• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.5
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• pp.438-444
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• 2000

The prediction of mechanical properties for WC-Co alloys by evaluation of coercive force and magnetic saturation were studied in relation to their microstructure. The WC-8%Co alloys were prepared using different WC particle size, carbon content and various sintering temperature by PM process. The magnetic properties such as coercive force and magnetic saturation of sintered WC-Co alloys were critically dependent upon their final composition and microstructure. Slight changes of carbon contents and small variation of WC grain size result in marked changes of magnetic properties, hardness and transverse rupture strength of sintered WC-Co alloys. It was found that the coercive force and hardness were increased by fine WC grain size of sinterd alloys, and the coercive force was proportional to hardness. With decreasing total carbon content below the stoichiometric value in WC-8%Co alloys the volume fraction of $\eta$ phase increased steadily, while the magnetic saturation and transverse rupture strength decreased. The magnetic saturation was inversely proportional to the coercive force of WC-Co alloys.

• Journal of Korea Port Economic Association
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• v.30 no.1
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• pp.23-55
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• 2014

The purpose of this paper is to show the clustering trend and to choose the clustering ports for 3 Korean ports(Busan, Incheon and Gwangyang Ports) by using the self organizing maps based on neural network(SOM) and Tier models for 38 Asian ports during 11 years(2001-2011) with 4 input variables(birth length, depth, total area, and number of crane) and 1 output variable(container TEU). The main empirical results of this paper are as follows. First, clustering results by using SOM show that 3 Korean ports[Busan(26.5%), Incheon(13.05%), and Gwangyang(22.95%) each]can increase the efficiency. Second, according to Tier model, Busan(Hongkong, Sanghai, Manila, and Singapore), Incheon(Aden, Ningbo, Dabao, and Bangkog), and Gwangyang(Aden, Ningbo, Bangkog, Hipa, Dubai, and Guangzhou) should be clustered with those ports in parentheses. Third, when both SOM and Tier models are mixed, (1) efficiency improvement of Busan Port is greater than those of Incheon and Gwangyang ports. (2) Incheon port has shown the slow improvement during 2001-2007, but after 2008, improvement speed was high. (3) improvement level of Gwangyang port was high during 2001-2003, but after 2004, improvement level was constantly decreased. The policy implication of this paper is that Korean port policy planner should introduce the SOM, and Tier models with the mixed two models when clustering among the Asian ports for enhancing the efficiency of inputs and outputs.

• Journal of Korea Port Economic Association
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• v.37 no.1
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• pp.19-30
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• 2021

The 21st Century Maritime Silk Road (MSR) is an important part of Belt and Road Initiative(BRI). As an economic and trade corridor for dozens of countries in Asia, Europe and Africa, and the port as an important link node, the efficiency of port operation directly affects the implementation of BRI's strategy. On the basis of combining BRI and related evaluation methods of port efficiency, this paper uses DEA-BCC model to select port production berth number and production berth length as input index container throughput and cargo throughput as output index to analyze the port efficiency of 14 ports in China. The results show that: (1) The overall efficiency level of the ports along the MSR is relatively low. Most of the ports have not reached the DEA efficiency and there are different degrees of problems in scale investment and technological improvement. However, this situation is accompanied by the implementation of China's maritime cooperation strategy and becoming better year by year. (2) The low operating efficiency of ports along China's MSR is mainly due to the lack of coordination between scale efficiency and technical efficiency, which is caused by insufficient scale investment in the port itself, weak economic linkage between the hinterland and the port, (3) Whether a port has a strong comprehensive strength does not entirely depend on the cargo throughput or scale but also includes the port's operating efficiency.

