• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.28 no.6
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• pp.224-231
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• 2016

When aiming to reduce the low frequency noise of a subway guest room through sound absorbing treatment methods inside the wall of a tunnel the resonator is often more effective than a porous sound absorbing material. Therefore, the perforated panel type resonator embedded with a perforated panel is proposed. The perforated panel is installed in the neck, which is then extended into the resonator cavity so that it can ensure useful volume. The absorption performance of the perforated panel type of resonator is obtained by acoustic analysis and experiment. The analytical results are in good agreement with the experimental results. In the case of multiple perforated panel type resonators, as the number of perforated panels increase, the 1st resonance frequency is moved to a low frequency band and sound absorption bandwidth is extended on the whole. In order to obtain excellent absorption performance, the impedance matching between multi-panels should be considered. When the perforated panel in the resonator is combined with a porous material, the absorption performance is highly enhanced in the anti-resonance and high frequency range. In case of the resonator inserted with perforated panels of 2, the 2nd resonance frequency is shifted to a low frequency band in proportion to the distance between perforated panels.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.406-416
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• 2019

This study aims to examine whether a parental neglect affects an adolescent's peer attachment and adult media immersion has a mediating effect. To achieve this goal, the first year of middle school panel of 'the 6th(2015) Korean Children and Youth Panel Survey(KCYPS)' was utilized. Using SPSS PROCESS Macro developed by Hayes, 'Bootstrapping' was employed to examine the significancy of the mediating effect on 563 objectives. According to the study, first of all, more parental neglect gave rise to less peer attachment. Second, the adult media immersion partly mediates the parental neglect and the adolescent's peer attachment. The practical implications of this results are below : First, parents' care and affection inside a home is necessary to formulate the healthy peer attachment of adolescent. Second, a parent education is important to prevent an adolescent's adult media immersion. Third, an adult media education for an adolescent is desired.

• 한국사회정책
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• v.24 no.1
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• pp.187-211
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• 2017

This study aimed to examine the relationship between children's perceived levels of neglect and abuse and community characteristics. For this, it analyzed data from the Korean Children & Youth Panel Survey and data collected from the Statistics Korea. Main findings are as follows. First, children who resided in the communities with higher report rates of child maltreatment perceived higher levels of neglect. Second, children who resided in the communities with higher rates of welfare recipients, lower residential mobility, or lower rates of those who responded they had someone to ask for help when they were sick tended to perceive higher levels of neglect. Third, while the perceived levels of abuse were explained by the child factors, those of neglect were explained by child, family, and community factors. Based on these findings, this study suggested the interventions on the community levels and future research directions.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.91-92
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• 2023

With the development of technology, interest in the implementation of free-form buildings is increasing, and research on producing free-form panels is being conducted accordingly. Since free-form buildings are curved and consist of geometric shapes, there are many problems with the production technology of free-form panels that implement them. Due to the inability to reuse molds, the cost of disposal of construction waste and waste of manpower for assembly increase the construction period and construction cost. To improve these limitations, a 3D printed concrete nozzle for FCP production was developed. However, this technology is not quantitatively extruded according to the shape of the panel, and there is a problem that residues are generated. Therefore, an free-form panel extrusion experiment was conducted to analyze the limitations of existing nozzles and to analyze the requirements for the development of new concrete extrusion nozzles. Existing nozzles were unable to be quantitatively extruded, resulting in errors. Due to the weak pressure of the screw and the inability to adjust the internal pressure, detailed extrusion speed control was impossible, and residue generation in the opening and closing device seemed to be the cause. Therefore, a pump capable of quantitative concrete pressure transfer and a pressure control device for easy extrusion of concrete are required. In addition, it is judged that it is necessary to develop an opening and closing device and an extrusion device that do not generate residues. The results of this study are expected to provide information for FCP production and production and to be a basic study of technologies necessary for the production of free-form building panels.

• Korean Journal of Social Welfare
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• v.64 no.2
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• pp.185-212
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• 2012

This study examines changes in income inequality and income mobility associated with a transition to old age. In understanding the dynamics of income distribution over the later life course, it is important to explore the changes in income dispersion and the changes in relative income positions jointly. Data come from Korean Labor and Income Panel Study(KLIPS) 2nd, 7th, 12th wave. The results are as follows. First, a transition to old age is associated with an increase in income inequality. The Gini index of inequality increased steadily over the life course. Second, a transition to old age is associated with substantial income mobility. The Spearman's rank correlation coefficient between two periods was the lowest at the time of the transition. Increasing income dispersion and significant income mobility can be conceptualized as "income insecurity", since the older population are less likely to cope with income fluctuations. Third, in explaining such changes over time, changes in work life during old age and a subsequent decrease in earnings seem to be the most influential factor.

