• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.23-30
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• 2007

The ultimate objective of this study is to develop oxygen-enriched combustion techniques applicable to the system of practical industrial boiler. To this end the combustion characteristics of lab-scale LNG combustor were investigated as a first step using the method of numerical simulation by analyzing the flame characteristics and pollutant emission behaviour as a function of oxygen enrichment level. Several useful conclusions could be drawn based on this study. First of all, the increase of oxygen enrichment level instead of air caused long and thin flame called laminar flame feature. This was in good agreement with experimental results appeared in open literature and explained by the effect of the decrease of turbulent mixing due to the decrease of absolute amount of oxidizer flow rate by the absence of the nitrogen species. Further, as expected, oxygen enrichment increased the flame temperatures to a significant level together with concentrations of $CO_2$ and $H_2O$ species because of the elimination of the heat sink and dilution effects by the presence of $N_2$ inert gas. However, the increased flame temperature with $O_2$ enriched air showed the high possibility of the generation of thermal $NO_x$ if nitrogen species were present. In order to remedy the problem caused by the oxygen-enriched combustion, the appropriate amount of recirculation $CO_2$ gas was desirable to enhance the turbulent mixing and thereby flame stability and further optimum determination of operational conditions were necessary. For example, the adjustment of burner with swirl angle of $30\sim45^{\circ}$ increased the combustion efficiency of LNG fuel and simultaneously dropped the $NO_x$ formation.

• Journal of Pharmaceutical Investigation
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• v.26 no.2
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• pp.71-82
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• 1996

This study has been undertaken to evaluate hydrophobic cyclodextrin(CD) derivatives as a sustained release carrier of azidothymidine(AZT), AZT, which has potent activity against AIDS and AIDS-related complex as thymidine analogue, has been reported that it has significant toxicity and short half life. Therefore, it is necessary to design sustained release oral dosage form to avoid undesirable side effects attributable to an excessive plasma concentration and to reduce the frequency of administration of AZT. Inclusion complexes of AZT with $acetyl-{\beta}-cyclodextrin\;(AC{\beta}CD)$ and $triacetyl-{\beta}-cyclodextrin(TA{\beta}CD)$ were prepared by solvent evaporation method. Interactions of AZT with CD were investigated by Differential Scanning Calorimetry(DSC) and Infrared Spectrophotometry(IR). The decreasing order of water solubilities of AZT and AZT-CD inclusion complexes were as follows; $AZT\;(27.873{\pm}0.015,mg/ml)\;>\;AZT-AC{\beta}CD\;(3.377{\pm}0.003)\;>\;AZT-TA{\beta}CD\;(2.528{\pm}0.001)$. Partition coefficients of $AZT-AC{\beta}CD\;and;\AZT-TA{\beta}CD$ inclusion complexes were increased by 1.27-fold, 1.54-fold in pH 1.2 and 1.32-fold, 1.47-fold in pH 6.8 in comparison with that of AZT. The mean dissolution time (MDT, min) which represents the rapidity of dissolution rate of AZT, $AZT-AC{\beta}CD,\;AZT-TA{\beta}CD$ were 5.12, 14.02 and 19.38 min in pH 1.2 and 2.52, 15.19 and 18.19 min in pH 6.8. AZT was very rapidly and completely dissolved in pH 1.2 and pH 6.8 within 5 minutes. But AZT-CD inclusion complexes showed the sustained release pattern in comparison with AZT alone. The simultaneous in situ nasal and jejunal recirculation study to compare the intrinsic absorptivity and the property of absorption sites revealed that the absorption of $AZT-TA{\beta}CD\;(N:35.35{\pm}1.08%,\;J:27.47{\pm}1.18%)$ was more than that of $AZT\;(N:16.89{\pm}2.25%,\;J:15.86{\pm}2.33%)$. The above results suggest that $TA{\beta}CD$ which is a hydrophobic cyclodextrin may serve as sustained release carrier with absorption enhancing effect.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.5
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• pp.288-291
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• 1988

