• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.3
• /
• pp.130-134
• /
• 2017

In this study, numerical simulation was performed to focus on optimized process condition for obtaining a long-term growth and high quality SiC crystal. It could be optimized by considering the change of fluid and a carbon flow in the Si melt added with 40 % Cr. The Crystal Growth Simulator ($CGSim^{TM}$, STR Group Ltd.) was used as a numerical simulation. It was confirmed that many parameters such as temperature, rotation speed of seed crystal and crucible, and seed position during the crystal growth step had a strong influence on the speed and direction of solution flow for uniform temperature gradient and stable crystal growth. The optimized process condition for the solution growth of SiC crystal was successfully exhibited by adjusting various process parameters in the numerical simulation, which would be helpful for real crystal growth.

• Horticultural Science & Technology
• /
• v.34 no.5
• /
• pp.719-726
• /
• 2016

The effect of high and low temperatures on seedling quality while raising of paprika (Capsicum annuum L.) seedlings, and their early development after planting was investigated. The control raising seedling temperature (RST) was $23^{\circ}C$; high temperature, $31^{\circ}C$; and low temperature, $15^{\circ}C$ throughout the raising seedling period. At $15^{\circ}C$ and $30^{\circ}C$, plant height, stem diameter, fresh weight, dry weight, number of leaves, and seedling leaf area were significantly lower than those at $23^{\circ}C$. At 4 weeks after planting, seedling's growth characteristics showed a similar pattern. Compared to $23^{\circ}C$, seedlings raised at $15^{\circ}C$ and $30^{\circ}C$ had an increased dry weight and leaf area per unit time after planting than during the seedling raising period. At 4 weeks after planting, crop growth rate and leaf area index were unaffected by RST, and relative growth rate and net assimilation rate at RSTs of $15^{\circ}C$ and $31^{\circ}C$ were higher than those those at RST of $23^{\circ}C$. At an RST of $15^{\circ}C$, growth speed and net assimilation rates were higher after planting than before planting, according to increased photosynthetic rate. Thus, high and low temperatures during the seedling raising period significantly reduced seedling growth and plant growth after planting. After planting, seedlings raised at $15^{\circ}C$ recovered more quickly than did those raised at $31^{\circ}C$.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.02a
• /
• pp.342-343
• /
• 2013

AlSb is a promising material for optical devices, particularly for high-frequency and nonlinear-optical applications. And AlSb offers significant potential for devices such as quantum-well lasers, laser diodes, and heterojunction bipolar transistors. In this work we study molecular beam epitaxy (MBE) growth of an unstrained AISb film on a GaAs substrate and identify the real-time monitoring capabilities of in situ spectroscopic ellipsometry (SE). The samples were fabricated on semi-insulating (0 0 1) GaAs substrates using MBE system. A rotating sample stage ensured uniform film growth. The substrate was first heated to $620^{\circ}C$ under As2 to remove surface oxides. A GaAs buffer layer approximately 200 nm- thick was then grown at $580^{\circ}C$. During the temperature changing process from $580^{\circ}C$ to $530^{\circ}C$, As2 flux is maintained with the shutter for Ga being closed and the reflection high-energy electron diffraction (RHEED) pattern remaining at ($2{\times}4$). Upon reaching the preset temperature of $530^{\circ}C$, As shutter was promptly closed with Sb shutter open, resulting in the change of RHEED pattern from ($2{\times}4$) to ($1{\times}3$). This was followed by the growth of AlSb while using a rotating-compensator SE with a charge-coupled-device (CCD) detector to obtain real-time SE spectra from 0.74 to 6.48 eV. Fig. 1 shows the real time measured SE spectra of AlSb on GaAs in growth process. In the Fig. 1 (a), a change of ellipsometric parameter ${\Delta}$ is observed. The ${\Delta}$ is the parameter which contains thickness information of the sample, and it changes in a periodic from 0 to 180o with growth. The significant change of ${\Delta}$ at~0.4 min means that the growth of AlSb on GaAs has been started. Fig. 1b shows the changes of dielectric function with time over the range 0.74~6.48 eV. These changes mean phase transition from pseudodielectric function of GaAs to AlSb at~0.44 min. Fig. 2 shows the observed RHEED patterns in the growth process. The observed RHEED pattern of GaAs is ($2{\times}4$), and the pattern changes into ($1{\times}3$) with starting the growth of AlSb. This means that the RHEED pattern is in agreement with the result of SE measurements. These data show the importance and sensitivity of SE for real-time monitoring for materials growth by MBE. We performed the real-time monitoring of AlSb growth by using SE measurements, and it is good agreement with the results of RHEED pattern. This fact proves the importance and the sensitivity of SE technique for the real-time monitoring of film growth by using ellipsometry. We believe that these results will be useful in a number of contexts including more accurate optical properties for high speed device engineering.

