• Journal of Navigation and Port Research
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• v.39 no.6
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• pp.439-450
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• 2015

This study objects to find characteristics in chemical tanker markets and to determine optimal chemical tanker size using a total shipping cost in main trading route of asia chemical tankers .Precedent studies of determination of the optimal ship size and case studies about chemical tankers was carried out and tried to introduce a cost model which is applicable to chemical tanker. This study is dependant on numerical analysis and involves scenario analysis to minimize sensitivity of results. This analysis shows as follows. First, 12,000DWT tanker is an optimal size on the 'Far East-Middle East' services, 9,000DWT tanker is a most competitive on the 'Far East-South East Asia' services and 3,000DWT tanker is a most economic size on the 'Inner Far East' services at average market situation. Second, the bigger size of chemical tanker, the more competitive advantage the tanker will obtain when bunker fuel prices rise. Small size ship gets more competitive during bunker prices down. Third, market fluctuation of time charter rate for chemical tanker is less than 20% against its average time charter hire which means less volatile. And tanker's competitiveness per each size is remained mostly same when time charterer rates rise at same proportion. Fourth, bigger size chemical tankers have cost advantages when tanker's quantity of each part cargo increase. And small-sized tanks are more competitive when part cargo scales decrease. For the last, ship's port stay strongly influences on the determination of the optical tanker size. When vessel has shorter port stay, bigger-sized tanker will be more competitive and even can be competitive if applies in short voyage as well.

• Journal of the Society of Disaster Information
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• v.9 no.4
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• pp.449-461
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• 2013

As the hydrofluoric acid leak in Gumi-si, Gyeongsangbuk-do or hydrochloric acid leak in Ulsan, Gyeongsangnam-do demonstrated, chemical related accidents are mostly caused by large amounts of volatile toxic substances leaking due to the damages of storage tank or pipe lines of transporter. Safety assessment is the most important concern because such toxic material accidents cause human and material damages to the environment and atmosphere of the surrounding area. Therefore, in this study, a hydrofluoric acid leaked from a storage tank was selected as the study example to simulate the leaked substance diffusing into the atmosphere and result analysis was performed through the numerical Analysis and diffusion simulation of ALOHA(Areal Location of Hazardous Atmospheres). the results of a qualitative evaluation of HAZOP (Hazard Operability)was looked at to find that the flange leak, operation delay due to leakage of the valve and the hose, and toxic gas leak were danger factors. Possibility of fire from temperature, pressure and corrosion, nitrogen supply overpressure and toxic leak from internal corrosion of tank or pipe joints were also found to be high. ALOHA resulting effects were a little different depending on the input data of Dense Gas Model, however, the wind direction and speed, rather than atmospheric stability, played bigger role. Higher wind speed affected the diffusion of contaminant. In term of the diffusion concentration, both liquid and gas leaks resulted in almost the same $LC_{50}$ and ALOHA AEGL-3(Acute Exposure Guidline Level) values. Each scenarios showed almost identical results in ALOHA model. Therefore, a buffer distance of toxic gas can be determined by comparing the numerical analysis and the diffusion concentration to the IDLH(Immediately Dangerous to Life and Health). Such study will help perform the risk assessment of toxic leak more efficiently and be utilized in establishing community emergency response system properly.

• Journal of Microbiology
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• v.45 no.2
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• pp.113-121
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• 2007

