• Journal of the Microelectronics and Packaging Society
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• v.29 no.2
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• pp.73-79
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• 2022

In this study, a reaction study between Ga, which has recently been spotlighted as a low-temperature bonding material, and Cu, a representative electrode material, was conducted to investigate information necessary for low-temperature soldering applications. Interfacial reaction and intermetallic compound (IMC) growth were observed and analyzed by reacting Ga and Cu/Au substrates in the temperature range of 80-200℃. The main IMC growing at the reaction interface was CuGa₂ phase, and AuGa₂ IMC with small particle sizes was formed on the upper part and Cu₉Ga₄ IMC with a thin band shape on the lower part of the CuGa₂ layer. CuGa₂ particles showed a scallop shape, and the particle size increased without significant shape change as the reaction time increased, similar to the case of Cu₆Sn₅ growth. As a result of analyzing the CuGa₂ growth mechanism, the time exponent was calculated to be ~3.0 in the temperature range of 120-200℃, and the activation energy was measured to be 17.7 kJ/mol.

• Journal of Audiology & Otology
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• v.23 no.4
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• pp.193-196
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• 2019

Background and Objectives: Facial nerve stimulation (FNS) is a complication of cochlear implantation (CI). This study compared the thickness and density of the bone separating the upper basal turn of the cochlea (UBTC) and the labyrinthine segment of the facial nerve (LSFN) on preoperative computed tomography (CT) in patients with and without FNS after CI. Subjects and Methods: Adult patients who underwent CI from January 2011 to February 2017 with preoperative CT at a tertiary referral hospital were considered for this retrospective case-control study. Patients were divided into two groups: with FNS (n=4) and without FNS (n=53). The density and thickness of the bone between the LSFN and UBTC were measured on preoperative CT. Charts were reviewed for other parameters. Results: A statistically significant difference was seen in the thickness (p=0.007) but not in the density (p=0.125) of the bone between the UBTC and LSFN. Four patients had FNS at the mid-range electrode arrays, and one of them additionally had FNS at the basal arrays. Conclusions: Decreased thickness of the bone between the UBTC and LSFN can explain postoperative FNS, confirming the histologic and radiologic findings in previous studies, which indicated that the thickness of the temporal bone between the LSFN and UBTC is less in patients who experience FNS. While the density in this region was also less, it was not statistically significant.

• Korean Journal of Audiology
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• v.23 no.4
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• pp.193-196
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• 2019

Background and Objectives: Facial nerve stimulation (FNS) is a complication of cochlear implantation (CI). This study compared the thickness and density of the bone separating the upper basal turn of the cochlea (UBTC) and the labyrinthine segment of the facial nerve (LSFN) on preoperative computed tomography (CT) in patients with and without FNS after CI. Subjects and Methods: Adult patients who underwent CI from January 2011 to February 2017 with preoperative CT at a tertiary referral hospital were considered for this retrospective case-control study. Patients were divided into two groups: with FNS (n=4) and without FNS (n=53). The density and thickness of the bone between the LSFN and UBTC were measured on preoperative CT. Charts were reviewed for other parameters. Results: A statistically significant difference was seen in the thickness (p=0.007) but not in the density (p=0.125) of the bone between the UBTC and LSFN. Four patients had FNS at the mid-range electrode arrays, and one of them additionally had FNS at the basal arrays. Conclusions: Decreased thickness of the bone between the UBTC and LSFN can explain postoperative FNS, confirming the histologic and radiologic findings in previous studies, which indicated that the thickness of the temporal bone between the LSFN and UBTC is less in patients who experience FNS. While the density in this region was also less, it was not statistically significant.

• Composites Research
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• v.27 no.4
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• pp.146-151
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• 2014

In this study, the experimental study has been performed by varying the polarization of the electric field and impact force to check the piezoelectric characteristics of piezoelectric paint sensor. Piezoelectric paint sensor used in this study is composed of epoxy resin with a hardener and PNN-PZT powder in 1:1 weight ratio. The dimensions of the paint sensor specimen are $40{\times}40{\times}1mm^3$ and regular specimens were made using a mold. The voids are removed from the specimen in the vacuum desiccator. Both upper side and bottom side of the paint sensor were coated with silver paste for making an electrode and then dried at room temperature for a day. The poling treatment has been carried out under controlled conditions of the electric field in order to check the effect of piezoelectric sensitivities, while the poling temperature was fixed at room temperature and the poling time was set to 30 min. The piezoelectric sensitivities have been measured by comparing output voltage from paint sensor with output force from impact hammer when the impact hammer hits the paint sensor. In result, the effect of the electric field has been evaluated for the sensitivity and describe the result.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.7
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• pp.577-582
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• 2020

Electricity produced at power plants is distributed to consumers through several stages of substations. At this time, an ultra-high voltage transformer is needed in the initial transmission stage to transmit a voltage suitable for each consumer. A high voltage, non-uniform electric field is formed at the end of the winding of the ultra-high voltage transformer, which carries a risk of dielectric breakdown. The winding of the ultra-high voltage transformer is an electrode, which is the key to converting the magnitude of the voltage. A non-uniform electric field is formed along the shape of the winding end, resulting in high electrical stress. The static ring installed at the upper and lower ends of the winding is used to disperse the stress at the winding end. Several variables should be considered when designing a static ring. Among them, this study examined how the curvature of the static ring, the thickness of the insulating paper, the number of barriers, and barrier thickness affect the electrical stress of the static ring using the Finite Element Method. Suggestions to be considered when designing the static ring are proposed through the FEM results.