• Title/Summary/Keyword: Power Spectrum Density

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Analysis on the Power Spectrum of Electromagnetic Waves Radiating from the Distributorless Spark Ignition System (무배전기식 불꽃 점화 시스템에서 복사되는 전자파의 전력 스펙트럼 분석)

  • Choe, Gwang-Je;Jho, Shi-Gie;Jeung, Weol-Rark;Jang, Sung-Kuk;Kang, Shin-Han
    • Transactions of the Korean Society of Automotive Engineers
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    • v.16 no.1
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    • pp.45-51
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    • 2008
  • This paper presents theoretical and experimental analysis on the characteristics of the power spectrum of electormagnetic waves radiating from the spark plug and their cables of a distributorless ignition system. The theoretical study was conducted applying the microwave transmission line theory and the antenna theory. The experimental works were carried out to measure the standing wave ratio(SWR) and the radiation power spectrum of this system. As a result, it has been found that a spark plug and its cable is working as a monopole antenna radiating elelctromagnetic waves. Because of its similar structure to a monopole antenna, the envelope of radiation power spectrum distribution has a bell shape which can be obtained from a monopole antenna operating as a series resonant circuit. The frequency characteristics from the SWR measurements show a similar frequency characteristics of power spectrum of the system studied. Also, it has been found that the density of the power spectrum of the system fitting a long time used spark plug is higher than that of fitting a new spark plug.

ATSC Digital Television Signal Detection with Spectral Correlation Density

  • Yoo, Do-Sik;Lim, Jongtae;Kang, Min-Hong
    • Journal of Communications and Networks
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    • v.16 no.6
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    • pp.600-612
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    • 2014
  • In this paper, we consider the problem of spectrum sensing for advanced television systems committee (ATSC) digital television (DTV) signal detection. To exploit the cyclostationarity of the ATSC DTV signals, we employ spectral correlation density (SCD) as the decision statistic and propose an optimal detection algorithm. The major difficulty is in obtaining the probability distribution functions of the SCD. To overcome the difficulty, we probabilistically model the pilot frequency location and employ Gaussian approximation for the SCD distribution. Then, we obtain a practically implementable detection algorithm that outperforms the industry leading systems by 2-3 dB. We also propose various techniques that greatly reduce the system complexity with performance degradation by only a few tenths of decibels. Finally, we show how robust the system is to the estimation errors of the noise power spectral density level and the probability distribution of the pilot frequency location.

A Study on Artificial Wheel Load Generation Method Using PSD Analysis (PSD 함수를 이용한 인공윤하중의 생성기법에 대한 연구)

  • Cho, Kwang-Il;Choi, Moon-Seock;Lim, Ji-Young;Kim, Sang-Hyo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2008.04a
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    • pp.184-189
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    • 2008
  • In this study, an artificial wheel load generation method is proposed to assist practical engineers performing dynamic analysis with simple procedure. To generate an artificial wheel loads from running vehicle, PSD(Power Spectrum Density) profiles of actual wheel load were sampled in terms of various road roughnesses. A detailed truck and bridge models were used for sampling actual wheel load to represent the real motion of moving vehicle. These wheel load profiles were simplified for the artificial wheel load. The simplification of actual wheel load profiles was performed by regression analysis. The result showed that the artificial wheel load well represents the real profiles of wheel load.

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Chaotic Behavior of a Double Pendulum Subjected to Follower Force (종동력을 받는 이중진자의 혼돈운동 연구)

  • 장안배;이재영
    • Journal of KSNVE
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    • v.7 no.3
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    • pp.439-447
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    • 1997
  • In this study, the dynamic instabilities of a nonlinear elastic system subjected to follower forces are investigated. The two-degree-of-freedom double pendulum model with nonlinear geometry, cubic spring, and linear viscous damping is used for the study. The constant, the initial impact forces acting at the end of the model are considered. The chaotic nature of the system is identified using the standard methods, such as time histories, power density spectrum, and Poincare maps. The responses are chaotic and unpredictable due to the sensitivity to initial conditions. The sensitivities to parameters, such as geometric initial imperfections, magnitude of follower force, direction control constant, and viscous damping, etc., are analysed. Dynamic buckling loads are computed for various parameters, where the loads are changed drastically for the small change of parameters.

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OBSERVATIONAL STATUS OF THE TEXTURE LARGE-SCALE STRUCTURE FORMATION MODEL

  • UMEDA HIDEYUKI;FREESE KATHERINE
    • Journal of The Korean Astronomical Society
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    • v.29 no.spc1
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    • pp.23-24
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    • 1996
  • We reexamined CDM texture large-scale structure (LSS) formation model. We confirmed that texture model is consistent with 4-year COBE data both in an open and a critical matter density (${\Omega}_0$ = 1) universes, and then obtained normalization for density perturbation power spectrum. We next compare the power spectrum with LSS observation data. Contrary to the previous literature, we found that texture model matches with these data in an open universe no better than in an ${\Omega}_0$ = 1 universe. We also found that the model is more likely to fit these data in a cosmological constant dominated ($\Lambda-$) universe.

