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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean society of Fisheries Technology
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Journal DOI :
The Korean Society of Fisheries Technology
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Volume & Issues
Volume 21, Issue 2 - Jun 1985
Volume 21, Issue 1 - Mar 1985
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Analysis of Underwater Noise in the North Sea
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 1~6
The underwater noise was measured by piezo-electric hydrophones submerged in the water at three different depths. The signals were led through connection cables to preamplifiers, and recorded simultaneously by a four channel tape recorder, and analysed by high resolution signal analyzer. The measurements were carried out at the fjord Skossvassen in archipelago off Bergen and at the cost of Norway in the North Sea. The results of the measurements and the analysis showed that the underwater noise consists of a steady broad band noise superposed by intermittent pulse of various strength. The noise levels measured in fjord Skossvassen indicated that they were generally higher at the shallow (10m) hydrophone than at the deeper hydrophone (25m, 50m). This tendency was not very distinct, however, the noise sources are close to the surface. The underwater noise spectrums measured in the open sea of Norway showed almost similar situation in all layers. This tendency showed that the noise sources are not close to the surface but they are far away from the measuring positions.
Vertical Distribution of the Underwater Ambient Noise Level in the Korea East Coast Areas
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 7~11
Underwater ambient noise in the depth 5m to 200m layers was measured at 14 point from the 24th of July to 2nd of August, 1984, in the Korean east sea areas. The underwater ambient noise pressure level was depended upon configuration of the sea bottom and sea condition, which was formed type of prevaling noise at a long distance from coast and type of intermittent and regional noise at a short distance from coast.
ARC Discharge Sound Source in Underwater
Chang, Jea-Hwan ; Chang, Jee-Won ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 12~18
In general the impulse sound sources of underwater generated by electric arc discharge had used static energy of the charged capacitors. The author proposed an underwater arc discharge sound source using secondary voltage of high voltage transformer without capacitors. The arc discharge device was composed of a high voltage transformer and a switching system. The impulse current in the primary turn of the high voltage transformer is controlled by the switching system and inductive current of the secondary turn in the high voltage transformer is used in making impulsive arc discharge. A series of experiment have been carried out to observe the acoustic characteristics of the impulse sound source generated by the arc discharge. The results obtained were as follows: 1. Secondary current at the time of arc discharge keeps after ohm's law in the beginning and the maximum current flows out as soon as arc discharge breaks out. 2. A time difference between a start of applied current and a generation of arc discharge sound is the 3msec and it is generated arc sound when breaking down electric insulation at maximum voltage. 3. The sharper the end of electrodes and the higher the secondary voltage, the higher the sound pressure level. 4. Arc discharge sound was generated even at the distance of 100cm between electrodes and was stably reproductive at the gap of 1cm to 100cm. 5. Electric arc discharge sound wave is a shock wave of pulse-width of 0.15msec and spectral distribution of it is plenty of low frequency components less than 10 KHz.
Response of Amber Fish, Seriola aureovitta to Electric Stimuli
Chang, Ho-Young ; Lee , Byoung-Gee ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 19~27
It is important to minimize the electric power consumption to stimulate the marine fish, for the much electric power consumption is required to induce the response. The experiment was made to find out the threshold value for the electrotaxis or electronarcosis on amber fish, Seriola aureovitta(TEMMINCK et SCHLEGEL). The impulse rate and width which minimize the electric power consumption were examined. The experiment was carried out in the acryl tank(49W
50Hcm) which is equipped with the two electrodes. The results obtained are as follows: 1) The electric power consumption which is required to induce the electorates and electronarcosis is tended to decrease as the lower impulse rate. 2) The mean electric power consumption for the electronarcosis is about 4.5~10 times of the electrotaxis. 3) The impulse width which minimize the electric power consumption is 0.5msec.
Characteristic of Damping Curve for the Directional System of Magnetic Compass
An, Yeong-Hwa ; Jeong, Gong-Heun ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 28~34
This paper describes that the characteristic of movement and the performance of the directional system of the liquid magnetic compass analyze and investigate in the kinds of compass and the coefficient of viscosity of the liquid of compass, which the horizontal magnetic field of the geo-magnetic is varied from the equator to the polar region (0.39 gauss-0.03 gauss) by use of apparatus generating artificial magnetic fields. The results are as follows; 1. It is confirmed that the measured values and the calculated values on the characteristic of damping curve by the type of compass and coefficient of viscosity has almost agree with one another. 2. As the horizontal magnetic force geo-magnetic field approaches around the equator (0.39 gauss), the horizontal magnetic field get near the polar region (0.03 gauss), its period is to be longer and the compass card prove not to be more stabilized. 3. The coefficient of viscosity of the liquid in the A, B, C, D and E compasses used in the experiment is estimated 0.03 poises, 0.02 poises, 0.02 poises, 0.015 poises and 0.048 poises respectively by computer simulation
Selective Response of Rock bream and Sea bass to the Color Nettings
An, Heui-Chun ; Yang, Yong-Rhim ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 35~40
The author carried out experiments to find out the response of rock bream, Oplegnathus fasciatus (TEMMINCK et SCHLEGEL) and sea bass, Epinephelus septemfasciatus (THUNBERG) to the color nettings. The experimental water tank(180L
55Hcm) was set up n a dark room and water level was maintained 50cm high from the bottom. The tank was devided three longitudinal sections marking 60 cm interval. The illumination systems, consisted of 20 watt fluorescent lamps and filter, were suspended adove the tank. Two different color nettings selected from five colors (red, yellow, green, blue, black) were placed in each end section of the tank. Ten fish were used in each experiment and the fish were acclimatized in the dark for 60 minutes before experiment. After the light on, the number of fish in each section of the tank was counted in every 30 seconds interval for 30 minutes. The results obtained are as follows: 1. The rock bream selected the color nettings in the order of yellow, black, blue, green and red. 2. The sea bass selected the color nettings in the order of green, black, red, blue and yellow.