The bacterial diversity inherent to the biofilm community structure of a modified rotating biological contactor wastewater treatment process, referred to as the Rotating Activated Bacillus Contactor (RABC) process, was characterized in this study, via both culture-dependent and culture-independent methods. On the basis of culture-dependent methods, Bacillus sp. were found to exist in large numbers on the biofilm (6.5% of the heterotrophic bacteria) and the microbial composition of the biofilms was quite simple. Only three phyla were identified-namely, the Proteobacteria, the Actinobacteria (High G+C Gram-positive bacteria), and the Firmicutes (Low G+C Gram-positive bacteria). The culture-independent partial 16S rDNA sequence analysis revealed a considerably more diverse microbial composition within the biofilms. A total of eight phyla were recovered in this case, three of which were major groups: the Firmicutes (43.9%), the Proteobacteria (28.6%), and the Bacteroidetes (17.6%). The remaining five phyla were minor groups: the Planctomycetes (4.4%), the Chlorobi (2.2%), the Actinobacteria (1.1%), the Nitrospirae (1.1%), and the Verrucomicrobia (1.1%). The two most abundant genera detected were the endospore-forming bacteria (31.8%), Clostridium and Bacillus, both of which are members of the Firmicutes phylum. This finding indicates that these endospore-forming bacteria successfully colonized and dominated the RABC process biofilms. Many of the colonies or clones recovered from the biofilms evidenced significantly high homology in the 16S rDNA sequences of bacteria stored in databases associated with advanced wastewater treatment capabilities, including nitrification and denitrification, phosphorus accumulation, the removal of volatile odors, and the removal of chlorohydrocarbons or heavy metals. The microbial community structures observed in the biofilms were found to correlate nicely with the enhanced performance of advanced wastewater treatment protocols.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.24 no.4
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• pp.436-445
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• 2014

Objectives: Time-activity studies have become an integral part of comprehensive exposure assessment and personal exposure modeling. The aims of this study were to estimate exposure levels to nitrogen dioxide($NO_2$) and volatile organic compounds(VOCs), and to compare estimated exposures by using time-activity patterns and indoor air concentrations. Methods: The major microenvironments for office workers were selected using the Time-Use Survey conducted by the National Statistical Office in Korea in 2009. A total of 9,194 and 6,130 workers were recruited for weekdays and weekends, respectively, from the Time-Use Survey. It appears that workers were spending about 50% of their time in the house and about 30% of their time in other indoor areas during the weekdays. In addition, we analyzed the time-activity patterns of 20 office workers and indoor air concentrations in Daegu using a questionnaire and time-activity diary. Estimated exposures were compared with measured concentrations using the time-weighted average analysis of air pollutants. Conclusions: According to the time-activity pattern for the office workers, time spent in the residence indoors during the summer and winter have been shown as $11.12{\pm}2.20$ hours and $12.48{\pm}1.77$ hours, respectively, which indicates higher hours in the winter. Time spent in the office in the summer has been shown to be 1.5 hours higher than in the winter. The target pollutants demonstrate a positive correlation ($R^2=0.076{\sim}0.553$)in the personal exposure results derived from direct measurement and estimated personal exposure concentrations by applying the time activity pattern, as well as measured concentration of the partial environment to the TWA model. However, these correlations were not statistically significant. This may be explained by the difference being caused by other indoor environments, such as a bar, cafe, or diner.

• Journal of dental hygiene science
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• v.11 no.3
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• pp.213-220
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• 2011

To examine the relationship between occurrence of oral malodor and smoking, drinking, oral health behavior characteristics. A total of 144 adults were measuring the malodor by use of Oral Chroma volatile sulfur compounds. Data were analyzed with t-test, one-way of variance and multiple regression analysis using SPSS 12.0. hydrogen sulfide($H_2S$) was indicated to be so higher concentration in the group of carrying out scaling sometimes than the regularly group(p<0.01). methyl mercaptan($CH_3SH$) was indicated to be higher concentration in previous smoker than non-smoker and smoker(p<0.05), smoking for over 20 years was higher than the under 20 years group(p<0.05). The group of drinking over 5 times a week was indicated to have higher concentration than the under once-twice a week group(p<0.01). The group of not toothbrushing before going to sleep had higher concentration than the group of toothbrushing before going to sleep(p<0.05). The group of scaling sometimes was indicated to have higher concentration than the group of scaling regularly(p<0.05). dimethyl sulfide($(CH_3)_2S$) was indicated to be higher concentration in the group with over 2 bottles of Soju than in the group with under 1 bottles of Soju(p<0.01). The regular scaling will need to be carried out in the preventive dimension for managing oral malodor. The guidance on non-smoking and moderation in drink will need to be surely included.

