• Physical Therapy Rehabilitation Science
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• v.4 no.1
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• pp.11-16
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• 2015

Objective: Prone bridge exercise is one of the core strengthening exercise for improving abdominal, lower and upper extremity muscles. In addition, coactivation of the trunk muscles and extremities is important for treatment of low back pain. This study aimed to investigate the correlation between the thickness, cross-sectional area of the target muscle, and endurance during prone bridge exercise. Our hypothesis was that an increase in muscle thickness is positively related to the hold time for the static prone bridge exercise. Design: Cross-sectional study. Methods: Fourteen healthy university students (8 men and 6 women) voluntarily participated in the study at Sahmyook University. Hold time for the prone bridge with one and both legs was measured. The resting and contracted thickness of the lateral abdominal, rectus femoris, and triceps muscles was measured using rehabilitative ultrasound imaging. The correlation between muscle thickness and endurance for maintenance time was evaluated. Results: The prone bridge with both legs and the contraction thickness of the triceps muscle showed a positive correlation (r=0.692, p<0.05); the prone bridge with one leg and the contraction thickness of the internal oblique and transversus abdominis muscles showed a positive correlation (r=0.545, 0.574, p<0.05, 0.05, respectively). Conclusions: Endurance for the prone bridge exercise with a stable support surface is correlated with the contraction thickness of arm muscles; the prone bridge exercise with an unstable support surface is correlated with the contraction thickness of the deep abdominal muscles.

• Korean Journal of Social Welfare
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• v.61 no.2
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• pp.85-106
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• 2009

The main purpose of this paper is to examine the structural determinants of regional variations of poverty in Korea. Poverty rates and independent variables in Seoul, 6 other metropolitan areas, and 8 provinces except Jejudo from the year of 1998 through 2006 were pooled as unit of analysis. The pooled cross-sectional time-series regression(TSCSREG) using SAS program was adapted for the analysis. As a result of the analysis, absolute poverty and relative poverty of Gangwondo and Chungcheongnamdo were relatively higher, and that of Seoul and Ulsan metropolitan area were lower than other areas. And, the increase of financial self-reliance, social welfare expenditure, rate of standard workers, and rate of workers in manufacturing sector were associated with lower poverty rates. Therefore, place-based policies should be considered as another poverty-fighting tool in conjunction with people-based policies.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.6
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• pp.3722-3730
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• 2015

The performance improvement of a small centrifugal compressor for waste water treatment has been conducted by the design change of vaneless diffuser and volute casing. Existing two compressors use a common impeller, but the width and length of the vaneless diffuser and the cross-sectional shape of the volute casing are different, respectively. Based on the experiment of the existing two compressors and their CFD results, the design of the vaneless diffuser and the volute casing has been changed. It was found that the strength of the interaction among the volute tongues, the vaneless diffusers and the impellers of two existing/one improved compressors, was affected by the cross-sectional area and inlet radial length of the volute casing including system losses' change. The efficiency of the impeller with one existing design was increased as the decrease of the width of the vaneless diffuser, but losses at the diffuser were accumulated. In conclusion, approximately 2.88%p efficiency increase at the design point of the new compressor with the improved design has been confirmed by CFD analysis results.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.437-446
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• 2006

A fabrication method fur high-aspect-ratio microchannels in stainless steel using laser-assisted thermochemical wet etching is reported in this paper. The fabrication of deep microchannels with an aspect ratio over ten is realized by applying a multiple etching process with an optimization of process conditions. The cross-sectional profile of the microchannels can be adjusted between rectangular and triangular shapes by properly controlling laser power and etchant concentration. Excellent dimensional uniformity is achieved among the channels with little heat-affected area. Microchannels with a width ranging from 15 to $50{\mu}m$ can be fabricated with an aspect ratio of ten and a pitch of 150 m or smaller. The effects of process variables such as laser power, scan speed, and etchant concentration on the fabrication results, including etch width, depth, and cross-sectional profile are closely examined.

