• 한국ITS학회 논문지
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• 제16권1호
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• pp.176-185
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• 2017

본 논문은 지능형교통시스템(ITS: Intelligent Transport System)을 위한 V2X 간의 무선통신시스템에 적용되는 WAVE(Wireless Access in Vehicle Environments) 안테나 시스템에 대한 연구이다. 5.825~5.9GHz 주파수대역의 WAVE 통신은 차량이 주행하면서 도로 인프라에 설치되어 있는 기지국과 다른 차량에 장착되어 있는 단말기간의 무선통신에 사용할 수 있도록 하는 표준화된 프로토콜이다. 최근의 WAVE 통신시스템 연구에서는 통신거리에 따른 통신성능을 향상시키기 위해서 기지국과 차량 단말기 기술개발 위주로 연구되고 있으나, 본 논문에서는 시스템 성능 개선 가능성을 검토하고자 차량 루프에 장착가능한 자동차용 안테나 시스템의 설계구조 개선에 대한 연구를 진행하였다. WAVE 안테나 베이스 구조에 EBG(Electro Band-Gap) 구조를 적용하여 비교시뮬레이션을 통해 반사손실이 저감되어 성능이 향상되는 것을 확인하였다.

• Steel and Composite Structures
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• 제31권6호
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• pp.641-653
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• 2019

In this paper, wave propagation is studied and analyzed in double-layered nanotubes systems via the nonlocal strain gradient theory. To the author's knowledge, the present paper is the first to investigate the wave propagation characteristics of double-layered porous nanotubes systems. It is generally considered that the material properties of nanotubes are related to the porosity and hygro-thermal effects. The governing equations of the double-layered nanotubes systems are derived by using the Hamilton principle. The dispersion relations and displacement fields of wave propagation in the double nanotubes systems which experience three different types of motion are obtained and discussed. The results show that the phase velocities of the double nanotubes systems depend on porosity, humidity change, temperature change, material composition, non-local parameter, strain gradient parameter, interlayer spring, and wave number.

• 한국전자통신학회논문지
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• 제8권10호
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• pp.1589-1594
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• 2013

차량통신은 IT기술과 차량산업을 결합한 대표적인 융합기술이다. WAVE 기술은 전 세계적으로 널리 채택되어 사용되어지고 있는 차량통신 표준이다. 본 논문에서는 WAVE 시스템 이용하여 실제 테스트베드상에서 구현한 서비스에 대해 소개한다. 먼저 전체적인 WAVE 시스템에 대해 간략히 살펴본 후 서비스를 구현하기 위한 테트스베드에 대해 소개하고, 테스트베드상에서 구현된 차량간통신 및 차량 기지국간통신을 이용한 다양한 응용 서비스에 대해 알아본다. 실제 응용 서비스의 구현을 바탕으로 하여 실제 시스템 구현에 필요한 사항 및 다른 분야와의 융합분야에 대해서도 논의한다.

• Journal of Advanced Marine Engineering and Technology
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• 제30권4호
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• pp.520-526
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• 2006

Wave Energy is a derivative of the solar energy input to the earth, which is accumulated on open water surfaces by the action of the winds Waves are disturbances in the water surface. This paper is interested primarily in progressive waves, which carry energy from one place to another Waves are irregular in size and frequency. Moreover the surface of the sea is one of the most hostile environments for engineering structures and materials. The idea of harnessing the tremendous power of the ocean's waves is not new. Hundreds of wave energy conversion techniques have been suggested over the last two centuries. Although many WECS (Wave Energy Conversion Systems) have been invented, only a few systems have been tested and evaluated. This paper describes the characteristic of WES (Wave Energy System) in terms of, devices, resource and potential, etc.. Finally, this paper provides a summary of general and specific conclusions and recommendations concerning WECS potential in Korea.

• Advances in Energy Research
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• 제6권2호
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• pp.103-129
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• 2019

While global demand for energy increases annually, at the same time the demand for carbon-free, sulphur-free and NO_x-free energy sources grows considerably. This state poses a challenge in the research for newer sources like biomass and shale gas as well as renewable energy resources such as solar, wind, geothermal and hydraulic energy. Although wave energy also is a form of renewable energy it has not fully been exploited technically and economically so far. This study tries to explain those reasons in which it is beyond doubt that the demand for wave energy will soon increase as fossil energy resources are depleted and environmental concerns gain more importance. The electrical energy supplied to the grid shall be produced from wave energy whose conversion devices can basically work according to three different systems. i. Systems that exploit the motions or shape deformations of their mechanisms involved, being driven by the energy of passing waves. ii. Systems that exploit the weight of the seawater stored in a reservoir or the changes of water pressure by the oscillations of wave height, iii. Systems that convert the wave motions into air flow. One of the aims of this study is to present the classification deficits of the wave energy converters (WECs) of the "wave developers" prepared by the European Marine Energy Center, which were to be reclassified. Furthermore, a new classification of all WECs listed by the European Marine Energy Center was arranged independently. The other aim of the study is to assess the technological state of the art of these WECs designed and/or produced, to obtain an overview on them.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제16권1호
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• pp.59-63
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• 2016

