.5, 1, 2, and 4 kHz. The dietary intake was examined with a food frequency questionnaire with 112 food items. The food items were classified into 25 food groups. A weighted logistic regression was used to investigate the association. Results: Individuals in the highest tertile of vegetables and nuts food groups were less likely to have hearing loss than those in the lowest tertile [Odds Ratio (OR) = 0.58 (95% Confidence interval (CI) 0.38-0.91), P = 0.019; OR = 0.59 (95% CI 0.39-0.90), P = 0.020, respectively], after adjusting for confounding variables of age, sex, body mass index, drinking, smoking, diabetes, hypertension, and physical activity. Conclusions: In this cross-sectional study, we observed that high intake of vegetables and nuts food groups revealed significant inverse associations with hearing loss, after adjusting for confounding variables among 1,312 participants.

• The Korean Journal of Pain
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• v.34 no.1
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• pp.72-81
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• 2021

Background: In the literature, there have been debates as to whether smartphone use has negative effects on physical and mental health. The present study investigated the extent to which smartphone addiction impacts on musculoskeletal pain prevalence among university students. Methods: The questionnaire consisted of three sections: demographic information, the Smartphone Addiction Scale (SAS), and the modified Nordic Musculoskeletal Questionnaire. Results: A total of 249 participants were included in this cross-sectional study. The body parts that were reported with highest prevalence of musculoskeletal pain were the upper back (70.3%), neck (65.9%), and wrists/hands (68.7%). The SAS scores were correlated with duration of smartphone use on a typical day (P = 0.001), duration of owning a smartphone (P = 0.027), and musculoskeletal pain prevalence in the neck (P = 0.001), wrists/hands (P = 0.001), shoulders (P = 0.025), and upper back (P = 0.023). The SAS score was significantly associated with prevalence of musculoskeletal pain in the neck (odd ratio [OR], 1.08; 95% confidence interval [CI], 0.98-1.10; P = 0.002), wrists/hands (OR, 1.07; 95% CI, 0.97-1.09; P = 0.001), and upper back (OR, 1.10; 95% CI, 0.98-1.11; P = 0.033). Conclusions: The findings indicated that the upper back, neck, and wrists/hands have a higher prevalence of musculoskeletal pain among smartphone users, particularly those with a smartphone addiction. Smartphone addiction scores were correlated with duration of smartphone use on a typical day, duration of owning smartphone, and musculoskeletal pain prevalence in the neck, wrists/hands, shoulders, and upper back.

• Journal of Preventive Medicine and Public Health
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• v.57 no.3
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• pp.242-251
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• 2024

Objectives: The aim of this study was to analyze the relationship between objective social isolation (SI) and unmet medical needs (UMN) in adults aged 19 and older. Methods: A cross-sectional analysis was conducted of 208 619 adults aged 19 and older, excluding missing data, using the 2019 Korea Community Health Survey. To analyze the association between objective SI and UMN, the chi-square test and logistic regression analysis were performed. Results: The prevalence of UMN was 1.14 times higher (odds ratio [OR], 1.14; 95% confidence interval [CI], 1.06 to 1.23) among those with SI than among those without SI, and the OR for groups with 5 SI types was 2.77 (95% CI, 1.86 to 4.12) compared to those with no SI types. In addition, a stratified analysis by age group showed that the association between SI and UMN existed even in groups under 64 years old. However, among those aged 65 and older, SI was associated with an OR of 1.53 (95% CI, 1.37 to 1.71) for UMN compared to non-SI. As the number of SI types increased, the prevalence of UMN also increased, indicating a strong association between SI and UMN in older adults. Conclusions: This study found that individuals with SI experienced UMN due to fear and anxiety about interpersonal relationships. Therefore, based on the results of this cross-sectional study, it is necessary to investigate the causal relationship between SI and UMN through future longitudinal data.

• Journal of Space Technology and Applications
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• v.4 no.1
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• pp.62-73
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• 2024

This study analyzed the effectiveness of orbital change through attitude change in nano-satellites operating in low Earth orbit (LEO) without thrusters, focusing on collision avoidance maneuvers. The results revealed that changes in the satellite's cross-sectional area significantly impact its in-track direction, influenced by the aspect ratio of cross-sectional area change and mission altitude. Notably, satellites at lower altitudes demonstrated significant reduction in collision risks with a small amount of attitude change. Through this study, it is judged that the changing the cross-sectional area through attitude maneuver is a sufficiently suitable method in the operation of nano-satellites without thrusters, and is expected to contribute to improving the safety of satellite operations in the New Space era.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.277-287
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• 2017

This paper describes the specifications on balanced steel ratio and maximum reinforcement for the design of RC flexural members by the Korean Highway Bridge Design Code based on limit states design. The Korean Highway Bridge Design Code (Limit States Design) is not provide for the balanced steel ratio specification for the calculation of required steel area of RC flexural members design. The maximum steel area limited the depth of the neutral axis at the ultimate limit states after redistribution of the moment, and also recommended the maximum steel area should not exceed 4 percent of the cross sectional area. However, from the maximum neutral axis depth provisions should increase the cross section is calculated to be less the maximum reinforcement area, and according to the 4% of the cross sectional area of the concrete, the tensile strain of the reinforcement is calculated to be greater than double the yielding strain, so can not guarantee a ductile behavior. This study developed a balanced reinforcement ratio that is basis for the required reinforcement calculation for tension-controlled RC flexural members design in the ultimate limit states verification provisons and material properties and applied the ultimate strain of the concrete compressive strength with a simple formular to be applied to design practice induced. And assumed the minimum allowable tensile strain of reinforcement double the yielding strain, and applying correction coefficient up to the ratio of maximum neutral axis depth, proposed maximum steel ratio that can be applied irrespective of the reinforcement yield strength and concrete compressive strength.

