• Proceedings of the Korean Vacuum Society Conference
• /
• 2013.08a
• /
• pp.287.1-287.1
• /
• 2013

The Isolation of few-layered transition metal dichalcogenides has mainly been performed by mechanical and chemical exfoliation with very low yields. in particular, the two-dimensional layer of molybdenum disulfide (MoS2) has recently attracted much interest due to its direct-gap property and potential application in optoelectronics and energy harvesting. However, the synthetic approach to obtain high-quality and large-area MoS2 atomic thin layers is still rare. In this account, a controlled thermal reductionsulfurization method is used to synthesize large-MoOx thin films are first deposited on Si/SiO2 substrates, which are then sulfurized (under vacuum) at high temperatures. Samples with different thicknesses have been analyzed by Raman spectroscopy and TEM, and their photoluminescence properties have been evaluated. We demonstrated the presence of single-, bi-, and few-layered MoS2 on as-grown samples. It is well known that the electronic structure of these materials is very sensitive to the number of layer, ranging from indirect band gap semiconductor in the bulk phase to direct band gap semiconductor in monolayers. This synthetic approach is simple, scalable, and applicable to other transition metal dichalcogenides. Meanwhile, the obtained MoS2 films are transferable to arbitrary substrates, providing great opportunities to make layered composites by stacking various atomically thin layers.

• Journal of the Institute of Convergence Signal Processing
• /
• v.12 no.2
• /
• pp.145-149
• /
• 2011

Recently, as the design of a system gets larger and more complex, functional verification method based on system-level becomes more important. The verification of a functional block mainly uses BFM(bus functional model). The larger the burden on functional verification is, the more the importance of configuring a proper verification environment increases rapidly. SystemVerilog unifies hardware design languages and verification languages in the form of extensions to the Veri log HDL. The processing of design description, function simulation and verification using same language has many advantages in system development. In this paper, we design DUT that is composed of AMBA bus and function blocks using SystemVerilog and verify the function of DUT in verification environment using layered testbench. Adaptive FIR filter and Booth's multiplier are chosen as function blocks. We confirm that verification environment can be reused through a minor adaptation of interface to verify functions of other DUT.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.21 no.1
• /
• pp.87-101
• /
• 2019

The sleeve is closely connected with activity in terms of costume. As a kind of overcoat, Dap-ho of the Joseon Dynasty is short-sleeved or sleeveless. Dap-ho, with simple sleeves is convenient for layering and taking off and since it is easily adjustable using a gusset, a slit, or coat string, and this can be applied to layered look-related designs. This study aims to suggest a design item, which sustains the existence of traditional costumes and facilitates diverse layered looks and co-ordination, using the formative elements of Dap-ho. For this study, theoretical backgrounds and relics of Dap-ho of the Joseon Dynasty were analyzed, based on the previous studies, ancient literature, "The Annals of the Joseon Dynasty", and relics preserved in museums. The analysis targeted nine relics that show the birth and death years and the constructive changes in shapes, colors, materials of Dap-ho. Formative elements of Dap-ho were applied to the designing and the manufacturing of clothes for middle-aged women in their fifties and the research conclusions are as follows. First, from a morphological perspective, the silhouette, gusset, slit, and the indirectly attached coat string of Dap-ho are good to be used as various design items for covering the body shapes of middle-aged women, and the short-sleeved or sleeveless type is convenient to be layered. Second, when it comes to the material, it is possible to emphasize a traditional image and practicality at the same time by mixing and matching the Hanbok cloth and cotton. Third, in relation to the colors, the coexistence-based color arrangement method considering the theory of Yin and Yang can be applied to modern clothes and this makes it possible to express a traditional image in a harmonious way.

• Journal of Electrochemical Science and Technology
• /
• v.14 no.3
• /
• pp.293-300
• /
• 2023

The global energy storage markets have gravitated to high-energy-density and low cost of lithium-ion batteries (LIBs) as the predominant system for energy storage such as electric vehicles (EVs). High-Ni layered oxides are considered promising next-generation cathode materials for LIBs owing to their significant advantages in terms of high energy density. However, the practical application of high-Ni cathodes remains challenging, because of their structural and surface instability. Although extensive studies have been conducted to mitigate these inherent instabilities, a two-step process involving the synthesis of the cathode and a dry/wet coating is essential. This study evaluates a one-step β-Li₂SnO₃ layer coating on the surface of LiNi_0.8Co_0.2O₂ (NC82) via the thermal segregation of Sn owing to the solubility limit with respect to the synthesis temperature. The doping, segregation, and phase transition of Sn were systematically revealed by structural analyses. Moreover, surface-engineered 5 mol% Sn-coated LiNi_0.8Co_0.2O₂ (NC82_Sn5%) exhibited superior capacity retention compared to bare NC82 owing to the stable surface coating layer. Thus, the developed one-step coating method is suitable for improving the properties of high-Ni layered oxide cathode materials for application in LIBs.

