• 한국안광학회지
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• 제4권1호
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• pp.15-20
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• 1999

상용전원을 사용한 평행판전극 방전장치에서 수소플라스마로부터 방사되는 가시광선의 스펙트럼을 분광기로 조사하였다. 기체압력과 방전전력에 따라 수소플라스마로부터 방사되는 가시광선의 세기를 조사하고, 같은 조건에서 탐침으로 플라스마밀도를 측정하여 가시광선의 세기와 비교하였다. 측정결과, 가시광선의 세기는 플라스마의 밀도에 영향을 받으며, 플라스마 밀도는 기체압력과 방전전력에 영향받았다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1999년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.61-68
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• 1999

In the nonlinear dynamic structural analysis the given ground excitation as an input should be well defined. Because of the lack of recorded accelerograms in Korea it is required to generate an artificial earthquake by a stochastic model of ground excitation with various dynamic properties rather than recorded accelerograms. It is well known that earthquake motions are generally non-stationary with time-varying intensity and frequency content. Many researchers have proposed non-stationary random process models. Yeh and Wen (1990) proposed a non-stationary modulation function and a power spectral density function to describe such non-stationary characteristics. Satio and Wen(1994) proposed a non-stationary stochastic process model to generate earthquake ground motions which are compatible with design reponse spectrum at sites in Japan. this paper shows the process to modify power spectrum compatible with target design response spectrum for generating of nonstationary artificial earthquake ground motions. Target reponse spectrum is chosen by ATC14 to calibrate the response spectrum according to a give recurrence period.

• 천문학회지
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• 제45권4호
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• pp.93-99
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• 2012

We present a 1.1mm emission map of the OMC1 region observed with AzTEC, a new large-format array composed of 144 silicon-nitride micromesh bolometers, that was in use at the James Clerk Maxwell Telescope (JCMT). These AzTEC observations reveal dozens of cloud cores and a tail of filaments in a manner that is almost identical to the submillimeter continuum emission of the entire OMC1 region at 450 and $850{\mu}m$. We perform Fourier analysis of the image with a modified periodogram and the density power spectrum, which provides the distribution of the length scale of the structures, is determined. The expected value of the periodogram converges to the resulting power spectrum in the mean squared sense. The present analysis reveals that the power spectrum steepens at relatively smaller scales. At larger scales, the spectrum flattens and the power law becomes shallower. The power spectra of the 1.1mm emission show clear deviations from a single power law. We find that at least three components of power law might be fitted to the calculated power spectrum of the 1.1mm emission. The slope of the best fit power law, ${\gamma}{\approx}-2.7$ is similar to those values found in numerical simulations. The effect of beam size and the noise spectrum on the shape and slope of the power spectrum are also included in the present analysis. The slope of the power law changes significantly at higher spatial frequency as the beam size increases.

• 한국산학기술학회논문지
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• 제14권2호
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• pp.561-566
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• 2013

본 연구는 유압식 자동차고 조절장치 개발 및 상기장치를 일반 상용차에 적용시키기 위한 것이다. 운전자의 승차감에 영향을 줄 진동특성을 주행시험을 통하여 파악하고자 하였다. 유압식 자동차고 조절장치는 현재 승용차에 가장 많이 사용되고 있는 맥퍼슨 형식의 형태로 설계되었다. 맥퍼슨 형식의 순정현가장치, 튜닝현가장치, 유압식 자동차고 조절장치를 장착한 차량으로 시험을 수행하였다. 자동차에 전달되는 진동특성은 랜덤형태이므로 PSD(Power Spectrum Density)값을 비교하였다.

• 대한조선학회논문집
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• 제47권6호
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• pp.813-820
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• 2010

The spread mooring system for FPSO is developed to explore deep sea area, in which swell is dominant. It is known that the tension response of mooring lines in this sea area shows bimodal spectrum. Assuming normal distribution of tension profile and Rayleigh distribution of tension amplitude, the power spectral density function (PSD) of the mooring tension under the bimodal stationary random process is applied for the calculation of spectrum fatigue. Three popular methods, which are simple summation method, combined spectrum method and Jioa-Moan method, are used to combine fatigue damages from bimodal spectrum characteristics. Each damage value is compared with damage using Rainflow Cycle Counting (RCC) method which is believed to be close to exact solution. Vanmarcke' parameter and RMS(Root Mean Square) ratio are employed to assess relative damage variations between from RCC method and from three combination methods. Finally the most reliable fatigue damage combining method for spread mooring system is suggested.

