• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.35 no.2
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• pp.18-25
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• 2003

The adsorption of co-cationic dual polymer system was investigated as was the fiber dispersion stability of a paper stock suspension. Polyaluminum chloride(PAC) and polyamidoamine epichlorohy-drin(PAE) polymers were used as wet-end additives. The adsorbed amounts of PAE polymer in a wet stock were measured by using polyelectrolytic PCD titration. The sheet forming experiments were carried out in a standard handsheet machine. Fiber dispersion stability and relative retention were evaluated in terms of M/K non-uniformity index and sheet basis weight, respectively. The PAE polymer adsorption of Langmuir-isothermal type decreased with increasing PAC addition level. The combination of the two cationic polymers presumably exerts a site-blocking effect by the low molecular weight PAC which gives a partial charge neutralization at a minimum level of addition. From a thermodynamic view point of PAE adsorption, an increase in adsorption entropy and a decrease in train number suggests that the PAR polymer has an extended conformation structure that potentially leads to an enhancement of the fiber dispersion stability. This conclusion is supported by handsheet experiments that examined the PAC-PAE dual polymer effects on the sheet formation and retention.

• Journal of Microbiology and Biotechnology
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• v.9 no.4
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• pp.457-463
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• 1999

The physical map of bacteriophage $\PhiFC1$ DNA was constructed with the restriction endonucleases SalI, BamHI, EcoRI, XbaI, and AvaI. The 40.5-kb DNA restriction map is shown to be circularly permuted representing the headful packaging mechanism of the phage. The DNA restriction fragments containing the packaging initiation site(pac) was localized on the restriction map and the nucleotide sequences of the region were analyzed. Four open reading frames (ORFs), following one another with the same orientation, were found at the region. The 2nd ORF (ORF-ts) has significant amino acid sequence homologies to the previously known terminase small subunits of other bacteriophages. The putative terminase small subunit gene has a presumptive NTP-hydrolysis motif and a helix-turn-helix motif. The cleavage site for the first round of packaging was found to be located at the coding sequence of the putative terminase small subunit gene. The fourth ORF, even if partially sequenced, has a good amino acid sequence homology to the portal vertex proteins of other bacteriophages representing the evolutionarily conserved arrangements of genes near the pac site of this bacteriophage, $\PhiFC1$.

• Bulletin of the Korean Chemical Society
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• v.20 no.8
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• pp.897-904
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• 1999

We have presented the thermodynamic, structural and dynamic properties of liquid pentane isomers - normal pentane, isopentane, and neopentane - using an expanded collapsed atomic model. The thermodynamic properties show that the intermolecular interactions become weaker as the molecular shape becomes more nearly spherical and the surface area decreases with branching. The structural properties are well predicted from the site-site radial, the average end-to-end distance, and the root-mean-squared radius of gyration distribution func-tions. The dynamic properties are obtained from the time correlation functions - the mean square displacement (MSD), the velocity auto-correlation (VAC), the cosine (CAC), the stress (SAC), the pressure (PAC), and the heat flux auto-correlation (HFAC) functions - of liquid pentane isomers. Two self-diffusion coefficients of liquid pentane isomers calculated from the MSD's via the Einstein equation and the VAC's via the Green-Kubo relation show the same trend but do not coincide with the branching effect on self-diffusion. The rotational re-laxation time of liquid pentane isomers obtained from the CAC's decreases monotonously as branching increases. Two kinds of viscosities of liquid pentane isomers calculated from the SAC and PAC functions via the Green-Kubo relation have the same trend compared with the experimental results. The thermal conductivity calculated from the HFAC increases as branching increases.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.2 no.2
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• pp.115-121
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• 1998

Train of chemical and biological processes was investigated to treat leachate from industrial waste landfill. Organics and nitrogen concentrations of landfill leachate studied in this research were high and their BOD/COD ratio was 0.3. Biological process should be combined with chemical process for optimum treatment of leachate. PAC(Polyaluminium chloride) was the best coagulant among three chemicals tested, and the optimum condition of PAC coagulation was pH 6 and 1,250 mg/L of dosage. When SBR was operated for simultaneous removal of organics and nitrogen, removal efficiency of COD and T-N reached over $82\%,\;71\%,$ respectively and time distribution of 2/4/2/1 was most effective for one cycle of anoxic/aerobic/anoxic/aerobic.

