• 한국전기전자재료학회논문지
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• 제35권6호
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• pp.622-625
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• 2022

YBa₂Cu₃O_7-y bulk as a high temperature oxide superconducting conductor has the high critical temperature of 92 K. YBa₂Cu₃O_7-y bulk superconductors have been fabricated by a seeded melting growth. Magnetic properties were studied by using superconductor of melted YBa₂Cu₃O_7-y oxides. It was demonstrated that Y₂BaCuO₅ particles acts as a pinning center which plays an important role on the magnetic properties. The thickness of the upper and lower pellets of the YBa₂Cu₃O_7-y bulk was formed at 40 mm with 55 g of the composition, and the YBa₂Cu₃O_7-y superconductor was manufactured through a heat treatment process. Manufacturing the superconducting bulk, it is possible to improve the pore density of the superconducting bulk by providing a path through which oxygen could be emitted.

• 분석과학
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• 제30권1호
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• pp.39-48
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• 2017

Roxithromycin (RXT), which is an antibiotic used to treat respiratory tract and urinary infections, is official in Korean Pharmacopoeia (KP) and is marketed in various dosage forms including tablet, granule, suspension, and tablet for suspension in Korea. This study presents how a universal and reliable method to quantify RXT in bulk drug and formulations was developed. Effects of factors including column type, buffer concentration, type and concentration of organic solvent, buffer pH, and type and concentration of mobile phase additive, were examined, and some categorical or crucial factors including the types of column, organic solvent, mobile phase additive and the buffer pH were optimized by one-factor-at-a-time approach. Subsequently, concentrations of the buffer and additive and column temperature were optimized by response surface methodology using Box-Behnken design aiming to acquire the RXT peak of good shape. The optimized method employed a Phenomenex Gemini $5{\mu}$ C18 110A ($150{\times}4.60mm$, $5{\mu}m$) maintained at $30^{\circ}C$ with the mobile phase consisting of 25 mM phosphate buffer (pH 6.0) with 0.3 % tetrabutylammonium hydroxide and methanol at a ratio of 37:63 (v/v). Method validation results showed that the developed method was linear, precise, and accurate. Compared to the compendial methods in KP 10 that exhibited a significant tailing of the RXT peak despite using unfavorably high buffer concentrations and were not harmonized among bulk drug and formulations, this method could be universally applied to RXT bulk drug and marketed products in various dosage forms and thus was adopted in KP 11.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2008년도 High Temperature Superconductivity Vol.XVIII
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• pp.88-88
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• 2008

• Bulletin of the Korean Chemical Society
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• 제33권1호
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• pp.199-203
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• 2012

A modified sol-gel method and $N_2$-plasma treatment were used to prepare bulk and surface doped N-$TiO_2$, respectively. XRD, TEM, UV-vis spectroscopy, $N_2$ adsorption, Elemental Analyzer, Photoluminescence, and XP spectra were used to characterize the prepared $TiO_2$ samples. The N doping did not change the phase composition and particle sizes of $TiO_2$ samples, but increased the visible light absorption. The photocatalytic activities were tested in the degradation of an aqueous solution of a reactive dyestuff, methylene blue, under visible light. The photocatalytic activity of surface doped N-$TiO_2$ prepared by $N_2$-plasma was much higher than that of bulk doped N-$TiO_2$ prepared by sol-gel method. The possible mechanism for the photocatalysis was proposed.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2001년도 학술대회 논문집
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• pp.61-64
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• 2001

Levitation force of a new magnetic levitation system using a super-conducting bulk magnet(SBM) and a permanent magnet(PM) was numerically calculated. The non-linear J-E relation of a SBM was modeled using a critical state model and iteration method, and demagnetization of a PM was considered using a demagnetization curve of a real PM. The maximum limitation of levitation force was found according to increasing the trapped field in a SBM. Finite element method was used for numerical calculation.

