• Journal of the Korean Magnetics Society
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• v.2 no.3
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• pp.233-238
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• 1992

Melt-spun $Nd_{14}Fe_{76}Co_4B_6$ and $Nd_{10.5}Fe_{79}Co_2Zr_{1.5}B_7$ ribbons were prepared under an externally applied magnetic field. Magnetic properties in terms of anisotropy were evaluated by discussing the effect of textured structure of the ribbon samples as well as its powders. About 32 % increase in $(B{\cdot}H)_{max}$ and 18.8 % increase in $B_r$ were observed along the perpendicular direction of the ribbon plane which is more prominent for the Nd-Fe-Co-Zr-B than for the Nd-Fe-Co-B alloy. The enhancement of magnetic anisotropy was monitored by measuring the anisotropy constant of each alloy as a function of quenching rate of the ribbon. It was found that for the melt-spun ribbon quenched at slow rate(less than 7 m/s) the magnetic field effect was overwhelmed by the heat gradient effect through the ribbon thickness while the field effect was prominent at intermediate quenching rate (more than 7~11 m/s). The reproducible maximum energy product, $(B{\cdot}H)_{max}$=16.4 MGOe can be obtained from the Nd-Fe-Co-Zr-B alloy.

• Nuclear Engineering and Technology
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• v.18 no.3
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• pp.200-208
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• 1986

The loss of coolant accident based on a double-ended cold leg break is analyzed with the discharge coefficient (Ca) of 0.4. This analysis covers the whole transient period from the start of depressurization to the complete refilling of the core by using RELAP4/MOD6-EM and RELAP4/ MOD6-HOT CHANNEL for the system thermal-hydraulics and the fuel performance during the blowdown phase respectively, and RELAP4/MOD6-FLOOD and TOODEE2 during the reflood phase. A simple analytical method has been developed to account for the lower plenum filling by approximating steam-water countercurrent flows and superheated wall effects at the downcomer during the refill period. Based on the informations. at the time of EOB (end-of-bypass), the refill duration time and the initial reflooding temperature were estimated and compared with the results from the RELAP4/MOD6, resulting in a good agreement. In addition, some parametric studies on the EOB were performed. The form loss coefficient between upper head and upper downcomer was found to be sensitive to the occurrence of the spurious EOB. Appropriate form loss coefficients should be taken into account to avoid the flow oscillations at the downcomer. The analyses with the six and three volume core nodalizations, respectively, show much similar trends in the system thermal-hydraulic performance, but the former case is recommended to obtain good results.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.10
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• pp.694-701
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• 2012

The main purpose of this study is to evaluate of backwash system of hydrodynamic separator filter (HSF) with solar powered submerged pumps. It consists of a photovoltaic solar array, control electronics, battery, and two submersible pump powered by a 12 voltage DC motor. The laboratory scale study on treatable potential of micro particles using backwash HSF that was a combined with perlite filter cartridge and backwash nozzles. Since it was not easy to use actual storm water in the scaled-down hydraulic model investigations, it was necessary to reproduce ranges of particle sizes with synthetic materials. The synthesized storm runoff was made with water and addition of particles; ion exchange resin partices, silica gel particles, and commercial area manhole sediment particles. HSF was made of acryl resin with 250 mm of diameter filter chamber and overall height of 800 mm. Four case test were performed with different backwashing conditions and determined the SS removal efficiency with various surface loading rates. The operated range of surface loading rate was about 308~$1,250m^3/m^2/day$. It was found that SS removal efficiency of HSF using two submersible pumps improved by about 18% compared with HSF without backwash. Nonpoint control devices with solar water pumping systems would be useful for backwashing the filter in areas with not suppling electricity and reduce filter media exchange cost.

