• Title/Summary/Keyword: Frequency shift

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Noninvasive measuring;Detections of materials and quantities on eddy current testing

  • Obayashi, Koji;Tamura, Muneyoshi;Zhang, X.;Aoyama, T.
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.1555-1560
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    • 2004
  • We made a simplified eddy-current-tester, and observed some materials for the ingredients and mass and locations. The tester detects the current as frequency shifts of a LC-resonance circuit, which are caused by the eddy currents. Using air-wick coil and a multi-piled ceramic capacitor, we made a resonance system whose frequency was 100KHz. The shift quantity is few; so, to detect it, we used a frequency counter, and counted the shift. We can detect 10Hz order's shift.

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Laser doppler velocimetry using the optogalvanic effect of $Co_2$ laser (광전류 효과를 이용한 $Co_2$ 레이저 도플러 속도 측정기)

  • 최종운;김용평;김윤명
    • Korean Journal of Optics and Photonics
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    • v.8 no.6
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    • pp.482-485
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    • 1997
  • A new laser Doppler velocimeter employing a $CO_2$laser has been developed by using its optogalvanic effect. A change in the electric impedance of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, was employed to detect the Doppler frequency shift. A Doppler frequency shift as much as 60 KHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

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Temperature Effect-free Impedance-based Local Damage Detection (온도변화에 자유로운 임피던스 기반 국부 손상검색)

  • Koo, Ki-Young;Park, Seung-Hee;Lee, Jong-Jae;Yun, Chung-Bang
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2007.04a
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    • pp.21-26
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    • 2007
  • This paper presents an impedance-based structural health monitoring (SHM) technique considering temperature effects. The temperature variation results in a significant impedance variation, particularly both horizontal and vertical shifts in the frequency domain, which may lead to erroneous diagnostic results of real structures. A new damage detection strategy has been proposed based on the correlation coefficient (CC) between the reference impedance data and a concurrent impedance data with an effective frequency shift which is defined as the shift causing the maximum correlation. The proposed technique was applied to a lab-sized steel truss bridge member under the temperature varying environment. From an experimental study, it has been demonstrated that a narrow cut inflicted artificially to the steel structure was successfully detected using the proposed SHM strategy.

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Photoacoustic Laser Doppler Velocimetrv Using the Self - mixing Effect of RF - excited CO2 Laser

  • Choi, Jong-Woon;You, Moon-Jong;Choi, Sung-Woong;Woo, Sam-Young
    • Journal of the Optical Society of Korea
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    • v.8 no.4
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    • pp.188-191
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    • 2004
  • A new laser Doppler velocimeter employing a $CO_2$ laser has been developed by using its photoacoustic effect. A change in the pressure of a discharge, induced by mixing of a returned wave with an originally existing wave inside the cavity, is employed to detect the Doppler frequency shift. We found that a Doppler frequency shift as small as 50 kHz was detected, and also a good linear relationship between the velocity and the Doppler frequency shift was obtained.

A Theoretical Study of CO Molecules on Metal Surfaces: Coverage Dependent Properties

  • Sang -H. Park;Hojing Kim
    • Bulletin of the Korean Chemical Society
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    • v.12 no.5
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    • pp.574-582
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    • 1991
  • The CO molecules adsorbed on Ni(111) surface is studied in the cluster approximation employing EH method with self-consistent charge iteration. The effect of CO coverage is simulated by allowing the variation of valence state ionization potentials of each Ni atom in model cluster according to the self-consistent charge iteration method. The CO coverage dependent C-O stretching frequency shift, adsorption site conversion, and metal work function change are attributed to the charge transfer between metal surface and adsorbate. For CO/Ni(111) system, net charge transfer from Ni surface to chemisorbed CO molecules makes surface Ni atoms be more positive with increasing coverage, and lowers Ni surface valence band. This leads to a weaker interaction between metal surface valence band and Co $2{\pi}^{\ast}$ MO, less charge transfer to a single CO molecule, and the bule shift of C-O stretching frequency. Further increase of coverage induces the conversion of 3-fold site CO to lower coordination site CO as well as the blue shift of C-O stretching frequency. This whole process is accompanied by the continuous increase of metal work function.

A Bandpass Filter with a Desired Phase Shift at The Center Frequency (중심주파수에서 원하는 위상변위가 가능한 대역통과 필터)

  • Kim, Hong-Joon
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.61 no.7
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    • pp.998-1000
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    • 2012
  • By cascading RHTL (Right-Handed Transmission Line) and LHTL (Left-Handed Transmission Line), we fabricated a BPF (Band Pass Filter) in which the phase propagation at the pass band center frequency is fixed as we want. We utilized a positive phase propagation of a RHTL which is a form of LPF (Low Pass Filter) and negative phase propagation of LHTL which is a form of HPF (High Pass Filter). Therefore, if RHTL and LHTL are cascaded, a BPF can be constructed and the phase propagation inside the passband is decided by the number of RHTLs and LHTLs. In this paper, we provide a detailed theory related to it and proved the theory with an actual experiment. In the experiment, we fabricated two BPFs with similar passband. One with $90^{\circ}$ phase shift and the other with $-90^{\circ}$ phase shift at the center of passband. The result of simulation and actual experiment agrees well. This proves the suggested theory is correct and feasible.

