• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.1-9
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• 2018

All ships should ensure stability in accordance with IMO regulations. However, GM is only used to determine ship stability because it takes a lot of time to validate all regulations. This is a problem given that the safety of vessels cannot be guaranteed, potentially leading to accidents. There is a need for a more intuitive and comprehensive method of confirming the stability of ships. This study developed a stability index that expresses ship stability in one value. An index equation is defined based on the 6 stability criteria for ships prescribed by IMO and the result of calculating the ship stability of a model ship. A stability index has been derived for each loading condition by applying the index equation to the same ship. It can clearly be seen that this stability index appropriately explains the criteria. In other words, it is possible to assess ship stability with one value and confirm whether the ship stability satisfies IMO regulations. This index will help masters and officers more easily and accurately check ship stability.

• The Journal of Korean Association of Computer Education
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• v.19 no.4
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• pp.59-66
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• 2016

It has been studied to reflect the number of co-rated items for solving data sparsity problem in collaborative filtering systems. A well-known method of Jaccard index allowed performance improvement, when combined with previous similarity measures. However, the degree of performance improvement when combined with existing similarity measures in various data environments are seldom analyzed, which is the objective of this study. Jaccard index as a sole similarity measure yielded much higher prediction quality than traditional measures and very high recommendation quality in a sparse dataset. In general, previous similarity measures combined with Jaccard index improved performance regardless of dataset characteristics. Especially, cosine similarity achieved the highest improvement in sparse datasets, while similarity of Mean Squared Difference degraded prediction quality in denser sets. Therefore, one needs to consider characteristics of data environment and similarity measures before combining Jaccard index for similarity use.

• Journal of Korean Society for Geospatial Information Science
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• v.20 no.1
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• pp.73-81
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• 2012

This study ultimately aims to suggest directions for development of U-City Competitiveness Index through thorough analyses of U-City competitiveness concepts and previous research in U-City-related index. In an attempt to reach the aforementioned goals, the concept of U-City competitiveness is presented based on existing publications on informatization age, future city, and U-City. Next, insights on the development of U-City Competitiveness Index are provided via analysis of research on indices regarding U-City and future city. Finally, the process of developing UCity Competitiveness Index and cautionary comments for each developmental step has been provided. Based on the research results, U-City competitiveness refers to the ability to respond to demands of residents in a timely manner as well as to manage U-City, ICT, U-City infrastructure, and U-City services that maximizes the efficiency of urban space management. In order for proper assessment of these criteria, development of assessment tools, selection of indices, standardization, allocation of weight per index, and construction of assessment framework are required.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.831-839
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• 2012

In this paper, an exponential model of Korea is proposed to minimize an altitude-error of high-altitude target due to atmosphere refraction at radar system. The relation between surface refractivity and refractivity gradient, which is extracted using the least square fit from the measured data at 7 weather stations, is applied to the exponential model. And in order to verify the proposed model, the altitude-errors for a standard atmosphere, a CRPL(Central Radio Propagation Lab.) exponential model, the proposed model are extracted and analyzed using a ray tracing. As a result, the proposed model can improve the altitude estimation performance of radar compared to conventional atmosphere refractive index models.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.53-53
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• 2011