• Journal of Adhesion and Interface
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• v.13 no.3
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• pp.137-144
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• 2012

Chemical functionalization of carbon nanomaterials (CNMs) is generally carried out for increasing interfacial adhesion between filler and polymer matrix for CNM-polymer nanocomposites. The chemically functionalized CNTs can produce strong interfacial bonds with many polymers, allowing CNT based nanocomposites to possess high mechanical and functional properties. Hence, increased surface adhesion can be measured indirectly by observing increased mechanical properties. However, there is a more direct way to observe interfacial bonds between polymer and CNM by measuring piezoresistivity behavior so that we can imagine the behavior of CNM particles in polymer matrix under deflection. Fuctionalization of MWCNT and rGO was carried out by oxidization reaction of MWCNT and rGO with $H_2SO_4/HNO_3$ solution. Electrical resistivities of MWCNT-PMMA and rGO-PMMA composites were decreased after functionalization because of the destructive fuctionalization process. Meanwhile, piezoresistivities of functionalized CNM-PMMA composites showed more sensitive behavior under the same deflection as compared to pristine CNM-PMMA composites. Therefore, mobility of CNM in polymer matrix was found to be improved with chemical functionalization.

• Journal of Forest and Environmental Science
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• v.14 no.1
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• pp.1-13
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• 1998

In this paper, it has been discussed on the relation between the anatomical features of woods and the penetration of methyl methacrylate monomer system into major Korean tree species, especially the Pinus koraiensis, Larix leptolepis, Quercus mongolica and Tilia amurensis. 1. There was some differences in penetration of polymers among different tree species, but generally the penetration of ring porous woods seems to be larger than that of diffuse porous woods and it was very difficult to penetrate to Larix leptolepis, especially to the that of heart wood. 2. The penetration on transeverse surface was relatively easy but radial and tangential impregnation were somewhat hard and differences between them were negligible. 3. The penetration of sapwood was larger than that of heartwood and its differences varied according to the existence of tyloses or contents in vessel. 4. Generally the polymer penetration of earlywood was larger than that of latewood in ring porous woods, but on the contrary, penetration of earlywood was small than that of latewood on diffuse porous woods. 5. Vessel diameter of wood had nearly no relation to polymers penetration. This seems to come from the reason that effective vessel diameter varies with the existence of tyloses or contents in vessel. 6. The penetration of ray tracheids was larger than that of ray parenchyma cells in softwoods, but penetration of hardwood rays seems to be small in comparison with softwood ray parenchyma cells. 7. Specific gravity and annual ring width had no relation to the penetration of polymer.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.95-102
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• 2012

In this study, practical verifications for an advanced C.I.P(Cast in Place Pile) construction method were carried out. The structural characteristics of the method is to attach an angular joint in the steel-casing. This joint plays an important role in boring vertically, connected pile to pile, and protects the permeation of the ground water. For verifications, experimental research and numerical analysis were performed. In the experimental research, two model-tests were set up with the real scale steel-casing. One is to examine the leakage in the joint of piles and the other is to compare earth pressures in the front and the joint, respectively. In addition, 3 point bending test and compressive loading test were carried out and numerical analysis was performed to simulate the loading test. As a result of model-tests, the leakage in the pile joints was not shown up to 300 KPa of water pressure and stress concentration in the joint is out of the question. From the results of bending and compressive test, it was found that the new advanced C.I.P method is more convenient and superior than the conventional method.

• Korean Chemical Engineering Research
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• v.48 no.5
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• pp.654-659
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• 2010

We have investigated the effect of rubrene-doped CuPc hole transport layer on the performance of p-i-n type bulk hetero-junction photovoltaic device with a structure of ITO/PEDOT:PSS/CuPc: rubrene/CuPc:C60(blending ratio 1:1)/C60/BCP/Al and have evaluated the current density-voltage(J-V) characteristics, short-circuit current($J_{sc}$), open-circuit voltage($V_{oc}$), fill factor(FF), and energy conversion efficiency(${\eta}_e$) of the device. By rubrene doping into CuPc hole transport layer, absorption intensity in absorption spectra decreased. However, the performance of p-i-n organic type bulk hetero-junction photovoltaic device fabricated with crystalline rubrene-doped CuPc was improved since rubrene shows higher bandgap and hole mobility compared to CuPc. Increased injection currents have effected on the performance improvement of the present device with energy conversion efficiency(${\eta}_e$) of 1.41%, which is still lower value compared to silicone solar cell and many efforts should be made to improve organic photovoltaic devices.

