• Journal of Environmental Health Sciences
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• v.46 no.5
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• pp.504-512
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• 2020

Objective: The purpose of this study was to evaluate the indoor to outdoor ratio (I/O ratio) of time activity patterns affecting PM_2.5 concentrations in homes in Korea through a simulation. Methods: The time activity patterns of homemakers were analyzed based on the 'Time-Use Survey' data of the National Statistical Office in 2014. From September 30 to October 2, 2019, the experimenter lived in multifamily housing located in Guro-gu, Seoul. The I/O ratio of PM_2.5 concentration was measured by installing sensor-based instruments. Results: The average indoor and outdoor PM_2.5 concentrations during the three days were 33.1±48.9 and 45.9±25.3 ㎍/㎥, respectively. The average I/O ratio was 0.75±0.60. The indoor concentration tended to increase when PM_2.5 source activity such cooking and cleaning was present and outdoor PM_2.5 was supplied through ventilation. Conclusions: This study could be used as basic data for estimating indoor PM_2.5 concentrations with personal activity pattern and weather conditions using outdoor concentrations.

• Membrane Journal
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• v.14 no.3
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• pp.192-200
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• 2004

It is an anaerobic germ that Lactobacillus cell concentrated using ceramic membrane has high stability and long lifetime as compared with polymeric membrane. The effects of operating pressure, temperature, crossflow velocity on cell harvesting have been studied. Also the variation of flux and transmembrane pressure (TMP) with increasing concentration ratio and the change of TMP at constant concentration ratio (volumetric concentration factor: VCF) regarding the optimization have been examined. It showed that the permeate flux increased gradually with the increasing of transmembrane pressure, crossflow velocity, and volumetric concentration factor. The higher initial flux was due to the reduction of viscosity at elevated temperature. However, as operating time progressed, the effect of temperature was negligible since the effect of viscosity became minor. As a result, that operate in a constant concentration ratio, decreased degree could know that become slowly although the flux decreases according as operating time progressed. The flux is a very stable in the condition of constant VCF range. The yield of Latobaciilus (PS 406) which was cultivated at $37^{\circ}C$ was concentrated about 4.9{\times}10^9$ after operation.

• Journal of Environmental Health Sciences
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• v.45 no.2
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• pp.186-191
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• 2019

Objectives: Subway is one of the most common transportation modes in Seoul, Korea. The objectives of this study were to determine characteristics of in-cabin $PM_{2.5}$ concentration in Seoul Metro Line Number 2 and to identify factors of the $PM_{2.5}$ concentration. Methods: In-cabin $PM_{2.5}$ concentrations in Seoul Metro Line Number 2 were measured using real-time monitors and the factors affecting $PM_{2.5}$ concentration in cabin were observed. Linear regression analysis of in-cabin $PM_{2.5}$ concentration and indoor/outdoor (I/O) ratio were performed. Results: In-cabin $PM_{2.5}$ concentration was associated with the in-cabin $PM_{2.5}$ concentration in previous station. In-cabin $PM_{2.5}$ concentration was correlated with ambient $PM_{2.5}$ concentration and associated with underground station with control of the in-cabin $PM_{2.5}$ concentration in previous station. I/O ratio increased as the number of passengers increased and when passing through the underground station with control of I/O ratio in previous station. Conclusion: In-cabin $PM_{2.5}$ concentration was affected by ambient $PM_{2.5}$ concentration. Therefore, management of in-cabin $PM_{2.5}$ concentrations should be based on outdoor air quality.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.26 no.2
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• pp.188-197
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• 2016

Objectives: The purpose of this study was to evaluate the ozone exposure levels and the variations in ozone concentration in a semiconductor fabrication facility and office in relation to the ozone concentration in the outdoor air. Methods: This study was performed in an office, semiconductor fabrication facility(such as etching, diffusion, diffusion plenum), and outdoors from June to August, 2015. Measurements were taken six times at the same places using an active sampler(pumped) and real-time equipment. Ozone monitoring by the active sampler method and analysis were carried out by OSHA Method ID-214. Real-time measurement was carried out by ozone measuring equipment using a non-dispersive ultraviolet absorption method. Results: Ozone concentrations in the semiconductor fabrication facility and office were 0.7~7.1 ppb in area samples and 0.72~4.07 ppb in real-time measurement, which were 0.88~8.88% of the occupational exposure limit. The concentration of ozone generated by a laser printer in the office was less than 2 ppb. There was not a significant difference between ozone concentrations before and after using the laser printer. The indoor/outdoor concentration ratio(I/O ratio) in the semiconductor fabrication facility and office was 0.05 and 0.06, respectively. Conclusions: All the samples contained ozone levels lower than the occupational exposure limit and it was confirmed that the concentration of outdoor ozone had no significant effect on indoor ozone concentration.

