The vertical distribution and activity patterns of fishes during the evening and morning transitions between day and night were studied acoustically and by bottom trawling in November 1990-1992 in thermally stratified waters of the East China Sea. The acoustic data were collected from six stations with a scientific echo-sounder operating at two frequencies of 25 and 100kHz, and the echograms were used to determine the vertical distributions of fish. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echograms, and the species and length compositions were determined. At each station, vertical profiles of water temperature, salinity and dissolved oxygen were taken with a CTD system and were related to the diel movements and the depth distributions of fish. During the day most fish were within several meters above bottom, but began to migrate upwards just before sunset, and during the night they were dispersed in midwater. Prior to sunrise with a thermocline present, one group of the fish aggregation occurred in dense schools slightly above the thermocline, while the other group occurred with the numerous single fish-traces bellow it. These groups of aggregations rapidly began to migrate toward the bottom across the thermocline from about 40 min before sunrise. Trawl hauls in the bottom strata below the thermocline with the characteristic single fish traces yieled invariably catches dominated by snailfish and fishing frog with minor quantities of other species in all stations. Hence, the results indicate that snailfish and fishing frog were the dominated scatterers in the depth strata below the thermocline, and the single-fish recordings were mainly snailfish. The fish species such as anchovy and juvenile mackerel in bottom trawl catches is poorly represented in relation to the mesh selectivity of the trawl net, but their occurrence suggest that the fish-school recording above the thermocline were due to these species which migrated vertically across the thermocline, with a temperature gradient of about 8$^{\circ}C$, from the water layers near the bottom at night. Accordingly, we conclude that the vertical distribution and activity patterns of snailfish were strongly temperature dependent and in the termally stratified waters, the upper limit to diel activity was closely linked to the position of the thermocline.

The speed of vertical migration and the volume backscattering strength of the scattering layers during the evening and morning transitions between day and night were measured in November 1990-1992 in thermally stratified waters of the East China Sea. Acoustical measurements were carried out using a scientific echo-sounder operating at t재 frequencies of 25 and 100kHz, and using an echo-integration system connected with a micro-computer. Biological sampling was accomplished by bottom trawling to identify fish species recorded on the echo sounder, and the species and length compositions were determined. The values of scattering strength were allocated to group of fishes according to the fish traces on the echo recording paper and the species composition of trawl catches. The vertical velocities of migration derived from the changes in the depths and the values of peak scattering strength of the dense layer vertically migrating toward the bottom or toward the surface. The trawl data suggest that snailfish and fishing frog were the most abundant fishes in all research stations. As sunrise approached, the fish formed a strong concentration just above the thermocline. The the highest values of scattering strength in the entire water column appeared in the depth strata above the thermocline just before the begining of downward migration. As soon as the fish began to migrate downwards across the thermocline, the values of the scattering strength in the depth strata above the thermocline rapidly decreased, while the values for the scattering layer moving slowly toward the bottom gradually increased. During the 1992 surveys, the speed of the vertical migration was estimated to be 0.38m/min in the upward migration and 0.32m/min in the downward migration, respectively. That is the rate of vertical migration was slightly higher at dusk than at dawn. Similar migration patterns were observed on different stations and under different weather conditions during the surveys in 1990.

The hardware and the software of the prototype telemtry system to monitor the behavior of the fish are designed. This system consistes of five parts I. e. three omni-directional hydrophones, three ultrasonic receivers, a single board computer for the signal processing, two RF transceivers for the data communication, and a personnel computer. The sensitivty of the hydrophones is -170dB(re 1V/$\mu$Pa), the gain and the 3dB receiving bandwidth of the ultrasonic receivers are 115dB and 1500Hz respectively, and the sampling period is 33.3$\mu$sec in the signal processing part. The positioning error of the system using hyperbolic method is estimated to be less than 0.2m in case that the pinger locates inside of the baselines. The perfomance of the system considering a practical use was examined by numerical simulation and a water tank test of a pinger tracking experiment. In results, the system developed in prototype was confirmed that it could be useful for monitoring the behavior of fish in the limited water area.

This paper describes about the behavior of the lseraeli carp (Cyprinus cartio. body length 43cm) and the Red seabream (Chrysophrys major. body length 35cm) aquacultured by telemetry techniques. The telemetry system consists of a pinger of 50kHz, three omni-directional hydrophones and ultrasonic receivers, a single board computer for the signal processing, two RF transceivers for the data communication, and a personnel computer. Those fish tagged the pingers were tracked by the LBL method, and its location was calculated by the hyperbolic method. The average speed of the lsraeli carp was about 1.0 times of the body length in a farming water tank (24$\times$24$\times$1m), and the Red seabream 1.3 times of the body length in a farming raft (10$\times$10$\times$5m). A variation of the speed of the lsraeli carp was higher than the other one.

This paper describes about the behavior of the Striped mullet (Mugil cephalus) in the setnet by telemetry techniques. The telemetry system consists of a pinger of 50KHz, three omni-directional hydrophones and ultrasonic receivers, a single board computer for the signal processing, two RF transceivers for the data comunication and a personnel computer. The fish tagged the pinger was tracked by the LBL method, and its location was calculated by the hyperbolic method. The fish escaped from sea surface to 7m deep right after release and had been swum near the sea surface after 30 minutes being released. Also, in horizontal movements, the fish stayed long time around the enterance of the square net in setnet, and showed the escaping behavior repeatly. The average speed of the fish was about 0.41m/sec(1.1 times of the body length)

Catching performance of a mechanized pollock longline system compared with traditional one were examined in order to evaluate the practicality during two cruises in the Sokcho area. Mechanized longline system consists of random baiter, bait cutting machine, storage rails, and line hauler. Baiting efficiency of random baiter was 90-95% with 4-5kt shooting speed. Catching performance of the first experiment, salted sand lance only used as a bait. shows no significant difference between mechanized operation with use fresh sand lance as a bait caught significantly more pollock than traditional one with use salted sand lance (P<0.016). Improved catch rates were about 2 times. As soak time goes on, relative catching efficiency shows a steady increase up to 6~7 hours and thereafter gradually decrease.

