• Journal of the Korean Recycled Construction Resources Institute
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• v.7 no.2
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• pp.109-115
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• 2019

In case of the cracks in concrete, the penetration of deterioration ions such as chloride ions in to cracks is accelerated. According to the penetration of chloride ions, structural and durability problems to RC(Reinforced Concrete) structures are caused. In this study, the accelerated chloride diffusion coefficient which is in steady state is evaluated for 2 year aged normal and high strength FA(Fly Ash) concrete, after a range of crack depths are induced up to 1.0 mm in 56 aged day. Considering crack effect by linear regression analysis, high strength concrete has slightly less increasing ratio of diffusion coefficient by crack than normal strength concrete, and diffusion coefficient increases non-linearly as crack width is increased. Also, In two types of concrete, crack effect decrease as the curing period increase. In the case of quantifying crack and curing effect by using exponential function form, the coefficients of determination are higher than those of linear regression analysis. Under steady state, it is thought that there is not a high correlation between the crack effect and the curing effect, and considering the two independent effects, it is believed that reasonable prediction equation for diffusion of concrete with crack can be proposed.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.1
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• pp.153-160
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• 2010

It is necessary to determine accurate 3-dimensional coordinates of the building corner points that could be control or check points in order to verify the accuracy of 3D digital maps in the near future. The usual process of obtaining the coordinates of the building corner points is to set up the ground control points with a GPS and then to practice terrestrial survey such as distance or angle measurements. However, since an error in the ground control points can be propagated through the terrestrial survey into the final coordinates of the buildings, accurately should be considered as much as possible. The actual effect of the GPS-derived ground control point error on the estimates of the unknowns through the terrestrial survey is mathematically analyzed, and the simulation data is tested numerically. The error of the ground control points is tested in the cases of 1-4 cm for the horizontal components and 2-8 cm for the vertical component. The vertical component error is assigned twice the horizontal ones because of the characteristics of the GPS survey. The distance measurement is assumed for convenience and the precision of the estimated coordinates of the building corner points is almost linearly increased according to the errors of the ground control points. In addition, the final estimates themselves can vary by the simulated random errors depending on the precision of the survey instrument, but the precision of the estimates is almost independent of survey accuracy.

• Korean Journal of Food Science and Technology
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• v.15 no.1
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• pp.56-61
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• 1983

Direct production of biomass from starch using amylolytic yeast, Sporobolomyces holsaticus FRI Y-5 was studied with varying the ratios between carbon and other nutrient sources in the medium. It was investigated under condition of constant C/P and C/S ratio to influence the initial concentration of starch $(S_o)$ and C/N ratio on its growth which is described as the specific growth rate $({\mu})$, cell yield (Y), the maximum concentration of cell $(X_m)$, and productivity (P). They were very dependent on both $S_o$ and C/N ratio. The form of the relationship between and ${\mu}$ and $S_o$ was observed to be similar to saturation kinetics at C/N = 100 but presented substrate inhibition at other C/N ratios. As $S_o$ was changed from 22.5 to 90 g/l, Y was observed to vary with C/N ratios but seemed to decrease as a wholes. $X_m$ was linearly related to $S_o$ at more than C/N = 50 but at less than C/N = 10 substrate inhibition was presented. P increased suddenly to $S_o$ = 45 g/l and then changed decreasingly at less than C/N = 50, but at more than C/N = 100 it changed increasingly. The effect of C/P ratio and C/S ratio on the yeast growth was also investigated at constant $S_o$ and C/N ratio. ${\mu}$ was dependent on C/P and C/S ratios, but Y, independent on them. But $X_m$ was reliant upon C/P ratio but not upon C/S ratio.

• Polymer(Korea)
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• v.29 no.2
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• pp.190-197
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• 2005

Nanocomposites of three different polyesters with dodecyltriphenylphosphonium-montmorillonite $(C_{12}PPh-MMT)$ as an organoclay are compared with their thermal properties, mechanical properties, and morphologies. Poly (butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and poly(trimethylene terephthalate) (PTT) were used as matrix polymers in the fabrication of polyester nanocomposite fibers. The variations of their properties with organoclay content in the polymer matrix and draw ratio (DR) are discussed. Transmission electron microscopy (TEM) micrographs show that some of the clay layers are dispersed homogeneously within the polymer matrix on the nano-scale, although some clay particles are agglomerated. We also found that the addition of only a small amount of organoclay is enough to improve the thermal stabilities and mechanical properties of the polyester nanocomposite fibers. Even polymers with low organoclay contents $(<5\;wt\%)$ were found to exhibit much higher strength and modulus values than pure polyester fibers. In the cases of all polyester hybrid fibers, the values of the tensile mechanical properties were found to decrease linearly with increasing DR. However, the initial tensile modulus of the PTT hybrid fibers were found to be independent of DR.

