• Title/Summary/Keyword: Excitation Frequency

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A Study on the Relationship between Flexural Beam Shape and Transport Characteristics for the Ultrasonic Transport Systems (초음파 이송 시스템에서 Flexural Beam의 형태 변화와 물체 이송과의 관계에 대한 연구)

  • 정상화;신병수
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.10a
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    • pp.25-29
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the object transport system using the excitation of ultrasonic wave is proposed. The experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The relationship of transporting speed according to the change of flexural beam shape is verified and the system performance for practical use is evaluated.

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A Study on Object Transport System Using 2-Mode Ultrasonic Wave (2-Mode 초음파를 이용한 물체 이송에 관한 연구)

  • 정상화;김택현;신병수;차경래
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2003.06a
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    • pp.1170-1173
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    • 2003
  • In the semiconductor and the optical industry a new transport system which can replace the common system is required. The common systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches, the optical lens. The ultrasonic wave driven system solve these problem. In this paper the object transport system using the excitation of ultrasonic wave is proposed. the experiments for finding the optimal excitation frequency, finding phase-difference between two ultrasonic wave generators are performed. The effect of transporting speed according to the change of amplification voltage is verified. In addition, the system performance for actual use is evaluated

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Enhanced Maximum Voiced Frequency Estimation Scheme for HTS Using Two-Band Excitation Model

  • Park, Jihoon;Hahn, Minsoo
    • ETRI Journal
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    • v.37 no.6
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    • pp.1211-1219
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    • 2015
  • In a hidden Markov model-based speech synthesis system using a two-band excitation model, a maximum voiced frequency (MVF) is the most important feature as an excitation parameter because the synthetic speech quality depends on the MVF. This paper proposes an enhanced MVF estimation scheme based on a peak picking method. In the proposed scheme, both local peaks and peak lobes are picked from the spectrum of a linear predictive residual signal. The average of the normalized distances of local peaks and peak lobes is calculated and utilized as a feature to estimate an MVF. Experimental results of both objective and subjective tests show that the proposed scheme improves the synthetic speech quality compared with that of a conventional one in a mobile device as well as a PC environment.

A study on 2-D wake flow control by acoustic excitation (음파 가진을 이용한 2차원 웨이크 유동 제어에 관한 연구)

  • Kim, Hyeon-Jin;Kim, Jae-Ho;Kim, Myeong-Gyun
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.6
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    • pp.860-873
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    • 1998
  • In a low speed open-type wind tunnel, a group of parallel wakes downstream of two dimensional grid model consisting of several circular cylinders were experimentally investigated to study the response of the wake flows to the acoustic excitation, in hoping to promote the understanding of the underlying mechanism behind the gross flow change due to artificial excitation. In the unexcited wake flows, the development of the individual wakes behind cylinders was almost uniform for the ratio of the spacing to the cylinder diameter of s/d.geq.1.5. For smaller s/d, however, the jet streams issued through the gaps between the cylinders became biased in one side and the cylinders had wakes of different sizes. At s/d=1.25, the gap flow directions change in time, leading to unstable wake patterns. Further reduction in s/d made this unstable flip-flopping of the jets stable. The most effective excitation frequency was found to be in the Strouhal number range of St=0.5-0.6. This frequency was related to the vortex shedding. At s/d=1.75, the excitation frequency was 2 or 4 times the vortex shedding frequency. When the flow was excited at this frequency, the vortex sheddings were energized, and pairings between neighboring vortices were generated. Also, the merging process between individual wakes was accelerated. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. The unstable and unbalanced wake patterns at s/d=2.15 were made stable and balanced. For smaller spacing of s/d .leq,1.0, the acoustic excitation became less effective in controlling the flow.

