• Smart Structures and Systems
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• 제22권5호
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• pp.621-630
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• 2018

Boundary effect and the noise robustness are the two crucial aspects which affect the effectiveness of the damage localization based on the mode shape measurements. To overcome the boundary effect problem and enhance the noise robustness in damage detection, a simple damage localization method is proposed based on the Singular Value Decomposition (SVD) for the mode shape of composite plates. In the proposed method, the boundary effect problem is addressed by the decomposition and reconstruction of mode shape, and the noise robustness in enhanced by the noise filtering during the decomposition and reconstruction process. Numerical validations are performed on plate-like structures for various damage and boundary scenarios. Validations show that the proposed method is accurate and effective in the damage detection for the two-dimensional structures.

• 소성∙가공
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• 제17권7호
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• pp.473-480
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• 2008

Sheet metal forming of Mg alloy is usually performed at elevated temperature because of the low formability at room temperature. Therefore, strain rates affected with the forming temperature and speed must be considered as important factor about formability. Effects of process parameters such as various temperatures and forming speeds were investigated in circular cup deep drawing. From the experimental results, it is known that LDR (Limit Drawing Ratio) increase as the strain rate increase. On the contrary, the FLD (Forming Limit Diagram) shows lower value as faster strain rate. Therefore, anisotropy values are investigated according to the temperature and strain rates at each forming temperature. R-values also represent higher value as faster strain rate. It is known that the formability can be different with the deformation mode on warm forming of AZ31 alloy sheet.

• 한국소음진동공학회논문집
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• 제16권12호
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• pp.1244-1251
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• 2006

The objective of this paper is to get excitation forces of the engine at each of the brackets for the prediction of the vehicle interior noise by the powertrain. A powertrain geometry model is produced by CATIA and its FE model is made by MSC/Patran. A vibration mode analysis and a running mode analysis are experimentally implemented. After getting a satisfied MAC value by doing a correlation about a measured mode analysis value and analyzed value through MSC/Nastran software, all components are assembled through MSC/ADAMS software which is a dynamic analysis tool. We can predict the vibration of brackets which is the last points to occur the force of the engine combustion by analyzing the combustion force produced by engine mechanism.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 춘계학술대회 논문집 초전도 자성체
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• pp.50-54
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• 2002

Influences of bending strain on the critical current ($I_c$) in Ag-sheathed Bi-2223 superconducting tapes at 77K were investigated. The effect of bending mode on the bending strain characteristics was discussed in viewpoints of sample geometry, n-value and damage morphology. Especially, in this paper, we reported the $I_c$ behavior in Ag alloy sheathed Bi-2223 multifilamentary superconducting tapes under hard bending. As a result, $I_c$ degradation behavior of the hard bending appeared remarkably than the case of easy bending, but it did not influence greatly on the n-value.

• Journal of Power Electronics
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• 제12권5호
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• pp.715-722
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• 2012

New discrete time domain models for the peak current controlled (PCC) power LED drivers in continuous conduction mode include for the first time the effects of the time delay in the pulse-width-modulator. Realistic amounts of time delay are found to have significant effects on the average output LED current and on the critical inductor value at the boundary between the two conduction modes. Especially, the time delay can provide an accurate LED current for the PCC buck converter with a wide input voltage. The models can also predict the critical inductor value at the mode boundary as functions of the input voltage and the time delay. The overshoot of the peak inductor current due to the time delay results in the increase of the average output current and the reduction of the critical inductor value at the mode boundary in all converters. Experimental results are presented for the PCC buck LED driver with constant-frequency controller.

• 동력기계공학회지
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• 제4권3호
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• pp.48-54
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• 2000

This paper describes the effect of molding pressure, specimen geometries for Mixed Mode I/II interlaminar fracture toughness of carbon fiber reinforced plastic composites by using asymmetrical double cantilever beam(ADCB) specimen. The value of $G_{I/IIC}$ as a function of various molding pressure is almost same at 307, 431, 585 kPa. However it shows the highest value under 307 kPa molding pressure. The effect of $G_{I/IIC}$ due to the change of initial crack length of ADCB specimen was almost negligible in this study. It turns out that the condition for mix mode quasi-static crack growth in ADCB specimen is the ratio of the crack length to that of the specimen, i.e., ${\alpha}/L<0.4$.