• Transactions of the Society of Information Storage Systems
• /
• v.1 no.1
• /
• pp.34-41
• /
• 2005

We report some recent results in the rewritable Blu-ray Disc with enhanced overwrite cyclability by using the growth dominant eutectic based Ge(Sb70Te30)+Sb recording layer, GeN interface layer and write strategy optimization. We have developed phase-change optical media with appropriate write strategy for 36(i.e., 1X)-72Mbps(i.e., 2X) dual speed Blu-ray Disc system and fur the future high speed optical data storage. For recording layer, eutectic-based Ge(Sb70Te30)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so called Time-Shifted Multipulse (TSMP) write strategy where starting position of multipulse parts are shined from reference clock. With this write strategy, the jitter characteristics of the disc was improved and we found that leading edge jitter was improved much more than trailing edge jitter in 1X-2X speed recording. Finally, we investigated the higher speed feasibility of 144Mbps(i.e., 4X) by adopting some elemental doping to the eutectic based Ag-In-Sb-Te recording layer and structural optimization of constitution layers in Blu-ray Disc. In the paper, we report the effect of Sn addition for the feasibility of higher speed recording. The addition of Sn shows increases of the crystallization speed of phase change recording layer.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.6
• /
• pp.288-293
• /
• 2023

To optimize the process parameters of laser powder bed fusion process to fabricate the high density STS316L alloy, the effect of laser power, scanning speed and hatching distance on the relative density was studied. Tensile properties of additively manufactured STS316L alloy using optimized parameters was also evaluated according to the build direction. As a result of additive manufacturing process under the energy density of 55.6 J/mm³, 83.3 J/mm³ and 111.1 J/mm³, high density STS316L specimens was suitably fabricated when the energy density, power and scan speed were 83.3 J/mm³, 225 W and 1000 mm/s, respectively. The yield strength, ultimate tensile strength, and elongation of STS316L specimens in direction perpendicular to the build direction, show the most competitive values. Anisotropic shape of the pores and the lack of fusion defects probably caused strain localization which result in deterioration of tensile properties.

• Proceedings of the KSR Conference
• /
• 2003.05a
• /
• pp.774-777
• /
• 2003

Importance of railway safety has drawn much attention with the growth of its contribution to the modernized society as a massive transport, high speed transportation system. Hence, safety regulations and organizations for railway vehicles are reviewed. The present status of domestic metro transit system is considered and compared with that of foreign countries. Some controversial points are raised and countermeasures are proposed.

