• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1995.10a
• /
• pp.280-283
• /
• 1995

계층형 신경회로망은 학습능력이나 비선형사상능력을 가지고 있고, 그 특징을 이용하여 패턴인식이나 동정 및 제어 등에의 적용이 시도되어 성과를 올리고 있다. 현재, 그 학습법으로 널리 이용되고 있는 것이 역전파학습법으로 최급 강하법이나 공액경사법 등의 최적화 방법이 적용되고 있지만, 학습에 많은 시간이 걸리는 점, 국소적 최적해(local minima)에 해의 수렴이 이루어져 오차가 충분히 작게 되지 않는 점 등이 문제점으로 지적되고 있다. 본 논문에서는 Hu에 의해 고안된 random 탐색법과 조합된 random tabu 탐색법으로 최적결합계수를 구하는 학습알고리즘으로, 국소적 최적해에 수렴하는 것을 방지하고, 수렴정도를 개선하는 새로운 방법을 이용하여 회전기계의 이상진동진단에 적용가능성을 검토하고 오차역전파법에 의한 진단결과와 비교검토한다.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.30 no.2
• /
• pp.111-117
• /
• 2017

In this paper, a local deformation effect in thin-walled box beams is investigated via a finite element modal analysis. The analysis is carried out for single-cell and multi-cell box beam configurations. The single-cell box beam with and without a neck, which mimics a simple wind-turbine blade, is analyzed first. The results obtained by shell elements are compared to those of one-dimensional(1D) beam elements. It is observed that the wall thickness plays a crucial role in the natural frequencies of the beam. The 1D beam analysis deviates from the shell analysis when the wall thickness is either thin or thick. The shell modes(local deformations) are dominant as it becomes thin, whereas the shear deformation effects are significant as it does thick. The analysis is extended to the single-cell box beam with a neck, in which the shell modes are confined to near the neck. Finally the multi-cell box beam with a taper, which is quite similar to real wind-turbine blade configuration, is considered to investigate the local deformation effect. The results reveal that the 1D beam analysis cannot match with the shell analysis due to the local deformation, especially for the lagwise frequencies. There are approximately 5~7% errors even if the number of segments is increased.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2012.04a
• /
• pp.178-185
• /
• 2012

In Korea, researches on the exposure assessment of the hand-transmitted vibration started from the mid-90, however, they were performed in the limited industries such as auto-assembly plants and the evaluation of the vibration was mostly conducted by ISO 5349(1986). Therefore, it was necessary to assess hand-transmitted vibration levels of workplace such as ship building/repairing industry or mining industry where occupational injuries are largely occurred and to evaluate the vibration levels using revised ISO 5349(2001). The SVAN 949 Four Channels Sound & Vibration Analyser was used for the measurement. The workers using a chain saw were exposed to $1.7{\sim}2.8m/s^2$ of daily vibration level. Workers using a rock drill in a coal mining were exposed to the highest vibration acceleration among workers and the levels were $7.1{\sim}10.8m/s^2$. Vibration levels of grinders were different according to the types of grinders. The hand-transmitted vibration of 3 types of grinders were measured and the levels were $3.3{\sim}11.1m/s^2$. Workers using a impact wrench were exposed to $1.5{\sim}1.6m/s^2$ of vibration. Out of 20 kinds of machines, only 4 tools provided the information of vibration acceleration on the instructions. In addition, the current condition of workplaces to control vibration was not much different from the past because there are no vibration exposure limit.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.22 no.10
• /
• pp.940-948
• /
• 2012

In Korea, researches on the exposure assessment of the hand-transmitted vibration started from the mid-90, however, they were performed in the limited industries such as auto-assembly plants and the evaluation of the vibration was mostly conducted by ISO 5349(1986). Therefore, it was necessary to assess hand-transmitted vibration levels of workplace such as ship building/repairing industry or mining industry where occupational injuries are largely occurred and to evaluate the vibration levels using revised ISO 5349(2001). The SVAN 948 Four Channels Sound & Vibration Analyser was used for the measurement. The workers using a chain saw were exposed to 1.7~2.8 $m/s^2$ of daily vibration level. Workers using a rock drill in a coal mining were exposed to the highest vibration acceleration among workers and the levels were 7.1~10.8 $m/s^2$. Vibration levels of grinders were different according to the types of grinders. The hand-transmitted vibration of 3 types of grinders were measured and the levels were 3.3~11.1 $m/s^2$. Workers using a impact wrench were exposed to 1.5~1.6 $m/s^2$ of vibration. Out of 20 kinds of machines, only 4 tools provided the information of vibration acceleration on the instructions. In addition, the current condition of workplace to control vibration was not much different from the past because there are no vibration exposure limit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 1994.10a
• /
• pp.121-125
• /
• 1994

