• The Journal of Advanced Prosthodontics
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• 제11권4호
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• pp.202-208
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• 2019

PURPOSE. Fabrication of zirconia restorations with ideal mechanical properties in a short period is a great challenge for clinicians. The purpose of the study was to investigate the effect of heating rate on the mechanical and microstructural properties of monolithic zirconia. MATERIALS AND METHODS. Forty monolithic zirconia specimens were prepared from presintered monolithic zirconia blanks. All specimens were then assigned to 4 groups according to heating rate as Control, Group $15^{\circ}C$, Group $20^{\circ}C$, and Group $40^{\circ}C$. All groups were sintered according to heating rates with the sintering temperature of $1500^{\circ}C$, a holding time of 90 minutes and natural cooling. The phase composition was examined by XRD analysis, three-point bending test was conducted to examine the flexural strength, and Weibull analysis was conducted to determine weibull modulus and characteristic strength. Average grain sizes were determined by SEM analysis. One-way ANOVA test was performed at a significance level of 0.05. RESULTS. Only tetragonal phase characteristic peaks were determined on the surface of analyzed specimens. Differences among the average grain sizes of the groups were not statistically significant. The results of the three-point bending test revealed no significant differences among the flexural strength of the groups (P>.05). Weibull modulus of groups was ranging from 3.50 to 4.74. The highest and the lowest characteristic strength values were obtained in Group $20^{\circ}C$ and Control Group, respectively. CONCLUSION. Heating rate has no significant effect on the flexural strength of monolithic zirconia. Monolithic zirconia restorations can be produced in shorter sintering periods without affecting the flexural strength by modifying the heating rate.

• 한국주거학회논문집
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• 제12권3호
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• pp.41-49
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• 2001

This study attempts to present a new interpretation of the Jeju province Waga, authorized as Jeju province Folklore, in the context of lifestyles of residents distinctive in the Jungji, Chatbang, and Gopang system. Study results uncovered that (1) only one Jungji, a traditional house kitchen, exists in one house boundary, in the form of detached building in the 4 units of Gaok (K-2 Gaok, K-3 Gaok, C-1 Gaok, and C-2 Gaok) (2) Chatbang had multifaced-functions; as a place for diet for mistress and children, a place for preparing meals for a mister who diet in the room, and as an auxiliary meal-preparation facility in time of domestic celebration day. (3) Gopang was mostly a place for grain storage, and K-3 Gaok has one unit, K-1 Gaok, C-1 Gaok, and C-2 Gaok had 2 units, and K-2 Gaok and H Gaok had 3 untis of Gopang. (4) Jungji and Chatbang were correlated for meal preparation and diet while activity-line of flow was divided each other. (5) Jungji and Gopang were located at the opposite edges of of each house, revealing no consideration of indoor activities. (6) The ratios of space of Jungji, Chatbang and Gopang out of the whole house space were, average 23% in the case of Jungji located in the inner house, and average 37% in the case of Jingji located in the detached building, average 14% larger in the case of detached Jungji system.

• Asian-Australasian Journal of Animal Sciences
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• 제12권3호
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• pp.395-399
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• 1999

Three experiments were conducted to determine the effects of conditioning a complex (20% whey, 10% lactose, 4% plasma protein, 4% wheat gluten and 2% blood meal) diet on growth performance of weanling pigs. In Exp. 1,180 pigs (average initial BW of 6.4 kg) were fed the experimental diet (1.7% lysine) during a 7-d growth assay. Treatments were a meal control (M), standard (ST), and expander (EX) conditioned mash or pellets. Rate and efficiency of gain were decreased by 39% and 21% (p<0.005) respectively, for pigs fed EX diets compared to those fed the ST diet. In Exp. 2,196 pigs (average initial BW of 6.5 kg) were used to determine the effects of EX operating conditions on nutritional value of a pelleted complex diet. When steam conditioning temperature (prior to expanding) was $54^{\circ}C$, increasing cone pressure of the EX from 0 to 7 to 14 kg/cm2 resulted in linear decreases in rate of gain of weaned pigs (p<0.006), suggesting heat damage of the diet. Increasing conditioning temperature (i.e., adding steam) of the diets from 46 to 54 to $63^{\circ}C$ (cone pressure at $12kg/cm^2$) resulted in improved rate of gain (p<0.04) of the pigs. However, none of the pigs fed expanded diets compared favorably to the pigs fed the conditioned $(54^{\circ}C)$ pellets processed with no cone pressure. In Exp. 3,168 pigs (average initial BW of 6.6 kg) were used to determine the effects of expanding the various components of the diet. Treatments were M and ST pellets as controls, EX-corn, EX-corn soybean-meal, EX corn-soybean meal-oil, and EX-complete diet. Efficiency of gain was increased by 13% with EX portions of the diet compared to the mash control, but there was a marked decrease in performance when the complete diet was expanded (p<0.001). Expanded corn-soybean meal-oil supported the greatest ADG with a 19% increase compared to the average of the EX corn and EX corn-soybean meal treatments (p<0.005). In conclusion, our results suggest no benefit from expanding complete phase-I diets.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
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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.

