• Journal of Ocean Engineering and Technology
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• v.31 no.2
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• pp.130-140
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• 2017

Typically, a submerged breakwater is one of the good scene-friendly coastal structures used to reduce wave energy and coastal erosion. However, sometimes, a submerged breakwater also has a negative aspect in that a strong rip current occurring around an open inlet due to a difference in mean water levels on the front and rear sides of the structure leads to scouring. Such scouring has a bad effect on its stability. In order to eliminate this kind of demerit, this study investigated four new types of submerged breakwaters with drainage channels. First, hydraulic experiments were performed the typical and new structures. Then, the wave height and mean water level distributions around the structures were examined using the experimental results. Finally, it was revealed that the new type of submerged breakwater could efficiently reduce the mean water level on its rear side. In particular, in the case of new-type submerged breakwater 2, an average reduction efficiency of 71.2% for the difference between the mean water levels at the front and rear sides was shown in comparison with the typical one.

• Journal of The Geomorphological Association of Korea
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• v.20 no.4
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• pp.71-83
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• 2013

In this study, the ecological presevation zone on uninhabited islands was established based on the setting of geomorphological landscape. The 14 uninhabited islands, which are scattered around the Goseong-gun and Tongyeong-si region have been surveyed on field. As a result of study, uninhabited island of Goseong-gun and Tongyeong-si was classified the absolute preservation areas(I), preservation areas(II), quasi-preservation areas(III), and a available areas(IV). These results evaluated 5 islands of Anjang Island(Maan-do), Bam Island, Saetgaekkeut, Dae Island(Juk-do) and Ttandok Island to be absolute preservation areas(I), the 8 islands of Mana Island, Yuk Island, Nabi Island, Sochi Island, Yongdu-do, Daeho-do, Jam-do, and Hwa-do to be preservation areas(II), the 1 island of Goeam Island to be quasipreservation areas(III). Those islands selected as absolute preservation areas and preservation areas have especially outstanding geomorphological landscape resources, and are expected to be able for use as natural study fields or as outdoor laboratories.

• Journal of Sericultural and Entomological Science
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• v.14 no.1
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• pp.37-42
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• 1972

This investigation was conducted to measure the effects of silkworm diseases on the cocoon crepe. The sample farmers were selected at three areas in Korea. a. Banga Ri, Namsa Myoen, Yongin Kun, Kyoenggi Do b. Moorim Ri, Yakmok Myeon, Chilkok Kun, Kyeongsangbuk Do c. Oero Ri, Buksam Myeon, Chilko Kun, Kyeongsangbuk Do 1. Reduction ratio of crops by the silkworm disease was 5.5% in spring season, and 8.9% in the autumn but 7.2% in a year. Including disease damaged cocoons being spoiled cocoons, it was 8.3%. 2. The ratio of disease-damage by the polyhedrosis virus and flacherie was 17.8% of whole disease at young instar and was 82.2% at advanced instar which showed highest ratio. 3. Average production amount of the cocoon was 27.74kg, The reduction amount by the silkworm disease against the estimated production aomunt was 2.411kg. 4. Reduction of amounts by unknown factors was 3.611 kg. This was 1.5 times of reduction amount by the disease. This nay be chiefly due to the missing silkworms and spoiled cocoons. 5. Ratio of farmers harvesting stable cocoon crops was 54.7% in spring rearing season but 21.9% in autumn. 6. Damage ratio of factors other than the silkworm disease was 10.70% and it was 17.87 % of total mortality.

• Journal of Sericultural and Entomological Science
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• v.21 no.1
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• pp.30-35
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• 1979

This experiment was conducted to investigate the effects of $\alpha$-amylase, added to artificial diet, on the larval growth and on the amount of blood sugar of the silkworm Bombyx mori L.. The artificial diet containing 20% mulberry leaf powder was fed on the 5th instar silkworm. The results obtained were summarized follows: 1. The digestibility in both sexes was increased by feeding artificial diet with $\alpha$-amylase and increase of the digestibility was greater in the female than in the male. 2. Larval body weight was increased in the female but was the male, compared with those in each sex of the control, respectively. 3. There was an increase of the single cocoon weight and cocoon shell weight, as compared with that of the control. 4. It was evident that the artificial diet containing $\alpha$-amylase was more effective than the control, and the effect of the diet was considerable higher in the female than in the male. 5. The amount of the blood sugar on the 7th day of 5th instar was decreased as compared with that of the control.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.9
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• pp.233-239
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• 2019