본 논문에서는 Hu에 의해 고안된 random 탐색법과 조합된 tabu 탐색법(radnom tabu 탐색법)을 결합계수를 구하는 학습 알고리즘으로 직접 사용하여 국소적 최적해에 수렴하는 것을 방지하고, 수렴정도를 개선하는 새로운 방법을 제안한다. 이 방법을 배타적 논리합 문제에 적용하여 역전파법 및 tabu 탐색법을 이용한 오차역전파법과 비교한다. 그리고, 각 파라메터가 오차함수의 수렴에 미치는 영향을 조사한다.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2011.06a
• /
• pp.967-968
• /
• 2011

• Journal of the Korean Society of Safety
• /
• v.24 no.1
• /
• pp.60-68
• /
• 2009

The aim of this paper is to evaluate the compatibility of anti-vibration gloves, to predict the attenuation of vibration with different types of anti-vibration gloves, to estimate the spectra of the ISO 10819 standard, and to present an oscillating spectrum adequate for vibrating tools. This paper use two ISO standards for the measurement and evaluation of hand-arm vibration. Some anti-vibration gloves can attenuate vibration, but all the anti-vibration gloves in this study do not satisfy the ISO 10819 requirements. In case of equal vibration types, the outside materials are effective in order of leather, fabrics and rubber-coating. Anti-vibration gloves manufactured in the United State satisfy ISO 10819 criteria using United State subjects, but do not satisfy ISO 10819 using Japanese subjects. M-spectrum acceleration exists below 10Hz and H-spectrum exists above 500Hz. Generally vibrating tools have the peak of Z-axis, but generation of vibration differ from each vibrating tools.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.1
• /
• pp.436-444
• /
• 2013

This article presents the dynamic response of nano-scale plates using the nonlocal continuum theory and higher-order shear deformation theory. The nonlocal elasticity of Eringen has ability to capture the small scale effects and the higher-order shear deformation theory has ability to capture the quadratic variation of shear strain and consequently shear stress through the plate thickness. The solutions of transient dynamic analysis of nano-scale plate are presented using these theories to illustrate the effect of nonlocal theory on dynamic response of the nano-scale plates. The relations between nonlocal and local theories are discussed by numerical results. Also, the effects of nonlocal parameters, aspect ratio, side-to-thickness ratio, size of nano-scale plate and time step on dynamic response are investigated and discussed. The amplitude and cycle increase when nonlocal parameter increase. In order to validate the present solutions, the reference solutions are used and discussed. The theoretical development as well as numerical solutions presented herein should serve as reference for nonlocal theories as applied to the transient dynamic analysis of nano-scale structures.

• IE interfaces
• /
• v.17 no.3
• /
• pp.375-383
• /
• 2004

The purpose of this study is to investigate the characteristics of vibration induced by the powered hand tools used in the automobile assembly lines, and estimate the prevalence of vibration syndrome. The acceleration levels of four major powered hand tools were measured using the ISO 5349 method along with the time of exposure to the vibration of the hand tools. Four-hour-energy-equivalent frequency-weighted accelerations ranged from $1.27m/s^2$ to $2.58m/s^2$, After exposure to vibration for 12.6 years, about 10% of the workers using impact ranches were expected to develop Raynaud's disease. For the workers using grinders, 16.6% of the workers were expected to develop Raynaud's disease. The results would be of help in developing the guidelines of local vibration control.

• Journal of the Korea Safety Management & Science
• /
• v.11 no.1
• /
• pp.67-73
• /
• 2009

The goal of this study was to assess the level of vibration in an walking-type cultivator, and to provide a basic information to manage the vibration exposure for farmers. The latent periods of vibration-induced white finger (VWF) were assessed through analyzing the vibration levels and frequency characteristics. Also, vibration acceleration levels based on the daily vibration exposure duration was suggested. The latent periods of vibration-induced white finger were assessed by ISO 5349 method. The latent periods were 4.5 and 10.1 years at 10% and 50% of farmer group, respectively. Also, under ACGIH (American Conference of Governmental Industrial Hygienists) standard, daily vibration exposure duration at 6.7 m/s2 of vibration acceleration has to be less than 4 hours. Therefore, education that maximum working hours should be less than 4 continuous hours is necessary for the operators of walking-type cultivators.