• The Journal of the Acoustical Society of Korea
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• 제16권6호
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• pp.5-11
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• 1997

Recently, the search for the whereabout of the huge Bell Imperial-Dragon-Temple becomes a great issue. If it happens to be found out and ringing at the original location of the Bell in Kyungjoo City, the Bell might be a great national treasure and lasting to the eternity with her beautiful sound. The Bell was so huge that the total weight of the raw material put into crucibles was 497,581 Kun (289 tons), the shoulder weight 10.3 Chuk (3.14 m) and the maximum thickness 9 Chon (27.4 cm). The Bell was erected in 754 in Shilla Dynasty and was assumed to be lost during the war time by the 3rd invasion of Mongolians (1235~8). However, the author found out that the huge Bell was recast into a new small Bell (8.1 ton) in 1103 by the people of Koryu Dynasty and then the new small Bell was hung in the same position as in the original huge Bell. 135 years later, the new small Bell was carried out by Mongolian forces as a spoil of war from Kyungjoo to the Bay Tonghaegoo, through the saddle point of Mountain Toham, Yangbuk and Riber Great Bell. At the bay, Mongolian forces wished to bring back the Bell to Mongolia by a ship, but they dropped the Bell into the sea by accident. So, if this was the case, the bell at the seabed may be the new small bell (7.4 ton) but not the original huge Bell (41.0 ton) For the evaluation of missing data of the two bells, the author sets up two equations relating all the dimensions and their weights, which seems to be a useful guide to the design of bells. The results of the evaluation of the Bells are as follows. The huge Bell The new small Bell Weight 41.0 ton 7.4 ton Shoulder ht. 3.14 m 2.07 m Mouth diameter 2.468 m 1.546 m Max. thickness 27.4 cm (9 Chon) 11.9 cm (3.9 Chon)

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• 제4권3호
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• pp.170-179
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• 1999

The SUS (Signal, Underwater Sound)-OAT experiment was carried out in the Ulleung Basin of the East Sea on 3 June 1997. The SUS-OAT system consisted of aircraft deployed shots as sources and a vertical line array (VLA) tethered by a receiver ship was used to survey a large area where a mesoscale warm eddy appears frequently. The experiment was carried out such that explosive charges set to detonate at 800 ft depth were dropped in a rectangular ($120{\times}120$ km). Sources were a rapidly deployable SUS charge (MK 61 MOD 0), and receiver is a fixed VLA, 90 m in length (150-240 m in receiver depth), composed of 10 elements equally spaced. The reference ray paths are computed by range-dependent acoustic model in canonical ocean based on the historical data. The singular value decomposition (SVD) method is used to obtain the horizontal perturbation of the temperature fields. Horizontal distributions of temperature fields at 150 m and 200 m depth show a weak warm eddy observed by AXBT and the inversely estimated temperature shows similar patterns in terms of the location of the warm eddy. In conclusion, the SUS-OAT experiment has been successful to estimate the position of warm eddy and its temperature field in the East Sea of Korea.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제40권1호
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• pp.47-53
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• 2004

For the purpose of comparison between the designed coverage and actual coverage of Korean DGPS (Differential Global Position System) beacon stations, we have received the ship‘s positions with states and IDs of their stations on the navigation route of Jeju-Tianjin by automatic selection mode of DGPS receiver and on them of Jeju-Inchun and Jeju-Vladibostok by manual mode. Also in case that some obstructions were on propagation routes from DGPS beacon stations to receiving positions, a restriction on available ranges of DGPS beacon signals was investigated. The results obtained are as follows : 1. The coverage of Korean DGPS beacon stations was designed 100NM (Nautical mails) at 40.0dB(over ${\mu}$V/m). But the actual coverages of them according to their stations and propagation routes were 0.3-3.6 times as wide as designed coverage. 2. In case that the propagation route of beacon signals from DGPS beacon stations was on the sea, the propagation distance of north direction from the stations was longer than south direction. 3. The coverages of Echongdo and Ulungdo stations were 366NM on the yellow sea and 342.3NM on the east sea of Korea respectively, and were widest than any other stations. 4. The coverage of Marado station on the south and yellow seas of Korea was very unstable because of the Halla mountain on the propagation route. Maximum receiving range to be measured by automatic selection mode of DGPS receiver was 145NM on the route of Jeju-Tianjin on June 22-July 1, 2002. Minimum receiving range to be not measured by manual selection mode was 28.7NM on the route of Jeju-Inchun on June 26-28, 2003

