• Journal of Powder Materials
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• v.2 no.3
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• pp.223-230
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• 1995

The effects of Mn and Co additions up to 0.6 and 2.0 wt% respectively and the amount of cold-rolled reduction on the thermal expansion coefficient (TEC) of powder rolled Fe-Ni Invar strips were investigated. The compacted strips were sintered, homogenized and cold-rolled to the final thickness of 0.8 mm, 0.65 mm and 0.4 mm. All the strips reached full density except the case of 0.8 mm sample which has a very few porosities. The interstitials which are well known to increase TEC were minimized to the level of 10 rpm C,5 and N,0 by the processing. TEC was found to decrease by increasing the cold reduction. The Mn content had little effect on the TEC. But in Fe-Ni-Co system, TEC decreased with Co content up to 0.4 wt% and then increased, yielding the minimum value of $0.2 {\times} 10-6/^{\circ}C$ at 0.4 wt% Co. This value is much lower than that of commercial Invar product. Such effect of Co is considered to be related with the maxiumum spontaneous- magnetostriction effect.

• Bulletin of the Korean Chemical Society
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• v.32 no.5
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• pp.1604-1612
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• 2011

We developed three-dimensional quantitative structure activity relationship (3D-QASR) models for 17 adamantyl derivatives as P-glycoprotein (P-gp) inhibitors. Eighteen different partial charge calculation methods were tested to check the feasibility of the 3D-QSAR models. Best predictive comparative molecular field analysis (CoMFA) model was obtained with the Austin Model 1-Bond Charge Correction (AM1-BCC) atomic charge. The 3D-QSAR models were derived with CoMFA and comparative molecular similarity indices analysis (CoMSIA). The final CoMFA model ($q^2$ = 0.764, $r^2$ = 0.988) was calculated with an AM1-BCC charge and electrostatic parameter, whereas the CoMSIA model ($q^2$ = 0.655, $r^2$ = 0.964) was derived with an AM1-BCC charge and combined steric, electrostatic, hydrophobic and HB-acceptor parameters. Leave-five-out (LFO) cross-validation was also performed, which yielded good correlation coefficient for both CoMFA (0.801) and CoMSIA (0.656) models. Robustness of the developed models was checked further with 1000 run bootstrapping analyses, which gave an acceptable correlation coefficient for CoMFA (BS-$r^2$ = 0.997, BS-SD = 0.003) and CoMSIA (BS-$r^2$ = 0.996, BS-SD = 0.018).

• Journal of Environmental Policy
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• v.6 no.4
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• pp.55-81
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• 2007

Most studies on $CO_2$ abatement cost with a computational general equilibrium(CGE) model focus on a specific country. On the contrary, this study compares and analyses the $CO_2$ abatement cost functions across 20 countries, consisting of OECD countries, China and Brazil, with a CGE model. For this purpose, we estimate the GDP loss from $CO_2$ emission reduction, assuming the 4 sector model. Our findings show that those cost curves are convex but different among the countries. However, despite of the difference in the cost curios, we have found that one group of countries has the relatively constant average abatement cost and the other group has the increasing average cost. The reason why such a pattern occurs is explained in terms of the variations of value-added and $Co_2$ emission coefficient by sector across the countries. As an environmental policy implication, this study presents information about which country is similar to one another in terms of the abatement cost.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.11
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• pp.1186-1191
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• 2004

ZnO varistor ceramics which were fabricated with variation of added of 0.5～1.0 mol% Co$_3$O$_4$, were sintered at 1150 $^{\circ}C$. In the specimen added 0.7 mol% Co$_3$O$_4$, sintered density was 6.03 g/㎤ and electrical properties were superior to any other compositions. The nonlinear coefficient a and clamping voltage ratio were 83 and 1.35, respectively. But, endurance surge current in the specimen added 0.5 mol% Co$_3$O$_4$ was 7000 A/$\textrm{cm}^2$, and deviation of varistor voltage was Δ-3.23 %. As P.C.T and T.C.T environmental test were succeed in all specimens, and deviation of varistor voltage in the specimen added 0.6 mol% Co$_3$O$_4$ was Δ-0.81 %. All specimens showed good leakage current property on the High Temperature Continuous Load Test(HTCLT) for 1000 hr at 85 $^{\circ}C$ and variation rate of the varistor voltage below Δ-2.0 %.

