• Bulletin of the Korean Chemical Society
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• v.11 no.6
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• pp.560-563
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• 1990

A.c. susceptibility for $Bi_{1.4}Pb_{0.6}Sr_2Ca_2Cu_{3.6}O_x$ superconductor is measured as a function of temperature at different value of a.c. magnetic field amplitude. Two transition steps are attributed to the intergranular and intragranular properties. Based on Bean's critical state model, intergranular critical current density, $J_c^{gb}$ (11 $A/cm^2$ at 77 K) and intragranular critical current density, $J_c^g (7{\times}10^3\;A/cm^2$ at 100 K) are estimated. The low values of $J_c^{gb}$and $J_c^g$ reflect a poor nature of coupling between grains and the low pinning force density of intragrain in $Bi_{1.4}Pb_{0.6}Sr_2Ca_2Cu_{3.6}O_x$ superconductor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.559-560
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• 2010

• Progress in Superconductivity and Cryogenics
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• v.19 no.1
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• pp.42-46
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• 2017

The effects of the heat treatment temperature ($600^{\circ}C-1050^{\circ}C$) on the formation of $MgB_2$ and the superconducting properties have been examined. The self-synthesized $MgB_4$ and commercial Mg powders were used as raw materials for the formation of $MgB_2$. The superconducting critical temperatures ($T_cs$) of $MgB_2$ bulk superconductors prepared at $600^{\circ}C-850^{\circ}C$ were as high as 37-38 K regardless of the heat treatment temperature. However, because $MgB_4$ is more stable than $MgB_2$ at above $850^{\circ}C$, no superconducting signals were detected in the susceptibility-temperature curves of the samples prepared above $850^{\circ}C$. As for the critical current density ($J_c$), the sample heat-treated at a low temperature ($600^{\circ}C$) for a prolonged period (40 h) showed a Jc higher than those prepared at $650^{\circ}C-850^{\circ}C$ for a short period (1 h). The FWHM (full width at half maximum) result showed that the grain size of $MgB_2$ of the $600^{\circ}C$ sample was smaller than that of the other samples. The high $J_c$ of the $600^{\circ}C$sample is attributed to the presence of large numbers of grain boundaries, which can act as flux pinning centers of $MgB_2$.

• Progress in Superconductivity and Cryogenics
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• v.15 no.1
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• pp.1-5
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• 2013

We transformed the shape of a YBCO sample with striation to reduce hysteresis and ac losses. And we chose several points to analyze in detail and visualized superconducting properties like critical transition temperature, distribution of the magnetic field, distribution of the current density and hysteresis in a non-destructive manner based on Low Temperature Scanning Laser Hall Probe Microscopy (LTSLHPM) to examine the homogeneity of the sample.

• Korean Journal of Soil Science and Fertilizer
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• v.14 no.4
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• pp.201-209
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• 1982

In 1980, the abnormal low temperature was lasted during the late stage of rice growing season, thus low temperature injury occurred severely. The severity of the injury and nutrition absorption were investigated. The result obtained were summarized as follows: 1. It was considered that the severe low temperature injury of rice was caused by the low temperature and shorts of sunshine in the late growing season of rice, especially, the minimum air temperature which was lasted for a few days below critical reproductive growing temperature in the meiosis stage affected high the injury. 2. The low tmperature injury was lightened in the no nitrogen applied plot, and becoming severe with high nitrogen levels, but the balanced application of NPK lessened the low temperature injury. 3. The low temperature injury was more severe in Indica and Japonica hybrid than in Japonica cultivar, and the injury was shown as sterilizing, degraded spiklets, ill emerging of head and inhibition of nutrition absorption, etc. 4. Under the low temperature condition, $SiO_2$ content of rice plant was significantly reduced according to the increase of nitrogen levels. 5. Under the low temperature condition, the optimum application amount of nitrogen for Milyang 23, was 13, 6 kg/10a, this was approximately 10kg/10a smaller than average in usual year. The highly reduced rice yield was resulted from the cool injury, and the reducing rate of yield was larger in Indica and Japonica hybrid cultivar than in Japonica cultivar.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.2
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• pp.37-42
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• 2016

While datacenter operation cost increases with electricity price rise, many researchers study low-power processor based supercomputers to reduce power consumption of datacenters. Reliability of low-power processors for supercomputers can be of concern since the reliability of many low-power processors are assessed based on mobile use conditions. This paper assessed the reliability of low-power processor packages based on supercomputer use conditions. Temperature cycling was determined as a critical failure cause of low-power processor packages through literature surveys and failure mode, effect and criticality analysis. The package temperature was measured at multiple processor load conditions to examine the relationship between processor load and package temperature. A physics-of-failure reliability model associated with temperature cycling predicted the expected lifetime of low-power processors to be less than 3 years. Recommendations to improve the lifetime of low-power processors were presented based on the experimental results.

• Textile Coloration and Finishing
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• v.24 no.1
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• pp.62-68
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• 2012

Cellulose was electrospun over water collector and the cellulose solution was prepared using N-methyl-morpholine N-oxide/water(nNMMO/$H_2O$). The morphology of electrospun cellulose was investigated by scanning electron microscopy (SEM). SEM images showed that the fiber formation depended on processing parameters such as solution concentration, applied electric field strength, solution feeding rate and temperature of water in coagulation bath. High concentration, low temperature of water bath, and low feeding rate were more favorable to obtain fiber morphology. All the variables affected on the fluidity of the cellulose solution and diffusion of NMMO. Low fluidity and fast diffuision of NMMO was critical for obtaining fiber morphology.

• Journal of Korean Vacuum Science & Technology
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• v.3 no.2
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• pp.139-144
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• 1999

Hydrogen concentration depth profiles in homoepitaxial Si(001) films grown from hyper-thermal Si beams generated by ultrahigh vacuum (UHV) ion-beam sputtering have been measured by nuclear reaction analyses as a function of film growth temperature and deposition rate. Bulk H concentrations CH in the crystalline Si layers were found tio be below detection limits, 1${\times}$1019cm-3, with no indication of significant H surface segregation at the crystalline/amorphous interface region. This is quite different than the case for growth by molecular-beam epitaxy (MBE) where strong surface segregation was observed for similar deposition conditions with average CH values of 1${\times}$1020cm-3 in the amorphous overlayer. The markedly decreased H concentrations in the present experiments are due primarily to hydrogen desorption by incident hyperthermal Si atoms. Reduced H surface coverages during growth combined with collisionally-induced filling of interisland trenches and enhanced interlayer mass transport provide an increase in critical epitaxial thicknesses by up to an order of magnitude over previous MBE results.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.7
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• pp.766-772
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• 1992

Bi-Sr-Ca-Cu-O superconducting system has both the low and high Tc phases. We added Pb and sintered for 200hrs. in OS12T atmosphere in order to get the superconductor above critical temperature 100K. Superconducting properties of the Bi(Pb)SrCaCuO system doped Sb were also investigated. When Sb of 0.1mol is added, the sintering time becomes shorter than that doped Pb only. We could get the critical temperature 102K at the samples sintered for 24hrs. and 109K for 210hrs.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.34 no.3
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• pp.209-215
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• 2008

Iodopropynyl butylcarbamate and climbazole as anti-dandruff agents widely used in cosmetics and pharmaceutics were micronized using supercritical fluid. Supercritical carbon dioxide was selected due to relatively low critical temperature and critical pressure. Iodopropynyl butylcarbamate and climbazole were chosen because of their solubility in supercritical carbon dioxide. The rapid expansion of supercritical solution (RESS) experiments involved investigations of the effect of pressure, temperature on particle size and morphology.