• 동력기계공학회지
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• 제3권1호
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• pp.55-59
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• 1999

Generally, T.G(Tacho-generator, Tachometer) sensor is used widely for sensing the angular velocity in rotary machine. By limitation of T.G sensor's structure, the sensed angular velocity include a periodic noise, and the noise is called "ripple" as an electrical term. To reduce the effecting of the ripple, many kinds of filters are designed and installed, but there is necessary a trade off between response time and adapted frequency band. In this paper, we propose a generalized observer to estimate an angular velocity from the output signal of T.G sensor. The generalized observer is proposed firstly for continue systems, and it is applied to DC servo motor with T.G sensor. For simulation, we measure T.G signals at 60, 400, 570 rpm respectively, and analysis those to obtain the resonance frequency of ripple by FFT method. To verify the effectiveness of the proposed algorithm, we compare the results with those of a RC low frequency band filter.

• 한국소음진동공학회논문집
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• 제12권11호
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• pp.856-863
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• 2002

Seismic qualification of the main control board(MCB) for the nuclear power plant Ulchin 5 and 6 has been performed with the guideline of ASME Section III and IEEE 344 code. As the size and weight of the MCB are too large and heavy to excite using the excitation table, finite element analysis is used in order to investigate the dynamic behaviors and structural integrity of the MCB. As the fundamental frequencies of the equipment are found to be less than 33 Hz, which is the upper frequency limit for the dynamic analysis, response spectrum analysis using ANSYS is performed in order to combine the modal stresses within the frequency limit. In order to confirm the electrical stability of the major components of the MCB. modal analysis theory has been adopted to derive the required response spectra at the component locations. As the all combined stresses obtained from the above procedures are less than the allowable stresses and no mechanical or electrical failures are found from the seismic testing, the authors can confirm the safety of the nuclear equipment MCB under the given seismic loading conditions.

• 한국조명전기설비학회지:조명전기설비
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• 제11권6호
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• pp.64-73
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• 1997

RPWM(Random Pulse Width Modulation)은 인버터의 스위칭 주파수를 랜덤(random)하게 변화시킴으로써 고조파 및 소음의 파워 스펙트럼을 광대역에 분산시켜 사람이 불쾌하게 느낄 수 있는 전자기적 가청 소음을 줄이기 위한 PWM 기법으로써 근래에 매우 각광받고 있다. 본 연구에서는 삼각파(반성파, carrier wave)의 주파수를 랜덤하게 변화시키는 방식의 RPWM에 의한 인버터 유도전동기 구동 장치를 구성하였다. 무항실에서 실험 측정한 소음의 파워 스펙트럼으로부터, 소음원에 대한 분석과 삼각파 주파수 변화 폭에 따른 스위칭 주파수대 소음의 저감 효과를 분석하였다. 고속의 DSP TMS320C31을 사용하여 속도 제어와 더불어 RPWM이 실시간적으로 가능하도록 하여, 부하 조건이 다양하게 변화하는 구동 장치에서도 삼각파 주파수의 중심 주파수 및 대역폭을 자유롭게 변화시킴으로써 효과적으로 스위칭 주파수대 가청 소음을 저감하였다.

• 한국항행학회논문지
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• 제14권6호
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• pp.808-816
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• 2010

무선통신시스템간의 주파수 공유는 새로운 기술의 출현 및 스펙트럼 부족으로 인해 중요한 이슈로 되고 있다. WRC-07에서 향후 4세대 이동통신(4G) 또는 IMT-Advanced 시스템을 위해 기존의 고정무선억세스(FWA) 시스템과 co-primary 기반으로 3400-3600MHz 대역을 할당함으로써 동일 주파수 대역에서 두 시스템간의 간섭문제 및 주파수 공유 문제 분석이 필요한 실정이다. 이에 본 논문에서는 셀룰러 이동통신 시스템에기반한 FWA 및 IMT-Advanced 시스템에서 다수의 기지국들에 의한 간섭 대 잡음전력비(I/N)를 구하여 간섭기준에 의한 최소 서비스 커버리지 분리거리를 파라미터로 두 시스템간의 주파수 공유기준을 제시한다. 특히 최악의 간섭 시나리오에서 비현실적인 서비스 커버리지 분리거리를 IMT-Advanced 기지국에 MIMO SDMA 기술을 적용함으로써 I/N 값을 획기적으로 개선시켜 향후 적절한 분리거리로 두 시스템의 주파수 공유가 가능함을 보인다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 춘계학술대회
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• pp.583-585
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• 2016

The recent advances in wireless networks area have led to new techniques, such as small cells or full-duplex (FD) transmission, have also been developed to further increase the network capacity. Particularly, full-duplex communication promises expected throughput gain by doubling the spectrum compared to half-duplex (HD) communication. Because this technique permits one set of frequencies to simultaneously transmit and receive signals. In this paper, we focus on the binary power control for the users and the base stations in full-duplex multiple cellulars wireless networks to obtain optimal sum-rate under the effect interference and noise. We investigate with a scenario in there one carrier is assigned to only one user in each cell and construct a model for this problem. In this work, we apply the binary power control by the its simplification in the implemented algorithm for both uplink and downlink simultaneously to maximize sum data rate of the system. At first, we realize the 2-cells case separately to check the optimal power allocation whether being binary. Then, we carry on with N-cells case in general through properties of binary power control.