We have veen already reported the distribution of PSP of bivalve mollusca in southern coast of Korea and also analyzed their characteristics. The purpose of this study was to develop detoxification method for PSP infested sea mussel, Mytilus edulis, by rearing methods or processing treatments. There was no significant detoxification effect when the PSP infested sea mussel was reared in a tank with water recirculation system, but the toxicity of sea mussel rapidly decreased during the rearing time in a water flow system with filtered water. The detoxification rate of PSP during the rearing for 5 days in a water flow system tank with $15-17^{\circ}C$ of sea water was $94\%$ in case of high toxic sample with more than $2,600{\mu}g/100g$ and about $40\%$ in case of low toxic sample with less than $100{\mu}g/100g$. The toxicity of PSP extracted from the sample with 0.1N/ HCl solution was about 2-5 times higher than that extracted with distilled water. When sea mussel contained $100-150{\mu}g-PSP$ per 100g of edible meat was boiled for 30 min with tap water, the toxicity was destroyed as the level of PSP undetected by mouse assay. We can suggest that boiling of sea mussel with tap water was one of the most significant detoxification methods, but it was not enough to be safe in case of extremely high intoxicated sea mussel with PSP. For example, the digestive gland of sea mussel contained more than $9593{\mu}g/100g$ was heated in a can with tap water at $116^{\circ}C$ for 65 min. the residual PSP was more than $170{\mu}g$.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.21 no.5
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• pp.297-302
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• 1988

We have veen already reported the distribution of PSP of bivalve mollusca in southern coast of Korea and also analyzed their characteristics. The purpose of this study was to develop detoxification method for PSP infested sea mussel, Mytilus edulis, by rearing methods or processing treatments. There was no significant detoxification effect when the PSP infested sea mussel was reared in a tank with water recirculation system, but the toxicity of sea mussel rapidly decreased during the rearing time in a water flow system with filtered water. The detoxification rate of PSP during the rearing for 5 days in a water flow system tank with $15-17^{\circ}C$ of sea water was $94\%$ in case of high toxic sample with more than $2,600{\mu}g/100g$ and about $40\%$ in case of low toxic sample with less than $100{\mu}g/100g$. The toxicity of PSP extracted from the sample with 0.1N/ HCl solution was about 2-5 times higher than that extracted with distilled water. When sea mussel contained $100-150{\mu}g-PSP$ per 100g of edible meat was boiled for 30 min with tap water, the toxicity was destroyed as the level of PSP undetected by mouse assay. We can suggest that boiling of sea mussel with tap water was one of the most significant detoxification methods, but it was not enough to be safe in case of extremely high intoxicated sea mussel with PSP. For example, the digestive gland of sea mussel contained more than $9593{\mu}g/100g$ was heated in a can with tap water at $116^{\circ}C$ for 65 min. the residual PSP was more than $170{\mu}g$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.1
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• pp.25-33
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• 2018

Renewable energy has been of interests in the area of modern alternative fuels. Biogas is produced in waste landfill sites through anaerobic digestion processes, including hydrolysis, acidogenesis, organic acid fermentation (acetogenesis), and methane fermentation (methanogenesis). High contents of fine dust and moisture limited its utilization for direct combustion, town gas and vehicle fuel. Thus, this study proposed a new design for a cooling device using a centrifugal cyclone for simultaneous removal of fine dust and moisture as a pretreatment in the purification processes. A heat exchanger and an ID fan, which are installed inside and outside of the cyclone, in order to cool the humid gas below the freezing point and form a foggy mist. Such an atmosphere enhanced to capture fine dust as recirculating the cold mist flow. The water removal rate was 80.8% at a relative humidity of 95%, and the particle removal efficiency was 98.3% for $2.5{\mu}m$. Simultaneous removal efficiency was 70.8% and 99.6% for particle and moisture respectively.

• Journal of the Korea Organic Resources Recycling Association
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• v.23 no.2
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• pp.28-35
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• 2015

In this study, the experiment was carried out to produce methane by applying Semi-Continuous Leachate Recirculation Anaerobic Digestion System fed with source separated food waste from school cafeteria. There were two systems and each system consisted of a bioreactor and a liquid tank. Each bioreactor had a screen near the bottom of the reactor. 2.5L of separated liquid was transferred to the liquid tank for 30min each day by using a tubing pump and the liquid from the liquid tank was pumped to the bioreactor at the upper of the bioreactor as soon as the transfer was ended. Through this circulation, the liquid having high concentration of VFAs was supplied to the top of bioreactor. At the beginning of the experiment, food waste/inoculum anaerobic sludge volume ratio was 2:8 that is 9g VS/L of OLR(Organic Loading Rate). Feeding was conducted every two weeks. Experimental results showed that the contents of moisture, combustible matter, ash were 65.91%, 32.73%, and 1.36%, respectively. Two different food waste loading were studied. The average organic loading rates were 3.51g VS/d for System A and 3.86g VS/d for System B, respectively. The average produced methane based on food waste fed to bioreactor were observed as $6.30m^3CH_4/kgVS{\cdot}d$ for system A and $4.94m^3CH_4/kgVS{\cdot}d$ for System B, respectively.

