• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1045-1050
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• 2003

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests are conducted on 2124-T851 aluminum alloy specimens. Three test spectra are generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results are compared with the data obtained from the flight-simulation loading. The experimental results show that omission of the load ranges below 5% of the maximum load does not significantly affect crack growth behavior, because these are below the initial stress intensity factor range. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decrease, and therefore crack growth curve deviates from the crack growth data under the flight-simulation loading. To optimize the load range that can be omitted, crack growth curves are simulated by the stochastic crack growth model. The prediction shows that the omission level can be extended to 8% of the maximum load and test time can be reduced by 59%.

• Wind and Structures
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• v.18 no.6
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• pp.669-691
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• 2014

Since low-rise residential buildings are the most common and vulnerable structures in coastal areas, a reliable prediction of their performance under hurricanes is necessary. The present study focuses on developing a refined finite element model that is able to more rigorously represent the load distributions or redistributions when the building behaves as a unit or any portion is overloaded. A typical 5:12 sloped low-rise residential building is chosen as the prototype and analyzed under wind pressures measured in the wind tunnel. The structural connections, including the frame-to-frame connections and sheathing-to-frame connections, are modeled extensively to represent the critical structural details that secure the load paths for the entire building system as well as the boundary conditions provided to the building envelope. The nail withdrawal, the excessive displacement of sheathing, the nail head pull-through, the sheathing in-plane shear, and the nail load-slip are found to be responsible for the building envelope damage. The uses of the nail type with a high withdrawal capacity, a thicker sheathing panel, and an optimized nail edge distance are observed to efficiently enhance the building envelope performance based on the present numerical damage predictions.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.4
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• pp.28-34
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• 2012

Installing surge protection devices for a low-voltage system is important to ensure the survival of electric or electronic devices and systems. If surge protection devices (SPD) are installed without consideration of the concept of lightning protection zones, the equipment to be protected might be damaged despite the correct energy coordination of SPDs. This damage is induced by the reflection phenomena on the cable connecting an external SPD and the load protected. These reflection phenomena depend on the characteristics of the output of the external SPD, the input of the loads, and the cables between the load and the external SPD. Therefore, the SPD has an effective protection distance under the condition of the specific load and the specific voltage protection level of SPD. In this paper, PSCAD/EMTDC software is used to simulate the residual voltage characteristics of SPD Entering the low-voltage device. And by applying a certain voltage level, the effective protection distances of SPD were analyzed according to the each load and length of connecting cable, and the effectiveness of SPD were verified.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.582-585
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• 2004

Most of hard disk drives currently employ fluid dynamic bearing (FDB) for their rotor support. Stiffness of the FDB is affected by many design factors such as bearing clearance, fluid viscosity, and rotational speed. For the high rotating speed HDDs stiffness of the rotor is normally high enough to accomodate load disturbances. However small form factor HDDs that are to be operated in low power consumption are often designed with low stiffness rotors. Although the low stiffness rotor clearly benefits low power operation, it could damage the entire motor structure or head disk interface even by a light mechanical load disturbance such as shock or vibration. In addition, since a single channel HDD does not provide gram load equilibrium in axial direction the rotor could be tilted and make a hard contact to stator. A non-symmetric groove pattern could successfully compensate the tilted rotor angle during operation.

• Journal of IKEEE
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• v.23 no.2
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• pp.552-556
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• 2019

This paper present a capless low drop out regulator (LDO) that improves the load transient response characteristics by using a current regulator. A voltage regulator circuit is placed between the error amplifier and the pass transistor inside the LDO regulator to improve the current characteristics of the voltage line, The proposed fast transient LDO structure was designed by a 0.18 um process with cadence's virtuoso simulation. according to test results, the proposed circuit has a improved transient characteristics compare with conventional LDO. the simulation results show that the transient of rising increases from 1.954 us to 1.378 us and the transient of falling decreases from 19.48 us to 13.33 us compared with conventional capless LDO. this Result has improved response rate of about 29%, 28%.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1656-1663
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• 2016

