• Journal of Radiation Protection and Research
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• v.18 no.1
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• pp.25-35
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• 1993

To develop a technique of theoretical alpha track density calculation for comparison with measured track density, an electrostatic ion spectrometer was specially designed and fabricated. The mobility spectrum of first radon daughter(Po-218) in the range of $0.07{\sim}5.0cm^2/V\;s$ from the radon chamber was measured using-the electrostatic ion spectrometer. Measurement was taken in a radon chamber operated using dry particle free air passed through silica gel, activated charcoal and molecular sieve filters. The mobility of a new-born Po-218 ion measured by the electrostatic ion spectrometer was determined to be $1.92cm^2/V\;s$. A comparison of the theoretical and measured alpha track densities was completed and uncertainties concerning the shape of the spectrum were analyzed. It was found that the discrepancies in track densities are primarily Que to the neglect of wall loss of ions in the theoretical track density calculation.

• Proceedings of the Optical Society of Korea Conference
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• 2003.02a
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• pp.80-81
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• 2003

DWDM 필터와 같은 간섭필터는 밴드폭이 좁아지고 투과파장에 해당하는 채널의 수가 증가함에 따라 투과파장의 외부환경에 대한 안정성이 중요하다. 기존의 전자빔 증착법으로 증착된 유전체 다층박막은 일반적으로 미세기둥구조로 인해 낮은 조밀도를 가지기 때문에 외부의 습도나 온도 변화 등에 민감하다. 낮은 조밀도의 유전체 다층박막을 대기 중에 노출되었을 때, 대기 중의 습기가 기둥과 기둥 사이로 침투되어 유효굴절률의 증가로 인하여 박막의 광학두께가 증가하게 되고 결국 스펙트럼이 장파장으로 이동하게 된다. (중략)

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.628-631
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• 2008

For the remote sensing purpose, radar systems extract the target information, such as the magnitude of reflectivity and the velocity from the spectrum analysis of return echoes through the Doppler filter bank. This conventional spectrum estimation method, FFT(Fast fourier Transform) is widely used in most radar systems. However, the frequency resolution of return echoes can be seriously degraded in fast moving targets because of the short acquisition time. Since the high Doppler frequency resolution is important in the detection and tracking of fast moving targets, it can cause very unsatisfactory results. Therefore, in this paper, the parameter spectrum estimation method called AR(Autoregressive) spectrum estimation, is investigated to overcome these problems.

• Journal of the KSME
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• v.28 no.2
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• pp.169-174
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• 1988

신호처리 및 해석에 대한 교육효과를 증대시키기 위해서는 응용사례의 발굴, 프로젝트 개발, P C를 이용한 그래픽스 교육도 이루어져야 하며, 스펙트럼 분석기술 이외에 시간영역 파라미터 모형에 의한 신호해석기법〔예를 들어 자동회귀-이동평균(ARMA)등의 시계열 모형화〕도 최근 에는 실시간 응용의 가능성이 높아지는 추세에 있으므로 PC를 이용한 신호처리 및 해석 교육에 반영하는 것이 바람직하다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.48-55
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• 2009

The feedback interference channels are those made through the multipaths that are built by moving and stationary objects around transmit and receive antennas mounted at the same point. This paper describes the method to measure the feedback interference channels in the rural regions and sides of highways and the analysis on channel characteristic parameters. Using the measured samples, we estimated scattering functions, delay power spectra, and Doppler power spectra, and we analyzed the channels using eight parameters including coherence bandwidth, coherence time, maximum excess delay, average excess delay, rms delay spread, Doppler shift, Doppler spread, and spread factor, and delay and Doppler cumulative distributions. Even though many observations are made, note that the feedback signals of high Doppler frequencies and large energy are observed in the sides of highways due to high speed vehicles while low Doppler frequencies occurred in the rural region due to rare traffic.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.20-21
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• 2009

