• Journal of Korean Society of Forest Science
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• v.8 no.1
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• pp.140-148
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• 1968

Ginkgo biloba L., which was distributed in Korea, was x-rayed with 100, 250, 500, 1000, 2000, 6000R. The results of responses about germination, morphological variations in seedling and early stage growth may be summarized as follows : 1. The germination percent was decreased with X-ray increasing dose from 500R except the slight stimulation of 100R. 2. The germination $LD_{50}$ seemed to be 765R. 3. The seedling height was depressed significantly but only slightly in 100R. 4. The loaf index was increased proportionally to high dose but T/R ratio was reduced apparently. 5. The dry or fresh weight decreased from 250R. It was highly significant except 100R. 6. Many morphological variations were indicated in plants.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.179-184
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• 2000

The I-V characteristics of $ZnO-Pr_6O_{11}-CoO-Dy_2O_3$ based varistors were investigated in the $Pr_6O_{11}/CoO$ composition ratio range of 0.5/0.5 to 1.0/1.0 and sintering temperature range of 1300 to $1350^{\circ}C$ as the basic study to develop the advanced $Pr_6O_{11}$-based ZnO varistors. All varistors except for $Pr_6O_{11}$/CoO = 0.5/1.0 exhibited the best I-V characteristics at $1350^{\circ}C$. However, the varistors with $Pr_6O_{11}$/CoO= 0.5/1.0 exhibited the best I-V characteristics at $1350^{\circ}C$. The varistors with $Pr_6O_{11}$/CoO= 0.5/1.0 of all varistors exhibited the best I-V characteristics, which the nonlinear exponent is 36.9 and the leakage current is 7.6 ${\mu}A$ Therefore, it was estimated that ZnO-$Pr_6O_{11}-CoO-Dy_2O_3$ ceramics with $Pr_6O_{11}$/CoO= 0.5/1.0 will be usefully used as varistor materials in the future.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.190-195
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• 2000

The electrical properties and stability of ZPCE varistors consisted of $ZnO-Pr_6O_{11}-CoO-Er_2O_3$ ceramics were investigated. $ZnO-Pr_6O_{11}-CoO-Er_2O_3$ based ceramics were sintered at $1300^{\circ}C$ and $1350^{\circ}C$, respectively, without and with 0.5 mol% $Er_2O_3$. The varistors sintered at $1300^{\circ}C$ exhibited a better nonlinearity than that $1350^{\circ}C$. The varistors with $Er_2O_3$ of 0.5 mol% exhibited a high nonlinear exponent of 52.8. However, they easily degraded due to the low density below 85% of TD. On the other hand, the varistors sintered at $1350^{\circ}C$ without $Er_2O_3$ exhibited an extremely poor nonlinearity, but the varistors with $Er_2O_3$ of 0.5 mol% exhibited a relatively good nonlinearity, which the nonlinear exponent is 34.8 and the leakage current is $7.4\;{\mu}A$ Morever, they exhibited a very high stability, which the variation rate of varistor voltage, nonlinear exponent, and leakage current are -0.9%, -2.9%, and +2.7%, respectively, under the third stress $(0.80 V_{1mA}/90^{\circ}C/12h)$ + $(0.85 V_{1mA}/115^{\circ}C/12h)$ + $(0.90 V_{1mA}/120^{\circ}C/12h)$. Consequently, it was estimated that $ZnO-Pr_6O_{11}-CoO-Er_2O_3$ ceramics will be usefully applied to develop the advanced $Pr_6O_{11}$-based ZnO varistors.

• Journal of the Korean Chemical Society
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• v.22 no.5
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• pp.304-310
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• 1978

The relative permeabilities, distribution coefficients and diffusion coefficient of some salts which are important components in blood plasma through a poly(HEMA) membrane were measured. The crosslinker which was used for preparing the membrane was tetraethylene glycol dimethacrylate(TEGDMA), the weight percentage of the latter was about 2.8. We found that the diffusion coefficients ($D_m$) of the solutes decrease exponentially with increasing molecular weight, and also that $D_m$'s decrease linearly (except urea) with cylindrical radius (a). These facts were explained by a sieve pore flow model. The relative permeability and diffusion coefficient of urea at various temperature were larger than those of other solutes such as glycine, ${\beta}$-alanine, D-glucose, saccharose and maleic acid. The result indicates that the poly(HEMA) membrane might be suitable for hemodialysis application.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.2
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• pp.151-155
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• 1990

A field experiment was conducted to study both the distribution characteristics of shortwave radiation in the soybean canopy and its relationship with dry matter production. The soybean 'Paldalkong' was sown with the space of 45${\times}$10cm at Suwon on May 27. 1988. The extinction coefficient of solar radiation remained constant (0.53) after full canopy was reached. The 31.9% of the incoming solar radiation was transmitted. The reflected radiation from the plant canopy increased lineary with incoming solar radiation (R$^2$=0.9346). As leaf area index become larger than 2.5. the reflected radiation showed more significant linear relationship with the differences in the radiations between incoming and transmitted radiation than incoming solar radiation (R$^2$=0.9558). The mean reflectance during the growing period was 24.7%. A significant linear relationship (R$^2$=0.9930) had been admitted between the accumulated solar radiation intercepted by the canopy and dry matter production of 'Paldalkong' until the 35th day of ripening stage. The conversion efficiency of solar radiation intercepted to dry matter of soybean was 1.45g MJ$\^$-1/.

