• The korean journal of orthodontics
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• v.15 no.2
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• pp.291-301
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• 1985

Fifty subjects who were to be treated with fixed orhodontic appliances by light wire edgewise technique were selected. Bands with different marginal depth were made in first molar and direct bonding brackets were bonded in second premolar. For determining the effects of fixed orthodontic appliance on the gingival tissue, the changes of clinical crown length, periodontal pocket depth, gingival sulcus fluid were checked. The results were as follows: 1. Gingival condition was deteriorated after wearing the fixed orthodontic appliance, and the deteriorative rate was decreased gradually. 2. The greatest gingival change was occurred in the maxillary first molar among the experimental teeth. 3. The gingival change of maxillary teeth was greater than that of mandibular teeth. $(p\leq0.01)$ 4. The greater gingival change was occurred around subgingivally located band than around supragingivally located band. 5. Comparing the gingival changes of banded teeth with them of bonded teeth, the gingival tissue was more effected by oral hygiene than by type of appliances. 6. In the quantitive changes of gingival crevicular fluid, there was no exact relationship with gingival inflammation.

• The Korean Journal of Financial Management
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• v.25 no.4
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• pp.25-51
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• 2008

In this paper, we analyse empirically the fixed asset investment smoothing of working capital of firms listed on Korea Securities Market. The main results of this study can be summarized as follows. Firms will seek to lower long-term cost by smoothing fixed asset investment and maintaining stationary investment with working capital. Working capital is not only an important use of fund, but also a source of liquidity that should be used to smooth fixed asset investment relative to cash flow shocks if firms face financial constraints. Working capital investment is more sensitive than fixed asset investment to cash flow fluctuations. If firms face financial constraints, working capital investment will compete with fixed asset investment for the limited pool of available cash flows. So, fixed asset investment will have negative relationship with working capital investment. However, criticism that the positive correlation between cash flows and fixed asset investment could arise simply because cash flows is proxy variable for investment demand. Finally, controlling for the fixed asset investment smoothing effects of working capital results in a much larger estimate of the long run impact of financial constraints. Financial constraints is measured by dividend payout ratio and market access level. Fazzari et al. (1988), Fazzari and Petersen (1993), and Faulkender et al. (2008) emphasize that low dividend firms or market unaccessible firms are more likely to face financial constraints, and rarely make use of new equity issuing. The results from empirical analysis show that financial constraints can be better explained using 'adjustment cost' concept. Specifically, the results show that financial constraints exist and that in order to measure financial constraint effects more succinctly, fixed asset investment smoothing effects with working capital should be considered.

• Journal of Family Resource Management and Policy Review
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• v.20 no.3
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• pp.1-23
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• 2016

This study analyzes the effects of caring for grandchildren on Korean grandparents' health, using the Korean Longitudinal Study of Aging from 2006 to 2012. We investigate how caregiving is provided and analyze the effects of caregiving on grandparents' physical health, mental health, and health-related behaviors. As elderly people's health is generally frail, it is unclear whether the provision of childcare affects their health negatively. We control for the endogeneity of caregiving by an individual fixed effect (FE) model and instrumental variable-fixed effect (FE-IV) models. Using these models, we determine the endogeneity of caregiving and show that the significant effects of caregiving on health disappear as we control for endogeneity in the FE and FE-IV models. Even after controlling for endogeneity, we find that caregiving increases the probability of feeling pain as well as the number of different types of pain. Furthermore, caregiving increases the probability of restrictions on daily activities because of pain. On the other hand, caregiving reduces the symptoms of depression. In relation to health-related behaviors, caregiving reduces the probability of physical exercise and regular meals. Our results imply that although caregiving has a positive effect on mental health, the increase in physical pain and in non-healthy behaviors may lead to a deterioration of the caregiver's long-term health, which in turn may increase the medical costs of the elderly. Potential policy alternatives are discussed in the paper.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.1
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• pp.85-93
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• 2015

Previous studies have estimated crash prediction models with the fixed effect model which assumes the fixed value of coefficients without considering characteristics of each intersections. However the fixed effect model would estimate under estimation of the standard error resulted in over estimation of t-value. In order to overcome these shortcomings, the random effect model can be used with considering heterogeneity of AADT, geometric information and unobserved factors. In this study, data collections from 89 intersections in Daejeon and estimates of crash prediction models were conducted using the random and fixed effect negative binomial regression model for comparison and analysis of two models. As a result of model estimates, AADT, speed limits, number of lanes, exclusive right turn pockets and front traffic signal were found to be significant. For comparing statistical significance of two models, the random effect model could be better statistical significance with -1537.802 of log-likelihood at convergence comparing with -1691.327 for the fixed effect model. Also likelihood ration value was computed as 0.279 for the random effect model and 0.207 for the fixed effect model. This mean that the random effect model can be improved for statistical significance of models comparing with the fixed effect model.

