• 제목/요약/키워드: Oscillatory

검색결과 714건 처리시간 0.031초

Linear oscillatory actuator를 이용한 구조물 진동의 능동 제어 연구 (Application of Linear Oscillatory Actuator to Active Structural Vibration Control)

  • 정태영;문석준;정종안;박희창;장석명
    • 소음진동
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    • 제7권2호
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    • pp.311-317
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    • 1997
  • In this paper the active vibration control system using a linear oscillatory actuator(LOA) is studied to suppress structural vibration. In the LOA, the AC-power-energized armature generates a shift field in an air gap, which produces a oscillating force to the mover in the magnetic field generated by high density permanent magnets. LOA has relatively simple structure with almost maintenance free, compared with a hydraulic actuator. Performance test of the active vibration control system using a LOA is carried out on a steel test structure under base excitation. From this test, it is confirmed that the acceleration level of the test structure is drastically reduced near the resonant region.

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Pt Thickness Dependence of Oscillatory Interlayer Exchange Coupling in [CoFe/Pt/CoFe]/IrMn Multilayers with Perpendicular Anisotropy

  • Lee, Sang-Suk;Choi, Jong-Gu;Kim, Sun-Wook;Hwang, Do-Guwn;Rhee, Jang-Roh
    • Journal of Magnetics
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    • 제10권2호
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    • pp.44-47
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    • 2005
  • The oscillatory interlayer exchange coupling (IEC) has been shown in pinned $[CoFe/Pt(t_{pt})/CoFe]/IrMn$ multi-layers with perpendicular anisotropy. The period of oscillation corresponds to about 2 monolayers of Pt. The oscillatory behavior of IEC depending on the nonmagnetic metallic Pt thickness is thought to be related the antiferromagnetic ordering induced by IrMn layer. Oscillatory IEC as function of insulating NiO thickness has been observed in $[Pt/CoFe]_4/NiO(t_{NiO})/[CoFe/Pt]_4$ multilayers. The effect of N (number of bilayer repeats) upon the magnetic property of [Pt/CoFe]N/IrMn is also studied.

높은 Prandtl 수 유체에서 축회전이 열모세관 유동의 진동에 미치는 영향 (Effect of axial rotation on oscillatory thermocapillary flow in half-zone of high Prandtl number fluid)

  • 전승원;이규정
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2008년도 추계학술대회B
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    • pp.2248-2253
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    • 2008
  • A numerical study on oscillatory thermocapillary flow in half-zone has performed to understand the effect of axial rotation. 2d unsteady code is developed to observe the onset of oscillation. 2cs Silicone oil with Prandtl number of 26.5 is used as a working fluid. The critical temperature difference at onset of oscillation is investigated under the different aspect ratios and rotation modes. It is shown that the onset of oscillation is delayed when aspect ratio reduces and rotating speed increases. The oscillatory flow is strongly reduced under top rotation and co-rotation modes, while it is augmented under bottom rotation and counter-rotation modes. It is thought that interaction between return flow and bottom wall is important to explain the oscillatory flow.

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Oscillatory Reaction in a Liquid-Liquid System with Nano-Particle Under Microwave Irradiation

  • Asakuma, Y.;Takahashi, S.;Saptoro, A.;Maeda, Y.;Araki, N.
    • 한국입자에어로졸학회지
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    • 제11권3호
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    • pp.77-85
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    • 2015
  • A Belousov-Zhabotinsky reaction in a liquid-liquid system under microwave radiation was observed under non-stirring conditions. To control this non-equilibrium reaction, nano-particle, which is active under microwave irradiation, was added to the solution. Color changes of the solution during the oscillatory reaction were found to be influenced by the irradiation power although the droplet temperature was equal to the temperature of surrounding oil. During the irradiation, the period of oscillation became shorter because the reaction rate was faster. It could also be observed that there is possibility to eliminate oscillatory behaviors of the reaction using higher power of microwave. The possibility of controlling non-linear reaction using microwave was shown since microwave can easily travel through oil phase and reach water phase.

Oscillatory 파형감지에 의한 보일러 플랜트 드럼수위 제어계통의 고장진단 (Detection of Oscillatory Pattern Signals and its Application to the Fault Diagnosis of a Boiler Drum-Level Control System)

  • 김재화;서열규;장태규
    • 대한전기학회논문지:전력기술부문A
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    • 제48권1호
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    • pp.44-51
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    • 1999
  • This paper proposes a new approach of plant fault diagnosis which is based on detecting the characteristic pattern signals and associating them with the corresponding faults. The new approach does not require analytic modeling of the target system but best reflects the expertise embedded in the experienced human operation by mimicking them in a systematic way. This paper intends to illustrate the feasibility of the proposed by developing the algorithms to detect and estimate the typical characteristic pattern signals, I. e., oscillatory patterns, and applying them to the diagnosis of various faults of a 500MW boiler control system including tube rupture, feed-water leak, and controller failure.

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AN EFFICIENT ALGORITHM FOR EVALUATION OF OSCILLATORY INTEGRALS HAVING CAUCHY AND JACOBI TYPE SINGULARITY KERNELS

  • KAYIJUKA, IDRISSA;EGE, SERIFE M.;KONURALP, ALI;TOPAL, FATMA S.
    • Journal of applied mathematics & informatics
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    • 제40권1_2호
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    • pp.267-281
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    • 2022
  • Herein, an algorithm for efficient evaluation of oscillatory Fourier-integrals with Jacobi-Cauchy type singularities is suggested. This method is based on the use of the traditional Clenshaw-Curtis (CC) algorithms in which the given function is approximated by the truncated Chebyshev series, term by term, and the oscillatory factor is approximated by using Bessel function of the first kind. Subsequently, the modified moments are computed efficiently using the numerical steepest descent method or special functions. Furthermore, Algorithm and programming code in MATHEMATICA® 9.0 are provided for the implementation of the method for automatic computation on a computer. Finally, selected numerical examples are given in support of our theoretical analysis.

