• YAKHAK HOEJI
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• v.36 no.3
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• pp.212-219
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• 1992

Although oral route is the most convenient route for drug administration, the short and variable transit of drug through GI tract restricts the sustained drug absorption after oral administration. Thus, for sustained absorption of drugs, it is desirable to prolong the GI transit time by retaining the dosage forms in the stomach. In this study, the enzyme-digestible swelling hydrogel was synthesized by heating the mixed solution of N-vinyl-2-pyrrolidone[monomer], acrylated albumin[crosslinking agent] and proxyphylline[drug] at $65^{\circ}C$ for 10 hours in the cylindrical test tube. The resultant hydrogel tablet (diameter; 0.77 cm, thickness; 0.47 cm) was designed to swell in the gastric fluid after oral administration to such a size that passing through the pylorus could be inhibited during the drug release. After releasing drug, the hydrogel was expected to be degraded by pepsin, an enzyme in the stomach, and eventually solubilized. Actually, the hydrogel synthesized in the study swelled to a size larger than the diameter of the pylorus ($1.3{\pm}0.7$ cm) and slowly digested in the presence of pepsin. Drug release from the hydrogel was prolonged up to about 12 hours. The swelling kinetics was dependent on albumin acrylation time, drug content and gel thickness. Particularly the gel thickness was the most important factor that influences on drug release. By adjusting these factors, the albumin-crosslinked hydrogel was expected to be retained in the stomach for up to 60 hours and used as a potential platform of drugs for long-term GI absorption.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.9
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• pp.969-974
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• 2011

A carbon nanotube (CNT) is a cylindrical carbon nanostructure with good transport properties along the tube's axis. As an approach for realizing the practical use of CNTs, CNT networks are fabricated and their applications in many fields are investigated. To fabricate thin CNT-based films, several methods have been proposed and used. Among these methods, the spray coating method is a robust method for fabricating a large area. However, it is difficult to achieve uniformity in the CNT network. To solve this problem, it is necessary to understand the effect of the sprayprocess parameters on the deposition thickness distribution. In this study, a numerical model for predicting the deposition thickness distribution during the spray process was developed. The spatial deposition thickness distributions obtained according to various nozzle paths were analyzed using the developed numerical model.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.6
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• pp.800-809
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• 2011

The reaction characteristics of an integrated reactor with steam reformer and catalytic combustor using anode offgas for high temperature fuel cells such as MCFC and SOFC have been experimentally investigated in the present study. The coupled reactor had a coaxial cylindrical shape, and the inner and the outer tube was packed with combustion catalysts and reforming catalysts, respectively. Thus, the endothermic steam reforming could proceed by absorbing heat from catalytic combustion of anode offgas. Results show that increasing inlet temperature and decreasing excess air ratio increased the reformer temperature, which led to the increase in $H_2$ yield. The reforming performance for SOFC conditions was better than that for MCFC conditions since the composition of flammable components became smaller for MCFC cases. Measured reformate composition under various test conditions correlated well with thermal equilibrium composition.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.130-136
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• 2002

A novel ozonizer has been developed using a high frequency surface discharge and a high purity Ti-Si-Al ceramic catalyst as its dielectric component. A cylindrical thin compound ceramic catalyst in reactor is adhered to inside of the film-like outside electrode. And, when experiment condition are oxygen gas temperature of 20 ［$^{\circ}C$］, inner reactor pressure of 1.6 atm 600［Hz］ and flow late of 2［l/min］. the ozonizer can easily produce ozone concentration(50～60［g/㎥］for oxygen) and power efficiency(180［g/kWh］for oxygen) without using a special enrichment means. At 2［l/min］, 20［$^{\circ}C$］, 1.6［atm］, 600［Hz］and 40［W］, the result of simulation to gas temperature of reactor using general code Phoenics, the maximum temperature of reactor was 132［$^{\circ}C$］in reactor. Ant the result electric field simulation of Ti-Si-Al type reactor using general code Flux 2D, maximum electric field was 0.131E.08［V/m］.

