Effects of Y₂O₃ additions on the oxygen diffusion in top-seeded melt growth processed YBa₂Cu₃O_7-y superconductors

Jun, B.H.,Jung, S.A.,Park, S.D.,Park, B.J.,Han, Y.H.,Kim, C.J. North-Holland 2011 Physica. C, Superconductivity Vol.471 No.21

To understand the effect of Y<SUB>2</SUB>BaCuO<SUB>5</SUB> (Y211)/YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> (Y123) interfaces on the oxygen diffusion in single grain YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> superconductors, single grain Y123 superconductors with 0.05 and 0.3moles of Y<SUB>2</SUB>O<SUB>3</SUB> additions were fabricated by a top-seeded melt growth (TSMG) process. Y123 compacts with Y<SUB>2</SUB>O<SUB>3</SUB> additions were subjected to melt growth heating cycles with a cooling rate of 1<SUP>o</SUP>C/h through a peritectic temperature (1015<SUP>o</SUP>C) and then annealed at 450<SUP>o</SUP>C for 200h in flowing oxygen. The superconducting temperature (T<SUB>c</SUB>) and critical current density (J<SUB>c</SUB>) were estimated for the three different regions (top surface (s), intermediate (i) and center (c)) of samples. The amount of Y211/Y123 interface area in single grain Y123 superconductors was successfully controlled by Y<SUB>2</SUB>O<SUB>3</SUB> additions. The T<SUB>c</SUB> values of s regions were higher than those of i and c regions, which indicates the presence of more oxygen at the sample surfaces. In addition, the T<SUB>c</SUB> values of i and c regions of the Y123 sample with 0.3mole Y<SUB>2</SUB>O<SUB>3</SUB> addition were higher than those of the same regions of the Y123 sample with 0.05mole Y<SUB>2</SUB>O<SUB>3</SUB> addition due to the promoted oxygen diffusion through Y211/Y123 interfaces and other related defects. In spite of the promoted oxygen diffusion by Y<SUB>2</SUB>O<SUB>3</SUB> addition, the large T<SUB>c</SUB> difference among the regions still existed, which suggests sluggish oxygen diffusion into single Y123 grains.

Effects of calcium doping on the superconducting properties of top-seeded melt growth processed Y_1.5Ba_2-xCa_xCu₃O_y superconductors

Park, S.D.,Kim, H.J.,Park, B.J.,Han, Y.H.,Jun, B.H.,Lee, J.S.,Kim, C.J. North-Holland 2011 Physica. C, Superconductivity Vol.471 No.21

The effect of calcium doping on the superconducting properties of top seeded melt growth (TSMG) processed Y<SUB>1.5</SUB>Ba<SUB>2-x</SUB>Ca<SUB>x</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB> superconductors was studied in terms of calcium content (X<SUB>ca</SUB>). YBa<SUB>2-x</SUB>Ca<SUB>x</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB> (X<SUB>ca</SUB>=0, 0.005, 0.01, 0.02, 0.04, 0.1, 0.3) powders were synthesized by the powder calcination method. YBa<SUB>2-x</SUB>Ca<SUB>x</SUB>Cu<SUB>3</SUB>O<SUB>7-δ</SUB> powders were mixed with 0.25mole Y<SUB>2</SUB>O<SUB>3</SUB> powder and 1wt.% CeO<SUB>2</SUB> as Y<SUB>2</SUB>BaCuO<SUB>5</SUB> (Y211) refiner, and finally made into Y<SUB>1</SUB>.<SUB>5</SUB>Ba<SUB>2-x</SUB>Ca<SUB>x</SUB>Cu<SUB>3</SUB>O<SUB>y</SUB> (Y1.5)+1wt.% CeO<SUB>2</SUB> composition. The single Y123 growth on the top surface was observed up to X<SUB>ca</SUB>=0.1, while the multiple Y123 growth was observed at X<SUB>ca</SUB>≥0.1. The superconducting transition temperature (T<SUB>c</SUB>) and critical current density (J<SUB>c</SUB>) of TSMG processed Y1.5 samples were inversely proportional to X<SUB>ca</SUB>. The Y211 size increased with increasing X<SUB>ca</SUB> due to the enhancement of Y211 coarsening by calcium doping. No Y211 refining effect by CeO<SUB>2</SUB> was observed in the calcium doped samples. The T<SUB>c</SUB> and J<SUB>c</SUB> decrease by calcium doping are likely to be due to the calcium incorporation with the Y123 lattice and formation of coarse Y211 particles.

