• Title/Summary/Keyword: multiple frequency

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Structural modal identification through ensemble empirical modal decomposition

  • Zhang, J.;Yan, R.Q.;Yang, C.Q.
    • Smart Structures and Systems
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    • v.11 no.1
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    • pp.123-134
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    • 2013
  • Identifying structural modal parameters, especially those modes within high frequency range, from ambient data is still a challenging problem due to various kinds of uncertainty involved in vibration measurements. A procedure applying an ensemble empirical mode decomposition (EEMD) method is proposed for accurate and robust structural modal identification. In the proposed method, the EEMD process is first implemented to decompose the original ambient data to a set of intrinsic mode functions (IMFs), which are zero-mean time series with energy in narrow frequency bands. Subsequently, a Sub-PolyMAX method is performed in narrow frequency bands by using IMFs as primary data for structural modal identification. The merit of the proposed method is that it performs structural identification in narrow frequency bands (take IMFs as primary data), unlike the traditional method in the whole frequency space (take original measurements as primary data), thus it produces more accurate identification results. A numerical example and a multiple-span continuous steel bridge have been investigated to verify the effectiveness of the proposed method.

Direct Missile Bending Frequency Estimation using the Robust Kalman Filter (강인 칼만필터를 이용한 유도탄 기체 진동 주파수 추정기 설계)

  • Ra, Won-Sang;Whang, Ick-Ho
    • Proceedings of the KIEE Conference
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    • 2005.07d
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    • pp.2477-2479
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    • 2005
  • A robust bending frequency tracker is proposed to design the adaptive notch filter which removes the time-varying missile structural modes from the sensor measurements. To do this, the state-space form of a bending frequency model is derived under the assumption that the bending signal could be described as the lightly damped sinusoid. Since the resultant bending frequency model contains the parametric uncertainties in the measurement matrix, the design problem of bending frequency tracker is tackled by applying the robust Kalman filter to the model. This technique could be easily expanded to the multiple frequencies case because it newly illuminates the bending frequency tracking problem in view of general state estimation.

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Detection of Leakage Point via Frequency Analysis of a Pipeline Flow

  • Kim, Sanghyun;Wansuk Yoo;Injoon Kang
    • Journal of Mechanical Science and Technology
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    • v.15 no.2
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    • pp.232-238
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    • 2001
  • Fast Fourier Transformation is employed to convert the head variation of a pipeline in the time domain to the amplitude of the frequency domain. Applying method of characteristics to a pipeline provides a significant frequency range for a surge introduced from the valve modulation. Inverse Fast Fourier Transformation and a Finite Impulse Response Filter can be used to remove any possible noise existing from the significant frequency range of an unsteady condition. A filtered signal shows higher potential for the inverse calculation of leakage detection than the noise-added signal does. The respective performances of Inverse Fast Fourier Transformation and a Finite Impulse Response Filter are compared in terms of leakage detection capability. Characteristics of the frequency range for multiple leakages were investigated to validate the effectiveness of the noise control method in the frequency domain.

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A Preliminary Study on the Prediction of School Facilities Repair Frequency and Rate (학교시설 수선주기 및 수선율 예측에 관한 기초적 연구)

  • Jung, Young-Han;Lee, Jae-Sung;Cho, Bong-Ho
    • The Journal of Sustainable Design and Educational Environment Research
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    • v.9 no.2
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    • pp.1-8
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    • 2010
  • This study is to present an engineering solution for the repair frequency and repair rates of a building. The existing data for the repair frequency and repair rates are used to draw the probability distribution for the generalized repair frequency and repair rate in a building. The suggested methodology can be widely used for most buildings to estimate the legal repair frequency and repair rates. Also, the methodology can be applied to resolve the risks on the maintenance costs in LC (Life Cycle) plans or LCC (Life Cycle Cost) analysis. As the future studies, there are the multiple regression analysis including the parameters on incurred costs and the decision methods on efficient repair and replacement.

Implementation of Frequency Relaying Algorithm based on Multi-Agent System using EMTP-MODELS (EMTP-MODELS를 이용한 Multi-Agent System 기반의 주파수 계전 알고리즘 구현)

  • Lee, Byung-Hyun;Kim, Chul-Hwan;Yeo, Sang-Min
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.56 no.12
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    • pp.2072-2077
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    • 2007
  • The primary objective of all power systems is to maintain the reliability and to minimize outage time for fault or the others. The frequency relaying algorithm perceives a variation of system frequency and thereafter detects the unbalance between generation and load. A multi-agent system is composed of multiple interacting computing elements that are known as agents. In this paper, frequency relaying algorithm is designed by multi-agent system and is implemented by EMTP-MODELS. To verify performance of the frequency relaying algorithm based on multi-agent system, simulations by EMTP have been carried out.

Optimal Compensation of Dual Carrier Frequency Offsets for MISO-mode DVB-T2

  • Jeon, Eun-Sung;Seo, Jeong-Wook;Yang, Jang-Hoon;Paik, Jong-Ho;Kim, Dong-Ku
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.6 no.2
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    • pp.610-628
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    • 2012
  • Dual carrier frequency offsets (CFOs) occur in multiple-input single-output (MISO)-mode DVB-T2 systems, where signals are transmitted simultaneously from two distributed transmitters in a single frequency network (SFN). In this paper, we first derive an optimal compensation frequency for dual CFOs. We also propose an algorithm that optimizes the compensation frequency for the MISO-mode DVB-T2 application. Its performance is compared with the conventional scheme by using a full DVB-T2 simulator.