• Korean Journal of Food Science and Technology
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• v.45 no.5
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• pp.545-549
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• 2013

Liquid paraffin is a mixture of heavier alkanes derived from petroleum. It can be used as a lubricant in processing machinery, as a coating agent, or as a releasing agent. The purpose of this study was to analyze liquid paraffins in foods by using a gas chromatography-flame ionized detector (GC-FID). Liquid paraffin was extracted from the food samples using n-hexane. Non-polar aromatic or olefinic co-extractives were removed by alkaline permanganate oxidation followed by clean up on an aluminium oxide SPE cartridge before the GC-FID analysis. The results of recovery tests were 91.5-103.2%. Based on this optimized method, we investigated the amount of liquid paraffin in various food samples purchased from domestic markets. The levels of liquid paraffin in bread were $95.5{\pm}156.0$ mg/kg (0.008%), those in capsules were $40.2{\pm}54.5$ mg/kg (0.001%), and those in dried fruits and vegetables were $3.0{\pm}18.1$ mg/kg (0.0001%). No liquid paraffin was detected in fresh fruits and vegetables. We propose that our method can be used to monitor and detect liquid paraffin in foods for food safety management.

• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.802-807
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• 2012

The autothermal reforming of methane to syngas has been carried out in a reactor charged with both a Ni (15 wt%)-Ru (1 wt%)/$Al_2O_3$-MgO metallic monolith catalyst and an electrically-heated convertor (EHC). The standalone type reactor has a start-up time of less than 2 min with the reactant gas of $700^{\circ}C$ fed to the autothermal reactor. The $O_2/CH_4$ and $H_2O/CH_4$ ratio governed the methane conversion and temperature profile of reactor. The reactor temperature increased as the reaction shifted from endothermic to exothermic reaction with decreasing $H_2O/CH_4$ ratio. Also the amount of $CO_2$ in the products increases with increasing $H_2O/CH_4$ ratio due to water gas shift reaction. The 97% of $CH_4$ conversion was obtained and the reactor temperature was maintained $600^{\circ}C$ at the condition of $GHSV=10,000\;h^{-1}$ and feed ratio ($H_2O/CH_4=0.6$ and $O_2/CH_4=0.5$). In this condition, the maximum flow rate of the syngas generated from the reactor charged with 170 cc of the metallic monolith catalyst is $0.94\;Nm^3/h$.

• Journal of the Korean Chemical Society
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• v.38 no.11
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• pp.827-832
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• 1994

The crystal structure of bis(N-methylphenazinium) bis(oxalato)palladate(II) has been determined by X-ray crystallography. Crystal data: ((C_{13}H_{11}N_2)_2[Pd(C_2O_4)_2]) $M_w$ = 672.93, Triclinic, Space Group P1 (No = 2), a = 7.616(8), b = 9.842(3), c = $20.335(7)\AA$, $\alpha$ = 103.53(3), $\beta$ = 90.00(5), $\gamma$ = $112.38(5)^{\circ}$, Z = 2, $V = 1363(2){\AA}^3\;D_c = 1.639\;gcm^{-3},\;{\mu} = 7.3\;cm^{-1},\;F(000) = 680.0$. The intensity data were collected with $Mo-K\alpha$ radiation (${\lambda}$= 0.7107\;\AA)$ on an automatic four-circle diffractometer with a graphite monochromater. The structure was solved by Patterson method and refined by full matrix least-square methods using Killean & Lawrence weights. The final R and S values were $R = 0.069,\;R_w = 0.050,\;R_{all} = 0.069$ and S = 5.45 for 3120 observed reflections. Both cation and anion complexes are essentially planar and have dihedral angles of 6.3(6) and $57.06(6)^{\circ}$ between their planes. The planar complex anions are sandwiched between slightly bent cations. The interplanar separations of two triads are 3.328 and 3.463 $\AA$, respectively. The triads are stacked along b-axis, but their orientations are different based on dihedral angle $59.08(9)^{\circ}$ of two complex anions.