• Proceedings of the Korea Information Processing Society Conference
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• 2022.11a
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• pp.341-343
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• 2022

온실가스 배출 문제가 세계적인 현안으로 부각되면서 수소를 에너지원으로 사용하는 수소경제가 주목받고 있다. 수소연료전지는 수소경제의 구성요소 중 하나로, 수소를 활용해 열과 전기를 생산하며 에너지 변환 효율이 높이는데 장점이 있다. 본 연구는 세계적인 온라인 커뮤니티인 레딧(Reddit)에서 수집한 수소연료전지와 관련된 소셜 데이터를 텍스트마이닝과 감성분석 기법으로 분석하였다. 분석 결과 9,211건의 댓글을 LDA(Latent Dirichlet Allocation)을 이용해 4개의 토픽 그룹으로 분류할 수 있었다. 이 중 수소연료전지와 관련이 높은 그룹을 선정해 STM(Structural Topic Model) 분석으로 10개 토픽을 추출하였고, 기후 환경, 수소 산업, 수소 차와 관련 있는 토픽 3개를 발견할 수 있었다. 이 연구 결과를 통해 수소연료전지의 세계적으로 실제적인 내용을 빠르고 효과적으로 파악하여 수소연료전지에 대한 예측하고, 우리나라의 수소연료전지 관련 국가R&D의 정책적 방향을 제시하고자 한다.

• Journal of Positioning, Navigation, and Timing
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• v.13 no.2
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• pp.117-129
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• 2024

In this paper, we survey recent trends of International Global Navigation Satellite System (GNSS) organizations such as the International Committee on GNSS (ICG), International Civil Aviation Organization (ICAO), International Maritime Organization (IMO), and International Telecommunication Union (ITU), and investigate their impact on the maritime and aviation sectors. Each international organization promotes international cooperation, improvement of service quality, assurance of security, compliance with international regulations, and technological innovation and development. ICG develops a variety of satellite navigation enhancement systems. ICAO establishes international aviation regulations and standards to enhance aviation safety and security. IMO establishes international shipping conventions and rules to protect and regulate the shipping environment. Lastly, ITU establishes international communication regulations and standards. Investigation of such international organizations plays an important role in increasing the efficiency and reliability of GNSS systems. Each international organization promotes international cooperation, improvement of service quality, assurance of security, compliance with international regulations, and technological innovation and development. In the future, interoperability and compatibility with new satellite navigation systems and other GNSS and satellite navigation enhancement systems must be secured, so and thus investigation of international organizations must be conducted first.

• Journal of IKEEE
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• v.15 no.1
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• pp.104-112
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• 2011

During the ground operation of Korean army, the voice message is mainly used for exchanging informations related to the surveillance and reconnaissance, command and control, and precision strike. However, in order to the battlefield visualization among fighting powers participating in the ground force operation, automatic situational awareness and variable message format (VMF) for command and control are required. For securing core technologies necessary for the battlefield visualization, message standard and message handler are established through several applied researches. Besides, the VMF for equipping a weapon system is in development. In this paper, a study on the Korean variable message format (KVMF), where interoperability of integrated battle management system (BMS) is guaranteed due to performing joint, ground, and combined operations so that the situation awareness and strike system can be automated in almost real time, is presented. From the modeling and simulation (M&S) results of the message processor, delay time is varied in accordance with the number of nodes in unit platoon network, message length, and generation interval of routine messages. Therefore, it is shown that the system performance can be optimized by establishing proper network protocol for each situation.