• Journal of the Korean Society of Visualization
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• v.19 no.2
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• pp.56-62
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• 2021

Solid oxide fuel cells (SOFCs) is the high efficiency fuel cell operating at high temperatures ranging from 700-1000℃. Design of the flow paths of the fuel and air in SOFCs is important to improve cell performance and prevent cell degradation. However, the uneven distribution of current density in the traditional type having one inlet and outlet causes cell degradation. In this regard, the parallel flow path with two inlet and outlets was designed and compared to the traditional type based on computational fluid dynamics (CFD) simulation. To check the cell performance, hydrogen distribution, velocity distribution and current density distribution were monitored. The results validated that the parallel designs with two inlets and outlets have a higher cell performance compared to the traditional design with one inlet and outlet due to a larger reaction area. In case of uniform-type paths, more uniform current density distribution was observed with less cross-sectional variation in flow paths. In case of contracted and expanded inflow paths, significant improvement of performance and uniform current density was not observed compared to uniform parallel path. Considering SOFC cell with uniform current density can prevent cell degradation, more suitable design of SOFC cell with less cross-sectional variation in the flow path should be developed. This work can be helpful to understand the role of flow distribution in the SOFC performance.

• The korean journal of orthodontics
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• v.52 no.5
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• pp.345-353
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• 2022

Objective: To investigate airway volumes using cone-beam computed tomography (CBCT) by skeletal patterns, sex, and cervical vertebral maturation (CVM) stages in Korean adolescents. Methods: The sample consisted of pretreatment CBCT and cephalograms of 95 adolescents (aged 12-19) obtained out of 1,611 patients examined for orthodontic treatment from 2018 to 2020 in Kyungpook National University Dental Hospital. The samples were classified into two sex groups; three skeletal pattern groups, four chronological age groups and four CVM stages. Nasopharyngeal volumes (NPV), oropharyngeal volumes (OPV), total pharyngeal airway volume (TAV) and minimum cross-sectional area (MCA) measurements were taken from the CBCT. Multiple linear regression analyses to find out which one of the independent variables are good predictors for airway variables. Significant factors were analyzed by two-way multivariate analysis of variance (MANOVA) then multiple comparisons were analyzed using a t-test, and Fisher least significant difference. Results: Age, sex, CVM, and Sella-Nasion-B point have significant influence on airway variable. Males and females showed similar patterns of change in chronological age groups 1-3; however, males had larger NPV, OPV, and MCA at CVM in group 4. According to CVM stages, males had larger OPV, TAV, and MCA at CVM stage 6 (p-value: 0.019, 0.021, 0.015, respectively) and no sex differences at CVM stages 3, 4, and 5. Conclusions: Skeletal patterns have an effect on airway volume. Sex differences were found in CVM 6.

• Journal of Trauma and Injury
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• v.35 no.1
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• pp.3-11
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• 2022

Purpose: The increasing use of electric personal mobility devices (ePMDs) has been accompanied by an increasing incidence of associated accidents. This study aimed to investigate the characteristics of ePMD-related injuries and their associated factors. Methods: This cross-sectional study was conducted using data from the Emergency Department-based Injury In-depth Surveillance database from 2014 to 2018. All patients who were injured while operating an ePMD were eligible. The primary outcome was the rate of severe injury, defined as an excess mortality ratio-adjusted Injury Severity Score of ≥25. We calculated the adjusted odds ratios (AORs) of outcomes associated with ePMD-related injuries. Results: Of 1,391,980 injured patients, 684 (0.05%) were eligible for inclusion in this study. Their median age was 28 years old, and most injuries were sustained by men (68.0%). The rate of ePMD-related injuries increased from 3.1 injuries per 100,000 population in 2014 to 100.3 per 100,000 population in 2018. A majority of the injuries occurred on the street (32.7%). The most commonly injured area was the head and face (49.6%), and the most common diagnosis was superficial injuries or contusions (32.9%). Being aged 55 years or older (AOR, 3.88; 95% confidence interval, 1.33-11.36) and operating an ePMD while intoxicated (AOR, 2.78; 95% confidence interval, 1.52-5.08) were associated with severe injuries. Conclusions: The number of emergency room visits due to ePMD-related injuries is increasing. Old age and drunk driving are both associated with serious injuries. Active traffic enforcement and safety regulations regarding ePMDs should be implemented to prevent severe injuries caused by ePMD-related accidents.

