• 한국의상디자인학회지
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• 제6권2호
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• pp.15-20
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• 2004

These days are referred to as 'the times of textile fashion,' owing to the emphasis on textile design in the fashion industry. Accordingly, apparel companies have increased their interests in developing new types of textiles to overcome the limits of style and silhouette. Now the ultra-fashion of textile, a new way of process and design development, is given much more attention. A Moire interference pattern has a longer wavy circle of interference, an effect of intensity interference, than one made by piling more than one reflecting plate or transmitting plate. Till now, Moire interference patterns have been used to confirm scientific theory and to measure the structure of a body or a subject in areas such as physics and medical science. Work has also been done on the Moire interference effects on TV screens said to cause dizziness and eye strain. This study focuses on the new types of textiles by creating the appearance of the Moire phenomena. Contrary to the present usual stationary patterns of textiles, it is a varying pattern according to the different gratings, different angles, piling gratings, and the movements of the human bodies. In the preceding study, we observed Moire fringes formed by overlapping two different or same kinds of gratings such as parallel line gratings, square gratings, conic gratings and semicircular gratings and tried to find a promising possibility of new textiles through the method of clothes design simulation.

• 대한전자공학회논문지TC
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• 제43권10호
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• pp.55-59
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• 2006

셀률러 OFDMA(Orthogonal Frequency Division Multiple Access) 시스템에서는 각 부반송파별로 주변 셀에서 오는 간섭의 양이 다를 수 있다. 만일 각 부반송파에 대해서 주변 셀로부터 오는 간섭의 양을 정확히 측정할 수 있다면 SINR(Signal to Interference and Noise Ratio) weighting을 통해서 성능을 대폭 향상시킬 수 있다. 이 논문에서는 셀률러 OFDMA 시스템에서의 셀간 간섭의 양을 측정하는 방법을 제안한다. 제안하는 방법은 각 파일럿 심벌들이 겪는 주파수 오차, 타이밍 오차, 단말의 이동 속도, 딜레이 스프레드에 의한 채널 변화의 영향을 제거하고 순수한 잡음 및 간섭에 의한 채널 변화를 측정한다.

• 한국항행학회논문지
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• 제13권3호
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• pp.344-350
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• 2009

본 논문에서는 비정지궤도 위성 수와 비정지궤도 위성과 정지궤도 위성간의 각도 차에 따른 간섭정도가 정지궤도 위성망의 성능에 미치는 영향을 BER 성능측면에서 분석하였다. 위성간의 각도와 간섭 영향을 분석하기 위해 정지궤도 위성과 비정지궤도 위성간의 이격 각도를 $1^{\circ}{\sim}8^{\circ}$ 변화시켰으며, 위성수의 영향을 분석하기 위해 비정지궤도 위성 수를 1~4개로 변화시켰다. 이러한 조건에서 실험한 결과 위성간의 각도가 감소하면 할수록 간섭의 영향은 더욱 증가되었으며, 특히 간섭위성과 정지궤도 위성과의 각이 작은 경우 이러한 간섭의 정도는 더욱 심해짐을 확인하였다. 또한, 간섭 위성의 수가 증가하면 할수록 정지궤도 위성 서비스로의 간섭 영향 역시 증가됨을 확인하였다. 하지만 간섭 위성 수 보다는 간섭위성과 이루는 각도가 더 시스템의 성능에 더 큰 영향을 미쳤다.