• Journal of Advanced Navigation Technology
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• v.14 no.5
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• pp.668-676
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• 2010

Optimal net residual dispersions (NRDs) of inline dispersion management (DM) for compensating the signal distortion of $24{\times}40$ Gbps WDM channels in optical transmission links, in which optical phase conjugator (OPC) is placed from 250 km to 750 km by spacing 50 km in 1,000 km total transmission length of single mode fiber (SMF), are induced as a function of various ope positions. And, performance improvement of WDM channels in transmission links with the induced optimal NRD is investigated by comparing with that in transmission links with NRD = 0 ps/nm. It is confirmed that optimal NRDs are decided by displacement of OPC from mid-way of total transmission length, i.e. 500 km, and the determinating and applying of optimal NRD in case of ope displacement into transmitters is more stable and effective than that in case of ope displacement into receivers from 500 km. Also, it is shown that eye opening penalties (EOPs) of WDM channels in transmission links with optimal NRD are improved by 1.5 dB to 3 dB, which are related with OPC position, from that obtained in transmission links with fixed NRD of 0 ps/nm.

• 한국사회정책
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• v.19 no.2
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• pp.9-38
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• 2012

Little research has empirically examined cross-sector job mobility between non-profit and for-profit sector despite the rise and increased importance of this phenomenon in Korea. Using the panel data of Graduates Occupational Mobility Survey(GOMS) by the Korea Employment Information Service, this study attempts to examine changes in job satisfaction(overall score and 10 facet scores) associated with four types(retention at non-profits, turnover from non-profits to for-profits, turnover from for-profits to non-profits, and retention at for-profits) of cross-sector job mobility among college graduates by employing a first difference model. Major results reveal that (1) in the group of retention at non-profits, 'overall job satisfaction' is consistently higher; (2) in the group of retention at non-profits, negative change in 'overall job satisfaction' is the largest; (3) in the group of 'for-profits to non-profits,' negative change in 'stability of employment' is the smallest; (3) in the group of 'non-profits to for-profits,' negative change in 'job contents' is the smallest; (4) in the group of 'non-profits to for-profits,' negative change in 'weekly work hours' is the largest; (5) in the group of retention at non-profits, negative change in 'potential growth & development' is the largest; and (6) in the group of retention at non-profits, negative change in 'social reputation' is the smallest;. This study has made a start in a new area of inquiring attempting to explain cross-sector job mobility and raises implications for future research.

• Journal of the Korea Institute of Building Construction
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• v.23 no.3
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• pp.251-260
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• 2023

The construction of free-form structures with intricate curved exteriors necessitates the use of bespoke molds. To fulfill this requirement, a blend of Phase Change Material(PCM) and Ultra-High Performance Concrete(UHPC) is utilized. PCM endows the solution with recyclability, while UHPC facilitates the effortless execution of curvature in the mold fabrication process. However, it's worth mentioning that the melting point of PCM hovers around 58-64℃, and the heat emanating from UHPC's hydration process can potentially jeopardize the integrity of the PCM mold. Hence, experimental validation of the mold shape is a prerequisite. In the conducted experiment, UHPC was poured into two distinct mold types: one that incorporated a 3mm silicone sheet mounted on the fabricated PCM mold(Panel A), and the other devoid of the silicone sheet(Panel B). The experimental outcomes revealed that Panel A possessed a thickness of 3.793mm, while Panel B exhibited a thickness of 5.72mm. This suggests that the mold lacking the silicone sheet(Panel B) was more susceptible to the thermal effects of hydration. These investigations furnish invaluable fundamental data for the manufacturing of ultra-high strength irregular panels and PCM molds. They contribute substantially to the enrichment of comprehension and application of these materials within the realm of construction.