Frequency Domain Processing Techniques for Pulse Shape Modulated Ultra Wideband Systems

  • Gordillo, Alex Cartagena;Kohno, Ryuji
    • Journal of Communications and Networks
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    • v.9 no.4
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    • pp.482-489
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    • 2007
  • In this paper, two frequency domain signal processing techniques for pulse shape modulation(PSM) ultra wideband(UWB) systems are presented. Firstly, orthogonal detection of UWB PSM Hermite pulses in frequency domain is addressed. It is important because time domain detection by correlation-based receivers is severely degraded by many sources of distortion. Pulse-shape, the information conveying signal characteristic, is deformed by AWGN and shape-destructive addition of multiple paths from the propagation channel. Additionally, because of the short nature of UWB pulses, timing mismatches and synchronism degrade the performance of PSM UWB communication systems. In this paper, frequency domain orthogonality of the Hermite pulses is exploited to propose an alternative detection method, which makes possible efficient detection of PSM in dense multipath channel environments. Secondly, a ranging method employing the Cepstrum algorithm is proposed. This method is partly processed in the frequency domain and can be implemented without additional hardware complexity in the terminal.

Distance Estimation Using Discretized Frequency Synthesis of Ultrasound Signals (초음파의 이산 주파수 합성을 이용한 거리 측정)

  • Park, Sang-Wook;Kim, Dae-Eun
    • Journal of Institute of Control, Robotics and Systems
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    • v.17 no.5
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    • pp.499-504
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    • 2011
  • In this paper, we suggest a method for discretized frequency modulations of ultrasonic signals. A continuous sweep of frequency modulation signals can be modelled with fine levels of discretization. If the ultrasound signals are modulated with monotonically decreasing frequencies, then the cross-correlation between an emitted signal and received signal can be used to identify the distance of multiple target objects. For the discretized frequency synthesis, CF ultrasounds with different frequencies are serially ordered. The auto-correlation test with the signal shows effective results for distance estimation. The discretized frequency syntheses have better distance resolution than CF ultrasound signals and the resolution depends on the number of the combined ultrasound frequencies.

The Impact of How Often Students Use Mobile Devices on Their Perceptions of the Usefulness and Convenience of the Devices

  • Inah KO;Yeon KIM
    • Educational Technology International
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    • v.24 no.2
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    • pp.331-358
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    • 2023
  • This paper explores the impact of mobile device usage frequency in the classroom on students' perceptions of their use. To assess this, we created a survey that measured students' perceived frequency, usefulness, and convenience of using mobile devices, using a reversed Technology Acceptance Model. Through the analysis of responses from 781 Korean students, utilizing confirmatory item factor analyses and a structural equation mixture model, we found that the effect of frequent mobile device use on students' positive perceptions is non-linear. As the frequency reaches to a certain level, the effect sizes of the frequency in the positive perceptions diminishes. Additionally, students who used mobile devices less frequently in class reported higher levels of difficulties in using the devices. This study introduces a tool for evaluating multiple aspects of students' perceptions regarding mobile device use and offers a framework for understanding the relationship between usage frequency, usefulness, and convenience.

A Novel High-speed CMOS Level-Up/Down Shifter Design for Dynamic-Voltage/Frequency-Scaling Algorithm (Dynamic-Voltage/Frequency-Scaling 알고리즘에서의 다중 인가 전압 조절 시스템 용 High-speed CMOS Level-Up/Down Shifter)

  • Lim Ji-Hoon;Ha Jong-Chan;Wee Jae-Kyung;Moon Gyu
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.43 no.6 s.348
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    • pp.9-17
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    • 2006
  • We proposed a new High-speed CMOS Level Up/Down Shifter circuits that can be used with Dynamic Voltage and Frequency Scaling(DVFS) algorithm, for low power system in the SoC(System-on-Chip). This circuit used to interface between the other voltage levels in each CMOS circuit boundary, or between multiple core voltage levels in a system bus. Proposed circuit have advantage that decrease speed attenuation and duty ratio distortion problems for interface. The level up/down shifter of the proposed circuit designed that operated from multi core voltages$(0.6\sim1.6V)$ to used voltage level for each IP at the 500MHz input frequency The proposed circuit supports level up shifting from the input voltage levels, that are standard I/O voltages 1.8V, 2.5V, 3.3V, to multiple core voltage levels in between of $0.6V\sim1.6V$, that are used internally in the system. And level down shifter reverse operated at 1Ghz input frequency for same condition. Simulations results are shown to verify the proposed function by Hspice simulation, with $0.6V\sim1.6V$ CMOS Process, $0.13{\mu}m$ IBM CMOS Process and $0.65{\mu}m$ CMOS model parameters. Moreover, it is researched delay time, power dissipation and duty ration distortion of the output voltage witch is proportional to the operating frequency for the proposed circuit.