• Title, Summary, Keyword: source spectrum

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Spectral Estimation of the Pass-by Noise of an Acoustic Source (등속 이동 음원의 통과소음 스펙트럼 추정에 관한 연구)

  • Lim Byoung-Duk;Kim Deok-Ki
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.29 no.12
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    • pp.1597-1604
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    • 2005
  • The identification of a moving noise source is important in reducing the source power of the transport systems such as airplanes or high speed trains. However, the direct measurement using a microphone running with noise source is usually difficult due to wind noise, white the source motion distorts the frequency characteristics of the pass-by sound measured at a fixed point. In this study the relationship between the spectra of the source and the pass-by sound signal is analyzed for an acoustic source moving at a constant velocity. Spectrum of the sound signal measured at a fixed point has an integral relationship with the source spectrum. Nevertheless direct conversion of the measured spectrum to the source spectrum is ill-posed due to the singularity of the integral kernel. Alternatively a differential equation approach is proposed, where the source characteristics can be recovered by solving a differential equation relating the source signal to the distorted measurement in time domain. The parameters such as the source speed and the time origin, required beforehand, are also determined only from the frequency-phase relationship using an auxiliary measurement. With the help of the regularization method, the source signal is successfully recovered. The effects of the parameter errors to the estimated frequency characteristics of the source are investigated through numerical simulations.

Spectrum Sensing for Cognitive Radio Networks Based on Blind Source Separation

  • Ivrigh, Siavash Sadeghi;Sadough, Seyed Mohammad-Sajad
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.7 no.4
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    • pp.613-631
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    • 2013
  • Cognitive radio (CR) is proposed as a key solution to improve spectral efficiency and overcome the spectrum scarcity. Spectrum sensing is an important task in each CR system with the aim of identifying the spectrum holes and using them for secondary user's (SU) communications. Several conventional methods for spectrum sensing have been proposed such as energy detection, matched filter detection, etc. However, the main limitation of these classical methods is that the CR network is not able to communicate with its own base station during the spectrum sensing period and thus a fraction of the available primary frame cannot be exploited for data transmission. The other limitation in conventional methods is that the SU data frames should be synchronized with the primary network data frames. To overcome the above limitations, here, we propose a spectrum sensing technique based on blind source separation (BSS) that does not need time synchronization between the primary network and the CR. Moreover, by using the proposed technique, the SU can maintain its transmission with the base station even during spectrum sensing and thus higher rates are achieved by the CR network. Simulation results indicate that the proposed method outperforms the accuracy of conventional BSS-based spectrum sensing techniques.

Response Analysis of the NE213-PSD System for Neutron Energy Spectreum Measurement (중성자 에너지 측정을 위한 NE213-PSD 장치의 감응 분석)

  • Lee, Kyung-Ju
    • Analytical Science and Technology
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    • v.5 no.4
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    • pp.367-372
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    • 1992
  • In order to measure the energy spectrum of a radioactive neutron source, the pulse shape discrimination (PSD) system with organic scintillator, NE-213, was characterized by using some of the gamma ray sources and neutron source, Am-Be. The figure of merit of the rise time spectrum of AmBe source measured by this system was about 1.13. This value agrees well with the value of 1.3 which is measured for monoenergetic source, $^{12}C(d,\;n)^{13}N$. The results of present experiment for performance test of NE213-PSD system will provide the useful technique to measure the spectrum of neutron-gamma mixed field and to establish the neutron energy spectrum and flux density standards.

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Noise Source Identification of a Car A/V System (차량탑재용 A/Y 시스템의 소음원 규명)

  • 홍종호;이상호;강연준
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.14 no.10
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    • pp.930-938
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    • 2004
  • This paper presents the noise source identification of a car A/V system. There are two different kinds of noise sources noise generated by loading mechanism and rattle noise by externally forced vibration. A dynamometer has been made to produce stationary inertia to the loading mechanism of A/V system. Sound pressure spectra and sound intensity were measured by operating the dynamometer setup as various motor speeds, and the results were analyzed. A dominant rattle noise source about A/V system's components has been found by multi-dimensional spectral analysis. Residual spectrum method was applied for eliminating coherence between the vibration sources. In result, the dominant rattle noise source was identified by partial coherent output spectrum of individual vibration component.

Source identification of abnormal noise caused in diesel railcars through spectrum analysis (스펙트럼 분석을 통한 디젤동차 애상소음 원인규명)

  • 이용관;강명석
    • Proceedings of the KSR Conference
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    • pp.208-217
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    • 1999
  • This paper presents spectrum analysis technique to identify abnormal noise produced in diesel railcars. Coherence and coherent power spectrum are very useful in determining source identifications. Experiments are applied to two different cars with similar phenomena about the case of stop and running condition. Metal contact in mounting bracket part which is excited by excessive transmission vibration is found to cause abnormal noise.

