• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.72-81
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• 2018

In this study, the sinusoidal-wave driving method, six-step driving method, and twelve-step driving method, which can be used in an inverter for permanent-magnet synchronous motors, were simulated, and the results were compared to review their operating performance. These driving methods were classified according to the electrical conduction angle and phase current of the motor. Conventionally, only the transition control technique between the sinusoidal-wave driving method and six-step driving method was studied for the efficiency of the inverter. In this paper, however, comparative analysis was focused on a variety of transition control applications to use the advantages of each driving method. For this purpose, computer simulations for these driving methods were carried out to obtain the motor torque, speed control characteristics, and THD of the motor phase currents. As a result, the sinusoidal-wave driving method showed the best performance in all respects. The six-step driving method has better speed control characteristics than the twelve-step driving method, and the twelve-step driving method has a lower THD of the motor phase currents than the six-step driving method.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.11
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• pp.23-30
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• 2017

Most superconducting magnets which generate more than 20 T consist of nested magnets. A combination of LTS and HTS magnets is conventionally used, but high field magnets which use only HTS magnets have been developed recently. As HTS wires have very strong magnetic anisotropy, appropriate techniques should be used to consider this effect properly. The load line method has been conventionally used to design nested magnets for high field generation. Because this method considers only parallel and perpendicular magnetic fields, the effect of their orientation is not taken into account. In this paper, the actual orientation of the magnetic fields from 0 to 90 degrees is considered. The critical currents of the two kinds of high field nested magnets designed using the proposed method are calculated. The finite element method is used to calculate the distribution of the magnetic fields and the evolution strategy is used to find the critical current which maximizes the central magnetic field.

• Journal of Nutrition and Health
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• v.43 no.6
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• pp.570-577
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• 2010

Water gets magnetically charged when it is contacted with a magnet. Although magnetic water products have been promoted since the 1930's, they have received very little recognition due to questionable effectiveness. Diethylnitrosamine (DEN) is a widely occurring nitrosamine that is one of the most important environmental carcinogens primarily inducing tumors of liver. In this study, the effect of magnetized water supplementation on lymphocyte DNA damage in ICR mice treated with DEN was evaluated using the Comet assay. Mice were divided into 3 groups: control, DEN, and DEN + magnetized water group. Fifteen mice were maintained in each group for the entire experimental period of 6, 12 and 18 weeks. Five mice in each group were sacrificed at 6, 12, and 18th weeks, followed by the Comet assay using the blood obtained from heart puncture of the mice. The level of lymphocyte DNA damage reflected by tail moment and other DNA damage indices of tail DNA (%) or tail length of the magnetized water group were significantly decreased after the 6th, 12th and 18th weeks of supplementation compared with the positive control, the DEN group. The relative DNA damage of the magnetized water groups compared to the DEN control group after 6th, 12th, and 18th weeks of supplementation were 42.2%, 40.8%, and 32.9% for DNA in tail, 31.2%, 32.6%, and 21.3% for tail length, and 33.8%, 33.8%, and 24.6% for tail moment, respectively. This is the first report demonstrating that magnetized water may be involved in the lowering effect of the DNA damage in DEN-treated ICR mice. This result suggests that the magnetized water might have minimized the DNA damage by improving the antioxidant status of the mice. However, further studies are needed to characterize the condition of the magnetization and examine the long-term effect of the water product.

• Resources Recycling
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• v.23 no.2
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• pp.3-16
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• 2014

Car exhaust $CO_2$ gas reduction and fuel efficiency of the car lighter for the current era is a big challenge. The developments of high-performance Nd magnets, Li-ion secondary battery and exhaust gas purification performance of PGM catalysts used in the lightweight EV and HEV are activated. Country in order to improve the car lighter and function that use the resources of rare metals are ubiquitous imported from China because of export supply control, as soaring prices have unstable supply and demand. Compared to the emissions from the next-generation automotive recycling, waste scarce resources need to be. This study investigated the recycling technology analysis and development of the information technology, or delivered to the researchers by giving national car industry aims to contribute to the development. Findings, pulmonary high-performance motor vehicle emissions in the exhaust gas purification PGM Catalysts, Li-ion battery and Nd magnets recycling technology, such as pre- and post-processing techniques to classify technology, pre-urban mining technology mechanical separation by screening techniques under development, the study and post-processing technology has, pyro and hydro metallurgical smelting technology is established. Waste Recycling in terms of economic efficiency of mechanical components for the intensive study of screening techniques is needed.