• Journal of the Institute of Electronics Engineers of Korea SC
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• 제46권2호
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• pp.61-71
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• 2009

In this paper, we propose a low-cost and compact motion capture system which enables to play motion games in PS2(Play Station 2). Recently, motion capture systems which are being used as a part in film producing and making games are too expensive and enormous systems. Now days, motion games using common USB camera are slow and have two-dimension recognition. But PSD sensor has a few good points, such as fast and low-cost. In recently year, 3D motion capture systems using 2D PSD (Position Sensitive Detector) optic sensor for motion capturing have been developed. One is Multi-PSD motion capture system applying stereo vision and another is Single-PSD motion capture system applying optical theory ship. But there are some problems to apply them to motion games. The Multi-PSD is high-cost and complicated because of using two more PSD Camera. It is so difficult to make markers having omni-direction equal intensity in Single-PSD. In this research, we propose a new theory that solves aforementioned problems. It can measure 3D coordination if separated two marker's intensity is equal to. We made a system based on this theory and experimented for performance capability. As a result, we were able to develop a motion capture system which is a single, low-cost, fast, compact, wide-angle and an adaptable motion games. The developed system is expected to be useful in animation, movies and games.

• Journal of Navigation and Port Research
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• 제29권1호
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• pp.35-42
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• 2005

This study aims at analyzing the extent of seafarers' perception on their stress and ways to cope with the stress and providing fundamental data for establishing on the stress management of seafarers. In this paper 428 seafarers, who were in the fire-fighting and survival technique training course in Korea Institute of Maritime and fisheries Technology, were sampled and asked to fill out two kinds of questionnaire. One is a questionnaire on seafarers' stress perception and the other is that on the measure of their coping with stress. The collected data were analyzed by using descriptive statistics, t-test and ANOVA by SPSS 10.1 package. The results of this study are as follow. 1) There were significant differences of stress perception in navigation area, marital status, amount of smoking, frequency of drinking, exercise, sleep pattern, sleeping hours, leisure time, and job satisfaction 2) There were significant differences of method coping with stress in current position, navigation area, age, ship career, level of education, marital status, yearly income, frequency of drinking, amount of drinking, exercise, sleep pattern, and job satisfaction 3) The relation between stress perception and ways of coping with stress showed that the group with higher stress perception tended to use emotion-focused coping style and desirable thinking.

• Journal of Korea Port Economic Association
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• 제30권4호
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• pp.219-254
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• 2014

Due to the recent development of globalization and supply chain management, growth of international trade has led to increasing cargo volume around the world. Since maritime logistics environments have changed, increased container ship size, improvement of harbor equipment, global port operation and rapid technological development have had an significant effects on shipping and port industry, which is contributing to competitiveness of port. Since a larger volume of port throughputs are generally regarded as an indicator of the more competitive port, inefficient port operation could reduce its competitiveness. On the other hand, high efficient ports could increase their competitive power while increasing cargo volume. This study aims at comparing competitiveness of the ports in the Northeast Asia by investigating changes of container throughputs and evaluating efficiency performance of ports. Shift-Share analysis and Data Envelopment Analysis(DEA) have been conducted with 21 Northeast Asian ports and then separated them into 4 groups for comparative analysis to identify competitive position of each port. The results of this study show that Incheon and Gwangyang port have been decreased container cargo volume, while volume of Busan port would increase by means of active marketing, various route development and incentive policy for the port.

• Journal of Ocean Engineering and Technology
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• 제33권2호
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• pp.168-177
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• 2019

