• Progress in Superconductivity and Cryogenics
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• v.5 no.3
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• pp.34-37
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• 2003

A 1 MVA single-phase high temperature superconducting (HTS) transformer with BSCCO-2223 wire was designed in this paper. The rated voltages of each sides of the transformer are 22.9 kV and 6.6 kV respectively. Double pancake HTS windings arranged reciprocally will be used for the transformer windings, because of the advantages of insulation and distribution of surge voltage in case of a large power and high voltage transformer. Single HTS wire was used for the primary windings and four parallel wires were used for the secondary windings of the transformer with transposition. A core of the transformer was designed as a shell type core separated with the windings by a cryostat made of GFRP with a room temperature bore. The operating temperature of the HTS windings will be about 65K with sub-cooled liquid nitrogen. A cryogenic cooling system using a GM-cryocooler for this HTS transformer by natural convection of liquid nitrogen was designed. This type of cooling system can be a good option for compactness, efficiency, and reliability of the HTS transformer.

• Fire Science and Engineering
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• v.31 no.4
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• pp.111-118
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• 2017

The present paper is a study on the risk analysis of complex electrical fire by the partial disconnection and tracking. First, in order to analysis the single cause of electrical fire risk by the partial disconnection, the thermal characteristic has been measured by the change in the number of strands and the rated current of a wire. And then, in order to analysis the electrical fire risk by complex cause, an experiment on the accelerated tracking has been carried out in a condition of partial disconnection and confirmed the fire relation between partial disconnection and tracking. From the experiment, if the partial wire disconnection acts as a single cause, the existing thermal characteristics generated by the flowing current has appeared more clearly by the increase in the flowing current due to the complex action of tracking. Accordingly, the disconnection of strands has appeared by the complex cause due to the drastic temperature increase which was not generated in the single cause. Namely, it has been confirmed that if the partial disconnection and tracking act complexly rather than the risk of electrical fire by the existing partial disconnection, relatively its risk has been increased in large.

• Archives of Plastic Surgery
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• v.36 no.5
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• pp.623-628
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• 2009

Purpose: In cases where nasal fractures involve frontal process of maxilla or perpendicular plate of ethmoid, 4 - 5 days of nasal packing may not provide sufficient support for avoiding displacement after packing removal. Therefore a single Kirschner - wire(K - wire) is used as an internal splint when nasal fractures involve the above two areas. Methods: Thirty five patients during the last 3 practical years were treated with a K -wire pinning according to the anatomic locations of nasal fractures. We performed a retrospective study using 13 nasal fractures out of total 35 patients. Among 13 cases, 10 patients involved frontal process of maxilla, and 3 patients were diagnosed as bilateral nasal side wall fractures accompanied with fractures of perpendicular plate of ethmoid. One patient of the last three cases had been augmented with dorsal silicone implant long before the trauma. We analyzed the anteroposterior displacement of key stone area and the width between both lateral walls by comparing immediate postoperative radiographs with 2 month follow - ups. To reduce the errors, the same measurements were taken by two different inspectors, and the mean of each inspector's measurements was compared. Patient satisfaction was analyzed using a questionnaire regarding the esthetic and functional outcomes. Results: Ten patients underwent a longitudinal K - wire fixation in submucoperiosteal plane underneath the frontal process of maxilla. And three patients underwent a transverse K - wire fixation from the one side of lateral wall to the perpendicular plate of ethmoid and to the other side of lateral wall. The mean postoperative anteroposterior displacement of the key stone area measured by two inspectors were 1.84% and 3.06%; mean narrowing of bony pyramid were 1.33% and 1.48%, respectively. Subjective satisfaction scores regarding the esthetic appearance and the maintenance of nasal shape compared with immediate post - operative state with the long term ones were not different (p>0.05). Conclusion: K - wire pinning after closed reduction is a reliable and useful method for the treatment of nasal fractures involving frontal process of maxilla or perpendicular plate of ethmoid. This is because it achieves longer intranasal support after reduction. This method also leaves conspicuous external scar, and minimal soft - tissue injury.

• Proceedings of the KIEE Conference
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• 1997.07d
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• pp.1339-1341
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• 1997

The various type Ag sheathed Bi-2223 tapes have been were fabricated by Powder-in-tube(PIT) process. The critical current density could be improved with the value of $23,000\;A/cm^2$(77 K, zero field) in the single concentric Bi-2223 tape. The bending property dependence of $I_c$ was improved in the double concentric Bi-2223 tape compared with single filamentary and single concentric one.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.41 no.10
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• pp.57-62
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• 2004

We report the fiber-optic current sensors composed of a side-polished single-mode fiber with the thermo-optic Polymer layer and the metal wire as a heater. The index change of polymer layers caused by the resistant heat of the metal wires induces the optical attenuation through the evanescent field of the side-polished single-mode fiber. Two types of the sensors are proposed and their characteristics as a current sensor are investigated.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.10
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• pp.1881-1887
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• 2009

