• Smart Structures and Systems
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• v.22 no.3
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• pp.315-326
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• 2018

This paper presents a novel time-domain method for the identification of plastic rotations and stiffness parameters of single-bay frames with nonlinear plastic hinges. Each plastic hinge is modelled as a pseudo-semi-rigid connection with nonlinear hysteretic moment-curvature characteristics at an element end. Through the comparison of the identified end rotations of members that are connected together, the plastic rotation that furnishes information of the locations and plasticity degrees of plastic hinges can be identified. The force consideration of the frame members may be used to relate the stiffness parameters to the elastic rotations and the excitation. The damped-least-squares method and damped-and-weighted-least-squares method are adopted to estimate the stiffness parameters of frames. A noise-removal strategy employing a de-noising technique based on wavelet packets with a smoothing process is used to filter out the noise for the parameter estimation. The numerical examples show that the proposed method can identify the plastic rotations and the stiffness parameters using measurements with reasonable level of noise. The unknown excitation can also be estimated with acceptable accuracy. The advantages and disadvantages of both parameter estimation methods are discussed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.5 s.110
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• pp.485-494
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• 2006

The state-of-the-art of low-noise fan design usually includes the consideration of optimal sound level and sound quality. The influential design parameters of the noise level by the centrifugal fan were selected based on the preliminary test. The centrifugal fans were designed according to the experiment plan method by specifying the selected design parameters. The experiment with these machined mock-up's of centrifugal impellers suggested the major design parameters among many, having impacts upon the indices of sound quality (e.g. loudness, sharpness, roughness and fluctuation strength) at the same operation point. With the response surface method, the major design parameters selected thereafter were analyzed to estimate each contribution upon the sound quality of the centrifugal fan, and the optimal values were drawn by the consideration of the sound quality levels and their regression equations. In addition, the validity of the regression equations was numerically verified by means of the coefficient of determination. Furthermore, the mechanism by which the centrifugal fan impeller influences the determinants of its sound quality was suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.826-829
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• 2005

The State of the art of low noise fan design requires the consideration of optimal sound quality. The influential design parameters of the noise level by the centrifugal fan were selected that based on a preliminary test. The centrifugal fans were designed according from the experiment plan method by specify the selected design parameters. The experiments with the machined mock-up's of centrifugal impellers revealed the major design parameters having impacts upon the indices of sound quality (e.g. loudness, sharpness, roughness and fluctuation strength) at the same performance condition. With a response surface method. the major design parameters selected were analyzed to estimate their contributions upon the sound quality of the centrifugal fan and the optimal values were drawn for the consideration of the sound quality by using each level and its regression equation. In addition, the validity of the regression equations were numerically verified by means of the coefficient of determination. Furthermore, the mechanism of how the centrifugal fans influence the determinants of sound quality was suggested.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.554-560
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• 1998

Acoustic performance of the absorptive mufflers used in air-conditioning and ventilating ducts, gas turbines, industrial fans influenced by the design parameters such as the length of mufflers, lining thickness, properties of the acoustic lining, and so forth. So we predicted the acoustic performance according to the design parameters. For the analysis, we assumed the radial propagation constant is locally reacted to the acoustic lining, and analyzed the acoustic performance based on the plane wave theory by using four-pole parameters.

• Journal of the Korean Institute of Navigation
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• v.16 no.3
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• pp.65-76
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• 1992

An algorithm to determine the optimum nominal value of geometrical and material parameters in divice modelling is proposed. The algorithm uses the yield and variance prediction formula and Monte-Carlo analysis. The performance specification of the noise figure must also be satisfied. In this paper, the total number of considered devices is 1000, and each parameter of geometrical and material parameters is generated randomly within the limits of ${\pm}3%$ of nominal value, and the distribution of 1000 geometrical and material parameters is gaussing distribution.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.5
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• pp.1051-1060
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• 2014

In this paper, performance of an orthogonal frequency division multiplexing (OFDM) system in an impulsive noise environment is analyzed. Here, it is verified that performance of the OFDM system with window nonlinearity, which is one of the impulsive noise mitigation algorithms, is dependent on the over-sampling rate and the size of window. With respect to the variation of those parameters, we also provide an appropriate region of threshold values that control amplitudes of the sampled waveform of received signals. As a result, a new combination of parameters which improves error performance of OFDM system in an impulsive noise environment as compared to the previously reported parameters is presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.04a
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• pp.367-368
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• 2012

In resent years, engineering thermoplastics represent a means for designers to integrate parts, facilitate assembly, reduce weight and lower the costs of their parts to improve the fuel efficiency and competitiveness of the cars. Thermoplastic turbo charger intake hose is one of most sophisticated application in thermoplastics under the hood. Used as part of weight & cost reduction and performance improvement program, thermoplastic turbo charger intake hose has been developed as rubber and metal replacement. For optimized product, NVH performance is a important criteria while keeping same durability required with current system. Though a number of studies have been conducted on the resonator hose and its analytical models, the most of studies were focused on transmission loss itself. This paper presents contribution of vehicle interior noise according to design parameters like profile, bellows type, bellows position, material characteristic. And we will review the design guidance for optimized product of thermoplastic turbo charger intake hose.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.4
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• pp.651-658
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• 2017

This paper proposes an analysis method of performance degradation of antenna due to radio frequency interference between an antenna and adjacent noise sources using active scattering parameters. The radio frequency interference can be analyzed by the measured or simulated scattering parameters and by excited noise sources in the circuit as well. In this paper, a planar inverted-F antenna and a noise source are designed and fabricated to analyze radio frequency interference between the planar inverted-F antenna and noise source. The proposed analysis method uses active scattering parameters, of which verification is experimentally verified, and in simulation as well.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.536-541
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• 2003

When a rail vehicle transverses tight curves, it often emits an intense, high-pitched squeal. This squeal has always been noticed as one of the most disturbing noise sources of railway systems. At present, w cannot predicted squeal noise that is influenced by a large number of dependent parameters. In this study, we performed structural analysis to find out the frequency of the wheel and measured squeal noise at Seoul subway. We also tested reduction effectiveness of squeal noise through rail lubricator

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.295-302
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• 2014

An internal gear pump is required to improve the flow rate and noise. Furthermore, such pumps are durable and small in size. In this study, equations of the rotor shape with multiple profiles (ellipse 1-involute-ellipse 2) were derived, and relevant performance parameters (pressure angle, irregularity, and specific sliding) of the internal gear pump to noise were predicted and compared. Rotor profiles and performance parameters were obtained by a prediction algorithm for theoretical analysis, and the effects between the design parameters and the performance parameters were analyzed. Based on the analysis results of the effects, an optimal design of the rotor profile was proposed, and a noise test of the prototype was performed to evaluate the reliability of the design.