• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.22 no.6
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• pp.1-16
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• 2023

Accurate traffic information prediction is considered to be one of the most important aspects of intelligent transport systems(ITS), as it can be used to guide users of transportation facilities to avoid congested routes. Various deep learning models have been developed for accurate traffic prediction. Recently, ensemble techniques have been utilized to combine the strengths and weaknesses of various models in various ways to improve prediction accuracy and stability. Therefore, in this study, we developed and evaluated a traffic information prediction model using various deep learning models, and evaluated the performance of the developed deep learning models as a stacking ensemble. The individual models showed error rates within 10% for traffic volume prediction and 3% for speed prediction. The ensemble model showed higher accuracy compared to other models when no cross-validation was performed, and when cross-validation was performed, it showed a uniform error rate in long-term forecasting.

• Journal of the Korea Convergence Society
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• v.9 no.8
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• pp.283-291
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• 2018

The purpose of this study is to identify the main factors influencing the culture of social welfare agencies and to find out the types of culture that they are combining through. The research method has two major processes. The first step was to conduct long-term surveys on one agency and find out the factors influencing the organizational culture. In the second step, we found a type of organizational culture by combining the elements in six agencies. As a result of research, we found leadership, openness, and locality as factors influencing organizational culture, and found that they were restricted-care, expanded-participatory, change-mixed, and stable-mixed. The results of this study are meaningful in that it reflects the complex situation of Korean social welfare organization. Future research will need to expand to the whole country in order to improve the generalization of typification.

• Journal of the Korean Geotechnical Society
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• v.28 no.5
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• pp.85-94
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• 2012

Recently, growing interests in frozen ground have stimulated us to advance fundamental theories and systematic researches on soil behavior under freezing conditions. Unlike the well-established soil mechanics theory, temperature variation and phase change of pore-water cause water migration to cold side, ground heaving, sharp increase in earth pressure, etc., which bring about serious problems in frozen geotechnical structures. Elasto-plastic mechanical constitutive model for frozen/unfrozen soil subjected to fully coupled THM phenomena is formulated based on a new stress variable that is continuous in frozen-unfrozen transitional regions. Numerical simulations are conducted to discuss numerical reliability and applicability of the developed constitutive model: one-dimensional heaving pressure, tri-axial compression test, and one-side freezing tests. The numerical results show that developed model can efficiently describe complex THM phenomena of frozen soil, and they can be utilized to analyze and design the geotechnical structures under freezing conditions, and predict their long-term behavior.

• Journal of the Korean GEO-environmental Society
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• v.21 no.11
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• pp.11-20
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• 2020

For water barrier and reinforcing grout in soft ground, the verification of durability was conducted over the initial and long-term ages under various curing conditions. The grout was made of water glass system, fast-hardening mineral (FHM) system, and acrylic polymer system. There were three types of curing conditions that were tab water curing, artificial seawater curing, and atmospheric curing. And the various tests were performed for each sample by age, uniaxial compressive strength, length change, and weight change. As artificial seawater, MgCl₂ and MgSO₄ aqueous solutions were prepared and used, respectively. As the test results, the fast-hardening mineral system and acrylic polymer system were cured stably without significant change in durability in tap water and artificial sea water, whereas water glass system showed a very rapid drop in durability under artificial sea water conditions compared to tap water. In atmospheric curing conditions, durability is lowered compared to water curing in all cases, and in particular, the weight loss in the FHM system and water glass system is about 62% and 60%, respectively, resulting in a significant decrease in durability.

• The Journal of the Korea Contents Association
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• v.13 no.7
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• pp.432-439
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• 2013

In this study, we evaluate the volatility of housing prices by using literature review and empirical analysis and furthermore we suggest how to improve. In order to diagnose housing market, the KB Bank's House Price Index, Real estate 114;s materials were compared. In addition, to examine the volatility, GARCH (Generalized Autoregressive Conditional Heteroskedasticity) and EGARCH (Exponential GARCH) model are used. By analysis of this research, we found the volatility of housing price also was reduced in the medium and the large houses since 1998, while the volatility of small housing price relatively was large. We proved that the price change rate of small housing was higher than the medium's. On the order hand, the supply of small apartments fell down sharply. The short-term oriented policy should be avoided, and the efficiency and credibility of policy should be increased. Furthermore, the long-term policy system should be established. and rental market's improvement is necessary for stabilization of housing market.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.04a
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• pp.6-6
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• 2018

