PES 기판위에 Sputter 증착된 비정질 실리콘 박막 특성

김용해,김동일,손충용,정중희,고영욱,임정욱,윤선진,이진호 한국진공학회 2004 한국진공학회 학술발표회초록집 Vol.- No.-

Shaking Motion Characteristics of a Cod-end Caused by an Attached Circular Canvas during Tank Experiments and Sea Trials

김용해 한국수산과학회 2013 Fisheries and Aquatic Sciences Vol.16 No.3

A shaking motion could be used to improve fish escapement from a cod-end net by creating a sieving effect over the swept volume or by disturbing the optomotor response of the fish. In this study, a perpendicular shaking motion was generated in a towed cod-end net by a circular canvas attached to the end of the codend, which formed a biased cap-like shape. This concept was tested by using a model in a flow tank and by towing a prototype cod-end during sea trials. For the model tests, the amplitude of the shaking motion was 0.6 ± 0.1 times the rear diameter of the cod-end, and the period of the shaking motion was 2.6 ± 0.1 s at a flow velocity of 0.6 or 0.8 m/s. In the sea trials, the amplitude was 0.5 ± 0.2 times the rear diameter of the cod-end, and the period of the shaking motion was 7 ± 4 s at towing speeds of 1.2 or 1.7 m/s. Thus, the shaking amplitude during the sea trials was equal to or less than that observed in the tank tests, and the shaking period was twice as long. The shaking motion described by the amplitude and period could be an effective means to stimulate fish escapement from cod-end during fishing operations considering the response of the fish.

Comparison of Tilt Variation in the Otter Board and Codend of Bottom Trawl Gear during Fishing Operations

김용해 한국수산과학회 2014 Fisheries and Aquatic Sciences Vol.17 No.1

The motion of the otter board on a trawl can affect the motion of trawl nets, and the motion of the codend can affect fish selectiv- ity. Preliminary measurements of the tilt of bottom trawl gear were carried out to compare the tilts of the otter board and codend. The tilt of the otter board was measured by Vector and tilt at 1.5 m anterior to the end of the codend, and the middle upper panel was measured with a micro-DST-tilt logger. Tilt data such as yaw, pitch, and roll were analyzed by the fast Fourier transforma- tion method and global wavelet and event analyses for the period or amplitude. The mean period ± standard deviation of the tilt in the otter board, (5-6) ± 2 s, was similar to the period of the codend, (4-6) ± (2-3) s, whereas the amplitude of the codend was greater than that of the otter board. The yaw and pitch periods were not significantly different between the otter board and codend, but roll was different. Furthermore, the tilt period frequencies of the otter board and codend were not significantly dif- ferent. Accordingly, the tilt motion of the codend was mostly related to the tilt of the otter board.

Fluttering Characteristics of the Ropes and Nets as an Active Stimulating Device inside the Cod End of a Trawl Net

김용해 한국수산과학회 2013 Fisheries and Aquatic Sciences Vol.16 No.2

An active stimulating device (ASD) consisting of a net panel or ropes fluttering in the turbulence inside the cod end was effective in driving fish near the cod end to reduce juvenile by-catch. The fluttering characteristics of the rope and net panel were examined by video observations and analyzed for fluttering amplitude and period in a water channel and in field experiments with a bottom trawl. The amplitude ratio of the fluttering ropes or nets in the tank test increased with the fluttering index as the diameter of the twine, mesh size, flexibility, and flow velocity changed, whereas the period decreased with the above factors. In bottom trawl experiments, the range of mean depth difference in the fluttering net panel was 12-17% of the length of the fluttering net, and the period of depth difference or three-dimensional (3D) tilt was revealed, with shorter ones ranging from 2 to 6 s. The amplitude as depth difference and period from field measurements were similar to those of nets in tank experiments and also to the period of 3D flow velocity inside the cod end. These results could be used to design an ASD that could be used for to the cod end of actual towed fishing gear to reduce juvenile by-catch.

Bycatch Reduction by Experimental Shaking Codend Attached with Canvas in a Bottom Trawl

김용해 한국수산과학회 2015 Fisheries and Aquatic Sciences Vol.18 No.3

An active stimulating method for juvenile fishes to drive escaping from mesh of the codend was examined by shaking canvas in the bottom trawl followed by shrimp beam trawl. Field fishing trials by a bottom trawl were carried out between the Gemoondo and Jejudo in west of South sea, Korea by cover net methods to examine the effect on the reduction of juvenile fish as a discard catch by generating a shaking movement of the codend using two pieces of asymmetrical semi-circular canvas. The mean period of the shaking motion with the round canvas was 10-15 s, and the range of amplitude as a vertical depth change was up to 0.4-0.6 m when towing speed 3.4-4.3 k’t as estimated by peak event analysis. The escape rate of juvenile fish in cover net by total juvenile bycatch (codend and cover-net) in 14 trials increased from 20% in a steady codend to 34% using a shaking codend in the bottom trawl, while the marketing catch or total bycatch was similar between steady and shaking cod ends. There was no difference in the body size of the fish and species composition between the steady and shaking cod ends. Above results demonstrate a new method for bycatch reduction actually up to 18% using an active stimulating device, although further experiments are needed to increase an effective shaking motion of the codend in amplitude and period for more bycatch reduction.

