• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.4
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• pp.473-481
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• 2012

For a mesa-isolated small geometry SOI MOSFET, the potentials in the silicon film, front, back, and side-wall oxide layers can be derived three-dimensionally. Using Taylor's series expansions of the trigonometric functions, the derived potentials are written in terms of the natural length that can be determined by using the derived formula. From the derived 3-D potentials, the minimum values of the front and the back surface potentials are derived and used to obtain the closed-form expressions for the front and back gate threshold voltages as functions of various device parameters and applied bias voltages. Obtained results can be found to explain the drain-induced threshold voltage roll-off and the narrow width effect of a fully depleted small geometry SOI MOSFET in a unified manner.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.298-303
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• 1997

Over the last few year, there has been a growing interest in quantitative representation of heat transfer phenomena in weld pools in order to relate the processing conditions to the quality of the weldment produced and to use this information for the optimisation and robotization of the welding process. Normally, a theoretical model offers a powerful alternative to check out the physical concepts of the welding process and to calculate the effects of varying any of parameters. To solve this problem, a transient 2D(two-dimensional) heat conduction were developed for determining bead geometry and temperature distribution for the GMA welding process. The equation was solved using a general thermofluid-mechanics computer program, PHOENICS code, which is based on the SIMPLE algorithm. The simulation results showed that the calculated bead geometry from the developed models reasonablely agree with the experiment results.

• Design & Manufacturing
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• v.6 no.2
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• pp.42-47
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• 2012

The paper deals with an analysis of an extrusion process with a divided material flow in a combined radial - backward extrusion. We have discussed the influences of tool geometry such as punch nose angle, relative gap height, die corner radius on material flow and surface expansion into can and flange region. To analyse the process, numerical simulations by the FEM and experiment by physical modeling using Al alloy as a model material have been performed. Based on the results, the influence of fixed parameters on the distribution of divided material flow and surface expansion are obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.8
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• pp.1666-1671
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• 2002

A lane sensing algorithm using vision sensors is developed based on lane geometry models. The parameters of the lane geometry models are estimated by a Kalman filter and utilized to reconstruct the lane geometry in the global coordinate. The inverse perspective mapping from image plane to global coordinate assumes earth to be flat, but roll and pitch motions of a vehicle are considered from the perspective of the lane sensing. The proposed algorithm shows robust lane sensing performance compared to the conventional algorithms.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.69-72
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• 2002

The geometry parameter of tool such as rake angle and clearance angle is defined clearly to solve the difference in communication between design and measurement stage. Using the developed simulation program, wheel is properly determined and end mill can be manufactured accurately. The performance test with well defined end mill provides sufficient information to decide optimal geometry. For machining hardened steel, end mills are designed and manufactured. Optimal rake angle and clearance angle is obtained from performance test. A specific software for automatic end mill production is developed far simulation and fur generation of NC code as Cad/CAM system.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1836-1841
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• 2007

Based on three-dimensional (3-D) FE limit analyses, this paper provides plastic limit and TES(Twice-Elastic-Slope) loads for pipe bends under combined pressure and out-of-plane bending. The plastic limit loads are determined from FE limit analyses based on elastic-perfectly-plastic materials using the small geometry change option, and the FE limit analyses using the large geometry change option provide TES plastic loads. A wide range of parameters related to the bend geometry is considered. Based on the FE results, closed-form approximations of plastic limit and TES plastic load solutions for pipe bends under out-of-plane bending are proposed.

• Journal of the Korean Society of Combustion
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• v.16 no.3
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• pp.1-11
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• 2011

The main objective of this paper is to investigate characteristic of steam reformer at various geometries and operating conditions. In this paper, the steam reforming is studied by a numerical method and three dimensional simulations were used for effective analytical study. User - Defined Function (UDF) was used to simultaneously calculate reforming and combustion reaction. And the numerical model is validated with experimental results at the same operating conditions. In order to understand the relationship between operating conditions such as gas hourly space velocity(GHSV), mass flow rate of combustor inlet, various numerical investigations are carries out for various geometries. Numerical results show that cylindrical geometry is more effective than rectangular geometry for heat transfer to reactors and reforming efficiency. As mass flow rate of combustor inlet increase, reaction occurs more faster and temperature increase with each geometry. On the other hand, reaction and hydrogen conversion decrease as mass flow rate of reactor decreases.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.404-407
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• 2008

Several ITO-less PDP cell structures are presented to improve luminous efficacy. The ITO-less PDP have been applied recently at actual panel manufacture. The influence of ITO-less PDP cell structure on the discharge characteristics has been investigated by using three-dimensional fluid simulation. The variations of electrode geometry parameters such as gap distance, cross bar length, and hump length are investigated for the optimization of cell design.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1639-1644
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• 2003

A hybrid genetic algorithm is developed for estimating the wall emissivities for an absorbing, emitting, and scattering media in a two-dimensional irregular geometry with diffusely emitting and reflecting opaque boundaries by minimizing an objective function, which is expressed by the sum of square errors between estimated and measured temperatures at only four data positions. The finite-volume method was employed to solve the radiative transfer equation for a two-dimensional irregular geometry. The results show that a developed hybrid genetic algorithms reduce the effect of genetic parameters on the performance of genetic algorithm and that the wall emissivities are estimated accurately without measurement errors.

• Proceedings of the KWS Conference
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• 1997.10a
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• pp.205-209
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• 1997

One of the major important tasks in the robotic $CO_2$ arc welding process is to understand how process variables affected bead geometry and to subsequently develop the mathematical models to predict the desired bead dimensions. Experiment results are compared to outputs obtained using a set of published formulae relating input variables to output parameters and also investigated process variables on bead geometry for robotic $CO_2$ arc welding process The university of results obtained using empirical equations taken from existing models provided to be limited in predicting experimental bead shapes.