• Journal of the Korean Society for Railway
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• v.13 no.1
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• pp.58-64
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• 2010

As a modem urban train is getting complex in terms of high-technology in its systems and components, the failure management should be performed with scientific and systematic technique. FMEA is a technique to analyze the failure trends of component parts and influences to the higher level system in order to discover the design incompleteness and potential defects, which is for improving reliability. Especially, FMECA (Failure Mode Effects, and Criticality Analysis) is used in case that the criticality that has an immense influence to the system is important. In case of urban train, in its design and manufacturing steps, FMEA is frequently used as an analysis technique to meet the safety objectives and eliminate potential hazards/failures since the concepts of reliability of train is introduced these days. Though, FMEA technique in the maintenances steps lacks in its investigation and applications yet. FMEA is also not applied to the trains operated by Seoul metro in the design and manufacture steps excepts the newest trains. In this paper, through analyzing the failures/maintenance data of the belt-type door systems used in trains operated in Seoul metro Line 1, which is accumulated in RIMS (Rolling-stock Information Maintenance System), FMEA procedures to the belt-type door engines are proposed. Especially, an effort is made, to approach the detailed FMECA procedures to the door magnet valve and switch and door engine devices which vastly influences the customer safety and satisfaction.

• Journal of the Korean Magnetics Society
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• v.14 no.5
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• pp.196-200
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• 2004

In order to improve dendritic formation of Nd$_2$Fe$\_$14/B phase in the strip-cast Nd-Fe-B alloys that are frequently used for production of high energy sintered magnets, effect of small substitutional additives such as Cu (0.3～1.0 at. %) and Co (0.5～1.5 at.%) on the phase formation and microstructures of the strip-cast alloys based on Nd$\_$14/Fe$\_$80/B$\_$6/ were investigated. As the amount of Cu addition increased, formation of Nd$_2$Fe$\_$14/B dendrites along the direction normal to the strip surface was suppressed with the reduction of the strip thickness mainly due to the increase of fluidity of the melt. However, both the dendrites and their <001> preferred orientation along the direction normal to the strip surface were improved with the increase of the strip thickness as the amount of Co addition increased. The dendrites became finer after small amount of Cu or Co was added. While small copper additions tended to stabilize the formation of primary Fe, small cobalt additions suppressed it. When small amount of Zr was added, however, the dendrite structures were totally collapsed with excessive grain growth of Nd$_2$Fe$\_$14/B.

• Journal of the Korean Magnetics Society
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• v.21 no.3
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• pp.116-119
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• 2011

A Chinese shipping boat collided with two Japanese coast guard boats in waters near the disputed Senkaku islands (known as Diaoyudao in China) in the East China Sea on September 7th last year. The boat was held and captain was arrested by Japanese Government. The incident soon turned into a big political and economic conflict between the two countries. Japan's intention was to show her tight control over Senkaku, whereas China's intention was to make it a disputed territory in the eyes of international politics. While the conflict was going on, a top-rank bilateral talk between the two countries was suspended, boycott of Japanese goods was suggested, numerous rallies were held in both countries. This situation lasted for several months until China used an extreme card of "Cutting Supply of Rare Earth to Japan". Under this pressure, Japan instantly released the captain and closed the case. Over this incident, public noticed the importance of rare earth and its impact on the global economy. Since then, the policy of Chinese Government for the rare earth has created more confusion and turmoil in the global market. The purpose of this article is to overview the price rally and future of the rare earth.