• 한국항공우주학회지
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• 제49권6호
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• pp.489-496
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• 2021

지구 관측위성의 데이터를 지상으로 전송하기 위해 활용되는 X-대역 주파수는 한정적이므로, 여러 위성들이 해당 동일 대역을 공유하는 방식으로 활용한다. 복수의 위성이 유사 주파수 대역을 활용하기 위해서 국제전기통신연합-전파통신부문(International Telecommunication Union - Radiocommunication; ITU-R)에서는 송신 대역 내 전력속밀도(Power Flux Density; PFD) 제한 조건이 있고, 이를 통해 위성 간 간섭 영향성을 극복하고 있다. 하지만 이러한 규정 하에서도 복수의 위성이 비교적 근접한 지상국에 접속하는 경우 간섭 영향성의 분석이 수행될 필요가 있다. 본 논문에서는 한반도 내에 임의 배치된 두 개의 지상국을 기준으로, 서로 다른 궤도를 따르는 두 개의 저궤도 위성에 각각 접속하여 통신할 경우에 대해 수신 신호대 간섭+잡음비(Signal to Interference plus Noise Ration; SINR) 기준으로 간섭 영향성 분석을 수행하였다. 간섭 영향성 분석을 통해 PFD 규격을 만족시키는 두 위성이라 하더라도 전체 임무 기간(365일 가정) 내에 간섭은 발생할 수 있으나 영향받는 기간이 짧고 미리 예측할 수 있음을 확인할 수 있었다.

• 한국항공우주학회지
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• 제36권7호
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• pp.621-627
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• 2008

풍동에서 측정된 공력자료에는 풍동벽면의 영향으로 인하여 불가항력적인 오차가 포함되어 있다. 벽면영향이 없는 공력자료를 얻기 위해서는 이러한 원하지 않는 벽면효과를 제거 하여야 한다. 유선곡률 효과는 풍동벽면의 영향으로 유선의 곡률이 자유 흐름의 것과 다르기 때문에 발생한다. 고정익 항공기에 사용되고 있는 전통적인 유선곡률 효과를 보정방법인 Glauert의 보정방법은 회전익 항공기에 적용이 적절하지 않다. 본 논문에서는 로터에 적절한 후류모델을 사용하는 Heyson의 보정방법을 사용하여 로터축 기울어짐 각과 동압을 보정하였다. Heyson 보정방법의 결과를 Glauert 보정방법의 결과와 비교하였다.

• Wind and Structures
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• 제28권2호
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• pp.71-87
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• 2019

The yaw and interference effects of blades affect aerodynamic performance of large wind turbine system significantly, thus influencing wind-induced response and stability performance of the tower-blade system. In this study, the 5MW wind turbine which was developed by Nanjing University of Aeronautics and Astronautics (NUAA) was chosen as the research object. Large eddy simulation on flow field and aerodynamics of its wind turbine system with different yaw angles($0^{\circ}$, $5^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$ and $45^{\circ}$) under the most unfavorable blade position was carried out. Results were compared with codes and measurement results at home and abroad, which verified validity of large eddy simulation. On this basis, effects of yaw angle on average wind pressure, fluctuating wind pressure, lift coefficient, resistance coefficient,streaming and wake characteristics on different interference zone of tower of wind turbine were analyzed. Next, the blade-cabin-tower-foundation integrated coupling model of the large wind turbine was constructed based on finite element method. Dynamic characteristics, wind-induced response and stability performance of the wind turbine structural system under different yaw angle were analyzed systematically. Research results demonstrate that with the increase of yaw angle, the maximum negative pressure and extreme negative pressure of the significant interference zone of the tower present a V-shaped variation trend, whereas the layer resistance coefficient increases gradually. By contrast, the maximum negative pressure, extreme negative pressure and layer resistance coefficient of the non-interference zone remain basically same. Effects of streaming and wake weaken gradually. When the yaw angle increases to $45^{\circ}$, aerodynamic force of the tower is close with that when there's no blade yaw and interference. As the height of significant interference zone increases, layer resistance coefficient decreases firstly and then increases under different yaw angles. Maximum means and mean square error (MSE) of radial displacement under different yaw angles all occur at circumferential $0^{\circ}$ and $180^{\circ}$ of the tower. The maximum bending moment at tower bottom is at circumferential $20^{\circ}$. When the yaw angle is $0^{\circ}$, the maximum downwind displacement responses of different blades are higher than 2.7 m. With the increase of yaw angle, MSEs of radial displacement at tower top, downwind displacement of blades, internal force at blade roots all decrease gradually, while the critical wind speed decreases firstly and then increases and finally decreases. The comprehensive analysis shows that the worst aerodynamic performance and wind-induced response of the wind turbine system are achieved when the yaw angle is $0^{\circ}$, whereas the worst stability performance and ultimate bearing capacity are achieved when the yaw angle is $45^{\circ}$.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권1호
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• pp.25-40
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• 2015

