• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2022년도 추계학술대회
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• pp.162-163
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• 2022

Maritime transportation is going to transfer to alternative fuels as a result of the worldwide demands toward decarbonization and tougher maritime emissions regulations. Methanol is considered as a potential marine fuel, which has the ability to reduce SOx and CO₂ emissions, reduce climate change effects, and achieve the objective of green shipping. This work proposes and combines the innovative combination system of direct methanol solid oxide fuel cells (SOFC), proton exchange membrane fuel cells (PEMFC), gas turbines (GT), and organic Rankine cycles (ORC) for maritime vessels. The system's primary power source is the SOFC, while the GT and PEMFC use the waste heat from the SOFC to generate useful power and improve the system's ability to use waste heat. Each component's thermodynamics model and the combined system's model are established and examined. The multigeneration system's energy and exergy efficiency are 76.2% and 30.3%, respectively. When compared to a SOFC stand-alone system, the energy efficiency of the GT and PEMFC system is increased by 19.2%. The use of PEMFC linked SOFC has significant efficiency when a ship is being started or maneuvered and a quick response from the power and propulsion plant is required.

• Journal of Advanced Marine Engineering and Technology
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• 제38권2호
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• pp.123-132
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• 2014

The maritime sector is advancing with dedicated endeavor to reduce greenhouse gas in addressing issues with regards to global warming. Since 01 January 2013, the International Maritime Organization (IMO) regulation mandatory requirement for Energy Efficiency Design Index (EEDI) has been in place and should be satisfied by newly-built ships of more than 400 gross tonnage and the Ship Energy Efficiency Management Plan (SEEMP) for all ships type. Therefore, compliance to this necessitates planning during the design stage whereas verification can be carried-out through an acceptable method during sea trial. The MEPC-approved 2013 guidance, ISO 15016 and ISO 19019 on EEDI serves the purpose for calculation and verification of attained EEDI value. Individual ships EEDI value should be lower than the required value set by these regulations. The key factors for EEDI verification are power and speed assessment and their synchronization. The shaft power can be measured by telemeter system using strain gage during sea trial. However, calibration of shaft power onboard condition is complicated. Hence, it relies only on proficient technology that operates within the permitted ISO allowance. On the other hand, the ship speed can be measured and calibrated by differential ground positioning system (DGPS). An actual test on a newly-built vessel was carried out to assess the correlation of power and speed. The Energy-efficiency Design Index or Operational Indicator Monitoring System (EDiMS) software developed by the Dynamics Laboratory-Mokpo Maritime University (DL-MMU) and Green Marine Equipment RIS Center (GMERC) of Mokpo Maritime University was utilized for this investigation. In addition, the software can continuously monitor air emission and is a useful tool for inventory and ship energy management plan. This paper introduces the synchronization and identification method between shaft power and ship speed for EEDI verification in accordance with the ISO guidance.

• Strategy21
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• 통권43호
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• pp.175-199
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• 2018

Recent marine territorial disputes in the East China Sea and the South China Sea have come to us as a great threat. China, which has recently established the China Coast Guard and has rapidly developed maritime security forces, is trying to overcome the various conflict countries with its power. Japan is also strengthening intensively its maritime security forces. Since Korea, China, and Japan are geographically neighboring and sharing maritime space in Northeast Asia, there is no conflict between maritime jurisdiction and territorial rights among the countries. The struggle for initiative in the ocean is fierce among the three coastal nations in Northeast Asia. therefore, Korea needs more thorough preparation and response to protect the marine sovereignty. As the superpowers of China and Japan are confronted and the United States is involved in the balance of power in strategic purposes, the East Asian sea area is a place where tension and conflict environment exist. China's illegal fishing boats are constantly invading our waters, and they even threaten the lives of our police officers. The issue of delimiting maritime boundaries between Korea and China has yet to be solved, and is underway in both countries, and there is a possibility that the exploration activities of the continental shelf resources may collide as the agreement on the continental shelf will expire between Korea and Japan. On the other hand, conflicts in the maritime jurisdictions of the three countries in Korea, China and Japan are leading to the enhancement of maritime security forces to secure deterrence rather than military confrontation. In the situation where the unresolved sovereignty and jurisdiction conflicts of Korea, China and Japan continue, and the competition for the strengthening of the maritime powers of China and Japan becomes fierce, there is a urgent need for stabilization and enhancement of the maritime forces in our country. It is necessary to establish a new long-term strategy for enhancing the maritime security force and to carry out it. It is expected that the Korean Coast Guard, which once said that it was a model for the establishment of China's Coast Guard as a powerful force for the enforcement of the maritime law, firmly establishes itself as a key force to protect our oceans with the Navy and keeps our maritime sovereignty firmly.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.214-215
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• 2008

Zinc-oxide(ZnO) films were deposited on PC(polycarboanate) and PES(polyethersulphone) substrates by using RF(radio-frequency)sputter with various rf sputtering Power at a room temperature. The effects of rf sputtering Power on the structural and optical properties of ZnO films were investigated by using atomic force microscopy, X-ray diffraction, and UV spectrophotometer. The most excellent structural and properties of a ZnO film are obtained in the condition of an rf-power of 150 W. This film shows larger Grain size and lower surface roughness and a higher optical transmittance of over 80 % in the visible range than other films deposited in the different conditions of rf- power. Regardless of substrate types, The presence of a strong diffraction peak indicates that films have a (0 0 2) preferred orientation associated with the hexagonal phase.

