• Proceedings of the Korean Institute of Building Construction Conference
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• 2011.11a
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• pp.211-212
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• 2011

It was very important to evaluate concrete experimentally at elevated temperature because concrete was filled with aggregate of concrete volume about 70 percent. Concrete exposure to high temperatures produces changes in its internal structure, for instance loss of its strength and deformation capacity, in extreme cases risking the service life of the structure. The work of this paper is performed to evaluate the thermal behavior of ultra-high strength concrete having different water to cement ratio (strength), fine aggregate to aggregate ratio and maximum size of coarse aggregate. For exposure to 500℃ during 1 hour, residual mechanical properties of the ultra-high strength concrete decreased as the s/a ratio decreases and the maximum size of coarse aggregate increases.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.11 no.1
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• pp.17-25
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• 2002

This system is composed of fine and coarse apparatus, measurement system and control system. Piezoelectric actuator is designed far fee positioning. We make a study of precision apparatus that is used in the various industrial machine. The study was carried out to develope a precision positioning apparatus, consisting of servo motor and piezoelectric actuator Coarse positioning using lead screw is thrived by servo motor. Control system output a signal from laser interferometer to amplifier of servo motor and piezoelectric actuator after digital signal processing (DSP). Resolution of this apparatus measure with laser interferometer. In this study, design method and control system with ultra precision position apparatus are researched. As the first step, we have estimated for control performance and system stability before an actual apparatus is manufactured by MATLAB with SIMUUNK including various frictions those are composed of pre-design and system modeling.

• Journal of Korea Foundry Society
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• v.10 no.5
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• pp.417-425
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• 1990

The purpose of this study is to investigate the effect of Be addition on the microstructure and mechanical properties of as-cast and homogenization treated Al-Li-(Be)alloys. The ductility of as-cast Al-Li alloy was increased by the addition of Be and the fracture morphology was changed from brittle to ductile mode. Also, hardness and strength have been decreased by homogenization treatment. The morphology of eutectic structure which consists of ${\alpha}(Al)$ and ${\alpha}(Be)$ was changed from lammellae to spherical type by homogenization treatment. The shape of ${\alpha}(Be)$ phase has been revealed as hollow type by TEM observation. It consists of outer surfaces with well defined crystal facets and the core filled with ${\alpha}(Al)$. The microstructure of as-cast Al-Li-Be alloys showed coarse ${\delta}'$, fine ${\delta}'$, and coarse ${\delta}$ phases. The coarse and fine ${\delta}'$ phases were formed at Be-rich phase /matrix interfaces and in matrix, respectively. By homogenization treatment, the ${\delta}$ phase in Al-Li and Al-Li-Be alloys dissolved and the size of ${\delta}$ phase in Al-Li-Be alloys was finer than that of Al-Li alloy.

• Journal of Korean Society for Atmospheric Environment
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• v.20 no.6
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• pp.833-838
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• 2004

The analysis of Pb in both PM$_{2.5}$ and PM$_{10}$ fraction of aerosols was made consecutively for every spring season during four year period of 2001 through 2004. To diagnose the impact of the Asian Dust (AD) on metal concentration levels, we compared our Pb measurement data after dividing the whole data sets into AD and NAD period. The results of our analysis indicated that the concentrations of coarse particles increased significantly during the AD period, whereas an increase in the fine counterpart was of moderate degree. However, when Pb concentrations between AD and NAD were compared, the patterns were quite different. From all particle fractions, the Pb concentrations of NAD were slightly or moderately higher than those of AD. The overall results of our study suggest that an increase in particle concentrations during the AD period can cause a rather slight reduction in Pb concentration levels; this can be explained by the dilution effect associated with the increase of Pb-depleted coarse particles.s.s.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.73.2-79
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• 2003

The purpose of this study is to provide the basic data on the optimum method for interfacial separation for an effective recycle of concrete waste by using the thermal properties of concrete. Therefore, this study is proceeded by dividing the interface of concrete into cement paste and fine aggregates or mortar and coarse aggregate, considering the aspect of recycled cement and aggregate as the recycling use of concrete waste. As results of the experiment, in case of recycle cement, the interfacial separation is easily appeared, but it is shown that the mixed amount of powder included in fine aggregate doesn't greatly decrease. But, in case of recycle coarse aggregate, the effect of interfacial separation by preliminary heating is predominant. Especially, the bonding rate of mortar is the lowest when it is heated 5 times for 120 minutes at $300^{\circ}C$. Hence, it is considered that it will be an excellent effect of quality control when the results of this study is applied to a manufacturing system of recycle coarse aggregate which is about to put into practical use.

