• Journal of the Korean Ceramic Society
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• v.48 no.5
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• pp.396-403
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• 2011

In this study, we investigated the mechanical behaviors of layered thermal barrier coatings by indentations. Various single and double-layered thermal barrier coatings were deposited by air plasma spray process using different type of commercialized YSZ (Yttria stabilized zirconia) starting powders. Indentation stress-strain curve, load-displacement curve and hardness of the single and the double-layered thermal barrier coatings were obtained experimentally and analyzed. The indentation damages at the same loads were compared, and thus, the results depend on the structure of each coating. The result indicates improvement in damage resistances from tailoring of layered structures in the component of gas turbine system is expected.

• Steel and Composite Structures
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• v.31 no.6
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• pp.641-653
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• 2019

In this paper, wave propagation is studied and analyzed in double-layered nanotubes systems via the nonlocal strain gradient theory. To the author's knowledge, the present paper is the first to investigate the wave propagation characteristics of double-layered porous nanotubes systems. It is generally considered that the material properties of nanotubes are related to the porosity and hygro-thermal effects. The governing equations of the double-layered nanotubes systems are derived by using the Hamilton principle. The dispersion relations and displacement fields of wave propagation in the double nanotubes systems which experience three different types of motion are obtained and discussed. The results show that the phase velocities of the double nanotubes systems depend on porosity, humidity change, temperature change, material composition, non-local parameter, strain gradient parameter, interlayer spring, and wave number.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.4
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• pp.358-373
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• 2024

Oxygen evolution reaction is a critical bottleneck for the development of efficient electrochemical hydrogen production because of its sluggish reaction. Among various catalysts, transition metal-based layered double hydroxide has drawn significant attention due to their excellent catalytic properties and cost-effectiveness. This paper begins with basic crystal structures, and then conventional adsorbate evolution mechanism of layered double hydroxide. Strategies for enhancing catalytic properties based on adsorbate evolution mechanism and lattice oxygen mechanism that could surpass theoretical limit of adsorbate evolution mechanism are discussed. This paper ends with a brief discussion on the challenges and future directions of layered double hydroxide-based oxygen evolution reaction catalysts.

• Journal of the Korean Society for Precision Engineering
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• v.31 no.3
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• pp.269-275
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• 2014

Conventional machining technologies such as a milling process have limitations in accuracy to fabricate microstructures. Deep X-ray lithography using the synchrotron radiation is a promising micromachining process with an excellent accuracy, whereas there are difficulties in the fabrication of multi-layered structures. Therefore, it is mainly used for fabricating simple mono-layered microstructures with a high aspect ratio. In this study, a novel technology for fabricating multi-layered microstructures is proposed by combining two processes. In advance, an X-ray resist material is cut and machined into various shapes and heights by the micro milling process. Subsequent X-ray irradiation process facilitates the fabrication of multi-layered microstructures. The proposed technology can overcome the limitation of the pattern accuracy in conventional milling process and the difficulty of the multi-layered machining in x-ray process. The usefulness of the proposed technology is demonstrated in this study by applying the technique in the realization of various multi-layered microstructures.

• Earthquakes and Structures
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• v.24 no.1
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• pp.65-79
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• 2023

A simplified analytical solution for seismic response of tunnel cross section in horizontally layered ground subjected to oblique incidence of SH wave is deduced in this paper. The proposed analytical solution consists of two main steps: free-field response in layered field and tunnel response. The free field responses of the layered ground are obtained by one-dimensional finite element method in time domain. The tunnel lining is treated as a thick-wall cylinder to calculate the tunnel response, which subject to free field stress. The analytical solutions are verified by comparing with the dynamic numerical results of two-dimensional ground-lining interaction analysis under earthquake in some common situations, which have a good agreement. Then, the appropriate range of the proposed analytical solution is analyzed, considering the height of the layered ground, the wavelength and incident angle of SH wave. Finally, by using the analytical solutions, the effects of the ground material, burial depth of the tunnel, and lining thickness and the slippage effect at the ground-lining interface on the seismic response of tunnels are investigated. The proposed solution could serve as a useful tool for seismic analysis and design of tunnels in layered ground.