Characteristics of tidal turbulence near the bottom at a coastal trench in Tongyoung, Korea

김용해,홍철훈 한국수산해양기술학회 2014 수산해양기술연구 Vol.50 No.4

Tidal turbulence was examined using three-dimensional tidal velocity data observed at a trench offshore of Tongyoung, Korea. The kinetic energy and intensity, including the variation period of the flow velocity and direction, were used to investigate the relationships between tidal turbulence and fishing gear dynamics, including the effects of swimming fish during fishing operations. As the resultant velocity increased from 0.2 to 0.9 m/s, the kinetic energy also significantly increased, while the turbulence intensity decreased from 50 to 10%. Tidal flow in strong flow fields displayed shorter periods of between 4 and 10 s, as determined by fast Fourier transform, the global wavelet method, and peak event analysis, and the periods were compared with the period of response to swimming fish and to oscillation of fishing gear. As mean velocity increased, velocity amplitude also increased from 0.1 to 0.6 m/s, and its directional amplitude changed markedly from 20 and 90°. Our study suggests that tidal turbulence can influence fish behavior or fishing gear geometry during fishing operations, although our analysis considered only a limited area. In future work, observations should be carried out over a more extensive depth and area.

Analysis of body size selectivity of by-catch using the cover net method for a shrimp beam trawl

김용해 한국수산해양기술학회 2015 수산해양기술연구 Vol.51 No.2

Selectivity and by-catch are the main features used to define fish catch for fisheries management or to determine fishing gear efficiency. A fish girth distribution analysis was carried out to determine the retention rate of juveniles discarded and to establish common selectivity for a multispecies catch. Total body length, body weight, and girth of juvenile fish retained in the cod-end and cover net separately were collected using an 18-mm mesh cover net during 12 fishing trials with a 41-mm cod-end beam trawl. The by-catch weight ratio in the cod-end was twice that of the by-catch ratio in number. The 50% selectivity of body length and 50% girth of redfin velvet fish were not significantly different between the cod-end and cover net, whereas those of other fish species were significantly different between the cod-end and cover net. The difference in 50% selectivity girth of other fish between the cod-end and cover net was similar between cod-end mesh size and cover net mesh size. Furthermore, the difference in 50% body length selectivity of other fish between the cod-end and cover net was almost double the difference in girth. Girth selectivity in a multispecies catch using towed fishing gear was effectively used to determine fish and net mesh size.

Complex Movements of Skipjack Schools Based on Sonar Observations during Pelagic Purse Seining

김용해 한국수산과학회 2007 Fisheries and Aquatic Sciences Vol.10 No.4

Simulation and Three-dimensional Animation of Skipjack Behaviors as Capture Process during Purse Seining

김용해,박명철,하석운 한국수산과학회 2008 Fisheries and Aquatic Sciences Vol.11 No.2

We modeled fish school movements as a capture process in relation to the purse seine method using the three steps of the stimulus-response process (i.e., input stimuli, central decision-making and output reaction). Input stimuli of the model were categorized as either physical stimuli such as visual stimulus, sound stimulus, water flow, and weather or as biological stimuli such as species and size, swimming performance, sensual sensitivity, and presence of prey or predators. The output process determining the spatial orientation of the fish school for 3-D movements was based on swimming speed and angular change in the fish response, and these movements were animated as the relative geometry between the fish school and the purse seine. Simulations were carried out for skipjack tuna (Katsuwonus pelamis) schools reacting to a pelagic purse seine in the southwest Pacific Ocean. Simulation results showed that escape ratios varied from 20 to 70% by the relevant ranges in the stimulus-response thresholds, swimming speeds, and angular changes of fish schools were similar to those observed in the field. Therefore, with knowledge of relevant parameters, this model can be used to predict capture and escape probabilities of purse seine operations for different fish species or conditions.

Generating Complex Klinokinetic Movement of 2-D Migration Circuits Using Chaotic Model of Fish Behavior

김용해 한국수산과학회 2007 Fisheries and Aquatic Sciences Vol.10 No.3