• Journal of IKEEE
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• v.15 no.1
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• pp.15-22
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• 2011

In order to performing the joint operation of Korean army efficiently, informations about surveillance, reconnaissance, and situation awareness need to be possessed jointly. In the first development phase (basis type) of the Korean joint tactical data link system (JTDLS-K), essential tactical information and recognized situation are owned among platforms in common by using existing wireless terminals. In the second development phase (completion type) of the JTDLS-K, a JTDLS which can perform network centric warfare (NCW) will be developed in due consideration of technology development of the basis type and common technology maturity degree. This is a joint battlefield system that can show fighting power simultaneous and polysynthetically through providing command and control messages effectively to each platform, which is participating in the joint and combined operations. In this paper, the development of JTDLS-K with a common data processor based on common link integration processing (CLIP) is described. From the test results of the system presented in this paper, it is demonstrated that quadrature phase shift keying (QPSK) signals can be applied to the system.

• Journal of IKEEE
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• v.22 no.2
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• pp.393-401
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• 2018

In this paper, a rectifier for WPC / A4WP wireless power transmission is designed. The proposed rectifier supports both WPC (Wireless Power Consortium) and A4WP (Alliance For Wireless Power) and is designed with full-bridge rectifier. WPC transmits power at the frequency of 100kHz to 205kHz and A4WP at the frequency of 6.75MHz. Since the bridge rectifier uses a MOSFET instead of a diode, the reverse current flows and the efficiency is affected if the output voltage is higher than the input voltage. Therefore, we added the reverse current detector that detects the current flowing through the MOSFET and shut off the reverse current. The frequency discriminator is used because the rectifier has different frequency band. The proposed rectifier was designed using $0.35{\mu}m$ CMOS high voltage process. The input voltage is up to 18V and the rectifier operates at 100kH to 205kHz, 6.78MHz frequency. The maximum efficiency is 94.8% and the maximum power transfer is 5.78W.

• Journal of IKEEE
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• v.19 no.3
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• pp.357-365
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• 2015

Recently, embedded systems such as aircraft and automobilie, are developed as modular architecture instead of federated architecture because of SWaP(Size, Weight and Power) issues. In addition, partition operating system that support multiple logical node based on partition concept were recently appeared. Distributed recovery block is fault tolerance design scheme that applicable to mission critical real-time system to support real-time take over via real-time synchronization between participated nodes. Because of real-time synchronization, single-core based computer is not suitable for partition based distributed recovery block design scheme. Multi-core and AMP(Asymmetric Multi-Processing) based partition architecture is required to apply distributed recovery block design scheme. In this paper, we proposed design scheme of distributed recovery block on the multi-core based supervised-AMP architecture partition operating system. This paper implements flight control simulator for avionics to check feasibility of our design scheme.

• Journal of the Korean association of regional geographers
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• v.8 no.2
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• pp.199-215
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• 2002

The socio-economic and environmental systems of world are in turmoil. International conflicts are placed in their geographical context through the integration of maps. Changes in the world political map have often been the outcome of wars and conflicts associated with major geopolitical transitions. We identify five basic types--proto-nationalism, unification nationalism, separation nationalism, liberation nationalism and renewal nationalism. Political leaders in a wide range of contexts have been able to appeal to the nationalist doctrine to justify their actions. In recent years indigenous peoples have found a new voice in their struggle for survival. Although colonial empire's ending followed long and bloody struggles in some places. We really cannot understand the modem world as a whole if we do not understand the dynamic of that part of it which has endured and struggled against colonialism. The patterns of the international conflicting area are divided internal conflict type, mixed conflict type, international conflict type. The formation factors of the international conflicting area are divided ethnic group, religion, colonialism, resource, territory. There has recently been a resurgence of Islam's importance in world affairs. The oil crises of the 1970s gave new international leverage to several Muslim states.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.9
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• pp.667-674
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• 2014