A capacitive wireless power transfer (C-WPT) system uses an electric field to transmit power through a physical isolation barrier which forms a pair of ac link capacitors between the metal plates. However, the physical dimension and low dielectric constant of the interface medium severely limit the effective link capacitance to a level comparable to the main switch output capacitance of the transmitting circuit, which thus narrows the soft-switching range in the light load condition. Moreover, by fundamental limit analysis, it can be proved that such a low link capacitance increases operating frequency and capacitor voltage stress in the full load condition. In order to handle these problems, this paper investigates optimal design of double matching transformer networks for C-WPT. Using mathematical analysis with fundamental harmonic approximation, a design guideline is presented to avoid unnecessarily high frequency operation, to suppress the voltage stress on the link capacitors, and to achieve wide ZVS range even with low link capacitance. Simulation and hardware implementation are performed on a 5-W prototype system equipped with a 256-pF link capacitance and a 200-pF switch output capacitance. Results show that the proposed scheme ensures zero-voltage-switching from full load to 10% load, and the switching frequency and the link capacitor voltage stress are kept below 250 kHz and 452 V, respectively, in the full load condition.

• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.63-69
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• 2010

A noble model of the whole lumbar spine (L1~L5) considering all the passive elements, especially the ligaments of the lumbar spine was developed. The purpose of this study was to investigate the relationship between the shear stress of the AVB and the ALL and the effect of a compressive follower pre-load on all ligaments with various motions. The result shows that the shear stress at the AVB and the ALL are positively correlated. This indicates that the shear stress of the ligament can be used an index of low back pain. Regarding the effect of a follower pre-load, contrary to our expectation, the shear stress of the ligaments was not always reduced by applying follower pre-load; flexion was decreased and axial rotation did not change, while extension and lateral bending were increased.

• Special Issue of the Society of Naval Architects of Korea
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• 2011.09a
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• pp.36-38
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• 2011

As the increase of the fuel oil price, the demand for saving of the ship running cost is growing. To meet the needs of the shipowners, the method for low load operation has been developed by engine licenser. As one of low load operation, the turbocharger cut-out system can be utilized flexibly both full and part load operation. It can be possible to optimize fuel consumption at both full and part load operation. Tests by engine licenser with 12K98MC engine have proven that the fuel oil consumption can be reduced approximately 5%. In this paper we will study the application of main engine turbocharger cut-out system onboard a vessel. One of four turbochargers with MAN Diesel & Turbo 12K98MC-C and 12K98ME-C engine is cut out with swing gate valve. The fuel oil consumption is measured during sea trial and engine shop test.

• Progress in Superconductivity and Cryogenics
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• v.3 no.1
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• pp.45-49
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• 2001

A magnet supporting post installed between the lower TF coil tooled by 4.5 K supercritical helium and the cryostat base is one of the most important components of the superconducting magnet supporting structure for KSTAR Tokamak. This structure should be flexible to absorb thermal shrink of the magnet and also should be rigid to support the magnet weight and the Plasma disruptions load. The Post was designed with stainless steel 316LN and CFRP that have low thermal conductivity and high structural strength at low temperature. In order to verify the possibility of fabrication and the structural safety. a whole scale prototype of the KSTAR magnet supporting post was manufactured and tested. Static and compressive cyclic load tests under the maximum Plasma vertical disruption load and the magnet dead weight were performed. The teat results showed that the magnet supporting post of KSTAR Tokamak was possible to manufacture and structurally rigid.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.2
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• pp.148-153
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• 2009

As the increasing of non-linear load, we have a growing interest in power quality. Power quality has come to the voltage quality. Voltage harmonics consist in at the PCC by the non-linear load. Capacitor is generally used for the power compensation and as the passive filter by the serial connection with reactor. Capacitor has low impedance as the frequency increases, so easily fall down by the harmonic component of non-linear load. Small voltage of low-order acts on quite a few at the capacitor by the current increase. In this paper, we measured the magnitude and angle of voltage at the PCC and calculated under the same condition. we checked out that lower voltage of higher order produces current magnification.