• 한국산학기술학회논문지
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• 제18권9호
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• pp.68-75
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• 2017

본 논문에서는 해안가의 수평 파력발전 장치에 도입되는 상단 힌지 진자 형태의 파랑에너지 1차 추출 시스템에 대한 동적 운동 특성을 수조에서 모형실험과 연동 시뮬레이션을 통해 고찰 하였다. 조파기의 일정한 파고와 주기의 정현파형태 파도가 수조 프레임에 고정된 상단 힌지 진자 체의 플랩 부이에 부딪쳤을 때 부이 전체의 토크와 운동 궤적을 측정하였다. 또한 파도가 플랩부이에 부딪치는 현상을 강체 동력학과 입자유체 거동에 대한 연동 시뮬레이션을 통해 유체입자가 플랩부이에 부딪칠 때의 압력을 구하여 전체 부이에서의 토크와 힌지에서의 반력을 도출하여 비교 고찰 하였다. 그리고 일 방향수평 파도에 따른 진자 체의 규칙적이고 효과적인 좌우 주기운동을 발생시키기 위한 인장력 조정 값을 도출하였다. 향후 상단 힌지 진자 형태의 에너지 추출장치를 특징으로 하는 해안가 수평파력 발전 장치의 개발 및 제작 시 본 연구에서 도출된 결과 값을 주요 설계 데이터로 적용하고자 한다.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.552-558
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• 2011

A 50 kW class rotating body type wave energy converter consisted of two floating bodies and a PTO (Power Takeoff) unit is studied. As an wave energy extractor, the body is designed to have a VLCO (Variable Liquid-Column Oscillator) having a liquid filled U-tube with air chambers. Owing to the oscillation of the liquid in the U-tube caused by the air spring effect of the air chambers, the amplitude of response of the VLCO becomes significantly amplified for a target wave period. The PTO converts the rotational moment introduced from the relative motion of the hinged bodies to an hydraulic power by means of a cylinder. A high pressure accumulator, hydraulic motor and a generator are equipped in the PTO to convert the hydraulic power to electric power. A control law for adjusting the oscillation period of the VLCO is proposed for the efficient operation of the VLCO with various wave conditions. It is found that the effect of the air spring has an important role to play in making the oscillation of the VLCO match with the ocean wave. In this way, the wave energy converter equipped with the VLCO provides the most effective mode for extracting energy from the ocean wave.

• 천문학회보
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• 제37권1호
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• pp.96.2-96.2
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• 2012

We statistically examined ULF Pc 3-5 wave power in the regions of undisturbed upstream solar wind, quasi-parallel shock (and foreshock), quasi-perpendicular shock, and the magnetosheath to understand how and to what extent the wave power changes as the solar wind propagates to the magnetosheath. For this study, we used the magnetic field data from the THEMIS spacecraft and Wind (as shifted to the bow shock nose) for May-November in 2008 and 2009. The statistical results show that, in the case of the Pc5 wave power, the sheath power is roughly proportional to the upstream power for both quasi-parallel (and foreshock) and quasi-perpendicular shock regions. Also we identified undisturbed upstream condition from WIND as being well away from foreshock region, and found that the sheath power can be larger for quasi-parallel shock region by a factor of 5-15 than for quasi-perpendicular shock region. In the cases of Pc 3 and Pc4 waves, we found the higher sheath power when associated with the foreshock than with the quasi-perpendicular shock region.

• Journal of Advanced Marine Engineering and Technology
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• 제32권8호
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• pp.1123-1128
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• 2008

Marine facilities like buoy, lighthouse are operated with stand alone power supply system. This power system can consist of a stand-alone type power system such as PV(Photovoltaic) system, wave system or hybrid system which is not cooperated with a commercial power system. Generally, PV power system for marine facilities can not supply a sufficient power to buoy, because it is so influenced from weather condition. For solving this problem the hybrid power system with PV and wave is studied on a various area, that is why a hybrid power system is requires to overcome these problems. This paper will describe a generation characteristic of WEC(Wave Energy Converter) for buoy, and an AFS(Anti-Fouling System) influence on WEC.

• 동력기계공학회지
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• 제17권5호
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• pp.38-43
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• 2013

In order to design a wave energy generating system, a 6-DOF analysis technique is applied to CFD analysis on of a floating body and the behavior is interpreted according to the nature of the incoming waves. A spring constant is adopted to control the motion of multi floating bodies and to calculate the total average power absorption. Three cases of different wavelengths namely 20D, 30D and 40D have been modeled to analyze the total average power absorption. The average power absorption not only varies with the position of the floating body but also varies with wavelength. From the results obtained, it is concluded that the maximum total average power absorption is 9W approximately in wavelength 30D and the minimum total average power absorption is 4.3W approximately in wavelength 40D.