• Journal of Marine Life Science
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• v.3 no.1
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• pp.31-37
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• 2018

We investigated natural habitat of seagrass and created replacement habitat to monitor for restoration of the habitat which is expected to be damaged at Cheonseong harbor in Busan. Depth of water for natural seagrass habitat at Cheonseong harbor was 1.2~3.1 m and the water temperature was 7.4℃, salt concentration was 29.1 psu and pH was 8.05 in January, 2013. The density of seagrass was 167.1±16.4 shoots m^-2, the total length was 48.5±18.1 cm, the height of sheath was 9.1±2.8 cm and the width of leaf was 4.8±1.1 cm, respectively. We transplanted in December 2014 and monitored the habitat during 9 months after transplanted. In the beginning, the density of seagrass was decreased to 8.5 shoots patch^-1 in January and was increased to 19.0 shoots patch^-1 in April. The total height were 73.3±2.9~121.3±6.1 cm, the length of sheath were 9.6±0.6-21.0±1.2 cm, the width of leaf were 5.7±0.1~6.8±0.2 mm. It showed that all values were increased steadily until July and was decreased rapidly in August. Flowering shoot, which was not observed in the beginning of transplanting, started to be spotted in March and was continued to be seen during the monitoring period. We were able to observe seedling of germinated seagrass in seeds in the replacement habitat next year.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.3
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• pp.209-229
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• 2001

Simultaneous field measurements of short-period and long-period waves were made at five stations inside or outside Okkye Harbor, which is located in the east coast of Korea. Based on the measured data, spacial and temporal variations of the long-period wave energy were examined. Three smoothing methods were examined for the spectral estimates: fixed interval averaging method, incremental interval averaging method, and moving averaging method. It was shown that a proper smoothing method should be chosen depending on the period of first resonant mode and the length of data being used. By comparing the results obtained using the long-term data with those obtained using two-day data, we showed that it is necessary to analyze the data of calm seas and storm seas separately. The Helmholtz resonant period in Okkye Harbor was found to be about 9.6 minutes with its relative amplification ratio of 9 to 10, and local amplifications were apparent at the periods of 1.2 to 1.3 minutes and 0.7 minute. During calm seas, both at the harbor entrance and inside the harbor the energy of the waves of 9 minutes or longer period was larger than the infra-gravity wave energy by more than 100 times. However, during storm seas the energy level was very high all over the period band, and local amplification was larger than that during calm seas by more than 100 times, especially inside the harbor, Finally it was shown that the energies of the Helmholtz resonant mode and the infra-gravity waves of 1 to 2 minutes are proportional to the storm wave height.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.36-42
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• 2018

This paper considers the Marine Traffic Risk Assessment for fixed and moving targets, which threaten officers during a voyage. The Collision Risk Assessment Formula was calculated based on a dynamic ship domain considering the length, speed and maneuvering capability of a vessel. In particular, the Navigation Risk Assessment Model that is used to quantitatively index the effect of a ship's size, speed, etc. has been reviewed and improved using a hybrid combination of a vessel's dynamic area and the Collision Risk Assessment Formula. Accordingly, a new type of Marine Traffic Risk Assessment Model has been suggested giving consideration to the Speed Length Ratio, which was not sufficiently reflected in the existing Risk Assessment Model. The larger the Speed Length Ratio (dimensionless speed), the higher the CJ value. That is, the CJ value is presented well by the Speed Length Ratio. When the Speed Length Ratio is large, states ranging from [Caution], [Warning], [Dangerous] or [Very Dangerous] are presented from a greater distance than when the Speed Length Ratio is small. The results of this study, can be used for route and port development, including dangerous route avoidance, optimum route planning, breakwater width, bridge span, etc. as well as the development of costal navigation safety charts. This research is also applicable for the selection of optimum ship routing and the prevention of collisions for smart ships such as autonomous vessels.

• Journal of Korea Port Economic Association
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• v.31 no.1
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• pp.85-110
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• 2015

The purpose of this paper is to show the clustering trend and the empirical comparison and to choose the clustering ports for 3 Korean ports(Busan, Incheon and Gwangyang Ports) by using the Fuzzy(Average Index Transformation) DEA and Cross-efficiency models for 38 Asian ports during 11 years(2001-2011) with 4 input variables(birth length, depth, total area, and number of crane) and 1 output variable(container TEU). The main empirical results of this paper are as follows. First, clustering results by using Fuzzy(AIT)DEA show that 3 Korean ports[Busan(56.29%), Incheon(57.96%), and Gwangyang(66.80%) each]can increase the efficiency. Second, according to Cross-efficiency model, Busan(Hongkong, Kobe, Manila, Singapore, and Kaosiung etc.), Incheon(Aquaba, Dammam, Karachi, Mohammad Byin Oasim and Davao), and Gwangyang(Damman, Yokohama, Nogoya, Keelong, Kaosiung, and Bangkok) should be clustered with those ports in parentheses. Third, when both Fuzzy(AIT)DEA and Cross-efficiency models are mixed, the empirical result shows that 3 Korean ports[Busan(71.38%), Incheon(103.89%), and Gwangyang(168.55%) each]can increase the efficiency. The efficiency ranking comparison among the three models by using Wilcoxon Signed-rank Test was matched with the average level of 66%-67%. The policy implication of this paper is that Korean port policy planner should introduce the Fuzzy(AIT)DEA, and Cross-efficiency models with the mixed two models when clustering is needed among the Asian ports for enhancing the efficiency of inputs and outputs. Also, the results of SWOT analysis among the clustering ports should be considered.