Effects of $BaCO_3$ purity on the superconducting properties of top seeded melt growth processed $Y_{1+x}Ba_2Cu_3O_y$ superconductors

Choi, J.S.,Park, S.D.,Jun, B.H.,Han, Y.H.,Sung, T.H.,Choo, K.N.,Kim, C.J. The Korean Society of Superconductivity and Cryoge 2009 한국초전도저온공학회논문지 Vol.11 No.2

Effects of $BaCO_3$ purity on the superconducting properties of top seeded melt growth (TSMG) processed $Y_{1+x}Ba_2Cu_3O_{7-y}$ (Y1+x, x=0.1 and 0.2) superconductors were investigated. $YBa_2Cu_3O_{7-y}$ (Y123) powder prepared using $BaCO_3$ with 99.75% purity and commercially available Y123 powder of 99.9% were used for the fabrication of single Y123 grain superconductors. $T_c$ values of the Y1+x samples prepared using low purity Y123 powder were slightly lower than those of the samples prepared using a high purity powder. In addition to the lower $T_c$, an anomalous peak effect in the intermediate magnetic fields was observed in Y1+x samples prepared using the low purity $BaCO_3$ powder. The slight decrease in $T_c$ and the anomalous peak effect are ascribed to the possible incorporation of a Y123 phase with impurity elements such as strontium and calcium included in the $BaCO_3$powder of 99.7%. The result suggests that the low purity $BaCO_3$ powder of a low price can be used as a raw power for the fabrication of single grain YBCO bulk superconductors.

Safety and Effectiveness of Daclatasvir and Asunaprevir in the Routine Clinical Practice in Korea: Interim Results of Post Marketing Surveillance

( D-w Jun ),( Sw Paik ),( Jh Kim ),( Y-j Lee ),( Ys Lim ),( B-c Song ),( K Yu ),( Sy Han ) 대한간학회 2017 춘·추계 학술대회 (KASL) Vol.2017 No.1

Aims: The objectives of this post marketing surveillance (PMS) are to describe the safety and effectiveness of the combination of Daclatasvir and Asunaprevir (DCV+ASV) for the treatment of chronic hepatitis C genotype 1b patients in real world practice in Korea. We report the interim findings of PMS to improve the understanding on safety and effectiveness of DCV+ASV in routine clinical setting. Methods: : Adult patients who were diagnosed with HCV genotype 1b infection with compensated liver disease and started DCV+ASV combination were enrolled. Patient background, administration status, concomitant medication, and measures of safety, efficacy, and pre-treatment NS5A resistance-associated substitutions (RASs) were collected for analysis. The risk factors associated with adverse events (AEs) and factors affecting effectiveness were analysed. This report includes data collected from October 2015 to December 2016. Results: From 182 patients registered, 177 patients (female, n=102 [57.63%]; mean age, 59.6 years [range: 32-85]; compensated cirrhosis, n=69 [40.0%]; treatment-experienced, n=57[32.2%]) were included in the safety analysis. 9 patients out of 169 patients terminated DCV+ASV treatment due to adverse events (n=2), virological breakthrough (VBT, n=4), economic reason (n=2) and withdrawal the consent (n=1), 8 patients were missed to follow up. Total 97 AEs were reported in 50 subjects (28.25%) and 20 Serious AEs were reported in 13 subjects (7.34%) regardless of causality, including 1 death due to progression of underlying hepatocellular carcinoma. Liver enzyme elevation were reported in 3 subjects (1.69%). Data for virological responses were available in 135 patients, SVR12 were confirmed in 127 patients (94.1%), except for 4 VBT, 2 relapsers and 2 patients with detectable HCV RNA at week 24. Pre-treatment NS5A RAS had been done in 170 patients and no pre-treatment RAS positivity on L31 either Y93 was observed. Conclusions: DCV+ASV was well tolerated and efficacious from this first interim analysis in Korean real-world practice.

