• Title, Summary, Keyword: Resonant Frequency Ratio

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Analysis and Modelling of Vibration Performance for Multi-layered Corrugated Structure

  • Kim, Jin Nyul;Sim, Jae Min;Park, Min Jung;Kim, Ghi Seok;Kim, Jongsoon;Park, Jong Min
    • Journal of Biosystems Engineering
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    • v.38 no.4
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    • pp.327-334
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    • 2013
  • Purpose: The purpose of this study was to analyze for resonant frequency, vibration transmissibility and damping ratio of multi-layered corrugated structures using a random vibration test. Methods: The random vibration test was performed by the ASTM D4728 specifications using two paperboards (S120, K180) and two types of flutes (A/F, B/F). Damping ratio of the multi-layered corrugated structures was estimated using a theoretical equation derived from the measured resonant frequency and transmissibility. Results: The resonant frequency and vibration transmissibility of the multi-layered corrugated structures of K180 and B-flute were higher than those of S120 and A-flute, respectively; however, the damping ratio of each sample had the opposite tendency. The resonant frequency was inversely proportional to the sample thickness and static stress; vibration transmissibility and damping ratio were not correlated with sample thickness and static stress. In addition, we developed a mathematical model of the resonant frequency with variables of sample thickness and static stress. Conclusions: Results of this study can be useful for environment-friendly and optimal packaging design since vibration has been a key factor in cushioning packaging design.

Ratio of predicted and observed natural frequency of finite sand stratum

  • Prathap Kumar, M.T.;Ramesh, H.N.;Raghavendra Rao, M.V.;Raghunandan, M.E.
    • Geomechanics and Engineering
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    • v.1 no.3
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    • pp.219-239
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    • 2009
  • Vertical vibration tests were conducted using model footings of different size and mass resting on the surface of finite sand layer with different height to width ratios and underlain by either rigid concrete base or natural red-earth base. A comparative study of the ratio of predicted and observed natural frequency ratio of the finite sand stratum was made using the calculated values of equivalent stiffness suggested by Gazetas (1983) and Baidya and Muralikrishna (2001). Comparison of results between model footings resting on finite sand stratum underlain by the rigid concrete base and the natural red-earth base showed that, the presence of a finite base of higher rigidity increases the resonant frequency significantly. With increase in H/B ratio beyond 2.0, the influence of both the rigid concrete and natural red-earth base decreases. Increase in the contact area of the footing increases the resonant frequency of the model footings resting on finite sand stratum underlain by both the types of finite bases. Both the predicted and the observed resonant frequency ratio decreases with increase in force rating and height to width ratio for a given series of model footing.

A Study on the Digital Control of Single Phase Induction Motor Driven by the Full Bridge Resonant Inverter(I) - The Current Characteristics of Full - bridge Resonant Inverter at Low Frequency - (전브리지 공진형 인버터에 의한 단상 유도전동기의 디지탈제어에 관한 연구(I) -저주파수에서 전브리지 공진형 이버터의 전류특성에 대하여-)

  • 노영오;박진길
    • Journal of the Korean Society of Marine Engineering
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    • v.17 no.3
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    • pp.70-79
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    • 1993
  • The application of A.C. motor to servo system is rapidly increased according to the recent advance of power electronics and digital control techniques. The induction motor which has a simple structure and needs less maintenance is used in the industrial field for the variable speed and position control recently. In this paper, the current characteristic of the full-bridge resonant inverter is studied by comparing with the computer simulation and the laboratory experiment when the ratio of forced frequency to the natural frequency and the ratio of conduction time to the period at the given frequency is changed. And then, the full-bridge resonant inverter is applied to the speed control of single phase induction motor.

