• 한국전산유체공학회지
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• 제19권3호
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• pp.77-84
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• 2014

The lattice Boltzmann (LB) method has been used to simulate rarefied gas flows in a micro-system as an alternative tool. However, previous results were mainly focused on a simple geometry with flat walls because the LB method is modeled on uniform Cartesian lattices. When previous boundary conditions for the microflows are applied to curved walls, the use of them requires approximation of the curved boundary by a series of stair steps, and introduces additional errors. For macroflows, no-slip curved wall boundary treatments have been developed remarkably in order to overcome these limits. However, the investigations for the slip curved wall boundary have rarely been performed for microflows. In this work, a curved boundary treatment of the LB method for a slip flow has been introduced. The results of the LB method for 2D microchannel and 3D microtube flows are in excellent agreement with the analytical solutions.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1559-1563
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• 2007

This paper presents a virtual machine design simulation program. Kinematics of various mechanisms can be modeled with 3 dimensional geometry and actuators. CAD data for any machine component can be easily imported in STL format. Machine components are assembled with kinematic joints simply by drag and drop function in virtual graphic simulator. Interference and collision of any component with other components can be identified during the motion simulation. Graphic user interface program is developed using Microsoft Direct X code. A precision micro stage system is demonstrated with the proposed virtual machine design simulator.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 춘계학술대회 논문집
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• pp.102-107
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• 1993

The achievable machining accuracy depends upon the level of the micro-engineering, and the dimensional tolerances in the order of 10nm and surface roughness in the order of 1nm are the accuracytargets to be achieved today. Suchrequirements cannot be satisfiedby the conventional machining processes. Single point diamond turning is one of the new techniques which can produce the parts with such accuracy limits. The aims of this thesis are to get a better understanding of the complex cutting process with a diamond tool and, consequently, to develope a predicting modelof a turned surface profile. In order to predict the turned surface profile, a numerical model has been developed. By means of this model, the influences of the cutting conditions, the material properties of the workpiece, the geometry of the cutting tool and the dynamic behaviour of the lathe and their influences via the cutting forces upon the surface roughness have been estimated.

• International Journal of Precision Engineering and Manufacturing
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• 제8권4호
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• pp.45-49
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• 2007

When drilling using electrical-discharge machining (EDM), severe electrode wear makes in-process measurements of the depth of the drilled hole and the volume of material removed impossible. To estimate the volume of material removed a reliable real-time discharge pulse counting method is proposed by assuming that the volume removed in EDM is proportional to the number of discharge pulses from an iso-energy pulse generator. The geometry of machined holes, including depths and cross-sectional profiles, is estimated using geometric analysis. A proportional relationship between the volume of material removed and the number of discharge pulses was developed and verified by experiments.

• Steel and Composite Structures
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• 제9권1호
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• pp.1-17
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• 2009

This paper is focused on the buckling and post buckling behaviour of rectangular corrugated board panels simply supported and subjected to compression load. The aim of the work is to understand the failure mechanism of investigated structure in order to quantify the effect of design parameters on the strength of a panel of given geometry. Two numerical models were developed adopting the finite element method. In the first one the corrugated board is represented by means of shell elements adopting an equivalent material, in the second the local structure is described in full detail modelling both straight and corrugated layers by means of shell elements and representing the connection between layers by special interface elements. The model correctness was checked by the comparison between out of plane central displacement predicted by the models and the experimental values found in literature. For the same case the effect of panel planarity error was evaluated. Finally a parametric analysis to investigate the effect of design parameters was carried out.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.213-216
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• 1996

This paper studies a class of in-parallel manipulators with special geometry where the forward displacement analysis problem can be solved easier than the fully parallel manipulators. Three horizontal links of this mechanism provide 3DOFs(Degrees of Freedom), which are one degree of orientational freedom and two degrees of translatory freedom. Three vertical links of this mechanism provide 3DOFs, which are two degrees of orientational freedom and one degree of translatory freedom. The main advantages of this manipulator, compared with the Stewart platform type, are the capability to produce pure rotation and to predict the motion of the moving platform easily. Since this manipulator has simple kinematic characteristics compared with the Stewart platform, controlling in real-time is possible due to less computational burden. The purpose of this investigation is to develope an analytical method and systematic method to analyze the basic kinematics of the manipulator. The basic kinematic equations of the manipulator are derived and simulation is carried out to show the performance of the mechanism.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.1-14
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• 2009

This paper proposes an interaction field concept based on the field theory of plasticity. Relative deformation between two arbitrary scales, e.g., macro and micro fields, is defined which can be implemented in the crystal plasticity-based constitutive framework. Differential geometrical quantities responsible for describing dislocations and defects in the interaction field are obtained, based on which dislocation density and incompatibility tensors are further derived. It is shown that the explicit interaction exists in the curvature or incompatibility tensor field, whereas no interaction in the torsion or dislocation density tensor field. General expressions of the interaction fields over multiple scales with more than three scale levels are derived and implemented into the present constitutive equation.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1989년도 가을 학술발표회 논문집
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• pp.65-70
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• 1989

Until recently post-processing of finite element model has been Heavily relied on expensive graphic peripheral devices. For this reason many engineers and researchers can not afford to access to the graphics. with the aid of inexpensive personal computers very econmical post-processor graphics program called MICRO-POST has been developed in conjunction with low-cost printers and plotters. Model geometry or results of analysis for the unlimitted meshes either produced by mainframe or microcomputer can be easily and economi-call presented in a number of different graphic devices. The paper presents the procedure obtaining the device the independent graphics, and the structure and functions of the program. It also describes a new error-preventive dialogue type input technique to control the plot operation in an interactive manner. Through the post-processing examples for the general purpose finite element programs, it demonstrates the usefulness of the program.

• Journal of Ship and Ocean Technology
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• 제3권1호
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• pp.1-11
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• 1999

Numerical simulation for the axisymmetric body with contractive and dilative periodic motion is carried out. The present analysis shows that a propulsive force can be obtained in highly viscous fluid by the contractive and dilative motion of axisymmetric body. An axisymmetric code is developed with unstructured grid system for the simulation of complicated motion and geometry. It is validated by comparing with the results of Stokes approximation with the problem of uniform flow past a sphere in low Reynolds number($R_n$ = 1). The validated code is applied to the simulation of contractive and dilative periodic motion of body whose results are quantitatively compared with the two dimensional case. The simulation is extended to the analysis of waving surface with projecting part for finding out the difference of hydrodynamics performance according to variation of waving surface configuration. The present study will be the basic research for the development of the propulsor of an axisymmetric micro-hydro-machine.

• International Journal of Quality Innovation
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• 제7권1호
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• pp.98-111
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• 2006

The paper presents the design of an optical profilometer, a device used for the reconstruction of the micro-geometry of mechanical parts in applications where high precision is needed. The design is based on Robust Design, a major' methodology for quality improvement of engineering systems. Several design solutions, namely different hardware and software setups of the device, are compared in order to select a configuration realising a desired trade-off between performance and cost. The peculiarity of the design strategy is the use of a computer model of the measurement process where the physical part of the process is simulated. This allows for an extensive exploration of the design space, thus opening the way to product innovation.