• Journal of Welding and Joining
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• v.26 no.2
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• pp.62-68
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• 2008

Effects of gravitational orientation on gas tungsten arc welding (GTAW) for 304 stainless steel were studied to determine the critical factors for weld pool formation, such as weld surface deformation and weld pool shape. This study was accomplished through an analytical study of weld pool stability as a function of primary welding parameters (arc current and arc holding time), material properties (surface tension and density), and melting efficiency (cross-sectional area). The stability of weld pool shape and weld surface deformation was confirmed experimentally by changing the welding position. The arc current and translational velocity were the major factors in determining the weld pool stability as a function of the gravitational orientation. A 200A spot GTAW showed a significant variation of the weld pool formation as the arc held longer than 3 seconds, however the weld pool shape and surface morphology for a 165A spot GTAW were 'stable', i.e., constant regardless of the gravitational orientation. The cross-sectional area of the weld (CSA) was one of the critical factors in determining the weld pool stability. The measured CSA ($13.5mm^2$) for the 200A spot GTAW showed a good agreement with the calculated CSA ($14.9mm^2$).

• The Korean Journal of Financial Management
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• v.26 no.2
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• pp.93-112
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• 2009

The purpose of this study is to examine market timing and volatility timing abilities in Korean equity funds by distinguishing 'skill' and 'luck' for individual funds. In this study, we use the funds, which exist more than consecutive 24 month non-overlapping periods. This procedure leaves 545 funds among total 1,904 funds during sample priod January 2001 to December 2007. To derive the 'luck' distribution, the cross-sectional bootrap approach is adopted. From our results, it is found that when the traditional regression approach is adopted, only few Korean equity funds possess market timing and volatility timing abilities. However, based on the 'luck' distributions, which are derived from cross-sectional bootstrap approach, it is found that market timing and volatility timing abilities of Korean equity funds are merely from 'luck' rather than 'skill'.

• Journal of Preventive Medicine and Public Health
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• v.35 no.4
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• pp.313-321
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• 2002

Objectives : To identify the risk factors of dementia among the elderly in a large city. Methods : A cross-sectional study was conducted in July 2001, with potential participants selected by stratified two stage cluster sampling of the elderly population of Keumgog dong, Busan. A total of 452 elderly people aged 65 years and over, underwent a two phase diagnostic procedure. Mini-mental State Examination-Korean (MMSE-K) and Samsung Dementia Questionnaire were used for the 1st stage, and the Clinical Dementia Rating Scale (CDR), the Bartel ADL, and IADL Index, the Korean Geriatric Depression Scale (KGDS), the Modified Hatchinski Ischemic Scale (MHIS), and other laboratory tests were used for the 2nd stage. Results : Of the 446 participants finally chosen, 45 were confirmed with dementia, and 363 as normal, with the rests not confirmed with dementia or as normal, were excluded from the analysis. According to the logistic regression analysis, the risk of dementia was significantly higher In: people aged 80 and above (OR=4.36, 95% CI=1.97-9.62), illiterate (OR=3.58, 95% CI=1.71-7.46), who had a history of strokes (OR=6.35, 95% CI=2.71-14.87), or who had 3 history of hyperlipidemia (OR=4.74, 95% CI=1.65-13.61), compared to their counterparts. Conclusions : These results suggest that efforts to prevent strokes and hyperlipidemia can significantly decrease the risk of dementia.

• 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.

• Nutrition Research and Practice
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• v.16 no.2
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• pp.248-259
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• 2022

BACKGROUND/OBJECTIVES: Adequate nutritional intake is essential for good health and well-being. We aimed to compare the nutrient intake from homemade meals, meals sourced externally ("eating out"), and meals from workplace foodservices, as well as the potential association between foodservices used and nutritional quality among adult Korean workers. SUBJECTS/METHODS: We used data from the Korea National Health and Nutrition Examination Survey, a nationwide cross-sectional survey on the health and nutritional status of the Korean population. Data from 6,845 workers aged 20-64 years were included. A survey on dietary behavior and nutrition was conducted using the 24-h dietary recall method. Nutritional quality was examined using the index of nutritional quality (INQ) score. Higher INQ scores reflected poorer nutritional quality, with insufficient intake of a higher number of nutrients. Multivariate linear regression was used to identify the association between the foodservices used and INQ scores after adjusting for other covariates. RESULTS: We found that foodservice users exhibited a higher 1-day intake of total energy and macronutrients (all P < 0.05) and lower INQ scores (P < 0.01) than non-users. The INQ scores for total daily meals decreased with the frequency of foodservice use (P < 0.01). A significant association was observed between the non-use of foodservices and INQ scores (β = 0.29, P < 0.01) after adjusting for other covariates. CONCLUSIONS: The use of workplace foodservices contributed to higher dietary nutritional quality among workers. This study highlights the importance of expanding the scope of workplace foodservices to promote higher nutritional quality and healthy dietary habits among workers.

