• 한국재료학회지
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• 제32권12호
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• pp.528-532
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• 2022

Recently, the necessity of designing and applying tool materials that perform machining of difficult-to-cut materials in a cryogenic treatment where demand is increasing. The objective of this study is to evaluate the performance of cryogenically treated WC-5 wt% NbC hard materials fabricated by a pulsed current activated sintering process. The densely consolidated specimens are cryogenically exposed to liquid nitrogen for 6, 12, and 24 h. All cryogenically treated samples exhibit compressive stress in the sintered body compared with the untreated sample. Furthermore, a change in the lattice constant leads to compressive stress in the specimens, which improves their mechanical performance. The cryogenically treated samples exhibit significant improvement in mechanical properties, with a 10.5 % increase in Vickers hardness and a 60 % decrease in the rupture strength compared with the untreated samples. However, deep cryogenic treatment of over 24 h deteriorates the mechanical properties indicating that excessive treatment causes tensile stress in the specimens. Therefore, the cryogenic treatment time should be controlled precisely to obtain mechanically enhanced hard materials.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2011년도 춘계학술대회 논문집
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• pp.1331-1332
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• 2011

• 한국윤활학회:학술대회논문집
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• 한국윤활학회 2002년도 proceedings of the second asia international conference on tribology
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• pp.249-250
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• 2002

In this paper, the relationship among the 3-D surface topography parameters are studied. Several surface topography parameters that are important in tribology are calculated against various surface topography data. 3-D surface data with desired properties are generated by using the non-causal 2-D auto-regressive (AR) model. The non-causal 2-D AR model is a random 3-D surface topography model that can generate 3-D surface topography data with specified parameters.

• Archives of Metallurgy and Materials
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• 제66권4호
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• pp.997-1000
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• 2021

In this study, a novel composite was fabricated by adding the Hafnium diboride (HfB₂) to conventional WC-Co cemented carbides to enhance the high-temperature properties while retaining the intrinsic high hardness. Using spark plasma sintering, high density (up to 99.4%) WC-6Co-(1, 2.5, 4, and 5.5 wt. %) HfB₂ composites were consolidated at 1300℃ (100℃/min) under 60 MPa pressure. The microstructural evolution, oxidation layer, and phase constitution of WC-Co-HfB₂ were investigated in the distribution of WC grain and solid solution phases by X-ray diffraction and FE-SEM. The WC-Co-HfB₂ composite exhibited improved mechanical properties (approximately 2,180.7 kg/mm²) than those of conventional WC-Co cemented carbides. The high strength of the fabricated composites was caused by the fine-grade HfB₂ precipitate and the solid solution, which enabled the tailoring of mechanical properties.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 2004년도 추계학술발표회 발표논문집
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• pp.1143-1144
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• 2004

In this study, we analyze electric field properties in the GEM by using a finite element method. Compared with 3D simulation, modeling of the GEM in 2D rz coordinates is very efficient because of exact simulation results and much saved computational time. The ECE, which is an important measure designating the GEM performance, is estimated by calculating the fractional field-line transparencies. The ECE for various GEM structures and operational parameters are investigated and the results will be presented. This simulation work is very useful for the better design of the GEM.

• 한국기계가공학회지
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• 제20권10호
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• pp.38-43
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• 2021

Photocurable hydrogels are widely used as 3D printing materials in tissue engineering (e.g., scaffold fabrication) as well as optical fibers (or optical sensors) materials. Photocurable hydrogels can control optical and mechanical properties such as chemical or fabrication conditions. In previous research, we introduced a new 3D printing method to fabricate a freestanding overhanging hydrogel structure without supporting structure. This study was measured and analyzed the difference of the mechanical properties of the photocurable hydrogel according to the light intensity using a micro tensile tester. In practically, it was difficult to perform a direct tensile test on a micro (less than 1 mm) size fiber. In this study, the tensile test of the hydrogel fibers could be measured simply and repeatedly using a paper carrier.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 춘계학술대회 논문집
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• pp.1115-1116
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• 2012

• Composites Research
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• 제26권4호
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• pp.213-217
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• 2013

The focus in the present work is to study the agro-waste corn husk bio-filler as reinforcement for polypropylene. These materials have been created by extrusion and injection molding. The effect of filler content by 10, 20, 30 and 40 wt. % and mesh sizes of 50~100, 100 and 300 on the mechanical properties was studied. For the un-notched specimens, the results of flexural strength showed a declining trend with increase the filler loading and the results of impact strength showed an increasing trend with increase the mesh size. In contrast, enhanced flexural modulus was observed with increasing filler loading and size.

• 한국의류산업학회지
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• 제15권4호
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• pp.620-629
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• 2013

This study examines the rustling sound characteristics of electrospun nanofiber web laminates according to layer structures. This study assesses mechanical properties and frictional sounds (such as SPL); in addition, Zwicker's psychoacoustic parameters (such as Loudness (Z), Sharpness (Z), Roughness (Z), and Fluctuation strength (Z)) were calculated using the Sound Quality Program (ver.3.2, B&K, Denmark). The result determined how to control these characteristics and minimize rustling sounds. A total of 3 specimens' frictional sound (generated at 0.63 m/s) was recorded using a Simulator for Frictional Sound of Fabrics (Korea Patent No. 10-2008-0105524) and SPLs were analyzed with a Fast Fourier Transformation (FFT). The mechanical properties of fabrics were measured with a KES-FB system. The SPL value of the sound spectrum showed 6.84~58.47dB at 0~17,500Hz. The SPL value was 61.2dB for the 2-layer PU nanofiber web laminates layered on densely woven PET(C1) and was the highest at 65.1dB for the 3-layer PU nanofiber web laminates (C3). Based on SPSS 18.0, it was shown that there is a correlation between mechanical properties and psychoacoustic characteristics. Tensile properties (LT), weight (T), and bending properties (2HB) showed a high correlation with psychoacoustic characteristics. Tensile linearity (LT) with Loudness (Z) showed a negative correlation coefficient; however, weight (T) with Sharpness (Z) and Roughness (Z), and bending hysteresis (2HB) with Roughness (Z) indicated positive correlation coefficients, respectively.

• International Journal of CAD/CAM
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• 제8권1호
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• pp.11-20
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• 2009

The conventional methods of boundary-conformed 2D surfaces generation usually yield some problems. This paper deals with two boundary-conformed 2D surface generation methods, one conventional approach, the linear Coons method, and a new method, boundary-conformed interpolation. In this new method, unidirectional 2D surface has been generated using some of the geometric properties of the given boundary curves. A method of simultaneous displacement of the interpolated curves from the opposite boundaries has been adopted. The geometric properties considered for displacements include weighted combination of angle bisector and linear displacement vectors at all the data-points of the two opposite generating curves. The algorithm has one adjustable parameter that controls the characteristics of transformation of one set of curves from its parents. This unidirectional process has been extended to bi-directional parameterization by superimposing two sets of unidirectional curves generated from both boundary pairs. Case studies show that this algorithm gives reasonably smooth transformation of the boundaries. This algorithm is more robust than the linear Coons method and capable of resolving the 2D boundary-conformed parameterization problems.