• Journal of Korean Society on Water Environment
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• v.28 no.2
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• pp.232-237
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• 2012

Total suspended solids (TSS), settleable suspended solids (SSS) and nonsettleable suspended solids (NSSS) were compared in streams and lakes during rain events. Samples were collected in Lake Soyang and nine agricultural streams during storm events over two years. To measure NSSS, samples were settled in 1 L cylinders for one hour and then 50% of the total sample volume was taken from the center of the cylinder. The SSS/TSS ratio in streams (0.50) was higher than in Lake Soyang (0.20). The ratio of TSS to turbidity decreased from 1.21 in the inflowing river to 0.69 in the reservoir outlet. Turbidity and NSSS showed higher correlation ($r^2$=0.82) compared with the correlation between turbidity and TSS ($r^2$=0.66). Median particle size decreased from $11.4\;{\mu}m$ in the inflowing river to $4.2\;{\mu}m$ in the lake outlet. The results indicate that only fine particles of less than $5{\sim}10\;{\mu}m$ can be transported downstream of the lake. Because fast-flowing water in streams includes not only fine particles but also coarse particles, an overestimation of suspended sediment concentration results if only TSS is measured. Consequently, TSS and NSSS should be measured separately to evaluate the effect of suspend sediment loadings of turbid streams on aquatic habitat during the monsoon season.

• Journal of Korean Society of Water and Wastewater
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• v.27 no.4
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• pp.429-438
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• 2013

This study was to develop effective water quality management measures using LDC (Load Duration Curve) curves for TMDL (Total Maximum Daily Loads) unit watershed. Using LDC curves, major factors for BOD and T-P concentration loads generation (i.e. point source or non-point source) in the case study area (Geumho river basin) were found for different hydrologic conditions. Different measures to deal with the pollutant loads were suggested to establish BMPs (Best Management Practices). It was found that the target area has urgent T-P management methods especially at moist and midrange hydrologic conditions because of point source pollutants occurred in developed areas. One example measure for this could be establishment of advanced treatment facility. This study proved that the use of LDC was a useful way to achieve TWQ (Target Water Quality) on the target watershed considered. It was also expected that the methodology applied in this study could have a wider application on the establishment of watershed water management measures.

• Journal of the Ergonomics Society of Korea
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• v.33 no.2
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• pp.125-134
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• 2014

Objective: The purpose of this study is to evaluate integral seat desk used in universities through comparison of real dimension values of the desk with KS/ISO standard and questionnaire survey. Background: School furniture that helps students sit comfortably for longer periods of time and allows for better concentration on learning is important. However, seat and desk have been generally designed based on the industry practice rather than user's anthropometry, and seats and desks used in universities of Korea have not been ergonomically evaluated. Method: Real 13 dimensions of the desk used in K University were measured using tape measure and inclinometer, and the dimension values were compared to the KS standard of desk and chair for lecture room (KS G 4210) and ergonomic design principles found in relevant references. Subjective appropriacies and preference for the desk were investigated based on questionnaire survey, in which 121 (male: 91, female: 30) college students participated. Results: Several dimensions for the desk and chair investigated except desk depth and width, leg room width, seat width have not met the KS standard, but all dimensions satisfied ergonomic design principles available in references. The questionnaire survey revealed that appropriacies for desk surface size, seat pan depth, seat pan cushion and backrest curvature were under middle point of 3.0, and that those for the other dimensions showed higher scores exceeding 3.0. Conclusion: The integral seat desk widely used in universities showed some design problems in terms of standards of KS G 2010 and KS G 4210, and ergonomic design principles. Compared to the general desk with separated desk and seat, subjective preference on the integral seat desk was low. Application: This would be used as a valuable guideline when designing or choosing new integral seat desk with high satisfaction of students.

