• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.349-352
• /
• 2004

The improvement of critical temperature $(T_c)$, critical magnetic field $(H_c)$, and critical current density $(J_c)$ of superconductor is important for practical applications. In this study, the additives such as metal oxides were used to improve the preparation conditions of $YBa_2Cu_3O_x$ superconducting bulk samples and depending on additives the properties of $YBa_2Cu_3O_x$ superconductor were studied. The effects of additives to the density, grain alignment, and porosity of samples that affect the critical current density of superconductor also have been investigated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.13 no.10
• /
• pp.834-839
• /
• 2000

The structural properties that SEM photograph of ZnO varistors surface studied by fractal mathematics program were investigated to verify the relations of electrical characteristics. The SEM photograph of ZnO varistors surface were changed by binary code and the grain shape of that were analyzed by fractal dimension. The void of ZnO varistors surface was found by fractal program. The relation between grain density and electrical properties depend on fractal dimension. The grain size in ZnO varistors surface was decreased by increasing of Sb$_2$O$_3$ addition. The spinel structure was formed by Sb$_2$O$_3$addition and it was depressed the ZnO grain formation. The grain size of ZnO by Sb$_2$O$_3$addition were from 5 to 10[${\mu}{\textrm}{m}$]. Among of ZnO varistors, fractal dimension of ZnO4 was very high as a 1.764. The density of grain boundary in ZnO2 and ZnO3 varistors surface was 15[%] by formed spinal structure. The breakdown electric field of ZnO2 that fractal dimension has 1.752 was very high to be 8.5[kV/cm]. When the fractal dimensin was high, the grain shape of ZnO varistors was complex and the serial layers of ZnO grain was increased.

• Journal of the Korean Magnetics Society
• /
• v.23 no.1
• /
• pp.12-17
• /
• 2013

Nanocrystalline nickel (Ni) tick films were synthesized by direct current electrodeposition at current density from 1 to $30mA/cm^2$ and pH = 4. The basic composition of the bath, which was prepared by dissolving Ni metal particles in HCl, was 0.2M Ni ions. The effects of the current density on the average grain size of Ni deposits were investigated by XRD and SEM techniques. The results showed that the surface roughness was decreased as the saccharin addition was increased up to 2 g/l. The experimental results showed that the increase in the current density had a considerable effect on the average grain size of the Ni deposits. The perpendicular magnetization was raised as the thickness of coating layer was increased.

• Journal of Biosystems Engineering
• /
• v.25 no.2
• /
• pp.97-106
• /
• 2000

To develop the grain moisture meter using microwave free space transmission technique, a 10.5GHz microwave signal with the power of 11mW generated by an oscillar with a dielectric resonator is transmitted to an isolator and radiated from a transmitting $2{\times}2$ microstrip patch array antenna into the sample holder filled with the 12 to 26%w.b. of Korean Hwawung paddy rice. the microwave signal, attenuated through the grain with moisture, is collected by a receiving $2{\times}2$ microstrip patch array antenna and detected using a Shottky diode with excellent high frequency characteristic. A pair of light and simple microstrip patch array antenna for measurement of grain moisture content is designed and implemented on atenflon substrate with trleative dielectric constant of 2.6 and thickness of 0.54 by using Ensemble ver. 4.02 software. The aperture of microstrip patch arrays is 41 mm width and 24mm high. The characteristics of microstrip patch antenna such as grain. return loss, and bandwidth are 11.35dBi, -38dB and 0.35GHz($50^{\circ}$ at far-field pattern of E and H plane. The width of the sample holder is large enough to cover the signal between the antennas temperature and bulk density respectively. The calibration model for measurement of grain moisture content is proposed to reduce the effects of fluectuations in bulk density and temperature which give serious errors for the measurements . From the results of regression analysis using the statistically analysis method, the moisture content of grain samples (MC(%)) is expressed in terms of the output voltage(v), temperature (t), and bulk density of samples(${\rho}b$)as follows ;$$MC(%)\;=\;(-3.9838{\times}10^{-8}{\times}v^{3}+8.023{\times}10^{-6}{\times}v^{2}-0.0011{\times}v-0.0004{\times}t+0.1706){\frac{1}{{\rho}b}}{\times}100$ Its determination coefficient, standard error of prediction(SEP) and bias were found to be 0.9855, 0.479%w.b. and -0.0.369 %w.b. respectively between measured and predicted moisture contents of the grain samples.

• Proceedings of the KIEE Conference
• /
• 1997.07d
• /
• pp.1430-1432
• /
• 1997

A solar cell conversion effiency was degraded by grain boundary effect in polycrystalline silicon. To reduce these effects of the grain boundaries, we investigated various influencing factors such as preferential chemical etching of grain boundaries, grid design, transparent conductive thin film, and top metallization along grain boundaries. Pretreatment in $N_2$ atmosphere and gettering by $POCl_3$ and Al were performed to obtain polycrystalline silicon of the reduced defect density. Structural, electrical, and optical properties of solar cells were characterized. Improved conversion efficiencies of solar cell were obtained by a combination of Al diffusion into grain boundaries on rear side, fine grid finger, top Yb metal grid on Cr thin film of $200{\AA}$ and buried contact metallization along grain boundaries.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.17 no.2
• /
• pp.75-81
• /
• 2007

Densification and grain growth have been investigated in 5 wt% $U_3O_8$ seeded $UO_2$ and compared with those of the common $UO_2$ pellet. $UO_2$ compacts and $U_3O_8$ seeded $UO_2$ compacts were sintered at $1300{\sim}1700^{\circ}C$ for 0 h to 4 h. Density and grain size of the sintered pellets were measured by the water immersion method and the image analyzer, respectively. The seeded pellet has a slightly lower density during the intermediate sintering stage. However, the difference of density between two pellets decreases to about 0.5%TD with increasing the sintering temperature. The grain size of the two pellets is similar until $1600^{\circ}C$ but that of the seeded pellet rapidly increases with increasing the sintering temperature.

