• KSBB Journal
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• v.6 no.1
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• pp.79-83
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• 1991

Using PHB biopolymer as polymer matrix, the release mechanism of a model drug, silver sulfadiazine was studied. The release behavior actually conformed to the Higuchi's diffusion controlled model. The release rate was delayed with an increasing proportion of PHB, whereas decreased as glycerine concentration incresed. The release rate was increased as the polymer matrix thickness increased.

• Journal of the korean Society of Automotive Engineers
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• v.4 no.2
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• pp.58-68
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• 1982

It is well known to diesel engineers that the heat release pattern is one of the most important factors affecting engine performance. Thorough research in heat release pattern has materially helped the progress in high-speed diesel engine development . This paper is based on the research conducted at KAIST and Daewoo Heavy Industry last year. The purpose of this paper is to determine the heat release pattern in combustion chamber of MAN M type, the famous low-noise engine. Thermodynamic cycle simulation was performed using Whitehous-Way's heat release pattern with modified coefficients and Annand's heat transfer model. Instantaneous temperature and pressure of gas in cylinder could be determined by the numerical solution of simultaneous equation of mass conservation, equation of energy conservation, and state equation of ideal gas. Calculated results were compared with measured values in some details emphasizing upon the factors affecting rate of heat release. The agreement was fairly good and revealed why M type should have lower burning velocity at the early part of combustion in spite of high injection rate. Additional results by parametric studies were given in relation to fuel injection conditions for further application to engine development.

• Journal of Pharmaceutical Investigation
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• v.21 no.2
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• pp.111-116
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• 1991

Dextromethorphan HBr (DMP HBr) ion exchange albumin microcapsules were prepared by the interfacial polymerization method. The incorporation of drugs in empty albumin microcapsules was more increased in case of glutaraldehyde (GA) and formaldehyde (FA) than terephthaloyl chloride (TC) as a cross linking agent. The amount of DMP HBr incorporated into empty albumin micorcapsules was augemented with increasing DMP HBr concentration and the amount of empty microcapsules in the incorporation medium. Increasing the salt concentration in the release medium, the release rate and the DMP HBr amount released from microcapsules were increased. The release rates of DMP HBr from microcapsules retarded considerably compared with DMP HBr powder.

• Korean Journal of Materials Research
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• v.33 no.11
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• pp.458-464
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• 2023

In order to develop catechin patches for skin regeneration at wound sites, patches with varying concentrations of catechin and chitosan were manufactured. An optimal composition ratio was determined by adjusting the drug release rate and amount, to maximize efficiency. The catechin used in this study was extracted from green tea leaves using a solvent/ultrasonication method, and its characteristics were confirmed through Fourier transform-infrared spectroscopy (FT-IR) and high-performance liquid chromatography (HPLC) analyses. Patches were prepared with different concentrations of catechin and chitosan, and various properties were analyzed using techniques such as FT-IR, water contact angle analysis, and UV-Vis spectroscopy. It was observed that as the chitosan concentration increased, the release of catechin slowed down or almost ceased. A patch manufactured with 1.5 mg/cm² of catechin at a 1 % chitosan concentration exhibited a high initial release rate over 24 h and demonstrated cellular biocompatibility. Consequently, these patches, with tailored release characteristics based on the concentrations of chitosan and catechin, hold promise for use as drug delivery systems in wound healing applications.

• Journal of Pharmaceutical Investigation
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• v.21 no.4
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• pp.237-245
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• 1991

Matrix type silicone rubber devices were designed for long-term implantable drug delivery system. Release controlling agents (RCA), i.e., polypropylene glycol, polyethylene glycol, were employed to control drug release from the devices. The release rate of drug from RCA dispersed silicone matrices was mainly dependent on hydrophilicity-hydrophobicity of drug and RCA. In the case of hydrophilic drug, the release from the RCA dispersed matrix was regulated by swelling kinetics. Especially when the relatively hydrophobic polypropylene glycol was used, swelling control mechanism induced zero-order release kinetics. Whereas, the release of hydrophobic drug was resulted from partition mechanism. The effect of RCA was to increase drug diffusivity.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.6
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• pp.476-481
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• 2004

The aim of this study was to formulate a sustained release system for indomethacin (IND) with rosin gum obtained from a pine tree. Rosin microparticles were prepared by a disper­sion and dialysis method without the addition of surfactant. In order to investigate the influence of solvents on the formation of colloidal microparitcles, various solvents like ethanol, DMF, DMAc, and acetone were used. The rosin microparticles containing IND were characterized by X­ray differactometry (XRD) and differential scanning calorimetry (DSC). The morphologies of rosin microparticles observed by scanning electron microscopy (SEM) were spherical. The solvents used to dissolve rosin significantly affected the drug content and drug release rate of IND. The release behaviors of IND from the rosin microparticles were dependent on the drug content and size of the particles. Rosin micorparticles with a higher drug content and of a larger particle size had a slower drug release rate. Also, the IND release rate from the rosin microparticles could be regulated by the rosin content in the microparticles. From these results, rosin microparticles have the potential of being used as a sustained release system of IND.

