• YAKHAK HOEJI
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• v.44 no.6
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• pp.511-520
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• 2000

Various bupivacaine-loaded microspheres were prepared from poly (d,l-lactide) (PLA) or poly (d,l-lactic-co-glycolide) (PLGA) by a solvent evaporation method for the sustained release of drug. PLA and PLGA microspheres were prepared by w/o/w and w/o/o multiple emulsion solvent evaporation, respectively. The effects of process conditions such as emulsification speed, emulsifier type, emulsifier concentration and internal/external phase ratio on the characteristics of microspheres were investigated. The prepared microspheres were characterized for their drug loading, size distribution, surface morphology and release kinetics. Drug loading efficiency was higher in the microspheres prepared by w/o/o multiple emulsion than that by w/o/w multiple emulsion method, because the solubility of bupivacaine HCI was decreased in oil phase compared with water phase. The prepared microspheres had an average diameter between 1 and $2\;{\mu}M$ in all conditions of two methods. In morphology studies the PLA microspheres showed an irregular shape and smooth surface, but PLGA microspheres had a spherical shape and smooth surface. The release pattern of the drug from microspheres was evaluated on the basis of the burst effect and the extent of the release after 24h. The in vitro release of bupivacaine HCl from microspheres showed a large initial burst release and $60{\sim}80%$ release within one day in all conditions of two methods. The extents of the burst release against PLA and PLGA microspheres were $30{\sim}50%$ and $50{\sim}80%$ within 20min, respectively. This burst release seems to be due to the smaller size of microspheres and the solubility of drug in water.

• Korean Journal of Environment and Ecology
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• v.33 no.2
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• pp.228-236
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• 2019

This study investigated the effect of the sediment phosphorus fraction sampled from the southern coast of Korea on the release characteristics of sediments by environmental changes of water quality. We conducted the release experiment in the laboratory for 20 days and measured the phosphorus fraction properties, the environmental factors of water quality, and the release rate of total phosphorus. The results showed a decrease in dissolved oxygen by the growth of microorganisms in the water layer, leading to the anaerobic condition in which the redox potential of the sediments decreased. As such, the decreasing variability of phosphates bonded to iron oxide in the sediment phosphorus was higher after 20 days of the release experiment than the first day. It means that the metal ions and the separated inorganic phosphorus transfer into the water when the iron oxide is reduced. The separated inorganic phosphorus is easily absorbed by the plankton. The analysis of total phosphorus in the water layer showed that it continuously increased to up to 0.304 mg/L for 20 days, and the release rate had a high correlation with the decrease of dissolved oxygen after 5 days of culture. Therefore, it is necessary to pay attention to the characteristics of iron bonded to phosphorus in the phosphorus fraction and dissolved oxygen to manage the eutrophication of the system.

• Archives of Pharmacal Research
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• v.20 no.6
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• pp.555-559
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• 1997

The three different batches of an oral sustained release melatonin (MT) delivery system were prepared by aqueous-based fluid-bed coating of the sugar spheres for the evaluation of in vitro release characteristics and plasma concentration profiles in human subjects. The MT contents in 20% coated sugar spheres of three batches (B1, B2 and B3) were $3.3{\pm}0.08$, $2.4{\pm}0.1$ and $2.5{\pm}0.13$ mg per gram of coated sugar spheres, respectively. The release profiles of three different batches had a very similar fashion. However, the release profiles of three different batches had a very similar fashion. However, the release half-lives $(T_{50%})$ of MT from B1, B2 and B3 was $3.70{\pm}0.2$, $5.2{\pm}0.2$ and $4.9{\pm}0.07h$, respectively. Plasma concentration profiles of sustained release 0.2mg melatonin-loaded sugar spheres containing 10% immediate release melatonin in gelatin capsules (B1 and B2) were then evaluated in human subjects. The in vivo plasma concentration profies of the two batches (B1 and B2) were very similar each other and located between the physiological endogenous ranges. The time to reach the peak concentration $(T_max)$ was more advanced in case of B1 when compared to B2. However, there was no statistically significant difference in the maximum concentration $(C_max)$ and the area under the curve (AUC) between B1 and B2. The AUC of melatonin-loaded sugar spheres containing 10% and 20% immediate release MT in human subjects had a good linearity between dose and AUC, regardless of the fraction of immediate release MT, indicating the first order elimination process of MT within these doses. The current oral sustained release MT delivery system may be utilized to treat circadian rhythm disorders if it is proven to be more clinically useful when compared to immediate release MT.

