• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.22 no.5
• /
• pp.199-206
• /
• 2021

This paper describes the feasibility and reliability verification of installing a protective structure to protect attack periscopes. The attack periscope is the critical equipment of a submarine to enable the user to monitor surface and air activity, collect navigational data, and detect and identify targets. The attack periscope provides target information acquired through TV, IR camera, and laser range finder to the combat system. In the product improvement program, the upper part of the masts was exposed to the outside of the sail because the existing attack periscope was replaced with a new one. On the other hand, the head sensor can be damaged by floating objects, such as fishing nets, during sea navigation. Therefore, the installation of a protective structure for an attack periscope improved the equipment operation performance. The feasibility and reliability of the installation of the protective structure were verified by examining the influence of URN.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.58 no.2
• /
• pp.141-152
• /
• 2022

As a method to understand the ecological habits around the artificial reef, various reports such as fishing gear survey, diving, sound survey, underwater CCTV and camera, etc. are reported. Among them, the sound survey method is carried out by installing an acoustic system on the ship and can be investigated regardless of the marine environment such as time constraints and turbidity. Such method, however, takes a lot of manpower and time as the ship travels at a constant speed. Investigations around artificial reefs are being conducted in an artificial way, and a lot of time and labor are consumed as such. Maritime buoys have been operated for various purposes such as route signs, weather observation, marine environment monitoring and defense monitoring for navigation safety in the past, but studies on monitoring systems for ecological habits and distribution of fish using marine buoys are remarkably insufficient. Therefore, this study aims to develop a system that allows users to directly monitor fish group detector data by estimating the distribution of fish groups around artificial reefs and using wireless communication at sea. In order to confirm the suitability of the maritime buoy used in this study, it was operated to compare data using LTE-equipped buoys capable of wireless communication and a data logger-type system buoy. Data transmission of buoys capable of LTE communication was carried out in a 10-minute ON, 10-minute OFF method due to the limitation of the power supply capacity, and data of the data logger-type buoy received full data. We compared and analyzed the data received from the two fish detectors. It is expected that real-time monitoring of the wireless buoy detection device using LTE will be possible through future research.

• The Journal of Information Systems
• /
• v.32 no.4
• /
• pp.137-147
• /
• 2023

Purpose The domestic aquaculture industry in South Korea utilizes both formulated feeds and live feeds for the cultivation of fish. While nutrient-rich live feeds, particularly using fry, have been preferred since the past, formulated feeds are gaining attention due to issues related to overfishing and environmental concerns. Formulated feeds are advantageous for storage and supply but require a sustained feeding regimen due to the comparatively slower growth rate compared to live feeds. As the aging population in rural areas leads to a shortage of labor, automated feeding systems are increasingly being adopted in aquaculture facilities. To enhance the efficiency of such systems, it is crucial to quantitatively analyze the behavioral changes in fish based on the presence or absence of feed. Design/methodology/approach In the study, RGB cameras and infrared cameras were used to analyze fish activity according to feeding, and an outline extraction algorithm was applied to analyze the differences resulting from this. Findings Unlike RGB cameras, infrared cameras are more suitable for analyzing underwater fish activity as they convert objects' thermal energy into images. It was observed that Canny, Sobel, and Prewitt filters showed the most distinct identification of fish activity.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.34 no.3
• /
• pp.274-282
• /
• 1998

This study deals with sinking resistance for purse seine, in the case of different d/l, ratio of twine diameter and leg length. Experiments carried out on the six types simplified reduced model seines which were made of knotless netting. The nettings were woven in different leg length 4.3, 5.0, 5.5, 6.0, 6.6 and 7.7mm of polyester 28 tex two threads two -ply twine, and each of the seines were named I, II, III, IV, V and Ⅵ seine. Dimension of seine models were 450cm for corkline and 85cm for seine depth, each seines rigged up 160g of float for a floatline and 50g (underwater weight) of lead for a leadline. Experiments were measured in the observation channel of a flume tank at the static conditions Sinking motion was recorded by the two sets TV-camera for VTR which were placed in top and side of the model seine, and reading coordinate carried out by the video digitization system. An analysis were calculated out by simultaneous differential equations for numerical method by Runge - Kutta - Gill sub - routine. The results obtained were as follows: 1. Average sinking speed of seine of seine margin was fastest for Ⅵ seine followed by V, IV, III, II and I seines. 2. The coefficient of resistance for a seine wall was depended upon the ratio of d/l : KD =0.081 (d/l )-0.5 3. The coefficient of resistance for netting bundle was not depended upon the ratio of d/l :CR = 0.91 (), d : Twine diameter, l : Leg length, : Density of netting materals, $\omega$ : Density of water