An unmanned underwater vehicle is a major weapon system that allows surveillance and reconnaissance missions in border areas or threatening areas where enemy submarines are present. Unmanned underwater vehicles can be used to explore underwater resources, predict disasters, and survey the topography of the ocean floor in the civilian fields, while in the defense fields, it can be used for anti-submarine reconnaissance and mine countermeasures. In this paper, we first investigate the main classification of unmanned underwater vehicles, and foreign R&D trends are analyzed based on the main classification criteria by weight, such as portable, light, heavy and large-scale unmanned underwater vehicles. Then we examine the trends in the development of domestic unmanned underwater vehicles. Finally, through the analysis of both domestic and foreign unmanned underwater vehicles, we present future development trends of unmanned underwater vehicles in order to set defense goals to counter the anticipated threats and diversified potential environment.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.454-461
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• 2019

In autonomous interventions using an underwater vehicle with a manipulator, grasping based on target detection and recognition is one of the core technologies. To complete an autonomous grasping task, the vehicle body approaches the target closely and then holds it through operating the end-effector of the manipulator, while the vehicle maintains its position and attitude without unstable motion. For vehicle motion control, it is very important to identify the hydrodynamic parameters of the underwater vehicle, including the propulsion force. This study examined the propulsion characteristics of the autonomous intervention ROV developed by KRISO, because there is a difference between the real exerted force and the expected force. First, the mapping between the input signal and thrusting force for each underwater thruster was obtained through a water tank experiment. Next, the real propulsion forces and moments of the ROV exerted by thrusting forces were directly measured using an F/T (force/torque) sensor attached to the ROV. Finally, the differences between the measured and expected values were confirmed.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.300-311
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• 2019

An ROV trencher is a type of heavy-duty work class ROV equipped with high-pressure water jet tools for cutting into the sea floor and burying cables. This kind of trencher is mostly used for PLIB operations. This paper introduces the development of this kind of ROV trencher, which has a 698 kW power system, with a 250 kW hydraulic system and two 224 kW water jet systems. The project was launched in January 2014. After four years of design, manufacturing, and system integration, we carried out two sea trials near the Yeongilman port (about 20-30 m in depth) in Pohang to evaluate the system performance in November 2017 and August 2018. Through tests, we found that most of specifications were satisfied, including a maximum bury depth of 3 m, maximum bury speed of 2 km/h, and maximum forward speed of 1.54 m/s.

• Journal of Ocean Engineering and Technology
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• v.33 no.3
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• pp.289-299
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• 2019

Various sizes of ROVs are being utilized in offshore industrial, scientific, and military applications all around the world. Because of innovative developments in science and technology, image acquisition devices such as sonar devices and cameras have been reduced in size and their performance has been improved. Thus, we can expect better accuracy and higher resolution even in the case of exploration using a small ROV. The purpose of this paper is to prepare a standard procedure for the identification of unidentified hazardous materials found during the National Oceanographic Survey. In this paper, we propose an IDEF (Integrated DEFinition) method modeling technique to identify unidentified targets using a small ROV. In accordance with the proposed procedure, an ROV survey was carried out on target No.16 with a four-ton-class fishing boat as a support vessel on September 18th of 2018 in the sea near Daebu Island. Unidentified targets, which were not known by the multi-beam data obtained from the ship, could be identified as concrete pipes by analyzing the HD camera and high-resolution sonar images acquired by the ROV. The whole proposed procedure could be verified, and the survey with the small ROV required about 10 days to identify the target in one place.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.125-133
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• 2019

In this paper, a new study was performed on the docking of AUV to docking station using light and light sensor system under the water. For this, a guiding system for AUV loading sensor system composed of lense, light sensor, signal processor, and processor and docking system with LED are proposed. An analysis on light sensor system and light-collecting lense to obtain accurate relative angle and measurement accuracy was performed. To prove this, the system was built and a basic experiment was performed. Finally, the feasibility of the developed docking system was verified the test in the water tank.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1417-1423
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• 2020

This paper proposes a waypoint guidance algorithm for the Autonomous Underwater Vehicle(AUV). The proposed simplified guidance algorithm is presented, which is combined LOS guidance and cross-track guidance for path following. Cross-track error is calculated using the position of the AUV and reference path. LOS guidance and cross-track guidance are appropriately changed according to cross-track error. And the stability of the system has been improved using variable cross-track control gain by cross-track error. Also, in this paper, navigation hardware in-the loop simulation(HILS) is implemented to verify navigation algorithm of AUV that performs combined navigation using inertial navigation device and doppler velocity log(DVL). Finally, we design integrated system HILS (including navigation HILS) for performance verification of guidance algorithm of the autonomous underwater vehicle. By comparing the sea test result with HILS result, the proposed guidance algorithm and HILS configuration were confirmed be correct.