벼 機械移秧 育苗의 播種量 및 種子處理가 苗素質에 미치는 影響

金容在,丁弘仁,李仁 全南大學校 農業科學技術硏究所 2001 農業科學技術硏究 Vol.36 No.-

In raising infant rice seedling, in order to shorten seedling period and decrease the number of seedling box per unit area, we investigated infant rice seedling growth, matured seedling ratio and root mat with seeding rates and seedtreatments (pregerminated seed+prochloraz, pregerminated seed+prochloraz+ metalaxyl, soaked seed+prochloraz, soaked seed+prochloraz+metalaxyl). In case of sowing 220~300g seeding rate per box, seedling height in seed treated prochloraz+metalaxyl is the less seeding rate. Top dry weight increase the more in the less seeding rate, but the pregerminated seed+prochloraz+metalaxyl treatment of seeding rate 220g is the heaviest. Endosperm consumption is more in the much seeding rate. Therefore minimum seeding period for mechanical rice transplanting is 8 days in soaked seed, and that in pregerminated seed is about 7 days, with 220~300g seeding rate per box. Root mat formation is good in pregerminated seed+prochloraz+metalaxyl treatment of 260, 300g seeding rate, and pregerminated seed+prochloraz treatment of 300g seeding rate. At 7 days after seeding, 220, 260g seeding rate per box maintain high ratio of matured seedling, and 300g seeding rate also maintains matured seeding ratio to be capable of mechanical rice transplanting, 220g seeding rate require 160~169 boxes per ha for mechanical rice transplanting, 260g seeding rate can decrease the number of the box by 15%, 300g by 23%.

Suppression of samarium diffusion in top seeded melt growth processed Y123 superconductors using a Sm123 seed

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

To suppress the samarium diffusion from a SmBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> (Sm123) seed into an YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> (Y123) compact during a top seeded melt growth (TSMG) process, Y211 buffer disks of various thicknesses (t) were inserted at the seed/compact interface. The effectiveness of the Y211 buffer insert on the suppression of samarium diffusion was estimated from the susceptibility curve and composition analysis for the three top surface regions (region just below the seed/buffer, intermediate region between the buffer and compact edge and compact edge). The difference in the superconducting temperature (T<SUB>c</SUB>) and the superconducting transition width (ΔT) in the three regions was large, when no buffer or thin buffers (t is smaller than 1mm) were used. As a buffer disk of an appropriate thickness was inserted into the seed/compact interface, the difference in T<SUB>c</SUB> and ΔT in the three regions was much reduced. The composition analysis across the seed/buffer/compact region clearly revealed that the T<SUB>c</SUB> decrease was caused by the samarium diffusion from a seed, which led to the formation of Y<SUB>1-x</SUB>Sm<SUB>x</SUB>Ba<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7-y</SUB> in the Y123 compact region. The buffer insert technique was demonstrated to insure the uniform superconducting properties of the top surface of TSMG processed Y123 superconductors.

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.

다중물리 유한요소해석에 의한 SiC 단결정의 용액성장 공정 설계

윤지영,이명현,서원선,설용건,정성민,Yoon, Ji-Young,Lee, Myung-Hyun,Seo, Won-Seon,Shul, Yong-Gun,Jeong, Seong-Min 한국결정성장학회 2016 한국결정성장학회지 Vol.26 No.1

