• Journal of the Korea Furniture Society
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• v.26 no.4
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• pp.467-473
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• 2015

Natural dyeing is considered to be an alternative to chemical staining in terms of harmful VOC-free and environmentally-friendly ingredient. This study was concerned with an evaluation of color performance of naturally dyed- and painted veneer for cylindrical laminated veneer lumber etc. according to the used condition in terms of existence of light and heat in drying. From the results, the color changes by the color of dyed veneer and the type of paint are likely to be affected by fading condition of light or heat. In the future, long-term outdoor exposure test needs to be additionally followed in order to evaluate durable usability of colored veneers.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.126-127
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• 2017

This study investigates the effect of improving the heat resistance performance when carbon fiber is mixed in the polyurea coating material. A tensile strength test method was carried out with the carbon fiber mixed polyurea specimens at an interval of 7, 14, and 21 days after heat treatment at 140±2℃. The test results showed that there was a significant decrease in the tensile strength performance. While the elongation and tensile performance decreased greatly, it was confirmed nevertheless the overall performance was maintained. This study proposes that mixing carbon fiber to the polyurea resin can effectively secure long-term heat resistance, thereby solving the problem of deterioration of physical properties caused by exposure to ultraviolet rays.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.9 s.240
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• pp.1253-1261
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• 2005

Cast stainless steel (CSS) is thermally aged by a long term exposure in the range of nuclear power plant operating temperature. The thermal aging is a cause of concern for the continued safe and reliable operation of CSS nuclear components. Therefore, an assessment of degradation in material properties of these components has been importantly considered. In this study the ball indentation tests were performed on four cast stainless steels aged at $400^{\circ}C$ for 3600 hours, to investigate the applicability of ball indentation test to the assessment of aging degradation of cast stainless steels. Thus, the reliability of ball indentation test for aged CSS was analyzed by evaluating the scattering of data tested from each material and by comparing tensile properties obtained from ball indentation test and standard tensile test. Also, the tensile properties of aged CSS obtained from ball indentation test were compared with those predicted by the evaluation procedure developed on the basis of material database for aged CSS.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.25 no.4
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• pp.525-533
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• 2015

Objectives: Alongside smoking, occupational exposure is an important risk factor for chronic obstructive pulmonary disease. The purpose of this study was to evaluate factors associated with occupational pulmonary function decline that can be used to create guidelines for the health management of shipyard workers Materials: This study analyzed spirometry from 10,597 male shipbuilding workers. Functional decline in spirometry was defined as FEV1/FVC <70% and logistic regression for work duration and occupational hazard exposure was performed Results: Among the subjects, 4.2% showed an obstructive pattern in pulmonary function. The odds ratios for hazard exposure were 1.67(indirect) and 3.54(direct), and for work duration 1.97(10-18 years), 2.29(19-27), and 5.02(28+). After adjusting for smoking and work-related factors, the odds ratios for work durations of over 10 years were 1.73(10-18 years), 1.99(19-27), and 4.09(28+), but for hazards exposure was 1.71(direct) alone after adjustment. Conclusions: Occupational COPD is insidious and chronic, and thus long-term hazard exposed(especially over 10 years) shipyard workers with functional decline in spirometry need to prevent and manage COPD. This study is important for establishing guidelines to manage hazard exposure among shipyard workers and prevent COPD.

• KIEAE Journal
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• v.1 no.2
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• pp.21-28
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• 2001

Naturally-ocurring short-lived decay products of radon gas in indoor air are the dominant source of ionizing radiation exposure to the general public. It is written in BEIR VI Report(l999l the radon progeny were identified as the second cause of lung cancer next to cigarette or 10 % to 14 %(15,400 to 21,800 persons p.a.) of all lung cancer deaths in USA. Indoor radon concentrations in houses typically result from radon gaining access to houses mainly from the underlying soil. In the States, they have "Indoor Radon Abatement Act" which was converted from "Toxic Substance Control Act" in 1988 to establish the national long-term goal that indoor air should be as free of radon as the ambient air outside of buildings. To review and study techniques for controlling radon, two test cells were constructed for a series of tests and are under measuring indoor and soil gas (underneath of floor slab)radon concentrations according to EPA's measurement protocol. In this paper, important theoretical studies are previewed and the following paper will explain the test results and confirm the theories reviewed to find out suitable coefficients. On the basis of test analysis, it will be described and evaluated various techniques that can be used to mitigate elevated indoor concentration of radon including the control of radon and its decay products.

