• Title/Summary/Keyword: Time-Frequency Analysis

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A Comparative Study of the Dietary Behavior of Adults Aged 20 and Over according to the Mukbang Viewing Time (20세 이상 성인의 먹방 시청 시간에 따른 식행동 비교 연구)

  • Nam, Ha-Yan;Jung, Bok-Mi
    • Korean Journal of Community Nutrition
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    • v.26 no.2
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    • pp.93-102
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    • 2021
  • Objectives: This study was conducted to investigate the relationship between watching mukbang (eating broadcasts) and dietary and health behavior in adults who watch mukbang. Methods: The questionnaire was administered on a self-written basis through online and offline formats to 800 adults (400 men and 400 women). The contents of the survey consisted of general characteristics, mukbang viewing time per week, breakfast intake frequency, preference for menus when viewing mukbang, delivery food intake frequency per week, late meal intake frequency per week, and health behavior. The subjects were divided into three groups according to mukbang viewing time. Results: The body weight of viewers was significantly higher when mukbang viewing time was over 14 hours for both men and women. In particular, based on the BMI (body mass index), those who watched mukbang for more than 14 hours were found to be overweight. People with more than 14 hours of mukbang viewing time per week were found to prefer mostly carbohydrate-rich food and meat, while those with less than 7 hours of mukbang viewing time per week showed a higher preference for vegetables and fruits. An analysis of the frequency of breakfast eaten showed that the rate of skipping breakfast was the highest for those who watched mukbang for more than 14 hours per week, and the rate of eating breakfast daily was the highest in the case of fewer than 7 hours of viewing. In the case of high mukbang viewing time per week, the frequency of food delivery and night eating was high. When mukbang viewing time was high, the viewer's interest in health was low and the frequency of exercising too was low. Conclusions: Viewers with high mukbang viewing time showed undesirable health and eating behavior. Thus, it is believed that proper nutrition education on improving eating habits and raising the awareness of correct eating habits is necessary for such viewers.

The Comparision of Analysis Methods in dynamic Design of Dam based on Shaking Table tests (진동대시험에 근거한 댐의 내진설계시 해석 방법의 비교)

  • Hwang, Seong-Choon;Oh, Byung-Hyun
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2005.05a
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    • pp.732-737
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    • 2005
  • This paper performed pseudo static analysis and dynamic analysis for CFRD and evaluated reliability with the results of Shaking Table Test. The Seismic coefficient method, modified seismic coefficient method, Newmark method of Pseudo static analysis and frequency domain response analysis, time domain history analysis of dynamic analysis were used. The analysis results were differ between analysis method, but the trends of acceleration and displacement were good agreement with the results of shaking table test.

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Fatigue Life Evaluation in Frequency Domain of aircraft Equipment Exposed to Random Vibration (무작위 진동에 노출된 항공기 탑재 장비의 주파수영역 피로수명 평가)

  • Jung, Hyun Su;Kim, Ki Seung;Kim, Jun Su;Lee, Seong Woo
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.45 no.8
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    • pp.627-638
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    • 2017
  • Expecting fatigue life of mounted radar in aircraft is very important when designing, because the mounted radar in aircraft is exposed to long-term external random vibration. Among the methods of predicting the fatigue life, Fatigue analysis method in frequency domain has continuously been proposed in this field. In this paper, four fatigue analysis methods in frequency domain, which are widely used, have been selected and compared with the results for Specimen fatigue test. As a result, Dirlik and Benascicutti-Tovo methods have been matched better with fatigue analysis in time domain than the method in frequency method through the comparison between the fatigue analysis method in time domain and the method in frequency domain by conducting the specimen fatigue test with strain gage. Based on the results of the specimen fatigue test, We have conducted fatigue analysis of mounted radar in aircraft with Dirlik and Benasciutti-Tovo methods in the finite element model, and confirmed that the required life was satisfying.

