• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.12 no.6
• /
• pp.3-9
• /
• 2013

Aluminum Oxide($Al_2O_3$) ceramics are excellent candidates for such applications due to their outstanding mechanical, thermal, and tribological properties. However, they are difficult to machine using conventional mechanical methods. Carbon fillers, such as carbon nanotubes(CNT) and graphene nanoplatelets(GNP)can be dispersed in a ceramic matrix to improve the mechanical and electrical properties. In this study, CNT and Graphene reinforced hybrid ceramic composites were fabricated using the spark plasma sintering method at a temperature of $1,500^{\circ}C$, pressure of 40 MPa, and soaking time of 10min. Besides this, the material properties such as microstructure, crystal structure, hardness, and electrical conductivity were analyzed using FE-SEM, XRD, Vickers, and the 4-point probe method. A micro machining test was carried out to compare the effects of the material properties and the machining performance for CNT and Graphene reinforced ceramic composites.

• Elastomers and Composites
• /
• v.55 no.3
• /
• pp.215-221
• /
• 2020

Silica/SBR (styrene-butadiene rubber) compounds are the primary constituents of tire treads. Furthermore, the excellent dynamic viscoelastic properties of silica lead to good fuel efficiencies. However, the silanol group on the surface of silica does not mix well with non-polar rubber because of its polarity. This incompatibility causes aggregation due to the occurrence of hydrogen bonding between the hydroxyl groups, thereby reducing the dispersibility of silica. Recently, the wet master batch (WMB) process has been applied to overcome these disadvantages, and research on silica dispersants that can be used in the WMB process has been increasing. In this study, we prepared silica/SBR compounds by using three types of eco-friendly cellulose-based dispersants in the WMB process, namely: cellulose-, sodium carboxymethyl cellulose, and nanocellulose-based dispersants. Subsequently, we compared the vulcanization characteristics, viscoelastic properties, and mechanical properties of the compounds. The silica dispersibility in the rubber compounds was improved with the addition of the nano-cellulose dispersant, resulting in the enhancement of the workability, hardness, tensile strength, and wear resistance of the SBR compound.

• Textile Coloration and Finishing
• /
• v.34 no.2
• /
• pp.102-108
• /
• 2022

The physicochemical properties of stainless steel fibers which were modified by oxygen plasma treatment were analyzed through microscopy and XPS analysis. The wettability of the surface of the stainless steel fiber was observed by measuring water contact angle to find out the effect of the plasma treatment time on the surface characteristics of the stainless steel fiber. In addition, in order to understand the effect of oxygen plasma treatment on the deterioration of the stainless steel fiber properties, the physical properties due to plasma treatment was investigated by measuring the weight reduction, tensile strength, elongation, tensile modulus of the stainless steel fibers according to the treatment time. As a result, the stainless steel fiber surface was etched by the oxygen plasma and the surface became more wettable by the introduction of hydrophilic functional groups. However the physical properties of the stainless steel fiber were not significantly deteriorated even if the surface of the stainless steel fiber made hydrophilic.

• Journal of the Korean Society of Industry Convergence
• /
• v.27 no.3
• /
• pp.555-561
• /
• 2024

This paper derives material properties of steel bars that simulate the distribution of stress and strain of prestressed tendons used in Prestressed concrete(PSC) girders and presents an optimal material model. ABAQUS software was used to establish the 3D solid model of the PSC girder and strand wire rope for a PS(Prestressed) tendon. Then the model of steel wire rope was imported into the Isight interface plugin directly through the ABAQUS and the Data Matching. In ABAQUS, the contact pairs were established, the models were meshed, the constraints were applied to solve the finite element model and an axial tension of 0.5m/s was loaded to analyze the stress and deformation distributions in the normal working range of the PS strand wire rope. In Data Matching, classical experimental data is fitted to the optimal material properties through finite element analysis and multi-objective optimization. The results show that the steel bar with optimal material properties presents a similar linear area and stress distribution with the PS tendon.