• Journal of The Korean Society of Clinical Toxicology
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• v.19 no.2
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• pp.100-109
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• 2021

Purpose: The purpose of this study was to investigate effect of N-acetylcysteine (NAC) on the injury of putative parvalbumin positive interneurons defined by molecular marker and hippocampal long-term potentiation (LTP), a marker of neural plasticity following acute carbon monoxide (CO) poisoning. Methods: Adult Sprague-Dawley rats were exposed to 1100 ppm CO for 40 minutes followed by 3000 ppm CO for 20 minutes. Animals received daily intraperitoneal injection of NAC (150 mg/kg) for 5 days after CO exposure. Changes in learning and spatial memory were evaluated by Y-maze test 5 days after the poisoning. In vivo LTP in hippocampal CA1 area was evaluated by using extracellular electrophysiological technique. Immunohistochemical staining were adopted to observe expressional damages of parvalbumin (PV) immunoreactive interneurons in the hippocampus following the poisoning. Results: Acute CO intoxication resulted in no changes in memory performance at Y-maze test but a significant reduction of LTP in the in hippocampal CA1 area. There was also a significant reduction of PV (+) interneurons in the hippocampal CA1 area 5 days after CO poisoning. Daily treatment of NAC significantly improved hippocampal LTP impairment and reduced immunoreactivity for PV in the hippocampus following the acute CO poisoning. Conclusion: The results of this study suggest that reduction of hippocampal LTP and PV (+) interneurons in the hippocampus is sensitive indicator for brain injury and daily NAC injections can be the alternative therapeutics for the injury induced by acute CO poisoning.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.10
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• pp.141-150
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• 2006

In this study we developed accelerated aging test cycle and equipment which can simulate domestic weather condition. And we proposed long term reliability assessment method for polymer housed distribution surge arresters. We carried out electrical and chemical analysis of the arresters which are used for accelerated aging test and outdoor exposure test. Through the analysis we verified the capability of the proposed method and we presented characteristic data for maintenance of domestic arresters.

• Korean Journal of Biological Psychiatry
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• v.4 no.2
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• pp.237-245
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• 1997

The study was designed to evaluate the significant roles of SSRI in rat of depression model. Chronic exposure to mild unpredictable stress has been found to depress the consumption of sweet 1% sucrose solutions in the Sprague-Dawley rats. We applied the variety of 11 types of stress regimens and identified depressive behaviours(developed by Willner) in 70 Sprague-Dawley rats. Rats in experiments were stratified into 6 groups, ie ; 3 kinds of SSRI(paroxetine, fluoxetine, sertraline), clomipramine, choline and saline control. Memory function was evaluated by passive avoidance learning and retention test. The authors determined how long memory retention would remain improved with 24 hour, 1 week, 2 weeks, 3 weeks, and 4 weeks at training-testing interval in depressive states of the Sprague-Dawley rats. The results were as follows ; 1) There were no significant differences between the 6 groups at the 24 hour training-testing interval. 2) The paroxetine treated group showed significant differences from the control group at the 1 week and 2 weeks training-testing interval. 3) The paroxetine and the fluoxetine treated groups showed singificant differences from the control group at 3 week training-testing interval. 4) The paroxetine and the choline treated groups showed significant differences from the control group at 4 week training-testing interval. In summary, paroxetine had an effect on long term memory processing from 1st week to 4th week. Also, fluoxetine(at 3rd week) and choline(at 4th week) had effect on long term memory processing. Sertraline, clomipramine were ineffective on memory processing during 4 weeks observation. Possible explanations why paroxetine had early effect on memory processing than the other selective serotonin reuptake inhibitors are rapid bioavailability, which is the characteristics of pharmacokinetics of paroxetine. In clinical situation, author carefully suggest that SSRI would be beneficial to improve the memory function caused by depressive neurochemical changes.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.659-662
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• 2005

Electrochemical impedance spectroscopy (EIS) has been extensively used to try to evaluate the corrosion state of the steel/concrete system. This technique is attractive because, in theory, used in a wide range of frequencies, it can give detailed information about the mechanisms and kinetics of the electrochemical reactions. Impedance measurements were performed using potential control and measuring the corresponding current response. One-year-old southern exposure test. specimens were used in the current study. The effectiveness of corrosion inhibiting additives was evaluated. The corrosion current densities estimated by impedance measurements were confirmed by those determined using linear polarization techniques. The purpose of this study was to evaluate the long-term-performance potential of the corrosion inhibitors in chloride contaminated reinforce concrete.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.333-338
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• 2003

Polymeric composite structures used in ground transportation applications such as the carbody of tilting train may be exposed to a ground environmental conditions during long-term missions. In this study, the degradation of mechanical and physical properties of graphite/epoxy composite and glass fabric/phenol composite under ground environmental conditions was investigated. Accelerated environmental conditions of ultraviolet radiation, temperature, and moisture were considered. Several types of specimens were used to investigate the effects of environmental conditions on mechanical properties of the composites. Also, storage shear modulus, loss shear modulus, and tan 8 were measured as a function of exposure times through a dynamic mechanical analyzer. Finally, composite surfaces exposed to environmental conditions were examined using a scanning electron microscope.