• Bulletin of the Society of Naval Architects of Korea
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• v.58 no.2
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• pp.12-16
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• 2021

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.93-95
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• 2019

일반적으로 항만 내 선박 교통류 평가는 AIS 데이터를 이용하여 수행이 되어져 왔다. AIS 데이터는 선박의 위치 확인에 용이하여 항로상 선박 교통분포 분석에 용이하였다. 하지만, AIS 데이터는 VTS에 저장되어 있는 기간이 짧고, 처리할 데이터의 양이 많은 단점이 있다. 한편, PORT-MIS 선박 입출항 데이터는 10년 이상 저장이 되어 있으며, 통항로상 통계적 선박교통밀도 분석에 활용이 용이하다. 본 연구에서는 PORT-MIS 빅데이터 분석 방법과 선박 입출항 데이터를 항로상의 통항데이터로 변환하는 방법을 개발하여 제시하고자 한다.

• Ocean and Polar Research
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• v.40 no.4
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• pp.191-202
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• 2018

In this study we conducted a weekly monitoring exercise at a fixed station in the saltwater zone during the dry season (Jan-Mar, 2013) and wet season (Jun-Aug, 2013) to understand the fluctuations in phytoplankton communities and environmental factors in the Youngsan River estuary altered by a dike constructed in the coastal area. Phytoplankton communities displayed seasonality; diatoms were dominant during the dry season whereas dinoflagellates were dominant during the wet season. T-test analysis showed that water temperature was significantly different between the seasons whereas freshwater discharge from the dike was not significantly different. This suggests that seasonal variations of phytoplankton are more likely affected by water temperature than freshwater discharge. However, a short-term fluctuation was also observed in response to freshwater discharge; freshwater species appeared during or after the discharge in the dry and wet seasons and blooms of harmful species developed after the discharge. Phytoplankton communities may be affected by changes in physical factors such as turbidity and salinity and nutrient supply resulting from freshwater discharge. Especially, the nutrient supply may directly contribute to the harmful algal blooms (HABs) composed of dinoflagellates which can adapt to low salinity after freshwater discharge.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.2
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• pp.290-296
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• 2022

According to an investigation performed on shipping accidents, the number of domestic shipping accidents has been increasing despite the decrease in global shipping accidents. Therefore, to reduce domestic shipping accidents, the present study investigated the criteria for the stability of fishing vessels. The IMO, foreign, and domestic regulations regarding fishing vessel stability were investigated, and a comparative study was conducted. The results showed that domestic regulations were the most relaxed regarding vessel stability. Finally, we proposed five items for the KOREA FISHING VESSELS STABILITY CRITERIA AMENDMENTS on the basis of the comparative study.

• Journal of Environmental Science International
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• v.31 no.5
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• pp.431-445
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• 2022

The Gwangju Stream is a major tributary of the Yeongsan River. To maintain environmental and ecological functions in the stream, the flow is secured by natural water from the Mudeung Mountain as well as waters discharged from Lake Juam and the Gwangju sewage treatment plants. A substantial amount of water is supplied into the upper reaches of Gwangju Stream from Lake Juam. To examine the ecological effects of the water input from Lake Juam on the Gwangju Stream, a field survey of phytoplankton community species and an evaluation of water properties was conducted at five stations, from station GJ1 before the inflow to station GJ5 in the lower region. Nutrient levels decreased in the vicinity of the Lake Juam inflow, suggesting that this water inflow can contribute to the reduction of eutrophication in the stream. The phytoplankton community was mainly composed of Bacillariophyceae, Chlorophyceae, and Cyanophyceae, and the community structure was similar to that of the other study sites located near the water inflow regions. The inflow of water from Lake Juam can affect water quality and the phytoplankton community over a limited area, reducing eutrophication and increasing water flow in the Gwangju Stream.

• Ocean and Polar Research
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• v.45 no.3
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• pp.113-123
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• 2023

Humic substances are refractory organic compounds that are relatively low in biological activity but known to stimulate phytoplankton growth in estuarine and marine environments. The effect of humic substances on phytoplankton growth was investigated in the seawater zone of the Yeongsan River estuary where an episodic anthropogenic freshwater is discharged, affecting its water properties directly. Water samples and data of water properties were collected at three stations (Sts. A-C) along the channel of the seawater zone in February, May, August and November, 2009. The collected water samples were incubated after humic acids (HA) were added in mesocosm experiments. Phytoplankton (chlorophyll-a) were fractionated into net- (> 20 ㎛) and nano-size (< 20 ㎛) to examine the response of phytoplankton according to size. Their response to HA treatment was assessed by repeated measures analysis of variance (RM-ANOVA). The experiments showed that phytoplankton biomass (chlorophyll-a) significantly increased after HA were added at the stations near the sea dike. Especially, nano-sized chlorophyll-a concentrations increased significantly throughout the seasons. This indicates that understanding the behavior of refractory organic matters such as humic substances is required to better manage altered estuarine ecosystems including the Yeongsan River estuary which are affected by episodic discharge of freshwater from sea dikes.

