• Smart Structures and Systems
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• v.25 no.4
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• pp.459-469
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• 2020

The presence of cracks in mechanical components is a very important problem that, if it is not detected on time, can lead to high economic costs and serious personal injuries. This work presents a methodology focused on identifying cracks in unbalanced rotors, which are some of the most frequent mechanical elements in industry. The proposed method is based on Artificial Neural Networks that give a solution to the presented inverse problem. They allow to estimate unknown crack parameters, specifically, the crack depth and the eccentricity angle, depending on the dynamic behavior of the rotor. The necessary data to train the developed Artificial Neural Network have been obtained from the frequency spectrum of the displacements of the well- known cracked Jeffcott rotor model, which takes into account the crack breathing mechanism during a shaft rotation. The proposed method is applicable to any rotating machine and it could contribute to establish adequate maintenance plans.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.3
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• pp.367-376
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• 2016

Objectives: The production and use of nanoparticles have been increased. In 2014 Workplace Survey Results, 335 companies produce and treat nanoparticls. However, lack of data on nano-toxicity and a method for risk management and regulation on nanoparticles and the standard test method are not sufficient. Protective equipment selection guidelines for nanoparticles are not established. It is required to carry out respirator efficiency test against nanoparticles. This study was performed to evaluate filtration efficiency and manikin-based total inward leakage of particle filtering mask using in Korean country challenged with silver nanoparticles. Methods: We investigated filtration efficiency and total inward leakage of 7 respirator with silver nanoparticle. Results: The geometric mean diameters of Silver nanoparticles were 30 nm and number concentration were about $10^6{\sharp}/cm^3$. Filtration efficiency of six of the seven particle filtering masks was more than 98% and one particle filtering masks filtration efficiency was 94.9%. The filtration efficiency of particle filtering masks to 20 nm silver nanoparticels was highest. Artificial breathing machine with manikin based total inward leakage were 7.6% ~ 42.3%. Conclusions: The results of this study nano-silver filter efficiency was high but the total inward leakage was higher than filter penetration. Therefore, education on how to wear a respirator should be demanded. Especially for workers handling nanoparticles and toxic material, user seal checking and fit test must be performed.

• Journal of Haehwa Medicine
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• v.12 no.1
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• pp.103-121
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• 2003

Human being can't live without nature, then the changes of nature affect human body. It means that human body has corresponding changes to the KI(vital energy) of nature. There is a stream of changes in human body which circulate mysteriously and punctually by the laws of nature. If this stream of changes fits into human's life style, it would be most effective. It has a certain mode continuously. So if a person has a habit fitting into it, he will get the healthiest body. Then the researcher tries to explain the changes in human body by the time, mainly focused on within 24 hours. it is showing not only the oriental view, but also the western's. The researcher can find the coincidence as followings. At In-Si(3-5 am), the body function and the body temperature get to the bottom, therefore it's good for him to wake up and to run the vital energy. At Sa-Si(9-11 am), the patience on pain anxiety and the psychic concentration get to the top, he'd better start the work. At O-Si(11am-1pm), the heart energy has a vital move, then the blood concentration of Hb(hemoglobin) gets to the top. At Mi-Si(1-3 pm), the muscle strength, the squeeze, and the breathing rate increase. The reflex nerve sensitivity gets to the top. Creativity, observation, and working efficiency go high, so it's time to work hard. At Hae-Si(9pm-1am), the body function falls, sleeping is needed. At Chuck-Si(1-3 am), the cell spontaneity gets to the top, immune lymphocyte moves actively, and the blood concentration of growth hormone gets to the top. These are liver's work. In west, there has been active studies on how to reduce the side effect by using a person's bio-rhythm based on the 'time treatment', and how to reorganize the bio-rhythm by using the machine and the age resistance based on the 'bio-watch'. Though the 'time treatment' means something, the artificial resistance on bio-rhythm seems to give bad effects to human body. If a person lives by regimen of oriental medicine, he will maintain the healthiest body. Regimen is that human body follows the laws of nature, and moves its mysterious, Punctual and periodical changes.