• 한국항해항만학회지
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• 제32권10호
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• pp.765-770
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• 2008

본 논문은 하이브리드 전기 추진 시스템의 전력 제어에 관한 연구를 수행하였다. 하이브리드 전기 추진 시스템은 기본적으로 발전기와 축전지 전원을 이용하여 선박을 추진하는 시스템이다. 하이브리드 추진 시스템은 공급되는 전력을 최소화하기 위한 제어 알고리즘으로 동작한다. 본 논문에서는 하이브리드 전기 추진 시스템의 효율을 증가시키기 위한 축전지 충전 알고리즘을 제안한다. 실험을 통하여 제어 알고리즘이 하이브리드 전기 추진 시스템에서 정상적으로 동작하는 것을 알 수 있었다.

• 대한전자공학회논문지
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• 제24권1호
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• pp.115-122
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• 1987

In this paper, we proposed an improved weakly-coupled power divider(TAP UNIT) for CATV and/or MATV systems, by which the degree of freedom in design and density of coupling interval are signifcantly increased compared with the intrinsic one even though the turn ratios are still of discrete values. On the other hand, the new design theory of a generalized n-way power divider with arbitrary dividing ratios, for CATV and/or MATV systems, which consists of ideal multiwinding transformers and resistors only was presented. Since the circuit elements is not frequency dependent, the proposed power divider is to be of considerably broad bandwidth. Furthermore, the experimental verification has been achieved, and, hence, the validity of the design theory proposed here is confirmed.

• 해양환경안전학회:학술대회논문집
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• 해양환경안전학회 2017년도 추계학술발표회
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• pp.40-40
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• 2017

• Strategy21
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• 통권40호
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• pp.5-36
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• 2016

Recently, the Japanese government revised the three guidelines of its security policy, the National Security Strategy(NSS), the National Defense Program Outline and Midterm Defense Buildup Plan, exceptionally at one time. This means Japan has been seeking the new strategy and strengthening military power considering changing regional security environment. Moreover, Japan revised the security laws for the right to collective self-defense, which authorized the use of force even when Japan is not under attack. Also, Japan renewed the Guidelines for Japan-U.S. Defense Cooperation in twenty years, and has expanded JSDF's scope of activity to a worldwide level. These changes imply Japan would constantly seek to build military forces focusing on naval forces. Because Japan's naval forces, the JMSDF is the means that allow Japan to use its force at anywhere overseas and expand its roles and missions in international society by the basis of the right to collective self-defense. This research will analyze Japan's new maritime strategy and trend of force development and eventually look for the implication on our maritime security These days, Japan has perceived Chinese rapid increase of naval power and pursuing of maritime hegemony as a grave threat. In response to this, Japan is designing new maritime strategy, which are "remote islands defense and recapture" and proactively develop a new type of naval forces to accomplish this new strategy. The Japan's "remote island defense and recapture strategy" is to harden its defensive posture in Nansei islands which correspond to China's 1st island chain for chinese A2/AD strategy and directly encounter with China and to protect its own dominium and maritime interest while supporting US national strategy in East Asia. Japan continues to build compact, multi-functional ship to accomplish "remote island defense and recapture strategy" and keep strengthening its maritime power projection capability to include build of new amphibious ship, and large, multi-functional ship which can provide effective C2. These changes imply that Japan is shifting its strategy from passive and defensive to proactive and aggressive way and continues to pursue naval buildup.The implication of Japan's new maritime strategy and naval buildup needs to be observed carefully and we need to keep developing naval power required to protect our maritime sovereignty and interest.

• Journal of Power Electronics
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• 제15권3호
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• pp.741-752
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• 2015

This study proposes a new solution for the parallel operation of microgrid inverters in terms of circuit topology and control structure. A combined three-phase four-wire inverter composed of three single-phase full-bridge circuits is adopted. Moreover, the control structure is based on adaptive three-order sliding-mode control and wireless load-sharing control. The significant contributions are as follows. 1) Adaptive sliding-mode control performance in inner voltage loop can effectively reject both voltage and load disturbances. 2) Virtual resistive-output-impedance loop is applied in intermediate loop to achieve excellent power-sharing accuracy, and load power can be shared proportionally to the power rating of the inverter when loads are unbalanced or nonlinear. 3) Transient droop terms are added to the conventional power outer loop to improve dynamic response and disturbance rejection performance. Finally, theoretical analysis and test results are presented to validate the effectiveness of the proposed control scheme.

• 한국항해항만학회지
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• 제26권3호
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• pp.289-294
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• 2002

본 논문에서는 디지털 TV 중계기용 고출력 광대역의 3-Way 전력결합기를 설계.제작하였다. 대역폭 증가와 고출력을 동시에 이루기 위하여 Wilkinson 형태의 전력분배기를 채택하였다. 우선 Wilkinson 전력분배기를 균등(1 : 1) 및 비균등(2 : 1) 분배시켜, 동위상 4 포트 전력결합기를 시뮬레이션 하였다. 시뮬레이션 결과에 따라서 두께 120 mil인 유전체 기판을 사용하여 제작된 전력결합기는 디지털 TV 중계기 주파수 470~806 MHz 대역에서 삽입손실 -6.53dB 이하, 반사계수 -13dB 이하, 포트 간 분리도 -15 dB 이하, 출력 포트 간 위상차가 13$^{\circ}$이하의 특성을 보였다. 새롭게 만든 전력결합기는 회로에서의 고 임피던스로 인한 마이크로스트립 선로 폭의 한계와 고출력의 경우 선로간의 상호작용으로 인한 전력의 손실 및 협대역의 문제를 동시에 개선이 가능함을 알 수 있었다. 나아가서, 제작된 3-Way 결합기의 삽입손실, 반사계수, 포트간의 분리도 및 위상차가 디지털 TV 중계주파수 470~806 MHz에서 양호한 특성을 나타내는 것을 확인함으로써 고출력 및 광대역화가 실현가능하다는 것을 알 수 있었다.