• Journal of Multimedia Information System
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• 제5권2호
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• pp.143-146
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• 2018

The eigen value problem of a coaxial cavity and a modified pill box cavity is investigated using the mode matching technique. The coaxial cavity has a cylindrical cavity with beam ports and center conductor. The pill box cavity is the same as a coaxial cavity without center conductor. The electric field and magnetic field are formulated in propagation region and resonance region. The boundary and orthogonal conditions are applied to the electric and magnetic fields. We derived the eigen value equation by the proposed procedure in a coaxial cavity and a modified pill box cavity. The electromagnetic field of the real structure is disturbed by the coaxial wire. The effect of the coaxial wire in pill box cavity with beam ports increase the dominant resonant frequency. The coaxial line method of the coupling impedance is not adequate for a cylindrical cavity. The results of the mode matching technique and simulation agree well. The results confirm the proposed formulation is valid.

• 대한기계학회논문집B
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• 제31권8호
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• pp.702-710
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• 2007

Direct numerical simulation (DNS) is performed to investigate suppressed wake transition and occurrence of lock-on in the wake of a circular cylinder disturbed by sinusoidal perturbation at the Reynolds number of 220 (A-mode instability regime). The sinusoidal perturbation, of which the frequency is near twice the natural shedding frequency, is superimposed on the free stream velocity. It is shown that the wake transition behind the circular cylinder can be suppressed due to the perturbation of the free stream velocity. This change causes a jump in the Strouhal number from the value corresponding to A-mode instability regime to the value corresponding to retarded wake transition regime (extrapolated from laminar shedding regime) in the Strouhal-Reynolds number relationship. As a result, vortex shedding frequency is locked on the perturbation frequency depending not on the natural shedding frequency but on the modified shedding frequency.

• 전기학회논문지P
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• 제58권1호
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• pp.20-26
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• 2009

In this paper, the switching mode conversion type pulse charger by fly-back converter method for lead battery of the solar cell generator equipment is proposed. And we propose the control circuit and design method of insulated switching mode convert type pulse charger by fly-back convert method in the lead battery. The proposed system can minimize the current consumption by digital pulse. Also the proposed system can generate the constant 10[KHz] frequency, transmit the signal with main control system in the power control system. And it supervises the state of lead battery using one chip micro processor. The proposed the switching mode conversion type pulse charger by the fly-back converter method can charge fast and stabilize lead battery with nominal value 12[V], 20[AH]. Also we propose the design procedure of the power control circuit for turn ratio of fly-back inductor and determining method of values such as the charging current, bulk current, partial current, over current value and fixed charging voltage. The experiment results for the voltage and current wave for partial, bulk, over and fixed charging period show the good charging effect and performance. And the PCB and internal coupling diagram of the switching mode conversion type pulse charger by fly-back converter method is presented.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 IWAIT
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• pp.142-147
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• 2009

The recent H.264/AVC video coding standard provides a higher coding efficiency than previous standards. H.264/AVC achieves a bit rate saving of more than 50 % with many new technologies, but it is computationally complex. Most of fast mode decision algorithms have focused on Baseline profile of H.264/AVC. In this paper, a fast block mode decision scheme for P- slices in High profile is proposed to reduce the computational complexity for H.264/AVC because the High profile is useful for broadcasting and storage applications. To reduce the block mode decision complexity in P- pictures of High profile, we use the SAD value after $16{\times}16$ block motion estimation. This SAD value is used for the classification feature to divide all block modes into some proper candidate block modes. The proposed algorithm shows average speed-up factors of 47.42 ${\sim}$ 67.04% for IPPP sequences.