• The korean journal of orthodontics
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• v.53 no.5
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• pp.317-327
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• 2023

Objective: This study aimed to evaluate the association between low tongue position (LTP) and the volume and dimensions of the nasopharyngeal, retropalatal, retroglossal, and hypopharyngeal segments of the upper airway. Methods: A total of 194 subjects, including 91 males and 103 females were divided into a resting tongue position (RTP) group and a LTP group according to their tongue position. Subjects in the LTP group were divided into four subgroups (Q1, Q2, Q3, and Q4) according to the intraoral space volume. The 3D slicer software was used to measure the volume and minimum and average cross-sectional areas of each group. Airway differences between the RTP and LTP groups were analyzed to explore the association between tongue position and the upper airway. Results: No significant differences were found in the airway dimensions between the RTP and LTP groups. For both retropalatal and retroglossal segments, the volume and average cross-sectional area were significantly greater in the patients with extremely low tongue position. Regression analysis showed that the retroglossal airway dimensions were positively correlated with the intraoral space volume and negatively correlated with A point-nasion-B point and palatal plane to mandibular plane. Males generally had larger retroglossal and hypopharyngeal airways than females. Conclusions: Tongue position did not significantly influence upper airway volume or dimensions, except in the extremely LTP subgroup.

• Physical Therapy Korea
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• v.30 no.3
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• pp.211-220
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• 2023

Background: Smartphone addiction has emerged as a significant social problem. Numerous studies have indicated the association between smartphone use and discomfort in the musculoskeletal system of the upper extremities. Objects: This cross-sectional survey aimed to compare the characteristics of musculoskeletal pain in the neck, trunk, and upper limbs between individuals with smartphone addiction and those without addiction. Methods: We collected a total of 326 healthy individuals' data from China and Korea who had owned and used smartphones for more than 5 years between 20-50s through an online questionnaire consisting of 84 questions in four major sections. The first part contained basic information on the participant's personal characteristics and smartphones. The second part contained questions about smartphone use and posture. The third part was the smartphone addiction. The fourth part was to investigate musculoskeletal pain in various upper body parts. Results: Smartphone addiction has a weak negative correlation with age (r = -0.20, p < 0.01) and a weak positive correlation with the hours of smartphone use (r = 0.376, p < 0.01). Frequent musculoskeletal pain symptoms related to smartphone use were observed in the neck, shoulder, lower back, and wrists. The hours of smartphone use was slightly positively associated with the prevalence of musculoskeletal pain in the shoulder (r = 0.162, p < 0.05) and lower back (r = 0.125, p < 0.05). The prevalence of musculoskeletal pain in the neck (χ² = 3.993, p < 0.05), shoulder (χ² = 6.465, p < 0.05), and wrist (χ² = 4.645, p < 0.05) was significantly higher among females than males. Conclusion: The results suggest that smartphone addiction should be recognized as a dual concern encompassing both physical health and psychosocial aspects. Furthermore, healthcare professionals, including physicians and physical therapists, should consider clients' smartphone usage patterns when assessing and treating with musculoskeletal pain.

• Imaging Science in Dentistry
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• v.53 no.4
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• pp.375-381
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• 2023

Purpose: This study assessed the diagnostic performance of stitched and non-stitched cross-sectional cone-beam computed tomography (CBCT) images of non-displaced ovine mandibular fractures. Materials and Methods: In this ex vivo study, non-displaced fractures were artificially created in 10 ovine mandibles (20 hemi-mandibles) using a hammer. The control group comprised 8 hemi-mandibles. The non-displaced fracture lines were oblique or vertical, <0.5 mm wide, 10-20 mm long, and only in the buccal or lingual cortex. Fracture lines in the ramus and posterior mandible were created to be at the interface or borders of the 2 stitched images. CBCT images were obtained from the specimens with an 80 mm×80 mm field of view before and after fracture induction. OnDemand software (Cybermed, Seoul, Korea) was used for stitching the CBCT images. Four observers evaluated 56 (28 stitched and 28 non-stitched) images to detect fracture lines. The diagnostic performance of stitched and non-stitched images was assessed by calculating the area under the receiver operating characteristic curve (AUC). Sensitivity and specificity values were also calculated (alpha=0.05). Results: The AUC was calculated to be 0.862 and 0.825 for the stitched and non-stitched images, respectively (P=0.747). The sensitivity and specificity were 90% and 75% for the non-stitched images and 85% and 87% for the stitched images, respectively. The inter-observer reliability was shown by a Fleiss kappa coefficient of 0.79, indicating good agreement. Conclusion: No significant difference was found in the diagnostic performance of stitched and non-stitched cross-sectional CBCT images of non-displaced fractures of the ovine mandible.

• Imaging Science in Dentistry
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• v.54 no.2
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• pp.147-157
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• 2024

Purpose: The aim of this study was to explore the correlations of cone-beam computed tomographic findings with the apnea-hypopnea index in patients with obstructive sleep apnea. Materials and Methods: Forty patients with obstructive sleep apnea were selected from the ear-nose-throat (ENT) outpatient clinic, Faculty of Medicine, Mansoura University. Cone-beam computed tomography was performed for each patient at the end of both inspiration and expiration. Polysomnography was carried out, and the apnea-hypopnea index was obtained. Linear measurements, including cross-sectional area and the SNA and SNB angles, were obtained. Four oral and maxillofacial radiologists categorized pharyngeal and retropalatal airway morphology and calculated the airway length and volume. Continuous data were tested for normality using the Kolmogorov-Smirnov test and reported as the mean and standard deviation or as the median and range. Categorical data were presented as numbers and percentages, and the significance level was set at P<0.05. Results: The minimal value of the cross-sectional area, SNB angle, and airway morphology at the end of inspiration demonstrated a statistically significant association (P<0.05) with the apnea-hypopnea index, with excellent agreement. No statistically significant difference was found in the airway volume, other linear measurements, or retropalatal airway morphology. Conclusion: Cone-beam computed tomographic measurements in obstructive sleep apnea patients may be used as a supplement to a novel radiographic classification corresponding to the established clinical apnea-hypopnea index classification.

• 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.