• Advanced Composite Materials
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• v.17 no.3
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• pp.235-246
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• 2008

This paper is concerned with geotextiles bonded chemically with geogrid to form a geocomposite. Geotextiles, thermally bonded and non-woven, play an important role as a separator. Also, this study investigates the resistance to the application environment of geotextile composites. Here, numerous tests have been performed and it was revealed from experimental results that thermally bonded geotextile in geosynthetic composites showed superior characteristics to that manufactured from needle punched non-woven method in terms of tensile strength, tensile strain and high separation performance. It was noted from experiments that the geotextile prepared for separation purpose and manufactured in a thermal bonding method showed relatively low permittivity so that it could be used as a smooth separator. In addition, PVA geotextile/HDPE geomembrane composites were designed and manufactured to investigate the waste landfill related properties. Numerous experiments have been performed and experimental results were summarized to evaluate practical applicability of PVA geotextile/HDPE geomembrane composites. Among the properties of proposed geomembrane composites, evaluation has been focused on the investigation of mechanical properties, AOS (apparent opening size), permittivity and ultraviolet stability.

• Tribology and Lubricants
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• v.40 no.3
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• pp.97-102
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• 2024

The next-generation Molten Salt Reactor is known for its high safety because it uses nuclear fuel dissolved in high-temperature molten salt, unlike traditional solid atomic fuel methods. However, the high-temperature molten salt causes severe corrosion in internal structural materials, threatening the reactor's safety. Therefore, it is crucial to investigate the high-temperature corrosion resistance and wear performance of materials used in reactors to ensure safety. In this study, the high-temperature corrosion resistances and wear performances of corrosion samples in a NaCl-MgCl2-KCl (20-40-40 [wt%]) molten salt are investigated to evaluate the applicability of economically viable stainless steels, 316SS and 304SS. Hastelloy C276 and a new alloy containing a small amount of Nb are used as reference samples for comparative analysis. The mass loss, mass loss rate per unit volume, and surface roughness of each sample are measured to understand the corrosion mechanisms. Scanning electron microscopy and energy-dispersive spectroscopy analyses are employed to analyze the corrosion mechanisms. Wear tests on the corroded samples are also conducted to assess the extent of corrosion. Based on the experimental results, we predict the lifespans of the materials and evaluate their suitability as candidate materials for molten salt reactors. The data obtained from the experiments provide a valuable database for structural materials that can enhance the stability of molten salt reactors and recommend high-temperature corrosion-resistant materials suitable for next-generation reactors.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.28-34
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• 2014

A planetary gear train is more compact and endures greater amounts of transmission power compared to other gear systems. Although planetary gear systems operate in small volumes, they are capable of very high efficiency due to the compact combination of their gears in the planetary gear system. They also have outstanding efficiency of only 3% for power transmission, tantamount to the power loss that occurs in each of the shift stages. Given these advantages, planetary gear systems are used in the driving systems of, which are widely used in automobile transmissions, machine tools, semiconductor equipment, and in other areas in industrial fields. Current structural equipment requires higher efficiency and greater torque levels. According to these needs, we have designed a complex planetary gear system which creates higher levels of torque. In this paper, an evaluation of strength designs for the proposed planetary gear system was conducted to ensure the stability of the gear. In addition, a durability analysis based on Miner's rule was performed using RS B 0095 device.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.8
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• pp.687-692
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• 2015

LAM (Laser-Assisted Machining) is an effective method for processing difficult-to-cut workpieces. The focal length of a LAM system is changed by the change of the workpiece shape during laser preheating; this problem is solved by changing the lens of the laser module. Linear- and rotary-type lens changers were developed to change the laser lens of a LAM system. The linear-type lens changer is operated by a motor with a ball-screw, and the rotary type is operated by a stepping motor. The natural frequency and structural stability of the laser lens changers were confirmed by using a finite element analysis; in addition, the functions of the lens changers were verified by measuring the iterative accuracy. The measured results show that the rotary-type lens changer is more accurate than the linear-type changer.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.349-354
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• 2000

A use of Titanium alloy as a structural material is increasing lately. Among those titanium alloys, Ti-6A1-4V alloy is the most popular one with taking 2/3 of it's market. Also, Ti-6A1-4V alloy can get the stability of organization and product measure, and the evaluation of the cutting ability and the mechanical characteristics. The point in titanium alloy work is on how treat the heat generated during grinding. Because the heat conductivity of titanium alloy is unnegligibly low, the grinding heat is accumulated in workpiece, and it cause the increasing of grinding grits' wear and the rough grinding surface. So, these characteristics in grinding of titanium alloy will change the mechanical characteristics of the titanium alloy. From this study, the mechanical characteristics of annealed Ti-6A1-4V alloy after grinding was concerned with checking out the bending strength values, and the factor of the change and the difference was analyzed after analyzing the surface roughness and the image from SEM.

