• Journal of the Korean Chemical Society
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• v.21 no.6
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• pp.395-403
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• 1977

Significant structure theory was applied to some liquid mixture systems ranging from simple monatomic molecule systems to polyatomic molecule systems, and the activity coefficients ${\gamma}$ of the liquid mixture systems were calculated over whole mole fractions using the following thermodynamic relation $RTln_{{\gamma}i} = (\frac{{\partial A}^E}{{\partial N}_i})_{T,V,N_i} $ where $A^E$ represents the excess Helmholtz free energy, and $N_i$ is the number of molecules of component i. The activity coefficients of the solutions such as monatomic molecule systems (Ar-Kr, Kr-Xe) and diatomic molecule systems $(Ar-O_2,\;N_2-CO)$ and $CH_4-Kr$ systems whose components have similar shapes for intermolecular potential curves were calculated successfully only with the ${\delta}E_s$, correction parameter for energy $E_s$, for mixture systems. For other systems such as $Ar-N_2,\;O_2-N_2\;and\;CH_4-C_3H_8$ whose components have dissimilar intermolecular potential curve shapes an additional correction parameters ${\delta}$V and even one more parameter ${\delta}$n were necessary [see Eqs.(10)∼(12)].

• Bulletin of the Society of Naval Architects of Korea
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• v.17 no.2
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• pp.11-16
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• 1980

For vibration analysis of stiffened plates the orthotropic plate analogy is commonly accepted. As to stiffened plates in contact with water, however, there is still much uncertainty in estimation of the added mass because of the lack of direct methods. The authors, considering that for added mass of plates there are many reliable data derived theoretically or experimentally available, suggest a method to estimate the added mass of a stiffened plate by combining the mass increase factor, $\beta$, of an equivalent orthotropic plate and the correction factor, $\kappa$, for the effects of stiffeners. The latter is to be derived from systematic experimental investigations. Then, the natural frequency in water, f', can be calculated from that in air, f, by the equation $f'=f/\sqrt{1+\kappa\beta}$. To investigate practical applicability of this method, a systematic experiment was carried out with five uniaxially stiffened plates. Each of them had a plate of same size, $600mm{\times}600mm{\times}3.2mm$, but stiffeners of different size in the web-depth, 41.6mm, 51.2mm or 66.8mm and of different spacing 75mm, 100mm, or 150mm. Natural frequencies were measured under simply supported-edge conditions in both air and water, and corresponding $\kappa$ values derived. In spite of wide variations of web-depth and spcae of stiffeners, the experimental results show that the diversity of $\kappa$ values is not remarkable; mean values of $\kappa$ are 1.31 with standard deviation of 0.025 for the first modes and 1.27 with that 0.077 for the second modes. Hence, the authors concluded that the above $\kappa$ values can be used generally for the cases of uniaxially stiffened plates both sides of which contact with water, and that $\kappa$ values of general use for the cases of cross-stiffened plates may also be obtainable from similar experiments.

• Journal of Environmental Science International
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• v.12 no.10
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• pp.1085-1093
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• 2003

This study was conducted to investigate anoxic-RBC (rotating biological contactor) and its application in advanced municipal wastewater treatment process to remove biologically organics and ammonia nitrogen. Effluent COD and nitrogen concentration increased as the increase of volumetric loading rate. But, the concentration changes of NO$_2$$\^$-/ -N and NO$_3$$\^$-/ -N were little, as compared to COD and NH$_4$$\^$+/ -N. When the volumetric loading rate increased, COD removal efficiency and nitrification appeared very high as 96.7∼98.8% and 92.5∼98.8%, respectively. However, denitrification rate decreased to 76.2∼88.0%. These results showed that the change of volumetric loading rate affected to the denitrification rate more than COD removal efficiency or nitrification rate. The surface loading rates applied to RBC were 0.13～6.0lg COD/㎡-day and 0.312∼1.677g NH$_4$$\^$+/-N㎡-day and they were increased as the increase of volumetric loading rate. However, the nitrification rate showed higher than 90%. The thickness of the biofilm in RBC was 0.130 ∼0.141mm and the density of biofilm was 79.62∼83.78mg/㎤. They were increased as surface loading rate increased. From batch kinetic tests, the k$\_$maxH/ and k$\_$maxN/ were obtained as 1.586 g C/g VSS-day, and 0.276 g N/g VSS-day, respectively. Kinetic constants of denitrifer in anoxic reactor, Y, k$\_$e/, K$\_$s/, and k were 0.678 mg VSS/mg N, 0.0032 day$\^$-1/, 29.0 mg N/l , and 0.108 day$\^$-l/, respectively. P and K$\_$s/, values of nitrification and organics removal in RBC were 0.556 g N/㎡-day and 18.71 g COD/㎡-day, respectively.

