• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.23 no.4
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• pp.157-164
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• 2023

This paper suggests O(n²) polynomial time heuristic algorithm for corporate tax structure optimization problem that has been classified as NP-complete problem. The proposed algorithm constructs tax tree levels that the target holding company is located at root node of Level 1, and the tax code categories(T_e) 1,4,3,2 are located in each level 2,3,4,5 sequentially. To find the maximum tax-relief path from source(S) to target(T), firstly we connect the minimum witholding tax rate _minr_w(u, v) arc of node u point of view for transfer the profit from u to v node. As a result we construct the spanning tree from all of the source nodes to a target node, and find the initial feasible solution. Nextly, we find the alternate path with minimum foreign tax rate _minr_fi(u, v) of v point of view. Finally we choose the minimum tax-relief path from of this two paths. The proposed heuristic algorithm performs better optimal results than linear programming and Tabu search method that is a kind of metaheuristic method.

• Journal of Navigation and Port Research
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• v.47 no.4
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• pp.202-211
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• 2023

In maritime accidents, collisions involving fishing vessels are more frequent and severe than those involving other types of vessels. Previous cases of collision accidents caused by fishing vessels causing serious damage implied that fishing vessels maintained high speeds until just before the collision and that they collided with much larger vessels. This study investigated the correlation between the severity of ship damage resulting from fishing vessel collisions and the vessel's speed. The effective impact speed commonly used in the road transport sector was utilized to analyze ship collision accidents. The study collected collision data between fishing vessels and between fishing vessels and non-fishing vessels from accident investigation reports from 2016 to 2022. The effective impact speed was calculated for a total of 617 vessels. After using binary and multinomial logistic regression methodology, the analysis was carried out with effective impact speed as the independent variable and severity of accident as the dependent variable. The analysis revealed a statistically significant correlation between the effective impact speed and the severity of ship damage, indicating that the severity of ship damage is influenced not only by the effective impact speed but also by the tonnage of the vessel.

• Korean Journal of Social Welfare Studies
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• v.40 no.1
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• pp.197-234
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• 2009

Typological theories of offending postulate that childhood-onset delinquents have a high likelihood of being serious and chronic offenders and that there are a distinct set of risk factors predicting early-onset antisocial behaviors. It is useful to empirically classify children into subgroups based on their deviant behaviors because it helps us to identify unique factors associated with each subgroup. Using the first two waves of the Korean Youth Panel Survey, Elementary School Data, this study aimed(a) to empirically classify 5th graders into latent delinquent subgroups, and (b) to examine the impact of individual, familiar, school, and peer factors on the latent delinquent classes. Latent class analysis yielded three latent classes based on 15 indicators of deviant behaviors - delinquent class, low-level delinquent class, & normative class. The results from multivariate multinomial logistic regression analyses revealed that being male, reporting low self-control, coming from poor family, high association with deviant peers, and being bullied increased the risk of being in the delinquent class. Moreover, low self-control, aggression, domestic violence, low level of attachment to teachers, and deviant peers independently increased the risk of being in the low-level delinquent class compared to the normative class. Based on the study findings, implications for practice as well as future studies were discussed.

• The Journal of the Convergence on Culture Technology
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• v.9 no.1
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• pp.685-690
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• 2023

It was analyzed that the volume of deep excavation works adjacent to existing underground structures is increasing according to the population growth and density of cities. Currently, many underground structures and tracks are damaged by external factors, and the cause is analyzed based on the measurement results in the tunnel, and measurements are being made for post-processing, not for prevention. The purpose of this study is to analyze the effect on the deformation of the structure due to the excavation work adjacent to the urban railway track in use. In addition, the safety of structures is evaluated through machine learning techniques for displacement of structures before damage and destruction of underground structures and tracks due to external factors. As a result of the analysis, it was analyzed that the model suitable for predicting the structure management standard value time in the analyzed dataset was a polynomial regression machine. Since it may be limited to the data applied in this study, future research is needed to increase the diversity of structural conditions and the amount of data.

• Journal of Korean Society of Forest Science
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• v.112 no.2
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• pp.248-257
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• 2023

Because of various societal changes, such as the recent improvement in income levels and extension of the flexible work system, the demand for forest recreation activities and their use patterns are undergoing a change. Accordingly, it is necessary to identify the characteristics of each type through the segmentation of the overall forest recreation and welfare markets and to plan differentiated policies for each market type. This study classifies the forest recreation and welfare activities according to four types of users (i.e., passive usage type, ordinary type, active lover type, and indifferent type) using the Latent Class Analysis and examines their demographic and socioeconomic characteristics to explain the differences between the groups. Three policy implications were derived from the results obtained: 1) the group experiencing forest recreation welfare is subdivided; 2) the socioeconomic characteristics that distinguish the groups undertaking forest recreation activities were identified; and 3) the policy targets and characteristics that can increase the experience of forest recreation welfare were identified. This study is insightful as it suggests differentiated policies for each group and proposes policy measures to move to the desirable group.

• Nuclear Engineering and Technology
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• v.18 no.1
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• pp.1-8
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• 1986

A magnetic quadrupole doublet was fabricated for use at the pre-target position of SNU 1.5MV Van de Graaff accelerator and then its optical characteristics were measured and analysed. The physical dimensions are: pole length 180mm, aperture radius 25mm, pole tip radius 28.75mm. Material for poles and return yokes is carbon steel KS-SM40C. Coils have 480 turns per one pole and air-cooling is adopted. Applying the d.c. current 2.99$\pm$0.03A to the lens, and using the Hall probe, magnetic field elements $B_{\theta}$ , $B_{\gamma}$, were measured at the selected Points along each coordinate direction r,$\theta$, z. From the area integration and orthogonal polynomial fitting for the measured data, the magnetic Field gradient G=566.3$\pm$2.1 gauss/cm at lens center, the effective length L=208.3$\pm$1.44mm along the lens axis have been obtained. The harmonic contents were determined up to 20-pole from the generalized least squares fitting. The results indicate that sextupole/quadrupole is below 1.4$\pm$0.9% and all the other multipoles are below 0.5% in the region within 18mm radius at the center of lens.

