• Journal of Korean Society of Coastal and Ocean Engineers
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• v.35 no.4
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• pp.84-94
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• 2023

The wave height and period regression curve is widely used to estimate the design wave period. In this study, the parameters of the curves are estimated, compared, and evaluated using the linear, robust linear, and nonlinear regression methods, respectively. The data used in the design wave height estimation are the annual maxima (AM) wave height and period data sets divided by typhoon and non-typhoon conditions, provided by the Ministry of Oceans and Fisheries (2019). The estimation parameters show significant differences in the local coastal waters and the estimation methods. The estimation parameters based on the Suh et al. (2008, 2010) method show the apparent bias, under-estimation in the intercept (scale) parameter, and over-estimation in the slope (exponent) parameter, respectively.

• The Journal of the Acoustical Society of Korea
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• v.42 no.6
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• pp.511-518
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• 2023

Accurate ranging is one of the key factors in the test and evaluation process of underwater vehicles. In particular, when estimating range using Time of Arrival (ToA) values, signals such as Linear Frequency Modulation (LFM), a chirp signal, are highly applicable due to their correlated nature. However, in a Doppler shift environment with mobility, measurement errors may occur due to the range-Doppler coupling effect. In this paper, we propose a signal that compensates for the distance-Doppler coupling effect to reduce the measurement error of the arrival time value. The proposed signal is constructed by superimposing two types of LFM signals, and the range-Doppler coupling effect can be minimized. Through simulations, it is confirmed that the proposed signal is a way to compensate for the distance-Doppler coupling effect in the distance estimation of underwater mobile bodies, reducing the measurement error of the arrival time value.

• Strategy21
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• s.30
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• pp.236-262
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• 2012

Morgenthau claims that in international relations, there are the economic, political, and military powers that enable a nation to achieve its political and diplomatic goals. This paper explores the possibility of resolving international conflicts with naval power. First, the theoretical and historical perspective, naval power was used as a final resort to force a nation's political or diplomatic objective on an enemy nation when negotiations failed, and this was done through the physical and psychological destruction of the enemy by naval power. But as the use of military power has decreased because of the invention of the nuclear weapon, the existence of a large and capable navy deterrent has become one of the most useful military options among a nation's diplomatic measures. In other words, he focused on the political usefulness of naval power as a deterrent and coercive diplomatic tool for persuading other nations to acquiesce, rather than using naval power and actual military action as a final resort. The reason for this is that compared to army and air force, navy's flexibility, continuity, and the ability to deter are greater. The navy provides excellent accessibility through its wide mobility on the sea, and it has been shown through research that the navy possesses a political usefulness that facilitates the solution of conflicts through presence, naval intervention, and naval blockade. On the other hand, among the factors that could improve the influence of the navy are alliance relations, a reliable and powerful navy, carrots and sticks that it would have to deal with in the case of successful or unsuccessful negotiations, and support from international opinion. On this paper I introduce E.N.Luttwak's naval suasion theory. By the his theory, there are two mode of naval suasion. One is latent naval suasion the other is active suasion. Latent suasion there are deterrent mode and supportive mode. Active naval suasion there are coercive mode and supportive mode. Coercive mode has positive and negative. The limitations of naval suasion have been identified as follows. First, because the objective of the use of naval power is persuading enemy nations, the results are unpredictable. Second, the leaders of all countries possess limited understanding on the complexities of naval power and therefore lack understanding of the usefulness of naval power when choosing options. Third, in case of failure through naval suasion, prestige and reputation of a nation can be damaged. Finally, the following are additional possible research topic. First, a research on the decision making process of choosing naval power as a measure to resolve conflicts is needed. Lastly, research on the size of the navy and types of ships required for efficient naval suasion is needed. Today's world requires cooperative security regime so that middle class navy also requires political use of naval power in solving international conflicts. Therefore, additional research on this topic is needed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.1
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• pp.64-75
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• 2009

The shipbuilder's requirement for a higher power output rating has led to the development of a super large two stroke low speed diesel engines. Usually a large-sized bore engine ranging from $8{\sim}14$ cylinders, this engine group is capable of delivering power output of more than 100,000 bhp at maximum continuous rating(mcr). Other positive aspects of this engine type include higher thermal efficiency, reliability, durability and mobility. This plays a vital role in meeting the propulsion requirement of vessels, specifically for large container ships, of which speed is a primary concern to become more competitive. Consequently, this also resulted in the modification of engine parameters and new component designs to meet the consequential higher mean effective pressure and higher maximum combustion pressure. Even though the fundamental excitation mechanisms unchanged, torsional vibration stresses in the propulsion shafting are subsequently perceived to be higher. As such, one important viewpoint in the initial engine design is the resulting vibration characteristic expected to prevail on the propulsion shafting system(PSS). This paper investigated the torsional vibration characteristics of these super large engines. For the two node torsional vibration with a nodal point on the crankshaft, a tuning damper is necessary to reduce the torsional stresses on the crankshaft. Hence, the tuning torsional vibration damper design and compatibility to the shafting system was similarly reviewed and analyzed.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.247-256
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• 2014

Recently, camera and RADAR are used for more effective and accurate observation of the bird migration. In recent years, many researches on the bird migration using RADAR are undertaking and in active, thus causes the advent of "RADAR ornithology" as a new academic field. Due to the lack of accessibility, economic feasibility and mobility of weather RADAR, airport searching RADAR and tracking RADAR, Nowadays, a marine RADAR is widely used for a bird observation. In this paper, we deals with a study on development of a remote bird observation system using marine FMCW RADAR, which monitors, records and analyzes bird movement by RADAR image processing and target recognition technology. Also, we conduct first test and second test for availability of the developed system, and verify the system to apply in bird observation domain. Consequently, we figured problems out, and correct the problems to improve the system. The developed system can apply in other domains such as environment evaluation. In the future, the system needs to improve accuracy of statistics and to track migration route of bird.