• Journal of The Korean Astronomical Society
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• v.24 no.2
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• pp.151-159
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• 1991

Using the photographic imagery of the SO galaxy NGC 5102, the equivalent luminosity profile and the fractional integrated luminosity curve have been derived. Several photometric parameters of the galaxy, such as a total magnitude ($B_T$), equivalent radius ($r^*_e$), effective surface brightness (${\mu}^*_e$), and concentration indices ($C_{21}$, $C_{32}$) were derived from the luminosity profiles. According to the decomposition method from the nonlinear least squares fitting, photometric parameters of the bulge (${\mu}_e$, $r_e$) and the exponential disk (${\mu}(0)$, ${\alpha}^{-1}$), and the bulge to total luminosity ratio (B/T) were obtained. The derived central disk surface brightness (${\mu} (0)\;=\;22.06\;{\pm}\;0.18\;mag/\Box"$) and the evaluated B/T ratio (= 0.52) of the NGC 5102 are close to the mean values (${\mu} (0)\;=\;21.65\;{\pm}\;0.3\;mag/\Box"$, B/T=0.63) of the SO galaxies. Analysis showed that a lens-like hump is embedded in the equivalent luminosity profile of the NGC 5102.

• Korean Journal of Materials Research
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• v.18 no.4
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• pp.218-221
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• 2008

A $Fe(OH)_2$ suspension was prepared by mixing iron sulfate and a weak alkali ammonia solution. Following this, iron oxides were synthesized by passing pure oxygen through the suspension (oxidation). The effects of different reaction temperatures ($30^{\circ}C$, $50^{\circ}C$, $70^{\circ}C$) and equivalent ratios ($0.1{\sim}10.0$) on the formation of iron oxides were investigated. An equilibrium phase diagram was established by quantitative phase analysis of the iron oxides using the Rietveld method. The equilibrium phase diagram showed a large difference from the equilibrium phase diagram of Kiyama when the equivalent ratio was above 1, and single $Fe_3O_4$ phase only formed above an equivalent ratio 2 at all reaction temperatures. Kiyama synthesized iron oxide using iron sulfate and a strong alkali NaOH solution.

• Journal of the Korea Institute of Building Construction
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• v.2 no.4
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• pp.177-182
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• 2002

The purpose of this study is to develope the strength prediction model by Maturity Method. A maturity function is a mathematical expression to account for the combined effects of time and temperature on the strength development of a cementious mixture. The method of equivalent ages is to use Arrhenius equation which indicates the influence of curing temperature on the initial hydration ratio of cement. For the experimental factors of this study, we selected the concrete mixing of W/C ratio 45, 50, 55 and 60% and curing temperature 5, 10, 20 and $30^{\circ}C$. And we compare and evaluate with logistic model that is existing strength prediction model, because we have to verify adaption possibility of new strength prediction model which is proposed by maturity method. As the results, it is found that investigation of the activation energy that are used to calculate equivalent age is necessary, and new strength prediction model was proved to be more accurate in the strength prediction than logistic model in the early age. Moreover, the use of new model was more reasonable because it has low SSE and high decisive factor.

• Journal of the Korea Concrete Institute
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• v.27 no.6
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• pp.687-693
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• 2015

The present study proposed a k-value to determine the water-to-binder ratio of concrete using fly ash (FA) or ground granulated blast-furnace slag (GGBS) as a partial replacement of ordinary portland cement (OPC) with regard to an equivalent strength of OPC concrete. From the regression analysis using an extensive database including 7076 concrete mixes, k-values were determined for various water-to-binder ratios when the replacement ratio of OPC by the addition of FA or GGBS were below 50%. For deriving an equation to identify k-value, the relationship of concrete compressive strength and water-to-binder ratio was generalized by an exponential function. In general, k-values decreased with the increases in the addition of FA or GGBS for replacement of OPC and water-to-binder ratio. The rate in decreasing k-value against water-to-binder ratio was marginally affected by the addition of FA or GGBS, although a higher k-value was commonly obtained for GGBS concrete than for FA concrete at the same water-to-binder ratio. Consequently, the determined k-values were simplified as a function of water-to-binder ratio and the addition ratio of FA or GGBS as replacement of OPC.

• Journal of the Korean Geotechnical Society
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• v.31 no.4
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• pp.45-55
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• 2015

The stability of the adjcent structures or slopes under blasting is typically evaluated using an empirical vibration attenuation curve or dynamic numerical analysis. To perform a dynamic analysis, it is necessary to determine the blast load and the damping ratio of rock mass. Various empirical methods have been proposed for the blast load. However, a study on representative values of damping ratio of a rock mass has not yet been performed. Therefore, the damping ratio was either ignored or selected without a clear basis in performing a blast analysis. Selection of the dampring ratio for the rock mass is very difficult because the vibration propagation is influenced by the layout and properties of the rock joints. Besides, the vibration induced by blasting is propagated spherically, whereas plane waves are generated by an earthquake. Since the geometrical spreading causes additional attenuation, the damping ratio should be adjusted in the case of a 2D plane strain analysis. In this study, we proposed equivalent damping ratios for use in continuum 2D plane strain analyses. To this end, we performed 2D dynamic analyses for a wide range of rock stiffness and investigated the characteristics of blast vibration propagation. Based on numerical simulations, a correlation between the attenuation equation, shear wave velocity, and equivalent damping ratio of rock mass is presented. This novel approach is the first attempt to select the damping ratio from an attenuation relationship. The proposed chart is easy to be used and can be applied in practice.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.175-177
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• 2007

An analysis on a passive current sharing characteristics of a multi-phase synchronous buck converter is presented. The passive current sharing method is simple but its characteristics depend on the converter equivalent resistance and PWM uniformity. In this paper, the load sharing and power consumption of the passive current sharing system for the converter equivalent resistance and duty ratio inequalities are investigated through the simulation and experiment.