• 상하수도학회지
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• 제19권4호
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• pp.487-496
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• 2005

Chlorine bulk decay tests were carried out by bottle test under controlled conditions in a laboratory. Experiments were performed at different temperatures: $5^{\circ}C$, $15^{\circ}C$, $25^{\circ}C$, and the water temperatures when samples were taken from the effluent just before entering to its distribution system. 38 bulk tests were performed for water of Al (water treatment plant), 4 bulk tests for A2 (large service reservoir), and A3(pumping station). Residual chlorine concentrations in the amber bottles were measured over time till about 100 hours and bulk decay coefficients were evaluated by assuming first-order, parallel first-order, second-order. and $n^{th}-order$ reaction. The $n^{th}-order$ coefficients were obtained using Fourth-order Runge-Kutta Method. A good-fit by the average coefficient of determination ($R^2$) was first-order ($R^2=0.90$) < parallel first-order ($R^2{_{fast}}=0.92$, $R^2{_{slow}}=0.95$) < second-order ($R^2=0.95$) < $n^{th}-order$ ($R^2=0.99$). But if fast reaction of parallel first-order bulk decay were applied to the effluent of large service reservoir with ca. 20 hours of travel time and slow reaction in the water distribution system following the first 20 hours, parallel first-order bulk decay would be best and easy for application of water quality modeling technique.

• 한국해양공학회지
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• 제13권4호통권35호
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• pp.182-189
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• 1999

The robust design technology which can determine design variables getting best performance function with insensitivity to the environment noise, is an important method for improving the performance of products at low cost. Applying the robust design technology in ship design, Koh et al[10] introduced the planing hull design. This paper reports the application this technology to a 150K bulk carrier which has many design variables and shows that the robust design technology is superior to optimization technique in practical use.

• 펄프종이기술
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• 제42권1호
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• pp.48-53
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• 2010

Commercial micro pulps(Arbocel) were coated with three kinds of polymers using spray method. These coated micro pulps were used to papermaking additives to evaluate retention, drainage and physical properties of paper. The retention and drainage were improved with addition of polymer coated micro pulp. The bulk index of paper was also increased, but tensile and tear strength were decreased slightly, probably due to weakening of internal bonding. These results showed that the use of polymer coated micro pulp was an effective method to improve retention, drainage and bulk index of paper.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2006년도 춘계학술대회 논문집
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• pp.409-412
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• 2006

Bulk metallic glass (BMG) strips of $Cu_{54}Ni_6Zr_{22}Ti_{18}$ were produced by warm rolling of the amorphous powder canned with copper. Controlling of temperatures of the rolled sample and rolls was essential for the successive rolling process. Because improper controlling of the sample temperature gave rise to the crystallization of BMG loading to the catastrophic fracture of BMG strips, the temperature of rolls should be properly controlled for achieving successful powder rolling of BMG. The variations of the strain state and temperature in the roll gap was simulated by the finite element method(FEM) using various roll temperatures.

• 한국유체기계학회 논문집
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• 제9권3호
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• pp.14-21
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• 2006

Leakage reduction through annular type seals of turbomachinery is necessary for enhancing their efficiency and the precise prediction method of seal leakage is needed. The analysis based on Bulk-flow concept has been mainly used in predicting seal leakage. However, full Navier-Stokes Equations with turbulent model derived in the seal flow passage have to be solved for improving the prediction of seal leakage. FLUENT 6 which is commercial CFD(Computational Fluid Dynamics) code based on FVM(Finite Volume Method) and SIMPLE algorism has been used to analyze leakage of various non-contact-type seals in this presentation. Comparing with the results of Bulk-flow model analysis and experiment, the result of CFD analysis shows good agreement with that of existing theoretical analysis for the incompressible grooved seal and compressive plain and staggered seal. The CFD analysis also shows improvement on the leakage prediction of the incompressible plain seal and compressive see-through-type labyrinth seal.