• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.6
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• pp.333-342
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• 2022

The blast analysis method entails the use of an empirical equation and application of the pressure-time history curve as an explosive load. Although this method is efficient owing to its simple model and short run time, previous studies indicate that it may not be appropriate for near-field explosions. In this study, we investigated why different results were observed for the analysis method by considering an RC beam under near-field explosion conditions with the scaled distance of 0.4-1.0 as an example. On this basis, we examined the application range of the empirical analysis method by using the finite element analysis program LS-DYNA. The results indicate that the empirical analysis method based on data from far-field explosion tests underestimates the impulse. Thus, the calculated deflection of the RC beam would be smaller than the measured deflection and arbitrary Lagrangian-Eulerian (ALE) analysis result. The ALE analysis method is more suitable for near-field explosion conditions wherein the structural responses are large.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.10-17
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• 2023

This paper describes the research and development of a 3.0 m Solar-Powered UAV system for mission flight that is based on the 4.2 m Solar-powered UAV. Both the Solar-Powered UAVs were lightened in weight by applying a composite fuselage and solar charging system. Also, a deep stall landing application and airbag module were installed for usability in mission performance. The flight performance of the Solar-Powered UAV system was verified through flight test. In particular, the 3.0 m Solar-Powered UAV performed continuous flight along the coastline of Jeju Island for 147 km in 3 hours and 50 minutes, and its performance as a mission flight was also confirmed.

• Journal of Korea Port Economic Association
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• v.39 no.1
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• pp.115-129
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• 2023

This study analyzed the risk spillover of BDI on shipping company stock prices through the Copula-CoVaR method based on daily data from January 4, 2010, to October 31, 2022. The main empirical analysis results and policy implications are as follows. First, copula results showed that there was a weak dependence between BDI and shipping company stock prices, and PAN, KOR, and YEN were selected as the most fitting model for dynamic Student-t copula, HMM was selected as the rotated Gumbel copula, and KSS was selected as the best model. Second, in the results of CoVaR, it was confirmed that the upside (downside) CoVaR was significantly different from the upside (downside) VaR in all shipping companies. This means that BDI has a significant risk spillover on shipping companies. In addition, as for the risk spillover, the downside risk is generally lower than the upside risk, so the downside and upside risk spillover were found to be asymmetrical. Therefore, policymakers should strengthen external risk supervision and establish differentiated policies suitable for domestic conditions to prevent systematic risks from BDI shocks. And investors should reflect external risks from BDI fluctuations in their investment decisions and construct optimal investment portfolios to avoid risks. On the other hand, investors propose that the investment portfolio should be adjusted in consideration of the asymmetric characteristics of up and down risks when making investment decisions.

• Korean Journal of Culture and Social Issue
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• v.25 no.4
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• pp.249-277
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• 2019

This study examined the involuntary retirement of executives in conglomerates based on Williams' need-threat temporal model of ostracism(2009), which explains the psychology of individuals facing social exclusion in the stages of reflexive, reflective and resignation. In-depth interviews were conducted on 15 retirees from conglomerates, and their contents were used for phenomenological method of analysis. As a result, in the reflexive stage of need-threat temporal model of ostracism, they experienced cognitive panic and emotional panic immediately following retirement. Due to an unexpected shocking experience of retirement notice, they experienced cognitive numbness first, and repressed the following negative feelings cognitively to hide them. In the reflective stage, retirees dream of 'a complete restoration to their best performance in the past', but as such expectation fails, they don't adjust to the reality more due to 'unrealistic thought', 'self-deception', and 'shift responsibility'. In resignation stage, a long-term failure to satisfy the desire led them to experience a sense of defeat and helplessness. Such results were reviewed and compared to Williams' need-threat temporal model of ostracism, and the implications of such result on the nation, companies and retirees in terms of the response to retirement.

• Land and Housing Review
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• v.14 no.3
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• pp.37-53
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• 2023

This study conducted an empirical analysis of how different types of living retail businesses affected housing prices during the COVID-19 pandemic, with a particular focus on both global and local time series effects. The main findings are three folds: First, from a global perspective, the study discovered that the presence of living retail businesses had a significant impact on prices of nearby apartment, varying according to their type. Secondly, the impact of COVID-19 on the retail industry varied depending on the type of business. Thirdly, when viewed from a local standpoint, the impact of the retail business sector on apartment prices due to COVID-19 pandemic was substantial, varying across regions and business types. This implies that external shocks like COVID-19 have the potential to alter the role and perception of living retail businesses. In light of this, the study has put forth policy implications aimed at mitigating the adverse effects of living retail businesses and enhancing residential quality.

• Land and Housing Review
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• v.14 no.3
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• pp.55-75
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• 2023

Based on prior studies on real estate policy, tax policy, and financial policy, this study examined how tax policy and financial policy affected real estate prices using monthly data from January 2014 to December 2021. We performed a VAR model using unit root tests, cointegration tests, as well as conducted impulse response analysis and variance decomposition analysis. The results are as follows. First, the tax regulation index and the financial regulation index had no discernible impact on housing prices. Specifically, a one-sided stabilizing regulatory policy was ineffective and, instead, led to unintended side effects, such as price increases resulting from reduced transaction volume. Secondly, mortgage rates had a negative impact on the housing sale price index. In other words, an increase in interest rates might led to a decrease in housing prices. Thirdly, an increase in the transfer difference, which involves capital gains tax, has a positive effect on housing prices. This led to rising housing prices because the transfer taxes were shifted to buyers, causing them to hesitate to make purchases due to the increased tax burden. Fourthly, both acquisition taxes and mortgage loans had relatively little impact on housing prices.