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Dielectric, Piezoelectric Properties and Temperature Stability of Resonant Frequency in PSN-PMN-PZT Ceramics (PSN-PMN-PZT 세라믹스의 유전 및 압전 특성과 공진 주파수의 온도안정성)

  • 윤광희;류주현;민석규;이명수;서성재
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.391-395
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    • 2000
  • In this study, the temperature coefficient of resonant frequency(TC $F_{r}$), dielectric and piezoelectric properties of Pb[(S $b_{1}$2/N $b_{1}$2/)$_{0.0035}$-(M $n_{1}$3/N $b_{2}$3/)$_{0.0065}$-(Z $r_{x}$ $Ti_{1-x}$ )$_{0.90}$] $O_3$ceramics is investigated with Zr/Ti ratio. The dielectric constant and electromechanical coupling factor( $k_{p}$) showed the highest values of 1257, 0.562 respectively when the Zr/Ti ratio is 49.5/50.5. The mechanical quality factor( $Q_{m}$) is the lowest value of 713 when the Zr/Ti ratio is 49.5/50.5, and increased with the decrease of the Zr/Ti ratio. The temperature coefficient of resonant frequency(TC $F_{r}$) change abruptly at the morphotropic phase boundary(MPB), which is between the rhombohedral phase with highly negative TC $F_{r}$ of -106ppm/$^{\circ}C$ and the tetragonal phase with highly positive TC $F_{r}$ of +64pp $m^{\circ}C$ as Zr/Ti ratio changes from 50/50 to 49.5/50.5.50.5..5.50.5.5.

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Analysis and Design of a Multi-resonant Converter with a Wide Output Voltage Range for EV Charger Applications

  • Sun, Wenjin;Jin, Xiang;Zhang, Li;Hu, Haibing;Xing, Yan
    • Journal of Power Electronics
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    • v.17 no.4
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    • pp.849-859
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    • 2017
  • This paper illustrates the analysis and design of a multi-resonant converter applied to an electric vehicle (EV) charger. Thanks to the notch resonant characteristic, the multi-resonant converter achieve soft switching and operate with a narrowed switching frequency range even with a wide output voltage range. These advantages make it suitable for battery charging applications. With two more resonant elements, the design of the chosen converter is more complex than the conventional LLC resonant converter. However, there is not a distinct design outline for the multi-resonant converters in existing articles. According to the analysis in this paper, the normalized notch frequency $f_{r2n}$ and the second series resonant frequency $f_{r3n}$ are more sensitive to the notch capacitor ratio q than the notch inductor ratio k. Then resonant capacitors should be well-designed before the other resonant elements. The peak gain of the converter depends mainly on the magnetizing inductor ratio $L_n$ and the normalized load Q. And it requires a smaller $L_n$ and Q to provide a sufficient voltage gain $M_{max}$ at ($V_{o\_max}$, $P_{o\_max}$). However, the primary current increases with $(L_nQ)^{-1}$, and results in a low efficiency. Then a detailed design procedure for the multi-resonant converter has been provided. A 3.3kW prototype with an output voltage range of 50V to 500V dc and a peak efficiency of 97.3 % is built to verify the design and effectiveness of the converter.

Backlash Estimation of a Seeker Gimbal with Two-Stage Gear Reducers (2 단 기어 감속기를 갖는 탐색기 짐발의 백래시 추정)

  • Baek, Joo-Hyun;Hong, Sung-Min;Kwak, Yoon-Keun;Kim, Soo-Hyun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.26 no.10
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    • pp.2130-2141
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    • 2002
  • A unique technique to estimate the magnitude or contribution ratio of each stage backlash in a system with a two-stage gear reducer is proposed. The concept to estimate the magnitude or contribution ratio of each stage backlash is based on the change of frequency response characteristic, in particular, the change of anti-resonant frequency and resonant frequency, due to the change of each stage backlash magnitude, even though the total backlash magnitude of a system with a two-stage gear reducer is constant. The validity of the technique is verified in a seeker gimbal and satisfactory results are obtained. It is thought that the diagnosis and maintenance of the manufacturing machines and systems with two-stage gear reducers will become more efficient and economical by virtue of the proposed technique.

