• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.3
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• pp.632-638
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• 2011

This paper presents on-chip Design-for-Testability (DFT) circuit for radio frequency System-on-Chip (SoC) applications. The proposed circuit measures functional specifications of RF integrated circuits such as input impedance, gain, noise figure, input voltage standing wave ratio (VSWRin) and output signal-to-noise ratio (SNRout) without any expensive external equipment. The RF DFT scheme is based on developed theoretical expressions that produce the actual RF device specifications by output DC voltages from the DFT chip. The proposed DFT showed deviation of less than 2% as compared to expensive external equipment measurement. It is expected that this circuit can save marginally failing chips in the production testing as well as in the RF system; hence, saving tremendous amount of revenue for unnecessary device replacements.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1088-1097
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• 2021

Vibration data of mechanical equipment inevitably have noise. This noise adversely af ects the maintenance of mechanical equipment. Accordingly, the performance of a learning model depends on how effectively the noise of the data is removed. In this study, the noise of the data was removed using the Denoising Auto Encoder (DAE) technique which does not include the characteristic extraction process in preprocessing time series data. In addition, the performance was compared with that of the Wavelet Transform, which is widely used for machine signal processing. The performance comparison was conducted by calculating the failure detection rate. For a more accurate comparison, a classification performance evaluation criterion, the F-1 Score, was calculated. Failure data were detected using the One-Class SVM technique. The performance comparison, revealed that the DAE technique performed better than the Wavelet Transform technique in terms of failure diagnosis and error rate.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.11
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• pp.1962-1969
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• 2008

According to the increase of power demand and expansion of downtown, it is necessary to install transformers additionally in operating substations and construct substations in residential area. But the public complaint is increased due to the transformer noise of the substation. KEPCO has used a vibration preventing pad, various soundproof walls and an encloser to transformers in outdoor substations, and a soundproof door, shutter and wind-path soundproof equipment in indoor substations to block the sound propagation of the transformers. But these noise reduction methods are not satisfied. It should be considered to reduce transformer noise itself. In this paper, we investigated core noise reduction techniques to develope a low noise transformer. The techniques to reduce core noise of the transformer are application of high permeability grain oriented silicon sheets, decrease of magnetic flux density of core, application of 6step-lap core stacking method, improvement of core binding method(binding addition, band fixing) and application of rubber damper in oder to reduce transmission of core vibration, etc.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2019.05a
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• pp.214-216
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• 2019

Recently, as the use of digital equipment increases in various fields, the importance of image and signal processing is increasing. However, many kinds of noise occur in the digital signal during transmission and reception, and this noise greatly affects the final output of the system. In this paper, we propose an algorithm that effectively restores the image by removing noise according to pixel similarity in a mixed noise environment with impulse noise and AWGN. The proposed algorithm sets the reference value according to the noise type and applies the filtering to pixels similar to the reference value to obtain the final output. Simulation results show that the proposed algorithm has good noise canceling performance and compared with conventional methods using PSNR.

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.431-434
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• 1991

To develop the EHV transmission technology, the electrical environment problems such as Audible Noise etc. have been studied by the use of Corona Cage with artifical water spray equipment. However, this study has difficulties in simulating the amount of natural conditions. Therefore, We will plan to install full scale EHV test line to prove the measuring values of Corona Noise, and to selection of Conductors, Insulators, and to economical design, construction data.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1995.10a
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• pp.305-311
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• 1995

본 논문에서는 정밀 장비에 대한 전반적인 진동성능시험에 대하여 개설하고 주파수응답함수를 이용한 정밀 장비의 진동허용규제치를 결정할 수 있는 새로운 간편한 방법을 모색하고자 한다. 그리고 이러한 방법을 HDD(Hard Disk Driver)의 진동허용규제치를 결정하는 것에 적용하여 그 유용성을 확인하고자 한다.

