• 센서학회지
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• 제16권3호
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• pp.202-210
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• 2007

The aim of this study is to acquire useful information of lower urinary tract symptom (LUTS) diagnosis through urophonography signal as a noninvasive method. The hardware and software which could evaluate the function of compensatory hypertrophy with noninvasive and comfortable method was implemented to measure uroflow and urophonography signal during urination. The PSD (power spectrum density) and the log-log plot gradient analysis were accomplished in frequency domain. For evaluation of the system and analysis method, a model system for the lower urinary system of men was used. From the evaluation of the model system, the PDS and the log-log plot gradient were dependent on the occlusion degree significantly. In a pilot study on normal and abnormal male subjects, the PSD and the log-log plot gradient were highly correlated with the artificial urethral obstruction.

• 한국운동역학회지
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• 제18권4호
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• pp.49-57
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• 2008

이 연구는 고령자를 대상으로 탄성저항운동을 수행하였을 경우 운동 전 후로 보행 시 지면반력 신호 크기와 이들의 variability에 어떠한 영향을 미치는 가를 구명하고자 하였다. 이를 위하여 여성 고령자 12명을 대상으로 12주간 탄성저항운동을 실시하였으며, 운동 전 후로 보행 시 3방향 지면반력 신호의 주파수 크기와 variability 값을 산출하였다. FFT(fast Fourier transform)를 이용하여 주파수 분석을 하였으며, PSD(power spectral density)를 계산하였다. 총 대상자들의 변이 계수(SD/Mean*100)을 이용하여 집단 간 variability를 계산하였다. 그 결과 다음과 같은 결론을 얻었다. 지면반력 신호의 주파수 크기는 좌우 방향에서 운동 전보다 운동 후에 작은 값을 보였으며, 통계적으로도 유의한 차이(p<.05)가 나타났다. 지면반력 신호의 variability에서는 좌우 방향에서 운동 전보다 운동 후에 큰 값이 나타났으며, 통계적으로도 유의한 차이(p<.05)가 나타났다.

• 한국전기전자재료학회논문지
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• 제22권6호
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• pp.537-545
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• 2009

In this paper, new parameters were developed to estimate the depth of anesthesia during a general anesthesia using EEG. Power spectral density(PSD) analysis was used for these parameters because EEG became slow wave during anesthesia. The new parameters were DTR, ATR, TDR, ADR, BTR and BDR applied to PSD. These parameters were compared with SEF which is conventionally used at clinic and confirmed clinical value. As the results, DTR, ATR, TDR, ADR among parameters were not useful compared with SEF but BTR and BDR is valuable for clinic. 15 patents, at pre-operation BDR the value is $265.36{\pm}25.29$, at induction the value is $129.23{\pm}34.92$, at operation the value is $154.99{\pm}38.34$, at awaked the value is $283.83{\pm}39.80$ and at post-operation the value is $234.80{\pm}23.46$. Also at pre-operation BTR value is $183.38{\pm}13.59$, at induction the value is $104.09{\pm}25.11$, at operation the value is $115.38{\pm}23.42$, at awaked the value is $190.33{\pm}23.31$ and at post-operation the value is $172.38{\pm}19.08$. Trend of BDR and BTR is similar to change of SEF, so two parameters are useful. to estimate the depth of anesthesia.

• 한국정보통신학회논문지
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• 제26권7호
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• pp.981-988
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• 2022

정보통신기술(ICT)를 적용한 스마트팩토리로 불리는 지능형 생산 공장은 각종 센서를 통해 공정 데이터를 실시간으로 수집하고 있다. 이렇게 수집된 데이터를 효과적으로 활용하는 연구가 많이 진행되고 있는데, 본 논문에서는 생산 공정에서 발생되는 음향 신호를 기반으로 공구 상태를 진단하는 기법을 제안한다. 첫 번째로 결함이 있는 공구를 감지할 뿐만 아니라 공회전 및 공정 운용에 따른 다양한 공구 상태를 제시한다. 두 번째로 푸리에 분석을 이용하여 사운드의 전력스펙트럼을 영상으로 표현하고, 데이터에 숨겨진 건강한 패턴을 드러내고, 강조하기 위해 일부 변형을 적용한다. 마지막으로 이렇게 획득한 대비 강화된 PSD 영상은 CNN을 이용해 상태별로 진단한다. 그 결과 제안한 음향 PSD 영상 + CNN 방법은 데이터의 차별화된 특징이 잘 반영되어 공구 상태에 따른 높은 진단 결과를 보여준다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.304-311
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• 1998

An algorithm to enhance spectra matching of acceleration time history used in the seismic analysis of nuclear power plants(NPP) is proposed. The new scheme provides the solution on the highly fluctuating and over conservatism problems that happened in order to satisfy design spectrum enveloping criteria in the traditional method. To obtain optimized spectrum for a time history, a spectrum matching procedure that adapts a system identification technique is also developed. The algorithm also introduces maximum displacement control, baseline correction, clipping and raising of maximum peak of time history, and power spectral density (PSD) control of time history. It is verified through numerical examples that this new scheme can definitely generate acceleration time history, closely matching the target spectra and satisfying other stipulated requirements.