• Journal of the Korean GEO-environmental Society
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• v.13 no.5
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• pp.35-40
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• 2012

In this study, adsorption characteristics of expanded graphite (EG) were investigated by a series of batch adsorption tests using p-Xylene as a model volatile organic compounds (VOCs). After acid treatment, graphite were expanded at various temperature from $600^{\circ}C$ to $1000^{\circ}C$ for one minute. The optimal temperature was $800^{\circ}C$, where the expansion ratio reached 195 times of original volume. The BET specific surface area of EG was $92.4m^2/g$, which was only 1/10 of granular activated carbon (GAC), however the adsorption of p-Xylene by EG was almost completed within 5 minutes while that of GAC continued for 7 days because the majority of pores of EG was consisted with meso- and macro-pores. According to the Langmuir isotherm analysis, the maximum specific adsorption of p-Xylene onto EG was 24.0 mg/L with the adsorption constant of 7.94. In conclusion, the adsorption capacity of EG was much less than that of GAC due to the significantly lower specific surface area, but the first order kinetic constant was more than 500 times larger than GAC. Overall, EG might be effective where the fast adsorption is required.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.3
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• pp.192-202
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• 2010

This study aimed to suggest the severity of indoor air pollutants in screen gold arenas which were not sufficiently investigated in Korea up to now and to help users to enjoy golf in more pleasant indoor environment. The indoor environment survey was conducted with 21 screen gold arenas in Seoul from Oct. 28, 2008 to March 13, 2009. Indoor air quality was measured and analyzed in accordance with the Air Pollution Process Test Method specified bu NIOSH(2005). The screen golf arenas are mostly in the underground floors in this study, 4 on the ground floors(19.0%) and 17 in the underground floors(81.0%). In the air in screen golf arenas, the geometric mean of benzene, toluene, ethylbenzene and xylene were 2.92 ${\mu}g/m^3$, 70.34 ${\mu}g/m^3$, 14.00${\mu}g/m^3$ and 31.43 ${\mu}g/m^3$, respectively, which exceeded the exposure limites. Each arena exceeded the exposure limit for one pollutant each. However, styrene didn't exceed the limit as 8.09 ${\mu}g/m^3$. Furthermore, the geometric mean of formaldehyde was 63.11${\mu}g/m^3$ and 7 arenas exceeded the limit. The geometric mean of volatile organic compounds(VOCs) was 428.41${\mu}g/m^3$ and 10 arenas exceeded the limit. For the density distribution of pollutants by location, benzene, toluene, ethylbenzene, xylene, styrene and formaldehyde showed higher density distribution in underground spaces, for which the statistically significant difference was not found. However, PM10 showed the statistically significant difference (p<0.05). In accordance with the analysis on the correlation between the density of pollutants in the screen golf arenas, Pearson correlation coefficient between ethylbenzene and styrene was 0.980, very significant correlation(p<0.01). The correlation coefficients between the density of toluene, ethylbenzene, xylene and styrene and that of VOCs were 0.543, 0.434, 0.451 and 0.459, respectively, which demonstrated the statistically significant difference (p<0.05).

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.795-801
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• 2012

Nanoparticles have received significant attention because of their unusual characteristics including high surface area to volume ratios. Thiol ligand have been used as stabilizers of metal nanoparticles since Brust et al. They reported the preparation method of ligand capped metal nanoparticles by protecting the nanoparticles with a self-assembled monolayer of dodecanethiolate. In this method, volatile organic compounds (VOCs) were used as sovents. This study was carried out to replace these VOCs with room temperature ionic liquids (RTILs). We used two type of ILs to prepare metal nanoparticles. One is a hydrophobic IL, [BMIM][[$PF_6$] (1-Butyl-3-methylimidazolium hexafluorophosphate) purchased from IL maker, C-Tri from Korea and the other one is a hydrophilic one, [BMIM][Cl] (1-Buthy-3-methylimdazolium chloride) sinthesized by us. In the case of preparing Ag and Au nanoparticles using [BMIM][Cl], we didn't use phase transition reagents and ethanol because it has hydrophilic property and preparing Au, Ag nanoparticles using [BMIM][[$PF_6$] the method is as same as Brust et al.'s except using [BMIM][[$PF_6$] instead of organic solvent because it has hydrophobic property. FT-IR and UV-vis, TEM, TGA analysis have been used in an attempt to determine the particle size and verify functional groups. The particle size obtained from TEM was very similar to those obtained by Brust et al. This is a clear example of ligand capped metal nanoparticles prepared using ionic liquids. And the experimental result demonstrated ionic liquids can act as a highly effective medium for the preparation and stabilization of gold and silver metal nanoparticles.

