• The Journal of the Acoustical Society of Korea
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• v.23 no.5
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• pp.376-382
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• 2004

The interaction between a vibrating structure and a surrounding acoustic medium determines the acoustic power propagating into the far-field. A straightforward method to reduce the radiated power is to reduce the vibration of the structure. However it is more efficient to control the modes of the structure separately since each vibration mode of the structure has different radiation efficiency. An efficient method to reduce the sound radiation in the low frequency region is proposed by reducing the radiation efficiency of the structure. Numerical simulations are carried out for a simply-supported beam in which the feed-forward control is applied to reduce the volume velocity of each structural mode. This method is found to be very efficient in reducing low frequency sound radiation.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1055-1060
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• 2009

Noise is one of the major environmental problems in human life. But hot water distributers with the flow rate control valve bring about often noise according to the heating control condition in residential buildings. The sound power level increased as the flow rate and pressure difference increased. And thus, experimental analyses for the flow rate control and the pressure difference control were carried out in this study to reduce the noise emitted from the flow rate control valve. As the results, the flow rate control method using a SMA(Shape Memory Alloy)-valve and the flow rate control system using a pressure difference sensor can be expected to control noise in the region of below 50 dB of sound power level.

• Journal of Korean Academy of Fundamentals of Nursing
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• v.10 no.3
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• pp.399-407
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• 2003

Purpose: This study was done to identify levels of physical fitness in student nurses and to ascertain the relationship among the different aspects of physical fitness of strength, power, muscle endurance, agility, balance and flexibility. Method: The participants were 266 students selected from one college of nursing. From May 1 to July 31 in 2003, physical constitution, muscle strength (grip strength, back strength), power (standing long jump), muscle endurance (sit-ups), agility (whole body reaction time-light, sound), balance (close-eyes foot-balance), and flexibility (sitting trunk flexion) were measured. Result: The mean(standard deviation) for grip strength was 22.59(3.93) kg., for back strength, 48.52(12.85) kg., for standing long jump, 135.29(20.54) m., for sit-up's, 23.66(9.35) per minute, whole body reaction time (light), 0.43(0.11) sec, whole body reaction time (sound), 0.50(0.16) sec, close-eyes foot-balance, 33.35(38.67) sec, and sitting trunk flexion 34.72(9.37) cm. Conclusion: This study showed that the physical fitness of student nurses is very low compared to the results in a report from the Korea Sports Science Institute. It is necessary to include exercise programs for student nurses in order to improve their physical fitness.

• Journal of Korea Multimedia Society
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• v.19 no.4
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• pp.756-764
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• 2016

In this paper, we present electroencephalography (EEG)-based power spectra analysis and auditory stimuli methods as coping mechanisms for disgust affection and phobia. Disgust affection is a negative emotion generated from trying to eliminate something harmful to one. It is usually related to mental illnesses such as obsessive-compulsive disorder, specifically phobia and depression. In our experiments, participants watched videos on horrible body mutilation and disgusting creatures, with either the original sound track or relaxing and exciting music as auditory stimulation. After watching the videos with original sound track, the participants watched the same video with a different audio background, such as soothing or cheerful music. We analyzed the EEG data utilizing relative power spectra and examined survey results of the participants. The results demonstrated that disgust affection is decreased when participants watched the video with relaxing or exciting music instead of the original soundtracks. Moreover, we confirmed that human's brainwave reacts according to types of audio and sources of disgust affection.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2002.05a
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• pp.314-319
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• 2002

To inspect how the different sensitivities in BAS (or BIS) moderate on the HRV pattern stimulated by positive or negative affective sound, we measured the electrocardiogram (ECG) of 25 students, consisted of 4 groups depending on the BAS (or BIS) sensitivity, while listening music or being exposed to noise. The power spectral density of HRV was derived from the ECG, and the power of HRV was calculated for 3 major frequency ranges (low frequency [LF], medium frequency [MF], and high frequency [HF]). We found that the index MF/(LF+HF), while listening music, was 20 % higher in the individuals with a low BIS but high BAS than in the individuals with a low sensitivity In both BIS and BAS. Moreover, in the former group this index was 30 % higher while listening music than while being exposed to noise. From these results we suggest that individuals with a low BIS but high BAS be more sensitive to positive affective stimuli than other groups, and the index MF/(LF+HF) be applicable to evaluate positive affects.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.1
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• pp.1-9
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• 2009

