• 생물정신의학
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• 제22권2호
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• pp.87-94
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• 2015

Objectives The power spectral analysis of electroencephalogram has been widely used to reveal the pathophysiology of the alcoholic brain. However, the results were not consistent and the three dimensional study can be hardly found. The purpose of this study was to investigate characteristics of the three dimensional electroencephalographic (EEG) activity of alcohol dependent patients using standardized low resolution electromagnetic tomography (sLORETA). Methods The participants consisted of 30 alcohol dependent patients and 30 normal healthy controls. All the participants were males who had refrained from alcohol at least one month and were not taking any medications. Thirty two channel EEG data was collected in the resting state with eyes-closed condition during 30 seconds. The three dimensional data was compared between two groups using sLORETA for delta, theta, alpha, beta1, beta2, and beta3 frequency bands. Results sLORETA revealed significantly increased brain cortical activity in alpha, beta1, beta2, and beta3 bands each in alcohol dependent patients compared to normal controls. The voxels showing the maximum significance were in the left transverse temporal gyrus, left superior temporal gyrus, left anterior cingulate, and left fusiform gyrus in alpha, beta1, beta2, and beta3 bands respectively. Conclusions These results suggest that chronic alcohol intake may cause neurophysiological changes in cerebral activity. Therefore, the measuring of EEG can be helpful in understanding the pathophysiology of cognitive impairements in alcohol dependence.

• 천문학논총
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• 제30권2호
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• pp.433-437
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• 2015

We show the results of a time series analysis of the long-term light curves of four blazars. 3C 279, 3C 345, 3C 446, and BL Lacertae. We used densely sampled light curves spanning 32 years at three frequency bands (4.8, 8, 14.5 GHz), provided by the University of Michigan Radio Astronomy Observatory monitoring program. The spectral indices of our sources are mostly flat or inverted (-0.5 < ${\alpha}$ < 0), which is consistent with optically thick emission. Strong variability was seen in all light curves on various time scales. From the analyses of time lags between the light curves from different frequency bands and the evolution of the spectral indices with time, we find that we can distinguish high-peaking flares and low-peaking flares according to the Valtaoja et al. classification. The periodograms (temporal power spectra) of the light curves are in good agreement with random-walk power-law noise without any indication of (quasi-)periodic variability. We note that random-walk noise light curves can originate from multiple shocks in jets. The fact that all our sources are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars. We are going to generalize our approach by applying our methodology to a much larger blazar sample in the near future.

• Bulletin of the Korean Chemical Society
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• 제10권6호
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• pp.535-543
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• 1989

We have investigated the infrared absorption spectra for carbon monoxide chemisorbed on reduced and oxidized Rh/$SiO_2$ with and without potassium coating within the frequency range of 1800-2200 $cm^{-1}$ at various Rh concentrations, CO pressures, and temperatures. In case of no potassium coating, only two bands at 2070 and 1900 $cm^{-1}$ appeared for CO adsorbed on reduced Rh/$SiO_2$ while for oxidized Rh/$SiO_2$ four bands were found at 2100, 2070, 2040, and 1900 $cm^{-1}$. We have successfully tried to explain the differences between our observations and those by other investigators who used the Rh/$Al_2O_3$ system instead of Rh/$SiO_2$ on the basis of the suggestions by Yates et al. Accordingly, we propose that the surface OH groups are deeply involved in producing the $Rh^{+1}$ sites which are responsible for the gem-dicarbonyl species. On coating with potassium all the IR bands for three carbonyl species were found to suffer red shift, the magnitude of which increased with increasing Rh/CO ratio.

• International journal of advanced smart convergence
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• 제4권2호
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• pp.29-33
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• 2015

In this paper, we propose the method to improve the performance of the antenna system that contains three bands, such as Lte3G, WLAN and Lte4G. This antenna has an advantage that can cover the three different frequency bands 2.1GHz, 2.4GHz and 2.6GHz through one antenna design. The design and simulations are done using CST Microwave Studio 2014 program. The antenna is designed by using the FR-4 (lossy) substrate with the dielectric constant of er=4.3 and dielectric loss tangent 0.025. The substrate dimensions are the following; Thickness[h] is 1.6mm, Length is 90mm, and Width is 40mm. The ground is designed by using the PEC material with h=0.035mm. The patch is designed by using the copper with h=0.035mm. In the near future, we will fabricate the antenna, which we have designed, and then apply this antenna to the mobile communication system. And we will test this mobile communication system for the diverse environments.

