• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1146-1149
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• 2014

단자 표식이 불분명한 3상유도전동기에서 고정자 권선의 극성을 판별하는 데는 외부 여자전류에 의해 유도되는 기전력 특성에 기초하거나 또는 회전자의 잔류자기를 이용하는 방법이 가능하다. 회전자의 잔류자기로 유도되는 권선에서의 기전력은 자속 크기와 수동 구동의 회전자 속도 및 위상 관계에 따라 정해지며 이 같은 극성 판별이 작업현장에서 가능하려면 기전력의 크기가 멀티테스터로 확인될 수 있는 정도이어야 하고 또한, 코일 간 위상 특성이 극성 판별에 적합해야 한다. 잔류자기에 의한 기전력들이 3상 평형 관계에 있다면 전체 합성 전압은 권선들의 극성 연결 상태가 정상일 때 0이 되어야 하는 한편, 극성 연결의 오류 시에는 상대적으로 큰 출력 전압을 나타낸다는 점에서 본 연구에서는 각 경우에 대한 특성을 분석하였다. 또한, 잔류자기에 의한 판별 방식을 실험용 전동기에 적용하여 극성의 정상 및 이상 상태에서의 출력 파형을 비교함으로써 제시된 방식이 극성 판별 방법으로서 현장에서 용이하게 활용될 수 있는지를 확인한다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1141-1145
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• 2014

3상유도전동기의 고정자 권선에 이상이 발생하면 직류 여자로 인한 권선 간 상호유도 응답에도 변화를 일으키므로 해당 특성을 전동기의 상태진단에 활용하는 것이 가능하다. 3상 평형 관계에 있는 고정자 권선 하나에 직류 전류를 흘릴 때 나머지 권선에서 유도되는 기전력은 항상 일치된 형태로 나타나며 이들 응답의 불일치 정도는 역으로 전동기의 이상 상태를 나타내는 척도가 된다. 과도 시 유도 기전력 간 불평형은 3상권선의 극성 결선에 오류가 있을 때 특히 크므로 기전력의 차동신호는 권선의 극성 판단 방법으로 활용하기에 적합하다. 본 연구에서는 직류 여자 신호와 이로 인한 나머지 권선에서의 유도전압 간 응답 관계를 전달함수로 나타내는 한편, 응답의 불일치 정도를 가리키는 차동 신호 전압을 멀티테스터로 측정하는 실험을 통해 권선 극성의 이상여부를 현장에서 용이하게 판단할 수 있는지를 확인하는 한편 교류여자의 경우도 함께 살펴보기로 한다.

• Journal of Advanced Marine Engineering and Technology
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• 제38권9호
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• pp.1137-1140
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• 2014

선박의 전동기에 고장이 발생하면 대개 육상에서 수리 후 본선에 다시 재설치 되고 있으나 연결 단자의 기호 표시가 지워지거나 분명치 않을 때는 결선과정에서 전동기 권선의 극성 구별이 어려워진다. 이로 인해 Y-${\delta}$ 기동의 전동기에서 한 권선의 극성을 반대로 잘못 연결하는 경우 전원 투입과 동시에 과다한 전류가 흐르면서 재차 2차 고장으로 이어질 위험이 있다. 이러한 문제와 관련하여 본 논문은 고정자의 1상 권선에 미소 직류전류를 흘릴 때 나머지 권선들에서 유도되는 과도 기전력의 특성을 토대로 아날로그 멀티테스터를 이용한 고정자 권선의 극성 판별법을 제시하고 관련 특성을 분석한다. 또한, 이 같은 방식을 실제 전동기에 적용하여 단계적인 측정과정을 통해 단자연결의 이상여부를 현장에서 용이하게 판별할 수 있는지를 확인해 보기로 한다.

• 수산해양기술연구
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• 제51권3호
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• pp.405-413
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• 2015

Acoustic target strength (TS) measurement and theoretical acoustic scattering models were applied to estimate the TS for assessing the fish biomass. TS measurement was made of ex situ sailfin sandfish Arctoscopus japonicus at 70 and 120 kHz, and then compared to backscatter model prediction. The live sandfish was tethered in seawater using monofilament lines. Measurements were made versus incidence angle, $-50^{\circ}$ to $50^{\circ}$ relative to dorsal aspect directions. Distorted wave Born approximation (DWBA) model was used to calculated TS pattern. The TS values of sandfish (body length: 16.2 cm) at 70 and 120 kHz were -66.94 dB and -64.45 dB, respectively, and were about 20 dB lower than TS of other fishes in Korea waters. These TS levels were distributed within the range of the theoretical TS. Ex situ measurement and theoretical TS may be applied to improve acoustical detection and biomass estimation of the sandfish, and is necessary to measure with various lengths.

• 수산해양기술연구
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• 제49권3호
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• pp.270-281
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• 2013

Hydro-acoustic surveys with scientific echo sounder were carried out to estimate the total density and distribution of the juvenile cod in Jinhae bay, Korea. The surveys were conducted 4 times from May to June using 2 frequency method (38kHz and 120kHz) and beam trawl were used to investigate the species composition. Also the catch amounts of juvenile cod were compared with the cod density estimated by the hydro-acoustic method. It was confirmed that the juvenile cod was stayed in Jinhae bay in early June and There was the relationship between catch of juvenile cod and the estimated density by hydro-acoustic survey. The number of juvenile cod was consequently about 365,000 fish (CV 12.9%) in May and 113,000 fish (CV 9.2%) in May based on the hydro-acoustic data.

