• Korean Journal of Agricultural Science
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• v.12 no.1
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• pp.118-127
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• 1985

The grain temperature is a crucial factor determining the deterioration rate of stored grain. Therefore, it is used to be predicted in order to evaluate the various stored methods rapidly and inexpensively. In this study, a mathematical model was developed to simulate the temperatures of grain stored in a cylinderical bin. It was formulated for the two dimensional heat transfer by the finite difference method. Then, it was verified statistically using the actual test deta and the predicted. The changes of grain temperature were analyed using the simulated data of one year for a safe stoarge and the following results were obtained: 1. Simulation model developed by the finite difference method was validated with the actual and the predicted grain temperatures and it's result showed that it could predict the grain temperature of storage bin reasonably well. 2. Grain temperature near the wall of storage bin were changed with $6-7^{\circ}C$ higher then average atmospheric temperature from June to September. Therefore, the parts of stored grain near the wall is supposed to be deteriorated fast. 3. When the dimension of bin diameter is about the same as the bed height, the changes of grain temperature of radial direction was higher than the verticals. 4. The predicted temperature showed that the grain temperature of which were from the end of April to mid October were higher than the safe storage limit at Yusung, Korea.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.28 no.1
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• pp.12-40
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• 1983

Heading behaviour of native japonica (GI) and Japanese varieties (GII) grown during 1910-1920s were thermo-sensitive, home bred varieties during 1930s (GIII) - 1950s (GIV) were photo-sensitive and semi-dwarf indica derived varieties released since 1971 (GV) were controlled by basic vegetative phase. Number of leaves on main culm was increased with varietal improvement and culm length was gradually shortened as variety improved. GV variety had the shortest plant height among the groups. The first internode length was about 30cm in all groups and difference of 2nd-4th internode length was caused shortening the culm length. Panicle length and diameter of panicle neck were shortened and became thinner as variety developed from GI to GIV, however, GV had longer panicle and thick panicle neck, respectively. Number of panicles/hill and straw weight/hill increased and became heavier as variety improve from GI to GIV but GV had moderate number of panicle/hill and relatively light straw weight. Number of spikelet/panicle has been reduced with varietal improvement but GV had the biggest number. Grain yield/hill also increased as variety improved, however, it was decreased as transplanting season postponed and GV had shown the most sensitive difference. Top dry matter weight at heading stage and at 20 days after heading (20 DAH) had no difference among the groups except GI which was the smallest. Average grain weight at 20 DAH was heavier in the order of GI > GII, GV > GIV > GIII. It had a little variation in GI & GII while that of other variety group showed significant decrease as transplanting delayed. Harvest index (HI) of GV was the highest at 54% for the earlier transplanting and GIII had the lowest HI. Difference of HI became conspicuous for the later transplanting, the varieties bred later had the lower HI when transplanting of rice delayed. At the earliest transplanting applied (May 15), the grain yield was higher in the order of GI > GIV > GIII > GII > GI, however, that of Tongil type variety (GV) was the lowest for the latest transplanting (June 29). Interrelationship among the agronomical characteristics and grain yield was discussed.

• Transactions of Materials Processing
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• v.21 no.3
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• pp.207-214
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• 2012

High temperature deformation behavior of a $Ni_{30}Fe_{53}Co_{17}$ alloy, with its extraordinary low coefficient of thermal expansion less than $10{\times}10^{-6}K^{-1}$ at temperatures ranging from room temperature to 673K, was investigated by conducting a series of compression tests. From an empirical processing map, the appropriate working temperature-strain rate combination for optimum forming was deduced to be in the ~1373K, $10^{-2}s^{-1}$ region. This region has a relatively high power dissipation efficiency, greater than 0.36. Furthermore, open die forging of a 100mm diameter billets was performed to confirm the variation of thermo-physical properties in relation to microstructure. The coefficient of thermal expansion was found to increase considerably with increasing the open die forging temperature and decreasing the cooling rate, which in turn provides a drastic increase in the average grain size.

• Journal of the Korean Society of Safety
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• v.19 no.2
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• pp.6-10
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• 2004

The magnetic polishing is the useful method to finish using magnetic power of magnet. This method is one of precision polishing techniques and has an aim of the clean technology using for the pure of gas and inside of the clean pipe for transportation. The magnetic abrasive polishing method is not so common for machine that it tis not spreaded widely. There are rarely researcher in this field because of non-effectiveness of magnetic abrasive. Therefore, in ths paper deals with development of the magnetic abrasive using sludge. In this development, abrasive grain WA and GC used to resin bond fabricated low temperature. And magnetic material was fabricated from the sludge which were crused into 200 mesh and average diameter ${\o}$1.2mm ball type. The XRD analysis result show that only WA and GC abrasive and sludge crystal peaks detected which explains resin bond was not any more chemical reaction. From SEM analysis it tis found that WA and GC abrasive and sludge were stron bonding with each other by bond.

