• 한국음향학회:학술대회논문집
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• 한국음향학회 1999년도 학술발표대회 논문집 제18권 1호
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• pp.189-197
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• 1999

To investigate internal waves (IW) effect on acoustic wave propagation, m analysis is conducted on mode travel time and model simulation. Based on the thermistor string data, it can be shown that the thermocline depth variation may cause travel time difference as much as 4-10 ms between mode 1 and 2 over range 10 km. This travel time difference causes interference among modes and thus fluctuation from range-independent stratified ocean structure. In real situations, however, there exist additionally spatial variation of IW. Model simulation with all modes and simple IW shows clear responses of acoustic signals to IW, amplitude and phase fluctuation.

• 한국융합학회논문지
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• 제9권9호
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• pp.47-52
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• 2018

와이파이 기반의 사물인터넷 장치는 사회, 경제, 산업에 막대한 영향을 미치고 있다. 그러나 와이파이와 같은 비면허 대역에서 동작하는 무선 전송 기술은 간섭에 취약하다. 장거리의 밀집 네트워크에서 무선 연결을 시도하는 경우에는 동적으로 변하는 간섭 상황과 비대칭적인 간섭 조건 때문에 성능 열화가 발생한다. 본 논문에서는 장거리 사물인터넷을 위한 ACK 전송 방법을 제안한다. 본 연구 논문에서 제안한 방법에 따르면, 송신 장치와 수신 장치의 간섭 상황이 다른 비대칭적 간섭 환경에서 송신 장치가 간섭 레벨을 측정한 후 응답 프레임의 전송 속도를 추천해 응답 프레임의 전송 성공률을 향상시킨다. 그리고 고품질의 무선 채널 환경이 보장되는 경우에는 더 높은 전송 속도로 전송할 수 있다. 성능 평가 결과에 따르면 제안하는 방법에 의해 비대칭 간섭 상황에서 20 MHz 대역폭 전송 모드에서 스루풋이 최대 9 Mbps 향상됨을 알 수 있다.

• 한국생산제조학회지
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• 제8권4호
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• pp.130-135
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• 1999

The main scale of linear encoder greatly effects on the precision of displacement measurement. Especially when needing the long range measurement the length of main scale should be increased accordingly. In this paper we propose a linear encoder that uses laser interference pattern as main scale for long range measurement. The linear encoder is similar to Michelson interferometer excepting that the reference mirror is tilted so as to obtain interference fringe pattern and a grating panel is attached on a quadratic photo diodes. Four kinds of grating having phase difference of 0. $\pi$/4, $\pi$/2, 3$\pi$/4 are arranged on the panel. The experimental results show that signals of quadratic photo diode A, B, {{{{ {-}atop {A } }}}} and {{{{ {- } atop {B } }}}} are cosine wavelike and successive signals have phase difference of $\pi$/4 each other. So the proposed method can achieve improved measurement resolution.

• Journal of Communications and Networks
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• 제6권2호
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• pp.163-172
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• 2004

Ultra Wide Bandwidth (UWB) spread-spectrum techniques will playa key role in short range wireless connectivity supporting high bit rates availability and low power consumption. UWB can be used in the design of wireless local and personal area networks providing advanced integrated multimedia services to nomadic users within hot-spot areas. Thus the assessment of the possible interference caused by UWB devices on already existing narrowband and wideband systems is fundamental to ensure nonconflicting coexistence and, therefore, to guarantee acceptance of UWB technology worldwide. In this paper, we study the coexistence issues between an indoor UWB-based system (hot-spot) and outdoor point to point (PP) links and Fixed Wireless Access (FWA) systems operating in the 3.5 - 5.0 GHz frequency range. We consider a realistic UWB master/slave system architecture and we show through computer simulation, that in all practical cases UWB system can coexist with PP and FWA without causing any dangerous interference.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.456-464
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• 2013

Passive sonar in submarine can detect the target in long range and can attack using it. There are many noises which can be received at passive sonar of submarine. When noise received in the sonar it make diverse interference pattern depend on the ocean ambient and movement scenario. Interference pattern can be explained by theory of waveguide invariant. In this paper, analyze the interference pattern according to the relative motions of surface ship and submarine. And analyze the occurrence reason of 2 kinds of interference patterns those are usually display on the submarine console. The results show that if relative speed of submarine and target increase then gradient of interference pattern will increase. And closest point approach of submarine and target decrease then gradient of interference pattern will increase. Bathtube pattern usually appear when target pass though close to submarine and Pinetree pattern appear target pass though above of submarine.

