• Korean Journal of Soil Science and Fertilizer
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• v.37 no.6
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• pp.365-370
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• 2004

To invesligate the characteristics of silica sorption on soils silica sorption experiments were conducted with 9 soils at 4 pH levels (5, 6, 7, and 8). Silica sorption increased in great extent with increase of pH. At the same pH level silica sorption increased linearly with increase of equilibrium $SiO_2$ concentration. Silica sorption characteristics was C-type. The C-type slope, i.e., the slope of linear regression of silica sorption isotherm, increased exponentially with increase of pH in all soils. Log(C-type slope) increased linearly with increase of pH in all soils. The slopes of linear regression were similar in most soils from 0.29 to 0.34 except Sachon and Jonggog soil. None of the soil properties showed any correlation with the slope of linear regression of Log(C-type slope) to pH. Only $Fe_o$ (oxalate extractable Fe oxides) was significantly correlated with the Log(C-type slope) at pH 7 in simple correlation analysis, and was shown to be the principal contributor as determined by standardized multiple linear regression.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.5 s.96
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• pp.541-548
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• 2005

The research deals with the prediction and the measurement of electromagnetic wave propagation in rectangular shaped tunnels at f=2.65 GHz. The received power level was measured in the straight and the curved tunnel by using a spectrum analyzer and Satellite DMB mobile phone. Thus we have gotten the data for two cases, the straight and the curved tunnel whose radius is 300m. In addition, the prediction of wave propagation was conducted based on the ray-launching method, in same tunnel where measurement was performed. A good agreement of the measured and the predicted path loss could be confirmed. The measured path loss shows a marked difference in propagation loss: the path-loss exponent, 3.21, and 3.98, for a straight and a curved tunnel, respectively. The reason that path-loss exponent is high in a curved tunnel is that there is no direct wave but only the reflected waves, which attenuates rapidly with distance due to multiple reflections. Also the predicted path loss shows path loss exeponent, 3.2 and 3.95, for a straight and a curved tunnel which are similar to the simulation results.

• Journal of the Korean Ceramic Society
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• v.40 no.11
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• pp.1067-1072
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• 2003

The electrical stability of the varistor ceramics composed of Zn-Pr-Co-Cr-Dy oxides-based varistors was investigated at 0.0∼2.0 mol% Dy$_2$O$_3$ content under DC accelerated aging stress. The ceramic density was increased up to 0.5 mol% Dy$_2$O$_3$ whereas further addition of Dy$_2$O$_3$ decreased sintered ceramic density. The density sailently affected the stability due to the variation of conduction path. The nonlinearity of varistor ceramics was greatly improved above 45 in the nonlinear exponent and below nearly 1.0 ${\mu}$A by incorporating Dy$_2$O$_3$. Under 0.95 V$\_$1mA/150$^{\circ}C$/24 h stress state, the varistor ceramics doped with 0.5 mol% Dy$_2$O$_3$ exhibited the highest electrical stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current were -0.9%, -14.4%, and +483.3%, respectively. The variation rates of relative permittivity and dissipation factor were +7.1% and +315.4%, respectively. The varistors with further addition of Dy$_2$O$_3$ exhibited very unstable state resulting in the thermal runaway due to low density.

• The Journal of the Petrological Society of Korea
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• v.26 no.1
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• pp.45-54
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• 2017

The characteristics of the rock cleavage in Jurassic Geochang granite were analysed using the distribution of microcrack lengths and spacings. The phases of distribution of the above lengths and spacings were derived from the enlarged photomicrographs(${\times}6.7$) of the thin section. First, the length and spacing-cumulative diagrams for the six directions of rock cleavages were arranged in increasing order($H2{\rightarrow}R1$) on the density(${\rho}$) of microcrack length. The various parameters were extracted through the combination of the above two types of diagrams. The discrimination factors representing the three quarrying planes and three rock cleavages were acquired through the mutual contrast between the values of parameters. The analysis results of the research are summarized as follows. The evaluation for the six directions of rock cleavages was performed using the parameters such as (1) intersection angle(${\alpha}-{\beta}$) and (2) exponent difference(${\lambda}_S-{\lambda}_L$) between two exponential straight lines related to spacing(${\alpha}$, ${\lambda}_S$) and length(${\beta}$, ${\lambda}_L$). The values of parameters(1 and 2) are in order of H(hardway, (H1 + H2)/2) < G(grain, (G1 + G2)/2) < R(rift, (R1 + R2)/2). On the contrary, the values of the above two parameters for three planes are in order of R < G < H. Meanwhile, the direction of convergence between two exponential straight lines was derived. The above direction is compliant to arrangement of the line os' centering around the line ol. The above two lines converge in the direction of the Y-axis when the line ol and line os' occupy the upper region on the left and the lower region on the right, respectively(R-type). On the contrary, the above two lines converge in the direction of the X-axis when the order of arrangement between line ol and line os' is reversed(H-type). Especially, the positive(+) or negative(-) value of intersection angle(${\alpha}-{\beta}$) is determined by the arrangement of two vertical lines. This type of correlation analysis is useful for evaluating the relative strength of rock cleavage and discriminating three quarrying planes.