• Journal of the Korean Magnetics Society
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• v.19 no.2
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• pp.52-56
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• 2009

Interlayer coupling field, coercivity, magnetoresitance ratio, and magnetic sensitivity depending on the thickness of free CoFe layer for the CoFe/Cu/CoFe/IrMn multilayer are investigated. In case of CoFe layer of $30\;{\AA}$ thickness for the CoFe(t)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)/IrMn($80\;{\AA}$) multilayer with ferromagnet/non-magnet/ferromagnet structure induced by IrMn layer, the lowest coercivity and the highest magnetic sensitivity, which is contained soft magnetic property, are observed. On the other side, in case of CoFe layer of $90\;{\AA}$ thickness, there are the highest coercivity and the lowest magnetic sensitivity. The fabricated CoFe($30\;{\AA}$)/Cu($25\;{\AA}$)/CoFe($60\;{\AA}$)]/IrMn($80\;{\AA}$) spin valve device with $2{\times}8{\mu}m^2$ patterning size are measured by two probe method, which is selected the sensing current as the longitudinal direction and the easy axis as the transversal direction. The measuring magntoresistance ratio and magnetic sensitivity of GMR-SV device having the soft magnetic property are 3.0% and 0.3%/Oe, respectively.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.685-689
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• 2001

We carried out these experiments to examine the effects of element substitution of Co and La-Co for Sr-ferrite. The calcined properties of Co and La-Co element substitution were examined, and also the sintered magnetic properties were measured with the stoichiometric condition. The magnetic properties of $(La-Co)_{0.3}-SrM$ composition are as follows; $(M_s)$: 71.08 emu/g, $iH_c$: 4.38 kOe and $B_r$ : 4.18 kG, $iH_ c$ :4.35 kOe, $BH_{max}$: 4.3 MGOe. The $BH_{max}$ value was increased up to 10 % compared with conventional values. Our results imply that the magnetic properties of Sr-ferrite can be improved by the substitution of those elements.

• KIEAE Journal
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• v.17 no.1
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• pp.63-68
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• 2017

Purpose: Various studies to solve the problem of increased energy consumption in the buildings are being carried out recently. Especially, the economic feasibility and insulation performance of the air-cap have been verified so that various studies regarding the reduction of building energy consumption have been carried out. However, previous studies regarding the air-cap were only carried out based on the verification of its insulation performance according to the size and attachment position of the air-cap. Therefore, the purpose of this study is to suggest a detachable air-cap module for improving the performance of the windows, evaluate the performance based on cooling, heating and light environments and verify its effectiveness through a real-scale testbed. Method: In this study, the energy saving performance in the circumstance where there is no attachment of an air-cap (Case 1), the circumstance where there is the attachment of air-cap on the glass surface of window (Case 2) and the circumstance where there is the attachment of an air-cap on the window frame (Case 3) were compared in order to verify the performance of the detachable air-cap module (Case 4), and the electricity consumption of cooling, heating and lighting equipment to maintain the appropriate indoor temperature and Illuminance for each case was calculated and utilized as indicators for the performance evaluation. Result: The result of this study is as follows. 1) In this study, the detachable air-cap module which was easily detachable through the principle of the magnet was suggested. 2) When Case 4 is applied, the electricity consumption of cooling and heating equipment can be reduced by 27.5%, 13.2% and 3.4% in comparison with Case 1, Case 2 and Case 3 respectively. 3) When the air-cap is applied to the window, the lighting energy consumption increases by 4 % in comparison to the non application of the air-cap, and this factor or aspect should be considered when applying the air-cap. 4) According to the performance evaluation result in consideration of cooling, heating and light environments, Case 4 demonstrates an energy saving ratio of 22.6%, 10.6% and 2.7% in comparison to Case 1, Case 2 and Case 3 respectively, indicating that it is effective for improving the performance of windows.