• Journal of Wetlands Research
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• v.20 no.2
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• pp.145-154
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• 2018

In this study, three pilot-scale wetland systems were built for treating stormwater runoff from asphalt road. Each of the system consists of a settling tank and a vertical flow wetland packed with 25%, 50%, and 75% woodchip as treatment media. According to the analysis of the distributions of particle size, it was found that solids ranging in size $0.52-30{\mu}m$ were predominant in the stormwater runoff. After 24-hours settling, those coarser than $20{\mu}m$ were significantly detained. Further retention, especially for the finer-sized fraction, occurred in the wetland through internal recirculation during the dry day periods. As a primary media of the wetland, woodchip showed a high filtration and attachment capacity for the particulates in pre-settled stormwater, whereas overall amount of solids in the wetland effluent increased due to the detachment of woody elements from the media. This was observed mainly during the initial 75 days of operation, and the size and detachment rate were found to be strongly related with the woodchip packing ratio. The mechanism involving woody particle detachment was modeled as a first-order form. In addition, water quality factors and operational parameters affecting the detachment were analyzed and discussed.

• Applied Chemistry for Engineering
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• v.18 no.1
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• pp.29-35
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• 2007

Recently, due to narrow margin on design factor of flue gas desulfurization (FGD) systems or aging of systems, some problems such as decrease of $SO_2$ removal efficiency and difficulty on coping with unstable state are arising on FGD systems. On this study, to cope with these problems several methods such as adjustment of reagent pH, inlet $SO_2$ concentration, variation of units of operation pump, installation of liquid distribution ring (LDR) were attempted to increase the $SO_2$ removal using spray type simulated FGD system. Also, sulfite and Al/Fx ion effects on limestone blinding were experimented. When three absorber recirculation pumps were operated, $SO_2$ removal was increased by 12% in comparison with that of two pumps operation. $SO_2$ removal was increased by 2~7% after installation of LDR. Dissolved oxygen increased up to 0.5 ppm and limestone binding effect was alleviated after injection of dibasic acid (DBA) with the concentration of 500 and 1,000 ppm. When $Al^{3+}$ and $F^-$ ions were coexisting, the dissolution rate of limestone was decreased by 20%.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.5
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• pp.2285-2290
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• 2012

This study is about atherosclerosis which occupies the highest rate in many diseases people have and we have studied about atherosclerosis for abdominal aorta. Atherosclerosis is the phenomenon which blood vessel gets narrower, harder and thicker due to the stenosis of colesterol in blood vessel. If it becomes worse, arteries will be hard and blood can't flow smoothly, and even it can reach to death. In this study, the geometric models of the considered stenotic blood flow are two different types of constriction of cross-sectional area of blood vessel; 20 and 45% of constriction in each elastic wall and rigid wall. We have modeled by using finite element method to observe the changes of velocity and pressure. In case of the diameter of blood vessel decreased 45% in elastic wall model, the values of velocity and pressure were higher than the case of 20% and in case of the diameter of blood vessel decreased 45% in rigid wall model, the values of velocity and pressure were higher than the case of 20%. In cases of elastic wall models of the diameters of blood vessels decreased each of 20% and 45%, recirculation zones appeared. This results show understanding of hemodynamic properties depending on stenosed blood vessels.

• Fisheries and Aquatic Sciences
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• v.19 no.8
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• pp.32.1-32.6
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• 2016

A feeding trial was conducted to evaluate the effects of two different sizes of extruded pellets (EP) ($EP_1$ - 3 mm or $EP_2$ - 5 mm) and a moist pellet (MP) in olive flounder, Paralichthys olivaceus, reared in semi-recirculation system. A total of 450 fish with an average initial weight of $5.0{\pm}0.2g$ (mean ${\pm}$ SD) were fed one of the three experimental diets in triplicate groups. At the end of a 6-week feeding trial, weight gain, specific growth rate, and feed efficiency of fish fed EP diets were significantly higher than those of fish fed MP (P < 0.05). Water quality parameters like turbidity, total ammonia nitrogen, and total phosphorous from tanks of fish fed $EP_1$ and $EP_2$ were significantly lower than those from tanks of fish fed MP. Blood plasma glutamic oxaloacetic transaminase and glucose concentration were significantly higher in fish fed MP diet compared to fish fed EP diets (P < 0.05). Whole body crude protein contents in fish fed EP diets were higher than those from the fish fed MP diet. Whole body amino acid content like threonine, aspartic acid, serine, tyrosine, and cystine were found to be significantly higher in fish fed EP diets than those in fish fed MP diet. In considering overall performance of olive flounder, $EP_2$ diet could be recommended for the successful aquaculture of this important fish species.