• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.12 s.243
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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.

• 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.

• 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.

• 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.

• Proceedings of the KSR Conference
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• 1999.05a
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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.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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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.

• 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.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.1
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• pp.222-226
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• 2007

We suggest the fluorescence endoscope system that has light source apparatus providing selectable white or excitation light. White light source generates normal color images and is easily switched over to excitation light with the wide spectrum range from 380 nm to 580 nm. 5-ALA is deposited selectively in the abnormal tissue like cancer and causes fluorescence in the red spectrum range when excited by blue spectrum range. In addition, the others of excitation light make the color background image by reflected light to allow accurate orientation and visualization of the abnormal tissue and around. According to clinical studies, the fluorescence intensity contrast that defines the fluorescence intensity of lesion over the fluorescence intensity of around has more than 2 in tumour. Proposed system is useful and objective way in early diagnosis. Furthermore, it can be used in the biopsy for tumour classification at the highest fluorescence intensity point.

• 한국지구물리탐사학회:학술대회논문집
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• 2005.05a
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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