Multi-step wind speed forecasting synergistically using generalized S-transform and improved grey wolf optimizer

  • Ruwei Ma;Zhexuan Zhu;Chunxiang Li;Liyuan Cao
    • Wind and Structures
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    • v.38 no.6
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    • pp.461-475
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    • 2024
  • A reliable wind speed forecasting method is crucial for the applications in wind engineering. In this study, the generalized S-transform (GST) is innovatively applied for wind speed forecasting to uncover the time-frequency characteristics in the non-stationary wind speed data. The improved grey wolf optimizer (IGWO) is employed to optimize the adjustable parameters of GST to obtain the best time-frequency resolution. Then a hybrid method based on IGWO-optimized GST is proposed to validate the effectiveness and superiority for multi-step non-stationary wind speed forecasting. The historical wind speed is chosen as the first input feature, while the dynamic time-frequency characteristics obtained by IGWO-optimized GST are chosen as the second input feature. Comparative experiment with six competitors is conducted to demonstrate the best performance of the proposed method in terms of prediction accuracy and stability. The superiority of the GST compared to other time-frequency analysis methods is also discussed by another experiment. It can be concluded that the introduction of IGWO-optimized GST can deeply exploit the time-frequency characteristics and effectively improving the prediction accuracy.

APPLICATIONS OF THE HILBERT-HUANG TRANSFORM ON THE NON-STATIONARY ASTRONOMICAL TIME SERIES

  • HU, CHIN-PING;CHOU, YI;YANG, TING-CHANG;SU, YI-HAO;HSIEH, HUNG-EN;LIN, CHING-PING;CHUANG, PO-SHENG;LIAO, NAI-HUI
    • Publications of The Korean Astronomical Society
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    • v.30 no.2
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    • pp.605-607
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    • 2015
  • The development of time-frequency analysis techniques allow astronomers to successfully deal with the non-stationary time series that originate from unstable physical mechanisms. We applied a recently developed time-frequency analysis method, the Hilbert-Huang transform (HHT), to two non-stationary phenomena: the superorbital modulation in the high-mass X-ray binary SMC X-1 and the quasi-periodic oscillation (QPO) of the AGN RE J1034+396. From the analysis of SMC X-1, we obtained a Hilbert spectrum that shows more detailed information in both the time and frequency domains. Then, a phase-resolved analysis of both the spectra and the orbital profiles was presented. From the spectral analysis, we noticed that the iron line production is dominated by different regions of this binary system in different superorbital phases. Furthermore, a pre-eclipse dip lying at orbital phase ~0:6-0:85 was discovered during the superorbital transition state. We further applied the HHT to analyze the QPO of RE J1034+396. From the Hilbert spectrum and the O-C analysis results, we suggest that it is better to divide the evolution of the QPO into three epochs according to their different periodicities. The correlations between the QPO periods and corresponding fluxes were also different in these three epochs. The change in periodicity and the relationships could be interpreted as the change in oscillation mode based on the diskoseismology model.

A Quantitative Analysis of Activation Pattern of Active Elbow Muscles (주관절 근육의 활성화 유형에 대한 정량적 분석)

  • Lee, Du-Hyoung;Lee, Young-Seock;Lee, Jin;Kim, Sung-Hwan
    • Journal of Biomedical Engineering Research
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    • v.18 no.4
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    • pp.413-420
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    • 1997
  • In this paper, we analyzed the contraction patterns of active elbow muscles during isometric, concentric and eccentric contraction. The analysis parameters consist of frequency domain parameters (mean frequency, median frequency, peak frequency, peak power, skewness, kurtosis) and time domain paraseters (zero crossing, positive maxima, integrated EMG). The results of this study were as follows; The BR/BB of isometric contraction appeared to be Venter as the elbow joint was more extended. The BR /BB during concentric and eccentric contraction tended to increase with more extension of the elbow joint angle, but there was no significant difference between concentric and eccentric contraction. Further, the EMG power spectrum due to the type of contraction were different betwen eccentric and concentric contraction. According to the results, it was found that the activation pattern in elbow flexor muscles was different during three different muscle contraction pattern. Therefore, elbow flexor muscles should not be considered a single functioning unit. Especially, at the time domain analysis, IEMG is a dominant parameter for analysis of activation patterns, and the skewness kurtosis can be useful parameters in functional recognition for prosthesis control purpose.

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A Study on the Application of Wavelet Transform to Faults Current Discrimination (Wavelet 변환을 이용한 고장 전류의 판별에 관한 연구)

  • Jeong, Jong-Won;Jo, Hyun-Woo;Kim, Tae-Woo;Lee, Joon-Tark
    • Proceedings of the Korean Institute of Intelligent Systems Conference
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    • 2002.12a
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    • pp.427-430
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    • 2002
  • Recently the subject of "wavelet analysis" has be drawn by both mathematical and engineering application fields such as Signal Processing, Compression/Decomposition, Wavelet-Neural Network, Statistics and etc. Even though its similar to Fourier analysis, wavelet is a versatile tool with much mathematical content and great potential for applications. Especially, wavelet transform uses localizable various mother wavelet functions in time-frequency domain. Therefore, wavelet transform has good time-analysis ability for high frequency component, and has good frequency-analysis ability for low frequency component. Using the discriminative ability is more easy method than other conventional techniques. In this paper, Morlet wavelet transform was applied to discriminate the kind of line fault by acquired data from real power transformation network. The experimental result presented that Morlet wavelet transform is easier,and more useful method than the FFT (Fast Fourier Transform).