• Journal of Navigation and Port Research
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• v.26 no.1
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• pp.43-49
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• 2002

In this Paper, the mechanical behavior of two reかangular plates spot-welded under free vibration is investigated in detail. The focus of the analysis is to evaluate the effect of thickness of reinforced plates with equivalent thickness. The results of this the investigation are compared with detailed finite element analysis end experiments of the plates spot-welded for various parameters, such as aspect ratio, arm ratio, and distance ratio of spot-welding Points. The conclusion obtained are as followed. 1. The effect thickness due to spot-weld is very large, such as 55% in comparison with area ratio of spot-welding joint is just 4.52%. 2 The effect of thickness with respect to the distance ratio is maximized when the distance ratio is 0.4.

• The Korean Journal of Physiology
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• v.2 no.2
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• pp.53-61
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• 1968

Maximal oxygen debt, lactate and excess lactate were measured in 13 men with low hematocrit ratio before and after maximal exercise. Maximal exercise run was performed on a treadmill and the duration of run was 2 minutes 45 seconds in each subject. Hematocrit ratio ranged between 35 and 47%, the mean being 39.8%. The following results were obtained. 1. Maximal oxygen debt expressed on basis of body weight increased as the hematocrit ratio decreased. The correlation coefficient between the two was r= -0.770. 2. The time necessary for decreasing to 50% of total maximal $O_2$ debt(half time) became longer as the hematocrit ratio decreased. In normal men the half time was about 4 minutes and at the longest it was 12 minutes in men with the lowest hematocrit ratio. 3. The lactate concentration reached its peak value after 3 minutes of recovery. Thereafter, the time course of decrease in lactate concentration coincided roughly with that of respiratory oxygen debt curve. To reach to the resting level, however, it took longer time than that of respiratory oxygen debt. 4. Resting concentrations of lactate was 1.28 mM/l, pyruvate 0.13 mM/l and L/P ratio was 9.8. Peak value of ${\Delta}L$ after exercise reached to the value of 10.4 mM/l and ${\Delta}L/P$ reached 26.0. Peak excess lactate after exercise was 6.34 mM/l. 5. The part of oxygen debt accounted for by the oxygen equivalent of excess lactate was only 38.4%. A better relationship between lactate and oxygen debt was observed and the part of oxygen debt accounted for by the oxygen equivalent of lactate was 63.3%. 6. Peak value of lactate after maximal exercise increased as the hematocrit ratio decreased. 7. Respiratory oxygen debt of 100 ml/kg was accounted for by lactate more than 60% and only 30% was by excess lactate. 8. Excess lactate was not a good index of respiratory oxygen debt.

• Steel and Composite Structures
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• v.13 no.1
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• pp.47-70
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• 2012

To enhance cable stiffness, this paper proposed a combined application of carbon fiber reinforced polymers (CFRP) and steel materials, resulting in a novel type of hybrid stay cable system especially for the cable-stayed bridges with main span lengths of 1400~2800 m. In this combination, CFRP materials can conserve all their advantages such as light weight and high strength; while steel materials help increase the equivalent stiffness to compensate for the low elastic modulus of CFRP materials. An increase of the equivalent stiffness of the hybrid stay cable system could be further obtained with a reasonable increase of its safety factor. Following this concept, a series of parametric studies for the hybrid stay cable system with the consideration of stiffness and cost were carried out. Three design strategies/criteria, namely, best equivalent stiffness with a given safety factor, highest ratio of equivalent stiffness to material cost with a given safety factor, and best equivalent stiffness under a given cost were proposed from the stiffness and cost viewpoints. Finally, a comprehensive design procedure following the proposed design strategies was suggested. It was shown that the proposed hybrid stay cable system could be a good alternative to the pure CFRP or traditional steel stay cables in the future applications of super long span bridges.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.2
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• pp.339-348
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• 1990

Techniques which are able to predict and control dynamic characteristics, not affecting the vibrational characteristics on the modification of structural design, are being studied. As one of these techniques, experimental modal analysis is widely applied by many researchers. In this study, modal analysis is performed using transfer matrix method by a macro computer. The developed program would estimate the structural modal parameters precisely, and the validity of this program is certified by comparing with the experimental results of .GAMMA A. structure. Estimated modal parameters(natural frequency, vibrational mode, equivalent mass, etc.) are in accord with the experimental results. Also, the optimal location of the additive mass is determined by the evaluation of the vibrational mode and the equivalent mass. The relation between the additive mass and the equivalent mass is specified, and we come to know that the ratio of equivalent mass to additive mass alter linearly within the range of 20%.