• Korean Journal of Social Welfare Studies
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• v.42 no.1
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• pp.399-432
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• 2011

The purpose of this study is to understand the adjustment process of families adopting an older child, and to generate a substantial theory. To achieve this purpose, we conducted in-depth interviews with mothers adopting an older child and analyzed data with qualitative analysis approach. From the analysis, theoretical model has been made, and the model includes the adoptive families' diverse experiences, barriers to adjustment as well as resources and strategies that they mobilized and used for smooth adjustment. Their experiences in the process of adjustment consisted of five phases: unfamiliar meeting, shock, fighting alone without support, control, and stability. Barriers to adjustment process were composed of adoptees' problem behaviors, loss of time, lack of preparation, lack of experiences, repetition of the vicious circle, withstanding alone, improper resources, lack of support, and being criticized. Resources and strategies that families adopting an older child utilized were individual resources and ability such as rearing experiences, intellectual ability, willingness, belief, and perspective change; family system such as spouse and other offsprings; informal support system such as extended families, relatives, friends, neighbors, and other families adopting an older child; formal resources such as adoption workers and helping professionals. From our results, we suggested policy and practice guidelines to help adjustment experiences for families adopting an older child.

• Journal of the Daesoon Academy of Sciences
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• v.32
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• pp.109-136
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• 2019

The purpose of this study is to look at the concept of Gaebyeok as used by Kang Jeungsan (姜甑山) from a civilizational perspective. The combination of East Asian civilization during the period of Korea's port-opening and the subsequent inflow of Western powers with material civilization all at the forefront in the late Joseon Korea, served as the driving force for a new civilizational transition. Unlike the Chuk-sa Party and the Gae-hwa Party, modern Korean religions that emphasized Gaebyeok also responded to Western civilization and suggested a new view of civilization. Kang Jeung-san, resisting discrimination and oppression, presented a civilization built upon mutual beneficence while criticizing Western civilizations which centered on reason. Amid this process of the spread of modern Western civilization, Jeungsan declared the construction of a new civilization to the people who were negatively impacted by various social factions, such as class and gender discrimination, political corruption, exploitation via political corruption, and the inflow of Western powers. Jeungsanist Thought developed criticisms of materialism and human alienation, and this resulted in the claim of Gaebyeok. This was an expression of efforts to build a new civilization that aimed to harmonize, integrate, and thrive. The new civilization envisioned by Jeungsan was that of a society run according to mutual beneficence, and it can be summarized as a 'Civilization of Harmonious Union' that integrates philosophical thought and civilizational models of both East and West. This could also be referred to a 'Civilization of Public-commons and Harmony between Divine Beings and Human Beings (神人公共).' The life of Jeungsan was a life spent in the service of curing the world to save the lives of humanity. Since then, his 'movement of mutual beneficence' as observed in Mugeuk-do and Taegeuk-do were also efforts to build the new civilization envisioned by Jeungsan.

• Journal of the Korean Geotechnical Society
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• v.26 no.12
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• pp.5-17
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• 2010

Coarse granular material is used as important fill material in most of large embankments such as railway, road, dam and so on. Therefore, the accurate design parameters of the coarse granular material are necessarily required in design and construction. The behavior of the coarse granular material was not well understood because of the lack of large testing equipment capable of coarse granular material. A large triaxial testing system was developed in this research, capable of large specimens of 500 mm, 300 mm and 150 mm in diameter. In the new large triaxial testing system, the load cell is installed inside the triaxial cell and axial displacement is measured locally on a specimen in order to improve control and measurement in small strain level. Urethane specimens of 300 mm and 50 mm in diameter were prepared. The large triaxial tests were performed on the 300 mm diameter urethane specimens while RC/TS and impact echo tests on the 50 mm diameter urethane specimens to verify this testing system. In this verification test results, we could ascertain the reasonable test results of the KRRI large triaxial testing system.

• Applied Chemistry for Engineering
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• v.34 no.3
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• pp.285-290
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• 2023

Poly-lactic acid (PLA) is the most promising polymer in additive manufacturing as an alternative to acrylonitrile butadiene styrene (ABS). Since it is produced from renewable resources such as corn starch and sugar beets, it is also biocompatible and biodegradable. However, PLA has a couple of issues that limit its use. First, it has a comparatively low glass transition temperature of around 60 ℃, such that it exhibits low thermal resistance. Second, PLA has low impact strength because it is brittle. Due to these problems, scientists have found methods to improve the crystallinity and ductility of PLA. Polyethylene glycol (PEG) is one of the most studied plasticizers for PLA to give it chain mobility. However, the blend of PLA and PEG becomes unstable, and phase separation occurs even at room temperature as PEG is self-crystallized. Thus, it is necessary to investigate the optimal mixing ratio of PLA-PEG at the molecular scale. In this study, molecular dynamics will be conducted with various ratios of L-type PLA (PLLA) or DL-type PLA-PEG (PDLA-PEG) systems by using BIOVIA Materials Studio.