• Title/Summary/Keyword: Reduced Frequency

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A Simple Scheme for Jitter Reduction in Phase-Differential Carrier Frequency Recovery Loop

  • Lim, Hyoung-Soo;Kwon, Dong-Seung
    • ETRI Journal
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    • v.28 no.3
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    • pp.275-281
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    • 2006
  • A very simple and efficient scheme for jitter reduction is proposed for a carrier frequency recovery loop using phase differential frequency estimation, which estimates the current frequency offset based on the difference of the average phases of two successive intervals. Analytical and numerical results presented in this paper show that by simply overlapping the observation intervals by half for frequency offset estimations, both the steady-state and transient performances can be improved. The proposed scheme does not require any additional hardware circuitry, but results in improved performance even with reduced complexity.

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A Study on Development of a Hearing Impairment Simulator considering Frequency Selectivity and Asymmetrical Auditory Filter of the Hearing Impaired (난청인의 주파수 선택도와 비대칭적 청각 필터를 고려한 난청 시뮬레이터 개발에 관한 연구)

  • Joo, Sang-Ick;Kang, Hyun-Deok;Song, Young-Rok;Lee, Sang-Min
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.59 no.4
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    • pp.831-840
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    • 2010
  • In this paper, we propose a hearing impairment simulator considering reduced frequency selectivity and asymmetrical auditory filter of the hearing impaired, and we verified the reduced frequency selectivity and asymmetrical auditory filter affected in speech perception through experiments. The reduced frequency selectivity has made embodied by spectral smearing using LPC(linear prediction coding). The shapes of auditory filter are asymmetrical different with each center frequency. Hearing impaired person which has hearing loss was differently changed with that of normal hearing people and it has different value for speech of quality through auditory filter. The experiments confirmed subjective test and objective test. The subjective experiments are composed of 4 kinds of tests: pure tone test, SRT(speech reception threshold) test, and WRS(word recognition score) test without spectral smearing, and WRS test with spectral smearing. The experiment of the hearing impairment simulator was performed from 9 subjects who have normal ears. The amount of spectral smearing was controlled by LPC order. The asymmetrical auditory filter of proposed hearing impairment simulator was simulated and then some tests to estimate the filter's performance objectively were performed. The objective experiment as simulated auditory filter's performance evaluation method used PESQ(perceptual evaluation of speech quality) and LLR(log likelihood ratio) for speech through auditory filter. The processed speech was evaluated objective speech quality and distortion using PESQ and LLR value. When hearing loss processed, PESQ and LLR value have big difference according to asymmetrical auditory filter in hearing impairment simulator.

Comparison of Projection-Based Model Order Reduction for Frequency Responses (주파수응답에 대한 투영기반 모델차수축소법의 비교)

  • Won, Bo Reum;Han, Jeong Sam
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.38 no.9
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    • pp.933-941
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    • 2014
  • This paper provides a comparison between the Krylov subspace method (KSM) and modal truncation method (MTM), which are typical projection-based model order reduction methods. The frequency responses are compared to determine the numerical accuracies and efficiencies. In order to compare the numerical accuracies of the KSM and MTM, the frequency responses and relative errors according to the order of the reduced model and frequency of interest are studied. Subsequently, a numerical examination shows whether a reduced order can be determined automatically with the help of an error convergence indicator. As for the numerical efficiency, the computation time needed to generate the projection matrix and the solution time to perform a frequency response analysis are compared according to the reduced order. A finite element model for a car suspension is considered as an application example of the numerical comparison.

EMI reduction of PWM converter By Binary Switching Frequency Modulation (2진 스위칭 주파수 변조에 의한 PWM 컨버터의 EMI 저감)

  • Jin, In-Su;Park, Seok-Ha;Yang, Kyeong-Rok;Kim, Yang-Mo
    • Proceedings of the KIEE Conference
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    • 1999.07f
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    • pp.2650-2652
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    • 1999
  • To satisfy the demand for small size, light weight. high density power supply, the switching frequency of DC/DC converters has been increased. The PWM control of the conventional SMPS have a switching frequency that a level of the conducted noise spectra contribute to switching frequency band. So the electronic equipment is not only affected from that but is restricted to internal regulation like CISPR, FCC, and VDE. In this paper, we analyzed Bi-FM. Bi-FM is two fixed switching frequency with a modulation frequency. So emission spectrum of Bi-FM control signal is spreaded and spectral power level is reduced. In this paper, we analyze the spectral analysis of Bi-FM control signal and the spectral comparison between the PWM control and Bi-FM control. And we confirm that reduced the spectrum power level through simulation using Pspice and experiment.

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Particular Noise Reduction Method used to Mass Law (질량법칙을 이용한 연료펌프 특정음 저감 방법)

  • 강태식;심재기
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.759-763
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    • 2004
  • High frequency noise of fuel pump has does claimed by user. But high frequency of fuel pump can't heat in the car. But this noise Is an offensive noise outside car. In this study is noise reduction used to mass law. Especially high frequency (for example BPF(blade pass frequency)) is influenced of this law. In detail used to transmission and add to mass according to mass law, reduced particular noise. As a result high frequency is down until can't perception.