• Korean Journal of Soil Science and Fertilizer
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• v.30 no.2
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• pp.135-139
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• 1997

Vegetation indices were analyzed from the LANDSAT images of Yeoju, Kwangju and Yangpyong Gun of Kyunggi Province, obtained on September 22, 1983 and September 12, 1994, to evaluate the changes in landuses. It was found that there were notable changes in the landuses in the observed area over 11 years. Particularly, in Choweol Myun of Kwanju Gun, in Yangpyong Eup of Yangpyong Gun, and in Heungcheon Myun of Yeoju Gun, decrease in the area under vegetatin was most remarkable. These changes in the area under vegetatin are considered as the results of the construction of highways and the expansion of urban areas. The LANDSAT images overestimated the area under rice cultivation, when compared to the official statistic year book. However, it was found that the areas of the land under rice cultivation estimated by LANDSAT images for each Myun were close enough to those from the official statistics suggesting that the LANDSAT images can be used for the estimation of landuse status.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.41 no.1
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• pp.34-44
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• 1996

Several major agronomic traits of 4 isogenic lines for tillering(Kindred, Morex)were investigated under the different seeding rates and seedling mortality grown in the pots. The normal-tillering phenotypes had higher grain yield(46％) and leaf area index(56％) than their uniculm isogenic counterparts. The assortment rate(69％) and 1,000 grain weight(27％) in uniculm type were greater than the normal type. Uniculm plants were earlier in heading(4∼8days) and maturing(2∼3 days) dates compared with their counterparts. The grain yield was fitted to linear regression, ranged 0.659g to 0.5g per spike number. On increasing the seedling mortality rates, the grains per spike and 1,000 grain weight were slightly decreased, but the grain yield per plot was decreased markedly because of decrease of spikes per plot. The assortment rate, leaf photosynthetic capacity and reproductive tiller number were increased with increase of seedling mortality. The grain yield was largely dependent on the number of spikes per plot on occurrence of seedling mortality. For the uniculm genotypes to be introduced and bred into a present leading variety, the isogenic lines were precisely tested in the open field for a couple of years.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.451-456
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• 1984

Rheological properties of gelatinized rice starch solutions were investigated with Brookfield rotational viscometer. The 8% starch solution showed thixotropic behavior with yield stress. The alkali gelatinized starch was more thixotropic than the thermal gelatinized one. The time dependent characteristics of starch solutions followed Tiu's model. The value of rate constant $(a_1)$ in Tiu's model increased linearly with shear rate, and was exponentially dependent on concentration and temperature. Temperature dependency of rate constant and apparent viscosity followed Arrhenius type equation and the activation energy were about 14.3 and 6.8 Kcal/g mole, respectively. The $a_1-value$ was found to be useful to evaluate changes in structaral decay on the shearing time of gelatinized rice starch solutions.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.1
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• pp.66-71
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• 1982

Field experiments of nitrogen application (0, 100, 200, 400, 800kg N/ha year) were carried out to study the nitrogen response of Sudangrass at College Farm, Seoul National Univ., in 1979 and 1980. Dry matter yield and leaf area index increased up to 400kg N/ha in 1979 and 800kg N/ha in 1980. The forage yield of 1980 was less than that of 1979, due to the extraordinarily low temperature and the decreased solar radiation during summer. Total nitrogen contents in forage increased with nitrogen application, but maximum contents were found either 400 or 800kg N levels depend on each cutting stages. Nitrate nitrogen content in forage exceded over 2000 ppm at 800kg N application. Overall percentages of N recovery were below 50% with average 34%. Net assimilation rate and nitrogen use efficiency of Sudangrass were improved in higher temperature and more sunlight condition during regrowth period.

• Journal of the Korea Concrete Institute
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• v.20 no.4
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• pp.477-486
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• 2008

External bonding of carbon fiber reinforced plastic sheets has recently emerged as a popular method for strengthening reinforced concrete structures. The behavior of CFRP-strengthened RC structure is often controlled by the behavior of the interface between CFRP sheets and concrete. In this study, a review of models on bond strength, bond-slip, and interfacial stresses has been first carried out. Then a new bond-slip model is proposed. The proposed bond-slip model has bilinear ascending regions and exponential descending region derived from modifications mode on the conventional bilinear bond-slip model. The comparison of the results with those of existing experiment researches on bond-slip models indicate good agreements.