KRISO (Korea Research Institute of Ship & Ocean Engineering) started a project to develop the core algorithms for autonomous intervention using an underwater robot in 2017. This paper introduces the development of the robot platform for the core algorithms, which is an ROV (Remotely Operated Vehicle) type with one 7-function manipulator. Before the detailed design of the robot platform, the 7E-MINI arm of the ECA Group was selected as the manipulator. It is an electrical type, with a weight of 51 kg in air (30 kg in water) and a full reach of 1.4 m. To design a platform with a small size and light weight to fit in a water tank, the medium-size manipulator was placed on the center of platform, and the structural analysis of the body frame was conducted by ABAQUS. The robot had an IMU (Inertial Measurement Unit), a DVL (Doppler Velocity Log), and a depth sensor for measuring the underwater position and attitude. To control the robot motion, eight thrusters were installed, four for vertical and the rest for horizontal motion. The operation system was composed of an on-board control station and operation S/W. The former included devices such as a 300 VDC power supplier, Fiber-Optic (F/O) to Ethernet communication converter, and main control PC. The latter was developed using an ROS (Robot Operation System) based on Linux. The basic performance of the manufactured robot platform was verified through a water tank test, where the robot was manually operated using a joystick, and the robot motion and attitude variation that resulted from the manipulator movement were closely observed.

• Journal of Navigation and Port Research
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• 제43권3호
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• pp.143-152
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• 2019

In this paper, the towing stability of the LNG bunker barge was estimated. Currently, LNG bunkering barge is being developed for the bunkering of LNG (Liquefied Natural Gas), an eco-friendly energy source. Since the LNG bunkering barge assumes the form of a towed ship connected to the tow line, the towing stability of the LNG bunker barge is crucial f not only for the safety of the LNG bunker barge but also the neighboring sailing vessels. In the initial stages, a numerical code for towing simulation was developed to estimate the towing stability of the LNG bunkering barge. The MMG (Maneuvering Mathematical modeling Group) model was applied to the equations of motion while the empirical formula was applied to the maneuvering coefficients for use in the initial design stage. To validate the developed numerical code, it was compared with published calculation and model test results. Towing simulations were done based on the changing skeg area and the towing position of the LNG bunkering barge using the developed numerical codes. As a result, the suitability of the designed stern skeg area was confirmed.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• 제57권3호
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• pp.236-245
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• 2021

In this study, a drifting test using a experimental vessel (2,966 tons) in the northern waters of Jeju was carried out for the first time in order to obtain the fundamental data for drift. During the test, it was shown that the average leeway speed and direction by GPS position were 0.362 m/s and 155.54° respectively and the leeway rate for wind speed was 8.80%. The analysis of linear regression modes about leeway speed and direction of the experimental vessel indicated that wind or current (i.e. explanatory variable) had a greater influence upon response variable (e.g. leeway speed or direction) with the speed of the wind and current rather than their directions. On the other hand, the result of multiple regression model analysis was able to predict that the direction was negative, and it was demonstrated that predicted values of leeway speed and direction using an experimental vessel is to be more influential by current than wind while the leeway speed through variance and covariance was positive. In terms of the leeway direction of the experimental vessel, the same result of the leeway speed appeared except for a possibility of the existence of multi-collinearity. Then, it can be interpreted that the explanatory variables were less descriptive in the predicted values of the leeway direction. As a result, the prediction of leeway speed and direction can be demonstrated as following equations. Ŷ₁= 0.4031-0.0032X₁+0.0631X₂-0.0010X₃+0.4110X₄ Ŷ₂= 0.4031-0.6662X₁+27.1955X₂-0.6787X₃-420.4833X₄ However, many drift tests using actual vessels and various drifting objects will provide reasonable estimations, so that they can help search and rescue fishing gears as well.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제34권3호
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• pp.137-149
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• 2021

Cable-stayed bridges are infrastructure facilities of a highly public nature; therefore, it is essential to ensure operational safety and prompt response in the event of a collapse or damage caused by natural and social disasters. Among social disasters, impact accidents can occur in bridges when a vehicle collides with a pier or when crashes occur due to aircraft defects. In the case of offshore bridges, ship collisions will occur at the bottom of the pylon. In this research, a procedure to evaluate the structural behavior of a cable-stayed bridge for aircraft impact is suggested based on a numerical analysis approach, and the feasibility of the procedure is demonstrated by performing an example assessment. The suggested procedure includes 1) setting up suitable aircraft impact hazard scenarios, 2) structural modeling considering the complex behavior mechanisms of cable-stayed bridges, and 3) structural behavior evaluation of cable-stayed bridges using numerical impact simulation. It was observed that the scenario set in this study did not significantly affect the target bridge. However, if impact analysis is performed through various scenarios in the future, the load position and critical load level to cause serious damage to the bridge could be identified. The scenario-based assessment process employed in this study is expected to facilitate the evaluation of bridge structures under aircraft impact in both existing bridges and future designs.