• Journal of the Korean Vacuum Society
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• v.8 no.3A
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• pp.213-217
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• 1999

Fe/MnO multilayers with different bilayer thicknesses were grown by pulsed laser deposition method. Grazing incidence X-ray reflectivity results showed obvious multilayer Bragg peaks implying highly layered samples and, through their analysis, some structural parameters were quantiatively estimated. From the X-ray diffraction peak corresponding to MnO(111), Mn-oxide turned out to be dominantly MnO. To characterize the magnetic properties of $Mn^{+2}$, XMCD were carried out. Magnetic moments of MnO near interfaces were ordered in the opposite direction to those of Fe.

• Corrosion Science and Technology
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• v.17 no.6
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• pp.265-271
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• 2018

CRUD specimens, scraped from twice-burned fuel cladding in the Korean Nuclear Power Plant, were analyzed using Shielded-EPMA. The principal elements of the CRUD were identified as Ni and Fe, at an approximate ratio of 1.3 Ni/Fe. To investigate the morphology and composition of the pure metallic materials in the CRUD, coolant impurities must be removed. This can be accomplished by increasing the EPMA current to an abnormally high intensity until the impurities are melted. Normally, EPMA applications are performed at conditions of 20 kV voltage and 20 nA current. But in our study, the applied current was increased up to 1200 nA, over time increments ranging from 5 to 30 seconds. This technique was performed by opening an adjustable aperture for the gun alignment. Results showed impurities contained in the CRUD material disappeared and pure metal materials, e.g., Ni and Fe, remained. This method presents an innovative way to analyze CRUD.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.5
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• pp.345-352
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• 2017

In this study, squeal noise with respect to pressure variation is measured by a lab-scaled brake dynamometer and estimated by a complex finite element (FE) eigenvalue analysis. From the FE eigenvalue sensitivity analysis, unstable frequencies occur due to a mode-coupling mechanism and are found to change with variation in contact stiffness. In the experiment, squeal frequencies near 1 kHz, 2.5 kHz, 3.5 kHz, and 4 kHz are increased with pressure variation. The sensitivity of squeal modes to contact stiffness variation obtained from the FE analysis is shown to approximate the variation of squeal frequencies under pressure variation in the experiment.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.6
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• pp.583-588
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• 2015

Asymptotic method has been often used to theoretically analyze the complete contact problem. The error of the asymptotic results increases as the distance from the contact edge increases. The singularity cannot be properly obtained from a finite element (FE) analysis owing to the finiteness of the element size. In the present work, the complete contact problem in bonded condition is analyzed using a combined experimental-numerical approach to assist and/or compare with the asymptotic results. Al and Cu alloys are used for the material combination of the punch and substrate. 120 and 135 degrees are used for the punch angle. The FE models are validated by comparison of displacement distributions obtained by the FE analysis and $moir{\acute{e}}$ experiment. Generalized stress intensity factors are evaluated using the validated FE models. Stress field in the vicinity of the sharp contact edges obtained from the FE and asymptotic analyses are compared. The discrepancies are also discussed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.703-709
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• 2017

Creep analysis takes much more time than elastic or elastic-plastic analysis. In this study, we conducted elastic and elastic-plastic analysis and compared the results with creep analysis results. In the elastic analysis, we used primary stress, which can be classified by the $M{\alpha}-tangent$ method and stress intensities recommended in the ASME code. In the elastic-plastic analysis, we calculated the parameters recommended in the R5 code. For the FE models, a bending load, uniaxial load, and biaxial load were applied to the cross shaped welded plate, and a bending load and internal pressure were applied to the elbow pipe. To investigate the element size sensitivity, we conducted FE analysis for various element sizes for the cases where bending load was applied to the cross shaped welded plate. There was no significant difference between the creep stress and the alternative methods; however, in the $M{\alpha}-tangent$ method, the results were affected by the element size.

• Korean Journal of Computational Design and Engineering
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• v.1 no.1
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• pp.65-75
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• 1996

This paper describes an automatic finite element(FE) mesh generation for three-dimensional structures consisting of free-form surfaces. This mesh generation process consists of three subprocesses: (a) definition of geometric model, i.e. analysis model, (b) generation of nodes, and (c) generation of elements. One of commercial solid modelers is employed for three-dimensional solid and shell structures. Node is generated if its distance from existing node points is similar to the node spacing function at the point. The node spacing function is well controlled by the fuzzy knowledge processing. The Delaunay method is introduced as a basic tool for element generation. Automatic generation of FE meshes for three-dimensional solid and shell structures holds great benefits for analyses. Practical performances of the present system are demonstrated through several mesh generations for three-dimensional complex geometry.

• Applied Microscopy
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• v.45 no.4
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• pp.214-217
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• 2015

This study introduces metal coating as an effective sample preparation method to remove charge-up caused by the shadow effect during field emission scanning electron microscope (FE-SEM) analysis of dynamic structured samples. During a FE-SEM analysis, charge-up occurs when the primary electrons (input electrons) that scan the specimens are not equal to the output electrons (secondary electrons, backscattered electrons, auger electrons, etc.) generated from the specimens. To remove charge-up, a metal layer of Pt, Au or Pd is applied on the surface of the sample. However, in some cases, charge-up still occurs due to the shadow effect. This study developed a coating method that effectively removes charge-up. By creating a converted sample stage capable of simultaneous tilt and rotation, the shadow effect was successfully removed, and image data without charge-up were obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.1
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• pp.121-131
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• 1998

This paper applies the FE analysis procedure, developed in the Part I of the companion article, to the three-dimensional rubber pad deformation during rubber-pad forming process. Effects of different algorithms corresponding to incompressibility constraint and time integration methods on numerical solution responses are investigated. Laboratory scale experiments support the validity of the developed FE procedure an demonstrate the accuracy of the numerical models. Full scale model responses are also predicted using the reasonable method and parameters obtained in laboratory modeling.

• KSBB Journal
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• v.16 no.6
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• pp.609-613
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• 2001

New protein-based biosensors using fluorescence for the detection heavy metal ions were developed. The detection range of heavy metal ions was between 10$\^$-3/ mM - 1 mM using casein and albumin as a transducer of biosensor, respectively. Casein showed better results for detecting heavy metal ions than albumin. Simple assay method was developed for the selective analysis of the two heavy metal ions by the fluorescence at wavelength of excitation and emission. This method was successfully applied to determining the concentrations Of Co$\^$2+/ and Fe$\^$3+/.

• Proceedings of the Korea Concrete Institute Conference
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• 2010.05a
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• pp.37-38
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• 2010

The deflection of RC half slabs with rids was much smaller than that of the conventional RC half slabs. In this study, the deflection of RC half slabs with rids was calculated by using a FE method and a elastic analysis. The deflections predicted by the FE method and the elastic analysis predicted the deflection measured by tested slabs with reasonable agreement.