• Journal of the Korean Ceramic Society
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• v.40 no.10
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• pp.954-960
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• 2003

To develop mobile phone antenna modules, glass-ceramics composites that are 20∼80 dielectric constant materials which has been fabricated. The glass-ceramics composites were based in the BNT (BaO-Nd$_2$O$_3$-TiO$_2$), and properties-a sintering and dielectric property-were investigated in its composites according to the $K_2$O-CaO-P$_2$O$_{5}$ system glass frits. The prepared ceramics were sintered at 900∼120$0^{\circ}C$ with the glass frit contents ranging from 10 to 40 wt%. The shrinkage and relative density grew into increasing glass frits and sintering temperature. Sintered composites showed the tendency that the dielectric constant ($\varepsilon$$_{r}$) and quality factor (Q${\times}$f) decreased in increasing glass frits and sintering temperature.

• Journal of the Korean Electrochemical Society
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• v.2 no.1
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• pp.5-12
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• 1999

By the PVA-precursor method, polycrystalline powder of $Li_xNi_{1-y}Co_yO_2$, cathode material for lithium battery, was synthesized. Using the powder as the cathode material, lithium ion batteries were fabricated, whose electrochemical properties were measured. The effect of changing synthetic conditions, such as PvA/metal mole ratio, concentration of PVA, degree of polymerization of PVA, pyrolysis condition, and metal stoichiometry, on the battery performance was investigated. Considering the initial performance of the cell, the optimum stoichiometry of the $Li_xNi_{1-y}Co_yO_2$, synthesized by the PVA-precursor method was observed to be x: 1.0 and y=0.26. A minor phase of $Li_2CO_3$, which was generated by the residual carbon in the powder precursor, deteriorated the performance of the cell. In order to eliminate the minor phase, the precursor had to be pyrolyzed under the flow of dry air. Annealing the powder at $500^{\circ}C$ under the flow of dry air also eliminated the minor phase, and the performance of the cell was largely improved by the treatment.

• Journal of the Korean Magnetics Society
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• v.22 no.3
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• pp.109-115
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• 2012

NeFeB anisotropy bonded magnet has proposed a new paradigm of weight reduction of small motors by replacing the conventional ferrite permanent magnets with its high magnetic property of 25 MGOe during last five years. It has also advanced by leaps and bounds in the field of motor industry for automobiles and electric power tools. And it has led a new innovation of fifty percent weight lightening compared to its current motors by correctly focusing on fuel performance improvement through weight lightening that automobile industry chased. There was, however, another price skyrocketing in 2011 after China had announced its export regulation in rare earth materials in July, 2010. And this price change has an extensive impact on the industries that consume rare earth magnets. This environmental change has caused technical challenge to improve the performance by using least amount of rare earth elements in NdFeB anisotropy bonded magnets, and led to make a new technical approach to a new applied field. In this article, we will show how each nation deals with this industrial issue, and introduce development trend and application of anisotropic NdFeB bonded magnets, so-called MAGFINE made by Aichi Steel Corp.

• Korean Journal of Acupuncture
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• v.22 no.4
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• pp.57-65
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• 2005

Objectives : Circium japonicum is a pharmacologically active used in traditional Korean medicine. An aqua-acupuncture solution of the Circium japonicum was assessed to determine the mechanism of its antioxidant activity. Materials : Circium japonicum was obtained from a Dongguk Korean Medicine Hospital (Kyung-ju, Kyungbuk). The freeze-dry powder was collected (yield 5.1%) for the aqua-acupuncture solution. Scavenging activity on DPPH free radicals by the Circium japonicum aqua-acupuncture solution (CJAS) was assessed according to the method followed by Gyamfi et al.. and then scavenging activity orl superoxide radicals $(O_2^-{\cdot})$ was assessed by the method described by Gotoh et al. with slight modification. Deoxyribose assay to determine the rate constant for the reactions between either antioxidants and hydroxyl radicals or antioxidants and iron ions. We tested by; (1) Non-site-specific scavenging assay (hydroxyl radicals, OH), (2) Site-specific scavenging assay (chelate iron ions), and (3) Pro-oxidant effect of the CJAS on iron dependent hydroxyl radical generation. Finally, we determined hydroxyl radical-mediated DNA nicking formation. Conclusion : Our study demonstrated that CJAS has antioxidant activities and we investigated the potential effectiveness of CJAS in preventing oxidative stress-mediated disease further.

• Journal of the Korean Wood Science and Technology
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• v.41 no.4
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• pp.318-326
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• 2013

The effect of finger joint location and distance from joint to joint one another on 3 point mid-concentration bending strength properties was investigated in this experiment. Resorcinol-phenol formaldehyde (RPF) and aqueous vinyl urethane (AVU) was used to domestic Pinus densiflora Sieb. et Zucc and imported Picea sitchensis Carr. that have been cut to different width of 0.15 mm between finger tip and root width and the distance from loading point to finger joint was 0, 30, 40, 50, 60 mm. The effect was not found on the location and distance of finger joint for bending modulus of elasticity, while the efficiency of bending strength property increased proportionally as the location of finger joint from the load point and the distance between finger joint increased. No influence was shown by finger joint location and distance beyond 3 times of specimen thickness, since similar values were shown between the solid wood and no destruction occurred materials.