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A New Approach on the Correction for Compton Escape Component in X-Ray Unfolding Algorithm

  • Kim, Soon-Young;Kim, Jong-Kyung
    • Proceedings of the Korean Nuclear Society Conference
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    • pp.925-930
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    • 1995
  • A new approach on the correction for Compton escape component in X-ray unfolding algorithm was investigated to obtain more accurate X-ray source spectrum. The X-ray detector used in this study was a planar type HPGe detector(EG&G ORTEC, GLP-32340/13-P-LP) whose energy response has been blown and ISO narrow beam series were employed as source spectrum. At lower energy Part of measured X-ray spectrum including the correction for Compton escape component more accurate unfolded spectrum was obtained by letting down the starting energy level of the collection in existing spectrum correction procedure to consider multiple scattering effects. It is, from this study, concluded that accurate correction for Compton escape component is needed in X-ray unfolding procedure since Compton scattering becomes more important as incident X-ray energies increase.

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Characteristics of the Point-source Spectral Model for Odaesan Earthquake (M=4.8, '07. 1. 20) (오대산지진(M=4.8, '07. 1. 20)의 점지진원 스펙트럼 모델 특성)

  • Yun, Kwan-Hee;Park, Dong-Hee
    • Geophysics and Geophysical Exploration
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    • v.10 no.4
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    • pp.241-251
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    • 2007
  • The observed spectra from Odaesan earthquake were fitted to a point-source spectral model to evaluate the source spectrum and spatial features of the modelling error. The source spectrum was calculated by removing from the observed spectra the path and site dependent responses (Yun, 2007) that were previously revealed through an inversion process applied to a large accumulated spectral dataset. The stress drop parameter of one-corner Brune's ${\omega}^2$ source model fitted to the estimated source spectrum was well predicted by the scaling relation between magnitude and stress drop developed by Yun et al. (2006). In particular, the estimated spectrum was quite comparable to the two-corner source model that was empirically developed for recent moderate earthquakes occurring around the Korean Peninsula, which indicates that Odaesan earthquake is one of typical moderate earthquakes representative of Korean Peninsula. Other features of the observed spectra from Odaesan earthquake were also evaluated based on the commonly treated random error between the observed data and the estimated point-source spectral model. Radiation pattern of the error according to azimuth angle was found to be similar to the theoretical estimate. It was also observed that the spatial distribution of the errors was correlated with the geological map and the $Q_0$ map which are indicatives of seismic boundaries.

Noise-source Analysis of Tactical Vehicle Using Partial Coherence Function (부분기여도함수를 이용한 전술차량 소음원 분석)

  • Park, Sungho;Lee, Kyunghyun;Han, HyungSuk;Jeon, Soohong
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.26 no.7
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    • pp.774-780
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    • 2016
  • In this paper noise source and transfer path of tactical vehicle are analyzed with partial coherence function and spectrum analysis. Engine, transmission, structure panel and aerodynamic are main source of cabin noise. To reduce cabin noise, identifying transfer path of sources and analyzing their contribution is important. With modeling of transfer path and partial coherence function, transfer path and principal noise source can be identified. Engine/transmission and structural resonance are principal source of low frequency noise and by adding stiffener and sound absorbing material, resonance of vibration and inflow air problem can be solved.

Site responses of Japanese stations near the epicenter and Korean stations for the Fukuoka earthquake (후쿠오카 지진('05. 3. 20, $M_{JMA}=7.0$)에 대한 일본 인근 지진관측소와 국내 지진관측소의 주파수응답특성 비교)

  • Yun Kwan-Hee;Park Dong-Hee;Chang Chun-Jung;Choi Weon-Hack;Lee Dae-Soo
    • 한국지구물리탐사학회:학술대회논문집
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    • pp.79-86
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    • 2005
  • The apparent source spectrum of the Fukuoka earthquake is estimated at the seismic basement by removing from the observed spectra at Korean seismic stations the path and site responses that were previously revealed through inversion process applied to large spectral D/B accumulated until 2004. The approximate source spectrum is also estimated by using data recorded near the epicenter from various Japanese seismic networks and compared with the Korean source spectrum. The comparison result shows that there is good agreement among source spectra estimated based on the data from seismic networks of Korea at large distances (190km

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Site Responses of Japanese Stations Near the Epicenter and Korean Stations for the Fukuoka Earthquake (후쿠오카 지진 ('05. 3. 20, $M_{JMA}=7.0$)에 대한 일본 인근 지진관측소와 국내 지진관측소의 주파수응답특성 비교)

  • Yun, Kwan-Hee;Park, Dong-Hee;Chang, Chun-Jung;Choi, Weon-Hack;Lee, Dae-Soo
    • Journal of the Korean Geophysical Society
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    • v.8 no.1
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    • pp.15-21
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    • 2005
  • The apparent source spectrum of the Fukuoka earthquake is estimated at the seismic basement by removing from the observed spectra at Korean seismic stations the path and site responses that were previously revealed through inversion process applied to large spectral D/B accumulated until 2004. The approximate source spectrum is also estimated by using data recorded near the epicenter from various Japanese seismic networks and compared with the Korean source spectrum. The comparison result shows that there is good agreement among source spectra estimated based on the data from seismic networks of Korea at large distances (190 km

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