• Journal of the Korean Vacuum Society
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• v.18 no.4
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• pp.310-317
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• 2009

Vertical wet equipment for the BGA develop process was newly developed substituted for conventional horizontal wet equipment. The benefits of vertical equipment are that the pattern damages generated by the collision between the patterns and transferring rollers can be eliminated because the direct contact between the equipment's transferring units and the soft dry film patterns does not occurs. Taguchi experiment was conducted to optimize the process characteristics for the vertical equipment. The experiment was organized as the smaller the better problem which includes adequate uncontrollable factor and controllable factors. The uncontrollable factors are the 4 sides of two panels which are loaded to the equipment at the same time. By the analysis of the experiment, temperature of the develop chemicals and develop spraying time are analyzed as the main controllable factors. Finally, line pattern's minimum width which is not damaged for the develop process was improved from $13.8{\mu}m$ for the horizontal equipment to $10.4{\mu}m$ for the vertical equipment. And dot pattern's minimum width is improved from $22.1{\mu}m$ to $16.3{\mu}m$.

• Korean Journal of Occupational Health Nursing
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• v.15 no.1
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• pp.5-13
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• 2006

Purpose: The research were conducted to identify the knowledge, attitude and the preventive behaviour of noise according to noise-induced hearing loss prevention education and to provide primary data for effective noise-induced hearing loss prevention education for noise-exposed workers. Method: 104 noise-exposed workers were included in this study. The instrument used in this study was knowledge, attitude and preventive behavior of noise tool by Lee & Lee(1996). The first data were collected before the noise education from August to September, 2002. During 6 months, the education was provided, and then the second data were collected from April to May, 2003. Data were analyzed by SPSS 10.0 win program for finding frequency, percentage, mean, standard deviation, t-test, and ANOVA. Results: The results of this study were as follows: There were statistically significant differences of knowledge and attitude of noise related education level, and adhesion quality of wearing ear protection equipment after noise education. Also, otitis media's history, received education of the personal protective devices for the hearing conservation was significant in the preventive behaviour of noise. Conclusion: In conclusion, the noise-induced hearing loss prevention education was effective in changing the knowledge, attitude and the prevention behaviour of noise. Therefore, the noise-induced hearing loss prevention education is strongly recommended for noise-exposed workers and it will be necessary repeated education for changing prevention behaviour of noise.

• Journal of the Korean housing association
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• v.18 no.5
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• pp.85-91
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• 2007

This is a case study for improving the sound environmental quality of cafeteria in university campus. The purpose of the study is to find out the present condition of physical level, type, and cause of indoor noise of cafeteria in university campus by comparison with a restaurant near campus. Research methods were field survey and questionnaire survey. Field survey was consisted of measurement on equivalent and instant noise level and observation on noise type. Respondents of questionnaire survey were 60 students using subject cafeteria or restaurant. Surveys were carried out in the 8th and in the 14th of December 2005. The results are as follows. 1) Indoor noise levels of the cafeteria were measured as $67.2{\sim}76.6$ (average 73.3) dB(A)Leq5min and $60.3{\sim}90.5$ (average 71.2) dB (A), exceeded the indoor noise recommended value of ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers). But noise levels of the restaurant were $61.6{\sim}70.4$ (average 66.9) dB(A)Leq5min and $59.8{\sim}70.6$ (average 64.9) dB(A). 2) The users's responses on major noise type in the cafeteria were 'noise by handling equipment and tableware', 'noise by moving chairs', and 'talcing noise', but 'taking noise' and 'background music' in the restaurant. 3) It was found that indoor noise level of the cafeteria was caused by sound reflection of finishing materials, noise diffusion by open type kitchen, and dragging noise of movable furniture.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.8
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• pp.726-735
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• 2007

Inside the factory buildings of aprecision industry (which produces semiconductors or TFT-LCD), thousands of vibration-sensitive precision equipments operate in the clean rooms. Various utility equipments that are installed around them for proper operation cause various sources of noise and of vibration to exist inside the clean rooms and thus deteriorate the noise and the vibration environment within. In this study, we check if the existing transient vibration phenomenon is caused by the vibrations that arise from operating the utility installed near these equipments; compare and evaluate the vibration criteria of precision equipments regarding the transient vibration phenomenon; and check the efficiency of these criteria.