• Structural Engineering and Mechanics
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• v.15 no.6
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• pp.653-668
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• 2003

Many papers which deal with the dynamic instability of shell-like structures under the STEP load have been published. But, there have been few papers related to the dynamic instability of hybrid cable domes. In this study, the dynamic instability of hybrid cable domes considering geometric nonlinearity is investigated by a numerical method. The characteristic structural behaviour of a cable dome shows a strong nonlinearity, so we determine the shape of a cable dome by applying initial stress and examine the indirect buckling mechanism under dynamic external forces. The dynamic critical loads are determined by the numerical integration of the nonlinear equation of motion, and the indirect buckling is examined by using the phase plane to investigate the occurrence of chaos.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.78-85
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• 2002

This paper deals with the finite element model of the monitor for the simulation of directional free drop tests such as backward, sideward, edge and vertex drop. The model was made for an unconditional stable solution for the explicit integration algorithm. The general behaviors at the time of impact were found to well correlate with the actual situation in terms of acceleration, displacement, contact force and stress of monitor components even though the experiment of the associated drop is performed for the validity of the model.

• Journal of the Semiconductor & Display Technology
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• v.3 no.4
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• pp.33-37
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• 2004

As the high speed and high integration of semiconductor devices and the generation of heat increases resulted in the effective heat dissipation influences on the performance and lifetime of semiconductor devices. The heat resistance or heat spread function of EMC(epoxy molding compound) which protects these devices became one of very important factors in the evaluation of semiconductor chips. Recently, silica, alumina, AlN(aluminum nitride) powders are widely used as the fillers of EMC. The filler loading in encapsulants was high up to about 80 vol%. A high loading of filler was improved low water absorption, low stress, high strength, better flowability and high thermal conductivity. In this study, the thermal properties were investigated through thermal, mechanical and microstructure. Thermophysical properties were investigated by laser flash and differential scanning calorimeter(DSC). For detailed inspection of materials, the samples were examined by SEM.

• Journal of Forest and Environmental Science
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• v.25 no.3
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• pp.195-204
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• 2009

Agrobacterium-mediated genetic transformation has been widely used for the production of genetically modified transgenic plants to obtain specific desired traits. Most of the molecular mechanisms that underlie the transformation steps have been well elucidated over the years. However, a few steps, such as nuclear targeting, T-DNA integration, and Agrobacterium-plant proteins involved remain largely obscure and are still under extensive studies. This review describes the major steps involved in the molecular mechanism of Agrobacterium-mediated transformation and provides insight in the recent developments in studies on the Agrobacterium-mediated genetic transformation system. Some factors affecting the transformation efficiency are also briefly discussed.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.06a
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• pp.71-74
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• 1998

In this Paper, we investigate the electrical properties of ultra-thin(70${\AA}$) nitrided(NO) and reoxidized nitrided oxide(ONO) film that ale considered to be premising candidates for replacing conventional silicon dioxide film in ULSI level integration. we studied I$\sub$g/-V$\sub$g/ characteristics to know the effect of nitridation and reoxidation on the current conduction, leakage current time-dependent dielectric breakdown(TDDB) to evaluate charge-to-breakdown(Q$\sub$bd/), and the effect of stress temperature(25, 50, 75, 100$^{\circ}C$) and compared to those with thermal gate oxide(SiO$_2$) of identical thickness. From the measurement results, we find that reoxidized nitrided oxide(ONO) film shows superior dielectric characteristics, leakage current, and breakdown-to-charge(Qbd) performance over the NO film, while maintaining a similar electric field dependence compared to NO layer. Besides, ONO film has strong resistance against variation in temperature.

• Coupled systems mechanics
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• v.6 no.4
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• pp.501-522
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• 2017

This paper introduces a numerical procedure to incorporate elasto-plastic local deformation effects in the dynamic analysis of beams. The appealing feature is that simple beam type finite elements can be used for the global model which needs not to be altered by the localized elasto-plastic deformations. An overlapping local sophisticated 2D membrane model replaces the internal forces of the beam elements in the predefined region where the localized deformations take place. An iterative coupling technique is used to perform this replacement. Comparisons with full membrane analysis are provided in order to illustrate the accuracy and efficiency of the method developed herein. In this study, the membrane formulation is able to capture the elasto-plastic material behaviour based on the von Misses yield criterion and the associated flow rule for plane stress. The Newmark time integration method is adopted for the step-by-step dynamic analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.04a
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• pp.53-60
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• 1997

The strain localization of concrete is a phenomenon such that the deformation of concrete is localized in finite region along with softening behavior. The objective of this paper is to develope a consistent algorithm for the finite element modeling of localized zone in the analysis of the strain-localization in concrete. For modeling of the localized zone in concrete under strain localization, a general Drucker-Prager failure criterion which can consider nonlinear strain softening behavior of concrete after peak-stress is introduce. The return-mapping algorithm is used for the integration of the elasto-plastic rate equation and the consistent tangent modulus is derived. Using finite element program implemented with the developed algorithms, strain localization behaviors for the different sizes of concrete specimen under compression are simulated.

• Wind and Structures
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• v.1 no.2
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• pp.127-144
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• 1998

In this paper, the wake structures behind a square cylinder at the Reynolds number of 22,000 are simulated using the large eddy simulation, and the main features of the wake structure associated with unsteady vortex-shedding are investigated. The Smagorinsky model is used for parametrization of the subgrid scales. The finite element method with isoparametric linear elements is employed in the computations. Unsteady computations are performed using the explicit method with streamline upwind scheme for the advection term. The time integration incorporates a subcycling strategy. No-slip condition is enforced on the wall surface. A comparative study between two-and three-dimensional computations puts a stress on the three-dimensional effects in turbulent flow simulations. Simulated three-dimensional wake structures are compared with numerical and experimental results reported by other researchers. The results include time-averaged, phase-averaged flow fields and numerically visualized vortex-shedding pattern using streaklines. The results show that dynamics of the vortex-shedding phenomenon are numerically well reproduced using the present method of finite element implementation of large eddy simulation.

• Journal of Power Electronics
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• v.17 no.3
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• pp.621-631
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• 2017

A KY converter integrated with a conventional synchronously rectified (SR) boost converter and a coupled inductor is presented in this paper. This improved KY converter has the following advantages: 1) the two converters use common switches; 2) the voltage gain of the KY converter can be improved due to the integration of a boost converter and a coupled inductor; 3) the leakage inductance of the coupled inductor is utilized to achieve zero voltage switching (ZVS); 4) the current stress on the charge pump capacitors and the decreasing rate of the diode current can be limited due to the use of the coupled inductor; and 5) the output current is non-pulsating. Moreover, the active switches are driven by using one half-bridge gate driver. Thus, no isolated driver is needed. Finally, the operating principle and analysis of the proposed converter are given to verify the effectiveness of the proposed converter.

• Journal of Welding and Joining
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• v.27 no.6
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• pp.49-54
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• 2009

In this study, the numerical analysis model for fatigue life prediction of welded structures are presented. In order to evaluate the structural degradation of welded structures due to fatigue loading, continuum damage mechanics approach is applied. Damage evolution equation of welded structures under arbitrary fatigue loading is constructed as a unified plasticity-damage theory. Moreover, by integration of damage evolution equation regarding to stress amplitude and number of cycles, the simplified fatigue life prediction model is derived. The proposed model is compared with fatigue test results of T-joint welded structures to obtain its validation and usefulness. It is confirmed that the predicted fatigue life of T-joint welded structures are coincided well with the fatigue test results.