• 제목, 요약, 키워드: Signal to Noise Ratio

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잡음 감소를 위한 창 함수의 선택에 관한 연구 (Appropriate Choice of Window Function for Noise Reduction)

  • 백문열
    • 한국안전학회지
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    • v.12 no.4
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    • pp.3-8
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    • 1997
  • This paper shows a performance estimation of windowing a single tone with added Gaussian noise and uniform noise. Signal-to-noise ratio can be determined by the ratio of the output noisy signal variance to the input noisy signal variance of a window. Standard deviation of noise is reduced by windowing Signal-to-noise ratio of the noisy signal is reduced by the windowing operation. Thus, performance of window function can be determined by this filtering operation that improved the signal-to-noise ratio.

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Analysis of Images According to the Fluid Velocity in Time-of-Flight Magnetic Resonance Angiography, and Contrast Enhancement Angiography

  • Kim, Eng-Chan;Heo, Yeong-Cheol;Cho, Jae-Hwan;Lee, Hyun-Jeong;Lee, Hae-Kag
    • Journal of Magnetics
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    • v.19 no.2
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    • pp.185-191
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    • 2014
  • In this study we evaluated that flow rate changes affect the (time of flight) TOF image and contrast-enhanced (CE) in a three-dimensional TOF angiography. We used a 3.0T MR System, a nonpulsatile flow rate model. Saline was used as a fluid injected at a flow rate of 11.4 cm/sec by auto injector. The fluid signal strength, phantom body signal strength and background signal strength were measured at 1, 5, 10, 15, 20 and 25-th cross-section in the experienced images and then they were used to determine signal-to-noise ratio and contrast-to-noise ratio. The inlet, middle and outlet length were measured using coronal images obtained through the maximum intensity projection method. As a result, the length of inner cavity was 2.66 mm with no difference among the inlet, middle and outlet length. We also could know that the magnification rate is 49-55.6% in inlet part, 49-59% in middle part and 49-59% in outlet part, and so the image is generally larger than in the actual measurement. Signal-to-noise ratio and contrast-to-noise ratio were negatively correlated with the fluid velocity and so we could see that signal-to-noise ratio and contrast-to-noise ratio are reduced by faster fluid velocity. Signal-to-noise ratio was 42.2-52.5 in 5-25th section and contrast-to-noise ratio was from 34.0-46.1 also not different, but there was a difference in the 1st section. The smallest 3D TOF MRA measure was $2.51{\pm}0.12mm$ with a flow velocity of 40 cm/s. Consequently, 3D TOF MRA tests show that the faster fluid velocity decreases the signal-to-noise ratio and contrast-to-noise ratio, and basically it can be determined that 3D TOF MRA and 3D CE MRA are displayed larger than in the actual measurement.

INFLUENCE OF SIGNAL-TO-NOISE RATIO ON EDDY CURRENT SIGNALS OF CRACKS IN STEAM GENERATOR TUBES

  • Hur, Do Haeng;Choi, Myung Sik;Shim, Hee-Sang;Lee, Deok Hyun;Yoo, One
    • Nuclear Engineering and Technology
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    • v.46 no.6
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    • pp.883-888
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    • 2014
  • This work presents the influence of noise originating from the tube itself on the detectability and sizing accuracy for laboratory-induced outer diameter axial cracks in nuclear steam generator tubes. The variations of signal amplitude and phase angle of the same cracks were analyzed when increasing the signal-to-noise ratio of the tube itself from 9 to 18. It was experimentally verified that the detectability for small cracks was enhanced by increasing the signal-to-noise ratio. The phase angle also rotated to a value representing the actual position and depth of a crack when increasing the signal-to-noise ratio.

교통시설에서의 스피커 안내음과 배경소음의 신호대잡음비 (Signal to Noise Ratio of the Announcement from Reinforced Sound System and Background Noise in Transportation Facility)

  • 송한솔;류종관;진민규;성창주
    • 한국건축친환경설비학회 논문집
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    • v.11 no.5
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    • pp.355-363
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    • 2017
  • This study investigated signal to noise ratio (S/N) of the signal sound and announcement in transportation facilities such as subway and railway station, bus-terminal and airport. The result of survey in subway station showed that 82% of participants were dissatisfied with the signal sound and announcement. Acoustical characteristic and S/N of the signal sound and announcement were also analysed after measuring the signal sound, announcement, train arriving noise and background noise in transportation facilities. In the subway station, the S/N ratios ranged from - 14.4~13.8 dB and mostly were lower than 10 dB, which is suitable value for word recognition of elderly person. The S/N ratio in the railway station ranged from 0.7 to 5.7 dB, and the ratio in the bus terminal and airport was 8.4 dB and 9.2 dB, respectively. For the subway station, the S/N ratio in separated platform was 2 dB higher than that of island platform, and the ratio in platform with screen door was about 7 dB higher than that in platform without screen door.

Weighting된 펄스 열을 사용하는 DMTI 시스템의 S/N북 개선 특성 (An Improvement Performance of S/N Ratio in DMTI System Using Weighted Pulse Trains)

  • 고성선;이재균;윤현배
    • 대한전자공학회논문지
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    • v.22 no.2
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    • pp.60-65
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    • 1985
  • A method of weighting of a staggered pulse train is presented and an improvement per-formance of the signal-to-noise ratio for each case is compared. As the result of a computer simulation, the signal-to-noise ratio for weighting of a stagger-ed pulse train is a great improvement on the case of an uniform pulse train. The signal-to-noise ratio of optimum weighting is more improved than that of binomial weighting, it is known that the signal-to-noise ratio is improved as the increasing of the number of delay line cancellers, and it is shown that the signal-to-noise ratio is improved by weighting of the MTI output pulses before the integration process.