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Low Frequency Characteristics Analysis of EMG Signal on the Probability Density Function of the IPI (IPI의 확률밀도함수에 의한 근신호의 저주파 특성 해석)

  • 류재춘;조원경;박종국;김성환
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.25 no.3
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    • pp.335-342
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    • 1988
  • In this paper, we proposed a new algorithm for EMG low frequency analysis. Through the power spectrum analysis of Gaussian's, Gamma's and Erlang's PDF(probability density function) based on the proposed algorithm, the proper PDF of IPI (inter pulse interval) representing the firing rate of muscle was suggested. In order to verify the proposed algorithm EMG signals of masseter and biceps muscle were detected by surface electrode and its power spectrum analysis was performed. The experimental results are compared with the computer simulaiton. As a result, the masseter muscle's IPI was fitted by Gamma PDF, having a 10Hz fundamental frequency including n(1+\ulcornerfp high harmnic frequency on 10% MVC(maximum voluntary contaraction). And the biceps muscle's IPI was fitted by Gaussian PDF, also it have a 14Hz fundamental frequency.

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DYNAMIC CHARACTERISTICS OF CYLINDRICAL SHELLS CONSIDERING FLUID-STRUCTURE INTERACTION

  • Jhung, Myung-Jo;Kim, Wal-Tae;Ryu, Yong-Ho
    • Nuclear Engineering and Technology
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    • v.41 no.10
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    • pp.1333-1346
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    • 2009
  • To assure the reliability of cylinders or shells with fluid-filled annulus, it is necessary to investigate the modal characteristics considering fluid-structure interaction effect. In this study, theoretical background and several finite element models are developed for cylindrical shells with fluid-filled annulus considering fluid-structure interaction. The effect of the inclusion of the fluid-filled annulus on the natural frequencies is investigated, which frequencies are used for typical dynamic analyses such as responses spectrum, power spectral density and unit load excitation. Their response characteristics are addressed with respect to the various representations of the fluid-structure interaction effect.

A Study of Biosignal Analysis System for Sensibility Evaluation (감성을 평가하기 위한 생체신호 분석 시스템에 관한 연구)

  • Lee, Ji-Hyeoung;Kim, Kyung-Ho
    • Proceedings of the Korean Society of Computer Information Conference
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    • 2010.07a
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    • pp.35-38
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    • 2010
  • 본 논문에서는 일상생활 속에서 무자각적으로 생체신호를 측정하고 분석하여 감성을 평가할 수 있는 임베디드 시스템에 관하여 연구하였다. 지속적으로 변화하는 감성을 일관적이며 신뢰성이 높은 생리적인 방법으로 평가하기 위해 심전도(ECG:Electrocardiogram), 맥파(PPG:Photoplethysmogram)의 두 가지 생체신호를 측정하고, 무선전송(Bluetooth) 장치를 이용하여 측정한 생체신호를 실시간으로 노트북PC로 전송하여 분석하였다. 생체신호의 분석방법은 FFT(Fast Fourier Transform)과 전력스펙트럼밀도(Power Spectrum Density)를 이용한 주파수 분석방법으로 두 생체신호의 특정 주파수 대역이 가지는 자율신경계의 활성도의 비율을 분석하여 비교 연구하였다. 또한 보다 빠르고 정확한 감성을 평가하기 위하여 분석알고리즘의 연산을 최소화 하였으며 그래프를 이용한 분석결과의 시각화를 하였다. 본 논문에서는 무자각적인 생체신호 측정 시스템을 이용하여 다양한 상황에서 생체신호를 측정하고, 개발한 분석 알고리즘으로 분석한 결과의 차이를 연구하여 정확도 및 신뢰도를 기준으로 감성을 평가하기 위한 분석 시스템을 평가하였다.

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Generation of critical and compatible seismic ground acceleration time histories for high-tech facilities

  • Hong, X.J.;Xu, Y.L.
    • Structural Engineering and Mechanics
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    • v.26 no.6
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    • pp.687-707
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    • 2007
  • High-tech facilities engaged in the production of semiconductors and optical microscopes are extremely expensive, which may require time-domain analysis for seismic resistant design in consideration of the most critical directions of seismic ground motions. This paper presents a framework for generating three-dimensional critical seismic ground acceleration time histories compatible with the response spectra specified in seismic design codes. The most critical directions of seismic ground motions associated with the maximum response of a high-tech facility are first identified. A new numerical method is then proposed to derive the power spectrum density functions of ground accelerations which are compatible with the response spectra specified in seismic design codes in critical directions. The ground acceleration time histories for the high-tech facility along the structural axes are generated by applying the spectral representation method to the power spectrum density function matrix and then multiplied by envelope functions to consider nonstationarity of ground motions. The proposed framework is finally applied to a typical three-story high-tech facility, and the numerical results demonstrate the feasibility of the proposed approach.