• KSBB Journal
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• v.14 no.3
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• pp.297-302
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• 1999

The polymeric matrices coated with poly(DL-lactide) were prepared using chitosan derivatives such as chitosan, chitosan hydrochloride, and sulfonated chitosan for application of drug delivery systems. The drug release study using prednisolone as a model drug was performed in the hydrochloride solution at pH 1.2. The release rate of drug was decreased according to the increased content of matrices. The release rate of prednisolone according to the kinds of polymeric matrices coated were decreased in the order to chitosan, sulfonated chitosan, and chitosan hydrochloride. Drug release rate of polymeric matrices coated with poly(DL-lactide) was not only two times slower than noncoated one, but also the burst effect of initial period of drug release was decreased in comparison with noncoated one. From these results, it was expected that these formulations based on the chitosan derivative matrices coasted with poly(DL-lactide) were acceptable drug delivery devices for a sustained-release dosage form of drug.

• Archives of Pharmacal Research
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• v.16 no.2
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• pp.129-133
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• 1993

Temperature sensitive liposomes(TSL) containing adriamycin (ADM) and cytarabine (Ara-C) were prepared. ADM and Ara-C were selected as model compounds of amphiphilic and hydrophilic drug, respectively. Encapsulation efficiency of ADM entrapped into TSL was about twice greater than that of Ara-C. It might be due to different polarity of the drug, Lipid compositions of TSL had no effect on the encapsulation efficiency of drugs. Thermal behavior of TSL using a differential scanning calorimetry (DSC) was also investigated. Phase transition of TSL using a differential scanning calorimetry (DSC) was also investigated. Phase transition temperature $(T_c)$ of TSL was dependent on the lipid compositions of TSL ADM broadened thermogram of TSL but Ara-C did not. However, $T_c$ of TSL was not changed by any drug. Release rate of drugs was highly dependent on temperature. The release profile of ADM was similar to that of Ara-C. The maximum release rate of drugs from TSL was occurred at the near $T_c$ and observed at $39-41^\circ{C}$ for DPPC (Dipalmitoylphosphatidylcholine) only, $52-54^\circ{C}$ for DPPC and DSPC (1:1), respectively. Effect of human serum alburmin (HAA) on the release rate of ADM was investigated. HSA had no significant effect on the release of ADM below $T_c$. However, ADM release from TSL was increased at the near and above $T_c$. The HSA-induced leakage of drug may result from the interaction of liposomal constituents with HSA structure at the near TEX>$4^\circ{C}$. From the fact that the release profiles of ADM from freshly prepared TSL and stored TSL for 1 week at TEX>$4^\circ{C}$ was not changed, the TSL was considered to be stable for at least 1 week at TEX>$4^\circ{C}$. Based on these findings, TSL may be useful to deliver drugs to preheated target sites due to its thermal behaviors.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.9
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• pp.1003-1012
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• 2007

In this study, we analyzed the release differences for some critical pollution compounds according to the surrounding conditions in order to predict water quality due to the sedimental releases and the release characteristics at different sedimental locations in Lake Leewon, in Tae-An area. COD, nitrogens and phosphates were analyzed using the standard methods for water quality, based on high chloride ion concentration(greater than 2,000 ppm). For COD, the release rate increased in the anoxic basin but almost the same in the oxic basin. For $NH_3$-N, the release rate decreased in the oxic basin as you go A through C point meanwhile, for $NO_3$-N and T-N, the tendency was reversed because of nitrification of them. In the anoxic basin, the release rates of $NH_3$-N and $NO_3$-N went up with A through C path. However, the release rate of T-N was found to decrease. Also, for $PO_4$-P and T-P, the release rates in the oxic basin were lowest at B point mainly because the phosphates were at less released in the highly $O_2$ concentrated environment. In the anoxic reactor, $PO_4$-P was released similarly regardless of the sampling points. In summary, the release rates in the oxic reactor were greater than those in the anoxic reactor for COD and $NO_3$-N. For the other components, the anoxic basin generated the higher release rates.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.368-376
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• 2004

The estimation of the diffusion coefficients of the Gaussian plume model and the release rate by assimilation of tracer-gas measurements on Younggwang site was tested. Diffusion coefficients were modified by linear programming of both the measurements and the simulated using the Gaussian plume model. The application of the modified diffusion coefficients improved the prediction ability of the Gaussian plume model on both 3 km and 8 km arc lines. And, the release rate of tracer gas was estimated using least squares method. The optimal source rate was estimated by minimizing the errors between the measured concentrations and the computed ones by the Gaussian plume model. The obtained release rate showed a good agreement with the real release rate of the Younggwang experiment in 24%.