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.55 no.2
• /
• pp.121-128
• /
• 2019

Various artificial reefs provide the fish habitat and nursery, and contribute the improvement of fisheries productivity. The evaluation methods of fishery resources in the artificial reefs have been done by fishing, scuba diving, underwater camera, and scientific echo sounder/sonar. There are a number of studies using echosounders on the quantitative and qualitative evaluations of artificial reefs in various seas around the world. This study focused on the spatial distribution of fishes around artificial reefs and the influential area of reefs off Bukchon, Jeju Island. Not only acoustic data but also various properties of artificial reefs were used in the geographic information system to extract relevant results. As a result, the major material of reefs on this study site was concrete and the number of reefs with that material was the most. The volume of reefs consisted of steel only and steel with riprap was considerably large compared to other reefs. The average NASC in the vertical distribution of fishes in artificial reefs was $31.6m^2/nm^2$ in April, and that was $61.3m^2/nm^2$ in June. The distance between the fish school and their nearest reef in June morning had a wide range from 750 to 3250 m. On the basis of the influence ray of artificial reefs, it had a tendancy of NASC to decrease with distance from the reef in the June morning. It is a preliminary study to present the geospatial analysis example to understand a better way of comprehensive artificial reef environments.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.60 no.2
• /
• pp.142-151
• /
• 2024

Recently, domestic fishing production of Japanese horse mackerel has been continuously decreasing. To achieve sustainable fishing of this species, it is essential to acquire its target strength (TS) for accurate biomass estimation and to study its ecological characteristics. To date, there has been no TS research using a broadband echosounder targeting Japanese horse mackerel. In this study, for the first time, we synchronized an underwater camera with a broadband frequency (nominal center frequency of 200 kHz, range: 160-260 kHz) to measure the TS according to the body size (16.8-35.5 cm) and swimming angle of the species. The relationship between Japanese horse mackerel length and body weight showed a general tendency for body weight to increase as length increased. The pattern of the frequency spectra (average values) by body length exhibited a similar trend regardless of body length, with no significant fluctuations in frequency observed. The lowest TS value was observed at 243 kHz while the highest TS values were recorded at 180 and 257.5 kHz. The frequency spectra for the swimming angles appeared to be flat at angles of -5, 0, 30, 60, 75, and 80° while detecting more general trends of frequency spectra for swimming angle proved challenging. The results of this study can serve as fundamental data for Japanese horse mackerel biomass estimation and ecological research.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.35 no.2
• /
• pp.93-101
• /
• 1999

A simple experimental method was used in an attempt to realize the elevation of the fishing ability of purse seine in the sea area of Cheju Island, the changes of seine volume and tension in the purseline during pursing. Experiments carried out on the six types simplified reduced model seines which were made of knotless nettings. The nettings were woven in different leg length 4.3, 5.0, 5.5, 6.0, 6.6 and 7.7mm of polyester 28 tex two threads two-ply twine, and each of the seines were named I, II, III, IV, V and Ⅵ seine. Dimension of seine models were 450cm for corkline and 85cmfor seine depth, each seines rigged up 160g of float for a floatline and 50g (underwater weight) of lead for a leadline. These model purse seines were made of the scale of 1/200 of its full scale, a 120 ton in the near sea of Cheju Island. Designing and testing for the model purse seines were based on the Tauti's law. Experiments were measured in the observation channel of a flume tank at the static conditions set up shooting and pursing equipments. Motion of purse seine during purse line was recorded by the two sets video camera for VTR which were placed in top and front of the model seine. The reading coordinate of seine volume carried out by the video digitization system, disk data for the purseline tension. An analysis were performed on the changes seine volume and tension in the purseline during pursing. The results obtained were as follows: 1. The seine volume during pursing was largest for Ⅵ seine with smallest d/l followed by V, IV, III, II and I seines, and tension in the purseline was small. 2. Seine volume during pursing can be expressed by the following equation; CVt=l-EXP[｛2.79 (d/l）＋0.35｝t-33.37 (d/l) ＋ 0.57] Where CVt is volume ratio, d is twine diameter, l is leg length and t is pursing time (sec). 3. Tension in the purse line during pursing can be expressed by the following equation; T= 1- EXP ｛0.57t ＋ 13.36 (d/l)+2.97｝ Where T is tension (kg) in the purseline during pursing.