• Journal of the Korean institute of surface engineering
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• v.51 no.6
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• pp.421-429
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• 2018

In this study, various electrochemical experiments were carried out to compare the corrosion characteristics of AA5052-O, AA5083-H321 and AA6061-T6 in seawater. The electrochemical impedance and potentiostatic polarization measurements showed that the corrosion resistance is decreased in the order of AA5052-O, AA5083-H321 and AA6061-T6, with AA5052-O being the highest resistant. This is closely associated with the property of passive film formed on three tested Al alloys. Based on the slope of Mott-Schottky plots of an n-type semiconductor, the density of oxygen vacancies in the passive film formed on the alloys was determined. This revealed that the defect density is increased in the order of AA5052-O, AA5083-H321 and AA6061-T6. Considering these facts, it is implied that the addition of Mg, Si, and Cu to the Al alloys can degrade the passivity, which is characterized by a passive film structure containing more defect sites, contributing to the decrease in corrosion resistance in seawater.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.11a
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• pp.105-106
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• 2009

본 논문은 선박USN 정보 제공을 위한 응용서비스를 제안한다. 제안하는 응용서비스는 실시간모니터링서비스, 기본정보서비스, 해양네비게이션서비스, 환경설정서비스, 부가서비스로 구성된다. 실시간모니터링서비스는 선박의 주요기관과 장치로부터 수집된 선박 내부의 온도, 습도, 조도, 소리, 뒤틀림, 기울임 등의 상태정보를 사용자에게 수치와 그래프로 볼 수 있도록 하고, 또한 이상발생시 알림서비스를 제공한다. 기본정보서비스는 선박명, 선급, 승선인원 등 선박에 대한 기초적인 정보를 제공한다. 해양네비게이션서비스는 GPS를 사용하여 수집된 선박의 위치 정보 제공과 운항의 편리성을 위한 운항도우미서비스를 제공한다. 환경설정서비스는 모니터링 주기와 센싱 타이밍을 조절하기 위한 설정 기능을 제공한다. 부가서비스는 시스템에 사용자 편리성을 제고하기 위한 서비스이며, 날씨정보, 정비이력, 운항일지 등으로 구성된다. 이러한 응용서비스는 선박USN 모니터링시스템에 적용되어 선박 운항의 지식과 경험이 부족한 초보 운항자들이 편리하고 안전한 운항을 하도록 돕는 역할을 할 것으로 기대된다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.6
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• pp.1044-1053
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• 2022

Time domain reflectometry (TDR) is a diagnostic technique to evaluate the physical integrity of cable and finds application in leak detection and localization of piping system. In this study, a cable-shaped leak detection sensor was proposed using the TDR technique for monitoring leakage detection of ship's engine room seawater piping system. The cable sensor was developed using a twisted pair arrangement and wound by an absorbent material. The availability and performance of the sensor for leak detection and localization were evaluated on a lab-scale pipeline set up. The developed sensor was installed onto the pipes and flanges of the lab-scale set up and various TDR waveforms were acquired and analyzed according to the dif erent variables including the number of twists and sheath thickness. The result indicated that the twisted cable sensor was able to produce clear and smooth signal as compared to the TDR sensor with a parallel arrangement. The optimal number of twist was determined to be above 10 per the unit length. The optimal diameter of sheath thickness that results in the desired sensitivity was determined to be ranging from 80% up to 120% of the diameter of the conductor. The linear regression analysis for estimation of leak localization was carried out to estimate the location of the leakage, and the result was a determination coefficient of 0.9998, indicating a positive relationship with the actual leakage point. The proposed TDR based leak detection method appears to be an effective method for monitoring leakage of ship's seawater piping system.

• Journal of the Korean Society of Marine Environment & Safety
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• v.30 no.1
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• pp.97-107
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• 2024

Despite the rapid advancement in image recognition technology, achieving perfect digitization of tabular documents and handwritten documents still challenges. The purpose of this study is to improve the accuracy of digitizing the logbook by correcting errors by utilizing associated rules considered during logbook entries. Through this, it is expected to enhance the accuracy and reliability of data extracted from logbook through OCR programs. This model is to improve the accuracy of digitizing the logbook of the training ship "Saenuri" at the Mokpo Maritime University by correcting errors identified after Optical Character Recognition (OCR) program recognition. The model identified and corrected errors by utilizing associated rules considered during logbook entries. To evaluate the effect of model, the data before and after correction were divided by features, and comparisons were made between the same sailing number and the same feature. Using this model, approximately 10.6% of errors out of the total estimated error rate of about 11.8% were identified, and 56 out of 123 errors were corrected. A limitation of this study is that it only focuses on information from Dist.Run to Stand Course sections of the logbook, which contain navigational information. Future research will aim to correct more information from the logbook, including weather information, to overcome this limitation.