• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.742-745
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• 2003

Piezoelectric elements driven ultra-precision stages have been used for high accuracy, fast response and high load rapacity. which are allowable to apply the stages to AFMs. Most of the piezoelectric driven stages are guided by flexure hinges for force transmission and mechanical amplification. However the flexure hinge mechanisms cause lack of position accuracy due to coupled and parasitic motions. Hence it is important that the mechanism design of the stage is focused on the stiffness of the flexure hinges to accomplish fast response and hish accuracy without the coupled and parasitic motions. In this study, some constraints for optimal design of a piezoelectric elements driven stage and a design method are proposed. Next, an optimal design is carried out using mathematical calculation. Finally the designed results are verified by FEM.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.315-320
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• 2000

The optimal design for the shape of metal ring obturator under the high pressure using parameter study on the stress analysis considering effects of design variable is presented and is compared to experimental results. The design variables are such as thickness, taper, radius of shape of the obturation ring. For optimization of the obturation ring, the weight is maximized subject to maximum stress of the obturator within allowable stress. The design constraints are geometric elements of design variables. The trends of parametric study are in good agreement with the experimental results.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.03a
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• pp.512-517
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• 2009

Resistance factors for static bearing capacity of driven steel pipe piles were calibrated in the framework of reliability theory. A comprehensive foundation design case study on an actual bridge was performed using resistance factors developed in this study. Comparing with Allowable Stress Design (ASD), LRFD design method provides quantitative evaluation of safety level of designed foundation and exhibits considerable potential economy in design.

• Structural Engineering and Mechanics
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• v.63 no.5
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• pp.607-615
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• 2017

This study presents optimum design of plane steel bridges considering corrosion effect by using teaching-learning based optimization (TLBO) method. Optimum solutions of three different bridge problems are linearly carried out including and excluding corrosion effect. The member cross sections are selected from a pre-specified list of 128 W profiles taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB to carry out optimum design interacting with SAP2000 using OAPI (Open Application Programming Interface). The stress constraints are incorporated as indicated in AISC Allowable Stress Design (ASD) specifications and also displacement constraints are applied in optimum design. The results obtained from analysis show that the corrosion effect on steel profile surfaces causes a crucial increase on the minimum steel weight of bridges. Moreover, the results show that the method proposed is applicable and robust to reach the destination even for complex problems.

• Proceedings of the Korean Geotechical Society Conference
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• 1994.09a
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• pp.60-78
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• 1994

For the optimum design of pile foundations, the determination of allowable load should take both the material strength and the geotechnical characteristics of the site into consideration. Through survey of previous construction records in Korea, it was found that most of the design is overconservative and in some cases the design load was higher than the constructed quality. Proper analysis making use of WEAP and monitoring of pile driving by PDA have been proved to solve most of the prevailing problems. In addition, the time effect in the evaluation of pile bearing capacity has the must significant effect and should not be ignored in the pile design.

• Structural Engineering and Mechanics
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• v.48 no.1
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• pp.93-102
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• 2013

An optimization work was developed in this work to provide design information for sandwich beam in civil engineering applications. This research is motivated by the wide-range applications of sandwich structures such as; slab, beam, girder, and railway sleeper. The design of a sandwich beam was conducted by using analytical and numerical optimization. Both analytical and numerical procedures consider the optimum design with structure mass objective minimization. Allowable deflection was considered as design constraints. It was found that the optimized core to the skins mass ratio is affected by the skin to core density and elastic modulus ratios. Finally, the optimum core to skin mass ratio cannot be constant for different skin and core materials.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.335-342
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• 2005

Using higher order Mindlin plates and piezoelectric materials, eigenvalue problems are considered. Since piezoelectric crystal resonators produce a proper amount of electric signal for a thickness-shear frequency, the objective is to decouple the thickness-shear mode from the others. Design variables are the bulk material densities corresponding to the mass of masking plates for electrodes. The design sensitivity expressions for the thickness-shear frequency and mode shape vector are derived using direct differentiation method(DDM). Using the developed design sensitivity analysis (DSA) method, we formulate a topology optimization problem whose objective function is to maximize the thickness-shear component of strain energy density at the thickness-shear mode. Constraints are the allowable volume and area of masking plate. Numerical examples show that the optimal design yields an improved mode shape and thickness-shear energy.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.3
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• pp.356-363
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• 2013

Mechanical molding press which is used for transformation process during semiconductor manufacturing process has structural deformations by pressure. If these deformations have over limit range, life of the press itself can be reduced and it will be exerted on a bad effect for quality of the semiconductor. In this research, the main plates and links of a press are analyzed in relation to the structural deformations caused by pressure excluding thermal deformations. After modifying the modeling, the analysis is performed again to determine optimal design of the press, and this design is introduced to ensure that most of the stresses on the main plates are within safe allowable limits. As a result, an optimal design method for the structure is investigated to produce the desired pressure even when the size of the main structure is minimized.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.05a
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• pp.19-22
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• 2003

In this study, the design of prestressed die for spur gear forging have been investigated. The stress concentration at notch of the die insert is very important in the design of die for the forging of spur gear such as non-axisymmetric geometry. In the previous study, the flexible tolerance method was used in order to search the optimal value of design variables considering the constrain conditions. In the design process, it was also involved the safety factor to the yield strength of each ring by considering allowable tensile or compressive hoop stress in each ring. Using this technique, the die deign for spur gear forging has been successfully performed without yielding of the die after shrink fitting and during forging.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.711-715
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• 1995

In the concept design stage of the product design process, it is desirable that a designer makes alternative designs sufficiently, examines and analyzes them, and finally determines an appropriate design. To efficiently investigate several alternative designs, it should be facilitated to modify the model and transfer the model data to analysis program. In this research, a concept design process for tank is automated using I-DEAS feature-based modeling system from SDRC. Additionally, the facility for the pre-estimation of the performance of product, the useful volume calculation, the mass calculation, the confirmation of the allowable workspae, and the interface to analysis propram are developed using API functions of OPen-link and Open-data. Graphic User Interface (GUI) makes it extrmely easy to utilize functions.