This study presents an analytical model of an automotive steering hose containing tuner(flexible spiral metal tube) to reduce the ripple pressure induced by steering vane pump. The double-wall side branch composed in a steering hose containing tuner was analogically considered as a filter in a conduit. Specialized test equipment was manufactured for the estimation of speed of sound in a conduit and measurement of amplitude ratio between the propagated ripple pressures of inlet and outlet of the steering hose. Experimental data of entire frequency ranges can be obtained through the test once in short time. The results of three points' measurement method and cross-correlation method to estimate the speeds of sound in a hose, tuner, and side branch respectively reveal that cross-correlation method can be used practically. The results of simulation and experiment were so close, especially in the range of engine idling speed, that the proposed analytical model in this study was validated. Sensitivity analyses and experiments show that longer tuner is preferable, and that the positive-positive composition of the steering hoses containing tuner is superior to others to attenuate ripple pressure.

• Journal of the Institute of Convergence Signal Processing
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• v.6 no.1
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• pp.23-26
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• 2005

This paper describes the algorithm for deciding the status of the operating machines in the power plants. It is very important to decide whether the status of the operating machines is good or not in the industry to protect the accidents of machines and improve the operation efficiency of the plants. There are two steps to analyze the status of the running machines. First, we extract the features from the input original data. Second, we classify those features into normal/abnormal condition of the machines using the wavelet transform and the input RMS vector through the K-means algorithm. In this paper we developed the algorithm to detect the fault operation using the K-means method from the sound of the operating machines.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.7
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• pp.622-628
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• 2011

The purpose of this study was to analyze the vibro-acoustic characteristics of a stiffened rectangular plate at high frequencies. The stiffeners attached along the plate surface were assumed to have rotational and translational stiffness and inertia. The harmonic response of the stiffened plate were predicted and compared using the Rayleigh-Ritz method with two different trial functions - polynomial and beam functions. The variation of the spatially averaged mean square velocity and the modal characteristics with the number of stiffeners were obtained. The use of the beam function ensured fast convergence which was essential for analyzing the high frequency vibration responses. Using the calculated modal characteristics and the Rayleigh-integral, the radiated sound power was predicted, and the effects of stiffeners were investigated. The proposed model can be applied to study optimal layout of stiffeners for minimal noise generation of the stiffened structures.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.7
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• pp.605-616
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• 2013

An important source of noise from railways is rolling noise caused by wheel and rail vibrations induced by acoustic roughness at the wheel-rail contact. In the present paper, characteristics of rail vibration and radiated sound power from concrete slab tracks for domestic high speed train(KTX) is investigated by means of a numerical method. The waveguide finite element and boundary element are combined and applied for this analysis. The concrete slab track is modelled simply with a rail and rail pad regarding the concrete slab as a rigid ground. The wave types which contribute significantly to the rail vibration and radiated noise are identified in terms of the mobility and decay rates. In addition, the effect of the rail pad stiffness on the radiated power is examined for two different rail pad stiffnesses.

• CELLMED
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• v.8 no.2
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• pp.9.1-9.3
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• 2018

The purpose of this article is to discuss that ajaeng sanjo music playing (ASMP) can change a person's life. Ajaeng is often called a Korean cello and is the largest and lowest-pitched instrument in the string instrument family in Korean music. From far away it has a deep, low sound. Its low sound adds to its comfort and peace. Listening to a low tone music can help you calm down and heart-easing. As soon as he listened ajaeng sanjo music he felt that low sound is mildly under his patronage. He felt much more interesting energy and vitality about our minds and bodies are in ajaeng sanjo music. He could immerse himself in playing ajaeng sanjo music (ASMP) for several years. The Korean music, tune is one of expression, meaning it is inseparable from the feeling. Many studies show that low tone music not only activates brain power, but soothes minds. Music always stood by him during difficult times. In a word, ASMP leads him to change of life and music is the language of emotion to him.