• Proceedings of the Korean Society of Crop Science Conference
• /
• 2017.06a
• /
• pp.232-232
• /
• 2017

Rice yields are determined by the number of spikes per unit area, the number of rice per grain, the rate of ripening, and the weight of brown rice gravel. Among these yield components, the most important factor that reflects the characteristics of rice is the number of rice per grain and the number of rice per grain. The characteristics of rice panicle are influenced by genetic factors rather than environmental factors and revealed that it had different genetic characteristics in each of Japonica, Indica and Japonica ${\times}$ Indica type. In general, the number of rice per grain is affected by number of secondary rachis branches and generated spikelets number of secondary rachis branches. This study conducted to investigate the characteristics of the grain according to the planting density of two varieties of Jap. ${\times}$ Ind. type. Number of primary rachis branches and number of primary rachis branches of Palbangmi variety were 9.9 ~ 10.6 and 53.4 ~ 58.5, respectively. Number of secondary rachis branches and number of secondary rachis branches were 25.8 ~ 29.6, 85.8 ~ 101.4, Number of tertiary rachis branch and number of tertiary rachis branches were 1.0 ~ 2.4 and 2.0 ~ 6.1, respectively. Number of primary rachis branches and number of primary rachis branches of Semimyeon variety were 8.6 ~ 9.5 and 43.1 ~ 47.8, respectively. Number of secondary rachis branches and number of secondary rachis branches were 21.0 ~ 24.9, 66.2 ~ 77.9, Number of tertiary rachis branch and number of tertiary rachis branches were 1.6 ~ 2.6 and 3.8 ~ 6.3, respectively. The ratio of the spikelets of primary, secondary and tertiary rachis branches of Palbangmi variety were 37.7 ~ 39.4, 58.0 ~ 60.5 and 1.2 ~ 3.1%, respectively, and those of Semimyeon were 40.1 ~ 42.6 55.0 ~ 56.4 and 2.5 ~ 3.4% respectively. Number of primary and secondary rachis branches of Palbangmi variety showed no difference among the planting density. However, generated spikelets number of secondary rachis branches and ripening rate were higher with lower planting density. The number of secondary rachis branches and generated spikelets number of secondary rachis branches per acre decreased as the planting density increased in the Semimyeon variety

• The Journal of Korean Academy of Prosthodontics
• /
• v.40 no.4
• /
• pp.323-334
• /
• 2002

The purpose of this study is to investigate which current densities and etching times will result in an optimal etching depth and surface roughness when an Ni-Cr-Be alloy is etched with 30% perchloric acid($HClO_4$). For this study, observations were made by means of an optical three-dimensional surface roughness measuring machine and a scanning electron microscope. The etchings took place under the following conditions using current densities of $300mA/cm^2\;450mA/cm^2,\;600mA/cm^2$ and $750mA/cm^2$, and using etching time of three, five, six, seven and nine minutes. Under the conditions, the experiments reached the following conclusions. 1. When the current density is above $450mA/cm^2$ and the etching time is longer than five minutes, the etching depth increased as the current density and etching time increased. And the surface roughness was significantly influenced by the interaction of the current density and etching time. 2. Under the etching conditions of $600mA/cm^2$ and five minutes, the optimal etching depth for a resin cement space and the highest surface roughness for mechanical retention were obtained. The etching depth and surface roughness were $32.86{\mu}m$ and $7.90{\mu}m$, respectively. 3. Observations under the scanning electron microscope showed that both the corrosion at the grain boundary and the corrosion within the grain occurred on the etched surface. It was also observed that the corrosion at the grain boundary became more severe as the current density and etching time increased. In addition. at higher current densities and longer etching times general corrosion appeared.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.14 no.4
• /
• pp.151-154
• /
• 2004

Issues of ferroelectric high-density memories (>64 Mb) indispensable for upcoming ubiquitous era have been on the cell integration less than $0.1\;\mu\textrm{m}^2$ and reliabilities. Thus nanoscale control of microstructures of ferroelectric films with large switching polarization has been one of the issues to obtain the uniform electrical properties for realization of high-density memories. In this study the grain orientations and distributions of BT-based films by spin-on coatings were examined by FEG-SEM/EBSD. Ferroelectric domain characteristics by PFM were also performed to study the dependence of reliabilities on the grain orientations and distributions. It is believed that understandings of the nucleation and growth mechanisms of the a- or b-axis oriented films during the thermal processes such as RTA and furnace annealing affecting on grain orientation and uniformity could be possible based on our experimental results.

• Journal of the Korea Safety Management & Science
• /
• v.11 no.4
• /
• pp.311-317
• /
• 2009

In this paper deals with behavior of the magnetic abrasive using Ba-Ferrite on polishing characteristics in a new internal finishing of STS304 pipe applying magnetic abrasive polishing. The magnetic abrasive using Ba-Ferrite grain WA used to resin bond fabricated low temperature. And Ba-Ferrite of magnetic abrasive powder fabricated that Ba-Ferrite was crused into 200 mesh. The previous research have made an experiment in the static state the movement of magnetic abrasive grain is nevertheless in the dynamic state. In this paper, We could have investigated into the changes of the movement of magnetic abrasive grain. In reference to this result, we could have made the experiment which is set under the condition of the magnetic flux density, polishing velocity according to the form of magnetic brush.