• Magazine of the Korean Society of Agricultural Engineers
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• v.37 no.1
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• pp.73-80
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• 1995

This study was carried out to investigate the engineering properties of no-fines con- crete, consisting only of coarse aggregate, cement and water. The used coarse aggregates were two, one is natural coarse aggregate grading 4.75~ lOmm, the other is synthetic lightweight coarse aggregate grading 3~8mm. The results of this study are summarized as follows; 1. The W/C ratio of each type was increased with increase of additional amount of coarse aggregate. 2. The unit weight of used ndtural coarse aggregate was shown 1.762~2.184g/cm$^3$, and synthetic lightweight coarse aggregate was shown 0.756 ~ 1 .348g/cm$^3$. 3. The ahsorption rate of used natural coarse aggregate was shown 8.4 ~ 9.4 %, and synthetic lightweight coarse aggregate was shown 17.0~42.4%. 4. The compressive, tensile and hending strength was decreased with increase of coarse aggregate, respectively. The compressive strength of natural coarse aggregate 1:3 was shown 309kg/cm$^2$. 5. The ultrasonic pulse velocity and dynamic medulus of elasticity of each type was de- creased with increase coarse aggregate, respectively. Also, the decreasing rate of the natural aggregate was larger than that of the synthetic lightweight coarse ag- gregate.

• Journal of Korean Society on Water Environment
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• v.23 no.2
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• pp.193-200
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• 2007

The AOPs research defined by creating a sufficient amount of OH radicals from the dissolution of organic materials through photoxidation and research for a complete elimination of residual organic materials by membrane are actively ongoing. This research focuses on the hybrid processing of AOPs and M/F membrane to dissolve and eliminate organic chemicals in drinking water which are suspected of carcinogens. For this purpose, underground water was used as a source of drinking water for the hybrid processing of AOPs oxidation and M/F membrane, and a pilot plant test device was installed indoor. Carcinogenic chemicals of VOCs and pesticide were artificially mixed with the drinking water, which was then diluted close to natural water in order to examine treatment efficiency and draw optimal operation conditions. The samples used for this experiment include four chemicals phenol, chloroform, in VOCs and parathion, carbaryl in pesticide. As a result of the experiments conducted with simple, and compound solutions, the conditions to sufficiently dissolve and eliminate carcinogenic chemicals from the hybrid processing of where carcinogens were artificially added are : (hydrogen peroxide) prescribed solution 100 mg/L under pH 5.5~6.0, and the temperature $12{\sim}16^{\circ}C$, at the normal temperature and pressure. $d-O_3$ volume of 5.0 ppm and above and 30-40 minutes of reaction time are most appropriate and using MF/UF for membrane was ideal.

• Water for future
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• v.18 no.4
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• pp.335-345
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• 1985

The purpose of stochastic models for synthetic generation of river flows based on the short-term observed data is to provide abundant input data to the water resources systems of which the system performance and operation policy are to be determined beforehand. Among many of such models the Monte Carlo Method of synthetic generation, which is usually known to be appropriate for annual data generation, is employed to check if it can be applied for the generation of monthly flows. For the purpose of comparisons the statistical parameters of the generated monthly flows by Monte Carlo model based on the appropriate probability distribution for each month were compared with those of the generated flows by Thoms-Fiering multiseason model and with those of the observed monthly flows. On the other hand, the statistical parameters of the annual river flows obtained by adding the generated monthly flows year by year based on the Monte Carlo and Thomas-Fiering models were compared with those of the annual flows generated directly by annual Monte Carlo model with reference to those for the observed annual river flows. Based on the above comparative studies, the discussions are made and conclusions derived.

• KSBB Journal
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• v.17 no.3
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• pp.235-240
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• 2002

The surface of polypropylene was modified by 1 keV $Ar^+$ ion beam in an $O_2$ environment in order to enhance wettability. Contact angle of deionized water on modified polypropylene was reduced from $78^{\circ}$to $22^{\circ}$. The enhanced wettability is originated from newly formed functional groups such as ether, carbonyl, and carbonyl groups. During immersion in deionized water, the enhanced wettability has remained nearly same. After washing in water, the hydrophilic functional groups on the polymer surface have been very stable. The modified polypropylene was adopted as bio-film media to remove organics in synthetic wastewater. Microbe adhesion on the polypropylene surface was improved due to the newly formed hydrophilic groups.

• Journal of the Korea Organic Resources Recycling Association
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• v.15 no.3
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• pp.71-79
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• 2007

The effects of synthetic bulking agent (SBA) on the composting reaction were investigated with a lab-scale composting reactor. The positive effects of SBA addition were observed in composting reactions where relatively tough composting conditions like high water content and no addition of seed compost were provided. Such effects were assumed to be caused by the enhanced free air space in compost mixture. It was additional benefits of using SBA, a bulking agent, that the amount of saw dust, another bulking agent, could be reduced to 50% compared to composting without SBA. Although SBA would be used as a bulking agent, two options are thought to be very important to ensure composting reaction well. One is that optimal water content should be maintained around 60%. The other is that saw dust is inevitable bulking agent to prevent food waste from lumping, so combination use of two ones are necessary.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.6
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• pp.615-624
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• 2010

