• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1409-1415
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• 2021

The Gysel divider has the advantage of easily setting the resistor in the circuit. If the line impedance in the Gysel divider is set differently, the input signal can be distributed to the two output ports at various distribution ratios. This paper proposes the Gysel divider that can change the power distribution to 1:3 or 3:1 by changing the line impedance. The impedance change of the line can be implemented by placing a floating copper plate on the bottom of the microstrip-line. When the floating copper plate and the ground plane are connected, the line operates as the microstrip-line, and when the floating copper plate and the ground plane are disconnected, the line operates as the coplanar-line. The proposed Gysel divider was fabricated at the center frequency of 1.5GHz. The fabricated 3:1 Gysel divider has a stable value S₁₁ of below -17dB, S₂₁/S₃₁ of 4.8±0.2dB, S₂₁(to high output port) of -1.39±0.12dB and S₃₁(to low output port) of -6.15±0.08dB over 1.3~1.7GHz.

• Journal of the Korean Wood Science and Technology
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• v.49 no.4
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• pp.315-327
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• 2021

Purpose of this study is reviewing the use method for the sawdust (sawmilling by-product) and rice husk (Agriculture by-product) by adding charcoal, an eco-friendly material. Mixed composite boards were manufactured with those materials with each density and mixing ratio, and bending performance was investigated. When the addition ratio of sawdust, rice husk and charcoal is 50:20:20 and the resin addition ratio is 10%, as the density of the prepared mixed board ranges from 0.5 g/cm³ to 0.7 g/cm³, the bending strength was 0.42~3.24 N/mm², dynamic modulus of elasticity was 94.5~888.4 N/mm², and the static modulus of elasticity was in the range of 31.4~220.7 N/mm². As the density increased, the bending performance increased, indicating that the density had a significant effect on the bending performance. In a board prepared by setting the density of 0.6 g/cm³, the addition ratio of sawdust to 50%, and the addition ratio of rice husk and charcoal at different ratios, the bending performance showed a tendency to decrease as the addition ratio of charcoal increased. The relationship between the addition ratio of rice husk and charcoal, bending strength, resonance frequency, and dynamic and static bending modulus showed a rather low correlation with the values of the coefficient of determination (R²) of 0.4562, 0.4310, 0.4589, and 0.5847, respectively. Thus, we found that the effect of the addition ratio on the bending performance was small.

• Journal of The Korean Society of Clinical Toxicology
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• v.19 no.1
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• pp.1-7
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• 2021

Purpose: The purpose of this study was to conduct a systematic review to investigate the socio-economic benefits of the poison control center (PCC) and to assess whether telephone counseling at the poison control center affects the frequency of emergency room visits, hospitalization, and length of stay of patients with acute poisoning. Methods: The authors conducted a medical literature search of the PubMed, EMBASE, and Cochrane Library databases. Two reviewers evaluated the abstracts for eligibility, extracted the data, and assessed the study quality using a standardized tool. Key results such as the cost-benefit ratio, hospital stay days, unnecessary emergency room visits or hospitalizations, and reduced hospital charges were extracted from the studies. When meta-analysis was possible, it was performed using RevMan software (RevMan version 5.4). Results: Among 299 non-duplicated studies, 19 were relevant to the study questions. The cost-benefit ratios of PCC showed a wide range from 0.76 to 36 (average 6.8) according to the level of the medical expense of each country and whether the study included intentional poisoning. PCC reduced unnecessary visits to healthcare facilities. PCC consultation shortened the length of hospital stay by 1.82 (95% CI, 1.07-2.57) days. Conclusion: The systematic review and meta-analysis support the hypothesis that the PCC operation is cost-beneficial. However, when implementing the PCC concept in Korea in the future, it is necessary to prepare an institutional framework to ensure a costeffective model.

• Journal of The Korean Association For Science Education
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• v.41 no.2
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• pp.71-82
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• 2021

Learning efficiency can be maximized by careful matching of text features to expected reader features (i.e., linguistic and cognitive abilities, and background knowledge). The present study aims to explore whether this systematic principle is reflected in the development of science textbooks. The current study examined science textbook texts on 20 measures provided by Auto-Kohesion, a Korean language analysis tool. In addition to surface-level features (basic counts, word-related measures, syntactic complexity measures) which have been commonly used in previous text analysis studies, the present study included cohesion-related features as well (noun overlap ratios, connectives, pronouns). The main findings demonstrate that the surface measures (e.g., word and sentence length, word frequency) overall increased in complexity with grade levels, whereas the majority of the other measures, particularly cohesion-related measures, did not systematically vary across grade levels. The current results suggest that students of lower grades are expected to experience learning difficulties and lowered motivation due to the challenging texts. Textbooks are also not likely to be suitable for students of higher grades to develop the ability to process difficulty level texts required for higher education. The current study suggests that various text-related features including cohesion-related measures need to be carefully considered in the process of textbook development.