• KIPS Transactions on Computer and Communication Systems
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• v.6 no.10
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• pp.415-420
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• 2017

Virtualization technique of OS-level is a new paradigm for deploying applications, and is attracting attention as a technology to replace traditional virtualization technique, VM (Virtual Machine). Especially, docker containers are capable of distributing application images faster and more efficient than before by applying layered image structures and union mount point to existing linux container. These characteristics of containers can only be used in layered file systems that support snapshot functionality, so it is required to select appropriate layered file systems according to the characteristics of the containerized application. We examine the characteristics of representative layered file systems and conduct write performance evaluations of each layered file systems according to the operating principles of the layered file system, Allocate-on-Demand and Copy-up. We also suggest the method of determining a appropriate layered file system principle for unknown containerized application by learning block I/O usage history of each layered file system principles in artificial neural network. Finally we validate effectiveness of artificial neural network created from block I/O history of each layered file system principles.

• Journal of the Korean Ceramic Society
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• v.53 no.4
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• pp.417-428
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• 2016

In this review, an attempt is made to calculate one-dimensional (1-D) electron density profiles from experimentally determined (00l) XRD intensities and possible structural models as well in an effort to understand the collective intracrystalline structures of intercalant molecules of two-dimensional (2-D) nanohybrids with heterostructures. 2-D ceramics, including layered metal oxides and clays, have received much attention due to their potential applicability as catalysts, electrodes, stabilizing agents, and drug delivery systems. 2-D nanohybrids based on such layered ceramics with various heterostructures have been realized through intercalation reactions. In general, the physico-chemical properties of such 2-D nanohybrids are strongly correlated with their heterostructures, but it is not easy to solve the crystal structures due to their low crystallinity and high anisotropic nature. However, the powder X-ray diffraction (XRD) analysis method is thought to be the most powerful means of understanding the interlayer structures of intercalant molecules. If a proper number of well-developed (00l) XRD peaks are available for such 2-D nanohybrids, the 1-D electron density along the crystallographic c-axis can be calculated via a Fourier transform analysis to obtain structural information about the orientations and arrangements of guest species in the interlayer space.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.4
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• pp.244-248
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• 2015

We proposed and demonstrated the double layered metallic nano-hole structure using polystyrene beads process to enhance the sensitivity of surface plasmon resonance (SPR). The double layered SPR structures are calculated using the finite-difference time-domain (FDTD) method for the width, thickness, and period of the metallic nano-hole structures. The thickness of the metal film and the metallic nano-hole is 30 and 20 nm in the 214 nm wide nano-hole size, respectively. The double layered SPR structures are fabricated with monolayer polystyrene beads of 420 nm wide. The sensitivities of the conventional SPR sensor and the double layered SPR sensor are obtained to 42.2 and 52.1 degree/RIU, respectively.

• Earthquakes and Structures
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• v.24 no.4
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• pp.259-274
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• 2023

In this paper, mechanical properties of periodic foundation made of concrete and rubber are investigated by a parametric study using the finite element method (FEM). Periodic foundation is a special type of seismic isolation foundation used in civil engineering, which is inspired by the meso-scale structure of phononic crystals in solid-state physics. This type of foundation is capable of reducing the seismic wave propagating though the foundation, therefore providing additional protection for the structures. In the FEM analysis, layered periodic foundation is frequently modelled due to its simplicity in numerical modeling. However, the isolation effect of periodic foundation on nuclear power plant has not been fully discussed to the best knowledge of authors. In this work, we construct four numerical models of nuclear power plant with different foundations to investigate the seismic isolation effects of periodic foundations. The results show that the layered periodic foundation can increase the natural period of the nuclear power plant like traditional base isolation systems, which is beneficial to the structures. In addition, the seismic response of the nuclear power plant can also be effectively reduced in both vertical and horizontal directions when the frequencies of the incident waves fall into some specific frequency bandgaps of the periodic foundation. Furthermore, it is demonstrated that the layered periodic foundation can reduce the amplitude of the floor response spectrum, which plays an important role in the protection of the equipment.

• Structural Engineering and Mechanics
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• v.34 no.6
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• pp.685-702
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• 2010

In this paper, a nonlinear finite element procedure is presented for the dynamic analysis of reinforced concrete shell structures. A computer program, named RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), was used. A 4-node flat shell element with drilling rotational stiffness was used for spatial discretization. The layered approach was used to discretize the behavior of concrete and reinforcement in the thickness direction. Material nonlinearity was taken into account by using tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach was incorporated. The low-cycle fatigue of both concrete and reinforcing bars was also considered to predict a reliable dynamic behavior. The solution to the dynamic response of reinforced concrete shell structures was obtained by numerical integration of the nonlinear equations of motion using Hilber-Hughes-Taylor (HHT) algorithm. The proposed numerical method for the nonlinear dynamic analysis of reinforced concrete shell structures was verified by comparison of its results with reliable experimental and analytical results.