• 수산해양기술연구
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• 제49권1호
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• pp.29-39
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• 2013

Fishing vessels have been causing more than 70% of marine casualty in Korea. As a view of the occurring number of marine casualty, it is obvious for fishing vessel to account for the absolute high portion of that in comparison with the non-fishing vessels. That is a natural outcome because fishing vessels have occupied more than 90% of all registered Korean vessels. If we consider it not occurring number, but occurring ratio, we could find out that fishing vessels accounted for 5 times lower than non-fishing vessels in marine casualties. Nevertheless, fishing vessels have not immunity from responsibility for marine casualties at all, because the tendency of it in fishing vessel has been dominating the whole marine casualties in Korea. So for reduction of them, it is indispensable to decrease the casualties of fishing vessel. In this study, the authors tried to carry out many items of them to compare the occurring number with the occurring ratio, and dealt with the casualties of collision and machine damage in detail, because those have not only been occurring most frequently in casualties in Korea, but also led to the death and injury of lives. To reduce the collision and the machine damage, the operator have to keep the watch more strictly and check and keep the machine in good order. And it is necessary for the operator to take more education and training intended to decrease those systematically and continuously, especially for the crews of fishing vessels.

• 수산해양기술연구
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• 제53권4호
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• pp.413-422
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• 2017

The objective of this study was to prove possible effects of a habitable place for fish around semi-submersible drilling rig which measured underwater radiated noise, irradiance distribution of rig's light and conducted experimental fishing in Malaysia territory and observed for distribution of fishes around the rig by ROV during drilling operation in the East Sea of Korea. As a result underwater radiated noise was $130dB/{\mu}Pa$ from 156.25 to 187.50 Hz, irradiance distribution of light was between 21.5 and 43.1 lx. Despite this result, underwater radiated noise was not a threat to fish around rig and low irradiance distribution of light also played a role in the luring influence of the fishes at night. Fish showed up in the beginning of drilling operation and at the end of drilling operation. However, there are few fish in the midst of drilling operation. The main reason for this result was the destruction of the habitable place due to blow out mud and broken pieces of ground formation in drilling hole. The results are expected to contribute to reasonable fishery management around rig.

• 수산해양기술연구
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• 제52권4호
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• pp.356-363
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• 2016

To suggest more efficient fishing operation, it was analyzed using five years (2011~2015) catch data of six Korean-flagged tuna purse seiners (with 1000 mt of haul capacity) operating in the western and central Pacific Ocean. In terms of annual total catch, it presented a two-year cycle of variation on catch, showing that catches of 2012, 2014 and 2015 were high, whereas those of 2011 and 2013 were low. The proportions on fishing effort of associated set were around 21.9~30.8% having 21.5~45.0% of total catch. In this study, there was no significant difference between catches of unassociated set and associated set. When considered having good fishing conditions, fishing activities were concentrated in the areas of Papua New Guinea (PNG) and Kiribati, while it showed that fishing ground spreaded out to the areas of not only PNG and Kiribati but also Federated States of Micronesia (FSM), Tuvalu and Solomon islands. The average number of fishing days was 271 with a range of 246~285. As restriction on fishing operation such as reduction of fishing days and higher fishing fee are expected to strengthen, the result of this study will be helpful to select more efficient fishing methods for purse seine fishery based on fishing conditions.

• 수산해양기술연구
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• 제56권2호
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• pp.155-162
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• 2020

The adjudication of Korean Maritime Safety Tribunal (KMST) was analyzed to collect basic data to identify the cause of the risk that did not appear in the current data provided by the fishermen's occupational accidents of the National Federation of Fisheries Cooperative (NFFC) in stow net fishing vessel from 2015 to 2019. The personnel's carelessness was the most common in 29 out of 33 accidents (87.9%), followed by 25 cases (75.8%) of inadequacy of instructions, 24 cases (72.7%) of inadequacy of education on hazard factor, 20 cases (60.6%) of no personal protection equipment, 18 cases (54.5%) of poor guard, 17 cases (51.5%) of inadequacy of work method, 16 cases (48.5%) of absence of emergency stop button, 14 cases (42.4%) of work practice of poor safety precautions that affected more than 40% of all accidents as accident causes. These causes had a strong influence on each other, and the ratio of accident causes is high. With this relationship, accidents can be prevented or the severity of human injury can be reduced if types of accident process can be estimated with a scenario, and the key points before the accident in the scenario are switched to safe points.

• 한국융합학회논문지
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• 제8권3호
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• pp.265-273
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• 2017

본 연구의 목적은 골프전공 대학생의 사회적 지지, 진로결정 자기효능감, 진로결정수준 간의 관계를 검증하는데 있다. 이런 목적을 위해 편의표집방법을 이용하여 서울과 수도권에 소재한 215명의 골프전공 대학생을 표본으로 추출하였고 기술통계, 상관관계 분석, 그리고 다중회귀분석을 실시하였다. 연구결과를 요약하면 다음과 같다. 첫째, 골프전공 대학생의 사회적 지지는 진로결정 자기효능감에 유의한 영향을 미치는 것으로 나타났다. 둘째, 골프전공 대학생의 사회적 지지는 진로결정수준에 유의한 영향을 미치는 것으로 나타났다. 셋째, 골프전공 대학생의 진로결정 자기효능감은 진로결정수준에 유의한 영향을 미치는 것으로 나타났다. 본 연구는 골프전공 학생들의 진로결정에 필요한 사회적 지지와 진로결정 자기효능감의 역할에 대한 실증적 자료를 제공했다는데 그 의의가 있다.