용액성장법에 의한 SiC 단결정 성장은 Si 또는 Si-금속합금의 융액으로부터 SiC를 성장시키는 방법으로서, 통상의 상부종자 용액성장법(Top Seeded Solution Growth)에서는 Si 융액을 담는 흑연도가니로부터 C가 Si 융액에 용해되고 용해된 C이 상부에 위치한 종자결정으로 이동하여 종자결정상에 SiC 형태로 재결정화하는 단계를 거쳐 SiC의 단결정을 성장시키는 과정을 거치게 된다. SiC 용액성장에 있어서는 SiC의 단결정성장을 위하여 흑연도가니의 형상, 크기, 재질 및 상대적 위치 배열 등 온도제어와 유체흐름 제어를 위해 다양한 공정변수를 선정해야한다. 본 연구에서는 용액성장공정의 설계를 위해 상용의 유한요소해석 패키지인 COMSOL Multiphysics를 이용하여 전자기장해석, 열전달해석, 유체해석에 대한 다중물리해석모델을 구축하고 이 모델을 이용하여 결정성장공정을 설계하였다. 해석결과에 기초하여 2 inch off-axis 4H-SiC 단결정을 종자결정으로 적용하여 $1700^{\circ}C$에서 상부종자 용액성장법에 의하여 SiC 단결정을 성장시켰다. 광학현미경 및 고분해능 X선회절분석을 통해 결정성을 분석한 결과 해당 성장조건에서 양호한 품질의 단결정이 성장함을 확인하였다. 이로써 본 연구에서 구축된 다중물리해석모델이 SiC의 용액성장 공정설계에 유효함을 확인하였다. A top-seeded solution growth (TSSG) is a method of growing SiC single crystal from the Si melt dissolved the carbon. In this study, multiphysics modeling was conducted using COMSOL Multiphysics, a commercialized finite element analysis package, to get analytic results about electromagnetic analysis, heat transfer and fluid flow in the Si melt. Experimental results showed good agreements with simulation data, which supports the validity of the simulation model. Based on the understanding about solution growth of SiC and our set-up, crystal growth was conducted on off-axis 4H-SiC seed crystal in the temperature range of $1600{\sim}1800^{\circ}C$. The grown layer showed good crystal quality confirmed with optical microscopy and high resolution X-ray diffraction, which also demonstrates the effectiveness of the multiphysics model to find a process condition of solution growth of SiC single crystal.

Suppression of the surface nucleation of YBa$_2$Cu$_3$O$_7-y$ by CeO$_2$ coating of the top-seeded melt processed YBCO superconductors

Kim, Ho-Jin,Jun, Byung-Hyuk,Kim, Chan-Joong The Korea Institute of Applied Superconductivity a 2003 한국초전도저온공학회논문지 Vol.5 No.3

The effect of CeO$_2$ coating on the surface nucleation of the top-seeded melt-growth processed YBCO superconductors was studied. It was effective that the coating of Y123 compact surfaces by CeO$_2$ powder suppressed the undesirable subsidiary YBa$_2$Cu$_3$O$_{7-y}$ (Y123) nucleation during melt processing. BaCeO$_3$ was formed in the CeO$_2$-coated layers, which might cause a CuO-excessive liquid at the partial melt stage of $Y_2$BaCuO$_{5}$(Y211) plus liquid, and thus the Y123 nucleation at the YBCO compact surfaces could be suppressed during the melt growth of Y123 grain. In addition, the CeO$_2$ refined the Y211 particles near the compact / coating interface. While the levitation forces of the top surfaces with and without CeO$_2$ coating were similar to each other, the levitation force of the interior of the CeO$_2$ coated sample was higher than that of the interior of the sample without CeO$_2$ coating, which was attributed to the suppression of subsidiary Y123 nucleation at the compact walls.s.s.

종자 결정 성장법으로 제조된 $GdBa_2Cu_3O_{7-y}$ 벌크 초전도체의 자기적 특성

김광모,박순동,전병혁,고태국,김찬중,Kim, K.M.,Park, S.D.,Jun, B.H.,Ko, T.K.,Kim, C.J. 한국초전도학회 2012 Progress in superconductivity Vol.14 No.1

The fabrications condition and superconducting properties of top-seeded melt growth (TSMG) processed $GdBa_2Cu_3O_{7-y}$ (Gd123) bulk superconductors were studied. Processing parameters (a maximum temperature ($T_{max}$), a temperature for crystal growth ($T_G$) and a cooling rate ($R_G$) through a peritectic temperature ($T_P$) for the fabrication of single grain Gd123 superconductors were optimized. The magnetic levitation forces, trapped magnetic fields, superconducting transition temperature ($T_c$) and critical current density ($J_c$) of the Gd123 bulks superconductors were estimated. Single grain Gd123 bulk superconductors were successfully fabricated at the optimized processing condition. The $T_c$ of a TSMG processed Gd123 sample was 92.5 K and the $J_c$ at 77 K and 0 T was approximately $50kA/cm^2$. The trapped magnetic field contour and magnetic levitation forces were dependent on the top surface morphology of TSMG processed Gd123 samples. The single grain Gd123 samples, field-cooled at 77 K using a Nd-B-Fe permanent magnet with 5.27 kG and 30 mm dia., showed the trapped magnetic field contour of a single grain with a maximum of 4 kG at the sample center. The maximum magnetic levitation forces of the single grain Gd123 sample, field-cooled or zero field-cooled, were 40 N and 107 N, respectively.