• Journal of Environmental Science International
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• v.8 no.6
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• pp.711-716
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• 1999

This research explored the feasibility of preparing and utilizing a prefonned polymeric solution of Al(III) for coagulation in water treatment. Slow base(NaOH) injection into supersaturated aluminum chloride and aluminum sulfate solutions did produce high yields of Al polymers useful to water treatment applications. The method of characterization analysis was based on timed spectrophotometer with ferron as a color developing reagent. The hydrolytic Al species were divided into $monomeric(Al_a),\;polymeric(Al_b),\;and\;precipitate(Al_c)$ from the difference in reaction kinetics. The analysis of PACl's characteristics showed that the quantity of polymeric Al produced at value of$ r(OH_{added}/AI)=2.2$ was $83\%$ of the total aluminum in solution, as showing maximum contents and precipitated Al was dramatically increased when r was increased above 2.35. In addition, the characteristics of polyaluminum sulfate (PAS) showed that polymeric Al contained at r = 0.75 was $18\%$ of the total aluminum in solution. The synthesized PACI and PAS were stable during storing period, as indicating negligible aging effect. The effect of sulfate ion on PACI was dependent on the concentration of sulfate ion. That is, polymeric species decrease and precipitate species increase as sulfate ion concentration increased. It can be concluded that the sulfate cause the formation of $Al(OH)_{3(S)}$ at low pH. However, The effect of calcium ion was negligible for distribution of Al species.

• International Journal of Human Ecology
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• v.16 no.2
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• pp.1-9
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• 2015

This study investigated the effects of persimmon-dyed clothing materials upon thermophysiological responses and subjective comfort sensations during exercise and rest in a warm environment. Six healthy, untrained women participated in two separate testing sessions, with cotton materials dyed with astringent persimmon extract (DC) and undyed cotton materials (UDC). The physical characteristics associated with heat and moisture transfer were improved in DC; also, stiffness, anti-drapery stiffness and crispness in the primary hand values were higher in DC. The experimental protocol consisted of a 10-min rest, 15-min exercise on a treadmill (at ${7km{\cdot}h^{-1}}$) and 25-min recovery at $28{\pm}0.2^{\circ}C$ and $50{\pm}3%\;RH$. The results were as follows: When wearing DC rather than UDC, mean body temperature, heart rate, heat storage and body mass loss were significantly lower during the whole experimental period. Clothing microclimate temperature showed different profiles between the two clothing materials, being lower with DC than UDC during the first half of exercise and the second half of recovery. Clothing microclimate humidity was significantly lower with DC than UDC during the whole experimental period. When wearing UDC, subjects felt significantly warmer and less comfortable during exercise, and sensed greater humidity during exercise and recovery. These results suggest that eco-friendly clothing materials dyed with astringent persimmon extract can reduce exercise-induced heat load and improve subjective sensations when exercising and resting in a warm environment, due to greater heat dissipation from the body to the outside environment compared with undyed clothing materials.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.135-149
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• 2017

The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value $f_{cc}$ (at zero eccentricity) to the unconfined value $f^{\prime}_c$ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of $P-{\varepsilon}$ and $M-{\varphi}$ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.41.2-41.2
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• 2016