• Journal of Powder Materials
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• v.21 no.1
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• pp.50-54
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• 2014

A powder-in-sheath rolling method was applied to a fabrication of a carbon nano tube (CNT) reinforced aluminum composite. A STS304 tube with an outer diameter of 34 mm and a wall thickness of 2 mm was used as a sheath material. A mixture of pure aluminum powders and CNTs with the volume contents of 1, 3, 5 vol was filled in the tube by tap filling and then processed to 73.5% height reduction by a rolling mill. The relative density of the CNT/Al composite fabricated by the powder-in-sheath rolling decreased slightly with increasing of CNTs content, but exhibited high value more than 98. The grain size of the aluminum matrix was largely decreased with addition of CNTs; it decreased from $24{\mu}m$ to $0.9{\mu}m$ by the addition of only 1 volCNT. The average hardness of the composites increased by approximately 3 times with the addition of CNTs, comparing to that of unreinforced pure aluminum. It is concluded that the powder-in-sheath rolling method is an effective process for fabrication of CNT reinforced Al matrix composites.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.29 no.1
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• pp.241-254
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• 1999

The purpose of this study was to investigate whether a radiometric analysis of radicular cysts and periapical granulomas is useful in the differential diagnosis. In this experiment, twenty-nine periapical radiographs of the radicular cyst and those periapical granuloma were used. The periapical radiography was taken by intraoral paralleling device. The X-ray film was digitized and digitally filtered to reduce film-grain noise. We estimated density difference of the inner/outer area, roundness or circularity, bone profile or scan line of the margin and cumulative percentage frequency curve of radicular cyst & periapical granuloma. The obtained results were as follows; 1. The differences in density between ROIs of inner and outer area of radicular cysts were smaller than those of periapical granulomas. 2. The equivalent circular diameter was over 6.3mm, there was significant difference between periapical cyst and periapical granuloma. 3. In differential diagnosis of radicular cyst and periapical granuloma using bone profile. sensitivity. specificity and accuracy were considerably high(0.83. 0.86. 0.86) respectively. 4. Cumulative percentage frequency curve of the radicular cyst was closer to the pseudo-pixel value of 50 than average curve, whereas periapical granuloma was closer to that of 0. Hence we conclude that digital radiometric features might be useful in the differential diagnosis between radicular cyst and periapical granuloma.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05a
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• pp.80-83
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• 2003

$SrSO_4$ were systematically added on Bi2212 from 0 to 10wt% to study the effect of Bi2212 superconductor tube characteristics. After mixing, the melted solution of Bi2212 and $SrSO_4$ was initially poured into the cylinder type of steel mold preheated at $550^{\circ}C$ for 30min and rotated at 1000rpm. Following that, tube was annealed at $840^{\circ}C$ for 72hrs. The tube dimension was 60 in diameter, 60mm in length and 2mm in thickness. XRD data suggests that there was no typical segregation phase related with $SrSO_4$. Well textured grain with typical 2212 phase was observed and average size was $20{\mu}m$. The measured critical current and critical current density of Bi2212 tube added by 5% $SrSO_4$ at 77K were 495A and $202A/cm^2$ respectively.

• Korean Journal of Metals and Materials
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• v.50 no.4
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• pp.263-270
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• 2012

This study investigates the effect of heat treatment on the mechanical properties of a forged Ni-based superalloy called Nimonic 80A. Nimonic 80A ingot samples were fabricated by vacuum spray casting to achieve a fine and homogenized microstructure. The ingot samples were subsequently hot-forged with the diameter of 220 mm at 1373 K. From the center to the surface of the forged Nimonic 80A, its average grain size decreased and its micro-Vickers hardness increased slightly. Solution treatment was carried out at 1353 K with 8 hours of air cooling followed by aging treatment, which was carried out in the range of 873-1073 K with various times from 0.5 to 256 hours. To set the optimum aging conditions, micro-Vickers hardness tests were performed. The maximum hardness value of 388.0 Hv was obtained by aging at 973 K for 32 hours. Also, tensile tests were performed for optimum aging conditions at room temperature and 873 K. The results can be used effectively to perform reasonable heat treatment of Nimonic 80A superalloy.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.154-155
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• 2012

