• 수산해양기술연구
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• 제30권1호
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• pp.13-24
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• 1994

Purse seiner detects a fish school navigating in full speed with the aid of fish finder, sonar, helicopter, etc., and casts a net quickly to enclose the fish school in purse seine net according to the movement of the fish school, wind, and current. At this moment, if the time of casting a net, direction, speed, and turning circle are net suitable, it is unavoidable to lose fish school founded with hard efforts and we only consume our efforts of casting and hauling the net. Therefore, in order to enclose the fish school to enhance the amount of fish for each casting, the author investigated the type of ships equipped with purse seiners and examined maneuvering tests so that we provide some basic information to figure out the ability of steerage correctly. The results obtained are summarized as follows: 1. Block coefficients of pelagic tuna purse seiners with gross tonnage between 500 and 1500 tons are recorded between 0.50 and 0.55 which are greater than those of off shore purse seiners recorded as between 0.44 and 0.54 and less than those of various cargo ships recorded as between 0.56 and 0.84. 2. L/B, L/D, B/D, B/T, and T/D of the class of gross tonnage between 75 and 130 tons are respectively 4.49, 11.00, 2.45, 2.85 and 0.86 as their average and those of the class of between 500 and 1500 tons are 4.89, 10.53, 2.15, 2.73 and 0.75 respectively, which are quite different from those of various cargo ships recorded as 6.0~7.5, 11.0~12.0, 1.6~2.0, 2.2~2.8 and 0.65~0.75 respectively. 3. Rudder area ratio of purse seiners of the class of between 75 and 130 tons is 1/24~1/31 and that of the clase of between 500 and 1500 tons is 1/36~1/42 which is greater than that of various cargo ships recorded as 1.45~1.75. 4. On speed-length ratio of purse seiners. 111 Dong-a has the biggest value 2.94 the class of 130 tons has 2.52 the class of between 75 and 100 tons has 2.30~2.35 and the class of between 500 and 1500 tons has 1.99~2.05. 5. Turning circle of stern trawlers Pusan 404 and Haelim 3 are measured as below according to rudder angles 5$^{\circ}$, 15$^{\circ}$, 25$^{\circ}$ and 35$^{\circ}$ respectively. Advances are 11.3~13.6, 6.0~7.1, 3.6~4.8 and 2.5~3.5 times of LPP respectively. Tactial diameters are 15.2~18.6, 6.9~8.0, 4.2~4.9 and 2.9~3.5 times of LPP. Purse seiner 111 Dong-a with rudder angle 35$^{\circ}$ has a good yaw with quick responsibility since its advance is 2.2~2.3 times of LPP and since its tactial diameter is 2.0~2.1 times of LPP. 6. In full ahead going of purse seiner 111 Dong-a, it takes about 2 minutes and 10.6 times of LPP from the reverse turning its engine into full astern to the ship speed 0. In its full astern going, it takes about 1 minute and 5.1 times of LPP from the reverse turning its engine into full ahead to the ship speed 0. In its full ahead going, it takes about 2 minutes and 50 seconds and 12.3 times of LPP from stopping its engine to the dead slow ahead speed 3.2 knots.

• 수산해양기술연구
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• 제19권1호
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• pp.25-32
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• 1983

레이다에서 전파반사표식으로 사용하고 있는 코오너리프렉터를 수중 초음파반사표지로 응용하기 위하여, 코오너리프렉터의 수중초음파반사특성을 이론적으로 고찰하고, 28,50,75KHz의 주파수에 대하여 주파수가 높을수록 높았고, 반사지향성은 직경이 증가함에 따라 예리하였다. 2. 직경이 150mm이고, 코오너각이 15$^{\circ}$, 30$^{\circ}$, 45$^{\circ}$, 60$^{\circ}$, 90$^{\circ}$인 코오너리프렉터의 최대반사강도는 각각 -25.0dB, -17.2dB, -15.2dB, -13.4dB, -11.0dB로서, 코오너각이 증가함에 따라 점차 증가하는 경향을 나타내었으나, 그 주엽 수는 코오너각이 증가함에 따라 점차 감소하였다. 3. 직경이 80mm이고, 코오너각이 90$^{\circ}$인 코오너리프렉터를 2,3,4,5,6,7개씩 음속축을 중심으로 간격없이 평면배열한 경우에 있어서, 반사강도는 각각 -18.2dB, -16.5dB, -15.4dB, -14.3dB, -13.4dB, -12.9dB로서, 이론치와 거의 일치하였으며, 코오너리프렉터수의 평방근에 비례하였다. 4. 직경이 80mm인 코오너리프렉터의 방향각(0,$\theta$sub(a))이 0$^{\circ}$, 2.5$^{\circ}$, 5$^{\circ}$, 7.5$^{\circ}$, $10^{\circ}$, 12.5$^{\circ}$인 경우, 반사강도는 각각 -21.2dB, -21.9dB, -23.4dB, -26.0dB, -30.0dB, -36.8dB로서, 방향성이 증가함에 따라 반사강도는 급격히 감소하는 경향을 나타내었다.