• 제목/요약/키워드: Reduced Frequency

검색결과 3,068건 처리시간 0.031초

축소된 유한요소모델을 이용한 하드디스크 구동부의 고유치 및 주파수응답 해석 (Eigenvalue and Frequency Response Analyses of a Hard Disk Drive Actuator Using Reduced Finite Element Models)

  • 한정삼
    • 대한기계학회논문집A
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    • 제31권5호
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    • pp.541-549
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    • 2007
  • In the case of control for mechanical systems, it is highly useful to be able to provide a compact model of the mechanical system to control engineers using the smallest number of state variables, while still providing an accurate model. The reduced mechanical model can then be inserted into the complete system models and used for extended system-level dynamic simulation. In this paper, moment-matching based model order reductions (MOR) using Krylov subspaces, which reduce the number of degrees of freedom of an original finite element model via the Arnoldi process, are presented to study the eigenvalue and frequency response problems of a HDD actuator and suspension system.

CDMA 이동통신시스템에서의 저속 멀티미디어 서비스를 위한 호 수락 방식 (Call admission scheme for low speed multimedia services in CDMA mobile communication systems)

  • 최경수;권수근;전형구;유영갑
    • 전자공학회논문지S
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    • 제35S권7호
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    • pp.14-21
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    • 1998
  • In providing with low speed multimedia services, a call blocking rate is greatly varied according to the transmission rate, and thereofr, the call blocking rate is remarkably increased for a service having a high transmission rate compared to a service having a low transmission rate. This paper presents three methods of solving this problem; Packing Scheme in which available channels distributed to each frequency channel are concentrated on one frequency channel and a call having a high transmission rate is assigned to the frequency channel; Queuing Scheme in which queuing is assigned to calls under service is temporarily reduced and a call having a high transmission rate is allowed. The result of performance analysis for 13 Kbps and 128 Kbps service through computer simulation showed that the call blocking rate for 128 Kbpx service was reduced by tens of percent accoring to loads.

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3상 절연형 변압기를 이용한 다중레벨 (Multi-level Inverter Using 3-Phase isolated Transformers)

  • 이화춘;송성근;박성준;김광헌
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2007년도 제38회 하계학술대회
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    • pp.1134-1135
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    • 2007
  • In this paper, we proposed the isolated multi-level inverter using 3-phase transformers. It makes possible to use a single DC power source due to employing low frequency transformers. In this inverter, the number of transformer could be reduced comparing with an exiting 3-phase multi-level inverter using single phase transformer. Also, using phase angle control method with switching frequency equal to output fundamental frequency, harmonics component of output voltage and switching losses can be reduced. Finally, we made a prototype inverter to clarify the proposed electric circuit and reasonableness of control signal.

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Cooling Tower System 진동 진단 (The Diagnosis of Cooling Tower System)

  • 이선휘
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2007년도 추계학술대회논문집
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    • pp.1090-1094
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    • 2007
  • The aim of this study is to estimate the cause of Cooling Tower vibration and eliminate the faults of fan with high vibration in spite of overhaul. The cause of high vibration was that the natural frequency of fan blade coincide with second blade pass frequency. To achieve reduction of Cooling Tower vibration, change motor speed from 1784rpm to 1714rpm, and then the vibration has reduced conspicuously.

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DC - DC콘버어터의 소형화와 안정성 (A Miniturization and Stability of DC-to-DC Converters)

  • Kim, Hee-Jun
    • 대한전기학회논문지
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    • 제37권8호
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    • pp.528-533
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    • 1988
  • The miniturization of a DC-to-DC converter 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 rasing 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 the buck-boost converter is suitable for the miniturization of circuit is cleared in the high frequency region above a certain switching frequency.

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Ge-Si-Te 기억소자의 온도 및 주파수영향 (The Effect of Temperature and Frequency on Ge-Si-Te Memory Devices)

  • 박창엽;정홍배
    • 전기의세계
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    • 제24권5호
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    • pp.91-96
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    • 1975
  • In this paper, with a view to study the impurity effect, Ge-Si-Te memory devices are investigated experimentally about the dependence of temperature and frequency. Conductivity depends upon temperature and frequency and it is some-what influenced by heat treatment. With increasing frequency, conductivity has a tendency to be independent of temperature. We found that switching time and threshold voltage are reduced by it.

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견인전동기의 정격운전점 선정에 따른 전동기의 무게와 견인력 비교 (Comparison of weight and tractive effort of traction motor by choosing different rated operating point)

  • 박창순
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1997년도 하계학술대회 논문집 A
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    • pp.361-363
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    • 1997
  • Rated frequency of inverter driven induction motor for a traction system can be chosen lower or higher. Traction motor with higher rated frequency can be lighter than the lower. But the maximum torque must be checked, because it is very important for starting and acceleration and it should be reduced with high frequency operation. In the paper, two motors with different rated frequency are designed and compared.