• Journal of Korea Entertainment Industry Association
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• v.13 no.5
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• pp.127-138
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• 2019

This study was a secondary data analysis using statistics from the 13th (2017) Korea Youth Risk Behavior Web-based Survey (KYRBS) to investigate the relationship between health behaviors and physical activity among Korean adolescents. A total of 62,276 adolescents in middle and high schools enrolled in this study. Physical activity utilized moderate and vigorous physical activity variables. Health behaviors used smoking, drinking, eating, sedentary behavior, and sleep duration variables. Statistical analyses were performed applying complex sample analysis method. Chi-square tests were used to compare physical activity according to health behaviors. Multivariate multinomial logistic regression analyses were conducted to examine the relationship between health behaviors and physical activity, adjusted for general characteristics. Current smoking and current drinking were associated with high levels of moderate and vigorous physical activity. Consuming fruits≥1 times/day, vegetables≥3 times/day, and sweet drinks≥3 times/week were associated with high levels of moderate and vigorous physical activity. Eating breakfast≥5 times/week was associated with high levels of moderate physical activity, but not with vigorous physical activity. Sedentary behavior≥2 hour/day was associated with low levels of moderate and vigorous physical activity. Sleep duration<7 hour/day was associated with high levels of moderate physical activity and low levels of vigorous physical activity. These findings suggest that since there is an interrelationship between health behaviors and physical activity among adolescents, intervention programs aiming at promoting physical activity and healthy lifestyles should consider a multiple behavior approach rather than an individual behavior approach.

• 한국노년학
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• v.29 no.4
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• pp.1463-1478
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• 2009

The purpose of this study is to investigate the characteristics of the elderly based on the types of Kyungrodang participation and explores ways toward development of Kyungrodang. A national sample data, collected by the Korean Institute for the Health and Social Welfare in 2004 is analyzed by employing Chi-Square test of independence, ANOVA, and multiple logistic regression(n=3,005). A significant difference is noted in age, area, and socioeconomic status among the elderly based on the types of Kyungrodang participation. The results show that those elderly living in rural areas with older and lower socioeconomic status are more likely to participate at Kyungrodang, whereas, elderly living in urban areas with younger and higher socioeconomic status are less likely to participate at Kyungrodang and discontinue to use the services. Although there is a difference between the gender, the most significant reason for not using and discontinuing Kyungrodang is because the elderly can not get along with the other participants. In other words, the major problem that needs to be solved is to socializing and providing service programs satisfying all participants. Based on the results and recent socioeconomic changes of the older population, some policy issues are suggested for the development of Kyungrodang.

• 한국노년학
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• v.34 no.2
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• pp.387-407
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• 2014

This study aims to identify the multiple trajectories of depressive symptoms and the characteristics of each trajectory group among the elderly. This study uses five waves of longitudinal data from the Korean Welfare Panel Study (KWPS, 2006-2010). Subjects were older adults aged 60 and over who had completed at least three waves between 2006 and 2010. A total of 4,181 respondents were analyzed. The latent growth mixture model and the multiple logistic regression model were mainly used for data analysis. The major findings were as follows: After controlling for the variables of gender, age, education, marital status, self-assessed health, and poverty, this study identified four different trajectory classes: stable low depressive symptoms (71.8%), high but decreased depressive symptoms (10.6%), moderate but increased depressive symptoms (7.9%), and an increased, then a decreased pattern of depressive symptoms (9.7%). The characteristics of theses trajectories as compared to previous studies were a lower percentage of 'stable low depressive symptoms', no 'persistently high depressive symptoms', and higher level of depressive symptoms. Also, the elderly in the stable low trajectory group had better health status, higher self-esteem and a good relationship with family members, having longer working periods, and more living in non-poverty. In addition, chronic health problems, loss of spouse, and household income differentiated the increased and then decreased pattern from the low stable pattern. Also, age and public pension differentiated the moderated but increased pattern from the low stable pattern. Based on the findings of this study, the researchers suggested political and practical implications for reducing depressive symptoms in later life.

• 한국노년학
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• v.31 no.1
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• pp.15-31
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• 2011

The purpose of this study is to explore the transition to retirement of the middle-aged in Korea according to the notion of "the career job" and "the bridge job". In order to scrutinize basic elements for the transition, three aspects such as the job history of the middle-aged, the characteristics of the demographic and economic status were investigated through the one to three wave of Korean Retirement and Income Study(KReIS). In addition, the characteristics of the career job and the bridge job were analyzed by both descriptive statistics and the conditional transition probability. Moreover, the influential factors to the job status of the middle-aged were examined by the multi-nominal logistic regression. The results of the study are as followed: first, gradual retirement is increasing in the transition to retirement of the middle-aged in Korea. Over time, the career job is decreasing whilst bridge job is increasing. However, the quality of the bridge job is poorer than the career job in terms of wage, employment status, industry, and occupation. Lastly, the middle-aged who work in the bridge job have vulnerable characteristics, so they work in the bridge job to supplement their economic needs. The results can be influential in the adjustment of the labor policies for the middle-aged in Korea. Moreover, the partial pension system could be a good alternative since the pension system is needed to protect the vulnerable situation of the middle-aged in Korea.