• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 추계학술대회논문집; 한국과학기술회관; 6 Nov. 1997
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• pp.237-243
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• 1997

Most outdoor sounds go from sources relatively near the ground to receivers near the ground. When either source or receiver are near the ground, interference can occur between the direct sound and that reflected at the ground which travels a slightly longer path. The sound pressure at the receiver is very different depending on the state of ground surface i.e. ground impedance. Ground impedances could be characterized by the value of a single parameter, namely the flow resistivity of the ground surface. This study suggests the measurement method of the flow resistivity using two microphones and predicts the flow resistivities of various ground surfaces.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.897-902
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• 2001

This paper describes the evaluation of noise influence for residental and boundary areas in 75MW thermal power plant. It includes the measurements of noise level around the boundary area of the plant, identification of noise propagating path, and discussion on the measures. Noise assessments are carried out based on the ISO 3744, ISO 9613-1 and ISO 9613-2 to predict the noise distribution of specific locations from the noise sources such as power transformers, flash vent-pipe, I.D.fan, and stack. It is identified the vent-pipe of flash tank in thermal power plant as the root cause of the environmental noise during the plant commissioning process.

• 한국산업융합학회 논문집
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• 제25권4_1호
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• pp.505-511
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• 2022

The objective of this article is finding optimized locations of active mounts applied to 6-DOF beam structure with two active paths. When sinusoidal excitation forces are applied to the beam structure, secondary forces from two active mounts which can minimize (ideally becoming zero) transmitted forces are calculated mathematically and the vibration attenuation performance is validated through computer simulations. When the force applied to two active mounts are relatively low, those specific locations are considered as optimized location of active mounting system. As the location of mount changes, amplitude and phase of secondary forces in each path are analyzed with 3D plots. Based on the simulation results, a criterion for selecting mounting location is suggested and it would be very useful for selecting actuators for active mounts appropriately.

• Nuclear Engineering and Technology
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• 제56권2호
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• pp.375-388
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• 2024

In this study, to evaluate the shock and vibration load characteristics of used fuel, a sea transportation test was conducted using simulated fuel assemblies under normal transport conditions. An overall test data analysis was performed based on the measured strain and acceleration data obtained from cruise, rotation, acceleration, braking, depth of water, and rolling tests. In addition, shock response spectrum and power spectral densities were obtained for each test case. Amplification and attenuation characteristics were investigated based on the load path. The load was amplified as it passed from the overpack to the simulated used fuel-assembly. As a result of the RMS trend analysis, the fuel-loading position of the transportation package affected the measured strain in the fuel rod, and the maximum strains were obtained at the spans with large spacing. However, even these maximum strains were very small compared to the fatigue strength and the cladding yield strength. Moreover, the fuel rods located on the side exhibited a larger strain value than those at the center.

• 소음진동
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• 제1권2호
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• pp.141-147
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• 1991

A vectorial approach is used to reduce the objectionable booming noise in the vehicle interior cabin. After identifying the structural transmisson paths, the structural-acoustic transfer functions are evaluated at those mounting positions. Using the measured deformations in the mounting elements and multiplying them with each dynamic stiffness value one can easily get the dynamic input forces acting on the mounting elements. By summing all the contributors vectorially, most important contributor or transmission path can be determined. According to the experimental information, devised countermeasures are applied to a development car and good results are obtained.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.48.3-48
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• 2002

1) Linear state feedback control design problem for plant with unknown deterministic disturbance is considered and a method to realize state feedback by using adaptive observer which estimates the unknown disturbance simultaneously is proposed. 2) From the viewpoint of practical application, we propose an extended adaptive observer with direct plant path from input to output, which is necessary to use the acceleration type sensors as plant output. 3) Theoretical result is confirmed by numerical simulation of 1-DOF vibration control system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.806-811
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• 2007

In this study, we propose a more systematic design process for the structure-borne noise. The proposed way consists of 4 steps: Problem definition, Cause analysis, Development of counter-measure and Validation. Especially, we improved the second step: Cause analysis. According to the PCA(Panel Contribution Analysis), a reduction in vibration of the panels of which panel contribution is positive and larger, results in a reduction in structure-borne noise. We have, however, met the case in which the concept of PCA is no valid in a few vehicle tests. In order to understand this phenomenon, we compared the major panels selected by PCA with the one chosen by DSA(Design Sensitivity Analysis). After investigating the difference between the two results, a more improved process is suggested. The proposed one for the second step in the design process consists of not only the previous way: PCA with deformation analysis results but also DSA. It is finally validated that the proposed design process decreases the sound pressure of the concerned noise transfer function more than 3.5 dB.

• 한국소음진동공학회논문집
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• 제22권8호
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• pp.720-728
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• 2012

It is important for identification of noise and vibration problem of tire to consider influence of interaction between road and tire. A quantification of road noise is a challenging issue in vehicle NVH due to extremely complicated transfer paths of road noise as well as the difficulty in an experimental identification of input force from tire-road interaction. A noise caused by tire is divided into road noise(structure-borne noise) and pattern noise(air-borne noise). Pattern noise is caused by pattern shape of tire, which has larger than 500 Hz, but road noise is generated by the interactions between a tire and a vehicle body. In this paper, we define the quantitative analysis for road noise caused by interactions between tire and road parameters. For the identification of road noise, the chassis dynamometer that is equipped $10mm{\times}10mm $ square cleat in the semi-anechoic chamber is used, and the tire spindle forces are measured by load cell. The vibro-acoustic transfer function between ear position and wheel center was measured by the vibro-acoustic reciprocity method. In this study three tires with different type of mechanical are used for the experiment work.

• 한국소음진동공학회논문집
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• 제22권4호
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• pp.335-343
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• 2012

As a matter of fact, it has been not allowed to modify the shape of a vehicle body skeleton since the technical definition for the structure was fixed and the corresponding molds were developed. By the way, if it is available to apply an alternative to reinforce the skeleton without changing its mold, it must be much flexible to improve the performance qualities relevant to not only NVH(noise, vibration and harshness) but also crash and durability. Recently, a solution of so-called composite body becomes available for the need. We present a design method to insert the composite body inside a vehicle body skeleton in order to improve a structure-borne noise at the idle condition. The algorithms, topology optimization and design sensitivity analysis, are applied to mainly search the sensitive structural sections in the body skeleton and to extract the target stiffness of the sections. Inserting the composite bodies into the sensitive portions, it is predicted to achieve the countermeasures which can compromize the design availability in terms of the idle noise and weight. According to the validation result with test vehicles, the concerned noise transfer function is reduced and the idle booming noise is resultantly improved.

• 한국소음진동공학회논문집
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• 제23권4호
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• pp.315-323
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• 2013

Tire noise is divided into a road noise(structure-borne noise) and a pattern noise(air-borne noise). Whilst the road noise is caused by the structural vibration of the components on the transfer path from tire to car body, the pattern noise is generated by the air-pumping between tire and road. In this paper, a practical method to estimate the pattern noise inside a passenger car is proposed. The method is developed based on the sound intensity and airborne source quantification. Sound intensity is used for identifying the noise sources of tire. Airborne source quantification is used for estimating the sound pressure level generated by each noise source of a tire. In order to apply the airborne source quantification to the estimation of the sound pressure, the volume velocity of each source should be obtained. It is obtained by using metrics inverse method. The proposed method is successfully applied to the evaluation of the interior noises generated by four types of tires with different pattern each other.