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High Frequency Switching and Stability of DC-DC Converters (DC-DC 콘버어터의 고주파화와 안정성)

  • Kim, Hee-Jun
    • Proceedings of the KIEE Conference
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    • 1987.07a
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    • pp.824-827
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    • 1987
  • The miniturization of a DC-DC converter circuit in connection with the stability is investigated in this paper. As both the capacitance of the smoothing capacitor and the inductance of the reactor are reduced by raising the switching frequency, it is known that the stability of the buck converter declines with the switching frequency but the buck-boost converter has a nearly uniform stability. Furthermore, that in the frequency region above a certain switching frequency the buck-boost converter is suitable for the miniturization of circuit is cleared.

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Investigation on spanwise coherence of buffeting forces acting on bridges with bluff body decks

  • Zhou, Qi;Zhu, Ledong;Zhao, Chuangliang;Ren, Pengjie
    • Wind and Structures
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    • v.30 no.2
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    • pp.181-198
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    • 2020
  • In the traditional buffeting response analysis method, the spanwise incomplete correlation of buffeting forces is always assumed to be same as that of the incident wind turbulence and the action of the signature turbulence is ignored. In this paper, three typical bridge decks usually adopted in the real bridge engineering, a single flat box deck, a central slotted box deck and a two-separated paralleled box deck, were employed as the investigated objects. The wind induced pressure on these bridge decks were measured via a series of wind tunnel pressure tests of the sectional models. The influences of the wind speed in the tests, the angle of attack, the turbulence intensity and the characteristic distance were taken into account and discussed. The spanwise root coherence of buffeting forces was also compared with that of the incidence turbulence. The signature turbulence effect on the spanwise root coherence function was decomposed and explained by a new empirical method with a double-variable model. Finally, the formula of a sum of rational fractions that accounted for the signature turbulence effect was proposed in order to fit the results of the spanwise root coherence function. The results show that, the spanwise root coherence of the drag force agrees with that of incidence turbulence in some range of the reduced frequency but disagree in the mostly reduced frequency. The spanwise root coherence of the lift force and the torsional moment is much larger than that of the incidence turbulence. The influences of the wind speed and the angle of attack are slight, and they can be ignored in the wind tunnel test. The spanwise coherence function often involves several narrow peaks due to the signature turbulence effect in the high reduced frequency zone. The spanwise coherence function is related to the spanwise separation distance and the spanwise integral length scales, and the signature turbulence effect is related to the deck-width-related reduced frequency.

Evaluation of Impact Sound Insulation Properties of Light-Framed Floor with Radiant Floor Heating System

  • Nam, Jin-Woo;Park, Joo-Saeng;Lee, Jun-Jae
    • Journal of the Korean Wood Science and Technology
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    • v.30 no.3
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    • pp.75-84
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    • 2002
  • In order to find out impact insulation properties, various types of current radiant floor heating systems and light-framed floors that are used in light-framed residential buildings were evaluated for two types of impact sources at the same time. Sound Pressure Level (SPL) was different from each impact sources for those spectrum patterns and peaks. In case of light-framed floor framework, the excitation position and the assumed effective vibrating area have effects on sound pressure level but it is not considerable, and Normalized SPL was reduced for each frequency by increasing the bending rigidity of joist. The mortar layer in the radiant heating system had relatively high density and high impedance, therefore, it distributed much of the impact power when it was excited, and reduced the Normalized SPL considerably. Nevertheless, Increasing a thickness of mortar layer had little influence on SPL. Ceiling components reduced the sound pressure level about 5~25 dB for each frequency. Namely, it had excellent sound insulation properties in a range from 200 to 4,000 Hz frequency for both heavy and lightweight impact sources. Also, there was a somewhat regular sound insulation pattern for each center frequency. The resilient channel reduced the SPL about 2~11 dB, irrelevant to impact source. Consequently, current radiant floor heating systems which were established in light-framed residential buildings have quite good impact sound insulation properties for both impact sources.

Design of reduced-order controllers in two-degree-of-freedom control systems

  • Nakamura, T.;Obinata, G.;Inooka, H.
    • 제어로봇시스템학회:학술대회논문집
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    • 1988.10b
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    • pp.753-758
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    • 1988
  • In this paper, we propose a new method of designing a reduced-order controller for a linear discrete-time system. Firstly, we study a design problem for a two-degree-of-freedom control system with a feedforward controller. Secondly, in order to obtain a reduced-order controller, frequency-weighted least squares approximation problems are considered. Thirdly, we propose a synthesis procedure of a reduced-order controller. Finally, an example is given to illustrate the effectiveness of this proposed method.

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Investigation of the accuracy of different finite element model reduction techniques

  • Ghannadi, Parsa;Kourehli, Seyed Sina
    • Structural Monitoring and Maintenance
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    • v.5 no.3
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    • pp.417-428
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    • 2018
  • In this paper, various model reduction methods were assessed using a shear frame, plane and space truss structures. Each of the structures is one-dimensional, two-dimensional and three-dimensional, respectively. Three scenarios of poor, better, and the best were considered for each of the structures in which 25%, 40%, and 60% of the total degrees of freedom (DOFs) were measured in each of them, respectively. Natural frequencies of the full and reduced order structures were compared in each of the numerical examples to assess the performance of model reduction methods. Generally, it was found that system equivalent reduction expansion process (SEREP) provides full accuracy in the model reduction in all of the numerical examples and scenarios. Iterated improved reduced system (IIRS) was the second-best, providing acceptable results and lower error in higher modes in comparison to the improved reduced system (IRS) method. Although the Guyan's method has very low levels of accuracy. Structures were classified with the excitation frequency. High-frequency structures compared to low-frequency structures have been poor performance in the model reduction methods (Guyan, IRS, and IIRS).