• Journal of the Korean Wood Science and Technology
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• v.31 no.4
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• pp.81-90
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• 2003

In this study, we investigated the weathering properties of Korean Rhus lacquers containing tung oil and their potential use as exterior coatings. The finished lacquers were prepared with a raw Korean Rhus lacquer or refined Korean Rhus lacquer content of 10, 20, 30 and 40 wt.% (corresponding to ratios of 10/90, 20/80, 30/70 and 40/60 by weight of Korean Rhus lacquer/tung oil, respectively). The curing temperature of the prepared lacquer increased with increasing the content of the raw Korean Rhus lacquer. This increased curing temperature is related to higher proportion of hydroxyl groups in the prepared lacquer, due to the content of the raw Korean Rhus lacquer. In accelerated weathering testing, the changes in the gloss and contact angle of the prepared lacquers showed a similar trend to that of traditional exterior oil stain. In addition, the prepared lacquers containing tung oil showed greater discoloration than traditional exterior oil stain. However, the discoloration of the prepared lacquer with a raw Korean Rhus lacquer content of 40 wt.%, and that of the prepared lacquer with refined Korean Rhus lacquer contents of 30 wt.% and 40 wt.%, showed a similar trend to that of traditional exterior oil stain. Consequentially, these prepared lacquers showed a potential for being used as exterior coatings.

• Journal of the Korean Electrochemical Society
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• v.24 no.4
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• pp.106-112
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• 2021

Catalyst poisoning by ionomers in membrane electrode assemblies of alkaline membrane fuel cells has been reported recently. We tried to improve the membrane electrode assembly's performance by controlling the solvent's ratio during electrode manufacturing. 4 Different mixing ratios of N-Methyl-2-pyrrolidone (NMP) and ethylene glycol (EG) gave four different cathode electrodes with platinum and Fuma-Tech ionomers. The electrode with higher EG improved polarization performance by about 36% compared to the NMP-based commercial ionomer. The dependence of the ionomer's dispersibility on the solvent seems responsible for the difference, which means that the non-uniform distribution of ionomers improves the performance of the electrode. High-frequency resistance, internal resistance corrected polarization curve, Tafel slope, mass activity, and impedance spectroscopy characterized the electrode. We can find that the existence of poor solvent improves cathode electrode performance. It seems to be the result of reduced poisoning of the catalyst according to the particle size distribution of the ionomer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.707-717
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• 2006

As an alternative to conventional prestressed concrete (PSC) girders, various types of PSC girders are either under development or have already been applied in bridge structures. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these new types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the dynamic interaction between bridge superstructures and passing trains is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate modal parameters of newly designed bridges before doing dynamic analyses. In the present paper, a 25 meters long full scale PSC girder was fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios at every prestressing stage. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied, in order to obtain precise frequency response functions and the modal parameters are evaluated varying with construction stages. Prestressed force effects on changes of modal parameters are analyzed at every incremental prestressing stage. With the application of reliable properties from modal experiments, estimation of dynamic performances of PSC girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of moving train. Dynamic displacements, impact factor, acceleration of the slab, end rotation of the girder, and other important dynamic performance parameters are checked with various speeds of the train.

• Journal of Nutrition and Health
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• v.57 no.2
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• pp.211-227
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• 2024

Introduction: Seaweed is a sustainable and underexplored source of bioactive compounds with potent anti-inflammatory activities. However, studies on the interaction between seaweed and genes on inflammation are limited. Purpose: We aimed to evaluate the relationships between seaweed consumption and the polygenic risk scores (PRS) and their interactions with high-sensitivity C-reactive protein (hs-CRP) levels. Methods: Information on seaweed consumption was collected using a food frequency questionnaire, which included laver, kelp, and sea mustard among the items consumed. A total of 31 hs-CRP-related single nucleotide polymorphisms (SNPs) were selected using genome-wide association studies and clumping analysis, and the individual PRS were calculated by weighting the effect size of each allele in the selected SNPs of 39,369 middle-aged (≥40 years) Koreans using the Korean Genome and Epidemiology Study (KoGES)-Health Examinees (HEXA) cohort data. To investigate the interaction between seaweed intake and the PRS on hs-CRP levels >1 mg/L, hazard ratios (HRs) and 95% confidence intervals (CIs) were assessed using multivariable Cox proportional hazards models. Results: During a mean follow-up period of 4.8 years, we recorded 436 patients with elevated hs-CRP levels. Women in the highest tertile of the PRS with the lowest quartile of seaweed intake had an increased incidence of elevated hs-CRP levels compared with women in the lowest tertile of the PRS with the lowest seaweed intake quartile (HR 2.34, 95% CI 1.23-4.45). No significant association was observed among the men. Conclusion: In conclusion, we identified a new interaction between the PRS, seaweed intake, and inflammation in Korean women, and this study suggests that the interaction between the identification of genetic predisposition and dietary seaweed intake may have an impact on determining the risk of developing hyperinflammation in the future.