An Accurate Design Method of Wideband BPF Considering Frequency Dependence of Inverters

  • Youna, Jang;Dal, Ahn
    • Journal of information and communication convergence engineering
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    • v.21 no.1
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    • pp.1-8
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    • 2023
  • This paper presents a design method for a wideband bandpass filter (BPF) which compensates for frequency dependency based on the image admittance and image phase. In the proposed method, new compensation methods for the admittance and phase are integrated with the conventional method. The proposed method improves the frequency shift and reduces the unwanted bandwidth when designing more than 20% of the Fractional Bandwidth (FBW), whereas the conventional method exhibits frequency degradation at only 10% FBW. The proposed design theory was verified by applying it to both lumped elements and distributed lines through circuit simulation and measurements without an optimization process. The measurement results demonstrate improvements in the frequency shift and target bandwidth. In the future, an accurate design method based on frequency dependence can be implemented for the next-generation broadband communication system applications.

Acoustic Analysis of KSR-III Combustion Chamber with Various 5-Blade Baffles under Non-Reacting Condition (5-블레이드 배플이 설치된 로켓엔진 연소실에서의 상온음향 해석)

  • Kim, Hong-Jip;Kim, Seong-Ku;Sohn, Chae-Hoon
    • 한국연소학회:학술대회논문집
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    • 2003.05a
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    • pp.167-171
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    • 2003
  • Acoustic characteristics of baffled combustion chamber to elucidate suppressing effect of baffle on combustion instability are numerically investigated by linear acoustic analysis. A hub-blade baffle of 5 blades is selected as a candidate one and five variants of baffles with various configuration are designed. Resonant-frequency shift and damping factor are analyzed quantitatively as damping parameters. When the hub is located radially at the pressure node, the decrease of resonant frequency and increase of damping factor in 1R mode are dominant. But sub-1T mode is formed within hub, therefore, there would be a possibility of initiating 1T mode in unbaffled region, which would occur another problem. For smaller hub size, four kinds of axial baffle length is selected. As the axial baffle length increases, resonant frequency shift and increase of damping factor of transverse acoustic modes is obtained. Especially, two close acoustic modes such as 1L and 1T could be overlapped for a certain axial length, resulting in extreme increase of damping factor. The present study based on linear acoustic analysis is expected to be a useful confirming tool to predict acoustic field and design a passive control devices such as baffle and acoustic cavity.

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MEASURING THE CORE SHIFT EFFECT IN AGN JETS WITH THE EXTENDED KOREAN VLBI NETWORK

  • JUNG, TAEHYUN;DODSON, RICHARD;HAN, SEOG-TAE;RIOJA, MARIA J.;BYUN, DO-YOUNG;HONMA, MAREKI;STEVENS, JAMIE;VICENTE, PABLO DE;SOHN, BONG WON
    • Journal of The Korean Astronomical Society
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    • v.48 no.5
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    • pp.277-284
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    • 2015
  • We present our efforts for extending the simultaneous multi-frequency receiver system of the Korean Very Long Baseline Interferometry (VLBI) Network (KVN) to global baselines in order to measure the frequency-dependent position shifts in Active Galactic Nuclei (AGN) jets, the so called core shift effect, with an unprecedented accuracy (a few micro-arcseconds). Millimeter VLBI observations with simultaneous multi-frequency receiver systems, like those of the KVN, enable us to explore the innermost regions of AGN and high precision astrometry. Such a system is capable of locating the frequency dependent opacity changes accurately. We have conducted the feasibility test-observations with the interested partners by implementing the KVN-compatible systems. Here we describe the science case for measuring the core shift effect in the AGN jet and report progress and future plans on extending the simultaneous multi-frequency system to global baselines.

The power regulation of a High-Frequency Induction Heating System with time variance load using a neural fuzzy controller (뉴로퍼지 제어기를 이용한 고주파 유도 가열기의 시변부하에 대한 정전력 제어)

  • 장종승;김승철;임영도
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.2 no.2
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    • pp.223-230
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    • 1998
  • This paper describes a phase-shift pulse-width modulation and pulse-frequency modulation series resonant high-frequency inverter using IGBT(Insulated-Gated Bipolar Transistor) for the power control of high-frequency induction heating using neuro-fuzzy, which is practically applied for 20KHz~500KHz induction-heating and melting power supply in industrial fields. The adaptive frequency tracking based phase-shifting PWM(Pulse-Width Modulation) regulation scheme is presented in order to minimize switching losses. The trially-produced breadboards using IGBT are successfully demonstrated and discussed.

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