Design of a Vibration-Powered Piezoelectric Energy-Harvesting Module by Considering Variations in Excitation Frequency (외부 가진 가변 주파수를 고려한 압전 진동 에너지 수확 모듈의 설계)

  • Kim, Jae-Eun
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.5
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    • pp.637-644
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    • 2010
  • A vibration-powered piezoelectric energy harvester yields the maximum power output when its resonant frequency is made equal to the excitation frequency; however, the power output is dramatically decreased when the energy harvester is operated at off-resonance frequency. It has been observed that the resonant frequency of a piezoelectric energy harvester may change with time and that the excitation frequency often varies when the energy harvester is used in real applications. Hence, in this study, we propose a piezoelectric energy-harvesting module that is suitable for excitations in a certain frequency range. The frequency characteristics of the electrical output of the module are studied through analysis and experiment. A simple frequency tuning method is also suggested for the proposed energy-harvesting module; in this method, frequency tuning is achieved by changing the electrical connections between the constituent energy-harvesting units of the module.

Analysis of Acoustic Excitation Effect on Lean Blowoff in Premixed Bluff Body Flames (예혼합 보염기 화염의 희박 화염 날림에 음향 가진이 미치는 영향에 관한 연구)

  • Jeong, Chanyeong;Hwang, Jeongjae;Yoon, Jisu;Kim, Taesung;Shin, Jeoik;Yoon, Youngbin
    • 한국연소학회:학술대회논문집
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    • 2014.11a
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    • pp.149-151
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    • 2014
  • The blowoff phenomenon was experimentally investigated in a ducted combustor according to the acoustic excitation. The blowoff equivalence ratio rapidly increases at specific acoustic excitation frequencies. A resonance phenomenon occurs when the excitation frequency approaches the harmonic frequency of the combustor. The resonance increases the velocity fluctuation in the combustor and the infiltration velocity of the unburned gas in the shear layer. Consequently, the mixture velocity exceeds the burning velocity and the blowoff occurs at the higher equivalence ratio.

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Stochastic Responses of a Spring-Pendulum System under Narrow Band Random Excitation (협대역 불규칙가진력을 받는 탄성진자계의 확률적 응답특성)

  • Cho, Duk-Sang
    • Journal of the Korean Society of Industry Convergence
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    • v.4 no.2
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    • pp.133-139
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    • 2001
  • The nonlinear response statistics of an spring-pendulum system with internal resonance under narrow band random excitation is investigated analytically- The center frequency of the filtered excitation is selected to be close to natural frequency of directly excited spring mode. The Fokker-Planck equations is used to generate a general first-order differential equation in the dynamic moment of response coordinates. By means of the Gaussian closure method the dynamic moment equations for the random responses of the system are reduced to a system of autonomous ordinary differential equations. The nonlinear phenomena, such as jump and multiple solutions, under narrow band random excitation were found by Gaussian closure method.

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Probabilistic study of the influence of ground motion variables on response spectra

  • Yazdani, Azad;Takada, Tsuyoshi
    • Structural Engineering and Mechanics
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    • v.39 no.6
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    • pp.877-893
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    • 2011
  • Response spectra of earthquake ground motions are important in the earthquake-resistant design and reliability analysis of structures. The formulation of the response spectrum in the frequency domain efficiently computes and evaluates the stochastic response spectrum. The frequency information of the excitation can be described using different functional forms. The shapes of the calculated response spectra of the excitation show strong magnitude and site dependency, but weak distance dependency. In this paper, to compare the effect of the earthquake ground motion variables, the contribution of these sources of variability to the response spectrum's uncertainty is calculated by using a stochastic analysis. The analytical results show that earthquake source factors and soil condition variables are the main sources of uncertainty in the response spectra, while path variables, such as distance, anelastic attenuation and upper crust attenuation, have relatively little effect. The presented formulation of dynamic structural response in frequency domain based only on the frequency information of the excitation can provide an important basis for the structural analysis in some location that lacks strong motion records.

Consistency of PPP GPS and strong-motion records: case study of Mw9.0 Tohoku-Oki 2011 earthquake

  • Psimoulis, Panos;Houlie, Nicolas;Meindl, Michael;Rothacher, Markus
    • Smart Structures and Systems
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    • v.16 no.2
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    • pp.347-366
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    • 2015
  • GPS and strong-motion sensors are broadly used for the monitoring of structural health and Earth surface motions, focusing on response of structures, earthquake characterization and rupture modeling. Several studies have shown the consistency of the two data sets within at certain frequency (e.g., 0.03