Understanding the effects of the parameters affecting the interaction of tandem hydrofoil system is a crucial subject in order to fully comprehend the aero/hydrodynamics of any vehicle moving inside a fluid. This study covers a parametric study on tandem hydrofoil interaction in both potential and viscous fluids using iterative Boundary Element Method (BEM) and RANSE. BEM allows a quick estimation of the flow around bodies and may be used for practical purposes to assess the interaction inside the fluid. The produced results are verified by conformal mapping and Finite Volume Method (FVM). RANSE is used for viscous flow conditions to assess the effects of viscosity compared to the inviscid solutions proposed by BEM. Six different parameters are investigated and they are the effects of distance, thickness, angle of attack, chord length, aspect ratio and tapered wings. A generalized 2-D code is developed implementing the iterative procedure and is adapted to generate results. Effects of free surface and cavitation are ignored. It is believed that the present work will provide insight into the parametric interference between hydrofoils inside the fluid.

• 전자공학회논문지 IE
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• 제45권1호
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• pp.38-43
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• 2008

본 논문은 RF 중계기에서 발생되는 궤환 신호로 인한 발진현상을 제거하는 간섭제거 방법을 제시한다. 본 논문에서는 LMS(Least Mean Square) 알고리즘을 이용하여 궤환 신호를 추정하고, 그에 상응하는 감쇄신호를 만들어 간섭을 제거하도록 하였다. 본 제안 방법을 이용하여 도플러(Doppler) 주파수를 변화시키면서 성능시험을 수행한 결과 궤환 신호를 상쇄시키는 -30dB의 감쇄신호를 발생시켜 발진을 방지할 수 있었다.

• IEIE Transactions on Smart Processing and Computing
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• 제3권5호
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• pp.275-284
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• 2014

This paper considers two-tier networks consisting of macrocells and femtocells operating in the same spectrum. This paper proposes a femtocell spectrum reuse scheme that determines the shared spectrum and transmit power for the femtocells to mitigate the effects of cross-tier interference between the macrocells and femtocells. The proposed scheme provides macrocell throughput that is unaffected by the increasing number of femtocells per cell site and improves the femtocell signal quality at the same time by limiting the cross-tier interference. This study analyzed the per-tier signal-to-interference ratio (SIR) and outage probability of the proposed scheme to investigate the macrocell and femtocell performance. The total throughput of the proposed scheme was analyzed based on the outage probabilities. The analysis and numerical results proved that high femtocell throughput can be achieved using only a small fraction of the spectrum while protecting the macrocell throughput. As a result, an improved total throughput was achieved enforcing higher spatial reuse.

• Journal of electromagnetic engineering and science
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• 제10권3호
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• pp.99-103
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• 2010

Motivated by recent works on spectrum-sharing systems, this paper investigates the effects of transmit diversity on the peak interference power limited cognitive radio(CR) networks. In particular, we derive the ergodic and outage capacities of a spectrum-sharing system with multiple transmit-antennas. To derive the capacities, peak interference power constraint is imposed to protect the primary receiver. In a CR transmitter and receiver pair with multiple antennas at the transmitter side, the allowable transmit power is distributed over the transmit-antennas to achieve transmit diversity at the receiver. We investigate the effect of this power distribution when a peak interference power constraint is imposed to protect the primary receiver. We show that the transmit diversity does not improve the ergodic capacity compared to the single-antenna system. On the other hand, the transmit diversity significantly improves the outage capacity. For example, two transmit-antennas improve the outage capacity 10 times compared to the single-antenna with a 0 dB interference constraint.