A ship's propulsion shafting system is subjected to varying magnitudes of intermittent loadings that pose great risks such as failure. Consequently, the dynamic characteristic of a propulsion shafting system must be designed to withstand the resonance that occurs during operation. This resonance results from hydrodynamic interaction between the propeller and fluid. For ice-class vessels, this interaction takes place between the propeller and ice. Producing load- and resonance-induced stresses, the propeller-ice interaction is the primary source of excitation, making it a major focus in the design requirements of propulsion shafting systems. This paper examines the transient torsional vibration response of the propulsion shafting system of an ice-class research vessel. The propulsion train is composed of an electric motor, flexible coupling, spherical gears, and a propeller configuration. In this paper, the theoretical analysis of transient torsional vibration and propeller-ice interaction loading is first discussed, followed by an explanation of the actual transient torsional vibration measurements. Measurement data for the analysis were compared with an applied estimation factor for the propulsion shafting design torque limit, and they were evaluated using an existing international standard. Addressing the transient torsional vibration of a propulsion shafting system with an electric motor, this paper also illustrates the influence of flexible coupling stiffness design on resulting resonance. Lastly, the paper concludes with a proposal to further study the existence of negative torque on a gear train and its overall effect on propulsion shafting systems.

• Journal of the Korean Geotechnical Society
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• v.23 no.7
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• pp.5-16
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• 2007

The monitoring and investigation of underwater landslide help to understand its mechanism, increase the usefuless of design and construction and reduce the losses. This paper presents three high resolution geophysical techniques electrical resisitance, ultrasonic wave reflection imaging, and shear wave tomography conducted to determine the lab-scaled submerged landslide. Electrical resistance profiles of a soil mass obtained by an electrical resistance probe provide detailed information to assess the spatial distribution of the soil mass with milimetric resolution. An ultrasonic wave image obtained by recording the reflections from interfaces of different impedance materials permits detecting layers and landslide with submilimetric resolution. The pixel based image of immersed landslides is created by the inversion of the boundary information achieved from the traveling time of shear waves. The experimental results show that the ultrasonic wave imaging and the electrical resistance can provide complementary information; and their association with S-wave tomography image can produce a 3-D view of the underwater landslide. This study suggests that geophysical techniques may be effective tools for the detection of the underwater landslides and spatial distribution offshore.

• The Bulletin of The Korean Astronomical Society
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• v.40 no.1
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• pp.83.1-83.1
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• 2015

세계전파통신회의 (WRC; World Radiocommunication Conference)회의는 국제전기통신연합 (ITU)에서 규정하는 국제 전파법 제개정을 위해, 3-4년 간격으로 개최되는 전파통신 관련 최고회의이다. 2015년 11월 2일-27일에 개최되는 WRC-15 본회의에서 다루는 28개 의제에 대해서는 의제별 주파수대역별로 공유/양립성/보호 연구결과가 제시되어야 한다. 따라서 2015년 3월 23일-4월 2일에는 스위스 제네바에서 190여개 ITU회원국의 국가대표 1,000여명이 모여서 의제별 최종연구결과보고서를 작성하며(CPM-15 2차회의, Conference Preparatory Meeting), 그 결과는 11월의 WRC회의에서 중요한 잣대 역할을 하게 된다. 동 회의에서 다루는 의제 가운데, 과학업무 연구반에서 다루는 주요 의제들은 다음과 같다. 1) 7145-7250 MHz 대역의 지구탐사위성(지구대우주)업무의 1순위 분배연구, 2) 8,700~10,500MHz대역의 지구탐사위성업무의 신규 SAR용대역(연속 1.2GHz) 분배방안 연구, 3) 우주선 근거리통신용 410-420MHz 대역 규제 철폐 관련 검토, 4) 윤초 삭제 또는 개정 방안 연구가 있다. 그리고 모바일 광대역 응용 실현을 위한 이동통신업무 추가 분배 및 IMT 추가 지정 연구, 나노 위성 및 피코 위성 규제 관련 연구들이 있다. 따라서 본 발표에서는 3월에 개최된 CPM-15 2차회의의 과학업무 의제 관련 최종결과를 소개하고, WRC-15회의에 대비하여 국내 전파천문업무 보호를 위해 준비가 필요한 주요 이슈에 대해 소개를 하고자 한다.