• Computers and Concrete
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• v.31 no.3
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• pp.253-265
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• 2023

In this research, the gene expression programming (GEP) technique was employed to provide a new model for predicting the maximum loading capacity of concrete-encased steel (CES) columns. This model was developed based on 96 CES column specimens available in the literature. The six main parameters used in the model were the compressive strength of concrete (f_c), yield stress of structural steel (f_ys), yield stress of steel rebar (f_yr), and cross-sectional areas of concrete, structural steel, and steel rebar (A_c, A_s and A_r respectively). The performance of the prediction model for the ultimate load-carrying capacity was investigated using different statistical indicators such as root mean square error (RMSE), correlation coefficient (R), mean absolute error (MAE), and relative square error (RSE), the corresponding values of which for the proposed model were 620.28, 0.99, 411.8, and 0.01, respectively. Here, the predictions of the model and those of available codes including ACI ITG, AS 3600, CSA-A23, EN 1994, JGJ 138, and NZS 3101 were compared for further model assessment. The obtained results showed that the proposed model had the highest correlation with the experimental data and the lowest error. In addition, to see if the developed model matched engineering realities and corresponded to the previously developed models, a parametric study and sensitivity analysis were carried out. The sensitivity analysis results indicated that the concrete cross-sectional area (A_c) has the greatest effect on the model, while parameter (f_yr) has a negligible effect.

• Safety and Health at Work
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• v.14 no.4
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• pp.375-383
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• 2023

Background: Working despite feeling ill - presenteeism - is a widespread behavioral phenomenon. Previous research has shown that presenteeism is influenced by various work-related and personal factors. It's an illness behavior leading to a range of negative but also positive consequences. Due to coronavirus disease 2019 (COVID-19) pandemic, remote work has become the "new normal" for many employees. But so far, little is known about presenteeism in remote work. This study aims to investigate presenteeism in remote work by looking at the extent of remote presenteeism, differences to presenteeism in on-site work, and associated factors. Methods: A nationwide cross-sectional online survey was conducted in Germany with N = 233 participants. Data were analyzed using descriptive statistics, t-tests, and correlation analysis. Results: The results reveal that presenteeism is prevalent in remote work x = 4.13 days (Md = 3; D = 2; s = 4.95). A low ability to detach from work (r = -.17; p = .005) and low supervisor support (r = -.14; p = .02) is associated with more remote presenteeism days. Remote working conditions seem to facilitate presenteeism. Conclusion: This study provides empirical insights into a subject area of great societal relevance. The results show that awareness should be raised for presenteeism in remote work. It should be regarded as a behavior that can be functional or dysfunctional, depending on the individual situation. Supervisor support and detachment should be fostered to help reduce dysfunctional presenteeism. Promotion of health literacy might help remote workers to decide on a health-oriented illness behavior. Further research is vital to analyze to what extent and under which circumstances presenteeism in remote work is (dys)functional and to derive clear recommendations.

• Clean Technology
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• v.12 no.4
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• pp.211-216
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• 2006

In this study, we investigated the potential changes in the cross sectional area of the rectangular microchannel with various zeta potentials and hydraulic diameters. We changed height/width ratio as 1, 1/2, and 1/3 and investigated its effect on the potential change. For this research, FEMLAB(Comsol, verson 3.0) was used to investigate the theoretical potential distribution. The potential changes in the cross section shows that right and left surfaces affect to some ranges. For the same area and shape, the potential value is directly proportional to the zeta potential change. With the decrease in the H/W ratio, the electrical double layer is condensed to the side surfaces.