Analysis of the Face-Mounted PZT Piezoelectric Transformer (적층형 PZT 압전변합기의 특성해석)

  • 박창엽;한득영
    • The Transactions of the Korean Institute of Electrical Engineers
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    • v.33 no.9
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    • pp.355-363
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    • 1984
  • An ideal and an approximate eauivalent circuits of a face-mounted PZT piezoelectric transformer were introduced from the equivalent circuit taking into account the mechanical loss of a PZT piezoelectric disk vibrator. And several expressions for the resonant frequencies and for the voltage ratios were derived from the approximate circuit of the transformer. From the experiments on the vltage ratios regarding the frequency variation without load and on the load variation at resonant frequency, it was found that the voltage ratio increased with the increase of load resistance and decreased sharply with the slight deviation from the resonant frequency, and that no-load voltage ratio at the resonant frequency was proportional to the product of the mechanical quality factor and the square of the electromechanical coupling factor of the vibrator.

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Resonance Characteristics of a 1-3 Piezoelectric Composite Transducer of Circular Arch Shape (원호형 1-3 압전 복합재 변환기의 공진 특성)

  • Kim, Dae-Seung;Kim, Jin-Oh
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.19 no.3
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    • pp.301-312
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    • 2009
  • This paper presents a theoretical approach to calculate the resonant frequency of a thickness vibration mode in the radial direction for a 1-3 piezoelectric composite transducer of circular arch shape. For the composite transducer composed of a piezoelectric ceramic and a polymer, vibration parameters were derived according to the volume ratio of a ceramic, and a vibration characteristic equation was derived from the piezoelectric governing equations with adequate boundary conditions. The fundamental resonant frequencies were calculated numerically and verified by comparing them with those obtained from the finite element analysis and the experiment. The volume ratio and the thickness are more substantial than the curvature radius to determine the fundamental resonant characteristics, and the fundamental resonant frequency becomes higher for the larger volume ratio of the piezoelectric ceramic and for the smaller thickness.

Analytical Surge Behaviors in Systems of a Single-stage Axial Flow Compressor and Flow-paths

  • Yamaguchi, Nobuyuki
    • International Journal of Fluid Machinery and Systems
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    • v.9 no.1
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    • pp.1-16
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    • 2016
  • Behaviors of surges appearing near the stall stagnation boundaries in various fashions in systems of a single-stage compressor and flow-path systems were studied analytically and were tried to put to order. Deep surges, which enclose the stall point in the pressure-mass flow plane, tend to have either near-resonant surge frequencies or subharmonic ones. The subharmonic surge is a multiple-loop one containing, for example, in a (1/2) subharmonic one, a deep surge loop and a mild surge loop, the latter of which does not enclose the stall point, staying only within the stalled zone. Both loops have nearly equal time periods, respectively, resulting in a (1/2) subharmonic surge frequency as a whole. The subharmonic surges are found to appear in a narrow zone neighboring the stall stagnation boundary. In other words, they tend to appear in the final stage of the stall stagnation process. It should be emphasized further that the stall stagnation initiates fundamentally at the situation where a volume-modified reduced resonant-surge frequency becomes coincident with that for the stagnation boundary conditions, where the reduced frequency is defined by the acoustical resonance frequency in the flow-path system, the delivery flow-path length and the compressor tip speed, modified by the sectional area ratio and the effect of the stalling pressure ratio. The real surge frequency turns from the resonant frequency to either near-resonant one or subharmonic one, and finally to stagnation condition, for the large-amplitude conditions, caused by the non-linear self-excitation mechanism of the surge.

Design of Miniaturized Dual-Band Artificial Magnetic Conductor with Easy Control of Second/First Resonant Frequency Ratio

  • Ta, Son Xuat;Park, Ikmo
    • Journal of electromagnetic engineering and science
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    • v.13 no.2
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    • pp.104-112
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    • 2013
  • A novel miniaturized artificial magnetic conductor (AMC) is proposed for dual-band operation. An AMC unit cell that employs four slots in the metallic patch is used to achieve miniaturization as well as easy control of the second/first resonant frequency ratio, which can be varied from 1.5 to 3.26 by simply changing the slot shape for a given metallic patch size. A dual-band antenna composed of a wideband monopole suspended over the proposed AMC surface is designed and tested to validate this approach. The measurements result in a satisfactory and good matching condition for the dual-band antenna.