The promise of nano-crystalites (nc) as a technological material, for applications including display backplane, and solar cells, may ultimately depend on tailoring their behavior through doping and crystallinity. Impurities can strongly modify electronic and optical properties of bulk and nc semiconductors. Highly doped dopant also effect structural properties (both grain size, crystal fraction) of nc-Si thin film. As discussed in several literatures, P atoms or radicals have the tendency to reside on the surface of nc. The P-radical segregation on the nano-grain surfaces that called self-purification may reduce the possibility of new nucleation because of the five-coordination of P. In addition, the P doping levels of ${\sim}2{\times}10^{21}\;at/cm^3$ is the solubility limitation of P in Si; the solubility of nc thin film should be smaller. Therefore, the non-activated P tends to segregate on the grain boundaries and the surface of nc. These mechanisms could prevent new nucleation on the existing grain surface. Therefore, most researches shown that highly doped nc-thin film by using conventional PECVD deposition system tended to have low crystallinity, where the formation energy of nucleation should be higher than the nc surface in the intrinsic materials. If the deposition technology that can make highly doped and simultaneously highly crystallized nc at low temperature, it can lead processes of next generation flexible devices. Recently, we are developing a novel CVD technology with a neutral particle beam (NPB) source, named as neutral beam assisted CVD (NBaCVD), which controls the energy of incident neutral particles in the range of 1~300eV in order to enhance the atomic activation and crystalline of thin films at low temperatures. During the formation of the nc-/pm-Si thin films by the NBaCVD with various process conditions, NPB energy directly controlled by the reflector bias and effectively increased crystal fraction (~80%) by uniformly distributed nc grains with 3~10 nm size. In the case of phosphorous doped Si thin films, the doping efficiency also increased as increasing the reflector bias (i.e. increasing NPB energy). At 330V of reflector bias, activation energy of the doped nc-Si thin film reduced as low as 0.001 eV. This means dopants are fully occupied as substitutional site, even though the Si thin film has nano-sized grain structure. And activated dopant concentration is recorded as high as up to 1020 #/$cm^3$ at very low process temperature (＜ $80^{\circ}C$) process without any post annealing. Theoretical solubility for the higher dopant concentration in Si thin film for order of 1020 #/$cm^3$ can be done only high temperature process or post annealing over $650^{\circ}C$. In general, as decreasing the grain size, the dopant binding energy increases as ratio of 1 of diameter of grain and the dopant hardly be activated. The highly doped nc-Si thin film by low-temperature NBaCVD process had smaller average grain size under 10 nm (measured by GIWAXS, GISAXS and TEM analysis), but achieved very higher activation of phosphorous dopant; NB energy sufficiently transports its energy to doping and crystallization even though without supplying additional thermal energy. TEM image shows that incubation layer does not formed between nc-Si film and SiO2 under later and highly crystallized nc-Si film is constructed with uniformly distributed nano-grains in polymorphous tissues. The nucleation should be start at the first layer on the SiO2 later, but it hardly growth to be cone-shaped micro-size grains. The nc-grain evenly embedded pm-Si thin film can be formatted by competition of the nucleation and the crystal growing, which depend on the NPB energies. In the evaluation of the light soaking degradation of photoconductivity, while conventional intrinsic and n-type doped a-Si thin films appeared typical degradation of photoconductivity, all of the nc-Si thin films processed by the NBaCVD show only a few % of degradation of it. From FTIR and RAMAN spectra, the energetic hydrogen NB atoms passivate nano-grain boundaries during the NBaCVD process because of the high diffusivity and chemical potential of hydrogen atoms.

• Journal of the Korean Wood Science and Technology
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• v.36 no.1
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• pp.69-78
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• 2008

Shearing strength test in tension type was investigated to determine the shear resistance of bolt and drift-pin connection of domestic larix glulam. The specimen was connected with bolt and drift-pin in the inserted plate type, and only bolt in the side plate type. The diameter of bolt and drift-pin used in the experiment are 12, 16 and 20 mm. The hole of bolt was drilled at the end-distance 5 d and 7 d. Tension load was loaded in the direction parallel to grain. The shear resistance was evaluated according to end-distance through this, the yield load was compared with the experimental yield load, using Larsen's formula. The prototype design strength is based on the yield load of end-distance 7 d and the reduction factor of end-distance 5 d was calculated. The results were as follows. 1. The average of maximum load of drift-pin connection was higher by 3~30% at the inserted type than at bolt connection with increasing diameter. In bolt connection, the average of maximum load of the side type was 1.54~2.07 times higher than that of the inserted type. In the same diameter, the average of maximum load of end-distance 7 d was higher by 8~44% than that of 5 d. 2. The bearing stress was 1.16~1.41 times higher at the inserted connection than at drift-pin connection, and 1.37~1.86 times higher at 7 d than at 5 d. Also, when the slenderness ratio was below 7.5 at drift-pin connection and below 6.0 at inserted connection, the lateral capacity was good. 3. The ratio of the experimental yield load and the predicted yield load calculated by Larsen's formula proposed by Larsen was 0.80~1.10 at inserted connection, and 0.75~1.46 at side connection. 4. When the inserted bolt connection was based on the yield load of end-distance 7 d, the reduction factor was 0.89 at 12 mm connection, 0.93 at 16 mm and 0.85 at 20 mm. The reduction factor was 0.89 at 12 mm the inserted drift-pin connection, 0.93 at 16 mm, 0.93 at 20 mm. The reduction factor was 0.79 at the side connection of the 12 mm bolt connection and 0.80 at 16 mm.