• Journal of the Korean Chemical Society
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• v.37 no.12
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• pp.1025-1034
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• 1993

We have measured ${\pi}^*$, $\alpha$ and $\beta$ polarity parameters of 2-propanol / hexane and ethyl acetate / hexane mixed solvents over the entire range of composition. For the ethyl acetate / hexane system, only ${\pi}^*$ and $\beta$ were measured since $\alpha$ of these mixed solvents are defined zero. We have corrected the measured polarity parameters to obtain consistent data with the existing literature data assuming a good linear correlation between the measured and the true values. The variation patterns are consistent with the expected trends based on the chemistry of the solvent components. The general trends of the two solvent systems are summarized as follows. ${\pi}^*$ merely increases as the content of the more polar solvent increases while $\alpha$ and $\beta$ increase with the increase of the content of the more polar solvent, then decrease upon continuing addition of the more polar solvent.

• Korean Journal of Food Science and Technology
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• v.28 no.3
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• pp.538-544
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• 1996

A highly viscous biopolymer from alkali-tolerant Bacillus sp. was purified and its rheological properties were studied. 1% (w/v) solution of purified biopolymer showed pseudoplastic fluid behavior with the yield stress similar to those of xanthan and guar gum, and its consistency index was exponentially dependent on concentration and temperature. The concentration dependency of consistency index exhibited two rectilinear plots with different slopes at 1% concentration and pseudoplastic property increased with the increase of biopolymer concentration. The biopolymer solution exhibited a low temperature dependency and the activation energy of flow was 1.16 kacl/g mol. The apparent viscosity was very dependent on the change of pH and the addition of salt. However, no organic solvent effects were observed effects of viscosity synergism with the addition of viscosifier were not observed.

• Korean Journal of Food Science and Technology
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• v.16 no.3
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• pp.314-318
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• 1984

Rheological properties of gelatinized chestnut starch solution were investigated with a narrow gap rotational viscometer. The starch solutions at 1.2-1.8% concentration showed pseudoplastic behaviour with yield stress. At higher concentrations (1.65 and 1.8%), the starch solution showed more pseudoplastic tendency and time-dependent characteristics. Values of yield stress were small and independent of concentrations 1.2, 1.35 and 1.5%. Significant increase of yield stress was observed at 1.65% concentration. Consistency index was exponentially dependent on concentration and temperature. The activation energy for 1.65% starch solution was about 5 Kcal/g.mol.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.30 no.3
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• pp.252-258
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• 1985

An experiment was conducted at the Yeongnam Crop Experiment Station to obtain basic informations about cultural techniques for high yielding by manipulating plant spacing using two rice cultivars, Samgangbyeo (Indica/Japonica type) and Nakdongbyeo (Japonica type), and four plant spacings, 10${\times}$10cm, 20${\times}$20cm 30${\times}$30cm and 40${\times}$40cm, with 4 kinds of seedling number per hill, 1,3,5 and 7, respectively. High photosynthetic efficiency (Eu) exhibited at the Samgangbyeo compared to Nakdongbyeo regardless of plant spacings and seedling numbers. For Samgangbyeo, Eu value was the highest at the 20${\times}$20cm plant spacing and five seedlings and seven seedlings per hill showed high Eu values at 10${\times}$10cm plant spacing and 20${\times}$20cm plant spacing, respectively, while other plant spacings were not significantly differed among seedling numbers. For Nakdongbyeo, however, one seedling plot obtained high Eu value at the 10${\times}$10cm plant spacing while this Eu value increased as the seedling number per hill increased in other plant spacings. There was a high positive correlation between rice grain yield and total competition index for both cultivars while kind of relationships differed in these two cultivars; linear relationship for Samgangbyeo and exponential relationship for Nakdongbyeo, respectively. Competition index between rice hill was more significant than within rice hill for Samgangbyeo while both competition indexs were important for Nakdongbyeo to increase rice yield.

• Journal of Yeungnam Medical Science
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• v.7 no.1
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• pp.51-60
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• 1990

In order to assess the physical growth of primary school student in the rural area, body height, weight, chest circumference and sitting height of 923 students(469 males, 454 females) in the town of Angang, Kyungpook province, Korea, were measured from April to May, 1988. The most growth age of body height was 10-11 years old in both sex and the growth curves were crossed at 9-11 years old. The most rapid growth age of body weight was 10-11 years old and growth curves were crossed at 9-11 years old. The most rapid growth age of chest circumference was 10-11 years old in female, whereupon female outgrows male by contrast with male's slow and linear growth. The most rapid growth age of sitting height was 10-11 years old and the growth curves were crossed at 9-10 years old. The Rother index was 1.17-1.30 in male, 1.16-1.29 in female, and male's index was in general superior to female's.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.15 no.12
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• pp.7018-7024
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• 2014

This study examined the squared returns and absolute returns of KOSPI 200 with GPH (Geweke and Porter-Hudak, 1983) estimators. GPH was estimated by the long-term memory preserving time series parameter d in linear regression. This called the GPH estimator, which depends on a bandwidth m. m was decided by confirming the stable section of the point estimate by validating the track of the GPH estimator according to the value of m. The result suggests that by satisfying 0< d <0.5, the squared returns and absolute returns of KOPI 200 retains long-term memory.