• Journal of Korean Society on Water Environment
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• v.30 no.5
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• pp.532-538
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• 2014

A cylinder-shaped filter was developed to manage the runoff from construction sites. Compressed air was used for back-washing and pore sizes of filter were $23{\mu}m$ and $46{\mu}m$. The turbid water was prepared using sediments in construction sites. The grain size analysis showed that grains smaller than $38{\mu}m$ and larger than $335{\mu}m$ in size constituted 34.4 % and 37.6 %, respectively. Removal efficiency of the filter on turbidity, SS, COD, TN and TP showed 25~37%, 20~40%, 50~55%, 23~27% and 14~20%, respectively, whereas their removal efficiecy by using coagulant PAC showed 77~84%, 70~83%, 53~60%, 27~36%, and 59~75%, respectively. The filtration time was determined to be around 10 to 20 minutes. Back-washing for 10 seconds by pressurized air resulted in a satisfactory regeneration efficiency. According to the aforementioned test results, the cylinder-shaped filter is effective in reducing turbidity and would be suitable for practical application in construction sites and farms.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.3139-3143
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• 2007

The objective of this paper was to investigate the mixing characteristics of an three-stage inline coagulant mixing system experimentally. Wastewater samples of pH 8.5 and initial turbidity 1,000NTU were taken from a site of tunneling work. At the constant dosage, 0.36mL/L, of polymer as coagulant aids, the coagulation efficiency with the dosage of PAC as coagulant was about 4${\sim}$6% at 10 minutes after sampling. In the case of 2 different velocity gradient conditions, the efficiency of turbidity removal was increased about 6.5${\sim}$8% with increasing the dosage of coagulant while, the efficiency was increased about 20${\sim}$21.5% with increasing the dosage of coagulant aids. The efficiency of turbidity removal with the settling time after sampling was about 90% after 1 minute, and the efficiency was about 95% after 5 minutes.

• Journal of Korean Society of Water and Wastewater
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• v.21 no.1
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• pp.91-99
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• 2007

It is well-known that the presence of NOM (natural organic matter) in water has a negative effect on removing taste and odor compounds by activated carbon adsorption. Therefore, various means such as enhanced coagulation are applied to reduce the NOM. The presence of taste & odor compounds in drinking water even parts per trillion, is enough to generate customer dissatisfaction. Therefore, the aim of this study was to evaluate carbon usage rate (CUR) for conventional coagulation (CC) and enhanced coagulation (EC) in order to improve the efficiency of adsorption of taste and odor compounds. Also, Effect of CC and EC on molecular weight fraction and the early stage breakthrough of 2-MIB and Geosmin are evaluated. When the enhanced coagulation was adapted for pretreatment for activated carbon adsorption the operation period could be prolonged by 3.5~4 times. CUR for CC was about 2 times greater than CUR for EC and this means that EC has more adsorption capacity than CC. To analyze effect of EC and CC on breakthrough of 2-MIB quantitatively, adsorbed NOM mass was calculated based on unit mass of activated carbon. In the early stage breakthrough of 2-MIB, total adsorbed NOM was 23.72mg/g for CC and 34.56mg/g for EC. Therefore, it is shown that the early breakthrough term of 2-MIB and Geosmin was improved due to increased adsorbability. The low-molecular-weight NOM (500~2000Da) compounds were the most competitive, participating in direct competition with 2-MIB for adsorption site.

