• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.7
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• pp.1013-1018
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• 2014

This paper described the development of equalizing spacer for minimization of voltage drop according to DC feeder extension. Power consumption is increased as shorter interval of train driving time and transportation capacity increase in urban subway. Therefore we investigated voltage drop of catenary at a point in case of traction driving of a train in parallel to the DC power supply system. Based on it's result, equalizing spacer is designed and fabrication to minimize the voltage drop in accordance with the power supply line arranged in three rows, and then its performance was confirmed that the stress distribution of main body and the distributed load are satisfied through the body structure modeling.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.117-123
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• 2015

The need for drop simulations for board-leveled flip chips in micro-system packaging has been increasing. There have been many studies on flip chips with various solder ball compositions. However, studies on flip chips with Sn-1.0Ag-0.5Cu and Sn-3.0Ag-0.5Cu have rarely been attempted because of the unknown material properties. According to recent studies, drop simulations with these solder ball compositions have proven feasible. In this study, predictions of the impact lifetime by drop simulations are performed considering Cu and Cu/Ni UBMs using LS-DYNA to alter the design parameters of the flip chips, such as thickness of the flip chip and size of the solder ball. It was found that a smaller chip thickness, larger solder ball diameter, and using the Cu/Ni UBM can improve the drop lifetime of solder balls.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.109-110
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• 2023

Domestic ultra-hard road repair materials require a lot of time before the road can be opened to traffic. Therefore, in this study, Methyl Methacrylate (MMA) based road repair material was used to improve the above problems. Furthermore, the basic physical properties of MMA-based pavement repair materials are examined to confirm their suitability in concrete pavements. For this study, two types of MMA road repair materials (A type and B type) were selected. Then, the curing of the test specimens prepared for painting was carried out under three conditions. The experimental items were viscosity (drop time) and drying time (set to touch, dry-hard). As a result of the experiment, viscosity (drop time) was faster in type A than in type B. The drying time results were as follows. In the case of set ti touch, both type A and type B dried in about 10 minutes regardless of the curing conditions. In the case of dry-hard, regardless of the curing conditions, A type dried longer than B type, but it dried faster than conventional road repair materials. Therefore, within the scope of this study, it is considered that A type has a high potential for utilization as a road repair material.

• Korean Journal of Optics and Photonics
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• v.27 no.5
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• pp.174-180
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• 2016

A tunable optical delay line is designed, fabricated, and characterized. The tunable delay line consists of four polymer-ring add/drop filters with delay waveguides between adjacent ones. The polymer waveguide is a buried structure, designed to be square with core width and height of $1.8{\mu}m$. The refractive indices of the core and cladding polymer are 1.48 and 1.37 respectively. The large index difference and small cross section of the waveguide enable us to realize a compact device using a small radius of curvature. Four pairs of electrodes are evaporated above the add/drop filters to provide heating currents for thermal tuning. In measurements we can identify variable time delays of 110, 225, and 330 ps in proportion to the number of delay lines.

• Journal of Korean Society for Quality Management
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• v.25 no.2
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• pp.15-27
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• 1997

This paper describes a highly accelerated life test (HALT, USPCBT) method for rapid qualification testing of STH PWB(Silver Through Hole Printed Wiring Boards). This method was carried out to be an alternative to the present time-consuming standard 1344 hours life testing(THB). The accelerated life test conditions were $121^{\circ}C$/95%R.H. at 50V bias and without bias. Their results are compared with those observed in the standard 1344 hours life test at $40^{\circ}C$/95%R.H. at 50V bias and without bias. The studies were focused on the samples time-to-failure as well as the associated conduction and failure mechanisms. The abrupt drop of insulation resistance is due to the absorption of water vapour. And the continuous drop of insulation resistance is due to the Ag migration. The ratios of time-to-failure of HALT(USPCBT) to THB were 25 and 11 at 50V bias and without bias respectively.

• Proceedings of the Korean Nuclear Society Conference
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• 1999.10a
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• pp.100-100
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• 1999

• Korean Journal of Optics and Photonics
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• v.15 no.3
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• pp.193-199
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• 2004

We present the double resonance optical pumping(DROP) spectra in the transition 5P$_{3}$2/-4D$_{3}$2/ and 5P$_{3}$2/-4D$_{5}$ 2/ of ($^{87}$ Rb) and the frequency stabilization in the $1.5mutextrm{m}$ region using those spectra. Those spectra have high signal-to-noise ratio and narrow spectral linewidth, which is about 10 MHz. We could account fur the relative intensities of the hyperfine states of those spectra by the spontaneous emission into the other state. When the frequency of the $1.5mutextrm{m}$ laser diode was stabilized to the DROP spectrum, the frequency fluctuation was about 0.2 MHz fDr sampling time of 0.1 s and the Allan deviation(or the square root of the Allan variance) was about 1${\times}$10$^{-11}$ for averaging time of l00s.

• Applied Chemistry for Engineering
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• v.20 no.1
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• pp.15-20
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• 2009

In this study, solubilization experiments of n-octane oil were performed by micellar solutions of polymeric nonionic surfactant Pluronic L64 ($EO_{13}PO_{30}EO_{13}$) at room temperature. A single spherical drop of n-octane was injected into aqueous surfactant solution using an oil drop contacting technique and solubilization rate of n-octane was measured by observing the size of oil drop with time. It was found that solubilization rate was independent of initial oil drop size but inversely proportional to the initial surfactant concentration. These results revealed that solubilization of n-octane oil by L64 micellar solution is controlled by interface-controlled mechanism rather than diffusion-controlled mechanism. Dynamic interfacial tension measurements showed that interfacial tension decreases such as from $2.59{\times}10^{-2}$ to $2.45{\times}10^{-2}$, and further to $2.13{\times}10^{-2}mN/m$ as surfactant concentration increases from 8 to 9 and further to 10 wt% respectively. The equilibration time was also found to decrease slightly with an increase in surfactant concentration. All three systems reached an equilibrium within 7 minutes.

• 한국생물공학회:학술대회논문집
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• 2003.10a
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• pp.381-383
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• 2003

In the experimental result of the pressure-drop classified by media, the fibrous media was not much as compared with other media and maintained a stabilized removal efficiency in long-time operation.

• Proceedings of the Korean Society of Veterinary Pathology Conference
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• 2002.11a
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• pp.66-79
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• 2002

The basic treatments - Epithelial ＆ stromal debridement with a swab or diamond burr. - Possible placement of a collagen shield or nictitans flap. - Topical treatment with Adequan IM diluted in artificial tears : 1 ml Adequan + 4 ml tears : One drop four times daily. - Topical treatment with an antibiotic drop : Three times daily - 5％ sodium chloride ointment : Four times daily. If inflammation is severe - Topical treatment with nonsteroidal agent : Four times daily (Voltaren, Ocufen, or Profenyl) - Cyclosporine A (Optimmune) : Twice daily Healing time - Healing typically occurs rapidly - Fluorescein negative : 7-10 days - Vascular keratitis : Often several months