• Journal of Korean Society of Environmental Engineers
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• v.32 no.1
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• pp.1-8
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• 2010

To investigate the effects of sediments on the water quality of an estuary reservoir, Asan reservoir, we analyzed physical and chemical characteristics of the sediments and estimated nutrients release rate from the sediments. The sediments characterized as sandy loam are mainly composed of Nonapatite-P(64.7%) which has strong influence on the eutrophication of the reservoir by releasing from the sediments under the condition of increasing pH and anaerobic environment. High nutrient release rates was observed in April. Negative release rates in June show that there is no significant nutrient release from the sediments. The nutrient release was active at the Site B around the confluence of tributary compared to the Site A near the embankment. Based on the information of nutrient release rates and sediments surface area, daily average nutrient release rates of Asan reservoir are estimated; TN 6,609 kg/d, TP 3,877 kg/d. Since the amount of N and P released from the sediments corresponds to the 7.06% of N and 22.04% of P incoming from the watershed, it can be concluded that there is little influence of sediments on the water quality of Asan reservoir.

• Journal of ILASS-Korea
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• v.3 no.3
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• pp.23-32
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• 1998

The effect of reentrant type bowl geometry on combustion characteristics was investigated in a D.I. diesel engine. The main factor was the aspect ratio (Bowl Diameter / Bowl Depth) of bowl of combustion chamber, and the cylinder pressure, engine performance and emissions of the engine using the 4 kinds of the combustion chamber were meadured. Also, the combustion characteristics compared of the experimented and the calculated values which is used by the Hiroyasu's combustion model. The results are as follows; The effect of $d_c/H$ on ignition delay period are small. The smoke is corerelated to the heat release of the premixed and the diffusion combustion, i.g, the smoke decreased by decreasing the premixed combustion or increasing the diffusion combustion on cumulative heat release. The premixed combustion process has more effect than the diffusion combustion on smoke. The formal tendency of $d_c/H$ on engine performance has not appear.

• Fire Science and Engineering
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• v.25 no.5
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• pp.47-53
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• 2011

Fire load in buildings greatly contribute to the time and scale of fire according to the type and quantity of the fire load. Because bookstores have a large quantity of fire load compared with other buildings which may lead to large scale fires, however, their heat release characteristics have been hardly investigated. In this study, to obtain the data applicable for the performance-based fire safety design of bookstores, the specimens representing stacked fire loads were heated in a furnace in compliance with the standard heating curve of ISO834-1:1999 to investigate their heat release characteristics. From the experiment result, the combustion velocity and heat release rate required for performancebased fire safety designs are obtained.

• Fire Science and Engineering
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• v.24 no.6
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• pp.120-125
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• 2010

Wood-Plastic Composites (WPCs) are one of spotlighting materials for the residential construction and the industry for furniture. At this study, the limiting oxygen index (LOI) was measured by ASTM D 2863 and the cone calorimeter test was done by ISO 5660-1 to find the combustion characteristics of WPCs. In addition, the identical test was implemented to compare the combustion characteristics between the red pine and the antiseptic wood. The result of LOI measurement showed that the LOI of WPCs was lower than that of red pine or antiseptic wood. The cone calorimeter test showed that the heat release rate (HRR) of WPCs was the highest and the Peak HRR as well as the average HRR and total heat release of WPCs was higher than those of red pine or antiseptized wood

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.398-403
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• 2009

The theoretical bases on characteristics of heat release rate in compartment of building for scenario of smoke management are introduced and the numerical applications to simple compartment model are carried out. The growth stage which is important for smoke management design is modelled as t-squared fire curve including fire growth coefficient with related to growth rate. The conditions for the happening of flashover is presented such as $600^{\circ}C$ of temperature or $20kW/m^2$ of radiation heat flux. After the flashover happen, the fire in compartment changes to fully developed fire having the characteristics of ventilation-controlled fire. As the result of numerical analysis to simple compartment model, the time to reach 900K under ceiling for condition of medium growth is twice for condition of fast growth.

• Journal of the Korean Wood Science and Technology
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• v.39 no.3
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• pp.244-251
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• 2011

The combustion characteristics were evaluated for Japanese Red Pine (Pinus Densiflora) and Korean Pine (Pinus Koraensis). These two species are widely used as building member of Korea-style house and volume density of Japanese Red Pine is relatively higher than that of Korean Pine. The combustion characteristics are closely connected with volume density. The differences of two species in both total heat release (THR) and average heat release rate (HRR) seemed to be resulted from the volume density. Toxicity of smoke from the specimens was increased because of fire-retardant treatment.

• Journal of the Korean Wood Science and Technology
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• v.42 no.6
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• pp.675-681
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• 2014

The purpose of this study is to analyze fundamental combustion characteristics of woods used for indoor applications. The combustion characteristics such as heat release rate, total heat release, gas yield, and mass loss were analyzed by the method of cone calorimeter or thermogravimetry. These analysis results show that material properties of wood are closely related to flammability. It was shown that the relationship between the mass loss and gas emission. The results of combustion properties of woods would be useful for fundamentals of guiding the safe use of wood indoor application.