Mechanical behavior and cutting performance of nano-multi-layer TixAl1-xN coated tools for high-speed machining of AISI D2 die steel

Y.G. Jeong,강명창,김정석,K.H. Kim,W.G. Kim,I.D. Park,Y.H. Jun 한국물리학회 2009 Current Applied Physics Vol.9 No.3

Nano-multi-layer TixAl1-xN coatings were successfully synthesized on WC–Co substrates by a cathodic arc ion plating (AIP). The synthesized TixAl1-xN films were revealed as nano-multi-layer consisting of nano-sized fine (Ti,Al)N crystallites by characteristics of microstructure, hardness, residual stress and oxidation resistance. The tool performances for the high-hardened AISI D2 die steel (60 HRC) were studied under high-speed cutting conditions. The reliable evaluation system for tool wear of coated tools was introduced.

Mechanical behavior and cutting performance of nano-multi-layer Ti_xAl_1-xN coated tools for high-speed machining of AISI D2 die steel

Jeong, Y.G.,Kang, M.C.,Kim, J.S.,Kim, K.H.,Kim, W.G.,Park, I.D.,Jun, Y.H. Elsevier 2009 CURRENT APPLIED PHYSICS Vol.9 No.3

Nano-multi-layer Ti<SUB>x</SUB>Al<SUB>1-x</SUB>N coatings were successfully synthesized on WC-Co substrates by a cathodic arc ion plating (AIP). The synthesized Ti<SUB>x</SUB>Al<SUB>1-x</SUB>N films were revealed as nano-multi-layer consisting of nano-sized fine (Ti,Al)N crystallites by characteristics of microstructure, hardness, residual stress and oxidation resistance. The tool performances for the high-hardened AISI D2 die steel (60 HRC) were studied under high-speed cutting conditions. The reliable evaluation system for tool wear of coated tools was introduced.

Microbial quality assessment and pathogen inactivation by electron beam and gamma irradiation of commercial seed sprouts

Waje, C.K.,Jun, S.Y.,Lee, Y.K.,Kim, B.N.,Han, D.H.,Jo, C.,Kwon, J.H. Elsevier 2009 Food control Vol.20 No.3

<P><B>Abstract</B></P><P>The microbiological quality of fresh sprouts and their seeds and the potential use of electron beam and gamma irradiation in inactivating inoculated pathogens in both samples were evaluated. High levels of aerobic bacteria and coliforms were enumerated in sprouts. Red radish, alfalfa and broccoli sprouts were positive for <I>Listeria monocytogenes</I>, while all seed samples were negative for pathogens. Red radish and broccoli sprouts and their seeds were inoculated with <I>Escherichia coli</I> O157:H7, <I>Salmonella typhimurium, L. monocytogenes</I> and <I>Bacillus cereus</I> and irradiated up to 3.0kGy. The <I>D</I><SUB>10</SUB> values of the inoculated pathogens were lower in both broccoli and red radish samples treated with gamma ray than with electron beam, while the <I>D</I><SUB>10</SUB> values obtained in seeds were relatively higher compared with sprouts. This study demonstrated the poor microbiological quality of commercial sprout and the potential health risk it poses. Irradiation at appropriate doses is a promising approach for producing safe and pathogen-free sprouts for consumers.</P>

Effects of oxide coating on the growth of single grain YBCO bulk superconductors

Park, S.D.,Jun, B.H.,Park, B.J.,Jung, S.Y.,Seong, B.S.,Kim, C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