• JSTS:Journal of Semiconductor Technology and Science
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• 제12권3호
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• pp.360-369
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• 2012

The causes of showing different subthreshold slopes (SS) in programmed and erased states for two different charge trap flash (CTF) memory devices, SONOS type flash memory with gate-all-around (GAA) structure and TANOS type NAND flash memory with planar structure were investigated. To analyze the difference in SSs, TCAD simulation and low-frequency noise (LFN) measurement were fulfilled. The device simulation was performed to compare SSs considering the gate electric field effect to the channel and to check the localized trapped charge distribution effect in nitride layer while the comparison of noise power spectrum was carried out to inspect the generation of interface traps ($N_{IT}$). When each cell in the measured two memory devices is erased, the normalized LFN power is increased by one order of magnitude, which is attributed to the generation of $N_{IT}$ originated by the movement of hydrogen species ($h^*$) from the interface. As a result, the SS is degraded for the GAA SONOS memory device when erased where the $N_{IT}$ generation is a prominent factor. However, the TANOS memory cell is relatively immune to the SS degradation effect induced by the generated $N_{IT}$.

• 한국군사과학기술학회지
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• 제26권1호
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• pp.1-9
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• 2023

The skin structure of sensor pod mounted on the exterior of aircraft can be exposed to the acoustic dynamic load and static load such as aerodynamic pressure and inertial load during flight. Fatigue life prediction of structural model under acoustic load should be performed and also differential stiffness of model modified by static load should be considered. The acoustic noise test spectrum of MIL-STD-810G was applied to the structural model and the stress response power spectral density (PSD) was calculated. The frequency response analysis was performed with or without prestress induced by inplane static load, and the response spectrum was compared. Time series data was generated using the calculated PSD, and the time and frequency domain fatigue life were predicted and compared. The variation of stress response spectrum due to static load and predicted fatigue life according to the different structural model considering mean stress were examined and decreasing fatigue life was observed in the model with prestress of compressive static load.

• 한국전자파학회논문지
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• 제18권7호
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• pp.757-765
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• 2007

OFDM(Orthogonal Frequency Division Multiplexing) 시스템은 이동성이 있는 고속 데이터 전송에 적합한 전송 방법으로 널리 알려져 있지만, 위상 잡음과 직교 불균형(IQ imbalance)에 매우 민감한 특성을 보이는 단점이 있다. 그러므로, 본 논문에서는 위상 잡음 특성에 따른 위상 잡음 분산을 계산한 다음, 직교 불균형이 있는 OFDM 시스템의 통신 성능을 분석하였다. 시뮬레이션 결과, 위상 잡음의 분산과 직교 불균형의 크기 변화에 따라 통신 성능이 변화하는 것을 분석하였다. 분석 결과, 진폭 불균형이 ${\varepsilon}$=0.2; 0.3; 0.4이고, 위상 불균형이 ${\phi}=10^0$이고, 위상 잡음의 분산 ${\sigma}^2=0.012$일 때, BER은 $10^{-5}$에서 각각 2.88 dB, 3.61 dB, 4.69 dB의 SNR penalty가 존재한다.

• ETRI Journal
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• 제35권3호
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• pp.550-553
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• 2013

Due to limited spectrum resources and differences in link loads, network congestion is one of the key issues in cognitive radio wireless mesh networks. In this letter, a congestion avoidance model with power control, channel allocation, and routing under the signal-to-interference-and-noise ratio is presented. As a contribution, a nested optimization scheme combined with a genetic algorithm and linear programming solver is proposed. Extensive simulation results are presented to demonstrate the effectiveness of our algorithm.

• 소음진동
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• 제6권6호
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• pp.709-715
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• 1996

In recent years, the piping vibration in many Power Plants is being increased by the aged generating facilities due to a long time use. Generally, the pressure fluctuations associated with the flow-induced excitations in this case are broadband in nature. Mainly, the dominant sources of vibration are a vortex-shedding, plane waves and boundary layer turbulence. The peak level of the spectrum is proportional to the dynamic head. A severe disturbance in pipeline results in the generation of intense broadband internal sound waves which can propagate through the piping system. The characteristic frequencies of operating loads of 20%, 57%, 70%, 100% are 4 - 6 Hz and coincide with the results from impact hammering test and FEM analysis. We chose the wire energy absorbing rope restraint as a vibration reduction method after reviewing the various conditions such as site, installing space and economic cost etc. After installation, the vibration level was reduced about 54% in velocity.