• 수산해양교육연구
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• 제5권2호
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• pp.90-97
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• 1993

Pair trawling is one of the important fishing methods for Korean fisheries, and is working in the western sea of Korea - the Yellow Sea and the East China Sea. On the engine power of the trawlers, 72% of 190 pairs of trawlers were equipped with 450ps class engine, and 21% with 450~750ps and merely 7% with in 750ps class 1980. Thereafter the engine power has grown up, so that 450~750ps occupy 28% and 750ps or more 27% in 1992. Main objective fishes of pair trawling were traditionally flat fishes, so the fundamental shape of pair trawl net was a four - seam net, but by the gradual shortage of flat fishes, roundfishes has been noticed. So the six - seam net which performs high opening of net mouth has been used widely since 1985. In the six - seam net, the length of wing was not so short in the beginning but became short in the later instead of the net pendant elongated, and also the pendant was separated into three pieces according to the change of wing structure. Since the 1990's, the objective fishes has gradually been changed into pelagic fishes, the fishing technique is required to fit the behavior of fishes. So the midwater trawling or the multi -layer trawling became required.

• 수산해양기술연구
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• 제24권2호
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• pp.78-82
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• 1988

한국근해의 중층 트로올선에서 전개판의 수중중량을 경감시켜서 끌줄을 길게 주므로서 전개력을 향상시키기 위하여 스티로폴뜸을 전개판의 천정판에 고정시키고 끌줄 길이와 예망속력을 변화시켰을 때의 전개판의 깊이와 전개간격을 실측한 것을 분석.검토한 결과는 다음과 같다. 1. 전개판 깊이는 끌줄 길이가 100m이고 예망속력이 101~108m/sec인 범위에서 뜸이 있을 경우 41~25m, 뜸이 없을 경우 45~26m이고, 뜸줄 길이가 150m일 경우는 뜸이 있을 경우 68~44m, 뜸이 없을 경우 74~46m로서 뜸이 있을 경우가 없을 경우보다도 9~4% 정도 얕았다. 또 실측치는 어느 경우나 계산치보다도 15% 작았다. 2. 전개판의 전개간격은 끌줄 길이가 100m이고, 예망속력이 1.1~1.8m/sec인 범위에서는 뜸이 있을 경우 34~41m, 뜸이 없을 경우 30~38m이고, 끌줄 길이가 150m일 때는 뜸이 있을 경우 44~50m, 뜸이 없을 경우 37~46로서 있을 경우가 없을 경우보다도 끌줄 길이 100m에서 10%, 150m에서 15%정도 더 컸다. 또, 실측치는 계산치보다 항상 컸으며 계산치에 대한 실측치의 비는 끌줄 길이가 100m일 때 1.17~1.14, 150m일 때 1.17~1.09이었다. 3. 날개 끝 간격은 끌줄 길이 100m인 때 뜸이 있을 경우가 없을 경우보다 1m 정도 크고 유효망구면적으로는 10% 정도 크며, 끌줄 길이가 150m인 때는 그 차이가 2m로서 유효망구면적으로는 20% 정도 크다고 추정된다. 따라서 전개판에 뜸을 달아서 전개판의 수중중량을 일시적으로 가볍게 해 주는 것은 유효망구면적을 크게 하므로 어획성능향상에 상당히 도움이 될 것이 기대된다

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권5호
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• pp.2674-2697
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• 2019

Identity authentication is a crucial line of defense for network security, and passwords are still the mainstream of identity authentication. So far trawling password attacking has been extensively studied, but the research related with personal information is always sporadic. Probabilistic context-free grammar (PCFG) and Markov chain-based models perform greatly well in trawling guessing. In this paper we propose a systematic targeted attacking model based on structure partition and string reorganization by migrating the above two models to targeted attacking, denoted as TG-SPSR. In structure partition phase, besides dividing passwords to basic structure similar to PCFG, we additionally define a trajectory-based keyboard pattern in the basic grammar and introduce index bits to accurately characterize the position of special characters. Moreover, we also construct a BiLSTM recurrent neural network classifier to characterize the behavior of password reuse and modification after defining nine kinds of modification rules. Extensive experimental results indicate that in online attacking, TG-SPSR outperforms traditional trawling attacking algorithms by average about 275%, and respectively outperforms its foremost counterparts, Personal-PCFG, TarGuess-I, by about 70% and 19%; In offline attacking, TG-SPSR outperforms traditional trawling attacking algorithms by average about 90%, outperforms Personal-PCFG and TarGuess-I by 85% and 30%, respectively.

