• International Journal of Naval Architecture and Ocean Engineering
• /
• 제10권6호
• /
• pp.782-793
• /
• 2018

A small-scale horizontal axis hydrokinetic turbine is designed, manufactured and studied both experimentally and numerically in this study. The turbine is expected to work in most of China's sea areas where the ocean current velocity is low and to supply electricity for remote islands. To improve the efficiency of the turbine at low flow velocities, a magnetic coupling is used for the non-contacting transmission of the rotor torque. A prototype is manufactured and tested in a towing tank. The experimental results show that the turbine is characterized by a cut-in velocity of 0.25 m/s and a maximum power coefficient of 0.33, proving the feasibility of using magnetic couplings to reduce the resistive torque in the transmission parts. Three dimensional Computational Fluid Dynamics (CFD) simulations, which are based on the Reynolds Averaged Navier-Stokes (RANS) equations, are then performed to evaluate the performance of the rotor both at transient and steady state.

• 한국전자파학회논문지
• /
• 제11권8호
• /
• pp.1313-1321
• /
• 2000

본 논문에서는 필터의 설계 및 구현이 용이하고 소형화가 가능한 새로운 구조의 고온초전도 마이크로스트립 형태의 의사 집중상수 소자 공진기를 제안하였다. 또한, 공진기들 사이의 비 인접 결합을 이용하여 notch를 갖는 필터특성의 7-극 대역통과 필터를 설계, 제작하였다. 7-극 notch를 갖는 필터는 두께 0.5mm, 유전율 23.5의 $LaAlO_{3}$ 기판상에 YBCO를 양면 증착하여 제작하였다. 측정결과, 절대 온도 20K에서 중심 주파수 1774MHz 차단대역(cut-off-band)에서 33㏈감쇠를 나타내었다.

• Journal of Electrical Engineering and Technology
• /
• 제13권4호
• /
• pp.1655-1662
• /
• 2018

This paper studies the magnetic fields between the power lines which are finite length and other ones which are infinitely long around the first tower in the proximity of the power transformers. They will be used as a source of disturbance applied to the power line. The method applied in this study was gradual; develop the theoretical formulation of the magnetic fields of these lines which are finite length and other ones which are infinitely long, examine the effects of different couplings between the different neighboring lines and the distribution transformers on behavior of magnetic fields. The method also focused on the experimental results analyzing the magnetic fields which will be used as a source applied to the auditory implants EMC. The theoretical and experimental results were compared and discussed for three power lines (90kV, 150kV and 225kV) near the power station, and it proved the effect of these substations on the simulated and measured results of the magnetic field. The maximum intensities of magnetic fields measured at the height of 1m from the ground for the circuit of three lines close to each substation were significantly lower than the ICNIRP reference levels for occupational and non occupational exposures.

• Applied Biological Chemistry
• /
• 제41권7호
• /
• pp.550-555
• /
• 1998

Fluoro-quinolone carboxilic acid 유도체에서, 탄소-불소간 one bond coupling constants는 위치와 무관하게 249 Hz에서 257 Hz 사이의 값을 갖는데, geminal 및 vicinal coupling constants는 위치에 따라 그 값의 차이가 많이 생긴다. 즉, seminal coupling constants는 6 Hz에서 23 Hz의 값을 보이고 vicinal coupling constants는 1.9 Hz에서 7 Hz의 값을 보인다. 또한 수소-불소간 three bond coupling constants는 9 Hz에서 10.3 Hz의 값을 보이고, four bond coupling constants는 6 Hz에서 8.3 Hz의 값을 보인다.

• 한국정보통신학회논문지
• /
• 제15권2호
• /
• pp.286-291
• /
• 2011

방향성 결합기는 RF 및 마이크로파 대역에서 신호를 분배하거나 감시하는 데 이용된다. 본 논문에서는 마이크로스트립 선로로 구현한 결합선로를 이용한 새로운 구조의 브랜치 선로 방향성 결합기를 제안하였다. 브랜치 선로 방향성 결합기는 결합도가 낮아지면 병렬로 연결된 선로의 특성 임피던스가 높아서 마이크로스트립 선로로 구현하기 어려워진다. 이를 극복하기 위하여 단락된 평형 결합 선로를 이용하여 높은 특성 임피던스를 구현하였다. 제안한 브랜치 선로 방향성 결합기의 시뮬레이션 결과 및 제작하여 측정한 결과를 보였다. 제작한 10 dB 브랜치 선로 방향성 결합기는 10% 대역폭에서 반사 손실이 30 dB 이상, 8% 대역폭에서 고립도 35 dB 이상인 결과를 보였다.