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선형 보간법을 이용한 시간과 주파수 조합영역에서의 피치 추정 방법 (Pitch Estimation Method in an Integrated Time and Frequency Domain by Applying Linear Interpolation)

  • 김기출;박성주;이석필;김무영
    • 대한전자공학회논문지SP
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    • 제47권5호
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    • pp.100-108
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    • 2010
  • 본 논문은 피치를 추출하는 방법으로 자기상관을 이용하였다. 시간과 주파수 영역의 자기상관은 서로 다른 특성을 가지고 있으며, 각각 피치주기와 기본주파수에 대응된다. 본 논문에서는 시간과 주파수 영역에서의 자기상관을 결합하는 방법을 이용하였다. 이 방법은 자기상관에서 발생하는 피치 doubling과 having 에러를 크게 개선시킬 수 있었다. 하지만, 시간과 주파수 영역에서 유성음의 주기적 특성인 피치주기와 기본주파수는 서로 역수 관계이며, 특히 기본주파수의 에러는 FFT의 분해능에 의하여 발생된다. 이러한 영향을 줄이기 위하여 시간 영역과 주파수 영역에서의 자기상관 결합에 보간법을 적용함으로써 피치 검출율을 향상 시킬 수 있었다. 자기상관을 결합할 때 시간영역에서 찾은 피치후보들에 대해서만 주파수영역의 자기상관을 구함으로써 계산량은 감축될 수 있었다. 또한, 선형보간을 이용하여 기존방법 보다 FFT 계수를 8배 줄일 수 있었다. 그 결과, FFT 연산량과 주파수영역의 자기상관 계산량을 크게 감축하여 기존 방법 대비 알고리즘 처리시간을 약 9.5배 줄일 수 있었다.

합곡(合谷)(LI4)의 고주파 온침 자극이 흰쥐의 족과(足踝) 관절염(關節炎)에 미치는 효과 (Effects of High Frequency Warm Needling of LI4 Acupoint on the Carrageenan-induced Arthritis in Rats)

  • 박상연;권오상;최원종;김재효;김경식;손인철;안성훈
    • Korean Journal of Acupuncture
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    • 제26권2호
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    • pp.61-74
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    • 2009
  • Objectives: The warm needling technique is a method which combines the effects of acupuncture with those of moxibustion. The purpose of this study was to find the stimulus effects of a high frequency warm needling device when stimulating acupoint $LI_4$ on the carrageenan-induced arthritis. Methods: This study was to observe the effects to edema reaction, WBF(weight bearing force), NO concentration, nNOS expression after the electro high frequency stimulus of high frequency warm needling device on LI4 with insulated acupuncture needle. Results: The effect of the high frequency warm needling device is to rise up the temperature in proportion to the current intensity. After stimulating on the acupoint $LI_4$ of the carrageenan-induced arthritis in rats with the high frequency warm needling device, it significantly reduced edema in the rat's foot. In addition, WBF, NO concentration of spinal cord (nmol/mg), and nNOS relative expression were reduced. Conclusions: The above results support the idea that stimulus by the high frequency warm needling device on $LI_4$ produces a potent analgesic effect in the arthritis pain model of the rat. Moreover, stimulus by the high frequency warm needling device modulates endogenous NO through the suppression of nNOS protein expression.

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백래시 크기 변화 감지를 위한 주파수응답특성의 활용 (The Utilization of Frequency Response Characteristic for the Detection of Change of Backlash Magnitude)

  • 백주현
    • 한국시뮬레이션학회논문지
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    • 제24권3호
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    • pp.45-54
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    • 2015
  • 본 논문에서는 기어감속 서보시스템의 모터입력전압 크기를 적절히 감소시키면 모터입력전압에 대한 모터각속도에서 나타나는 주파수응답특성에 미치는 백래시 영향이 매우 커지게 됨을 보여 주였다. 또한 주파수응답선도에서 나타나는 반공진 및 공진주파수 변화량을 관찰하여 기어감속 서보시스템 내 기어 백래시 변화를 감지할 수 있는 방법의 유용성을 이론적, 시뮬레이션 및 실험적으로 검증하였다. 반공진주파수 변화가 공진주파수 변화 보다 안정적으로 계측될 수 있으므로 백래시 크기 변화감지 시 반공진주파수 변화량 관찰이 좀 더 유용하며, 공진주파수는 모터입력전압을 충분히 감속시켜야 급격한 변화를 관찰할 수 있음을 보여주었다. 본 연구는 기어감속 서보시스템 내 백래시 크기 변화 감지에 대한 향후 연구에 있어서 유용하게 사용될 수 있을 것이라고 생각한다.