• Fire Science and Engineering
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• 제26권1호
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• pp.16-22
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• 2012

In fire test, accurate heat release rate measurements provide important information to define the fire safety characteristics of products. The calculation of heat release rate depends on the errors of measuring parameters in experimental set-up. In this study, the uncertainty factors of heat release rate in the room corner test facility, which is installed at Korea Railroad Research Institute, were analyzed. Through the fire testings for the KTX interior materials, the uncertainties of heat release rate were calculated. Results showed that uncertainty was high in the initial stage of fire test and gradually decreased with the growth of fire. The oxygen concentration was a major factor contributing to the combined relative standard uncertainty.

• Journal of ILASS-Korea
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• 제8권4호
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• pp.9-16
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• 2003

The Purpose of this study is to investigate the relationships between the local heat release rate and CH concentration have been investigated by numerical simulations of methane-air premixed flames. And simultaneous CH and OH PLIF(Planar Laser Induced Fluorescence) measurement has been also conducted for lean premixed flame as well as for laminar flames. Numerical simulations are conducted for laminar premixed flames and turbulent ones by using PREMIX in CHEMKIN and two dimensional DNS code with GRI mechanism version 2.11, respectively. In the case of laminar premixed flame, the distance between the peak of heat release rate and that of CH concentration is under $91{\mu}m$ for all equivalence ratio calculated in present work. Even for the premixed flame in high intensity turbulence, the distribution of the heat release rate coincides with that of CH mole fraction. For CH PLIF measurements in the laminar premixed flame burner, CH fluorescence intensity as a function of equivalence ratio shows a similar trend with CH mole fraction computed by GRI mechanism. Simultaneous CH and OH PLIF measurement gave us useful information of instantaneous reaction zone. In addition, CH fluorescence can be measured even for lean conditions where CH mole fraction significantly decreases compared with that of stoichiometric condition. It was found that CH PLIF measurements can be applicable to the estimation of the spatial fluctuations of heat release rate in the engine combustion.

• Nuclear Engineering and Technology
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• 제55권8호
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• pp.2977-2983
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• 2023

During normal operation, some parts of the fission product in the defective fuel rods can release into the primary loops in PWR and the escape rate coefficients are widely used to assess quantitatively the release behaviors of fission products in the industry. The escape rate coefficients have been standardized and have been validated by some drilling experiments before the 1970s. In the paper, the model to determine the escape rate coefficients of fission products has been established and the typical escape rate coefficients of noble gas and iodine have been deduced based on the measured radiochemical data in one operating PWR. The result shows that the apparent escape rate coefficients vary with the release-to-birth and decay constants for different fission products of the same element. In addition, it is found that the escape rate coefficients from the defective rod with large defects are much higher than the standard escape rate coefficients, i.e., averagely 4.4 times and 1.8 times for noble gas and iodine respectively. The enhanced release of fission products from the severe secondary hydriding of several defective fuel rods in one cycle may lead to the potential risk of the temporary shutdown of the operating reactors.

• Journal of Pharmaceutical Investigation
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• 제19권3호
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• pp.145-154
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• 1989

Methyl methacrylate-butyl methacrylate copolymer (MMBM)-povidone (PVP) films were investigated as a potential topical drug delivery system for the controlled release of econazole nitrate as a model drug. The effect of changes in film composition, drug concentration, film thickness, pH and temperature of release medium on the in vitro release of econazole nitrate were studied. The release rate constant was found to be increased with increasing povidone content in dry films. Drug release followed zero-order kinetics in the initial stage and then release rate increased gradually with time, espicially in the films having larger proportions of PVP. The release rate was found to be dependent on drug content, film thickness, the pH and temperature of release medium. Antimicrobial test showed that microbial growth was inhibited markedly with increasing proportions of PVP in films. Also drug content and film thickness affected the antimicrobial activity.

• Journal of Pharmaceutical Investigation
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• 제31권1호
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• pp.37-41
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• 2001

Various characteristics of polyethylene oxide (PEO) are useful for drug delivery systems. In this study, PEO was used as a sustained release matrix system containing cefatrizine propyleneglycol (Cefa-PG) which is a new semi-synthetic broad-spectrum and orally active cephalosporin. Five kinds of sustained release matrix tablets were formulated with various content of PEO and other ingredients. And three types of matrix tablets were formulated of which compositions were the same but the hardness was different. It was found that PEO content influenced drug release rate. Increasing PEO content, the drug release rate from matrix tablets was decreased. In addition, Avicel, one of the ingredients of matrix components, changed the drug release from the sustained release PEO matrix tablets. With increasing Avicel content, the rate of drug release was increased. For the effect of hardness of matrix tablets, the rate of drug release is decreased with increasing hardness. In comparison of bioavailability parameters after oral administration of Cefa-PG PEO matrix tablets and general Cefa-PG capsule in beagle dog, the sustained release PEO matrix tablets is more useful than a general dosage form. $AUC^{0-12}$ of the sustained release PEO matrix tablet and the general dosage form was 1.16 and 0.644 respectively.

