• Journal of Power Electronics
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• v.12 no.2
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• pp.258-267
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• 2012

An interleaved single-stage AC/DC converter with a boost converter and an asymmetrical half-bridge topology is presented to achieve power factor correction, zero voltage switching (ZVS) and load voltage regulation. Asymmetric pulse-width modulation (PWM) is adopted to achieve ZVS turn-on for all of the switches and to increase circuit efficiency. Two ZVS half-bridge converters with interleaved PWM are connected in parallel to reduce the ripple current at input and output sides, to control the output voltage at a desired value and to achieve load current sharing. A center-tapped rectifier is adopted at the secondary side of the transformers to achieve full-wave rectification. The boost converter is operated in discontinuous conduction mode (DCM) to automatically draw a sinusoidal line current from an AC source with a high power factor and a low current distortion. Finally, a 240W converter with the proposed topology has been implemented to verify the performance and feasibility of the proposed converter.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.465-465
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• 2000

The paper presents the fuzzy control technique to adjust the gain schedule in the fuzzy controller. The micro computer is designed to the fuzzy controller to execute the proportional gain with the data of the error and speed command. The gain schedule is the fuzzy set which execute based on the fuzzy rule. The gain schedule from the fuzzy controller is fed to the sinusoidal pulse width modulation (SPWM) inverter for control the response and speed of the induction motor. The induction motor coupling to the DC motor and tachogenerator which DC motor as a load. The test result of the fuzzy control technique in the open loop control, it provides a good response and in the closed loop control it can control speed in the any condition of load design

• Tunnel and Underground Space
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• v.4 no.3
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• pp.261-273
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• 1994

Direct shear tests were carried out on the rock joints and artificial discontinuities to investigate the influence of joint roughness on the shear strength and deformation behaviour. Single direct shear testing apparatus used in experiment was designed and manufactured. Its capacity is 200 tons of shear load, 20 tons of normal load and 50$\textrm{cm}^2$ of maximum shear area. Test samples were cement mortar with artificial discontinuity and sandstone with natural joint. Peak shear strength was increased as joint roughness or normal stress was increased, especially, linearly increased with roughness angle in cement mortar. If joint roughness angle was constant at low normal stress, shear strength was not affected by width and height of joint roughness in cement mortar. Peak shear strengths obtained from tests were larger than the values calculated by Barton's equation, and shear stiffness was increased with joint roughness coefficient.

• Journal of Welding and Joining
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• v.19 no.3
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• pp.298-304
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• 2001

Turbine blade is subject to force of three types ; the torsional force by torsional mount, the centrifugal force by the rotation of rotor and the cyclic bending force by steam pressure. The cyclic bending force was a main factor on fatigue strength. SEM fractography in root of turbine blade showed micro-clack width was not dependent on stress intensity factor range. Especially, fatigue did not exist on SEM photograph in root of turbine blade. To clear out the fracture mechanism of turbine blade, nanofractography was needed on 3-dimensional crack initiation and crack growth with high magnification. Fatigue striation partially existed on AFM photograph in root of turbine blade. Therefore, to find a fracture mechanism of the torsion-mounted blade in nuclear power plant, the relation between stress intensity factor range and surface roughness measured by AFM was estimated, and then the load amplitude ΔP applied to turbine blade was predicted exactly by root mean square roughness.

• Proceedings of the KWS Conference
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• 2007.11a
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• pp.181-183
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• 2007

Experimental analysis was carried out to understand the fatigue phenomena of different thickness stainless steel overlap joining structure by Nd:YAG laser welding. The fatigue life was obtained through fatigue tests with the various levels of applied load. The fatigue life is related with the parameters such as gap condition and penetration depth through experiment. As the results, tensile and fatigue strength were proportional in heat input level and bead width was identified the major factor for joining strength. Also the fatigue life were decreased depend on gap condition, it was more affected at the low load level.

• Journal of the Korean Institute of Telematics and Electronics
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• v.27 no.9
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• pp.1427-1435
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• 1990

This paper proposes the Selected Harmonic Elimination Pluse Width Modulation (SHE PW) scheme toreduce the ahrmonic components of source line current. To eliminate the low order harmonics which affects the source dominatly, we apply the Fourier series analysis to line current waveforms and then find out the switching patterns using the SHE PWM scheme. In addition to the analysis of harmonic effects, the three phase filter circuit is used to reduce high order harmonics. For the experimental realization, the converter circuit with power Transistor(PTR) is designed and the Pulse Time Control(PTC) is applied. The line current and the load voltage are measured under the condition of three phase application, highly inductive load.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.199-205
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• 2008

The monorail system as new transportation system mostly has being constructed as an elevated construction and the track beam as mostly main work type occupy the important parts. The structure of monorail system, the track beam support directly vehicle's load and comprised of the track beam structure to be traveling side and understructure to be transmitted from their load to the ground. In particular, in case of construction to elevated structure in the center of a city, it is important to decision plan for span to be considered the economic, execution and maintenance according to transport, installation, and the structure problem, scene and civil appeals to be decided the beam elevation and span. Therefore the standard span of monorail track beam shall be considered the efficient execution, economic and transportation. And propose to reasonable decision plan incorporated the minimizing the road occupied width due to openness to center of a city and bridge pole, minimize to basis size.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.10a
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• pp.183-190
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• 1998

In this study, I-type girders, main members of a steel composite bridge, are designed by Load and Resistance Factor Design method as well as Allowable Stress Design method. The width, height web thickness and flange thickness of main girders are set as design variables. The design program connects optimization program ADS, which is coded with FORTRAN, and a main program coded with $C^{++}$. In this study, it is shown that in this particular steel composite bridge, the design by The Load and Resistance Factor Design method is more economical than that by The Allowable Stress Design method.d.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.87-94
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• 1999

The structural behavior of welded steel box columns subjected to axial compression and combined load of axial and horizontal load is described. The nonlinear stress-strain relation of the material and residual stress resulted from welds were included in the analysis. Inelastic buckling analysis of hollow rectangular sections of various width-thickness and slenderness ratios was carried out using the semi-analytical and spline finite strip method to investigate the local and global bucking stress and mode interaction. The buckling stress was compared with test results and design curves. Post-buckling behavior was traced by the finite element program(ADINA) and compared with experimental results. The comparison showed that the ultimate stress can be used for the design purpose.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.144-149
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• 2001

A study for the structural strength analysis on the doubler plate subjected to the axial, biaxial in-plane compression and shear load has been performed through the systematic evaluation process. In order to estimate the proper static strength of doubler plate, non-linear elasto-plastic analysis is introduced. Gap element modeling for contact effect between main plate and doubler is prepared and nonlinear analysis procedures are illustrated based on MSC/N4W . In addition, some design guides are suggested through the consideration of several important effects such as corrosion of main plate, doubler width, doubler length and doubler thickness. Finally theses results are compared with developed design formula based on the buckling strength and general trends and design guides according to the variation of design parameters are discussed.