진동전단유동장에서 점탄성 반고형 연고기제(바셀린)의 레올로지 거동 (Rheological Behavior of Viscoelastic Semi-Solid Ointment Base (Vaseline) in Oscillatory Shear Flow Fields)

  • 송기원;장갑식
    • Journal of Pharmaceutical Investigation
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    • 제36권1호
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    • pp.31-38
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    • 2006
  • Using a Rheometries Dynamic Analyzer (RDA II), the dynamic viscoelastic properties of a semi-solid ointment base (vaseline) in large amplitude oscillatory shear flow fields were measured over a temperature range of $25{\sim}45^{\circ}C$ and the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a wide range of angular frequencies. In this article, the nonlinear viscoelastic behavior was reported from the experimentally obtained data and the effect of temperature on this behavior was discussed in detail. In addition, the angular frequency and temperature dependencies of a linear viscoelastic behavior were explained. Finally, the applicability of a time-temperature superposition principle originally developed for polymeric materials was examined using a shift factor. Main results obtained from this study can be summarized as follows : (1) At very small strain amplitude region, vaseline shows a linear viscoelastic behavior independent of the imposed deformation magnitudes. Above a critical strain amplitude $({\gamma}_{0}=0.1{\sim}0.2%)$, however, vaseline exhibits a nonlinear viscoelastic behavior ; indicating that both the storage modulus and dynamic viscosity are sharply decreased with increasing deformation magnitude. (2) In large amplitude oscillatory shear flow fields, an elastic behavior (storage modulus) has a stronger strain amplitude dependence and begins to show a nonlinear behavior at a smaller strain amplitude region than does a viscous behavior (dynamic viscosity). (3) In small amplitude oscillatory shear flow fields, the storage modulus as well as the loss modulus are continuously increased as an increase in angular frequency and an elastic nature is always superior to a viscous behavior over a wide range of angular frequencies. (4) A time-temperature superposition principle can successfully be applicable to vaseline. This finding allows us to estimate the dynamic viscoelastic behavior of vaseline over an extraordinarily extended range (11 decades) of angular frequencies inaccessible from the experimentally measured range (4 decades).

정사각단면 $180^{\circ}C$ 곡덕트에서 층류진동유동의 유동 특성에 관한 연구 (A study on flow characteristics of laminar oscillatory flows in a square-sectional $180^{\circ}C$ curved duct)

  • 박길문;조병기;봉태근
    • 대한기계학회논문집B
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    • 제22권2호
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    • pp.139-152
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    • 1998
  • In the present study, the flow characteristics of developing laminar oscillatory flows in a square -sectional 180 deg. curved duct are investigated experimentally. The experimental study using air in a square-sectional 180 deg. curved duct is carried out to measure velocity distributions with a data acquisition and LDV (Laser Doppler Velocimetry) processing system. In this system, Rotating Machinery Resolver (RMR) and PHASE program are used to obtain the results of unsteady flows. The major flow characteristics of developing oscillatory flows are found by analyzing velocity curves, mean velocity profiles, time-averaged velocity distribution of secondary flow, wall shear stress distributions, and entrance lengths. In a lower dimensionless angular frequency, the axial velocity distribution of laminar oscillatory flow in a curved duct shows a convex shape in a central part and axial symmetry. The maximum value of wall shear stress in a lower dimensionless angular frequency is located in an outside wall, but according to increasing the dimensionless angular frequency, the maximum of wall shear stress is moved to inner wall. The entrance lengths of laminar oscillatory flows in a square-sectional 180 deg. curved duct is obtained to 90 deg. of bended angle of duct in this experimental conditions.

Numerical simulation in time domain to study cross-flow VIV of catenary riser subject to vessel motion-induced oscillatory current

  • Liu, Kun;Wang, Kunpeng;Wang, Yihui;Li, Yulong
    • International Journal of Naval Architecture and Ocean Engineering
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    • 제12권1호
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    • pp.491-500
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    • 2020
  • The present study proposes a time domain model for the Vortex-induced Vibration (VIV) simulation of a catenary riser under the combination of the current and oscillatory flow induced by vessel motion. In this model, the hydrodynamic force of VIV comprises excitation force, hydrodynamic damping and added mass, which are taken as functions of the non-dimensional frequency and amplitude ratio. The non-dimensional frequency is related with the response frequency, natural frequency, lock-in range and the fluid velocity. The relatively oscillatory flow induced by vessel motion is taken into account in the fluid velocity. Considering that the added mass coefficient and the non-dimensional frequency can affect each other, an iterative analysis is conducted at each time step to update the added mass coefficient and the natural frequency. This model is in detail validated against the published test models. The results show that the model can reasonably reflect the effect of the added mass coefficient on the VIV, and can well predict the riser's VIV under stationary and oscillatory flow induced by vessel motion. Based on the model, this study carries out the VIV simulation of a catenary riser with harmonic vessel motion. By analyzing the bending moment near the touchdown point, it is found that under the combination of the ocean current and oscillatory flow the vessel motion may decrease the VIV response, while increase the excited frequencies. In addition, the decreasing rate of the VIV under vessel surge is larger than that under vessel heave at small vessel motion velocity, while the situation becomes opposite at large vessel motion velocity.