The new course distances of a ship are one of the important factors of the safety handling as the indices to indicate directly her abilities of course alteration. Recently, International Maritime Organization (IMO) exhorts that all vessels should use maneuvering booklets in which are drawn the curves of new course distances obtained from the test of measuring them and noted other maneuvering performance standard in various navigation conditions. This paper describes the method to calculate many new course distances for many rudder angles by turning circle test without observation or using other calculating methods. The main results are as follows: 1) The mean difference of the distances between two new course distances by the turning circle test and heading test of the experimental ship was about 7.7% vaules of the ones by the heading test. when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$ . These new course distances were therefore found to be small in difference of those. 2) The mean difference of the distance between two new course distances by the turning circle test and the maneuvering indices of the experimental ship was about 4.5% values of the ones by the maneuvering indices, when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$, these new course distances were therefore found to be small in difference of those. 3) The mean difference of the distance between two new course distances by the turning circle test and the observation of the experimental ship was about 6.1% values of the ones by the observation, when her altering angles were $48^{\circ}$, $63^{\circ}$and $70^{\circ}$, using the rudder angle of $35^{\circ}$. These new course distances were therefore found to be small in difference of those. 4) It is confirmed that many new course distances for many angles can be calculated easily by using the method of ship's simple turning circle test, without observation or using the maneuvering indices and heading test method. 5) It is considered to be helpful for the safety of ship handling to draw curves of new course distances by turning circle test and $\phi_4$ - $\phi_2 by heading test, and utilize them at sea.

Recently, with the rapid development in the industries such as an iron mill and chemical plants, there is enlarged by the use of the piping. Sepecially, the piping connected with a fluid, if it is increase the speed of running fluid, ought to generate cavitation phenomenon with unbalanced pressure. So, the cavitation phenomenon cause serious damage of the piping, because it generate erosion and corrosion in the piping. In this study, the steel pipe piping water (SPPW) and SPPW on weldment were tested by using of cavitation-erosion test apparatus with nozzle and were investigated under the marine environment of liquid. (specific resistance : 25 $Omega$. cm) The main results obtained are as follows : 1) The total weight loss and weight loss rate of affected zone of weldment by corrosion-erosion in the sea water are more increased than that of base metal. 2) The electrode potential by corrosion-erosion in the sea water becomes less noble than that of base metal, and current density is more increased. 3) As time goes by, the total weight loss and weight loss rate by cavitation erosion-corrosion in air-liquid 2 phase flow become more increased then those in only liquid solution. but these values turn to be decreased.

In 1980 s to 1990 s the marine propulsion diesel engines have been developed into lower speed and longer stroke for the enegy saving (small S.F.O.C). As these new trends the conventional mechanical-hydraulic governors were not adapted to the new requirements and the digital governors have been adopted in the marine use. The digital governors usually use the control algorithms such as the PID control, optimal control, adaptive control and etc. While the engine has delay time and parameter variations these control algorithms have difficulty in considering the stability and the robustness for the model uncertainty. In this study, the $H_{\infty}$ controller design method are applied in order to design the feedback controller K(s) to the speed control of the low speed marine diesel engine, and the two-degree-of-freedom control system is constituted with $H_{\infty}$controller. By comparison of responses of the two-degree-of-freedom control system under the delay time and parameter variations is confirmed.

This paper presents a dynamic compensation methodology for robust trajectory tracking control of uncertain robot manipulators. To improve tracking performance of the system, a full model-based feedforward compensation with continuous VS-type robust control is developed in this paper(i.e,. robust decentralized adaptive control scheme). Since possible bounds of uncertainties are unknown, the adaptive bounds of the robust control is used to directly estimate the uncertainty bounds(instead of estimating manipulator parameters as in centralized adaptive control0. The global stability and robustness issues of the proposed control algorithm have been investigated extensively and rigorously via a Lyapunov method. The presented control algorithm guarantees that all system responses are uniformly ultimately bounded. Thus, it is shown that the control system is evaluated to be highly robust with respect to significant uncertainties.

From the results of model tests, statistical regression analysis for EHP estimation based on hull form parameters is adopted in this study. From this result, the method for estimation of EHP and optimization of hull form parameters at the initial design stage of fishing boats is developed. This method is applied to two standard fishing boats with chine lines. The EHP s are estimated and compared to experimental results. From the optimization of four principal hull form parameters of these fishing boats, approximately 19% of resistance reduction at the design speed is achieved and thus certifies that this method can be used efficiently for the initial design of hull forms of fishing boats.

We have prepared superconducting Bi-Pb-Sr-Ca.Cu-O thin films by RF magnetron sputtering technique, on heated MgO(100) substrates. Sputtering was carried out in a mixture of argon and oxygen(10%) and the pressure was maintained at 5 mTorr during deposition. The substrate temperature was maintained $400^{\circ}C$ during deposition. The films sputtered were amorphous and insulating. All the films became superconducting by annealing, The films annealed at $880^{\circ}C$ for 30 minutes in air showed high-Tc phase with zero resistivity of 93K. These results indicate that the growth of the high-Tc phase is promoted by the presence of Pb at annealing temperature.