Environment of the Purse-seiner Fishing Ground in the Tsushima a Current
Cho, Kyu-Dae ; Yang, Yong-Rhim ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 41~61
The purse-seine fishery is very important in the coastal fishery of Korea and the main fish species of this fishery are mackerals and also the main fishing grounds are Tushima Current region, To investigate the relationship between the fishing grounds of mackerels and oceanographic condition, the distribution of mean catches of mackerals of each size (1974~1982) was firstly examined and the oceanographic observation carried out in eastern and western area of Cheju island, being main fishing grounds, in July and October, 1983. The results are as follows: The main fishing grounds of mackerals were also in the Tsushima Current region in southern sea of Korea and the season of the good catches are in May and September to October. The small and medium size of mackerals of which the body lengths are 27 cm to 31 cm, about 2-3 ages, occupied about 90% but the smaller size mackerals of which body lenth is 22 cm (1 age)were about 40 to 70% in February to March. The locations of seasonal fishing grounds could founded by 15
isotherm which indicates the Tsushima Current Water. With trace of this isotherm it was founded that the fishing grounds near the Korean Strait than that of south of Cheju island moves faster northward and/or later southward. The main fishing grounds eastward and westward of Cheju island were the front areas formed between the Tsushima Current Water and the southern coastal water of Korea or Yellow Sea Bottom Cold Water. And also the distributions of transparences, water colors and the penetration of sun light of this fishing grounds were similar to that of the temperature, the salinity or volume of planktonic organism.
Secular Variations of Surface Water Temperature in Youngil Bay
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 62~66
The periodic variations of the surface water temperature and the relationships between the surface water and air temperature are found in Youngil bay as follows: It is considered that the average surface water temperature is the lowest in February and the highest in August in the Youngil bay (Pohang bay and Janggi cape) from January, 1962 to December, 1981. It is only in October and November that the average surface water temperature was higher in pohang bay than in the Janggi cape from January, 1962 to December, 1981. Since the periodic secular variation in the vincity of Youngil bay and the variation of the Tsushima Current seem to have similar tendencies, we may conclude that the changes of the surface water temperature in Youngil bay are primarily influenced by the Taushima Current. The average temperature of surface water is 14.5
in Pohang bay and 15.
in Janggi cape in the secular variation.
Analysis on the Structual Response of Ship Structures Subjected to Slamming Impact
Goo, Ja-Sam ; Hong, Bong-Ki ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 67~74
This paper describes a method for evaluating the vertical hull girder vibratory response associated with slamming of a ship at sea. The ship hull is considered as a nonuniform beam divided into twenty equal sections. Impact forces and structural parameters are used as input quantities on the computer (PRIME 550-II) to obtain the hull girder response in terms of relative displacements, accelerations, bending moments, shear forces, and stresses. Sample calculations are made on a MARINER-Class hull form using first three modes and again using first ten modes and again using first ten modes. The computed response is compared with Antonides's result in order to evaluate the adequacy of the method employed. It is believed that the method is another noticeable one to obtain whipping stresses of a ship to a seaway.
Influence of Glass Fiber Orientation on the Bi-directional GFRP Characteristics
Suh, Jung-Joo ; Moon, Duk-Hong ;
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 75~81
The tensile and dielctric strength of the epoxied resin with bi-directional woven glass fibers with a laminate of two layers(G-10) are studied, and the test parameter is the angle between fiber orientation and the tensile axis. The obtained results may be summaried as follows: 1) when the angle between fiber orientation and tensile axis was varied from 0
the yield and fracture stresses have a tendency to decrease with increase in the angle. Especially, the decrease rates in the yield and fracture stresses are changed remarkably in the range of 0
. 2) The fracture strain has showed the maximum value when the angle between fiber orientation and tensile axis is 45
, and showed the rapid rate of change from 15
. 3) For the sample with same angle between fiber orientation and tensile axis the maximum dielectric strength under compressive stress is decreased with increase in tensile stress, when the compressive stress is increased as a parameter of tensile stress. 4) When the angle between fiber orientation and tensile axis is 45
, the dielectric strength showed the worst value, as the mechanical strength did.
Journal of the Korean society of Fisheries Technology , volume 21, issue 1, 1985, Pages 82~87