• Journal of the Society of Naval Architects of Korea
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• v.41 no.2
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• pp.33-46
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• 2004

The cavitating noise of underwater propeller is considered numerically in this study. The main purpose of this research is to analyze these noise sources from marine propeller. The approach for investigation is a potential based panel method coupled with acoustic analogy. To predict propeller sheet cavitation noise, the blade surface cavity is considered as a single valued pulsating volume of vapor attached to the blade surface. The time dependent cavity volume data are used for noise prediction. Furthermore, we analyze hydrofoil cavitation bubble behavior and noise using Eulerian/Lagrangian approach. Through this study, we can analyze dominant noise source of marine propeller and provide a basis for proper noise control strategies.

• Journal of information and communication convergence engineering
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• v.3 no.2
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• pp.84-89
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• 2005

Goal of this study is to implement 3-dimensional underwater appearance graphical display, fishery measured information display, sonar data representation and display, and 3-dimensional underwater appearance animation based on coefficient data of chaos behavior and fishing modeling of fishing gears from PC cluster system. In order to accomplish the goals of this study, it is essential to compose user interfacing and realistic description of image scenes in the towing-net fishery simulator, and techniques to describe sand cloud effects under water using particle systems are necessary. In this study, we implemented graphical representations and animations of the simulator by using OpenGL together with C routines.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.4
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• pp.66-72
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• 2021

Since the behavior of an autonomous underwater vehicle (AUV) is influenced by disturbances and moments that are not accurately known, the depth control law of AUVs must have the ability to track the input signal and to reject disturbances simultaneously. Here, we proposed robust tracking control for controlling the depth of an AUV. An augmented closed-loop system is represented by an error dynamic equation, and we can easily show the asymptotic stability of the overall system by using a Lyapunov function. The robust tracking controller is consisted of the internal model of the command signal and a state feedback controller, and it has the ability to track the input signal and reject disturbances. The closed-loop control system is robust to parameter uncertainties. Simulation results showed the control performance of the robust tracking controller to be better than that of a P + PD controller.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.48 no.2
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• pp.1-8
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• 2011

An underwater robot S/W framework consists of various sub-modules such as sensory data processing module, thruster control module, cognition module and behavior control module. Performance of a robot is determined by not only the efficiency of algorithms used but also effectiveness of their implementations. One most important factor of the effective implementation is the efficiency of data sharing module, as it transmits signals and data between the sub-modules and thus is directly related to the cycles of sensing and control The ideal data sharing module enables immediate access to any data source irrespective of system configurations. In reality, however, there are lots of obstacles including limitation of processing capacity of source modules, delay over network, and scheduling latency of operating systems. The paper proposes a new data sharing architecture and programming models to effectively handle such obstacles in implementation of underwater S/W framework on a small scale distributed computing system.

• Korean Journal of Environmental Biology
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• v.31 no.1
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• pp.45-52
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• 2013

The fish fauna of Munsom in Jeju-do, Korea, was investigated for a total of five times underwater from April 2009 to October 2010. Fish specimens were collected with a small net by SCUBA diving and fish specimens difficult to collect were photographed underwater using a underwater camera and a camcorder. The fish specimens collected from the sea around Munsom were identified as 91 species, belonging to 73 genera, 39 families, and 11 orders. Among them, the largest group was Order Perciformes, comprising 54 species and 21 families, consisting 59.3% in total number of species and the following 19 species of Order Scorpaeniformes was 20.8%. In this study Amblyeleotris sp. of family Gobiidae was discovered as new species by underwater photography in Korea. It was more the demersal fishes (55%) than the pelagic fishes (45%) and in social behavior pattern it was much more species swimming alone than schooling.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.283-291
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• 1994

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)

• Korean Journal of Fisheries and Aquatic Sciences
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• v.33 no.4
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• pp.348-355
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• 2000

This paper described the relationship between the behavior of the Israeli carp, Cyprinus carpio and the environmental noise level due to the dynamite explosion work. The experiment was conducted in the cage ($L10{\times}W4{\times}D4 m$) of aquaculture located at Chungjoo Lake, Chechon, in 1997. The fish trajectory was obtained by the telemetry system in which a pulsed ultrasonic pinger ($50 kHz, {\phi}16{\times}L70 mm$) attached to the fish was tracked three dimensionally, and the underwater noise levels were measured. The results of the study were as follows: 1. The underwater noise levels in the normal blasting measured at a distance of 400 m from the source of noise increased by $40 dB (re 1 {\mu}Pa)$ compared to the levels before explosion. The dominant frequency and the increased power spectrum level of the underwater noise by the explosion work were $75 to 100 Hz and 22.9 to 35.3 dB$, respectively. 2. The underwater noise levels in the test blasting measured at a distance of 350 m from the source of noise increased by average $49.5 dB (re 1 {\mu}Pa)$compared to the levels before explosion. 3. The swimming area of the fish was reduced with the time after explosion, and after more than one hour the fish represented the similar swimming area and behavior to the status of right before explosion. 4, The swimming depth layer of the fish was most of the case at the sea surface less than 1,0 m except during explosion or right after of it. But the fish swam downward when an external stimulus like the explosion noise was given to the fish. 5. The average swimming speeds of the fish before, during and after the works were about 1.2 times, 1.9 times and 1.0 times of the body length, respectively, and the speed of the fish with explosion was faster 1.6 times than the speed without of that. Consequently, the explosion noise levels measured by this study were sufficiently high to affect the fish, and the heavy shock by the explosion works could produce a considerable unfavorable effects to the fish.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.273-282
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• 1994

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.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.4
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• pp.263-272
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• 1994

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.

• Journal of the Korea Concrete Institute
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• v.12 no.5
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• pp.13-23
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• 2000

In this study, an flexural test on half-scale spliced PSC-I girder was conducted to verify the efficiency of the long span spliced girder as suggested by the Korean Highway Design Specification. The experimental results showed that the specimens developed a complex failure mode due to flexural-compression and torsional stress. The cracking moment of each girder was higher the experiment than was calulated by the ACI and the ultimate strength were the almost same. To estimate the safety and the structural efficiency of the spliced girder, the proposed Yielding Resistance Index(YRI) and ductility index by American Concrete Institutes were used based on the energy concept. The proposed YRI defined the ratio of crack resisting energy and the total energy calculated from load-displacement relationship. Based on the analysis of YRI and ductility index, the flexural behavior of the spliced girder was found to be efficient. Through the experimental results, the structural behavior of proposed spliced PSC I-type girder for long span bridge was found to be more efficient than the exsisting PSC I-type girders.