• Journal of Power Electronics
• /
• 제17권6호
• /
• pp.1694-1706
• /
• 2017

Models and experiments for magnetic resonance coupling wireless power transmission (MRC-WPT) topologies such as the chain topology and branch topology are studied in this paper. Coupling mode theory based energy resonance models are built for the two topologies. Complete energy resonance models including input items, loss coefficients, and coupling coefficients are built for the two topologies. The storage and the oscillation model of the resonant energy are built in the time domain. The effect of the excitation item, loss item, and coupling coefficients on MRC systems are provided in detail. By solving the energy oscillation time domain model, distance enhancing models are established for the chain topology, and energy relocating models are established for the branch topology. Under the assumption that there are no couplings between every other coil or between loads, the maximum transmission capacity conditions are found for the chain topology, and energy distribution models are established for the branch topology. A MRC-WPT experiment was carried out for the verification of the above model. The maximum transmission distance enhancement condition for the chain topology, and the energy allocation model for the branch topology were verified by experiments.

• 한국수자원학회:학술대회논문집
• /
• 한국수자원학회 2015년도 학술발표회
• /
• pp.218-218
• /
• 2015

Urbanization and waterworks construction in natural watershed have been causing higher flood risks in lowland areas. Detention basins have become one of the most efficient fundamental instruments for storm water and environmental management at watershed scale. Nowadays, there are many studies coupled numerical methods of flood routing with optimization algorithms to investigate factors that impact on the efficiency of detention basins in flood reduction in a watershed, such as detention basin location, size, and cost and watershed characteristics. Although these couplings have been become more widespread but cumbersome computation and hydraulic data requirement still are their limitations. To tackle the procedure efforts due to numerical integration and data collection, simple approach is proposed to primarily estimate effects of detention basins. The approach basis is the linear system theory applied to the solution of hydrologic flood routing. The paper introduces an analytical method for estimating detention effects deriving by recent studies and innovatively analyses this equation on fractal perspective. Then, an optimization technique is performed by applying harmony search algorithms (HSA) to optimize efficiency of detention basins at watershed scale. The location and size of upstream detention basin are simultaneously obtained. Finally, the proposed methodology, practically applied for a real watershed in Kan river, Iran.

• 반도체디스플레이기술학회지
• /
• 제18권4호
• /
• pp.51-56
• /
• 2019

LuAG:Ce(Lu₃Al₅O₁₂:Ce³⁺) nano phosphor were synthesized by applying the coprecipitation method. It is used to increase the color rendering of phosphor ceramic plate for high power LEDs and laser lighting. Internal quantum efficiency and absorption of LuAG:Ce nano phosphor are 51.5 % and 64.4 %, respectively, which is higher than the previously studied nano phosphors. The maximum absorption wavelength of this phosphor is 450 nm blue light, and the emission wavelength is 510 nm. The emission wavelength shifted to longer wavelength when the concentration of Ce increased in the heat treatment of the reducing atmosphere. Thermal quenching of LuAG nano phosphor was 70 % at 200 ℃, it was explained by their significant quenching of all raman scattering modes, implying the restriction of electron-phonon couplings caused by their defects.

• Nuclear Engineering and Technology
• /
• 제41권9호
• /
• pp.1157-1170
• /
• 2009

A variety of Generation III/III+ reactor designs featuring enhanced safety and improved economics are being proposed by nuclear power industries around the world to solve the future energy supply shortfall. Nanofluid coolants showing an improved thermal performance are being considered as a new key technology to secure nuclear safety and economics. However, it should be noted that there is a lack of comprehensible design works to apply nanofluids to Generation III+ reactor designs. In this work, the review of accident scenarios that consider expected nanofluid mechanisms is carried out to seek detailed application spots. The Axiomatic Design (AD) theory is then applied to systemize the design of nanofluid-engineered nuclear safety systems such as Emergency Core Cooling System (ECCS) and External Reactor Vessel Cooling System (ERVCS). The various couplings between Gen-III/III+ nuclear safety features and nanofluids are investigated and they try to be reduced from the perspective of the AD in terms of prevention/mitigation of severe accidents. This study contributes to the establishment of a standard communication protocol in the design of nanofluid-engineered nuclear safety systems.

• Nuclear Engineering and Technology
• /
• 제54권5호
• /
• pp.1760-1768
• /
• 2022

When gamma-camera sensor modules, which are key components of radiation imagers, are derived from the coupling between scintillators and photosensors, the light collection efficiency is an important factor in determining the effectiveness with which the instrument can identify nuclides via their derived gamma-ray spectra. If the pixel area of the scintillator is larger than the pixel area of the photosensor, light loss and cross-talk between pixels of the photosensor can result in information loss, thereby degrading the precision of the energy estimate and the accuracy of the position-of-interaction determination derived from each active pixel in a coded-aperture based gamma camera. Here we present two methods to overcome the information loss associated with the loss of photons created by scintillation pixels that are coupled to an associated silicon photomultiplier pixel. Specifically, we detail the use of either: (1) light guides, or (2) scintillation pixel areas that match the area of the SiPM pixel. Compared with scintillator/SiPM couplings that have slightly mismatched intercept areas, the experimental results show that both methods substantially improve both the energy and spatial resolution by increasing light collection efficiency, but in terms of the image sensitivity and image quality, only slight improvements are accrued.