• 한국전자통신학회논문지
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• 제19권1호
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• pp.1-10
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• 2024

실내 로비 환경에서 다중 경로에서 6, 10, 17 GHz 주파수 대역의 전파 특성을 분석하였다. 가시선(Line-of-sight, LOS) 및 비가시선(Non-line-of-sight, NLOS) 경로는 송신 안테나 위치에서 수신 안테나 위치까지 2-16 m (0.5 m 간격) 거리에서 측정되었다. 기본 전송 손실은 경로에 해당하는 FI(Floating intercept) 경로 손실 모델을 사용하여 세 가지 매개변수를 비교하였다. RMS(Root mean square) 지연 확산은 측정 결과를 누적 확률 10, 50, 90%로 비교하였다. 기둥의 존재와 특이한 로비 구조로 인해 측정된 모든 주파수에서 전파 손실과 전파 지연이 발생하였다. 이에 실내 로비 환경에 대한 측정 시나리오와 표준 측정 데이터 제공을 제안하였다. 이를 통해 다양한 구조의 실내 로비 환경에서 5G 및 밀리미터파 대역의 전파 특성에 대한 연구에 기여할 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 A
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• pp.560-562
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• 2002

This paper describes measurement and diagnosis methods for electromagnetic wave using a VHF(Very High Frequency) antenna. In the laboratory partial discharges are generated on a needle-plate and a plate-plate configuration. The detected electromagnetic wave is analyzed by FFT(Fast Fourier Transform). We propose a methode to classify creeping partial discharge and corona partial discharge that are detected in three frequency bands.

• ETRI Journal
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• 제31권1호
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• pp.77-79
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• 2009

The wave concept iterative procedure (WCIP) is used to analyze a quasi-square open metallic ring frequency selective surface (FSS). The quasi-square open metallic ring FSS is dual-polarized. When the incident plane wave is polarized in a direction parallel to the FSS' coupled parallel strips, it shows two rejecting bands. Moreover, another rejecting band can be obtained if the source plane wave is perpendicularly polarized with respect to the FSS' coupled parallel strips. The three resonant frequencies are inversely proportional to the length of the FSS' coupled strips to provide an easy fine tuning of the FSS structure. The simulated results obtained using WCIP are compared to the measured results, and a good agreement is reported.

• 한국통신학회논문지
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• 제12권3호
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• pp.224-238
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• 1987

본 논문에서 제안된 스펙트럼 분석장치는 개루프 방식의 VCO를 모듈러 함수를 이용한 PLL 주파수 합성기로 대치시킴으로써 단일루우프의 주파수 합성기로 개개의 다른 주파수 대역 및 채널간격을 얻을 수 있었다. 스펙트럼의 추출은 자승검파방식을 이용함으로써 종래의 포락선 검파방식보다 입력감도를 개선할 수 있었고 Z80 마이크로프로세서를 이용한 제어기는 주파수 합성기를 제어하는 동시에 추출된 스펙트럼을 메모리에 저장함으로써 비주기성 신호의 분석을 가능케 하였다.

• 한국음향학회지
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• 제37권5호
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• pp.276-283
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• 2018

이 연구는 헬름홀쯔 공명기 구조를 갖는 매미 소리의 중심주파수에 주요 영향을 주는 발음기관이 무엇인지를 최초로 초고속영상분석을 통해 규명하는 데 목적이 있다. 말매미와 참매미를 대상으로 소리를 녹음 후 분석하였고, 초고속카메라로 촬영한 진동막의 움직임을 분석하여 소리의 주파수와 진동막 운동 사이의 관계를 비교하였다. 연구결과, 말매미와 참매미 모두 유인음과 비명음의 주파수분포에는 차이가 거의 없었으며, 말매미의 진동막은 3개, 참매미의 진동막은 1개 모드로 진동하였다. 두 매미 모두 양쪽 진동막의 진동수에는 차이가 나타나지 않았으며, 말매미의 진동막의 3개 진동 모드는 서로 다른 진동수 대역의 소리가 발생하였다. 두 매미 모두 진동막의 진동수 대역과 유인음의 중심주파수 대역이 매우 유사하였다. 결론적으로, 헬름홀쯔 공명기 구조를 갖는 매미 소리의 주파수는 복부의 공명조건보다는 진동막의 모드별 진동수에 의해 결정되는 것으로 추정된다.

• 전기전자학회논문지
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• 제28권1호
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• pp.72-77
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• 2024

본 논문에서는 최근 요구되는 이동통신 서비스의 다양한 주파수 대역 요구를 충족시키기 위해 3중 모드 주파수 가변 필터를 제안한다. 이 필터는 가변 커패시터를 활용하여 공진 주파수를 조절할 수 있는 튜닝 가능한 구조를 가지고 있다. 품질 계수를 향상하기 위해 SIW (Substrate Integrated Waveguide) 구조를 도입하였고, 중앙에 위치한 원형 홀을 통해 세 개의 공진 모드를 유발하는 구조를 구현하였다. 가변 커패시터에 의해 변화에 따른 전계분포와 공진 주파수의 변화를 EM 전파해석툴인 HFSS를 사용하여 시뮬레이션하였으며, 3중 모드의 전계분포와 공진 주파수의 변화를 확인하였다.