• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.3
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• pp.304-311
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• 2018

Objectives: The purpose of this study was to compare the self-reported symptoms of occupational asthma, occupational rhinitis, and respiratory symptoms between a direct exposure to flour dust group and a non-exposure group from the bakery industry. Methods: The participants were 62 workers directly exposed to flour dust and 30 non-exposed workers. The survey was composed of questions related to general characteristics. Korean self-reported respiratory symptoms(SNU-93), occupational asthma, and occupational rhinitis data was collected from April to July 2017. Results: The smoking rate among the direct exposure to flour dust workers was 67.7% and the mean of working hours(11-12) was 96.8%. The SNU-93 questionnaire revealed that respiratory symptoms in the chest and wheezing or whistling were significantly higher among the direct-exposure group than non-exposure group. The response for occupational asthma symptoms was significantly higher in the direct exposure group(2.4 points) than in the non-exposure group(1.6 points). Conclusion: In order to decrease the symptoms of these respiratory diseases among bakery workers exposed to flour dust, it is necessary to reduce working hours and the smoking rate. The performance of periodic medical examinations is needed to find abnormal respiratory diseases. In addition, workers who have been diagnosed with asthma and rhinitis should consider switching to a process that is not exposed to flour dust.

• Korean Journal of Environmental Biology
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• v.36 no.4
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• pp.456-462
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• 2018

The purpose of this study was to assess cross-generational effects of bisphenol A exposure in benthic copepods, Tigriopus west. Nauplii (<24 hours old) were exposed to graded concentrations of bisphenol A, and toxicity end-points such as survival, development, sex ratio, and fecundity were measured. $F_1$ generations were grown under innoxious conditions, and similarly assessed. Significant differences were observed in development of nauplii and copepodites, between exposed and non-exposed copepods; however, there were no differences in survival of nauplii or copepodites, sex ratio, or brooding rate in parental generation. In contrast, in the $F_1$ generation, there were significant differences between the control group and exposed group in survival and development of nauplii. Length, width, and biomass of parental and $F_1$ generations were reduced in the exposed group compared to the control group. In addition, some deformities, such as swelling of the prosome, abnormally shaped egg sac, and dwarfism were observed after exposure to bisphenol A. So, our study demonstrates that a cross-generation toxicity test and monitoring of morphological deformities in harpacticoid copepods, can be useful for development of potential bioindicators for environmental monitoring, and assessment of chemical impact.

• Journal of fish pathology
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• v.15 no.2
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• pp.57-64
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• 2002

Phenanthrene-induced changes in blood organic components. transaminase and ALP activities of Paralichthys oIivaceus were investigaled. The aim of this study was to obtain a holistic view of the toxic responses, and compensations of fish exposed to waterborne phenanthrene. Fish were exposed to 0, 0.5, 1, 2$\mu$M of phenanthrene for 4 weeks. The most noticeable changes were concentration-dependent increase in levels of blood GOT and GPT activities. At concentrations 1.0 and 2.0 $\mu$M of phenanthrene GOT, GPT and ALP enzyme activities in plasma were increased. Plasma albumin concentration was stable in phenanthrene-exposed fish, however, plasma total protein level was reduced significantly at the 4-week sampling points (2.0$\mu$M). Plasma glucose levels were found to be increased significantly over the cootrol throughout duration of the experiment with phenanthrene. Overall the results suggest that phenanthrene has the potential to alter some physiological functions in olive flounder.

• Journal of Technologic Dentistry
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• v.36 no.2
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• pp.111-118
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• 2014

Purpose: Production of dental prosthesis by a dental technician causes a loud noise. Thus, we investigated stress of dental technicians due to a noise using a structured questionnaire. Methods: A survey was conducted on working dental technicians across the country from July 2013 to November 2013; among 200 sets of survey distributed, 166 were completed and returned, and excluding the 11 that deemed unsuitable, 155 sets were used for statistics. The program SPSS 19.0 was used to analyze the correlation among the collected data. Results: The stress of noise was found to be 2.83/5 points (2.93/5 for physical stress, 2.72/5 for emotional stress). Recognition of noise was found to be 2.71/5 points (3.39/5 for recognition of noise, 2.64/5 for accidents caused by noise, 2.29/5 for experiencing disability due to noise). For general items, the highest stress were shown for the following catogories: by gender, females (p=.008); by position, chief engineer (p=.033); by monthly pay, 2.51M-3.0M KRW (p=.023); by interior comfort, 'very unpleasant' was the highest recognized (p=.014). For the effect of time exposed to noise, its stress (p=.000) and recognition (p=.000) rose with increase of time. Conclusion: Dental technicians performs tasks in work environments exposed to extreme noise. This research attempts to re-emphasize the necessity for improving the work environment for noise and provide measures of blocking noise and precaution.

• Bulletin of the Korean Chemical Society
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• v.16 no.11
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• pp.1046-1056
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• 1995

A topological theory has been introduced to evaluate the degree of complexation and the viscosity of polymer complexes by extending the theory of Iliopoulos and Audebert for aqueous polymer solutions. The previous theory of Iliopoulos and Audebert has offered only a semiquantitative theoretical model for polymer complex systems, whereas our present work gives a general theoretical model applicable to all the polymer complex systems. Their theories considered only the physical property term caused by the displacement of complexed points between polymer solute chains, while our theory deals with all the physical effects, caused by the displacement of complexed points entangled points in polymer solute chains. There have been predicted the characteristics of physical properties from the expression. It is exposed that the predictive values show good agreement with the experimental data for polymer complexes.