• 한국군사과학기술학회지
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• 제26권1호
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• pp.1-9
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• 2023

The skin structure of sensor pod mounted on the exterior of aircraft can be exposed to the acoustic dynamic load and static load such as aerodynamic pressure and inertial load during flight. Fatigue life prediction of structural model under acoustic load should be performed and also differential stiffness of model modified by static load should be considered. The acoustic noise test spectrum of MIL-STD-810G was applied to the structural model and the stress response power spectral density (PSD) was calculated. The frequency response analysis was performed with or without prestress induced by inplane static load, and the response spectrum was compared. Time series data was generated using the calculated PSD, and the time and frequency domain fatigue life were predicted and compared. The variation of stress response spectrum due to static load and predicted fatigue life according to the different structural model considering mean stress were examined and decreasing fatigue life was observed in the model with prestress of compressive static load.

• Journal of Communications and Networks
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• 제8권2호
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• pp.187-193
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• 2006

In this paper, we study the coexistence of orthogonal frequency division multiplexing (OFDM)-based systems beyond 3G (B3G) and point-to-point (P-P) fixed service (FS) microwave systems. The advanced general analytical model derived via a power spectral density (PSD) analysis proposed in this paper has two advantages in comparison with the conventional minimum coupling loss (MCL) method. First, the interfering signal power that appears in the band of a victim system can be easily assessed without a spectrum emission mask. Second, when transmit power is not allocated to some subcarriers overlapping the band of the victim system in order to mitigate B3G OFDM-based systems interference with other systems, the general analytical model can successfully assess the interference from the B3G systems into FS systems, whereas the MCL method incorporating the spectrum emission mask cannot be applied in the presence of the same interference condition. The proposed model can be derived in a closed form and is simply implemented with the help of simulation, and thus the solution can be obtained in significantly reduced time. Through application of the proposed model, coexistence results are analyzed in a co-channel and adjacent channel with respect to guard band and minimum separation distance.

• 한국지구과학회지
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• 제33권5호
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• pp.395-400
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• 2012

One of the main problems concerning the shallow seismic survey is how to generate high frequency signals with large amplitudes using small seismic sources. If one could focus the seismic energy in the direction of the survey line, it will be much helpful in identifying the first break. In this research, we have used hammer as an impulsive source and compared the signal powers generated by different shapes of the hammer plates: circular, square, and rectangular. The experiment was conducted by calculating the power spectral density function to compare the frequency spectrum and signal power. In the direction perpendicular to the long side of the rectangular plate, the largest seismic energy with the highest frequency was achieved even with the same weights of hammer plates. Our conclusion is that it is more efficient to use a rectangular plate than a circular (or square) one when conducting a 2-D shallow seismic survey.

• 대한원격탐사학회지
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• 제22권5호
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• pp.397-402
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• 2006

China Coastal Water (CCW) usually appears in the seas surrounding Jeju Island annually (June-October) and is very pronounced in August. The power spectrum density (PSD), sea level anomalies (SLAs), and sea surface temperatures (SSTs) were found to peak annually and semiannually. The peaks at intervals of 80-, 60-, and 43-days are considered to be influenced by CCW and the Kuroshio Current. Generally, low-salinity water appears to the west of Jeju Island from June through October and gradually propagates to the east, where CCW meets the Tsushima Current. Empirical orthogonal function (EOF) analysis of SLAs and SSTs indicated that the variance in SLAs and SSTs was 55.70 and 98.09% in the first mode, respectively. The PSD for the first mode of EOF analysis of SLAs was stronger in the western than in the eastern waters because of the influence of CCW. The PSD for the EOF analysis of SSTs was similar in all areas (the Yangtze Estuary and the waters to the west and east of Jeju Island), with a period of approximately 260 days.

• Earthquakes and Structures
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• 제13권2호
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• pp.193-200
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• 2017

To overcome the difficulty of performing multi-point response spectrum analysis for engineering structures under spatially varying ground motions (SVGM) using the general finite element code such as ANSYS, an approach has been developed by improving the modelling of the input ground motions in the spectral analysis. Based on the stochastic vibration analyses, the cross-power spectral density (c-PSD) matrix is adopted to model the stationary SVGM. The design response spectra are converted into the corresponding PSD model with appropriate coherency functions and apparent wave velocities. Then elements of c-PSD matrix are summarized in the row and the PSD matrix is transformed into the response spectra for a general spectral analysis. A long-span high-pier bridge under multiple support excitations is analyzed using the proposed approach considering the incoherence, wave-passage and site-response effects. The proposed approach is deemed to be an efficient numerical method that can be used for seismic analysis of large engineering structures under SVGM.