• Journal of the Korean Geosynthetics Society
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• v.23 no.2
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• pp.19-27
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• 2024

Geotechnical structures such as dams, tunnels, and slopes require regular inspection and monitoring to ensure stability. Domestically, drones and accelerometers have become common tools for inspecting and monitoring various structures. However, drones have difficulty identifying internal changes in structures and the subsurface, and accelerometers generally serve for seismic design or strain measurement purposes. Therefore, this paper proposes to utilize accelerometers to monitor the internal information of the ground on a real-time or periodic basis. The proposed method utilizes a part of the analysis technique from the SASW test to monitor the stability and state changes of geotechnical structures. Cases where SASW was used to evaluate the safety of geotechnical structures, such as slopes, dams, and tunnels, were reviewed to verify the suitability of the technology. To make the proposed method more practical, the study considered using only the first-step analysis to derive the dispersion curve rather than the second-step analysis to determine the shear wave velocity profile, which requires complex analysis. The proposed technique is expected to enable the continuous monitoring and inspection of geotechnical structures by utilizing accelerometers.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.36 no.4
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• pp.149-157
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• 2024

In this study, hydraulic model tests were conducted to investigate the effect of a horizontal damping plate on the motion of the pontoon-type floating structure. The floating structures with and without the horizontal damping plates were fabricated with the scale of 1/20 and their motion responses to the regular and irregular wave conditions were investigated. From the comparison for the responses of each model with 16 wave conditions, it could be known that the damping plate made the response of the the pontoon to be smaller by about 5 to 10 % compared with the normal rectangular pontoon.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.525-536
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• 2020

The study data used for the analysis of this study were obtained from the raw data during the 1st survey of the 2nd wave of the 2019 Panel Survey on the Employment of Persons with Disabilities conducted by the Korea Employment Agency for Persons with Disabilities. The results showed that, for regular workers, when there was a fixed term of employment contract, it was more likely that the job was retained for 12 months or longer. For the day laborers, workers without a fixed-term employment contract were more likely to retain their jobs for 12 months longer. This suggests that owing to the types of jobs that did not consider disabilities, people with disabilities were facing difficulties in terms of the options available in their job choices and their self-decisions. Therefore, the state would have to develop more job types and skills for these individuals to expand their career options. The growth in the employment of people with disabilities by small businesses that hire day laborers will depend on the diversification of the employment subsidy, which is again dependent on the size of the businesses.

• Journal of the Korean Applied Science and Technology
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• v.37 no.2
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• pp.354-361
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• 2020

The purpose of this study was to investigate the effects of regular taekwondo training on neurotrophic factors and cognitive function in obese middle-aged women. Thirty-three middle-aged women with obesity were selected for this study and randomly assigned into a control group(CG, n=18) and an taekwondo group(TG, n=15). The TG performed taekwondo training 5 times weekly for 16 weeks, while the CG did not exercise training. Serum brain-derived neurotrophic factor(BDNF), vascular endothelial growth factor(VEGF), and insulin-like growth factor-1(IGF-1) levels were analyzed and Stroop Color and Word tests were performed before and after the intervention. The serum BDNF and IGF-1 levels were significantly increased in the TG after the intervention(p<.05). On the other hand, no statistically significant differences were found in the serum VEGF levels, or in the Stroop Color and Word Test scores(p>.05). These results suggest that regular taekwondo training may be affects levels of peripheral neurotrophic factors but not cognitive function in obese middle-aged women.

• The Journal of the Acoustical Society of Korea
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• v.36 no.2
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• pp.108-114
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• 2017

We have experimentally analyzed the self-radiation impedance of an ultrasonic transducer with a square radiation surface that is used as a vibrator in underwater ultrasonic detection systems. The radiation reactance and the radiation resistance were measured in the range from 1 to 3 of ka that is the product of a wave number and a length of the edge of the square vibrator. By comparing the measured results with those of theoretical calculation of the radiation impedance using a series, we confirmed the validity of the experimental method and experimentally confirmed the variation trend in the radiation impedance of the square radiation surface.