백두대간은 백두산에서 시작된 큰 산줄기로 금강산, 설악산, 덕유산 등을 거쳐 지리산까지 이어지는 우리나라 중심 산줄기이다. 백두대간은 우리 민족 고유의 사회 문화적 가치는 물론 자연 생태적 측면에서 매우 중요한 지역이다. 백두산에서 지리산까지 약 1,400km, 남한 지역은 약 700km가 남북으로 길게 연결되어 우리나라 주요 산들을 연결하는 한반도 중심축을 형성하고 있다. 백두대간은 생물다양성의 보고이자 주요강의 발원지로 중요한 역할을 하고 있다. 이러한 주요 지역에 위치함 국립백두대간수목원은 수목원 정원의 조성 및 진흥에 관한 법률에 근거하여 기후대 및 식생권역별 국가수목원의 확충 계획에 따라 온대 북부 권역에 조성되었다. 백두대간 산림생물 다양성 유지와 산림생물자원의 보전 및 활용을 위한 다양한 연구를 수행하고 있다. 국립백두대간수목원의 시드볼트는 생물다양성 보존과 산림생물유전자원의 지속가능한 활용을 위하여 종자보존 협력 네트워크를 구축 하고 있다. 또한 아시아를 포함한 전세계 야생 종자를 수집하기 위한 기후대 생태권역별 종합계획 수립과 표준화 모델 개발을 통해 체계적인 협력체를 구축 중이다. 종자의 안정적인 장기 보존을 위한 형태학적, 분자생물학적 연구를 통해 종자의 저장특성 연구 및 수명연구를 통해 예측 모델을 연구하며 이를 기반으로 생태계 복원을 위한 종자 활용 연구를 수행하고 있다. 국립백두대간수목원은 백두대간 생물종의 조사, 생태계 보전 복원연구를 위한 현지 조사, 서식지외 보전 기관 역할, 유용자원 발굴 및 연구 등 백두대간 생물다양성 보전을 위한 다양한 역할을 하고 있다.

• Management & Information Systems Review
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• v.31 no.3
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• pp.21-46
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• 2012

This paper attempts to offer an effective strategy of hedge fund based on trade probability control in the futures market. By using various technical indicators, we create an association rule and transforms it into a trading rule to be used as an investment strategy. Association rules are made by the combination of various technical indicators and the range of individual indicator value. Adjustments of trade probabilities are performed by depending on the rule combinations and it can be utilized to establish an effective investment strategy onto the risk management. In order to demonstrate the superiority of the investment strategy proposed, we analyzed a profitability using the futures index based on KOSPI200. Experiments results show that our proposed strategy could effectively manage and response the dynamics investment risks.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.50.2-50.2
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• 2011

염료감응형 태양전지는 기존의 실리콘 태양전지에 비해 저렴한 가격과 다양한 날씨 조건에서도 태양광과의 반응성이 안정하다는 여러 가지 장점을 갖고 있다. 하지만 광전 변환 효율이 기존의 실리콘 태양전지에 비해 현저히 떨어진다는 문제점과 장기적으로 안정하지 못하다는 단점을 가지고 있다. 이러한, 염료감응형 태양전지에서 크게 광전 변환 효율을 향상시킬 수 있는 재료는 염료, $TiO_2$와 같은 반도체 산화물전극 재료, 전해질이다. 이 중 $TiO_2$의 특성 및 크기는 염료감응형 태양전지의 효율에 영향을 미친다. 염료감응형 태양전지의 광전 변환 효율을 증가시키기 위해서 $TiO_2$는 넓은 비표면적, 높은 전자의 이동성 및 태양광과의 우수한 반응성을 가져야 한다. Microwave hydrothermal 방법에 의해 제조된 hollow $TiO_2$를 염료감응형 태양전지에 적용시킬 경우 기존의 $TiO_2$의 광흡수 반응이 200~400 nm 사이에서 발생하는 반면, hollow $TiO_2$의 광흡수 반응은 기존의 UV 영역인 200~400 nm 뿐만 아니라 가시광 영역인 400~460 nm 에서도 광흡수 반응이 가능하기 때문에 염료감응형 태양전지에서 광전 변환효율을 증가 시킬 수 있을 것으로 기대된다. 또한, microwave hydrothermal법에 의해 제조된 hollow $TiO_2$는 150-200 nm의 크기를 갖으며 20-30 nm 크기의 $TiO_2$ particle들로 이루어져 있다. hollow $TiO_2$ (150-200 nm)를 기존의 $TiO_2$ (10-20 nm) 층 위에 올려 염료감응형 태양전지의 electrode에 적용할 경우 기존의 $TiO_2$ 단층을 이용한 것보다 우수한 light-scattering 효과를 갖게 되어 광전 변환 효율 증가에 긍정적인 영향을 미칠 것이다. 본 연구에서는 hollow $TiO_2$의 광학적 특성 및 결정성이 염료감응형 태양전지에 미치는 영향을 조사하였다. hollow $TiO_2$의 광학적 특성 및 결정성의 변화를 위하여 microwave hydrothermal 법의 합성 온도 및 합성시간에 변화를 주었다. hollow $TiO_2$의 광학적 특성은 UV-visible spectrometer를 이용하여 조사하였으며, hollow $TiO_2$의 형상과 결정학적 특성은 TEM과 SEM 그리고 X선 회절 분석을 이용하여 관찰되었고, hollow $TiO_2$의 비표면적 측정은 BET 측정법을 이용하였다. 또한 염료감응형 태양전지 cell을 제작하여 $100mW/cm^2$(AM 1.5G) 기준에서 광전 변환 효율을 측정하였다.

