• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.152-163
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• 2022

In this paper, we present a method to enable an unmanned aerial vehicle to drop the sonobuoy, an essential element of anti-submarine warfare, in an optimal deployment. To this end, an environment simulating the distribution of sound detection performance was configured through the Unity game engine, and the environment directly configured using Unity ML-Agents and the reinforcement learning algorithm written in Python from the outside communicated with each other and learned. In particular, reinforcement learning is introduced to prevent the accumulation of wrong actions and affect learning, and to secure the maximum detection area for the sonobuoy while the vehicle flies to the target point in the shortest time. The optimal placement of the sonobuoy was achieved by applying the Deep Deterministic Policy Gradient (DDPG) algorithm. As a result of the learning, the agent flew through the sea area and passed only the points to achieve the optimal placement among the 70 target candidates. This means that an autonomous aerial vehicle that deploys a sonobuoy in the shortest time and maximum detection area, which is the requirement for optimal placement, has been implemented.

• Geophysics and Geophysical Exploration
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• v.8 no.1
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• pp.104-111
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• 2005

Dmitri Donskoi, the Russian cruiser launched in 1883, is known to have sunk near Ulleung Island (East Sea, Korea) on May 29, 1905, while it was participating in the Russo-Japanese War. In order to find this ship, information about its possible location was obtained from Russian and Japanese maritime historical records. The supposed location of the ship was identified, and we conducted a five-year geophysical survey from 1999 to 2003. A reconnaissance three-dimensional topographic survey of the sea floor was carried out using multi-beam echo sounder, marine magnetometer, and side-scan sonar. An anomalous body identified through the initial reconnaissance survey was identified by a detailed survey using a remotely operated vehicle, deep-sea camera, and the mini-submarine Pathfinder. Interpretation of the acquired data showed that the ship is hanging on the side of a channel, at the bottom of the sea 400 m below sea level. The location is about 2 km from Port Jeodong, Uleung Island. We discovered 152 mm naval guns and other war materiel still attached to the hull of the ship. In addition, the remnants of the steering gear and other machinery that were burnt during the final action were found near the hull. Strong magnetic fields, resulting from the presence of volcanic rocks in the survey area, affected the resolution of the magnetic data gathered; as a result, we could not locate the ship reliably using the magnetic method. Severe sea floor topography in the gully around the hull gave rise to diffuse reflections in the side-scan sonar data, and this prevented us from identifying the anomalous body with the side-scan sonar technique. However, the sea-floor image obtained from the multi-bean echo sounder was very useful in verifying the location of the ship.

• Strategy21
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• s.34
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• pp.128-148
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• 2014

In south Korea, the so-called 'conservative-liberal' rivalry over the assessment of the government's North Korean policies is seen to be impeding the road to right policy choices. For example, the liberals accused former President Lee Myung-bak's hardline policy of provoking Pyongyang and leading to a deterioration of inter-Korean relations, while the conservatives appreciated it for helping nurture mutually beneficial inter-Korean relations in the longer term by compelling North Korea to observe international norms. However, such debate over the vices and virtues of Seoul's North Korea policies is hardly meaningful as the measuring sticks used by the liberals and the conservatives are entirely different matters. The two major goals South Korea must pursue with its North Korean policies should be 'peaceful management of division' and 'change in North Korea'. The former is related to maintaining stability within South Korea and promoting co-prosperity with North Korea. For this, the nation needs to engage, encompass and assist the Pyongyang regime. The second goal is also necessary since South Korea, as a divided nation, must seek a unified Korea under the system of democracy and market economies by bringing change in North Korea. For this, South Korea needs powerful leverages with which it can persuade and coerce the North. This means that the nation is destined to simultaneously chase the above-mentioned two goals, while also both recognizing and negating the legitimacy of the North Korean regime. This situation necessitates Seoul to apply flexibility in reconciling with Pyongyang while applying firm principles to sever the vicious circle involving the North's military provocations. The May 25 Measures, which banned trade and economic cooperation with the North except those related to humanitarian assistance, were taken as sanctions against Pyongyang for sinking the South Korean corvette Chonan in March 2010. The Measures were taken by the Seoul government immediately after a multinational investigation team discovered evidence confirming that the South Korean naval ship had been torpedoed by a midget North Korean submarine. Naturally, the May 24 Measures have since then become a major stumbling block in inter-Korean exchange, prompting opposition politicians and concerned entrepreneurs to demand Seoul to unilaterally lift the Measures. Given the significant damages the Measures have inflicted on inter-Korean economic relations, removing them remains as homework for both Koreas. However, the Measures pertains to the 'principles on national security' the Seoul government must adhere to under all circumstances. This is why North Korea's apology and promises not to repeat similar provocations must come first. For now, South Korea has no alternative but to let North Korea solve the problems it has created. South Korea's role is to help the North do so.