• Membrane and Water Treatment
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• v.2 no.1
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• pp.63-74
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• 2011

A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.4
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• pp.413-422
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• 2005

The ozone concentration measured by HALOE (Ver 19) from Oct. 1991 to Dec. 2003 is used for analyzing the variation of ozone concentration. The HALOE loaded in UARS is observing several gases in the atmosphere, from 10km to 80km. Fourier analysis of these data in the middle latitude northern hemisphere is reported in this paper. To detect any possible long term trends, the fourier transformed time series was back transformed after removing signals with time periods of less than 6 months. Although the results clearly show the strong annual cycle, it is difficult to show any long term trends from the fourier series. We also compared the ozone volume mixing ratio's from HALOE with that from the ground-based radiometry to evaluate the accuracy of microwave observation at Sookmyung Women's University.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.4
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• pp.727-732
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• 2006

The object of this study was to investigate the influence of composition and concentration of electrolyte, ratio of cation to anion exchange resin of mixed ion exchange column in the performance of ion exchange. Also this work examined the removal capability of suspended solids by ion exchange resin and the effect of particule on the characteristics of ion exchange. Breakthrough time was extended as the amount of ions and particles present in liquid was decreased. The case of anion, the breakthrough sequence is $Cl^{-}, but the case of cation, the breakthrough sequence is $Na^{+}. As for the ratio of cation to anion exchange resin of 1:2, the breakthrough time was prolonged compared with that of 1:1 and 1:3. For the electrolyte of equal concentration containing suspended solid, breakthrough time was contracted less than 20%. It results in the increase in the removal capacity of cation exchange resin. For the higher ratio of cation exchange resin, suspended solids are shorten the cation's breakthrough time so that the runtime of ion exchange resin tower is increased.

• Journal of the Korean Society of Safety
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• v.29 no.2
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• pp.18-23
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• 2014

Foam extinguishing agent is widely used for extinguishing combustible liquid fires. Compared to other foam type extinguishing agents, protein foam has relatively low cost and low toxicity and produces stable foam blanket which is excellent in heat resistance and sealability, despite it has weak fluidity. Therefore the study investigated foaming characteristics followed by various factors affecting the fluidity of the protein foam extinguishing agent. The extinguishing characteristics differentiated by the changes in fluidity were also experimented. Foaming performance was compared by measuring the expansion ratio and the 25% drainage time. Moreover, the 25% drainage time and the extinguishing time was compared. The results showed that the 25% drainage time and the expansion ratio were increased as the pressure of nozzle and the concentration of hydrolyzed protein liquid enlarged. However the foaming and extinguishing performance were not improved when the condition exceeded certain level of pressure and concentration. The fastest fire extinguishing condition was the nozzle pressure 4bar with the 85wt.% of concentration of hydrolyzed protein liquid.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.2
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• pp.1-8
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• 2004

A cylindrical constant volume combustion chamber was used to investigate the exhaust emission characteristics of homogeneous charge, stratified pattern and inhomogeneous charge under various conditions using gas chromatography. In the case of homogeneous charge condition, the $CO_2$ concentration is proportional to excess air ratio and overall charge pressure, the $CO_2$ concentration is proportional to excess air ratio and the UHC concentration is inversely proportional to ignition time and overall charge pressure. In the case of stratified pattern, the RI(rich injection) condition shows better exhaust emission characteristics, especially $CO_2$, than that of HI (homogeneous injection) or LI (lean injection) conditions. In inhomogeneous charge conditions, when initial charge pressure is increased, $CO_2$ and UHC concentration is reduced but $O_2$ concentration is increased. And when the excess air ratio of initial charge mixture is 3.0, UHC and $CO_2$concentration show lowest values.

• Journal of Korean Society of Water and Wastewater
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• v.10 no.4
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• pp.119-126
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• 1996

Influence factors and efficiency characteristics for treatment of wastewater containing phenol were studied with using Pseudomonas sp. B3. It took 130 hours to remove phenol, when only activated sludge of terminal disposal palnt of sewage was innoculated in batch culture, but it was required just 36 hours, when bacteria degrading phenol and activated sludge were simultaneously innoculated. If only phenol an carbon source was used, it necessary 36 hours for biodegradation of phenol, while glucose was added to medium, it took 73 hours. It was revealed as excellent effluent and SVI, when the F/M ratio, COD and phenol concentration were 53mg/l and 1.2mg/l, respectively, and optimum F/M ratio was revealed 0.31. The reactor were seriously shocked as reducing hydraulic retention time at constant phenol concentration more than increasing phenol concentration at constant hydraulic retention time, when volumetric loading rate was increased to $0.8kg\;phenol/m^3{\codt}d$ from $1.6kg\;phenol/m^3{\codt}d$. And also the effluent phenol concentration was 34mg/l after starting 12 hours of shocking and reactor was recovered as steady state after 65 hours of changing in the former test. Although the effluent phenol concentration was maximum value with 12mg/l after starting 20 hours of shocking and reactor was recovered as steady state after 54 hours of changing in the later test.