• Tunnel and Underground Space
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• v.28 no.2
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• pp.156-169
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• 2018

The relationship between the mechanical and textural properties of sedimentary rocks has been studied for decades. However, inconsistencies in the results have arisen from both the inhomogeneity of natural rocks and the difficulties encountered in controlling just one textural factor of interest in each experiment. This work produced artificial sedimentary rocks to enable control of every independent parameter at all times. Their homogeneity lowered the deviation of the results, and thus they produced clearer correlations than for natural rocks. The samples were made by mixing bassanite powder with water and silica sand, which produced rocks consisting of sand and gypsum cement. The effect of grain content and size on mechanical properties such as uniaxial compressive strength, Young's modulus, and seismic velocity was estimated. Increasing grain content lowered the compressive strength but raised Young's modulus and seismic velocity. Overall, grain size did not linearly affect the mechanical properties of the samples, but affected them in some way. In future, these results can be compared and integrated with similar experiments using different cement or grain types. This should allow comparison of the effects of the rock constituents themselves and their interactions, with applicability to all kinds of sedimentary rocks.

• Journal of the Korean Magnetics Society
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• v.6 no.6
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• pp.397-404
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• 1996

The magnetic properties of $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ have been studied by X-ray diffractometry and $M\"{o}ssbauer$ Spectroscopy at room temperature. The X-ray diffraction study show that spinel structure is formed in all x, lattice constants linearly increased from $8.3111{$\AA$}~8.4184{$\AA$}({\pm}0.0003)$ with increasing x from 0 to 1, and oxygen parameter increase with increasing x. $M\"{o}ssbauer$ spectrum shows that $Ni_{1-x}Zn_{x}Fe_{2}O_{4}(x=0)$ has two antiparallel magnetic structure due to $Fe^{3+}$ octahedral site and $Fe^{3+}$ tetrahedral site. $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ with $0.2{\leq}x{\leq}0.6$ has magnetic structure of Yafet and Kittel, in particularly, specimen with x=0.6 shows relaxation effect. Specimen with $x{\geq}0.8$ show paramagnetic quadrupole splitting. The isomer shift is independent of x, but quadrupole splittings decrease with increasing x in the range of $0.8{\leq}x{\leq}1$, and nuclear magnetic fields decrease with in¬creasing x in the range of $0{\leq}x{\leq}0.6$. The magnetic properties of $Ni_{1-x}Zn_{x}Fe_{2}O_{4}$ change from ferrimagnetics to pararnagnetics with increasing x.

• Korea journal of population studies
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• v.26 no.2
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• pp.33-62
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• 2003

The purpose of this study is to analyze the relative importance of three factor -socioeconomic development, public health development, egalitarian nature of socioeconomic development- affecting mortality declines. Infant mortality rate and life expectancy at birth are used as the mortality index, that is the dependent variables, while GNP is used as the indicator of socioeconomic development, primary school enrollment ratio of female as the indicator of egalitarian nature of socioeconomic development, population per hospital bed as the indicator of public health. The data of these variables are collected two time-periods -before 1970 and during 1970-1980- over 50 countries. The explanatory data analysis is used as the statistical technique. We can find whether the relationship between dependent variable and independent variables are linear or nonlinear, and which case is the influential case in our model. The main results of this study are followings. First, the association between infant mortality rates and four indices are not linear. The most important factor explaining the variation of infant mortality is GNP, while primary enrollment of female is the second and GINI is the third important factor. However, population per hospital bed does not have a significant effect on the infant mortality rates in this study. Second, life expectancy at birth is log-linearly related to GNP. Unlike infant mortality rates, the most important factor explaining the variation of life expectance at birth is women's education and the next important factor GNP, and then the third one GINI. But, still population per hospital bed is not significantly related to the variation of life expectance in this study.