• The Journal of Korean Academy of Prosthodontics
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• v.58 no.2
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• pp.103-109
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• 2020

Purpose: The purpose of this study was to evaluate the preload maintenance of the retaining screw when using anaerobic sealing agents in implant fixture and abutment components. Specifically, the study examines the effects of anaerobic sealing agents on different types of screws. Materials and methods: External hexagon implants made of titanium and anti-rotational abutments were used. Titanium abutment screws and ebony abutment screws from the same manufacturer were used. The experiment was divided into four groups (n = 10 in each group). In the control group, no sealing agent was used at the implant fixture and abutment screw interface. All abutment screws were tightened according to the manufacturer's recommended torque (30 N.cm). After 24 hours, the removal torque (detorque) of each screw was measured using a digital torque gauge device. The data were analyzed by two-way ANOVA test according to normality distribution satisfaction. Results: Looking at the results for each group, titanium screws and no treatment showed detorque values of 20.3 ± 1.6 N.cm. titanium screws and applied anaerobic sealing agent showed detorque values of 32.4 ± 6.7 N.cm. Ebony screws and no treatment showed detorque values of 20.2 ± 1.5 N.cm. ebony screws and applied anaerobic sealing agent showed detorque values of 30.4 ± 4.5 N.cm. Conclusion: The detorque value was higher in the case of using anaerobic sealing agents in both the titanium screw and ebony screw groups. But there was no difference between the two screws.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.29 no.2
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• pp.106-110
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• 2021

In this study, the main factors affecting the number of passengers and cargo volume transported by air between Korea, China and Japan over the past 20 years are to be identified. For the analysis, data from three countries' GDP and per capita as well as exchange rates and international oil prices were used, and OLS multiple regression analysis and fixed effect analysis were performed. As a result of the analysis, both the number of passengers and cargo volume transported by air showed a negative (-) direction for GDP, which represents the country's economic power, and a positive (+) direction, for per capita GDP, which represents income level. And the increase in the exchange rate between China and Japan acted in a positive (+) direction on the increase in the number of passengers, and the effect of oil prices was found to be limited.

• Journal of Digital Convergence
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• v.17 no.3
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• pp.79-92
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• 2019

This study analyzes the effects of freight transportation income, capital, asset, non-operating expenses, and debt ratio on the debts of inner port freight transportation businesses through the GLS of panel regression analysis and the estimation of fixed effects model. The factors and hypotheses were established through a theoretical background review, and the financial statement and profit and loss data of inner port freight transportation businesses for 10 years from 2006 to 2015 were analyzed. The results showed that assets had positive effects on debts, and negative effects on capital, non-operating expenses, and debt ratio, but no effect on freight transportation income. This result empirically demonstrates the tendency of inner port freight transportation businesses to secure assets by increasing debts, creation of debt reduction leverage effect using non-operating expenses such as interest expenses through bank borrowing, and the adoption of management characteristics and financial operation method to lower the debt ratio by reducing capital more than debts. In future studies, it is necessary to analyze coastal port freight transportation business by industry (oil tankers, cargo ships, and barge ships), and regions such as East, West and South sea.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.367-374
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• 2019

We investigate the effect of soil-structure interaction (SSI) on the response of LNG storage tanks to vertical seismic excitation depending on the type of foundation. An LNG storage tank with a diameter of 71 m on a clay layer with a thickness of 30 m upon bedrock, was selected as an example. The nonlinear behavior of the soil was considered in an equivalent linear method. Four types of foundation were considered, including shallow, piled raft, and pile foundations (surface and floating types). In addition, the effect of soil compaction within the group pile on the seismic response of the tank was investigated. KIESSI-3D, an analysis package in the frequency domain, was used to study the SSI and the stress in the outer tank was calculated. Based on an analysis of the numerical results, we arrived at three main conclusions: (1) for a shallow foundation, the vertical stress in the outer tank is less than the fixed base response due to the SSI effect; (2) for foundations supported by piles, the vertical stress can be greater than the fixed base stress due to the increase in the vertical impedance due to the piles and the decrease in radiation damping; and (3) soil compaction had a miniscule impact on the seismic response of the outer tank.

• Korean Journal of Social Welfare Studies
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• v.43 no.2
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• pp.61-85
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• 2012

The purpose of this study is to examine whether the national pension affects the life satisfaction of old age, using the first and third-wave data from the Korean Retirement and Income Study. The study analyzes the relationship between the national pension and life satisfaction, using several operational definitions of these two variables. This study utilizes the Difference-in-Difference(2D) models and panel data analysis. The main results are : First, the result of simple 2D shows that there is not significantly difference between the pensioner and that of non-pensioner. Second, the result of 2D regression also shows that pension is not significantly associated with life satisfaction of the old age. Lastly, the result of fixed-effect model confirms that the national pension does not have a statistically meaningful effect on the life satisfaction, controling for the unobserved characteristics of the old age. This study also conducts sensitivity analysis and discusses policy implications.