• Biotechnology and Bioprocess Engineering:BBE
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• 제9권6호
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• pp.428-434
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• 2004

Coarse clumping of solid materials within diseased biological cells can have a marked influence on the light scattering pattern. Perturbations in refractive index lead to distinct varia­tions in the cytometric signature, especially apparent over wide scattering angles. The large dynamic range of scattering intensities restricts collection of data to narrow angular intervals be­lieved to have the highest potential for medical diagnosis. We propose the use of an interfer­ence filter to reduce the dynamic range. Selective attenuation of scattering intensity levels is expected to allow simultaneous data collection over a wide angular interval. The calculated angu­lar transmittance of a commercial shortwave-pass filter of cut-off wavelength 580 nm indicates significant attenuation of scattering peaks below ${\~}\;10^{circ}$, and reasonable peak equalization at higher angles. For the three-dimensional calculation of laser light scattered by cells we use a spectral method code that models cells as spatially varying dielectrics, stationary in time. How­ever, we perform preliminary experimental testing with the interference filter on polystyrene microspheres instead of biological cells. A microfluidic toolkit is used for the manipulation of the microspheres. The paper intends to illustrate the principle of a light scattering detection system incorporating an interference filter for selective attenuation of scattering peaks.

• 한국광학회지
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• 제20권4호
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• pp.207-210
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• 2009

공초점 방식을 이용하여 두 기판사이의 얇은 공기갭의 두께를 측정하는 방법을 제안하였다. 공기갭이 약 200 nm 이내 일때는 두 기판면이 초점의 레일리 영역 안에 있으므로 완전한 간섭신호를 측정할 수 있었다. 또 초점영역 근처에서의 간섭무늬만 측정되므로 다층 박막중에 존재하는 공기갭이라도 측정할 수 있는 장점이 있다. 간섭무늬 변화가 작은 영역을 제외하면 1 nm 이내의 안정도를 가진다.

• Biomaterials and Biomechanics in Bioengineering
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• 제3권2호
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• pp.85-104
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• 2016

Stability and loosening of implanted femoral stems in Total Hip Replacement have been well established as barriers to the primary concerns of osseointegration and long term implant survival. In-vitro experiments and finite element modeling have for years been used as a primary tool to assess the bone stem interface with variable methodologies leading to a wide range of micromotion, interference fit and stress shielding values in the literature. The current study aims to provide a comprehensive review of currently utilized methodologies for in-vitro mechanical testing as well as finite element modeling of both micromotion and interference of implanted femoral stems. A total of 12 studies detailed in 33 articles were selected for inclusion. Experimental values of micromotion ranged from 12 to $182{\mu}m$ while finite element analysis reported a wider range from 2.74 to $1,277{\mu}m$. Only two studies were found that modeled bone/implant contact with consideration for interference fit. In studies evaluating stem micromotion in THA, the reference surface at the bone/stem interface should be well defined. Additionally, the amount of penetration considered should be disclosed and associated with bone density and roughness.

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.2025-2035
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• 2014

The read range of UHF mobile readers can be extended by a booster for mobile RFID readers (BoMR). But in an environment where multiple BoMRs are installed, the read success rate may be decreased due to signal interference. This paper proposes three arbitration methods based on interference estimation with the purpose of enhancing the read success rate. A central arbitration server manages global information in centralized arbitration method (CAM) without broadcast/multicast communication facility. In fully distributed arbitration method (FDAM), all the arbitration messages are broadcasted from a BoMR to every BoMR, and each BoMR decides with broadcasted global information. Events in FDAM are serialized naturally with broadcasted messages. Cluster Distributed Arbitration Method (CDAM) forms clusters with multicasted BoMRs and a selected BoMR acts as an arbiter in the cluster. Such effects as lengthened read range, improved the read success rates of readers can be obtained by the proposed methods without any hardware modification. In order to evaluate the arbitration methods, the RFID system is modeled by using the DEVS formalism and simulated by using the DEVSim++.

• 제어로봇시스템학회논문지
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• 제22권9호
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• pp.723-732
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• 2016

This paper proposes an approach to fused navigation of an unmanned surface vehicle(USV) and to detection of the outlier or interference of global positioning system(GPS). The method fuses available sensor measurements through extended Kalman filter(EKF) to find the location and attitude of the USV. The method uses error covariance of EKF for detection of GPS outlier or interference. When outlier or interference of the GPS is detected, the method excludes GPS data from navigation process. The measurements to be fused for the navigation are GPS, acceleration, angular rate, magnetic field, linear velocity, range and bearing to acoustic beacons. The method is tested through simulated data and measurement data produced through ground navigation. The results show that the method detects GPS outlier or interference as well as the GPS recovery, which frees navigation from the problem of GPS abnormality.