가뭄은 강수 부족 및 온도 상승에 따른 물 수지의 불균형으로, 그 특성상 점진적이고 홍수에 비해 피해규모가 광범위 하여 효율적인 대처방안을 마련하기가 어려운 특성을 가지고 있다. 현재 국내의 경우 가뭄관리를 위해 비구조적 대책 방안인 가뭄지수를 활용하여 해당 지역의 부족한 용수의 정도를 시 공간적으로 측정하고 크기와 강도에 대한 정량적 또는 정성적인 평가를 수행하고 있다. 그러나 대부분 강수 및 기온자료를 토대로 한 평가가 주를 이루고 있으며, 그나마 제공되는 지수들의 경우 가뭄을 나타내는 기준이 상이하여 사용자에게 많은 혼란을 가중시키고 있는 실정이다. 따라서 효율적인 가뭄관리를 위해서는 장주기 기상정보를 토대로 국가 또는 권역별 가뭄감시가 이루어져야하며, 기상 분만 아니라 지표와의 물 수지 해석이 반영된 수문정보(유량, 토양수분 등) 기반의 가뭄 정보가 생산되어야 할 것이다. 본 연구에서는 전지구 수문해석이 가능한 지표수문해석모형을 활용하여 남한에 대한 수문성분 기반의 가뭄평가를 수행하고자 한다. 우선 남한 전역에 대한 기상 및 지형 정보를 구축하고 지표수문해석모형에 적용하여 격자별 수문성분을 생산하였다. 수문성분은 가뭄평가에 필요한 정보로 전환되어야 하며, 본 연구에서는 빈도해석기법을 적용하여 가뭄에 대한 발생 빈도 및 규모를 정량화 하였다. 즉, 모형에서 산정된 수문정보로 부터 빈도해석을 수행하여 적정 확률분포형을 결정한 후, 해당기간에 대한 확률값을 산정하여 과거 대비 가뭄에 대한 여부를 판단하였다. 산정된 지수에 대한 평가를 위해 국내 과거 가뭄기록사례를 조사 및 기존 가뭄지수인 SPI 및 PDSI를 활용하였다. 평가 방법은 시계열 및 지역별 분석과 유역별 물수지 분석으로 구분되며, 주로 가뭄기간동안의 가뭄심도와 가뭄 발생 및 해갈에 따른 재현여부를 평가하였다. 평가 결과 가뭄발생 및 해갈시기 그리고 피해지역에 대한 표현에 있어 기록된 사항을 적절히 반영하는 것으로 나타났으며, 기존 가뭄지수 보다 가뭄 재현에 있어 비교적 신뢰성이 높은 것으로 확인되었다. 따라서 지표수문해석모형 기반의 가뭄평가의 경우 적용성이 우수한 것으로 판단되며, 이상의 연구결과는 향후 국내 및 동아시아 가뭄감시 전망에 있어 기초자료로 활용될 것이다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.5
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• pp.519-526
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• 2019

This study proposes a methodology for estimating the appropriate capacity of anchorage for ports requiring the establishment of waiting anchorage and then applying the methodology to the ports in Jinhae Bay to compare it with the anchorage capacity of major ports in Korea. To estimate the appropriate anchorage capacity, the "Anchorage Capacity Index" was used, which was calculated from the "Total Gross Tonnage" and "Simultaneous Anchoring Capacity". The calculations were made according to the anchorage capacity index of 0.89 of the target harbors. The adequate anchorage capacity index for the new waiting anchorage was analyzed at a level of 6.0. If the concept of anchorage capacity index suggested in this study is reflected as a new design criteria of waiting anchorage, it will be helpful for the safety of berth, safety of anchorage and effective operation of harbor.

• The Journal of the Korea Contents Association
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• v.21 no.8
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• pp.640-650
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• 2021

The purpose of this study was to identify factors affecting the Quality of Life of Ankylosing Spondylitis Patients Based on Korean Bath Ankylosing Spondylitis Disease Activity Index (KBASDAI) and Korean Bath Ankylosing Spondylitis Functional Index (KBASFI). The subjects of this study were 19 years of age or older who were diagnosed with ankylosing spondylitis(AS). Data was collected through an online survey. A univariate analysis of differences in quality of life according to variable characteristics was performed, and multiple regression analysis was performed to examine factors affecting quality of life. As a result of regression analysis, the higher the KBASFI (𝛽=0.622, p<0.001) and the KBASDAI (𝛽=0.180, p=0.032) scores, and the lower the average monthly household income(𝛽= 0.186, p=0.001), the worse the quality of life. In order to improve the quality of life of AS patients, intervention studies that can lower disease activity and improve function are needed.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.485-485
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• 2022