• Journal of applied mathematics & informatics
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• v.41 no.1
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• pp.107-121
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• 2023

An epidemic infectious disease model consists of six compartments viz. Susceptible, Exposed, Infected, Quarantine, Recovered, and Virus with nonlinear saturation incidence rate is proposed to know the viral disease dynamics. There exist two biological equilibrium points for the model system. The system's local and global stability is done through Lyapunov's direct method about equilibrium points. The sensitivity analysis has been performed for the basic reproduction number and equilibrium points through the normalized forward sensitivity index. Sensitivity analysis shows that virus growth and quarantine rates are more sensitive parameters. In support of mathematical conclusions, numerical experimentation has been shown.

• Korean Journal of Environment and Ecology
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• v.8 no.2
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• pp.167-176
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• 1995

Autumn visitors to Chuwangsan National Park was more than summer's. About 89% of total visitors used main trail but approximately 35% visited to the Third Falls. The entire width, bare width, maximum depth and slope of trail as the trail condition surveyed at the total of 103 points were significantly greater on the more heavily-used trail. Trail conditons of rock-exposed, root-exposed, deepening points as the deterioration types of trail were significantly different from those of non-deteriorated points. According to the topographic position of trail, severe difference of dominant trees in the edge vegetation was found and Lespedeza maximowiczii, Rhododendron yedoense and Fraxinus sieboldana were dominant in shrub layer of trail edge vegetation. The crown coverage, number of species and individuals of shrub layer in edge vegetation were generally higher than those in the other national parks with more heavily-used trail.

• Korean Journal of Environment and Ecology
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• v.7 no.2
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• pp.241-251
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• 1994

Use impacts on environmental deteriorations were studied on the four major trails and a campsite of Tokyuksan National Park in 1993. The entire width, bare width, maximum depth and slope of trail as the trail condition were significantly greater on the more heavily used trail. Percentages of rock-exposed, deepening, root-exposed points as the deterioration types of trail which were surveyed at the total of 106 points were higher and trail conditions were significantly different from those of non-deteriorated points. On the Paekryon trail, the damaged area more severe than Class 4 reaches about 910$m^2$/km and the use impact and deterioration on campsites were accelerated. The dominant trees of the the upper and lower layer in trail edge vegetation could be Quercus serrata and Acer pseudo-sieboldianum for Paekryon trail, Q. mongolica and Tripterigium regelii for the other trails. A. pseudo-sieboldianum, Q. serrata, Rhus trichocarpa, Fraxinus sieboldiana, Lespedeza maximowiczii, Symplocos chinensis for Pilosa were classified for tolerant species to use impacts.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.3 no.2
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• pp.177-187
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• 1993

The exposure levels of mixed organic solvents for 66 exposed workers in six paint manufacturing plants were evaluated. In 66 exposed workers and 30 control subjects, we also determined the concentrations of toluene and xylene metabolites, hippuric acid, ($o^-$, $m^-$, and $p^-$)methylhippuric acid. The results were as follow ; 1. Seven organic compounds, which on averge accounted for approximately 90% of the identified mass in each painting plants air samples, were selected for quantification : methyl ethyl ketone, ethyl acetate, methyl isobutyl ketone, toluene, butyl acetate, ethyl benzene, ($o^-$, $m^-$, $p^-$)xylene. 2. The average mixed organic solvent exposure levels in 66 points with workplce were 3.8ppm of MEK, 12.2ppm of ethyl acetate, 4.0ppm of MIBK, 28.7ppm of toluene, 3.8ppm of butyl acetate, 10.2ppm of ethyl benzene, 14.6ppm of xylene, respectively. 3. For the total 66 points with workplace, the rate of them of which mixed solvents in air was exceeded th TLV of 1.0 were obtained for 23%(15/66 point). 4. The concentrations of hippuric acid in urine of exposed group and control were $0.94{\pm}0.65g/g$ of creatinine, $0.16{\pm}0.11g/g$ of creatinine, respectively. 5. There was a linear correlation between the end shift hippuric acid acid levels in urine and exposed toluene in air : y=0.02079X+494.2, r=0.6488, n=55 y:hippuric acid in urine(mg/g of creatinine), x:toluene levels in air(ppb) Toluene levels of 100ppm in air have been caculated to hippuric acid of 2.57g/g of creatinine in urine. 6. There was a linear correlation between the end shift methylhippuric acid acid levels in urine and exposed xylene in air : y=0.01664X+31.6, r=0.7264, n=55 y:methylhippuric acid in urine(mg/g of crea.), x:xylene levels in air(ppb) Xylene levels of 100ppm in air have been caculated to methylhippuric acid of 1.69g/g of creatinine in urine.

• Structural Engineering and Mechanics
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• v.60 no.4
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• pp.655-665
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• 2016

This paper aims to develop models to accurately predict the behavior of fresh concrete exposed to vibration using artificial neural networks (ANNs) model and regression model (RM). For this purpose, behavior of a full scale precast concrete mold was investigated experimentally and numerically. Experiment was performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on mold while both mold is empty and full of fresh concrete. Modeling of empty and full mold was made using both ANNs and RM. For the modeling of ANNs: Experimental data were divided randomly into two parts. One of them was used for training of the ANNs and the remaining part was used for testing the ANNs. For the modeling of RM: Sinusoidal regression model equation was determined and the predicted data was compared with measured data. Finally, both models were compared with each other. The comparisons of both models show that the measured and testing results are compatible. Regression analysis is a traditional method that can be used for modeling with simple methods. However, this study also showed that ANN modeling can be used as an alternative method for behavior of fresh concrete exposed to vibration in precast concrete structures.