• Journal of radiological science and technology
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• v.4 no.1
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• pp.55-62
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• 1981

This study was conducted, during the period of 20-30th, July in 1981, to survey measurement methods in thyroid uptake rate test in Seoul city. The results were summarized as follows: 1. For the great part of nuclear medcine department, a mount of radioiodine($^{131}I$) administrated to the patients was $50-100{\mu}Ci$ in thyroid uptake rate test. 2. Distribution of scintillation, counter with crystal size of $1\frac{1}{2}inch$ was 43%, 3inch(22%), 2.5inch(14%) and $2\frac{1}{2}inch$ was 7% in RAI uptake rate test. 3. When RAI uptake rate test was performed, distribution of collimator in use was flat field type collimator(78%) in general and cylindrical type collimator was 22%. 4. High voltage applied to the P-M tube was $900{\sim}1000V$(50%) and most units provided $3{\sim}15%$ of the window range for the $^{131}I$ peak $\gamma-ray$ energy. 5. Distribution on the use of neck phantom for measurements standard solution was 57% and distribution of b filter in use for room background counts and extrathyroidal tissue was 43% and 50%. 6. The distance between the counter and the source was 25cm(58%) in measuring radioactivity of standard solution, thyroid tissue and background radioactivity count. 7. The early uptake measurements(2, 4, 6 hours) are done after administration of the radioiodine dose and also 24-hour and 48-hour uptake measurements are done in routine test.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.435-435
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• 2010

A inclined slot-excited plasma source is newly designed and constructed for higher flux HNB(Hyperthermal Neutral Beam) generation. The present source is different from the vertical SLAN(SLot ANtenna) sources [1] in two aspects. One is that the slots are inclined, and the other is that the magnetic field is configured to a cusp type. These modifications are intended to make the source plasma operated in sub-milli-torr pressure regime and as thin as possible, both of which is to get higher HNB flux by decreasing the re-ionization rate of the reflected atoms from the neutralizer [2]. The plasma is generated in a quartz tube of internal diameter 170 mm enclosed in a aluminum application chamber of larger diameter 250 mm. The microwave power is fed to the plasma chamber by 8 inclined slots cut into the application chamber wall. The slots are coupled the chamber to a WR280 waveguide wound around it to form a ring resonator. In order to make two slots $\lambda_g/2$ apart in phase, the adjacent slots are rotated in opposite directions. The rotation angle of the slots are set to $60^{\circ}$ from the chamber axis. Between the quartz chamber and the aluminum cylindrical chamber 8 NdFeB magnets are equally spaced and fixed to form the cusp magnetic field confinement and ECR (Electron Cyclotron Resonance) field. In this presentation, the magnetic and electromagnetic simulations, and the measured plasma parameters are given for both the inclined and the vertical slot-excited plasma sources. We also discuss how the sources can be tailored to suit better-performing HNB sources.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.14-24
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• 2018

Several typical hyper-elastic constitutive models that encompass both conventional and advanced ones were investigated for the application of instability problems, including the biaxial tension of a rubber patch and inflation of spherical or cylindrical balloons. The material models included the neo-Hookean model, Mooney-Rivlin model, Gent model, Arruda-Boyce model, Fung model, and Pucci-Saccomandi model. Analyses can be done using membrane equations with particular strain energy density functions. Among the typical strain energy density functions, Kearsley's bifurcation for the Treloar's patch occurs only with the Mooney-Rivlin model. The inflation equation is so generalized that a spherical balloon and tube balloons can be taken into account. From the analyses, the critical material parameters and limit points were identified for material models in terms of the non-dimensional pressure and inflation volume ratio. The bifurcation was then identified and found for each material model of a balloon. When the finite element method was used for the structural instability problems of rubber-like materials, some careful treatments required could be suggested. Overall, care must be taken not only with the analysis technique, but also in selecting constitutive models, particularly the instabilities.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.407-410
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• 2002