• ETRI Journal
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• 제33권2호
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• pp.279-282
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• 2011

Coexistence analysis is extremely important in examining the possibility for spectrum sharing between orthogonal frequency-division multiplexing (OFDM)-based international mobile telecommunications (IMT)-Advanced and other wireless services. In this letter, a new closed form method is derived based on power spectral density analysis in order to analyze the coexistence of OFDM-based IMT-Advanced systems and broadcasting frequency modulation (FM) systems. The proposed method evaluates more exact interference power of IMT-Advanced systems in FM broadcasting systems than the advanced minimum coupling loss (A-MCL) method. Numerical results show that the interference power is 1.3 dB and 3 dB less than that obtained using the A-MCL method at cochannel and adjacent channel, respectively. This reduces the minimum separation distance between the two systems, which eventually saves spectrum resources.

• 대한의용생체공학회:의공학회지
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• 제30권4호
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• pp.327-332
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• 2009

In this paper, new index was developed to estimate the depth of anesthesia during general anesthesia using EEG. Analysis of the power spectral density(PSD) of EEG was used to develop new parameters because EEG signal tends to have slow wave during anesthesia. Classifier for index creator was developed by using SEF, BDR and BTR parameters, which are calculated by power spectral density. EEG data were obtained from 7 patients (ASA I, II) during general anesthesia with Sevoflurane. The anesthetic depth evaluation indexes ranged from 0 to 100. The average were $86.05{\pm}10.1$, $36.98{\pm}20.2$, $15.33{\pm}13.6$, $50.87{\pm}16.5$ and $87.72{\pm}11.7$ for the states of pre-operation, induction of anesthesia, operation, awaked and post-operation, respectively. The results show that while the depth of anesthesia was evaluated, more accurate information can be provided for anesthetician.

• Journal of Biosystems Engineering
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• 제22권1호
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• pp.41-48
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• 1997

A nondestructive quality inspection technique using acoustic impulse response method was studied to investigate the feasibility of egg shell inspection. An experimental system was built to generate impact force, to measure the response signal and to analyze the frequency spectrum. This system includes an impulse generating unit, an egg holding seat, a microphone with preamplifier, and a digital oscilloscope connected to Personal Computer by RS-232C interface. The factors such as impulse generating method, egg holding method, and sensor location were evaluated by analyzing the power spectrum density of the measured signal. The results obtained are summarized as follows : 1. From the sampled eggs, the proper conditions for detecting damaged eggs were found as followings; ceramic for the impact ball material, rubber for egg seat material, 20 degrees for an impact angle of pendulum, 10mm for the distance between egg and sensor, the sharp side for impacting part, and 180 degrees for the location of sensor. 2. Examination of the Fourier transformed analysis in beth normal and damaged eggs revealed that those factors such as the resonant frequency, a number of peak frequencies and the magnitude of power spectrum were important to detect damaged eggs.

• 한국군사과학기술학회지
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• 제3권1호
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• pp.191-197
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• 2000

This paper provides the test results of tracked vehicle at each driving condition and life cycle. Fatigue Damage Spectrum(FDS) has evaluated with the Power Spectrum Density(PSD) and the life time of equipment. Finally, provisional vibration qualification test level is evaluated.

• Journal of Advanced Marine Engineering and Technology
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• 제23권4호
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• pp.514-522
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• 1999

The laser-induced plasma affects greatly on the results of welding process. moreover selective evaporation loss of alloying elements leads to change in chemical composition of weld metal as well as the mechanical properties of welded joint. this study was undertaken to obtain a fundamental knowledge of pulsed laser welding phenomena especially evaporation mechanism of different aluminum alloys. The intensities of molecular spectra of AlO and MgO were different each other depeding on the power density of a laser beam Under the low power density condition the MgO band spectrum was predominant in intensity while the AlO spectra became much stronger with an increase in the power density. These behaviors have been attributed to the difference in evaporation phenomena of Al and Mg metals with different boiling points and latent heats of vaporization. The time-averaged plasma temperature and electron number density were determined by spectroscopic methods and consequently the obtained temperature was $3,280{\pm}150K$ and the electron number density was $1.85{\times}10^{19}\;l/m^3$.