• 제목/요약/키워드: frequency variation

검색결과 2,865건 처리시간 0.039초

압전기판을 이용한 마이크로스트립 안테나의 대역주파수 조정 (Tunable Microstrip Antennas using Piezoelectric Substrates)

  • 조익현;김영훈;박영;정규원;송준태
    • 대한전기학회논문지:전기물성ㆍ응용부문C
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    • 제49권5호
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    • pp.278-282
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    • 2000
  • This paper investigated that resonant frequencies of microstrip patch antenna were tunable when piezoelectric materals were used as the antenna substrates. The resonant frequencies of the antenna using the piezoelectric substrate were able to be controlled by applied voltage. The frequency variation of the air gap antenna was 16MHz when the voltage variation was 13[KV/cm], and the frequency variation of microstrip patch antenna made of $LiNbO_3$ substrate was 11MHz when voltage variation was 480[V/cm].

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방해물 감지 장치용 캐패시턴스 변화 감지기의 설계 (The Design of Capacitance Variation Detector for the Obstacle Detection System)

  • 김재민;송윤섭;이상렬;김수원
    • 센서학회지
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    • 제13권2호
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    • pp.133-138
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    • 2004
  • Today, the obstacle detection system has massive size and restrictive detection range. To solve these problems, this paper proposes the capacitance variation detector using the variated capacitance value as a result of the obstacle approaching. If obstacle approaches, the capacitance value of capacitance sensor is increased and the operating frequency of oscillator is decreased. Then this changed frequency appears to the output of the mixer that operate down conversion. The capacitance variation detector is produced by Hynix$0.35{\mu}$ CMOS process. In experiment result, the frequency of final output is 6.81 MHz at no obstacle and 31.45 MHz at approaching obstacle. In conclusion, proposed capacitance variation detector has small size, low power consumption and easiness to set up anywhere. So it is expected to substitute the obstacle detector.

Analysis of Stability of PV System using the Eigenvalue according to the Frequency Variation and Requirements of Frequency Protection

  • Seo, Hun-Chul;Kim, Chul-Hwan
    • Journal of Electrical Engineering and Technology
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    • 제7권4호
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    • pp.480-485
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    • 2012
  • Use of photovoltaic (PV) power generation system will become more widespread in the future due to anticipated cost reduction in PV technology. As the capacity of PV systems increases, a variation of power system frequency may prevent the stable output of PV system. However, the standard for the frequency protection of distributed generation in Korea Electric Power Corporation (KEPCO)'s rule does not include the setting of frequency protection. Therefore, this paper analyzes the correlation between the frequency protection requirements and the stability of grid-connected PV system for the adjustable operating setting of frequency protection. The distribution system interconnected with 3 MW PV system is modeled by Matlab/Simulink. The various values of frequency are simulated. For studied cases, the stability of PV system is analyzed. It is concluded that the setting of frequency protection is necessary to consider the stability of PV system.

전원 전압 왜곡과 주파수 변동 시 단상 PWM 컨버터의 전류 제어 (Current Control of a Single-phase PWM Converter under the Distorted Source Voltage and Frequency Condition)

  • 안창헌;김상훈
    • 전력전자학회논문지
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    • 제20권4호
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    • pp.356-362
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    • 2015
  • This paper presents a current control strategy in the synchronous reference frame for a single-phase PWM converter, which ensures sinusoidal input current control under the distorted source voltage and frequency condition. Given that the distorted source voltage distorts the phase angle for PWM converter control, the input current contains the same harmonics as the source voltage. Aside from the distorted voltage, the variation in source frequency reduces the performance of input current control. To achieve sinusoidal input current control under the distorted source voltage and frequency condition, this paper proposes a compensation strategy of current reference with the distortion component extracted from the phase angle and a detection strategy of frequency variation from the output of a synchronous reference frame phase-lock loop. The experimental results confirm the validity of the proposed method under the distorted source voltage and frequency condition.

온도 및 주파수 변화에 의한 $PVF_2$ 필름의 전기적 특성 연구 (A Study on the Electrical Characteristics of $PVF_2$ Film by the Variation of Temperature and Frequency)

  • 김기준;김상진;전동근
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1995년도 하계학술대회 논문집 C
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    • pp.1102-1104
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    • 1995
  • This study presents the results of an investigation on the electrical characteristics of $PVF_2$ film, to be regarded as the excellent piezo and pyroelectricity, using dielectric relaxation technique by the variation of temperature and frequency. As one of the results, we confirmed that crystal form with Infrared absorption and XRD was ${\alpha}$ type and its crystalline was 59[%]. Also, the results of observation conformed to Debye theory for frequency variation of relative permitivity and dielectric relaxation. Especially, we confirmed each constant values in comparision with equation related to diffusion behavior of ion, so we obtained that activation energy was computed 17.25[kcal/mole] from the relation curve with frequency and temperature.