• Clinical and Experimental Reproductive Medicine
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• v.45 no.2
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• pp.88-93
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• 2018

Objective: The aim of this study was to measure reactive oxygen species (ROS) production and total antioxidant capacity (TAC) in the seminal fluid of the male partners in couples undergoing intrauterine insemination and to evaluate correlations between these values and their semen parameters. Methods: The study was conducted at Vamsam Fertility Center, Coimbatore, India and enrolled 110 male patients from whom semen samples were collected. ROS production was measured by a thiobarbituric acid reactive species assay, and TAC was measured by a 2,2-diphenyl-2-picrylhydrazyl free radical assay. The differences in the TAC and malondialdehyde (MDA) levels between the subfertile and fertile groups were analysed. Correlations between sperm parameters and TAC and MDA levels were statistically analysed, and cutoff values with respect to the controls were determined. All hypothesis tests used were two-tailed, with statistical significance assessed at the level of p< 0.05. Results: A total of 87 subfertile and 23 fertile men were included in the study. The mean MDA level was significantly higher in the subfertile subjects than in the fertile subjects, and the mean antioxidant level was significantly lower in the subfertile subjects than in the fertile subjects. Seminal MDA levels were negatively associated with sperm concentration, motility, and morphology, whereas the opposite was seen with TAC levels. Conclusion: Measurements of seminal TAC and ROS are valuable for predicting semen quality, and hence predicting the outcomes of fertility treatment.

• Journal of Environmental Health Sciences
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• v.44 no.4
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• pp.370-379
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• 2018

Objectives: Bisphenol A (BPA) has been extensively used in a variety of consumer products, resulting in widespread non-occupational human exposure. It is often detected in the human body. Studies have reported many health effects associated with endocrine and metabolic disruptions, including obesity, diabetes, hypertension, and cardiovascular diseases. This study was performed to explain the relationship between BPA exposure and obesity in the Korean adult population. Methods: The second stage of the Korean National Environmental Health Survey (KoNHES) was conducted from 2012 to 2014 with 6,478 persons participating. Using the results of the survey, we analyzed the exposure levels for BPA and the influence on obesity of BPA. Results: In model 1, the volume-based measure concentration of BPA, total, female and the 30s to 60s age group were positively related with BMI. In model 2, creatinine adjusted as a covariate and positive associations for BPA with BMI were observed in the female group and was marginally significantly associated in low body weight group. In model 3, creatinine adjusted (g/g-creatinine), BPA exposure, and BMI were positively related with sex, in females, and there was a marginally significant association with the low body weight group in the BMI categories. BMI was significantly associated with BPA in the female group in all three models. Conclusion: This study added further evidence that exposure to EDCs, include bisphenol A, is related with obesity among the general population. Given the environmental health concerns over BPA, it is necessary to develop comprehensive measures to reduce BPA exposure.

• Journal of Environmental Science International
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• v.22 no.9
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• pp.1199-1211
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• 2013

Mobile sources produce a significant fraction of total anthropogenic emissions in Korea and have harmful effects on air quality. Mobile emissions are intrinsically difficult to estimate due to complicated road networks and variations of traffic volume with location and time. To measure traffic pollutants with high temporal and spatial resolution under real conditions a mobile laboratory was designed. The mobile laboratory provide concentrations of $SO_2$, CO, NO, $NO_2$ and location coordinate value. This approach allowed for pollutant level measurements on many roads within short periods of time. In this study, on-road concentrations of $SO_2$, CO, NO and $NO_2$ were measured using mobile platform measurement along the 25 main roads in Busan to estimate the average air pollution level in short time difference. The measurements were conducted on favorable meteorological days from 2010 to 2012 and the overall concentrations of $SO_2$, CO, NO and $NO_2$ were 0.006, 0.8, 0.182 and 0.055 ppm respectively. The result showed that the concentration of CO, NO and $NO_2$ on road were twice, 18 times and 2.5 times higher than regional air quality monitoring sites mean in same period.