• Journal of Pharmaceutical Investigation
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• 제20권2호
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• pp.89-95
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• 1990

Ethylcellulose-PEG 4000 film coated on core tablets was investigated as a potential drug delivery system for the controlled release of chlorpheniramine maleate (CPM). The kinetic analysis of the release data indicated that CPM release followed a diffusion-controlled model, where the quantity released per unit area is proportional to the square root of time. The effect of the film composition, CPM concentration, plasticizer concentration and CPM solubility on the release characteristics were examined. The release rate constant increased as CPM concentration increased. It also increased as the PEG 4000 content in the film increased above 10%(w/w), however, it decreased as the PEG 4000 content increased in the concentration range below 10%(w/w). The release rate constant was not affected by the coated weight on the core tablet. The film-coated tablets which contain CPM only in the coated film layer seemed to be a potential oral drug delivery system for the controlled release of CPM.

• Proceedings of the Korean Nuclear Society Conference
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• 한국원자력학회 1995년도 추계학술발표회논문집(2)
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• pp.879-884
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• 1995

The results of performance assessment analyses have shown that the long-lived radionuclides such as I-129 control the potential individual dose impact to the public. I-129 is difficult-to-measure(DTM) in low-level waste because it is non-gamma emitting radionuclides and exists at extremely low concentrations in radioactive waste generated by nuclear reactors. In this study, computer modeling technique to predict release rate of I-129 is developed to provide another tools far performance assessment of land disposal facilities and characteristics of radwaste. Model suggested in this study will give conservative values of I-129 release rate far determination of radwaste characteristics. More detailed approach is implemented to account for release conditions of fuel source-nuclides. 1-131 concentration measured from reactor coolant and released fraction from tramp fuel have dominant roles in calculating release rate of I-129 with fuel defect conditions.

• Korean Journal of Ecology and Environment
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• 제39권3호통권117호
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• pp.331-339
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• 2006

This research was carried out to understand the impacts of thickness of sand capping to control phosphorus release from sediment into overlying water. As capping effectively retards release flux, phosphorus concentration in water body can be maintained if phosphorus release rate was kept under microbial degradation rate. With capping thickness increases, deaeration rate become less, while reaeration coefficient become higher. Phosphorus release rate and capping thickness were linearly correlated. The results of regression analysis indicated that phosphorus release can be controlled effectively by sand capping of least 20${\sim}$40 mm thickness.

• Coupled systems mechanics
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• 제11권3호
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• pp.217-231
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• 2022

The present paper is concerned with a delamination analysis of a multilayered frame structure that exhibits non-linear creep behavior. A solution to the strain energy release rate is obtained by considering the time-dependent complementary strain energy in the frame. The mechanical behavior of the frame is treated by using a non-linear stress-strain-time relationship. The time-dependent solution to the strain energy release rate obtained in the present paper holds for a multilayered frame made of arbitrary number of adhesively bonded layers of different thicknesses and material properties. Besides, the dealamination is located arbitrary along the thickness. The solution to the strain energy release rate is verifiedby applying the J-integral approach. A parametric study of the strain energy release rate is carried-out. Two three-layered frame configurations are analyzed in order to evaluate the influence of the delamination crack location along the thickness on the strain energy release rate. The strain energy release is analyzed also for the case when a notch is cut-out in the inner delamination crack arm. The results obtained are compared with these for a frame without a notch.

• Journal of Pharmaceutical Investigation
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• 제17권2호
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• pp.75-78
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• 1987

The release rate of heparin from monolithic devices composed of raffinose, ${\beta}-cyclodextrin$, polyethylene oxide (Mw 20,000, PEO), and hydrophobic polyether urethane (biomer) was investigated. Water soluble raffinose, ${\beta}-cyclodextrin$, and PEO blended into the biomer provided a controlled release of heparin. The release rate of heparin could be controlled by the content of raffinose, ${\beta}-cyclodextrin$, and PEO in the devices. The mechanism of release rate increased by the raffinose, ${\beta}-cyclodextrin$, and PEO may result from the formation of channels and pores in the biomer matrices following the swelling and the change in the physical structure of polymer net work. Hydrophobic polyurethane containing raffinose, ${\beta}-cyclodextrin$, and PEO can provide a hydrophilic antithrombogenic material for prolonged release of heparin.