This paper discusses the effects of ECC (Earth Continuity Conductor) for reducing the level of induced sheath overvoltages at the single point bonded section of combined transmission lines which are mixed underground power cable with overhead line in one T/L. In previous papers, the characteristics of ECC on only underground power cable systems were sufficiently analyzed. However, the result of only underground power cable systems are totally different from that of combined transmission lines because ECC is commonly grounded with overhead grounding wire at mesh of cable head. Therefore, in this paper, the installation effects of ECC have been variously analyzed considering the three kinds of fault positions, cable formation of duct and trefoil, spacing between phase conductor and ECC, and the change of overhead transmission line section length on 154kV combined transmission line. Finally, simulation results show that ECC can effectively reduce the induced sheath voltage.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1315-1324
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• 2018

A novel three-phase four-wire inverter topology is presented in this paper. This topology is equipped with a special capacitor balance grid without magnetic saturation. In response to unbalanced load and unequal split DC-link capacitors problems, a qusi-full-bridge DC/DC topology is applied in the balance grid. By using a high-frequency transformer, the energy transfer within the two split dc-link capacitors is realized. The novel topology makes the voltage across two split dc-link capacitors balanced so that the neutral point voltage ripple is inhibited. Under the condition of a stable neutral point voltage, the three-phase four-wire inverter can be equivalent to three independent single phase inverters. As a result, the three-phase inverter can produce symmetrical voltage waves with an unbalanced load. To avoid forward transformer magnetic saturation, the voltages of the primary and secondary windings are controlled to reverse once during each switching period. Furthermore, an improved mode chosen operating principle for this novel topology is designed and analyzed in detail. The simulated results verified the feasibility of this topology and an experimental inverter has been built to test the power quality produced by this topology. Finally, simulation results verify that the novel topology can effectively improve the inhibition of an inverter with a three-phase unbalanced load while decreasing the value of the split capacitor.

• Smart Structures and Systems
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• v.22 no.4
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• pp.481-493
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• 2018

Ultrasonic guided waves have attracted increasing attention for non-destructive testing (NDT) and structural health monitoring (SHM) of bridge cables. They offer advantages like single measurement, wide coverage of acoustical field, and long-range propagation capability. To design defect detection systems, it is essential to understand how guided waves propagate in cables and how to select the optimal excitation frequency and mode. However, certain cable characteristics such as multiple wires, anchorage, and polyethylene (PE) sheath increase the complexity in analyzing the guided wave propagation. In this study, guided wave modes for multi-wire bridge cables are identified by using a semi-analytical finite element (SAFE) technique to obtain relevant dispersion curves. Numerical results indicated that the number of guided wave modes increases, the length of the flat region with a low frequency of L(0,1) mode becomes shorter, and the cutoff frequency for high order longitudinal wave modes becomes lower, as the number of steel wires in a cable increases. These findings were used in design of transducers for defect detection and selection of the optimal wave mode and frequency for subsequent experiments. A magnetostrictive transducer system was used to excite and detect the guided waves. The applicability of the proposed approach for detecting and locating wire breakages was demonstrated for a cable with 37 wires. The present ultrasonic guided wave method has been found to be very responsive to the number of brokenwires and is thus capable of detecting defects with varying sizes.

• Journal of the Microelectronics and Packaging Society
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• v.19 no.4
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• pp.45-50
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• 2012

A family of multi-die DRAM packages was developed that incorporate the full functionality of an SODIMM into a single package. Using a common ball assignment analogous to the edge connector of an SODIMM, a broad range of memory types and assembly structures are supported in this new package. In particular DDR3U, LPDDR3 and DDR4RS are all supported. The center-bonded DRAM use face-down wirebond assembly, while the peripherybonded LPDDR3 use the face-up configuration. Flip chip assembly as well as TSV stacked memory is also supported in this new technology. For the center-bonded devices (DDR3, DDR4 and LPDDR3 ${\times}16$ die) and for the face up wirebonded ${\times}32$ LPDDR3 devices, a simple manufacturing flow is used: all die are placed on the strip in a single machine insertion and are sourced from a single wafer. Wirebonding is also a single insertion operation: all die on a strip are wirebonded at the same time. Because the locations of the power signals is unchanged for these different types of memories, a single consolidated set of test hardware can be used for testing and burn-in for all three memory types.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.327-330
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• 1998

A 2watts MMIC(Monolithic Microwave Integrated Circuits) SSPA(Solid State Power Amplifiers) for 20GHz band communication systems has been designed, manufactured and measured. The 0.15um pHEMT technologywith the gate size of 400um for single device was used for the fabrication of MMIC Power Amplifier chips. The precision MIC patterns for the peripherals like power combiner/divider and microstrip lines were realized using hard substrate for gold wire/ribbon bonding. The measured data shows that this MMIC SSPA has the linear gain of 18dB, output power of 33.42dBm(2.2Watts)at 20~21GHz.