• Title, Summary, Keyword: Vibrating Absorber

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Anechoic Chamber Design using Broadband Compact Absorber (패널형 흡음재를 이용한 무향실의 설계)

  • ;;Peter Brandstatt;Helmut V. Fuchs
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.393-396
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    • 2003
  • Conventional method for designing and installing anechoic chambers is to utilize porous wedges for the sound absorbers. As cutoff frequency lowers down such as 63Hz or 50Hz, the corresponding long wedges diminish the free field area of the chamber. In this study, a new broadband compact absorber(BCA) is introduced which absorbs acoustic energy down to 50Hz. Most prominent is that it measures only 250mm thick. A freely vibrating panel between the non-fibrous absorbers allows tuned absorption at the low frequency region in addition to the high frequency absorption resulted from the conventional absorber installed at the front. Standing waves at low frequency range are suppressed as the BCA modules which are tuned to the corresponding modes absorb sound energy effectively, resulting in anechoic condition. Not only the low frequency performances, but the high frequency absorption is measured to meet adequate conditions for the anechoic chamber. Realized BCA chambers are presented.

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Active Control of Vibrational Intensity in a Compound Vibratory System (복합진동계의 진동 인텐시티 능동 제어)

  • Kim, Gi-Man
    • Journal of the Korean Society for Precision Engineering
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    • v.19 no.6
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    • pp.109-118
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    • 2002
  • The vibrational intensity and the dynamic response of a compound vibratory system had been controlled actively by means of a feedforward control method. A compound vibratory system consists of a flexible beam and two discrete systems - a vibrating source and a dynamic absorber. By considering the interactive motions between discrete systems and a flexible beam, the equations of motion for a compound vibratory system were derived using a method of variation of parameters. To define the optimal conditions of a controller the cost function, which denotes a time averaged power flow, was evaluated numerically. The possibility of reductions of both of vibrational intensity and dynamic response at a control point located at a distance from a source were fecund to depend on the positions of a source, a control point and a controller. Especially the presence of a dynamic absorber gives the more reduction on the dynamic response but the less on the vibrational intensity than those without a dynamic absorber.

Vibration Control of Engine Body for Two Stroke Low Speed Diesel Engine using Dynamic Vibration Absorber (동흡진기에 의한 저속 2행정 디젤엔진의 본체진동 제어)

  • 이돈출;유정대;김정렬
    • Journal of the Korean Society of Marine Engineering
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    • v.26 no.6
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    • pp.631-637
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    • 2002
  • Two stroke low speed diesel engines are used as a power supplier not only for marine vessel but also diesel power plant with a benefit of its higher mobility and durability than the other thermal engines. However, there are some disadvantages such as the bigger vibrating excitation forces generated by high combustion pressure in cylinders which various kinds of vibrations are caused. In this paper, it is theoretically studied to control engine body vibration using dynamic vibration absorber. As an actual case, dynamic absorbers are designed for controlling X-mode vibration of 9K80MC-S engine on the diesel power plant and its performance is identified by the vibration test both in shop and site

An Experimental Study on the Characteristics of Impact Vibration Absorber with Free Mass (자유질량체를 갖는 충격식 흡진기의 특성에 관한 실험적 연구)

  • Yang, Bo-Suk;Kim, Jong-Wan
    • Journal of the Korean Society for Precision Engineering
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    • v.9 no.1
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    • pp.75-81
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    • 1992
  • In this paper, an impact vibration absorber that reduces the high vibration amplitude of a vibrating system is studied. This absorber consists of a free mass allowed to impact on to the secondary leaf spring so that the vibration energy is dissipated by converaion into noise and heat. The experimental parameters are weight of the free mass and impat clearance. According to the measured results, the high vibration in resonance region is reduced more effectively by the impact clearance ratio than by the mass ratio.

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Adaptive group of ink drop spread: a computer code to unfold neutron noise sources in reactor cores

  • Hosseini, Seyed Abolfazl;Afrakoti, Iman Esmaili Paeen
    • Nuclear Engineering and Technology
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    • v.49 no.7
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    • pp.1369-1378
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    • 2017
  • The present paper reports the development of a computational code based on the Adaptive Group of Ink Drop Spread (AGIDS) for reconstruction of the neutron noise sources in reactor cores. AGIDS algorithm was developed as a fuzzy inference system based on the active learning method. The main idea of the active learning method is to break a multiple input-single output system into a single input-single output system. This leads to the ability to simulate a large system with high accuracy. In the present study, vibrating absorber-type neutron noise source in an International Atomic Energy Agency-two dimensional reactor core is considered in neutron noise calculation. The neutron noise distribution in the detectors was calculated using the Galerkin finite element method. Linear approximation of the shape function in each triangle element was used in the Galerkin finite element method. Both the real and imaginary parts of the calculated neutron distribution of the detectors were considered input data in the developed computational code based on AGIDS. The output of the computational code is the strength, frequency, and position (X and Y coordinates) of the neutron noise sources. The calculated fraction of variance unexplained error for output parameters including strength, frequency, and X and Y coordinates of the considered neutron noise sources were $0.002682{\sharp}/cm^3s$, 0.002682 Hz, and 0.004254 cm and 0.006140 cm, respectively.