본 연구에서는 낙동강 수계에서 어류의 수생태 건강성이 악화된 지점, 장기간 수질이 악화되거나 수위가 저하된 지점, 보호종이 지정된 지점을 중심으로 어류 서식지적합도지수(Habitat Suitability index, HSI)를 산정하였다. 현장조사는 하천유량이 감소하는 4월부터 6월 사이 총 4회 실시하였고, 투망과 족대를 이용해 어류 채집하였다. 어류의 서식지 특성 조사를 위해 채집 지점에서 수심, 유속, 하상재료를 조사하고 기록하여 엑셀 자료를 구축하였다. 본 연구에서는 실제 하천 단면의 물리적 특성을 잘 반영할 수 있는 WDFW(Washington Dept. of Fish and Wildlife) 방법을 이용하여 어류 서식처적합도지수를 산정하였다. 낙동강 수계 10개 지점에서 실시한 어류 조사 결과는 전체 9과 35종 2,227개체이다. 낙동강 수계 10개 지점의 대표어종을 선정하기 위해 법정보호종, 유영성종, 고유종, 기타 중요종을 검토한 다음 각 지점별 대표어종, 대리어종, 유사어종 등을 산정하였다. 낙동강 수계 전반에 걸쳐 피라미가 우점종으로 조사되었으며, 낙동강 상류지역에는 모래무지, 하류에는 수수미꾸리와 유사한 종의 출현빈도가 높은 것으로 나타났다. 낙동강 전역에 걸쳐 서식하고 있는 피라미는 가능한 대표어종에서 제외하고, 보호종과 고유종을 중심으로 대표어종을 선정하였다. 그 결과 낙동강 상류 내성천 합류전 지점에서는 피라미, 내성천에서 참마자, 위천에서 참몰개, 갑천에서 돌고기, 황강에서 모래무지, 금호강에서 돌마자, 밀양강에서 쉬리. 남강에서 피라미, 형산강에서 참갈겨니, 태화강에서 피라미로 대표어종을 각각 결정하였다. 다음으로 각 지점별 대표어종에 대한 수심, 유속, 하상재료 조사 자료를 이용해 대표어종에 대한 서식지적합도지수를 산정하였다. 최근 갈수기 유량 감소로 생태계가 위협받는 기간이 증가하고 있다. 하천의 정상적인 생태기능 유지를 위한 최소한의 유량이 필요하고, 이를 확보하기 위한 노력이 요구된다. 어류의 서식지적합도지수를 활용해 갈수기 어류 서식에 필요한 최소한의 유량을 결정하거나, 수생태계 복원을 위한 기초자료로 활용성이 높을 것으로 판단된다.

• Korea Trade Review
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• v.48 no.1
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• pp.127-163
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• 2023

The objective of this study is to investigate the volatility spillover effects among BDI, CCFI and SCFI. This paper will divide the empirical analysis section into two periods to analyze and compare the differences in volatility spillover effect between shipping freight indices before and after the outbreak of COVID-19 separately. First, in order to compare the mean spillover impact and index lead-lag correlations in BDI and CCFI indices, along with BDI and SCFI indices before and after COVID-19, the co-integration analysis and the test of Granger causality built on the VAR model were utilized. Second, the impulse response and variance decomposition are employed in this work to investigate how the shipping freight index responds to shocks experienced by itself and other freight indices in a short period. Before the COVID-19 epidemic, the results demonstrated that the BDI freight index is the Granger cause of the variable CCFI freight index. But the BDI and CCFI freight indices have no apparent lead-lag relationships after COVID-19, and this empirical result echoes the cointegration test result. After the COVID-19 epidemic, the SCFI index leads the BDI index. This study employs the VAR-BEKK-GARCH joint model to explore the volatility spillover results between dry bulk and container transport markets before and after COVID-19. The empirical results demonstrate that after COVID-19, fluctuations in the BDI index still affect the CCFI index in the maritime market. However, there is no proof of a volatility spillover relationship between the BDI and SCFI after the COVID-19 epidemic. This study will provide an insight into the volatility relationship among BDI, CCFI and SCFI before and after the the COVID-19 epidemic occurred.

• Journal of the Korean Society for information Management
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• v.30 no.4
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• pp.111-131
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• 2013

This study describes the meaning of and the formula for Kor-$h_T$, which is a modified index built on the tapered h-index by applying 'the ranking according to the number of citations of journals'. This study evaluated the de-duplication rate of index values of Kor-$h_T$ and analyzed the change in the correlation between the index values and evaluation elements using the Korea Citation Index data from 2008 to 2010. Kor-$h_T$ is compared with h-index, tapered h-index, and IF. As a result, Kor-$h_T$ appeared to be superior to other indexes on de-duplication rate. It is also shown that there is a very strong positive correlation between the evaluation elements, the number of citations and the number of articles of journals, and the index values of Kor-$h_T$.