• ETRI Journal
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• v.39 no.2
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• pp.284-291
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• 2017

Drain-induced barrier lowering (DIBL) is one of the main parameters employed to indicate the short-channel effect for nano metal-oxide semiconductor field-effect transistors (MOSFETs). We propose a new physical model of the DIBL effect under two-dimensional approximations based on the energy-conservation equation for channel electrons in FETs, which is different from the former field-penetration model. The DIBL is caused by lowering of the effective potential barrier height seen by the channel electrons because a lateral channel electric field results in an increase in the average kinetic energy of the channel electrons. The channel length, temperature, and doping concentration-dependent DIBL effects predicted by the proposed physical model agree well with the experimental data and simulation results reported in Nature and other journals.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.129-137
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• 1999

The time of the onset of double-diffusive convection in time-dependent, nonlinear concentration fields is investigated theoretically. The initially quiescent horizontal fluid layer with a uniform temperature gradient experiences a sudden concentration change from below, but its stable thermal stratification affects concentration effects in such way to invoke convective motion. The related stability analysis, including Soret effect, is conducted on the basis of the propagation theory. Under the linear stability theory the concentration penetration depth is used as a length scaling factor, and the similarity transform for the linearized perturbation equations. The newlly obtained stability equations are solved numerically. The resulting critical time to mark the onset of regular cells are obtained as a function of the thermal Rayleigh number, the solute Rayleigh number, and the Soret effect coefficient. For a certain value of the Soret effect coefficient, the stable thermal gradient promote double-diffusive convective motion.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.111-115
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• 2003

Nanoindentation is simply an indentation test in which the length scale of the penetration is measured in nanometres rather than microns or millimetres, the latter being common in conventional hardness tests. Three-dimensional molecular dynamics simulations have been conducted to evaluate the nanoindentation test. Molecular dynamics simulations were carried out on single crystal copper by varying crystal orientations to investigate nano-behavior of material beneath an indenter in nanoindentation. Morse potential function was used as an interatomic force between indenter and thin film. The result of the simulation shows that crystal orientation significantly influenced the slip system, dislocation nucleation and dislocation behavior.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.2
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• pp.126-131
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• 2003

Convective instability driven by surface tension is analyzed in an initially quiescent water absorbing ammonia gas with heat transfer using the linear stability analysis. The propagation theory is adapted to find the critical conditions of the onset of Marangoni convection. In this theory, the solutal penetration depth is chosen as the length scale factor. The results show that the liquid layer becomes more stable with decreasing the Schmidt number and increasing the Lewis number. It is also found that there is a critical Biot number to make the liquid layer be most unstable, and there is a linear relationship between the thor-mal Marangoni number and the solutal Marangoni number.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.10 s.175
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• pp.167-173
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• 2005

The Berkovich nano-indentation is an indentation test method analyzing mechanical properties of materials such as hardness and elastic modulus. The length scale of the penetration is measured in nanometers. Therefore, this method becomes widely useful for analyzing the mechanical property of thin film which can not be measured before. In this paper, comparing two results of the load-displacement curve obtained by the Berkovich nano-indentation and the 3-D finite element analysis, it was confirmed that the 3-D finite element analysis is useful. The phenomenon of pile-up and sink-in due to material properties was discussed by the finite element analysis.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.14 no.6
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• pp.450-455
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• 2002

Convective instability driven by surface tension is analyzed in an initially quiescent water absorbing ammonia gas using the linear stability theory. The propagation theory is adapated to find the critical conditions of the onset of solutal Maragoni convection. In this theory, the solutal penetration depth is chosen as the length scale factor. The results show that the liquid layer becomes more stable with decreasing the Schmidt number It is interesting that for a smaller Biot number than 100, the system becomes stable with decreasing Bi but for a larger Bi, it becomes unstable with decreasing Bi.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.3
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• pp.603-609
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• 1990

Detection and non-propagating cracks of small fatigue crack for smooth and pre-cracked specimens were examined in a carbon steel. The fretting oxide induced crack closure triggered by the roughness induced crack closure has an important role in determing the length. The fatigue limit for the with no cracks or with a short pre-crack is lower at R=-1 than that at R=0. A non-propagating crack are quite different between points near the specimen's surface and those of deepest penetration.

• Journal of ILASS-Korea
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• v.15 no.2
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• pp.61-66
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• 2010

Fuel spray characteristics of the gasoline engine injector has been studied experimentally. To provide fundamental performance data of 4-hole and 12-hole injectors, spray fuel-mass distribution, wall wetting fuel amount and visualization of injectors have been tested and measured with various fuel supply pressure conditions. Spray visualization has been performed to analyze spray formation, spray angle, stream width and penetration length. Test result shows that wall wetting is greatly influenced by the induction air amount and spray atomization. Spray visualization shows that the 12-hole injector has robust performance characteristics with various fuel supply pressure conditions compared with the 4-hole injector. 4-hole injector generates relatively less wall-wetting fuel amount than 12-hole injector does.

• Journal of Advanced Marine Engineering and Technology
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• v.19 no.3
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• pp.9-23
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• 1995

To analyze the spray and flame in D.I. diesel engine, the visualizing methods by schlieren photograph and diffused background illumination photograph with high speed camera are applied to optically accessible D.I.diesel engine. Wcaporating spray, spray droplets and brightness flame are taken with high speed camera by visuallizing method in accordance with various suction air temperature and injection time. The spray and flame image on the film was analyzed by image analyzer. The optically accessible D.I. diesel engine had the similar pressure characteristic to the real D.I. diesel engine. Experimental results showed that shadow areas of the evaporating spray were extended at higher suction air temperature, spray droplets had a max. Penetration length and their penetrating patterns were dependent on the surrounding gas temperature, and flame size after ignition was largely governed by the evaporated fuel quantity at ignition point and by the surrounding gas condition due to piston motion.

• Journal of ILASS-Korea
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• v.8 no.4
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• pp.31-38
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• 2003

Constant volume combustion chamber has been designed to investigate diesel spray characteristics with Common-Rail injection system to realize high pressure injection. In this study, two methods of measurements, Schlieren shadowgraphy and Mie scattering imaging method ate applied experimentally to study spray form and liquid phase zone in high pressure, high temperature conditions. Diesel fuel is injected at the point which ignited mixture gas is completely burned. The effect of injection pressure, injector hole diameter, ambient gas temperature and density are investigated experimentally.