• Journal of Microbiology and Biotechnology
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• v.27 no.7
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• pp.1266-1271
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• 2017

Lactobacillus fermentum strain JDFM216, isolated from a Korean infant feces sample, possesses the ability to enhance the longevity and immune response of a Caenorhabditis elegans host. To explore the characteristics of strain JDFM216 at the genetic level, we performed whole-genome sequencing using the PacBio system. The circular draft genome has a total length of 2,076,427 bp and a total of 2,682 encoding sequences were identified. Five phylogenetically featured genes possibly related to the longevity and immune response of the host were identified in L. fermentum strain JDFM216. These genes encode UDP-N-acetylglucosamine 1-carboxyvinyltransferase (E.C. 2.5.1.7), ErfK/YbiS/YcfS/YnhG family protein, site-specific recombinase XerD, homocysteine S-methyltransferase (E.C. 2.1.1.10), and aspartate-ammonia ligase (E.C. 6.3.1.1), which are involved in peptidoglycan synthesis and amino acid metabolism in the gut environment. Our findings on the genetic background of L. fermentum strain JDFM216 and its potential candidate genes for host longevity and immune response provide new insight for the application of this strain in the food industry as newly isolated functional probiotic.

• Journal of Environmental Health Sciences
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• v.44 no.1
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• pp.44-54
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• 2018

Objectives: To protect individuals working at the site as well as the surrounding general population from a chemical accident, several emergency exposure guidance levels have been used to set a level of concern for certain chemicals. However, a level of concern has not been established for many substances that are frequently used or produced in large quantities in Korean workplaces. In the present study, we investigated the guidance levels for protecting populations from chemical exposure and the estimation of level of concern using acute inhalation and oral toxicity data. Methods: The number of chemicals to which emergency exposure guidance levels (e.g., ERPG-2, AEGL-2, PAC-2, and IDLH) can be applied were determined among 822 hazardous chemicals according to the 'Technical Guidelines for the Selection of Accident Scenarios (revised December 2016)'. The ERPG and AEGL values were compared across all three tiers for the 31 substances that appeared on both lists. We examined the degree of difference between the emergency exposure guidance levels and the estimates of level of concern calculated from acute inhalation or acute oral toxicity data. Results: Among the 822 hazardous chemicals, emergency exposure guidance levels can be applied to 359 substances, suggesting that the estimates of level of concern should be calculated using acute toxicity data for 56.3% of the hazardous chemicals. When comparing the concordance rates of ERPG and AEGL for 31 substances, the difference between the two criteria was generally small. However, about 40% of the substances have values diverging by more than three-fold in at least one tier. Such discrepancies may cause interpretation and communication problems in risk management. The emergency exposure guidance levels were similar to the estimates of level of concern calculated using acute inhalation toxicity data, but the differences were significant when using acute oral toxicity data. These results indicate that the level of concern derived from acute oral toxicity data may be insufficient to protect the population in some cases. Conclusion: Our study suggests that the development of standardized guidance values for emergency chemical exposure in the Korean population should be encouraged. It is also necessary to analyze acute toxicity data and fill the information gaps for substances that are important in Korean workplace situations.

• Journal of Korean Society of Water Science and Technology
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• v.26 no.6
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• pp.61-72
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• 2018

In this study, applicability of the decentralized water supply system were investigated by the high flux evaluation using ceramic membrane with combined pretreatment process. A) filtration process increased the transmembrane pressure of 1.4 kPa and 89.5 kPa on 2 and $5m^3/m^2{\cdot}d$ of filtration flux, respectively, the physical backwashing recovery rate were less than 28.6%. The (B) Coag./Floc. - Sedi. combined process with 4 mg / L of A-PAC showed that the transmembrane pressure increased to within 6 kPa, the physical backwashing recovery rate was over 37.9 % higher than (A) Filtration process. (C) Coag./Floc. combined process showed an increase of transmembrane pressure compared with (B) Coag./Floc. - Sedi. combined process, physical backwashing recovery rate was over 84%. As a result of the membrane fouling analysis using the resistance in series model, the combined pretreatment process showed that the cake resistance (Rc) was more than 92% at membrane filtration flux of $2m^3/m^2{\cdot}d$. In the (C) Coag./Floc. combined process, cake resistance(Rc) was over 86% on high flux conditions. The coagulation floc contained in influent was removed by the membrane, and the cake layer formed with the removed floc was identified as reversible fouling resistance which could be recovered by physical backwashing. The decentralized water supply system, which has the limitation of site area and installation space, is considered to could be operation of high flux of ceramic membrane by applying (C) Coag./Floc. combined process without sedimentation process.