• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.555-556
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• 2006

• Proceedings of the KSME Conference
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• 2002.08a
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• pp.419-422
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• 2002

A three-dimensional inlet flow structure inside a microfluidic element has been investigated using a micro-PIV(particle image velocimetry) measurement as well as a numerical analysis. The present study employs a state-of-art micro-PIV system which consists of epi-fluorescence microscope, 620nm diameter fluorescent seed particles and an 8-bit megapixel CCD camera. For the numerical analysis, a commercial software CFD-ACE+(V6.6) was employed for comparison with experimental data. Fixed pressure boundary condition and a 39900 structured grid system was used for numerical analysis. Velocity vector fields with a resolution of $6.7{\times}6.7{\mu}m$ has been obtained, and the attention has been paid on the effect of varying measurement conditions of particle diameter and particle concentration on the resulting PIV results. In this study, the microfluidic elements were fabricated on plastic chips by means of MEMS processes and a subsequent melding process.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.754-758
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• 2000

Milli-structure components are classified as component group whose size is between macro and micro scale. that is, about less than 20mm and larger than 1mm. The forming of these components has a typical phenomenon of bulk deformation with thin sheets because of the forming size. In order to conventional metal forming, where numerical process simulation is already fully applied, the micro-forming process is characterized by some scale effects which have to be considered in an advanced process simulation. milli-structure rectangular cup drawing is analyzed and designed using the finite element method and experiment. The result of the finite element analysis is confirmed by a series of experiments.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.711-715
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• 1996

This paper describes an automated computer-aided engineering (CAE) system for micromachines whose size range 10 to 10$^3$${\mu}{\textrm}{m}$. An automatic finite element mesh generation technique, which is based on the fuzzy knowledge processing and computational geometry techniques, is incorporated into the system, together with one of commercial finite clement (FE) analysis codes, MARC, and one of commercial solid modelers, Designbase. The system allows a geometry model of concern to be a automatically converted to different FE models, depending on physical phenomena to be analyzed, i.e. electrostatic analysis, stress analysis, modal analysis and so on. The FE analysis models are then exported to the FE analysis code, and then analyses are performed. This system is successfully applied to an electrostatic micro actuator.

• Journal of Welding and Joining
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• v.19 no.1
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• pp.88-94
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• 2001

DUPIC (Direct use of spent PWR fuel in CANDU reactors) nuclear fuel is a CANDU fuel fabricated remotely from spent PWR fuel materials in a hot cell. The soundness of the end closure welds of nuclear fuel elements is an important factor for the safety and performance of nuclear fuel. To evaluate the soundness of the end closure welds of DUPIC fuel element, a precise X-ray inspection system is developed using a micro-focus X-ray generator with an image intensifier and a real time camera system. The fuel elements made of Zircaloy-4 and stainless steel by an Nd:YAG laser welding and a TIG welding aye inspected by the developed inspection system. The soundness of the welds of the fuel elements was confirmed by the X-ray inspection process, and the irradiation test of DUPIC fuel elements has been successfully completed at the HANARO research reactor.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1029-1032
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• 2002

This paper describes a design of a tactile sensor, which can measure three components force and temperature due to thermal conductive. The bio-mimetic tactile sensor, alternative to human's finger, is comprised of four micro force sensors and four thermal sensors, and its size being 10mm$\times$10mm. Each micro force sensor has a square membrane, and its force range is 0.1N - 5N in the three-axis directions. On the other hand, the thermal sensor for temperature measurement has a heater and four temperature sensor elements. The thermal sensor is designed to keep the temperature. $36.5^{\circ}C$, constant, like human skin, and measure the temperature $0^{\circ}C$ to $50^{\circ}C$. The MEMS technology is applied to fabricate the sensing element of the tactile sensor.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.7
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• pp.409-416
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• 2004

This paper presents the selection method o( the input current wave forms for the thrust force ripple of linear pulse motor (LPM). We have developed and tested a prototype 2-phase 4-poles LPM with the permanent magnet and its control driver. To obtain the thrust performance curve of LPM, the performance curve at the air gap and the thrust are calculated and estimated by the analytical method on the base of the magnetic equivalent circuit and the finite element method. And, the thrust characteristics at the static operation state are analyzed and experimented with the respect to the input wave forms such as the rectangular, the triangular micro-step and the sine micro-step wave forms to investigate the thrust ripple and the vibration effects of LPM.

• Interaction and multiscale mechanics
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• v.3 no.2
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• pp.111-121
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• 2010

Dynamic analysis of nano/micro bio-sensors based on a multiscale atomistic/continuum theory is introduced. We use a generalized atomistic finite element method (GAFEM) to analyze a bio-sensor which has $3{\times}N_a{\times}N_p$ degrees of freedom, where $N_p$ is the number of representative unit cells and $N_a$ is the number of atoms per unit cell. The stiffness matrix is derived from interatomic potential between pairs of atoms. This work contains two studies: (1) the resonance analysis of nano bio-sensors with different amount of target analyte and (2) the dependence of resonance frequency on finite element mesh. We also examine the Courant-Friedrichs-Lewy (CFL) condition based on the highest resonance frequency. The CFL condition is the criterion for the time step used in the dynamic analysis by GAFEM. Our studies can be utilized to predict the performance of micro/nano bio-sensors from atomistic perspective.

• Coupled systems mechanics
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• v.8 no.2
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• pp.111-127
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• 2019

In this paper, we present a 2D multi-scale coupling computation procedure for localized failure. When modeling the behavior of a structure by a multi-scale method, the macro-scale is used to describe the homogenized response of the structure, and the micro-scale to describe the details of the behavior on the smaller scale of the material where some inelastic mechanisms, like damage or plasticity, can be defined. The micro-scale mesh is defined for each multi-scale element in a way to fit entirely inside it. The two scales are coupled by imposing the constraint on the displacement field over their interface. An embedded discontinuity is implemented in the macro-scale element to capture the softening behavior happening on the micro-scale. The computation is performed using the operator split solution procedure on both scales.

• Advances in Computational Design
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• v.2 no.2
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• pp.107-119
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• 2017

The Micro circular diaphragm (MCD) is the mechanical actuator part used in the micro electro-mechanical sensors (MEMS) that combine electrical and mechanical components. These actuators are working under harsh mechanical and thermal conditions, so it is very important to study the mechanical and thermal behaviors of these actuators, in order to do with its function successfully. The objective of this paper is to determine the thermo-mechanical behavior of MCD by developing the traditional bulge test technique to achieve the aims of this work. The specimen is first pre-stressed to ensure that is no initial deflection before applied the loads on diaphragm and then clamped between two plates, a differential pressure (P) and temperature ($T_b$) is leading to a deformation of the MCD. Analytical formulation of developed bulge test technique for MCD thermo-mechanical characterization was established with taking in-to account effect of the residual strength from pre-stressed loading. These makes the plane-strain bulge test ideal for studying the mechanical and thermal behavior of diaphragm in both the elastic and plastic regimes. The differential specimen thickness due to bulge effect to describe the mechanical behavior, and the temperature effect on the MCD material properties to study the thermal behavior under deformation were discussed. A finite element model (FEM) can be extended to apply for investigating the reliability of the proposed bulge test of MCD and compare between the FEM results and another one from analytical calculus. The results show that, the good convergence between the finite element model and analytical model.