• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.537-537
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• 2012

We have studied a fabrication of vapor phase polymerized Poly(3,4-ethylenedioxythiophene) (PEDOT) nanowire arrays for the first time. The vapor-phase polymerization (VPP) technique is a bottom-up processing method that utilizes the organic arrangement of macromolecules to easily produce ordered aggregates, including on the nanoscale, or prepare thin films of self-assembled molecules, micropatterns, or modified microstructures of pure conducting polymers. Also, liquid-bridge-mediated nanotransfer molding (LB-nTM), which was reported as a new direct patterning method recently, is for the arrayed formation of two- or three-dimensional structures with feature sizes as small as tens of nanometers over large areas up to 4 inches across and is based on the direct transfer of various materials from a mould to a substrate through a liquid bridge between them. The PEDOT nanowires grown by VPP method and transferred on a substrate to use LB-nTM method have been fabricated to single crystal PEDOT nanowires investigated Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Selected Area Electron Diffraction (SAED), X-Ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), and electrical properties.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.787-792
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• 2004

LRB(Lead rubber bearing) has small resistance force against slowly acting loadings such as temporal and creep loadings vice versa large resistance force against rapid loadings such as earthquake and braking loadings. By those mechanical characteristics, it has the advantage to reduce longitudinal load acting on abutments and piers, and moreover to in1prove the running stability of train by restricting the behavior of bridge under the required level. In this study, a stability evaluation method of CWR on the bridge with LRB is presented. Several parametric studies are carried to investigate how LRB contributes to the improvement of CWR stability.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.63 no.4
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• pp.345-350
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• 2014

DC electrolytic capacitor is widely used in the power converter including PWM inverter, switching power supply and PFC Boost converter system because of its large capacitance, small size and low cost. In this paper, basic characteristics of DC electrolytic capacitor vs. frequency is presented and the real-time estimation scheme of ESR and capacitance based on the bandpass filtering is adopted to the single phase boost converter of uninterruptible power supply to diagnose its split dc-link capacitors. The feasibility of this real-time failure prediction monitoring system is verified by the computer simulation of the 5[kW] singe phase PFC half-bridge boost converter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.683-692
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• 2000

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The auxiliary circuit adopted to assist ZCS for the leading leg is composed of only one small transformer and two diodes. It has a simple and robust structure, and load current control capability even in short circuit conditions. Possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC/DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12.5KW prototype designed for welding application was verified by experiments.

• Structural Engineering and Mechanics
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• v.42 no.1
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• pp.55-72
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• 2012

Precast-cast insitu concrete bridge construction is widely practiced for small to medium span structures. These bridges consist of precast pre-stressed concrete beams of various cross-sections with a cast in-situ reinforced concrete slab. The connection between the beams and the slab is via shear links often included during the manufacturing process of the beams. This form of construction is attractive as it provides for standardisation, reduced formwork and construction time. The assessment of the integrity of shear connectors in existing bridges is a major challenge. A procedure for assessment of shear connectors based on vibration testing and finite element model updating is proposed. The technique is applied successfully to a scaled model bridge model and an existing bridge structure.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2006.03a
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• pp.284-291
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• 2006

This paper presents a seismic response analysis of bridge structures considering foundation-soil interaction and multi-support input motion. In the earthquake analysis of structures it is usually assumed that the input ground motion is the same at all supports. However, this assumption is not justified for long structures like bridges, because observations have shown the earthquake ground motion can vary considerably within relatively small distances. When the soil under the foundation is relatively soft and deep, analysis for foundation-soil interaction always must be peformed. To consider foundation-soil interaction, soil response analysis is preceded, and after determining the material characteristics of foundation element obtained by foundation-soil interaction analysis at the frequency domain, the seismic response analysis of bridge superstructure with the equivalent spring and damper is performed. Finally, influences of multi-support input motion, which are affected by different soil characteristics, are also considered in this paper.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.1
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• pp.66-69
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• 2019

This study proposes a high-efficiency phase-shifted full-bridge (PSFB) converter with a wide input voltage range. The conventional PSFB converter is a useful topology in high-power applications. This converter not only achieves the zero-voltage switching of the primary switches, but also has small RMS current in the primary side. However, because the conventional PSFB converter has large freewheeling current in the primary side when it is designed considering the hold-up time of the converter, such a converter has high conduction loss at the primary switches. To solve this problem, a new PSFB converter is proposed in this study. The experiment is implemented with an input voltage ranging from a 320 V-400 V and an output power specification of 715 W.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.333-336
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• 2009

the equipment increase switching frequency in order to achieve small size, a low noise, and light weight. however, the power switches have high power losses and switching stresses as the switching frequency is increased. In order to solve like this problem point from the present paper it proposed Intese Pulse Light of the half bridge methods which apply the start current circuit which applies the auxiliary equipment. Simulation and experimental result it leads and it brings is more qualitative there is 20% improvement and it confirmed that a possibility of measuring to the patient.

• Journal of Korean Society of Steel Construction
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• v.24 no.5
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• pp.559-569
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• 2012

Cross-beam in the existing temporary bridge system is usually installed to prevent the lateral-torsional buckling of girders and to promote the construction efficiency. However, most of this cross-beams are connected to the girder web by bolts, and therefore, gravitational load resisting capacity of the cross-beams are negligibly small. In recent years, new temporary bridge system, in which the cross-beams and girders are connected to resist the external loads as a unit, was developed. In this paper, we present the experimental and analytical study results pertaining to the structural behavior and load carrying capacity of new temporary bridge system. From the results of study, it was found that the continuous cross-beam increased the flexural rigidity and reduced the maximum flexural stress in the girder. In addition, it was also found that the new temporary bridge system developed is more appropriate for the application in the long-span temporary bridge.

• Steel and Composite Structures
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• v.10 no.6
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• pp.541-561
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• 2010

This paper presents finite element analyses, experimental measurements and finite element model updating of an arch type steel laboratory bridge model using semi-rigid connections. The laboratory bridge model is a single span and fixed base structure with a length of 6.1 m and width of 1.1m. The height of the bridge column is 0.85 m and the maximum arch height is 0.95 m. Firstly, a finite element model of the bridge is created in SAP2000 program and analytical dynamic characteristics such as natural frequencies and mode shapes are determined. Then, experimental measurements using ambient vibration tests are performed and dynamic characteristics (natural frequencies, mode shapes and damping ratios) are obtained. Ambient vibration tests are performed under natural excitations such as wind and small impact effects. The Enhanced Frequency Domain Decomposition method in the frequency domain and the Stochastic Subspace Identification method in the time domain are used to extract the dynamic characteristics. Then the finite element model of the bridge is updated using linear elastic rotational springs in the supports and structural element connections to minimize the differences between analytically and experimentally estimated dynamic characteristics. At the end of the study, maximum differences in the natural frequencies are reduced on average from 47% to 2.6%. It is seen that there is a good agreement between analytical and experimental results after finite element model updating. Also, connection percentages of the all structural elements to joints are determined depending on the rotational spring stiffness.