• Journal of Mushroom
• /
• v.12 no.1
• /
• pp.41-51
• /
• 2014

Cauliflower mushroom widely known high concent of ${\beta}$-glucan for farm cultivation invigoration verified characteristics of mycelia growth, genetic diversity, resistance to Trichoderma by replacement culture with Trichoderma and growth characteristics of new variety crossbleeding strain. The result of replacement culture with Trichoderma for verification resistance about Trichoderma, 6951 (T. viride) strain did not show special change after formation of confrontation line and 6952 (T. spp.) strain was showed more formation of spore after formation of confrontation line. But 6426 (T. harzianum) strain found to encroach part of growth area of cauliflower mushroom mycelia. Among 10 kinds cauliflower mushroom strain, JF02-06 strain collected by Gurye, found did not spore of Trichoderma and thought to be resistant to Trichoderma. The result of crossbleeding after selected that mother strain good growth and formation of fruit body, verified good mycelia growth at JF02-47, 49 and 50 strain in Korean pine of wood-chip media. The result of gene sequence about ITS1, 5.8S and ITS4 for analysis of genetic diversity at crossbleeding strain, found high significance to other cauliflower mushroom in registered Genebank. The result of growth characteristic of spore and mycelia of cauliflower mushroom by observation microscope, size of spore showed water drop shape to major axis $6{\mu}m$ and minor axis $5{\mu}m$ and clamp showed 3 types in mycelia. The wide of mycelia was $3{\mu}m$. The characteristic of mycelia of cauliflower mushroom found to grow mycelia in clamp at approximately 50%. The growth speed of mycelia was $0.507{\mu}m/min$ and 2nd mycelia grown similar speed to mother mycelia at parallel with mother mycelia after growth speed at $0.082{\mu}m/min$. The formation of clamp made small clamp for 5 hours after shown transfer of electrolyte in mycelia inside. The septum formation started after 3 hours and then finally completed after 2 hours. In this study, strain of cauliflower mushroom verified resistance of Trichoderma, genetic diversity and characteristic of mycelia growth. Therefore, basic knowledge of cauliflower mushroom will improve and further contribute to development of mushroom industry.

• Journal of Plant Biology
• /
• v.28 no.3
• /
• pp.253-259
• /
• 1985

The results of the conducted experiment obtained basic data on seed germination for Phragmites communis and Atriplex gmelini were; Seed germination was not influenced till 0.5% NaCl, but at over 1.0% NaCl it dropped remarkably. The germination limit fro degree of NaCl was 2.0% in Phragmites communis. Atriplex gemelini was 2.5% and in accordance with the increase of the degree of NaCl. Germination speed showed a negative correlation being highly significant and the germination period lengthened. Compared with growing top plants, growth of roots was largely influenced by a high degree of NaCl. In accordance with the rise of temperature, the germination rate, and speed of both plants remarkably increased and the germination period was shortened. Ubride of Atriplex gmelini was germinated at the early days of picking but was not as the passing of the period. The seeds also did not germinated likewise Ubride. By a seedcoat breaking germination became 81%. During 20 min soaking treatment in conc H2SO4 seed germination possibility of 63% was known to be hard. Adequate soaking time in conc H2SO4 was 17.5 min.

• Proceedings of the KSME Conference
• /
• 2000.11a
• /
• pp.339-344
• /
• 2000

In this study, the fracture phenomena of optical disks are discussed and then some recommendations are presented to prevent the fracture. The fracture occurs when disks have crack on the inner radius of the disks. Since the crack growth and the fracture result from the stress concentration on the tip of the crack, a measure should be taken to overcome the stress concentration. This problem can be resolved by the structural modification of a disk. This study proposes 3 types of improved optical disks, which are robust to the disk fracture due to the high spinning speed of a disk. The first type is a disk reinforced by wire rings, the second type is a disk added by texture fibers, and the third type is a rubber-coated disk.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1996.11a
• /
• pp.164-168
• /
• 1996

The relation between crystallinity and thermal history in low density polyethylene thin films and their effect on electric conduction phenomena and dielectric breakdown was studied. The low density polythylene thin films obtained by the solution growth method heat-treated at 140[$^{\circ}C$] for 2 h and subsequently cooling to various ways. The degree of crystallinity was estimated by the X-ray diffraction measurement for the specimen of slowly cooling, ICE quenching and liquid nitrogen quenching. The result shows that the crystallinity decreases become faster as the cooling speed increased, and that conduction phenomenon is governed by the space charge limited current in high field. It was found that the dielectric breakdown field increases with an increase in cooling speed and test number in self-healing breakdown method.