• Journal of the Korean Operations Research and Management Science Society
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• v.32 no.1
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• pp.27-51
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• 2007

We analyze the effects of the sellers' strateiges on the final bid prices in internet auctions. We focus on the following three strategies of the seller adoption of the buy-price, setting the starting bid price, and adoption of 'the effective fixed price' which means that the starting bid price is set near the buy-price. In addition, the number of units sold single-unit or multi-unit, and item characteristics, such as whether the food is a search product (functional product) or an experience product (non-functional product), are also considered. We use real data on bids for 4 items from an online auction site. We find that in an auction for experience products when sold as single units, adopting the buy-price strategy raises the final bid price. We also find that in multi-unit auctions, starting the auction at 'the effective fixed price' raises the final bid price.

• Journal of Korea Trade
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• v.23 no.2
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• pp.76-87
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• 2019

Purpose - This study empirically analyzes the effects of the European Union-South Korea Free Trade Agreement on Korean exports in major sectors. Design/Methodology - This study is based on the augmented gravity model with a panel data set covering 51 countries between the years 2000 and 2015. Findings - Main findings of the present study is that the agreement has affected the chemical sector the most. Fixed effects estimation predicted a positive trade effect of 38.3%, while Poisson maximum likelihood estimation predicted an impact of 4.75% in the chemical export sector. Regression results for the other sectors only show insignificant effects. Originality/value - The findings imply that the effects of the EU-South Korea free trade agreement on the Korean exports are quite specific compared to the European ones, meaning that the Korean government should focus on sector-specific programs to maximize the welfare benefits of the free trade agreement.

• Journal of the Korean Data and Information Science Society
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• v.17 no.1
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• pp.123-130
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• 2006

This paper discusses about how to build up a mixed-effects model using cumulative logits when some factors are fixed and others are random. Location effects are considered as random effects by choosing them randomly from a population of locations. Estimation procedure for the unknown parameters in a suggested model is also discussed by an illustrated example.

• The korean journal of orthodontics
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• v.24 no.1 s.44
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• pp.221-231
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• 1994

The short-term effects of plaque control instruction were studied in 42 adolescent orthodontic patients under active fixed treatment. At first visit, all the patients were received plaque control instruction using materials such as oral hygiene education slides, dentiform, disclosing agents, tooth brush and interdental brush. After that, Pateints were asked to perform the tooth brushing according to instructions. Such a procedure was repeated every week lot 3 weeks. Plaque index and bleeding index were scored once a week for 4 weeks and were compared according to ages, sex and duration with fixed appliance. The results were as follows: 1. Plaque control instruction was effective in reducing plaque accumulation and gingival inflammation of the orthodontic patients. 2. The effect of plaque control instruction was continued during 3 weeks among all groups of subjects, and it was prominent at the first week. 3. There was no statistically significant difference in the effects of the plaque control of instruction according to sex, ages, or duration with fixed appliances.

• Wind and Structures
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• v.21 no.6
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• pp.625-639
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• 2015

Monopiles have been most widely used for supporting offshore wind turbines (OWTs) in shallow water areas. However, multi-member lattice-type structures such as jackets and tripods are also considered good alternatives to monopile foundations for relatively deep water areas with depth ranging from 25-50 m owing to their technical and economic feasibility. Moreover, jacket structures have been popular in the oil and gas industry for a long time. However, several unsolved technical issues still persist in the utilization of multi-member lattice-type supporting structures for OWTs; these problems include pile-soil-interaction (PSI) effects, realization of dynamically stable designs to avoid resonances, and quick and safe installation in remote areas. In this study, the effects of PSI on the dynamic properties of bottom-fixed OWTs, including monopile-, tripod- and jacket-supported OWTs, were investigated intensively. The tower and substructure were modeled using conventional beam elements with added mass, and pile foundations were modeled with beam and nonlinear spring elements. The effects of PSI on the dynamic properties of the structure were evaluated using Monte Carlo simulation considering the load amplitude, scouring depth, and the uncertainties in soil properties.

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1155-1163
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• 2012

This paper suggests a method for getting sums of squares due to sources of variation under the assumption of two-way fixed effects model. The method used for calculating the quantities due to fixed-effects is based on the projections of an observation vector y on the column space generated by the model matrix X under the assumed model. The suggested method shows that the calculation of Type II sums of squares by projections is much easier than the classical Type II analysis.