• 한국광학회:학술대회논문집
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• 한국광학회 2003년도 제14회 정기총회 및 03년 동계학술발표회
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• pp.158-159
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• 2003

In four-wave-mixing wavelength converter, we investigated the performance through simulation by using VPI tool, changing the input signal power and CW power at 2.SGb／s. Controlling optimal CW power to each input signal power, we extended the input signal power range to 20dB, which guarantees the minimum power penalty.

• Wind and Structures
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• 제10권5호
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• pp.401-420
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• 2007

Field measurements of the wind-induced response of two residential reinforced concrete buildings, among the tallest in the world, have been performed during two typhoons. Natural periods and damping values have been determined and compared with other field measurements and empirical predictors. Suitable and common empirical predictors of natural period and structural damping have been obtained that describe the trend of tall, reinforced concrete buildings whose structural vibrations have been measured in the collection of studies in Hong Kong compiled by the authors. This data is especially important as the amount of information known about the dynamic parameters of buildings of these heights is limited. Effects of the variation of the natural period and damping values on the alongwind response of a tall building for serviceability-level wind conditions have been profiled using the gust response factor approach. When using this approach on these two buildings, the often overestimated natural periods and structural damping values suggested by empirical predictors tended to offset each other. Gust response factors calculated using the natural periods and structural damping values measured in the field were smaller than if calculated using design-stage values.

• 신재생에너지
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• 제20권2호
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• pp.26-34
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• 2024

Floating offshore wind turbines (FOWTs) have been developed to overcome large water depths and leverage the abundant wind resource in deep seas. However, wind-wave misalignment can occur depending on the weather conditions, and most megawatt (MW)-class turbines are horizontal-axis wind turbines subjected to yaw errors. Therefore, the power performance and dynamic response of super-large FOWTs exposed simultaneously to these external conditions must be analyzed. In this study, several scenarios combining wind-wave misalignment and yaw error were considered. The IEA 15 MW reference FOWT (v1.1.2) and OpenFAST (v3.4.1) were used to perform numerical simulations. The results show that the power performance was affected more significantly by the yaw error; therefore, the generator power reduction and variability increased significantly. However, the dynamic response was affected more significantly by the wind-wave misalignment increased; thus, the change in the platform 6-DOF and tower loads (top and base) increased significantly. These results can be facilitate improvements to the power performance and structural integrity of FOWTs during the design process.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제18권7호
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• pp.2047-2066
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• 2024

In order to improve the coverage and achieve massive spectrum access, non-orthogonal multiple access (NOMA) technology is applied in millimeter wave massive multiple-input multiple-output (mMIMO) communication network. However, the power assumption of active sensors greatly limits its wide applications. Recently, Intelligent Reconfigurable Surface (IRS) technology has received wide attention due to its ability to reduce power consumption and achieve passive transmission. In this paper, spectral efficiency maximum problem in the millimeter wave mMIMO-NOMA system with IRS is considered. The sparse RF chain antenna structure is designed at the base station based on continuous phase modulation. Furthermore, a joint optimization problem for power allocation, power splitting, analog precoding and IRS reconfigurable matrices are constructed, which aim to achieve the maximum spectral efficiency of the system under the constraints of user's quality of service, minimum energy harvesting and total transmit power. A three-stage iterative algorithm is proposed to solve the above mentioned non-convex optimization problems. We obtain the local optimal solution by fixing some optimization parameters firstly, then introduce the relaxation variables to realize the global optimal solution. Simulation results show that the spectral efficiency of the proposed scheme is superior compared to the conventional system with phase shifter modulation. It is also demonstrated that IRS can effectively assist mmWave communication and improve the system spectral efficiency.

• Current Optics and Photonics
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• 제2권1호
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• pp.90-95
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• 2018

Stimulated polariton scattering from the $B_1$-symmetry modes of a $KNbO_3$ crystal to generate a terahertz wave (THz-wave) with a noncollinear phase-matching scheme is investigated. The frequency-tuning characteristics of the THz-wave by varying the phase-matching angle and pump wavelength are analyzed. The expression for the effective parametric gain length under the noncollinear phase-matching condition is deduced. Parametric gain and absorption characteristics of the THz-wave in $KNbO_3$ are theoretically simulated. The characteristics of $KNbO_3$ for a terahertz parametric oscillator (TPO) are compared to those of $MgO:LiNbO_3$. The analysis indicates that $KNbO_3$ is an excellent optical crystal for a TPO, to enhance the THz-wave output.