Surface oxide coating and bottom inserting of oxide plates have been conducted to top seeded melt growth (TSMG) processed YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> (Y123) bulk superconductors with an aim of controlling the Y123 nucleation and growth. The coating medium for surfaces was Yb<SUB>2</SUB>O<SUB>3</SUB> solution and the bottom inserts were Yb<SUB>2</SUB>O<SUB>3</SUB>/Y<SUB>2</SUB>O<SUB>3</SUB> powder compact. Many vertical cracks were found to develop at the compact/insert interfaces when an Yb<SUB>2</SUB>O<SUB>3</SUB> insert was used, but the crack evolution was greatly reduced when a (Yb<SUB>2</SUB>O<SUB>3</SUB>+Y<SUB>2</SUB>O<SUB>3</SUB>) insert was used. The formation of the vertical cracks is ascribed to the difference in thermal expansion between the YBCO compact and bottom insert. Presence of vertical cracks was found to be crucial to the trapped magnetic field and levitation forces of single grain YBCO bulk superconductors. The Y123 nucleation and growth in TSMG-processed YBCO bulk superconductors were successfully controlled by conducting surface coating and bottom plating using a (Yb<SUB>2</SUB>O<SUB>3</SUB>+Y<SUB>2</SUB>O<SUB>3</SUB>) insert and as a result, the levitation properties were much enhanced.

Improvement of the superconducting properties of an infiltrated YBCO bulk superconductor by a BaCeO₃ addition

Mahmood, A.,Park, S.D.,Jun, B.H.,Youn, J.S.,Han, Y.H.,Sung, T.H.,Kim, C.J. North-Holland 2009 Physica. C, Superconductivity Vol.469 No.15

Single grain YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-x</SUB> (Y123) bulk superconductors with Y<SUB>2</SUB>BaCuO<SUB>5</SUB> (Y211) and various amounts of BaCeO<SUB>3</SUB> (5-45wt.% by an increment of 10wt.%) were fabricated by a seeded infiltration process. The addition of BaCeO<SUB>3</SUB> was found to be effective for a modification of the microstructure and an improvement of the superconducting properties. The refinement effect for Y211 particles within an entire superconducting YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-x</SUB> (Y123) matrix was achieved by BaCeO<SUB>3</SUB> additions. The critical current density (J<SUB>c</SUB>) values were increased as the BaCeO<SUB>3</SUB> contents were increased (maximum J<SUB>c</SUB> at 35wt.% BaCeO<SUB>3</SUB> addition). The J<SUB>c</SUB> improvement by BaCeO<SUB>3</SUB> additions might be due to the microstructure modifications associated with the finely distributed Y211 and BaCeO<SUB>3</SUB> particles. With the addition of BaCeO<SUB>3</SUB> the onset T<SUB>c</SUB> values decreased slightly, indicating highly limited Ce substitution for Y site. It can be concluded that the BaCeO<SUB>3</SUB> addition has a beneficial effect on the morphology, the size and the distribution of the Y211 inclusions and the microstructure regarding pinning improvement.

IDI형 정적연소기에서 연락공 각도가 연소특성에 미치는 영향

전대수,이태원,윤수한,하종률 동아대학교 생산기술연구소 1999 生産技術硏究所硏究論文集 Vol.4 No.1

The IDI type constant volume chamber is used in this study, which is applied Indirect Injection stratified charge method to solve the problems of lean-bum such as misfire and cycle-variation by the unstable initial ignition. It has a sub-chamber formed the ignitable mixture under the low mean equivalence ratio. After combustion starts in the sub-chamber, the flame issues as a jet through the passage hole into the main chamber, and the entrained flame ignite the lean mixture in the main chamber. There are many factors to effect on the combustion characteristics in indirect injection stratified engine. The passage hole angle is the most important factor in that determine the direction of issued fuel and flame to the main chamber. In this study, we measured combustion pressure, surface temperature of wall and computed heat flux to clarify the combustion characteristics and heat loss on each passage hole angle and equivalence ratio in the main chamber