The follow-up BVRI photometric observations of NSVS 1461538, which was discovered as an $Algol/{\beta}$ Lyr eclipsing variable by Hoffman, Harrison & McNamara (2009), were performed for three years from 2011 to 2013 by using the 61-cm telescope and CCD cameras of Sobaeksan Optical Astronomy Observatory (SOAO). New light curves have deep depths both of the primary and secondary eclipses, rounded shapes outside eclipses and a strong O'Connell effect, indicating that NSVS 1461538 is a typical W UMa close binary system rather than an $Algol/{\beta}$ Lyr type binary star. A period study with all the timings shows that the orbital period may vary in a sinusoidal way with a period of about 5.6 yr and a small semi-amplitude of about 0.008 d. The cyclical period variation was interpreted as a light-time effect due to a tertiary body with a minimum mass of $0.66M{\odot}$. The first photometric solution with the Wilson-Devinney binary model shows that the system is a W-subtype contact binary with the mass ratio ($q=m_c/m_h$) of 3.46, orbit inclination of 85.6 deg and fill-out factor of 30%. From the existing empirical relationship between parameters, the absolute dimension was estimated. The masses and radii of the component stars are $0.28M{\odot}$ and $0.71R{\odot}$ for the less massive but hotter primary star, respectively, and $0.96M{\odot}$ and $1.21R{\odot}$ for the more massive secondary, respectively. Possible evolution of the system is discussed in the mass-radius and the mass-luminosity planes.

• Proceedings of the KIEE Conference
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• 2003.07a
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• pp.283-286
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• 2003

The electric traction load is quite differ from general power system load which is single-phase, high-speed heavy load receiving power from 3-phase power system and also has variable load characteristics over time and space. Therefore, there are inevitably power quality problems such as steady state or transient voltage drop, voltage imbalance and harmonic distortion. In addition, it is expected that transient voltage sag could affect the safety of feeding system. Thus, in this paper transient analysis and voltage sag compensation of AT(Auto Transformer) feeding system are studied. The fault study of traction network is analysed by using PSCAD/SMTDC simulation tool. In addition, application of DVR in electric traction system is proposed to compensate the voltage sag of traction network which is occurred by the fault of utility source. The results of fault study will be a useful research works for operation and setting of electric traction relay. Also, it can be shown that application of the DVR in electric system is very useful to compensate the voltage sag from the result of related simulated work. The results of study will be a useful research works for management and planning of power quality in electric traction system.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.4
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• pp.229-234
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• 2017

In this study, we fabricated a TFT gas sensor with ZnO nanorods grown by hydrothermal synthesis. The suggested devices were compared with the conventional ZnO film-type TFTs in terms of the gas-response properties and the electrical transfer characteristics. The ZnO seed layer is formed by atomic-layer deposition (ALD), and the precursors for the nanorods are zinc nitrate hexahydrate ($Zn(NO_3)_2{\cdot}6H_2O$) and hexamethylenetetramine ($(CH_2)6N_4$). When 15 ppm of NO gas was supplied in a gas chamber at $150^{\circ}C$ to analyze the sensing capability of the suggested devices, the sensitivity (S) was 4.5, showing that the nanorod-type devices respond sensitively to the external environment. These results can be explained by X-ray photoelectron spectroscopy (XPS) analysis, which showed that the oxygen deficiency of ZnO nanorods is higher than that of ZnO film, and confirms that the ZnO nanorod-type TFTs are advantageous for the fabrication of high-performance gas sensors.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.9-12
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• 2019

We performed Raman spectroscopy on two different over-doped Bi₂Sr₂CaCu₂O_8+x (BSCCO), of which superconducting transition temperatures are 89 K and 77 K. Line-shape analysis of the Raman-spectrum was done, focused on B_1g bond buckling mode which have drawn a lot of attention, since photoemission studies showed an evidence for strong coupling between the mode and electron. The line-shapes show asymmetry and are well fitted by the Fano line-shape formula. Remarkably, we found that the peak line-widths from B_1g bond buckling mode in BSCCO show much broader than those in YBa₂Cu₃O_7-x. The broad line width can be attributed to the superstructure modulation of BSCCO. Our results imply that B_1g bond buckling mode may have close relation to the origin of superconductivity or to boosting the superconducting transition temperature in BSCCO.