• Economic and Environmental Geology
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• v.38 no.2 s.171
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• pp.143-153
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• 2005

Euiseong subbasin, included in the Kyungsang Basin, was created by the result of volcanic activity in the late Cretaceous, and contacts with Milyang and Youngyang subbasins by Palgongsan and Andong faults, respectively. In this study, geophysical survey is implemented fur investigating surface and subsurface geologic structure in Euiseong subbasin which composed with the complex of volcanic and plutonic rocks. To understand surface geologic feature, IRS satellite image and DEM(Digital Terrain Map) are used for analyzing lineament and its density. The numbers of lineaments show major trend in $N55^{\circ}\~65^{\circ}W$, and aspects of lineament lengths show major trend in $N55^{\circ}\~65^{\circ}W$ and N-S directions. 13 delineate subsurface density discontinuity; Power spectrum analysis was implemented for gravity anomaly data, resulting $4-5{\cal}km$ depth of basin basement and $0.5-0.6{\cal}km$ depth of shallow discontinuity. From the result of power spectrum analysis, 2.5-D modelings were implemented along two profiles of A-A' and B-B', and they show subsurface geology in detail. Analytic signal method for detecting boundaries of magnetic basements show 0.001-130 nT/m values, and high energy area show good correspondency with the boundaries of Palgongsan granite and caldera areas in Euiseong subbasin.

• Sleep Medicine and Psychophysiology
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• v.17 no.2
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• pp.91-99
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• 2010

Objectives: Deficit schizophrenia (DS) constitutes a disease separate from non-deficit schizophrenia (NDS). The aim of the current study was to compare the quantitative EEG and low resolution electromagnetic tomography (LORETA) imaging between DS and NDS. Methods: This study was performed by 32 channels EEG for 42 schizophrenia patients who we categorized into DS and NDS using proxy instrument deficit syndrome (PDS). We performed the absolute power spectral analyses for delta, theta, alpha, low beta and high beta activities. We compared power spectrum between two groups using Independent t-test. Partial correlation test was performed with clinical parameters. Standardized LORETA (sLORETA) was used for comparison of cortical activity, and statistical nonparametric mapping (SnPM) was applied for the statistical analysis. Results: DS showed significantly increased delta and theta absolute power in fontal and parietal region compared with NDS (p<0.05). Power spectrum showed significant correlation with 'anergia' and 'hostility/suspiciousness' subscale of brief psychiatric rating scale (BPRS)(p<0.05). sLORETA found out the source region (anterior cingulate cortex/limbic part) that delta activity was significantly increased in DS (p=0.042). Conclusions: DS showed different cortical activity compared with NDS. Our results may suggest QEEG and LORETA could be the marker in differentiating between DS and NDS.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.43-53
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• 1990

The manufacturing errors such as pitch error and run-out error in planetary gear system bring about the irregular displacement of the center of each gear, which cause the torqe variation, vibration and noise. In this study, the relation between manufacturing errors and error motions of the center of gear was analyzed, and it can be applied to identyfy the errors of gears by investigating the measured locus of the center of each gear. Also, another identification method of power spectrum estimation using FFT algorithm was introduced, which analyze the frequency of the measured error motions. The results show that the error of each gear had a corresponding unique frequency, therefore, this method proved to be more effective.

• Journal of Biomedical Engineering Research
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• v.19 no.2
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• pp.113-118
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• 1998

By their rapid and periodic actions, the cilia of the human respiratory tract play an important role in clearing inhaled noxious particles. Based on the automated image-processing technique, we studied the method analyzing ciliary beat frequency (CBF) objectively and quantitatively. Microscopic ciliary images were transformed into digitized gray ones through an image-grabber, and from these we extracted signals for CBF. By means of a FFT, maximum peak frequencies were detected as CBFs in each partitioned block for the entire digitized field. With these CBFs, we composed distribution maps visually showing the spatial distribution of CBFs. Through distribution maps of CBF, the whole aspects of CBF changes for cells and the difference of CBF of neighboring cells can be easily measured and detected. Histogram statistics calculated from the user-defined polygonal window can show the local dominant frequency presumed to be the CBF of a cell or a crust the region includes.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.383-386
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• 2005

CCW(China Coastal Water) is different each year. It appears clearly from June to October in the neighboring sea of Jeju island. It appears in June, and it's strong most in August, after tat disappears in October. CCW appeared clearly at 1996 and 1999 during investigation period(1995 to 1999). SLA and SST appear annual variations(about 365day), semi-annual variations(about 180day) from power spectral density. After PCA(Principal component analysis), it's different. PCA of SLA shows 43day variations and PCA of SST shows 259day variations. SLA and SST appear annual variation, semi-annual variation and seasonal variation from power spectral density. SLA appeared that summer and fall of 1996 and 1999 is higher than other years. It seem to be being the relationship which is close with the severe rain strom. Temperature distribution of sea surface according to season is different, but clearly water temperature boundary divides this area into Yellow Sea and East China Sea. It considered that CCW follow according to boundary of temperature. The variation which it follows at time of SLA and SST is faster about one month to three month at Yangtz.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.273-273
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• 2012