• Annals of Occupational and Environmental Medicine
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• v.34
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• pp.15.1-15.9
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• 2022

Background: Most previous longitudinal studies on lifestyle and gastroesophageal reflux disease (GERD) have focused on physical activity rather than sitting time. The main purpose of this study was to investigate the relationship between prolonged sitting time and the development of erosive esophagitis (EE). Methods: A self-report questionnaire was used for measuring sitting time in the Kangbuk Samsung Health Study. Sitting time was categorized into four groups: ≤ 6, 7-8, 9-10, and ≥ 11 hours/day. Esophagogastroduodenoscopy (EGD) was performed by experienced endoscopists who were unawared of the aims of this study. Hazard ratios (HRs) and 95% confidence intervals (CIs) for the development of EE were estimated using Cox proportional hazards analyses with ≤ 6 hours/day sitting time as the reference. Results: There were 6,524 participants included in the study. During a mean follow-up of 3.14 years, 2,048 incident cases developed EE. In age- and sex-adjusted models, the HR in the group sitting ≥ 11 hours per day compared ≤ 6 hours per day was 0.88 (95% CI: 0.76-0.99). After further adjusting for alcohol intake, smoking status, educational level, history of diabetes, and history of dyslipidemia, sitting time was still significantly related to the risk of EE (HR, 0.87; 95% CI: 0.76-0.98). After further adjustment for exercise frequency, this association persisted (HR, 0.86; 95% CI: 0.76-0.98). In subgroup analysis by obesity, the relationship between sitting time and EE was only significant among participants with body mass index < 25 kg/m² (HR, 0.82; 95% CI: 0.71-0.95). Conclusions: Generally, prolonged sitting time is harmful to health, but with regard to EE, it is difficult to conclude that this is the case.

• Journal of Gastric Cancer
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• v.24 no.4
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• pp.436-450
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• 2024

Purpose: This study aims to explore the relationship between soy food consumption and gastric cancer (GC) risk, accounting for Helicobacter pylori infection status. Materials and Methods: We analyzed data from patients with GC and healthy individuals prospectively enrolled by 6 hospitals between 2016 and 2018. Dietary intake was evaluated using questionnaires that categorized seven dietary habits and 19 food groups. Multivariate logistic regression models were applied to examine associations. Model I adjusted for various epidemiological factors, while Model II included further adjustments for H. pylori infection. Primary exposures examined were consumption frequencies of nonfermented, unsalted soy foods (soybean/tofu) and fermented, salty soy foods (soybean paste stew). Results: A total of 5,535 participants were included, with 1,629 diagnosed with GC. In Model I, the frequency of soybean/tofu consumption was inversely related to GC risk; adjusted odd ratios (aORs) were 0.62 (95% confidence interval [CI], 0.48-0.8), 0.38 (95% CI, 0.3-0.49), 0.42 (95% CI, 0.33-0.53), and 0.33 (95% CI, 0.27-0.42) for 1 time/week, 2 times/week, 3 times/week, and ≥4 times/week. Consumption of 2 servings/week of soybean paste stew showed the lowest GC association, forming a V-shaped curve. Both low (aOR, 4.03; 95% CI, 3.09-5.26) and high serving frequencies of soybean paste stew (aOR, 2.23; 95% CI, 1.76-2.82) were associated with GC. The association between soy foods and GC in Model II was similar to that in Model I. The soy food-GC associations were consistent across sexes in Model I. Nonetheless, the positive correlation between frequent consumption of soybean paste stew (≥5 times/week) and GC was more pronounced in women (aOR, 7.58; 95% CI, 3.20-17.99) compared to men (aOR, 3.03; 95% CI, 1.61-5.88) in Model II. Subgroup analyses by H. pylori status and salty diet revealed a consistent inverse relationship between soybean/tofu and GC risk. In contrast, soybean paste stew showed a V-shaped relationship in H. pylori-positive or salty diet groups and no significant association in the H. pylori-negative group. Conclusions: Soybean/tofu intake is consistently associated with a decreased risk of GC. However, the relationship between soybean paste stew consumption and GC risk varies, depending on H. pylori infection status and dietary salt intake.