• Particle and aerosol research
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• v.9 no.3
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• pp.133-137
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• 2013

Measuring particle size distribution is one of the primary concerns in aerosol studies. For a nano-particle size distribution measurement, many scientists use a combination of a differential mobility analyzer (DMA) and a condensation particle counter (CPC) system, which is a called scanning mobility particle sizer (SMPS). Although it has a very high particle size resolution, some issues still remain. These problems include residence time between a DMA and a CPC, discontinuity of a CPC, and disturbance due to long scanning time during the precise measurement of particles. In particular, long scanning time is not adequate for measuring particle size distribution since the particle concentration is changing during the measurement. In this study, we developed radial exhaust multi-port system (REM-system) with no scanning time and high resolution to measure real-time particle size distribution. As a result of the REM-system performed using mono-disperse particle, it is expected that this system will be suitable for measuring continuously changing aerosol. If the counting efficiency of multi-condensation particle counter (M-CPC) and data inversion matrix are completed, REM-system will be a very adequate system for unsteady aerosol, which changes for SMPS scanning time.

• Biotechnology and Bioprocess Engineering:BBE
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• v.8 no.4
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• pp.233-239
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• 2003

For the quantitative analysis of an unknown sample a calibration curve should be obtained, as analytical instruments give relative, rather than absolute measurements. Therefore, researchers should make standard samples with various known concentrations, measure each standard and the unknown sample, and then determine the concentration of the unknown by comparing the measured value to those of the standards. These procedures are tedious and time-consuming. Therefore, we developed a polymer based microfluidic device from polydimethylsiloxane, which integrates serial dilution and capillary electrophoresis functions in a single device. The integrated microchip can provide a one-step analytical tool, and thus replace the complex experimental procedures. Two plastic syringes, one containing a buffer solution and the other a standard solution, were connected to two inlet holes on a microchip, and pushed by a hydrodynamic force. The standard sample is serially diluted to various concentrations through the microfluidic networks. The diluted samples are sequentially introduced through microchannels by electro-osmotic force, and their laser-induced fluorescence signals measured by capillary electrophoresis. We demonstrate the integrated microchip performance by measuring the fluorescence signals of fluorescein at various concentrations. The calibration curve obtained from the electropherograms showed the expected linearity.

• Korean Chemical Engineering Research
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• v.47 no.2
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• pp.213-219
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• 2009

Crystallization experiments were performed by addition of various amino acids into biomineralization mixture of calcium carbonate. Liquid-liquid reaction of calcium carbonate was investigated by mixing calcium chloride, sodium carbonate and additives such as silk fibroin, asparagine, aspartic acid, glutamic acid and glycine. Also, the effects of reaction time, pH and solution concentration were observed. Analysis of crystals was done by FE-SEM, XRD, FT-IR equipments. FE-SEM was used in order to analyze morphology and crystal size. XRD was used to measure peak intensities and presence of $CaCO_3$ crystal. Two kinds of crystals were confirmed by FT-IR spectrum. Crystal distribution with reaction time was identified with measured peak areas of XRD and FT-IR data.

• International Journal of Oral Biology
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• v.41 no.4
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• pp.243-251
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• 2016

This study was undertaken to achieve a high bleaching efficacy with plasma, through longer application and reparative bleaching processes, by different shade evaluation methods. Extracted human teeth were divided into 6 groups (n=10). All teeth were treated in pairs. Low concentration of 15% carbamide peroxide (CP) was applied, with and without plasma, for 10, 20, and 30-min tooth bleaching, respectively. The bleaching procedure was repeated once daily for four days. The teeth were maintained in a moist environment provided by artificial saliva. The Vitapan Classical shade guide and Commission Internationale de L'Eclairage (CIELAB) color system were collectively used to measure the bleaching efficacy. Color evaluation was statistically analyzed using Student t-test and one-way analysis of variance (ANOVA) complemented by Tukey's test. Combining the plasma with 15% CP showed significantly greater color changes compared to bleaching without plasma (p<0.05). A high bleaching efficacy with plasma is proportional to the repetitive application and the treatment time. A 30-min application with plasma provided the best bleaching. Repetitive bleaching showed lower probability of color relapse of the bleached tooth. The color change by shade guide correlated with the changes in CIELAB color system. A value of 1 color change units (CCU) conversion factor for overall color change (${\Delta}E$) values comparisons was 3.724 values. The two measuring methods provide a more accurate correspondence of color change. The repetitive and longer application for tooth bleaching, combined with plasma, has a strong bleaching effect and produces whiter teeth.