• 수산해양기술연구
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• 제45권4호
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• pp.223-233
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• 2009

It has been considered that fishing areas for shrimp beam trawl have been in ruin because Korean local governments have permitted trawling into the areas limited by the fisheries local regulations from 1994. Physical and biological effects of the trawling were investigated in the study. Physical effects were investigated by optical methods such as trawling tracking by side scan sonar and comparing the gear both before and after trawling. Biological aspects were investigated by grab sampling of benthic animals, concentration of trace metals in sediment and a flux evaluation of ${NH_4}^+,\;{PO_4}^-,\;and\;SiO_2$ by coring. The fishing activity had physical impacts on the seabed but these recovered naturally in less than fourty days naturally, which increased the benthic biodiversity, increases the trace metal concentration of and nutrient flux into the seawater, especially phosphate and silicate. This method and these results can help in further studies looking for disturbances by fishing.

• Journal of Species Research
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• 제11권3호
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• pp.188-193
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• 2022

Araeosoma owstoni Mortensen, 1904, a newly recorded sea urchin, was collected from the Korea Strait by trawling during a research expedition in April 2017. The specimen was damaged and was severely peeled off on the aboral side during trawling. However, a test and the surface of the oral side of the sample were well preserved, allowing us to successfully identify it. The species was distinguished by the large and flexible test, the tiny apical section, and the interambulacra width which is twice of the ambulacra. Pedicellaria tridentate and triphyllous were presents, but tetradactyle pedicellaria was absent due to severe peeling on the aboral side. Moreover, a length of 1,212 bp sequence from mitochondrial COI gene was obtained and this sequence covered the general DNA barcoding region. The mean of interspecific divergence within A. owstoni from Korea and other eight species of Araeosoma from the GenBank was 6.8%. This value indicated that our species was clearly distinguishable from the others. Thus, the first Araeosoma species occurring in South Korea is presented in this study.

• 한국해양환경ㆍ에너지학회지
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• 제3권4호
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• pp.91-98
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• 2000

본 연구는 남해안에 위치한 진해만의 바다 밑에서 수집한 쓰레기를 유형별로 분류하는 과정을 포함하고 있다. 1998년 2월부터 1999년 1월까지 저인망을 사용하여 총 11회의 수집 과정을 통하여 바다쓰레기를 수집하였다. 1회에 60-90분의 간격으로 바다밑 쓰레기를 채취하였으며 이를 8가지(플라스틱, 어구, 금속성 물질, 나무, 고무 혹은 피혁, 유리, 섬유 및 기타)의 형태로 분류하였으며 이를 통하여 8가지의 형태별로 분류된 쓰레기의 개수와 무게 그리고 분포 등의 결과를 얻게 되었다. 본 연구의 결과 조사지역의 단위면적(ha) 당 27.8개(총 1,612개), 3,130 g(총 193,820 g)의 바다쓰레기가 조사되었으며 이중 항목별 조성에 있어서 플라스틱류와 어구류의 구성비가 높았으며 무게별 조성에 있어서는 금속류와 어구류가 가장 높은 것으로 조사되었다.

• 수산경영론집
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• 제45권1호
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• pp.63-77
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• 2014

This study is to estimate the recent changes in total factor productivity of 15 Korean adjacent water fisheries based on Malmquist productivity indices. The study adopted both input and output oriented productivity measures utilizing a hyperbola distance function. In addition to this point, the study also calculated the 95% confidence interval for the various components of the productivities in order to access the statistical significance of estimates using 2000 times of re-sampling process through the smoothed bootstraping. The results of the study showed us that there was 18% reduction in the overall total factor productivity during the study period from 2007 to 2011, which turned out to be 5% of annual decrease in productivity. The study found that the main reason of this decrease in total productivity is about 22% downward shift of a fisheries production function due to recent conditions of a devastated fishing ground. When we evaluated the statistical significance of changes in technical efficiency combining both pure technical and scale efficiency based on the 95% confidence intervals, we could not find any evidence of changes in those components of total factor productivity. When we accessed the productivity of the each of 15 adjacent water fisheries methods, only the large danish seine fisheries showed us about 7% increase in productivity. Even though the large trawling and the large tow-boat trawling revealed no changes in productivity, all of the other 12 fisheries suffered the decreases in productivities.

