• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.183-184
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• 2016

This study investigated the evolution of electro-mechanical impedance (EMI) of piezoelectricity (PZT) sensor embedded in hydrating steel fiber reinforced mortar to determine the setting times of that. Penetration resistance test was also conducted in order to justify the valid of EMI sensing technique. As a result, the setting times of steel fiber reinforced mortar can be effectively monitored through the EMI sensing technique using PZT sensor.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.7
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• pp.601-606
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• 2016

In this paper, an energy harvester is developed that has advantages regarding piezoelectric noise minimization, mass production, and an easily available environmental energy source, electromagnetic induction, as well as low-frequency bandwidth and high amplitude. A process for fabricating a three-dimensional multilayered planar coil using micro-electro-mechanical systems (MEMS) on a flexible printed circuit board FPCB is introduced. Optimal shape and size were calculated via internal resistance and inductance, and a prototype was fabricated through the MEMS procedure while considering the possibility of mass production. Although the internal resistance matched the designed value, the electromotive force generated did not reach the intended amount. The main reason for the decrease in efficiency was the low area of coil outskirt exposed to the magnetic field while there was relative motion between the magnet and the coil.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1210-1213
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• 2005

Micro heat flux sensor is used in various industries to measure heat flux. In this study, a micro heat flux sensor is fabricated using the MEMS (Micro Electro Mechanical Systems) techniques. The fabricated sensor is composed in thermopile for sensor and SU-8 for thermal resistance layer. The new method of fabrication SU-8 is proposed in this study. The sensitivity is $44\;\mu{V/(W/cm^2)}$ at steady state and Reynolds number is 91322.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.846-848
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• 2001

In this paper, electromagnetic fields of a linear induction motor with cage-type secondary are analyzed by the finite element method. Contact resistances between end-bars and secondary conductors are considered in the finite element analysis. The field quantify is a magnetic vector potential transformed into a phasor form. As a result, the sensitivities of a phase current thrust and normal force are presented according to the variation of the contact resistance.

• Solar Energy
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• v.9 no.2
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• pp.58-68
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• 1989

This paper describes an experimental study that was performed to determine the limiting factors on the power output in the closed cycle Electro-Hydro-Dynamic generator of small capacity. A corona discharge for producing unipolar charged particles used as the charging method. The experiment demonstrated that the corona method of charging was an efficient and effective means of producing unipolar charged particles. Four factors having an effect on the power output characteristics of EHD generator are discussed and examined experimentally, using methyl alcohol and kerosene as working fluides; a. The conversion length between attractor and collector. b. The corona current of Emitter. c. The flow velocity of working fluids. d. Load resistance. This results are as follows; 1) There in a critical value in conversion length for its maximum power output. 2) Power output increases almost linearly with corona current and flow velocity. 3) There is the critical value of load resistance producing a maximum power output. 4) Kerosene is known better working fluid than Methyl alcohol in this EHD generator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.537-540
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• 2001

This paper presents the characteristics of Ta-N thin-film for high precision resistors, which were deposited on Si substrate by DC reactive magnetron sputtering in an argon-nitrogen atmosphere(Ar-(4~16 %)$N_2$). Structural properties studied using X-ray diffraction(XRD) indicate the presence of TaN, $Ta_3N_5$ or a mixture of Ta-N phases in the films depending on the amount of nitrogen in the sputtering gas. The chemical composition are investigated by auger electro spectroscopy(AES). The optimized conditions of Ta-N thin-film resistors were deposited in 4 % $N_2$ gas flow ratio. Under optimum conditions, the Ta-N thin-film resistors are obtained a high resistivity, $\rho=305.7{\mu}{\Omega}cm$, a low temperature coefficient of resistance, TCR=-36 $ppm/^{\circ}C$.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.352-352
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• 2000

ESR(ElectroSlag Remelting) Process is secondary fine process and melts steels by electric resistance heat and fines the melting steels by an appropriate solidification process parameters which affects the melting and solidification processes to get the high quality products. This paper describes a method to derive the mathematical model and analysis the dynamic characteristics for designing a controller of the ESR processes. The ESR process consists of a melting and solidificating processes and electrical system include the contact resistance mechanism. In this paper, we consider only the static relationship between inputs and outputs of the electric system because the dynamics of the electric system is so fast compared with the melting and solidificating processes which are analysed by using finite difference method. As the results, the fine processing in ESR is analysed and the process controller could be designed based on the process dynamic analysis.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2788-2793
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• 2008

A numerical analysis has been conducted for flow characteristics and performance of a micropump with piezodisk and MHD(Magnetohydrodynamics) fluid. Various micro systems which could not be considered in the past have been recently growing with the development of MEMS(Micro Electro Mechanical System) and micro machining technology. Especially, micropumps, essential part of micro fluidic devices, are being lively studies by many researchers. In the present study, the piezo electric micropump with electromagnetic resistance for electrically conducting fluids is considered. The prescribed grid deformation method is used for the displacement of the membrane. The change of the performance of the micropump and flow characteristics of the electrically conducting fluid with the magnitude of the magnetic fields, duct size, the position of the inlet and outlet duct are investigated in the present study.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.537-540
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• 2001

This paper presents the characteristics of Ta-N thin-(ibm for high precision resistors, which were deposited oni substrate by DC reactive magnetorn sputtering in an argon-nitrogen atmosphere(Ar-(4∼16%)N$_2$). Sturcutural properties sutided using X-ray diffraction (XRD) indicate the presence of TaN, Ta$_3$N$\sub$5/ or a mixture of Ta-N phases in the films depending on the amount of nitrogen in the sputtering gas. The chemical composition are investigated by auger electro spectroscopy(AES). The optimized conditions of Ta-N thin-film resistors were deposited in 4 % N$_2$ gas flow ratio. Under optimum conditions, the Ta-N thin-film resistors are obtained a high resistivity, $\rho$=305.7 ${\mu}$Ωcm, a low temperature coefficient of resistance, TCR=-36 ppm/$^{\circ}C$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09a
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• pp.109-110
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• 2006

We have studied the effect of C/Ti atomic ratio of TiCx (x=0.5, 0.75 and 1.0) raw powder on the properties of the Ti-Mo-WTiC sintered hard alloy. The decrease of C/Ti atomic ratio accelerated the densification in the sintering process. The hardness was remarkably improved up to 1350HV with decreasing the C/Ti atomic ratio because of increase of TiCx phase volume content and its fine dispersion. From the results of electro-chemical tests in acid and 3% NaCl solutions, it was obvious that every alloy had excellent corrosion resistance, which meant about 200 times better than that of WC-Co cemented carbide.