컷오프 진단법은 두 개의 탐침 형태로 제작된 마이크로 웨이브 진단법으로, 간단한 수식을 통해 전자밀도, 전자온도 등을 측정할 수 있다. 컷오프 탐침은 방사 안테나, 측정 안테나와 네트워크 분석기로 구성되어 있다. 네트워크 분석기는 두 안테나 사이의 플라즈마 투과 스펙트럼을 만드는데 쓰이며, 스펙트럼 분석을 통해 플라즈마 변수들을 측정할 수 있다. 이 진단법은 장치나 분석방법이 매우 간단한 장점을 지니며, 약 1 mW 정도의 적은 파워를 사용하여 플라즈마 상태를 거의 변화시키지 않는 측정이 가능하다. 또한 CF4와 같은 공정 가스를 이용한 플라즈마에서도 사용이 가능하다. 그러나 컷오프 진단법을 사용한 측정은 다른 종류의 진단법과 마찬가지로, 약 1초 정도의 긴 시간을 필요로 하는 단점이 있어, 펄스 플라즈마나 토카막과 같이 빠르게 변하는 플라즈마를 측정하기에는 무리가 있다. 최근에 개발된 푸리에 컷오프 탐침(Fourier Cutoff Probe, FCP)는 기존의 컷오프 탐침의 느린 시간분해능을 개선하기 위해 개발되었다. [1] 펄스 형태의 단일신호를 플라즈마를 투과하기 전후로 비교하면 투과 스펙트럼 및 플라즈마 변수들을 얻을 수 있으며, 기존 연구에서 구한 시간 분해능은 약 15 나노초였다. 이 값은 펄스 발생장치의 스펙에 따라 변하게 된다. 펄스폭이 짧을수록 시간분해능이 좋아지지만, 무한정 좋아질 수는 없다. 이 논문에서는 FCP 측정의 시간 분해능을 이론적으로 구하고, 시간 분해능의 이론적 한계를 구했다.

• Korean Journal of Clinical Laboratory Science
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• v.48 no.2
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• pp.144-152
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• 2016

Carotid-artery stenosis may reduce cerebral perfusion, and affect cerebral neuronal activities. We examined the question of whether the recovery of cerebral-perfusion reserve after carotid-artery stenting (CAS) can affect the EEG power-spectrum. Nineteen candidates for CAS were initially recruited. Subtraction imaging of single photon emissary computerized tomography (SPECT) and an electroencephalogram (EEG) were taken twice, before and 1 month after CAS. At each time point, the EEGs were recorded before and after injection of acetazolamide (pre-ACZ EEG and post-ACZ EEG). Finally, 7 patients were enrolled after exclusion of incomplete studies. We obtained the spectral ratio (SR) of each hemisphere. SR was defined as the divided value of the power-spectrum sum of fast activities by that of slow activities. The power-spectrum values between hemispheres were compared using the inter-hemispheric index of spectral ratio (IHISR), and we examined the correlation between the power-spectrum and the cerebral-perfusion reserve. Cerebral-perfusion reserve improved after CAS on the stent side in 6 of 7 patients. In 3 patients with unilateral carotid-artery stenosis, CAS increased SR on the pre-ACZ EEGs, and IHISR on the post-ACZ EEGs. The increases of SR and IHISR were concordant with the increment of cerebral-perfusion reserve. In contrast, the results in the other patients with bilateral stenosis showed complex patterns. The SR of pre-ACZ EEGs and IHISR of post-ACZ EEGs may be useful electrophysiological markers for the blood-flow reserve after CAS in patients with unilateral carotid-artery stenosis, but not in those with bilateral stenosis.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.1
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• pp.41-48
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• 2022

Vehicle vibration was introduced in the time and frequency domains using fast Fourier transform (FFT) analysis. In particular, a vibration mode analysis and characteristics of the frequency response function (FRF) in a sport utility vehicle (SUV) passing over a bump barrier at different speeds was performed systematically. The response behavior of the theoretical acceleration was obtained using a numerical method applied to the forced vibration model. The amplitude and frequency of the external force on the vehicle cause various power spectra with individual intrinsic system frequencies. In this regard, several modes of power spectra were acquired from the spectra and are discussed in this paper. The proposed technique can be used for monitoring the acceleration in a vehicle passing over a bump barrier. To acquire acceleration signals, various experimental runs were performed using the SUV. These acceleration signals were then used to acquire the FRF and to conduct mode analysis. The vehicle characteristics according to the vehicle condition were analyzed using FRF. In addition, the vehicle structural system and bump passing frequencies were discriminated based on their power spectra and other FRF spectra.

• Proceedings of KOSOMES biannual meeting
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• 2017.04a
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• pp.190-190
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• 2017

• Journal of IKEEE
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• v.13 no.4
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• pp.96-102
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• 2009

We investigate the characteristics of RJ (random jitter) in an analog fiber-optic link employing a MZM (Mach-Zehnder modulator) and an EDFA (Erbium-doped fiber amplifier). RJ has been measured using two methods, one of which derived from the noise spectrum of a RF spectrum analyzer and the other from the histogram data of a sampling oscilloscope. If the optical power and/or the RF power input to the MZM increase, RJ decreases due to the output signal power increase. For the optical link without EDFA, the minimum RJ is about 1 ps at an RF power of 10 dBm and an optical power of 8 dBm measured using the noise spectrum method. For the optical link with an EDFA, RJ decreases toward a jitter floor as the EDFA gain increases. If the gain increases further, it has been observed that RJ increases from the minimum. If the EDFA gain is fixed, RJ is smaller for the case of larger optical input power. As the EDFA gain increases, RJ reduction rate becomes greater for the case of lower optical input power.