우리는 전면 발광 소자에서 두께에 따른 발광 스펙트럼을 연구하였다. 소자 구조는 Al(100nm)/TPD(40nm)/Alq3(60nm)/LiF(0.5nm)/Al(2nm)/Ag(30nm)으로 하였다. N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine(TPD)와 tris-(8-hydroxyquinoline) aluminium(Alq3)는 전공 수송층과 발광층으로 각각 사용되었다. 반투명 전극은 Li/Al/Ag로 하였다. 유기물층과 전극은 $2\times10-5$torr의 진공도에서 열 증착하였다. 유기물과 금속의 증착 속도는 $0.5\sim1.0{\AA}/s$과 $0.5\sim5{\AA}/s$로 하였다. 제작된 소자는 두께가 증가할 수록 장파장으로 이동하는 현상을 보였다. 이러한 현상은 마이크로 캐비티 이론으로 설명할 수 있다. 소자는 이론적인 마이크로 캐비티 수식을 이용하여 분석하기 위해 각각의 변수를 이용하여 실험과 이론을 비교하였을 때, 각각의 스펙트럼이 거의 일치하는 것을 확인할 수 있었다.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.2 no.3
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• pp.119-127
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• 1990

Wave directional spectrum estimation methods for irregular waves were considered in this study. Until now, the Longuet-Higgins Method (LHM) initiated by Longuet-Higgins et al. (1963) has been widely used, but resolutions of the estimation were found to be low. Kobune's Maximum Entropy Method (MEM) for the estimation of wave directional spectrum, bas-ed on the entropy Principle showed higher resolutions comparing with the LHM . If the wave directional spectrum is of Delta functions, the MEM is exact in its estimation. It was also found that for a unimodal spectrum, if the Mitsuyasu's spreading coefficient is above 5, the estimation resolutions were high. In bimodal spectrum, as the angle difference between the two peaks increased, the resolution improved. The energy seems to transfer to the smoother peak in the smoothing of peak's peakedness. LHM has a tendency to estimate bimodal spectrum as a unimodal spectrum ； thus, except for its computational speed, the resolution of LHM falls far below that of MEM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.28 no.9C
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• pp.876-883
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• 2003

In this paper, we propose an algorithm for organ recognition in ultrasound images using log power spectrum. The main procedure of the algorithm consists of feature extraction and feature classification. In the feature extraction, as a translation invariant feature, log power spectrum is used for extracting the information on echo of the organs tissue from a preprocessed input image. In the feature classification, Mahalanobis distance is used as a measure of the similarity between the feature of an input image and the representative feature of each class. Experimental results for real ultrasound images show that the proposed algorithm yields the improvement of maximum 30% recognition rate than the recognition algorithm using power spectrum and Euclidean distance, and results in better recognition rate of 10-40% than the recognition algorithm using weighted quefrency complex cepstrum.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.12
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• pp.1365-1372
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• 2012

This paper presents a methodology to accurately evaluate the spectral components of impulse signals which are delivered from an impulse generator through the measurement system. The complicated terms for uncertainty measurement of impulse spectrum amplitude and their analysis methods and experimental results are discussed. The expanded uncertainty of the impulse spectrum measurement is 0.015, which is believed to be the best domestic measurement capability and comparable to those of world class.

• The Journal of the Korea Contents Association
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• v.16 no.7
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• pp.681-688
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• 2016

This study assess their quality of radiation on analysis of the spectrum of resolution suggesting IEC 61267 in radiation quality that RQA3, RQA5, RQA7, RQA9 and combination of clinical condition using several quality of radiation. In experiments edge method first, the spatial resolution assessment used image of the additional filter and SID is obtained the IEC 62220-1, spatial resolution and sharpness of the obtained image was evaluated in the MTF value 10%(0.1), MTF value 50%(0.5) using a Matlab program. Second, MCNPX simulation used spatial resolution analysis was radiation quality particle fluence and spectrum analysis in energy. As a result, make use of additional filter, image quality evaluation of SID that RQA3 radiation quality combination qualification is higher spatial resolution and sharpness make unused of additional filter and SID 100cm. RQA7 radiation quality combination qualification is higher that spatial resolution make unused of additional filter and SID 150cm. RQA9 radiation quality combination qualification is higher that spatial resolution and sharpness make used of additional filter and SID 180cm. spectrum analysis of radiation quality by reducing consequent errors occurring in the experiment that error due to the reproducibility of the X-ray tube, occur in an error of correction the detector suggest ideal conditions from spectrum analysis through MCNPX simulation. In conclusion, by suggesting spatial resolution and sharpness of result for various radiation quality, It provide basic data that radiation quality condition and quantitative assessment method for laboratory in clinical using detector evaluation.