• Fire Science and Engineering
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• v.27 no.5
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• pp.1-7
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• 2013

Fire at building can occur enormous damages to life, properties, and environment and the risk of fire breakout is going up higher because of application of combustible materials than before. Therefore, the steel industries are trying to develop fire resistant steel in order to sustain the load bearing capacity of steel structures during fire situation. In this paper, to give the basis data-bases for evaluation of structural stability of steel structures applied fire resistant steel, FR 490, the tests of mechanical and thermal properties at high temperature were conducted and the comparisons are done with the SM 490 that has the same mechanical one.

• Journal of the Society of Disaster Information
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• v.7 no.1
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• pp.32-42
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• 2011

Many researches have been conducted to evaluate the performance of modified asphalt concrete mixtures. The research was conducted to estimate the laboratory mechanical characteristics of Elvaloy-modified asphalt concrete mixture. To achieve its intended objective, indirect tensile test and resilient modulus test were performed. The rest results revealed that indirect tensile strengths and resilient moduli of the Elvaloy-modified asphalt concrete mixture were higher than those of the conventional dense-graded. As a result, within the limits of the tests conducted in this research, it is predicted that the performance and stability of the Elvaloy-modified asphalt concrete mixture are better than that of the conventional dense-graded one.

• Journal of Mechanical Science and Technology
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• v.20 no.12
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• pp.2218-2229
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• 2006

A conservative finite-volume numerical method for unstructured grids with the cell-centered method has been developed for computing flow and heat transfer by combining the attractive features of the existing pressure-based procedures with the advances made in unstructured grid techniques. This method uses an integral form of governing equations for arbitrary convex polyhedra. Care is taken in the discretization and solution procedure to avoid formulations that are cell-shape-specific. A collocated variable arrangement formulation is developed, i.e. all dependent variables such as pressure and velocity are stored at cell centers. For both convective and diffusive fluxes the forms superior to both accuracy and stability are particularly adopted and formulated through a systematic study on the existing approximation ones. Gradients required for the evaluation of diffusion fluxes and for second-order-accurate convective operators are computed by using a linear reconstruction based on the divergence theorem. Momentum interpolation is used to prevent the pressure checkerboarding and a segregated solution strategy is adopted to minimize the storage requirements with the pressure-velocity coupling by the SIMPLE algorithm. An algebraic solver using iterative preconditioned conjugate gradient method is used for the solution of linearized equations. The flow analysis code (PowerCFD) developed by the present method is evaluated for its application to several 2-D structured-mesh benchmark problems using a variety of unstructured quadrilateral and triangular meshes. The present flow analysis code by using unstructured grids with the cell-centered method clearly demonstrate the same accuracy and robustness as that for a typical structured mesh.

• Journal of the Korean Society of Clothing and Textiles
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• v.31 no.1 s.160
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• pp.68-76
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• 2007

The purpose of this study is to investigate change of mechanical and physical properties, shape behavior and hand value in weft knit when rib stitch and milan stitch are combined. The knit stitches used in this study are plain stitch, half milan rib stitch, milan rib stitch, $2{\times}1$ rib stitch, $2{\times}1$ half milan rib stitch and $2{\times}1$ milan rib stitch. We analyzed physical and mechanical properties(tensile, bending, shear, compression, surface properties, thickness and weight) of the knit stitches and calculated their primary hand value and total hand value through translational formulas using the KES(Kawabata Evaluation System). The results are as follows; In evaluation of mechanical properties and hand values of knit stitches, plain stitch had the highest flexibility and the lowest T.H.V. as women's winter knit wear. Since $2{\times}1$ rib stitch had too high elongation in one direction, although it had the highest T.H.V, it needs to be careful when plain stitch and $2{\times}1$ rib stitch are applied for women's winter knit wear. Since Milan rib stitch and $2{\times}1$ milan rib stitch had high T.H.V. similarly, it is considered that they are suitable for women's winter knit wear. Specially, when Milan stitch is combined with $2{\times}1$ rib stitch, its shape stability and fullness are contained and flexibility is added on it. Therefore, $2{\times}1$ milan rib stitch can be also applied for women's winter knit wear.

• Tunnel and Underground Space
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• v.32 no.6
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• pp.411-434
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• 2022

In deep geological disposal concept for spent nuclear fuel, it is well-known that rock mass at near-field experiences the thermal-hydraulic-mechanical (THM) coupled behavior. The mechanical properties of rock changes during the coupled process, and it is important to consider the changes into the analysis of numerical simulation and in-situ tests for long-term stability evaluation of nuclear waste disposal repository. This report collected the previous studies on indirect coupled behaviors of rock. The effects of water saturation and temperature on some mechanical properties of rock was considered, while the change in hydraulic conductivity of rock due to stress was included in the indirect coupled behavior.