• Journal of the Economic Geographical Society of Korea
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• v.13 no.4
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• pp.697-709
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• 2010

The purpose of this paper is to analyze the effects of education and training on labor productivity of the leading firms in Busan during the period of 1999~2000. In order to control for firm heterogeneity and the endogeneity problem of education and training, we employed fixed effects model and 2SLS. Our empirical results showed that firms expenditures per capita on education and training were positively correlated with their labor productivity. We also tested whether the effects of education and training on labor productivity vary with firm size or across industries. It is shown that, while firm size makes no statistical differences, the effect of education and training on labor productivity is smaller in service industry than in manufacturing one. From heterogeneous effect of education and training across industries, we could infer that policies to support various education and training programs in service industry are needed to be reinforced to improve the competitiveness of service industry.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.4
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• pp.95-106
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• 1992

This paper presents a comparative evaluation of five different types of steel fibers used as reinforcing material in concrete beams. Two types of plain and RC beams were prepared to compare the relative flexural behavior. The fibers used were dog bone (paddled), both ends hooked. コ-type straight. crimped and wavy type with aspect ratio of 43 to 75. Fiber volume fraction of 1 to 2% were used while shear span to depth ratio (aid) and steel ratio p were fixed. Fiber reinforcement effect index Ef and effective toughness index Te were adopted to evaluate fiber reinforcing effects. The effect of fiber reinforcement on flexural strength is higher in plain beams than in RC beams. Hooked and dog bone type fibers were found to be more effective than the other type ones in enhancing the flexural strength and post-peak energy absorption capacity of concrete beams.

• Journal of the Korean Data and Information Science Society
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• v.23 no.4
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• pp.649-656
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• 2012

The present study was carried out to summarize the effect of caffeine in the lipid metabolic by meta-analysis. The association measure to test effect of caffeine was the Hedges's standardized mean difference (HG). In this particular fixed-effect model of Hedges's standardized mean difference, weight gain, heart weight, serum total lipid, serum triglycerides and liver triglycerides were significantly decreased (p < 0.05). Also, serum HDL cholesterol and serum LDL cholesterol were significantly increased. In this case of heterogeneous variable, random effect model was applied. In this model, weight gain, heart weight, serum total lipid, serum triglycerides, serum LDL cholesterol and liver triglycerides were significantly decreased in caffeine treated group. Also HDL-cholesterol was significantly increased in caffeine treated group.

• Korean Journal of Cognitive Science
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• v.31 no.4
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• pp.103-136
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• 2020

This study compares the parafovea preview effect of adolescent group and adult group with different ages using eye tracking experiment. Also, this study confirms that the starting point parameter of the one boundary diffusion model can explain the data obtained through eye tracking experiments. In two experiments, parafoveal information processing was examined using the boundary technique. In Experiment 1, reading times were compared between the conditions given high frequency words preview versus masking preview. In Experiment 2, the condition in which low frequency words were given to parafovea preview information and the condition in which parafovea preview was masked were compared. We found that both the adolescent group and the adult group showed a parafovea preview effect. Also, first fixation, single fixation, and gaze duration of the two groups were different based on the word property shown in the parafovea. The first fixation data obtained in the two experiments were divided into quantiles and fitted into one boundary diffusion model. From the results, we argue that the parafovea preview information processing in the reading was described as the starting point parameter of the one boundary diffusion model.

• International Area Studies Review
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• v.14 no.3
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• pp.178-204
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• 2010

This study analyzes the effects Korea's grant aid to 53 African countries, focusing on its impacts on improving HDI (Human Development Index) of each recipient country, through panel data analysis. According to the OLS panel analysis, Korea's grant aid on information and communication (IC) sector showed positive and significant correlation with HDI, but aid on administrative system and environment showed negative correlation with HDI. Also, according to the fixed effect panel analysis, aid on IC sector showed positive correlation with HDI, but aid on administrative system showed negative correlation with HDI. In particular, effects of aid was different across the region. In North African region, aid on health improved HDI. However, in Sub-Saharan African region, aid on IC was more effective in improving HDI. This results imply that grand aid on Africa needs to be coordinated strategically across regions and sectors. This paper is meaningful in providing ways that can be mutually beneficial both to donor and recipient countries of grant aid.