• Korea Trade Review
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• v.43 no.3
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• pp.169-198
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• 2018

The purpose of this paper is to investigate the impact of exchange rate volatility on the export of Korean machinery intermediate goods to East Asian countries using the export demand model. In order to secure the validity of the estimation of the exchange rate volatility for the export of machinery intermediate goods, various methods of volatility measurement are used including the GARCH model, the moving average standard deviation and the 12-month fixed average standard deviation. The long-term relationship between variables was analyzed by applying the panel cointegration tests and DOLS & FMOLS panel estimations. Analysis results found that prior to the global financial crisis in 2008, the total exports of machinery and exchange rate volatility positively affect the exports of intermediate goods such as general machinery, electronic machinery and transportation equipment, but did not affect the exports of precision machinery intermediate goods. After the global financial crisis, however, exchange rate volatility negatively affected total exports and the exports of all machinery intermediate goods. When analyzing the period before and after the global financial crisis, it had a positive impact on exports of precision machinery intermediate goods and a negative effect on total exports and the exports of other machinery intermediate goods.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.128-128
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• 2018

최근 디스플레이 기술은 보다 가볍고, 얇고, 선명한 스마트 형태로 발전되고 있다. 특히 스마트산업의 성장으로 터치스크린패널(Touch Screen Panel, TSP)을 사용하는 기술이 다양해짐에 따라 더 높은 감도와 해상도를 달성하기 위한 핵심기술이 필요한 실정이다. TSP는 저항막 방식, 정전용량 방식, 적외선 방식, 초음파 방식 등 다양한 방식이 있다. 그 중 정전용량방식 터치 패널 (Capacitive type touch panel, CTTP)은 다른 유형에 비해 빠른 반응속도 및 멀티 터치 기능 등의 이점을 가지고 있기 때문에 연구의 초점이 되고 있다. 이를 실현하기 위해서 CTTP은 가시광영역의 높은 투과율과 낮은 비저항을 필요로 하기 때문에 박막의 초 슬림화 및 고 결정화도가 선행되어야만 한다. CTTP에 사용되는 투명전극 소재 중에서 40%의 비중을 차지하고 있는 ITO박막은 내구성과 시인성이 좋으나 생산 비용이 비싸다는 단점이 있다. 한편, 반응성 스퍼터링은 기존에 단일 소결체를 사용한 DC마그네트론 스퍼터링법보다 높은 증착률과 낮은 생산 비용으로 초박막을 만들 수 있다는 장점을 가진다. 본 실험에서는 In/Sn (2wt%) 금속 합금 타깃을 사용한 반응성 스퍼터링법을 이용하여 기판 온도 (RT 및 $140^{\circ}C$)에서 두께 30 nm의 In-Sn-O (ITO)박막을 증착하고, 대기 중 $140^{\circ}C$ 온도에서 시간에 따라 열처리한 후 박막의 물성을 관찰하였다. 증착 중 기판 가열을 하지 않은 ITO 박막의 경우, 열처리 시간이 증가함에 따라 비저항은 감소하였고, 홀 이동도는 현저하게 증가하였으며 캐리어 밀도에서는 별다른 차이가 없었다. 이를 통해 비저항의 감소는 캐리어 농도보다는 결정화를 통한 이동도의 증가와 관련 있다는 것을 확인할 수 있었다. 열처리 시간에 따른 박막의 핵 생성 및 결정 성장은 투과 전자 현미경(TEM)으로 명확하게 확인하였으며, 완전 결정화 된 박막의 grain size는 300~500 nm로 확인되었다. 기판온도 $140^{\circ}C$에서 증착한 박막의 경우, 후 열처리를 하지 않은 상태에서도 이미 결정화 된 것을 확인할 수 있었으며, 후 열처리 시에도 grain size에는 큰 변화가 없었다. 이는 증착 중에 박막의 결정화가 이미 완결된 것으로 판단된다. 또한, RT에서 증착한 박막의 경우에는 후 열처리 초기에는 산소공공등과 같은 결함들의 농도가 감소하여 투과율이 증가하였으나 완전한 결정화가 일어난 후에는 투과율이 약간 감소한 것을 확인할 수 있었다. 이는 결정화 시 박막의 표면 조도가 증가하였고 이로 인해 빛의 산란이 증가하여 투과율이 감소한 것으로 판단된다. 이러한 결과로 반응성 스퍼터링 공정으로 제조한 ITO 초박막은 후열처리에 의한 완전한 결정화를 이룰 수 있으며, 이를 통해 얻은 낮은 비저항과 높은 투과율은 고품질 TSP에 적용될 가능성을 가진다고 판단된다.