Suppression of the surface nucleation of YBa2Cu3O7-y by CeO2 coating of the top-seeded melt processed YBCO superconductors

Ho-Jin Kim,Byung-Hyuk Jun,Chan-Joong Kim 한국초전도저온학회 (구 한국초전도저온공학회) 2003 한국초전도저온공학회논문지 Vol.5 No.3

고상반응법으로 합성한 분말로부터 Gd_1.5Ba₂Cu₃O_7-y 벌크 초전도체의 제조

김용주,박승연,유병윤,박순동,김찬중,Kim, Yong Ju,Park, Seung Yeon,You, Byung Youn,Park, Soon-Dong,Kim, Chan-Joong 한국재료학회 2013 한국재료학회지 Vol.23 No.6

$GdBa_2Cu_3O_{7-y}$(Gd123) powders were synthesized by the solid-state reaction method using $Gd_2O_3$ (99.9% purity), $BaCO_3$ (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with $Gd_2O_3$ addition ($Gd_{1.5}Ba_2Cu_3O_{7-y}$(Gd1.5)) were used as raw powders for the fabrication of Gd123 bulk superconductors. The Gd123 and Gd1.5 bulk superconductors were fabricated by sintering or a top-seeded melt growth (TSMG) process. The superconducting transition temperature ($T_{c,onset}$) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The $T_{c,onset}$ of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density ($J_c$) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/$cm^2$. The addition of 0.25 mole $Gd_2O_3$ and 1 wt.% $CeO_2$ to Gd123 enhanced the $T_c$, $J_c$ and magnetic flux density (H) of the TSMG processed Gd123 sample owing to the formation of the superconducting phase with high flux pinning capability. The $T_c$ of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The $J_cs$ at 77 K (0 T and 2 T) were $3.2{\times}10^4\;A/cm^2$ and $2.5{\times}10^4\;A/cm^2$, respectively. The H at 77 K of the TSMG-processed Gd1.5 was 1.96 kG, which is 54% of the applied magnetic field (3.45 kG).

Effects of Straw Mulching and Nitrogen Fertilization on the Growth of Direct Seeded Rice in No-tillage Rice/Vetch Cropping System

Young-Son Cho,Zhin-Ryong Choe 韓國作物學會 1999 Korean journal of crop science Vol.44 No.2

No-till direct seeding cultivation of rice has major advantages such as saving of labor and cost by eliminating tillage, preparation of seed bed and trans-planting procedure compared to the conventional transplanting cultivation. A field experiment was conducted to evaluate the effects of straw treatment and nitrogen levels on the rice growth in no-till direct-seeding cultivation. Rice straw, vetch straw, and the mixture of both of the straws were mulched on the surface of soil before seeding while 4 levels of nitrogen fertilizer, 0, 7, 9, and 11 kkg/10a respectively, were applied at 3 split times, 3-weeks after sowing, 5-weeks after sowing and the panicle initiation stage. Mulching of vetch straw significantly reduced seedling establishment of rice which may be attributed to low oxidation-reduction potential of soil by vetch mulching treatment. Vetch straw increased the concentration of soil ammonium leading to an extension of the greenish leaf to panicle initiation stage. Agronomic nitrogen use efficiency (AD EN ) in heavy-mixed straw mulching plots was lower than other treatments. Grain yield and AU EN in the vetch treatment were less affected by fertilized N levels. Conclusively, it is suggested that heavy straw mulching was not efficient for rice seedling establishment and nitrogen usage.e.