• Korean Journal of Labor Studies
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• v.24 no.1
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• pp.107-156
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• 2018

This article examines the history of the in - house subcontracting and the stabilization of labor - management relations in the steel industry in Japan. The ratio of in-house subcontract workers among steel workers has increased steadily until the mid-2000s, and about 70% in case of the largest company. In-house subcontracting was used as a strategy of the company to increase the quantity flexibility of employment and to save labor costs. The in-house subcontracting company needed company-specialized skills, and the internal labor market was formed because the rate of full-time workers was high and the turnover rate was low. The in-house subcontractor introduced long-term business relationship with the steel factory by introducing the equipment and materials necessary for the performance of the work, and the factory implemented the productivity improvement policy of the in-house subcontractor, and the win-win relationship between the factory and in-house subcontractor was developed. The trade union did not oppose the idea that the expansion of in-house subcontracting contributed to corporate profits, the stability of employment of the members and maintenance of their working conditions. Since 2000, the steel factory has pursued the transformation of in - house subcontractors into subsidiaries, which has been supported by capital relations. By the way, since the mid-2000s, there has been an increase in the number of regular workers' employment. The major factors are as follows: more strengthened compliance with laws and regulations, the higher quality request of customers, stricter keeping of deadlines, and problem in recruiting of workers at in-house subcontract companies. The wage gap between the factory and in - house subcontracting was less at company B than at company S, and the wage level of in - house subcontracting was about 90% of the factory at company B. The relatively small gap at company B seems to be due to the union's movement of narrowing the gap, low market dominance and unfavorable labor market. The internal labor market has been formed in the in-house subcontracting, and the wage gap is not large, and the possibility of labor disputes is low. Industrial relations are stable in the in-house subcontract company as well as the factory. The stabilization of labor-management relations in the steel industry in Korea is required to reduce the wage gap between the factory and in-house subcontract enterprises by raising productivity and expanding the internal labor market at in-house subcontract enterprises.

• Resources Recycling
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• v.19 no.5
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• pp.50-57
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• 2010

Ternary blended concrete(TBC), which contains both fly ash and granulated blast furnace slag, has an initial cost effective and is environment friendly. Furthermore, it has a lot of technical advantages such as the improvement of long term compressive strength, high workability, and the reduction of hydration heat. However, as the use and study on the performance of ternary blended concrete is limited, it is low short term compressive strength. This study was performed to evaluate the characteristics which are a long and short term compressive strengths, permeability and chemical attacks resistance of hardened high early concrete containing slag powder and fly-ash using high early strength cement(HE-TBC). Replacement rate of FA is fixed on 10% and replacement rate of slag powder are 0%, 10%, 20% and 30%. The test results showed that compressive and flexural strength of HE-TBC increased as the slag contents increased from 0% to 30% at the short term of curing. The permeability resistance of HE-TBC(fly ash 10%, blast 30%) was extremely good at the short and long terms. However, high early strength ternary blended concrete had weak on carbonation of chemical attack.