• Journal of Korea Port Economic Association
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• v.29 no.1
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• pp.143-175
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• 2013

The purpose of this paper is to show the clustering trend by using the variable group benchmarking(VGB) and categorical variable(CV) models for 38 Asian ports during 9 years(2001-2009) with 4 inputs(birth length, depth, total area, and number of crane) and 1 output(container TEU). The main empirical results of this paper are as follows. First, clustering results by using VGB show that Shanghai, Qingdao, and Ningbo ports took the core role for clustering. Second, CV analysis focusing on the container throughputs indicated that Singapore, Keelong, Dubai, and Kaosiung ports except Chinese ports are appeared as the center ports of clustering. Third, Aqaba, Dubai, Hongkong, Shanghai, Guangzhou, and Ningbo ports are recommended as the efficient ports for the target of clustering. Fourth, when the ports are classified by the regional location, Dubai, Khor Fakkan, Shanghai, Hongkong, Keelong, Ningbo, and Singapore ports are the core ports for clustering. On the whole, other ports located in Asia should be clustered to Dubai, Khor Fakkan, Shanghai, Hongkong, Ningbo, and Singapore ports. The policy implication of this paper is that Korean port policy planner should introduce the VGB model, and CV model for clustering among the international ports for enhancing the efficiency of inputs and outputs.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2013.10a
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• pp.11-12
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• 2013

수리조선산업은 기술 및 노동집약적 산업으로 기계, 철강, 전기전자, 화학 등 연관산업에 대한 생산 유발효과 및 고용효과가 높은 산업이다. 또한 연계 산업에 대한 직접적인 생산증가 효과와 선원 체류에 따른 부가가치 증가 등의 부수효과를 함께 고려할 때 지역경제에 대한 기여도가 높은 산업적 역할을 수행하고 있으며, 특히 부산 경남 울산 지역은 세계 5위권 전후에 해당하는 해운물동량을 처리하는 입지조건과 신조선 분야 1위의 우수한 기술 및 노동력을 보유하고 있다. 이러한 긍정적인 측면에도 불구하고 여러 요인들로 인해 수리조선산업이 경쟁력이 확보되지 못하고 있는 실정이며, 2013년 들면서 부산항의 컨테이너 물동량 실적이 7위로 하락하고 있는 실정이다. 따라서 본 연구에서는 부산항을 중심으로 수리조선산업 공급망 관리를 위하여 정보화 네트워크 구축사례를 분석하고, 이를 통하여 수리조선산업 정보화 네트워크의 성공적인 구축 방안을 모색하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.708-709
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• 2015

최근 선박의 연안 선박의 안전사고가 증가함에 따라 기존 항만 중심으로 운영되고 있던 해상교통관제센터의 관제 범위가 연안까지 확대되고 있다. 이에 따라 해상교통관제센타(Vessel Traffic Service Center, VTS) 간에 데이터 교환의 필요성도 증가하고 있다. 국제항로표지협회 IALA(International Association of Lighthouse Authorities, IALA)는 이러한 필요성을 인지하고 해상교통관제센터간 데이터 교환 프로토콜인 IVEF(Inter-VTS Exchange Format)를 제정하였다. 그러나 IVEF 프로토콜 특성상 외부 해상교통관제센터간 데이터가 전송됨으로 데이터 변조등의 위험성이 있다. 하지만 IVEF 프로토콜은 보안 관련 요소들이 미미한 실정이다. 본 논문에서는 IVEF 데이터의 무결성을 보장하는 방법을 제안한다.