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FT-ICR 질량분석기의 신호 충실성 향상 (The Improvement in Signal Integrity of FT-ICR MS)

  • 김승용;김석윤;김현식
    • 전기학회논문지
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    • v.60 no.1
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    • pp.201-204
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    • 2011
  • For efficient noise reduction in a Fourier transform ion cyclotron resonance (FT-ICR) mass spectrum, a new algorithm was proposed. The suggested algorithm reduces white and electrical noise, and it improves signal-to-noise ratio. This algorithm has been optimized to reduce the noise more efficiently using the traces of signal level. The algorithm has been efficiently combined with derivative window to improve the resolution as well S/N. Time domain data was corrected for DC voltage interference. $t^n$ window was applied in time domain data to improved the resolution. However, $t^n$ window can improve the signal resolution, it will also increase the noise level in frequency domain. Therefore, newly developed noise reduction algorithm will be applied to make a balance between resolving power and S/N ratio for magnitude mode. The trace algorithm can determine the current data point with several data points (mean, past data, calculated past data). In the current calculations, we assumed data points with S/N ratio more than 3 were considered as signal data points. After the windowing and noise reduction, both resolution and signal-to-noise ratio were improved. This algorithm is applicable more efficiently to frequency dependent noise and large size data.

Noise Estimation based on Standard Deviation and Sigmoid Function Using a Posteriori Signal to Noise Ratio in Nonstationary Noisy Environments

  • Lee, Soo-Jeong;Kim, Soon-Hyob
    • International Journal of Control, Automation, and Systems
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    • v.6 no.6
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    • pp.818-827
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    • 2008
  • In this paper, we propose a new noise estimation and reduction algorithm for stationary and nonstationary noisy environments. This approach uses an algorithm that classifies the speech and noise signal contributions in time-frequency bins. It relies on the ratio of the normalized standard deviation of the noisy power spectrum in time-frequency bins to its average. If the ratio is greater than an adaptive estimator, speech is considered to be present. The propose method uses an auto control parameter for an adaptive estimator to work well in highly nonstationary noisy environments. The auto control parameter is controlled by a linear function using a posteriori signal to noise ratio(SNR) according to the increase or the decrease of the noise level. The estimated clean speech power spectrum is obtained by a modified gain function and the updated noisy power spectrum of the time-frequency bin. This new algorithm has the advantages of much more simplicity and light computational load for estimating the stationary and nonstationary noise environments. The proposed algorithm is superior to conventional methods. To evaluate the algorithm's performance, we test it using the NOIZEUS database, and use the segment signal-to-noise ratio(SNR) and ITU-T P.835 as evaluation criteria.

길쌈부호를 사용한 Embedded DPCM 방식에 관한 연구 (A Study on an Embedded DPCM with Convolutional Coding)

  • 임종수;이상곤;문상재
    • 전자공학회논문지A
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    • v.28A no.1
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    • pp.1-7
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    • 1991
  • Degradation of communication quality is due to transmission error rather than quantization noise when DPCM signal is transmitted over a heavily noise channel. The communication quality can be improved by employing an error correcting code to the DPCM signal transmission over such a channel. We considered both quantization noise and transmission error simultaneously in evaluating the signal to noise ratio. To efficiently improve the signal to noise ratio, we analyze the unequal symbol error probability of convolutional code, and encoded to more protect significant symbols from channel errors than least ones, so that the signal to noise ratio is improved. We derived related formulas and also made computer simulations.

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차동검출기를 이용한 무선광연결에서 신호대잡음비의 개선 (Signal to Noise Improvement in Optical Wireless Interconnection Using A Differential Detector)

  • 이성호;강희창
    • 한국전자파학회논문지
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    • v.10 no.1
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    • pp.54-62
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    • 1999
  • 본 논문에서는 실내 무선광연결에 사용될 수 있는 차동검출기에서 잡음광의 결합비와 차동이득비에 따른 신호대 잡음비의 개선에 대하여 분석하고 실험하였다. 차동검출기는 2개의 포토다이오드와 1개의 차동증폭기 로 이루어지며, 차동이득비가 잡음광의 결합비와 같을 때 잡음광이 소거되어 약 20 dB의 선호대잡음비를 개 선하였다. 차통검출기는 실내의 무선광연결에서 주변의 강한 잡음광의 영향을 개선하거나 인접된 채널광에 의한 혼선의 영향을 없애는 데에 매우 효과적이다. 이 방법은 선호광과 유사한 파장의 잡음광이 발생하는 경 우에도 잡음개선효과가 았다.

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Entropy-based Spectrum Sensing for Cognitive Radio Networks in the Presence of an Unauthorized Signal

  • So, Jaewoo
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.9 no.1
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    • pp.20-33
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    • 2015
  • Spectrum sensing is a key component of cognitive radio. The prediction of the primary user status in a low signal-to-noise ratio is an important factor in spectrum sensing. However, because of noise uncertainty, secondary users have difficulty distinguishing between the primary signal and an unauthorized signal when an unauthorized user exists in a cognitive radio network. To resolve the sensitivity to the noise uncertainty problem, we propose an entropy-based spectrum sensing scheme to detect the primary signal accurately in the presence of an unauthorized signal. The proposed spectrum sensing uses the conditional entropy between the primary signal and the unauthorized signal. The ability to detect the primary signal is thus robust against noise uncertainty, which leads to superior sensing performance in a low signal-to-noise ratio. Simulation results show that the proposed spectrum sensing scheme outperforms the conventional entropy-based spectrum sensing schemes in terms of the primary user detection probability.