• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.10
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• pp.1044-1051
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• 2003

In this paper, a compact planar microwave duplexer on the high dielectric substrate is presented. As the Ba(Mg$\sub$1/3/Ta$\sub$2/3/)O$_3$(BMT) has good dielectric performances with a high dielectric constant of $\varepsilon$$\sub$r/=23, it is suitable to apply to a printed circuit board fur reducing its circuit size. The BMT substrate is fabricated by using a tape casting fabrication process, and circuit patterns are screen-printed on it by suing silver paste. The open-loop ring type duplexer is designed and implemented on the BMT substrate, and it achieves the smaller size by 80% than one on a commercial substrate($\varepsilon$$\sub$r/=6.15) without degenerating its performance. Therefore the proposed BMT substrate has provided the miniaturization of the duplexer, moreover it can make a contribution towards reducing the size of microwave passive circuits.

• Progress in Superconductivity and Cryogenics
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• v.17 no.1
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• pp.10-13
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• 2015

High-temperature superconducting coated conductors (HTS-CCs) are good candidates for resistive superconducting fault current limiter (RSFCL) applications. However, the high current density they can carry and their low thermal diffusivity expose them to the risk of thermal instability. In order to find the best compromise between stability and cost, it is important to study the heat transfer between HTS-CCs and the liquid nitrogen ($LN_2$) bath. This paper presents an experimental method to monitor in real-time the temperature of a quenched HTS-CC during a current pulse. The current and the associated voltage are measured, giving a precise knowledge of the amount of energy dissipated in the tape. These values are compared with an adiabatic numerical thermal model which takes into account heat capacity temperature dependence of the stabilizer and substrate. The result is a precise estimation of the heat transfer to the liquid nitrogen bath at each time step. Measurements were taken on a bare tape and have been repeated using increasing $Kapton^{(R)}$ insulation layers. The different heat exchange regimes can be clearly identified. This experimental method enables us to characterize the recooling process after a quench. Finally, suggestions are done to reduce the temperature increase of the tape, at a rated current and given limitation time, using different thermal insulation thicknesses.

• 한국초전도학회:학술대회논문집
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• v.11
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• pp.60-60
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• 2001

• 한국초전도학회:학술대회논문집
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• v.12
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• pp.79-79
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• 2002

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.373-376
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• 2000

The modified Moonie(Cymbal) transducer has been investigated for an accelerometer application. This paper present a wind-mill type ultrasonic motors using ternary piezoelectric ceramics and aluminum endcaps applied by cymbal transducer. The maximum displacement was increased depend on applied voltage and layer number. The multi-layer was fabricated by tape casting using doctor-blade process. The maximum displacement of multi-layered ultrasonic motor was much higher than that of one-layered.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.7
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• pp.2213-2222
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• 1996

This paper presents the design process and evaluaation results of a two-axis force transducer for measuring flange reaction forces. A double-cantilever beam structure is used as a sensing element, and its optimal configuration is determined based on the derived strain equations to maximize the sensitivity and minimize the regid body displacements. To reduce the coupling errors between two-axis forces, strain distributions by finite elemetns analysis are utilized and the Wheaststone bridge cricuits composed of strain gages are built such that the output voltage should be zero, although strains of four strain gages are not zero. Calibration test shows that the two-azxis force transducer developed in this paper is useful in measuring flange reaction forces within the coupling error of 5.53%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.652-655
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• 2001

In this paper, I have studied minimization of the kerf-width and surface burning which are occurred after the singulation process of multi layer $\mu$-BGA( thickness 1.1 mm, 0.9 mm) with a pulsed Nd:YAG( = 532 nm, repetition rate = 10 Hz) laser. The thermal energy of a pulsed Nd:YAG laser is used to cut the copper layer. I have studied are minimization of the surface burning and kerf-width using a photo resist, $N_2$blowing and polyester double sided tape as a cutting parameter. The $N_2$blowing reduces a laser energy loss by debris and suppresses a surface carbonization. Also, I have studied characters of cutting with a choice of side of laser beam incidence. The SEM(Scanning Electron Microscope), non-contact 3D inspector and high-resolution microscope are used to measure kerf width and surface state. The optimum value of 1.1 mm $\mu$-BGA singulation is 524 $\mu$m that is reduced kerf width of 60 % with $N_2$blowing. And I obtained reduction of carbonization of 68 % with a polyester double side tape in 0.9 mm $\mu$-BGA. I used laser intensity of 1.91$\times$10$^{6}$ / $\textrm{cm}^2$ in this study.

• Proceedings of the KIEE Conference
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• 2001.07b
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• pp.714-716
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• 2001

This paper is about the characteristic analysis of a heater-trigger HTS switch. It is composed of a BSCCO tape wire and a heater as a thermal quench source. To minimize the heat flow to the liquid nitrigen, the epoxy was used around them. The heater-trigger switch operates in the process that the HTS tape is thermally quenched by the current flowing through the heater. Since the switch works in coolant, it needs to be designed by the accurate thermal characteristic analysis. Here, we focus on FEM for it.

• Journal of the Korean Ceramic Society
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• v.33 no.11
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• pp.1267-1275
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• 1996

Green sheet was prepared by tape casting in the composition of (1-x)Pb(Mg1/3Nb2/3)O3-PbTiO3 system using Pb(Mg1/3Nb2/3)O3 and PbTiO3 synthesized with PbO, Nb2O5 MgO and TiO2 The densest green sheet was obtained in the weight ratio 70:30 of powder to binder. Green sheet wasmultilayered in metal mould and formed into lamination at 7$0^{\circ}C$, 300kg/cm2 The lamination was sintered at 110$0^{\circ}C$ 2hr, Dielectric constant and Curie temperature of disc type sintered body was highered with increasing the amount of PbTiO3 and was in the range of 19000-21000, -7~45$^{\circ}C$ respectively. Green and sintered relative density of lamination was 61% and 95% respectively.

• Progress in Superconductivity and Cryogenics
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• v.16 no.4
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• pp.7-16
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• 2014

Rare-earth barium copper oxide (REBCO) coated conductor (CC) tapes have already been commercialized but still possess some issues in terms of manufacturing cost, anisotropic in-field performance, $I_c$ response to mechanical loads such as delamination, homogeneity of current transport property, and production length. Development on improving its performance properties to meet the needs in practical device applications is underway and simplification of the tape's architecture and manufacturing process are also being considered to enhance the performance-cost ratio. As compared to low temperature superconductors (LTS), high temperature superconductor (HTS) REBCO CC tapes provide a much wider range of operating temperature and a higher critical current density at 4.2 K making it more attractive in magnet and coil applications. The superior properties of the REBCO CC tapes under magnetic field have led to the development of superconducting magnets capable of producing field way above 23.5 T. In order to achieve its optimum performance, the electromechanical properties under different deformation modes and magnetic field should be evaluated for practical device design. This paper gives an overview of the effects of mechanical stress/strain on $I_c$ in HTS CC tapes due to uniaxial tension, bending deformation, transverse load, and including the electrical performance of a CC tape joint which were performed by our group at ANU in the last decade.