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有機態 燐酸과 칼슘의 葉面撒布 및 灌注處里가 배(Pyrus pyrifolia N.) 樹體生育과 果實 品質에 미치는 影響
鄭賢德,李相炫,金月洙 전남대학교 농업과학기술연구소 2000 農業科學技術硏究 Vol.35 No.-
To establish the system of orchard fertilization the study was to carried out by foliar spray and fertigation with organic calcium and phosphate in the five year old 'Youngsan' pear trees (Pyrus pyrifolia) planted in Kochang, Chonbuk. The five hundred times diluted solutions of organic calcium and phosphate were sprayed on the surface of pear leaves at intervals of 7 to 10 days from June 1 to August 31. Also five hundred times diluted solutions of organic calcium and phosphate were fertigated under the canopy at intervals of 7 to 10 days from June 1 to August 31. The calciums treatments with foliar spray as well as feritgation increase leaf size on twigs and shoots. Meanwhile organic phosphate treatment showed smaller leaf size in shoots and large on twigs. Calcium content of leaves was higher by the treatment of foliar spray and fertigation. Phosphate content of leaves was much higher by the treatment of organic phosphate. In inorganic substance of fruit peel tissues, calcium content was high by the treatment of organic calcium + phosphate. On the other hand phosphate content in flesh of fruit was high by the treatment of organic phosphate. Fruit weight and firmness were increased by the treatment of organic calcium. Soluble solid was high by the treatment of organic phosphate.
볼밀 공정 중 점도와 음향 데이터의 실시간 수집 및 상관관계 분석
정현덕,김영범,류성수,김세기,Jeong, Hyeondeok,Kim, Young-Beom,Ryu, Sung-Soo,Kim, Seiki 한국분말재료학회 (*구 분말야금학회) 2020 한국분말재료학회지 (KPMI) Vol.27 No.6
In this study, acoustic and viscosity data are collected in real time during the ball milling process and analyzed for correlation. After fast Fourier transformation (FFT) of the acoustic data, changes in the signals are observed as a function of the milling time. To analyze this quantitatively, the frequency band is divided into 1 kHz ranges to obtain an integral value. The integrated values in the 2-3 kHz range of the frequency band decrease linearly, confirming that they have a high correlation with changes in viscosity. The experiment is repeated four times to ensure the reproducibility of the data. The results of this study show that it is possible to estimate changes in slurry properties, such as viscosity and particle size, during the ball milling process using an acoustic signal.
MgB<sub>2</sub> 초전도체의 임계특성에 대한 Fe 입자 크기의 영향
정현덕,이동건,류성수,박해웅,김찬중,전병혁,Jeong, Hyeondeok,Lee, Dong-Gun,Ryu, Sung-Soo,Park, Hai-Woong,Kim, Chan-Joong,Jun, Byung-Hyuk 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.5
This study demonstrates the effect of addition of Fe particles of different sizes on the critical properties of the superconductor $MgB_2$. Bulk $MgB_2$ is synthesized by ball milling Mg and B powders with Fe particles at $900^{\circ}C$. When Fe particles with size less than $10{\mu}m$ are added in $MgB_2$, they easily react with B and form the FeB phase, resulting in a reduction in the amount of the $MgB_2$ phase and deterioration of the crystallinity. Accordingly, both the critical temperature and the critical current density are significantly reduced. On the other hand, when larger Fe particles are added, the $Fe_2B$ phase forms instead of FeB due to the lower reactivity of Fe toward B. Accordingly, negligible loss of B occurs, and the critical properties are found to be similar to those of the intact $MgB_2$.
MgB<sub>4</sub>와 Mg 분말을 원료로 사용하여 고상반응법으로 제조한 MgB<sub>2</sub> 초전도체의 상생성과 초전도 특성
정현덕,김찬중,전병혁,김설향,박해웅,Jeong, Hyeondeok,Kim, Chan-Joong,Jun, Byung-Hyuk,Kim, Seolhyang,Park, Hai-Woong 한국분말야금학회 2015 한국분말재료학회지 (KPMI) Vol.22 No.5
$MgB_2$ bulk superconductors are synthesized by the solid state reaction of ($MgB_4$+xMg) precursors with excessive Mg compositions (x=1.0, 1.4, 2.0 and 2.4). The $MgB_4$ precursors are synthesized using (Mg+B) powders. The secondary phases ($MgB_4$ and MgO) present in the synthesized $MgB_4$ are removed by $HNO_3$ leaching. It is found that the formation reaction of $MgB_2$ is accelerated when Mg excessive compositions are used. The magnetization curves of $Mg_1+_xB_2$ samples show that the transition from the normal state to the superconducting state of the Mg excessive samples with x=0.5 and x=0.7 are sharper than that of $MgB_2$. The highest $J_c-B$ curve at 5 K and 20 K is achieved for x=0.5. Further addition of Mg decreases the $J_c$ owing to the formation of more pores in the $MgB_2$ matrix and smaller volume fraction of $MgB_2$.
구상 페놀수지 분말과 푸르프릴 알코올로부터 주형성형에 의한 매크로 다공성 카본 폼의 제조
정현덕,김세기,Jeong, Hyeondeok,Kim, Seiki 한국분말야금학회 2019 한국분말재료학회지 (KPMI) Vol.26 No.6
Macro-porous carbon foams are fabricated using cured spherical phenolic resin particles as a matrix and furfuryl alcohol as a binder through a simple casting molding. Different sizes of the phenolic resin particles from 100-450 ㎛ are used to control the pore size and structure. Ethylene glycol is additionally added as a pore-forming agent and oxalic acid is used as an initiator for polymerization of furfuryl alcohol. The polymerization is performed in two steps; at 80℃ and 200℃ in an ambient atmosphere. The carbonization of the cured body is performed under Nitrogen gas flow (0.8 L/min) at 800℃ for 1 h. Shrinkage rate and residual carbon content are measured by size and weight change after carbonization. The pore structures are observed by both electron and optical microscope and compared with the porosity results achieved by the Archimedes method. The porosity is similar regardless of the size of the phenolic resin particles. On the other hand, the pore size increases in proportion to the phenol resin size, which indicates that the pore structure can be controlled by changing the raw material particle size.