• Title/Summary/Keyword: frequency characteristics

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Determination of Operating frequency its Design of the Self-exited electronic Ballast (자려식 전자안정기의 동작 주파수 결정과 설계)

  • 박종연;전경준;한재현
    • Proceedings of the IEEK Conference
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    • 2002.06e
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    • pp.315-318
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    • 2002
  • In this paper, we have studied about the determination methode of the operating frequency, and the design technique for the self-exited electronic ballast. Because we use the saturation characteristics of the ferrite core, the variation of the B/H curve characteristics for the selected core in the most important factor for the stabilization. Although it is impossible to fix the operation frequency, the self-exited electronic ballast is widely used because of its cost and the simplicity of its structure.

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Analysis of Speech Signals Depending on the Microphone and Micorphone Distance

  • Son, Jong-Mok
    • The Journal of the Acoustical Society of Korea
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    • v.17 no.4E
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    • pp.41-47
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    • 1998
  • Microphone is the first link in the speech recognition system. Depending on its type and mounting position, the microphone can significantly distort the spectrum and affect the performance of the speech recognition system. In this paper, characteristics of the speech signal for different microphones and microphone distances are investigated both in time and frequency domains. In the time domain analysis, the average signal-to-noise ration is measure ration is measured for the database we collected depending on the microphones and microphone distances. Mel-frequency spectral coefficients and mel-frequency cepstrum are computed to examine the spectral characteristics. Analysis results are discussed with our findings, and the result of recognition experiments is given.

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Design of Broadband Electromagnetic Wave Absorber with Square Ferrite Cylinders in the Second Layer (초광대역특성을 갖는 정방형 페라이트 기둥구조의 전파흡수체 설계법)

  • 김동일;전상엽;이창우;정세모
    • Journal of the Korean Institute of Navigation
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    • v.19 no.2
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    • pp.99-106
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    • 1995
  • A wide band design method of an electromagnetic wave absorber with square ferrite cylinders in the second layer, which has very wide band frequency characteristics, is proposed and discussed. A theoretical model using the equivalent material constants method is also evaluated and proposed for its accuracy by comparison with Hashin-Shtrikman formulas. Based on the developed model, wide band electromagnetic wave absorbers with excellent reflective frequency characteristics in the frequency range of 30MHz to 3, 690MHz were designed.

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Design of Broad Band Electromagnetic Wave Absorbers with Cross-Shaped Ferrite. (십자형 광대역 페라이트 전자파흡수체의 설계)

  • 김동일;전상엽;정세모
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • 1996.09a
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    • pp.125-134
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    • 1996
  • A design method of double layered electromagnetic wave absorbers with cross-shaped ferrite prominence in the second layer which has broad band frequency characteristics was proposed. The broad band electromagnetic wave absorber can be designed under some approximations by the theoretical model using the equivalent material constants method for the second layer. Based on the developed model broad band electromagnetic wave absorbers with excellent reflectivity frequency characteristics in the frequency range of 30MHz to 3,990MHz were designed.

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Analysis of Frequency Hopping Signals using Wavelet Transform-Based Scalogram (Wavelet 변환기저 Scalogram을 이용한 주파수 도약신호 분석)

  • 박재오;이정재
    • Proceedings of the Korea Institute of Convergence Signal Processing
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    • 2000.08a
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    • pp.45-48
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    • 2000
  • In this paper algorithms of frequency hopping sequences generation such as Lempel-Greenberger, optimum Lempel-Greenberger and Kumar sequences for spread spectrum communications are described. Using the scalogram based on wavelet transform, time-frequency characteristics of frequency hopped signals corresponding to the considered hopping sequences are analyzed.

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The change of spray characteristics on hydraulic acoustic wave influence and prediction of low combustion instability (수력파동에 의한 분무변화 및 저주파 연소불안정에의 영향 예측)

  • Kim, Tae-Kyun;Lee, Sang-Seung;Yoon, Woong-Sup
    • 한국연소학회:학술대회논문집
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    • 2004.11a
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    • pp.152-160
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    • 2004
  • Studies to investigate the influence on hydraulic acoustic wave were conducted using pressure swirl atomizer under making frequency range from 0 to 60Hz using water as a propellant. Pressure oscillation from hydraulic sources gives a strong influences on atomization and mixing processes. The ability to drive these low frequency pressure oscillations makes spray characteristics changeable. The effect of pressure perturbation and its spray characteristics showed that low injector pressure with pressure pulsation gives more significantly than high injector pressure with pressure perturbation in SMD, spray cone angle, breakup length. Moreover, this data could be used for prediction of low combustion instability getting G factor.