• 한국지구과학회:학술대회논문집
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• 2010.04a
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• pp.58-58
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• 2010

The sediment geochemistry, including REE of surface and core samples in the western part off Jeju Island have been carried out in order to understand the provenance and hydrolic sorting. The sediment in the study area were primarily composed of coarse silt with a mean grain size of $2.8{\sim}82.8{\mu}m$. The ratios of TOC over total nitrogen (TN) showed that the study area sediments contained more organic matters of marine origin than those of terrigenous origin. The total A1203, Fe203, K20, MgO, and MnO contents and REE concentration of the fine sediments are higher than those of the coarse sediments. The higher Zr/Th and Zr/Yb ratios in coarse sediments relative to fine-grained detritus indicates sedimentary sorting. Grain size influence the REE concentrations of the study area sediment significantly. The < $63{\mu}m$ fraction of the sediment has higher REE concentration and different REE patterns when compared with those in bulk samples, due to the presence of REE-enrich heavy minerals. The REE distribution patterns of the western part of Jeju Island sediments are relatively enriched in most LREEs than the Yellow River sediment and depleted in the Changjiang River, but the LaN/YbN ratios are similar to the Changjiang sediment. The Eu/Eu* ratios ranged from 0.594~0.665(0.631) is much similar to the Yellow River sediment, possibly mixture of the sediments from these two rivers.

• Journal of the Korean Ceramic Society
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• v.35 no.8
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• pp.807-812
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• 1998

Mechanical properties of two types of polycrystlline {{{{ { { Ti}_{3 }SiC }_{2 } }} with different grain size were investigated. A fine grain {{{{ { { Ti}_{3 }SiC }_{2 } }} has a higher fracture strength and hardness. Plot of strength versus Vickers indentation load indicated that {{{{ { { Ti}_{3 }SiC }_{2 } }} has a high flaw tolerance. Hertzian indentation test using a spherical indenter was used to study elastic and plastic behavior in {{{{ { { Ti}_{3 }SiC }_{2 } }}. Indentation stress-strain curves of each material are made to evaluate the plasticity of {{{{ { { Ti}_{3 }SiC }_{2 } }} Both find and coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} showed high plasticity. In-dentation stress-strain curve of coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} deviated even more from an ideal elastic limit in-dicating exceptional plasticity in this material. Deformation zones were formed below the contact as well as around the contact area in both materials but the size of deformation zone in coarse grain {{{{ { { Ti}_{3 }SiC }_{2 } }} was much larger than that in fine grain {{{{ { { Ti}_{3 }SiC }_{2 } }} Intragrain slip and kink would account for high plasticity. Plastic behavior of {{{{ { { Ti}_{3 }SiC }_{2 } }} was strongly influenced by grain size.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.23-24
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• 2021

The use of recycled concrete aggregates (RCA) as a substitute for natural aggregates in new concrete produces both economic and environmental advantages. Most of the RCA applications for pavements have been primarily applied to support layers for roads and airfields. This paper summarizes a work completed at the University of Illinois in partnership with the O'Hare Modernization Program to examine the effect of coarse and fine RCA on the concrete's fresh and hardened properties for airfield rigid pavement applications. Ten different RCA concrete mixtures were prepared with the incorporation of different percentages of RCA fines as well as replacement of cement with high volume percentages of supplementary cementitious materials such as Class C fly ash and ground granulated blast furnace slag to improve the workability and long-term properties of RCA concrete. All the mixes on this stage included 100% recycled coarse aggregates and the Two-Stage Mixing Approach was used as a mixing procedure. Based on the results obtained in the research, mixes with high percentages of recycled fine and coarse aggregates could be used for construction of airfield concrete pavements in conjunction with supplementary cementitious materials

• International Journal of Korean Welding Society
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• v.2 no.1
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• pp.25-28
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• 2002

In the coarse grain HAZ adjacent to the fusion line, most of the TiN particles in conventional Ti added steel are dissolved and austenite grain growth is easily occurred during welding process. To avoid this difficulty, thermal stability of TiN particle is improved by increasing the nitrogen content in steel. In this study, the effect of hlgh nitrogen TiN particle on preventing austenite grain growth in HAZ was investigated. Increased thermal stability of TiN particle is helpful for preventing the austenite grain growth by pinning effect. High nitrogen TiN particle in simulated HAZ were not dissolved even at high temperature such as 1400'E and prevented the austenite grain growth in simulated HAZ. Owing to small austenite grain size in HAZ the width of coarse grain HAZ in high nitrogen TiN steel was decreased to 1/10 of conventional TiN steel. Even high heat input welding, the microstructure of coarse grain HAZ consisted of fine polygonal ferrite and pearlite and toughness of coarse grain HAZ was significantly improved.

• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.509-510
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• 2006

FLL (Frequency Locked Loop) is the core block for high-speed transceiver. It incorporates a PLL for fine locking action, and a coarse controller for coarse locking action. A coarse controller compares frequencies coarsely and is applied to detected frequency difference directly. Compare to conventional FLL, frequency is applied to proposed FLL. Proposed FLL in this paper achieves only 5 cycles for coarse lock and total frequency locking time is 5 times faster than conventional FLL. Thus, proposed FLL is more useful to Ethernet transceiver application that requires high-speed data transfer than conventional FLL. Proposed FLL is based on $0.18{\mu}m$ process.