A Performance Evaluation of MB-OFDM UWB System Considering the Domestic DAA Regulation (국내 DAA 기술 기준을 고려한 MB-OFDM UWB 성능 평가)

  • Shin, Cheol-Ho;Choi, Sang-Sung
    • The Journal of Korean Institute of Electromagnetic Engineering and Science
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    • v.19 no.9
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    • pp.1000-1009
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    • 2008
  • The purpose of this paper is to analyze the performance of MB-OFDM UWB system when the interference signal that can be WIMAX signal or 4 G system signal is received by detection limit of -80 dBm/MHz proposed in Korea for DAA(Detect And Avoid) to permit UWB in $3.1{\sim}4.8$ GHz. MB-OFDM UWB system supports two transmission modes; one is TFI(Time frequency Interleaving) mode that transmits OFDM symbols using different carrier frequency from symbol to symbol according to Time Frequency(TF) codes, the other is FFI(Fixed Frequency Interleaving) mode that transmits OFDM symbols using a specific carrier frequency. In this paper, we considered the TX average power and the synchronization structure to reflect the effect of frequency hopping according to TFC. Interference analysis results show that the WiMAX system is fenced thoroughly from UWB interference in domestic DAA regulation, but the performance of MB-OFDM UWB system is degraded seriously by an interference signal with the DAA detection limit even in frequency Hopping mode that can get frequency diversity effect.

A Study on Frequency Domain Fatigue Damage Prediction Models for Wide-Banded Bimodal Stress Range Spectra (광대역 이봉형 응력 범위 스펙트럼에 대한 주파수 영역 피로 손상 평가 모델에 대한 연구)

  • Park, Jun-Bum;Kang, Chan-Hoe;Kim, Kyung-Su;Choung, Joon-Mo;Yoo, Chang-Hyuk
    • Journal of the Society of Naval Architects of Korea
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    • v.48 no.4
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    • pp.299-307
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    • 2011
  • The offshore plants such as FPSO are subjected to combination loading of environmental conditions (swell, wave, wind and current). Therefore the fatigue damage is occurred in the operation time because the units encounter the environmental phenomena and the structural configurations are complicated. This paper is a research for frequency domain fatigue analysis of wide-band random loading focused on accuracy of fatigue damage estimation regarding the proposed methods. We selected ideal bi-modal spectrum. And comparison between time-domain fatigue analysis and frequency-domain fatigue analyses are conducted through the fatigue damage ratio. Fatigue damage ratios according to Vanmarcke's bandwidth parameter are founded for wide-band. Considering safety, we recommend that Jiao-Moan and Tovo-Benasciutti methods are optimal way at the fatigue design for wide-band response. But, it is important that these methods based on frequency-domain unstably change the accuracy according to the material parameter of S-N curve. This study will be background and guidance for the new frequency-domain fatigue analysis development in the future.

Evidence of Difference on the Results of VAR Analysis Impacted the Time Frequency and Time Span of Time Series Data (시계열 자료의 관찰빈도 및 기간이 VAR 분석결과에 미치는 영향 차이 검증 - 한국 환율과 주가를 중심으로 -)

  • Hwang, Yun Seop;Yoo, Seung Jick;Kim, Soo Eun
    • International Area Studies Review
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    • v.13 no.1
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    • pp.81-102
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    • 2009
  • The discussion of the relationship between macro-economic variables is very important research topic. the most economic variables discussed in connection with the liberalization of capital is the exchange rate and stock prices and these two variables have a relationship of mutual influence are identified. However, the results on the time frequency and the time span of a variable appear differently. Therefore, the purpose of this research describes a cause that the result of prior research varied and presents more reliable research methodology. In this research, when the time frequency and span varied, the VAR analysis of the exchange rate and stock prices appeared differently. So, we use the Monte Carlo simulation method in order to performing our purpose. Our research supports the existing research said the ratio that each coefficient VAR model contained 95% confidence interval of estimated coefficient in Monte Carlo simulation is higher when it is applied more the long term and frequent observation.