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Effects of Mixture Flow and Ignition Characteristics on the Engine Performance (혼합기의 유동과 점화특성이 기관성능에 미치는 영향)

  • 이중순;김진영;정성식;하종률;배충식
    • Transactions of the Korean Society of Automotive Engineers
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    • v.6 no.5
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    • pp.37-44
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    • 1998
  • Lean burn combustion is an important concept for improving the fuel consumption and exhaust emissions. However, the lean burning is associated with increased cycle-to-cycle combustion variations due to the ignition instabilities and redu- ced flame propagation rates. Engine stability under lean mixture conditions could be improved by increasing flame speed through enhanced flow characteristics and by securing ignitability with improvement of ignition systems. The effects of flow motion and ignition characteristics on the combustion performances were investigated in a 4-valve SI engine. Flow motions of tumble-swirl were varied with a swirl control valve attached at the inlet ports, while ignition energy and its distribution were controlled in a high -frequency ignition system by changing spark duration and spark frequency. The improvement of lean burn performance by the optimum flow motion and ignition characteristics is discussed.

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A Study on Wear Characteristics of Surface-Hardened SM53C Steel by High Frequency Induction (표면경화된 SM53C강의 마모특성에 관한 연구)

  • Park, Won-Jo;Song, Tae-Hoon;Hur, Chung-Weon;Song, Hong-Tae
    • Journal of the Korean Society of Safety
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    • v.23 no.1
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    • pp.18-23
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    • 2008
  • The abnormal wears such as unfair-wear and early-wear happen in the earn shaft surface of automobiles. These abnormal wears make efficiency of engines decrease and threaten safety of automobiles. The wear characteristics of the cam shaft is very important for the automobile safety. The cam shaft is surface-hardened by the high frequency induction. In this study, we investigated the wear characteristics of the hardened surface with a SM53C steel. The wear characteristics is examined according to the hardened depth and the amount of load.

A Small Ultra-Wideband (UWB) Antenna with Combination of Electric-Magnetic Radiators (전기-자기계 방사체 결합형 소형 초광대역 안테나)

  • Kim, Yong-Jin;Jung, Chang-Won;Kim, Young-Bong;Kwon, Do-Hoon
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.1
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    • pp.33-37
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    • 2009
  • In this paper, a printed small Ultra-Wideband (UWB) antenna with directive radiation characteristics based on combination of electric-magnetic radiators is presented. The combinations of the electric and magnetic type antennas result in the directive radiation patterns for all observed UWB frequency band. Simple combination of dipole antenna and loop antenna is also presented to show that proper configuration of electric radiator and magnetic radiator can produces directive radiation characteristics. The target frequency is from 3.1 GHz to 10.6 GHz with size of $15\;mm{\times}31\;mm$. A proto-type of the combined antenna is simulated, fabricated and measured. Simulation and experimental results of input impedance and gain characteristics of the proposed antenna are presented. There are good agreements between the simulated and measured VSWR curves. Also, the results show the directive radiation characteristics with small antenna form factor over the target frequency range.

A Study on Low-Pass Filter using All-Pass Filter of Parallel Structure (병렬 구조의 올패스 필터를 사용한 LPF에 관한 연구)

  • 김승영;김남호
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.5 no.3
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    • pp.533-541
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    • 2001
  • In this paper, we proposed lowpass filter using all-pass sums of flat delay characteristics. this filter consisted of all-pass filter of parallel structure, the general analog filter is impossible to adjust the phase and the delay, using the Proposed filter, it has advantage to adjust them. And, we compared and analyzed this filter with passband width and magnitude characteristics, and the relation of group delay characteristics and cut-off frequency. Also, in order to obtain desired cut-off frequency, forming the weighing, we obtained desired cut-off frequency and group delay characteristics.

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