• Journal of electromagnetic engineering and science
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• v.10 no.1
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• pp.13-17
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• 2010

In this paper, we have described a simple CPW-fed UWB antenna for wireless UWB communication. The proposed antenna consists of two symmetrical strips having two steps and CPW feeding. Two techniques(symmetrical structure, two steps) are used to produce good low-dispersion and impedance matching. The proposed UWB antenna has an omni directional radiation pattern, compact size, low dispersion, and low cost.

• Earthquakes and Structures
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• v.6 no.6
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• pp.647-664
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• 2014

A reduction of the response of irregular structures subjected to earthquake excitation by control devices equipped by suitable control algorithm is proposed in this paper. The control algorithm, which is used, is the pole placement one. A requirement of successful application of pole placement algorithm is a definition-selection of suitable poles (eigen-values) of controlled irregular structures. Based on these poles, the required action is calculated and applied to the irregular structure by means of control devices. The selection of poles of controlled irregular structure, is a critical issue for the success of the algorithm. The calculation of suitable poles of controlled irregular structure is proposed herein by the following procedure: a fictitious symmetrical structure is considered from the irregular structure, adding vertical elements, such as columns or shear walls, at any location where is necessary. Then, the eigen-values of symmetrical structure are calculated, and are forced to be the poles of irregular controlled structure. Based on these poles and additional damping, the new poles of the controlled irregular structure are calculated. By pole placement algorithm, the feedback matrix is obtained. Using this feedback matrix, control forces are calculated at any time during the earthquake, and are applied to the irregular structure by the control devices. This procedure results in making the controlled irregular structure to behave like a symmetrical one. This control strategy can be applied to one storey or to multi-storey irregular buildings. Furthermore, the numerical results were shown that with small amount of control force, a sufficient reduction of the response of irregular buildings is achieved.

• Applied Chemistry for Engineering
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• v.4 no.3
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• pp.505-514
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• 1993

Defined oligoglycerol monolaurate esters were synthesized by means of step by step synthesis methods, and monoglycerol monolaurate, diglycerol monolaurate, symmetrical triglycerol monolaurate and symmetrical tetraglycerol monolaurate were obtained in a rate of 85~95% yields. All the reacted products could be separated by means of column and thin layer chromatography, and the structure of products has been analyzed with IR, $^1H\;NMR$ spectra respectively.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.3
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• pp.161-168
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• 2019

This study introduces a new topology to decrease the voltage stress experienced by a 13.56 MHz electrical variable capacitor (EVC) circuit with an asymmetrical switch structure applied to the impedance matching circuit of a radio frequency (RF) plasma system. The method adopts a symmetrical switch structure instead of an asymmetrical one in each of the capacitor's leg in the EVC circuit. The proposed topology successfully reduces voltage stress in the EVC circuit due to the symmetrical charging and discharging mode. This topology can also be applied to the impedance matching circuit of a high-power and high-frequency RF etching system. The target features of the proposed circuit topology are investigated via simulation and experiment. Voltage stress on the switch of the EVC circuit is successfully reduced by more than 40%.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.232-232
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• 2010

Simulation Program (AFORS-HET 2.4.1) was used, include the basic structure of crystalline silicon thin film as above, under the intrinsic a-Si:H films bonded symmetrical structure (Symmetrical structure) were used. The structure of ITO, a-Si p-type, intrinsic a-Si, c-Si, intrinsic a-Si, a-Si n-type, metal (Al) layer has one of the seven. When thickness for each layer was given the change, the changes of a-Si p-type layer and the intrinsic a-Si layer on top had an impact on efficiency. Efficiency ratio of p-type a-Si:H layer thickness was sensitive to, especially a-Si: H layer thickness is increased in a rapid decrease in Jsc and FF, and efficiency was also decreased.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2006.10a
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• pp.79-84
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• 2006

A novel design of compact low-pass filter based on microstrip structure and its equivalent-circuit model are developed. The philosophy of the structure behind this novel microstrip low-pass filter is simple as it is composed of a pair of symmetrical parallel coupled-line and an open-stub. With this configuration, a finite attenuation pole near the stopband cutoff frequency is available and adjustable by simply tuning the circuit parameters. Furthermore, the rejection bandwidth of this type of low-pass filter can be extended. In order to validate the feasibility of the proposed design method, a low-pass filter based on a microstrip structure is designed, fabricated, and measured. Experimental results agree very well with the simulation and analytical results.

• Journal of Power Electronics
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• v.15 no.3
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• pp.587-601
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• 2015

A high step-up dc-dc converter is proposed for photovoltaic power systems in this paper. The proposed converter consists of an input current doubler, a symmetrical switched-capacitor doubler and an active-clamp circuit. The input current doubler minimizes the input current ripple. The symmetrical switched-capacitor doubler is composed of two symmetrical quasi-resonant switched-capacitor circuits, which share the leakage inductance of the transformer as a resonant inductor. The rectifier diodes (switched-capacitor circuit) are turned off at the zero current switching (ZCS) condition, so that the reverse-recovery problem of the diodes is removed. In addition, the symmetrical structure results in an output voltage ripple reduction because the voltage ripples of the charge/pump capacitors cancel each other out. Meanwhile, the voltage stress of the rectifier diodes is clamped at half of the output voltage. In addition, the active-clamp circuit clamps the voltage surges of the switches and recycles the energy of the transformer leakage inductance. Furthermore, pulse-width modulation plus phase angle shift (PPAS) is employed to control the output voltage. The operation principle of the converter is analyzed and experimental results obtained from a 400W prototype are presented to validate the performance of the proposed converter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.366-366
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• 2010

Simulation Program (AFORS-HET 2.4.1) was used, include the basic structure of crystalline silicon thin film as above, below Intrinsic a-Si:H films bonded symmetrical structure (Symmetrical structure) were used. Efficiency with variation of the concentration was grown by the a-Si p-type with increasing concentrations of Na, efficiency with increasing a-Si n-type of Nd Concentrations was not changed, was decreased rapidly when concentrations were decreased. Efficiency was increased when c-Si n-type of Nd concentration was increased, otherwise efficiency was decreased when concentration was decreased.

• Transactions on Electrical and Electronic Materials
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• v.3 no.4
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• pp.32-35
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• 2002

In this work, we test electrode material of TFD (Thin Film Diode) device subject to flexible substrate. Al, that is ductile metal, was proper for flexible electrode to fabricate flexible display. The fabricated devices had symmetric electrode structure on both sides of insulation layer. The electrode was made of ductile Al so as to reduce the mismatch of properties between the electrode and substrate. The TFD device was successfully fabricated applying our own etch-free process. Electrical properties were improved by post-annealing.

• Wind and Structures
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• v.7 no.1
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• pp.55-70
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• 2004

Aerostatic instability of a suspension bridge may suddenly appears when the deformed shape of the structure produces an increase in the value of the three components of displacement-dependent wind loads distributed in the structure. This paper investigates the aerostatic stability of suspension bridges using an advanced nonlinear method based on the concept of limit point instability. Particular attention is devoted to aerostatic stability analysis of symmetrical suspension bridges. A long-span symmetrical suspension bridge (Hu Men Bridge) with a main span of 888 m is chosen for analysis. It is found that the initial configuration (symmetry or asymmetry) may affect the instability configuration of structure. A finite element software for the nonlinear aerostatic stability analysis of cable-supported bridges (NASAB) is presented and discussed. The aerostatic failure mechanism of suspension bridges is also explained by tracing aerostatic instability path.