• Carbon letters
• /
• v.26
• /
• pp.95-101
• /
• 2018

• ETRI Journal
• /
• v.32 no.4
• /
• pp.626-629
• /
• 2010

In this letter, we present an enhanced block-based adaptive loop filter (E-BALF) with multiple filter symmetric structures. The E-BALF adapts various filter symmetric structures in a rate-distortion optimization sense, reflecting the statistical properties of each image in a video sequence. Experimental results show that the proposed method achieves a reduction in the Bj${\phi}$ntegaard delta (BD)-bitrate by an average of 9.60% compared with Joint Model 11.0 of H.264/AVC. Compared to the state-of-the-art BALF, a reduction of up to 1.13% in BD-bitrate is achieved.

• Bulletin of the Korean Mathematical Society
• /
• v.57 no.6
• /
• pp.1451-1473
• /
• 2020

Widely orthant dependence (WOD, in short) is a special dependence structure. In this paper, by using the probability inequalities and moment inequalities for WOD random variables, we study the L_p convergence and complete convergence for the partial sums respectively under the conditions of RCI(α), SRCI(α) and R-h-integrability. We also give an application to nonparametric regression models based on WOD errors by using the L_p convergence that we obtained. Finally we carry out some simulations to verify the validity of our theoretical results.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2010.04a
• /
• pp.1062-1065
• /
• 2010

Plasma 물성 데이터는 Plasma내에서 일어나는 입자(전자, 원자, 이온, 분자 등)들의 충돌에 대한 데이터로써 Plasma 발생 장치 설계 및 제어의 핵심 요소이며, Plasma 공정조건 확립을 위한 필수 정보가 된다. 참조표준은 과학기술데이터나 정보에 대하여 정확도와 신뢰도에 대한 분석 및 평가가 이루어진 공인데이터를 말한다. 이러한 플라즈마 물성 정보를 체계적으로 관리하고 신뢰성 있는 데이터를 필요로 하는 산업체에 지원하기 위하여 특정 참조표준과 참조데이터로 제정, 보급하는 Plasma 물성 참조표준 수집평가 시스템이 필요하고, 이에 대한 설계가 필요하다.

• Computers and Concrete
• /
• v.19 no.6
• /
• pp.659-666
• /
• 2017

Based on the Arrhenius equations, several hydration exothermic models that precisely calculate the influence of concrete's self-temperature duration on its hydration exothermic rate have been presented. However, the models' convergence is difficult to achieve when applied to engineering projects, especially when the activation energy of the Arrhenius equation is precisely considered. Thus, the models' convergence performance should be improved. To solve this problem and apply the model to engineering projects, the relationship between fast iteration and proper expression forms of the adiabatic temperature rise, the coupling relationship between the pipe-cooling and hydration exothermic models, and the influence of concrete's self-temperature duration on its mechanical properties were studied. Based on these results, the rapid convergence of the hydration exothermic model and its coupling with pipe-cooling models were achieved. The calculation results for a particular engineering project show that the improved concrete hydration exothermic model and the corresponding mechanical model can be suitably applied to engineering projects.

• Current Photovoltaic Research
• /
• v.3 no.3
• /
• pp.97-100
• /
• 2015

The kesterite $Cu_2ZnSnSe_4$ (CZTSe) thin film solar cells were synthesized by selenization of sputtered Cu/Sn/Zn metallic precursors on Mo coated soda lime glass substrate in Ar atmosphere. Cu/Sn/Zn metallic precursors were deposited by DC magnetron sputtering process with 30 W power at room temperature. As-deposited metallic precursors were placed in a graphite box with Se pellets and selenized using rapid thermal processing furnace at various temperature ($480^{\circ}C{\sim}560^{\circ}C$) without using a toxic $H_2Se$ gas. Effects of Selenization temperature on the morphological, crystallinity, electrical properties and cell efficiency were investigated by field emission scanning electron microscope (FE-SEM) and X-ray diffraction (XRD), J-V measurement system and solar simulator. Further details about effects of selenization temperature on CZTSe thin films will be discussed.