• Restorative Dentistry and Endodontics
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• v.31 no.2
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• pp.96-102
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• 2006

There are various factors affecting the fracture of NiTi rotary files. This study was performed to evaluate the effect of cross sectional area, pecking motion and pecking distance on the cyclic fatigue fracture of different NiTi files. Five different NiTi $files-Profile^{(R)}$ (Maillefer, Ballaigue, Switzerland), $ProTaper^{TM}$(Maillefer, Ballaigue, Switzerland), $K3^{(R)}$ (SybronEndo. Orange, CA) , Hero $642^{(R)}$ (Micro-mega, Besancon, France), Hero $Shaper^{(R)}$ (Micro-mega, Besancon, France)-were used. Each file was embedded in temporary resin, sectioned horizontally and observed with scanning electron microscope. The ratio of cross-sectional area to the circumscribed circle was calculated. Special device was fabricated to simulate the cyclic fatigue fracture of NiTi file in the curved canal,. On this device, NiTi files were rotated (300rpm) with different pecking distances (3 mm or 6 mm) and with different motions (static motion or dynamic pecking motion) . Time until fracture occurs was measured. The results demonstrated that cross-sectional area didn't have any effect on the time of file fracture. Among the files, $Profile^{(R)}$ took the longest time to be fractured. Between the pecking motions, dynamic motion took the longer time to be fractured than static motion. There was no significant difference between the pecking distances with dynamic motion, however with static motion, the longer time was taken at 3mm distance. In this study, we could suggest that dynamic pecking motion would lengthen the time for NiTi file to be fractured from cyclic fatigue.

• Structural Engineering and Mechanics
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• v.32 no.6
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• pp.705-724
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• 2009

The two major widely used building design code documents of reinforced concrete structures are the ACI 318-05 and Eurocode for the Design of Concrete Structures EC2. Therefore, a thorough comparative analysis of the provisions of these codes is required to confirm their validity and identify discrepancies in either code. In this context, provisions of flexural computations would be particularly attractive for detailed comparison. The provisions of safety concepts, design assumptions, cross-sectional moment capacity, ductility, minimum and maximum reinforcement ratios, and load safety factors of both the ACI 318-05 and EC2 is conducted with parametric analysis. In order to conduct the comparison successfully, the parameters and procedures of EC2 were reformatted and defined in terms of those of ACI 318-05. This paper concluded that although the adopted rationale and methodology of computing the design strength is significantly different between the two codes, the overall EC2 flexural provisions are slightly more conservative with a little of practical difference than those of ACI 318-05. In addition, for the limit of maximum reinforcement ratio, EC2 assures higher sectional ductility than ACI 318-05. Overall, EC2 provisions provide a higher safety factor than those of ACI 318-05 for low values of Live/Dead load ratios. As the ratio increases the difference between the two codes decreases and becomes almost negligible for ratios higher than 4.

• Journal of Nutrition and Health
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• v.33 no.8
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• pp.873-881
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• 2000

Recent research reported health risks associate with high carbohydrates diets. Objectives of this study were to evaluate in a cross-sectional study if high carbohydrate diet is associated with coronary heart disease(CHD) risk factors: examined blood concnetration of triglyceride(TG), total cholesterol, high density lipoprotein cholesterol(HDL-C), plasma glucose, systolic blood pressure(BP), body mas index(BMI), wasit-hip ratio(WHR) and waist-stature ratio(WSR). Using the most recent US National Health and Nutrition Examination Survey(IIINHANES III) data, the nationally representative US population (3772 men, 4095 women of 25-64 years of age) was divided into low vs. high carbohydrate diet groups(below 40% vs. above 60% energy intake from cab carbohydrates) and compared by the CHD risk factors. Triglyceride was higher(p<0.001) in the high carbohydrate group, whereas high density-lipoprotein cholesterol(HDL-C)was lower(p<0.01) in the high carbohydrate diet group. In plasma glucose, there was no significant differences between high carbohydrate diet and low carbohydrate diet. In adiposity(BMI, WHR and WSR), it also showed no significant differences, After adjustment for age, ethnicity, alcohol and smoking in upper 60%-carbohydrate diet, Odds Ratio of TG and HDL-C were 1.42 and 1.23 in men and 1.22 and 1.17 in women. 50-60% carbohydrate diet was associated with decreased risk of CHD. Dietary guidelines for Koreans recommend 60-70% of total energy from carbohydrate, as Koreans traditionally consumed high carbohydrate diets. In a cross-sectional population of adults, diets containing 55-60% energy from carbohydrate were suggested as a dietary guideline of carbohydrate intake for Koreans. (Korean J Nutrition 33(8) : 873-881, 2000)

• Fire Science and Engineering
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• v.27 no.3
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• pp.30-37
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• 2013

The ultimate purpose of the present study is to secure a effective method for foam liquid discharge when the mixing ratio deviates from the permissible range due to a decrease in the bypass flow rate resulting from a decrease in the cross sectional area of the foam liquid piping ranging from the branching header of one foam proportioner to the branching headers of multiple branching foam fire-extinguishing systems in the region for fire extinguishing and then to the standpipe at the lower part of the storage tank when a fire occurred in a combustible tank. To this end, the cause of mixing ratio variations following changes in the flow rates of existing foam fire extinguishing systems was analyzed, methods for compensation for constant mixing ratios were investigated, and it was proved that metering orifice replacements that could expand the cross sectional area of the stock solution inhaling piping was the most effective way for the improvement of form fire extinguishing systems' mixing ratios through foam proportioner venturi, foam chamber orifice, and metering orifice replacement experiments.