• Journal of Korea Port Economic Association
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• v.31 no.4
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• pp.1-15
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• 2015

During global recessions, such as the 2008 financial crisis, Korean shipping companies have been undergoing a liquidity crisis that is comparably worse than other shipping companies worldwide. One of the reasons behind this repetitive vicious cycle can be the lack of ability to foresee the future by analyzing and understanding the volatile shipping market. Traditionally, in order to assimilate the shipping market, larger Korean shipping companies have been purchasing market reports published by Europe-based research companies and shipping brokers, leading to a digital divide by company size. To resolve this issue, the Maritime Exchange Information Center (MEIC) has been publishing shipping market reports that include essential shipping information such as freight rates by different routes; commodity trends for iron ore, grain, and coal; ship-building trends for new-building, second-hand, and demolition markets; as well as bunker price and port congestion. This research was conducted to analyze the effectiveness of four variables-information usefulness, market reflection, information composition, and latest information-on information satisfaction. If the information satisfaction was found to be adequate, the analysis of actual proof was used to determine if the customers would be willing to purchase MEIC's report when it is chargeable. All the four variables were found to have positive effects on information satisfaction. In particular, latest information was found to directly affect the intention to purchase. Furthermore, high information satisfaction was related to the intention to purchase.

• Environmental Analysis Health and Toxicology
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• v.14 no.1_2
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• pp.35-43
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• 1999

A number of disinfection by-products (DBPs) are formed as a result of the addition of chlorine into the public water supply and some of them have been suggested to cause adverse health effects on humans. However, the estimation of human ingestion exposure to each DBP has been performed simply by multiplying the concentration of a chemical in the cold tap water by the volume of water consumed during a given period of time. However, a questionnaire concerning water consumptions administered to sixty people residing in Chunchon showed that the volume of tap water consumed accounted for approximately 70% of the total volume of water consumed and that of heated water represented approximately 94% of tap water ingested. Heating durations for water-containing foods (e. g., soups and pot stews) and heated beverages (e. g., barley tea) were grouped into 10, 20, 30, and 35 minutes. Based on these time frames, an aluminum pot containing one liter of tap water was heated for the above respective time periods using a gas range to determine the variations of the concentrations of individual DBPs by heating. The pH and total residual chlorine were measured before and after heating. Collected water samples were carried to the laboratory and analyzed for eight DBPs and total organic carbon. Chloroform, bromodichloromethane, chloral hydrate, 1, 2-dichloro-2-propanone, 1, 1, 1-trichloropropanone, and dichloroacetonitrile were not detected following heating for 10 minutes and longer. The concentration of dichloroacetic acid (DCAA) was elevated with heating duration, resulting in the averages of 2.0, 3.1, 4.7, and 12 times the initial concentration, respectively, for 10, 20, 30, and 35 minute heating periods. On the other hand, the concentration of trichloroacetic acid (TCAA) decreased with heating duration, with 0.65, 0.40, 0.34, and 0.19 times lower than the initial concentration. Therefore, it is suggested that ingestion exposure to DCAA increases with heating duration but that ingestion exposure to TCAA decreases. In addition, while the amount of DCAA was elevated at the initial time periods (10 or 20 minutes) and then slowly decreased, that of TCAA was rapidly decreased. In conclusion, water-heating processes during cooking influence the concentrations of individual DBPs in the tap water, with lower levels for volatile DBPs and TCAA, and higher levels for DCAA. Therefore, concentration change needs to be taken into consideration in the estimation of human ingestion exposure to DBPs.