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Myung-Ho Kim

Other affiliations: Changwon National University
Bio: Myung-Ho Kim is an academic researcher from Inha University. The author has contributed to research in topics: Microstructure & Alloy. The author has an hindex of 16, co-authored 68 publications receiving 641 citations. Previous affiliations of Myung-Ho Kim include Changwon National University.


Papers
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TL;DR: In this article, the diffuse phase transition behavior of the (Bi1/2 Na 1/2)1−x Bax TiO 3 TiO3 solid solutions was investigated from the e (T ) curve.
Abstract: The diffuse phase transition behavior of the (Bi1/2 Na1/2)1−x Bax TiO3 TiO3 solid solutions were investigated from the e ( T ) curve. The temperature due to the structural change coincided with the abrupt jump in e ( T ) curve. The dielectric constant maximum and the dielectric constant minimum were important parameters to define the phase transition. (Bi1/2 Na1/2)1−x Bax TiO3 TiO3 system has the phase transition sequence from rohmbohedral to tetragonal. The phase transition of (Bi1/2 Na1/2)1−x Bax TiO3 TiO3 system was accompanied with structural changes. When x is 0.06, 0.08 and 0.12, (Bi1/2 Na1/2)1−x Bax TiO3 TiO3 showed the diffuse phase transition as a relaxor. (Bi1/2 Na1/2)1−x Bax TiO3 TiO3 system related to the diffuse phase transition had the antiferroelectric phase. (Bi1/2 Na1/2)0.9 Ba0.1 TiO3 system showed the ferroelectric properties with the remanent polarization of 18 μ C/cm2 and the coercive electric field of 10 kV/cm.

55 citations

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TL;DR: In this article, emission spectra measurements by using optical emission spectroscopy (OES) were performed for various treatment temperatures, duty factors and different gas pressures in the reactor.
Abstract: In order to investigate the behavior of nitrogen active species during the pulsed d.c. plasma nitriding process, emission spectra measurements by using optical emission spectroscopy (OES) were performed for various treatment temperatures, duty factors and different gas pressures in the reactor. Results of the OES were compared to those of the metallurgical analysis of plasma nitrided sintered steel and high speed steel substrates. The spectral intensities of N 2 + and N 2 were influenced by process parameters (gas pressure, treatment temperature and duty factor). The thickness of the nitride layer and the size of micro-pore increased with increasing treatment temperature. Especially, the thickness of the compound layer was mainly influenced by the gas pressure in the reactor.

47 citations

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TL;DR: In this paper, the mixing enthalpy, which was calculated by the Miedema model, was considered as a new parameter to select effective modifying agent for Al-Si alloys, in addition to conventional parameters such as the crystal structure and lattice constant.
Abstract: To select effective modifying agent for Al–Si alloys, in addition to conventional parameters such as the crystal structure and lattice constant, the mixing enthalpy, which was calculated by the Miedema model, was newly considered. The large negative value of mixing enthalpy was counted as a new parameter. According to the result of calculation, four elements, including Sr, Y, Sm and Gd, which have large negative mixing enthalpies with Si, were selected as modifying agent for eutectic Si crystals. It was observed that these elements result in the modification of the eutectic Si crystals and that the eutectic depression of the modified alloy is larger than 6 K.

41 citations

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TL;DR: In this paper, the effects of pulse frequency and treatment temperature on the formation of nitrided layers and surface characteristics during plasma nitriding were examined using a pulsed d.c. plasma with various frequencies in an atmosphere of N 2 -H 2 gas mixture.
Abstract: This work was initiated to examine the effects of pulse frequency and treatment temperature on the formation of nitrided layers and surface characteristics during plasma nitriding. Plasma nitriding experiments were performed with 316L austenitic stainless steel at the temperatures of 400 and 500°C using a pulsed d.c. plasma with various frequencies in an atmosphere of N 2 –H 2 gas mixture. The microstructure and thickness of the nitrided layers and morphology of the nitrided surfaces were investigated using optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM). XRD patterns revealed that the surface layer formed at 400°C consisted of S-phase only and CrN+Fe 4 N nitrides at 500°C, and no change of phase composition with frequency was observed. The compound layer thickened slightly with increased frequency. In addition, the surface roughness also increased as the frequency of the pulsed plasma was increased from 50 to 5000 Hz.