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발성시 음도 및 강도의 변화가 음성분석검사 결과에 미치는 영향 (The Effect of Frequency and Intensity of /a/ Phonation on the Result of Acoustic Analysis)

  • 손영익;윤영선;권중근;추광철
    • 대한후두음성언어의학회지
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    • 제8권1호
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    • pp.12-17
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    • 1997
  • Measuring phonatory stability using MDVP(Multi-dimensional voice program, Kay Elemetrics Corp., NJ, USA) are becoming popular in many Korean clinics and laboratories, yet questions about standardization and reference values have remained. The purpose of present study was to examine the effects of frequency and intensity variation on the results of acoustic analysis related to phonatory stability. Twenty young adults(ten females and ten males) were asked to sustain vowel /a/ for more than 3 seconds under 9 different pitch and loudness conditions. Using MDVP, nine voice samples were analyzed, and jitter percent, fundamental frequency variation, shimmer percent, peak amplitude variation, noise to harmonic ratio, amplitude tremor intensity index, and degree of subharmonics were compared. The results showed that intensity changes can significantly affect various phonatory stability measures, and the lowest perturbation values can be obtained from slightly louder(10dB) phonatory condition than comfortable level phonation.

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주파수와 감쇠비 변화에 강인한 Convolution 입력성형기 설계 (Design of Robust Convolution Input Shaper for the Variation of Frequency and Damping Ratio)

  • 박운환;이재원;임병덕
    • 대한기계학회논문집A
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    • 제26권1호
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    • pp.67-73
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    • 2002
  • The flexibility of long reach manipulators presents a difficult control problem when accurate end-point position is required. Input shaping by convolving system commands with impulse sequences has been shown to be an effective method of reducing residual vibrations in flexible systems. However, existing shapers have been considered robustness fur only frequency uncertainty. However, this paper presents new multi-hump convolution(CV) input shaper that could accommodate with the simultaneous variation of natural frequency and damping ratio. Comparisons with previously proposed input shapers are presented to illustrate the qualities of the new input shaper. These new shapers will be shown to have better robustness fur the variation of frequency and damping ratio.

전압의 주파수 변화를 이용한 동기탈조 검출 알고리즘에 관한 연구 (A Study on the Out-of-Step Detection Algorithm using Voltage Frequency Variation)

  • 소광훈;허정용;김철환
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 2003년도 하계학술대회 논문집 A
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    • pp.335-337
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    • 2003
  • The protection against transient instability and consequent out-of-step condition is a major concern for the utility. The unstable system may cause serious damage to system elements such as generators and transmission lines. Therefore, out-of-step detection is essential to operate a system safely. This paper presents the Out-of-Step detection algorithm using voltage frequency variation. The digital filters based on Discrete Fourier Transforms (DFT) to calculate the frequency of a sinusoid voltage are used, and the generator angle is estimated using the variation of the calculated voltage frequency. The proposed out-of-step algorithm is based on the assessment of a transient stability using equal area criterion. The proposed out-of-step algorithm is verified and tested by using EMTP MODELS.

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Structural detection of variation in Poisson's ratio: Monitoring system for zigzag double walled carbon nanotubes

  • Hussain, Muzamal;Asghar, Sehar;Ayed, Hamdi;Khadimallah, Mohamed A.;Alshoaibi, Adil;Tounsi, Abdelouahed
    • Advances in nano research
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    • 제12권4호
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    • pp.345-352
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    • 2022
  • In this paper, natural frequency curves are presented for three specific end supports considering distinct values of nonlocal parameter. The vibrational behavior of zigzag double walled carbon nanotubes is investigated using wave propagation with nonlocal effect. Frequency spectra of zigzag (12, 0) double walled carbon nanotubes have been analyzed with proposed model. Effects of nonlocal parameters have been fully investigated on the natural frequency against against variation of Poisson's ratio. A slow increase in frequencies against variation of Poisson's ratio also indicates insensitivity of it for suggested nonlocal model. Moreover, decrease in frequencies with increase in nonlocal parameter authenticates the applicability of nonlocal Love shell model. Also the frequency curves for C-F are lower throughout the computation than that of C-C curves.

콤팩트 형광램프용 전자식 안정기의 주파수 제어에 의한 온도보상 (Compensation of temperature characteristics by frequency control of an electronic ballastfor a compact fluorescent lamp)

  • 송상빈;곽재영;여인선
    • 대한전기학회논문지:전기기기및에너지변환시스템부문B
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    • 제48권1호
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    • pp.27-33
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    • 1999
  • Compact fluorescent lamps are very sensitive to the variation of ambient temperature. This paper investigates the temperature characteristics of a 15[W] compact fluorescent lamp, and compensates the variation of light output by frequency control of its electronic ballast. Circuit parameters for the inverter of the electronic ballast are obtained by analyzing the R-L-C equivalent circuit for the inverter and the lamp. The optimum ratio of the two capacitance($C_1$/$C_2$), which are connected with the lamp in series and in parallel, respectively, is determined which consideration of the temperature variation within a range of 10~35[$^{\circ}C$]. As a result a value of 10 for the ratio is obtained at an operating frequency of 57[kHz], and with this value the frequency control works well for temperature compensation. Its validity is verified by investigating light output stabilization characteristics resulting from frequency control of the lamp at various temperatures.

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