• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.115-118
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• 2004

In this study, amplitudes of turbulence excitation are obtained for selected tubes inside the KSNP SG and their normal work-rates are investigated to estimate the magnitude of fretting-wear. From the results of numerical calculation, row 40&41 tubes show the maximum work-rates. Up to this row number, the work-rates inside the row 41 have much larger values than those of outside tubes. This phenomenon reveals the particular central one which has larger normal work-rate than that of outside zone. It turns out that both of the higher local mode at the U-bend region and the larger value of effective mass in the central region Increase the normal work-rate enormously.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.919-924
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• 2005

Fretting-wear caused by turbulence excitation for KSNP(Korea standard nuclear power plant) steam generator is investigated numerically. Secondary sides density and normal velocity are obtained by the thermal-hydraulic data of the steam generator. Because nonlinear finite element analysis is complex and time consuming, work rate is estimated by using linear analysis for simple straight 2-span tube. Wear volume and depth by using work rate calculation are estimated. Span length, secondary side fluid density and normal velocity are adopted to study the effects on the fretting-wear by turbulence excitation. When secondary sides density and normal velocity is increased, It turns out that secondary side density and normal gap velocity are very important paramater for fretting-wear phenomena of the steam generator.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.9 s.114
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• pp.904-911
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• 2006

A modified energy method for the fretting wear of the steam generator tube is proposed to calculate the wear-out depth between the nuclear steam generator tube and its support. Estimation of fretting-wear damage typically requires a non-linear dynamic analysis with the information of the gap velocity and the flow density around the tube. This analysis is very complex and time consuming. The basic concept of the energy method is that the volume wear rate due to the fretting-wear phenomena Is related to work rate which is time rate of the product of normal contact force and sliding distance. The wearing motion is due to dynamic interaction between vibrating tube and its support structure, such as tube support plate and anti-vibration bar. It can be assumed that the absorbed work rate would come from turbulent flow energy around the vibrating tube. This study also numerically obtains the wear-out depth with various wear topologies. A new dissection method is applied to the multi-span tubes to represent the vibrational mode. It turns out that both the secondary side density and the normal gap velocity are important parameters for the fretting-wear phenomena of the steam generator tube.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.302-307
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• 2004

The major flow-induced vibration mechanisms such as fluid-elastic and turbulence excitation can cause the various types of wear of the steam generator tubes in unclear power plant. It is generally accepted that the tube wear due to vibration is affected by the presence of gap clearance between tube and support plate. Connors showed that the tube wear depth could be estimated by using the relationship between wear volume and sliding distance for contact time. Au-Yang predicted the wear depth by using the nonlinear characteristics of normal work rate to contact time. In this study the effect of gap size on the steam generator tubes wear is analyzed by deriving the wear depth versus normal work rate relationship from these previous results.

• Korean Journal of Mathematics
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• v.23 no.1
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• pp.1-10
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• 2015

This paper concerns the rate of convergence in the multidimensional normal approximation of functional of Gaussian fields. The aim of the present work is to derive explicit upper bounds of the Kolmogorov distance for the rate of convergence instead of Wasserstein distance studied by Nourdin et al. [Ann. Inst. H. Poincar$\acute{e}$(B) Probab.Statist. 46(1) (2010) 45-98].

• Speech Sciences
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• v.14 no.1
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• pp.151-162
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• 2007

This study focuses on the classification of pathological voice using GMM (Gaussian Mixture Model) and compares the results to the previous work which was done by ANN (Artificial Neural Network). Speech data from normal people and patients were collected, then diagnosed and classified into two different categories. Six characteristic parameters (Jitter, Shimmer, NHR, SPI, APQ and RAP) were chosen. Then the classification method based on the artificial neural network and Gaussian mixture method was employed to discriminate the data into normal and pathological speech. The GMM method attained 98.4% average correct classification rate with training data and 95.2% average correct classification rate with test data. The different mixture number (3 to 15) of GMM was used in order to obtain an optimal condition for classification. We also compared the average classification rate based on GMM, ANN and HMM. The proper number of mixtures on Gaussian model needs to be investigated in our future work.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.3
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• pp.359-364
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• 2014