The aims of this study were to investigate and confirm the occurrence and distribution patterns of synthetic musk compounds (SMCs) in Nakdong river basin (mainstream and its tributaries). 4 (HHCB, AHTN, AHMI and ADBI) out of 6 polycyclic musk compounds (PMCs) and 1 (musk xylene, MX) out of 5 nitro musk compounds (NMCs) were detected in 29 sampling sites and HHCB (>50%) was predominant compound followed by musk ketone (MK) and AHTN. The total concentration levels of SMCs on February 2009 and on September 2009 in surface water samples ranged from N.D. to 2147 ng/L and N.D. to 1386 ng/L, respectively. The highest concentration level of SMCs in the mainstream and tributaries in Nakdong river were Goryeong and Jincheon-cheon, respectively. The sewage treatment plants (STPs) along the river affect the SMCs levels in river and the SMCs levels decreased with downstream because of dilution effects.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.317-317
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• 2018

Baseflow which is one of the unmeasurable components of streamflow and slowly flows through underground is important for water resource management. Despite various separation methods from researches preceded, it is difficult to find a significant separation method for baseflow separation. This study applied the MRC method and developed the improved approach to separate baseflow from total streamflow hydrograph. Previous researchers utilized the whole streamflow data of study period at once to derive synthetic MRCs causing unreliable results. This study has been proceeded with total nine areas with gauging stations. Each three areas are selected from 3 domestic major watersheds. Tool for drawing MRC had been used to draw MRCs of each area. First, synthetic MRC for whole period and two other MRCs were drawn following two different criteria. Two criteria were set by different conditions, one is flow condition and the other is seasonality. The whole streamflow was classified according to seasonality and flow conditions, and MRCs had been drawn with a specialized program. The MRCs for flow conditions had low R2 and similar trend to recession segments. On the other hand, the seasonal MRCs were eligible for the baseflow separation that properly reflects the seasonal variability of baseflow. Comparing two methods of assuming MRC for baseflow separation, seasonal MRC was more effective for relieving overestimating tendency of synthetic MRC. Flow condition MRCs had large distribution of the flow and this means accurate MRC could not be found. Baseflow separation using seasonal MRC is showing more reliability than the other one however, if certain technique added up to the flow condition MRC method to stabilize distribution of the streamflow, the flow conditions method could secure reliability as much as seasonal MRC method.

• Journal of Microbiology and Biotechnology
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• v.9 no.4
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• pp.464-468
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• 1999

The effectiveness of current biodegradation test methods for degradable polymers under controlled composting conditions was studied in regards to the test temperature and compost condition. When biodegradability tests for the natural (starch, cellulose, PHB/HV) and synthetic (PCL, SG, PLA) polymers were conducted at temperature levels of 35 and $55^{\circ}C$ with compost cured at ambient temperature, the degradations of cellulose and starch were higher at $35^{\circ}C$ because of the priming effect. On the other hand, degradations of other polymers were higher at $55^{\circ}C$. In the biodegradation test at $55^{\circ}C$, compost harvested right after the thermophilic degradation stage showed higher biodegradation activities than the cured compost for both the synthetic aliphatic polyester (SG) and a natural polymer, cellulose. These results suggest that the biodegradation test conducted at $55^{\circ}C$ with the compost, harvested right after the thermophilic degradation stage during composting, showed the highest biodegradation activity under controlled composting conditions.

• Environmental Analysis Health and Toxicology
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• v.7 no.3_4
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• pp.69-79
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• 1992

Recently, concerns of water pollution and health risks caused by synthetic detergents have emerged, as the use of various detergents has increased It has been suggested that some surfactants are cocarcinogens. The surfactants tested were linear alkylbenzene sulfonate, sodium lauryl sulfate, polyoxyethylene sorbitan monooleat (tween 80), and the mutagens were 1-nitropyrene, N -methyl- N'-nitro-N -nitrosoguanidine, benzo (a) pyrene, and aflatoxin B$_1$. This study was undertaken to investigate the effects of surfactants on the activity of mytagens using the Ames mutagenic assay with Salmonella typhimurium TA98, TA100. The results were summarized as follows: 1. The surfactants have no mutagenic activity of themselves. 2. Higher doses of surfactants than 100 $\mu\textrm{g}$/plate reduced the number of revertants. It is assumed that the reduction would inhibited cell growth. 3. When the comutagenic ratio is defined as the ratio between mutagenic activity itself and the activity with mutagen and surfactant (drinking water quality standard), LAS showed the comutagenic ratio 0.86-1.17 and SLS 0.74-1.10 as well. According to the comparisons, it could not be recognised for the comutagenicity of drinking water quality standard of surfactant. 4. As increasing the amount of mutagens, the designated amount of surfactant did not affected the mutagen's activity statistically. From the above result, syunthetic surfactants do not present mutagenicity and comutagenicity in the microbial assay.

• Journal of Korean Society of Water and Wastewater
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• v.28 no.1
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• pp.83-89
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• 2014

The aim of this study is to investigate the sorption/ion exchange of radioactive nuclides such as $Cs^+$ and $Sr^{2+}$ by synthetic Na-micas. In order to prepare Na-micas, two natural micas (phlogopite and biotite) were used as precursor materials. XRD, SEM, and EDS analyses were used to examine material characterization of synthetic Na-micas. Analyses of materials revealed that Na-micas were successfully obtained from natrual micas by K removal treatment. On the other hand, single solute (Cs or Sr) and bi-solute (Cs/Sr) sorption experiments were carried out to determine sorption capacity of Na-micas for Cs and Sr under different pH and ionic strength conditions. Uptake of Cs and Sr by micas in bi-solute system was lower than in single-solute system. Additionally, Langmuir and Langmuir competitive models were applied to describe sorption isotherm of Na-micas. bi-solute system was well described by Langmuir competitive models. For the results obtained in this study, Na-micas could be promising sorbents to treat multi-radioactive species from water and groundwater.