Theoretical Investigation of 2DOF Vibrating System and Its Application to Dynamic Vibration Absorber (2자유도 진동계에 관한 이론적 고찰 및 진동흡진기로의 응용)

  • Jang, Seon-Jun;Brennan, M.J.;Rustigh, E.;Jung, Hyung-Jo
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.4
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    • pp.371-377
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    • 2009
  • In this paper, the dynamic characteristic of vibrating system which has translational and rotational degrees of freedom is studied. The moment of inertia of the system is modeled here as the inerter and the equivalent model to the system is proposed using dynamic stiffness method. It is shown that the size of inerter plays a major role to determine the dynamic characteristic of the system. This two degree of freedom system(DOF) is applied as a dynamic vibration absorber(DVA) to the elimination of single peak of main body. The solution for the undamped DVA is presented in analytical form while the damped DVA is designed using fixed point theory. The numerical examples are presented for verifying the methods.

Theoretical Investigation of 2DOF Vibrating System and Its Application to Dynamic Vibration Absorber (2자유도 진동시스템에 관한 이론적 고찰 및 진동흡진기로의 응용)

  • Jang, Seon-Jun;Brennan, M.J.;Rustighi, E.;Jung, Hyung-Jo
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.125-129
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    • 2009
  • 본 연구에서는 동강성법을 이용하여 2자유도 진동시스템을 모델링하였다. 등가 모델을 구성한 후 Inertance의 크기에 따라 변화되는 시스템의 특성을 규명하였다. 2자유도 진동 시스템을 단일 모우드 소거에 적용할 경우 해석적인 설계 방법론을 1) 감쇠가 없는 경우 2) 1개의 감쇠기를 갖는 경우로 나누어 제시하였다.

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A Study on the Control System of Dynamic Vibration Absorber for Ship Superstructure (선박용 동흡진기 시스템에 관한 연구 - 중력진자식 및 원심진자식 동흡진기에 대한 -)

  • S.S. Kim;S.Y. Han;J.K. Eom;M.H. Hyun;J.H. Kim;M.H. Kim;D.K. Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.32 no.3
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    • pp.1-18
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    • 1995
  • This paper deals with the vibration absorbers of gravitational and centrifugal pendulum types for vibration controls of ship's substructures such as radarmasts, bridgewings and funnels. The mathematical model of such a vibrating system with an absorber is described as a 2 degree of freedom system and an efficient formulation for optimum design of the absorber is presented. For investigation applicability of the two types of the absorbers to a structure system, numerical calculations and experiments hove been performed with variation of mass ratios for each type. According to the results of investigations, the vibration absorber of gravitational type proved to be more useful and efficient than one of centrifugal pendulum type in a view point of mass ratio.

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Effects of Sheet Thickness on the Electromagnetic Wave Absorbing Characterization of Li0.375Ni0.375Zn0.25-Ferrite Composite as a Radiation Absorbent Material

  • Kim, Dong-Young;Yoon, Young-Ho;Jo, Kwan-Jun;Jung, Gil-Bong;An, Chong-Chul
    • Journal of electromagnetic engineering and science
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    • v.16 no.3
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    • pp.150-158
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    • 2016
  • This paper reports on a study of LiNiZn-ferrite composite as a radiation absorbent material (RAM). The electromagnetic (EM) wave absorbers are composed of an EM wave absorbing material and a polymeric binder. The surface morphology, chemical composition, weight percent of the ferrite composite of the toroid sample, magnetic properties, and return loss are investigated using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), vibrating sample magnetometer (VSM), and network analyzer. For preparing the absorbing sheet, chlorinated polyethylene (CPE) is used as a polymeric binder. The EM wave absorption properties of the prepared samples were studied at 4 - 8 GHz. We can confirm the effects of the thickness of the samples for absorption properties. An absorption bandwidth of more than a 10-dB return loss shifts toward a lower frequency range along with an increase in the thickness of the absorber.

Isobaric Vapor-Liquid Equilibrium of 1-propanol and Bromochloromethane System at Subatmospheric Pressures (감압하에서 1-propanol과 Bromochloromethane의 정압 기-액 평형)

  • Jang, Hoi-Gu;Kang, Choon-Hyoung
    • Applied Chemistry for Engineering
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    • v.21 no.3
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    • pp.295-300
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    • 2010
  • A binary system of 1-propanol and bromochloromethane which exhibits an azeotropic point and a considerable nonideal phase behavior probably due to the large boiling point difference is not amenable in the actual chemical processes such as the distillation tower and absorber. Therefore, experimental data of phase behavior data of this mixture are indispensable in understanding the inherent thermodynamic characteristics for an efficient application of the system in the industrial processes. In this work, the isobaric vapor-liquid equilibrium of a binary mixture consisting of 1-propanol and bromochloromethane was measured by using a recirculating equilibrium cell at various pressures ranging from 30 to 70 kPa. The measured VLE data were correlated in a satisfactory manner by using the UNIQUAC and NRTL models along with the thermodynamic consistency test based on Gibbs/Duhem equation. In addition, the excess molar volume of the mixture was also measured by using a vibrating densitometer and correlated with a Redlich-Kister polynomial.