Monochromatic x-ray CT has several advantages over conventional CT, which utilizes bremsstrahlung white x-rays from an x-ray tube. There are several methods to produce such monochromatic x-rays. The most popular one is crystal diffraction monochromatization, which has been commonly used because of the fact that the energy spread is very narrow and the energy can be changed continuously. The alternative method is the use of fluorescent x-ray, which has several advantages such as large beam size and fast energy change. We have developed a parallel-beam and a fan-beam monochromatic x-ray CT, and compared some characteristics such as accuracy of CT numbers between those systems. The fan beam monochromatic x-rays were generated by irradiating target materials by incident white x-rays from a bending magnet beam line NE5 in 6.5 GeV Accumulation Ring at Tukuba. The parallel beam monochromatic x-rays were generated by using a silicon double crystal monochromator at the bending magnet beam line BL-20BM in Spring-8. A Cadmium telluride (CdTe) 256 channel array detector with 512mm sensitive width capable of operating at room temperature was used in the photon counting mode. A cylindrical phantom containing eight concentrations of gadolinium was used for the fan beam monochromatic x-ray CT system, while a phantom containing acetone, ethanol, acrylic and water was used for the parallel monochromatic x-ray CT system. The linear attenuation coefficients obtained from CT numbers of those monochromatic x-ray CT images were compared with theoretical values. They showed a good agreement within 3%. It was found that the quantitative measurement can be possible by using the fan beam monochromatic x-ray CT system as well as a parallel beam monochromatic X-ray CT system.

• YAKHAK HOEJI
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• v.37 no.5
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• pp.511-519
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• 1993

The short and variabke transit of drug throught GI tracj and the inter-and intra-subject variations of the transit restrict the sustained drug absorption after oral adminstration. These restrictions may be solved by retaining the dosage forms in the stomach. Then the dosage form will act as a platform which releases the drug slowly and makes the GI absorption occur for a long time. In this study, as the platforms, PVP hydrogels were synthesized by chemical and y-irradiation method in the cylindrical test tube. The chemical method means the synthesis of the hydrogel by heating the mixed solution of N-vinyl-2-pyrrolidone [monomer], acrylated albumin [crosslinking agent], 2, 2'-agobis(2-methylpropionitrile) [initiator] and proxyphylline [drug] at $65^{\circ}C$ for 5 hr. The $\gamma$-irradiation method means the synthesis of the hydrogel by irradiation with $^{60}$ Co $\gamma$-ray of the mixed solution of the monomer, acrylated albumin, and flurbiprofen [drug] at room temperature with total 0.2 Mrad for 3 hr. Our intention is to design the hydrogel tablet (diameter : 1.20 cm, thickness : 0.60 cm) which swells in the gastric fluid after oral administration to such a size that passing through the pylorus could be inhibited during the period of drug release. After releasing drug, the hydrogel should be degraded by the enzymeatic digestion in the stomach, or by hydrolysis and eventually solubilized. Thus, in votro tests were performed to examine the factors that affect swelling and drug release from the PVP hydrogels. Experimental results show that the hydrogels swell to a size larger than the diameter of the pylorus(l.3$\pm$0.7 cm) and the hydrogel prepared by the chemical method is digested by pepsin. But the hydrogel prepared by the $\gamma$-irradiation method was not digested by the pepsin and just collapsed with time. Thus, the swelling of the hydrogel synthesized by $\gamma$-irradiation was independent albumin acrylation time and pepsin concentration. But drug content and radiation dose affected the swelling and drug release kinetics of the hydrogel. Drug release from the hydrigels was prolonged up to about 24 hr. Therefore, it was concluded that by adjusting these factors, the albumin-crosslinked PVP hydrogel synthesized by $\gamma$-irradiation method is expected to be retained in the stomach for up to 60hr and be a potential platform of drugs for long-term GI absorption.

• Journal of the Korea Institute of Building Construction
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• v.11 no.5
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• pp.426-434
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• 2011

Recently, the use of mineral admixtures in concrete has been studied in many laboratories, and been applied in the field. But the non-destructive testing equation proposed in Japan for normal strength concrete has been used to determine compressive strength, because there has been a lack of systematic research on the compressive strength of concrete using mineral admixtures. For this reason, it is essential to suggest a non-destructive testing equation to estimate the compressive strength of concrete using mineral admixtures. Therefore, this study made a cylindrical specimen and core tube specimen of concrete using a mineral admixture, and suggested a strength estimation of long-term age (4 years) through non-destructive and destructive tests. The results of the research are as follows. Comparing error rates between conventional suggested equations and this estimated equation shows some differences by age, but the error rate of this study was reduced to 0.3 %~115.0 % compared to conventional equations by re-bound hammering, 0.2 %~22.8 % by the ultrasound velocity method and 0.5 %~102.3 % by complex method. Accordingly, it is judged to be suitable for assessing the compressive strength of concretes using mineral admixtures.