• The Korean Journal of Community Living Science
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• v.28 no.3
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• pp.429-446
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• 2017

The current study aims to identify factors associated with private tutoring of college students in Korea. For this purpose, this study used the Korean Education and Employment Panel survey, which contains items regarding whether or not college students receive private tutoring as well as the monthly costs of private lessons. The current study focuses on private English lessons due to the very low response rates of other types of private tutoring. For the analysis, the 5th wave of KEEP collected in 2008 was selected, and a Heckman selection model was employed, including three categories of variables: individual, school, and parent/household factors. The results have revealed that for the selection model (receiving private English tutoring or not), having received private lessons in high school, gender, and level of satisfaction regarding the respondent's current university were significant. In terms of the outcome model (cost for private English tutoring in college), university admission type (rolling vs. regular), living with parents, school type (4-yr university vs. others), being in debt to cover private lesson fees in high school, and monthly household income had significant effects. This article also discusses the results and implications for future research and policy makers.

• Journal of the Society of Naval Architects of Korea
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• v.47 no.3
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• pp.421-429
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• 2010

In this paper, in order to analyze the dynamic response of a floating crane when it lifts a heavy cargo, the boom of the floating crane is considered as an elastic beam. The boom is divided into elements based on finite element formulation and the floating frame of reference formulation and nodal coordinates are employed to model the boom as a flexible body. As an extension of the previous study, in order to consider spatial motion in waves, the coupled equations of motions of the 6 degree of freedom (DOF) floating crane and 6 DOF cargo are developed based on the flexible multibody system dynamics. The 3 dimensional deformation of the elastic boom is considered with 18 DOF. The dynamic simulation of the floating crane and the cargo is performed under regular wave conditions with various cargo weights. Finally, the effects of the elastic boom on lifting cargo are discussed by comparing the simulation results between the elastic boom and a rigid boom.

• Journal of The Korean Astronomical Society
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• v.48 no.4
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• pp.207-212
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• 2015

We introduce the Lee Sang Gak Telescope (LSGT), a remotely operated, robotic 0.43-meter telescope. The telescope was installed at the Siding Spring Observatory, Australia, in 2014 October, to secure regular and exclusive access to the dark sky and excellent atmospheric conditions in the southern hemisphere from the Seoul National University (SNU) campus. Here, we describe the LSGT system and its performance, present example images from early observations, and discuss a future plan to upgrade the system. The use of the telescope includes (i) long-term monitoring observations of nearby galaxies, active galactic nuclei, and supernovae; (ii) rapid follow-up observations of transients such as gamma-ray bursts and gravitational wave sources; and (iii) observations for educational activities at SNU. Based on observations performed so far, we find that the telescope is capable of providing images to a depth of R = 21:5 mag (point source detection) at 5-σ with 15 min total integration time under good observing conditions.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.4 no.1
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• pp.10-17
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• 1992

An elliptic finite difference numerical model is presented for the effective calculation of wave transformation on the water of slowly varying sea bed with currents. Elliptic governing equation has been used, which is derived by Joeng(1990) and Chae et al(1989). Numerical results are compared with analytic solution and laboratory data(Ito and Tanimoto, 1972), and show good agreement. This model is very efficient for modelling large area because of no numerical stable condition and high calculation speed. The capability and utility of the model are illustrated by application to current coexisting area.

• Health Policy and Management
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• v.23 no.2
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• pp.162-175
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• 2013

Background: The purpose of this study was to analyze the association between social support, psychosocial factors, and health behaviors of old adults in korean society. Methods: The data which was used in this study was extracted from the second wave of the Korean longitudinal study of aging in 2008. A total of 3,978 elderly aged 65 years or older were included in this study. We conducted $X^2$-test, t-test for the elderly health behavior in accordance with their social support and psychosocial factors. Also, multivariate logistic regressive analysis was performed in order to find how degree social support and psychosocial factors are associated with health behavior after adjusting sex, age, smoking (alcohol drinking), and other significant variables. The data was processed by SAS ver. 9.1 and Stata SE ver. 11. Results: Social support in older adults was significantly associated with lower smoking, alcohol drinking, exercise, and eating habit. Also, psychosocial factors were positively associated with smoking, alcohol drinking, regular exercise, and eating habit. Conclusion: health behaviors of old adults are likely to be vulnerable to social support and psychosocial factors. To increase effectiveness of the health policy for the elderly in Korea, it is important to adapt new strategy to include the empowerment of elderly's social networks, policy support to enhance subjective expectation, and life satisfaction.