Objectives: The principal aim of this study is to provide fundamental data for suggesting substantial management plan of personal air sampler by investigating current situation of work environment monitoring service provider. Materials and Methods: The questionnaires regarding a personal air sampler were sent by electronic mail to 150 institutions, except for 22 institutions which are out of business or closed temporarily, among total 172 domestic work environment monitoring service providers designated by Ministry of Employment and Labor based on 2013. The institutions which did not reply to the questionnaire for 30 days were required directly by phone call. Finally 97 institutions gave an answer to the questionnaire and therefore the respondence rate was 65%. Results: The normal operation rate of personal air sampler exceeded 70% in all the types (particle, gas and both combination) in terms of purchased year. Furthermore the personal air sampler purchased recently showed a trend of high operation rate compared to the personal air sampler purchased previously. The distribution patterns of personal air sampler In terms of manufacturers were Gillian>MSA>SKC for particle, Gillian>SKC>AMETEK for gas and Gillian>MSA>Casella for both combination, respectively. As a result, it was found that the personal air sampler manufactured by Gillian company was utilized the most in domestic work environment monitoring service provider regardless of types of personal air sampler. Conclusions: Based on the results obtained from this study, the normal operation rate according to types of personal air sampler was as follows: 94% for personal air sampler for collecting particle only, 93% for personal air sampler for collecting gas only and 89% for collecting both particle and gas. Overall, the numbers of personal air sampler possessed and operated normally in domestic work environment monitoring service provider were 5,458 and 5,062, which indicates the normal operation rate of personal air sampler in total aspect is 93%.

• The Journal of the Korea Contents Association
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• v.11 no.10
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• pp.355-369
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• 2011

The purpose of this study was to determine the subjective symptoms of respiratory disease and factors related to prevalent status among dental technicians by analyzing the questionnaire data from 300 dental technicians in Seoul and GyeongGi-Do, using SPSS WIN 18.0 program. The results are followings; 1. There were significant differences among subjects in the normal complaints rate for cough by presence smoking, total career, and work days per week. 2. There was significant difference among subjects in the normal complaints rate for sputum only by work days per week.(P<0.05) 3. There were significant differences among subjects in the normal complaints rate for continuance of sputum or congestion by work days per week and required measures for improvement in pain. 4. There were significant differences among subjects in the normal complaints rates for blocked nose and coryza by sex, age, work days per week and average length of breaking time during working (P<0.05). 5. There were significant differences among subjects in the normal complaints rates for shortness of breath by sex, exercise frequency, average length of exercise, main job. 6. There was significant difference among subjects in the experience rate due to symptom of pulmonary disease only by main job.(P<0.05).

• KSTLE International Journal
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• v.3 no.1
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• pp.49-53
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• 2002

Inconel 690 for nuclear steam generator tube has more chromium than the conventionally used Inconel 600 in order to increase the corrosion resistance. TD evaluate the tribological characteristics under fretting condition the fretting tests as well as sliding tests were carried out in elevated temperature water environment. Fretting tests of the cross-cylinder type were done under various vibrating amplitudes and applied normal loads in order to measure the friction forces and wear volumes. Also, the conventional sliding tests of pin-en-disk type were carried out to compare the test results. In fretting, the friction was very sensitive to the load and the amplitude. The friction coefficient decreased with increasing load and decreasing amplitude. Also, the wear of Inconel 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and of ten drastically different wear rates can occur. It was fecund that the fretting wear coefficients in water were increased as increasing the temperature of water.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.84-89
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• 2004

When the tube contacted to support, anti-vibration bar of the steam generator in nuclear power plant, the contact area is worn out by their relative displacement and contact force. Connors and Au-Yang found the relation between tube worn displacement and volume, or normal work rate at given gap size. The present analysis is obtained the relation between tube worn displacement and normal work rate at various gap size modifying Au-Yang's result. The results are compared with Connors and Yettisir and Pettigrew's results. The comparison shows that Yettisir and Pettigrew result is fairly good agreement with Connors and present results with gap clearance, 0.015in.