• Journal of the Korean Geotechnical Society
• /
• v.25 no.1
• /
• pp.55-64
• /
• 2009

One of the important use of piles is to furnish lateral support and nowadays it is getting highlighted due to the increase of skyscrapers, transmission towers, wind turbines, and other lateral action dependent structures. After Broms (1964), many researchers have suggested methods for estimating lateral capacity of pile. But each method assumes different earth pressure distribution and lateral earth pressure coefficient causing confusion on the part of pile designers. Lateral earth pressure, essential in lateral capacity estimation, is influenced by pile's rotational behavior under lateral load. Prasad and Chari (1999) assumed the rotation point of pile and suggested an equation of ultimate lateral load capacity. In this study, we investigate the depth of rotation point in both homogeneous soil and multi layered soil, and compare with the estimation value by previous research. Test results show that measured rotation point and estimated value by Prasad and Chari's equation show good agreement and multi layered condition affects the location of rotation point to be changed.

• Korean Journal of Materials Research
• /
• v.33 no.10
• /
• pp.377-384
• /
• 2023

Exploring earth-abundant, highly effective and stable electrocatalysts for electrochemical water splitting is urgent and essential to the development of hydrogen (H₂) energy technology. Iron-cobalt layered double hydroxide (FeCo-LDH) has been widely used as an electrocatalystfor OER due to its facile synthesis, tunable components, and low cost. However, LDH synthesized by the traditional hydrothermal method tends to easily agglomerate, resulting in an unstable structure that can change or dissolve in an alkaline solution. Therefore, studying the real active phase is highly significant in the design of electrochemical electrode materials. Here, metal-organic frameworks (MOFs) are used as template precursors to derive FeCo-LDH from different iron sources. Iron salts with different anions have a significant impact on the morphology and charge transfer properties of the resulting materials. FeCo-LDH synthesized from iron sulfate solution (FeCo-LDH-SO₄) exhibits a hybrid structure of nanosheets and nanowires, quite different from other electrocatalysts that were synthesized from iron chloride and iron nitrate solutions. The final FeCo-LDH-SO₄ had an overpotential of 247 mV with a low Tafel-slope of 60.6 mV dec^-1 at a current density of 10 mA cm^-2 and delivered a long-term stability of 40 h for the OER. This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

• The Journal of the Acoustical Society of Korea
• /
• v.17 no.3E
• /
• pp.35-42
• /
• 1998

Transient acoustic and elastic wave propagation in inhomogeneous media are studied by using the Fourier method. It is known that the fourier method has advantages in memory requirements and computing speed over conventional methods such as FDM and FEM, because the Fourier method needs less grid points for achieving the same accuracy. To verify the proposed numerical scheme, several examples having analytic solutions are considered, where two different semi-infinite media are in contact along a plane boundary. The comparisons of numerical results by the Fourier method and analytic solutions show good agreements. In addition, the fourier method is applied to a layered half-plane, in which an elastic semi-infinite medium is covered by an elastic layer of finite thickness. It is showed how to derive the analytic solutions by using the Cagniard-de Hoop method. The numerical solutions are in excellent agreements with analytic results.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2006.04a
• /
• pp.891-897
• /
• 2006

The volume control method which utilize a pressure node added into a finite shell element can overcome the drawbacks of conventional load control method and displacement control method. In this study, an improved volume control method is introduced for effective analysis of path-dependant behaviors of RC structures subjected to cyclic loading. RC shell structures including RC hollow columns are anlayized by discretizing the structures with layered shell elements and by applying in-plane two dimensional constitutive equations for concrete layers and reinforcement layers of the shell elements. The so-called path dependant volume control method is verified by comparing analysis results with other data including experimental results.

• Structural Engineering and Mechanics
• /
• v.22 no.3
• /
• pp.331-349
• /
• 2006

The stresses and deflections in a laminated rectangular plate under thermal vibration are determined by using the moving least squares differential quadrature (MLSDQ) method based on the first order shear deformation theory. The weighting coefficients used in MLSDQ approximation are obtained through a fast computation of the MLS shape functions and their partial derivatives. By using this method, the governing differential equations are transformed into sets of linear homogeneous algebraic equations in terms of the displacement components at each discrete point. Boundary conditions are implemented through discrete grid points by constraining displacements, bending moments and rotations of the plate. Solving this set of algebraic equations yields the displacement components. Then substituting these displacements into the constitutive equation, we obtain the stresses. The approximate solutions for stress and deflection of laminated plate with cross layer under thermal load are obtained. Numerical results show that the MLSDQ method provides rapidly convergent and accurate solutions for calculating the stresses and deflections in a multi-layered plate of cross ply laminate subjected to thermal vibration of sinusoidal temperature including shear deformation with a few grid points.

• Journal of the Korean Geotechnical Society
• /
• v.17 no.6
• /
• pp.85-98
• /
• 2001

Cone penetration was analyzed by arbitrary Lagangian-Eulerian(ALE) method. In order to simulate full penetration, steady state analyses were performed using ABAQUS/Explicit, which models upward flow of soil layers. In the analysis of homogeneous layer it was found that the paths and the strain of soil particles were consistent with the result of the strain path method and that the ultimate resistance were reasonably evaluated. The cone penetration through different soil layers was also analyzed and that showed the transfer of cone resistance. The steady state ALE analysis could perform full penetration through the layered soils.