Secondary damage to the user is a problem in biometrics. A brain-wave has no shape and a malicious user may not cause secondary damage to a user. However, if user sends brain-wave signals to an authentication system using a network, a malicious user could easily capture the brain-wave signals. Then, the malicious user could access the authentication system using the captured brain-wave signals. In addition, the dataset containing the brain-wave signals is large and the transfer time is long. However, user authentication requires a real-time processing, and an encryption scheme on brain-wave signals is necessary. In this paper, we propose an efficient encryption scheme using a chaos map and adaptive junk data on the brain-wave signals for user authentication. As a result, the encrypted brain-wave signals are produced and the processing time for authentication is reasonable in real-time.

• Ocean Systems Engineering
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• 제7권4호
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• pp.345-369
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• 2017

The ocean environment offshore West Africa is considered to be mild. However, the generated swell from distant North and South Atlantic during austral winter and summer can reach high wave amplitudes with relatively low wave periods or low wave amplitudes with long wave periods, the later can be a crucial scenario to consider when the assessment of vessel resonance is of importance. Most offshore operations, which include offshore drilling, and installation in West Africa, are carried out from floating systems. The response of these systems and performance are governed by characteristics, such as amplitude and frequency of the wave and swell seas. It is therefore important to fully understand the sea conditions offshore Nigeria. This study covers the description of the swell sea offshore Nigeria using Bonga offshore wave measurements collected from the directional wave-rider (DWR), positioned at the Bonga site off the coast of Nigeria.

• Ocean Systems Engineering
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• 제12권1호
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• pp.23-38
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• 2022

In this paper, a pitch-type wave energy converter (WEC-rotor) is investigated in irregular wave conditions for the real sea testing at the west coast of Jeju Island, South Korea. The present research builds on and extends our previous work on regular waves to irregular waves. The hydrodynamic characteristics of the WEC-rotor are assessed by establishing a quasi-two-dimensional numerical wave tank using computational fluid dynamics by solving the Reynolds-averaged Navier-Stokes equation. The numerical solution is validated with physical experiments, and the comparison shows good agreement. Furthermore, the hydrodynamic performance of the WEC-rotor is explored by investigating the effect of the power take-off (PTO) loading torque by one-way and two-way systems, the wave height, the wave period, operational and high sea wave conditions. Irrespective of the sea wave conditions, the absorbed power is quadratic in nature with the one-way and two-way PTO loading systems. The power absorption increases with the wave height, and the increment is rapid and mild in the two-way and one-way PTO loading torques, respectively. The pitch response amplitude operator increases as the wave period increases until the maximum value and then decreases. For a fixed PTO loading, the power and efficiency are higher in the two-way PTO loading system than in the one-way PTO loading system at different wave periods.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2000년도 KIASC Conference 2000 / 2000년도 학술대회 논문집
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• pp.43-47
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• 2000

Two modes of shock waves, a compression shock wave and a thermal shock wave, propagating in He II have been investigated. The shock waves are at a time generated by the impingement of a gasdynamic shock wave onto a He II free surface in the newly developed superfluid shock tube facility. Superconductive temperature sensors, piezo-type pressure transducers and visualization photograph were used for the measurement of them and the phenomena induced by them were investigated in detail. It is found that the compression by a compression shock wave in He II causes temperature drop because He II has negative thermal expansion coefficient. the thermal shock wave is found to be of a single triangular waveform with a limited shock strength. The waveform is similar to that generated by stepwise strong heating from an electrical heater for relatively long heating time. In the experiments at the temperatures near the lambda temperature, no thermal shock wave is sometimes detected in shock compressed He II. It can be understood that shock compression makes He Ii convert to He I in which no thermal shock wave is excited.

• 한국해양공학회지
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• 제22권2호
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• pp.1-6
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• 2008

Recently Oscillating Water Column (OWC) plants have been widely employed in wave energy conversion applications. It is necessary to investigate the chamber and optimize its shape parameters for maximizing air flow and energy conversion due to wave conditions. A 2D numerical wave tank based on a Fluent and VOF model is developed to generate the incident waves and is validated by theoretical solutions. The oscillating water column motion in the chamber predicted by the numerical method is compared with the available experimental data. Several geometric scales of the chamber are calculated to investigate the effect of the shape parameters on the oscillating water column motion and wave energy conversion.