• Transactions on Electrical and Electronic Materials
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• 제15권5호
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• pp.284-289
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• 2014

The effects of additives (Nb, Bi and Cr) on the microstructure, varistor properties, and aging behavior of V/Mn/Co/ La/Dy co-doped zinc oxide ceramics were systematically investigated. An analysis of the microstructure showed that all of the ceramics that were modified with various additives were composed of zinc oxide grain as the main phase, and secondary phases such as $Zn_3(VO_4)_2$, $ZnV_2O_4$, and $DyVO_4$. The $Bi_2O_3$-modified samples exhibited the lowest density, the $Nb_2O_5$-modified sample exhibited the largest average grain size, and the $Cr_2O_3$-modified samples exhibited the highest breakdown field. All additives improved the non-ohmic coefficient (${\alpha}$) by either a small or a large margin, and in particular an $Nb_2O_5$ additive noticeably increased the non-ohmic coefficient to be as large as 36. The $Bi_2O_3$-modified samples exhibited the highest stability with variation rates for the breakdown field and for the non-ohmic coefficient (${\alpha}$) of -1.2% and -26.3%, respectively, after application of a DC accelerated aging stress of 0.85 EB/$85^{\circ}C$/24 h.

• Transactions on Electrical and Electronic Materials
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• 제13권5호
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• pp.262-265
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• 2012

The Microstructure and nonlinear electrical properties of the ZPCCYT (ZnO-$Pr_6O_{11}$-CoO-$Cr_2O_3$-$Y_2O_3$-$Tb_4O_7$) varistors were investigated for different amounts of $Tb_4O_7$. The addition of $Tb_4O_7$ has a significant effect on microstructure and electrical properties. Analysis of the microstructure indicated that the ceramics consisted of ZnO grain as a main phase and a few secondary phases as a mix of $Pr_6O_{11}$, $Y_2O_3$, and $Tb_4O_7$. As the amount of $Tb_4O_7$ increased, the sintered densities of pellets increased from $\rho$ = 5.70 to $5.78g/cm^3$ and the average grain size decreased from d = 4.8 to $3.6{\mu}m$. The increase in the amount of $Tb_4O_7$ increased from $E_B$ = 7,473 to 10,035 V/cm and from ${\alpha}$ = 39.7 to 52.2. In particular, it was found that the ceramics modified with 1.0 mol% in the amount of $Tb_4O_7$ are suited for the varistors for high voltage in the light of a high sintered density and a high voltage gradient.

• Journal of Welding and Joining
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• 제30권6호
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• pp.92-97
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• 2012

Using the pulsed current activated sintering method, the WC-10wt.% Co materials were densified using a WC and Co powder. The WC-Co almost completely dense with a relative density of up to 99.5 % after the simultaneous application of a pressure of 60 MPa and an electric current for 3 minutes almost without any significant change in the grain size. The average grain size of about $0.3{\mu}m$. The hardness and fracture toughness at $1000^{\circ}C$ were about $2200kg/mm^2$ and $9.8MPa.m^{1/2}$, respectively.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.390.1-390.1
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• 2016

The present work explains the interfacial energetics of all oxide transparent photodiodes. The optical, structural and morphological of copper oxides were systematically analyse by UV-Visible spectrometer, X-Ray diffraction, Raman spectroscopy, Scanning electron microscopy (SEM) and Atomic force microscopy measurements (AFM). The UV-Visible result exhibits optical bandgap of Cu2O and CuO as 2.2 and 2.05 eV respectively. SEM and AFM result shows a uniform grain size distribution in Cu2O and CuO thin films with the average grain size of 45 and 40 nm respectively. The results of Current-Voltage and Kelvin probe force microscope characteristics describe the electrical responses of the Cu2O/ZnO and CuO/ZnO heterojunctions photodiodes. The obtained electrical response depicts the approximately same knee voltages with a measurable difference in the absolute value of net terminal current. More over the present study realizes the all oxide transparent photodiode with zero bias photocurrent. The presented results lay the template for fabricating and analysing the self-bias all oxide transparent photodetector.

• 대한기계학회논문집
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• 제12권2호
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• pp.241-251
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• 1988

본 연구에서는 숫돌입자, 결합자 및 기공으로 조성된 연삭숫돌의 구조를 다공질 포성체로 보고, WA계 비트리파이드(vitrified) 및 레지노이드(resinoid) 결합자의 연삭숫돌시험편에 대하여 AE 계측방법을 이용한 인장, 압축, 굽힘 및 압렬시험을 실시하여 Babel과 Sines의 2축응력장해소이론과 연삭숫돌의 파괴조건을 관련시켜 평가함과 동시에, 이 때 검출되는 AE 신호 처리 파라미터(Parameter) 로부터 연삭숫돌의 자인자가 파괴강도 및 AE특성에 미치는 영향을 구명하여 파괴의 예지및 연삭숫돌수명의 예측가능성등의 파괴강도특성을 평가고찰하였다.

• 한국작물학회지
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• 제52권1호
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• pp.55-59
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• 2007

This experiments were conducted to evaluate suitable plant-type and cultivars for producing fresh pod peanut from late seeding as succeeding crop, compared with early seeding as proceeding crop or single cropping. 12 cultivars according to grain weight and plant types, 6 virginia typed cultivars(ssp. hypogaea) and 6 shinpung typed cultivars(ssp. fastigiata), were used for early and late seedings. The plant growth and yield potential in early seeding were better than those in late seeding. But the ratios of dry/fresh pod and of mature pod in late seeding were higher than those of early seeding. The yield of fresh pod by cultivars in two seeding times showed significant correlation with pod scale such as fresh pod weight, 100-grain weight, and dry seed yield positively, but pod number negatively in early seeding only. Yield of fresh peanut between Virginia and Shinpung types didn't show significant difference in early seeding, but showed in late seeding. Average yield of Virginia typed cultivars showed significantly higher than that of Shinpung typed ones. This yield gap between two plant types was the same tendency on extending seedings to July 20.