41 citations

Journal ArticleDOI
TL;DR: In this article, a polycrystalline Zr was deformed by equal channel angular pressing (ECAP) and the microstructural characteristics were analyzed by X-ray diffraction and electron backscattered diffraction (EBSD).
Abstract: Pure polycrystalline Zr was deformed by equal channel angular pressing (ECAP), and the microstructural characteristics were analyzed. By repeated alternating ECAP, it was possible to, refine the grain size from 200 to 0.2 μm. Subsequent annealing heat treatment at 550°C resulted in a grain growth of up to 6 μm. Mechanical twinning was an important deformation mechanism, particularly during the early stage of deformation. The most active twinning system was identified as 85.2 deg \(\left\{ {10\bar 12} \right\}\left\langle {\bar 1011} \right\rangle \) tensile twinning, followed by 57.1 deg \(\left\{ {10\bar 11} \right\}\left\langle {\bar 1012} \right\rangle \) compressive twinning. Crystal texture as well as grain-boundary misorientation distribution of deformed Zr were analyzed by X-ray diffraction (XRD) and electron backscattered diffraction (EBSD). The ECAP-deformed Zr showed a considerable difference in the crystallographic attributes from those of cold-rolled Zr or Ti, in that texture and boundary misorientation-angle distribution tend toward more even distribution with a slightly preferential distribution of boundaries of a 20 to 30 deg misorientation angle. Furthermore, unlike the case of cold rolling, the crystal texture was not greatly altered by subsequent annealing heat treatment. Overall, the present work suggests ECAP as a viable method to obtain significant grain refining in hexagonal close-packed (hcp) metals.

34 citations


Cited by
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Journal ArticleDOI
TL;DR: In this article, a review examines recent developments related to the use of ECAP for grain refinement including modifying conventional ECAP to increase the process efficiency and techniques for up-scaling the procedure and for the processing of hard-to-deform materials.

3,669 citations

Journal ArticleDOI
TL;DR: In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented, ranging from atom to phase diagram, and the current development stage in lead free piezoceramics is then critically assessed.
Abstract: A large body of work has been reported in the last 5 years on the development of lead-free piezoceramics in the quest to replace lead–zirconate–titanate (PZT) as the main material for electromechanical devices such as actuators, sensors, and transducers. In specific but narrow application ranges the new materials appear adequate, but are not yet suited to replace PZT on a broader basis. In this paper, general guidelines for the development of lead-free piezoelectric ceramics are presented. Suitable chemical elements are selected first on the basis of cost and toxicity as well as ionic polarizability. Different crystal structures with these elements are then considered based on simple concepts, and a variety of phase diagrams are described with attractive morphotropic phase boundaries, yielding good piezoelectric properties. Finally, lessons from density functional theory are reviewed and used to adjust our understanding based on the simpler concepts. Equipped with these guidelines ranging from atom to phase diagram, the current development stage in lead-free piezoceramics is then critically assessed.

2,510 citations

01 Jan 1979
TL;DR: This special issue aims at gathering the recent advances in learning with shared information methods and their applications in computer vision and multimedia analysis and addressing interesting real-world computer Vision and multimedia applications.
Abstract: In the real world, a realistic setting for computer vision or multimedia recognition problems is that we have some classes containing lots of training data and many classes contain a small amount of training data. Therefore, how to use frequent classes to help learning rare classes for which it is harder to collect the training data is an open question. Learning with Shared Information is an emerging topic in machine learning, computer vision and multimedia analysis. There are different level of components that can be shared during concept modeling and machine learning stages, such as sharing generic object parts, sharing attributes, sharing transformations, sharing regularization parameters and sharing training examples, etc. Regarding the specific methods, multi-task learning, transfer learning and deep learning can be seen as using different strategies to share information. These learning with shared information methods are very effective in solving real-world large-scale problems. This special issue aims at gathering the recent advances in learning with shared information methods and their applications in computer vision and multimedia analysis. Both state-of-the-art works, as well as literature reviews, are welcome for submission. Papers addressing interesting real-world computer vision and multimedia applications are especially encouraged. Topics of interest include, but are not limited to: • Multi-task learning or transfer learning for large-scale computer vision and multimedia analysis • Deep learning for large-scale computer vision and multimedia analysis • Multi-modal approach for large-scale computer vision and multimedia analysis • Different sharing strategies, e.g., sharing generic object parts, sharing attributes, sharing transformations, sharing regularization parameters and sharing training examples, • Real-world computer vision and multimedia applications based on learning with shared information, e.g., event detection, object recognition, object detection, action recognition, human head pose estimation, object tracking, location-based services, semantic indexing. • New datasets and metrics to evaluate the benefit of the proposed sharing ability for the specific computer vision or multimedia problem. • Survey papers regarding the topic of learning with shared information. Authors who are unsure whether their planned submission is in scope may contact the guest editors prior to the submission deadline with an abstract, in order to receive feedback.

1,758 citations

Journal ArticleDOI
TL;DR: In this paper, texture development in metals of fcc, bcc, and hcp crystal structure processed by a severe plastic deformation (SPD) technique called equal-channel angular extrusion (ECAE) or equal channel angular pressing (ECAP) is discussed.

419 citations

Journal ArticleDOI
TL;DR: In this article, the evolution of microstructure and the mechanical response of copper subjected to severe plastic deformation using equal channel angular pressing (ECAP) was investigated, and it was shown that the microstructures produced through adiabatic shear localization during high strain rate deformation and ECAP are very similar.

401 citations