• Electrical & Electronic Materials
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• v.16 no.1
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• pp.63.2-63
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• 2003

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.246-247
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• 2005

The paper presents the heat transfer characteristics during cooling process of carbon dioxide($CO_2$) in a helically coiled tube. The main components of the apparatus consist of a receiver, a variable speed pump, a mass flowmeter, a pre-heater, a gas cooler(test section) and an isothermal tank. The test section with the inner diameter 4.55 [mm] is a tube in tube type heat exchanger with refrigerant flowing in the inner tube and water flowing in the annulus. The main results were summarized as follows : The heat transfer coefficient increases with respect to the decrease of the gas cooler pressure in a supercritical region and the increase of the refrigerant mass flux. The pressure drop decreases in increases of the gas cooler pressure and increases with respect to increases the refrigerant mass flux.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.149-157
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• 2014

In this paper, we investigated the sensitivity of aerostatic force coefficients of multi-layer radom in the various wind speeds. The test was conducted in KOCED Wind Tunnel Center in Chonbuk National University, and wind speeds were in the range from 5 m/s to 26 m/s in order to determine the Reynolds number independence. The test results of present multi-layer radom were not affected by the Reynolds number, The maximum positive pressure coefficient was found to be 1.08 at the center of the front of the plane in angle of attack of 0 degree, the maximum negative pressure coefficient was -2.03 at the upper right corner in angle of attack of 120 degree, while maximum drag coefficient was 1.11 in angle of attack of 180 degree.

• Journal of the Korean Chemical Society
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• v.41 no.8
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• pp.385-391
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• 1997

Diffusion Coefficient$(D_0)$ and electrode reaction rate Constant$(K_0)$ of Co$(dimethyl bipyridine)_3(ClO_4)_2$ were determined by cyclic voltammetry and chronoamperometry. It was also investigated that the effects of solvent, concentration, and scan rate, etc. on the diffusion coefficient and the temperature effect on the rate constant. The peak currents and diffusion coefficients were dcreased as increasing the viscosity of solvent. Diffusion coefficient was $5.54{\times}10^{-6 }cm^2/sec$ and the reaction rate constant was $2.39{\times}10^{-3 }/s$ at 25$^{\circ}C$. The thermodynamic parameters such as ${\Delta}G^{\neq},\;{\Delta}H^{\neq},\;and\;{\Delta}S$ were calculated from plotting the reaction rate constants versus the solution temperatures. This compound was shown the catalytic effect on the oxygen reduction that the reduction peak current of oxygen was greatly enhanced and the peak potential was shifted to +0.2 volt.

• Bulletin of the Korean Chemical Society
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• v.23 no.3
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• pp.417-422
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• 2002

Comparison studies of the Quantitative Structure Activity Relationship (QSAR) methods with new imidazo-quinolinedione derivatives were conducted using Comparative Molecular Field Analysis (CoMFA), Comparative Molecular Similarity Indices Analysis (CoMSIA), and the Hologram Quantitative Structure Activity Relationship (HQSAR). When the CoMFA crossvalidation value, q2, was 0.625, the Pearson correlation coefficient, r2, was 0.973. In CoMSIA, q2 was 0.52 and r2 was 0.979. In the HQSAR, q2 was 0.501 and r2 was 0.924. The best result was obtained using the CoMSIA method according to a comparison of the calculated values with the real in vitro cytotoxic activities against human ovarian cancer cell lines.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.9
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• pp.942-946
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• 2004

The crystalline and dielectric properties on Al$_2$O$_3$ filled glass frit (CaO-Al$_2$O$_3$-SiO$_2$-MgO-B$_2$O$_3$) with admixtures of TiO$_2$ have been investigated. The dielectric constant value of 7.5 ∼ 7.8, qualify factor value of 700 were obtained for glass frit : Al$_2$O$_3$(50 : 50 wt%) ceramics. Addition of TiO$_2$ less than 5 wt% slightly increased the dielectric constant from 7.8 to 8.8 due to higher dielectric constant of TiO$_2$. With increasing the amount of TiO$_2$ up to 5 wt%, the temperature coefficient of dielectric properties was improved. When the TiO$_2$ 5 wt% were added, dielectric properties were dielectric constant 8.8, quality factor 840 and the temperature coefficient of dielectric 45 ppm/$^{\circ}C$ at a sintering temperature 920$^{\circ}C$.