• Journal of the Korean Magnetics Society
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• v.12 no.6
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• pp.212-217
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• 2002

The pseudo spin valve with a structure of Tl/CoFe(t $\AA$)/Cu(30 $\AA$)/NiFe(50 $\AA$)/Ta, showing giant magnetoresistance properties by utilizing coercivity difference between only two soft ferromagnetic layers were produced by d.c UHV magnetron sputtering system. In pseudo spin valve Ta/CoFe/Cu/NiFe/Ta, the magnetic and magnetoresistance properties with change of CoFe thickness were investigated. When the thickness of CoFe was 60 $\AA$, a typical MR curve of pseudo spin valve structure was obtained, showing MR ratio of 3.8 cio and the coercivity difference of 27.4 Oe with a sharp change of hard layer switching. When the CoFe thickness was varied from 20 to 100 $\AA$, coercivity difference between two layers was increased to 40 $\AA$. and decreased to 100 $\AA$ gradually. It is thought the change in coercivity of hard layer was due to the crystallinity and magnetostriction of thin CoFe layer. In order to improve the MR property in CoFe/Cu/NiFe trier layer structure, CoFe layer with change of 2-20 $\AA$ thick was inserted between Cu and NiFe. When the thickness of CoFe was 10 $\AA$, MR ratio was 6.7％, showing excellent MR property. This indicates 50 ％ higher than that of CoFe/Cu/NiFe pseudo spin valve.

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.447-454
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• 2006

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.10
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• pp.16-26
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• 2014

This paper proposes new 13-level inverter topology and DC/DC converter buck-boost structure topology for multilevel, compounding uni-directional and bi-directional switches, and proposes high-efficient multilevel inverter system in which the proposed two PCS(Power Conditioning System) was connected in series. In proposed multilevel inverter of forming a output 13-level phase voltage by using total 18 switching parts, Then bi-directional switch has a characteristic of reducing conduction loss and controlling the reactive power effectively by separating electrically from the neutral point. DC/DC converter for supplying in dependent 3 DC voltage to the proposed multi-level inverter generates 180-degree phase shifted PWM by the symmetrically combined structure of 2 buck-boost converter and twice switching frequency efficiency can be obtained, meanwhile, the converter can step up/down the output voltage and 20% output can be generated comparing the input voltage. This proposed system is verified with the simulation and laboratory test.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.290-295
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• 2005

Hydraulic actuators are important in modern industry due to high power, fast response, and high stiffness. In recent years, hybrid actuation system, which combines electric and hydraulic technology in a compact unit, can be adapted to a wide variety of force, speed and torque requirements. Moreover, the hybrid actuation system has dealt with the energy consumption and noise problem existed in the conventional hydraulic system. Therefore, hybrid actuator has a wide range of application fields such as plastic injection-molding and metal forming technology, where force or pressure control is the most important technology. In this paper, the solution for force control of hybrid system is presented. However, some limitations still exist such as deterioration of the performance of transient response due to the variable environment stiffness. Therefore, intelligent switching control using Learning Vector Quantization Neural Network (LVQNN) is newly proposed in this paper in order to overcome these limitations. Experiments are carried out to evaluate the effectiveness of the proposed algorithm with large variation of stiffness of external environment. In addition, it is understood that the new system has energy saving effect even though it has almost the same response as that of valve controlled system.

• Journal of the Korean Magnetics Society
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• v.14 no.1
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• pp.25-28
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• 2004

The dependence of sensitivity, MR ratio, coercivity (Hc) and switching fields as a function of thickness of each magnetic layers(Co, NiFe and Cu) were investigated in pseudo spin valves with a structure of Ta/NiFe/Cu/Co. As measured results dependence of the thickness of each magnetic layer, we obtained MR ratio of 7.26% for Ta(4 nm)/NiFe(7.5 nm)/Cu(3 nm)/Co(5 nm) pseudo spin valves. Also, we could control properties of magnetoresistance for independent magnetization courses of each magnetic layer. Especially, we found that we could control coercivity as constant MR ratio dependence of Co thickness.

• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.98-103
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• 2013

The magnetic easy axis of the ferromagnetic layer for the dual-type GMR-SV (giant magnetoresistance-spin valve) having NiFe/Cu/NiFe/IrMn/NiFe/Cu/NiFe multuilayer structure controlled by the post annealing treatment. The magnetoresistive curves of a dual-type IrMn based GMR-SV depending on the direction of the magnetic easy axis of the free and the pinned layers are measured by the different angles for the applied fields. By investigating the switching process of magnetization for an arbitrary measuring direction, the optimum annealing temperature having a steady and isotropy magnetic sensitivity of 2.0 %/Oe was $105^{\circ}C$. This result suggests that the in-plane orthogonal magnetization for the dual-type GMR-SV film can be used by a high sensitive biosensor.

• Design & Manufacturing
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• v.2 no.5
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• pp.30-33
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• 2008

Injection Molding is the most effective process for mass production of plastic parts. The injection molding process is composed with several steps such as Filling, Packing, Holding, Cooling, Ejecting. Among them, filling and packing process should be considered carefully to improve accuracy of dimension, surface quality of plastic parts. Usually the quality above-mentioned is managed with weight of part after molding on the field. In this paper, a series of experiment for molding automotive front bumper was conducted with cavitity temperature sensor to optimize switch-over time(V-P switching), hot runner vale gate sequence time during filling and packing step for the purpose of uniform quality, weight at every molding. As a result, it was found that it is effective method to use temperature sensor in injection molding for quality control of plastic molding.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.794-795
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• 2011

The DC side voltage and current of a HVDC transmission system are directly affected by non-linear switching devices such as the thyristor valve which causes real power losses, even under the superconducting conditions of a high temperature superconducting (HTS) power cable. This paper deals with the development of miniaturized superconducting DC cable system. The authors designed and fabricated two thyristor converters for DC transmission system. One is operated as a rectifier and the other is an inverter. The HTS model cable was connected between the DC side of the rectifier and inverter. Real DC transport current and voltage were applied to the miniaturized HTS DC cable. Experimental results are discussed in detail.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.13 no.1
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• pp.66-71
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• 2001

In the air-conditioning industry, the refrigerant charging amount is one of the most important parameters affecting the energy efficiency ratio of heat pumps. An experimental study was performed on the characteristics of an inverter driven air-to-air heat pump system with a variation of compressor frequency and charging amount of refrigerant. The frequency was altered from 40Hz to 70Hz and the charging amount was changed from 1.6kg to 2.8kg in tests. The variation of performance was measured with switching of the expansion valve on each frequency and charging amount. All the tests were performed at the Korean Standard and test conditions of the air conditioners. As results, it was found that there existed the charging amount and the level of the suction gas superheat which provided the highest energy efficiency ratio at all the frequency bands.

• Journal of the Korean Society of Combustion
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• v.15 no.2
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• pp.27-33
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• 2010

Recently, much attention has been paid to utilizing highly preheated air up to $1,000^{\circ}C$ through waste gas in industrial furnaces. The regenerative burner technology has shown to provide significant reduction in energy consumption (up to 60%), downsizing of the equipment (about 30%) and lower emissions (about 30%) while maintaining high thermal performance of the system since 2000. The object of this study is to develop the flameless regenerative burner for industrial furnaces based on the FLOX(Flameless Oxidation) principle and it has been designed and manufactured as pilot scale. Performance tests are experimentally done and their results are discussed. They showed 1) a very good uniformity in temperature distribution, 2) about 100 ppm in NOx at the temperature $1,300^{\circ}C$, 3) about 95% in temperature efficiency. Besides, the regenerative burner has advantage in easy maintenance and high usage rate of regenerator due to the separate and portable type of heat exchanger.