• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1992.11a
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• pp.3-6
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• 1992

A new analytical expression for the saturated I-V characteristics of hydrogenerated amorphous silicon thin film transistors(a-si:H TFT) is presented and experimentally verified. The results show that the experimental transfer and output characteristics at several temperatures are easily modeled. The model is based on three functions obtained from the experimental data of $I_D$ versus $V_G$. Theoretical results confirm the simple form of the model in terms of the device geometry. It was determined that the saturated drain current increased at a fixed gate voltage and the device saturated at increasingly larger drain voltages while the threshold voltages decreased.

• Journal of computational fluids engineering
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• v.14 no.3
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• pp.1-8
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• 2009

Diverging channel from gas engine exit to the inlet section of Heat Recovery Steam Generator (HRSG) has been re-designed for 1 MW system. To improve the uniformity in velocity and temperature distribution of existing design(Case A and B), two additional test geometries have been chosen for the numerical simulation. At first, gas burner exit section has been centered to the inlet section of the boiler(Case C) and uniformity in velocity and temperature distribution has been improved considerably. Secondly, the diverging channel length can be further reduced to compact geometry with new guide vane design (Case D and E). Proposed design shows overall improvement in uniformity in velocity and temperature distribution compared to existing one.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.155-160
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• 2008

Using a three-dimensional (3-D) FE analyses, this paper provides the shape optimization of the standard test specimen for the torsion test, as well as a method for analyzing effects of misalignment under the angular and concentric misalignment. For verification, FE analysis is performed, which is designed for the perfectly full-model. To optimize the design shape of the torsion-controlled fatigue test specimen, we performed sensitivity analysis using shape parameters. Additionally, two kinds of misalignment (angular misalignment and concentric misalignment) are applied to the circular and tubular specimens to show effects of misalignments in the FE analysis. The present results will provide valuable information for designing shafts for every kind of mechanical system under torsional force.

• 한국전산유체공학회:학술대회논문집
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• 2007.04a
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• pp.99-102
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• 2007

NUFLEX is a general purpose program for the analysis 3D thermo/fluid flow and pre/post processor in a complex geometry. NUFLEX is composed various physical models, such as phase change(solidification/melting) and spray, MHD(Magneto Hydraulic Dynamics) models. It is possible to simulate of continuous cast iron process and spray droplet breakup/collision phenomenon. For the verification of these models, compared with the experimental data and commercial CFD code's results. The results show good agreements with experimental and comercial CFD codes's results.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1419-1424
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• 2003

Impact analysis of TFT-LCD module is very complicated because the structure is assisted with thin, small and non-uniform geometry. Especially, finite element modeling is more difficult and need time-consuming efforts. In this study, we developed LCD Impact Analysis System (LIAS) for the purpose of reducing the analysis time without accuracy reduction. This system contains pre-meshing data, material database, shock condition, auto-reporting etc. PATRAN and DYNA3D is used for meshing and solving. Previously, we performed impact test and reviewed the accuracy of analysis results. Simply we can control design parameters, the procedure such as meshing, running and reporting which are partially auto-prepared. By adopting proposed system, it is expected to achieve efficient impact analysis of LCD module.

• Design & Manufacturing
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• v.12 no.2
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• pp.11-15
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• 2018

In this study, we proposed three analysis methods to calculate the flatness of torque-angle sensors (TAS). We introduced two statistical and one geometrical methods in evaluating the precision of the flat plane in the axis direction for TAS. To verified the results, we fabricated TAS and a reference sample using a injection molding machine, mold, polyester as a raw material. We measured ($x_i$, $y_i$) position using 3D contact automated system and applied three analysis methods developed for TAS and a reference sample to see the feasibility. While each analysis method has its own pros and cons, the analysis using the shortest optimal distance was the most precise technique for the flatness evaluation of TAS components.

• Transactions of the Korean Society of Automotive Engineers
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• v.1 no.3
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• pp.22-33
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• 1993

A theoretical analysis of predicting the detailed motion of a piston-crank mechanism within piston-guide clearance is presented, and the analysis is applied to the piston motion in a gasoline engine. A piston movement program is developed to calculate the piston attitude relative to the bore, the piston to bore impact velocity and kinetic energy loss and the net transverse force acting on the piston. This paper presents the formulation of a set of differential equations governing the transverse and rotational motion of a piston. These equations of motion were solved by well established Runge-Kutta method. As a result of this study, it is possible to predict the effects of piston geometry and piston pin offset on a piston motion and kinetic energy loss.

• 한국연소학회:학술대회논문집
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• 2002.11a
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• pp.215-222
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• 2002

It has been well acknowledged that intake system plays great role in the performance of reciprocating engine. Well-designed intake system is expected to not only increase engine efficiency but also decrease engine emission, which is one of the most urgent issues in the automotive society. Thorough understanding of the flow in intake system helps great to design adequate intake system. Even though both experimental and numerical methods are used to study intake flow, numerical analysis is more widely used due to its merits in time and economy. Intake system of In-line 6-Cylinder CNG engine was chosen for the analysis ICEM CFD HEXA was used to create 3-D structured grid and FIRE code was used for the flow analysis in the intake system. Due to the complexity of the geometry standard ${\kappa}-{\varepsilon}$ turbulence model was applied. Numerical analysis was performed for various inlet and outlet boundary conditions under both steady and transient flow. Inlet mass flow rate and outlet pressure variation were changing parameters with respect to engine speed. Flow parameters, such as velocity, pressure and flow distribution, were evaluated to provide adequate data of this intake system.

• Korea-Australia Rheology Journal
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• v.20 no.3
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• pp.143-152
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• 2008

Simulations of solutions of flexible polymer molecules during flow in simple or complex confined geometries are performed. Concentrations from ultradilute up to near the overlap concentration are considered. As concentration increases, the hydrodynamic migration effects observed in dilute solution unidirectional flows (Couette flow, Poiseuille flow) become less prominent, virtually vanishing as the overlap concentration is approached. In a grooved channel geometry, the groove is almost completely depleted of polymer chains at high Weissenberg number in the dilute limit, but at finite concentration this depletion effect is dramatically reduced. Only upon inclusion of hydrodynamic interactions can these phenomena be properly captured.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.14 no.10
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• pp.939-944
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• 2004

The numerical methods including the performance analysis and the noise prediction of the centrifugal compressor impeller are coupled with the optimization design skill, which consists of response surface method, statistical approach, and genetic algorithm. The flow-field Inside of a centrifugal compressor is obtained numerically by solving Wavier-Stokes equations. and then the propagating noise is estimated from the distributed surface pressure by using Ffowcs Williams-Hawkings formulation. The quadratic response surface model with D-optimal 3-level factorial experimental design points is constructed to optimize the impeller geometry for the advanced centrifugal compressor. The statistical analysis shows that the quadratic model exhibits a reasonable fitting quality resulting in the impeller blade design with high performance and low far-field noise level. The influences of selected design variables, objective functions, and constraints on the impeller performance and the impeller noise are also examined as a result of the optimization process.