• Fire Science and Engineering
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• v.29 no.2
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• pp.79-83
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• 2015

The fire accident is a representative type of disaster that can largely impact on business. Therefore, precautionary measures and rapid initial response is very important when a disaster occurs. The storage of porous combustibles is inevitable in coal yard, plywood processing industry, and others that are currently operating. Initial fire fighting of fire and identifying the ignition point in such a porous combustible storage space are so difficult that if the initial response is failed, being led to deep-seated fire, surface fire is likely to result in secondary damage. In addition, deep-seated fire can cause personal injuries and property damage due to a large amount of toxic gases and reignition. Therefore damage reduction measures is required around the storage space to handle a porous flammable. Improving the penetration performance of the concentration of the surfactant is carried out as underlying study, which is about an deep-seated fire extinguishing efficiency augmentation when using wetting agents. The porous materials used in the experiments is radiata pine wood flour, which occupies more than 75% of the domestic wood market. Fire fighting water is selected as Butyl Di Glycol (BDG), which is being used for infiltration extinguishing agent, and the experiment was carried out by producing a standard solution. The experiment was carried out on the basis of the Deep-Seated Fire Test of NFPA 18. The amount of watering, porous material to the internal amount of penetration, and runoff measurement out of the porous material was conducted. According to experimental results, as the surface tension is reduced, the surfactant concentration macroscopic penetration rate decreases, but infiltration to a porous material is shown to have growth characteristics.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.6
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• pp.397-405
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• 2012

In this study, performance evaluation of newly developed technology for the economical and safe removal of volatile organic compounds (VOCs) coming out from electronic devices washing operation and offensive odor induction materials was made. Metal oxidization catalyst has shown 50% of removal efficiency at the temperature of $220^{\circ}C$. Composite metal oxidization catalyst applied in this study has shown that the actual catalysis has started at the temperature of $100^{\circ}C$. Comprehensive analysis on the catalyst property using Mn-Cu metal oxidization catalyst in the pilot-scale unit was made and the removal efficiency was variable with temperature and space velocity. Full-scale unit developed based on the pilot-scale unit operation has shown 95% of removal efficiency at the temperature of $160^{\circ}C$. Optimum elimination effective rates for the space velocity was found to be $6,000hr^{-1}$. The most appropriate processing treatment range for the inflow concentration of VOCs was between 200 ppm to 4,000 ppm. Catalyst control temperature showed high destruction efficiency at $150{\sim}200^{\circ}C$ degrees Celsius in 90~99%. External heat source was not necessary due to the self-heat reaction incase of VOCs inflow concentration is more than 1,000 ppm. Equipment and fuel costs compared to the conventional RTO/RCO method can be reduced by 50% and 75% respectively. And it was checked when there was poisoning for sulfide and acid gas.

• Composites Research
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• v.28 no.6
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• pp.356-360
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• 2015

In this paper, the carbon fiber reinforced plastic is processed as the double cantilever beam in order to estimate the fracture behavior of composite and is carried out with the static analysis as the mode I. The specimen sizes are 25 mm, 30 mm, 35 mm and 40 mm. And the material property is used with carbon. As the analysis result of mode I, the adhesive part is detached latest by the small force at the specimen thickness of 25 mm. The largest force is happened at the specimen thickness of 40 mm. The defection of the adhesive interface is shown slowest at the displacement of 9.75 mm at the specimen thickness of 25 mm. And the defection is shown quickest at the displacement of 7.82 mm at the specimen thickness of 40 mm. This defection is due to the fracture of specimen. The result of this study on the defection of the adhesive interface and the reaction force due to this defection is thought to be contributed to the safe structural design of the carbon fiber reinforced plastic.

• Journal of the Korea Concrete Institute
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• v.24 no.3
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• pp.315-322
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• 2012

Alkali-activated slag (AAS) is the most obvious alternative materials that can replace OPC. But, AAS industrial usage as a structural material should be evaluated for its durability. Carbonation resistance is one of the most important factors in durability evaluation. Test results for 18 slag-based mortars activated by sodium silicate and 6 OPC mortars were obtained in this study to verify the carbonation property. Main variables considered in the study were flow, compressive strength before and after carbonation, and carbonation depth. Mineralogical and micro-structural analysis of OPC and AAS specimens prior to and after carbonation was conducted using XRD, TGA, FTIR FE-SEM. Test results showed that CHS was major hydration products of AAS and, unlike OPC, no other hydration products were found. After carbonation, CSH of hydration product in AAS turned into an amorphous silica gel, and alumina compounds was not detected. From the analysis of the results, it was estimated that the micro-structures of CSH in AAS easily collapsed during carbonation. Also, the results showed that this collapse of chemical chain of CSH lowered the compressive strength of concrete after carbonation. By increasing the dosage of activators, carbonation resistance and compressive strength were effectively improved.

• Journal of the Korea Concrete Institute
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• v.24 no.2
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• pp.137-145
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• 2012

Strength model for blasted furnace slag mortar blended with sodium was investigated in this study. The main parameters of AAS (alkali activated slag) mortar were dosage of alkali activator, water to binder ratio (W/B), and aggregate to binder ratio (A/B). For evaluating the property related to the dosage of alkali activator, sodium carbonate ($Na_2CO_3$) of 4~8% was added to 4% dosage of sodium hydroxide (NaOH). W/B and A/B was varied 0.45~0.60 and 2.05~2.85, respectively. An alkali quality coefficient combining the amounts of main compositions of source materials and sodium oxide ($Na_2O$) in sodium hydroxide and sodium carbonate is proposed to assess the compressive strength of alkali activated mortars. Test results clearly showed that the compressive strength development of alkali-activated mortars were significantly dependent on the proposed alkali quality coefficient. Compressive strength development of AAS mortars were also estimated using the formula specified in the previous study, which was calibrated using the collected database. Predictions from the simplified equations showed good agreements with the test results.