• 수산해양기술연구
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• 제32권1호
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• pp.1-6
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• 1996

Towing tension of the model nets were determined by the load cell(O~20kg, 20DBBP) in front of W$T_mA$ = 1.57 . $V^1.86$ (unit: kg, mlsec) $T_mB$= 1.58 . $V^1.90$ 2. The towing tension of the full scale net was almost coincided with the results obtained by the model experiment. The towing tension(T) can be expressed as a function of the towing veJocity(V) as T=479$V^1.75$(unit: kg, k't)

• 수산해양기술연구
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• 제29권3호
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• pp.183-190
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• 1993

A cooperative Korea-Japan investigation for the demersal fisheries resources of the East China Sea carried out by using the training ship Oshoro Maru belong to Hok-kaido University, Japan, during 1-8 November, 1991. The research vessel sampled 15 stations with demersal trawls on the East China Sea, and 1,364 nautical miles of track line were surveyed hydroacoustically. The hydroacoustic observations were taken with a scientific echo sounder operating at two frequencies of 25 kHz and 100 kHz, and a microcomputer-based echo integrator. Fish samples were collected by demersal trawling, and temperature, salinity and dissolved oxygen were measured with a CTD system. The target strength of fish school was estimated from the relationship between mean scattering strength and catches caught by demersal trawling. The results obtained can be summarized as follows: 1. The mean backscattering strength for 15 layers occupied by demersal trawls at 25 kHz ranged from -70.4 dB to -59.1 dB. Then the catch per one hour ranged from 8.2 to 587.5 kg/hour. 2. The mean backscattering strength for the entire layer between transducer and seabed in the survey area of the East China Sea at 25 kHz and 100 kHz were -68.0 dB and -73.1 dB, respectively. 3. The mean fish-school target strength per one kilogram at 25 kHz and 100 kHz were -28.3 dB/kg, and -30.4 dB/kg, respectively.

• 수산해양기술연구
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• 제37권2호
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• pp.85-94
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• 2001

1997년 10월 2일부터 10일 사이에 동해에서 계량어군탐지기를 이용하여 수집한 어탐기록과 CTD를 이용한 해양관측 결과 및 중층트롤에 의한 어획물의 생물학적 조성 등을 비교, 분석하여 어족생물의 일주기적인 유영행동특성을 검토, 고찰한 결과를 요약하면 다음과 같다. 1. 1997년 10월 3일에 북위 $36^\circ$04', 동경 $130^\circ$53'의 조사 해역의 경우, 수온약층은 수심 60~110m의 수층에 형성되었고, 혼합층과 수심 250m이 저층 수괴 사이의 온도차와 염분 차는 각각$21^\circ$, 0.6%이었다. 2. 조사대상해역에 있어서 1997년 10월 2일~3일에 대한 일주기적 연직회유행동을 고찰할 때, 주간에 수온약층 아래쪽 수심 250 m 전후에 분포하는 생물군의 평균상승속도는 시간대에 따라 약간의 차이는 있으나 0.51m/min이었고, 일출을 전후하여 100~ 125 m 수층에서 하향 이동하는 생물군의 평균하강 속도는 0.41 m/min이었다. 3. 조사대상해역에 있어서 어군의 체적산란강도는 표층, 중층, 저층의 순으로 높았고, 개체 생물의 반사강도는 저층, 중층, 표층의 순으로 높게 나타났다. 4. 중층트롤에 의한 시험조업의 결과, 초음파 산란층에 분포하는 어획 생물 중에서 살오징어가 점유하는 비율이 가장 높아 95.7%이었고, 그 평균 외투장과 평균체중은 각각 25.3 cm, 390.0g이었으며, 위 내용물은 살오징어, 갑각류, 치어류 등이었다.