• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2000.10a
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• pp.82-85
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• 2000

In cold forging, the final product is usually given by multi-stage process and the preform with stepped shape can be manufactured through the various forging method. The forward extrusion and upsetting processes for preform with stepped shape have been analyzed by using the rigid-plastic finite element analysis code, InteFORM and compared for load and stroke according to ae reduction of weを An engineer should select the proper processes considering the capacity and the stroke of the corresponding press in the forging of the preform with stepped shape.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.3
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• pp.102-107
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• 2000

This study describes computer-aided design system for stepped asymmetric forgings. To establish the appropriate process sequence, an integrated approach based on a rule-base system was accomplished. This system has four modules, which are undercut prevention module, shape cognition module, 3D modelling module and corner/fillet correction module. These modules can be used independently or at all. The proposed shape cognition method could be widely used in forging design of asymmetric parts.

• 한국전산유체공학회:학술대회논문집
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• 2008.03a
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• pp.229-232
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• 2008

This study presents a numerical procedure to optimize the shape of stepped circular pin-fins to enhance turbulent heat transfer. The KRG method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The objective function is defined as a linear combination of heat transfer and friction loss related terms with a weighting factor. Ten training points are obtained by Latin Hypercube Sampling for two design variables. Optimum shape has been successfully obtained with the increased objective function.

• 한국전산유체공학회:학술대회논문집
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• 2008.10a
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• pp.229-232
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• 2008

This study presents a numerical procedure to optimize the shape of stepped circular pin-fins to enhance turbulent heat transfer. The KRG method is used as an optimization technique with Reynolds-averaged Navier-Stokes analysis of fluid flow and heat transfer with shear stress transport turbulent model. The objective function is defined as a linear combination of heat transfer and friction loss related terms with a weighting factor. Ten training points are obtained by Latin Hypercube Sampling for two design variables. Optimum shape has been successfully obtained with the increased objective function.

• JSTS:Journal of Semiconductor Technology and Science
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• v.11 no.1
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• pp.65-72
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• 2011

In this paper, the T-shape stepped impedance resonators are adopted for the design of microstrip bandpass filters for wide harmonics suppression. The proposed filters are operated at the center frequency of 2.44 GHz and 5.20 GHz, respectively. These bandpass filters have been also applied for a high performance diplexer. The insertion losses at the center frequencies of 2.44 and 5.20 GHz are 1.23 and 1.18, respectively. The applicable return losses for both frequency bands and a wide stopband better than 17 dB up to 20 GHz have been obtained.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.6
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• pp.145-150
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• 2003

This paper is on the study of flow force compensation for spool type valves. A simple method for flow force compensation using a stepped spool is presented in this paper. It is easy to manufacture the stepped spool of the presented method because the shape of it is simple. The method has another merit that the size of valve need not be increased. Actuating force required for driving the spool can be decreased through the compensation of flow force. The effect of presented method is predicted through CFD analysis. The results of the CFD analysis are also utilized for the optimization of step shape. The prototypes of flow force compensated Direct Drive Servo-Valve are manufactured, and the measurements of flow force are carried out. The measured effect of flow force compensation is very similar to that from the CFD analysis.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.21 no.4
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• pp.401-410
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• 2008

The natural frequency of a beam plays an important role in not only vibration analysis but also understanding its dynamic characteristics. It is complicated to analyse the natural frequency of a stepped beam with discontinuously varying section. Approximate analysis methods such as Rayleigh-Ritz method, FEM, etc. are frequently used for the vibration analysis of stepped beams. In such a case, accuracy of these methods depends upon the number of partitioned elements, the number of the iterations in calculation and the assumed mode shape. This study presents an approximate analysis method for the fundamental natural frequency analysis of stepped cantilever beam, using equivalent beam transformation technique. Validity and usefulness are verified by comparing the proposed method with FEM for several example problems.

• Journal of the Korean Institute of Navigation
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• v.22 no.2
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• pp.33-38
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• 1998

Approximate design formulse for bandpass filter using stepped microstrip lines are derived. The coupling length of which can be adjusted according to the factor K.Some advantages fo this filter, thus, are the abilities to control the size and shape by changing the structure of the resonator. Using the design formulas an experimental filter was designed and fabricated . The experimental results have been agree with the designed ones, and hence, the validity of the proposed method has been confirmed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.745-749
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• 2002

This paper is on the study of flow force compensating method of spool type valve. A simple flow force compensating method using stepped spool is presented in this paper. It is easy to manufacture stepped spool in the presented method because the shape of it is simple. The method has the merit that the size of valve need not be increased. Actuating force required for driving means of spool can be decreased by the compensation of flow force. The effect of presented method is predicted through CFD analysis. The prototypes of flow force compensating Direct Drive Servo-Valve where the result of CFD analysis is reflected are manufactured, and the measurement of flow force is carried out. It is known from the measurement that the effect of flow force compensation is very similar to from CFD analysis.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.341-348
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• 2000

The differential equations governing the free vibrations of stepped horizontally circular curved beams with circular cross-section are derived and solved numerically. In numerical method, the Runge-Kutta and Determinant Search methods are used for computing the natural frequencies and mode shapes. Frequencies and mode shapes are reported as the functions of non-dimensional system parameters. The numerical method developed herein for computing frequencies and mode shapes are efficient and reliable.